Emerging micropollutant oxidation during disinfection processes using UV-C, UV-C/H2O2, UV-A/TiO2 and UV-A/TiO2/H2O2

Regeneration of wastewater treatment plant effluents constitutes a solution to increase the availability of water resources in arid regions. Water reuse legislation imposes an exhaustive control of the microbiological quality of water in the operation of disinfection tertiary treatments. Additionally, recent reports have paid increasing attention to emerging micropollutants with potential biological effects even at trace level concentration. This work focuses on the evaluation of several photochemical technologies as disinfection processes with the aim of simultaneously achieving bacterial inactivation and oxidation of pharmaceuticals as examples of emerging micropollutants typically present in water and widely studied in the literature. UV-C-based processes show a high efficiency to inactivate bacteria. However, the bacterial damages are reversible and only when using H2O2, bacterial reproduction is affected. Moreover, a complete elimination of pharmaceutical compounds was not achieved at the end of the inactivation process. In contrast, UV-A/TiO2 required a longer irradiation time to inactivate bacteria but pharmaceuticals were completely removed along the process. In addition, its oxidation mechanism, based on hydroxyl radicals (OH), leads to irreversible bacterial damages, not requiring of chemicals to avoid bacterial regrowth. For UV-A/TiO2/H2O2 process, the addition of H2O2 improved Escherichia coli inactivation since the cell wall weakening, due to OH attacks, allowed H2O2 to diffuse into the bacteria. However, a total elimination of the pharmaceuticals was not achieved during the inactivation process. [Display omitted] ► UV-C leads to a fast disinfection but negligible degradation of micropollutants. ► UV-A/TiO2 disinfection allows the simultaneous oxidation of micropollutants. ► Inactivation of bacteria with UV-C is reversible during dark storage of water. ► UV-A/TiO2 leads to the irreversible inactivation of bacteria. ► Addition of H2O2 improves both UV-C and UV-A/TiO2 processes.