Abstract Phosphorus (P) leaching from agricultural to tile drainage land contributes to nonpoint pollution of surface waters. Drainage filter technologies are potentially cost-effective technologies at the field scale for mitigating P losses. The objective of this study was to evaluate the removal efficiency for dissolved P (PRE) in a porous reactive filter constructed from crushed seashells, which was part of a full-scale filter system. The hydraulic properties (hydrodynamic and hydrodispersive) were estimated by performing salt (NaCl) tracer tests at two different flow rates representative for in situ discharge conditions in Denmark. The reactive properties of the filter material were determined in the laboratory by measuring P sorption in batch experiments. The hydraulic and reactive parameters were subsequently used as input parameters in a numerical model, which was calibrated based on flow data and dissolved P concentrations collected between May 2015 and 2017. Results show a homogeneous distribution of the tracer in drainage water outside the reactive P-filter and a uniform dissolved P load into the seashell material. The in situ saturated hydraulic conductivity was one order of magnitude lower than the estimation from previous column experiments. The model described accurately dissolved P concentrations at the filter outlet (Nash-Sutcliffe index = 0.79) and the P removal efficiency (PRE) of the reactive filter was equal to 62% during the monitored period. The model presented in this work can be integrated in a larger model addressing the complexity of P sorption processes for the evaluation of the removal efficiency in full-scale filter systems.

中文翻译：

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反应过滤器处理农用瓷砖排水的除磷效率建模

摘要 磷（P）从农业用地浸出到瓦片流域会导致地表水面面污染。排水过滤技术在现场规模上是一种潜在的成本效益高的技术，可用于减轻 P 损失。本研究的目的是评估由碎贝壳构成的多孔反应过滤器中溶解磷 (PRE) 的去除效率，该过滤器是全尺寸过滤系统的一部分。水力特性（水动力和水分散性）是通过在代表丹麦原位排放条件的两种不同流速下进行盐 (NaCl) 示踪剂测试来估计的。过滤材料的反应特性是在实验室中通过在批量实验中测量 P 吸附来确定的。随后将水力和反应参数用作数值模型中的输入参数，该模型根据 2015 年 5 月至 2017 年期间收集的流量数据和溶解的 P 浓度进行校准。过滤器和均匀溶解的 P 负载到贝壳材料中。原位饱和水力传导率比之前的柱实验估计值低一个数量级。该模型准确地描述了过滤器出口处溶解的 P 浓度（Nash-Sutcliffe 指数 = 0.79），并且在监测期间反应过滤器的除磷效率 (PRE) 等于 62%。