Revealing hydrodynamic effects on flocculation performance and surface properties of sludge by comparing aeration and stirring systems via computational fluid dynamics aided calculation
Revealing hydrodynamic effects on flocculation performance and surface properties of sludge by comparing aeration and stirring systems via computational fluid dynamics aided calculation
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DOI：
10.1016/j.watres.2020.115500
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发表时间：
2020-04-01
期刊：
影响因子：
12.8
通讯作者：
Li, Ming
中科院分区：
文献类型：
--
作者：
Feng, Qian;Ge, Ran;Li, Ming
采用计算流体力学（CFD）模型分析了曝气和搅拌系统对污泥物理性质的影响。本研究的目的是（1）在相同的湍流混合强度下比较曝气和搅拌对污泥性质的影响;（2）揭示污泥性质与水动力学指标之间的关系，以确定水动力条件如何影响污泥絮凝。在2 L烧杯中进行搅拌和通气的混合实验，平均速度梯度（G）设置为90、190或280 s（-1）。分析了污泥絮凝性能、zeta电位和吉布斯自由能（Δ G），计算了流速、湍动能、湍动能耗散率和Kolmogorov微尺度等水动力学参数。在相同的G值下，搅拌系统的平均流速和湍流耗散率明显高于曝气系统。但曝气系统的湍流能量和Kolmogorov微尺度远高于搅拌系统。曝气系统的zeta电位和Δ G均低于搅拌系统。两种系统的zeta电位和Δ G结果表明，尽管搅拌和曝气系统的污泥絮凝性能F/F-0没有明显差异，但曝气比搅拌更有利于污泥絮凝。计算流体力学模型的基础上计算的流体动力学参数和稳定相的污泥性质的平均值之间的显着关系表明，Kolmogorov微尺度，平均流速，湍流能量是适当的流体动力学参数用于评估絮凝性能F/F-0，zeta电位，和Δ G，分别。(C)2020爱思唯尔有限公司保留所有权利。
The effects of aeration and stirring systems on the physical properties of sludge were analyzed using a computational fluid dynamics (CFD) model. The aims of this study were to (1) compare the effects of aeration and stirring on sludge properties using the same turbulent mixing intensity, and (2) to reveal the relationship between sludge properties and hydrodynamic indicators to determine how hydrodynamic conditions influence sludge flocculation. Mixing experiments with stirring and aeration were carried out in 2-L beakers with the average velocity gradient (G) set to 90, 190, or 280 s(-1). The sludge flocculation performance, zeta potential, and Gibbs free energy (Delta G) were analyzed and the flow velocity, turbulence energy, turbulence dissipation rate, and Kolmogorov microscale were calculated as hydrodynamic parameters. The average flow velocity and the turbulence dissipation rate were obviously higher in the stirring system than in the aeration system at the same G. However, the turbulence energy and Kolmogorov microscale in the aeration system were much higher than those in the stirring system. Both the zeta potential and Delta G were lower in the aeration system than the stirring system. The zeta potential and Delta G results for the two systems suggest that aeration is more beneficial for sludge flocculation than stirring even though the sludge flocculation performance F/F-0 in the stirring and aeration systems showed no obvious differences. Significant relationships between hydrodynamic parameters calculated based on the CFD model and average values of sludge properties in the stable phase showed that the Kolmogorov microscale, average flow velocity, and turbulence energy were appropriate hydrodynamic parameters for evaluating the flocculation performance F/F-0, zeta potential, and Delta G, respectively. (C) 2020 Elsevier Ltd. All rights reserved.