Background and purpose: There are limited studies on the natural systems of wastewater treatment by artificial wetlands subsurface in Northern Iran. The goal of this study was determining the efficiency of the artificial wetlands pilot system and the efficiency of horizontal subsurface flow systems for a variety of pollutants. Materials and methods: This study used artificial wetlands pilot system for removal of BOD, COD, TSS, TKN and TP in wastewater. Dimensions of reactors used in this study were 4 to 6 m length, 1.5m width and 0.8 m depth. Reactor No. 2 was used as a blank (unplanted) reactor. Reactors were located in parallel and Phragmites Australis -a commonly found plant in the area- was used in this study. Samples of wastewater were taken from the input and output of constructed wetland’s subsurface and tested in laboratory of faculty of health in Mazandaran University of Medical Sciences based on the standard reference method for experiments in water and wastewater. Results: Average removal using subsurface wetland showed that the unplanted reactor efficiency for removal of BOD,COD,TSS,TKN and TP was 47.11, 70.26, 50.83,19.69 and 91.69 percent and for reactors with Phragmitis Australis the percentage was 81.47, 78.5 ,87.87,76.18 and 97.80, respectively. Optimum hydraulic detention time was six days and gravel size 10 mm was better than 20 mm. Conclusion: This system as an efficient system can reduce the conventional pollutants of wastewater to the standards of secondary wastewater treatment. Furthermore, this system can remove nitrogen and phosphorus from effluent discharges more than conventional systems.

Keywords: Subsurface Constructed Wetland, Pollutant Removal

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