Sewage treatment system and method for nitrogen and phosphorus removal through denitrification coupling of external carbon source and internal carbon source

Abstract

The invention discloses a sewage treatment system and method for nitrogen and phosphorus removal through denitrification coupling of an external carbon source and an internal carbon source. The sewage treatment system comprises a sewage inlet pipe channel I, a biochemical pool, a secondary sedimentation tank, an outer return pipe channel and an inner return pipe channel, the biochemical pool comprises an anaerobic zone, an anoxic zone I, an aerobic zone, an anoxic zone II and an aerobic-anoxic switching zone which are communicated in sequence, the sewage inlet pipe channel I is communicated with the anaerobic zone, and the secondary sedimentation tank is communicated with the aerobic zone; a sludge pipe at the bottom of the secondary sedimentation tank is communicated with the anaerobic zone through an outer return pipe channel, and the aerobic zone is communicated with the anoxic zone I through an inner return pipe channel. When the sewage treatment system is used for sewage treatment, the internal carbon source and the external carbon source are coupled, so that the carbon source in the domestic sewage can be fully utilized in situ, the removal degree and the removal rate of total nitrogen of a biochemical system are improved, the reflux quantity of sludge is remarkably reduced, and the sewage treatment efficiency is improved under the condition that no extra cost is increased. And the effluent quality is improved.

Description

Technical Field

[0001] The present application relates to the field of sewage treatment, and more specifically, to a sewage treatment system and method for denitrification and phosphorus removal by coupling denitrification with external and internal carbon sources. Background Art

[0002] With the rapid development of industry and agriculture and the improvement of people's living standards, the discharge of urban sewage is increasing. Since urban sewage contains a large amount of harmful substances, direct discharge will cause serious pollution to rivers, lakes and other water bodies. In particular, nitrogen and phosphorus-containing pollutants will cause eutrophication of water bodies, trigger excessive reproduction of algae and form algal blooms. Therefore, it is necessary to remove these harmful substances through sewage treatment to protect the cleanliness and safety of water resources.

[0003] The traditional denitrification and phosphorus removal process is the AAO (anaerobic-anoxic-aerobic) process, which is based on the traditional denitrification and phosphorus removal theory. Different functional units are set according to the characteristics of different functional bacteria. The anaerobic unit releases phosphorus through polyphosphate bacteria; the anoxic unit uses denitrifying bacteria to complete denitrification; and the aerobic unit performs nitrification and phosphate absorption. The AAO process is widely used because it takes into account both denitrification and phosphorus removal functions and has stable effects. However, this process mainly relies on the use of external carbon sources at the front end of the nitrification liquid return to remove nitrogen and phosphorus. This results in its denitrification efficiency not only being restricted by the return volume of the nitrification liquid, but also the phenomenon of insufficient utilization of the in-situ carbon source of the sewage. Even if the return volume of the nitrification liquid is infinitely increased, the improvement of the total nitrogen removal rate is still limited; in addition, due to the unsatisfactory denitrification effect, the sludge returned from the secondary sedimentation tank carries a large amount of nitrate nitrogen, which inhibits the release of phosphorus by polyphosphate bacteria in the anaerobic tank, resulting in poor phosphorus removal.

[0004] In order to improve the shortcomings of the AAO process, people have studied a new type of denitrification and phosphorus removal process, namely the AOA (anaerobic-aerobic-anoxic) process. This process is based on the AAO process, with the anoxic tank placed after the aerobic tank, and the nitrification liquid return is cancelled. At the same time, the sludge in the secondary sedimentation tank is double-returned, that is, returned to the anaerobic zone and the anoxic zone, and the carbon source in the polyphosphate and polysaccharide bacteria is used for deep denitrification and phosphorus removal. It has great advantages and application prospects in the treatment of low C / N urban sewage. However, the AOA process still has the following problems: (1) Since the core of the AOA process is the conversion and storage of carbon sources by saccharide-accumulating bacteria in the anaerobic zone, it focuses on denitrification of internal carbon sources, which makes the total nitrogen removal rate of the process low, and inhibits the activity of polyphosphate-accumulating bacteria in the anaerobic zone, resulting in general phosphorus removal effect of the process; (2) In order to achieve good carbon source conversion and storage effects, the return volume of the sludge double recirculation in the AOA process needs to be 200-300% of the sewage inlet volume, while the designed sludge return volume of the secondary sedimentation tank is generally 50-100%, which leads to a high solid flux in the secondary sedimentation tank and poor sludge settling and concentration performance, which is not conducive to the stability of the secondary sedimentation tank. Summary of the invention

[0005] In order to solve the above technical problems, the present application provides a sewage treatment system and method for denitrification and phosphorus removal by coupling denitrification with external carbon sources and internal carbon sources.

