When chlorine is used in water treatment, what form is the effective disinfectant?

The effective disinfectant form of chlorine in water treatment is hypochlorous acid, represented as HOCl. When chlorine gas (Cl₂) is added to water, it reacts with water to form hypochlorous acid and hydrochloric acid. Hypochlorous acid is a highly effective disinfectant due to its strong oxidative properties, allowing it to effectively inactivate bacteria, viruses, and other pathogens present in the water.

It's important to note that while chlorine gas and sodium chloride (NaCl) are related to the chlorination process, they do not serve as the active disinfecting agent in water treatment. Sodium chloride is simply table salt and does not have disinfecting properties on its own in this context. Water (H₂O) is the solvent in which these reactions take place but is not a disinfectant. Thus, hypochlorous acid becomes the key component in achieving effective disinfection when chlorine is applied in water treatment systems.