Sewage treatment system and treatment method
By combining a multi-stage wastewater treatment system with microbial functions, the problem of unstable effluent quality in the MSBR activated sludge process after changes in water source has been solved. This has achieved stable compliance with total nitrogen and total phosphorus standards and control of suspended solids, reduced the risk of sludge runoff, and ensured stable effluent quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANXI TAIGANG STAINLESS STEEL CO LTD
- Filing Date
- 2026-02-05
- Publication Date
- 2026-04-21
AI Technical Summary
The conventional MSBR activated sludge process suffers from unstable effluent quality after changes in the water source. The total nitrogen and total phosphorus contents are difficult to consistently meet the standards, suspended solids are prone to exceed the standards, and there is a high risk of sludge runoff.
A multi-stage wastewater treatment system is adopted, including an anaerobic tank, an anoxic tank, an aerobic tank, and two sets of sequencing batch reactors. Through the dual reflux of sludge and mixed liquor and multi-stage sequential reaction, combined with the functions of polyphosphate-accumulating bacteria, denitrifying bacteria and other microorganisms, a multi-stage sequence of anoxic-aerobic-anoxic-aerobic-anoxic-aerobic-sludge discharge is achieved, which strengthens the microbial environment and stabilizes nitrogen and phosphorus removal.
It improves the stability of effluent water quality, ensures that the total nitrogen and total phosphorus content meet the standards, reduces the risk of excessive suspended solids, reduces sludge runoff, and achieves effluent suspended solids control below 5, thus improving water quality stability.
Smart Images
Figure CN121894869A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of wastewater treatment technology, and particularly relates to a wastewater treatment system and treatment method. Background Technology
[0002] MSBR (Modified Sequencing Batch Reactor) is a modified continuous flow sequencing batch reactor process. It's a new wastewater treatment process developed by combining the characteristics of the traditional A2 / O process with the SBR process. Due to its integrated, modular structure, small footprint, low operating costs, high solids content in residual sludge, and low sludge volume, it is widely used. This method creates optimal environmental and hydraulic conditions for the growth and reproduction of various dominant microorganisms, maintaining highly efficient reactions in biochemical processes such as organic matter degradation, ammonia nitrification, denitrification, and phosphorus release and absorption. This effectively increases the biochemical reaction rate. Each MSBR reactor contains one anaerobic tank, one anoxic tank, one aerobic tank, and two sequencing batch tanks. The two sequencing batch tanks have the same function, reacting alternately to produce effluent. When the water source changes, conventional MSBR activated sludge processes often fail to meet effluent quality requirements, exhibiting unstable effluent quality, difficulty in consistently meeting total nitrogen and total phosphorus standards, easy exceedance of suspended solids, and a high risk of sludge runoff. Summary of the Invention
[0003] The purpose of this invention is to provide a wastewater treatment system and method that solves the problems of conventional MSBR activated sludge process failing to meet the required effluent quality standards, unstable effluent quality, difficulty in consistently meeting the standards for total nitrogen and total phosphorus content, easy exceedance of suspended solids, and high risk of sludge runoff after changes in water source.
[0004] To achieve the above objectives, the present invention adopts the following technical solution: A wastewater treatment system includes an anaerobic tank, an anoxic tank, an aerobic tank, a first batch reactor, and a second batch reactor, arranged sequentially. The aerobic tank is connected to both ends of the first and second batch reactors. The inlet of the anaerobic tank is connected to a wastewater pipe and a sludge return pipe from the pre-anoxic tank, while its outlet is connected to the inlet of the anoxic tank. The system operates without a pump, relying on gravity flow. Simultaneously, the inlet of the anoxic tank is connected to the mixed liquor return pipe of the aerobic tank, and a mixed liquor return pump is installed in the aerobic tank's effluent channel. The outlet of the anoxic tank is connected to the inlet of the aerobic tank, also relying on gravity flow. An aerator is installed within the aerobic tank and connected to a blower for oxygen supply. Meanwhile, the aerobic tank outlet is divided into two paths: one path connects to the anoxic tank via a mixed liquor return pump, and the other path connects to the inlet of the first and second batch tanks. The second path is gravity-fed without a pump. Both the first and second batch tanks are equipped with decanters for discharging the supernatant. Sludge return pumps and mixed liquor return pumps are installed at the bottom of the first and second batch tanks. The first and second batch tanks are respectively connected to the sludge thickening tank. The two tanks operate alternately. If the first batch tank is used as a sedimentation tank for effluent discharge, the second batch tank will first undergo anoxic reaction and then aerobic reaction, or alternate between anoxic and aerobic reactions.
