10 pts) A wastewater is to be treated in a typical completely mixed activated-sludge system to a effluent BOD of 5 mg/L. The average flow rate is 18,300 m3/d. The influent BOD is 160 mg/L. The system is to operate at a concentration of 4,000 mg/L MLSS and 15 d mean cell residence time. The secondary clarifier is designed to thicken the sludge to 12,000 mg/L. Assume a yield coefficient of 0.5, an endogenous decay rate (kd) of 0.04 d-1 and the solids concentration in the effluent can be ignored. Design the secondary treatment system by determining: a) The volume of the aeration tank b) The flow rate of the WAS c) The flow rate of the RAS d) The sludge recycle ratio (RAS%) e) The mass of sludge wasted each day (in kg/day) f) Check the F:M