In Situ Chemical Oxidation of Dioxane Using Slow-Release Chemical Oxidant Candles

Transcription

1 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

2 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

3 Technology Description Solid product formed as candle or chipped for barrier applications or 2.5-inch diameter 18 inches long 3

4 Permanganate Candle Release from Wax 4

5 Permanganate Candle Release from Wax As permanganate solids dissolve void spaces are created 5

6 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

7 Permanganate Candle Release from Wax As permanganate releases/reacts porosity develops inward to the core of the candle Diffuses across a greater distance 7

8 Permanganate Candle Release from Wax This is why we see and initial spike of permanganate in early time 8

9 Permanganate Candle Release from Wax And a significantly slower and lower release of permanganate at later times 9

10 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

11 Passive Treatment with In Situ Reactive Zones / Barriers Water Table Receptor Well GW Flow Contaminated Groundwater Clay lens Treated Groundwater Bedrock 11

12 Technology / Methodology Description 12

13 Dioxane Removal Dioxane Destruction with Permanganate and Unactivated Persulfate Not Tested Not Tested 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Site A Site B Site C Both permanganate and unactivated persulfate oxidize dioxane at various sites 13

14 Comparison of TCE and Dioxane Oxidation 14

15 [1,4-Dioxane] (μg/l) Laboratory Oxidant Kinetics Results Permanganate Test Conditions Incubation Time (days) Control-D PM-0.05 PM PM PM-0.25 PM-0.50 PM-0.75 PM

16 First Order Rate Constant, k (s-1) First Order Rate Constant. k (s-1) Laboratory Oxidant Kinetics Results 4.0E-05 Pseudo-2nd Order Rate Constant for Persulfate 4.0E-06 Pseudo-2nd Order Rate Constant for Permanganate 3.5E E E-05 k = M -1 S E-06 k = M -1 S E E E E E E E-06 y = x - 4E-07 R² = E E E-07 y = 4E-05x + 7E-08 R² = E Persulfate (M) 0.0E Permanganate (M) 1st order rate constant - k (s-1) 1st order rate constant - k (s-1) 16

17 Column Results for Dioxane Removal Persulfate SR cylinder 97%-100% 1,500 ppm unactivated persulfate 93%-100% 17

18 Results TCE Removal in 1D Columns TCE mass removal 86%-100% over 170 days or > 470 PVs 18

19 Oxidant Release Kinetics and Modeling Measured permanganate concentrations match model! 19

20 CASE STUDY Cozad Former Solid Waste Disposal Site University of Nebraska Dr. Steve Comfort 20

21 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 ( ppb) Darcy velocity = 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

22 SRPC Reactive Barrier Installation 105 two-inch DPT SRPCs 50 three-inch injection well SRPCs Credit: Steve Comfort, Univ. Nebraska 22

23 Results Barrier installed June 2010 After 85 days 64%-82% TCE reduction (Christenson et al., 2012) ( g/l) Contaminant Concentration in Reactive Barrier Well MW-8, 11 ft (bgs) Before SRPC Installation 85 Days After SRPC Installation TCE cis- 1,2 DCE 1,1 DCE 1,1 DCA VC Credit: Steve Comfort, Univ. Nebraska 23

24 CASE STUDY Industrial Site Hamilton, Canada Grant Walsom XCG 24

25 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

26 Barrier Design Credit: Grant Walsom and XCG 26

27 Plan View and Cross-Section Barrier Design 10-3 m/s 10-5 m/s 10-7 m/s 10-9 m/s Credit: Grant Walsom and XCG 27

28 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

29 Field Installation Direct-Push Cylinder installed through drill rods Easy installation Credit: Grant Walsom and XCG 29

30 Cost Review Cost Analyses Total of $163,500: Cylinders (per cylinder $250) = $120,000 Direct Push Installation & Locates = $23,500 Engineering / Consulting / Oversight = $12,500 Monitoring and Analytical = $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

31 Monitoring Effectiveness Location MW20B observed an almost immediate increase in electrical conductivity (distance ~ 1.5m) Dec 2012 Credit: Grant Walsom and XCG 31

32 downgradient Plume Core barrier treatment zone upgradient Monitoring Effectiveness Location ORP MW7R -133 MW8R -32 MW14R -154 MW12R 261 MW13-51 MW20A 555 MW20B 345 MW MW23-44 MW19 31 MW24AR -82 MW24BR -11 MW24CR -49 NSC3A -104 NSC3B -102 NSC4A 164 NSC4B 187 NSC5A 105 ROW1B -117 Credit: Grant Walsom and XCG 32

33 Monitoring Effectiveness MW24B installed at 5.5 meters below ground surface, located within 1.0 meter of the barrier MW24B 06-Dec- 15-Apr- 12-Aug c-dce PCE TCE V/C Credit: Grant Walsom and XCG 33

34 ESTCP Demonstration: Naval Air Station North Island ESTCP Environmental Security Technology Certification Program 34

35 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 2 s -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 -1 s -1 ): Hydraulic conductivity (cm/s): Hydraulic gradient (dh/dl): Porosity: *guidance provided in 'site characteristics guidance' tab Simulation Simulation time: Simulation or compliance distance downgradient: Dropdown menus Contaminant characteristics Dispersion parameters Oxidant demand rate and extent Flow properties Simulation time and distance of interest 35

36 Oxidant Concentration > Oxidant concentrations vs. distance at a given time Engineering Design Tool Oxidant concentrations at a given point over time Time > Oxidant release from candles Contaminant concentrations vs. distance at a given time C/C o Distance ----> 36

37 Conclusions Dioxane and other contaminants often create large dilute plumes Unactivated persulfate and permanganate have potential for treatment Slow-release chemical oxidant candles can be used for plume treatment Various configurations include permeable reactive barriers, funnel and gate, and grid An ESTCP field demonstration will yield practical cost and performance data 37

38 Thank You! Pat Evans (206)