Handbook of industrial and hazardous wastes treatment - Part 7 (end) potx

30
Treatment of Rubber Industry Wastes
Jerry R. Taricska
Hole Montes, Inc., Naples, Florida, U.S.A.
Lawrence K. Wang
Zorex Corporation, Newtonville, New York, U.S.A., and
Lenox Institute of Water Technology, Lenox, Massachusetts, U.S.A.
Yung-Tse Hung
Cleveland State University,
Cleveland, Ohio, U.S.A.
Joo-Hwa Tay
Nanyang Technological University, Singapore
Kathleen Hung Li
NEC Business Network Solutions, Irving, Texas, U.S.A.
30.1 INDUSTRY DESCRIPTION
30.1.1 General Description
The US rubber processing industry encompasses a wide variety of production activities ranging
from polymerization reactions closely aligned with the chemical processing industry to the
extrusion of automotive window sealing strips. The industry is regulated by seven Standard
Industrial Classification (SIC) codes [1]:
. SIC 2822: Synthetic Rubber Manufacturing (vulcanizable elastomers);
. SIC 3011: Tire and Inner Tube Manufacturing;
. SIC 3021: Rubber Footwear;
. SIC 3031: Reclaimed Rubber;
. SIC 3041: Rubber Hose and Belting;
. SIC 3069: Fabricated Rubber Products, Not Elsewhere Classified; and
. SIC 3293: Rubber Gaskets, Packing, and Sealing Devices.
Approximately 1650 plants exist in the United States and have production ranges from
1.6 Â 10
3
kkg/year (3.5 Â 10

6
lb/year) to 3.7 Â 10
8
Kkg/year (8.2 Â 10
8
lb/year). Table 1
presents a summary of the rubber processing industry regarding the number of subcategories and
the number and types of dischargers. Table 2 presents a subcategory profile of best practical
control technology currently available (BPT) regulations (daily maximum and 30-day aver ages)
[2]. The effluent limitations are shown as kilogram of pollutant s per 1000 kg of raw material
processed (kg/kkg).
1233
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
The rubber processing industry is divided into 11 subcategories based on raw waste loads
as a function of production levels, presence of the same or similar toxic pollutants resulting from
similar manufacturing operations, the nature of the wastewater discharges, frequency and
volume of discharges, and whether the discharge is composed of contact or noncontact
wastewater. Other primary considerations are treatment facilities and plant size, age, and
location. The 11 subcategories are listed below. A brief description of each subcategory follows.
. Subcategory 1: Tire and Inner Tube Manufacturing;
. Subcategory 2: Emulsion Crumb Rubber Production;
. Subcategory 3: Solution Crumb Rubber Production;
. Subcategory 4: Latex Rubber Production;
. Subcategory 5: Small-Sized General Molding, Extruding, and Fabricating Rubber
Plants;
. Subcategory 6: Medium-Sized General Molding, Extruding, and Fabricating Rubber
Plants;
. Subcategory 7: Large-Sized General Molding, Extruding, and Fabricating Rubber
Plants;
. Subcategory 8: Wet Digestion Reclaimed Rubber;

. Subcategory 9: Pan, Dry Digestion, and Mechanical Reclaimed Rubber;
. Subcategory 10: Latex-Dipped, Latex-Extruded, and Latex Molded Goods;
. Subcategory 11: Latex Foam.
Subcategory 1. Tire and Inner Tube Manufacturin g
The production of tires and inner tubes involves three general steps: mixing and preliminary
forming of the raw materials, formation of individual parts of the product, and constructing and
curing the final product. In total, 73 plants use these general steps to produce tires in the United
States.
The initial step in tire construction is the preparation or compounding of the raw materials.
The basic raw materials for the tire industry include synthetic and natural rubber, reinforcing
agents, fillers, extenders, antitack agents, curing and accelerator agents, antioxidants, and
pigments. The fillers, extenders, reinforcing agents, pigments, and antioxidant agents are added
and mixed into the raw rubber stock. This stock is nonreactive and can be stored for later use.
When curing and accelerator agents are added, the mixer becomes reactive, which means it has a
short shelf-life and must be used immediately.
Table 1 Industry Summary
Industry: Rubber processing
Total number of subcategories: 11
Number of subcategories studied: 3
a
Number of dischargers in industry:
† Direct: 1054
† Indirect: 504
† Zero: 100
a
Wet digestion, although not a paragraph 8 exclusion, was
not studied because of the lack of plant-specific data.
Emulsion and solution crumb rubber, although candidates
for exclusion, were studied, because data were available
Source: USEPA.

1234 Taricska et al.
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
Table 2 BPT Limitations for Subcategories of Rubber Processing Industry (kg/kkg of raw material)
Tire and inner
tube plants
b
Emulsion crumb
rubber
Solution crumb
rubber Latex rubber Small GMEF
c
Medium GMEF
c
Pollutant
Daily
max
30-day
avg.
a
Daily
max
30-day
avg.
a
Daily
max
30-day
avg.
a
Daily

max
30-day
avg.
a
Daily
max
30-day
avg.
a
Daily
max
30-day
avg.
a
COD 12.0 8.0 5.9 3.9 10.0 6.8
BOD
5
0.60 0.40 0.60 0.40 0.51 0.34
TSS 0.096 0.064 0.98 0.65 0.98 0.65 0.82 0.55 1.3 0.64 0.80 0.40
Oil and grease 0.024 0.016 0.24 0.16 0.24 0.16 0.21 0.14 0.70 0.25 0.42 0.15
Lead 0.0017 0.0007 0.0017 0.0007
Zinc
pH
d
Large GMEF
c
Wet digestion
reclaimed
Pan, dry digestion,
mechanical

reclaimed LDEM
e
Latex foam
Daily
max
30-day
avg.
a
Daily
max
30-day
avg.
a
Daily
max
30-day
avg.
a
Daily
max
30-day
avg.
a
Daily
max
30-day
avg.
a
COD 15 6.1 6.2
f

2.8
BOD
5
3.7 2.2 2.4 1.4
TSS 0.50 0.25 1.0 0.52 0.38 0.19 7.0 2.9 2.3 0.94
Oil and grease 0.26 0.093 0.40 0.14 0.40 0.14 2.0 0.73
Lead 0.00017 0.0007
Zinc 0.058 0.024
Chromium 0.0086
g
0.0036
a
Computed from average daily value taken over 30 consecutive days.
b
Oil and grease limitations for nonprocess wastewater from plants placed in operation before 1959: daily max ¼ 10 mg/L; 30-day avg. ¼ 5mg/L.
c
General molded, extruded, and fabricated rubber.
d
Limitation is 6 –9 pH units for all subcategories.
e
Latex-dipped, latex-extruded, and latex-molded goods.
f
Allowable when the pan, dry digestion, mechanical reclaimed processes are integrated with a wet digestion reclaimed rubber process.
g
Allowable when plants employ chromic acid for cleaning operations.
Source: USEPA.
Treatment of Rubber Industry Waste 1235
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
After compounding, the stock is sheeted out in a roller mill and extruded into sheets or
pelletized. This new rubber stock is tacky and must be coated with an antitack solution, usually a

