Towards integrating micro- and macro- scale processes and tools to improve dewatering and rheology assessments in soft and ultra-soft tailings

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The tailings water from oil sands extraction contains suspended particles of ultra-fine clays and residual bitumen. These stable suspensions take a long time to settle to the bottom of the ponds (> 10 years). Hence, reducing the volume of tailings in a shorter duration is a major challenge. In addition, the reclaimed land still has a poor mechanical strength for it to be returned to nature. Adding thickeners such as polyacrylamide (PAM) to these processes is considered an attractive method for improved soil consolidation. Even though the polymers are cheap, the overall treatment cost remains high. In addition, the issues of fate and transport of such polymers, as well as their ecotoxicity, are still not resolved. It is also not yet clear if the final strength of consolidated soil will meet the Alberta government's minimum requirements of geotechnical strength.****The goal of this project is to investigate the influence of the micro-scale structure of the flocculated tailings systems on the macro-scale dewatering and rheological properties of soft and ultra-soft fines dominated deposits. Flocs are a clumped group of clay particles and, if added, a polymer that forms the basic structure of soft tailings. Observing, understanding and quantifying the flocculation mechanisms during critical processes such as dewatering and deposition (e.g. under shear) can potentially represent a fundamental big step forward in the prediction of consolidation and deposition operation, hence in the effective management of oil sands tailings. If successful, this allows direct correlation between the choice of a specific treatment of fluid tailings (e.g. addition of the flocculant, mixing and deposition rate) and long-term dewatering and strength performance (e.g. deep deposit consolidation rate, sand segregation, fines capture), with potential for future extrapolation to long-term reclamation objective.****** ****