Photocatalytic inactivation of viruses using titanium dioxide nanoparticles and low-pressure UV light

The carcinogenic potential of chlorine disinfection by-products and recent changes in water quality regulations have led to a greater emphasis on alternative disinfection mechanisms. In this study, the efficacy of bench-scale and pilot-scale titanium dioxide (TiO2) photocatalytic disinfection was explored using four bacteriophages (MS2, PRD1, phi-X174, and fr). The optimized bench-scale experiments indicated that 1 mg/L of Degussa P25 TiO2 irradiated by low-pressure ultraviolet (UV) light reduced the dose requirements for viral inactivation in comparison to UV light alone. The highest UV dose reductions for 4-log inactivation of PRD1, MS2, phi-X174, and fr were 19%, 15%, 6%, and 0%, respectively. Bench-scale photocatalysis was inhibited by limited adsorption of the viruses onto the TiO2 nanoparticles, as indicated by the poor results for high TiO2 concentrations. Subsequently, pilot-scale experiments were completed using the Photo-Cat Lab from Purifics. The annular reactor configuration and increased viral adsorption dramatically improved photocatalytic inactivation for samples with high TiO2 concentrations. Using the Photo-Cat Lab, 2-log inactivation of the bacteriophages was achieved with 400 mg/L of Degussa P25 TiO2 and a UV dose of approximately 34 mJ/cm2 (energy consumption of 0.33 kWh/m3) - a 700-fold decrease in energy use compared to bench-scale photocatalysis.