Device and method for realizing domestic sewage mainstream anammox by establishing carbon confinement area as anaerobic ammonia oxidation hotspot ecological niche based on carbon metabolism regulation and control

Abstract

The invention relates to a device and a method for realizing domestic sewage mainstream anammox by establishing a carbon confinement area as an anaerobic ammonia oxidation hotspot ecological niche based on carbon metabolism regulation and control, and belongs to the field of sewage treatment. By combining the advantages of endogenous denitrification of an anaerobic (A) / aerobiotic (O) / anoxic (A) process and exogenous denitrification of a step-feed process, an organic carbon source in domestic sewage is fully utilized, and an anoxic carbon confinement zone is constructed as a hotspot ecological niche of anaerobic ammonium oxidation bacteria. The device comprises a domestic sewage raw water tank, an AOA tank and a secondary sedimentation tank which are connected in sequence, and has the advantages of coordinating high efficiency of exogenous denitrification and energy conservation of endogenous denitrification coupled anaerobic ammonia oxidation by adjusting the sectional water inlet proportion and prolonging the retention time of an anoxic zone. Meanwhile, an anaerobic ammonium oxidation filler is added at the anoxic end section to establish a carbon confinement area so as to realize high enrichment and retention of anaerobic ammonium oxidation bacteria on the filler, and finally deep denitrification of the domestic sewage is realized. The method has the advantage of saving aeration energy consumption and organic carbon sources.

Description

Technical Field

[0001] This invention relates to a process technology for achieving mainstream anammox in domestic sewage by establishing a carbon-restricted zone as an anammox hotspot ecological niche based on carbon metabolism regulation, which belongs to the field of biological sewage treatment. Background Technology

[0002] Traditional wastewater treatment technologies consume significant amounts of energy and resources. Improving these methods to achieve energy conservation and reduced consumption is a top priority in wastewater treatment research. Anaerobic ammonia oxidation (ANAO) is currently the most economical and energy-efficient wastewater denitrification process. However, ANAO is primarily used for denitrification of high-ammonia-nitrogen wastewater. For low-concentration wastewater, such as municipal sewage, short-cut nitrification methods still face the challenge of effectively suppressing and washing away nitrite-oxidizing bacteria (NOB), inevitably resulting in varying levels of nitrate nitrogen (NO3) in the effluent. - This results in unsatisfactory anaerobic ammonia oxidation denitrification. Therefore, stable nitrite nitrogen (NO2) is not ideal. - The source of NO3 is a bottleneck issue for the practical application of anaerobic ammonia oxidation technology. Short-cut denitrification can remove NO3 under anoxic conditions. - Transform into NO2 - This provides a stable substrate for anaerobic ammonia oxidizing bacteria (AnAOB) and reduces the amount of carbon source added. This process does not require aeration, thus saving some aeration energy consumption. It provides a new approach to achieving partial anaerobic ammonia oxidation in mainstream urban wastewater and proposes a new technology with certain application potential for wastewater denitrification.

[0003] Urban domestic wastewater generally has a low carbon-to-nitrogen ratio, with complex carbon sources, mostly consisting of recalcitrant organic matter, leaving few carbon sources available for microbial utilization. These water quality characteristics result in low efficiency of short-cut denitrification, making it difficult to accumulate large amounts of nitrite nitrogen and providing sufficient substrate for anaerobic ammonia oxidizing bacteria, thus hindering the full utilization of autotrophic nitrogen removal advantages. Therefore, utilizing the organic matter in the raw water to initiate a short-cut denitrification anaerobic ammonia oxidation process is of great significance for energy conservation, emission reduction, and fully leveraging the advantages of autotrophic nitrogen removal.

