Formation of iodinated trihalomethanes during UV/chloramination with iodate as the iodine source

摘要

Iodinated trihalomethanes (I-THMs) are a group of emerging disinfection by-products with high toxicity, and iodide (I-) as well as iodinated organic compounds are expected to be their iodine sources. Nevertheless, in this study, iodate (IO3-) was proven to be a new iodine source of I-THM formation during UV/chloramination. In the iodate-containing waters (without any other iodine sources), I-THM formation increased with the increase of UV dose, IO3- and NH2Cl concentrations. With the increase of Br-/IO3- molar ratio, I-THM formation (especially for the brominated species) increased. Besides, NOM species could affect I-THM formation from IO3- during UV/chloramination. Fulvic acid could promote IO3- phototransformation to I- but humic acid impeded the production of I- during UV irradiation. Under realistic drinking water treatment conditions (DOC = 5.0 mg-C/L, IO3- = 12.7 mu g-I/L, UV dose = 50 mJ/cm(2), NH2Cl = 5 mg-Cl-2/L), CHCl2I was detected as 0.17 mu g/L using solid-phase microextraction method, and the production rate of I-THMs from IO3- was about 7% of that from I-. (C) 2016 Elsevier Ltd. All rights reserved.