Method and system for enhancing greenhouse gas emission reduction based on aeration regulation and control

Abstract

The invention provides a method and system for enhancing greenhouse gas emission reduction based on aeration regulation, and belongs to the technical field of sludge and wastewater treatment.The method comprises the steps that denitrification sludge is subjected to micro-aerobic aeration pretreatment so as to improve expression of nitrous oxide reducing genes in the denitrification sludge and convert part of ammonia nitrogen in the denitrification sludge into nitrate nitrogen at the same time; the concentration of dissolved oxygen in the micro-aerobic aeration pretreatment is 0.2 mg / L; refluxing the micro-aerobic aerated sludge into the first denitrification reaction tank, distributing inlet water, reducing nitrate nitrogen into nitrous oxide, and promoting conversion of nitrous oxide into nitrogen by utilizing improved expression of nitrous oxide reducing genes; conveying the obtained first denitrified muddy water into a first nitration reaction tank, and controlling the concentration of dissolved oxygen at 0.2 mg / L so as to convert ammonia nitrogen into nitrate nitrogen; and conveying the obtained first nitrified muddy water into a secondary sedimentation tank for carrying out muddy water separation, refluxing the obtained denitrified sludge, and repeating the process.

Description

Technical Field

[0001] The present invention belongs to the technical field of sludge and wastewater treatment, and particularly relates to a method and a system for enhancing greenhouse gas emission reduction based on aeration regulation. Background Art

[0002] The greenhouse gas (GHG) emissions from waste treatment continue to increase. Among them, the contribution of carbon dioxide (CO2) gas emissions has decreased to 1.5%, and currently, non-CO2 type GHG emissions are the main ones. Among them, non-CO2 type greenhouse gases include nitrous oxide (N2O). Although its concentration is far lower than that of CO2, its warming potential is 310 times that of CO2, and its residence time in the atmosphere is 114 years.

[0003] Sewage treatment is an important source of N2O emissions. In traditional sewage treatment, biological nitrogen removal mostly adopts the aerobic nitrification - anoxic denitrification reaction process. This method generally has problems such as large emissions of greenhouse gas N2O and poor nitrogen removal effect. Moreover, with the increase in the number and scale of sewage treatment plants, the N2O emissions from this process still show an increasing trend. How to effectively reduce N2O emissions during the sewage treatment process is an urgent problem to be solved currently. Summary of the Invention

[0004] In view of the above technical problems, the present invention provides a method and a system for enhancing greenhouse gas emission reduction based on aeration regulation, in order to solve at least part of the above technical problems. For this purpose, the technical solutions provided by the present invention are as follows.

[0005] As the first aspect of the present invention, a method for enhancing greenhouse gas emission reduction based on aeration regulation is provided, including Step 1 - Step 4.

[0006] Step 1, perform micro-aerobic aeration pretreatment on denitrifying sludge to improve the expression of nitrous oxide reduction genes in the denitrifying sludge, and at the same time perform nitrification reaction to convert part of the ammonia nitrogen in the denitrifying sludge into nitrate nitrogen, obtaining micro-aerobic aeration sludge. Among them, the concentration of dissolved oxygen in the micro-aerobic aeration pretreatment is 0.2 mg / L.

[0007] Step 2, return the micro-aerobic aeration sludge to the first denitrification reaction tank and distribute the influent. The nitrate nitrogen in the micro-aerobic aeration sludge is reduced to nitrous oxide through the denitrification reaction, and the enhanced expression of nitrous oxide reduction genes is utilized to promote the conversion of nitrous oxide to nitrogen gas, obtaining the first denitrification sludge water mixture.

[0008] Step 3, transport the first denitrification sludge water mixture to the first nitrification reaction tank and control the concentration of dissolved oxygen at 0.2 mg / L, so that the ammonia nitrogen in the first denitrification sludge water mixture is converted into nitrate nitrogen through the nitrification reaction, obtaining the first nitrification sludge water mixture.

[0009] Step 4: Transport the first nitrification sludge water to a secondary sedimentation tank for sludge-water separation to obtain denitrified sludge. Among them, the denitrified sludge in Step 1 is the denitrified sludge from the secondary sedimentation tank in Step 4, and Steps 1 to 4 are repeated.

[0010] As the second aspect of the present invention, there is provided a system for enhancing greenhouse gas emission reduction based on aeration regulation, which is applicable to implementing the method for enhancing greenhouse gas emission reduction based on aeration regulation as described above. The system includes: a secondary sedimentation tank, a micro-aerobic aeration pretreatment unit, a first denitrification reaction tank, and a first nitrification reaction tank that are connected in sequence and form a circulation loop, as well as an inlet tank for distributing influent water to the first denitrification reaction tank, an outlet tank for receiving the effluent from the secondary sedimentation tank, agitators and gas monitoring units located in the first denitrification reaction tank and the first nitrification reaction tank, an aeration assembly located in the first nitrification reaction tank, and pipes for connection.

[0011] Based on the above technical solutions, the method and system for enhancing greenhouse gas emission reduction based on aeration regulation provided by the present invention have at least the following beneficial effects.

[0012] (1) In the technical solution of the present invention, by utilizing the different sensitivities of various gene expressions in the denitrified sludge to oxygen, micro-aerobic aeration pretreatment (dissolved oxygen concentration is 0.2 mg / L) of the denitrified sludge discharged from the secondary sedimentation tank can improve the expression of nitrous oxide (N2O) reduction genes and simultaneously oxidize part of the ammonia nitrogen in the denitrified sludge into nitrate nitrogen. The micro-aerobic aeration sludge obtained through micro-aerobic aeration pretreatment enters the first denitrification reaction tank. Under an anoxic or anaerobic environment, the denitrifying bacteria in the micro-aerobic aeration sludge utilize the organic matter in the distributed influent water as a carbon source, and can convert the nitrate nitrogen in the micro-aerobic aeration sludge into N2O through denitrification reaction. By utilizing the improved expression of nitrous oxide reduction genes through micro-aerobic aeration pretreatment, N2O can be effectively reduced to nitrogen gas (N2), reducing the emission of greenhouse gas (N2O) and achieving denitrification simultaneously.

