An energy-saving cleaning process for MBR membrane modules

Abstract

This invention relates to an energy-saving cleaning process for MBR membrane modules. By monitoring the fouling status of the MBR membrane modules and comparing the monitored fouling values ​​with preset thresholds, the process selects an aeration-based cleaning method when the fouling value is below the preset threshold, and an online air-water combined cleaning method when the fouling value reaches the preset threshold. This allows for adaptive selection of the cleaning mode based on the fouling status of the MBR membrane modules, effectively mitigating MBR membrane module fouling, reducing transmembrane pressure differential, stabilizing the permeate flow rate of the MBR membrane modules, reducing reagent and energy consumption, and lowering operation and maintenance costs. It is well-suited for various MBR wastewater treatment projects, including municipal and industrial projects, with stable wastewater treatment efficiency and effects, and significant energy-saving and environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of membrane bioreactor technology, and more specifically to an energy-saving cleaning process for MBR membrane modules. Background Technology

[0002] MBR (Membrane Bioreactor) is a new type of wastewater treatment system that organically combines membrane separation technology and biological treatment technology. The core component of MBR is the MBR membrane module, and the performance of the MBR membrane module directly determines the operation effect of the entire system. It has the advantages of good effluent quality, small footprint, and high sludge concentration, and has been widely used in the fields of municipal sewage and industrial wastewater treatment.

[0003] During MBR operation, membrane fouling is an inevitable problem. Membrane fouling mainly includes inorganic, organic, and biological fouling, which can lead to increased transmembrane pressure and decreased membrane flux. In severe cases, it can even necessitate shutdown and replacement of the membrane modules, significantly increasing operating costs. Therefore, cleaning the MBR membrane modules is a crucial step in ensuring stable system operation.

[0004] However, existing MBR membrane modules typically employ a fixed-cycle offline cleaning mode. This means that during periods when the MBR is not in operation, cleaning agents are added at a preset frequency regardless of the degree of membrane fouling. This not only easily leads to waste of cleaning agents and accelerates membrane material aging, shortening the service life of the MBR membrane module, but also significantly reduces the effective operating time of the system due to frequent offline cleaning, severely restricting the wastewater treatment efficiency. Summary of the Invention

[0005] Therefore, it is necessary to provide an energy-saving cleaning process for MBR membrane modules.

[0006] The technical solution of this invention to solve the above-mentioned technical problems is as follows: An energy-saving cleaning process for MBR membrane modules, comprising the following steps:

[0007] The fouling status of the MBR membrane module is monitored to obtain membrane fouling values;

[0008] The cleaning mode is adaptively selected by comparing the membrane fouling value with a preset threshold.

[0009] Specifically, when the membrane fouling value is lower than the preset threshold, the aeration cleaning method is selected for cleaning; when the membrane fouling value reaches the preset threshold, the online air-water combined cleaning method is selected for cleaning.

[0010] In one embodiment, if the membrane fouling value still does not decrease after the online air-water combined cleaning method is selected, an offline chemical dosing cleaning method is selected.

[0011] In one embodiment, monitoring the fouling status of the MBR membrane module includes:

[0012] Real-time monitoring of the transmembrane pressure difference of the MBR membrane module and the sludge concentration and DO concentration in the water body, with the transmembrane pressure difference used as the membrane fouling value.

[0013] In one embodiment, when comparing the membrane fouling value with a preset threshold, the preset threshold range is set to 0.08 MPa-0.12 MPa.

[0014] In one embodiment, when the membrane fouling value is below a preset threshold, selecting aeration as the cleaning method includes:

[0015] The bottom and sides of the MBR membrane module are aerated through bottom aeration pipes and side rotating aeration pipes. The rotation angle and aeration intensity of the side rotating aeration pipes and the aeration flow rate of the bottom aeration pipes are dynamically adjusted according to the transmembrane pressure difference, sludge concentration and DO concentration.

[0016] In one embodiment, when the membrane fouling value reaches a preset threshold, selecting an online air-water combined cleaning method for cleaning includes:

[0017] The MBR membrane module is flushed with a combination of air and water through a cleaning nozzle, with the air-to-water ratio controlled at 3-5:1 and the cleaning time at 10-15 minutes.

