Device and method for improving autotrophic nitrogen removal performance of MABR reactor

Abstract

The invention relates to the technical field of biological sewage treatment, in particular to a device and a method for improving the autotrophic nitrogen removal performance of an MABR (Membrane Ammonia Baffled Reactor). Coupling of partial nitrosation reaction and anaerobic ammonia oxidation reaction is completed; through a circular reaction zone and a membrane reaction zone in the reaction tank, nitrate nitrogen generated by anaerobic ammonia oxidation and excessive nitrite nitrogen during instability regulation are circularly removed, and the purpose of improving the total nitrogen removal effect of the reactor is achieved; a proper amount of a sodium nitrite solution is added at proper time, the concentration of free nitrous acid in a mixed solution of the reactor is increased, and the intermittent proportion of MABR intermittent aeration is synchronously regulated and controlled, so that the activity of nitrite oxidizing bacteria is synergistically inhibited by low dissolved oxygen and high free nitrous acid, and the unstable short-cut nitrification reaction is recovered again; the autotrophic nitrogen removal performance of the reactor is improved.

Description

Technical Field

[0001] The invention relates to the technical field of biological sewage treatment, and in particular to a device and a method for improving the autotrophic denitrification performance of a MABR reactor. Background Art

[0002] Membrane aerated biofilm reactor (MABR) is a type of membrane carrier biofilm reactor that combines the characteristics of traditional biofilm technology and gas separation membrane technology. Its membrane components have the functions of efficient oxygenation and microbial attachment carrier. Compared with traditional activated sludge method and biofilm method, this process has significant advantages in operating energy consumption, denitrification performance, etc., and is a sewage treatment technology with great development prospects.

[0003] The MABR process has unique technical characteristics. First, the process uses a non-porous oxygen-permeable membrane. Oxygen is transferred to the biofilm attached to it in molecular form through the membrane. This bubble-free aeration mode gives it a very high oxygen mass transfer efficiency. Second, the biofilm is easy to attach and grow on the surface of the MABR membrane fibers. There is anisotropic mass transfer of oxygen and pollutants in it, which makes the biofilm produce obvious microbial community stratification, forming aerobic, anoxic and anaerobic functional areas from the inside to the outside. It can achieve efficient removal of organic matter, ammonia nitrogen and total nitrogen in a single reactor. Third, it has high energy efficiency and permeability. The extremely high oxygen transfer efficiency of the oxygen membrane makes the aeration energy consumption required for this process significantly lower than that of the traditional activated sludge method, thus reducing the operating cost. Studies have shown that the MABR process can reduce operating energy consumption by 40% to 80% compared with the traditional activated sludge method. In addition, the electron donors and acceptors in the MABR biofilm have the characteristics of "reverse diffusion", which makes it easy to control the nitrite reaction, making it feasible to combine it with autotrophic denitrification reactions such as anaerobic ammonium oxidation, thereby making MABR technology naturally applicable in simultaneous nitrification and denitrification, short-term nitrification and denitrification, and short-term nitrification-anaerobic ammonium oxidation autotrophic denitrification.

[0004] The autotrophic denitrification technology based on anaerobic ammonia oxidation (Anammox) has the characteristics of high denitrification efficiency, 50-60% less power consumption than traditional processes, no need for organic carbon sources, and very little residual sludge production, and has broad development prospects. This autotrophic denitrification technology is a biological oxidation-reduction process that converts ammonia nitrogen and nitrite nitrogen into nitrogen gas under the action of anaerobic ammonia-oxidizing bacteria, using ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor. In practical applications, partial short-range nitrification is usually coupled with the anaerobic ammonia oxidation process to short-range nitrify about half of the ammonia nitrogen in the sewage into nitrite nitrogen, and the anaerobic ammonia oxidation reaction occurs with the remaining ammonia nitrogen to complete the removal of total nitrogen. The heterogeneous mass transfer biofilm in the MABR process has low organic matter concentration and high dissolved oxygen conditions on the inside, which is conducive to the growth of aerobic ammonia oxidizing bacteria (AOB). When the oxygen supply is adjusted to make the liquid phase in anoxic state, the outside of the biofilm has high organic matter concentration and low dissolved oxygen conditions, which is conducive to the growth of anaerobic ammonia oxidizing bacteria and heterotrophic nitrifying bacteria. This unique microbial stratification feature is conducive to inhibiting the activity of nitrite oxidizing bacteria (NOB), making it easy for short-range nitrification reactions to proceed in the MABR reactor, thereby realizing the coupling of nitrite and anaerobic ammonia oxidation reactions in the same reactor, forming a single-stage autotrophic denitrification MABR process.

[0005] The key to achieving efficient autotrophic denitrification in the MABR reactor is to provide stable nitrite nitrogen through partial short-term nitrification reactions and effectively enrich and retain anaerobic ammonia-oxidizing bacteria in the reactor. The short-term nitrification process mainly utilizes the differences in physiological characteristics and kinetic properties between ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), and their different adaptability to different environmental factors. The reaction conditions are controlled within a range suitable for AOB growth and NOB activity is inhibited, and NOB is continuously eliminated from the reactor to achieve the nitrification process. Currently, the commonly used short-term nitrification control factors mainly include: temperature, dissolved oxygen (DO), pH value, sludge age (SRT), free ammonia (FA), free nitrite (FNA), toxicity inhibitors, etc. Among them, dissolved oxygen (DO) is a very important factor in distinguishing ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB). It uses the fact that ammonia oxidizing bacteria (AOB) have a higher affinity for oxygen than nitrite oxidizing bacteria (NOB). Therefore, controlling a lower dissolved oxygen will inhibit the activity of nitrite oxidizing bacteria (NOB), while ammonia oxidizing bacteria (AOB) will not be affected. The main ways to control dissolved oxygen are aeration volume, intermittent aeration mode, etc. Ammonia oxidizing bacteria (AOB) are more sensitive to temperature than nitrite oxidizing bacteria (NOB). Increasing the temperature is conducive to the proliferation of ammonia oxidizing bacteria (AOB) and the elimination of nitrite oxidizing bacteria (NOB), especially when the temperature exceeds 30°C, it is conducive to the production of nitrite. The accumulation of salt nitrogen; the inhibitory concentration of free ammonia (FA) for nitrite oxidizing bacteria (NOB) is much lower than that for ammonia oxidizing bacteria (AOB). Higher free ammonia (FA) is conducive to the inhibition of the activity of nitrite oxidizing bacteria (NOB), thereby achieving the accumulation of nitrite nitrogen. Usually, the free ammonia control strategy is used in conjunction with a higher pH value. A higher concentration of free ammonia is easily produced in the reactor under alkaline conditions; the inhibitory concentration of free nitrite (FNA) for ammonia oxidizing bacteria (AOB) is dozens of times that for nitrite oxidizing bacteria (NOB). The free nitrite (FNA) produced under lower pH conditions can be used to inhibit nitrite oxidizing bacteria (NOB) and produce nitrite nitrogen accumulation. To increase the enrichment and retention of anaerobic ammonium oxidizing bacteria in the reactor, mainly adopt methods such as inoculating flocculent sludge or granular sludge with high abundance of anaerobic ammonium oxidizing bacteria, adding fillers in the reactor that are easy for anaerobic ammonium oxidizing bacteria to attach and grow, and controlling the suitable growth conditions of anaerobic ammonium oxidizing bacteria (dissolved oxygen, temperature, pH value, alkalinity, nitrogen load).

[0006] Due to the growth characteristics of nitrite oxidizing bacteria (NOB), controlling the above-mentioned regulatory factors within the inhibitory range can quickly inhibit their growth, causing nitrite nitrogen accumulation in the reactor and reaching a state of short-term nitrification. However, the regulatory measures will directly affect the actual operation of the autotrophic denitrification reactor, especially for autotrophic denitrification in special reactors such as MABR. During the long-term operation of the reactor, especially when a single inhibitory factor control strategy is adopted, nitrite oxidizing bacteria (NOB) will gradually develop tolerance to the above-mentioned inhibitory factors, and the tolerance of nitrite oxidizing bacteria (NOB) will be more obvious. As a result, nitrite oxidizing bacteria (NOB) will continue to proliferate in the reactor, causing nitrite nitrogen to be oxidized to nitrate nitrogen, and the short-term nitrification state will be destroyed, which will make the anaerobic ammonia oxidation reaction unable to obtain sufficient nitrite nitrogen, resulting in a decrease in reaction efficiency. The operation of the autotrophic denitrification reactor will become unstable, and its denitrification performance will be significantly reduced. At the same time, MABR biofilm belongs to a long sludge age biofilm system, and it is impossible to directly rely on the principle of microbial growth kinetics to wash nitrite oxidizing bacteria (NOB) out of the reactor or produce a long-term inhibitory effect on nitrite oxidizing bacteria (NOB). Therefore, it is very difficult to achieve long-term stable occurrence of short-range nitrification reaction in MABR reactor. The current solution is to use a multi-factor combined control strategy to maintain long-term inhibition or elimination of nitrite oxidizing bacteria (NOB), that is, to adopt a comprehensive control strategy such as low dissolved oxygen and high free ammonia (FA), low dissolved oxygen and high free nitrite (FNA), high temperature and low dissolved oxygen and low sludge age. However, there are still some problems in actual engineering applications. For the autotrophic denitrification reactor of high-concentration ammonia-containing wastewater, a comprehensive control strategy can make full use of the higher concentration of ammonia nitrogen to produce enough free ammonia (FA) or free nitrite (FNA) to effectively inhibit nitrite oxidizing bacteria (NOB). The regulation effect is obvious and the nitrite reaction is relatively stable. However, when mainstream autotrophic denitrification is carried out for wastewater with medium and low ammonia nitrogen concentrations or domestic sewage, it is difficult to use free ammonia (FA) or free nitrite (FNA) and low concentration dissolved oxygen for joint control, which makes the insufficient stability of the reactor operation more obvious.

[0007] When nitrite oxidizing bacteria are inhibited by free nitrite, precise control of its concentration is difficult to achieve. When the free nitrite concentration exceeds 0.2 mg / L, all nitrifying bacteria, including AOB and NOB, will be inhibited. At the same time, the optimum pH value for ammonia oxidizing bacteria is 8-9, and the optimum pH value for nitrite oxidizing bacteria is 6.5-7.5. In the process of synergistic inhibition of nitrite oxidizing bacteria (NOB) by low dissolved oxygen and free nitrite (FNA), a lower pH value (generally 6.0-6.5) and a higher concentration of nitrite nitrogen are required, and these conditions are difficult to meet in the actual operation of wastewater treatment processes. When the pH value is controlled within a lower range, a large amount of acid needs to be added artificially, which will have a serious impact on ammonia oxidizing bacteria and nitrite oxidizing bacteria, and will also affect the survival of most activated sludge microorganisms. And the MABR reactor is quite different from the traditional biofilm reactor. There is a heterogeneous mass transfer process in the MABR biofilm, so that nitrite oxidizing bacteria cannot be completely eliminated from the reactor like the traditional biofilm. Nitrite oxidizing bacteria and ammonia oxidizing bacteria coexist in the MABR biofilm. Therefore, the sodium nitrite solution addition strategy and reactor stability control adopted in the present invention need to be dynamically adjusted and implemented during continuous operation. It is impossible to obtain a stable short-range nitrification process and a stable autotrophic denitrification process by one-time inhibition or killing of nitrite oxidizing bacteria by high concentration of free nitrite at the beginning of the reactor operation. Therefore, improving the performance of the autotrophic denitrification reactor by improving the stability of the nitrite process during the operation of the reactor is still a problem that needs to be solved urgently in current research and application.

[0008] In the invention patent application documents that have been published, the addition of hydroxylamine, continuous alternating addition of hydroxylamine and hydrazine, etc., are used to inhibit the activity of nitrite oxidizing bacteria (NOB) to enhance autotrophic denitrification. The application document mentions that hydroxylamine, as an intermediate product of nitrification and anaerobic ammonia oxidation, can enhance the activity of ammonia oxidizing bacteria (AOB), and can affect the synthesis of nitrite oxidoreductase to inhibit the activity of nitrite oxidizing bacteria (NOB). As an intermediate product of anaerobic ammonia oxidation, hydrazine has a strong inhibitory effect on the Nitrobacter genus in nitrite oxidizing bacteria (NOB) while enhancing the activity of anaerobic ammonia oxidizing bacteria (AnAOB). The control strategy of adding these two substances has only been carried out in laboratory autotrophic denitrification pilot studies, and has not yet been confirmed and applied in actual engineering. The main problems are: ① The long-term addition of a single hydroxylamine increases the NOB tolerance, which is easy to cause the migration of nitrite oxidizing bacteria (NOB) species and leads to the recovery of nitrite oxidizing bacteria (NOB) activity. ②Hydroxyamine is unstable and easily absorbs moisture. It will decompose rapidly when absorbing water vapor and carbon dioxide at room temperature and explode violently when heated. It is a potential mutagen and is also highly toxic, so its practical application is very dangerous. ③There is a lack of systematic research on the effects of hydrazine on all major bacteria involved in denitrification. A slightly higher concentration can slow down the denitrification process. ④Hydrazine is a Class 2A carcinogen with strong toxicity. It will explode and decompose when exposed to air for a long time or exposed to high temperature for a short time. It has strong water absorption, so its engineering application is very dangerous.

