AOA process adaptive MBR membrane tank optimization design method

Abstract

The application discloses an AOA process adaptive MBR membrane tank optimization design method, which comprises the following steps: according to the water quality characteristic difference of each reaction section of the AOA process, the MBR membrane tank is divided into a pretreatment area, a core filtration area and a sludge buffer area along the water flow direction; according to the sludge concentration distribution law of the AOA process along the pipeline, the core filtration area is divided into a first filtration sub-area and a second filtration sub-area, and membrane components are arranged at different intervals to form an asymmetric arrangement pattern matched with the sludge load gradient; independent control aeration units are arranged at different spatial positions, and the aeration intensity is dynamically adjusted according to the AOA process operation parameters and the membrane tank state parameters; two reflux branches connected to the anaerobic section and the aerobic section of the AOA process are constructed, and the reflux amount is dynamically adjusted according to the sludge concentration and the dissolved oxygen demand; a pollutant interception unit is arranged in the pretreatment area, and a membrane pollution prevention and control system combining online cleaning and offline maintenance is constructed.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to an MBR (membrane bioreactor) membrane tank optimization design method that is deeply adapted to the characteristics of AOA (anaerobic-aerobic-anoxic) biological treatment process, applicable to the deep treatment and resource utilization of municipal sewage and industrial wastewater. Background Technology

[0002] The AOA process achieves highly efficient removal of organic matter, nitrogen, and phosphorus through a multi-stage synergistic effect of anaerobic phosphorus release, aerobic phosphorus uptake / nitrification, and anoxic denitrification, offering advantages such as high carbon source utilization and low energy consumption. The MBR process utilizes the physical retention of membrane modules to replace traditional secondary sedimentation tanks, offering advantages such as high solid-liquid separation efficiency, excellent effluent quality, long sludge age, and small footprint. The coupling of these two processes to form the AOA-MBR process has become one of the mainstream technologies in the field of advanced wastewater treatment and reuse.

[0003] However, existing AOA-MBR processes mostly employ simple modular designs, failing to fully consider the unique hydraulic characteristics and microbial metabolic features of the AOA process on the MBR membrane tank, resulting in limited overall system efficiency. The main technical problems are as follows: I. The spatiotemporal heterogeneity of AOA process effluent has been overlooked. Significant differences exist in the effluent quality across the various reaction zones (anaerobic, aerobic, and anoxic) of the AOA process. Measured data show that the effluent from the anoxic zone typically exhibits low dissolved oxygen (DO≤0.3mg / L), high nitrate nitrogen (NO3-N≥10mg / L), and the presence of specific denitrifying sludge flocs; while the effluent from the aerobic zone is characterized by high dissolved oxygen (DO≥2mg / L) and low nitrate nitrogen. Directly introducing this effluent with significant spatiotemporal heterogeneity into a traditional, single-structure MBR membrane tank will cause turbulent flow patterns and uneven dissolved oxygen distribution within the membrane tank, affecting membrane filtration efficiency and exacerbating membrane fouling.

[0004] Second, the spatial gradient of sludge loading within the membrane tank is ignored. The sludge concentration in the AOA process exhibits a regular variation, typically higher in the aerobic section (6000-8000 mg / L) and relatively lower in the anoxic section (4000-5000 mg / L). This spatial gradient of sludge concentration results in an uneven distribution of sludge loading entering the membrane tank, exhibiting a pattern of high loading near the influent and low loading further away. Existing membrane tanks use a uniform arrangement of membrane modules, which is mismatched with this spatial gradient of sludge loading, leading to uneven sludge loading within the membrane tank. Areas near the influent experience severe sludge deposition, while areas further away have insufficient sludge concentration.

[0005] Third, the functional coupling of the aeration system leads to a contradiction between energy consumption and efficiency. Traditional MBR membrane tank aeration systems couple the functions of "membrane purging" and "biological oxygen supply" together, operating in a single aeration mode. This design has an inherent contradiction: to meet the membrane purging requirements, a high aeration intensity is needed to generate sufficient hydraulic shear force, but this leads to excessive oxygen supply, disrupting the anoxic denitrification environment; conversely, reducing the aeration intensity to protect the denitrification environment results in insufficient membrane purging, accelerating membrane fouling. This contradiction makes it impossible for the system to simultaneously achieve low-energy operation and high treatment efficiency.

[0006] Fourth, the rigid design of the recirculation system leads to resource waste. Existing recirculation systems mostly use a fixed recirculation ratio, failing to dynamically adjust according to the real-time needs of each stage of the AOA process. On the one hand, excess sludge from the membrane tank cannot be accurately reused to control sludge age; on the other hand, the dissolved oxygen (typically 2-4 mg / L) in the effluent from the membrane tank is directly discharged, resulting in energy waste. Furthermore, when the influent carbon-nitrogen ratio is low, there is a lack of means to supplement the anoxic zone with trace amounts of dissolved oxygen to promote simultaneous nitrification and denitrification.

