Two-stage anaerobic ammonia oxidation coupling denitrification system and use method

Abstract

The present application relates to sewage treatment technical field, specifically to a two-stage anaerobic ammonia oxidation coupled denitrification system and use method, the system includes volume ratio 1:2-4 of anoxic reaction zone and aerobic reaction zone, the anoxic reaction zone is added with anaerobic ammonia oxidation granular sludge in the form of net bag, the treatment method includes: first, optimizing the traditional process to the energy-saving working condition of C / N = 5:1, then adding anaerobic ammonia oxidation granular sludge, and gradually reducing the influent C / N to 2.5:1, and reducing the aeration amount simultaneously, the present application realizes stable and efficient denitrification under low carbon-nitrogen ratio conditions through the synergistic regulation of net bag retention function flora, carbon-nitrogen ratio and aeration amount, the carbon source demand is reduced by 50%, the aeration energy consumption is reduced by 30%, and greenhouse gas emissions are significantly reduced, which has good economic and environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a two-stage anaerobic ammonia oxidation coupled denitrification system and its usage method. Background Technology

[0002] Traditional biological nitrogen removal processes (nitrification-denitrification) face significant challenges, including insufficient carbon sources, high energy consumption, and substantial greenhouse gas emissions. Traditional processes typically require an influent carbon-to-nitrogen ratio (C / N) of at least 4:1, while some domestic wastewater often has a C / N ratio below this value, necessitating the addition of large amounts of external carbon sources, which can account for 30%-50% of wastewater treatment plant operating costs. While anammox technology does not require a carbon source, it suffers from slow bacterial proliferation, easy loss of microorganisms, and unstable nitrite supply.

[0003] In recent years, various coupling process schemes have been proposed in existing technologies. For example, invention patent CN110217889B discloses a device and method for treating urban domestic sewage using a two-stage enhanced semi-short-cut nitrification coupled with anaerobic ammonia oxidation based on a biofilm. This device consists of a raw water tank, an enhanced semi-short-cut nitrification (SBBR) reactor, an intermediate water tank, and an anaerobic ammonia oxidation (MBBR) reactor connected sequentially, retaining anaerobic ammonia oxidizing bacteria through a biofilm. Invention patent CN107032506B discloses a device and method for treating domestic sewage using segmented effluent short-cut nitrification-Anammox / denitrification, utilizing a biofilm to couple anaerobic ammonia oxidizing bacteria with denitrifying bacteria, and fully utilizing the carbon source of the raw water to achieve simultaneous nitrogen and phosphorus removal from domestic sewage with a low carbon-to-nitrogen ratio. Invention patent CN116199336B discloses a method for rapidly restoring the activity of anaerobic ammonia oxidizing bacteria by adding nitrate nitrogen in AOA mode to achieve autotrophic denitrification of domestic sewage. Invention patent CN115353193B discloses an apparatus and method for simultaneous deep nitrogen and phosphorus removal in municipal wastewater through side-flow phosphorus release and short-cut nitrification / anammox. Invention patent CN114772725B discloses an apparatus and method for enhanced nitrogen and phosphorus removal in domestic wastewater through sulfur autotrophic short-cut denitrification coupled with anammox. Furthermore, patent CN119461654A discloses a two-stage short-cut denitrification-anammox dual-granular sludge device for wastewater treatment; this device uses granular sludge but is a completely continuous flow process.

[0004] However, the existing technologies mentioned above still have the following shortcomings when treating low C / N domestic sewage: the use of biofilm packing has problems such as easy clogging of the packing and difficulty in enrichment and migration of bacteria; the continuous flow process has poor adaptability to fluctuations in influent water quality; and most existing processes do not clearly provide a coordinated control strategy for the carbon-nitrogen ratio and aeration rate when transitioning from traditional processes to coupled processes.

