In Situ Thermal Remediation Conceptual Design/Remedial Action ...
In Situ, Low Temperature Thermal Remediation of LNAPL with ...In-Situ Thermal Bench Test: Results 7...
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The world’s leading sustainability consultancy
In Situ, Low Temperature Thermal Remediation of LNAPL with Pesticides and Other
Recalcitrant CompoundsRemTech 2017, Banff Springs Hotel and Conference Centre
October 11, 2017Presented by - Jay Dablow, ERM, Inc., Irvine, CA, USA
James Baldock, ERM, Oxford, UK;
Joanne Dinham, ERM, Manchester, UK ,and
Kathryn Johnson, ERM, Edinburgh, UK.
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© Copyright 2017 by ERM Worldwide
Group Limited and/or its affiliates
(‘ERM’). All Rights Reserved. No part
of this work may be reproduced or
transmitted in any form or by any
means, without prior written
permission of ERM.
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Background
2
■ The Site has been used since the late 1960’s
for the manufacture of wood preservatives,
damp proofing chemicals and specialist
coatings
■ The Site comprises two main buildings
(offices and laboratory, which remain in use
and a central area comprising mainly storage
and disused offices)
■ The Site is bounded by a railway line to the
south beyond which lie residential properties.
A river is located approximately 500m
downgradient of the site.
The clients goals for the Site include:
• Establish the current environmental status with respect to the presence and
significance of historic soil and groundwater contamination; and
• Manage potential liabilities associated with these impacts in the context of UK
contaminated land legislation
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■ The Site is underlain by Made Ground (typically <1m thickness), sands and gravels, and
Chalk.
■ Both the sands and gravels and Chalk form unconfined aquifers with relatively high
permeability.
■ Lower permeability silts and clays are present towards the top of the sands and gravels in
some parts of the Site.
■ Soil source zones appear to correlate well to the main areas where chemicals were
previously used, stored or disposed.
■ Multiple overlapping plumes are present, beneath and downgradient of the source areas,
although impact from a more limited range of compounds has been identified within the
Chalk.
■ Likely that the recent channel identified within the centre of the Site may be influencing
contaminant migration towards the south-west corner of the Site.
■ The dominant controlling mechanism for contaminant migration into the Chalk is likely to be
contaminant properties (those which sink) or be related to preferential flow through
soakaways.
Geology and Hydrogeology
3
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4
Properties and Distribution of Selected Contaminants
Contaminant Physical
state
Molecular weight
Water solubility
Log KOC VapourPressure
Henry's Law Constant
mg l-1 25oC cm3 g-1 Pa Pa m3 mol-1 (25oC)
Aldrin solid 364.91 0.02 5.34 1.35E-02 50.3Dieldrin solid 380.91 0.2 3.59 4.18E-08 5.88gamma HCH solid 290.82 7.3 3.07 3.70E-03 0.375>C10-C12 Aliphatics liquid 3.40E-02 5.40 63.83>C12-C16 Aliphatics liquid 7.60E-04 6.70 4.86Benzene liquid 78.11 1780 1.83 6240 557Tetrachloroethene liquid 165.83 225 2.43 1010 1730
Environment Agency 2008 SR7 Compilation of da ta for priority organic pollutants for derivation of Soil Guideline Values
PPDB: Pesticide Properties Data Base http://sitem.herts.ac.uk/aeru/projects/ppdb/index.htm
TPHCWG Vol 3
KOC - organic carbon partition coefficient
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Conceptual Site Model
Not to scale
625m
Chalk
Permeability: 2 to 192m/day
Top of Chalk identified 5 to
8.5m bgl
Gravels
Permeability: 0.2 to 0.7 m/day
4 to 7.5m thickness
River
Off-site
current
and
former
industrial
land uses
Made Ground
Historical Sources: Kerosene
and Dieldrin
Main surface water
receptor
Main groundwater
receptor at risk: Chalk
Vertical migration of Dieldrin
into Chalk
5
Future potential leaching of
COCs into Gravels
Mobile LNAPL causing enhanced transport of
COCs within Gravels
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Initial Remedial Concept
6
■ Mass removal
■ Limited LNAPL in wells
■ circa 8,000kg mass (mostly Kerosene).
■ Pesticides (dieldrin) solubilized in carrier oil
■ Remedial options appraisal identified limited mass recovery
options
■ Excavation requiring building demolition
■ Thermal considered most applicable, but target temperature challenges
■ Boiling points:
■ Kerosene 150ºC (minimum)
■ Dieldrin 350ºC!
■ Only applicable heating method to volatilize both ISTD
■ Thermal remediation questions for bench testing
■ Are temperatures even achievable?
