AO-AOA coupling MABR sewage treatment method

Abstract

The application provides an AO-AOA coupled sewage treatment method, a sewage treatment tank is used, and the sewage treatment tank is internally divided into a first anoxic zone, a first aerobic zone, an intermediate anaerobic carbon releasing zone, a second aerobic zone, a second anoxic zone, a sedimentation zone and a water outlet zone; at least one of the first anoxic zone, the intermediate anaerobic carbon releasing zone and the second anoxic zone is provided with an MABR membrane tank; the method comprises the following steps: in the flow process of sewage along the first anoxic zone, the second aerobic zone, the intermediate anaerobic carbon releasing zone, the second aerobic zone, the second anoxic zone and the sedimentation zone in sequence, part of the sewage in the sedimentation zone is backflowed into the intermediate anaerobic carbon releasing zone and / or the first anoxic zone; part of the effluent in the first aerobic zone is backflowed into the first anoxic zone, and / or part of the effluent in the second aerobic zone is backflowed into the first anoxic zone. The method provided by the application can realize the synergistic coupling of AO and AOA, low-oxygen zone protection and deep denitrification without setting an independent MABR reaction zone, and is suitable for the treatment of rural decentralized domestic sewage.

Description

Technical Field

[0001] This invention relates to an AO-AOA coupled MABR wastewater treatment method. Background Technology

[0002] Rural decentralized sewage treatment typically deals not with continuous, stable, large-flow municipal sewage, but with small water volume, large fluctuations, obvious intermittent water inflow, weak operation and maintenance conditions, and limited civil engineering conditions. Therefore, compact, integrated, and easy-to-maintain equipment is more suitable.

[0003] Due to the characteristics of rural sewage, the denitrification effect is usually poor, and the total nitrogen index in the effluent often exceeds the standard. Therefore, there is an urgent need for a small-scale and efficient denitrification treatment method and equipment that is suitable for rural sewage treatment.

[0004] MABR relies on a breathable membrane to supply oxygen to the inside of the biofilm, which can form an oxygen gradient from the inside of the membrane to the outside of the membrane. Therefore, it has a high oxygen transfer efficiency and is conducive to the formation of nitrification / denitrification stratification reactions within the same biofilm.

[0005] Existing MABR-AOA or MABR-AO routes can be broadly categorized into several types: One type involves setting up a separate MABR reaction zone, such as the publicly disclosed series structure of "anaerobic zone—MABR reaction zone—aerobic zone—anoxic zone—sedimentation zone" in AOA-MABR equipment, with a cleaning branch pipe extending to the bottom of the MABR in the aerobic zone; another type places the MABR between the aerobic and anoxic tanks, and is equipped with carbon source addition or aeration / internal reflux optimization control. The existing problems with MABR-AOA or MABR-AO routes are: (1) When MABR is introduced into existing AOA or AO, independent MABR zone or in-pool frame structure is often adopted, which occupies a large area and is inconvenient to modify old pools; short flow and dissolved oxygen crosstalk are easily generated at the junction of anoxic / anaerobic zone and aerobic zone, affecting the stability of low oxygen environment. (2) The existing MABR maintenance structure is too complex, and disassembly and replacement still rely on large components or lifting devices inside the pool, which is not conducive to low-cost maintenance in rural scenarios. (3) The front-end enhancement of AO and the deep denitrification of the back-end of AOA are often designed separately, and there is a lack of membrane module structures suitable for the series coupling of the two. (4) MABR equipment is mostly geared towards urban wastewater treatment plants or large-scale systems, and is not suitable for decentralized, low-flow scenarios in rural areas; (5) Existing integrated AO and AOA rural equipment has insufficient denitrification stability under low C / N and low load fluctuation conditions; (6) In the existing schemes, MABR and AO-AOA are often simply connected in series, which does not adequately demonstrate how the two are integrated and how they can be run in small devices. Summary of the Invention

[0006] The purpose of this invention is to provide an AO-AOA coupled MABR wastewater treatment method.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: An AO-AOA coupled MABR wastewater treatment method is disclosed. The method employs a wastewater treatment tank, internally divided into a first anoxic zone, a first aerobic zone, an intermediate anaerobic carbon release zone, a second aerobic zone, a second anoxic zone, a sedimentation zone, and an effluent zone, sequentially distributed along the water flow direction. At least one of the first anoxic zone, the intermediate anaerobic carbon release zone, and the second anoxic zone is equipped with a MABR membrane tank. The wastewater treatment method includes: During the flow of wastewater through the first anoxic zone, the second aerobic zone, the intermediate anaerobic carbon release zone, the second aerobic zone, the second anoxic zone, and the sedimentation zone, a portion of the wastewater in the sedimentation zone flows back into the intermediate anaerobic carbon release zone and / or the first anoxic zone; a portion of the effluent in the first aerobic zone flows back into the first anoxic zone, and / or a portion of the effluent in the second aerobic zone flows back into the first anoxic zone. During operation, based on one or more of the following indicators: the second anoxic zone indicator, the intermediate anaerobic carbon release zone indicator, the second aerobic zone indicator, and the effluent indicator, one or more of the following are adjusted: air supply to the MABR membrane tank, aeration rate of the first aerobic zone, aeration rate of the second aerobic zone, auxiliary air washing frequency, external sludge distribution ratio, and internal reflux flow rate. The external sludge distribution ratio is the ratio of the amount of sludge from the sedimentation zone to the first anoxic zone to the amount of sludge from the sedimentation zone to the intermediate anaerobic carbon release zone. The internal reflux flow rate refers to the amount of effluent from the first aerobic zone that flows back into the first anoxic zone, or the amount of effluent from the second aerobic zone that flows back into the first anoxic zone, or the sum of the amounts of effluent from the first aerobic zone and the second aerobic zone that flows back into the first anoxic zone. The second anoxic zone indicator, the intermediate anaerobic carbon release zone indicator, and the second aerobic zone indicator all include oxidation-reduction potential and dissolved oxygen. The effluent parameters include one or more of the following: nitrate nitrogen, ammonia nitrogen, TP, TN, and phosphorus release; the effluent parameters include one or more of the following: TP, TN, COD, ammonia nitrogen, and SS in the effluent from the effluent zone.

[0008] According to some embodiments of the present invention, a first MABR membrane box is provided in the first anoxic zone, and a second MABR membrane box and a third MABR membrane box are provided in the second anoxic zone, wherein the second MABR membrane box is closer to the second aerobic zone than the third MABR membrane box.

[0009] According to some embodiments of the present invention, when the effluent NO3-N in the second anoxic zone is >2.0 mg / L and the effluent TN is >15 mg / L: The air supply to the second MABR membrane chamber was adjusted to 0.05-0.06 m³. 3 / h; The air supply to the third MABR membrane chamber is adjusted to 0.03-0.05m³. 3 / h; The aeration rate in the second aerobic zone was adjusted to 0.25-0.35 m³ / h. 3 / h; The internal reflux flow rate from the second aerobic zone to the first hypoxic zone is adjusted to 100-150%Q; The ratio of the sludge from the sedimentation zone to the first anoxic zone to the sludge from the sedimentation zone to the intermediate anaerobic carbon release zone is (40:60) - (50:50).

[0010] According to some embodiments of the present invention, a fourth MABR membrane box is provided in the intermediate anaerobic carbon release zone. If the ORP of the anaerobic carbon release zone is lower than -250 mV, the fourth MABR membrane box is started at a low frequency; if the ORP of the anaerobic carbon release zone is in the range of -120 mV to -250 mV, the fourth MABR membrane box is not started.

[0011] According to some embodiments of the present invention, if the ORP of the anaerobic carbon release zone is lower than -250 mV, the gas supply range of the fourth MABR membrane chamber is 0.01–0.03 m³ / s. 3 / h.

