Closing the loop. Repurposed iron-coated granulate improves pollutant removal in nature-based solutions

Area of Science:

• Environmental Engineering
• Water Treatment Technologies
• Nature-Based Solutions

Background:

• Optimizing nature-based solutions (NBS) for pollutant removal is crucial for urban drainage systems.
• Repurposed materials offer sustainable amendments for NBS.

Purpose of the Study:

• To evaluate iron-coated granulate as a bioretention amendment for dissolved pollutant removal.
• To compare the performance of amended and unamended bioretention systems under various configurations.

Main Methods:

• Column experiments using pumice and coconut fiber media, with and without 10% iron-coated granulate.
• Testing four configurations: media-only, media with vegetation, saturated zone, and both.
• Assessing removal of phosphorus, copper, zinc, and nitrate from semi-synthetic stormwater.

Main Results:

• Amended systems achieved >90% removal for phosphorus, copper, and zinc.
• Significant improvements in removal rates were observed compared to control systems.
• Copper removal occurred in upper layers; phosphorus and zinc removal required a saturated zone.
• Nitrate removal was higher in unamended systems, possibly due to iron inhibition of denitrification.

Conclusions:

• Iron-coated granulate is a promising amendment for enhancing pollutant removal in bioretention systems.
• Saturated zones are critical for effective phosphorus and zinc removal.
• Careful consideration of carbon addition, contaminant mobilization, and granulate quality (including arsenic) is necessary for practical implementation.