Ammonia direct oxidation denitrification system and method for municipal sewage

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to an ammonia direct oxidation denitrification system and method for municipal wastewater, and the method comprises the following steps: S1, the municipal wastewater enters an anoxic acetone production reactor, and under the anoxic condition, part of organic carbon sources in the municipal wastewater are directionally converted into acetone through functional microorganisms; s2, the effluent from the S1 enters an aerobic AMAO denitrification reactor, and ammonia nitrogen in the municipal sewage is directly oxidized into nitrogen through AMAO functional microorganisms under the aerobic condition; and S3, carrying out solid-liquid separation on a mixed solution discharged by the aerobic AMAO denitrification reactor in the S2, and refluxing a part of sludge obtained by separation to the anoxic acetone production reactor. According to the method, part of organic matters are directionally converted into a recyclable acetone dielectric conductor under an anoxic condition, then ammonia nitrogen is driven by acetone to be directly oxidized into nitrogen under an aerobic condition, and a carbon source in the system is recycled through sludge backflow, so that deep denitrification is realized under the condition that no or few additional carbon sources are needed.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a direct ammonia oxidation denitrification system and method for municipal wastewater. Background Technology

[0002] Municipal wastewater treatment plants generally face pressure to meet strict standards for total nitrogen (TN) in effluent (e.g., below 15 mg / L). Currently, the most widely used biological nitrogen removal technology remains the traditional nitrification-denitrification process and its variants (such as A). 2 The / O process. However, this technical approach has two inherent drawbacks: First, it requires a sufficient organic carbon source to drive the denitrification process. However, the typical carbon-to-nitrogen ratio of municipal wastewater is usually only 3-8, resulting in a relative shortage of carbon sources, leading to incomplete denitrification and high nitrate concentrations in the effluent. To solve this problem, it is often necessary to add exogenous carbon such as methanol and sodium acetate, which not only significantly increases operating costs (carbon source costs can account for more than 30% of operating expenses), but also poses the risk of complex addition control and excessive addition leading to excessive chemical oxygen demand (COD) in the effluent. Second, the process path is circuitous and lengthy, requiring high-energy-consuming complete nitrification (requiring a large amount of aeration) and anoxic denitrification in sequence, resulting in high total energy consumption. Although innovative technologies such as short-cut nitrification-anaerobic ammonium oxidation can save carbon sources and energy consumption, their successful application heavily depends on the stable maintenance of nitrite, and the control requirements for organic matter, temperature, pH, and dissolved oxygen are extremely stringent. Moreover, they are difficult to start up and operate unstablely under the low-temperature and low-carbon conditions of municipal wastewater, making large-scale promotion difficult.

[0003] Therefore, developing a new denitrification technology that can adapt to municipal wastewater quality, make full use of internal carbon sources, operate stably, and save energy is an urgent need for the industry.

[0004] In recent years, we have made significant progress in exploring novel microbial ammonia oxidation processes, discovering a process called acetone-mediated ammonium oxidation (AMAO, where acetone + ammonia → acetone oxime → acetone + nitrogen). This discovery not only breaks through the traditional framework of nitrogen cycle understanding but also provides a completely new approach to solving the problem of nitrogen removal in municipal wastewater. AMAO functional microorganisms are widely distributed in natural ecosystems and are often dominant bacteria in the environment, involving most bacterial phyla, including common phyla such as Proteobacteria, Bacteroidetes, Firmicutes, Acidobacteria, and Actinobacteria. This provides a feasibility for enriching and cultivating a stable AMAO bacterial community in municipal wastewater systems. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to overcome the above-mentioned shortcomings and provide a direct ammonia oxidation denitrification system and method for municipal wastewater, thereby solving the problems of existing municipal wastewater denitrification technologies such as heavy reliance on external carbon sources, high process energy consumption, and complex control.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for direct ammonia oxidation denitrification of municipal wastewater includes the following steps: S1. Municipal wastewater enters an anaerobic acetone-producing reactor. Under anaerobic conditions, functional microorganisms directionally convert some of the organic carbon sources in the municipal wastewater into acetone. S2. The effluent from S1 enters the aerobic AMAO denitrification reactor. Under aerobic conditions, acetone from S1 is used as a carbon source and electron mediator. AMAO functional microorganisms directly oxidize ammonia nitrogen in municipal sewage into nitrogen gas. S3. The mixed liquid discharged from the aerobic AMAO denitrification reactor in S2 is subjected to solid-liquid separation to obtain the supernatant as effluent, and part of the separated sludge is returned to the anoxic acetone production reactor to realize internal carbon source recycling.