[0012] According to some embodiments of the present invention, when the ammonia nitrogen in the effluent of the second aerobic zone is >1.5 mg / L, the dissolved oxygen in the second aerobic zone is <1.0 mg / L, and the ammonia nitrogen in the effluent of the effluent zone is >1.0 mg / L: The air supply to the first MABR membrane chamber in the first anoxic zone was adjusted to 0.12-0.16 m³. 3 / h; The air supply to the second MABR membrane chamber was adjusted to 0.10-0.12 m³. 3 / h; The air supply volume of the third MABR membrane chamber is adjusted to 0.05-0.08 m³. 3 / h; The aeration rate of the first aerobic zone was adjusted to 0.50-0.60 m³. 3 / h; The aeration rate in the second aerobic zone was adjusted to 0.45-0.60 m³ / s. 3 / h; The internal return flow rate range is 180-250%Q; The frequency of auxiliary air washing should be adjusted to 3-5 min / 4h; The total amount of sludge from the sedimentation zone to the first anoxic zone and the intermediate anaerobic carbon release zone is 50%–100% of the influent flow rate Q.

[0013] According to some embodiments of the present invention, a fourth MABR membrane tank is provided in the intermediate anaerobic carbon release zone. If the ORP of the intermediate anaerobic carbon release zone is higher than -100 mV, the phosphorus release rate of the intermediate anaerobic carbon release zone is less than 20%–30% of the influent TP, and the effluent TP is greater than 0.5 mg / L: The fourth MABR membrane chamber is closed; The ratio of sludge from the sedimentation zone to the first anoxic zone and sludge from the sedimentation zone to the intermediate anaerobic carbon release zone is (70:30) - (80:20). The air supply to the first MABR membrane chamber was adjusted to 0.06-0.08 m³. 3 / h; The DO range for the second aerobic zone is 1.5-2.0 mg / L.

[0014] According to some embodiments of the present invention, a fourth MABR membrane tank is provided in the intermediate anaerobic carbon release zone. If the ORP of the intermediate anaerobic carbon release zone is lower than -250 mV, the effluent TP rises to 0.6–1.5 mg / L, or the effluent TP is higher than 0.5 mg / L for 2–3 consecutive detection cycles, and the fluctuation range of the orthophosphate concentration in the effluent of the intermediate anaerobic carbon release zone is >20%–30% between adjacent detection cycles, or the phosphorus release fluctuates >0.5–1.0 mg / L, The air supply of the fourth MABR membrane chamber is then adjusted to 0.01-0.03 m³. 3 / h, and operate intermittently at 5-10 min / 2-4 h; the ORP of the intermediate anaerobic carbon release zone is controlled at -150 to -220 mV; the ratio of sludge from the sedimentation zone to the first anoxic zone and from the sedimentation zone to the intermediate anaerobic carbon release zone is (50:50)-(60:40); the dissolved oxygen in the second aerobic zone is 1.5-2.0 mg / L.

[0015] According to some embodiments of the present invention, when the ammonia nitrogen concentration in the second aerobic zone increases or the dissolved oxygen is lower than a set value, the air supply of the first MABR membrane box is increased, and the aeration of the first MABR membrane box and the second aerobic zone is increased, thereby increasing the internal return flow from the second aerobic zone to the first anoxic zone.

[0016] According to some embodiments of the present invention, the second aerobic zone is provided with dissolved oxygen detection points and / or ammonia nitrogen detection points; the intermediate anaerobic carbon release zone is provided with oxidation-reduction potential detection points; the second anoxic zone is provided with nitrate nitrogen detection points; and the effluent zone is provided with total nitrogen and / or ammonia nitrogen detection points.

[0017] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: The AO-AOA coupled wastewater treatment method provided by this invention adjusts the air supply of the MABR membrane tank, the aeration rate of the first aerobic zone, the aeration rate of the second aerobic zone, the auxiliary air scrubbing frequency, the external return sludge distribution ratio, and the internal return flow rate based on the nitrate nitrogen in the second anoxic zone, the oxidation-reduction potential of the intermediate anaerobic carbon release zone, the dissolved oxygen / ammonia nitrogen in the second aerobic zone, and the effluent indicators. This invention can achieve synergistic coupling between enhanced denitrification in the AO front stage and deep denitrification / carbon source reuse in the AOA rear stage, as well as low-oxygen zone protection and deep denitrification, without setting up an independent MABR reaction zone. It is suitable for decentralized rural domestic wastewater treatment. By separately controlling the air supply and air scrubbing strategies of the MABR membrane tank, ineffective aeration can be reduced. By setting up sludge distribution and the intermediate anaerobic carbon release zone, the internal carbon source utilization efficiency under low C / N conditions can be improved. Attached Figure Description

[0018] Figure 1 This is a structural diagram of the wastewater treatment tank of the present invention; Figure 2 This is a structural diagram of the MBRA membrane module of the wastewater treatment tank of the present invention from a first-view perspective. Figure 3 This is a structural diagram of the MBRA membrane module of the wastewater treatment tank of the present invention from a second perspective. Figure 4 This is a top view of the MBRA membrane module of the wastewater treatment tank of the present invention from a first perspective. Figure 5 This is a structural diagram of the inner wall and support of the wastewater treatment tank of the present invention.

[0019] in: 1-First anoxic zone; 2-First aerobic zone; 3-Intermediate anaerobic carbon release zone; 4-Second aerobic zone; 5-Second anoxic zone; 6-Sedimentation zone; 7-Effluent zone; 8a-First MABR membrane box; 8b-Second MABR membrane box; 8c-Third MABR membrane box; 8d-Fourth MABR membrane box; 81-Frame; 82-Hollow fiber composite membrane filament; 83-Upper end cap; 84-Lifting part; 85-Auxiliary microporous gas washing tube; 86-Flow guide baffle; 87-Flow guide vane; 88-Gas supply line; 89-Snap-fit ​​part; 9-Support section; 10-Sludge return pipeline; 11-Liquid return pipeline. Detailed Implementation

[0020] like Figures 1 to 5The wastewater treatment tank shown is divided into a first anoxic zone 1, a first aerobic zone 2, an intermediate anaerobic carbon release zone 3, a second aerobic zone 4, a second anoxic zone 5, and a sedimentation zone 6, which are distributed sequentially along the water flow direction. The wastewater treatment tank also has an effluent zone 7. Both the effluent zone 7 and the sedimentation zone 6 are located on the side of the second anoxic zone 5 away from the second aerobic zone 4.

[0021] The first anoxic zone A1 in the AO pre-section has a detachably mounted first MABR membrane chamber 8a, which is located on the side of the first anoxic zone A1 near the first aerobic zone O1, and preferably on the upper part of that side. The first aerobic zone O1 in the AO pre-section is adjacent to the intermediate anaerobic carbon release zone A2 in the AOA post-section. The second aerobic zone A3 in the AOA post-section is adjacent to the intermediate anaerobic carbon release zone A2. In the second anoxic zone A3 of the AOA downstream section, a second MABR membrane tank 8b and a third MABR membrane tank 8c are provided. The second MABR membrane tank 8b and the third MABR membrane tank 8c are detachably installed in the second anoxic zone A3. The second MABR membrane tank 8b faces the second aerobic zone O2 more than the third MABR membrane tank 8c. The second MABR membrane tank 8b is located on the side of the second anoxic zone A3 facing the second aerobic zone O2, and preferably on the lower part of that side. The third MABR membrane tank 8c is located on the side of the second anoxic zone A3 facing the sedimentation zone 6, and preferably on the upper part of that side.

[0022] A fourth MABR membrane box 8d is provided in the intermediate anaerobic carbon release zone 3. The MABR membrane box is detachably installed in the intermediate anaerobic carbon release zone 3. The fourth MABR membrane box 8d is located on the side of the intermediate anaerobic carbon release zone 3 facing the second aerobic zone, and preferably on the upper part of that side.

