If the chlorine residual is measured at 0.6 mg/L and 6.6 mg/L has been applied, what is the chlorine demand?

To calculate chlorine demand, you subtract the chlorine residual from the amount of chlorine that was applied. The chlorine residual measures the amount of chlorine left in the water after some of it has reacted with substances in the water, while the applied amount reflects the total chlorine added.

In this scenario, 6.6 mg/L of chlorine has been applied, and the measured chlorine residual is 0.6 mg/L. Thus, the chlorine demand is calculated as follows:

Chlorine Demand = Applied Chlorine - Chlorine Residual

Chlorine Demand = 6.6 mg/L - 0.6 mg/L

Chlorine Demand = 6.0 mg/L

Therefore, the chlorine demand is 6.0 mg/L. This indicates how much chlorine has reacted with materials in the water, which is essential in assessing water treatment efficiency and ensuring adequate disinfection levels. Understanding chlorine demand is vital for water quality management, as it helps determine the proper amount of chlorine needed to maintain effective disinfection while ensuring safety for the water supply.