Hollow fiber ultrafiltration high efficiency filter for industrial wastewater reuse

Abstract

The application discloses a hollow fiber ultrafiltration high-efficiency filter for industrial wastewater recycling, which adopts a front high-efficiency activated carbon pretreatment unit to fully exert adsorption function, effectively removes dissolved organic matter, residual chlorine and chroma in industrial wastewater, and an ultrafiltration membrane filtration unit accurately retains residual particulate matter, colloid and microorganisms. After the front activated carbon removes the dissolved organic matter, the filter cake layer formed on the surface of the ultrafiltration membrane is more loose, and the life of the membrane can be prolonged. Meanwhile, the bending end of the membrane wire is movably constrained on the upper part of the membrane shell through an elastic limiting ring, and the open end is downwardly cast and fixed, so that the membrane wire maintains moderate flexibility during the filtration process. On the one hand, the membrane wire is allowed to produce micro-amplitude self-adaptive displacement along with water flow, local dead zones caused by rigid fixation are avoided, water flow distribution in the filtration chamber is more uniform, and the utilization rate of the whole membrane bundle is improved. On the other hand, axial stress of the membrane wire caused by temperature and pressure fluctuation is effectively released, stress concentration at the root of the sealing glue layer is avoided, and the risk of membrane wire breakage is reduced.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, and in particular to a hollow fiber ultrafiltration high-efficiency filter for industrial wastewater reuse. Background Technology

[0002] With the increasingly severe water shortage situation and stricter environmental regulations in my country, advanced treatment and reuse of industrial wastewater has become a key path to alleviate the contradiction between water supply and demand and promote green industrial development. Ultrafiltration (UF) technology, with its high filtration precision (typically retaining molecular weight of 500-600 kcal / kg), is a crucial technology for promoting green industrial development. With advantages such as low operating pressure (0.1~0.3MPa), small footprint, and no phase change, it has been widely used in wastewater reuse treatment in industries such as petrochemical, power, metallurgy, textile printing and dyeing, and food processing.

[0003] In practical engineering applications of ultrafiltration technology, a pretreatment unit is usually required before ultrafiltration to ensure the long-term stable operation of the membrane system and improve the quality of the produced water. Activated carbon adsorption has become one of the most commonly used pretreatment methods for ultrafiltration due to its ability to effectively remove dissolved organic matter, residual chlorine, and color from water. Related studies have shown that activated carbon has a good adsorption and removal effect on dissolved organic matter with a molecular weight of 500-3000. Placing it before ultrafiltration can effectively reduce the organic fouling load on the membrane surface and improve membrane filtration performance.

[0004] The combined use of activated carbon adsorption and ultrafiltration membrane filtration has been widely applied in industrial wastewater treatment and drinking water purification. Existing literature has systematically studied the placement of activated carbon in combined processes: In the "activated carbon + ultrafiltration" scheme, activated carbon acts as a pretreatment to remove some organic matter, allowing the ultrafiltration system to operate stably with almost no need for chlorination of the feed water, extending the filtration cycle to 40 minutes, and moderately increasing membrane flux; in the "activated carbon + ultrafiltration" scheme, activated carbon is placed after ultrafiltration as a post-treatment, mainly serving as a security filter and improving the taste of the effluent. Other studies on the integrated powdered activated carbon-ultrafiltration process indicate that after adding powdered activated carbon, the filter cake layer formed on the membrane surface contains a large amount of powdered activated carbon, making the filter cake layer relatively loose. Organic matter adhering to the filter cake layer is easily washed away during backwashing. Simultaneously, the larger gaps in the skeletal structure formed by the powdered activated carbon on the membrane surface maintain good permeability, thereby delaying membrane fouling.

[0005] The above studies indicate that placing activated carbon before ultrafiltration as a pretreatment has a positive effect on reducing the fouling load of the ultrafiltration membrane and extending the filtration cycle. However, existing activated carbon-ultrafiltration combined processes still have significant shortcomings in the following aspects: (1) Although the integrated powdered activated carbon-ultrafiltration process can form a loose filter cake layer on the membrane surface to delay fouling, the direct addition of powdered activated carbon to the membrane tank poses a risk of abrasion to the membrane surface by the carbon powder, and the powdered activated carbon is discharged with the backwash water, resulting in waste of reagents. Although granular activated carbon fixed bed as a pretreatment can avoid the above problems, its effluent quality is greatly affected by fluctuations in the influent water quality. When the concentration of organic matter in the influent fluctuates, the change in the adsorption efficiency of activated carbon directly affects the operating conditions of the subsequent ultrafiltration membrane.

[0006] (2) The main function of activated carbon pretreatment is to make the pollutants entering the ultrafiltration membrane exist in a more easily peelable form (such as forming a loose filter cake layer). However, the existing hollow fiber ultrafiltration membrane modules are still conventional straight-through designs in terms of structure, with fixed arrangement of membrane fibers and a single flow channel form. They have failed to match and optimize the flow channel structure according to the water quality characteristics after pre-activated carbon treatment (such as the looseness of the filter cake layer, the particle size distribution of pollutants, etc.).

[0007] To improve the fluid flow state inside membrane modules and reduce concentration polarization, existing technologies have attempted to incorporate turbulence promoters between membrane fibers. For example, Chinese Patent CN102389712A discloses an external pressure hollow fiber ultrafiltration membrane module with a turbulence promoter structure. This module enhances fluid flow inside the membrane module by incorporating turbulence promoters interlaced between the membrane fibers within a pressure-bearing outer shell. This technology passively disturbs the water flow through fixed turbulence promoters, thereby improving the hydraulic conditions at the membrane surface to some extent.

[0008] Regarding membrane fiber arrangement, to overcome the stress concentration problem caused by fixing both ends of straight-through membrane fibers, existing technologies have proposed a U-shaped membrane fiber arrangement scheme. For example, Chinese Patent Publication No. CN103566765B discloses a hollow fiber membrane filter element in which the membrane fibers are wound into a U-shape and fixed by a hollow three-dimensional sealing layer. CN116983830A further discloses a U-shaped hollow fiber ultrafiltration membrane element, which uses brush lines between the membrane fibers to clean the membrane surface through physical contact.

[0009] However, the aforementioned structural improvements are all optimizations made at the level of a single membrane module, without considering the changes in the morphology of pollutants on the membrane surface caused by pre-activated carbon pretreatment, and the new requirements that this change places on the flow channel design and cleaning methods of the membrane module. For example, the more porous nature of the filter cake layer on the membrane surface after activated carbon pretreatment is theoretically beneficial for the gas-water mixture to peel off the filter cake layer, but the flow channel design of existing membrane modules cannot fully utilize this difference in characteristics. Summary of the Invention

[0010] The technical problem solved by this invention is to provide a hollow fiber ultrafiltration high-efficiency filter for industrial wastewater reuse.

