Sewage treatment method suitable for low-carbon-nitrogen-ratio water quality and sewage treatment equipment thereof

Abstract

The invention relates to the field of wastewater treatment, in particular to a sewage treatment method suitable for low-carbon-nitrogen-ratio water quality and sewage treatment equipment thereof.The sewage treatment method comprises the following steps that after sewage with the low-carbon-nitrogen-ratio water quality is subjected to physicochemical treatment, the water quality and the water quantity of the sewage are adjusted; sequentially conveying to a denitrification primary tank and a denitrification secondary tank to remove nitrate nitrogen; the C / N / P weight ratio of the effluent of the denitrification secondary tank is (95-105): (4-6): 1; after adjusting the pH value of effluent of the denitrification secondary tank, conveying the effluent to a biochemical system for hydrolysis, denitrification and aeration treatment; effluent of the biochemical system is conveyed to a buffer pool for treatment, effluent of the buffer pool is filtered through an MBR membrane, and the water filtered through the MBR membrane is discharged after being monitored to reach the standard. The two-stage denitrification tank is arranged in front of the biochemical system, part of phosphorus is removed while nitrogen is removed, the biochemical system is helped to adjust the carbon-nitrogen ratio of inlet water quality, the carbon source load of the biochemical system is reduced, the treatment efficiency of the biochemical system is improved, and the device has the advantages of high efficiency, low cost and simplicity in maintenance.

Description

Technical Field

[0001] The present invention relates to the field of wastewater treatment, and in particular to a wastewater treatment method suitable for low carbon-nitrogen ratio water quality and wastewater treatment equipment thereof. Background Art

[0002] The most common problem in treating industrial wastewater, such as PCB wastewater and electroplating wastewater, is the difficulty in reducing total nitrogen. Total nitrogen is typically divided into ammonia nitrogen and nitrate nitrogen. Current treatment processes primarily convert ammonia nitrogen into nitrate nitrogen in the aerobic tank of the biochemical system. The nitrate nitrogen is then removed by converting it into nitrogen gas in the anoxic tank of the biochemical system. However, the conversion of nitrate nitrogen into nitrogen gas in the current anoxic tank consumes a carbon source, which often results in insufficient carbon source. To ensure that the effluent total nitrogen meets the standard, regular carbon source addition is required. The amount of carbon source added must be adjusted based on the quality of the biochemical influent, which fluctuates during actual treatment. This makes it difficult to accurately determine the amount of carbon source added. Insufficient carbon source addition can easily lead to excessive total nitrogen, while excessive carbon source addition can easily lead to excessive COD. When effluent requirements are high, it is difficult to simultaneously control both total nitrogen and COD within standards. Therefore, carbon source addition is a major factor affecting the stability of effluent quality.

[0003] With the development of technology, industrial wastewater with high nitrogen content, or low carbon-nitrogen ratio, has emerged. This increased nitrogen content increases the rate of carbon source consumption, significantly increasing treatment costs at wastewater treatment plants, making it difficult for companies to afford them. It also increases the frequency of adding carbon sources to anoxic tanks, posing greater challenges to the stability of the effluent quality. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide a sewage treatment method and sewage treatment equipment suitable for low carbon-nitrogen ratio water quality. By setting a two-stage denitrification tank in front of the biochemical system, part of the phosphorus is removed while removing nitrogen, helping the biochemical system to adjust the carbon-nitrogen ratio of the inlet water quality, which not only reduces the carbon source load of the biochemical system and improves the treatment efficiency of the biochemical system, but also reduces the difficulty of controlling the carbon source dosage and improves the stability of the effluent water quality. It has the advantages of high efficiency, low cost and simple maintenance.

