CN102583743A - Dual-sludge denitrification dephosphorizing and denitrifying A/A-O device and method - Google Patents

Abstract

The invention discloses an A/AO device for dual sludge denitrification, phosphorus and nitrogen removal, which is mainly composed of a primary sedimentation tank, anaerobic-anoxic device, a secondary sedimentation tank, an intermediate water tank, an aerated biological filter tank and a clear water tank ; The primary settling tank is connected with the anaerobic zone of the anaerobic-anoxic device, and the degassing zone of the anaerobic-anoxic device is connected with the secondary settling tank, and the secondary settling tank is connected with the anaerobic-anoxic device by a sludge pump The anaerobic zone is connected; the effluent of the secondary sedimentation tank is connected to the intermediate tank, the intermediate tank is connected to the biological aerated filter, and the biological aerated filter is connected to the clear water tank; the clear water tank is connected to the anaerobic-anoxic device connection. Through process adjustment, the denitrifying phosphorus-accumulating bacteria become the dominant genus of the AAO unit, realize the separation of phosphorus-accumulating bacteria and nitrifying bacteria, the separation of sedimentation and mud storage in the secondary sedimentation tank, and the separation of nitrification and filtration functions in the biological aerated filter. Finally, energy saving, stable and efficient nitrogen and phosphorus removal and sludge reduction of the combined system will be realized.

Description

A/A-O device and method for double sludge denitrification, phosphorus and nitrogen removal

technical field

The invention belongs to the technical field of sewage biological treatment, and is particularly suitable for upgrading sewage treatment plants and building new sewage advanced treatment plants, and in particular relates to an A/A-O device and method for enhanced denitrification of sewage treatment.

Background technique

At present, more than 95% of sewage treatment plants in my country cannot meet the increasingly stringent Class A discharge standards. The key problem is that TN, TP and SS cannot meet the standards stably. Since the C/N of urban sewage in my country is generally low, and the VFA that can be used for anaerobic phosphorus release is even lower, a large amount of additional carbon sources need to be added in the process of biological nitrogen and phosphorus removal, and sewage plants have not adopted energy-saving and consumption-reducing technologies. The operating cost is generally high, and the operating cost per ton of water is nearly twice that of developed countries. Moreover, a large amount of excess sludge produced by the sewage plant is not properly treated, causing significant environmental problems.

In the AAO denitrification and phosphorus removal system, phosphorus accumulating bacteria, denitrifying bacteria and nitrifying bacteria coexist, and there are contradictions in sludge age and competition in carbon sources, which makes the anaerobic phosphorus release efficiency of phosphorus accumulating bacteria low, and the nitrification efficiency of nitrifying bacteria is low. Aeration consumes a lot of energy, and it is difficult to obtain good results of nitrogen and phosphorus removal in a single biochemical system at the same time; moreover, the nitrate nitrogen in the effluent water of the aerobic zone is prone to denitrification in the secondary sedimentation tank, causing the sludge to float up. affect the normal operation of the system. Since the C/N of urban sewage in my country is generally low, the VFA that can be used for anaerobic phosphorus release is lower, and the lack of carbon sources makes the original problems in the nitrogen and phosphorus removal of AAO process more prominent.

Biological Aerated Flilter (BAF) is a sewage treatment technology that integrates biofilm biochemical degradation and filter layer filtration functions. However, when BAF is used alone to treat domestic sewage, it generally has a short working cycle, frequent backwashing, and fillers. Easy to block and harden and other problems.

AAO-BAF integrates the advantages of AAO and biological aerated filter, has strong hydraulic load resistance, and strong adaptability to temperature changes. Through the separation of phosphorus accumulating bacteria and nitrifying bacteria, it can stably realize denitrification phosphorus removal technology and realize one-carbon Dual-purpose, save aeration, reduce sludge production, and reduce operating costs. However, there are still some problems in this combined process, such as the high DO in the BAF effluent, which makes the aerobic heterotrophic bacteria multiply in the anoxic zone of the AAO unit, which restricts the efficiency of AAO denitrification and phosphorus removal; the pollutants intercepted by the upward flow BAF are mainly in the filter material. In the lower part of the layer, the pollutants intercepted during recoil in the forward direction pass through the entire filter material layer, which not only consumes high energy, but also pollutes the clear water in the upper part of the BAF; the filtration performance of the BAF is weakened due to the interference of aeration, and the biofilm that falls off, etc. Make the water suspension SS higher.

