Comparison of horizontal and vertical constructed wetland systems for landfill leachate treatment

The main purpose of this study was to treat organic pollution, ammonia and heavy metals present in landfill leachate by the use of constructed wetland systems and to quantify the effect of feeding mode. The effect of different bedding material (gravel and zeolite surface) was also investigated. A pilot-scale study was conducted on subsurface flow constructed wetland systems operated in vertical and horizontal mode. Two vertical systems differed from each other with their bedding material. The systems were planted with cattail (Typha latifolia) and operated identically at a flow rate of 10 l/day and hydraulic retention times of 11.8 and 12.5 day in vertical 1, vertical 2 and horizontal systems, respectively. Concentration based average removal efficiencies for VF1, VF2 and HF were NH4–N, 62.3%, 48.9% and 38.3%; COD, 27.3%, 30.6% and 35.7%; PO4–P, 52.6%, 51.9% and 46.7%; Fe(III), 21%, 40% and 17%, respectively. Better NH4–N removal performance was observed in the vertical system with zeolite layer than that of the vertical 2 and horizontal system. In contrast, horizontal system was more effective in COD removal.