An anaerobic backwash system for heterotrophic autotrophic post-denitrification filter

Abstract

The present application relates to an anaerobic backwashing system for a heterotrophic autotrophic post-denitrification filter, which comprises a filter body, a filter water inlet channel, a filter unit, an underwater nitrogen collection system, a nitrogen storage and utilization system and a pressure reducing device, wherein the filter unit comprises a backwashing water and air distribution device, a supporting layer and a filter material layer, and nitrogen is used to flush and remove impurities in the filter material; the underwater nitrogen collection system comprises an ultrasonic gas collection system, a gas-water separation device and a negative pressure vacuum pump, and ultrasonic vibration is used to assist in removing blockages and ensure the high efficiency of nitrogen collection; the nitrogen storage and utilization system comprises a nitrogen storage tank and a nitrogen flow channel, and the effective storage and reuse of nitrogen are realized. The present application achieves the technical effect of improving the operation efficiency of the filter and reducing the backwashing energy consumption and maintenance cost.

Description

Technical Field

[0001] The present application relates to the field of sewage treatment equipment, and in particular to an anaerobic backwashing system for a heterotrophic autotrophic post-denitrification filter. Background Art

[0002] In recent years, with the continuous improvement of environmental standards, urban sewage treatment plants need to meet more stringent pollutant emission standards, especially in terms of total nitrogen (TN) indicators. In order to meet this standard, post-denitrification filters have become an important technical means for upgrading sewage treatment plants. This technology can be divided into heterotrophic and autotrophic types. Heterotrophic denitrification filters are filled with quartz sand or ceramsite filter media, and additional organic carbon sources (such as methanol, sodium acetate, etc.) are added for denitrification; while autotrophic denitrification filters are mainly based on sulfur autotrophic denitrification, and sulfur and other mineral powders are granulated and then placed in the filter. Although both methods can effectively remove total nitrogen, there are still many problems and challenges in actual application.

[0003] Whether heterotrophic or autotrophic filters, they all need to undergo denitrification under strict anoxic conditions and use a combined air-water backwashing method to clean the filter media. However, the air-water backwashing process will introduce dissolved oxygen from the air, resulting in a decrease in denitrification efficiency, which in turn affects the effluent quality. In addition, it takes a long time for the filter to recover its denitrification capacity after backwashing.

[0004] In the prior art, the design of heterotrophic / autotrophic post-denitrification filter tanks generally has a high degree of redundancy. There are two main reasons for this. First, the backwashing process destroys the biological environment of the filter bed, and the filter tank needs a certain recovery period after backwashing. Second, the traditional nitrogen removal method requires frequent water stoppage to remove the nitrogen accumulated between the filter media, resulting in reduced filter efficiency. In order to solve these problems, the overall filtration area and the number of filter cells are usually increased in current projects, but this will undoubtedly increase construction and operating costs. Therefore, how to reduce the dissolved oxygen introduced during the backwashing process and achieve continuous nitrogen removal without interrupting water intake has become a key technical problem that needs to be solved in this field. Summary of the invention

[0005] In order to improve the operating efficiency of a denitrification filter, the present application provides an anaerobic backwashing system for a heterotrophic autotrophic post-denitrification filter.

[0006] The heterotrophic autotrophic post-denitrification filter anaerobic backwashing system provided in this application adopts the following technical solution:

[0007] A heterotrophic autotrophic post-denitrification filter anaerobic backwashing system, comprising:

[0008] A filter tank body, sewage flows into the interior of the filter tank body;

[0009] A filter tank water inlet channel, wherein the filter tank water inlet channel is arranged above the inner side of the filter tank body;

[0010] A filter unit, the filter unit comprising a backwash water and air distribution device disposed at the bottom of the filter tank body, a support layer located above the backwash water and air distribution device, and a filter material layer located above the support layer, nitrogen is evenly distributed in the filter material layer through the backwash water and air distribution device, impurities in the filter material are removed by the flushing effect of nitrogen, and the support layer supports the filter material in the filter material layer and evenly distributes the backwash gas;