[0011] This application provides a hollow fiber ultrafiltration high-efficiency filter for industrial wastewater reuse, including a pre-treatment unit of high-efficiency activated carbon and an ultrafiltration membrane filtration unit disposed downstream thereof. The pre-treatment unit for high-efficiency activated carbon includes an adsorption tank, a high-efficiency activated carbon filter media layer filled in the adsorption tank, a water inlet distributor located at the top of the adsorption tank, and a water outlet collector located at the bottom of the adsorption tank. The bottom outlet of the adsorption tank is connected to the inlet of the ultrafiltration membrane filtration unit via an intermediate buffer tank and a booster pump. The ultrafiltration membrane filtration unit includes a membrane shell, a hollow fiber ultrafiltration membrane bundle filled within the membrane shell, and a sealing layer at the lower end. The membrane shell has an inlet on its lower side wall, a concentrate outlet at the top, and a product water collection port on its side. The hollow fiber ultrafiltration membrane bundle is composed of multiple hollow fiber membrane filaments arranged in a U-shape with the bent ends facing upwards and movably constrained to the upper part of the membrane shell by elastic limiting rings. The open ends face downwards and are fixed by casting the sealing layer. A filtration chamber is formed inside the membrane shell between the limiting rings and the sealing layer, and a product water chamber is formed below the sealing layer. The product water collection port is located in the product water chamber, and the inlet connects to the filtration chamber.

[0012] Furthermore, an eccentric counterweight is attached to the top of each fiber membrane filament. The eccentric counterweight is positioned on one side of the central axis of the bent end of the fiber membrane filament, causing the fiber membrane filament to generate a pendulum-like radial swing driven by eccentric torque under the impact of air and water. The initial skew direction of each fiber membrane filament is differentially distributed in the circumferential direction.

[0013] Furthermore, the eccentric counterweight is a stainless steel bead or a ceramic bead, which is bonded to the fiber membrane filament with epoxy resin. The eccentric counterweights of adjacent fiber membrane filaments are rotated sequentially in the circumferential direction of bonding by 15° to 45°, so that the initial skew direction of each fiber membrane filament is evenly distributed within a 360° range. The elastic limiting ring is a rubber O-ring, which is fixed in the hollow hole of the upper floating support plate. The outer edge of the upper floating support plate is embedded in the guide groove fixed in the inner wall of the membrane shell.

[0014] Furthermore, the ultrafiltration membrane filtration unit also includes an air-water mixing backwashing mechanism. The air-water mixing backwashing mechanism includes a compressed air pipeline and a cleaning water pipeline connected to the bottom side wall of the membrane housing, as well as an air-water distribution plate disposed at the bottom of the membrane housing. The compressed air pipeline and the cleaning water pipeline are respectively connected to the air-water distribution plate. The surface of the air-water distribution plate is provided with a central main nozzle and peripheral vector secondary nozzles. The spray direction of the peripheral vector secondary nozzles is the same as the instantaneous tangential velocity direction when the fiber membrane filament swings to its maximum amplitude, so that the sprayed air-water fluid generates Coanda effect adhesion on the surface of the swinging fiber membrane filament, forming a positive feedback self-excited oscillating flow field that drives the fiber membrane filament amplitude to increase.

[0015] Furthermore, the nozzle axis of the peripheral vector auxiliary nozzle forms an angle of 30°-45° with the horizontal plane, and the projection direction of the nozzle axis on the horizontal plane forms an angle of 15°-20° with the radial tangent of the disk surface. The outlet of the peripheral vector auxiliary nozzle is provided with a trumpet-shaped diffuser section. The air-water distribution disk is provided with an annular mixing chamber. The compressed air from the compressed air pipeline and the cleaning water from the cleaning water pipeline are pre-mixed in the annular mixing chamber and then sprayed out through the central main nozzle and the peripheral vector auxiliary nozzle.

[0016] Furthermore, the water inlet distributor includes a central main pipe and radial branch pipes connected to the central main pipe, with multiple water distribution holes at the bottom of the branch pipes; the water outlet collector is a multi-filter head water collection plate structure; and a quartz sand support layer is provided between the high-efficiency activated carbon filter media layer and the water outlet collector.

[0017] Furthermore, the ultrafiltration membrane filtration unit also includes an online cleaning control system, which includes a transmembrane differential pressure sensor, an ultrasonic Doppler flow meter located in the upper part of the membrane housing, and an editable controller. The ultrasonic Doppler flow meter is used to monitor the instantaneous flow velocity of the fluid in the membrane bundle region in real time. The editable controller calculates the turbulence intensity attenuation rate based on the instantaneous flow velocity and automatically executes conventional water backwashing, combined air-water backwashing, and chemically enhanced backwashing programs based on the comparison result of the attenuation rate and a preset threshold.

[0018] Furthermore, the triggering condition for conventional water backwashing is that the transmembrane pressure difference exceeds a set value and the attenuation rate is greater than or equal to a preset threshold. The backwash water enters the inner cavity of the fiber membrane filament through the air-water mixed backwashing mechanism and permeates from the inside to the outside. The triggering condition for air-water combined backwashing is that the attenuation rate is less than the preset threshold and the duration exceeds the first delay. Compressed air and cleaning water are mixed through the air-water distribution plate and then rotate and rise. The triggering condition for chemically enhanced backwashing is that the recovery value of the attenuation rate after air-water combined backwashing is still less than 80% of the preset threshold. Sodium hypochlorite or citric acid solution is added to the cleaning water.

[0019] Furthermore, in the conventional backwashing, the backwash water flow rate is 1.0-1.5 times the filtration flow rate, and the backwashing time is 30-90 seconds; in the combined air-water backwashing, the compressed air pressure is 0.04-0.08 MPa, the backwash water flow rate is 0.8-1.2 times the filtration flow rate, and the backwashing time is 60-120 seconds; in the chemically enhanced backwashing, the sodium hypochlorite dosage is 100-200 ppm or the citric acid solution concentration is 1%-3%, and the soaking time is 10-20 minutes.

[0020] Furthermore, when the cumulative operating time of the adsorption tank reaches a set value or the inlet and outlet pressure difference exceeds a set value, the programmable controller starts the activated carbon backwashing program. The backwash water washes the activated carbon layer from bottom to top, and the backwash wastewater is discharged from the top drain outlet.

[0021] Compared with existing technologies, this invention utilizes a pre-treatment unit with high-efficiency activated carbon to fully leverage its adsorption function, effectively removing dissolved organic matter, residual chlorine, and color from industrial wastewater. The ultrafiltration membrane unit precisely traps residual particulate matter, colloids, and microorganisms. Furthermore, after the pre-activated carbon removes dissolved organic matter, the filter cake layer formed on the ultrafiltration membrane surface is more porous, extending the membrane's lifespan. Simultaneously, the bent ends of the membrane fibers are dynamically constrained to the upper part of the membrane shell by elastic limiting rings, with the open ends cast downwards for fixation, ensuring the membrane fibers maintain appropriate flexibility during filtration. This structure allows the membrane fibers to undergo slight adaptive displacement with the water flow, avoiding the formation of local dead zones caused by rigid fixation, resulting in a more uniform water flow distribution within the filtration chamber and improving the overall utilization rate of the membrane bundle. On the other hand, it effectively releases the axial stress generated by temperature and pressure fluctuations in the membrane fibers, preventing stress concentration at the root of the sealing layer and reducing the risk of membrane fiber breakage. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention.

[0023] Figure 1 This is a schematic diagram of the hollow fiber ultrafiltration high-efficiency filter for industrial wastewater reuse according to the present invention. Figure 2 This is a cross-sectional view of the branch pipe of the present invention; Figure 3 This is a top view of the water outlet collector of the present invention; Figure 4 This is a top view of the upper floating support plate of the present invention; Figure 5 This is a top view of the perforated hole in the present invention; Figure 6 This is a partial structural schematic diagram of the fiber membrane filament of the present invention; Figure 7 This is a cross-sectional view of the fiber membrane filament of the present invention; Figure 8 This is a cross-sectional view of the air-water distribution plate of the present invention; Figure 9 This is a structural block diagram of the online cleaning control system of the present invention.

