performance challenges encountered with permeable reactive...

Performance Challenges Encountered with Permeable Reactive Barriers

David Blowes

University of Waterloo

Permeable Reactive BarrierPermeable Reactive Barrier

PermeablePermeableReactiveReactiveBarrierBarrierContaminantContaminant

SourceSource

Contaminant PlumeContaminant Plume

Reactive Barriers for Dissolved Reactive Barriers for Dissolved Metals and Inorganic ContaminantsMetals and Inorganic Contaminants•• Designed to:Designed to:

•• Change redox state of dissolved metalChange redox state of dissolved metal•• Precipitate insoluble solidsPrecipitate insoluble solids•• Adsorb contaminantsAdsorb contaminants

•• Objective:Objective:•• Passive treatment consistent with the scale and Passive treatment consistent with the scale and

duration of contamination problemsduration of contamination problems•• Status:Status:

•• Initial installations now in place for > 10 yearsInitial installations now in place for > 10 years

PRB for Treating Inorganic PRB for Treating Inorganic ContaminantsContaminants

United States

Canada

Pilot-ScaleFull-Scale

EuropeEuropeEuropeEurope

Typical Cost ComparisonTypical Cost Comparison

$0

$1,000,000

$2,000,000

$3,000,000

$4,000,000

$5,000,000

$6,000,000

$7,000,000

$8,000,000

$9,000,000

$10,000,000

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

Cum

ulat

ive

Pre

sent

Cos

tC

umul

ativ

e P

rese

nt C

ost

Time (Years)Time (Years)

Pump And Treat

Natural Attenuation

PRB with NA (10 yr life cycle)

PRB (10 yr life cycle)

R. Landis, R. Landis, DuPontDuPont Inc.Inc.

Fe(II), SO4

Fe(II) oxidationH release+

Fe(II), SO4Near Neutral

pH Groundwater

Acid Neutralization

Sulfide Oxidation

Fe(II), SO4

Fe(II), SO4 Fe(II) Oxidation H+ release

River or Lake

H2OO2

O2

Mine Waste Sites

Sulfide Oxidation Fe(II) Oxidation

Permeable Reactive Barrier

Groundwater Flow

Bedrock

Fluvial/Glacial Deposits

Mine Tailings

Earthen/Rock TailingsDam (permeable)

AMD Plume

Reactive MaterialsReactive Materials

Reduction and PrecipitationReduction and Precipitation•• Zero Zero valentvalent ironiron•• Organic carbonOrganic carbon•• MixturesMixtures

AdsorptionAdsorption•• Basic Oxygen Furnace (BOF) oxides and Basic Oxygen Furnace (BOF) oxides and

slagsslags•• ZeolitesZeolites

Construction Challenges Construction Challenges

•• Depth of plumeDepth of plume•• Most techniques limited to <100 mMost techniques limited to <100 m

•• InfrastructureInfrastructure•• Buildings, service corridors, utilitiesBuildings, service corridors, utilities

•• Regulatory approvalsRegulatory approvals•• Land titlesLand titles•• CostCost

Implementation Challenges Implementation Challenges •• Inadequate site characterizationInadequate site characterization

•• Poorly defined plume characteristicsPoorly defined plume characteristics•• Size, depth, concentration rangesSize, depth, concentration ranges

•• Insufficient characterization of aquifer Insufficient characterization of aquifer propertiesproperties

•• Incomplete data interpretationIncomplete data interpretation•• Unrealistic expectationsUnrealistic expectations

•• Overly pessimistic Overly pessimistic –– high costshigh costs•• Overly optimistic Overly optimistic –– incomplete incomplete

treatmenttreatment

Performance Challenges Performance Challenges

Zero Zero valentvalent ironiron•• Residence time/high velocityResidence time/high velocity

•• Exceed reaction rate limitationsExceed reaction rate limitations•• pH increase pH increase •• Excessive carbonate precipitation Excessive carbonate precipitation YY CloggingClogging

Contaminants Suitable for Contaminants Suitable for Treatment using Zero Treatment using Zero ValentValent IronIron