[0011] An underwater nitrogen collection system, the underwater nitrogen collection system comprising an ultrasonic gas collection system, a gas-water separation device, and a negative pressure vacuum pump, the ultrasonic gas collection system comprising a main gas channel connected to the gas-water separation device, branch gas channels uniformly arranged in the filter material layer, and a capillary diffusion tube connected to the branch gas channel and located in the filter material layer, the main gas channel, the branch gas channel and the capillary diffusion tube remove blockages in the filter material through ultrasonic vibration, the gas-water separation device comprising a liquid level gauge and an alkaline desiccant, the negative pressure vacuum pump is connected to the side of the gas-water separation device away from the filter tank body, the negative pressure vacuum pump draws a gas and water mixture in the filter tank body into the gas-water separation device, the liquid level gauge monitors the liquid level to ensure effective separation of gas and water, and the alkaline desiccant absorbs the separated water to ensure the purity of the nitrogen;

[0012] A nitrogen storage and utilization system, comprising a nitrogen storage tank and a nitrogen flow channel, wherein the nitrogen flow channel comprises a nitrogen collection channel, a nitrogen backwash channel and a raw water return channel, wherein the nitrogen storage tank is connected to the gas-water separation device through the nitrogen collection channel, and is connected to the filter tank body through the nitrogen backwash channel, and the raw water return channel is connected to the gas-water separation device, so that the liquid after gas-water separation flows into the interior of the filter tank body.

[0013] By adopting the above technical solution, when the filter needs to be expelled by nitrogen, the negative pressure vacuum pump is started to pump the gas and water mixture in the filter into the gas-water separation device, and the dry nitrogen treated by the gas-water separation device is stored in the nitrogen storage tank. When backwashing is required, the backwash water is evenly distributed in the filter material layer through the backwash water and gas distribution device, and the recovered nitrogen is evenly distributed in the filter material layer through the main gas channel, the branch gas channel and the capillary diffusion tube. The impurities in the filter material are removed by the flushing effect of nitrogen and water. At the same time, the ultrasonic generator can generate ultrasonic waves to assist in removing the blockages in the filter material that are difficult to remove, so as to improve the filtration efficiency. The liquid level gauge in the gas-water separation device monitors the liquid level to ensure the effective separation of gas and water. The alkaline desiccant is used to absorb the separated water and neutralize acidic gases such as hydrogen sulfide to ensure the purity of the nitrogen, thus realizing the anaerobic backwash system of the heterotrophic / autotrophic post-denitrification filter. The collected nitrogen is relatively pure without the dissolution of dissolved oxygen in the air, which reduces the recovery time of the denitrification performance after backwashing, realizes continuous and efficient nitrogen removal, and improves the operation efficiency of the filter.

[0014] Preferably, the ultrasonic generator and the main gas channel simultaneously serve as sources of ultrasonic waves, transmitting the vibration frequency to the branch gas channels and the capillary diffusion tubes.

[0015] By adopting the above technical solution, the ultrasonic generator and the main gas channel simultaneously serve as the source of ultrasonic waves, transmitting the vibration frequency to the branch gas channel and the capillary diffusion tube, effectively improving the nitrogen collection efficiency and the pollution-absorbing capacity of the filter, delaying the clogging of the filter material layer, extending the backwashing cycle, and further improving the operation efficiency of the filter.

[0016] Preferably, the outer part of the capillary diffusion tube includes a wear-resistant fiber skeleton layer, a waterproof and breathable membrane layer and a supporting fiber skeleton layer, and the inner part includes a porous supporting carrier.

[0017] By adopting the above technical scheme, the outer part of the capillary diffusion tube includes a wear-resistant fiber skeleton layer, a waterproof and breathable membrane layer and a supporting fiber skeleton layer, and the inner part includes a porous supporting carrier, which effectively ensures the high-purity collection of nitrogen and reduces the mixing of raw water. At the same time, it ensures the efficient operation of the ultrasonic gas collection system and improves the backwashing effect of the filter and the nitrogen collection efficiency.

[0018] Preferably, the capillary diffusion tube has a diameter of 6 to 9 mm.

