EPA 440/1-73/013
Development Document for
Proposed Effluent Limitations Guidelines
and New Source Performance Standards
for the
TIRE and SYNTHETIC
Segment of the
Rubber Processing
Point Source Category
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
SEPTEMBER 1973
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DEVELOPMENT DOCUMENT
for
PROPOSED FFFLUENT LIMITATIONS GUIDELINES
and
NEW SOURCE PERFORMANCE STANDARDS
for the
TIRE AND SYNTHETIC SEGMENT
OF THE RUBBER PROCESSING
POINT SOURCE CATEGORY
Russell E. Train
Administrator
Robert. I. Sansom
Assistant Administrator for Air f/ Water Programs
Allen Cyv/in
Director, Effluent Guidelines Division
John E. Riley
Project Officer
September 1973
Effluent Guidelines Division
Office of Air and Water Programs
U.S. Environmental Protection Agency
Washington, D.C. 20460
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ABSTPACT
This document presents the findings of a study of the tire and inner-
tube and synthetic rubber segments of the rubber processing industry by
Poy F. Weston, Inc. for the Environmental Protection Agency, for tha
purpose of developinq effluent limitation guidelines, Feueral standards
of performance, and pretreatment standards for tne industry, to
implement Sections 304, 306, and 307 of the Federal Water Pollution
Control Act, as amera-ft (33 USC 1251, 1314, and 1316; 86 Stat 816).
Effluent limitation quidelinks contained hereir set fortn tne degree of
effluent reduction af-ainable through the application of the best
practicable control -^chr.oloqy currently available and tne aegree of
effluent reduction attainable through the application of tne Lest
available technoloqy economically achievable, which must be acnieved by
existing point sources by July 1, 1977 and July 1, 1983, respectively.
The Standards of Performance for new sources contained nerein set, forth
the degree ot effluent reduction which is achievable through the
-application of the bes4- available demonstrated control tecnnology,
processes, operaninq methods, or other alternatives.
The development ot" data and recommendations in the document relate to
the tire and inn-r tube and synthetic rubber segments of the rubber
processing industry. These two segments are further divided into five
subcateqories on thQ 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, and
for the synthetic rubber subcategories treatment of the secondary
effluent by carbon adsorption.
Supportive data and the rationale for development of the proposed
effluent limitation guidelines and standards of performance are
contained in this document.
11
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CONTENTS
Section Page
ABSTRACT ii
CONTENTS iii
FIGURES vi
TABLES vii
I CONCLUSIONS 1
II RECOMMENDATIONS 5
III INTRODUCTION 7
Purpose and Authority 7
Summary of Methods Used for Development of the 8
Effluent Limitation Guidelines and Standards
of Performance
General Description of the Industry 10
Tire and Inner Tube Industry 10
Tire Manufacture 10
Inner Tube Manufacture 21
Synthetic Rubber Industry 23
General 23
Synthetic Rubber Production 27
Emulsion Crumb Production 27
Solution Crumb Production 32
Latex Production 38
Summary 40
IV INDUSTRY CATEGORIZATION 43
Introduction 43
Tire and Inner Tube Industry 43
Synthetic Rubber Industry 49
V WASTE CHARACTERIZATION 53
Tire and Inner Tube Industry 53
Synthetic Rubber Industry 58
General 58
Emulsion Crumb Rubber Subcategory 58
Solution Crumb Rubber Subcategory 62
Latex Rubber Subcategory 65
111
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VI SELECTION OF POLLUTION PARAMETERS 69
Tire and Inner Tube Industry 69
Synthetic Rubber Industry 71
VII CONTROL AND TREATMENT TECHNOLOGY 75
Survey of Selected Plants 75
General Approach and Summary 75
Tire and Inner Tube Plants 75
Synthetic Rubber Plants 88
Summary of Control and Treatment Technology 105
Tires and Inner Tubes 105
In-Planr Control 105
End-of-Pipe Treatment 108
Synthetic Rubber 109
In-Planr Control 109
End-of-Pipe Treatment HO
VIII COST, ENERGY AND NON-WATER QUALITY ASPECTS H5
Tire and Inner Tube Industry H5
Synthetic Rubber Industry 122
Emulson Crumb Subcategory 122
Solution Crumb Sutcategory 127
Latex Subcategory 131
Derailed Cost Infomration for All Subcategories 132
IX BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY 153
AVAILABLE-EFFLUENT LIMITATIONS
Tire and Inner Tube Facilities 153
Identification of Best Practicable Control 153
Technology Currently Available
Effluent Loadings Attainable With Proposed ^55
Technologies
Synthetic Rubber Industry 156
Identification of Best Practicable Control ^55
Technology Currently Available
Emulsion Crumb Subcategory 156
Solution Crumb Sutcategory 159
Latex Subcaregory 159
Effluent Loadings Attainable With Proposed 160
Technologies
Emulsion Crumb Sutcategory 160
Solution Crumb Subcategory 162
Latex Subcategory 164
IV
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5f BEST AVAILABLE TECHNOLOGY ECONOMICALLY 167
ACHIEVABLE--EFFLUENT LIMITATIONS
Tire and Inner Tube Industry 167
Synthetic Pubber Industry 167
Identification of Besr Available Technology 157
Economically Achievable
Fmulsior. Crumb Subcategory 167
Solurion Crumb Subcategory 159
Latex Subcategory ^59
Effluent Lo-aaing Attainable with Proposed 170
Technologies
Emulsion Crumb Subcategory ^70
Solu-ion Crumb Subcategory 170
Larex Pubcategory 171
XI NEW SOURCE PERFORMANCE STANDARDS
Tire and Inner Tube Production Facilitif-s 173
Synthetic Rubber Industry 173
Pretr'" atment Recommendations 173
Tir- and Inner Tube Industry 173
Rubber Industry
KIT ACKNOWLEDGEMENTS 175
XIII PEFEPENCES 177
XIV GLOSSARY 18i
XV METPIC UNITS AND CONVFPSION FACTORS 18g
V
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FIGURES
Figure
1 Flow Diagram for Typical Tire and 14
Camelback Production Facility
2 Flow Diagram for a Typical Inner Tube 22
Production Facility
3 General Water Flow Diagram for an Emulsion 28
Polymerized Crumb Rubber Production
Facility
4 General water Flow Diagram for a Solution 34
Polymerized Crumb Rubber Production
Facility
5 General Water Flow Diagram for an Emulsion 39
Latex Rubber Production Facility
6 Location of Tire Manufacturing Plants, 46
Production Greater than 20,000 Units/Day,
and Synthetic Rubber Production Plants,
Production Greater than 60,000 Long Tons/
Day, Within the U.S., 1972
7 Plant J: Chemical Coagulation and Clarifi- 91
cation Plus Sludge Handling System Followed
by Bio-Oxidation Treatment
8 Plant K: Air Flotation and Bio-Oxidation 94
Wastewater Treatment Facility
9 Plant N: Activated Sludge Waste Water 100
Treatment Facility
10 Hypothetical Waste Water Segregation and 119
Treatment Facility for Tire and Inner
Tube Plants
11 Hypothetical End-of-Pipe Secondary Waste Water 124
Treatment Facility for Synthetic Rubber
Plants
12 Hypothetical End-of-Pipe Advanced Waste Water 125
Treatment Facility for All Sub-categories
of Synthetic Rubber Plants
VI
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TABLES
Table Title Page
1 U.S. Tire and Inner Tube Production from 12
1967-1971
2 Summary of Potential Process-Associated 20
Waste Water Sources from the Tire and
Inner Tube Industry
3 U.S. Synthetic Rubber Production by Type 24
for 1967-1971 and the Projected Growth
Rate to 1980
4 Families of Synthetic Rubbers Included in 26
SIC 2822, Polymerization Processes, and
Annual U.S. Production (1972)
5 Summary of Potential Process-Associated 33
Waste Water Sources from Crumb Rubber
Production via Emulsion Polymerization
Processing
6 Summary of Potential Process-Associated 37
Waste Water Sources from Crumb-Rubber
Production via Solution Polymerization
Processing
7 Summary of Potential Process-Associated 41
Waste Water Sources from Latex Production
via Emulsion Polymerization Processing
8 Major Tire Production Facilities in the 45
United States
9 Raw Waste Loads of Untreated Effluent from 54
Tire and Inner Tube Facilities
10 Average Values of Raw Waste Loads from Tire 56
Industry
11 Raw Waste Loads of Process Waste Waters from 57
Tire and Inner Tube Facilities
12 Raw Waste Loads for Emulsion Crumb Rubber 59
VII
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Plants
1? Paw Waste Loads cf the Principal Individual 61
Waste Water Streams in an Emulsion Crumb
Rubber Plant
14 Raw Waste Loads tor Solution Crumb Rubber Plants 63
15 Raw Waste Loads for Latex Rubber Plants 66
16 Waste '
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SECTION I
CONCLUSIONS
Two major and distinct segments exist within the rubber processing
industry: 1) the tire and inner tube industry; 2) the synthetic rubber
industry.
For the purpose of establishing limitations, the tire and inner tube
industry has been subcategorized according to the age of the production
facility. Waste loads and costs of control technologies substantiate
this. Factors such as the manufacturing process, final product, raw
materials, plant size, geographic location, air pollution equipment, and
the nature and treatability of waste waters are similar and furrher
substantiate the subcategorization of the tire and inner tube plants by
age.
Process waste waters for both subcategories of the tire and inner tube
industry include discharges of solutions used in the manufacturing pro-
cess, washdown of processing areas, run-off from raw material storage
areas, and spills and leakage of cooling water, steam, processing
solutions, organic solvents and lubricating oils. Primary pollutants in
these waste waters are oil and grease, suspended solids, and acidity and
alkalinity (pH) .
In the tire and inner tube industry, the emphasis of present environ-
mental guality control and treatment technologies is placed on the
control of particulate emission and the reduction of pollutants in
nonprocess waste waters. Control and treatment of many process waste-
waters has been given secondary priority. As a result, no adeguate
overall control and treatment technology is employed by plants within
the industry. A treatment system, practicable and available to the
industry, has therefore been proposed for both subcategories. It
encompasses a combination of the various technologies employed by the
different segments of the industry to control one or more constituents
in the process waste waters.
Proposed effluent limitations and standards for the best practicable
control technology currently available are:
Suspended Solids 0.06U kg/kkg (lb/1000 Ib) raw material
Oil and Grease 0.016 kg/kkg (lb/1000 Ib) raw material
pH 6.0 to 9.0
No additional reduction is proposed for the limitations and standards
represented by best available technology economically achievable or for
new sources coming on stream after the guidelines are put into effect.
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For the purpose of establishing effluent limitations guidelines and
standards of performance, the synthetic rubber industry has been sub-
categorized, on the basis of processing techniques, product type, and
waste water characterizations, into three separate subcategories:
1. Emulsion crumb
2. Solution crumb
3. Lat ex
All three subcategories generate waste waters which contain the same
general constituents. However, the concentration and loading of these
constituents, termed "raw waste load", vary between the subcategories.
The significant waste water constituents are COD, BOD, suspended solids,
dissolved solids, and oil and grease. Latex production waste waters,
although lower in flow per unit of production than the other two
categories, have the highest raw waste loads.
The waste water parameters selected to be the subject of tne effluent
limitations are COD, BOD, suspended solids, oil and grease and pH.
These parameters are present in the waste water as a result of organic
contamination. Heavy metals, cyanides and phenols were not found in
significant quantities (less than 0.1 mg/L) in synthetic rubber process
waste waters.
Existing control and treatment technology, as practiced by the industry,
emphasizes end-of-pipe treatment rather than in-plant reductions. This
is because in-plant modifications which might lead to improved waste-
water management could affect processing techniques or quality of the
final product.
Current treatment technology for both emulsion crumb and latex plants
involves primary clarification with chemical coagulation of latex
solids, followed by biological treatment. As an alternative to chemical
coagulation, air flotation clarification of primary and secondary solids
is successfully practiced. Biological treatment systems include
activated sludge systems and aerated lagoon and stabilization pond
systems. Best practicable control technology currenty available for
emulsion crumb and latex plants has been defined as that achieved by
chemical coagulation and biological treatment.
Current treatment technology for solution crumb requires conventional
primary clarification of rubber solid fines followed by biological
treatment. Existing biological treatment systems employ aerated lagoon
and stabilization pond systems or activated sludge plants. Best
practicable control technology economically achievable for solution
crumb production facilities has been defined as comparable to primary
clarification and biological treatment.
Best available technology economically achievable technology for the
three subcategories has been defined as equivalent to dual-media
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filtration followed by activated carbon treatment of the effluent from
the biological treatment system to achieve acceptable COD removal.
Standards of performance for new sources are identical to
practicable control technology currently avaiable.
best
The proposed effluent limitations and standards of performance for
plants within the three synthetic rubber subcategories are summarized as
follows:
Best Practicable Control Technology Currently Avaiable
and Standards of Performance for New sources
Emulsion Crumb Solution Crumb Latex
Plants Ei§.Qis Plants
kg/kkg kg/kkg kg/kkg
(lb/1000 Ib) (lb/1000 Ib) (lb/1000 Ib)
COD
BOD
Suspended solids
Oil and Grease
PH
00
40
65
16
0 to
9.0
3.92
0.40
0.65
0. 16
6.0 to 9.0
6.85
0.34
0.55
0.14
6.0 to 9,
Best Available Technology Economically Achievable
Emulsion^ Crumb Solution Crumb Latex
Plants
COD
BOD
Suspended solids
Oil and Grease
PH
Plants
2.08
0.08
0. 16
0.08
6.0 to 9.0
2.08
0.08
0. 16
0.08
6.0 to 9.0
Plants
1.78
0.07
0.14
0.07
6.0 to 9.0
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SECTION II
RECOMMENDATIONS
Implicit in the recommended guidelines for the tire and inner tube
industry is the fact that process wastes can be isolated from nonprocess
wastes such as utility discharges and uncontaminated storm runoff.
Isolation of process waste water is the first recommended step in the
accomplishment of the reductions in oil and suspended solid loading
necessary to meet the guidelines. Treatment of process waste waters in
a combined process/nonprocess system is ineffective due to dilution by
the relatively large volume of nonprocess waste waters.
It is further suggested that uncontaminated waters, such as storm run-
off , be detoured from outdoor areas where the potential exists for
contamination by oil or solids. This could include roofing and curbing
of storage areas and the collection and treatment of runoff which cannot
be isolated from such areas.
The training of operators and maintenance personnel is important in any
control technology. Negligent dumping of various processing solutions
and lubricants into unsegregated drains within the plant must be
eliminated or at least severely diminished. Washdown of potentially
contaminated areas must be eliminated whenever possible. Tne number and
location of in-plant drains should be kept at a minimum, to reduce the
possibility of process waste water contamination to as few sources as
possible.
Wet air pollution equipment should be kept to a minimum. Discharges
from wet equipment already in service should be recycled when possible.
The use of dry-type pollution equipment is consistent with recovery
efficiencies and prevention of waste water control problems.
In-plant modifications should be implemented which will lead to
reductions in waste water flow, increased quantity of water used for
recycle or reuse, and improvement in raw waste water quality.
End-of-pipe treatment technologies equivalent to secondary treatment
should be applied to the waste waters from all synthetic rubber sub-
categories to achieve best practicable technology currently available.
For emulsion crumb and latex plants, chemical coagulation and
clarification should be provided prior to biological treatment.
To achieve standards for best available technology economically
achievable, end-of-pipe treatment technolgies equivalent to activated
carbon adsorption of secondary treatment effluent is required on all
waste waters originating in synthetic rubber plants.
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Standards of performance for new sources, are identical to best
practicable control technology currently available for all synthetic
rubber subcategories.
Synthetic rubber utility, or nonprocess, waste waters as boiler
blowdowns, cooling tower blowdowns, and water treatment plant wastes are
commonly discharged to the plants' main waste water treatment
facilities. With the exception of total dissolved solids and, in some
cases, heavy metals such as chromium and zinc, the utility wastes are
adequately treated at the main treatment facility. However, the
control, pretreatment, and treatment technologies, and effluent
limitation for nonprocess or utility waste waters in the rubber
manufacturing subcategory will be covered by effluent guideline
documents and regulations promulgated separately and at a future date.
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SECTION III
INTRODUCTION
Purpogg and^AuthQrity
section 301(b) of the Act requires the achievement, by not later than
July 1, 1977, of effluent limitations for point sources (other than
publicly-owned treatment works) which are based on the application of
the "best practicable control technology currently available" as defined
by the Administrator pursuant to Section 304(b) of the Act.
Section 301 (b) also requires the achievement, by not later than July 1,
1983, of effluent limitations for point sources (other than publicly-
owned treatment works) which are based on the application of the "best
available technology economically achievable" which will result in
reasonable further progress toward the national goal of eliminating the
discharge of all pollutants, as determined in accordance with
regulations issued by the Administrator pursuant to Section 304(b) to
the Act.
Section 306 of the Act requires the achievement by new sources of a
Federal standard of performance providing for the control of the dis-
charge 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 tne 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 in-
novations, operation methods, and other alternatives).
The regulations proposed herein set forth effluent limitations
guidelines pursuant to Section 304(b) of the Act for the tire and inner
tube and the synthetic rubber subcategories of the Rubber Processing
Industry.
Section 306 of the Act requires the Administrator, within one year after
a category of sources is included in a list published pursuant to
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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 tire and inner tube and 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 nonwater quality environmental impacts (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 limitations 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
materails used, product produced, manufacturing process employed, and
other factors such as plant age. Published literature was consulted to
verify the raw waste characteristics and treatabilities in order to
support the initial industry categorizations and subcategorizations.
The raw waste characteristics for each tentative subcategory were then
fully identified. Factors considered 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.
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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 ot 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 non-water quality environmental impact, 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". factors were considered. These included the total cost of
application of technology in relation to the effluent reduction benefits
to be achieved from such application, the age of equipment and
facilities involved, the process employed, the engineering aspects of
the application of various types of control technique process changes,
the non-water quality environmental impact (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 tire, inner -tube,
and synthetic rubber production plants throughout the United States to
confirm and supplement the above data. All factors potentially
influencing industry subcategorizations were represented by the on-site
visits. Detailed information on production schedules and capacities,
and product breakdowns as well as water use and waste water control and
treatment management practices were obtained. 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
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methods. Duplicate samples were analyzed by the participating companies
to confirm the analytical results.
General Description of the Industry
The categories of the rubber processing industry covered by this docu-
ment are the tire and inner tube (SIC 3011) and the synthetic rubber
(SIC 2822). The manufacture of tires and inner tubes utilizes
completely different processing techniques than the production of
synthetic rubber. In a tire or inner tube plant, stock rubber
production follows a very definite formulation or recipe, and is a
batching operation.
The mixed stock production is used to produce the five main components
of a tire: tire bead coating, tire treads, tire side wall, inner liner
stock and coated cord fabric. These five components enter the tire
building plant, where a significant amount of hand and machine lay-up is
required to produce the green tires.
The synthetic rubber (or vulcanizable elastomer) industry is character
ized essentially by the chemical process and unit operations necessary
to convert the particular monomers or starting-block materials into a
stabilized, granulated, extruded, or baled material suitable for more
conventional rubber processing. The processes are characterized by
separation of unreacted monomer, recovery, purification and recycle of
the monomer, and processing of the converted elastomer. These reactions
are normally carried out batch-wise or batch/continuous.
In view of the fact that these two industry classifications, tire and
inner tube manufacture and synthetic rubber production, differ consider-
ably it is appropriate, from this point on, to describe and evaluate
their water uses and waste water generations separately.
Tire_and_lnner_Tube Industry
Tire Manufacture
There are many events that have had a significant effect on the tire and
inner tube industry. The first is the discovery, by Charles Goodyear in
1839, that rubber could be cured or vulcanized with sulfur. Thus,
Goodyear was able to overcome the tacky, plastic properties of rubber,
thereby creating a product of commercial applicability (1).
The year 1906 saw the development of the first organic accelerators.
Accelerators are substances which affect the rate of vulcanization.
With the entry of such substances, better products could be produced in
a shorter period of time (1,2).
The next major event to affect the tire industry was trie advent of the
Second World War. With the drastic reduction in the supply of natural
10
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rubber, new sources had to be developed. The first substitute was re-
claimed rubber which, by 1943, had completely replaced natural rubber as
the basic tire material. It was not until the mid 1940's that synthetic
rubber, made available due to a major governmental effort, became the
major substitute for natural rubber. By 1945, approximately 98 percent
of the natural rubber had been replaced by this synthetic substitute
(3). The years following the war saw the return, to a great extent, of
natural rubber. However, with the technological boost given the syn-
thetic rubber industry, it would soon again become the larger portion of
the tire.
The next major event which occurred in the mid-1950's was the
introduction of tubeless tires as original equipment on new cars. This
development sent the inner tube industry into rapid decline. The total
number of passenger car and motorcycle inner tube units dropped from in
excess of 49 million in 1954 to less than 25 million in 1955 (4) .
The tire industry has had three eras of rapid expansion to coincide with
these events. The post World War I era (1916-1929) brought the first
such development. As the automobile and truck industry expanded, so did
the tire industry. Large capacity tire plants were built in Ohio, Cali-
fornia, and New England. The depression reversed this trend however,
and it was not until World War II created an increased demand for tires
that the tire industry again began to expand. New plants were erected
in Ohio, New England, and the South. The third building expansion
started in the early 1960's and is still proceeding, again occurring
simultaneously with the expansion of the economy.
With the current expansion, tire companies are now located throughout
the United States. Whereas the older plants of the first two expansions
are located in the urban areas of Ohio, California, and New England, the
newer plants are being located in rural areas with no particular
emphasis placed on geography.
Today's tire manufacturer produces many types of tires designed for a
multitute of uses. General product categories include passenger, truck
and bus, farm tractor and implement, and aircraft. Table 1 presents a
breakdown of these products for the last five years.
The key to the performance of all tires is the selection of the raw
rubber and compounding materials and the proportion of these materials
in any particular part of the tire. Basically, the tire consists of
five parts, namely: the tread, the sidewall, the cord, the bead, and
the inner liner. Each part has different service requirements;
therefore, each requires a different proportion of the raw materials.
For example, longevity and good traction are requirements of the tread,
whereas a high degree of flexibility is the requirement for sidewalls.
Basic tire ingredients include synthetic rubbers, natural rubber,
various fillers, extenders and reinforcers, curing and accelerator
agents, antioxidants, and pigments.
11
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A wide variety of synthetic rubbers are used including styrene budadiene
rubber (SBR), polybutadiene, butyl, polyisoprene, and ethylene-propylene
diene rubber (EPDM). Of the three categories of compounding materials
used, the fillers, extenders and reinforcers are the most important.
These are used:
1. To dilute the raw crumb rubber in order to produce a
greater weight or volume.
2. To increase the strength, hardness, and abrasion resistance to
the final product.
Of these, carbon black and oil are the most common. A typical
rubber compound might be described as follows (1):
100 parts rubber
50 parts fillers, extenders, and reinforcers
3.5 parts curing and accelerator agents
8.0 parts antioxidants and pigments
The typical tire manufacturing process consists of the following:
1. Preparation or compounding of the raw materials.
2. Transformation of these compounded materials into the five tire
components.
3. The building, molding, and curing of the final product.
A flow diagram for the typical plant is shown in Figure 1.
The basic machinery units used in the compounding operation are the
Banbury mixer and the roller mill. A Banbury mixer is a batch-type in-
ternal mixing device and is the hub of this compounding operation. The
Banbury is used for two operations. In the first, the tillers,
extenders and reinforcing agents, and the pigments and anticxidant
agents are added and mixed into the raw rubber stock. The resulting
mixture is known as non-productive or non-reactive rubber stock.
Because no curing agents have been added, this material will have a long
shelf life, thus allowing large quantities of a particular recipe to be
made and stored for later use. In the second operation, the curing and
accelerator agents, in additon to a small quantity of the original list
of elements, are added. This mixture, known as productive or reactive
rubber stock, now meets the particular compounding requirements of its
final destination. Since it contains the curing agents, this mixture
has a short shelf life and will be used almost immediately.
Carbon black and oil are added to the rubber in the compounding
operation. To avoid many of the housekeeping problems created by both
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carbon black and oil, these ingredients are added automatically. Carbon
black is a finely divided amorphous material that has the consistency of
dust and is easily airborne. The compounding area is equipped with air
pollution equipment to control this problem. Bag house particulate
collectors are normally used which can produce removal efficiences of
essentially 100 percent when designed, maintained, and operated
correctly.
After mixing, the compound is sheeted out in a roller mill, extruded
into sheets, or pelletized. The process depends on the type or batch
(reactive or non-reactive) and the manufacturer. Pelletizing of a non-
reactive batch enables the weighing and mixing of the reactive stock to
be done automatically. The reactive compounded rubber is always sheeted
out.
The sheeted material is tacky and must be coated with a soapstone solu-
tion. This solution is a slurry which, when allowed to dry on the
sheeted materials, prevents them from sticking together during storage.
Because it is a slurry the soapstone solution is usually recirculated.
Releasing the material into a waste water stream would create a
difficult solids problem. Spills in the soapstone area are common and
do create a maintenance and waste water problem.
If a manufacturer wishes to exclude soapstone in his final effluent, he
must provide a method for coping with these spills. Current techniques
include the blocking of all drains in the area, diking of the area, and
the use of steel grates on the floors. The diking and sealing ot drains
prevents the slurry from entering the drainage system. The use of steel
grates helps decrease the risk of workers slipping on spilled soapstone.
Maintenance and housekeeping problems in this area are turther compli-
cated by the leakages of oil and water from the oil seals in the mills,
and oil and dust from the dust ring seals of the Banburys. Eacn has the
potential to become a waste water pollutant if allowed to mix with the
cooling water discharges or to be washed down and discnarged without
treatment.
The rubber stock once compounded and mixed must be molded or transformed
into the form of one of the final parts of the tire. This consists of
several parallel processes by which the sheeted rubber and otner raw
materials, such as cord and fabric, are made into the following basic
tire components: tire beads, tire treads, tire cords, and tire belt
(fabric) . Tire beads are coated wires inserted in the pneumatic tire at
the point where the tire meets the steel wheel rim (on which it is
mounted) ; they insure a seal between the rim and the tire (2). The tire
treads are the part of the tire that meets the road surface; their
design and composition depend on the use of the tire. Tire cords are
woven synthetic fabrics (rayon, nylon, polyester) impregnated with
rubber; they are the body of the tire and supply it with most of its
15
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strength. Tire belts stabilize the tires and prevent the lateral
scrubbing or wiping action that causes tread wear.
In the formation of tire treads, the rubber stock as it is received from
the compounding section is manually fed to a warm-up roller mill. Here
the rubber is heated and further mixed. Heat is provided by the con-
version of mechanical energy. Temperature control is provided by the
use of cooling water within the rolls of the mill.
The heated stock passes from the warm-up mill to a strip-feed mill where
it receives its final mixing. This mill is also cooled to control the
temperature of the stock. The stock is peeled off the rollers of the
mill in a thin strip which is fed continuously to an extruder. The mix-
ing of the stock in these mills insures that the final tread will have
homogeneous properties. The heating or temperature control of the stock
is necessary to insure a proper extrusion with a minimum consumption of
power (2) .
At the extruder, two types of rubber stocks originating from two differ-
ent strip mills are joined together to form the tire tread and
sidewalls. The tread leaves the extruder as a continuous strip while
still hot and therefore tacky. Next a cushioning layer is attached to
the under side of the tread. The tread is then cut to the proper width,
cooled in a water trough, labeled, and then cut to the proper length.
Trimmings are either manually or automatically transferred back to the
proper strip-feed mill and reprocessed. The ends are coated with rubber
cement and the tread is then placed in a "tread book" and senr to the
tire building machines.
Wastewater problems in this area arise from the spillage of the solvent
base cements, from oil and water leakages from the various mills, and
from accidental overflows from the cooling water system. The cooling
water overflow would not normally be a problem since the rubber tread is
relatively inert and therefore does not contaminate the water. However,
it does serve as a washdown agent for an area contaminated with the ce-
ments and oils.
To produce tire cords and belts, rubber stock must be impregnated onto a
pretreated fabric. The fabric is let off a roll, spliced onto the tail
of the previous roll (either adhesively or by a high-speed sewing
machine), and fed under controlled tension (via a festooner) to a latex
dip tank. After dipping and while still under tension, tne fabric is
fed past vacuum suction lines or rotating beater bars to remove the
excess dip before the fabric rises through a drying and baking oven.
After pretreatment, and still under tension, the fabric is passed
through a calendering machine where rubber is impregnated into the
fabric. The rubber fabric is next cooled by large water or refrigerant
cooled drums; after cooling, the tension can be released. This treated
fabric is still not ready for the tire building operation. To achieve
16
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the proper bias it must be cut to the proper angle and length, and then
spliced together again. The angle and length will var> depending on the
size of the tire for which it is used and whether it is a cord or belt.
Once spliced, the fabric is rolled in cloth and sent to the tire
building.
The rubber used to impregnate the fabric proceeds througn an operation
similar to that of the tread process. It passes through both a warm-up
mill and a strip-feed mill prior to impregnation onto the fabric.
Wastewater problems in this area arise due to the latex dripping
operation and to problems with oil and water leaks and spillages which
are similar to those of the tread process.
Many tire manufacturers are transferring their latex dip operations from
individual plants to one large central facility. In most cases, the
reasons behind such a decision are as follows:
1. A minimal dipping operation requires a large capital
expenditure.
2. The fabric dipping and coating operation is one of the fastest
operations in the plant and, as such, is readily capable of
over-supplying the plant with fabric.
3. Dipped fabric is not that more expensive to ship then undipped
fabric.
4. The maintenance and housekeeping requirements of the dip oper-
ation are limited to one facility.
In the processing of rubber stock to tire beads, the rubber is extruded
onto a series of copper-plated steel wires, which are then cemented,
wrapped, and cut. The rubber stock is pretreated, as before, in a warm-
up mill and strip-feed mill. Excess rubber is trimmed from the bead
before it leaves the extruder and is fed back to the strip feed mills.
To apply cement the coated wire is passed through a trough or set of
brushes. The cement is necessary to insure the proper adhesion of the
bead when it is wrapped.
Wastewater problems can arise due to the use of the mills or from the
spillage or overflow of the cement. They will be similar in nature to
those found in this tread formation process.
The inner lining for the tire is formed by calendering or extruding the
rubber stock in a manner similar to either the formation of cord fabric
or tread rubber. It is this inner liner that enables a tire to be tube-
less since it is light and air impervious.
17
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The tire is built up as a cylinder on a collapsible, round rotating
drum. First the inner liner is applied to the drum. Tnen layers of
cord are applied, one layer tying the beads together in one direction
and another layer in the other direction. The beads are attached to the
tire by folding over the ends of the cord fabric. Next the tire belt
fabric is laid onto the cord. Finally the tire tread is placed over the
cords and fabric and wrapped around the beads. The cylinder is removed.
These green tires (uncured tires) are now ready for final processing.
Before molding and curing, the green tire is sprayed with release
agents. These agents aid in the release of air from the tire during
molding and of the tire from the mold after curing. Both water- and
solvent-based sprays are used. Excess spray is released to the
atmosphere. In most plants the tires are placed in a nood during
spraying to reduce atomospheric contamination. Wastewater is generated
by wet scrubbers where used to scrub the excess spray from the air.
The potential for waste water streams exist due to the possibility of
solvent spills within this area. If wet scrubbers are used to scrub the
excess spray from the air, another waste water stream will exist.
