Predatory enhanced cascade fixed biological membrane sewage treatment process double-environment-three-component coupling model

Abstract

The invention belongs to the technical field of environmental engineering, and discloses a predation-enhanced cascade fixed biological membrane sewage treatment process dual-environment-three-component coupling model. Metabolism of autotrophic microorganisms and heterotrophic microorganisms in activated sludge and a biological membrane and predation effects of protozoan and metazoan are comprehensively considered, on the basis of a mass balance principle, a substance conversion way in a biological predation enhanced sewage treatment reactor is analyzed, and dynamic changes of bacteria and pollutants are disassembled into diffusion, metabolism and predation processes; a material flow model framework is established, on the basis of an ASM1 activated sludge model and a biological membrane model, a primary animal predation model and a metazoan predation model are coupled, and a dual-environment-three-component coupling model is recreated. According to the method, the pollutant removal process and the dynamic change of the microbial community are dynamically simulated through multi-model coupling, and the method is suitable for optimizing the design and operation parameters of a sewage treatment reactor and particularly has remarkable application value in regulation and control of a cascade fixed bio-membrane reactor.

Description

Technical Field

[0001] The present invention belongs to the field of environmental engineering technology, and relates to a dual-environment-three-component coupling model of a predation-enhanced cascade fixed biofilm sewage treatment process, which is particularly suitable for the optimized design and operation control of a multi-stage fixed biofilm reactor. Background Art

[0002] Wastewater treatment systems are complex ecosystems composed of bacteria, fungi, protozoa, and metazoans. Specific microbial communities perform different functions, promoting the removal of pollutants. The predation behavior of protozoans and metazoans stimulates stress responses in bacteria, enhancing their metabolic activity. Predators play an important role in improving the system's nutrient transfer efficiency and water purification effectiveness. However, traditional process models have shortcomings when simulating these complex ecological interactions. They rarely address the effects of predation by protozoans and metazoans on bacterial activity and metabolism in reactors, hindering the model's accurate simulation of the process. Therefore, introducing biological predation behavior into the model is of great significance for improving the simulation accuracy of the process model and improving the process efficiency.

[0003] Among many sewage treatment models, the coupling of activated sludge model and biofilm model is often used to characterize the operation of sewage treatment plants containing biological carriers / fillers. In "Fully coupled activated sludge model (FCASM): model development", Peide et al. proposed a model that couples multiple functional microorganisms (such as heterotrophic microorganisms, autotrophic microorganisms, etc.) to describe the denitrification and phosphorus removal and material transfer processes in activated sludge systems. This model embodies the coupled application of biofilm and activated sludge models, focusing on optimizing filler mass transfer and biofilm performance to improve denitrification effects. In "Mathematical modelling of an intermittent anoxic / aerobicMBBR: Estimation of nitrification rates and energy savings", Montecchio et al. used the mixed culture biofilm equation and activated sludge model ASM1 to calculate the biological process of an anoxic / aerobic-moving bed biofilm reactor. The model determined the maximum absorption rate (μ A 2.5d -1 ) and the half-saturation constant (K OA 0.2 mg O2 L -1), and distinguished the removal of total ammonia nitrogen by biofilm and suspended sludge. About 85% of the total ammonia nitrogen was removed by biofilm, and only the remaining part was removed by suspended biomass. In addition, Xu Tao et al. established a biofilm model with the same structural form of the rate equation of microbial growth process in the ASM1 model in "Establishment and Simulation of Composite Model of Activated Sludge and Biofilm", and combined it with the modified ASM1 model for ASM1. 2 These methods improve the water quality indication of process effluents by optimizing model design, but their simulation models still focus primarily on pollutant degradation and mass transfer balance, lacking consideration of predators at the top of the ecosystem food chain, and particularly ignoring the predation mechanism and its dynamic regulation in the reactor.

[0004] Predation models (such as extended models based on Lotka-Volterra dynamics) are used to describe the predation behavior of protozoans and metazoans on bacteria and their regulatory effects on system stability. In sewage treatment systems, predation can effectively reduce the amount of excess sludge and enhance the system's organic matter degradation efficiency. In "Analysis and modelling of predation on biofilm activated sludge process: Influence on microbial distribution, sludge production and nutrient dosage", Revilla et al. constructed a biological predation model based on a biofilm activated sludge system, arguing that predation is the main factor leading to reduced nutrient demand and sludge production. However, the model is divided into two stages: predation in the biofilm system and predation in the activated sludge system, and fails to take into account the suspended activated sludge in the biofilm system. This independence limits the application of predation models in complex multi-stage fixed reactors and cannot fully simulate the nonlinear dynamic interactions between predators and prey.

[0005] In response to the problems of lack of biological predation effect and insufficient accuracy in the simulation model of biofilm wastewater treatment reactor, the present invention innovatively proposes a coupling model of predation-enhanced cascade fixed biofilm wastewater treatment process, organically combining the protozoan and metazoan predation models with the activated sludge model (ASM1) and the biofilm model, and deeply considering the interaction between predators and prey, providing a new theoretical tool and technical support for the simulation of fixed biofilm wastewater treatment process. Summary of the Invention

[0006] The present invention provides a dual-environment, three-component coupling model for a predation-enhanced cascade fixed biofilm wastewater treatment process. Compared to traditional models, this model is based on a multi-stage fixed biofilm wastewater treatment reactor where activated sludge, biofilm, and protozoan and metazoan predation coexist. It introduces the predation behavior of protozoans and metazoans (see Formulas 3-5) and couples the biological predation model, the ASM1 activated sludge model, and the biofilm model. This model clarifies the mass conservation relationship between bacteria, predators (protozoans and metazoans), and pollutants, characterizes the flow and dynamic changes of bacteria, predators (protozoans and metazoans), and pollutants in the activated sludge and biofilm, simulates the effects of biological predation on microbial metabolism, and effectively explains the synergistic effects between microbial growth, degradation efficiency, and the predation process. This model addresses the limitation of traditional ASM1-biofilm coupling models, which rarely address the predation of higher-trophic-level organisms (described in the background art), ensuring the model's accuracy in simulating pollutant removal in multi-stage fixed biofilm wastewater treatment.

