bound chlorine : chloramines

Chloramines are only used in disinfection (see the oxidants and disinfectants). They are prepared on site through the reaction of chlorine with ammonia or ammonia salts.

Compared with monochloramines, chlorine at a pH lower or equal than 7 is 200, 50 and 2.5 times more active for the inactivation bacteria, viruses, spores and cysts respectively (table 3).

Therefore, chloramines are not used in primary disinfection. However, they are used in the following secondary disinfection cases because of their high remanence:

• high levels of THM precursors in treated water, prohibiting the use of chlorine;
• extensive networks with high temperatures and contact times;
• lined pipes creating an unpleasant taste when chlorine is used.

Chloramines have become increasingly widespread in the USA (public accustomed to the taste of chlorine).