Comparison of Bioleaching of Heavy Metals from Sewage Sludge of Different Solid Concentrations Using Two Inocula

Two 10%(v/v) different inocula, iron-oxidizing bacteria and sulfur-oxidizing bacteria, were used to investigate the bioleaching of heavy metals from sewage sludge with 10-40 g/L sludge concentration in the batch experiment. The results demonstrated that most of bioleaching rates of Zn and Cu achieved above 80% and 60%, respectively, after 12 d in the sludge with different concentrations and inocula. The lower the solid concentration, the higher the removal rate of heavy metals and the quicker the removal speed in sludge. The system with iron-oxidizing bacteria had faster startup speed and was influenced by solid concentration lightly, while in the system with sulfur-oxidizing bacteria, the removal efficiency was affected by concentration seriously.