[0007] The technical solution of the present invention:

[0008] A dual-environment, three-component coupled model for a predation-enhanced cascade fixed biofilm wastewater treatment process is constructed. The following steps are taken: The metabolism of autotrophic and heterotrophic microorganisms in the activated sludge and biofilm, as well as the effects of predation by protozoa and metazoans, is comprehensively considered. Based on the mass balance principle, the material transformation pathways within the biopredation-enhanced wastewater treatment reactor are analyzed. The dynamic changes of bacteria and pollutants are decomposed into three main processes: diffusion, metabolism, and predation. A material flow model framework is established. Based on the ASM1 activated sludge and biofilm models, the protozoa and metazoan predation models are coupled to recreate a coupled model for a multi-stage fixed biofilm wastewater treatment reactor enhanced by biopredation. The model includes three general framework equations. The Monod kinetic equation describes the microbial growth rate and details the dynamic changes of nitrogen, organic matter (COD), dissolved oxygen (DO), and microbial community in the reactor. The Lotka-Volterra kinetic equation is used to describe the predation process by protozoa and metazoans. The relevant model parameters are range-calibrated and optimized using the Monte Carlo method. Simulation based on the established coupling model can accurately reflect the pollutant degradation process of the multi-stage fixed biofilm wastewater treatment reactor enhanced by biological predation, providing support for optimizing and regulating process parameters to improve pollutant degradation efficiency and reduce carbon emissions.

[0009] The specific steps are as follows:

[0010] Step 1: Establish the model framework

[0011] (1) Dual environment division;

[0012] Activated sludge environment: heterotrophic microorganisms X bh and autotrophic microorganisms Xba They metabolize suspended and dissolved pollutants and exchange substances with biofilms through diffusion. Protozoa and metazoa regulate microbial population density by preying on suspended bacterial communities, and the predation rate follows the Lotka-Volterra kinetic equation.

[0013] Biofilm environment: microorganisms attach to the surface of the filler to form a layered structure, heterotrophic microorganisms X bh,bf and autotrophic microorganisms X ba,bf The metabolism of bacteria is limited by local mass transfer, and pollutants enter the biofilm through the diffusion gradient; protozoa and metazoa mainly prey on suspended bacterial communities, and their predation mechanism is consistent with that in activated sludge environments. The predation efficiency parameter adopts a global unified value.

[0014] The exchange of substances between the two environments is achieved through diffusion, which dynamically balances the regulatory effect of predation on the microbial community.

[0015] (2) Definition of three components;

[0016] (2.1) Bacteria: including heterotrophic microorganisms in activated sludge environments bh and autotrophic microorganisms X ba , and heterotrophic microorganisms X in biofilm environments bh,bf and autotrophic microorganisms X ba,bf ;

[0017] (2.2) Predators: including protozoa and metazoa;

[0018] (2.3) Pollutants: They are divided into dissolved and particulate states. Dissolved states include dissolved rapidly biodegradable organic matter S s , ammonia nitrogen S NH , nitrate nitrogen S NO , dissolved oxygen S O , dissolved biodegradable organic nitrogen S ND ; Particles include slowly degradable organic matter X s , particulate products produced by microbial decay X P , granular biodegradable organic nitrogen X ND ;

[0019] (3) Multi-stage series structure;

[0020] The reactor consists of multiple anoxic tanks and aerobic tanks connected in series, where the effluent from the previous stage serves as the inlet to the next stage, forming a cascade pattern of "anoxic tank → aerobic tank". The series connection order of the anoxic tanks and aerobic tanks is fixed, and there is no alternating structure.

[0021] (4) Mass conservation framework equation;

[0022] The coupled model is constructed based on the following three global mass conservation equations: the activated sludge environmental mass conservation equation, the biofilm environmental mass conservation equation, and the population dynamics of protozoa and metazoa;

[0023] (4.1) Total mass conservation equation for activated sludge environment;

[0024]

[0025] Among them, Q exchange is the difference in the input and output rates of pollutants in the activated sludge and the effluent, g COD / (m 3 ·d); D exchange is the diffusion mass transfer rate between activated sludge and biofilm, g COD / (m 3 ·d), the diffusion direction is the pollutant from the activated sludge S i Towards biofilm S i,bf Diffusion; R metabolism is the pollutant change rate caused by microbial metabolism in activated sludge, g COD / (m 3 ·d); α sludge is the conversion coefficient from biomass to COD, g COD / mg; G predation is the population growth rate caused by predation, mg / (m 3 d);

[0026] (4.2) The total mass conservation equation for the biofilm environment;

[0027]

[0028] Among them, R metabolism,bf is the pollutant change rate caused by microbial metabolism in the biofilm, g COD / (m 3 ·d); α biofilm is the conversion factor from biomass to COD, g COD / mg;

[0029] (4.3) Equations for the overall dynamics of protozoan and metazoan populations;

[0030]

[0031] Among them, G consumed is the population consumption rate caused by predation, mg / (m 3 ·d); M is the natural mortality rate of protozoa and metazoa, 1 / d; W j is the density of the jth species of protozoa and metazoa, mg / m 3 ;

[0032]

