An external anaerobic sludge flotation sedimentation separator and its application method

Abstract

The present invention discloses an external anaerobic sludge flotation sedimentation separator and its application method, which is applicable to the efficient separation and reflux of sludge and clear liquid in the anaerobic sewage treatment process. The separator structure includes components such as a tank body with a jet release device, an internal baffle, a scum trough, and inclined plates. The high-speed jet of the influent of the flotation sedimentation separator is used to suck in biogas to form dissolved air water, replacing the pressurized dissolved air system to release fine bubbles. Through flotation, the sludge floats up and is separated from the scum. At the same time, the heavy sludge sinks and refluxes, and the clear liquid overflows after further sedimentation through the inclined plates. The system realizes the synergistic effect of flotation, sedimentation, and liquid-sealed water discharge, and improves the separation efficiency, prevents biogas leakage, and achieves 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 volume loading, low energy consumption, shock load resistance, and the ability to degrade macromolecular and toxic substances to improve 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, while collecting biogas for comprehensive utilization, and the sludge is returned 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 using anaerobic treatment for large-volume, low-concentration organic wastewater, 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, electronic industry developer wastewater), 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 built-in three-phase separator of an existing anaerobic reactor fails to meet the usage requirements due to long-term use or improper maintenance, opening the tank for maintenance or replacement of the original three-phase separator is a time-consuming task with extremely high safety requirements. The anaerobic shutdown 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 stoppage 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 equipmentization of an 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 loading rate, has a large floor area and unsatisfactory sedimentation effect.

[0009] Patent application for invention 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 its explosion limit when mixed 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 mixed gas 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 board. The active reflux part is located in the center. The digestion material in the anaerobic digestion main tank is transported into the air flotation screening part through a feed pump, flows upward to the top of the active reflux part, and 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 an emptying 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. 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 and has no water outlet function of a general separator, and has little relevance to the separator in wastewater treatment. Summary of the Invention

[0011] The object 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 effluent of the anaerobic reactor is mixed with biogas to generate dissolved air water, replacing the pressurized dissolved air system, separating and recovering the sludge in the effluent of the anaerobic reactor, and no air is introduced throughout the process, eliminating potential safety hazards.

[0012] In order to achieve the above object, the present invention adopts the following technical solutions:

[0013] An external anaerobic sludge air flotation sedimentation separator is used for the efficient separation and reflux of sludge and clear liquid in an anaerobic sewage treatment process, and includes a tank body, a jet release device arranged at the bottom of the tank body, and a baffle vertically arranged inside the tank body;

[0014] 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 to communicate with the biogas collection area of the anaerobic reactor for discharging biogas;

[0015] 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 return tank through a sludge outlet to regularly discharge sludge;

[0016] The baffle is cylindrical with a diameter smaller than that of the tank body, and the upper and lower ends are open structures. 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. 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.

[0017] The area inside the baffle forms a cylindrical air flotation separation zone in the tank body. A slag discharging device is provided in the center of the air flotation separation zone for collecting overflow floating slag and discharging the floating slag externally through a sludge return tank connected externally;

[0018] A jet device is provided at the bottom of the air 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 upward by releasing microbubbles.

[0019] Preferably, a plurality of inclined plates are provided at the lower part of the clear liquid zone for separating a small amount of anaerobic sludge carried in the clear liquid.

[0020] Preferably, the inclination angle of the inclined plates is 50-60°, and the distance between the plurality of inclined plates is 50-150 mm.

[0021] 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.

[0022] Preferably, the slag discharging device includes a floating slag tank. The floating slag tank is connected through a floating sludge discharge pipe to a floating sludge port provided on the side wall of the tank body and is externally connected to a sludge return tank to discharge the floating slag, and the discharge amount of the floating sludge is controlled by setting an automatic control valve on the floating sludge discharge pipe.