[0007] Fifth, membrane fouling control lacks specificity. Characteristic pollutants generated by the AOA process, such as extracellular polymeric substances (EPS) produced in the anaerobic stage and denitrifying sludge flocs produced in the anoxic stage, foul the membrane surface through mechanisms different from those of conventional activated sludge. EPS easily forms a dense gel layer on the membrane surface, while denitrifying sludge flocs have a loose structure but strong adhesion. Common physical and chemical cleaning strategies are insufficient to efficiently remove these characteristic pollutants.

[0008] Of particular importance is the long-standing technical bias held by those skilled in the art that MBR membrane tanks should maintain a uniform and stable hydraulic environment to facilitate the stable operation of the membrane modules. Therefore, existing technical solutions primarily focus on homogenizing the water quality, quantity, and dissolved oxygen entering the membrane tank as much as possible (e.g., by setting up large homogenization or equalization tanks) to avoid impacting the membrane tank. This "passive homogenization" approach has led those skilled in the art, when facing AOA-MBR process optimization problems, to consistently limit themselves to how to "eliminate" differences in effluent from different stages, without ever considering how to "utilize" these differences for optimization design. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of the prior art and provide an optimized design method for an AOA process-adaptive MBR membrane tank, which achieves efficient collaborative operation of the AOA process and the MBR membrane tank through multi-dimensional collaborative optimization.

[0010] To solve one of the aforementioned technical problems, the following technical solution is adopted: An optimized design method for an AOA process-compatible MBR membrane tank includes the following steps: Step S1: Membrane Tank Zoning Design Based on the Spatiotemporal Heterogeneity of AOA Process Effluent This step first obtains the effluent quality characteristic parameters of the anaerobic, aerobic, and anoxic sections of the AOA process through online monitoring or historical data analysis. These characteristic parameters include at least dissolved oxygen concentration (DO), nitrate nitrogen concentration (NO3-N), sludge concentration (MLSS), and extracellular polymeric substances (EPS).

[0011] Based on the differences in the aforementioned characteristic parameters, this invention divides the MBR membrane tank into three functional zones along the water flow direction: a pretreatment zone, a core filtration zone, and a sludge buffer zone. The core idea behind this zoned design is not to make the AOA effluent more uniform, but to achieve a "divide and conquer" approach to different water quality characteristics through zoning.

[0012] The pretreatment zone is directly connected to the effluent from the anoxic section of the AOA process, and its effective volume V1 accounts for 15%-20% of the total effective volume V of the membrane tank. The function of this zone is to reconstruct the flow regime of the AOA anoxic effluent (low DO, high nitrate nitrogen, containing denitrifying sludge flocs). Specifically, inclined plate sedimentation units and microbubble aeration devices are installed in the pretreatment zone. The inclined plate sedimentation units have an inclination angle of 60-70° and a plate spacing of 8-10 cm, used to remove large sludge flocs and suspended impurities. The aeration intensity of the microbubble aeration device is precisely controlled to maintain the dissolved oxygen concentration in the pretreatment zone at a microaerobic state of 0.5-1.0 mg / L. The ingenuity of this design lies in two aspects: firstly, moderately increasing DO can inhibit excessive aggregation of denitrifying sludge flocs and improve their settling performance; secondly, maintaining a microaerobic environment avoids the destruction of denitrifying bacteria activity by completely aerobic processes, preserving the carbon source potential required for subsequent denitrification.

[0013] The core filtration zone is located between the pretreatment zone and the sludge buffer zone, with an effective volume V2 accounting for 60%-70% of V. It is the core area for membrane module installation and solid-liquid separation. A guide channel with a slope of 1.5%-2.0% is installed at its bottom to guide the sludge to flow directionally towards the sludge buffer zone, preventing sludge from settling at the bottom of the membrane tank.

[0014] The sludge buffer zone is located at the effluent end of the membrane tank, with an effective volume V3 accounting for 10%-15% of V. This zone is equipped with a sludge concentration sensor and a sludge discharge device, and is connected to both the anaerobic and aerobic sections of the AOA process. When the sludge concentration sensor reading exceeds 8000 mg / L, the sludge discharge device automatically activates, discharging excess sludge to the anaerobic section of the AOA process, achieving precise closed-loop control of sludge age. Simultaneously, the connection between this zone and the aerobic section of the AOA process provides a pathway for subsequent dissolved oxygen recovery and utilization.

[0015] The three functional zones are separated by a guide plate with flow guide holes. The diameter of the flow guide holes is 5-8mm and the spacing between the holes is 15-20cm to ensure a smooth water flow and avoid damage to the membrane module caused by water impact.

