Successful Biostimulation Treatment of PCE/TCE DNAPL at...

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Successful Biostimulation Treatment of PCE/TCE DNAPLat Redevelopment Sites

EKOS IV International Seminar on Remediation and Redevelopment of Contaminated Sites

Andre Rebouças – ARCADIS Hidro Ambiente S/A

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Business Reducing Risk

+

-

Remed

iation

Infra

struc

ture

Pre-D

evelo

pmen

t

New us

ers/m

arke

ts

Inves

tigati

on

value “as is” value after cleanup

Value

High risk / low profit zone of industrial property owners

Risk

Low risk/ high profit • Approved plan• Future users identified• Best/ highest use

determined • Remediation/risk

assessment completed/approved

Buildin

gs

value after development

3

Presentation Overview

• DNAPL Source Zone Characteristics – The Challenge

– Structure and cleanup problems associated with DNAPLs and other persistent contaminant sources

– The politics of DNAPL – Are regulators open to changing its approach to persistent source management?

- Adaptive design approaches- Alternative closure approaches- Alternatives for site development

• Case Studies - DNAPL Source Zones

• Conclusions and Implications

4

DNAPL Accessibility/Recoverability

• Challenges to Removing DNAPL

– Weathered NAPLs: viscosity/interfacial tension effects

– Partitioning: Low Solubility Hydrophobic Compounds

– Matrix Effects and Heterogeneity: Drainable Fractions (migratory porosity vs. total porosity)

– Dense Targets: gravity vs. hydraulic gradient

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Potential Applicability of Biostimulation

Possible passive candidateDrain first then treat residual as needed

Drainable mixed DNAPL

No - drain first, then treat residualDrainable neat DNAPL

Low probability✓(possible passive)

Mixed DNAPL residual

Low probability✓Neat DNAPL residual

✓✓Sorbed phase

✓✓Dissolved phase

Achieve Standards in Groundwater

Reduce Long-Term Care Cost

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Microbiology/Bio-Geochemistry

• Biostimulation- Electron donor loading

exceeding natural electron acceptor recharge

- Microbial ecology shift from aerobic to strongly anaerobic communities (sulfate-reducing and methanogenic)

- Fermentation reactions to enhance solubility of sorbed and NAPL mass

7

Reactive Zone Approach

0 1 2 3 4 5 6Time of travel (years)

Plan view

reactive zones

desorption zones

1 12

8

groundwater flow

Conceptual DNAPL Source Plume (Plan View)

Oil-saturated drainable

NAPL

water-saturated drainable NAPL

water-wetted residual NAPL

sorbed-phase-dominant zone

aqueous-phase-dominant zone

MCL

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sorbed mass

drainable

residual

Aqu

ifer S

olve

nt M

ass

(kg/

m3 )

MCL

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

10310 mg/L

foc = 0.0051 mg/L

foc = 0.0001

mobile dissolved

phase

immobile dissolved

phase

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Field Condition DNAPL - Transition from “Oil/Grease Dissolved in Solvent” to “Solvent Dissolved in Oil/Grease”

Neat PCE Neat TCEField

DNAPL 17% CVOC

Field DNAPL

<0.1% CVOCDensity (g/cm3)

Interfacial tension

(dynes/cm)

Dynamic viscosity

(cP)

1.63

44.4

1.47

34.5

0.844 0.444

1.05

11.6

10.4

1.04

14.3

51.7

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The Aging Process - Mixed NAPLs Become Increasingly Inaccessible

Solv

ent L

each

ing

Rat

e

Solvent Mass Remaining100% 50% 0%

0

Max oil/grease dissolved in solvent

solvent dissolved in oil/grease

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The Multi-Porosity Aquifer Matrix:NAPL Distribution and Fluid Mobility

Soil Particle

MIGRATORYW

ATER

Resident Water

Soil Organic Matter

MOVEMENT

Residual NAPL

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Plan View

Total non-aqueous-phase mass

Sorbed mass

NAPL massdrainable

residual

Migrating aqueous-phase mass

Static aqueous-phase mass

10-6

10-5

10-4

10-3

10-2

10-1

100

101

Aqu

ifer S

olve

nt M

ass

(kg/

m3 )

Typical Treatment Standard

Total aqueous-phase mass

groundwater flow

102

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Organic Carbon Fraction (foc)0.000 0.002 0.004 0.006 0.008 0.010

Perc

ent S

orbe

d

0

20

40

60

80

100

Koc = 265 (PCE)

Koc = 36 (cis-1,2-DCE)

Koc = 94 (TCE)

Koc = 19 (vinyl chloride)

blan

king

Koc = 1,191 (Naphthalene)

Aquifer Matrix Sorption Effects

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What Processes are Stimulating DNAPL and Sorbed-Phase Source Mass Dissolution?