How to improve the denitrification and phosphorus removal effect of the combined process system on the basis of energy saving and consumption reduction and effective use of raw water carbon sources, and at the same time realize the reduction of sludge process has become a major demand in the field of sewage treatment at this stage.

Contents of the invention

The purpose of the present invention is to address the current AAO process problems, and combine three key technologies of energy saving, effective utilization of carbon sources and sludge reduction, to propose a sewage treatment device and method, through process adjustment to make denitrifying phosphorus-accumulating bacteria become AAO The dominant bacterial genus of the unit realizes the separation of phosphorus accumulating bacteria and nitrifying bacteria, the separation of the sedimentation and mud storage functions of the secondary sedimentation tank, the separation of the nitrification and filtration functions of the biological aerated filter, and finally realizes the energy saving, stable and efficient denitrification of the combined system Phosphorus removal and sludge reduction.

In order to achieve the above-mentioned design purpose, the technical scheme adopted in the present invention is as follows:

A double-sludge denitrification A/A-O device for phosphorus and nitrogen removal, mainly composed of a primary sedimentation tank, anaerobic-anoxic device, a secondary sedimentation tank, an intermediate water tank, aerated biological filter and a clear water tank; The primary settling tank is connected to the anaerobic area of the anaerobic-anoxic device, the degassing area of the anaerobic-anoxic device is connected to the secondary settling tank, and the secondary settling tank is connected to the anaerobic area of the anaerobic-anoxic device through a sludge pump. District connection; the effluent of the secondary sedimentation tank is connected to the intermediate tank, the intermediate tank is connected to the biological aerated filter, and the biological aerated filter is connected to the clean water tank; the deficient of the clean water tank and the anaerobic-anoxic device The oxygen area is connected; the clear water tank is connected with the bottom water distribution area of the biological aerated filter.

Preferably, the packing layer of the biological aerated filter is provided with a two-phase separator, and the two-phase separator is connected to the degassing area of the anaerobic-anoxic device through a valve and an air pump.

Preferably, the secondary sedimentation tank is provided with a discharge pipe; the bottom of the biological aerated filter is provided with a vent valve; and the clean water tank is provided with an outlet pipe.

More preferably, the device for removing phosphorus and nitrogen by double sludge denitrification further includes a blower, which is connected to the biological aerated filter through an aeration pipeline and a gas flow meter.

More preferably, the biological aerated filter is a nitrification/filtration type reactor, the lower part of the filter material is a nitrification section, and the upper part is an air-free interference nitrification deoxygenation filtration section.

An A/A-O method for double sludge denitrification, phosphorus and nitrogen removal, the specific steps of the method are:

1) Sewage enters the anaerobic zone of the anaerobic-anoxic device from the primary sedimentation tank, releases phosphorus in the anaerobic zone, and the mud-water mixture flows through the anaerobic zone and In the anoxic zone, denitrification, phosphorus, nitrogen, and organic matter are carried out, and degassing is carried out in the degassing zone;

2) The sewage enters the secondary sedimentation tank from the above-mentioned degassing area to realize the separation of mud and water, and the supernatant liquid containing ammonia nitrogen flows into the intermediate pool, and enters the bottom of the biological aerated filter through a high-pressure pump; the sludge is discharged through the discharge pipe;

3) The dominant bacteria in the above-mentioned biological aerated filter are nitrifying bacteria that convert the ammonia nitrogen in the above-mentioned supernatant into nitrate nitrogen. The hydraulic retention time is 0.5-1h, and the gas-water ratio is 6-10. After deoxidation and deoxidation, it enters the clean water pool, and the treated water is discharged through the outlet pipe;

4) the phosphorus-rich sludge that does not contain nitrate in the secondary settling tank in the above step 2 enters the anaerobic zone of the anaerobic-anoxic device through the sludge reflux pump, and a stirring device is established in the pool, and the sludge reflux ratio is 100%. The hydraulic retention time is 1-2h. The phosphorus accumulating bacteria in the sludge use the low-molecular volatile organic acids (VFA) in the sewage to synthesize PHB, complete a large amount of phosphorus release, and the phosphorus release rate is high; a large amount of organic matter in the sewage is rapidly transformed , the removal of COD in the anaerobic zone 4 accounts for 70-80% of the combined process; the proportion of denitrifying phosphorus accumulating bacteria is close to 80%;

