Double-environment three-component coupling method for wastewater treatment process of predation reinforced cascade fixed biofilm

Abstract

The present application belongs to the technical field of environmental engineering, and discloses a double-environment-three-component coupling method of a predation-enhanced gradient fixed biofilm sewage treatment process. The metabolism of autotrophic microorganisms and heterotrophic microorganisms in activated sludge and biofilm, and the predation effect of pro-and metazoan are comprehensively considered, the mass balance principle is used to analyze the material conversion path in the sewage treatment reactor with biological predation enhancement, the dynamic changes of bacteria and pollutants are disassembled into diffusion, metabolism and predation processes, a material flow model framework is established, and on the basis of the ASM1 activated sludge model and the biofilm model, the predation model of pro-and metazoan is coupled to re-create the double-environment-three-component coupling model. Through the coupling of multiple models, the present application dynamically simulates the pollutant removal process and the dynamic change of the microbial community, and is suitable for optimizing the design and operation parameters of the sewage treatment reactor, and has significant application value in the regulation and control of the gradient fixed biofilm reactor.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environmental engineering, and relates to a double-environment-three-component coupling method for a predation-enhanced gradient fixed biofilm wastewater treatment process, which is especially suitable for the optimized design and operation control of a multi-stage fixed biofilm reactor. BACKGROUND

[0002] A wastewater treatment system is a complex ecological system composed of bacteria, fungi, protozoa, metazoans, etc., and specific microbial groups perform different functions to promote the removal of pollutants. The predation behavior of protozoa and metazoans stimulates the stress response of bacteria and enhances their metabolic activity. Predators play an important role in improving the efficiency of nutrient transfer and water purification performance of the system. However, traditional process models have shortcomings in simulating these complex ecological interactions, and less mention is made of the influence of protozoan and metazoan predation on bacterial activity and material metabolism in the reactor, which hinders the accurate simulation and modeling of the process by the model. Therefore, it is of great significance to introduce biological predation behavior into the model to improve the simulation accuracy of the process model and improve the treatment efficiency of the process.

[0003] Among numerous wastewater treatment models, the coupling of activated sludge models and biofilm models is often used to represent the operation of wastewater treatment plants containing biological carriers / fillers. Peide et al. in “Fully coupled activated sludge model (FCASM): model development” proposed a model that couples multiple functional microorganisms (such as heterotrophic microorganisms, autotrophic microorganisms, etc.) to describe the nitrogen and phosphorus removal and material transfer processes in activated sludge systems. This model embodies the coupling application of biofilm and activated sludge models, and focuses on optimizing the mass transfer of fillers and the performance of biofilms to improve the denitrification effect. Montecchio et al. in “Mathematical modelling of an intermittent anoxic / aerobic MBBR: Estimation of nitrification rates and energy savings” used a mixed culture biofilm equation and activated sludge model ASM1 to calculate the biological processes of an anoxic / aerobic-moving bed biofilm reactor. This model determines the maximum absorption rate (μ A = 2.5 d -1 ) and 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 total ammonia nitrogen was removed by biofilm, only the remaining part was removed by suspended biomass. In addition, Xu Tao et al. in “Establishment and simulation of activated sludge and biofilm combined model” established a biofilm model with the same structure as the microbial growth process rate equation in the ASM1 model, and combined it with the modified ASM1 model for A 2 O process simulation. These methods improve the indication of water quality of process effluent by optimizing model design, but the design of simulation model still mainly focuses on pollutant degradation and mass transfer balance, lacking consideration of predators in the upper layer of the food chain in the ecological system, especially 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 protists and metazoans on bacteria and their regulation of system stability. In wastewater treatment systems, predation behavior can effectively reduce the amount of excess sludge and enhance the efficiency of organic matter degradation. Revilla et al. in “Analysis and modelling of predation on biofilm activated sludge process: Influence on microbial distribution, sludge production and nutrient dosage” constructed a biological predation model based on a biofilm activated sludge system, considering predation as the main factor leading to reduced nutrient demand and sludge production. However, this model is divided into two stages of predation in the biofilm system and predation in the activated sludge system, without considering the suspended activated sludge in the biofilm system. This independence limits the application of the predation model in complex multi-stage fixed reactors and cannot fully simulate the nonlinear dynamic interaction between predators and prey.

[0005] In view of the problems of lack of biological predation effect and insufficient precision in the simulation model of biofilm wastewater treatment reactor, the invention innovatively puts forward a coupling model of predation enhanced gradient fixed biofilm wastewater treatment process, which organically combines the predation model of protists and metazoans with the activated sludge model (ASM1) and the biofilm model, deeply considers the interaction between predators and prey, and provides a new theoretical tool and technical support for the simulation of fixed biofilm wastewater treatment process. SUMMARY

[0006] The application provides a double environment-three component coupling method of a predation enhanced gradient fixed biofilm sewage treatment process. Compared with a traditional model, the application is based on a multi-stage fixed biofilm sewage treatment reactor of activated sludge, biofilm and predation coexistence of protozoa and metazoan, introduces predation behavior of protozoa and metazoan (see formulas 3-5), couples a biological predation model, an ASM1 activated sludge model and a biofilm model, clearly defines the mass conservation relationship of bacteria, predators (protozoa and metazoan) and pollutants, characterizes the flow process and dynamic change of bacteria, predators (protozoa and metazoan) and pollutants in activated sludge and biofilm, simulates the influence of biological predation on microbial metabolism, effectively explains the synergistic effect between microbial growth, degradation efficiency and predation process, solves the problem that the traditional ASM1-biofilm coupling model rarely mentions high trophic level biological predation (the limitation described in the background art), and ensures the accuracy of the model in simulating the pollutant removal of the multi-stage fixed biofilm sewage treatment.

