Denitrification oxidation ditch

Abstract

The application relates to the technical field of sewage treatment, and discloses a denitrification oxidation ditch, which comprises a plurality of ring channels, the ring channels are sequentially sleeved from inside to outside, a channel is formed between two adjacent ring channels, the channel is divided into a first channel, a second channel and a third channel, the first channel and the third channel are both communicated with the second channel, the first channel is provided with a water inlet, the third channel is provided with a water outlet one, and the dissolved oxygen concentration ratio of the first channel, the second channel and the third channel is (0.5-1):(0-0.5):(2-3). Through the technical scheme, the problem of low total nitrogen removal efficiency of the outlet water of the Orbal oxidation ditch in the prior art is solved.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more specifically, to a denitrification oxidation ditch. Background Technology

[0002] The Aubel oxidation ditch is an activated sludge wastewater treatment process consisting of several concentric or elliptical ditches separated by ring channels. Each ditch is connected to a channel containing activated sludge, and each channel functions as an independent reactor. Rotary disc aeration is typically used, with the discs submerged to a certain depth. The rotation of the discs supplies oxygen to the oxidation ditch and propels the sludge-water mixture. A three-channel configuration is commonly used, with the dissolved oxygen concentrations in the first, second, and third channels increasing sequentially, typically 0 mg / L, 1.0 mg / L, and 2.0 mg / L respectively (this concentration usually indicates an anaerobic environment in the first channel, an anoxic environment in the second channel, and an aerobic environment in the third channel), to achieve carbon and nitrogen removal. While the Aubel oxidation ditch has advantages such as low sludge production, its inherent technical limitations, such as the inability to precisely control dissolved oxygen due to mechanical aeration, result in a lower total nitrogen removal efficiency compared to traditional A / B oxidation ditch processes. 2 O process.

[0003] The total nitrogen in the influent of wastewater treatment plants is mainly ammonia nitrogen, accounting for 70%-80% of the total nitrogen content. The remainder is some organic nitrogen. Organic nitrogen can be decomposed into ammonia nitrogen under both aerobic and anaerobic conditions. The basic principle of total nitrogen removal is as follows: Under aerobic conditions, organic nitrogen is converted into ammonia nitrogen. Ammonia nitrogen is then converted into nitrate nitrogen through nitrification by microorganisms. Nitrate nitrogen is converted into nitrogen gas by denitrifying bacteria in an anaerobic environment (generally considered to be dissolved oxygen below 0.5 mg / L) and a carbon source (electron donor), and is discharged from the water, thus achieving total nitrogen removal. Theoretically, the carbon-to-nitrogen ratio for denitrification by nitrifying bacteria is about 3:1. The carbon source can be provided by the organic matter in the influent. When the carbon-to-nitrogen ratio of the influent is low, additional carbon source needs to be added. Simultaneous nitrification and denitrification in oxidation ditches can make full use of the carbon source in the influent. However, due to the different dissolved oxygen concentrations required for nitrification and denitrification, the treatment efficiency of simultaneous nitrification and denitrification is relatively low.

[0004] With the tightening of wastewater treatment plant discharge standards in my country, some local standards have reduced the total nitrogen (TNO) discharge from 15 mg / L to 10 mg / L. This has placed significant pressure on wastewater treatment plants to meet TNO standards, especially those initially constructed using the Orbal oxidation ditch, where achieving TNO compliance is even more challenging. To achieve TNO compliance in the effluent, some improvements have been made to the existing Orbal oxidation ditch. For example, the surface aeration method has been changed to bottom aeration, and a sludge-water mixture return pump and carbon source addition point have been added, making its operation closer to that of A... 2The O process, while meeting the standards, also increases energy consumption and carbon source addition, and changes the original simultaneous nitrification and denitrification operation mode of the Orbel oxidation ditch.

[0005] Meanwhile, the Aubel oxidation ditch itself also has the following problems:

[0006] 1. The external channel is anaerobic, which has a good hydrolysis effect on the COD of the influent and the COD is significantly reduced. However, it does not significantly remove ammonia nitrogen. The dissolved oxygen concentration in the second channel is about 1 mg / L, which is greater than 0.5 mg / L. Nitrification is the main process. Under these conditions, ammonia nitrogen is converted into nitrate nitrogen. However, because the dissolved oxygen is higher than 0.5 mg / L, the denitrification efficiency is low and the removal of nitrate nitrogen is small. Therefore, the total nitrogen removal efficiency is low.

[0007] 2. The second channel has a smaller volume and a shorter simultaneous nitrification and denitrification reaction time, which also leads to a lower total nitrogen removal efficiency.

