Pilot Plant Studies of Copper, Zinc, and Trivalent Chromium Removal by Adsorbing Colloid Foam Flotation

摘要

Design parameters were considered for adsorbing colloid foam flotation (ACFF) for treating metal finishing industry wastewaters. Combinations of copper, zinc, and chromium (III) were studied, as well as the effects of pH, hydraulic loading rate, coagulant and surfactant doses, ionic strength, and air flowrate on metal removal. These data led to the development of mathematical expressions relating coagulant dose with metal removal. The study results indicated that ACFF is a feasible method for treating heavy metal-bearing wastewaters. Coagulant doses of about 100 mg/liter lowered metal concentrations from 20 mg/liter at optimum pH (7.0-7.6) and low ionic strength (below 0.05), to 0.1-0.5 mg/liter. Hydraulic loadings up to 15 cu m per sq m per hour. Economic analysis of the ACFF process indicated it to be less expensive than alkaline precipitation. The ACFF process found to be simple and rapid, requiring low space and energy for operation, and yielding small concentrated sludge volumes. The low residual metal levels consistently achieved were below currently mandated regulatory effluent standards, as well as the 1984 BAT-equivalent guidelines.