Which chlorine residual is required in the distribution system when using chloramines?

When using chloramines as a disinfectant in drinking water treatment systems, maintaining a chlorine residual of 0.5 mg/l in the distribution system is important for several reasons. Chloramines are a more stable form of chlorine that provide longer-lasting disinfection compared to free chlorine. However, they typically require a minimum residual concentration to ensure that disinfection persists throughout the distribution system.

A residual of 0.5 mg/l is effective in achieving adequate pathogen control while minimizing the formation of disinfection byproducts, which can occur with higher doses of free chlorine. This concentration strikes a balance between sufficient disinfection and the low chemical reactivity associated with chloramines. It is important for water utility operators to monitor and maintain this residual level as part of their water quality management practices to ensure safe drinking water is delivered to consumers.