In the chlorination process, what term refers to the point where the addition of more chlorine produces free residual chlorine?

In the chlorination process, the term "breakpoint" refers to the specific point at which the addition of chlorine results in a measurable level of free residual chlorine in the water. This concept is essential in water treatment because it signifies that all combined chlorine (chloramines) has been oxidized or reacted with organic and inorganic materials present in the water, and any additional chlorine added beyond this point will contribute to the free residual chlorine.

At the breakpoint, the water treatment operator can achieve effective disinfection, as free chlorine is the form that actively kills pathogens. This threshold is critical for ensuring safe drinking water, making it vital for operators to know where this breakpoint occurs in their specific treatment processes. Understanding the chlorine demand of the water being treated and the characteristics of various contaminants allows operators to manage chlorination effectively and ensure adequate disinfection without adding excessive chlorine, which could lead to undesirable taste or formation of harmful byproducts.