[0004] Prior to the discovery of autotrophic denitrification processes, researchers conducted extensive research to overcome the challenge of insufficient carbon sources in conventional wastewater treatment. Among these, carbon source configuration optimization strategies, exemplified by stepwise dosing and anaerobic-aerobic-anoxic (AOA) processes, have shown significant effectiveness. By optimizing the influent flow rate ratio, the efficient denitrification capacity of exogenous denitrification can be fully utilized to improve the system's nitrogen removal performance. However, exogenous carbon metabolism competes with anammox for nitrite, and the activity of anammox bacteria is inhibited in the presence of excess organic carbon, leading to the collapse of the anammox pathway. The combination of anaerobic-aerobic-anoxic (AOA) processes with anammox has attracted considerable attention because its endogenous denitrification metabolic potential can be effectively coupled with anammox, thereby promoting the enrichment and activity maintenance of AnAOB. ​​However, endogenous denitrification, indirectly utilizing the original wastewater carbon source, exhibits suboptimal nitrogen removal efficiency, while inappropriate ammonia nitrogen (NH4) at the aerobic terminal stage... + Adjustments can negatively impact the system's nitrogen removal performance. Furthermore, the denitrification efficiency of endogenous carbon sources is low during the AOA process, necessitating an extended hydraulic retention time (HRT) after anoxic conditions to ensure the reaction completes.

[0005] Recent studies have shown that carbon-limited anoxic regions are potential anammox hotspots. In the competition for nitrite substrates, AnAOB (Anoxically Absorbed Biological Organisms) and denitrifying bacteria exhibit competitive exclusion, with the niche establishment and functional expression of anammox communities heavily dependent on the intensity of environmental inhibition against denitrifying bacteria. Under carbon-limited conditions, by weakening the substrate competition ability of denitrifying bacteria, the metabolic microenvironment of AnAOB is indirectly optimized. AnAOB achieves functional breakthroughs through its high affinity for nitrite and its autotrophic metabolic advantages.

[0006] Based on the problems and challenges faced by short-cut denitrification anaerobic ammonium oxidation (ANAO) processes in treating urban wastewater, this invention innovatively proposes to construct a carbon-limiting zone by optimizing the influent ratio and the duration of the post-anoxic stage. Balancing endogenous / exogenous metabolic advantages, an anammox hotspot niche is established: (1) efficient exogenous denitrification is carried out in the carbon-rich zone to improve nitrogen removal efficiency; (2) by controlling the release of endogenous carbon, a carbon-limiting zone is established as an anammox hotspot niche, providing a stable and efficient new technology for the advanced treatment of urban wastewater and promoting the widespread application of ANAO processes in wastewater treatment. This research provides the necessary theoretical foundation and technical support for the advanced treatment of domestic wastewater and energy conservation and consumption reduction, and has significant research significance and application value. Summary of the Invention

[0007] In response to the characteristics of urban domestic sewage, which generally has a low carbon-to-nitrogen ratio and complex carbon sources, mostly consisting of degraded organic matter, this invention innovatively proposes to construct carbon-rich / carbon-limited zones by combining the advantages of segmented influent and AOA processes, optimizing the influent ratio and HRT in the post-anoxic stage. By balancing the advantages of endogenous / exogenous metabolism, an anammox hotspot niche is established: (1) efficient exogenous denitrification is carried out in the carbon-rich zone to improve nitrogen removal efficiency; (2) by controlling the release of endogenous carbon, a carbon-limited zone is established as an anammox hotspot niche. The system's autotrophic denitrification advantage is leveraged by promoting the activity of anammox bacteria.

[0008] This invention proposes a technology for deep and efficient denitrification of urban domestic sewage with low C / N ratio by establishing a carbon-limited zone as an ecological niche for anaerobic ammonia oxidation through carbon metabolism regulation, based on anaerobic ammonia oxidation autotrophic denitrification technology, nitrite-producing short-cut denitrification technology, segmented influent carbon source optimization and allocation technology, and AOA internal carbon source optimization technology.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A device for realizing mainstream anammox in domestic sewage by establishing a carbon-limited zone as an anammox hotspot ecological niche based on carbon metabolism regulation is characterized in that: the main device used includes a domestic sewage tank (1), an inlet pump (2), an inlet pipe (3), an inlet control valve (4), a segmented inlet AOA tank (5), an anaerobic zone (6), an aerobic zone (7), an anoxic zone (8), a stirrer (9), a secondary sedimentation tank (10), a blower (11), a rotor flow meter (12), a microporous aeration head (13), a sludge return control valve (14), a sludge discharge valve (15), anammox packing (16), and a sludge return pump (17);

