Emmanuelle Demers
Project
Resistance and treatment capacity of four macrophytes species to leachate with wood preservativesWood poles treated by preservatives such as pentachlorophenol (PCP) and chromated copper arsenate (CCA), are exposed to weather conditions and leach organic (phenols, dioxins and furans) and inorganic (chromium, copper and arsenic) pollutants. Constructed wetlands are a low cost and low energy consumuing method compared to the chemicals and physicals methods used to treat pole yard leachate but its treatment efficiency, as well as the resistance of plants to such contaminated leachate still need to be demonstrated. The aim of this study is to assess the resistance and treatment capacity of 3 indigeneous macrophytes species (Typha angustifolia, Phalaris arundinacea, P. australis americanus) and one invasive macrophytes (P. australis australis) with regards to leachate containing PCP, CCA, dioxin and furan. Four pilot-scale HSSF (7m2 each) were built on a wood pole yard site, planted with the four macrophytes species in monocultures, and operated since april 2012. Each pilot is fed directly with a real leachate coming from the pole yard. The influent discharge is 125 L J-1 with a hydraulic retention time of the void (HRTv) of 19.5 days. Besides, a pot experiment was performed, during 10 weeks to assess the effects of the pollutant concentration on the resistance of plants and biosorption abilities. The inlet and outlet concentration of metals, phenolic compounds, dioxins and furans for each CW pilots units was measured during summer 2013. For the pot experiment, the plants growth and survival were measured and the plant tissues were analysed for the presence of pollutants. The removal capacity were of 74.89, 79.09, 76.57 and 79,69% for metals and 96.89, 97.87, 95.33 and 96.96 for dioxins and furans forTypha angustifolia, P. australis australis Phalaris arundinacea and P. australis americanus respectivel. In the pot experiment, i) no signs of growth loss were observed for any concentration, ii) arsenic was the only metal detected in the roots of the four plants species and dose-response correlation was observed, iii) most of the phenolic compounds were detected in the roots of the plants. To conclude, no growth loss were observed and the three macrophytes species have pollutants removal efficency and bioaccumulation capacity comparable to the invasive P. australis australis and could be good candidate to treat water contaminated with wood preservatives in a full scale constructed wetland.
