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 wastewaters 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 .
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 pg/L and any value below 10 pg/L is 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.
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