In Situ Thermal Hydrolysis of 1,2-Dichloroethane (EDC) in Fine-Grained Soil: Pilot Test October 2014 Michael Singer/KNV
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Acknowledgements • Joanne West/Dow • Audrey Sidebottom/Dow • Jason Cole/CH2M HILL • Jake Eimers/CH2M HILL • Phil Smith/CH2M HILL • John Mason/CH2M HILL • Gary Hickman/CH2M HILL
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Agenda • Site Background • Hydrolysis of EDC • Pilot Study Approach • Heating History and Issues • Sampling Results • Summary and Conclusions
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Site Background
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Why the need for the project • Elevated EDC in soil and groundwater due to historical operations (former EDC product rail loading facilities) • Limited Access – cannot disrupt operational rail lines
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Site Geology
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Extent of Contamination
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Hydrolysis of 1,2-dichloroethane
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EDC Transformation • Neutral Hydrolysis – reaction with water at neutral pH conditions • EDC Hydrolysis • • • •
C2H4Cl2 (EDC) + 2H2O → C2H6O2 (ethylene glycol) + 2H+ + 2ClAbiotic production of ethylene glycol Ethylene glycol is biodegradable Temperature strongly accelerates hydrolysis rate
+ H2O EDC
Ethylene Glycol DOW CONFIDENTIAL - Do not share without permission
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Thermal Hydrolysis Lab Test • 2008 Lab Study: • Site soil/groundwater • Closed batch reactors incubated at approx.:
EDC Mass Degradation Based on Degradation Products
• 20°C • 80°C • 100°C
• Monitored for EDC and abiotic degradation products (Cl-, glycol)
Thermal hydrolysis laboratory study conducted at CH2M HILL’s Applied Sciences Laboratory in Corvallis, Oregon to evaluate abiotic degradation of EDC in soil taken from site.
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Field Scale Pilot Test
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Field-scale Pilot Study Pilot Objectives: 1. To reduce the concentration of EDC in soil at Block 270 Former Railcar Loading Area. 2. Develop a better understanding of the effectiveness and applicability of in situ thermal hydrolysis as a remedial technology for EDC 3. Provide operational data to help optimize the design and operation of future in situ thermal hydrolysis at other sites. 4. Target Concentrations: 500 mg/kg in soil DOW CONFIDENTIAL - Do not share without permission
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Electrical Resistance Heating
Alternating current is applied to subsurface electrode arrays Electrical resistance of the soil generates heat ERH relies on water for electrical conductance SVE for contaminant recovery when needed Temperature limited to boiling point of water at local pressure
Typical energy applied – 200 to 300 kW-hrs/cy DOW CONFIDENTIAL - Do not share without permission
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Site Layout • 24 vertical electrodes • 15 Monitoring Locations (Temperature, Water Samples) • Initial target temp.: 60°C • Depth: 2-7 m interval • Target area: ~16m x 27m • Treatment Soil Volume: 2,160 m3
Water Tank Power Distribution Panel
Heat Water Control System Trace DOW CONFIDENTIAL - Do not share without permission Panel
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Site Photos Site Preparation
Electrode Connections
Site Looking Southwest
Monitoring Well
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Heating History and Issues
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Average Subsurface Temperature 100
Unexpected Observations:
Electrodes dried/multiple tap changes and modifications
90
Multiple daily shutdowns Multiple tap changes
80
70 Average Temperature, Celsius
• Rapid response to system changes • Area near center of site difficult to heat
60 Water shutoff due to leak
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Dec.16 System Shutdown 40
30
20 24 hour shutdown 10
0
24 hour shutdown Mar.12 System Startup
Date
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Soil Temperatures Varied in Pilot Test Area • Differences in soil properties (EC)? • Unknown source of water in area?
