What dosage is required if the chlorine demand is 2.3 mg/l and the desired chlorine residual is 0.2 mg/l?

To determine the required dosage of chlorine, you need to combine the chlorine demand with the desired residual. The chlorine demand represents the amount of chlorine that will be consumed to react with impurities in the water, while the desired chlorine residual is the amount you want to remain after this reaction to ensure adequate disinfection.

In this scenario, the chlorine demand is 2.3 mg/l and the desired chlorine residual is 0.2 mg/l. When you sum these two figures, you find the total chlorine dosage needed:

• Chlorine Demand: 2.3 mg/l

• Desired Chlorine Residual: 0.2 mg/l

This gives a total dosage requirement of:

2.3 mg/l + 0.2 mg/l = 2.5 mg/l

Thus, the correct dosage required to meet the chlorine demand and achieve the desired residual is 2.5 mg/l. This ensures that the chlorine added will not only satisfy the demand but will also leave a sufficient residual to protect against potential pathogens in the water supply.