[0018] In one embodiment, when the membrane fouling value has not decreased, and offline cleaning is selected, the cleaning method includes:

[0019] Add a biodegradable cleaning agent to the MBR membrane module, then soak it for 30-60 minutes, and finally rinse it with clean water.

[0020] In one embodiment, the biodegradable cleaning agent is prepared from citric acid, bio-enzymes, and deionized water.

[0021] In one embodiment, when selecting the offline dosing cleaning method for cleaning, the method further includes:

[0022] The wastewater from the cleaning process is recycled, pretreated, and then returned to the inlet of the membrane bioreactor.

[0023] In one embodiment, the MBR membrane module includes a membrane frame and a membrane module, the membrane module being disposed on the membrane frame, the membrane frame having a modular structure and having flow channels formed thereon, the membrane module being composed of multiple hollow fiber ultrafiltration membranes, and the hollow fiber ultrafiltration membranes being coated with an antifouling coating.

[0024] The beneficial effects of this invention are as follows: The energy-saving cleaning process for MBR membrane modules provided by this invention monitors the fouling status of the MBR membrane modules and compares the monitored membrane fouling value with a preset threshold. When the membrane fouling value is lower than the preset threshold, an aeration cleaning method is selected for cleaning; when the membrane fouling value reaches the preset threshold, an online air-water combined cleaning method is selected for cleaning. This allows for adaptive selection of the cleaning mode based on the fouling status of the MBR membrane modules, effectively mitigating MBR membrane module fouling, reducing transmembrane pressure difference, stabilizing the permeate flow of the MBR membrane modules, reducing reagent and energy consumption, lowering operation and maintenance costs, and making it well-suited for various MBR wastewater treatment projects such as municipal and industrial projects. The wastewater treatment efficiency and effect are stable, and it has significant energy-saving and environmental benefits. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic flowchart of an energy-saving cleaning process for an MBR membrane module according to an embodiment of the present invention. Detailed Implementation

[0027] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0028] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0030] In one embodiment, such as Figure 1 As shown, an energy-saving cleaning process for MBR membrane modules includes the following steps:

[0031] Step 110: Monitor the fouling status of the MBR membrane module and obtain the membrane fouling value.

[0032] In this embodiment, monitoring the fouling status of the MBR membrane module specifically includes: real-time monitoring of the transmembrane pressure difference (TMP) of the MBR membrane module and the sludge concentration (MLSS) and dissolved oxygen (DO) concentration in the water, which can comprehensively determine the degree of fouling of the MBR membrane module; wherein, the transmembrane pressure difference is used as the membrane fouling value characterizing the degree of membrane fouling.

[0033] In one embodiment, the MBR membrane module includes a membrane frame and a membrane module. The membrane module is disposed on the membrane frame, which has a modular structure and flow channels. The membrane module is composed of multiple hollow fiber ultrafiltration membranes, and the hollow fiber ultrafiltration membranes are coated with an antifouling coating. Specifically, by making the membrane frame a modular structure, maintenance is facilitated, and the membrane module can be disassembled and replaced. The flow channels on the periphery of the membrane frame enhance water flow disturbance near the membrane surface of the MBR membrane module, reducing concentration polarization and particle deposition, thus reducing sludge accumulation on the surface of the MBR membrane module. The MBR membrane module is composed of hollow fiber ultrafiltration membranes with a pore size of 0.02μm-0.1μm. An antifouling coating, a modified polyvinylidene fluoride layer with a contact angle ≤60°, is coated on the surface of the hollow fiber ultrafiltration membranes, effectively reducing the adsorption of organic pollutants and bioattachment on the surface of the MBR membrane module, thereby reducing the fouling rate of the MBR membrane module.

[0034] In one embodiment, the modification method of the modified polyvinylidene fluoride layer is as follows: hydroxyl groups are generated on the PVDF surface using Fenton's reagent, and the initiator BIBB is fixed on the PVDF surface through the hydroxyl groups to form a haloalkyl initiator (PVDF-Br). Then, on the PVDF-Br surface, hydrophilic monomer hydroxyethyl methacrylate (HEMA) and antibacterial monomer dimethylaminoethyl methacrylate (DMAEMA) are grafted onto the PVDF-Br surface to synthesize PVDF-g-PHEMA and PVDF-g-PDMAEMA polymer brushes. The grafting time is controlled within 10 min-1 h. Finally, the grafted copolymers PVDF-g-PHEMA and / or PVDF-g-PDMAEMA are used as macromolecular additives and blended with the PVDF matrix through an immersion precipitation phase inversion method to form a modified polyvinylidene fluoride material, so that the hydrophilic segments migrate directionally to the surface and pore walls of the polyvinylidene fluoride material.

