Acute toxicity of chrome electroplating wastes to microorganisms: adsorption of chromate and chromium(VI) on a mixture of clay and sand

Chrome electroplating wastes were collected from two industrial sites and analyzed for color, turbidity, pH, alkalinity, sulfate, chloride, N-ammonia, N-nitrate, N-nitrite, acid hydrolyzable P, dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, chromate and chromium(VI). The effect of these wastes on saprophytic and nitrifying bacteria was studied with varying concentrations of the waste using sucrose substrate as a source of C chain for microorganisms. The use of clay sand mixtures as adsorbents for chromate and chromium(VI) was investigated. Mixtures high in clay content were found to be suitable media for the removal of Cr from the wastes. The clay used was characterized by determination of the following parameters: pH, electrical conductivity, water soluble salts, osmotic pressure, cation exchange capacity, CaCO₃ and organic matter.