Multi-point water inlet inverted A / A / O mud film composite MBBR sewage nitrogen and phosphorus removal device and method

Abstract

The invention relates to the technical field of sewage treatment, in particular to a multi-point water inlet inverted A / A / O mud film composite MBBR sewage nitrogen and phosphorus removal device and method.The sewage sequentially enters an anoxic tank, an anaerobic tank and an aerobic tank, and effluent of the aerobic tank flows back into the anoxic tank through a lifting pump and is mixed with sewage in the anoxic tank to form a mixed solution for nitrogen removal through denitrification; effluent of the anoxic tank enters an anaerobic tank to synthesize PBH for storage, and phosphorus is discharged at the same time; effluent of the anaerobic tank enters an aerobic tank, ammonia nitrogen in the sewage is converted into nitrate nitrogen by nitrifying bacteria, and phosphorus in the sewage is excessively absorbed by phosphorus-accumulating bacteria; effluent of the aerobic tank flows to the secondary sedimentation tank, one part of sludge in the secondary sedimentation tank flows back to the anoxic tank, and the other part of the sludge is discharged as residual sludge, so that phosphorus is removed, the nitrogen and phosphorus removal effect is improved, an organic carbon source in sewage is effectively utilized, the carbon source requirement of anoxic denitrification is reduced, and the energy consumption of sewage treatment is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a multi-point water inlet inverted A / A / O mud membrane composite MBBR sewage denitrification and dephosphorization device and method. Background Art

[0002] The A / A / O process is called the anaerobic-anoxic-aerobic combination system. It is a traditional biological denitrification and phosphorus removal process, which is widely used in the field of sewage treatment at home and abroad. The so-called inverted A / A / O process is to swap the positions of the anoxic tank and the anaerobic tank, and place the anoxic tank before the anaerobic tank. The inverted A / A / O process removes ammonia nitrogen from sewage. In the first stage, the organic nitrogen in the sewage is converted into ammonia nitrogen by the ammonia oxidizing bacteria in the aerobic tank, and then the ammonia nitrogen is converted into nitrate nitrogen under the action of nitrite bacteria and nitrifying bacteria to complete the nitrification process; in the second stage, the nitrified liquid (containing nitrate nitrogen) produced at the end of the aerobic tank is returned to the anoxic tank, and under the condition of low dissolved oxygen (DO less than 1mg / l), the nitrate nitrogen is converted into nitrogen gas under the action of denitrifying bacteria and removed from the system.

[0003] Biological phosphorus removal utilizes the characteristics of polyphosphate bacteria that absorb phosphorus under aerobic conditions and release phosphorus under anaerobic conditions, and removes phosphorus from the system through the discharge of residual sludge. The traditional biological denitrification and phosphorus removal process is arranged in the form of anaerobic (A1) / anoxic (A2) / aerobic (O). The traditional A / A / O process has the following disadvantages: First, urban sewage generally has insufficient influent carbon source and too low C / N ratio. Since the anoxic zone is located in the middle of the system, denitrification is in a disadvantageous position in carbon source distribution, thus affecting the denitrification effect of the system; second, since the anaerobic zone is in the front, the nitrate in the return sludge has an adverse effect on the anaerobic zone, affecting the phosphorus removal effect of the system; third, due to the existence of internal circulation, only a small part of the residual sludge discharged by the traditional process system actually undergoes a complete process of phosphorus release and absorption, and the rest basically enters the aerobic zone directly from the anoxic zone without anaerobic state, resulting in poor phosphorus removal effect.

