Biofiltration for the on-site management of micropollutants in urban runoff: lessons from a field study

International audienceThe present work focuses on lessons learned from the monitoring of total and dissolved concentrations of a wide range of micropollutants (TM, PAH, BPA, AP, PAE) in a biofiltration swale (BFS) treating runoff from a suburban highway during 15 rain events over a 14 month period. This study showed the ability of biofiltration to improve runoff quality with respect to micropollutants, especially those associated with the particulate phase. However, both smaller runoff particle sizes and the formation of cracks in the filter media were associated with degraded particle retention during some events. In addition, materials commonly used in biofilter construction (asphalt, geomembranes, drains and filter fabric), were shown to be sources of BPA, AP and PAE, which led to degraded performance for these pollutants, and should thus be avoided in biofilter design wherever possible. Finally, significant overflow from the studied system limited its annual load reductions significantly, underlining the importance of good hydrologic design in pollutant load removal