[0006] The external carbon source and the internal carbon source of the present application are both carbon sources from domestic sewage, and the external carbon source is not an organic carbon source that is additionally added to the system, such as methanol, ethanol, and glucose.

[0007] In the first aspect, the present application provides a sewage treatment system that utilizes external carbon source and internal carbon source for denitrification coupling denitrification and phosphorus removal, which adopts the following technical solution: A sewage treatment system for denitrification and phosphorus removal by coupling external and internal carbon sources, comprising a sewage inlet channel I, a biochemical pool, a secondary sedimentation tank, an external return channel and an internal return pipe, wherein the biochemical pool comprises an anaerobic zone, an anoxic zone I, an aerobic zone, an anoxic zone II and an aerobic-anoxic switching zone which are sequentially connected, the sewage inlet channel I is connected to the anaerobic zone, the bottom sludge pipe of the secondary sedimentation tank is connected to the anaerobic zone via an external return channel, and the aerobic zone is connected to the anoxic zone I via an internal return channel.

[0008] Preferably, the anoxic zone I is also connected to a sewage inlet channel II.

[0009] In the second aspect, the present application provides a wastewater treatment method for denitrification and phosphorus removal by coupling denitrification with external carbon sources and internal carbon sources, which adopts the following technical scheme: A sewage treatment method for denitrification and phosphorus removal by coupling denitrification with an external carbon source and an internal carbon source comprises the following steps: S1. The domestic sewage to be treated is passed into the anaerobic zone and mixed with the return sludge from the secondary sedimentation tank for reaction; S2, passing the domestic sewage treated in the anaerobic zone into the anoxic zone I to react with the return domestic sewage from the aerobic zone, then passing it into the aerobic zone for reaction, and then passing it into the anoxic zone II for reaction; S3. The domestic sewage treated in the anoxic II zone is passed into the aerobic-anoxic switching zone for aeration treatment to increase the dissolved oxygen concentration, and then passed into the secondary sedimentation tank for mud-water separation to obtain return sludge and supernatant. The supernatant is discharged from the secondary sedimentation tank and the return sludge is passed into the anaerobic zone.

[0010] Through the above technical scheme, the present application introduces the domestic sewage to be treated into the anaerobic zone of the biochemical pool through the sewage inlet pipe I, mixes it with the return sludge from the secondary sedimentation tank, and mainly utilizes polyphosphate bacteria to release phosphorus biologically as an internal carbon source in the anaerobic zone; then the domestic sewage treated in the anaerobic zone is continuously introduced into the anoxic zone I, and the return sludge from the secondary sedimentation tank entering the anoxic zone from the anaerobic zone is mainly used to denitrify the anoxic zone I by denitrification of the external carbon source, and at the same time, the polysaccharide bacteria transform and store the organic matter in the domestic sewage to be treated; then continue The domestic sewage treated in the anoxic zone I is passed into the aerobic zone, where nitrifying bacteria are used to oxidize the ammonia nitrogen in the domestic sewage into nitrate nitrogen, and polyphosphate bacteria perform aerobic phosphorus absorption; then the domestic sewage is continued to be passed into the anoxic zone II, where the internal carbon source of denitrifying polysaccharide bacteria is used to perform denitrification to achieve deep denitrification; then the domestic sewage treated in the anoxic zone II is passed into the aerobic-anoxic switching zone for aeration to remove nitrogen from the domestic sewage and increase the dissolved oxygen concentration to reduce the release of phosphorus in the sludge of the secondary sedimentation tank. The domestic sewage after the aerobic-anoxic switching zone is discharged into the secondary sedimentation tank for mud and water separation to obtain return sludge and supernatant. The supernatant is discharged from the secondary sedimentation tank and enters the deep treatment system for subsequent treatment, and the return sludge is passed into the front end of the anaerobic zone through the sludge pump.

