12. Routine operation and maintenance processes in a water treatment plant include chemical feed,mixing, coagulation, flocculation, sedimentation, filtration, chlorination, fluoridation, pH adjustment, and pumping. You are asked to review the

treatment processes for a 3.0 MGD plant and provide answers for the following equations. (a) The gas chlorination system is set to feed chlorine at a rate of 16 lb/day into a daily water flow of 3,000,000 gallons for Spring operation. The chlorine residual is 0.4 mg/L. Estimate the chlorine demand (mg/L). (b) The water treatment plant uses filters that are 10 ft in diameter. If the filters are back washed at 15 gpm/ft for 12 minutes, estimate the amount (gallons per wash) of wash water used.