Membrane biological reaction system and online cleaning method thereof

Abstract

The invention relates to the technical field of membrane biological reaction systems, and particularly discloses a membrane biological reaction system and an online cleaning method thereof. The MBR membrane assembly does not need to be disassembled from the MBR pool for cleaning, the cleaning efficiency is high, mechanical damage to membrane filaments in the disassembling and reassembling process is effectively avoided, and the cleaning cost is reduced. While a radial high-pressure jet water flow is generated by a cleaning spray pipe arranged in the middle of the membrane filaments, the hollow fiber membrane filaments are controlled to generate twisting action, so that mutual twisting is generated between the hollow fiber membrane filaments on the inner layer and the outer layer, and sludge generates relative displacement to be stripped and cracked; sludge can be more effectively washed away by combining radial high-pressure jet water flow in the middle, and each hollow fiber membrane filament sweeps over a certain area when twisted, so that the jet water flow washes the hollow fiber membrane filaments more comprehensively, and washing dead angles are greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of membrane bioreactor systems, and more specifically to a membrane bioreactor system and its online cleaning method. Background Technology

[0002] A membrane bioreactor (MBR) system is a novel water treatment device that combines membrane separation technology with biological treatment. It is primarily used in municipal wastewater, industrial wastewater treatment, and reclaimed water reuse. Its core component replaces the traditional secondary sedimentation tank with a membrane module, achieving highly efficient separation of sludge and water through ultrafiltration / microfiltration technology, significantly improving treatment efficiency. The membrane module, as the core component of the MBR system, directly determines the overall system's treatment efficiency and effluent quality through its filtration performance.

[0003] Membrane fouling is an unavoidable problem during the long-term operation of MBR systems. Impurities such as activated sludge, colloidal particles, microorganisms, organic matter, and inorganic salts in wastewater will continuously adsorb and deposit on the membrane surface or clog the membrane pores, forming a sludge cake, biofilm, and scale. If the membrane modules are not cleaned in time, it will lead to a sharp increase in transmembrane pressure (TMP) and a significant decrease in membrane flux, resulting in increased system energy consumption, deterioration of effluent quality, and in severe cases, membrane fiber breakage and irreversible damage to the membrane modules, significantly shortening the service life of the membrane modules and increasing the system's operating costs and maintenance burden.

[0004] Currently, the main cleaning method for MBR membrane modules is offline cleaning. Offline cleaning involves disassembling the membrane modules from the MBR reactor, transporting them to a dedicated cleaning area, and cleaning them using methods such as chemical immersion and high-pressure rinsing. This cleaning method has the following drawbacks: 1) The process of disassembling, transporting, and reassembling the membrane modules is cumbersome, requiring significant manpower, resources, and time, leading to a decrease in wastewater treatment efficiency; 2) The disassembly and reassembly process can easily cause mechanical damage to the membrane fibers, further shortening the service life of the membrane modules; 3) Offline cleaning requires dedicated cleaning sites and equipment, resulting in high cleaning costs; 4) Due to the large amount of stubborn sludge adhering to the outer wall of the membrane fibers and between the fibers, the fibers have become bonded together without gaps, making cleaning with a simple water jet significantly less effective. Summary of the Invention

[0005] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art: to provide a membrane bioreactor system and its online cleaning method. The membrane bioreactor system of this invention allows for convenient online cleaning without disassembling the membrane modules, provides good cleaning results, is easy to operate, and, combined with the online cleaning method, minimizes mechanical damage to the membrane fibers.

[0006] The technical solution of the present invention is as follows: A membrane bioreactor system includes an MBR tank, a cleaning pump, and a suction pump; the MBR tank is provided with multiple arrayed MBR membrane modules; each MBR membrane module includes an outlet pipe with a top wall, multiple hollow fiber membrane filaments, a cleaning spray pipe, and a rotating disk; one end of each hollow fiber membrane filament is sealed to the top wall of the outlet pipe, and the other end is sealed to the rotating disk, with the hollow portion of the hollow fiber membrane filament communicating with the outlet of the outlet pipe; the rotating disk is rotatably engaged with the cleaning spray pipe; multiple hollow fiber membrane filaments are distributed around the cleaning spray pipe; the wall of the cleaning spray pipe is uniformly provided with radially arranged spray holes; the outlet pipe is connected to the inlet of the suction pump; the outlet of the cleaning pump is connected to the upper end of the cleaning spray pipe.