5) The mixed sludge in step 4 enters the anoxic zone from the above-mentioned anaerobic zone, and a stirring device is set in the tank, and the deoxidation and nitrification liquid entering the clear water tank from the biological aerated filter enters the anoxic zone through the nitrification liquid return pump, and the anoxic zone The concentration of dissolved oxygen in the anaerobic zone is very low, and DO is less than 0.3mg/L, which inhibits the plundering of carbon sources by aerobic heterotrophic bacteria. The phosphorus accumulating bacteria use nitrate nitrogen as the electron acceptor and PHB as the electron donor to denitrify and remove phosphorus. The reflux ratio of the nitrification solution is 200-400%, and its hydraulic retention time is 7-8h;

6) The mixed sludge in step 5 flows from the anoxic zone into the degassing zone. The hydraulic retention time in the degassing zone is 1h, and the oxidation of ammonia nitrogen does not occur. The main function is to complete the stripping of nitrogen and the removal of residual phosphorus, and improve the sludge Sedimentation performance, the mixed liquor sludge concentration is 2500-3000mg/L;

7) The sewage enters the secondary sedimentation tank from the above-mentioned degassing area to realize the separation of mud and water. The sludge is discharged through the discharge pipe, and the supernatant flows into the intermediate pool, enters the biological aerated filter through the high-pressure pump, and is discharged after being treated in the biological aerated filter .

Preferably, the two-phase separator set in the middle of the filter material of the biological aerated filter collects exhaust gas, and realizes secondary aeration in the degassing area of the anaerobic-anoxic device through the aeration pipeline, and completes the blowing of nitrogen. To improve the sludge settling performance.

More preferably, after the biological aerated filter has been operated for 10-15 days, the concentration of suspended solids in the middle water layer increases significantly and phosphorus is released, and the biological aerated filter is backwashed to absorb the suspended solids in the middle water layer . The recoil intensity of air and water is 3-7L/(m2.s), and the time is 2-5min for air flushing, 2-4min for air-water flushing, and 3-6min for water flushing.

More preferably, the backwashing water of the biological aerated filter is the effluent of the clear water tank, and the backwashing drainage containing a large amount of pollutants is discharged through a drain pipe arranged in the middle water layer, and the biological aerated filter is not disturbed during backwashing The upper clear water layer shortens the recoil operation time.

The beneficial effects of the double-sludge denitrification A/A-O device and method for phosphorus and nitrogen removal of the present invention are: the system sludge yield is low, the biological aerated filter has strong filtration performance and long backwashing period, and realizes low C Under the condition of /N, the urban sewage is highly efficient, stable, and deeply removes nitrogen and phosphorus and removes suspended solids.

The combined process applies denitrification and phosphorus removal technology to the greatest extent, the system has low sludge yield, low energy consumption, strong filtration performance of biological aerated filter and long backwashing cycle, realizing high efficiency and stability of urban sewage under low C/N conditions , Deep nitrogen and phosphorus removal to remove suspended solids.

The AA-BAF combination process realizes the separation of phosphorus accumulating bacteria and nitrifying bacteria, and the nitrification efficiency is high. All sludge has undergone a complete anaerobic and anoxic process, and the denitrification and phosphorus removal power is strong;

The application of denitrification and phosphorus removal technology realizes the process reduction of one carbon and two uses and sludge;

The AA unit does not nitrify, removes the influence of nitrate nitrogen in the return sludge on anaerobic phosphorus release, alleviates the floating or disintegration of the sludge in the secondary settling tank, and ensures the stable operation of the secondary settling tank;

The setting of the two-phase separator in the BAF realizes the separation of nitrification and filtration, eliminates the disturbance of filtration by aeration, strengthens the filtration function, and effectively intercepts suspended matter formed by shedding biofilms;

The setting of the two-phase separator in the BAF reduces the DO in the reflux of the nitrifying liquid, inhibits the competition of aerobic heterotrophic bacteria for carbon sources in the anoxic zone of the AA unit, and improves the deficiency of denitrifying bacteria and denitrifying phosphorus-removing bacteria in the AA unit. Oxygen environment, improve the efficiency of nitrogen and phosphorus removal;

The backwashing drainage of the biological aerated filter is discharged through the drainage pipe installed in the middle water layer of the BAF. The backwashing does not disturb the upper clear water layer of the BAF, and the backwashing operation time is short.

