Vers une maîtrise à la source de la contamination des eaux pluviales urbaines: Rétention et devenir de micropolluants dans deux ouvrages de filtration végétalisés

Stormwater biofilters aim to manage pollutant loads associated with urban stormwater close to the source through vegetated systems designed for the storage, filtration and sometimes infiltration of water. The polluant management performance is evaluated in situ for two stormwater biofilters, a vegetative filter strip and a biofiltration swale, for a wide range of contaminants, including trace metals and organic micropollutants - polycyclic aromatic hydrocarbons (PAH), alkylphenols, bisphenol-A (BPA), phthalates - in the total and dissolved phases. Mainly particulate pollutants (Pb, Zn and PAH) were very well retained (concentration reductions > 90%) for the majority of rain events. However, a period of degraded particle retention was observed during winter, which was attributed to the relative abundance of fine particles during this period. Dissolved concentration reductions were rarely significant and tended to be lower than those observed for suspended solids and particulate pollutants. Therefore, the lower total concentration reductions were observed for moderately particulate micropolluants, such as BPA, alkylphenols and phthalates. The retention of dissolved trace metals appears to have been limited by their association with dissolved organic matter, while that of the dissolved phase of organic micropollutants was essentially limited by the contamination of the initial filter media or emissions from synthetic construction materials. At the annual scale, the biofiltration swale in its final configuration intercepts between 33-81% of pollutant loads, depending on the contaminant.