[0007] As an optimization, the MBR membrane module includes a driven wheel and a cylindrical shaft that rotatably engage with the upper end of the cleaning spray pipe; the driven wheel and the cylindrical shaft are coaxially and fixedly connected; the turntable is coaxially and fixedly connected to the cylindrical shaft, or the turntable and the cylindrical shaft are circumferentially limited and axially elastically connected.

[0008] As an optimization, the turntable is located on the lower side of the top wall of the MBR tank, and the driven wheel is located on the upper side of the top wall of the MBR tank; the cylindrical shaft is rotatably engaged with the through hole on the top wall of the MBR tank.

[0009] As an optimization, the driven wheel is either a gear or a synchronous belt pulley; the top wall of the MBR tank is provided with a drive mechanism to drive the driven wheel.

[0010] As an optimization, the driven wheel is a synchronous belt pulley; the driving mechanism is a drive motor, and a drive pulley is coaxially provided on the output shaft of the drive motor; the drive pulley and the driven wheel are connected by a synchronous belt drive.

[0011] As an optimization, the lower opening of the cleaning spray pipe is sealed to the top wall of the water outlet pipe; the upper end of the cleaning spray pipe passes through the turntable, the cylindrical shaft and the driven wheel in sequence and rotates in cooperation with them.

[0012] As an optimization, the length of the hollow fiber membrane filament is greater than the distance between the turntable and the top wall of the outlet pipe.

[0013] This invention provides an online cleaning method for the membrane bioreactor system, comprising the following steps: 1) First, after draining the water from the MBR tank, turn on the cleaning pump and pump washing water into the cleaning spray pipe through the pipeline so that the cleaning spray pipe generates a radial jet of water. 2) The driven wheel of the MBR membrane module is driven by the drive mechanism to rotate alternately in both directions, causing the hollow fiber membrane filaments surrounding the cleaning spray pipe to twist, so that the inner and outer hollow fiber membrane filaments rub against each other, making the sludge more effectively washed away by the sprayed water.

[0014] As an optimization, when the driven wheel rotates to its maximum angle in either the forward or reverse direction, the hollow fiber membrane filaments are at their maximum length.

[0015] As an optimization, the online cleaning method of the membrane bioreactor system further includes the following steps: 3) Pumping washing water at a certain pressure into the outlet pipe through the pipeline to achieve backwashing of the hollow fiber membrane filaments.

[0016] The beneficial effects of this invention are as follows: This invention eliminates the need to disassemble the MBR membrane module from the MBR tank for cleaning, resulting in high cleaning efficiency and effectively avoiding mechanical damage to the membrane fibers during disassembly and reassembly, thus reducing cleaning costs. This invention generates radial high-pressure jets of water through a cleaning spray pipe located in the middle of the membrane fibers, while simultaneously controlling the hollow fiber membrane fibers to twist. This causes the inner and outer layers of hollow fiber membrane fibers to rub against each other, leading to relative displacement and peeling / cracking of the sludge. Combined with the radial high-pressure jets of water in the middle, the sludge is more effectively washed away. Furthermore, each hollow fiber membrane fiber sweeps across a certain area during twisting, allowing the jets to more comprehensively clean the hollow fiber membrane fibers, greatly reducing cleaning dead zones. Preferably, this invention can also combine backwashing of the hollow fiber membrane fibers to further improve the cleaning effect. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the membrane bioreactor system in Example 1.

[0018] Figure 2 This is a three-dimensional structural diagram of the MBR membrane module in Example 1.

[0019] Figure 3 This is a cross-sectional view of the MBR membrane module in Example 1.

[0020] Figure 4 This is a three-dimensional cross-sectional view of the MBR membrane module in Example 1.

[0021] Figure 5 This is a three-dimensional structural diagram of the MBR membrane module in Example 1.

[0022] Figure 6 This is a schematic diagram of the spatial state of the outermost hollow fiber membrane filaments of the MBR membrane module in Example 1 after the turntable is twisted at a certain angle.

[0023] Figure 7This is a schematic diagram of the driven wheel structure in Example 1, which uses one drive motor to simultaneously drive four MBR membrane modules.

[0024] Figure 8 This is a partial cross-sectional view of the MBR membrane module in Example 2.

[0025] In the diagram: 1. MBR tank; 2. Cleaning pump; 3. Suction pump; 4. MBR membrane module; 41. Outlet pipe; 42. Hollow fiber membrane filament; 43. Cleaning spray pipe; 44. Turntable; 45. Driven wheel; 46. Cylindrical shaft; 47. Tension spring; 48. Guide rod; 5. Drive motor. Detailed Implementation

[0026] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions apply.