[0011] The segmented AOA pool (5) includes an anaerobic zone (6), an aerobic zone (7), and an anoxic zone (8) that are connected in sequence, with each zone accounting for 1-2:2-4:5-8. The domestic sewage tank (1) is connected to the anaerobic zone (6) and the anoxic zone via the inlet pump (2) and the inlet pipe (3); the sludge return and the discharge of excess sludge in the secondary sedimentation tank are controlled by the sludge return control gate valve (14) and the sludge discharge gate valve (15), respectively, and the sludge is returned to the first compartment (6) of the anaerobic zone; the aeration rate of the aerobic zone (7) is controlled by the blower (11) and the rotor flow meter (12), and aerated by the microporous aeration head (13); the anaerobic ammonia oxidation packing (16) is hung in the last 3-4 compartments of the anoxic zone (8), all of which are made of polyethylene packing with a diameter of 25mm and a filling ratio of 25%-30%; the agitator (9) is installed in the anaerobic zone (6) and the anoxic zone (8);

[0012] A method of using the device includes the following steps:

[0013] (1) Process start-up

[0014] 1) Inoculate the secondary sedimentation tank return sludge of the urban sewage treatment plant into the segmented influent AOA tank (5) and cultivate it to reach a sludge concentration of 4000-5000 mg / L. Then inoculate the polyethylene packing material with anaerobic ammonia oxidation biofilm attached into the last 3-4 compartments of the anoxic zone (8) in the segmented influent AOA tank (5), with a filling ratio of 25% to 30%.

[0015] 2) Raw water enters the segmented inlet AOA tank (5) from the domestic sewage tank (1) via the inlet pump (2). 60%-80% of the inlet water enters the anaerobic zone (6) via the inlet pipe (3) and the inlet control valve (4), and 20%-40% of the inlet water enters the anoxic zone (8) via the inlet trunk pipe (3) and the inlet control valve (4). Sludge from the secondary sedimentation tank (10) is returned to the anaerobic zone (6) via the sludge return pump (17), and the sludge return ratio is controlled at 70%-120%. The mixed liquor flows from the anaerobic zone (6) into the aerobic zone (7), from the aerobic zone (7) into the anoxic zone (8), and from the anoxic zone (8) into the anoxic zone (9). The oxygen zone (8) enters the secondary sedimentation tank (10) through the effluent pipe. The residence time in the secondary sedimentation tank is 2-3 hours, thereby achieving mud-water separation. The returned sludge is pumped back to the anaerobic zone (6) through the sludge return pump (17). The effluent is discharged through the overflow weir and the outlet. The discharge of the remaining sludge is controlled by the sludge discharge gate valve (15), and the sludge age of the flocculent sludge in the segmented influent AOA tank (5) is controlled to be 13-17 days. The oxygenation of the aerobic zone is regulated by controlling the opening of the blower (11) and the aeration of the rotor flow meter (12), and the dissolved oxygen concentration of the aerobic zone (8) is controlled to be 2mg / L-3mg / L.

[0016] 3) The average hydraulic retention time (HRT) of the segmented AOA tank (5) was controlled at 15-18 h, with an anaerobic:aerobic:anoxic ratio of 1-2:2-4:5-8. Mature anaerobic ammonia oxidation packing material (10) was inoculated into the last 3-4 cells of the anoxic zone (7) to establish a carbon-limited zone as a hotspot ecological niche for anaerobic ammonia oxidation. All packing materials used were 25 mm diameter polyethylene packing materials with a filling ratio of 25%-30%. Successful process startup was indicated by an increase in the abundance of anaerobic ammonia oxidation bacteria on the packing material in the carbon-limited zone to 10. 9 The nitrogen removal rate is calculated as copies / gVSS, and the nitrogen removal rate of anammox reaches more than 50%. The following formula is the formula for calculating the contribution rate of anammox, where AMX is the contribution rate of anammox; ΔNH4 + It is the hypoxia stage from beginning to end. NH4 + Changes in mass concentration; TIN inf and TIN effThese represent the mass concentrations of total inorganic nitrogen in the influent and effluent, respectively. Total inorganic nitrogen includes ammonia nitrogen, nitrate nitrogen, and nitrite nitrogen; D is the discharge rate (%); and 2.06 is the calculation parameter for anaerobic ammonia oxidation.