[0033] Where e is the assimilation efficiency of protozoan and metazoan predation; Is a protozoa, metazoa j The resources that can be preyed on include debris, microorganisms, and low-trophic-level protozoa in the water and on the biofilm; N res is the number of resources; N con It is a predator of protozoa and protozoa j the number of higher trophic level species; Is a protozoa, metazoa j Resources The predation coefficient; Is a protozoa, metazoa β Protozoa and metazoa j The predation coefficient, and is the half-saturation coefficient corresponding to the predation term;

[0034] Step 2: Q exchange 、D exchange Refinement of dynamic processes;

[0035]

[0036] Where t1 is the hydraulic retention time, d; S i,in It is the effluent concentration of the previous stage reaction tank, and the material flow between multiple stages is achieved through cascade transmission, g COD / m 3 ;S i is the concentration of different substances in activated sludge, g COD / m 3 ;D i is the diffusion coefficient of substance i, m 2 / d; A is the surface area of the biofilm, m 2 ;S i,bf is the concentration of substances on the biofilm, g COD / m 3 ; Predators have the same predation efficiency on bacteria in activated sludge and biofilm;

[0037] Step 3: Refine the change rates of multiple pollutants caused by microbial metabolism;

[0038] (1) In activated sludge:

[0039]

[0040] Among them, Y H is the productivity coefficient of heterotrophic microorganisms in activated sludge, g COD / g COD; Refers to the attenuation product coefficient corresponding to substance i, g COD / g COD; Y Ais the productivity coefficient of autotrophic microorganisms in activated sludge, g N / g COD; δ is the growth coefficient of autotrophic microorganisms; ρ is the organic carbon hydrolysis rate coefficient; b H is the heterotrophic microbial decay coefficient, 1 / d; b A is the decay coefficient of autotrophic microorganisms, 1 / d; K a is the amination rate coefficient, m 3 / (g COD·d); S ND is dissolved biodegradable organic nitrogen, g N / m 3 ; Refers to the aerobic growth rate of heterotrophic microorganisms in activated sludge, 1 / d; Refers to the anoxic growth rate of heterotrophic microorganisms in activated sludge, 1 / d; Refers to the hydrolysis rate of organic carbon in activated sludge, 1 / d; Refers to the nitrification rate of autotrophic microorganisms in activated sludge, 1 / d;

[0041] Table 1 Values of activated sludge related parameters

[0042]

[0043]

[0044] In the table, Y h is the heterotrophic microbial productivity coefficient in activated sludge, g COD / g COD; i xb is the nitrogen content coefficient in microorganisms, g N / g COD; i xp is the nitrogen content coefficient in the decay product, g N / g COD; Y a is the productivity coefficient of autotrophic microorganisms in activated sludge, g COD / g N; f p is the attenuation product coefficient, g COD / g COD; X P It is a particulate product produced by microbial decay, g COD / m 3 ;D s is the diffusion coefficient of dissolved rapidly biodegradable organic matter, m 2 / d;D NO is the nitrate nitrogen diffusion coefficient, m 2 / d;D NH is the ammoniacal nitrogen diffusion coefficient, m 2 / d;D ba is the diffusion coefficient of autotrophic microorganisms, m 2 / d;D bh is the diffusion coefficient of heterotrophic microorganisms, m 2 / d;

[0045] (2) In biofilm environment:

[0046]

[0047] Among them, Y Haer is the productivity coefficient of heterotrophic microorganisms on the biofilm, g COD / g COD; Y Hanx is the anoxic productivity coefficient of heterotrophic microorganisms on the biofilm, g N / g COD; Refers to the aerobic growth rate of heterotrophic microorganisms on the biofilm, 1 / d; Refers to the anoxic growth rate of heterotrophic microorganisms on biofilm, 1 / d; Refers to the nitrification rate of autotrophic microorganisms on the biofilm, 1 / d;

[0048] Table 2 Values of relevant parameters on biofilm

[0049]

[0050]

[0051] In the table, S s,bf It is the rapidly biodegradable organic matter dissolved on the biofilm, g COD / m 3 ;S O,bf is the dissolved oxygen on the biofilm, g / m 3 ;S NO,bf is the nitrate nitrogen on the biofilm, g NO3 - -N / m 3 ;S NH,bf It is ammonia nitrogen on the biofilm, gNH4 + -N / m 3 ;X bh,bf It is heterotrophic microorganisms on biofilm, g COD / m 3 ;X ba,bf It is the autotrophic microorganism on the biofilm, g COD / m 3 ; Y haer is the aerobic productivity coefficient of heterotrophic microorganisms on the biofilm, g COD / g COD; Y hanx is the anoxic productivity coefficient of heterotrophic microorganisms on the biofilm, g COD / g COD;

[0052] Step 4: Based on the modeling principles of the substance quantity model, a coupling model is established by combining the activated sludge model, the biofilm model, and the protozoan and metazoan predation model:

[0053] Based on equations (1), (6), (7), and (8), the dynamic equation (10) for activated sludge environmental pollutants is derived as follows:

[0054]

[0055] Among them, aerobic growth of heterotrophic microorganisms consumes COD; anoxic growth of heterotrophic microorganisms consumes nitrate; nitrification of autotrophic microorganisms consumes ammonia nitrogen; hydrolysis of organic carbon converts particulate organic matter into s Converted into dissolved organic matter S s The decline of heterotrophic microorganisms leads to a decrease in bacterial population; the decline of autotrophic microorganisms leads to a decrease in bacterial population; ammoniation consumes organic nitrogen;

[0056] Based on formulas (2), (6), (7), and (8), the dynamic formula (11) for biofilm environmental pollutants is obtained as follows:

[0057]

[0058] Based on equations (3), (4), and (5), the population dynamics of primary and secondary animals (12) are obtained as follows:

[0059]

[0060] Step 5: Further refine the calculation of microbial metabolic rate;

[0061] (1) Specific calculation equation for the metabolic rate of microorganisms in activated sludge;

