In Situ Bioreduction of Uranium (VI) to Submicromolar Levels and Reoxidation by Dissolved Oxygen

Journal Article · Mon Jan 01 04:00:00 EST 2007 · Environmental Science & Technology

DOI:https://doi.org/10.1021/es062657b· OSTI ID:945330

Wu, Weimin ^[1]; Carley, Jack M ^[1]; Luo, Jian ^[2]; Ginder-Vogel, Matthew A. ^[2]; Cardenas, Erick ^[3]; Leigh, Mary Beth ^[3]; Hwang, Chaichi ^[4]; Kelly, Shelly D ^[5]; Ruan, Chuanmin ^[1]; Wu, Liyou ^[6]; Van Nostrand, Joy ^[6]; Gentry, Terry J ^[1]; Lowe, Kenneth Alan ^[1]; Mehlhorn, Tonia L ^[1]; Carroll, Sue L ^[1]; Luo, Wensui ^[1]; Fields, Matthew Wayne ^[4]; Gu, Baohua ^[1]; Watson, David B ^[1]; Kemner, Kenneth M ^[5] ; Marsh, Terence ^[3]; Tiedje, James ^[3]; Zhou, Jizhong ^[6]; Fendorf, Scott ^[2]; Kitanidis, Peter K. ^[2]; Jardine, Philip M ^[1]; Criddle, Craig ^[1]

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1. ORNL
2. Stanford University
3. Michigan State University, East Lansing
4. Miami University, Oxford, OH
5. Argonne National Laboratory (ANL)
6. University of Oklahoma, Norman

Groundwater within Area 3 of the U.S. Department of Energy (DOE) Environmental Remediation Sciences Program (ERSP) Field Research Center at Oak Ridge, TN (ORFRC) contains up to 135 {micro}M uranium as U(VI). Through a series of experiments at a pilot scale test facility, we explored the lower limits of groundwater U(VI) that can be achieved by in-situ biostimulation and the effects of dissolved oxygen on immobilized uranium. Weekly 2 day additions of ethanol over a 2-year period stimulated growth of denitrifying, Fe(III)-reducing, and sulfate-reducing bacteria, and immobilization of uranium as U(IV), with dissolved uranium concentrations decreasing to low levels. Following sulfite addition to remove dissolved oxygen, aqueous U(VI) concentrations fell below the U.S. Environmental Protection Agency maximum contaminant limit (MCL) for drinking water (<30 {micro}g L{sup -1} or 0.126 {micro}M). Under anaerobic conditions, these low concentrations were stable, even in the absence of added ethanol. However, when sulfite additions stopped, and dissolved oxygen (4.0-5.5 mg L{sup -1}) entered the injection well, spatially variable changes in aqueous U(VI) occurred over a 60 day period, with concentrations increasing rapidly from <0.13 to 2.0 {micro}M at a multilevel sampling (MLS) well located close to the injection well, but changing little at an MLS well located further away. Resumption of ethanol addition restored reduction of Fe(III), sulfate, and U(VI) within 36 h. After 2 years of ethanol addition, X-ray absorption near-edge structure spectroscopy (XANES) analyses indicated that U(IV) comprised 60-80% of the total uranium in sediment samples. At the completion of the project (day 1260), U concentrations in MLS wells were less than 0.1 {micro}M. The microbial community at MLS wells with low U(VI) contained bacteria that are known to reduce uranium, including Desulfovibrio spp. and Geobacter spp., in both sediment and groundwater. The dominant Fe(III)-reducing species were Geothrix spp.

• Research Organization: Oak Ridge National Laboratory (ORNL)
• Sponsoring Organization: SC USDOE - Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 945330
• Journal Information: Environmental Science & Technology, Journal Name: Environmental Science & Technology Journal Issue: 16 Vol. 41
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
BACTERIA
BIODEGRADATION
ETHANOL
GROUND WATER
IN-SITU PROCESSING
OAK RIDGE RESERVATION
REDUCTION
URANIUM