[0005] Preferably, a sludge thickening tank is provided at the front end of the anaerobic tank, and a pre-anoxic tank is provided at the front end of the sludge thickening tank. The bottoms of the pre-anoxic tank and the sludge thickening tank are connected.
[0006] Preferably, the anaerobic tank contains polyphosphate-accumulating bacteria, volatile fatty acids (VFA), and phosphates (PO4). 3- The anoxic tank contains denitrifying bacteria, nitrate nitrogen, and organic carbon sources, while the aerobic tank contains ammonia nitrogen (NH4). + ), nitrate nitrogen (NO3) - ), phosphate (PO4) 3- The pre-anoxic tank contains sludge particles, nitrate nitrogen, and denitrifying bacteria, as well as aerobic bacteria, polyphosphate-accumulating bacteria, and dissolved oxygen (DO).
[0007] A wastewater treatment method based on the above wastewater treatment system includes the following specific steps: S1: Incoming wastewater is pretreated to remove large particles and inorganic sand, and to balance water quality and quantity, in order to avoid clogging of subsequent tanks, wear on equipment, or impact on the biological system. S2: Anaerobic stage The pretreated wastewater and the return sludge from the pre-anoxic tank enter the anaerobic tank. The mixture of the two, rich in phosphorus sludge, undergoes a phosphorus release reaction by polyphosphate-accumulating bacteria in the anaerobic tank. The polyphosphate-accumulating bacteria decompose polyphosphates in their bodies to produce ATP and use VFA in the wastewater to synthesize poly-β-hydroxybutyric acid (PHB), while releasing phosphates into the mixture. S3: Hypoxia Phase Wastewater that has undergone phosphorus release reaction by polyphosphate-accumulating bacteria and the return mixed liquor from the aerobic tank enter the anoxic tank, where denitrification occurs. Denitrifying bacteria use organic carbon as an electron donor to reduce nitrate nitrogen in the return liquid from the aerobic tank to nitrogen gas. S4: Aerobic phase Wastewater that has passed through the anoxic stage and the supernatant from the sludge thickening tank enter the aerobic tank, where nitrification, organic matter degradation, and polyphosphate accumulation by polyphosphate bacteria occur simultaneously. Nitrifying bacteria convert ammonia nitrogen into nitrate nitrogen; aerobic bacteria decompose the remaining organic substrate; and polyphosphate accumulation by polyphosphate bacteria absorbs and stores the phosphate in the mixed liquor. S5: Multi-stage step sequence phase The mixed wastewater enters either the first or second batch tank. If the first batch tank is used as the effluent from the sedimentation tank, the second batch tank first undergoes anoxic reaction, followed by aerobic reaction, or alternates between anoxic and aerobic reactions, forming a multi-stage sequence of anoxic-aerobic-anoxic-aerobic-anoxic-aerobic-sludge discharge. This enhances the biological environment for microorganisms and stabilizes the nitrogen, phosphorus, and COD removal effects. During the sedimentation stage, gravity separation of sludge and water occurs, leaving activated sludge flocs and supernatant (low in organic matter, nitrogen, and phosphorus). The supernatant is gravity-returned to the aerobic tank. S6: Sludge Thickening Stage In the multi-stage process of anoxic and aerobic conditions, the supernatant from the first or second batch tank is discharged through a decanter, and the concentrated sludge is transported to the sludge thickening tank as return sludge. S7: Pre-hypoxia phase The settled sludge in the sludge thickening tank enters the pre-anoxic tank. In the pre-anoxic tank, it undergoes endogenous anoxic denitrification to remove nitrogen and degrade the nitrate nitrogen in the returned sludge. The effluent then enters the anaerobic tank and mixes with the incoming wastewater to release phosphorus. This process is repeated to prevent the effluent from entering the anaerobic tank and interfering with phosphorus release.
