Moura – (Queensland) – Chloramine
2014 Oct-Dec: Moura WTP (Queensland) Chloramine 58mg/L
Monochloramine is used as a disinfectant for drinking water supplies. It is increasingly being used in conjunction with chlorine, or in its own right, to provide primary disinfection of drinking water entering the distribution system and/or maintain a disinfectant residual through the distribution network. Although it is not as strong an oxidant as chlorine, monochloramine can be quite useful and effective in distribution systems with long water ages as it persists for longer. Where monochloramine is used overseas, concentrations typically range from 1.5 to 2.5 mg/L (as Cl2).
Use of monochloramine for primary disinfection at the treatment facility needs to be considered carefully in terms of the range of C.t (disinfectant concentration × contact time) values achievable prior to the first customer.
Use of monochloramine can significantly reduce the level of disinfection by-products compared to that produced by similar levels of chlorine. If not managed proactively, however, use of chloramine can lead to nitrification in the distribution system resulting in a reduction of its effectiveness.
Monochloramine is formed by the addition of ammonia and chlorine in drinking water. This reaction can also result in the formation of dichloramine and trichloramine, both of which have lower taste and odour thresholds than monochloramine, and which should be minimised. The preferential formation of monochloramine is affected by the pH and the physical arrangements of adding the two chemicals.
Monochloramine has an odour threshold of 0.5 mg/L.