[0007] The technical scheme of the application is as follows:

[0008] The double environment-three component coupling method of the predation enhanced gradient fixed biofilm sewage treatment process is as follows: considering the metabolism of autotrophic microorganisms and heterotrophic microorganisms in activated sludge and biofilm and the predation effect of protozoa and metazoan, based on the mass balance principle, analyzing the material conversion path in the biological predation enhanced sewage treatment reactor, decomposing the dynamic change of bacteria and pollutants into three main processes of diffusion, metabolism and predation, establishing a material flow model framework, coupling the predation model of protozoa and metazoan on the basis of the ASM1 activated sludge model and the biofilm model, and re-creating a biological predation enhanced multi-stage fixed biofilm sewage treatment reactor coupling model. The model includes three total framework equations, the growth rate of microorganisms is described by the Monod kinetic equation, and the dynamic change of nitrogen, organic matter (COD), dissolved oxygen (DO) and microbial community in the reactor is characterized in detail. The predation process of protozoa and metazoan is described by the Lotka-Volterra kinetic equation. The related parameters in the model are calibrated in a range, and the related parameters are optimized according to the Monte Carlo method. Based on the simulation of the established coupling model, the pollutant degradation process of the biological predation enhanced multi-stage fixed biofilm sewage treatment reactor can be accurately reflected, which provides support for optimizing and regulating process parameters, improving pollutant degradation efficiency and reducing carbon emission.

[0009] The specific steps are as follows:

[0010] Step one: establishing a model framework

[0011] (1) double environment division;

[0012] Activated sludge environment: heterotrophic microorganism X bh and autotrophic microorganism Xba Metabolize pollutants in suspended and dissolved states, and exchange substances with biofilm through diffusion; protozoa and metazoan regulate microbial population density by preying on suspended bacteria, and the predation rate follows the Lotka-Volterra dynamics equation;

[0013] Biofilm environment: microorganisms attach to the surface of fillers to form a layered structure, and heterotrophic microorganisms X bh,bf and autotrophic microorganisms X ba,bf Metabolism is limited by local mass transfer, and pollutants enter the interior of the biofilm through a diffusion gradient; protozoa and metazoan mainly prey on suspended bacteria, and the predation mechanism is consistent with that in activated sludge environment, and the predation efficiency parameter is a global uniform value;

[0014] The exchange of substances between the two environments is realized through the diffusion term, and the dynamic balance of predation behavior regulates the microbial community;

[0015] (2) Three-component definition;

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

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

[0018] (2.3) Pollutants: divided into dissolved and particulate states, among which, the dissolved state includes 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 ; the particulate state includes slowly degradable organic matter X s , particulate products produced by microbial decay X P , and particulate biodegradable organic nitrogen X ND ;

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

[0020] The reactor is composed of multiple series of anoxic tanks and aerobic tanks, i.e., the effluent of the previous stage is used as the influent of the next stage, forming a cascade mode of "anoxic tank→aerobic tank"; the series order of anoxic tank and aerobic tank is fixed, and there is no alternating structure;

[0021] (4) Mass conservation framework equation;

[0022] The coupling model is constructed based on three global mass conservation equations, i.e., activated sludge environment mass conservation equation, biofilm environment mass conservation equation, and population dynamics of protozoa and metazoan;

[0023] (4.1) The total mass conservation equation of activated sludge environment is as follows:

[0024] (1)

[0025] wherein, Q exchange is the input and output rate difference of pollutants in and out of activated sludge, g COD / (m3·d); D exchange is the diffusion mass transfer rate between activated sludge and biofilm, g COD / (m3·d), and the diffusion direction is that the pollutants diffuse from activated sludge S i to biofilm S i,bf ; R metabolism is the change rate of pollutants caused by microbial metabolism in activated sludge, g COD / (m3·d); X is the conversion coefficient of biomass to COD, g COD / mg; G predation is the population growth rate caused by predation behavior, mg / (m3·d);

[0026] (4.2) The total mass conservation equation of biofilm environment is as follows:

[0027] (2)

[0028] wherein, R metabolism,bf is the change rate of pollutants caused by microbial metabolism in biofilm, g COD / (m3·d); X is the conversion coefficient of biomass to COD, g COD / mg;

[0029] (4.3) The total population dynamics equation of protozoa and metazoan is as follows:

[0030] (3)

[0031] wherein, G consumed is the population consumption rate caused by predation behavior, mg / (m3·d); M is the natural mortality rate of protozoa and metazoan, 1 / d; W j is the density of the jth protozoa and metazoan, mg / m 3 ;

[0032] (4)

[0033] (5)

