Anaerobic BTEX degradation in oil sands tailings ponds: Impact of labile organic carbon and XXXX -reducing bacteria.

@entity11574 @entity137 @entity598 @entity7294 @entity7935 @entity8336 @entity18008 @entity597
UNASSIGNED: The extraction of bitumen from oil sands in Alberta (Canada) produces volumes of tailings that are pumped into large anaerobic settling-basins. Beside bitumen, tailings comprise fractions of @entity7935 , @entity8336 , @entity18008 and @entity11574 (BTEX) that derive from the application of industrial solvents. Due to their @entity137 and volatility, BTEX pose a strong concern for gas- and water-phase environments in the vicinity of the ponds. The examination of two pond profiles showed that concentrations of indigenous BTEX decreased with depth, pointing at BTEX transformation in situ. With depth, the relative contribution of @entity18008 and @entity11574 to total BTEX significantly decreased, while @entity7935 increased relatively from 44% to 69%, indicating preferential @entity7294 degradation. To predict BTEX turnover and residence time, we determined BTEX degradation rates in tailings of different depths in a 180-days microcosm study. In addition, we evaluated the impact of labile organic substrates (e.g. @entity598 ) generally considered to stimulate @entity7294 degradation and the contribution of @entity597 -reducing bacteria (SRB) to BTEX turnover. In all depths, BTEX concentrations significantly decreased due to microbial activity, with degradation rates ranging between 4 and 9 gkg(-1)d(-1). BTEX biodegradation decreased linearly in correlation with initial concentrations, suggesting a concentration-dependent BTEX transformation. SRB were not significantly involved in BTEX consumption, indicating the importance of methanogenic degradation. BTEX removal decreased to 70-90% in presence of organic substrates presumptively due to an accumulation of @entity598 that lowered BTEX turnover due to product inhibition. In those assays SRB slightly stimulated BTEX transformation by reducing inhibitory @entity598 levels.