[0004] In order to solve the problems of insufficient carbon source in the influent water and the influence of nitrate in the reflux nitrification liquid on anaerobic phosphorus release in the A / A / O process, improvements were made in the influent mode, A / A / O optimization sorting, and point-by-point influent, resulting in a multi-point inverted A / A / O improved process. The MBBR process is to add suspended fillers to the anoxic and aerobic reaction tanks of the A / A / O to allow the fillers to be covered with biofilms. The biofilms have a rich microbial functional flora, such as nitrifying bacteria, nitrite bacteria, anaerobic ammonia oxidizing bacteria, heterotrophic bacteria, etc. These bacteria can carry out simultaneous nitrification and denitrification, anaerobic ammonia oxidation reactions, and have deep denitrification functions. Some existing equipment or processes combine the inverted A / A / O process with the MBBR process. For example, CN218860456U provides an anaerobic ammonium oxidation reactor based on MBBR filler, including a pre-denitrification zone, an anaerobic zone, an MBBR short-range nitrification zone, an MBBR anaerobic ammonium oxidation zone, an MBBR aerobic zone, a horizontal flow sedimentation zone and a clear water outlet weir connected in sequence by pipelines; a total water inlet is provided on one side of the pre-denitrification zone, and a total water outlet is provided on the clear water outlet weir; perforated aeration pipes are respectively provided in the MBBR short-range nitrification zone and the MBBR aerobic zone, and a mixed liquor reflux pump is provided in the MBBR short-range nitrification zone; the perforated aeration pipes are respectively fixed on the bottom of the MBBR short-range nitrification zone and the MBBR aerobic zone; a sludge reflux pump is placed in the horizontal flow sedimentation zone; the total inlet The water inlets are respectively connected to the output ends of the mixed liquor reflux pump, the sludge reflux pump and the primary sewage treatment unit; CN216303560U discloses sewage treatment equipment based on an inverted AAO-MBBR-MBR process, including an integrated device, wherein the integrated device is connected to a regulating tank, a reagent tank one, a reagent tank two, a fan, a sludge tank and a clear water tank through pipelines, and the integrated device includes a substrate, a box, an anoxic tank, an anaerobic tank, an aerobic tank, an MBR membrane tank tank, an equipment tank, an inlet pipe, an outlet pipe and a connecting pipe, the box is fixed to the top of the substrate, and a plurality of cavities are provided inside the box, the anoxic tank and the anaerobic tank are connected by pipelines and are arranged side by side inside the box, and the areas of both are smaller than the aerobic tank, and the aerobic tank is connected between the MBR membrane tank tank and the anaerobic tank through a pipeline. However, its cost is relatively high, it is difficult to effectively utilize the organic carbon source in the sewage, and the denitrification and phosphorus removal effects are difficult to achieve the expected results. Therefore, it is urgent to design a multi-point water inlet inverted A / A / O mud membrane composite MBBR sewage denitrification and phosphorus removal device and method. Summary of the invention

[0005] In order to overcome the technical defects of the prior art, the present invention provides a multi-point water inlet inverted A / A / O mud film composite MBBR sewage denitrification and phosphorus removal device and method, which adopts a dual sludge system of activated sludge system and biofilm sludge system, so that the whole process has a double sludge age and has better denitrification and phosphorus removal functions.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] In the first aspect, the present invention provides a multi-point water inlet inverted A / A / O mud film composite MBBR sewage denitrification and phosphorus removal device, comprising an anoxic tank, an anaerobic tank, an aerobic tank and a secondary sedimentation tank arranged in sequence along the sewage flow direction, the anoxic tank, the anaerobic tank, the aerobic tank and the secondary sedimentation tank are respectively connected to the sewage inlet pipeline, the activated sludge return pipe of the secondary sedimentation tank is connected to the inlet of the anoxic tank, the nitrification liquid return pipe of the aerobic tank is connected to the inlet of the anoxic tank, and the outlet of the secondary sedimentation tank is discharged outside the factory.

[0008] As a further technical solution of the present invention, an underwater propeller is provided in the anoxic tank for mixing and stirring the anoxic reaction tank.

[0009] As a further technical solution of the present invention, a microporous aerator is provided in the aerobic tank.

[0010] As a further technical solution of the present invention, suspended fillers are added to the anoxic pool and the aerobic pool, and the volume ratio of the suspended fillers is not greater than 30%.

[0011] As a further technical solution of the present invention, the secondary sedimentation tank adopts a radial flow sedimentation tank with peripheral water inlet and peripheral water outlet.

[0012] The second invention provides a method for denitrification and phosphorus removal of sewage by a multi-point water inversion A / A / O mud membrane composite MBBR, which specifically comprises the following steps:

[0013] S1. The pre-treated sewage enters the anoxic tank, anaerobic tank and aerobic tank respectively, and the influent ratio is determined according to the influent water quality;

[0014] S2. The nitrification mixed liquid of the effluent sludge from the aerobic tank is returned to the anoxic tank through the lifting pump, mixed with the sewage sent to the anoxic tank to form a mixed liquid, and denitrification is carried out to eliminate the influence of nitrate in the returned sludge on anaerobic phosphorus release;

[0015] S3, the effluent from the anoxic tank enters the anaerobic tank, where polyphosphate bacteria absorb organic matter in the influent under anaerobic conditions and react with phosphate in the body. The phosphate in the polyphosphate bacteria decomposes the phosphate to provide energy, synthesize PBH (polyhydroxybutyrate) for storage, and release phosphorus at the same time, and remove the phosphorus from the system through the residual sludge;

[0016] S4. The effluent from the anaerobic tank enters the aerobic tank. While heterotrophic bacteria degrade organic matter, nitrifying bacteria convert ammonia nitrogen in the sewage into nitrate nitrogen, and polyphosphate bacteria absorb excessive phosphorus in the sewage and store it in a polymerized form, forming high-phosphorus sludge.