[0034] Wherein, e is the assimilation efficiency of protozoa, metazoan predation; protozoa, metazoan The resources that can be preyed on by protozoa, metazoan, including detritus, microorganisms, low-nutrient level protozoa in water and on biological membranes; The number of resources; The number of high-nutrient level species that prey on protozoa, protozoa ; The predation coefficient of protozoa, metazoan on resources ; The predation coefficient of protozoa, metazoan on protozoa, metazoan ; And The half-saturation coefficient of the corresponding predation term;

[0035] Step two: Q exchange , D exchange Kinetics process refinement;

[0036] (6)

[0037] (7)

[0038] Wherein, t1 is the hydraulic retention time, d; S i,in is the effluent concentration of the previous reaction tank, and the material flow between multiple stages is realized by 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 i substance, m 2 / d; A is the biological membrane surface area, m 2 ; S i,bf is the concentration of substances on the biological membrane, g COD / m 3 ; The predation efficiency of predators on bacteria in activated sludge and biological membrane is the same;

[0039] Step three: Refine the rate of change of multiple pollutants caused by microbial metabolism;

[0040] (1) In activated sludge:

[0041] (8)

[0042] Wherein, Y H is the yield coefficient of heterotrophic microorganisms in activated sludge, g COD / g COD; is the decay product coefficient corresponding to i substance, g COD / g COD; Y A is the yield coefficient of autotrophic microorganisms in activated sludge, g N / g COD; is the growth coefficient of autotrophic microorganisms in good conditions; is the organic carbon hydrolysis rate coefficient; b H is the decay coefficient of heterotrophic microorganisms, 1 / d; b A is the decay coefficient of autotrophic microorganisms, 1 / d; K a is the ammonification rate coefficient, m³ / (g COD·d); S ND is the dissolved biodegradable organic nitrogen, g N / m³; φ1 refers to the growth rate of heterotrophic microorganisms in activated sludge under aerobic conditions, 1 / d; φ2 refers to the growth rate of heterotrophic microorganisms in activated sludge under anoxic conditions, 1 / d; φ3 refers to the hydrolysis rate of organic carbon in activated sludge, 1 / d; φ4 refers to the nitrification rate of autotrophic microorganisms in activated sludge, 1 / d;

[0043] Table 1 Values of activated sludge related parameters

[0044]

[0045] In the table, Y h is the yield coefficient of heterotrophic microorganisms 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 decay products, g N / g COD; Y a is the yield coefficient of autotrophic microorganisms in activated sludge, g COD / g N; is the decay product coefficient, g COD / g COD; X P is the particulate product produced by microbial decay, g COD / m³; D s is the diffusion coefficient of dissolved rapidly biodegradable organic matter, m 2 / d; D NO is the diffusion coefficient of nitrate nitrogen, m 2 / d; D NH is the diffusion coefficient of ammonia nitrogen, 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;

[0046] (2) In the biofilm environment:

[0047] (9)

[0048] wherein YHaer is the yield coefficient of heterotrophic microorganisms on biofilm, g COD / g COD; Y Hanx is the anoxic yield coefficient of heterotrophic microorganisms on biofilm, g N / g COD; refers to the aerobic growth rate of heterotrophic microorganisms on 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 biofilm, 1 / d;

[0049] Table 2: Values of relevant parameters on biofilm

[0050]

[0051] In the table, S s,bf is the dissolved readily biodegradable organic matter on biofilm, g COD / m³; S O,bf is the dissolved oxygen on biofilm, g / m³; S NO,bf is the nitrate nitrogen on biofilm, g NO3 - -N / m³; S NH,bf is the ammonia nitrogen on biofilm, g NH4 + -N / m³; X bh,bf is the heterotrophic microorganisms on biofilm, g COD / m³; X ba,bf is the autotrophic microorganisms on biofilm, g COD / m³; is the aerobic yield coefficient of heterotrophic microorganisms on biofilm, g COD / g COD; is the anoxic yield coefficient of heterotrophic microorganisms on biofilm, g COD / g COD;

[0052] Step four: according to the modeling principle of the material quantity model, combined with the activated sludge model, the biofilm model and the model of primary and secondary animal predation, a coupled model is established:

[0053] Based on formula (1), (6), (7), (8), the activated sludge environmental pollutant dynamic formula (10) is derived as follows:

[0054] (10)

[0055] Among them, the aerobic growth of heterotrophic microorganisms consumes COD; the anoxic growth of heterotrophic microorganisms consumes nitrate; the nitrification of autotrophic microorganisms consumes ammonia nitrogen; the hydrolysis of organic carbon converts particulate organic matter X s into dissolved organic matter S s ; the decay of heterotrophic microorganisms leads to the reduction of bacteria; the decay of autotrophic microorganisms leads to the reduction of bacteria; ammonification consumes organic nitrogen;

[0056] Based on formula (2), (6), (7), (8), the dynamic formula (11) of pollutants in biofilm environment is obtained:

[0057] (11)

[0058] Based on formula (3), (4), (5), the dynamic formula (12) of protozoan and metazoan population is obtained:

[0059] (12)

[0060] Step five: further refine the microbial metabolic rate calculation;

