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FRC Area 3 Site Bioremediation (August 24, 2003 – August 7, 2005)

FRC Area 3 Site Bioremediation (August 24, 2003 – August 7, 2005). Tests were performed in two phases: (1) a clean water flush to remove bulk nitrate, Al, and Ca (days 9-137). (2) biostimulation by repeated ethanol injection (days 138-present).

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FRC Area 3 Site Bioremediation (August 24, 2003 – August 7, 2005)

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  1. FRC Area 3 Site Bioremediation (August 24, 2003 – August 7, 2005) • Tests were performed in two phases: (1) a clean water flush to remove bulk nitrate, Al, and Ca (days 9-137). (2) biostimulation by repeated ethanol injection (days 138-present). • Uranium is immobilized in the sediments at 700-2000 mg/kg • Uranium concentration in the groundwater has dropped below US EPA drinking water maximum limit (0.03 mg/l) in the monitoring wells. • An active remediation zone has been established with high microbial activity for denitrification, Fe(III) reduction, sulfate reduction and U(VI) reduction.

  2. Well System for Field-scale Test for in situ Bioremediation of Uranium Contaminated site, FRCArea 3

  3. Injection of Electron Donor (ethanol) for Bioremediation (day 137-710) Started ethanol injection on day 137

  4. Nitrate Concentration Changes during Remediation Clean water flush (day 9-137) Bioremediation (day 138-670) To avoid production of nitrogen gas bubbles in subsurface and inhibition, nitrate should be reduced below 1 mM

  5. U(VI) Concentrations in inner loop wells and MLS wells Injection and extraction wells Monitoring wells The maximum concentration of uranium in drinking water is 0.03 mg/l (US EPA).

  6. Uranium Content in Sediments from Injection, Monitoring and Extraction Wells during Bioremediation injection well monitoring well extraction well Variability in the content of U in the injection well sediment is likely due to variability in the removal of U during the surging operation. Before bioremediation the uranium content in core samples from FW104 ranged from 0.03 to 0.8 g/kg Day 409 Day 247 Day 535 Day 622 Day 670

  7. Uranium Redox State – Day 535

  8. The sediment changes color as microbial reduction progresses Day 333 monitoring well injection well brown Day 670 extraction well sample from day 670 incubated 3 days with no added ethanol extraction well sample from day 670 incubated 3 days after adding 100 mg/L ethanol injection well extraction well monitoring well Now black

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