chloraminering

Chloramination, also called chloraminating, is a method of disinfecting drinking water by forming chloramines through the controlled reaction of chlorine with ammonia or ammonium. The process is used by many municipal water systems to provide a longer-lasting disinfectant residual in the distribution network and to reduce formation of certain disinfection byproducts, such as trihalomethanes and haloacetic acids, that tend to form with free chlorine.

The chemistry involves dosing chlorine to react with an added ammonia source in a controlled sequence and under careful pH and temperature conditions to favor monochloramine formation. The goal is to produce predominantly monochloramine (NH2Cl) rather than dichloramine or trichloramine, which can be more irritating and less stable. Typical operating parameters aim for a chlorine-to-ammonia ratio that promotes monochloramine, a near-neutral pH, and moderate temperatures. The chloramine residual is then maintained in the distribution system by ongoing dosing and monitoring.

Advantages of chloramination include a more persistent residual disinfectant in large or extended networks and reduced formation of certain disinfection byproducts compared with free chlorine. It can also improve taste and odor stability in many systems. Disadvantages include the potential for reduced disinfection power against some pathogens, the risk of nitrification if ammonia accumulates, and the need for careful management of ammonia and chlorine dosing. Chloramines can be toxic to fish and certain aquatic life, and water intended for aquariums or sensitive applications may require dechlorination.

Monitoring is essential, including residual chloramine levels, pH, temperature, and indicators of nitrification, to ensure safe and effective operation.