An AAO sewage treatment system

Abstract

The present invention provides an AAO sewage treatment system, which includes an anaerobic tank, a facultative aerobic tank, an aerobic tank, a guide tube, a propeller and a degassing device, wherein the anaerobic tank is arranged in the middle of the system, and the facultative aerobic tank and the aerobic tank are arranged around the anaerobic tank, thereby saving land use. When the system is working, after the sewage to be treated is sent into the anaerobic tank, it diffuses from the surrounding areas of the anaerobic tank to the center of the anaerobic tank in the anaerobic tank, and the sludge is sent into the center of the anaerobic tank through the guide tube. Under the action of the propeller, the incoming water can be transferred from the surrounding areas of the anaerobic tank to the center of the anaerobic tank, and at the same time, the sludge diffuses from the center of the anaerobic tank to the surrounding areas of the anaerobic tank. The sewage sent into the system and the returned sludge form convection, so that the mud and water are mixed more fully, thereby improving the effective volume utilization rate of the anaerobic tank.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and in particular relates to an AAO sewage treatment system. Background Art

[0002] Fine chemical wastewater contains a wide variety of organic nitrogen and phosphorus compounds with complex structures and high concentrations, making their conversion in biochemical systems challenging and resulting in low conversion rates. The anaerobic-anoxic-oxygen (AAO) process, also known as the A2O process, is a commonly used wastewater treatment process for secondary and tertiary wastewater treatment, as well as for reclaimed water reuse, and offers excellent nitrogen and phosphorus removal results. The "Outdoor Drainage Design Code" stipulates that the conventional AAO process requires a tank volume ratio of 1:1:3 for anaerobic, facultative, and aerobic conditions, with minimal aeration for the facultative aeration phase and a requirement for dissolved oxygen to be controlled at 0.2mg / L to 0.5mg / L. However, when applied to wastewater with high concentrations of organic nitrogen and organic phosphorus, this process suffers from insufficient retention time in the hydrolysis and acidification stages, resulting in low organic nitrogen and phosphorus conversion efficiency. The continuous release of ammonia nitrogen in the downstream stage also leads to excessively high levels of organic nitrogen, nitrate nitrogen, and organic phosphorus in the secondary sedimentation tank, ultimately compromising the removal efficiency of total nitrogen and total phosphorus.

[0003] The traditional AAO process maintains a dissolved oxygen supply in the facultative oxygen tank within the range of 0.2mg / L to 0.5mg / L, which is feasible for common wastewater and processes. However, for wastewater high in organic nitrogen, a dissolved oxygen level of 0.2mg / L to 0.5mg / L is too high, and higher dissolved oxygen levels are detrimental to the further conversion of organic nitrogen and organic phosphorus in fine chemical wastewater. Simply removing the aeration system and relying solely on underwater propulsion will not achieve optimal process operation. Low propulsion speeds are insufficient for thorough sludge mixing and can lead to significant sludge floating due to denitrification, which also affects sludge utilization. Excessive sludge thickness makes it difficult for technicians to assess daily operational conditions from the tank surface. High-power propulsion also introduces dissolved oxygen and breaks up the sludge, hindering the accumulation of nitrifying bacteria in the aerobic tank and the settling of sludge in the secondary sedimentation tank.

[0004] In view of the above shortcomings, a new AAO system still needs to be developed. Summary of the Invention

[0005] The present invention aims to address at least one of the aforementioned technical problems in the prior art. To this end, the present invention provides an AAO wastewater treatment system that achieves higher tank capacity utilization, better hydrolysis and acidification, more complete ammonia nitrogen release, and greater benefits for nitrification and denitrification in both aerobic and anoxic zones.

[0006] A first aspect of the present invention provides an AAO sewage treatment system, comprising:

[0007] Anaerobic tanks;

[0008] an aerobic tank, the aerobic tank being arranged around the outside of the anaerobic tank and being connected to the anaerobic tank;

[0009] an aerobic tank, the aerobic tank being arranged around the outside of the facultative aerobic tank and being in communication with the facultative aerobic tank;

[0010] A guide tube is provided in the anaerobic tank;

[0011] Propellers are provided in the anaerobic tank, the facultative aerobic tank and the aerobic tank;

[0012] The degassing device is arranged in the aerobic tank.

