1. Four trickling filters with plastic packing are operating in parallel to treat wastewater at a total flowrate of 10,000m3/d. There is no re-circulation. The overall influent BOD5 concentration is 500mg/L and the overall effluent BOD5 concentration is 300mg/L. The height of each filter is 6m. The constants for the design equation for plastic packing are n =0.5 and k=0.084(L/s)0.5/m2. Calculate the diameter of each filter (in meter). (15 points)