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

[0062] Heterotrophic microbial aerobic growth in activated sludge:

[0063] (13)

[0064] Heterotrophic microbial anoxic growth in activated sludge:

[0065] (14)

[0066] Nitrification of autotrophic microorganisms in activated sludge:

[0067] (15)

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

[0069] (16)

[0070] Wherein, is the specific growth rate coefficient of heterotrophic microbial aerobic growth, 1 / d; is the specific growth rate coefficient of autotrophic microbial aerobic growth in activated sludge, 1 / d; K S is the substrate half-saturation coefficient of heterotrophic microorganisms in activated sludge, g COD / m³; S O is dissolved oxygen, g / m 3 ;K OH is the oxygen half-saturation coefficient of heterotrophic microorganisms in activated sludge, g O2 / m³; K NO is the nitrate half-saturation coefficient of heterotrophic microorganisms in activated sludge, g NO3 - -N / m³; S NO is nitrate nitrogen, g N / m³; is the anoxic growth correction coefficient of heterotrophic microorganisms in activated sludge, k h maximum specific hydrolysis rate coefficient, g COD / g COD; k bis the half-saturation coefficient of particulate slow biodegradable organic matter, g COD / g COD; is the anoxic hydrolysis correction coefficient of heterotrophic microorganisms in activated sludge;

[0071] (2) Specific calculation equation of microbial metabolic rate on biofilm;

[0072] Aerobic growth of heterotrophic microorganisms on biofilm:

[0073] (17)

[0074] Anoxic growth of heterotrophic microorganisms on biofilm:

[0075] (18)

[0076] Aerobic growth of autotrophic microorganisms on biofilm:

[0077] (19)

[0078] wherein S s,bf is the dissolved fast biodegradable organic matter on biofilm, g COD / m³; is the concentration of dissolved oxygen on biofilm, g / m³; is the anoxic growth rate correction coefficient of heterotrophic microorganisms on biofilm; K SH,aer,bf is the substrate half-saturation coefficient of aerobic growth of heterotrophic microorganisms on biofilm, g COD / m³; K OH,aer,bf is the oxygen half-saturation coefficient of heterotrophic microorganisms on biofilm, g O2 / m³; K SH,anx,bf is the substrate half-saturation coefficient of heterotrophic microorganisms on biofilm, g COD / m³; K OH,anx,bf is the substrate half-saturation coefficient of anoxic growth of heterotrophic microorganisms on biofilm, g COD / m³; K NO,bf is the nitrate half-saturation coefficient of heterotrophic microorganisms on biofilm, g NO3 - -N / m³; S NO,bf is nitrate nitrogen, g N / m³; K NH,bf is the nitrate half-saturation coefficient of heterotrophic microorganisms in activated sludge, g NO3 - -N / m³; K OA,bf is the oxygen half-saturation coefficient of autotrophic microorganisms on biofilm, g O2 / m³;

[0079] Step six: temperature half-saturation constant correction

[0080] The effect of temperature change on microbial metabolic rate is achieved by adjusting the half-saturation constant; considering that temperature change will affect the half-saturation constant of relevant parameters, the temperature half-saturation constant is calculated by the following formula:

[0081] (20)

[0082] (21)

[0083] where k T is the half-saturation constant at temperature T ℃, k 20 is the half-saturation constant at reference temperature 20 ℃, is the temperature correction coefficient, determined by experimental data fitting; T1, T2 are experimental temperature points.

[0084] Step seven: parameter calibration and experimental verification.

[0085] (1) Parameter calibration

[0086] Combined with literature and experimental data, the key parameters (such as half-saturation constant, predation efficiency coefficient, etc.) are determined. Based on Monte Carlo method, the related parameters are optimized.

[0087] (2) Simulation method (fourth-order Runge-Kutta method implementation):

[0088] In order to realize the dynamic simulation of multi-stage fixed biofilm reactor, the model equation set needs to be converted into a calculable numerical form, and the cascade logic of multi-pool series is realized through programming. The specific steps are as follows:

[0089] a. Equation discretization and RK4 algorithm design: Discretize the coupled model differential equations (equations 11, 12, 13) established in step four, 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. Multi-stage reaction pool series calculation: Through loop, realize the cascade logic of multi-stage reaction pool, and the effluent of the former stage is used as the influent of the latter stage.

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

[0093] (3) Experimental verification:

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

[0095] The beneficial effects of the present application are:

[0096] The coupling model of the application dynamically simulates the removal process of various pollutants (such as COD, ammonia nitrogen and nitrate nitrogen) by coupling the models of predator-prey between protists and metazoans, ASM1 activated sludge model and biofilm model, and optimizes the synergistic effect of heterotrophic microorganisms and autotrophic microorganisms in the biofilm and suspended sludge. The degradation efficiency of pollutants is improved by predating microorganisms to attenuate products and organic particulate matter, while the accumulation of sludge is reduced. The balance of microbial population is adjusted by predation, and the stable metabolic activity of heterotrophic microorganisms and autotrophic microorganisms is maintained, avoiding the risk of ecological imbalance of the system. The coupling model reflects the regulation of protists and metazoans on microbial community, optimizes the relationship between predation behavior, biofilm thickness, oxygen concentration and metabolic rate, significantly improves the precision and reliability of the wastewater treatment model, provides important technical support for the low-carbon development of the wastewater treatment industry, and exhibits significant environmental benefits and economic value.

