Carbon source and electro-stimulation modulates performance, microbial ecology, and metabolism in U (VI) bioreduction systems

The uranium (U(VI)) removal performance and associated U(VI) metabolism mechanisms of uranium reduction systems under different carbon sources and electro-stimulation remain unknown. This study developed organic carbon-dependent biostimulation (ODB) and electrode-dependent biostimulation (EDB) systems to investigate the effects of three carbon sources (sodium acetate, glucose, and lactate) and electrodes on U(VI) removal performance, metabolic products, and ecological structures in bioreactors. Bioreactors in different systems exhibited significant differences in uranium removal rates, organic substrate consumption rates, and electrochemical properties. Glucose was the most effective carbon source, but sodium acetate could serve as an alternative electron donor in EDB system. Different biostimulation strategies induced microbial communities to evolve into distinct ecological structures with varying metabolic patterns. However, all ecological structures effectively reduced U(VI) and enhanced electron transfer capabilities. This study provides valuable insights into enhancing the bioremediation of uranium mine wastewater and facilitating uranium recovery.