[0016] Step S2: Membrane Module Adaptive Layout Based on Sludge Load Gradient Changes. This step first involves sampling along the process to determine the sludge concentration distribution curve of the AOA process, identifying the sludge concentration decay pattern from the anaerobic to the anoxic stage. Based on this pattern, the core filtration zone is divided into two sub-zones: a first filtration sub-zone near the pretreatment zone and a second filtration sub-zone near the sludge buffer zone. 60%-70% of the membrane modules are arranged in the first filtration sub-zone, and 30%-40% are arranged in the second filtration sub-zone, forming an asymmetric layout that matches the sludge load gradient. The physical significance of this design is that the first filtration sub-zone bears a higher sludge load and requires more membrane modules to treat the high-concentration sludge; the second filtration sub-zone bears a lower sludge load, with fewer membrane modules, mainly used for deep filtration to ensure effluent quality.

[0017] In terms of spacing, a gradient spacing arrangement is adopted, gradually increasing in density: the spacing d1 of the membrane modules in the first filtration sub-zone is 0.8-1.0m, and the spacing d2 of the membrane modules in the second filtration sub-zone is 1.2-1.5m, with d1 < d2. The hydrodynamic principle of this design is as follows: in the area with high sludge loading (the first filtration sub-zone), a smaller membrane spacing can enhance hydraulic turbulence, and the stronger hydraulic shear force generated by the dense arrangement can prevent sludge from accumulating on the membrane surface; in the area with low sludge loading (the second filtration sub-zone), a larger membrane spacing is conducive to stable water flow, achieving deep filtration and ensuring the quality of the effluent.

[0018] The membrane module uses hollow fiber ultrafiltration membranes with a pore size of 0.03-0.05 μm and a fiber inner diameter of 0.8-1.0 mm. The effective filtration area of ​​a single membrane module is 30-50 m², and the designed operating flux is controlled at 15-25 L / (m²·h) to adapt to the high sludge concentration (4000-8000 mg / L) operating conditions of the AOA process. The distance between the membrane module and the core filtration zone wall is 0.5-0.8 m, and the distance between the bottom of the membrane module and the bottom of the tank is 0.3-0.5 m to ensure uniform distribution of aeration bubbles and smooth sludge flow.

[0019] Step S3: Spatiotemporal Coupling Aeration Control Based on Influent Water Quality Fluctuations and Membrane Fouling Status. The core of this step is to spatially separate the two intertwined functions of "membrane purging" and "biochemical oxygen supply" in traditional aeration systems and allocate them on demand in time to achieve precise energy delivery.

[0020] Specifically, a first aeration unit is arranged at the bottom of the pretreatment area, a second aeration unit is arranged below the membrane module in the core filtration area, and a third aeration unit is arranged above the membrane module. The second aeration unit uses medium-bubble aeration heads, mainly for generating hydraulic shear force to clean the membrane surface; the third aeration unit uses micro-bubble aeration heads, mainly for supplementing dissolved oxygen to promote nitrification reaction.

[0021] Three key control parameters are collected in real time: the ammonia nitrogen concentration N1 in the effluent of the aerobic section of the AOA process, the nitrate nitrogen concentration N2 in the effluent of the anoxic section, and the transmembrane pressure difference TMP of the membrane module. An aeration regulation model is constructed, and the aeration intensity of each aeration unit is dynamically adjusted according to the following rules: Rule 1 (membrane fouling response): When TMP > the first threshold T1 (30 kPa), it indicates that membrane fouling intensifies. At this time, increase the aeration intensity of the second aeration unit to Q1 (1.2 - 1.5 m³ / (m²·h)), and continuously aerate for a time t1 (30 - 60 min) to restore the membrane flux through strong hydraulic flushing.

[0022] Rule 2 (nitrification demand response): When N1 > the second threshold A1 (5 mg / L), it indicates that the nitrification reaction is insufficient. At this time, increase the aeration intensity of the third aeration unit to Q2 (0.8 - 1.0 m³ / (m²·h)) to strengthen the oxidation of residual ammonia nitrogen.

[0023] Rule 3 (denitrification protection response): When N2 > the third threshold B1 (10 mg / L), it indicates that the denitrification environment may be damaged. At this time, reduce the aeration intensity of the third aeration unit to Q3 (0.4 - 0.6 m³ / (m²·h)), and Q3 < Q2, to avoid excessive aeration bringing in too much dissolved oxygen and protecting the anaerobic / anoxic microenvironment of subsequent denitrifying bacteria.

[0024] This aeration regulation strategy of spatial decoupling and time adaptation solves the functional coupling contradiction between "membrane surface purging" and "biochemical oxygen supply" in the traditional aeration system, enabling the system to dynamically adjust according to real-time demands and achieving the unity of low energy consumption and high efficiency.

[0025] Step S4: Dual-path dynamic reflux regulation based on coordinated recovery of matter and energy. The core of this step is to reuse the surplus sludge and dissolved oxygen in the membrane tank for the AOA process, forming an internal cycle of matter and energy to improve the overall energy efficiency.

