12 Treatment of Rubber Industry Wastes Jerry R. Taricska Hole Montes, Inc., Naples, Florida, U.S.A. Lawrence K. Wang Lenox Institute of Water Technology and Krofta Engineering Corporation, Lenox, Massachusetts and Zorex Corporation, Newtonville, New York, 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. 12.1 INDUSTRY DESCRIPTION 12.1.1 General Description The U.S. 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 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 averages) [2]. The effluent limitations are shown as kilogram of pollutants per 1000 kg of raw material processed (kg/kkg). 545 © 2006 by Taylor & Francis Group, LLC presents a summary of the rubber processing industry regarding the number of subcategories and 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 Manufacturing 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. 546 Taricska et al. © 2006 by Taylor & Francis Group, LLC 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 Wastes 547 © 2006 by Taylor & Francis Group, LLC 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 uncured, tires which are then cured in an automatic press. Curing times range from less 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” (277–280 K, 103–206 kPa) or “hot” (323 K, 380–517 kPa) rubber. The cold SBR polymers, produced at the 548 Taricska et al. © 2006 by Taylor & Francis Group, LLC lower temperature and stopped at 60% conversion, have improved properties 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 stripping 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 solution (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 Wastes 549 © 2006 by Taylor & Francis Group, LLC 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 washed 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 caustic 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 removes 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 materials, 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 550 Taricska et al. © 2006 by Taylor & Francis Group, LLC forces the material into a heated mold. The applied force combined 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 rubber are sent on for further processing. The steam condensate 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 Wastes 551 © 2006 by Taylor & Francis Group, LLC 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 tackiness. 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. 12.1.2 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, while wastewaters from synthetic rubber manufacturing had 1900–9600 mg/L total solids, 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. 12.1.3 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 552 Taricska et al. © 2006 by Taylor & Francis Group, LLC 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 Wastes 553 © 2006 by Taylor & Francis Group, LLC 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)phthalates 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 554 Taricska et al. © 2006 by Taylor & Francis Group, LLC [...]... primary treatment for seven of the nine dischargers, equalization for one discharger, and biological treatment for the other plant 12. 3.4 Tire and Inner Tube Manufacturing There are a total of 73 tire and inner tube manufacturing facilities in the United States, of which 39 were placed in operation prior to 1959 Twenty-three of the pre-1959 plants do not treat their wastewaters, and six of these plants... flow rate: 12, 100 cu m/day Source: USEPA Ten of the plants discharging to surface streams employ some form of biological treatment for waste load reduction Two of the plants discharging to surface streams use in- process controls, oil removal, and primary treatment prior to discharge In- process control employed at one plant consists of steam stripping of wastewaters, while in- process control at the second... rubber sheet plant wastewaters [8] A combined algae and water hyacinth system has been used to remove 96.41% COD, 98.93% TKN, 99.28% NH3-N, 100% NO2-N, and 100% NO3-N [9] 12. 5 TREATMENT TECHNOLOGY COSTS The investment cost, operating, and maintenance costs, and energy costs for the application of control technologies to the wastewaters of the rubber processing industry have been analyzed These costs were... Rubber Industry Wastes Latex rubber manufacturing 562 Table 4 Continued General molding, extruding, and fabricating rubber Tire and inner tube manufacturing Treatment in uent Toxic Pollutants (Kg/Mg) Number of samples Di-n-butyl phthalate N-nitrosodiphenylamine Pentachlorophenol Phenol Benzene Chloroform 1,1-Dichloroethane 1,1-Trans-dichloroethylene 1,2-Dichloroethane Tetrachloroethylene 1,1,1-Trichloroethane... emulsion crumb industry, with about 75% of 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 12. 1.6 Latex Rubber Production No in- process contact... 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 m3/kkg (56 gal/ 1000 lb)], but is highly contaminated, requiring treatment before discharge The mechanical reclaiming process. .. USEPA 12. 4 TREATMENT METHODS The treatment methods for ruber wastewaters consist of various biological processes, and physico-chemical processes including coagulation, ozonation, activated carbon adsorption, aeration, sulfonation, chlorination, and aeration, and biological nutrient removal processes The purpose of the treatment is to meet USEPA effluent limitations [4] 12. 4.1 Coagulation Municipal wastewaters... general contaminants for this industry 12. 1.7 General Molding, Extruding, and Fabricating Rubber Plants Toxic pollutants resulting from production processes 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... Occupational Safety and Health Administration SIC Division Structure, http://www.osha.gov/cgi-bin/sic/sicser5, 2003 USEPA Subchapter N – Effluent Guidelines and Standards in CFR Title 40, Protection of Environment; http://www.epa.gov/docs/epacfr40/chapt-I.info/subch-N.htm, 2003 Sechrist, W.D.; Chamberlain, N.S Chlorination of phenol bearing rubber wastes In Proceedings of 6th Industrial Waste Conference, Purdue... Source: USEPA 12. 3.2 Solution Crumb Rubber Plants There are 13 solution crumb rubber plants in the United States Twelve of these plants discharge treated wastewater to surface streams; the other plant discharges its treated wastewater into a neighboring oil refinery’s noncontact cooling water system © 2006 by Taylor & Francis Group, LLC Treatment of Rubber Industry Wastes Table 13 571 Plant-Specific Verification . manufacturing processes in the rubber fabrication industry. General steps for the processes include warming the raw materials, preforming the warm stock into the approximate shape, cooling and treating. 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. 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