Processes and Drivers of Nitrogen Removal in Stormwater Biofiltration

Biofiltration systems harness the treatment capabilities of plants, microorganisms, and soil to mitigate impacts of polluted stormwater. However, their effectiveness for nitrogen removal can vary, from concentration reductions exceeding 70% to net leaching. Performance is particularly sensitive to plant species selection, presence of a saturated zone with carbon source, and the frequency of inflows. The authors review controls on nitrogen cycling in natural and modified environments to identify important processes and influences within biofilters. Key factors include plant-microbial interactions, root architecture, plant strategy, and moisture heterogeneity. They note a critical lack of studies comparing nitrogen removal through denitrification and plant assimilation.