Description of drawings

Fig. 1 is the structural representation of the A/A-O device of double sludge denitrification dephosphorization and denitrification described in the present invention;

Among them: 1-primary sedimentation tank; 2-sludge denitrification tank; 3-anaerobic-anoxic device; 4-anaerobic zone; 5-anoxic zone; 6-degassing zone; 7-secondary sedimentation tank; 8- Intermediate pool; 9-high pressure pump; 10-biological aerated filter; 11-clear water tank; 12-outlet pipe; 13-nitrating liquid return pump; 14-sludge return pump; 15-blower; 16-gas flow meter; 17-two-phase separator; 18-air valve; 19-air pump; 20-backwash pump; 21-backwash inlet valve; 22-backwash drain pipe; 23-vent valve; 24-discharge pipe.

Detailed ways

The best embodiment of the present invention will be further described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, the A/A-O device for double sludge denitrification dephosphorization and nitrogen removal described in the embodiment of the present invention mainly consists of primary sedimentation tank 1, anaerobic-anoxic device 3, secondary sedimentation tank 7, and intermediate pool 8. The biological aerated filter 10 and the clean water tank 11 are sequentially connected to form; the anaerobic-anoxic device 3 is the AA device of the AAO treatment process, and the primary sedimentation tank 1 is connected to the anaerobic-anoxic device by the water inlet pump 2 The anaerobic zone 4 of 3 is connected, and the mud-water mixture flows through the anoxic zone 5 and the degassing zone 6 of the anaerobic-anoxic device 3 under the action of gravity, and the degassing zone 6 of the anaerobic-anoxic device 3 and the secondary sedimentation tank 7, and the secondary settling tank 7 is connected to the anaerobic zone 4 of the anaerobic-anoxic device 3 through the sludge pump 14. After the sludge enters the secondary settling tank 7, it is pumped to the anaerobic zone of the anaerobic-anoxic device 3 Circulation, the secondary settling tank 7 is provided with a discharge pipe 24, and the remaining sludge is discharged from the discharge pipe 24; the outlet water of the secondary settling tank 7 is connected to the intermediate pool 8, and the intermediate pool 8 is connected with the biological aerated filter through the high-pressure pump 9 10, the biological aerated filter 10 is connected to a clean water tank 11, and the clean water tank 11 is provided with an outlet pipe 12.

The clear water tank 11 is connected to the anoxic zone 5 of the anaerobic-anoxic device 3 through the nitrifying liquid return pump 13, so that the nitrifying liquid formed in the biological aerated filter is used as an electron acceptor to return to the anaerobic-anoxic device 3 The clear water tank 11 is connected with the water distribution area at the bottom of the biological aerated filter 10 through the backwash pump 20 and the valve 21, and the water in the clear water tank 11 returns to the biological aerated filter 10 as backwash water; The packing layer of filter tank 10 is provided with the two-phase separator 17 that is used to collect lack gas, and two-phase separator 17 is connected with the degassing zone 6 of anaerobic-anoxic device 3 by air valve 18 and air pump 19; During use, aeration The exhaust gas collected by the two-phase separator 17 in the biological biofilter 10 realizes secondary aeration in the degassing zone of the anaerobic-anoxic device 3 through the aeration pipeline and the aerator, and completes the stripping of nitrogen, Improve the sludge sedimentation performance, reduce the energy consumption of aeration in the biological system; there is no filter material in the middle of the upward-flowing biological aerated filter 10, forming an intermediate water layer, and the upper clear water layer of the biological aerated filter 10 is not disturbed during backwashing. The flushing water is discharged from the drain pipe 22 of the biological aerated filter 10; the bottom of the biological aerated filter 10 is provided with a vent valve 23.

