A short-cut denitrification coupled with anaerobic ammonia oxidation composite biofilm based on carbon load regulation and a preparation method and application thereof

Abstract

This invention provides a short-cut denitrification coupled with anaerobic ammonia oxidation composite biofilm based on carbon load regulation, its preparation method, and its application, belonging to the field of wastewater treatment technology. The method of this invention includes the following steps: adding biofilm packing material enriched with denitrifying bacteria inside a sequencing batch reactor (SBR); adjusting the influent flow rate and carbon source dosage; gradually reducing the influent carbon-to-nitrogen ratio (C / N ratio); and in-situ enriching anaerobic ammonia oxidizing bacteria on the biofilm packing material to form a composite biofilm with symbiotic short-cut denitrifying bacteria and anaerobic ammonia oxidizing bacteria. The gradual reduction of the influent C / N ratio includes multiple continuous and stable operation stages. This invention directionally enriches anaerobic ammonia oxidizing bacteria on existing denitrifying bacterial membranes, resulting in a strong synergistic effect of functional bacterial communities. Under a C / N ratio of 2.5, the anaerobic ammonia oxidation nitrogen removal contribution rate is ≥60%, and the total nitrogen removal rate is consistently above 70%. It has advantages such as no need for additional inoculation, short construction cycle, and stable nitrogen removal efficiency.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a short-range denitrification coupled with anaerobic ammonia oxidation composite biofilm based on carbon load regulation, its preparation method, and its application. Background Technology

[0002] With the continuous increase in urban sewage discharge, sewage denitrification is a core component in controlling eutrophication and ensuring water environment safety. Traditional biological denitrification processes mainly rely on the nitrification-denitrification pathway, which has problems such as high carbon source demand, high energy consumption, and large sludge production. Especially considering the low carbon-to-nitrogen ratio commonly found in urban sewage, traditional processes require a large amount of external carbon source to achieve compliant discharge, significantly increasing the operating costs of sewage treatment plants.

[0003] Anammox technology is a new generation of biological nitrogen removal technology for wastewater. It uses ammonia nitrogen as an electron donor and nitrite as an electron acceptor to directly convert nitrogenous pollutants into nitrogen gas. It requires no external organic carbon source, has low aeration energy consumption, and produces little sludge, making it a research hotspot in the field of nitrogen removal from wastewater with a low carbon-to-nitrogen ratio. However, anammox bacteria are autotrophic microorganisms with slow growth and a generation doubling time of over 11 days, making them difficult to effectively accumulate in conventional wastewater treatment systems. Furthermore, they are sensitive to environmental conditions, severely limiting their engineering applications.

[0004] The short-cut denitrification coupled with anaerobic ammonia oxidation (PD / A) process precisely reduces nitrate to nitrite through short-cut denitrification, continuously providing substrate for the anaerobic ammonia oxidation reaction. This solves the problem of substrate source limitations for anaerobic ammonia oxidizing bacteria and simultaneously achieves efficient utilization of organic carbon sources, demonstrating significant technical advantages and application prospects in low C / N ratio wastewater treatment. However, the construction of existing PD / A process systems still faces several technical bottlenecks: First, most existing processes require additional inoculation with special seed sludge rich in anaerobic ammonia oxidizing bacteria. Obtaining such bacterial sources is difficult, and transportation and inoculation costs are high, making it difficult to promote in large-scale wastewater treatment projects. Second, the conventional method of in-situ enrichment of anaerobic ammonia oxidizing bacteria using activated sludge suffers from long start-up cycles, low enrichment efficiency, poor process stability, and weak synergy among functional bacterial communities, resulting in a low success rate in engineering applications. Third, existing technologies cannot utilize existing mature denitrification biofilm carriers in wastewater treatment plants to achieve targeted superposition of functional bacterial communities and rapid construction of PD / A composite biofilms, failing to fully realize the upgrading potential of existing wastewater treatment facilities.

