Anaerobic reactor for preventing sludge floating

Abstract

This invention discloses an anaerobic reactor for preventing sludge floating, comprising a reactor body, an influent distribution system, a circulation pipe, a circulation pump, a primary separator, a secondary separator, and a sludge return pump. The secondary separator is installed at the bottom of the anaerobic reactor and is used to settle and separate anaerobic sludge in the effluent from the primary separator. The secondary separator is fully enclosed and includes a sedimentation module and a sludge hopper. The sedimentation module has a top plate with an inlet connected to the outlet of the primary separator. The sludge hopper has a sludge return port at the bottom, connected to the sludge return port at the bottom of the reactor. The degassing effect of this invention is superior to that of commonly used three-phase separators that rely solely on inertial collisions or hydraulic deflection. It produces fewer air bubbles in the wastewater and sludge, resulting in faster settling speeds and excellent separation of granular or flocculent sludge. Simultaneously, it prevents uneven hydraulic load distribution and maximizes the utilization of the sedimentation area.

Description

Technical Field

[0001] This invention relates to the field of anaerobic reactor technology, and more particularly to an anaerobic reactor that prevents sludge from floating. Background Technology

[0002] The formation of a floating sludge layer in anaerobic reactors for wastewater treatment is a common phenomenon, and the main reasons are as follows:

[0003] 1. Wastewater produces biogas after anaerobic degradation. The anaerobic sludge carrying biogas bubbles has a lower specific gravity. In particular, flocculent sludge has a relatively loose structure and is more likely to float after carrying bubbles.

[0004] 2. Common anaerobic reactors are all upflow type, with water entering from the bottom and exiting from the top. As the wastewater flows upward, the water pressure continuously decreases. According to Henry's Law (p = H·x), when the pressure p decreases, the solubility of the gaseous solute in the liquid decreases accordingly, causing the originally dissolved gas to transform into the gas phase, forming bubbles that escape and carry the sludge to the surface. This is equivalent to the working principle of an air flotation machine.

[0005] 3. Many wastewaters contain surface-active substances or hydrophobic components, such as surfactants, proteins, and oils. Under the action of these components, the wastewater is prone to producing foam and adhering to the anaerobic sludge, causing the sludge to float to the surface of the reactor liquid and forming a continuously thickening sludge layer.

[0006] 4. Common effluent formats from anaerobic reactors have shortcomings; there are no measures specifically addressing floating sludge. (See attached document) Figure 1 This is a top overflow effluent system used in UASB and IC reactors. Once floating sludge is generated, it enters the overflow collection tank with the effluent and is discharged together with the reactor effluent, leading to increased suspended solids (SS) in the effluent and sludge loss. Figure 2 It is another common type of inclined plate three-phase separator with an integrated effluent tank. Its characteristic is that the top of the three-phase separator is higher than the liquid surface of the reactor. Before entering the three-phase separator, the wastewater flows downward and enters the inclined plate sedimentation zone from below. The floating mud, due to its light density, cannot flow downward and is instead trapped at the top of the liquid surface outside the three-phase separator, forming a layer of stagnant floating mud.

[0007] Floating sludge in anaerobic reactors poses several hazards: whether it flows away with the effluent or remains on the top of the liquid surface, it gradually reduces the amount of sludge actually participating in the anaerobic reaction, leading to a decrease in the reactor's treatment capacity and ultimately causing "acidification" due to overload. Floating sludge entering the subsequent aerobic treatment system increases oxygen demand, reduces aeration capacity, and shortens sludge age, resulting in excessive COD and nitrogen levels in the aerobic effluent. Furthermore, the floating sludge layer on top of the liquid surface affects the normal release of biogas, causing a sudden release of biogas after a pressure increase, carrying a large amount of floating sludge into and clogging biogas pipelines, posing a safety hazard.

[0008] Based on the above, we have designed an anaerobic reactor to prevent sludge from rising and solve the above problems. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of existing technologies by proposing an anaerobic reactor that prevents sludge from floating.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] An anaerobic reactor for preventing sludge from floating includes a reactor body, an influent distribution system, a circulation pipe, a circulation pump, a primary separator, a secondary separator, and a sludge return pump.