[0008] 3. The influent is mostly ammonia nitrogen, while the dissolved oxygen in the first channel is low. The external channel, which accounts for 60% of the total volume, only denitrifies the nitrates carried in the returned sludge to remove total nitrogen. The channel capacity is wasted, and the total nitrogen removal efficiency is still low when the carbon-nitrogen ratio is low and the returned nitrates are insufficient. Summary of the Invention

[0009] This invention proposes a denitrification oxidation ditch, which solves the problem of low total nitrogen removal efficiency in the effluent of the Aubel oxidation ditch in related technologies.

[0010] The technical solution of the present invention is as follows:

[0011] A denitrification oxidation ditch, comprising:

[0012] A plurality of ring channels are nested sequentially from the inside out, with a channel formed between adjacent ring channels. The channel is divided into a first channel, a second channel, and a third channel, and the first channel and the third channel are both connected to the second channel.

[0013] The first channel has an inlet, and the third channel has an outlet. The dissolved oxygen concentration ratio of the first channel, the second channel, and the third channel is (0.5-1):(0-0.5):(2-3).

[0014] As a further technical solution, there are four ring channels, namely a first ring channel, a second ring channel, a third ring channel, and a fourth ring channel. A first channel is formed between the first ring channel and the second ring channel, a second channel is formed between the second ring channel and the third ring channel, and a third channel is formed between the third ring channel and the fourth ring channel.

[0015] The inlet is located on the first ring channel, and the outlet is located on the fourth ring channel. The cross-sectional areas of the first ring channel, the second ring channel, the third ring channel, and the fourth ring channel gradually decrease.

[0016] As a further technical solution, it also includes:

[0017] A rotating shaft is rotatably mounted on the annular channel, and the rotating shaft passes through the first annular channel, the second annular channel, the third annular channel, and the fourth annular channel.

[0018] A plurality of discs are disposed on the rotating shaft, and the discs are distributed in both the first channel and the third channel.

[0019] As a further technical solution, there are two rotating shafts, which are symmetrically arranged, and several discs are symmetrically arranged on the rotating shafts. The relevant rotating shaft equipment is equipped with a frequency converter. Through the frequency converter, the rotation speed of the rotating shaft can be controlled, thereby controlling the speed and concentration of dissolved oxygen carried into the water by the discs during rotation, and controlling the dissolved oxygen concentration within a certain range.

[0020] As a further technical solution, in order to achieve an absolutely anaerobic environment in the second channel, it also includes:

[0021] A flow promoter is disposed within the second channel, and the flow promoter is used to propel the sludge flow within the second channel.

[0022] This is an underwater propeller located below the liquid surface. It achieves mud-water mixing and propulsion by underwater flow, avoiding the disc from rotating on the water surface and entraining oxygen into the water. This effectively achieves absolute anaerobic conditions in the second channel and makes it easier to control dissolved oxygen at (0-0.5) mg / L, thus realizing the denitrification reaction.

[0023] As a further technical solution, due to the large differences in wastewater concentration in wastewater treatment plants (variable indicators can change several times within a day), adjusting the disc rotation speed cannot adapt to large changes in dissolved oxygen, and the rotating shaft cannot achieve single-channel dissolved oxygen adjustment. To more precisely control the dissolved oxygen in the first channel, the following additional measures are also included:

[0024] Several aeration elements are spaced apart within the first channel. These aeration elements supply oxygen to the first channel and agitate the sludge within it. Specifically, each aeration element is a main pipe with several equally spaced branch pipes. A perforated aeration pipe is vertically installed at the end of each branch pipe. The perforation ratio of the perforated aeration pipe is 10-30%. When the dissolved oxygen in the first channel influent is low, the aeration device can supplement the system with a certain amount of dissolved oxygen. When the influent carbon-to-nitrogen ratio is relatively low, the system dissolved oxygen is relatively high, allowing the disc frequency to be reduced (reducing dissolved oxygen in both the first and third channels). Furthermore, some discs can be stopped, and the perforated aeration pipes can be activated to replace the discs for oxygen supply and agitation.

[0025] As a further technical solution, it also includes:

[0026] Carbon source inlet 1 and carbon source inlet 2 are provided. Carbon source inlet 1 is used to add carbon source to the first channel, and carbon source inlet 2 is used to add carbon source to the second channel. The carbon source flow rate ratio of carbon source inlet 1 and carbon source inlet 2 is (0-3):(5-9).

[0027] When the influent carbon-nitrogen ratio is relatively low, the carbon source dosage is increased in the first channel. When the influent carbon source (COD) is relatively sufficient, the carbon source dosage in the first channel is 0, and the carbon source is mainly added in the second channel.