[0008] Preferably, the specific steps of the preprocessing in step S1 are as follows: (1) Coarse grid treatment With a grid spacing of 10~20mm, it intercepts larger floating and suspended objects in wastewater, such as tree branches, plastic bags, strips of cloth, bottles and cans, to prevent them from entering subsequent processes and causing pipe blockage or equipment damage. (2) Fine grid treatment The grid spacing is 1~5mm, which further intercepts fine impurities that are not removed by the coarse grid, such as hair, fibers, and small plastic fragments, reducing the accumulation of these substances in the MSBR tank and avoiding affecting the properties of activated sludge and process operation. (3) Grit chamber treatment The sedimentation tank is a circular sedimentation tank. Wastewater enters the circular sedimentation tank tangentially from the inlet channel. The eddy current generated by the water flow causes the sand particles to separate from the water under the action of centrifugal force, so as to achieve the purpose of sand removal. (4) Equalization tank treatment Balance the quality and quantity of wastewater and buffer fluctuations in influent load (such as flow rate changes and water quality concentration fluctuations during peak water usage periods in the morning and evening).
[0009] Preferably, the time required for anaerobic, anoxic, aerobic, and sludge thickening processes can be adjusted according to actual needs to achieve multiple operating modes.
[0010] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: (1) The entire system combines a pre-anoxic tank, a sludge thickening tank, an anaerobic tank, anoxic tank, an aerobic tank, a first batch tank and a second batch tank, and performs multiple sedimentation processes to improve and stabilize the effluent quality. (2) In this method, sludge from the aerobic tank is returned to the anoxic tank, adding anoxic-aerobic on the original basis. At the same time, the mixed liquor from the first and second sequencing batch tanks is returned to the sludge-water separation tank. After denitrification by endogenous anoxic denitrification, it is lifted into the anaerobic tank and mixed with the incoming sewage to release phosphorus. This cycle is repeated, adding the anoxic-aerobic process again. The sequence of the sequencing batch tank SBR is changed from the original anoxic-aerobic-sludge discharge sequence to anoxic-aerobic-anoxic-aerobic-anoxic-aerobic-sludge discharge multi-stage sequence, realizing double return + multi-stage process, strengthening the biological environment of microorganisms, stabilizing the denitrification, phosphorus removal and COD reduction effect, so that the total nitrogen content and total phosphorus content can be stably met, the suspended solids can meet the standard, and the risk of sludge runoff is reduced. Attached Figure Description
[0011] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention.
[0012] Explanation of the attached diagram labels: 1. Sludge thickening tank; 2. Pre-anoxic tank; 3. Anaerobic tank; 4. Anoxic tank; 5. Aerobic tank; 6. First batch tank; 7. Second batch tank. Detailed Implementation
[0013] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.
