Photocatalytic inactivation of E. faecalis in secondary wastewater plant effluents

Photocatalytic inactivation of Enterococcus faecalis using TiO₂ suspensions was investigated and compared to the inactivation of the most commonly used faecal indicator strain Escherichia coli. In contrast to the inactivation in pure deionized water, disinfection of effluents from the biological process of an urban wastewater plant showed a longer initial lag phase and higher survival fractions after several hours of irradiation. Moreover, the fluctuation of the composition of the effluents strongly affects the overall inactivation rate, not directly related to changes in the values of organic matter content. Additionally, it was found that E. faecalis seems to be more resistant than E.coli towards the photocatalytic treatment. These results could be related to the differences in the cell wall structure of both microorganisms. The main conclusion of this work is that attention must be paid when transferring results obtained for model organism to real bacteria consortia and from laboratory experiments with deionized water to effluents from sewage plants.