Masters Theses
Reduction of uranium by Desulfovibrio desulfuricans in high sulfate and nitrate containing solutions
Date of Award
5-1994
Degree Type
Thesis
Degree Name
Master of Science
Major
Environmental Engineering
Major Professor
Gregory D. Reed, Kevin Robinson
Committee Members
R.B. Robinson
Abstract
Biological reduction of uranium has been found to be important in the formation of iron and uranium ore deposits in anaerobic sediments. This discovery forms the basis of a new treatment technology that may be capable of selectively removing uranium from wastewaters. This study evaluated the potential for biological removal of uranium in surrogate solutions containing constituents similar to those found in actual wastewaters.
Batch laboratory experiments were performed to determine the effect of high concentrations of sulfate and nitrate on the removal of uranium by D. desulfuricans. The experiments were performed with sulfate concentrations up to 10,000 mg/L, nitrate concentrations up to 50,000 mg/L, and with uranium concentrations at 100 mg/L. All of the experiments were run in a bicarbonate solution with lactic acid as the carbon source. The reactors were sampled by filtering through a 0.2 micron filter. The filtrate was stored in a 4°C cooler until it was analyzed. The samples were analyzed for uranium, sulfate, and/or nitrate as required. Combined nitrate/sulfate solutions were tested for any significant changes in the rate of uranium removal.
In test reactors containing 100 mg/L uranium and <5,000 mg/L sulfate, uranium was removed to <0.1 mg/L in approximately one day. Results of a 10,000 mg/L sulfate solution experiment demonstrated a slight drop in the rate of uranium removal. A more significant decline in the rate of removal was observed in all of the sulfate reactors containing lower initial concentration of uranium. In test reactors containing <10,000 mg/L nitrates, uranium was removed to <0.1 mg/L within one day. At 50,000 mg/L nitrate, uranium removal occurred more slowly. In the combined nitrate/sulfate solutions, the D. desulfuricans removed uranium from 100 mg/L to <0.1 mg/L within one day in the reactors containing <5,000 mg/L nitrate. In the reactors containing 50,000 mg/L nitrate, uranium removal to <1 mg/L occurred over 10 days. These results were independent of the sulfate concentrations. Possible explanations for the decline in the rates of uranium removal include competitive interference between the uranyl and sulfate ions, sodium inhibition, and ionic strength inhibition.
A computer model was utilized to identify the potential uranium species that would be present in the test solutions. These data were compared to data gathered for actual nitrate-containing wastes. Modeling of waste indicates this stream may not be suitable for biological uranium removal under current conditions. The model predicted most of the waste streams would have very little soluble uranium, if any. The phosphate concentration in these wastewaters were relatively small; however, it seems to have sufficient affinity to complex with uranium and precipitate. If, however, the wastewater does not contain phosphate nor significant quantities of calcium, it may be possible to selectively remove the uranium from the wastewater using D. desulfuricans.
Recommended Citation
Kucsmas, Daniel A., "Reduction of uranium by Desulfovibrio desulfuricans in high sulfate and nitrate containing solutions. " Master's Thesis, University of Tennessee, 1994.
https://trace.tennessee.edu/utk_gradthes/11589