MBR membrane cleaning method

Abstract

The invention discloses an MBR (Membrane Bioreactor) membrane cleaning method. The method comprises the following steps: S1, preparing and activating a cleaning solution; s2, performing gravity infiltration or negative pressure suction of the cleaning liquid into a membrane wire cavity; s3, suction cleaning; s4, a pulse desorption stage; S5, pollution discharge and rinsing; and S6, operation recovery. The sludge stripping agent is diluted according to the mass ratio and is heated, so that the catalytic activity of the enzyme preparation is enhanced, the sludge stripping agent is easier to permeate a sludge structure in an inner cavity of a membrane filament, meanwhile, the desorption capacity on inorganic colloid and metal ions is improved, and the problem of poor permeability of a cleaning agent in the prior art is effectively solved. By means of negative pressure suction and positive pressure pulse, the cleaning liquid can quickly enter the inner cavity of the membrane filament, the reaction between the slime stripping agent and the sludge in the inner cavity of the membrane filament is accelerated, and the slime stripping agent can react and strip as soon as possible. The device can effectively open dirt and plug deposition in the inner cavity of the membrane filament, so that pollutants are stripped from the inner wall of the membrane filament and taken away through a circulation loop, the cleaning efficiency is greatly improved, and the problem that a traditional cleaning method is difficult to go deep into the inner cavity of the membrane filament is solved.

Description

Technical Field

[0001] This invention relates to the field of MBR membrane cleaning, and more specifically to an MBR membrane cleaning method. Background Technology

[0002] With the continuous development of wastewater treatment technology, membrane bioreactors (MBRs) have been widely used in wastewater treatment due to their advantages such as small footprint, strong resistance to water quality shock loads, and good effluent quality. However, during MBR operation, sludge deposition and blockage can easily occur in the membrane fiber lumen due to fiber breakage or improper backwashing, leading to a decrease in membrane flux and affecting the normal operation of the system. Traditional cleaning methods, such as chemical soaking, high-pressure water rinsing, backwashing, and ultrasonic cleaning, can remove contaminants on the membrane surface to a certain extent, but they are difficult to penetrate deep into the membrane fiber lumen channels and cannot effectively solve the problem of deep fouling.

[0003] CN119236690A discloses a cleaning and regeneration method for failed MBR membrane modules. This method incorporates enzyme cleaning into conventional physical and chemical cleaning methods, with the cleaning sequence being physical cleaning first, followed by enzyme cleaning, and finally chemical cleaning. It primarily addresses the cleaning of various contaminants on the membrane surface and within the membrane pores. CN112591876A discloses an offline restorative cleaning method for decentralized wastewater treatment MBR systems. This method controls the sludge discharge operations of the anoxic tank, aerobic tank, membrane tank, and return tank of the MBR system to empty the membrane tank. Alkaline / acidic washing solutions are then prepared using the MBR permeate to soak and clean the membrane modules. Finally, the alkaline / acidic washing solutions are discharged into the biological system for disposal.

[0004] Existing cleaning technologies, such as chemical immersion, high-pressure water rinsing, backwashing, and ultrasonic cleaning, primarily act on the membrane surface and struggle to penetrate deep into the membrane fiber channels. They are mainly used for routine cleaning and maintenance, removing contaminants from the membrane fiber surface and pores, but cannot effectively address deep fouling issues. When fouling occurs inside the membrane fibers, the cleaning solution has difficulty entering the inner cavity, making it challenging to remove slime and ensuring the cleaning solution penetrates evenly into the deep membrane fiber channels. This is especially true at low flux rates or when the inner cavity is clogged by dense flocs, where traditional chemical penetration and removal methods are insufficient. Disassembly of the membrane stack is generally required, increasing labor and operational risks, resulting in limited cleaning effectiveness, high costs, and low efficiency. Furthermore, existing cleaning technologies lack precise control and parameterized management of the cleaning process, leading to unsatisfactory cleaning results and failing to achieve the goals of high-efficiency and energy-saving cleaning. Summary of the Invention

[0005] Technical problem: The technical problem to be solved by the present invention is to provide an MBR membrane cleaning method that solves the problems of membrane fiber blockage, high cleaning difficulty, low cleaning efficiency, insufficient flux recovery, need to disassemble the membrane stack and lack of intelligent control in the prior art.

