Jean ParéChemco inc.
Evaluation of ISCR PRB Longevity under High Sulfateand High Flux
www.vertexenvironmental.ca
SMART RemediationO awa, ON │ February 7, 2019
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1
Evaluation of ISCR PRB Longevity under High Sulfate
and High FluxPresented by Jean Paré, P. Eng.
February 2019
Series
Presentation Outline• About us
• Chemical Reduction – Technology Review
• New Geobiochemical process
• Field Application Example
2
About us • Canadian Company founded in 1988
• Production and warehouses throughout Canada• Quebec• Ontario• Alberta• British Columbia
• Sectors of activity:
• Industrial and Municipal Potable & Waste Water• Contaminated Soil and Groundwater• Air, Odours and Atmospheric Emissions (Activated Carbon,
filtering medias)• Process Water & Thermal Exchange Fluids (Glycols)• Drilling Fluids (Oil and Gas & Diamond exploration)• Aircraft De-icing Fluids
Chemical Oxidation Chemical Reduction Co solvent-Surfactant soil
Washing Enhanced
Bioremediation
Our product and services
v
Expert
Technical
Team
Field-Proven
Technologies
Field Support
R&D
and
Treatability
Laboratories
Mixing and
Handling
Equipment
Technical andDesign Support
Training &
Education
3
Excellence & Science through proud Suppliers & Partners
Since 2014
Since 2005
Since 2016
Since 2017Since 2017
Since 2014
Since 2016
Since 2014
ADVANCED OXIDATION TECHNOLOGY (AOT) Since 2005
Since 2018
hemBio
Since 2017
Formulation
Since 2014
What is Chemical Reduction?
• Transfer of electrons to contaminants from reduced metals (ZVI, ferrous iron) or reduced minerals (magnetite, pyrite)
• Major dechlorination pathway is β-elimination = dechlorination of TCE & PCE with less accumulation of metabolites (cis-DCE, VC) than enzymatic systems
• Secondary dechlorination pathway is biological (hydrogenolysis, hydrogenation)
4
β elimination (abiotic) pathway
7
Cl
C
Cl
Cl
ClCl Cl
H
Cl
Cl
Cl
Tetrachloroethene TrichloroetheneDichloroacetylene Chloroacetylene AcetyleneDichloroethene
H H
Fe( )0II Fe ( )0II Fe ( )0II
CC C C C
e‐e‐
e‐e‐e‐e‐
Redox Potential in Soil during Reductive Phase
treatment time (days)
redo
x po
tent
ial (
mV
)
-600
-400
-200
0
200
400
0 5 10
15 2520
Control FermentableCarbon
ZVI + Fermentable Carbontechnology
5
Fermentable Carbon + ZVI Synergies Generate Multiple Dechlorination Mechanisms: ISCR
3. Biostimulation:• Serve as electron donor and nutrient source for
microbial activity
• VFAs reduce precipitate formation on ZVI
surfaces to increase reactivity
• Facilitate consumption of competing electron
acceptors such as O2, NO3, SO4
• Increase rate of iron corrosion/H2 generation
4. Enhanced Thermodynamics:• Very low redox reached by addition of
fermentable carbon and ZVI (-500 mV)
• Two processes simultaneously reduce Eh
• Enhances kinetics of dechlorination reactions
via higher electron/H+ pressure
1. Direct Iron Effects:
2. Indirect Iron Effects: Dissolved iron
precipitates to reactive minerals
Hydrocarbon generation:
Material
Solid Organic Carbon
Iron Metal
Oxide Film
Fer
men
tatio
n
H+VFA
ISCR ZVI + Fermentable Carbon Treatment Mechanisms
Water table
Injection layers
Groundwater flow20m
Direct Chemical Reduction
20m
20m 20m
Indirect Chemical Reduction
Stimulated Biological Reduction
Enhanced Thermodynamic Decomposition
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Biotic and Abiotic Reductive Pathways
Biotic AbioticPCE
TCE
Cis 1,2‐DCE Trans 1,2‐DCE
VC
Ethene
Ethane
PCE
TCE
VC
Ethene
Ethane
Chloroacetylene
Acetylene
1,1‐DCE, trans 1,2‐DCE, cis1,2‐DCE
Dichloroacetylene
Hydrogenolysis
β‐elimination
α‐elimination
Hydrogenation
CO2 , CH4 , H2OCO2, CH4,H2O
In Situ Chemical Reduction (ISCR) Groundwater
Remediation Technology
ZVI + FOC
7
ZVI + FOC Reagent Composition
• Product is delivered as a dry powder and includes:
Micro-scale zero valent iron (standard ~40%)
Controlled-release, food grade, complex carbon (plant fibers) (standard ~60%)
Major, minor, and micronutrients
Food grade organic binding agent
Sustainable Solutiono By-product ZVIo Food production by-products
• PRB amendment longevity dictates reapplication frequency
• High substrate longevity prevents rebound.
