Long-term phosphorus removal by Ca and Fe-rich drainage filter materials under variable flow and inlet concentrations

Area of Science:

• Environmental Science
• Water Quality Management
• Agricultural Engineering

Background:

• Phosphorus (P) runoff from agricultural fields contributes to surface water eutrophication.
• Edge-of-field technologies, such as compact filter systems, are crucial for mitigating P discharge.
• Understanding long-term filter material performance is essential for effective water quality protection.

Purpose of the Study:

• To evaluate the long-term phosphorus removal efficiency of five different filter materials.
• To compare the performance of iron-based and calcium-based filter materials under varying conditions.
• To assess the impact of flow rates and P concentrations on filter efficacy.

Main Methods:

• Column experiments simulating tile drainage were conducted over 696 days.
• Five filter materials were tested: calcinated diatomaceous earth (CDE), ferric hydroxide granules (CFH), seashells, limestone, and Filtralite-P.
• Variable flow rates and inlet P concentrations were applied to artificial drainage water (pH 6).

Main Results:

• Iron-based materials (CFH and CDE) showed higher P retention than calcium-based materials.
• Ferric hydroxide granules (CFH) achieved 99% P removal at high and 98% at low concentrations.
• Limestone demonstrated low P retention (25% at high load), while Filtralite-P and Seashells were sensitive to P concentration.

Conclusions:

• Ferric hydroxide granules (CFH) are highly effective for long-term phosphorus removal from agricultural drainage.
• Filter material selection significantly impacts phosphorus removal efficiency, with iron-based options generally superior.
• CFH exhibits the lowest sensitivity to P loading variations, indicating robust performance in diverse field conditions.