[0006] Technical solution: The purpose of this invention is to overcome the shortcomings of existing technologies by providing an MBR membrane cleaning method, comprising the following steps:

[0007] The sludge stripping agent is diluted to 1–5 wt% by mass, stirred until homogeneous, and the solution is heated to 30–45°C (preferably 38°C). The sludge stripping agent is a mixture of surfactant (nonionic / amphoteric), chelating agent, low-dose oxidant or enzyme preparation, swelling / penetration aid, pH adjuster, and corrosion inhibitor in a specific mass ratio. This step enhances the catalytic activity of the enzyme preparation, makes it easier for the surfactant to penetrate the sludge structure within the membrane fiber lumen, and simultaneously improves the desorption capacity of the chelating agent for inorganic colloids and metal ions.

[0008] The cleaning solution is injected into the membrane fibers using gravity immersion or negative pressure suction, allowing the cleaning solution to enter the inner cavity of the membrane fibers. Simultaneously, the MBR membrane stack aeration is activated. As the slime-removing agent reacts with the sludge inside the membrane fibers, the physical vibration of the membrane fibers is intensified, facilitating rapid reaction and sludge removal. This ensures that the inner cavity of the membrane fibers is completely filled with the cleaning solution without any gas retention.

[0009] The suction pressure is -0.01 to -0.08 MPa.

[0010] A low-flow-rate directional circulation (5-15 LMH) is maintained by a suction pump, allowing the cleaning solution to flow continuously along the membrane fiber lumen to enhance diffusion, migration, and contact reaction. The single suction time can be set from 30 to 1200 s depending on the degree of contamination. The suction solution is filtered and then enters a buffer tank.

[0011] This step continuously replenishes active ingredients to the membrane filament fouling interface, accelerating the swelling of EPS, protein, and slime layer into the liquid phase.

[0012] After the suction cleaning is completed, the liquid in the buffer tank is extracted by the booster pump and injected into the bottom of the membrane stack for flushing. Positive pressure pulses are implemented to form periodic pressure waves. The duration of a single booster pulse is set to 5–20 seconds, the positive pressure pulse pressure is 0.03–0.08 MPa, and the interval is 5–30 seconds.

[0013] The pressurized pulse action can disturb the fouling layer to cause structural fatigue, accelerate the stripping of enzymatic cleavage products, and carry loose contaminants out of the membrane fiber lumen until the suction pressure drops to the normal value and the permeate flow rate recovers to 80%-95% of the new membrane flow rate. This cycle can be repeated 10-100 times (generally, significant changes in pressure differential and flux will occur 3-6 hours after cleaning).

[0014] After cleaning, drain the wastewater and rinse with clean water 2–5 times until the effluent is clear, the residual concentration is below 15 ppm, and the transmembrane pressure difference (ΔP) recovers to 80–95% of the initial operating level.

[0015] After rinsing, aeration and water intake can be resumed directly without additional chemical neutralization.

[0016] Beneficial effects: Compared with the prior art, the present invention provides an MBR membrane chemical cleaning system, which has the following beneficial effects: This invention employs a solution preparation and activation step. By diluting the sludge stripping agent according to a mass ratio and heating it to 30-45℃, the catalytic activity of the enzyme preparation is significantly enhanced, making it easier for the surfactant to penetrate the sludge structure inside the membrane fiber cavity. At the same time, it improves the desorption capacity of the chelating agent for inorganic colloids and metal ions, effectively solving the problem of poor permeability of cleaning agents in the prior art.

[0017] This invention introduces cleaning fluid into the membrane fiber cavity via gravity immersion or negative pressure suction, enabling the cleaning fluid to quickly enter the membrane fiber cavity. When the slime remover reacts with the slime in the membrane fiber cavity, it intensifies the physical shaking of the membrane fiber, causing it to react and peel off as quickly as possible. This effectively avoids the limitation of traditional physical cleaning methods that can only disturb the membrane surface, and significantly improves the cleaning effect.