[0035] Step 120: The membrane fouling value is compared with a preset threshold to adaptively select a cleaning mode. Specifically, when the membrane fouling value is lower than the preset threshold, aeration cleaning is selected; when the membrane fouling value reaches the preset threshold, online air-water combined cleaning is selected.

[0036] In this embodiment, when comparing the membrane fouling value with a preset threshold, the preset threshold range is set to 0.08 MPa-0.12 MPa. Taking a preset threshold of 0.08 MPa as an example, when the transmembrane pressure difference is lower than 0.08 MPa, the aeration cleaning method is selected for online cleaning of the MBR membrane module; when the transmembrane pressure difference reaches 0.08 MPa, the online air-water combined cleaning method is selected for online cleaning of the MBR membrane module.

[0037] In one embodiment, when the membrane fouling value is lower than a preset threshold, the cleaning method of selecting aeration includes: aerating the bottom and sides of the MBR membrane module through bottom aeration pipes and lateral rotating aeration pipes, and dynamically adjusting the rotation angle and aeration intensity of the lateral rotating aeration pipes and the aeration flow rate of the bottom aeration pipes according to the transmembrane pressure difference, sludge concentration, and DO concentration. Specifically, by adopting an aeration structure with multiple bottom aeration pipes and multiple lateral rotating aeration pipes distributed at intervals, and combining real-time monitoring of transmembrane pressure difference, sludge concentration, and DO concentration, the aeration direction and intensity are dynamically adjusted, that is, the rotation angle and aeration intensity of the lateral rotating aeration pipes and the aeration flow rate of the bottom aeration pipes are adjusted. This can eliminate aeration blind spots, enhance the shear force on the membrane surface of the MBR membrane module, thereby mitigating membrane fouling from the source and reducing the membrane fouling rate of the MBR membrane module by more than 50%.

[0038] In one embodiment, when the membrane fouling value reaches a preset threshold, the online air-water combined cleaning method is selected for cleaning, which includes: flushing the MBR membrane module with air and water through a cleaning nozzle, controlling the air-water ratio at 3-5:1, and the cleaning time at 10-15 minutes. Specifically, during online air-water combined cleaning of the MBR membrane module, the cleaning nozzle flushes the MBR membrane module from the bottom with air and water, the air-water ratio is controlled at 3-5:1, and the cleaning time is 10-15 minutes. During the cleaning process, the MBR membrane module can be partially operated without affecting the continuous operation of the overall treatment system. After cleaning, the change in transmembrane pressure difference is monitored. If the decrease in transmembrane pressure difference is ≥15%, the cleaning is deemed effective; if the decrease in transmembrane pressure difference is <5%, the cleaning is deemed ineffective.

[0039] In one embodiment, if the membrane fouling value does not decrease after online gas-water combined cleaning, an offline cleaning method is selected. Specifically, if the transmembrane pressure difference decreases little and the cleaning has no significant effect after online gas-water combined cleaning, the process is switched to offline cleaning for the MBR membrane module.

[0040] In one embodiment, if the membrane fouling value has not decreased, and offline cleaning is selected, the cleaning method includes: adding a biodegradable cleaning agent to the MBR membrane module, then soaking for 30-60 minutes, and finally rinsing with clean water. Specifically, when cleaning the MBR membrane module offline, the dosage of the cleaning agent is adjusted according to the degree of fouling of the MBR membrane module as determined by the transmembrane pressure difference, sludge concentration, and dissolved oxygen concentration. This avoids waste of cleaning agents. After soaking for 30-60 minutes, the effluent pH is rinsed with clean water until it is close to neutral. Using a biodegradable cleaning agent and dynamically adjusting the dosage not only reduces agent waste but also helps extend the service life of the MBR membrane module, increasing it by more than 30%.

