UV pretreatment reduced biofouling of ultrafiltration and controlled opportunistic pathogens in secondary water supply systems

Secondary water supply systems (SWSSs) with low residual chlorine may pose a risk to consumers due to the regrowth of some pathogenic microbes. This study investigated how UV pretreatment would affect biofouling of UF membrane when it was used to remove opportunistic pathogens (OPs) in SWSSs. Our results indicated that UV pretreatment inactivated OPs effectively through OH. and O2.−, when residual chlorine was present in water from SWSSs. After UV-UF treatment, Legionella spp., Legionella pneumophila, Mycobacterium spp., and Acanthameoba spp. were undetected in the water. After UV pretreatment, the extracellular polymeric substances (EPS) production and associated β-sheet in the protein of EPS were reduced due to the inhibition of related functional genes. Foulant analysis indicated that biofilms formed on the UF membrane after UV pretreatment had visible crevices and small pores, a lower bacterial volumetric fraction and lower roughness than the untreated UF membrane. This structure improved the UF flux and reduced the biofouling. The transmembrane pressure (TMP) of UF membrane gradually decreased from 74 KPa to 60 KPa after 70 days running. Therefore, UV pretreatment could be used to reduce the potential microbial risk of water from SWSSs, and mitigate biofouling of UF membranes.