Modeling and verification method for nitrous oxide kinetics model of short-cut denitrification process

Abstract

The application discloses a short-range denitrification process nitrous oxide kinetics modeling and verification method, and specifically comprises the following steps: simplifying the ASM3 model, retaining the core biochemical processes and components related to the growth, storage and endogenous respiration of heterotrophic bacteria; expanding the reaction mechanism to construct the biochemical process involved in the short-range denitrification process to produce N2O; constructing a new way of directly using NO2- as an electron acceptor to produce N2O in the endogenous respiration stage of microorganisms; considering different electron donors and acceptors in each biochemical process, constructing a process rate equation; selecting high-quality short-range nitrification-denitrification experimental data published to test the constructed model; taking self-test data as a benchmark, iteratively fitting and calibrating key parameters, so that the model prediction value and the actual measured value are optimally fitted.

Description

Technical fields:

[0001] This invention belongs to the field of wastewater biological treatment and resource utilization technology, and specifically relates to a method for modeling and verifying the kinetic model of nitrous oxide oxidation in a short-range denitrification process. Background technology:

[0002] Nitrous oxide (N2O) is a significant greenhouse gas with a global warming potential significantly higher than that of carbon dioxide. While very stable in the troposphere, N2O can rise to the stratosphere and undergo photochemical reactions with ozone, thus depleting the ozone layer and contributing to acid rain. It can also mix with particulate matter to form smog, causing serious public health problems. N2O emissions from wastewater treatment processes are a major source of this pollution.

[0003] Currently, researchers have established corresponding kinetic models for various N2O generation pathways based on different theoretical assumptions. These models are mainly divided into N2O kinetic models based on the incomplete oxidation of NH2OH, N2O kinetic models based on the denitrification of nitrifying bacteria, and comprehensive kinetic models. However, these three types of models still fail to fully explain the emission characteristics of N2O. This lack of theoretical explanation directly leads to the poor performance of kinetic models in controlling N2O in traditional biological nitrogen removal processes. The Activated Sludge Model 3 (ASM3) proposed by the International Water Association (IWA) provides a detailed explanation of the growth decline of microorganisms, endogenous respiration, and the pathways of material production. This model is of key significance for constructing short-cut nitrification-denitrification N2O kinetic models.

[0004] Therefore, this invention aims to construct a kinetic model and verification method for N2O in the short-range denitrification stage based on the modeling theory of the ASM3 model, so as to accurately simulate and verify the N2O generation and release during the short-range denitrification process. This will provide a more scientific theoretical basis for environmental protection aspects such as carbon emission reduction and resource recycling in my country and has important engineering application value. Based on the above analysis, this invention proposes a kinetic model and verification method for N2O generation in the short-range denitrification process. Summary of the Invention:

[0005] The present invention aims to solve the above-mentioned problems.

[0006] This invention discloses a modeling and verification method for the nitrous oxide kinetics model of short-range denitrification process, which mainly includes the following steps: (1) Simplifying the ASM3 model, retaining the core biochemical processes and corresponding components related to heterotrophic bacteria growth, storage, and endogenous respiration; (2) Expanding the reaction mechanism to construct the biochemical processes involved in the production of N2O in the short-range denitrification process; (3) Constructing a new pathway for microorganisms to directly utilize NO2 as an electron acceptor to produce N2O during the endogenous respiration stage; (4) Considering different environmental factors and different electron donors and acceptors in each biochemical process, constructing the process rate equations for each biochemical process; (5) Selecting publicly published, high-quality short-range nitrification and denitrification experimental data to verify the rationality of the constructed model; (6) Using proprietary experimental data as a benchmark, iteratively fitting and calibrating these key parameters to achieve the optimal fit between the model prediction value and the actual measured value.

[0007] In addition, the N2O kinetic model and verification method for the short-cut denitrification process in wastewater proposed according to the present invention also have the following additional technical features:

[0008] Furthermore, the ASM3 model described in step (1) is simplified, retaining the core biochemical processes and corresponding components related to heterotrophic bacterial growth, storage, and endogenous respiration, specifically: COD-induced hypoxic storage, heterotrophic bacterial hypoxic endogenous respiration, and intracellular storage-induced hypoxic respiration; the corresponding component is: S S S NH4 X I X STO X H .

