Enhanced Bioremediation (EK of in · 2019. 11. 14. · • Patent application filed by Geosyntec...
Transcript of Enhanced Bioremediation (EK of in · 2019. 11. 14. · • Patent application filed by Geosyntec...
-
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
SMART isPowered by:
-
1
FULL‐SCALE EK‐BIOTM OF PCE DNAPL SOURCE AREA IN CLAY TILL
Evan [email protected]
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
-
2
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
-
3
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
-
4
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
-
5
Reductive Dechlorinationof PCE to Ethene
DehalobacterDehalospirillum
DesulfitobacteriumDesulfuromonasDehalococcoides
Only Dehalococcoides &
Dehalobacter
Can accumulate if requisite bacteria are absent
9
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
-
6
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
-
7
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
-
8
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
-
9
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
-
10
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
-
11
• 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
-
12
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)
-
13
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