The Use of Horizontal Subsurface Flow Constructed Wetland for Nitrogen Components Removal in Cold and Dry Climate: A Case Study of Birjand, Iran

The aims of this study are investigation of nitrogen components including TKN, NH4+ and NO3- removal by horizontal subsurface flow constructed wetland (HSSFCW) in cold and dry climate and also survey on vegetation, hydraulic loading rate (HLR) and media substrate effects on the system efficiency. Six parallel cells sized 2.2×0.75×0.45 m was built by Wastewater Treatment Plant of Birjand University. The results showed that removal efficiency of TKN and NH4+ in unplanted cells was lower in compare to planted (Phragmitesaustralis) cells, but removal efficiency of NO3- was higher in unplanted cells. Cells with fine gravel media in compare to cells with coarse gravel media, were found to have the higher removal efficiency of TKN and NH4+ but lower removal efficiency of NO3-. Also, decreasing of HLR caused an increase in removal efficiency of TKN and decreasing in removal of NH4+ and NO3-. Regarding low removal efficiency of nitrogen components in HSSFCW, usage of hybrid constructed wetland for providing a good condition of nitrification/denitrification process and increasing nitrogen removal is recommended.