The tire is molded and cured in an automatic press. Here an inflatable
rubber bladder bag is inflated inside the tire, causing the tire to take
its characteristic doughnut shape. The mold is simultaneously closed
over the shaped tire. Heat is applied by steam via the mold and bladder
bag. Excess rubber and trapped air escape through weepholes. After a
timed, temperature-controlled cure, the press is cooled, tne bladder is
deflated via a vacuum, and the tire is removed. The tire is next in^
flated with air and left to cool in the atmosphere. This last inflation
insures product quality and uniformity by allowing the tire to "set up"
or achieve the final limits of its cure under controlled conditions.
Because of the large number of presses in the typical plant, there is
always the potential for a mold to leak or for a bladder to break. This
water is released and scavenges some of the large amounts of lubricating
oil used in this area. This oily water creates a water contamination
problem if it is discharged.
After the molding and curing operations, the tire proceeds to the grind-
ing operation where the excess rubber which escaped through the
weepholes is ground off. If the tire is designated to be a whitewall,
additional grinding is performed to remove a black protective strip.
Most tires receive further grinding of the tread in order to balance the
tire.
The weepholes which are ground off are relatively large particles of
rubber which fall to the floor and are swept up. Their final destina-
tion is a landfill. The grindings from the white sidewall operation are
relatively small and will stay airborne for long periods of time. The
industry generally uses a particulate collection device sucn as cyclone
18
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or wet scrubber to control these emissions. The discharge from a wet
scrubber will have a high solids content and will therefore be a waste-
water problem. The balancing operation suffers the same problems as the
white sidewall grinding operation.
After the grinding operations, the whitewall portion of a tire receives
a protective coat of paint. The paint is generally water based. This
operation usually occurs in a hooded area. Again, any wet air pollution
equipment or runoff due to over spraying of the paint will create pol-
lution problems. After inspection and possibly some final repairs, the
tire is ready to be shipped.
Table 2 presents a review of the potential sources of waste water
streams as discussed above.
The discussion thus far has described a typical tire plant, and applies
most readily to the production of the passenger tire. There are several
variations. The first of these is due to the production of truck and
industrial tires. Truck tires tend to have a greater amount of natural
rubber in their treads. Natural rubber, as received in the plant, is
much harder to handle than synthetic rubber. Additional roller mills
are needed to break up and soften the rubber before it enters the
Banbury mixer. There are also major differences in the building and
molding of the tires as the larger sizes are approached. The building
of a "giant off-the-road tire" requires the services of two men each for
a half a day, whereas the passenger tire can be built in less than 5
minutes. Larger tires are cured in giant molds which are not automati-
cally operated. Cranes or hoists are required to open and close these
molds. Curing can take up to 24 hours. Hot water, instead of steam, is
used in the curing operation. The process variations associated with
truck and industrial tire production do not have a significant effect or.
the quantity and quality of the waste waters generated when compared to
those from automobile tire production.
Another variation in the typical tire production is the manufacture of
camelback. Camelback is tread used for tire retreading (2). It is pro-
duced in the same manner as tread used for newer tires. (See flow
diagram, Figure 1.) since camelback production operations are usually
part of a tire production facility feeding off the same machinery, waste
water problems will be similar to those already discussed.
Radial tire production offers another variation to the overall process.
Radial tires, like truck tires, contain more natural rubber, thus re-
quiring more machinery in the compounding area. Whereas bias-ply tires
are built in the form of a hollow cylinder, radial tires are built in
the doughnut shape of the final product. Like truck tires, radial tires
are cured using hot water instead of steam. Again waste water problems
will be very similar to those of the typical passenger tire manufacture.
19
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Inn ermTube__ Manufacture
Inner tube manufacture is very similar to tire manufacture in that the
process consists of the following steps:
1. Preparation or compounding of the raw materials.
2. The extension of these compounded materials to form a tube.
3. The building, molding, and curing to form the final product.
A flow diagram for the typical process is shown in Figure 2.
The basic machinery used in the compounding operation is similar to that
used in tire manufacture; namely, Banbury mixers and roller mills. Both
non-reactive and reactive stocks are prepared. One minor distincrion of
inner tube manufacture is the high usage of butyl rubbers. In addition,
a soap rather than a soapstone solution is sometimes used to coat the
non-reactive stock. The soap solution is not discharged and is used in
a completely closed-loop system with solution make-up. In general,
waste water problems arising from this section are similar to those of
the typical compounding area of a tire plant; that is, leakages and
drippings of oily and particulate material.
The process by which the tube is formed is similar to the extrusion of
the tread. The compounded rubber is fed to an extruder via a warm-up
mill and strip-feed mill. Here the rubber is extruded into a continuous
cylinder. To keep the inside of the tube walls from sticking to each
other, a dry soapstone powder is sprayed inside the tube as it is formed
in the extruder. The tube is labelled and passed through a water
cooling tank. After cooling, the water is blown oif the tube and
soapstone powder is sprayed on the outside of the tube. Excess powder
must be collected in either a dry or wet collection device. if a wet
collection device is used, the discharge will be heavily laden with
solids. Other waste water problems are similar to those found in the
tread formation process of tire manufacture.
Once extruded, the tube must be cut to length and the ends spliced to-
gether. A valve must also te attached. There is no potential waste-
water problem arising from this area of operation.
Once formed, the tube must be molded and cured. Again, this operation
is very similar to that of the tire manufacture. Wastewater problems
include only water leakage and spills.
After curing, the tube is inspected for defects, packaged and sent to
warehousing and shipping. Table 2 summarizes the potential sources of
waste water streams as discussed above.
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Synthetic Rubber Industry
General
The synthetic rubber industry is responsible for the sythesis of vulcan-
izable elastomers by polymerization or co-polymerization processes. For
the purpose of this classification, an elastomer is a rubber-like ma-
terial capable of vulcanization.
The U.S. Synthetic Rubber Industry was fostered by tne commencement of
World War II when it was realized that supplies of natural rubber could
be shut off by the enemy. The rubber first chosen for production was
called GR-S (Government Rubber-Styrene) and would now be grouped under
SBR (styrene-butadiene rubber). Since the war the price of natural
rubber has been subject to great fluctuations, whereas the price
stability of synthetic rubbers has undoubtedly contributed to their
acceptance by the consumer. Since the introduction of GR-S, many new
synthetic rubbers have been synthesized and produced on a commercial
scale.
The demand for the various types of synthetic rubber is greatly affected
by th^ needs of the tire manufacturers. Not only are tire sales impor-
tant, but process and product changes within the tire industry also in-
fluence the relative demands for the various rubbers. For example,
radial tires at present contain considerably more natural rubber than
conventional tires. At this moment, this has little effect on the con-
sumption of synthetic rubber because radial tires constitute a small
percentage of total tire production, but it does illustrate the kind of
factor which can influence synthetic rubber consumption. The U.S. pro-
duction of the principal synthetic rubbers for the last several years is
presented in Table 3 together with the growth projections for the period
between now and 1980. It can be seen that production of SbR-type rubber
overshadows other synthetic rubber. Although the greatest growth rates
over the next several years will be associated with polyisoprene and
-thylene-propylene terpolymer (EPT) productions, overall the relative
levels of synthetic rubber production will not be appreciably different
from what they are today because the present base productions of
polyisoprene and EPT are considerably lower than tnat of SBR, the
principal synthetic rubber (5). This supports the assumption that there
will be no radical changes in the industry, its products, and even its
production processes in the foreseeable future.
The synthetic rubbers as listed under SIC 2822 include botn the socalled
tire rubbers and the specialty rubbers. The tire rubbers are typically
high production volume commodities, and, as their name suggests, they
are used predominantly by the tire industry. Rubber used in the tire
industry is supplied in a solid form termed crumb rubber. Several
different families of tire rubber are made in order to provide all the
essential and varying properties required in a modern venicle tire.
23
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Not all tire rubber production is used in tire manufacture, however.
Much is used to manufacture rubber hose, belting, electrical wire and
cable, footwear, mechanical rubber goods, and many other rubber-based
products. Due to their superior oil and heat resistance, botn nitrile
and neoprene type rubbers are used more for hose, seals, gaskets, and O-
rings than for tire manufacture. However, because their annual
production
volume is comparable with four of the other five major synthetic rubbers
used in tire manufacture, they will be considered here as tire rubbers.
The tire rubbers are grouped into seven families based on their
monomsric ingredients as shown in Table 4. The annual U.S. production,
polymerization process, principal end-use and other family members are
also presented.
By contrast, the speciality rubbers are low production volume
commodities with more diverse compositions and end uses. Tne largest
production volume family of the speciality rubbers are the butadiene
rubbers. Butadiene rubbers are generally sold in latex form. The
production is similar to the production of all synthetic rubber latexes
(2). Epichlorohydrin is solution polymerized with various monomers to
produce the family of epichlorohydrin co-j,olymer rubbers. The process
is similar to that for solution tire rubbers. Epichlorohydrin rubbers
are used for seals, gaskets, and O-rings, etc. (6). The acrylic rubbers
areproduced by an emulsion polymerization process similar tothe emulsion
processes used for the tire rubbers. Acrylics are usea lor high
temperature service in drive=train and axle seals, hose, tubing, and
molded parts. Polyisobutylene is produced by a solution polymerization
process similar to that for butyl rubber (1). It is used primarily as a
blend in caulking compounds, adhesives, and plastics.
Three of the so-called specialty rubber families (silicone rubbers,
urethane rubbers, and fluorocarbon derivative rubbers) are being studied
as part of the plastics industry and, as such, are not covered in this
document. The chlorinated and chlorosulfonated polyethylene rubbers are
manufactured by processes similar to those employed for the polyethylene
type plastics and are not covered in this document (2). The polysulfide
rubbers are produced by a condensation process which is different from
the general emulsion and solution polymerizations (2). In addition, the
waste waters generated by polysulfide production are highly contaminated
and deemed more difficult to treat than the waste waters produced by
conventional emulsion or solution polymerization processes. It is
therefore intended that a separate study will be made of the polysuifide
rubber sector of the synthetic rubber industry.
The various methods of production of the synthetic rubber have much in
common. The monomers are not particularly difficult to handle at
reasonable pressures, and suitable inhibitors have been developed to
impart storage stability. Dissipation of the heat of polymerization is
frequently the controlling consideration. Adjustment of reaction rate
25
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TABLE 4
Families of Synthetic Rubbers Included in SIC 2822, Poiymerization Processes, and Annual U.S. Production (1972)
Principal Synthetic Rubber
T i jre_Rtjbbe£s
Styrene-Butadiene rubbers (SBR)
Polybutad iene rubbers (PBR)
Polyisoprene rubbers
Poly isobutyIene-Isoprene rubbers (Butyl)
Ethylene-Propylene Co-polymer rubbers (EPR)
Acrylonitrile-Butadlene rubbers (Nitrile)1
Polychloroprene rubber (Neoprene)
Tire Rubber Sub-Total: 2,992 Chloroprene rubber
S.pe_cja_l_ty_ .Rubbers
Butadiene rubbers 64 Emulsion Adhesives, dipped goods, Pyridine-Butadiene
paints rubber
Ep ichlorohyd r in rubber
Aery 1ic rubbers
Po1y i sobuty]ene rubbe rs
S 11 icone rubbers
Polyurethane rubbers
Chlorosulfonated Polyethylenes
Annual U.S. Product ion
(1 ,000 Metric Tons/year)
1,678
139
368
139
163
169
159
177
Poiymerizat ion
Process
Emulsion
Solution
Solut ion
Solution
Solution
Solut ion
Emulsion
General tire use
Tire treads
Tire treads
Tire treads
Inner tubes
General tire use, non-tire EPDM
goods
Hose, sea Is, gaskets,
0-rings
use prene rubber, Styrene-
9
2
It
10
lit
1
15
10
129
3,121
Sol ut ion
Emu 1 s i on
Solut ion
Condensat ion
Condensat ion
Emulsion
Pos t -polymer iza-
Condensat ion
Seals, gaskets and 0-rings
Seals , hos ing, tubing
Caulking, adhes ives ,
plastics
Sea Is, gaskets , electri-
cal tape
Sol id ti res, rol lers,
foams , fibers
Seal s , gaskets , 0-ring ,
high temperature service
Wire and cable, shoes,
Seal ing, glazing, hose
Cyclo rubber
Aery late type rubber,
Aery late- Butadiene rubber
Adi prene, Estane , 1 so-
cynate type rubber
Viton, Fluoro rubber
Chlor inated rubber,
Hypalon
Thiol
Specialty Rubber Sub-Total
1 Although Nitrile and Neoprene-type rubbers are not normally termed tire rubbers, they are relatively large production volume rubbers and, for convenience,
can be included with the major tire rubbers.
2 Silicone, Polyurethane and Ftuorocarbon derivative rubbers are considered part of the Plastics and Synthetics Industry and are not covered by this
document.
3 Chlorosulfonated and chlorinated polyethylenes should be considered part of the Plastics and Synthetics Industry. They are not covered by this
document.
k. Polysulfide rubbers are produced by a condensation-type reaction which is not directly comparable to either emulsion or solution polymerization.
Per unit of rubber production, generated wastewaters are of considerably poorer quality and more troublesome to treat than those of either emulsion
or solution or solution processes. Polysulfide rubber production is not covered by this document. It is recommended that a separate study be made
of the polysulfide rubber industry.
Source- "The Rubber Industry Statistical Report" - C.F. Ruebensaal, International Institute of Synthetic Rubber Producers, Inc.
26
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to distribute the heat generation over a reasonable period of time, the
use of refrigeration cooling, and operation in dilute media such as
emulsions or solutions are necessary for the adequate control of
polymerization reactions.
Control of molecular weight and of molecular configuration has become a
very important quality consideration. The ability to control molecular
weight has led to the development of oil-extended rubber. It nas been
found that rubber of unusually high molecular weight and normally TOO
tough to process through factory equipment can be made workable by the
addition of up to 50 parts of petroleum-base oils per 100 parts of
rubber. These extending oils make the rubber easier to process without
sacrifice in physical properties. Another improvement has been the
preparation of black masterbatches, the name given to mixtures of carbon
black and rubber without the curing ingredients. This process is of
great importance to small manufacturers and tire rerreaders who lack
facilities for mixing in carbon tlack or who wish to avoid atmospheric
pollution with the fine black.
gynthetic Rubber Production
Emulsipn__Crumb_Productign
Of the several methods of polymerization employed to produce synthetic
rubber, the two most commonly used processing techniques are
polymerization in homogeneous solution and polymerization in emulsion.
Solution polymerization may be considered to include bulk polymerization
where excess monomer serves as a solvent. Emulsion polymerization may
be considered as the bulk polymerization of droplets of monomers
suspended in water. Emulsion polymerization is performed with
sufficient emulsifier to maintain a stable emulsion. Solution
polymerizations generally proceed by ionic mechanisms. Polymerization
initiators which operate by ionic mechanisms are usually too reactive to
be stable in water, emulsion polymerization systems are initiated by
agents which produce free radicals (2).
Emulsion polymerization is the traditional process for the production of
synthetic rubber. Since World war II (and for the foreseeable future),
the bulk of synthetic rubber has been produced via emulsion
polymerization. The use of emulsion polymerization systems is common
because both high conversion rates and high molecular weights are
possible. In addition, other advantages are: a high rate of transfer
of the heat of polymerization through the aqueous phase, ready removal
of unreacted monomers, and high fluidity even at high concentrations of
polymer. The majority (more than 90 percent) of styrene-butadiene
rubber (SBR), the principal synthetic rubber, is produced by emulsion
polymerization. The emulsion polymerization process is used to produce
either rubber latex or rubber crumb. Crumb is solid and is usually
formed into 75 pound bales.
27
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Figure 3 shows a generalized materials flow diagram lor the continuous
production of crumb SBR by the emulsion polymerization process. This
schematic is essentially typical of all emulsion processes. In the
typical production facility, operation is 24 hours per day, 3b5 aays per
year. Each plant consists of several production lines wnere different
process recipes can be applied and various types of SBR can be produced,
including non-extended, oil extended, and carbon black masterbatch vari-
eties.
Styrene and butadiene (monomers) are either piped to the plant from
adjacent suppliers, or shipped in by tank car or tank truck. Th<=
monomers are stored in a tank farm which is diked to retain major
monomers spills and leakages and, in the case of fire, to control tl<-.
spread of flaming liquid. The fresh monomers are piped to tne plant
from the tank farm and, if necessary, passed through a caustic soda
scrubber before mixing with recycle monomers. Some monomers, such as
butadiene, have inhibitors added to prevent premature polymerization
during shipment and storage. These must be removed oetore the monomer
can be polymerized. The inhibitor is removed in the caustic scrubber by
the circulation of a caustic soda solution, approximately 20 percent.
The caustic soda solution is discarded periodically or can be subjected
to continual make-up and blowdown.
Soap solution, catalyst, activator, and modifier are aauea to the
monomer mixture prior to entering the polymerization reactors. The soap
solution is used to produce an emulsion of the monomers in an aqueous
medium. The principal ingredients of this solution are generally a
rosin acid soap and a fatty acid soap. The catalyst is a free radical
initiator and can be a hydroperoxide or a peroxysulfate. Tne catalyst
initiates and promotes the polymerization reaction. The activator
assists in generating the free radicals more rapidly and at lower
temperatures than by thermal decomposition of the cataxyst alone. The
modifier is an additive which adjusts the chain length and molecular
weight distribution of the rubber product during polymerization. It is
necessary that all the above solutions be made with high quality water.
Usually city or well water is deionized for the preparation of the
solutions.
The polymerization proceeds stepwise through a train of reactors. The
reactor system is capable of producing either " (40-45°F, 0-1b psig) or
"hot" (122°F, 40-60 psig) rubber. The "cold" SBR polymers, produced at
the lower temperature and stopped at 60 percent conversion, have im-
proved properties when compared to "hot" SBR's. The "hot" process is
the older of the two. For "cola" polymerization, the monomer-additive
emulsion is cooled prior to entering the reactors, generally by using an
ammonia refrigerant cooling medium. Depending on the polymerization
temperature, the medium could be chilled brine or chillea water. In ad-
dition, each reactor has its own set of cooling coils, usually contain-
ing ammonia refrigerant, and is agitated by a mixer. The residence time
in each reactor is approximately one hour. Any reactor in the train can
29
-------
be by-passed. The react.or system contributes significantly to the high
degree of flexibility of the overall plant in producing ditterent grades
of rubber. The overall polymerization reaction is ordinarily carried to
no greater than 60 percent conversion of monomer to rubber since the
rate of reaction falls off beyond this point and product quality begins
to deteriorate. The product rubber is formed in the emulsion phase of
the reaction mixture, The reaction mixture is a milky white emulsion
called latex.
Short stop solution is added to the latex leaving the reactors to stop
the polymerization at the desired conversion. Two common short stop
ingredient are sodium dimethyl dithiocarbamate and hydroquinone. The
"stopped" latex is held in blowdown tanks prior to the stripping
operation. The blowdown tanks act as flow regulating holding ranks.
Recovery of the unreacted monomers and their purification is an
essential step in economic synthetic rubber production. Butadiene,
which has a lower boiling point than styrene, is first vacuum stripped
from the latex. The stripping operation is generally carried out in a
vacuum flash tank at about 80-90°F. The butadiene vapors are compressed
and condensed before entering a receiver. A very small quantity of
water collects in the receiver and is discharged periodically. The
condensed butadiene is recycled to the feed area and mixea with fresh
monomer prior to the polymerization step. Styrene recovery from the
latex usually takes place in perforated plate stripping columns. These
operate with steam injection at approximately 140°F. The steam-styrene
vapor mixture is condensed and sent to a receiver where the styrene and
water are decanted. The top styrene layer is recycled to the monomer
feed stage; the bottom layer of the receiver, which is styrene-laden
water, is discharged. Both the vacuum and steam strappers foul
periodically with rubber solids. These must be removed by hand,
followed with both steam or water jets. This cleaning operation puts
the stripper out of commission and produces large quantities of waste
water.
An antioxidant to protect the rubber from attack by oxygen and ozone is
added to the stripped latex in a blend tank. The latex is now
stabilized and, as a result, different batches, recipes, or dilutions
can be mixed. These mixing operations take place in the blend tanks.
The latex is pumped from the blend tank to the coagulation step where
dilute (pH U-4.5) sulfuric acid and sodium chloride solution are added.
The acid brine mixture is called the coagulation liquor and causes the
rubber to precipitate from the latex. Theoretically, precipitation will
occur with a coagulation liquor consisting of any combination of
electrolyte and dilute acid. However, the quality and intended end use
of the rubber limit the choice of coagulants. For example, some types
of "hot" SBR which are used as insulation covering on electrical wire
are coagulated with an acid-polyamine solution in order to produce a
rubber with low electrical conductivity.
30
-------
As mentioned earlier, rubber can be extended to improve its properties
by using oils and carbon black. Carbon black and oil can be added to
rhe latex durinq the coagulation step to produce a more intimate mixture
than can be obtained by the subsequent addition of these materials to
the crumb rubber as is the case with conventional rubber compounding.
Wastewaters generated subsequent to the masterbatch operation (addition
of carbon black) are usually black due to colloidal carbon black
particles. The oil is added as an aqueous emulsion, and carbon Dlack is
blended into the latex as an aqueous slurry (approximately 5 percent by
weight). There are various types of extending oils; some are staining
and others non-staining Rubber extended with non-staining oil will not
mark surfaces and is required for some non-tire uses. It a non-stained
rubber is to be produced, not only must the extender oil be non-
s^aining, but also lighter-colored soaps, short stops, ana antioxidants
must be used.
The coagulated crumb is separated from the coagulation liquor on a
shaker screen. The coagulation liquor is recycled after make-up with
fresh acid and brine and blowdown of part of the diluted liquor. The
screened crumb is resuspend«=d and washed with water in a reslurry tank.
This operation serves to remove extraneous compounds from the rubber,
particularly residual coagulation liquor. The crumb rubber*- slurry is
then dewater-d, generally using a vacuum filter, and the filtrate wash
water is recycled to the reslurry tank for reuse with fresh water makeup
and as an overflow. The overflow is necessary to blowdown accummulating
rubber solids and contaminants. The coagulation liquor blowdown and
crumb slurry water overflows are usually passed through separators.
These facilities, called crumb pits, are generally outside tne process-
ing building and trap the floatable crumb rubber. The clarified under-
flow is discharged to the main treatment facility.
The rinsed and filtered rubber crumb is finally dried witn hot air in a
continuous belt or screen dryer. After drying, the rubber is weighed
and pressed in bales and stored prior to shipment. Normally rubber
bales weigh 75 pounds and are wrapped in polyethylene film. ine balers
are operated hydraulically with oil or water as the hydraulic fluid.
Due to the jarring baling action and the high hydraulic pressures, fluid
leaks are frequent and, in the case of oil-driven balers, the ieajced oil
should be prevented from entering the plant drain system.
In addition to the processing operations described above, other opera-
tions are carried out regularly, though not necessarily continuously,
which generate considerable quantities of waste water. These include
equipment cleanout and area washdown operations. Principal equipment
cleanouts include the polymerization reactors, blowdown tanks, butadiene
flash tanks, styrene stripping columns, and latex blend tanks. In most
cases, high volumes of waste water are produced that are laden with un-
coagulated latex solids and are characterized by a milky white
appearance. When the flash tanks and stripping columns are cleaned, the
waste waters contain rubber solids, due to premature coagulation of the
31
-------
latex, in addition to uncoagulated latex. Area washdowns are frequent,
and the wash waters pick up primarily latex, rubber solids, and oil.
The carbon black slurrying area is generally contaminated with carbon
powder. Area washdowns and stcrm run off typically pick up the carbon,
resulting in a fine carbon suspension.
It is opportune at this point to review the potential waste water
sources in a typical emulsion plant. Table 5 summarizes the principal
wastewaters and the nature or appearance of their constituents.
Solution Crumb Production
As pointed out earlier, solution polymerization is a newer, less tradi-
tional process for the commercial production of crumb rubber in the U.S.
Solution polymerization systems permit the use ot stereospecific
catalysts of the Ziegler-Natta or alkyl-lithium types which have made it
possible to polymerize monomers, such as iscprene or butadiene, in a
suitable organic solvent so as to obtain the cis structure (up to 98
percent) characteristic of tne natural rubber molecule and witn a high
degree of regularity. Rubbers with the cis structure are desired since
they are usually rubbery, whereas the trans-configuration is more rigid
and similar to plastics. Cis-polybutadiene, for example, has nigher
abrasion resistance than the usual SEP type and is being used mainly to
extend and partially replace both SBR and natural rubber in tires.
Reports indicate that tread wear is improved by up to 35 percent in a
50-50 blend of polybutadiene and SBR.
A relative newcomer on the rubber scene is based on the cheap monomers,
ethylene and propylene. Although not stereo-regular, these polymers can
be produced in solution plants and can use similar catalysts. The
polymer chain, based on ethylene and propylene, does not contain
sufficient unsaturation for conventional curing. The incorporation of a
third monomer, usually a diene (thus EPDM - ethylene propylene diene
monomer), adds unsaturation and facilitates conventional curing.
The production of synthetic rubbers by solution polymerization processes
is a stepwise operation, and, in many aspects, is very similar to pro-
duction by emulsion polymerization. There are distinct differences in
the two technologies, however. For solution polymerization, the
monomers must be extremely pure and the solvent (hexane, tor example)
should be completely anhydrous. In contrast to emulsion polymerization,
where the monomer conversion is taken to approximately 60 percent,
solution polymerization systems are polymerized to conversion levels
which are typically in excess of 90 percent. The polymerization
reaction is also more rapid, usually complete in one to two hours.
Figure 4 is a generalized materials flow diagram for the production of
crumb SBR by a solution polymerization process. The processing steps
shown are essentially typical of all solution polymerization processes.
As in the case with emulsion plants, solution plants comprise several
32
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processing lines where different types of rubber for distinct end uses
can be produced (including non-extended, oil-extended, and carbon black
master batch varieties). Plant operation is typically 24 hours per day,
365 days per year.
The fresh monomers are pumped to the plant from the tank farm.
Inhibited monomers are passed through a caustic soda scruboer to remove
the inhibitor. The monomers are then sent to fractionator drying towers
where extraneous water is removed. Fresh and recycled solvent (for
example,
hexane) is also passed through a drying column tc remove water anl ex-
traneous light and heavy components. The light- and heavy-components
build up in the system as unwanted by-products or unreccvered monomer
during the polymerization step and must be removed. Tht purified scl-^
vent and monomers are then blended. The mixture is generally termed the
"mixed feed". The mixed feed can be further dried to remove final
traces of water using a desiccant column.
The dried mixed feed is new ready for the polymerization step and
catalysts can be added to the solution (solvent plus monomers). The
catalyst systems used vary. Typically they are titanium nalide plus
aluminum alkyl combinations or butyllithium compounds. The catalysts
can be added to the mixed feed just prior to the polymerization stage or
to the lead polymerization reactor.
The blend of solution and catalysts is polymerized in a series of re-
actors. The reaction is highly exothermic and heat is removed continu-
ously by either an ammonia refrigerant or by chilled brine or glycol
solutions. The reactors are similar in both design and operation to
those used in emulsion polymerization. The mixture leaves tne reactor
train as a rubber cement, i.e., polymeric rubber solids dissolved in
solvent.
A. short stop solution is added to the cement after tne desired
conversion is reached. The stabilized cement is pumped to cement
storage tanks prior to subsequent processing. At this point other
ingredients, such as antioxidants, can be added. If the rubber is to be
oil extended, oil can be added to the cement. The oil is usually
blended with the cement at some point between the storage tanks and the
steam stripping operation.
The rubber cement is pumped from the storage tank to tne coagulator
where the rubber is precipitated into crumb form with not water under
violent agitation. Wetting agents (surfactants) can be added to promote
the control of crumb size and to prevent reagglomeration. In addition
to coagulation, much of the solvent and unreacted monomer are stripped
overhead. For carbon black masterbatch rubbers, the carbon black slurry
is added to the coagulator in much the same manner as for emulsion crumb
rubber.
35
-------
The resultant crumb slurry passes to a series of strippers where steam
stripping drives off the remaining monomers and solvent. The strippers
are generally a flash tank or agitated kettle strippers. The steam,
solvent, and monomer vapors are condensed and sent to a decant system.
The bottom decant layer, saturated in monomers and solvent, is
discharged. The organic layer is sent to a multi-stage fractionator
(described earlier). Light fractions are removed in the first column
and generally consist of unreacted light monomer (for example,
butadiene). This is normally reclaimed at the monomer supply plant.
The second column produces purified solvent, a heavy monomer-water
fraction, and extraneous heavy components.
The heavy monomer (for example, styrene) is condensed, decanted, and re-
cycled. The bottom water layer is discharged. The purifiea solvent is
dried and reused. The heavy extraneous component stream is a waste
which can either be decanted before disposal or can be incinerated as a
slop oil.
The stripped crumb slurry is separated and further washed with water on
vibrating screens. The slurry rinse water is recycled in part to the
coagulation stage with water or steam makeup. The remaining portion of
the slurry rinse water overflows and is discharged. This water contains
floating crumb rubber fines and is generally passed through a crumb pit
before discharge. The crumb fines are trapped in the pit. The screened
rubber is passed through an extruder-dryer for further dewatering and
drying. Dewatering and drying can also be carried out with a rotary
filter and hot air oven dryer. The dried rubber is pressed into 75-
pound bales and is usually wrapped in polyethylene for shipment.
Balers, identical to those employed in emulsion processing, are used in
solutionpolymerized rubber production. Cil leaks are a potential
problem.
In addition to the processing operations described above, area washdowns
occur. These are frequent and produce large volumes of waste water
which can be contaminated with dissolved organics, floating organics,
oils, and suspended solids. Since the majority of the processing steps
are operated on a strict water-free basis, there is little need for
equipment cleanout operations with water. The processing units which
are kept free of water are cleaned out with solvent when necessary.
This cleaning solvent is stored separately and is used solely for the
cleanout operation. Process pumps, handling in particular the dried
mixed feed prior to and during the polymerization stage, use a non-
aqueous fluid (usually an oil) as a seal in lieu of water to prevent
contamination of the process streams with water. Leaking fluid is a
potential source of oil which can be picked up by area washdown waters.
The carbon black slurrying area is a source of waste waters laden with
carbon fines.
The main waste water sources in a typical solution polymerization plant
are summarized in Table 6.
36
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Latex_Production
In addition to solid crumb rubber, emulsion polymerization is also used
to produce latex rubber. Latex production follows the same processing
steps as emulsion crumb production with the exception of latex
coagulation and crumb rinsing, drying, and baling. Only about 5 to 10
percent of SBR is used as latex, but approximately 30 percent of the
nitrile rubbers (NBR) enter the market as latex. Commercially available
SBR latexes contain about 45- to 55-percent solids, although some can be
as high as 68 percent. Most NBR latexes are in the 45- to 55-percent
solids class. The polymerizations are taken essentially to completion
(about 98 to 99 percent conversion) as opposed to emulsion crumb rubber
production where conversion per polymerization pass is approximately 60
percent.
As a result, the recovery of unused monomer is not economical. Process
economics are directed towards maximum conversion on a once-through
basis.