[0026] Construct a first reflux branch for the return of the sludge mixture, and return the sludge mixture in the sludge buffer zone to the anaerobic section of the AOA process. Monitor the sludge concentration C in the anaerobic section in real time, and dynamically adjust the reflux ratio R1 of the first reflux branch according to the following rules: When C < Cmin (4000 mg / L), R1 = R1max (120% - 150%); When C > Cmax (6000 mg / L), R1 = R1_min (50% - 80%); When Cmin ≤ C ≤ Cmax, R1 = f(C), where f(C) is a monotonically decreasing function, ensuring that the sludge concentration in the anaerobic section is stable within the optimal range of 4000 - 6000 mg / L.

[0027] Construct a second return branch for the membrane tank effluent reflux, and return the membrane tank effluent to the aerobic section of the AOA process. Monitor the dissolved oxygen concentration DO in the aerobic section in real time, and dynamically adjust the reflux ratio R2 of the second return branch according to the following rules: When DO < DO_min (2.0 mg / L), R2 = R2_max (80%); When DO > DO_max (3.0 mg / L), R2 = R2_min (30%); When DO_min ≤ DO ≤ DO_max, R2 = g(DO), where g(DO) is a monotonically decreasing function.

[0028] Through the second return branch, the dissolved oxygen (2 - 4 mg / L) rich in the membrane tank effluent is recycled. After being returned to the aerobic section, it can replace part of the fresh aeration, reducing the aeration energy consumption in the aerobic section.

[0029] Meanwhile, when the C / N ratio of the AOA process influent is lower than the fourth threshold K1 (3), part of the effluent of the second return branch is selectively returned to the anoxic section of the AOA process, and the reflux ratio R3 is controlled at 20% - 40%. This seemingly "counterintuitive" design (bringing oxygen into the anoxic zone) actually utilizes the synchronous nitrification and denitrification (SND) mechanism under a micro-aerobic environment - the introduction of trace dissolved oxygen can form aerobic microzones on the surface of sludge flocs to achieve the oxidation of ammonia nitrogen, while the interior of the flocs remains anoxic for denitrification, thereby improving the total nitrogen removal efficiency without consuming additional carbon sources.

[0030] To better achieve the invention purpose, the present invention also has the following more optimal technical solutions: In some embodiments, it further includes step S5 of constructing a three-level membrane pollution prevention and control system of "source interception - online cleaning - offline maintenance": Source interception: Set an interception unit above the inclined plate sedimentation component in the pretreatment area, specifically an extracellular polymer interception net (EPS interception net) with a pore size of 100 - 150 mesh, used to intercept the extracellular polymers and large-size denitrifying sludge flocs carried by the AOA process effluent, reducing the contact between pollutants and the core filtration area and membrane components. Clean the interception net regularly, and the cleaning cycle is 7 - 10 days.

[0031] Online Cleaning: An online cleaning unit is constructed, employing a combination of "air-water combined backwashing + chemically enhanced backwashing". The air-water combined backwashing cycle is 30-60 minutes, the backwashing pressure is 0.1-0.15 MPa, the backwashing time is 1-2 minutes, and the air-water volume ratio is 5:1. The chemically enhanced backwashing cycle is 7-10 days, using alternating oxidizing cleaning agents (500-800 mg / L sodium hypochlorite solution) and acidic cleaning agents (1000-1500 mg / L citric acid solution), with each cleaning agent lasting 30-60 minutes. For EPS contamination generated by the AOA process, 0.1%-0.2% surfactant is added to the chemical cleaning solution. The solubilizing and dispersing effects of the surfactant significantly improve the EPS removal efficiency.

[0032] Offline Maintenance: An offline maintenance unit is constructed. When the membrane module's TMP (Total Molecular Pressure) continuously exceeds the fifth threshold T2 (35 kPa) and online cleaning cannot restore its performance, offline regeneration is performed. Offline maintenance combines 0.3-0.5 MPa high-pressure water rinsing with chemical immersion. Chemical immersion uses a mixture of 1%-2% sodium hydroxide solution and 1000-1500 mg / L sodium hypochlorite solution, with an immersion time of 12-24 hours. Simultaneously, a membrane module maintenance record is established, recording the membrane module's operating time, number of cleaning cycles, and TMP changes. The replacement cycle of the membrane module is determined based on the maintenance record.

[0033] In some embodiments, step S6 is also included: adaptability calibration of the overall parameters of the membrane tank. This step calibrates the overall parameters of the membrane tank according to the design treatment capacity Q of the AOA process, the influent water quality and the target effluent water quality: total effective volume of the membrane tank V = Q × HRT / 24, where HRT is the hydraulic retention time, controlled at 1.5-2.5h. The total number of membrane modules N = Q × 1000 / (24 × F × J), where F is the effective filtration area of ​​a single membrane module (m² / module) and J is the design operating flux (L / (m²·h)), which is controlled at 15-25 L / (m²·h).