[0097] In contrast, traditional coupling models, such as simple activated sludge and biofilm models or the coupling of predation and wastewater treatment models, have obvious limitations. They ignore the complex interactions between different microbial populations, especially in multi-stage wastewater treatment systems. Traditional models also fail to fully consider the dynamic changes of biofilm, the succession of microbial community and the influence of predation behavior on system stability and sludge reduction. In addition, many models have deficiencies in multi-species coupling and nonlinear ecological interactions, which limits their adaptability and accuracy in practical applications.

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

[0099] Figure 1 Figure 1 is a conversion relationship diagram between various components in the biological predation-ASM1-biofilm coupling model.

[0100] Figure 2 Figure 4 is a comparison diagram of predicted and measured data of the activated sludge model in the anoxic tank. (a) is a comparison diagram of predicted and measured data of dissolved rapidly biodegradable organic matter in the activated sludge, (b) is a comparison diagram of predicted and measured data of particulate biodegradable organic nitrogen in the activated sludge, (c) is a comparison diagram of predicted and measured data of particulate products produced by microbial attenuation in the activated sludge, and (d) is a comparison diagram of predicted and measured data of particulate slowly biodegradable organic matter in the activated sludge.

[0101] Figure 3 Figure 5 is a comparison diagram of predicted and measured data of the biofilm model in the No. 1 aerobic tank. (a) is a comparison diagram of predicted and measured data of dissolved rapidly biodegradable organic matter on the biofilm, (b) is a comparison diagram of predicted and measured data of nitrate nitrogen (NO3- -N and NO2 - Fig. 1 is a schematic diagram of a multi-stage fixed biofilm treatment process, Fig. 2 is a graph of predicted and measured data comparison, Fig. 3 is a graph of predicted and measured data comparison of autotrophic microorganisms in activated sludge, and Fig. 4 is a graph of predicted and measured data comparison of heterotrophic microorganisms in activated sludge. DETAILED DESCRIPTION

[0102] The specific embodiments of the present application are further described below in conjunction with the accompanying drawings and technical solutions.

[0103] In practical application, the present application is verified by a model developed based on a reclaimed water station of a university in Beijing adopting a multi-stage fixed biofilm treatment process. The process includes one anoxic tank and six aerobic tanks, with a daily treatment capacity of 200-300 tons, and the influent is domestic sewage from the office building of the university. All the tanks are connected through overflow holes, the anoxic tank is provided with polyurethane fiber suspended fillers, and the fillers are stirred by a stirring device. Each aerobic tank is provided with a microporous aerator at the bottom to continuously and uniformly aerate the reaction tank, and the aerobic tank is installed with fixed nylon fiber fillers. The sewage enters the reactor from the influent port, passes through the anoxic tank and the aerobic tank in sequence, and finally flows to the sedimentation tank and the clear water tank and is discharged from the effluent port. The relevant data required for constructing the model are obtained through actual measurement, literature research and theoretical simulation. In the simulation process, the anoxic tank and the first aerobic tank are selected for model calibration, and the second to sixth aerobic tanks are used for model verification. The present application is further described in detail below in conjunction with the accompanying drawings and examples.

[0104] Example 1

[0105] Basic data are obtained. An anaerobic tank and six aerobic tanks are set up for experiments, and COD and ammonia nitrogen under different influent conditions, dissolved rapidly biodegradable organic matter (S S ), nitrate nitrogen in activated sludge (S NO ), autotrophic microorganisms in activated sludge (X ba ), and heterotrophic microorganisms in activated sludge (X bh ) are monitored. The experimental values are used as parameter input values. The input and output rate difference (Q exchange ) of pollutants between influent and effluent and the diffusion mass transfer rate (D exchange ) between activated sludge and biofilm are calculated according to formulas (6) and (7).

[0106] The fillers in different biochemical tanks are sampled, and the biofilm weight per unit volume of filler is calculated by the dry weight difference before and after the filler is colonized. The protozoa and metazoans on the fillers are sampled and examined under a microscope to determine the types and density (W j ) of protozoa and metazoans per unit area of filler. The concentration density (g / m 3The behavior of protozoa and metazoans, as well as population dynamics, were calculated. Heterotrophic microorganisms (X-rays) on the packing material were determined by microscopic counting. bh ) and autotrophic microorganisms (X ba The quantity of COD was converted to concentration (g COD / m³) based on the dry weight of the biofilm. Predation behavior of protozoa and metazoans in anoxic ponds was simulated through predation. Predators preyed on resources. They acquire energy to promote their own population growth. The population growth rate (G) caused by predation behavior is calculated and summed according to formula (4-5). predation ) and the rate of population depletion caused by predation (G consumed ).

