Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of Education, College of Environment, Hohai University, Nanjing, 210098, China; College of Environment, Hohai University, No. 1 Xikang Road, Nanjing, 210098, China.
College of Natural Resources and Environment, Northwest A&F University, Yangling, 712100, China.
Water Res. 2020 Apr 1;172:115500. doi: 10.1016/j.watres.2020.115500. Epub 2020 Jan 14.
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. The sludge flocculation performance, zeta potential, and Gibbs free energy (ΔG) 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 ΔG were lower in the aeration system than the stirring system. The zeta potential and ΔG results for the two systems suggest that aeration is more beneficial for sludge flocculation than stirring even though the sludge flocculation performance F/F 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, zeta potential, and ΔG, respectively.
采用计算流体动力学（CFD）模型分析了曝气和搅拌系统对污泥物理性质的影响。本研究旨在（1）比较相同的紊流混合强度下曝气和搅拌对污泥性质的影响，以及（2）揭示污泥性质与水动力指标之间的关系，以确定水动力条件如何影响污泥絮凝。在装有 2-L 烧杯的搅拌和曝气混合实验中，平均速度梯度（G）设定为 90、190 或 280 s。分析了污泥絮凝性能、ζ电位和吉布斯自由能（ΔG），并计算了流速、湍流能量、湍流耗散率和柯尔莫哥洛夫微尺度作为水动力参数。在相同的 G 下，搅拌系统中的平均流速和湍流耗散率明显高于曝气系统，而曝气系统中的湍流能量和柯尔莫哥洛夫微尺度远高于搅拌系统。曝气系统中的ζ电位和ΔG均低于搅拌系统。尽管搅拌和曝气系统的污泥絮凝性能 F/F 没有明显差异，但两个系统的ζ电位和ΔG 结果表明，曝气比搅拌更有利于污泥絮凝。基于 CFD 模型计算的水动力参数与稳定阶段污泥性质的平均值之间存在显著关系，表明柯尔莫哥洛夫微尺度、平均流速和湍流能量分别是评价絮凝性能 F/F、ζ电位和ΔG 的合适水动力参数。
