The fate of heavy metals during thermal and ultrasound treatment of activated sludge

International audienceThe fate of cadmium and copper during thermal and ultrasound treatments of activated sludge was studied in terms of mixed liquor physicochemical modifications. Biochemical composition of sludge testfied to the solubilization of its biopolymers. Granulometric measurements demonstrated that ultrasound and temperature induced respectively floe disintegration and macrofloc deflocculation. The uptake of the two metals by sludge floes was improved with an increase in temperature. Both metals were in a different way adsorbed by sludge floes, since mass transfer improvement together with the extended surface area offered by sonicated floes increased the cadmium adsorption. At the same time, an increase in soluble organic ligands limited copper uptake