The biological aerated filter 10 is a nitrification/filtering reactor, and the lower part of the filter material is a nitrification section, where autotrophic nitrifying bacteria are the dominant bacteria to complete the nitrification of ammonia nitrogen while retaining suspended solids; the upper part is an airless interference nitrification section. The deoxygenation filter section effectively intercepts the suspended matter formed by the exfoliated biofilm, etc., and at the same time uses the remaining dissolved oxygen to complete the oxidation of the remaining ammonia nitrogen, thereby further reducing the dissolved oxygen and ensuring that the effluent SS with low dissolved oxygen concentration meets the first-class A discharge standard.

The device for double sludge denitrification, phosphorus and nitrogen removal also includes a blower 15 , and the blower 15 is connected to the biological aerated filter 10 through an aeration pipeline and a gas flow meter 16 .

The specific process of domestic sewage treatment using this device is as follows:

1) Sewage enters the anaerobic zone 4 of the anaerobic-anoxic device 3 from the primary sedimentation tank 1, releases phosphorus in the anaerobic zone 4, and the mud-water mixture flows through the anaerobic-anoxic device 3 in a churning manner under the action of gravity The anaerobic zone 4 and the anoxic zone 5 are used for denitrification, phosphorus and nitrogen removal, and the nitrogen bubbles generated in the degassing zone 6 are removed;

2) The sewage enters the secondary sedimentation tank 7 from the above-mentioned degassing zone 6 to realize the separation of mud and water, and the supernatant liquid containing ammonia nitrogen flows into the intermediate pool 8, and enters the bottom of the biological aerated filter tank 10 through the high-pressure pump 9; the sludge is discharged through the discharge pipe 24 , the secondary settling tank 7 operates stably without sludge floating or disintegrating;

3) The dominant bacteria in the above-mentioned biological aerated filter are nitrifying bacteria that convert ammonia nitrogen into nitrate nitrogen. The hydraulic retention time is 1h, and the gas-water ratio is 6. After filtering and deoxidizing, the nitrifying liquid enters the clear water pool 11, and the treated water Discharge through outlet pipe 12;

4) The phosphorus-rich sludge not containing nitrate in the secondary sedimentation tank 7 in the above step 2 enters the anaerobic zone 4 of the anaerobic-anoxic device 3 through the sludge return pump 14, and a stirring device is provided in the pool, and the sludge return ratio is 100%, and the hydraulic retention time is 2h. The phosphorus accumulating bacteria in the sludge use the low molecular volatile organic acids (VFA) in the sewage to synthesize PHB, complete a large amount of phosphorus release, and the phosphorus release rate is high; a large amount of organic matter in the sewage is obtained Rapid transformation, the removal of COD in the anaerobic zone 4 accounts for 80% of the combined process; denitrifying phosphorus-accumulating bacteria account for nearly 80% of the phosphorus-accumulating bacteria;

5) The mixed sludge in step 4 enters the anoxic zone 5 from the above-mentioned anaerobic zone 4, and a stirring device is set in the pool, and the deoxidation and nitrification liquid entering the clear water tank 11 from the biological aerated filter 10 enters the anoxic zone through the nitrifying liquid backflow pump 13 at the same time. Zone 5, the dissolved oxygen concentration in anoxic zone 5 is very low, less than 0.3mg/L, which inhibits the plundering of carbon source by aerobic heterotrophic bacteria, and the denitrifying bacteria use the remaining carbon source of phosphorus accumulating bacteria in the anaerobic zone to reflect Nitrification and denitrification, denitrifying phosphorus accumulating bacteria use nitrate nitrogen as the electron acceptor and PHB as the electron donor to denitrify and remove phosphorus. The reflux ratio of the nitrification solution is 300%, and its hydraulic retention time is 8h;

6) The mud-water mixture in step 5 flows into the degassing zone 6 from the anoxic zone 5, and the hydraulic retention time of the degassing zone 6 is only 1h, and the oxidation of ammonia nitrogen does not occur, and the main function is to complete the removal of remaining phosphorus and the stripping of nitrogen , to improve the sludge settling performance, the mixed liquid sludge concentration is 2200mg/L;

7) Sewage enters the secondary sedimentation tank 7 from the above-mentioned degassing zone 6 to realize the separation of mud and water, and the sludge is discharged through the discharge pipe 24, and the supernatant liquid flows into the intermediate pool 8, and enters the biological aerated filter 10 through the high-pressure pump 9, and after aeration After being treated by the biological filter 10, it flows into the clean water pool.

