Membrane bioreactor

Abstract

A membrane bioreactor is provided, comprising a membrane tank, membrane modules, an effluent tank, and a pulse aeration device located at the bottom of the membrane tank. The pulse aeration device scrubs the membrane during aeration. The membrane element includes two filter membranes, a flexible flow guide mesh, and a water collection element. The two filter membranes and the intermediate flexible flow guide mesh form a bag-like structure, with the two long sides of the bag closed and at least one of the two short sides open. The water collection element at least at the top has a water collection tank or two longitudinally parallel water collection channels, with at least one open end connected to the water collection tank or water collection channel. One end of the water collection element is sealed, and the other end has at least two effluent nozzles. One end of each nozzle connects to the water collection tank or water collection channel, and the other end connects to a main water collection pipe. The water collection element is formed by injection molding in one step. A new pulse aeration device and membrane separation process are designed using the principle of communicating vessels, improving the overall system performance.

Description

Technical Field

[0001] This invention generally relates to membrane bioreactors. Background Technology

[0002] Membrane bioreactors (MBRs) are biochemical reaction systems that integrate membrane separation technology and the biodegradation process of bioreactors.

[0003] Figure 1 The diagram schematically illustrates the composition and process of a traditional MBR (Membrane Bioreactor). A typical MBR includes the following components: a membrane tank, membrane modules, a pulse aeration device located below the membrane tank, and a filtered clean water collection section (including a clean water tank, etc.). The membrane module is the core component; for example, in a biological system, it achieves sludge-water separation. Membrane modules are placed inside the membrane tank, and wastewater is injected into the membrane tank and filtered by the membrane modules.

[0004] To obtain a system with superior filtration performance, it is necessary to optimize various aspects such as membrane modules, membrane separation processes, and aeration systems. Summary of the Invention

[0005] This invention proposes improvements to membrane modules, membrane separation processes, and aeration systems, achieving progress in these three aspects and in the overall system.

[0006] A membrane bioreactor (MBR) is a biochemical reaction system that integrates membrane separation technology and the biodegradation process of a bioreactor. MBRs use membrane filter modules as their core to achieve sludge-water separation in the biological treatment tank. Traditional MBR membrane filter modules mainly include rigid flat-sheet membranes, spiral wound membranes, and hollow fiber membranes. Rigid flat-sheet membranes, with two layers of membrane fabric and an intermediate support plate, are the most widely used type of membrane module in wastewater treatment.

[0007] In recent years, flexible flat sheet membranes have emerged. Compared to traditional rigid flat sheet membranes, flexible flat sheet membranes do not have a support plate, offering the following advantages: eliminating the rigid support plate significantly reduces manufacturing costs; the membrane element thickness can be made very thin, which helps increase the filtration area per unit volume of the membrane module, increase the membrane tank packing density, and reduce project costs. Other advantages include smaller footprint, lower aeration energy consumption, and reduced sludge buildup on the membrane sheet, making them widely recognized.

[0008] However, flexible sheet membranes must remain stretched during application, meaning their edges require a certain degree of support and fixation to prevent them from curling or folding under the influence of water flow. Therefore, maintaining the stretchability of flexible sheet membranes and collecting permeate still necessitates rigid materials and components. Currently, the size of flexible membrane elements and the effective membrane area per unit on the market are generally small, resulting in a permeate flow rate far lower than that of rigid sheet membranes, thus limiting the realization of other advantages of flexible sheet membranes.

[0009] The main problems with existing flexible sheet films on the market are:

[0010] (1) The effective filtration area of ​​a single membrane element is too small, much smaller than that of a flat sheet membrane with rigid plate support; the flexible flat sheet with the same membrane requires a large number of accessories, resulting in high assembly costs.

[0011] (2) The water collection design of individual membrane elements is generally clumsy. Although the thickness of the filter membrane is small enough, the membrane elements cannot be arranged tightly when integrated together, so the filling density of the membrane module is not high.

[0012] (3) A membrane module is composed of multiple membrane elements. Each membrane element cannot be disassembled individually. When repairing or replacing a membrane element, the entire membrane module needs to be disassembled, which is time-consuming and labor-intensive.

[0013] (4) Or, although the flexible membrane element of the membrane module can be disassembled independently, the water collection of the membrane element is achieved by bridging with a hose, resulting in a large number of connecting parts, many potential leakage risks, and increased cost of the membrane module.

[0014] In view of the above, the present invention is proposed.

[0015] According to one aspect of the present invention, a membrane bioreactor is provided, comprising a membrane tank, a membrane module, an effluent tank, and a pulse aeration device located at the bottom of the membrane tank, wherein the pulse aeration device scrubs the membrane during aeration; the membrane module is formed by sequentially stacking bag-type flexible flat sheet membrane elements; the bag-type flexible flat sheet membrane element comprises: two filter membrane sheets, a flexible flow guiding mesh sandwiched in the middle, and water collection components located at both ends of the bag; the two filter membrane sheets and the flexible flow guiding mesh in the middle constitute a bag shape, the two long sides of the bag are closed, and at least one of the two short sides is open; at least the top water collection component has a hollow water collection tank or two parallel water collection channels extending along the short side, and the at least one open end of the bag is connected to the water collection tank or water collection channel of the water collection component; one end of the water collection component is sealed, and the other end has at least two effluent nozzles, one end of the effluent nozzle is connected to the water collection tank or water collection channel, and the other end is used to connect to a main water collection pipe; the water collection component is formed by one-time injection molding.

[0016] Preferably, in the membrane bioreactor, the pulse aeration device includes a gas chamber, an inner tube, an outer tube, an air supply pipe, and a fixing component: the gas chamber is an open container at the bottom, used to accumulate and temporarily store gas from the gas source; the air supply pipe connects to the gas source outside the gas chamber, used to supply gas to the gas chamber; the outer tube connects the inside and outside of the gas chamber, is open at the top and bottom, and is sealed on all sides, with the upper part extending a certain distance above the top outer wall of the gas chamber and the lower part a certain distance from the bottom of the gas chamber, serving as a channel for the gas inside the gas chamber to be released to the outside; the inner tube and the outer tube are fixed in position to each other by a component, the upper part of the inner tube is open and located inside the gas chamber, wherein the bottom of the inner tube is connected to the bottom of the outer tube, and the structure of the outer tube and the inner tube is equivalent to combining multiple U-shaped tubes into one, wherein one arm of each U-shaped tube is combined into a shared arm of all U-shaped tubes, and the remaining arms of each U-shaped tube are separated or combined into one.

[0017] Preferably, in the membrane bioreactor, the upper edge of the effluent tank is on the same horizontal plane as the upper edge of the membrane tank, the membrane module is installed inside the membrane tank and submerged in the water to be filtered in the membrane tank, the water collection pipe of the membrane module is connected to the effluent tank and its port is located below the minimum allowable water level of the effluent tank, and the membrane module is not directly connected to the water pump.

[0018] Preferably, in the membrane bioreactor, the water collection device has a hollow water collection tank, and the two short sides of the capsule are respectively sealed together with the upper and lower water collection devices, so that the inner cavity of the capsule is connected to the water collection tank of the water collection device.