[0017] (2) Stable operation of the process

[0018] 1) Raw water is pumped into the segmented AOA tank (5) in two stages via the inlet pump (2). In the first stage, 60%-80% of the water enters the anaerobic zone (6), and in the second stage, 20%-40% enters the anoxic zone (8). Sludge from the secondary sedimentation tank (10) is returned to the anaerobic zone (6), with the sludge return ratio controlled at 70%-120%. The mixed liquor flows from the anaerobic zone (6) into the aerobic zone (7), from the aerobic zone (7) into the anoxic zone (8), and from the anoxic zone (8) into the secondary sedimentation tank (10) via the outlet pipe. The retention time in the secondary sedimentation tank is 2-3 hours. The returned sludge is pumped back to the anaerobic zone (6) via the sludge return pump (17), and the effluent is discharged through the overflow weir and outlet. The average hydraulic retention time (HRT) is controlled at 15-18 hours, with the ratio of anaerobic:aerobic:anoxic = 1-2:2-4:5-8. The sludge age of the flocculent sludge should be controlled at 13–17 days. The dissolved oxygen concentration in the aerobic zone (8) should be controlled at 2 mg / L–3 mg / L.

[0019] 2) In the second stage of influent, external carbon sources from domestic sewage are introduced to directly drive external denitrification in the first 1-2 cells of the anoxic zone (8), while internal carbon sources are used to drive the reduction of nitrate nitrogen to nitrite nitrogen in the last 2-3 cells of the anoxic zone (8). A carbon-limited zone is established in the last 2-3 cells of the anoxic zone (7) as a hotspot ecological niche for anaerobic ammonia oxidation. Ultimately, deep denitrification of domestic sewage is achieved, with the total inorganic nitrogen concentration in the effluent being less than 8 mg / L.

[0020] This invention provides a device and method for establishing a carbon-limited zone as an anammox hotspot ecological niche based on carbon metabolism regulation to achieve mainstream anammox in domestic sewage, which has the following advantages:

[0021] 1) This invention establishes a carbon-limited zone as an ecological niche for anaerobic ammonia oxidation by regulating carbon metabolism, thereby utilizing the carbon source in domestic sewage to achieve short-cut denitrification. This provides a stable substrate of nitrite for anaerobic ammonia oxidizing bacteria, promoting their activity. Efficient denitrification is achieved by introducing raw water carbon sources into the carbon-rich zone, and the slow-release characteristics of the endogenous denitrification carbon source are used to promote the proliferation of anaerobic ammonia oxidizing bacteria in the anoxic zone. This process has advantages such as saving on external carbon sources and aeration, achieving energy conservation and consumption reduction in sewage treatment.

[0022] 2) Reduce the regulation of denitrification gene expression by decreasing the carbon source gradient, thereby weakening their competition for nitrite substrates. Construct a nitrite "slow-release utilization" coupling system by utilizing the metabolic lag effect of endogenous denitrification. In carbon-limited regions, anaerobic ammonia oxidation is used to reversely inhibit the competitive consumption of GAOs, ensuring the ecological site advantage of anaerobic ammonia oxidizing bacteria.

[0023] 3) The method is simple, flexible in operation, and highly operable. It is suitable for upgrading and renovating existing urban sewage treatment plants and for treating urban domestic sewage with low carbon-nitrogen ratios. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the device structure of the present invention.

[0025] 1—Domestic sewage tank; 2—Inlet pump; 3—Inlet pipe; 4—Inlet control valve; 5—Sectional inlet AOA tank; 6—Anaerobic zone; 7—Aerobic zone; 8—Anoxic zone; 9—Agitator; 10—Secondary sedimentation tank; 11—Blower; 12—Rotameter; 13—Microporous aeration head; 14—Sludge return control valve; 15—Sludge discharge valve; 16—Anaerobic ammonia oxidation packing; 17—Sludge via sludge return pump.

