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

30100

30200

30300

30400

30500

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

50

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