correlating gas phase dispersion in unsaturated soils · correlating gas phase dispersion in...

Correlating Gas Phase Correlating Gas Phase Dispersion In Unsaturated Dispersion In Unsaturated

SoilsSoils

Darryl Cann, Darryl Cann, M.ScM.Sc. Eng Candidate. Eng CandidateWarren H. Warren H. StiverStiver, Ph.D., , Ph.D., P.EngP.Eng., Professor., ProfessorRichard G. ZytnerRichard G. Zytner, Ph.D., Ph.D., P.EngP.Eng., Professor., Professor

University Of University Of GuelphGuelph, School of Engineering, School of Engineering

RemTechRemTech 2004 2004 --22

OutlineOutline

ØØ IntroductionIntroductionØØ Research GoalsResearch GoalsØØ Experimental ApproachExperimental ApproachØØ ResultsResultsØØ Future WorkFuture Work


IntroductionIntroduction

ØØ 10% of 10% of USTsUSTs in USA and Canada are in USA and Canada are currently leakingcurrently leaking


Introduction Introduction –– cont.cont.

ØØ Superfund Remedial Actions (EPA, Superfund Remedial Actions (EPA, 2004): 2004):

•• 35.3% SVE35.3% SVE•• 17.6% Bioremediation/Bioventing17.6% Bioremediation/Bioventing


Bioventing and SVE ModelingBioventing and SVE Modeling

ØØ AdvectionAdvection--dispersion equationdispersion equation

ØØ Longitudinal Dispersion CoefficientLongitudinal Dispersion Coefficient

DiffL DD += αν

iL rxc

xc

Dtc

∑±∂∂

−∂∂

=∂∂

ν2

2


SVE and BioventingSVE and Bioventing

ØØ Rule of Thumb DesignRule of Thumb Design

ØØ ModelsModels•• Performance estimatesPerformance estimates•• Lack of reliable coefficientsLack of reliable coefficients


DispersionDispersion

ØØ Gradual spreading and mixing of Gradual spreading and mixing of solute with advective flowsolute with advective flow

•• Velocity GradientsVelocity Gradients•• Concentration GradientsConcentration Gradients

to t2t1to


Dispersion MechanismsDispersion Mechanisms

ØØ Path TortuosityPath Tortuosity

ØØ Friction in Pore Friction in Pore

ØØ Pore SizePore Size


Research Goals Research Goals -- OverallOverall

Soils Research GroupSoils Research Group

MTC DispersionBiological

Degradation

SVE and BV Models


Research Goals Research Goals -- DispersionDispersion

ØØ Phase IPhase I•• Develop experimental apparatusDevelop experimental apparatus•• Develop correlationsDevelop correlations•• Disturbed soilsDisturbed soils

ØØ Phase IIPhase II•• Test correlations on field core samplesTest correlations on field core samples•• Modify correlations for field predictionsModify correlations for field predictions


MethodologyMethodology

ØØ 11--D NonD Non--Reactive Tracer experimentsReactive Tracer experiments

ØØ Open Vessel Boundary ConditionsOpen Vessel Boundary Conditions


Methodology Methodology –– cont.cont.

ØØ Soil and ColumnsSoil and Columns

ØØ Water Content Water Content •• Air Dry (~5%) to Field CapacityAir Dry (~5%) to Field Capacity

Soil Properties OS SLS ESL BC

% Sand (by weight) 98.8 69.4 34.0 21.0% Silt (by weight) 1.2 24.4 50.1 35.1% Clay (by weight) 0 6.2 15.9 43.9• OS – Ottawa Sand

• SLS – Simcoe Loamy Sand

• ESL – Elora Silt Loam

• BC – Brookston Clay



ØØ Tracer InjectionTracer Injection•• Solenoid ValveSolenoid Valve•• Tracer Tracer -- HeliumHelium•• Carrier Carrier -- Nitrogen Nitrogen

ØØ Two sampling Two sampling locationslocations

Sampling Probe Configuration

Soil Column

Probe

To TCD



ØØ Thermal Conductivity Detector (TCD)Thermal Conductivity Detector (TCD)

ØØ RealReal--Time Data CollectionTime Data Collection•• NI DAC NI DAC •• LabVIEWLabVIEW


Experiment SchematicExperiment Schematic

He N2

Main Flow

Control

Mass Flow Meter

Solenoid Valve

Soil Column

Data Collection

TCD

ExhaustFlow

Meters

Exhaust

Water Bath

Heat Exchanger/Humidifier

Vacuum pump


Heat Exchanger/ Humidifier

Soil Column

Flow MeterTCD

Vacuum Pumps

Solenoid Valve

Probes

Flow Valve


Data Analysis Data Analysis

ØØ Residence Time DistributionResidence Time Distribution•• Variance, Mean residence time, DispersionVariance, Mean residence time, Dispersion

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

0 10 20 30 40

Time (s)

TC

D r

esponse

(mV

) Channel 1Channel 2

s 21

s 22

t1 t2


ResultsResults

ØØ New, working apparatusNew, working apparatus•• Disturbed Disturbed •• UndisturbedUndisturbed

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

0 10 20 30 40

Time (s)

TC

D re

sponse

(mV) Channel 1

Channel 2


Results Results –– contcont’’dd

ØØ Preliminary Air Dry Ottawa SandPreliminary Air Dry Ottawa Sand•• Dispersivity (Dispersivity (aa ) = 0.042 cm ) = 0.042 cm

ØØ GiddaGidda et al. (2004)et al. (2004)Soil Type Moisture Content Observed Dispersivity (cm)

Ottawa Sand Air Dry 0.63% 1.2

Delhi Loamy Sand Air Dry 1.220% 2.6

Elora Silt Loam Air Dry 1.620% 1.130% 1.9

Brooksten Clay Air Dry 1.340% 2.4


DiscussionDiscussion

ØØ Reliable dispersivity valuesReliable dispersivity valuesØØ SVE and BVSVE and BV

•• Improved closure predictionsImproved closure predictions

•• Improved system designsImproved system designs


Future WorkFuture Work

ØØ Disturbed soil are ongoing Disturbed soil are ongoing

ØØ Collect field core samplesCollect field core samples

ØØ Compare results with correlations Compare results with correlations


AcknowledgementsAcknowledgements

ØØ NSERC Strategic NSERC Strategic Grant Grant

ØØ Dr. Dr. TejwantTejwant GiddaGiddaØØ Jon BrookerJon BrookerØØ EyadEyad BarakatBarakat


Thank YouThank You

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correlating gas phase dispersion in unsaturated soils · correlating gas phase dispersion in...

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