[0009] There is also a way to control the instability of the reactor by side inhibition, which also has defects: ① The existing method of determining the instability of the MABR reactor is single and cannot meet the requirements for determining the stability of the actual operation process. Because there are short-term digestion and anaerobic ammonia oxidation in the MABR reactor, there are some organic matter in its influent, which causes heterotrophic denitrification or heterotrophic short-term denitrification reactions, etc. At the same time, there are many endogenous denitrification reactions that use the death of bacteria to produce organic matter, which makes the nitrate nitrogen ratio in the effluent of the autotrophic denitrification reactor have a large range of variation. In particular, heterotrophic denitrification will greatly reduce the nitrate nitrogen in the effluent of the integrated reactor, thereby making the single determination of the nitrite nitrogen generation ratio in the effluent invalid. ② The side inhibition method will also cause a large lag in the main process of the MABR autotrophic denitrification reaction. For the main process reactor where NOB has over-proliferated, the amount of side inhibition is not enough to quickly change the instability state in the main process reactor in a timely manner, so that the restoring process of the entire autotrophic denitrification reactor is relatively long. ③ The lateral inhibition device can only perform lateral inhibition operations on the suspended sludge in the integrated autotrophic denitrification device, but has no way to inhibit the proliferation of NOB in the biofilm attached to and growing on the filler in the integrated autotrophic denitrification device, thereby reducing the actual efficiency of the device.

[0010] The existing MABR reactors have the following disadvantages when used for autotrophic biological denitrification: ① The MABR membrane components and the biofilm filter, contact oxidation and other modules are arranged in the same reactor in a simple up-and-down arrangement. There is a risk of overlapping disadvantages of the two types of treatment modules during long-term operation. The problems of biofilm blockage or membrane filament contamination are still serious, and the membrane components are very inconvenient to backwash, maintain and overhaul. ② Multiple MABR reactors are connected in series as a multi-stage treatment process, which has a more complicated structure, increased infrastructure investment, and more complicated operation and management. The process parameters of each stage of the reactor need to be controlled separately, especially the first stage reactor requires a higher alkalinity for buffering during nitrification or nitrite, which reduces the stability of operation. Summary of the invention

[0011] In order to improve the stability of the autotrophic denitrification process of the MABR reactor and improve its autotrophic denitrification performance, the present invention proposes a device and method for improving the autotrophic denitrification performance of the MABR reactor, and adopts a composite membrane component that combines a curtain-type silica gel silk membrane with excellent oxygen permeability and a spatial three-dimensional mesh filler that is easy to attach anaerobic ammonia oxidizing bacteria to complete the coupling of partial nitrite reaction and anaerobic ammonia oxidation reaction; by timely and appropriate addition of sodium nitrite solution, the free nitrite (FNA) concentration of the reactor mixed solution is increased, and in the process where the short-range nitrification gradually degenerates into complete nitrification due to the continuous proliferation of nitrite oxidizing bacteria (NOB) in the MABR biofilm, the nitrite removal is enhanced. The inhibitory effect of anaerobic ammonia oxidation (ANAOM) on NOB; the intermittent proportion of intermittent aeration in MABR is regulated simultaneously to achieve the synergistic inhibition of nitrite oxidizing bacteria (NOB) activity by low dissolved oxygen (DO) and high free nitrite (FNA), so that the unstable short-range nitrification reaction can be restored, and part of the ammonia nitrogen is converted into nitrite nitrogen as needed, thereby meeting the needs of anaerobic ammonia oxidation reaction and improving the autotrophic nitrogen removal performance of the reactor; and through the circulating reaction zone and membrane reaction zone set inside the single MABR reactor, the nitrate nitrogen generated by anaerobic ammonia oxidation and the excess nitrite nitrogen during the unstable adjustment period are circulated and removed, so as to achieve the purpose of improving the total nitrogen removal effect of the reactor.

[0012] In order to solve the above technical problems, the present invention provides a device for improving the autotrophic denitrification performance of a MABR reactor, comprising:

[0013] The reaction tank is internally divided into a circulation reaction zone and a membrane reaction zone connected at the bottom, the water inlet pipe is connected to the circulation reaction zone, the water outlet pipe is connected to the membrane reaction zone, the circulation reaction zone is provided with a stirring circulation system, the membrane reaction zone is provided with a water distribution porous plate, the lower part of the water distribution porous plate is a sludge zone, and the upper part is provided with multiple groups of MABR membrane modules;

[0014] The reagent dosing system includes a plurality of groups of membrane zone dosing components disposed between the MABR membrane components and the water distribution porous plate and corresponding to each group of the MABR membrane components;

[0015] The air supply system is used to aerate each of the MABR membrane modules;

[0016] The mixed liquid reflux system is used to reflux the mixed liquid in the membrane reaction zone to the circulation reaction zone;

[0017] The sludge return system is used to return the sludge in the sludge area to the circulation reaction area;

[0018] The air stirring system is used to flush each of the MABR membrane modules with airflow;

[0019] The online monitoring instrument system is used to monitor the water quality indexes in the membrane reaction zone and the inlet water quality indexes in real time, and includes a PLC control cabinet connected to the reagent dosing system and the gas supply system signal.

[0020] Furthermore, the MABR membrane assembly includes a membrane assembly outer frame, a spatial three-dimensional mesh filler layer, a membrane assembly inner frame and a curtain-type membrane fiber element which are arranged in sequence from the outside to the inside. The curtain-type membrane fiber element includes a plurality of filamentous silicone membranes evenly distributed horizontally and an air intake vertical pipe and an exhaust vertical pipe which are arranged on both sides and are respectively connected to the two ends of the filamentous silicone membranes. The air intake vertical pipe is connected to the aeration pipe of the air supply system, and the exhaust vertical pipe is connected to the exhaust pipe of the air supply system.

[0021] Furthermore, the membrane zone dosing component includes a dosing main pipe, on which are provided a plurality of parallel dosing perforated pipes, the plurality of dosing main pipes extending to the outside of the reaction tank are provided with dosing main pipe valves and are connected to a dosing distribution pipe, the dosing distribution pipe is connected to the dosing pipe, the dosing pipe is connected to the nitrite storage tank, and the dosing pipe is provided with a valve, a nitrite dosing flowmeter and a nitrite dosing metering pump.

[0022] Further, the mixed liquor return system includes a mixed liquor return pipe connected to the upper part of the membrane reaction zone, the sludge return system includes a sludge return pipe connected to the sludge zone, the sludge return pipe is provided with a sludge discharge pipe, the mixed liquor return pipe and the sludge return pipe are connected to the circulation reaction zone through a return main pipe, and the return main pipe is provided with a heat exchange system;

[0023] The air stirring system includes an air stirring assembly corresponding to each group of MABR membrane assemblies in the sludge area, and the air stirring assembly is connected to the corresponding air stirring branch pipe;

[0024] The stirring circulation system comprises a circulation guide tube arranged in the circulation reaction zone, and an upflow stirrer is arranged in the circulation guide tube.

[0025] Furthermore, the online monitoring instrument system includes an online dissolved oxygen meter, an online ORP meter, an online ammonia nitrogen meter for the membrane reaction zone, an online nitrate nitrogen meter, an online nitrite nitrogen meter for the membrane reaction zone, and an online pH meter for the membrane reaction zone, which are arranged in the membrane reaction zone and connected to the PLC control cabinet through a secondary membrane reaction zone monitoring instrument, and an online water inlet pH meter and an online water inlet ammonia nitrogen meter which are arranged on the water inlet pipe and connected to the PLC control cabinet through a secondary water inlet monitoring instrument.

[0026] The present invention also provides a method for improving the autotrophic denitrification performance of a MABR reactor, using the above-mentioned device for improving the autotrophic denitrification performance of a MABR reactor, and the steps are:

[0027] S001. Inoculate and form biofilm in the MABR reactor, and make the MABR reactor operate normally for autotrophic denitrification;

[0028] S002, establishing the reference values ​​of various data during the normal operation of the autotrophic denitrification process of the MABR reactor and storing them in the PLC controller, wherein the data include: dissolved oxygen, pH value, redox potential, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen and temperature in the membrane reaction zone (4); and ammonia nitrogen, pH value and temperature in the influent;

[0029] S003. Establish a database for determining the stability decline of the autotrophic denitrification process of the MABR reactor: Based on the changing trend of water quality indicators in the autotrophic denitrification process of the MABR reactor, list the main reasons for the instability of the autotrophic denitrification of the MABR reactor;

[0030] S004. Continuously collect various online monitoring data of the autotrophic denitrification process of the MABR reactor and input them into the PLC controller, compare the various online monitoring data with the reference values ​​of the various data, and determine the cause of the instability of the autotrophic denitrification of the MABR reactor based on the data trend in the determination database;

[0031] S005. According to the cause of the instability of the autotrophic nitrogen removal in the MABR reactor in step S004, corresponding regulation is performed.

[0032] Furthermore, in step S005, the reason for the instability of the autotrophic nitrogen removal in the MABR reactor is that the activity of nitrite oxidizing bacteria in the MABR biofilm increases and there is a trend of complete nitrification:

[0033] (1) Turn on the reagent dosing system, add sodium nitrite solution into the membrane reaction zone, increase the intermittent aeration ratio of the air supply system and maintain it for a period of time;

[0034] (2) When the nitrate nitrogen concentration decreases and approaches the baseline value, reduce the amount of sodium nitrite added and maintain it for a period of time;

[0035] (3) When the pH value in the membrane reaction zone recovers to above 7.0 and the redox potential recovers to 50-100 mV, stop adding sodium nitrite and restore the intermittent aeration ratio to the normal operating value.

[0036] Furthermore, in step S005, when the reason for the instability of the autotrophic nitrogen removal in the MABR reactor is excessive or insufficient short-range nitrification reaction of the MABR biofilm, the intermittent aeration mode and the influent nitrogen load are regulated:

[0037] a. When the short-range nitrification reaction of MABR biofilm is excessive:

[0038] Analyze the intermittent aeration ratio and influent nitrogen load before and after the MABR autotrophic denitrification reactor becomes unstable; if the influent nitrogen load does not change significantly, increase the intermittent aeration ratio to 2.0-3.0; if the influent nitrogen load decreases, restore the influent nitrogen load; if the influent nitrogen load cannot be restored in the short term, increase the intermittent aeration ratio to 2.0-4.0 and reduce the aeration time to 15-20 minutes;

[0039] b. When the short-range digestion reaction of the MABR biofilm is insufficient:

[0040] Analyze the intermittent aeration ratio and influent nitrogen load before and after the MABR autotrophic denitrification reactor becomes unstable; if the influent nitrogen load does not change significantly, reduce the intermittent aeration ratio to 0.5-1.0; if the influent nitrogen load increases, restore the influent nitrogen load; if the influent nitrogen load cannot be restored in the short term, reduce the intermittent aeration ratio to 0.5-1.0, and increase the aeration time to 30min-60min.

[0041] Furthermore, in step S001, the method for establishing the autotrophic denitrification process of the MABR reactor is as follows:

[0042] S0011, Nitrification biofilm:

[0043] (1) Inoculate aerobic activated sludge into the circulating reaction zone, and continuously start the stirring circulation system, mixed liquid reflux system, and air supply system; intermittently add water, intermittently start the air stirring system; and close the sludge reflux system and heat exchange system;

[0044] (2) When the pH value in the membrane reaction zone drops to below 6.5-7.0 and the ammonia nitrogen concentration is 5%-10% of the influent ammonia nitrogen concentration, gradually increase the proportion of influent time;

[0045] (3) When the continuous water inflow mode is achieved and the pH value and ammonia nitrogen concentration of the effluent are significantly reduced, the nitrification biofilm is formed;

[0046] S0012. Establishment of short-range nitrification process:

[0047] (1) Continuously open the mixed liquor return system and the sludge return system, adjust the air supply system to intermittent aeration with an intermittent aeration ratio of 1.0 to 1.5, and reduce the aeration pressure and aeration flow rate;

[0048] (2) starting the reagent dosing system and continuously adding sodium nitrite solution into the membrane reaction zone;

[0049] (3) Turn on the heat exchange system and control the temperature of the mixed liquid to 25°C to 30°C;

[0050] (4) When the nitrate nitrogen value in the membrane reaction zone drops to 80% to 90% of the nitrate nitrogen value when the nitrification biofilm is formed, stop adding the sodium nitrite solution, keep the heat exchange system open, keep the water inlet and aeration open, and intermittently open the air stirring system, and then continue to operate. When the removal rate of ammonia nitrogen in the effluent of the membrane reaction zone is 92% to 98% and the nitrite nitrogen accumulation rate reaches 85% to 95%, the establishment of the short-range nitrification process is completed;

[0051] S0013. Start-up of anaerobic ammonium oxidation autotrophic denitrification process:

[0052] (1) regulating the short-range nitrification reaction in the MABR reactor to a partial short-range nitrification state;

[0053] (2) Increase the intermittent aeration ratio of the air supply system to 1.5-3.0, further reduce the aeration pressure and aeration flow rate; the ratio of residual ammonia nitrogen to nitrite nitrogen concentration in the effluent is controlled between 1:1 and 1:1.3;

[0054] (3) Open the sludge discharge pipe and close the sludge return system to discharge about 50% of the sludge in the sludge area;

[0055] (4) Inoculating sludge containing anaerobic ammonium-oxidizing bacteria in the circulating reaction zone, closing the stirring circulation system, continuously opening the mixed liquid reflux system, the air supply system and the heat exchange system, and intermittently opening the air stirring system;

[0056] (5) The reagent dosing system is coordinated with the intermittent aeration mode. The reagent dosing system is turned on during the last 20% to 30% of the period after aeration is stopped to add sodium nitrite solution into the membrane reaction zone;

[0057] (6) Continue to operate until the effluent pH value rises to 7.2-7.7, the redox potential value drops to 50mV-100mV, the nitrate nitrogen concentration rises to 10%-15% of the inlet ammonia nitrogen concentration, and the effluent total nitrogen removal rate reaches 70%-80%, completing the start-up of the anaerobic ammonia oxidation autotrophic denitrification process;

[0058] S0014. Establishment of a stable autotrophic denitrification process: Close the chemical dosing system, continuously open the sludge return system, mixed liquor return system and stirring circulation system, maintain intermittent aeration of the air supply system, and continue to operate until the total nitrogen removal rate of the effluent reaches 80-85%, the ammonia nitrogen removal rate exceeds 95%, the pH value is 7.0-8.0, and the redox potential is 50mV-100mV, completing the establishment of the autotrophic denitrification process of the MABR reactor.