[0028] As a further technical solution, the second channel has two water inlets, which are respectively located on the second ring channel and the third ring channel. The first channel and the third channel are both connected to the second channel through the water inlets.

[0029] As a further technical solution, it also includes:

[0030] The sedimentation tank includes a sedimentation tank and an effluent pipe. The sedimentation tank is connected to an outlet 1 via the effluent pipe. The sedimentation tank also has an outlet 2 and a sludge discharge outlet.

[0031] Two sludge return pipes are provided. One sludge return pipe is connected to the sedimentation tank at one end and to the first channel at the other end. The other sludge return pipe is connected to the sedimentation tank at one end and to the second channel at the other end.

[0032] The advantage of setting up two sludge return points here is that, since the sludge returned from the sedimentation tank contains nitrates, different nitrate return ratios can be achieved in the first and second channels by adjusting different sludge return ratios. This controls the amount of nitrates entering the first and second channels, and thus allows for artificial control of different nitrate denitrification degrees in the first and second channels. The sludge return ratios can be 1:1, 2:1, 1:2, etc. To facilitate ratio allocation, valves and flow meters can be installed on the sludge return pipes.

[0033] As a further technical solution, it also includes:

[0034] Three online monitoring instruments are used to monitor the dissolved oxygen concentration, ammonia nitrogen concentration, and nitrate concentration in the first channel, the second channel, and the third channel, respectively.

[0035] In addition to the above concentrations, pH levels can also be monitored. Online data feedback allows for understanding of the nitrification and denitrification status of the sludge (denitrification produces alkalinity, causing a pH increase; nitrification consumes alkalinity, causing a pH decrease), enabling better control of dissolved oxygen in each channel. When the dissolved oxygen in the first channel exceeds the set value, the disc rotation frequency is reduced to decrease oxygen injection into the water. Based on the sludge settling ratio, the perforated pipe can be opened (at this time, the oxygen utilization rate of the perforated pipe is low, and its main function is stirring the sludge) to agitate it.

[0036] The working principle and beneficial effects of this invention are as follows:

[0037] In this invention, to address the problems inherent in traditional Aubel oxidation ditches and their improved structures, a denitrification oxidation ditch is designed to achieve efficient denitrification. The basic denitrification technology principle is as follows: In wastewater treatment plant influent, ammonia nitrogen is the main component, accounting for 70%-80% of the total nitrogen content. The majority of the remainder is organic nitrogen. Organic nitrogen can decompose into ammonia nitrogen under both aerobic and anaerobic conditions. Under aerobic conditions, the ammonia nitrogen converted from organic nitrogen is transformed into nitrate nitrogen through microbial nitrification. Under anaerobic conditions (generally considered to be dissolved oxygen below 0.5 mg / L), nitrate nitrogen further reacts with denitrifying bacteria and carbon sources, becoming nitrogen gas which is discharged from the water, thus achieving the purpose of total nitrogen removal. Theoretically, the carbon-to-nitrogen ratio required for denitrification by nitrifying bacteria is approximately 3:1. The carbon source can be provided by the organic matter in the influent. When the carbon-to-nitrogen ratio of the influent is low, additional carbon source needs to be added.

[0038] This scheme still uses the commonly used three-channel form, utilizing four sets of concentric ring channels. Each pair of adjacent ring channels forms channels with different volumes, forming three channels with decreasing volumes in sequence: the first channel, the second channel, and the third channel. When the entire denitrification oxidation ditch is working, the sewage enters the first channel from the inlet, gradually flows into the second channel, and then flows from the second channel to the third channel. Finally, the sludge-water mixture is discharged from the outlet, and the sewage fully contacts and reacts with the activated sludge in the denitrification oxidation ditch.

[0039] This scheme aims to change the dissolved oxygen concentration from the outer ditch to the inner ditch from the traditional 0:1:2 to (0.5-1):(0-0.5):(2-3). The outer ditch maintains synchronous nitrification and denitrification reactions, the middle ditch maintains the dissolved oxygen level below 0.5 mg / L for denitrification, and the inner ditch has higher dissolved oxygen, providing an aerobic environment to facilitate nitrification. At the same time, the carbon source addition points are adjusted, changing the traditional method of adding carbon source at the influent to two addition points in the outer and middle ditches, with a carbon source addition flow rate ratio of (0-3):(5-9). Currently, through the above improvements, a water plant with a daily influent volume of 25,000 tons can reduce the carbon source addition from 10 tons per day to 4 tons per day, greatly reducing costs. Moreover, the total nitrogen in the effluent is 4-6 mg / L, far below the standard requirement of 10 mg / L.

