This study evaluated the long-term phosphorus (P) removal efficiency of five filter materials in column experiments simulating drainage water treatment from agricultural fields. Two iron-based materials (calculated diatomaceous earth CDE, and ferric hydroxide granules CFH) and three calcium-based materials (seashells, limestone, and calculated silicate/ calcium oxide (Filtralite-P) were tested under varying flow rates and P concentrations (0.14 and 0.7 mg/L). Iron-based filters, particularly CFH, showed the highest removal efficiency retaining up to 99%, independent of inlet concentration. CDE performed moderately well regardless of P concentration, Calcium-based materials showed variable performance, limestone retaining only 25% of high P loads while seashells and Filtralite-P removed P effectively at high P input. The findings highlight iron-based filters CFH as a robust candidate for edge-of-field P mitigation in tile-drained systems.
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