[0059] Furthermore, in step S003, the determination database includes:

[0060]

[0061] The beneficial effects of the present invention are as follows:

[0062] (1) The present invention proposes a device for improving the autotrophic denitrification performance of an MABR reactor for efficient autotrophic biological denitrification treatment of medium and low concentration ammonia-containing wastewater or domestic sewage. A double-layer frame is set in the MABR membrane assembly, and a spatial three-dimensional mesh filler is built in to increase the attachment of autotrophic denitrifying bacteria such as anaerobic ammonia-oxidizing bacteria. A composite membrane assembly combining a curtain-type filamentous silica gel membrane and a spatial three-dimensional mesh filler is used to construct a MABR short-range nitrification biofilm, anaerobic ammonia-oxidizing biofilm, and heterotrophic denitrification biofilm coupled symbiotic system. At the same time, different reaction areas such as a circulation reaction zone and an MABR reaction zone are set in a single reactor, thereby promoting the coordination and integration of multiple denitrification reactions such as short-range nitrification and denitrification, anaerobic ammonia oxidation and heterotrophic denitrification in a single-stage reactor, thereby improving the autotrophic denitrification efficiency of the reactor, and solving the problems existing in the existing MABR reactor for autotrophic denitrification, such as the MABR membrane assembly and the biofilm method are simply arranged in the same reactor, which will cause the disadvantages of the two processes to overlap, and the multi-stage MABR reactor is complicated to operate in series.

[0063] (2) The present invention proposes a method for establishing an autotrophic denitrification process in an MABR reactor. For nitrogen-containing industrial wastewater and domestic sewage with a low carbon-nitrogen ratio, the process of establishing an autotrophic denitrification process in an MABR reactor can be carried out in steps, including nitrification biofilm formation, establishment of a short-term nitrification process, start-up of an anaerobic ammonium oxidation autotrophic denitrification process, and establishment of a stable autotrophic denitrification process. The intermittent aeration mode is used to control the low dissolved oxygen (DO) in the MABR reactor and to add a sodium nitrite solution to produce a high concentration of free nitrite (FNA), thereby performing a multi-factor synergistic inhibition on nitrite oxidizing bacteria (NOB) and accelerating the establishment of a short-term nitrification process in the MABR reactor; at the same time, the addition of sodium nitrite solution and the regulation of the intermittent aeration mode increase the start-up speed of the anaerobic ammonium oxidation autotrophic denitrification process and the establishment speed of a stable autotrophic denitrification process; that is, in the establishment of a short-term digestion reaction at the initial stage of the reactor operation, the establishment of an anaerobic ammonium oxidation process, and the re-regulation process after the reactor becomes unstable, the addition strategy of the sodium nitrite solution is different. Furthermore, the addition of sodium nitrite solution and the intermittent aeration mode solve the disadvantage of poor persistence of single factor inhibition on the activity of nitrite oxidizing bacteria (NOB). At the same time, sodium nitrite is stable in nature, safe in operation, cheap and easy to obtain, which also makes the control strategy of the present invention easier to implement in actual operation.

[0064] (3) The present invention proposes a method for evaluating the stability of autotrophic denitrification of MABR reactors. By establishing a benchmark value for the normal operation of the autotrophic denitrification process of the MABR reactor and a judgment database for the decline in the stability of the autotrophic denitrification process, the continuously collected online monitoring data is compared with the benchmark value of the reactor, and the main reason for the instability of the autotrophic denitrification reaction is obtained according to the trend in the judgment database. The method for determining the stability of the autotrophic denitrification reactor used in the present invention is based on a large amount of historical operation data, and adopts the change trend of multiple parameters of the autotrophic denitrification reactor to determine the stability of the autotrophic denitrification reactor under complex operating conditions. The comprehensive judgment method of the change trend of multiple parameters can meet the operation of the MABE membrane assembly composed of silica gel membrane filaments with high efficiency oxygen transfer and spatial three-dimensional mesh fillers in the MABR reactor. Among them, ammonia oxidizing bacteria, anaerobic ammonia oxidizing bacteria, heterotrophic denitrifying bacteria and other organisms coexist and coexist, forming a dynamic and stable autotrophic denitrification stabilizer. The method for determining the instability of its operation does not adopt a single value or a fixed value, and can obtain the accurate cause of the instability of the reactor.

[0065] (4) The present invention proposes a method for improving the autotrophic denitrification stability and denitrification performance of the MABR reactor, and adopts different targeted strategies for dynamic regulation according to different causes of instability of the autotrophic denitrification reaction. The key to the regulation process of the instability of the short-range nitrification process is to add sodium nitrite solution so that a sufficient concentration of free nitrite (FNA) is generated in the reactor mixed liquid at a relatively low pH value. That is, in the present invention, during the continuous operation of the reactor, sodium nitrite solution is continuously added according to the operation of the reactor to control the pH value to be between 6.0 and 6.5. This pH value is the pH drop interval that can be achieved in the complete nitrification process. There is no need to add acid artificially. The control of the FNA concentration will not have an excessive impact on the ammonia oxidizing bacteria while inhibiting nitrite oxidizing bacteria. Furthermore, through the online addition method, it can directly affect the status of various microorganisms in the MABR reactor, especially the excessive proliferation of nitrite oxidizing bacteria in a timely manner without the hysteresis of lateral inhibition. It can directly produce a regulatory effect on the suspended ecological flocculent sludge in the reactor, the MABR biofilm grown on the surface of the MABR membrane fibers, and the anaerobic biofilm attached to and grown on the three-dimensional mesh filler, thereby being more conducive to the stable operation of the reactor. The addition of sodium nitrite solution combined with the low dissolved oxygen brought by the intermittent aeration mode inhibits the nitrite oxidizing bacteria (NOB) in the MABR biofilm, restores the short-term nitrification process, and stabilizes the autotrophic denitrification reaction again. The key to the regulation process of the decline in the activity of anaerobic ammonium oxidizing bacteria is to periodically add sodium nitrite during the operation of the reactor to stabilize the short-term nitrification process. At the same time, it can increase the substrate of the anaerobic ammonium oxidizing reaction, stimulate the growth of anaerobic ammonium oxidizing bacteria, increase its attachment growth in the composite membrane component, and improve its retention.

[0066] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 It is a schematic structural diagram of a device for improving the autotrophic denitrification performance of a MABR reactor according to the present invention;

[0068] Figure 2 It is a schematic structural diagram of the MABR membrane assembly of the present invention;

[0069] Figure 3 It is a schematic structural diagram of the membrane area drug adding component of the present invention.

[0070] In the attached figure: 1—MABR reactor; 2—circulation reaction zone; 3—support beam on guide tube; 4—membrane reaction zone; 5—partition wall; 6—circulation guide tube; 7—upstream mixer; 8—support beam under guide tube; 9—MABR membrane assembly; 10—support beam; 11—water passage; 12—sludge zone; 13—water distribution porous plate; 14—water inlet main pipe; 15—flow-through detection barrel; 16—reactor water inlet pipe; 17—exhaust valve; 18—water inlet online pH meter; 19—water inlet online ammonia nitrogen meter; 20—water outlet pipe; 21—air supply fan; 22—air supply main pipe valve ; 23—air flow meter for air supply main pipe; 24—air supply main pipe; 25—air supply branch pipe valve; 26—air flow meter for air supply branch pipe; 27—pressure sensor for air supply branch pipe; 28—air supply branch pipe; 29—exhaust branch pipe; 30—exhaust branch pipe valve; 31—exhaust main pipe; 32—mixed liquid discharge pipe; 33—mixed liquid reflux pump; 34—mixed liquid reflux pipe valve; 35—mixed liquid reflux pipe check valve; 36—mixed liquid reflux flow meter; 37—mixed liquid reflux pipe; 38—reflux main pipe; 39—heat exchange barrel; 40—heat exchange coil; 41—electric heating pipe; 4 2—electric heating power supply; 43—sludge return pump inlet pipe; 44—sludge return pump; 45—sludge discharge valve; 46—sludge discharge pipe; 47—sludge return valve; 48—sludge return pipe check valve; 49—sludge return flowmeter; 50—sludge return pipe; 51—air agitation blower; 52—air agitation main pipe; 53—air agitation main pipe valve; 54—air agitation main pipe pressure sensor; 55—air agitation branch pipe air flowmeter; 56—air agitation branch pipe valve; 57—air agitation branch pipe; 58—air agitation assembly; 59—air agitation perforated pipe ; 60—Nitrite dosing pump outlet pipe; 61—Nitrite dosing flowmeter; 62—Nitrite dosing metering pump; 63—Nitrite dosing pump inlet pipe; 64—Nitrite storage tank; 65—Membrane area dosing assembly; 66—Online dissolved oxygen meter; 67—Online ORP meter; 68—Membrane reaction area online ammonia nitrogen meter; 69—Online nitrate nitrogen meter; 70—Online nitrite nitrogen meter; 71—Membrane reaction area online pH meter; 72—Membrane reaction area monitoring secondary instrument; 73—Inlet water monitoring secondary instrument; 74—Heat exchange barrel online thermometer; 75—PLC control cabinet;

[0071] 901—external frame of membrane assembly; 902—three-dimensional mesh packing layer; 903—internal frame of membrane assembly; 904—curtain-type membrane element; 905—air inlet vertical pipe of membrane element; 906—air inlet pipe of membrane element; 907—exhaust vertical pipe of membrane element; 908—exhaust pipe of membrane element;

[0072] 6501—dosing distribution pipe; 6502—dosing main pipe valve; 6503—dosing main pipe; 6504—dosing perforated pipe; 6505—pool wall. DETAILED DESCRIPTION

[0073] Specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0074] Reference Figures 1 to 3 The present invention provides an embodiment of a device for improving the autotrophic denitrification performance of a MABR reactor.

[0075] A device for improving the autotrophic denitrification performance of a MABR reactor comprises a reaction tank 1, a reagent dosing system, an air supply system, a mixed liquid reflux system, a sludge reflux system, an air stirring system and an online monitoring instrument system.

[0076] The reaction pool 1 is a rectangular pool. According to the different treatment scales, a reinforced concrete pool or a steel pool can be used. The interior of the pool is divided into a circulating reaction zone 2 and a membrane reaction zone 4 connected at the bottom by a partition wall 5. A water hole 11 is provided at the bottom of the partition wall 5 to connect the bottom of the circulating reaction zone 2 and the membrane reaction zone 4. The mixed liquid flow rate at the water hole 11 is 0.3-0.6 m / s. The volume ratio of the circulating reaction zone 2 and the membrane reaction zone 4 is 1:4-1:5. The effective water depth of the reaction pool 1 is 3-5 m, and a protective height of 0.5-0.8 m is provided at the top.