[0023] Preferably, the liquid level of the floating slag tank is monitored in real time through an on-line liquid level instrument for controlling the discharge amount of the floating sludge, ensuring that the liquid level in the floating slag tank is maintained above 0.6 m to prevent biogas from leaking through the floating sludge discharge pipe.

[0024] Preferably, the jet device includes a jet release device. One end of the jet release device is connected through a pipeline to a biogas inlet provided on the side wall of the tank body and is externally connected to a biogas collection area, and the other end of the jet release device is connected through a pipeline to a water inlet provided on the side wall of the tank body and is externally connected 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.

[0025] Preferably, the jet release device is made of PP or stainless steel.

[0026] Preferably, the outlet pipe is immersed below 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.

[0027] An application method of an external anaerobic sludge air flotation sedimentation separator according to the present invention is as follows:

[0028] Step S1: Pretreatment of influent water and gas

[0029] The mixed liquor at the top of the anaerobic reactor enters the jet release device in the tank from the water inlet through the connecting pipeline and the jet pump, forming a high-speed water flow;

[0030] Step S2: The jet release device sucks in air and mixes to form a dissolved air water flow

[0031] 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 water 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;

[0032] Step S3: Form an air flotation effect to promote the sludge to float

[0033] 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 liquor to form flocs with a lower density, which rise under the action of buoyancy, forming an obvious scum layer;

[0034] Step S4: Scum collection and liquid level control

[0035] 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;

[0036] Step S5: Control the discharge of floating sludge

[0037] 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;

[0038] Step S6: Sedimentation of heavy sludge

[0039] The part of the heavy particles in the mixed liquor 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;

[0040] Step S7: Further sedimentation

[0041] The clarified liquid after the removal of suspended substances 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;

[0042] Step S8: Discharge of clarified liquid

[0043] The clarified liquid finally forms a liquid seal and is discharged through the submerged outlet. The clarified liquid can enter the subsequent treatment section or be directly discharged.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (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's own gas production and avoids the problem of gas production interference in the separation method with precipitation as the main body.

[0046] (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 again. No air is introduced throughout the process, eliminating the safety hazards brought by air flotation.

[0047] (3) The present invention sucks in biogas by the self-priming effect of pressurized jet injection of the influent water, and forms a dissolved air water flow by the jet release device to mix air and water, replacing dissolved air equipment such as biogas compressors and dissolved air tanks, greatly simplifying the system, and avoiding common problems of biogas compressors such as corrosion, air leakage, and noise.

[0048] (4) The present invention arranges inclined plates between the baffle and the inner wall, effectively intercepting residual suspended particles, further purifying the effluent, improving the transparency of the clarified liquid, and meeting the subsequent treatment or discharge standards.

[0049] In summary, the present invention is applicable to the efficient separation and reflux of sludge and clarified 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 air water flow formed by the jet release device releases microbubbles, 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 clarified liquid overflows and discharges after further precipitation through the inclined plates. The system realizes the synergistic effect of air flotation, precipitation, and liquid-sealed effluent, and improves the separation efficiency, prevents biogas leakage, and realizes the effect of sludge recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 FIG. is a schematic structural diagram of an external anaerobic sludge air flotation and sedimentation separator and its application provided for an embodiment of the present invention.

[0051] The serial numbers in the figure are as follows:

[0052] 1. Tank body; 11. Baffle; 12. Scum tank; 13. Inclined plate; 14. Sludge hopper; 141. Sludge outlet; 15. Clarified 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 DESCRIPTION OF THE EMBODIMENTS

[0053] 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.

[0054] Embodiment

[0055] 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.

[0056] A baffle 11 is provided in the tank body 1 to divide the entire cross-section into an outer supernatant area 15 and an inner flotation separation area 16. A scum trough 12 is provided above the flotation separation area 16, and the jet release device 2 is installed at the bottom of the flotation separation area 16.