Figure 5 is a generalized materials flow diagram for the production of
latex SBR by emulsion polymerization. The steps shown are typical of
all latex production processes. Although latex plants are generally
operated 24 hours per day and 365 days per year, the production runs for
each recipe or type of latex are shorter than in emulsion or solution
crumb rubber plants because latex consumption is on a smaller scale and
latex consumers are usually outside companies with varying product
needs. By contrast, the majority of crumb rubber is made for tire
manufacture, is consumed by major tire companies, and is produced by
their own synthetic rubber producing divisions. This has the effect of
limiting the number of types of product and recipe, rationalizing
production schedules, and, in the final analysis, leading to long
production runs. Latexes are used to manufacture dipped gooas, paper
coatings, paints, carpet backing, and many other commodities.
The monomers are piped from the tank farm to the processing plant.
Monomer inhibitors are scrubbed out by using caustic soda solution.
Soap solution, catalysts, and modifiers are added to the monomer to pro-
duce a feed emulsion prior to feeding to the reactors. The water used
in the preparation of the above solutions is generally deionized city or
well water. The number of reactors in the reactor train is usually
smaller than that used for emulsion crumb production. The temperature
is generally kept at approximately 40 to 45»o«F and, therefore, most
latexes are made by the "cold" process. When the polymerization is com-
plete, the latex is sent to a blowdown tank for intermediate storage or
holding. Stabilizers are usually added to the latex at this point to
stop the polymerization and to stabilize the latex.
The latex passes from the blowdown tanks to a vacuum stripper where the
unreacted butadiene is removed. The butadiene is vented to the atmos-
phere. The vacuum is pulled with either a vacuum pump or steam jet.
38
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The excess styrene is stripped from -the latex in a steam stripper. The
steam and styrene are condensed and sent to a receiver. The bottom
water layer is decanred off and discharged. The styrene layer is not
recycled but can be containerized and sent to disposal.
The stripped latex is passed through a series of screen filters to re-
move unwanted large rubber solids. The latex is finally stored in
blending tanks where various additives (for example, antioxiaants) are
mixed with the latex. The latex is shipped from the blending tanks by
tank car or tank truck, or is drummed ready for dispatch.
Since short production runs are common to the industry, the major waste-
waters generated in a synthetic latex plant stem from equipment cleanout
operations. When production is switched from one type 01 rubber t.o an-
other, reactors, blowdown tanks, strippers, and filters require cleaning
for the new product. In addition, tank cars and tank trucks owned or
leased by the plant require cleaning after each trip. Area washdowns
are frequent inside the processing buildings and at the vehicle loading-
unloading areas. All the above waste waters will contain oils,
dissolved organics, and high concentrations of latex solids.
Table 7 summarizes the origins and nature of the principal wastewater
sources generated in a typical synthetic latex plant.
Summary_
The growth of the tire and inner tube industry has been closely linked
to the growth of the automobile industry. Current production is over
210 million tires per year with one quarter of this production destined
for original equipment on new vehicles. The production of both tires
and inner tubes consist of the compounding, extruding, calendering, and
molding of solid raw materials. There is considerable heat generated by
these processes and it must be dissipated and controlled to insure the
quality of the final product. Water used in other than for utilities,
consists of makeup water for soapstone solution and latex dip solutions.
The production capacity and output of the synthetic rubber industry are
expanding steadily and are linked very closely to consumption by the
tire industry. The relative production levels for the various types of
synthetic rubber will not change significantly over the next several
years to affect the operations or waste water impact of the industry as
a whole. Two distinct processing technologies (emulsion and solution)
exist. Process variations within each of these two technologies are
only minor. Two different types of rubber product are manufactured:
crumb and latex rubbers. The so-called specialty rubbers are
manufactured by processes similar to those used to produce the so-called
40
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tire rubbers and are in similar product forms, i.e., solid and latex
rubbers.
42
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SECTION IV
INDUSTRY CATEGORIZATION
Introduction
Industry categories and subcategories were established so as to define
those- sectors of the rubber industry where separate effluent limitations
and standards should apply. In the final analysis, the underlying dis-
tinctions between the various categories and subcategories have been
based on the waste water generated, its quantity, characteristics, and
applicability of control and treatment. The factors considered in
determining whether such categorizations are justified we.re "rhp
following:
1. Manufacturing Process.
2. Product.
3. Paw Materials.
4. Plant Size.
5. Plant Age.
6. Plant Location.
7. Air Pollution Control Equipment.
8. Nature of Wastes Generated.
9. Treatability of Wastewaters.
As indicated in Section III, there are inherent differences between trie
tire and inner tube sector, and the synthetic rubber sector of th^
rubber industry; therefore, the two have been separated to produce th^_-
tvo principal industry categorizations.
T ir. e_ a n d_ I n n e r _T ub e_ Industry
Manufacturing, Process
The process steps by which tires are made are similar tnrougnout the
industry. Although there are variations due to equipment manufacturer
and automation, these differences do not lead to significant variations
in the volume or constituents of process waters.
Product
Examination of existing plants indicates that the end product is not a
reasonable basis for categorization. Manufacturing steps for all tire
production are similar; inner tube manufacture, altnough different in
some respects, generates the same type of process waste water streams as
does the tire production. The characteristics of the waste stream and
the potential treatment technologies are not significantly different.
43
-------
Radial tire manufacture is different in the building, molding, and
curing operations; however, these differences do not significantly
impact on waste water quantity or quality. In addition, radial tires
are generally produced in the same plants as bias tires.
Raw Materials
Since the basic raw materials for the entire industry are rubber, carbon
black and oil, categorization based on raw material usage is not rea-
sonable. The quantities and form of the different raw materials re-
ceived varies, but these do not significantly affect the control or
treatment technologies applicable to the industry. The handling of raw
materials, particularly the carbon black, also varies within the indus-
try. However, this again does not affect the process waste waters or
their treatability.
Plant Size
A listing of most plants currently operating and their production rates
is given in Table 8. The distribution of-these is presented in Figure
6. From inspection of existing and plant visit data, it was learned
that plant size has not significant effect on the quality or
treatability of waste waters. Process effluent quantities varied signi-
ficantly but was not directly related to plant size. The only signifi-
cance of size is the cost of treatment of waste water streams, which, of
course, is related to other factors.
Plant^Age
The aqe of plants currently in operation will fall into three basic
categories depending on the expansion period in which the plant was
built. The oldest plant in operation is an innet tube facility built in
1888.
As constructed, production facilities built during the first two expan-
sion periods tend to be multi-storied, with process lines located on
many floors and confined to small areas. In addition, plants ±rom the
first expansion period most probably have undergone modifications in
order to update their machine processing technology (for example, the
installation of internal mixers). Most likely this would further con-
gest the processing area. Much of the equipment in these older plants
is old and of designs that have since been updated to reduce maintenance
and operational costs. Process, nonprocess, and domestic wastewater
sewers exist as a combined sewer, thus making process contaminants
difficult to locate or treat once thy reach the drainage system. Engi-
neering diagrams of sewers within the plant are dated and possibly non-
existent. Drains that do exist were located for ease of washdown of
contaminants, thus making their position inappropriate by current think-
ing and standards.
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Fhr newer planrs of the last expansion period have the benerit c± modern
H=siqn criteria and updated thinkinq in both the sanitaiy and
nrdintf.nance engineering fields. Buildings are single-story ana contain
more ?r-°a per process line. Equipment and area locations have been
designed for a cleaner, more maintenance-free operation. Sewers are no
longer combined, thus making process sever waste waters easier to locate
ani trecit. Drains are not located in areas where contaminants can gain
-d.sy r-iiT ranee.
py f-h-- above reasoning, the process waste water streams trom older
plant? should be larger in volume and should contain nigher loadings of
noth oily and solid materials. Control and treatment should ct ruor-
Jitficult. Fxamination of plant waste water streams trom all these
ar-r-^s b=ars this out.
TV- years between 1950 and 1960 are the transition period between the
s-.cond and third expansion period. Plants constructed in the early
IQbO's wer° built during the Korean War and will most likely have the
same protlems as those built in the foorld War 11 era. Few (if any)
plarts were built after the Korean War until 1959, when tne curren*
r. xpunsion b^gan. The year 1959, therefore, is the demarcation poinr
between old and new facilities.
Plan^__Lgcat ion
Prom inspection and waste water sampling of plants located in three
qeoaraphical areas of the- country and from analysis or existing data,
plant location will have no effect on the quality or quantity of the
process waste water streams. These geographical areas included the
Routh, the Far West, and the northern Midwest. Geographical location
has a significant effect on the supply of water; therefore, management
of nonprocess streams such as cooling water and steam varied £rom region
to region. Recirculation of cooling water is very common in tne Far
W<=st (where water supplies are short) , whereas it is less common in
other sections of the country. Reduction of nonprocess waste waters by
recycle increases the treatability of process waste waters wnen combined
with nonprocess waste waters in an end-of-pipe treatment facility.
Treatability of process waste water streams, however, is more
effectively carried out before combination with nonprocess streams. In
addition, geography does not limit the use of recirculated water to the
Far West. Plants in other parts of the country are also using recycle,
though not necessarily for the same reasons.
Plants visited also respresented both rural and urban areas. Plant lo-
cated in urban areas tended to occupy and own less land, thus increasing
treatment cost where available open land is a consideration. However,
bo-'-h the location and the characteristics and quantity of tne water to
be treated are better related to the age of the plant. Urban plants are
older facilities, whereas rural plants tend to be newer. Tnerefore,
location is not a reasonable basis for categorization.
47
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Air Pollutipn_C'ontrol Equipment
The type of air pollution equipment employed by a facility can nave a
great effect on the characteristics and treatability of tne process
waste water streams. The use of dry equipment or the recycling of dis-
charges from wet equipment was observed in all areas of tne plant, which
are currently served by such devices. Therefore, since company policy
(rather than r.he situation to be controlled) dictates the type 01 equip-
m°nt used, air pollution equipment does not form a suitable basis for
categorization.
Nature of Wastes Generated
From evaluation of all available data, the type of wastes generated by
all facilities in the tire and inner tube industry are similar. The
addition or subtraction of the latex dipping of fabric from tae process
line can affect the characteristics of the process waste waters.
However, as supported by existing data, this discharge is nor large and
can be easily contained. Therefore, it does not necessarily atiect the
treatability of process waste waters and does not form a basis for
categorization.
Treatability of Wastewaters
The treatment technologies employed by companies throughout tne industry
are similar. Wastewater constituents are also very similar: mainly oil
and solids. Treatability is more a factor of age than ot tne specific
pollutant and, therefore, dees not form a basis for categorization.
Summary
Only the age of the production facility forms a rational basis for
categorization. As indicated, tire manufacturing facilities built in
earlier periods, although using similar manufacturing techniques, have
greater waste water problems than do new plants built in recent times.
On this basis, there should be two separate categories: old plants, and
newer plants. Plants built prior to 1959 are considered old; those
built during and after 1959 are considered new. inner tuiae facilities,
although producing a different product, incur the same difficulties as
do the older plants and should be included in the "old" category.
Camelback operation, a small segment of the industry, should also be
included in the "old" or "new" categorization of tire plants depending
on the tire facility of which it is a part. If located by itself, the
camelback should meet standards according to the date of its construc-
tion. Compounding operations, another small segment of the industry,
should fall into the category of the plants with which they coexist. If
located by itself in a separate location, the compounding facility
should meet standards of "old" or "new" tire plants depending on its
original date of operation.
48
-------
\s a consequence, only two categories are indicated for ^IC code 3011,
namely "old" and "new" tire facilities. The demarcation date between
the categories is the year 1959.
Synthetic Pubber Industry
Manufacturing Process
As described in Section III of this document, there are two t/asic pro-
cessing techniques in common use in the industry to produce synthetic
rubber: emulsion polymerization processing and solution polymerization
processinct.
Emulsion polymBrization as a commercial process dates bacK to World War
IT. No significant changes have been made in the basic process since
the first emulsion polymerization plants were built. Emulsion polymeri-
zation processing is used, however, to make both emulsion crumb and
latex rubber. From both operational and waste water points oi view,
crumb and latex production techniques should be considerea separately.
Solution polymerization production facilities are dil£er=nt from emul-
sion plants from both process and waste water points of view ana have
been considered as a separate sufccategory. Differences among solution
rubber production plants are minor. All solution plants consist of feed
preparation, polymerization, solvent and monomer recovery, coagulation,
and rubber finishing operations. The operations that have tae greatest
was to wat^r impact in solution plants are those operations wriich are
mo fit- similar plant to plant.
It was therefore concludeu that there are essentially three
manufacturing process variations which merit separate subcategories:
emulsion polymerization to crumb rubber; solution polymerization to
crumb rubber; and emulsion polymerization to latex.
Product
There are two principal product subcategories in the syntnetic rubber
industry, crumb and latex product.
Within the crumb subcat^gory there are several product variations which
involved the type of rubber (styrene-butadiene, or polybutadiene, etc.)
and whether the rubber is extended or not. The two principal products
made by emulsion polymerization are SEP and nitrile rubber. The process
operations for the two rubbers are identical, and the same or similar
^quipmf-nt is used. Several types of rubber are produced by solution
polymerization processes; in many cases similar solvents and monomers
ar^ used, equivalent processing operations are carried out, and
identical processing equipment is used.
49
-------
The processing variations involved in the manufacture of either oil-
extended or carbon-black-extended rubber are minor. In addition, the
oil and carbon black are very effectively tied up with tne rubber, thus
reducing the potential for waste water impact.
Th-^ effects that the various types of latex rubber (for example, SBR and
NBR) have on the production operations and waste waters are minor. The
same equipment and processes are used for all types.
As pointed out in Section III, the specialty rubbers are essentially
similar to the tire rubbers from a processing point o£ view, and no
separate categorization is deemed necessary.
It has been concluded that only two principal product subcategories are
required tc adequately define the synthetic rubber industry. Tney are
crumb and latex rubber.
Paw_Mater_ials
The monomeric raw materials used to produce the various types of syn-
thetic have similar properties. They are usually unsaturatea hydrocar-
bons with extremely low solubility in water. Chloroprene, a chlorinated
hydrocarbon used to ir.ak^ neoprene rubber, is also insoluble in water.
In addition to low solubility, most of the monomers used nave high
volatility and, consequently, a monomer floating on waste water soon
evaporates. Most solvents used also have low solubility and high
volatility and do not remain in a waste water. The catalysts,
modifiers, antioxidants, etc. used in polymerizations are generally
similar and are used in such low concentrations that their effect on
waste water is minimal. Their presence is generally unaetectable in the
waste waters.
In conclusion, there is no need for a subcategorization based on the raw
materials used.
Plant_Size
Most emulsion and solution crumb rubber plants consist o± several par-
allel and integral processing lines. Each of these lines tends to be of
similar size. The waste waters generated by a plant, therefore, are
normally directly proportional to the production capacity.
Small production facilities (for example, latex plants), will bear a
somewhat higher treatment cost than larger plants. However, these
plants are generally part of a larger synthetic rubber or organic
chemical complex, and the treatment cost can be shared. In any case,
latex plants are considered as a separate subcategory.
For these reasons, sub-categorizaticn according to plant size is not
necessary.
50
-------
Plant
Many emulsion plants (crumb and latex rubber) were ouilt during or
shortly after World War II. Few have been built since. In addition,
technoloay has not changed appreciably since that time.
Solution plants are gen-rally newer, but all have been built in the last
1? yt-ars. The technology has not changed radically during that time
period.
!* har been concluded that plant age is not a significant ractor for
rate subca4- egorization.
Plan+_Locati_on
Most ot tne larger synthetic rubber plants are located in one geographic
regior. (Pef^r to Figure 6.) This fact is closely connected to the
availability of the mcnontcric raw materials. The location ot the plants
Ice? not influence the processing operation. However, geographic
locati )r. car. influence the performance of aeratea lagoons and
stabilization ponds. comparable secondary waste water treatment alter-
native?, ?uch as activated sludge, do exist, but the perrormance is not
depend-- P.* en Geographic location. It is not necessary to subcategorize
*:he syn -* tit ic rubber industry by plant location.
Generally, air pollution control devices are not required by trie indus-
try. odor problems do ^xist at some plants, hut these axe controlled by
devic-.-s wnich are either dry or which do not impact on the wastewaters
of th- plant.
Air oollution control is not a subject for subcategori^ation of the
syn^h-tic rubb-r industry.
ria^ur^_of _wastes_Genf:rat.ed
Thc differences in the characteristics of waste waters generated by
production ot non-extended, oil-extended, and carDOn-Diack-ext ended
emulsion crumb rubber were not discernible. Similarly, tne waste water
characteristics produced by non-extended, oil-extended, ana carbonblack-
extended solution crumb plants were essentially identical; however,
waste waters from emulsion crumb, solution crumb, and latex rubber
production facilities were significantly different to warrant
subca^egoriza+iion.
These facts indicate the separate subcategories are required only for
emulsion crumb, solution crumb, and latex rubber production.
Treat a_bility_of_Wastewaters
51
-------
Since the waste waters generated by emulsion crumb and latex production
require chemical coagulation prior to primary clarification wnereas the
waste waters produced by solution crumb plants do not, there is a dif-
ference in the treatability of synthetic rubber wastes. In addition,
the COD and BOD loading from latex plants is considerably higher than
from emulsion and solution crumb plants, and requires more extensive
treatment.
It was concluded that, based on the treatability of the waste waters,
three subcategories were required: emulsion crumb, solution crumb, and
lat<=x rubber production.
Summary
For the purpose of establishing effluent limitations guidelines arid
standards, the synthetic rubber industry should be separated into thr^0-
subcatfqories which are based on distinct processing and product dif-
ferences. These subcategories are:
1. Emulsion crumb rubber.
2. Solution crumb rubber.
3. Latex rubber.
52
-------
SECTION V
WASTE CHARACTERIZATION
Tirg and Inney Tube Industry
A general process flow diagram for a typical tire production facility is
presented in Fiqure 1. Figure 2 presents a typical inner tube
production process diagram.
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solid loadings in process waste water can increase due to spills,
leakage, and soapstone discharge. Loadings for old plants rend to be
higher than those for new plants. This is due in part to the use of
older water treatment techniques and the larger volumes of process waste
water containing solids discharged by older facilities.
The quantity of dissolved solids discharged is related to the amount of
recirculated nonprocess water and the water supply source. Plants using
well water typically have higher dissolved solid loadings, than those
using municipal or river water sources.
Table 9 also shows that the plant1s final end product has no significant
effect upon the raw waste loading in the final effluent. Data from
Plant H, which produces primarily truck and industrial tires, is not
substantially very different from Plants E, F, or G, which, while pro-
ducing a combination of products, produce mainly passenger tires. Load-
ings from Plant I are similar to the others, even though this plant's
primary product is the manufacture of inner tubes.
To substantiate the data and conclusions on total final effluent, Corps
of Engineers water discharge permit applications were obtained for a
large segment of the tire and inner tube industry. Comparison or Corps
permits for plants considered old and new revealed that the aoove find-
ings and conclusions are substantially correct. Table 10 lists the main
characteristics and the loadings corresponding to a typical old and
typical newer tire production facility.
Raw waste loads in the process waste waters leaving the production
facility are presented in Table 11. Flow rates are estimates only,
mainly du<= to the intermittent nature of the waste discnarges. Although
there appears to be no significant difference in the measured flow rates
as shown by data, the composition of the flows originating from old and
new plants differs greatly. New Plant A uses large amounts of washdown
water which comprises the bulk of their process waste waters. New Plant
B process waste waters consist largely of discharges from an extensive
wet air pollution train. The discharges from this equipment are the
primary constituent of the process waste waters. The process waste
water flow rates leaving older plants are due to other factors such as
spills, leakage, runoff from storage areas and inherent plant practices
of older facilities. Therefore the data indicate that, given the same
housekeeping policies and the same degree of wet air pollution equipment
and controls, the process waste water flow rates from older plants will
be higher than from newer plants.
Two important characteristics of the process waste waters are suspended
solids and oil. The suspended solids are generally higher from older
plants due to greater maintenance and poorer housekeeping and control
practices. The same can be said for the oil. Suspended soilias evolve
from the powdered substances used in the compounding area and from the
collection of particulates by wet air pollution control equipment. The
55
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oil is primarily lubrication and hydraulic oils from in-plant sources,
and extender and fuel oil from run-off in storage areas. Both
parameters can be treated successfully. Plant B is using a
sedimentation lagoon to settle solids collected in the compounding area
from wet air pollution equipment. It has been demonstrated by Plants A
and E that solids collected in other areas can be separated easily by
conventional equipment. American Petroleum Institute (API) type
separators are being used to treat oily waste effluents of Plants B, D,
and E.
Synthetic^Rubber_Industry
General
Wastewater characterization data was obtained from literature, EPA docu-
ments, and company records. Plant visits (refer to Section VII) were
made to selected plants to confirm existing data and fill the data gaps.
Figures 3, 4, and 5 are generalized flow diagrams of emulsion crumb,
solution crumb, and latex production facilities, respectively; they
indicate the location of water supply and waste water generation.
Data on total effluent flow and characteristics include utility waste-
waters. It is virtually impossible to determine meaningfully total
plant effluent flows and characteristics exclusive of utility wastes.
It should be noted here that utility waste waters are amenable to
treatment by the existing treatment facilities in use and commonly
practiced by the industry.
Emulsion Crumb Rubber^Subcategory
Flow Analysis
Table 12 lists the total effluent flows for plants producing various
emulsion crumb rubber products based on a. unit of production. This data
was obtained by plant visits. Although three plants were sampled, six
cases of emulsion crumb production were studied. The waste water con-
tributions of other facilities included solution crumb production and
non-rubber commodities.
It can be seen from Table 12 that, for similar products, separate plants
appear to have different effluent flows. However, different products at
the same plant seemingly produce identical waste water flows. This is
due to the following distinct facts:
1. The water use practices in one plant for different emulsion
crumb products are based on one technology, namely that of the
company's process design and engineering.
58
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2. The inability of the sampling team to discern small differences
in effluent flows for different products at the same plant.
It can also be noted that there is no significant trend in waste water
generation rate between the various types of emulsion crumb rubber pro-
duct (non-extended, "hot", oil extended, and carbon black extended).
The average effluent flow rate for emulsion crumb is 16,600 L/kkg (2000
gal/1000 Ib) of production.
Raw Waste Loads
Table 12 also summarized the raw waste loads for the six cases. It can
be seen that the parameter with the highest concentration is COD. The
BOD values are generally much lower. The high COD to BOD ratio is in-
dicative of the high resistance of many of the constituents in the
wastewaters to biological oxidation.
The raw suspended solids concentration in the emulsion crumb waste
waters were determined after separation of the rubber fines in the crumb
pits. Since all emulsion crumb plants have separation pits, this raw
waste load data is applicable to the industry. Much of the suspended
solids contribution is due to uncoagulated latex solids. The
concentration of oil does not appear to be related to the degree to
which the crumb rubber is oil extended. The oil analysis cited is
really "carbon tetrachloride extractables" and will also include
insoluble monomers.
Another significant parameter in emulsion crumb waste waters is total
dissolved solids. This is due to the use of salt in the crumb
coagulation process and associated rinse over flows.
Surfactants are another characteristic produced by the emulsifying
agents. The level of surfactants in the waste water is considerably
lower than the parameters reported in Table 13.
Individual_Waste Streams
Table 13 presents the major constituent loadings of the principal waste-
water streams in an emulsion crumb plant. The most significant
parameter is total dissolved solids which is produced by the acid and
brine coagulation liquors. The coagulation liquor and crumb rinse
overflows, along with the utility wastes, provide the bulk of the total
dissolved solids in the plant effluent. It can be seen that the
quantity of surfactants produced are much lower than the other
parameters. Surfactants are generated in appreciable quantities only by
waste streams included in Table 12. The suspended solids are much
higher than in the total effluent since the crumb pits remove much of
the suspended solids in the crumb rinse overflow. Removals better than
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95 percent are common. Oil entrained in the rubber is also removed
along with rubber crumb solids.
When comparing the sub-total parameter values of Table 13 with the
average total effluent loads of Table 12, it can be seen that the three
streams listed in Table 13 are the major contributors to the total
effluent.
The spent caustic scrub solution is an extremely low flow rate waste
water which has very high COD, alkalinity, pH, and color
characteristics. It is not, however, a significant waste stream when
combined in the total effluent. It is usually bled-in at low flow rates
into the effluent.
Area washdown and equipment clean-out waste waters are highly loaded
with COD and suspended solids, and, by nature, are intermittent in flow.
They cannot be characterized because they are generated on an irregular
basis and have greatly variable concentration loadings.
Chromium and zinc are present in low concentrations (0.1 mg/L) in the
final effluent. They are present due to cooling water treatment, and in
some cases can be eliminated or reduced by substitution of chromium^free
corrosion inhibitors. Heavy metals from catalysts and other reaction
ingredients are not present in measurable concentrations in emulsion
plant waste water effluents.
Solution Crumb Rubber Subcateggry
Flow Analysis
Table 14 presents the total effluent waste water flows for facilities
producing various solution crumb rubber products. The flow data is
given in terms of liters per metric ton (kkg) of production. Five
plants were visited and eight types of solution crumb product were
sampled. Some plants are multi-product facilities, and the
contributions of the solution crumb facilities were accounted for.
Table 14 shows that there is no discernible difference in the effluent
flows between types of product. There appears to be more correlation
between products at the same plant site. This is similar to the
findings for emulsion crumb rubber production.
One plant (Plant M) has a considerably lower effluent flow than all the
other facilities. The apparent reason for this difference is the use of
a special rubber-finishing process which generates very little or no
waste water.
The average effluent flow for solution plants is similar to emulsion
plants, and typically approximates 16,600 L/kkg (2000 gal/1000 Ib) of
production.
62
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Raw_ Waste Loads
Table 14 also presents the raw waste loads for the four main parameters.
It can be seen that the constituent levels are approximately one half of
those present in emulsion crumb waste waters. This supports literature
and company data which indicate that the solution production processes
are "cleaner" than their emulsion counterparts. The main factor behind
this is the absence of coagulation liquor and uncoagulated latex. The
COD to BOD ratio is high which indicates that a consideraole proportion
of the raw waste water components are not readily biologically
oxidizable.
The total dissolved solids content of solution crumb waste water is con-
siderably lower than for emulsion crumb plants. This again is mainly
due to the absence of the coagulation liquor.
Surfactant concentrations in the total plant effluent are low.
Surfactants are used to de-agglomerate the crumb rubber during
coagulation and rinsing.
The solvent recovery systems do not produce any significant effect on
the COD or BOD content of the effluent.
One plant (Plant M) has considerably lower loadings than the others.
This is probably due to the fact that rubber for non-tire use is
produced at this plant. This rubber is used to manufacture impact-
res istant resins, and its quality and production controls are extremely
critical. In addition, special finishing equipment appears to be used.
Individual_Waste_Streams
The crumb rinse overflow produced at a solution crumb plant is similar
to that produced at an emulsion crumb plant, with the exception that un-
coagulated latex is not present. The suspended solids, mostly crumb
rubber fines, are similar to those in emulsion crumb rinse overflows;
the crumb pits produce the same reductions.
The monomer and solvent recovery wastes are comparable to the monomer
recovery wastes from emulsion plants. Although heavy slops are produced
in some plants, these are usually disposed of by drumming or
incineration. Since monomer purities must be high, recovered butadiene,
for example, is returned to the monomer supply plant and has no impact
on the solution crumb rubber waste water.
Equipment clean-out waste waters are less of an environmental problem in
a solution plant because much of the processing equipment must be kept
dry or water free. Area washdowns are similar in volume, but do not
contain latex. These washdowns do pick-up rubber solids and oil from
pumps and machinery areas.
64
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The spent caustic scrub solution, where used, is identical to that used
in emulsion crumb production. In plants where emulsion and solution
crumb rubber is produced, the same caustic scrub system is used for both
facilities.
Catalysts and other reaction ingredients do not produce discernible
quantities of heavy metals or toxic constituents. chromium and zinc in
cooling tower blowdown are present in some plant effluents, but in
concentrations of 0.1 mg/L or less in the final effluent. These can be
eliminated or reduced by using cheromiurn-free corrosion inhibitors.
Latex Pubber Subcategory
Flow Analysis
Table 15 lists the total effluent flows for latex rubber plants. Only
tvo plants are presented, but the similarity between the data values is
good. Latex plants are generally part of larger complexes, and flow
data for latex operations is difficult to obtain. The rlow from latex
plants appears to be lower than from either emulsion crumb or solution
crumb facilities. The major flow contributions at latex plants
originate with equipment cleaning, area washdown operations, and waters
from vacuum pump seal systems.
Raw_Waste_Loads
The raw waste loads of latex plant waste waters are considerably higher
than either emulsion or solution crumb plants. Equipment cleanout and
area washdowns are frequent due to smaller produce runs, and
considerable quantities of uncoagulated latex are contained in these
waste waters. The high COD to BOD ratio is typical of all synthetic
rubber subcategories and underlines the resistance to biological
oxidation of the waste water constituents. Oil concentration is lower
than in emulsion or solution crumb facilities and is contributed by
separable monomers, such as styrene, in the wastes. The suspended
solids in the effluent are due mainly to uncoagulated latex. Total
dissolved solid levels are lower than for emulsion plants because of
coagulation liquor stream. Surfactants are present, but in much lower
concentrations than the other parameters.
Individual_Was_te_Streams
Tank, reactor, and filter cleaning produces considerable quantities of
waste water. These are characterized by high COD, BOD, and suspended
solids. In addition, unloading and product loading areas and general
plant areas are frequently washed down. The characteristics of these
wastes are similar to those produced by usual equipment cleaning in this
industry. Vacuum pump seal waters contain small quantities of organics
which produce moderate levels of COD from the vacuum stripping
operation. The stripping condensates contain condensed monomers. Most
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of these monomers are decanted from the water and re-used. The water
layer overflow from the decanter has high COD and BOD concentrations.
Spent caustic scrub solution is an extremely low flow waste and has
similar characteristics to spent solutions produced in emulsion crumb
and solution crumb plants.
67
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SECTION VI
SELECTION OF POLLUTION PARAMETERS
Tire and Inner Tube Industry
From review of the Army Corps of Engineers Permit Applications for
direct discharge of waste waters from tire and inner tube production
facilities and examination of related published data, it appears that
the following constituents are present in measurable quantities in the
waste water effluents from tire and inner tube production facilities:
BOD
COD
Suspended Solids
Total Dissolved Solids
Oil and Grease
PH
Temperature (Heat)
Chromium
Examination of in-plant and anlytical data obtained during the on-site
inspections of a number of production facilities indicates that certain
parameters are present only in insignificant amounts or are contributed
by discharges unrelated to the process facilities. These nonprocess
effluents result mainly from utility and water treatment discharges and
from domestic waste water discharges generated within the plant bounda-
ries. Such nonprocess-related discharges are the subject ol other
studies and are covered by other EPA documents.
In the following part of this section, the rationale for elimination or
selection of the aforementioned parameters is discussed and recommen-
dations proposed.
BOD
Biochemical oxygen demand (BOD) refers to the amount of oxygen required
to stabilize biodegradable organic matter under aerobic conditions. BOD
concentrations measured in waste waters discharged by tire and inner
tube production facilities are very low. Their presence is due primar-
ily to the organics used in the soapstone and latex dipping solutions.
Concentration values range from less than 1 mg/L to 30 mg/L for process
waste waters at the plants visited; most of the values ootainea in the
course of these visits were less than 5 mg/L. Consequently, this
parameter was considered insignificant in this segment of the rubber
industry. Higher concentration values of BOD in the effluents did
result when domestic wastes were combined with the process and
nonprocess waters and also after combining certain chemical boiler water
treatment discharges.
