滤料粒径对BAF小尺度下流场形态及挂膜速度的影响

Effects of media size on flow pattern and biofilm growth speed of BAF

为探讨颗粒粒径对曝气生物滤池(BAF)运行效果的影响,采用数值模拟和实验研究方法分析了滤料粒径对曝气生物滤池流场形态及挂膜速度的作用机理.选用5个颗粒尺寸结构空间作为计算区域,利用Fluent软件对相同颗粒间隙、不同颗粒粒径下BAF小尺度下的流场形态进行模拟分析,并通过对3种粒径下流线图、速度矢量图、压力分布及湍流强度变化的对比分析,发现颗粒粒径为3 mm时流场形态最好,最有利于气水混合及氧传质的进行.同时,为验证模拟结果的正确性,对同种材质、相同运行条件下3种不同颗粒粒径进行挂膜速度对比,通过考察挂膜启动28 d的COD去除率变化及污泥生物量的对比分析,发现颗粒粒径为3 mm时,运行最为稳定,系统运行第16 d时就达到了80%的COD去除效率.

A numerical method was used to simulate the flow pattern of BAF with three different sizes of granule media,2 mm,3 mm,and 4 mm. A small flow field of 5 granules was designated as the calculation zone,and the Fluent software was employed to analyze the flow pattern of the small scale field at the same granule space and different media sizes. The streamline chart,velocity vector,stress distribution,and turbulence strength were obtained. By comparing the output of simulation of flow patterns of three different sizes of media,3 mm is the favor size for the mix of gas and water,and oxygen transportation. Three parallel small-scale BAFs were packaged by three different size media separately,with the same materials and at the same operation condition employed. After 28 days operation,the BAF with 3 mm of media showed better characteristics on stabilization,biofilm growth speed,biomass and COD removal. The COD removal of BAF with 3mm of media was 80%.