Optimizing the gas distributor based on CO bubble dynamic behaviors to improve microalgal biomass production in an air-lift photo-bioreactor.

Dynamic behavior of bubbles would significantly affect CO mass transfer and may cause microalgae cells uneven distribution due to the bubble carrying effect. To improve microalgae growth, the gas distributor and aeration conditions was optimized according to the bubble rising behavior. The CO bubble rising trajectory is similar to a Zigzag. The amplitude and wavelength of the Zigzag, which reflected the influenced zone of microalgae suspension in horizontal direction and disturbance intensity on culture, respectively, was controlled by the structure of gas distributor and aeration conditions. An optimized round gas distributor that full of holes with an inner diameter of 0.5mm and spacing of 1.5mm was designed. When cultivated with the optimized gas distributor aerating 5% CO gas at 0.250vvm, the maximum biomass concentration of Chlorella pyrenoidosa achieved 2.88gL, increased by 83.44% compared to that of 1.57gLcultivated with the commercial micro-bubbles aerator.