EFFICIENCY OF NITROGEN REMOVAL IN CONSTRUCTED WETLAND:A SIMULATION STUDY IN THE WEST JINLIN,CHINA

Plenty of inorganic nitrogen in wastewater can cause the eutrophication in water bodies, so it is an important task to remove nitrogen. Purification role was realized by absorption, filtration, depositon, evaporation, nitrification and denitrification of microbes. Although the studies of Phragmites austrilis bed in the constructed wetland are popular, the purification performances of constructed wetland filled by saline-alkali soil substrate are less reported. In the paper, the purification efficiency of nitrogen with Phragmites austrilis bed in the constructed wetland filled by saline-alkali soil substrate was discussed through a simulation study. Results to date indicated that the first order plug flow model was adequate to describe the nitrogen removal. The experiment showed that the diminishing concentration of TN, NO 2-N, NO 3-N, NH 4-N were closely related to hydrological retention time (HRT), the correlation coefficient was R 2=0.98499, R 2=0.9911, R 2=0.89407 and R 2=0.95459, respectively. According to the data, the most suitable hydrological retention time (HRT) for this kind of constructed wetland should be determined to 4 days. In addition, the experiment showed the purification efficiency of nitrogen has very broad range and drastic vibration, TN (17%-79%), NO 2-N (33%-98%), NO 3-N(13%-93%), NH 4-N (28%-64%). The study will promote wetland's design and operation procedures in large saline-alkaline soil areas.