[0017] S5. The effluent from the aerobic tank is sent to the secondary sedimentation tank. Part of the sludge in the secondary sedimentation tank is returned to the anoxic tank, and the rest is used as residual sludge and discharged by a central drive or peripheral drive scraper to achieve phosphorus removal.

[0018] As a further technical solution of the present invention, the water inflow of the anoxic tank is 30-50%, the water inflow of the anaerobic tank is 10-15%, the water inflow of the aerobic tank is 30-50%, and the total percentage of the water inflow is 100%.

[0019] As a further technical solution of the present invention, the retention time of the anoxic tank is 1.0h-2.0h, the retention time of the anaerobic tank is 1.5h-2.0h, the retention time of the aerobic tank is 6.0h-8.0h, and the retention time of the secondary sedimentation tank is 1.5h-2.0h.

[0020] As a further technical solution of the present invention, the DO (dissolved oxygen) concentration of the anoxic tank is less than 1 mg / L, the DO (dissolved oxygen) concentration of the anoxic tank is 0 mg / L, and the DO (dissolved oxygen) concentration of the aerobic tank is 2-4 mg / L.

[0021] As a further technical solution of the present invention, the mixed liquor return ratio in step S2 is 100% to 200%, and the sludge return ratio in step S5 is 30% to 50%.

[0022] As a further technical solution of the present invention, the denitrification process in step S2 includes three parts: (1) denitrification and phosphorus removal process: (2) Denitrification by anoxic denitrification process: (3) Denitrification by anaerobic ammonium oxidation process:

[0023] As a further technical solution of the present invention, the specific process of step S4 is as follows: under sufficient aeration conditions, organic matter (COD) is degraded into carbon dioxide and water through biochemical reactions, and at the same time, under aerobic conditions, ammonia oxidizing bacteria (AOB) and nitrite bacteria undergo nitrification reactions to convert organic nitrogen into ammonia nitrogen and further into nitrate nitrogen. The effluent from the aerobic tank contains rich nitrate nitrogen to form sludge nitrification liquid, and the sludge nitrification liquid is returned to the anoxic tank.

[0024] As a further technical solution of the present invention, the surface load of the secondary sedimentation tank is 1.5 to 2.0 m3 / m2.h, and the sedimentation time is 1.5 to 2.5 h.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) Based on the traditional A / A / O process, the anoxic tank is placed before the anaerobic tank, thereby reducing or eliminating the impact of nitrate on the anaerobic phosphorus release process and improving the phosphorus removal effect.

[0027] (2) Water is introduced from the anoxic tank, anaerobic tank, and aerobic tank in multiple stages, which effectively utilizes the organic carbon source in the sewage, reduces the carbon source demand for anoxic denitrification, and reduces the energy consumption of sewage treatment.

[0028] (3) Suspended fillers were added to the anoxic tank and aerobic tank to form an MBBR moving bed biofilm and a double sludge system, which further improved the denitrification efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the traditional A / A / O process flow chart.

[0030] Figure 2 This is a process flow chart for the wastewater denitrification and phosphorus removal process according to the present invention. DETAILED DESCRIPTION

[0031] The present invention will be further described below by way of embodiments in conjunction with the accompanying drawings.

[0032] Example:

[0033] like Figure 2 As shown, this embodiment provides an inverted A / A / O mud film composite MBBR sewage denitrification and phosphorus removal device with multi-point water inlet, including an anoxic tank, an anaerobic tank, an aerobic tank and a secondary sedimentation tank arranged in sequence along the sewage flow direction, the anoxic tank, the anoxic tank, the aerobic tank and the secondary sedimentation tank are respectively connected to the sewage inlet pipe, the activated sludge return pipe of the secondary sedimentation tank is connected to the inlet of the anoxic tank, the nitrification liquid return pipe of the aerobic tank is connected to the inlet of the anoxic tank, the outlet of the secondary sedimentation tank is discharged outside the plant, the anoxic tank is provided with an underwater propeller, the aerobic tank is provided with a microporous aerator, and suspended fillers are added to the anoxic tank and the aerobic tank, and the volume ratio of the suspended fillers is not more than 30%.