[0026] Figure 2 This is a schematic diagram illustrating the principle of the present invention. Detailed Implementation

[0027] The present invention is described in detail with reference to the accompanying drawings and implementation examples. A device for realizing mainstream anammox in domestic sewage by establishing a carbon-limited zone as an anammox hotspot ecological niche based on carbon metabolism regulation is characterized in that: the main device used includes a domestic sewage tank (1), an inlet pump (2), an inlet pipe (3), an inlet control valve (4), a segmented inlet AOA tank (5), an anaerobic zone (6), an aerobic zone (7), an anoxic zone (8), a stirrer (9), a secondary sedimentation tank (10), a blower (11), a rotor flow meter (12), a microporous aeration head (13), a sludge return control valve (14), a sludge discharge valve (15), anammox packing material (16), and a sludge return pump (17); the segmented inlet AOA tank (5) includes an anaerobic zone (6), an aerobic zone (7), and an anoxic zone (8) connected in sequence, with the ratio of each zone being 1~2:2~4:5~8. The domestic sewage tank (1) is connected to the anaerobic zone (6) and the anoxic zone via the inlet pump (2) and the inlet pipe (3); the sludge return and discharge of the secondary sedimentation tank are controlled by the sludge return control gate valve (14) and the sludge discharge gate valve (15), respectively, and the sludge is returned to the first compartment (6) of the anaerobic zone; the aeration rate of the aerobic zone (7) is controlled by the blower (11) and the rotor flow meter (12), and aerated by the microporous aeration head (13); the last three compartments of the anoxic zone (8) are equipped with anaerobic ammonia oxidation packing (16), all of which are polyethylene packing with a diameter of 25mm and a filling ratio of 25%-30%; the anaerobic zone (6) and the anoxic zone (8) are equipped with agitators (9);

[0028] The method of using the device is characterized by comprising the following steps:

[0029] (1) Process start-up

[0030] 1) Inoculate the secondary sedimentation tank return sludge of the urban sewage treatment plant into the segmented influent AOA tank (5) and cultivate it to a sludge concentration of about 4000-5000 mg / L. Then inoculate the polyethylene packing material with anaerobic ammonia oxidation biofilm attached into the last 3-4 compartments of the anoxic zone (8) in the segmented influent AOA tank (5), with a filling ratio of 25% to 30%.

[0031] 2) Raw water enters the segmented inlet AOA tank (5) from the domestic sewage tank (1) via the inlet pump (2). 60%-80% of the inlet water enters the anaerobic zone (6) via the inlet pipe (3) and the inlet control valve (4), and 20%-40% of the inlet water enters the anoxic zone (8) via the inlet trunk pipe (3) and the inlet control valve (4). Sludge from the secondary sedimentation tank (10) is returned to the anaerobic zone (6) via the sludge return pump (17), and the sludge return ratio is controlled at 70%-120%. The mixed liquor flows from the anaerobic zone (6) into the aerobic zone (7), from the aerobic zone (7) into the anoxic zone (8), and from the anoxic zone (8) into the anoxic zone (9). The oxygen zone (8) enters the secondary sedimentation tank (10) through the effluent pipe. The residence time in the secondary sedimentation tank is 2-3 hours, thereby achieving mud-water separation. The returned sludge is pumped back to the anaerobic zone (6) through the sludge return pump (17). The effluent is discharged through the overflow weir and the outlet. The discharge of the remaining sludge is controlled by the sludge discharge gate valve (15), and the sludge age of the flocculent sludge in the segmented influent AOA tank (5) is controlled to be 13-17 days. The oxygenation of the aerobic zone is regulated by controlling the opening of the blower (11) and the aeration of the rotor flow meter (12), and the dissolved oxygen concentration of the aerobic zone (8) is controlled to be 2mg / L-3mg / L.

[0032] 3) The average hydraulic retention time (HRT) of the segmented AOA tank (5) is controlled at 15-18 h, with an anaerobic:aerobic:anoxic ratio of 1-2:2-4:5-8. Mature anaerobic ammonia oxidation packing material (10) is inoculated into the last 3-4 cells of the anoxic zone (7) to establish a carbon-limited zone as a hotspot niche for anaerobic ammonia oxidation. All packing materials are 25 mm diameter polyethylene packing materials with a filling ratio of 25%-30%. Successful process startup is indicated by an increase in the abundance of anaerobic ammonia oxidation bacteria on the packing material in the last 2-3 cells of the anoxic zone to 10. 9 The nitrogen removal rate is calculated as copies / gVSS, and the nitrogen removal rate of anammox reaches more than 50%. The following formula is the formula for calculating the contribution rate of anammox, where AMX is the contribution rate of anammox; ΔNH4 + It is the hypoxia stage from beginning to end. NH4 + Changes in mass concentration; TIN inf and TIN eff These represent the mass concentrations of total inorganic nitrogen in the influent and effluent, respectively. Total inorganic nitrogen includes ammonia nitrogen, nitrate nitrogen, and nitrite nitrogen; D is the discharge rate (%); and 2.06 is the calculation parameter for anaerobic ammonia oxidation.

