Bioremediation of metal-contaminated industrial effluents using waste sludges

Metal contaminated industrial effluent, from a metal plating company, was exposed to waste activated sludge to optimise the biosorption process at laboratory scale. Metals assessed were Zn²⁺, Cu²⁺, Cd²⁺, Ni²⁺, Cr³⁺ and Cr⁶⁺, of which, Zn²⁺ was most prevalent. Biosorption rates of up to 96% were recorded for Zn²⁺ within the first 15 min., of the reaction, at initial concentrations of 110mg.1⁻¹. Biomass displayed an average adsorptive capacity of 80% at metal concentrations of 50mg.1⁻¹ and above. Both fully mixed and upflow column bioreactors were employed during experimentation, using wet and dried sludge. The findings of this study show that wet sludge, utilised as biosorbent in a fully mixed process, has superior potential for metal ion biosorption from an industrial effluent.