[0005] The technical solution of the present invention is achieved by the following methods:

[0006] A sewage treatment method suitable for low carbon-nitrogen ratio water quality comprises the following steps:

[0007] After the wastewater with low carbon-nitrogen ratio is subjected to physical and chemical treatment, its water quality and quantity are adjusted and then transported to the primary denitrification tank and the secondary denitrification tank in sequence to remove nitrate nitrogen; the C / N / P weight ratio of the effluent of the secondary denitrification tank is (95-105):(4-6):1; the primary denitrification tank and the secondary denitrification tank are sulfur autotrophic denitrification tanks;

[0008] After adjusting the pH value of the effluent from the secondary denitrification tank, the effluent is transported to the biochemical system for hydrolysis, denitrification and aeration treatment;

[0009] The effluent from the biochemical system is transported to a buffer tank for treatment. The effluent from the buffer tank is filtered using an MBR membrane, and the water filtered through the MBR membrane is discharged after being monitored to meet standards.

[0010] The sewage treatment method suitable for low carbon-nitrogen ratio water quality described in the present invention sets a two-stage denitrification tank in front of the biochemical system, removes part of the phosphorus while removing nitrogen, and helps the biochemical system to adjust the carbon-nitrogen ratio of the influent water quality. It not only reduces the carbon source load of the biochemical system and improves the treatment efficiency of the biochemical system, but also reduces the difficulty of controlling the carbon source dosage and improves the stability of the effluent water quality. It has the advantages of high efficiency, low cost and simple maintenance.

[0011] Furthermore, the pH value of the effluent from the secondary denitrification tank is adjusted to 8 to 9. Adjusting the pH value of the effluent from the secondary denitrification tank to 8 to 9 before entering the biochemical system is beneficial to ensuring high treatment efficiency of the biochemical system.

[0012] Furthermore, the method further includes the following steps: detecting the pH value of the effluent from the primary denitrification tank; if the pH value of the effluent from the primary denitrification tank is ≤7, adding sodium carbonate or sodium bicarbonate to the primary denitrification tank; and stopping the addition when the pH value of the effluent from the primary denitrification tank is 8 to 9. Ensuring that the pH of the water before entering the secondary denitrification tank is greater than 7 is beneficial to ensuring the overall nitrogen removal effect.

[0013] Furthermore, two primary denitrification tanks are provided in parallel. The provision of two primary denitrification tanks is beneficial for increasing the treatment load and extending the maintenance period of the primary denitrification tanks.

[0014] Furthermore, the first denitrification tank and the second denitrification tank are sulfur autotrophic denitrification tanks.

[0015] Furthermore, the method further comprises the following steps: transporting the nitrified liquid in the buffer tank to the biochemical system for denitrification and aeration treatment, and treating the nitrified liquid in the buffer tank to reduce the generation of sewage.

[0016] Furthermore, the method further includes the following steps: transporting the sludge in the buffer tank and the sludge filtered by the MBR membrane to the biochemical system for denitrification and aeration treatment. Reprocessing the sludge generated during the treatment process is beneficial to reducing sludge generation.

[0017] Furthermore, the process includes the following steps: if the water after MBR membrane filtration does not meet the standards, it is transferred to the secondary denitrification tank for treatment. If the nitrogen content of the low carbon-nitrogen ratio wastewater is high, resulting in the total nitrogen still exceeding the standard after the system treatment, it is transferred to the secondary denitrification tank for re-treatment to ensure that the total nitrogen meets the standard.

[0018] The present invention also provides a sewage treatment device suitable for any of the above-mentioned sewage treatment methods suitable for low carbon-nitrogen ratio water quality, comprising a biochemical intermediate water tank, a first-level denitrification tank, a second-level denitrification tank, a pH adjustment tank, a biochemical system, a buffer tank, an MBR membrane tank and a discharge monitoring tank arranged in sequence, wherein the biochemical intermediate water tank accommodates sewage with low carbon-nitrogen ratio water quality after physical and chemical treatment and adjusts its water quality and water quantity; the pH adjustment tank is used to adjust the pH value of the effluent from the second-level denitrification tank to 8-9; the MBR membrane tank is provided with an MBR membrane for filtering the effluent from the buffer tank; the sludge output end of the buffer tank is connected to the part of the biochemical system performing denitrification treatment through a pipeline, the nitrified liquid output end of the buffer tank is connected to the part of the biochemical system performing denitrification treatment through a pipeline; the sludge output end of the MBR membrane tank is connected to the part of the biochemical system performing denitrification treatment through a pipeline; the filtrate output end of the MBR membrane tank is also connected to the second-level denitrification tank through a pipeline.

