Uranium speciation and distribution in Shewanella putrefaciens and anaerobic granular sludge in the uranium immobilization process

The uranium (U) in Shewanella putrefaciens ( S. putrefaciens ) and anaerobic granular sludge (AnGS) were fractionated, and the contents and forms of U in each fraction were investigated. The functional groups of microorganisms for U binding and the deposition of U in microbial aggregates were also analyzed. Four main approaches were found involved in U immobilization, including biosorption/complexation by microbial cells and their extracellular polymeric substances (EPS), non-reductive biomineralization, bioreduction and intracellular accumulation. Results show that non-reductive biomineralization was found to be dominated in the U(VI) immobilization process. Besides, the contribution of EPS to U removal could not be ignored.