Comparison of Approaches to Engineered In Situ Biogeochemical Transformation of Chlorinated Solvents

19 October 2012

Remediation Technology Symposium (RemTech) 2012

Bruce M. Henry, PG

Acknowledgements

AFCEE Tech Transfer – Dr. Seb Gillette Air Force Demonstration Hosts Joint Base Pearl Harbor-Hickam (JBPHH), Hawaii –

Bill Grannis Altus Air Force Base (AFB), Oklahoma – Dan Stanton Joint Base Elmendorf-Richardson (JBER), Alaska –

Donna Baumler Little Mountain Test Annex (LMTA), Hill AFB, Utah –

Kyle Gorder

Parsons – John Hicks, John Hall, Mitch Jensen

2

Presentation Topics

Technical Approaches Engineered Systems – Case Studies Materials Bioreactors Direct Injection

Factors Impacting Performance Amendment Properties and Distribution Utilization of Iron, Sulfate, and Organics Design Considerations – Special Considerations

3

Engineered In Situ Biogeochemical Transformation

Chlorinated compounds degraded by abiotic reactions with naturally occurring or biogenically-formed reactive minerals

Abiotic processes typically do not produce intermediate dechlorination products

Alternative or complement to biostimulation using selective Dehalococcoides species

4

Framboidal Pyrite

Demonstrate an in situ technology capable of sustained degradation of

chlorinated solvents without accumulation of cis-DCE or VC

AFCEE Objective

Three General Approaches

Production of reactive iron monosulfide (FeS) minerals while limiting biological activity – “one and done” approach (Dover AFB injection; Kennedy et al., 2006)

Continual production of FeS with high sulfate consumption rate (Altus AFB biowalls and bioreactors; Lebron et al., 2010)

Synergistic approach stimulating both production of reactive FeS minerals and biotic dechlorination with bioaugmentation (JBPHH bioreactor study; Leigh et al., 2011)

5

Engineered Systems – Case Studies

Materials Iron Amendments Sulfate Amendments

Bioreactors LF05 Bioreactor, JBPHH, HI LF03 Bioreactor, Altus AFB, OK

Direct Injection DP98, JBER, AK North Disposal Area,

LMTA, Hill AFB, UT

6

Sulfate amendments are soluble (up to 26,000 mg/L) and migrate with groundwater flow, but dissolution rate may vary (anhydrous versus hydrated forms)

Potential Sulfate Amendments

7

Material (most common form)

Percent Sulfate

Percent Iron

Notes

Ferrous Sulfate (heptahydrate) - FeSO4 • 7H2O

35% 20% Soluble

Magnesium Sulfate (heptahydrate) - MgSO4 • 7H20

39% 0% Soluble - Epsom Salt

Calcium Sulfate (dihydrate) - CaSO4 • 2H20

56% 0% Moderate Solubility - Gypsum

Sodium Sulfate (decahydrate) - Na2SO4 • 10H20

30% 0%

Highly Soluble

Percent by weight in hydrated form

Ferrous Sulfate (FeSO4•7H2O)

Solid iron amendments have a broad range of bioavailability

– ranging from 250 to 25,000 mg/kg

Potential Iron Amendments

8

Material (most common form)

Percent Sulfate

Percent Iron

Notes

Crushed or Powdered Hematite - Fe2O3

0% 68% Natural or Synthetic (pigment)

Crushed or Powdered Magnetite – Fe3O4

0%

67% Natural or Synthetic (pigment)

Ferrous Chloride (anhydrous) - FeCl2

0% 34% Soluble (corrosive - low pH)

Ferrous Lactate - Fe(C3H5O3)2

0% 28% Soluble – Food Additive

Ferrous Sulfate (heptahydrate) - FeSO4 • 7H2O

35% 20% Soluble

Powdered Hematite (Fe2O3)

LF05 DNAPL Source Bioreactor, JBPHH

9

High Iron Native Basalt Sand

Plan View of Hickam LF05 Bioreactor

10

Groundwater Flow

Data Shown

Recirculation

1

10

100

1000

10000

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

400,000

450,000

-1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Tota

l Mo

lar

Ch

lori

nat

ed E

then

es (

mm

ol/L

)

Co

nce

ntr

atio

n (

µg/L

)

Months Since Installation

PCE TCE

Total DCE VC

Ethene + Ethane Total Molar Chloroethenes

Chlorinated Ethenes at Well MW-18

11

96% reduction in total molar concentration of chloroethenes

1

10

100

1000

10000

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

400,000

-1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Tota

l Mo

lar

Ch

lori

nat

ed E

then

es (

mm

ol/L

)

Co

nce

ntr

atio

n (

µg/L

)

Months Since Installation

PCE TCE

Total DCE VC

Ethene + Ethane Total Molar Chloroethenes

Chlorinated Ethenes at Well MW-38

12

95% reduction in total molar concentration of chloroethenes

Contrast to MW-04 for a Prior Bioremediation Pilot

13

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

100,000C

on

cen

trat

ion

(µg

/L)

