A study on electrokinetic dewatering of oil sands tailings

Oil sands tailings (mature fine tailing (MFT)) are the final product of oil sands processing and are in the form of slurry with a very low solid content. After sedimentation, due to a low hydraulic conductivity of the tailings, dewatering and consolidating the tailings is difficult. Since electrokinetics (EK) has been successfully applied on dewatering and consolidation of low permeability soils, this study is carried out to assess the effectiveness and efficiency of EK dewatering of MFT, a man-made geomaterial. Two series of tests were conducted in this study. In the first series, four EK cell tests were performed on oil sands tailings to measure the electroosmotic permeability, ke, which is the key parameter for assessment of the EK treatment. In the second series, the model tests were designed and carried out to investigate the feasibility of EK dewatering on oil sands tailings. The performance of the EK dewatering was compared under two conditions — under a surcharge load of 5 kPa for consolidation, followed by EK dewatering and under simultaneous treatment of a surcharge load of 5 kPa and EK treatment. The final water content, undrained shear strength and plasticity of MFT were measured after all tests. It was observed that the EK dewatering model tests resulted in significant overall increases in the undrained shear strength and reductions in the water content of tailings samples, along with significant changes of the tailings plasticity.