A composite fluidized bed reactor and a method for treating wastewater using the same

Abstract

The present application provides a kind of composite fluidized bed reactor and the method for treating wastewater, the reactor includes coaxially arranged middle cylinder and outer cylinder, and at least one inner cylinder is arranged in the middle cylinder, so that the filler attached with aerobic microorganism is circulated in the inner cylinder and the middle cylinder, the filler attached with anaerobic microorganism is arranged between the middle cylinder and the outer cylinder, and the aerobic reaction, anaerobic reaction, facultative reaction and anoxic reaction exist simultaneously in the reactor. 2 The present application can directly carry out A / O biological treatment process and A / O biological treatment process, has high integration degree, small floor area, can effectively overcome the problems of filler loss and unstable operation of traditional biological fluidized bed reactor, has strong impact resistance, can run under larger air volume and high expansion rate, improves liquid-solid mass transfer effect and treatment efficiency.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of wastewater treatment, more particularly, relates to a composite fluidized bed reactor and a method for treating wastewater by using the composite fluidized bed reactor, especially a method for treating wastewater by using biofilm. BACKGROUND

[0002] With the improvement of industrial level and people's living standard, the discharge of sewage is increasing, people have higher requirements for a better living environment, and the discharge standard of sewage is becoming more and more strict, which puts forward higher requirements for sewage treatment technology. Most of the traditional biological treatment methods have problems such as low treatment efficiency, large reaction tank area, high energy consumption, etc., among which the biochemical reaction tank in biological treatment occupies the largest area. Subsequently, people developed the biological membrane treatment technology, which uses microorganisms to form a layer of biological structure similar to membrane on the filler, and realizes the removal of sewage pollutants through biological metabolism, synthesis and transformation. The biological membrane treatment technology has the advantages of high concentration, high biomass, high biochemical reaction rate, strong adaptability to changes of organic matter load in the influent, etc. Subsequently, people improved the biological phase control (such as biomass, biological membrane thickness, etc.) and the hydraulic condition of the reactor. According to the state of microbial attachment growth carrier in the biological membrane reactor, it can be divided into fixed bed biological membrane reactor and fluidized bed biological membrane reactor. Among them, the fluidized bed biological membrane reactor has been well developed due to its good mass transfer effect.

[0003] The commonly used treatment process in the biochemical treatment unit of sewage treatment is A / O treatment process and A 2 / O treatment process, which contains aerobic biological treatment and anaerobic biological treatment. Aerobic biological treatment mainly degrades organic matter in water, while denitrification reaction is mainly carried out in anaerobic biological treatment. Therefore, through A / O treatment process and A 2 / O treatment process, organic matter and nitrogen in wastewater can be effectively removed. However, these processes contain aerobic biological treatment and anaerobic biological treatment, which need to establish aerobic biological reaction tank and anaerobic biological reaction tank, often causing the problem of large area. How to integrate anaerobic biological treatment and aerobic biological treatment to improve the integration degree is the key to solve the above problems. The application of fluidized bed reactor in A / O treatment process and A 2 / O treatment process can further improve the solid-liquid mass transfer efficiency, improve the treatment effect of sewage and the anti-shock capacity. The development of integrated treatment process with fluidized state anaerobic biological treatment and aerobic biological treatment can well solve the problems of low integration degree and large area of sewage biological treatment, and at the same time, increase the contact opportunity between pollutants and biological carrier, improve the mass transfer effect, have good mixing effect and strong anti-shock load capacity, which will greatly promote the rapid development of sewage biological treatment. SUMMARY

[0004] In order to overcome the above problems, the present application provides a method for treating wastewater by using a composite fluidized bed reactor, which adopts a specific design of an internal circulation fluidized bed reactor device, and a method for treating wastewater by using the same. The method adopts a mode of internal layer top water inlet and middle layer top water outlet, which can effectively overcome the problems of filler loss and unstable operation of the traditional biological fluidized bed reactor, has strong impact resistance, high integration degree, small land occupation, compact structure, and internal circulation of sewage instead of external circulation, without the need of an external circulation pump, and can improve the impact resistance of the biofilm, the liquid-solid mass transfer efficiency and the treatment efficiency.

