CH2M PRESENTATION - UNDERSTANDING IN-SITU THERMAL TREATMENT - APPLICATION AND PERFORMANCEJason Cole, PhD, PE
Agenda
Source Treatment Continuum What is In-situ Thermal Treatment & What It Can Offer Technology Overview Performance Monitoring Concepts and Strategies Performance Examples Similar to Velsicol Site
– Solvents – Pesticides – Combined Remedies
Source Treatment Continuum
Partial source removal plus containment/long-term management
Complete or near complete source removal
Hydraulic displacement, ISCO, ISSM, plus containment and long- term management options
Timeframe: many decades to centuries
In-situ Thermal Treatment
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What is Thermal Treatment?
Subsurface heating for remediation of soil and groundwater – Optimal application is treatment of NAPL source zones – Three demonstrated methods; one additional considered emerging – Coupled with fluid extraction for contaminant source removal &
recovery
In-situ thermal treatment (ISTT) is a mature technology – Evolved to a group of powerful and robust remediation technologies – Applications number in the 100’s; mainly for chlorinated solvents
Coming Soon to St. Louis – Selected for NAPL/DBCP Area 1 and 2 on the former plant site – Proposed for use at the former burn pit area
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Subsurface Heating Effects
Physical Removal – Stripping – Displacement – NAPL Viscosity reduction
Secondary – Chemical destruction
Temperature (oC)
P re
ss ur
e (a
heat af vaporization
Heat of vaporization for TCE calculated from the Thiesen corre;ation/Watson relation and the n-value calculated according to Fishtine referenced in Lyman et al. (1990)
35.8166655977
35.3152153031
34.8016082196
34.54
34.2750470032
33.7346462604
33.1794185273
32.6082572702
32.019916098
31.4129831089
30.9951447421
30.7858489113
30.1366663156
28.7632544557
27.6565981027
26.4707460702
25.1890255858
23.7882333577
21.6742235714
19.1452254162
16.8009989956
13.7263131815
10.7706998883
7.3704527232
0
Chart2
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359.7
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&A
heat of caporization (kJ/mol)
Second order polynomial regression on formula on heat of vaporization calculated from the Thiesen relation
35.8166655977
35.3152153031
34.8016082196
34.54
34.2750470032
33.7346462604
33.1794185273
32.6082572702
32.019916098
31.4129831089
30.9951447421
30.7858489113
30.1366663156
28.7632544557
27.6565981027
26.4707460702
25.1890255858
23.7882333577
21.6742235714
Chart3
273
&A
#REF!
1
Chart4
200 180 165 150 135 120 100 90 86.7 80 70 60 50 40 30 25 20 10 0
&A
Vapor pressure (Atm)
Vapor pressure of TCE calculated from heat of vaporization data using a second-order polynomium approximation to the Thiessen relation valid between 0 and 200 degrees C
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Chart6
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86.7
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TCE vapor pressure calculated from three different regression equations
1
1
0.0224672397
0.0409568052
0.0705637816
0.0909013783
0.1157764476
0.1820440826
0.2757626472
0.4042218333
0.5755190257
0.6365601354
0.6579817027
0.7256001818
0.7984472272
0.981334611
1.0823645689
1.437052855
2.3991155534
3.3818599405
4.6260193659
6.1638026116
8.0252239705
11.0572943971
Chart7
&A
Toluene
Naftalene
h
a
b
c
Contaminant source removal – Minimum residual mobility
Mass flux reduction Synergy with remedies Rapid implementation Lower sensitivity to
– Contaminant mass – Subsurface conditions
Treatment in a variety of geologic settings Implementation around structures
– Even ones that are occupied (with appropriate care)
Controlled extraction and treatment of contaminants
Im ag
e by
T er
ra Th
er m
, I nc
Some Disadvantages of In Situ Thermal
High price point and cost variability Mechanically complex Limited commercial suppliers (and they are often busy) Typically area cannot be used during treatment Can be impacted by high permeability zones; cold water inflow Performance variability Energy availability
Technology Overview
Just the Facts
treatment equipment – In-situ temperature
Steam Enhanced Extraction (SEE)
Thermal Conduction Heating (TCH) • In-situ Thermal Desorption (ISTD) • Gas Thermal Remediation (GTR)
Emerging Heating Approach • Self-Sustaining Treatment for
Active Remediation (STAR)
(10-8 cm/s) Low Permeability
Electrical Resistance Heating
Heating process – Alternating current supplied to
subsurface electrodes – Electrical resistance of soil
generates heat Temperature limited to boiling point
of water at local pressure Specific heating approaches vary
by technology provider Im ag
e by
M cM
ill an
-M cG
ee C
or p.
