Method and device for deeply purifying municipal sewage by using AOA process

Abstract

The invention relates to a method and a device for deeply purifying urban sewage by using an AOA (Automated Optical Architecture) process. According to the method for deeply purifying the municipal sewage by applying the AOA process, the sludge in the anaerobic zone is subjected to anaerobic fermentation to provide a carbon source for the anoxic zone, so that the problem of treatment of a large amount of excess sludge is effectively solved, and the natural defects of lack of carbon sources and low C / N of the domestic sewage are overcome; meanwhile, the defect that additional chemical phosphorus removal is needed for sludge fermentation of a traditional secondary sedimentation tank is also avoided; besides, sludge circulation of the aerobic zone and the anoxic zone can be blocked through ingenious arrangement of the secondary sedimentation tank, the stability of a microbial flora structure of the anoxic zone is ensured, and the anoxic zone takes anaerobic ammonium oxidation bacteria as unique functional bacteria to carry out a process of coupling short-range nitrate dissimilatory reduction into ammonium and anaerobic ammonium oxidation. The problem of performance fluctuation caused by large fluctuation of water quality and water quantity of raw water can be solved, and meanwhile, starting, operation and maintenance are simpler and more convenient.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a method and apparatus for deep purification of urban wastewater using the AOA process. Background Technology

[0002] Currently, the modified anaerobic / aerobic / anoxic (AOA) processes used for nitrogen and phosphorus pollutants in urban wastewater treatment mainly include three types: post-denitrification, post-anaerobic ammonia oxidation, and post-short-cut denitrification-anaerobic ammonia oxidation. However, each of these processes has its own limitations and is difficult to achieve the expected discharge standards efficiently and stably. In addition, these processes generate a large amount of excess sludge, and the current treatment and disposal costs have reached 50%-60% of the total operating costs of water plants. Moreover, existing sludge treatment technologies themselves still have many problems, such as poor volume reduction, complex operation, numerous steps, and low resource recovery rates, and have not achieved the treatment requirements of sludge stabilization, harmlessness, and resource recovery.

[0003] Current technologies cannot achieve efficient and stable deep nitrogen and phosphorus removal from wastewater, necessitating the development of novel continuous-flow AOA (Automatic Aeration) processes. Simultaneously, for the treatment of excess sludge, more economical and effective methods should be explored to reduce the operating costs of wastewater treatment plants and improve overall environmental benefits. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method and apparatus for deep purification of urban sewage using the AOA process.

[0005] In a first aspect, the present invention provides a method for deep purification of urban wastewater using the AOA process, the method comprising: Domestic sewage and anaerobic sludge concentrate are separately fed into the anaerobic zone for anaerobic phosphorus release and denitrification reactions to obtain anaerobic effluent. The anaerobic effluent is passed into the aerobic zone to undergo partial nitrification and aerobic phosphorus uptake, resulting in aerobic effluent. The aerobic effluent is fed into the secondary sedimentation tank to perform sedimentation and separation treatment, resulting in supernatant and bottom sludge from the secondary sedimentation tank. The supernatant from the secondary sedimentation tank and the sludge fermentation liquid from the anaerobic zone are separately introduced into the anoxic zone for short-range nitrate dissimilatory reduction to ammonium coupled with anaerobic ammonia oxidation reaction, thereby achieving deep denitrification and obtaining purified water. At the same time, the bottom sludge is returned to the anaerobic zone to maintain the sludge concentration in both the anaerobic and aerobic zones at 3000-5000 mg / L.

[0006] In conjunction with the first aspect, the steps of separately introducing domestic sewage and anaerobic sludge concentrate into the anaerobic zone for anaerobic phosphorus release and denitrification reactions to obtain anaerobic effluent include: Under conditions where dissolved oxygen is below 0.2-0.5 mg / L and redox potential is -100 ~ -200 mV, domestic sewage and anaerobic sludge concentrate undergo anaerobic phosphorus release, organic matter storage, and denitrification reactions to produce anaerobic effluent.

[0007] In conjunction with the first aspect, the step of introducing anaerobic effluent into an aerobic zone for partial nitrification and aerobic phosphorus uptake to obtain aerobic effluent includes: The ammonia nitrogen removal rate in the aerobic zone is 50%-70%.