[0018] This invention employs a suction pump to maintain a low flow rate and directional circulation, allowing the cleaning solution to flow continuously along the inner cavity of the membrane fibers. This enhances diffusion, migration, and contact reaction, thus solving the problem of low cleaning efficiency in existing technologies.

[0019] This invention uses pressurized pulses during the pulsed desorption stage to form periodic pressure waves, which can disturb the contaminant layer to cause structural fatigue, accelerate the stripping of enzymatic cleavage products, and carry loose contaminants out of the membrane fiber lumen, effectively solving the problem of membrane fiber breakage caused by the need for frequent disassembly of the membrane stack in the prior art.

[0020] This invention employs a reasonable ratio of cleaning solutions and setting of cleaning parameters, which makes the cleaning process gentle and orderly. It can effectively clean the membrane fibers without causing irreversible damage to the MBR membrane, thus extending the service life of the MBR. Attached Figure Description

[0021] Figure 1 This is one embodiment of an MBR membrane chemical cleaning system.

[0022] The diagram shows: 1. Cleaning tank; 2. Membrane stack; 3. Permeate pipe; 4. Pressure sensor; 5. Suction pump; 6. Turbidity sensor; 7. Pipe heater; 8. Booster pump; 9. Filter; 10. Jet distributor; 11. PLC controller; 12. Circulation pipe; 13. Buffer tank; 14. Temperature sensor; 15. Air inlet pipe; 16. Aeration pipe. Detailed Implementation

[0023] This invention employs an MBR membrane chemical cleaning system, which includes a cleaning tank 1, a membrane stack 2, a cleaning fluid circulation system, a temperature control system, a pressure sensor 4, and a PLC controller 11. The membrane stack 2, equipped with a permeate pipe 3 and an aeration pipe 16, is placed within the cleaning tank 1. One end of the cleaning fluid circulation system is connected to the permeate pipe 3, and the other end is connected to the cleaning tank 1, forming a circulation loop from the membrane stack 2 to the cleaning tank 1. The aeration pipe 16 is connected to an air inlet pipe 15, providing aeration and flushing to the membrane stack. The temperature control system and pressure sensor 4 are located on the cleaning fluid circulation system loop, and both are connected to the PLC controller 11. The system also includes a buffer tank 13 and a booster pump 8. The buffer tank 13 is used to temporarily store the pumped cleaning fluid, and the booster pump 8 pressurizes the cleaning fluid in the buffer tank and pumps it back to the membrane stack for pressurized flushing.

[0024] The cleaning fluid circulation system includes a variable frequency suction pump 5 and a circulation pipeline 12. The membrane stack 2 is equipped with a product water pipe 3. The cleaning tank 1 is used to store the cleaning fluid. The cleaning fluid is drawn out by the membrane stack product water pipe 3 under the action of the variable frequency suction pump 5 and returned to the cleaning tank 1 through the circulation pipeline 12.

[0025] The temperature control system includes a constant-temperature heating module and a temperature sensor 14. The constant-temperature heating module can be a pipe heater 7 or a heating plate installed at the bottom or side wall of the cleaning tank. The temperature sensor is used to monitor the temperature of the cleaning fluid in real time and feed the signal back to the PLC controller 11. The constant-temperature heating module is used to heat the cleaning fluid to the preset optimal reaction temperature. A filter 9 is provided in the cleaning fluid circulation system loop, located after the turbidity sensor 6 and pressure sensor 4.

[0026] The PLC controller 11 controls each component according to a preset program. Subsystem The operation includes the start and stop frequency of the variable frequency self-priming pump 5 and the start and stop of the heater 7, so as to realize the automated control of the cleaning process. Example

[0027] A method for cleaning an MBR membrane includes the following steps:

[0028] Dilute the sludge stripping agent to 1 wt% by mass, stir well, and heat the solution to 30°C.