• Increased Concentration Gradients

• Co-Solvent Effects

• Biosurfactant Effects

- Decreased Interfacial Tension- Increased NAPL Surface Area

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The Ideal ERD Outcome - Desorption

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Anaerobic In-Situ Reactive Zones (IRZs)

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Example: Gaining Access to Non-Aqueous Sorbed Contaminant Mass

Elapsed Time (days)-600 -400 -200 0 200 400 600 800 1000 1200

Con

cent

ratio

n (u

mol

/L)

0

10

20

30

40

50

60

70PCETCEcis-1,2-DCEVinyl chlorideEtheneEthane

The Biostimulation Process is Mining Sorbed-Phase MassIncreased DCE

Concentrations

Ethene Production –Complete Dechlorination

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Case Studies – DNAPL Source Zone ERD

Case Study #1 – Southeastern United States

- PCE DNAPL Source Zone (100% saturation)

Case Study #2 – Location

- TCE DNAPL Source Zone (20% TCE saturation)

Case Study #3 – Location

- PCE DNAPL (25% PCE saturation)

DRYCLEANERS

1998

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Generalized lithology

Low-permeability silts and clays

Site land surfaceSa

tura

ted

thic

knes

s =

10 m

ts

Weathered bedrock

Moderate-permeability at the weathered bedrock interface with

some sand strata

Initial Carbon Injection

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Case Study #1: PCE DNAPL in Unconsolidated Formation Remedial Approach: Scope and Results

• PCE DNAPL Source Zone (100% saturation)

• Existing Pumping Sysytem: 5 to 30m3/day at 4 wells

- 15 years operation

• Challenging:- Site development requires to enhance the remediation- Risk reduction as site development step- Remediation project has to fit on the development budget

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Case Study #1: PCE DNAPL in Unconsolidated Formation Remedial Approach: Scope and Results

• PCE DNAPL Source Zone (100% saturation)

• Existing Pumping Sysytem: 5 to 30m3/day at 4 wells- 15 years operation

• 43 IRZ Injection Wells Installed to 9 m

• 10 Monitoring Wells

• Loading: 2000 L/well at 10% TOC (6 to 12 week intervals)

• 3 Years of Enhanced Reductive Dechlorination- Concentrations in Mws peaked at one year of treatment- Mass removal increases in extraction wells increased by several

orders of magnitude

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0 200

feet

Solvent release areawith DNAPL present

(pre-1989)

Groundwater extraction wells - installed 1989

Approximate Direction of Groundwater Flow

Baseline Site Conditions

Areal extent ≈ 1.9 ha (4.7 acres)Saturated thickness ≈ 8 m (25 ft)Conductive zone ≈ 1.5 m (5 ft)

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PCE DNAPL Site – Injection (Source) Zone

Elapsed Time (days)

-400 -200 0 200 400 600 800 1000

Con

cent

ratio

n (u

mol

/L)

0

1000

2000

3000

4000

5000

6000

PCETCEcis-DCEVCEtheneEthanePCE solubility limit

160 PPM PCE

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PCE DNAPL Site - Downgradient of Source Zone

Elapsed Time (days)

-400 -200 0 200 400 600 800 1000

Con

cent

ratio

n (u

mol

/L)

0

2

4

6

8

10

12

14 PCETCEcis-DCEVCEtheneEthane

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Elapsed time (days)

-2500 -2000 -1500 -1000 -500 0 500 1000

Extr

actio

n w

ell y

ield

S u

m o

f PC

E to

VC

(mol

/day

)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

EW-A

PCE DNAPL Site - Extraction Well Mass Recovery

Initial Injection

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Elapsed time (days)

-2500 -2000 -1500 -1000 -500 0 500 1000

Extr

actio

n w

ell y

ield

S u

m o

f PC

E to

VC

(mol

/day

)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

EW-B


Initial Injection

31Elapsed time (days)

-2500 -2000 -1500 -1000 -500 0 500 1000

Extr

actio

n w

ell y

ield

S u

m o

f PC

E to

VC

(mol

/day

)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

EW-C


Initial Injection

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Elapsed time (days)

-2000 -1500 -1000 -500 0 500 1000

Extr

actio

n w

ell y

ield

S u

m o

f PC

E to

VC

(mol

/day

)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

EW-D


Initial Injection

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Changing Mass Flux Composition: Extraction Well EW-C

Elapsed Time (days)

-400 -200 0 200 400 600 800 1000

Con

cent

ratio

n (u

mol

/L)

0

20

40

60

80

100

120

140 PCETCEcis-DCEVCEtheneEthane

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PCE DNAPL Site - Performance Summary

• Mass flux reduction ~ 4-fold compared to immediate pre-treatment pumping well yield

• Contaminant composition – shift from PCE and cis-DCE to VC, ethene and ethane

• Cost ~ $1.43 MM USD for 150,000 m3 = $9.50/m3

• Was it worth it?

