upgradient persulfate injection and downgradient ozone ......upgradient persulfate injection and...

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, PEJim.Leu@parsons.com

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)

22

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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