Effects of medium composition on the bacterial leaching of metals from digested sludge.

The effects of parameters (soluble iron, K(2)HPO(4), MgSO(4), Ca(NO(3))(2), KCl and (NH(4))(2)SO(4)) on bacterial leaching of heavy metals from anaerobically digested sludge have been studied in a batch process using a strain of Thiobacillus ferrooxidans. The sludge was found to be a deficient iron source. Metal leaching rate was increased proportionally with the ferrous iron. Amendment of the sludge with a nitrogen source increased the metal solubilization efficiency to a very small extent. Addition of phosphate and other nutrients did not show any effect on the microbial leaching rate.