69
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COD
Chemical oxygen demand (COD) provides a measure of the equivalent oxygen
required to chemically oxidize the organic/inorganic material present in
a waste water sample. COD in tire and inner tube process waste waters
is attributable to principally washdown and runoff from oil
contaminated, soapstone and latex dip areas. In addition intermittent
discharges of spent soapstone and latex solutions contribute to the COD
of the process waste waters. COD levels generally range from 5 mg/L to
30 mg/L. Accordingly it is not necessary to subject tire and inner tube
plant process effluents to COD limitations.
Suspended Solids
Suspended solids after discharge to a water course can settle to the
bottom and blanket spawning grounds, interfere with fish propagation, an
may exert an appreciable oxygen demand on the body of water. Suspended
solids (SS) in tire and tube plant waste waters are due to washdown and
runoff from compounding areas, discharges of soapstone solution, and
boiler blowdowns and water treatment wastes. In the normal daily
production operation, 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/L (with proper in-plant controls) to over 20,000 mg/L
during soapstone solution dumping and discharge.
Total Dissolved_Solids
High concentrations of dissolved solids (TDS) originate from the non-
process 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 rather than city water.
Oi1_and_Gre ase
Oil and Grease (carbon tetrachloride extractables) is a measure of the
insoluble hydrocarbons and free-floating and emulsufied oil in a waste-
water sample. Oil and grease are critical to waste water treatment and
stream ecology because they interfere with oxygen transfer. 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 extender oil from storage areas. Concentration values in
the total effluent range from less than 5 mg/L to 83 mg/L. Concen-
trations in the total plant effluent are not indicative of the oil and
grease problem because of dilution by nonprocess waste waters. Loadings
in the plants visited ranged from less than 1 kg/kkg to 5.47 kg/kkg of
raw material. Since oily wastes result from intermittent flows,
instantaneous values could be much higher at times.
70
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Control and adjustment of pH in the process waste waters generated in
+he tire and inner tube segment 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.
Elevated temperatures in total plant effluents occur only when collected
steam condensate (utility waste) is not recycled but is discharged into
the plant effluent. Excessive temperatives are not encountered in
process waste waters. Consequently, a temperature limitation for
process waste waters is not considered necessary. Although temperature
is a potential problem for direct discharge, it appears to be
insignificant in the total plant effluent when controlling and treating
process waste waters.
Chromium
Heavy metals such as chromium are toxic to micro-organisms because of
their ability to tie up the proteins in the key enzyme systems of the
micro-organism. Chromium appears in the nonprocess discharges mainly
from the cooling tower blowdown. Chromium compounds are used as a
corrosion inhibitor and added to the tower basin or cooling tower make-
up. Chromium and other heavy metals will normally not be a problem to
the process waste water effluent.
Summary of Significant Pollutants
Of the pollutants examined, only, suspended solids, oil and grease, and
pH are significant characteristics when considering process waste water
discharges. All three parameters, suspended solids, and oil and grease,
and pH need to be controlled, treated, and monitored. The recommended
list of control parameters for tire and inner tube plants, therefore, is
as follows:
Suspended Solids
Oil and Grease
PH
Synthetic: Rubber Industry
In view of the fact that similar processing techniques and similar
catalysts and monomeric raw materials are used in emulsion crumb rubber,
solution crumb rubber, and latex rubber production, it is appropriate to
consider the same waste water parameters for the three synthetic rubber
subcategories .
71
-------
Review of the published literature, EPA documents, industry records and
the findings of the plant visits indicated that the following chemical,
physical and biological constituents are pollutants (as defined in the
Federal Water Pollution Control Act Amendments of 1972) found in
measurable quantities from synthetic rubber plant waste water effluents:
COD
BOD
Suspended Solids
Total Dissolved Solids
Oil and Grease
pH
Acidity/Alkalinity
Surfactants
Color
Temperature (Heat)
These parameters are present in the raw waste streams of all synthetic
rubber plants. Pollutants in utility and service water systems and in
water treatment system regenerations and backwashes are outside the
scope of this document and will be the subject of a separate study and
at a future date.
COD
Since numerous organic compounds contact process waste waters, COD will
occur in the plant effluent. Values range from 9.3 kg/kkg(lb/1000 Ib)
of production for solution crumb. to 34.95 kg/kkg(lb/1000 Ib) of
production for latex rubber.
Treatment techniques reduce this contaminant, but high residual levels
still exist in the treated effluent. This is indicative of the fact
that some waste water constituents have high biological oxidation
resistance or inorganic oxygen demand.
BOD
For the same reasons as for COD, moderate to high BOD concentrations are
present in synthetic rubber plant waste waters. Values range from 1.13
kg/kkg(lb/1000 Ib) of production for solution crumb to 5.30
kg/kkg(lb/1000 Ib) of production for latex rubber. Typical industry-
wide flow and production data show that this pollutant can be reduced by
biological treatment to reasonably low levels (10 mg/L) .
Suspended_Solids
In emulsion crumb and latex plants, uncoagulated latex contributes to
high suspended solids. These can be removed by chemical coagulation or
air flotation followed by clarification. In both the emulsion crumb and
the solution crumb subcategories, suspended solids are produced by
72
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rubber crumb fines. Gravity separation readily reduces tnese solids.
Suspended solids ranging rom 6,17 kg/kkg(lb/1000 Ib) of production
(latex rubber) to 2.81 kg/kkg (lb/1000 Ib) of production (solution crumb)
are common in the raw waste water.
Tptal^Dissolved^Solids
The coagulation liquor used in emulsion crumb production is a major
contributor of total dissolved solids in emulsion crumb effluents. The
solution crumb and latex subcategories also produce waste water
containing appreciable amounts of total dissolved solids. Because of
the technical risk, excessive costs and dubious benefits involved in the
application of treatments systems for total dissolved solids removal in
this industry, no limitations for total dissolved solids have been set.
Oil and Grease
Insoluble monomers, solvents and extender oils are used r>y two sub-
categories, emulsion and solution crumb rubber. Latex production also
utilizes the same insoluble monomer. In addition, miscellaneous
machinery and hydraulic oils are used. Moreover, genuine oil and
grease, measured by solvent extraction (generally carbon tetrachloride)
analytical methods, are present in the raw waste waters from these
plants. Oil and grease entering the waste water are treated for removal
by chemical coagulation and clarification, air flotation clarification,
gravity settling, and, to some degree, by biological oxidation.
2H
Since neutralization is practiced prior to biological treatment at all
synthetic rubber plant waste water treatment facilities, extreme pH
variations outside the range pH 6.0 to 9.0 are not foreseen.
Acidity/Alkalinity
Acidic coagulation liquors are used and discharged in emulsion crumb
production, and strong caustic soda solutions are bled into plant
effluents where monomer inhibitors are removed. Incidentally, this
latter flow is extremely low and does not constitute a problem.
However, neutralization is carried out in all industry subcategories
prior to biological treatment systems, and, therefore, treated wastes
will have little residual acidity or alkalinity.
Surfactants
Surfactants are used in all the industry sub-cateogries; however, their
concentrations in the raw waste load is very low and is further reduced
after biological treatment. Surfactants are the primary cause of foamy
plant effluents, but it is difficult to relate surfactant effluent con-
centration to visual foaming problems. Therefore, limitations for
73
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surfactants in effluents having foaming problems should be based on
local aesthetic requirements, individual plant location, and stream
quality criteria for the receiving body of water.
Color
Color is objectionable form an aesthetic standpoint and also because it
interferes with the transmission of sunlight into streams, thereby
lessening photosynthetic activity. Some waste streams in synthetic
rubber plants, such as spent caustic scrub discharges and carbon black
rubber rinse waters, have appreciable color. However, after dilution
with the combined plant total effluent and after undergoing biological
treatment, there is no discernible color in synthetic rubber plant ef-
fluents.
Temperature JHeat)
In synthetic rubber plants there are individual waste water streams,
such as condenser flows and crumb slurry overflows, which have high
temperatures. However, after combination with other effluent streams,
equalization and biological treatment, thermal equilibrium with ambient
temperature is approached. Consequently, a temperature parameter for
the final effluent is not considered significant or subject to
limitations.
Summary of Significant Pollutants
Although the pollutants represented by the previously mentioned list of
parameters will occur in synthetic rubber production, only five should
be monitored to insure that pollutant levels are minimized and gross
discharge prevented. These are:
COD
BOD
Suspended Solids
Oil and Grease
pH
74
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SECTION VII
CONTROL AND TREATMENT TECHNOLOGY
Survey of Selected ^Plants
In order to review and fully evaluate the waste water control and treat-
ment technologies used in the rubber processing industry, selected
plants were visited to conduct operation analyses, review water and
waste water management programs, and evaluate waste water treatment
facilities. The plants were selected as being exemplary or advanced in
their waste water control and treatment technologies, based on effluent
and treatment data from the technical literature, EPA documents. Corps
of Engineers Permit to Discharge Applications, and individual company
treatment data.
Plants producing passenger tires (both bias and radial ply) , true*
tires, camelback, and inner tubes were visited and studied to determine
if the type of product affected the quality and quantity o± waste water
streams and/or the control and treatment technology employed. Both
singleproduct and multiproduct plants were included so that the effects
of combined lines on the plant waste waters could be evaluated;
likewise, plants of various sizes were studied to determine the impact
of production levels. Age was a major consideration because
determination of the effect, if any, of newer processing technology and
machinery on the control and treatability of process waste streams, was
one of the principal objectives of the investigative phase of this
project. Table 16 is a summary of the products manufactured, raw
material usage, and wastewater control and treatment technologies
utilized at the tire and inner tube plants visited.
In the synthetic rubber production segment of the industry, the field
visits included plants employing emulsion and solution polymerization
processing methods and involving all types of synthetic ruboer products:
"cold crumb", "hot crumb", non-extended, oil-extended, carbon-black-
extended, and latex rubbers. As in the tire and inner tube segment, the
effects of single- and multi- product lines, plant size, and plant age on
waste water volume and characteristics and related control and treatment
technology were evaluated. A summary of the products, processes,
production capacities, and waste water control and treatment
technologies of the exemplary synthetic rubber plants visited is
presented in Table 17.
Ti r e_a n d_ln n er_Tub e_ Plants
Plant A
75
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This plant, built in 1961 and located in an arid rural community, pro-
duces passenger tires, small-implement tires, and front tractor tires.
Production rate for passenger tires at the time of the visit was 12,000
units per day. In addition to the normal tire processing and production
lines, this plant has a latex fabric-dip operation. Raw material
consumption was over 120,000 kg (264,000 Ibs) per day.
The actual production facility occupies approximately 16 ha (40 ac) of
land. The plant boundaries surround another 140 ha (350 ac) of land
currently devoted to agricultural use.
The only source of raw water supply is well water. It is used for
cooling, steam generation, domestic use, and all other plant needs.
The principal process waste waters from this plant are water and steam
leakages, and wash waters from the cleaning of equipment and general
work areas. Water leakage occurs at various water-cooled machinery
units, including mills, Banburys, tread extruders, and tread-cooling
tanks. In addition, water can escape from the hydraulic water system
used in the Banbury and press areas. Water and steam occur in the
process waste water in the press area as the result of broken seals or
failinq bladder bags. Oil and solid matter which have collected on the
floors are carried along by these various water streams into the area
drainage system. The oil is lubrication oil which has dripped or leaked
from oil seals on mills, pumps and like equipment, from open gears, from
gear boxes, and from the hydraulic water system. Additional oil and
solid materials result from leakage at the Banbury dust and oil rings.
Daily washdowns include steam and solvent cleaning of the tread books
and miscellaneous machinery parts and the cleaning of the latex dip
tank. Weekly cleanups, which occur on the weekends (non-production
days), include washdown of the steel grates in the soapstone area.
This plant was specially laid out and engineered so as to keep spills
and leakages from becoming a problem. Drains are non-existent in the
soapstone area and in many of the mill areas. Removable steel qrates
have been provided in the soapstone dip area so that spilled soapstone
solution will not create a work hazard. Housekeeping practices and
schedules have been set up to keep leaks and spills of lubricating oil
on the floors of the plant to a minimum. When steam and water leakages
do occur, they are directed (along with other process and nonprocess
wastes) to a collection pond. Equipment-cleaning waste waters are also
discharged to this pond.
The principal nonprocess waste waters are boiler and cooling pond
blowdowns. In addition, there is a hot-water-sump overflow. The hot-
water sump is used as a collection point for recycled press cooling
water. Contaminants in these wastes are suspended and dissolved solids.
78
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End-of-pipe treatment at this plant includes pH control and the lagoon-
ing of all effluents, both process and nonprocess. The waste waters,
after pH adjustment, are directed to the 11,000 cubic meter (3 million
gallon) collection and storage pond. The residence time in this pond is
approximately four days. Settling of suspended solids and the reduction
of both COD and oil occur during this period of time. From here, the
waste waters are fed to a second pond. Water leaving the second
retention pond can be used for any of three functions. It can be used
for irrigation on the company-owned farm acreage around the production
facility (its primary function), it can evaporate, or it can percolate
into the sandy ground below the pond. (The water table at this plant is
approximately 76 meters (250 feet) below the surface.)
In addition to containment of all process and nonprocess waste waters,
all storm runoff from within and around the plant confines is directed
to and contained in these lagoons.
Plant_B
This plant, located in a rural area, started operating in 19b4. Plant-
owned ground is now almost entirely utilized by processing and ware-
housing buildings, parking lots, and waste water treatment £acilit.ir-s.
The facility produces passenger tires and heavy off-the-road tires.
Production rates are currently running at 24,000 passenger and 2,000
off-the-road tires per day.
Water for all plant uses, including makeup for the cooling towers,
boiler and various dipping solutions, is supplied by the municipality.
The principal process waste waters from this plant are: water ana steam
leakages, runoff from the process oil storage area, and discharges from
wet air-pollution control equipment.
Water and steam leakages occur in the press room of both the passenger-
tire and truck-tire facilities. These streams become contaminated with
oil scavenged off machinery parts and the floor. Punoft from the oil
storage area is continuous due to the placement of a steam blowdown pipe
nearby; oil is scavenged from the area and becomes entrained with the
condensate waste water stream.
Wet scrubbers are used to control air emissions from the compounding
area and from the green tire painting area. Collectively, these
scrubbers represent the largest single discharge in the plant.
Contaminants include COD and suspended solids, as well as some oil
matter.
Maintenance and housekeeping practices at this plant are directed at
keeping leakage at a minimum and well contained. Kunoff from the
process oil-storage areas is pretreated in a baffled oil separator
79
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chamber before flowing to the end-of-pipe treatment facilities. The
separator unit effectively removes oil from the small volume of water in
the influent.
Water discharged from air pollution equipment passes into the plant's
endof-pipe treatment facility untreated.
The principal nonprocess waste waters are boiler and cooling tower blow-
downs, and water treatment wastes; these are segregated from the process
waste waters and are discharged, without subsequent treatment, into the
storm drainage system.
In addition, there are blowdowns from various presses throughout the
plant; these contain COD, suspended solids, and dissolved solids.
End-of-pipe treatment at this plant involves the use of two lagoons.
The wet scrubbers and steam blowdowns flow into the first lagoon, which
is used to separate settleable solids and separable oil. This pond has
a surface area of 0.21 ha (0.52 ac) and a baffled effluent weir. Wet
scrubbers, and some once-through cooling water flow to the second
lagoon. This has approximately 0.30 ha (0.74 ac) of surface area and is
also used to remove separable solids and oil from the influent.
Plant_C
This production facility consists of two plants, the older of the two
dating from 1945 and the newer one coming on stream witnin the last
decade. The facility is located in an industrialized area on the
fringes of an urban center. Most of the land within the plant
boundaries is occupied by production buildings and by the necessary
auxiliary buildings, waste treatment facilities, and parking areas. The
facility produces only passenger tires (both bias ply and radial). Raw
material consumption is approximately 349,000 kilograms (770,000 pounds)
per day. Exact unit production rates are unknown, although the figure
is known to be well above 20,000 units per day.
The principal process waste waters are water and steam leakages,
overflow from various sumps, and runoff from oil storage areas. Water
leakages occur throughout the plant wherever there is water-cooled
machinery, such as mills and Banburys. Water and steam leakages occur
in the press area due to leaking seals, failing bladder bags, and
leakages in the hydraulic water system. The process waste waters
scavenge oil and solid materials, which flow to the nearest drain. Oil
and solid material accumulate on the floor and in the various machinery
basins due to dripping and leaks from the Banbury dust rings, mill and
pump oil seals, open gears, and the hydrualic water system. Runoff from
oil storage areas occurs during rainstorms and washdowns, and is another
source of oily process waste water.
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This plant at one time had a process waste water discharge of soapstone
solution. After extensive studies showed that this solution caused
excessive BOD and total solids in the waste water, this discharge was
eliminated. The current practice is to recycle this solution.
Wastewater streams resulting from the use of other solutions in the
plant, such as the latex dip, have also been eliminated. These streams
are dumped into a sump, which is periodically emptied into drums and
sent to a landfill site.
The principal nonprocess waste waters are boiler and cooling tower blow-
down, once-through tread cooling water, and water treatment wastes. In
all cases, dissolved solids are a problem, and suspended solids will be
a problem in the water treatment waste and boiler blowdown.
Process waste waters and all the nonprocess waste water (with the
exception of boiler blowdown) are combined and then directed to a
primary treatment facility. This treatment facility consists of two
settling basins, operating in parallel. Each provides 24 nour retention
for the waste streams. Settleable sclids are removed periodically
(approximately every two years), and floating oil is removed by a belt
filter. Boiler blowdown and sanitary wastes are treated in a package
extended aeration sanitary wastewater treatment plant. All treated
waste waters are discharged to the river.
Plant D
This plant, started up in the early 1940's, is located in an urban,
industrialized area. It has recently undergone extensive modifications,
and, therefore, production levels are not well established. However,
past data indicate that the plant is producing 22,000 passenger, truck,
and tractor tires per day. The plant also produces camelbacK. Raw
material consumption is in the neighborhood of 840,000 kilograms (1.85
million pounds) per day.
Raw water is supplied by the municipality and from company-owned deep
wells. The city water is used to supply domestic and air conditioner
cooling needs. The wells supply once-through cooling water, cooling
tower makeup, boiler feed water, and processing solution makeup.
The principal process waste waters from this plant include: water
leakages, steam leakages, a weekly washdown of the soapstone
recirculation system, equipment and floor cleaning washdowns, and minor
runoff from the oil storage area.
Water leakages arise from the oil seals and open gears on mill calendars
and pumps and from the hydraulic water system used in the Banburys and
presses. Steam leakages occur in the press room from broken or leaking
seals and failing bladder bags. Both types of leakage are heavily laden
with oil picked up from the seals and from lubricating oil drippings.
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The soapstone recirculation system is cleaned out once a week, and the
effluent has high BOD and suspended solids loadings. The floors are
cleaned with an automatic sweeper that uses a soapy water solution as a
cleaning agent. Drainage from this sytem also has a high BOD and
suspended solids loadings. Steam cleaning is used for small machinery
parts, and the discharges are significantly contaminated with oil.
Water and steam leaks in the press area are pumped to an oil separator,
where the floating oil is removed an disposed of by an outside
contractor. Water leakages in the mill area are kept at a minimum by
careful housekeeping and maintenance practices, and do not appear to be
a serious problem. Runoff from oil storage areas is collected in sumps,
which are pumped out on an "as required" basis.
Floor-cleaning machinery discharges and steam-cleaning discharges flow
into the sanitary sewer.
The principal nonprocess waste waters are boiler and cooling tower blow-
downs, water treatment wastes, and once-through cooling water. In the
first three cases, dissolved sclids constitute a problem. Boiler
blowdowns and water treatment wastes may also contain high
concentrations of suspended solids, depending on the treatment process
being used. COD and pH may also be problems.
Ther is no end-of-pipe waste water treatment facility which covers the
entire process waste water stream. Some nonprocess waste water and the
weekly dump of the soapstone slurry are directed to a holding basin for
removal of settleable solids before discharge.
Plant_E
This facility which was started up in 1920, is a sprawling complex
occupying 25 major buildings and more than 74 acres of ground. Although
it is located in a very congested urban area, the plant boundaries en-
close approximately 13 acres of open ground.
The plant was originally set up to produce many rubber products, includ-
ing tires, belting, an inner tubes. However, with the passage of time
and because of specialization, production of all rubber products with
the exception of tires has been discontinued. Current production levels
are 10,400 passenger tires per day and 4,400 truck tires per day. Total
raw material consumption is 210,160 kilograms (462,900 pounds) per day.
Production facilities are located in three buildings. The Banburys and
mills of the compounding operation and the presses of the molding and
curing operations are located in separate buildings (Banbury and Press
Buildings). The mills, extruders, calendars, etc. of the tread and bead
formation lines and of the fabric-coating operations are all located in
a large building (Rubber Mill Building) located between the compounding
and curing buildings. The buildings are interconnected so as to
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approximate a continuous production line. Fabric is shipped to this
plant pretreated, and no additional dipping operations are preformed.
The plant has two separate sources of raw water supply: well water and
municipally supplied water. The well water is used primarily for
cooling tower makeup, and the municipal (city) water is used as boiler
makeup, after treatment. The city water is also used in making the
soapstone and other solutions used in tire manufacture.
The principal process waste waters include water and steam leakages,
steam cleaning, and wet air-pollution equipment discharges. Water
leakages arise from water-cooled machinery, such as mills, Banburys,
tread extruders, and tread cooling tanks. In addition, water can escape
from the hydraulic water system used in the Banbury and press areas.
Water and steam leakages occur in the press building due to broken seals
and failing bladder bags. These waste water streams are heavily laden
with oil picked up from the seals and from floor areas and basins.
Machinery parts such as gears and bearings are cleaned with steam, and
the resulting wastes contains both oil and suspended solids. Grinding
operations within the plant are eguipped with wet particulate
collectors. Effluents from these collectors are small in volume but
contain a high concentration of heavy rubber as suspended particules.
Zinc and chromium are used as corrosion inhibitors and will tnerefore be
present in the collector discharge.
Leakages, both steam and water, are collected in two sumps, one located
in the press building and the other in the rubber mill building. These
sumps separate the oil, and the resulting underflow is released to a
sanitary sewer. Sanitary sewers within the plant are connected to the
municipal sanitary sewer system and eventually to the municipal waste-
water treatment plant. Oil from the sump is removed periodically by
maintenance personnel.
Steam cleaning of machinery parts is carried out in a non-congested out-
door area of the plant. Curbing and concrete flooring are used to
direct the waste waters into three small basins connected in series.
The area is supplied with a roof to prevent storm water from diluting
the wash water and upsetting the settling operation. Storm runoff from
this area is directed into the storm-water catch basins. These catch
basins act as gravity separators, allowing the separable suspended
solids to settle out and oil to float to the surface. The effluent from
the basin discharges into the sanitary sewer. Solids and oil are
removed from these basins periodically.
The effluent from the wet particulate collectors flows into a set of
similar settling basins, where most of the solids are settled out. The
effluent then discharges into the sanitary sewer. These basins are
equipped with automatic solids-removal equipment.
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All solids and oil removed from the various treatment facilities are
containerized and disposed of by contract hauler to a landfill.
The principal nonprocess waste waters are boiler and cooling tower blow-
downs, and water treatment wastes. In all cases, dissolved solids are
present in the waste water, generally at high concentrations. Boiler
blowdowns and water treatment wastes also contain high concentrations of
suspended solids. The water makeup for the cooling tower which supplies
cooling water to the press building is treated with a corrosion
inhibitor containing chromium and zinc, and these metals are present in
the blowdowns.
At this plant, there is nc end-of-pipe treatment facility. All contam-
inated process and nonprocess waste waters (with the exception of the
main cooling tower) are discharged to a municipal treatment facility,
Plant_F
This production facility, built in 1928, is located in a minor urban
area, on a large (more than 280 hectacres (700 acres)) plot of ground,
of which the actual production facility occupies only a small
proportion.
Production lines include passenger tires, truck tires, inner tubes,
flaps, bladders, and camelback. The plant, as currently designed, is
divided up into separate product unit buildings for each end product.
Daily production rates are currently running at 40,000 passenger and
truck tires, 36,000 inner tubes, 13,000 bladders and flaps, and 27,000
kilograms (60,000 pounds) of camelback. Daily raw material consumption
is 681,000 kilograms (1.5 million pounds). This plant utilizes river
water for production and utility purposes and city water for domestic
purposes.
The principal process waste waters from this plant include: water and
steam leakages and overflows, runoff from process oil-storage areas,
soapstone solution spillages, and wash downs and runoff from process or
storage areas.
Water leakages occur at various water-colled machinery units, including
mills, Banburys, tread extruders, and tread cooling tanks. In addition,
water can escape from the hydraulic water system used in the Banbury and
press areas. Water and steam leakages occur in the press area due to
broken seals, failing bladder bags, and overflows from the collection
pumps. Oil and solid matter which have collected on the floor are
scavenged by these various water streams and are carried untreated to
the drainage system. Oil on the floor spaces is lubricating oil which
has dripped or leaked from oil seals on mills, pumps, and like
equipment, from open gears, from gear boxes and from the hydraulic water
system. Oil and solid materials result from leakages at the Banbury
dust and oil rings.
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Soapstone solution which has spilled and dripped on the floor is washed
down periodically and enters the drainage system untreated. Typical
contaminants are BOD, suspended solids, and dissolved solids.
Washdown water and storm runoff are allowed to drain through tne process
oil-storage area, where oil is scavenged and carried to the drainage
system. Before discharge to the sewer, this stream is pretreated in a
baffled sump, where oil is separated, removed by a belt filter, and
disposed of at a sanitary landfill. The sump is baffled, but provides
no excess capacity for oil separation during a storm runoff.
The aforementioned process waste waters are mixed with nonprocess waste-
waters in the drainage system. The nonprocess waste waters include
oncethrough river water, boiler blowdown, and a small overflow from the
numerous small pump sumps located throughout the plant,
End-of-pipe treatment facilities consist of a two-stage detention basin.
The primary facilities provide approximately 2,000 square meters for
bottom and surface removal of separable materials. During dry-weather
flow the surface loading is 49,000 L/day/sq m (1,200 gal/day/sq ft)
which is too high for effective treatment of waste water of this
character. It is estimated that the facilities provide little or no
treatment whatsoever during periods of significant runoff. The primary
facilities are followed in series by a pond baffled down the middle to
retain floatable materials. Some additional settleable materials are
also contained, but no facilities are provided for removal of floatable
or settleable materials except on "as required" basis.
The secondary pond provides a theoretical detention time of twelve hours
during dry-weather flow. However, this is significantly reduced by
short circuiting attributable to the location of the inlet and outlet
connections. Surface loading on this pond is adequate for removal of
separable materials during dry-weather flow as well as during storm
weather runoff conditions. However, the surface of the pond is subject
to wind turbulence, which may remix the separated floatable materials.
Plant_G
This production facility, built in 1928 is located in a highly
congested, highly industrialized suburban area. Built and originally
operated by another company, it was bought by the current operator in
the 1930's and converted to tire manufacture. The facility produces
passenger and truck tires. Daily production rates are currently running
at 18,300 passenger tires and 1,150 truck tires. Raw material
consumption is over 246,000 kilograms (541,000 pounds) per day.
The plant occupies approximately 28 hectacres (70 acres) of ground, with
most of the land occupied by production and warehousing buildings.
Because of the industrial development around the plant, there are no
foreseeable plans for expansion at the current facility.
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Well water is the only source of raw water supply to this plant, and is
used for all plant water needs.
The principal process waste waters from this plant are water and steam
leakages, and washdown and runoff from the machine shop area. Water
leakages occur in the press are due tc broken or leaking seals and
failing bladder bags. These process waste waters scavenge oil and solid
materials as they flow to the drains. Oil and solid materials
accumulate on the floor and in various machinery basins due to drippings
and leaks from the Banbury dust rings, mill and pump oil seals, open
gears, and the hydraulic water system. In the machine shope area, steam
used for cleaning of parts and runoff from painting and washdown
operations is allowed to enter the storm drain; these waste waters may
be contaminated with both oil and solid material.
Runoff from the oil-storage is not a problem in this plant, because the
drain in this area has been surrounded by a curb which prevents normal
spills from entering the sewer system. In addition, there is a straw
filter covering the drain inlet. Oil that spills in this area is pumped
into a special storage tank which is periodically emptied; this waste
oil is sent to a landfill site.
Both process and nonprocess waste waters flow to a common sewer, where
they are discharged to the municipal storm sewer. Before leaving the
plant, all waste waters must flow through a shredded plastic filter
which retains floatable oil. This filter is replaced periodically. The
oil trapped behind the filter is also removed periodically.
Plant_H
This facility, built in 1945, is located in highly congested and highly
industrialized area. Essentially all of the plant-owned land is
utilized for production and warehousing facilities, utility systems, and
waste water treatment facilities. Expansion of the current plant would
necessitate the leasing of land from adjacent ladowners.
The facility produces truck tires, industrial and farm tires, giant off-
the-road tires, and various other minor products including bladders and
rubber gaskets for the curing presses.
Current production levels for the major products are 6,850 truck tires
and 2,430 industrial, farm and giant off-the-road tires per day.
Sources of raw water include surface water from a nearby river and muni-
cipally supplied water. Surface water is used as the primary source of
once-through cooling water and for makeup to the cooling tower and other
recirculating water systems. City water is used as for boiler feed
water and also as a backup for the surface water in recirculating water
systems.
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The principal process waste waters are from water and steam leakages
from presses and mills. These leakages occur at the oil seals of mills,
at the hydraulic water system, and at the curing presses. The leakages
scavenge oil and solids spilled in press and mill basins due to open
bearings and lubrication of machinery parts.
The principal nonprocess waste waters are the overflows and blowdowns
from various recirculating water systems, the once-through cooling
water, boiler blowdown, and water treatment wastes, contaminants in
these waste waters include suspended and dissolved solids; these waste
waters also reguire pH adjustment.
Whenever possible, oil that leaks or spills onto the floors or basin
areas is collected. This oil either is drummed and sent to a sanitary
landfill or is filtered and reused. Plant engineers are currently
examining the feasibility of using this oil as a fuel admixture in the
boilers. With the oil on the floor kept at a minimum, less can be
scavenged by water or steam contact. There is however, no treatment at
this plant for the oily wastewaters that do occur; they would be
discharged with either once-through cooling water or the utility waste
waters.
There is no end-of-pipe treatment for the once-througn (non-contact)
cooling water; except for oil picked up due to leakages and spills this
water is uncontaminated, and discharges back to the river. Discharges
from the other utility systems, such as boiler blowdown, cooling tower
blowdown, and water treatment wastes are directed to an effluent basin,
where settleable solids are removed. The surface loading is 600
L/day/sg m (15 gal/day/sq ft) and the theoretical detention time is 24
hours. There is no provision for continuous removal of solids or oil.
Discharges from the effluent basin are directed via a sanitary sewer
system to a municipally operated treatment plant.
Plant_I
This plant, built in the late 19th century, is now involved in the manu-
facture of inner tubes, valves, flaps, and similar items associated with
automobile tire applications. Raw material consumption is approximately
75,000 kilograms (165,000 Ibs) per day. This amounts to an equivalent
of over 50,000 inner tubes per day.
The production facilities occupy a multi-story building in the downtown
area of a major city. There has been no expansion at this plant ror the
last fifty years. Because of the extremely tight land situation and
because of the relatively stable tire-tube market, no expansion is
planned in the foreseeable future.
All the raw water used in this facility is provided by the city.
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Principal process waste waters are water and steam leakages, and the
washdown of dusty areas within the plant. These streams become
contaminated with oil and dust that is scavenged from floor and
machinery areas. These waste waters streams flow into a sewer and are
combined with nonprocess waste waters before discharge from the plant.