[0077] The water inlet pipe 16 is connected to the circulation reaction zone 2, and the water outlet pipe 20 is connected to the membrane reaction zone 4. The circulation reaction zone 2 is provided with a stirring circulation system, and the stirring circulation system includes a circulation guide tube 6 arranged in the circulation reaction zone 2. The circulation guide tube 6 is made of stainless steel (SS304) or polypropylene (PP) barrel. The length of the circulation guide tube 6 is 2 / 3 to 3 / 4 of the effective water depth of the circulation reaction zone 2, and its diameter is 1 / 4 to 2 / 5 of the net width of the circulation reaction zone 2. The circulation guide tube 6 is vertically fixed to the center of the circulation reaction zone 2 by the guide tube upper support beam 3 and the guide tube lower support beam 8. The two layers of support beams are cross steel beams made of stainless steel (SS304), and the two ends of the cross steel beam are firmly fixed to the inner wall of the reaction pool 1 and the outer wall of the circulation guide tube 6 respectively. The circulation guide tube 6 is provided with an upflow agitator 7 for lifting the mixed liquid in the circulation guide tube 6, so that the mixed liquid in the circulation guide tube 6 flows from bottom to top, and the mixed liquid outside the circulation guide tube 6 flows from top to bottom, thereby generating a circulating flow of the mixed liquid. The upflow agitator 7 adopts frequency conversion control, and the rotation speed can be adjusted according to the process requirements to change the circulation ratio of the liquid inside and outside the guide tube; the stirring paddle of the upflow agitator 7 adopts a hyperbolic type, and the slurry surface is made of glass fiber reinforced plastic (FRP) or stainless steel (SS304); the agitator motor is a variable frequency motor, which is installed at the top of the circulation reaction zone 2. The inlet water 14 of the MABR reactor enters from the top of the circulation reaction zone 2 through the water inlet pipe 16, the mixed liquid return pipe 37 at the top of the membrane reaction zone 2, and the sludge return pipe 50 at the bottom of the membrane reaction zone 2, and is fully mixed and reacted therein.

[0078] The membrane reaction zone 4 is the main area for the MABR reactor to carry out autotrophic denitrification reaction. The membrane reaction zone 4 is provided with a water distribution porous plate 3. The water distribution porous plate 13 divides the membrane reaction zone 4 into two parts, the upper and lower parts. The lower part of the water distribution porous plate 13 is the sludge zone 12, and the upper part is provided with multiple groups of MABR membrane components 9, which are placed vertically on the water distribution porous plate 13 in parallel; the height of the sludge zone 12 is 1 / 5 to 1 / 4 of the effective water depth of the membrane reaction zone. The water distribution porous plate 13 is made of stainless steel (SS304), and is evenly provided with multiple circular water holes with a hole diameter of 15mm to 25mm. The total opening area accounts for 15% to 30% of the top surface area of ​​the water distribution porous plate 13. The water distribution porous plate 13 is arranged horizontally, and the four sides are firmly fixed on the inner wall of the reaction tank 1 and the support beam 10 on the partition plate 5. The sludge and mixed liquid in the bottom sludge zone 12 can evenly enter the membrane reaction zone 4 through the water distribution porous plate 13.

[0079] Furthermore, the MABR membrane assembly 9 is a rectangular frame structure, the frame is made of stainless steel (SS304), and includes a membrane assembly outer frame 901, a spatial three-dimensional mesh filler layer 902, a membrane assembly inner frame 903, and a curtain-type membrane wire element 904, which are arranged in sequence from the outside to the inside. Multiple groups of curtain-type membrane wire elements 904 are vertically installed in the membrane assembly inner frame 903, as oxygen-permeable components to provide dissolved oxygen for aerobic microorganisms, and at the same time provide a surface for aerobic microorganisms to attach and grow to form MABR biofilms. The single-piece curtain-type membrane silk element 904 is flat curtain-type as a whole, and its two sides are respectively connected to the air intake vertical pipe 905 and the exhaust vertical pipe 907. The air intake vertical pipe 905 is connected to the aeration pipe of the air supply system, and the exhaust vertical pipe 907 is connected to the exhaust pipe of the air supply system. The air intake vertical pipe and the exhaust vertical pipe are made of ABS material with a nominal diameter of 25mm-50mm. Between the two vertical pipes are multiple horizontally evenly distributed silk-like silicone membranes with an inner diameter of 0.5mm-1.2mm and a wall thickness of 0.25mm-0.5mm. The silk-like silicone membranes are arranged horizontally, staggered with the influent flow direction, or even perpendicular to each other to form a cross-flow mode, which helps to improve the mass transfer rate of the substrate and metabolites in the biofilm on the membrane silk surface, has a high oxygen transfer rate, stable properties, and a wide pressure tolerance range, which can provide good oxygen supply for the reactor, thereby improving the treatment efficiency. . The three-dimensional mesh filler layer 902 formed between the outer frame 901 of the membrane assembly and the inner frame 903 of the membrane assembly is filled with a three-dimensional mesh filler for attaching autotrophic denitrifying bacteria such as anaerobic ammonia-oxidizing bacteria. Usually, the spacing between the two layers of frames is 150mm to 250mm. The three-dimensional mesh filler is made of modified polypropylene (PP) with a porosity of 97% to 98% and a specific surface area of ​​120 to 140m2 / m3.

[0080] The air supply system is used to aerate each of the MABR membrane components 9, and includes an air supply fan 21, an air supply main pipe 24, an air supply branch pipe 28, and matching valves, flow meters and pressure sensors. The air supply main pipe 24 is connected to the air outlet of the air supply fan 21, and an air supply main pipe valve 22 and an air supply main pipe air flow meter 23 are arranged on it in sequence. Each set of membrane components 9 is provided with an independent air supply branch pipe 28, one end of which is connected to the air supply main pipe 24, and the other end is connected to the membrane wire element air inlet pipe 906. Specifically, the air inlet vertical pipe 905 of each curtain-type membrane wire element 904 is connected to the membrane wire element air inlet pipe 906, and each membrane wire element air inlet pipe 906 is connected to the air supply branch pipe 28. The air supply branch pipe 28 is provided with an air supply branch pipe valve 25, an air supply branch pipe air flow meter 26 and an air supply branch pipe pressure sensor 27 in sequence. The gas supply branch pipe valve 25 is an electric regulating ball valve, which is used to adjust the gas supply of the membrane assembly 9; the gas supply branch pipe air flow meter 26 is a vortex gas flow meter, and the gas supply branch pipe pressure sensor 27 is an online pressure sensor, which respectively measures the flow rate and pressure of the MABR membrane assembly 9. Each set of membrane assemblies 9 of the MABR reactor is provided with an exhaust branch pipe 29, which is connected to the membrane wire element exhaust pipe 908, and an exhaust branch pipe valve 30 is arranged on it. The exhaust branch pipes 29 of each membrane assembly are connected to the exhaust main pipe 31, and finally emptied. Specifically, the exhaust vertical pipe 907 of each curtain-type membrane wire element 904 is connected to the membrane wire element exhaust pipe 908, and each membrane wire element exhaust pipe 908 is connected to the exhaust branch pipe 29 of the membrane assembly.

[0081] The reagent dosing system is used to add sodium nitrite solution to the membrane reaction zone 4 as needed, including multiple groups of membrane area dosing components 65 between the MABR membrane assembly 9 and the water distribution porous plate 13 and corresponding to each group of the MABR membrane assembly 9, wherein the membrane area dosing components 65 are arranged in multiple groups horizontally, installed under the membrane assembly outer frame 901 and above the water distribution porous plate 13, and the bottom of the membrane assembly outer frame 901 is provided with a certain height of legs for accommodating the membrane area dosing components 65, which are usually 150mm to 200mm high, and the membrane area dosing components 65 are made of chemical grade UPVC. The membrane area dosing components 65 are used for adding sodium nitrite solution for regulation during the operation or startup of the MABR autotrophic denitrification reactor. The membrane group dosing components 65 make the added reagents evenly distributed at the bottom of the membrane assembly 9 to ensure the uniform and effective reaction.

[0082] The membrane zone dosing component 65 includes a dosing main pipe 6503, which extends to the west of the corresponding MABR membrane component 9 and extends upward, and a plurality of parallel dosing perforated pipes 6504 are provided on the dosing main pipe 6503, and holes are evenly opened on both sides of the dosing perforated pipes 6504, with a hole diameter of 4 to 5 mm and a spacing of 100 to 150 mm. A plurality of the dosing main pipes 6503 extend to the outside of the reaction tank 1, and each of the dosing main pipes 6503 is provided with a dosing main pipe valve 6502, and is connected to the same dosing distribution pipe 6501, the dosing distribution pipe 6501 is connected to a dosing pipe, the dosing pipe is connected to a nitrite storage tank 64, a nitrite dosing metering pump 62 is provided on the dosing pipe, the nitrite dosing pump inlet pipe 63 and the nitrite dosing pump outlet pipe 60 of the nitrite dosing metering pump 62 are both provided with valves, and a nitrite dosing flowmeter 61 is provided between the nitrite dosing pump outlet pipe 60 and the nitrite dosing metering pump 62.

[0083] The mixed liquor return system is used to return the mixed liquor in the membrane reaction zone 4 to the circulation reaction zone 2; the sludge return system is used to return the sludge in the sludge zone 12 to the circulation reaction zone 2, which can maintain sufficient nitrifying bacteria and other denitrifying bacteria in the circulation reaction zone 2. At this time, the mixed liquor contains nitrate nitrogen produced by anaerobic ammonia oxidation reaction and a small amount of nitrate nitrogen generated by nitrite oxidizing bacteria (NOB), which are returned to the circulation reaction zone 2. Under the action of heterotrophic denitrifying bacteria, part of the organic matter in the influent is used to cause heterotrophic denitrification reaction, and the nitrate nitrogen is reduced to nitrogen gas, thereby achieving the purpose of denitrification.

[0084] Specifically, the mixed liquor reflux system includes a mixed liquor reflux pipe 37 connected to the upper part of the membrane reaction zone 4, and the sludge reflux system includes a sludge reflux pipe 50 connected to the sludge zone 12, and the sludge reflux pipe 50 is provided with a sludge discharge pipe 46. The mixed liquor reflux pipe 37 and the sludge reflux pipe 50 are connected to the circulation reaction zone 2 through a reflux main pipe 38, and the reflux main pipe 38 is provided with a heat exchange system.

[0085] Furthermore, the mixed liquid at the top of the membrane reaction zone 4 is discharged from the cell body through the mixed liquid discharge pipe 32, and then transported to the reflux main pipe 38 through the mixed liquid reflux pipe 37 by the mixed liquid reflux pump 33, and finally refluxed to the circulation reaction zone 2 of the reactor 1. The mixed liquid reflux pipe valve 34, the mixed liquid reflux pipe check valve 35 and the mixed liquid reflux flowmeter 36 are sequentially arranged on the mixed liquid reflux 37.

[0086] The sludge in the sludge zone 12 at the bottom of the membrane reaction zone 4 is connected to the reflux main pipe 38 through the sludge reflux pump 44 and the sludge reflux pipe 50, and is refluxed to the circulation reaction zone 2 together with the mixed liquid. A valve is provided in the sludge reflux pump inlet pipe 43. On the sludge reflux pipe 50, starting from the outlet of the sludge reflux pump 44, a sludge reflux valve 47, a sludge reflux pipe check valve 48, and a sludge reflux flowmeter 49 are sequentially arranged.

[0087] Furthermore, the heat exchange system includes a heat exchange barrel 39, a heat exchange coil 40, an electric heating tube 41, an electric heating power supply 42, and an on-line thermometer 74 for the heat exchange barrel. The heat exchange barrel 39 is filled with softened water and replenished regularly. After the electric heating power supply 42 is turned on, an appropriate heating temperature is controlled. The reflux main pipe 38 is connected to the heat exchange coil 40, and the mixed liquid flows in the heat exchange coil 40 and is indirectly heated to the required water temperature. The mixed liquid after heat exchange flows to the circulation reaction zone 2.

[0088] The air agitation system is used to conduct air scouring on each of the MABR membrane modules 9; the air agitation system includes: an air agitation blower 51, an air agitation main pipe 52, air agitation branch pipes 57, air agitation assemblies 58, and auxiliary valves and flow and pressure detection instruments. Specifically, the air agitation blower 51 is connected to the air agitation main pipe 52, and an air agitation main pipe valve 53 and an air agitation main pipe pressure sensor 54 are provided on the air agitation main pipe 52. A plurality of air agitation branch pipes 57 are branched from the air agitation main pipe 51, and each set of membrane modules 9 corresponds to an air agitation branch pipe 57. An air agitation branch pipe air flowmeter 55 and an air agitation branch pipe valve 56 are provided on the air agitation branch pipe 57, which are a vortex street air flowmeter and an electric regulating ball valve respectively, and are used for the measurement and adjustment of the agitation air volume. Each air agitation branch pipe 57 is correspondingly connected to an air agitation assembly 58. A plurality of groups of air agitation assemblies 58 are arranged in the bottom sludge zone 12 of the membrane reaction zone 4. Each group of air agitation assemblies 58 corresponds to a group of MABR membrane modules 9, and is used to disperse the introduced air into small bubbles and uniformly distribute them at the bottom of the MABR membrane modules 9 through the water distribution perforated plate 13. The small bubbles float upward to conduct air shear and scrub on the silica gel membrane filaments in the MABR membrane modules 9, and maintain the normal renewal of the MABR biofilm. The air agitation assembly 58 is in a "rich" shape and is horizontally arranged at the bottom of the pool. The center of the air agitation assembly 58 is a gas distribution main pipe, on which a plurality of air agitation hole pipes 59 are vertically and uniformly distributed. One end of the gas distribution main pipe is closed, and the other end is connected to the air agitation branch pipe 57.