[0005] In order to achieve the above technical purposes, the technical solutions of the present application are as follows:

[0006] The first aspect of the present application is to provide a composite fluidized bed reactor, which comprises coaxially arranged middle and outer cylinders, and at least one inner cylinder arranged in the middle cylinder, the bottom of the inner cylinder, the middle cylinder and the outer cylinder are communicated, the bottom end of the middle cylinder is higher than the top end of the inner cylinder, at least one gas distribution device is arranged at the bottom of each inner cylinder, the gas distribution device is connected to a gas inlet, the upper end of the inner cylinder extends to the upper part of the middle cylinder, the opening of the upper part of the inner cylinder is communicated with the inside of the middle cylinder, a ring of cylindrical water baffle is arranged in the gap between the inner cylinder and the middle cylinder, the bottom end of the water baffle is slightly lower than the top end of the inner cylinder, the top of the water baffle, the middle cylinder and the outer cylinder are jointly sealed, at least one water inlet is arranged at the upper part of the outer cylinder, at least one water outlet is arranged at the upper part of the middle cylinder and extends to the outside through the outer cylinder, at least one baffle is arranged at the lower part of the water outlet between the middle cylinder and the outer cylinder, the bottom of the outer cylinder is conical, a transverse filter screen is arranged in the conical area, and a sludge discharge port is arranged at the lower part of the filter screen.

[0007] Further, the inner cylinder, the gap between the inner cylinder and the middle cylinder are arranged with fillers attached with aerobic microorganisms.

[0008] Further, the gap between the middle cylinder and the outer cylinder is arranged with fillers attached with anaerobic microorganisms.

[0009] Further, at least one exhaust port is arranged above the top end of the reactor above the inner cylinder. At least one exhaust port is arranged above the reactor corresponding to the outer cylinder and the middle cylinder.

[0010] Further, the upper part of the middle cylinder has a diameter not less than the lower part. As a preferred technical solution, the middle cylinder is divided into an upper part with a larger diameter and a lower part with a smaller diameter, and the two parts are connected by a conical slope.

[0011] Further, the ratio of the distance between the bottom end of the water baffle and the top end of the inner cylinder to the height of the inner cylinder is 1-50:100, and preferably 5-20:100.

[0012] Further, the inner diameter of the baffle is smaller than the diameter of the upper part of the middle cylinder and larger than the diameter of the inner cylinder. The ratio of the diameter of the upper part of the middle cylinder to the diameter of the baffle is 100:20-98, preferably 100:70-95. The bottom end of the baffle forms the entrance of the channel for the wastewater to rise, with the wall of the middle cylinder (when the diameters of the upper and lower parts of the middle cylinder are the same) or the tapered slope of the middle cylinder (when the diameters of the upper and lower parts of the middle cylinder are different).

[0013] Further, the water outlet provided on the upper part of the middle cylinder is located lower than the reaction liquid level in the reactor.

[0014] Further, the number of the inner cylinders is 1-10, preferably 1-5. In order to facilitate the filling of the packing into the inner cylinder during the circulation, the bottom opening of the inner cylinder is outwardly flared.

[0015] Further, the ratio of the diameter of the reactor to the height of the reactor is 1:1-20, preferably 1:3-10.

[0016] Further, when the diameters of the upper and lower parts of the middle cylinder are the same, the ratio of the cross-sectional area of the outer cylinder to the cross-sectional area of the middle cylinder is 100:20-90, preferably 100:30-70. The ratio of the sum of the cross-sectional area of the middle cylinder to the cross-sectional area of the inner cylinder is 100:5-70, preferably 100:8-50.

[0017] Further, when the diameters of the upper and lower parts of the middle cylinder are different, the ratio of the cross-sectional area of the outer cylinder to the cross-sectional area of the upper part of the middle cylinder is 100:20-90, preferably 100:40-82; the ratio of the cross-sectional area of the outer cylinder to the cross-sectional area of the lower part of the middle cylinder is 100:10-70, preferably 100:20-50; the ratio of the sum of the cross-sectional area of the lower part of the middle cylinder to the cross-sectional area of the inner cylinder is 100:5-80, preferably 100:10-40; and the ratio of the diameter of the upper part of the middle cylinder with a larger diameter to the diameter of the lower part of the middle cylinder with a smaller diameter is 1-3:1, preferably 1-2:1, most preferably 1-1.5:1.

