Modelling phosphorus removal efficiency of a reactive filter treating agricultural tile drainage water

• Published in: Ecological engineering Vol. 156; p. 105968
• Main Authors: Pugliese, Lorenzo, De Biase, Michele, Chidichimo, Francesco, Heckrath, Goswin J., Iversen, Bo V., Kjærgaard, Charlotte, Straface, Salvatore
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.09.2020; Elsevier BV
• Subjects: Agricultural tile drainage water; Dissolved phosphorus; Drainage; Drainage water; Efficiency; Evaluation; Flow rates; Flow velocity; Hydraulic loading; Hydraulic properties; Hydraulics; Hydrodynamics; In situ leaching; Land pollution; Leaching; Mathematical models; Nonpoint source pollution; Numerical modelling; Numerical models; Parameters; Phosphorus; Phosphorus removal; Phosphorus removal efficiency; Pollution effects; Porous reactive filter; Properties; Removal; Seashell filter media; Shells; Sodium chloride; Sorption; Surface water; Tile drainage; Tracers; Water pollution; Water purification; Phosphorus removal efficiency; Dissolved phosphorus; Numerical modelling; Seashell filter media; Agricultural tile drainage water; Porous reactive filter
• ISSN: 0925-8574; 1872-6992
• DOI: 10.1016/j.ecoleng.2020.105968

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. •NaCl tracer tests allowed the hydrodynamic and hydrodispersive parameter evaluation.•The in situ saturated hydraulic conductivity was lower than the lab estimation.•Model predictions were validated using 2-year dissolved reactive P data.•The numerical model estimated a phosphorus removal efficiency of 62%.•High flow values have low frequency and lower the phosphorus removal efficiency.