Disinfection Breakpoint Chlorination

What is breakpoint chlorination?

The breakpoint chlorination is the point where chlorine levels exceed the oxidant demand (neutralising the nasties in the water). Once they are all dealt with, the water begins to build a residual amount of free available chlorine (FAC). In theory, after exceeding the “breakpoint” the extra chlorine prevents increased levels of disinfectant by-products (like chloramines) in the water.

• Trihalomethanes (THMs). When chlorine used for disinfecting tap water and natural organic matter in the water the initial result of a reaction are Trihalomethanes.
• Monochloramine often called simply chloramine.
• Disinfectants Chloramines are formed during a reaction between chlorine (Cl₂) and ammonia (NH₃). Chloramines are amines that contain at least one chlorine atom, which can directly bond to nitrogen atoms (N). Inorganic chloramines are formed when dissolved chlorine and ammonia react. During this reaction three different inorganic chloramines are formed; monochloramine (NH₂Cl), dichloramine (NHCl₂) and trichloramine (NCl₃).

Inorganic chloramines, free chlorine and organic chloramines are chemically related and can change into each other freely (easily). These compounds cannot be found in isolated form. Inorganic chloramines are not persistent, however, these compounds are more persistent than freely available chlorine compounds. Research has shown that the half-lives of inorganic chloramines can vary from one minute to 23 days, depending on the circumstances.

What the disinfect breakpoint is in water chlorination.

From the American Water College, this video explains what the disinfect breakpoint is in water chlorination.

Learn about breakpoint chlorination and what happens when chlorine is added to water for disinfection purposes.