Bioremediation of Atomic Bomb Wastes:

Developing a Strategy for Long-term Immobilization of

Uranium Under Field Conditions

C. CriddleStanford University

Federal Remediation Technologies RoundtableNov 15, 2007

Contributing research teams

David Watson

George HouserKenneth

Lowe

Kirk Hyder

ERSP Field Research Center

Michigan State UniversityMary Beth LeighEric CardenasTerrence MarshJames Tiedje

Stanford University

Matthew A.

Ginder-Vogel

Scott FendorfMichael Fienen

Craig Criddle

Margaret E.

Gentile

Peter KitanidisJian

LuoJennifer Nyman

Wei-Min Wu

Scott BrooksSue CarollJack CarleyTerry Gentry

Philip JardineTonia MehlhornHui

YanBaohua

Gu

Oak Ridge National Laboratory

Matthew FieldsChaichi

Hwang

Shelly KellyKenneth Kemner

Argonne

National Laboratory

RetecRobert HickeyRaj

RajanDaniel Wagner

University of Oklahoma

Jizhong

ZhouLiyou

Wu

Miami University

1951-1984 : wastes stored in unlined ponds

The Oak Ridge S3 ponds

Major groundwater contaminants

Depleted uranium: 40-50 mg/L (EPA standard 30 µg/L)

Strong acids: pH 3.4-3.6, 8-10 g/L nitrate, 1 g/L sulfate

Chlorinated solvents: 2-3 mg/L PCE, 1 mg/L cDCE

Metals: 540 mg/L Al, 930 mg/L Ca, 11-14 mg/L Ni

QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.

Where the water goes

Field research station

S-3 ponds parking lot

Geology

Overlying Saprolites Underlying Bedrock

•

Highly interconnected fracture network with 100-

200 fractures/m.

•

Fractures are < 5-10% of the total porosity, but carry >95% of the flow.

•

Fractures are surrounded by a high porosity, low permeability matrix that is a source and sink for contaminants.

Uranium Geochemistry

After slide from Mary emphasize U(IV) precip

and phosphate complexation

Geochemistry

Gaseous Phase

Aqueous Phase

U(IV) Solid Phases

CO2

(g)

CO2

(aq)

H2

CO3

CO32- UO2

(CO3

)n2-2n+UO2

2+

+

Cl-

UO2

Cln2-n

+HO-UO2

(OH)n2-n

Natural Organic Matter,Mineral Colloids

Sorption

Oxides, Carbonates,

Silicates, Phosphates, Clays, etc.

Reduction Precipitation

(UO2

)3

(PO4

)2

·4H2

O UO2

CoprecipitatesOther phases

U(VI) Solid Phases

Uranium Geochemistry

UO3

·nH2

O

Na4

UO2

(CO3

)3

·nH2

O

Na2

U2

O7UO2

(OH)2

·nH2

OLow solubility

Uranium AdsorptionpH~4

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14 16 18Uranium in Solution (mg/L

Sample 101-8Sample 100-1Sample 101-7

At the S3 ponds, the solid phase is a long-term source of U (VI).

The aqueous phase U concentrations exceed the U.S. EPA drinking water standard by over 1000 times. But most of the U is still on the soil, as illustrated by the sorption isotherm at pH 4.

U sorption and desorption are strongly pH dependent.

sorption

desorption

0.1 g soil/15 mL solution

13.5 g soil/15 mL solutionSource: Catalano (2004)

Complexes at surfaces:

Fe(II), Mn(II)Fe(III), Mn(IV)

DMRB

Lactate, Acetate, H2

CO2

, H+

H2

S

S0, SO42-

Fe(II)

Fe(III)

Fe(II) sorbed on hematite or goethite

SRB

H2

S S, SO42-

H2

, Lactate, Pyruvate, Ethanol

CO2

, H2

O

O2

H2

O

NO, N2

O, NO2-

N2

Fe(III)

Fe(II)

Mn(IV)

Mn(II)

U(IV)(Insoluble)

