Reducing phosphorus loading of surface water using iron-coated sand

Area of Science:

• Environmental Science
• Agricultural Engineering
• Water Quality Management

Background:

• Agricultural soil phosphorus (P) losses significantly impair surface water quality.
• Pipe drainage systems are a major pathway for P transport from agricultural lands to surface waters.
• Effective mitigation strategies are crucial to reduce P enrichment in aquatic ecosystems.

Purpose of the Study:

• To evaluate the efficacy of a novel pipe drain design for removing P from agricultural drainage water.
• To assess the long-term performance and stability of Fe-coated sand as a P-binding material under submerged conditions.

Main Methods:

• A field trial was conducted using pipe drains enveloped with Fe-coated sand, a byproduct rich in P-binding compounds.
• The system's performance was monitored over multiple hydrological seasons.
• Analysis included P removal efficiency and the stability of the Fe-coated sand under prolonged submersion.

Main Results:

• The Fe-coated sand pipe drains demonstrated a high P removal efficiency of 94%.
• The Fe-coated sand remained stable under submerged conditions, with no significant reduction of Fe(III) observed.
• This stability was attributed to the presence of manganese oxides, which prevented Fe(III) reduction.

Conclusions:

• Enveloped pipe drains using Fe-coated sand are highly effective in reducing P concentrations in drainage effluent to meet water quality criteria.
• The system is estimated to maintain effectiveness for approximately 14 years, though manganese oxides may deplete sooner (5-10 years).
• Further long-term research is needed to fully understand the sustained performance and stability of this P mitigation technology.