Which of the following is a characteristic of combined residual chlorine?

Combined residual chlorine refers to the chlorine that has reacted with ammonia and other nitrogen-containing compounds in water, resulting in the formation of chloramines. This form of chlorine is generally less effective as a disinfectant compared to free residual chlorine, which is the chlorine that is available to react with pathogens in the water.

One of the main reasons combined residual chlorine is considered less effective is that chloramines, while they do provide some level of disinfection, are not as powerful as the free chlorine species. Free residual chlorine can more effectively kill bacteria, viruses, and other pathogens in a shorter period of time, which is crucial for maintaining water quality. Although combined chlorine can help maintain residual levels in water distribution systems and is less prone to rapid depletion than free chlorine, its overall disinfection capability is inferior.

Understanding this distinction is vital for water treatment operations, particularly when determining the appropriate methods and levels of chlorine to ensure effective disinfection while maintaining water quality throughout distribution systems.