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Microbial degradation of Cold Lake Blend and Western Canadian Select Dilbits by freshwater enrichments
Citation:
Deshpande, R., D. Sundaravadivelu, S. Techtmann, R. Conmy, J. Santodomingo, AND P. Campo. Microbial degradation of Cold Lake Blend and Western Canadian Select Dilbits by freshwater enrichments. JOURNAL OF HAZARDOUS MATERIALS. Elsevier Science Ltd, New York, NY, 352:111-120, (2018).
Impact/Purpose:
The main objectives of this work were to gain insight into biodegradability of diluted bitumen and the types bacterial groups potentially engaged in dilbit degradation. The effect of temperature was much more pronounced at 25 than 5 ºC. Different bacterial groups were identified that may play important role in dilbit degradation.
Description:
Although there are different physical and chemical properties between conventional crude oils and diluted bitumen (dilbit) information on the biodegradation patterns of dilbit is scarce. To address this issue, treatability experiments were conducted with two types of dilbits at 5 and 25 ºC for 72 and 60 days, respectively. Microbial consortia obtained from the Kalamazoo River Enbridge Energy spill site was enriched on dilbit at both 5 (cryo) and 25 (meso) ºC. On every sampling day, triplicates were sacrificed and residual hydrocarbon concentrations (alkanes and polycyclic aromatic hydrocarbons) were determined by gas chromatography tandem mass spectrometry. Additionally, the composition and the relative abundance of each bacterial group were identified by 16S rRNA gene sequencing analysis at both temperatures. While minor differences in viscosity, total acid number, and total alkane content were observed between the two dilbits, their biodegradation profiles were similar. The effect of temperature was much more pronounced as faster degradation rates and larger degradation extents were observed at 25 than 5 ºC. Specifically, the meso consortium metabolized 99.9% of alkanes and 97.5 % of aromatics, while the cryo consortium degraded 99.9% of the alkanes and 70% of aromatics. Several known hydrocarbon-degrading bacteria such as Pseudomonas, Rhodococcus, Hydrogenophaga, Parvibaculum, Arthrobacter, Acidovorax, Polaromonas were present in both consortia, while their relative abundances differed based on the temperatures at which they were enriched. During the experiments, the microbial community profiles significantly changed as a response to the diminishing hydrocarbon load regardless of the dilbit type. Overall, the results from this study provided evidence on the biodegradation of diluted bitumen.
URLs/Downloads:
Free access through PubMed Central
https://www.sciencedirect.com/science/article/pii/S0304389418301821