soapstone solution or clay slurry, to prevent the sheets or pellets from sticking together during
storage.
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 other raw materials, such as cord and fabric, are made into the following
basic tire components: tire beads , tire treads, tire cords, and the tire belts (fabric). Tire beads are
coated wires inserted in the pneumatic tire at the point where the tire meets the wheel rim (on
which it is mounted); they ensure a seal between the rim and the tire. 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 strength. Tire belts stabilize the tires and
prevent the lateral scrubbing or wiping action that causes tread wear.
The processes used to produce the individual tire components usually involve similar
steps. First, the raw stock is heated and subjected to a final mixing stage before going to a roller
mill. The material is then peeled off rollers and continuously extruded into the final component
shape. Tire beads are directly extruded onto the reinforcing wire used for the seal, and tire belt is
produced by calendering rubber sheet onto the belt fabric.
The various components of the tire are fitted together in a mold to build green, or u ncured,
tires which are then cured in an automatic press. Curing times range from les s than one hour for
passenger car tires to 24 hours for large, off-the-road tires. After curing, the excess rubber on the
tire is ground off (deflashed) to produce the final product.
This subcategory is often subdivided into two groups of plants: (a) those starting
operations prior to 1959, (applies to 39 plants) and (b) those starting operations after 1959. This
subdivision must be recognized in applying limitations on plant effluents of oil and grease
because BPT limitations are different for the two groups of plants. For plants placed in operation
after 1959, the 30-day average oil and grease limitation is 0.016 kg/kkg of product. For plants
placed in operation prior to 1959, the limitation is the same (0.016 kg/kkg) but only for process
wastewater. Process wastewater for these pre-1959 plants comes from soapstone solution
applications, steam cleaning operations, air pollution control equipment, unroofed process oil
unloading areas, mold cleaning operations, latex applications, and air compressor receivers.

Water used only for tread cooling and discharges from other areas of such plants is classified as
nonprocess wastewater, in which oil and grease levels are limited to 5 mg/L as a 30-day average
and 10 mg/L as a daily maximum.
Emulsion polymerization, the traditional process for synthetic rubber production, is the
bulk polymerization of droplets of monomers suspended in water. Emulsion polymerization is
operated with sufficient emulsifier to maintain a stable emulsion and is usually initiated by
agents that produce free radicals. This process is used because of the high conversion and the
high molecular weights that are possible. Other advantages include a high rate of heat transfer
through the aqueous phase, easy removal of unreacted monomers, and high fluidity at high
concentrations of product polymer. Over 90% of styrene butadiene rubber (SBR) is produced by
this method. Approximately 17 plants use the emulsion crumb rubber process.
Raw materials for this process include styrene, butadiene, catalyst, activator, modifier, and
soap solution.
Polymerization proceeds stepwise through a train of reactors. This reactor system
contributes significantly to the high degree of flexibility of the overall plant in producing
different grades of rubber. The reactor train is capable of producing either “cold” (277–28 0 K,
103–206 kPa) or “hot” (323 K, 380–517 kPa) rubber. The cold SBR polymers, produced at the
1236 Taricska et al.
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
lower temperat ure and stopped at 60% conversion, have improved prope rties when compared to
hot SBRs. The hot process is the older of the two. For cold polymerization, the monomer–
additive emulsion is cooled prior to entering the reactors. Each reactor has its own set of cooling
coils and is agitated by a mixer. The residence time in each reactor is approximately one hour.
Any reactor in the train can be bypassed. The overall polymerization reaction is ordinarily
carried to no greater than 60% 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 milky white emulsion phase of the reaction mixture called latex. Short stop solution is added
to the latex exiting the reactors to quench the polymerization at the desired conversion. The
quench latex is held in blowdown tanks prior to the stripp ing operation.
The stripping operation removes the excess butadiene by vacuum stripping, and then

removes the excess styrene and water in a perforated plate stripping column. The water and
styrene from the styrene stripper are separated by decanting and the water is discharged to the
treatment facility. The recovered monomers are recycled to the monomer feed stage. The latex is
now stabilized and is precipitated by an electrolyte and a dilute acid. This coagulation imparts
different physical characteristics to the rubber depending on the type of coagulants used. Carbon
black and oil can be added during this coagulation/precipitation step to improve the properties
of the rubber. This coagulated crumb is separated from the liquor, resuspended and washed with
water, then dewatered, dried, and pressed into bales for shipment. The underflow from the
washing is sent to the wastewater treatment facility.
Subcategory 3: Solution Crumb Rubber Production
Solution polymerization is bulk polymerization in which excess monomer serves as the solvent.
Solution polymerization, used at approximately 13 plants, is a newer, less conventional process
than emulsion polymerization for the commercial production of crumb rubber. Polymerization
generally proceeds by ionic mechanisms. This system permits the use of stereospecific catalysts
of the Ziegler–Natta or alkyl lithium types which make it possible to polymerize monomers into
a cis structure characteristic that is very similar to that of natural rubber. This cis structure yields
a rubbery product, as opposed to a trans structure which produces a rigid product similar to
plastics.
The production of synthetic rubbers by solution polymerization processes is a stepwise
operation very similar in many aspects to production by emulsion polymerization. There
are distinct differences in the two technologies, however. For solution polymerization, the
monomers must be extremely pure and the solvent should be completely anhydrous. In contrast
to emulsion polymerization, where the monomer conversion is taken to approximately 60%,
solution polymerization systems are polymerized to conversion levels typically in excess of
90%. The polymerization reaction is also more rapid, usually being completed in 1 to 2 hours.
Fresh monomers often have inhibitors added to them while in storage to prevent premature
polymerization. These inhibitors and any water that is present in the raw materials must be
removed by caustic scrubbers and fractionating drying columns to provide the solution process
with the high purity and anhydrous materials needed. The purified solvent and monomers are
then blended into what is termed the “mixed feed,” which may be further dried in a desiccant

column.
The dried mixed feed is now ready for the polymerization step, and catalysts can be added
to the solu tion (solvent plus monomers) just prior to the polymerization stage or in the lead
polymerization reactor.
The blend of solution and catalysts is polymerized in a series of reactors. The reaction is
highly exothermic and heat is removed continuously by either an ammonia refrigerant or by
Treatment of Rubber Industry Waste 1237
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
chilled brine or glycol solutions. The reactors are similar in both design and operation to those
used in emulsion polymerization. The mixture leaves the reactor train as a rubber cement, that is,
polymeric rubber solids dissolved in solvent. A short stop solution is added to the cement after
the desired conversion is reached.
The rubber cement is then sent to storage tanks where antioxidants and extenders are
mixed in. The rubber cement is pumped from the storage tank to the coagulator where the rubber
is precipitated with hot water under violent agitation. The solvent and unreacted monomer are
first steam stripped overhead and then condensed, decanted, and recycled to the feed stage.
The bottom water layer is discharged to the wastewater treatment facility.
The stripped crumb slurry is further was hed with water, then dewatered, dried, and baled
as final product. Part of the water from this final washing is recycled to the coagulation stage, and
the remainder is discharged for treatment.
Subcategory 4: Latex Rubber Production
The emulsion polymerization process is used by 17 production facilities to produce latex rubber
products as well as solid crumb rubber. Latex production follows the same processing steps as
emulsion crumb rubber production up to the finishing process. Between 5 and 10% of emulsion
polymerized SBR and nearly 30% of nitrile rubber production (NBR) are sold as latex. Latex
rubber is used to manufacture dipped goods, paper coatings, paints, carpet backing, and many
other commodities.
Monomer conversion efficiencies for latex production range from 60% for low-
temperature polymerization to 98% for high-temperature conversion.
The monomers are piped from the tank farm to the causti c soda scrubbers where the

