Solar disinfection is an augmentable, in situ-generated photo-Fenton reaction—Part 1: A review of the mechanisms and the fundamental aspects of the process

The present manuscript is a conceptual review concerning the photo-Fenton reaction at near-neutral pH,used for bacterial inactivation. In this first Part, an overview of the mechanisms involved, as well as thefundamental concepts governing the near-neutral photo-Fenton reaction are critically assessed. The twoconstituents of the process, namely solar light and the Fenton reagents, are dissociated, with their directand indirect actions thoroughly analyzed. The effects of UVB and UVA on the bacterial cell are firstlydiscussed, followed by the presentation of the indirect oxidative stress-related inactivation mechanismsinitiated into the microorganism, in presence of light. Afterwards, the effect of each Fenton reagent (H2O2,Fe) is analyzed in a step-wise manner, with H2O2 and Fe as enhancements of the solar disinfection mode ofaction. This approach proves that in fact, the solar photo-Fenton reaction is an enhanced solar disinfectionprocess. Finally, the photo-Fenton reaction is put into context by considering the possible interactionsof the separate parts of the combined process with the constituents of the natural environment that canplay an important role in the evolution of the bacterial inactivation.