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1050 colleques

250 environmentalists

Tom HeronDivision Director, geologist

Thermally enhancedremediation

In Situ Thermal Desorption

Joakim Andersson

Karin Tornberg

Emma Evertsson

Ebba Svanström

Important tools in the toolbox

• Heavily contaminated source zones• Stringent remediation requirements• Fast clean-up• Large volumes• Clay/silts/fractured• Deep contamination• Many contaminants and mixtures

Source zone

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• Chlorinated Ethenes• Oil products, BTEX• Coal Tar• Creosote• PAH’s, Naphthalene• PCB’s• Chlorobenzenes• Pentachlorophenol (PCP)• Dioxins• Mercury• Many pesticides• Mixtures

Treatable contaminants

Data on much of this in NIRAS’ and Krügers booth up stairs!!

Remediation Mechanisms

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• Boiling point in multiphase system and steam-drive

Mechanisms and values for TCE

• Vapor pressure increases• TCE: 18 times for 10 - 100 °C

• Henrys law constant increases• TCE: 12 times for 25 - 100 °C

• The enthalpy of sorption decreases• TCE: 20 % from 10 - 100 °C

• In Situ degradation

• Viscosity, interfacial tensions and densityreduced: ~ 1 – 2 times

Liquid

Gas Phase25

20

15

10

5

00 20 40 60 80 100

TCE

Nafthalene

TemperatureoC

R

Boiling point in a two phase system

1,50

1,25

1,00

0,75

0,50

0,25

0,00

0 20 40 60 80 100 120 140

Water + PCE

Water

PCE

Pres

sure

(atm

)

Temperature oC

87 121

4

Technologies

SEE - heating governed by hydraulic conductivity – non-uniform steam flow

ERH - heating governed by electrical conductivity

ISTD/TCH - heating governed by thermal conductivity – nearly uniform distribution of heat

Important Heating Technologies - Summary

Electrical

Conductive

Steam

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In Situ Thermal Desorption and destruction

Heater-OnlyWell

Heater-VacuumWell

To Off-Gas Treatment Unit

Volatilization and Destruction of Contaminants

Target T: 100oC to 300oC

Very Hot Thermal Destruction Zone300oC to 700oC

Off-Gas Residence Time Several Hours

1 to 2 feet 1 to 2 feet

Important design issues:

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• Goals / effect on risk or value• Time• Price

• Liquid and vapor capture• Condensation fronts• Boiling water is expensive• Temperature distribution• Energy balance• Organic rich soils• Underground utilities / buildings etc.

Important design issues

Examples of completed projects

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UC Berkeley

TCE: 2 mg/kg og 5 µg/l

Typical chromatogram:Soil before Steam

After thermal treatment

Naval Air Station Alameda, Site 5, San Francisco

Goal: MCL in soil and groundwater for BTEX og chlorinated solvents

Motor oil

TCE,

BTE

X, e

tc

Courtesy of Kent S. Udell

ISTD – Free phase PCE in tight alluvial clay

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0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

Soil

Con

cent

ratio

n - u

g/kg

PCE TCE cis-1,2-DCE VC

AVG PostRemedial GoalsAVG Pre

2,000 2,000

17,000

23012 < RL 65 5

34,222

1,055

6,650

932

99.96% 99.63% 99.03% 99.49%Reductions:

Results are based on 17 pre-treatment and 64 post-treatment samples

Results – Average concentrations

Ongoing Danish Projects

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Knullen – Odense, Denmark

Worlds first thermal remediation using af combinationof steam and ISTD

TTZ

COC’s: PCE, chlorinatedsolvents (800 kg)

Soil: Clay and sand

Treatment interv.: 3 – 14 m.b.g.

Area: 240 m2

Volume: 1.900 m3

Estimated cost: 15 mio. dkr

Number of HV-borings: 45

Steam injection wells: 5

Steam extraction wells: 2

All wells installed under a building

Skuldelev – Denmark

Full-scale design based on results from pilot testCOC’s: PCE, chlorinatedsolvents (4000 kg)

Soil: Clay and sand

Treatment depth: 7,5 meters

Area: 250 m2

Volume: 1.600 m3

Estimated cost: 12 mio. dkr

ISTD-wells: 53

Vacuum wells: 21

Water extraction wells: 3

Building

Sheet piling

TTZ

Lake

ISTD-heater

Water extraction boring

Vacuum boring

Pilot test, Skuldelev

Monitoring well, Skuldelev

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Ongoing projects

Reerslev – DenmarkCOC: PCE – 10.000 kg

Soil: Clay

Treatment depth: 8 meters

Area: 900 – 4.700 m2

Netherlands – Confidential siteCOC: Diesel (mass currently unknown)

Soil: Fractured limestone

Treatment depth: 6,5 meters

Area: 100 – 3.500 m2

Design based on treatability study –indicated remediation efficiencies better than 99.9% at treatment temperatures between 100 and 200 °C.

