pilot study to evaluate h2 injection for si l …...pilot study to evaluate h 2 injection for si l...

Pilot Study to Evaluate H2 Injection for S i l i d i d bili i fStimulating Reduction and Immobilization of

Uranium in Groundwater at an ISR Site

L Cl J C b Y th G bLee Clapp, Jose Cabezas, Yaneth Gamboa, Waldy Fernandez, Revathi Eti, Dayo Ogungbe,

Uche Eziukwu, Daniel Heuston, , ,Muhammad Ibrahim, Ashutosh Deshpande,

Denis Guleiof, Geraldo Carmona

Department of Environmental EngineeringInstitute for Energy & the Environment

1

st tute o e gy & t e o e tTexas A&M University‐Kingsville

Uranium in the Natural Environment• “Primordial” element part of Earth’s formation 4.5 billion years

ago (originated in supernovas).g ( g p )

• Deposited on land by volcanic action over geologic time.

• Dissolved by rainfall and carried into underground formations.

• Chemical conditions in some locations resulted in concentration into “ore bodies.”

• Fairly common element in Earth’s crust (soil, rock) at about 2‐4 mg/kg and in groundwater and seawater (at about 3 µg/L) ‐ as common as tin tungsten molybdenum etccommon as tin, tungsten, molybdenum, etc.

• A square mile of earth, one foot deep, will typically contain over a ton of uranium; one acre of land, one foot deep, typically has 3 ‐ 4 lbs.

2

Uranium in Groundwater

3

Sources of Radiation to Humans

Update from NCRP Report 160, National Council on Radiation Protection and Measurements Ionizing Radiation Exposure of the Population of the United States, 2006

4

ISR Uranium Mining in South Texas

5http://www.uraniuminfo.org

Survey of U and Rn in Groundwaterin Kleberg and Kenedy Countiesin Kleberg and Kenedy Counties

6

Field Sampling Locations

7

U and Rn Concentrations in Private Wells

Kingsville

UraniumU_ppb

< 1010.01-30.00

30.01 - 100.00

Kingsville

_p< 300301 - 1000

1001- 4000

RadonRn (pCi/L)

30.01 100.00

> 100

1001 4000

> 4001

8

What is uranium used for?

• One pound of yellowcake has energy equivalence of 35 barrels of oil and one 7‐gram (1/4‐ounce) uranium fuel pellet g ( ) phas an energy‐to‐electricity equivalent 17,000 cubic feet of natural gas or 1,780 pounds of coal.

• Nuclear energy provides about 20% of the electricity generated in the U.S.

9

What is “In‐Situ Recovery” Mining?

10http://www.curnamona-energy.com.au/figure5.html

How is Groundwater Currently Restored?

~25% rejection~25% rejection

11www.uraniumresources.com/photos.htm

Effectiveness of Current Restoration Methods

12USGS (2009). Groundwater Restoration at Uranium In-Situ Recovery Mines, South Texas Coastal Plains.

Better Methods for Groundwater Restoration at ISR Sites?

• RO alone does not return the ore zone to its original bi diti

Restoration at ISR Sites?

anaerobic condition.

• Another restoration method that can complement RO treatment is in‐situ reduction and immobilization.

• This involves injecting reductants (e.g., organic j g ( g , gsubstrates, reduced sulfur compounds, H2 gas) to return the aquifer to an anaerobic condition.

• Once the aquifer is anaerobic, dissolved uranium precipitates back into an immobile solid phase.

13

p p p

Eh‐pH‐log PEh pH log PCO2Stability Diagram for

U SpeciesU Species

U(VI) solubility decreases with:U( ) so ub ty dec eases t

Decreasing Eh

Increasing pHIncreasing pH

Decreasing PCO2

14

Research Objective

To evaluate the feasibility of injecting H2 to restore anaerobic conditions and stimulate esto e a ae ob c co d t o s a d st u atein‐situ microbial reduction of uranium.

H th i d th t H i j ti ill ti l t th fHypothesized that H2 injection will stimulate growth of autotrophic IRB and SRB.

H i j ti l d b t t tiH2 injection may also decrease carbonate concentrations, and thus inhibit formation of highly soluble uranyl‐carbonate complexes. p

Autotrophic bacteria also have lower growth yields than heterotrophic bacteria, and are thus less likely to cause

15

heterotrophic bacteria, and are thus less likely to cause bioclogging problems.

