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FIELD SCALE EVALUATION OF BIOSTIMULATION FOR REMEDIATION OF URANIUM-CONTAMINATED GROUNDWATER
Stanford University
Olaf CirpkaCraig CriddleLaurel CrosbyScott FendorfMichael FienenMargy Gentile
Oak Ridge National Laboratories
Craig BrandtMatthew FieldsBaohua GuPhilip JardineTonia Mehlhorn
David Watson
NABIR Field Research CenterRetec
Robert Hickey Raj RajanDan Wagner
Jizhong ZhouPeter Kitanidis Jian Luo Anna MichalakJennifer NymanWeimin Wu
FRC workshop 2002
The Oak Ridge S3 pondsA legacy of the Cold War: 32 years of atomic waste
- Uranium- Nitric and sulfuric acid- Chlorinated solvents- Heavy metals
How to get rid of it?
- Dump into an unlined pond - Cover with a parking lot
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
Tributary 1 to Bear Creek
• Evaluate rates and mechanisms of microbially-mediated reduction of uranium in a highly heterogeneous field setting.
PRIMARY OBJECTIVE
U(VI) is converted to U(IV)
UO2(CO3) + H+ + 2e- = UO2 + HCO3 - E°’ = +0.105 V
Good thing: a few electrons goes a long ways - 119 mg U/ meq
Bad thing: Nitrate is the preferred electron acceptor. It inhibits U(VI) reduction. Moreover, the products of partial denitrification (NO2
-, N2O) oxidize U(IV) (Senko et al., 2002). Partialdenitrification is common at low pH.
PHASE 1: SITE CHARACTERIZATION
PHASE 2: SITE CONDITIONING
PHASE 3: BIOSTIMULATION
51800 51900 52000 52100 52200 52300 52400Easting (feet)
30000
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30600
Nor
thin
g (fe
et)
S-3 Ponds Cap
FW007
FW008
FW009
FW010
FW011
FW012FW013
FW014FW022FW023
FW024
GW-101
GW-127
GW-244
GW-245GW-246
GW-247GW-615
GW-837
TPB10
TPB11
TPB25
TPB28
TPB31
FW006GW-243
TPB32
FW005
FW026groundwater flow direction study area
Geophysics transect
• Seismic refraction tomography: close contours = consolidated material
• Electrical resistivity: light to dark blue = high ionic strength
• Both sets of data agree with auger penetration and geochemistry
Geophysics used to identify probable areas of contaminant transport
Doll, 2001
Well D
Presumptivegroundwater flow direction
Well configuration
well A
well C
0.9 m
0.9 m
well B
well D1.5 m
1.2 m
MLS wells
Can you find the FRC science advisor?
Well D
Well C
Well BWell A
I see his shoes, but where is his head?
Groundwater Flux at FRC Area 3
Distance Strike Parallel in Feet0 2 4 6 8 10 12 14 16 18 20
Vertical Distance From
Surface in Feet
10
15
20
25
30
35
40
45
50
Well D
Flux (m/d)0.0 0.2 0.4 0.6 0.8 1.0
Well B
0.0 0.2 0.4 0.6 0.8 1.0Flux (m/d)
•90-95 % of groundwater flow is within the 30 to 50 ft. depth interval. These results are consistent with independent measurements using a boreholeflowmeter.
•Groundwater flux within this interval is on average 0.5 m/d.
•Consistent data for each borehole suggest flow is strike parallel.
Groundwater Uranium at FRC Area 3
Distance Strike Parallel in Feet0 2 4 6 8 10 12 14 16 18 20
Vertical Distance From
Surface in Feet
10
15
20
25
30
35
40
45
50
Well D
Uranium (mg/L)0 10 20 30 40 50
Well B
0 10 20 30 40 50Uranium (mg/L)
•Groundwater concentrations of U in the fast flowing zone are very high with average values above 40 mg/L. Pumping at 1.4 lpm (achieved at Well D) gives a U mass flow rate of 81 g/d or 29 kg/yr.
•Consistent data for each borehole suggest flow is strike parallel.