•• ChromiumChromium•• SeleniumSelenium•• ArsenicArsenic•• UraniumUranium•• TechnetiumTechnetium•• MercuryMercury•• MolybdenumMolybdenum•• VanadiumVanadium•• Other elements with lower Other elements with lower solubilitiessolubilities in in

reduced formsreduced forms

Treatment of ChromateTreatment of Chromate--Contaminated Contaminated GroundwaterGroundwater

Reduction:Reduction:8H8H++ + CrO+ CrO44

22-- + Fe+ Fe00(s)(s) ⇒⇒ FeFe3+3+ + Cr+ Cr3+3+ + 4H+ 4H22OO

FeFe00 + 2H+ 2H22O O YY FeFe2+2+ + H+ H2(g) 2(g) + 2OH+ 2OH--

Precipitation: Precipitation: CrCr3+3+ + 3OH+ 3OH-- ⇒⇒ Cr(OH)Cr(OH)33 (s)(s)

CrCr3+ 3+ + Fe+ Fe3+3+ +3OH+3OH-- ⇒⇒ (Fe,Cr)(OH)(Fe,Cr)(OH)3(s)3(s)

Scale (km)Scale (km)

00

22

NixontonNixontonWeeksvilleWeeksville

ElizabethElizabethCityCity

REACTIVEREACTIVEBARRIERBARRIERSTUDY SITESTUDY SITE

Elizabeth City Reactive BarrierElizabeth City Reactive Barrier

Installed: 1996

Collaborators

US EPA

US Coast Guard

0 10

meters

N

Cr (mg/L)June 1994

Building 78

Pasquotank River

1.6

<0.01

<0.01 <0.01

<0.01

<0.01

<0.01

<0.01

<0.01

5.6

8.2

0.22

3.8

0.08<0.01

0.050.05

2.52.5

0.050.05

2.52.5

Bui

ldin

g 78

HANGAR 79

Reactive MaterialReactive Material

•• 150 m150 m33 zero zero valentvalent iron (280 tons)iron (280 tons)•• 46 m long, 7.3 m deep and 0.6 m wide barrier46 m long, 7.3 m deep and 0.6 m wide barrier

Continuous Trenching MachineContinuous Trenching Machine

USCG Wall InstallationUSCG Wall Installation

pHpH

--66

--44

--22

Depth (m)

Groundwater flow directionGroundwater flow direction 00 50 cm50 cm

55667788991010

WallWall

Dep

th (m

)D

epth

(m)

Eh (mV S.H.E.)Eh (mV S.H.E.)

--66

--44

--22

Depth (m)


--600600--400400--20020000200200400400

WallWall

Dep

th (m

)D

epth

(m)

Cr(VI) (mg/L)Cr(VI) (mg/L)

--66

--44

--22

Depth (m)


000.050.051.01.02.02.0

WallWall

Dep

th (m

)D

epth

(m)

Electrical Conductivity (Electrical Conductivity (μμSS/cm)/cm)

--66

--44

--22


200200400400600600800800

WallWall170.01

00

Dep

th (m

)D

epth

(m)

CaCOCaCO33 (mg/L)(mg/L)

--66

--44

--22

Depth (m)


00202040406060

WallWall

135.00

Dep

th (m

)D

epth

(m)

Mineralogical CharacterizationMineralogical Characterization

•• Increased solidIncreased solid--phase carbonphase carbon•• carbonate minerals isolated carbonate minerals isolated •• CaCOCaCO33•• siderite (FeCOsiderite (FeCO33))•• Fe Fe HydroxycarbonateHydroxycarbonate

•• Iron oxyhydroxides Iron oxyhydroxides •• goethitegoethite•• ferrihydriteferrihydrite•• green rust green rust

•• Iron SulfidesIron Sulfides

Modelling Barrier PerformanceModelling Barrier Performance

•• Reactive transport model: MIN3PReactive transport model: MIN3P

•• Groundwater transportGroundwater transport•• Use siteUse site--specific data specific data

•• Reaction kineticsReaction kinetics•• Lab determined rate constantLab determined rate constant•• Field observationsField observations