Nonprocess waste waters include once-through cooling water, cooling
tower and boiler blowdowns, and water treatment wastes. Suspended
solids will be present in substantial quantities in the blowdowns and
water treatment wastes.
The city sewers are combined sewers; consequently, domestic, process,
and nonprocess waste waters are mixed and 'treated in the municipal waste
water treatment facility.
The housekeeping practices in the plant are unique. Spillages of soap
and soapstone solutions do occur, but the quantities are so slight that
they tend to evaporate on the spot; soapstone solution is neither dumped
nor recirculated. In processing areas, water is not used for washdown.
Dust is such a problem (due to thy use of soapstone in dry form) that
any attempt to use water for washdown merely complicates the problem.
There were no waste water treatment facilities operating at the plant at
the time of the visit. The upgrading of air quality within tne plant
has completely occupied the attention of the engineering stafi, thus
relegating concern for water effluent quality to a secondary position.
Synthetic Rubber Plants
Plant J
Emulsion styrene-butadiene (SBR) and acrylonitrile-butadinee (NBR)
synthetic rubbers are produced at this plant. The annual production
capacity is 390,000 kkg (430,000 tons) of SBR and approximately 10,000
kkg (11,000 tons) of NBR. The plant is located in an industrial area
with land available for expansion.
Both SBR and NBR are produced by emulsion polymerization processes. The
monomers are shipped into the complex from adjacent plants. The SBR
crumb is produced in non-extended, oil-extended, and carbon-black-
extended forms, while the NBR is produced in non-extended form only.
The crumb rubber is used principally as tire rubber. There are sixteen
coagulation and finishing lines in the plant.
The plant's intake water comes from two sources. River water is used
for cooling tower makeup, crumb rubber washing-slurrying, and area
washdown. Plant well water is softened and then used for solution
preparation. The plant does not have its own steam generating plant and
purchases steam from an adjacent facility.
88
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The main process waste waters are generated at monomer recovery, crumb
coagulation, and rubber washing operations. Decant water Irom the
monomer decant system is recycled in part to the crumb slurrying
operation. The remainder, containing styrene and acrylonitrile, is
discharged to the process sewer system and has a significant COD. The
coagulation liquor overflow is a brine-sulfuric acid mixture, with a low
pH, high total dissolved solids, and moderate COD, The crumb slurry
overflow contains COD, crumb rubber particles as suspended solids, and
oil (when oil-extended forms are produced) . The crumb-'laden slurry
overflow and the overflow of coagulation liquor pass through crumb
settling pits where the crumb separates and is removed periodically by a
scoop. The cleaning of the crumb pits results in a temporary upset as
the settled crumb is disturbed and re-suspended. This results in poor
effluent quality from the pits for a short period.
The cleanup wastes from the latex vacuum and steam stripping units are
another process waste water source. This waste water is
characteristically high in COD and suspended solids, and contains
uncoagulated latex. The units are cleaned periodically and large
volumes of water are used in this operation. The resulting waste waters
are passed through settling sumps, where rubber solids settle out.
Clean-out waste waters from reactors and holding tanks are also produced
on an intermittent basis. These waste waters, containing COD and
suspended solids, both as rubber solids and as uncoagulated latex, are
also passed through settling pits. Spent caustic soda scrub solution
used to remove inhibitor from butadiene prior to its polymerization, is
bled into the plant effluent; this waste stream has high COD, pH,
alkalinity and color, and contains some phenols. Its Ifow rate,
however, is very low.
The carbon black storage facilities, consisting of railroad unloading
equipment, a storage hopper, and slurrying equipment, generates a waste-
water which is laden with fine carbon black particles. This waste water
is the result of the washdown and cleanup of carbon clack spills and
air-borne fallout. These waste waters pass through two settling pits,
which operate in parallel. When one pit is full of carbon black waste-
water, the waste water is allowed to settle and the second pit is
filled. The settling pits achieve satisfactory clarification of the
waste water.
The utility waste waters consist of cooling tower blowdown and water
softener regeneration wastes. (There is no boiler blowdown, since the
plant's steam is purchased.) One cooling tower has a very low blowdown
rate, since a high proportion of the tower's makeup is steam condensate.
The other cooling tower has a normal blowdown rate and generates waste
water containing chromium, zinc, and othe/heavy metal ions.
The plant's effluent treatment system consists of chemical coagulation
and primary settling, followed by an aeration lagoon and a settling
89
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lagoon. The primary settling facility and the sludge handling system
are shown in Figure 7. In the chemical coagulation process, the pH of
the influent waste water is first adjusted using sulfuric acid and
caustic soda. Cogulation chemicals (alum and polyelectrolyte) are
added, together with clay. The latex and fine suspended solids
coagulate around the clay, which causes the coagulated solids in the
primary clarifier to sink. The solids from the primary clarifier are
thickened and pressure filtered, using a lime slurry and filter aid.
The filter cake is hauled away by truck to a landfill. The thickener
supernatant is returned to the head end of the plant, and the filtrate
is discharged to the aeration lagoon. The plant effluent quality is
good:
COD 325 mg/L
BOD 25 mg/L
SS 30 mg/L
The high residual COD concentration is typical of the high biological
resistance of the waste water components. The plant currently is
conducting pilot studies to investigate the feasibility of using
activated carbon to reduce the residual COD. The results to date
indicate that a final effluent COD of 130 mg/L could be reached, but the
company concluded that the costs to implement this system would be
prohibitive.
Plant K
The plant complex consists of emulsion and solution stryene-butadiene
rubber (SBR) production facilities. The annual production capacity of
emulsion SBR is 2,000,000 kkg (2,200,000 tons) and of solution SBR is
130,000 kkg (144,000 tons). The complex is located in an industrial
area with virtually no land available for further expansion.
The emulsion crumb rubber is produced in non-extended, oil-extended, and
carbon-black-extended forms. The emulsion rubber processing plant is
arranged into essentially two parallel operations; each operation con-
sists of a solution preparation building, a polymerization area, a coag-
ulation and finishing building, and a monomer recovery complex. The
solution crumb rubber is produced also in non-extended, oil-extended and
carbon-black forms. The solution rubber processing facilities are simi-
larly divided into two parallel units; each unit consists of a polymer-
ization area, a crumb slurrying and finishing building, and a solvent
and monomer recovery complex. The solvent used is hexane.
The plant water supply is from on-site wells. The boiler feed water is
subjected to hot lime softening and normal boiler feed treatment chemi-
cals. The cooling tower makeup is treated with corrosion inhibitors,
anti-sealing agents, and slimicides. The process water used in emulsion
rubber production is zeolite softened. Untreated well water is used for
slurrying, rinsing, and washdown.
90
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The principal emulsion process waste waters are the coagulation liquor
overflow, the crumb rinse overflow, and the monomer recovery streams.
The coagulation liquor is a sulfuric acid-brine mixture with a low pH,
high total dissolved solids, and moderate COD. The crumb rinse overflow
contains floatable crumb rubber as suspended solids. In addition, the
slurry overflows have high total dissolved solids and moderate COD.
The coagulation liquor and crumb slurry overflow pass through settling
pits, where the rubber solids separate. Under normal operation, the
separator pits work well, but they are not cleaned frequently enough,
and short-circuiting occurs. Furthermore, during the cleanout operation
.the pit is distrubed, and the once-separated rubber escapes into the
effluent. Some pits contain an oil layer because baler hydraulic fluid
or extender oil leaks onto the floor and is washed down into the
settling pit.
The waste waters from the monomer recovery area are characterized by
high COD and suspended solids. These waste waters originate at monomer
decant systems and cleanup operations, and contain uncoagulated latex.
The wastewaters from the periodic cleaning of the monomer recovery
stripping columns contain high concentrations of COD arid of latex and
rubber solids. These waters pass through settling sumps to separate the
rubber solids and the floating oils. These pits are also cleaned out
periodically.
The caustic scrub solution is discharged to the final effluent when it
becomes saturated with inhibitor. This waste water is of very low flow
(less than 1 gpm), but has high COD, pH, alkalinity and color. When the
latex storage and the blend tanks are cleaned, the latex-laden rinse
water can be used for latex blending if its solids content is greater
than 2 percent. Tankage rinse waters with rubber solids levels of less
than 2 percent are discharged to the plant effluent. The major
contaminant in this water is uncoagulated latex.
The carbon black slurrying area is equipped with a settling pit which
receives spillages and washdown waste waters. The carbon black settles
out, and the waste water overflows at a very low flow rate into the
final effluent. The settling pit is cleaned out periodically with a
vacuum truck.
The solution rubber process waste waters are very similar to those of
other solution rubber production facilities. The principal streams
originate at the crumb slurrying operation and the solvent-monomer
recovery areas. The crumb slurry overflow has moderate COD, suspended
solids, and total dissolved solids. It passes through a settling sump,
where suspended solids are removed. The waste waters from the solvent
and monomer recovery areas are stripped condensates and decants, and are
characterized by moderate amounts of COD and floating oils.
92
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The utility waste waters are boiler and cooling tower blowdown ana water
treatment wastes. The boiler blowdown has high total dissolved solids
and a high pH. The cooling tower blowdown contains high total dissolved
solids and moderate levels of chromium and zinc from chemical
inhibitors. The spent lime slurry from the hot lime water treatment
system exhibits a high pH and suspended solids level. The lime slurry
settles out in the plant drain and must be mechanically removed at
periodic intervals. The waste from the zeolite softener regeneration is
a concentrated brine solution with high total dissolved solids.
The waste water treatment system consists of air flotation clarification
and biological treatment (refer to Figure 8). The waste water first
passes through a mechanical tar screen which removes large rubber
solids, and is neutralized to pH 7.0 and dosed with coagulant and
flocculant aids in a rapid-mix tank. The waste water then passes
through a flocculator tank and into the primary clarifier, whre a slip-
stream laden with air is released near the bottom of the unit. The
rinsing air bubles carry the suspended solids and oil-type contaminants
to the surface, where they are skimmed off. The clarified effluent
flows into an aerated lagoon, equipped with six aerators, where it is
retained for 24 hours.
Effluent from the aerated lagoon is pumped to the secondary air flota-
tion clarifier, where biological solids are removed. Operations include
rapid mix of coagulation chemicals, flocculation, and clarification.
The primary and secondary sludges are pumped to an on-site sludge lagoon
for dewatering and drying. Studies are being conducted to dispose of
this sludge by off-site landfill or via incineration. The treatment
plant produces a high-quality effluent. Pollution parameters which are
still present at substantail levels after treatment are total dissolved
solids and COD. The residual COD underlines the inherent biological
resistivity of some of the waste water constitutents.
giant L
This plant has SBR, polybutadiene, resin, and oil-additive production
facilities. In addition, there is a rubber compounding facility which
produces sheet rubber as a customer service. The annual production
rates are:
Cold-emulsion SBR
Hot-emulsion SBR
Solution-type polybutadiene
Solution SBR
120,000 metric tons (133,000 tons)
3,700 metric tons (4,100 tons)
52,000 metric tons (58,000 tons)
10,000 metric tons (11,000 tons)
The plant is located in a rural area with land available tor expansion.
Emulsion rubber production started in 1943, solution type polybutadiene
in 1960, and solution type SBR in 1963.
93
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The cold-emulsion type SBR is produced in non-extended, oil-extended,
and carbon-black-extended forms. It is used primarily in tire manu-
facture. This type of emulsion SBR is similar to that produced at the
other plants described in this section. The process for hot-emulsion
SBR is a higher-temperature polymerization and is non-extended; this
product is used primarily for electrical wire covering. The solution
type polybutadiene is produced as non-extended and oil-extended rubbers
and is used primarily in tire manufacture; toluene is the solvent.
Solution SBR is non-extended and has several end uses. The buradiene
used in the plant is received by pipeline from a neighboring plant, and
the styrene is shipped in by tank truck.
The plant's water supply consists of well water. The plant does not
have steam generating facilities but purchases steam from an adjacent
plant. The well water is treated with corrosion inhibitors, slimicides,
and dispersants for cooling tower makeup and is softened to provide
process water for preparation of the emulsion rubber solution.
The process waste waters from emulsion rubber production originate
principally in two areas: crumb slurrying and monomer recovery oper-
ations. These waste waters are typical of emulsion rubber production
facilities. The slurry overflow is passed through a crumb pit to
separate the crumb rubber fines. The monomer strippers are cleaned
periodically. The vacuum stripping vessels and steam stripping columns
are flooded with wash water, and the residual latex and rubber solids
are discharged with the wash water. The units are finally rinsed, pro-
ducing more waste water with additional suspended solids.
Both of the solution type rubbers are produced by similar processes.
The main process waste waters are the crumb slurry overflow and the
solvent-monomer recovery wastes. The slurry overflow is passed through
a pit, where the crumb rubber is separated and periodically removed. As
is the case with all the plants visited, the crumb pits are not cleaned
regularly, and during cleanining the crumb is disturbed and escapes the
pit. The waste waters from the solvent-monomer recovery area are
condensates from monomer decant systems and solvent distillation
condensates. They are characteristically high in COD, BOD, and total
dissolved solids.
The plant's utility waste waters are cooling tower blowdown and zeolite
softener regeneration wastes. The blowdown has high chromium and zinc
concentrations, from the corrosion inhibitor. The softener regeneration
waste is a strong brine solution and therefore has a high total dis-
solved solids concentration.
The plant's waste water treatment facilities consist of settling ponds,
followed by aerated and stabilization lagoons. The plant's final ef-
fluent is treated with alum and polyelectrolyte to obtain proper coagu-
lation of latex solids and fine rubber crumb particles.
95
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The waste water flows through two parallel sets of two settling ponds
each, where the settleable solids and oils separate. The waste water
then flows through two further settling ponds in series. The total
detention time in the six settling ponds is four days. Troublesome oil
is skimmed from the ponds. The waste water then passes to a
mechanically aerated lagoon, which provides approximately three days of
detention. The aerated lagoon effluent passes through two oxidation
ponds, which stabilize the waste waters and settle the biological
solids. The total detention time in the oxidation ponds is
approximately thirteen days.
Although overall treatment provided by the facilities is good, the
effluent quality (BOD particularly) does not meet the State
requirements. It has been established by analyses that the
stabilization ponds are not producing the soluble BOD removals that were
expected, but the cause of the problem has not been determined. There
are indications that the effectiveness of the ponds is dependent on the
water temperature (and, therefore, the time of the year) but this
hypothesis has yet to be confirmed.
Plant_M
The total plant complex consists of a butadiene plant and a
polybutadiene production facility. The butadiene plant started
production in 1957 and the polybutadiene facility in 1961. The
polybutadiene production facility, which uses butadiene as a feed
monomer, has a capacity of 85,000 metric tons per year and is adjacent
to the butadiene facility. The complex is located in a rural area with
good potential for expansion and land acquisition.
The polybutadiene is produced by a solution-type polymerization process
using butadiene as the feed monomer and hexane as the solvent. The
crumb polybutadiene rubber is used principally as a tire rubber. In
addition, a high-grade variety is used as an ingredient in the
manufacture of impact-resistant plastic. The rubber is not oil- or
car bon-black-extended.
The polybutadiene plant has two sources for water supply, well water and
river water. The well water is used primarily for boiler and cooling
tower makeup, while the river water (after clarification, filtration,
and softening) is used in the crumb slurrying operation and for general
plant cleanup.
The principal process waste waters originate in the solvent-monomers
reclaim area and in the crumb slurrying operation. The waste waters
produced in the reclaim area originate from several operations: solvent
recovery, monomer recovery, and feed drying. The major component of
these waste waters is produced by a decant system fed from the solvent
and monomer stripping operation. This waste water is relatively clean,
its only contamination being due to hexane at saturation solubility.
96
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The other waste water streams from the reclaim area have very low flow
and are essentially innocuous with the exception of dissolved hexane.
Impure recovered butadiene monomer is returned to the butadiene
production plant for purification. Heavy slops (oily wastes) produced
in the hexane recovery operation are sent to the butadiene plant for
disposal or are used as a waste fuel. The other major process waste
water, the crumb slurrying overflow, is laden with rubber crumb in the
form of suspended solids. The suspended solids are significantly
reduced by in-plant screening and clarification in a pit.
At least one finishing line recovers the solid rubber product directly
from the rubber cement. No water rinse system is used. The "finishing
machine" takes cement and produces material ready for baling and
packaging. This machine was not seen, and presumably is some type of
extruder for removing solvent. It obviously has a potential for
reducing the effluent flow and leading attributable to the crumb rinse
overflow.
There are two other process-associated waste waters. Spent caustic soda
solution, from scrubbing of butadiene inhibitor (to prevent premature
polymerization during storage and shipping), is batch discharged. This
stream has extremely high COD, pH, alkalinity, and color, and contains,
phenols. The batch discharge is containerized in a pit and bled into
the plant effluent at a very low flow rate. With sucn handling or pre-
treatment, it poses no waste water problem.
The other waste water which should be mentioned results from frequent
area washdowns. This picks up primarily crumb rubber and oils. The
oils originate from leaks in baler hydraulic systems and leaks of pump
seal oil. In solution-type polymerization, water must be eliminated
from much of the process equipment. Oil is used to seal and lubricate
the process pumps. The washdown waste waters contribute tne major
proportions of suspended solids, soluble organics, and oils in the final
effluent.
The principal nonprocess waste waters are boiler and cooling tower
blowdowns and water treatment wastes. The waste water characteristics
of these streams are high total dissolved solids, and moderate COD,
suspended solids, and pH. The cooling tower makeup is treated with a
corrosion inhibitor containing chromium and zinc. These metals appear
in the cooling tower blowdowns.
The total effluent from the butadiene and polybutadiene plants passes
through an oil separator and straw filter before discharge. Since the
quantity and loading of the waste waters from the butadiene plant are
far greater than those from the polybutadiene plant, no meaningful
treatment data could be obtained. The raw waste water flow and loading
of the polybutadiene plant were the lowest of any of the synthetic
rubber plants visited.
97
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It is planned to expand the synthetic rubber plant production facilities
shortly. This expansion will approximately double the existing
synthetic rubber production capacity.
Plant_N,/
The plant complex consists of iosprene, polyolefin resin, polyisoprene,
and polybutadiene production facilities. The complex was completed in
1962. Polyisoprene production capacity is 65,000 metric tons (72,000
tons) per year and the annual production of polybutadiene is 110,000
metric tons (122,000 tons). The complex is located in a rural area with
expansion capability and undeveloped land of its own.
The polyisoprene is produced by solution polymerization with hexane as
the solvent, using isoprene from the neighboring isoprene plant as feed
monomer. Several types of polyisoprene are produced in this facility.
Each type requires a separate production run on common processing
equipment. The crumb rubber is used mainly for tire manufacture and is
not oil or carbon black extended.
There are two polybutadiene lines which employ slightly different
processing techniques. There is no significant difference in the over-
all waste water flows and loadings from these two processes. The
polybutadiene is consumed principally in tire manufacture, and
approximately 50 percent of the polybutadiene is oil extended.
The plant1s water supply is river water. Process and boiler makeup
water receives extensive treatment, consisting of coagulation, clari-
fication, filtration, chlorination, and softening.
The main process waste waters are produced in the monomer-solvent
reclaim area and the crumb slurrying operation. The waste waters
generated in the reclaim area have low flow rates and, with the
exception of saturation with solvent or monomers, are relatively clean.
Part of the recovered isoprene is sent in a slip stream to the isoprene
production plant for purification. This procedure serves to blow down
the accumulated impurities. Impure butadiene recovered from the poly-
butadiene plant is hauled from the plant as a waste. The crumb
slurrying overflows are passed through settling pits where the crumb is
trapped and periodically removed. Surfactants are added to the crumb-
water mix during the coagulation operation to prevent the crumb from
agglomerating into masses which are toe large. These surfactants enter
the crumb slurry overflow.
One type of polyisoprene produces a crumb slurry effluent which has a
considerably higher dissolved organic loading than the other
polyisoprenes or the polybutadiene types. This difference is inherent
in the chemistry of the process and is not a general or widespread
problem in the synthetic rubber industry.
98
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Area wash-down and cleanup is a major contributor of contaminants to the
final effluent. Crumb screens used inside the processing areas are
hosed down to remove coagulated rubber. The resulting waste water has
high suspended solids levels and is passed through the crumb settling
pits. Spent caustic solution from the inhibitor removal system is
containerized and bled into the final effluent. It has the typical
high, COD, pH, alkalinity, and color.
Typical utility waste waters, principally boiler and cooling tower
blowdowns and water treatment wastes, are generated at tnis plant.
Characteristics of these wastes are high total dissolved solids, with
moderate COD, suspended solids, and pK. The cooling tower makeup is
treated with a low chromium corrosion inhibitor. This produces chromium
levels in the cooling tower blowdown that are less than one quarter of
those associated with conventional cooling tower corrosion treatments.
The wa<3te water treatment system consists of an equalization basin
(four-day detention), a neutralization sump, with nutrient addition,
followed by an activated sludge plant (refer to Figure 9) . The waste
activated sludge is first thickened and then pumped to a sludge drying
basin on the plant property. The treatment plant gives very good BOD
effluent levels (10 mg/L), however, the effluent COD level is
considerable (250 mg/L). This is due to the biological stability of
many of the waste water components such as the monomers and solvents,
which, although generally considered insoluble, do have some solubility
in water.
An apparent characteristic of the plant's waste water which can be
attributed to the synthetic rubber production is foaming in tne aeration
basins and in the final outfall. This is apparently caused by excessive
us0 of surfactants by the production personnel in the crumb rinse
operation. Another problem is poor settling of the biological sludge in
the secondary clarifier. Efforts were made to assist settling, and
achieve additional COD removal, by adding activated carbon granules to
the aeration basins upon which biological solids could nucleate. This
did not produce satisfactory results. The current technique wnich is
proving more successful is the addition of coagulation aids to the
clarifier influent. This, however, is proving to be expensive on an
annual-cost basis. A less frequent problem, but more serious, is an
apparent high BOD slug loading, with associated toxicity, tnat
unpredictably occurs in the plant influent. This problem is
uncontrolled at present, but appears to originate with the production of
either the polyolefin resin or one type of polyisoprene.
Piant_O ^
Th^ plant complex consists of polybutadiene, polyisoprene and entylene-
propylene diene terpolymer (EPDM) rubber production facilities. The
commissioning of all the production facilities occurred between 1967 and
1970. The annual production capacities are: polybutadiene 56,000
99
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metric tons (62,000 tons), polyisoprene 50,000 metric tons (55,000
tons), and EPDM 25,000 metric tons (28,000 tons). The plant is located
in a rural areas and has considerable land for expansion. Each of the
three synthetic rubber products has its own production racility and is
produced in a solution polymerization process. Polybutadiene rubber is
carbon black extended. The principal end-use of the crumb rubbers is in
tire manufacture.
The plant's water supply is well water. Well water is treated with
corrosion inhibitors and slimicides for use as cooling rower makeup, and
softened for use as boiler quality water.
Principal process waste waters originate in the crumb slurrying overflow
and presumably in the solvent, monomer, and reclaim areas. Carbon black
added at the coagulation-slurrying stage is essentially trapped in the
crumb rubber matrix. Carbon black spills and leaks pass through a
settling sump and are allowed to overflow into the final effluent. The
settled carbon black is removed by vacuum truck.
Extender oil thar is not entrained in the rubber crumb can contaminate
the slurry overflow waste water. It is understood that screens, with
higher crumb removals than conventional equipment, have been installed
in this plant. The butadiene monomer is inhibited and presumably there
is an associated spent caustic scrub solution discharge. Area washdown
and cleanup is on a shift-by-shift basis. Whenever possible, the
material is cleaned up in such a manner to eliminate wastes trom the
waste water system.
The plant1s utility waste waters are characterized by high levels of
total dissolved solids and moderate pH. The cooling tower blowdown has
high chromium and zinc content originating from the cooling tower
corrosion inhibitors used.
The plant's waste waters are first passed through skimming and settling
basins where the rubber crumb is trapped. The waste crumb rubber is
removed every two to three months by dip bucket. The effluent, from
these pits flows into two 1.2 hectacre (3-acre) lagoons. The process
effluent from the lagoons combines with treated sanitary, storm, and
utility waste waters before entering first a 6.0 hectacre (15-acre)
lagoon and finally a 12.0 hectacre (30-acre) lagoon before discharge to
the receiving waters. The final waste water quality is good. COD, BOD,
and suspended solids are at an approximate level of 50, 5, and 10 mg/L,
respectively. This plant, however, is particularly fortunate in having
considerable land for use as waste water lagoons. it is not possible
for all synthetic plants to have the same or even comparable facilities.
Plant_P
This plant produces styrene-butadiene (SEP.) and acrylonitrile-butadiene
(NBF) latexes. In addition, the plant produces polyvinyl acetate
101
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emulsions and hot melt adhesives. The annual production rates of the
latexes are: styrene-butadiene latex 18,000 metric tons (20,000 tons),
acrylonitrilebutadiene latex 3,000 metric tons (3,300 tons). The plant
is located in a rural area with land available for expansion.
The butadiene latexes manufactured at the plant are made similarly
utilizing equipment trains of a similar nature. The monomers are
shipped into the plant by both tank car and tank truck. Tne latexes
produced are used for carpet backing, dipped goods, and adhesives.
The plant's water comes from on-site wells. The water is treated in a
dual-bed demineralizer to supply bciler quality makeup water and process
water for solution preparation. The coding tower water is treated with
a corrosion inhibitor and algicide.
The principal process waste waters produced in the plant are generated
by equipment cleanout, area washdown, and stripper condensates. Tank
cars and tank trucks are rinsed with water and the contaminated water is
discharged to the waste water treatment facility. These waste waters
will contain monomers and uncoagulated latex. Reactors and strippers
are cleaned of solid deposits with a high pressure warergun and then
water rinsed. Blowdown tanks, filters, compound tanks, and storage
tanks are rinsed with water. In all cases the waste waters discharged
to the waste water treatment facility contain organic compounds and
latex. Latex spills and leakages are first coagulated with alum,
cleaned up in-place, and finally washed down. The washings are sent to
the treatment facility.
Excess monomers are stripped from the latex with steam under vacuum.
The vacuum is produced using steam jets and not vacuum pumps. The
exc3ss styrene, or acrylonitrile, is condensed and discharged to a
receiver. Although the receiver is periodically decanted and the con-
densed styrene or acrylonitrile drummed for disposal, styrene and
acrylonitrile still enter the effluent waste waters. A caustic scrub
solution is used to remove the butadiene inhibitor, which is bled
gradually to the final effluent. Characteristics of this stream are
high COD, pH, alkalinity, and color.
The plant utility waste waters enter the storm sewer system. The boiler
blowdown has a low flow rate but high total dissolved solids.
Demineralizer regeneration wastes are both acidic and alkaline and may
potentially produce pH peaks. The cooling tower blowdown is high in
total dissolved solids but, because the corrosion inhibitors used are
chromium and zinc free, these heavy metals do not appear in the
blowdown. The vacuum pump seal water is currently discharged on a once-
through basis to the storm sewer system. This water picks up small
quantities of organic compounds but has only a moderate COD
concentration. Studies are being made to recycle the bulk of the seal
water and discharge the blowdown only to the treatment facility.
102
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The plant's treatment facility consists of chemical coagulation and
clarification followed by activated sludge secondary treatment. The
final effluent after secondary treatment is discharged to a municipal
treatment plant. All the latex plant process waste waters are
discharged to two coagulation pits. They operate so that one pir is
being filled with waste water, while water in the second pit is being
treated, settled, and emptied. The pH of the waste water is first
adjusted with lime and then treated with ferrous sulphate, a
polyelectrolyte, and limestone. The latex solids coagulate around the
limestone which serves to sink the solids. The settled solias are
removed from the pits periodically when the solids depth becomes
excessive. The clarified waste water "enters four aeration basins
operated in parallel. The basins are equipped with four 15-horsepower
aerators. The aeration basin effluent enters a secondary clarifier and
overflows to a sump from which it is pumped to the city treatment plant.
The clarifier underflow is sent to a sludge thickener, while the
supernatant is returned to the aeration basins. The oiological sludge
in the thickener is periodically removed and landfilled. The
coagulation pit solids and the thickened biological solids are not
suitable for satisfactory landfill because of their high water content.
Studies are currently underway to determine adequate techniques for
dewatering and disposing these sludges. The coagulation pits provide
good quality primary effluent. The COD and BOD of this effluent are
high, however. The secondary treatment plant produces a final effluent
having a COD and BOD of approximately 600 and 50 mg/L respectively. The
high COD:BOD ratio indicates high biological resistance of the waste
water constituents from this latex plant. Although the BOD level (50
mg/L) would not be suitable for direct discharge, it is very amenable to
acceptable discharge to secondary treatment plants.
Plant_2
This plant is responsible for the manufacture of stryene-butadiene
latexes. The annual production rate is approximately 21,000 metric
tons. The plant commenced production in 1952 and is located in an urban
area with limited room for expansion. The plant also has a research
facility and a pilot plant.
The stryene-butadiene family of latexes produced at the plant can be
classified by three groups: stryene-butadiene latex, styrene-butadiene
carboxylated latex, and stryren-butadiene-vinyl pyridine latex. All
these latexes are produced by similar processing techniques and equip-
ment. The monomers used (styrene, butadiene, organic acids, and vinyl
pyridine) are shipped to the plant by tank car and tank truck. The
latexes produced are used for tire fabric coating, backing material, and
paper coatings.
The plant uses city water for process water, boiler makeup water, and
cooling tower makeup. The boiler makeup is softened before injection.
The cooling tower makeup is treated with a dispersant, corrosion
103
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inhibitor, and slimicide. The process water, used for solution
preparation, is deionized before use.
The principal process waste waters generaged in the plant originate from
equipment cleanout, area washdown, and stripper condensates. Excess
monomers are not recovered. Reactors, strippers and storage tanks are
periodically cleaned of rubber build-up by hand and then rinsed with
water. Generally, large quantities of water are used for eacn cleanout.
The latex filters are frequently cleaned. This involves nrst removing
the trapped rubber solids and flushing the filter with water. The rinse
waters contain suspended solids, COD, and uncoagulated latex. Floors
and loading-unloading areas are flushed with water. These wastewaters
contain COD, suspended solids, and uncoagulated latex. The vapors from
steam stripping operations are condensed and discharge into a receiver.
The receiver waters which overflow to the plant sewers have a higft
organic loading with correspondingly high COD and oil levels. The seal
water for the vacuum pump serving the vacuum stripping equipment is
slightly contaminated with organics, and presently discharges on a once-
through basis. Studies are being made to collect individual seal water
discharges and recycle the bulk of them with a controlled blowdown of
contaminated water. This will reduce the total volume in tne plant's
final effluent.
The regeneration waste from the boiler water makeup softener is a
concentrated salt solution and therefore contributes high total
dissolved solids to the effluent. The process water deionizer is
regenerated with sulphuric acid and caustic soda. The discharge of
these solutions will produce both acid and alkali peaks in the effluent,
although there is generally an excess of sulphuric acid in the daily
regeneration discharges. The boiler and cooling tower blowdowns
contribute high total dissolved solids and moderate COD to the plant's
final effluent.
