The reclamation of oil sands process-affected water (OSPW) is a matter of environmental importance because of the aquatic toxicity to biota. This study describes refinements in advanced analytical methods to assess the performance of biological treatment systems for OSPW, such as constructed wetland treatment systems (CWTSs). Assessment of treatment efficiency by measurement of the degradation of naphthenic acid fraction compounds (NAFCs) in OSPW is challenging in CWTS due to potentially interfering constituents such as humic acids, organic acids, salts, and hydrocarbons. Here we have applied a previous weak anion exchange (WAX) solid-phase extraction (SPE) method and high-resolution Orbitrap-mass spectrometry (MS) to remove major interferences from the NAFC analysis. The refinements in data processing employing principal component analysis (PCA) indicates that the relative abundance of NAFCs decreased with time in the treated OSPW relative to the untreated OSPW. The most saturated NAFCs with higher carbon numbers were relatively more degraded as compared to unsaturated NAFCs. The use of Kendrick plots and van Krevelen plots for assessment of the performance of the CWTS is shown to be well-suited to detailed monitoring of the complex composition of NAFCs as a function of degradation. The developments and application of analytical methods such as the WAX SPE method and high-resolution Orbitrap-MS are demonstrated as tools enabling the advancement of CWTS design and optimization, enabling passive or semi-passive water treatment systems to be a viable opportunity for OSPW treatment.

Naphthenic acid fraction compounds (NAFCs) are highly recalcitrant constituents of oil sands tailings. Although some microorganisms in the tailings can individually and synergistically metabolize NAFCs, the biochemical mechanisms that underpin these processes are hitherto unknown. To this end, we isolated two microorganisms, Pseudomonas protegens and Pseudomonas putida, from oils sands tailings and analyzed their transcriptomes to shed light on the metabolic processes employed by them to degrade and detoxify NAFCs. We identified 1048, 521 and 1434 genes that are upregulated in P. protegens, P. putida and a 1:1 co-culture of the strains, respectively. We subsequently enumerated the biochemical activities of enriched genes and gene products to reveal the identities of the enzymes that are associated with NAFC degradation. Separately, we analyzed the NAFCs that are degraded by the two pseudomonads and their 1:1 co-culture and determined the composition of the molecules using mass spectrometry. We then compared these molecular formulas to those of the cognate substrates of the enriched enzymes to chart the metabolic network and understand the mechanisms of degradation that are employed by the microbial cultures. Not only does the consortium behave differently than the pure cultures, but our analysis also revealed the mechanisms responsible for accelerated rate of degradation of NAFCs by the co-culture. Our findings provide new directions for engineering or evolving microorganisms and their consortia for degrading NAFCs more stably and aggressively.

Tailings ponds in northeastern Alberta, Canada contain massive amounts of oil sands process water (OSPW) that cannot currently be released due to the toxicity of some components. Limited space and the need for reclamation of oil sands operation sites will necessitate the release of OSPW in the near future. Knowledge of the composition and toxicity of OSPW is lacking yet is crucial for both risk assessment and management planning. This study examines chronic toxicity of a mixture of OSPW components sodium naphthenate and naphthenic acid (NA) to nymphs of the mayfly Hexagenia spp. in control and polycyclic aromatic hydrocarbons (PAH)-spiked sediment treatments. The objective of this study was to determine whether the addition of the PAH-spiked sediment significantly contributed to or masked responses of these sensitive mayflies to mixtures of NA. Mean survival in nymphs exposed to NA and PAH-spiked sediment treatments was reduced by 48% compared to those exposed to the NA mixture alone. Lethal responses were observed in all of the PAH-spiked sediment treatments. However, within PAH-spiked and control sediment treatments, there was no significant difference in nymph survival due to NA concentration, indicating that changes in survivorship were predominantly a reflection of increased mortality associated with sediment PAHs and not to the NA mixture treatment. Sublethal effects on body segment ratios suggest that mayflies exposed to NA and PAH-spiked sediment, as well as those exposed to the highest NA concentration tested (1 mg/L) and control sediment, made developmental trade-offs in order to emerge faster and escape a stressful environment. These results reveal that the release of OSPW to the surrounding environment could cause a reduction in mayfly populations. Mayflies provide ecosystem services and are an important food source for higher trophic levels in both the aquatic and terrestrial communities.