[0023] The first MABR membrane tank 8a, the second MABR membrane tank 8b, the third MABR membrane tank 8c, and the fourth MABR membrane tank 8d each include a frame 81, hollow fiber composite membrane filaments 82, an upper end cap 83, a lower end cap, and an air supply pipeline 88. The upper end cap 83 and the lower end cap are respectively connected to the opposite ends of the hollow fiber composite membrane filaments 82. The upper end cap 83 and the lower end cap are connected to the frame 81. The air supply pipeline 88 is connected to the upper end cap 83. The hollow fiber composite membrane filaments 82 extend along the height direction of the wastewater treatment tank.

[0024] The wastewater treatment tank is equipped with a support section 9, which can be a guide rail or hook. The frame 81 is connected to the support section 9 inside the wastewater treatment tank via plug-in, hook-on, or snap-on methods, and can be lifted and removed as a whole. When the biofilm on the membrane fiber surface is found to be too thick or partially blocked, the air supply can be turned off, the lifting part 84 on the frame can be lifted, and the frame 81 can be removed as a whole for flushing or replacement. This method does not require complex mechanisms such as winches or sliding frames, making it suitable for simplified operation and maintenance in rural settings.

[0025] In this example, the frame is provided with a snap-fit ​​part 89, and the sewage treatment tank is provided with a support part 9 that mates with the snap-fit ​​part 89 (see [reference]). Figure 5 The inner wall m). In some embodiments, see Figure 3 The snap-fit ​​part 89 is a hook; the support part 9 is L-shaped. The frame is provided with a lifting part 84, which allows the operator to easily remove the entire frame for washing or replacement by operating the lifting part 84. The lifting part 84 can be a handle, a lifting lug, or a lifting ring.

[0026] In some embodiments, the first MABR membrane tank 8a, the second MABR membrane tank 8b, the third MABR membrane tank 8c, and the fourth MABR membrane tank 8d are provided with flow guide vanes 87 on the effluent side (aerobic side). The flow guide vanes 87 extend outward at an angle and are used to guide the flow of sewage, avoid short-circuiting, and prevent dissolved oxygen from flowing to the low-oxygen side (or aerobic side).

[0027] Furthermore, flow guide baffles 86 are installed on the upper side of the frames of the first MABR membrane tank 8a, the second MABR membrane tank 8b, the third MABR membrane tank 8c, and the fourth MABR membrane tank 8d to prevent wastewater from bypassing or short-circuiting and to increase the contact opportunity between wastewater and the membrane fibers. The flow guide baffles 86 on the anoxic side and the flow guide vanes 87 on the aerobic side form an asymmetrical structure, which is more suitable for adjacent arrangement of AO / AOA low-oxygen and high-oxygen zones, and is beneficial for the protection of the low-oxygen zone.

[0028] At least one of the first MABR membrane chamber 8a, the second MABR membrane chamber 8b, the third MABR membrane chamber 8c, and the fourth MABR membrane chamber 8d also includes an auxiliary microporous gas washing pipe 85. The auxiliary microporous gas washing pipe 85 is located below the hollow fiber composite membrane filament 82. The hollow fiber composite membrane filament 82 is connected to the gas supply pipeline 88, which can reduce the disturbance to the anoxic / aerobic side caused by lifting the MABR membrane chamber.

[0029] In some embodiments, aeration devices are provided in the first aerobic zone 2 and the second aerobic zone 4.

[0030] In this example, the first MABR membrane module 8a, the second MABR membrane module 8b, the third MABR membrane module 8c, and the fourth MABR membrane module 8d are all biased structures. Biased means that the main body of the MABR membrane module is arranged biased towards the side that needs to be kept oxygen-deficient. The oxygen-deficient side is shielded by a flow guide baffle, so that the mixture passes through the membrane fiber area first, rather than bypassing it through short flows on both sides.

[0031] Sedimentation zone 6 is connected to intermediate anaerobic carbon release zone 3 and / or first anoxic zone 1 via sludge return pipeline 10, allowing some sludge to be returned to intermediate anaerobic carbon release zone 3 and / or first anoxic zone 1. When sludge from sedimentation zone 6 is returned to first anoxic zone 1, it primarily maintains the upstream sludge concentration and denitrification activity, achieving efficient nitrogen and phosphorus removal. When sludge from sedimentation zone 6 is returned to intermediate anaerobic carbon release zone 3, it primarily enhances the anaerobic carbon and phosphorus release capacity, providing more internal carbon sources for the subsequent second anoxic zone and powering subsequent deep phosphorus uptake. This forms a synergistic operation mechanism of "upstream recirculation for nitrogen removal + midstream carbon release and phosphorus replenishment + downstream deep nitrogen and phosphorus removal."

[0032] The first aerobic zone 2 and the first anoxic zone 5 are connected by a liquid return pipeline 11, allowing a portion of the mixed liquor in the first aerobic zone 2 to be returned to the first anoxic zone 1, and / or, a portion of the mixed liquor in the second aerobic zone 4 to be returned to the first anoxic zone 1. Specifically, the return of a portion of the mixed liquor from the first aerobic zone 2 to the first anoxic zone 1 is used to carry back the nitrate nitrogen formed in the first aerobic zone for pre-denitrification in the first anoxic zone, with a return ratio of 200%-400%. The return of a portion of the mixed liquor from the second aerobic zone 4 to the first anoxic zone 1 is used to carry back the nitrate nitrogen formed in the later stages for pre-denitrification in the first anoxic zone 1. This reduces the denitrification pressure in the second anoxic zone 5 and also fully utilizes the pre-treatment AO process to supplement some of the total nitrogen conversion. Combined with denitrification in the second anoxic zone 5, this ensures that the total nitrogen in the effluent meets the standards, with a return ratio of 100%-200%.

[0033] Other coordinated operation logic: Auxiliary air washing operates intermittently only within the membrane tank to ensure bubble-free aeration; when nitrate nitrogen levels rise in the second anoxic zone 5 (NO3N at the effluent > 2.0 mg / L, preferably 2.0–5.0 mg / L), the recirculation ratio of nitrified liquid from the first aerobic zone 2 and the second aerobic zone 4 to the first anoxic zone 1 is preferentially increased (the recirculation ratio from the first aerobic zone 2 to the first anoxic zone 1 is increased to 80%–150%Q, and the recirculation ratio from the second aerobic zone 4 to the first anoxic zone 1 is increased to 150%–300%Q, an increase of approximately 50% compared to conventional operation), or the proportion of sludge entering the intermediate anaerobic carbon release zone 3 is increased (the external recirculation sludge distribution ratio is adjusted from A1:A2=70:30 or 60:40 to 50:50 or 40:60). When the ORP in the intermediate anaerobic carbon release zone 3 is high, the aeration frequency and aeration rate in the first aerobic zone 2 are preferentially reduced.

[0034] Wastewater treatment methods include: The influent mixes with the returned sludge and nitrified liquor in the first anoxic zone A1 and then enters the first aerobic zone O1. The first MABR membrane tank continuously supplies air, creating localized enhanced oxygenation and primary denitrification in the front AO section. The effluent from the first aerobic zone O1 enters the intermediate anaerobic carbon release zone A2, while sludge from the sedimentation zone also enters the intermediate anaerobic carbon release zone A2. A fourth MABR membrane tank is installed at the outlet of the intermediate anaerobic carbon release zone A2, and the wastewater is guided through the fourth MABR membrane tank into the second aerobic zone O2. Part of the effluent from the first aerobic zone O1 flows back into the first anoxic zone A1. Part of the effluent from the second aerobic zone O2 flows back into the first anoxic zone A1. The effluent from the second anoxic zone A3 enters the sedimentation zone through the third MABR membrane tank. The effluent from the second aerobic zone O2 enters the second anoxic zone A3 through the second MABR membrane tank. The sludge from the sedimentation zone is returned to the first anoxic zone A1 and the intermediate anaerobic carbon release zone A2.