[0040] Because the traditional Orbell oxidation ditch's second channel primarily focuses on nitrification with only partial denitrification and has a small volume, while the first channel, despite its large volume, lacks a high dissolved oxygen concentration and carries relatively little nitrate in the returned sludge, resulting in low total nitrogen removal efficiency, the inventors adjusted the dissolved oxygen concentration in each channel. This transformed the second channel into an anaerobic zone (primarily for denitrification), while the first channel, with its large volume and high dissolved oxygen levels within a set range, facilitated efficient simultaneous nitrification and denitrification. Under these conditions, ammonia nitrogen in the wastewater underwent nitrification directly within the first channel, consuming dissolved oxygen. Simultaneously, the low dissolved oxygen concentration allowed for simultaneous denitrification. The second channel maintained denitrification, and finally, nitrification continued in the third channel. This fully utilized the volume and dissolved oxygen concentration to improve the overall nitrogen removal efficiency. Attached Figure Description

[0041] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0042] Figure 1 This is a schematic diagram of the present invention;

[0043] Figure 2 This is a schematic diagram of the aeration element in this invention;

[0044] In the diagram: 1. First channel, 2. Second channel, 3. Third channel, 4. Inlet, 5. Outlet 1, 6. First ring channel, 7. Second ring channel, 8. Third ring channel, 9. Fourth ring channel, 10. Rotary shaft, 11. Disc, 12. Flow promoter, 13. Aeration component, 14. Carbon source inlet 1, 15. Carbon source inlet 2, 16. Water outlet, 17. Sedimentation tank, 18. Concealed effluent pipe, 19. Outlet 2, 20. Sludge discharge port, 21. Sludge return pipe, 22. Online monitoring instrument. Detailed Implementation

[0045] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0046] like Figure 1-2 As shown, this embodiment proposes a denitrification oxidation ditch, comprising:

[0047] Several ring channels are nested sequentially from the inside out, with adjacent ring channels forming a channel. The channel is divided into a first channel 1, a second channel 2, and a third channel 3. The first channel 1 and the third channel 3 are both connected to the second channel 2.

[0048] The first channel 1 has an inlet 4, and the third channel 3 has an outlet 5. The dissolved oxygen concentration ratio of the first channel 1, the second channel 2 and the third channel 3 is (0.5-1):(0-0.5):(2-3).

[0049] In this embodiment, to address the problems inherent in traditional Orbel oxidation ditches and their improved structures, a denitrification oxidation ditch was designed to achieve efficient denitrification. The basic denitrification technology principle is as follows: In wastewater treatment plant influent, ammonia nitrogen is the main component, accounting for 70-80% of the total nitrogen content. The remainder is mostly organic nitrogen. Organic nitrogen can be decomposed into ammonia nitrogen under both aerobic and anaerobic conditions. Under aerobic conditions, ammonia nitrogen converted from organic nitrogen is converted into nitrate nitrogen through microbial nitrification. Under anaerobic conditions (generally considered to be dissolved oxygen below 0.5 mg / L), nitrate nitrogen further reacts with denitrifying bacteria and carbon sources, becoming nitrogen gas which is discharged from the water, thus achieving the purpose of total nitrogen removal. Theoretically, the carbon-to-nitrogen ratio required for denitrification by nitrifying bacteria is approximately 3:1. The carbon source can be provided by the organic matter in the influent. When the influent carbon-to-nitrogen ratio is low, additional carbon source needs to be added.

[0050] This scheme still uses the commonly used three-channel form, utilizing four sets of ring channels arranged sequentially from the inside out. Each pair of adjacent ring channels forms channels with different volumes, forming a total of three channels with decreasing volumes, namely Channel 1, Channel 2, and Channel 3. When the entire denitrification oxidation ditch is working, the sewage enters Channel 1 from the inlet 4 of Channel 1, gradually flows into Channel 2, and then flows from Channel 2 to Channel 3. Finally, the sludge-water mixture is discharged from the outlet, and the sewage fully contacts and reacts with the activated sludge in the denitrification oxidation ditch.

[0051] This scheme aims to change the dissolved oxygen concentration from the outer ditch to the inner ditch from the traditional 0:1:2 to (0.5-1):(0-0.5):(2-3). The outer ditch maintains synchronous nitrification and denitrification reactions, the middle ditch has a dissolved oxygen level below 0.5 mg / L to facilitate denitrification, and the inner ditch has a higher dissolved oxygen level, providing an aerobic environment for nitrification. At the same time, the carbon source addition points are adjusted, changing the traditional method of adding carbon source at the influent to two addition points in the outer and middle ditches, with a carbon source addition flow rate ratio of (0-3):(5-9). Currently, through the above improvements, a water plant with a daily influent volume of 25,000 tons can reduce the carbon source addition from 10 tons per day to 4 tons per day, greatly reducing costs. Moreover, the total nitrogen in the effluent is 4-6 mg / L, far below the standard requirement of 10 mg / L.

