Chlorination and chloramination are widely used in drinking water disinfection. These disinfection processes successfully protect human beings from pathogen contamination in drinking waters, but they may produce unintended halogenated disinfection byproducts (DBPs) due to the reactions of disinfectants with natural organic matter (NOM), bromide, and iodide in source waters. Because it is unlikely to identify all halogenated DBPs, to synthesize corresponding standards and quantify each of them, the formation of overall halogenated DBPs in chlorination and chloramination was investigated. A collective parameter, total organic halogen (TOX), can be used to indicate all halogenated DBPs in a disinfected water sample. TOX can be differentiated into halogen-specific components, i.e., total organic chlorine (TOCl), total organic bromine (TOBr) and total organic iodine (TOI). In this work, the formation of TOCl, TOBr, and TOI during chlorination and chloramination was kinetically modeled. According to the modeling results, hypobromous acid and hypoiodous acid were approximately 10 and 100 times, respectively, more reactive than hypochlorous acid in substitution reactions with NOM to form halogen-specific TOX. Chlorine residual (mainly including hypochlorous and hypobromous acids) might cause the decomposition of certain halogenated DBPs during the chlorination. In chloramination, >98% TOCl and >97% TOBr came from the reactions of monochloramine/monobromamine and NOM. Due to the lack of iodamines, hypoiodous acid was the only iodine species for TOI formation. Meanwhile, <20% of iodide was transformed to some unknown products.

Formation and kinetics of TOCl, TOBr and TOI during chlorination and chloramination

248th National Meeting (2014)

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