Electrokinetic removal of heavy metals from municipal sewage sludge

Electrokinetic was applied to the studied sludge to remove heavy metals present in sludge under some conditions such as different current levels, preacidification by using different acids, EDTA addition and the mixture of kaolin-sewage sludge. Also in the each of the experimental series, sequential chemical extractions were applied to determine the bioavailability and the fractions of heavy metals during electrokinetic process.The highest removals of Cr, Pb and Zn were 56 %, 39 % and 39 %, respectively. The fractions of heavy metals did not change by different currents, EDTA addition and the mixture of kaolin-sewage sludge. In preacidification by using acetic acid and nitric acid, exchangeable and reducible fractions of heavy metals increased near the anode while oxidisable and residual fractions increased near the cathode. Total cost increased in the experimental applications, which the higher removals of heavy metals were obtained. In the preacidifacition of acedic acid at pH:3 in which the achieved removals of Cr, Pb and Zn were 54 %,37 % and 39%, respectively, total cost was calculated to be 315.3 $/ton dry sludge . On the other hand, in the preacidifacition of nitric acid at pH:3, total cost was calculated to be 171 $/ton dry sludge .