Synergistic Bioleaching Compound Heavy Metals From Polluted Sediment In Xiangjiang River

The bioleaching experiment was conducted based on the high organic matter, compound heavy metals polluted alkaline sediment in Xiawan port of Zhuzhou city, Hunan province. Several factors including bioleaching pattern, bioleaching microorganism, synergistic combination and bacteria community transformation which affect the bioleaching process were investigated.The study on bioleaching multiple heavy metals from contaminated alkaline sediment by auto and heterotrophic bacteria in successive multibatch method was conducted first. The key factors which inhibit the activation of bioleaching were the high buffering effect and alkalinity of the sediment. Acidophil bacteria cannot proliferate under this environment. Successive multibatch method can solve this problem successfully. Two strains of heterotrophic bacteria isolated from the sediment which can tolerate acid environment and heavy metals have the ability to utilize the dissolved organic matter and reduce the damage of DOM to acidophil bacteria. Heterotrophic bacteria can improve the bioleaching efficiency and shorten the bioleaching time. The results showed substrate combination elemental sulfur and pyrite can be effectively utilized by mesophilic bacteria A.ferrooxidans, A. thiooxidans, L. ferriphilum. In the system adopted batch method and inoculated heterotrophic, the bioleaching efficiency of Zn, Mn, Cu and Cd was94.74%,94%,90.9%,84.2%. The main fraction of Zn, Mn, Cu and Cd after bioleaching are Fe-Mn oxide-associated form, organic associated form, and residual form. The bioleaching effect of As, Pb, Hg was not very good.The mix combination of A. ferrooxidans、A. thiooxidans、L. ferrooxidans has better bioleaching efficiency than single strain one. Elemental sulfur was the main substrate utilized at the early stage of the bioleaching. FeS2would be utilized with the decreasing of pH. The bioleaching efficiency of heavy metals varied in interim and almost identical at the later stage. A. ferrooxidans and A. thiooxidans which possess the S oxidation ability are the dominant bacteria in the early stage and L. ferrooxidans become the dominant one at later stage.The bioleaching period adopted with moderate thermophile S. thermotolerans and A. caldus was shorter than the mesophilic bacteria one. The bioleaching efficiency of mix combination better than single strain one. The substrate S and FeS2can be effectively utilized. A. caldus was the dominant strain during the whole bioleaching process.