[0034] The specific process of achieving sewage denitrification and phosphorus removal in this embodiment is as follows:

[0035] S1. The pretreated sewage of the sewage treatment plant first enters the anoxic tank. The K value distribution ratio of the inlet water of the anoxic tank is 30-50%. The K value of the inlet water is determined according to the C / N ratio of the inlet water. When the C / N ratio of the inlet water is greater than 5, it indicates that the carbon source of the inlet water is relatively sufficient. At this time, the K value can be taken as a smaller value; when the C / N ratio of the inlet water is less than 5, it indicates that the carbon source of the inlet water is relatively insufficient. At this time, the K value can be taken as a larger value, and the DO (dissolved oxygen) of the anoxic tank is controlled to make the DO less than 1 mg / L;

[0036] The nitrification liquid return ratio from the aerobic tank to the anoxic tank is 100% to 200%, and the activated sludge return ratio from the secondary sedimentation tank to the anoxic tank is 30% to 50%. When suspended fillers are added to the anoxic tank, the nitrification liquid return ratio and the activated sludge return ratio can be reduced. At the same time, the power of the underwater propeller should be increased by 10 to 15% accordingly.

[0037] S2. The effluent from the anoxic tank enters the anaerobic tank. The K value distribution ratio of the inlet water of the anaerobic tank is 10-15%. Since the polyphosphate bacteria consume less organic carbon sources, when the inlet phosphate concentration is less than 3 mg / L, the inlet K value distribution coefficient is reduced; in the anaerobic tank, the polyphosphate bacteria absorb organic matter in the inlet water under anaerobic conditions and react with phosphate in the body. The phosphate in the polyphosphate bacteria body is decomposed to provide energy, synthesize PBH (polyhydroxybutyrate) for storage, and release phosphorus at the same time, and the phosphorus is removed from the system through the residual sludge;

[0038] S3. The effluent from the anaerobic tank enters the aerobic tank. The K value distribution ratio of the inlet water of the aerobic tank is 30-50%. Aeration is an important process in the aerobic biological treatment system of sewage. At present, the blower aeration system is widely used. The blower provides purified air and sends it to the special microporous aerator at the bottom of the aerobic tank through the pipeline system. The function of the special microporous aerator is to disperse the air into bubbles and diffuse it into the mixed liquid, so that the oxygen in the bubbles dissolves into the mixed liquid, providing the dissolved oxygen required for the biochemical reaction of microorganisms, and at the same time ensuring the full mixing of sewage, so that the activated sludge is in a suspended state, and through the full contact of mud, water and gas, it is ensured that the activated sludge makes full use of water. The dissolved oxygen in the aerobic pool is used to decompose organic pollutants and nutrients containing N / P. In this embodiment, the microporous aerator provided in the aerobic pool is a tubular microporous aerator. The gas transmission and gas distribution of the tubular microporous aerator are combined into one. The aeration system using the tubular microporous aerator does not require the laying of a special horizontal gas transmission pipeline. Under the fully aerated conditions in the aerobic pool, organic matter (COD) is degraded into carbon dioxide and water through biochemical reactions. At the same time, under aerobic conditions, ammonia oxidizing bacteria (AOB) and nitrite bacteria undergo nitrification reactions to convert organic nitrogen into ammonia nitrogen and further into nitrate nitrogen. The effluent from the aerobic pool contains rich nitrate nitrogen to form sludge nitrification liquid, which is returned to the anoxic pool.

[0039] S4, the effluent from the aerobic tank enters the secondary sedimentation tank. The secondary sedimentation tank of this embodiment adopts a radial flow sedimentation tank with central water inlet (or peripheral water inlet) and peripheral water outlet. The inflow area of ​​the radial flow sedimentation tank with central water inlet and peripheral water outlet is set in the central guide tube of the pool, and the outflow trough is set at the periphery of the sedimentation tank. According to its function, it is divided into four areas: water inlet (guide tube), sedimentation area, water outlet area (outflow trough), and sludge area. The guide tube is evenly provided with water distribution holes, and a reflective baffle is preferably set. The water outlet of the guide tube radiates from the center to the outlet trough and is finally discharged along the outlet weir. The design load of the outlet weir plate should comply with the design specifications and regulations. The sludge is precipitated in the sedimentation area, gathered in the sludge hopper, and discharged through a mechanical scraper. The surface load of the radial flow sedimentation tank is preferably 1.5-2.0m 3 / m 2 .h, precipitation time 1.5~2.5h.