[0018] Further, the ratio of the volume of the packing with aerobic microorganisms to the sum of the volumes of the middle cylinder and the inner cylinder is 1:1-5, preferably 1:1.2-2.0.

[0019] Further, the ratio of the volume of the packing with anaerobic microorganisms to the volume between the middle cylinder and the outer cylinder is 1:1.2-5.0, preferably 1:1.4-2.5.

[0020] Further, the composite fluidized bed reactor is used for the treatment of wastewater by biofilm.

[0021] The technical purpose of the second aspect of the present application is to provide a method for treating wastewater by using the above-mentioned composite fluidized bed reactor, which is as follows: arranging the fillers in the inner cylinder, the gap between the inner cylinder and the middle cylinder, and the gap between the middle cylinder and the outer cylinder respectively, introducing the wastewater to be treated into the device through the water inlet arranged at the upper part of the outer cylinder, and performing anaerobic biochemical treatment on the wastewater by the fillers attached with anaerobic microorganisms in the gap between the middle cylinder and the outer cylinder, introducing the gas into the composite fluidized bed reactor through the gas inlet and the gas distribution device, and aerating the wastewater, wherein after the wastewater enters the reactor, it reaches the bottom, and under the driving of the gas flow, the wastewater carries the fillers attached with aerobic microorganisms to go up through the inner cylinder and simultaneously performs reaction, after reaching the top end of the inner cylinder, the wastewater enters the annular area between the inner cylinder and the middle cylinder and goes down, and under the action of the water baffle, most of the fillers, biological sludge and wastewater are separated by sedimentation, part of the wastewater goes up through the gap between the water baffle and the middle cylinder and is discharged through the water outlet on the middle cylinder, the fillers, biological sludge and part of the wastewater go down into the bottom of the reactor, the fillers are intercepted by the filter screen and enter the inner cylinder under the driving of the pressure generated by the gas flow, realizing internal circulation, and part of the sludge enters the inner cylinder together with the fillers to perform internal circulation, and part of the biological sludge is discharged through the sludge discharge port after passing through the filter screen.

[0022] Further, the particle size of the fillers attached with aerobic microorganisms is 0.1-50 mm, preferably 1.0-20 mm. The fillers are at least one of activated carbon, resin, ceramsite, polymeric plastic ring and sponge.

[0023] Further, the particle size of the fillers attached with anaerobic microorganisms is 1-50 mm, preferably 10-30 mm. The fillers are at least one of activated carbon, ceramsite, polymeric plastic ring and sponge.

[0024] Further, the pH of the wastewater to be treated is 5-10, preferably 6-9. The residence time of the wastewater to be treated in the reaction device is 24-200 h, preferably 48-96 h.

[0025] Further, the gas inlet of the reactor can be air or pure oxygen.

[0026] In the composite fluidized bed reactor, by controlling the gas inlet amount and the water outlet amount, the fluidization speed of the reaction material inside the reaction device can be controlled, and the fillers cannot enter the outer cylinder in large quantities or go up through the gap between the water baffle and the middle cylinder.

[0027] The technical solution of the present application has the following advantages:

[0028] (1) The present application adopts the internal circulation type composite fluidized bed reactor to realize the biological membrane treatment of wastewater, adopts the mode of water inlet at the top of the inner layer and water outlet at the top of the middle layer, can effectively overcome the problems of filler loss and unstable operation of the traditional biological fluidized bed reactor, has strong impact resistance, can operate under large gas amount and high expansion rate, and improves the liquid-solid mass transfer effect and treatment efficiency.

[0029] (2)Wastewater enters the composite fluidized bed reactor, first passes through the gap between the middle cylinder and the outer cylinder, which is an anaerobic reaction zone, then enters the bottom of the inner cylinder and the outer cylinder, which is an anoxic reaction zone, and then enters the inner cylinder with the filler driven by gas, and the inner cylinder and the top area of the inner cylinder are aerobic reaction zones, so the wastewater treatment process of the present application simultaneously includes anaerobic biological treatment, anoxic biological treatment and aerobic biological treatment, and can directly carry out A / O biological treatment process and A 2 / O biological treatment process, and the effluent area has a certain sedimentation effect, has high integration degree, small land occupation, compact structure, and the internal circulation of wastewater replaces external circulation, so that external circulation pump is not needed, energy consumption is greatly reduced, and treatment efficiency is improved.

