Problem $2$: During drinking water treatment, $17lb.$ of chlorine $(Cl$ are added daily to disinfect $5$ million gallons of water. What is the aqueous concentration of chlorine in $m\frac{g}{L}?($b$)$ The chlorine demand is the concentration of chlorine used during disinfection. The chlorine residual is the concentration of chlorine that remains after treatment, so the water maintains its disinfecting power in the distribution system. If the residual concentration is $0\mathrm{.}20m\frac{g}{L},$ what is the chlorine demand in $m\frac{g}{L}?$