[0033] (2) Stable operation of the process

[0034] 1) Raw water is pumped into the segmented AOA tank (5) in two stages via the inlet pump (2). In the first stage, 60%-80% of the water enters the anaerobic zone (6), and in the second stage, 20%-40% enters the anoxic zone (8). Sludge from the secondary sedimentation tank (10) is returned to the anaerobic zone (6), with the sludge return ratio controlled at 70%-120%. The mixed liquor flows from the anaerobic zone (6) into the aerobic zone (7), from the aerobic zone (7) into the anoxic zone (8), and from the anoxic zone (8) into the secondary sedimentation tank (10) via the outlet pipe. The retention time in the secondary sedimentation tank is 2-3 hours. The returned sludge is pumped back to the anaerobic zone (6) via the sludge return pump (17), and the effluent is discharged through the overflow weir and outlet. The average hydraulic retention time (HRT) is controlled at 15-18 hours, with the ratio of anaerobic:aerobic:anoxic = 1-2:2-4:5-8. The sludge age of the flocculent sludge should be controlled at 13–17 days. The dissolved oxygen concentration in the aerobic zone (8) should be controlled at 2 mg / L–3 mg / L.

[0035] 2) In the second stage of influent, external carbon sources from domestic sewage are introduced to directly drive external denitrification in the first 1-2 cells of the anoxic zone (8), while internal carbon sources are used to drive the continuous reduction of nitrate nitrogen to nitrite nitrogen in the last 2-3 cells of the anoxic zone (8). A carbon-limited zone is established in the last 2-3 cells of the anoxic zone (7) as a hotspot ecological niche for anaerobic ammonia oxidation. Ultimately, deep denitrification of domestic sewage is achieved, with the total inorganic nitrogen concentration in the effluent being less than 8 mg / L.

Claims

1. A device for establishing a carbon-limited zone as an anaerobic ammonia oxidation (anammox) hotspot niche to realize mainstream anammox of domestic sewage based on carbon metabolism regulation, characterized in that: The device comprises a domestic sewage tank (1), a water inlet pump (2), a water inlet pipeline (3), a water inlet control gate valve (4), a segmented water inlet AOA tank (5), an anaerobic zone (6), an aerobic zone (7), an anoxic zone (8), a stirrer (9), a secondary sedimentation tank (10), a blower (11), a rotor flowmeter (12), a microporous aeration head (13), a sludge return control gate valve (14), a sludge discharge gate valve (15), an anammox filler (16), and a sludge return pump (17). The segmented water inlet AOA tank (5) comprises the anaerobic zone (6), the aerobic zone (7), and the anoxic zone (8) connected in sequence, and the proportion of each zone is 1-2:2-4:5-8. The domestic sewage tank (1) is connected with the anaerobic zone (6) and the anoxic zone (8) through the water inlet pipeline (3) via the water inlet pump (2). The sludge return and the discharge of the residual sludge in the secondary sedimentation tank are controlled by the sludge return control gate valve (14) and the sludge discharge gate valve (15) respectively, and the sludge return is to the first compartment of the anaerobic zone (6). The aeration amount of the aerobic zone (7) is controlled by the blower (11) and the rotor flowmeter (12) and aerated by the microporous aeration head (13). The anammox filler (16) is hung in the last three compartments of the anoxic zone (8), and all the fillers are polyethylene fillers with a filling ratio of 25%-30%. The anaerobic zone (6) and the anoxic zone (8) are provided with the stirrers (9).