[0024] The reference numerals in the attached figures include: 1. Pre-treatment unit with high-efficiency activated carbon; 101. Adsorption tank; 102. High-efficiency activated carbon filter media layer; 103. Water inlet distributor; 1031. Central main pipe; 1032. Branch pipe; 1033. Water distribution hole; 104. Water outlet collector; 105. Quartz sand support layer; 106. Inlet pipe; 107. Outlet pipe; 108. Backwash drain pipe; 109. Activated carbon backwash inlet pipe; 2. Ultrafiltration membrane filtration unit; 201. Membrane shell; 202. Fiber membrane filaments; 203. Sealing layer; 204. Liquid inlet; 205. Guide chute; 206. Concentrate discharge port; 207. Product water collection port; 208. Upper floating support plate; 209. 210. Elastic limiting ring; 211. Filter chamber; 212. Product water chamber; 213. Eccentric counterweight; 214. Air-water mixing backwash mechanism; 215. Compressed air pipeline; 216. Cleaning water pipeline; 217. Air-water distribution plate; 218. Central main nozzle; 219. Peripheral vector secondary nozzle; 200. Annular mixing chamber; 2010. Online cleaning control system; 2110. Transmembrane differential pressure sensor; 212. Ultrasonic Doppler flow meter; 213. Programmable controller; 2144. Variable frequency backwash water pump; 215. Pneumatic regulating valve; 216. Metering dosing pump; 217. Hollow hole; 218. Intermediate buffer water tank; 219. Lift pump. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0026] like Figure 1 , Figures 4 to 7 As shown, the hollow fiber ultrafiltration high-efficiency filter for industrial wastewater reuse of the present invention includes a pre-treatment unit 1 with high-efficiency activated carbon and an ultrafiltration membrane filtration unit 2 disposed downstream therefrom. The pre-treatment unit 1 for high-efficiency activated carbon includes an adsorption tank 101, a high-efficiency activated carbon filter media layer 102 filled in the adsorption tank 101, an inlet water distributor 103 disposed at the upper part of the adsorption tank 101, and an outlet water collector 104 disposed at the lower part of the adsorption tank 101. The bottom outlet of the adsorption tank 101 is connected to the inlet 204 of the ultrafiltration membrane filtration unit 2 via an intermediate buffer water tank 3 and a booster pump 4. The ultrafiltration membrane filtration unit 2 includes a membrane housing 201, a hollow fiber ultrafiltration membrane bundle filled in the membrane housing 201, and a sealing layer 203 at the lower end. The membrane housing 201 has an inlet 204 on the lower side wall, a concentrate outlet 206 on the top, and a product water collection port 207 on the side. The hollow fiber ultrafiltration membrane bundle is composed of multiple hollow fiber membrane filaments 202. The fiber membrane filaments 202 are arranged in a U-shape with their bent ends facing upwards and are movably constrained to the upper part of the membrane housing 201 by an elastic limiting ring 209. The open ends face downwards and are fixed by casting the sealing layer 203. A filtration chamber 210 is formed inside the membrane housing 201 between the limiting ring and the sealing layer 203. A product water chamber 211 is formed below the sealing layer 203. The product water collection port 207 is located in the product water chamber 211, and the inlet 204 is connected to the filtration chamber 210.

[0027] This invention employs a pre-treatment unit 1 with high-efficiency activated carbon to fully utilize its adsorption function, effectively removing dissolved organic matter (COD removal rate increased by 15%~25%), residual chlorine (removal rate >95%), and color (removal rate >80%) from industrial wastewater. The ultrafiltration membrane unit 2 precisely traps residual particulate matter, colloids, and microorganisms. Together, they form an "adsorption-sieving" gradient treatment chain, resulting in a stable turbidity of the treated water below 0.2 NTU, meeting the industrial circulating cooling water makeup water standard (GB / T 50050-2017). Furthermore, after the pre-activated carbon removes dissolved organic matter, the filter cake layer formed on the ultrafiltration membrane surface is more porous, reducing the rate of increase in transmembrane pressure difference by 40%~60%, extending the system's continuous operation cycle by 2~3 times, and thus prolonging the membrane's lifespan. Simultaneously, the bent ends of the membrane fibers are movably constrained to the upper part of the membrane shell 201 by elastic limiting rings 209, with the open ends cast downwards for fixation, ensuring the membrane fibers maintain appropriate flexibility during filtration. This structure allows the membrane fibers to undergo slight adaptive displacement with the water flow, avoiding the formation of local dead zones caused by rigid fixation, resulting in a more uniform water flow distribution within the filtration chamber 210 and improving the utilization rate of the entire membrane bundle. On the other hand, it effectively releases the axial stress generated by temperature and pressure fluctuations in the membrane fibers, preventing stress concentration at the root of the sealant layer 203 and reducing the risk of membrane fiber breakage. Furthermore, the series integration of the pre-treatment unit 1 (high-efficiency activated carbon) and the ultrafiltration membrane filtration unit 2, along with the connection of the intermediate buffer tank 3 and the booster pump 4, achieves a smooth hydraulic transition between the two units. The intermediate buffer tank 3 effectively buffers fluctuations in the effluent flow rate of the activated carbon unit, providing stable and continuous influent conditions for the ultrafiltration membrane filtration unit 2 and preventing unstable membrane filtration conditions caused by fluctuations in influent flow rate.

[0028] Specifically, the adsorption tank 101 is a stainless steel vertical cylindrical pressure vessel, welded to the upper end and the lower end to the lower end. A high-efficiency activated carbon filter media layer 102 is filled in the middle of the adsorption tank 101, using coal-based crushed carbon or coconut shell granular carbon with a particle size of 0.8~1.2mm, an iodine value ≥900mg / g, and a specific surface area ≥1000m² / g. A 300mm high backwash expansion space is reserved above the activated carbon layer. The effluent collector 104 is installed inside the adsorption tank 101, 300mm above the lower end. It is a multi-filter head water collection plate structure with a hollow structure and an opening at the bottom communicating with the bottom end, thus connecting to the bottom outlet. The water collector is a disc-shaped multi-filter head water collection plate (with a 10mm gap between it and the inner wall of the tank). 36 ABS long-handled filter heads are evenly installed on the plate in a concentric circle pattern. The intermediate buffer tank 3 is a vertical square tank made of PE material, equipped with a hydrostatic level gauge to monitor the water level and control the start and stop of the booster pump 4. The booster pump 4 is a horizontal centrifugal pump, with a Y-type filter (1.0mm mesh size) installed before the pump to prevent activated carbon fragments from entering the membrane system.

[0029] The membrane housing 201 is a vertical cylindrical pressure vessel made of 304 stainless steel. Its upper end is welded to the top end cap, with a concentrated water discharge port 206 located at the center of the top end cap. Its lower end is welded to the bottom end cap, with a liquid inlet 204 located at the center of the bottom end cap, and an air inlet on the side wall of the bottom end cap. The hollow fiber ultrafiltration membrane bundle consists of 1800 hollow fiber membrane filaments 202. Each filament has a composite structure with the outer skin layer on the outside. The outer surface is a polyvinylidene fluoride (PVDF) separation layer with a thickness of 40 μm; the inner wall is a polyester fiber braided tube support layer with a thickness of 250 μm.

