06-19 (mz 8.28) (augmented by jj) during drinking water treatment, 17 lb. of chlorine are added daily to disinfect 5 million gallons of water. (a) what is the aqueous concentration of chlorine (in mg/l) resulting from this mixture? (b) if the measured chlorine residual is 0.20 mg/l, what is the chlorine demand in mg/l?0.41 mg/l, 0.21 mg/l. the chlorine demand is the difference between the concentration of chlorine added during disinfection and the chlorine residual. the chlorine residual is the concentration of chlorine that remains after treatment so the water maintains its disinfecting power in the distribution system. we normally measure demand in the lab and then calculate the chlorine application required at the plant to achieve a desired residual. (c) if the desired chlorine residual is 0.5 mg/l, how many pounds per day must be added to the flow?29.6 lb/d.