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Biological fixation of CO2 using microalgae is a potential CO2 reduction strategy which can be applied to the oil sands operations in Alberta. These operations also produce large amounts of oil sands process water (OSPW), which can act as a growth medium for the microalgae. In this study, three different microalgae: Botryococcus braunii, Chlorella pyrenoidosa and Chlorella kessleri were investigated for their ability to grow in OSPW, and to uptake CO2. Also, the effect of phosphate, nitrate, CO2 concentrations and light intensity were studied using a fractional two-level and a full two-level factorial design. These investigations eliminated Botryococcus braunii as it cannot grow in OSPW, and demonstrated that Chlorella kessleri has a higher CO2 uptake rate than Chlorella pyrenoidosa. Moreover, CO2 concentration, light intensity and phosphate concentration proved to have the strongest effects (in that order) on the growth and CO2 uptake rate of Chlorella kessleri.

Nine distinct anaerobic benzene-degrading cultures were enriched from sediment samples from four different sites. These cultures used nitrate, sulphate or CO2 as electron acceptors. The shortest doubling times were observed in nitrate-reducing cultures, although cell yield was lowest in these cultures. The highest substrate concentration utilized and maximum absolute rates of benzene degraded (in micro M day-1) were observed in methanogenic cultures. The microbial compositions of a methanogenic and nitrate-reducing culture were determined from a clone library of 16S rRNA genes. Five Bacterial 16S rRNA sequences, one of which resembled a clone previously found in a sulphate-reducing, benzene-degrading culture and four Archaeal 16S rRNA sequences were identified in a methanogenic culture. Four Bacterial and no Archaeal 16S rRNA sequences were identified in a nitrate-reducing culture. The relative abundance of the four nitrate-reducing putative species was determined by slot blot hybridization. Two green sulphur bacteria together formed 52% of the clone library, but were found to be less than 4% of the culture by slot blot analysis. One of the cloned 16S rRNA gene sequences comprised 70% of the culture and was phylogenetically 93% similar to both Azoarcus and Dechloromonas species, which have been shown to degrade aromatic compounds, including benzene, under nitrate-reducing conditions.