Phosphorus removal structures for tile-drained agricultural systems: design principles and field-scale performance

• Phosphorus removal structures (PRS) intercept DRP from agricultural drainage system • Performance of PRS is controlled by design parameters such as hydraulic design, PSM • Field PRS showed 30-90% DRP removal depending on system type Phosphorus (P) loss through tile-drained agricultural systems is a major contributor to eutrophication, necessitating effective edge-of- field treatment strategies. Phosphorus removal structures (PRS) have emerged as a promising solution to intercept and treat dissolved reactive phosphorus (DRP). This mini review provides a design-oriented evaluation of field-scale PRS linking hydraulic conditions, media characteristics, and structural configurations to treatment performance. PRS are categorized into compact filters, modular reactors, subsurface and ditch-based systems, hybrid bioreactors and biochar-based chambers, each exhibiting distinct trade-offs between hydraulic capacity and removal efficiency. Field studies demonstrated that while adsorption-based systems can achieve high initial removal efficiencies, performance often declines over time due to media saturation and clogging, whereas precipitation-based systems offer greater flow handling but exhibit variable removal under field conditions. Key design parameters controlling performance include hydraulic loading, residence time, media reactivity, flow distribution and clogging potential. This review identifies critical gaps related to transient flow conditions, media longevity and system scalability and provides insights for developing process informed and field applicable PRS design strategies.