Metals subcategory pollutants concentrations

Each metal subcategory uses different processes and emits different pollutant concentrations and types in the process wastewater. The following paragraphs and tables present information on the wastewater streams for each of the subcategories.2-3... 

Many toxic pollutants were detected in the process wastewaters from metal molding and casting processes. The toxic pollutants detected most frequently in concentrations at or above 0.1 mg/L were phenolic compounds and heavy metals. The pollutants include 2,4,6-trichlorophenol, 2,4-dimethyl-phenol, phenol, 2-ethylhexyl, cadmium, chromium, copper, lead, nickel, and zinc. Each type of operation in the foundry industry can produce different types of pollutants in the wastewater stream. Also, because each subcategory operation often involves different processes, pollutant concentrations per casting metals may vary. 

Pollutant parameters found in the common metals subcategory raw waste stream from sampled plants are shown in Table 9.4. The major constituents shown are parameters, which originate in process solutions (such as from plating or galvanizing) and enter wastewaters by drag-out to rinses. These metals appear in waste streams in widely varying concentrations. 

Concentrations of Pollutants Found in the Common Metals Subcategory of Raw Wastewater... 

Table 9.5 shows the concentrations of pollutant parameters found in the precious metals subcategory raw waste streams. The major constituents are silver and gold, which are much more commonly used in metal finishing industry operations than palladium and rhodium. Because of their high cost, precious metals are of special interest to metal finishers. 

Pollutant parameters and their concentrations found in the oily waste subcategory streams are shown in Table 9.9. The oily waste subcategory for the metal finishing industry is characterized by both concentrated and dilute oily waste streams that consist of a mixture of free oils, emulsified oils, greases, and other assorted organics. Applicable treatment of oily waste streams is dependent on the concentration levels of the wastes, but oily wastes normally receive specific treatment for oil removal prior to solids removal waste treatment. 

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