Reactive Nitrogen Species Mediated Inactivation of Pathogenic Microorganisms during UVA Photolysis of Nitrite at Surface Water Levels

摘要

UVA photolysis of nitrite(NO2) occurs in a number of natural and engineered aquatic systems.This study reports for the first time that pathogenic microorganisms can be effectively inactivated during the coexposure of UVA irradiation and NO_2~-under environmentally relevant conditions.The results demonstrated that more than 3 log inactivation of Escherichia coli K-12,Staphylococcus aureus,and Spingopyxis sp.BM1-1 was achieved by UVA photolysis of 2.0 mg-N L~(-1) of NO_2~-in synthetic drinking water and real surface water.The inactivation was mainly attributed to the reactive species generated from UVA photolysis of NO_2~-rather than UVA irradiation or NO_2~-oxidation alone.The inactivation was predominantly contributed by the reactive nitrogen species(NO2· and ONOO~-/HOONO) instead of the reactive oxygen species(HO· or O_2~(·-)).A kinetic model to simulate the reactive species generation from UVA photolysis of NO_2~-was established,validated,and used to predict the contributions of different reactive species to the inactivation under various environmental conditions.Several advanced tools(e.g.,D2O-labeling with Raman spectroscopy) were used to demonstrate that the inactivation by the UVA/NO_2~-treatment was attributed to the DNA destruction by the reactive nitrogen species,which completely suppressed the viable but nonculturable(VBNC) states and the reactivation of bacteria.This study highlights a novel process for the inactivation of pathogenic microorganisms in water and emphasizes the critical role of reactive nitrogen species in water disinfection and purification.