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Naphthenic acids (NAs) found in oil sands process-affected waters (OSPW) have known environmental toxicity and are resistant to conventional wastewater treatments. The granular activated carbon (GAC) biofilm treatment process has been shown to effectively treat OSPW NAs via combined adsorption/biodegradation processes despite the lack of research investigating their individual contributions. Presently, the NAs removals due to the individual processes of adsorption and biodegradation in OSPW bioreactors were determined using sodium azide to inhibit biodegradation. For raw OSPW, after 28 days biodegradation and adsorption contributed 14% and 63% of NA removal, respectively. For ozonated OSPW, biodegradation removed 18% of NAs while adsorption reduced NAs by 73%. Microbial community 454-pyrosequencing of bioreactor matrices indicated the importance of biodegradation given the diverse carbon degrading families including Acidobacteriaceae , Ectothiorhodospiraceae , and Comamonadaceae . Overall, results highlight the ability to determine specific processes of NAs removals in the combined treatment process in the presence of diverse bacteria metabolic groups found in GAC bioreactors. [ABSTRACT FROM AUTHOR]

Abstract: This study evaluated the treatment of oil sands process-affected water (OSPW) using a fluidized bed biofilm reactor (FBBR) with granular activated carbon (GAC) as support media. The bioreactor was operated for 120 days at different organic and hydraulic loading rates. The combined GAC adsorption and biodegradation process removed 51% of chemical oxygen demand (COD), 56% of acid-extractable fraction (AEF) and 96% of classical naphthenic acids (NAs) under optimized operational conditions. Bioreactor treatment efficiencies were dependent on the organic loading rate (OLR), and to a lower degree, on the hydraulic loading rate (HLR). Further ultra performance liquid chromatography/high resolution mass spectroscopy (UPLC/HRMS) analysis showed that the removal of classical NAs increased as the carbon number increased. Compared with planktonic bacterial community in OSPW, more diverse microbial structures were found in biofilms colonized on the surface of GAC after 120-day treatment, with various carbon degraders namely Polaromonas jejuensis, Algoriphagus sp., Chelatococcus sp. and Methylobacterium fujisawaense in the GAC-biofilm reactor. The results of this study, therefore, showed that the GAC-biofilm seems to be a promising biological treatment method for OSPW remediation. [Copyright &y& Elsevier]