[0008] In conjunction with the first aspect, before the step of separately introducing domestic sewage and anaerobic sludge concentrate into the anaerobic zone for anaerobic phosphorus release and denitrification reactions to obtain anaerobic effluent, the following steps are also included: After the urban sludge in the anaerobic zone is fed into the thickening tank for thickening treatment, concentrated anaerobic sludge and anaerobic sludge concentrate with a water content of 90%-95% are obtained. The concentrated anaerobic sludge is fed into a fermenter for anaerobic fermentation to obtain anaerobic sludge fermentation liquid. At the same time, the concentrated anaerobic sludge liquid is returned to the anaerobic zone.

[0009] In conjunction with the first aspect, the step of introducing concentrated anaerobic sludge into a fermenter for anaerobic fermentation to obtain anaerobic sludge fermentation liquid includes: Under conditions of pH 10.0 - 11.0 and temperature 25 - 30℃, concentrated anaerobic sludge is introduced into a fermenter and the sludge retention time is controlled to be 5 - 11 days to allow the concentrated anaerobic sludge to undergo anaerobic fermentation, thereby obtaining anaerobic sludge fermentation liquid.

[0010] In conjunction with the first aspect, the steps of separately introducing the supernatant from the secondary sedimentation tank and the sludge fermentation broth from the anaerobic zone into the anoxic zone for short-cut nitrate dissimilatory reduction to ammonium coupled with anaerobic ammonia oxidation reaction, thereby achieving deep denitrification and obtaining purified water, include: Under conditions of pH control of 7.27-7.29 and a carbon-to-nitrogen ratio of 1.14-2.14, the anaerobic ammonia oxidation sludge filled in the anoxic zone undergoes a short-range nitrate dissimilatory reduction to ammonium coupled with an anaerobic ammonia oxidation reaction. The supernatant of the secondary sedimentation tank and the sludge fermentation broth of the anaerobic zone can achieve deep denitrification, resulting in purified effluent that meets the specified requirements.

[0011] Secondly, this application also provides an apparatus for deep purification of urban sewage using the AOA process, for performing the above-mentioned method. The apparatus includes: an anaerobic zone, an aerobic zone, and an anoxic zone connected in sequence, with a secondary sedimentation tank provided between the aerobic zone and the anoxic zone; a first inlet end of the anaerobic zone is connected to domestic sewage; and the secondary sedimentation tank is also connected to a second inlet end of the anaerobic zone.

[0012] In conjunction with the second aspect, the volume ratio between the anaerobic zone and the aerobic zone is 1:1 to 1:2.

[0013] In conjunction with the second aspect, the anaerobic zone is also sequentially connected to the thickener, fermenter, and anoxic zone.

[0014] In conjunction with the second aspect, the anoxic zone is filled with anaerobic ammonia oxidation biofilm packing material or granular sludge.

[0015] This invention brings the following beneficial effects: This application provides a method and apparatus for deep purification of urban sewage using the AOA process. The method includes: passing domestic sewage and anaerobic sludge concentrate into the anaerobic zone for anaerobic phosphorus release and denitrification reactions to obtain anaerobic effluent; passing the anaerobic effluent into the aerobic zone for partial nitrification and aerobic phosphorus uptake to obtain aerobic effluent; passing the aerobic effluent into a secondary sedimentation tank for sedimentation and separation treatment to obtain secondary sedimentation tank supernatant and bottom sludge; passing the secondary sedimentation tank supernatant and anaerobic sludge fermentation liquid into the anoxic zone for short-range nitrate dissimilatory reduction to ammonium coupled with anaerobic ammonia oxidation reaction to achieve deep denitrification and obtain purified water; and simultaneously, returning the bottom sludge to the anaerobic zone to maintain the sludge concentration in both the anaerobic and aerobic zones at 3000-5000 mg / L.

[0016] The present invention provides a method for deep purification of urban sewage using the AOA process. This method employs anaerobic fermentation of sludge from the anaerobic zone to provide a carbon source for the anoxic zone. This not only effectively solves the problem of treating large amounts of excess sludge but also overcomes the natural deficiencies of domestic sewage, such as a lack of carbon sources and a low C / N ratio. It also avoids the drawbacks of traditional secondary sedimentation tank sludge fermentation requiring additional chemical phosphorus removal. Furthermore, the clever design of the secondary sedimentation tank blocks sludge flow between the aerobic and anoxic zones, ensuring the stability of the microbial community structure in the anoxic zone. Consequently, the anoxic zone can utilize anaerobic ammonia oxidizing bacteria as the sole functional bacteria to perform a short-range nitrate dissimilatory reduction to ammonium coupled with anaerobic ammonia oxidation. This not only solves the performance fluctuations caused by large fluctuations in raw water quality and quantity but also simplifies start-up and maintenance.

