The difference in the amount of chlorine applied to a flow and the residual chlorine remaining after a given contact time is called?

The difference in the amount of chlorine applied to a flow and the residual chlorine remaining after a given contact time is called?

• A. Residual
• B. Demand
• C. Breakpoint
• D. Dosage

Answer: (B)

Chlorine demand is the amount of chlorine that is consumed by reactions with substances in the water during mixing and contact time. When you dose chlorine, some of it reacts with organics, ammonia, and other reducing compounds, and the remainder remains as residual chlorine after the contact period. The difference between what you inject (dosage) and the residual you measure is the chlorine demand. The residual is simply what’s left, and the dosage is the amount initially added. Breakpoint chlorination is a different concept related to the point at which free chlorine starts to appear after all reducing substances have been oxidized.

Chlorine demand is the amount of chlorine that is consumed by reactions with substances in the water during mixing and contact time. When you dose chlorine, some of it reacts with organics, ammonia, and other reducing compounds, and the remainder remains as residual chlorine after the contact period. The difference between what you inject (dosage) and the residual you measure is the chlorine demand. The residual is simply what’s left, and the dosage is the amount initially added. Breakpoint chlorination is a different concept related to the point at which free chlorine starts to appear after all reducing substances have been oxidized.