[0013] (2) In the technical solution of the present invention, transporting the first denitrification sludge water in the first denitrification reaction tank to the first nitrification reaction tank, controlling the dissolved oxygen concentration to 0.2 mg / L and maintaining it, can oxidize the ammonia nitrogen in the first denitrification sludge water into nitrate nitrogen, reduce the concentration of ammonia nitrogen in the effluent, lower the toxicity of the water body, and simultaneously convert ammonia nitrogen into utilizable nitrate nitrogen. Transporting the first nitrification sludge water in the first nitrification reaction tank to the secondary sedimentation tank for sludge-water separation, the obtained denitrified sludge can be recycled and the aforementioned micro-aerobic aeration pretreatment, denitrification reaction, and nitrification reaction can be repeated to enhance greenhouse gas emission reduction and denitrification. Description of the Drawings

[0014] Figure 1 It is a flowchart of enhancing greenhouse gas emission reduction based on aeration regulation in an embodiment of the present invention;

[0015] Figure 2 For implementing Figure 1 The schematic structural diagram of the system for enhancing greenhouse gas emission reduction based on aeration regulation in the shown process;

[0016] Figure 3 The schematic structural diagram of the system for enhancing greenhouse gas emission reduction based on aeration regulation in another embodiment of the present invention;

[0017] Figure 4 The diagram showing the change of sewage water quality during the denitrification process in the micro-aerobic aeration pretreatment (experimental group) and the control group in Embodiment 1 of the present invention;

[0018] Figure 5 The diagram showing the N2O emission during the denitrification reaction in the micro-aerobic aeration pretreatment (experimental group) and the control group in Embodiment 1 of the present invention;

[0019] Figure 6 The diagram showing the transcriptional expression of nitric oxide reduction genes in the sludge before and after micro-aerobic aeration pretreatment in Embodiment 1 of the invention;

[0020] Figure 7 The diagram showing the transcriptional expression of nitrous oxide reduction genes in the sludge before and after micro-aerobic aeration pretreatment in Embodiment 1 of the invention;

[0021] Figure 8 The diagram showing the change of enzyme activity in the sludge of the experimental group and the control group during the denitrification reaction in Embodiment 1 of the present invention;

[0022] Figure 9 The N2O gas emission in Stage I in Embodiment 2 of the present invention;

[0023] Figure 10 The N2O gas emission in Stage II in Embodiment 2 of the present invention;

[0024] Figure 11 The N2O gas emission in Stage III in Embodiment 2 of the present invention;

[0025] Figure 12 The N2O gas emission in Stage IV in Embodiment 2 of the present invention.

[0026]

Description of the reference numerals

[0027] 1 - Secondary sedimentation tank, 2 - Effluent tank, 3 - Micro-aerobic aeration pretreatment unit, 4 - Inlet tank, A1 - First denitrification reaction tank, O1 - First nitrification reaction tank, A2 - Second denitrification reaction tank, O2 - Second nitrification reaction tank. Detailed implementation manners

[0028] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In the following detailed description, for the sake of explanation, numerous specific details are set forth in order to provide a comprehensive understanding of the embodiments of the present invention. However, it is obvious that one or more embodiments can be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.

[0029] In the biological denitrification process, the nitrification-denitrification reaction is an important N2O conversion pathway. The heterotrophic denitrification reaction under anaerobic or anoxic conditions is both a source and a sink of N2O, and is an effective path for regulating N2O emission reduction. However, how to effectively enhance the reduction of N2O during the denitrification reaction is an urgent problem to be solved currently. In response to the foregoing problems, the present invention proposes a method and system for enhancing greenhouse gas emission reduction based on aeration regulation. Before the denitrification sludge undergoes the denitrification reaction, the denitrification sludge is pretreated with micro-aerobic aeration to enhance the expression of the N2O reduction gene, so that during the denitrification reaction, the generated N2O can be effectively converted into N2, reducing greenhouse gas emissions, and can also effectively remove nitrogen pollutants in the sewage.

[0030] Figure 1 FIG. is a flowchart of enhancing greenhouse gas emission reduction based on aeration regulation in an embodiment of the present invention. Figure 2 For execution Figure 1 FIG. is a schematic structural diagram of a system for enhancing greenhouse gas emission reduction based on aeration regulation for implementing the process shown. The system includes: a secondary sedimentation tank 1 for sludge-water separation, an effluent tank 2, a micro-aerobic aeration pretreatment unit 3 for micro-aerobic aeration pretreatment, an influent tank 4, a first denitrification reaction tank A1 for performing the denitrification reaction, and a first nitrification reaction tank O1 for performing the nitrification reaction.

[0031] Combined with Figure 2 the system shown, as Figure 1 shown, the method for enhancing greenhouse gas emission reduction based on aeration regulation includes: steps S1 - S4.

[0032] Step S1, the denitrification sludge is pretreated with micro-aerobic aeration to increase the expression of the nitrous oxide reduction gene in the denitrification sludge, and at the same time, the nitrification reaction is carried out to convert part of the ammonia nitrogen in the denitrification sludge into nitrate nitrogen, obtaining micro-aerobic aeration sludge. Among them, the concentration of dissolved oxygen in the micro-aerobic aeration pretreatment is 0.2 mg / L.

[0033] Step S2, the micro-aerobic aeration sludge is refluxed into the first denitrification reaction tank A1 and the influent is distributed. The nitrate nitrogen in the micro-aerobic aeration sludge is reduced to nitrous oxide through the denitrification reaction, and the increased expression of the nitrous oxide reduction gene is utilized to promote the conversion of nitrous oxide into nitrogen, obtaining the first denitrification sludge-water mixture.

[0034] Step S3: Transport the first denitrified sludge water to the first nitrification reaction tank O1 and control the dissolved oxygen concentration at 0.2 mg / L so that the ammonia nitrogen in the first denitrified sludge water is converted into nitrate nitrogen through nitrification reaction to obtain the first nitrified sludge water.

[0035] Step S4: Transport the first nitrified sludge water to the secondary sedimentation tank 1 for sludge-water separation to obtain denitrified sludge. Among them, the denitrified sludge in Step S1 is the denitrified sludge from the secondary sedimentation tank 1 in Step S4, and Steps S1 to S4 are repeated.

