title: Anaerobic BTEX degradation in oil sands tailings ponds: Impact of labile organic carbon and sulfate-reducing bacteria.
abstract: 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 benzene, toluene, ethylbenzene and xylenes (BTEX) that derive from the application of industrial solvents. Due to their toxicity 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 ethylbenzene and xylenes to total BTEX significantly decreased, while benzene increased relatively from 44% to 69%, indicating preferential hydrocarbon 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. acetate) generally considered to stimulate hydrocarbon degradation and the contribution of sulfate-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 μg kg(-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 acetate that lowered BTEX turnover due to product inhibition. In those assays SRB slightly stimulated BTEX transformation by reducing inhibitory acetate levels.
authors.affiliation: Department of Lake Research, UFZ - Helmholtz Centre for Environmental Research, Brückstraße 3a, 39114 Magdeburg, Germany. Electronic address: sebastian.stasik@ufz.de.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Stasik
authors.affiliation: Department of Environmental Microbiology, UFZ - Helmholtz Centre for Environmental Research, Permoserstraße 15, 04318 Leipzig, Germany.
authors.forename: Lukas Y
authors.initials: LY
authors.lastname: Wick
authors.affiliation: Department of Lake Research, UFZ - Helmholtz Centre for Environmental Research, Brückstraße 3a, 39114 Magdeburg, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Wendt-Potthoff
mesh_terms: D000085:Acetates / Q000737:chemistry; D000416:Alberta; D000693:Anaerobiosis; D001554:Benzene / Q000032:analysis; D001555:Benzene Derivatives / Q000032:analysis; D001673:Biodegradation, Environmental; D002244:Carbon / Q000737:chemistry*; D004785:Environmental Pollutants / Q000032:analysis*; D061329:Oil and Gas Fields; D061005:Ponds / Q000737:chemistry*; D013431:Sulfates / Q000032:analysis; D016999:Sulfur-Reducing Bacteria / Q000254:growth & development*; D014050:Toluene / Q000032:analysis; D014992:Xylenes / Q000032:analysis
chemical_list: D000085:Acetates; D001555:Benzene Derivatives; D004785:Environmental Pollutants; D013431:Sulfates; D014992:Xylenes; D014050:Toluene; D002244:Carbon; D001554:Benzene; C004912:ethylbenzene
keywords: BTEX; Biodegradation; Methanogenesis; Oil sands tailings ponds; Sulfate reduction