[0089] The online monitoring instrument system is used to monitor the water quality index and the influent water quality index in the membrane reaction zone 4 in real time, including a PLC control cabinet 75 connected to the reagent dosing system and the gas supply system signal, and the PLC control cabinet 75 contains a programmable controller and a touch control screen. Specifically, the online monitoring instrument system includes an online dissolved oxygen meter 66, an online ORP meter 67, an online ammonia nitrogen meter 68, an online nitrate nitrogen meter 69, an online nitrite nitrogen meter 70, and an online pH meter 71 and a thermometer in the membrane reaction zone, which are arranged in the membrane reaction zone 4 and connected to the PLC control cabinet 75 through the membrane reaction zone monitoring secondary instrument 72, and is used to monitor the water quality index in the membrane reaction zone 4 in real time, and to determine the autotrophic denitrification rate and stability index of the continuously running reactor in real time through the online monitoring data, so that when the short-range nitrification reaction tends to be unstable, sodium nitrite is added, and combined with other environmental factors, the activity of nitrite oxidizing bacteria (NOB) is inhibited, thereby ensuring the poor operation stability of the MABR autotrophic denitrification reactor.

[0090] The online monitoring instrument system also includes an online water inlet pH meter 18 and an online water inlet ammonia nitrogen meter 19, which are arranged on the water inlet pipe 16 and connected to the PLC control cabinet 75 through the water inlet monitoring secondary instrument 73. The detection probes of the online water inlet pH meter and the online water inlet ammonia nitrogen meter 19 are arranged in the flow-through detection barrel 15. The inlet water 14 of the MABR reactor is connected to the circulation reaction zone of the reactor 1 through the flow-through detection barrel 15 and the reactor water inlet pipe 16. The flow-through detection barrel 15 is a sealed round barrel with a top cover, made of transparent acrylic material, with a diameter of 200mm to 250mm and a height of 300mm to 400mm, which is used to install online monitoring probes to monitor the water quality indicators of the inlet water. The top cover of the flow-through detection barrel 15 is connected to the barrel by a flange and maintains a good seal. An exhaust valve 17 is provided on the top cover to remove air from the flow-through detection barrel 15. The inlet water 14 enters from the lower part of the flow-through detection barrel 15 and flows out from the upper part to the reactor water inlet pipe 16. Valves are provided on the inlet and outlet pipes of the flow-through detection barrel 15.

[0091] When the above device for improving the autotrophic denitrification performance of the MABR reactor is used in normal operation:

[0092] ① The inlet water of the MABR reactor enters from the top of the circulation reaction zone 2, and the refluxed mixed liquid and sludge also enter the reactor from the top of the circulation reaction zone 2. The upflow mixer 7 in the circulation guide tube 6 is continuously turned on to continuously lift the mixed liquid in the circulation guide tube 6, and then it descends outside the circulation guide tube 6, so that it circulates inside and outside the circulation guide tube 6 to produce sufficient mixing and reaction.

[0093] Since there are a small amount of heterotrophic denitrifying bacteria in the inoculated sludge, a part of them grows on the surface of the three-dimensional mesh filler, and the other part exists in the suspended sludge in the sludge area 12. Through the sludge return system, the suspended heterotrophic denitrifying bacteria circulate between the sludge area 12 and the circulation reaction area 2. The heterotrophic denitrifying bacteria use the organic matter in the influent as a carbon source, and undergo a denitrification reaction in the circulation reaction area 2, converting the nitrate nitrogen generated by the anaerobic ammonium oxidation reaction in the reflux mixed liquor into nitrogen gas, which helps to further reduce the total nitrogen in the effluent of the MABR reactor.

[0094] ② The sewage passing through the circulation reaction zone 2 passes through the water hole 11 at the bottom of the partition wall 5, enters the sludge area 12 at the bottom of the membrane reaction zone 4, and then passes through the water distribution porous plate 13 to evenly enter the MABR membrane assembly 9 in the membrane reaction zone 4.

[0095] The MABR biofilm grown on the surface of the filamentous silica membrane in the MABR membrane assembly 9 is in a partial short-range nitrification state. Due to the guided mass transfer effect, the MABR biofilm has obvious stratification, which is aerobic bacteria and facultative bacteria from the inside to the outside. The inner layer of the biofilm close to the surface of the filamentous silica membrane is mainly aerobic ammonia oxidizing bacteria (AOB) and a small amount of nitrite oxidizing bacteria (NOB). The outer layer of the biofilm is mainly facultative bacteria, containing a small amount of heterotrophic denitrifying bacteria and anaerobic ammonia oxidizing bacteria.

[0096] The ammonia nitrogen in the influent is partially nitrified by the MABR biofilm to produce nitrite nitrogen. By adjusting the intermittent aeration ratio, the degree of short-term nitrification reaction is controlled at 50% to 55%, which is conducive to the efficient anaerobic ammonia oxidation denitrification reaction.

[0097] ③ The anaerobic biofilm attached and grown in the spatial three-dimensional mesh filler layer 902 of the MABR membrane assembly 9 and the anaerobic ammonium oxidation sludge particles trapped in the lower pores are rich in anaerobic ammonium oxidizing bacteria and heterotrophic denitrifying bacteria. The anaerobic ammonium oxidizing bacteria use the remaining ammonia nitrogen in the sewage as an electron donor and the nitrite nitrogen produced by the short-range nitrification reaction of the MABR biofilm as an electron acceptor, and the anaerobic ammonium oxidation reaction occurs to convert the two into ammonia nitrogen, thereby completing autotrophic denitrification.

[0098] The biofilm on the surface of the three-dimensional mesh filler layer 902 contains a certain amount of heterotrophic denitrifying bacteria, which can utilize the remaining small amount of available organic matter in the effluent of the circulating reaction zone as a carbon source, and denitrify part of the nitrate nitrogen produced by the anaerobic ammonia oxidation reaction and the excess nitrite nitrogen produced by the short-range nitrification reaction into nitrogen gas, thereby reducing the nitrate nitrogen and nitrite nitrogen in the effluent of the MABR reactor.

[0099] Finally, the remaining nitrate nitrogen and nitrite nitrogen in the membrane reaction zone 4 are refluxed to the circulation reaction zone 2 with the mixed liquid to undergo denitrification reaction again.

[0100] Among them, the parameters for normal operation of autotrophic denitrification in the MABR reactor are:

[0101] The MABR reactor is continuously fed with water, which is ammonia-containing industrial wastewater or domestic sewage with a low carbon-nitrogen ratio (ratio of organic matter BOD concentration to ammonia nitrogen concentration), with a carbon-nitrogen ratio of 0.5 to 2.0. The influent COD is 100 to 200 mg / L, ammonia nitrogen is 50 to 120 mg / L, total nitrogen is 50 to 120 mg / L, and pH is 6.5 to 7.5.

[0102] Continuous mixed liquid reflux, the mixed liquid reflux ratio is 200% to 400%;

[0103] Maintain intermittent aeration membrane, adjust the intermittent aeration ratio to 1.0-2.0, that is, aerate for 30 minutes, stop aeration for 30 minutes-60 minutes, supply pressure 5Kpa-30Kpa, supply flow rate 2-4L / (h·m 膜丝 ) Intermittent air stirring, every 15min~20min, air stirring for 15s~20s, air stirring intensity is 0.3~0.6m 3 空气 / m 3 池容 .

[0104] The sludge return is continuously turned on, and the sludge return ratio is 50% to 100%.

[0105] When the inlet water temperature is 20-30℃, the indirect heat exchange system of the return main pipe can be stopped, and the MABR reactor can maintain normal operation. In the low temperature season, when the inlet water temperature is lower than 15℃, the indirect heat exchange system of the return main pipe needs to be turned on to ensure that the temperature inside the MABR reactor is 20℃-25℃.

[0106] When the MABR autotrophic denitrification reactor operates normally, the removal rate of ammonia nitrogen is 95% to 98%, the removal rate of total nitrogen is 85% to 95%, and the removal rate of COD is 50% to 80%.

[0107] In a normally operating MABR autotrophic denitrification reactor, the stability of the short-range nitrification reaction will directly affect the conversion rate of influent ammonia nitrogen to nitrite nitrogen and the fluctuation range of the nitrite nitrogen accumulation rate in the short-range nitrification process, thereby affecting the autotrophic denitrification stability and total nitrogen removal performance of the reactor. Therefore, it is necessary to monitor and evaluate the stability of the autotrophic denitrification process of the MABR reactor, determine the main factors affecting the stability of the autotrophic denitrification, so as to regulate and control in a timely and accurate manner. Therefore, the present invention also provides a method for improving the autotrophic denitrification performance of the MABR reactor.

[0108] An embodiment of a method for improving the autotrophic denitrification performance of a MABR reactor.

[0109] A method for improving the autotrophic denitrification performance of a MABR reactor, using the above-mentioned device for improving the autotrophic denitrification performance of a MABR reactor, the steps are:

[0110] S001. Inoculate and form biofilm in the MABR reactor, and make the MABR reactor operate normally for autotrophic denitrification;

[0111] S002. Establish the reference values ​​of various data when the autotrophic denitrification process of the MABR reactor is operating normally and store them in the PLC controller. The data include: dissolved oxygen, pH value, redox potential, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen and temperature in the membrane reaction zone 4; and ammonia nitrogen, pH value and temperature in the influent. When the autotrophic denitrification process is successfully established in the MABR reactor and the influent is continuously operated, record the online monitoring data in the membrane reaction zone 4 and the online detection instrument data in the influent flow-through detection barrel 15 at the same time, take the monitoring data for 48 consecutive hours, and take the average value of each monitoring data as the reference value for the normal operation of the autotrophic denitrification process of the reactor.

[0112] S003. Establish a database for determining the stability decline of the autotrophic denitrification process of the MABR reactor: Based on the changing trend of water quality indicators in the autotrophic denitrification process of the MABR reactor, list the main reasons for the instability of the autotrophic denitrification of the MABR reactor;

[0113] Among them, the judgment database mainly includes the following contents:

[0114]

[0115] Note: “↗↗”: The concentration increases significantly. For pH, it usually means the fluctuation range is +(0.8~1.2);

[0116] “↗”: Concentration increases, which usually means the fluctuation range of pH is +(0.5~0.8);

[0117] “↘”: concentration decreases, which usually refers to a fluctuation range of (-0.5 to -0.8) for pH.

[0118] “↘↘”: The concentration drops significantly. For pH, it usually means the fluctuation range is (-0.8 to -1.2);

[0119] “~0”: The concentration is very low or close to 0.

[0120] S004, continuously collect various online monitoring data of the autotrophic denitrification process of the MABR reactor, and input them into the PLC controller through the membrane reaction zone monitoring secondary instrument 72 and the water inlet monitoring secondary instrument 73, compare the various online monitoring data with the reference value of each data, that is, compare the real-time online data in the membrane reaction zone 4, including dissolved oxygen, pH value, redox potential, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, and temperature with the reference value in step S002, and determine the cause of the instability of the autotrophic denitrification of the MABR reactor based on the data trend in the determination database;

[0121] S005. According to the cause of the instability of the autotrophic nitrogen removal in the MABR reactor in step S004, corresponding regulation is performed.

[0122] In some embodiments, the reasons for the instability of autotrophic nitrogen removal in the MABR reactor are:

[0123] ①The activity of nitrite oxidizing bacteria in the MABR biofilm increases, and there is a trend of complete nitrification.

[0124] During long-term operation, the MABR autotrophic denitrification reactor mainly adopts intermittent aeration to limit the dissolved oxygen concentration in the reactor and inhibit the activity of nitrite oxidizing bacteria (NOB) to achieve a partial short-term nitrification process. However, due to the heterogeneous mass transfer process of dissolved oxygen and substrate in the MABR biofilm, that is, the dissolved oxygen concentration in the part of the MABR biofilm that contacts the outer surface of the membrane is high and the substrate concentration is low; the dissolved oxygen concentration in the part of the MABR biofilm that contacts the mixed liquid is low and the substrate concentration is high, which makes it easy for nitrite oxidizing bacteria (NOB) to survive inside the biofilm. Moreover, since both ammonia oxidizing bacteria and nitrite oxidizing bacteria attach and grow on the surface of the MABR membrane, the sludge age is not directly affected by the hydraulic retention time, so it is difficult to eliminate nitrite oxidizing bacteria through differences in microbial dynamics. For the above reasons, in the MABR autotrophic denitrification reactor, nitrite oxidizing bacteria (NOB) cannot be completely eliminated and always coexist with ammonia oxidizing bacteria (AOB). Controlling a single low dissolved oxygen or other factors cannot obtain a stable short-term nitrification process.

[0125] Therefore, when the reason for the instability of autotrophic nitrogen removal in the MABR reactor is the increased activity of nitrite oxidizing bacteria and a tendency towards complete nitrification, the pH value of the mixed liquor will drop significantly, usually falling within the range of 6.0 to 6.5. The control method is to add sodium nitrite solution to the membrane reaction zone 4 so that a sufficient concentration of free nitrite (FNA) is produced in the reactor mixed liquor at a lower pH value. Combined with the low dissolved oxygen brought by the intermittent aeration mode, the nitrite oxidizing bacteria (NOB) in the MABR biofilm are inhibited, the short-range nitrification process is restored, and the autotrophic nitrogen removal reaction is stabilized again.