[0019] By adopting the above technical solution, the diameter of the capillary diffusion tube is set to 6-9 mm, which can ensure efficient collection of nitrogen while efficiently transmitting the vibration frequency transmitted by the ultrasonic source, effectively preventing suspended matter in the raw water from clogging the tube mouth, and ensuring the continuity and stability of the nitrogen collection process.

[0020] Preferably, the capillary diffusion tubes are arranged alternately in upper and lower layers, and the vertical spacing is no more than 0.5 m.

[0021] By adopting the above technical solution, the capillary diffusion tubes are arranged alternately in the upper and lower layers, with a vertical spacing of no more than 0.5m, so that the collection pipelines are fully arranged between the filter media layers, ensuring full coverage of nitrogen collection and backwashing gas between the filter media layers, thereby improving the overall operation efficiency of the filter bed.

[0022] Preferably, the liquid level meter in the gas-water separation device is set to a high liquid level and a low liquid level.

[0023] By adopting the above technical solution, the liquid level gauge in the gas-water separation device is set to high liquid level and low liquid level, and the nitrogen collection process can be automatically controlled according to the liquid level change. At this time, the filter tank runs continuously to ensure the filter tank operation efficiency.

[0024] Preferably, the negative pressure vacuum pump is controlled in linkage with the gas-water separation device.

[0025] By adopting the above technical solution, the negative pressure vacuum pump and the gas-water separation device are controlled in linkage, so that the system can automatically adjust the operating frequency of the negative pressure vacuum pump according to the change of the liquid level in the gas-water separation device, thereby ensuring the high efficiency of nitrogen collection and reducing energy consumption.

[0026] Preferably, the nitrogen flow channel further comprises an excess nitrogen exhaust channel, and the nitrogen storage tank is connected to the atmosphere via the excess nitrogen exhaust channel.

[0027] By adopting the above technical solution, when too much nitrogen accumulates in the nitrogen storage tank, the excess nitrogen can be discharged into the atmosphere through the excess nitrogen exhaust channel to prevent the nitrogen storage tank pressure from being too high and ensure the safety and stability of the system.

[0028] Preferably, the nitrogen flow channel further includes a nitrogen collection and backwash channel, and the nitrogen collection and backwash channel is connected to the ultrasonic gas collection system.

[0029] By adopting the above technical solution, by setting up nitrogen collection and backwashing channels, and connecting the nitrogen collection and backwashing channels with the ultrasonic gas collection system, the reversible switching of nitrogen in the collection and backwashing process is achieved, reducing the complexity of the system; at the same time, the backwashing process can be assisted by ultrasonic or backwashing nitrogen pulse supply to perform deep backwashing, thereby achieving the purpose of saving backwashing water and nitrogen.

[0030] Preferably, a pressure reducing device is further included, and the nitrogen storage tank is connected to the nitrogen backwashing channel via the pressure reducing device.

[0031] By adopting the above technical solution, the nitrogen storage tank is connected to the nitrogen backwash channel through a pressure reducing device. The pressure reducing device can adjust the pressure of the nitrogen to make it suitable for the backwashing requirements, avoiding the secondary pressurization process in the traditional technology and reducing energy consumption. At the same time, different pressure adjustments improve the backwashing effect.

[0032] In summary, the present application includes at least one of the following beneficial technical effects:

[0033] 1. By using nitrogen for backwashing, the introduction of dissolved oxygen during the backwashing process is avoided, which helps to restore the denitrification volume load of the filter after air-water backwashing and reduces the design redundancy of the filter area and the number of cells;

[0034] 2. The negative pressure vacuum pump is linked to the gas-water separation device to automatically adjust the operating frequency of the negative pressure vacuum pump according to the change of liquid level, ensuring stable operation of nitrogen expulsion and continuous operation of the filter tank during nitrogen expulsion;

[0035] 3. Use capillary diffusion tubes to release backwash gas, and assist ultrasonic vibration in the ultrasonic gas collection system to remove blockages in the filter material. At the same time, pulse backwashing can be achieved, extending the backwashing cycle and improving the filtration efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The present invention discloses a schematic structural diagram of an anaerobic backwashing system for a heterotrophic autotrophic post-denitrification filter.

