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In Situ Chemical Oxidation of VOCs and BTEX Plume in Low-Permeability SoilsAmit Haryani, PE, LSRP
Process Map
• Diesel, gasoline, solvents
Maintenance Yard
• Attain NJ GWQS - Rapidly
Client Goals
• Mixed plume in low perm soil
Challenges
• Benefits of real time CSM evolution
Evolution of CSM
Page 2
Process Map
• Low perm soils & MIP results
Thoughts on Data Interpretation
Evolution of
• Alternate oxidants
Evolution of Remedial Approach
Results & Path Forward
Page 3
Site History
2001
2002 -2005• Wells Installed• BTEX; MTBE;
TBA
2007 - 2008• Previous
COCs• PCE
Page 4
1998• 4,000g
Diesel UST• 2,000g
Diesel UST
2001• 10,000g Gas
UST• VOC Storage
Bldg• Fuel dispenser
TBA• Lead• TCE; cis-1,2-
DCE; VC• 1,2-DCA; 1,1-
DCE
Initial Conceptual Site Model – Hydrogeology
Asphalt
Brown to grey Silt + med to fine sand,
trace clay
10 ft
0.5 ft
2 ft, occasionally
Page 5
Dark grey clayey Silt
90 ft
Remedial Notions - Based on 2008 CSM
• Site geochemistry preferable for CHP• High dissolved iron content• Site pH is low (4-6) range
• Iron a catalyst for hydroxyl radical generation• Acidic pH assists keeping iron in solution & available for reaction• Site contaminants susceptible to immediate oxidation by CHP• Cons: potential TBA (as by-product MTBE oxidation) generation
CHP as remedial approach
• Cons: potential TBA (as by-product MTBE oxidation) generation
• Oxygen generated by hydrogen peroxide decomposition aids aerobic biological systems
• Site contaminants (TBA, MTBE, benzene, and VC) susceptible to long-term aerobic biological degradation
Plus, added benefits :
Page 6
Remedial Focus
• One saturated (8 – 13 ft bgs) soil sample• Groundwater• Sample from or adjacent to well with highest concentration (MW-10 @
MIP-6 and MIP-7)• Acidic buffer capacity / Peroxide reactivity / Oxidant effectiveness
EXTERNAL BENCH STUDY
BENCH RESULTS
2009
• Initial VOCs: gw 1.5 mg/L VOCs; soil 0.404 mg/kg• Soil pH
Recent History
2010
2011• SPS
Injections
Page 8
2009• Aug to Sep
- Peroxide Injections
• Nov – MIP / HPT
• Revise CSM
Phase I ISCO Application Summary
• Could not inject target volume (500 gal of 14% H2O2) due to surfacing.
• Reduced H2O2 from 14% to 8% to 4%.
• Eliminated addition of iron after IP-12.
Round 1 – August 20092009
• Used Hydraulic Profile Tool (HPT) on day 1 to establish permeable zones to target injections.
• Completed injections (IP 17 - 78) but at reduced target volume (120 gallons).
• Overall, actual volume
1800
3400
71
340
620
730
5400
270
2100
2200
610
1100
1300
1600
100
1000
10000
Tert Butyl Alcohol (TBA)
ppb
Phase I ISCO Results Summary
71
5.8
37
17
11
40
5
16
6.3
22
1
10
100
MW-1 MW-5 MW-6 MW-7 MW-10 MW-12 MW-102S MW-103S MW-105S MW-106S
Jan-08 Mar-09 Oct-09 Dec-09
Phase I ISCO Results Summary140 170
170
230
38
270
9.9
150
19
4248
350
13
85
100
680
140
12
80
140
35
57
47
420
11
80
10
48
100
1000
Methyl Tert Butyl Ether (MTBE)
ppb
3.2
3.8
9.9
1
6.2
8.5
6.4
0.93
2.8
4.9
10
0.1
1
10
MW-1 MW-5 MW-6 MW-7 MW-8 MW-9 MW-10 MW-11 MW-12 MW-102S MW-103S MW-105S MW-106S
Jan-08 Mar-09 Oct-09 Dec-09
Phase I ISCO Results Summary
71
780
61
450
37
110
980
61
210
690
40
100
1000
Pechloroethene (PCE)
ppb
1.4
2.7
4.5
5.3
1.2
16
5.3
4.6
5.3
1.6
1.4
14
18
1.1
4.3
6.7
1
10
MW-6 MW-8 MW-9 MW-10 MW-11 MW-12 MW-103S MW-105S MW-106S
Jan-08 Mar-09 Oct-09 Dec-09
Phase I ISCO Lessons Learned
• Poor performance > 7ft bgs.
Injection volumes restricted
• Injections forced to target 5 to 7 feet depth interval.
HPT data clarifies delivery issues.
Rapid reaction of Catalytic Hydrogen Peroxide
• Back pressure reduces ability to inject further oxidant solution.• Difficult to inject volumes into areas previously injected.
