O3/H2O2 and UV-C light irradiation treatment of oil sands process water

The oil sands industry generates large volumes of oil sands process water (OSPW). There is an urgent need for OSPW treatment to reduce process water inventories and to support current reclamation approaches. This study discusses how efficient ozone (O3)-based combined advanced oxidation processes (AOPs), including hydrogen peroxide (H2O2) and UV-C, are at achieving mineralization while reducing the toxicity arising from such organic components as naphthenic acids (NAs) in OSPW. The results showed that the dissolved organic carbon (DOC) removals of 45%, 84%, 84% and 98%, obtained after 90-min treatments with O3, O3/H2O2, UVC/O3 and UVC/O3/H2O2, respectively, at a production rate of 6 g/L·h O3 were considerably higher than at lower O3 production rates. The acute toxicity on Vibrio fischeri was significantly reduced by all the treatments, which explains the high percentages of NA removal (up to 99% as confirmed by UPLC-QTOF-HRMS.) Mineralization (expressed as DOC removal) was highest with UVC/O3/H2O2 at ca. 2 mg C/L in the treated effluent, which means that it could be used as cooling/boiling process water in bitumen upgrading units. However, considering the energy demand of the treatments tested, the treatment using O3/H2O2 was found to be the most realistic for large-scale applications.