U(VI)(Soluble)

Biostimulation promotes biotic and secondary abiotic reductions

Chemistry considerations

High U(VI) on solid phase: is it accessible?~98% on the soil (~400 mg/kg)~2% in groundwater(~ 40 mg/L) - 40 mg U/L inhibits sulfate- reducer growth

Low pH (~3.5): bad for robust microbial activitybuffered by Al3+ acidity (~20 mM), Al precipitates at pH 4.5-5

High NO3-: inhibits U(VI) reduction, precursor to N2 clogging,

oxidizes U(IV), present in the matrix130-480 mM in groundwater

High Ca2+: inhibits U(VI) reduction at 5 mM; precipitates at pH>7~20 mM in groundwaterUO2

(CO3

) + H+

+ 2e-

= UO2

+ HCO3 -

E°’ = +0.105 VCa2

UO2

(CO3

)3 + 2e-

= 2Ca2+ + UO2

+ 3CO3 2-

E°’ = -0.046 V

Field Research Center

• Selection of a treatment zone

• Gaining hydraulic control

• Flushing and conditioning

• Biostimulation

• Stability tests

Overview

Location: adjacent to the source zone.

Rationale:

The source zone is a reservoir of U(VI) for long-term groundwater and surface water contamination.

Conversion of solid-associated U(VI) into highly insoluble U(IV) will prevent dissolution and desorption, decreasing the time and cost of remediation.

• Selection of a treatment zone

• Gaining hydraulic control

• Flushing and conditioning

• Biostimulation

• Stability tests

Overview

Stepwise strategy

Step 1: Establishing hydraulic control

• Nested recirculation wells

S-3 Ponds parking lot

Above ground treatment system in tent

Well field for thebelow ground treatment system

On site lab trailer

Electron donor

U(VI) U(IV)

MLS wells

Nested Recirculation Loops Tap water

Treatment

Protected inner loop

Outer loop

Step 2: Conditioning of subsurface by removal of clogging agents and

inhibitors

•

Acidified clean water tracer study and flush

•

Aboveground removal of clogging agents and inhibitors

• pH increase

QuickTime™ and aTIFF (PackBits) decompressorare needed to see this picture.

Well B Well C

MLS wells

Effect of tracer clean water flush on nitrate in MLS wells

Mid-depths were flushed wellBottom depth was poorly flushed

All depths were flushed

Updip

Downdip

Removal of clogging agents and pH adjustment

1. Recirculate and flush at pH 4-4.5

Sorption of U increases compared to pH 3.4

While recirculating, remove clogging and

inhibitory agents ex-situ: Al, Ca, NO3- , VOCs, N2

2. Recirculate and flush at pH 6-6.3

Sorption of U now becomes maximum

Favorable for SRB and FeRB, but not

methanogens

Source well

Outer loop injection well

Influent tank

Effluent tank

Vacuum stripper

Vacuum stripper tank

Filters Bag filter

Injection water tank

Mixing tank

Settling tank

Mixing tank

Settling tank

CO2

FBR

GAC separator

Filtration tank

Settling tank

ABOVEGROUND PROCESS TRAIN

Solids holding tanks

N2

pH pH

tap water

Nitrate removal at injection extraction wells

0.1

1.0

10.0

100.0

1000.0

0 20 40 60 80 100 120 140

Nitr

ate,

mM

FW103

FW026

A

Extraction well

Injection well

Al and Ca removal at injection extraction wells

0.00

0.10

0.20

0.30

0.40

0.50

70 80 90 100 110 120 130 140

Al C

once

ntra

tion,

mM

FW026

FW103

A

0.0

1.0

2.0

3.0

4.0

70 80 90 100 110 120 130 140

Ca

Con

cent

ratio

n, m

M

FW026FW103

B

Extraction well

Injection well

Injection wellExtraction well

• Selection of the treatment zone

• Gaining hydraulic control (step1)

• Flushing and conditioning (step 2)

• Biostimulation (step 3)