•The vertical extent of the U plume is consistent with geophysical resistivity data.
Groundwater pH at FRC Area 3
Distance Strike Parallel in Feet0 2 4 6 8 10 12 14 16 18 20
Vertical Distance From
Surface in Feet
10
15
20
25
30
35
40
45
50
Well D
pH0 1 2 3 4
Well B
0 1 2 3 4pH
•Groundwater pH is consistently low (e.g. ~3.5) and highly buffered.
•Unconfined groundwater degasses CO2 since the soil solid phase is carbonate rich and buffered near 6.5 to 7.
•The low pH is not conducive to U sorption on the solid phase which is consistent with downhole in situ detection of U using a NaI detector. Maximum U sorption was noted from 10 to 20 ft. with less sorption occurring in the fast flowing 30 to 50 ft. interval.
Groundwater Nitrate at FRC Area 3
Distance Strike Parallel in Feet0 2 4 6 8 10 12 14 16 18 20
Vertical Distance From
Surface in Feet
10
15
20
25
30
35
40
45
50
Well D
Nitrate (mg/L)0 2000 4000 6000 8000 10000
Well B
0 2000 4000 6000 8000 10000Nitrate (mg/L)
•Average nitrate concentrations in the groundwater are near 8 g/L. The vertical extent of the plume is consistent with co-contaminant U and geophysical resistivity data.
Undisturbed column from Area 3 treatment zone (42 ft. depth)
Experiments designed to quantify solutemass transfer kinetics, uranium reactivity,and propensity for bioreduction underdynamic flow conditions.
Uranium AdsorptionpH~4
0
100
200
300
400
500
600
700
800
0 2 4 6 8 10 12 14 16 18
Uranium in Solution (mg/L)
Ura
nium
Ads
orbe
d (m
g/kg
)
Sample 101-8
Sample 100-1
Sample 101-7
2 3 4 5 6 7 8 9 10 110
20
40
60
80
100
pH
U(VI) pH adsorption envelopeson ORNL saprolite
Model fit
Observed
Uranium adsorption on Area 3 treatment zone soils
Mineral precipitation zone Concentration dependent U sorptionon FRC soils.
U sorption is strongly pH dependent.
%adsorbed
Key groundwater quality parameters at Well D.
InorganicConstituents Concentrations
OrganicConstituents Concentrations
pH 3.4-3.6TIC 202-401 mg/L COD 200 mg/L*
Chloride 249-298 mg/L TOC 65-81 mg/LSulfate 843-1116 mg/L 2-Butanone 69-84 µg/LNitrate 7500-8963 mg/L Acetone 340-700 µg/LNitrite LowUranium 42-51 mg/L Chloroform 34-36 µg/LTechnetium-99 35-40 nCi/L
(80-89 dpm/ml)Tetrachloroethene 2100-3300 µg/L
Ni 11.5-14 mg/L Trichloroethene 94-130 µg/LCd 0.45 mg/L
Al 541±47 mg/L 1,1,2-trichloro-1,2,2-trifluoroethane
1200-1500 µg/L
Ca 931±74 mg/L Methylenechloride
39-42 µg/L
Mg 174±11 mg/L Citric acid ~6 mg/L #
Mn 130±9 mg/LSb <0.003 mg/LCr 0.17 mg/LPb 0.03 mg/LSe 0.02 mg/L
* estimated value: a measurement is needed.# values for MLS FW 100, 40’ depth.
Precipitate atpH 5
Neutralize
volatile
Remove as N2
Precipitate atpH 7-8
PHASE 2. SITE CONDITIONING
o VOC removal
o pH adjustment (Al, U, Ca, Mg, Mn removal)
o Nitrate removal
pH adjusted to 7 with 50% liquid from these denitrifying batch cultures
Denitrifier cultures were grown in fed batch mode with synthetic groundwater (pH 3.4) amended with lactate-ethanol and organic P. CO2was periodically removed by He sparging (pH in the serum bottles: 6.8-7.2).
