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

Laurent J., Pierra M., Casellas M., Dagot C.

Environment Protection Engineering

2009

Vol. 35, nr 3

5-15

The 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 floc disintegration and macrofloc deflocculation. The uptake of the two metals by sludge flocs was improved with an increase in temperature. Both metals were in a different way adsorbed by sludge flocs, since mass transfer improvement together with the extended surface area offered by sonicated flocs increased the cadmium adsorption. At the same time, an increase in soluble organic ligands limited copper uptake.

Impact of activated sludge flocs properties after sonication in relation with heavy metal uptake

Laurent J., Casellas M., Dagot C.

Archives of Environmental Protection

2008

Vol. 34, no. 3

229-238

The effects of activated sludge sonication on floes surface properties and heavy metal uptake was investigated. Negative surface charge and specific surface area were estimated by correlation with dye adsorption whereas relative hydrophobicity was measured by adhesion to hexadecane. Experimental results show that ultrasound treatment leads to a simultaneous increase of specific surface area and availability of negatives and/or hydrophilic sites. Thus, fixation sites for heavy metal uptake are made free by sonication. Both increase of specific surface area and fixation sites availability leads to an increase of uptake of Cd(II). For Cu(II), organic matter released in soluble phase during the treatment acts as a ligand and limits adsorption on floes surface.