Photocatalytic Inactivation of Airborne Bacteria in a Continuous-Flow Reactor

In this study, a continuous annular reactor was used to characterize the TiO2-mediated inactivation of an aerosolized Gram-negative bacterium, Escherichia coli K-12 (ATCC 10798), by varying UV-A intensity (0.5−3.4 mW/cm2), relative humidity (RH) (from 51 ± 0.61 to 85 ± 4.7%), and photocatalyst loading (960 and 1516 mg/m2) at an air flow rate of 1 L/min. Inactivation rate of E. coli K-12 increased with an increase in TiO2 loading, UV-intensity, and RH. A UV-A dose of 0.03−0.204 J/cm2 at an average UV-A intensity of 0.5−3.4 mW/cm2, at a residence time of 1.1 min, is sufficient to fully and continuously inactivate E. coli K-12 passing through the reactor. The photocatalytic inactivation rates obtained in the continuous flow reactor compared well with our earlier batch inactivation rates conducted at a UV-A intensity of 0.015 mW/cm2 and a TiO2 loading of 1516 mg/m2. This demonstrates the possibility of scaling up of the photocatalytic inactivation process for bioaerosol based on batch kinetic data.