[0037] Figure 2 It is a schematic diagram of the bottom layer layout of the ultrasonic gas collection system.

[0038] Figure 3 It is a schematic diagram of the upper layout of the ultrasonic gas collection system.

[0039] Figure 4 It is the principle diagram of the gas-water separation device.

[0040] Figure 5 It is the recovery curve of the structure of this application after backwashing.

[0041] Figure 6 It is the recovery curve after backwashing of the prior art structure.

[0042] Explanation of the reference numerals: 1. Filter body; 2. Filter water inlet channel; 3. Filter unit; 31. Backwash water and air distribution device; 32. Support layer; 33. Filter material layer; 4. Underwater nitrogen collection system; 41. Ultrasonic gas collection system; 411. Main gas channel; 412. Branch gas channel; 413. Capillary diffusion tube; 42. Gas-water separation device; 421. Liquid level gauge; 422. Alkaline desiccant; 43. Negative pressure vacuum pump; 5. Nitrogen storage and utilization system; 51. Nitrogen storage tank; 52. Nitrogen flow channel; 521. Nitrogen collection channel; 522. Nitrogen backwash channel; 523. Raw water return channel; 524. Excess nitrogen exhaust channel; 525. Nitrogen collection and backwash channel; 6. Pressure reducing device. DETAILED DESCRIPTION

[0043] The following is combined with Figure 1-4 This application is described in further detail.

[0044] The present application embodiment discloses an anaerobic backwashing system for a heterotrophic autotrophic post-denitrification filter. Figure 1 The heterotrophic autotrophic post-denitrification filter anaerobic backwashing system includes a filter body 1, a filter water inlet channel 2, a filtration unit 3, an underwater nitrogen collection system 4, a nitrogen storage and utilization system 5 and a pressure reducing device 6, which realizes the efficient recycling of nitrogen in the backwashing process, reduces the introduction of dissolved oxygen, and improves the denitrification performance of the filter.

[0045] Reference Figure 1 Specifically, the sewage flows into the filter tank body 1, and the sewage flows into the filter tank from the filter tank water inlet channel 2 arranged on the upper inner side of the filter tank body 1. The size L×B×H of the filter tank body 1 can be set to 3m×1m×3m.

[0046] The filter unit 3 includes a backwash water and air distribution device 31 disposed at the bottom of the filter tank body 1 , a supporting layer 32 located above the backwash water and air distribution device 31 , and a filter material layer 33 located above the supporting layer 32 .

[0047] Specifically, the filter unit 3 includes a backwash water and air distribution device 31, a supporting layer 32 and a filter material layer 33, which is used to remove impurities and nitrogen pollutants in the raw water. The backwash water and air distribution device 31 can be made of a variety of corrosion-resistant materials, such as metal (such as stainless steel), plastic (such as high-density polyethylene and ABS), concrete, etc. The supporting layer 32 can be made of materials such as pebbles and quartz sand to ensure that the filter material layer 33 will not move or be damaged during the backwashing process. The filter material layer 33 can use biofilm carrier filter materials with high mechanical strength, such as quartz sand, ceramsite, etc., or consumable filter materials such as natural pyrite and composite sulfur autotrophic materials. The filter material is irregular in shape and has a particle size of 2~8mm. The filling height is adjusted according to the water quality and water outlet requirements, generally ranging from 1.8 meters to 2.4 meters. The filter tank body 1 can be designed as a rectangular or circular structure according to different application scenarios, and the reactor material can use reinforced concrete, stainless steel or carbon steel.

[0048] Reference Figure 1-Figure 3 The underwater nitrogen collection system 4 includes an ultrasonic gas collection system 41, an air-water separation device 42 and a negative pressure vacuum pump 43. The ultrasonic gas collection system 41 includes a main gas channel 411 connected to the air-water separation device 42, branch gas channels 412 uniformly arranged in the filter material layer 33, and a capillary diffusion tube 413 connected to the branch gas and located in the filter material layer 33. The main gas channel 411, the branch gas channel 412 and the capillary diffusion tube 413 are subjected to ultrasonic vibration to assist in removing difficult-to-remove blockages in the filter material during the backwashing process. At the same time, it can effectively prevent suspended matter in the raw water from clogging the capillary diffusion tube 413 in the nitrogen drive mode, and can also disturb the accumulated nitrogen in the filter material to improve the nitrogen collection efficiency.