[0052] Because the traditional Orber oxidation ditch's second channel 2 is primarily for nitrification with only partial denitrification and has a small volume, while the first channel 1 has a large volume, it lacks a high dissolved oxygen concentration, and the returned sludge carries relatively little nitrate, resulting in low total nitrogen removal efficiency. Therefore, the dissolved oxygen concentration in each channel is adjusted. The second channel 2 becomes an anaerobic zone (primarily for denitrification), while the first channel 1, with its large volume and dissolved oxygen within a set range, allows for efficient simultaneous nitrification and denitrification. Under these conditions, ammonia nitrogen in the wastewater undergoes nitrification directly in the first channel 1, consuming dissolved oxygen. Simultaneously, the low dissolved oxygen concentration also allows for simultaneous denitrification. The second channel 2 maintains denitrification, and finally, nitrification continues in the third channel 3. This fully utilizes the volume and dissolved oxygen concentration to improve the overall nitrogen removal efficiency.

[0053] Furthermore, there are four ring channels, namely a first ring channel 6, a second ring channel 7, a third ring channel 8, and a fourth ring channel 9. A first channel 1 is formed between the first ring channel 6 and the second ring channel 7, a second channel 2 is formed between the second ring channel 7 and the third ring channel 8, and a third channel 3 is formed between the third ring channel 8 and the fourth ring channel 9.

[0054] The inlet 4 is located on the first ring channel 6, and the outlet 5 is located on the fourth ring channel 9. The cross-sectional areas of the first ring channel 6, the second ring channel 7, the third ring channel 8, and the fourth ring channel 9 gradually decrease.

[0055] In this embodiment, four ring channels are specifically set as the first ring channel 6, the second ring channel 7, the third ring channel 8, and the fourth ring channel 9. The inlet 4 is set on the first ring channel 6 to facilitate the entry of sewage into the denitrification oxidation ditch, and the outlet 5 is set on the fourth ring channel 9 to facilitate the discharge of mud-water mixture without affecting others.

[0056] Furthermore, it also includes:

[0057] A rotating shaft 10 is rotatably mounted on the annular channel, and the rotating shaft 10 passes through the first annular channel 6, the second annular channel 7, the third annular channel 8, and the fourth annular channel 9.

[0058] A plurality of discs 11 are disposed on the rotating shaft 10, and the discs 11 are distributed in both the first channel 1 and the third channel 3.

[0059] Furthermore, there are two rotating shafts 10, symmetrically arranged, and several discs 11 are symmetrically arranged on the rotating shafts 10. Each rotating shaft 10 is equipped with a frequency converter, which can control the rotation speed of the rotating shaft 10, thereby controlling the speed and concentration of dissolved oxygen carried into the water by the discs 11 during rotation. The dissolved oxygen concentration can be controlled within a certain range. For newly built oxidation ditches, in order to better control dissolved oxygen, rotating shafts 10 can be arranged separately in each ditch. The rotating shafts 10 between ditches do not share the same motor and shaft. This arrangement facilitates individual control of dissolved oxygen in each ditch. However, due to individual control, each rotating shaft 10 needs to be installed with a separate motor and supporting equipment, which is inconvenient for management. In order to facilitate maintenance, more platforms and corridors must be set up near the rotating shafts 10 to realize equipment maintenance. The engineering design is complex and the cost is relatively high. In contrast, the first, second and third ditches share rotating shafts 10, the number of equipment is small, and it is easy to manage. For existing oxidation ditch renovation technologies, this solution only requires adding agitator and removing disc 11 in the second channel 2 to control dissolved oxygen and maintain mechanical aeration. It does not require water outages for construction, making it simple to operate. This provides a possibility for upgrading existing pollution control projects when water intake cannot be stopped, while converting to traditional A... 2 The O process not only has a long modification time, but also requires a large number of aeration heads and complicated installation, which requires water outages for construction and installation of aeration heads, making it impossible for some sewage treatment plants.

[0060] Furthermore, to achieve an absolutely anaerobic environment in the second channel 2, the following measures are also included:

[0061] A flow promoter 12 is disposed in the second channel 2, and the flow promoter 12 is used to promote the flow of sludge in the second channel 2.

[0062] The propeller 12 is an underwater propeller 12, located below the liquid surface. It achieves mud-water mixing and propulsion through underwater propulsion, preventing the disc 11 from rotating on the water surface and entraining oxygen into the water. This effectively achieves absolute anaerobic conditions in the second channel 2, and is more conducive to controlling dissolved oxygen at (0-0.5) mg / L to achieve denitrification.