[0019] Preferably, in the membrane bioreactor, the water collection device has two water collection channels arranged in parallel along the short side of the membrane element, and an inlet hole in a direction perpendicular to the water collection channels, which connects the two water collection channels and one end of the inlet hole communicates with the inner cavity of the capsule.

[0020] Preferably, in the membrane bioreactor, the inlet holes are evenly distributed along the water collection channels with a spacing of 20-30 mm.

[0021] Preferably, in the membrane bioreactor, one end of the water collecting component has two parallel outlet nozzles, which are double-ended pagoda-shaped. Each outlet nozzle has two grooves for placing O-rings, and is equipped with four pairs of O-rings for connecting to the main water collecting pipe in a socket manner. The two ends of the water collecting component also have two wedge-shaped transition connection parts for the transition between the water collecting component and the membrane at the welding point.

[0022] Preferably, in the membrane bioreactor, the water collection element is 400-600mm long and 4-12mm thick, the inner diameter of the outlet nozzle on the water collection element is 3-6mm, and the flexible flat sheet membrane element is 500-1500mm long.

[0023] Preferably, in the membrane bioreactor, the water collection element is 480 mm long and 6 mm thick, and the inner diameter of the outlet nozzle is 3 mm.

[0024] Preferably, in the membrane bioreactor, the bottom and sides of the inner tube are sealed, the inner tube completely encloses the bottom of the outer tube and a portion of the outer wall of the outer tube, the upper part of the inner tube is a certain distance from the top inner wall of the gas chamber, the lower part is a certain distance from the bottom of the gas chamber, and the side is connected to the gas supply pipe.

[0025] Preferably, in the membrane bioreactor, the outer tube has a polygonal shape. When viewed from the side, its upper part is rectangular, its middle part is an inverted trapezoid, and its lower part is rectangular. The upper rectangle is located outside the gas chamber, and the middle trapezoidal part and the lower rectangle are located inside the gas chamber. The outer tube is the channel for the release of pulsed gas flow, and its bottom is narrow and its top is wide.

[0026] Preferably, in the membrane bioreactor, the first end of the gas supply pipe passes through the inner tube and is located in the U-shaped channel, and the second end is connected to the gas source outside the gas chamber.

[0027] Preferably, in the membrane bioreactor, two independent pulse aeration devices are designed as an integrated structure, and the fixing components are shared by both pulse aeration devices.

[0028] Preferably, in the membrane bioreactor, the outer tube is located on both sides of the inner tube, the bottom of both sides of the outer tube is connected to the inner tube, the outer tube is closed around the perimeter, and the inner channels of the outer tube and the inner tube form a W-shaped aeration channel.

[0029] Preferably, in the membrane bioreactor, one end of the gas supply pipe is located at the bottom of the inner tube, and the other end is connected to the gas source.

[0030] Preferably, in the membrane bioreactor, the external water supply to the effluent tank is kept constant under normal operating conditions and is lower than the injection flow rate of the inlet pipe (101) of the membrane tank (10), so that the water level of the membrane tank is constant, while the water level of the effluent tank changes in real time with the filtration process and self-regulates.

[0031] Preferably, in the membrane bioreactor, when the water level in the effluent tank (30) drops to the minimum threshold level, the influent pipe of the membrane tank is closed, the current filtration cycle ends, and the membrane cleaning process is started.

[0032] Preferably, in the membrane bioreactor, the immersion membrane separation system performs the following membrane separation method:

[0033] (1) Preparatory stage: First, open the inlet pipe (101) of the membrane tank (10) to inject water into the membrane tank at a certain flow rate. The water level in the membrane tank (10) rises and submerges the highest point of the water collection pipe (201) of the membrane module (20). Water begins to pass through the filter membrane of the membrane module (20) and flows through the water collection pipe (201) to the outlet tank (30), which causes the water level in the outlet tank (30) to rise. At this time, close the outlet of the outlet tank (30). The water level in the outlet tank (30) will continue to rise until it reaches the same level as the water level in the membrane tank (10). The pressure difference between the upstream and downstream sides of the filter membrane of the membrane module (20) disappears, and the filtration process is temporarily terminated.

[0034] (2) Open the outlet water tank (30) to maintain a constant external water supply flow rate and equal to or lower than the injection flow rate of the inlet pipe (101) of the membrane tank (10); thereby keeping the water level in the membrane tank (10) constant, which is determined by the overflow port height of the overflow pipe (102) of the membrane tank (10) and always submerging the membrane module (20); the water level in the outlet water tank (30) slowly decreases as the water continues to flow out, thereby forming a static pressure difference on the water level of the membrane tank (10);

[0035] (3) When the water level in the outlet tank 30 drops to the minimum allowable level, close the inlet pipe of the membrane tank and the outlet pipe of the outlet tank to end the current filtration cycle.

[0036] Preferably, in the membrane bioreactor, after step (3), the cleaning process of the filter membrane is started, and after the cleaning process, the process returns to step (1) and the above process is repeated.

[0037] Preferably, in the membrane bioreactor, the water level is determined by the height of the overflow port of the overflow pipe (102) of the membrane tank (10) and always submerges the membrane module (20).

[0038] Preferably, in the membrane bioreactor, the water level in the effluent tank changes in real time with the filtration process and self-regulates as follows:

[0039] As the outlet tank (30) begins to supply water, the water level in the outlet tank (30) drops. As the water level in the outlet tank (30) drops, the pressure difference between the upstream and downstream sides of the filter membrane increases, and the water flow rate through the membrane module (20) also increases until it is the same as the flow rate of the outlet pipe (301) of the membrane tank (30), at which point the water level in the outlet tank (30) stops dropping. Subsequently, the filtration process continues, and the outlet pipe (301) of the outlet tank (30) and the outlet pump (301a) maintain a constant external water flow rate, and the cumulative water volume through the filter membrane of the membrane module (20) also increases. As the flow rate increases, suspended impurities trapped on the upstream surface of the filter membrane accumulate, and the resistance of the filter membrane to the permeate water flow also increases, resulting in a decrease in the flow rate of water passing through the filter membrane. When the filtration flow rate of the filter membrane decreases, the water level in the outlet tank (30) decreases accordingly, thereby increasing the pressure difference between the upstream and downstream sides of the filter membrane. The increase in pressure difference compensates for the increase in the resistance of the filter membrane. Thus, at every moment, the increase in the resistance of the filter membrane caused by the accumulation of impurities on the filter membrane surface is just compensated by the increase in the water level difference between the upstream and downstream sides of the filter membrane caused by the decrease in the water level in the outlet tank (30).

