Jean ParéChemco inc.

Evaluation of ISCR PRB Longevity under High Sulfateand High Flux

www.vertexenvironmental.ca

SMART RemediationO awa, ON │ February 7, 2019

SMART isPowered by:

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

6

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

9

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

10

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

11

• 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

13

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

14

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.

15

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.

16

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

17

-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

19

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

20

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:

21

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

22

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)

23

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

24

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