[0007] Furthermore, the functional microorganisms in the anoxic acetone-producing reactor are a complex microbial community including Clostridium species.

[0008] Furthermore, the anoxic acetone-producing reactor converts 5%-30% of the biodegradable chemical oxygen demand (COD) in municipal wastewater into acetone by controlling the hydraulic retention time to 2-6 hours and the pH to 5.5-6.5.

[0009] Furthermore, the aerobic AMAO denitrification reactor stabilizes the dissolved oxygen concentration at 0.5-2.0 mg / L by controlling aeration, and the hydraulic retention time is 3-8 hours, so as to control the total nitrogen removal load of the aerobic AMAO denitrification reactor to be 0.05-0.4 kg N / (m3·d), and the concentrations of nitrite and nitrate in the effluent are both below 1 mg / L.

[0010] Furthermore, in step S3, the sludge return ratio is 30%-100% of the municipal sewage flow rate. The microbial residues, unused dissolved organic matter, and intermediate products contained in the returned sludge are converted back into acetone as a supplementary carbon source in the anoxic acetone-producing reactor.

[0011] Traditional processes treat the complex organic matter in wastewater as a homogeneous "denitrification carbon source." This invention, however, is based on a re-examination and control of the "quality" and "quantity" of carbon sources in municipal wastewater. By introducing the concept of "directed biotransformation," an anoxic acetone-producing reactor is set up at the front end of the system. The core function of this reactor is not to maximize COD removal, but rather to act as a "biological factory." Under specific process conditions (strict anoxic, suitable pH, and residence time), dominated by acetone-producing bacteria such as Clostridium, some organic matter in the wastewater is selectively and efficiently converted into acetone. Unlike traditional methods that use carbon sources as consumable electron donors, acetone, as a medium, can be recycled. Therefore, the demand for acetone is not high (the molar ratio of acetone to ammonia nitrogen ranges from 0.01 to 0.1, and the C / N ratio is 0.26 to 2.6). Generally, municipal wastewater can produce enough acetone to maintain the AMAO reaction. If there is insufficient acetone production due to drastic fluctuations in water quality, a small amount of acetone can be added. Subsequently, wastewater rich in acetone and ammonia nitrogen enters the aerobic AMAO denitrification reactor. Here, specific AMAO functional microorganisms utilize acetone as a medium to directly oxidize ammonia nitrogen into nitrogen gas in one step under micro-aerobic conditions. This reaction pathway is extremely short, requiring minimal aeration (far less than nitrification).

[0012] To address the challenge of fluctuating total carbon sources in municipal wastewater, this invention proposes a "carbon source internal circulation" strategy to enhance the supply of substrates for acetone synthesis. Part of the sludge (rich in microbial cell matter and potentially adsorbed organic matter) from the sedimentation tank following the aerobic AMAO denitrification reactor is recycled to the upstream anoxic acetone-producing reactor. Under the action of anoxic acetone-producing bacteria, the organic components in this recycled sludge can be decomposed again and partially converted into acetone, thus forming an internal carbon cycle within the system. This recaptures and utilizes carbon that would normally be discarded as waste sludge, effectively increasing the total effective carbon source of the system without increasing the influent carbon load.

