A waste treatment system is to be designed for raw wastewater containing 200 mg/L of carbonaceous oxygen demanding material (BOD). The wastewater flow rate of 0.45 million gallons per day (mgd) is to be introduced into a reactor tank having a theoretical detention time of 1 day. The organic matter is oxidized at the rate of 1.0 day-1 (first-order rate constant). Note that 1 mgd = 1.55 ft3/sec. All tanks are 6 feet deep. Calculate the expected effluent concentrations for steady-state treatment in each of the following tank configurations all having the same total theoretical detention time: a. A fully-mixed circular tank, 113 feet in diameter, with inflow at center and outflow along the perimeter. b. A rectangular plug -flow tank, 200 feet long and 50 feet wide c. A rectangular plug -flow tank, 100 feet long and 100 feet wide d. Three equal size fully-mixed circular tanks in series with 1/3 the exact volume of the tank in (a) e. Which configuration would you recommend and why?