[0034] After calibration, the total energy consumption for aeration is reduced by 15%-25% compared to traditional MBR membrane tanks, the rate of increase in transmembrane pressure difference is reduced by 30%-40%, the service life of membrane modules is extended by 20%-30%, and the effluent quality consistently meets the Class IV standard of the "Surface Water Environmental Quality Standard" (COD≤30mg / L, ammonia nitrogen≤5mg / L, total nitrogen≤10mg / L, total phosphorus≤0.5mg / L). Thanks to the aforementioned technical solutions, this application achieves a 10%-15% increase in nitrogen removal efficiency and an 8%-12% increase in phosphorus removal efficiency compared to the traditional AOA-MBR process. Combined with dissolved oxygen reuse in the membrane tank effluent, the total energy consumption for aeration is reduced by 15%-25% compared to traditional MBR membrane tanks. Through source interception, targeted cleaning, and optimized hydraulic conditions, the rate of increase in transmembrane pressure difference (TMP) is reduced by 30%-40%, and the membrane module lifespan is extended by 20%-30%. Even with influent COD and ammonia nitrogen concentration fluctuations of ±30%, the effluent quality from the membrane tank remains consistently up to standard, demonstrating a significantly improved resistance to shock loads. Attached Figure Description

[0035] Figure 1 This is a flowchart of the optimized design method for an AOA process-adapted MBR membrane tank according to the present invention; Figure 2 This is a schematic diagram of the membrane pool partition structure and the gradient arrangement of the membrane modules of the present invention; Figure 3 This is a block diagram of the intelligent control logic of the aeration system and the reflux system of the present invention; Figure 4 This is a schematic diagram illustrating the synergistic mechanism of each step in the present invention. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The embodiments are only intended to provide a clearer understanding of the technical features, objectives and effects of the present invention.

[0037] This application provides an optimized design method for an AOA process-adaptive MBR membrane tank, including the following steps: Step S1: Based on the spatiotemporal heterogeneity of the AOA process effluent, the membrane tank is partitioned to obtain characteristic parameters of the effluent quality in the anaerobic, aerobic, and anoxic sections of the AOA process. These characteristic parameters include at least dissolved oxygen concentration, nitrate nitrogen concentration, sludge concentration, and extracellular polymeric substance content. According to the differences in these characteristic parameters, the MBR membrane tank is divided into three functional zones along the water flow direction: a pretreatment zone, a core filtration zone, and a sludge buffer zone. The pretreatment zone is directly connected to the effluent end of the anoxic section of the AOA process, and its effective volume V1 accounts for 15%-20% of the total effective volume V of the membrane tank. It is used to receive influent with low dissolved oxygen and high nitrate nitrogen and to reconfigure the flow pattern. The effective volume V2 of the core filtration zone accounts for 60%-70% of V and is used to arrange membrane modules and achieve solid-liquid separation. The effective volume V3 of the sludge buffer zone accounts for 10%-15% of V and is used for sludge thickening and recirculation control.

[0038] Step S2: Based on the adaptability of membrane module arrangement to change sludge loading gradient, determine the sludge concentration distribution curve along the AOA process and identify the sludge concentration decay pattern from the anaerobic section to the anoxic section. According to the attenuation law, the core filtration area is divided into a first filtration sub-area close to the pretreatment area and a second filtration sub-area close to the sludge buffer area; 60%-70% of the membrane modules are arranged in the first filtration sub-area, and 30%-40% of the membrane modules are arranged in the second filtration sub-area, forming an asymmetric layout pattern matching the sludge load gradient; the distance d1 between the membrane modules in the first filtration sub-area is set to 0.8-1.0 m, and the distance d2 between the membrane modules in the second filtration sub-area is set to 1.2-1.5 m, and d1 < d2, forming a gradient distance layout that gradually becomes sparser.

[0039] Step S3: Spatiotemporal coupling aeration regulation based on influent water quality fluctuations and membrane fouling status. A first aeration unit is set at the bottom of the pretreatment area, a second aeration unit is set below the membrane modules in the core filtration area, and a third aeration unit is set above the membrane modules; the ammonia nitrogen concentration N1 in the effluent of the aerobic section of the AOA process, the nitrate nitrogen concentration N2 in the effluent of the anoxic section, and the transmembrane pressure difference TMP of the membrane modules are collected in real time; an aeration regulation model is constructed, and the aeration intensity of each aeration unit is dynamically adjusted according to the following rules: when TMP > the first threshold T1, increase the aeration intensity of the second aeration unit to Q1 and continuously aerate for a time t1; when N1 > the second threshold A1, increase the aeration intensity of the third aeration unit to Q2; when N2 > the third threshold B1, decrease the aeration intensity of the third aeration unit to Q3, and Q3 < Q2.