OvenFlow of nitrogen

Condensing system Temperature measurements

OvenFlow of nitrogen

Condensing system Temperature measurements

Test setup – laboratory experiments

? ?

? ?

ThankThank youyou and:and:

the@niras.dk+45 87323256+45 21418302

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Component property Oil based LNAPL

Chlorinated solvents Creosote Coal tar PCB Comment

Vapor pressure increase factor 20-40 20-40 20-40 20-40 20-40 Abundance of data in literature

Solubility increase factor 2-100? 1.5-3 10-1000 10-1000 10-1000Chlorinated solvent less affected than larger hydrocarbons

Henry's constant increase factors 10-20 0-10 0-10 0-10

Data absent for most compounds, some decrease?

Viscosity reduction factor 2 to 100+ 1.3-3 5-10 20-100+ 3-100 The higher initial viscosity, the more reduction

Interfacial tension reduction factor <2 <2 2-5 1-5 <5 Typically not dramatic effect (less than

factor 2)

Density reduction (%) 10-20 10-20 10-20 10-20 10-20 Note that DNAPL may become LNAPL

Kd (reduction factor) ? 1-10 5-100 5-100 NA Estimates based on limited data

Udell (1989, 1991, 1993, 1996). Davis (1997, 1999).Imhoff et al. (1997).Sleep and Ma (1997).Heron et al. (1998, 2000).

Physical processes/changes (below 120 °C)

Energy consumption (kWh/m3)

91117219347Heating to 200 ºC

4369171299Heating to 100 ºC & evaporating all porewater

43476180Heating to 100 ºC, wet

0 %10 %80 %100 %

Initial water content

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100 -120 oC partial removal (ERH, SEE, ISTD low int.)300 oC complete removal (ISTD, dewater)

100-120 oC(ERH, SEE, ISTD)

Below water table

300 oC(ISTD)

90-100 oC(ERH, SEE, ISTD)

Above water table

SVOCVOC

Target temperatures

ERH: Electrical Resistivity HeatingSEE: Steam Enhanced ExtractionISTD: In Situ Thermal Desorption

In Situ Thermal Desorption

PCB´s

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< 0.17800PCB 1254Ferndale, CA

< 110,000PCB 1254/1260Saipan, NMI

< 0.0332,200PCB 1254/1260Vallejo, CA

< 0.03320,000PCB 1260Cape Girardeau, MO

< 0.85,000PCB 1248/1254S. Glens Falls, NY

Final Concentration

(ppm)

Initial Max. Concentration

(ppm)

ContaminantLocation

Source: Stegemeier and Vinegar (2001)Terratherm Inc.

ISTD: PCB Field Projects - Results

ISTD

PAH´s and Dioxins

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Soil:Fill, Silt with clay lenses and sand stringers

Woodtreatment facility, Alabama

0

100,000

200,000

300,000

400,000

500,000

600,000

Soil

Con

cent

ratio

n - u

g/kg

PCE TCE cis-1,2-DCE VC

Max PostRemedial GoalsMax Pre

2,000 2,000 17,000 230

44 < RL 1,500 24

510,000

6,500

57,000

6,500

99.96% 99.63% 99.03% 99.49%Reductions:Results are based on 17 pre-treatment samples and 64 post-treatment samples.

Post-treatment samples were collected from centroids (i.e., coolest locations) at random and biased depths (15 or 23% were collected between 18 and 20 ft bgs).

Results – Maximum concentrations

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Steam Zone

Sand Pack

HO Well

Mod. To high K

Tight clay/Bay

mud

DNAPL

In-Situ Temperatures

ISTD: Remediation concept

oC

1.8 –3.0 m

3.0 –4.9 m

4.9 –6.1 m

Centroi

250

354

275

200

101

101

102

94

101

96

9978

0 –1.8 m

HeaterCentroid1.8 m1.8 m

1.2 m 0.6 m 1.2 m

y

101

9496

78

101

102

101

99

250

354

275

200

1.8 –3.0 m

3.0 –4.9 m

4.9 –6.1 m

Centroi

250

354

275

200

101

101

102

94

101

96

9978

0 –1.8 m

HeaterCentroid1.8 m1.8 m

1.2 m 0.6 m 1.2 m

y

101

9496

78

101

102

101

99

250

354

275

200

Horizontal Vapor Collection Screen