[0049] The nitrogen is evenly distributed in the filter material layer 33 through the capillary diffusion tube 413, and the impurities in the filter material are removed by the flushing effect of the nitrogen and the backwash water. The supporting layer 32 supports the filter material and ensures that the backwash water is evenly distributed.

[0050] Reference Figure 2-Figure 3Specifically, the ultrasonic gas collection system 41 includes an ultrasonic generator and a main gas channel 411, a branch gas channel 412 and a capillary diffusion tube 413. The ultrasonic generator not only serves as the main gas channel 411 of nitrogen, but also serves as the source of ultrasonic waves, transmitting the vibration frequency to the branch gas channel 412. The branch gas channel 412 can be made of rigid materials, such as stainless steel or carbon steel, and can be square, circular or other special-shaped structures in order to transmit ultrasonic waves to the capillary diffusion tube 413. The capillary diffusion tube 413 uses a wear-resistant fiber skeleton layer, a waterproof and breathable membrane layer and a supporting fiber skeleton layer as the outer structure, and the interior is divided into a porous supporting carrier. The wear-resistant fiber skeleton layer can be made of polyamide fiber (such as nylon), nylon, aramid and other materials, in order to effectively resist the wear of the filter material particles on the device. The waterproof and breathable membrane layer can be made of a water-based foamed resin material, in order to most efficiently penetrate nitrogen and intercept raw water, while the gas can pass through in reverse to achieve the recoil of the surrounding filter material gas. The supporting fiber skeleton layer can use glass fiber material to provide structural support for the porous support carrier at the hole. The diameter of the capillary diffusion tube 413 is 6-9mm, and the spacing between two adjacent horizontal arrangements is no more than 0.5m. The extended length when laid is three to five times the straight length, and the upper and lower layers are staggered, and the vertical spacing between the upper and lower layers is no more than 0.5m, which improves the comprehensiveness of gas collection. There are 4 layers of capillary diffusion tubes 413, with a total length of about 200m; the wear-resistant fiber skeleton layer can freely pass water and gas, and the filtrate accuracy is 5~10μm; the waterproof and breathable membrane layer has an air permeability of not less than 500mL / min / cm²@7KPa; the supporting fiber skeleton layer, the glass fiber material can freely pass water and gas, and the filtrate accuracy is not higher than 100μm; the porous support carrier adopts a HDPE porous structure tube hollow flexible support body, which is designed with an internal channel for gas circulation, a circular structure, and an opening rate of not less than 60%.

[0051] Reference Figure 1 , Figure 4 The gas-water separation device 42 includes a liquid level meter 421 and an alkaline desiccant 422. The negative pressure vacuum pump 43 is connected to the gas-water separation device 42 to draw the gas and water mixture in the filter tank body 1 into the gas-water separation device 42. The liquid level meter 421 monitors the liquid level to ensure effective separation of gas and water.

[0052] Specifically, the gas-water separation device 42 includes a liquid level meter 421 and an alkaline desiccant 422, and a high liquid level and a low liquid level are set. The liquid level changes automatically control the continuous collection of nitrogen. The liquid level meter 421 monitors the liquid level to ensure the effective separation of gas and water. The alkaline desiccant 422 absorbs the separated moisture and neutralizes the acidic gas to ensure the purity of the nitrogen. The negative pressure vacuum pump 43 is linked with the gas-water separation device 42 and can automatically adjust the operating frequency of the negative pressure vacuum pump 43 according to the liquid level changes in the gas-water separation device 42, thereby ensuring the high efficiency of nitrogen collection. The negative pressure vacuum pump 43 draws the gas and water mixture in the filter tank body 1 into the gas-water separation device 42, and the negative pressure vacuum pump 43 is frequency-converter controlled.

