Impact of Electron Donor and Other Factors on in-Situ Biosequestration of Uranium.

In-situ biosequestration for treatment of uranium contaminated groundwater is a current focus of research. Electron donor substrates are introduced to enhance microbial-associated reduction of uranium from its soluble form U(VI) to its less labile form U(IV). A pilot-scale test of in-situ biosequestration for uranium in groundwater is in progress at a former uranium mining site in Monument Valley, Arizona. Complementary miscible-displacement experiments were conducted to examine the impact of different electron donors on the effectiveness of biosequestration. In addition, the impact of co-occurring contaminants such as nitrate and sulfate was examined. Columns were packed with aquifer sediments collected form the site. Groundwater collected from the site was used as the background solution for all experiments. Comparison between four electron donors revealed that uranium biosequestration in the column was more effective under ethanol injection than acetate, glucose, and benzoate. In addition, ethanol was the most effective at stimulating microbial reduction of nitrate and sulfate. The impact of different concentrations of nitrate and sulfate on U sequestration was also examined.