[0036] In the embodiment of the present invention, according to the different sensitivities of various gene expressions in the denitrified sludge to oxygen, the N2O reduction gene can be highly expressed under low dissolved oxygen (0.2 mg / L) conditions to maintain the ability to reduce N2O. By performing micro-aerobic aeration pretreatment (dissolved oxygen concentration is 0.2 mg / L) on the denitrified sludge discharged from the secondary sedimentation tank 1, the expression of nitrous oxide (N2O) reduction gene can be improved, and at the same time, part of the ammonia nitrogen in the denitrified sludge is oxidized into nitrate nitrogen. It can also effectively reduce the N2O emission during the biological denitrification process in the denitrification reaction section after subsequent supplementary water inflow. That is, the micro-aerobically aerated sludge obtained through micro-aerobic aeration pretreatment enters the first denitrification reaction tank A1, and using the organic matter in the distributed influent as a carbon source, the nitrate nitrogen in the micro-aerobically aerated sludge can be converted into N2O through denitrification reaction. Utilizing the improved expression of the nitrous oxide reduction gene by micro-aerobic aeration pretreatment, N2O is effectively reduced to nitrogen gas (N2), reducing greenhouse gas (N2O) emissions while achieving denitrification. In addition, quickly changing from a micro-aerobic environment (dissolved oxygen concentration is 0.2 mg / L) to an anoxic or anaerobic environment can enable the denitrifying bacteria in the micro-aerobically aerated sludge to adapt to the environment faster, improve the denitrification efficiency, and at the same time have no impact on the expression of the N2O reduction gene. Further, transport the first denitrified sludge water to the first nitrification reaction tank O1 for nitrification reaction, oxidize the ammonia nitrogen in the first denitrified sludge water into nitrate nitrogen, reduce the ammonia nitrogen concentration in the effluent of the secondary sedimentation tank 1, and reduce the toxicity and eutrophication problems of the water body. After performing micro-aerobic aeration pretreatment on the denitrified sludge separated by the secondary sedimentation tank 1 again, it enters the first denitrification reaction tank A1 and the first nitrification reaction tank O1 again for denitrification reaction and nitrification reaction, effectively achieving denitrification while reducing greenhouse gas emissions.

[0037] According to the embodiment of the present invention, improving the expression of the nitrous oxide reduction gene includes improving the transcriptional expression of the nitrous oxide reduction gene and / or enhancing the activity of nitrous oxide reductase.

[0038] According to an embodiment of the present invention, in step S1, the reflux ratio of denitrifying sludge is 50%-100%, for example, it can be 50%, 80%, 90%, 100%. Among them, the reflux ratio is expressed as the ratio of the flow rate of reflux sludge to the influent flow rate. The denitrifying sludge reflux ratio within the above range can maintain the denitrifying sludge concentration in the reaction tank. The time for micro-aerobic aeration pretreatment is 1.5-3h, for example, it can be 1.5h, 2h, 2.5h, 3h, and preferably 2h. Micro-aerobic aeration pretreatment can also solve problems such as N2O generated during the sludge sedimentation process and the increase in ammonia nitrogen caused by anaerobic decomposition of sludge.

[0039] According to an embodiment of the present invention, the "denitrifying sludge" is the sludge after denitrification treatment through denitrification reaction and nitrification reaction. When the denitrifying sludge is activated sludge, the concentration of the denitrifying sludge is 3-5g / L, where the activated sludge includes: denitrifying bacteria, nitrite-oxidizing bacteria, and ammonia-oxidizing bacteria. During the micro-aerobic aeration pretreatment process, the expression of N2O reduction genes in the denitrifying sludge can be fully enhanced, and at the same time, the ammonia nitrogen (NH3 / NH4 + or expressed as NH4 + -N) in the denitrifying sludge is converted into nitrate nitrogen through micro-aerobic nitrification reaction. Nitrate nitrogen includes nitrite nitrogen (NO2-N) and nitrate nitrogen (NO3-N). Nitrite nitrogen (NO2-N) can be oxidized into nitrate nitrogen (NO3-N) under micro-aerobic (0.2mg / L) conditions.

[0040] According to an embodiment of the present invention, when the denitrifying sludge is a mixed sludge of activated sludge and anaerobic ammonium oxidation sludge, the mass ratio of the two mixtures is 1:1, and the concentration of the denitrifying sludge is 3-5g / L. In addition to the various bacteria in the aforementioned activated sludge, the denitrifying sludge also includes anaerobic ammonium oxidizing bacteria in the anaerobic ammonium oxidation sludge. Therefore, during the micro-aerobic aeration pretreatment process, by controlling the dissolved oxygen concentration at 0.2mg / L, in addition to enhancing the expression of N2O reduction genes in the denitrifying sludge, it will not inhibit the activity of anaerobic ammonium oxidizing bacteria. Furthermore, during the micro-aerobic aeration pretreatment process, a nitrification reaction is accompanied by an anaerobic ammonium oxidation reaction, converting ammonia nitrogen and nitrite nitrogen in the denitrifying sludge into nitrogen gas to achieve denitrification. If the dissolved oxygen concentration is higher than 0.2mg / L during the micro-aerobic aeration pretreatment process, the activity of anaerobic ammonium oxidizing bacteria in the anaerobic ammonium oxidation sludge will be inhibited; if the dissolved oxygen concentration is lower than 0.2mg / L, the purpose of enhancing the expression of N2O reduction genes cannot be achieved.

[0041] According to an embodiment of the present invention, by controlling the dissolved oxygen concentration in the micro-aerobic aeration pretreatment and nitrification reaction at 0.2mg / L, it can also reduce the aeration energy consumption and operating costs, save energy, and have no secondary pollution.

[0042] According to an embodiment of the present invention, in step S2, the distributed influent in the first denitrification reaction tank A1 is 50%-100%, for example, it can be 50%, 70%, 80%, 90%, 100%. The distributed influent can be domestic sewage or livestock and poultry breeding sewage. The influent includes organic matter and ammonia nitrogen. By distributing the influent, sufficient organic carbon source and ammonia nitrogen are provided for denitrifying bacteria to ensure their normal physiological activities. The "first denitrification reaction tank A1" can represent an anoxic zone or an anaerobic zone (preferably an anoxic zone), where denitrification reaction occurs, and continuous stirring is carried out during this period to promote the mass transfer process. The denitrification effect of the sewage is determined according to the concentration change trend of nitrite and nitrate in the sewage; the dynamic chamber method is used to collect the gas generated during the denitrification reaction, so as to determine the effect of micro-aerobic aeration pretreatment on N2O emission reduction during the denitrification process. The term "denitrification reaction" refers to the reduction of nitrate nitrogen (NO3-N) or nitrite nitrogen (NO2-N) to nitrogen gas in an anaerobic or anoxic environment. The specific reduction process can be expressed as: nitrate nitrogen (NO3-N) → nitrite nitrogen (NO2-N) → nitric oxide (NO) → nitrous oxide (N2O) → nitrogen gas (N2). These four-step reactions are completed by the transcriptional expression of four types of functional enzymes using nitrate reductase gene, nitrite reductase gene, nitric oxide reductase gene (norB), and nitrous oxide reductase gene (nosZ).

