Treatment of Uranium in Subsurface Water

This study investigates the in-situ treatment of uranium (U) contaminated pond and subsurface water across various Department of Energy and mining sites. The research highlights the challenges presented by dissolved U and high total dissolved solids typically found in hard rock uranium mining. Noteworthy constituents include U and sulfate, with particular attention given to groundwater contamination resulting from in-situ leaching processes in natural porous sandstone deposits, leading to elevated concentrations of U and selenium. A range of chemical treatments were employed to mitigate soluble hexavalent uranium (U[VI]), including pH adjustment, flocculation, phosphate addition, and adsorption using activated red mud, a byproduct from bauxite processing. Geochemical modeling confirmed the feasibility of U[VI] removal through phosphate precipitation and adsorption, while also addressing limitations posed by soluble magnesium sulfate complexes. Laboratory tests corroborated model predictions. Furthermore, the study elucidates the biological reduction of U[VI] to U[IV] under reducing conditions, facilitated by bacterial processes that enhance the precipitation of stable U[IV] minerals. The research emphasizes that a combination of laboratory-scale testing, field studies, and computer simulations is crucial for effective in-situ treatment strategies.