[0005] Therefore, developing a method for constructing PD / A biofilms that requires no additional inoculation with special bacterial sludge, has a short construction cycle, high enrichment efficiency, and stable operation has become a pressing technical challenge in this field, and has significant engineering implications for the low-carbon and high-efficiency upgrading and transformation of urban wastewater treatment plants. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing PD / A process systems, such as high dependence on bacterial sources, long start-up period, low enrichment efficiency of anaerobic ammonia oxidation, and poor process stability. This invention provides a short-range denitrification coupled with anaerobic ammonia oxidation composite biofilm based on carbon load regulation, its preparation method, and its application. By adjusting the carbon load management strategy of the influent carbon-nitrogen ratio, anaerobic ammonia oxidizing bacteria are enriched in situ on existing biofilm packing material enriched with denitrifying bacteria, achieving rapid and stable construction of the PD / A composite biofilm, reducing process costs, and improving the denitrification efficiency and operational stability of wastewater with low carbon-nitrogen ratios.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a short-range denitrification coupled with anaerobic ammonia oxidation composite biofilm based on carbon loading regulation, comprising the following steps: Biofilm packing material is added inside the sequencing batch reactor, and the influent flow rate and carbon source dosage are adjusted to gradually reduce the influent carbon-nitrogen ratio. Anaerobic ammonia oxidizing bacteria are enriched in situ on the biofilm packing material to form a composite biofilm in which short-range denitrifying bacteria and anaerobic ammonia oxidizing bacteria coexist. The biofilm packing material is a biofilm packing material enriched with denitrifying bacteria; The stepwise reduction of the influent carbon-nitrogen ratio includes three continuous and stable operating stages: the first stage has a carbon-nitrogen ratio of 3.3 to 3.7, the second stage has a carbon-nitrogen ratio of 2.8 to 3.2, and the third stage has a carbon-nitrogen ratio of 2.4 to 2.6.

[0008] Preferably, the sequencing batch reactor is equipped with a stirring device, which keeps the biofilm packing material in suspension during operation of the sequencing batch reactor, with a stirring rate of 40-80 rpm; the drainage ratio of the sequencing batch reactor is 30-70%.

[0009] Preferably, the hydraulic retention time of the sequencing batch reactor is 4 to 12 hours, and it operates for one or more cycles per day, with a single cycle operating time of 2 to 6 hours. The biofilm packing material is polyethylene, and the packing rate of the biofilm packing in the sequencing batch reactor is 30-60%. The temperature of the sequencing batch reactor is 20~35℃, the pH value is 7.0~8.0, and the dissolved oxygen concentration in the sequencing batch reactor is ≤0.5mg / L.

[0010] Preferably, the first, second, and third stages are run independently for ≥10 days; the second stage begins after the total nitrogen removal rate stabilizes at 40-50%, and the third stage begins after the total nitrogen removal rate stabilizes at 55-65%.

[0011] Preferably, the influent is actual domestic sewage or simulated domestic sewage. The actual domestic sewage has a nitrate nitrogen concentration of 10-25 mg / L, an ammonia nitrogen concentration of 40-70 mg / L, and a COD concentration of 120-350 mg / L. The nitrate nitrogen comes from the effluent of the secondary sedimentation tank of the sewage treatment plant. The simulated domestic sewage has an ammonium chloride concentration of 13-17 mg / L, a sodium nitrate concentration of 23-27 mg / L, and COD comes from anhydrous sodium acetate. The COD concentration is added according to the target carbon-to-nitrogen ratio.

[0012] The present invention also provides a short-range denitrification coupled with anaerobic ammonia oxidation composite biofilm prepared by the above preparation method.

[0013] This invention also provides the application of the aforementioned short-range denitrification coupled with anaerobic ammonia oxidation composite biofilm based on carbon load regulation in denitrification of wastewater with low carbon-to-nitrogen ratio.