Rapid reaction of Catalytic Hydrogen Peroxide evolves gas = back pressure.
• Rebound / back diffusion?• Permanent injection wells?
Follow up treatment of residual “hot spots” warranted.
Phase II
• Strategy focusing on greatest residual• Use MIP/HPT direct sensing to focus “Hot Spot”
treatment efforts• Identify zones of flux
“Hot Spot” treatment
Apply different oxidant - SPS
2010
Page 14
• Strong oxidizing radical• Catalyzed by native iron• No temperature increase• No off-gas• Oxidation & reduced formation of TBA (suggested
in lit.) • More Persistent• Lower affinity for natural soil organics (Brown
2003); greater efficiency
MIP in Low Perm Soil
• PID readings >11 ft bgssuggestive of mg/L to 10s mg/L conc.?
• Signal in multiple areas of high soil conductivity
MIP Operator Observations
Multiple grab samples at depth do not confirmdepth do not confirm
• Others (Quinnan, et al) have documented bias in MIP within low permeability units
• + varying sensitivity depending on chlorine substitution
Signal Bias in Low Perm Soil
Phase II ISCO Application – January 2011
• 23 injection points• Catalyst – 575-gallon• 15% persulfate – 1,885-gallon• Flow Rate – 1 gpm – 3.57 gpm
Area 1
• 42 injection points• Catalyst – 1,710-gallon
Area 2
2011
• Catalyst – 1,710-gallon• 15% persulfate – 5,925-gallon• Flow Rate – 0.76 gpm – 3.85gpm
• 24 injection points• Catalyst – 600-gallon• 15% persulfate – 2,200-gallon• Flow Rate – 0.58 gpm – 2.78 gpm
Area 3
730
5400
37
270
2100
790
580
310
960
740
2002
90 380
48
340
1802
80
470
170
53
920
58
100
1000
10000
Phase II ISCO Results Summary - TBA
5.8
37
17
116.
2 7.7
6.5
12
7.2
1818
11
18
1
10
MW-1 MW-5 MW-6 MW-7 MW-8 MW-9 MW-10 MW-11 MW-12 MW-102S MW-103S MW-104S
MW-105S MW-106S
Mar-09 11-Mar 11-May 11-Aug
48
350
13
85
100
6.2
680
8.5
140
140
12
80
39 39
100
180
9.2
50
60
95
34
44
20
90
30
52
8.1
72
30
23
15
7.2
58
22
12
45
190
42
150
10
100
1000
Phase II ISCO Results Summary - MTBE
1.0
6.2 8
.5
2.7
1.8
1.7
5.6
4.7
0.7
4.8
8.1
7.2
0.56
0
1
10
MW-1 MW-5 MW-6 MW-7 MW-8 MW-9 MW-10 MW-11 MW-12 MW-102S MW-103S MW- 104SMW-105S MW-106S
Mar-09 11-Mar 11-May 11-Aug
110
980
56 61
99
200
51
67
81
210
48
95
170
46
80
97
100
1000
Phase II ISCO Results Summary - PCE
1.2
16
5.3
4.6 5.
3
1.1
1.1 1.
3
5
3.1
1.5
1.1 1.
3
1.3
3.5
6.6
2.3
1.7
2.4
1.6
2.6
15
1
10
MW-1 MW-5 MW-6 MW-7 MW-8 MW-9 MW-10 MW-11 MW-12 MW-102S MW-103S MW- 104SMW-105S MW-106S
Mar-09 11-Mar 11-May 11-Aug
Phase II ISCO Results Summary
• MW-5, MW-10, and MW-12
HOT spot wells = Significant reduction in concentrations
• Except: MW-1, MW-5, and MW-10
TBA below GWQS in all on-site wells
2011
• Except: MW-10
MTBE below GWQS in all on-site wells
• MW-104S and MW-106S
Off Site contaminant increases
Next Steps to Site Closure
• Past system behavior suggest anaerobic conditions exist(ed)• PCE degradation via RD with daughter products and ~50 %
reduction of COCs without active treatment over 4 yrs (‘04 – ’08)• In fuel release source areas, e-acceptors (e.g., oxygen, nitrate, iron
and sulfate) often absent/limited – handicapping biodegradation• Anerobic biodegradation systems benefit from Fe-SPS once redox
potential decreases again as the process supplements iron and sulfate
MNA Considerations – Anaerobic
Life Cycle Costs: MNA with LTM vs. Additional ISCO
• Given past plume stability (pre-ISCO perturbations), LTM could be in perpetuity
• One additional targeted applications of Fe-SPS equivalent to 2 years of LTM
• Additional ISCO shortens LTM time by years• Sequential injection events within target interval = mass reduction in
zones of flux.
Life Cycle Costs: MNA with LTM vs. Additional ISCO with Re-assessment
The End
Amit Haryani, PE, LSRPSenior Project Manager(732) [email protected]