Enhanced performances of the coupled thermal conductive heating-groundwater circulation well approach

Most studies about the groundwater circulation well (GCW) and relevant approaches coupled with other remediation techniques were conducted under ambient temperature conditions. To address this gap, using a series of laboratory-scale sandbox experiments, complemented by numerical simulations, the present study aims to evaluate the remediation performances of this coupled thermal conductive heating (TCH) - GCW system for both the conservative tracer (brilliant blue) and the semi-volatile organic pollutant (nitrobenzene). For the conservative tracer, the remediation processes of the GCW were significantly expedited by heating, but the final remediated area and the remediation efficiency demonstrated similar results for different heating conditions. For example, under the heating temperature of 110 °C, the required remediation time consumption results for observation points had reduced by 2.5%-50% compared with the no-heating condition, but the final remediated area results under heating conditions only increased by less than 6%. For nitrobenzene, higher heating temperatures can lead to better remediation performances, especially in tailing zones. Under the heating conditions, the remediated areas of nitrobenzene increased from 53.95% to 99.74%, and the required remediation time consumption results decreased by 4%-95%. Based on scenario analysis using numerical simulations, the relative contributions of four mechanism processes for removing nitrobenzene using the TCH-GCW approach were quantified and ranked as: convection > > hydrodynamic dispersion > volatilization > adsorption, while the removal of the conservative tracer was attributed to convection. The removed masses and relative contributions of nitrobenzene due to dispersion and volatilization increased as the heating temperature increased.