[0035] In this process, the effluent from the first aerobic zone O1 is partially returned to the first anoxic zone A1, and the effluent from the second aerobic zone O2 is partially returned to the first anoxic zone A1, which is carried out simultaneously and continuously. The sludge from the sedimentation zone is returned to the first anoxic zone A1, and the sludge from the sedimentation zone is returned to the intermediate anaerobic carbon release zone A2, which is carried out simultaneously and continuously.

[0036] During operation, based on nitrate nitrogen in the second anoxic zone, oxidation-reduction potential in the intermediate anaerobic carbon release zone, dissolved oxygen / ammonia nitrogen in the second aerobic zone, and effluent indicators, the following adjustments are made: air supply to the first, second, and third MABR membrane tanks; aeration rate in the aerobic zone; auxiliary air washing frequency; external sludge return ratio (the ratio of sludge from the sedimentation zone to the first anoxic zone to sludge from the sedimentation zone to the intermediate anaerobic carbon release zone); and internal return flow rate (the sum of the amount of effluent from the first aerobic zone returned to the first anoxic zone, or the amount of effluent from the second aerobic zone returned to the first anoxic zone, or the sum of the amount of effluent from the first aerobic zone returned to the first anoxic zone and the amount of effluent from the second aerobic zone returned to the first anoxic zone). The fourth MABR membrane tank is activated based on the phosphorus removal effect. Wherein, ORP is oxidation-reduction potential, NO3–N is nitrate nitrogen, DO is dissolved oxygen, and NH3 is nitrogen. 4+ -N represents ammonia nitrogen, and TP represents total phosphorus (orthophosphate). Details are as follows: Operating Condition 1 When the NO3-N (nitrate nitrogen) in the effluent from the second anoxic zone is high (>2.0 mg / L) and the TN (total nitrogen) is high (>15 mg / L): The air supply capacity of the second MABR membrane box is increased from 0.05-0.10 m³ / h under normal operating conditions. 3 / h decreased to 0.05-0.06m 3 / h; the air supply of the third MABR membrane box is 0.04-0.08m³ / h under normal operating conditions. 3 / h decreased to 0.03-0.05m 3 / h; the aeration rate in the second aerobic zone is maintained or slightly reduced to 0.25-0.35m³ / h. 3 / h; the recirculation rate from the second aerobic zone to the first anoxic zone is reduced from 200%Q to 100-150%Q to avoid excessive nitrate load; the external recirculation sludge distribution is adjusted from A1:A2=60:40 to 50:50 or 40:60, that is, the ratio of sludge from the sedimentation zone to the first anoxic zone and sludge from the sedimentation zone to the intermediate anaerobic carbon release zone is 50:50 or 40:60.

[0037] If the ORP of the intermediate anaerobic carbon release zone A2 is below -250mV, the fourth MABR membrane chamber can be started at a low frequency (the gas supply range of the fourth MABR membrane chamber is 0.01–0.03 m³ / s). 3 / h); if the ORP of the intermediate anaerobic carbon release zone A2 is normal (-120mV-250mV), then the fourth MABR membrane chamber should not be started. Auxiliary gas washing should be maintained for 2 minutes / 6 hours to avoid excessive gas washing introducing oxygen.

[0038] The difficulty in this operating condition lies in the fact that it is not simply a matter of "increasing aeration or increasing reflux when TN is high".

[0039] An unexpected approach: When TN is high, the conventional approach is to increase the air supply to the MABR to enhance treatment. However, in this case, the air supply to the second and third MABR membrane boxes is reduced to avoid disrupting the anoxic denitrification environment. Furthermore, more of the externally returned sludge is allocated to the intermediate anaerobic carbon release zone A2. By increasing the carbon release capacity of A2, a carbon source for denitrification is provided for the subsequent A3, rather than just adjusting it locally in A3.

[0040] Operating Condition 2 When the ammonia nitrogen in the effluent from the second aerobic zone is high (>1.5 mg / L), and the final effluent ammonia nitrogen is >1.0 mg / L, while the DO in the second aerobic zone is <1.0 mg / L: The first MABR membrane box has an air supply capacity of 0.10m³. 3 / h increased to 0.12-0.16m 3 / h; the air supply of the second MABR membrane box is increased from 0.08m³ / h. 3 / h increased to 0.10-0.12m 3 / h; the air supply of the third MABR membrane box is maintained at 0.05-0.08m³ / h. 3 / h, to avoid over-oxygenation at the tail end; the aeration rate of the second aerobic zone is reduced from 0.35m³ / h. 3 / h increased to 0.45-0.60m 3 / h; the aeration rate in the first aerobic zone is 0.40m³ / h. 3 / h increased to 0.50-0.60m 3 / h; the internal return flow rate (the sum of the internal return flow rates from the first aerobic zone to the first anoxic zone and from the second aerobic zone to the first anoxic zone) should be maintained at around 200%Q to avoid excessive dilution; the frequency of auxiliary air washing should be increased from 2min / 6h to 3-5min / 4h; the total amount of externally returned sludge (the total amount of sludge from the sedimentation zone to the first anoxic zone and the total amount of sludge from the sedimentation zone to the intermediate anaerobic carbon release zone) should be 50%–100% of the influent flow rate Q to maintain the nitrifying bacteria count.

[0041] The challenge in adjusting this operating condition lies in restoring nitrification capacity without increasing the gas supply to the first MABR membrane tank in the first anoxic zone and the second MABR membrane tank in the second anoxic zone to the point of disrupting denitrification. High ammonia nitrogen levels require oxygen supply, but excessive oxygen supply will affect the anoxic environment of the first anoxic zone A1 and the second anoxic zone A3.

[0042] A less obvious approach: Prioritize increasing the air supply to the first and second MABR membrane tanks, rather than just increasing the aeration in the first and second aerobic zones; utilize the local oxygen supply capacity of the first MABR membrane tank in the first anoxic zone and the second MABR membrane tank in the second anoxic zone for in-situ nitrification supplementation to reduce the O2 load in the second aerobic zone.

[0043] Elevated ammonia nitrogen levels are not necessarily due to insufficient aeration; they could also be caused by an excessively thick biofilm on the membrane surface, which restricts mass transfer. Therefore, air washing can be used to restore the oxygen transfer efficiency of the MABR membrane chamber.

[0044] Operating Condition 3 When the ORP of the intermediate anaerobic carbon release zone A2 is high (above -100mV), phosphorus release is insufficient (the increase in orthophosphate concentration in the effluent of the intermediate anaerobic carbon release zone compared to the influent (raw water) is <1.0mg / L, or the phosphorus release in the intermediate anaerobic carbon release zone is <20%–30% of the influent TP (raw water), and the effluent TP increases (>0.5mg / L): The fourth MABR membrane chamber remains closed to prevent further increases in ORP; the external return sludge distribution is adjusted from A1:A2=60:40 to 70:30 or 80:20; the air supply to the first MABR membrane chamber is reduced to 0.06-0.08 m³ / h. 3 / h, to prevent excessive A1 oxidation in the first anoxic zone from consuming carbon source; the aeration rate in the second aerobic zone is maintained at DO 1.5-2.0mg / L to ensure subsequent excessive phosphorus uptake; auxiliary gas washing is not increased to avoid disturbing the anaerobic environment.

[0045] The difficulty in adjusting this condition lies in the fact that when TP increases, the aeration in the aerobic zone cannot be simply increased; the root cause of insufficient aerobic phosphorus uptake may be the insufficient phosphorus release in the intermediate anaerobic carbon release zone at the front end, while the phosphorus release in the intermediate anaerobic carbon release zone is affected by the entry of nitrates and oxygen into the intermediate anaerobic carbon release zone A2.

[0046] An approach that is not easily thought of: Although the fourth MABR membrane box has a regulation function, when the ORP of the intermediate anaerobic carbon release zone A2 is already too high, starting the gas supply will further damage the anaerobic environment. Therefore, it is better to choose not to start or keep the fourth MABR membrane box closed.

