IN SITU CHEMICAL OXIDATION OF CARBON DISULFIDE IMPACTED SOIL

摘要

Between 1996 and 1998, Witco Corporation (now Crompton Corporation), EnvironmentalResources Management (“ERM”), Fahrenthold & Associates and Terra Constructorssuccessfully developed and implemented an innovative, and now patented, in situ chemicaloxidation treatment technique for carbon disulfide (CS_2) impacted soils at the Halby ChemicalSuperfund Site located in Delaware (“Site”). The project involved technology research anddevelopment, laboratory and field treatability testing, and full-scale implementation.The literature suggested that chemical oxidation of CS_2 might be viable, although industryexperience was limited, especially with high concentrations and large soil volumes, and thereaction could be potentially explosive. Nonetheless, in situ chemical oxidation was pursued as arelatively safe, aggressive and cost-effective approach compared to other alternatives.Laboratory treatability testing was performed to evaluate the efficacy of peroxide-basedoxidants, including hydrogen peroxide, sodium percarbonate, and sodium perborate. Thetreatability testing demonstrated that all three peroxidants could provide 99+% CS_2 removal;however, sodium percarbonate was selected for field pilot testing based on ease of application,controlled reaction kinetics, reaction byproducts, cost, and treated soil consistency.Two field pilots (Phases I and II) were conducted to verify the results of laboratory testing. PhaseI was conducted using a low-pressure direct injection unit, selected as a less intrusive deliverysystem. The results of the Phase I pilot showed limited CS_2 reduction, which was believed to becaused by the system’s inability to deliver sufficient oxidant to the entire soil mass. Phase II wasconducted using a Single Auger Mixing (SAM) unit, a six-foot diameter crane-mounted soilauger, which was selected as a more aggressive application method. Phase II demonstratedconsistent 99+% removal of CS_2 under actual field conditions. Based on these results, full-scaletreatment using the SAM unit was initiated.Full-scale treatment was completed in approximately 20 weeks. Over 10,000 cubic yards of soil,with up to 16% CS_2, were successfully treated to an average CS_2 concentration of approximately200 mg/kg (1/5 the cleanup goal). The treatment operations were completed safely, includingover 10,000 man-hours without a health or safety incident. The cost of this project, includingdevelopment, field treatability testing and full-scale treatment, was an order of magnitude lessthan excavation/off-site disposal, and approximately 1/2 to 1/3 the cost of other technologiesconsidered.