Biosurfactant Enhanced Bioelectrokinetic Remediation of Petrochemical Contaminated Soil

Abstract

Soil pollution in recent years has emerged as an issue of great environmental concern. Contamination of soil by improper disposal or spillage of petrochemicals and products containing petroleum hydrocarbons is one of such pollution cases highly reported. To remediate petroleum contaminated soil, A DC powered electrokinetic reactor was used with biosurfactants as an enhancement for the remediation process. To begin with, studies were made under voltage variations of 10 V and 30 V with an electrode spacing of 185 mm. Biosurfactant with its producing microbes and biosurfactant free cells were introduced in the soil chamber after which the reactor was left to run for 10 days under the electric field. The technology was able to achieve the highest oil recovery of 75.15 % from the soil in 96 hours at 30 V. With other factors remaining constant, the reactor was also operated under a constant voltage of 30 V with configurations of fixed electrodes spacings of 335 mm, 260 mm,185 mm and continuous approaching electrodes at 335 mm, 260 mm and 185 mm. The current in the electrolyte was highest with the least electrode distance of 185 mm. The increase in current led to a direct proportional increase in the electroosmotic flow towards the cathode leading to increased coalescence of the oil from the soil as compared to the other electrode distances. The analysis of the results showed reduction in the total carbon content in the soil with viable oil recovery rates for all the electrode distances with 185 mm being the most effective in both oil recovery and degradation. The reactor was further operated with amended biosurfactant concentrations of 28 g/L, 56 g/L and 84 g/L to enhance the recovery of oil from the soil and aid in biodegradation of the remaining oil by hydrocarbon degrading microbes. The highest oil recovery of 83.15 % was obtained with the biosurfactant concentration of 56 g/L showing that the hyper increase in concentration of the biosurfactants is not necessary to have an efficient process. In all experiments the microorganisms were able to survive under the electro-halo-thermal environment in the reactor and degraded the remaining hydrocarbons to acceptable amounts in the environment. The bacteria were however affected by the constantly changing pH in all experiments. The presence of biosurfactants was so significant in aiding oil recovery and increasing bioavailability of hydrocarbons to the microbes. Production of biosurfactants in the reactor followed up by kinetic suggestions of the processes in the bioelectrokinetic reactor should be studied in future.