Application of Microbial Culture and Rhamnolipid for Improving the Sedimentation of Oil Sand Tailings

Densification of oil sand tailings deposited in the tailing ponds and recovering water from them are two major challenges in the oil sands surface mining industry. A small increase in the tailings settlement rate (which normally is very slow) can improve the densification of tailings and significantly reduce water consumption and the volume of the tailing ponds. In this work, the objective was to evaluate the role of a mixed culture of two microbial strains isolated from weathered oil and rhamnolipid (JBR 425) together with these strains in the sedimentation of fine tailing particles. It has been found that a mixed culture of two microbial strains isolated from weathered oil increased the sedimentation. Rhamnolipid (0.5%) together with these two microbial strains at 15°C ± 2°C showed significant increases in sedimentation (by a factor of 5.1), the concentration of larger particles (by a factor of 2.63), the particle mean diameter (by a factor of 2.70) and flocculation in the tailings samples compared to the control while the zeta potential is still negative. This means that the mechanism of flocculation is probably due to increasing the hydrophobicity of the particles, interaction of biosurfactant and high molecular weight microbial organic compounds through a bridging mechanism with clay particles. This work shows the potential of using rhamnolipid and microbial culture in order to increase the oil sand sedimentation through flocculation and microbial activity in a more environmentally friendly densification process.