Characteristics of oxygen transfer in microbubble aeration
微气泡曝气中氧传质特性研究

Oxygen transfer is the essential function of bubble aeration and very important for aerobic biological treatment process. The effects of operational conditions and wastewater properties on oxygen transfer in microbubble aeration were investigated with a hydraulic gyratory shear type of microbubble generator. The results indicated that high gas holdup and retention time in aeration tank were obtained and surfactant SDS increased gas holdup and retention time further in microbubble aeration. The volumetric oxygen transfer coefficient increased and oxygen transfer efficiency decreased when air flow rate increased. The volumetric oxygen transfer coefficient and oxygen transfer efficiency in microbubble aeration were higher than these in traditional bubble aeration and more sensitive to the variation of air flow rate. When temperature increased, the volumetric oxygen transfer coefficient also increased in microbubble aeration, showing the same with traditional bubble aeration but a little more sensitive to the variation of temperature. Surfactant SDS only made the volumetric oxygen transfer coefficient decrease a little in microbubble aeration, showing weaker negative effect than that in traditional bubble. The volumetric oxygen transfer coefficient was also influenced by the salinity (NaCl concentration) which made the volumetric oxygen transfer coefficient increase to a constant gradually after NaCl concentration was larger than 5 000 mg/L.