Laboratory-scale analysis of aquifer remediation by in-well vapor stripping 1. Laboratory results

This study is a laboratory test of the aquifer remediation concept proposed by Gvirtzman and Gorelick (1992, Transp. Porous Media, 8: 71-92), which involves the removal of volatile organic compounds (VOCs) dissolved in groundwater. The principle is to inject air into a well, creating air-lift pumping, which is used as a means of in-well vapor stripping. The partially treated water is separated from the VOC vapor and infiltrates back to the water table. A laboratory-scale aquifer model containing a remediation-well prototype was used to trace VOC removal over time. The removal rates of trichloroethylene (TCE), toluene and chloroform were monitored using eight triple-level observation wells. The continuous decrease of VOC concentrations in space and time was interpreted based on three processes: (1) the diffusional mass transfer between the contaminated water and the air bubbles during their rise within the well; (2) the desorption of VOCs from the solid matrix to the water phase; (3) the flow field in the saturated zone driven by the continuous water circulation between the pumping well and the recharging area. In a companion paper (Pinto et al., 1997), three-dimensional flow and transport modeling with inter-phase mass transfer is carried out to simulate these processes.