The device specifically carries out the sewage treatment process and also adds a blower 15: the blower 15 aerates from the lower part of the biological aerated filter 10 through the gas flow meter 16 and the aeration pipeline, and is arranged in the middle part of the filter material of the biological aerated filter 10. The two-phase separator 17 collects exhaust gas, and realizes secondary aeration in the degassing zone 6 of the anaerobic-anoxic device 3 through the aeration pipeline.

After the operation of the biological aerated filter 10 for 15 days, the concentration of suspended solids in the middle water layer increased significantly and the release of phosphorus occurred, and the biological aerated filter 10 was backwashed, and the gas and water recoil intensity was 5L/(m .s), the time is 4 minutes for air flushing, 3 minutes for air and water flushing, and 4 minutes for water flushing.

The backwashing water of the biological aerated filter 10 is the effluent of the clear water tank 11, and the backwashing drainage containing a large amount of pollutants is discharged through the drain pipe 22 arranged in the middle water layer, and the biological aerated filter 10 is not disturbed during backwashing. The upper clear water layer has low energy consumption for backwashing, and the working cycle of the biological aerated filter is extended.

In order to ensure the stable and efficient operation of the combined system, the present invention creatively applies two key technologies in the AA-BAF system: denitrification phosphorus removal reactor and deoxidation BAF. The AA unit is a denitrification dephosphorization reactor, without nitrification, which removes the influence of nitrate nitrogen in the return sludge on anaerobic phosphorus release, alleviates the denitrification and floating of the sludge in the secondary settling tank, and ensures the stable operation of the secondary settling tank; The deoxygenation BAF is a nitrification/filtering reactor, a two-phase separator is set in the middle of the filter material, and the lower part is a nitrification section, where the autotrophic nitrifying bacteria are the dominant bacteria to complete the nitrification of ammonia nitrogen while retaining suspended solids; the upper part of the deoxygenation BAF is a no Air interferes with the nitrification and deoxygenation filter section, efficiently intercepts the suspended solids formed by the shedding biofilm, etc., and ensures that the effluent SS reaches the first-class A standard; the setting of the two-phase separator in the BAF reduces the DO in the reflux of the nitrification liquid.

The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, so that those skilled in the art can understand and apply the present invention, and it cannot be assumed that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, some simple deductions or substitutions can be made without departing from the concept of the present invention without creative work. Therefore, simple improvements made to the present invention by those skilled in the art based on the disclosure of the present invention should all be within the protection scope of the present invention.

Claims (10)