[0053] Reference Figure 1 The nitrogen storage and utilization system 5 includes a nitrogen storage tank 51 and a nitrogen flow channel 52. The nitrogen flow channel 52 includes a nitrogen collection channel 521, a nitrogen backwash channel 522 and a raw water return channel 523. The nitrogen storage tank 51 is connected to the gas-water separation device 42 through the nitrogen collection channel 521, and is connected to the filter tank body 1 through the nitrogen backwash channel 522. The raw water return channel 523 is connected to the gas-water separation device 42, and the liquid after gas-water separation flows into the interior of the filter tank body 1, thereby realizing the collection and backwash utilization of nitrogen.

[0054] Specifically, the nitrogen circulation channel 52 includes a nitrogen collection channel 521, a nitrogen backwash channel 522 and a raw water return channel 523. The nitrogen storage tank 51 is connected to the gas-water separation device 42 through the nitrogen collection channel 521, and is connected to the filter tank body 1 through the nitrogen backwash channel 522. The nitrogen circulation channel 52 also includes an excess nitrogen discharge channel 524, and the nitrogen storage tank 51 is connected to the atmosphere through the excess nitrogen discharge channel 524. The nitrogen circulation channel 52 also includes a nitrogen collection and backwash channel 525, which is connected to the ultrasonic gas collection system 41. In addition, it also includes a decompression device 6, and the nitrogen storage tank 51 is connected to the nitrogen backwash channel 522 through the decompression device 6. The repeated opening and closing of the nitrogen collection and backwash channel 525 can realize deep gas pulse backwashing during the backwashing process.

[0055] The specific process of nitrogen collection is as follows:

[0056] The nitrogen generated by the filter layer 33 is driven by the negative pressure of the negative pressure vacuum pump 43, and the nitrogen in the filter layer 33 is negatively absorbed by the ultrasonic gas collection system 41 of the device; the ultrasonic generator and the main gas channel 411 of the device are used as ultrasonic generating sources at the same time, and finally the vibration is transmitted to the capillary diffusion tube 413, and the capillary diffusion tube 413 slightly vibrates the surrounding water body to slowly drive out the nitrogen in the filter tank. At the same time, the capillary diffusion tube 413 acts as a capillary unit for negative pressure absorption, and quickly collects the free nitrogen accumulated in the filter layer 33; at this time, the nitrogen collection and backwash channel 525 and the nitrogen collection channel 521 are opened, the nitrogen backwash channel 522 and the raw water return channel 523 are closed, and the gas and water flow through the gas-water separation device 42, and finally stored in the nitrogen storage tank 51. When the nitrogen storage tank 51 of the device reaches the saturation pressure, the excess nitrogen discharge channel 524 is automatically opened to transport the excess nitrogen to the outside. The nitrogen collection process does not run continuously according to different working conditions. When the liquid level in the gas-water separation device 42 of the device reaches a high level, the negative pressure vacuum pump 43 and the nitrogen collection and backwash channel 525 stop running, and the nitrogen backwash channel 522, the nitrogen collection channel 521, and the raw water return channel 523 are running. The pressure reducing device 6 automatically increases the air pressure in the nitrogen backwash channel 522, and the gas in the gas-water separation device 42 is pressurized and forced to be discharged. After the liquid level in the container of the device drops rapidly to a low level, the nitrogen collection procedure is carried out again, and this cycle is repeated.

[0057] Reference Figure 5-Figure 6 In a specific embodiment, the filter reactor model adopts the company's own post-denitrification filter pilot platform. The filter design can refer to the patent for a sulfur autotrophic denitrification filter; the platform is designed as 3 parallel filter tanks, that is, parallel water inlet and parallel water outlet do not affect each other; this implementation case selects 2 of the filter tanks for technical comparison, 1# filter tank adopts this technical solution and operates in the form of anaerobic backwashing; 2# filter tank adopts traditional existing technology; 3# filter tank is idle; focus on comparing three effect indicators before and after the establishment of the anaerobic backwashing system: ① before and after backwashing, the recovery time of the denitrification volume load before backwashing of the filter tank; ② when the maximum filtration head is reached, the interval time between two backwashings; ③ the time occupied by nitrogen expulsion causes the cumulative time of the filter tank to stop operating and.