[0014] Located in northern China, Taiyuan Iron & Steel Group (TISCO) experiences significant temperature fluctuations with the seasons. The daytime and nighttime temperature difference is typically around 10°C, with winter and summer temperatures fluctuating by over 30°C. Summer average temperatures range from 10-35°C, while winter average temperatures range from -16°C to -5°C. Consequently, water temperature also varies considerably, reaching as low as 10°C in winter. These temperature variations negatively impact the growth of microorganisms in the water, especially during winter when low temperatures can cause microbial dormancy or even death. Starting in April, rising temperatures accelerate microbial growth and reproduction, causing dead sludge to float to the surface of the pools, affecting effluent quality. By early October, falling temperatures slow microbial growth, resulting in fewer microorganisms in the pools, preventing the formation of flocs and sedimentation. Fine sludge is then carried into subsequent systems by the water flow. The entire adjustment process must be gradual, not completed all at once, to allow microorganisms time to adapt. This embodiment treats domestic wastewater from the Shahe River, the northern suburbs, and the TISCO plant area. Wastewater flows from the Jiancaoping outlet, the standard parts outlet, and the TISCO plant area drainage ditch to the inlet canal of the Phase IV booster pump station.
[0015] Sludge loading: F / M = 0.17~0.23 kg(BOD5) / kg(MLSS).d Mixture concentration: X = 2400~3200 mg / L Operating cycle: T=4.0h The wastewater treatment system uses two MSBR (Mixed Stem Batch Reactor) tanks. Each MSBR tank includes a sludge thickening tank 1, a pre-anoxic tank 2, an anaerobic tank 3, an anoxic tank 4, an aerobic tank 5, a first batch tank 6, and a second batch tank 7. The anaerobic tanks 3, 4, and 5 are arranged sequentially. The aerobic tank 5 is connected to the first batch tank 6 and the second batch tank 7 at both ends. The inlet of the anaerobic tank 3 is connected to the wastewater pipe and the sludge return pipe of the pre-anoxic tank 2, while its outlet is connected to the inlet of the anoxic tank 4. It operates without a pump, relying on gravity flow. Simultaneously, the inlet of the anoxic tank 4 is connected to the mixed liquor return pipe of the aerobic tank 5. A mixed liquor return pump is installed in the effluent channel of the aerobic tank 5. The outlet of the anoxic tank 4 is connected to the inlet of the aerobic tank 5. It operates without a pump, relying on gravity flow. Aerators are installed in the aerobic tank 5, and a blower is connected to supply oxygen. The outlet of the aerobic tank 5 is divided into two paths, one through a mixed liquor return pipe... A liquid return pump is connected to the anoxic tank 4, and another line is connected to the inlet of the first batch tank 6 and the second batch tank 7. No pump is used; the flow relies on gravity. Both the first batch tank 6 and the second batch tank 7 are equipped with decanters for discharging the supernatant. Sludge return pumps and mixed liquor return pumps are installed at the bottom of the first batch tank 6 and the second batch tank 7. The first batch tank 6 and the second batch tank 7 are respectively connected to the sludge thickening tank 1. The two tanks operate alternately. If the first batch tank 6 is used as a sedimentation tank for effluent, the second batch tank 7 first undergoes anoxic reaction, then aerobic reaction, or alternates between anoxic and aerobic reactions. The anaerobic tank 3 is connected to the sludge thickening tank 1 at the front end, and a pre-anoxic tank 2 is connected to the sludge thickening tank 1 at the front end. The bottom of the pre-anoxic tank 2 and the sludge thickening tank 1 are connected. The anaerobic tank 3 contains polyphosphate-accumulating bacteria, volatile fatty acids (VFA), and phosphate (PO4).3- The anoxic tank 4 contains denitrifying bacteria, nitrate nitrogen, and organic carbon sources, while the aerobic tank 5 contains ammonia nitrogen (NH4+). The substrates include organic matter (such as glucose and organic acids). + ), nitrate nitrogen (NO3) - ), phosphate (PO4) 3- ), aerobic bacteria, polyphosphate-accumulating bacteria, dissolved oxygen (DO), and pre-anoxic tank 2 contains sludge particles, nitrate nitrogen, and denitrifying bacteria.