[0011] The present application gives full play to the coordination between different functional units by reasonably setting up each unit in the biochemical pool, so that polyphosphate bacteria can fully release phosphorus in the anaerobic zone, reducing the possibility of the activity of polyphosphate bacteria being inhibited, and at the same time, polysaccharide bacteria can fully convert the external carbon source into the internal carbon source, and use the converted internal carbon source to carry out deep denitrification in the anoxic II zone, which greatly improves the removal rate of total nitrogen and total phosphorus in domestic sewage. And the present application comprehensively utilizes external carbon source denitrification and internal carbon source denitrification, which greatly improves the removal rate of total nitrogen compared to only using internal carbon source denitrification. In addition, since the present application still has a high total nitrogen removal rate and total phosphorus removal rate without adding any additional organic carbon source, the processing cost of denitrification and phosphorus removal is reduced without adding any additional cost, and the effluent water quality is improved.

[0012] Preferably, in step S1, the reaction time of the anaerobic zone is 0.5-3.0 hours, and the volume ratio of the return sludge from the secondary sedimentation tank to the domestic sewage to be treated is 50-200%.

[0013] Through the above technical scheme, compared with the traditional AOA process, the present application significantly reduces the sludge return volume of the secondary sedimentation tank, reduces the solid flux of the secondary sedimentation tank, improves the sedimentation and concentration performance of the sludge, and enhances the stability of the secondary sedimentation tank.

[0014] Preferably, in step S2, domestic sewage to be treated is also directly introduced into the anoxic zone I.

[0015] Through the above technical scheme, the present application can also directly introduce the domestic sewage to be treated into the anoxic zone I through the sewage inlet pipe II, and mix and react with the domestic sewage treated in the anaerobic zone, thereby further balancing the C / N of the domestic sewage in the anoxic zone I, which is beneficial to improving the removal rate of total nitrogen and total phosphorus.

[0016] Preferably, in step S2, the volume ratio of the returned domestic sewage from the aerobic zone in the anoxic zone I to the domestic sewage treated in the anaerobic zone is less than or equal to 400%.

[0017] Preferably, in step S2, the reaction time of the anoxic zone I is greater than or equal to 1 hour.

[0018] Through the above technical scheme, the present application introduces the domestic sewage treated in the aerobic zone into the anoxic zone I through the internal reflow pipe and mixes it with the domestic sewage treated in the anaerobic zone, thereby providing the anoxic zone I with nitrate nitrogen as a substrate for denitrification of the external carbon source, so that the external carbon source that has not been converted into the internal carbon source can be used for denitrification and denitrification of the system in a timely manner, and the denitrification of the external carbon source can be fully utilized to increase the total nitrogen removal rate.

[0019] Preferably, in step S2, the reaction time in the aerobic zone is 2-8 hours.

[0020] Preferably, in step S2, the reaction time of the anoxic zone II is greater than or equal to 2 hours.

[0021] Preferably, in step S3, the aerobic-anoxic switching zone realizes the functional switching of the biochemical reaction by installing an agitator and an aeration device.

[0022] The start and stop of the agitator and aeration device are controlled by the nitrate nitrogen sensor installed in the anoxic zone II. Specifically, the nitrate nitrogen sensor, agitator and aeration device are all connected to the automatic control system. The nitrate nitrogen sensor transmits the detected nitrate nitrogen concentration to the automatic control system, and the automatic control system automatically adjusts the start and stop of the agitator and aeration device according to the nitrate nitrogen concentration signal. When the nitrate nitrogen concentration is lower than the critical value of the nitrate nitrogen concentration, the automatic control system turns off the agitator and turns on the aeration device; when the nitrate nitrogen concentration is higher than the critical value of the nitrate nitrogen concentration, the automatic control system turns on the agitator and turns off the aeration device.

[0023] The aeration volume of the aeration device is controlled by the ammonia nitrogen sensors installed in the aerobic zone and the anoxic zone II. Specifically, the ammonia nitrogen sensors are connected to the automatic control system, and the ammonia nitrogen sensors accurately detect the ammonia nitrogen concentration at the end of the aerobic zone and the end of the anoxic zone II. The automatic control system automatically adjusts the aeration volume by receiving the ammonia nitrogen concentration signal to avoid excessive or insufficient aeration.