[0107] The dynamic changes of microorganisms in the anoxic tank were calculated based on models of microbial attenuation, consumption, and hydrolysis. This includes the aerobic growth of heterotrophic microorganisms. ), Anaerobic growth of heterotrophic microorganisms ( ), aerobic growth of autotrophic microorganisms ( ), organic carbon hydrolysis model ( According to the improved activated sludge model ( ) Calculate the dynamic changes of dissolved and particulate pollutants in the anoxic tank, as well as the impact on microbial metabolic growth; based on the improved biofilm model ( ) Calculate the consumption of substances on the biofilm and the metabolic growth of microorganisms.

[0108] See the interrelationships between protozoa, metazoa, microorganisms, and various components. Figure 1 .

[0109] A graph comparing experimental and simulated values ​​was plotted with time (days) on the x-axis and pollutant concentration on the y-axis. In the experiment, the dissolved rapidly biodegradable organic matter (S) in the anoxic tank was measured. S ), particulate slow-biodegradable organic matter (X) S ), particulate products generated by microbial attenuation (X) P ), particulate biodegradable organic nitrogen (X ND The concentrations were: 46.28 gCOD / m³ 3 107.98 g COD / m 3 0.04 g / m 3 and 0.03 g N / m 3 Using these data as starting values, a program was written in MATLAB to establish an overall mathematical model based on the experimental process described above, simulating the changes in the concentration values ​​of each component over time. Figure 2 As shown in the figure, the simulation results agree well with the actual observations, verifying the reliability and accuracy of the model of this invention.

[0110] Example 2

[0111] Further calibrated by the biofilm model in the No. 1 aerobic tank, including the dynamic changes of dissolved rapidly biodegradable organic matter, nitrate nitrogen, heterotrophic microorganisms and autotrophic microorganisms, the reactions involved are calculated by the following formula:

[0112] Wherein S S , S NO , X bh , X ba all use experimental values as parameter input values, and S O is the dissolved oxygen concentration. The substrate half-saturation coefficient (K SH,aer,bf ) of aerobic growth of heterotrophic microorganisms on the biofilm, the oxygen half-saturation coefficient (K OH，aer,bf ) of anoxic growth of heterotrophic microorganisms on the biofilm, the nitrate half-saturation coefficient (K NO,bf ) of heterotrophic microorganisms on the biofilm, and the ammonia half-saturation coefficient (K NH,bf ) of autotrophic microorganisms on the biofilm are 48 g COD / m³, 2 g O2 / m³, 12 g NO3 - -N / m³ and 4 g NH3-N / m³ respectively at 20°C by querying relevant literature.

[0113] Because the concentration of components on the membrane is not much different from that in water, the values of S s,bf and S NO,bf are the same as in water, and the concentrations of X bh,bf and X ba,bf are 19.03 g COD / m 3 and 0.7 g COD / m 3 respectively. A program is written in MATLAB, and the overall mathematical model is established according to the process flow of the above experiment to simulate the concentration values of each component with time. As shown in Figure 3 , the simulation results are in good agreement with the actual observed values, further verifying the reliability and accuracy of the model.

[0114] Example 3

[0115] On the basis of the implementation examples 1 and 2, the accuracy of the model is further verified. The No. 2-6 aerobic tanks are verified, and the measured parameters include dissolved rapidly biodegradable organic matter (S S ), particulate slowly biodegradable organic matter (X S ), autotrophic microorganisms in activated sludge (X ba ), and heterotrophic microorganisms in activated sludge (X bh), particulate products (X) produced by microbial decay in activated sludge p ), nitrate nitrogen (S NO ), ammonia nitrogen (S NH ), dissolved biodegradable organic nitrogen (S ND ), particulate biodegradable organic nitrogen (X ND ).

[0116] The relative deviation is used as an important index for evaluating the measurement accuracy, and smaller relative deviation reflects higher measurement accuracy. The simulation values of the No. 2-6 aerobic tanks are obtained through MATLAB simulation, the relative errors between the simulation values and the measured values are calculated, and the relative deviations of 81% of the variables are less than 0.3, which shows that the coupled model can provide high-precision measurement results in most cases, and the reliability and accuracy of the model are verified, thereby providing a solid foundation for further application and research.

[0117] The above is a further detailed description of the present application in combination with specific preferred embodiments, which is convenient for the technical personnel in the technical field to understand and apply the present application, and cannot be regarded as the limitation of the specific implementation of the present application. For the ordinary technical personnel in the technical field to which the present application belongs, a number of simple deductions or substitutions can be made without departing from the concept of the present application, and without having to have creative labor. Therefore, the simple improvement of the present application made by the technical personnel in the field according to the disclosure of the present application should be within the protection scope of the present application.