Date

TCE

cis-1,2-DCE

VC

Persistent cis-1,2-DCE, accumulation of VC

LF-03 Recirculating Bioreactor, Altus AFB, OK

14

Solar-powered recirculating bioreactor – built in November 2003

Emulsified vegetable oil (EVO) and ferrous sulfate injected in May-June 2010

LF-03 Injection – EVO + Ferrous Sulfate

15

Ferrous Sulfate Product

Direct Injection into Bioreactor Frozen Mulch Sample

Mixed w/ GW + AquaBufpH™

Cumulative and Average Daily Flow

16

Sulfate Loading/Consumption Rate Over Time

17

0

4,000

8,000

12,000

16,000

20,000

24,000

28,000

32,000

0

100

200

300

400

500

600

700

800

Nov-03 Nov-04 Nov-05 Nov-06 Nov-07 Nov-08 Nov-09 Nov-10 Nov-11

Flo

w R

ate

(L/d

ay)

Su

lfate

Rat

e (m

g/L

/day

)

Date

Sulfate Loading Rate

Sulfate Consumption Rate

Flow Rate

October 2006 Enhancement

May 2010Enhancement

Sulfate consumption up to 200 mg/L/day

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Molar Concentrations of CAHs Over Time at SW3

0

500

1,000

1,500

2,000

2,500

3,000

Baseline 4 Months 7 Months 11 Months

Co

nc

en

tra

tio

n (n

mo

l/L)

Months After EVO/Ferrous Sulfate Injection

TCE

DCE

VC

Ethene

Total CAHs

Transition to biotic degradation due to iron depletion

Abiotic degradation signature

Molar Concentrations of Chloroethenes and Ethene in Deeper Zone Beneath Bioreactor

19

0

30,000

60,000

90,000

120,000

150,000

180,000

Baseline 4 Months 7 Months 11 Months

Co

nce

ntr

atio

n (n

mo

l/L)

Months After EVO/Ferrous Sulfate Injection

TCE

DCE

VC

Ethene

Total CAHs

Reduction in TCE without accumulation of DCE or VC

Cumulative Mass Removal

0

5

10

15

20

25

30

35

40

45

50

May

-03

May

-04

May

-05

May

-06

May

-07

May

-08

May

-09

May

-10

May

-11T

ota

l CA

H M

ass

Rem

ova

l (kg

)

Date

May 2010 Enhancement

October 2006 Enhancement

Note: Bioreactor was down for an unknown period prior to repair in January 2010.

Mass removal = 0.042 kg/day

Mass removal = 0.015 kg/day

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Influent versus Bioreactor Concentrations

Compound Influent (May 2010)

Within Bioreactor (May 2010)

Within Bioreactor (May 2011)

Percent Reduction (May 2010)

Percent Reduction (May 2011)

TCE (µg/L) 3,600 183 2.6 95% 99.7%

cis-DCE (µg/L) 2,300 725 169 69% 91%

VC (µg/L) 80 50 174 38% +2.3%

Ethene (µg/L) 9 3.3 29 Decrease Increase

Total Molar Chloroethenes (nmol/L)

52,900 9,890 4,800 81% 85%

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May 2010 and May 2011 (1 mo. pre- and 11 mo. post-injection)

Dechlorination efficiency for TCE, DCE, and Total Molar Chloroethenes improved after injection

Case Study: DP98, JBER, Alaska

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Direct-Push Injection Test Cell No. 1 (May 2010)

DP98 Test Cell Scenarios

Site/Location Amendments

Notes

Test Cell No. 1 EHC® Control Tight silty clay with silty sand layers, low to moderate GW flow

Test Cell No. 2 Gypsum, Hematite, Emulsified Vegetable Oil (EVO)

Tight silty clay with silty sand layers, low to moderate GW flow

Test Cell No. 3 Ferrous Sulfate with EVO Injected in former bioremediation pilot test

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A buffered EVO product was used to stabilize pH

Chloroethenes at Test Cell No. 2 (EVO + Hematite + Gypsum)

24

215134

7

3

3,531 3,3212,048

1,394

1.9

1114 20

7.9

1.7

3.2

1.00

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

1

10

100

1,000

10,000

100,000

0 2 4 6 8 10 12 14 16

To

tal l

Mo

lar

CA

Hs

(n

mo

l/L

)

Co

nc

en

tra

tio

n (µ

g/L

)

Months Since Installation

TCE Total DCE VC Ethene + Ethane Total Molar

61% decrease in Total DCEand Total Molar CAHs

Stable VCTCE reduced to below MCL

Contrast with 2005 Biostimulation with EVO

25

4,920 1,980

ND ND

15

6,366 4,696 11,147 7,838

11,068

ND ND

74

ND

200

1.2 1.2 1.7 1.4

1

10

100

1,000

10,000

100,000

0 6 12 18 24 30 36

Co

nce

ntr

atio

n (µg

/L)