[0030] Other features and advantages of the present application will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The composite fluidized bed bioreactor of the present application. DETAILED DESCRIPTION

[0032] The following non-limiting examples can enable those skilled in the art to more fully understand the present application, but do not limit the present application in any way.

[0033] The following Figure 1 The device and method of the present application will be described in detail.

[0034] The present application is a composite fluidized bed reactor and a method for treating wastewater by using the same, wherein the composite fluidized bed reactor, as shown in Figure 1As shown, it comprises a middle cylinder 9 and an outer cylinder 10 arranged coaxially, and an inner cylinder 7 arranged in the middle cylinder, the bottom of the inner cylinder 7, the middle cylinder 9 and the outer cylinder 10 are communicated, the upper part of the middle cylinder 9 has a larger diameter than the lower part, the diameter ratio of the upper part to the lower part of the middle cylinder 9 is 1.5:1, the upper part with larger diameter and the lower part with smaller diameter of the middle cylinder 9 are connected by a tapered slope 19; the bottom end of the middle cylinder 9 is higher than the bottom end of the inner cylinder 7, a gas distribution device 6 is arranged at the bottom of the inner cylinder 7, the gas distribution device 6 is connected to the gas inlet 4, the upper end of the inner cylinder 7 extends to the upper part of the middle cylinder 9, the opening of the upper part of the inner cylinder 7 is communicated with the inside of the middle cylinder 9, a circle of water baffle plates 8 are arranged in the gap between the inner cylinder 7 and the middle cylinder 9, the bottom end of the water baffle plates 8 is 10 cm lower than the top end of the inner cylinder 7, the inner diameter of the water baffle plates 8 is consistent with the inner diameter of the lower part with smaller diameter of the middle cylinder 9, the bottom end of the water baffle plates 8 and the tapered slope 18 of the middle cylinder 9 form a channel entrance 19 for the wastewater to rise, the height of the channel entrance 19 is 5 cm. The top of the water baffle plates 8, the middle cylinder 9 and the outer cylinder 10 are collectively sealed, two water inlets 101 and 102 are oppositely arranged at the upper part of the outer cylinder 10, two water outlets 21 and 22 are oppositely arranged at the upper part of the middle cylinder 9 and extend to the outside through the outer cylinder 10, the water outlets 21 and 22 are lower than the reaction liquid level in the reactor, the bottom of the outer cylinder 10 is tapered, a transverse filter screen 5 is arranged in the tapered area, a sludge discharge port 3 is arranged at the lower part of the filter screen 5, three gas outlets are arranged at the top of the reactor, the gas outlet I 201 is arranged directly above the reactor and is the same as the inner cylinder, the gas outlet II 202 and the gas outlet 203 are arranged above the reactor and are communicated with the gap between the middle cylinder and the outer cylinder, the filler 17 attached with aerobic microorganisms is arranged in the gap between the inner cylinder 7 and the middle cylinder 9, the filler 23 attached with anaerobic microorganisms is arranged between the outer cylinder 10 and the middle cylinder 9, and the baffle 18 is arranged.

[0035] The ratio of the cross-sectional area of the outer cylinder 10 to the cross-sectional area of the lower part of the middle cylinder 9 is 100:25, the ratio of the cross-sectional area of the upper part with larger diameter of the middle cylinder 9 to the cross-sectional area of the inner cylinder 7 is 100:44.4. The ratio of the volume of the filler 17 attached with aerobic microorganisms to the sum of the volume of the middle cylinder 9 and the volume of the inner cylinder 7 is 1:3. The ratio of the volume of the filler 23 attached with anaerobic microorganisms to the volume between the middle cylinder 9 and the outer cylinder 10 is 1:2.