[0012] The water inlet distribution system is installed at the bottom of the reactor and adopts a perforated water distribution method with an opening diameter of 15-50mm. After the reactor inlet water flow, the circulating water flow delivered by the circulating pump and the return sludge delivered by the sludge return pump are combined, the water is evenly distributed to the bottom of the anaerobic reactor.

[0013] The circulation pipe is installed in the middle of the reactor and is in the form of a perforated pipe with an opening diameter of 15-50 mm. The mixed liquid in the reactor is returned to the inlet water through the circulation pump. Its function is to maintain the upward flow velocity in the anaerobic reactor within the range of 2-8 m / h, so that the anaerobic sludge and wastewater are fully mixed.

[0014] The primary separator is installed at the top of the reactor and is used to collect the water, gas and mud mixture after the anaerobic reaction, and to separate the biogas and floating mud in advance.

[0015] The primary separator includes an outer cylinder, an inner cylinder, and a vortex distributor. The upper part of the outer cylinder is cylindrical or prismatic, with an overflow inlet at the top; the lower part is conical or pyramidal, with an outlet at the bottom. A vortex distributor is provided on the upper part of the outer cylinder, which consists of a ring of umbrella-shaped plates.

[0016] The secondary separator is installed at the bottom of the anaerobic reactor and is used to separate the anaerobic sludge in the effluent of the primary separator by sedimentation. The secondary separator is fully enclosed and includes a sedimentation module and a sludge hopper. The sedimentation module has a top plate with an inlet connected to the outlet of the primary separator. The sludge hopper has a sludge return port at the bottom, which is connected to the sludge return port at the bottom of the reactor. The end plate at the end of the second compartment has an outlet connected to the reactor outlet pipe.

[0017] Preferably, the reactor body is cylindrical or cuboid in shape, and is made of either metal or reinforced concrete. The reactor body has a diameter or side length of 3 to 20 m and a height of 8 to 28 m. It has a fully enclosed top cover, a water inlet, a sludge inlet and a sludge return inlet at the bottom of the side wall, a circulation inlet and a sludge outlet in the middle of the side wall, a water outlet at the top of the side wall, and a biogas outlet at the top.

[0018] Preferably, the angle between the plates and the generatrix of the umbrella-shaped cone is 10–60°, the plates overlap, and there are gaps allowing liquid to pass through. The top of the vortex distributor has a vent. The inner cylinder is a cylinder or prism concentric with the outer cylinder, with its top opening 200–800 mm lower than the outer cylinder, and its bottom opening communicating with the outer cylinder. A sludge-floating pipe is installed at the upper part of the inner cylinder, angled downwards at 30–60°, and passes through the outer cylinder to connect to the sludge return pump.

[0019] Preferably, the surface load u of the primary separator is less than 0.5m. 3 / (m 2 .s); One or more primary separators are installed at the same height within the reactor body.

[0020] Preferably, the sedimentation module is equipped with a longitudinal internal partition, dividing the module into a first compartment and a second compartment. Water enters the sedimentation module from the first compartment, deflects at 180° at the end of the first compartment before entering the second compartment, and exits from the end of the second compartment, forming a U-shaped flow path. The surface loading of the sedimentation zone is 0.2–0.6 m². 3 / (m 2 .h), horizontal flow velocity 1~7mm / s.

[0021] Preferably, each of the first and second compartments is provided with two transverse partitions to divide the compartments into an inlet area, a sedimentation area and an outlet area. The transverse partitions have water passage holes with a flow velocity of <0.5m / s.

[0022] Preferably, the sedimentation zone is provided with 2 to 6 layers of inclined plates from top to bottom, running longitudinally through the entire sedimentation zone. The cross-section of the inclined plates is "V" shaped or inverted "V" shaped, and the wastewater flows horizontally between the inclined plates. Sludge settles to the surface of the inclined plates under gravity, and then falls into the sludge hopper for collection through the sludge return slits between the inclined plates. The sludge return slits are 50 to 150 mm in size. The sludge hoppers are located below the sedimentation module, with 1 to 3 sludge hoppers arranged along the length direction, and the inclination angle of the sludge hoppers is 50 to 60°.

[0023] Preferably, one or more secondary separators may be installed at the bottom of the reactor body.