■ Is there an alternate thermal mass removal mechanism
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In-Situ Thermal Bench Test: Results
7
■ Contaminant Mobility test
■ oil sheen appeared at temperatures of approximately 60°C after 24 hours of heating;
■ visual observations of contaminant release from the soil into the water
■ greater contaminant mobility observed at 100°C.
■ Post heating, soil concentrations appeared to increase from baseline concentrations;
■ not expected;
■ likely due to pre-test concentrations being under reported due to analytical interference caused by the
presence of both pesticides and hydrocarbons in the same sample.
■ Results
■ At 70ºC Dieldrin and C10 - C28 TPH concentrations of liquids increase significantly, suggesting
mobilization of both carrier oil and pesticide (solubilized) via the heating process.
■ At 100ºC concentrations of both compounds remain above baseline, but significantly lower.
■ The decrease may reflect a combined mass removal mechanism
■ Volatilization for the TPH compounds at 100ºC, since Dieldrin’s boiling point is nearly four times the temperature
attained during the test.
■ Mobilization of TPH and Dieldrin
■ Both compounds could be recovered at lower temperatures via mobilization of solubilized NAPL and
limited volatilization of TPH.
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Thermal Bench Test Results
8
0
20
40
60
80
100
120
140
160
180
0
10000
20000
30000
40000
50000
60000
20 70 100
Die
ldri
nC
on
cen
trati
on
µ
g/l
TP
H C
on
cen
trati
on
µ
g/l
Temperature °C
C6-C10 C10-C28 Dieldrin
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Thermal Model: Methodology and Objectives
9
■ The results from bench test suggested that a target temperature of
between 70ºC and 100ºC would be sufficient to remove the COCs.
■ Temperatures can be accomplished via steam injection.
■ A thermal model was created using PC based PetraSim™ software to
estimate the following design parameters for implementation of steam
injection system in the upper margins (contaminated area) of the
saturated zone:
■ Mass and energy balance;
■ Energy consumption;
■ Prediction of heating duration;
■ Sensitivity to heating and extraction well spacing including number of
heater wells, energy cost and duration.
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ISTD Heating Models
10
Model 1:
■ 4m spacing (36 wells)
■ SVE wells at 6m spacing
Model 2:
■ 3m spacing (64 wells)
■ SVE wells at 6m spacing
SVE
ISTD
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ISTD Model Results (3m spacing)
11
Made Ground
Clay
Silt
Chalk
Gravel
Note: X- Cross Section through the
centre of the heating zone
1 month
Vadose
ZoneAfter 3 months:
• Range in target zone = 130 – 200oC
• Vadose zone = ~ 170oC
• Saturated zone = ~ 130oC
Not high enough for ISTD
2 month
3 month
Vadose
Zone
Saturated
Zone
Vadose
Zone
Saturated
Zone
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Model Input Parameters – Steam Injection Well Configuration
12
Remedial system well configuration:
■ Soil Vapour Extraction (SVE) well:
■ 6 m Radius of Influence
■ 3.5 m depth
■ 0.5 – 3.5 m screened section (3 m)
■ Steam Injection Well:
■ 6 m Radius of Influence
■ 3.5 m depth
■ 2.5 to 3.5 m screened section. (1 m)
SVE
Steam
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Steam Injection Model Results
13
Note: X- Cross
Section through
the centre of
the heating
zone
1 month
2 month
3 month
After 3
months the
saturated and
unsaturated
zones are
predicted to
reach a
temperature
of 100°C
Water Table
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Model Conclusions
14
■ Maximum heat achievable in the unsaturated zone is 150°C (3m
spacing)
■ After 3 months, temperature stabilizes and does not increase above the
maximum predicted
■ Implication: Kerosene can potentially be volatilized, but dieldrin
cannot
■ Are there benefits to the closer spaced/higher temperature ISTD
approach?
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Effect on Remedial Strategy
15
■ TTT reduced from 150°C to 70ºC
■ Change in methodology meant steam rather than ISTD could be used to
heat the subsurface (less wells and energy)
■ Lowest carbon footprint heating approach developed using the model:
0
500,000
1,000,000
1,500,000
2,000,000
2,500,000
3,000,000
Model 1 Model 2 Model 3
ISTD: 3m heater well
spacing
150 – 200ºC
ISTD: 4m heater well
spacing
130 – 170ºC
Steam injection
<100ºC
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Enhanced ISTR Implementation
16
■ Rental steam boiler
■ Piping Layout
■ Treatment compound
■ Vapor extraction system – Vapor phase GAC
■ GW extraction system - Liquid phase GAC
■ NAPL recovery
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Heating Progress (3 April – 31 May 2017)
17
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Remediation Performance Evaluation (Area 4)
18
Project Endpoint Evaluation Endpoint
Achieved?
