What does chlorine residual refer to?

Chlorine residual refers to the amount of chlorine that remains in the water after it has been added for disinfection purposes. This residual is essential for maintaining water quality, as it indicates that there is still enough chlorine present to continue effectively disinfecting the water and preventing the growth of harmful microorganisms.

The measurement of chlorine residual provides important information about the effectiveness of the chlorination process and helps ensure that the pool is safe for swimmers. A properly maintained chlorine residual is crucial for effective sanitation and aids in identifying whether more chlorine needs to be added to the pool to maintain safe levels.

In contrast, the other options deal with different aspects that do not accurately describe chlorine residual. For example, simply adding chlorine to the pool does not reflect its ongoing presence or effectiveness. The total volume of chlorine in the water does not specifically denote what remains after it has been utilized. Lastly, noting the percentage of chlorine lost to evaporation does not provide a measure of the residual influence necessary for ongoing disinfection.