[0014] The beneficial effects of this invention are: 1) Utilize existing resources: Directly utilize the existing denitrifying bacteria biofilm packing material in the wastewater treatment plant as a foundation, eliminating the need to cultivate biofilm from scratch and significantly shortening the start-up time; 2) No additional inoculation required: No additional inoculation of anaerobic ammonia oxidizing bacteria is required. The anaerobic ammonia oxidizing bacteria are derived from the in-situ enrichment on the existing denitrifying bacteria biofilm, reducing dependence on the source of bacteria and costs. 3) Precise enrichment strategy: By controlling the influent carbon-nitrogen ratio, anaerobic ammonia oxidizing bacteria are directionally enriched on the existing denitrifying bacterial membrane, forming a harmonious symbiosis between anaerobic ammonia oxidizing bacteria and short-range denitrifying bacteria, with a strong synergistic effect of functional bacterial groups; 4) Short construction cycle: Based on existing biofilm carriers, the enrichment rate of anaerobic ammonia oxidizing bacteria is accelerated, and the construction of PD / A composite packing material can be completed and stable denitrification can be achieved within 210 days; 5) Stable nitrogen removal efficiency: Under the condition of a carbon-to-nitrogen ratio of 2.5, the contribution rate of anaerobic ammonia oxidation to nitrogen removal is ≥60%, and the total nitrogen removal rate can be stably maintained at over 70%. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the SBR reactor of the present invention; Figure 2 This is a graph showing the change in total nitrogen removal rate under the stepwise reduction of the carbon-nitrogen ratio in Example 1. Detailed Implementation

[0016] This invention provides a method for preparing a short-range denitrification coupled with anaerobic ammonium oxidation (PD / A) composite biofilm based on carbon loading regulation, comprising the following steps: Biofilm packing material is added inside the sequencing batch reactor (SBR), and the influent flow rate and carbon source dosage are adjusted to gradually reduce the influent carbon-to-nitrogen ratio (COD / NO3). - -N), anaerobic ammonia oxidizing bacteria are enriched in situ on the biofilm packing material to form a composite biofilm in which short-range denitrifying bacteria and anaerobic ammonia oxidizing bacteria coexist. The biofilm packing material is a biofilm packing material enriched with denitrifying bacteria; The stepwise reduction of the influent carbon-nitrogen ratio includes three continuous and stable operating stages: the first stage has a carbon-nitrogen ratio of 3.3 to 3.7, the second stage has a carbon-nitrogen ratio of 2.8 to 3.2, and the third stage has a carbon-nitrogen ratio of 2.4 to 2.6.

[0017] In this invention, the carbon-nitrogen ratio in the first stage is preferably 3.4 to 3.6, more preferably 3.5; the carbon-nitrogen ratio in the second stage is preferably 2.9 to 3.1, more preferably 3.0; and the carbon-nitrogen ratio in the third stage is preferably 2.45 to 2.55, more preferably 2.5.

[0018] In this invention, the sequencing batch reactor is equipped with a stirring device. During the operation of the sequencing batch reactor, the biofilm packing is kept in a suspended state by the stirring device. The stirring speed is preferably 40~80 rpm, more preferably 50~70 rpm, and more preferably 60 rpm. The drainage ratio of the sequencing batch reactor is preferably 30~70%, more preferably 40~60%, and more preferably 50%.

[0019] In this invention, the hydraulic retention time of the sequencing batch reactor is preferably 4 to 12 hours, more preferably 4 to 10 hours, and even more preferably 4 to 6 hours. It operates for one or more cycles per day, and the single cycle operation time is preferably 2 to 6 hours, more preferably 2 to 5 hours, and even more preferably 2 hours. The biofilm packing material is preferably polyethylene, and the filling rate of the biofilm packing in the sequencing batch reactor is preferably 30-60%, more preferably 30-40%, and even more preferably 30-35%.

[0020] In this invention, the temperature of the sequencing batch reactor is preferably 20~35℃, more preferably 25~33℃, and even more preferably 30~32℃; the pH value is preferably 7.0~8.0, and even more preferably 7.5; and the dissolved oxygen concentration in the sequencing batch reactor is preferably ≤0.5mg / L, and even more preferably ≤0.4mg / L.

