微气泡曝气中氧传质特性研究

气泡曝气过程中氧传质对于好氧生物处理过程具有重要意义。采用水力旋转剪切微气泡发生装置,考察了运行条件和水质特性对微气泡曝气中氧传质特性的影响。结果表明,微气泡曝气可获得较高的气含率和气泡停留时间;表面活性剂十二烷基磺酸钠(SDS)可以提高微气泡曝气的气含率和气泡停留时间。微气泡曝气中氧的总体积传质系数明显高于传统气泡曝气。总体积传质系数随着空气流量的增加而增加;氧传质效率随着空气流量的增加而减小,且对空气流量的变化更为敏感。在温度15~35℃范围内,微气泡曝气中氧的总体积传质系数随着温度的增加而增加,变化关系与传统气泡曝气基本相同,但对温度的变化更为敏感。微气泡曝气中,表面活性剂SDS会使氧的总体积传质系数略有降低,其不利影响明显小于传统气泡曝气;氧的总体积传质系数随盐度(NaC l浓度)增加而逐渐增加,并在NaC l浓度5 000 mg/L后趋于稳定。

Characteristics of oxygen transfer in microbubble aeration

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.