title: Effects of combined UV and chlorine treatment on chloroform formation from triclosan.
abstract: The co-exposure to UV irradiation and free chlorine may occur in certain drinking water and wastewater treatment systems. This study investigated the effects of simultaneous low pressure ultraviolet (LPUV) irradiation and free chlorination on the formation of chloroform from triclosan which is a commonly used antibacterial agent. Different treatment systems (i.e., combined UV/chlorine, UV alone, and chlorine alone) were applied to examine the degradation of triclosan and formation of chloroform. The fate of representative intermediates, including chlorinated triclosan, dechlorinated triclosan intermediates and 2,4-dichlorophenol, were tracked to deduce the effect of combined UV/chlorine on the transformation of chloroform formation precursors. The relation between intermediates degradation and chloroform formation was investigated in depth by conducting stepwise experiments with UV and chlorine in different sequences. Results indicate that the combined UV/chlorine notably enhanced the chloroform formation from triclosan. From the reaction mechanism perspective the combined UV/chlorine, where the direct photolysis may play an important role, could accelerate the decay of intermediates and facilitate the generation of productive chloroform precursors. The radicals had modest influence on the degradation of triclosan and intermediates and partly hindered the formation of chloroform. These results emphasize the necessity of considering disinfection by-products formation in the application of combined UV/chlorine technology during water treatment.
authors.affiliation: Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, People's Republic of China; School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta 30332, GA, United States.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Ben
authors.affiliation: School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta 30332, GA, United States.
authors.forename: Peizhe
authors.initials: P
authors.lastname: Sun
authors.affiliation: School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta 30332, GA, United States. Electronic address: ching-hua.huang@ce.gatech.edu.
authors.forename: Ching-Hua
authors.initials: CH
authors.lastname: Huang
mesh_terms: D002713:Chlorine / Q000737:chemistry*; D002725:Chloroform / Q000737:chemistry*; D054879:Halogenation; D010782:Photolysis; D014260:Triclosan / Q000737:chemistry*; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D014874:Water Pollutants, Chemical; D014260:Triclosan; D002713:Chlorine; D002725:Chloroform
keywords: Chlorination; Chloroform; Disinfection by-products; Triclosan; UV treatment