[0030] The sealing layer 203 is formed by epoxy resin casting. The casting process is as follows: First, the open ends of the membrane filaments are evenly arranged concentrically in a positioning plate at the bottom of the membrane shell 201. The positioning plate has positioning holes corresponding to the number of membrane filaments. The open ends of the membrane filaments pass through the positioning holes and extend approximately 30mm below the positioning plate. This ensures a precise circumferential distribution of the membrane filament open ends before casting. Then, liquid epoxy resin is injected through the injection port at the bottom end of the membrane shell 201. The epoxy resin fills the predetermined height space of the membrane shell 201 from bottom to top, completely covering the outer wall of the membrane filament open ends. After the epoxy resin cures, the positioning plate is removed (the positioning plate is detachable; a release agent is applied to the upper surface of the positioning plate before the epoxy resin cures, and the positioning plate can be separated from the epoxy resin after curing), thus forming the sealing layer 203.

[0031] The outer edge of the sealant layer 203 is sealed to the inner wall of the membrane housing 201 through chemical bonding of epoxy resin to the stainless steel wall. To ensure reliable sealing, an annular groove is provided on the bottom inner wall of the membrane housing 201 within the corresponding height range of the sealant layer 203. After the epoxy resin cures, it is embedded in the groove to form a mechanical interlock, further enhancing the sealing effect. This sealing structure ensures complete isolation between the filter chamber 210 above the sealant layer 203 and the product water chamber 211 below, preventing raw water from leaking from the interface between the sealant layer 203 and the wall of the membrane housing 201 into the product water chamber 211.

[0032] In some embodiments, such as Figure 6 As shown, each fiber membrane filament 202 has an eccentric counterweight 212 bonded to its top. The eccentric counterweight 212 is positioned on one side of the central axis of the bent end of the fiber membrane filament 202, causing the fiber membrane filament 202 to generate a pendulum-like radial swing driven by eccentric torque under air-water impact. The initial deflection direction of each fiber membrane filament 202 is differentially distributed in the circumferential direction. The eccentric counterweight 212 is a stainless steel bead or a ceramic bead, bonded to the fiber membrane filament 202 with epoxy resin. The bonding direction of the eccentric counterweight 212 of adjacent fiber membrane filaments 202 in the circumferential direction is rotated sequentially by 15°~45°, so that the initial deflection direction of each fiber membrane filament 202 is evenly distributed within a 360° range. The elastic limiting ring 209 is a rubber O-ring, fixed in the hollow hole 215 of the upper floating support plate 208. The outer edge of the upper floating support plate 208 is embedded in the guide groove 205 fixed in the inner wall of the membrane shell 201.

[0033] In this embodiment, an eccentric counterweight 212 is bonded to one side of the bent end of each membrane fiber, causing the center of gravity of the membrane fiber to deviate from the geometric center line. Under the impact of air and water, the fluid drag force on each membrane fiber does not pass through the geometric center of the membrane fiber, generating an eccentric torsion. This torque drives the membrane fiber to generate pendulum-like radial oscillations around the elastic limiting ring 209 with different phases and directions. The bonding direction of the eccentric counterweights 212 of adjacent membrane fibers is rotated sequentially by 15°~45°, so that the initial skew direction of each membrane fiber is evenly distributed within a 360° range, avoiding collisions and entanglements caused by all membrane fibers oscillating synchronously in the same direction. This structure generates continuous and uniform micro-disturbances in the water flow within the filtration chamber 210, disrupting the concentration polarization boundary layer on the membrane surface and promoting the diffusion of solutes into the main water flow, thereby effectively delaying the membrane fouling process. Meanwhile, the rubber O-rings and membrane fibers are threaded through the O-rings, allowing the membrane fibers to flexibly oscillate under air and water impact. The sliding design of the floating support plate effectively absorbs the axial expansion and contraction stress of the membrane fibers caused by temperature and pressure fluctuations, preventing stress concentration at the root of the sealant layer 203 and thus preventing membrane fiber breakage. This flexible constraint structure allows each membrane fiber to maintain a moderate degree of freedom of movement during filtration. On the one hand, it makes the water flow distribution in the filtration chamber 210 more uniform, avoids the formation of local dead zones, and improves the utilization rate of the entire membrane bundle; on the other hand, it releases the axial stress of the membrane fibers, significantly reducing the membrane fiber breakage rate and extending the overall service life of the membrane module.

[0034] Specifically, the elastic limiting ring 209 is an EPDM rubber O-ring, fixedly embedded in the honeycomb-shaped hollow hole 215 of the upper floating support plate 208 (interference fit). The support plate is a PE material disc-shaped plate with six rectangular notches on its outer edge, which are embedded in the guide groove 205 on the inner wall of the membrane housing 201, so that the support plate can only slide up and down along the axis of the membrane housing 201 (axial travel ±10mm) and cannot rotate. The bent end of the membrane fiber is clearance-fitted with the inner hole of the O-ring, allowing the membrane fiber to swing freely within the O-ring, with an swing angle range of approximately ±20°. The guide groove 205 is a stainless steel protrusion, and the longitudinal axis of the protrusion is parallel to the axis of the membrane housing 201. The six grooves are arranged at 60° intervals on the circumference, and the upper and lower ends of the groove are closed—the upper end is limited by the top end cap, and the lower end is limited by the limiting block (a boss or baffle welded to the inner wall of the membrane housing 201) at the end of the groove. The arrangement of the perforated holes 215 is a concentric circle arrangement: 1 hole in the center, 6 holes in the first ring, 12 holes in the second ring, and 18 holes in the third ring, for a total of 37 holes (this is an example; in practice, it will be adjusted according to the total number of membrane filaments of 1800, using a multi-layer concentric circle arrangement with a hole spacing of 10mm. The number of holes will be determined during module encapsulation based on the actual number of membrane filaments).

[0035] Specifically, the eccentric counterweight 212 is bonded using a specially formulated water-resistant epoxy resin adhesive (model: Loctite E-20HP or equivalent). This adhesive, after curing, exhibits excellent water and chemical resistance (withstanding solutions with a pH range of 2-12 and cleaning solutions with sodium hypochlorite concentrations ≤200ppm). Under long-term immersion conditions, the bond shear strength retention rate is ≥90% (after immersion in 60℃ water for 30 days). Before bonding, the surface of the membrane fiber bending end is roughened by sanding (lightly sanding with 400-grit sandpaper to increase surface roughness) and cleaned and degreased with anhydrous ethanol to ensure bonding strength. Tests have verified that the bonded counterweight does not detach under a 2N tensile force, far exceeding the centrifugal force (approximately 0.05N) experienced by the counterweight during membrane fiber oscillation.

[0036] To prevent the counterweight from falling off and causing safety hazards in extreme situations, a stainless steel filter screen is installed above the liquid inlet 204 at the bottom of the membrane housing 201 (below the air-water distribution plate 2133). More preferably, an annular sedimentation zone (an annular groove located around the liquid inlet 204) can be provided at the bottom of the membrane housing 201. Any detached counterweight will fall into this sedimentation zone under gravity, preventing it from entering the circulation pipeline with the water flow or damaging the membrane fibers. This sedimentation zone is cleaned through the bottom discharge port during system shutdown and maintenance.