[0024] Preferably, in step S3, the aeration treatment time is 0.5-2.0 hours, and the dissolved oxygen content in the domestic sewage after aeration treatment is greater than 0.2 mg / L.

[0025] In summary, this application has the following beneficial technical effects: 1. The sewage treatment method of the present application fully utilizes the carbon source in domestic sewage in situ by coupling the denitrification and denitrification of internal carbon sources and external carbon sources, thereby improving the degree and rate of total nitrogen removal in the biochemical system. In addition, due to the efficient denitrification effect, the concentration of nitrate nitrogen in the return sludge of the secondary sedimentation tank is extremely low, which reduces the possibility of inhibition of anaerobic phosphorus release by polyphosphate bacteria. At the same time, the synergistic effect of internal carbon sources and external carbon sources is combined to improve the anaerobic phosphorus release effect of polyphosphate bacteria, thereby significantly improving the removal efficiency of total phosphorus in the biochemical system. 2. The sewage treatment method of the present application makes full use of the internal carbon source of glycogen-accumulating bacteria and phosphate-accumulating bacteria for denitrification and phosphorus release, significantly reduces the sludge return volume, reduces the solid flux of the secondary sedimentation tank, improves the sedimentation and concentration performance of the sludge, and enhances the stability of the secondary sedimentation tank; 3. The sewage treatment method of the present application fully and in situ utilizes the carbon source in domestic sewage, and still has a high total nitrogen removal rate and total phosphorus removal rate without adding additional organic carbon sources. Therefore, without adding any additional costs, it reduces the treatment cost of nitrogen and phosphorus removal and improves the effluent water quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the flow of the sewage treatment system of the present application; Figure 2 It is a scatter diagram of the total nitrogen concentration of the inlet and outlet water of the biochemical pool in the sewage treatment system of this application; Figure 3 It is a scatter diagram of the total phosphorus concentration in the inlet and outlet of the biochemical pool in the sewage treatment system of this application. DETAILED DESCRIPTION

[0027] The following is combined with Figure 1-3 The present application is further described in detail with reference to the following embodiments and comparative examples.

[0028] The sewage treatment method of the embodiment of the present application is carried out by using a sewage treatment system, such as Figure 1As shown, a sewage treatment system for denitrification and phosphorus removal by coupling denitrification with external carbon source and internal carbon source includes a sewage inlet channel I, a sewage inlet channel II, a biochemical pool, a secondary sedimentation tank, an internal return channel and an external return channel, wherein the biochemical pool includes an anaerobic zone, an anoxic zone I, an aerobic zone, an anoxic zone II and an aerobic-anoxic switching zone connected in sequence, and the anaerobic zone, anoxic zone I, aerobic zone, anoxic zone II and anoxic-anoxic switching zone are realized in sequence by gravity flow. The reaction front ends of the anaerobic zone and the anoxic zone I are both provided with sewage inlets, the sewage inlet channel I is connected to the sewage inlet of the anaerobic zone, and the sewage inlet channel II is connected to the sewage inlet of the anoxic zone I. The reaction end of the aerobic zone is connected to the reaction front end of the anoxic zone I through the internal return channel, and the bottom sludge pipe of the secondary sedimentation tank is connected to the front end of the anaerobic zone through the external return channel. An ammonia nitrogen sensor is provided in the aerobic zone, an ammonia nitrogen sensor and a nitric nitrogen sensor are provided in the anoxic II zone, and an agitator and an aeration device are provided in the aerobic-anoxic switching zone. The ammonia nitrogen sensor, the nitric nitrogen sensor, the agitator and the aeration device are all connected to the automatic control system. The automatic control system controls the start and stop of the agitator and the aeration device and automatically adjusts the aeration volume of the aeration device according to the ammonia nitrogen concentration and nitric nitrogen concentration signals sent by the ammonia nitrogen sensor and the nitric nitrogen sensor. A water outlet is provided at the top of the secondary sedimentation tank, and a water outlet pipe is connected to the water outlet, and the water outlet pipe is connected to the deep treatment system. Example