[0040] Step S4: Dual-path dynamic reflux regulation based on the synergistic recovery of substances and energy. A first reflux branch is constructed to reflux the sludge mixture in the sludge buffer area to the anaerobic section of the AOA process, and the sludge concentration C in the anaerobic section is monitored in real time. The reflux ratio R1 of the first reflux branch is dynamically adjusted according to the following rules: When C < Cmin, R1 = R1_max; when C > Cmax, R1 = R1_min; when Cmin ≤ C ≤ Cmax, R1 = f(C), where f(C) is a monotonically decreasing function; A second reflux branch is constructed to reflux the effluent of the membrane tank to the aerobic section of the AOA process, and the dissolved oxygen concentration DO in the aerobic section is monitored in real time. The reflux ratio R2 of the second reflux branch is dynamically adjusted according to the following rules: When DO < DO_min, R2 = R2_max; when DO > DO_max, R2 = R2_min; when DO_min ≤ DO ≤ DO_max, R2 = g(DO), where g(DO) is a monotonically decreasing function; at the same time, when the C / N ratio of the influent of the AOA process is lower than the fourth threshold K1, part of the effluent of the second reflux branch is selectively refluxed to the anoxic section of the AOA process, and the reflux ratio R3 is controlled to be 20%-40%.

[0041] The flow regime reconstruction in the pretreatment zone in step S1 includes: setting up an inclined plate sedimentation assembly in the pretreatment zone with an inclination angle of 60-70° and a plate spacing of 8-10cm to remove large sludge flocs and suspended impurities; setting up a microbubble aeration device at the bottom of the pretreatment zone to precisely control the dissolved oxygen concentration in the pretreatment zone at a micro-oxygen state of 0.5-1.0mg / L by controlling the aeration intensity, so that the water entering the core filtration zone maintains the activity of denitrifying bacteria while improving sludge settling performance.

[0042] The three functional zones mentioned in step S1 are separated by a guide plate with flow guide holes. The diameter of the flow guide holes is 5-8mm and the spacing between the holes is 15-20cm. This is to ensure a smooth water flow transition and avoid water impact causing damage to the membrane module.

[0043] In step S1, a sludge concentration sensor and a sludge discharge device are installed in the sludge buffer zone. The sludge discharge device is connected to the anaerobic section of the AOA process. When the sludge concentration sensor detects a value exceeding 8000 mg / L, the sludge discharge device is automatically activated to return excess sludge to the anaerobic section, thereby achieving closed-loop control of the system's sludge age.

[0044] In step S2, the membrane module is a hollow fiber ultrafiltration membrane with a pore size of 0.03-0.05 μm, a fiber inner diameter of 0.8-1.0 mm, and an effective filtration area of ​​30-50 m² for a single membrane module. The distance between the membrane module and the core filtration zone wall in step S2 is 0.5-0.8 m, and the distance between the bottom of the membrane module and the bottom of the tank is 0.3-0.5 m to ensure uniform distribution of aeration bubbles and smooth sludge flow.

[0045] In step S3, the first threshold T1 is 30 kPa, the second threshold A1 is 5 mg / L, and the third threshold B1 is 10 mg / L; the aeration intensity Q1 of the second aeration unit is 1.2-1.5 m³ / (m²·h), and the continuous aeration time t1 is 30-60 min; the aeration intensity Q2 of the third aeration unit is 0.8-1.0 m³ / (m²·h), and Q3 is 0.4-0.6 m³ / (m²·h).

[0046] In step S4, Cmin is 4000 mg / L, Cmax is 6000 mg / L, R1_max is 120%-150%, and R1_min is 50%-80%; DO_min is 2.0 mg / L, DO_max is 3.0 mg / L, R2_max is 80%, and R2_min is 30%; the fourth threshold K1 is 3, and R3 is 20%-40%.

[0047] In some implementations, step S5 is also included: a three-stage membrane fouling control for characteristic pollutants of the AOA process is implemented by setting up an interception unit above the solid-liquid separation device in the pretreatment zone to intercept extracellular polymers and denitrification sludge flocs carried in the effluent of the AOA process. An online cleaning unit was constructed, employing a combination of air-water backwashing and chemically enhanced backwashing. The chemically enhanced backwashing involved alternating between oxidizing and acidic cleaning agents, with the addition of surfactants. An offline maintenance unit is constructed to perform offline regeneration of the membrane module when the membrane module's TMP continuously exceeds the fifth threshold T2 and online cleaning cannot restore it.

[0048] In some implementations, step S6 is also included: Adaptability calibration of overall membrane tank parameters. Based on the design treatment capacity Q of the AOA process, the influent water quality, and the target effluent water quality, the overall parameters of the membrane tank are calibrated. The total effective volume of the membrane tank is V = Q × HRT / 24, where HRT is the hydraulic retention time, controlled at 1.5-2.5h; the total number of membrane modules is N = Q × 1000 / (24 × F × J), where F is the effective filtration area of ​​a single membrane module, and J is the design operating flux, controlled at 15-25 L / (m²·h).

