What are combined residual chlorine compounds?

Combined residual chlorine compounds refer specifically to the chloramines formed when chlorine reacts with ammonia in water treatment processes. The correct answer highlights that monochloramine, dichloramine, and trichloramine are derivatives created through this reaction.

Monochloramine is formed when one chlorine atom combines with ammonia, while dichloramine and trichloramine result from the further addition of chlorine atoms to the ammonia. These compounds are considered combined residuals because, unlike free residual chlorine (which consists primarily of molecular chlorine and hypochlorous acid), they are not readily available to sanitize water since they are stabilized complexes that contribute to disinfection by controlling microbial growth while causing less taste and odor issues compared to free chlorine.

Understanding the nature of combined residuals is crucial for water operators, as these compounds play a significant role in maintaining the chlorine residual needed for effective and safe drinking water without producing undesired byproducts.