Main Redox Reactions

• Uranium oxidation+ +21UO O 2H UO H O

• Uranium reduction

( ) ( )+ ++ + → +2

2 2 2 2s aqUO O 2H UO H O2

www.ch.man.ac.uk/centreforradiochemistryresearch/

( ) ( )+ ++ → +2

2 2 aq 2 sH UO UO 2H

• Ferric iron reductionwww.ch.man.ac.uk/centreforradiochemistryresearch/

( ) ( ) ( ) OH3FeH2OHFeH21

22aqs32 +→++ ++

• Sulfate reduction

( ) ( ) ( )2 2aqs32

3 1 1

1616

− + −+ + → + +22 4 2 2

3 1 14H SO H H S HS 4H O2 2 2

Bottle Sediment Donor Initial pH

Microcosm ExperimentsBottle Sediment Donor Initial pH

1 Mesteña H2 6.52 Mesteña H2 6.53 Mesteña H2 6.54 Mesteña H2 8.55 Mesteña H2 8.56 Mesteña H2 8.57 Mesteña Acetate 6.58 M t ñ A t t 6 58 Mesteña Acetate 6.59 Mesteña Acetate 6.510 Mesteña Acetate 8.5 11 Mesteña Acetate 8.512 Mesteña Acetate 8.513 URI H2 6.514 URI H2 6.515 URI H2 6.516 URI H2 8.517 URI H2 8.518 URI H2 8.519 URI Acetate 6.520 URI Acetate 6.521 URI Acetate 6.522 URI Acetate 8.523 URI Acetate 8.524 URI Acetate 8.525 None None 7.426 None None 7.4

-0.63812-0.46559

Cube Plot for Change in Log U

Acetate0.568750.88581

17

URI

MestenaH28.56.5

Sediment

Reductant

Initial pH

-1.86726-1.65236

-0.70697-0.27857

Microcosm Experiments Comparing H2 and Acetate

Comparing H2 and Acetate

http://www.biocomplexity.usf.edu/pages/pichler_photos.htm

Photographs of the microcosm bottles after one month (top) and two months (bottom) of

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incubation (1st row: Mesteña sediments amended with H2; 2nd row: Mesteña sediments amended with acetate; 3rd row: URI sediments amended with H2; 4th row: URI sediments amended with acetate; two control bottles with groundwater only are at back in lower photo).

Microcosm Study Results

C

2.11

A Initial pHB ReductantC Sediment

Factor Name

Pareto Chart of Standardized Effects for U(95% Confidence Level)

AB

AC

A

B

Term

0.00

-0.25

Init ial pH Reductant

Main Effects Plot for Change in Log UData Means

BC

2520151050Standardized Effect

8.56.5

-0.50

-0.75

-1.00

AcetateH2

0.00

Mea

n

Sediment

URIMestena

-0.25

-0.50

-0.75

-1.00A cetateH2 URIMestena

0

1Initial pH

6.58.5

Initial pH

Interaction Plot for Change in Log UData Means

-1

-2

0

-1

-2

Reductant

H2Acetate

Reductant

19

Sediment

Follow‐up Microcosm Studies

1 2 3 4 5 6

2 5 4 31 43 2 12 5 4 31 43 2 1

20

Column Studies

21

Column Studies Results

4 0 l

3.0

3.5

4.0Ethanol ColumnControl Column

on (p

pm)

2 5

3.0

3.5

4.0 Hydrogen ColumnControl Column

ation (ppm

)

1.5

2.0

2.5

umCo

ncen

tratio

1 0

1.5

2.0

2.5

nium

Concen

tra

0.0

0.5

1.0

1 MOD1 2 3 4 5 MOD2 6 7 8 9Uraniu

0.0

0.5

1.0

1 MOD1 2 3 4 5 MOD2 6 7 8 9

Ura

Sampling PortSampling Port

Hydrogen Column Uranium Concentrations (February 2011)

Ethanol Column Uranium Concentrations (February 2011)( y ) ( y )

22

Pilot Field Study

23

N2

PLC 15’ high vent line In-line

filtersFlow

tFlow

t

2-in ID HDPE hose

NaBr 40% injection

Sampling valve

Choke valve

H2 Control box

metermeter

O2 sensor

LEL sensor

1.25-inch x 200 ft coiled tubing110 ft deep static

water level

multistage ESP at 300 ft deep

¼-inch injection hose

5.5 in PVC casing

1” ID tubing (sparger)

Injection well Extraction well

Goliad Fm C sand

550 ftWell screen

24

Injection well Extraction well

Groundwater Restoration System Schematic 24

Mining Site History

• 1986‐1988: Well drilling and completion.

• 1989‐1998: ISR (oxidation and dissolution of uraninite).

• 1999 2004: Water restoration by RO & permeate reinjection• 1999‐2004: Water restoration by RO & permeate reinjection.

• 2005‐2009: Water stabilization & monitoring (no pumping).

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H2 Injection Groundwater Restoration:5 Stages5 Stages

• Stage 1 ‐ Equilibration (Jan‐March 2009): GW circulation at 40 gpm without amendments.

• Stage 2 ‐ H2 & Br‐ injection (March‐May 2009): GW circulation at 40 gpm with H2 and Br‐.

