Abstract:Lots of heterotrophic bacteria died after sewage sludge bioleaching. The exploration of microbial communities using scanning electron microscopy and transmission electron microscopy illustrated that the bacteria distribution in bioleaching sludge was more intensive than that in the control sludge, and the rod-shaped and short rod-shaped bacteria appeared to increase with the extension of time. The damaged bacteria cell and residual cell without intracellular matter emerged at the anaphase of bioleaching. The weight percentage of extracellular polymeric substances (EPS) in the sludge leachate increased after bioleaching. The EPS ratio of loosely bound fraction to tightly bound fraction exhibited an upward trend followed with a downward trend, which indicated that large quantities of bacteria were at accelerated growth phase during the prophase of bioleaching while at deceleration growth phase during the anaphase of bioleaching. The content of heavy metals in the EPS showed a continuous increase after several days of run. The highest content percentages of Cu, Pb and Zn in the EPS with respect to the total sludge content were 14.7%、20.3% and 24.2% respectively. EPS could be hydrolyzed under prolonged bioleaching, resulting in a decrease of heavy metals content in EPS.