[0005] Therefore, there is an urgent need to develop a coupled denitrification system and its application method that can effectively retain anaerobic ammonia-oxidizing bacteria, reduce carbon source and aeration energy consumption, and has a clear control strategy to solve this problem. Summary of the Invention

[0006] To address the problems of high cost, high energy consumption, difficulty in retaining anaerobic ammonia oxidizing bacteria, and lack of systematic control strategies in the denitrification of domestic sewage with low carbon-to-nitrogen ratio in existing technologies, this invention provides a two-stage coupled denitrification system and its usage method.

[0007] The specific technical solution is as follows: A two-stage anaerobic ammonia oxidation coupled denitrification system, including: anoxic reaction zone, aerobic reaction zone, influent system, reflux system, effluent system, control system, sludge discharge system and sludge storage device; The anoxic reaction zone is made of transparent plexiglass and serves as the main site for denitrification and anaerobic ammonium oxidation reactions. It is equipped with a stirrer and contains at least one mesh bag filled with anaerobic ammonium oxidation granular sludge. The bottom is equipped with a sludge discharge port. The aerobic reaction zone is made of polyethylene plastic and serves as the main site for nitrification. It is connected to the anoxic reaction zone. A microporous aeration device is installed at the bottom and connected to an aeration pump and a gas flow meter. The gas flow meter is a rotor flow meter with a range of 0-1.5L / min. A sludge discharge port is also provided at the bottom. The volume ratio of the hypoxic reaction zone to the aerobic reaction zone is 1:2-4; The water inlet system includes an inlet tank and an inlet pump. The inlet tank is used to store domestic sewage with a low carbon-to-nitrogen ratio to be treated. The inlet pump is connected to the bottom of the anoxic reaction zone and is used to pump the sewage to be treated into the bottom of the anoxic reaction zone. The reflux system includes a reflux pump, which is connected to the end of the aerobic reaction zone and the bottom of the anoxic reaction zone, and is used to transport the mixed liquid at the end of the aerobic reaction zone to the bottom of the anoxic reaction zone; the effluent system includes an effluent tank and an effluent pump, which is used to collect, temporarily store and treat the treated water to meet the standards, and the effluent pump is connected to the end of the aerobic reaction zone and the effluent tank, and is located at the end of the aerobic reaction zone. The sludge discharge system includes a sludge discharge pump, and the sludge storage device is a sludge bucket. The sludge discharge pump is connected to the sludge discharge port of the anoxic reaction zone and the aerobic reaction zone and the sludge bucket, and is used to periodically discharge the remaining sludge of the system. The control system is used to control the start and stop of each pump and aeration device to achieve cyclic operation, and a time-controlled switch is used for unified control.

[0008] As a further technical solution, the mesh size of the net bag is 10-100 mesh, which is used to retain anaerobic ammonia-oxidizing bacteria and prevent the loss of bacteria.

[0009] As a further technical solution, the anaerobic ammonia oxidation granular sludge is a dark red granule that has been domesticated in the laboratory for a long time, with a particle size of 2-5mm. The dosage is 10%-20% of the effective volume of the anoxic reaction zone. After being put into a mesh bag, it is placed in the anoxic reaction zone to achieve efficient retention and gradual migration and diffusion of anaerobic ammonia oxidation bacteria.

[0010] As a further technical solution, the anoxic reaction zone and the aerobic reaction zone are connected by an overflow method to ensure the smooth flow of the reaction liquid.

[0011] As a further technical solution, the outer wall of the anoxic reaction zone is provided with a water bath insulation layer, and a heating rod is installed inside. The heating rod works in conjunction with the water bath insulation layer to maintain a stable reaction temperature. The outer wall of the aerobic reaction zone is provided with an electric heating insulation layer, specifically an electric heating pad covering the outer wall of the aerobic reaction zone, which is used to maintain the temperature required for the nitrification reaction in the aerobic reaction zone.

