A Preliminary Study On Denitrification Mechanism Of Artificial Aerated Wetlands

With the growth of population and the development of society,the problem of sewage treatment is becoming more and more serious.As a widely used treatment technology,more and more attention has been paid to Artificial Aeration Constructed Wetland（AACW）.A micro aeration vertical flow wetland model was built in July 2016.Under the condition of continuous aeration,a preliminary study on the mechanism of denitrification in artificially aerated wetlands was carried out.The purpose of this study is to analyze the removal law of pollutants in micro aeration vertical flow wetland model under continuous aeration condition;Revealing the kinds of denitrification and respective contribution rate by comparing the removal effects of pollutants under different operating conditions;Carrying out the microbial sampling on the bottom、middle and surface of the model under the optimal working condition and Microbial diversity analysis,The whole research was expected to develop an effective technique to optimize the process parameters、improve space utilization and nitrogen removal efficiency The main results are as follows:1.Micro aeration vertical flow wetland model has a good oxidation environment,the concentration of DO increased with the rise of height;the removal of COD_cr,TN and TP mainly occurred at the bottom of 20cm,while the removal rate and speed of NH₄⁺-N in the system were mainly determined by the ratio of gas to water.2.Under different hydraulic load,the gas water ratio 0:1、1:2、2:3、1:1、3:2、2:1 has the same change rule of pollutants removal rate,and the gas water ratio 3:2 is a critical point.In the critical point,with the increase of gas water ratio,the comprehensive removal effect is continuously improved.But over critical point,the removal effect of a certain pollutant will decrease.3.With the change of hydraulic load,the gas water ratio 0:1、1:2、2:3、1:1、3:2、2:1 has the similar change rule of pollutants removal rate,the removal efficiency decreases with the rise of hydraulic load.The difference is that the high gas water ratio is more stable,the influence of high gas to water is less than the ratio of base water.4.Aerobicandanaerobicdenitrificationcanbecarriedout simultaneously in the vertical flow wetland model after continuous aeration.5.Continuous aeration will change the number of strains on the microbial membrane and affect the relative abundance of microorganisms.The number of dominant species also decreased after continuous aeration.The number of dominant species decreased with the rise of aeration.6.In continuous aeration conditions,the relative abundance of nitrifying Spirillum than middle and surface at the bottom.the aeration intensity will also affect the nitrification Spirillum in the model of competitiveness,the competition power of nitrifying bacteria is enhanced with the increase of aeration,and the nitrification was enhanced,which provided a guarantee for the subsequent denitrification.