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Sampling Results
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Sample Locations
Groundwater
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Groundwater Results - Summary Location Name 12MW0005-270
12MW0008-270
12MW0009-270
12MW0011-270
12MW0012-270
Sample Date
EDC (mg/L)
11-Mar-13
2510
34.1
31-May-14
19.3
127
11-Mar-13
71.9
96.2
31-May-14
56.3
158
28-Aug-13
1540
298
31-May-14
10.5
62.5
11-Mar-13
2590
26.8
31-May-14
0.0958
10.5
28-Aug-13
153
108
31-May-14
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192
Chloride (Cl) (mg/L) % Reduction ([O-E]/E)
-99%
-22%
-99%
-100%
-85%
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EDC vs. Chloride
MW05 Chloride
3000
250
2500
200
2000
150
1500 100
1000
50
500 0 1/26/13
5/6/13
8/14/13
MW08
2500 2000
150
1500 100
1000
50
500 8/14/13
11/22/13
3/2/14
6/10/14
0 9/18/14
EDC (mg/L)
200
Chloride (mg/L)
EDC (mg/L)
EDC
250
5/6/13
3/2/14
6/10/14
0 9/18/14
MW11
Chloride
3000
0 1/26/13
11/22/13
Chloride
3000
250
2500
200
2000
150
1500 100
1000
50
500 0 1/26/13
Chloride (mg/L)
EDC
Chloride (mg/L)
EDC (mg/L)
EDC
5/6/13
8/14/13
11/22/13
3/2/14
6/10/14
0 9/18/14
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EDC Vs. Temperature
3000
EDC (mg/L)
2500 2000 1500 1000 500 0 1/6/13
3/7/13
5/6/13
7/5/13 EDC
1000 500 0 1/6/13
3/7/13
5/6/13
7/5/13 EDC
9/3/13 11/2/13 1/1/14 Temperature
2500 2000 1500 1000 500 0 1/6/13
3/7/13
5/6/13
7/5/13 EDC
9/3/13 11/2/13 1/1/14
100 90 80 70 60 50 40 30 20 10 3/2/14
Temperature Deg C
1500
3000
EDC (mg/L)
2000
100 90 80 70 60 50 40 30 20 10 3/2/14
Temperature Deg C
EDC (mg/L)
2500
Temperature
MW011
MW08 3000
9/3/13 11/2/13 1/1/14
100 90 80 70 60 50 40 30 20 10 3/2/14
Temperature Deg C
MW05
Temperature
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Soil Results 4500 4000
600
EDC in Soil
500
3500 3000
400
EG, mg/Kg
EDC, mg/Kg
Ethylene Glycol in Soil
2500 2000 1500
300
200
1000 100
500 0
BH07
Pre-Test
BH08
Oct-13
BH09
Dec-13
BH10
0
BH07
BH08
Oct-13
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BH09
BH10
Dec-13
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Summary and Conclusions
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Summary and Conclusions • EDC Reduced in soil and groundwater (pilot test objectives met) • Indications that hydrolysis occurred • Some reductions may be result of other factors (volatilization?) • Uneven soil heating was a problem • Final soil and groundwater sampling underway this week • Wells are being slug tested to evaluated differences in hydraulic K across the site
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Factors affecting choice of in situ hydrolysis • Only appropriate for chemicals that hydrolyze at relatively low temperatures (for example, EDC, 1,1,1-TCA) • Site hydrogeology (low groundwater flow velocities helpful in achieving target temperatures) • Site factors, such as access restrictions or presence of structures, that might preclude other approaches, such as soil mixing • Availability and cost of energy • Local infrastructure, especially occupied buildings
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EDC, Chloride, and Ethylene Glycol MW009 3000
90 80 70 60
2000
50 40
1500
30 1000
20
Ethylene Glycol, mg/L
EDC and Chloride, mg/L
2500
10
500
0 0 07/05/13
09/03/13
11/02/13
EDC
01/01/14
Chloride
03/02/14
Ethylene Glycol
05/01/14
-10 06/30/14 28
