23th International Petroleum Environmental Conference
Upgradient Persulfate Injection and Downgradient Ozone Sparging to Accelerate Closure of a Petroleum Hydrocarbon-Impacted Site
November 9, 2016
� Parsons’ Authors:� Jim Leu, PhD, PE� Michelle Morales, EIT
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� Michelle Morales, EIT
Parsons’ Presenter:Jim Leu, PhD, [email protected]
Authors and Presenter
Presentation Overview
� Site Background� Groundwater Modeling
� Capture Zone Analysis (MODFLOOW)� By-products Impacts Evaluation (MT3D)
� Upgradient Persulfate Injection � Upgradient Persulfate Injection � Injection and Monitoring Program� Geotechnical Monitoring
� Downgradient Ozone Sparging� Pilot Test� Interaction with Persulfate
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TPH Site Background
� Former natural gas processing station (1960 to 1980s)� Interbedded layers of sand and silty sand (0 to 30 ft bgs)� Shallow unconfined zone (15 to 30 ft bgs)� Chemicals of concern
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Matrix GRO DRO ORO
Upgradient GW (µg/L) 3,500 3,700 440
Downgradient GW (µg/L) 3,500 5,600 520
Clean-up Levels (µg/L) 100 100 100
Chronology of Key TPH Site Events
1999 –vapor intrusion
study
2005 –ORC
injection study
2009 –ozone bench
test
1999 to 2013 –groundwater extraction
2012 –ISCO bench test
2015 –NFA
request
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study
2007 –remedial process
optimization
2013 to 2014 –Full-scale ISCO implementation
2001 to 2006 –soil vapor
extraction/air sparging
remediation
2010 –ozone pilot
test
test request
Persulfate Injection and Ozone Sparging
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GW Flow
Persulfate ROI Ozone Sparging ROI Oxygen Sparging ROI
MODFLOW – Capture Zone
Existing 5 EWs at 3 gpm
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Proposed 2 EWs at 3 gpm
MT3D – Predicted TDS Impact Distribution
One month after
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Nine months after
MT3D – Predicted TDS Concentration at EW-5
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Vertical/Angle Drilling and Injection
� Open field� Points: 6� Depth: 15 to 23 feet vertical
Vertical Drilling/Injection
Angle Drilling/Injection
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� Below the building� Points: 6� Angles: 10 to 20 degrees� Depth: 14 to 21 feet vertical
Angle Drilling/Injection
Geotechnical Monitoring Results
� Visual inspection: No observable changes
� Crack monitoring � No expansion or extension
of existing cracks
� Settlement monitoring � Differential settlement less
than 1%� Total settlement less than
0.5 inches
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Ozone Sparging Pilot Test
� Injection well: 2 � Pressure: 5.5 to 6.0 psi� Flow rate: 3.5 cfm per well� Equivalent to ~ 2 lb O3/day� ROI ~ 20 feet
Pilot Test Injection Specifications
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� ROI ~ 20 feet� Injection time: 60 minutes
Pilot Test Results – DRO Concentration
Injection start
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Injection end
Pilot Test Results – Secondary Impacts (Bromate and Hexavalent Chromium)
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Full-scale Ozone Sparging Implementation
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Full-scale Ozone Injection Implementation
� Injection wells: 6� Ozone sparging wells: 4� Oxygen sparging wells: 2
� Injection pressure: 12 to 25 psi� Sparge flow rate: 6.8 cfm per well� Sparge flow rate: 6.8 cfm per well� Ozone capacity: 27 ppd� ROI: 20 feet based on DO and ORP measurements
� Treatment monitoring wells: 8 � Transition and compliance wells: 10
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Groundwater Monitoring Well Locations
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Persulfate Injection Contingency Plan
� Trigger: TDS concentrations at transition wells (TW-2, TW-3) exceed 20% of baseline concentration continuously for 3 times
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� Response: Initiate GWETS at extraction wells
TDS Concentration Trends in Downgradient Groundwater Wells
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Groundwater Monitoring Well Locations
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Ozone Treatment Wells – pH
7.00
8.00
9.00
10.00
pH
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4.00
5.00
6.00
Jul-13 Aug-13 Sep-13 Oct-13 Dec-13 Jan-14 Feb-14 Mar-14 Apr-14 May-14 Jun-14 Jul-14 Aug-14 Sep-14
Sample DateMW-2 MW-3 MW-5 EW-1 EW-2 EW-6 V-11 V-13 TW-2 TW-3
EW-2
Ozone Treatment Wells – Conductivity
6,000
8,000
10,000
12,000
14,000
16,000
Con
duct
ivity
(um
hos/
cm)
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0
2,000
4,000
6,000
Jul-13 Aug-13 Sep-13 Oct-13 Dec-13 Jan-14 Feb-14 Mar-14 Apr-14 May-14 Jun-14 Jul-14 Aug-14 Sep-14
Con
duct
ivity
(
Sample Date
MW-2 MW-3 MW-5 EW-1 EW-2 EW-6 V-11 V-13 TW-2 TW-3
TW-2
TW-3
Ozone Treatment Wells – ORP
0.0
100.0
200.0
300.0
400.0
500.0
600.0
OR
P (
mV
)
EW-2
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-400.0
-300.0
-200.0
-100.0
0.0
Jul-13 Aug-13 Sep-13 Oct-13 Dec-13 Jan-14 Feb-14 Mar-14 Apr-14 May-14 Jun-14 Jul-14 Aug-14 Sep-14
OR
P (
mV
)
Sample DateMW-2 MW-3 MW-5 EW-1 EW-2 EW-6 V-11 V-13 TW-2 TW-3
GRO Results
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Prior to remediation One year after remediation 95% removal after rebound
DRO Results
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Prior to remediation One year after remediation 65% removal after rebound
MW-2 Chromatography – Polar Compounds
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DRO with Silica Gel CleanupDRO
BIOSCREEN – Polar Compounds Biodegradation in MW-2
5 years
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10 years
20 years
Conclusions
� Successfully destroys COCs in saturated zone� Byproduct impacts
� Injected chemicals (TDS, sulfate) captured � Oxidized chemicals (Cr(VI), BrO3
-) contained
� Interaction monitoring parameters� Interaction monitoring parameters� pH – decreased� Conductivity – increased� ORP – increased
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Questions
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