Study On The Effect And Microbiology Mechanism Of Constructed Wetlands On Wastewater With A Higher Concentration Of Nitrate/Nitrite

With the improvement of national requirements on surface water quality, sewage treatment plant effluent and surface water quality requirement of contradiction is increasingly outstanding. Artificial wetland sewage treatment system has stable operation, convenient management and the characteristics of low operation cost in sewage depth processing. However, in actual operation of the wetland, the water may exist NO3-/NO2- overweight problem.The main ways of wetland nitrogen removal include plant uptakeing, soil adsorption and microbial metabolism, permanent removal of nitrogen rely on denitrification process, which is conducted by denitrifying bacteria. Since constructed wetlands has been overwhelming applying in our country, we gradually get a clear understanding of bottlenecks in dealing with special high nitrogen waste water encountered, and has accumulated rich experience in large-scale practice.In this study, we use high concentrations of NO3-/NO2- wastewater as main studying objects to explore total effect of constructed wetland system purifying high concentrations of NO3-/NO2- wastewater, analyze the law of nitrogen removal process when C Ws migrate and transform nitrogen to other pattern, and figure out the microbial community structure and main characteristics of their communities, and thus explain how high concentrations of NO3-/NO2- wastewater influence nitrogen’s migration and transformation process. The main conclusions are as follows:(1) Through the study of contaminant removal we found that pollutants concentration of the three devices shows little difference which means CWs removes pollutants for waste water containing high concentrations of NO3-/NO2- very efficiently.(2) The result of base analysis for artificial wetlands material circulation and balance showed that the most efficient way of carbon removal is bacterial respiration, followed by base accumulation; that the most efficient way of nitrogen removal is bacterial denitrification, followed by base accumulation and plant absorption; that the most efficient way of phosphorus removal is base accumulation, followed by plant absorption.(3) Analysis of Nitrogen-related bacterium in CWs showed that the denitrifying bacteria abundance and activity of the nitrate group was significantly stronger than the other groups, but the nitrite group showed the highest total bacterial abundance; the N2O reduction efficiency of the nitrate group has been greatly improved, in this way its N2O emission rate is significantly lower than other groups.(4) Analysis of microbial community structure showed that wastewater with proper concentration of nitrate promote the process of wetland nitrogen removal, because the denitrifying bacteria activity of the nitrate group was significantly stronger than the other groups.However, the overall nitrification rate in three devices is quite weak.