Enhancing bioretention efficiency for pollutant mitigation in stormwater runoff: Exploring ecosystem cycling dynamics...

Area of Science:

• Environmental Engineering
• Ecosystem Science
• Water Quality Management

Background:

• Bioretention systems are crucial for managing stormwater runoff and improving water quality.
• Understanding the long-term operational efficiency of bioretention systems is essential for sustainable urban development.
• The integration of biological components like plants and earthworms can enhance the ecosystem services of bioretention.

Purpose of the Study:

• To evaluate the operational efficiency of bioretention systems with fillers, plants, and earthworms under varying time scales.
• To determine the impact of drying periods on pollutant removal in the short term.
• To assess the influence of plants and earthworms on nutrient and organic matter removal in the long term.

Main Methods:

• Established three distinct bioretention setups with varying combinations of fillers, plants, and earthworms.
• Monitored pollutant removal (NO₃⁻-N, TP, COD, NH₄⁺-N) under short-term and long-term operating conditions.
• Conducted microbial community analysis to understand biological processes.

Main Results:

• Short-term: Extended drying periods increased removal of nitrate-nitrogen (NO₃⁻-N), total phosphorus (TP), and chemical oxygen demand (COD) by 5–7%, 4–12%, and 5–10%, respectively.
• Long-term: Plants significantly improved COD removal (10–20%), while earthworms enhanced NH₄⁺-N, NO₃⁻-N, and particularly TP removal (9–16%).
• Microbial analysis confirmed positive impacts on nitrogen and phosphorus metabolism, especially with plants and earthworms.

Conclusions:

• Bioretention systems incorporating plants and earthworms demonstrate enhanced pollutant removal capabilities across different time scales.
• Optimizing drying periods is effective for short-term pollutant reduction.
• The synergistic effects of plants and earthworms are crucial for long-term nutrient and organic matter management in bioretention systems.