[0012] A method of using the system, specifically a method for treating domestic wastewater with a low carbon-to-nitrogen ratio, includes the following steps: S1 Traditional Process Start-up and Parameter Optimization Stage: Activated sludge is inoculated into the anoxic and aerobic reaction zones. The activated sludge is taken from the CASS tank of a municipal wastewater treatment plant, pretreated, and added with an initial sludge concentration of approximately 4000 mg / L. A cyclical operation mode is adopted, with each cycle including influent and aeration, sedimentation, effluent discharge, and idle. Under the premise that the total nitrogen in the effluent meets the standard, the energy-saving operating conditions of the traditional process are determined as follows: influent C / N = 5:1, reflux ratio = 200%-400%, aeration rate of 1.3 L / min, and dissolved oxygen in the aerobic reaction zone maintained at 4-5 mg / L. S2 Coupling Process Construction Stage: Under the energy-saving operating conditions, anaerobic ammonia oxidation granular sludge is introduced into the anoxic reaction zone by adding it through mesh bags, keeping the operating parameters of the energy-saving operating conditions unchanged, so that denitrifying bacteria and anaerobic ammonia oxidation bacteria gradually work together. S3 Low C / N Ratio Adaptation and Stable Operation Phase: Gradually reduce the influent C / N ratio to 2.5-5:1, simultaneously reduce the aeration rate, and implement phased coordinated regulation. The specific regulation path is as follows: C / N ratio from 5:1 → 4:1 → 3:1 → 2.5:1, aeration rate from 1.3L / min → 1.1L / min → 0.9L / min, dissolved oxygen in the aerobic reaction zone is maintained at 2-3 mg / L to avoid high oxygen inhibiting anaerobic ammonia-oxidizing bacteria. Stable operation is achieved under these conditions, realizing stable nitrogen removal with low carbon source and low energy consumption. During operation, the single-cycle water treatment volume is matched with the effective volume of the anoxic reaction zone. After treatment, the effluent ammonia nitrogen is 0.2-0.6 mg / L (removal rate ≥98%), and total nitrogen is 10-13 mg / L (removal rate 55%-60%), meeting the Class A standard. The effluent luminescence inhibition rate is ≤20%, and the biological safety is good. During operation, the anoxic reaction zone achieves denitrification through both denitrification and anaerobic ammonia oxidation, while the aerobic reaction zone completes the nitrification reaction. The abundance of Candidatus Brocadia in the system gradually increases and diffuses to the suspended sludge, increasing the proportion of β-fold structure in the sludge, resulting in a bimodal particle size distribution and significantly improved settling performance.

[0013] As a further technical solution, in step S3, the influent C / N ratio is finally stabilized at 2.5:1, at which point the system achieves optimal denitrification and energy-saving effects.

[0014] As a further technical solution, the cycle operation mode described in step S1 is as follows: each cycle is 4 hours, including 2 hours of water intake and aeration, 30 minutes of sedimentation, 50 minutes of water output and 40 minutes of idle time, with a single cycle water treatment capacity of 9L.

[0015] As a further technical solution, the reflux ratio in step S1 is 300%, which is the optimal energy-saving reflux parameter.

[0016] As a further technical solution, the method also includes step S4, greenhouse gas monitoring: during the stable operation phase, gas samples are collected from the anoxic reaction zone and the aerobic reaction zone to measure the concentrations of CO2, CH4, and N2O, and to evaluate the greenhouse gas reduction effect of the process. Monitoring shows that the process can reduce CO2 by 45%-50% and N2O by 85%-90%. The reduction principle is that the reduction of carbon source consumption reduces CO2 production, and the anaerobic ammonia oxidation pathway significantly inhibits N2O generation. At the same time, this method can reduce the system's carbon source demand by 50% and aeration energy consumption by 30%, making it suitable for efficient and low-carbon treatment of domestic sewage with a low carbon-to-nitrogen ratio.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) Significantly reduce operating costs: Compared with traditional processes, this invention can reduce the influent carbon-nitrogen ratio from 5:1 to 2.5:1 while ensuring stable effluent quality, and reduce carbon source demand by 50%; aeration energy consumption is reduced by about 30%.

