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Abstract: This study investigated the application of polyaluminum chloride (PACl) and potassium ferrate(VI) for the treatment of oil sands process-affected water (OSPW). In addition, the performance of potassium ferrate(VI) was compared with other oxidation processes, including UV/hydrogen peroxide (H2O2), and ozonation with and without hydroxyl radical (∙OH) scavenger. The comparison of the performance not only involved the removal of naphthenic acids (NAs) and aromatics, but also the oxidation of sulfur and nitrogen containing species. PACls are commonly used in water treatment with the most effective species reported to be Al13. In this research, PACl with 83.6% Al13 was synthesized using the slow base titration method and compared with a commercially available PACl in terms of aluminum species distribution, coagulation/flocculation (CF) performance, floc morphology, and contaminant removal. Both coagulants were effective in removing suspended solids, achieving over 96% turbidity removal at all applied coagulant doses (0.5-3.0 mM Al). The removal efficiencies of metals varied among different metals depending on their pKa values. Metal cations with pKa values (Fe, Al, Ga, and Ti) below OSPW pH of 6.9-8.1 (dose dependent) were removed by more than 90%, while metal cations with higher pKa values (K, Na, Ca, Mg and Ni) had removals of less than 40%. NAs were not removed due to their low molecular weights, negative charges, and hydrophilic characteristics at the OSPW pH. At the highest applied coagulant dose of 3.0 mM Al, the synthetic PACl reduced Vibrio fischeri inhibition effect to 43.3±3.0% from 49.5±0.4% in raw OSPW. In contrast, no reduction of toxicity was found for OSPW treated with the commercial PACl. Based on water quality and floc analyses, the dominant CF mechanism for particle removal during OSPW treatment was considered to be enmeshment in the precipitates (i.e., sweep flocculation). Potassium ferrate(VI) showed high selectivity in oxidizing the organic fraction of OSPW. It preferentially removed two-ring and three-ring fluorescing aromatics at doses