Evolution of micropollutants in a constructed wetland treating road runoff in Paris (France)

In order to reduce impacts on river Seine, the municipality of Paris (France) has set up a reed bed filter for urban runoff treatment as a part of the European Life Adsorb project. The constructed wetland is separated in two parts with a slightly different substrate composition, one only with sand and second with an additional adsorbent layer. The main objectives are to monitor the evolution of the treatment efficiency and to understand the fate of contaminants within the different substrates.

This paper proposes a short balance of the accumulation of metallic and organic micro pollutants after one year of functioning. The first results show a fast accumulation of micro pollutants in a newly formed sediment layer and a starting retention in the sand layer just below. The accumulation is more important in the surface layers and at the inlet than in the lower layers and at the filter outlet. Accumulation is more important for trace metals are than for alkylphenols. At this stage, the data are not sufficiently consistent to confirm a better retention capacity of the specific absorbent substrate.