Chloramine

Chloramine refers to a family of chemical compounds containing nitrogen–chlorine bonds. The most common inorganic chloramines are monochloramine (NH2Cl), dichloramine (NHCl2), and trichloramine (NCl3). They form when ammonia or ammonium ions react with chlorine-based disinfectants, especially hypochlorous acid (HOCl), in water. In aqueous systems, HOCl oxidizes ammonia stepwise: NH3 + HOCl → NH2Cl + H2O; NH2Cl + HOCl → NHCl2 + H2O; NHCl2 + HOCl → NCl3 + H2O. The distribution among these species depends on pH, with monochloramine favored around neutral pH and more stable in drinking-water applications.

In practical use, monochloramine is employed as a disinfectant in drinking-water and wastewater treatment to provide a long-lasting residual and to reduce formation of some disinfection byproducts compared with free chlorine, such as chlorinated organics. It is slower to inactivate microorganisms but penetrates biofilms effectively. However, chloramines can produce other byproducts, and under certain conditions can generate N-nitrosodimethylamine (NDMA). In addition to inorganic chloramines, several organic chloramines are used as antiseptics or reagents (for example chloramine-T), but these are distinct from the inorganic chloramines used in water treatment.

Safety and handling: chloramines can irritate the eyes, skin, and respiratory tract at elevated concentrations, and exposure requires proper control measures. In the environment, chloramines tend to be less reactive with natural organic matter than free chlorine and gradually degrade to chloride.