[0017] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained in accordance with the structures particularly pointed out in the description, claims and drawings.

[0018] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 A schematic flowchart of a method for deep purification of urban sewage using the AOA process, provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a device for deep purification of urban sewage using the AOA process, provided as an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] To facilitate understanding of this embodiment, the technical terms used in this application will be briefly introduced below.

[0023] The AOA (Anaerobic-Oxic-Anoxic) process is an improved activated sludge process that achieves deep nitrogen and phosphorus removal by adjusting the reaction zone sequence of the traditional AAO (Anaerobic-Anoxic-Oxic) process. This process consists of three parts: 1. Anaerobic tank (A): Polyphosphate-accumulating bacteria release phosphorus and store volatile fatty acids (VFAs) here, providing energy for subsequent phosphorus uptake; 2. Aerobic tank (O): This tank completes organic matter degradation, nitrification (conversion of ammonia nitrogen to nitrate), and phosphorus absorption by polyphosphate-accumulating bacteria; 3. Anoxic tank (A): This tank utilizes internally returned nitrates and residual carbon sources for denitrification, generating nitrogen gas which is then discharged.

[0024] After introducing the technical terms used in this application, the application scenarios and design concepts of the embodiments of this application will be briefly described below.

[0025] With the rapid development of the human economy, water pollution has become increasingly serious. Eutrophication of water bodies caused by nitrogen and phosphorus has come into the public eye and become a focus of attention, and wastewater discharge standards for nitrogen and phosphorus pollutants are becoming increasingly stringent. Currently, the modified AOA processes used in my country's wastewater treatment plants to treat nitrogen and phosphorus pollutants mainly include three types: post-denitrification process, post-anaerobic ammonium oxidation (Anammox) process, and post-short-cut denitrification-anaerobic ammonium oxidation process. However, each of these processes has its own limitations.

[0026] Specifically, post-denitrification processes require the addition of a large amount of external carbon source in the anoxic zone to enhance nitrogen removal; post-anaerobic ammonium oxidation processes require the aerobic zone to provide substrate nitrite nitrogen through short-cut nitrification. The realization of this process relies on ammonium oxidizing bacteria (AOB) to stably provide nitrite nitrogen to anaerobic ammonium oxidizing bacteria, but nitrite oxidizing bacteria (Nitrite oxidizing bacteria) coexisting with AOB also play a role. NOB bacteria can further oxidize nitrite nitrogen to nitrate nitrogen, and NOB is usually difficult to wash off. In particular, at mainstream low temperatures, NOB grows faster than AOB, which will significantly affect the denitrification performance of short-cut nitrification-anammox processes and even cause them to collapse. The post-short-cut denitrification-anammox process is jointly executed by denitrifying bacteria and anammox bacteria. The realization of this process depends on the denitrifying bacteria to stably provide substrate nitrite nitrogen for anammox bacteria. However, denitrifying bacteria are both suppliers of nitrite nitrogen and competitors for nitrite nitrogen with anammox bacteria. At the same time, denitrifying bacteria require a suitable type of carbon source and a relatively high C / N ratio, while high COD inhibits the activity of functional bacteria in the anammox reaction. Obviously, this process has a relatively high risk of instability. Therefore, to achieve efficient and stable deep denitrification and phosphorus removal from wastewater, it is still necessary to develop a new continuous flow AOA process.

[0027] Furthermore, urban wastewater treatment plants generate a large amount of excess sludge, and the current cost of its treatment and disposal accounts for 50%-60% of the total operating costs of the plants. At the same time, existing sludge treatment technologies themselves still have many problems, such as poor volume reduction, complex operation, numerous steps, and low resource recovery rates, failing to meet the requirements of sludge stabilization, harmlessness, and resource recovery. How to economically and effectively treat and dispose of sludge has become a hot issue of concern in the environmental field.

[0028] Based on this, this application provides a method and apparatus for deep purification of urban sewage using the AOA process.