[0063] In this embodiment, each channel in the traditional Aubel oxidation ditch is equipped with a disc 11. The rotation of the disc 11 causes the mud-water mixture to flow in a certain direction within the channel. At the same time, the rotation of the disc 11 carries oxygen from the air into the activated sludge, achieving different concentration gradients of oxygen supply and dissolved oxygen within the oxidation ditch. However, the discs 11 generally share a common shaft running through the outer, middle, and inner channels. This design, because the rotating shaft 10 rotates at the same speed in all three channels, makes it impossible to adjust the dissolved oxygen in each channel individually. Instead, it relies on different tank volumes to maintain a certain level of dissolved oxygen consumption. Furthermore, if the carbon source in the influent is low, the dissolved oxygen consumption is relatively low, which can easily lead to the inability to control the dissolved oxygen in the outer channel at a low level, thus failing to achieve the operating condition of a dissolved oxygen concentration ratio of 0:1:2.

[0064] Therefore, this scheme uses the rotation of the shaft 10 to drive the discs 11 distributed in the first channel 1 and the third channel 3 to rotate, thereby supplying oxygen to the channel and controlling the flow within the channel. The discs 11 in the second channel 2 are eliminated to ensure the anaerobic environment of the second channel 2. At the same time, in order to prevent the second channel 2 from becoming stagnant and causing sludge deposition, an underwater propeller 12 is further installed in the second channel 2 to promote the flow of sludge. Furthermore, the number and position of the shaft 10 and the discs 11 are designed to comprehensively improve the overall flowability and enhance the denitrification effect.

[0065] Furthermore, due to the large differences in wastewater concentration at the wastewater treatment plant (variable indicators changing exponentially within a day), adjusting the rotation speed of disc 11 is insufficient to accommodate significant changes in dissolved oxygen. Therefore, to more precisely control the dissolved oxygen in the first channel 1, the following additional measures are also included:

[0066] A plurality of aeration elements 13 are spaced apart in the first channel 1. The aeration elements 13 are used to supply oxygen to the first channel 1 and to stir the sludge in the first channel 1.

[0067] Specifically, the aeration element 13 refers to a main pipe with several equally spaced branch pipes. A perforated aeration pipe is vertically installed at the end of each branch pipe. The perforation ratio of the perforated aeration pipe is 10-30%. When the carbon-nitrogen ratio of the influent is relatively low, the dissolved oxygen in the first channel 1 is relatively high. The frequency of the disc 11 can be reduced. Furthermore, some discs 11 can be stopped, and the perforated aeration pipe can be turned on to replace the discs 11 for oxygen supply.

[0068] In this embodiment, several aeration elements 13 are spaced apart in the first channel 1 to provide oxygen and stir the sludge. This is to reduce the rotation speed of the shaft 10 when the dissolved oxygen demand is low. At this time, the operation of the aeration elements 13 directly stirs the sludge, without the need for the disc 11 to rotate to supply oxygen, thus ensuring the normal operation and flow of the whole system. At the same time, under the condition of low carbon-nitrogen ratio influent, the influent carbon source is relatively low, and the consumption of dissolved oxygen is relatively low. The aeration elements 13 can be activated to achieve dissolved oxygen at around 0.5-1 mg / L, thereby realizing the nitrification and denitrification reaction.

[0069] Furthermore, it also includes:

[0070] Carbon source inlet 14 and carbon source inlet 2 15 are provided. Carbon source inlet 14 is used to add carbon source to the first channel 1, and carbon source inlet 2 15 is used to add carbon source to the second channel 2. The mass ratio of carbon source added by carbon source inlet 14 and carbon source inlet 2 15 is (0-3):(5-9).

[0071] In this embodiment, two carbon source inlets are set in the first channel 1 and the second channel 2, and the carbon source inlet flow rate ratio of carbon source inlet 14 to carbon source inlet 15 is (0-3):(5-9). The carbon source is added synchronously with the sewage. When the carbon source in the sewage is high, the carbon source can be added only in the second channel 2 to achieve sufficient nitrification reaction in the second channel 2. When the carbon-nitrogen ratio of the influent is relatively low, the carbon source inlet is increased in the first channel 1. When the carbon source (COD) in the influent is sufficient, the carbon source inlet ratio in the first channel 1 is 0, and the carbon source is mainly added in the second channel 2.

