How is the chlorine dose calculated?

The calculation of chlorine dose is based on understanding both the chlorine residual and the chlorine demand of the water being treated. Chlorine demand refers to the quantity of chlorine that is needed to react with substances in the water, such as organic matter, bacteria, and other contaminants. The chlorine residual represents the amount of chlorine that remains after these reactions have taken place.

To effectively achieve a desired level of disinfection, the total chlorine dose must overcome the chlorine demand and still leave an adequate residual. Therefore, by adding the chlorine residual to the chlorine demand, you arrive at the total chlorine dose required to ensure that sufficient disinfectant is present in the water to meet treatment objectives. This ensures that after accounting for the demand of the water, there is still a necessary residual available for effective disinfection throughout the distribution system.