|Title||The application of algae for the removal of metals and naphthenic acids from oil sands tailings pond water|
|Year of Publication||2014|
|Publisher||University of Alberta Department of Civil and Environmental Engineering|
|Place Published||Edmonton, AB|
|Keywords||aquatic species, Biodegradation, bioremediation, metals, microbiology, naphthenic acids, Syncrude, tailings water, UofA, wastewater, wastewater treatment|
Bitumen recovery produces a large volume of TPW, which must be reclaimed using an efficient and cost-effective method. In this thesis, the ability of algae for in situ treatment of TPW, with a focus on metal and total acid-extractable organics (TAOs) removal, was assessed. An indigenous alga, found in cyclone overflow water, was capable of removing metals 53Cr, Mn, Co, 60Ni, 65Cu, 66Zn, As, 88Sr, 95Mo and Ba. Through the amplification of the 23S rRNA gene, the indigenous alga was identified as Parachlorella kessleri. Highest metal removal was achieved with the highest nutrient supplements (1.98 mM NO3- and 0.20 mM PO43-) in Syncrude TPW, and the lowest nutrient supplements (0.24 mM NO3- and 0.016 mM PO43-) in Albian TPW. This implies that higher concentrations of nutrient supplements do not necessarily improve the metal removal efficiency. FT-IR spectra revealed the presence of amide I, amide II bands, and carboxylic functional groups on the surface of P. kessleri; these sites likely contribute to metal removal. However, an acid-base titration showed that the carboxylic group was the only active proton binding site for metal binding. Intracellular bioaccumulation was the dominant mechanism of metal removal, with extracellular bioaccumulation and precipitation playing a smaller role. For the biodegradation of TAOs, a consortium of indigenous algae-bacteria was employed. Bacteria demonstrated the greatest removal of TAOs with a half-life removal rate of 203 days (first-order kinetics). The TAO removal rate did not correlate with detoxification of TPW, where most toxicity reduction was observed in samples containing the algae-bacteria consortium. Principal component analysis (PCA) was conducted on the FT-IR spectra. The significant loading wavenumbers, which likely indicated bio-transformed functional groups and bonds in the TAO molecules, were identified as: hydroxyl, carbocyclic and amid groups along with C-H, aryl-H, aryl-OH and N-H bonds. The observations from this research indicate that indigenous algae play an important role in the removal of metals and TAOs from oil sands TPW. However, for future engineering application, more investigates are required to optimize the operating conditions to improve the removal efficiency.