STABILISATION AND SPECIATION OF HEAVY METALS IN SEWAGE SLUDGE

Abstract

The potential stabilisation of heavy metals in sludge by microwave and chemical treatments has been demonstrated. The direct microwave treatment of the sewage sludge resulted in some reduction in the EDTA and ammonium acetate extractable metal concentrations and the moisture contents. The treatment of the sludge with zeolite was most effective in reducing the concentrations of the ammonium acetate extractable metals, while treatment with lime was most effective in reducing the concentrations of the EDTA extractable metals. Electrochemical analysis by stripping voltammetry revealed that a substantial amount of the ammonium acetate extractable metals as present in the “bound” or “complexed” forms. The total heavy metal concentrations and the EDTA extracts were determined by atomic absorption spectroscopy.