pH adjusted to 7 with Na2CO3
pH adjusted to 7 with KOH
pH adjustment and precipitate formation
Solid production from synthetic groundwater
0.000
0.500
1.000
1.500
2.000
2.500
3.000
3.500
4.000
4 5 6 7 8 9 10pH
Most U(VI) precipitates along with Al(OH)3 at pH~5 and resolubilizes at pH>6
3.82 7607.6 50.44 26763.3 453.12 937.804.47 7936.2 27.09 9329.0 93.24 946.204.93 6589.4 6.01 2226.1 24.66 955.565.76 7981.0 3.72 1808.3 0.75 902.526.32 6970.1 15.55 5340.7 0.50 787.206.86 7966.4 23.09 7088.0 0.51 707.647.11 6039.3 23.86 6784.1 0.49 449.207.67 5909.3 28.07 8379.4 0.97 111.208.93 7889.4 36.65 11570.0 5.66 18.83
pHNO3
- U(VI)----------------------- mg/L ------------------------------
99Tc Al Ca
• Soluble U(VI)-CO3 species exist at pH >6 - a pH regime that is conducive to microbial stimulation
• Recall that the pH of the native soils is 6.5 to 7.0
ABOVE GROUND TREATMENT
U, Tc, Al Ca, Mg, Mn
K2CO3 N2
FBR
pH4.9pH3.4 pH8
e- donor
VOCsK2CO3
N2ON2
UO2(CO3) 22-Slurry disposal
Sourcewells
CO2
Well D
pH9 pH7.5pH3.4
biomass
Bag filter disposal
vacuum vacuum
Well A
Ion exchange
e- donor +inoculum
Well CIn-situ experiment
Continuously removes NO3
- as N2EfficientCheapRaises pH; creates bicarbonate/carbonate for U complexationDemonstrated in two continuous pilot-scale systems (pH 7.4 and 9.2)
Nitrate removal by denitrification in an FBR
Synthetic groundwaterfeed pump
NO3-
Electron donor tank
Recirculation pump
Electron donorfeed pump
Pilot Scale FBR
Synthetic Groundwater
Tank
LactateEthanol
Effluent
N2
Denitrifying biofilms growing on granular activated carbon
Pilot scale FBR
Zoogloea-likeL=87 S=55 (85-99%)
Ralstonia-like L=5 (55-99%) Dechlorosoma-like S=8 L=13 (90-99%)
Sterolibacterium-like L=4 (96-99%) Azoarcus-like S=2 L=2 (94-99%)
Dechlorosoma/Dechloromonas-like S=63 L=17 (97-99%)
Shewanella-like L=2 (83%) Pseudomonas-like L=9 (70-99%)
Xanthomonas-like S=12 L=10 (90-99%) Xanthomonas-like L=51 (90-99%)
unknown episolon L=5 S=3 Bacteroides-like????
Agrobacterium-like L=2 S=1 (98-99%) Terrebacter-like low G+C clone
Sporomusa-like (Acetonema-like)S=16 L=15 (60-99%)0.1
16S rDNA + ITSClonal Library--FBR
Estimated diversity: 120-140 species!(Fields & Zhou, 2002)
PHASE 3. BIOSTIMULATION
o Well configuration
o Start-up
o Intermittent lactate addition
o Management issues
Qr
Qo
Qo+Qr
B C D
FBR
Strip volatiles, neutralize acid, precipitate metals
A
U(VI)Electron donor
U(VI) U(IV)
N2
NO3-
Electron donor
VolatilesmetalsNO3
-
U(VI)
Cross-sectional view of the injection/extraction wells and the MLS wells.
ScreenedInterval = 37-45’
Start-up
Strategy
• Treat water extracted from Well D
• Stockpile treated water (and U)
• Inject treated water at Wells B and C
First flush - pH matches groundwaterSecond flush - alkalinity added
Objectives
• Rapidly prepare subsurface for FBR effluent
• Avoid clogging
• Titrate acidity on soil (not much there)
3. Settle 4. Decant
lactate & ethanol
denitrifying inoculum
2. React
Batch treatment of Al-U Sludge
5. Remove sludge.
Ultimate disposal
Al-U sludge
1. Fill
U-enriched supernatant(to U solution storage tank)
N2
E = electron donor (ethanol + lactate) added to give an initial COD of 200 mg COD/l.
