Department of Civil and Environmental Engineering, University of Alberta, Edmonton, Alberta T6G 1H9, Canada.
Department of Civil and Environmental Engineering, University of Alberta, Edmonton, Alberta T6G 1H9, Canada.
Sci Total Environ. 2021 Aug 15;782:146742. doi: 10.1016/j.scitotenv.2021.146742. Epub 2021 Mar 26.
Adopting nature-based solutions for the bioremediation of oil sands process water (OSPW) is of significant interest, which requires a thorough understanding of how bacterial communities behave within treatment systems operated under natural conditions. This study investigates the OSPW remediation potential of delayed petroleum-coke (PC), which is a byproduct of bitumen upgrading process and is readily available at oil refining sites, in fixed-bed biofilters particularly for the degradation of naphthenic acids (NAs) and aromatics. The biofilters were operated continuously and total and active bacterial communities were studied by DNA and RNA-based amplicon sequencing in a metataxonomic fashion to extrapolate the underlying degradation mechanisms. The results of total community structure indicated a high abundance of aerobic bacteria at all depths of the biofilter, e.g., Porphyrobacter, Legionella, Pseudomonas, Planctomyces. However, redox conditions within the biofilters were anoxic (-153 to -182 mV) that selected anaerobic bacteria to actively participate in the remediation of OSPW, i.e., Ruminicoccus, Eubacterium, Faecalibacterium, Dorea. After 15 days of operation, the removal of classical NAs was recorded up to 20% whereas oxidized NAs species were poorly removed, i.e., O-NAs: 4.8%, O-NAs: 1.2%, O-NAs: 1.7%, and O-NAs: 0.5%. Accordingly, monoaromatics, diaromatics, and triaromatics were removed up to 16%, 22%, and 15%, respectively. The physiology of the identified genera suggested that the degradation in the PC-based biofilters was most likely proceeded in a scheme similar to beta-oxidation during anaerobic digestion process. The presence of hydrogenotrophic methanogens namely Methanobrevibacter and Methanomassiliicoccus and quantification of mcrA gene (2.4 × 10 to 8.7 × 10 copies/mg of PC) revealed that methane production was likely occurring in a syntrophic mechanism during the OSPW remediation. A slight reduction in toxicity was also observed. This study suggests that PC-based biofilters may offer some advantages in the remediation of OSPW; however, the production of methane could be of future concerns if operated at field-scale.
采用基于自然的解决方案来修复油砂工艺水（OSPW）具有重要意义，这需要深入了解在自然条件下运行的处理系统中细菌群落的行为。本研究调查了延迟石油焦（PC）修复 OSPW 的潜力，PC 是沥青升级过程的副产品，在炼油厂随处可得，特别适用于固定床生物滤池降解环烷酸（NAs）和芳烃。生物滤池连续运行，通过 DNA 和 RNA 扩增子测序以分类学方式研究总细菌和活性细菌群落，推断潜在的降解机制。总群落结构的结果表明，生物滤器的所有深度都存在大量好氧菌，例如，Porphyrobacter、Legionella、Pseudomonas、Planctomyces。然而，生物滤器内的氧化还原条件为缺氧（-153 至-182 mV），选择了厌氧菌来积极参与 OSPW 的修复，即 Ruminicoccus、Eubacterium、Faecalibacterium、Dorea。运行 15 天后，记录到经典 NAs 的去除率高达 20%，而氧化 NAs 物种的去除率较差，即 O-NAs：4.8%、O-NAs：1.2%、O-NAs：1.7%和 O-NAs：0.5%。相应地，单芳烃、二芳烃和三芳烃的去除率分别高达 16%、22%和 15%。鉴定出的属的生理学表明，PC 基生物滤器中的降解很可能类似于厌氧消化过程中的β-氧化进行。存在产氢甲烷菌，即 Methanobrevibacter 和 Methanomassiliicoccus，以及 mcrA 基因的定量（2.4×10 至 8.7×10 拷贝/mg PC）表明，在 OSPW 修复过程中，甲烷的产生可能发生在一种共生机制中。毒性也略有降低。本研究表明，PC 基生物滤池在修复 OSPW 方面可能具有一些优势；然而，如果在现场规模运行，甲烷的产生可能是未来的关注点。
