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Institut für Wasser- und Umweltsystemmodellierung - IWS



"Steam-Air injection to remove CHC from fractured bedrock"

In situ thermally enhanced remediation methods (steam-air injection and thermal wells), developed and verified in several field applications by the Research Facility for Subsurface Remediation, VEGAS, are proposed for source zone remediation of NAPL in the saturated and the unsaturated zone. Contaminants can be effectively removed within several months if hydrogeological conditions are suitable.
A novel application of steam-air injection was the removal of chlorinated hydrocarbons from a fractured sandstone aquifer. A pilot application was conducted by VEGAS on the site of Biswurm (Villingen-Schwenningen, Germany). Its goal was to determine the effectiveness of the technology in order to design the full scale thermally enhanced remediation scheme.
The pilot remediation lasted from March 2009 until September 2009. After two weeks of "cold" soil vapour extraction an air-sparging phase was operated for four weeks followed by a steam-air injection of 19 weeks. Different zones of the aquifer were treated stepwise, starting with the base of the aquifer. The concurrent treatment of both the groundwater fluctuation zone and the unsaturated zone resulted in a mass removal rate of up to 8 kg CHC per day. The remediation was completed by a cooling phase of approximately five weeks.