[0021] In this invention, no additional activated sludge is inoculated when the sequencing batch reactor is started up, and the single cycle process is sequentially: water inlet, stirring reaction, sedimentation, drainage, and idle.

[0022] In this invention, the biofilm packing material is preferably a polyethylene packing material from an urban wastewater treatment plant that has been enriched with short-range denitrifying bacteria.

[0023] In this invention, the first, second, and third stages are preferably operated independently for ≥10 days, more preferably ≥20 days, and even more preferably ≥30 days; after the total nitrogen removal rate stabilizes at 40-50%, the second stage begins, preferably at 42-48%, more preferably at 45-46%; after the total nitrogen removal rate stabilizes at 55-65%, the third stage begins, preferably at 57-62%, and even more preferably at 59-60%; when the total nitrogen removal rate stabilizes at 70% or higher, the load can be gradually increased to the design value.

[0024] The first, second, and third stages constitute the total construction cycle of the PD / A composite biofilm. By adjusting the carbon source dosage and influent flow rate in the reactor, the carbon-nitrogen ratio is reduced in stages to precisely control the carbon load. Anaerobic ammonia-oxidizing bacteria are in-situ and directionally enriched on the basis of existing denitrifying bacteria biofilm packing material, which is divided into three continuous control stages.

[0025] Phase 1: High C / N Ratio Stabilization Period. Continuous and stable operation cultivates and maintains the activity of short-range denitrifying bacteria, providing a stable substrate source and biofilm carrier basis for the subsequent colonization of anaerobic ammonia oxidizing bacteria. Phase 2: Medium C / N Ratio Induction Period. Continuous and stable operation induces anaerobic ammonia oxidizing bacteria to colonize, grow, and reproduce within the biofilm under low substrate pressure, gradually establishing the population dominance of anaerobic ammonia oxidizing bacteria. Enrichment of anaerobic ammonia oxidizing bacteria under low substrate pressure allows them to grow within the biofilm. Phase 3: Continuous and stable operation further enhances substrate synergy and spatial distribution of functional bacterial communities, forming a stable PD / A composite biofilm packing with an outer layer of short-range denitrifying bacteria and an inner layer of anaerobic ammonia oxidizing bacteria.

[0026] In this invention, the stirring device of the sequencing batch reactor is used to enhance the mass transfer efficiency between microorganisms and the substrate, and promote the mass transfer contact between microorganisms and the substrate; the dissolved oxygen concentration in the reactor is strictly controlled at ≤0.5mg / L to ensure the anaerobic reaction environment.

[0027] During stable operation of the sequencing batch reactor of this invention in three stages, the flow rate, pH, dissolved oxygen, and temperature are recorded, and the nitrogen concentration of the influent and effluent is measured every 2 hours. If pH < 7.0, the stirring speed can be appropriately increased to promote mass transfer. If dissolved oxygen > 0.5 mg / L, the reactor's sealing performance needs to be checked. If the total nitrogen removal rate < 70%, fluctuations in the influent water quality need to be investigated or the hydraulic retention time can be appropriately extended. For short-term shutdowns, the tank level can be maintained at full capacity, and the water should be changed once a week to keep the packing material moist. For long-term shutdowns, the water level should be maintained at 50%, and the water should be changed once a month. Before restarting, the reactor should be run at 50% load for 2-3 days, and then gradually increased to the design load.

