Determine the volume (m3 ) of three identical activated-sludge tanks following primary clarification to aerate 38,000 m3 /d with a BOD concentration of 170 mg/l at a BOD loading of 550 g/m3 •d. What is the aeration time (hr)? For a F/M of 0.35, what MLSS concentration (mg/L) should be maintained in the aeration tanks? Estimate the operating sludge age (days), assuming an effluent suspended solid of 30 mg/l and a daily amount of waste-activated sludge solids of 950 kg/d.