Design characteristics of pooled circular stepped cascade aeration system

• Design characteristics of pooled circular stepped cascade (PCSC) aerator were investigated.
• Simulation equations for oxygen transfer and power consumption were developed.
• Prototype propeller pump based PCSC aerator was fabricated and tested.
• Standard aeration efficiency based on brake power ranged between 2.43 and 3.23 kg O2/kWh.

Aeration experiments were conducted in a brick masonry tank of dimension 4 m × 4 m × 1.5 m to study the design characteristics of pooled circular stepped cascade (PCSC) aeration system. Based on dimensional analysis, non-dimensional numbers related to geometric, dynamic and process parameters were proposed. The non-dimensional geometric parameters – number of steps (N), ratio of total height of cascade (H) to the bottom radius of cascade (Rb), % coverage of circumference of each step by enclosure (Pe) and number of enclosures in each step (Ne) were optimized. Maintaining the optimized geometric parameters (N = 6, H/Rb = 0.25, Pe = 20% and Ne = 9), aeration experiments were further conducted at different discharges (Q) to develop simulation equations for prediction of aeration characteristics of PCSC aeration system at different dynamic conditions. Simulation equations for oxygen transfer and power consumption based on Froude (Fr) criterion were developed subject to 0.0014 ≤ Fr ≤ 0.0144. SAE of the developed prototype PCSC aerators based on estimated brake power ranged between 2.43 and 3.23 kg O2/kWh.