Which factor does NOT increase chlorine demand?

Which factor does NOT increase chlorine demand?

• A. Turbidity < 0.1 NTU
• B. High organic content
• C. Elevated temperature
• D. pH level around 7

Answer: (A)

Chlorine demand reflects how much chlorine is consumed by substances in the water before a residual can be established. When turbidity is extremely low, there are few particles and organics to react with chlorine, so the amount of chlorine needed to reach a residual is not increased. In contrast, high organic content provides more substances for chlorine to oxidize, raising demand. Elevated temperature speeds these reactions, causing more chlorine to be used up. A pH around seven shifts chlorine to a form that is highly reactive with organics, also increasing the chlorine consumed before a residual remains. So, very clear water with turbidity below 0.1 NTU does not raise chlorine demand.

Chlorine demand reflects how much chlorine is consumed by substances in the water before a residual can be established. When turbidity is extremely low, there are few particles and organics to react with chlorine, so the amount of chlorine needed to reach a residual is not increased. In contrast, high organic content provides more substances for chlorine to oxidize, raising demand. Elevated temperature speeds these reactions, causing more chlorine to be used up. A pH around seven shifts chlorine to a form that is highly reactive with organics, also increasing the chlorine consumed before a residual remains. So, very clear water with turbidity below 0.1 NTU does not raise chlorine demand.