[0024] Preferably, the sludge return pump is installed outside the anaerobic reactor, with the pump inlet connected to the sludge return pipe at the bottom of the reactor and the pump outlet connected to the reactor's inlet water distribution system.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1. The primary separator adopts an overflow water inlet method. If there is floating mud on the surface of the reactor liquid, it will enter the primary separator with the water flow and be separated by the primary separator, so that no floating mud layer will be generated on the surface of the reactor liquid.

[0027] 2. In the primary separator, the cyclone distributor disperses the incoming water into droplets, increasing the gas-liquid contact area, which is beneficial for biogas to escape from the water to the gas phase; the inertial collision of the water flow on the surface of the umbrella plate promotes the separation of biogas bubbles from anaerobic sludge. These designs make the degassing effect of the present invention better than that of commonly used three-phase separators based solely on inertial collision or hydraulic deflection.

[0028] 3. In the first-stage separator, after the influent is dispersed into droplets by the cyclone distributor, it falls on the top of the annular area between the outer and inner cylinders, causing continuous disturbance to the liquid surface, making it impossible for a stable layer of floating mud to form in this area; while the hydraulic static state of the inner cylinder is conducive to the accumulation of floating mud in the inner cylinder.

[0029] 4. The floating sludge collected in the inner cylinder is returned to the anaerobic reactor via a sludge return pump, avoiding the loss of effective sludge caused by the retention of floating sludge, thereby ensuring the efficient and stable operation of the anaerobic reactor.

[0030] 5. The secondary separator is located at the bottom of the reactor, with high liquid column pressure and more gas existing in dissolved form. There are fewer bubbles in the wastewater and sludge, and the settling speed is fast, which has a good separation effect on granular sludge or flocculent sludge.

[0031] 6. The secondary separator adopts a horizontal flow sedimentation tank, with the water flow direction and sludge settling direction forming an angle of 90°, which will not interfere with the downward sludge settling.

[0032] 7. The horizontal flow inclined plate in the secondary separator ensures that the wastewater must flow through the entire length of the sedimentation zone before reaching the effluent zone, preventing short-circuiting of the water flow and making higher utilization of the sedimentation area. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of an anaerobic reactor for preventing sludge from floating, as proposed in this invention.

[0034] Figure 2 This is a schematic diagram of an integrated effluent device for an inclined plate three-phase separator in an anaerobic reactor to prevent sludge from floating, as proposed in this invention.

[0035] Figure 3This is a three-dimensional structural schematic diagram of an anaerobic reactor for preventing sludge floating according to the present invention.

[0036] Figure 4 The diagram shows a plan view and a cross-sectional view of the primary separator of an anaerobic reactor for preventing sludge formation, as proposed in this invention.

[0037] In the diagram: 1 Reactor body, 2 Inlet water distribution system, 3 Circulation pipe, 4 Circulation pump, 5 Primary separator, 6 Secondary separator, 7 Sludge return pump, 8 Inlet, 9 Sludge inlet, 10 Sludge return inlet, 11 Circulation port, 12 Floating sludge inlet, 13 Outlet, 14 Biogas inlet, 15 Outer cylinder, 16 Inner cylinder, 17 Swirl distributor, 18 Floating sludge pipe, 19 Outlet, 20 Sedimentation module, 21 Sludge hopper, 22 Top plate, 23 Inlet, 24 Outlet, 25 Sludge return inlet, 26 End plate, 27 Side plate, 28 Internal partition, 29 Transverse partition, 30 First compartment, 31 Second compartment, 32 Inclined plate. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0039] The influent to the anaerobic reactor is lifted by the influent pump and merged with the circulating flow from the circulation pump and the return sludge from the sludge return pump. Then, it is evenly distributed to the bottom cross section of the anaerobic reactor by the influent distribution system at the bottom of the anaerobic reactor, and then flows upward through the anaerobic sludge bed. The COD in the wastewater is decomposed into biogas by anaerobic microorganisms. At the top of the reactor, the anaerobic mixture flows into the primary separator, where the biogas and floating sludge are effectively separated by the dispersion effect of the water flow and inertial collision of the cyclone distributor. The separated biogas is led out of the reactor through the biogas pipe at the top of the reactor, while the floating sludge is returned to the influent distribution system through the floating sludge pipe and the sludge return pump. The effluent from the primary separator flows through a pipe to the secondary separator at the bottom of the anaerobic reactor, which is a fully enclosed horizontal flow sedimentation tank with horizontal flow inclined plates. The sludge-water mixture flows sequentially through the first and second compartments, and the anaerobic sludge is separated by gravity sedimentation. The effluent after sludge separation is discharged from the reactor through the effluent pipe. The anaerobic sludge is collected in the sludge hopper of the secondary separator and returned to the influent distribution system through the sludge return pipe and the sludge return pump.