[0047] Reduce the proportion of externally returned sludge entering the intermediate anaerobic carbon release zone A2: By allocating more externally returned sludge to the first anoxic zone A1, the amount of nitrate entering the intermediate anaerobic phosphorus release zone A2 is reduced.

[0048] Operating Condition 4 If the ORP of the intermediate anaerobic carbon release zone A2 is too low (below -250mV), the effluent TP fluctuation increases (effluent TP increases from ≤0.5mg / L to 0.6–1.5mg / L, or exceeds 0.5mg / L for 2–3 consecutive monitoring cycles), an anaerobic putrid odor appears, and anaerobic phosphorus release fluctuates greatly (the effluent orthophosphate concentration (TP) in the intermediate anaerobic carbon release zone fluctuates by >20%–30% in adjacent monitoring cycles, or the phosphorus release fluctuates by >0.5–1.0mg / L). When the effluent TP fluctuation increases: The air supply to the fourth MABR membrane chamber was adjusted to 0.01-0.03 m³ / h. 3 / h; the fourth MABR membrane box operates intermittently for 5-10 min / 2-4 h; the ORP control target for the intermediate anaerobic carbon release zone A2 is -150 to -220 mV; the external return sludge distribution is adjusted to A1:A2=50:50 or 60:40; the aeration rate of the second aerobic zone is maintained at DO 1.5-2.0 mg / L; the auxiliary air washing frequency adopts the fourth MABR membrane box without strong air washing, only low-frequency micro-disturbance.

[0049] The difficulty in adjusting this condition lies in the fact that A2 is the intermediate anaerobic carbon release zone, and the conventional approach is to "not supply oxygen." However, if the ORP is too low, not adjusting it at all may lead to putrefaction, decreased sludge activity, and fluctuations in phosphorus release.

[0050] Methods that are not easy to think of: The fourth MABR membrane chamber is activated for low-intensity, intermittent micro-gas supply. This is not to turn the intermediate anaerobic carbon release zone A2 into an aerobic zone, but to use the fourth MABR membrane chamber to modify the local microenvironment.

[0051] Using ORP as the fourth MABR membrane box start-up boundary: start-up only when ORP is below a certain value, and stop when it returns to the target range, to avoid long-term gas supply disrupting anaerobic phosphorus release.

[0052] Operating Condition 5 When the effluent TN (>15mg / L) and effluent TP (>0.5mg / L) in the effluent zone increase simultaneously, and if the ORP of the intermediate anaerobic carbon release zone A2 is high (ORP>-100mV), then reduce the amount of nitrate-containing sludge entering the intermediate anaerobic carbon release zone A2, and adjust the external return flow to A1:A2=70:30. When the effluent TN (>15 mg / L) and effluent TP (>0.5 mg / L) in the effluent zone rise simultaneously, and if the ORP of the intermediate anaerobic carbon release zone A2 is too low (ORP < -250 mV), the fourth MABR membrane tank is activated, with an air supply of 0.01-0.03 m³ / L. 3 / h, auxiliary air washing 5-10min / 2-4h; When the effluent TN (>15mg / L) and effluent TP (>0.5mg / L) in the effluent zone increase simultaneously, and if the NO3-N in the second anoxic zone A3 is high (NO3-N>2.0mg / L), reduce the gas supply to the second and third MABR membrane tanks and increase the carbon release in the intermediate anaerobic carbon release zone A2. When the effluent TN (>15 mg / L) and effluent TP (>0.5 mg / L) in the effluent zone both increase simultaneously, and if the ammonia nitrogen in the second aerobic zone is also high (NH4+), 4+ When -N > 1.5 mg / L, increase the O2 aeration rate in the second aerobic zone to 0.45-0.60 mg / L. 3 / h; the internal return flow rate is controlled at 150%-250%Q to avoid nitrate shock; the auxiliary gas washing is adjusted to 3min / 4h according to the membrane surface condition.

[0053] The difficulty in adjusting this operating condition lies in the fact that the adjustment directions of TN and TP may conflict with each other. Increasing aeration is beneficial to nitrification and phosphorus uptake, but may inhibit denitrification; increasing sludge return is beneficial to maintaining polyphosphate-accumulating bacteria, but may carry nitrates into the intermediate anaerobic carbon release zone, inhibiting phosphorus release.

[0054] Methods that are not easy to think of: First, determine the ORP of the intermediate anaerobic carbon release zone A2, and then adjust TN and TP. Do not directly adjust TN or TP as a single index, but first determine whether the anaerobic phosphorus release zone has been damaged. Based on the ORP of the intermediate anaerobic carbon release zone A2, decide whether the fourth MABR membrane box should be shut down or slightly started. When ORP is too high, the fourth MABR membrane chamber is shut down; when ORP is too low, it is started only slightly to avoid a "one-size-fits-all" approach.

[0055] When the nitrate level in the second anoxic zone A3 is high, the solution is not simply to add carbon or aeration, but to reduce the gas supply to the second and third MABR membrane chambers and adjust the carbon release load in the intermediate anaerobic carbon release zone A2.

[0056] The wastewater treatment methods in operating conditions 1-5 are explained in detail below: 1. Operating logic of the front-end AO and the first MABR membrane box After pretreatment, the wastewater enters the first anoxic zone, where the first MABR membrane tank begins operation. The first MABR membrane tank supplies oxygen to the biofilm on the membrane surface through a hollow fiber composite membrane. At the same time, the first anoxic zone receives mixed liquor recirculation from the first and second aerobic zones. Under anoxic conditions, the nitrate nitrogen in the mixed liquor recirculation preferentially undergoes denitrification, thereby achieving pre-denitrification and reducing the nitrification load of the subsequent aerobic stage.

[0057] The first aerobic zone relies solely on traditional blower aeration, thus creating an aerobic environment of "oxygenation within the membrane of the first anoxic zone + aeration of the aqueous phase in the first aerobic zone." Under this environment: The inner layer of the biofilm receives sufficient oxygen, which is conducive to the growth of nitrifying bacteria and promotes ammonia nitrogen oxidation; the outer layer of the biofilm has a low oxygen concentration and is in a hypoxic or anaerobic state, which is conducive to the formation of a microenvironment for simultaneous nitrification and denitrification; the first aerobic zone has the functions of removing organic matter, enhancing nitrification, and removing part of the total phosphorus.

[0058] The first MABR membrane tank is not an independent reactor, but rather an enhanced core for denitrification in the anoxic zone before AO.

[0059] 2. Fusion logic between the AOA downstream section and the second and third MABR membrane boxes The effluent from the first aerobic zone enters the intermediate anaerobic carbon release zone. The function of this intermediate anaerobic carbon release zone is not simply to flush water, but to use the returned sludge and residual organic matter to perform anaerobic carbon and phosphorus release. On the one hand, it releases internal carbon sources that can be used for subsequent denitrification, and on the other hand, it decomposes polyphosphates in the body and absorbs organic matter to synthesize polyhydroxy fatty acid esters, providing an energy basis for subsequent aerobic phosphorus uptake.

[0060] The effluent from the intermediate anaerobic carbon release zone enters the second aerobic zone, where residual ammonia nitrogen is oxidized, and the resulting nitrate nitrogen flows into the second anoxic zone. At this point, the second MABR membrane tank is activated for enhanced downstream denitrification. Since the intermediate anaerobic carbon release zone has already completed a certain degree of carbon release, the second anoxic zone can utilize this endogenous carbon source to further denitrify the nitrate nitrogen output from the second aerobic zone, thus achieving deep denitrification. When the total nitrogen content in the raw wastewater is high, the third MABR membrane tank in the second anoxic zone is activated. Compared to the first MABR membrane tank, the second and third MABR membrane tanks focus more on: further denitrifying the remaining nitrate nitrogen to ensure that the effluent total nitrogen meets standards; and maintaining stable biofilm activity under low dissolved oxygen conditions.

