What constitutes Free Chlorine?

Free chlorine refers specifically to the concentration of residual chlorine in water that is available for disinfection purposes. This includes chlorine in its molecular (Cl2) or hypochlorous acid (HOCl) form, which effectively kills bacteria and other pathogens in water. The presence of free chlorine is essential in water treatment processes as it ensures that harmful microorganisms are eradicated and helps to maintain water quality during distribution.

In the context of water treatment, free chlorine is distinct from combined chlorine, which consists of chloramines formed when chlorine reacts with ammonia or organic nitrogen compounds. The measurement of free chlorine is critical because it indicates the disinfection capacity of the water and helps operators ensure that the levels are appropriate for maintaining safe drinking water standards.