In Situ Chemical Oxidation of Carbon Disulfide Using Activated Persulfate

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1 In Situ Chemical Oxidation of Carbon Disulfide Using Activated Persulfate Ian Ross Ph.D., FMC Environmental Solutions Mark O Neill & Jeff Burdick, ARCADIS Saipem Innovation Award 2012

2 Presentation Outline Introduction to CS 2 The state of the art for remediation of CS 2 Project Background The approach: R&D Treatability Trials Laboratory proof of concept Field Pilot Trials Full scale remediation

3 Carbon Disulfide -Properties Carbon disulphide (CS 2 ) has been widely used as a solvent It is generated in small quantities by natural processes, (stagnant water bodies). It is highly volatile and extremely flammable, having a wider explosive range in air than hydrogen and a lower ignition energy. (LEL 1%) Odour of rotting cabbages/ radishes. Boiling point 38 o C Specific Gravity 1.26 Water solubility 2.3 g/l

4 1946 Site Layout

5 1995 Site Layout

6 CS 2 Remediation State of the Art 2008 Removal of CS 2 DNAPL-contaminated soils after in situ mixing with bentonite slurry to stabilise the CS 2 saturated material. Stabilised material was excavated and removed to approved off-site landfill Permeable Reactive Barrier (PRB) funnel and gate system comprising a bentonite wall directing groundwater flow to two reactive zero-valent iron gates in which dissolved-phase CS 2 reacts to yield innocuous end-products. In situ techniques Hot Water and Co-Solvent Flushing tested at lab scale Bentonite Stabilised Dig & Dump Increased Volume for Hazardous Waste Disposal Demolition of Houses Utilities Disruption Lorries in Residential Neighbourhood Sustainability

7 In Situ Destruction of Carbon Disulfide CS 2 is a volatile flammable liquid which has a wider explosive range in air than hydrogen. Therefore, CS 2 compound poses multiple technical difficulties for in situ remediation However, ARCADIS developed a completely novel remedial approach for destruction of CS 2 using in situ chemical oxidation with activated persulfate Novel high sensitivity MIP with flame photometric detector (FPD) for CS 2 Novel detection method developed to measure persulfate in groundwater on site Bespoke telemetry system for temperature and vapour monitoring Novel vapour control system design for CS 2 ATEX Cat. 6 gas Novel soil mixing technology under vacuum for CS 2 Innovative use of CO 2 and dry ice during soil mixing to create an inert atmosphere

8 Laboratory Studies No academic research, world first persulfate oxidation of CS 2 in laboratory Determined whether S 2 O 8 can degrade CS 2 Identify Appropriate Activator CS 2 destruction with no measureable off-gas or temperature increase

9 Persulfate Advantages for ISCO for CS 2 Persulfate is a strong oxidant Thermodynamically very powerful Can oxidise all organic compounds when dissolved in water Kinetics of oxidation are relatively slow / can be controlled Large zone of influence for oxidant delivery Heat is not generally formed Kinetics are controlled by chosen activator and activator concentrations Persulfate breaks down to form sulfate sulfate is not gaseous (no pressure generation) sulfate is non toxic; has a DWS at 250 mg/l (based on taste threshold) and promotes biodegradation Persulfate can be activated to form radicals Persulfate becomes a very aggressive radical based oxidant following activation Activation can be achieved using chelated iron, ph adjustment, heat or hydrogen peroxide Persulfate is a granular solid with high water solubility (>40% w/v) Persulfate is relatively safe to handle on the surface High oxidant concentrations can be added to source areas

10 Detailed Laboratory Experiments Manometer Manometer Air Equilibration Valve Thermocouple Off-gas connection to manometer Sealed Reaction Vessel Dreschel Bottle Magnetic Stirrer

11 CS 2 destruction using activated persulfate C/C Control S2O8 S2O8 + NaOH S2O8 + Ca(OH) Time (Days)

12 Activated Persulfate vs Free Phase CS2

13 Temperature Monitoring Free Phase CS 2 Oxidation

14 Pilot Trial Objectives Demonstrate effectiveness of S 2 O 8 for treating CS 2 in situ Verify at field scale the activation chemistry and dosing requirements Evaluate mechanisms for delivering persulfate into the subsurface To validate that the remedial technology can be applied successfully under domestic properties To prove the validation process and communicate to all stakeholders

15 Pilot Site Plan

16 Cross-Section: East-West East West BH06410 BH06421 BH06419 BH06521 BH06520 BH06505 BH mg/kg 3.6 mg/kg 128 mg/kg 40.7 mg/kg 0.02 mg/kg 5.9 mg/kg Carbon disufide

17 Remedial Pilot Equipment

18 First series of Surgical Injections of Activated Persulfate

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22 Injection under house

23 Persulfate Distribution

24 Pilot Trial Results Mean concentrations of CS 2 in soil had reduced from 11mg/kg prior to treatment to 0.35mg/kg following remediation works. Post remediation monitoring showed the mean CS 2 concentration in perched groundwater had reduced by from 4,300µg/l to 63µg/l

25 Full Scale Project

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39 Full Scale Results Concentrations in groundwater have decreased from a maximum of 13,000µg/l, prior to remediation, to a maximum of 12µg/l following remediation. The results of the validation investigation indicate that the true mean concentrations (at the 95% confidence limit) of CS 2 in soil from the site have decreased from 4.9mg/kg and 2.3mg/kg, for the two remediation areas of the site, to 0.64mg/kg and 0.082mg/kg following remediation. Concentrations of CS2 in soil reduced from max. >400 mg/kg to <10 mg/kg with one application of activated persulfate.

40 In Situ Destruction of Carbon Disulfide with Activated Persulfate Summary Fundamental research Laboratory trials Field scale pilot trial Full scale implementation Novel MIP technology using FPD detector proven for CS 2 Activated persulfate provided a proven cost-effective in situ remedial solution Implementation of more cost effective, sustainable in situ, remediation approach: reduction of impacted material disposed to landfill.

41 Project Team Ian Ross Ph.D. Cecilia MacLeod Ph.D. Jeff Burdick Bryony Harvey Neil Thurston Mark O Neill Adam Bethel Dave Washbrook Simon Hay Jon Weston Jake Hurst Neil Beswick Saipem Innovation Award 2012

42 Any Questions? Dr. Ian Ross Technical Manager EMEA FMC Environmental Solutions Phone: +44 (0) EIT-DL