[0019] Furthermore, the biochemical system includes an anaerobic tank, an anoxic tank and an aerobic tank arranged in sequence, the anaerobic tank is used for hydrolysis treatment, the anoxic tank is used for denitrification treatment, and the aerobic tank is used for aeration treatment; the sludge output end of the buffer tank is connected to the anoxic tank through a pipeline, and the nitrification liquid output end of the buffer tank is connected to the anoxic tank through a pipeline; the sludge output end of the MBR membrane tank is connected to the anoxic tank through a pipeline.

[0020] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of a process flow of a sewage treatment method suitable for low carbon-nitrogen ratio water quality according to one embodiment of the present invention; DETAILED DESCRIPTION

[0022] It should be clear that the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the embodiments of the present application.

[0023] The terms used in the embodiments of the present application are for the purpose of describing specific embodiments only and are not intended to limit the embodiments of the present application. The singular forms "a," "the," and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0024] When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims. In the description of the present application, it should be understood that the terms "first", "second", "third", etc. are only used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence, nor can they be understood as indicating or implying relative importance. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0025] In addition, in this application, unless otherwise specified, "plurality" refers to two or more. "And / or" describes the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, or B exists alone. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0026] It should be understood that the embodiments of the present application are not limited to the precise structures described above and shown in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the embodiments of the present application is limited only by the appended claims.

[0027] See also Figure 1 As an embodiment of the present invention, this embodiment provides a sewage treatment method suitable for low carbon-nitrogen ratio water quality, comprising the following steps:

[0028] After the wastewater with low carbon-nitrogen ratio is subjected to physical and chemical treatment, its water quality and quantity are adjusted and then transported to the primary denitrification tank and the secondary denitrification tank in sequence to remove nitrate nitrogen; the C / N / P weight ratio of the effluent of the secondary denitrification tank is (95-105):(4-6):1; the primary denitrification tank and the secondary denitrification tank are sulfur autotrophic denitrification tanks;

[0029] After adjusting the pH value of the effluent from the secondary denitrification tank, the effluent is transported to the biochemical system for hydrolysis, denitrification and aeration treatment;

[0030] The effluent from the biochemical system is transported to a buffer tank for treatment. The effluent from the buffer tank is filtered using an MBR membrane, and the water filtered through the MBR membrane is discharged after being monitored to meet standards.

[0031] Furthermore, the pH value of the effluent from the secondary denitrification pool is adjusted to 8-9.

[0032] Furthermore, the method further comprises the following steps: detecting the pH value of the effluent from the first-level denitrification tank; if the pH value of the effluent from the first-level denitrification tank is ≤7, adding sodium carbonate or sodium bicarbonate to the first-level denitrification tank; and stopping the addition when the pH value of the effluent from the first-level denitrification tank is 8-9.

[0033] Furthermore, it comprises two primary denitrification tanks, which are arranged in parallel.

[0034] Furthermore, the first denitrification tank and the second denitrification tank are sulfur autotrophic denitrification tanks.

[0035] Furthermore, the method further comprises the following steps: transporting the nitrified liquid in the buffer tank to the biochemical system for denitrification and aeration treatment.

[0036] Furthermore, the method further comprises the following steps: transporting the sludge in the buffer tank and the sludge filtered by the MBR membrane to the biochemical system for denitrification and aeration treatment.

[0037] Furthermore, the process includes the following steps: if the water after MBR membrane filtration does not meet the standards, it is transferred to the secondary denitrification tank for treatment. If the nitrogen content of the low carbon-nitrogen ratio wastewater is high, resulting in the total nitrogen still exceeding the standard after the system treatment, it is transferred to the secondary denitrification tank for re-treatment to ensure that the total nitrogen meets the standard.