[0058] The raw water is taken from the secondary biochemical tail water of the sewage treatment plant. The filter inlet TN ≥ 25mg / L, the inlet SS ≤ 10mg / L, the outlet TN ≤ 5mg / L, and the single filter treatment water volume is 336m 3 / d; air backwash intensity ≤40m 3 / m 2 h, duration 5min, air-water combined washing, air intensity ≤40m 3 / m 2 h, duration 10min, water backwash, backwash intensity ≤15m 3 / m 2h, duration 5min, single backwashing gas consumption is about 30m 3 ;

[0059] Ultrasonic frequency range: 20KHz~28KHz; effective volume of gas-water separation device: 800L, working pressure: -0.3MPa~0.3MPa; effective volume of nitrogen storage tank: 10m 3 , Working pressure 0~1.0MPa;

[0060] The deadline is when the two filters are running to their highest filtration heads:

[0061] The 1# filter tank runs continuously for 24 hours, and the water does not stop entering during the nitrogen removal process. The minimum nitrogen removal capacity is monitored to be 6.72 kg / day. The density of nitrogen at normal temperature and pressure is about 1.25 g / L, and the daily nitrogen production is about 5.376 m 3 The gas volume required for backwashing is about 30m 3 , the excess gas is discharged, and the most unfavorable filtering head is reached after 14 days of cumulative operation; the 2# filter tank drives nitrogen once every 1 hour, lasting for 2 minutes, that is, each time the water intake is stopped for 2 minutes, the actual working time of the filter tank is 23.2 hours per day, and its minimum denitrification is monitored to be 6.5kg / day, and the most unfavorable filtering head is reached after 11 days of cumulative operation;

[0062] After the two groups of filters reached the most unfavorable filtration head, they were backwashed with air and water respectively. The nitrate nitrogen data of the inlet and outlet water after backwashing were monitored, and the recovery time of the denitrification volume load (nitrate nitrogen removal rate) was calculated. In this application scheme, the recovery time is about 80 minutes, which can be referred to Figure 5 ; The existing technical solution is about 120 minutes, which can be referred to Figure 6 ; The new technology solution significantly reduces the time it takes for the filter to recover and improves the filter's operating efficiency;

[0063] Through specific examples, it is shown that: ② The interval difference between the backwashing time of the two schemes is 3 days, and the new technology scheme increases the pollution holding capacity of the filter tank by about 27% compared with the existing technology scheme, prolonging the backwashing cycle and improving the filter tank operation efficiency; ③ The new technology scheme continuously drives nitrogen, avoiding the 0.8h nitrogen drive time per day of the traditional technology, and improving the filter tank operation efficiency. The implementation principle of the anaerobic backwashing system of a heterotrophic autotrophic post-denitrification filter tank in the embodiment of the present application is: the heterotrophic autotrophic post-denitrification filter tank anaerobic backwashing system can effectively remove the blockage in the filter material through the use of an ultrasonic gas collection system 41 with an ultrasonic generating function, a gas-water separation device 42 and a nitrogen circulation channel 52, while ensuring the high purity and efficiency of nitrogen collection. The blockage is removed by ultrasonic wave and the nitrogen backwashing channel 522 is used to achieve efficient backwashing of the filter tank, which improves the operation efficiency of the denitrification filter tank, avoids the introduction of dissolved oxygen, and further improves the denitrification capacity and work efficiency of the filter tank.

[0064] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A heterotrophic / autotrophic post-denitrification filter anaerobic backwashing device, characterized in that: include: A filter tank body (1), sewage flows into the interior of the filter tank body (1); A filter tank water inlet channel (2), wherein the filter tank water inlet channel (2) is arranged above the inner side of the filter tank body (1); A filter unit (3), the filter unit (3) comprising a backwashing water and air distribution device (31) arranged at the bottom of the filter tank body (1), a supporting layer (32) located above the backwashing water and air distribution device (31), and a filter material layer (33) located above the supporting layer (32), the supporting layer (32) supporting the filter material in the filter material layer (33) and evenly distributing the backwashing gas; An underwater nitrogen collection system (4), the underwater nitrogen collection system (4) comprising an ultrasonic gas collection system (41), a gas-water separation device (42), and a negative pressure vacuum pump (43), the ultrasonic gas collection system (41) comprising an ultrasonic generator, a main gas channel (411) connected to the gas-water separation device (42), branch gas channels (412) uniformly arranged in the filter material layer (33), and a capillary diffusion tube (413) connected to the branch gas channel (412) and located in the filter material layer (33). ), the gas-water separation device (42) comprises a liquid level meter (421) and an alkaline desiccant (422), the negative pressure vacuum pump (43) is connected to the gas-water separation device (42) at a side away from the filter tank body (1), the negative pressure vacuum pump (43) draws the gas and water mixture in the filter tank body (1) into the gas-water separation device (42), the liquid level meter (421) monitors the liquid level to ensure effective separation of gas and water, and the alkaline desiccant (422) absorbs the separated water to ensure the purity of the nitrogen; A nitrogen storage and utilization system (5), the nitrogen storage and utilization system (5) comprising a nitrogen storage tank (51) and a nitrogen flow channel (52), the nitrogen flow channel (52) comprising a nitrogen collection channel (521), a nitrogen backwash channel (522) and a raw water return channel (523), the nitrogen storage tank (51) being connected to the gas-water separation device (42) via the nitrogen collection channel (521), and being connected to the filter tank body (1) via the nitrogen backwash channel (522), the raw water return channel (523) being connected to the gas-water separation device (42), so that liquid after gas-water separation flows into the interior of the filter tank body (1); The nitrogen flow channel (52) further comprises a nitrogen collection and backwash channel (525), and the nitrogen collection and backwash channel (525) is connected to the ultrasonic gas collection system (41); When backwashing is required, backwash water and nitrogen are evenly distributed in the filter material layer through the backwash water and gas distribution device, and the recovered nitrogen is evenly distributed to the filter material layer through the main gas channel, branch gas channel and capillary diffusion tube. The flushing effect of nitrogen and water is used to remove impurities in the filter material. At the same time, the ultrasonic generator generates ultrasonic waves to assist in removing difficult-to-remove blockages in the filter material.

2. The heterotrophic / autotrophic post-denitrification filter anaerobic backwashing device according to claim 1, characterized in that: The outer part of the capillary diffusion tube (413) comprises a wear-resistant fiber skeleton layer, a waterproof and breathable membrane layer and a supporting fiber skeleton layer, and the inner part comprises a porous supporting carrier.

3. The heterotrophic / autotrophic post-denitrification filter anaerobic backwashing device according to claim 2, characterized in that: The capillary diffusion tube (413) has a diameter of 6 to 9 mm.

4. The heterotrophic / autotrophic post-denitrification filter anaerobic backwashing device according to claim 3, characterized in that: The capillary diffusion tubes (413) are arranged in a staggered manner in upper and lower layers, and the vertical arrangement interval is no greater than 0.5 m.

5. The heterotrophic / autotrophic post-denitrification filter anaerobic backwashing device according to claim 1, characterized in that: The liquid level meter (421) in the gas-water separation device (42) is set to a high liquid level and a low liquid level.

6. The heterotrophic / autotrophic post-denitrification filter anaerobic backwashing device according to claim 1, characterized in that: The negative pressure vacuum pump (43) is controlled in linkage with the gas-water separation device (42).

7. The heterotrophic / autotrophic post-denitrification filter anaerobic backwashing device according to claim 1, characterized in that: The nitrogen flow channel (52) further comprises an excess nitrogen discharge channel (524), and the nitrogen storage tank (51) is connected to the atmosphere via the excess nitrogen discharge channel (524).

8. The heterotrophic / autotrophic post-denitrification filter anaerobic backwashing device according to claim 1, characterized in that: It also includes a decompression device (6), and the nitrogen storage tank (51) is connected to the nitrogen backwashing channel (522) via the decompression device (6).

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