[0028] In this invention, the influent is preferably actual domestic sewage or simulated domestic sewage. The concentration of nitrate nitrogen in the actual domestic sewage is preferably 10-25 mg / L, more preferably 13-22 mg / L, and even more preferably 15-20 mg / L; the concentration of ammonia nitrogen is preferably 40-70 mg / L, more preferably 45-65 mg / L, and even more preferably 50-60 mg / L; and the concentration of COD is preferably 120-350 mg / L, more preferably 150-300 mg / L, and even more preferably 200-250 mg / L. The nitrate nitrogen originates from the effluent of the secondary sedimentation tank of a sewage treatment plant. The concentration of ammonium chloride in the simulated domestic sewage is preferably 13-17 mg / L, more preferably 14-16 mg / L, and even more preferably 15 mg / L; the concentration of sodium nitrate is preferably 23-27 mg / L, more preferably 24-26 mg / L, and even more preferably 25 mg / L. The COD originates from anhydrous sodium acetate, and the COD concentration is added according to the target carbon-to-nitrogen ratio.

[0029] The present invention also provides a short-range denitrification coupled with anaerobic ammonia oxidation composite biofilm prepared by the above preparation method.

[0030] The sequencing batch reactor of this invention is the core treatment unit. When the PD / A composite biofilm packing is used for wastewater treatment, under a carbon-to-nitrogen ratio of 2.5, the contribution rate of anaerobic ammonia oxidation for nitrogen removal is ≥60%, and the total nitrogen removal rate is consistently above 70%. The method of this invention does not require additional inoculation of anaerobic ammonia oxidizing bacteria, as the anaerobic ammonia oxidizing bacteria are derived from in-situ enrichment on existing biofilms.

[0031] The PD / A composite biofilm prepared by this invention forms a distinct spatial partitioning structure: the outer layer of the biofilm consists of short-cut denitrifying bacteria (dominant genera such as Thaurea), which preferentially utilize the organic carbon source in the influent to complete the short-cut denitrification reaction and reduce nitrate to nitrite; the inner layer of the biofilm consists of anaerobic ammonia oxidizing bacteria (dominant genera such as Candidatus Brocadia), which utilize the ammonia nitrogen in the influent and the nitrite produced by short-cut denitrification to complete the anaerobic ammonia oxidation reaction. The two functional bacterial groups form a stable micro-ecosystem with complementary substrates and synergistic functions.

[0032] This invention also provides the application of the aforementioned short-range denitrification coupled with anaerobic ammonia oxidation composite biofilm based on carbon load regulation in denitrification of wastewater with low carbon-to-nitrogen ratio.

[0033] The short-cut denitrification coupled with anaerobic ammonia oxidation composite biofilm based on carbon load regulation of the present invention is suitable for biological denitrification treatment of wastewater with low carbon-to-nitrogen ratio, and is especially suitable for upgrading and deep denitrification treatment of urban wastewater treatment plants.

[0034] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0035] Example 1

[0036] The sequencing batch reactor (SBR) comprises a reactor body, a stirring device within the reactor body, and biofilm packing material placed within the reactor body. The biofilm packing material is polyethylene packing material from a wastewater treatment plant enriched with short-range denitrifying bacteria. Anaerobic ammonia oxidizing bacteria are then enriched on this material to form a PD / A composite biofilm. No additional inoculation of anaerobic ammonia oxidizing bacteria sludge is required during reactor startup and operation. The biofilm packing material constitutes 30% of the reactor's capacity.

[0037] The reactor is started by introducing simulated domestic sewage (ammonium chloride concentration of 15 mg / L, sodium nitrate concentration of 25 mg / L, COD provided by anhydrous sodium acetate, added according to the required carbon-to-nitrogen ratio) into the reactor. The reactor discharge ratio is 50%, maintaining the dissolved oxygen concentration in the reactor ≤0.5 mg / L, the water temperature at 25℃, and the pH value at 7.5. The stirring speed is controlled at 60 rpm by the stirring device to keep the packing material in a suspended state. The hydraulic retention time of the SBR reactor is 4 hours, and it operates once a day for 2 hours. The process is as follows: water inlet, stirring reaction, sedimentation, discharge, and idle. Adjusting the influent flow rate and carbon source dosage, the influent carbon-nitrogen ratio is reduced in stages: In the first stage (1-13 days), the carbon-nitrogen ratio is controlled at 3.5 to maintain the activity of short-cut denitrifying bacteria; in the second stage (14-39 days), the carbon-nitrogen ratio is reduced to 3.0 to induce the growth of anaerobic ammonia oxidizing bacteria on the biofilm; in the third stage, the carbon-nitrogen ratio is reduced to 2.5. After the reactor has been running for a total of 210 days, a PD / A composite biofilm packing material with symbiotic short-cut denitrifying bacteria and anaerobic ammonia oxidizing bacteria is formed; the treated wastewater is discharged from the reactor.