[0062] Aerobic growth of heterotrophic microorganisms in activated sludge:

[0063]

[0064] Anoxic growth of heterotrophic microorganisms in activated sludge:

[0065]

[0066] Nitrification by autotrophic microorganisms in activated sludge:

[0067]

[0068] Hydrolysis rate of organic carbon in activated sludge:

[0069]

[0070] Among them, μ H,max is the aerobic specific growth rate coefficient of heterotrophic microorganisms, 1 / d; μ A,max is the aerobic specific growth rate coefficient of autotrophic microorganisms in activated sludge, 1 / d; K S is the half-saturation coefficient of heterotrophic microbial matrix in activated sludge, g COD / m 3 ;S O is dissolved oxygen, g / m 3 ;K OH is the oxygen half-saturation coefficient of heterotrophic microorganisms in activated sludge, g O2 / m 3 ;KNO is the nitrate half-saturation coefficient of heterotrophic microorganisms in activated sludge, g NO3 - -N / m 3 ;S NO is nitrate nitrogen, g N / m 3 ;η g is the correction factor for the anoxic growth of heterotrophic microorganisms in activated sludge, k h Maximum specific hydrolysis rate coefficient, g COD / g COD; k b is the half-saturation coefficient of slowly biodegradable organic matter in particulate form, g COD / g COD; η h is the correction factor for anoxic hydrolysis of heterotrophic microorganisms in activated sludge;

[0071] (2) Specific calculation equations for the metabolic rate of microorganisms on biofilms;

[0072] Aerobic growth of heterotrophic microorganisms on biofilms:

[0073]

[0074] Anoxic growth of heterotrophic microorganisms in biofilms:

[0075]

[0076] Aerobic growth of autotrophic microorganisms in biofilms:

[0077]

[0078] Among them, S s,bf It is the dissolved rapidly biodegradable organic matter on the biofilm, g COD / m 3 ;S O,bf is the concentration of dissolved oxygen on the biofilm, g / m 3 ;η g ′ is the correction coefficient for the anoxic growth rate of heterotrophic microorganisms on the biofilm; K SH,aer,bf is the substrate half-saturation coefficient for aerobic growth of heterotrophic microorganisms on biofilm, g COD / m 3 ;K OH,aer,bf is the oxygen half-saturation coefficient of heterotrophic microorganisms on the biofilm, g O2 / m 3 ;K SH,anx,bf is the half-saturation coefficient of the heterotrophic microbial matrix on the biofilm, g COD / m 3 ;K OH,anx,bf is the substrate half-saturation coefficient for the anoxic growth of heterotrophic microorganisms on biofilm, g COD / m 3 ;K NO,bf is the nitrate half-saturation coefficient of heterotrophic microorganisms on the biofilm, g NO3 - -N / m 3 ;SNO,bf is nitrate nitrogen, g N / m 3 ;K NH,bf is the nitrate half-saturation coefficient of heterotrophic microorganisms in activated sludge, g NO3 - -N / m 3 ;K OA,bf is the oxygen half-saturation coefficient of autotrophic microorganisms on the biofilm, g O2 / m 3 ;

[0079] Step 6: Temperature half-saturation constant correction

[0080] The effect of temperature change on the metabolic rate of microorganisms is achieved by adjusting the half-saturation constant. Considering that temperature change will affect the half-saturation constant of related parameters, the temperature half-saturation constant is calculated by the following formula:

[0081] k T =k 20 ·exp(θ T ·(T-20)) (20)

[0082]

[0083] Among them, k T is the half-saturation constant at temperature T℃, k 20 is the half-saturation constant at the reference temperature of 20°C, θ T is the temperature correction coefficient, which is determined by fitting the experimental data; T1 and T2 are the experimental temperature points.

[0084] Step 7: Parameter calibration and experimental verification.

[0085] (1) Parameter calibration

[0086] Combine literature and experimental data to determine key parameters (such as half-saturation constant, predation efficiency coefficient, etc.) and optimize relevant parameters based on Monte Carlo methods.

[0087] (2) Simulation method (implemented by the fourth-order Runge-Kutta method):

[0088] To achieve dynamic simulation of a multi-stage fixed biofilm reactor, the model equations need to be converted into a computable numerical form, and the cascade logic of multiple tanks in series needs to be implemented through programming. The specific steps are as follows:

[0089] a. Equation discretization and RK4 algorithm design: Discretize the coupled model differential equations (Formulas 11, 12, and 13) established in step 4 and use the fourth-order Runge-Kutta method for time advancement.

[0090] b. Parameter initialization and adjustment: Load the initial parameters according to Table 1 and Table 2, and optimize the key parameters through loop iteration.

[0091] c. Serial calculation of multi-stage reaction pools: The cascade logic of the multi-stage reaction pool is realized through circulation, and the effluent of the previous stage is used as the inlet of the next stage.

[0092] d. Simulation result output and verification: Output the pollutant concentration and microbial dynamics of each pool and compare them with experimental data.

[0093] (3) Experimental verification:

[0094] COD removal dynamics ( Figure 2 a): Root mean square error between the simulated value and the measured value = 9.2 mg / L (Nash coefficient = 0.92).

[0095] Beneficial effects of the present invention:

[0096] The coupling model of the present invention dynamically simulates the removal process of various pollutants (such as COD, ammonia nitrogen, and nitrate nitrogen) by coupling the predation model of protozoa and metazoans, the ASM1 activated sludge model, and the biofilm model, and optimizes the synergistic effect of heterotrophic microorganisms and autotrophic microorganisms in biofilms and suspended sludge. By preying on microbial attenuation products and organic particulate matter, the pollutant degradation efficiency is improved, and sludge accumulation is reduced. The balance of microbial populations is regulated by predation, the stable metabolic activity of heterotrophic and autotrophic microorganisms is maintained, and the risk of ecological imbalance in the system is avoided. The coupling model reflects the regulatory effect of protozoa and metazoans on microbial communities, optimizes the relationship between predation behavior and biofilm thickness, oxygen concentration, and metabolic rate, significantly improves the accuracy and reliability of the sewage treatment model, provides important technical support for the low-carbon development of the sewage treatment industry, and demonstrates significant environmental benefits and economic value.