[0040] The calculation formula for the denitrification efficiency of the anoxic pool in this embodiment is:

[0041]

[0042] Where: R A is the denitrification phosphorus removal and nitrogen removal rate, R AN is the denitrification rate, ρ 0，Ana，N is the ammonia nitrogen concentration entering the anoxic pool, ρ Ana，N is the effluent ammonia nitrogen concentration of the anoxic tank, K is the water distribution ratio allocated to the anoxic unit, R and SR are the nitrification solution return ratio and sludge return ratio, respectively.

[0043] After adding suspended fillers into the anoxic tank, the anaerobic ammonium oxidation (Anammox) biological process can be formed under low DO conditions. The denitrification efficiency of this part is:

[0044]

[0045] The phosphorus removal efficiency is:

[0046]

[0047] Where R A is the anaerobic ammonium oxidation denitrification rate, R AN is the anaerobic ammonium oxidation phosphorus removal efficiency, ρ 0，Ana，N is the ammonia nitrogen concentration entering the anoxic pool, ρ Ana，N is the effluent ammonia nitrogen concentration of the anoxic pool, ρ 0，Ana，P is the phosphate concentration entering the anoxic pool, ρ Ana，P is the effluent phosphate concentration of the anoxic tank, K is the water distribution ratio to the anoxic unit, R and SR are the nitrification solution return ratio and the sludge return ratio, respectively.

[0048] The calculation formula for phosphorus removal efficiency in the anaerobic tank of this embodiment is:

[0049]

[0050] Where: R O is the phosphorus release efficiency of the anaerobic tank, ρ 0，O，P is the phosphate concentration entering the anaerobic tank, ρ O，P is the effluent phosphate concentration of the anaerobic tank, K is the water distribution ratio to the anoxic unit, R and SR are the nitrification solution return ratio and the sludge return ratio, respectively.

[0051] The treatment process for denitrification and phosphorus removal in this embodiment has a good effect on removing pollutants, and the effluent indicators can be stably maintained at BOD5≤10mg / L, CODcr≤50mg / L, ammonia nitrogen≤5mg / L, total phosphorus TP≤0.5mg / L, and total nitrogen TN≤15mg / L. Various effluent water quality indicators meet and exceed the national emission standard Level A standard.

[0052] This embodiment integrates multi-point water inlet, inverted A / A / O, and MBBR moving bed biofilm, which can effectively distribute the organic carbon source in the inlet water, reduce the carbon source replenishment of the anoxic tank, and reduce the energy consumption of the system; at the same time, the inverted A / A (anoxic, anaerobic) is adopted to avoid the influence of the nitrification liquid backflow on the phosphorus release of polyphosphate bacteria in the anaerobic tank, thereby improving the denitrification efficiency of the system; and suspended fillers are added to the anoxic zone and the aerobic zone respectively to form an MBBR moving bed biofilm, making full use of the SND (simultaneous nitrification and denitrification) and Anammox (anaerobic ammonia oxidation) of the biofilm to improve the denitrification efficiency of the entire system.

Claims

1. A multi-point water inlet inverted A / A / O mud membrane composite MBBR sewage denitrification and phosphorus removal device, characterized in that: The invention comprises anoxic tank, anaerobic tank, aerobic tank and secondary sedimentation tank which are arranged in sequence along the flow direction of sewage. The anoxic tank, anaerobic tank, aerobic tank and secondary sedimentation tank are respectively connected with the sewage inlet pipe, the activated sludge return pipe of the secondary sedimentation tank is connected with the inlet of the anoxic tank, the nitrification liquid return pipe of the aerobic tank is connected with the inlet of the anoxic tank, and the outlet of the secondary sedimentation tank is discharged outside the factory; an underwater propeller is arranged in the anoxic tank for mixing and stirring the anoxic reaction tank; a microporous aerator is arranged in the aerobic tank; suspended fillers are added in both the anoxic tank and the aerobic tank, and the volume ratio of the suspended fillers is not more than 30%; the secondary sedimentation tank adopts a radial flow sedimentation tank with peripheral water inlet and peripheral water outlet.