Area 4: • The thermal system successfully operated for
up to 20 weeks;
• or until asymptotic mass recovery (of Total
Petroleum Hydrocarbons (TPH) and/or total
Drins) is demonstrated, whichever is the sooner
• Mass recovery has reached
asymptotic conditions
• Total system operational time was 20
weeks
Yes
Area 4:• In the event that Drin mobilisation is not
reflective of the results of the pilot studies then
conditions are created to enable the
application of In-Situ Chemical Oxidation
(ISCO)
• ISCO success demonstrated through the
creation of conditions conducive to oxidation
processes and additional mass destruction of
Drins is demonstrated to the extent
reasonably practicable
• Dieldrin concentrations have been
detected within the recovered NAPL
and liquid at concentrations greater
than detected during the bench scale
testing, demonstrating success.
• ISCO implemented in two isolated
hot spots (Ara 3 and 4S). Conducive
oxidation conditions demonstrated.
Yes
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1.0
10.0
100.0
1000.0
10000.0
25/01/17 14/02/17 06/03/17 26/03/17 15/04/17 05/05/17 25/05/17 14/06/17 04/07/17 24/07/17
Mass R
eco
very
(kg
)
Date
Vapour Mass Recovery Dissolved Phase Recovery LNAPL Recovery Total Recovery
Steam Off Steam On Steam Off Steam On Steam Off
Total Mass Recovered/Removed (Area 4)
19
Asymptotic
recovery
achieved
Mass composition is mainly TPH (kerosene) –
4,160kg recovery estimated.
Circa 7.5kg of mass is OCPs (recovered as
free, dissolved phase and ‘sludge’)
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In Situ Chemical Oxidation – Activated Persulfate
■ In-Situ Chemical Oxidant (ISCO)
■ ISCO injection undertaken in
northern site area (7 – 22 June
2017)
■ ISCO injection undertaken in
southern site area (27 June – 12
July 2017)
■ Activation via sodium hydroxide
■ Field monitoring (pH, conductivity,
ORP, DO and temperature in
observation wells) carried out
during injection and into early
August
20
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Remediation Performance Evaluation (Area 3/4S)
21
Project Endpoint Evaluation Endpoint
Achieved?
Area 3:• Where ISCO is deployed, groundwater
conditions are demonstrated to be
conducive to oxidation processes and
mass destruction of Drins is
demonstrated to the extent reasonably
practicable
• Significant changes from pre-injection
negative ORP to positive ORP recorded,
proving effective oxidant injection.
Yes
Area 4S:
• Where ISCO is deployed,
groundwater conditions are
demonstrated to be conducive to
oxidation processes and mass
destruction of Drins is demonstrated
to the extent reasonably practicable
• Significant changes from pre-injection
negative ORP to positive ORP recorded,
proving effective oxidant injection (see
measurements in observation wells MW1 –
MW5, Figure 3)
Yes
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ORP Field Monitoring Data (Area 3)
22
-200.0
-100.0
0.0
100.0
200.0
300.0
400.0
6-Jun-17 13-Jun-17 20-Jun-17 27-Jun-17 4-Jul-17 11-Jul-17 18-Jul-17 25-Jul-17
OR
P (
mV
)
MW6 Top MW6 Middle MW6 Bottom MW7 Top
MW7 Middle MW7 Bottom MW8 Top MW8 Middle
MW8 Bottom MW9 Top MW9 Middle MW9 Bottom
MW10 Top MW10 Middle MW10 Bottom
Injection Period
■ ORP shows an increasing positive trend following ISCO injection in all monitoring wells (successful oxidant delivery)
■ Low dieldrin concentrations detected both pre- and post oxidant injection. Concentrations remain at <0.005mg/l
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-200.0
-100.0
0.0
100.0
200.0
300.0
400.0
22-Jun-17 29-Jun-17 6-Jul-17 13-Jul-17 20-Jul-17 27-Jul-17
OR
P (
mV
)
MW1 Top MW1 Middle MW1 Bottom MW2 Top
MW2 Middle MW2 Bottom MW3 Top MW3 Middle
MW3 Bottom MW4 Top MW4 Middle MW4 Bottom
MW5 Top MW5 Middle MW5 Bottom
ORP Field Monitoring Data (Area 4S)
23
Injection Period
■ ORP shows an increasing positive trend following ISCO injection in all monitoring wells (successful oxidant delivery)
■ Low dieldrin concentrations detected both pre- and post oxidant injection. Concentrations remain at <0.03mg/l