[0072] For example: when the influent carbon-nitrogen ratio is higher than 4:1 (COD: total nitrogen) or COD is greater than 150 mg / L, carbon source is added only in the second channel 2; when the influent ratio is lower than 3:1 and COD is lower than 100 mg / L, a carbon source addition ratio of 3:5 or higher is adopted; when the influent ratio is between 3:1 and 4:1, a carbon source addition ratio of 2:6 is adopted.

[0073] Furthermore, the second channel 2 has two water inlets 16, which are respectively located on the second ring channel 7 and the third ring channel 8. The first channel 1 and the third channel 3 are both connected to the second channel 2 through the water inlets 16.

[0074] In this embodiment, water outlets 16 are respectively provided on the second ring channel 7 and the third ring channel 8 to facilitate the connection between the first channel 1 and the third channel 3 and the second channel 2, and to ensure the normal operation of the entire oxidation ditch.

[0075] Furthermore, it also includes:

[0076] The sedimentation tank 17 and the effluent pipe 18 are connected to the first effluent outlet 5 via the effluent pipe 18. The sedimentation tank 17 also has a second effluent outlet 19 and a sludge discharge outlet 20.

[0077] Two sludge return pipes 21 are provided. One sludge return pipe 21 is connected to the sedimentation tank 17 at one end and to the first channel 1 at the other end. The other sludge return pipe 21 is connected to the sedimentation tank 17 at one end and to the second channel 2 at the other end.

[0078] The advantage of setting up two sludge return points is that, since the sludge returned from the sedimentation tank contains nitrates, different nitrate return ratios can be achieved in the first channel 1 and the second channel 2 by adjusting different sludge return ratios. This controls the amount of nitrates entering the first channel 1 and the second channel 2, and thus allows for artificial control of different nitrate denitrification degrees in the first channel 1 and the second channel 2. The sludge return ratio can be 1:1, 2:1, 1:2, etc. To facilitate ratio allocation, valves and flow meters can be installed on the sludge return pipes.

[0079] When the sludge concentration in the oxidation ditch is relatively low and needs to be increased, prioritizing maintaining the sludge concentration, the sludge return flow rate in Channel 1 should be greater than that in Channel 2, for example, a return ratio of 2:1. During this process of maintaining a stable sludge concentration, if Channel 2 requires a large amount of nitrates, the sludge return ratio can be 1:2. Most of the sludge, carrying nitrates, is returned to Channel 2 for denitrification. This achieves the desired sludge concentration in Channel 1 while simultaneously providing nitrates for denitrification in Channel 2, with a return ratio of 1:1.

[0080] In this embodiment, after the mud-water mixture is discharged through outlet 5, it flows into the underground outlet pipe 18 to the sedimentation tank 17 for sedimentation. After sedimentation and separation of mud and water, the treated water is discharged from outlet 19, most of the mud is discharged from the sludge discharge port 20, and the remaining part of the sludge carrying nitrates is returned to the oxidation ditch. The Orber oxidation ditch usually returns directly to the first channel 1, where dissolved oxygen and nitrates are not fully utilized, and the nitrification and denitrification reactions are not sufficient. Therefore, two sludge return pipes 21 are set up. Under the premise that the dissolved oxygen concentration ratio of the first channel 1, the second channel 2 and the third channel 3 is (0.5-1):(0-0.5):(2-3), the sludge is returned to the first channel 1 and the second channel 2 respectively. The sludge returned to the first channel 1 ensures the nitrate concentration and realizes a small amount of simultaneous nitrification and denitrification reaction, making full use of the carbon source of the incoming water. The other part of the sludge returned to the second channel 2 undergoes further denitrification reaction, thereby greatly improving the denitrification effect.

[0081] Furthermore, it also includes:

[0082] Three online monitoring instruments 22 are used to monitor the dissolved oxygen concentration, ammonia nitrogen concentration, and nitrate concentration in the first channel 1, the second channel 2, and the third channel 3, respectively.

[0083] In addition to the above concentrations, pH value can also be monitored. Through online data feedback, the dissolved oxygen in each channel can be better controlled. When the dissolved oxygen in the first channel 1 is higher than the set value, the rotation frequency of disc 11 is reduced to reduce the amount of oxygen injected into the water. Depending on the sludge settling ratio, the perforated pipe can be opened (the perforated pipe has low oxygen utilization and mainly acts as a stirrer for the sludge) to stir the sludge.

[0084] In this embodiment, online monitoring instruments 22 are added to the three channels respectively to monitor the dissolved oxygen concentration and nitrogen concentration. The parameters of each stage are adjusted according to the conditions and indicators. The online measurement of ammonia nitrogen and nitrate can dynamically monitor the nitrification and denitrification reaction rate and treatment effect of each section of the oxidation ditch. The dissolved oxygen measurement value provides feedback on the oxygen concentration of each ditch in the system, which facilitates the control of the rotation speed of the disc 11 and the start and stop of the perforated aeration device.