[0040] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0041] Example 1

[0042] like Figure 3 As shown, an anaerobic reactor includes: a reactor body 1, an influent distribution system 2, a circulation pipe 3, a circulation pump 4, a primary separator 5, a secondary separator 6, and a sludge return pump 7.

[0043] The reactor body 1 is cylindrical or cuboid in shape, made of metal or reinforced concrete, with a diameter (or side length) of 3–20 m and a height of 8–28 m (in this embodiment, it is cylindrical, made of corrosion-resistant carbon steel, with a diameter of 6 m and a height of 16 m). It has a fully enclosed top cover, with a water inlet 8, a sludge inlet 9, and a sludge return inlet 10 at the bottom of the side wall; a circulation inlet 11 and a sludge floating inlet 12 in the middle of the side wall; a water outlet 13 at the top of the side wall; and a biogas inlet 14 at the top.

[0044] The influent distribution system 2 is installed at the bottom of the reactor 1. It adopts a perforated water distribution method with an opening diameter of 15-50mm (21mm in this embodiment). After the reactor influent water flow, the circulating water flow delivered by the circulating pump 4 and the return sludge delivered by the sludge return pump 7 are combined, the water flow is evenly distributed to the bottom of the anaerobic reactor.

[0045] The circulation pipe 3 is installed in the middle of the reactor 1. It is a perforated pipe with an opening diameter of 15-50 mm (25 mm in this embodiment). The mixed liquid in the reactor is returned to the influent distribution system 2 through the circulation pump 4. Its function is to maintain the upward flow velocity in the anaerobic reactor in the range of 2-8 m / h (3 m / h in this embodiment) so that the anaerobic sludge and wastewater are fully mixed.

[0046] The primary separator 5 is installed at the top of the reactor to collect the water, gas, and sludge mixture after the anaerobic reaction, and to pre-separate the biogas and floating sludge, as shown in the attached diagram. Figure 4 As shown in (a) and (b).

[0047] The primary separator 5 includes: an outer cylinder 15, an inner cylinder 16, and a vortex distributor 17.

[0048] The upper part of the outer cylinder 15 is cylindrical or prismatic, with an overflow inlet at the top; the lower part is conical or pyramidal, with an outlet 19 at the bottom. A vortex distributor 17 is installed on the upper part of the outer cylinder 15. The vortex distributor 17 consists of a ring of umbrella-shaped plates, with the angle between the plates and the generatrix of the umbrella cone being 10–60° (45° in this embodiment). The plates overlap and have gaps allowing liquid to pass through. A vent is located at the top of the vortex distributor 17. The inner cylinder 16 is concentric with the outer cylinder 15, cylindrical or prismatic, with its top opening 200–800 mm lower than the outer cylinder (400 mm in this embodiment), and its bottom opening communicating with the outer cylinder 15. A sludge-floating pipe 18 is installed on the upper part of the inner cylinder 16, at an angle of 30–60° downwards (45° in this embodiment). The sludge-floating pipe 18 passes through the outer cylinder and communicates with the sludge-floating port 12 in the middle of the side wall of the reactor 1.

[0049] The surface load u of the first-stage separator 5 is less than 0.5m. 3 / (m 2 .s).

[0050] In this embodiment, a single primary separator is installed in reactor 1.

[0051] The secondary separator 6 is installed at the bottom of the anaerobic reactor and is used to separate the anaerobic sludge in the effluent of the primary separator 5 by sedimentation.

[0052] The secondary separator 6 is a fully enclosed type, including a sedimentation module 20, a sludge hopper 21 and support legs 34; the sedimentation module 20 has a top plate 22, on which an inlet 23 is provided, which is connected to the outlet 19 of the primary separator 5; the sludge hopper 21 has a sludge return port 25 at the bottom, which is connected to the sludge return port 10 at the bottom of the reactor 1; the sedimentation module 20 has an outlet 24 on the end plate 26, which is connected to the outlet pipe 13 on the upper side wall of the reactor 1.