[0027] Example 1 The following is combined Figure 1-7 A membrane bioreactor system is described, comprising an MBR tank 1, a cleaning pump 2, and a suction pump 3. The MBR tank 1 contains multiple vertically arrayed MBR membrane modules 4. Each MBR membrane module 4 includes an outlet pipe 41 with a top wall, multiple hollow fiber membrane filaments 42, a cleaning spray pipe 43, and a rotating disk 44. One end of each hollow fiber membrane filament 42 is sealed to the top wall of the outlet pipe 41, and the other end is sealed to the rotating disk 44. The hollow portion of the hollow fiber membrane filament 42 communicates with the outlet of the outlet pipe 41. The rotating disk 44 rotatably engages with the cleaning spray pipe 43. The multiple hollow fiber membrane filaments 42 are distributed around the cleaning spray pipe 43. The wall of the cleaning spray pipe 43 is uniformly provided with radially arranged spray holes. The outlet pipe 41 is connected to the inlet of the suction pump 3. The outlet of the cleaning pump 2 is connected to the upper end of the cleaning spray pipe 43.

[0028] The MBR membrane module 4 includes a driven wheel 45 and a cylindrical shaft 46 that are rotatably engaged with the upper end of the cleaning spray pipe 43; the driven wheel 45 and the cylindrical shaft 46 are coaxially and fixedly connected; the turntable 44 is coaxially and fixedly connected with the cylindrical shaft 46.

[0029] The turntable 44 is located on the lower side of the top wall of the MBR tank 1, and the driven wheel 45 is located on the upper side of the top wall of the MBR tank 1; the cylindrical rotating shaft 46 is rotatably engaged with the through hole on the top wall of the MBR tank 1; the MBR tank 1 is also provided with a sewage inlet pipe.

[0030] The driven wheel 45 is either a gear or a synchronous belt pulley; the top wall of the MBR tank 1 is provided with a drive mechanism to drive the driven wheel 45.

[0031] like Figure 7 As shown, in this embodiment, the driven wheel 45 is a synchronous belt pulley; the driving mechanism is a drive motor 5, and a drive pulley is coaxially provided on the output shaft of the drive motor 5; the drive pulley and the driven wheel 45 are connected by a synchronous belt drive. Figure 7 Using one drive motor 5 to drive four MBR membrane modules 4 simultaneously is just one example of the driving method. The driving method can also be conventional gear transmission, or each MBR membrane module 4 can be driven by a separate motor. This should not be regarded as a limitation of the present invention. Conventional driving methods are all within the protection scope of the present invention.

[0032] The lower end opening of the cleaning spray pipe 43 is sealed to the top wall of the water outlet pipe 41; the upper end of the cleaning spray pipe 43 passes through the turntable 44, the cylindrical shaft 46 and the driven wheel 45 in sequence and rotates with them.

[0033] The length of the hollow fiber membrane filament 42 is greater than the distance between the turntable 44 and the top wall of the water outlet pipe 41.

[0034] In this embodiment, the driven wheel 45 is coaxially and fixedly connected to the cylindrical shaft 46; the turntable 44 is also coaxially and fixedly connected to the cylindrical shaft 46. To avoid excessive stretching of the hollow fiber membrane filament 42 during the rotation of the turntable 44, the length of the hollow fiber membrane filament 42 should be greater than the distance between the turntable 44 and the top wall of the outlet pipe 41. Specifically, the length is adjusted according to the rotation amplitude, and is controlled so that when the driven wheel 45 rotates to its maximum angle in either the forward or reverse direction, the hollow fiber membrane filament 42 is at its maximum natural length, thus preventing excessive stretching of the hollow fiber membrane filament 42.

[0035] In the initial state of the MBR membrane module 4, the line connecting the two ends of each hollow fiber membrane filament 42 is perpendicular to the lower surface of the turntable 44 and the upper surface of the top wall of the outlet pipe 41. In order to achieve the efficient spray cleaning function of the cleaning spray pipe 43, the hollow fiber membrane filament bundle of the MBR membrane module 4 cannot be covered by an outer shell, and the MBR membrane modules 4 need to be spaced apart.