[0061] If the total phosphorus content in the raw water is high, the fourth MABR membrane tank, located in the intermediate anaerobic carbon release zone, is activated. This tank works in conjunction with suspended polyphosphate-accumulating bacteria in the wastewater to release phosphorus and decompose organic matter, thus providing conditions for excessive phosphorus uptake in the subsequent aerobic zone.

[0062] The second and third MABR membrane tanks, together with the second anoxic zone, constitute the core denitrification unit of the AOA downstream section. Therefore, the AOA downstream section in this invention is not arranged in a simple "anaerobic-aerobic-anoxic" sequence in the traditional sense. Instead, by leveraging the enhanced denitrification characteristics of the second and third MABR membrane tanks, the second anoxic zone obtains conditions more suitable for denitrification, thus achieving the goal of efficient denitrification.

[0063] By leveraging the low-oxygen enhanced oxygen supply characteristics of the second MABR membrane tank, the second anoxic zone achieves more suitable influent conditions for denitrification. Specifically, ammonia nitrogen is sufficiently converted; nitrate nitrogen concentration is suitable for deep denitrification; excess dissolved oxygen is suppressed; and the internal carbon source is effectively integrated. After the second MABR membrane tank is installed in the second anoxic zone, the main liquid phase remains anoxic, creating a localized oxygen-supplying microenvironment within the membrane biofilm. This forms a macro-micro nitrification-denitrification environment, where nitrifying and denitrifying bacteria coexist in spatial stratification, which is conducive to the nitrogen removal process.

[0064] In addition, with the addition of a second MABR membrane tank in the second anoxic zone, the zone itself has a certain local nitrification capacity. That is, it no longer relies entirely on external nitrate transport, but can generate some nitrate / nitrite in situ in the inner layer of the biofilm within the zone, and it can be immediately denitrified and utilized in the outer layer or surrounding liquid phase. This changes the situation from "anoxic zone can only consume nitrate" to "anoxic zone can locally generate and simultaneously consume nitrate", which is more conducive to improving nitrogen removal efficiency.

[0065] Mechanistically speaking, the second MABR membrane tank in the second anoxic zone forms a localized aerobic-anoxic stratified microenvironment in the anoxic main environment through oxygen supply within the membrane, causing nitrification in the inner layer of the biofilm and denitrification in the outer layer and the main liquid phase, thereby promoting simultaneous nitrification and denitrification in the second anoxic zone.

[0066] 3. The division of labor and coordination logic of the first MAB membrane box, the second MAB membrane box, the third MABR membrane box, and the fourth MABR membrane box. In this invention, the first MAB membrane box, the second MAB membrane box, the third MABR membrane box, and the fourth MABR membrane box are not redundant, but rather serve different functions.

[0067] (1) The function of the first MABR membrane box is to: focus on reducing the load in the front end, enhance the removal of organic matter, and improve the primary denitrification capacity.

[0068] Specifically: The first MABR membrane tank is a pre-denitrification enhanced type, its function being to reduce ammonia nitrogen load upfront. It provides localized oxygenation within the anoxic environment, promoting the formation of a simultaneous nitrification and denitrification microenvironment in the first anoxic zone. Partial nitrification occurs through localized oxygenation of the inner layer of the biofilm, causing some ammonia nitrogen to be oxidized prematurely. This directly benefits the reduction of nitrification load in the subsequent O-tank (second aerobic zone) and provides greater stability for rural wastewater with large flow fluctuations. Simultaneously, it utilizes influent primary carbon to achieve simultaneous pre-denitrification, i.e., nitrification and denitrification occur simultaneously.

[0069] The first MABR membrane tank is a pre-denitrification enhancement unit, mainly used to form a local oxygen supply micro-zone in the anoxic environment, and to utilize the original carbon in the influent to achieve partial in-situ oxidation of ammonia nitrogen and simultaneous denitrification, so as to reduce the load of the subsequent aerobic tank and improve the denitrification stability of the upstream AO process.

[0070] (2) The function of the second MABR membrane box is to: prioritize the reduction of deep nitrogen in the later stage, prevent the second aerobic zone from disturbing the dissolved oxygen in the second anoxic zone, and create conditions for deep denitrification.

[0071] The second MABR membrane tank is an in-situ nitrification / start-up type located upstream of the anoxic tank. It's not simply for "re-oxygenation," but rather to rapidly establish a controlled local reaction zone upstream of the second anoxic zone. Its function is to reduce influent disturbance, mitigate the impact of instantaneous flow rate and nitrate load changes on denitrification efficiency, and quickly establish reaction order upstream of the second anoxic zone. Simultaneously, it oxidizes some residual ammonia nitrogen in the effluent from the O-tank (second aerobic zone) into NOx, which is then rapidly utilized by denitrification, thus achieving deep nitrogen reduction in the later stages.

[0072] The second MABR membrane tank is located near the inlet of the second anoxic zone at the end. It is mainly used to establish a synchronous nitrification and denitrification start-up zone at the front end of the second anoxic zone, buffer the fluctuations of the preceding aerobic effluent, and promote the local conversion of residual ammonia nitrogen to nitrate nitrogen / nitrite nitrogen and its immediate denitrification utilization.

[0073] (3) The function of the third MABR membrane tank is to focus on high concentration of ammonia nitrogen in raw water, complete the reduction of remaining total nitrogen, and ensure that the total nitrogen of the effluent meets the standard.

[0074] The third MABR membrane tank is a polished and stabilized type located at the rear end of the second anoxic zone. Its function is to locally oxidize residual ammonia nitrogen that has not been fully converted in the upstream section, or to further couple and remove residual nitrogen in the tank. It is equivalent to adding a "self-stabilizing barrier" to the effluent, which can improve the stability of the total nitrogen (TN) in the system effluent.

[0075] The third MABR membrane tank is located at the effluent end of the second anoxic zone. It is mainly used to form a tail-end polishing reaction zone to further convert the nitrogen that was not completely removed in the front section of the tank, stabilize the effluent quality of the terminal anoxic tank, and improve the stability of total nitrogen removal in the system.

[0076] (4) The function of the fourth MABR membrane box is to focus on the decomposition of organic matter and the release of phosphates, so as to provide conditions for the subsequent removal of total phosphorus.

[0077] The anaerobic phosphorus release synergistic regulation type functions to adjust the local microenvironment and membrane biofilm community structure without significantly disrupting the main anaerobic environment, creating more favorable conditions for phosphorus release and subsequent excessive phosphorus uptake. Utilizing the extremely low oxygen supply from the fourth MABR membrane chamber, a controlled microecological zone can be formed on the membrane surface, helping to stabilize sludge activity and inhibiting unfavorable fermentation or excessive putrefaction in the intermediate anaerobic carbon release zone; forming a more stable functional community helps maintain a better phosphorus release-carbon storage preparation state in the anaerobic section.

[0078] The goal of the fourth MABR is to stabilize the anaerobic phosphorus release process and optimize the distribution of functional microbial communities through local microenvironment regulation without disrupting the main anaerobic phosphorus release reaction, and to provide conditions for improving the stability of anaerobic phosphorus release and subsequent excessive phosphorus uptake.

[0079] In summary, the first MAB membrane tank, the second MAB membrane tank, the third MABR membrane tank, and the fourth MABR membrane tank work together to form an overall operating pattern of "front-end steady-state treatment + back-end deep nitrogen and phosphorus removal". This ensures that the equipment maintains good treatment stability under conditions of low flow, intermittent water inflow, and load fluctuations in rural decentralized sewage, and guarantees that the total effluent nitrogen and phosphorus meet the discharge standards.