[0057] Among them, the upper part of the tank body 1 is cylindrical and fully enclosed. An inlet 19 is provided at the bottom of the side wall, a biogas inlet 21 and a floating sludge outlet 20 are provided in the middle of the side wall, an outlet 18 is provided at the upper part of the side wall, and an air outlet 17 is provided at the top. A circle of baffle 11 is provided in the tank body. The annular area between the baffle 11 and the tank wall is the supernatant area 15, and an outlet 18 is provided on the lower side wall of the supernatant area 15; the circular area inside the baffle 11 is the flotation separation area 16, and a scum trough 12 is provided at the upper center. The scum overflows into the scum trough 12 for collection. The scum trough 12 is connected to the floating sludge outlet 20 provided on the side wall of the tank body 1 through a floating sludge discharge pipe 201, and the floating sludge is discharged out through an external sludge return trough; 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 trough through a sludge outlet 141 to discharge sludge regularly.

[0058] In this embodiment, the scum and sludge are discharged to the same sludge return trough and returned to the anaerobic reactor through a sludge return pump.

[0059] Furthermore, a self-control valve 32 is installed on the floating sludge discharge pipe 201 in this embodiment to control the discharge amount of floating sludge.

[0060] The jet release device 2 is installed at the bottom of the flotation separation area 16. Negative pressure is generated through the jet action to suck in biogas and mix 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. In this embodiment, the jet release device 2 is made of stainless steel.

[0061] The 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 air outlet 17 on the tank body 1 are respectively connected to the biogas collection area at the top of the anaerobic reactor.

[0062] 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.

[0063] In the clear liquid area 15, inclined plates 13 are provided to separate a 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.

[0064] The bottom of the outlet pipe is immersed in the liquid surface to a height of 0.6 m to prevent biogas from leaking through the outlet pipe.

[0065] 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.

[0066] 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, ensuring that there is a liquid level of more than 0.6 m in the scum tank to prevent biogas from leaking through the floating sludge pipe 122.

[0067] Comparative Example 1

[0068] The anaerobic reactor adopts an internal three-phase separator in the form of inclined plates, and the inclined plate settlement area is 50 m 2 . The effluent of the reactor is not treated by an external separator.

[0069] Comparative Example 2

[0070] The anaerobic reactor adopts an internal three-phase separator in the form of inclined plates, and the inclined plate settlement area is 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).

[0071] Application Example 1

[0072] The following is a detailed description in combination with specific parameters. The effluent mixed liquid of a developing waste liquid anaerobic reactor is separated by using the embodiment and Comparative Example 1 and Comparative Example 2 respectively. The designed influent water volume is 10 m 3 / h, and the influent water quality: pH = 7 - 9, TSS = 50 mg / L, TN = 625 mg / L.

[0073] The embodiment adopts one air flotation sedimentation separator of the present invention. The diameter of the tank body is 4.2 m, the upper height is 3.5 m, the height of the sludge hopper is 2.5 m, and the diameter of the air flotation separation area is 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 sediment separator is the mixed liquid at the top of the anaerobic reactor and is not treated by any internal or external separator.

[0074] The treatment data in three cases are as follows:

[0075]

[0076] 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.

[0077] 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 of the present invention.

[0078] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating 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, "plurality" means two or more unless otherwise specifically defined.

[0079] 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, making equivalent substitutions or changes, should be covered within the protection scope of the present invention.