[0029] The cleaning solution prepared in step 1 is injected into the inner cavity of the membrane fibers using gravity immersion; the MBR membrane stack aeration system is turned on, and the aeration rate is controlled at 0.4 m³ / m²·h; during the cleaning process, the membrane fibers are physically shaken by aeration to increase the contact between the membrane fibers and the cleaning solution and promote sludge shedding.

[0030] A self-priming pump is used to draw the cleaning fluid at a flow rate of -0.08MPa to achieve directional circulation; the single drawing time is set to 30s according to the degree of contamination; the drawn fluid enters the buffer tank after filtration.

[0031] After the suction cleaning is completed in step 3, the liquid in the buffer tank is intermittently pumped into the bottom of the membrane stack at a pressure of 0.04 MPa using a booster pump; periodic positive pressure pulses are implemented, with a pulse duration of 10 s and a pulse interval of 20 s.

[0032] Step 5, Drainage and Rinsing: After cleaning, drain the wastewater and rinse 2-3 times with clean water until the effluent is clear, the residual concentration is below 15 ppm, and the transmembrane pressure difference (ΔP) recovers to 80-95% of the initial operating level.

[0033] Step 6: Restore operation: After rinsing, aeration and water intake can be resumed directly without additional chemical neutralization treatment. Example

[0034] A method for cleaning an MBR membrane includes the following steps:

[0035] Dilute the sludge stripping agent to 5 wt% by mass, stir well, and heat the solution to 45°C.

[0036] The cleaning solution prepared in step 1 is injected into the inner cavity of the membrane fibers using a suction method; the MBR membrane stack aeration system is turned on, and the aeration rate is controlled at 0.6 m³ / m²·h; during the cleaning process, the membrane fibers are physically shaken by aeration to increase the contact between the membrane fibers and the cleaning solution and promote sludge shedding.

[0037] A self-priming pump is used to draw the cleaning fluid at a flow rate of -0.02 MPa to achieve directional circulation; the single drawing time is set to 1200s according to the degree of contamination; the drawn fluid enters the buffer tank after filtration.

[0038] After the suction cleaning is completed in step 3, the liquid in the buffer tank is intermittently pumped into the bottom of the membrane stack at a pressure of 0.06 MPa using a booster pump; periodic positive pressure pulses are implemented, with a pulse duration of 20 s and a pulse interval of 30 s.

[0039] Step 5, Drainage and Rinsing: After cleaning, drain the wastewater and rinse 2-3 times with clean water until the effluent is clear, the residual concentration is below 15 ppm, and the transmembrane pressure difference (ΔP) recovers to 80-95% of the initial operating level.

[0040] Step 6: Restore operation: After rinsing, aeration and water intake can be resumed directly without additional chemical neutralization treatment. Example

[0041] A method for cleaning an MBR membrane includes the following steps:

[0042] Dilute the sludge stripping agent to 3 wt% by mass, stir well, and heat the solution to 38°C.

[0043] The cleaning solution prepared in step 1 is injected into the inner cavity of the membrane fibers using a suction method; the MBR membrane stack aeration system is turned on, and the aeration rate is controlled at 0.4 m³ / m²·h; during the cleaning process, the membrane fibers are physically shaken by aeration to increase the contact between the membrane fibers and the cleaning solution and promote sludge shedding.

[0044] A self-priming pump is used to draw the cleaning fluid at a flow rate of -0.04 MPa to achieve directional circulation; the single drawing time is set to 600s according to the degree of contamination; the drawn fluid enters the buffer tank after filtration.

[0045] After the suction cleaning is completed in step 3, the liquid in the buffer tank is intermittently pumped into the bottom of the membrane stack at a pressure of 0.08 MPa using a booster pump; periodic positive pressure pulses are implemented, with a pulse duration of 5 seconds and a pulse interval of 10 seconds.

[0046] Step 5, Drainage and Rinsing: After cleaning, drain the wastewater and rinse 2-3 times with clean water until the effluent is clear, the residual concentration is below 15 ppm, and the transmembrane pressure difference (ΔP) recovers to 80-95% of the initial operating level.

[0047] Step 6: Restore operation: After rinsing, aeration and water intake can be resumed directly without additional chemical neutralization treatment. Example

[0048] A method for cleaning an MBR membrane includes the following steps:

[0049] Dilute the sludge stripping agent to 2 wt% by mass, stir well, and heat the solution to 30°C.