[0043] According to an embodiment of the present invention, when the denitrifying sludge is activated sludge, only denitrification reaction occurs in the first denitrification reaction tank A1, reducing the nitrate nitrogen in the micro-aerobic aeration sludge to N2O. At the same time, the expression of the N2O reductase gene improved by micro-aerobic aeration pretreatment is utilized to increase the activity of nitrous oxide reductase, effectively reducing N2O to nitrogen gas, achieving greenhouse gas emission reduction and nitrogen removal.

[0044] According to an embodiment of the present invention, when the denitrifying sludge is a mixed sludge of activated sludge and anaerobic ammonium oxidation sludge, anaerobic ammonium oxidation reaction occurs simultaneously with the denitrification reaction in the first denitrification reaction tank A1. Through the anaerobic ammonium oxidation reaction, ammonia nitrogen and nitrite nitrogen (NO2-N) are converted into nitrogen gas (N2), and nitrogen removal can also be achieved.

[0045] According to an embodiment of the present invention, the "first nitrification reaction tank O1" can represent an aerobic zone with a dissolved oxygen concentration of 0.2 mg / L, where nitrification reaction occurs. The term "nitrification reaction" refers to the conversion of ammonia nitrogen into nitrate nitrogen in an aerobic environment. Specifically, the oxidation process can be expressed as ammonia nitrogen (NH3 / NH4 + )→ nitrite nitrogen (NO2-N) → nitrate nitrogen (NO3-N). The reaction bacteria involved in these two steps are ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) respectively.

[0046] Figure 3Schematic diagram of the system structure for enhancing greenhouse gas emission reduction based on aeration regulation in another embodiment of the present invention.

[0047] As Figure 3 shown, a second denitrification reaction tank A2 is arranged downstream of the first nitrification reaction tank O1 and upstream of the secondary sedimentation tank 1, thereby constructing a denitrification-nitrification-denitrification (AOA) process system. Therefore, before the first nitrified sludge water is transported to the secondary sedimentation tank 1, it further includes: transporting the first nitrified sludge water into the second denitrification reaction tank A2 to reduce the nitrate nitrogen in the first nitrified sludge water to nitrogen gas through denitrification reaction, obtaining the second denitrified sludge water.

[0048] In another embodiment of the present invention, compared with the second denitrification reaction tank A2, the first nitrification reaction tank O1 can improve the expression of N2O reduction gene in the first nitrified sludge water by micro-aeration treatment and controlling the dissolved oxygen concentration to 0.2 mg / L, while converting the ammonia nitrogen in the first nitrified sludge water into nitrate nitrogen and converting nitrite nitrogen into nitrate nitrogen. When the first nitrified sludge water enters the second denitrification reaction tank A2, the micro-aerobic environment quickly changes to an anoxic or anaerobic environment, which can enable denitrifying bacteria to more quickly adapt to the environment and fully play their roles, reducing the nitrate nitrogen in the first nitrified sludge water to N2O, and then effectively reducing N2O to N2 by using the highly expressed N2O reduction gene, obtaining the second denitrified sludge water, and realizing nitrogen removal and greenhouse gas (N2O) emission reduction. The sludge water treated by the second denitrification tank A2 can be directly transported to the secondary sedimentation tank 1 for sludge-water separation, and the obtained nitrogen-removed sludge can be recycled and repeatedly subjected to the aforementioned micro-aeration pretreatment, and then sequentially enter the first denitrification reaction tank A1, the first nitrification reaction tank O1, and the second denitrification reaction tank A2 for nitrogen removal treatment. When the sludge water in the second denitrification reaction tank A2 reaches the discharge standard, after sludge-water separation by the secondary sedimentation tank 1, it can be directly discharged into the effluent tank 2. Further, when the nitrogen-removed sludge is activated sludge, only denitrification reaction occurs in the second denitrification reaction tank A2; when the nitrogen-removed sludge is a mixed sludge of activated sludge and anaerobic ammonium oxidation sludge, denitrification reaction is accompanied by anaerobic ammonium oxidation reaction in the second denitrification reaction tank A2, converting the nitrate nitrogen (NO3-N) in the first nitrified sludge water into nitrite nitrogen (NO2-N), and then converting it into nitrogen gas (N2) through anaerobic ammonium oxidation reaction, contributing to nitrogen removal.

[0049] Further, the method for enhancing greenhouse gas reduction based on aeration regulation further includes: distributing influent water into the second denitrification reaction tank A2; wherein, the distributed influent water in the first denitrification reaction tank A1 is 50%-100%, and the distributed influent water in the second denitrification reaction tank A2 is 0%-50% (preferably 5%-50%), with a total of 100%. For example: the distributed influent water in the first denitrification reaction tank A1 is 100%, and the distributed influent water in the second denitrification reaction tank A2 is 0%, that is, there is no need to distribute influent water into the second denitrification reaction tank A2; or the distributed influent water in the first denitrification reaction tank A1 is 80% and the distributed influent water in the second denitrification reaction tank A2 is 20%; or the distributed influent water in the first denitrification reaction tank A1 is 50% and the distributed influent water in the second denitrification reaction tank A2 is 50%.

[0050] In another embodiment of the present invention, when the organic matter in the first nitrified muddy water is sufficient, influent water may not be distributed, but the organic matter contained in the first nitrified muddy water is used for denitrification reaction; when the organic matter in the first nitrified muddy water is insufficient, the influent water can be distributed and the proportion of the distributed influent water in the first denitrification reaction tank A1 and the second denitrification reaction tank A2 (5%-50%) can be controlled to provide sufficient organic carbon sources for the denitrifying bacteria in the second denitrification reaction tank A2 to ensure their normal physiological activities and also help reduce greenhouse gas (N2O) emissions.