[0038] In this embodiment, at the end of the first stage, the total nitrogen removal rate in the reactor stabilized at 45%. In the second stage, the total nitrogen removal rate gradually and steadily increased to 60%. Under the condition of a carbon-to-nitrogen ratio of 2.5, the total nitrogen removal rate of the reactor stabilized at 72%, with anaerobic ammonia oxidation contributing 65% to nitrogen removal, achieving highly efficient nitrogen removal. The PD / A composite biofilm packing material was confirmed by fluorescence in situ hybridization (FISH) to form a distinct spatial partitioning structure: the outer layer was enriched with short-range denitrifying bacteria (such as Thaurea), and the inner layer was enriched with anaerobic ammonia oxidizing bacteria (such as Candidatus Brocadia). The total nitrogen (TN) concentration in the effluent was below 3 mg / L.

[0039] Example 2

[0040] The simulated domestic sewage in Example 1 (ammonium chloride concentration of 15 mg / L, sodium nitrate concentration of 25 mg / L, COD provided by anhydrous sodium acetate, added according to the required carbon-nitrogen ratio) was replaced with actual domestic sewage and the combined effluent from the secondary sedimentation tank. In a wastewater treatment plant, the effluent from the secondary sedimentation tank had an ammonium chloride concentration of 15 mg / L, a sodium nitrate concentration of 25 mg / L, and a COD of 20 mg / L. Sodium acetate was added to adjust the carbon-nitrogen ratio based on the actual water quality. Other process conditions remained the same as in Example 1.

[0041] In this embodiment, after the SBR reactor operated for 210 days, the total nitrogen removal rate of the reactor stabilized at 70-72%, and the total nitrogen concentration in the effluent was ≤5mg / L, which is close to the Class A standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" GB 18918-2002.

[0042] Comparative Example 1

[0043] The stepwise reduction of the influent carbon-nitrogen ratio in Example 1 was replaced by a fixed influent carbon-nitrogen ratio of 2.5. The system operated at a carbon-nitrogen ratio of 2.5 for 210 days, with other process conditions remaining the same as in Example 1.

[0044] After 210 days of operation, the total nitrogen removal rate of the SBR reactor in this comparative example fluctuated greatly, averaging only 50-55%, and the enrichment effect of anaerobic ammonia oxidizing bacteria was poor, failing to form a clear PD / A composite structure.

[0045] Comparative Example 2

[0046] The stepwise reduction of the influent carbon-nitrogen ratio in Example 1 was replaced by a stepwise increase of the influent carbon-nitrogen ratio. The carbon-nitrogen ratio was controlled at 2.5 in the first stage, increased to 3.0 in the second stage, and increased to 3.5 again in the third stage. Other process conditions were the same as in Example 1.

[0047] After 210 days of operation, the total nitrogen removal rate of the SBR reactor in this comparative example remained below 50%, indicating poor enrichment of anaerobic ammonia oxidizing bacteria and the failure to form a stable PD / A composite structure. The results suggest that a stepwise decrease in the carbon-to-nitrogen ratio is crucial for the in-situ enrichment of anaerobic ammonia oxidizing bacteria, and that reverse regulation cannot achieve the synergistic construction of functional bacterial communities.

