What type of disinfection is known as secondary disinfection in water treatment?

Secondary disinfection refers to the process used to maintain a residual disinfectant in the distribution system after the primary disinfection has occurred. Chloramine treatment is considered a secondary disinfection method because it provides a longer-lasting residual effect in the water supply compared to chlorine alone.

Chloramines are formed by combining chlorine with ammonia, which helps to reduce the formation of disinfection byproducts while still ensuring that harmful microorganisms are effectively controlled as the water moves through the distribution system. This is especially important for maintaining water quality over longer distances and during storage in tanks where water may be stagnant.

While direct chlorination is typically used for primary disinfection due to its immediate effectiveness, and breakpoint chlorination is a technique used during the chlorination process to ensure the complete reaction with ammonia, they do not fit the definition of secondary disinfection. Ozonation is also a powerful treatment method primarily used for primary disinfection rather than maintaining a residual disinfectant. Thus, chloramine treatment stands out as the method that successfully fulfills the role of secondary disinfection within water treatment processes.