Removal of Heavy Metals Contained in Sewage Sludges Using Thiobacillus Ferrooxidans and Thiobacillus Thiooxidans

The removal of heavy metals from sewage sludges is a problem that is exigent to be solved. Bioleaching is a new method for removing heavy metals from sewage sludges. It is considered to be an effective method with low costs and without causing secondary pollution. In this study, bioleaching method was applied to leach metals such as Cu, Zn, Mn, Cr and Cd contained in sewage sludges. Firstly, thiobacillus ferrooxidans (T.f) and thiobacillus thiooxidans (T.t) were obtained from a hot spring containing sulphur after a series of cultivating, separating and purifying. Then, the leach characteristics of T.f and T.t were investigated at different levels of substrate respectively and the influences of some basic factors such as substrate concentration, sludge concentration and initial pH on removal of heavy metals during bioleaching were studied. The results show that the efficiency of removing heavy metals of T.f is better than T.t and most of the heavy metals contained in sewage sludge can be effectively removed by T.f and T.t.