Synergistic approach of GCW-ISTR for enhanced remediation of semi-volatile organic contaminants in groundwater: Modeling and experimental validation.

The poor remediation performance of groundwater circulation well (GCW) on semi-volatile organic contaminants (such as aniline) has severely limited its practical application. To address the challenges posed by the low volatility and solubility of these contaminants, an innovative integration of GCW with in-situ thermal remediation (ISTR) was proposed to create a thermal enhanced circulation well (GCW-ISTR) in this study. Laboratory experiments and model simulations were performed to evaluate the heat transfer and enhanced remediation effect by GCW-ISTR. Results demonstrate that the heat transfer process is controlled by the water circulation around GCW-ISTR and is influenced by factors such as aeration flow rate, groundwater velocity and aquifer permeability. Heating area is directly proportional to the seepage velocity of groundwater which can be analyzed by multiplying the water head difference between the upper and lower screens with the aquifer permeability. Therefore, the heat transfer model, based on Darcy's seepage theory and the energy conservation equation, effectively simulates the heat transfer with an error margin of less than 10%. Compared to individual GCW, GCW-ISTR exhibits a 25.8% improvement in aniline remediation efficiency, resulting in a decrease in the average concentration from 97.95 mg/L to 0.168 mg/L within 48 h, effectively mitigating the occurrence of tailing phenomena. This study provides a feasible method of enhancing the remediation of GCW on semi-volatile contaminants and is anticipated to broaden the applicability of GCW in site application.