[0036] During operation, wastewater in the MBR tank 1 enters the hollow portion of the hollow fiber membrane filaments 42 through the porous outer wall, then converges into the outlet pipe 41. The filtered water is then continuously pumped out of the outlet pipe 41 via a suction pump 3, achieving continuous filtration. However, over time, a large amount of sludge accumulates on the outer wall of the hollow fiber membrane filaments 42 and between the membrane filaments, reducing the filtration efficiency. If online cleaning of the hollow fiber membrane filaments 42 is required, the present invention employs the following steps: 1) First, after draining the water from the MBR tank 1, turn on the cleaning pump 2 and pump washing water into the cleaning spray pipe 43 through the pipeline so that the cleaning spray pipe 43 generates a radial jet of water; the washing water can be clean water or conventional cleaning solution.

[0037] 2) The driven wheel 45 of the MBR membrane module 4 is driven by the drive mechanism to rotate alternately in both directions (e.g., starting from 0°, first rotating clockwise to 30°, then counterclockwise back to the original position of 0°, and then continuing to rotate to -30°). This causes the hollow fiber membrane filaments 42 surrounding the cleaning spray pipe 43 to twist, so that the inner and outer layers of hollow fiber membrane filaments 42 rub against each other, making the sludge more effectively washed away by the sprayed water. Because a large amount of stubborn sludge is attached to the outer wall of the hollow fiber membrane filaments 42 and between the membrane filaments, the membrane filaments have become bonded together without gaps. Directly relying on water spray cannot maximize the shear force of the water flow, resulting in poor cleaning effect. However, this invention generates radial high-pressure spray water flow through the cleaning spray pipe 43 located in the middle of the membrane filaments, while controlling the twisting action of the hollow fiber membrane filaments 42. Figure 6 The spatial state of the outermost hollow fiber membrane filament 42 is shown after the turntable 44 is twisted at a certain angle. At this time, the spatial state of the hollow fiber membrane filament 42 changes, and the inner and outer hollow fiber membrane filaments 42 will also rub against each other, causing the sludge to be relatively displaced and peeled off and cracked, which makes it easier for the high-pressure jet water flow to more effectively wash away the sludge. Moreover, when each hollow fiber membrane filament 42 is twisted, it sweeps across a certain area, so that the jet water flow can more comprehensively wash the hollow fiber membrane filament 42, greatly reducing the dead corners of washing. The length of the hollow fiber membrane filament 42 is generally controlled at 30° when the driven wheel 45 rotates to the maximum angle in either the forward or reverse direction. The hollow fiber membrane filament 42 is just at its maximum length, so as to avoid excessive stretching of the hollow fiber membrane filament 42.

[0038] 3) Washing water at a certain pressure is pumped into the outlet pipe 41 through the pipeline to achieve backwashing of the hollow fiber membrane filaments 42, further improving the cleaning effect. The working direction of the suction pump 3 can be directly adjusted to pump in, pumping the washing water through the pipeline into the outlet pipe 41 of each MBR membrane module 4, which then enters the hollow part of the hollow fiber membrane filaments 42 and is discharged from its porous outer wall. The pumping pressure of the washing water is the same as the working pressure of the hollow fiber membrane filaments 42; the hollow fiber membrane filaments 42 are made of conventional polyvinylidene fluoride membrane material.

[0039] Example 2 like Figure 8 As shown, unlike the MBR membrane module 4 structure in Embodiment 1, the turntable 44 and the cylindrical shaft 46 are circumferentially limited and axially connected by a tension spring 47 coaxially arranged. The two ends of the tension spring 47 are respectively embedded inside the turntable 44 and the cylindrical shaft 46. The turntable 44 is provided with two guide holes perpendicular to its surface, and the cylindrical shaft 46 is provided with a guide rod 48 that slides with the guide holes. The MBR membrane module structure of this embodiment can make the length of the hollow fiber membrane filament 42 equal to the distance between the turntable 44 and the top wall of the outlet pipe 41 when the turntable 44 is in the initial position, without reserving too much redundant membrane filament length to accommodate the membrane filament twisting space. This allows each membrane filament to be stretched straighter, maintaining a larger gap between the hollow fiber membrane filaments 42 and reducing sludge adhesion during operation. After the turntable 44 and the cylindrical shaft 46 are circumferentially limited by the guide rod 48 and axially elastically connected by the tension spring 47, when the turntable 44 rotates from its initial position by a certain angle, the turntable 44 can move downward elastically, ensuring that the movement stroke of the turntable 44 is within the stroke range of the guide rod 48. This avoids excessive pulling of the membrane filaments during the rotation of the hollow fiber membrane filaments 42 by the turntable 44, and a certain degree of tension in the membrane filaments can effectively peel off the sludge on their surface, further improving the cleaning effect.

