Forested Infiltration Areas as a Natural Solution for Nitrate Mitigation in Contaminated Water

A Managed Aquifer Recharge (MAR) approach is being utilized through a Forested Infiltration Area (FIA) to mitigate nitrate contamination in an aquifer situated within a Nitrate Vulnerable Zone. This innovative technique is deployed at a pilot site where the groundwater nitrate contents is higher than the threshold of regulatory limits defined by the EU Directive 91/676/EEC. Drainage water, sourced from a nearby dewatering pumping station and containing an average nitrate concentration of 70 mg L−1, is channeled into the area. The infiltration process occurs through six recharge trenches, totaling 300 m in length and one meter in depth, filled with a mixture of eucalyptus wood chips (50% by volume), inert material, clay and iron oxides. This blend termed the “Passive Treatment System” (PTS), enhances the activity of denitrifying bacteria that transform nitrate (NO3−) into nitrogen gas (N2). The objective is to lower nitrate levels in the drainage water entering the trenches and subsequently use this treated water to recharge and dilute the polluted underlying aquifer. Hydrogeochemical monitoring results indicate a notable decrease in NO3− in the infiltrated water, demonstrating that the FIA method can be an effective Nature-Based Solution for the remediation of nitrate-contaminated water.