Natural Geo-Filter Bed and Halophyte Wetland: An Eco-Engineering System to Mitigate Saline Highway Runoff Impacts

R. Galvez, S. Leroueil, G. Triffault-Bouchet, L. Martel, and B. Morteau (Canada)

Keywords

Geofilter, wetland, halophytes, highway runoff, salts, heavy metals

Abstract

Snow fall and ice storm events are major problems for road security in Canada. As a consequence provinces and territories spread salt and other de-icing products on road and motorway networks in order to protect drivers and transporters. Ecosystems located close to transport networks are affected by salt contamination, in particular small lakes and ponds suffer from contamination due to their low water renewal rates. The Saint-Augustin lake (0.60 km2 ) and its watershed (7.46 km2 ) near Old Quebec City are subject of these impacts as every spring high amount of salts are carried with highway runoff. Preliminary studies have shown that water conductivity has increase rapidly from the construction of motorway in 1974 (from 350 to 1300 uS/cm) and saline algae have been identified in the sediments of the lake. The goal of this research project is to evaluate a two-step treatment system that will be used to treat saline highway runoff which contains typically: Na and Ca chlorides, Phosphorus (P), Heavy metals and hydrocarbons. The system includes two unit processes; one is an active filter bed packed with an adsorbent geomaterial and an adapted constructed wetland which uses halophytes plants from the Saint-Lawrence estuary (Kamouraska, Qu├ębec). This article presents the preliminary results on the choice of geomaterial and halophyte plants. The article also presents adsorption (by the geomaterial) and absorption (by halophytes) to retain salt and the other targeted contaminants.

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