SMELTING AND REFINING (NONFERROUS METAL MANUFACTURING)
Approximately 7,700,000 Mg (8,470,000 megatons) of wastes are generated per year by the smelting and refining industry. The smelting and refining industry includes primary recovery of usable metal from metal ore, and secondary recovery from scrap metal. Smelting and refining facilities are located throughout the United States, generally close to power sources and ore production sites. Major nonferrous metals that are smelted and refined include copper, lead, zinc, silver, and aluminum. Smelting occurs in two basic steps. The first step is sintering, which agglomerates the particles, drives off volatiles, produces metallic oxides, and removes sulfur as sulfur dioxide. The second step is the reduction process, in which the sinter is smelted further in a blast furnace and then separated into layers that can be processed further for recovery of the metals.
Wastes in the form of slurries or sludges are generated during the first stage of sintering. Cadmium and lead are two metals common to all wastes generated in the nonferrous smelting industry. Other metals found in many waste streams include copper, zinc, silver, aluminum, and hexavalent chromium. Approximately 90 percent of the wastes are stockpiled on-site, 7 percent are used within the plant, and 3 percent are sent to an off-site landfill.5 Table 9 presents concentration ranges for metals found in wastes from various nonferrous metal smelting/refining processes. These wastes include EPA Hazardous Waste Nos. <064, <065, <066, <069, and <100.
PAINT, INK, AND ASSOCIATED PRODUCTS
The two major products of the paint industry sector are 1) exterior/interior paints for buildings and structures; and 2} industrial chenical coatings for automobiles, machinery, and furniture. Other products include varnishes, lacquers, epoxy compounds, adhesives, plastisols, paint removers, and sealants. The principal raw materials used in the manufacture of these products are oils, resins, solvents, and pigments that contain metallic constituents. Plants are centered around populated areas; 45 percent of them are located in five states; California, Ohio, New Jersey, Illinois, and New York.
The ink industry primarily manufactures printing ink. The three main ingredients for ink production are the vehicle, the drying agent, and the pigment. Inks may be of four types: letterpress, which has an oil or varnish base; lithographic, which has a higher concentration of pigments; gravure, which dries through solvent evaporation; and flexographic, which has a solvent or water base. Varnish is also produced by 20 percent of the ink production plants. The production plants are scattered throughout the United States, but 42 percent of them are located in five states: New York, Ohio, New Jersey, California, and Illinois.
In the paint and ink industry, wastewater is generated primarily through tank washes, floor washes, caustic washes, spills, and spoiled batches. An estimated 1.5 million gallons of wastewater is generated daily from these
TADLE 9 CONCENTRATION RANGES FOR METALS IN WASTES FROM TUE SMELTING AND REFINING INDUSTRY3
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