inhibitors are removed. Soap solution, catalysts, and modifiers are added to produce a feed
emulsion which is fed to the reactor train. Fewer reactors are normally used than the number
required for a crumb product line. When polymerization is complete, the latex is sent to a
holding tank where stabilizers are added.
A vacuum stripper rem oves any unwanted butadiene, and the steam stripper following it
removes the excess styrene. Neither the styrene nor butadiene is recycled. Solids are removed
from the latex by filters , and the latex may be concentrated to a higher solids level.
Subcategories 5, 6, 7: Small-, Medium-, and Large-Sized General Molding,
Extruding, and Fabricating Plants
These three closely related subcategories are divided based on the volume of wastewater
emanating from each. These subcategories include a variety of processes such as compression
molding, transfer molding, injection molding, extrusion, and calendering. An estimated 1385
plants participate in these subcategories.
A common step for all of the above processes is the compounding and mixing of the
elastomers and compounding ingredients. The mixing operation is required to obtain a thorough
and uniform dispersion of the rubber and other ingredients. Wastewater sources from the mixing
operation generally derive from leakage of oil and grease from the mixers.
Compression molding is one of the oldest and most commonly used manufacturing
processes in the rubber fabrication industry. General steps for the processes include warming the
raw mater ials, preforming the warm stock into the approximate shape, cooling and treating with
antitack solution, molding by heat and pressure, and finally deflashing. Major products from this
process include automotive parts, medical supplies, and rubber heels and soles.
Transfer molding involves the forced shifting of the uncured rubber stock from one part
of the mold to another. The prepared rubber stock is placed in a transfer cavity where a ram
1238 Taricska et al.
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
forces the material into a heated mold. The applied forc e combine d with the heat from the mold
softens the rubber and allows it to flow freely into the entire mold. The molded item is cured,
then removed and deflashed. Final products include V-belts, tool handles, and bushings with
metal inserts.

Injection molding is a sophisticated, continuous, and essentially automatic process that
uses molds mounted on a revolving turret. The turret moves the molds through a cyclic process
that includes rubber injection, curing, release agent treatment, and removal. Deflashing occurs
after the product has been removed. A wide range of products is made by this process, including
automotive parts, diaphragms, hot-water bottles, and wheelbarrow tires.
The extrusion process takes unvulcanized rubber and forces it trough a die, which results
in long lengths of rubber of a definite cross-section. There are two general subdivisions of this
technique; one extrudes simple products and the other builds products by extruding the rubber
onto metal or fabric reinforcement. Products from these techniques include tire tread, cable
coating, and rubber hose.
Calendering involves passing unformed or extruded rubber through a set or sets of rolls to
form sheets or rolls of rubber product. The thickness of the material is controlled by the space
between the rolls. The calender may also produce patterns, double the product thickness by
combining sheets, or add a sheet of rubber to a textile material. The temperature of the calender
rolls is controlled by water and steam. Products produced by this process include hospital
sheeting and sheet stock for other product fabrication.
This subcategory represents a process that is used to recover rubber from fiber-bearing
scrap. Scrap rubber, water, reclaiming and defibering agents, and plasticizers are placed in a
steam-jacketed, agitator-equipped autoclave. Reclaiming agents used to speed up depolymer-
ization include petroleum and coal tar-base oils and resins as well as various chemical softeners
such as phenol alkyl sulfides and disulfides, thiols, and amino acids. Defibering agents
chemically do the work of the hammer mill by hydrolyzing the fiber; they include caustic soda,
zinc chloride, and calcium chloride.
A scrap rubber batch is cooked for up to 24 hours and then discharged into a blowdown
tank where water is added to facilitate subsequent washing operations. Digester liquor is
removed by a series of screen washings. The washed rubber is dewatered by a press and then
dried in an oven. Two major sources of wastewater are the digester liquor and the washwater
from the screen washings.
Two rubber reclaiming plants use the wet digestion method for reclamation of rubber.
Subcategory 9: Pan, Dry Digestion, and Mechanical Reclaimed Rubber

This subcategory combines processes that involve scrap size reduction before continuing the
reclaiming process. The pan digestion process involves scrap rubber size reduction on steel rolls,
followed by the addition of reclaiming oils in an open mixer. The mixture is discharged into
open pans, which are stacked on cars and rolled into a single-cell pressure vessel where live
steam is used to heat the mixture. Depolymerization occurs in 2 to 18 hours. The pans are then
discharged and the cakes of rubbe r are sent on for further processing. The steam conden sate is
highly contaminated and is not recycled.
The mechanical rubber reclaiming process, unlike pan digestion, is continuous and
involves fiber-free scrap being fed into a horizontal cylinder containing a screw that works the
scrap against the heated chamber wall. Reclaiming agents and catalysts are used for
depolymerization. As the depolymerized rubber is extruded through an adjustable orifice, it is
quenched. The quench vaporizes and is captured by air pollution control equipment. The
captured liquid cannot be reused and is discharged for treatment.
Treatment of Rubber Industry Waste 1239
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
Subcategory 10: Latex-Dipped, Latex-Extruded, and Latex-Molded Goods
These three processes involve the use of latex in its liquid form to manufacture products. Latex
dipping consists of immersing an impervious male mold or article into the latex compound,
withdrawing it, cleaning it, and allowing the adhering film to air dry. The straight dip process is
replaced by a coagulant dip process when heavier films are desired. Fabric or other items may be
dipped in latex to produce gloves and other articles. When it has the required coating, the mold is
leached in pure water to improve physical and electrical properties. After air drying, the items
are talc-dusted or treated with chlorine to reduce tac kiness. Water is often used in several
processes, for makeup, cooling, and stripping. Products from dipping include gloves, footwear,
transparent goods, and unsupported mechanical goods.
Latex molding employs casts made of unglazed porcelain or plaster of paris. The molds are
dusted with talc to prevent sticking. The latex compound is then poured into the mold and
allowed to develop the required thickness. The mold is emptied of excess rubber and then oven
dried. The mold is removed and the product is again dried in an oven. Casting is used to
manufacture dolls, prosthetics, printing matrices, and relief maps.