• Traditional trenched PRBs containing granular ZVI with or without solid carbon sources (sawdust, woodchips) have very long life.
Amended aquifer zone / PRB
• Injected PRBs using fine-grained ZVI and carbon substrates have gained popularity allows for more efficient delivery and installation into more complex geologies, but potentially offer a more limited PRB life.
PRB Type Field Application
8
ISCR + Biogeochemical Reduction
Geobiochemical process
Biogeochemical Degradation
GeoFormTM
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Improved Distribution Properties
Advection and Dispersion of Soluble
Components
FeS Minerals Formed on Soil Particles
Direct Chemical Reduction Requires Contact with ZVI Particle
Extended Zone with Biological Reduction and Reactive Mineral Formation
VFAs H2
Nutrients
SO4‐ Fe+2
Diffusion Between Reagent Seams
Direct Push Injection Point
Iron Sulfide Minerals May Serve as a Reservoir of Electrons
FeS Minerals formed on Soil Particles downgradient from PRB
Iron Sulfide
Precipitate
CT
Methane
Fe2+ Fe3+ + e‐
• Fe2+ will be oxidized to Fe3+ during reaction with chlorinated contaminants
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Regeneration of Reactive Minerals –Iron Redox Cycle
Iron Sulfide
Precipitate
CT
Methane
Fe2+ Fe3+ + e‐
e‐ donor(reduced carbon)
oxidized carbon
Fe3++ e‐ Fe2+
• Remaining smaller concentrations of organic carbon and/or natural background TOC (~2 mg/L) may be sufficient to continuously restore Fe3+ to Fe2+
FeS Minerals formed on Soil Particles downgradient from PRB
Biogeochemical Transformation Processes where contaminants are degraded by abiotic reactions with naturally occurring and biogenically‐
formed minerals in the subsurface.
Reactive minerals include iron sulfides (e.g. pyrite, mackinawite, greigite) and oxides (e.g. magnetite)
Pyrite (FeS2) Mackinawite (Fe(1+x)SMagnetite(Fe3O4)
ß–Elimination does not generate stable toxic daughter products
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• All-In-One BioGeoChemical Reagent
• Provides All Building Blocks Needed for Reactive Mineral Formation
• Combines Sulfate, Ferrous Iron, Electron Donors, pH Buffer, and Nutrients (ZVI in Geoform Extended Release )
• Effective for Chlorinated Organics and Many Heavy Metals
• Promotes ISCR, ERD and reactive mineral formation
• Composition has been optimized to maximize generation of reactive iron sulfide minerals
• Reagents will migrate with groundwater and form an expanded treatment zone
• Increased reactive surface area for abiotic dehalogenation
ISCR
ERD
Reactive Mineral Zone
12
Engineering Reactive Iron Sulfide Minerals In Situ
Sulfate+
Fe(II) +
Electron donor
REACTIONS PROMOTEDPyrite FeS2
Mackinawite FeS
Organic Substrate Fermentation Reduced RedOx Conditions
Sulfate reduction by SRBs:2CH2O(s) + SO4
2‐ + 2H+(aq) H2S + 2CO2(aq) + H2O
Precipitation of Ferrous Iron with Sulfide:Fe2+(aq)+ H2S(aq) FeS(s) + 2H
+(aq)
Injection of GeoForm
Expanded Surface Area for Abiotic Pathway
Particle Size (µm)
Surface Area
(m2/kg)
Micro‐Scale ZVI 50‐250 ~5‐30
Framboidal Pyrite 20 ~10
FeS Coatings 3 ~80
Euhedral Pyrite 1 >200
Electron microprobe analyses performed on iron sulfide precipitation products estimated that 4.7 ft2 of very reactive surface area was generated per liter of groundwater with 3,000 mg/L sulfate reduced to an estimated 3 µm thick FeS precipitate (Leigh et al).
Euhedral FeS2~1 µm
Framboidal FeS2~20 µm
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GeoForm Formulations
• Provides a longer lasting source of electron donors for continued rejuvenation of reactive minerals.
• Extended Release Organic Carbon, Micro‐Scale ZVI, Sulfate, Ferrous Iron, pH buffers and nutrients
• Longevity of 5-10 years
• Injects as a solution forming long lasting solids.
• Proprietary blend of Soluble Organic Carbon, Sulfate, Ferrous Iron, pH buffer and nutrients.