[0040] The flexible flat sheet membrane assembly of this invention has the following advantages compared to the prior art:

[0041] (1) Manufacturing costs decreased by 30% to 60%;

[0042] (2) Significantly increases filling density by more than 1 / 3;

[0043] (3) Facilitates chemical cleaning of membrane elements;

[0044] (4) It can achieve the filtration effect of conventional flat-sheet membrane modules with very small amounts of raw materials. Utilizing a small initial investment, minimal floor space, and a small amount of process piping, the filtration efficiency of this flat-sheet membrane module in membrane system applications can be fully realized. For example, with 200 modules and a membrane area of ​​1.0m²... 2 Total water production 5m 3 Based on the calculation, compared to traditional rigid flat sheet membranes, each membrane box saves at least 0.5m² of floor space. 2 The membrane module weighs 98kg (unloaded), which is only 8.5% of the weight of a traditional flat-panel membrane module.

[0045] (5) This invention enables the use of flexible flat-sheet membrane modules with large filtration areas and dense installation, which can significantly reduce the accumulation and adsorption of surface pollutants, and indirectly reduce the energy consumption of aeration and cleaning. Specifically, since there is no support between the membrane sheets, they are prone to friction between the two sides. The ultra-high suspended solids and flocs in the water act as a lubricant to prevent the accumulation of pollutants. At the same time, in conjunction with the bottom aeration system, the membrane sheets sway, shake, are washed by bubbles, and collide with each other with the rising water flow. The irregular distribution of the membrane sheets significantly reduces the accumulation and adsorption of surface pollutants. At the same time, it helps to "remove" the accumulation of pollutants and uneven cleaning effect caused by the large filtration area, and indirectly reduces the energy consumption of aeration and cleaning.

[0046] (6) Compared with traditional flexible flat sheet membrane module production lines, the large-area filtration flexible flat sheet membrane module of the present invention can be prefabricated in advance, "tailor-made", with simple overall molding process, no special requirements for production machinery, environment and site, and no secondary pollution.

[0047] (7) The installation process of flexible flat sheet membrane modules is simple, with high single-sided interface accuracy and no special procedures or precision control. Individual membrane modules can be inspected or replaced without interrupting the project.

[0048] The immersion membrane filtration system of this invention is a pure water dynamic immersion membrane filtration system, which has at least the following advantages:

[0049] (1) The control of the filtration process does not rely on mechanical or electronic devices, which significantly improves the system reliability;

[0050] (2) Maintain a dynamic balance between the resistance of the filter membrane and the transmembrane pressure difference in real time to truly achieve ideal constant-speed filtration;

[0051] (3) The membrane module is not directly connected to the water pump, thus completely avoiding possible damage to the membrane module caused by water hammer or human error.

[0052] The pulse aeration device in this embodiment has the following advantages:

[0053] (1) Effectively prevents sediment from clogging the pulse airflow channel. Since pulse aerators are mostly used in mixed liquid environments rich in suspended solids, when the air supply is interrupted (such as during power outages or maintenance), suspended solids such as silt will accumulate at the bottom of the airflow channel, i.e., the bottom of the U-shaped tube. In severe cases, this may block the airflow channel, causing pulse aeration to fail upon restart. In this embodiment of the invention, a continuous airflow (pressurized air from a blower) is used to purge the bottom of the U-shaped tube, preventing suspended solids such as silt from accumulating there and preventing the already formed sediment from being stirred up when the air supply is restarted after an interruption, thus ensuring the smooth flow of the aeration channel.

[0054] (2) The W-shaped aeration channel design in this embodiment is equivalent to combining two U-shaped tubes into one, that is, merging the inner tubes of the two U-shaped tubes into one. This not only makes the connection between the aeration channel and the air chamber easier and more secure, but also increases the service area of ​​a single pulse aerator by dividing the pulse airflow into two. Attached Figure Description

[0055] Figure 1 The diagram schematically illustrates the components and process of a conventional MBR.

[0056] Figure 2 This is a schematic diagram of the structure of a bag-type flexible flat sheet membrane element according to an embodiment of the present invention. Figure 3 A cross-sectional schematic diagram of a water collection component with a central groove design according to an embodiment of the present invention is shown. Figure 4 A schematic diagram of the arrangement of water inlets on a water collecting device according to an embodiment of the present invention and an enlarged cross-sectional view of the vicinity of the water inlets are shown. Figure 5 This is a schematic diagram of the structure of an immersion membrane separation system according to an embodiment of the present invention.

[0057] Figure 6 This is a top view of an anti-clogging pulse aerator according to an embodiment of the present invention. Figure 7 It is a bottom view. Figure 8 This is a cross-sectional view of AA. Figure 9 This is a cross-sectional view of BB.

[0058] Figure 10 A schematic diagram of a pulse aeration device according to another embodiment of the present invention is shown.

[0059] Explanation of reference numerals in the attached figures:

[0060] Water collection component 1, filter membrane 2-1, flexible flow guide mesh 2-2,

[0061] 10 Membrane tank, 101 Membrane tank inlet pipe, 102 Membrane tank overflow pipe, 103 Membrane tank drain pipe; 20 Membrane module, 201 Water collection pipe; 30 Outlet tank, 301 Outlet pipe, 301a Outlet pump

[0062] 100 air chamber, 200 outer pipe, 300 inner pipe, 400 air supply pipe, 500 fixing components.

[0063] 100' air chamber, 200' outer tube, 300' inner tube, 400' air supply tube, 500' fixed components. Detailed Implementation

[0064] The present invention will now be described with reference to the accompanying drawings and specific embodiments.

[0065] The following section introduces specific implementation examples from three aspects: improvements to membrane modules, membrane separation processes, and aeration systems.

[0066] Example 1: Bag-type flexible flat sheet membrane element

[0067] Figure 2 This is a schematic diagram of the structure of a bag-type flexible flat sheet membrane element according to an embodiment of the present invention.

[0068] like Figure 2 As shown, the bag-type flexible flat sheet membrane element includes: two filter membrane sheets 2-1, a flexible flow guiding mesh 2-2 sandwiched in the middle, and water collection components 1 located at both ends of the bag.

[0069] Two filter membranes 2-1 and a flexible flow-guiding mesh 2-2 in the middle form a bag-like structure. The two long sides of the bag are closed, and at least one of the two short sides is open. The water collecting component 1 has a hollow water collecting trough or two parallel water collecting channels extending along the short side. The at least one open end of the bag is connected to the water collecting trough or water collecting channel of the water collecting component. One end of the water collecting component is sealed, and the other end has at least two water outlet nozzles 1-1. One end of the water outlet nozzle 1-1 is connected to the water collecting trough or water collecting channel, and the other end is connected to the main water collecting pipe. The water collecting component 1 is formed by injection molding in one piece.

[0070] In one example, considering the injection molding requirements and water outlet speed, the water collection component in this embodiment of the invention is designed as an open groove in the middle and two water outlet nozzles are arranged in the vertical direction. This allows the water collection component to be injection molded in one go, and the arrangement of the groove and the two water outlet nozzles can ensure the water outlet speed requirements.

[0071] Figure 3 A schematic diagram shows the water collection component with a groove in the middle. Label 3-1 indicates the groove, 3-2 indicates the outlet nozzle, and 3-3 indicates the wedge-shaped transition area. The wedge-shaped transition area is the transition zone where the filter membrane is welded or bonded to the water collection component, and then directly welded or bonded to the two filter membranes and the flexible mesh.

