In situ bioreduction of uranium (VI) to submicromolar levels and reoxidation by dissolved oxygen.

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 microM 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 Agengy maximum contaminant limit (MCL) for drinking water (< 30/microg L(-1) or 0.126 microM). 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(-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 microM 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. Atthe completion of the project (day 1260), U concentrations in MLS wells were less than 0.1 microM. 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.

[1]  D. Watson,et al.  Speciation of uranium in sediments before and after in situ biostimulation. , 2008, Environmental science & technology.

[2]  Baohua Gu,et al.  GeoChip: a comprehensive microarray for investigating biogeochemical, ecological and environmental processes , 2007, The ISME Journal.

[3]  Peter K. Kitanidis,et al.  Hydraulic performance analysis of a multiple injection-extraction well system , 2007 .

[4]  Eoin L Brodie,et al.  Application of a High-Density Oligonucleotide Microarray Approach To Study Bacterial Population Dynamics during Uranium Reduction and Reoxidation , 2006, Applied and Environmental Microbiology.

[5]  Huifang Xu,et al.  Kinetics of uranium(VI) reduction by hydrogen sulfide in anoxic aqueous systems. , 2006, Environmental science & technology.

[6]  P. Kitanidis,et al.  Pilot-scale in situ bioremediation of uranium in a highly contaminated aquifer. 1. Conditioning of a treatment zone. , 2006, Environmental science & technology.

[7]  Jizhong Zhou,et al.  Pilot-scale in situ bioremedation of uranium in a highly contaminated aquifer. 2. Reduction of u(VI) and geochemical control of u(VI) bioavailability. , 2006, Environmental science & technology.

[8]  C. Criddle,et al.  Thermodynamic constraints on the oxidation of biogenic UO2 by Fe(III) (Hydr)oxides. , 2006, Environmental science & technology.

[9]  Michael N Fienen,et al.  A Nested‐Cell Approach for In Situ Remediation , 2006, Ground water.

[10]  T. Marsh,et al.  Heterogeneous response to biostimulation for U(VI) reduction in replicated sediment microcosms , 2006, Biodegradation.

[11]  Jizhong Zhou,et al.  Changes in bacterial community structure correlate with initial operating conditions of a field-scale denitrifying fluidized bed reactor , 2005, Applied Microbiology and Biotechnology.

[12]  P. Lens,et al.  Developments in Bioremediation of Soils and Sediments Polluted with Metals and Radionuclides – 1. Microbial Processes and Mechanisms Affecting Bioremediation of Metal Contamination and Influencing Metal Toxicity and Transport , 2005 .

[13]  P. Zhou,et al.  Extraction of oxidized and reduced forms of uranium from contaminated soils: effects of carbonate concentration and pH. , 2005, Environmental science & technology.

[14]  B. Peyton,et al.  Reoxidation of reduced uranium with iron(III) (hydr)oxides under sulfate-reducing conditions. , 2005, Environmental science & technology.

[15]  Eoin L. Brodie,et al.  Reoxidation of bioreduced uranium under reducing conditions. , 2005, Environmental science & technology.

[16]  Jizhong Zhou,et al.  Uranium (VI) Reduction by Denitrifying Biomass , 2005 .

[17]  M. A T T H E,et al.  Bioreduction of Uranium in a Contaminated Soil Column , 2005 .

[18]  D. Balkwill,et al.  Change in Bacterial Community Structure during In Situ Biostimulation of Subsurface Sediment Cocontaminated with Uranium and Nitrate , 2004, Applied and Environmental Microbiology.

[19]  W. C. Lin,et al.  Geobacter sulfurreducens Can Grow with Oxygen as a Terminal Electron Acceptor , 2004, Applied and Environmental Microbiology.

[20]  D. Watson,et al.  In situ bioreduction of technetium and uranium in a nitrate-contaminated aquifer. , 2004, Environmental science & technology.

[21]  J. Zeikus,et al.  Energetics and regulations of formate and hydrogen metabolism by Methanobacterium formicicum , 2004, Archives of Microbiology.

[22]  Scott Fendorf,et al.  Inhibition of bacterial U(VI) reduction by calcium. , 2003, Environmental science & technology.

[23]  R. Csencsits,et al.  Reduction of uranium(VI) by mixed iron(II)/iron(III) hydroxide (green rust): formation of UO2 nanoparticles. , 2003, Environmental science & technology.

[24]  Chongxuan Liu,et al.  Reduction kinetics of Fe(III), Co(III), U(VI), Cr(VI), and Tc(VII) in cultures of dissimilatory metal-reducing bacteria. , 2002, Biotechnology and bioengineering.

[25]  J. Banfield,et al.  Radionuclide contamination: Nanometre-size products of uranium bioreduction , 2002, Nature.

[26]  D. Lovley,et al.  Multiple influences of nitrate on uranium solubility during bioremediation of uranium-contaminated subsurface sediments. , 2002, Environmental microbiology.

[27]  Dawn E. Holmes,et al.  Enrichment of Members of the Family Geobacteraceae Associated with Stimulation of Dissimilatory Metal Reduction in Uranium-Contaminated Aquifer Sediments , 2002, Applied and Environmental Microbiology.

[28]  J. Suflita,et al.  In-situ evidence for uranium immobilization and remobilization. , 2002, Environmental science & technology.

[29]  L. Figueroa,et al.  Modeling Reduction of Uranium U(VI) under Variable Sulfate Concentrations by Sulfate-Reducing Bacteria , 2000, Applied and Environmental Microbiology.

[30]  H. Cypionka,et al.  Oxygen respiration by desulfovibrio species. , 2000, Annual review of microbiology.

[31]  D. Lovley,et al.  Geothrix fermentans gen. nov., sp. nov., a novel Fe(III)-reducing bacterium from a hydrocarbon-contaminated aquifer. , 1999, International journal of systematic bacteriology.

[32]  L. Figueroa,et al.  Modeling the Removal of Uranium U(VI) from Aqueous Solutions in the Presence of Sulfate Reducing Bacteria , 1999 .

[33]  N. Valentine,et al.  Kinetics of U(VI) reduction by a dissimilatory Fe(III)-reducing bacterium under non-growth conditions. , 1997, Biotechnology and bioengineering.