What is an example of a secondary disinfectant commonly used in water distribution?

Chloramine is a commonly used secondary disinfectant in water distribution systems. It is formed by the reaction of chlorine with ammonia and provides a longer-lasting disinfectant residual compared to chlorine alone. This characteristic is particularly valuable in large distribution systems where it helps to maintain disinfection throughout the pipeline network, preventing microbial growth and ensuring the water remains safe for consumption.

Secondary disinfectants like chloramine are beneficial because they do not produce the same harmful disinfection byproducts that can occur with primary disinfectants such as chlorine when used alone. This makes chloramine a favorable choice for water utilities seeking to optimize water quality while minimizing health risks to consumers.

Other options include disinfectants typically used for primary purposes or in specific scenarios, such as chlorine gas and ozone, which serve different roles in water treatment processes. These are less suitable for maintaining long-term residuals in distribution systems, highlighting the unique advantages of using chloramine as a secondary disinfectant.