[0013] On the other hand, the present invention also provides an ammonia direct oxidation denitrification system for municipal wastewater, comprising an anoxic acetone-producing reactor, an aerobic AMAO denitrification reactor, and a sedimentation tank connected in sequence, wherein: The anoxic acetone-producing reactor is used to convert some of the organic carbon sources in wastewater into acetone through functional microorganisms under anoxic conditions. The aerobic AMAO denitrification reactor is used to directly oxidize ammonia nitrogen into nitrogen gas by using acetone as a carbon source and electron mediator under aerobic conditions through AMAO functional microorganisms. The sedimentation tank is used to perform solid-liquid separation on the mixed liquid discharged from the aerobic AMAO denitrification reactor, and to return part of the separated sludge to the anoxic acetone-producing reactor to achieve internal carbon source circulation within the system.

[0014] Furthermore, the anoxic acetone-producing reactor is inoculated with a complex microbial community including Clostridium species and equipped with a pH control device to maintain the pH at 5.5-6.5.

[0015] Furthermore, the aerobic AMAO denitrification reactor is equipped with a microporous aeration device, a dissolved oxygen probe, and a controller to control the dissolved oxygen concentration at 0.5-2.0 mg / L.

[0016] The beneficial effects of this invention are as follows: This invention addresses the challenges of low carbon-to-nitrogen ratios in municipal wastewater and the dual requirements of stable compliance with standards and energy conservation. Based on a novel acetone-mediated ammonia direct oxidation process (AMAO), it proposes a core technical solution: "pre-anoxic acetone production coupled with aerobic AMAO denitrification, supplemented by internal carbon source recycling." This solution involves the directional conversion of some organic matter into recyclable acetone under anoxic conditions. Subsequently, under aerobic conditions, acetone drives the direct oxidation of ammonia nitrogen into nitrogen gas. The system also utilizes sludge recirculation to reuse the internal carbon source. This achieves deep denitrification, significant energy savings, and stable operation with minimal or no external carbon source input, making it particularly suitable for upgrading existing wastewater treatment plants.

[0017] 1. One of the most prominent advantages of this invention is the significant reduction in the need for external carbon sources. Traditional processes rely on consumable carbon sources for denitrification, while this invention uses acetone as a recyclable medium, requiring only a small amount (acetone to ammonia nitrogen molar ratio of 0.01-0.1) to efficiently drive the AMAO reaction. Through the directional conversion of influent organic matter in the front-end anoxic acetone-producing reactor and the "carbon capture and recycling" mechanism formed by sludge recirculation, microbial residues and unused organic matter are converted back into acetone, maximizing and optimizing the utilization of both influent and endogenous carbon sources, thereby essentially eliminating the need for external carbon sources and significantly reducing operating costs.

[0018] 2. Achieving deep nitrogen removal and ensuring stable effluent compliance is the core effect of this invention. The AMAO pathway directly oxidizes ammonia nitrogen into nitrogen gas in one step, bypassing the traditional nitrification-denitrification process and avoiding the risk of nitrite and nitrate accumulation. The concentrations of both nitrite and nitrate in the effluent are below 1 mg / L, with a total nitrogen removal rate consistently above 95%, and total nitrogen in the effluent can be as low as below 2 mg / L. This pathway is highly adaptable to fluctuations in temperature, pH, and organic matter, and its operational stability is significantly better than technologies such as short-cut nitrification-anaerobic ammonium oxidation, meeting stringent effluent total nitrogen standards.

[0019] 3. Significant energy savings and lower sludge production further enhance economic viability. The AMAO reaction directly oxidizes ammonia to nitrogen, with a theoretical oxygen demand of only 37.5% of that required for traditional complete nitrification to nitrate. Actual aeration energy consumption is reduced by more than 50% compared to traditional processes. Simultaneously, due to the elimination of the need for external carbon sources and the optimization of carbon source utilization pathways, sludge production is significantly reduced, correspondingly lowering sludge treatment and disposal costs, resulting in a substantial decrease in overall operating energy consumption and expenses.

[0020] 4. The simplicity of the process and ease of engineering implementation are another significant advantage of this invention. The core system comprises only three units: an anoxic acetone-producing reactor, an aerobic AMAO denitrification reactor, and a sedimentation tank. The process is short, with few control parameters, facilitating integration into existing A... 2 This system is a modification based on traditional processes such as / O. Combined with a stable microbial functional group and internal circulation mechanism, it features rapid start-up and possesses high engineering application value and promotion potential.

