Traditionally, wastewater, which contains ammonia, is disinfected by the addition of chlorine. This reaction of chlorine with ammonia produces a mixture of chloramines, monochloramine (NH2Cl), dichloramine (NHCl2), and trichloramine (NCl3), depending on reactant concentrations and conditions. This is advantageous as chloramines have a longer retention time and produce less toxic byproducts, and they also have the advantage of reducing biofouling of membranes in the treatment train. However, with Advanced Oxidation Processes (AOPs) being increasingly considered for the polishing treatment of wastewater for recycling options, it is important to understand the chemistry of chloramines with AOP radicals, particularly the hydroxyl radical, under all anticipated treatment conditions. In this study we have determined the absolute temperature-dependent kinetics for hydroxyl radical reaction with these three chloramines in aqueous solution as well as identifying the radical products (●NHCl, ●NCl2 and Cl●) of these reactions. Preliminary data on the additional reactivity of these product radicals will also be reported. The measured kinetics demonstrates that the overall AOP efficiency could be reduced in the presence of chloramines.

Kinetics of hydroxyl radical reactions with chloramines in support of recycling wastewater

249th National Meeting (2015)

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