[0029] Example 1 This application provides a method for deep purification of urban wastewater using the AOA process, combined with... Figure 1As shown, the method includes: S110 introduces domestic sewage and anaerobic sludge concentrate into the anaerobic zone for anaerobic phosphorus release and denitrification reactions, respectively, to obtain anaerobic effluent.

[0030] S120 introduces anaerobic effluent into the aerobic zone for partial nitrification and aerobic phosphorus uptake, resulting in aerobic effluent.

[0031] S130 introduces aerobic effluent into a secondary sedimentation tank for sedimentation and separation treatment, yielding supernatant and bottom sludge from the secondary sedimentation tank.

[0032] S140 involves passing the supernatant from the secondary sedimentation tank and the sludge fermentation liquid from the anaerobic zone into the anoxic zone for short-range nitrate dissimilatory reduction to ammonium coupled with anaerobic ammonia oxidation reaction, thereby achieving deep denitrification and obtaining purified water. At the same time, the bottom sludge is returned to the anaerobic zone to maintain the sludge concentration in both the anaerobic and aerobic zones at 3000-5000 mg / L.

[0033] Combination Figure 2 As shown in the figure, solid arrows represent the direction of water flow, and dashed arrows represent the direction of sludge flow. This application improves the existing AOA process. In this embodiment, the improved AOA process sets the secondary sedimentation tank between the aerobic and anoxic zones, reducing the energy consumption for sludge return, avoiding damage to the anaerobic environment, and maintaining the stability of the microbial system in the anoxic zone; anaerobic fermentation is carried out using sludge from the anaerobic zone, improving the performance of the fermentation liquid and reducing the operating cost of the water plant; in the anoxic zone, anaerobic ammonia oxidation biofilm packing or granular sludge is used to achieve simultaneous removal of ammonia nitrogen and nitrate through a short-cut dissimilatory nitrate reduction to ammonium (PDNRA) coupled with anaerobic ammonia oxidation (PDNRA-Anammox) process, eliminating the need for short-cut nitrification or short-cut denitrification and simplifying operation and maintenance. This invention can achieve efficient and stable deep nitrogen and phosphorus removal from wastewater, and has significant engineering application value. In conjunction with the first aspect, step S110 includes: Under conditions where dissolved oxygen is below 0.2-0.5 mg / L and oxidation-reduction potential is -100 ~ -200 mV, domestic sewage and anaerobic sludge concentrate undergo anaerobic phosphorus release, organic matter storage, and denitrification reactions to produce anaerobic effluent.

[0034] Understandably, by strictly controlling the dissolved oxygen (DO) and oxidation-reduction potential (ORP) to create an anaerobic environment, after the sludge concentrate in the anaerobic zone is mixed with domestic sewage, polyphosphate-accumulating bacteria decompose the polyphosphate (Poly-P) stored in their cells and release orthophosphate (PO4). 3-The bacteria transport volatile fatty acids (VFAs, such as acetic acid and propionic acid) out of the cell and simultaneously produce ATP. Using ATP, they actively transport these VFAs into the cell to synthesize polyhydroxyalkanoates (PHAs) (such as PHB and PHV), providing a carbon source for subsequent aerobic reactions. At the same time, denitrifying bacteria can utilize organic matter (COD) in wastewater for denitrification, removing some nitrates (NO3). - ).

[0035] In conjunction with the first aspect, step S120 includes: The ammonia nitrogen removal rate in the aerobic zone is 50%-70%.

[0036] The anaerobic effluent enters the aerobic zone for partial nitrification and aerobic phosphorus uptake. Partial nitrification refers to oxidizing only 50%-70% of the ammonia nitrogen in the anaerobic effluent to the nitrate stage. This saves oxygen and carbon sources while ensuring an appropriate ratio of ammonia nitrogen and nitrate in the anoxic zone for simultaneous removal. Understandably, further increasing the ammonia nitrogen removal rate in the aerobic zone to 100% would result in a complete dissimilatory nitrate reduction to ammonium (DNRA) coupled with anaerobic ammonium oxidation (DNRA-Anammox) in the anoxic zone, which would not only take longer but also consume more oxygen and carbon sources. Furthermore, in the aerobic environment, polyphosphate-accumulating bacteria utilize stored PHA as an energy and carbon source, absorbing large amounts of phosphate from the environment and resynthesizing polyphosphate (Poly-P), forming phosphorus-rich sludge. Phosphorus removal is ultimately achieved through sludge discharge.