[0051] According to another embodiment of the present invention, continue as Figure 3 shown, a second nitrification reaction tank O2 is arranged downstream of the second denitrification reaction tank A2 and upstream of the secondary sedimentation tank 1 to construct a denitrification-nitrification-denitrification-nitrification (AOAO) process system, and the dissolved oxygen concentration in the second nitrification reaction tank O2 is controlled. Therefore, before the second denitrified muddy water enters the secondary sedimentation tank 1, it further includes: conveying the second denitrified muddy water into the second nitrification reaction tank O2 and controlling the dissolved oxygen concentration at 0.2 mg / L, so that the ammonia nitrogen in the second denitrified muddy water is converted into nitrate nitrogen through nitrification reaction to obtain the second nitrified muddy water. By setting the second nitrification reaction tank O2, the ammonia nitrogen in the second denitrified muddy water can be converted into nitrate nitrogen, and the converted nitrate nitrogen can be used as the substrate for the subsequent denitrification reaction; or when the discharge requirements are met, it can be directly introduced into the secondary sedimentation tank 1 for mud-water separation and then discharged through the effluent tank 2. Further, when the denitrifying sludge is activated sludge, only nitrification reaction occurs in the second nitrification reaction tank O2; when the denitrifying sludge is a mixed sludge of activated sludge and anaerobic ammonium oxidation sludge, nitrification reaction occurs in the second nitrification reaction tank O2 and is accompanied by anaerobic ammonium oxidation reaction (i.e., nitrite-anaerobic ammonium oxidation reaction), converting the ammonia nitrogen and nitrite nitrogen (NO2-N) in the second denitrified muddy water into nitrogen gas (N2), contributing to nitrogen removal and emission reduction.

[0052] As a second aspect of the present invention, there is provided a system for enhancing greenhouse gas emission reduction based on aeration regulation, which is applicable to implementing the method for enhancing greenhouse gas emission reduction based on aeration regulation in the above-mentioned embodiments. As Figures 2 - 3 shown, the system includes: a secondary sedimentation tank 1, a micro-aerobic aeration pretreatment unit 3, a first denitrification reaction tank A1, a first nitrification reaction tank O1 that are connected in sequence and form a circulation loop, an inlet tank 4 for distributing influent water to the first denitrification reaction tank A1, an outlet tank 2 for receiving the effluent from the secondary sedimentation tank 1, stirrers and gas monitoring units located in the first denitrification reaction tank A1 and the first nitrification reaction tank O1, an aeration assembly located in the first nitrification reaction tank O1, and pipes for connection.

[0053] In an embodiment of the present invention, the first nitrification reaction tank O1 is arranged downstream of the first denitrification reaction tank A1 to construct a denitrification-nitrification (AO) process system. In the present invention, a micro-aerobic aeration pretreatment unit 3 is arranged between the secondary sedimentation tank 1 and the first denitrification reaction tank A1, so that the denitrifying sludge is subjected to micro-aerobic aeration pretreatment before entering an anoxic or anaerobic environment, improving the expression of N2O reduction genes in the denitrifying sludge, and at the same time converting the ammonia nitrogen in the denitrifying sludge into nitrate nitrogen. After being subjected to micro-aerobic aeration pretreatment by the micro-aerobic aeration pretreatment unit 3, it flows back into the first denitrification reaction tank A1 and quickly changes from a micro-aerobic environment to an anoxic or anaerobic environment, enabling the denitrifying bacteria in the micro-aerobic aeration sludge to quickly adapt to the anoxic or anaerobic environment, and carrying out denitrification reaction under the condition of distributed influent water to achieve efficient biological nitrogen removal from sewage while effectively reducing the emission of greenhouse gas N2O.

[0054] According to another embodiment of the present invention, as Figure 3As shown in the figure, the above system for enhancing greenhouse gas reduction based on aeration regulation further includes: a second denitrification reaction tank A2 provided downstream of the first nitrification reaction tank O1 and upstream of the secondary sedimentation tank 1, thereby constructing a denitrification-nitrification-denitrification (AOA) process system; wherein, a stirrer is provided in the second denitrification reaction tank A2; and an inlet pipeline connected to the inlet tank 4 is also optionally provided to distribute or not distribute the influent water to the second denitrification reaction tank A2. The constructed AOA process system can also achieve sewage denitrification and enhanced greenhouse gas reduction. Further, according to the water quality characteristics, the proportion of influent water distributed in the first denitrification reaction tank A1 and the second denitrification reaction tank A2, and the residence time (i.e., the operation time) of each reaction tank are controlled to improve the denitrification and N2O emission reduction effects. For example: the residence time of the first denitrification reaction tank A1 is 2h, the residence time of the first nitrification reaction tank O1 is 3 - 4h, and the residence time of the second denitrification reaction tank A2 is 2h. The traditional AO process requires sludge and mixed liquor reflux, and the reflux ratio of the mixed liquor is 300% - 400%, with relatively high energy consumption. However, in the present invention, through the use of micro-aerobic aeration pretreatment, the expression of N2O reduction genes is improved while the denitrification effect of the denitrification reaction is enhanced; or through the AOA process system, further denitrification reaction is carried out in the second denitrification reaction tank A2, without the need for mixed liquor reflux, which helps to reduce the energy consumption of mixed liquor reflux.

[0055] According to another embodiment of the present invention, continue as Figure 3 As shown in the figure, the above system for enhancing greenhouse gas reduction based on aeration regulation further includes: a second nitrification reaction tank O2 provided downstream of the second denitrification reaction tank A2 and upstream of the secondary sedimentation tank 1, thereby constructing a denitrification-nitrification-denitrification-nitrification (AOAO) process system; wherein, a stirrer and an aeration assembly are provided in the second nitrification reaction tank O2. The constructed AOAO process system can reduce greenhouse gas emissions while achieving denitrification.

[0056] According to the embodiment of the present invention, gas detection units are also installed in the second denitrification reaction tank A2 and the second nitrification reaction tank O2 for detecting N2O gas.

[0057] According to the embodiment of the present invention, the micro-aerobic aeration pretreatment unit 3 is provided with an aeration assembly, which is the same as the aeration assemblies provided in the first nitrification reaction tank O1 and the second nitrification reaction tank O2. The aeration assembly may include at least one of an aeration blower, an aeration pipeline, a valve, a flowmeter, and an aeration head, and the concentration of dissolved oxygen is controlled while aerating.

[0058] The following combines specific embodiments to detail the method for enhancing greenhouse gas reduction based on aeration regulation provided by the present invention. Unless otherwise specified, the reagents and materials used can be obtained from commercial sources.

