Malcolm Pirnie/ARCADIS, Lansing, MI 48906, United States.
Sci Total Environ. 2011 Nov 15;409(24):5444-53. doi: 10.1016/j.scitotenv.2011.08.045. Epub 2011 Sep 29.
Urban runoff is primarily treated by settling particles. One important parameter in the design of these settling basins is particle settling velocity. Yet, this parameter is rarely measured. A modified elutriation device is developed to measure particle settling velocity distribution for use in stormwater runoff treatment design and performance evaluation. The elutriation device has distinct advantages over settling column measurement, including (1) less time requirement to make measurements, and (2) flexibility to operate at various flow rates to cover wide ranges of particle settling velocity. Major modifications of the existing elutriation devices include using a variable speed pump, changing the glass column to plastic, and adding screens at the flow inlet for more uniform velocity distribution while making the column shorter. The results of the experiments showed that the particles retained in each column of the modified elutriation device could be predicted by assuming a fully-developed, laminar velocity profile across the cross-section of each column. Operation of the device under two flow rates and multiple columns increased the range of settling velocities measured. The information presented in this paper may be used to develop standard protocols for the evaluation of particle settling velocity in stormwater.
城市径流主要通过沉降颗粒来处理。在这些沉降池的设计中，一个重要的参数是颗粒沉降速度。然而，这个参数很少被测量。开发了一种改良的淘析装置来测量用于雨水径流处理设计和性能评估的颗粒沉降速度分布。与沉降柱测量相比，淘析装置具有明显的优势，包括（1）测量所需的时间更少，以及（2）能够在各种流速下灵活运行，以覆盖广泛的颗粒沉降速度范围。对现有淘析装置的主要改进包括使用变速泵、将玻璃柱改为塑料柱，并在流入口处添加筛网，以在使柱体更短的同时实现更均匀的流速分布。实验结果表明，通过假设每个柱截面的速度分布完全发展为层流，可以预测改良淘析装置中每个柱内截留的颗粒。在两种流速和多个柱体下操作增加了测量的沉降速度范围。本文介绍的信息可用于制定雨水颗粒沉降速度评估的标准协议。
