Farm-to-Tap Water Treatment: Naturally-Sourced Photosensitizers for Enhanced Solar Disinfection of Drinking Water

Universal access to basic drinking water services remains elusive, especially for rural communities of low- and lower-middle income countries where financial constraints restrict the implementation of existing drinking water development approaches. With the need for cheaper and more accessible point-of-use water treatment technologies, this study proposes a near-zero cost modification for solar disinfection (SODIS) using a suite of natural, plant-sourced photosensitizers to produce singlet oxygen and accelerate microbial inactivation under simulated sunlight. Chlorophyll, curcumin, and Saint John's Wort extract are applied with edible dispersants, enhancing the inactivation of bacteriophage MS2, a human enteric virus surrogate. Chlorophyll exhibited the most dramatic enhancement, increasing the disinfection rate up to 180 times that of SODIS alone. The potential for this approach to be successfully applied in different geographic regions was evaluated using the experimentally obtained disinfection kinetics and annual average daytime surface sunlight intensity data across the globe. The findings suggest that locally sourced natural photosensitizers and dispersants (e.g., chlorophyll extracted from alfalfa and saponin extracted from quinoa husks) can be a particularly useful point-of-use water disinfection technology for rural regions of low- and lower-middle income countries that have been previously underserved by safe water initiatives.