In Situ Chemical Oxidation of Dioxane Using
Slow-Release Chemical Oxidant Candles
Second Annual RE3 Conference
Patrick Evans, Ph.D.
Pamela Dugan (Carus)
Michelle Crimi (Clarkson U.)
January 28, 2014
Problem Statement
• Dioxane is a challenging contaminant:
– More widespread than previously thought
– Large and dilute plumes
– Increased cancer slope factor published in 2010
• Current approaches don’t work well or are
expensive:
– Pump and treat / advanced oxidation processes
– Biodegradation (Evans, Parales, & Parales 2007)
• Slow release oxidant candles are a solution:
– Permanganate or unactivated persulfate oxidize dioxane
– Applicable to co-contaminants and large / dilute plumes
2
Technology Description
• Solid product formed as candle or
chipped for barrier applications
– 1.35- or 2.5-inch diameter
– 18 inches long
3
Permanganate Candle Release from Wax
4
Permanganate Candle Release from Wax
• As permanganate
solids dissolve void
spaces are created
5
Permanganate Candle Release from Wax
• Newly created void
spaces expose
permanganate solids
for dissolution and
diffusion
• Process occurs
radially from the
“core” of the candle
to the candle exterior
6
Permanganate Candle Release from Wax
• As permanganate
releases/reacts
porosity develops
inward to the core
of the candle
• Diffuses across a
greater distance
7
Permanganate Candle Release from Wax
• This is why we see
and initial spike of
permanganate in
early time…
8
Permanganate Candle Release from Wax
• And a significantly
slower and lower
release of
permanganate at
later times
9
Technology Description
• Configurations
– Permeable reactive barrier (PRB)
– Funnel and gate (F&G)
– Grid
• Emplacement Methods
– Direct push
– Wells
– Drop-in cassettes
• Oxidants
– Permanganate
– Persulfate
10
Passive Treatment with
In Situ Reactive Zones / Barriers
Receptor
Well
Water
Table
Contaminated
Groundwater
GW Flow
Clay lens
Bedrock
Treated
Groundwater
11
Technology / Methodology Description
12
Site A
Site B
Site C
Not Tested
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Not Tested
Dioxane Removal
Dioxane Destruction with
Permanganate and Unactivated Persulfate
Both permanganate and unactivated persulfate oxidize dioxane at various sites
13
Comparison of TCE and Dioxane Oxidation
14
Laboratory Oxidant Kinetics Results
14000
Permanganate Test Conditions
[1,4-Dioxane] (μg/L)
12000
10000
8000
6000
4000
2000
0
0
1
2
6
9
Incubation Time (days)
14
Control-D
PM-0.05
PM-0.075
PM-0.125
PM-0.25
PM-0.50
PM-0.75
PM-1.00
21
28
15
Laboratory Oxidant Kinetics Results
Pseudo-2nd Order Rate Constant for
Permanganate
4.0E-06
4.0E-05
k’= 1.36×10-3 M-1S-1
3.5E-05
First Order Rate Constant. k (s-1)
First Order Rate Constant, k (s-1)
Pseudo-2nd Order Rate
Constant for Persulfate
k’= 4.30×10-5 M-1S-1
3.5E-06
3.0E-05
3.0E-06
2.5E-05
2.5E-06
2.0E-05
2.0E-06
1.5E-05
y = 0.0014x - 4E-07
R² = 0.9975
1.0E-05
5.0E-06
y = 4E-05x + 7E-08
R² = 0.9988
1.5E-06
1.0E-06
5.0E-07
0.0E+00
0.0E+00
0
0.01
0.02
Persulfate (M)
1st order rate constant - k (s-1)
0.03
0
0.02
0.04
0.06
0.08
0.1
Permanganate (M)
1st order rate constant - k (s-1)
16
Column Results for Dioxane Removal
• Persulfate SR
cylinder 97%-100%
• 1,500 ppm unactivated
persulfate 93%-100%
17
Results – TCE Removal in 1D Columns
TCE mass removal 86%-100% over 170 days or > 470 PVs
18
Oxidant Release Kinetics and Modeling
Measured permanganate concentrations match model!
