Evan CoxGeosyntec Consultants, Inc.

Full‐Scale Electrokinetic‐Enhanced Bioremediation (EK‐BIO) of PCE DNAPL Source Area in Clay Till 

www.vertexenvironmental.ca

SMART RemediationToronto, ON

January 29, 2015

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FULL‐SCALE EK‐BIOTM OF PCE DNAPL SOURCE AREA IN CLAY TILL

Evan Coxecox@geosyntec.com

THE CHALLENGE OF LOW PERMEABILITY MATERIALS

Over time, contaminants diffuse into low permeability (low K) materials

Clays/silts serve as secondary sources for decades after cleanup of sands/gravels

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IN SITU REMEDIATION IS ALL ABOUT DELIVERY AND CONTACT

Bio and ISCO are effective technologies, but amendment distribution is poor in Low K and heterogeneous materials

Better amendment delivery techniques are required for low K sites

SOLUTION = ELECTROKINETIC MIGRATION

Application of direct current (dc) to saturated subsurface

Amendments move through clays and silts by:

• Electro‐migration (EM) – movement of charged ions

• Electro‐osmosis (EO) – bulk movement of water

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As Kh decreases, EK becomes the most efficient delivery method

Why will EK work in low‐K formations where conventional injection techniques commonly fail?

Advection

WHY EK WORKS?

electron donor amendment

low power requirementsreverse polarization

cross‐circulation for pH control

amendmentsupply well

amendmentsupply well

electron donorsfollow electric field

CLAY

sand stringers

SAND

clay stringers

more uniform distributionof amendment

HOW EK IS APPLIED IN THE FIELD

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EK‐BIOTM = Distribution of electron donors (lactate) or acceptors (oxygen, nitrate) and/or microorganisms (Dehalococcoides, Dehalobacter) to promote biodegradation

EK‐ISCOTM = Distribution of permanganate (MnO4‐) to promote oxidation

EK‐TAPTM = Distribution of persulfate (S2O82‐) by EK (DC current), followed by thermal activation of the persulfate (AC current)

EK TERMINOLOGY

EK‐BIOTM

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Reductive Dechlorinationof PCE to Ethene

DehalobacterDehalospirillum

DesulfitobacteriumDesulfuromonasDehalococcoides

Only Dehalococcoides &

Dehalobacter

Can accumulate if requisite bacteria are absent

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FULL‐SCALE EK‐BIOSITE LOCATION

Treatment area: Hot Spot IV

PCE DNAPL

10.000-100.000 µg CVOC/L

1.000-10.000 µg CVOC/L

100-1.000 µg CVOC/L

AREA A

AREA B

Groundwater Flow Direction

Area 150 m2, depth 8 m

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THE ROAD TO FULL‐SCALE

Start: 100 mg PCE/kg Day 100: 

All PCE degradedto ethene

2009 ERD Microcosms• 100% PCE degradation 

via ERD with Dehalococcoides (Dhc) bioaugmentation

2010 EK‐BIO Lab Test• Lactate transport 

rate 3.2 cm/day• Increase in vcrA

numbers• PCE dechlorination 

to VC and ethene

2011 EK‐BIO Field Pilot Test• Lactate transport rate 

2.5‐5 cm/day• Increase in vcrA in 

groundwater and clay• PCE dechlorination to VC 

and ethene• PCE desorption and 

dissolution

Stage 2

Stage 1

Stage 3

Stage 1

Stage 4

Stage 3

Stage 2

Stage 4

Stage 2

Stage 3

Stage 4

Stage 1

FULL‐SCALE PROJECT SCHEDULE

Cycle 1:2012‐2014 Cycle 2:2014‐2015 Cycle 3:2016‐2017

Status today

BioaugmentationArea A Bioaugmentation Area B

• Alternating active‐passive phases of 90 days per area

• Full‐scale remedial duration estimated at 3‐5 years

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ELECTRICAL FIELD & LAYOUTAREA A  – STAGE 1 + 3

Anodes (+)

Cathodes (‐) 

