Sequential UV and chlorine disinfection induced change of biofilm-originated disinfection byproducts formation potential in drinking water distribution system: Effect of UV dose and influencing mechanism

Abstract

To address the growing concern on biofilm-related disinfection byproducts (DBPs) formation in drinking water distribution system (DWDS), this study investigated the changes of biofilm-originated DBPs formation potential (bio-ori-DBPFP) in simulated continuous-flow DWDS under the impact of sequential UV and chlorine disinfection (UV/Cl2) under different UV doses and discussed the involved influencing mechanism. Overall, the bio-ori-DBPFP of pipeline following UV/Cl2 showed a more obvious change than that of pipeline following Cl2 (UV dose of 0 mJ/cm2). UV/Cl2 disinfection at UV dose of 80 mJ/cm2 produced pipeline biofilm with the minimum bio-ori-DBPFP as well as the lowest amount of protein and polysaccharide in extracellular polymeric substance (EPS). Bacterial community composition characterization together with metabolic function analysis indicated that dominant bacteria varied and metabolic function shifted due to UV/Cl2 disinfection. The correlation analysis suggested that UV/Cl2 disinfection induced a change in water matrix including organics, inorganics, bacteria, and components providing oxidation pressure for biofilm. These changed factors finally influenced the properties of biofilm EPS, which directly correlated with bio-ori-DBPFP.