[0048] This invention provides a simple method for efficiently constructing a PD / A composite biofilm by enriching anaerobic ammonia oxidizing bacteria through carbon-nitrogen ratio regulation. This invention utilizes existing denitrifying bacteria biofilm packing in a wastewater treatment plant within a single reactor. It selectively enriches anaerobic ammonia oxidizing bacteria by stepwise reduction of the carbon-nitrogen ratio, simultaneously achieving functional synergy between short-range denitrifying bacteria and anaerobic ammonia oxidizing bacteria. By stepwise reducing the carbon-nitrogen ratio, a mild transitional environment is created for different functional bacterial communities: short-range denitrifying bacteria preferentially utilize organic carbon sources to reduce nitrate to nitrite, while anaerobic ammonia oxidizing bacteria utilize influent ammonia nitrogen and nitrite produced during denitrification within the system for metabolism. The two bacterial communities form a substrate-complementary and functionally synergistic micro-ecosystem within the same biofilm, achieving highly efficient nitrogen removal. Wastewater treated by the PD / A composite biofilm constructed using this method exhibits a stable total nitrogen removal rate of over 70%, providing a new strategy for constructing PD / A composite packing within SBR reactors using existing denitrifying bacteria biofilms.

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A preparation method of a short-cut denitrification coupled with anaerobic ammonia oxidation composite biofilm based on carbon load regulation, characterized in that, The preparation method comprises the following steps: adding biofilm fillers in a sequencing batch reactor, adjusting the water inflow and the amount of carbon source, stepwise reducing the carbon-nitrogen ratio of the water inflow, enriching anaerobic ammonia oxidation bacteria in situ on the biofilm fillers, and forming a composite biofilm in which short-cut denitrifying bacteria and anaerobic ammonia oxidation bacteria coexist; the biofilm fillers are biofilm fillers rich in denitrifying bacteria; the stepwise reduction of the carbon-nitrogen ratio of the water inflow comprises three continuous stable operation stages, the carbon-nitrogen ratio of the first stage is 3.3-3.7, the carbon-nitrogen ratio of the second stage is 2.8-3.2, and the carbon-nitrogen ratio of the third stage is 2.4-2.

6.

2. The production method according to claim 1, characterized by, the sequencing batch reactor is provided with a stirring device, and the biofilm fillers are in a suspended state through the stirring device during the operation of the sequencing batch reactor, the stirring rate is 40-80 rpm, and the drainage ratio of the sequencing batch reactor is 30-70%.

3. The production method according to claim 1 or 2, characterized by, the hydraulic retention time of the sequencing batch reactor is 4-12 h, and one or more cycles are operated per day, and the operation time of a single cycle is 2-6 h; the material of the biofilm fillers is polyethylene, and the filling rate of the biofilm fillers in the sequencing batch reactor is 30-60%; the temperature of the sequencing batch reactor is 20-35℃, the pH value is 7.0-8.0, and the dissolved oxygen concentration in the sequencing batch reactor is ≤0.5 mg / L.

4. The production method according to claim 3, characterized by, the operation time of the first stage, the second stage and the third stage is independently ≥10 days; after the total nitrogen removal rate is stabilized at 40-50%, the second stage is entered, and after the total nitrogen removal rate is stabilized at 55-65%, the third stage is entered.

5. The production method according to claim 4, characterized by, the water inflow is actual domestic sewage or simulated domestic sewage, the concentration of nitrate nitrogen in the actual domestic sewage is 10-25 mg / L, the concentration of ammonia nitrogen is 40-70 mg / L, and the concentration of COD is 120-350 mg / L, the nitrate nitrogen is from the effluent of the secondary sedimentation tank of a sewage treatment plant; the concentration of ammonium chloride in the simulated domestic sewage is 13-17 mg / L, the concentration of sodium nitrate is 23-27 mg / L, and the COD is from anhydrous sodium acetate, and the concentration of the COD is added according to the target carbon-nitrogen ratio.

6. The short-cut denitrification coupled with anaerobic ammonia oxidation composite biofilm based on carbon load regulation prepared by the preparation method in any one of claims 1-5.

7. The short-cut denitrification coupled with anaerobic ammonia oxidation composite biofilm based on carbon load regulation in claim 6 is applied to denitrification of low carbon-nitrogen ratio sewage.

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