Nitrate and phosphate removal through enhanced bioretention media: mesocosm study

Area of Science:

• Environmental Engineering
• Water Quality Management
• Green Stormwater Infrastructure (GSI)

Background:

• Bioretention systems are crucial Green Stormwater Infrastructure (GSI) for managing stormwater runoff.
• These systems aim to reduce peak flows, decrease runoff volume, and treat contaminants.
• Enhancing bioretention soil mixtures with specific amendments is an active area of research.

Purpose of the Study:

• To evaluate the efficacy of a bioretention soil mixture amended with aluminum-based drinking water treatment residuals.
• To assess the impact of a saturation zone and vegetation on nutrient removal (nitrate and ortho-phosphate) from stormwater.
• To determine the optimal configuration for nutrient reduction in bioretention systems.

Main Methods:

• Experimental setup using columns with and without a saturation zone and vegetation.
• Testing a bioretention soil mixture composed of sand and compost, enhanced with aluminum-based residuals.
• Monitoring nitrate and ortho-phosphate concentrations in effluent water to quantify removal rates.

Main Results:

• A saturation zone significantly improved nitrate removal (71% with vs. 33% without).
• Ortho-phosphate removal was more effective in columns without a saturation zone (80% vs. 67%).
• Vegetation did not show a significant impact on nutrient removal in this study.

Conclusions:

• Aluminum-based amendments are effective for phosphorus removal in bioretention systems.
• A saturation zone is beneficial for nitrogen removal, particularly during the initial establishment phase.
• Optimizing bioretention design, including the presence of a saturation zone, is key for targeted nutrient management in stormwater.