Which type of chlorine is considered bound?

Bound chlorine, often referred to as combined chlorine, is formed when chlorine reacts with organic substances in water, such as ammonia, nitrogenous compounds, and other contaminants. This reaction results in chloramines, which are less effective as disinfectants compared to free chlorine. When evaluating water treatment processes, understanding the difference between free and combined chlorine is essential, as free chlorine (unreacted chlorine) is the portion available to kill pathogens, whereas combined chlorine indicates the presence of forms that have already reacted with contaminants and are not as effective for disinfection.

Total chlorine is a measurement that includes both free and combined chlorine, thus it does not specifically refer to one type. Residual chlorine refers to the amount of chlorine remaining in the water after the disinfection process, but again, it encompasses both free and combined forms. Recognizing that combined chlorine specifically refers to the chlorine that is bound to other molecules helps identify its role in water treatment and the need for monitoring and possibly reducing its levels to maintain effective disinfection.