Combination of ZVI and EVO to Remediate a Large, Shallow TCE DNAPL Plume at a Former Industrial Facility
• Krista Parra (NAVFAC, Norfolk, VA, USA) • Robert Kelley, Ph.D. Michael Liskowitz, and Eric
Moskal (Cascade Technical Service, New Brunswick, NJ, USA)
• Laura Cook, P.G. (CH2M, Virginia Beach, VA).
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Site Overview: St. Julien's Creek Annex (SJCA)
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Site Background • 490 Acres • Began operation in 1849 • One of the largest ammunitions
Facility • Ceased Ordnance operations in
1977
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Conceptual Site Model
• Fine to coarse silty
• Clayey sands
• Clay
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Site Map
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Shallow Groundwater TCE Plume
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Site 21: OU-12-Building 187
• Locomotive Maintenance Facility
• COCs: TCE and Daughters
• No vapor intrusion problems
• Two-phased approach – ISCR with ZVI – ERD with EVO
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Remediation Approach Phase I (Nov. 2010) • 202 ZVI Injection points • 85,800 lbs. ZVI • 149 EVO Injection
points • 18,300 lbs. EVO
Phase II (2012) • 37 EVO Injection
Points • 4,500 lbs. EVO
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Technology fit versus mass/concentrations
High Concentration Low
NAPL pools Mobile NAPL Ganglia Droplets Adsorbed/dissolved Trace
Thermal
ISCO/ISCR
MNA
ISB
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Combined Remedies
• Spatial—Separate parts of the plume
• Temporal—Different Times (e.g. Sequentially)
• Spatial & Temporal
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Marriage of Chemistry & Biology
• Kinetics – Bio: PCE>>TCE>>DCE>>VC – ZVI: VC>>DCE>>TCE>>PCE
• pH – Bio: Decrease pH – ZVI: Increase pH
• Mass Action – Bio: Typical operates at lower (ppb)
concentrations – Chem: Higher concentration (ppm) more favorable
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Ferox™ Patent Claims
• Reductive CHEMISTRY using Zero Valent Iron (ZVI)
• Pneumatically Emplaced (i.e good distribution)
• Loading Rate Between 0.6% and 0.4% w/w
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Injection Point Layout
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Results within 3 years
~294,000 sf. ~18,000 sf.
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After 3.5 years of Treatment: Source Area
99.9% Reduction
80% Reduction
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After 3 years of Treatment: Source Area
100% Reduction
100% Reduction
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After Seven Semi- Annual Sampling
• COCs: TCE and Daughters – TCE—0.51 – 214 ug/L – VC 18.3 – 150 ug/L
• pH 5.72 -7.49 • TOC <20 mg/L • ORP <50 mV
Conclusions • TCE concentrations
decreasing – 294,000 sf. 18,000 sf.
• Daughter Products are being formed
• VC concentration stable • ZVI and EVO achieving the
remedial goals • Second Round of EVO
starting to work
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Second Round of EVO: DPT and Injection Wells
Results: • TCE concentrations decreasing
– 294,000 sf. 18,000 sf. • Daughter Products are being
formed • VC concentration stable • ZVI and EVO achieving the
remedial goals • Second Round of EVO starting
to work
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Summary of TCE Degradation
0
2000
4000
6000
8000
10000
12000
14000
NOV2010
MAR2011
MAY2011
DEC2011
MAY2012
NOV2012
MAY2013
NOV2013
JUL2014
NOV2014
MAY2015
NOV2015
TCE - St. Julien's Creek Site 21 ZVI Treatment Area Wells
MW02
MW12S
MW14S
MW15S
MW16S
MW20SR
MW27SR
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Summary of cis-1,2-DCE Degradation
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
NOV2010
MAR2011
MAY2011
DEC2011
MAY2012
NOV2012
MAY2013
NOV2013
JUL2014
NOV2014
MAY2015
NOV2015
cis-1,2 DCE - St. Julien's Creek Site 21 ZVI Treatment Area Wells
MW02
MW12S
MW14S
MW15S
MW16S
MW20SR
MW27SR
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Summary of Vinyl Chloride Degradation
0
200
400
600
800
1000
1200
1400
1600
NOV2010
MAR2011
MAY2011
DEC2011
MAY2012
NOV2012
MAY2013
NOV2013
JUL2014
NOV2014
MAY2015
NOV2015
Vinyl Chloride - St. Julien's Creek Site 21 ZVI Treatment Area Wells
MW02
MW12S
MW14S
MW15S
MW16S
MW20SR
MW27SR
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Classic Reductive Dechlorination Pathway MW-15S
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
20000
TCE
cis-1,2 DCE
1,1-DCE
VC
Total COCs
MW15S
Concentration, µg/L
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Beta-Elimination Pathway MW-16s
0
2000
4000
6000
8000
10000
12000
14000
16000
RI BASELINE 1 MO ZVI 3 MO ZVI 1st SA 2nd SA 3rd SA 4th SA 5th SA 6th SA 7th SA 8th SA 9th SA
TCE
cis-1,2 DCE
1,1-DCE
VC
Total COCs
MW16S
Concentration, µg/L
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TCE Concentrations Historical Comparison Map
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Cis-1,2 DCE Concentrations Historical Comparison Map
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Vinyl Chloride Concentrations Historical Comparison Map
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Dissolved Arsenic Concentration
0
10
20
30
40
50
60
NOV 2010 MAR 2011 MAY 2011 DEC2011
MAY 2012 NOV 2012 MAY 2013 NOV 2013 JUL2014
NOV 2014 MAY 2015 NOV 2015
Dissolved Arsenic - St. Julien's Creek Site 21 ZVI Treatment Area Wells
MW02S MW12S MW14S MW15S MW16S MW20SR MW27SR
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Arsenic Concentrations Historical Comparison Map
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Conclusions
• Combining chemical reduction with biological reduction can reduce TCE concentrations from DNAPL to below 5 ppb.
• Using ZVI can limit the amount of vinyl chloride that is produced and provide a treatment for multiple years after application.