[0072] Traditionally, the water collection device usually has a hole in the middle. In order to facilitate injection molding, the inner diameter of the hole cannot be too small. However, considering the space constraints of the membrane module, it is desirable to have the spacing between the membrane elements in the membrane module as small as possible. If the inner diameter of the hole is too large, it will not be able to meet the requirement of having the spacing between the membrane elements as small as possible.

[0073] exist Figure 3In the example shown, the water collecting component in this embodiment of the invention is designed as a groove in the middle and has two water outlet nozzles in the vertical direction. This allows the water collecting component to be injection molded in one step, reducing manufacturing costs and gaining significant manufacturing advantages. Moreover, the spacing between the membrane elements can be very small, and the arrangement of the two water outlet nozzles ensures the required water flow rate while preventing the inner diameter of the water outlet nozzles from being too large.

[0074] In another example, the water collecting element has two longitudinally parallel water collecting channels extending along the short side of the membrane element. In this case, there is an inlet hole perpendicular to the water collecting channel, which connects the two water collecting channels and connects one end to a flow channel inside the bag. The inlet holes are, for example, evenly distributed along the water collecting channels, and the number can be 15-25.

[0075] Figure 4 A schematic diagram of the arrangement of water inlets on a water collecting device according to an embodiment of the present invention and an enlarged cross-sectional view near the water inlets are shown. As shown, a plurality of water inlets are arranged on the water collecting device 1, and the water inlets connect the water collecting channel (marked as flow channel in the figure) on the water collecting device and the flow channel (not shown in the figure) inside the bag.

[0076] Compared to traditional flexible flat sheet membrane elements where the outlet is located in the middle of the long side, this embodiment of the invention arranges water collection components on the upper and lower sides of the membrane element. These components not only support the unfolded membrane but also collect water evenly and summarize the outflow. Furthermore, they facilitate the injection of chemicals into the bag during membrane cleaning, offering multiple advantages.

[0077] The two short sides of the bag are respectively encapsulated with the upper and lower water collection components, so that the inner cavity of the bag is connected to the water collection groove or water collection channel of the water collection component.

[0078] In one example, one end of the water collection component has two parallel water outlet nozzles, which are double-ended pagoda-shaped. Each water outlet nozzle has two grooves for placing O-rings, and is equipped with four pairs of O-rings. It is connected to the main water collection pipe in a socket manner. The two ends of the water collection component also have two wedge-shaped transition connectors for the transition between the water collection component and the diaphragm welding joint.

[0079] The water collecting element is preferably 400-600mm long and 4-12mm thick. The inner diameter of the water outlet nozzle on the water collecting element is 3-6mm. The length of the flexible flat sheet membrane element is 500-1500mm.

[0080] In one example, the water collection unit is 480mm long and 6mm thick, and the inner diameter of the water outlet nozzle is 3mm.

[0081] According to another embodiment of the present invention, a method for preparing the aforementioned bag-type flexible flat sheet membrane element is provided, comprising:

[0082] Step 1: Weld the pre-made elastic film to the wedge-shaped transition on both sides of the water collection component using a spot welding machine;

[0083] Step 2: Place the two water collection components on the spot welding station, where the distance between the two water collection components is controlled to be 500-1500mm, and spot weld a membrane sheet to one side of the water collection component.

[0084] Step 3: Turn the above-mentioned spot-welded parts over, place the flow guide net in a fixed position, use a spot welding machine to spot weld the flow guide net to the diaphragm, and then place another diaphragm on top and use a spot welding machine to fix it to the water collection component.

[0085] Step 4: Lay the spot-welded membrane element flat on the hot melt machine;

[0086] Start the hot melt machine, control the hot melt temperature at 120-170 degrees Celsius, the pressure at 0.05-0.15 MPa, and the hot melt duration at 10-30 seconds;

[0087] Step 5: Quickly remove the entire film, lay it flat to dry, cool down, and set its shape.

[0088] According to another embodiment of the present invention, a method for preparing the aforementioned bag-type flexible flat sheet membrane element is provided, comprising:

[0089] Step 1: Place two water collection components on the spot welding station, where the distance between the two water collection components is controlled to be 500-1500mm. Spot weld a membrane sheet to one side of the water collection component.

[0090] Step 2: Turn the above-mentioned spot-welded parts over, place the flow guide net in a fixed position, use a spot welding machine to spot weld the flow guide net to the diaphragm, and then place another diaphragm on top and use a spot welding machine to fix it to the water collection component.

[0091] Step 3: Apply liquid elastic adhesive to the wedge-shaped transition on both sides of the water collection component;

[0092] Step 4: Lay the film element, which has been spot-welded and coated with adhesive, flat on the hot melt machine; start the hot melt machine, and control the hot melt forming temperature at 120-170 degrees, the pressure at 0.05-0.15MPa, and the hot melt duration at 10-30 seconds.

[0093] Step 5: Quickly remove the entire film, lay it flat to dry, cool down, and set its shape.

[0094] In the aforementioned method for preparing a bag-type flexible flat sheet membrane element, the thickness of the pre-made film or the coated liquid colloid can be 0.2 mm, and the distance between the two water collection elements can be 500-1500 mm, preferably 1000-1200 mm.

[0095] According to another embodiment of the present invention, a flexible flat sheet membrane module is provided, which is formed by stacking a plurality of the aforementioned flat sheet membrane elements in sequence, wherein: the spacing between the membrane elements is 4-10 mm; the flat sheet membrane elements are installed on the membrane module by insertion; and at least two outlet ports of the water collection element of each flat sheet membrane element are connected to the main water collection pipe.

[0096] In a flexible flat sheet membrane module, at least two outlet ports of the water collection element of each membrane element can be inserted into the main water collection pipe.

[0097] In the membrane element of this invention embodiment, both water collecting elements can be connected to the flow channel of the bag for water collection, or only one water collecting element can collect water. However, it is preferable that both water collecting elements collect water, so that the water flow of the entire water collecting element is unobstructed, the water production is high, and it is easy to clean the membrane element.

[0098] In this specific implementation example, the prepared membrane module weighed approximately 80.7g, and 1m 2 The water production capacity of a single membrane reached 31.8 L / h.

[0099] The flexible flat sheet membrane assembly of the present invention has the following advantages compared with the prior art:

[0100] (1) Manufacturing costs decreased by 30% to 60%;

[0101] (2) Significantly increases filling density by more than 1 / 3;

[0102] (3) Facilitates chemical cleaning of membrane elements;

[0103] (4) It can achieve the filtration effect of conventional flat-sheet membrane modules with very small amounts of raw materials. Utilizing a small initial investment, minimal floor space, and a small amount of process piping, the filtration efficiency of this flat-sheet membrane module in membrane system applications can be fully realized. For example, with 200 modules and a membrane area of ​​1.0m²... 2 Total water production 5m 3 Based on the calculation, compared to traditional rigid flat sheet membranes, each membrane box saves at least 0.5m² of floor space. 2 The membrane module weighs 98kg (unloaded), which is only 8.5% of the weight of a traditional flat-panel membrane module.