Subcategory 11: Latex Foam
No latex foam facilities are known to be in operation at this time.
30.1.2 Wastewater Characterization
The raw wastewater emanating from rubber manufacturing plants contains toxic pollutants that
are present due to impurities in the monomers, solvents, or the actual raw materials, or are
associated with wastewater treatment steps. Both inorganic and organic pollutants are found in
the raw wastewater, and classical pollutants may be present in significant concentrations.
Wastewater from reclaimed rubber manufacturing had 16,800–63,400 mg/L total solids,
1000–24,000 mg/L suspended solids, 3500–12,500 mg/L BOD (biochemical oxygen
demand), 130– 2000 mg/L chlorides, pH of 10.9–12,2, wile wastewater s from synthetic
rubber manufacturing had 1900– 9600 mg/L total solid, 60–3700 mg/L suspended solids,
75–1600 mg/L BOD, and pH of 3.2– 7.9 [3].
Table 3 presents an industry-wide profile of the concentration of toxic pollutants found at
facilities in each subcategory (no data are available for Subcategories 9, 10, and 11). Table 4
gives a subcategory profile of the pollutant loadings (no data are available for Subcategories 8,
10, and 11). These tables were prepared from available screening and verification sampling data.
The minimum detection limit for toxic pollutants is 10 mg/L and any value below 10 mg/Lis
presented in the following tables as BDL, below detection limit.
In-plant management practices may often control the volume and quality of the treatment
system influent. Volume reduction can be attained by process wastewater segregation from
noncontact water, by recycling or reuse of noncontact water, and by the modification of plant
processes. Control of spills, leakage, washdown, and storm runoff can also reduce the treatment
system load. Modifications may include the use of vacuum pumps instead of steam ejectors,
recycling caustic soda solution rather than discharging it to the treatment system, and
incorporation of a more efficient solvent recovery system.
30.1.3 Tire and Inner Tube Manufacturing
The tire and inner tube manufacturing industry has several potential areas for wastewater
production, but water recycle is used extensively. The major area for water use is in processes
1240 Taricska et al.
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.

Table 3 Concentrations of Toxic Pollutants Found in the Rubber Processing Industry by Subcategory, Verification, and Screening
Toxic pollutants (mg/L)
Tire and inner tube manufacturing
Treatment influent Treatment effluent
Number of
samples Average Median Maximum
Number of
samples Average Median Maximum
Metals and Inorganics
Chromium 1 10 1 BDL
Copper 1 BDL 0
Lead 2 25 50 0
Zinc 5 260 150 770 1 330
Phenols
2,4,6-Trichlorophenol 0 1 ,14
Aromatics
Toluene 0 1 ,10,000
Halogenated aliphatics
1,2-Trans-dichloroethylene 0 1 16
Methylene chloride 0 2 ,5,000 ,10,000
Trichloroethylene 0 1
a
40
Pesticides and metabolites
Isophorone 0 1 BDL
Emulsion crumb rubber manufacturing
Metals and Inorganics
Cadmium 2 46 90 1 BDL
Chromium 5 230 250 720 2 140 220
Copper 1 200 0

Lead 1 390 0
(continues)
Treatment of Rubber Industry Waste 1241
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
Table 3 Continued
Toxic pollutants (mg/L)
Tire and inner tube manufacturing
Treatment influent Treatment effluent
Number of
samples Average Median Maximum
Number of
samples Average Median Maximum
Mercury 3 BDL BDL BDL 3 BDL BDL BDL
Nickel 2 380 590 1 400
Selenium 1 20 1 ,24
Zinc 3 100 BDL 290 2 BDL BDL
Phthalates
Bis(2-ethylhexyl)phthalats 3 310 260 530 3 250 200 430
Dimethyl phthalate 1 11 2 BDL 14
Nitrogen compounds
Acrylonitrile
b
4 BDL BDL 4 BDL
Phenols
2-Nirophenol 1 BDL 1 BDL
Phenol 3 180 57 440 3 30 19 37
Aromatics
Acenapthene
c
1 BDL 1 BDL

Acenapthylene
c
1 BDL 1 BDL
Benzene
Benzopyrene
c
Ethylbenzene
Napthalene
c
Toluene
Halogenated aliphatics
Dichlorobromoethane 1 .3,100 1 BDL
Emulsion crumb rubber manufacturing
1242 Taricska et al.
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
Carbon tetrachloride 1 BDL 1 BDL
Chloroform 3 130 100(c) 270 2 BDL BDL
1,1-Dichloroethane 1 BDL 1 BDL
1,2-Dichloroethane 1 93 0
1,2-Trans-dichloroethylene 1 16 0
Methylene chloride 3 29 15 73 3 220 150 520
1,1,2,2-Tetrachloroethane 1 BDL 1 BDL
Solution crumb rubber manufacturing
Metals and Inorganics
Metals and inorganics
Cadmium 3 31 BDL 90 2 BDL BDL
Chromium 4 350 310 720 3 170 67 410
Copper 3 72 BDL 200 2 BDL 14
Lead 1 390
Mercury 3 BDL BDL BDL 2 BDL BDL

Nickel 1 160 0
Zinc 2 8,100 16,000 1 190,000
Phthalates
Bis(2-ethylhexyl)phthalate 3 260 140 530 3 190 120 430
Dimethyl phthalate 1 BDL 1 BDL
Phenols
Phenol 3 210 180 440 3 15 BDL 37
Aromatics
Acenapthene 1 BDL 1 BDL
Acenapthylene 1 BDL 1 BDL
Benzopyrene 1 BDL 1 BDL
Benzene 3 1,200 50 3,400 3 BDL BDL 10
Ethylbenzene 2 BDL 10 2 BDL 10
Tolunene 4 BDL BDL 10 5 88 BDL 420
(continues)
Treatment of Rubber Industry Waste 1243
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
Table 3 Continued
Toxic pollutants (mg/L)
Tire and inner tube manufacturing
Treatment influent Treatment effluent
Number of
samples Average Median Maximum
Number of
samples Average Median Maximum
Halogenated aliphatics
Carbon tetrachloride 1 35 1 1,400
Chloromethane 1 4,900 1 2,200
Chloroform 2 BDL BDL 2 BDL BDL
1,2-Trans-dichloroethylene

Methylene chloride 2 BDL 15 2 ,260 520
1,1,2,2-Tetrachloroethane 1 BDL 1 BDL
1,1,2,2-Trichloroethane 1 BDL 1 BDL BDL
Trichloroethylene 1 BDL 1 BDL
Pesticides and metabolites
Acrolein 1 BDL 1 BDL
General molding, extruding, and fabricating
Metals and Inorganics
Lead 1 20 0
Mercury 0 1 BDL
Zinc 0 1 970
Phthalates
Bis(2-ethylhexyl)phthalate 1 17 2 BDL 16
Di-n-butyl phthalate 0 1 36
Nitrogen compounds
N-nitrosodiphenylamine 2 35 53 0
Solution crumb rubber manufacturing
1244 Taricska et al.
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
Phenols
Pentachlorophenol 1 BDL 0 12,000
Phenol 0 1
Aromatics
Benzene 0 1 BDL
Halogenated aliphatics
Chloroform 1 25 2 BDL 10
1,1-Dichloroethane 0 1 110
1,2-Dichloroethane 0 1 BDL
1,2-Trans-dichloroethylene 0 1 290
1,1,2,2-Tetrachloroethane 0 1 BDL

