Approaching electrodes configurations in bio-electrokinetic deoiling of petrochemical contaminated soil

Abstract

The expeditious growth of the petroleum industry and its products in the last three decades has led to increased pollution of soil which is of great concern considering the effects it poses to the environment. Oil waste usually considered as hazardous due to its composition presents the same problems as other petroleum-based products to the environment. An electrokinetic reactor with an inoculum of biosurfactant producing bacteria was studied at a bench scale with different electrode spacing configurations. A DC powered electrokinetic reactor consisting of electrode/electrolyte compartments, and a matrix chamber was operated under a constant voltage of 30 V with configurations of fixed electrodes spacing’s of 335 mm, 260 mm,185 mm and continuous approaching electrodes at 335 mm, 260 mm and 185 mm. The biosurfactant producing microbes and cell-free biosurfactant were introduced in the matrix chamber after which the reactor was left to run for 10 days under the electric field. The electroosmotic flow, electrical current, pH and biodegradation of the hydrocarbons in the soil were observed and assessed. The current in the reactor was highest with the least electrode distance of 185 mm. The increase in current led to a directly proportional increase in the electroosmotic flow towards the cathode leading to the increased coalescence of the oil from the soil as compared to the other electrode distances. The analysis of the results showed a 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. The viable cell counts in the reactor showed significant growth of the bacteria in the first 6 days under the applied voltage of 30 V enabling the biodegradation of the petrochemical pollutants by the strain for all the four different electrode configurations.