[0097] In contrast, traditional coupled models, such as those combining activated sludge with biofilms or predation with wastewater treatment, have significant limitations. They overlook the complex interactions between different microbial populations, particularly in multi-stage wastewater treatment systems. Traditional models also fail to fully account for the impact of biofilm dynamics, microbial community succession, and predation on system stability and sludge reduction. Furthermore, many models lack multispecies coupling and nonlinear ecological interactions, limiting their adaptability and accuracy in practical applications.

[0098] The method of the present invention dynamically simulates the pollutant removal process and the dynamic changes of the microbial community through multi-model coupling, and is suitable for optimizing the design and operating parameters of sewage treatment reactors, especially in the regulation of multi-stage fixed biofilm reactors. BRIEF DESCRIPTION OF THE DRAWINGS

[0099] Figure 1 This is a diagram showing the transformation relationship between the components in the biological predator-ASM1-biofilm coupling model.

[0100] Figure 2 Comparison charts of the model predictions and measured data for activated sludge in anoxic tanks. (a) Comparison chart of the predicted and measured data for dissolved rapidly biodegradable organic matter in activated sludge, (b) Comparison chart of the predicted and measured data for particulate biodegradable organic nitrogen in activated sludge, (c) Comparison chart of the predicted and measured data for particulate products produced by microbial decay in activated sludge, and (d) Comparison chart of the predicted and measured data for particulate slowly biodegradable organic matter in activated sludge.

[0101] Figure 3 The graphs are the comparison between the prediction and measured data of the biofilm model of aerobic pool No. 1. Among them, (a) is the comparison between the prediction and measured data of dissolved rapidly biodegradable organic matter on the biofilm, and (b) is the comparison between the prediction and measured data of nitrate nitrogen (NO3 - -N and NO2 - -N) is a comparison chart of the predicted and measured data, (c) is a comparison chart of the predicted and measured data of autotrophic microorganisms in activated sludge, and (d) is a comparison chart of the predicted and measured data of heterotrophic microorganisms in activated sludge. DETAILED DESCRIPTION

[0102] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0103] In practical application, the present invention was studied and modeled at a reclaimed water station at a university in Beijing that uses a multi-stage fixed biofilm treatment process. The process comprises one anoxic tank and six aerobic tanks, with a daily treatment capacity of 200 to 300 tons. The influent is domestic sewage from the school office building. All tanks are connected via overflow holes. The anoxic tank is equipped with a polyurethane fiber suspended filler and stirred by a stirring device. Each aerobic tank is equipped with a microporous aerator at the bottom to provide continuous and uniform aeration for the reaction tank. Fixed nylon fiber fillers are installed in the aerobic tank. Sewage enters the reactor from the water inlet, passes through the anoxic tank and aerobic tank in sequence, and finally flows into the sedimentation tank and clear water tank and is discharged from the outlet. The relevant data required for model construction were obtained through actual measurements, literature research, and theoretical simulations. During the simulation process, the anoxic tank and aerobic tank No. 1 were first selected for model calibration, and aerobic tanks No. 2 to 6 were used for model verification. The present invention is further described in detail below in conjunction with the accompanying drawings and examples.

[0104] Example 1

[0105] To obtain basic data, set up an anaerobic tank and six aerobic tanks for experiments, and monitor COD, ammonia nitrogen, dissolved rapidly biodegradable organic matter (S S ), nitrate nitrogen in activated sludge (S NO ), autotrophic microorganisms in activated sludge (X ba), heterotrophic microorganisms in activated sludge (X bh ) are all based on experimental values as parameter input values. According to formula (6) (7), the difference in the input and output rates of inlet and outlet water pollutants (Q exchange ) and the diffusion mass transfer rate between activated sludge and biofilm (D exchange ).

[0106] The fillers in different biochemical pools were sampled, and the biofilm weight per unit volume of filler was calculated by the difference in dry weight before and after biofilm formation. The protozoa and metazoa on the fillers were sampled and examined microscopically to determine the species and density (W) of the protozoa and metazoa on the fillers per unit area. j ), the concentration density of protozoa and metazoa was calculated using the volume method (g / m 3 ), calculate the behavior of protozoa and metazoa and the dynamic changes of population. The heterotrophic microorganisms (X bh ) and autotrophic microorganisms (X ba ) quantity, combined with the dry weight of the biofilm, was converted into concentration (g COD / m 3 ). The predation behavior of protozoa and metazoa in the anoxic pool is simulated by predation of protozoa and metazoa. Obtain energy and promote the growth of its own population. The population growth rate (G predation ) and the population consumption rate caused by predation (G consumed ).

[0107] The dynamic changes of microorganisms in the anoxic tank are calculated based on the microbial decay, consumption and hydrolysis model. The above includes the aerobic growth of heterotrophic microorganisms (μ H ), anoxic growth of heterotrophic microorganisms Aerobic growth of autotrophic microorganisms (μ A ), organic carbon hydrolysis model (K kh ). According to the improved activated sludge model (R metabolism ) calculates the dynamic changes of dissolved and particulate pollutants in the anoxic tank, as well as the effects of microbial metabolic growth; based on the improved biofilm model (R metabolism,bf )Calculate the consumption of substances on the biofilm and the metabolic growth of microorganisms.

[0108] The relationships among protozoa, metazoa, microorganisms and their components are shown in Figure 1 .