0 0.5 1 1.5 2 2.5 3 3.5 4distance [m]

4

4.5

5

5.5

6

6.5

7

dept

h[m

]11.010.29.48.67.87.06.2

pH

[-]

0 0.5 1 1.5 2 2.5 3 3.5 4distance [m]

4

4.5

5

5.5

6

6.5

7

dept

h[m

]

6.0E-032.4E-039.6E-043.8E-041.5E-046.1E-052.4E-05

Fe(OH)2

[-]

pH and Fe(OH)pH and Fe(OH)22

Precipitation of Secondary MineralsPrecipitation of Secondary Minerals

1.50 1.75 2.00 2.25 2.50distance [m]

0.000

0.001

0.002

0.003

0.004

0.005

φ[−]

calcitedolomitesideriteFe(OH)2(s)ferrihydritemackinawite

Inorganic Carbon and SulfurInorganic Carbon and Sulfur

Sediment treatment material mixing zoneSediment treatment material mixing zone

Data from Wilkins et al., 2002Data from Wilkins et al., 2002

distance [cm]

conc

entra

tion

[ppm

]

0 10 20 30 40 50 600

1000

2000

3000

4000

5000

6000

Inorganic carbon - simulatedSulfur - simulated

distance [cm]

conc

entra

tion

[ppm

]

0 10 20 30 40 50 600

1000

2000

3000

4000

5000

6000

Inorganic carbon - observedSulfur - observed

LongLong--Term EfficiencyTerm Efficiency

0.0 0.1 0.2 0.3 0.4 0.5distance [m]

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

ϕ Fe

[-]

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

φ[-

]

ϕFe - T = 5 yearsϕFe - T = 10 yearsϕFe - T = 20 yearsφ - T = 5 yearsφ - T = 10 yearsφ - T = 20 years

porosity

volume fraction of secondary minerals

volume fraction ofzero-valent iron

Porosity ChangesPorosity Changes

distance [cm]

poro

sity

loss

[%]

0 10 20 30 40 50 6001234567

porosity loss - calculatedbased on solid phasecharacterization(Wilkins et al., 2002)

porosity loss - simulated

distance [cm]

poro

sity

loss

[%]

0 10 20 30 40 50 6001234567

Monticello CanyonMonticello CanyonReactive BarrierReactive Barrier

Installed: 1998

Decline in permeability limits performance

Potential SolutionsPotential Solutions

Mix zero Mix zero valentvalent iron and organic carboniron and organic carbon+− ++→+ HCOaqCHOHOCH 2

321

421

221

2 )(

OHaqSHHCOSOOCH 2221

32

421

2 )( ++→+ −−

Reactions release H+ and CO2 and buffer pH

Avoid funnel & gate installations for high TDS water

PRB’s not suitable for some waters types

Challenges EncounteredChallenges Encountered

Organic carbonOrganic carbon•• Permeability variations in mediaPermeability variations in media

•• Insufficient preparationInsufficient preparation•• Decline in reactivityDecline in reactivity•• Temperature effectsTemperature effects

Nickel Rim Barrier InstallationNickel Rim Barrier Installation

SandSand

SandSand

CompostCompost

Nickel Rim WallNickel Rim WallInstalled 1995Installed 1995

Sampled Sampled annuallyannually

Nickel Rim Groundwater PlumeNickel Rim Groundwater Plume

•• Sulfate Sulfate 20002000-- 4000 mg/L4000 mg/L•• IronIron 500500--2000 mg/L2000 mg/L•• pHpH slightly acidic (pH 6)slightly acidic (pH 6)•• AlkalinityAlkalinity 00--50 mg/L CaCO50 mg/L CaCO33

BedrockBedrock

SandSand

Sand

Reactive MaterialReactive Material

Direction ofDirection ofGroundwater flowGroundwater flow

4 m4 m8 m8 m

3.6 m3.6 m

15 m

Permeable Reactive Barrier InstallationPermeable Reactive Barrier Installation

reactivematerial

Barrier

sand sand

Clay Cap

Wells

0 5meters

Recharging acidic surface water

Reactive Barrier Dam

Bedrock

Bedrock

Tailings

Moose Lake

5X verticalexaggeration

Flow from Bain et al., 1999

Nickel Rim Aquifer

Acid Generating Potential (meq/L)