• Stage 3 ‐ Stabilization (May‐Nov 2009):No pumping.

• Stage 4 – Reverse flow (Nov 2009‐Oct 2010):g f ( )Reverse GW circulation at 6 gpm without amendments.

• Stage 5 – Stabilization Nov 2010‐June 2011

26

Stage 5 Stabilization Nov 2010 June 2011No pumping.

Field Monitoring

28

N1.9 acre within circle

130 ft between injection & extraction

Injection well

Extraction well

Injection well

23

4141

29

Groundwater Restoration: 41-day flow pathlines at 40 gpm

x ?x ? N

xx

41Br-

??XBr-

No Br-

x x?

x x?

30

Detection of Bromide Tracer in Swept Wells

Bromide ConcentrationGroundwater Stabilization Phase

180180w-51

Bromide (ppm)

140

160

7

140

160

w-50w-49

Bromide (ppm)

120

nort

hing

4

5

6

120

w 49

w-53w-46

80

100

y (m

)

2

3

80

100

I-9w-44w-43

41

40

60

0

1

40

60

w-25

w-41

3140 60 80 100 120 140 160

x (m) easting40 60 80 100 120 140 160

w-27 w-28

Modeled vs Measured Br‐ Concentrations

32

Modeled vs Measured Br‐ Concentrations

33

U(VI) ConcentrationGroundwater stabilization phase

180180w-51

U VI (ppm)

140

160

2.8

3.2

140

160

w-50w-49

(pp )

100

120

m) n

orth

ing

1.6

2

2.4

100

120 w-47w-53

w-46

80

y (m

0 4

0.8

1.2

80 w-43I-9

w-44

w-41

40

60

0

0.4

40

60

w-25

34

40 60 80 100 120 140 160

x (m) easting40 60 80 100 120 140 160

w-27 w-28

Sulfate ConcentrationGroundwater stabilization phase

180180w-51

Sulfate (ppm)

p

140

160

780140

160

w-50w-49

100

120

) nor

thin

g

620

700

100

120w-53

w-46

w-47

80

100

y (m

)

460

540

80

100

w-44

w-41I-9

w-43

40

60

380

40

60

w-25

35

40 60 80 100 120 140 160

x (m) easting40 60 80 100 120 140 160

w-28w-27

14Bromide

stop f lowand H2

start H2/Br

stop Br

start reversegw f low12

Stop reversegw f low

8

10

c (p

pm) Estabilization

(without pumping) Estabilization(without pumping)

6Con

c Well 23

Well 41

2

4

0

36

Date

stop flow start reverse6

Uranium

stop reversestart H2stop flow and H2

start reversegw flow

5

U) Stabilization

(without pumping)Stabilization

(without pumping)

stop reversegw flow

4

(ppm

as

U

Well 23

Well 41

( p p g) ( p p g)

2

3

Con

c

1

0

37

Date

start stop H2300

Calcium

stop reversestartH2

stop H2and f low start reverse

gw f low

250 stabilization (without pumping)

stabilization(without pumping)

stop reversegw f low

200

pm)

100

150

Con

c (p

W ll 23

50

Well 23

Well 41

0

41

Date

8 1

pH

start H2stop H2and f low

start reversegw f low

7.9

8.1

t bili ti


7.5

7.7

Well 23

Well 41



7.1

7.3

pH

6.7

6.9

6.5

42Date

600

Bicarbonate

startH2

stop H2and f low


450

500

550




300

350

400

(ppm

)

200

250

300

Con

c

50

100

150Well 23

Well 41

0

43

Date

300

Chloride

start H2stop H2and f low

start gwreverse f low

250 stabilization(without pumping)



200

ppm

)

100

150

Con

c (

50

100Well 23

Well 41

0

44

Date

220Redox Potential

stop H2and f low

startH2


140

160

180

200

Well 23stabilization

(without pumping)



80

100

120

140

(mV)

Well 23

Well 41

( g)( g)

20

40

60Eh

60

-40

-20

0

-80

-60

45

Date

0 7

Manganese

startH2

stop H2and f low


0.6

0.7

stabilization( i h i )

stabilization


0.4

0.5

ppm

)

(without pumping)(without pumping)

0.3

Con

c (p

0.1

0.2Well 23

Well 41

0.0

46

Date

50

Magnesium

startH2

stop H2and f low

start reverse gw f low

40

50

stabilization( ith t i )


30

0

m)

(without pumping)stabilization(without pumping)

20

Con

c (p

pm

Well 23

10

C Well 23

Well 41

0

47Date

0.0010

0.0012

)

Oxidized Species in Solution

Fe(3)

U(6)0.0010

0.0012

L)

Reduced Species in Solution

Fe(2)

U(4)

a b

0.0004

0.0006

0.0008

oncentration (mole/L

S(6)

0.0004

0.0006

0.0008

oncentration (mole/ S(‐2)