[0029] A sewage treatment method for denitrification and phosphorus removal by coupling denitrification with an external carbon source and an internal carbon source comprises the following steps: S1. The designed sewage treatment system has a treatment capacity of 225,000 m 3 / day, the domestic sewage to be treated is introduced into the anaerobic zone and the anoxic zone I through the sewage inlet pipe I and the sewage inlet pipe II respectively, the water volume ratio of the domestic sewage entering the anaerobic zone through the sewage inlet pipe I and the domestic sewage entering the anoxic zone I through the sewage inlet pipe II is remotely controlled by valves and flow meters, and the domestic sewage is mixed with the return sludge from the secondary sedimentation tank in the anaerobic zone for 0.5-3.0 hours, and the volume ratio of the return sludge from the secondary sedimentation tank to the domestic sewage to be treated is 50-200%; S2, passing the domestic sewage treated in the anaerobic zone into the anoxic zone I for reaction, the reaction time is greater than or equal to 1 hour, and then passing it into the aerobic zone for reaction for 2-8 hours, the domestic sewage treated in the aerobic zone is passed into the anoxic zone I through the internal return pipe, the volume ratio of the returned domestic sewage to the domestic sewage treated in the anaerobic zone is 0-400%, and then passing it into the anoxic zone II for reaction, the reaction time is greater than or equal to 2 hours; S3. The domestic sewage treated in the anoxic II zone is passed into the aerobic-anoxic switching zone for aeration treatment to increase the dissolved oxygen concentration. The aeration treatment time is 0.5-2.0 hours. The dissolved oxygen content in the domestic sewage after aeration treatment is greater than 0.2 mg / L. It is then passed into the secondary sedimentation tank for mud-water separation to obtain return sludge and supernatant. The supernatant is discharged from the outlet pipe to the secondary sedimentation tank and enters the deep treatment system for subsequent treatment. The return sludge is passed from the bottom sludge pipe of the secondary sedimentation tank through the sludge pump into the front end of the anaerobic zone.

[0030] According to the above method, the system was stably operated for 218 days. During the operation, the inlet water quality (TN content and TP content) of the sewage inlet channel I and the sewage inlet channel II and the effluent water quality (TN content and TP content) of the aerobic-anoxic switching zone were tested every day, and the parameter changes of each step were adjusted within the above range according to the actual test results of the day, such as the water ratio of domestic sewage entering the anaerobic zone through the sewage inlet channel I and the domestic sewage entering the anoxic zone I through the sewage inlet channel II, the time for the mixed reaction of domestic sewage and the return sludge from the secondary sedimentation tank in the anaerobic zone, the volume ratio of the return sludge from the secondary sedimentation tank to the domestic sewage to be treated, the reaction time of the anoxic zone I, the reaction time of the aerobic zone, the volume ratio of the return domestic sewage to the domestic sewage treated in the anaerobic zone, the reaction time of the anoxic zone II, the time of aeration treatment, etc. The test results are as follows: Figure 2-3 shown.

[0031] from Figure 2-3 It can be seen that during the operation of the sewage treatment system of this application, the specific water quality of the inlet water is: TN 16.4-64.7mg / L, TP 0.95-15.5mg / L. After 218 days of stable operation, it was tested that the TN of the effluent from the aerobic-anoxic switching zone was 3.87mg / L on average, the TP was 0.28mg / L on average, the average removal rate of total nitrogen was 87%, and the average removal rate of total phosphorus was 93%. Without the addition of an additional organic carbon source, the supernatant discharged from the outlet pipe of the secondary sedimentation tank can reach the quasi-fourth category standard after the deep treatment system, where TN ≤ 10mg / L.

