6.10) A final settling tank for a 2-million-gallon-per-day (2mgd) activated-sludge treatment plant it to be designed to have an average overflow rate of 800 g/day-ft^2. the tank needs to have a minimum detention time of 2.0 hr and to allow proper settling it must be at least 11 ft deep. If the tank is circular, what should its diameter and depth be?© BrainMass Inc. brainmass.com March 4, 2021, 7:13 pm ad1c9bdddf
Detention time is the volume of the cylinder divided by the outflow. The surface overflow rate is the influent flow divided by surface area. So you have two equations:
t = V/Q
Q = ...
The solution determines the size needed for settling tank given flow rate and detention time.