[0013] One of the technical solutions of the present invention regarding the AAO sewage treatment system has at least the following beneficial effects:

[0014] In the AAO sewage treatment system of the present invention, an anaerobic tank is set in the middle position, and an anaerobic tank and an aerobic tank are respectively arranged around the anaerobic tank, thereby saving land use. When the system is working, after the sewage to be treated is sent into the anaerobic tank, it diffuses from the surrounding areas of the anaerobic tank to the center of the anaerobic tank. The sludge is sent into the center of the anaerobic tank through the guide tube. Under the action of the propeller, the incoming water can be transferred from the surrounding areas of the anaerobic tank to the center of the anaerobic tank. At the same time, the sludge diffuses from the center of the anaerobic tank to the surrounding areas of the anaerobic tank. The sewage sent into the system and the returned sludge form convection, thereby making the mud and water mixing more complete, thereby improving the effective volume utilization rate of the anaerobic tank. After treatment, the sewage is finally discharged from the aerobic tank.

[0015] Nitrogen is generated in the anoxic tank, and the density of the sludge in the sewage will decrease after being wrapped with nitrogen, so that it floats up. In the AAO sewage treatment system of the present invention, a degassing device is provided in the anoxic tank, and the degassing device can form a degassing zone in the anoxic tank to remove the nitrogen on the sludge, thereby changing the mixing mode of traditional aeration. It can not only separate the sludge floating up due to denitrification from the nitrogen, but also use the rising effect of degassing to form a local upward and downward circulation, and fully replace the muddy water at the bottom of the anoxic tank. After the sludge in the sewage leaves the degassing zone, the sludge density increases and gradually sinks, gradually accumulating nitrogen in the denitrification process, obtaining the buoyancy force of the bubbles and slowly rising again until it enters the next degassing zone. During the water circulation process, the power and energy consumption of the propeller is reduced, and the mixing of mud and water in the anoxic tank is achieved. The system of the present invention is more energy-efficient. Based on the above improvements, the optimization of anaerobic and facultative hydraulic flow states in the AAO system can be achieved, and the residence time of the hydrolysis reaction can be effectively extended, the release of ammonia nitrogen can be advanced, the denitrification capacity of the system can be improved, and the hydrolysis of organic phosphorus and the removal rate of total phosphorus can also be improved.

[0016] In the AAO wastewater treatment system of the present invention, sludge is returned to the center of the anaerobic tank. A flow guide is installed at the center of the anaerobic tank. Without the flow guide, the water flow in the anaerobic tank is circular, and the linear velocity of the water flow in the center of the anaerobic tank is lower than that in the surrounding areas. Sludge entering the anaerobic tank will form a dead zone at the center of the tank bottom. The flow guide creates a disturbance at the center of the anaerobic tank, thereby adjusting the hydraulic flow pattern of the anaerobic tank and strengthening the water flow.

[0017] According to some embodiments of the present invention, the anaerobic tank, the facultative aerobic tank and the aerobic tank are all circular and have the same center.

[0018] The anaerobic tank, facultative aerobic tank and aerobic tank are all circular and have the same center. Without changing the tank volume ratio, the hydraulic flow state of the central circular anaerobic tank can be improved, and the sludge can be returned to the center point, so as to better realize the diffusion of the incoming water from the periphery to the center and then from the center to the periphery, forming convection and sufficient mixing with the returned sludge, further improving the effective volume utilization rate of the anaerobic tank and improving the sewage treatment efficiency.

[0019] According to some embodiments of the present invention, the outlet of the guide tube is located at the center of the anaerobic tank. Such a design is more conducive to the sludge flowing back into the anaerobic tank to spread from the center of the anaerobic tank to the surrounding areas of the anaerobic tank.

[0020] According to some embodiments of the present invention, the guide tube is a swirl guide tube, and the diameter ratio of the top to the bottom of the swirl guide tube is 2 to 4:1.

[0021] The diameter ratio of the top and bottom of the swirl guide tube is 2 to 4:1, so that the swirl guide tube forms an inverted cone structure, which is conducive to further adjusting the hydraulic flow state of the anaerobic tank and strengthening the water flow.

[0022] According to some embodiments of the present invention, the guide tube is a swirl guide tube, and the diameter ratio of the top and bottom of the swirl guide tube is 3 to 4:1.

[0023] According to some embodiments of the present invention, the guide tube is a swirl guide tube, and the diameter ratio of the top and bottom of the swirl guide tube is about 3:1.

[0024] The diameter ratio of the top and bottom of the swirl guide tube is 3:1, which makes the swirl guide tube form an inverted cone structure, which is further conducive to adjusting the hydraulic flow state of the anaerobic tank and strengthening the water flow.

[0025] According to some embodiments of the present invention, the distance between the bottom of the cyclone guide tube and the bottom of the anaerobic tank is 0.5m to 1m.

[0026] The distance between the bottom of the swirl guide tube and the bottom of the anaerobic tank is 0.5m to 1m, which is further conducive to adjusting the hydraulic flow state of the anaerobic tank and strengthening the water flow.

