What is breakpoint chlorination?

Breakpoint chlorination refers to the process of adding chlorine to water until all combined chlorine compounds are oxidized and only free chlorine remains in the solution. This process is crucial for effective disinfection, as it ensures that the chlorine present in the water is available to kill pathogens rather than being bound to organic material or other contaminants.

When breakpoint chlorination is achieved, it indicates that the chlorine level has exceeded the amount needed to react with the contaminants, meaning that all chloramines and other combined chlorine forms have been broken down. The result is an increase in the concentration of free chlorine, which is the active form effective in disinfecting the water.

While the other options touch on related aspects of chlorine usage in water treatment, they do not accurately define the breakpoint concept. For example, while it may seem like the point where all chlorine is consumed implies some form of effectiveness, this does not capture the essence of breakpoint chlorination and its goal of maximizing free chlorine. The stage of high free chlorine after breaking down combined forms is what truly represents breakpoint chlorination.