The treatment of the plant's waste waters include equalization, cnemical
coagulation and settling, and secondary treatment in the local munici-
pality's treatment plant. The waste waters are first pumped from the
plant effluent trench into an equalization basin, which provides
approximately 24 hours detention and is aerated with two aerators. The
pH of the equalized waste water is adjusted from normally alkaline by
addition of sulfuric acid to the neutralization sump. The waste waters
are pumped from the sump to a reactor-clarifier where alum, coagulant,
and polyelectrolyte are added in the mixing chamber. The latex and fine
rubber particles are coagulated and collected as a sludge from the
bottom of the clarifier. The clarified effluent overflows the clarifier
to the city's sanitary sewer for secondary treatment. The clarified
sludge is sent to a thickener and finally to a sludge holding tank, and
is then loaded into a tank truck for disposal. The supernatant from the
thickener is returned to the reactor-clarifier. The treatment system
described above produces a good quality primary effluent. COD and BOD
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are reduced by approximately 70 and 50 percent, respectively. The
suspended solids and oil are decreased by 80 and 50 percent, each.
Summary of _ Control._ and^Treatment Technology
In-plant control technology covers segregation and measures for
handling, reuse, modification of processing, and disposal of various
types of waste waters, including spills and leakage, washaowns, control
of runoffs, and housekeeping practices. End-of-pipe treatment
technology covers the treatment of various combinations of process and
nonprocess wastewaters. separate discussions are presented for the Tire
and Inner Tube and the Synthetic Rubber segments of the industry.
Tires_and_Inner_Tubes
In-Plant^Control
In-plant measures included the proper handling of soapstone, of the
latex dip, and of discharges from air pollution equipment.
Soapstone
Soapstone is a slurry normally consisting of clay, an emulsifying agent,
and water. According to one plant representative, soapstone, if
continually discharged, will contribute a high solids and BOD loading to
the process waste waters. The standard method of eliminating a
continuous discharge of large quantities of soapstone is the use of a
closed-loop recirculation system. Such a system needs periodic
cleaning, usually on a weekly basis. This cleaning operation can, but
does not necessarily, lead to a discharge. Prior to cleaning, the
soapstone solution in the system is generally transferred to storage
tanks. The alternative to recirculation is to discharge the solution
directly into the process sewers. Both practices were observed during
the field survey, the first being the better from a waste water control
standpoint. soapstone washwater is potential discharge which is
commonly sent to end-of-pipe treatment. However, it was observed that
this washwater could be stored and used as makeup for the soapstone
solutions for future operations. Alternative methods for controlling
discharges from weekly washdown include the use of substitute solutions
which require the system to be cleaned on aless frequent basis.
Control of minor discharges of soapstone, such as spills and leakage, is
achieved by the use of curbing and by blocking off drains in the dipping
area. In addition, drip pans are provided for stock during the air-
drying operation. Soapstone that is spilled into the curbed area is
periodically vacuumed out and sent to a landfill site. Newer plants are
constructed without drains in this area, thus eliminating the
possibility of soapstone contamination of process waste waters. Instead
of curbing, steel grates are placed en the floor; these can oe removed
when cleaning the area.
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Latex Dip
The most common practice of the larger manufacturers is to eliminate
this operation from the tire facility. Fabric is dipped by a centrally
located facility and then shipped to the tire plant. However, in plants
that still dip fabric, the accepted procedure is to seal off drains in
the immediate area, supply the area with curbing, and drum the waste
solutions for disposal at landfill sites. The alternative is to dump
the waste solutions into process sewers which are destined for end-of-
pipe treatment systems. The amount of waste from this operation is
small, less than 230 liters (60 gals) per day. Drumming of the solution
is therefore preferred, since treatment of "this stream once diluted with
other streams is difficult.
Air^Pollution_Control_Residues
It is not common for manufacturers to use large quantities of wer
particulate-collection systems. In the compounding area, in particular,
bag-houses, rather than wer scrubbers are used. Wet systems are more
common in the tire-finishing area, where they collect the grindings from
the white sidewall grinding machines, balancing machines, and tne tire-
repair area.
Discharges from wet scrubbers contain high loadings of sertleable
solids, which must be removed before final discharge. The solids
collected from the tire-finishing area can be settled our in a small
sump. The particulates are large, and with a properly designed
separator, the clarified water can be, and frequently is completely
reused.
The discharges from wet scrubbers used in the compounding area are much
finer and require longer settling times. Only one plant visited used
wet scrubbers in this area. This plant used a 2,100 sq. meter (0.52-
acre) lagoon to separate the solids from this discharge. Unless
specifically required to meet air pollution ordinances, wet scrubbers in
this area are not recommended.
Additional air pollution equipment can be found in the tire-painting
areas. Stricter air emission standards and OSHA standards are forcing
tighter controls on particulate and solvent emissions from this area.
Consequently, the industry is currently attempting to substitute water-
based paints and sprays for solvent-based materials, but with only
limited success. Wet air pollution equipment in this area was found at
only one plant; there was not waste water discharge, because all the
scrubber water was reused.
Spi 1 1 s_ and^_ L
To control oily waste waters resulting from spills ana leakage, the
common practice is to provide curbing and oil sumps and to seal drains.
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In older plants, the roller mills are located in basins. The blocking
off of drains in these basins as a control measure is nor feasible
because electrical machinery is located in the basins. A broken water
pipe would fill the basin, thus shorting out the machinery. Curbing is
used to keep normal area washdown and periodic leakages and spills from
entering the basin and thus contaminating process waters. In newer
plants, machinery is located on the floor surface. Updated seal designs
prevent the leakage of oil. In many cases, potentially contaminating
areas have no drains, thus eliminating the possibility of oil in these
process waste waters.
In plants where recirculated water is the'primary source for cooling,
'-he process and nonprocess sewers are separate. Oil sumps and API
separators can therefore be provided to treat oily process waste waters.
The separable oil from these devices is removed either periodically by
maintenance peiple or continuously by a belt filter: the continuous
removal is considered the better practice. During periodic removal of
oil, the agitation supplied will result in a large quantity of oil being
released to the effluent, thus reducing the separator's overall average
removal efficiency.
In plants where the primary source of cooling is once-tnrough water,
process and nonprocess sewers are combined. Removal of oil must be
accomplished in an end-of-pipe treatment facility. Dilution by non-
process waste waters directly affects the removal efficiencies of oil in
the end-of^pipe treatment facility.
Washdowns and Maghine Cleaning
Common practice for prevention of process-area washdowns from
contaminating waste waters is the use of dry sweeping equipment. These
include automatic sweepers, brooms, and shovels. Oily spills are
cleaned using solvents and rags, the resulting contaminated material
being drummed and sent to a landfill. Practices employed in nonprocess
areas (such as the boiler house and storage areas) are similar.
Machines and machinery parts are normally cleaned with solvents or
steam. Spent solvents are drummed and sent to a landfill. The use of
steam requires a special area supplied with curbing and an API separator
to remove separable oil and soids. Discharges of untreated oil- and
solid-contaminated steam condensate occur and constitute a significant
source of process waste waters. Although steam cleaning has the
disadvantage of having a discharge that must be treated, it eliminates
the possiblity of a careless operator discharging large quantities of
organic solvents into an untreated process waste water stream.
Molds from the curing presses are normally cleaned by sand- or air-
blastirg equipment. These are dry, and involve no waste water problem.
Runoff
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Runoff from oil-storage areas occurs due to oil spills, storm water, and
various blowdowns which occur in the storage area. Handling practices
vary within the industry. Minimal control involves the diking of all
oil-storage areas to prevent contamination of wastewater by large oil
spillages which can occur during unloading or due to leaking tanks.
These dikes generally are provided with drainage ports to prevent normal
storm water from filling the diked area. This allows minor oil spills,
attributable to operator negligence, to contaminate storm runoff. A
better system involves the diking cf the storage area, the roofing of
storage area to prevent storm runoff contamination, and use of an oil
sump to collect minor spills and leakage. Collected oil is drummed and
sent to a landfill. To prevent oil from unlaoding areas from
contaminating the waste waters, drains are diked and covered with straw
filters. This control technique suffers from the possibility of storm
runoff contamination.
Other treatment schemes include the use of separators to treat oil
storage runoff. The primary emphasis here is to treat runoffs due to
continual water running through the area. The systems generally are not
designed to handle increased loads due to storm runoff.
Solvent storage and maintenance areas are normally confined to build-
ings. To decrease the possibility of contamination due to operator or
maintenance negligence, these areas are not supplied with drains.
End-of-Pipe Treatment
End-of-pipe treatment in this segment of the industry generally involves
the treatment of combined process and nonprocess waste water in a
primary sedimentation basin or lagoon. Once-through, non-contact
cooling water usually is not treated even though the possibility exists
for oil contamination from process waste water. Primary emphasis is on
removal of separable solids from the nonprocess boiler blowdowns and
water treatment wastes and from the process washdown waters (if any)
from the soapstone area.
The most effective system although not generally applicable because of
land requirements, is the use of judicious water mangement techniques to
minimize nonprocess discharges and of holding lagoons to contain all
wastes including process, nonprocess, and storm runoff. Other lagooning
systems used for treatment of all process (including once-through
cooling water) and nonprocess waste waters were observed. Residence
times varied from twelve to twenty-four hours with surface laodings as
high as 12,000 liters/min/sq meter (1,200 gal/min/sq ft). Auxiliary
equipment observed included oil skimmers and sludge handling equipment.
From the standpoint of treating process waste waters, these systems
suffer heavily from dilution, particularly in the treatment of grease or
oily wastes. Dilution by process streams was as high as 75 to 1.
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Dilution by heavy storm runoff was an additional problem at many
locations.
Synthet ic^Rubbe r
In-plant^Control
Since the synthetic rubber industry is highly technological, involving
many proprietary and confidential processing techniques, many potential
in-plant waste water control methods would call for radical changes in
processing or product quality. Such techniques are obviously nor
feasible. However, some potential control methods deserve mention so
that their applicability may be evaluated.
Crumb Pinge_Oyerflow
It was observed that some crumb rubber plants generate crumb rinse
overflows which have a lower loading of rubber fines than other plants.
Generally, however, such losses cannot be reduced witii finer in-plant
screens since they are a function of both the type ana the coagulation
properties of the rubber. One plant did use a proprietary mttnod to
finish the rubber cement in which a water slurry is not used. This
system eliminates the crumb slurry overflow and the contained rubber
fines. It is not necessarily applicable wholesale to crumb rubber
production, but does merit investigation by industry.
Coagulation_Liguor Overflow
Most emulsion crumb rubber processes use an acid and brine coagulation
liquor. One plant, however, coagulates the latex with an acidpolyamine
liquor which reduces the quantity of total dissolved solids discharged
in the coagulation liquor overflow. The use of this type of coagulation
liquor is not always possible, but if employed could significantly
reduce the total dissolved solids in the final effluent.
yacuum_Sy_s1:ems
Several plants are converting vacuum systems from steam jet ejectors to
vacuum pumps for efficiency and waste water reasons. In order to
maximize the waste water benefits derived from the use of vacuum pumps,
the seal water should be recycled. An overflow is generally required
from the seal water recycle system; this overflow is normally slightly
contaminated with oil but has a better quality than the steam jet
condensate.
Caustic^Scrubbers
In some plants, the caustic soda solution used to remove inhibitors from
some monomers (notably butadiene) is replaced batchwise. The spent
caustic soda solution, usually 10-20 percent sodium hydroxide, should
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not be discharged batchwise. It should be containerized and bled into
the total plant effluent, thereby diluting its high pH, alkalinity, COD,
and color contributions.
Carbon Black Sluyrieg
The usual method is to slurry the carbon black for addition to the
rubber with water. One plant visited employs a steam grinding- slurrying
technique which reduces carbon black spillage and consequently washdown
and runoff waste waters laden with black fines; this tecnnique avoids
the need for carbon black settling pits and the associated pit cleaning
costs.
Latex^Spills
Latex spills and leakages occur from time to time in all emulsion crumb
and latex plants. In most cases, the spill is washed to the nearest
plant drain using a water hose. In many cases, this produces
unnecessary washdown water and dilutes the latex so that subsequent
treatment by coagulation is much more difficult. An alternative
technique is to coagulate the latex in situ with alum, for example, and
remove the coagulated rubber solids with scrapers. The volume of
subsequent washdown water required is less and the latex solids in the
washdown water are greatly reduced.
Baler_Oil
As a result of the high hydraulic pressures involved and the continual
jarring action of the balers, oil leaks are frequent. Back-welding the
hydraulic lines, although more expensive as an initial equipment cost,
does significantly reduce the occurrence of baler oil leaks and can
produce appreciable savings in baler oil usage. In addition, plant
floor drains should be sealed and, if necessary, retention curbing
installed to keep leaked oil from leaving the baler area. Balers using
water as the hydraulic fluid are also available and are being used in
some plants; oil leakage with this type of machine is obviously elimi-
nated.
Treatm en t
Emulsion Crximb Plants - grimary_
It is normal practice for crumb rubber producers to recycle part of the
crumb rinse water. The remainder of the crumb rinse water is discharged
in order to blow down accumulating fine rubber solids, dissolved solids
and organics. The rinse water discharge or overflow is clarified before
final treatment in a crumb separation pit. The trapped rubber solids
are removed periodically by scoop. A very common shortcoming of these
separators is that they are operated as single units and are not cleaned
frequently enough. This results in short-circuiting followed by poor
110
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separation. In addition, when the pits are cleaned, the separated
rubber solids are distrubed and rubber solids -that had previously
separated recombine with the pit effluent until the condition of the pit
stabilizes. Dual pits would solve this problem: one pit would stay in
operation while the other was cleaned and allowed to stabilize.
Since waste waters from emulsion crumb plants contain considerable quan-
tities of latex, it is necessary to coagulate the latex in order to
achieve a good quality effluent. Chemical coagulation by itself is
seldom sufficient, because the density of the coagulated rubber is
normally close to that of water. Therefore, it is customary to add a
"sinker" (clay or limestone) to the coagulation mixture to sink the
coagulated rubber and effect the separation. For a small waste water
flow, chemical coagulation using (for example) alum, polyelectrolyte,
and clay in a rapid mix tank can be followed by flocculation in a
flocculator tank. Clarification can then be accomplished in a rectan-
gular clarifier equipped with solids removal equipment. Larger waste
water flows can be treated in a reactor-clarifier with rim overflow and
central sludge draw-off.
The collected sludge can be thickened and dewatered before disposal in a
landfill. Dewatering studies on this type of sludge concluded that a
plate-and-frame pressure filter performed well. The installed filter
was automatically controlled for feed shut-off, filter opening, core
blowout, filter closing, precoating, and feed restoration (refer to
Plant J).
One plant (Plant K) uses chemical coagulation followed by air flotation
for primary clarification (6). Instead of sinking, tne rubber solids
are floated to the clairfier surface with air bubbles and removed by
surface solids removal equipment. This treatment facility is relatively
new and has had start-up troubles, although they have been
satisfactorily resolved. Air flotation in this application produces
primary effluent of good quality.
The collected surface solids are pumped to a sludge impoundment lagoon
where they dry out. The use of this lagoon is limited and a long-term
solids dewatering and disposal technique will have to be found.
Where adequate land is available, rubber solids separation has been
achieved using primary settling ponds. Chemical coagulation of the
solids prior to discharge to the ponds is usually necessary. The
settled and floating solids (since both types are produced) are removed
from the ponds periodically by vacuum truck or scoop.
Emulsion Crumb Plants - Secondary
Biological oxidation of the primary effluent is achieved in aerated
lagoons or in activated sludge plants. Generally, a nutrient must be
added. Both technologies obtain satisfactory oxidation of the dissolved
111
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contaminants; problems can arise in the clarification of the secondary
effluent. Good secondary clarification of effluent from an aerated
lagoon has been obtained with the aforementioned air flotation plant,
which is a dual system with both primary and secondary air flotation
clarif iers.
If sufficient land is available, the effluent from the aerated lagoons
can be clarified and stabilized in stabilization ponds. This type of
facility is temperature dependent, of course, and performs better in
warmer climates.
Clarifiers are commonly used for secondary clarification in activated
sludge plants. They are generally adequate, but cases exist where high
solids carryover is a problem. Secondary clarification can be assisted
with coagulation chemicals in much the same manner as for primary
clarification, but the additional chemical cost is high.
One plant in the industry, in an area where water is in short supply, is
evaluating evaporation to remove waste water contaminants (7) .
Satisfactory operation has not been achieved to date because of
corrosion and fouling of the evaporator tubes. It is proposed that
satisfactory operation can be achieved with the use of more effective
corrosion resistant materials of construction as well as pretreatment to
reduce the quantities of certain organics and sulfides. Efforts to
demonstrate this will be made by EPA-Office of Research and Development
during 1973-1974.
Emulsion Crumb Plants - Advanced
After secondary treatment, emulsion crumb waste waters still contain
high levels of COD. A high COD level appears to be a common charac-
teristic of secondary effluents from emulsion crumb, solution crumb, and
latex plants, and indicates that certain constituents of the waste
waters generated in synthetic rubber plants are refractory to biological
oxidation.
With the exception of the evaporation treatment described above, only
one other study has been made of teritary or advanced treatment of
emulsion crumb rubber waste waters. This was carried out on a pilot
plant scale using activated carbon treatment (refer to the Survey of
Plant J - Section VII) . Approximately 70% of the COD remaining after
secondary treatment was removed by the carbon.
ution^Cr u mb_P 1 a nt s _^_ Primary
Primary clarification of the solution crumb plant waste water is carried
out in crumb pits. These pits are similar in design to those for emul-
sion crumb production facilities. To avoid re- suspending the separated
rubber solids, dual crumb pits should be used.
112
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Other forms of primary treatment are not required for solution crumb
waste waters, since uncoagulated latex is not present and the fine
rubber solids separate readily.
So1ution_Crumb_Plants - Secondary
Secondary treatment technology uses both activated sludge and aerated
lagoon systems. Good BOD removals are achieved, but poor secondary
clarification is a problem in most cases. The reasons for this are not
certain. A high level of COD remains after biological treatment,
indicating that much of the waste water constituents are biologically
refractory.
Solution Crumb Plants - Advanced
Advanced or tertiary treatment technologies have not been used on
secondary effluents from solution crumb plants. It is probable that
activated carbon treatment would give CCD removals similar to those for
emulsion crumb waste water, since the raw waste water constituents (for
example, traces of monomer) are similar for both types of waste water.
Latex,Plants-_?rimary
Since latex plant waste waters con-tain uncoagulated latex solids,
primary clarification is assisted by chemical coagulation. In much the
same manner as for emulsion crumb waste waters, clarification can be
effected in reactor-clarifiers or systems with separate rapid mix,
flocculation, and clarification tanks. Latex waste waters can also be
clarified by air flotation.
Latex Plants - Secondary
Activated sludge plants are used for the secondary treatment ot latex
waste water. High residual COD levels are a problem. These levels are
higher than for either emulsion crumb or solution crumb plants, because
the initial COD loading of the raw was-te water from latex plants is much
higher. It is feasible that aerated lagoons and stabilization ponds
will produce satisfactory oxidation and stabilization of latex waste
waters.
Latex Plants - Advanced
Advanced or tertiary treatment technologies have not been used on latex
waste waters. It is probable that COD removals similar to those
achieved by emulsion plants can be achieved for latex waste water by
using activated carbon columns.
Additional Studies on Activated Carbon Treatment o± Synthetic Rubber
Waste Water
113
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Subsequent to the original draft of this document, additional studies
were performed by the EPA Advanced Waste Treatment Research Laboratory,
Cincinnati, Ohio, on the feasibility of using activated carbon
technology to reduce COD levels in synthetic rubber waste waters (8).
From the results of the studies it was concluded that COD removal is
feasible. With the three types of synthetic rubber waste waters:
emulsion crumb, solution crumb and latex rubber, COD removal with a
maximum carbon dose ranged from 50 to 97%. Estimated cost of COD
removal based on an average removal rate of 10% COD would be $369.00 per
million gallons of waste water treated.
114
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SECTION VIII
COST, ENERGY AND NON-WATEF QUALITY ASPECTS
Tire and Inner Tube Indus-try
Based onCQSts
Two alternative approaches exist for the control and treatment of
process waste waters from both old and -newer tire and inner tube
production plants.
The first approach is to combine process and nonprocess waste waters and
to treat the entire plant effluent. Where land is available, end-ofpipe
treatment is the approach favored by many of the tire manufacturers.
Generally, the reasons supporting this approach are as follows:
1. In older plants, in-plant sewers for process and nonprocess
waste waters are usually combined, thus making combined treat-
ment 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. High suspended solid loadings in
blowdown and water treatment wastes are the major pollutant in
the combined plant effluent from tire facilities.
However, end-of -pipe treatment systems also have several disadvantages:
1. The combined effluent treatment system usually requires one or
two lagoons for settlement and retention. Lagooning of the
wastes requires large land area, which is not readily available
at many plant locations.
2. Because of dilution, the effectiveness of treatment tor oil
removal from process waste water is reduced. In several of the
systems observed, oil passed through untreated (although it was
present in significant quantities) , because its concentration
was below the capabilities of the treatment system employed.
The second approach employed is control and treatment of a segregated
and undiluted process waste water. This approach has been followed in
plants having partially or wholly segregated process and nonprocess
sewers. This would, of course, include any plant using recirculated
cooling water. The main advantages for this treatment scneme over
combined endof-pipe treatment are:
1 . Higher pollutant removal rates.
115
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2. Smaller land area required for treatment facilities.
The primary disadvantage of a segregated system approach is that
separate process and nonprocess sewers are required.
Upon examining these alternatives, control and treatment of segregated
process waste waters was considered to be most applicable to the tire
producing industry. End-of-pipe treatment of combined waste waters is
not feasible for pollution control because of: 1) tne inertectiveness
of such systems in removal of process waste water contaminants; and 2)
the large land requirements. All costs, therefore, are related to the
treatment of a segregated process waste stream.
With proper in-plant control, the process streams consist of readily
separable lubricating and extender oils and settleable solids. Vol-
umetric flow rates for process waste waters are small. Therefore, the
initial treatment applicable from a cost and proven operation basis is
an API-type gravity separator. The performance and efficiency of a
gravity separator can be improved by addition of an absoroent filter.
Effluent quality data for older tire and inner tube and for newer tire
facilities are presented (along with cost data) in Tables 18 and 19.
The treatment technology involves the isolation of wastes with curbing,
the protection of oily areas to prevent storm runoff contamination, and
the separation of settleable solids and oily material from the waste
water.
A more detailed description of recommended facilities is presented in
the tire and inner tube portion of Section IX, and a flow diagram of the
system used as a basis for costing is presented in Figure 10.
Treatment Cost Data
Data from corps of Engineers permit: applications and plant data obtained
during inspection visits were used to obtain the average or typical
plant size and waste water discharge flows, and raw waste loadings as
described in Section V.
In order to adequately estimate the waste water discharge flow rates,
the plant effluent was divided into process waste waters and nonprocess
waste waters. The process waste waters consist of mill area oily
waters, soapstone slurry and latex dip wastes, area washdown waters, and
emission scrubber waters, contaminated storm waters from raw material
storage areas. The nonprocess waste waters are sanitary and clean storm
waters, utility waste waters such as once through cooling water, boiler
blowdown, cooling tower blowdown, water treatment wastes and
uncontaminated contact cooling water like tread cooling waters.
From these data, a typical process waste water flow was estimated to be
3.785 L/sec (60 gpm) for a plant consuming 205,000 kg (450,000 Ibs) of
116
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raw materials per day. For the older tire and inner tube plant sub-
category the average oil loading is 0.2U6 kg/kkg(lb/1000 Ib) of raw
material consumed. The suspended solids loading for this subcategory is
estimated to be 0.319 kg/kkg(lb/1000 Ib) of raw material. Based on
these typical profiles for old and new production facilities, treatment
cost data were generated and are presented in Tables 18 and 19. The
costs shown for a typical older facility are based on the worst case of
having to install a completely segregated sewer system rather than
isolating the process waste water stream from the combined sewer line.
The total annual costs for the proposed BPCTCA and BATEA control and
treatment technologies can be interpreted in terms of incremental costs
per unit of production. Study of the cost data for a typical older tire
or inner tube plant consuming 205,000 kg (450,000 Ibs) of raw materials
p-r day indicates that -che treatment costs for both the BPCTCA and BATEA
is approximately 0.59 cents per kg (0.27 cents/lb) of raw materials.
The treatment cost per unit of production for both the BPCTCA and BATEA
for a newer tire or inner tube facility of similar size (205,000 kg raw
material) is estimated to be approximately 0.46 cents per kg (0.21
cents/lb) of raw material consumed. In otherwords the proposed
treatments will add approximately 6 cents to the cost of a passenger
tire manufactured in an older plant and about 5 cents to the cost of a
passenger tire prduced in a newer facility.
Investment costs have been factored to August 1971 dollars using Engin-
eering News Record cost indices. Depreciation was calculated on the
basis of straight-line depreciation with a five year life ana zero
salvage value.
Designs for the proposed model treatment systems were costed to evaluate
the economic impact of the proposed effluent limitations. The design
considerations (i.e., the influent raw 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 category. 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.
120
-------
Percent of Unit.
!±!ffi Process Capital Cost
Electrical 12
Piping 15
Instrumentation 8
Site Work 3
Fngineering 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.
Annual costs were computed using the following cost basis:
Item Cost Allocation
Capitalization 10 percent of investment
Depreciation 5-yr straight line with zero discharge
value
Operations and Includes labor and supervision,
Maintenance chemicals, sludge hauling and dis-
posal, insurance and taxes (com-
puted at 2 percent of the capital
cost), and maintenance (4 percent
of capital cost)
Power Based on $0.01 kw-hr for electrical
power.
The short-term capitalization and depreciation write-off period is what
is currently acceptable under current Internal Revenue Service Regula-
tions pertaining to pollution control equipment.
All costs were computed in terms of August, 1971 dollars, which corres-
pond to an Engineering News Record Index (ENR) value of 1580.
Energy Requirementg
Energy input is related to the need for electric pumps to pump process
waste waters from the plant area and through the treatment system.
Electricity costs are estimated at one cent per kilowatt hour. The
extra power required for treatment and control systems is negligible
compared to the power requirement of the tire manufacturing equipment.
Non-Water Quality Aspects
121
-------
The primary non-water 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 non-regenerative type absorbent filter.
Solid waste disposal is a major problem confronting the industry as a
whole. Typically 3,100 kg (6,800 Ibs) of solid waste are generated by a
tire plant each day. Additional solid waste results from the drumming
of the waste 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, not be significant.
Land requirements for the treatment system are small; nevertheless,
certain older 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 control measures
and/or to pre-treat for disposal and discharge of the process waste
waters to publically owned treatment works.
S_y n th e t ic_Rubbe r _ Indus try
Emulsion^Cgumb Subcategory
Selection_of Controlling Treatment Technologies
Four degrees of control and treatment were considered in weighing treat-
ment effectiveness versus cost of treatment: primary clarification;
biological oxidation; and advanced treatment to two levels of COD re-
moval .
Since emulsion crumb waste waters contain uncoagulated latex solids, it
is necessary to coagulate these solids prior to clarification. Tne cost
alternatives for the primary clarification of emulsion crumb waste water
have been developed on the basis of a treatment model involving chemical
coagulation, with a sinking material such as clay to sinx the coagulated
solids. This, however, is only one of several possible methods of
achieving primary clarification. Air flotation is another approach to
primary clarification which as been applied to emulsion crumb waste
waters with success. Chemical coagulation has been used to develop the
cost data because there are more cases of its successful application for
this type of waste water, and, therefore, there is less uncertainty
about the effectiveness of this technology for this subcategory.
After primary clarification, emulsion crumb rubber waste waters
invariably have high BOD and COD concentrations. Biological treatment
is necessary (and is commonly practiced by the industry) to remove these
contaminants. In order to develop the cost alternatives for biological
122
-------
reatment, activated sludge processes were used as a model treatment,.
It is, of course, only one method for obtaining biological oxidation,
since other comparable technologies, such as aerated lagoons and
stabilization ponds exist and are used to some extent by the industry.
The activated sludge process was chosen as a model treatment because its
performance is not as temperature- and climate-dependent as is an
aerated lagoon or stabilization pond system and because the resulting
cost data are independent cf geographic location. In addition, an
aerated lagoon or stabilization pond system requires considerably larger
areas, which are not always available. Activated sludge racilities, by
contrast, require minimal land.
The major pollutant remaining in emulsion crumb waste waters alter bio-
logical treatment is COD. Its concentration is much higher than the
o-rher principal parameters and if advanced waste water treatment is to
be carried out, it is logical that the treatment technology should be
}ppli°d to reduction of the high COD levels. For the waste water flow
rates involved in emulsion crumb rubber production, activated carbon
treatment is the only technology currently applicable for COD removal.
Ir order to prevent blinding of the carbon beds and columns with fine
suspended solids, a dual-media filtration system is required upstream of
thp columns. Activated carbon adsorption of emulsion crumb secondary
effluent has been studied in pilot-scale test equipment. However, be-
cause of the technical risk with respect to performance and the un-
certainity of the associated capital and operating costs, two levels cf
activated carbon treatment have been modeled. These two levels are
equivalent to overall COD reductions of 75 and 90 percent.
Basis of the_T Treatment Co§t__Dat a
An emulsion crumb industry profile was made, based on industry produc-
tion capacity data, to determine the typical size of an emulsion crumb
production facility. The average, or typical, plant is rated at 128,000
metric tons per year. The waste water flow for such a plant would ap-
proximate 66 L/sec (1,050 gpm) . The model treatment plant, using
chemical coagulation and clarification followed by activated sludge
biological treatment, is shown in Figure 11. The degree or treatment
afforded by this technology is equivalent to best practicable control
technology currently available. The recommended treatment technology to
attain best available technology economically achievable is presented in
Figure 12. This treatment technology includes dual-media filtration
followed by activated carbon adsorption.
Designs for the proposed model treatment systems were costed to evaluate
the economic impact of the proposed effluent limitations. The design
considerations (i.e. the influent raw waste loads) were selected to
represent the highest expected raw waste load. This results in the
generation of cost data which should be conservative when applied to
most of the plants in the emulsion crumb subcategory. Relatively
123
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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.
Pereent of Unit
Item Process Capital Cost
Electrical 12
Piping 15
Instrumentation 8
Site Work 3
Engineering Design and
Supervision Construction 10
Construction Contingency 15
The total annual treatment costs for emulsion crumb plants can be presenter
in terms of incremental costs per unit cf production.
The cost data cited for a typical emulsion crumb production facility
of 128,000 metric tons per year preduct that the BPCTCA
treatment will cost 0.66 cents per kg (0.3 cents/lb) of production and
that the additional cost of the BATEA treatment will approximate 0.37 cents
per kg (0.17 cents/lb) of production.
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-yr straight line with zero salvage value
Operations and Includes labor and supervision, chemicals,
Maintenance sludge hauling and disposal, insurance and
taxes (computed at 2 percent of the capital
costs), and maintenance (computed at U per-
cent of the capital cost) .
Power Based on $0.01/kw-hr for electrical power.
126
-------
T'he short-term capitalization and depreciation write-off period is what
is currently acceptable under current Internal Revenue Service Kegula-
tions pertaining to industrial pollution control equipment.
All costs were computed in terms of August, 1971 dollars which corres-
pond to an Engineering News Record Index (ENR) value of 1580.
The total capital and annual costs for the model treatment technologies
are presented for a typical emulsion crumb plant in Table 20, together
with raw waste load and treated effluent quality.
Ene rgY^Peguirements
The primary clarification and biological oxidation treatment
technologies require electrical energy only for operation of equipment
such as pumps and aerators. The filtration and activated carbon
treatment system, in addition to power requirements, needs a tuel source
to regenerate the carbon. The energy and power needs of the recommended
treatment technologies are deemed to be low.