[0036] The process for treating wastewater by using the above reaction device is as follows:

[0037] The packing 17 with aerobic microorganism and the packing 23 with anaerobic microorganism are used as the carrier for the growth of biofilm. The wastewater to be treated is introduced into the reactor through the water inlet 101 and the water inlet 102 at the top of the outer cylinder, and is subjected to anaerobic denitrification in the anaerobic zone 14. The gas is introduced into the reactor through the gas inlet 4 and the gas distribution device 7, and is used to aerate the wastewater. The wastewater from the anaerobic zone 14 is carried by the packing 17 with aerobic microorganism to the gas lifting zone 11 of the inner cylinder 7, and is introduced into the aerobic reaction zone 12. The microorganism in the packing and the wastewater degrades the wastewater. The degraded wastewater, the packing and the biological sludge are introduced into the anoxic zone 13 between the inner cylinder 7 and the middle cylinder 9. When the wastewater passes through the bottom of the baffle 8, part of the wastewater is introduced into the water outlet 121 and the water outlet 122, and part of the wastewater, the packing and the biological sludge are introduced into the anoxic reaction zone 15 at the bottom of the middle cylinder 9. Part of the biological sludge and the packing 17 with aerobic microorganism are precipitated, and the packing is intercepted by the filter screen 5. The biological sludge is precipitated into the precipitation zone 16, and is finally discharged through the sludge discharge port 3. Part of the biological sludge, the packing 17 with aerobic microorganism and the wastewater are carried by the gas to the aerobic reaction zone 12. The gas produced in the anaerobic reaction zone 14 and the aerobic reaction zone 12 is discharged through the gas discharge port 20.

[0038] In the wastewater treatment process, the activated sludge should be collected from the sewage treatment plant and inoculated into the reactor system. The anaerobic microorganism is inoculated into the anaerobic reaction zone 14, and the aerobic microorganism is inoculated into the aerobic reaction zone 12. The intermittent culture is carried out at a temperature of 25-35°C, so that the microorganism completes the biofilm formation on the surface of the carrier packing. After the biofilm formation, the continuous culture is carried out at a low flow rate for a period of time, so that the microorganism film on the packing is more stable.

[0039] The inoculated bacteria in the example are the conventional bacteria in the biochemical treatment unit of the urban sewage treatment plant. The inoculated MLSS is 2000 mg / L. The influent COD is 600 mg / L during the culture of the bacteria. The NO3 - The concentration of N is about 200 mg / L. The pH of the solution is controlled to be 6.5-8.5. The temperature is 25-30°C. The effective solution volume of the reactor used is 7L. The residence time is 48h. The gas inlet amount is 4L / h.

[0040] The fresh artificial simulated wastewater is prepared. The COD is 1000 mg / L. The NO3 -- N concentration 300 mg / L, pH 7.5, per liter of trace elements containing FeCl3-6H2O (1.5 g), ZnSO4-7H2O (0.12 g), MnCl2-4H2O (0.12 g), H3BO (0.15 g), Na2MoO4-2H2O (0.06 g), CuSO4-5H2O (0.03 g).

[0041] The following examples were all carried out using the above treatment method for sewage treatment.

[0042] Example 1

[0043] Using the reaction device of Figure 1 , the filler 17 attached with aerobic microorganisms in the inner layer is activated carbon with a particle size of 2.0-3.0 mm, the ratio of the volume of the filler to the sum of the volumes of the middle cylinder and the inner cylinder is 1:3, the filler 23 attached with anaerobic microorganisms between the middle layer and the outer layer is light ceramic with a particle size of 5-20 mm, and the ratio of the volume of the filler to the volume between the middle cylinder and the outer cylinder is 1:1.5. The influent of the experiment is artificially simulated biochemical sewage. After 30 days of continuous operation, the content of nitrate nitrogen in the wastewater after biochemical treatment is less than 15 mg / L, the nitrogen removal rate is greater than 95%, the content of COD is less than 60 mg / L, and the COD removal rate is greater than 94%.