[0053] The sedimentation module 20's housing consists of two end plates 26, two side plates 27, and a top plate 22. An internal longitudinal partition 28 divides the module into a first compartment 30 and a second compartment 31. Water enters from the first compartment 30, deflects at 180° at the end of the first compartment 30, and exits from the end of the second compartment 31, following a U-shaped flow path. The surface loading of the sedimentation zone is 0.2–0.6 m². 3 / (m 2 The horizontal flow rate is 1–7 mm / s (in this embodiment, the surface load of the sedimentation zone is 0.45 m). 3 / (m 2 (h), with a horizontal flow velocity of 2 mm / s).

[0054] The sedimentation module 20 is also equipped with two horizontal partitions 29, which divide the compartment into an inlet area, a sedimentation area and an outlet area. The horizontal partitions 29 have water passage holes 33, and the flow velocity through the water passage holes is <0.5m / s (0.03m / s in this embodiment).

[0055] The sedimentation zone is equipped with 2 to 6 layers (5 layers in this embodiment) of inclined plates 32 arranged vertically throughout the entire sedimentation zone. The cross-section of the inclined plates 32 is "V" shaped or inverted "V" shaped, and the wastewater flows horizontally in the sedimentation zone. Sludge settles to the surface of the inclined plates 32 under gravity, and then falls into the sludge hopper for collection through the sludge return slits between the inclined plates 32. The size of the sludge return slits is 50 to 150 mm (55 mm in this embodiment).

[0056] Below the sedimentation module 20, there are 1 to 3 sludge hoppers arranged along the length direction, and the inclination angle of the sludge hoppers is 50 to 60° (in this embodiment, there are 2 sludge hoppers with an inclination angle of 55°).

[0057] In this embodiment, a secondary separator 6 is installed inside the reactor 1, and the secondary separator 6 is fixed to the bottom plate of the reactor 1 by support legs 34.

[0058] The sludge return pump 7 is installed outside the anaerobic reactor 1. The pump inlet is connected to the sludge return pipe 10 at the bottom of the side wall of the reactor 1 and the floating sludge pipe 12 in the middle of the side wall. The pump outlet is connected to the reactor inlet 8.

[0059] In use, the influent to the anaerobic reactor 1 is lifted by the influent pump and merged with the circulating flow from the circulating pump 4 and the return sludge from the sludge return pump 7. Then, it is evenly distributed to the bottom cross section of the anaerobic reactor through the influent distribution system 2 at the bottom of the anaerobic reactor 1, and then flows upward through the anaerobic sludge bed. The COD in the wastewater is decomposed into biogas by anaerobic microorganisms. At the top of reactor 1, the anaerobic mixture flows into the primary separator 5, where biogas and floating sludge are effectively separated by the dispersion effect of the water flow and inertial collision of the cyclone distributor. The separated biogas is led out of the reactor through the biogas pipe 14 at the top of the reactor, and the floating sludge is returned to the influent distribution system 2 through the floating sludge pipe 12 and the sludge return pump 7. The effluent from the primary separator 5 flows through the pipe to the secondary separator 6 at the bottom of the anaerobic reactor, which is a fully enclosed horizontal flow sedimentation tank with horizontal flow inclined plates. The mud-water mixture flows through the first compartment 30 and the second compartment 31 in sequence, and the anaerobic sludge is separated by gravity sedimentation. The effluent after sludge separation is discharged from the reactor through the effluent pipe 13. The anaerobic sludge is collected in the sludge hopper 21 of the secondary separator and returned to the influent distribution system 2 through the sludge return pipe 10 and the sludge return pump 7.

[0060] The anaerobic reactor described in this invention employs an innovative two-stage separator and an improved effluent configuration. The primary separator enhances the removal of biogas and floating sludge, while the overflow influent prevents the formation of a floating sludge layer at the top of the reactor liquid surface and continuously separates and returns the sludge to the main reaction zone. The bottom secondary separator utilizes high water pressure to dissolve the gas, reducing the interference of air bubbles on sludge settling. Simultaneously, a horizontal flow sedimentation system with inclined plates is used to enhance solid-liquid separation. Compared to conventional anaerobic reactors, this effectively prevents the formation of a floating sludge layer and the loss of anaerobic sludge, maintaining a high sludge concentration within the reactor and ensuring its efficient and stable operation.