[0018] (2) Effective retention of functional microbial community: The mesh bag granular sludge addition strategy provides a physical retention space for the slow-growing anaerobic ammonia-oxidizing bacteria, solving the problem of easy loss. This increases the abundance of Candidatus Brocadia in the system from 40.94% to over 69%, and the bacteria successfully migrate to the suspended sludge, with an abundance of 16.20% in the aerobic zone and 10.77% in the anaerobic zone.

[0019] (3) Significant greenhouse gas reduction effect: The method of the present invention can reduce CO2 emissions by 45%-50% and N2O emissions by 85%-90%, achieving low-carbon wastewater treatment.

[0020] (4) Improved sludge settling performance: The introduction of anaerobic ammonia oxidizing bacteria promoted the increase of the proportion of β-sheet structure in extracellular polymeric substances (EPS) (from 27.02% to 31.96%), enhanced the mechanical strength and aggregation ability of sludge, and changed the sludge particle size from a single-peak distribution to a double-peak distribution, with the main strong peak concentrated in 800-1000μm, thus improving the sludge settling performance.

[0021] (5) Clear process control strategy: This invention provides a specific strategy for achieving stable operation of the coupled process by synergistic control of carbon-nitrogen ratio and aeration volume, starting from the energy-saving conditions of traditional processes. It is operable and repeatable.

[0022] (6) Good biological safety of effluent: Acute toxicity test showed that the luminescence inhibition rate of effluent during the stable period of the coupled process was controlled within 20%, which is comparable to that of the traditional process. This indicates that the coupled process does not reduce the system’s ability to remove toxic substances while achieving efficient denitrification. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A schematic diagram of the two-stage coupled denitrification system of the present invention.

[0025] Figure 2 This invention provides a time allocation diagram for each stage within a single operating cycle.

[0026] Figure 3 A comparison chart of total nitrogen removal rates between the conventional process and the coupled process of this invention at different carbon-nitrogen ratios.

[0027] Figure 1 In the middle section: 1. Inlet tank; 2. Anaerobic tank; 3. Aerobic tank; 4. Outlet tank; 5. Heating rod; 6. Added Anammox granular sludge mesh bag; 7. Agitator; 8. Electric heating pad; 9. Aeration disc; 10. Aeration pump; 11. Rotor flow meter; 12. Sludge tank; P1. Inlet pump; P2. Return pump; P3. Outlet pump; P4. Sludge discharge pump. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0029] Example 1: This embodiment employs a two-stage nitrification-denitrification-anaerobic ammonium oxidation coupled nitrogen removal system, with the structure as follows: Figure 1 As shown, the components are described below: Inlet Tank 1: Used to store domestic sewage with low carbon-to-nitrogen ratio to be treated, providing a stable source of inlet water for the system.

[0030] Anaerobic tank 2: also known as the anoxic reaction zone, with an effective volume of 9L, a diameter of 20cm, a height of 40cm, and made of transparent plexiglass; it is the main site for denitrification and anaerobic ammonia oxidation reactions.

[0031] Aerobic tank 3: also known as the aerobic reaction zone, with an effective volume of 27L, a length of 40cm, a width of 20cm, and a height of 36cm, made of polyethylene plastic; it is the main site for nitrification reaction and is connected to anaerobic tank 2 by overflow.

[0032] Water outlet tank 4: Used to collect and temporarily store the treated water that meets the standards after being treated in aerobic tank 3.

[0033] Heating rod 5: Installed inside the anaerobic tank 2, used in conjunction with the outer wall water bath insulation layer to maintain a stable reaction temperature inside the anaerobic tank 2.

[0034] Anammox granular sludge mesh bag 6: 100 mesh, filled with anaerobic ammonia oxidation granular sludge, placed inside anaerobic tank 2 to retain anaerobic ammonia oxidation bacteria and prevent bacterial loss.

[0035] Agitator 7: Installed inside anaerobic tank 2, used to stir the sludge-water mixture to keep the sludge suspended and the substrate mass transfer uniform.

[0036] Electric heating pad 8: Covers the outer wall of aerobic tank 3 to maintain the temperature required for nitrification reaction in aerobic tank 3.