[0016] Total hydraulic retention time (HRT) = 15 hours, total sludge retention time (SRT) = 8 days, and total effective volume (V_total) of each tank group = 15670 m³. 3 There are a total of 7 units, and the dimensions of each unit are as follows: First batch pool: Dimensions 33750×15000×6800mm=3442; Sludge thickening tank: Dimensions 12000×6500×8800mm=686; Pre-anoxic tank: Dimensions 12000×7000×8800mm=739; Anaerobic tank: Dimensions 12000×10000×8800mm=1056; Anoxic tank: Dimensions 12000×9500×8800mm=1003; Aerobic tank: Dimensions 42900×25000×6800mm=7293; Second batch pool: Dimensions 33750×15000×6800mm=3442; The wastewater treatment system is equipped with the following equipment: One shared control system Mixers with skimming function: 8 units of N=11kW; 6 units of N=7.5kW; Aeration control switch valve: DN250, 4 units; Microporous aerators: Sequencing batch tank: 12 sets of microporous aerators; Aerobic tank: 8 sets of fixed microporous aerators; Aeration control regulating valve: DN250, 4 units; Aeration control regulating valve: DN400, 2 units; Air-controlled outlet weir: 4 sets, including on-site control; Sludge removal system: 4 sets of 7.5kW sludge pumps; Mixture reflux system: 6 sets, 15kW reflux pump; Sludge return system: 4 sets, 5.5kW sludge return pumps; Manually adjustable weir gate: 800x800, 8 sets; Manual skimming pipes: 4 sets.
[0017] A wastewater treatment method based on the above wastewater treatment system includes the following specific steps: S1: Incoming wastewater undergoes pretreatment to remove large particulate impurities and inorganic sand particles, and to balance water quality and quantity. The pretreatment steps are as follows: (1) Coarse grid treatment The screen spacing is 10mm. Two circulating mechanical screen cleaners are installed between the screens of the coarse screen to intercept larger floating and suspended objects in the sewage, such as branches, plastic bags, strips of cloth, bottles and cans. The rake teeth of the screen cleaner are set to turn on automatically at a timer, with the rake teeth turning for 10 minutes every hour. The sewage passing through the coarse screen flows by gravity to the underground collection well of the lift pump station. Three submersible sewage pumps are installed in the underground collection well, one in use and two on standby. All of them adopt variable frequency speed regulation. When the liquid level reaches the set value, they will automatically turn on and when the liquid level drops to the set value, they will automatically stop. (2) Fine grid treatment The fine screen channel is integrated with the sedimentation tank, with a screen spacing of 1mm, further intercepting fine impurities not removed by the coarse screen, such as hair, fibers, and small plastic fragments. The fine screen distribution channel has a planar dimension of 3.8×1.8m and a depth of 1.8m, with the channel bottom located 3.72m above ground. Two CBZ1400×1200 flat steel gates are installed on the fine screen inlet channel. Two cylindrical wedge-shaped fine screen cleaners are installed to remove smaller floating objects in the water, and each fine screen is equipped with a screw press. The water flow velocity through the screen is 1.0m / s, the screen width is 1.4m, and the screen gap is 5mm. The time relay for the screen conveying screw of the fine screen is set to run for 30 minutes every 2 hours. (3) Grit chamber treatment The sedimentation tanks are circular, with two tanks. Each sedimentation tank has an inlet channel and an outlet channel: the inlet channel is 0.65m wide, the outlet channel is 1.3m wide, and the total outlet channel is 2.0m wide. The flat steel gates installed on the inlet channels are of the following models: CBZ650×800, 2 units; CBZ1300×800, 4 units, all equipped with hand-cranked gate openers. Wastewater enters the circular sedimentation tank tangentially through the inlet channel. The eddy current generated by the water flow causes the sand particles to separate from the water under the action of centrifugal force. Each sedimentation tank has a diameter of Ф=3.05m, a depth of 1.60m, and a total height of 4m. The sand hopper has a diameter of Ф=1.00m, a depth of 2.40m, and a hydraulic retention time of t=25s. Each sand hopper is equipped with a submersible pump to suck the silt into the sand-water separator for separation. The squeezed-dry silt is then transported away by handcarts within the plant, while the squeezed-out wastewater flows back to the lifting suction well for reprocessing. (4) Equalization tank treatment Oil-water separators remove suspended solids and oil from wastewater. The separators are of a horizontal flow design, consisting of two sets, each set comprising two tanks. Each tank has dimensions