The increased water utility disinfection of wastewater using chloramines instead of free chlorine is due to the advantageous behavior of chloramines in the wastewater stream, including a longer retention time and reduced production of deleterious disinfection by-products. Chloramination is achieved by the in situ reaction of ammonia and added free chlorine to form a mixture of monochloramine (NH2Cl), dichloramine (NHCl2), and trichloramine (NCl3), with each present in proportions that depend on initial reactant concentrations and mixing conditions. For facilities that incorporate an advanced oxidation processes (AOP) as a final polishing step, the behavior of the chloramine residual under AOP conditions is of particular interest. In this study the absolute temperature-dependent kinetics for hydrogen peroxide reaction with these three chloramines in aqueous solution have been determined. Also, the pH-dependent quantum yields for the photolysis of each of these chloramine species have been measured at room temperature. The measured kinetics and quantum yields demonstrate that the overall AOP efficiency could be significantly reduced due to the presence of chloramines.

Chloramine chemistry in AOP treated wastewaters

253rd National Meeting (2017)

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