Treatment of Stormwater Runoff and Landfill Leachates Using a Surface Flow Constructed Wetland

Abstract

A surface flow wetland was constructed in the Burnside Industrial Park, Dartmouth, Nova Scotia, to treat stormwater runoff from the surrounding watersheds which are comprised primarily of commercial properties and two former landfills. The aim was to protect a freshwater ecosystem that consists of a 4.6 km long brook and two lakes. The ability of the constructed wetland to retain iron and manganese from the influent water was investigated and the change in pH of the water as it flowed through the cells was assessed. In 2004, the total iron removal efficiency of the constructed wetland ranged from a low of 47.13 % to a high of 84.74 % and in 2006 ranged from a low of 35.56 % to a high of 78.49 % depending on rain events. The outlet total iron concentrations in 2006 were not significantly different from those reported for 2004. In 2004, the total manganese removal efficiency of the constructed wetland ranged from a low of 25.75 % to a high of 51.61 % and in 2006 ranged from a low of 0.0 % to a high of 33.33 % depending on rain events. The inlet and the outlet total manganese concentrations in the constructed wetland from August to October 2006 were significantly higher than the inlet and the outlet total manganese concentrations reported for August to October 2004 because water levels in the constructed wetland were very low and the average pH of the outlet water was lower in 2006. In 2004 and 2006, the pH of the water in the constructed wetland had average inlet values of 6.70 and 6.26 and average outlet values of 7.28 and 6.70, respectively.