[0027] According to some embodiments of the present invention, a swirl guide plate is provided in the swirl guide cylinder, and the setting direction of the swirl guide plate is parallel to the propulsion direction of the propeller.

[0028] The setting direction of the swirl guide plate is parallel to the propulsion direction of the propeller, which is conducive to forming a co-directional water flow, reducing the loss of kinetic energy of the water, and promoting the full mixing of mud and water in the center.

[0029] The propeller installed in the anaerobic tank can form a circulation of water flow, which can increase the linear velocity of the central water flow without increasing equipment and energy consumption, promote the mixing of sludge in the center of the anaerobic tank, and improve the effective volume utilization rate of the anaerobic tank.

[0030] The number of propellers in the anaerobic tank can be 2-4.

[0031] According to some embodiments of the present invention, the bottom velocity of the push flow channel of the aerobic pool is greater than 0.2 m / min.

[0032] Generally speaking, relevant design specifications require a bottom flow velocity greater than 0.3 m / min. However, in the system of the present invention, the deaerator enhances the water flow, so the bottom flow velocity of the aeration tank can be greater than 0.2 m / min. This reduces the power consumption of the propulsion device, i.e., the propeller, making the system more energy-efficient. The number of propellers in the aeration tank can be 2-4.

[0033] According to some embodiments of the present invention, the dissolved oxygen in the anaerobic tank is lower than 0.1 mg / L, or the redox potential is lower than -150 mv.

[0034] The dissolved oxygen in the facultative oxygen tank is lower than 0.1 mg / L, or the redox potential is lower than -150 mv, ensuring an anaerobic environment for the hydrolysis and acidification reaction.

[0035] According to some embodiments of the present invention, the degassing device is a degassing tube, and the degassing tube is provided with degassing holes.

[0036] The degassing holes are opened in the upper middle part of the degassing tube, the number of the holes can be 6-10, and the bottom is sealed.

[0037] According to some embodiments of the present invention, the pore diameter of the degassing pipe in the aerobic tank is about 1 mm, which belongs to macropore aeration.

[0038] Unlike the microporous aeration used in existing technologies, the macroporous aeration in the aerobic tank in this invention primarily serves to degas, rather than supply oxygen. Macroporous aeration can further reduce the oxygen enrichment level in the aerobic tank, prolong the hydrolysis reaction time, and increase the ammonia nitrogen release rate. It also promotes the escape of nitrogen generated by denitrification, preventing sludge loss caused by sludge floating.

[0039] According to some embodiments of the present invention, the aeration holes in the aerobic tank have a pore size of 80 μm to 100 μm.

[0040] According to some embodiments of the present invention, the aeration in the aerobic tank is a commercially available microporous aeration membrane tube.

[0041] According to some embodiments of the present invention, the aeration in the aerobic tank may also be other microporous aerator products.

[0042] According to some embodiments of the present invention, a plurality of degassing pipes are arranged in the aeration tank along a radial direction of the aeration tank, and a distance between the plurality of degassing pipes is 5 m to 7 m.

[0043] The interval between the oxygen pipes is 5m to 7m, which is conducive to the formation of a degassing zone.

[0044] According to some embodiments of the present invention, the degassing pipe is located in the aerobic tank at a position 2 to 3 meters below the water surface.

[0045] If the degassing pipe of the facultative aeration tank is installed too deep below the water surface, it will increase the dissolved oxygen in the water phase. The installation height of the degassing pipe of the facultative aeration tank is set at 2m to 3m below the water surface to help reduce the entry of dissolved oxygen into the water phase.

[0046] According to some embodiments of the present invention, the degassing pipe may be divided into several branch pipes from a main pipe.

[0047] According to some embodiments of the present invention, the AAO sewage treatment system further includes a water inlet pipe, which is connected to the anaerobic tank.

[0048] According to some embodiments of the present invention, the AAO sewage treatment system further includes a sludge return pipe, one end of which is connected to the guide tube, and the other end of which is connected to a secondary sedimentation tank.

[0049] According to some embodiments of the present invention, the sludge return pipe is close to one end of the guide tube and is perpendicular to the central axis of the guide tube.

[0050] The sludge return pipe is close to one end of the guide tube and is perpendicular to the central axis of the guide tube, ensuring that the returned sludge can cut into the guide tube in a horizontal direction.

[0051] The sludge can be cut into the guide tube horizontally, which is conducive to the formation of vortex flow.

