The combined application of a high voltage, low electrode spacing, and biosurfactants enhances the bio-electrokinetic remediation of petroleum contaminated soil

Abstract

This study examined the effect of voltage variation, the distance between electrodes and the application of a biosurfactant on the bio-electrokinetic remediation of soil contaminated with petrochemicals. The study was meant to correlate the relationship between voltage, electrode distance, and application of biosurfactants on the efficacy of decontamination. The remediation process involved the application of voltages of 30 V and 10 V with changing electrode spacing of 335 mm and 185 mm. All the electrokinetic setups were spiked with 28 g/L of a biosurfactant. The experiments containing the biosurfactant and run at the highest voltage of 30 V with an electrode spacing of 185 mm had the highest oil recovery efficiency as compared to the other configurations. Decontamination was improved under a high voltage due to the enhancement of electroosmosis and electrophoresis. 30 V increased the energy budget as compared to 10 V in 240 h, but 30 V was more efficient in terms of attaining satisfactory decontamination in the same remediation time. The application of a biosurfactant and lower electrode spacings enhanced desorption and demulsification which led to a reduction in the energy expenditure by accelerating the decontamination process. The variation in voltage did not have detrimental effects on the bacteria but pH affected microbial growth especially in areas closest to the cathode and the anode compartments. The 185 mm electrode spacing presented better bacterial growth conditions as compared to 335 mm electrode spacing. The results were able to show that a high voltage, low electrode spacing and application of a biosurfactant as a combined configuration were able to increase the efficiency and reduce the energy expenditure if satisfactory decontamination was to be achieved. The results also show that electrokinetic remediation can be combined with biosurfactant enhanced bioremediation to remediate soil-water systems. Further studies should be done to study the viability of field scale applications to relate field scale environmental conditions to these lab scale propositions.