[0044] Example 2

[0045] Using the reaction device of Figure 1 , the filler 17 attached with aerobic microorganisms in the inner layer is polymeric plastic ring with a particle size of 3-7 mm, the ratio of the volume of the filler to the sum of the volumes of the middle cylinder and the inner cylinder is 1:2, the filler 23 attached with anaerobic microorganisms is polymeric sponge with a particle size of 10-20 mm, and the ratio of the volume of the filler to the volume between the middle cylinder and the outer cylinder is 1:2. The influent of the experiment is artificially simulated biochemical sewage. After 30 days of continuous operation, the content of nitrate nitrogen in the wastewater after biochemical treatment is about 10 mg / L, the nitrogen removal rate is greater than 96%, the content of COD is less than 50 mg / L, and the COD removal rate is greater than 95%.

[0046] Comparative Example 1

[0047] The traditional biochemical sludge treatment method is adopted, a 4.5L anaerobic tank is established and a stirring device is installed, a 1.5L aerobic tank is established and a stirring device is installed, and then a 1L sedimentation tank is established. The wastewater is firstly treated by anaerobic treatment in the anaerobic tank, then treated by aerobic treatment in the aerobic tank, and finally discharged from the sedimentation tank. The artificial simulated biochemical wastewater is used as the influent, the anaerobic tank is filled with 1 / 2 volume of light ceramic filler, and the aerobic tank is filled with 1 / 3 volume of activated carbon. The total residence time is 48h. After 30 days of continuous operation, the nitrate nitrogen content in the wastewater treated by the biochemical treatment is about 50mg / L, the denitrification rate is greater than 80%, the COD is less than 200mg / L, and the COD removal rate is greater than 80%.

[0048] From the above experimental results, it can be seen that the composite fluidized bed reactor can directly carry out A / O biological treatment process and A 2 / O biological treatment process, the effluent area has a certain sedimentation effect, the integration degree is high, the land occupation area is small, the structure is compact, the internal circulation of the wastewater replaces the external circulation, no external circulation pump is needed, no stirring is needed, the energy consumption is greatly reduced, and the treatment efficiency is improved.

Claims

1. A composite fluidized bed reactor characterized by, The reactor comprises coaxially arranged middle cylinder and outer cylinder, and at least one inner cylinder arranged in the middle cylinder. The bottom of the inner cylinder, the middle cylinder and the outer cylinder are communicated. The bottom end of the middle cylinder is higher than the bottom end of the inner cylinder. At least one gas distribution device is arranged at the bottom of each inner cylinder. The gas distribution device is connected to the gas inlet. The upper end of the inner cylinder extends to the upper part of the middle cylinder. The opening of the upper part of the inner cylinder is communicated with the inner part of the middle cylinder. A circle of water baffle is arranged in the gap between the inner cylinder and the middle cylinder. The bottom end of the water baffle is slightly lower than the top end of the inner cylinder. The top of the water baffle, the middle cylinder and the outer cylinder are jointly sealed. At least one water inlet is arranged at the upper part of the outer cylinder. At least one water outlet is arranged at the upper part of the middle cylinder and extends to the outer cylinder to be communicated with the outside. At least one baffle is arranged at the lower part of the water outlet between the middle cylinder and the outer cylinder. The bottom of the outer cylinder is conical. A transverse filter screen is arranged in the conical area. A sludge discharge port is arranged at the lower part of the filter screen. The diameter of the upper part of the middle cylinder is equal to the diameter of the lower part of the middle cylinder, or the middle cylinder is divided into upper part with larger diameter and lower part with smaller diameter. The two parts are connected by a conical slope. The filler with aerobic microorganism is arranged in the gap between the inner cylinder and the middle cylinder. The filler with anaerobic microorganism is arranged in the gap between the middle cylinder and the outer cylinder. The inner diameter of the water baffle is smaller than the diameter of the upper part of the middle cylinder and larger than the diameter of the inner cylinder. The ratio of the diameter of the upper part of the middle cylinder to the diameter of the water baffle is 100:20-98. The bottom end of the water baffle and the wall of the middle cylinder or the conical slope of the middle cylinder form the inlet of the wastewater rising channel. The water outlet arranged at the upper part of the middle cylinder is lower than the reaction liquid level in the reactor.

2. The composite fluidized bed reactor of claim 1, wherein, At least one exhaust port is arranged above the reactor at the top of the inner cylinder of the reactor. At least one exhaust port is arranged above the reactor corresponding to the outer cylinder and the middle cylinder.