[0052] According to some embodiments of the present invention, the AAO wastewater treatment system further comprises a submersible nitrification liquid reflux pump, which is installed on a hole in the wall shared by the aerobic and facultative aerobic tanks to push the mixed liquid from the aerobic tank into the facultative aerobic tank.

[0053] According to some embodiments of the present invention, the reflux ratio of the nitrating solution is 100%-400%.

[0054] According to some embodiments of the present invention, the AAO sewage treatment system further includes an outlet pipe, which connects the aerobic tank and the secondary sedimentation tank.

[0055] After being treated by the AAO sewage treatment system of the present invention, the sewage flows into the secondary sedimentation tank, where the sludge is precipitated and the upper part of the secondary sedimentation tank is the supernatant. The sludge precipitated in the secondary sedimentation tank is sent back into the AAO sewage treatment system by the sludge return pump.

[0056] According to some embodiments of the present invention, the sludge return ratio is 50%-100%.

[0057] The AAO wastewater treatment system of the present invention is suitable for treating fine chemical wastewater. Fine chemical wastewater includes production wastewater, cleaning water, and pre-treated wastewater from fine chemical workshops. It includes process wastewater such as waste mother liquor, washing wastewater, recycle wastewater, neutralization wastewater, and wastewater pre-treated by Fenton oxidation, alkaline hydrolysis, electrocatalytic oxidation, and iron-carbon micro-electrolysis. Its components contain organic nitrogen and organic phosphorus.

[0058] The present invention can be widely used in the biochemical treatment of various organic nitrogen and phosphorus chemical wastewaters, and has the functions of denitrification and phosphorus removal. By improving the anaerobic sludge return mode and the aerobic aeration mixing mode to design the deaeration zone, the problems of easy sludge deposition in the anaerobic tank and easy floating of the aerobic sludge in the current traditional AAO process are solved, the hydrolysis reaction efficiency can be significantly improved, and the denitrification and phosphorus removal efficiency of the AAO process is further improved.

[0059] The AAO sewage treatment system of the present invention has a higher pool capacity utilization rate, better hydrolysis and acidification effect, more thorough release of ammonia nitrogen, and is more conducive to nitrification and denitrification in the aerobic and anoxic sections. Without increasing the pool capacity, compared with the traditional AAO process, the effluent COD is reduced by about 30%, the total nitrogen is reduced by about 50%, no ammonia nitrogen is detected, nitrate nitrogen is reduced by more than 70%, and total phosphorus is reduced by about 25%. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 It is a structural schematic diagram of the AAO sewage treatment system of the present invention.

[0061] Figure 2 It is a side view of the AAO sewage treatment system of the present invention.

[0062] Reference numerals:

[0063] 100: anaerobic tank;

[0064] 200: facultative oxygen pool;

[0065] 300: aerobic tank, 310: nitrification liquid submersible reflux pump;

[0066] 400: guide tube;

[0067] 500: thruster;

[0068] 600: degassing device, 610: macroporous aeration tube, 620: microporous aeration tube;

[0069] 700: water inlet pipe;

[0070] 800: Secondary sedimentation tank;

[0071] 900: Water outlet pipe. DETAILED DESCRIPTION

[0072] The following are specific embodiments of the present invention, and the technical solutions of the present invention are further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0073] refer to Figure 1 and Figure 2 As shown, in some embodiments of the present invention, the present invention provides an AAO sewage treatment system, comprising:

[0074] Anaerobic tank 100;

[0075] The facultative aerobic tank 200 is arranged around the outside of the anaerobic tank 100 and is connected to the anaerobic tank 100;

[0076] The aerobic pool 300 is arranged around the outside of the aerobic pool 200 and is connected to the aerobic pool 200;

[0077] The guide tube 400 is provided in the anaerobic tank 100;

[0078] The propeller 500 is provided in the anaerobic tank 100, the facultative aerobic tank 200 and the aerobic tank 300;

[0079] The degassing device 600 is provided in the aeration tank 200 .

[0080] It can be understood that in the AAO sewage treatment system of the present invention, the anaerobic tank is set in the middle, and the anaerobic tank is surrounded by a facultative aerobic tank and an aerobic tank, thereby saving land use. When the system is working, after the sewage to be treated is sent into the anaerobic tank, it diffuses from the surrounding areas of the anaerobic tank to the center of the anaerobic tank. The sludge is sent into the center of the anaerobic tank through the guide tube. Under the action of the propeller, the incoming water can be transferred from the surrounding areas of the anaerobic tank to the center of the anaerobic tank. At the same time, the sludge diffuses from the center of the anaerobic tank to the surrounding areas of the anaerobic tank. The sewage sent into the system and the returned sludge form convection, so that the mud and water are mixed more fully, thereby improving the effective volume utilization rate of the anaerobic tank. After treatment, the sewage is finally discharged from the aerobic tank.

