A completely mixed high rate-activated sludge plant with recycling treats 17,500 m3/day of industrial wastewater. The in uent to the activated sludge reactor has a BOD5 of 1000 mg/L. It is desired to reduce the in uent BOD5 to 120 mg/L, prior to discharge to a municipal sewer. Pilot plant analysis gave the following results: mean cell residence time = 6 d, MLSS concentration in reactor = 5500 mg/L, Y = 0.6 kg/kg, kd = 0.03 d–1.

Determine the following: a. The hydraulic retention time and volume of the activated sludge reactor. b. The volumetric loading rate in kg BOD5/m3-day to the reactor. c. The F/M ratio in the reactor. d. The mass and volume of solids wasted each day, at an under ow solids concentration, Xu = 10,000 mg/L. e. The sludge recirculation ratio.