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6. (1) A water treatment plant applies chlorine for disinfection so that 10 mg/L chlorine is...

6. (1) A water treatment plant applies chlorine for disinfection so that 10 mg/L chlorine is achieved immediately after mixing. The volume of water treated each day is 25,000,000 gal. What is the mass of chlorine needed by this plant every day? (2) The disinfection takes place in a contact tank which is a CSTR at steady state. Chlorine concentration in the contact tank is constant at 3 mg/L. Effluent of this contact tank will enter drinking water distribution systems directly. 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 (chlorine concentration, pH, temperature, etc.). How long does it take to get 3-log Giardia inactivation under the same condition?

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