Evaluation of the disinfection effect and mechanism of SO4•- and HO• in UV / persulfate salts from the perspective of VBNC bacteria

Abstract

Abstract Although ultraviolet (UV) and persulfate (PS) have been widely used in water disinfection process, their incompleteness of disinfection, such as inducing the production of viable but non-culturable cells (VBNC), has attracted extensive attention. In this study, the disinfection effect of combined UV and PS was evaluated from the perspective of inducing Pseudomonas aeruginosa into VBNC, and the roles of SO4•− and HO• radicals in UV/PS disinfection were also analyzed. UV/PS more effectively inactivated cells and reduced the number of culturable cells, but induced more VBNC cells. On the other hand, the test of bacterial dark activation suggested that UV/PS disinfection effectively prolongs the recovery time of VBNC cells. The mechanisms of UV/PS disinfection were the increase of membrane permeability and oxidative stress, where SO4•− radicals played more role than HO• radicals. Furthermore, UV/PS disinfection more significantly perturbed the metabolism of Pseudomonas aeruginosa (p < 0.05), mainly involving glyoxylate and dicarboxylic acid metabolism, aminoacyl-tRNA biosynthesis, Alanine, aspartate and glutamate metabolism, citric acid cycle (TCA cycle). This study, from the production and recovery of VBNC, provides a new idea for the evaluation of UV, persulfate and their combined disinfection effect, and provides guidance for improving disinfection process.