Non-Water Quality^Aspects
Sludge cake is produced by vacuum filtration of the primary coagulation
solids and the digested biological solids. Sludge disposal costs were
based on sanitary landfill. Sludge incineration costs were not eval-
uated because the economics depend, to a large degree, on tne accessi-
bility of a landfill site and on the relative costs for sludge haulage
and site disposal. The annual quantities of solid waste generated are:
Primary coagulated solids 2,940 cu m (3,900 cu yd)
Biological solids 245 cu m (325 cu yd)
Solution Crumb Subcateqory
Selection of Control and Treatment Technologies
Only two degrees of control and treatment have been considered in the
evaluation of treatment effectiveness versus cost data. Since latex
solids are not contained in waste waters from solution crumb plants,
clarification with chemical coagulation is not required; clarification
in crumb pits is sufficient. In addition, after biological treatment,
the residual COD concentration is much lower than is the case in the
emulsion crumb counterpart. Consequently, carbon adsorption to only one
level of overall COD reduction (65 percent removal) is reasonable. COD
reductions greater than this would involve additional risk and
uncertainty in the costing processes.
The first degree of treatment proposed includes primary clarirication of
crumb-laden waste water in dual-unit crumb pits, followed by biological
treatment to remove soluble organics. The cost data have oeen developed
127
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on the basis of an activated sludge system for the same reasons as given
previously for the emulsion crumb subcategory. Depending on land
availability, biological treatment could be aerated lagoons and
stabilization ponds. The second degree of treatment consists of dual-
media filtration followed by activated carbon adsorption. Carbon
adsorption was selected because it is the most currently feasible
technique for reducing the soluble COD content.
Ba s ±s _o f_ _t h _Tr eatment Cost Data
A profile of the solution crumb rubber industry defined the typical size
of a solution crumb production facility as 30,000 metric tons per year.
The waste water flow for such a plant would approximate 15.75 L/sec (250
gpm) .
The model treatment plant using activated sludge biological treatment is
shown in Figure 11. The treatment given by the proposed system is
equivalent to BPCTCA.
The recommended treatment technology to attain EATEA presented in Figure
12, consists of dual-media filtration followed by activated carbon
adsorption.
The influent raw waste loads upon which the treatment system designs
were based were selected to represent the highest expected raw waste
load in this subcategory. The same cost criteria used for emulsion
crumb plants were applied for solution crumb rubber facilities.
The total capital and annual costs for the model treatment tecnniques
for a typical solution crumb plant are presented in Table 21, together
with the raw waste loads and treated effluent qualities.
The treatment costs for solution crumb plants can be expressed as an
incremental cost per unit of production. The cost data prepared for a
typical solution crumb rubber plant of 30,000 metric tons per year
indicate that the BPCTCA treatment will cost 1.05 cents per kg (0.48
cents/lb) of production and that the additional costs of the BATEA
treatment will approximate 0.85 cents per kg (0.38 cents/lb) of
production.
Ene rqv Requirements
The only energy or power need is electricity, and electricity
consumption is low. The carbon is not regenerated on- site because of
the unfavorable economics of small-scale carbon regeneration systems.
Aspectg
Solid waste generation with this treatment system is associated with
biological solids and spent activated carbon. The activated carbon
129
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canisters may be returned for regeneration off-site by the supplier.
However, annual operating data have been based on disposal or the spent
carbon at a landfill site. The annual quantities of solid waste
generated are:
Biological solids
Spent carbon
102 cu m (135 cu yd)
140 cu m (185 cu yd)
the
Air quality and noise levels will not be significantly affected by
operations proposed in these treatment systems.
Latex Subcategory
Selection^of^Control and Treatment Technologies
Four degrees of control and treatment were considered in weighing the
treatment effectiveness versus cost of treatment. These degrees of
treatment are the same as for emulsion crumb waste water and include
primary clarification, biological oxidation, and advanced treatment to
two levels of COD removal.
Latex rubber waste water contains uncoagulated latex solids and the pro-
posed primary treatment (chemical coagulation and clarification) is
similar to that recommended for emulsion crumb waste waters. The bio-
logical treatment cost data have been based on activated sludge for the
same reasons as were cited for the emulsion crumb subcategory. The
advanced treatment cost data were modeled on two levels of overall COD
reduction, 87 and 95 percent. Overall removals greater than 95 percent
would call for undue technical risk, and uncertainty about capital and
operating costs.
Basis^of_the Treatment Cost Pata
A latex rubber industry profile was made to determine the typical size
of a latex rubber production facility. The average, or typical, plant
has an annual capacity of 10,000 metric tons, and its waste water flow
approximates 4.4 L/sec (70 gpm).
consisting
The model treatment plant,
fication followed by activat
illustrated in Figure 11. This is
of chemical coagulation and clari"
ed sludge biological treatment, is
equivalent to BPCTCA.
The recommended treatment
technology economically achievea
dual-media filtration followed by
technology
The treatment designs upon which the
the highest expected raw waste loald
to achieve best available
, presented in Figure 12, includes
cle
activated carbon adsorption.
cost data are based
within each category.
correspond to
131
-------
The same cost criteria used for the emulsion crumb subcategory were
applied to latex rubber. See Table 22.
The total annual treatment costs for latex rubber production facilities
can be presented in terms of incremental costs per unit of production.
Treatment cost data for a typical latex plant producing 10,000 metric
tons per year of latex rubber solids indicate that the BPCTCA treatment
will cost 2.51 cents per kg (1.14 cents/lb) of latex solids produciton
and that the BATEA treatment will produce an incremental cosr of 1.01
cents per kg (0.46 cents/lb) of latex solids production.
Energy Requirements
Since on-site carbon regeneration is not proposed for economic reasons,
the only power or energy requirement of these treatment systems is
electric power for pumps and other motive equipment.
Non-Water Quality^Aspects
Solid wastes are produced by chemical coagulation and clarification,
wasted biological sludge, and spent activated carbon. For cost pur-
poses, it is proposed that these all be hauled to a landfill. The
annual quantities of solid wastes are listed below:
Primary coagulated solids 214 cu m (283 cu yd)
Biological solids 62 cu m (82 cu yd)
Spent carbon 126 cu m (167 cu yd)
Neither air quality nor noise levels will be adversely affected by the
proposed treatment technologies.
Detailed Cost Information for All Subcategories
The following pages of this section 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. The individual
unit processes included in each of the proposed treatment systems are
discussed in considerable detail in Sections IX and X.
Detailed capital and cost estimates for a typically older tire and inner
tube plant and a typically newer tire plant are presented in Tables 23
and 24 respectively.
Table 25 to 27 contain capital cost estimate breakdowns for BPCTCA
control and treatment for typical emulsion crumb, solution crumb, and
latex rubber production facilities.
132
-------
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Capital cost estimates are given in Tables 28 to 30 for typical emulsion
crumb, solution crumb, and latex rubber plants which represent the
incremental capital costs required to increase BPCTCA treatment to BATEA
treatment.
Tables 31 to 38 describe the annual operating and maintenance costs
associated with each of the BPCTCA and BATEA treatment technologies
proposed for tire and inner tube plants and synthetic rubber production
facilities.
Table 39 lists the major cost bases used to compute the annual operating
and maintenance costs.
134
-------
TABLE 23
BPCTCA and BATEA Treatment Capital Costs for a
Typical Old Tire and Inner Tube Plant
(ENR 1580 - August 1971 Costs)
Daily Raw Material Consumption = 205 metric tons
Estimated Total Effluent Flow = 2,004,000 gallons per day
Estimated Process Effluent Flow = 86,000 gallons per day
Description of Treatment Facility Estimated Capital Cost
In-plant Sewer Segregation1 $ 89,000
In-plant Process Sumps and Pumps 32,000
Process Wastewater Force Main 31,000
Outdoor Wastewater Segregation System 116,000
Outdoor Process Sumps and Sump Pumps 72,000
Oily Wastewater Storage Tank 8,000
Oil Separator 52,000
Filter 17,000
Waste Oil Handling 9,000
Process Effluent Sewer and Monitoring Station 18,000
Total Effluent Monitoring Station 18,000
Sub-Total $462,000
Site Work 23,000
Electrical 55,000
Piping 69,000
Instrumentation 37,000
Sub-Total $646,000
Engineering Fees 65,000
Contingency 97,000
Total Capital Cost (Investment)
$808.000
Includes sealing existing floor drains, installation of new process drains
and sewers, and oily Wastewater retainment curbing
2
Includes roofing, curbing, and process wastewater drains and sewers
Land Costs are not included
135
-------
TABLE 24
BPCTCA and BATEA Treatment Capital Costs
for a Typical New Tire Plant
(ENR 1580 - August 1971 Costs)
Daily Raw Material Consumption = 205 metric tons
Estimated Total Effluent Fow = 569,000 gallons per day
Estimated Process Effluent Flow = 86,000 gallons per day
Description of Treatment Facility Estimated Capital Costs
In-plant Sewer Segregation $ 17,000
In-plant Process Sumps and Pumps 16,000
Process Wastewater Force Main 16,000
Outdoor Wastewater Segregation System2 116,000
Outdoor Process Sumps 72,000
Oily Wastewater Storage Tank 8,000
Oil Separator 52,000
Filter 17,000
Waste Oil Handling 9,000
Process Effluent Sewer and Monitoring Station 18,000
Total Effluent Monitoring Station 18,000
Sub-Total $359,000
Site Work 18,000
Electrical 43,000
Piping 54,000
Instrumentation 29.000
Sub-Total $503,000
Engineering Fees 50,000
Contingency 75,000
Total Capital Cost (Investment)3 $628,000
Includes installation of new process drains and sewers, and oily
wastewater retainment curbing.
2
Includes roofing, curbing, and process wastewater drains and sewers.
o
Land Costs are not included.
136
-------
Table 25
BPCTCA Treatment Capital Costs for a
Typical Emulsion Crumb Rubber Plant
(ENR 1580 - August 1971 Costs)
Annual Production Capacity = 128,000 metric tons
Estimated Wastewater Flow = 1,483,000 gallons per day
Description of Treatment Unit
Equalization Basin
Pumping Station
pH Adjustment and Coagulant Feed
Nutrient Addition
Reactor-C1ar i fier
Primary Sludge Pumps and Station
Aeration Basin
Secondary Clarifier
Sludge Return Pumps and Station
Biological Sludge Thickener
Aerobic Digestion
Combined Sludge Thickener
Vacuum Fi1ter
Sludge Handling System
Control Bui 1di ng
Moni tori ng Stat ion
Sub-Total
Site Work
Electri ca1
Piping
Instrumentati on
Sub-Total
Eng i neer i ng Fees
Cont i ngency
Total Capital Cost (Investment)
Estimated Capital Cost
$
$1
$1
314,000
19,000
28,000
3,000
101 ,000
33,000
119,000
120,000
66,000
33,000
128,000
45,000
68,000
13,000
38,000
16,000
,144,000
57,000
137,000
172,000
92,000
,602,000
160,000
240,000
$2.002.000
1
Land Costs are not included.
137
-------
Table 26
BPCTCA Treatment Capital Costs for a
Typical Solution Crumb Rubber Plant
(ENR 1580 - August 1971 Costs)
Annual Production Capacity = 30,000 metric tons
Estimated Wastewater Flow = 353,000 gallons per day
Description of Treatment Unit
Crumb Rinse Overflow Pits
Equali zat ion Bas i n
Pumping Station
Nutrient Addition and Neutralization
Aeration Basin
Secondary Clarifier
Sludge Return Pumps and Station
Biological Sludge Thickener
Aerobic Digestion
Vacuum Fi1ter
Control BuiIding
Monitoring Station
Sub-Total
Site Work
Electri cal
Pi pi ng
Instrumentat ion
Sub-Total
Engineering Fees
Cont i ngency
Total Capital Cost (Investment)
Estimated Capital Cost
$ 37,000
72,000
54,000
2,000
62,000
77,000
40,000
13,000
48,000
29,000
13,000
16.000
$ 463,000
23,000
56,000
69,000
37.000
$ 648,000
65,000
97.000
$ 810.000
1
Land Costs not included.
138
-------
Table 27
BPCTCA Treatment Capital Costs for a
Typical Latex Rubber Plant
(ENR 1580 - August 1971 Costs)
Annual Production Capacity = 10,000 metric tons
Estimated Wastewater Flow = 101,000 gallons per day
Description of Treatment Unit
Equa1i zat ion Bas i n
Purnp i ng Stat ion
pH Adjustment and Coagulant Feed
Nutrient Addition
Mix and Flocculation Tanks
Clar i f ier
Primary Sludge Pumps and Station
Aeration Basin
Secondary Clarifier
Sludge Return Pumps and Station
Biological Sludge Thickener
Aerobic Digestion
Combined Sludge Thickener
Vacuum Fi1ter
Control Bui 1di ng
Moni tor i ng Stat ion
Sub-Tota1
Site Wo r k
Electrical
Pi pi ng
I nstrumentat ion
Sub-Tota 1
Engineering Fees
Cont i ngency
Total Capital Cost(Investment)
Estimated Capital Cost
$ 49,000
3,000
8,000
1 ,000
8,000
34,000
4,000
62,000
34,000
4,000
11,000
46,000
16,000
42,000
30,000
13,000
$ 365,000
18,000
44,000
54,000
29,000
$ 510,000
51,000
76,000
$ 637.000
1
Land Costs not included.
139
-------
Table 28
BATEA Treatment Incremental Capital Costs
for a Typical Emulsion Crumb Rubber Plant
. (ENR 1580 - August 1971 Costs)
Annual Production Capacity = 128,000 metric tons
Estimated Wastewater Flow = 1,483,000 gallons per day
Description of Treatment Unit Estimated Capital Cost
Backwash Holding Tank $ 13,000
Filter Feed Pumps 18,000
Backwash Pumps 20,000
Dual Media Filters 145,000
Activated Carbon Columns 227,000
Carbon Charge System 23,000
Carbon Regeneration Furnace 122,000
Subtotal $ 568,000
Site Work 28,000
Electrical 68,000
Piping 84,000
Instrumentation 45,000
Land Costs are not included
Subtotal $ 793,000
Engineering Fees 79,000
Contingency 119.000
Total Capital Cost (Investment)1 $ 991,000
140
-------
Table 29
BATEA Treatment Incremental Capital Costs
for a Typical Solution Crumb Rubber Plant
(ENR 1580 - August 1971 Costs)
Annual Production Capacity = 30,000 metric tons
Estimated Wastewater Flow = 353,000 gallons per day
Description of Treatment U_n.JJL
Backwash Holding Tank
Fi1ter Feed Pumps
Backwash Pumps
Dual Media FiIters
Activated Carbon Columns
Carbon Charge System
Sub-Total
Site Work
Electrica1
Pi p i ng
Inst rumentat ion
Sub-Tota1
Engineering Fees
Conti ngency
Total Capital Cost (Investment)
Estimated Capital Cost
$ 13,000
7,000
18,000
73,000
88,000
14,000
$213,000
11,000
25,000
31,000
17.000
$297,000
30,000
45.000
$372,000
1
Land Costs are not included
141
-------
Table 30
BATEA Treatment Incremental Capitals Costs
for a Typical Latex Rubber Plant
(ENR 1580 - August 1971 Costs)
Annual Production Capacity = 10,000 metric tons
Estimated Wastewater Flow = 101,000 gallons per day
Description of Treatment Unit Estimated Capital Cost
Backwash Holding Tank $ k,OQO
Filter Feed Pumps ^,000
Backwash Pumps 7,000
Dual Media Fi1ters 21,000
Activated Carbon Columns 38,000
Carbon Charge System 13.000
Sub-Total $ 86,000
Site Work if,000
Electrical 9,000
Piping 12,000
Instrumentation 6.000
Sub-Total $117,000
Engineering Fees 12,000
Contingency 18.000
Total Capital Cost(Investment) $1^7.000
Land Costs are not included
142
-------
Table 31
BPCTCA and BATEA Operating and Maintenance Costs
for a Typical Old Tire and Inner Tube Plant
Daily Raw Material Consumption = 205 metric tons
Estimated Total Effluent Flow = 2,00^,000 gallons per day
Estimated Process Effluent Flow = 86,000 gallons per day
Description of Cost Item Annual Cost
Absorbent $ 800
Waste Oi1 Disposal 300
Sludge Disposal 1,100
Labor 5,^00
Power and Energy 1 ,000
Maintenance 12,900
Insurance and Taxes 6,500
Total Annual Operating and Maintenance Cost $28,000
143
-------
Table 32
BPCTCA and BATEA. Operating and Maintenance Costs
for a Typical New Tire Plant
Daily Raw Material Consumption = 205 metric tons
Estimated Total Effluent Flow = 2,00if,000 gallons per day
Estimated Process Effluent Flow = 86,000 gallons per day
Description of Cost I terns Annual Cost
Absorbent $ 800
Waste Oi1 Disposal 100
Sludge D isposal 1,100
Labor 5,^00
Power and Energy 1,000
Maintenance 11,700
Insurance and Taxes 5»9QO
Total Annual Operating and Maintenance Cost $26,000
144
-------
Table 33
BPCTCA Operating and Maintenance Costs
for a Typical Emulsion Crumb Rubber Plant
Annual Production Capacity = 128,000 metric tons
Estimated Wastewater Flow = 1,^83,000 gallons per day
Description of Cost I tern Annual Cost
Chemica1s
Nutrients $ 9,500
Acid/Alkali 15,700
Coagulating Chemicals 29,000
Fi Her Aid 9,200
Solid Waste Disposal 11,700
Labor 39,500
Power and Energy 20,000
Maintenance 76,900
Insurance and Taxes 38,500
Total Annual Operating and Maintenance Cost $250.OOP
145
-------
Table 34
BPCTCA Operating and Maintenance Costs
for a Typical Solution Crumb Rubber Plant
Annual Production Capacity = 30,000 metric tons
Estimated Wastewater Flow = 353,000 gallons per day
Description of Cost I tern Annual Cost
Chemica1s
Nutrients $ 2,500
Acid/Alkali 3,500
FiIter Aid 300
Solid Waste Disposal 700
Labor 1^,600
Power and Energy 4,000
Maintenance 31,100
Insurance and Taxes 15,300
Total Annual Operating and Maintenance Costs $72,000
146
-------
Table 35
BPCTCA Operating and Maintenance Costs
for a Typical Latex Rubber Plant
Annual Production Capacity = 10,000 metric tons
Estimated Wastewater Flow = 101,000 gallons per day
Description of Cost I tern Annual Cost
Chemicals
Nutrients $ 600
Acid/Alkali 1,200
Coagulating Chemicals 2,000
Filter Aid 1,000
Solid Waste Disposal 1,000
Labor 1^,600
Power and Energy 3,000
Maintenance 2^,400
Insurance and Taxes 12 .200
Total Annual Operating and Maintenance Cost $60,000
147
-------
Table 36
BATEA Incremental Operating and Maintenance Cost
for a Typical Emulsion Crumb Rubber Plant
Annual Production Capacity = 128,000 metric tons
Estimated Wastewater Flow = 1,483,000 gallons per day
Description of Cost I tern Annual Cost
Activated Carbon Regeneration $84,500
Labor 24,500
Power and Energy 9,000
Maintenance 38,000
Insurance and Taxes 19,000
Total Annual Operating and Maintenance Costs $175,000
148
-------
Table 37
BATEA Incremental Operating and Maintenance Costs
for a Typical Solution Crumb Rubber Plant
Annual Production Capacity = 30,000 metric tons
Estimated Wastewater Flow = 353,000 gallons per day
Description of Cost Item Annual Cost
Activated Carbon Purchase $37,^00
Spent Carbon Disposal 800
Labor 17,500
Power and Energy 2,000
Maintenance 1^,200
Insurance and Taxes 7,100
Total Annual Operating and Maintenance Costs $79,000
149
-------
i
Table 38
BATEA Incremental Operating and Maintenance Cost
for a Typical Latex Rubber Plant
Annual Production Capacity = 10,000 metric tons
Estimated Wastewater Flow = 101,000 gallons per day
Description of Cost Item Annual Cost
Activated Carbon Purchase $33,500
Spent Carbon Disposal 600
Labor 17,500
Power and Energy 300
Maintenance 5,^00
Insurance and Taxes 2,700
Total Annual Operating and Maintenance Costs $60,000
150
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Table 39
Operational and Maintenance Cost Bases
Chemical Costs
Nutrients
Dibasic Ammonium Phosphate
Ammonium Sulfate
Coagulat ing Aids
Alum
Clay
Polyelectrolyte
F i1ter Aid
Activated Carbon
Oi 1 Absorbent
Solid Waste Disposal Costs
Oil D i sposal
Sludge Disposal
Haulage (10 cu.yd. dumpster)
Labor
Operator
Supervisor
Power
Electricity
Fuel Oil
Ma intenance
Insurance
$100/L.ton
$ 50/L.ton
$ UU/L.ton
$ 50/L.ton
$ 1/lb.
$ 1/lb.
$0.30/lb.
$900/L.ton
$ 5/55 ga1.drum
$ 1/cu.yd.
$20/trip
$ 5/hour
$ 7/hour
$0.01/Kwhr.
$0.l8/gal.
3.2% of Total Capital Cost
1.6% of Total Capital Cost
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SECTION IX
BEST PRACTICABLE CONTROL TECHNOLOGY
CURRENTLY AVAILABLE EFFLUENT LIMITATIONS
Tire and_Inner Tube Facilities
Identification of Best Practicable Control
The best control and treatment technologies currently in use emphasize
in-house control of solution wastes with end-of-pipe treatment of com-
bined process and nonprocess waste waters. However, as discussed pre-
viously, end-of-pipe treatment of process waste waters after combination
with nonprocess waste waters is considered inadequate.
Of the plants visited, only one plant performs a totally adequate end-
of-pipe treatment of all process waste water streams. The Treatment
facility involves the use of holding lagoons for combined process and
nonprocess effluents and the re-use of the waste water for irrigation of
farm land. The very large land requirements involved Keep this type of
treatment from being applied to the industry as a whole. Otner end-of-
pipe treatment facilities examined were not very effective in removal of
the oil constitutent in the wastes, due to dilution by nonprocess waste
waters.
There are many in-plant control and treatment facilities. Recirculation
of the soapstone solution was considered adequate and effective. How-
ever, the weekly washing and dumping of the system in most plants
reduced this effectiveness. Oil sumps and separators are common to the
tire industry, but their effectiveness is reduced by dilution with other
wastes or by improper maintenance.
Since process wastes are best treated before dilution with nonprocess
waste waters and because no plant obtained effective control and treat-
ment for all the waste waters it generated, the proposed treatment
technology for a typical plant is a combination of the best features of
various plants examined and visited.
Since only the loadings vary between the Older Tire and Inner Tube Pro-
duction Facilities subcategory and the Newer Tire Production Facilities
subcategory, the treatment schemes described below will be the same for
both.
Basically, the technology employed consists of:
1. Elimination of any discharge of soapstone or latex-dip solution.
2. Segregation, control, and treatment of all oily waste streams.
A flow diagram of the proposed system is shown in Figure 10.
153
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II
Zero discharge of soapstone and latex solutions is currently practiced
by production facilities in each of the subcategories. Elimination of
soapstone solution discharges involves:
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 washwater as make-up for
fresh soapstone solution.
The re-use of the recirculating system washwater is the key to zero dis-
charge of this waste. In emptying the system for cleaning, the
soapstone used should be stored in tanks. The washwater 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 washwater can then be re-
used as make-up water to the soapstone bath during the normal production
run.
Eliminating the discharge of latex solution is achieved by:
1. The use of curbing around the latex dipping area.
2. Sealing of all drains in the dipping area.
3. Containment of all waste waters from the area.
Several plants have already achieved zero discharge by these methods.
The contained and collected wastes are disposed of off-site in a
landfill.
Control and treatment of oily waste streams involves segregation, col-
lection, 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 process water raw waste load, all process water should
be isolated from the nonprocess waste water used in the plant. This can
be achieved by collecting drippings from machinery, the latex dip area
and the molding and curing areas, etc. in sumps. The sumps can be
either pumped to the process waste water treatment system or collected
batchwise and hauled to the treatment or disposal area. Only as the
cost benefits would indicate, would ripping out and installing new sewer
lines be recommended. Once isolated, these waste waters are collected
in sumps located in strategic areas throughout the plant. Waste flows
will be intermittent by nature and, therefore, a sizable flow rate will
hardly ever be obtained without first collecting all wastes in
centralized locations. Wastewaters collected in these sumps will be
periodically pumped to an API-type gravity separator, where the
separable oil and solids fraction is removed. To provide for large
154
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spills or leakage of a major water supply line, a 37,850-liter (10,000-
gal.) storage tank is provided.
Separated oil is removed by a manually operated slotted pipe. A decant
tank is provided to allow water removed with the oil to settle out.
Concentrated oil-water mixtures are then removed from the decant tank,
drummed, and sealed, and sent to a landfill. Water removed from the
tank is pumped back to the separator.
Settleable solids collected in the separator are periodically removed
and also sent to a landfill. The separator is provided with two dual-
operating chambers in order to provide for uninterrupted service during
clean-out.
The gravity separator is provided with a straw filter to remove any
large oil globules still remaining due to possible short circuiting or
unforeseen peak overload conditions. Additional treatment for oil
removal is obtained by passing the effluent from the separator through
an absorbent filter.
Effluent Loadings Attainable with Propoged Technologies
Based on the control technology data obtained from tire manufacturer
sources, and treatment data obtained from industries naving similar
waste water problems, it was determined that the proposed control and
treatment technologies are compatible with the following effluent
quality for both Older Tire and inner tube and newer tire racilities:
Suspended solids 40 mg/L
Oil and Grease 10 mg/L
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/L. The use of an absorbent filter
will further reduce the effluent oil concentration to 10 mg/L.
A reduction of suspended solids to 40 mg/L will result from tne use of
an API type separator. Additional reduction is deemed likely after
pasage through the absorbent filter.
Effluent guality is best expressed in terms of the waste load per unit
of material consumed and is thereby independent of the flow and size of
the plant. Recommended limitations for the proposed BPCTCA are as
follows:
Suspended solids 0.064 kg/kkg (lb/1000 Ib) of raw material
Oil 0.016 kg/kkg (lb/1000 Ib) of raw material
pH 6.0 to 9.0
155
-------
Through the application of treatment technologies equivalent in
performance to gravity separation and filtration, two of the plants
visited are currently achieving the proposed standards for oil, Table
40. In addition, four of the plants visited are achieving the proposed
standard for suspended solids. The plants achieving the oil standard
are both classified as "new" for the basis of this report. However, one
of these plants (Plant. D) would technically be classified as old when
applying the standards. Recent in-plant modifications to both
manufacturing and process waste water treatment and control facilities
were comprehensive. As a result this plant can be considered in the
newer tire plant subcategory for analysis and waste water management
purposes. The control and treatment technologies employed by this plant
consisted of segregation of oil and suspended solids laden wastes and
the use of local gravity separators to treat these contaminated waste
waters. Similar modifications in other old plants, would result in
similar performance levels supporting the selection of the proposed
effluent limitations.
Although the application of control and treatment technologies designed
to reduce oil and suspended solid concentrations in the process waste
waters for both older and newer tire plants will be similar to those
employed at Plant D, the implementation costs for such technologies at
old facilities will, in general, be higher than the costs at newer tire
plants.
Sy_H t he t ic_Ru b be r_ Industry
^ of Best._ Practicable Control
In view of the fact that all sutcategories of the synthetic rubber in-
dustry are highly technical and proprietary in nature, it is not
possible to base effluent limitation guidelines and standards of
performance on in-plant control technologies which might impact on
processing procedures and product quality. Instead, these guidelines
have been formulated around the best practicable end-of-pipe treatment
technologies employed by the synthetic rubber industry. In order to
achieve the contaminant reductions recommended for this guideline, the
synthetic rubber industry will require better Housekeeping and
maintenance practices, as well as in-plant processing modifications, to
assist the end-of-pipe treatment plant in attaining the required
reductions. The effluent limitations have been based on the effluent
quality and contaminant removal efficiencies of well designed and
properly-operated treatment facilities.
-Cr umb_ Subcategory
The coagulation liquor and crumb rinse overflow stream should be passed
through crumb pits to remove crumb rubber fines. These pits should be
dual units so that good crumb separation can be achieved during pit unit
156
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cleaning operations. Figure 11 shows a hypothetical end-of-pipe
secondary treatment facility applicable to the treatment of emulsion
crumb waste waters. This treatment includes chemical coagulation and
clarification, and biological treatment. The total plant effluent
should be passed through an equalization basin, providing approximately
24 hours detention, to smooth out waste load peaks and to equalize
hydraulic flow. The equalization basin should be aerated to insure good
mixing, prevent anaerobic conditions, and assist in the biological
oxidation process.
From the equalization basin, the waste waters are pumped to a mixing
basin, where the pH of the waste waters is adjusted to achieve optimum
coagulation conditions. The desired pH value is approximately neutral
(pH = 7) and is suitable for biological treatment with no changes.
Nutrients to facilitate biological treatment will also be added in this
basin.
After pH adjustment, the waste waters flow into a reactor-clarifier,
where coagulating chemicals (alum and polyelectrolyte) are added in the
reactor compartment. A clay slurry is also added, to weight down the
coagulated rubber solids. The waste water flows from the reactor
compartment to the clarifier, where the settleable solids and coagulated
solids settle and are removed. The clarified waste water overflows the
clarifier and enters the biological treatment system. The clarified
waste water flows into aeration basins 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 matter is 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 basin 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 is 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 re-
mainder 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 of the aeration basins. The thickened
sludge underflow enters an aerobic digester, where the biological sludge
is wasted by endogenous respiration utilizing oxygen to aerate and re-
duce the bio-solid bulk. This process is referred to as aerobic
digestion.
158
-------
This digested sludge is then mixed with the primary solids underflows
from the reactor-clarifier unit and enters a secondary thickener. The
clear supernantant from this thickener is also recycled to the aeration
basins. The thickened underflow is then discharged to a vacuum filter
for further conditioning and concentration.
A drum-type vacuum filter separates thickened sludge into a dewatered
cake, which discharges by belt conveyor to a dumpster bin and into a
filtrate that is recycled to the aeration basin. The dewatered sludge
cake is biologically stable and can be disposed of at a sanitary
landfill. Filter aid and precoat preparations are used to assist and
maintain the quality of the filtrate.
Solution_Crumb Subcategory
The plant waste waters are first passed through crumb pits to remove
rubber crumb fines. As previously noted in the discussion of the
emulsion crumb subcategory, these pits should be dual units.
Figure 11 represents a hypothetical secondary treatment alternative
which is applicable to solution crumb rubber waste waters, as well as to
the emulsion crumb waste waters previously discussed. Since solution
crumb waste waters do not contain uncoagulated latex solids, and if ade-
quate separation of the rubber fines has been achieved in the crumb
pits, neither the chemical coagulation process nor the primary clarifier
is required. The waste waters can then pass from tne pH arid nutrient
addition basin directly into the aeration basin (refer to Figure 11).
In addition, since there are no primary solids, the second thickener is
not necessary and the wasted biological sludge passes directly from the
digester to the vacuum filter. The solution crumb secondary waste water
treatment facility is similar tc the emulsion crumb waste waters in all
other aspects.