[0085] A wastewater treatment plant requires an effluent total nitrogen concentration of 10 mg / L and a treatment capacity of 25,000 tons / day. The influent carbon source concentration is 60-100 mg / L, and the influent total nitrogen concentration is 30-35 mg / L. The effluent carbon source concentration is required to be 20 mg / L, and the total nitrogen concentration to be below 10 mg / L. Due to the low influent carbon-to-nitrogen ratio, liquid sodium acetate (equivalent to approximately 200,000 mg / L) is initially used as the supplementary carbon source at a daily dosage of 10-12 tons / day. When the effluent total nitrogen concentration is below 10 mg / L, and the carbon source dosage is below 8 tons / day, the effluent concentration exceeds 10 mg / L. However, after adjustments to the treatment plan, carbon source is initially added at both the external and internal channels. After stable operation, the amount added to the external channel is gradually reduced until only the internal channel is used, with a daily dosage of 3.8-4.2 tons. This results in an effluent total nitrogen concentration of approximately 7 mg / L, meeting the discharge standards.

[0086] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A denitrification oxidation ditch, characterized in that, include: Several ring channels are arranged sequentially from the inside to the outside, and a channel is formed between two adjacent ring channels. The channel is divided into a first channel (1), a second channel (2) and a third channel (3). The first channel (1) and the third channel (3) are both connected to the second channel (2). The first channel (1) has an inlet (4), and the third channel (3) has an outlet (5). The dissolved oxygen concentration ratio of the first channel (1), the second channel (2), and the third channel (3) is (0.5-1):(0-0.5):(2-3). There are four ring channels, namely the first ring channel (6), the second ring channel (7), the third ring channel (8) and the fourth ring channel (9). The first ring channel (6) and the second ring channel (7) form a first channel (1), the second ring channel (7) and the third ring channel (8) form a second channel (2), and the third ring channel (8) and the fourth ring channel (9) form a third channel (3). The inlet (4) is located on the first ring channel (6), and the outlet (5) is located on the fourth ring channel (9). The cross-sectional areas of the first ring channel (6), the second ring channel (7), the third ring channel (8), and the fourth ring channel (9) gradually decrease. Also includes: A rotating shaft (10) is rotatably mounted on the ring channel, and the rotating shaft (10) passes through the first ring channel (6), the second ring channel (7), the third ring channel (8) and the fourth ring channel (9). A plurality of discs (11) are disposed on the rotating shaft (10), and the discs (11) are distributed in both the first channel (1) and the third channel (3). There are two rotating shafts (10), which are symmetrically arranged, and a number of discs (11) are symmetrically arranged on the rotating shafts (10); A plurality of aeration elements (13) are spaced apart in the first channel (1). The aeration elements (13) are used to supply oxygen to the first channel (1) and to stir the sludge in the first channel (1).

2. The denitrification oxidation ditch according to claim 1, characterized in that, Also includes: A flow promoter (12) is disposed in the second channel (2) and is used to promote the flow of sludge in the second channel (2).

3. The denitrification oxidation ditch according to claim 1, characterized in that, Also includes: Carbon source inlet 1 (14) and carbon source inlet 2 (15) are provided. Carbon source inlet 1 (14) is used to add carbon source to the first channel (1), and carbon source inlet 2 (15) is used to add carbon source to the second channel (2). The carbon source inlet flow rate ratio of carbon source inlet 1 (14) and carbon source inlet 2 (15) is (0-3):(5-9).

4. The denitrification oxidation ditch according to claim 1, characterized in that, The second channel (2) has two inlets (16), which are respectively located on the second ring channel (7) and the third ring channel (8). The first channel (1) and the third channel (3) are both connected to the second channel (2) through the inlets (16).

5. A denitrification oxidation ditch according to claim 1, characterized in that, Also includes: The sedimentation tank (17) and the effluent pipe (18) are connected to the first effluent outlet (5) through the effluent pipe (18). The sedimentation tank (17) has a second effluent outlet (19) and a sludge discharge outlet (20). Two sludge return pipes (21), one of which is connected to the sedimentation tank (17) at one end and to the first channel (1) at the other end, and the other of which is connected to the sedimentation tank (17) at one end and to the second channel (2) at the other end.

6. The denitrification oxidation ditch according to claim 1, characterized in that, Also includes: Three online monitoring instruments (22) are used to monitor the dissolved oxygen concentration, ammonia nitrogen concentration and nitrate concentration of the first channel (1), the second channel (2) and the third channel (3), respectively.

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