Successful RemediationSuccessful Property Redevelopment

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Case Study #2: TCE DNAPL

• TCE NAPL located under building with groundwater concentrations greater than 300 mg/L (25% of solubility mg/L)

• Water table aquifer consisting of silty sand to a depth of 35 feet bgs

• Anaerobic IRZ in conjunction with pump-and-treat selected as remedy for groundwater

- 43 injection wells- Quarterly injection

• Groundwater extraction used to promote migration of organic carbon beneath site building

• Anaerobic IRZ accesses NAPL and sorbed-phase mass, making it available for bioremediation

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January 2003

January 2004

TCE up to 300 ppm(solubility ~ 1,100 ppm)

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December 2005

November 2004

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January 2003

January 2004

December 2005

LEGEND:

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0

2

4

6

8

10

12

0 100 200 300 400 500 600 700 800 900 1000Time (Days)

pH (S

U)

pH

0

50

100

150

200

250

300

0 100 200 300 400 500 600 700 800 900 1000Time (Days)

TOC

(mg/

L)

0

5,000

10,000

15,000

20,000

25,000

30,000

TOCInjectionsMethane

0

50

100

150

200

250

0 100 200 300 400 500 600 700 800 900 1000Time (Days)

Mol

arity

(µm

oles

/L)

TCEc-DCEVCEtheneTotal

pH (>6) in optimal range for ERD

Increased methane (methanogenesis) with arrival of TOC

Sequential dechlorination of parent and daughter products

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Degradation Trends Demonstrating Solubilization and Treatment of NAPL

0

50

100

150

200

250

May-03 Jul-03 Sep-03 Nov-03 Jan-04 Nov-04 Feb-05 May-05 Sep-05 Dec-05

Date

Mol

ar T

CE,

cis

-DC

E, V

C, &

Eth

ene

Con

cent

ratio

ns (u

mol

/L)

Ethene

VC

cis-DCE

TCE

0.01

0.1

1

10

100

1000

10000

Met

hane

and

TO

C

conc

entra

tion

(mg/

L)

TOCMethane

2x increase in total molarity from baseline demonstrates mining/solubilization of NAPL, making it available for treatment

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Case Study #3: TCE DNAPL in Fractured Rock

• Property Boundary IRZ

- ERD system controls plume at property boundary- Replaced former pump and treat system- Optimization of injection program (frequency and volume) used to

maximize cost savings- IRZ Line #2 shutdown in 2006- Initiated plume control prior to implementing source zone IRZ

• Source Area IRZ- Innovative combination of pneumatic fracturing and ZVI/molasses

injection has resulted in accelerated source reduction- Molasses injection supports active PCE biodegradation- PCE declined 77-99.9% in all source area wells following ZVI injection

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1,000

100

10

1

5,000

PCE

CO

NC

ENTR

ATI

ON

(PPB

)

1998

44

1,000

100

10

1

5,000

PCE

CO

NC

ENTR

ATI

ON

(PPB

)

2000

45

IRZ TREATMENTLINE 2

IRZ TREATMENT LINE 1(SOURCE AREA TREATMENT)

1,000

100

10

1

5,000

PCE

CO

NC

ENTR

ATI

ON

(PPB

)

2002

46

IRZ TREATMENTLINE 2


1,000

100

10

1

5,000

PCE

CO

NC

ENTR

ATI

ON

(PPB

)

2003

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IRZ TREATMENTLINE 2


1,000

100

10

1

5,000

PCE

CO

NC

ENTR

ATI

ON

(PPB

)

2004

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IRZ TREATMENTLINE 2


1,000

100

10

1

5,000

PCE

CO

NC

ENTR

ATI

ON

(PPB

)

2005

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Case Study #3 - Summary of Biostimulation Results

• Substantial dissolution/desorption in areas of sorbed mass and residual DNAPL

• Complete dechlorination achieved at sites with moderate contaminant levels

• Strong association between carbon distribution, onset of methanogenesis and late-stage dechlorination

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Imagine the Result

……. Questions?

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Thank You …….

Andre Rebouças Arcadis Hidro Ambiente S/AR. Dom Joaquim 1168 - Granja Viana - Cotia06709 202 – BRASIL

Tel: +55 11 4612 7799 Email: [email protected]

www.hidroambiente.com.br

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