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.
Well System for Field-scale Test for in situ Bioremediation of Uranium Contaminated site, FRC Area 3
Injection of Electron Donor (ethanol) for Bioremediation
(day 137-710)
Accumulated ethanol injected
0
2000
4000
6000
8000
10000
100 200 300 400 500 600 700 800
Time, day
Accumulated ethanol (g as COD)
Started ethanol injection on day 137
Nitrate Concentration Changes during Remediation
0.010
0.100
1.000
10.000
100.000
1000.000
0 100 200 300 400 500 600 700
Time, day
Nitrate, mM
FW101-2 Nitrate
FW101-3 Nitrate
FW102-2 Nitrate
FW102-3 Nitrate
0.010
0.100
1.000
10.000
100.000
1000.000
0 100 200 300 400 500 600 700
Time, day
Nitrate, mM
FW104 Nitrate
FW026 Nitrate
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
U(VI) Concentrations in inner loop wells and MLS wells
The maximum concentration of uranium in drinking water is 0.03 mg/l (US EPA).
0.001
0.010
0.100
1.000
10.000
160 210 260 310 360 410 460 510 560 610 660 710
Time, day
U(VI) mg/l
FW101-2 U(VI)FW101-3 U(VI)FW102-2 U(VI)FW102-3 U(VI)
U(VI) Concentrations in injection and extraction wells
0.01
0.10
1.00
10.00
160 210 260 310 360 410 460 510 560 610 660 710
Time, day
U(VI) mg/l
FW104 U(VI)
FW026 U(VI) Injection and extraction wells
Monitoring wells
0.00
1.00
2.00
3.00
4.00
5.00
1 2 3 4 5
Uranium (g/kg)
FW104
FW101-2
FW026
Before bioremediation the uranium content in core samples from FW104 ranged from 0.03 to 0.8 g/kg Day 247 Day 409 Day 535 Day 622 Day 670
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.
injection well
monitoring well
extraction well
Uranium Content in Sediments from Injection, Monitoring and Extraction Wells during Bioremediation
Energy (eV)
17140 17150 17160 17170 17180 17190 17200
Normalized Flourescence
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Uraninite [U(IV)]Injection Well - 51% U(IV)MLS Well - 35% U(IV)Extraction Well - 28% U(IV)Uranyl Nitrate [U(VI)]
Uranium Redox State – Day 535
The sediment changes color as microbial reduction progresses
injection wellmonitoring well
Day 333
Day 670
extraction well
monitoring well
injection well
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
Now black
brown