[0104] (5) This invention enables the use of flexible flat-sheet membrane modules with large filtration areas and dense installation, which can significantly reduce the accumulation and adsorption of surface pollutants, and indirectly reduce the energy consumption of aeration and cleaning. Specifically, since there is no support between the membrane sheets, they are prone to friction between the two sides. The ultra-high suspended solids and flocs in the water act as a lubricant to prevent the accumulation of pollutants. At the same time, in conjunction with the bottom aeration system, the membrane sheets sway, shake, are washed by bubbles, and collide with each other with the rising water flow. The irregular distribution of the membrane sheets significantly reduces the accumulation and adsorption of surface pollutants. At the same time, it helps to "remove" the accumulation of pollutants and uneven cleaning effect caused by the large filtration area, and indirectly reduces the energy consumption of aeration and cleaning.

[0105] (6) Compared with traditional flexible flat sheet membrane module production lines, the large-area filtration flexible flat sheet membrane module of the present invention can be prefabricated in advance, "tailor-made", with simple overall molding process, no special requirements for production machinery, environment and site, and no secondary pollution.

[0106] (7) The installation process of flexible flat sheet membrane modules is simple, with high single-sided interface accuracy and no special procedures or precision control. Individual membrane modules can be inspected or replaced without interrupting the project.

[0107] Example 2: Membrane Separation Process

[0108] Membrane separation processes are classified into two types based on their operation: immersion membrane separation and pressure membrane separation. In immersion membrane separation, the membrane module is submerged in the liquid to be purified, and a negative pressure is created on one side of the filter membrane by a suction pump, thereby achieving membrane separation. In pressure membrane separation, the liquid to be purified is first pressurized by a pump, and the pressurized liquid flows through the filter membrane, thus achieving membrane separation.

[0109] Immersion membrane separation technology is gaining increasing application due to its simple structure and ease of large-scale application. During membrane separation, the accumulation of trapped impurities on the feed side (or upstream surface) of the filter membrane creates resistance, making the process complex and variable. As the amount of liquid passing through the membrane increases, more impurities accumulate on the membrane surface, increasing resistance and making separation increasingly difficult. This leads to a problem: initially, the outflow rate is high, but gradually decreases, resulting in a rapid decline in membrane efficiency.

[0110] To maximize the efficiency of the filter membrane and maximize its output within a cycle (the time period available for production between two adjacent cleaning operations), it is usually necessary to control the outflow rate of the filter membrane and maintain it at a roughly constant level (i.e., constant-rate filtration). This requires adjusting the pressure difference applied to both sides of the filter membrane in real time according to the resistance of the filter membrane, so that the pressure difference on both sides of the filter membrane and the resistance of the filter membrane are always balanced.

[0111] To achieve this goal, the market currently uses variable frequency speed control (VFD) for the filtrate suction pump. Automated instruments monitor the filtrate flow rate and the pressure upstream and downstream of the filter membrane in real time, inputting these signals to a programmable logic controller (PLC). An algorithm then modifies the VFD's output frequency, thereby changing the speed of the suction pump's drive motor. While this automated control method can largely achieve the control objectives required for membrane separation, it suffers from drawbacks such as a large number of devices, high investment, complex management and maintenance, and low reliability. Furthermore, due to the limitations of the VFD and the algorithm, it is impossible to achieve true real-time balance between the pressure difference applied across the filter membrane and the membrane resistance.

[0112] like Figure 5 As shown, an immersion membrane separation system according to another embodiment of the present invention includes a membrane tank 10, a membrane module 20, and an effluent tank 30.

[0113] The upper edge of the effluent tank 30 is at the same horizontal level as the upper edge of the membrane tank 10. The membrane module 20 is installed inside the membrane tank 10 and submerged in the water to be filtered within the membrane tank 10. The water collection pipe 201 of the membrane module 20 enters the effluent tank 30, and its port is located below the minimum allowable water level of the effluent tank 30. Unlike the conventional method of using a filtrate suction pump to control the pressure difference across the membrane module, in this embodiment, the membrane module 20 is not directly connected to the water pump.

[0114] In the illustrated example, the membrane tank 10 also has an inlet pipe 101 for replenishing the water to be filtered, an overflow pipe 102 for preventing the water to be filtered from overflowing, and an empty pipe 103, with an empty valve on the empty pipe; the outlet tank 30 is equipped with an outlet pipe 301 for sending water out and an outlet pump 301a.

[0115] The upper edges of the membrane tank 10 and the outlet tank 30 are at the same level to prevent overflow caused by the water level rising in the outlet tank 30 when the outlet tank 30 stops supplying water.

[0116] In the immersion membrane separation system of this embodiment, under normal working conditions, the external water supply of the outlet tank is controlled to be constant and lower than the injection flow of the inlet pipe (101) of the membrane tank (10). By utilizing the siphon principle of hydraulics, the water level of the membrane tank is kept constant, while the water level of the outlet tank changes in real time with the filtration process and self-regulates.

[0117] The working principle and control process of the immersion membrane separation system in this embodiment are described below.

[0118] According to one embodiment of the present invention, the control process of the immersion membrane separation system is as follows:

[0119] (1) Preparation stage: First, open the inlet pipe (101) of the membrane tank (10) to inject water into the membrane tank at a certain flow rate. The water level in the membrane tank (10) rises and submerges the highest point of the water collection pipe (201) of the membrane module (20). Water begins to pass through the filter membrane of the membrane module (20) and flows to the outlet tank (30) through the water collection pipe (201), which causes the water level in the outlet tank (30) to rise. In the preparation stage, close the outlet of the outlet tank (30). The water level in the outlet tank (30) will continue to rise until it reaches the same level as the water level in the membrane tank (10). The pressure difference between the upstream and downstream sides of the filter membrane of the membrane module (20) disappears, and the filtration process is temporarily terminated.

[0120] (2) Open the outlet water tank (30) to maintain a constant external water supply flow rate and equal to or lower than the injection flow rate of the inlet pipe (101) of the membrane tank (10); thereby keeping the water level in the membrane tank (10) constant. The maximum value of the water level is determined by the overflow port height of the overflow pipe (102) of the membrane tank (10) and always submerges the membrane module (20); the water level of the outlet water tank (30) slowly decreases as the water continues to flow out, thereby forming a static pressure difference on the water level of the membrane tank (10). The water level of the outlet water tank changes in real time with the filtration process and self-regulates.

[0121] (3) When the water level in the outlet tank 30 drops to the minimum allowable level, close the inlet pipe of the membrane tank and the outlet pipe of the outlet tank to end the current filtration cycle.

[0122] Normally, during normal filtration of the system, after step (3), the filter membrane cleaning process is started, and after the cleaning process, the process returns to step (1) and repeats the above process.