[0081] Specifically, nitrogen is generated in the anoxic tank, and the density of the sludge in the sewage becomes smaller after being wrapped in nitrogen, so that it floats up. In the AAO sewage treatment system of the present invention, by adding a degassing device to the anoxic tank, the degassing device can form a degassing zone in the anoxic tank to remove the nitrogen on the sludge, changing the mixing mode of traditional aeration, which can not only separate the sludge floating up by denitrification from the nitrogen, but also use the rising effect of degassing to form a local upward and downward circulation, fully replacing the mud and water at the bottom of the anoxic tank. After the sludge in the sewage leaves the degassing zone, the sludge density increases and gradually sinks, gradually accumulating nitrogen in the denitrification process, obtaining the buoyancy force of the bubbles and slowly rising again until it enters the next degassing zone. During the water circulation process, the power and energy consumption of the propeller is reduced, and the mixing of mud and water in the anoxic tank is achieved. The system of the present invention is more energy-efficient. Based on the above improvements, the optimization of anaerobic and facultative hydraulic flow states in the AAO system can be achieved, and the residence time of the hydrolysis reaction can be effectively extended, the release of ammonia nitrogen can be advanced, the denitrification capacity of the system can be improved, and the hydrolysis of organic phosphorus and the removal rate of total phosphorus can also be improved.

[0082] It is understood that in the AAO sewage treatment system of the present invention, if there is no guide tube, due to the circular flow direction of the water in the anaerobic tank, the linear velocity of the water flow in the center of the anaerobic tank is lower than that in the surrounding area, and the sludge fed into the anaerobic tank will form a dead spot in the center of the tank bottom. The present invention places the guide tube in the center of the anaerobic tank, ensuring that the sludge can flow directly back to the center of the anaerobic tank, which is conducive to forming a disturbance in the central area of ​​the anaerobic tank, thereby adjusting the hydraulic flow pattern of the anaerobic tank and strengthening the water flow, thus solving the problem of sludge fed into the anaerobic tank forming a dead spot in the center of the tank bottom.

[0083] In some embodiments of the present invention, the anaerobic tank, the facultative aerobic tank, and the aerobic tank are all circular and have the same center.

[0084] It should be noted that the anaerobic tank, facultative aerobic tank and aerobic tank are all circular and have the same center. Without changing the tank volume ratio, the hydraulic flow state of the central circular anaerobic tank can be improved to return the sludge to the center point, so as to better realize the diffusion of the incoming water from the surroundings to the center and then from the center to the surroundings, forming convection and sufficient mixing with the returned sludge, further improving the effective volume utilization rate of the anaerobic tank and improving the sewage treatment efficiency.

[0085] In some embodiments of the present invention, the outlet of the guide tube is located at the center of the anaerobic tank. Such a design is more conducive to the sludge flowing back into the anaerobic tank to spread from the center of the anaerobic tank to the surrounding areas of the anaerobic tank.

[0086] In some embodiments of the present invention, the guide tube is a swirl guide tube, and the diameter ratio of the top and bottom of the swirl guide tube is 2 to 4:1.

[0087] The diameter ratio of the top and bottom of the swirl guide tube is 2 to 4:1, so that the swirl guide tube forms an inverted cone structure, which is conducive to further adjusting the hydraulic flow state of the anaerobic tank and strengthening the water flow.

[0088] In some embodiments of the present invention, the guide tube is a swirl guide tube, and the diameter ratio of the top and bottom of the swirl guide tube is 3 to 4:1.

[0089] In some embodiments of the present invention, the guide tube is a swirl guide tube, and the diameter ratio of the top and bottom of the swirl guide tube is about 3:1.

[0090] The diameter ratio of the top and bottom of the swirl guide tube is 3:1, which makes the swirl guide tube form an inverted cone structure, which is further conducive to adjusting the hydraulic flow state of the anaerobic tank and strengthening the water flow.

[0091] In some embodiments of the present invention, the distance between the bottom of the cyclone guide tube and the bottom of the anaerobic tank is 0.5m to 1m.

[0092] The distance between the bottom of the swirl guide tube and the bottom of the anaerobic tank is 0.5m to 1m, which is further conducive to adjusting the hydraulic flow state of the anaerobic tank and strengthening the water flow.

[0093] In some embodiments of the present invention, a swirl guide plate is provided in the swirl guide cylinder, and the arrangement direction of the swirl guide plate is parallel to the propulsion direction of the propeller.

