Coupling electrokinetic soil flushing with bioremediation for the removal of chlorinated benzenes and hexachlorocyclohexane.

The improper deposit of the lindane production wastes in the Sardas landfill (Sabiñánigo, Huesca) during the last century led to the pollution of this site, mainly with hexachlorocyclohexane (HCH) isomers and chlorobenzenes. The pollution affected different soil layers, including the silts and groundwater. Previous works have used electrokinetic (EK) remediation techniques to address this problem in fine-grained soil layers. However, EK often needs to be coupled with other remediation techniques. In this work, the impact of establishing a biobarrier during the application of the electroremediation (electro-bioremediation system, EBS) is studied to compare with the case in which no biological treatment is conducted. Experiments were conducted at bench scale using 1.5 dm3-containers filled with polluted silts and groundwater from Sardas, and biobarriers with bacterial cultures enriched from the polluted groundwater of Sardas. Applying 1 V/cm did not prevent the biological activity, and the EBS improved by 54 % and 36 % the remediation of HCHs and chlorinated benzenes, respectively, in the silts under aerobic conditions, in contrast to the case in which only electroremediation was performed. Microbial relative population analysed by sequencing 16S genes from silts pointed out that the direct electric current affected the microorganisms' distribution along the containers due to the oxidative or reductive conditions promoted by the anode and the cathode, respectively.