[0123] The process by which the water level in the outlet tank changes in real time and self-regulates during the filtration process in step (2) above is as follows:

[0124] As the outlet tank (30) begins to supply water, the water level in the outlet tank (30) drops. As the water level in the outlet tank (30) drops, the pressure difference between the upstream and downstream sides of the filter membrane increases, and the water flow rate through the membrane module (20) also increases until it is the same as the flow rate of the outlet pipe (301) of the membrane tank (30), at which point the water level in the outlet tank (30) stops dropping. Subsequently, the filtration process continues, and the outlet pipe (301) of the outlet tank (30) and the outlet pump (301a) maintain a constant external water flow rate, and the cumulative water volume through the filter membrane of the membrane module (20) also increases. As the flow rate increases, suspended impurities trapped on the upstream surface of the filter membrane accumulate, and the resistance of the filter membrane to the permeate water flow also increases, resulting in a decrease in the flow rate through the filter membrane. When the filtration flow rate of the filter membrane decreases, the water level in the outlet tank (30) decreases accordingly, thereby increasing the pressure difference between the upstream and downstream sides of the filter membrane. The increase in pressure difference compensates for the increase in filter membrane resistance. Thus, at every moment, the increase in filter membrane resistance caused by the accumulation of impurities on the filter membrane surface is exactly compensated by the increase in the water level difference between the upstream and downstream sides of the filter membrane caused by the decrease in the water level in the outlet tank (30). Moreover, this adjustment process is real-time and continuous. In other words, at every moment, the increase in filter membrane resistance caused by the accumulation of impurities on the filter membrane surface is exactly compensated by the increase in the water level difference between the upstream and downstream sides of the filter membrane caused by the decrease in the water level in the outlet tank (30).

[0125] The control of the immersion membrane filtration process described above can be achieved entirely based on hydraulic principles, without the need for external force or automated instruments. This also applies to the temporary termination of the filtration process. For example, if the outlet pipe 301 of the outlet tank 30 or the external water pump 301a suddenly stops working due to a malfunction or power outage, the filtration process will also stop immediately without external force or manual intervention.

[0126] The immersion membrane filtration system of this invention is a pure water dynamic immersion membrane filtration system, which has at least the following advantages:

[0127] (1) The control of the filtration process does not rely on mechanical or electronic devices, which significantly improves the system reliability;

[0128] (2) Maintain a dynamic balance between the resistance of the filter membrane and the transmembrane pressure difference in real time to truly achieve ideal constant-speed filtration;

[0129] (3) The membrane module is not directly connected to the water pump, thus completely avoiding possible damage to the membrane module caused by water hammer or human error.

[0130] Example 3: Aeration System

[0131] According to an embodiment of the present invention, a pulse aeration device is provided, comprising an air chamber, an inner tube, an outer tube, an air supply pipe, and a fixing component: the air chamber is an open container at the bottom for accumulating and temporarily storing gas from an air source; the air supply pipe connects to an air source outside the air chamber for supplying gas to the air chamber; the outer tube connects the inside and outside of the air chamber, is open at the top and bottom, is sealed on all sides, extends a certain distance above the top outer wall of the air chamber at the top, and is a certain distance from the bottom of the air chamber at the bottom, serving as a channel for releasing gas from the air chamber to the outside; the inner tube is fixed in position to the outer tube by a component, the upper part of the inner tube is open and located inside the air chamber, wherein the bottom of the inner tube is connected to the bottom of the outer tube, and the structure of the outer tube and the inner tube is equivalent to combining multiple U-shaped tubes into one, wherein one arm of each U-shaped tube is combined into a common arm of all U-shaped tubes, and the remaining arms of each U-shaped tube are separate or combined into one.

[0132] Figure 6 This is a top view of an anti-clogging pulse aerator according to an embodiment of the present invention. Figure 7 It is a bottom view. Figure 8 This is a cross-sectional view of AA. Figure 9 This is a cross-sectional view of BB.

[0133] like Figure 6-9 As shown, the pulse aerator consists of an air chamber 100, an outer pipe 200, an inner pipe 300, an air supply pipe 400, and a fixing component 500.

[0134] The gas chamber 100 is a container with an open bottom and sealed top and sides. Its cross-sectional shape can be square, circular, or any other shape. The gas chamber is used to collect the gas entering through the gas supply pipe, and the gas is released all at once after filling the chamber. An outer pipe 200 is provided at the top of the gas chamber 100.

[0135] The outer tube 200 connects the inside and outside of the gas chamber 100. It is open at the top and bottom and sealed on all sides. The upper part is higher than the outer wall of the top of the gas chamber by a certain distance, and the lower part is a certain distance from the bottom of the gas chamber. The outer tube 200 is the channel for gas release and also the channel for liquid to enter the gas chamber 100. Its cross-sectional area can be square, circular or any shape.

[0136] In one example, the outer tube has a polygonal shape, viewed from the side ( Figure 9 The structure consists of a rectangular upper section, an inverted trapezoidal middle section, and a rectangular lower section. The upper rectangle is located outside the air chamber, while the middle trapezoidal section and the lower rectangle are located inside the air chamber. The outer tube serves as the channel for releasing the pulsed gas flow; it is narrow at the bottom and wide at the top. As gas is released, the gas flow channel widens, and the corresponding gas pressure decreases. As the gas flows upward, the volume of the bubbles gradually increases, forming larger bubbles. Larger bubbles have a stronger turbulent effect on the water than smaller bubbles, thus providing a stronger scrubbing effect on the membrane surface and effectively mitigating membrane fouling.

[0137] The inner tube 300 is connected to the outer tube 200, with an open top and sealed bottom and sides. The inner tube 300 completely encloses the bottom of the outer tube 200 and partially or completely encloses the outer walls of the outer tube 200, forming a U-shaped channel between the internal cavity of the inner tube 300 and the outer wall of the outer tube 200. The upper part of the inner tube 300 is a certain distance from the top inner wall of the air chamber 100, and the lower part is a certain distance from the bottom of the air chamber 100. A gas supply pipe 400 is connected to the side, which serves as the gas supply channel for the air chamber 100. After the air chamber 100 is filled with gas, it also serves as the gas release channel within the air chamber 100. Its cross-sectional area can be square, circular, or any shape.

[0138] The bottom opening of the outer pipe is close to the bottom of the inner pipe. Since the gas in the air chamber can only be discharged through the outer pipe and form aeration when it reaches the bottom opening of the outer pipe, the lower the bottom opening of the outer pipe, the greater the water pressure and air pressure will be, and the more the aeration intensity can be increased within a limited space.

[0139] The air supply pipe 400 connects the inner pipe 300 to the main air supply pipe (not shown) and is the air source for the air chamber 100. It extends a certain distance into the U-shaped channel formed by the outer pipe 200 and the inner pipe 300. In this preferred example, the air supply pipe 400 has a circular cross-section.

[0140] The fixing component 500 consists of mounting holes and reinforcing ribs, and its main function is to fix the pulse aerator to the membrane frame.

[0141] The materials used for processing pulse aerators can include ABS, PVC, stainless steel, etc.

[0142] Figure 6-9 In the example of the pulse aeration device shown, the structure of the outer tube and the inner tube is equivalent to combining multiple U-shaped tubes into one. One arm of each U-shaped tube is combined into a common part of all U-shaped tubes, and the remaining arms of each U-shaped tube are combined into one. In other words, the inner tube can be regarded as a combination of one arm of countless U-shaped tubes, and the outer tube can be regarded as a combination of the other arm of those countless U-shaped tubes.