1,1,1-Trichloroethane 0 1 7,100
1,1,2-Trichloroethane 0 1 BDL
Trichloroethylane 0 1 1,600
Wet digestion reclaimed rubber
Metals and Inorganics
Cadmium
d
1100
Lead 1 50 0
Zinc
d,e
2 250 350 0
Nitrogen compounds
Phenol
e
1 BDL 0
Pesticides and metabolites
Isophorone
e
1 BDL 0
Analytic methods: V.7.3.29, Data sets 1,2.
BDL, below detection limit.
a
40 mg/L of trichloroethylene also measured in city water.
b
Detection limit of acrylonitrile by direct aqueous injection was 2300 mg/L.
c
This value believed to be a glassware contaminant.
d
These pollutants appear to be attributed to tire operation.

e
Wastewater is from both tire and reclaiming processes.
Source: USEPA.
Treatment of Rubber Industry Waste 1245
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
Table 4 Industry Profile of Toxic and Classical Pollutant Loadings, Verification, and Screening Data (Toxic Pollutants Kg/kkg)
Tire and inner tube manufacturing
Treatment influent Treatment effluent
Toxic Pollutants (Kg/Mg)
Number of
samples Average Median Maximum
Number of
samples Average Median Maximum
Toxic metals
Chromium 0 1 0.000005
Copper 1 0.001 0
Lead 1 0.001 0
Zinc 3 0.003 0.004 0.006 1 0.0007
Toxic organics
Phenol 1 BDL 0
Methylene chloride 0 1 BDL
2,4,6-Trichlorophenol 0 1 BDL
Isophorone 1 BDL 1 BDL
Classical pollutants (kg/day)
TSS 4 590 200 2,000 47 270 32 2,400
Oil and grease 8 17 7.2 120 35 7.3 2.1 42
pH, pH units 10 7.6 2.4 9.4 44 7.5 7.5 10.3
Toxic pollutants (kg/Mg) Emulsion crumb rubber manufacturing
Toxic metals
Cadmium 2 0.0004 0.0006 1 0.00001

Chromium 5 2.6 0.003 13 4 3.0 0.0005 12
Copper 1 0.003 0
Lead 1 0.006 0
Mercury 2 0.00003 0.00003 2 0.00002 0.00002
Nickel 2 0.006 0.008 1 0.005
Selenium 1 ,1.0 1 1.3
Zinc 3 0.002 BDL 0.005 2 BDL BDL
1246 Taricska et al.
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
Toxic organics
Bis(2-ethylhexyl)phthalate 3 ,2.4 0.0017 ,7.3 3 ,2.3 0.0016 , 7.0
Dimethyl phthalate 2 0.0002 0.0002 2 0.0001 0.0002
Acrylonitrile 4 BDL BDL BDL 5 ,240 BDL ,1,200
N-nitrosodiphenylamine 1 BDL 1 BDL
2-Nitrophenol 1 ,0.5 1 0.26
Phenol 4 0.75 0.003 3.0 4 ,0.25 0.0004 ,0.98
Benzene 3 0.01 0.0007 0.01 2 0.0003 0.0005
Ethylbenzene 5 , 0.01 BDL ,0.05 4 ,0.001 BDL ,0.005
Nitrobenzene 1 , 0.0004 1 ,0.0004
Toluene 6 ,0.009 0.002 ,0.05 5 ,0.001 0.000001
Carbon tetrachloride 1 0.00001 1 , 0.000002
Chloroform 3 0.14 0.0004 0.40 2 0.04 0.09
1,1-Dichloroethane 1 0.00002 1 ,0.00002
1,1-Trans-dichloroethylene 1 ND 0
1,2-Dichloroethane 1 ND 0
Methylene chloride 3 ,1.3 0.0002 ,3.8 3 ,1.9 0.00007 ,5.7
1,1,2,2-Tetrachloroethane 1 0.00002 1 0.000001
Acenapthene 1 BDL 1 BDL
Acenapthylene 1 BDL 1 BDL
Napthalene 1 BDL 1 BDL

Benzo-pyrene 1 BDL 1 BDL
Dichlorobromomethane 1 ,1.6 1 7.0
Acrolein 1 BDL 1 BDL
Solution crumb rubber manufacturing
Metals and Inorganics
Toxic metals
Cadmium 3 0.01 0.0007 0.04 2 0.5 0.09
Chromium 4 ,4.3 0.0006 ,17 3 ,0.42 0.0004 ,1.3
Copper 3 ,0.09 0.00007 ,0.28 2 ,0.17 ,0.34
Lead 1 0.006 0
Mercury 1 0.00003 1 0.00001
Nickel 1 0.003 0
Zinc 2 0.07 0.14 1 2.0
(continues)
Treatment of Rubber Industry Waste 1247
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
Table 4 Continued
Tire and inner tube manufacturing
Treatment influent Treatment effluent
Toxic Pollutants (Kg/Mg)
Number of
samples Average Median Maximum
Number of
samples Average Median Maximum
Toxic organics
Bis(2-ethylhexyl)phthalate 3 ,1.8 0.007 ,5.4 3 ,2.7 0.006 ,8.1
Dimethyl phthalate 1 0.0001 1 0.00008
Phenol 3 2.4 7.1 3 ,0.25 0.0005 ,0.76
Benzene 4 43 0.0004 130 4 ,0.002 ,0.0001 ,0.007
Ethylbenzene 2 0.00005 0.00005 2 , 0.00001 ,0.00002

Toluene 4 0.001 0.00006 0.004 5 0.003 0.0001 0.007
Carbon tetrachloride 1 0.0003 1 0.0001
Chloroform 2 0.06 0.12 2 0.03 0.06
Methylene chloride 2 0.0001 0.0002 2 0.004 0.007
1,1,2,2-Tetrachloroethane 1 0.004 1 ,0.007
1,1,2-Trichloroethane 1 ,0.0000008 1 , 0.000001
Trichloroethylene 1 ,0.0000008 1 , 0.000001
Acenapthene
Acenapthylene
Benzo-pyrene
Chloromethane 1 0.04 2 0.02 0.02
Acrolein 1 BDL 1 BDL
Classical pollutants (kg/day)
BOD
5
6 2,900 900 15,000 9 200 86 1,100
COD 4 2,300 2,500 4,400 8 310 320 1,200
TSS 4 540 920 1,200 8 270 85 1,100
Oil and grease 3 96 110 130 7 ,25 11 ,92
pH (pH units) 1 9.5 4 6.8 7.5 8.2
Solution crumb rubber manufacturing
1248 Taricska et al.
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
Latex rubber manufacturing
Metals and Inorganics
Toxic metals
Chromium 2 BDL BDL 2 BDL BDL
Zinc 2 BDL BDL 2 BDL BDL
Toxic organics
Bis(2-ethylhexyl)phthalate 1 0.0004 1 ,0.00004

