Assessment of the sources and biodegradation potential of hydrocarbons and naphthenic acids in an oil sand end pit lake

• Main Author: Elwaraky, Mohamed
• Other Authors: Slater, Greg, Earth and Environmental Sciences
• Format: Thesis
• Language: English
• Published: 2021
• Subjects: Beaver Creek
• Online Access: http://hdl.handle.net/11375/27319

Reclamation efforts have been ongoing to manage and reclaim the mined-out pits and the tailings produced from oil sands production. Syncrude has implemented the first end pit lake, known as Base Mine Lake (BML), by using water cap tailing technology (WCTT). The lake was constructed by capping 186 million m3 of fluid fine tailings (FFT) with a 65 million m3 water column from OSPW (oil sand process water) and Beaver Creek Reservoir (BCK) forming a total depth of 48m. The organic compounds present within the FFT, such as hydrocarbons and naphthenic acids (NAs), are residual organic matter from the bitumen after extraction or the diluent naphtha. Consumption of residual organic compounds through syntrophic fermentation coupled to methanogenesis in the FFT generates methane that can be transported upward to the water column through advection, diffusion or ebullition. The oxidation of the methane by methanotrophs depletes the oxygen concentration in the water column. An integral part of the success of the WCTT is the demonstration of stable oxygen conditions in the water column that would facilitate the biodegradation of residual organic matter which can be transported into the water column from the FFT. This dissertation utilized multidimensional chromatography to assess the residual organic compounds in BML and evaluate their biodegradation potential. Assessment of the hydrocarbons in the FFT indicated that the low molecular weight compounds are being biodegraded at shallower intervals and potentially driving methane production. The analysis of NAs distribution in BML revealed that additional input of NAs into the water column, through biodegradation of hydrocarbons or advection from the FFT, is being balanced by ongoing microbial degradation in the water column. Evaluation of the biodegraded metabolites revealed that hydrocarbons are anaerobically degraded in the FFT while NAs are aerobically degraded in the water column of BML. This study demonstrates that studying the molecular fingerprint distribution of ...