[0061] Comparative Example 1

[0062] The anaerobic EGSB reactor, with its three-phase separator and effluent configuration, is attached. Figure 2 The inclined plate type three-phase separator integrated water outlet device shown is the same as in Example 1;

[0063] Application Example 1

[0064] Organic waste liquid from the electronics industry was treated using Example 1 and Comparative Example 1, respectively. The reactor was designed with an influent TOC concentration of 4400 mg / L.

[0065] The reactor is cylindrical, made of corrosion-resistant carbon steel, with a diameter of 6m, a height of 16m, and an effective water depth of 15m.

[0066] A water distribution system is installed at the bottom of the reactor, which adopts a perforated water distribution method with an opening diameter of 21mm and a distance of 0.2m from the bottom plate.

[0067] A circulation pipe, using a perforated pipe design, is installed in the middle of the reactor. The perforation diameter is 25mm, the height is 13.5m, and the circulation pump flow rate is 110m³ / h. 3 / h, reactor upflow velocity 4m / h.

[0068] The reactor has a water treatment capacity of 10m³. 3 The system operates at a rate of [number] / h, with one primary separator installed at the top. The outer cylinder has a diameter of 1000mm, a total height of 2950mm, and the top surface of the outer cylinder is flush with the liquid level. The surface load of the primary separator is u = 0.004m. 3 / (m 2 .s).

[0069] A two-stage separator with dimensions of 4000×2200×3500mm is installed at the bottom and fixed to the reactor base plate by support legs. It has 5 layers of inclined plates with an inclination angle of 50° and a sludge return slit size of 55mm.

[0070] Install one sludge return pump with a flow rate of 5m³ / h. 3 / h.

[0071] The reactor was inoculated with flocculent anaerobic sludge, with an initial sludge concentration of 7.50 g / L.

[0072] During operation, in Example 1, the reactor surface remained free of floating sludge, maintaining a consistently high TOC removal rate and low effluent SS concentration, while the amount of anaerobic sludge in the reactor steadily increased. In Comparative Example 1, floating sludge gradually appeared on the reactor surface during operation, and the sludge layer thickened continuously with prolonged operation, leading to sludge entering the effluent and biogas pipelines. This resulted in a significant decrease in sludge concentration within the reactor and a sharp reduction in treatment capacity. Operational data are shown in Tables 1-2.

[0073] Table 1. Comparison of removal rates between Example 1 and Comparative Example 1

[0074]

[0075] Note:

[0076] (1) In the "Water Inflow" column, the value before the " / " sign is the water inflow of Example 1, and the value after the " / " sign is the water inflow of Comparative Example 1.

[0077] Table 2. Comparison of sludge volume between Example 1 and Comparative Example 1

[0078]

[0079]

[0080] As can be seen from Tables 1 and 2, the operating results of Comparative Example 1 and Example 1 are significantly different:

[0081] (1) Comparative Example 1

[0082] In the initial stage of operation (0-30 days), Comparative Example 1 showed that the sludge gradually adapted to the water quality and the TOC removal rate gradually increased. However, the SS in the effluent was always higher than that in Example 1. Moreover, the SS in the effluent increased significantly with the increase of the influent concentration. The reason for this is that as the influent concentration increases, the biogas production also increases, the degassing effect of the three-phase separator decreases, and the sludge retention effect also deteriorates significantly, resulting in the loss of anaerobic sludge with the effluent. The result reflected in the data is that the sludge concentration in the anaerobic reactor continues to decrease slowly, and the TOC removal rate also shows a downward trend.

[0083] On-site observation through a sight glass revealed a large amount of floating sludge on the surface of the reactor in Comparative Example 1. After approximately 75 days of operation, the sludge concentration in the reactor in Comparative Example 1 decreased significantly. This was because the floating sludge layer in the reactor was too thick, which caused an abnormal increase in biogas pressure and its instantaneous release. The floating sludge entered the biogas pipeline, resulting in a large loss of anaerobic sludge. It was necessary to take measures to reduce the influent flow rate.