[0032] Comparative Example 1 The AAO process is used for sewage treatment, which specifically includes the following steps: S1. The designed sewage treatment system has a treatment capacity of 225,000 m 3 / day, the domestic sewage to be treated is passed into the anaerobic zone, where the domestic sewage is mixed with the return sludge from the secondary sedimentation tank for reaction for 0.5-3.0h, and the volume ratio of the return sludge from the secondary sedimentation tank to the domestic sewage to be treated is 50-200%; S2. The domestic sewage treated in the anaerobic zone is passed into the anoxic zone for reaction for a reaction time of 2 hours or more, and then passed into the aerobic zone for reaction for 2-8 hours. The domestic sewage treated in the aerobic zone is passed into the anoxic zone through the internal return pipe, and the volume ratio of the returned domestic sewage to the domestic sewage treated in the anaerobic zone is 0-400%; S3. The domestic sewage treated in the aerobic zone is passed into the aerobic-anoxic switching zone for aeration treatment to increase the dissolved oxygen concentration. The aeration treatment time is 0.5-2.0h. The dissolved oxygen content in the domestic sewage after aeration treatment is greater than 0.2mg / L. It is then passed into the secondary sedimentation tank for mud-water separation to obtain return sludge and supernatant. The supernatant is discharged from the outlet pipe to the secondary sedimentation tank and enters the deep treatment system for subsequent treatment. The return sludge is passed from the bottom sludge pipe of the secondary sedimentation tank through the sludge pump into the front end of the anaerobic zone.

[0033] According to the above method, the system was stably operated for 218 days. During the operation, the influent water quality (TN content and TP content) of the anaerobic zone and the effluent water quality (TN content and TP content) of the aerobic-anoxic switching zone were tested every day, and the parameter changes of each step were adjusted within the above range according to the actual test results of the day, such as the time for the mixed reaction of domestic sewage and the return sludge from the secondary sedimentation tank in the anaerobic zone, the volume ratio of the return sludge from the secondary sedimentation tank to the domestic sewage to be treated, the reaction time of the anoxic zone, the reaction time of the aerobic zone, the volume ratio of the return domestic sewage to the domestic sewage treated in the anaerobic zone, the aeration treatment time, etc. After testing, after 218 days of stable operation, the TN of the effluent of the aerobic-anoxic switching zone of Comparative Example 1 was 7.89 mg / L on average, and the TP was 0.95 mg / L on average.

[0034] Comparative Example 2 The AOA process is used for sewage treatment, which specifically includes the following steps: S1. The designed sewage treatment system has a treatment capacity of 225,000 m 3 / day, the domestic sewage to be treated is passed into the anaerobic zone, where the domestic sewage is mixed with the return sludge from the secondary sedimentation tank for reaction for 0.5-3.0h, and the volume ratio of the return sludge from the secondary sedimentation tank to the domestic sewage to be treated is 50-200%; S2. The domestic sewage treated in the anaerobic zone is passed into the aerobic zone for reaction for 2-8 hours, and then passed into the anoxic zone to react with the return sludge from the secondary sedimentation tank in the anoxic zone. The reaction time is greater than or equal to 2 hours, and the volume ratio of the return sludge from the secondary sedimentation tank to the domestic sewage treated in the aerobic zone is 50-200%; S3. The domestic sewage treated in the anoxic zone is passed into the aerobic-anoxic switching zone for aeration treatment to increase the dissolved oxygen concentration. The aeration treatment time is 0.5-2.0h. The dissolved oxygen content in the domestic sewage after aeration treatment is greater than 0.2mg / L. It is then passed into the secondary sedimentation tank for mud-water separation to obtain return sludge and supernatant. The supernatant is discharged from the outlet pipe to the secondary sedimentation tank and enters the deep treatment system for subsequent treatment. The return sludge is passed from the bottom sludge pipe of the secondary sedimentation tank through the sludge pump into the front end of the anaerobic zone.

[0035] According to the above method, the system was stably operated for 218 days. During the operation, the influent water quality (TN content and TP content) of the anaerobic zone and the effluent water quality (TN content and TP content) of the aerobic-anoxic switching zone were tested every day, and the parameter changes of each step were adjusted within the above range according to the actual test results of the day, such as the time for the mixed reaction of domestic sewage and the return sludge from the secondary sedimentation tank in the anaerobic zone, the volume ratio of the return sludge from the secondary sedimentation tank to the domestic sewage to be treated, the reaction time of the aerobic zone, the reaction time of the anoxic zone, the volume ratio of the return sludge from the secondary sedimentation tank to the domestic sewage treated in the aerobic zone, the time of aeration treatment, etc. After testing, after 218 days of stable operation, the TN of the effluent of the aerobic-anoxic switching zone of Comparative Example 2 was 5.17 mg / L on average, and the TP was 0.56 mg / L on average. On this basis, the system continued to be operated. After running for 268 days, the TN of the effluent was 4.86 mg / L on average, and the TP was 0.48 mg / L on average.