[0109] A comparison chart of experimental and simulated values is drawn with time (days) as the horizontal axis and pollutant concentration as the vertical axis. S ), granular slowly biodegradable organic matter (X S), particulate products produced by microbial decay (X P ), particulate biodegradable organic nitrogen (X ND ) concentrations are: 46.28g COD / m 3 、107.98g COD / m 3 , 0.04g / m 3 and 0.03 g N / m 3 Using these data as starting values, a program was written in MATLAB, and an overall mathematical model was established based on the process flow of the above experiment to simulate the concentration values of each component changing over time. Figure 2 The simulation results are in good agreement with the actual observations, verifying the reliability and accuracy of the model.

[0110] Example 2

[0111] Further calibration was performed using a biofilm model in aerobic tank No. 1, including the dynamic changes in dissolved rapidly biodegradable organic matter, nitrate nitrogen, heterotrophic microorganisms, and autotrophic microorganisms. The reactions involved were calculated using the following formula:

[0112] Among them S S 、S NO 、X bh 、X ba The experimental values are used as parameter input values, S O is the dissolved oxygen concentration. The substrate half-saturation coefficient (K SH,aer,bf ), oxygen half-saturation coefficient (K OH，aer,bf ), nitrate half-saturation coefficient of heterotrophic microorganisms on biofilm (K NO,bf ), ammonia half-saturation coefficient of autotrophic microorganisms on biofilm (K NH,bf ) at 20℃, the half-saturation constants were 48g COD / m 3 , 2g O2 / m 3 、12g NO3 - -N / m 3 、4g NH3-N / m 3 .

[0113] Since the concentration of components on the membrane is not much different from that in water, S s,bf and S NO,bf The value of X is the same as in water. bh,bf and X ba,bf The concentrations are: 19.03g COD / m 3 and 0.7g COD / m 3. Write a program in MATLAB and build an overall mathematical model based on the process flow of the above experiment to simulate the concentration values of each component changing with time. With time (days) as the horizontal axis and concentration as the vertical axis, the experimental values and simulation values of the four variables are compared as shown below. Figure 3 As shown in Figure 3, the simulation results are in good agreement with the actual observations, which further verifies the reliability and accuracy of the model of the present invention.

[0114] Example 3

[0115] Based on the implementation examples 1 and 2, the accuracy of the model was further verified. The aerobic pools 2-6 were verified, and the measured parameters included dissolved rapidly biodegradable organic matter (S S ), granular slowly biodegradable organic matter (X S ), autotrophic microorganisms in activated sludge (X ba ), heterotrophic microorganisms in activated sludge (X bh ), granular products produced by microbial decay in activated sludge (X p ), nitrate nitrogen in activated sludge (S NO ), ammonia nitrogen in activated sludge (S NH ), dissolved biodegradable organic nitrogen in activated sludge (S ND ), particulate biodegradable organic nitrogen in activated sludge (X ND ).

[0116] Relative deviation is a key indicator for evaluating measurement accuracy; smaller relative deviations reflect higher precision. MATLAB simulations were used to obtain simulated values for aerobic pools 2-6. The relative errors between the two values were calculated based on the measured values. The results showed that 81% of the variables had relative deviations less than 0.3, demonstrating that the coupled model provides highly accurate measurements in most situations. This result validates the model's reliability and accuracy, providing a solid foundation for further application and research.

[0117] The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, which is convenient for those skilled in the art to understand and apply the present invention. It cannot be determined that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art of the present invention, several simple deductions or replacements can be made without departing from the concept of the present invention, without having to go through creative work. Therefore, simple improvements made to the present invention by those skilled in the art based on the disclosure of the present invention should be within the scope of protection of the present invention.

Claims

1. A dual-environment-three-component coupling model for predation-enhanced cascade fixed biofilm wastewater treatment process, characterized in that: Here are the steps: Step 1: Establish the model framework (1) Dual environment division; Activated sludge environment: heterotrophic microorganisms X bh and autotrophic microorganisms X ba They metabolize suspended and dissolved pollutants and exchange substances with biofilms through diffusion. Protozoa and metazoa regulate microbial population density by preying on suspended bacterial communities, and the predation rate follows the Lotka-Volterra kinetic equation. Biofilm environment: microorganisms attach to the surface of the filler to form a layered structure, heterotrophic microorganisms X bh,bf and autotrophic microorganisms X ba,bf The metabolism of bacteria is limited by local mass transfer, and pollutants enter the biofilm through the diffusion gradient; protozoa and metazoa mainly prey on suspended bacterial communities, and their predation mechanism is consistent with that in activated sludge environments. The predation efficiency parameter adopts a global unified value; The exchange of substances between the two environments is achieved through diffusion, which dynamically balances the regulatory effect of predation on the microbial community. (2) Definition of three components; (2.1) Bacteria: including heterotrophic microorganisms in activated sludge environments bh and autotrophic microorganisms X ba , and heterotrophic microorganisms X in biofilm environments bh,bf and autotrophic microorganisms X ba,bf ; (2.2) Predators: including protozoa and metazoa; (2.3) Pollutants: They are divided into dissolved and particulate states. Dissolved states include dissolved rapidly biodegradable organic matter S s , ammonia nitrogen S NH , nitrate nitrogen S NO , dissolved oxygen S O , dissolved biodegradable organic nitrogen S ND ; Particles include slowly degradable organic matter X s , particulate products produced by microbial decay X P , granular biodegradable organic nitrogen X ND ; (3) Multi-stage series structure; The reactor consists of multiple anoxic and aerobic tanks connected in series, with the effluent from the previous stage serving as the inlet for the next stage, forming a cascade pattern of "anoxic tank → aerobic tank". The order of the anoxic and aerobic tanks in series is fixed, and there is no alternating structure. (4) Mass conservation framework equation; The coupled model is constructed based on the following three global mass conservation equations: the activated sludge environmental mass conservation equation, the biofilm environmental mass conservation equation, and the population dynamics of protozoa and metazoa; Step 2: Q exchange 、D exchange Refinement of dynamic processes; Where t1 is the hydraulic retention time, d; S i,in It is the effluent concentration of the previous stage reaction tank, and the material flow between multiple stages is achieved through cascade transmission, g COD / m 3 ;S i is the concentration of different substances in activated sludge, g COD / m 3 ;D i is the diffusion coefficient of substance i, m 2 / d; A is the biofilm surface area, m 2 ;S i,bf is the concentration of substances on the biofilm, g COD / m 3 ; Predators have the same predation efficiency on bacteria in activated sludge and biofilm; Step 3: Determine the rate of change of multiple pollutants caused by microbial metabolism; Step 4: Based on the modeling principles of the substance quantity model, a coupling model is established by combining the activated sludge model, the biofilm model, and the protozoan and metazoan predation model: Step 5: Further determine the microbial metabolic rate; Step 6: Temperature half-saturation constant correction; Step 7: Parameter calibration and experimental verification.