[0041] In one embodiment, the biodegradable cleaning agent is formulated from citric acid, a bio-enzyme, and deionized water. Specifically, the biodegradable cleaning agent formulated from citric acid, a bio-enzyme, and deionized water can dissolve inorganic scale and metal oxides and degrade organic pollutants and biofilms. Citric acid and the bio-enzyme work synergistically, resulting in excellent cleaning performance with zero damage to the membrane material. For example, the biodegradable cleaning agent is formulated from 2%-5% citric acid, 0.1%-0.5% a bio-enzyme composed of a protease and lipase, and deionized water to a total concentration of 100%.

[0042] In one embodiment, when selecting the offline dosing cleaning method, the method further includes: recycling the cleaning wastewater, pre-treating it, and then returning it to the inlet of the membrane bioreactor. Specifically, after sedimentation and filtration pre-treatment, the cleaning wastewater is returned to the inlet of the membrane bioreactor, which can reduce water consumption, realize the recycling of water resources, and reduce cleaning energy consumption by 20%-30%. This makes it well-suited for various MBR wastewater treatment projects, such as municipal wastewater treatment plant MBR process sections, industrial park high-concentration organic wastewater treatment, and medical wastewater treatment. It is especially suitable for scenarios with high sludge concentration and easy membrane fouling, with stable wastewater treatment efficiency and effect, and significant energy-saving and environmental benefits.

[0043] The present invention will be further described below with reference to specific embodiments.

[0044] An energy-saving cleaning process for MBR membrane modules includes the following steps:

[0045] Real-time monitoring of the transmembrane pressure difference of the MBR membrane module and the sludge concentration and dissolved oxygen concentration in the water body is used to comprehensively determine the degree of fouling of the MBR membrane module; among which, the transmembrane pressure difference is used as the membrane fouling value to characterize the degree of membrane fouling.

[0046] The cleaning mode is adaptively selected by comparing the membrane fouling value with a preset threshold of 0.08 MPa.

[0047] When the transmembrane pressure difference is below 0.08 MPa, the MBR membrane module is cleaned online by aeration. The bottom and sides of the MBR membrane module are aerated through the bottom aeration pipe and the side rotating aeration pipe. The rotation angle and aeration intensity of the side rotating aeration pipe and the aeration flow rate of the bottom aeration pipe are dynamically adjusted according to the transmembrane pressure difference, sludge concentration and DO concentration.

[0048] When the transmembrane pressure difference reaches 0.08 MPa, the online air-water combined cleaning method is selected to clean the MBR membrane module online. The MBR membrane module is flushed with air and water from the bottom through the cleaning nozzle. The air-water ratio is controlled at 3-5:1 and the cleaning time is 10-15 minutes.

[0049] When the transmembrane pressure drop is less than 5% after online air-water combined cleaning, offline cleaning is selected. The dosage of cleaning agent is adjusted according to the degree of MBR membrane module fouling, which is determined by the transmembrane pressure, sludge concentration, and dissolved oxygen concentration. The biodegradable cleaning agent is prepared by adding 2%-5% citric acid, 0.1%-0.5% protease and lipase compounded biological enzymes, and deionized water to a final concentration of 100%. After adding the biodegradable cleaning agent to the MBR membrane module, it is soaked for 30-60 minutes. Finally, it is rinsed with clean water until the pH of the effluent is close to neutral.

[0050] The cleaning wastewater is collected, pretreated, and then returned to the inlet of the membrane bioreactor.

[0051] Compared with the prior art, the present invention has at least the following advantages:

[0052] This invention provides an energy-saving cleaning process for MBR membrane modules, which can adaptively perform graded cleaning to reduce energy consumption. By using the transmembrane pressure difference as a quantitative indicator of membrane fouling and comparing it with a preset threshold, the cleaning mode is adaptively selected. When fouling is light, aeration cleaning is used, resulting in the lowest energy consumption; when fouling is heavy, online air-water combined cleaning is used; offline chemical cleaning is only employed when air-water combined cleaning is ineffective. This graded cleaning approach, from light to heavy and on-demand cleaning, avoids over-cleaning. Compared to traditional fixed cleaning methods, it can reduce energy consumption by 20%-30% and reduce chemical reagent usage by more than 40%. While effectively alleviating MBR membrane module fouling, reducing transmembrane pressure difference, and stabilizing MBR membrane module permeate production, it also helps reduce operation and maintenance costs.

