Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China E-mail:
Renming University of China, Beijing 100872, China.
Water Sci Technol. 2014;69(9):1846-52. doi: 10.2166/wst.2014.079.
The airlift external circulation membrane bioreactor (AEC-MBR) is a new MBR consisting of a separated aeration tank and membrane tank with circulating pipes fixed between the two tanks. The circulating pipe is called a H circulating pipe (HCP) because of its shape. With the complex configuration, it was difficult but necessary to master the AEC-MBR's hydraulic characteristics. In this paper, simulation and optimization of the AEC-MBR was performed using computational fluid dynamics. The distance from diffusers to membrane modules, i.e. the height of gas-liquid mixing zone (h(m)), and its effect on velocity distribution at membrane surfaces were studied. Additionally, the role of HCP and the effect of HCP's diameter on circulation were simulated and analyzed. The results showed that non-uniformity of cross-flow velocity existed in the flat-plate membrane modules, and the problem could be alleviated by increasing hm to an optimum range (h(m)/B ≥ 0.55; B is total static depth). Also, the low velocity in the boundary layer on the membrane surface was another reason for membrane fouling. The results also suggested that HCP was necessary and it had an optimum diameter to make circulation effective in the AEC-MBR.
气升式外循环膜生物反应器（AEC-MBR）是一种新型的 MBR，由一个分离的曝气池和膜池组成，两者之间通过循环管道固定。由于其形状，循环管道被称为 H 型循环管（HCP）。由于其复杂的结构，掌握 AEC-MBR 的水力特性是困难但必要的。在本文中，使用计算流体动力学对 AEC-MBR 进行了模拟和优化。研究了从曝气器到膜组件的距离，即气液混合区的高度（h(m)）及其对膜表面速度分布的影响。此外，还模拟和分析了 HCP 的作用以及 HCP 直径对循环的影响。结果表明，在平板膜组件中存在着横向速度的不均匀性，通过将 hm 增加到最佳范围（h(m)/B ≥ 0.55；B 是总静态深度）可以缓解这个问题。此外，膜表面边界层中的低速也是导致膜污染的另一个原因。结果还表明，HCP 是必要的，并且它有一个最佳直径，可以使 AEC-MBR 中的循环有效。