[0009] Furthermore, the extended reaction mechanism described in step (2) involves the biochemical process of N2O production in the short-range denitrification process, specifically by dividing the anaerobic growth of denitrifying bacteria into three steps, namely NO2 - →NO→N2O→N2; This process adds four components: SNO2, SNO, SN2O, and SN2, as well as three corresponding biochemical processes.

[0010] Furthermore, the novel pathway described in step (3) for constructing microorganisms to directly utilize NO2 as an electron acceptor to generate N2O during the endogenous respiration stage is mainly manifested as follows: Under hypoxic conditions, ammonia-oxidizing bacteria (AOB) and heterotrophic bacteria in their decay phase undergo endogenous respiration to maintain basic life activities. The electrons released in this process, in the absence of oxygen and sufficient organic carbon sources, can be directly transferred to NO2 in the system, reducing it to N2O; this process increases the model's X... A A component and a corresponding biochemical process.

[0011] Furthermore, the process rate equations for each biochemical stage described in step (4) are specifically manifested as follows: clarifying the electron acceptors and donors in the seven biochemical processes described above, and establishing corresponding reaction rate equations for each biochemical process.

[0012] Furthermore, step (5) involves selecting publicly available, high-quality short-range nitrification-denitrification experimental data to verify the rationality of the constructed model. Specifically, this involves using MATLAB numerical calculation software to integrate the stoichiometric matrix and process rate matrix of the aforementioned short-range denitrification process, thereby achieving initial value solving, sensitivity analysis, and acclimatization of each reaction parameter in the N2O kinetic model. Then, the literature data and simulation data are compared using the coefficient of determination (R²). 2 To measure the rationality of the model.

[0013] Furthermore, step (6) uses the existing experimental data as a benchmark to iteratively fit and calibrate these key parameters, so that the model predictions and actual measurements achieve the optimal fit. Specifically, the experimental data obtained by running the SBR reactor were used to further acclimatize the model parameters. After acclimatization, simulation was performed again and compared with the experimental data to obtain the coefficient of determination (R²). 2 This is used to verify the correctness of the model.

[0014] This invention is based on a reasonable simplification of the ASM3 model. By adding descriptions of the pathway for N2O production using NO2 as an electron acceptor during short-cut denitrification and a new pathway for N2O production using NO2 as an electron acceptor during microbial decay, a kinetic model for simulating nitrous oxide production during short-cut denitrification in wastewater is constructed. A complete and operable integrated method for model construction and verification is proposed, enabling the model to move from theoretical construction to practical application verification, thus highlighting its engineering application value. Attached image description:

[0015] Figure 1 This is a schematic diagram of the process for modeling and verifying the kinetic model of nitrous oxide oxidation in a short-range denitrification process proposed in this invention.

[0016] Figure 2 This is a fitting analysis of N2O simulation data and literature data from a short-range denitrification stage model.

[0017] Figure 3 This is a schematic diagram of the process for modeling and verifying the kinetic model of nitrous oxide oxidation in a short-range denitrification process proposed in this invention.

[0018] Figure 4 It is a short-range denitrification stage model for NO2 - Fitting analysis of simulated data and literature data

[0019] Figure 5 It is a short-range denitrification stage model for NO2 - Fitting analysis of simulated data and reactor test data

[0020] Figure 6 This analysis is a fitting analysis of N2O simulation data and reactor experimental data from the short-range denitrification stage model.

[0021] Figure 7 Fitting analysis of COD simulation data and reactor experimental data from the short-range denitrification stage model. Detailed implementation method:

[0022] Figure 1 This is a schematic diagram illustrating the construction process of a kinetic model for simulating nitrous oxide production during wastewater denitrification, as proposed in this invention. The following is in conjunction with... Figure 1 A detailed explanation of each step in the nitrous oxide oxidation kinetic model of the wastewater denitrification process:

[0023] Step (1): Simplify the ASM3 model, retaining the core biochemical processes and corresponding components related to heterotrophic bacterial growth, storage, and endogenous respiration.

