At lower water temperatures, how does the kill rate for chlorination change?

At lower water temperatures, the kill rate for chlorination is indeed lower, necessitating increased residuals to achieve effective disinfection. This is primarily because the effectiveness of chlorination is influenced by temperature; as the temperature decreases, the reaction rate of chlorine with pathogens also slows down. Consequently, to compensate for the reduced efficiency in killing microorganisms, water treatment facilities need to maintain higher levels of chlorine residuals to ensure adequate disinfection.

By increasing the chlorine concentration, they can offset the slower reaction rates in cooler water, allowing for the same level of microbial inactivation that would be achieved at higher temperatures. Thus, the necessity for increased residuals at lower temperatures is a crucial consideration in water treatment processes to ensure public health safety.