Construction Of Pollutant Degradation Kinetics Model In Artificial Aerobic Wetland And Engineering Practice

Artificial aeration wetlands are widely used in the treatment of contaminated water,which has the incomparable advantages of traditional constructed wetlands.However,aeration vertical flow wetland units,as the core of Artificial aeration wetlands,play an irreplaceable role in purifying wastewater Role.Based on the application of aeration vertical flow unit in the actual project of three Artificial aeration wetlands and two model tests,according to the kinetic relationship between pollutant removal and hydraulic load in model test,a first-order kinetic model of pollutant removal was established.The results of the study reveal the purification effect of aeration vertical flow wetland units and the influence law of gas-water ratio,hydraulic load and pollution load on the pollutants,and improve the space utilization efficiency and pollutant removal efficiency of the aeration vertical flow wetland unit.unified design guide of artificial aeration wetland process in our research group,provided a scientific basis and theoretical guidance on further optimization of artificial aerobic wetland technology.The main conclusions are as follows?1?The average CODcr removal efficiencies of the three aeration vertical flow wetlands in Kunming,Changge and Hefei were 41.9%,30.8%and 14.2%,respectively.The average removal rates for NH₃-N were 55.3%,52.2%and 25.2%,respectively.The average removal rates for TN were 25.8%,18.7%and 25.0%,respectively.The average removal rates for TP were 36.2%,30.2%and 33.9%,respectively.The order of wetland removal is as follows:Kunming wetland>Changge wetland>Hefei wetland.The removal efficiency of CODcr,NH₃-N,TP is better,while the removal efficiency of TN is slightly worse.?2?The removal rates of COD_cr,NH₃-N,TN and TP in the aeration vertical flow wetland project were affected to different degrees by the season,the general removal effect is best in summer,worst in winter.The removal of NH₃-N and TP was the least influenced by the seasons.The removal rates of NH₃-N in Kunming wetland and Changge wetland were relatively stable at about 50%,and artificial aeration could effectively improve the efficiency of oxygen transfer in winter and enhance wetland treatment performance.The removal rate of TP ranged from 25%to 40%,with little difference between different wetlands.?3?In different seasons,the effluent concentrations of COD_cr,NH₃-N,TN,TP in aeration vertical flow wetland project are different.Except the effluent concentration of CODcr in Changge and Kunming wetland reach the corresponding effluent requirement,other pollutants did not reach the effluent requirements.Wetland project only through the pretreatment system+aeration vertical flow wetland can not completely make the pollutant concentration reach the effluent requirements,the subsequent horizontal subsurface flow or oxidation pond process was essential.?4?Through the model test,the change of gas-water ratio has a significant effect on the changes of CODcr,NH₃-N and TN.With the increase of gas-water ratio,the removal rate of CODcr gradually increases.The average removal rates of NH₃-N were 31.8%,36.9%,40.4%,54.0%,60.8%and 64.1%respectively.The NH₃-N removal rate rised firstly and then declined with the increase of gas-water ratio,the average removal of NH₃-N were 40.7%,62.5%,79.5%,89.7%,76.3%and 71.9%.The TN removal rate was similar to that of NH₃-N,TN also showed the trend of first rising and then declining with the increase of gas-water ratio,and the average removal of TN were 26.2%,27.6%,35.8%,48.04%,45.8%and 43.9%respectively.The change of air-water ratio has no significant effect on the average removal rate of TP,and the removal rates of TP are 43.9%,45.5%,44.1%,45.3%,47.1%and 43.5%,respectively.?5?The results of model tests show that the hydraulic?pollution?load has little effect on the removal efficiency of CODcr at different gas-water ratios,and there is no significant correlation between hydraulic?pollution?load and CODcr removal rate.With aeration vertical flow wetland hydraulic?pollution?load increases,NH₃-N,TN,TP removal rate decreased gradually.There was a good linear relationship between hydraulic?pollution?load and NH₃-N,TN and TP removal rates.?6?For the aeration vertical flow wetland unit in the model test,the first-order kinetic model can better simulate the removal rule of NH₃-N,TN and TP,while the data were no significant correlation between the hydraulic load and CODcr removal rate.CODcr removal process does not meet the first-order kinetic model equation.With the gas-water ratio of 1:2,1:1,2:1 increased on aeration vertical flow wetlands,NH₃-N degradation kinetic coefficients K were 0.2869,0.4525,0.5008,respectively;TN degradation kinetic coefficients K were 0.0838,0.1052 and 0.1018,respectively.The kinetic coefficients K of TP were 0.4142,0.4349 and 0.2274,respectively.The model has some application value for the design optimization of aeration vertical flow wetland and prediction of effluent quality.