[0038] The present invention also provides a sewage treatment device suitable for any of the above-mentioned sewage treatment methods suitable for low carbon-nitrogen ratio water quality, comprising a biochemical intermediate water tank, a first-level denitrification tank, a second-level denitrification tank, a pH adjustment tank, a biochemical system, a buffer tank, an MBR membrane tank and a discharge monitoring tank arranged in sequence, wherein the biochemical intermediate water tank accommodates sewage with low carbon-nitrogen ratio water quality after physical and chemical treatment and adjusts its water quality and water quantity; the pH adjustment tank is used to adjust the pH value of the effluent from the second-level denitrification tank to 8-9; the MBR membrane tank is provided with an MBR membrane for filtering the effluent from the buffer tank; the sludge output end of the buffer tank is connected to the part of the biochemical system performing denitrification treatment through a pipeline, the nitrified liquid output end of the buffer tank is connected to the part of the biochemical system performing denitrification treatment through a pipeline; the sludge output end of the MBR membrane tank is connected to the part of the biochemical system performing denitrification treatment through a pipeline; the filtrate output end of the MBR membrane tank is also connected to the second-level denitrification tank through a pipeline.

[0039] Furthermore, the biochemical system includes an anaerobic tank, an anoxic tank and an aerobic tank arranged in sequence, the anaerobic tank is used for hydrolysis treatment, the anoxic tank is used for denitrification treatment, and the aerobic tank is used for aeration treatment; the sludge output end of the buffer tank is connected to the anoxic tank through a pipeline, and the nitrification liquid output end of the buffer tank is connected to the anoxic tank through a pipeline; the sludge output end of the MBR membrane tank is connected to the anoxic tank through a pipeline.

[0040] The physical properties and test methods of the embodiments of the present invention are as follows:

[0041] COD was determined using the dichromate reflux method (HJ 828—2017);

[0042] TN was detected by alkaline potassium persulfate digestion and UV spectrophotometry (HJ 636-2012);

[0043] TP was determined by ammonium molybdate spectrophotometry (GB 11893-1989).

[0044] Example 1

[0045] See also Figure 1 The present embodiment provides a sewage treatment method suitable for low carbon-nitrogen ratio water quality. The sewage with low carbon-nitrogen ratio water quality in a certain electronic circuit industrial park is treated. The system operates for 24 hours a day and treats 15t / h of water. After the system runs stably, the operating data is continuously tested for about 3 months. The water quality of the sewage with low carbon-nitrogen ratio water quality in the present embodiment is continuously tested. The test results show that the COD of the sewage with low carbon-nitrogen ratio water quality is between 300mg / L and 500mg / L, the TN is between 150mg / L and 200mg / L, and the TP is between 6mg / L and 15mg / L. The sewage treatment method suitable for low carbon-nitrogen ratio water quality in the present embodiment includes the following steps:

[0046] After the sewage undergoes physical and chemical treatment, it is transported to a biochemical intermediate water tank. After the water volume and concentration are adjusted in the biochemical intermediate water tank, it is transported to a denitrification primary pool for treatment. The denitrification primary pool is used to remove nitrate nitrogen. The denitrification primary pool of this embodiment adopts a sulfur autotrophic denitrification pool, and this embodiment has two denitrification primary pools arranged in parallel. The effluent of the biochemical intermediate water tank is simultaneously transported to the two denitrification primary pools for treatment, and the effluent of the two denitrification primary pools is transported to the same denitrification secondary pool.

[0047] The pH value of the effluent from the first-level denitrification pool is detected. If the pH value of the effluent from the first-level denitrification pool is ≤7, sodium bicarbonate solution is added to the first-level denitrification pool. When the pH value of the effluent from the first-level denitrification pool is 8-9, the addition of sodium bicarbonate solution is stopped. The second-level denitrification pool is used to remove residual nitrate nitrogen. The second-level denitrification pool of this embodiment adopts a sulfur autotrophic denitrification pool. After the first-level denitrification pool and the second-level denitrification pool, the total nitrogen in the water is mainly composed of ammonia nitrogen, and the total nitrogen concentration is greatly reduced as a whole. There are polyphosphate-accumulating bacteria, and the substances dissolved by the filter material can also react with some phosphorus-containing substances, so that some phosphorus in the water can also be removed. The water quality of the effluent from the secondary denitrification pool of this embodiment is continuously tested, and the test results show that the COD is between 290 mg / L and 450 mg / L, the TN is between 60 mg / L and 90 mg / L, and the TP is between 5 mg / L and 8 mg / L. The C / N / P weight ratio is close to 100:5:1, the carbon source load of the biochemical system is greatly reduced, and the treatment efficiency is improved.

