Airlift reactors are widely used m chemical, biochemical and environmental processes[1].In some processes, the gas-liquid mass transfer is the rate-limiting step.The volumetric mass transfer coefficient is determined by the gas-liquid mass transfer coefficient and interfacial area[2].There are two approaches to increase the interfacial area: one is to increase the gas holdup,and the other is to decrease the bubble size.Usually, smaller bubble sizes lead to larger gas holdup and interfacial area.