The concentration of residual chlorine which is combined with ammonia (NH3) and/or organic nitrogen in water as a chloramine (or other chloro derivative) yet is still available to oxidize organic matter and utilize its bactericidal properties.
COMBINED AVAILABLE RESIDUAL CHLORINE
Meaning of COMBINED AVAILABLE RESIDUAL CHLORINE in English
Environmental engineering English vocabulary. Английский словарь экологического инжиниринга. 2012