[0048] The effluent from the secondary denitrification tank is transported to the pH adjustment tank, where the pH is adjusted to between 8 and 9 to ensure that the microorganisms in the subsequent ecosystem can better play their role;

[0049] The effluent from the pH adjustment tank is transported to a biochemical system. The ecosystem of this embodiment includes an anaerobic tank, an anoxic tank, and an aerobic tank, which are arranged in sequence. That is, the effluent from the pH adjustment tank is transported to the anaerobic tank, the anoxic tank, and the aerobic tank for treatment in sequence. The anaerobic tank mainly plays a hydrolysis role, which is used to hydrolyze large molecules in the sewage into small molecules. The anoxic tank of this embodiment adopts a heterotrophic denitrification tank, which mainly plays a denitrification role to remove nitrate nitrogen, while part of the phosphorus is utilized by the metabolism of the microorganisms themselves. The aerobic tank is composed of an aeration system and aerobic microorganisms (including aerobic microorganisms and phosphorus-accumulating bacteria that produce and convert ammonia nitrogen into nitrate nitrogen or nitrite nitrogen), which plays a role in removing ammonia nitrogen and phosphorus in the sewage.

[0050] The effluent from the aerobic tank is transported to the buffer tank, which is equipped with a sludge discharge system, which mainly plays the role of buffering, sedimentation and separation, and can perform preliminary mud-water separation. After the mud-water separation in the buffer tank, part of the supernatant will continue to flow back to the anoxic tank through the pipeline in the form of nitrification liquid, and the other part of the supernatant will enter the MBR tank through the pipeline, while the sludge will continue to flow back to the anoxic tank through the pipeline. The setting of the buffer tank can reduce the sludge and suspended matter in the supernatant entering the MBR tank, thereby reducing the blockage of the MBR tank membrane and the frequency of MBR tank cleaning;

[0051] The effluent from the buffer tank is transported to the MBR membrane tank. The sludge filtered by the MBR membrane tank is continuously returned to the anoxic tank through a pipeline for treatment. The effluent from the MBR membrane tank is discharged to the discharge monitoring tank. When the SV30 concentration of the sludge in this embodiment is too high (greater than 35%), sludge is discharged.

[0052] After treating the sewage using the sewage treatment method suitable for low carbon-nitrogen ratio water quality of this embodiment, the effluent water quality meets the Class A standard for urban sewage discharge, where COD is between 20 mg / L and 25 mg / L, TN is between 4 mg / L and 10 mg / L, and TP is between 0.1 mg / L and 0.2 mg / L.

[0053] The sewage treatment method of the present embodiment, which is suitable for water with a low carbon-nitrogen ratio, has the advantages of high efficiency, low cost, simple maintenance, no sludge production during the denitrification process, simultaneous phosphorus removal, assistance in load regulation of the biochemical system, and ensuring that the total nitrogen in the effluent meets the standard. On the other hand, since the two-stage sulfur autotrophic denitrification is pre-placed and taken over by the biochemical system, it can effectively prevent the filler from releasing excess reducing substances when the total nitrogen concentration of the influent is low, and the substances are directly discharged into the emission monitoring pool without being utilized, resulting in a high COD test value.

[0054] In other embodiments, if the ammonia nitrogen content of the effluent from the secondary denitrification tank is very high, resulting in the total nitrogen still failing to meet the standard after treatment by the biochemical system, the effluent from the MBR tank is not discharged into the discharge monitoring tank, but is pumped to the secondary denitrification tank through a reflux pump for re-treatment.

[0055] The above-described embodiments merely represent several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, and the present invention is intended to encompass such modifications and variations.

