Sources Of Cadmiumbearing Wastewaters

Because the largest consumption of cadmium (60%) is for plating, performed in aqueous baths, there is a drag-out of plating chemicals from the plating bath to the following rinse bath. The amount of drag-out is a function of the size of the article being plated, its intricacy, the presence of blind holes, and the duration of pause to drip over the plating tank.

Cadmium is a by-product of zinc production and is a valuable source of revenue for the zinc smelter. During zinc smelting, evolved cadmium fumes are collected. Consequently, if the gases from electric furnaces, autobody incineration, and certain domestic products are water scrubbed, cadmium is found in the scrubbing water. Whenever zinc or brass is electroplated, the drag-out also contains cadmium, as these plating tanks serve as cadmium concentrators.

In the manufacture, incineration, and careless disposal of primary cells, there is cadmium loss.

The 1962 USPHS Drinking Water Standards set a cadmium limit of 0.01 mg/l. The toxicity of cadmium and certain disease manifestations necessitate treatment of waste-waters containing cadmium to reduce treated effluent concentration to the level of 0.01 mg/l.

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