A first approximation kinetic model to predict methane generation from an oil sands tailings settling basin.
A small fraction of the naphtha diluent used for oil sands processing escapes with tailings and supports methane (CH(4)) biogenesis in large anaerobic settling basins such as Mildred Lake Settling Basin (MLSB) in northern Alberta, Canada. Based on the rate of naphtha metabolism in tailings incubated in laboratory microcosms, a kinetic model comprising lag phase, rate of hydrocarbon metabolism and conversion to CH(4) was developed to predict CH(4) biogenesis and flux from MLSB. Zero- and first-order kinetic models, respectively predicted generation of 5.4 and 5.1 mmol CH(4) in naphtha-amended microcosms compared to 5.3 (+/-0.2) mmol CH(4) measured in microcosms during 46 weeks of incubation. These kinetic models also predicted well the CH(4) produced by tailings amended with either naphtha-range n-alkanes or BTEX compounds at concentrations similar to those expected in MLSB. Considering 25% of MLSB's 200 million m(3) tailings volume to be methanogenic, the zero- and first-order kinetic models applied over a wide range of naphtha concentrations (0.01-1.0 wt%) predicted production of 8.9-400 million l CH(4) day(-1) from MLSB, which exceeds the estimated production of 3-43 million l CH(4) day(-1). This discrepancy may result from heterogeneity and density of the tailings, presence of nutrients in the microcosms, and/or overestimation of the readily biodegradable fraction of the naphtha in MLSB tailings.
Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada T6G 2E9.
Tariq
T
Siddique
Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, Canada T6G 2G6.
Rajender
R
Gupta
Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada T6G 2E9.
Phillip M
PM
Fedorak
Syncrude Canada Ltd., Edmonton Research Centre, Edmonton, AB, Canada T6N 1H4.
Michael D
MD
MacKinnon
Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada T6G 2E9. Electronic address: julia.foght@ualberta.ca.
Julia M
JM
Foght
D000416:Alberta; D000473:Alkanes / Q000378:metabolism; D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D004783:Environmental Microbiology; D007700:Kinetics; D008697:Methane / Q000378:metabolism*; D008962:Models, Theoretical; D010578:Petroleum / Q000378:metabolism
D000473:Alkanes; D010578:Petroleum; C004544:naphtha; D008697:Methane