Spiral Motion of Air Bubbles in Multiphase Mixing for Wastewater Treatment

Abstract

Vortex flow forms due to spiral motion of the air bubbles around water in the aeration tank. The formation of vortices would indicate the mixing pattern of water and air in the aeration tank. The mixing of two phases such as air-water or water-air flow systems in the aeration tank is important to increase oxygen transfer efficiency in aeration process. With different process parameters of the aeration tank such as the diameter of pore size of the membrane, diameter of diffuser and air mass flow rate are simulated using ANSYSTM CFD software. When the air mass flow rate increasing, the diameter of pore size decreasing, the air-water or vice versa are mixed homogenously and increases the oxygen transfer efficiency. The air-water mixing efficiency increases if the diameter of membrane pore size decreases at higher mass flow rate and the diameter of diffuser is in the practical range which is between 4 to 12. An improvement of vortices occurs in an aeration tank when higher strength of air velocity curl occurs.