[0080] The effects of using the wastewater treatment method of the present invention are as follows: With 10m 3 Taking the / d equipment as an example, after 30 days of continuous operation, the following average operating parameters were measured: Table 1

[0081] Table 2 Average water discharge effect data over 30 consecutive days

[0082] The effluent quality can be stably achieved as follows: COD≤50mg / L, ammonia nitrogen≤1.0mg / L, TN≤15mg / L, preferably≤10mg / L, TP≤0.5mg / L, SS≤10mg / L.

[0083] In other embodiments, when the nitrate nitrogen level in the second anoxic zone increases, the recirculation ratio of nitrified liquid from the first aerobic zone and the second aerobic zone to the first anoxic zone is preferentially increased (the recirculation ratio from the first aerobic zone to the first anoxic zone is 80%–150%Q, and the recirculation ratio from the second aerobic zone to the first anoxic zone is 150%–250%Q; the recirculation flow rate from the second aerobic zone to the second anoxic zone is 50%–150%Q, where Q is the influent flow rate), or the proportion of sludge entering the intermediate anaerobic carbon release zone is increased (the external recirculation sludge distribution ratio is adjusted from A1:A2=70:30 or 60:40 to 50:50 or 40:60).

[0084] In other embodiments, when the ammonia nitrogen concentration in the second aerobic zone increases or the dissolved oxygen (DO) falls below a set value (ammonia nitrogen concentration in the second aerobic zone > 1.5 mg / L, or dissolved oxygen (DO) in the second aerobic zone < 1.0 mg / L), the gas supply to the first MABR membrane chamber is increased (from 0.08–0.12 m³ / L). 3 / h increased to 0.12–0.16m 3 / h), and increase the aeration intensity of the first and second aerobic zones (increase the aeration rate of the first aerobic zone to 0.45–0.60 m³ / h). 3 / h, the aeration rate in the second aerobic zone is increased to 0.45–0.60 m³ / h. 3 / h); Increase the internal recirculation flow rate from the second aerobic zone to the first anoxic zone (from 100%–200%Q to 150%–300%Q, where Q is the influent flow rate).

[0085] In other embodiments, when the redox potential of the intermediate anaerobic carbon release zone is higher than a set threshold, the frequency of auxiliary gas rinsing is reduced (from 2 min / 6 h to 1 min / 8–12 h, or auxiliary gas rinsing is suspended), and the gas supply intensity of the upstream membrane tank (preferably the first MABR membrane tank, and if necessary, a second MABR membrane tank) is reduced (the gas supply of the first MABR membrane tank is reduced to 0.04–0.08 m³ / h). 3 / h, the air supply to the second MABR membrane chamber is reduced to 0.03–0.06m³ / h. 3 ( / h), prioritize reducing the aeration frequency and volume in the first aerobic zone (from continuous aeration to intermittent aeration, with intermittent aeration lasting 20–40 min followed by a 20–40 min pause; reduce the aeration volume in the first aerobic zone to 0.20–0.35 m³ / h). 3 / h).

[0086] In other embodiments, the first MABR membrane box and the second MABR membrane box adopt different gas supply operation modes, wherein the first MABR membrane box is in continuous gas supply mode, and the second MABR membrane box is in continuous gas supply or intermittent gas supply mode.

[0087] The following provides six different operating modes, see Examples 1-6 below.

[0088] Example 1: Conventional Continuous Operation Mode of Municipal Wastewater Treatment The influent first enters the first anoxic zone, where it mixes with the internal reflux mixed liquor from the first and second aerobic zones, as well as the reflux sludge from the sedimentation zone. The mixed liquor then enters the first aerobic zone via the first MABR membrane tank. The effluent from the first aerobic zone enters the intermediate anaerobic carbon release zone, where it contacts the reflux sludge from the sedimentation zone to release carbon, and then enters the second aerobic zone. The effluent from the second aerobic zone enters the second anoxic zone via the second MABR membrane tank, and then re-enters the sedimentation zone. During operation, the first MABR membrane tank maintains continuous aeration, while the second MABR membrane tank provides continuous or variable-frequency aeration based on the nitrate nitrogen load of the downstream second anoxic zone. The auxiliary air scrubbing pipe is intermittently activated.

[0089] Example 2: Low C / N influent deep denitrification operation mode When the influent carbon-to-nitrogen ratio is low, the proportion of sludge returned from the sedimentation zone to the intermediate anaerobic carbon release zone is increased, allowing more internal carbon sources to be released in the intermediate anaerobic carbon release zone. Simultaneously, the air supply within the membranes of the second aerobic zone and the second MABR membrane chamber is increased, creating more stable enhanced nitrogen removal conditions in the transition section from the second aerobic zone to the second anoxic zone. Under this mode, the air supply to the first MABR membrane chamber remains at a moderate level, prioritizing the removal of total nitrogen in the upstream section; the air supply to the second MABR membrane chamber is moderately increased, with the downstream second anoxic zone primarily regulated by nitrate nitrogen feedback.

[0090] Example 3: High ammonia nitrogen shock load operation mode When the ammonia nitrogen level in the influent rises instantaneously, increase the gas supply within the membrane of the first MABR membrane chamber (from 0.08–0.12 m³ / s). 3 / h increased to 0.12–0.18m 3 / h), and increase the conventional aeration intensity of the first and second aerobic zones (increase the aeration rate of the first aerobic zone to 0.45–0.65 m³ / h). 3 / h, the aeration rate in the second aerobic zone is increased to 0.45–0.60 m³ / h. 3 / h); increase the internal recirculation flow from the second aerobic zone to the first anoxic zone (from 100%–200%Q to 150%–300%Q, where Q is the influent flow); simultaneously start the third MABR membrane tank. In this mode, the second MABR membrane tank maintains basic air supply, while the first MABR membrane tank still undertakes the enhanced denitrification function at the front end; once the influent ammonia nitrogen recovers, the normal air supply level will be restored.

[0091] Example 4: Operation mode during low-temperature seasons During the low temperatures of winter, the nitrification rate decreases, so an operation mode of "continuous air supply to the first MABR membrane tank + continuous low-frequency air supply to the second MABR membrane tank + low-frequency intermittent auxiliary air washing" is adopted. By reducing the air washing frequency and minimizing unnecessary disturbances, the stability of the biofilm on the membrane surface is maintained; at the same time, by appropriately increasing the residence time in the second aerobic zone and the air supply to the second MABR membrane tank, the distribution of denitrifiable substrates before the second anoxic zone is maintained.

[0092] Example 5: Energy-saving intermittent coordinated operation mode When the total nitrogen in the effluent has stabilized and met the standard, and the nitrate nitrogen load in the second anoxic zone is low, the first MABR membrane tank maintains low-amplitude continuous air supply, while the second MABR membrane tank switches to intermittent air supply. The third and fourth MABR membrane tanks are adjusted according to the nitrogen and phosphorus levels in the effluent. Auxiliary air scrubbing is only activated within a set cycle. This mode is used to reduce overall energy consumption and minimize disturbance to dissolved oxygen in the intermediate anaerobic carbon release zone and the subsequent anoxic zone.

[0093] Example 6: High Phosphorus Load Operation Mode When the total phosphorus in the influent suddenly increases, the membrane in the first MABR tank maintains continuous low-pressure air supply, reducing the aeration rate in the first aerobic zone to prevent dissolved oxygen from flowing into the intermediate anaerobic carbon release zone. Simultaneously, the regular aeration intensity in the second aerobic zone is increased, increasing the proportion of sludge returned from the sedimentation zone to enter the intermediate anaerobic carbon release zone, allowing more sludge to complete phosphorus release in the intermediate anaerobic carbon release zone and over-phosphorus uptake in the first and second aerobic zones. The third MABR tank is then activated. In this mode, the second and third MABR tanks maintain basic air supply until the total phosphorus in the influent recovers, at which point the aeration rates in the first and second aerobic zones are restored.