[0021] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a flowchart of an ammonia direct oxidation denitrification system for municipal wastewater according to the present invention; Figure 2 This is a graph showing the influent COD and effluent acetone concentration of the anoxic acetone-producing reactor in this invention during stable operation. Figure 3 This is a graph showing the concentrations of ammonia nitrogen and total nitrogen in the influent and effluent of the aerobic AMAO denitrification reactor during stable operation in this invention. Detailed Implementation

[0023] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0024] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0025] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0026] like Figure 1 The image shows a direct ammonia oxidation denitrification method for municipal wastewater, comprising the following steps: S1. Municipal wastewater enters an anaerobic acetone-producing reactor. Under anaerobic conditions, functional microorganisms directionally convert some of the organic carbon sources in the municipal wastewater into acetone. S2. The effluent from S1 enters the aerobic AMAO denitrification reactor. Under aerobic conditions, acetone from S1 is used as a carbon source and electron mediator. AMAO functional microorganisms directly oxidize ammonia nitrogen in municipal sewage into nitrogen gas. S3. The mixed liquid discharged from the aerobic AMAO denitrification reactor in S2 is subjected to solid-liquid separation to obtain the supernatant as effluent, and part of the separated sludge is returned to the anoxic acetone production reactor to realize internal carbon source recycling.

[0027] Furthermore, the functional microorganisms in the anoxic acetone-producing reactor are a complex microbial community including Clostridium species.

[0028] Furthermore, the anoxic acetone-producing reactor converts 5%-30% of the biodegradable chemical oxygen demand (COD) in municipal wastewater into acetone by controlling the hydraulic retention time to 2-6 hours and the pH to 5.5-6.5.

[0029] Furthermore, the aerobic AMAO denitrification reactor stabilizes the dissolved oxygen concentration at 0.5-2.0 mg / L by controlling aeration, and the hydraulic retention time is 3-8 hours, so as to control the total nitrogen removal load of the aerobic AMAO denitrification reactor to be 0.05-0.4 kg N / (m3·d), and the concentrations of nitrite and nitrate in the effluent are both below 1 mg / L.

[0030] Furthermore, in step S3, the sludge return ratio is 30%-100% of the municipal sewage flow rate. The microbial residues, unused dissolved organic matter, and intermediate products contained in the returned sludge are converted back into acetone as a supplementary carbon source in the anoxic acetone-producing reactor.

[0031] Traditional processes treat the complex organic matter in wastewater as a homogeneous "denitrification carbon source." This invention, however, is based on a re-examination and control of the "quality" and "quantity" of carbon sources in municipal wastewater. By introducing the concept of "directed biotransformation," an anoxic acetone-producing reactor is set up at the front end of the system. The core function of this reactor is not to maximize COD removal, but rather to act as a "biological factory." Under specific process conditions (strict anoxic, suitable pH, and residence time), dominated by acetone-producing bacteria such as Clostridium, some organic matter in the wastewater is selectively and efficiently converted into acetone. Unlike traditional methods that use carbon sources as consumable electron donors, acetone, as a medium, can be recycled. Therefore, the demand for acetone is not high (the molar ratio of acetone to ammonia nitrogen ranges from 0.01 to 0.1, and the C / N ratio is 0.26 to 2.6). Generally, municipal wastewater can produce enough acetone to maintain the AMAO reaction. If there is insufficient acetone production due to drastic fluctuations in water quality, a small amount of acetone can be added. Subsequently, wastewater rich in acetone and ammonia nitrogen enters the aerobic AMAO denitrification reactor. Here, specific AMAO functional microorganisms utilize acetone as a medium to directly oxidize ammonia nitrogen into nitrogen gas in one step under micro-aerobic conditions. This reaction pathway is extremely short, requiring minimal aeration (far less than nitrification).

