Fluid fine tailings (FFT) management is one of the main challenges that oil sand developers continue to face. Syncrude Canada Ltd, independently or in collaboration with Canadas Oil Sands Innovation Alliance (COSIA) member companies, has developed various technologies to accelerate FFT dewatering to meet progressive mine closure and reclamation objectives. One of the technologies is FFT clay treatment that targets the problematic clays in FFT. The basis of this step-out technology is the use of a polymeric flocculant to enlarge the effective size of clays and a collector to change the clay surfaces from hydrophilic to hydrophobic. In this way, the treated FFT dewaters very fast. An effective, easy to use collector is key to the success of this technology. Collectors are chemical compounds added to FFT that change the clay hydrophobicity, promote aggregation of clay particles and assist in FFT dewatering. Theoretically, it is possible to directly use a cationic collector or a combination of a metal ion and an anionic collector to make the negatively charged FFT clays hydrophobic. Building on this concept, several process technology scenarios have been developed and tested. This paper demonstrates how fundamental research provides a simple and cost-effective method for screening collectors for operational FFT clay treatment.
Waste isolation is a key strategy for mitigating risk from municipal solid waste (MSW) and hazardous waste streams. Conventional covers at MSW facilities are designed for a 30-yr post-closure period where compacted soils and geosynthetics are used to minimize percolation into buried waste. Recently, evapotranspiration (ET) covers have shown beneficial use for MSW management. Evapotranspiration covers encourage infiltration, storage, and transpiration of precipitation to minimize percolation. Such covers may also have beneficial use for long-term waste issues, such as at Uranium Mill Tailings Radiation Control Act (UMTRCA) sites. These sites were covered by a clay radon barrier to create tortuous flow paths that allow radioactive decay and attenuation of short-lived, radon-222 gas. For long-term waste isolation, an ET-radon cover may provide greater resilience by exploiting natural processes instead of resisting them. This update presents a review of the current state-of-the-science regarding ET covers and considerations for long-term applications.