微孔曝气器充氧性能的影响因素

EFFECT FACTORS AFFECTING OXYGEN TRANSFER PERFORMANCE OF FINE BUBBLE DIFFUSERS

基于双膜理论,研究者提出了曝气器充氧过程中氧传质的基本方程dρ/dt=KL a(ρ*∞-ρL),叙述了氧总转移系数KL a和饱和DO质量浓度ρ*∞的主要影响因素,包括几何参数(曝气器浸没深度、曝气器密度、池表面积、曝气器布局)、运行工况(水平流、通气量、污泥龄)和水质条件(表面活性剂、TDS含量)。在一定范围内增大池表面积、通气量或施加水平流均可提高KL a;微孔曝气器采用均匀布置方式或增大曝气器浸没水深有利于氧传质,提高氧转移效率;TDS的质量浓度超过2 g/L,KL a将明显增大;但曝气器浸没深度、曝气器密度和TDS含量对微孔曝气器充氧性能的影响和机理解释仍需进一步研究。温度越低,压力越大或水深越深,ρ*∞越大,这有利于提高曝气器的充氧能力。对微孔曝气器充氧性能影响因素的研究,可为污水处理厂曝气系统的优化运行提供参考。

On the basis of two-film theory, researchers have proposed a fundamental equation, dρ/dt=KLa （ρ∞-ρL）. This paper reviewed the main effect factors on KLa and ρ∞, including geometric parameters （e.g. diffuser submergence, diffuser density, surface area, and diffuser layout）, operating parameters （horizontal flow, air flow rate, and SRT）, and water characteristics （surfactants, and TDS）. The reported results revealed that KLa can be improved by increasing surface area, air flow rate, or applying horizontal flow. In addition, it would also improve oxygen transfer efficiency by using total floor coverage way, or increasing submergence depth of fine bubble diffusers. KLa will increase evidently when the concentration of TDS was more than 2 g/L. However, some mechanisms about the effects of diffuser submergence, diffuser density, and TDS on oxygen transfer are still unclear. The results about p∞ showed that the lower temperature, the greater pressure or the larger water depth, the higher p∞. Increasing p∞ allows to the improvement of oxygen transfer rate. Thus, the review for impacts of different aeration parameters on oxygen transfer can provide a reference for optimizing operation in wastewater treatment plants.