of 38.0 × 8.0 m, an effective water depth of 3.8 m, and a hydraulic retention time of 1.5 h. Both sets share a common sludge discharge ditch. Each set of separators is equipped with a PB-type truss-type sludge suction machine with a span of 16 m. This machine scrapes away sludge from the bottom of the tank and oil residue floating on the surface. The suction machine scrapes oil (residue) at a speed of 1 m / min, performing sludge suction and oil scraping simultaneously. Oil floating on the surface is scraped by the scraper blades into the oil collection pipe and flows by gravity into the sludge discharge ditch. Sludge from the bottom of the sedimentation tank is suctioned to the sludge discharge ditch by the combined action of the sludge scraping and collection mechanism and the suction machine. Each sludge suction machine is equipped with two sludge suction pumps, one for operation and one for standby. Each pump has four suction ports, employing a rectangular flat-nozzle structure to eliminate dead zones. Sludge from the discharge ditch is pumped into the third-phase sludge treatment thickening tank for further processing. The sludge pumps are started and stopped by setting a high liquid level and stopping at a low liquid level. The supernatant from the bottom of the sedimentation tank flows out through a sawtooth weir, collects through the effluent pipe, and then flows into the MSBR distribution well. The water from the oil-water separator sedimentation tank is distributed to the MSBR tank by the water distribution well. The water distribution well has a planar dimension of 4.0×2.0 and a water depth of 2.70m. The main inlet pipe is DN1000, and there are two outlet pipes with a diameter of DN700. Two flat steel gates of 1.5×1.5 are installed. To balance the quality and quantity of wastewater and buffer fluctuations in influent load, such as changes in flow rate and water quality concentration during peak water usage periods in the morning and evening. S2: Anaerobic stage The pretreated wastewater and the return sludge from the pre-anoxic tank enter the anaerobic tank. The mixture of the two, rich in phosphorus sludge, undergoes a phosphorus release reaction by polyphosphate-accumulating bacteria in the anaerobic tank. The polyphosphate-accumulating bacteria decompose polyphosphates in their bodies to produce ATP and use VFA in the wastewater to synthesize poly-β-hydroxybutyric acid (PHB), while releasing phosphates into the mixture. S3: Hypoxia Phase Wastewater that has undergone phosphorus release reaction by polyphosphate-accumulating bacteria and the return mixed liquor from the aerobic tank enter the anoxic tank, where denitrification occurs. Denitrifying bacteria use organic carbon as an electron donor to reduce nitrate nitrogen in the return liquid from the aerobic tank to nitrogen gas. S4: Aerobic phase Wastewater that has passed through the anoxic stage and the supernatant from the sludge thickening tank enter the aerobic tank, where nitrification, organic matter degradation, and polyphosphate accumulation by polyphosphate bacteria occur simultaneously. Nitrifying bacteria convert ammonia nitrogen into nitrate nitrogen; aerobic bacteria decompose the remaining organic substrate; and polyphosphate accumulation by polyphosphate bacteria absorbs and stores the phosphate in the mixed liquor. S5: Multi-stage step sequence phase The mixed wastewater enters either the first or second batch tank. If the first batch tank is used as the effluent from the sedimentation tank, the second batch tank first undergoes anoxic reaction, followed by aerobic reaction, or alternates between anoxic and aerobic reactions, forming a multi-stage sequence of anoxic-aerobic-anoxic-aerobic-anoxic-aerobic-sludge discharge. This enhances the biological environment for microorganisms and stabilizes the nitrogen, phosphorus, and COD removal effects. During the sedimentation stage, gravity separation of sludge and water occurs, leaving activated sludge flocs and supernatant (low in organic matter, nitrogen, and phosphorus). The supernatant is gravity-returned to the aerobic tank. S6: Sludge Thickening Stage In the multi-stage process of anoxic and aerobic conditions, the supernatant from the first or second batch tank is discharged through a decanter, and the concentrated sludge is transported to the sludge thickening tank as return sludge. S7: Pre-hypoxia phase The settled sludge in the sludge thickening tank enters the pre-anoxic tank. In the pre-anoxic tank, it undergoes endogenous anoxic denitrification to remove nitrogen and degrade the nitrate nitrogen in the returned sludge. The effluent then enters the anaerobic tank and mixes with the incoming wastewater to release phosphorus, and the cycle continues.