[0032] To address the challenge of fluctuating total carbon sources in municipal wastewater, this invention proposes a "carbon source internal circulation" strategy to enhance the supply of substrates for acetone synthesis. Part of the sludge (rich in microbial cell matter and potentially adsorbed organic matter) from the sedimentation tank following the aerobic AMAO denitrification reactor is recycled to the upstream anoxic acetone-producing reactor. Under the action of anoxic acetone-producing bacteria, the organic components in this recycled sludge can be decomposed again and partially converted into acetone, thus forming an internal carbon cycle within the system. This recaptures and utilizes carbon that would normally be discarded as waste sludge, effectively increasing the total effective carbon source of the system without increasing the influent carbon load.

[0033] On the other hand, the present invention also provides an ammonia direct oxidation denitrification system for municipal wastewater, comprising an anoxic acetone-producing reactor, an aerobic AMAO denitrification reactor, and a sedimentation tank connected in sequence, wherein: The anoxic acetone-producing reactor is used to convert some of the organic carbon sources in wastewater into acetone through functional microorganisms under anoxic conditions. The aerobic AMAO denitrification reactor is used to directly oxidize ammonia nitrogen into nitrogen gas by using acetone as a carbon source and electron mediator under aerobic conditions through AMAO functional microorganisms. The sedimentation tank is used to perform solid-liquid separation on the mixed liquid discharged from the aerobic AMAO denitrification reactor, and to return part of the separated sludge to the anoxic acetone-producing reactor to achieve internal carbon source circulation within the system.

[0034] Furthermore, the anoxic acetone-producing reactor is inoculated with a complex microbial community including Clostridium species and equipped with a pH control device to maintain the pH at 5.5-6.5.

[0035] Furthermore, the aerobic AMAO denitrification reactor is equipped with a microporous aeration device, a dissolved oxygen probe, and a controller to control the dissolved oxygen concentration at 0.5-2.0 mg / L.

[0036] Example 1 according to Figure 1 A continuous flow device was constructed, consisting of three plexiglass reactors connected in series, serving as an anoxic acetone production reactor, an aerobic AMAO denitrification reactor, and a sedimentation tank, with a total effective volume of 30L. The pH values ​​in the anoxic acetone production reactor and the aerobic AMAO denitrification reactor were automatically controlled by adding dilute hydrochloric acid or sodium hydroxide solution.

[0037] The anoxic acetone-producing reactor has an effective volume of 10L and a built-in magnetic stirrer. Aerobic AMAO denitrification reactor: Effective volume 15L, equipped with microporous aeration heads (microporous aeration devices) at the bottom, connected to a gas flow meter and air pump, and linked to a controller via an online DO probe (dissolved oxygen probe) to precisely control the aeration rate. An agitator is also installed inside the aerobic AMAO denitrification reactor to keep the sludge suspended. Sedimentation tank: 5L effective volume, achieving sludge-water separation; reflux system: a precision peristaltic pump recirculates sludge from the bottom of the sedimentation tank to the inlet of the anoxic acetone-producing reactor (sludge recirculation ratio set at 50%). The anoxic acetone-producing reactor is inoculated with Clostridium species enriched and screened from anaerobic digested sludge of municipal wastewater treatment plants. Clostridium A mixed fermentation microbial community, primarily composed of AMAO (Amino Acid Oxygenation Agent) bacteria, was used as the inoculation agent in the aerobic AMAO denitrification reactor. The treated wastewater was pretreated from a large municipal wastewater treatment plant.

[0038] The influent water quality of the anoxic acetone production reactor is as follows: COD 120-160 mg / L, NH4+ + -N 35-40 mg / L, TN 40-45 mg / L. Operation at room temperature (16-32℃). Anoxic acetone production reactor: Hydraulic retention time (HRT) controlled at 2 hours, pH stabilized at 5.5-6.5 by an automatic control system. Aerobic AMAO denitrification reactor: HRT controlled at 5 hours, DO concentration stabilized at 0.5-1.0 mg / L through precise aeration, pH maintained at 7.2-8.5. Total HRT 7 hours. After approximately 15 days of start-up and acclimatization, a 30-day stable operation monitoring period begins.

