Waste activated sludge remediation of metal-plating effluents

Abstract

Waste activated sludge is capable of binding and removing metal ions from solution. Sludge was exposed to an industrial metalplating effluent, containing a range of heavy metals, in order to assess its bioadsorptive capacity. Experiments were conducted in fully mixed reactors on a batch basis. Greatest affinity was shown for the Zn cation which consistently proved to be present i n untreated waste water samples in the highest concentration. Although Zn dominated the forward adsorption reaction, ionic competition amongst the other metals analysed showed Cr3+ and Cu to be the most weakly bound, often displaced to the soluble phase by other metal contaminants. Three agents viz., HCl, H2SO4 and NaCl, were assessed for their ability to desorb immobilised metals from the surface of the sludge biomass. Based upon performance and cost, H 2SO4 showed greatest potential for further experimentation and process optimisation. This study shows that waste activated sludge, with further process optimisation, is suitable as a bioadsorbent material for the remediation of metal-plating effluents.

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