[0094] The setting direction of the swirl guide plate is parallel to the propulsion direction of the propeller, which is conducive to forming a co-directional water flow, reducing the loss of kinetic energy of the water, and promoting the full mixing of mud and water in the center.

[0095] In some embodiments of the present invention, the bottom velocity of the push flow channel of the aerobic pool is greater than 0.2 m / min.

[0096] It should be noted that, generally speaking, relevant design specifications require that the ditch bottom flow velocity be greater than 0.3m / min (see industry standard HJ 578-2010 "Technical Specifications for Oxidation Ditch Activated Sludge Process Wastewater Treatment Engineering"). Since the degassing device in the system of the present invention strengthens the water flow, the bottom flow velocity of the aeration tank only needs to be greater than 0.2m / min. The power and energy consumption of the flow-pushing equipment, i.e., the propeller, is lower, and the system is more energy-efficient.

[0097] The propeller installed in the anaerobic tank can form a circulation of water flow, which can increase the linear velocity of the central water flow without increasing equipment and energy consumption, promote the mixing of sludge in the center of the anaerobic tank, and improve the effective volume utilization rate of the anaerobic tank.

[0098] The number of propellers in the anaerobic tank, the facultative aerobic tank and the aerobic tank can be 2-4 respectively.

[0099] In some embodiments of the present invention, the dissolved oxygen in the facultative oxygen tank is lower than 0.1 mg / L, or the redox potential is lower than -150 mv.

[0100] The dissolved oxygen in the facultative oxygen tank is lower than 0.1 mg / L, or the redox potential is lower than -150 mv, ensuring an anaerobic environment for the hydrolysis and acidification reaction.

[0101] In some embodiments of the present invention, the degassing device is a degassing tube, and the degassing tube is provided with degassing holes.

[0102] The degassing holes are located in the upper middle part of the degassing tube, the number of holes can be 6-10, and the bottom is sealed.

[0103] In some embodiments of the present invention, the diameter of the degassing holes on the degassing pipe in the facultative aeration tank is about 1 cm, which belongs to macropore aeration. The degassing pipe in the facultative aeration tank is a macropore aeration pipe 610.

[0104] It should be noted that in the prior art, the aeration holes in the aeration tank are relatively small in diameter, which is microporous aeration. The disturbance generated is small and it is impossible to effectively remove the bubbles on the sludge. Therefore, the main function of microporous aeration is to supply oxygen. In the present invention, unlike the microporous aeration in the prior art, the degassing holes on the degassing tube in the aeration tank are about 1 cm in diameter. The large diameter generates a large enough disturbance, so the bubbles on the sludge can be removed. The main function of macroporous aeration is degassing, rather than the oxygen supply function of microporous aeration in the prior art. Macroporous aeration can not only further reduce the oxygen enrichment of the aeration tank, prolong the hydrolysis reaction time, and increase the release rate of ammonia nitrogen. It can also promote the overflow of nitrogen generated by denitrification, and prevent sludge loss caused by sludge floating.

[0105] In some embodiments of the present invention, the diameter of the aeration holes in the aerobic tank is 80 μm to 100 μm, which is microporous aeration. The aeration pipe in the aerobic tank is a microporous aeration pipe 620 .

[0106] In some embodiments of the present invention, the aeration in the aerobic tank may also be other microporous aerator products.

[0107] In some embodiments of the present invention, a plurality of degassing pipes are arranged in the aeration tank along the radial direction of the aeration tank, and the interval between the plurality of degassing pipes is 5m to 7m.

[0108] In the aeration tank, the spacing between the degassing pipes is 5m to 7m, which is conducive to the formation of a degassing zone. It should be noted that the spacing between the degassing pipes can be adjusted according to the wastewater quality and water flow rate.

[0109] In some embodiments of the present invention, the degassing pipe is located in the aeration tank at a depth of 2 to 3 meters below the water surface.

[0110] It should be noted that if the degassing pipe of the aeration tank is installed too deep below the water surface, it will increase the dissolved oxygen in the water phase. Therefore, the degassing pipe of the aeration tank should be installed at a height of 2m to 3m below the water surface to help reduce the entry of dissolved oxygen into the water phase.

[0111] In some embodiments of the present invention, the degassing pipe may be divided into several branch pipes from one main pipe.

[0112] In some embodiments of the present invention, the AAO sewage treatment system further includes a water inlet pipe 700 , which is connected to the anaerobic tank 100 .

[0113] In some embodiments of the present invention, the AAO sewage treatment system further includes a sludge return pipe, one end of which is connected to the guide tube, and the other end of which is connected to the secondary sedimentation tank 800.

[0114] In some embodiments of the present invention, the sludge return pipe is close to one end of the guide tube and is perpendicular to the central axis of the guide tube.

