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Investigations on phosphorus retention in subsurface flow constructed wetlands
1AKUT Umweltschutz Ingenieurgesellschaft mbH, Sydower Feld 4, 16359 Biesenthal, Germany. rustige@akut-umwelt.de
Summary
Constructed wetlands effectively remove phosphorus, with horizontal flow (HF) systems showing superior performance at low hydraulic loading rates. Phosphorus accumulation primarily occurs in the influent zone of both HF and vertical flow (VF) systems.
Area of Science:
- Environmental Engineering
- Water Treatment Technologies
- Ecosystem Services
Background:
- Constructed wetlands are increasingly utilized for wastewater treatment.
- Phosphorus removal is a critical aspect of wetland performance for preventing eutrophication.
- Understanding factors influencing phosphorus removal and accumulation is essential for optimizing wetland design and management.
Purpose of the Study:
- To evaluate the phosphorus removal performance of 62 sand-based constructed wetlands across Germany, Austria, and Switzerland.
- To investigate phosphorus removal mechanisms and accumulation within filter beds of selected wetlands.
- To identify key factors affecting phosphorus removal efficiency in horizontal flow (HF) and vertical flow (VF) systems.
Main Methods:
- Comparative analysis of phosphorus removal data from 62 constructed wetlands.
- Intensive monitoring of phosphorus removal and accumulation in five selected wetlands.
- Time series analysis to assess seasonal, saturation, and redox effects on performance.
- Soil analysis to determine phosphorus accumulation zones.
Main Results:
- Horizontal flow (HF) reed beds demonstrated predictable performance with a derived regression equation, unlike vertical flow (VF) systems.
- HF systems with hydraulic loading rates ≤ 10 mm/d exhibited the highest phosphorus removal efficiency.
- Average phosphorus output concentrations were lower in HF wetlands (≤ 2.1 mg/L) compared to VF wetlands (≤ 3.3 mg/L).
- Phosphorus retention peaked during warmer seasons, with a minor positive correlation to intermittent low redox levels.
- Highest phosphorus accumulation was observed in the influent zones of both HF and VF wetlands.
Conclusions:
- Sand-based constructed wetlands, particularly HF systems, are effective for phosphorus removal.
- Optimizing hydraulic loading rates and considering seasonal variations are crucial for maximizing phosphorus removal.
- Understanding phosphorus accumulation patterns is vital for long-term wetland sustainability and management strategies.