ABSTRACT

Nitrogen pollution of surface water systems is becoming a global problem, especially within river networks that receive run-off from agricultural land. Methods such as riparian buffering and the construction of artificial wetlands have proven effective when the conversion of land is achievable. An alternate approach is to consider in-stream remediation methods that capture and process incoming river flow. Their design must consider a number of factors, such as effective remediation capacity within the system, and the delivery of water to the treatment region. Computational modelling can be an efficient means for exploring these large design spaces. The results from our models show that unit performance is influenced by flow penetration into the unit, which typically improves with increasing void fraction until through-flow is achieved, after which removal performance decreases, due to decreasing functional surface area. Splitting units into smaller sub-units placed in tandem parallel to the stream-wise flow also results in a performance increase, although only if sufficient spacing is given between the upstream and downstream units to prevent wake interactions, and allow freestream flow to mix into the wake of the upstream unit. Unit efficiency is also observed to improve with increased occlusion of the channel cross section.

摘要

地表水系统的氮污染正在成为一个全球性问题，特别是在从农业用地流走的河流网络中。当可以转换土地时，已证明诸如河岸缓冲和人工湿地建设等方法是有效的。另一种方法是考虑采用流域修复方法来捕获和处理流入的河水。他们的设计必须考虑许多因素，例如系统内的有效修复能力以及向处理区域的水输送。计算建模可以成为探索这些大型设计空间的有效方法。我们模型的结果表明，单元性能受流体渗透到单元的影响，通常会随着孔隙率的增加而提高，直到实现通流为止。之后，由于功能表面积的减少，去除性能会下降。尽管将上游单元和下游单元之间留有足够的间距以防止尾流相互作用，并允许自由流混入水流中，但将单元拆分成多个与水流平行的较小子单元也可提高性能。上游单元唤醒。还观察到单元效率随着通道横截面闭塞的增加而提高。并允许自由流混入上游装置的尾流。还观察到单元效率随着通道横截面闭塞的增加而提高。并允许自由流混入上游装置的尾流。还观察到单元效率随着通道横截面闭塞的增加而提高。