1. A/A-O device for double sludge denitrification dephosphorization and denitrification, characterized in that: it mainly consists of primary sedimentation tank, anaerobic-anoxic device, secondary sedimentation tank, intermediate pool, biological aerated filter and clear water pool composition; the primary settling tank is connected with the anaerobic area of the anaerobic-anoxic device, the degassing area of the anaerobic-anoxic device is connected with the secondary settling tank, and the secondary settling tank is connected with the anaerobic-anoxic plant through a sludge pump. The anaerobic zone of the oxygen device is connected; the effluent of the secondary sedimentation tank is connected to the intermediate tank, the intermediate tank is connected to the biological aerated filter tank, and the biological aerated filter tank is connected to the clear water tank; the clear water tank is connected to the anaerobic- The anoxic area of the anoxic device is connected; the clear water tank is connected with the bottom water distribution area of the biological aerated filter. 2. The A/A-O device for double sludge denitrification dephosphorization and nitrogen removal according to claim 1, characterized in that: the packing layer of the biological aerated filter is provided with a two-phase separator, and the two-phase separator passes through The aeration line is connected to the degassing zone of the anaerobic-anoxic unit. 3. The A/A-O device for double sludge denitrification, phosphorus and nitrogen removal according to claim 1, characterized in that: the secondary settling tank is provided with a sludge discharge pipe; the bottom of the biological aerated filter is provided with a vent valve; the clear water pool is provided with an outlet pipe. 4. The A/A-O device for double sludge denitrification, phosphorus and nitrogen removal according to claim 1, characterized in that: the device for double sludge denitrification, phosphorus and nitrogen removal also includes a blower, and the blower passes through the aeration pipeline And the gas flow meter is connected with the biological aerated filter. 5. The A/A-O device of double sludge denitrification dephosphorization and nitrogen removal according to claim 1, characterized in that: the biological aerated filter is a nitrification/filtration reactor, and the lower part of the filter material is a nitrification section, The upper part is an air-free interference nitrification deoxidation filter section. 6. An A/A-O method for double sludge denitrification dephosphorization and denitrification, characterized in that: the specific steps of the method are: 1) Sewage enters the anaerobic zone of the anaerobic-anoxic device from the primary sedimentation tank, releases phosphorus in the anaerobic zone, and the mud-water mixture flows through the anaerobic zone and Anoxic zone, denitrification, phosphorus and nitrogen removal, and degassing in the degassing zone; 2) The mud-water mixture enters the secondary sedimentation tank from the above-mentioned degassing area to realize the separation of mud and water, and the supernatant liquid containing ammonia nitrogen flows into the intermediate pool, and enters the bottom of the biological aerated filter through a high-pressure pump; the sludge is discharged through the discharge pipe; 3) The dominant bacteria in the above-mentioned biological aerated filter are nitrifying bacteria that convert the ammonia nitrogen in the above-mentioned supernatant into nitrate nitrogen, and the nitrifying liquid enters the clear water pool after filtration and deoxygenation, and the treated water is discharged through the outlet pipe; 4) The nitrate-free phosphorus-rich sludge in the secondary settling tank in the above step 2 enters the anaerobic zone of the anaerobic-anoxic device through the sludge return pump, and the phosphorus-accumulating bacteria in the sludge utilize the low-molecular-weight sludge in the sewage. Volatile organic acids, synthetic PHB, release a large amount of phosphorus, and the phosphorus release rate is high; a large amount of organic matter in sewage is rapidly transformed, and the removal of COD in the anaerobic zone accounts for 70-80% of the combined process; denitrifying phosphorus accumulating bacteria The proportion of phosphorus accumulating bacteria is close to 80%; 5) The mixed sludge in step 4 enters the anoxic zone from the above-mentioned anaerobic zone, and at the same time, the deoxidized nitrification liquid entering the clear water tank from the biological aerated filter enters the anoxic zone through the nitrification liquid return pump, and the denitrifying bacteria use the anoxic zone The remaining carbon source of phosphorus accumulating bacteria is denitrified and denitrified, and the denitrifying phosphorus accumulating bacteria use nitrate nitrogen as the electron acceptor to absorb phosphorus; 6) The mud-water mixture in step 5 flows into the degassing zone from the anoxic zone, and completes the removal of remaining phosphorus and the stripping of nitrogen; 7) The sewage enters the secondary sedimentation tank from the above-mentioned degassing area to realize the separation of mud and water. The sludge is discharged through the discharge pipe, and the supernatant flows into the intermediate pool, enters the biological aerated filter through the high-pressure pump, and is discharged after being treated in the biological aerated filter . 7. According to the A/A-O method of double sludge denitrification dephosphorization and nitrogen removal according to claim 6, it is characterized in that: said device specifically carries out the sewage treatment process and also adds a blower: the blower passes through the gas flow meter and the aeration pipeline Aeration from the lower part of the biological aerated filter. 8. according to the A/A-O method of double sludge denitrification dephosphorization and denitrification described in claim 7, it is characterized in that: the two-phase separator that is arranged in the middle part of the filter material of biological aerated filter collects exhaust gas, through aeration The pipeline realizes secondary aeration in the degassing area of the anaerobic-anoxic device to complete the stripping of nitrogen. 9. According to the A/A-O method of double sludge denitrification dephosphorization and denitrification according to claim 8, it is characterized in that: after the operation of the biological aerated filter for 10-15 days, the concentration of suspended matter in the middle water layer increases significantly Or the release of phosphorus occurs, and the biological aerated filter is backwashed to absorb the suspended solids in the middle water layer. 10. according to the A/A-O method of double sludge denitrification denitrification dephosphorization and denitrification according to claim 9, it is characterized in that: the backwash inflow of the biological aerated filter is the effluent of the clear water tank, which contains a large amount of pollutants. The flushing water is discharged through the drainage pipe installed in the middle water layer, and the upper clear water layer of the biological aerated filter is not disturbed during backwashing, so the backwashing operation time is shortened and the working cycle of the filter is prolonged.

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