[0115] The sludge return pipe is close to one end of the guide tube and is perpendicular to the central axis of the guide tube, ensuring that the returned sludge can cut into the guide tube in a horizontal direction.

[0116] The sludge can be cut into the guide tube horizontally, which is conducive to the formation of vortex flow.

[0117] In some embodiments of the present invention, the AAO sewage treatment system further includes an outlet pipe 900 , which connects the aerobic tank 900 and the secondary sedimentation tank 800 .

[0118] It is understood that after being treated by the AAO sewage treatment system of the present invention, the sewage flows into the secondary sedimentation tank. In the secondary sedimentation tank, sludge settles in the lower part of the secondary sedimentation tank, and the upper part of the secondary sedimentation tank is the supernatant. If the supernatant passes the test, it is discharged. If it fails, it is returned to the AAO sewage treatment system through the water inlet pipe for treatment. The sludge settled in the secondary sedimentation tank is sent back to the AAO sewage treatment system by the sludge return pump.

[0119] In some embodiments of the present invention, the sludge return ratio is 50%-100%.

[0120] It should be noted that the AAO wastewater treatment system of the present invention is suitable for treating fine chemical wastewater. Fine chemical wastewater refers to production wastewater, cleaning water, and pre-treated wastewater from fine chemical workshops. It includes process wastewater such as waste mother liquor, washing wastewater, recycle wastewater, neutralization wastewater, and wastewater pre-treated by Fenton oxidation, alkaline hydrolysis, electrocatalytic oxidation, and iron-carbon micro-electrolysis. Its components contain organic nitrogen and organic phosphorus.

[0121] It should also be noted that the present invention can be widely used in the biochemical treatment of various organic nitrogen and phosphorus chemical wastewaters, and has the functions of denitrification and phosphorus removal. By improving the anaerobic sludge return mode and the aerobic aeration mixing mode to design the degassing zone, the problems of easy sludge deposition in the anaerobic tank and easy floating of the aerobic sludge in the current traditional AAO process are solved, the hydrolysis reaction efficiency can be significantly improved, and the denitrification and phosphorus removal efficiency of the AAO process is further improved.

[0122] The AAO sewage treatment system of the present invention has a higher pool capacity utilization rate, better hydrolysis and acidification effect, more thorough release of ammonia nitrogen, and is more conducive to nitrification and denitrification in the aerobic and anoxic sections. Without increasing the pool capacity, the effluent COD is reduced by about 20%, the total nitrogen is reduced by about 46%, no ammonia nitrogen is detected, nitrate nitrogen is reduced by more than 70%, and total phosphorus is reduced by about 20%.

[0123] In the AAO wastewater treatment system of the present invention, water enters the anaerobic tank through an inlet pipe at a single point on the periphery of the tank. Two propellers rotate the water counterclockwise, with the tank outlet located 180° opposite the inlet. A sludge return pipe cuts horizontally through the top of the sludge return pipe, which is equipped with a guide plate. Returned sludge forms a swirl within the pipe before entering the anaerobic tank through the bottom opening.

[0124] The facultative aerobic and anaerobic tanks are connected. The facultative aerobic tank inlet is the same as the anaerobic tank outlet. The facultative aerobic tank is annular and equipped with four propellers. Water forms a circular flow within the facultative aerobic tank, with a flow rate of no less than 0.2 m / s. Two aeration branches are installed between each pair of propellers, each equipped with two large-pore aeration tubes. The bottom of the large-pore aeration tube is 2 m above the liquid surface, and the upper middle portion of the tube has 10 openings with a diameter of 1 cm. When aeration is activated, a deaeration zone approximately 2 m wide is formed along the water flow direction.

[0125] refer to Figure 2 As shown, the aerobic tank 300 and the facultative aerobic tank 200 are connected. It is understood that the inlet of the aerobic tank 300 (not shown) is the outlet of the facultative aerobic tank 200. The aerobic zone uses a traditional activated sludge process, with water flowing counterclockwise along the annular tank body, combining the advantages of plug flow and complete mixing. The nitrification liquid flows through perforations in the shared wall and is then returned from the aerobic tank 300 to the facultative aerobic tank 200 by a nitrification liquid submersible return pump 310, saving piping and reducing power losses along the way.

[0126] The technical solution of the present invention will be better understood with reference to specific embodiments below.

[0127] The water quality in a chemical wastewater distribution tank was 1200mg / L COD, 150mg / L total nitrogen, 38mg / L ammonia nitrogen, and 7.9mg / L total phosphorus. After treatment with the traditional AAO process, the effluent COD was approximately 300mg / L, total nitrogen approximately 65mg / L, ammonia nitrogen approximately 10mg / L, nitrate nitrogen 10-20mg / L, and total phosphorus 3mg / L.