[0059] Example 1

[0060] (I) Micro-aerobic aeration treatment

[0061] Add 200 mL of denitrifying sludge into a 500 mL wide-mouth bottle, and the concentration of the denitrifying sludge is 4.0 g / L. Use an aeration component (such as an aeration pump) to perform micro-aerobic aeration pretreatment on the denitrifying sludge for 2 hours, and use a flow meter to control the aeration rate to maintain the dissolved oxygen concentration at 0.2 mg / L during the micro-aerobic aeration process. Among them, the initial source of the denitrifying sludge is the activated sludge taken from a municipal wastewater treatment plant and the anaerobic ammonium oxidation sludge mixed at a mass ratio of 1:1, and the sludge is washed 3 times with deoxygenated phosphate buffer solution.

[0062] (II) Prepare sludge with different treatments

[0063] Prepare two identical wide-mouth bottles. Add the micro-aerobic aeration sludge obtained by the above micro-aerobic aeration pretreatment into one wide-mouth bottle, that is, the experimental group; add sludge with the same biomass (i.e., without micro-aerobic aeration pretreatment) into the other wide-mouth bottle and let it stand for 2 h to simulate the sludge sedimentation and reflux process in the wastewater treatment plant, and keep it sealed during the standing period as the control group.

[0064] (III) Denitrification reaction - nitrification reaction

[0065] Add 100 mL of actual domestic sewage taken from a municipal wastewater treatment plant into the sludge systems of the above experimental group (after micro-aerobic aeration pretreatment) and the control group (standing treatment) respectively. Continuously purge the headspace with nitrogen (40 mL / min) to maintain an anoxic environment, and stir at a speed of 120 rpm so that the sludge and the actual domestic sewage in the experimental group and the control group can fully contact. Continuously stir and maintain anoxia for 2 hours.

[0066] After entering the anoxic denitrification reaction stage, continuously purge nitrogen into the wide-mouth bottles of the experimental group and the control group, and the nitrogen flow rate is 40 mL / min. Collect the gas every 15 minutes and transfer it to a gas bag to detect the production amount of nitrous oxide (N2O) gas. At the same time, take the sewage through a 0.45 μm membrane every 30 minutes to detect the total nitrogen (TN) and chemical oxygen demand (COD) in the water body; and take the denitrifying sludge before the test (without micro-aerobic aeration pretreatment, that is, the inoculated sludge), the sludge samples 5 minutes after the distribution of the influent, and the sludge samples at the end of the denitrification reaction respectively to measure the enzyme activities of nitrous oxide reductase (NOS) and nitric oxide reductase (NOR).

[0067] Figure 4 It is a graph showing the changes in the sewage quality during the denitrification reaction of the micro-aerobic aeration pretreatment (experimental group) and the control group in Example 1 of the present invention.

[0068] AsFigure 4 As shown, regardless of whether micro-aerobic aeration pretreatment is carried out, the nitrogen concentrations in ammonia nitrogen (NH4 + -N), nitrate nitrogen (NO3-N), and nitrite nitrogen (NO2-N) in the water quality do not change significantly, and the pollutant removal in the experimental group after micro-aerobic aeration pretreatment is similar to that in the control group, indicating that micro-aerobic aeration pretreatment has no adverse effect on the biological nitrogen removal reaction of sewage and has an emission reduction effect on N2O emissions.

[0069] Furthermore, N2O emitted during the anoxic biological nitrogen removal process in the first denitrification reaction tank A1 of the experimental group and the control group was collected, and the N2O emission situation was analyzed. The specific test results are as Figure 5 shown.

[0070] Figure 5 This is the N2O emission situation diagram of the micro-aerobic aeration pretreatment (experimental group) and the control group in the denitrification reaction process in Example 1 of the present invention.

[0071] As Figure 5 shown, after micro-aerobic aeration pretreatment, the obtained micro-aerobic aeration sludge undergoes denitrification reaction in an anoxic environment, and the N2O emission situation is significantly lower than that of the control group (without micro-aerobic aeration pretreatment) after 15 minutes. Moreover, with the progress of the denitrification reaction, the experimental group pretreated with micro-aerobic aeration can achieve a cumulative N2O gas emission reduction of 23%.

[0072] Furthermore, ribonucleic acid (RNA) was extracted from the sludge before and after micro-aerobic aeration pretreatment, and reverse transcription quantitative PCR (RT-qPCR, reverse transcription real-time quantitative polymerase chain reaction) was used to measure the transcriptional expression of nitric oxide reductase genes (qnorB and cnorB) and nitrous oxide reductase gene (nosZ) in the sludge. Specifically, an RNA extraction kit (R6828 Omega, USA) was used to extract RNA from the sludge samples. The extracted RNA was reverse transcribed into complementary DNA (cDNA) using a QuantiTect reverse transcription kit (QIAGEN, Hilden, Germany). A standard curve was made using plasmids constructed with three genes, and a quantitative PCR instrument (7900HT, ABIPRISM, USA) was used for measurement. The test results Figures 6 - 7 are shown.

[0073] Figure 6 This is the diagram of the transcriptional expression of nitric oxide reductase genes in the sludge before and after micro-aerobic aeration pretreatment in Example 1 of the invention.

[0074] As Figure 6As shown, after microaerobic aeration pretreatment, the transcriptional expression levels of the two nitric oxide reduction genes (qnorB and cnorB) decreased by approximately 20% compared to before microaerobic aeration pretreatment.

[0075] Figure 7 It is a diagram showing the transcriptional expression of nitrous oxide reduction genes in the sludge before and after microaerobic aeration pretreatment in Example 1 of the invention.

[0076] As Figure 7 shown, after microaerobic aeration pretreatment, the transcriptional expression level of the nitrous oxide reduction gene (nosZ) increased by 69% compared to before microaerobic aeration pretreatment. This indicates that microaerobic aeration pretreatment can enhance the expression of N2O reduction genes, increase the rate of N2O reduction to N2 in the denitrification reaction, and thus reduce the emission of the greenhouse gas N2O.

[0077] Furthermore, the enzyme activities in the sludge in the first denitrification reaction tank A1 were measured to determine the activities of nitrous oxide reductase (NOS) and nitric oxide reductase (NOR). Specifically, the process of extracting NOS and NOR functional enzymes from the sludge and measuring their activities is as follows.

[0078] Extraction and measurement of proteins: ① Extraction of proteins from the sludge: The cells in the sludge were broken by ice-bath ultrasonic waves (power 300w, ultrasonic wave for 3 seconds, interval 7 seconds, total breaking time 3 min); then centrifuged at a speed of 10000 rpm at 4°C for 10 min, and the supernatant was taken and placed on ice for further measurement. ② Detection of the protein content in the sludge by the bicinchoninic acid (BCA) method: To the proteins extracted from the sludge by ultrasonic waves in the ice bath, add the BCA working solution and a color reaction occurs. The absorbance is measured by spectrophotometry, and the standard curve is prepared by gradient dilution of bovine serum albumin.