[0037] In conjunction with the first aspect, prior to step S110, the following also includes: S010, after the urban sludge in the anaerobic zone is fed into the thickening tank for thickening treatment, concentrated anaerobic sludge and anaerobic sludge concentrate with a water content of 90%-95% are obtained. S020, the concentrated anaerobic sludge is fed into the fermentation tank for anaerobic fermentation to obtain anaerobic sludge fermentation liquid, and at the same time, the concentrated anaerobic sludge liquid is returned to the anaerobic zone.

[0038] Step S010 concentrates the sludge from the anaerobic zone, yielding concentrated sludge and sludge concentrate with lower water content. The sludge concentrate contains high concentrations of ammonia nitrogen and phosphate, making it unsuitable for direct discharge. It must be returned to the anaerobic zone and undergo subsequent pollutant conversion and removal processes before meeting discharge standards. Step S020 involves anaerobic fermentation of the concentrated sludge to produce a low-phosphorus, high-carbon fermentation broth. This provides a carbon source for the PDNRA-Anammox process in the anoxic zone, addressing the natural carbon deficiency and low C / N ratio in domestic wastewater. Steps S010 and S020 are crucial pretreatment steps that directly impact the water quality parameters of the anaerobic effluent (S110).

[0039] In conjunction with the first aspect, step S020 involves feeding the concentrated anaerobic sludge into a fermenter for anaerobic fermentation to obtain anaerobic sludge fermentation broth, specifically including: S021, under the conditions of pH 10.0 - 11.0 and temperature 25 - 30℃, the concentrated anaerobic sludge is introduced into the fermenter and the sludge retention time is controlled to be 5 - 11 days to enable the concentrated anaerobic sludge to undergo anaerobic fermentation, thereby obtaining the anaerobic sludge fermentation liquid.

[0040] A pH of 10-11 is considered a strongly alkaline environment, and a temperature of 25-30℃ is considered a mesophilic environment. Anaerobic fermentation typically occurs at neutral pH and higher temperatures, such as mesophilic (around 35℃) or hyperthermic (around 55℃). A high pH promotes alkaline fermentation, producing more volatile fatty acids (VFAs), while avoiding ammonia inhibition and inorganic salt accumulation.

[0041] In conjunction with the first aspect, step S130, in which the supernatant from the secondary sedimentation tank and the sludge fermentation broth from the anaerobic zone are respectively introduced into the anoxic zone for PDNRA-Anammox reaction, thereby achieving deep denitrification and obtaining purified water, includes: Under conditions of pH control of 7.27-7.29 and a carbon-to-nitrogen ratio of 1.14-2.14, the anaerobic ammonia oxidation sludge filled in the anoxic zone undergoes a PDNRA-Anammox reaction. The supernatant of the secondary sedimentation tank and the sludge fermentation broth of the anaerobic zone can achieve deep denitrification, resulting in purified effluent that meets the specified requirements.

[0042] In actual operation, the pH value in the anoxic zone is strictly controlled within the range of 7.27 to 7.29. This range provides a suitable reaction environment for the anammox sludge and promotes the PDNRA-Anammox reaction. Regarding the carbon-to-nitrogen ratio (C / N) in the influent, the actual C / N ratio in the anoxic zone is controlled within the range of 1.14 to 2.14 by adjusting the dosage ratio of the supernatant from the secondary sedimentation tank to the sludge fermentation broth from the anammox zone. This range satisfies the carbon source requirements of the PDNRA-Anammox process while avoiding secondary pollution caused by excessive carbon sources.

[0043] The above operating parameters have been optimized through laboratory studies, kinetic simulations, and long-term engineering verification, ensuring that the PDNRA-Anammox reaction can occur efficiently and stably in the anoxic zone. This process not only significantly improves the system's nitrogen removal efficiency but also greatly reduces the dependence on chemical reagents in traditional processes, achieving a more economical and sustainable wastewater treatment goal.

[0044] In this way, the effluent after the above treatment can meet high purification standards and satisfy specified requirements, such as the discharge standards of urban sewage treatment plants or the Class A indicators for specific industrial wastewater treatment.

[0045] Secondly, this application provides a device for deep purification of urban sewage using the AOA process, combined with... Figure 2 As shown, it includes: an anaerobic zone, an aerobic zone, and an anoxic zone connected in sequence, with a secondary sedimentation tank set between the aerobic zone and the anoxic zone; the first inlet end of the anaerobic zone is connected to domestic sewage; the secondary sedimentation tank is also connected to the second inlet end of the anaerobic zone.