Di-n-butyl phthalate 1 BDL 1 BDL
Acrylonitrile 2 BDL BDL 2 BDL BDL
Pentachlorophenol 1 0.0001 1 ,0.00004
Phenol 1 0.0001 1 ,0.00004
Benzene 1 BDL 1 BDL
Ethylbenzene 3 0.002 BDL 0.006 3 ,0.000007 BDL ,0.00002
Toluene 2 BDL BDL 2 BDL BDL
Methylene chloride 1 BDL 1 BDL
Butylbenzyl phthalate 1 BDL 1 BDL
Napthalane 1 BDL 1 BDL
Classical pollutants (kg/day)
BOD
5
0 5 86 15 340
COD 0 3 120 150 160
TSS 1 640 5 130 12 590
Oil and grease 0 3 2.8 3.2 4.0
pH (pH units) 0 3 10 10 10.0
Toxic pollutants (kg/Mg) General molding, extruding, and fabricating rubber manufacturing
Metals and Inorganics
Toxic metals
Lead 1 0.003 1 0.0001
Zinc 0 1 0.14
Toxic organics
Bis(2-ethylhexyl)phthalate 1 0.002 0 0.005
(continues)
Treatment of Rubber Industry Waste 1249
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
Table 4 Continued
Tire and inner tube manufacturing

Treatment influent Treatment effluent
Toxic Pollutants (Kg/Mg)
Number of
samples Average Median Maximum
Number of
samples Average Median Maximum
Di-n-butyl phthalate 0 1
N-nitrosodiphenylamine 1 0.0007 0
Pentachlorophenol 1 0.00003 0
Phenol 0 1 1.7
Benzene 0 1 0.001
Chloroform 0 1 0.0003
1,1-Dichloroethane 0 1 0.02
1,1-Trans-dichloroethylene 0 1 0.04
1,2-Dichloroethane 0 1 0.0006
Tetrachloroethylene 0 1 0.0006
1,1,1-Trichloroethane 0 1 1.0
1,1,2-Trichloroethane 0 1 0.0002
Trichloroethylene 0 1 0.23
Analytic methods: V.7.3.29, Data sets 1,2.
BDL, below detection limit.
ND, not detected.
Source: USEPA.
General molding, extruding, and fabricating rubber
1250 Taricska et al.
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
requiring noncontact cooling. The general practice of the industry is to recirculate the majority
of this water with a minimal blowdown to maintain acceptable concentrations of dissolved
solids. Another water use area is contact water used in cooling tire components and in air
pollution control devices. This water is also recirculated. Steam condensate and hot and

cold water are used in the mol ding and curing areas. The majority of the water is recycled back
to the boiler or hot water tank for use in the next recycle. Soapstone areas and plant and
equipment cleanup are the final water use areas. Most facilities try to recycle soapstone solution
because of its high solids content. Plant and equipment cleanup water is generally sent to the
treatment system. Table 5 presents a summary of the potential wastewater sources for this
subcategory.
Grease, oils, and suspended solids are the major pollutants within this industry. Organic
pollutants, pH, and temperature may also require treatment. The organics present are due
generally to poor housekeeping procedures.
30.1.4 Emulsion Crumb Rubber Production
In-process controls for the reduction of wastewater flows and loads for emulsion crumb rubber
plants include recycling of finishing line wastewaters and steam stripping of heavy monomer
decanter wastewater. Recycling of finishing line wastewater occurs at nearly all emulsion crumb
plants with the percent recycle depend ing primarily upon the desired final properties of the
crumb. Approximately 75% recycle is an achievable rate, with recycle for white masterbatch
crumb below this level and that for black masterbatch crumb exceeding it.
Organic toxic pollutants found at emulsion crumb rubber plants come from the raw
materials, impurities in the raw materials, and additives to noncontact cooling water. BOD,
COD, and TSS levels may also reach high loadings.
Table 5 Summary of Potential Process-Associated Wastewater Sources from the Tire and Inner
Tube Industry
Plant area Source
Nature and origin of
wastewater contaminants
Oil storage Runoff Oil
Compounding Washdown, spills, leaks,
discharges from wet air
pollution equipment
Solids from soapstone dip tanks; oil from seals
in roller mills; oil from solids from Banbury

seals; solids from air pollution equipment
discharge
Bead, tread, tube
formation
Washdown, spills, leaks Oil and solvent-based cements from the
cementing operation; oil from seals in roller
mills
Cord and belt
formation
Washdown, spills, leaks Organics and solids from dipping operation;
oil from seals, in roller mills, calenders, etc.
Green tire painting Washdown, spills, air
pollution equipment
Organics and solids from spray-painting
operation; soluble organics and solids from
air pollution equipment discharge
Molding and curing Washdown, leaks Oil from hydraulic system; oil from presses
Tire finishing Washdown, spills, air
pollution equipment
Solids and soluble organics from painting
operations; solids from air pollution
equipment discharge
Source: USEPA.
Treatment of Rubber Industry Waste 1251
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
Table 6 lists potential wastewater sources and general wastewater contaminants for the
emulsion crumb rubber industry.
30.1.5 Solution Crumb Rubber Production
Solution crumb rubber production plants have lower raw wastewater loads than emulsion crumb
plants because of the thorough steam stripping of product cement to remove solvent and permit

effective coagulation. Recycling in this industry is comparable to that in the emulsion crumb
industry, with about 75% o f the wastewater being recirculated.
Toxic pollutants found in the wastewater streams are normally related to solvents and
solvent impurities, product additives, and cooling water treatment chemicals. Table 7 presents a
listing of the potential wastewater sources and the associated contaminants for this industry.
30.1.6 Latex Rubber Production
No in-process contact water is currently used by the latex rubber industry. No raw material
recycling is practised because of poor control of monomer feeds and the buildup of impurities in
the water.
Organic toxic pollutants and chromium are present in the raw wastewater and normally
consist of raw materials, impurities, and metals used as cooling water corrosion inhibitors.
Table 8 presents potential wastewater sources and general contaminants for this industry.
30.1.7 General Molding, Extruding, and Fabricating Rubber Plants
Toxic pollutants resulting from production proce sses within this industry are generally the result
of leaks, spills, and poor housekeeping procedures. Pollutants include organics associated with
the raw materials and lead from the rubber curing process.
Table 6 Summary of Wastewater Sources From Emulsion Crumb Rubber Production Facilities
Processing unit Source Nature of wastewater contaminants
Caustic soda
scrubber
Spent caustic
solution
High pH, alkalinity, and color. Extremely low average
flow rate
Monomer recovery Decant water layer Dissolved and separable organics. Source of high BOD
and COD discharges
Coagulation Coagulation liquor
overflow
Acidity, dissolved organics, suspended and high dissolved
solids, and color. High wastewater flow rates relative to