[0079] The double antibody sandwich method was used to measure the activities of NOR and NOS. Test method: The sludge samples were ultrasonically broken in the ice bath to extract NOR and NOS enzyme proteins. The pretreated protein samples were added to the microtiter plate coated with purified enzyme antibodies, and then the labeled enzyme antibodies were added to form an antibody-antigen-enzyme-labeled antibody complex. The complex was stained with the label, and then the absorbance at a wavelength of 450 nm was measured. Using the purified NOR and NOS enzyme proteins as standard samples, a standard curve was drawn to determine the activity of the enzyme to be measured in the sample. The enzyme activity was characterized in units of ng / mg-protein (ng / mg-protein), and the test results are shown in Figure 8 .

[0080] Figure 8 It is a diagram showing the changes in enzyme activities in the sludge of the experimental group and the control group during the denitrification reaction in Example 1 of the present invention.

[0081] AsFigure 8 As shown in the figure, in the control group, by measuring the activities of NOR and NOS enzymes, it was found that: before the experiment (without any treatment), the activity of NOR in the denitrifying sludge without micro-aerobic aeration pretreatment was stronger than that of NOS. The reason is that the reduction of nitric oxide (NO) is the previous step of the reduction of nitrous oxide (N2O). NOR preferentially utilizes electrons compared to NOS, and the higher activity of NOR than NOS in the sludge is the main reason for the release of N2O in the denitrification reaction. After distributing the influent water and conducting the denitrification reaction for 5 minutes and at the end of the denitrification reaction, the activities of NOR and NOS in the control group were significantly higher than those before the experiment, and the activity of NOR was still higher than that of NOS. In the experimental group, before the experiment (i.e., without micro-aerobic aeration pretreatment), the activity of NOR was slightly stronger than that of NOS. After the sludge was pretreated by micro-aerobic aeration, during the distribution of influent water and the denitrification reaction, the nitrous oxide reduction gene (nosZ) in the sludge was highly expressed, resulting in a significant increase in the activity of NOS in the sludge pretreated by micro-aerobic aeration compared to the control group, and the activity of NOS was slightly higher than that of NOR. Among them, after the sludge pretreated by micro-aerobic aeration was subjected to the denitrification reaction for 5 minutes, the activity of NOS was 0.0137 ng / mg-protein (i.e., ng / mg-protein), which was significantly higher than 0.011 ng / mg-protein in the control group. This significantly improved the reduction ability of N2O during the denitrifying biological nitrogen removal process, and it was expected to achieve a balance between the production and reduction of N2O, ultimately effectively reducing the emission of the greenhouse gas N2O during the biological nitrogen removal process.

[0082] Example 2

[0083] The activated sludge taken from a municipal wastewater treatment plant was mixed with anammox sludge at a mass ratio of 1:1, and the mixture was used as the initial source of denitrifying sludge. The denitrifying sludge was pretreated by micro-aerobic aeration (0.2 mg / L) in a cylindrical reactor with a volume of 15.9 L. The pH in the reaction tank was maintained at 7.0 - 8.0, and the temperature was 26 - 30 °C. The test water was taken from a municipal wastewater treatment plant in Beijing, and the average carbon-nitrogen ratio (COD / N) of the influent water was 2.83, belonging to low-carbon-nitrogen ratio sewage. The hydraulic retention time of the reactor was 18 h.

[0084] In Example 2, the reactor is divided into four operating stages, including: Stage I is a denitrification-nitrification (AO) process, in which 100% of the influent is distributed to the first denitrification reaction tank A1; Stage II is a denitrification-nitrification-denitrification (AOA) process, in which 100% of the influent is distributed to the first denitrification reaction tank A1; Stage III is also an AOA process, in which 80% of the influent is distributed to the first denitrification reaction tank A1 and 20% of the influent is distributed to the second denitrification reaction tank A2; Stage IV is a denitrification-nitrification-denitrification-nitrification (AOAO) process, in which 50% of the influent is distributed to the first denitrification reaction tank A1 and 50% of the influent is distributed to the second denitrification reaction tank A2. The muddy water output from the denitrification reaction or nitrification reaction enters the secondary sedimentation tank 1 for sedimentation separation, and the obtained denitrified sludge is recycled back to the cylindrical reactor for micro-aerobic aeration pretreatment. Specifically, the operating conditions of the four stages (operating time of each stage; residence times of A1, O1, A2, O2; COD and ammonia nitrogen concentrations in the influent) are shown in Table 1, in which the first nitrification reaction tank O1 and the second nitrification reaction tank O2 are treated with micro-aerobic aeration, and the dissolved oxygen (DO) concentration is controlled at 0.2 mg / L for a duration of 2 h. The removal rates and removal efficiencies of COD and total nitrogen (TN) in the four stages are shown in Table 2.

[0085] Table 1. Operating Conditions and Influent Water Quality of Each Stage

[0086]

[0087] Table 2. COD and TN Removal Efficiencies and Removal Rates of Each Stage

[0088]

[0089] As shown in Tables 1-2, compared with Stage I, the removal effect of TN is significantly improved in Stages II to IV, indicating good sewage denitrification effect.

[0090] Furthermore, the dynamic chamber method is used to collect the N2O gas emissions in a single working cycle of the above four stages, and the dissolved N2O in each stage of the reactor is monitored using an N2O microelectrode. The specific test conditions are as Figures 9 - 12 shown.

[0091] Figure 9 This is the N2O gas emission situation in Stage I of Example 2 of the present invention, Figure 10 This is the N2O gas emission situation in Stage II of Example 2 of the present invention, Figure 11 This is the N2O gas emission situation in Stage III of Example 2 of the present invention, Figure 12 This is the N2O gas emission situation in Stage IV of Example 2 of the present invention.

