PHYSICOCHEMICAL CHARACTERIZATION OF COMPOST OF THE INDUSTRIAL TANNERY SLUDGE

It is very important that tannery wastes in the form of sludge are managed in anenvironmentally sound manner. This study focused on the heavy metal characterizationand the influence of changing the physico-chemical properties of the mediumthroughout the composting on the concentrations, bioavailability or chemical forms ofCr, Cu, Zn, Pb and Cd in tannery sludge. The physical and chemical properties of thecomposted sludge during treatment show the stability and maturity of end product.Total metal content in the final compost were much lower than the limit values ofcomposts to be used as good soil fertilizer. Furthermore, it was observed in using asequential extraction method in sludge compost at different phases of treatment, that alarge proportion of the heavy metals were associated to the residual fraction (70– 80%)and more resistant fractions to extraction X–NaOH, X–EDTA, X–HNO3 (12–29%).Less than 2% of metals bound to bioavailable fractions X–(KNO3 + H2O). Bioavailablefractions of all elements tend to decrease. Mobile fractions of metals are poorlypredictable from the total content.