Injectionwells

Monitoringwells

Electromigra‐tion: Donortransport

Elektro‐Osmosis: Biomasstransport

Stage 1: Operation period dec. 2012 – apr. 2013 Stage 3: Operation period sep. 2013 – dec. 2013

FULL‐SCALE EK‐BIO COMPONENTS

Katode

Lactate tanks

Lactic acid

NaOH

Injektionsboring

Anode

CathodeInjection well

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DISTRIBUTION OF DONOR (AS NVOC)‐ High donor concentration in treated areas‐ Partial donor depletion during passive stages

BASELINE STAGE 4STAGE 2

STAGE 1 STAGE 3

PCE DECHLORINATION TO ETHENE‐ Dechlorination to VC & ethene in all wells‐ PCE only present in 2 wells after Cycle 1

BASELINE

STAGE 3

STAGE 2

STAGE 1

STAGE 4

Molar

fraction

Molar

fraction

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SOIL CORE RESULTS AFTER CYCLE 1 

‐ Decrease in total CVOC‐ Decrease in PCE‐ Production of cDCE, VC and ethene

‐ Increase in vcrA in clay samples from 103/gram to 106/gram

‐ Production of chloride‐ Soil results support gw results

B: Baseline         C1: After Cycle 1

B B B

B B B

C1 C1 C1

C1 C1 C1ADJACENT MONITORING WELL

CONCLUSIONS AFTER YEAR 1

• Effective distribution of lactate across treatment area in clays• Increase in vcrA in groundwater and clay across treatment area• Complete dechlorination of PCE to ethene; PCE mass declining• PCE desorption and dissolution – should shorten remedial duration

• Soil data confirm that dechlorination is occurring in the clay till

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EK‐ISCOTMEK‐TAPTM

T = 12 hr w/ 8-hr EK(MnO4- flushing with EK)

T = 6 hr w/ 2-hr EK(MnO4- flushing with EK)

T = 12 hr(MnO4- flushing;No EK)

EK-ISCO

Med

ium

to F

ine

silt

Med

ium

to F

ine

silt

Coa

rse

san

d

Coa

rse

san

d

Coa

rse

san

d

T = 6 hr(MnO4- flushing;No EK)

Flow Direction

Electric Field Direction

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• Use of dual purpose EK-ERH electrodes

• EK uses direct current (DC) to inexpensively distribute

persulfate through clays and silts

• ERH then uses alternating current (AC) to heat soils

• Contaminant (incl. 1,4-Dioxane) is oxidized in situ at

~40oC rather than boiled/volatilized at 100oC

• Less energy use, no SVE = lower remediation cost

• Patent application filed by Geosyntec

EK-TAP(Thermally-Activated Persulfate)

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

0.0 5.0 10.0 15.0

Tota

l Sul

fur S

oil C

once

ntra

tion

(mg/

kg)

Distance from Anode (cm)

Initial Soil Concentration Soil Concentration Following EK(Total sulfur used as persulfate analogue)

EK-TAP in Clay Soil, Northern California

20 g/L persulfate

Anode CathodePersulfate Electromigration

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0

0.005

0.01

0.015

0.02

0.025

0.03

0 2 4 6 8 10 12 14

Tota

l mm

ols

CO

Cs

Distance From Anode (cm)

Following EK-TAPBackground

21 Days of EK2 Days Heating(45oC)

COCsPCETCE1,1DCEcis-DCE1,4-D

~99% Decrease

Anode CathodePersulfate Electromigration

EK-TAP in Clay Soil, Northern California

How Do I Get Me Some of That?

Treatability Testing ($15,000 - $40,000)

Kinetics (NOD, batch testing)

Column migration experiments or 2D box reactor experiments

Pilot test ($200,000 - $300,000, depends on scale)

Full-scale implementation ($85/yd3)

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Acknowledgements

– Geosyntec Consultants• David Reynolds• James Wang

– NIRAS A/S• Charlotte Riis• Martin Bymose

– US Army Engineer R&D Center• David Gent

– The Capital Region DK• Mads Terkelsen

– Western University• Denis O’Carroll• Ahmed Chowdhury

QUESTIONS EK‐Bio Wins a Green Innovation (Sustainability) Award from US Army Corps of Engineers