Feasibility Of Coupling Permeable Bio-Barriers And Electrokinetics For The Treatment Of Diesel Hydrocarbons Polluted Soils

• Electrokinetics and a biobarrier were combined to remediate of a diesel polluted soil.
• pH gradients did not affect the biobarrier activity located in soil central position.
• Microorganisms were partially detached from the biobarrier and moved across the soil.
• An anionic surfactant helped the contact between pollutant and microorganisms.
• A 39% of the diesel biodegradable fraction was homogeneously removed across the soil.

In this study, the remediation of a diesel hydrocarbon-polluted clay soil using an electrochemical-biological combined technology is assessed. The polluted soil was subjected to an electrokinetic (EK) treatment with a biological permeable reactive barrier. A lab-scale electrochemical cell for soil treatment was used. The biological barrier placed in the soil was a biofilm reactor previously adapted for diesel degradation. A batch experiment of 336 h was conducted in a synthetic clay soil spiked with 10 g·kg−1 of diesel and a constant voltage gradient of 1.0 V cm−1. Sodium dodecyl sulphate was used as an anionic surfactant in the cathodic well to allow for hydrocarbon emulsification during the treatment. At the end of the experiment, extreme pH values were observed near the electrodes. However, the pH remained constant at approximately 7.7 in the central biobarrier zone, which allowed for biological processes. Biological growth was observed in the biobarrier, and a part of the biofilm was detached and transported through the soil in both directions. Furthermore, the surfactant was transported across the soil due to electromigration and electroosmosis, which resulted in diesel emulsification. The combination of biological and EK phenomena finally resulted in a homogenous hydrocarbon removal of approximately 27% in the polluted soil, which indicated a 39% removal of the diesel biodegradable fraction. Due to the electroosmotic flow and the biological degradation, some of the water, surfactant and inorganic nutrients were removed from the soil and should be continuously replaced if a long-time experiment is conducted.

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