A water treatment plant applies chlorine for disinfection so that 10 mg/L chlorine is achieved immediately after mixing. The volume of water treated is 25,000,000 gal/day. What is the mass of chlorine needed by this plant per day? (2) As stated in part (a), chlorine does applied is 10 mg/L, and chlorine concentration in water existing the plant to enter drinking water distribution systems is 3 mg/L. What is the chlorine residual and chlorine demand, respectively, for water in this plant? (3) It takes 15 minutes to get 0.5-log Giardia inactivation under current operation condition (pH, temperature, etc.). How long does it take to get 3-log Giardia inactivation under the same condition, assuming chlorine concentration is constant?