[0046] In this embodiment, the secondary sedimentation tank is located between the aerobic zone and the anoxic zone to block sludge flow and ensure the stability of the microbial community structure in the anoxic zone. The anoxic zone uses anaerobic ammonia oxidizing bacteria as the sole functional bacteria for the PDNRA-Anammox process, which not only solves the performance fluctuations caused by large fluctuations in raw water quality and quantity, but also makes its start-up and operation and maintenance simpler and more convenient.

[0047] In conjunction with the second aspect, the volume ratio between the anaerobic zone and the aerobic zone is 1:1 to 1:2.

[0048] In conjunction with the second aspect, the anaerobic zone is also sequentially connected to the thickener, fermenter, and anoxic zone.

[0049] In this embodiment, anaerobic fermentation of sludge from the anaerobic zone is used to provide a carbon source for the anoxic zone. This not only effectively solves the problem of treating a large amount of excess sludge, but also overcomes the natural deficiencies of lack of carbon source and low C / N ratio in domestic sewage. It also avoids the drawback of the need for additional chemical phosphorus removal in traditional secondary sedimentation tank sludge fermentation.

[0050] Sludge from the anaerobic zone flows into a thickening tank via gravity or pumping. The primary function of the thickening tank is to initially concentrate the excess sludge generated in the anaerobic zone, reducing its volume and improving subsequent treatment efficiency. The concentrated sludge is then transported to a fermentation tank, where specific anaerobic microorganisms ferment it, converting complex organic matter into easily degradable small-molecule organic matter. These fermentation products are subsequently used as a carbon source for the PDNRA-Anammox reaction in the anoxic zone. This provides a stable carbon source, reduces the need for external carbon sources, achieves sludge resource utilization, and lowers sludge discharge.

[0051] In this process, the synergistic effect of the thickening tank and the fermentation tank enables the effective treatment and resource utilization of sludge, reducing the amount of residual sludge that needs to be disposed of in the end. The fermentation liquid generated by the fermentation tank provides a stable and efficient carbon source for the anoxic zone, reducing the demand for external carbon sources (such as sodium acetate) and thus saving operating costs.

[0052] In conjunction with the second aspect, the anoxic zone is filled with anaerobic ammonia oxidation biofilm packing material or granular sludge.

[0053] Biofilm packing is a carrier material, usually made of materials with high specific surface area and good biological adhesion properties (such as porous ceramsite, modified plastics, etc.). It can provide a stable attachment environment for anaerobic ammonia-oxidizing bacteria, promote their growth and reproduction, increase the biomass per unit volume, enhance reaction efficiency, and at the same time, improve the water flow state and form flow conditions that are conducive to mass transfer.

[0054] Granular sludge is a spherical or elliptical structure formed by the self-aggregation of microorganisms. It has high density and settling properties. In anoxic zones, granular sludge can effectively support anaerobic ammonia-oxidizing bacteria and reduce sludge loss. In addition, granular sludge has high biological activity and stability, strong adaptability, and can maintain high nitrogen removal capacity under a wide range of operating conditions.

[0055] Understandably, packing supports can also be installed in the anoxic zone. A packing support is a structural device used to fix or support the packing material, typically made of stainless steel, fiberglass, or other corrosion-resistant materials. Its main function is to provide stable space for the biofilm packing material and optimize water flow and mass transfer conditions. When a packing support is installed in the anoxic zone, it can evenly distribute the biofilm packing material within the reactor, preventing displacement or accumulation due to water flow impact, ensuring the effective contact area of ​​the packing material, and increasing the biomass per unit volume. It can also be used in conjunction with anaerobic ammonia oxidation biofilm packing material or granular sludge to further improve reaction efficiency and operational stability.