[0036] In summary, compared with the traditional AAO and AOA processes, the sewage treatment method of the present application has lower TN and TP contents in the effluent of the aerobic-anoxic switching zone under the same operating time, and the operating time to reach the lower content is shorter, thereby achieving deep denitrification and phosphorus removal, and has a higher total nitrogen removal rate, total phosphorus removal rate and removal efficiency.

[0037] The embodiments of this specific implementation method are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. Therefore, all equivalent changes made based on the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A sewage treatment system utilizing denitrification and denitrification coupling of external carbon sources and internal carbon sources, characterized in that: It includes a sewage inlet channel I, a biochemical pool, a secondary sedimentation tank, an external return channel and an internal return channel. The biochemical pool includes an anaerobic zone, an anoxic zone I, an aerobic zone, an anoxic zone II and an aerobic-anoxic switching zone which are connected in sequence. The sewage inlet channel I is connected to the anaerobic zone. The bottom sludge pipe of the secondary sedimentation tank is connected to the anaerobic zone through an external return channel. The aerobic zone is connected to the anoxic zone I through an internal return channel.

2. A sewage treatment system for denitrification and phosphorus removal using external carbon sources and internal carbon sources according to claim 1, characterized in that: The anoxic zone I is also connected to a sewage inlet pipeline II.

3. A sewage treatment method using denitrification and denitrification coupling of external carbon sources and internal carbon sources, characterized in that: The following steps are involved: S1. The domestic sewage to be treated is passed into the anaerobic zone and mixed with the return sludge from the secondary sedimentation tank for reaction; S2, passing the domestic sewage treated in the anaerobic zone into the anoxic zone I to react with the return domestic sewage from the aerobic zone, then passing it into the aerobic zone for reaction, and then passing it into the anoxic zone II for reaction; S3. The domestic sewage treated in the anoxic II zone is passed into the aerobic-anoxic switching zone for aeration treatment to increase the dissolved oxygen concentration, and then passed into the secondary sedimentation tank for mud-water separation to obtain return sludge and supernatant. The supernatant is discharged from the secondary sedimentation tank and the return sludge is passed into the anaerobic zone.

4. A method for treating wastewater by denitrification and dephosphorization coupled with external carbon source and internal carbon source according to claim 3, characterized in that: In the step S1, the reaction time of the anaerobic zone is 0.5-3.0 hours, and the volume ratio of the return sludge from the secondary sedimentation tank to the domestic sewage to be treated is 50-200%.

5. The method for treating sewage by denitrification and dephosphorization coupled with external and internal carbon sources according to claim 3, characterized in that: In the step S2, domestic sewage to be treated is also directly introduced into the anoxic zone I.

6. The method for treating sewage by denitrification and dephosphorization coupled with external and internal carbon sources according to claim 3, characterized in that: In step S2, the volume ratio of the returned domestic sewage from the aerobic zone in the anoxic zone I to the domestic sewage treated in the anaerobic zone is less than or equal to 400%.

7. The method for treating sewage by denitrification and dephosphorization coupled with external carbon source and internal carbon source according to claim 3, characterized in that: In step S2, the reaction time of the anoxic zone I is greater than or equal to 1 hour.

8. The method for treating sewage by denitrification and dephosphorization coupled with external carbon source and internal carbon source according to claim 3, characterized in that: In step S2, the reaction time in the aerobic zone is 2-8 hours.

9. The method for treating sewage by denitrification and dephosphorization coupled with external carbon source and internal carbon source according to claim 3, characterized in that: In step S2, the reaction time of the anoxic zone II is greater than or equal to 2 hours.

10. The method for treating sewage by denitrification and dephosphorization coupled with external carbon source and internal carbon source according to claim 3, characterized in that: In step S3, the aeration treatment time is 0.5-2.0 hours, and the dissolved oxygen content in the domestic sewage after the aeration treatment is greater than 0.2 mg / L.

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