Electronic Thesis and Dissertation Repository


Master of Engineering Science


Civil and Environmental Engineering


Julie Q Shang


The mature fine oil sands tailings (MFT) remain suspended in tailings disposal pond for decades because of the low sedimentation/consolidation rate. This study investigates the application of coagulation and electrokinetics to thicken, i.e., to increase the solid content of the MFT suspension. At first, the optimal ferric chloride concentration is identified as 350 mg/l in jar tests, under which the best thickening result is only 6.48% from an initial of 5% after 4 hours in cylinder coagulation tests. The electrokinetic thickening under an applied voltage gradient of 219 V/m reaches the final solid content of 18.75% after 7 hours. The combined coagulation (350 mg/l ferric chloride) and electrokinetic thickening under a continuous applied voltage gradient (219 V/m) is the most effective approach, which reaches the final solid content of 23.74%. The sedimentation theories in the free settling and hindered settling stages are validated using the experimental results, which is one of the major contributions of this research. The turbidity of the supernatant ranges between 4.8 NTU and 31 NTU in all treatments. Two regression models for the electrokinetic and the combined application of coagulation and electrokinetic tests are developed to relate the final solid content and the applied voltage gradient. The models and the independent variables are statically significant at 95% confidence level based on F-test and t-test results, respectively.