[0092] AsFigures 9 - 12 As shown, in the first denitrification reaction tank A1, after the influent is distributed, the denitrifying bacteria in the microaerobic aerated sludge use the organic matter in the distributed influent as a carbon source, and can reduce the nitrate nitrogen in the sludge to N2O through denitrification reaction. By using the enhanced expression of nitrous oxide reduction genes by microaerobic aeration pretreatment, N2O can be effectively reduced to nitrogen gas (N2), showing a decrease in the N2O concentration in the first denitrification reaction tank A1 and a reduction in gaseous N2O emissions. As the reaction progresses, the release of gaseous N2O gradually decreases with the prolongation of the denitrification reaction time. After microaerobic aeration treatment in the first nitrification reaction tank O1, the nitrous oxide reduction genes can still maintain good gene expression under microaerobic conditions, further realizing the reduction of N2O, showing a further decrease in the gaseous N2O concentration in the first nitrification reaction tank O1, and even no release of gaseous N2O. There is no release of gaseous N2O in the second denitrification reaction tank A2. Further, in stage III and stage IV, after distributing 20% or 50% of the influent to the second denitrification reaction tank A2, no gaseous N2O release is still detected in the second denitrification reaction tank A2, indicating that microaerobic aeration treatment has a good control effect on the N2O release in the second denitrification reaction tank A2.

[0093] In summary, the present invention promotes the enhanced expression of nitrous oxide reduction genes by microaerobic aeration treatment of denitrifying sludge, keeps the activities of NOS and NOR at the same level, helps to accelerate the reduction of N2O, balances the generation and reduction of N2O, effectively reduces the N2O emissions in the biological nitrogen removal process, and at the same time reduces the content of nitrogen-containing pollutants in the sewage. The system of the present invention based on aeration regulation to strengthen greenhouse gas emission reduction is simple to operate, has the dual effects of efficient pollutant removal and deep greenhouse gas emission reduction, and is also convenient for improvement on the existing sewage treatment process.

[0094] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for enhancing greenhouse gas reduction based on aeration regulation, characterized in that, The method includes: Step 1: Pre-treat the denitrifying sludge by micro-aerobic aeration to enhance the expression of nitrous oxide reduction genes in the denitrifying sludge, and simultaneously conduct nitrification reaction to convert part of the ammonia nitrogen in the denitrifying sludge into nitrate nitrogen, obtaining micro-aerobic aeration sludge. Among them, the concentration of dissolved oxygen in the micro-aerobic aeration pre-treatment is 0.2 mg / L. Step 2: Return the micro-aerobic aeration sludge to the first denitrification reaction tank and distribute the influent. The nitrate nitrogen in the micro-aerobic aeration sludge is reduced to nitrous oxide through denitrification reaction, and the promoted expression of the nitrous oxide reduction genes is utilized to facilitate the conversion of nitrous oxide into nitrogen gas, obtaining the first denitrification sludge-water mixture. Step 3: Transport the first denitrification sludge-water mixture to the first nitrification reaction tank and control the concentration of dissolved oxygen at 0.2 mg / L, so that the ammonia nitrogen in the first denitrification sludge-water mixture is converted into nitrate nitrogen through nitrification reaction, obtaining the first nitrification sludge-water mixture. Step 4: Transport the first nitrification sludge-water mixture to the secondary sedimentation tank for sludge-water separation, obtaining denitrifying sludge. Among them, the denitrifying sludge in Step 1 is the denitrifying sludge from the secondary sedimentation tank in Step 4, and Steps 1 to 4 are repeated.

2. The method according to claim 1, characterized in that, Before transporting the first nitrification sludge-water mixture to the secondary sedimentation tank, it further includes: Transporting the first nitrification sludge-water mixture to the second denitrification reaction tank to reduce the nitrate nitrogen in the first nitrification sludge-water mixture to nitrogen gas through denitrification reaction, obtaining the second denitrification sludge-water mixture.

3. The method according to claim 2, characterized in that, The method further includes: Distributing the influent into the second denitrification reaction tank; Among them, the distributed influent in the first denitrification reaction tank is 50%-100%, and the distributed influent in the second denitrification reaction tank is 0-50%, with a total of 100%.

4. The method according to claim 2 or 3, characterized in that, Before the second denitrification sludge-water mixture enters the secondary sedimentation tank, it further includes: Transporting the second denitrification sludge-water mixture to the second nitrification reaction tank and controlling the concentration of dissolved oxygen at 0.2 mg / L, so that the ammonia nitrogen in the second denitrification sludge-water mixture is converted into nitrate nitrogen through nitrification reaction, obtaining the second nitrification sludge-water mixture.

5. The method according to claim 4, characterized in that, The reflux ratio of the denitrifying sludge is 50%-100%; The time of the micro-aerobic aeration pre-treatment is 1.5-3 h; The nitrate nitrogen includes nitrite nitrogen and nitrate nitrogen; The components in the influent include: organic matter and ammonia nitrogen; The first denitrification reaction tank and the second denitrification reaction tank are anoxic zones or anaerobic zones.

6. The method according to claim 5, characterized in that, The denitrifying sludge is: activated sludge, or a mixed sludge of activated sludge and anaerobic ammonium oxidation sludge, with a mixing mass ratio of 1:1, and the concentration of the denitrifying sludge is 3-5 g / L.

7. The method according to claim 6, characterized in that, In the case where the denitrifying sludge is a mixed sludge of activated sludge and anaerobic ammonium oxidation sludge, during the denitrification reaction and nitrification reaction, an anaerobic ammonium oxidation reaction is simultaneously carried out to convert ammonia nitrogen and nitrite nitrogen into nitrogen gas, achieving nitrogen removal.

8. A system for enhancing greenhouse gas reduction based on aeration regulation, suitable for implementing the method according to any one of claims 1-7, characterized in that, The system includes: A secondary sedimentation tank, a micro-aerobic aeration pre-treatment unit, a first denitrification reaction tank, and a first nitrification reaction tank that are connected in sequence and form a circulation loop, and An inlet tank for distributing influent water to the first denitrification reaction tank, an outlet tank for receiving the effluent from the secondary sedimentation tank, agitators and gas monitoring units located in the first denitrification reaction tank and the first nitrification reaction tank, an aeration assembly located in the first nitrification reaction tank, and pipes for connection.

9. The system according to claim 8, characterized in that, The system further includes: a second denitrification reaction tank disposed downstream of the first nitrification reaction tank and upstream of the secondary sedimentation tank; wherein, an agitator is disposed in the second denitrification reaction tank; and an influent pipe connected to the inlet tank to distribute influent water to the second denitrification reaction tank or not.

10. The system according to claim 9, characterized in that, The system further includes: a second nitrification reaction tank disposed downstream of the second denitrification reaction tank and upstream of the secondary sedimentation tank; wherein, an agitator and an aeration assembly are disposed in the second nitrification reaction tank.

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