[0126] The specific method is:

[0127] (1) Open the reagent dosing system and add sodium nitrite solution to the membrane reaction zone 4, that is, open the valves on the nitrite dosing pump 62, the nitrite hydrochloric acid dosing pump inlet pipe 63, and the nitrite dosing pump outlet pipe 60, and evenly add sodium nitrite solution to the membrane reaction zone 4. Among them, the concentration of sodium nitrite solution in the nitrite storage tank is 1000-5000 mg / L. The amount of sodium nitrite added to the membrane reaction zone is 0.05-0.08Q, in kg / d, where Q is the water inlet. The dosage of the nitrite dosing pump is 0.01-0.08m3 / d. At this time, the concentration of free nitrite (FNA) in the mixed solution can reach 0.096-0.189 mg / L.

[0128] Increase the intermittent aeration ratio of the air supply system and maintain it for a period of time; at this time, the intermittent aeration ratio is 2.0-3.0, that is, aeration for 30 minutes, and aeration is stopped for 60 minutes-90 minutes. Other conditions, such as the air supply pressure, air supply volume and air stirring method remain unchanged, at this time the dissolved oxygen concentration in the mixed liquid can be controlled below 0.02 mg / L.

[0129] (2) During this process, the nitrate nitrogen concentration in the membrane reaction zone 2 is monitored in real time. When the nitrate nitrogen concentration decreases and approaches the baseline value, the instability control strategy is effective. Then, the dosage of sodium nitrite is reduced to 0.02-0.03Q, in kg / d, where Q is the water inlet volume, and maintained for a period of time.

[0130] (3) When the pH value in the membrane reaction zone 2 recovers to above 7.0 and the redox potential recovers to 50-100 mV, stop adding sodium nitrite and restore the intermittent aeration ratio to the normal operating value. At the same time, other control conditions are restored to the normal operating values ​​of the MABR reactor autotrophic denitrification.

[0131] In some embodiments, the reasons for the instability of autotrophic nitrogen removal in the MABR reactor are:

[0132] ② When the short-term nitrification reaction of the MABR biofilm is excessive or insufficient, it is regulated by intermittent aeration mode and influent nitrogen load.

[0133] a. When the short-range nitrification reaction of MABR biofilm is excessive:

[0134] Analyze the intermittent aeration ratio and influent nitrogen load before and after the MABR autotrophic denitrification reactor becomes unstable; if the influent nitrogen load does not change significantly, increase the intermittent aeration ratio to 2.0-3.0 and reduce the gas supply of the MABR reactor, that is, aerate for 30 minutes and stop aeration for 60 minutes to 90 minutes; if the influent nitrogen load decreases (including a decrease in influent ammonia nitrogen concentration or a decrease in influent volume, etc.), restore the influent nitrogen load, including increasing the influent volume or restoring the influent ammonia nitrogen concentration, etc.; if the influent nitrogen load cannot be restored in the short term, increase the intermittent aeration ratio and reduce the aeration time for regulation, that is, adjust the intermittent aeration ratio to 2.0-4.0, and reduce the aeration time to 15 minutes to 20 minutes;

[0135] b. When the short-range digestion reaction of the MABR biofilm is insufficient:

[0136] Analyze the intermittent aeration ratio and influent nitrogen load before and after the MABR autotrophic denitrification reactor becomes unstable; if the influent nitrogen load does not change significantly, reduce the intermittent aeration ratio to 0.5-1.0 and increase the air supply to the reactor, i.e., aerate for 30 minutes and stop aeration for 15 minutes to 30 minutes; if the influent nitrogen load increases (including an increase in the influent ammonia nitrogen concentration or an increase in the influent volume), restore the influent nitrogen load, including reducing the influent volume or restoring the influent ammonia nitrogen concentration; if the influent nitrogen load cannot be restored in the short term, reduce the intermittent aeration ratio and increase the aeration time for regulation, i.e., adjust the intermittent aeration ratio to 0.5-1.0 and increase the aeration time to 30 minutes to 60 minutes.

[0137] In some embodiments, the reasons for the instability of autotrophic nitrogen removal in the MABR reactor are:

[0138] ③The activity of anaerobic ammonia-oxidizing bacteria decreases.

[0139] The main reasons for the decrease in anaerobic ammonium oxidizing bacteria activity during long-term operation of the MABR autotrophic denitrification reactor include: the reduced retention of anaerobic ammonium oxidizing bacteria in the reactor; changes in environmental factors affecting the activity of anaerobic ammonium oxidizing bacteria; and the long-term instability of the short-range nitrification reaction, which causes a decrease in anaerobic ammonium oxidizing activity.

[0140] The control strategy of the present invention for the decreased activity of anaerobic ammonium oxidizing bacteria is to periodically add sodium nitrite to stabilize the short-range nitrification process, while increasing the substrate of the anaerobic ammonium oxidizing reaction, stimulating the growth of anaerobic ammonium oxidizing bacteria, increasing their attachment growth in the composite membrane assembly, and improving their retention.

[0141] In a normally operating MABR autotrophic denitrification reactor, the sodium nitrite dosing system is turned on for 3 days every 12 days, and the dosage of sodium nitrite is 0.02-0.03Q, in kg / d, where Q is the reactor inflow. During the addition of sodium nitrite, the intermittent aeration ratio is increased from 1.0-2.0 during normal operation to 2.0-3.0, and other conditions can maintain normal operating values. Every other sodium nitrite addition process, the dosage is increased to 0.03-0.05Q, in kg / d, and other conditions are the same.

[0142] In some embodiments, the reasons for the instability of autotrophic nitrogen removal in the MABR reactor are:

[0143] ④ In response to the situation where the concentration of organic matter in the influent continues to increase or the proportion of degradable organic matter continues to increase.

[0144] When the concentration of influent organic matter continues to rise or the degradable proportion of influent organic matter continues to increase, it is easy for heterotrophic nitrifying bacteria or other heterotrophic bacteria to over-proliferate, resulting in the living space of anaerobic ammonia-oxidizing bacteria being squeezed out, thus making the autotrophic denitrification process unstable.

[0145] The control strategy for the above situation is to increase the proportion of heterotrophic denitrification in the circulating reaction zone, while reducing the proportion of heterotrophic denitrification in the spatial three-dimensional mesh filler area of ​​the membrane reaction zone, thereby reducing the impact of denitrifying bacteria on anaerobic ammonia oxidizing bacteria.

[0146] Firstly, the operating frequency of the variable frequency motor of the upflow agitator 7 of the guide tube in the circulation reaction zone is increased to increase the rotation speed of the agitator, thereby increasing the circulation speed of the mixed liquid inside and outside the circulation guide tube, and further increasing the heterotrophic denitrification rate in the circulation reaction zone; secondly, the reflux ratio of the mixed liquid in the membrane reaction zone is increased from 200% to 400% in normal operation to 400% to 600% to reduce the nitrate nitrogen concentration in the membrane reaction zone, thereby reducing the reaction activity of heterotrophic denitrifying bacteria in the three-dimensional mesh filler area in the composite membrane module.

[0147] When the influent organic matter concentration continues to increase and the carbon-nitrogen ratio exceeds 3.0, it exceeds the applicable scope of the MABR autotrophic denitrification reactor of the present invention, and it is necessary to adopt an appropriate pretreatment unit (such as an activated sludge aeration tank, an aerated biological filter, etc.) to appropriately reduce the organic matter concentration before entering the MABR autotrophic denitrification reaction for treatment.

[0148] In some embodiments, a method for establishing an autotrophic denitrification process in a MABR reactor is provided.

[0149] For nitrogen-containing industrial wastewater and domestic sewage with a low carbon-nitrogen ratio, the process of establishing autotrophic denitrification in the MABR reactor can be carried out in steps, including nitrification biofilm formation, establishment of short-range nitrification process, start-up of anaerobic ammonia oxidation autotrophic denitrification process, and establishment of a stable autotrophic denitrification process.

[0150] The method for establishing the autotrophic denitrification process of the MABR reactor comprises the following steps: S0011, nitrification biofilm formation:

[0151] (1) Aerobic activated sludge is inoculated into the circulating reaction zone 2. The aerobic activated sludge has a nitrification function. The activated sludge in the aerobic zone or anoxic zone of the wastewater treatment system of the BNR (biological nutrient removal) process or the AAO (anaerobic / anoxic / aerobic) process can be taken. The supernatant is skimmed after settling for 30 minutes. The sludge is directly added to the pool from the top of the circulating reaction zone 2. The amount of inoculated sludge is (2.0-3.0)×V 膜反应区 , in kg, where V 膜反应区 is the effective volume of the membrane reaction zone 4. After inoculation, the sludge concentration (MLSS) value of the mixed liquor in the MABR reaction tank reaches 2000mg / L~3000mg / L.

[0152] Continuously open the stirring circulation system, the mixed liquid reflux system, and the gas supply system; that is, continuously open the upflow stirrer 7 of the circulation reaction zone 2, the mixed liquid reflux pump 33, the valve on the mixed liquid discharge pipe 32, and the mixed liquid reflux pipe valve 34; start the gas supply fan 21, the gas supply main pipe valve 22, the gas supply branch pipe valve 25, and the exhaust branch pipe valve 30, so that the MABR membrane assembly is in a continuous aeration state, the air intake pressure is 30-50 kPa, and the air intake flow rate is 6-8 L / (h·m 膜丝 ).

[0153] Intermittent water inflow, in a cycle mode of 1 hour of water inflow and 3 hours of water stop; intermittent air stirring system, that is, the air stirring system works intermittently during water inflow, that is, it is turned on for 10 to 20 seconds every 15 minutes; it works continuously during the period of water stop, and the intensity of air stirring is 0.6 to 0.9m 3 空气 / m 3 池容 .

[0154] Close the sludge return system and the heat exchange system on the return main pipe 38; close the sludge return pump 44 and the valve on the sludge return pump mud inlet pipe 43.

[0155] At this stage, the flow direction of the sludge-water mixture in the MABR reactor is "circulation reaction zone 2-sludge zone 12-water distribution porous plate 13-membrane reaction zone 4-circulation reaction zone 2". During the water inlet period, the excess water in the reactor is discharged from the outlet pipe 20. The intermittent water inlet mode and continuous MABR membrane aeration make the organic matter in the inlet water degrade more completely in the MABR reaction tank, which is conducive to the growth of aerobic nitrifying bacteria in the reactor; at the same time, the long-term operation of the air stirring system makes the activated sludge in the reactor in a suspended state, which is in good contact with the MABR membrane fibers, so that aerobic nitrifying bacteria can quickly attach and grow on the outer surface of the MABR membrane fibers to form MABR biofilm.

[0156] (2) When the pH value in the membrane reaction zone 4 drops to below 6.5-7.0 and the ammonia nitrogen concentration is 5%-10% of the ammonia nitrogen concentration in the influent, the water inlet time ratio is gradually increased, and the water inlet time is increased by 1 hour each time;

[0157] (3) When the continuous water inlet mode is achieved, the effluent pH value and ammonia nitrogen concentration drop significantly, and a uniform and dense biofilm is attached to the surface of the MABR membrane, the nitrification biofilm formation stage of the MABR reactor is completed, and a complete nitrification reaction state is established in the reactor.

[0158] S0012. Establishment of short-range nitrification process:

[0159] (1) The MABR reactor maintains continuous water inflow and continuous water outflow at normal flow rates, and the mixed liquor return system and sludge return system are continuously opened. The mixed liquor return ratio is 100% to 200%, and the sludge return ratio is 50% to 100%.

[0160] The aeration system was adjusted from continuous aeration to intermittent aeration with an intermittent aeration ratio (ratio of aeration stop time to aeration time) of 1.0-1.5. At the same time, the aeration pressure and aeration flow rate were reduced to reduce the dissolved oxygen concentration in the reactor. The activity of nitrite oxidizing bacteria (NOB) was initially inhibited by low dissolved oxygen concentration. At this time, the intermittent aeration mode was aeration for 30-60 minutes and aeration stop for 30-60 minutes. The air supply pressure was 10-30 Kpa and the air supply flow rate was 4-6 L / (h·m 膜丝 ).