2. The dual-environment-three-component coupling model of the predation-enhanced cascade fixed biofilm wastewater treatment process according to claim 1 is characterized in that: (4) The mass conservation framework equation is as follows: (4.1) Total mass conservation equation for activated sludge environment; Among them, Q exchange is the difference in the input and output rates of pollutants in the activated sludge and the effluent, g COD / (m 3 ·d); D exchange is the diffusion mass transfer rate between activated sludge and biofilm, g COD / (m 3 ·d), the diffusion direction is the pollutant from the activated sludge S i Towards biofilm S i,bf Diffusion; R metabolism is the pollutant change rate caused by microbial metabolism in activated sludge, g COD / (m 3 ·d); α sludge is the conversion coefficient from biomass to COD, g COD / mg; G predation is the population growth rate caused by predation, mg / (m 3 d); (4.2) The total mass conservation equation for the biofilm environment; Among them, R metabolism,bf is the pollutant change rate caused by microbial metabolism in the biofilm, g COD / (m 3 ·d); α biofilm is the conversion factor from biomass to COD, g COD / mg; (4.3) Equations for the overall dynamics of protozoan and metazoan populations; Among them, G consumed is the population consumption rate caused by predation, mg / (m 3 ·d); M is the natural mortality rate of protozoa and metazoa, 1 / d; W j is the density of the jth species of protozoa and metazoa, mg / m 3 ; Where e is the assimilation efficiency of protozoan and metazoan predation; Is a protozoa, metazoa j The resources that can be preyed on include debris, microorganisms, and low-trophic-level protozoa in the water and on the biofilm; N res is the number of resources; N con It is a predator of protozoa and protozoa j the number of higher trophic level species; Is a protozoa, metazoa j Resources The predation coefficient; Is a protozoa, metazoa β Protozoa and metazoa j The predation coefficient, and is the half-saturation coefficient corresponding to the predation term.

3. The dual-environment-three-component coupling model of the predation-enhanced cascade fixed biofilm wastewater treatment process according to claim 2, characterized in that: Step 3: Determine the change rates of multiple pollutants caused by microbial metabolism as follows: (1) In activated sludge: Among them, Y H is the productivity coefficient of heterotrophic microorganisms in activated sludge, g COD / g COD; Refers to the attenuation product coefficient corresponding to substance i, g COD / g COD; Y A is the productivity coefficient of autotrophic microorganisms in activated sludge, g N / gCOD; δ is the growth coefficient of autotrophic microorganisms; ρ is the organic carbon hydrolysis rate coefficient; b H is the heterotrophic microbial decay coefficient, 1 / d; b A is the decay coefficient of autotrophic microorganisms, 1 / d; K a is the amination rate coefficient, m 3 / (gCOD·d);S ND is dissolved biodegradable organic nitrogen, g N / m 3 ; Refers to the aerobic growth rate of heterotrophic microorganisms in activated sludge, 1 / d; Refers to the anoxic growth rate of heterotrophic microorganisms in activated sludge, 1 / d; Refers to the hydrolysis rate of organic carbon in activated sludge, 1 / d; Refers to the nitrification rate of autotrophic microorganisms in activated sludge, 1 / d; Table 1 Values of activated sludge related parameters In the table, Y h is the heterotrophic microbial productivity coefficient in activated sludge, g COD / g COD; i xb is the nitrogen content coefficient in microorganisms, g N / g COD; i xp is the nitrogen content coefficient in the decay product, g N / g COD; Y a is the productivity coefficient of autotrophic microorganisms in activated sludge, g COD / g N; f p is the attenuation product coefficient, g COD / gCOD; X P It is a particulate product produced by microbial decay, gCOD / m 3 ;D s is the diffusion coefficient of dissolved rapidly biodegradable organic matter, m 2 / d;D NO is the nitrate nitrogen diffusion coefficient, m 2 / d;D NH is the ammoniacal nitrogen diffusion coefficient, m 2 / d;D ba is the diffusion coefficient of autotrophic microorganisms, m 2 / d;D bh is the diffusion coefficient of heterotrophic microorganisms, m 2 / d; (2) In biofilm environment: Among them, Y Haer is the productivity coefficient of heterotrophic microorganisms on the biofilm, g COD / g COD; Y Hanx is the anoxic productivity coefficient of heterotrophic microorganisms on the biofilm, g N / g COD; Refers to the aerobic growth rate of heterotrophic microorganisms on the biofilm, 1 / d; Refers to the anoxic growth rate of heterotrophic microorganisms on biofilm, 1 / d; Refers to the nitrification rate of autotrophic microorganisms on the biofilm, 1 / d; Table 2 Values of relevant parameters on biofilm In the table, S s,bf It is the rapidly biodegradable organic matter dissolved on the biofilm, g COD / m 3 ;S O,bf is the dissolved oxygen on the biofilm, g / m 3 ;S NO,bf is the nitrate nitrogen on the biofilm, g NO3 - -N / m 3 ;S NH,bf It is ammonia nitrogen on the biofilm, gNH4 + -N / m 3 ;X bh,bf It is heterotrophic microorganisms on biofilm, g COD / m 3 ;X ba,bf It is the autotrophic microorganism on the biofilm, g COD / m 3 ; Y haer is the aerobic productivity coefficient of heterotrophic microorganisms on the biofilm, gCOD / g COD; Y hanx is the anoxic productivity coefficient of heterotrophic microorganisms on the biofilm, g COD / g COD.

