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A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Date post: 25-Jun-2015
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Background/Objectives. In 2003, 1,300 drums and over 3,000 tons of soil were excavated from a drum disposal area in New England. Residual DNAPL created a 2,500 foot long plume that includes chlorobenzenes, toluene, and chlorinated ethenes. The plume discharges to a wetland and has led to vapor intrusion concerns at downgradient properties. Full-scale source zone remediation has been implemented to mitigate potential risks to ecological and human receptors. Approach/Activities. Following extensive site characterization, bench-scale testing, and a successful field pilot test, the full-scale source zone remedy began in November 2010. The combined remedy approach uses physical, chemical, and biological treatment mechanisms to destroy the residual DNAPL in the vadose and saturated zones. Soil vapor extraction (SVE) and air sparging target the more volatile compounds, while in situ ozone injection (IOI) targets the less volatile compounds such as chlorobenzenes. Aerobic biological activity is also likely enhanced as a result of oxygen injection from IOI and air sparging. Three ozone injection systems deliver a total of 100 lbs of ozone per day to the subsurface; the SVE system extracts soil vapor at a rate of 650 scfm; the air sparge system continuously sparges air at 50 scfm at approximately 30 psi. Results/Lessons Learned. Performance monitoring includes analysis of VOC concentrations in soil, soil gas, and groundwater. Quarterly low-flow groundwater sampling has shown substantial decreases in groundwater VOC concentrations relative to baseline. In the first six months of operation, 18 of the 20 monitoring wells sampled showed decreases in total VOC concentrations ranging from 14 to 97% with an average decrease of 57%. Furthermore, the mass discharge of total VOCs in groundwater from the source area has decreased from approximately 105 g/day before pilot-test start-up to less than 4 g/day. Concentrations of VOCs in soil gas are monitored in real-time by an automated soil gas monitoring system equipped with a photoionization detector (PID), and on a periodic basis with Waterloo Membrane Samplers™ that provide a speciated analysis of VOCs in soil gas. Of the 47 soil gas monitoring points that were sampled during the first six months of operation, 36 show decreasing trends in soil gas TVOC concentrations. Minimal rebound was observed in soil gas concentrations after treatment was temporarily suspended. Performance monitoring data have informed periodic system optimization to increase the efficiency of the remedy. These results indicate that the combined remedial technologies are effectively reducing source mass and mass discharge, and that the aggressive two year remedial time-frame will likely be met.
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Combined Ozone, Air Sparge, and SVE Remedy for Treatment of a Mixed VOC DNAPL Source Zone Chapman M. Ross, G. Owen Cadwalader, Peter J. Zeeb – Acton, MA Bruce Marvin – Oakland, CA
Transcript
Page 1: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Combined Ozone, Air Sparge, and SVE Remedy for Treatment of a Mixed VOC

DNAPL Source Zone

Chapman M. Ross, G. Owen Cadwalader, Peter J. Zeeb – Acton, MABruce Marvin – Oakland, CA

Page 2: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

PresentationOutline

Site Background Performance Monitoring Methods Results Long-term trends

Optimization Conclusions

Page 3: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Site Background

Former sand and gravel borrow pit in New England

Removed 1,300 drums & 3,000 tons soil (up to 30 ft bgs)

18 Months into Full-Scale Treatment

Page 4: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Drum & Soil Removal

Ruptured Drums

Page 5: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Chemical Properties of Site COCs

Solubility KocVapor

PressureHenry's Law

Constant

mg/L ml/g mm Hg dimensionless

trichloroethene 1,100 125 60 0.4

cis-1,2-dichloroethene 800 50 210 0.2

1,1,1-trichloroethane 4,400 150 100 0.7

toluene 515 300 22 0.3xylene 200 240 10 0.3

chlorobenzene 500 330 12 0.13

1,2,3-trichlorobenzene 18 7,400 0.2 0.12

1,2,4-trichlorobenzene 30 9,200 0.3 0.06

Page 6: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Chemical Properties of Site COCs