[0161] (2) Start the reagent dosing system and continuously add sodium nitrite solution to the membrane reaction zone (4). The daily dosage of sodium nitrite is calculated according to the water intake (Q), that is, 0.03-0.05Q, in kg / d. By adding sodium nitrite solution to increase the concentration of nitrite nitrogen, when pH = 6.0-6.5, free nitrite sufficient to inhibit the concentration of nitrite oxidizing bacteria is generated to achieve the rapid establishment of the short-range nitrification process;

[0162] (3) Turn on the heat exchange system and control the water temperature in the heat exchange barrel 39 to 35-40°C. The refluxed mixed liquor and sludge can be continuously and indirectly heat exchanged in the heat exchange barrel while ensuring that the maximum tolerance temperature of the microorganisms is not exceeded. At this time, the dissolved oxygen concentration in the membrane reaction zone of the MABR reactor can be controlled at 0.1-0.2 mg / L, the nitrite nitrogen concentration in the influent water is 30-50 mg / L, and the mixed liquor temperature is 25-30°C;

[0163] Under the condition of pH value of 6.4-6.8 during nitrification reaction, the concentration of free nitrite (FNA) in the mixed solution of membrane reaction zone can reach 0.03-0.15 mg / L, reaching the concentration range of FNA inhibition on nitrite oxidizing bacteria (NOB), while having no adverse effect on ammonia oxidizing bacteria (AOB). Thus, the multi-factor synergistic inhibition of nitrite oxidizing bacteria (NOB) by low dissolved oxygen (DO) and high free nitrite (FNA) is achieved, and then the activity of nitrite oxidizing bacteria (NOB) in MABR biofilm is inhibited, ammonia oxidizing bacteria (AOB) continue to proliferate, and the biofilm on MABR membrane gradually changes from complete nitrification biofilm to short-range nitrification biofilm.

[0164] The reaction conversion state is monitored and characterized by online detection instruments in the membrane reaction zone 4. Usually, the dissolved oxygen (DO) is 0.1-0.2 mg / L, the pH value is 6.4-6.8, the oxidation-reduction potential (ORP) is 100-200 mV, and the ammonia nitrogen is 5%-10% of the ammonia nitrogen value of the influent.

[0165] (4) The nitrate nitrogen value in the membrane reaction zone 4 shows a gradual downward trend. When it drops to 40% to 50% of the stable nitrate nitrogen value when the nitrification biofilm is completed, the MABR biofilm has initially established a short-range nitrification state; when the nitrate nitrogen value in the membrane reaction zone 4 drops to 80% to 90% of the nitrate nitrogen value when the nitrification biofilm is completed, it indicates that the MABR reaction membrane has completed the conversion process of the short-range nitrification state and the addition of sodium nitrite solution is stopped.

[0166] The heat exchange system is kept open, water is continuously introduced and aeration is continued, and the air stirring system is intermittently opened, and then it is operated continuously. When the removal rate of ammonia nitrogen in the effluent of membrane reaction zone 4 is 92% to 98% and the nitrite nitrogen accumulation rate (the ratio of nitrite nitrogen concentration to the sum of nitrite nitrogen concentration and nitrate nitrogen concentration) reaches 85% to 95%, the establishment of the short-range nitrification process is completed.

[0167] S0013. Start-up of anaerobic ammonium oxidation autotrophic denitrification process:

[0168] (1) The short-range nitrification reaction in the MABR reactor is regulated to a partial short-range nitrification state, that is, 50% to 60% of the ammonia nitrogen is oxidized to nitrite nitrogen, while ensuring that the nitrite nitrogen accumulation rate is maintained above 95%.

[0169] (2) On the basis of continuous water inflow operation when the MABR reactor is in a short-range nitrification state, the intermittent aeration ratio of the air supply system is increased to 1.5-3.0, that is, aeration for 30 minutes and aeration is stopped for 45 minutes to 90 minutes; the aeration pressure and aeration flow rate are further reduced, and the air supply pressure is controlled at 5KPa-20KPa, and the air supply flow rate is 3-4L / (h·m 膜丝 ), thereby reducing the dissolved oxygen in the membrane reaction zone to 0-0.05 mg / L; the ratio of the residual ammonia nitrogen to nitrite nitrogen concentration in the effluent is controlled between 1:1 and 1:1.3, and the aeration intermittent ratio is adjusted accordingly to maintain the dynamic balance of the partial short-range nitrification state;

[0170] (3) Open the sludge discharge pipe and close the sludge return system, that is, open the sludge discharge valve 45 and close the sludge return valve 47 at the same time, and discharge about 50% of the sludge in the sludge area 12 to the outside of the system;

[0171] (4) Sludge containing anaerobic ammonium oxidizing bacteria is inoculated in the circulating reaction zone 2. The sludge is a mixture of flocculent sludge and granular sludge containing anaerobic ammonium oxidizing bacteria. The volume ratio of the two is 1:1 to 2:1. The abundance of anaerobic ammonium oxidizing bacteria in the mixed sludge is not less than 20%, and the inoculation volume is not less than 10% to 20% of the effective volume of the membrane reaction zone.

[0172] Keep the sludge return system closed, and close the stirring circulation system, and continuously open the mixed liquid return system, the air supply system and the heat exchange system on the return main pipe 38, and intermittently open the air stirring system. In this way, the seeded sludge is fully mixed with the sludge in the reaction tank, and circulates between the circulation reaction area and the membrane reaction area.

[0173] Other main operating parameters are: mixed liquid reflux ratio 400% to 600%; air stirring system is operated in the mode of opening for 20 seconds every 10 minutes, and air stirring intensity is 0.2 to 0.3 m 3 空气 / m 3 池容 .

[0174] During the rapid circulation of the mixed liquid, the flocculent sludge is in full contact with the composite membrane assembly 9. Since the pores in the curtain membrane filament element 904 region inside the composite membrane assembly 9 are large and the water flow rate is fast, it is difficult for anaerobic ammonia oxidizing bacteria to attach and grow; while the pores in the spatial three-dimensional mesh filler layer 902 are small and the water flow rate is slow, anaerobic ammonia oxidizing bacteria can easily attach to the filler surface and grow, forming an anaerobic biofilm. During the air stirring process, some of the low-density anaerobic ammonia oxidizing granular sludge can also be intercepted by the spatial three-dimensional mesh filler layer, and together with the anaerobic biofilm, form an anaerobic ammonia oxidation reaction area. At the same time, the aerobic biofilm on the surface of the curtain membrane filament element 904 grows more densely under the shearing action of the water flow, which helps to stabilize the short-range nitrification process.

[0175] (5) The reagent dosing system is coordinated with the intermittent aeration mode. The nitrite dosing system is intermittently turned on. The reagent dosing system is turned on during the last 20% to 30% of the period after aeration is stopped to add sodium nitrite solution into the membrane reaction zone 2. The dosage is calculated as 0.02 to 0.04Q based on the water inlet volume (Q), in kg / d. The addition of nitrite is stopped during other periods.

[0176] The main reason is the periodic change of the short-term nitrification reaction state during the intermittent aeration of the MABR reactor. The ratio of ammonia nitrogen to nitrite nitrogen shows periodic changes with the short-term nitrification reaction state. The ratio gradually decreases in the early stage of aeration and aeration cessation, and gradually increases in the later stage of aeration cessation. This periodic change of the reaction state will have a certain impact on the anaerobic ammonium oxidation reaction, especially during the start-up period of the anaerobic ammonium oxidation reaction. By intermittently adding sodium nitrite to ensure that there is enough nitrite nitrogen in the MABR reactor for the anaerobic ammonium oxidizing bacteria to react, the ratio of ammonia nitrogen to nitrite nitrogen in the MABR reactor can be stabilized and close to the theoretical value of 1:1.32 of the anaerobic ammonium oxidation reaction, the reaction activity of anaerobic ammonium oxidizing bacteria can be improved, and the time of autotrophic denitrification process extension due to the failure of some short-term digestion reactions to reach 50% can be reduced, shortening the start-up period of autotrophic denitrification.

[0177] (6) After a period of continuous operation, the spatial three-dimensional mesh filler layer in the membrane reactor 9 forms a relatively stable anaerobic biofilm; the operation is continued until the pH value of the effluent rises to 7.2-7.7, and the redox potential value drops to 50mV-100mV. At this time, when the nitrate nitrogen concentration rises to 10%-15% of the ammonia nitrogen concentration in the inlet water and the total nitrogen removal rate in the effluent reaches 70%-80%, the start-up of the anaerobic ammonia oxidation autotrophic denitrification process is completed.

[0178] S0014. Establishment of a stable autotrophic denitrification process: After the anaerobic ammonia oxidation autotrophic denitrification process is started, the operation of the MABR reactor can be switched from the startup phase to the normal operation phase.

[0179] Close the reagent dosing system, stop adding sodium nitrite solution, continuously open the sludge return system, and the sludge return ratio is 50% to 100%; continuously open the mixed liquor return system and the stirring circulation system to maintain intermittent aeration of the air supply system.

[0180] After a period of continuous operation, the total nitrogen removal rate of the MABR reactor effluent reaches 80-85%, the ammonia nitrogen removal rate exceeds 95%, the pH value is 7.0-8.0, the redox potential is 50mV-100mV, and when the inlet water temperature is 20-30℃, the indirect heat exchange system of the return main pipe can be stopped, and the MABR reactor can operate normally. At this time, the establishment of the autotrophic denitrification process of the MABR reactor is completed.

[0181] The beneficial effects of the present invention are as follows:

[0182] (1) The present invention proposes a device for improving the autotrophic denitrification performance of an MABR reactor for efficient autotrophic biological denitrification treatment of medium and low concentration ammonia-containing wastewater or domestic sewage. A double-layer frame is set in the MABR membrane assembly, and a spatial three-dimensional mesh filler is built in to increase the attachment of autotrophic denitrifying bacteria such as anaerobic ammonia-oxidizing bacteria. A composite membrane assembly combining a curtain-type filamentous silica gel membrane and a spatial three-dimensional mesh filler is used to construct a MABR short-range nitrification biofilm, anaerobic ammonia-oxidizing biofilm, and heterotrophic denitrification biofilm coupled symbiotic system. At the same time, different reaction areas such as a circulation reaction zone and an MABR reaction zone are set in a single reactor, thereby promoting the coordination and integration of multiple denitrification reactions such as short-range nitrification and denitrification, anaerobic ammonia oxidation and heterotrophic denitrification in a single-stage reactor, thereby improving the autotrophic denitrification efficiency of the reactor, and solving the problems existing in the existing MABR reactor for autotrophic denitrification, such as the MABR membrane assembly and the biofilm method are simply arranged in the same reactor, which will cause the disadvantages of the two processes to overlap, and the multi-stage MABR reactor is complicated to operate in series.

[0183] (2) The present invention proposes a method for establishing an autotrophic denitrification process in an MABR reactor. For nitrogen-containing industrial wastewater and domestic sewage with a low carbon-nitrogen ratio, the process of establishing an autotrophic denitrification process in an MABR reactor can be carried out in steps, including nitrification biofilm formation, establishment of a short-range nitrification process, start-up of an anaerobic ammonia oxidation autotrophic denitrification process, and establishment of a stable autotrophic denitrification process. The low dissolved oxygen (DO) in the MABR reactor is controlled by an intermittent aeration mode, and a sodium nitrite solution is added to generate a higher concentration of free nitrite (FNA), thereby performing multi-factor synergistic inhibition on nitrite oxidizing bacteria (NOB), and accelerating the establishment of a short-range nitrification process in the MABR reactor; at the same time, the addition of sodium nitrite solution and the regulation of the intermittent aeration mode improve the startup speed of the anaerobic ammonia oxidation autotrophic denitrification process and the establishment speed of a stable autotrophic denitrification process; and the addition of sodium nitrite solution and the intermittent aeration mode solve the shortcoming of poor persistence of single factor inhibition of nitrite oxidizing bacteria (NOB) activity. At the same time, sodium nitrite is stable in nature, relatively safe in operation, cheap and easily available, and the regulation strategy of the present invention is easier to implement in actual operation.

[0184] (3) The present invention proposes a method for evaluating the stability of autotrophic denitrification of MABR reactors. By establishing a benchmark value for the normal operation of the autotrophic denitrification process of the MABR reactor and a judgment database for the decline in the stability of the autotrophic denitrification process, the continuously collected online monitoring data is compared with the benchmark value of the reactor, and the main reason for the instability of the autotrophic denitrification reaction is obtained according to the trend in the judgment database. The method for determining the stability of the autotrophic denitrification reactor used in the present invention is based on a large amount of historical operation data, and adopts the change trend of multiple parameters of the autotrophic denitrification reactor to determine the stability of the autotrophic denitrification reactor under complex operating conditions. The comprehensive judgment method of the change trend of multiple parameters can meet the operation of the MABE membrane assembly composed of silica gel membrane filaments with high efficiency oxygen transfer and spatial three-dimensional mesh fillers in the MABR reactor. Among them, ammonia oxidizing bacteria, anaerobic ammonia oxidizing bacteria, heterotrophic denitrifying bacteria and other organisms coexist and coexist, forming a dynamic and stable autotrophic denitrification stabilizer. The method for determining the instability of its operation does not adopt a single value or a fixed value, and can obtain the accurate cause of the instability of the reactor.