3. The composite fluidized bed reactor of claim 1, wherein, The ratio of the distance between the bottom end of the water baffle and the top end of the inner cylinder to the height of the inner cylinder is 1-50:

100.

4. The composite fluidized bed reactor of claim 1, wherein, The number of the inner cylinders is 1-10. The opening of the bottom of the inner cylinder is outwardly trumpet-shaped.

5. The composite fluidized bed reactor of claim 1, wherein, The ratio of the diameter of the reactor to the height of the reactor is 1:1-20.

6. The composite fluidized bed reactor of claim 1, wherein, When the diameters of the upper and lower parts of the middle cylinder are the same, the ratio of the cross-sectional area of the outer cylinder to the cross-sectional area of the middle cylinder is 100:20-90. The ratio of the cross-sectional area of the middle cylinder to the sum of the cross-sectional areas of the inner cylinders is 100:5-70.

7. The composite fluidized bed reactor of claim 1, wherein, When the diameters of the upper and lower parts of the middle cylinder are different, the ratio of the cross-sectional area of the outer cylinder to the cross-sectional area of the upper part of the middle cylinder is 100:20-90. The ratio of the cross-sectional area of the outer cylinder to the cross-sectional area of the lower part of the middle cylinder is 100:10-70. The ratio of the cross-sectional area of the lower part of the middle cylinder to the sum of the cross-sectional areas of the inner cylinders is 100:5-80.

8. The composite fluidized bed reactor of claim 1, wherein, When the diameters of the upper and lower parts of the middle cylinder are different, the ratio of the diameter of the upper part of the middle cylinder with larger diameter to the diameter of the lower part of the middle cylinder with smaller diameter is 1-3:

1.

9. The composite fluidized bed reactor of claim 1, wherein, The ratio of the volume of the filler with aerobic microorganism to the sum of the volumes of the middle cylinder and the inner cylinder is 1:1-5. The ratio of the volume of the filler with anaerobic microorganism to the volume between the middle cylinder and the outer cylinder is 1:1.2-5.

0.

10. A method for treating wastewater by using the composite fluidized bed reactor according to any one of claims 1-9, wherein the fillers are arranged in the inner cylinder, the gap between the inner cylinder and the middle cylinder, and the gap between the middle cylinder and the outer cylinder, respectively, the wastewater to be treated is introduced into the device through the water inlet arranged at the upper part of the outer cylinder, the wastewater is subjected to anaerobic biochemical treatment by the fillers attached with anaerobic microorganisms in the gap between the middle cylinder and the outer cylinder, and the gas is introduced into the composite fluidized bed reactor through the gas inlet and the gas distribution device to aerate the wastewater, after the wastewater enters the reactor, it reaches the bottom, and under the action of the airflow, the wastewater carries the fillers attached with aerobic microorganisms to go up through the inner cylinder and simultaneously undergoes reaction, after reaching the top end of the inner cylinder, the wastewater enters the annular area between the inner cylinder and the middle cylinder and goes down, and under the action of the water baffle, most of the fillers, biological sludge and wastewater are subjected to sedimentation and separation, part of the wastewater goes up through the gap between the water baffle and the middle cylinder and is discharged through the water outlet on the middle cylinder, the fillers, biological sludge and part of the wastewater go down into the bottom of the reactor, the fillers are intercepted by the filter screen and enter the inner cylinder under the action of the pressure generated by the airflow to realize internal circulation, part of the sludge enters the inner cylinder together with the fillers to realize internal circulation, and part of the biological sludge is discharged through the sludge discharge port after passing through the filter screen.

11. The method of claim 10, wherein, The particle size of the fillers attached with aerobic microorganisms is 0.1-50 mm, and the fillers are at least one of activated carbon, resin, ceramsite, polymeric plastic ring and sponge; the particle size of the fillers attached with anaerobic microorganisms is 1-50 mm, and the fillers are at least one of activated carbon, ceramsite, polymeric plastic ring and sponge.

12. The method of claim 10, wherein, The pH of the wastewater to be treated is 5-10, and the residence time of the wastewater to be treated in the reaction device is 24-200 h.

13. The method of claim 10, wherein, The gas introduced into the reactor is air or pure oxygen.

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