2. A method for denitrification and phosphorus removal of sewage by using the device as claimed in claim 1 for multi-point water inversion A / A / O mud membrane composite MBBR, characterized in that: The specific steps include: S1. The pre-treated sewage enters the anoxic tank, anaerobic tank and aerobic tank respectively, and the influent ratio is determined according to the influent water quality; S2. The nitrification mixed liquid of the effluent sludge from the aerobic tank is returned to the anoxic tank through the lifting pump, mixed with the sewage sent to the anoxic tank to form a mixed liquid, and denitrification is carried out to eliminate the influence of nitrate in the returned sludge on anaerobic phosphorus release; S3, the effluent from the anoxic selection tank enters the anaerobic tank, where polyphosphate bacteria absorb organic matter in the influent under anaerobic conditions and react with phosphate in the body. The phosphate in the polyphosphate bacteria decomposes the phosphate to provide energy, synthesize polyhydroxybutyrate for storage, and release phosphorus at the same time, which is then removed from the system through the residual sludge; S4. The effluent from the anaerobic tank enters the aerobic tank. While heterotrophic bacteria degrade organic matter, nitrifying bacteria convert ammonia nitrogen in the sewage into nitrate nitrogen, and polyphosphate bacteria absorb excessive phosphorus in the sewage and store it in a polymerized form, forming high-phosphorus sludge. S5. The effluent from the aerobic tank is sent to the secondary sedimentation tank. Part of the sludge in the secondary sedimentation tank is returned to the anoxic tank, and the rest is used as residual sludge and discharged by a central drive or peripheral drive scraper to achieve phosphorus removal.

3. According to claim 2, the multi-point water inlet inverted A / A / O mud membrane composite MBBR sewage denitrification and phosphorus removal method is characterized in that: The water inflow of the anoxic pool is 30-50%, the water inflow of the anaerobic pool is 10-15%, the water inflow of the aerobic pool is 30-50%, and the total percentage of the water inflow is 100%.

4. According to claim 3, the multi-point water inlet inverted A / A / O mud membrane composite MBBR sewage denitrification and phosphorus removal method is characterized in that: The retention time of the anoxic tank is 1.0h to 2.0h, the retention time of the anaerobic tank is 1.5h to 2.0h, the retention time of the aerobic tank is 6.0h to 8.0h, and the retention time of the secondary sedimentation tank is 1.5h to 2.0h.

5. According to claim 4, the multi-point water inlet inverted A / A / O mud membrane composite MBBR sewage denitrification and phosphorus removal method is characterized in that: The dissolved oxygen concentration of the anoxic pool is less than 1 mg / L, the dissolved oxygen concentration of the anaerobic pool is 0 mg / L, and the dissolved oxygen concentration of the aerobic pool is 2-4 mg / L.

6. According to claim 5, the method for denitrification and phosphorus removal of sewage by multi-point water inversion A / A / O mud membrane composite MBBR is characterized in that: The mixed liquor reflow ratio in step S2 is 100% to 200%, and the sludge reflow ratio in step S5 is 30% to 50%.

7. The method for denitrification and phosphorus removal of sewage by multi-point water inversion A / A / O mud membrane composite MBBR according to claim 6, characterized in that: Step S2: The denitrification process includes three parts: (1) Denitrification and phosphorus removal process: (2) Denitrification by anoxic denitrification process: (3) Denitrification by anaerobic ammonium oxidation process:

8. The method for denitrification and phosphorus removal of sewage by multi-point water inversion A / A / O mud membrane composite MBBR according to claim 7, characterized in that: The specific process of step S4 is as follows: under sufficient aeration conditions, organic matter is degraded into carbon dioxide and water through biochemical reactions. At the same time, under aerobic conditions, ammonia oxidizing bacteria and nitrite bacteria undergo nitrification reactions to convert organic nitrogen into ammonia nitrogen and further into nitrate nitrogen. The effluent from the aerobic tank contains rich nitrate nitrogen to form sludge nitrification liquid, which is returned to the anoxic tank.

9. The method for denitrification and phosphorus removal of sewage by multi-point water inversion A / A / O mud membrane composite MBBR according to claim 8, characterized in that: The surface load of the secondary sedimentation tank is 1.5 to 2.0 m3 / m2.h, and the sedimentation time is 1.5 to 2.5 h.

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