Photocatalytically‐mediated disinfection of water using tio₂ as a catalyst and spore‐forming Bacillus pumilus as a model

Abstract

The photocatalytic oxidation process has been evaluated as a basis for disinfecting large volumes of water. A 95 percent reduction in viability of B. pumilus spores, suspended with TiO₂ in water, was observed after exposing the model organism to ultraviolet (UV) light (λ 365 nm). Kinetic plots showed that the viability of B. pumilus spores decreased exponentially. No reduction in viability occurred if B. pumilus spores were incubated in the dark (control) or if illumination occurred in the absence of a TiO2 catalyst (TiO2 condition). Intermittent illumination reduced viable B. pumilus spores more effectively than continuous exposure to UV. For various TiO₂ concentrations suspended in water from 1 mg/ml to 4 mg/ml, maximum losses of viability were observed at TiO₂ concentrations of 2 mg/ml of water and spore densities ≥ 10⁹ CFU/ml. On the basis of the data presented here, the TiO₂‐based photocatalytic process shows significant potential as a basis for both stationary and portable water disinfecting devices.