other sources
Crumb dewatering Crumb rinse water
overflow
Dissolved organics, and suspended and dissolved solids.
Source of highest wastewater volume from emulsion
crumb rubber production
Monomer strippers Stripper cleanout
rinse water
Dissolved organics, and suspended and dissolved solids.
High quantities of uncoagulated latex
Tanks and reactors Cleanout rinse
water
Dissolved organics, and suspended and dissolved solids.
High quantities of uncoagulated latex
All plant areas Area washdowns Dissolved and separable organics, and suspended and
dissolved solids
Source: USEPA.
1252 Taricska et al.
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
30.1.8 Rubber Reclamation
Wastewater effluents from this subcategory contain high levels of toxic organic and inorganic
pollutants. These pollutants generally result from impurities in the tires and tubes used in the
reclamation process. The wastewater from the pan process is of low volume [0.46 m
3
/kkg (56 gal/
1000 lb)], but is highly contaminated, requiring treatment before discharge. The mechanical
reclaiming process uses wateronly to quench the reclaimed rubber, but ituses a much higher quantity
(1.1 m
3
/kkg). Steam generated from the quenching process is captured in a scrubber and sent to the

treatment system. Wet digestion uses 5.1 m
3
of water per kkg (610 gal/1000 lb) of product in
processing, of which 3.4 m
3
/kkg (407 gal/1000 lb) of product is used in air pollution control.
30.1.9 Latex-Dipped, Latex-Extruded, and Latex-Molded Goods
Wastewater sources in this subcategory are the leaching process, makeup water, cooling water, and
stripping water. Toxic pollutants are present at insignificant levels in the wastewater discharges.
Table 7 Summary of Wastewater Sources From Solution Crumb Rubber Production
Processing unit Source Nature of wastewater contaminants
Caustic soda scrubber Spent caustic solution High pH, alkalinity, and color. Extremely low
average flow rate
Monomer and solvent
drying columns
Water removed from
monomers and solvent
Dissolved and separable organics. Very low
flow
Solvent purification Fractionator bottoms Dissolved and separable organics.
Monomer recovery Decant water layer Dissolved and separable organics.
Crumb dewatering Crumb rinse water
overflow
Dissolved organics, and suspended and
dissolved solids. Source of highest volume
wastewater flow
All plant areas Area washdowns Dissolved and separable organics, and
suspended and dissolved solids
Source: USEPA.
Table 8 Summary of Wastewater Sources From Latex Rubber Production

Processing unit Source Nature of Wastewater contaminants
Caustic soda scrubber Spent caustic solution High pH, alkalinity, and color. Extremely
low average flow rate
Excess monomer stripping Dacent water layer Dissolved and separable organics
Latex evaporators Water removed during
latex concentration
Dissolved organics, suspended and
dissolved solids. Relatively high
wastewater flow rates
Tanks, reactors, and strippers Cleanout rinse water Dissolved organics, suspended and
dissolved solids. High quantities of
uncoagulated latex
Tank cars and tank trucks Cleanout rinse water Dissolved organics, suspended and
dissolved solids. High quantities of
uncoagulated latex
All plant areas Area washdowns Dissolved and separable organics, and
suspended and dissolved solids
Source: USEPA.
Treatment of Rubber Industry Waste 1253
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
30.1.10 Latex Foam
No information is available on the wastewater characteristic s of this subcategory.
30.2 PLANT-SPECIFIC DESCRIPTION
Only two subcategories of the rubber industry have not been recommended as Paragraph 8
exclusions of the NRDC Consent Decree: Wet Digestion Reclaimed Rubber, and Pan,
Mechanical, and Dry Digestion Reclaimed Rubber. Of these two, plant specific data are
available only for the latter. Of the nine remaining subcategories, plant-specific information is
available only for Emul sion Crumb Rubber and Solution Crumb Rubber, and is presented below.
Two plants in each subcategory are described. They were chosen as representative of their
subcategories based on available data.

Plant 000012 produces 3.9 Â 10
4
kkg/year (8.7 Â 10
7
lb/year) of emulsion crumb
rubber, primarily neoprene. The contact wastewater flow rate is approximately 8.45 m
3
/day
(2.25 Â 10
3
gpd) and includes all air pollution control equipment, sanitary waste, maintenance
and equipment cleanup, and direct contact wastewater. The treatment process consists of
activated sludge, secondary clarification, sludge thickening, and aerobic sludge digestion.
Noncontact wastewater, with a flow rate of approximately 1.31 Â 10
5
m
3
/day (3.46 Â 10
7
gpd),
is used on a once-through basis and is returned directly to the river source. Contact wastewa ter is
also returned to the surface stream after treatment.
Plant 000033 produces three types of emulsion crumb rubber in varying quantities.
Styrene butadiene rubber (SBR) forms the bulk of production, at nearly 3.7 Â 10
5
kkg/year
(8.2 Â 10
8
lb/year), with nitrile butadiene rubber (NBR) and polybutadiene rubber (PBR)
making up the remainder of production [4.5 Â 10

3
kkg/year (1.0 Â 10
7
lb/year) and
4.5 Â 10
3
kkg/year, respectively]. Wastewater consists of direct contact process water,
noncontact blowdown, and noncontact ancillary water. The total flow of contact water is
approximately 1.27 Â 10
4
m
3
/day (3.355 Â 10
6
gpd), and the total flow of noncontact water is
340.4 m
3
/day (9 Â 10
4
gpd). Treatment of the wastewater consists of coagulation, sedimen-
tation, and biological treatment with extended aeration. Treated wastewater is discharged to a
surface stream.
Tables 9 and 10 present plant-specific toxic pollutant data for the selected plants.
Table 11 gives plant-specific classical pollutant data, including BPT regulations set for each
specific plant.
30.2.1 Solution Crumb Rubber Production
Plant 000005 produces approximately 3.2 Â 10
4
kkg/year (7.0 Â 10
7

lb/year) of isobutene–
isopropene rubber. Wastewater generally consists of direct processes and MEC water. Contact
wastewater flow rate is approximately 1040 m
3
/day (2.75 Â 10
5
gpd), and noncontact water
flows at about 327 m
3
/day (8.64 Â 10
4
gpd). Treatment consists of coagulation, flocculation,
and dissolved air flotation, and the treated effluent becomes part of the noncontact cooling
stream of the onsite refinery.
Plant 000027 produces polyisop rene crumb rubber [4.5 Â 10
4
kkg/year (1.0 Â 10
8
lb/
year)] polybutadiene crumb rubber, and ethylene-propylene-diene-terpolymer rubber [EPDM;
4.5 Â 10
4
kkg/year (1.0 Â 10
8
lb/year)]. Wastewater consists of contact process water,
MEC, cooling tower blowdown, boiler blowdown, and air pollution control. Wastewater is
produced at about 12,100 m
3
/day (3.2 Â 10
6

gpd). Treatment consists of API separators,
sedimentation, stabilization, and lagooning, followed by discharge to a surface stream.
1254 Taricska et al.
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
Tables 12 and 13 show plant specific toxic pollutant data for the above plants. Classical
pollutant data and BPT regulations are presented in Table 14.
30.2.2 Dry Digestion Reclaimed Rubber
A data summary for plant 000134 is given in Table 15. Production, wastewater flow, and
treatment data are currently not available for a plant within this subcategory.
30.3 POLLUTANT REMOVABILITY
In this industry, numerous organ ic compounds, BOD, and COD are typically found in plant
wastewater effluent. Industrywide flow and production data show that these pollutants can be
reduced by biological treatment. In emulsion crumb and latex plants, uncoagulated latex
contributes to high suspended solids. Suspended solids are produced by rubber crumb fines and
include both organic and inorganic materials. Removal of such solids is possible using a
combination of coagulation/flocculation and dissolved air flotation.
Solvents, extender oils, and insoluble monomers are used throughout the rubber industry.
In addition, miscellaneous oils are used to lubricate machinery. Laboratory analysis indicates
the presence of oil and grease in the raw wastewater of these plants. Oil and grease entering the
wastewater streams are removed by chemical coagulation, dissolved air flotation, and, to some
extent, biological oxidation.
Table 9 Plant-Specific Verification Data for Emulsion Production Plant 000012
Local in process line
Pollutant
Stripper
decant
Spray wash
water
Treatment
influent

