Microbial Communities in Oil Sands Tailings: Their Implications in Biogeochemical Processes and Tailings Management

A Deep Look into the Microbiology and Chemistry of Froth Treatment Tailings: A Review

“…Tailings ponds harbor diverse indigenous microbial communities, which are actively involved in the biodegradation of residual hydrocarbons (naphtha, paraffins and bitumen) to release GHGs [14]. Tailings-associated microbes also play an important role in element cycling (sulphur, nitrogen and iron) and accelerating the consolidation of tailings [7]. The microbial populations in tailings originate primarily from the oil sands ore and process water, while airborne microbes may contribute to their assembly over time [14].…”

“…The management and processing history of legacy tailings ponds are not very well documented, thus making it challenging to decipher the type and quantity of tailings held in each pond [14]. Furthermore, the microbial community structure is primarily shaped by gradients of physiochemical properties in the stratified waterbody such as availability of O 2 , temperature, pH, tailings density and type of hydrocarbons in stratified tailings ponds [7,43].…”

“…Previous studies estimated the viable population (most probable number) of sulphate reducers (10 5 -10 9 cells), nitrate reducers (10 9 cells), iron reducers (10 3 cells), and methanogens (10 2 -10 3 cells) in one gram (dry weight) of mature fine tailings [14]. These subsurface anaerobic microbial communities utilize residual hydrocarbons from diluent and bitumen as carbon sources under redox conditions (carbon dioxide-reducing, sulphate-reducing and iron-reducing conditions) [7]. Core microbiome analyses of samples taken from six oil sands tailings ponds identified 2-5 operational taxonomic units (OTUs) that were shared by the majority of samples and that could be involved in hydrocarbon degradation.…”

“…It has been widely accepted that diluent hydrocarbons (naphtha and paraffins) are the primary carbon sources for indigenous anaerobic microbial communities in tailings ponds that receive FTT streams [4,7,14]. Many studies (Table 1) used components of naphtha diluent to decipher structure and functions of tailings-residing microbial communities [25,43,49].…”

“…Froth treatment tailings (FTT) are a specific type of tailings that contain bioavailable diluent, which is the primary source of GHG emissions from FTT tailings ponds and has been associated with localized bubbling within some tailings ponds [4][5][6]. Characterizing the composition and biodegradation of FTT is important from an environmental perspective to better understand how to reduce GHG emissions and manage the risks associated with tailings [7,8].…”