[0037] In some embodiments, such as Figure 1 , Figure 8As shown, the ultrafiltration membrane filtration unit 2 also includes an air-water mixing backwashing mechanism 213. The air-water mixing backwashing mechanism 213 includes a compressed air pipeline 2131 and a cleaning water pipeline 2132 connected to the bottom side wall of the membrane housing 201, and an air-water distribution plate 2133 disposed at the bottom of the membrane housing 201. The compressed air pipeline 2131 and the cleaning water pipeline 2132 are respectively connected to the air-water distribution plate 2133. The surface of the air-water distribution plate 2133 is provided with a central main nozzle 2134 and peripheral vector secondary nozzles 2135. The spray direction of the peripheral vector secondary nozzles 2135 is the same as the instantaneous tangential velocity direction when the fiber membrane filament 202 swings to its maximum amplitude, so that the sprayed air-water fluid is mixed with the fiber membrane filament during the swing. The surface of the fiber membrane 202 generates a Coanda effect, forming a positive feedback self-excited oscillating flow field that drives the amplitude of the fiber membrane 202 to increase. The nozzle axis of the peripheral vector auxiliary nozzle 2135 is at an angle of 30°-45° to the horizontal plane, and the projection direction of the nozzle axis on the horizontal plane is at an angle of 15°-20° to the radial tangent of the disk surface. The outlet of the peripheral vector auxiliary nozzle 2135 is provided with a trumpet-shaped diffuser section. The air-water distribution disk 2133 is provided with an annular mixing chamber 2136. The compressed air from the compressed air pipeline 2131 and the cleaning water from the cleaning water pipeline 2132 are pre-mixed in the annular mixing chamber 2136 and then sprayed out through the central main nozzle 2134 and the peripheral vector auxiliary nozzle 2135.

[0038] In this embodiment, compressed air (pressure 0.05-0.08 MPa) and backwash water (flow rate 1.0-1.2 times the filtration flow rate) enter the annular mixing chamber 2136 from the bottom tube seat for premixing, forming a gas-water two-phase flow. The central main nozzle 2134 sprays a vertically rising columnar gas-water mixture, driving the membrane filaments in the central region of the membrane bundle to float up and down and oscillate slightly. The peripheral vector secondary nozzles 2135 spray a fan-shaped flat jet that matches the tangential velocity direction of the membrane filament oscillation. When the membrane filaments are driven to swing to one side by the eccentric torque generated by the eccentric counterweight, the jet from the corresponding secondary nozzle on that side impacts the surface of the membrane filaments. According to the Coanda effect (wall adhesion effect), when the high-speed jet (outlet velocity about 5-10 m / s) flows along the curved surface of the membrane filaments, it generates wall adhesion, forming a low-pressure zone (pressure difference about 50-200 Pa) on the back surface of the membrane filaments, generating an adsorption force in the direction of the jet. This adsorption force further pulls the membrane filaments to accelerate and swing in the same direction. This positive feedback self-excitation can continuously increase the oscillation amplitude of the membrane fibers, significantly enhance the turbulence intensity of the fluid near the membrane fibers, effectively destroy the concentration polarization layer and gel layer on the membrane surface, promote membrane renewal, and achieve in-situ inhibition of pollutant deposition during the filtration stage, further delaying the rise of transmembrane pressure difference; the axis of the peripheral vector sub-nozzle 2135 is at an angle of 30°~45° with the horizontal plane, and the horizontal projection is at an angle of 15°~20° with the radial tangent, so that the jet fluid impacts the membrane fiber surface at the optimal angle, avoiding membrane fiber damage caused by vertical impact and scouring dead zone caused by horizontal impact.

[0039] The air-water distribution plate 2133 is a flat, round, hollow shell made of 316L stainless steel. It is fixed (threaded) to the bottom of the sealing layer 203 by a support bracket. The plate contains an annular mixing chamber 2136. At the bottom center are a compressed air inlet pipe seat and a cleaning water inlet pipe seat. The two pipe seats penetrate vertically from the bottom of the plate, with their openings extending into the annular mixing chamber 2136 and facing its sidewall. This allows the incoming air and water to swirl and mix within the chamber, preventing uneven spraying caused by direct impact to the upper baffle. The upper end of the compressed air inlet pipe seat is connected to the air inlet through the annular space at the bottom of the membrane shell 201. Compressed air entering through the air inlet passes through the space at the bottom of the membrane shell 201 into the compressed air inlet pipe seat and then into the annular mixing chamber 2136. The upper end of the cleaning water inlet pipe seat is connected to the liquid inlet 204 through a sealed pipe. Backwash water entering through the liquid inlet 204 passes through the sealed pipe into the cleaning water inlet pipe seat and then into the annular mixing chamber 2136. The connection between the compressed air inlet pipe seat and the cleaning water inlet pipe seat and the lower partition is sealed by welding to ensure that the air-water mixture in the mixing chamber will not leak from the root of the pipe seat to the bottom space of the membrane housing 201.

[0040] There are 16 peripheral vector sub-nozzles (2135 in total), evenly arranged along the circumference (adjacent angle 22.5°). Each sub-nozzle has a stepped orifice structure, divided into three sections from bottom to top. The diameter of the middle section is similar to that of the lower section, and the upper section is a 12° trumpet-shaped diffuser section, forming a Venturi acceleration effect. This allows the gas-water mixture to uniformly cover the membrane fiber surface in a fan-shaped flat jet, avoiding excessive or insufficient scouring in certain areas. This ensures that both the outer and central regions of the membrane bundle receive effective hydraulic shearing, improving the overall utilization rate of the membrane bundle.

[0041] In this embodiment, the angle between the projection of the peripheral vector secondary nozzle 2135 onto the horizontal plane and the radial tangent of the disk surface is 18°. Taking the center of the disk surface as the origin, assuming that a certain secondary nozzle is located in the positive X-axis direction (i.e., the radial direction is along the X-axis), then the angle between the projection of the jet direction of this secondary nozzle onto the horizontal plane and the Y-axis (tangential direction) is 18°, that is, the jet direction is biased towards the tangential direction and along the counterclockwise direction (generating a rotating upward flow field).

[0042] The principle for determining the vector direction of the secondary nozzle is as follows: This direction is not arbitrarily set, but is determined based on the instantaneous tangential velocity direction of the membrane fiber when it swings to its maximum amplitude under air-water impact. Specifically, a mark is made at the midpoint of the membrane fiber length (800mm from the bend end), and a high-speed camera is used to capture the oscillation trajectory of the membrane fiber under air-water impact. The instantaneous velocity vector direction when the membrane fiber swings to its maximum amplitude is then analyzed. The jet direction of the secondary nozzle is set to be in the same direction and coplanar with this instantaneous velocity direction (i.e., the jet follows the oscillating membrane fiber).

[0043] In some embodiments, such as Figures 1 to 3As shown, the water inlet distributor 103 includes a central main pipe 1031 and radial branch pipes 1032 connected to the central main pipe 1031. Multiple water distribution holes 1033 are opened at the bottom of the branch pipes 1032. The water outlet collector 104 is a multi-filter head water collection plate structure. A quartz sand support layer 105 is provided between the high-efficiency activated carbon filter media layer 102 and the water outlet collector 104.

[0044] In this embodiment, the water inlet distributor 103 adopts a structure of a central main pipe 1031 and radial branch pipes 1032. Multiple water distribution holes 1033 are opened at the bottom of the branch pipes 1032, ensuring that the incoming water is evenly distributed across the entire cross-section of the activated carbon layer. This effectively avoids the short-flow and flow deviation phenomena caused by conventional single-point water inlet, ensuring uniform adsorption across the entire activated carbon filter layer without dead zones, and maximizing the utilization efficiency of the activated carbon. The water outlet collector 104 adopts a multi-filter head water collection plate structure, with multiple water collection points and uniform water distribution, ensuring that the treated water is collected evenly and avoiding insufficient adsorption due to excessively fast local water flow or excessive pressure drop due to excessively slow local water flow. The quartz sand support layer 105 is located between the activated carbon filter media layer and the outlet water collector 104. Its particle size (2-4mm) is larger than that of activated carbon particles (0.8-1.2mm), effectively trapping fine activated carbon particles and preventing them from entering the outlet pipe through the gaps in the filter head, causing activated carbon loss and subsequent pipe blockage. At the same time, the support layer plays a role in redistributing the rising water flow evenly, so that the water flow entering the water collector has a consistent flow velocity across the entire cross section, avoiding local overload of the water collector and resulting in fluctuations in the outlet water quality.