• Delivered in 2 parts allowing for custom designs
• Longevity of 2-3 years or more
GeoForm Extended ReleaseGeoForm Soluble
GeoForm™ Formulation
Treatment Mechanisms
Biotic ReductionAbiotic Reduction
Reductive Minerals ZVI
GeoForm™ Soluble • •
GeoForm™ Extended Release • • •
GeoForm ApplicationGeoform Soluble Geoform Extended Release
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ISCR + Biogeochemical Reduction
Application Case Study
Case Study - Introduction
• One of the first full-scale ISCR reagent injection
PRBs was installed in 2005 for treatment of carbon
tetrachloride (CT).
• EHC® ISCR reagent composed of:
~40% micro-scale zero valent iron (50 - 200 µm)
~60% fine-grained processed plant fiber particles
• This presentation assesses long-term performance
and geochemical parameter changes since
installation.
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Site Background
Site Background
• CT is believed to have transported
along the bedrock surface to the
downgradient aquifer.
• Access restrictions on residential
properties further complicated
source area clean-up.
Courtesy of Malcolm Pirnie (Arcadis)
• CT plume extends ~800 m from grain elevators and
discharges into small creek.
• Shale bedrock rises to ~3 m above the water table at the
grain mill.
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Remedial Approach
PRB installed April
2005 across plume
width to limit migration.
Single row of injection
points Installed along
road right-of-way using
EHC ISCR reagent.
Remedial approach
developed by Malcolm
Pirnie (Arcadis)
PRB
Source Area Remediation Activities
• Organic carbon substrate
applications at source area injection
wells (phased pilot test):
Molasses – August 2011, 2012 and October 2013
EVO – June 2014 and 2015
Reference: 2015 Monitoring Report
from Arcadis
PRB
Source Area Injection Wells
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-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
0 27 54 81 108 135 162 189 216 243 270
Distance from SBE [ft]
Inje
cti
on
de
pth
[ft
]
Cross Section from Injection Area
Saturated sand units targeted
PRB Dimensions = 270 ft Long x 10 ft wide x 10 ft
average thickness
24 tons of EHC ISCR Reagent injected
Application Rate = ~1% to targeted soil mass
Field Installation
A 30% EHC slurry injected via direct push
Field installation completed in 12 days
18
Evaluation of PlacementSoil cores used to verify ROI and determine injection spacing:
EHC slurry was found in discrete seams 5 ft away from injection locations
Injection points spaced 10 ft apart
Vertically dipping fracture
Horizontal fracture
Performance Evaluation CT and degradation products
ISCR Reagent indicator parameters
(TOC)
Geochemical parameters, including
ORP, nitrate, and sulfate
Voluntary Clean-up Plan goals
minimum 95% CT reduction from
baseline concentrations at
compliance points located 21 m and
42 m downgradient.
(CT concentrations March 2005 in ppb)
PRB
Compliance Points
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Performance Evaluation
MW-105 - 21 m downgradient at
plume center (~39 days travel time*).
MW-106 - 42 m downgradient at
plume edge (~78 days travel time*).
MW-VCl-6 ~180 m downgradient
(~333 days travel time*).
Inflowing concentrations monitored at
MW-VCI-4
*estimated groundwater flow velocity of
0.55 m/day
(CT concentrations March 2005 in ppb)
PRB
MW‐VCL4 (upgradient / inflowing) MW‐105 (21 m downgradient)
Geochemical Data
1
10
100
1000
‐1 4 9 16 22 36 48 79 91 109 120
TOC (mV)
Months since PRB installation
Total Organic Carbon
‐400
‐300
‐200
‐100
0
100
200
300
400
‐1 4 9 16 22 36 79 91 109 120ORP (mV)
Months since PRB installation
ORP
0
20
40
60
80
100
120
140
160
‐1 4 9 16 22 36 48 79 91 109 120
Sulfate (m
g/L)
Months since PRB installation
Sulfate
0
1
2
3
4
5
6
7
8
9
‐1 4 9 16 22 36 48 79 91 109 120
Nitrate (mg/L)
Months since PRB installation
Nitrate
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Micro-scale ZVI Longevity
Theoretical estimation of micro-scale ZVI longevity:
ZVI oxidation due to reduction of terminal electron acceptors; calculated based on
Stoichiometric demand from:
Naturally occurring terminal electron acceptors such as dissolved oxygen
(DO), nitrate and sulfate;
Chlorinated contaminant reduction.
