What is the primary purpose of a residual disinfectant in a water distribution system?

The primary purpose of a residual disinfectant in a water distribution system is to reduce the growth of biofilms and normally non-pathogenic microorganisms. Residual disinfectants, such as chlorine or chloramines, are used to maintain a certain level of disinfection throughout the distribution system. This ensures that any pathogens or microorganisms that remain in the water after treatment are killed or inhibited, ultimately protecting the public health by preventing waterborne diseases.

Maintaining a residual disinfectant also helps control the formation of biofilms, which are communities of microorganisms that can form on the surfaces of pipes and other water infrastructure. These biofilms not only harbor potentially harmful pathogens but can also contribute to taste and odor issues in the water supply. Therefore, the presence of a residual disinfectant is crucial for the safety and quality of drinking water delivered to consumers.