Definition - What does Chlorine Demand mean?
Chlorine demand is the difference between total chlorine added in the water and residual chlorine. It is the amount which reacts with the substances in water, leaving behind an inactive form of chlorine. Chlorine demand can be caused in a water body due to rain containing ammonia or the addition of fertilizers which can be oxidized by chlorine.
Corrosionpedia explains Chlorine Demand
To purify water supplies and make them suitable for purposes like drinking, cooking and swimming, chlorine is added. Chlorine demand from the total chlorine added can be explained using the following equation:
- Chlorine demand = Total chlorine – Chlorine residual
The purity of water can be determined by monitoring the value of chlorine demand. If the value is zero, the water is already free of pathogenic microorganisms. If the value is less than the total chlorine, it shows that the amount of chlorine added initially to the water was sufficient.