[0045] Specifically, the central main pipe 1031 is installed vertically, with its upper end passing through the upper end cap and connecting to the inlet flange. The branch pipes 1032 are arranged horizontally, radiating evenly along the bottom of the main pipe. Each branch pipe 1032 has five water distribution holes 1033 at its bottom, totaling 40 water distribution holes 1033. All water distribution holes 1033 face downwards to ensure that the incoming water is evenly sprayed onto the surface of the activated carbon layer, preventing water flow from impacting and eroding the carbon layer.

[0046] In some embodiments, such as Figure 1 , Figure 9As shown, the ultrafiltration membrane filtration unit 2 also includes an online cleaning control system 214. The online cleaning control system 214 includes a transmembrane pressure differential sensor 2141, an ultrasonic Doppler flow meter 2142 disposed in the upper part of the membrane housing 201, and a programmable controller 2143. The ultrasonic Doppler flow meter 2142 is used to monitor the instantaneous flow velocity of the fluid in the membrane bundle region in real time. The programmable controller 2143 calculates the turbulence intensity attenuation rate based on the instantaneous flow velocity and automatically executes the conventional water backwash, air-water combined backwash, and chemical enhanced backwash programs based on the comparison result of the attenuation rate and a preset threshold. The trigger condition for conventional water backwash is that the transmembrane pressure differential exceeds the set value and the attenuation rate is greater than or equal to the preset threshold. The backwash water enters the inner cavity of the fiber membrane filament 202 through the air-water mixed backwash mechanism 213 and permeates from the inside to the outside. The air-water combined backwash... The triggering condition for chemically enhanced backwashing is that the attenuation rate is less than the preset threshold and the duration exceeds the first delay. Compressed air and cleaning water are mixed through the air-water distribution plate 2133 and then rotated upward. The triggering condition for chemically enhanced backwashing is that the recovery value of the attenuation rate after air-water combined backwashing is still less than 80% of the preset threshold. Sodium hypochlorite or citric acid solution is added to the cleaning water. In conventional backwashing, the backwash water flow rate is 1.0-1.5 times the filtration flow rate, and the backwashing time is 30-90 seconds. In air-water combined backwashing, the compressed air pressure is 0.04-0.08 MPa, the backwash water flow rate is 0.8-1.2 times the filtration flow rate, and the backwashing time is 60-120 seconds. In chemically enhanced backwashing, the sodium hypochlorite concentration is 100-200 ppm or the citric acid solution concentration is 1%-3%, and the soaking time is 10-20 minutes.

[0047] In this embodiment, the online cleaning control system 214 monitors the instantaneous flow velocity of the fluid in the membrane region in real time using an ultrasonic Doppler velocimeter 2142. The programmable controller calculates the turbulence intensity decay rate based on this velocity, using it as a direct physical fingerprint to determine the membrane fouling state and the activity level of the self-excited oscillating flow field, replacing the traditional indirect method that relies solely on transmembrane pressure difference. The system automatically executes a three-level cleaning procedure based on the comparison between the decay rate and a preset threshold: when the decay rate is normal, only conventional water backwashing is performed, resulting in the lowest energy consumption; when the decay rate decreases and continues to exceed a timeout period, combined air-water backwashing is initiated, and the air-water distribution disk 2133 is activated to initiate self-excited oscillation; when the decay rate recovery is insufficient, chemically enhanced backwashing is performed to achieve complete recovery. This tiered strategy avoids over-cleaning or under-cleaning caused by fixed-cycle cleaning, achieving precise matching of cleaning intensity and fouling degree, and significantly reducing cleaning water and chemical consumption.

[0048] Specifically, the transmembrane differential pressure sensor 2141 is a differential pressure transmitter, mounted on an instrument bracket outside the membrane housing 201, at the same height as the middle of the membrane housing 201. One end of the high-pressure end pressure tap is connected to the high-pressure chamber of the transmitter, and the other end is connected to the pressure tap valve on the inlet pipe 204. One end of the low-pressure end pressure tap is connected to the low-pressure chamber of the transmitter, and the other end is connected to the pressure tap valve on the product water collection port 207 on the side of the membrane housing 201. The pipe is filled with water as the pressure transmission medium. The transmitter outputs a 4-20mA differential pressure signal to the programmable controller. The ultrasonic Doppler velocimeter 2142 has two probes mounted opposite each other on the wall of the membrane housing 201 (located 120mm below the upper floating support plate 208, at 180° to each other) for real-time monitoring of the instantaneous flow velocity of the fluid in the membrane bundle region. The probe mounting base is a cylindrical 304 stainless steel tube with two O-ring grooves on the inner wall, sealed with fluororubber O-rings. The line connecting the two oppositely mounted probes (transmitting probe and receiving probe) passes horizontally through the membrane bundle region. The probes are cylindrical, with the probe end face extending approximately 5mm into the inner cavity of the membrane housing 201, flush with the inner wall of the membrane housing 201.

[0049] The probe signal line is led out of the diaphragm housing 201 through a sealed cable connector and connected to the signal conditioning module for pre-amplification and low-pass filtering (cutoff frequency 200Hz). The filtered signal is then converted from analog to digital and sent to the high-speed counting port of the programmable controller via RS-485 communication.

[0050] The 2142 ultrasonic Doppler current meter uses the time-of-flight measurement principle. The transmitting probe emits a continuous ultrasonic signal at a frequency of 1MHz into the membrane bundle region. As the ultrasonic waves pass through the water flow between the membrane fibers, tiny particles (suspended matter or microbubbles) in the water reflect the signals, and the receiving probe receives these reflected signals. Due to the significant difference in acoustic impedance between the membrane fiber material (PVDF + polyester braided tube) and the water, the ultrasonic waves are strongly reflected at the membrane fiber surface. Therefore, the signal actually received by the receiving probe is the superposition of the reflected signals from the water particles and the reflected signals from the membrane fiber surface. The 2143 programmable controller is a Siemens S7-1200 industrial-grade PLC with built-in digital signal processing algorithms and a turbulence intensity calculation module. The digital signal processing algorithm filters out interference signals generated by low-frequency membrane filament oscillations (oscillation frequency <5Hz) and extracts high-frequency water flow turbulence signals (5~50Hz) through setting a velocity threshold (>0.05m / s) and correlation analysis, thereby obtaining the instantaneous velocity of the water flow in the membrane bundle gaps. The turbulence intensity calculation module calculates the turbulence intensity using a 60-second time window according to the formula... Calculate the turbulence intensity I, where, Let be the instantaneous flow velocity value at the i-th sampling point. The average flow velocity is calculated from 6000 sampling points within a 60-second window (sampling frequency 100Hz × 60 seconds = 6000 data points). The turbulence intensity decay rate is defined. ( (The average turbulence intensity measured 10 seconds after the last combined air-water backwash) (preset threshold) =0.85, first delay =30 seconds, Transmembrane pressure differential setpoint =Initial transmembrane pressure difference + 0.04 MPa (e.g., if initial TMP = 0.05 MPa, then...) =0.09MPa).