[0084] By day 90, the influent flow rate of Comparative Example 1 had dropped to only 30% of the designed flow rate. The TOC removal rate and effluent SS had basically returned to normal, but the sludge concentration in the reactor continued to show a slow downward trend.

[0085] (2) Example 1

[0086] In the initial stage of operation, there was little difference in TOC removal rate between Example 1 and Comparative Example 1, but the effluent SS was significantly lower than that of Comparative Example 1. As the influent concentration was further increased, the TOC removal rate of Example 1 was further improved and eventually stabilized at around 90%. The effluent SS remained relatively stable, there was no obvious floating sludge in the reactor, and the amount of anaerobic sludge continued to increase steadily.

[0087] The above operational results indicate that Comparative Example 1, which uses a traditional EGSB reactor to treat this organic wastewater, has two major drawbacks: 1) Poor degassing effect of the three-phase separator, with bubbles interfering with sludge settling, resulting in high SS in the effluent and loss of anaerobic sludge; 2) This wastewater is prone to producing floating sludge. The three-phase separator and effluent configuration of the EGSB reactor cause floating sludge to accumulate and gradually thicken at the reactor surface, hindering the normal release of biogas. In severe cases, the floating sludge may enter the biogas pipeline, posing safety hazards and causing significant sludge loss. These drawbacks result in Comparative Example 1's anaerobic reactor being unable to maintain sufficient anaerobic sludge volume, leading to a gradual decrease in treatment capacity and unstable operation of the anaerobic system. Example 1, using the anaerobic reactor of this invention, overcomes these drawbacks of the traditional EGSB reactor. The three-phase separation effect is significantly improved, and the sludge concentration in the reactor steadily increases, enabling stable operation under the design load while maintaining a high TOC removal rate and low effluent SS.

[0088] Comparative Example 2

[0089] The anaerobic UASB reactor, its three-phase separator, and effluent configuration are shown in the attached figure. Figure 1 As shown, the rest is the same as in Example 1;

[0090] Application Example 2

[0091] Organic wastewater from the food industry was treated using Example 1 and Comparative Example 1, respectively. The reactors were designed to treat a capacity of 350 m³. 3 / d, influent COD concentration 8500~12000mg / L.

[0092] Both the reactors in Example 1 and Comparative Example 2 are cylindrical with a corrosion-resistant carbon steel structure, and both adopt a granular sludge operation mode.

[0093] The operational results of Example 1 and Comparative Example 2 are shown in Table 3:

[0094] Table 3. Comparison of the operating effects of anaerobic reactors in Example 1 and Comparative Example 2

[0095]

[0096]

[0097] As shown in Table 2, Example 1 using the anaerobic reactor of this invention and Comparative Example 2 using a traditional UASB reactor have very similar COD removal rates, indicating that both have basically achieved sufficient COD degradation. Example 1, with its lower SS in the effluent, shows a slightly higher overall COD removal rate. However, there is a significant difference in reactor volumetric loading. This is because the traditional UASB reactor has a relatively simple three-phase separator structure, resulting in poor gas-liquid-solid separation and operation only at very low upflow velocities. This leads to poor sludge bed fluidization and low reactor volume utilization. In contrast, the anaerobic reactor of this invention incorporates enhanced degassing in the primary separator stage, effectively removing biogas even with high biogas production. Furthermore, the secondary separator at the bottom minimizes interference from air bubbles on sludge settling, making it particularly suitable for high-load, high-biogas-production conditions. The combined effect of biogas production and hydraulic circulation ensures thorough mixing and good mass transfer of the sludge bed, allowing the sludge bed height to reach the upper circulation pipe and the volumetric loading to reach 12 kg / (m²). 3 .d) and above.

