Study of Nitrogen and Phosphorus Removal from Simulated River Water by Integrated Vertical Flow Wetland

An unplanted and integrated vertical-flow wetland was constructed for research to treat the simulated water of rivers flowing into Meiliang Bay of Taihu Lake. A variety of zeolites with different particle sizes were applied to this wetland, in order to promote biofilm and nitrogen adsorption on the zeolites. The results from five-month operation indicated that, when the hydraulic loading was 0.375 m³/(m²•d) and influent concentrations of NH₃-N, NO₂^--N, TN and TP were 3.8-5.1, 0.9-1.8, 6.6-8.5 and 0.32-0.47 mg/L, the corresponding average removal rates were 97.5%, 95.5%, 26.6% and 18.9%, respectively. The nitrogen removal rate mainly depended on the nitrification and denitrification in the system. Due to lack of carbon source in the system, the denitrification process was strongly inhibited, and the denitrification was stronger than the nitrification, thus resulting in the increased NO₃^--N level in effluent, which accounted for 96.7% of TN in effluent.