[0039] like Figure 2 and Figure 3 As shown in the figure, the test results indicate that under the set operating conditions, the acetone concentration in the effluent of the anoxic acetone-producing reactor remained stable between 6.8 and 13.6 mg / L. Calculations show that this is equivalent to converting approximately 12%-20% of the COD in the influent into acetone, successfully achieving a stable upstream acetone supply. Daily monitoring was conducted on the system's influent and effluent, as well as the effluent from the aerobic AMAO denitrification reactor. Ammonia nitrogen and total nitrogen levels were as follows: Figure 3 As shown in the figure, the system achieves an ammonia nitrogen removal rate exceeding 99.5%, a TN removal rate consistently at 95.8%, and an average TN in the effluent as low as 1.8 mg / L, demonstrating deep nitrogen removal. The total nitrogen removal load is 0.280 kg N / (m³). 3 •d) falls within the high-efficiency range described in this invention. This embodiment verifies the feasibility of the process route of this invention and confirms that this invention has significant effects such as simple process, stable operation, deep denitrification, and energy saving and consumption reduction.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for direct ammonia oxidation denitrification of municipal wastewater, characterized in that, Includes the following steps: S1. Municipal wastewater enters an anaerobic acetone-producing reactor. Under anaerobic conditions, functional microorganisms directionally convert some of the organic carbon sources in the municipal wastewater into acetone. S2. The effluent from S1 enters the aerobic AMAO denitrification reactor. Under aerobic conditions, acetone from S1 is used as a carbon source and electron mediator. AMAO functional microorganisms directly oxidize ammonia nitrogen in municipal sewage into nitrogen gas. S3. The mixed liquid discharged from the aerobic AMAO denitrification reactor in S2 is subjected to solid-liquid separation to obtain the supernatant as effluent, and part of the separated sludge is returned to the anoxic acetone production reactor to realize internal carbon source recycling.

2. The method according to claim 1, characterized in that, The functional microorganisms in the anoxic acetone-producing reactor are a complex microbial community including Clostridium species.

3. The method according to claim 1 or 2, characterized in that, The anoxic acetone-producing reactor converts 5%-30% of the biodegradable chemical oxygen demand (COD) in municipal wastewater into acetone by controlling the hydraulic retention time to 2-6 hours and the pH to 5.5-6.

5.

4. The method according to claim 3, characterized in that, The aerobic AMAO denitrification reactor maintains a stable dissolved oxygen concentration of 0.5-2.0 mg / L by controlling aeration, and a hydraulic retention time of 3-8 hours, thereby controlling the total nitrogen removal load of the aerobic AMAO denitrification reactor to be 0.05-0.4 kg N / (m³). 3 ·d), the concentrations of nitrite and nitrate in the effluent were both below 1 mg / L.

5. The method according to claim 3, characterized in that, In step S3, the sludge return ratio is 30%-100% of the municipal sewage flow. The microbial residues, unused dissolved organic matter, and intermediate products contained in the returned sludge are converted back into acetone as a supplementary carbon source in the anoxic acetone-producing reactor.

6. A direct ammonia oxidation denitrification system for municipal wastewater, characterized in that, It includes an anoxic acetone-producing reactor, an aerobic AMAO denitrification reactor, and a sedimentation tank connected in sequence, wherein: The anoxic acetone-producing reactor is used to convert some of the organic carbon sources in wastewater into acetone through functional microorganisms under anoxic conditions. The aerobic AMAO denitrification reactor is used to directly oxidize ammonia nitrogen into nitrogen gas by using acetone as a carbon source and electron mediator under aerobic conditions through AMAO functional microorganisms. The sedimentation tank is used to perform solid-liquid separation on the mixed liquid discharged from the aerobic AMAO denitrification reactor, and to return part of the separated sludge to the anoxic acetone-producing reactor to achieve internal carbon source circulation within the system.

7. The system according to claim 6, characterized in that, The anoxic acetone-producing reactor is inoculated with a complex of Clostridium species and equipped with a pH control device to maintain the pH at 5.5-6.

5.

8. The system according to claim 6 or 8, characterized in that, The aerobic AMAO denitrification reactor is equipped with a microporous aeration device, a dissolved oxygen probe, and a controller to control the dissolved oxygen concentration at 0.5-2.0 mg / L.

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