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 Presentation Outline

Introduction to CS2

The state of the art for remediation of CS2 Project Background The approach: R&D Treatability Trials –Laboratory proof of concept Field Pilot Trials Full scale remediation

Carbon Disulfide -Properties

• Carbon disulphide (CS2) 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 oC • Specific Gravity 1.26 • Water solubility 2.3 g/L

1946 Site Layout 1995 Site Layout CS2 Remediation „State of the Art‟ 2008

Removal of CS2 DNAPL-contaminated soils after in situ mixing with bentonite slurry to stabilise the CS2 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 CS2 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

In Situ Destruction of Carbon Disulfide

CS2 is a volatile flammable liquid which has a wider explosive range in air than hydrogen.

Therefore, CS2 compound poses multiple technical difficulties for in situ remediation

However, ARCADIS developed a completely novel remedial approach for destruction of CS2 using in situ chemical oxidation with activated persulfate

Novel high sensitivity MIP with flame photometric detector (FPD) for CS2 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 CS2 ATEX Cat. 6 gas Novel soil mixing technology under vacuum for CS2 Innovative use of CO2 and dry ice during soil mixing to create an inert atmosphere

Laboratory Studies

• No academic research, world first persulfate oxidation of

CS2 in laboratory

• Determined whether S2O8 can degrade CS2 • Identify Appropriate Activator

• CS2 destruction with no measureable off-gas or temperature increase

Persulfate Advantages for ISCO for CS2

• 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 Detailed Laboratory Experiments

Manometer

Manometer Air Equilibration Valve Thermocouple

Off-gas connection to manometer

Dreschel Bottle Sealed Reaction Vessel

Magnetic Stirrer CS2 destruction using activated persulfate

1.4

1.2

1

0.8 Control

0 S2O8

C/C S2O8 + NaOH 0.6 S2O8 + Ca(OH)2

0.4

0.2

0 0 1 2 5 6 9 13 19 27 Time (Days) Activated Persulfate vs Free Phase CS2 Temperature Monitoring –Free Phase CS2 Oxidation Pilot Trial Objectives

• Demonstrate effectiveness of S2O8 for treating CS2 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 Pilot Site Plan Cross-Section: East-West

East West

BH06410 BH06421 BH06419 BH06521 BH06520 BH06505 BH06524

0.2 3.6 128 40.7 0.02 5.9 mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg

Carbon disufide Remedial Pilot Equipment First series of Surgical Injections of Activated Persulfate

Injection under house Persulfate Distribution Pilot Trial Results

Mean concentrations of CS2 in soil had reduced from 11mg/kg prior to treatment to 0.35mg/kg following remediation works. Post remediation monitoring showed the mean CS2 concentration in perched groundwater had reduced by from 4,300μg/l to 63μg/l Full Scale Project

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 CS2 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.

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 CS2 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. Project Team

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

Any Questions?

Dr. Ian Ross Technical Manager EMEA FMC Environmental Solutions Phone: +44 (0)7855745531 [email protected] www.environmental.fmc.com

59-01-EIT-DL www.environmental.fmc.com