Résumé - Abstract
The management of oil sands tailings has been an ongoing challenge for many years largely due to the presence of fine clay and silt particles in the tailings. These fine particles pose a significant challenge to End Pit Lakes (EPLs), which are expected to be a widely used method of reclaiming oil sands tailings, as surface water turbidity may be detrimental to the development of aquatic ecosystems in EPLs. Laboratory mixing experiments were conducted to investigate the effect of biofilms made up of microbial communities indigenous to tailings on reducing turbidity in EPLs. The impact of biofilm age (10 weeks versus 20 weeks old) on turbidity mitigation was also evaluated. Biofilms were characterized by chlorophyll a extractions, live and dead staining, scanning electron microscopy (SEM), and DNA sequencing. Biofilms formed on the mudline between the tailings and water cap reduced turbidity in the water cap by over 99%, depending on biofilm age and mixing speed. Gas production and lifting resulted in weaker attachment of older biofilms to the mudline and as such, younger biofilms performed better than older biofilms. However, older biofilms still reduced turbidity by 73 to 95%, depending on the mixing speed. These promising findings will inform planning and management decisions for current and future EPLs.