[0094] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An AO-AOA coupled MABR wastewater treatment method, wherein the method employs a wastewater treatment tank, the wastewater treatment tank being internally divided into a first anoxic zone, a first aerobic zone, an intermediate anaerobic carbon release zone, a second aerobic zone, a second anoxic zone, a sedimentation zone, and an effluent zone, distributed sequentially along the water flow direction; at least one of the first anoxic zone, the intermediate anaerobic carbon release zone, and the second anoxic zone is equipped with a MABR membrane tank, characterized in that... The wastewater treatment method includes: During the flow of wastewater through the first anoxic zone, the second aerobic zone, the intermediate anaerobic carbon release zone, the second aerobic zone, the second anoxic zone, and the sedimentation zone, a portion of the wastewater in the sedimentation zone flows back into the intermediate anaerobic carbon release zone and / or the first anoxic zone; a portion of the effluent in the first aerobic zone flows back into the first anoxic zone, and / or a portion of the effluent in the second aerobic zone flows back into the first anoxic zone. During operation, based on one or more of the following indicators—the second anoxic zone indicator, the intermediate anaerobic carbon release zone indicator, the second aerobic zone indicator, and the effluent indicator—one or more of the following are adjusted: air supply to the MABR membrane tank, aeration rate of the first aerobic zone, aeration rate of the second aerobic zone, auxiliary air washing frequency, external sludge distribution ratio, and internal reflux flow rate. The external sludge distribution ratio is the ratio of the amount of sludge from the sedimentation zone to the first anoxic zone to the amount of sludge from the sedimentation zone to the intermediate anaerobic carbon release zone. The internal reflux flow rate refers to the amount of effluent from the first aerobic zone that flows back into the first anoxic zone, or the amount of effluent from the second aerobic zone that flows back into the first anoxic zone, or the sum of the amounts of effluent from the first aerobic zone and the second aerobic zone that flows back into the first anoxic zone. The second anoxic zone indicator, the intermediate anaerobic carbon release zone indicator, and the second aerobic zone indicator all include oxidation-reduction potential and dissolved oxygen. The effluent parameters include one or more of the following: nitrate nitrogen, ammonia nitrogen, TP, TN, and phosphorus release; the effluent parameters include one or more of the following: TP, TN, COD, ammonia nitrogen, and SS in the effluent from the effluent zone.

2. The AO-AOA coupled MABR wastewater treatment method according to claim 1, characterized in that, A first MABR membrane chamber is provided in the first anoxic zone, and a second MABR membrane chamber and a third MABR membrane chamber are provided in the second anoxic zone. The second MABR membrane chamber is closer to the second aerobic zone than the third MABR membrane chamber.

3. The AO-AOA coupled MABR wastewater treatment method according to claim 2, characterized in that, When the effluent NO3-N in the second anoxic zone is >2.0 mg / L and the effluent TN is >15 mg / L: The air supply to the second MABR membrane chamber was adjusted to 0.05-0.06 m³. 3 / h; The air supply to the third MABR membrane chamber is adjusted to 0.03-0.05m³. 3 / h; The aeration rate in the second aerobic zone was adjusted to 0.25-0.35 m³ / h. 3 / h; The internal reflux flow rate from the second aerobic zone to the first hypoxic zone is adjusted to 100-150%Q; The ratio of the sludge from the sedimentation zone to the first anoxic zone to the sludge from the sedimentation zone to the intermediate anaerobic carbon release zone is (40:60) - (50:50).

4. The AO-AOA coupled MABR wastewater treatment method according to claim 3, characterized in that, A fourth MABR membrane chamber is provided in the intermediate anaerobic carbon release zone. If the ORP of the anaerobic carbon release zone is lower than -250 mV, the fourth MABR membrane chamber is started at a low frequency. If the ORP of the anaerobic carbon release zone is in the range of -120 mV to -250 mV, the fourth MABR membrane chamber is not started.

5. The AO-AOA coupled MABR wastewater treatment method according to claim 4, characterized in that, The air supply range of the fourth MABR membrane chamber is 0.01–0.03 m³. 3 / h.

6. The AO-AOA coupled MABR wastewater treatment method according to claim 2, characterized in that, When the ammonia nitrogen in the effluent from the second aerobic zone is >1.5 mg / L, the dissolved oxygen in the second aerobic zone is <1.0 mg / L, and the ammonia nitrogen in the effluent from the effluent zone is >1.0 mg / L: The air supply to the first MABR membrane chamber in the first anoxic zone was adjusted to 0.12-0.16 m³. 3 / h; The air supply to the second MABR membrane chamber was adjusted to 0.10-0.12 m³. 3 / h; The air supply volume of the third MABR membrane chamber is adjusted to 0.05-0.08 m³. 3 / h; The aeration rate of the first aerobic zone was adjusted to 0.50-0.60 m³. 3 / h; The aeration rate in the second aerobic zone was adjusted to 0.45-0.60 m³ / s. 3 / h; The internal return flow rate range is 180-250%Q; The frequency of auxiliary air washing should be adjusted to 3-5 min / 4h; The total amount of sludge from the sedimentation zone to the first anoxic zone and the intermediate anaerobic carbon release zone is 50%–100% of the influent flow rate Q.

7. The AO-AOA coupled MABR wastewater treatment method according to claim 2, characterized in that, A fourth MABR membrane tank is installed in the intermediate anaerobic carbon release zone. If the ORP of the intermediate anaerobic carbon release zone is higher than -100 mV, the phosphorus release rate of the intermediate anaerobic carbon release zone is less than 20%–30% of the influent TP, and the effluent TP is greater than 0.5 mg / L: The fourth MABR membrane chamber is closed; The ratio of sludge from the sedimentation zone to the first anoxic zone and sludge from the sedimentation zone to the intermediate anaerobic carbon release zone is (70:30) - (80:20). The air supply to the first MABR membrane chamber was adjusted to 0.06-0.08 m³. 3 / h; The dissolved oxygen range in the second aerobic zone is 1.5-2.0 mg / L.

8. The AO-AOA coupled MABR wastewater treatment method according to claim 2, characterized in that, A fourth MABR membrane tank is installed in the intermediate anaerobic carbon release zone. If the ORP of the intermediate anaerobic carbon release zone is lower than -250 mV, the effluent TP rises to 0.6–1.5 mg / L, or the effluent TP is higher than 0.5 mg / L for 2–3 consecutive monitoring cycles, and the fluctuation range of the orthophosphate concentration in the effluent of the intermediate anaerobic carbon release zone is >20%–30% between adjacent monitoring cycles, or the phosphorus release fluctuates >0.5–1.0 mg / L, The air supply of the fourth MABR membrane chamber is then adjusted to 0.01-0.03 m³. 3 / h, and operate intermittently at 5-10 min / 2-4 h; the ORP of the intermediate anaerobic carbon release zone is controlled at -150 to -220 mV; the ratio of sludge from the sedimentation zone to the first anoxic zone and from the sedimentation zone to the intermediate anaerobic carbon release zone is (50:50)-(60:40); the dissolved oxygen in the second aerobic zone is 1.5-2.0 mg / L.

9. The AO-AOA coupled MABR wastewater treatment method according to claim 2, characterized in that, When the ammonia nitrogen concentration in the second aerobic zone increases or the dissolved oxygen is lower than the set value, the air supply of the first MABR membrane box is increased, and the aeration of the first MABR membrane box and the second aerobic zone is increased, thereby increasing the internal return flow from the second aerobic zone to the first anoxic zone.

10. The AO-AOA coupled MABR wastewater treatment method according to claim 1, characterized in that, The second aerobic zone is equipped with dissolved oxygen and / or ammonia nitrogen detection points; the intermediate anaerobic carbon release zone is equipped with oxidation-reduction potential detection points; the second anoxic zone is equipped with nitrate nitrogen detection points; and the effluent zone is equipped with total nitrogen and / or ammonia nitrogen detection points.

Images