[0024] Specifically, the core biochemical processes related to the growth, storage, and endogenous respiration of heterotrophic bacteria are preserved: COD-induced anaerobic storage, heterotrophic bacterial anaerobic endogenous respiration, and intracellular storage product anaerobic respiration; the corresponding components are: S S S NH4 X I X STO X H The stoichiometric matrix of its components and biochemical processes is shown in Table 1.

[0025] Table 1: Stoichiometry matrix of components and biochemical processes after simplifying ASM3 model

[0026]

[0027]

[0028] Where S S S represents the organic components in wastewater. NH4 Indicates NH4 in wastewater + Component; X STO Indicates intracellular storage components; X H Indicates heterotrophic bacteria; X I This indicates inert particulate organic matter; this step also includes a total of 4 stoichiometric coefficients (i N,SS S represents S The content of N in the middle, i N,BM Indicates the content of N and Y in microorganismsSTO,NO Indicates NO - When used as an electron acceptor, the unit S S Oxygen-deficient yield of stored material, f I Indicates X in endogenous respiration I (yield), these parameters can be obtained from experiments or literature as needed.

[0029] Step (2): Expand the reaction mechanism to construct the biochemical process for generating N2O involved in the short-range denitrification process.

[0030] Specifically, the anaerobic growth of denitrifying bacteria is divided into three steps, namely NO2 - →NO→N2O→N2; This process adds four components: SNO2, SNO, SN2O, and SN2, as well as three corresponding biochemical processes; the stoichiometric matrix of each component and biochemical process is shown in Table 2.

[0031] Table 2: Stoichiometry Matrix of Anaerobic Growth Process of Denitrifying Bacteria

[0032]

[0033] Where S NO Indicates NO component in wastewater; S N2O Indicates the N2O component in wastewater; S N2 Indicates the N2 component in wastewater; S NO2 Indicates NO2 in wastewater - Components; this step also adds two stoichiometric coefficients (in the case of NO2). - Heterotrophic bacterial yield under hypoxic conditions when Y is an electron acceptor H,NO2 , Hypoxia yield of heterotrophic bacteria with N2O as electron acceptor - Y H,N2O These parameters can be obtained from experiments or literature as needed.

[0034] Step (3): Construct a new pathway for microorganisms to directly utilize NO2 as an electron acceptor to generate N2O during the endogenous respiration stage.

[0035] Specifically, constructing ammonia-oxidizing bacteria and heterotrophic bacteria using NO2 - Microbial endogenous respiration, acting as an electron acceptor, is thought to lead to the generation and release of N2O; the stoichiometry matrix of its components and biochemical processes is shown in Table 3.

[0036] Table 3: Chemometric Matrix of Components and Biochemical Processes in the Hypoxic Respiration Stage of Microorganisms

[0037]

[0038] Where X AThis indicates ammonia-oxidizing bacteria; this step also adds one stoichiometric coefficient (X). I The content of N in the middle - i N,XI This parameter can be obtained from experiments or literature as needed.

[0039] Step (4): Based on the differences in electron acceptors and electron donors in each biochemical process in the model, and in conjunction with the corresponding environmental influencing factors, establish the process rate equations for each biochemical stage.

[0040] Specifically, represents the specific growth rate of denitrifying bacteria at each step of the anaerobic growth process; represents the specific growth rate of ammonia-oxidizing bacteria using NO2. - The specific decay rate of microbial endogenous respiration when acting as an electron acceptor; the rate equations for each of its biochemical processes are shown in Table 4.

[0041] Table 4: Rate equations for the N2O kinetic model during the denitrification stage

[0042]

[0043] Where k STO η represents the COD storage rate constant; COD,NO Indicates the hypoxic storage reduction factor; μ x Indicates the maximum specific growth rate of heterotrophic bacteria in different biochemical processes; b x K represents the rate of hypoxic endogenous respiration in different microorganisms during various biochemical processes. x These represent the saturation constants of different substances; these parameters can be obtained from experiments or literature as needed.