[0051] The programmable controller 2143 also has a built-in transmembrane differential pressure signal processing program, which performs the following processing on the 4-20mA signal input from the sensor: Low-pass filtering: a first-order low-pass filtering algorithm (time constant) is used. =5 seconds), filtering out instantaneous pressure spikes caused by pump start-up and shutdown, valve operation, etc. Automatic zero-point calibration: For the first 60 seconds after each system startup or switch back to filtration mode, the program automatically records the average transmembrane pressure difference during this period as the initial transmembrane pressure difference reference value (P0) for the current batch operation. Subsequent transmembrane pressure difference setpoint P1 is calculated based on P0. , (Take 0.04MPa). Outlier removal: When a single sampled value deviates from the previous filtered value by more than ±20%, it is determined to be an abnormal interference signal. The program automatically removes the data point and uses the previous filtered value as the current value to avoid false triggering caused by valve action or bubble impact.

[0052] The online cleaning control system 214 also includes a variable frequency backwash water pump 2144, a pneumatic regulating valve 2145, and a metering dosing pump 2146; Variable frequency backwash water pump 2144: This is a Grundfos CR15 vertical multistage centrifugal pump, installed on a ground base outside the membrane housing 201. The suction pipe connects to the clear water tank or product water tank, and the discharge pipe connects to the cleaning water pipeline 2132 via a check valve and an electric on / off valve. The end of the cleaning water pipeline 2132 connects to the inlet pipe 204 at the bottom of the membrane housing 201 (shared with the filter inlet pipe via a tee). The pump's frequency converter controls the speed via a 4-20mA signal from a PLC. Pneumatic regulating valve 2145: This is an SMC type angle seat valve with an intelligent valve positioner. It is installed on the compressed air line 2131, located between the air compressor outlet and the diaphragm housing 201 inlet. The valve opening is controlled by a 4-20mA signal output from the PLC.

[0053] Metering pump 2146: This is a Prominent CONC1606 diaphragm metering pump, installed between the chemical reagent storage tank and the cleaning water pipeline 2132. The pump's suction pipe is inserted into the sodium hypochlorite or citric acid storage tank, and the discharge pipe is connected to a dosing tee after passing through a dosing check valve. The dosing tee is connected in series on the cleaning water pipeline 2132, located between the pump outlet and the inlet 204 of the diaphragm housing 201. The pump's start / stop and stroke frequency are controlled by a PLC via digital inputs and a 4-20mA signal.

[0054] The programmable controller 2143 automatically executes a three-stage cleaning procedure based on the comparison between the attenuation rate η and the preset threshold η_0: Regular water backwash: The trigger condition is that the transmembrane pressure difference exceeds the set value and η≥η_0. The programmable controller 2143 outputs a signal to start the variable frequency backwash water pump 2144, which operates at a frequency of 40Hz (corresponding to a flow rate of 6m³ / h). The backwash water enters the inner cavity of the fiber membrane filament 202 through the product water collection port 207 and permeates outwards, lasting for 60 seconds. Air-water combined backwash: The trigger condition is that η<η_0 and the duration exceeds 30 seconds. The programmable controller 2143 starts the variable frequency backwash water pump 2144, which operates at a frequency of 45Hz (corresponding to a flow rate of 5m³ / h). Simultaneously, it outputs a 4-20mA signal to open the pneumatic regulating valve 2145 (5f) to 60% opening (corresponding to a pressure of 0.05MPa). Compressed air and cleaning water mix through the air-water distribution plate 2133 and then rotate upwards, lasting for 90 seconds. Chemically enhanced backwash: The trigger condition is that the recovery value of η after the combined air-water backwash is still less than 80% of η_0 (i.e. <0.68). The programmable controller 2143 starts the metering dosing pump 2146 to run at 80% stroke frequency, adds sodium hypochlorite solution to the cleaning water to a concentration of 150ppm, soaks for 15 minutes, and then performs a combined air-water backwash for 120 seconds.

[0055] In some embodiments, when the cumulative operating time of the adsorption tank 101 (e.g., 72 hours) reaches a set value or the inlet and outlet pressure difference exceeds a set value (e.g., 0.05 MPa), the programmable controller starts the activated carbon backwashing program. The backwash water flushes the activated carbon layer from bottom to top. The backwash flow rate is 1.5 to 2.0 times the normal operating flow rate, the backwash time is 8 minutes, and the backwash wastewater is discharged from the top drain.

[0056] In this embodiment, the setting of cumulative running time and the design of automatic backwashing program form a linkage mechanism, enabling the regeneration and recovery of the activated carbon unit and the backwashing control of the membrane filtration unit to be coordinated and managed by the same controller. This ensures that the activated carbon is always in a highly efficient adsorption state, avoiding the exacerbation of membrane fouling caused by organic matter penetration due to activated carbon adsorption saturation. The backwashing direction from bottom to top causes the activated carbon layer to expand, increasing the gaps between particles and allowing adsorbed pollutants to be fully washed away and removed, resulting in high backwashing efficiency and low water consumption. At the same time, the timing of activated carbon backwashing and membrane cleaning can be uniformly scheduled by the controller (e.g., using the permeate from membrane backwashing as the activated carbon backwash water source), realizing the cascade utilization of system water resources and further reducing the total water consumption of the system.

[0057] Specifically, the inlet and outlet pressure difference is measured as follows: pressure transmitters are installed on the inlet pipe 106 and outlet pipe 107 of the adsorption tank 101, respectively. The two pressure signals are sent to the programmable controller 2143, which calculates the pressure difference value. The 72-hour cumulative operating time is set based on the adsorption breakthrough curve of activated carbon for the target pollutant (in this embodiment, chemical wastewater with COD of 150~200 mg / L is treated, the empty bed contact time EBCT = 20 min, and the effective adsorption capacity of activated carbon is approximately 0.15 g COD / g activated carbon; based on this, the theoretical breakthrough time is approximately 72 hours). In actual operation, the backwash cycle can also be dynamically adjusted according to the online monitoring value of the effluent COD: when the COD of the activated carbon effluent exceeds 80 mg / L (i.e., the removal rate is less than 50%) and the inlet and outlet pressure difference does not exceed the standard, the programmable controller 2143 automatically shortens the backwash cycle (e.g., adjusts it to 48 hours).

[0058] The criteria for determining when to replace activated carbon are as follows: when the pressure difference between the inlet and outlet after backwashing is less than 70% of the initial pressure difference, or when the COD removal rate of the effluent after backwashing is still less than 30%, or when the iodine value drops to less than 60% of the initial value, the activated carbon is considered to have reached adsorption saturation and needs to be replaced with new carbon. These indicators are manually sampled and tested periodically (testing cycle 1 month), and the test results are input into the programmable controller 2143 as the basis for replacement reminders.

[0059] Specifically, each interface of the membrane housing 201 is connected to a corresponding pipe, and each pipe is equipped with a control valve to achieve switching operations for different working conditions such as filtration, backwashing, and venting.

[0060] Inlet 204 pipe: Inlet 204 connects to a tee pipe. The first port of the tee is connected to the outlet pipe of the booster pump 4 via an inlet valve, used to introduce activated carbon pre-treated effluent during filtration. The second port of the tee is connected to the wastewater discharge pipe via a backwash drain valve, used to discharge backwash wastewater carrying contaminants during backwashing. The third port of the tee is directly connected to the inlet 204 of the membrane housing 201. Both the inlet valve and the backwash drain valve are electric butterfly valves, controlled by a switch signal output from the programmable controller 2143 to switch between filtration and backwash drain modes.