Solubility KocVapor

PressureHenry's Law

Constant

mg/L ml/g mm Hg dimensionless

trichloroethene 1,100 125 60 0.4

cis-1,2-dichloroethene 800 50 210 0.2

1,1,1-trichloroethane 4,400 150 100 0.7

toluene 515 300 22 0.3xylene 200 240 10 0.3

chlorobenzene 500 330 12 0.13

1,2,3-trichlorobenzene 18 7,400 0.2 0.12

1,2,4-trichlorobenzene 30 9,200 0.3 0.06

NAPL likely present. 7 VOCs in GW from

1 to ~20% of aq. solubility prior to treatment

Page 7: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Potential Receptors

Wetland/ Vernal Pool

Town Hall

Drum Excavation

Area

200 100 0 200 feet

VOC plume is approximately ½ mile long

Page 8: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Treatment Area

Pilot Test

Full Scale

Page 9: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Source Characterization – Soil and GW

Groundwater Flow

Page 10: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Source Characterization – Soil and GW

Groundwater Flow

Page 11: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Source Characterization – Soil and GW

Groundwater Flow

Page 12: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

SystemPilot Test Full-Scale

Treatment Area 2,500 ft2 10,000 ft2

Ozone 27 lb/day 100 lb/day

Air Sparge 25 scfm 55 scfmSVE 300 scfm 600 scfmDuration 7 months 2+ yearsPilot Test (25% of source)

Full-Scale

Pilot Test to Full-Scale Design

Page 13: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Ozone Injection and SVE

Ozone Injection

Ozone and Air Sparging

Full-Scale Cross-Section

Page 14: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Performance Monitoring

Soil Gas Real time monitoring system:

TVOC, O3, O2, CO2

Waterloo Membrane Samplers (WMSTM)

Handheld PID measurements Groundwater Analytical laboratory data ORP field data

Shutdown Test

Page 15: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Soil Gas Results – Vadose Zone TVOCs

Baseline

Page 16: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Soil Gas Results – Vadose Zone TVOCs

18 Months Operation

Page 17: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Soil Gas Results – Vadose Zone TVOCs

18 Months Operation

TVOC (ppm) Baseline Feb 2012 % ReductionAverage 794 13 98Median 112 4.9 96Maximum >10,000 101 >99

Page 18: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

WMSTM Soil Gas Results –Vadose Zone VOCs

Baseline

Page 19: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

WMSTM Soil Gas Results –Vadose Zone VOCs

18 Months Operation

Page 20: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

WMSTM Soil Gas Results –Vadose Zone VOCs

18 Months Operation

Vadose zone treatment now focused on these remaining high concentration areas.

Page 21: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Groundwater Sampling Results – VOCs

Baseline

Page 22: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Groundwater Sampling Results – VOCs

18 Months Operation

Page 23: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Groundwater Sampling Results – VOCs

18 Months Operation

GW treatment now focused on these remaining high

concentration areas.

Page 24: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Long-term Trends in GW in TCE Plume Core:LR-18S

Page 25: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Long-term Trends in GW in TCE Plume Core:LR-18S

99%

91%

97% Reduction

Page 26: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Long-term Trends in Capillary Fringe GW in TCB Plume Core: OZ-CAP-33

Page 27: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

NAPL Evaluation – Pre/Post-Treatment

(Cherry and Feenstra, 1991)

Page 28: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Mass Discharge of VOCs – Transect Method

6 wells K = 15 ft/day q = 0.045 ft/day B = 6 to 11 ft

Groundwater Flow

Einarson and Mackay, 2001

Page 29: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Mass Discharge of VOCs - Summary

18 months operation

18 tons of ozone injected total (pilot and full-scale)

Treatment Area Mass Discharge of VOCs in Groundwater

Page 30: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Optimization

Real-time Data• SGSS• ORP Probes

Efficient focused

treatment

Targeting recalcitrant zones early

Faster Site Closure

Optimization• Automatic data

processing & analysis using OptiRTC

• Decision matrix for laboratory data analysis

• Remote system control

See Owen Cadwalader’s presentation on Optimization Session A5 - Wednesday 9:40 A.M (Abstract #141)

Laboratory Data• Groundwater• Soil gas (WMSTM)

Page 31: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Conclusions

Decrease from 7 to 3 in number of VOCs present as NAPL

2 orders of magnitude reduction in groundwater VOC mass discharge

Moderate rebound in groundwater VOCs after 6-week shutdown test (increase by 90% on average)

On target to meet goal of <1 mg/L TVOC in groundwater

Page 32: A Combined Ozone Remedy for a Mixed VOC DNAPL Source Zone

Acknowledgements

Co-Authors – G. Owen Cadwalader, Peter J. Zeeb, Bruce K. Marvin (Geosyntec)

Peter Shellito and Chris Martin –Geosyntec Field Crew

Chapman Ross - [email protected]


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