The Efficiency of Novel Bubble Generator in Water Aeration

Inna Levitsky, Sami Shamoon College of Engineering, Beer - Sheva, Israel
Dorith Tavor, Chemical Engineering , Sami Shamoon College Of Engineering, Beer - Sheva, Israel
Vitaly Gitis, Unit Of Energy Engineering, Ben-gurion University Of The Negev, Beer - Sheva, Israel

Two - phase flow is widely used in wastewater treatment, water aeration, flotation, membrane filtration processes, etc. It was shown that the effectiveness of two-phase flow is very sensitive to the bubble size which is determined by the device geometry and the operating parameters. Along with a two-phase flow the using unsteady one is another mechanism for improving performance water treatment.

A new bubble generator design is developed, capable to generate air bubbles in big range sizes and unsteady flow at low energy consumption. The core of the generator is a vortex chamber where liquid supplied through tangentially-oriented ducts meets air supplied in the radial direction. The general factor for the receiving air bubbles with required diameter is the ratio of air and water volume flow rates which for bubbles with micron sizes (20-200 µm) are equal to 27-18 and to 7 for bubbles with a diameter of 2 mm. The proposed bubble generator creates pressure oscillations and installing a pin in exit cavity results in a drastic increase of the pressure amplitude both in flow without bubbles and in the case of gas supply. At the pin presence the frequency about 3 Hz was received.

The developed generator tested in the water aeration process has shown the oxygen concentration of 7.25 mg/L at air bubbles diameter 0.05 mm against 1.45 mg/L at d_b = 2 mm. With installing the pin the oxygen concentration increases to 8.9 mg/L and 3.96 mg/L, respectively. It must be noted that maximum value of oxygen concentration at test temperature is 9 mg/L. From received test results the oxygen transfer coefficient and oxygen transfer efficiency were calculated. These data confirm that the micron bubble sizes together with pressure oscillation considerably improve the water aeration process.