[0143] Figure 6-9 The example of the pulse aeration device shown can prevent the pulse airway from being blocked: the aerator tube is placed between the outer wall of the inner tube and the inner wall of the outer tube in the U-shaped channel. After aeration stops, aeration is restarted. The suspended matter deposited here is disturbed and becomes suspended, thereby eliminating the deposition of suspended matter here. This allows the airflow to enter the air chamber smoothly and form a pulse. The high-intensity pulse airflow can instantly wash away the sludge deposited at the bottom of the outer tube and in the inner tube, ensuring the stable formation of the pulse airflow.

[0144] Figure 6-9The pulse aeration device example shown has a simple structure: compared with the pulse aerator structure in the prior art, the pulse aerator structure provided in this embodiment of the present invention is simple, designing two independent pulse aerators into an integrated structure, reducing the number of parts of the pulse aerator (only two parts: the air chamber and the U-shaped channel), and saving the installation workload of the pulse aerator.

[0145] Figure 10 A schematic diagram of a pulse aeration device according to another embodiment of the present invention is shown.

[0146] Figure 10 This is a cross-sectional view of the aerator. The anti-clogging pulse aerator described in this invention includes an air chamber 100', an outer pipe 200', an inner pipe 300', an air supply pipe 400', and a fixing component 500'.

[0147] The gas chamber 100' is a rectangular cover with an open bottom and sealed top and sides, used to collect the gas entering through the gas supply pipe. The gas is released all at once after filling the gas chamber. An outer pipe 200' is provided on the top of the gas chamber 100'.

[0148] The inner tube 300' is open at the top and bottom, and sealed on all sides. The inner tube 300' can be polygonal in shape; in this example, it is a hollow cuboid. The inner tube 300' is open at the top and located inside the air chamber 100', and its bottom is connected to the outer tube 200' and the air supply tube 400'.

[0149] The bottom of the two outer pipes 200' is connected to the inner pipe 300', and their outlets are outside the air chamber 100'. The two outer pipes 200' and the inner pipe 300' form a W-shaped aeration channel.

[0150] More specifically, the inner and outer tubes together form a (rapid) release channel for the gas in the air chamber. That is, the inner tube is the first half of the release channel and the outer tube is the second half. When the gas accumulated in the air chamber reaches a certain volume ("full"), it will be rapidly released outside the air chamber (above the air chamber) through the aeration channel formed by the inner and outer tubes.

[0151] In this example, the inner tube is a hollow cuboid. As the gas is released and flows upwards, the volume of the bubbles gradually increases, forming larger bubbles. Larger bubbles have a stronger turbulent effect on the water than smaller bubbles, thus providing a stronger scrubbing effect on the membrane surface and effectively mitigating membrane fouling.

[0152] The inner and outer tubes can essentially be considered as two parts of the same curved channel (connecting pipe), roughly U-shaped overall. The key difference lies in the vertical relationship between the two ends of the channel: the end of the outer tube is higher than the end of the inner tube (the end of the inner tube is below the top plate of the air chamber, and the end of the outer tube is above the top plate of the air chamber).

[0153] One end of the air supply pipe 400' is located at the bottom of the cavity where the inner pipe 300' and the outer pipe 200' are connected, and the other end is connected to the air source. The air supply pipe is the air source for the air chamber, and its cross-section is circular.

[0154] The fixing component 500' consists of mounting holes and reinforcing ribs, and its main function is to fix the pulse aerator to the membrane frame.

[0155] Figure 10 In the example of the pulse aeration device shown, the structure of the outer and inner tubes is equivalent to merging two U-shaped tubes, where one arm of each of the two U-shaped tubes is combined into one unit, which is shared by both U-shaped tubes. In other words, the inner tube can be regarded as the combination of one arm of each of the two U-shaped tubes, and the two side arms of the outer tube can be regarded as the other arm of each of the two U-shaped tubes.

[0156] In this embodiment, the support plate is an ABS plate that is injection molded in one piece.

[0157] The pulse aeration device in this embodiment has the following advantages:

[0158] (1) Effectively prevents sediment from clogging the pulse airflow channel. Since pulse aerators are mostly used in mixed liquid environments rich in suspended solids, when the air supply is interrupted (such as during power outages or maintenance), suspended solids such as silt will accumulate at the bottom of the airflow channel, i.e., the bottom of the U-shaped tube. In severe cases, this may block the airflow channel, causing pulse aeration to fail upon restart. In this embodiment of the invention, a continuous airflow (pressurized air from a blower) is used to purge the bottom of the U-shaped tube, preventing suspended solids such as silt from accumulating there and preventing the already formed sediment from being stirred up when the air supply is restarted after an interruption, thus ensuring the smooth flow of the aeration channel.

[0159] (2) The W-shaped aeration channel design in this embodiment is equivalent to combining two U-shaped tubes into one, that is, merging the inner tubes of the two U-shaped tubes into one. This not only makes the connection between the aeration channel and the air chamber easier and more secure, but also increases the service area of ​​a single pulse aerator by dividing the pulse airflow into two.

[0160] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A membrane bioreactor, comprising a membrane tank, a membrane assembly, a water outlet tank and a pulse aeration device located at the bottom of the membrane tank, the pulse aeration device is used to scour the membrane when aeration; The membrane assembly is formed by stacking bag-type flexible flat membrane elements in sequence; The bag-type flexible flat membrane element comprises two filter membrane sheets, a flexible flow guide grid sandwiched in the middle and water collecting devices located at both ends of the bag, the two filter membrane sheets and the flexible flow guide grid in the middle form a bag shape, the two long edges of the bag are closed and at least one of the two short edges is open, the water collecting device at the top end has a hollow water collecting tank or two water collecting holes arranged in parallel along the short edge direction, the at least one open edge of the bag is communicated with the water collecting tank or the water collecting holes of the water collecting device, one end of the water collecting device is sealed, and the other end has at least two water outlet nozzles extending along the short edge of the membrane element and stacked in the membrane element long edge direction, one end of the water outlet nozzle is communicated with the water collecting tank or the water collecting holes, and the other end is used to be connected after being connected with the water collecting main pipe, the water collecting device is obtained by one-shot injection molding, wherein the two filter membrane sheets are welded or bonded on the outside of the water collecting device, and the two ends of the water collecting device have two wedge-shaped transition connection parts for the transition of the welding part of the water collecting device and the membrane sheet, and a prefabricated adhesive film or a coated liquid adhesive is used in the transition area, The length of the water collecting device is 400-600mm, the thickness is 4-6mm, the inner diameter of the water outlet nozzle on the water collecting device is 3-6mm, the length of the flexible flat membrane element is 500-1500mm, The pulse aeration device comprises a gas chamber, an inner pipe, an outer pipe, a gas supply pipe and a fixing part: The gas chamber is an open container at the lower part, which is used to accumulate and temporarily store the gas from the gas source; The gas supply pipe is connected to the gas source outside the gas chamber, which is used to supply gas to the gas chamber; The outer pipe is connected to the inside and outside of the gas chamber, which is open at the top and bottom and sealed around, the top is higher than the outer wall of the gas chamber top by a certain distance, and the bottom is away from the bottom of the gas chamber by a certain distance, which is a channel for the gas in the gas chamber to be released to the outside; The inner pipe is fixed with the outer pipe by a component, the upper part of the inner pipe is open and located in the gas chamber, Wherein the bottom of the inner pipe and the bottom of the outer pipe are communicated with each other, and the structure of the outer pipe and the inner pipe is equivalent to combining multiple U-shaped pipes into one, wherein one arm of each U-shaped pipe is combined for all U-shaped pipes, and the remaining arms of each U-shaped pipe are separated or combined into one, The upper edge of the water outlet tank is at the same level as the upper edge of the membrane tank, the membrane assembly is installed inside the membrane tank and immersed in the water to be filtered in the membrane tank, the water collecting pipe of the membrane assembly is connected to the water outlet tank and its port is below the lowest allowable water level of the water outlet tank, and the membrane assembly is not directly connected to the water pump, The bottom of the inner pipe is sealed around, the inner pipe contains the bottom of the outer pipe inside, and a part of the outer wall of the outer pipe is contained inside, the upper part of the inner pipe is away from the inner wall of the top of the gas chamber by a certain distance, the lower part is away from the bottom of the gas chamber by a certain distance, and the side is connected to the gas supply pipe.

