What happens to trihalomethane levels when water stays in the distribution system longer?

Trihalomethanes (THMs) are a group of organic compounds that can form when chlorine or other disinfectants used in water treatment react with natural organic matter present in the water. When water is stored in a distribution system for an extended period, several factors lead to the potential increase of THM levels.

As water sits in the distribution system, it experiences various physical and chemical changes. First, the contact time between chlorine and organic materials increases, resulting in more opportunities for the formation of THMs. Additionally, the water temperature may rise, and microbial activity may also alter the chemical balance, further promoting the synthesis of these compounds.

The presence of THMs is associated with longer water retention times, as the continued disinfection process can lead to further reactions, increasing the concentration of these byproducts in the water supply. Therefore, the longer water remains in the distribution system, the more likely THM levels will increase due to these chemical reactions and conditions.

In summary, prolonged contact time in the distribution system provides the necessary conditions for enhanced THM formation, leading to increased levels of these compounds in the water supply.