What does a chlorine residual measure represent?

A chlorine residual measure represents the amount of chlorine that remains in the water after the treatment process. This measurement is critical because it indicates the effectiveness of the disinfection process. Chlorine is widely used to eliminate harmful microorganisms in water supplies, and measuring the residual ensures that there is enough chlorine left in the water to continue providing protection as it travels through the distribution system.

Moreover, maintaining an appropriate chlorine residual is essential for ensuring water safety up to the point of use. If the residual is too low, it could mean that the water is no longer adequately disinfected, raising concerns about potential microbial contamination. On the other hand, options related to the total volume of chlorine compounds or the concentration of total hardness do not align with what chlorine residual measures, as they describe different characteristics of water quality unrelated to chlorine disinfection.