[0044] Step (5): Select publicly available, high-quality short-range nitrification-denitrification experimental data to test the rationality of the constructed model. The specific operation is as follows:

[0045] Sensitivity analysis was performed on the parameters of the constructed short-range denitrification N2O kinetic model relative to the three components of readily biodegradable substrate, nitrate nitrogen, and nitrous oxide. Key parameters that have a significant impact on the simulation results of the short-range denitrification N2O kinetic model were screened out and used for the re-acclimatization of key parameters of the subsequent short-range denitrification N2O kinetic model.

[0046] The key parameter selection method for this model. The verification formulas used are as follows:

[0047]

[0048] In the formula: P represents the relative sensitivity of the simulation model parameters to the influence of the model simulation. When P > 0, it indicates that the change in the simulation model parameters is in the positive direction; if P < 0, it is in the opposite direction. 初 For parameters in the simulation model; x 变To make x 初 The simulation model parameter values ​​after a certain change are taken as (1+10%)x in this study. 初 C 初 The initial concentration of the component is used to simulate the model; C 变 To obtain the concentration of the simulated component by varying the simulation model parameters by a certain range, parameters with values ​​between -0.3 and 0.3 were selected for acclimatization.

[0049] The key parameter that has a significant impact on the short-cut denitrification process is: k STO η COD,NO K 1,N2O K A,NO2 K 1,NO2 b A,NO2 K S K 1,STO K 2,STO b STO,NO2 .

[0050] The aforementioned parameters that significantly influence the short-range nitrification-denitrification (N2O) kinetic model were screened, and these parameters still require further refinement. The specific process for parameter refinement is as follows: First, the reaction processes and parameter variables of the short-range nitrification-denitrification (N2O) kinetic model constructed above are imported into MATLAB software. Then, key parameters with significant influence are defined, and parameters with less influence are assigned values. These values ​​are derived from literature and empirical methods, and multiple values ​​are taken to achieve small-interval assignment. Finally, the key parameters are re-refined using programming code.

[0051] After initial conditioning of the key parameters, the constructed short-range denitrification N2O kinetic model can be simulated against literature data to further verify the model's accuracy. The N2O and NO2 content in the short-range nitrification stage can be compared and fitted. - And model prediction data and literature data on the concentration changes of the three components of COD over time, with the coefficient of determination (R²) 2 To measure the goodness of fit of the model, the results of the fitting analysis between simulated data and literature data are analyzed. Figures 2-4 as follows:

[0052] The short-range denitrification stage N2O kinetic model for N2O and NO2 - And the fitting of simulated COD data with literature data R 2 The values ​​were 0.813, 0.831, and 0.970, respectively, indicating that the model simulated the short-range denitrification stage of N2O and NO2. - The concentration changes of the three components, including COD, also showed good accuracy.

[0053] Step (6) uses the existing experimental data as a benchmark to iteratively fit and calibrate these key parameters, so that the model predictions and actual measurements achieve the best fit. The specific operation is as follows:

[0054] To further improve the simulation accuracy of the existing short-range nitrification-denitrification N2O kinetic model, experimental data obtained from running an SBR reactor were used to further refine the model parameters. The refinement method was the same as that used for parameter refinement in the literature. The simulation data are shown below. Figures 5-7

[0055] pass Figures 5-7 Analysis shows that the N2O kinetic model for the short-range denitrification stage is relevant for NO2. - The simulated data of N2O and COD were fitted with the reactor test data. R 2 The values ​​were 0.822, 0.930, and 0.943, respectively. Compared with the fitting results of literature data, the model showed a higher goodness of fit to the experimental data. This indicates that the constructed N2O kinetic model has a better understanding of the NO2 content during the short-range denitrification stage. - The simulation of the concentration changes of the three components, namely N2O and COD, has a high degree of accuracy.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A kinetic model and verification method for nitrous oxide oxidation in a short-range denitrification process, characterized in that, Includes the following steps: Step (1): Simplify the ASM3 model while retaining the core biochemical processes and corresponding components related to heterotrophic bacterial growth, storage, and endogenous respiration; Step (2): Expand the reaction mechanism to construct the biochemical processes involved in the production of N2O in the short-range denitrification process; Step (3): Construct a new pathway for microorganisms to directly utilize NO2⁻ as an electron acceptor to generate N2O during the endogenous respiration phase; Step (4): Considering different environmental factors and different electron donors and acceptors in each biochemical process, construct the process rate equations for each biochemical process; Step (5): Select publicly available, high-quality short-range nitrification-denitrification experimental data to test the rationality of the constructed model; Step (6): Based on our own experimental data, iteratively fit and calibrate these key parameters to achieve the optimal fit between the model prediction and the actual measurement.

