What is the purpose of using chloramines in drinking water treatment?

The use of chloramines in drinking water treatment primarily serves the purpose of providing longer-lasting disinfection as water travels through pipes to consumers. Chloramines, which are formed by combining chlorine with ammonia, have a more stable and persistent effect compared to free chlorine. This characteristic makes chloramines particularly valuable for maintaining disinfectant residual levels in the distribution system.

While immediate disinfection is typically the role of free chlorine, chloramines are preferred for ensuring that the water remains safe from microbiological contaminants during transport and storage. This extended effectiveness is crucial, especially in larger water systems where water may take longer to reach end users. Chloramines also help in protecting the quality of water by reducing the potential regrowth of pathogens in the distribution network.

In contrast, the other choices do not align with the primary benefits of chloramines. They are not specifically used to remove heavy metals, to instantly disinfect, or to reduce pH levels, making the choice regarding longer-lasting water treatment the most accurate and relevant.