CHARACTERIZATION OF HEAVY-METAL MOBILE SPECIES IN SEWAGE-SLUDGE FOR AGRICULTURAL UTILIZATION

The determination of the chemical forms and of the bonding of heavy metals in sewage sludge is of great importance in evaluating the potential hazards deriving from the use of this sludge on agricultural land. In this paper two different kinds of sewage sludge which had undergone different treatments were used. A sequential extraction procedure (H2O, KNO3, EDTA) was utilized to determine mobile or mobilizable species of heavy metals, with a view to their agricultural use. The results obtained showed that the total amount of extractable metals was generally lower in the sludge conditioned by CaO and FeCl3 with the exception of Cu. The greatest differences were found in the case of Zn with a mean value of the total extractability of about 60% of the total concentration in the sludge conditioned by AlCl3, and about 1% in that conditioned by CaO and FeCl3.