0.0000

0.0002

0.000 0.001 0.002 0.003 0.004 0.005 0.006

Co

Moles of hydrogen added per liter of groundwater

0.0000

0.0002

0.000 0.001 0.002 0.003 0.004 0.005 0.006

Co



0.0010

0.0012

L)

Solid‐Phase Species

8

10pe and pH of Solutionc d

0.0004

0.0006

0.0008

ncentration (mole/L

0

2

4

6

or pH

pH

pe

0.0000

0.0002

0.000 0.001 0.002 0.003 0.004 0.005 0.006

Con Ferrihydrite, Fe(OH)3(s)

Uraninite, UO2(s)

Pyrrhotite, FeS(s)

‐6

‐4

‐2

00.000 0.001 0.002 0.003 0.004 0.005 0.006p

e

Changes in (a) oxidized species in solution, (b) reduced species in solution, (c) solid‐phase species, and (d) Eh and pH with increasing addition of H2.

48

Moles of hydrogen added per liter of groundwater ‐8 Moles of hydrogen added per liter of groundwater

0.0050

0.0060

0.0010

0.0012

le/L)

n (mole/L)

Oxidized Species in Solution

0.0010

0.0012

)

Reduced Species in Solutiona b

0.0020

0.0030

0.0040

0.0004

0.0006

0.0008

(6) Concentration (mo

nd U(6) Concentration

Fe(3)

U(6)

S(6)0.0004

0.0006

0.0008

oncentration (mole/L)

Fe(2)

U(4)

S(‐2)

0.0000

0.0010

0.0000

0.0002

0.0000 0.0005 0.0010 0.0015 0.0020

S(

Fe(3) an

Moles of dithionite added per liter of groundwater

0.0000

0.0002

0.0000 0.0005 0.0010 0.0015 0.0020

Co

Moles of dithionite added per liter of groundwater

0.0010

0.0012

(mole/L)

Solid‐Phase Species

6

8

10pe and pH of Solutionc d

0.0004

0.0006

0.0008

Phase Concentration (

Ferrihydrite, Fe(OH)3(s)

Uraninite, UO2(s)

Pyrrhotite, FeS(s) 0

2

4

6

pe or pH

pH

pe

0.0000

0.0002

0.0000 0.0005 0.0010 0.0015 0.0020

Solid‐P

Moles of dithionite added per liter of groundwater‐6

‐4

‐2

0.0000 0.0005 0.0010 0.0015 0.0020

Moles of diothinite added per liter of groundwater

Changes in (a) oxidized species in solution, (b) reduced species in solution, (c) solid‐phase species, and (d) Eh and pH with increasing addition of Na2S2O4.49

Moles of dithionite added per liter of groundwater Moles of diothinite added per liter of groundwater

Microbial CharacterizationW

ell 4

1

Wel

l 23

50

Microbial Characterization

C-CTC-CT

51

Summary of Key Results

• ~100,000 scf of H2 was dissolved and safely injected into 2.4 million gallons of groundwater.g g

• Br‐ tracer was detected as far as 160 ft from the injection well which was consistent with flow simulationwell, which was consistent with flow simulation.

• >95% reduction in U has been sustained near both well 23 and well 41 for a little over two years23 and well 41 for a little over two years.

52

Summary of Key Results• ~95% removal of Mo was initially observed near the injection well. However, when flow was reversed, Mo has rebounded to ~181% of the baseline concentration.

• Significant reduction of Fe, Mn, and particularly SO42‐

4was been observed.

• Reduction of 350 mg/L of sulfate corresponded toReduction of 350 mg/L of sulfate corresponded to utilization of 29 mg/L of H2, indicating that essentially all of the injected H2 was consumed before reaching the extraction well.

5353

Additional Observations

• DO consistently remained below 0.3 mg/L.

S th f ti b d ll 23• Some methane formation observed near well 23 during H2 injection (~0.7 mg/L).

• Higher soluble sulfide concentrations near well 23 (~1.0 mg/L)

54

Ongoing & Future Work

• MT3DMS modeling of bromide tracer results.

G h i d li• Geochemistry modeling.

• Future research should assess alternative H2 delivery strategies (e.g., pulsing) to minimize sulfate reduction at the injection well.

• Survey of concentrations of U, Rn and other constituents in private wells in region surround the ISR mining area.

55

Acknowledgments

This material is based upon work supported by UraniumThis material is based upon work supported by Uranium Resources, Inc. (URI), in part by the U.S. Department of Energy under Agreement No. DE‐FGO2‐08ER64519, and in part by the National Science Foundation under Agreement No. HRD‐0734850. Any opinions, findings, and conclusions or recommendations expressed in this material are thoseor recommendations expressed in this material are those of the author and do not necessarily reflect the views of the sponsors.p

56

Thank you!

Questions?

57

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