Physical Properties of Oil-contaminated Sand Affected by Microbial Activity under Aerobic Conditions

We present laboratory investigations of oil-contaminated sands inoculated with Pseudomonas indica, known as oil degrader, under aerobic conditions. Our results are based on the measurements of electrical parameters (resistivity, induced polarization and self-potential signals) and hydraulic conductivity. We also analyzed the moisture chemical composition and oil content in the sand, and acquired sand electron microscope images. The data revealed a decrease of oil content with time, which we relate to biodegradation. We argue that the biodegradation process leads to a decrease of the soil porosity, and to an increase of the pore water salinity. The evolution of bulk resistivity was found to be in accordance with these textural and chemical changes. We found the hydraulic conductivity to be dependent on the microbial activity: the more is sand affected by bacteria, the less is hydraulic conductivity. We show the electrokinetic coupling coefficient to be dependent on microbial activity. We show that the coefficient decreases with increase of the microbial activity.