Sulfate (mg/L)

Iron (mg/L)

groundwater flow direction

meters

0 5 mreactivematerial sandsand

>2010 - 200.0 - 10-10 - 0.0<-10

>2000 1500-2000 1000-1499 500-999 <500

>350250-350150-24950-149<50

Treatment ResultsTreatment Results

Fe Concentrations (mmol/L)

November1995

groundwater flow direction 0 5meters

September1996

October1998

October1997

No Data

surface recharge

surface recharge

surface recharge

surface recharge

14-21>21

7-141-7<1

Sulfa

te (m

mol

/L)

0

5

10

15

20

25

Date6/95 12/95 6/96 12/96 6/97 12/97 6/98 12/98 6/99

Alk

alin

ity (m

mol

/L)

0

10

20

30

40

Fe (m

mol

/L)

0

2

4

6

8

10

12

SO4removed

Feremoved

Alkalinity (CaCO3) generated

November

June

September

June

October

May

October

November

June

September

JuneOctober

May

October

November

June

September

June

October

May

October

ResultsResultsCores A and 6

S concentration (μmol g-1)

0 100 200 300 400 500

Dep

th (c

m)

0

50

100

150

200

250

300

Acid Volatile Sulphides 2002Total Reduced Sulphides 2002Acid Volatile Sulphides 1997Total Reduced Sulphides 1997

Cores B and 7S concentration (μmol g-1)

0 100 200 300 400 500

Dep

th (c

m)

0

50

100

150

200

250

300

Cores C and 8S concentration (μmol g-1)

0 100 200 300 400 500

Dep

th (c

m)

0

50

100

150

200

250

300

Sulfide AccumulationSulfide Accumulation

0

10

20

30

40

50

60

70

80

90

0 10 20 30 40 50 60 70 80 90

Time (months)

Rat

e (

μm

ol S

cm

-3a

-1)

Up-gradient core (NRW29)

Mid-gradient core (NRW30)

Down-gradient core (NRW31)

Sulfate Removal RatesSulfate Removal Rates

observed sulfate removal rate

observed sulfate removal rate(m odified from Benner et al., 2002)

0 1 2 3 4 5 6 7 80

30

60

90

120

150

180

simulated sulfate removal rate

Time (years)

Rat

e (m

mol

L-1

a-1 )

Potential SolutionsPotential Solutions

•• Design barriers for longDesign barriers for long--term sulfate term sulfate reduction ratesreduction rates

•• Increase barrier thickness to provide Increase barrier thickness to provide more complete treatmentmore complete treatment

•• More attention to mixture preparationMore attention to mixture preparation•• Add a small amount (5Add a small amount (5--11-- vol.%) of vol.%) of

ZVI to mixtureZVI to mixture

Dissolved Hydrogen GasDissolved Hydrogen Gas

•• HH2(g)2(g) is produced by iron corrosionis produced by iron corrosionFeFe00 + 2H+ 2H22O O ⇒⇒ FeFe2+2+ + + HH2(g)2(g) + 2OH+ 2OH--

•• HH2(g)2(g) is an electron donor is an electron donor 2CH2CH22O + SOO + SO44

22-- ⇒⇒ 2HCO2HCO33-- + 2H+ 2H++ + S+ S22--

4H4H2(g)2(g) + SO+ SO4422-- ⇒⇒ 4H4H22O + SO + S22--

•• Two mechanisms supporting sulfate reduction Two mechanisms supporting sulfate reduction

Test cell and pump shedTest cell and pump shed

FlowFlow

DischargeDischarge

InflowInflow

Balmer Balmer LakeLake

2 m

4.5

m

3015

45

mg/L

60

0

7 to 22

0

22

?

?

