Mechanism of nitrogen and phosphorus removal in free-water surface constructed wetland

The mechanism of nitrogen and phosphorus compound removal by the biological, physical and chemical processes in the free-water surface constructed wetlands is reviewed in this paper. Denitrification and sedimentation to the soil are widely accepted as the main pathways through which nitrogen and phosphorus are removed from the wastewater by free-water surface constructed wetlands, but there are significant differences among different researches, and further researches are still required to get detailed information of these processes and pathways for establishing the ecosystem dynamic models, in order to design and predict the performance of free-water surface constructed wetlands, and enhance its application to wastewater treatment.