Hydraulic circulation technology remediates the contaminated groundwater with petroleum hydrocarbon: Evidence from laboratory and field tests

Removal of contaminants in groundwater in situ conditions is still a challenging problem, with tailing and rebound issues occurring. This study presents a systematic in-situ remediation case by hydraulic circulation in petroleum hydrocarbon-contaminated groundwater in a historically industrial-used site in China. Lab-scale experiments of soil column leaching and in-situ remediation trials were conducted to show the effectiveness of this technology. It has been found that through regulation and optimization of operational measures in five stages, the clean-up goal (1140 μg/L) of the targeted contaminant in groundwater based on the former risk assessment of human health and the intervention value (600 μg/L) in the ‘Dutch Target and Intervention Values (2000)’ were both achieved, and the tailing rebound effect of traditional pump-and-treatment technology was well solved. The combination of groundwater monitoring by ways of pumping pipelines and groundwater monitoring wells could enable workers to timely and effectively grasp the temporal and spatial dynamic variation of pollutants in groundwater in response to the restoration activities, which played an important role in improving the pertinence of pumping-and-injection measures and efficiency of the hydraulic circulation. Discharge standards of wastewater can be reached after being treated with the mass content of added coagulants (Ferrous sulfate) reaching 0.4 g/L and adsorbents (activated carbon) reaching 0.2 g/L. The results demonstrated that it is feasible to conduct in-situ remediation of the contaminated groundwater through hydraulic circulation based on pumping and injection measures and process-monitoring activities, with a competitive operating cost of approximately Rmb 23/m³ and a measured GHG emissions level of 7.12 kg CO2-eq/m³. Overall, the results in this study provide a useful reference case for the realistic remediation of similar sites.