[0037] Aeration disc 9: There are 2 discs in total, each with a diameter of 15cm. They are located at the bottom of the aerobic tank 3 and are microporous aeration devices used for uniform air distribution.

[0038] Aeration pump 10: Located outside the aerobic tank 3, it is connected to the aeration disc 9 through a pipeline to provide aeration power for the aerobic tank 3.

[0039] Rotor flow meter 11: Connected in series in the pipeline between aeration pump 10 and aeration disc 9, with a range of 0-1.5L / min, used for precise adjustment and monitoring of aeration volume.

[0040] Sludge bucket 12: Connected to the bottom sludge discharge port of anaerobic tank 2 and aerobic tank 3 via pipeline, used to collect the system's excess sludge.

[0041] Pump body assembly: P1 Inlet Pump: Connects inlet tank 1 to the bottom of anaerobic tank 2, and pumps sewage into anaerobic tank 2; P2 reflux pump: Connected to the end of aerobic tank 3 and the bottom of anaerobic tank 2, it refluxes the nitrified liquid back to anaerobic tank 2; P3 effluent pump: Connects the end of aerobic tank 3 to effluent tank 4, and lifts the treated effluent to effluent tank 4; P4 sludge pump: connects anaerobic tank 2, aerobic tank 3 and sludge tank 12, and is used to periodically discharge excess sludge.

[0042] Overall system connectivity: The inlet tank 1 is connected to the bottom of the anaerobic tank 2 via the inlet pump P1; the overflow from the anaerobic tank 2 is connected to the aerobic tank 3; the bottom of the aerobic tank 3 is equipped with an aeration disc 9, which forms an aeration circuit via a rotor flow meter 11 and an aeration pump 10; the end of the aerobic tank 3 is connected to the bottom of the anaerobic tank 2 via a return pump P2 to form an internal return flow; the end of the aerobic tank 3 is connected to the outlet tank 4 via an outlet pump P3; the bottoms of the anaerobic tank 2 and the aerobic tank 3 are respectively connected to the sludge tank 12 via a sludge discharge pump P4; the anaerobic tank 2 is equipped with a heating rod 5, a stirrer 7, and an Anammox granular sludge mesh bag 6; the outer wall of the aerobic tank 3 is covered with an electric heating pad 8; all pumps and aeration devices are uniformly controlled by a timer switch of the control system to achieve periodic automatic operation.

[0043] 2. Source and dosing principle of inoculated sludge: Start-up activated sludge: taken from the CASS tank of the municipal wastewater treatment plant (Guilin Yanshan Wastewater Treatment Plant), pretreated and added to anaerobic tank 2 and aerobic tank 3, with an initial sludge concentration of about 4000 mg / L, to quickly build a basic nitrification-denitrification nitrogen removal system.

[0044] Anaerobic ammonia oxidation granular sludge: long-term laboratory acclimatization, dark red, particle size 2-5mm; dosage 1.2L, accounting for 13.3% of the effective volume of anaerobic tank 2, placed in mesh bag 6 and then placed in anaerobic tank 2 to achieve efficient retention and gradual migration and diffusion of anaerobic ammonia oxidation bacteria.

[0045] 3. System operation steps and control principles: The system operates on a 4-hour cycle: 2 hours of influent and aeration → 30 minutes of sedimentation → 50 minutes of effluent discharge → 40 minutes of idle time. The single-cycle water treatment capacity is 9L, which matches the effective volume of anaerobic tank 2.

[0046] (1) Start-up of traditional processes and optimization of energy-saving operating conditions S1: The optimized energy-saving operating conditions were determined as follows: influent C / N = 5:1, reflux ratio 300%, aeration rate 1.3L / min, and dissolved oxygen in aerobic tank 3 4-5mg / L, providing a stable foundation for the construction of the coupled process.

