Inactivation of four genera of dominant fungal spores in groundwater using UV and UV/PMS: Efficiency and mechanisms

- The UV resistance is in order: Cladosporium sp. > Penicillium sp. > Acremonium sp. > Trichoderma sp. > E. coli.
- UV/PMS exhibits higher inactivation efficiency compared to that of UV alone in both PBS and actual groundwater.
- UV/PMS inactivates fungal spores by damaging the cell membrane due to the function of reactive radicals.

Outbreaks of fungi in groundwater sources of drinking water can produce taste and odor problems, and cause ill health in immunocompromised individuals. The groundwater treatment process is simple; generally, only disinfection is used in China. Efficient disinfection methods to control fungi are required. In the present study, we investigated the inactivation efficiency of 4 dominant genera of fungal spores (a Trichoderma sp., Acremonium sp., Penicillium sp., and Cladosporium sp.) using ultraviolet irradiation (UV) and UV-based advanced oxidation processes, and explored the mechanisms of inactivation by monitoring the leakage of intracellular contents and changes in spore morphology. The inactivation of fungal spores is consistent with first-order Chick-Watson kinetics. The resistance of each of the fungi to UV (Cladosporium sp. > Penicillium sp. > Acremonium sp. > Trichoderma sp.) was greater than that of E. coli, due to their larger sizes and more complex structures. UV/peroxymonosulfate (UV/PMS) treatment had a markedly better inactivation rate constant than UV alone. Furthermore, UV/PMS exhibited similar effects on fungal inactivation in phosphate buffer and in groundwater, whereas UV inactivation efficiency markedly decreased in groundwater. UV/PMS treatment resulted in cell wall and cell membrane damage, the leakage of intracellular contents, and the shriveling of fungal spores, due to the reactive radicals produced by the treatment. Thus, UV/PMS is a promising method to control fungi in drinking water sources.

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