4. The dual-environment-three-component coupling model for the predation-enhanced cascade fixed biofilm wastewater treatment process according to claim 3, characterized in that: Step 4: Establish the coupling model as follows: Based on equations (1), (6), (7), and (8), the dynamic equation (10) for activated sludge environmental pollutants is derived as follows: Among them, aerobic growth of heterotrophic microorganisms consumes COD; anoxic growth of heterotrophic microorganisms consumes nitrate; nitrification of autotrophic microorganisms consumes ammonia nitrogen; hydrolysis of organic carbon converts particulate organic matter into s Converted into dissolved organic matter S s The decline of heterotrophic microorganisms leads to a decrease in bacterial population; the decline of autotrophic microorganisms leads to a decrease in bacterial population; ammoniation consumes organic nitrogen; Based on formulas (2), (6), (7), and (8), the dynamic formula (11) for biofilm environmental pollutants is obtained as follows: Based on equations (3), (4), and (5), the population dynamics of primary and secondary animals (12) are obtained as follows:

5. The dual-environment-three-component coupling model of the predation-enhanced cascade fixed biofilm wastewater treatment process according to claim 4, characterized in that: Step 5: Further determine the specific implementation process of microbial metabolic rate: (1) Specific calculation equation for the metabolic rate of microorganisms in activated sludge; Aerobic growth of heterotrophic microorganisms in activated sludge: Anoxic growth of heterotrophic microorganisms in activated sludge: Nitrification by autotrophic microorganisms in activated sludge: Hydrolysis rate of organic carbon in activated sludge: Among them, μ H,max is the aerobic specific growth rate coefficient of heterotrophic microorganisms, 1 / d; μ A,max is the aerobic specific growth rate coefficient of autotrophic microorganisms in activated sludge, 1 / d; K S is the half-saturation coefficient of heterotrophic microbial matrix in activated sludge, g COD / m 3 ;S O is dissolved oxygen, g / m 3 ;K OH is the oxygen half-saturation coefficient of heterotrophic microorganisms in activated sludge, g O2 / m 3 ;K NO is the nitrate half-saturation coefficient of heterotrophic microorganisms in activated sludge, g NO3 - -N / m 3 ;S NO is nitrate nitrogen, g N / m 3 ;η g is the correction factor for the anoxic growth of heterotrophic microorganisms in activated sludge, k h Maximum specific hydrolysis rate coefficient, g COD / g COD; k b is the half-saturation coefficient of slowly biodegradable organic matter in particulate form, g COD / g COD; η h is the correction factor for anoxic hydrolysis of heterotrophic microorganisms in activated sludge; (2) Specific calculation equations for the metabolic rate of microorganisms on biofilms; Aerobic growth of heterotrophic microorganisms on biofilms: Anoxic growth of heterotrophic microorganisms in biofilms: Aerobic growth of autotrophic microorganisms in biofilms: Among them, S s,bf It is the dissolved rapidly biodegradable organic matter on the biofilm, g COD / m 3 ;S O,bf is the concentration of dissolved oxygen on the biofilm, g / m 3 ;η g ′ is the correction coefficient for the anoxic growth rate of heterotrophic microorganisms on the biofilm; K SH,aer,bf is the substrate half-saturation coefficient for aerobic growth of heterotrophic microorganisms on biofilm, g COD / m 3 ;K OH,aer,bf is the oxygen half-saturation coefficient of heterotrophic microorganisms on the biofilm, g O2 / m 3 ;K SH,anx,bf is the half-saturation coefficient of the heterotrophic microbial matrix on the biofilm, g COD / m 3 ;K OH,anx,bf is the substrate half-saturation coefficient for the anoxic growth of heterotrophic microorganisms on biofilm, g COD / m 3 ;K NO,bf is the nitrate half-saturation coefficient of heterotrophic microorganisms on the biofilm, gNO3 - -N / m 3 ;S NO,bf is nitrate nitrogen, g N / m 3 ;K NH,bf is the nitrate half-saturation coefficient of heterotrophic microorganisms in activated sludge, g NO3 - -N / m 3 ;K OA,bf is the oxygen half-saturation coefficient of autotrophic microorganisms on the biofilm, g O2 / m 3 .

6. The dual-environment-three-component coupling model for the predation-enhanced cascade fixed biofilm wastewater treatment process according to claim 5, characterized in that: Step 5: Correction of temperature half-saturation constant is as follows: The effect of temperature change on the metabolic rate of microorganisms is achieved by adjusting the half-saturation constant. Considering that temperature change will affect the half-saturation constant of related parameters, the temperature half-saturation constant is calculated by the following formula: k T =k 20 ·exp(θ T ·(T-20)) (20) Among them, k T is the half-saturation constant at temperature T℃, k 20 is the half-saturation constant at the reference temperature of 20°C, θ T is the temperature correction coefficient, which is determined by fitting the experimental data; T1 and T2 are the experimental temperature points.

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