Claims

1. An external anaerobic sludge flotation sedimentation separator, used for efficient separation and reflow of sludge and clear liquid in anaerobic sewage treatment process, characterized by: It comprises a tank body (1), a jet releaser (2) arranged at the bottom of the tank body (1), and a baffle (11) vertically arranged inside the tank body; The upper portion of the tank body (1) is a cylindrical fully enclosed structure, and a gas outlet (17) is provided on 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 port (141) to discharge sludge regularly; The baffle (11) is cylindrical with a diameter smaller than that of the tank body (1), has an open structure at both ends, and is vertically arranged in the tank body (1). An annular clear liquid area (15) is formed at the upper portion between the baffle (11) and the inner wall of the tank body (1). The clear liquid area (15) is connected to a water outlet (18) provided on the inner wall of the tank body (1) through a water outlet pipe to discharge overflow clear liquid. The area within the baffle (11) forms a cylindrical flotation separation zone (16) in the tank body (1), and a slag discharge device is provided in the center of the flotation separation zone (16) for collecting overflow slag and connecting to an external sludge return trough for discharging slag; A jet device is provided at the bottom of the flotation separation zone (16), and the jet device forms a negative pressure through the jet action of the incoming water to absorb the biogas, mixes the biogas with the water flow to form a dissolved gas water flow, and releases fine bubbles to push the anaerobic sludge to float; The slag discharge device comprises a slag trough (12), the slag trough (12) being connected to a sludge outlet (20) provided on the side wall of the tank body via a sludge discharge pipe (201) and externally connected to a sludge return trough to discharge sludge, and the amount of sludge discharged is controlled by arranging an automatic control valve (32) on the sludge discharge pipe (201); The jet device comprises a jet releaser (2), one end of the jet releaser (2) is connected to a biogas inlet (21) provided on the side wall of the tank body through a pipe and is externally connected to a biogas collection area, and the other end of the jet releaser (2) is connected to a water inlet (19) provided on the side wall of the tank body through a pipe and is externally connected to a mixed liquid from the top of the anaerobic reactor, and the water inlet flow is controlled by a jet pump (23); the jet of the jet releaser (2) generates negative pressure to inhale biogas and mix it with water to form a dissolved gas water flow; A plurality of inclined plates (13) are provided at the lower portion of the clear liquid zone (15) for separating a small amount of anaerobic sludge carried in the clear liquid.

2. The external anaerobic sludge flotation sedimentation separator according to claim 1, characterized in that: The inclination angle of the inclined plate (13) is 50-60°, and the spacing between the plurality of inclined plates (13) is 50-150 mm.

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

4. The external anaerobic sludge flotation sedimentation separator according to claim 1, characterized in that: The liquid level of the scum tank (12) is monitored in real time by an online liquid level meter (31) to control the amount of sludge discharged, ensuring that the liquid level in the scum tank (12) is maintained above 0.6 m, thereby preventing biogas from leaking through the sludge discharge pipe (201).

5. The external anaerobic sludge flotation sedimentation separator according to claim 1, characterized in that: The jet releaser (2) is made of PP or stainless steel.

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

7. An application method of the external anaerobic sludge flotation sedimentation separator according to any one of claims 1 to 6, 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 pipe and the jet pump (23), forming a high-speed water flow; Step S2: The jet releaser absorbs air and mixes it to form a dissolved air water flow When high-speed water flows through the jet releaser (2), negative pressure is formed inside it, 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 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 an air flotation effect to make the sludge float The hydraulic load of the flotation separation zone (16) is 2-5m 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 lower density, which rise under the action of buoyancy and form a clear scum layer; Step S4: Scum collection and liquid level control The scum layer is lifted to the top of the 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 sludge tank (12) in real time to ensure that it is always maintained above 0.6m to prevent biogas from leaking through the sludge discharge pipe (201); Step S5: Controlling 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 The heavy particles in the mixed liquid that are not lifted up by the bubbles in the flotation separation zone (16) will settle to the bottom of the conical sludge hopper (14) under the action of gravity and be regularly discharged to the sludge return tank through the sludge outlet (141) at the bottom; Step S7: Further sedimentation After the suspended matter is removed, the clear liquid flows around the bottom of the baffle (11) and enters the outer clear liquid area (15). 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 The clear liquid is finally discharged through the submerged outlet (18) to form a liquid seal, and the clear liquid can enter the subsequent treatment section or be directly discharged.

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