The tank depth is solely a ...
Published by David Russell, President at Global Environmental Operations, Inc
The tank depth is solely a function of the pressure of the aerators and the efficiency of the gas transfer. You can run a SBR with shallow surface aerators, but it tends to be more work. So, depth is not the driving issue. Detention time and tank volume are more important for COD/BOD removal. That said, you do have to have some mixing in the tank, but the details are up to you. Curiously enough most systems in the US are designed with aerator depths of around 12 feet (3.7 meters) because that's the best pressure/delivery point for single stage compressors.