Treatment
effluent
Raw intake
water
Toxic pollutant (mg/L)
Cadmium , 1 ,1 ,2 ,1 ,1.0
Mercury 1.5 1.7 2.5 1.6 1.5
Nickel 60 690 610 400 ,10
Bis(2-ethylhexyl)phthalate 290 490 260 ,230 260
Dimethyl phthalate ,14 ,14 ,14 ,14 ,16
N-nitrosodiphenylamine 1.5 , 1.0 5.2 ,2.0 ,1.0
Phenol 19 29 41 19 ,2
Nitrobenzene ,30 ,30 ,30 ,30 , 30
Toluene 70 ,0.5 250 ,0.5 ,0.5
Carbon tetrachloride 41 0.1 4.7 ,0.2 0.3
Chloroform 110 14 27 4.1 8.5
1,1-Dichloroethylene 51 ,1.7 ,1.7 ,1.7 ,1.7
Methylene chloride 4.8 1.0 ,0.1 1.0 ,0.1
Tetrachloroethylene ,0.1 ,0.1 1.4 , 0.1 ,0.1
1,1,1-Trichloroethane ,1.6 0.3 ,1.1 0.3 0.2
Analytic methods: V.7.3.29, Data set 2.
Flow rate (cu. m/day): contact ¼ 8.45; noncontact ¼ 131,000.
Source: USEPA.
Treatment of Rubber Industry Waste 1255
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
Table 10 Plant-Specific Verification Data for Emulsion Crumb Rubber Production Plant 000033
Location in process line
Pollutant (mg/L)
SBR
stripper

Finishing
comp.
NBR
finishing
Treatment
influent
Treatment
effluent
NBR
decant
Raw intake,
well
Raw intake,
river
Cadmium ,180 ,140 40,2 , 1 ,1
Chromium 6 400 20 250 220 10 6 5
Copper 71 80 ,1 1,400 410 ,11 ,1
Mercury 0.8 63 2.2 3.2 3.1 0.7 0.6
Selenium ,4 ,30 ,6 ,20 ,25 ,6 ,4 ,4
Bis(2-ethylhexyl)phthalate ,350 ,210 ,170 ,130 ,130 ,120 ,110 ,110
Acrylonitrile ,26 ,23 94 32 ,23 48,000 ,23 ,23
2-
Nitrophenol ,4 ,4 ,17 ,10 ,5 ,5 ,4 ,4
Phenol 41 67 32 61 ,20 ,16 10 ,3
Ethylbenzene ,38 ,0.1 ,0.1 ,0.1 ,0.1 , 23 ,0.1 ,0.1
Toluene , 0.1 ,0.1 ,0.1 ,0.1 ,0.1 , 25 ,0.1 ,0.1
Chloroform 1.5 2.5 5.2 8.3 1.8 37 1.2 41
Dichlorobromomethane ,0.3 ,0.1 ,0.5 ,0.3 ,0.1 5.2 ,0.1 6.2
Methylene chloride ,110 ,0.1 ,80 ,67 ,110 180 ,2 , 2
Analytic methods: V.7.3.29, Data set 2.

Flow rate (cu.m/day): SBR–contact ¼ 10,200, noncontact ¼ 190; NBR–contact ¼ 1,250, noncontact ¼ 75.7; PBR–contact ¼ 1,250, noncontact ¼ 75.7; Total–contact ¼ 12,700,
noncontact ¼ 340.
Source: USEPA.
1256 Taricska et al.
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.
Wastewater sampling indicates that toxic pollutants found in the raw wastewater can be
removed. Biological oxidation (activated sludge) adequately treats all of the organic toxic
pollutants identified in rubber industry wastewater streams. Significant removal of metals was
also observed across biological treatment. The metals are probably absorbed by the sludge mass
and removed with the settled sludge. Treatment technologies currently in use are described in the
following subcategory descriptions.
30.3.1 Emulsion Crumb Rubber Plants
There are a total of 17 plants in the United States producing emulsion-polymerized crumb
rubber. Five of these plants discharge to POTWs; 10 discharge to surface streams; one plant
discharges to an evaporation pond; and one plant employs land application with hauling of
settled solids. Of the five plants discharging to POTWs, four pretreat using coagulation and
primary treatment and one employs equalization with pH adjustment. All 10 of the plants
discharging to surface streams employ biological waste treatment ranging from conventional
activated sludge to nonaerated wastewater stabilization lagoons.
Organic pollutants are generally found to be reduced to insignificant levels (,10 mg/L)
by biological treatment. Most metals are also found to be reduced across biological treatment;
they are generally at very low levels in the treated effluent. However, significant metal
concentrations may be found in some treated effluent.
At emulsion crumb rubber facilities, a well-operated biological treatment facility permits
compliance with BPT limitations and reduces organic toxic pollutant levels. Toxic metals that
may not be reduced include chromium, cadmium, copper , selenium, and mercury. Tables 16
and 17 show pollutant removal efficiencies at two emulsion crumb plants.
Table 11 Plant-Specific Classical Pollutant Data for Selected Emulsion Crumb Rubber Production
Plants, Verification Data
Waste load, plant 000012

Parameter Influent Effluent BPT regulation
BOD
5
1,200 (2,600) 5.0 (11) 44 (97)
COD 2,100 (4,600) 130 (280) 880 (1,900)
TSS 8 (18) 35 (77) 71 (160)
Oil and grease ,8(,18) 8 (18) 18 (39)
pH (pH units) 6 to 9
Phenol 0.014 (0.03) 30 (67)
Waste load, plant 000033
BOD
5
2,700 (5,900) 140 (320) 460 (1,000)
COD 8,600 (19,000) 2,700 (5,900) 9,200 (20,000)
TSS 2,100 (4,700) 240 (540) 750 (1,700)
Oil and grease 240 (530) 140 (310) 180 (410)
pH (pH units) 6 to 9
Phenol 4.8 (10.5) 0.35 (0.75)
Analytic methods: V.7.3.29, Data set 2.
Blanks indicate data not available.
Source: USEPA.
Treatment of Rubber Industry Waste 1257
Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved.