External anaerobic sludge air flotation precipitation separator and application method thereof

Abstract

The invention discloses an external anaerobic sludge air flotation precipitation separator and an application method thereof. The external anaerobic sludge air flotation precipitation separator is suitable for efficient separation and backflow of sludge and clear liquid in the anaerobic sewage treatment process. The separator structurally comprises a tank body with a jet releaser, an internal baffle, a scum tank, an inclined plate and the like, inlet water of the air flotation precipitation separator is jetted at a high speed to suck biogas to form gas dissolving water, a pressurized gas dissolving system is replaced to release fine bubbles, and sludge is promoted to float upwards and separated from scum through air flotation. Meanwhile, heavy sludge sinks and flows back, and clear liquid is further precipitated through an inclined plate and then overflows and is discharged. The system realizes the synergistic effect of air floatation, precipitation and liquid seal effluent, improves the separation efficiency, prevents biogas leakage and realizes the effect of anaerobic sludge recovery.

Description

Technical Field

[0001] The present invention belongs to the fields of environmental engineering and water treatment engineering, and particularly relates to an external anaerobic sludge flotation sedimentation separator and an application method thereof. Background Art

[0002] Anaerobic biochemical treatment plays an important role in the field of organic wastewater treatment due to its advantages such as high volumetric load, low energy consumption, high shock load resistance, and the ability to degrade macromolecular and toxic substances, thereby improving the efficiency of subsequent aerobic treatment. The forms of anaerobic reactors have developed from the earliest CSTR (Continuous Stirred-Tank Reactor), anaerobic filter to UASB (Upflow Anaerobic Sludge Blanket), EGSB (Expanded Granular Sludge Bed), IC (Internal Circulation), etc., and are still in continuous renewal. In the anaerobic treatment process, three-phase separation is an essential step, which is used to separate the water, gas, and sludge mixture after anaerobic degradation to obtain clarified effluent, collect biogas for comprehensive utilization, and return the sludge to the anaerobic reactor to maintain sufficient biomass in the reactor.

[0003] Considering the convenience of collecting biogas, most anaerobic reactors choose an internal three-phase separator. However, the internal type is not suitable for all cases. In some special cases, an external separator is necessary or a better choice. For example:

[0004] When treating large-volume, low-concentration organic wastewater by anaerobic treatment, there will be a contradiction between the volume of the reactor and the size of the three-phase separator: although the reactor size required for degrading COD (Chemical Oxygen Demand) is small, the three-phase separator that meets the water volume requirement occupies a large area. In order to install an internal three-phase separator, the reactor size has to be increased, and the water distribution system, circulation pump, and pipeline are also correspondingly enlarged, which is uneconomical in terms of investment and unreasonable in terms of process configuration;

[0005] When a single-stage three-phase separator cannot achieve an ideal separation effect, such as when the organic components in the wastewater are single and the growth rate of anaerobic microorganisms based on this organic matter is very low (such as terephthalic acid production wastewater, developer wastewater in the electronics industry), it is necessary to further recover the anaerobic sludge in the effluent of the anaerobic reactor to maintain the biomass in the reactor. At this time, an external secondary separator needs to be added;

[0006] When the existing anaerobic reactor has a decline in the effect of the built-in three-phase separator due to long service time or improper maintenance and cannot meet the usage requirements, opening the tank to repair or replace the original three-phase separator is a time-consuming task with extremely high safety requirements. The shutdown of anaerobic operation will bring huge pressure to the wastewater treatment system and even normal production. However, directly adding an external three-phase separator can achieve transformation without production shutdown and solve the problem at the lowest cost;

[0007] The daily observation and maintenance of the built-in three-phase separator are relatively difficult, which also makes it difficult for operators to master its actual operating status and make timely handling. The external separator has advantages in this regard.

[0008] The existing external anaerobic separator technologies can be divided into two categories: external anaerobic sedimentation tank and external air flotation sedimentation tank. Among them, the external anaerobic sedimentation tank is essentially the equipment of the anaerobic sedimentation tank. Since anaerobic sludge will continue to produce biogas during the sedimentation process, the presence of biogas bubbles is not conducive to the sedimentation of anaerobic sludge. Therefore, the anaerobic sedimentation tank requires a very low surface load, has a large floor area and an unsatisfactory sedimentation effect.

[0009] The invention patent application CN115367870 A discloses a UASB-coupled air flotation anaerobic sewage treatment system and method. In this system, the effluent of the UASB anaerobic reactor enters the air flotation separator, and pressurized dissolved air flotation is used to generate microbubbles to float and separate the anaerobic sludge in the effluent. The generated scum is collected by a scum scraper into the scum tank and then returned to the anaerobic influent tank through the anaerobic sludge return pipe. Pressurized dissolved air flotation uses an air source. The problem with this technology is that the biogas carried by the anaerobic effluent is a combustible gas, and the explosion limit of the mixture with air is 4.4% - 16%. When using an air source for air flotation, the air blows off the biogas in the water and generates a mixture of biogas and air near the air flotation separator, posing an explosion hazard.

[0010] The invention patent application CN110468033 A discloses an anaerobic digestion device for enhancing biogas production by self-sustaining air flotation, which includes an anaerobic digestion main tank unit, a self-sustaining air flotation screening unit, and a biogas metering and collection unit. The anaerobic digestion main tank is a completely mixed fermentation tank. The self-sustaining air flotation screening unit includes an air flotation screening part, a material precipitation part, an active reflux part, and a three-phase separation part. The air flotation screening part and the material precipitation part are located at the lower part and are separated by a middle partition; the active reflux part is located in the center. The digested material in the anaerobic digestion main tank is transported into the air flotation screening part through a feed pump and flows upward to the top of the active reflux part. The lighter part of the material containing highly active microorganisms overflows into the active reflux part and then returns to the anaerobic digestion main tank through a reflux pump; the heavier inert substances in the material settle at the bottom of the material precipitation part and are discharged through a drain valve; the three-phase separation part separates biogas and discharges it. The self-sustaining air flotation screening unit has no water outlet function, and the material is discharged through the discharge port at the bottom of the anaerobic digestion main tank after fermentation is completed. This technology is mainly used for anaerobic digestion of organic waste. The so-called self-sustaining air flotation screening unit separates the light part and the heavy part of the material by density difference, which is not a true air flotation separation, nor does it have the water outlet function of a general separator, and has little relevance to the separator in wastewater treatment. Summary of the Invention

[0011] The purpose of the present invention is to provide an external anaerobic sludge air flotation sedimentation separator and its application in view of the deficiencies of the existing external anaerobic sludge separator technology. By using the jet principle, the anaerobic reactor effluent is mixed with biogas to generate dissolved air water, replacing the pressurized dissolved air system, separating and recovering the sludge in the anaerobic reactor effluent, and no air is introduced throughout the process, eliminating potential safety hazards.

[0012] To achieve the above purpose, the present invention adopts the following technical solutions:

[0013] An external anaerobic sludge air flotation sedimentation separator for the efficient separation and reflux of sludge and clear liquid in an anaerobic sewage treatment process, including a tank body, a jet release device arranged at the bottom of the tank body, and a baffle vertically arranged inside the tank body; the upper part of the tank body is a cylindrical fully enclosed structure, and an air outlet is arranged at the top of the tank body and connected to the biogas collection area of the anaerobic reactor for discharging biogas;

[0014] The lower part of the tank body is connected to a conical sludge hopper, and the bottom of the sludge hopper is connected to a sludge reflux tank through a sludge outlet to regularly discharge sludge;

[0015] The baffle is cylindrical with a diameter smaller than that of the tank body and has open structures at both the upper and lower ends. It is vertically arranged in the tank body. An annular clear liquid area is formed between the baffle and the inner wall of the tank body at the upper part. The clear liquid area is connected to a water outlet arranged on the inner wall of the tank body through a water outlet pipe to discharge the overflowing clear liquid;

[0016] The area inside the baffle forms a circular flotation separation zone in the tank body. A slag discharging device is provided at the center of the flotation separation zone for collecting overflow floating slag and externally connecting to a sludge return tank to discharge the floating slag.

[0017] A jet device is provided at the bottom of the flotation separation zone. The jet device forms a negative pressure to suck in biogas through the jet action of the influent water, mixes the biogas with the water flow to form a dissolved air water flow, and promotes the anaerobic sludge to float by releasing microbubbles.

[0018] Preferably, a plurality of inclined plates are provided at the lower part of the clarified liquid zone for separating a small amount of anaerobic sludge carried in the clarified liquid.

[0019] Preferably, the inclination angle of the inclined plates is 50 - 60°, and the distance between the plurality of inclined plates is 50 - 150 mm.

[0020] Preferably, the upper position of the baffle provided inside the tank body is 0.5 - 1.2 m higher than the liquid level inside the tank body, and the lower part of the baffle is 0.3 - 0.8 m higher than the top end of the sludge hopper.

[0021] Preferably, the slag discharging device includes a floating slag tank. The floating slag tank is connected to a floating mud outlet provided on the side wall of the tank body through a floating mud discharge pipe to externally connect to a sludge return tank to discharge the floating slag, and the floating mud discharge amount is controlled by setting an automatic control valve on the floating mud discharge pipe.

[0022] Preferably, the liquid level of the floating slag tank is monitored in real time through an on-line liquid level meter to control the floating mud discharge amount, ensure that the liquid level in the floating slag tank is maintained above 0.6 m, and prevent biogas from leaking through the floating mud discharge pipe.

[0023] Preferably, the jet device includes a jet release device. One end of the jet release device is connected to a biogas inlet provided on the side wall of the tank body through a pipeline to externally connect to a biogas collection area, and the other end of the jet release device is connected to an influent water inlet provided on the side wall of the tank body through a pipeline to externally connect to the mixed liquid from the top of the anaerobic reactor, and the influent water flow is controlled by a jet pump; the jet of the jet release device generates a negative pressure to suck in biogas and mixes it with the water flow to form a dissolved air water flow.

[0024] Preferably, the jet release device is made of PP or stainless steel.

[0025] Preferably, the outlet pipe is immersed under the liquid level inside the tank body, and the immersion height is not less than 0.6 m to prevent biogas from leaking through the outlet pipe.

[0026] An application method of an external anaerobic sludge flotation and sedimentation separator according to the present invention is as follows:

[0027] Step S1: Pretreatment of influent water and gas

[0028] The mixed liquid at the top of the anaerobic reactor enters the jet release device inside the tank from the water inlet through the connecting pipeline and the jet pump, forming a high-speed water flow;

[0029] Step S2: The jet release device sucks in air and mixes to form a dissolved air water flow

[0030] When the high-speed water flow passes through the jet release device, a negative pressure is formed inside it, and biogas from the top of the anaerobic reactor is sucked in through the biogas inlet. The ratio of the biogas flow rate to the influent flow rate is 0.1 - 0.5. The biogas and water are mixed to form a dissolved air water flow, which is evenly released along the bottom of the air flotation separation zone, generating a large number of fine bubbles;

[0031] Step S3: Form an air flotation effect to promote the floating of sludge

[0032] The hydraulic load of the air flotation separation zone is 2 - 5 m 3 / (m 2 .h). A large number of fine bubbles combine with the suspended particles and scum in the mixed liquid to form flocs with a lower density, which rise under the action of buoyancy to form an obvious scum layer;

[0033] Step S4: Scum collection and liquid level control

[0034] The scum layer is lifted to the top of the air flotation separation zone by the bubbles and enters the scum trough for collection through overflow; The on-line liquid level meter continuously monitors the liquid level of the scum trough to ensure that it is always maintained above 0.6 m to prevent biogas leakage through the floating sludge discharge pipe;

[0035] Step S5: Control the discharge of floating sludge

[0036] The on-line liquid level meter continuously monitors the liquid level in the scum trough and controls the opening of the floating sludge valve through the control system to keep the liquid level in the scum trough within the set range. The floating sludge is discharged to the sludge return trough through the floating sludge outlet;

[0037] Step S6: Sedimentation of heavy sludge

[0038] The part of the heavy particles in the mixed liquid that is not lifted by the bubbles in the air flotation separation zone will settle to the bottom of the conical sludge hopper under the action of gravity and be regularly discharged to the sludge return trough through the sludge outlet at the bottom;

[0039] Step S7: Further sedimentation

[0040] The clarified liquid after the removal of suspended matter enters the outer clarified liquid area by flowing around the bottom of the baffle. The clarified liquid is further sedimented and separated in the inclined plate area, and the residual particles are intercepted by the inclined plates;

[0041] Step S8: Discharge of clarified liquid

[0042] The clarified liquid finally forms a liquid seal and is discharged through the submerged water outlet. The clarified liquid can enter the subsequent treatment section or be directly discharged.

[0043] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention adopts a method with air flotation as the main body to separate anaerobic sludge, which conforms to the characteristics of anaerobic sludge producing gas by itself and avoids the problem of gas production interference in the separation method with sedimentation as the main body.

[0044] (2) The present invention uses the mixed liquid at the top of the anaerobic reactor and biogas for air flotation treatment. After the biogas is used up, it returns to the biogas system. No air is introduced throughout the process, eliminating the potential safety hazards brought by air flotation.

[0045] (3) The present invention sucks in biogas by the self-priming action of pressurized jet injection of the influent, and forms a dissolved gas water flow by mixing gas and water through a jet release device, replacing dissolved gas equipment such as biogas compressors and dissolved gas tanks, greatly simplifying the system and avoiding common problems such as corrosion, air leakage, and noise of biogas compressors.

[0046] (4) The present invention arranges inclined plates between the baffle and the inner wall to effectively intercept residual suspended particles, further purify the effluent, improve the transparency of the clear liquid, and meet the subsequent treatment or discharge standards.

[0047] In summary, the present invention is applicable to the efficient separation and reflux of sludge and clear liquid in the process of anaerobic sewage treatment. The separator structure includes components such as a tank body with a jet release device, an internal baffle, a scum tank, and inclined plates. The dissolved gas water flow formed by the jet release device releases fine bubbles, and the sludge floats up and separates from the scum through air flotation. At the same time, the heavy sludge sinks and returns, and the clear liquid overflows after further precipitation through the inclined plates. The system realizes the synergistic effect of air flotation, sedimentation, and liquid-sealed effluent, and improves the separation efficiency, prevents biogas leakage, and achieves the effect of sludge recovery. Brief Description of the Drawings

[0048] Figure 1 It is a schematic structural diagram of an external anaerobic sludge air flotation sedimentation separator and its application provided for the embodiment of the present invention.

[0049] The serial numbers in the figure are as follows: 1. Tank body; 11. Baffle; 12. Scum tank; 13. Inclined plate; 14. Sludge hopper; 141. Sludge outlet; 15. Clear liquid area; 16. Air flotation separation area; 17. Gas outlet; 18. Water outlet; 19. Water inlet; 2. Jet release device; 20. Floating sludge outlet; 201. Floating sludge discharge pipe; 21. Biogas inlet; 23. Jet pump; 31. On-line liquid level meter; 32. Automatic control valve. Detailed Embodiment

[0050] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0051] Embodiment

[0052] As Figure 1 shown, an external anaerobic sludge flotation sedimentation separator and its application method provided in this embodiment. The external anaerobic sludge flotation sedimentation separator is an external biogas flotation sedimentation separator, including a tank body 1 and a jet release device 2.

[0053] A baffle 11 is provided in the tank body 1 to divide the entire cross-section into an outer clear liquid area 15 and an inner flotation separation area 16. A scum trough 12 is provided at the upper part of the flotation separation area 16, and the jet release device 2 is installed at the bottom of the flotation separation area 16.

[0054] Among them, the upper part of the tank body 1 is cylindrical and fully enclosed. There is a water inlet 19 at the bottom of the side wall, a biogas inlet 21 and a floating sludge port 20 in the middle of the side wall, a water outlet 18 at the upper part of the side wall, and a gas outlet 17 at the top. There is a circle of baffles 11 in the tank body. The annular area between the baffle 11 and the tank wall is the clear liquid area 15, and there is a water outlet 18 on the lower side wall of the clear liquid area 15; the circular area inside the baffle 11 is the flotation separation area 16, and there is a scum trough 12 at the upper center. The scum overflows into the scum trough 12 for collection. The scum trough 12 is connected to the floating sludge port 20 provided on the side wall of the tank body 1 through a floating sludge discharge pipe 201, and the floating sludge is discharged to the outside through a sludge return tank; the lower part of the tank body 1 is a conical sludge hopper 14, and the bottom of the sludge hopper 14 is connected to the sludge return tank through a sludge port 141, and the sludge is discharged regularly.

[0055] In this embodiment, the scum and sludge are discharged to the same sludge return tank and returned to the anaerobic reactor through a sludge return pump.

[0056] Furthermore, an automatic control valve 32 is installed on the floating sludge discharge pipe 201 in this embodiment to control the discharge amount of the floating sludge.

[0057] The jet release device 2 is installed at the bottom of the flotation separation area 16. Negative pressure is generated through the jet action, sucking in biogas and mixing it with water flow to form a dissolved gas water flow, which is released at the bottom of the flotation separation area 16 to form fine bubbles, carrying the anaerobic sludge to float upward. In this embodiment, the jet release device 2 is made of stainless steel.

[0058] The water inlet 19 on the tank body 1 is connected to a jet pump 23, and the water inlet of the jet pump 23 comes from the top mixed liquid of the anaerobic reactor. The biogas inlet 21 and the gas outlet 17 on the tank body 1 are respectively connected to the biogas collection area at the top of the anaerobic reactor.

[0059] The upper part of the baffle 11 is 0.8 m higher than the liquid level in the tank body, and the lower part is 0.3 m higher than the top of the sludge hopper. During operation, the scum rich in anaerobic sludge is lifted upward by bubbles and overflows into the scum tank 12 for collection. The heavy sludge precipitates into the sludge hopper, and the clear liquid flows around the bottom of the baffle 11 and enters the clear liquid area 15.

[0060] In the clear liquid area 15, inclined plates 13 are arranged to separate the small amount of anaerobic sludge carried in the clear liquid. The inclination angle of the inclined plates is 55°, and the plate spacing is 83 mm.

[0061] The bottom of the water outlet pipe is immersed 0.6 m below the liquid level to prevent biogas from leaking through the water outlet pipe.

[0062] The hydraulic load of the air flotation separation area 16 is 3 m 3 / (m 2 .h). The ratio of the biogas flow rate to the influent flow rate is 0.3.

[0063] Furthermore, in this embodiment, the liquid level of the scum tank 12 is monitored by an on-line liquid level meter 31 to control the discharge amount of floating sludge, ensure that there is a liquid level of more than 0.6 m in the scum tank, and prevent biogas from leaking through the floating sludge pipe 122.

[0064] Comparative Example 1

[0065] The anaerobic reactor adopts an internal three-phase separator in the form of inclined plates with an inclined plate settling area of 50 m 2 . The effluent of the reactor is not treated by an external separator.

[0066] Comparative Example 2

[0067] The anaerobic reactor adopts an internal three-phase separator in the form of inclined plates with an inclined plate settling area of 50 m 2 . After the reactor effluent, it is connected to an anaerobic sedimentation tank for secondary separation, and the surface load of the anaerobic sedimentation tank is 0.3 m 3 / (m 2 .h).

[0068] Application Example 1

[0069] The following is a detailed description in combination with specific parameters. An air flotation sedimentation separator of the present invention is used in the example, and the tank body has a diameter of 4.2 m, an upper height of 3.5 m, a sludge hopper height of 2.5 m, and an air flotation separation area with a diameter of 2 m. One jet pump 23 with a water volume of 10 m 3 / h, influent water quality: pH = 7 - 9, TSS = 50 mg / L, TN = 625 mg / L.

[0070] In the example, one air flotation sedimentation separator of the present invention is adopted, with a tank body diameter of 4.2 m, an upper height of 3.5 m, a sludge hopper height of 2.5 m, and an air flotation separation area diameter of 2 m. One jet pump 23, with a water volume of 10 m 3 / h, with a head of 10 m. The influent of the air flotation sedimentation separator is the mixed liquor at the top of the anaerobic reactor, without being treated by any internal or external separator.

[0071] The treatment data under three cases are as follows:

[0072] It can be seen that the separation effect of the embodiment is better than that of the internal three-phase separator in Comparative Example 1 and the internal three-phase separator + external sedimentation tank in Comparative Example 2. When operating under different influent water volumes and sludge concentrations, the effluent SS is lower than 80 mg / L.

[0073] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0074] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more, unless otherwise specifically defined.

[0075] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered by the protection scope of the present invention.

Claims

1. An external anaerobic sludge flotation sedimentation separator, which is used for the efficient separation and reflux of sludge and clear liquid in the anaerobic sewage treatment process, is characterized in that, It includes a tank body (1), a jet discharger (2) arranged at the bottom of the tank body (1), and a baffle (11) vertically arranged inside the tank body; The upper part of the tank body (1) is a cylindrical fully enclosed structure, and an air outlet (17) is arranged at the top of the tank body (1) to communicate with the biogas collection area of the anaerobic reactor for discharging biogas; The lower part of the tank body (1) is connected to a conical sludge hopper (14), and the bottom of the sludge hopper (14) is connected to a sludge return tank through a sludge outlet (141) to regularly discharge sludge; The baffle (11) is cylindrical with a diameter smaller than that of the tank body (1), and the upper and lower ends are open structures. It is vertically arranged in the tank body (1). An annular clear liquid area (15) is formed between the baffle (11) and the inner wall of the tank body (1). The clear liquid area (15) is connected to an outlet (18) arranged on the inner wall of the tank body (1) through a water outlet pipe to discharge the overflow clear liquid; The area inside the baffle (11) forms a circular air flotation separation area (16) in the tank body (1). A slag discharging device is arranged in the center of the air flotation separation area (16) for collecting the overflow floating slag and externally connecting to a sludge return tank to discharge the floating slag; A jet device is arranged at the bottom of the air flotation separation area (16). The jet device forms a negative pressure to suck in biogas through the jet action of the incoming water, mixes the biogas with the water flow to form a dissolved gas water flow, and promotes the anaerobic sludge to float by releasing fine bubbles.

2. The external anaerobic sludge air flotation sedimentation separator according to claim 1, characterized in that, A plurality of inclined plates (13) are arranged at the lower part of the clear liquid area (15) for separating a small amount of anaerobic sludge carried in the clear liquid.

3. An external anaerobic sludge flotation sedimentation separator according to claim 2, characterized in that, The inclination angle of the inclined plates (13) is 50 - 60°, and the distance between the plurality of inclined plates (13) is 50 - 150 mm.

4. An external anaerobic sludge flotation sedimentation separator according to claim 1, characterized in that, The upper position of the baffle (11) arranged inside the tank body (1) is 0.5 - 1.2 m higher than the liquid level inside the tank body (1), and the lower part of the baffle (11) is 0.3 - 0.8 m higher than the top of the sludge hopper (14).

5. An external anaerobic sludge air flotation sedimentation separator according to claim 1, characterized in that, The slag discharging device includes a floating slag tank (12). The floating slag tank (12) is connected to a floating mud outlet (20) arranged on the side wall of the tank through a floating mud discharge pipe (201) to externally connect to a sludge return tank to discharge the floating slag, and the floating mud discharge amount is controlled by setting an automatic control valve (32) on the floating mud discharge pipe (201).

6. The external anaerobic sludge flotation sedimentation separator according to claim 5, characterized in that, The liquid level of the floating slag tank (12) is monitored in real time through an on-line liquid level meter (31) to control the floating mud discharge amount and ensure that the liquid level in the floating slag tank (12) is maintained above 0.6 m to prevent biogas from leaking through the floating mud discharge pipe (201).

7. An external anaerobic sludge flotation sedimentation separator according to claim 1, characterized in that, The jet device includes a jet discharger (2). One end of the jet discharger (2) is connected to a biogas inlet (21) arranged on the side wall of the tank through a pipeline to externally connect to the biogas collection area, and the other end of the jet discharger (2) is connected to an inlet (19) arranged on the side wall of the tank through a pipeline to externally connect to the mixed liquid from the top of the anaerobic reactor, and the incoming water flow is controlled by a jet pump (23); the jet of the jet discharger (2) generates a negative pressure to suck in biogas and mixes it with the water flow to form a dissolved gas water flow.

8. An external anaerobic sludge air flotation sedimentation separator according to claim 7, characterized in that, The jet discharger (2) is made of PP or stainless steel.

9. An external anaerobic sludge flotation sedimentation separator according to claim 1, characterized in that, The water outlet pipe is immersed below the liquid surface in the tank body (1), and the immersion height is not less than 0.6 m, so as to prevent biogas from leaking through the water outlet pipe.

10. An application method of an external anaerobic sludge air flotation sedimentation separator, characterized in that, Here are the steps: Step S1: Influent and gas pretreatment The mixed liquid at the top of the anaerobic reactor enters the jet releaser (2) in the tank (1) from the water inlet (19) through the connecting pipeline and the jet pump (23), forming a high-speed water flow; Step S2: The jet releaser absorbs air and mixes to form a dissolved air water flow When high-speed water flows through the jet releaser (2), negative pressure is formed inside the jet releaser (2), and biogas from the top of the anaerobic reactor is sucked in through the biogas inlet (21). The ratio of biogas flow rate to water inlet flow rate is 0.1-0.5, and the mixture forms a dissolved gas water flow, which is evenly released along the bottom of the flotation separation zone (16), generating a large number of fine bubbles; Step S3: Forming air flotation to cause the sludge to float The hydraulic load of the air flotation separation zone (16) is 2 - 5 m 3 / (m 2 .h), a large number of fine bubbles combine with the suspended particles and scum in the mixed liquid to form flocs with a lower density, which rise under the action of buoyancy to form an obvious scum layer; Step S4: Scum collection and liquid level control The scum layer is lifted to the top of the air flotation separation zone (16) along with the bubbles, and flows into the scum tank (12) for collection through overflow; The online liquid level meter (31) monitors the liquid level of the scum tank (12) in real time to ensure that the liquid level is always maintained above 0.6 m, thereby preventing biogas from leaking through the sludge discharge pipe (201); Step S5: Control the discharge of floating mud The online liquid level meter (31) continuously monitors the liquid level in the scum tank (12), and controls the opening of the sludge valve through the control system to keep the liquid level in the scum tank (12) within a set range, and the sludge is discharged to the sludge return tank through the sludge port (20); Step S6: Heavy sludge sedimentation Step S7: Further sedimentation After the suspended matter is removed, the clear liquid flows around the bottom of the baffle (11) into the outer clear liquid area (15), and the clear liquid is further settled and separated in the inclined plate (13) area, and the residual particles are intercepted by the inclined plate (13); Step S8: Clear liquid out of water The clear liquid is finally discharged through the submerged water outlet (18) to form a liquid seal, and the clear liquid can enter the subsequent treatment section or be discharged directly.

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