2. The membrane bioreactor according to claim 1, wherein the water collecting device has a hollow water collecting tank, and the two short edges of the bag are packaged together with the upper and lower water collecting devices respectively, so that the inner cavity of the bag is communicated with the water collecting tank of the water collecting device.

3. The membrane bioreactor according to claim 1, wherein the water collecting member has two water collecting channels arranged in parallel along the short side of the membrane element, and a water inlet hole arranged in a direction perpendicular to the water collecting channels, the water inlet hole being arranged to communicate the two water collecting channels and to communicate with the inner cavity of the bag.

4. The membrane bioreactor according to claim 3, wherein the water inlet hole is uniformly distributed along the water collecting channel with a spacing of 20-30 mm.

5. The membrane bioreactor according to claim 1, wherein one end of the water collecting member has two stacked water outlet nozzles, each water outlet nozzle has two grooves for placing O-rings, and four pairs of O-rings are arranged to connect the water collecting member to the water collecting main pipe in a socket-and-spigot manner.

6. The membrane bioreactor according to claim 1, wherein the water collecting member has a length of 480 mm, and the inner diameter of the water outlet nozzle is 3 mm.

7. The membrane bioreactor according to claim 1, wherein the outer tube has a polygonal shape, and the upper part of the outer tube is rectangular, the middle part is inverted trapezoidal, and the lower part is rectangular, the upper rectangular part is located outside the air chamber, the middle inverted trapezoidal part and the lower rectangular part are located inside the air chamber, the outer tube is a channel for releasing pulse air flow, and the bottom of the channel is narrow and the top of the channel is wide.

8. The membrane bioreactor according to claim 7, wherein the first end of the air supply tube is arranged in the U-shaped channel through the inner tube, and the second end of the air supply tube is connected to an air source outside the air chamber.

9. The membrane bioreactor of claim 8, wherein, The two independent pulse aeration devices are designed as an integrated structure, and the fixing member is shared by the two pulse aeration devices.

10. The membrane bioreactor of claim 1 wherein, In the normal working state, the water supply to the water outlet tank is kept constant and lower than the injection flow rate of the water inlet pipe (101) of the membrane tank (10), so that the water level in the membrane tank is constant, and the water level in the water outlet tank changes in real time and is self-adjusted during the filtration process.

11. The membrane bioreactor according to claim 10, wherein when the water level in the water outlet tank (30) drops to the minimum threshold level, the water inlet pipe of the membrane tank is closed, the current filtration period is ended, and the cleaning process of the filtration membrane is started.

12. The membrane bioreactor according to claim 1, wherein the membrane bioreactor performs the following membrane separation method: (1) Preparation stage: first, open the water inlet pipe (101) of the membrane tank (10) to inject water into the membrane tank at a certain flow rate, the water level in the membrane tank (10) rises and submerges the highest point of the water collecting pipe (201) of the membrane assembly (20), the water starts to pass through the filtration membrane of the membrane assembly (20) and flows to the water outlet tank (30) through the water collecting pipe (201), thereby causing the water level in the water outlet tank (30) to rise; at this time, the water outlet of the water outlet tank (30) is closed, and the water level in the water outlet tank (30) will continue to rise until it reaches the same height as the water level in the membrane tank (10), the pressure difference between the upstream and downstream of the filtration membrane of the membrane assembly (20) disappears, and the filtration process is temporarily terminated. (2) open the outlet of the water tank (30) to keep the constant water supply flow rate and equal or lower than the injection flow rate of the inlet pipe (101) of the membrane tank (10), so that the water level in the membrane tank (10) remains constant, the maximum value of which is determined by the overflow height of the overflow pipe (102) of the membrane tank (10), and the membrane assembly (20) is always submerged; the water level in the water tank (30) slowly decreases with the continuous water outlet, thereby forming a static pressure difference for the water level in the membrane tank (10); (3) when the water level in the water tank (30) drops to the lowest level allowed, the inlet pipe of the membrane tank and the outlet pipe of the water tank are closed, and the current filtration period ends.

13. The membrane bioreactor of claim 12, after step (3), the cleaning process of the filtration membrane is started, and after the cleaning process, it returns to step (1) and the above process is repeatedly executed.

14. The membrane bioreactor of claim 10, characterized by, The process of the water level in the water tank changing in real time and self-regulating during the filtration process is as follows: As the water tank (30) starts to supply water, the water level in the water tank (30) decreases; as the water level in the water tank (30) decreases, the pressure difference between the upstream and downstream of the filtration membrane also increases, and the water flow through the membrane assembly (20) also increases, until the flow through the membrane assembly (20) is the same as the flow of the outlet pipe (301) of the water tank (30), and the water level in the water tank (30) stops decreasing; then the filtration process continues, the outlet pipe (301) of the water tank (30) and the water pump (301a) maintain a constant water supply flow rate, and the cumulative water volume through the filtration membrane of the membrane assembly (20) also increases accordingly, and the suspended impurities on the upstream surface of the filtration membrane also accumulate, and the resistance of the filtration membrane to the water flow through it also increases, thereby causing the water flow through the filtration membrane to decrease; when the filtration flow of the filtration membrane decreases, the water level in the water tank (30) decreases, thereby increasing the pressure difference between the upstream and downstream of the filtration membrane; the increase in the pressure difference compensates for the increase in the resistance of the filtration membrane, so that at any time, the increase in the resistance of the filtration membrane due to the accumulation of impurities on the surface of the filtration membrane is just compensated by the increase in the water level difference between the upstream and downstream of the filtration membrane caused by the decrease in the water level in the water tank (30).

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