[0049] In step S5, the interception unit is an extracellular polymeric filter with a pore size of 100-150 mesh, and the cleaning cycle is 7-10 days. The combined air-water backwashing cycle is 30-60 minutes, the backwashing pressure is 0.1-0.15 MPa, the backwashing time is 1-2 minutes, and the air-water volume ratio is 5:1. The chemically enhanced backwashing cycle is 7-10 days. The oxidizing cleaning agent is a 500-800 mg / L sodium hypochlorite solution, and the acidic cleaning agent is a 1000-1500 mg / L citric acid solution. The cleaning time for each cleaning agent is 30-60 minutes, and the amount of surfactant added is 0.1%-0.2%. Offline maintenance uses a combination of 0.3-0.5 MPa high-pressure water rinsing and chemical soaking. The chemical soaking uses a mixed solution of 1%-2% sodium hydroxide solution and 1000-1500 mg / L sodium hypochlorite solution, and the soaking time is 12-24 hours.

[0050] The technical effects of reducing total aeration energy consumption by 15%-25%, reducing the rate of increase in transmembrane pressure difference by 30%-40%, and extending membrane module lifespan by 20%-30% as described in step S6 are achieved through the synergistic effect of steps S1 to S5, specifically as follows: The zoned membrane tank design provides the physical basis for gradient arrangement and intelligent aeration. The gradient arrangement of membrane modules works in conjunction with spatiotemporal coupled aeration to configure stronger hydraulic shear in areas with high sludge load and more stable flow in areas with low load, achieving optimal matching between hydraulic conditions and sludge load. The dual-path dynamic recirculation reuses excess sludge and dissolved oxygen from the membrane tank for the AOA process, forming an internal cycle of matter and energy and improving overall energy efficiency. The three-level membrane fouling control system specifically controls pollutants characteristic of the AOA process, significantly slowing down the membrane fouling process.

Claims

1. A method for optimizing the design of an MBR membrane tank adapted to AOA process, characterized in that, It includes the following steps: Step S1: Partition the membrane tank based on the spatio-temporal heterogeneity of the effluent of the AOA process and obtain the characteristic parameters of the effluent quality of the anaerobic section, aerobic section, and anoxic section of the AOA process. The characteristic parameters at least include dissolved oxygen concentration, nitrate nitrogen concentration, sludge concentration, and extracellular polymer content; According to the differences in the characteristic parameters, divide the MBR membrane tank into three functional partitions: a pretreatment area, a core filtration area, and a sludge buffer area along the water flow direction; Among them, the pretreatment area is directly connected to the effluent end of the anoxic section of the AOA process, and its effective volume V1 accounts for 15%-20% of the total effective volume V of the membrane tank, and is used to receive the influent with low dissolved oxygen and high nitrate nitrogen and carry out flow pattern reconstruction; The effective volume V2 of the core filtration area accounts for 60%-70% of V, and is used to arrange membrane modules and achieve solid-liquid separation; The effective volume V3 of the sludge buffer area accounts for 10%-15% of V, and is used for sludge concentration and reflux regulation; Step S2: Measure the distribution curve of the sludge concentration along the AOA process based on the adaptability arrangement of the membrane modules with the change of the sludge load gradient, and identify the law of sludge concentration attenuation from the anaerobic section to the anoxic section; According to the attenuation law, divide the core filtration area into a first filtration sub-area close to the pretreatment area and a second filtration sub-area close to the sludge buffer area; Arrange 60%-70% of the membrane modules in the first filtration sub-area and 30%-40% of the membrane modules in the second filtration sub-area to form an asymmetric arrangement pattern matching the sludge load gradient; Set the spacing d1 between the membrane modules in the first filtration sub-area to be 0.8-1.0m, and the spacing d2 between the membrane modules in the second filtration sub-area to be 1.2-1.5m, and d1 < d2, forming a gradient spacing arrangement from dense to sparse; Step S3: Based on the spatio-temporal coupling aeration regulation of the influent water quality fluctuation and membrane fouling state, set a first aeration unit at the bottom of the pretreatment area, set a second aeration unit below the membrane modules in the core filtration area, and set a third aeration unit above the membrane modules; Real-time collect the ammonia nitrogen concentration N1 of the effluent of the aerobic section of the AOA process, the nitrate nitrogen concentration N2 of the effluent of the anoxic section, and the transmembrane pressure difference TMP of the membrane modules; Construct an aeration regulation model and dynamically adjust the aeration intensity of each aeration unit according to the following rules: When TMP > the first threshold T1, increase the aeration intensity of the second aeration unit to Q1 and continuously aerate for a time t1; When N1 > the second threshold A1, increase the aeration intensity of the third aeration unit to Q2; When N2 > the third threshold B1, decrease the aeration intensity of the third aeration unit to Q3, and Q3 < Q2; Step S4: Based on the dual-channel dynamic reflux regulation of the coordinated recovery of matter and energy, construct a first reflux branch, return the sludge mixture in the sludge buffer area to the anaerobic section of the AOA process, and continuously monitor the sludge concentration C in the anaerobic section. Dynamically adjust the reflux ratio R1 of the first reflux branch according to the following rules: When C < Cmin, R1 = R1_max; When C > Cmax, R1 = R1_min; When Cmin ≤ C ≤ Cmax, R1 = f(C), where f(C) is a monotonically decreasing function; Construct a second reflux branch to reflux the effluent from the membrane tank to the aerobic section of the AOA process. Monitor the dissolved oxygen concentration DO in the aerobic section in real time and dynamically adjust the reflux ratio R2 of the second reflux branch according to the following rules: When DO < DO_min, R2 = R2_max; When DO > DO_max, R2 = R2_min; When DO_min ≤ DO ≤ DO_max, R2 = g(DO), where g(DO) is a monotonically decreasing function; Meanwhile, when the C / N ratio of the influent to the AOA process is lower than the fourth threshold K1, part of the effluent of the second reflux branch is selectively refluxed to the anoxic section of the AOA process, and the reflux ratio R3 is controlled to be 20% - 40%.