Latex^ S\jbcategory_
The model secondary waste water treatment facility illustrated in Figure
11 is also applicable at latex rubber plants. Since latex plant waste
waters contain uncoagulated latex solids, primary clarification assisted
by chemical coagulation is required. However, because latex plants are
considerably smaller than emulsion crumb plants, the waste water flow
rate is much lower. The lower flow rates indicate the use of separate
rapid-mix, flocculator, and clarifier units, since small reactor-
clarifiers are not practicable in small diameters due to reduction in
efficiency, mixing, and settlement of solids.
Other than this basic difference (due to flow rate only) in the design
of the primary clarification equipment, the secondary treatment facility
for latex plant waste waters is identical to that described for emulsion
crumb waste water.
159
-------
Effluent^ Loadings_Attainable
with Proposed Technologies
Emulsion Crumb Subcategory
Based on raw waste load and the control and treatment data from emulsion
crumb plants, it was determined that the described proposed control and
treatment technologies are compatible with in the following effluent
guality:
COD 500 mg/L
BOD 25 mg/L
Suspended Solids 40 mg/L
Oil and Grease 10 mg/L
pH 6.0 to 9.0
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 technology standards currently available for the emulsion
crumb subcategory. Recommendations for proposed limitations are:
COD 8.00 kg/kkg(lb/1000 Ib) of product
BOD 0.40 kg/kkg(lb/1000 Ib) of product
Suspended Solids 0.65 kg/kkg(lb/1000 Ib) of product
Oil and Grease 0.16 kg/kkg(lb/1000 Ib) of product
pH 6.0 to 9.0
Table 41 presents the raw waste and final effluent loads for the
exemplary plants producing various emulsion crumb products. Data was
obtained by plant visits and company historical records. Altiiough three
plants were sampled, six cases of emulsion crumb production were
studied.
The proposed BOD, suspended solids, and oil and grease effluent
limitations for BPCTCA are commensurate with the calculated effluent
loads achieved by the selected plants. The values of the proposed
limitations for BOD, suspended solids, and oil and grease are based on
typical industry waste water flow rates, calculated raw waste loads, and
established performance characteristics (concentrations) of conventional
biological treatment systems.
The proposed COD effluent limitation for BPCTCA is higher than the
normal COD effluent load from the selected plants. This value was
conservatively selected in order to produce effluent limitations that
reflect minor processing variations and climatic conditions. Since in
practice the effluent COD from a biological treatment facility is
essentially independent of the treatment design and operation, it is not
feasible to develop COD limitations for a control and treatment
technology, namely biological treatment, that does not effectively
160
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remove COD. The important parameters associated with the BPCTCA are
therefore BOD, suspended solids, oil and grease.
Solution Crumb Subcateqory
Industry raw waste load and the control and treatment data indicate that
proposed control and treatment technologies for solution crumb rubber
waste water are compatible with the following effluent quality:
COD
BOD
Suspended Solids
Oil and Grease
PH
245 mg/L
25 mg/L
40 mg/L
10 mg/L
6.0 to 9.0
Effluent quality can also be expressed in terms of effluent waste loads,
which are independent of waste water flow. These effluent waste loads,
resulting from the application of treatment technologies equivalent to
primary clarification and biological treatment, constitute tne best
practicable control and treatment technology standards currently avail-
able for the solution crumb sutcategory. Recommendations for proposed
limitations are:
COD
BOD
Suspended Solids
Oil and Grease
PH
3.92 kg/kkg(lb/1000 Ib) of product
0.40 kg/kkg(lb/1000 Ib) of product
0.65 kg/kkg(lb/1000 Ib) of product
0.16 kg/kkg(lb/1000 Ib) of product
6.0 to 9.0
The raw waste and final effluent loads for selected solution crumb
rubber plants are given in Table 42. Five plants were visited and eight
types of solution crumb product were sampled.
Since most solution crumb is produced at the same location as emulsion
crumb rubber, it was necessary to calculate the raw waste load
contribution of solution crumb process in the treatment system final
effluent. The values of the proposed limitations for BOD, suspended
solids, and oil and grease, therefore, are based on typical waste water
flow rates, calculated raw waste loads, and established performance
characteristics (concentrations) of conventional biological tr atment
systems. The limitations proposed for suspended solids and o^l and
grease, are in general agreement with the effluent loads achieve^ by the
selected plants. The BOD limitation, however, is marginally hig/) r than
the effluent loads produced by some of the cited plants. Since tne best
BOD effluent load achievable by a solution crumb ruboer plant is
dependent on the waste water flow and the inherent process limitations
of biological treatment, an effluent limitation has been recommended for
BOD corresponding to the effluent quality of a well designed and
operated biological treatment facility.
162
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The proposed COD effluent, limitation for BPCTCA is higher than the COD
effluent from many of the selected plants. This value was selected as
conservative in order to produce effluent limitations that reflect minor
processing variations and climatic conditions throughout tne country.
The salient parameters for the BPCTCA are BOD, suspended solids, oil and
grease, and pH.
Latex_Subcategory
Raw waste load and the control and treatment data do not demonstrate
adequate treatment of the waste water from the selected plants. The
below listed performance characteristics are imposed upon this
subcategory as justified by established performance characteristics of
conventional biological and chemical coagulation systems.
COD
BOD
Suspended Solids
Oil and Grease
PH
500 mg/L
25 mg/L
40 mg/L
10 mg/L
6.0 to 9.0
Effluent quality can also be expressed in terms of effluent waste loads,
which are independent of waste water flow. These effluent waste loads,
resulting from the application of treatment technologies equivalent to
primary clarification with chemical coagulation followed by biological
treatment, constitute the best practicable control and treatment
technology standards currently available for the latex rubber
subcategory. Recommendations for proposed limitations are:
COD
BOD
Suspended Solids
Oil and Grease
PH
6.85 kg/kkg(lb/1000 Ib) of product
0.34 kg/kkg(lb/1000 Ib) of product
0.55 kg/kkg(lb/1000 Ib) of product
0.14 kg/kkg(lb/1000 Ib) of product
6.0 to 9.0
The raw waste and final effluent loads for two selected latex rubber
plants are given in Table 43.
164
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SECTION X
BEST AVAILABLE TECHNOLOGY ECONOMICALLY
ACHIEVABLE EFFLUENT LIMITATIONS
Tire and Inner Tube
Effluent limitations commensurate with best available technology econom-
ically achievable and best practicable technology currently available
are identical for both subcategories of the tire and inner tube
industry.
Complete water reuse (zero discharge) for this industry does not appear
feasible. Treatment of the waste water to approach influent water
quality in a recycle system requires removal of oils, suspended solids,
total dissolved solids and trace contaminants that cannot be justified
on a technical, cost or benefit basis.
§YS^heticRubbgr Industry
Identification of Best_Available^TechnolQgy Economically
Achievable
After review of the data and control and treatment technologies, it is
clear the principal pollutant load after biological treatment, for all
subcategories in the synthetic rubber industry, is due to COD. The
other parameters (BOD, suspended solids, and oil and grease) are reduced
to comparatively low levels. Therefore, advanced treatment snould be
addressed to COD removal and reduction.
None of the end-of-pipe systems observed in use by this industry was
considered completely adequate for establishing effluent limitations
commensurate with the best available technology economically achievable.
Emulsion Crumb Subcateggry
After biological treatment, emulsion crumb waste waters have low BOD,
suspended solids, and oil and grease concentrations, and high COD
concentrations (up to 500 mg/L). The most feasible technique to reduce
residual COD content after biological treatment is by using an activated
carbon adsorption technique. This technology has been studied in pilot
scale apparatus using as feed stock emulsion crumb waste waters which
had been subjected to secondary treatment. After treatment with carbon,
the resultant COD level was reduced to about 130 mg/L. Further studies
by EPA, NERC, Cincinnati showed that reductions of COD levels up to 70
percent are technically and (potentially) economically achievable. This
degree of removal has been used to establish COD effluent limitations
and standards of performance for the emulsion crumb subcategory.
167
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Figure 12 shows a hypothetical advanced waste water treatment facility
using activated carbon treatment to achieve COD removals adequate for
best available technology economically achievable.
The secondary effluent discharges into a holding tank which is normally
maintained full by a level-control signal to the feed pumps. The feed
pumps produce sufficient line pressure to pump the waste water through
the dual multi-media filters and the carbon columns.
The waste water is first filtered to remove the residual suspended
solids from the secondary treatment. Filtration before the carbon bed
will prevent fine particles from plugging the carbon. The filtration
media used generally are anthracite and fine graded sands. The filters
are dual or multiple units depending on the waste water flow rate and
standard equipment sizes available. Periodically, these filters require
backwashing indicated by a pressure buildup upstream or a pressure drop
across the filter bed. When filter backwashing is necessary, the feed
is switched to the dual unit, the backwash pumps are activated, and the
unit undergoes the complete backwash cycle. Backwash water containing
trapped solids is piped to the aeration basins of the secondary
treatment facility. The backwash cycle usually includes an air scour
and a final service flow period for resettlement of the filter media.
The flow rate during the backwash cycle is considerably higher than
during the normal service cycle and therefore requires a holding rank of
sufficient capacity to furnish the necessary water for the backwash
operation.
The filtered waste water flows down through the activated carbon
columns. Depending on the waste water flow rate, two or more parallel
carbon bed columns may be required. Due to solids buildup in the carbon
columns, periodic backwashing is also required. Each column is
backwasned when the pressure drop across the column exceeds a pre-*set
value. The backwashing water is discharged to the aeration basins of
the secondary treatment facility.
The carbon in the columns is replaced with fresh or regenerated carbon
when its activity is depleted. This is indicated by breakthrough or
leakage as detected in an automatic total carbon analyzer. The spent
carbon is discharged to a spent carbon storage bin, and a regenerated or
fresh charge of carbon is provided to the columns from a charge hopper.
The effluent from the carbon bed columns has low COD, BOD, suspended
solids, and oil and grease. The flow of this effluent is monitored
through a monitoring station where a 24 hour composite sample is col-
lected.
In most emulsion crumb plants, the carbon usage is sufficiently high to
justify on-site regeneration. Regeneration may be carried out in an
oilfired, multiple-hearth furnace. The spent carbon is continuously fed
from the spent carbon storage bin to the furnace. The regenerated and
168
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cooled carbon is then returned to a carbon charge hopper and is ready
for recharging. Overflow carbon quench and slurry waters from the
regeneration process are carbon (to replace carbon lost during
unloading, transfer, loading, and regeneration) is added at the charge
hopper. Losses normally amount to approximately 5 to 8 percent of the
regenerated carbon weight.
In smaller emulsion crumb production facilities, carbon usage is low and
on-site regeneration may not be feasible. The carbon can then either be
returned to the supplier for regeneration or can be disposed of as solid
waste in a landfill site.
Solution Crumb SubcategC;r₯
The hypothetical advanced waste water treatment facility illustrated in
Figure 12 is also applicable to a secondary effluent from solution crumb
waste water. The illustrated facility will produce an effluent
satisfactory for best available technology economically achievable.
Although this technology has not been used by plants in the solution
crumb subcategory, it has teen studied for emulsion crumb secondary
effluent. Because of the many similarities between solution crumb and
emulsion crumb waste water (e.g., use of the same monomers and similar
processing techniques by the two subcategories) , it is reasonable to
propose this advanced treatment technology for secondary solution crumb
waste water. The level of treatment representative of this technology
has been confirmed by the EPA National Environmental Research center,
Cincinnati, Ohio.
The advanced treatment facility for solution crumb is similar to that
for emulsion crumb, except that in most cases the carbon will be
disposed of or regenerated off-site, instead of being regenerated on-
site. This is due primarily to the fact that solution crumb plants are
generally smaller than emulsion crumb plants, and on-site carbon
regeneration is not judged to be economically feasible at this level of
cost analysis.
Latex Subcateqory
Again, the hypotehtical advanced waste water treatment facility
illustrated in Figure 12 is recommended for treatment of secondary
effluent latex rubber waste waters. This facility corresponds to the
proposed best available technology ecnomically achievable for latex
rubber plants.
This technology has not been used by latex rubber plants, but it has
been studied, for the advanced treatment of secondary effluent emulsion
crumb rubber waste waters. There are many similarities in materials
used and processing operations between latex and emulsion crumb
production, and hence similarities in their waste waters. Differences
169
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tend to revolve around the level of loadings rather than the
characteristics and constituents. It is, therefore, reasonable to
recommend this advanced treatment technology for secondary effluent
latex rubber waste waters. The level of treatment attainable by this
technology has been confirmed by the EPA National Environmental Research
Center, Cincinnati, Ohio. The hypothetical facility will be similar to
that proposed for emulsion crumb waste waters.
Effluent Loading Attainable with Proposed Technologies
Emulsion Crumb Subcategory
Based on secondary treatment data and pilot studies of activated carbon
adsorption, the proposed control and treatment technologies will result
in effluent quality better than or equal to the following values:
COD
BOD
Suspended Solids
Oil and Grease
PH
130 mg/L
5 mg/L
10 mg/L
5 mg/L
6.0 to 9
The proposed treatment will probably produce an effluent of higher
quality for BOD, Suspended Solids, and Oil and Grease than the above
values. However, the resultant limitations on these parameters are
governed by the accuracy of the analytical methods.
Effluent quality can also be defined in terms of effluent waste loads,
The effluent waste loads, resulting from the application of treatment
technologies equivalent to multi-media filtration and activated carbon
adsorption, constitute the best available treatment economically
achievable for the emulsion crumb subcategory. The proposed limitations
are as follows:
COD
BOD
Suspended Solids
Oil and Grease
PH
Solution Crumb Subcateggry
2.08 kg/kkg(lb/1000 Ib) of product
0.08 kg/kkg(lb/1000 Ib) of product
0.16 kg/kkg(lb/1000 Ib) of product
0.08 kg/kkg(lb/1000 Ib) of product
6.0 to 9.0
Industry secondary treatment data and data extrapolated from the pilot-
scale activated carbon adsorption studies on secondary effluent emulsion
crumb waste waters were used to quantify the effluent quality of
solution crumb waste waters following advanced treatment. The effluent
quality is given as follows:
COD
BOD
130 mg/L
5 mg/L
170
-------
Suspended Solids
Oil and Grease
PH
10 mg/L
5 mg/L
6.0 to 9.0
The effluent values for BOD, Suspended Solids, and Oil and Grease are
dictated by the lower limit of accuracy for the currently accepted
analytical methods.
The effluent waste loads following multi-media filtration and activated
carbon adsorption constitute the best available treatment economically
achievable for the solution crumb subcategory. The proposed limitations
are as follows:
COD
BOD
Suspended Solids
Oil and Grease
PH
2.08 kg/kkg(lb/1000 Ib) of product
0.08 kg/kkg(lb/1000 Ib) of product
0.16 kg/kkg(lb/1000 Ib) of product
0.08 kg/kkg(lb/1000 Ib) of product
6.0 to 9.0
Latex_Subcatec[ory_
Latex industry secondary treatment data and data extrapolated from
studies on the activated carbon adsorption treatment of emulsion crumb
secondary effluent were used to formulate the following effluent
qualities:
COD
BOD
Suspended Solids
Oil and Grease
PH
130 mg/L
5 mg/L
10 mg/L
5 mg/L
6.0 to 9.0
The effluent levels for BOD, Suspended Solids, and Oil and Grease are
dependent on the accuracy of the best accepted analytical methods.
Effluent quality can also be expressed in terms of effluent waste loads
which are independent of waste water flow. The effluent waste loads re-
sulting from the application of treatment technologies equivalent to
multimedia filtration and activated carbon adsorption form the basis for
the best available treatment economically available for the latex
subcategory. The proposed limitations are:
COD
BOD
Suspended Solids
Oil and Grease
pH
1.78 kg/kkg(lb/1000 Ib) of product
0.07 kg/kkg (lb/1000 Ib) of product
0.14 kg/kkg(lb/1000 Ib) of product
0.07 kg/kkg (lb/1000 Ib) of product
6.0 to 9.0
171
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SECTION XI
NEW SOURCE PERFORMANCE STANDARDS
Tire and Inner^Tube Production Facilities
Recommended effluent limitations for new sources are identical and com-
mensurate with best practicable technology currently available. These
effluent limitations are presented in Section IX of this report.
Synthetic^Fubber Industry
Because all stated subcategories of the synthetic rubber industry are
highly technical and involve proprietary processes, in-plant control
technologies cannot be fully defined or enumerated; such in-plant
measures might impact on manufacturing practices and product quality.
Since advanced waste water treatment technologies have been proposed for
the best available treatment economically achievable (BATEA) by existing
plants by 1983, the recommended effluent limitations for new sources
prior to 1983 are identical to those recommeded as £»est practicable
control technology currently available for each of the synthetic rubber
subcategories.
Pretreatrognt, Recommendatipng
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 whicii will inhibit
or upset the performance of publicly owned treatment works must be
eliminated from such discharges.
Tire and Inner Tube
Pretreatment recommendations for process waste waters from the tire and
inner tube industry 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 publically owned treatment
works. Oily wastes, after dilution in a public sewer system, will
remain untreated and therefore must be controlled before discharge from
the plant boundaries.
Pretreatment of other nonprocess waste waters from the tire and inner
tube industry will pose more difficult problems. These include
alkalinity in boiler blowdowns and both acidity and alkalinity in water
treatment wastes. Both boiler blowdowns and water treatment wastes will
contain high concentrations of suspended and dissolved solids. Cooling
tower water treatment wastes may contain heavy metals such as chromium
173
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and zinc used for corrosion inhibition. Potential problems such as
acidity, alkalinity, solids, oils, and heavy metals may require control
at the plant to conform to local ordinances for discharge to a publicly
owned treatment works. The control techniques and treatment methods are
described in earlier sections of this report. Equalization of the waste
load and waste water flow is the key step in the control of batch dumps
of production chemicals and solutions.
Synthetic Rubber Industry
Emulsion crumb and solution crumb slurry overflow waste waters should be
passed through crumb pits to remove floatable rubber crumb. Few pub-
licly owned treatment works have primary clarification equipment ade-
quate to handle large quantities of agglomerated rubber crumb solids.
Wastewaters from emulsion crumb and latex production facilities are in-
variably laden with uncoagulated latex solids. Since publicly owned
treatment works do not generally have coagulation capabilities, these
waste waters should, at least, be chemically coagulated with a sinking
agent and clarified.
Utility wastes often exhibit extreme pH peaks which should be
neutralized or, at least equalized, pricr to discharge to the publicly
owned treatment works. This problem is not so severe with emulsion
crumb and latex plants, where pH adjustment is required prior to
chemical coagulation, as it is with solution crumb production facilities
where adjustment of the waste water pH is normally not necessary. Heavy
metals, present in cooling tower blowdowns for example, should be
eliminated by substitution of inhibitor or equalized prior to discharge
to a publicly owned treatment works.
No compounds or species present in synthetic rubber process waste water
can be considered toxic or inhibitory to the performance of publicly
owned treatment works.
In summary, the following pretreatment requirements apply to waste water
discharges to publicly owned treatment works from synthetic rubber
plants:
Emulsion Crumb Subcateqory - Gravity separation of crumb fines in
crumb pits, chemical coagulation and clarification of latex-laden
waste waters, and neutralization or equalization of utility wastes.
Solution Crumb^Subcategory - Gravity separation of crumb fines in
crumb pits, and neutralization or equalization of utility wastes.
Latex_Subcateqory - Chemical coagulation of latex-laden waste
waters, and neutralization or equalization of utility wastes.
174
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SECTION XII
ACKNOWLEDGEMENTS
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 ot data relating to
process raw waste load and treatment plant performance at various tire,
inner tube and synthetic rubber facilities. Special acknowledgement is
made of Mr. Daniel G. Pennington of the Rubber Manufacturers Association
for coorindating the schedule of visits among the industry members.
Acknowledgement is made of the assistance provided in supplying ths
manifold copies of RAPP applications by the EPA Regional Administrators
as well as the physical assistance of the Regional Industry
Coordinator's staff personnel during the field sampling and ctnalysis
portions of the project. In addition acknowlegement is maae to Messrs.
John Convery, Jesse Cohen and Richard Cobbs and Robert Smith of the EPA
National Environmental Research Center, Cincinnati Ohio tor the special
studies on the activated carbon treatment of synthetic rubber production
waste waters.
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: George R.
Webster, Chairman and C. R. McSwiney, Legal Assistant, Effluent
Guidelines Division; Herbert S.Skovronek, PhD, Edison Water Quality
Research Laboratory Division of NERC, Cincinnati; Paul Ambrose,
Enforcement Division, EPA Region III; John Lank, Enforcement Division,
EPA Region IV; Charles H. Ris and Marshall Dick, Office of Research and
Development, Headquarters; Richard Insinger, Planning and Evaluation,
Economic Analysis Branch, Headguarters; Doris Ruopp, Office of Toxic
Materials, Headquarters; Alan W. Eckert, Office of General Counsel; and
John E. Riley, Project Officer, Rubber Industry, Effluent Guidelines
Division. Acknowledgement is made of the efforts of Jane D. Mitchell,
Effluent Guidelines Division for typing the final manuscript.
Acknowledgement is made of the overall guidance and direction provided
by Mr. Allen Cywin, Director, Effluent Guidelines Division and Mr. Ernst
P. Hall, Deputy Director and others within the Agency who provided many
helpful suggestions and comments.
175
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SECTION XIII
REFERENCES
1. Shreve, R.N., Chemical Process Industries, CPI; McGraw Hill, Inc.,
New York, (1967) .
2. Standen, A., ed. , Kirk-Othmerj_EncYclogedia^of Chemical Technology;
Vol. 17, John Wiley~and Sons, New York, (1968) .
3. Kestein, B. , "SBR and Polybutadiene Rubbers," Symposium on Tire
Material Decisions, AICHE 74th National Meeting, Minneapolis,
Minnesota, (August 29, 1972).
4. "Rubber Industry Facts", Rubber Manufacturers Association, New
York, 1972.
5. Private Communications from Chem Systems, Inc., New York.
6. "Air Flotation-Biological Oxidation of Synthetic Rubber and Latex
Wastewater", Firestone Synthetic Rubber and Latex Company, LaKe
Charles, Louisiana (October 15, 1972).
7. "Industrial Wastewater Reclamation with 400,000-gallon-per-day
Vertical Tube Evaporator, Design, Construction and Initial
Operation", The General Tire and Rubber Company, Akron, Ohio
(September, 1972) .
8. Unpublished internal EPA report to George R. Webster, Effluent
Guidelines Division, from J. M Cohen, Chief, Physical Chemical
Treatment Research NERC Cincinnati entitled "Feasibility of Treating
Synthetic Rubber Waste Water by Granular Activated carbon, August 24,
1973.
GENERAL BIBLIOGRAPHY
Rostenbach, R.E., "Status Report on Synthetic Rubber Wastes." sewage
and Industrial Waste, Vol. 24; No. 9, (September 1952), 1138-1143. ~
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 Rostenbach, R.E., "Industrial Waste Treatment and
Disposal." Indu^triaJ.^nd_E£.gineering_Chemistry_, Vol. 45, No. 12,
(December 1953) , 2680-2685.
"Putting the Closed Loop into Practice." Environmental Scienge_and
177
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Technology, Vol. 6, No. 13, (December 1972), 1072-1073.
Dougan, L.D. and Bell, J.C., "Waste Disposal at a Syntnetic 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 Rostenbach, R.E., "Rubber Industry."
Industrial and_Engineering_Chemistr_y_, Vol. 39, No. 5, (May 1947) ,
589-595.
Nemerow, N.L., Theories and Practices of Industrial WasterrTreatment,
Addison-Wesley Publishing Co., New York, (1963).
Alliger, G. and Weissert, F.C., "Elastomers." Industrial and Engineering
Chemistry., Vol. 59, No. 8, (August 1967), 80-90.
Herzlich, H.J., "Tire Compounding." Chemical Engineering Progress,
Vol. 69, No. 2, (February 1973), 77-78.
Montgomery, D.R., "Integrated System for Plant Wastes Combats Stream
Pollution." Chemical_Eng_ineering, 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 Industry."
International Institute of Synthetic Rubber Producers, Inc., New York,
(1972) .
Anderson, E.V., "Rubber, A $16 Billion Industry Turns on Tires."
Chemjcal_and_Engineering News, (July 14, 1969) , 39-83.
Hofmann, W. , V^lc^mi2a^on_and_Vulcanizing_Agents; Palmerton Publishing
Co., Inc., New York, (1967).
Hawley, G.G., The Condensed Chemical Dictionary; Reinhold Co., New York,
(1971).
Fawcett, R.J. and McDone, E.T., "Special Rubbers in Tires." Symposium
on Tire Material Decisions, AICHE 73rd National Meeting, Minneapolis,
Minnesota, (August 29, 1972).
Lund, H.F., ed., Industrial Pollution CQntrol_HandbQQk; MeGraw-Hill, Inc.,
New York, (1971).
"Methods for Chemical Analysis of Water and Wastes." Environmental Pro-
tection Agency, National Environmental Research Center, Analytical Quality
Control Laboratory, Cincinnati, Ohio, (1971).
178
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Taras, M.J., ed.r Standard Methods for "the Examinatign_Qf_Water_and
Wastewater. American Public Health Association, Washington, D.C.,
(1971) .
Water; Atmospheric Analysis, Part 23, "Standard Method of Test tor Bio-
chemical Oxygen Demand of Industrial Water and Industrial Wastewater."
1221L:^DliaI_B223s_2f._£S_Sta£djarj|s, American Society of Testing and
Materials, Philadelphia, Pennsylvania, (1970).
Eckenfelder, W.W., Industrial Water Pollution Control; McGraw-Hill, Inc.,
New York, (1966) .
Perry, J.H., ed., Chemical Engineers1 Handbook, 4th Ed.; McGraw-Hill, Inc.,
New York, (1963).
179
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SECTION XIV
GLOSSARY
Act
The Federal Water Pollution Control Act Amendments of 1972.
Actiyator
A metallic oxide that makes possible the crosslinking 01 sulfur in
rubber vulcanization.
Antioxidant
An organic compound added to rubber to retard oxidation or
deterioration.
Accelerator Agents
A compound which greatly reduces the time required for vulcanization of
synthetic or natural rubber.
Ban bury Mixer
Trade name for a common internal mixer manufactured Dy Farrel
Corporation used in the compounding and mixing of tire rubber stock.
Best Available Technology
Treatment required by July 1, 1983 for industrial discharges to surface
waters as defined by Section 301 (b) (2) (A) of the Act.
Best _Pr act i cable Control Technology^Currently Available JBP
Treatment required by July 1, 1977 for industrial discharges to surface
waters as defined by Section 301 (b) (1) (A) of the Act.
Be st^Ayailable Demonstrated control Technology (BADCT)^
Treatment required for new sources as defined by Section 306 of tne Act.
BOD5
Biochemical Oxygen Demand (5 day).
Bag House
181
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An air emission control device used to collect intermediate ana large
particles (greater than 29 microns) in a bag filter. A bag filter
constructed of fabric. Common usage in the tire industry is to control
and recover carbon black in a dry state from vapors leaving the
compounding area.
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 tire rubber compounds.
Catalyst
A substance that initiates a chemical reaction and enables it to proceed
at a greatly accelerated rate.
Category and Subcategpgy
Divisions 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.
Cement (Tire and Tubes)
An adhesive used in tire and inner tube manufacturing.
The combination or aggregation of previously emulsified particles into a
clot or mass.
COD
182
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Chemical Oxygen Demand.
Crumb
Small coagulated particles of synthetic rubber.
Curing Agent
Curing or vulcanization agents are substances which bring about the
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.
DrY_Air_Pgllution_Control
The technique of air pollution abatement without the use of water.
Emulgion
A stable mixture of two or more immersible liquids held in suspension by
small percentage of substances called emulsifiers.
Endogenous^ Resp_iratiQn
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. In tire and inner tube
manufacture treads and inner tubes are formed by extrusion.
Filler
183
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A high specific gravity (2.00-4.50) 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.
qpm
Gallons per minute,
IR
Polyisoprene rubber, the major component of natural rubber, amde syn-
thetically by the solution polymerization of isoprene.
Investment_ Costs
The capital expendistures reported in August 1971 dollars required to
bring the treatment or control technology into operation. Included are
expenditures for design, site preparation, purchase o± 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 colloid is a surface
active substance that prevents a dispersed phase of a suspension 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/L
Milligrams per liter. Nearly equivalent to parts per million concen-
tration.
Modifier
An additive which adjusts the chain length and molecular weight dis-
tribution of the rubber during polymerization.
Monomer
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A compound of a relatively low molecular weight which is capable of
conversion to polymers or othe/ compounds.
NBR
Nitrile rubber, a synthetic rubber made by emulsion polymerization of
acrylonitrile with butadiene.
New Source
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.
^QSzg£Qductive_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 reguired 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. A one unit change in pH indicates a 10 fold
change in acidity and alkalinity.
Pigment
Any substance that imparts color to the rubber. Pigment substances such
as zinc oxide or carbon black also act as reinforcing agents.
Plastic
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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, 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-
ized. Synonym for productive rubber stock.
Reinforcers or Reinforcing Agent
Fine powders used to increase the strength, hardness and abrasion
resistance of rubber. Reinforcing agents used in the rubber processing
include carbon bale, zinc oxide and hydrated silicas.
SBR
Styrene Butadiene Rubber, a synthetic rubber made either by emulsion or
solution polymerization of styrene and butadiene.
Soapstone
A substance used to prevent tire and inner tube 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 of 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
Navigable waters. The waters of the United States including the
territorial seas.
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Tire _Bead
Tire beads are coated wires inserted in the pneumatic tire at the point
where the tire meets the steel rim on which it is mounted. They insure
an air tight seal between the tire and rim.
Tire Cord
Woven synthetic or natural fabrics impregnated with rubber. They form
the body of the tire and supply it with most of its strength.
Tire Tread
Tire tread is riding surface of the tire. Their design and composition
are dependent on the end use of the tire.
Tread Book
A set of movable shelves designed for the temporary storage of extruded
tread sections between the extrusion and tire building operations. Each
shelf pivots like the page of a book, thus the name tread boox.
Vulcanization
Vulcanization is the process by which plastic rubber is converted into
-he elastic rubber or hard rubber state. The process is brought about
by linking of macro-molecules at their reactive sites.
W^t_Air_Pollution_Control
The technique of air pollution abatement utilizing water as an
absorptive media.
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English Unit
SECTION xv
TABLE 44
METRIC UNITS AND CONVERSION FACTORS
Abbrevi at ion
Conversion Factor by
Metric Unit
Abbreviation
acre
acre - feet
cubic feet
cubic feet
cubic inches
cubic yards
feet
gat Ion
gal Ion/minute
horsepower
inches
pounds
mi 1 1 ion gal Ions/day
square feet
square inches
tons (short) (2,000 Ibs)
tons (long) (2,240 Ibs)
yard
ac
ac ft
cu ft
cu ft
cu i n
cu yd
ft
gal
gpm
hp
i n
Ib
nigd
sq ft
sq in
ST
LT
yd
0.405
1233.5
0.028
28.32
16.39
0.7646
0.3048
3.785
0.0631
0.7^57
2.54
0.454
3,785
0.0929
6.452
0.907
1 .016
0.9144
hectares ha
cubic meters cu m
cubic meters cu m
liters L
cubic centimeters cu cm
cubic meters cu m
meters m
1 i ters L
liters/second L/sec
kilowatts kw
centimeters cm
kilograms kg
cubic meters/day cu m/day
square meters sq m
square centimeters sq cm
metric tons (1000 kilograms) kkg
metric tons (1000 kilograms) kkg
meters m
NOTE: Multiply the value of the English Unit by the indicated conversion factor to get the value of the corresponding
Metric Unit.
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