[0018] An improved sequencing batch reactor (SBR) and treatment method were adopted, with two SBR reactors reacting alternately to produce effluent. The SBR reactor as a whole produced continuous effluent, which is beneficial for the reuse of treated water in production. The improved effluent suspended solids were controlled below 5, and the effluent quality was stable.
Claims
1. A wastewater treatment system, characterized in that, It includes an anaerobic tank, an anoxic tank, an aerobic tank, a first batch tank, and a second batch tank, arranged in sequence. The aerobic tank is connected to the first and second batch tanks at both ends. The inlet of the anaerobic tank is connected to the sewage pipe and the sludge return pipe of the pre-anoxic tank, and the outlet is connected to the inlet of the anoxic tank. It is pumpless and relies on gravity flow. At the same time, the inlet of the anoxic tank is connected to the mixed liquor return pipe of the aerobic tank. The mixed liquor return pump is installed in the outlet channel of the aerobic tank. The outlet of the anoxic tank is connected to the inlet of the aerobic tank. It is pumpless and relies on gravity flow. Aerators are installed in the tank and connected to blowers for oxygen supply. At the same time, the outlet of the aerobic tank is divided into two paths: one path is connected to the anoxic tank through the mixed liquor return pump, and the other path is connected to the inlet of the first and second batch tanks. It is pumpless and relies on gravity flow. The outlets of the first and second batch tanks are equipped with decanters for discharging the supernatant. The bottom of the first and second batch tanks is equipped with sludge return pumps and mixed liquor return pumps. The first and second batch tanks are respectively connected to the sludge thickening tank. The two tanks operate alternately. If the first batch tank is used as the effluent from the sedimentation tank, the second batch tank will first undergo anoxic reaction and then aerobic reaction, or alternate between anoxic and aerobic reactions.
2. The wastewater treatment system according to claim 1, characterized in that, A sludge thickening tank is set at the front end of the anaerobic tank, and a pre-anoxic tank is set at the front end of the sludge thickening tank. The bottoms of the pre-anoxic tank and the sludge thickening tank are connected.
3. The wastewater treatment system according to claim 1, characterized in that, The anaerobic tank contains polyphosphate-accumulating bacteria, volatile fatty acids (VFA), and phosphate (PO4). 3- The anoxic tank contains denitrifying bacteria, nitrate nitrogen, and organic carbon sources, while the aerobic tank contains ammonia nitrogen (NH4). + ), nitrate nitrogen (NO3) - ), phosphate (PO4) 3- The pre-anoxic tank contains sludge particles, nitrate nitrogen, and denitrifying bacteria, as well as aerobic bacteria, polyphosphate-accumulating bacteria, and dissolved oxygen (DO).