2. The AOA process-adaptive MBR membrane tank optimization design method according to claim 1, characterized in that, It also includes step S5: For the three - level membrane pollution prevention and control of the characteristic pollutants of the AOA process, set an interception unit above the solid - liquid separation device in the pretreatment area to intercept extracellular polymers and denitrifying sludge flocs carried by the effluent of the AOA process; construct an online cleaning unit, adopting a combined mode of air - water combined backwashing and chemically enhanced backwashing, where the chemically enhanced backwashing is carried out alternately with an oxidizing cleaning agent and an acidic cleaning agent, and a surfactant is added; construct an offline maintenance unit. When the TMP of the membrane module continuously exceeds the fifth threshold T2 and cannot be restored by online cleaning, perform offline regeneration treatment on the membrane module.

3. The AOA process-adapted MBR membrane tank optimization design method according to claim 1, characterized in that, It also includes step S6: Adaptive calibration of the overall parameters of the membrane tank. According to the designed treatment capacity Q, influent quality and target effluent quality of the AOA process, calibrate the overall parameters of the membrane tank: The total effective volume V of the membrane tank = Q × HRT / 24, where HRT is the hydraulic retention time, controlled to be 1.5 - 2.5 h; the total number of membrane modules N = Q × 1000 / (24 × F × J), where F is the effective filtration area of a single group of membrane modules, and J is the designed operation flux, controlled to be 15 - 25 L / (m²·h).

4. The AOA process-adaptive MBR membrane tank optimization design method according to claim 1, characterized in that, The flow pattern reconstruction in the pretreatment area described in step S1 includes: Set a lamella sedimentation component in the pretreatment area, with an inclination angle of 60 - 70° and a plate spacing of 8 - 10 cm, to remove large - particle sludge flocs and suspended impurities; set a micro - bubble aeration device at the bottom of the pretreatment area, and precisely control the dissolved oxygen concentration in the pretreatment area at a micro - oxygen state of 0.5 - 1.0 mg / L by controlling the aeration intensity, so as to improve the sludge sedimentation performance while maintaining the activity of denitrifying bacteria in the water quality entering the core filtration area.

5. The AOA process-adaptive MBR membrane tank optimization design method according to claim 1, characterized in that, The three functional areas described in step S1 are separated by a baffle plate with diversion holes. The aperture of the diversion holes is 5 - 8 mm and the hole spacing is 15 - 6. The AOA process-adaptive MBR membrane tank optimization design method according to claim 1, characterized in that, ​ 7. The AOA process-adaptive MBR membrane tank optimization design method according to claim 1, characterized in that, The membrane module mentioned in step S2 is a hollow fiber ultrafiltration membrane with a pore size of 0.03-0.05μm, a membrane fiber inner diameter of 0.8-1.0mm, and an effective filtration area of ​​30-50m² for a single membrane module.

8. The AOA process-adaptive MBR membrane tank optimization design method according to claim 1, characterized in that, In step S2, the distance between the membrane module and the wall of the core filtration zone is 0.5-0.8m, and the distance between the bottom of the membrane module and the bottom of the tank is 0.3-0.5m, to ensure the uniform distribution of aeration bubbles and the smooth flow of sludge.

9. The AOA process-adaptive MBR membrane tank optimization design method according to claim 1, characterized in that, In step S3, the first threshold T1 is 30 kPa, the second threshold A1 is 5 mg / L, and the third threshold B1 is 10 mg / L; the aeration intensity Q1 of the second aeration unit is 1.2-1.5 m³ / (m²·h), and the continuous aeration time t1 is 30-60 min; the aeration intensity Q2 of the third aeration unit is 0.8-1.0 m³ / (m²·h), and Q3 is 0.4-0.6 m³ / (m²·h).

10. The AOA process-adaptive MBR membrane tank optimization design method according to claim 1, characterized in that, In step S4, Cmin is 4000 mg / L, Cmax is 6000 mg / L, R1_max is 120%-150%, and R1_min is 50%-80%; DO_min is 2.0 mg / L, DO_max is 3.0 mg / L, R2_max is 80%, and R2_min is 30%; the fourth threshold K1 is 3, and R3 is 20%-40%.

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