Thermal RemediationServices, Inc.

Thermal RemediationServices, Inc.

Electrical Resistance Heatingfor Rapid

Remediation of DNAPLApril 2003

David Fleming425-396-4266

dfleming@thermalrs.comwww.thermalrs.com

What is ElectricalResistance Heating?

What is ElectricalResistance Heating?

n Takes common 3-phase electricity anddirects it into the subsurface throughelectrodes

n Electrodes can be placed vertically to anydepth or may be placed horizontally

n Once in the subsurface, the electricalenergy resistively heats soil andgroundwater

n Contaminants are removed by directvolatilization and in situ steam stripping

Why ElectricalResistance Heating?

Why ElectricalResistance Heating?

§ Heating is uniform with no bypassedregions

§ Heating is rapid – months vs. years

§ Steam is produced in situ

§ Preferentially heats tight soil lenses andDNAPL hot spots

§ Cost effective: most commercial, full-scalesites range from $30-$90 per yds3 (sitespecific)

ApplicationsApplications

§ Low permeability & heterogeneous lithologies

§ DNAPL & LNAPL cleanups by aquifer andsmear zone heating

n Heavy hydrocarbon mobilization

n Bioremediation enhancement

n Remediation underneath operating facilities

n Remediation in the presence of buried utilitiesand hazardous waste drums

In-Situ SteamGeneration

In-Situ SteamGeneration

HEATEDZONE

Electrode & Co-located VR Wells

2. Steam generation is uniform through the heated zone

1. Soil grains act as electrical resistors

150 V to400 V

Safe<15 V

3. Discrete intervals canbe heated

Electrode & Co-located VR Wells

TMP

Typical SurfaceEquipment

Typical SurfaceEquipment

PhotoCourtesy ofBrown and

Caldwell

ERH 2000 kW PCUERH 2000 kW PCU

Vapor RecoverySystem

Vapor RecoverySystem

ERH Power Control Unit

Water Storage TankOr Sewer

VacuumPump

Carbonor

Catox

Condenser

1

23

4

5 6

T

T

>99% of thecontaminant mass

remains in thevapor state

Electrode

Co-located VR WellTemperature Point

TCE DNAPL RemediationAir Force Plant FourFort Worth, Texas

TCE DNAPL RemediationAir Force Plant FourFort Worth, Texas

PhotoCourtesy of

URS

Full-Scale ERH atAF Plant 4

Full-Scale ERH atAF Plant 4

§ Full-scale ERH covering 1/2 acre area inside andoutside of Bldg. 181, manufacturing operations 24/7§ 70 electrodes and co-located VR wells installed in and

around existing tanks, piping and equipment (32° angles)

§ Heterogeneous silt, clay and gravel with a highlyweathered limestone, competent bedrock at 32 ft bg§ Groundwater at 27 ft bg§ Electrodes electrically conductive 3 to 32 ft bg§ Two vapor and steam recovery intervals in perimeter

electrodes§ ERH operations May to Aug 2002; reduced – Dec ‘02§ Goal – average 90% reduction based on a 95% UCL

Full-Scale ERH LayoutFull-Scale ERH Layout

High TrafficCorridor

Location ofFormer Pilot

AngledElectrodes

Full-Scale ERH SubsurfaceX-Section

Full-Scale ERH SubsurfaceX-Section

DNAPL

Co-LocatedPerimeter

Electrode withDeep and Shallow

SVE Wells

Co-LocatedInternal

Electrode withShallow SVE

Walnut FormationWalnut Formation

E R H S u b s u r f a c e C r o s sS e c t i o n

E R H S u b s u r f a c e C r o s sS e c t i o n

GoodlandFormation

HighlyWeatheredLimestone

Angled Co-Located

Electrode andSVE

AST

SanitarySewer

System

Silty Clay(Medium

Plasticity)

Silty Gravel

ShallowGroundRods

TemperatureMonitoringPoint with

Thermocouples

T

T

T

T

T

T

T

12’

26’

32’

2’

7’

12’

17’

22’

26’

32’

Silty ClayWith SandAnd Gravel

Seams

ERH Remediation BeneathAir Force Plant Four

ERH Remediation BeneathAir Force Plant Four

SVE pipingelectric

al cable electrode

SVE well

PhotoCourtesy of

URS

VR PipingInside Bldg 181

VR PipingInside Bldg 181

8” Main VR Pipe

8” Main VR Pipe

Electrode w/ co-located VR well

Electrode w/ co-located VR well

Close Up ofERH Electrode

Close Up ofERH Electrode

Continuous Indoor AirMonitoring

Continuous Indoor AirMonitoring

§ URS operatedINNOVA Systemsampled air for TCEevery 5 minutes

§ Would shutdownERH system if TCE>3 ppm

§ Online remotemonitoring

§ Never exceededbackground TCEconcentrationsinside Bldg. 181

Final TCEConcentrations in Soil

Final TCEConcentrations in Soil

After ERH

0

2 0 0 0

4 0 0 0

6 0 0 0

8 0 0 0

10000

12000

1 4 0 0 0

16000

1 8 0 0 0

2 0 0 0 0

After ERH

Before ERH

TCE µg/kg

90%Average

Reduction

Final TCE Concentrationsin Groundwater

Final TCE Concentrationsin Groundwater

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

100,000

TC

E C

on

cen

trat

ion

(u

g/L

)13-Nov 4-Sep

August July

June April

S i t e C l e a n u p

G o a l

1 0 , 0 0 0

Outside of Remediation

Area

Monitoring Well Locations

Results at AF Plant 4Results at AF Plant 4

§ Area & volume treated - 22,000 sq. ft. & 27,400cubic yards – from May to Dec 2002

§ Average weekly power input – 563 kW§ Recovered ~ 1,600 lbs. TCE§ Met groundwater goal following 4 months of ERH

operations, ~ 93% average reduction in TCEconcentrations in groundwater

§ Met soil goal, 90% average reduction§ TCE concentrations never exceeded background

levels of TCE in the indoor breathing space§ No impacts to manufacturing operations§ $57 per cubic yard

Polishing MechanismsPolishing Mechanisms

n Hydrolysis of Halogenated Alkanesu Compounds such as TCA have a hydrolysis half-life of

less than one day at steam temperatures.

n Iron Reductive Dehalogenationu Steel shot used as electrode backfill provides an iron

source for reductive dehalogenation (iron filing wall)

n Temperature Accelerates Reactionsu The above reaction rates are increased by factor of

thousands at 100°C (Arrhenius Equation)

n Bioremediation by Thermophilesu Thermophilic bacteria are the most effective solvent

dehalogenators and prefer 40-70°C

www.Thermalrs.comwww.Thermalrs.com