[0050] The cleaning solution prepared in step 1 is injected into the inner cavity of the membrane fibers using a suction method; the MBR membrane stack aeration system is turned on, and the aeration rate is controlled at 0.8 m³ / m²·h; during the cleaning process, the membrane fibers are physically shaken by aeration to increase the contact between the membrane fibers and the cleaning solution and promote sludge shedding.

[0051] A self-priming pump is used to draw the cleaning fluid at a flow rate of -0.03 MPa to achieve directional circulation; the single drawing time is set to 800s according to the degree of contamination; the drawn fluid enters the buffer tank after filtration.

[0052] After the suction cleaning is completed in step 3, the liquid in the buffer tank is intermittently pumped into the bottom of the membrane stack at a pressure of 0.03 MPa using a booster pump; periodic positive pressure pulses are implemented, with a pulse duration of 5 seconds and a pulse interval of 5 seconds.

[0053] Step 5, Drainage and Rinsing: After cleaning, drain the wastewater and rinse 2-3 times with clean water until the effluent is clear, the residual concentration is below 15 ppm, and the transmembrane pressure difference (ΔP) recovers to 80-95% of the initial operating level.

[0054] Step 6: Restore operation: After rinsing, aeration and water intake can be resumed directly without additional chemical neutralization treatment.

[0055] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the specific embodiments described above. The specific embodiments and descriptions in the specification are merely for further illustrating the principles of the invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the claims and their equivalents.

Claims

1. A method for cleaning MBR membranes, characterized in that, Includes the following steps: S1: Preparation and activation of cleaning solution The sludge stripping agent is diluted with water to 1–5 wt% by mass, stirred evenly, and the solution temperature is controlled at 30–45℃ to obtain a cleaning solution; the sludge stripping agent includes surfactants, chelating agents, oxidants or enzyme preparations, swelling / penetration aids, pH adjusters and corrosion inhibitors. S2: Cleaning solution injection and soaking The cleaning solution is injected into the inner cavity of the MBR membrane fibers using gravity immersion or negative pressure suction, ensuring that the cleaning solution fills the inner cavity of the membrane fibers without any gas retention; at the same time, the aeration of the MBR membrane stack is turned on. S3: Low-flow-rate suction cleaning The cleaning solution inside the membrane fiber is aspirated by a suction pump and circulated at a flow rate of 5-15 LMH for directional circulation for 30-1200 seconds. The liquid discharged after suction is filtered and then enters a buffer tank. S4: Positive pressure pulse desorption After stopping the suction cleaning, the liquid in the buffer tank is extracted by the booster pump and injected into the bottom of the membrane stack for flushing. Positive pressure pulses are implemented, with a single pulse duration of 5–20 seconds. S5: Execute the cleaning cycle Repeat steps S3 and S4 to form a cleaning cycle that alternates between suction cleaning and positive pressure pulse; the cleaning cycle is repeated 10–100 times; or continues until the transmembrane pressure difference of the MBR membrane recovers to the set value; S6: Sewage Discharge and Rinsing After the cleaning cycle is completed, drain the sludge from the system and rinse the MBR membrane system with clean water 2–5 times until the effluent is clear and the transmembrane pressure difference recovers to 80–95% of the initial operating level; S7: Resume Operation After rinsing, the aeration and feed water operation of the MBR membrane system can be resumed directly.

2. The MBR membrane cleaning method according to claim 1, characterized in that, In step S1, the temperature of the cleaning solution is preferably 38°C.

3. The MBR membrane cleaning method according to claim 1, characterized in that, In step S2, the pressure of the negative pressure suction is -0.01 MPa to -0.08 MPa.

4. The MBR membrane cleaning method according to claim 1, characterized in that, After the positive pressure pulse is executed, a static aeration step is also included, with a static aeration time of 5–30 seconds.

5. The MBR membrane cleaning method according to claim 1, characterized in that, The pressure of the positive pressure pulse is between 0.03 MPa and 0.08 MPa.

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