Removal of Heavy Metals from Activated Sludge by Bioleaching Method

Abstract:

Native Acidithiobacillus ferrooxidans (A. f) and Acidithiobacillus thiooxidans (A. t) were isolated from excess activated sludge. Mixed and single cultures of them were used to bioleach for 9 days to remove heavy metals from activated sludge. The changes of pH and ORP (Oxidation Reduction Potential) were measured every day. Also, the changes of concentrations for heavy metals were measured. Results showed that the removing rate for mixed culture was the best in all runs. The removing rate for As, Cr, Cu, Ni, Zn is 96.09%, 93.47%, 98.32%, 97.88%, 98.60% respectively. The removing rate of Cd and Pb for mixed culture decreased rapidly after six days. However, the rates of removing Cd and Pb remained higher levels after leaching for 6 days by Acidithiobacillus thiooxidans.