BACTERIAL REDUCTION OF SOLUBLE URANIUM - THE FIRST STEP OF IN-SITU IMMOBILIZATION OF URANIUM

The mobility of uranium in groundwater is a problem of considerable ma gnitude. One approach would be to control the distribution of uranium by converting the water-soluble uranium ion to one that is less solubl e. This study focuses on the use of Desulfovibrio gigas, D. baculatus, D. vulgaris, D. desulfuricans, Pseudomonas putida, a denitrifying Pse udomonas strain and mixed cultures from sludge or uranium mill tailing sites for the bioconversion of uranyl, U (VI), to uraninite, U (IV). In general, 82% to 92% of U(VI) was reduced in pure cultures, while 45 % to 99% of added uranium was transformed by diverse bacteria present in groundwater. The oxyanions of selenium and vanadium had little effe ct on the uranium reduction by bacteria, while arsenic and molybdenum at 1.0 mM inhibited reduction of uranium. The product of uranium metab olism was U collected in needle-like crystals. A model is proposed for in situ bioremediation of uranium in groundwater at uranium mill tail ing sites.