Research On Establishment Of N₂O Dynamics Model And Key Control Factors In Sequencing Batch Reactor Wastewater Treatment Process

N₂O as a strong greenhouse gas,not only exacerbated the global greenhouse effect,causing damage to the ozone layer,and in certain meteorological conditions can promote the formation of acid rain.Furthermore,N₂O can easily convert into secondary particulate pollutants and increase the haze.The process of biological nitrogen removal is considered to be an important source of N₂O generation and release.Therefore,it is urgent to establish the N₂O emission reduction control strategy in the process of wastewater treatment.At present,most of the emission reduction control theories are based on the single factor or multiple factors,which are lack of detailed description of the N₂O production mechanism and the quantitative and accurate simulation.In this study,based on the discussion of the mechanism of N₂O production,the N₂O dynamics model of nitrification and denitrification was constructed based on ASM3 model.Aiming at the SBR technology,the model calculation and parameter fitting algorithm are established by the MATLAB software.In addition,based on the actual application of SBR technology and the previous research results,the key control factors of N₂O emission is determined and then carry out experimental research on key control factor.Finally,the recommended operating conditions are put forward according to the test results,and then the optimum condition of reduction N₂O emission which based on model is established.In order to construct a scientific and reasonable N₂O dynamics model,this study detailed describes the nitrification phase different reaction processes,and then a N₂O dynamics model based on reasonable simplification of Activated Sludge Model NO.3?ASM3?and coupling of nitrosyl radical?NOH?chemicaldecomposition and ammonia-oxidizing bacteria?AOB?denitrification pathways for N₂O productions is established during nitrification which can reflect the process of microbial growth and decay and as well as simulate scientifically for the consumption of organic compounds during nitrification.Furthermore,the four reaction processes of heterotrophic denitrification stage are described in this study,which reflect N₂O as the intermediate product of denitrification process.Based on previous studies and theory of microbial hypoxia endogenous respiration,a theoretical assumption of microorganism as electron donors and NO₂-as electron acceptors which can lead to N₂O generation was put forward,and then a N₂O dynamics model is established during denitrification by this theoretical assumption.In addition,this study uses the MATLAB mathematical software to construct the model calculation method,the initial value determination method and the parameter fitting method based on the SBR,and the parameters of high-sensitivity parameters in the N₂O dynamic model of nitrification and denitrification process were determined by using the literature data and experimental data respectively,and then two sets of kinetic and chemometrics parameters were determined by MATLAB software.At the same time,the concentration changes of COD,NH₄⁺,NO₂^-,NO₃^-,N₂O components innitrification process and COD,NO₂-,NO3^-,N₂O components in denitrification process were simulated respectively.And then the investigation of correlation coefficients?R²?between model predictions and experimental data is carried out and the result showed that the N₂O dynamics model have a great agreement between the predictions and experimental data.Finally,this study summarizes the research results of the research group and the problems that in the actual operation of SBR,determined the key control factorsof reduction N₂O emissionwhich are DO,carbon source dosage in denitrification process and running time.In addition,using artificial simulated wastewater,the the N₂O release law was explored in the DO,denitrification carbon source dosage and running time,and the results showed that the recommended operating conditions are as follows: DO=2.5mg/L,denitrification carbon source dosage was 75mg/L,running time was 8 hours.Then using MATLAB optimization algorithm,this study takes the recommended operation condition as the initial value and determine the optimal control conditions,which are as follows: the running time of nitrification and denitrification stages are 3 hours,the whole process of the sludge age of 35 days,the concentration of DO are 2mg/L and the denitrification carbon source dosage was 70mg/L.At the same time,under the optimal conditions,this study investigated the pollutants removal efficiency and N₂O release law,and the result proves that the optimal operating conditions are favorable for reducing the amount of N₂O produced in the SBR.