Months Since Injection

CONCENTRATIONS OF CHLOROETHENES AT INJECTION LOCATION DP98INJ-02

TCE Total DCE VC Ethene + Ethane

Biostimulation stalls at cis-DCE

North Disposal Area, LMTA, Utah

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TCE Plume in 2007

LMTA Performance Objectives

Generate FeS up to 1,000 to 3,000 mg/kg Enhance rates of degradation by an order of magnitude

or more over natural rates Reduce total molar concentrations by over 90 percent (no

increase in cis-1,2-DCE or VC)

Soil cores before injection, LMTA, Utah

Soil cores 6 months after injection, LMTA, Utah

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Ferrous Iron, Sulfate, and Sulfide at LM-679 in Test Cell No. 1 (Ferrous Sulfate + EVO)

28

ND

14.2

19.5

4.900.80

0.741.14

7.86

38.9

236

556

461

212 219

0

100

200

300

400

500

600

0

10

20

30

40

50

60

-1 0 1 2 3 4 5 6 7 8 9 10 11 12

Sul

fate

Con

cent

ratio

n (m

g/L)

Con

cent

ratio

n (m

g/L)

Months from InjectionFerrous Iron Sulfide Sulfate (secondary axis)

Build up of sulfide indicates iron is limiting factor

Ferrous Iron, Sulfate, and Sulfide at LM-683 in Test Cell No. 2 (Powder Hematite + Mg Sulfate)

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0.11 0.69

21.0

17.5

2.94

0.70

3.47ND

4.57118

1,348

52 13.3ND 0

300

600

900

1200

1500

0

10

20

30

40

50

-1 0 1 2 3 4 5 6 7 8 9 10 11 12

Sul

fate

Con

cent

ratio

n (m

g/L)

Con

cent

ratio

n (m

g/L)

Months from InjectionFerrous Iron Sulfide Sulfate (secondary axis)

Low sulfate is limiting factor

Sulfate utilized at a faster rate than iron

Chloroethenes at Test Cell No. 1 (Ferrous Sulfate w/ EVO)

30

Dissolved Organic Carbon in NDA Test Cells

31

0

100

200

300

400

500

-1 0 1 2 3 4 5 6 7 8 9 10 11 12

Con

cent

ratio

n (m

g/L)

Months from Injection

LM-679

LM-680

LM-683

LM-684

Excess of Substrate

Factors Impacting Performance

High sulfate consumption rate is desirable Substrate type should behave like amendment type

(soluble with soluble and solids with solids) Utilization rates – in general soluble sulfate

reduction will be greater than solid phase iron reduction

Mineral saturation/super saturation states for iron sulfide minerals (geochemical modeling)

32

Slow release substrates such as EVO are not a good fit with soluble amendments

Factors Impacting Performance (continued)

Adequate groundwater mixing – nucleation versus crystal growth

33

Pyrite Framboids with high surface area Large pyrite grain with low surface area

Design Considerations

Limit substrate to avoid over stimulation of biological processes, yet provide for continual production of fresh FeS minerals

Use conservative tracers to confirm utilization of soluble sulfate and ferrous iron amendments

Configurations suitable for multiple injections or recirculation allow the greatest potential for optimizing the ratio of organic substrate to sulfate to iron

34

Given the challenges to enhancing abiotic processes without significant biotic dechlorination, a synergistic approach optimizing biogeochemical processes along with bioaugmentation may be an optimal approach.

Optimal Approach

Special Considerations

Co-contaminants such as nitrate and heavy metals Low pH, poor buffering capacity Very high or very low rates of groundwater flow Overstimulation of biotic dechlorination Sites with high initial populations of dechlorinators (sites

with high concentrations of DCE, VC, or DCA)

35

Buffering products for pH control

Bioaugmentation for sites with DCE, VC, or DCA

Mitigation Measures

References

AFCEE. 2008. Technical Protocol for Enhanced Anaerobic Bioremediation Using Permeable Mulch Biowalls and Bioreactors. Prepared by Parsons, Denver, Colorado.

Lebrón, C., P. Evans, K. Whiting, J. Wilson, E. Becvar, and B. Henry. 2010. In situ Biogeochemical Transformation of Chlorinated Ethenes Using Engineered Treatment Systems. Prepared for NAVFAC ESC and ESTCP.

Kennedy, L., J.W. Everett, E. Becvar, and D. DeFeo. 2006. Field-scale demonstration of induced biogeochemical reductive dechlorination at Dover Air Force Base, Dover, Delaware. Journal of Contaminant Hydrology, Vol. 88:119-136.

Leigh, D.P., R.J. Steffan, W. Grannis, and E. Becvar. 2011. Biogeochemical Degradation of Chlorinated Ethenes at Hickam AFB, Hawaii, Using Sustainable Processes. Presentation C-01, 2011 Battelle Symposium, Reno, NV.

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Questions and Discussion

Comparison of Approaches to Engineered In Situ Biogeochemical Transformation of Chlorinated Solvents Bruce M. Henry, PG 19 October 2012