[0047] (2) Construction of S2 using coupling process: Under energy-saving conditions, the mesh bag 6 containing Anammox granular sludge is put into the anaerobic tank 2, and the operating parameters are kept constant, so that the denitrifying bacteria and anaerobic ammonia oxidizing bacteria gradually work together.

[0048] (3) Low carbon-nitrogen ratio adaptation and stable operation S3: Phased and coordinated regulation: C / N: 5:1→4:1→3:1→2.5:1; Aeration rate: 1.3L / min → 1.1L / min → 0.9L / min; The dissolved oxygen in aerobic tank 3 is maintained at 2-3 mg / L to avoid high oxygen levels inhibiting anaerobic ammonia-oxidizing bacteria, thus achieving stable nitrogen removal with low carbon source and low energy consumption.

[0049] 4. Operational Results and Principle Analysis: (1) Water quality effect: The effluent ammonia nitrogen is 0.2-0.6 mg / L (removal rate ≥98%), and total nitrogen is 10-13 mg / L (removal rate 55%-60%), meeting the Class A standard.

[0050] Nitrification is completed in aerobic tank 3; denitrification and anaerobic ammonia oxidation are carried out in anaerobic tank 2.

[0051] (2) Greenhouse gas reduction S4: CO2 reduction of 45%-50%, N2O reduction of 85%-90%.

[0052] Reduced carbon source consumption lowers CO2 production; anaerobic ammonia oxidation pathway significantly inhibits N2O generation.

[0053] (3) Microbial and sludge performance: The abundance of Candidatus Brocadia increased from 40.94% to 69.76% and diffused into suspended sludge; the proportion of β-fold structure in sludge increased, the particle size distribution was bimodal, and the settling performance was significantly improved.

[0054] (4) Water discharge safety: The luminescence suppression rate in the effluent is ≤20%, which is comparable to that of traditional processes, and the biosafety is good.

[0055] 5. Summary of Benefits: It reduces carbon source demand by 50%, aeration energy consumption by 30%, and significantly reduces greenhouse gases, making it suitable for efficient and low-carbon treatment of domestic sewage with a low carbon-to-nitrogen ratio.

[0056] Figure 2 The present invention provides a time allocation diagram for each stage within an operating cycle, wherein ① represents water inlet + aeration; ② represents sedimentation; ③ represents effluent; and ④ represents idle time.

[0057] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not describe all details exhaustively, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification.

Claims

1. A two-stage anaerobic ammonia oxidation coupled denitrification system, characterized in that, include: Anoxic reaction zone, aerobic reaction zone, influent system, reflux system, effluent system, control system, sludge discharge system and sludge storage device; The anoxic reaction zone is made of transparent plexiglass and serves as the main site for denitrification and anaerobic ammonium oxidation reactions. It is equipped with a stirrer and contains at least one mesh bag filled with anaerobic ammonium oxidation granular sludge. The bottom is equipped with a sludge discharge port. The aerobic reaction zone is made of polyethylene plastic and serves as the main site for nitrification. It is connected to the anoxic reaction zone. A microporous aeration device is installed at the bottom and connected to an aeration pump and a gas flow meter. The gas flow meter is a rotor flow meter with a range of 0-1.5L / min. A sludge discharge port is also provided at the bottom. The volume ratio of the hypoxic reaction zone to the aerobic reaction zone is 1:2-4; The water inlet system includes an inlet tank and an inlet pump. The inlet tank is used to store domestic sewage with a low carbon-to-nitrogen ratio to be treated. The inlet pump is connected to the bottom of the anoxic reaction zone and is used to pump the sewage to be treated into the bottom of the anoxic reaction zone. The reflux system includes a reflux pump, which is connected to the end of the aerobic reaction zone and the bottom of the anoxic reaction zone, and is used to transport the mixed liquid at the end of the aerobic reaction zone to the bottom of the anoxic reaction zone; the effluent system includes an effluent tank and an effluent pump, which is used to collect, temporarily store and treat the treated water to meet the standards, and the effluent pump is connected to the end of the aerobic reaction zone and the effluent tank, and is located at the end of the aerobic reaction zone. The sludge discharge system includes a sludge discharge pump, and the sludge storage device is a sludge bucket. The sludge discharge pump is connected to the sludge discharge port of the anoxic reaction zone and the aerobic reaction zone and the sludge bucket, and is used to periodically discharge the remaining sludge of the system. The control system is used to control the start and stop of each pump and aeration device to achieve cyclic operation, and a time-controlled switch is used for unified control.