19
CASE STUDY
Cozad Former Solid Waste Disposal Site
University of Nebraska
Dr. Steve Comfort
20
• Facility closed after TCE
contamination found in
underlying aquifer
• Majority of TCE in a low
permeable silty-clay unit near
surface of water table
• TCE (100-600 ppb)
• Darcy velocity = 0.045 in/day
• UNL with NDEQ wanted to
implement low-cost passive
system for TCE treatment in
low permeability unit
Credit: Steve Comfort, Univ. Nebraska
21
SRPC Reactive Barrier Installation
• 105 two-inch DPT SRPCs
• 50 three-inch
injection well SRPCs
Credit: Steve Comfort, Univ. Nebraska
22
Results
Contaminant Concentration in Reactive Barrier
Well MW-8, 11 ft (bgs)
500
Before SRPC Installation
85 Days After SRPC Installation
400
(g/L)
• Barrier installed
June 2010
• After 85 days
64%-82% TCE
reduction
(Christenson
et al., 2012)
300
200
100
0
E
TC
,2
-1
s
i
c
E
C
D
1,1
E
C
D
1,1
A
C
D
Credit: Steve Comfort, Univ. Nebraska
VC
23
CASE STUDY
Industrial Site
Hamilton, Canada
Grant Walsom
XCG
24
History of the Site and the Issue
• Off-site groundwater impacts…
– Higher concentrations of TCE and cis-1,2-DCE
– Near saturation levels
• Remediation stages…
excavation of soil
impacts
• Back-diffusion of
impacted groundwater following
excavation and
hydraulic
re-equilibration
Credit: Grant Walsom and XCG
25
Barrier Design
Credit: Grant Walsom and XCG
26
Barrier Design
Plan View and Cross-Section
10-3 m/s
10-5 m/s
10-7 m/s
10-9 m/s
Credit: Grant Walsom and XCG
27
Field Installation
•
•
•
•
First Site Application in Canada
December 2012 – use budget before end of year
Installed 476 cylinders in 119 boreholes over 8 days
Straight-forward installation – health and safety
Credit: Grant Walsom and XCG
28
Field Installation
• Direct-Push
• Cylinder installed through drill rods
• Easy installation
Credit: Grant Walsom and XCG
29
Cost Review
• Cost Analyses – Total of $163,500:
–
–
–
–
Cylinders (per cylinder $250)
Direct Push Installation & Locates
Engineering / Consulting / Oversight
Monitoring and Analytical
= $120,000
= $23,500
= $12,500
= $7,500
• Other barriers cost minimum of $500,000 (in 2002)
– ZVI, funnel and gate, barrier with pump / treat
Credit: Grant Walsom and XCG
30
Monitoring Effectiveness
• Location MW20B – observed an almost immediate
increase in electrical conductivity (distance ~ 1.5m)
Dec 2012
Credit: Grant Walsom and XCG
31
MW7R
MW8R
MW14R
-133
-32
-154
barrier treatment zone
MW12R
MW13
MW20A
MW20B
MW21
MW23
MW19
MW24AR
MW24BR
MW24CR
261
-51
555
345
285
-44
31
-82
-11
-49
NSC3A
NSC3B
NSC4A
NSC4B
NSC5A
ROW1B
-104
-102
164
187
105
-117
Plume Core
ORP
upgradient
Location
downgradient
Monitoring Effectiveness
Credit: Grant Walsom and XCG
32
Monitoring Effectiveness
MW24B installed at
5.5 meters below ground
surface, located within
1.0 meter of the barrier
06-Dec- 15-Apr- 12-Aug12
13
13
c-DCE
710
790
720
PCE
0
0
0
TCE
4600
950
700
V/C
170
5.6
19
MW24B
Credit: Grant Walsom and XCG
33
ESTCP Demonstration: Naval Air Station North Island
ESTCP – Environmental Security
Technology Certification Program
34
Engineering Design Tool
Slow Release Oxidant - release, reaction, and transport
Project:
Date:
Prepared by:
Basic project information
Oxidant Release Parameters
Oxidant:
Candle diameter (cm):
Oxidant solubility (mg/L):
Effective diffusion coefficient (cm 2s-1):
Amount of available oxidant:
Treatment depth:
Treatment width:
# candle delivery points (per row):
# candle rows:
Dropdown menus
(will autofill)
(will autofill)
(will autofill)
Auto-fill parameters
Factors affecting oxidant
release rate and resulting
concentration
Site Characteristics*
Primary contaminant:
Concentration (mg/L):
Secondary contaminant:
Concentration (mg/L):
Longidudinal dispersivity:
Transverse dispersivity:
Vertical dispersivity:
Natural oxidant demand (NOD) (mg/kg):
NOD rate (2nd order; M-1s-1):
Hydraulic conductivity (cm/s):
Hydraulic gradient (dh/dl):
Porosity:
Dropdown menus
Contaminant characteristics
Dispersion parameters
Oxidant demand – rate and
extent Flow properties
*gui da nce provi ded i n 's i te cha ra cteri s ti cs gui da nce' ta b
Simulation
Simulation time:
Simulation or compliance
distance downgradient:
Simulation time and
distance of interest
35
Engineering Design Tool
Oxidant concentrations
at a given point over time
Oxidant Concentration ------------>
Oxidant concentrations
vs. distance at a given time
Time ------------->
Contaminant concentrations
vs. distance at a given time
Oxidant release from candles
1.2
1
C/Co
0.8
0.6
0.4
0.2
0
Distance ---->
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Conclusions
• Dioxane and other
• Various configurations include
contaminants often create
permeable reactive barriers,
large dilute plumes
funnel and gate, and grid
• Unactivated persulfate
• An ESTCP field demonstration
and permanganate have
will yield practical cost and
potential for treatment
performance data
• Slow-release chemical oxidant
candles can be used for
plume treatment
37
Thank You!
Pat Evans
[email protected]
(206) 351-0228
38