[0056] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the system and apparatus described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0057] Furthermore, in the description of the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0058] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0059] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0060] Finally, it should be noted that the above embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for deep purification of urban sewage using AOA technology, characterized in that, The method includes: Domestic sewage and anaerobic sludge concentrate are separately fed into the anaerobic zone for anaerobic phosphorus release and denitrification reactions to obtain anaerobic effluent. The anaerobic effluent is passed into the aerobic zone for partial nitrification and aerobic phosphorus uptake to obtain aerobic effluent. The aerobic effluent is fed into a secondary sedimentation tank to perform sedimentation and separation treatment, resulting in supernatant and bottom sludge from the secondary sedimentation tank. The supernatant from the secondary sedimentation tank and the sludge fermentation liquid from the anaerobic zone are respectively introduced into the anoxic zone for short-range nitrate dissimilatory reduction to ammonium coupled with anaerobic ammonia oxidation reaction, thereby achieving deep denitrification and obtaining purified water; at the same time, the bottom sludge is returned to the anaerobic zone to maintain the sludge concentration in the anaerobic zone and the aerobic zone at 3000-5000 mg / L.

2. The method according to claim 1, characterized in that, The steps involved in separately introducing domestic sewage and anaerobic sludge concentrate into the anaerobic zone for anaerobic phosphorus release and denitrification reactions to obtain anaerobic effluent include: Under conditions where dissolved oxygen is below 0.2-0.5 mg / L and redox potential is -100 ~ -200 mV, the domestic sewage and the sludge concentrate from the anaerobic zone undergo anaerobic phosphorus release, organic matter storage, and denitrification reactions to obtain anaerobic effluent.

3. The method according to claim 1, characterized in that, The steps of passing anaerobic effluent into an aerobic zone for partial nitrification and aerobic phosphorus uptake to obtain aerobic effluent include: The ammonia nitrogen removal rate in the aerobic zone is 50%-70%.

4. The method according to claim 1, characterized in that, Before the step of separately introducing domestic sewage and anaerobic sludge concentrate into the anaerobic zone for anaerobic phosphorus release and denitrification reactions to obtain anaerobic effluent, the following steps are also included: After the urban sludge in the anaerobic zone is fed into a thickening tank for thickening treatment, concentrated anaerobic sludge with a water content of 90%-95% and concentrated anaerobic sludge liquid are obtained. The concentrated anaerobic sludge is fed into a fermenter for anaerobic fermentation to obtain the anaerobic sludge fermentation liquid. At the same time, the concentrated anaerobic sludge liquid is returned to the anaerobic zone.

5. The method according to claim 4, characterized in that, The steps of feeding concentrated anaerobic sludge into a fermenter for anaerobic fermentation to obtain anaerobic sludge fermentation broth include: Under conditions of pH 10.0 - 11.0 and temperature 25 - 30℃, the concentrated anaerobic sludge is introduced into a fermenter and the sludge retention time is controlled to be 5 - 11 days to allow the concentrated anaerobic sludge to undergo anaerobic fermentation, thereby obtaining anaerobic sludge fermentation liquid.

6. The method according to claim 1, characterized in that, The steps of introducing the supernatant from the secondary sedimentation tank and the sludge fermentation broth from the anaerobic zone into the anoxic zone for short-cut nitrate dissimilatory reduction to ammonium coupled with anaerobic ammonia oxidation, thereby achieving deep denitrification and obtaining purified water, include: Under conditions of pH control of 7.27-7.29 and a carbon-to-nitrogen ratio of 1.14-2.14, the anaerobic ammonia oxidation sludge filled in the anoxic zone undergoes a short-range nitrate dissimilatory reduction to ammonium coupled with anaerobic ammonia oxidation. The supernatant of the secondary sedimentation tank and the sludge fermentation broth of the anaerobic zone can achieve deep denitrification, resulting in purified effluent that meets the specified requirements.

7. A device for deep purification of urban sewage using AOA technology, characterized in that, The apparatus for performing the method as described in any one of claims 1-6 comprises: an anaerobic zone, an aerobic zone, and an anoxic zone connected in sequence, wherein a secondary sedimentation tank is provided between the aerobic zone and the anoxic zone; a first inlet end of the anaerobic zone is connected to domestic sewage; and the secondary sedimentation tank is also connected to a second inlet end of the anaerobic zone.

8. The apparatus according to claim 7, characterized in that, The volume ratio between the anaerobic zone and the aerobic zone is 1:1 to 1:

2.

9. The apparatus according to claim 7, characterized in that, The anaerobic zone is also sequentially connected to the concentration tank, fermentation tank, and anoxic zone.

10. The apparatus according to claim 9, characterized in that, The anoxic zone is filled with anaerobic ammonia oxidation biofilm packing material or granular sludge.

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