2. The system according to claim 1, characterized in that, The mesh size of the mesh bag is 10-100 mesh.

3. The system according to claim 1, characterized in that, The anaerobic ammonia oxidation granular sludge is a dark red granule that has been acclimatized in the laboratory for a long time, with a particle size of 2-5 mm. The dosage is 10%-20% of the effective volume of the anoxic reaction zone. After being put into a mesh bag, it is placed in the anoxic reaction zone.

4. The system according to claim 1, characterized in that, The hypoxic reaction zone and the aerobic reaction zone are connected by an overflow.

5. The system according to claim 1, characterized in that, The outer wall of the anoxic reaction zone is provided with a water bath insulation layer and a heating rod is installed inside; the outer wall of the aerobic reaction zone is provided with an electric heating insulation layer, specifically an electric heating pad covering the outer wall of the aerobic reaction zone.

6. A method of using the system according to any one of claims 1-5, characterized in that, Specifically, the method for treating domestic sewage with a low carbon-to-nitrogen ratio includes the following steps: S1 Traditional Process Start-up and Parameter Optimization Stage: Activated sludge is inoculated into the anoxic and aerobic reaction zones. The activated sludge is added after pretreatment, with an initial sludge concentration of approximately 4000 mg / L. A cyclical operation mode is adopted, with each cycle including influent and aeration, sedimentation, effluent discharge, and idle. Under the premise that the total nitrogen in the effluent meets the standard, the energy-saving operating conditions of the traditional process are determined as follows: influent C / N = 5:1, reflux ratio = 200%-400%, aeration rate of 1.3 L / min, and dissolved oxygen in the aerobic reaction zone maintained at 4-5 mg / L. S2 Coupling Process Construction Stage: Under the energy-saving operating conditions, anaerobic ammonia oxidation granular sludge is introduced into the anoxic reaction zone by adding it through mesh bags, keeping the operating parameters of the energy-saving operating conditions unchanged, so that denitrifying bacteria and anaerobic ammonia oxidation bacteria gradually work together. S3 Low C / N Ratio Adaptation and Stable Operation Phase: Gradually reduce the influent C / N ratio to 2.5-5:1, simultaneously reduce the aeration rate, and coordinate the control in stages. The specific control path is as follows: C / N from 5:14:13:12.5:1, aeration rate from 1.3L / min to 1.1L / min to 0.9L / min, and dissolved oxygen in the aerobic reaction zone is maintained at 2-3 mg / L. During operation, the single-cycle water treatment volume is matched with the effective volume of the anoxic reaction zone. After treatment, the effluent has ammonia nitrogen of 0.2-0.6 mg / L, total nitrogen of 10-13 mg / L, and luminescence inhibition rate of 20%.

7. The system usage method according to claim 6, characterized in that, In step S3, the influent C / N ratio eventually stabilizes at 2.5:

1.

8. The system usage method according to claim 6, characterized in that, The cycle operation mode described in step S1 is as follows: each cycle is 4 hours, including 2 hours of water intake and aeration, 30 minutes of sedimentation, 50 minutes of water effluent and 40 minutes of idle time, with a single cycle water treatment capacity of 9L.

9. The system usage method according to claim 6, characterized in that, The reflux ratio mentioned in step S1 is 300%.

10. The method of using the system according to claim 6, characterized in that, The method further includes step S4, greenhouse gas monitoring: during the stable operation phase, gas samples are collected from the anoxic reaction zone and the aerobic reaction zone to measure the concentrations of CO2, CH4, and N2O, and to evaluate the greenhouse gas emission reduction effect of the process.

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