Heterogenous photocatalytic inactivation of B. stearothermophilus endospores in aqueous suspensions under artificial and solar irradiation

TiO2 mediated photocatalytic disinfection constitutes an attractive emerging technology against waterborne diseases transmitted through pathogenic microorganisms. This study demonstrates the potential of TiO2 suspensions to fully inactivate highly resistant microorganisms, Bacillus stearothermophilus endospores in water, in the presence of artificial and solar irradiation. Photo-inactivation, however, in the absence of TiO2 led to twelve times lower reaction rates and in the inactivation of only 50% of the initial endospore population, in the same time intervals. The addition of limited amounts of ferric species, as well as catalyst surface modification by Ag and Pt deposition, clearly results in enhanced reaction rates. Furthermore, electron micrographs correlate endospore inactivation and inability to reactivate in the dark with extended morphological lesions of the spore structure, caused by the photocatalytically generated reactive oxygen species.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► B. stearothermophilus spores were inactivated by TiO2/UV-A in aqueous suspensions. ► Surface modification of TiO2 by Ag and Pt enhanced the photocatalytic efficiency. ► Solar photocatalysis led to results similar to the ones under UV-A. ► Photocatalysis caused severe damage of the cell structure.