• Stability tests

Overview

FBR

Strip volatiles, neutralize acid, precipitate metals

Electron donor

U(VI) U(IV)

N2

NO3-

A B C D

MLS wells

Adjust pHStrip volatiles

Tap water

Biostimulation Configuration

0.4 lpm 0.4 lpm

Days 137-402~0.5 lpm

0.4 lpm 1.3 lpmpH 5.5-

5.8

Days 137-402 Days 403-present0.9 lpm

Biofouling

of pump intake on inner loop extraction well -

Day 245

Surging allowed sediment sampling

Surging pulls sediment from around the well screen into the well

Anaerobically collected sediment

Surge block in use

Preparing to surge

Sediment is pumped to surface after settling

Anaerobically stored at 4 °C until time of analysis

Mounted as a wet paste for spectroscopy

pH in inner loop injection and extraction wells during biostimulation

3.0

4.0

5.0

6.0

7.0

8.0

9.0

130 180 230 280 330 380 430

Time, day

pH

FW104 pH

FW026 pH

Nitrate removal during biostimulation

0 .0 1 0

0 .1 0 0

1 .0 0 0

1 0 .0 0 0

1 0 0 .0 0 0

1 0 0 0 .0 0 0

0 1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 6 0 0 7 0 0

T im e , d a y

Nitr

ate,

mM

F W 1 0 1 -2 N i tra teF W 1 0 1 -3 N i tra te

F W 1 0 2 -2 N i tra te

F W 1 0 2 -3 N i tra te

0 .0 1 0

0 .1 0 0

1 .0 0 0

1 0 .0 0 0

1 0 0 .0 0 0

1 0 0 0 .0 0 0

0 1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 6 0 0 7 0 0

T im e , d a y

Nitr

ate,

mM

F W 1 0 4 N i tra te

F W 0 2 6 N i tra te

Conditioning

(day 9-137)Bioremediation

(days 138-750)

MLS Wells

Injection & Extraction Wells

Sulfate in inner loop injection and extraction wells

0.010.020.030.040.050.060.070.080.090.0

100.0110.0120.0

120 170 220 270 320 370 420

Time, day

Sulfa

te, m

g/l

FW104 Sulfate

FW026 Sulfate

Biostimulation

start

0.01

0.10

1.00

10.00

160 200 240 280 320 360 400 440 480 520 560 600 640 680 720

Time, day

U(V

I) m

g/l

FW104 U(VI)

FW026 U(VI)

0.001

0.010

0.100

1.000

10.000

160 200 240 280 320 360 400 440 480 520 560 600 640 680 720

Time, day

U(V

I) m

g/l

FW101-2 U(VI) FW101-3 U(VI)

FW102-2 U(VI) FW102-3 U(VI)

0.03

Dissolved U(VI) concentrations during biostimulation (Day 160-preset)

Key Findings

1. Ethanol adddition

stimulated In situ bioreduction

of U(VI).

2. U(VI) concentration dropped belowEPA MCL.

3. Sulfate reduction and Fe(III)reduction were concomitant withU(VI) reduction.

4. U(IV) was stable undercontrolled anaerobic conditions

O2 removed from outer loop

Maximum concentration of uranium in drinking water of 0.03 mg/l (US EPA) is achievable.

Aqueous U in the MLS Wells: Before and After

FW100

-50

-45

-40

-35

-30

-25

-20

0.01 0.1 1 10 100

Uranium, mg/L

Dep

th, f

t

After Before

FW101

-50

-45

-40

-35

-30

-25

-20

0.01 0.1 1 10 100

Uraniu, mg/L

Dep

th, f

t

After Before

FW102

-50

-45

-40

-35

-30

-25

-20

0.01 0.1 1 10 100

Uranium, mg/L

Dep

th, f

t

After Before

EPA MCL for U (< 0.03 mg/L)EPA MCL for U (< 0.03 mg/L)