[0040] The above are merely exemplary embodiments of the present invention and do not constitute any limitation on the scope of protection of the present invention. All technical solutions formed by equivalent exchange or substitution fall within the scope of protection of the present invention.

Claims

1. A membrane bioreactor system, characterized in that, The system includes an MBR tank (1), a cleaning pump (2), and a suction pump (3); the MBR tank (1) contains multiple arrayed MBR membrane modules (4); each MBR membrane module (4) includes an outlet pipe (41) with a top wall, multiple hollow fiber membrane filaments (42), a cleaning spray pipe (43), and a rotating disc (44); one end of each hollow fiber membrane filament (42) is sealed to the top wall of the outlet pipe (41), and the other end is sealed to the rotating disc (44). The hollow portion of the fiber membrane (42) is connected to the outlet of the water outlet pipe (41); the turntable (44) is rotatably engaged with the cleaning spray pipe (43); multiple hollow fiber membrane filaments (42) are distributed around the cleaning spray pipe (43); the wall of the cleaning spray pipe (43) is uniformly provided with radially arranged spray holes; the water outlet pipe (41) is connected to the inlet of the suction pump (3); the outlet of the cleaning pump (2) is connected to the upper end of the cleaning spray pipe (43).

2. The membrane bioreactor system according to claim 1, characterized in that, The MBR membrane module (4) includes a driven wheel (45) and a cylindrical shaft (46) that are rotatably engaged with the upper end of the cleaning spray pipe (43); the driven wheel (45) and the cylindrical shaft (46) are coaxially fixedly connected; the turntable (44) and the cylindrical shaft (46) are coaxially fixedly connected or the turntable (44) and the cylindrical shaft (46) are circumferentially limited and axially elastically connected.

3. The membrane bioreactor system according to claim 2, characterized in that, The turntable (44) is located on the lower side of the top wall of the MBR tank (1), and the driven wheel (45) is located on the upper side of the top wall of the MBR tank (1); the cylindrical shaft (46) is rotatably engaged with the through hole on the top wall of the MBR tank (1).

4. The membrane bioreactor system according to claim 3, characterized in that, The driven wheel (45) is either a gear or a synchronous belt pulley; the top wall of the MBR tank (1) is provided with a drive mechanism to drive the driven wheel (45).

5. The membrane bioreactor system according to claim 4, characterized in that, The driven wheel (45) is a synchronous belt pulley; the driving mechanism is a drive motor (5), and a drive pulley is coaxially provided on the output shaft of the drive motor (5); the drive pulley and the driven wheel (45) are connected by a synchronous belt drive.

6. The membrane bioreactor system according to claim 5, characterized in that, The lower end opening of the cleaning spray pipe (43) is sealed to the top wall of the water outlet pipe (41); the upper end of the cleaning spray pipe (43) passes through the turntable (44), the cylindrical shaft (46) and the driven wheel (45) in sequence and rotates with them.

7. The membrane bioreactor system according to claim 5, characterized in that, The length of the hollow fiber membrane filament (42) is greater than the distance between the turntable (44) and the top wall of the water outlet pipe (41).

8. An online cleaning method for the membrane bioreactor system according to claim 7, characterized in that, Includes the following steps: 1) First, after draining the water from the MBR tank (1), turn on the cleaning pump (2) and pump washing water into the cleaning spray pipe (43) through the pipeline so that the cleaning spray pipe (43) generates a radial jet of water. 2) The driven wheel (45) of the MBR membrane module (4) is driven by the drive mechanism to rotate alternately in the forward and reverse directions, so that the hollow fiber membrane filaments (42) surrounding the cleaning spray pipe (43) will rotate, so that the hollow fiber membrane filaments (42) of the inner and outer layers will rub against each other, so that the sludge will be more effectively washed away by the spray water flow.

9. The online cleaning method for a membrane bioreactor system according to claim 8, characterized in that, When the driven wheel (45) rotates to its maximum angle in either the forward or reverse direction, the hollow fiber membrane filament (42) is at its maximum length.

10. The online cleaning method for a membrane bioreactor system according to claim 8, characterized in that, It also includes the following steps: 3) Pump washing water at a certain pressure into the outlet pipe (41) through the pipeline to achieve backwashing of the hollow fiber membrane filaments (42).

Images