[0053] Meanwhile, during the aeration cleaning and combined air-water cleaning processes, the cleaning parameters such as aeration intensity, rotation angle, and air-water ratio can be dynamically adjusted based on real-time monitoring of transmembrane pressure difference, sludge concentration, and DO concentration. This ensures that the cleaning effect is always optimal, avoiding the blindness of cleaning with fixed parameters. Furthermore, the biodegradable cleaning agents used do not damage the membrane material and can extend the service life of MBR membrane modules by more than 30%. Finally, the cleaning wastewater can be pretreated and returned to the system inlet, realizing the recycling of water resources and reducing secondary pollution. It is well-suited for various MBR wastewater treatment projects, including municipal and industrial projects, with stable wastewater treatment efficiency and effect, and significant energy-saving and environmental benefits.

[0054] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0055] The embodiments described above are merely illustrative of several implementations of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. An energy-saving cleaning process for MBR membrane modules, characterized in that, Includes the following steps: The fouling status of the MBR membrane module is monitored to obtain membrane fouling values; The cleaning mode is adaptively selected by comparing the membrane fouling value with a preset threshold. Specifically, when the membrane fouling value is lower than the preset threshold, the aeration cleaning method is selected for cleaning; when the membrane fouling value reaches the preset threshold, the online air-water combined cleaning method is selected for cleaning.

2. The energy-saving cleaning process for MBR membrane modules according to claim 1, characterized in that, If the membrane fouling value still does not decrease after the online air-water combined cleaning method is selected, the offline chemical dosing cleaning method is selected.

3. The energy-saving cleaning process for MBR membrane modules according to claim 1, characterized in that, The monitoring of fouling of the MBR membrane module includes: Real-time monitoring of the transmembrane pressure difference of the MBR membrane module and the sludge concentration and DO concentration in the water body, with the transmembrane pressure difference used as the membrane fouling value.

4. The energy-saving cleaning process for MBR membrane modules according to claim 3, characterized in that, When comparing the membrane fouling value with a preset threshold, the preset threshold range is set to 0.08MPa-0.12MPa.

5. The energy-saving cleaning process for MBR membrane modules according to claim 4, characterized in that, When the membrane fouling value is lower than a preset threshold, the step of selecting aeration as the cleaning method includes: The bottom and sides of the MBR membrane module are aerated through bottom aeration pipes and side rotating aeration pipes. The rotation angle and aeration intensity of the side rotating aeration pipes and the aeration flow rate of the bottom aeration pipes are dynamically adjusted according to the transmembrane pressure difference, sludge concentration and DO concentration.

6. The energy-saving cleaning process for MBR membrane modules according to claim 5, characterized in that, When the membrane fouling value reaches a preset threshold, the online air-water combined cleaning method is selected for cleaning, including: The MBR membrane module is flushed with a combination of air and water through a cleaning nozzle, with the air-to-water ratio controlled at 3-5:1 and the cleaning time at 10-15 minutes.

7. The energy-saving cleaning process for MBR membrane modules according to claim 2, characterized in that, When the membrane fouling value still has not decreased, and offline cleaning is selected, the cleaning method includes: Add a biodegradable cleaning agent to the MBR membrane module, then soak it for 30-60 minutes, and finally rinse it with clean water.

8. The energy-saving cleaning process for MBR membrane modules according to claim 7, characterized in that, The biodegradable cleaning agent is prepared from citric acid, biological enzymes, and deionized water.

9. The energy-saving cleaning process for MBR membrane modules according to claim 7, characterized in that, When selecting the offline drug delivery cleaning method for cleaning, it also includes: The wastewater from the cleaning process is recycled, pretreated, and then returned to the inlet of the membrane bioreactor.

10. The energy-saving cleaning process for MBR membrane modules according to claim 1, characterized in that, The MBR membrane module includes a membrane frame and a membrane module. The membrane module is disposed on the membrane frame. The membrane frame has a modular structure and has flow channels. The membrane module is composed of multiple hollow fiber ultrafiltration membranes, and the hollow fiber ultrafiltration membranes are coated with an antifouling coating.

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