2. A method using the device according to claim 1, characterized in that: (1) Process start-up 1) The secondary sedimentation tank return sludge of a municipal sewage treatment plant is inoculated into the segmented water inlet AOA tank (5), and the sludge concentration is cultured to reach 4000-5000 mg / L. Then the polyethylene filler with anammox biofilm is inoculated into the last three compartments of the anoxic zone (8) in the segmented water inlet AOA tank (5) with a filling ratio of 25%-30%; 2) The raw water is fed from the domestic sewage tank (1) into the segmented water inlet AOA tank (5) via the water inlet pump (2). The first-stage water is fed into the anaerobic zone (6) via the water inlet pipeline (3) and the water inlet control gate valve (4). The second-stage water is fed into the anoxic zone (8) via the water inlet pipeline (3) and the water inlet control gate valve (4). The sludge from the secondary sedimentation tank (10) is returned to the anaerobic zone (6) by the sludge return pump (17), and the sludge return ratio is controlled to be 70%-120%. The mixed liquor flows from the anaerobic zone (6) into the aerobic zone (7), from the aerobic zone (7) into the anoxic zone (8), and from the anoxic zone (8) into the secondary sedimentation tank (10) via the water outlet pipeline. The sludge is separated in the secondary sedimentation tank with a residence time of 2-3 h. The return sludge is returned to the anaerobic zone (6) by the sludge return pump (17), and the effluent is discharged through the overflow weir. The discharge of the residual sludge is controlled by the sludge discharge gate valve (15), and the sludge age of the flocculation sludge in the segmented water inlet AOA tank (5) is controlled to be 13-17 d. The oxygenation amount of the aerobic zone is controlled by controlling the opening of the blower (11) and the aeration amount of the rotor flowmeter (12), and the dissolved oxygen concentration of the aerobic zone (8) is controlled to be 2 mg / L-3 mg / L; 3) The average hydraulic retention time HRT of the step-feed AOA tank (5) is controlled at 15-18 h, with anaerobic: aerobic: anoxic: = 1-2: 2-4: 5-8; the external carbon source in domestic wastewater introduced in the second-stage feed directly drives efficient external denitrification in the front section of the anoxic zone (8), while the internal carbon source stored in the anaerobic zone is used to slowly drive the reduction of nitrate nitrogen to nitrite substrate for anammox bacteria in the rear section of the anoxic zone (8), fully exerting the advantages of anammox autotrophic denitrification; the mature anammox filler (10) is inoculated in the last three grids of the anoxic zone (7) to establish a carbon-limited zone as the hot spot niche for anammox; the fillers are all polyethylene fillers with a diameter of 25 mm, and the filling ratio is 25%-30%; the successful start-up of the process is marked by an increase of 1 x 10 9 copies / gVSS in the anammox bacteria abundance on the fillers in the carbon-limited zone, and the anammox denitrification accounts for more than 50%; the following formula is the calculation formula of the anammox contribution rate, wherein AMX is the anammox contribution rate; ΔNH4+ is the change in NH4+ concentration from the beginning to the end of the anoxic stage; TINinf and TINeff are the total inorganic nitrogen of the influent and effluent, respectively; D is the drainage rate (%); and 2.06 is the parameter for calculating anammox of NH4+. (2) Process stable operation The raw water is divided into two sections by the water pump (2) and enters the sectional water-inlet AOA tank (5), the first section enters the anaerobic zone (6), and the second section enters the anoxic zone (8); the sludge in the secondary sedimentation tank (10) is returned to the anaerobic zone (6), and the sludge return ratio is controlled at 70% to 120%; the mixed liquid flows from the anaerobic zone (6) to the aerobic zone (7), from the aerobic zone (7) to the anoxic zone (8), and from the anoxic zone (8) to the secondary sedimentation tank (10) through the water outlet pipe, stays in the secondary sedimentation tank for 2 to 3 hours, the returned sludge is pumped back to the anaerobic zone (6) by the sludge return pump (17), and the effluent is discharged through the water outlet by the overflow weir; the average hydraulic retention time HRT is controlled at 15 to 18 hours, wherein the anaerobic:aerobic:anoxic ratio is 1 to 2:2 to 4:5 to 8; the sludge age of the flocculent sludge is controlled at 13 to 17 days; and the dissolved oxygen concentration in the aerobic zone (8) is controlled at 2 mg / L to 3 mg / L.

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