The recommended concentration of free chlorine is
0.2mg/dl
0.5mg/dl
5mg/dl
10mg/dl
The chlorine demand of water is the difference between the amount of chlorine added to the water and the amount of residual chlorine remaining at the end of a specific period of contact (usually 60 min)The point at which chlorine demand of water is met is called the &;breakpoint chlorine&;Chlorine added beyond breakpoint chlorine is free chlorine (HOCl and OCl). The minimum recommended concentration of free chlorine is 0.5 mg/L for one hour.The free chlorine provides a margin of safety against subsequent microbial contamination such as may occur during storage and distribution.Park 23e pg: 715
Environment and health