Thermal Conduction Heating
high temperature heaters. – Transfer heat by conduction to
the surrounding formation Treatment temperatures > 100oC
are readily attained Specific heating approaches vary
by technology provider
Ex-situ heating is also feasible – In constructed concrete cells – In covered soil piles
Im ag
e by
G E
O , I
TCH - In-situ Thermal Desorption
Conduction heating power distribution system
Vapor treatment
Knockout pot
Treated vapor to atmosphere
Vapor cover
Vapor treatment
Knockout pot
exchanger
Pump
Heater and shallow vapor recovery wells
Vapor cover
A ll
Im ag
es b
y Te
rr aT
he rm
, I nc
TCH - Gas Thermal Remediation
Liquid or gaseous fuels provide subsurface thermal energy
Soil and groundwater are heated to temperatures of 100-400oC by conduction
Volatilized contaminants are collected by soil vapor extraction and treated ex- situ
Im ag
e by
G E
O , I
Primary condensation Low mass - GAC High mass
– Thermal oxidation – GEO Compression/
All heating technologies yield excellent results – With proper method selection and performance monitoring – All excel at source removal
Design considerations – Contaminant characteristics – Remediation objectives – Treatment volume – Lithology – Site conditions – Treatment time
Performance monitoring
Subsurface Conditions Matter
ERH or TCH are likely candidates for these conditions
TCH may be the only viable candidate for sites with buried metal
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Thermal Treatment Systems are Readily Adapted to Site Conditions
18
Privacy Screen to Minimize Visual Impacts of Treatment Area
Im ag
e by
T er
ra Th
er m
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Thermal treatment in proximity to many residential receptors
Cap, insulation and aggressive fluid extraction limit heating of exterior walls
A ll
Im ag
es b
y Te
rr aT
he rm
, I nc
Monitoring Treatment Performance
Temporal measurement – In-situ pressure – Groundwater elevation – Vapor concentration – Process parameters
• Vapor, temperature, flow
Post treatment sampling – Soil and groundwater
Contaminant removal is assessed in many ways using multiple lines of evidence
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Process Monitoring Demonstrates Mass Removal
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M as
s R
em ov
al R
at e,
lb s/
da y
C um
ul at
iv e
M as
s PC
E R
em ov
ed , l
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Post-Treatment Sampling
Thermal Monitoring Tells All
Temperature at Elevation 1163 ft MSL Temperature at Elevation 1175 ft MSL
A ll
Im ag
es b
y M
cM ill
an -M
cG ee
C or
Temperature and Time Control Treatment Performance
D at
a by
T er
ra Th
er m
, I nc
Treatment Temperature and Mass Removal are Directly Correlated
D at
a by
T er
ra Th
er m
, I nc
Soil Sampling Confirms Mass Removal Observations
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0.001 0.01 0.1 1 10 100 1000 10000 Concentration Skuldelev [mg/kg]
D yb
de [m
u .t.
]
PCE in soil pre treatment [mg/kg] PCE in soil post treatment [mg/kg]
Detection Soil MCL
Different Site – Similar Results
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0.001 0.01 0.1 1 10 100 1000 10000 Concentration Reerslev [mg/kg]
D ep
th [m
b gs
.]
PCE in soil pre ISTD [mg/kg] PCE in soil post ISTD [mg/kg]
Detection limit Soil MCLClean-up goal
D at
a by
T er
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er m
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Analysis of Process Monitoring Data Determines Operation Endpoint
Temperature and time control technology performance – Thermal monitoring data document target temperature achievement – Operation time at target temperature drives contaminant removal
Instantaneous mass removal rate is measured with time – Mass removal typically peaks around co-boiling temperature – With increasing time and temperature removal rates decline
Rate analysis yields cumulative contaminant mass removed – Total mass removed approaches asymptotic conditions with time
The simultaneous evaluation of temperature, time and contaminant mass removal form the basis of the diminishing returns analysis – Results are the first line of evidence that treatment is complete
Performance Examples Solvent Treatment
Performance Data Illustrates Thermal Treatment Endpoint
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Treatment Zone Temperature
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0 10 20 30 40 50 60 70 80 90 100 Treatment Days
Te m
pe ra
tu re
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Soil Borings Confirm Performance Soil Sample Results MW00-318 / SB05-247
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0.00 0.01 0.10 1.00 10.00 100.00 1000.00 TCE Concentration (mg/kg)
D ep
th B
el ow
G ro
un d
Su rf
ac e
(fe et
Results Are Spatially Consistent Soil Sample Results MW00-314 / SB05-246
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0.00 0.01 0.10 1.00 10.00 100.00 1000.00 TCE Concentration (mg/kg)
D ep
th B
el ow
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un d
Su rf
ac e
(fe et
Concentration Reduction = Removal Soil Sample Results MW00-313 / SB05-245
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0.00 0.01 0.10 1.00 10.00 100.00 1000.00 TCE Concentration (mg/kg)
D ep
th B
el ow
G ro
un d
Su rf
ac e
(fe et
Mass Removal Follows Heating
Va po
D ep
th (f
Soil Treatment Performance Summary
Performance - Groundwater
Performance Example Combined Remedies
Oregon Solvent Site
Voluntary cleanup of an active manufacturing site Solvent release to shallow groundwater
– NAPL source contaminates groundwater – Dissolved contaminants migrate off site > 1000 feet
In-situ thermal treatment selected for source removal Containment system installed for interim plume control Groundwater remedy deferred until ISTT was complete
– Source removal by ISTT was successful – Removal immediately apparent on site groundwater – Containment no longer needed; Natural in-situ biological processes
took over following contaminant source removal
Combined remedy delivers No Further Action determination
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Combined Remedy Approach Example
TC E
Co nc
en tra
tio n
(µ g/
MCL = 5 µg/L
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Closing Thoughts for In-situ Thermal Treatment
Demonstrated and proven technology – Applications number in the 100s – Powerful treatment approach but highly site specific – Big hammer – Mechanically complex – Among the most effective strategies for controlled source removal
Time and temperature control performance – Methods to reliably monitor spatial performance are well documented
Discrete treatment footprint – Minimizes disruption to surrounding setting – Source removal occurs with the highest degree of control
Source contaminants are removed and destroyed – Statutory preference for treatment is fulfilled
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Questions
Agenda
Some Disadvantages of In Situ Thermal
Slide Number 8
Just the Facts
Electrical Resistance Heating
Thermal Conduction Heating
Subsurface Conditions Matter
Urban Applications are Well Documented
Slide Number 21
Monitoring Treatment Performance
Post-Treatment Sampling
Treatment Temperature and Mass Removal are Directly Correlated
Soil Sampling Confirms Mass Removal Observations
Different Site – Similar Results
Slide Number 31
Treatment Zone Temperature
Questions