An activated sludge system operates at a flow rate (Q) of 400 m3/day with an incoming BOD (So) of 300 mg/L. Throughout pilot plant work, the kinetic constants for this system are determined to be Y = 0.5 kg SS/kg BOD, Ks = 200 mg/L, d = 2/day. The volume of tank is 51.6 m3. A solids concentration of 4,000 mg/L in the aeration tank is considered appropriate and the sludge age (or mean cell residence time, MCRT) is 3.8 days. A treatment system must be designed that will produce an effluent BOD of 30 mg/L (90% removal).
Determine (a) the hydraulic retention time (b) the quantity of sludge wasted daily (c ) the F/M ratio