Corrosion is an important ZVI consumption process and rates are expected to be
more constant over time (estimated at 1.5 mmol/kg/day for micro-scale ZVI):
Fe0 + 2H2O Fe2+ + H2(aq) + 2OH-
Theoretical Calculation of ZVI Longevity
Influent (mg/L)
Mass flux (kg/yr)
Mass flux (kmol/yr)
ZVI used (kmol/yr)
ZVI used (kg/yr)
% ZVI used per year
Water corrosion ‐‐‐ ‐‐‐ ‐‐‐ ‐‐‐ 267.0 3.07%
DO 0.4 4.0 0.13 0.17 9.4 0.11%
CT 1 10.0 0.07 0.26 14.6 0.17%
CF 0.01 0.1 0.00 0.00 0.1 0.00%
NO3 4 40.2 0.65 2.59 145.2 1.67%
SO4 120 1,205.6 12.56 50.23 2,813.0 32.30%
Total 37.3%
Estimated ZVI Longevity (yrs) 2.7
PRB interface for gw flow (m2)
PRB width (m)
ZVI Dose Rate (mass)
ZVI Mass (kg)
GW velocity (m/day)
Effective porosity
Volume gw passing thru PRB (L/yr)
251 3 0.4% 8,709 0.59 0.2 100,462,501
Estimation assuming 100% of inflowing sulfate being reduced:
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Sulfate reduction over time
0
20
40
60
80
100
120
140
160
180
‐1 1 4 6 9
13
16
19
22
28
36
42
48
59
79
85
91
96
109
114
120
126
Sulfate (mg/L)
Months since PRB installation
MW‐VCL4 (upgradient / inflowing) MW‐105 (21 m downgradient)
MW‐106 (42 m downgradient)
0
250
500
750
1000
1250
1500
1750
-1 1 4 6 9 13 16 19 22 28 36 42 48 54 61 66 79 85 91 96 102 109 114 120 126 132 138 145 150
Co
nc.
(p
pb
)
Time post injection (months)
70 ft / 21 m downgradient from PRB
CM
DCM
CF
CT
02468
10121416
-1 1 4 6 9 13 16 19 22 28 36 42 48 54 61 66 79 85 91 96 102 109 114 120 126 132 138 145 150
Co
nc.
(p
pb
)
Time post injection (months)
140 ft / 43 m downgradient from PRB (edge of plume)
CM
DCM
CF
CT
Performance Data
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Performance Data
0
50
100
150
200
250
300
-1 1 4 6 9
13 16 19 22 28 36 42 48 54 61 66 79 85 91 96 102
109
114
120
126
132
138
145
150
Co
nc.
(p
pb
)
Time post injection (months)
600 ft / 183 m downgradient from PRB
CM
DCM
CF
CT
0
500
1000
1500
2000
2500
3000
-1 1 4 6 9
13 16 19 22 28 36 42 48 54 61 66 79 85 91 96 102
109
114
120
126
132
138
145
150
Co
nc.
(p
pb
)
Time post injection (months)
Inflowing concentrations measured 85 ft / 26 m upgradient of PRB
CM
DCM
CF
CT
Indirect Chemical Reduction
Definition - processes where contaminants are degraded by abiotic reactions with naturally occurring and biogenically-formed minerals in the subsurface.
Reactive minerals include iron sulfides (e.g. pyrite, mackinawite, greigite) and oxides (e.g. magnetite)
Inflowing sulfate = ~120 mg/L iron sulfides are likely precipitation products downgradient from PRB indirect chemical reduction may be an important mechanism to explain reactive life
Pyrite (FeS2) Mackinawite (Fe(1+x)SMagnetite(Fe3O4)
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Engineering Reactive Iron Sulfide Minerals In Situ
Sulfate+
Fe(II) +
Electron donor
REACTIONS PROMOTEDPyrite FeS2
Mackinawite FeS
Organic Substrate Fermentation Reduced RedOx Conditions
Sulfate reduction by SRBs:2CH2O(s) + SO4
2‐ + 2H+(aq) H2S + 2CO2(aq) + H2O
Precipitation of Ferrous Iron with Sulfide:Fe2+(aq)+ H2S(aq) FeS(s) + 2H
+(aq)
Injection of GeoForm
PRB EconomicsInstallation costs:
Amendment: 24 tons of EHC ISCR Reagent used in PRBProduct cost = ~$100,000
Injection: 2 weeks of GeoprobeInjection Cost = ~$50,000
Total Fixed Cost: $150,000
Operating Cost: None
Longevity:
A single application of EHC has remained active for a period of ~9.5 years before indications of breakthrough started to be observed, continuously supporting >95% removal of CT without the accumulation of catabolites.
PRB treated an estimated ~140,000 m3 GW over its reactive life
Product Cost = ~$0.71 /m3
This is significantly lower than the pump and treat alternative where just the annual O&M Costs can range from $ 50K to $ 300K
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ConclusionsCombination of ZVI and FOC synergistically provides multiple biological and chemical reductive pathways
FOC provides long term source of electrons, enhances biological reduction, maintains pH and limits ZVI passivation
Geoform enhances biological, chemical and biogeochemical degradation processes.
ZVI causes abiotic degradation, maintains pH,
Acknowledgement
• Peroxychem
Contact informationE‐mail: jean.pare@chemco‐inc.com Tel: 418‐953‐3480 / 800‐575‐5422
www.chemco‐inc.com