Claims

1. A sewage treatment method suitable for low carbon-nitrogen ratio water quality, characterized in that: The following steps are involved: After the wastewater with low carbon-nitrogen ratio is subjected to physical and chemical treatment, its water quality and quantity are adjusted and then transported to the primary denitrification tank and the secondary denitrification tank in sequence to remove nitrate nitrogen; the C / N / P weight ratio of the effluent of the secondary denitrification tank is (95-105):(4-6):1; the primary denitrification tank and the secondary denitrification tank are sulfur autotrophic denitrification tanks; After adjusting the pH value of the effluent from the secondary denitrification tank, the effluent is transported to the biochemical system for hydrolysis, denitrification and aeration treatment; The effluent from the biochemical system is transported to a buffer tank for treatment. The effluent from the buffer tank is filtered using an MBR membrane, and the water filtered through the MBR membrane is discharged after being monitored to meet standards.

2. The sewage treatment method suitable for low carbon-nitrogen ratio water quality according to claim 1, characterized in that: The pH value of the effluent from the secondary denitrification pool is adjusted to 8-9.

3. The sewage treatment method suitable for low carbon-nitrogen ratio water quality according to claim 1, characterized in that: The following steps are also included: The pH value of the effluent from the first-level denitrification tank is detected. If the pH value of the effluent from the first-level denitrification tank is less than or equal to 7, sodium carbonate or sodium bicarbonate is added to the first-level denitrification tank. When the pH value of the effluent from the first-level denitrification tank is 8-9, the addition is stopped.

4. The sewage treatment method suitable for low carbon-nitrogen ratio water quality according to claim 1, characterized in that: It includes two first-level denitrification pools, which are arranged in parallel.

5. The sewage treatment method suitable for low carbon-nitrogen ratio water quality according to claim 1, characterized in that: The following steps are also included: The nitrified liquid in the buffer tank is transported to the biochemical system for denitrification and aeration treatment.

6. The sewage treatment method suitable for low carbon-nitrogen ratio water quality according to claim 1, characterized in that: The following steps are also included: The sludge in the buffer tank and the sludge filtered by the MBR membrane are transported to the biochemical system for denitrification and aeration treatment.

7. The preparation method for treating sewage with low carbon-nitrogen ratio water quality according to claim 1, characterized in that: The following steps are also included: If the water filtered by the MBR membrane does not meet the monitoring standards, it is transported to the secondary denitrification tank for treatment.

8. A sewage treatment equipment suitable for the sewage treatment method suitable for low carbon-nitrogen ratio water quality according to any one of claims 1 to 7, characterized in that: It includes a biochemical intermediate water tank, a denitrification primary tank, a denitrification secondary tank, a pH adjustment tank, a biochemical system, a buffer tank, an MBR membrane tank and a discharge monitoring tank, which are arranged in sequence. The biochemical intermediate water tank accommodates the wastewater with low carbon-nitrogen ratio after physical and chemical treatment and adjusts its water quality and water quantity; the pH adjustment tank is used to adjust the pH value of the effluent from the denitrification secondary tank to 8-9; The MBR membrane pool is provided with an MBR membrane for filtering the effluent from the buffer pool; the sludge output end of the buffer pool is connected to the denitrification part of the biochemical system through a pipeline, and the nitrified liquid output end of the buffer pool is connected to the denitrification part of the biochemical system through a pipeline; the sludge output end of the MBR membrane pool is connected to the denitrification part of the biochemical system through a pipeline; and the filtrate output end of the MBR membrane pool is also connected to the secondary denitrification tank through a pipeline.

9. The sewage treatment equipment according to claim 8, characterized in that: The biochemical system includes an anaerobic tank, an anoxic tank and an aerobic tank arranged in sequence. The anaerobic tank is used for hydrolysis treatment, the anoxic tank is used for denitrification treatment, and the aerobic tank is used for aeration treatment; the sludge output end of the buffer tank is connected to the anoxic tank through a pipeline, and the nitrification liquid output end of the buffer tank is connected to the anoxic tank through a pipeline; the sludge output end of the MBR membrane tank is connected to the anoxic tank through a pipeline.

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