ABSTRACT
Cadmium was sorbed by sludge solids and had the tendency to achieve saturation at equilibrium concentrations above 15 mg/L. Sorption of phenol was relatively low along equilibrium concentrations of up to 10 mg/L, and then sorption substantially increased. Comparing the sorption of cadmium on sludges which have been stabilized at similar levels, a small advantage could be observed for sludge treated by anaerobic digestion. No significant differences between anaerobic and aerobic sludges were found for phenol sorption. The stabilization level appears to be an important factor in the sorption of cadmium and phenol on sludges originating from both aerobic and abaerobic digestion processes. Both contaminants have increased their sorption characteristics as the concentration of dissolved organic matter in the aqueous solution was higher. Phenol, especially, exerted low sorption in low organic solutions and increased significantly its sorption characteristics in the presence of dissolved organics. Soluble organics matter, originating from the sludge, was found as an important factor controlling the sorption of cadmium and phenol by sludge, which released dissolved organic matter proportionally to the stabilization level.
