Zinc biosorption by waste activated and digested sludges

Biological matter is known for its ability to biosorb solubilised heavy met al ions to its surface. Experiments were therefore conducted to assess the biosorptive capacity of two waste products of the wastewater treatment indu stry ie., waste activated and waste digested sludge. Surface charge of each was determined in order to relate electronegativity with biosorptive poten tial. Activated sludge was found to be more effective than digested sludge for removal of zinc from a metal plating effluent, viz., 5.9 mg Zn/(g sludg e)(-1) as opposed to 4.0 mg/g, respectively, as well as producing a higher net negative charge. It was also noted that as initial zinc concentrations in solution increased there was a concomitant increase in sludge biosorptio n capacity. Activated and digested sludges were capable of biosorbing zinc from a metal plating effluent although activated sludge showed better poten tial for industrial application. (C) 1999 Published by Elsevier Science Ltd on behalf of the LAWQ. All rights reserved.