Key Laboratory of Education Ministry of the Three Gorges Reservoir Region's Eco-Environment, Chongqing University, Chongqing, 400045, China.
Bioprocess Biosyst Eng. 2021 Sep;44(9):1865-1874. doi: 10.1007/s00449-021-02566-y. Epub 2021 Apr 19.
The flow velocity plays an important role in the growth and characteristics of biofilm in the bioreactor as well as its treatment efficiency, which has been a hot research topic. In a sewage treatment bioreactor, the type of flow is usually turbulence. According to the methods of Reynolds decomposition, the flow velocity of turbulence consists of the time-mean velocity and fluctuation velocity, which usually exist simultaneously in real flow. However, the current research on the influence of turbulence flow velocity mainly focuses on the time-mean velocity, while the fluctuation velocity has not been reported because of very difficult to control. To this end, in this paper, a laboratory oscillating-grid turbulence (OGT) bioreactor with zero time-mean velocity and only fluctuation velocity was designed. In this bioreactor, the fluctuation velocity could be easily manipulated by varying the operational parameters of the grid. Based on the numerical simulation of Gas-liquid two-phase flow, the distributions of fluctuation velocity and corresponding turbulence fluctuation intensity, gas holdup, and Reynolds stress were obtained. After that, the effects of the turbulent fluctuation intensity on the biofilm thickness, density, and composition of extracellular polymeric substances (EPS) were studied experimentally. The results showed that turbulent fluctuation had a significant effect on the physical and chemical properties of biofilms, and the fluctuation velocity promoted the increase in the biofilm density and the content of protein and carbohydrates in EPS. This study was intended to provide theoretical support for the design and operation optimization of bioreactors.
流速在生物反应器中生物膜的生长和特性及其处理效率中起着重要作用，这是一个热门的研究课题。在污水处理生物反应器中，流动类型通常为湍流。根据 Reynolds 分解方法，湍流的流速由时均速度和脉动速度组成，这两种速度通常同时存在于实际流动中。然而，目前关于湍流流速的影响的研究主要集中在时均速度上，而脉动速度由于难以控制，尚未得到报道。为此，本文设计了一种具有零时均速度且仅有时变速度的实验室振荡网格湍流（OGT）生物反应器。在该生物反应器中，通过改变网格的操作参数可以轻松地控制脉动速度。基于气-液两相流的数值模拟，获得了脉动速度及其对应的湍流脉动强度、气含率和雷诺应力的分布。之后，实验研究了湍流脉动强度对生物膜厚度、密度和胞外聚合物（EPS）组成的影响。结果表明，湍流脉动对生物膜的物理和化学性质有显著影响，并且脉动速度促进了生物膜密度以及 EPS 中蛋白质和碳水化合物含量的增加。本研究旨在为生物反应器的设计和运行优化提供理论支持。