U(VI) reduction by FBR effluent and biomass
0
10
20
30
40
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60
70
0 50 100 150 200
Time (day)
U(V
I) Co
ncen
trat
ion
(mg/
l)
Control FBR effluent0.3g/l FBR biomass 1.59 g/l FBR biomass
Very preliminary data for sediment + FBR effluent: ethanol looks promising…
MARCH
APRIL
JUNE
Trajectory ofMicrocosm
Communities(initiated with unwashed green, red,
and black sediment + denitrified synthetic groundwater)
T-RFLP Community profiles compared
with Neighbor Joining
(collaboration with T. Marsh)
Lactate or ethanol
Nitrate removal as N2VOCs
U(VI) + Br-
disposal
Sourcewell
In-situ experiment:reductivebiomineralization of uranium
System lay-out.
Monitoring wells
Injection/extraction wells
Outer cell
Inner cellQr
QoQo+Qr
Outer layer
Qo
Ex-situ treatment
streamlines
Chemical slurries
STREAM LINES FOR THE INNER AND OUTCELL
INNER CELL
OUTER CELL
Q°
Olaf’s simulation assumptions for U introduction:
1. Hydraulic conductivity =0.001 cm/s.2. Ambient hydraulic gradient =1.5%3. Screened interval = 2m4. Effective porosity = 0.355. No sorption of U
1. Initial sulfate = 10 mM2. No sorption of lactate, sulfate, U(VI)3. All biomass is immobile. 4. Initial SRB conc =1 mg/L5. Cometabolic reduction of U(VI) to UO2
by SRB.6. Operational schedule:
1. 0-10 h injection of 50 mg/L U(VI)2. 10h-5d no injection. Mixing of U(VI) within the
inner loop.3. 5d-100 d Daily one hour injection of lactate at
a ratio of o.23 mg lactate per mg U extracted.
Olaf’s assumptions for biostimulation:
U, Al, Tc
e- donor +organic P
Ca, Mg, Mn
K2CO3 N2
FBR
pH4.9pH3.4 pH8
e- donor
VOCsK2CO3
N2ON2
UO2(CO3) 22-
K2CO3
U recovery and denitrification
Slurry disposalpH8
Sourcewells
CO2
Experiment:reductivebiomineralization of uranium
System lay-out.
Monitoring wells
Injection/extraction wells
Outer cell
Inner cellQr
QoQo+Qr
A
B
C
D
pH9 pH7.5
biomass
Bag filter disposal
vacuum vacuum
Outer layer
Qo
Ion exchange
Acrobat DocumentFloor plans
Facility design, floor plans, and shelter
Envisioned applications…
The ex-situ system will be useful for remediating the source zone.
The in-situ system will be useful for immobilization of U at the plume periphery.
J F M A M J J A S O N DO N D
U system/FBR fabricated, shipped, tested
Tracer study
Install wells T1, T2, T3
Construct pad/tent
FBR start-up
Extract from Well A, adjust pH, remove metals, volatiles, nitrate, inject at well D
Training of personnel
Extract from Well B, inject at at well C. Add U solution, followed by pulsed e- donor.
Clean water experiment
Data collection and analysis
Modeling
Geophysics
Schedule Overview
2002 2003
Prepare U injection solution
FRC (Watson staff)
STANFORD (Wu)
RETEC (staff)
ORNL (Jardine, Gu, Zhou staff)
J F M A M J J A S O N D
TrainingTroubleshooting
ORNL (Brandt)Weekday oversite of system O&MExecution of experimentOrganization of data
Daily O & M of treatment systemOrganization of data
Monthly oversite of system O&MExecution of experimentOrganization of data
STANFORD (Criddle,Kitanidis)
Overall coordination
ProjectDatabase
Management structure for the system operation and data management
Information flowAdministrative responsibility