[0128] The AAO wastewater treatment system of the present invention was used to treat the wastewater from the chemical plant. The specific parameters of the system are:

[0129] The radius of the anaerobic tank is 12m.

[0130] The radius of the aerobic pool is 18m.

[0131] The radius of the aerobic pool is 26m.

[0132] The diameter ratio of the top and bottom of the swirl guide tube is 3:1.

[0133] The distance between the bottom of the cyclone guide tube and the bottom of the anaerobic tank is 0.75m.

[0134] The bottom velocity of the push flow ditch in the aeration pool is greater than 0.2m / min.

[0135] The aeration holes are located in the upper middle part of the aeration pipe, there are 8 holes, and the bottom is sealed.

[0136] The diameter of the aeration holes in the aerobic tank is 1 mm.

[0137] The aeration in the aerobic tank uses the common microporous aeration membrane tube or microporous aerator on the market.

[0138] The distance between facultative aeration pipes is 6m. The distance between aerobic aeration pipes is 2m.

[0139] The aeration pipe is located 2.5m below the water surface in the aeration tank.

[0140] The water flow rate is 350m 3 / h.

[0141] The sludge return ratio is 100%.

[0142] The reflux ratio of the nitrifying liquid is 300%.

[0143] The measured COD of process effluent was less than 200 mg / L, total nitrogen was below 35 mg / L, no ammonia nitrogen was detected, nitrate nitrogen was 2-4 mg / L, and total phosphorus was 2-2.3 mg / L.

[0144] It can be seen that the AAO sewage treatment system of the present invention has a higher pool capacity utilization rate, better hydrolysis and acidification effect, more thorough release of ammonia nitrogen, and is more conducive to nitrification and denitrification in the aerobic and anoxic sections. Without increasing the pool capacity, compared with the traditional AAO process, the effluent COD is reduced by about 30%, the total nitrogen is reduced by about 50%, no ammonia nitrogen is detected, nitrate nitrogen is reduced by more than 70%, and total phosphorus is reduced by about 25%.

[0145] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Various changes can be made within the scope of knowledge possessed by ordinary technicians in the relevant technical field without departing from the spirit of the present invention.

Claims

1. An AAO sewage treatment system, characterized in that: include: Anaerobic tanks; an aerobic tank, the aerobic tank being arranged around the outside of the anaerobic tank and being connected to the anaerobic tank; an aerobic tank, the aerobic tank being arranged around the outside of the facultative aerobic tank and being in communication with the facultative aerobic tank; A guide tube is provided in the anaerobic tank; Propellers are provided in the anaerobic tank, the facultative aerobic tank and the aerobic tank; A degassing device is provided in the anoxic tank to form a degassing zone in the anoxic tank; The guide tube is a swirl guide tube, and the diameter ratio of the top to the bottom of the swirl guide tube is 2-4:1; a water inlet pipe, the water inlet pipe being connected to the anaerobic tank; A sludge return pipe, one end of which is connected to the guide tube and the other end is connected to the secondary sedimentation tank; an outlet pipe, the outlet pipe connecting the aerobic tank and the secondary sedimentation tank; When the AAO sewage treatment system is in operation, the sewage to be treated enters from a single point around the anaerobic tank, is sent into the anaerobic tank, and then diffuses from the periphery of the anaerobic tank to the center of the anaerobic tank, and flows out of the anaerobic tank from the outlet of the anaerobic tank; the sludge is sent to the center of the anaerobic tank through the guide tube; under the action of the propeller, the influent is transferred from the periphery of the anaerobic tank to the center of the anaerobic tank, and at the same time, the sludge diffuses from the center of the anaerobic tank to the periphery of the anaerobic tank, and the sewage sent into the system and the returned sludge form convection; After the sludge in the sewage leaves the degassing zone, the sludge density increases and it gradually sinks. During the denitrification process, nitrogen is accumulated and it slowly rises after obtaining the buoyancy of bubbles until it enters the next degassing zone.

2. The AAO sewage treatment system according to claim 1, characterized in that: The anaerobic tank, facultative aerobic tank and aerobic tank are all circular and have the same center.

3. The AAO sewage treatment system according to claim 1, characterized in that: The distance between the bottom of the cyclone guide tube and the bottom of the anaerobic tank is 0.5m~1m.

4. The AAO sewage treatment system according to claim 1, characterized in that: The degassing device is a degassing tube, and the degassing tube is provided with degassing holes.

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