Study of the effectiveness of microfiltration, solar disinfection, photocatalysis, and UV-C254 radiation on water contaminated by Legionella pneumophila

Abstract

Legionella are opportunistic pathogens in artificial water systems and can cause a severe form of pneumonia called Legionnaires’ disease (LD), which is fatal in 5–50% of cases when contaminated aerosols are inhaled. LD emerged in the last half of the 20th century. Global challenges such as urbanization, aging populations, climate change, water scarcity, and circular economy approaches have led to an increase in the number of complex water systems and thus LD cases, which are expected to rise to around 2.5 billion by 2050. LD is a preventable disease if adequate measures are taken to control Legionella in water systems. Chlorine treatment and heat treatment are the methods of choice to sanitize a Legionella-contaminated water system. However, these two methods are not always effective in ensuring that the treated water is free of Legionella and safe for consumption and use. Therefore, we proposed to evaluate the efficacy of microfiltration, solar disinfection, photocatalysis, and UV-C254 irradiation on Legionella-contaminated water. Microfiltration was performed using a membrane filtration cell (SODIS). Solar disinfection and photocatalysis were performed with an experimental table consisting of six 1 L beakers, 3 for solar disinfection and 3 for photocatalysis. UV-C254 disinfection was also tested with 3 1 L beakers. For all four methods tested, the percentage of Legionella removal was over 99.99. The four disinfection systems tested provided satisfactory results and ensured that the treated water was free of Legionella and safe for consumption and use.