Metal and metalloid sequestration in a constructed wetland system for treatment of landfill leachate during 2003-2012

Abstract: Landfill leachate treatment can be expensive and energy consuming when carried out in wastewater treatment plants. However, there can be several possible solutions for reducing cost and energy requirements and one of them is on-site biological treatment of polluted landfill leachate in constructed wetland systems. This paper evaluates the sequestration of 15 metals and 2 metalloids in a free water surface flow constructed wetland consisting of 10 ponds at Atleverket near Örebro during a period of ten years. The operation and maintenance of treatment wetland is minimal and the retention time is highly variable but generally between 6-12 months. The water flows by gravity from one pond to another. The system which was designed for removal of nitrogen and organic material shows a good retention efficiency of these elements. The analyte concentrations in the effluent and influent were compared by using statistical software. The variations in inlet concentration were significantly higher than in the ones in the outlet. The removal efficiency for all elements but three (magnesium, sulfur and boron) was above 50%. Some elements were retained to a certain level during all years; these elements are Al, As, Ba, Ca, Cr, Cu, Pb, Fe, V, Zn and Mn. Long-term analysis of the operation has shown that the constructed wetland continues to perform well and it retains its ability to remove the metals studied.