Fast Fast flow flow zonezone

FW100 FW101 FW102

Samples before biostimulation: Feb - Apr, 2002Samples after biostimulation: Oct 10, 2006

Solid Phase Uranium SpeciationInjection Well

Sediment

Extraction WellSediment

350.91101-35ft535514.32Inj.535

281.14Extr.535532.79Inj.40901.29Extr.40951NDInj.333541.03Inj.271392.60Inj.258

% U(IV)U (g/kg)WellDay

Uranium L-edge XANES –

Day 535

Energy (eV)

17140 17150 17160 17170 17180 17190 17200

Nor

mal

ized

Inte

nsity

Uraninite [U(IV)]Injection Well 51% U(IV)Sampling Well #1 35% U(IV)Extraction Well 28% U(IV)Uranyl Nitrate [U(VI)]

Summary of XANES data

The sediment changes color as reduction progresses

injection wellmonitoring well

Day 333

Day 670

extraction wellmonitoring 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

Samples from FW102 at 45ft, 40 ft, 35ft and 30ft.

Sediment from the treatment zone give visual evidence of reductionand expansion of the zone of reduction

Samples from FW024, FW104, FW026, FW103 and FW105 (down gradient well).

Samples from FW100 at 45ft, 40 ft, 35ft and 30ft.

Samples from FW101 at 45ft, 40 ft, 35ft and 30ft.

Nested Well System

Outer loop:FW024 (injection)FW103 (extraction)

Inner loop:FW104 (injection)FW026 (extraction)

FW103FW103

FW024FW024

FW026FW026

FW104FW104

FW102FW102FW101FW101FW100FW100

5.5

6.0

6.5

7.0

7.5

400 401 402 403 404 405

pH

FW104 FW026

FW101-2 FW102-3EtOH

K2CO3 Off

B

0.0

0.1

0.2

0.3

0.4

400 401 402 403 404 405

Nitr

ate,

mM

FW104 FW026

FW101-2 FW102-3EtOH

K2CO3 Off

C

0.00

0.25

0.50

0.75

400 401 402 403 404 405

Time, day

Sulfa

te, m

M

FW104 FW026FW101-2 FW102-3

EtOH

K2CO3 Off

E

0.001

0.010

0.100

1.000

10.000

400 401 402 403 404 405

Time, day

Sulfi

de, m

M

FW101-2 FW102-3EtOH

K2CO3 Off

F

Examplesequence(days 399-409):

1. + carbonate 2. + ethanol3. - ethanol4. - carbonate

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

400 401 402 403 404 405

U(V

I) µ

M

FW104 FW026FW101-2 FW102-3

EtOH

K2CO3 Off

D

0

50

100

150

200

400 401 402 403 404 405

CO

D, m

g/l

FW104 FW026FW101-2 FW102-3

K2CO3 Off

EtOHA

0 100 200 300 400 500 600 700 800 900 10000

0.5

1p

Model calibration: ethanol and bromide tracer study

Br- Ethanol

Injection well

MLS well

MLS well

470 472 474 4760

50

100

150

Day470 472 474 476

0

50

100

150

Day

CO

D (

mg/

L)

470 472 474 4760

20

40

60

80

100

120

Day

400 405 4100

20

40

60

80

100

Day400 405 410

0

20

40

60

80

100

Day

CO

D (

mg/

L)

400 405 4100

20

40

60

80

100

Day

MeasurementsModel

FW101−2

FW101−2

FW102−3

FW102−3

FW026

FW026

Predictions for ethanol consumption

Reactive transport simulation (Days 399-409)

COD

HCO3-

SO42-

NO3-

U(VI)

pH

FamilyDominant Genus

Relative abundance (% of total clones)

104 101-2 101-3 102-2 102-3 26

Desulfovibrionaceae Desulfovibrio 7 15 5 4 12 5

Geobacteraceae Geobacter 2 1 1 11 1 1

Rhodocyclaceae Ferribacterium 12 6 38 10 17 18

Hydrogenophilaceae Thiobacillus 5 27 0 1 4 5

Acidobacteraceae Geothrix 12 7 10 4 10 16

Oxalobacteraceae Duganella 9 10 2 2 11 2

Xhantomonadaceae Rhodanobacter 6 2 0 5 5 0

Commanonadaceae Acidovorax 2 1 2 1 2 6

Sphingomonadaceae Sphingomonas 6 0 1 2 2 1

other families 39 31 41 60 36 46

Snapshot of dominant sediment organisms

(Day 774)

Groups listed comprised at least 5% of the total 16S rRNA gene clone libraries.

