An in-situ cosolvent/electrokinetics/pumping (CEP) technique to remediate the groundwater site contaminated by tetrachloroethylene

A novel integrated remediation system was constructed by combining the cosolvent, electrokinetics (EK), and pumping techniques (i.e., the CEP remediation) at the chlorinated-contaminated groundwater site. The groundwater site was a certain factory polluted for more than 10 years and the tetrachloroethylene (PCE) concentration of the groundwater was around 1.0 mg/L. The removal mechanisms of the CEP remediation comprise dissolution enhancement of PCE in the groundwater (cosolvent effect), the electro-osmotic flow (EO flow) to remove the PCE adsorbed on the soils (EK process) and the transport of PCE-contaminated groundwater to the wastewater treatment plant (pumping process). Under the sole cosolvent treatment (i.e., ethanol injected in the remediation well), the pH values of groundwater were maintained at 5.56-5.62 and removal efficiency of PCE was 28 % after 70-day treatment. In contrast, the pH and EC of groundwater could be stabilized at 6.3 and 1,200 mu S/cm, respectively; the PCE removal efficiency reached around 68 % (decreased from 0.954 mg/L to 0.303 mg/L) after 70-day CEP treatment and no rebound phenomenon occurred. In addition to the aforementioned physicochemical mechanisms, the addition of ethanol can promote the formation of microorganisms and its main dominant bacteria will degrade chlorine-containing pollutants. During the CEP operation, the groundwater qualities such as pH, EC, total organic carbon (TOC), and heavy-metal concentrations could meet the standard of discharge water. Accordingly, the CEP technique demonstrated its practical feasibility to clean up chlorinated-contaminated groundwater.