[0098] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention, all of which fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. An anaerobic reactor for preventing sludge floating, characterized in that, It includes the reactor body, influent distribution system, circulation pipe, circulation pump, primary separator, secondary separator, and sludge return pump; The water inlet distribution system is installed at the bottom of the reactor and adopts a perforated water distribution method with an opening diameter of 15~50mm. After the reactor inlet water flow, the circulating water flow delivered by the circulating pump and the return sludge delivered by the sludge return pump are combined, the water is evenly distributed to the bottom of the anaerobic reactor. The circulation pipe is installed in the middle of the reactor and is in the form of a perforated pipe with an opening diameter of 15~50mm. The mixed liquid in the reactor is returned to the inlet water through the circulation pump. Its function is to maintain the upward flow velocity in the anaerobic reactor within the range of 2~8m / h, so that the anaerobic sludge and wastewater are fully mixed. The primary separator is installed at the top of the reactor and is used to collect the water, gas and mud mixture after the anaerobic reaction, and to separate the biogas and floating mud in advance. The primary separator includes an outer cylinder, an inner cylinder, and a vortex distributor. The upper part of the outer cylinder is cylindrical or prismatic, with an overflow inlet at the top; the lower part is conical or pyramidal, with an outlet at the bottom. A vortex distributor is provided on the upper part of the outer cylinder, which consists of a ring of umbrella-shaped plates. The secondary separator is installed at the bottom of the anaerobic reactor and is used to settle and separate the anaerobic sludge in the effluent from the primary separator. The secondary separator is fully enclosed and includes a sedimentation module and a sludge hopper. The sedimentation module has a top plate with an inlet connected to the outlet of the primary separator. The sludge hopper has a sludge return port connected to the sludge return port at the bottom of the reactor. A longitudinal internal partition divides the sedimentation module into a first compartment and a second compartment. Influent enters the sedimentation module from the first compartment, deflects 180° at the end of the first compartment into the second compartment, and exits from the end of the second compartment, forming a U-shaped flow path. The surface loading of the sedimentation zone is 0.2~0.6 m³. 3 / (m 2 The horizontal flow rate is 1~7 mm / s; an outlet is provided on the end plate at the end of the second compartment, which is connected to the outlet of the reactor. The reactor body has an inlet, a sludge outlet and a sludge return outlet at the bottom of the side wall, a circulation outlet and a floating sludge outlet in the middle of the side wall, an outlet at the top of the side wall, and a biogas outlet at the top. The reactor body is cylindrical or cuboid in shape, and is made of either metal or reinforced concrete. The diameter or side length of the reactor body is 3-20m, and the height is 8-28m. The angle between the plates and the generatrix of the umbrella cone is 10~60°. The plates overlap and have gaps that allow liquid to pass through. The top of the vortex distributor has a vent. The inner cylinder is a cylinder or prism concentric with the outer cylinder. The top opening is 200~800mm lower than the outer cylinder, and the bottom opening is connected to the outer cylinder. A sludge-floating pipe is provided at the top of the inner cylinder at an angle of 30~60° downwards. The sludge-floating pipe passes through the outer cylinder and connects to the sludge return pump. The sedimentation zone is equipped with 2 to 6 layers of inclined plates from top to bottom, running longitudinally through the entire sedimentation zone. The cross-section of the inclined plates is "V" shaped or inverted "V" shaped, and the wastewater flows horizontally between the inclined plates. The sludge settles to the surface of the inclined plates under the action of gravity, and then falls into the sludge hopper for collection through the sludge return slits between the inclined plates. The size of the sludge return slits is 50 to 150 mm. The sludge hoppers are located below the sedimentation module, and 1 to 3 sludge hoppers are set along the length direction. The inclination angle of the sludge hoppers is 50 to 60°. The sludge return pump is installed outside the anaerobic reactor. The pump inlet is connected to the sludge return pipe at the bottom of the reactor, and the pump outlet is connected to the reactor's influent distribution system.

2. An anaerobic reactor for preventing sludge floating according to claim 1, characterized in that, The reactor body is equipped with a fully enclosed top cover.

3. An anaerobic reactor for preventing sludge floating according to claim 1, characterized in that, The surface load u of the first-stage separator is less than 0.5m. 3 / (m 2 .s); One or more primary separators are installed at the same height within the reactor body.

4. An anaerobic reactor for preventing sludge floating according to claim 1, characterized in that, The first and second compartments are each equipped with two transverse partitions, which divide the compartments into an inlet area, a sedimentation area and an outlet area. The transverse partitions have water passage holes with a flow velocity of <0.5m / s.

5. An anaerobic reactor for preventing sludge floating according to claim 1, characterized in that, One or more secondary separators can be installed at the bottom of the reactor body.

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