Claims

1. A predatory enhanced cascade fixed biofilm wastewater treatment process dual-environment three-component coupling method, characterized in that, The steps are as follows: Step one: Establishing the model framework (1) Double environment division; Activated sludge environment: heterotrophic microorganisms X bh with autotrophic microorganisms X ba Metabolic reactions with suspended and dissolved pollutants and exchange of substances with the biofilm by diffusion; protozoa and metazoan regulate the microbial population density by predation of the suspended bacterial population, the predation rate following the Lotka-Volterra kinetic equation; Biofilm environment: microorganisms attach to the surface of fillers to form a layered structure, heterotrophic microorganisms X bh,bf Metabolism of autotrophic microorganisms X ba,bf is limited by local mass transfer, and pollutants enter the interior of the biofilm through a diffusion gradient; protozoa and metazoan prey on suspended bacterial populations, and their predation mechanism is consistent with that in activated sludge environments, with a global uniform value for predation efficiency; The material exchange between the two environments is realized through the diffusion term, and the dynamic balance of the predation behavior regulates the microbial community; (2) Three-component definition; (2.1) Bacteria: including heterotrophic microorganisms X 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 metazoans; (2.3) Pollutants: divided into dissolved and particulate states, wherein the dissolved state includes dissolved fast-biodegradable organic matter S s , ammonia nitrogen S NH , nitrate nitrogen S NO , dissolved oxygen S O , dissolved biodegradable organic nitrogen S ND ; the particulate state includes slow-degradable organic matter X s , particulate state products produced by microbial decay X P , particulate biodegradable organic nitrogen X ND ; (3) Multi-stage cascade structure; The reactor is composed of multiple series of anoxic tanks and aerobic tanks, that is, the effluent of the previous stage is used as the influent of the next stage, forming a cascade mode of "anoxic tank→aerobic tank"; the series order of the anoxic tank and the aerobic tank 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, which are the activated sludge environment mass conservation equation, the biofilm environment mass conservation equation, and the population dynamics of protozoa and metazoans; Step two: Q exchange , D exchange Kinetic process refinement; （6）； （7）； where t1 is the hydraulic retention time, d; S i,in is the effluent concentration of the previous stage, and the material flow between stages is achieved by cascade transmission, g COD / m 3 ; S i is the concentration of different substances in the activated sludge, g COD / m 3 ; D i is the diffusion coefficient of i substance, 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 ; the predation efficiency of the predator on the bacteria in the activated sludge and the biofilm is the same; Step three: Determine the change rate of multiple pollutants caused by microbial metabolism; Step four: According to the modeling principles of the material quantity model, combined with the activated sludge model, the biofilm model, and the protozoan and metazoan predation model, the coupled model is established: Step five: Further determine the microbial metabolism rate; Step six: Temperature half-saturation constant correction; Step seven: Parameter calibration and experimental verification.

2. The double environment-three component coupling method of the predation enhanced cascade fixed biofilm sewage treatment process according to claim 1, characterized in that, (4) The mass conservation framework equation is as follows: (4.1) The total mass conservation equation of the activated sludge environment; （1） where Q exchange is the difference of the input and output rates of the pollutants in and out of the activated sludge, g COD / (m3·d); D exchange is the diffusion mass transfer rate between the activated sludge and the biofilm, g COD / (m3·d), the diffusion direction is that the pollutants diffuse from the activated sludge S i to the biofilm S i,bf ; R metabolism is the change rate of the pollutants caused by the metabolism of the microorganisms in the activated sludge, g COD / (m3·d); is the conversion coefficient of the biomass to COD, g COD / mg; G predation is the population growth rate caused by the predation behavior, mg / (m3·d). (4.2) The total mass conservation equation of the biofilm environment; （2）； wherein R metabolism,bf is the rate of change of pollutants due to microbial metabolism in the biofilm, g COD / (m3-d); is the conversion factor of biomass to COD, g COD / mg; (4.3) The total population dynamic equation of protozoa and metazoans; （3）； Wherein, G consumed is the population consumption rate caused by predation behavior, mg / (m3·d); M is the natural mortality rate of protozoa and metazoan, 1 / d; W j is the density of the jth protozoan and metazoan, mg / m 3 ; （4）； （5）； where e is the assimilation efficiency of protozoa, metazoan predation; is the resource quantity; is the resource quantity; is the resource quantity; is the resource quantity; is the resource quantity; is the resource quantity; is the resource quantity; is the resource quantity; is the resource quantity; is the resource quantity; is the resource quantity; is the resource quantity; is the resource quantity; 3. The double environment-three component coupling method of the predation enhanced cascade fixed biofilm sewage treatment process according to claim 2, characterized in that, Step three, the specific implementation process of determining the change rate of multiple pollutants caused by microbial metabolism is as follows: (1) In the activated sludge: （8）； wherein Y H is the yield coefficient of heterotrophic microorganisms in activated sludge, g COD / g COD; is the decay product coefficient corresponding to the i-th substance, g COD / g COD; Y A is the yield coefficient of autotrophic microorganisms in activated sludge, g N / g COD; is the growth coefficient of autotrophic microorganisms in good conditions; is the hydrolysis rate coefficient of organic carbon; b H is the decay coefficient of heterotrophic microorganisms, 1 / d; b A is the decay coefficient of autotrophic microorganisms, 1 / d; K a is the ammonification rate coefficient, m³ / (g COD·d); S ND is the dissolved biodegradable organic nitrogen, g N / m³; φ1 refers to the growth rate of heterotrophic microorganisms in activated sludge under aerobic conditions, 1 / d; φ2 refers to the growth rate of heterotrophic microorganisms in activated sludge under anoxic conditions, 1 / d; φ3 refers to the hydrolysis rate of organic carbon in activated sludge, 1 / d; φ4 refers to the nitrification rate of autotrophic microorganisms in activated sludge, 1 / d; (2) In the biofilm environment: （9）； where Y Haer is the yield coefficient of heterotrophic microorganisms on the biofilm, g COD / g COD; Y Hanx is the anoxic yield coefficient of heterotrophic microorganisms on the biofilm, g N / g COD; denotes the aerobic growth rate of heterotrophic microorganisms on the biofilm, 1 / d; denotes the anoxic growth rate of heterotrophic microorganisms on the biofilm, 1 / d; denotes the nitrification rate of autotrophic microorganisms on the biofilm, 1 / d.

