Fig. 2 An illustration of bitumen extraction process.
Research Background.
Northeastern Alberta, Canada, has the third-largest oil reserve in the world, following Saudi Arabia and Venezuela (Small et al., 2015). Covering over 141,000 km2, the Peace River, Cold Lake, and Athabasca oil sands regions were estimated to have about 300 billion barrels of recoverable bitumen (Masliyah et al., 2004; Small et al., 2015; Wayland et al., 2007). The Clark Hot Water Extraction Process (HWP) used by Albertan oil sand companies achieved over 90% bitumen recovery rate from the oil sand ore (Masliyah et al., 2004), (Richard et al., 2007). The addition of NaOH in the HWP for increasing bitumen recovery efficiency produces the water-in-bitumen emulsions which requires froth treatment for bitumen separation (Richard et al., 2007). Naphtha is a commonly used diluent in froth treatment, rich in aliphatic- and monoaromatic hydrocarbons. It will be deposited as the main component of froth treatment tailings, with coarse tailings and fine tailings, into oil sand tailing pond pending reclamation (Cossey et al., 2021). The term Fluid Fine Tailings is used in this study as a broad term to define the tailings samples obtained from Syncrude tailings ponds. Current Research Gaps. The greenhouse gas (GHG) emissions from tailing ponds has generated great concerns recently. In some areas of the |
tailing ponds operated by Syncrude Canada Ltd., 43,000 m3 of methane was estimated to release into the atmosphere per day (Holowenko et al., 2000; Siddique et al., 2012). Extensive investigations regarding the biogeochemical activities involved in methane generation and the applied mathematical models to predict methane production by endogenous microbial communities in tailing ponds have be conducted in the past decade. The iso-alkanes, short-chain n-alkanes (C6-C10), BTEX (benzene, toluene, ethylbenzene, and xylenes), and longer-chain n-alkanes (C14, C16, and C18) from naphtha or unrecovered bitumen have been reported to be biodegradable under methanogenic conditions and contribute to in-situ methane production in tailing ponds (Siddique et al., 2020, 2012, 2011). Previous stoichiometric methane production model predicted well the methane emissions from the biodegradation of diluents in different operators' tailings (Kong et al., 2019). However, there is a gap between the measured volumes of methane emitted from tailing ponds and the model predicted cumulative methane volumes (Kong et al., 2019). The differences can be the result of methanogenic biodegradation of other recalcitrant labile endogenous hydrocarbons apart from the hydrocarbons used in model development (Kong et al., 2019).
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Pyrene
Objectives of Study.
Polycyclic Aromatic Hydrocarbons (PAHs) are another family of hydrocarbons reported to exist in the tailing pond sediments through deposition of tailings (Raine et al., 2017; Wayland et al., 2007). PAHs have been investigated to be biodegradable under methanogenic conditions in various media followed by methane emission. Chang et al., 2002, 2003. found that some of PAHs with 2 to 4 rings can be biodegraded by methanogens in soil and petrochemical sludge. In another study, methane was monitored to produce from the anaerobic biodegradation of PAHs, which proved that PAHs are bioavailable to methanogenic consortiums in soil media (Sayara et al., 2010). Further discoveries showed that carboxylation is one of the key steps in the metabolic pathways of PAHs' methanogenic degradation (Sun et al., 2022; Zhang et al., 2019). Although some PAHs can be methanogenically degraded in water and soil media, the biodegradability of PAHs under methanogenic conditions in tailing ponds still remains scarcely known.
The objectives of this study are to investigate whether PAHs with 2 to 4 benzic rings can be biodegraded under methanogenic conditions in tailings; and to model the behavior of methane production from the degradation of hydrocarbons (toluene and PAHs). The discovery of this study will help to understand the bioavailability and biodegradability of PAHs to indigenous microbial communities in tailings ponds under methanogenic conditions, as well as to amend the previous models on predicting GHG emissions from talings ponds.
Polycyclic Aromatic Hydrocarbons (PAHs) are another family of hydrocarbons reported to exist in the tailing pond sediments through deposition of tailings (Raine et al., 2017; Wayland et al., 2007). PAHs have been investigated to be biodegradable under methanogenic conditions in various media followed by methane emission. Chang et al., 2002, 2003. found that some of PAHs with 2 to 4 rings can be biodegraded by methanogens in soil and petrochemical sludge. In another study, methane was monitored to produce from the anaerobic biodegradation of PAHs, which proved that PAHs are bioavailable to methanogenic consortiums in soil media (Sayara et al., 2010). Further discoveries showed that carboxylation is one of the key steps in the metabolic pathways of PAHs' methanogenic degradation (Sun et al., 2022; Zhang et al., 2019). Although some PAHs can be methanogenically degraded in water and soil media, the biodegradability of PAHs under methanogenic conditions in tailing ponds still remains scarcely known.
The objectives of this study are to investigate whether PAHs with 2 to 4 benzic rings can be biodegraded under methanogenic conditions in tailings; and to model the behavior of methane production from the degradation of hydrocarbons (toluene and PAHs). The discovery of this study will help to understand the bioavailability and biodegradability of PAHs to indigenous microbial communities in tailings ponds under methanogenic conditions, as well as to amend the previous models on predicting GHG emissions from talings ponds.
Disclaimer: All the contents presented in this website were produced by Henian Guo as an assignment for RENR 580 at the University of Alberta and should NOT be interpreted outside of the scope of this assignment. Parts of the findings were not from the real experiment.