16

6

22

41

8

0

17

0

3

23

16

24

0

12

0

1

21

0

0

9

70

0

Br North Side(8 to 14 days after injection)

Inflow OutflowJune 2004

Experiment Experiment -- Inject and Monitor Inject and Monitor Movement of Bromide TracerMovement of Bromide Tracer

•• Br tracer movement shows flow variabilityBr tracer movement shows flow variability•• Improved understanding of As removal Improved understanding of As removal trendstrends

8080--140 m/a140 m/a

3030--50 m/a50 m/a

? m/a? m/aParticle path

with fluctuating water table

DissDiss. H. H2(g)2(g)

0.10.05

0.15

mg/L

0.2

H , North Side2

0.0

0.00

0.00

0.0 0

0.02

0.00

0.00

0.12

0.00

0.10

0.09

0.00

0.00

0.00

0.06

0.04

0.03

0.05

0.00

0.00

0.00

0.0 7

0.36

0.00

0.08

0.00

0.00

0.05

H , North Side2Inflow OutflowJune 2004

0.10.05

0.15

mg/L

0.2

H , South Side2

0.0

0.0

0.06

0.00

0.0 0

0.00

0.00

0.00

0.07

0.00

0.08

0.12

0.00

0.05

0.00

0.02

0.04

0.00

0.05

0.00

0.0 7

0.14

0.17

0.07

0.00

0.00

0.06

H , South Side2

0.00

Inflow Outflow

FeFe00 + 2H+ 2H22O O ⇒⇒ FeFe2+2+ + + HH2(g)2(g) + 2OH+ 2OH--

ArsenicArsenicJune 2004 June 2004

100001000

10

ppb

100

0

152 17 3807

23300

As (ppb) South Side

269

806 6

6 9

10087

16

129

2

162

854

12

77

3131

4

14

30

2

3

2

2

2

1

9 72

Inflow Outflow

23300

141 5

685 0

18100 585

6

3

2641

1

2

As (ppb) North Side

1705

2

1

3

2

852 199

10087

580

16

458

2978

3

2

2

2

2 4

Inflow Outflow

'B' Points June 2004

0

5

10

15

20

25

0 1 2 3 4

Distance into Mixture (m)

mg/

LAs SAs N

ConclusionsConclusions•• LongLong--term monitoring indicates term monitoring indicates

continued treatment for > 10 yearscontinued treatment for > 10 years•• Treatment limitations:Treatment limitations:

•• Capacity of reactive materialsCapacity of reactive materials•• Permeability lossesPermeability losses

•• Alternative mixtures can alleviate Alternative mixtures can alleviate some problemssome problems

AcknowledgementsAcknowledgementsColleagues and StudentsColleagues and Students

C. C. PtacekPtacek, J. , J. JamborJamborR. R. PulsPuls, D. Gould, U. Mayer, S. Benner, E. , D. Gould, U. Mayer, S. Benner, E. FrindFrind, S. Morrison, R. , S. Morrison, R. Ludwig, C. Palmer, A. Pratt, J. Ludwig, C. Palmer, A. Pratt, J. WilkensWilkensJ. Bain, M. J. Bain, M. MoncurMoncur, C. , C. HantonHanton--Fong, D. Smyth, L. Fong, D. Smyth, L. GrozaGrozaT. Bennett, R. McGregor, C. McRae, N. T. Bennett, R. McGregor, C. McRae, N. DoerrDoerr, R. Johnson, , R. Johnson, S. Sale, E. S. Sale, E. DaignaultDaignault, R. Williams, R. Williams

FundingFundingNSERC: Discovery grants, CRC program, CRD program, NCENSERC: Discovery grants, CRC program, CRD program, NCEOntario: OCE, PREA, MOE, URIFOntario: OCE, PREA, MOE, URIFCanada: NR Can (CANMET), Environ. CanadaCanada: NR Can (CANMET), Environ. CanadaUS EPA, US DOE, USGSUS EPA, US DOE, USGSFalconbridge Ltd., Placer Dome Inc., Falconbridge Ltd., Placer Dome Inc., DuPontDuPont Company (USA)Company (USA)

performance challenges encountered with permeable reactive...

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