Source: Cardenas et al., unpublished data

FW-101-2 FW-104166d Unc. bacterium clone 300I-F12 (26%)

Herbaspirillum sp. isolate G8A1 (39%)Unc. bacterium clone 300I-F12 (23%)Herbaspirillum sp. isolate G8A1 (27%) Unc. soil bacterium clone D04 (11%)

535d Acidovorax delafieldii isolate N7-18

(10%)Acidovorax delafieldii isolate N7-18 (7%)Unc. δ-proteobacterium

clone 177T36 (6%) Unc. Actinobacteriaceae clone Hrh678 (6%)Dechlorosoma sp. C6 (5%)

Unc. Sludge bacterium H22 (15%)Unc. bacterium clone 300I-F12 (7%)Unc. Bacterium clone 015B-B03 (7%)Acaligenes defragans strain:PD-19 (6%)Dechlorosoma sp. C6 (10%)

641d Unc. bacterium clone TTMF87 (16%)Unc. δ-proteobacterium

clone 177T36 (14%)Unc. Desulfovibrionacaceae bacterium (7%)Desulfovibrio magneticus (6%) Unc. δ-proteobacterium

clone 036T7 (9%)Unc.

Geobacter sp. clone KB-1 1 (7%)Unc. Phyllobacterium sp. clone Ph (6%)Rhizobium sp

SDW058

(6%)

Unc. δ-proteobacterium

clone 177T36 (17%) Unc. Desulfovibrionacaceae bacterium (4%)Desulfovibrio magneticus (2%) Unc. Actinobacteriaceae clone Hrh678 (7%)Unc. δ-proteobacterium

clone 036T7 (6%)Unc.

Geobacter sp. clone KB-1 1 (4%)

Time series for wells FW-101-2 and FW-104 (source: Hwang et al., unpublished)

• Selection of a treatment zone

• Gaining hydraulic control (step 1)

• Flushing and conditioning (step 2)

• Biostimulation (step 3)

• Stability tests

Overview

Changes in DO in the inner and outer loop

0.00

2.00

4.00

6.00

8.00

10.00

12.00

530 560 590 620 650 680 710 740 770 800 830 860

Time, day

DO

mg/

l

FW104 FW026

FW024 FW103

No DO control With DO control No DO control

Outer loop

Inner loop

0.00

2.00

4.00

6.00

8.00

10.00

12.00

807 812 817 822 827 832

Time, day

DO

mg/

lFW104

FW026

FW024

FW103

0.00

0.10

0.20

0.30

0.40

0.50

0.60

807 812 817 822 827 832

Time, day

U(V

I), m

g/l

FW101-2FW101-3FW102-2 FW102-3FW104FW026

EPA Std.

U stability was spatially variable with O2 in system

Conclusions

•

Stepwise remediation enabled process control & gave insight into mechanisms. Useful steps: geophysics, tracer studies, removal of inhibitors and clogging agents, pH control over sorption/desorption.

•

The nested recirculation scheme is a useful pilot-scale strategy for highly contaminated sites.

•

Very low aqueous phase concentrations can be achieved despite high solid phase concentrations. This is evidently due to the low solubility of U(IV) and low rates of desorption/dissolution relative to rate of reduction.

•

For the anaerobic conditions tested (bicarbonate < 5 mM, Ca < 0.5 mM, pH near 6.0), bioreduced

U(IV) is stable.

Oxygen and nitrate reoxidize

U(IV) in current system.