4. A wastewater treatment method based on the wastewater treatment system of claim 1, characterized in that, The specific steps are as follows: S1: Incoming wastewater is pretreated to remove large particles and inorganic sand, and to balance water quality and quantity, in order to avoid clogging of subsequent tanks, wear on equipment, or impact on the biological system. S2: Anaerobic stage The pretreated wastewater and the return sludge from the pre-anoxic tank enter the anaerobic tank. The mixture of the two, rich in phosphorus sludge, undergoes a phosphorus release reaction by polyphosphate-accumulating bacteria in the anaerobic tank. The polyphosphate-accumulating bacteria decompose polyphosphates in their bodies to produce ATP and use VFA in the wastewater to synthesize poly-β-hydroxybutyric acid (PHB), while releasing phosphates into the mixture. S3: Hypoxia Phase Wastewater that has undergone phosphorus release reaction by polyphosphate-accumulating bacteria and the return mixed liquor from the aerobic tank enter the anoxic tank, where denitrification occurs. Denitrifying bacteria use organic carbon as an electron donor to reduce nitrate nitrogen in the return liquid from the aerobic tank to nitrogen gas. S4: Aerobic Phase Wastewater that has passed through the anoxic stage and the supernatant from the sludge thickening tank enter the aerobic tank, where nitrification, organic matter degradation, and polyphosphate accumulation by polyphosphate bacteria occur simultaneously. Nitrifying bacteria convert ammonia nitrogen into nitrate nitrogen; aerobic bacteria decompose the remaining organic substrate; and polyphosphate accumulation by polyphosphate bacteria absorbs and stores the phosphate in the mixed liquor. S5: Multi-stage sequence phase The mixed wastewater enters either the first or second batch tank. If the first batch tank is used as the effluent from the sedimentation tank, the second batch tank first undergoes anoxic reaction, followed by aerobic reaction, or alternates between anoxic and aerobic reactions, forming a multi-stage sequence of anoxic-aerobic-anoxic-aerobic-anoxic-aerobic-sludge discharge. This enhances the biological environment for microorganisms and stabilizes the nitrogen, phosphorus, and COD removal effects. During the sedimentation stage, gravity separation of sludge and water occurs, leaving activated sludge flocs and supernatant (low in organic matter, nitrogen, and phosphorus). The supernatant is gravity-returned to the aerobic tank. S6: Sludge Thickening Stage In the multi-stage process of anoxic and aerobic conditions, the supernatant from the first or second batch tank is discharged through a decanter, and the concentrated sludge is transported to the sludge thickening tank as return sludge. S7: Pre-hypoxia phase The settled sludge in the sludge thickening tank enters the pre-anoxic tank. In the pre-anoxic tank, it undergoes endogenous anoxic denitrification to remove nitrogen and degrade the nitrate nitrogen in the returned sludge. The effluent then enters the anaerobic tank and mixes with the incoming wastewater to release phosphorus. This process is repeated to prevent the effluent from entering the anaerobic tank and interfering with phosphorus release.
5. A wastewater treatment method according to claim 4, characterized in that, The specific steps of the preprocessing in step S1 are as follows: (1) Coarse grid treatment With a grid spacing of 10~20mm, it intercepts larger floating and suspended objects in wastewater, such as tree branches, plastic bags, cloth strips, and bottles, to prevent them from entering subsequent processes and causing pipe blockages or equipment damage. (2) Fine grid treatment The grid spacing is 1~5mm, which further intercepts the fine impurities that the coarse grid did not remove, such as hair, fibers and small plastic fragments, reducing the accumulation of these substances in the MSBR tank and avoiding affecting the properties of activated sludge and process operation. (3) Grit chamber treatment The sedimentation tank is a circular sedimentation tank. Wastewater enters the circular sedimentation tank tangentially from the inlet channel. The eddy current generated by the water flow causes the sand particles to separate from the water under the action of centrifugal force, so as to achieve the purpose of sand removal. (4) Equalization tank treatment It balances the quality and quantity of wastewater and buffers fluctuations in influent load.
6. The wastewater treatment method according to claim 4, characterized in that, The time required for anaerobic, anoxic, aerobic, and sludge thickening processes can be adjusted according to actual needs to achieve multiple operating modes.