Flower Pollen-Based Photosensitization Process for Enhanced Solar Disinfection of Drinking Water: Reactor Design and Inactivation Mechanisms

Solar disinfection (SODIS) is a chemical-free, low-cost, and user-friendly approach to achieving Sustainable Development Goal No. 6 (SDG 6). Herein, a natural flower pollen-based photosensitizer was fabricated in a facile way and used to enhance the conventional SODIS process. Complete inactivation of five biohazards (Escherichia coli K-12, Spingopyxis sp. BM1-1, Bacillus subtilis spores, Enterococcus faecalis, and tetracycline-resistant E. coli) at their culturable or viable but nonculturable states was achieved by both batch reactors and a flow-through reactor with a standing separation–recycling system. Herein, microorganisms adhered to the photosensitizer’s surface due to electrostatic attraction and topological interactions. The photosensitizer induced the localized heating effect under solar irradiation, and a portion of microorganisms was inactivated by the photothermal effect. Meanwhile, abundant reactive species (•OH and 1O2) were generated and contributed to the photocatalytic inactivation of microorganisms. Synergism between the photothermal and photocatalytic processes enhanced the destruction of cell membranes and the penetration of reactive species. A comprehensive inactivation pathway was proposed and verified. The findings suggested that the natural flower pollen-based photosensitization process is promising to enhance the SODIS for effective disinfection, which assists rural and underdeveloped areas in achieving SDG 6.