[0185] (4) The present invention proposes a method for improving the stability of autotrophic denitrification and improving the denitrification performance of the MABR reactor, and adopts different targeted strategies for regulation according to the causes of instability of different autotrophic denitrification reactions. The key to the regulation of the instability of the short-term nitrification process is to add sodium nitrite solution so that a sufficient concentration of free nitrite (FNA) is produced in the reactor mixed liquid at a lower pH value, combined with the low dissolved oxygen brought by the intermittent aeration mode, to jointly inhibit the nitrite oxidizing bacteria (NOB) in the MABR biofilm, so that the short-term nitrification process is restored and the autotrophic denitrification reaction is stabilized again. That is, in the present invention, during the continuous operation of the reactor, sodium nitrite solution is continuously added according to the operation of the reactor to control the pH value to 6.0-6.5, which is the pH value that can be achieved in the complete nitrification process. There is no need to add acid artificially, and the FNA concentration is controlled to inhibit nitrite oxidizing bacteria without excessively affecting ammonia oxidizing bacteria. Moreover, it can directly affect the state of various microorganisms in the MABR reactor through online addition, especially for the excessive proliferation of nitrite oxidizing bacteria, which is more timely and has no lag of lateral inhibition. It can directly produce a regulatory effect on the suspended ecological flocculent sludge in the reactor, the MABR biofilm grown on the surface of the MABR membrane, and the anaerobic biofilm attached to the spatial three-dimensional mesh filler, so as to be more conducive to the stable operation of the reactor. The key to the regulation process of the decline in the activity of anaerobic ammonia oxidizing bacteria is to periodically add sodium nitrite to stabilize the short-range nitrification process, while increasing the substrate of the anaerobic ammonia oxidation reaction, stimulating the growth of anaerobic ammonia oxidizing bacteria, increasing its attachment and growth amount in the composite membrane assembly, and improving its retention.

[0186] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0187] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A device for improving the autotrophic denitrification performance of a MABR reactor, characterized in that: include: A reaction tank (1) is internally divided into a circulation reaction zone (2) and a membrane reaction zone (4) which are connected at the bottom, a water inlet pipe (16) is connected to the circulation reaction zone (2), a water outlet pipe (20) is connected to the membrane reaction zone (4), a stirring circulation system is provided in the circulation reaction zone (2), a water distribution porous plate (13) is provided in the membrane reaction zone (4), a sludge zone (12) is provided below the water distribution porous plate (13), and a plurality of MABR membrane modules (9) are provided above the water distribution porous plate (13); The reagent dosing system comprises a plurality of groups of membrane zone dosing components (65) arranged between the MABR membrane components (9) and the water distribution porous plate (13) and corresponding to each group of the MABR membrane components (9); The air supply system is used to aerate each of the MABR membrane modules (9); The mixed liquid reflux system is used to reflux the mixed liquid in the membrane reaction zone (4) to the circulation reaction zone (2); The sludge return system is used to return the sludge in the sludge area (12) to the circulation reaction area (2); The air stirring system is used to flush each of the MABR membrane modules (9) with air flow; The online monitoring instrument system is used for real-time monitoring of water quality indicators in the membrane reaction zone (4) and inlet water quality indicators, and includes a PLC control cabinet (75) connected to the reagent dosing system and the gas supply system signal.

2. The device for improving the autotrophic denitrification performance of the MABR reactor according to claim 1, characterized in that: The MABR membrane assembly (9) comprises a membrane assembly outer frame (901), a spatial three-dimensional mesh filler layer (902), a membrane assembly inner frame (903) and a plurality of groups of curtain-type membrane wire elements (904) arranged in sequence from the outside to the inside. The curtain-type membrane wire elements (904) comprise a plurality of filamentary silicone membranes evenly distributed horizontally and an air intake vertical pipe (905) and an exhaust vertical pipe (907) arranged on both sides and connected to the two ends of the filamentary silicone membranes respectively. The air intake vertical pipe (905) is connected to the aeration pipe of the air supply system, and the exhaust vertical pipe (907) is connected to the exhaust pipe of the air supply system.

3. The device for improving the autotrophic denitrification performance of the MABR reactor according to claim 1, characterized in that: The membrane zone dosing component (65) includes a dosing main pipe (6503), on which a plurality of parallel dosing perforated pipes (6504) are provided. The plurality of dosing main pipes (6503) extend to the outside of the reaction tank (1) and are connected to a dosing distribution pipe (6501) through a dosing main pipe valve (6502). The dosing distribution pipe (6501) is connected to the dosing pipe, and the dosing pipe is connected to a nitrite storage tank (64). The dosing pipe is provided with a valve, a nitrite dosing flowmeter (61) and a nitrite dosing metering pump (62).

4. The device for improving the autotrophic denitrification performance of the MABR reactor according to claim 1, characterized in that: The mixed liquor return system comprises a mixed liquor return pipe (37) connected to the upper part of the membrane reaction zone (4), the sludge return system comprises a sludge return pipe (50) connected to the sludge zone (12), a sludge discharge pipe (46) is provided on the sludge return pipe (50), the mixed liquor return pipe (37) and the sludge return pipe (50) are connected to the circulation reaction zone (2) via a return main pipe (38), and a heat exchange system is provided on the return main pipe (38); The air stirring system comprises an air stirring assembly (58) arranged in the sludge area (12) and corresponding to each group of MABR membrane assemblies (9), and the air stirring assembly (58) is connected to the corresponding air stirring branch pipe (57); The stirring circulation system comprises a circulation guide tube (6) arranged in the circulation reaction zone (2), and an upflow stirrer (7) is arranged in the circulation guide tube (6).

5. The device for improving the autotrophic denitrification performance of the MABR reactor according to claim 4, characterized in that: The online monitoring instrument system comprises an online dissolved oxygen meter (66), an online ORP meter (67), an online ammonia nitrogen meter (68), an online nitrate nitrogen meter (69), an online nitrite nitrogen meter (70) and an online pH meter (71) for the membrane reaction zone, which are arranged in the membrane reaction zone (4) and connected to the PLC control cabinet (75) through a membrane reaction zone monitoring secondary instrument (72), and an inlet water online pH meter (18) and an inlet water online ammonia nitrogen meter (19) which are arranged on the inlet water pipe (16) and connected to the PLC control cabinet (75) through an inlet water monitoring secondary instrument (73).

6. A method for improving the autotrophic denitrification performance of a MABR reactor, characterized in that: A device for improving the autotrophic denitrification performance of a MABR reactor according to any one of claims 1 to 5 is used, wherein the steps are as follows: S001. Inoculate and form biofilm in the MABR reactor, and make the MABR reactor operate normally for autotrophic denitrification; S002, establishing the reference values ​​of various data during the normal operation of the autotrophic denitrification process of the MABR reactor and storing them in the PLC controller, wherein the various data include: dissolved oxygen, pH value, redox potential, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen and temperature in the membrane reaction zone (4); and ammonia nitrogen, pH value and temperature in the influent; S003. Establish a database for determining the stability decline of the autotrophic denitrification process of the MABR reactor: Based on the changing trend of water quality indicators in the autotrophic denitrification process of the MABR reactor, list the main reasons for the instability of the autotrophic denitrification of the MABR reactor; S004. Continuously collect various online monitoring data of the autotrophic denitrification process of the MABR reactor and input them into the PLC controller, compare the various online monitoring data with the reference values ​​of the various data, and determine the cause of the instability of the autotrophic denitrification of the MABR reactor based on the data trend in the determination database; S005. According to the cause of the instability of the autotrophic nitrogen removal in the MABR reactor in step S004, corresponding regulation is performed.

7. The method for improving the autotrophic denitrification performance of a MABR reactor according to claim 6, characterized in that: In step S003, the determination database includes:

8. The method for improving the autotrophic denitrification performance of a MABR reactor according to claim 6, characterized in that: In step S005, the reason for the instability of autotrophic nitrogen removal in the MABR reactor is that the activity of nitrite oxidizing bacteria in the MABR biofilm increases and there is a trend of complete nitrification: (1) Turn on the reagent dosing system, add sodium nitrite solution into the membrane reaction zone (4), increase the intermittent aeration ratio of the air supply system and maintain it for a period of time; (2) When the nitrate nitrogen concentration decreases and approaches the baseline value, reduce the amount of sodium nitrite added and maintain it for a period of time; (3) When the pH value in the membrane reaction zone (2) recovers to above 7.0 and the redox potential recovers to 50-100 mV, the addition of sodium nitrite is stopped and the intermittent aeration ratio is restored to the normal operating value.

9. The method for improving the autotrophic denitrification performance of a MABR reactor according to claim 6, characterized in that: In step S005, the reason for the instability of the autotrophic nitrogen removal in the MABR reactor is that the short-range nitrification reaction of the MABR biofilm is excessive or insufficient, and it is regulated by the intermittent aeration mode and the influent nitrogen load: a. When the short-range nitrification reaction of MABR biofilm is excessive: Analyze the intermittent aeration ratio and influent nitrogen load before and after the MABR autotrophic denitrification reactor becomes unstable; if the influent nitrogen load does not change significantly, increase the intermittent aeration ratio to 2.0-3.0; if the influent nitrogen load decreases, restore the influent nitrogen load; if the influent nitrogen load cannot be restored in the short term, increase the intermittent aeration ratio to 2.0-4.0 and reduce the aeration time to 15-20 minutes; b. When the short-range digestion reaction of the MABR biofilm is insufficient: Analyze the intermittent aeration ratio and influent nitrogen load before and after the MABR autotrophic denitrification reactor becomes unstable; if the influent nitrogen load does not change significantly, reduce the intermittent aeration ratio to 0.5-1.0; if the influent nitrogen load increases, restore the influent nitrogen load; If the influent nitrogen load cannot be restored in the short term, reduce the intermittent aeration ratio to 0.5-1.0 and increase the aeration time to 30-60 minutes.

10. The method for improving the autotrophic denitrification performance of a MABR reactor according to claim 6, characterized in that: In step S001, the method for establishing the autotrophic denitrification process of the MABR reactor is as follows: S0011, Nitrification biofilm: (1) Inoculating aerobic activated sludge into the circulating reaction zone (2), and continuously starting the stirring circulation system, the mixed liquid reflux system, and the air supply system; intermittently adding water, intermittently starting the air stirring system; and closing the sludge reflux system and the heat exchange system; (2) When the pH value in the membrane reaction zone (4) drops to below 6.5-7.0 and the ammonia nitrogen concentration is 5%-10% of the ammonia nitrogen concentration in the influent, gradually increase the proportion of the influent time; (3) When the continuous water inflow mode is achieved and the effluent pH value and ammonia nitrogen concentration drop significantly, the nitrification biofilm is formed; S0012. Establishment of short-range nitrification process: (1) Continuously open the mixed liquor return system and the sludge return system, adjust the air supply system to intermittent aeration with an intermittent aeration ratio of 1.0 to 1.5, and reduce the aeration pressure and aeration flow rate; (2) starting the reagent dosing system to continuously add sodium nitrite solution into the membrane reaction zone (4); (3) Turn on the heat exchange system and control the temperature of the mixed liquid to 25°C to 30°C; (4) When the nitrate nitrogen value in the membrane reaction zone (4) drops to 80% to 90% of the nitrate nitrogen value when the nitrification biofilm is formed, the addition of the sodium nitrite solution is stopped, the heat exchange system is kept on, the water is continuously fed and aeration is continued, and the air stirring system is intermittently turned on, and then the system is operated continuously. When the removal rate of ammonia nitrogen in the effluent of the membrane reaction zone (4) is 92% to 98% and the accumulation rate of nitrite nitrogen reaches 85% to 95%, the establishment of the short-range nitrification process is completed; S0013. Start-up of anaerobic ammonium oxidation autotrophic denitrification process: (1) regulating the short-range nitrification reaction in the MABR reactor to a partial short-range nitrification state; (2) Increase the intermittent aeration ratio of the air supply system to 1.5-3.0, further reduce the aeration pressure and aeration flow rate; the ratio of residual ammonia nitrogen to nitrite nitrogen concentration in the effluent is controlled between 1:1 and 1:1.3; (3) Open the sludge discharge pipe and close the sludge return system to discharge about 50% of the sludge in the sludge area (12); (4) Inoculating sludge containing anaerobic ammonium-oxidizing bacteria in the circulation reaction zone (2), closing the stirring circulation system, continuously opening the mixed liquid reflux system, the air supply system and the heat exchange system, and intermittently opening the air stirring system; (5) The reagent dosing system cooperates with the intermittent aeration mode, and the reagent dosing system is turned on during the last 20% to 30% of the period after the aeration is stopped, so as to add sodium nitrite solution into the membrane reaction zone (2); (6) Continue to operate until the effluent pH value rises to 7.2-7.7, the redox potential value drops to 50mV-100mV, the nitrate nitrogen concentration rises to 10%-15% of the inlet ammonia nitrogen concentration, and the effluent total nitrogen removal rate reaches 70%-80%, completing the start-up of the anaerobic ammonia oxidation autotrophic denitrification process; S0014. Establishment of a stable autotrophic denitrification process: Close the chemical dosing system, continuously open the sludge return system, mixed liquor return system and stirring circulation system, maintain intermittent aeration of the air supply system, and continue to operate until the total nitrogen removal rate of the effluent reaches 80-85%, the ammonia nitrogen removal rate exceeds 95%, the pH value is 7.0-8.0, and the redox potential is 50mV-100mV, completing the establishment of the autotrophic denitrification process of the MABR reactor.

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