Universidade da Coruña, Water and Environmental Engineering Research Team (GEAMA), Civil Engineering School, Elviña, 15071 A Coruña, Spain.
Universidade da Coruña, Water and Environmental Engineering Research Team (GEAMA), Civil Engineering School, Elviña, 15071 A Coruña, Spain.
Sci Total Environ. 2020 May 10;716:136923. doi: 10.1016/j.scitotenv.2020.136923. Epub 2020 Jan 25.
The deposition and resuspension of sediments are issues of considerable concern in combined sewer systems management. Sediments can produce the loss of hydraulic capacity and odour generation in sewers, and are also considered the main source of pollution due to their occasional uncontrolled discharges into the environment via Combined Sewer Overflows (CSO). Sewer sediments contain granular and cohesive organic fractions that can have a significant influence on bed resistance. In order to address the relationship between sewer sediment composition and its erodibility, accumulation and erosion experiments were performed in a flume test facility fed with wastewater. The flume was placed in a Wastewater Treatment Plant (WWTP), in which different circular pipe geometries were set. Wastewater flow inlet conditions and bed structures were monitored during the experiments. The photogrammetric technique Structure from Motion (SfM) was applied to record the bed deposit structures, providing accurate measurements of the accumulation rates. The SfM was also used to assess sediment transport and the characteristics of the bed forms after the erosion tests. In addition, velocity distributions and shear stress profiles were measured during the erosion tests to characterize flow resistance and sediment erosion. During both accumulation and erosion tests, sediments were sampled in order to analyse their physicochemical properties, thus highlighting the study of the biodegradability of the organic matter. Different deposition periods showed biological transformations in the bed deposit structure, which were seen to affect its cohesion, and in consequence, its erosion threshold. Tests with significant erosion rates agreed in broad terms with dimensionless sediment transport models derived from previous experimental studies performed with partly cohesive and organic materials in sewer pipes.
在合流制排水系统管理中，沉积物的沉积和再悬浮是一个非常值得关注的问题。沉积物会导致下水道水力容量的损失和气味的产生，并且由于其偶尔不受控制地排入环境中（通过合流制溢流），也被认为是主要的污染源。下水道沉积物含有颗粒状和粘性有机物质，这可能对床层阻力有重大影响。为了解决下水道沉积物组成与其可侵蚀性之间的关系，在一个以废水为进料的水槽测试设施中进行了沉积物积累和侵蚀实验。水槽被放置在一个污水处理厂（WWTP）中，其中设置了不同的圆形管道几何形状。在实验过程中监测了废水入口条件和床层结构。摄影测量技术结构光（SfM）被应用于记录床层沉积结构，提供了对积累率的精确测量。SfM 还被用于评估侵蚀试验后的泥沙输送和床层形态特征。此外，在侵蚀试验过程中测量了速度分布和剪切应力分布，以描述流动阻力和泥沙侵蚀。在积累和侵蚀试验过程中，都对沉积物进行了采样，以分析其物理化学性质，从而突出了有机物可生物降解性的研究。不同的沉积时期显示出床层沉积结构中的生物转化，这被认为会影响其粘性，从而影响其侵蚀阈值。具有显著侵蚀率的测试与从以前在下水道管道中进行的部分粘性和有机材料的实验研究中得出的无量纲泥沙输运模型基本一致。