4. The double environment-three component coupling method of the predation enhanced cascade fixed biofilm sewage treatment process according to claim 3, characterized in that, Step four, the coupled model is established as follows: Based on formulas (1), (6), (7), and (8), the activated sludge environment pollutant dynamic formula (10) is derived as: （10）； wherein the heterotrophic microorganisms consume COD in aerobic growth; the heterotrophic microorganisms consume nitrate in anoxic growth; the autotrophic microorganisms consume ammonia nitrogen in nitrification; the hydrolysis of organic carbon converts particulate organic matter X s into dissolved organic matter S s ; the decay of the heterotrophic microorganisms results in a decrease in biomass; the decay of the autotrophic microorganisms results in a decrease in biomass; ammonification consumes organic nitrogen; Based on formulas (2), (6), (7), and (8), the biofilm environment pollutant dynamic formula (11) is obtained as: （11）； Based on formulas (3), (4), and (5), the protozoan and metazoan population dynamic formula (12) is obtained as: （12）。 5. The double environment-three component coupling method of the predation enhanced cascade fixed biofilm sewage treatment process according to claim 4, characterized in that, Step five, the specific implementation process of further determining the microbial metabolism rate is as follows: (1) The specific calculation equation of the microbial metabolism rate in the activated sludge; The aerobic growth of heterotrophic microorganisms in the activated sludge: （13）； The anoxic growth of heterotrophic microorganisms in the activated sludge: （14）； The nitrification of autotrophic microorganisms in the activated sludge: （15）； The hydrolysis rate of organic carbon in the activated sludge: （16）； wherein, is the heterotrophic microorganism aerobic specific growth rate coefficient, 1 / d; is the autotrophic microorganism aerobic specific growth rate coefficient in the activated sludge, 1 / d; K S is the heterotrophic microorganism substrate half-saturation coefficient in the activated sludge, g COD / m3; S O is dissolved oxygen, g / m 3 ; K OH is the heterotrophic microorganism oxygen half-saturation coefficient in the activated sludge, g O2 / m3; K NO is the heterotrophic microorganism nitrate half-saturation coefficient in the activated sludge, g NO3 - -N / m3; S NO is nitrate nitrogen, g N / m3; is the heterotrophic microorganism anoxic growth correction coefficient in the activated sludge, k h is the maximum specific hydrolysis rate coefficient, g COD / g COD; k b is the half-saturation coefficient of particulate slow biodegradable organic matter, g COD / g COD; is the heterotrophic microorganism anoxic hydrolysis correction coefficient in the activated sludge; (2) The specific calculation equation of the microbial metabolism rate on the biofilm; The aerobic growth of heterotrophic microorganisms on the biofilm: （17）； The anoxic growth of heterotrophic microorganisms on the biofilm: （18）； The aerobic growth of autotrophic microorganisms on the biofilm: （19）； wherein S s,bf is dissolved readily biodegradable organic matter on the biofilm, g COD / m³; is the concentration of dissolved oxygen on the biofilm, g / m³; is the anoxic growth rate correction factor for heterotrophic microorganisms on the biofilm; K SH,aer,bf is the substrate half-saturation coefficient for aerobic growth of heterotrophic microorganisms on the biofilm, g COD / m³; K OH,aer,bf is the oxygen half-saturation coefficient for heterotrophic microorganisms on the biofilm, g O2 / m³; K SH,anx,bf is the substrate half-saturation coefficient for heterotrophic microorganisms on the biofilm, g COD / m³; K OH,anx,bf is the substrate half-saturation coefficient for anoxic growth of heterotrophic microorganisms on the biofilm, g COD / m³; K NO,bf is the nitrate half-saturation coefficient for heterotrophic microorganisms on the biofilm, g NO3 - -N / m³; S NO,bf is nitrate nitrogen, g N / m³; K NH,bf is the nitrate half-saturation coefficient for heterotrophic microorganisms in the activated sludge, g NO3 - -N / m³; K OA,bf is the oxygen half-saturation coefficient for autotrophic microorganisms on the biofilm, g O2 / m³.

6. The dual environment-three component coupled process of predatory enhanced cascade fixed biofilm wastewater treatment process of claim 5, characterized in that, Step five, the temperature half-saturation constant correction is as follows: The influence of temperature change on the metabolic rate of microorganisms is realized by adjusting the half-saturation constant; considering that the temperature change will affect the half-saturation constant of the related parameters, the temperature half-saturation constant is calculated by the following formula: （20）； （21）； wherein k T is the half-saturation constant at temperature T °C, k 20 is the half-saturation constant at reference temperature 20 °C, is the temperature correction factor, determined by experimental data fitting; T1, T2 are experimental temperature points.

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