What does terminal disinfection (postchlorination) involve?

Terminal disinfection, also known as postchlorination, specifically involves the application of chlorine to treated water before it enters the distribution system. This step is crucial as it serves to eliminate any remaining pathogens that may have survived the primary treatment processes and to ensure that the water remains safe for human consumption throughout its distribution.

Chlorine is used for this purpose because it is an effective disinfectant that can kill bacteria, viruses, and other microorganisms that pose health risks. By applying chlorine after the treatment process, water operators can achieve a residual level of disinfectant that continues to protect the water quality until it reaches consumers.

In contrast, applying chlorine to untreated water is part of the initial disinfection process rather than terminal disinfection, while blending chlorine with lime relates to adjusting pH levels and not specifically to disinfection. Neutralization of chlorine in the distribution system is a method used to reduce chlorine levels to comply with regulations or to address taste and odor concerns, but it does not fulfill the function of terminal disinfection.