2. The kinetic model and verification method for nitrous oxide oxidation in a short-range denitrification process according to claim 1, characterized in that, The simplification of the ASM3 model described in step (1) retains the core biochemical processes and corresponding components related to heterotrophic bacterial growth, storage, and endogenous respiration. Specifically, it retains the core biochemical processes related to heterotrophic bacterial growth, storage, and endogenous respiration: COD-induced hypoxic storage, heterotrophic bacterial hypoxic endogenous respiration, and intracellular storage product hypoxic respiration; the corresponding components are: S... S S NH4 X I X STO X H。 3. The kinetic model and verification method for nitrous oxide oxidation in a short-range denitrification process according to claim 1, characterized in that, The extended reaction mechanism described in step (2) involves the biochemical process of N2O production in the short-range denitrification process. Specifically, the denitrifying bacteria growth under anaerobic conditions is divided into three steps, namely, NO2 production... - →NO→N2O→N2, this process adds four components: SNO2, SNO, SN2O, and SN2, as well as three corresponding biochemical processes.

4. The kinetic model and verification method for nitrous oxide oxidation in a short-range denitrification process according to claim 1, characterized in that, The construction of a new pathway for microorganisms to directly utilize NO2⁻ as an electron acceptor to produce N2O during the endogenous respiration stage, as described in step (3), specifically involves: representing ammonia-oxidizing bacteria as those that utilize NO2⁻ as an electron acceptor to produce N2O. - Endogenous respiration when acting as an electron acceptor affects denitrifying bacteria, ammonia-oxidizing bacteria, and the construction of NO2-based systems. - Microbial endogenous respiration, acting as an electron acceptor, is considered to lead to the production and release of N2O, a biochemical process that increases the X-ray concentration in the model. A A component and a corresponding biochemical process.

5. The kinetic model and verification method for nitrous oxide oxidation in a short-range denitrification process according to claim 1, characterized in that, The process rate equations for each biochemical stage in the short-range denitrification N2O kinetic model described in step (4) are as follows: [Equations for specific growth rates of denitrifying bacteria in each step of the anoxic growth process, and equations for denitrifying bacteria, ammonia-oxidizing bacteria, and NO2-oxidizing bacteria are described in step (4).] - The specific decay rate of microbial endogenous respiration when acting as an electron acceptor.

6. The kinetic model and verification method for nitrous oxide oxidation in a short-range denitrification process according to claim 1, characterized in that, Step (5) involves selecting publicly available, high-quality short-range nitrification-denitrification experimental data to verify the rationality of the constructed model. Specifically, this involves: screening key parameters of the N2O kinetic model for the short-range denitrification process using sensitivity analysis; then using MATLAB software to preliminarily adapt the required parameters; running the model to obtain simulated and predicted data; and comparing and analyzing these data with literature data, using the coefficient of determination (R²) as the basis for the analysis. 2 ) measures the goodness of fit of the model.

7. The kinetic model and verification method for nitrous oxide oxidation in a short-range denitrification process according to claim 1, characterized in that, Step (6) describes using proprietary experimental data as a benchmark to iteratively fit and calibrate these key parameters to achieve the optimal fit between the model predictions and actual measurements. Specifically, this involves obtaining experimental data by running the SBR reactor, re-adjusting the model parameters using the experimental data, re-running the program to obtain new prediction data, and then comparing and analyzing this new data with the experimental data to determine the coefficient of determination (R²). 2 ) measures the goodness of fit of the model.

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