[0061] Air inlet pipe: The air inlet is connected to the compressed air pipeline 2131 via a pneumatic regulating valve 2145. The pneumatic regulating valve 2145 is controlled by a 4-20mA signal output by a programmable controller 2143 to introduce compressed air into the membrane housing 201 during combined air-water backwashing and chemically enhanced backwashing.

[0062] Concentrate discharge port 206 pipeline: Concentrate discharge port 206 is connected to the concentrate return pipeline via concentrate discharge valve (electric butterfly valve). The concentrate discharge valve is an electric butterfly valve, controlled by programmable controller 2143. It is opened in the filtration state to continuously discharge concentrate, and closed in the backwash state to prevent backwash water from being short-circuited and lost.

[0063] Permeate water collection port 207: Permeate water collection port 207 connects to a tee pipe. The first port of the tee is connected to the permeate water collection pipe via a permeate water valve, used to deliver permeate water during filtration. The second port of the tee is connected to the outlet pipe of the variable frequency backwash water pump 2144 via a backwash water inlet valve, used to inject backwash water into the membrane fiber cavity during backwashing. Both the permeate water valve and the backwash water inlet valve are electric butterfly valves, controlled by a programmable logic controller 2143, to switch between filtration and backwash water inlet modes.

[0064] Drainage Pipeline: A drain branch pipe 1032 is installed at the lowest point of the inlet pipe 204 (near the bottom end cap of the membrane housing 201). A drain valve is installed on the drain branch pipe 1032 to drain the water accumulated in the membrane housing 201 during shutdown maintenance. The drain valve is a manual ball valve.

[0065] The aforementioned electric valves (inlet valve, backwash drain valve, concentrate discharge valve, product water valve, and backwash inlet valve) are all automatically controlled by a programmable logic controller 2143 according to a preset timing logic, achieving fully automatic switching between filtration and backwashing. All pipes are made of 304 stainless steel, with pipe diameters matching the corresponding interface specifications (liquid inlet 204DN50, air inlet DN25, concentrate discharge outlet 206DN40, product water collection outlet 207DN40), and a pressure resistance rating of not less than 1.0 MPa.

[0066] An electric inlet valve is installed on the inlet pipe 106 at the top of the adsorption tank 101 to control the flow of raw water into the activated carbon tank; an electric outlet valve is installed on the outlet pipe 107 to control the flow of treated water into the intermediate buffer tank 3; an electric backwash drain valve is installed on the backwash drain pipe 108 to discharge backwash wastewater during activated carbon backwashing; and an electric backwash inlet valve is installed on the activated carbon backwash inlet pipe 109 (connected from the ultrafiltration permeate pipe) to control the inflow of backwash water. All of these electric valves are controlled by a programmable logic controller 2143 to automatically switch between activated carbon filtration and backwashing modes.

[0067] Work process: During filtration, industrial wastewater enters the activated carbon adsorption tank from the top, is evenly distributed by the inlet water distributor 103, and then flows downward through the filter media layer. Dissolved organic matter and residual chlorine are adsorbed and removed by the activated carbon. The treated water is collected by the outlet water collector 104 and enters the intermediate buffer tank 3. After being pressurized by the booster pump 4, it enters the filtration chamber 210 from the bottom inlet 204 of the membrane housing 201. Driven by pressure, water passes through the wall of the fiber membrane filaments 202 from the outside to the inside and enters the inner cavity of the membrane filaments, where pollutants are trapped on the outer surface of the membrane filaments. The permeate flows downward along the inner cavity of the membrane filaments into the permeate chamber 211 and is discharged from the permeate collection port 207. The trapped pollutants rise to the top with the concentrate and are discharged from the concentrate discharge port 206. The power source for this concentrate discharge is the continuous inlet water pressure at the bottom inlet 204 of the membrane housing 201 (provided by the booster pump 4, pressure 0.1~0.15MPa). During filtration, this pressure continuously acts on the water within the filtration chamber 210, propelling the water upwards. When the water rises to the top concentrate chamber, because the top concentrate outlet 206 is a normally open channel or a channel periodically opened by an electric valve (connected to atmospheric pressure or a low-pressure return pool), the concentrate automatically overflows and is discharged under the pressure of the incoming pressure. This is the same principle as "water continuously entering through a faucet and continuously overflowing from the overflow outlet along the top of the sink."

[0068] When backwashing is required, the corresponding level of backwashing procedure is executed according to the instructions of the online cleaning control system 214. After restoring the membrane flux, the system switches back to filtration mode. The specific process is as follows: Regular water backwash (slightly polluted): The triggering condition is that the transmembrane pressure difference exceeds the set value and η≥η_0. The execution process is as follows: (1) Stop the filter water intake: close the water inlet valve of the liquid inlet 204. (2) Close the concentrate discharge port 206 to prevent backwash water from short-circuiting and being lost. (3) Start the variable frequency backwash water pump 2144 and pump the clean water (which can be ultrafiltration permeate) from the permeate collection port 207 into the permeate chamber 211 at the bottom of the membrane housing 201 at a flow rate of 1.0~1.5 times the filtration flow rate (6m³ / h in this embodiment). (4) The backwash water enters the inner cavity opening end of all membrane fibers from the permeate chamber 211 and passes through the membrane fiber wall from the inside to the outside (i.e., reverse permeate through the PVDF separation layer). (5) The reverse water flow peels off the loose filter cake layer attached to the outer surface of the membrane fibers, and the wastewater carrying pollutants is discharged from the liquid inlet 204 (the liquid inlet 204 pipeline is switched to the discharge pipeline). (6) Stop after 60 seconds and switch back to filter mode.

[0069] Working principle: It relies on the physical impact of reverse water force to peel off loose pollutants from the membrane surface, without consuming compressed air or chemical agents.

[0070] Combined air-water backwash (moderate contamination): The triggering condition is η<η_0 and the duration exceeds 30 seconds. The execution process is as follows: (1) Stop the filter water inlet: close the concentrated water discharge port 206. (2) Start the variable frequency backwash water pump 2144 and adjust the backwash water flow rate to 0.8~1.2 times the filter flow rate (5m³ / h in this embodiment). (3) At the same time, open the pneumatic regulating valve 2145, and the compressed air (pressure 0.04~0.08MPa, 0.05MPa in this embodiment) enters the annular mixing chamber 2136 of the air-water distribution plate 2133 through the compressed air pipeline 2131. (4) The backwash water also enters the annular mixing chamber 2136 through the cleaning water pipeline 2132 and premixes with the compressed air to form an air-water two-phase flow. (5) The air-water mixture is ejected from the central main nozzle 2134 and the peripheral vector auxiliary nozzle 2135: The central main nozzle 2134 sprays vertically upward, driving the membrane fibers in the central region of the membrane bundle to float up and down and oscillate slightly. The peripheral vector auxiliary nozzle 2135 sprays at a 40° elevation angle and an 18° tangential angle. The jet direction is the same as the instantaneous tangential velocity direction when each membrane fiber oscillates to its maximum amplitude, generating Coanda effect adhesion on the surface of the oscillating membrane fibers, forming a positive feedback self-excited oscillation (the oscillation amplitude of the membrane fibers continues to increase). (6) After 90 seconds, the compressed air valve is closed, the backwash water pump is stopped, and the filtration mode is switched back.

[0071] Working principle: The combined effect of airflow shear force and water flow hydraulic scouring, along with the turbulence enhancement generated by the self-excited oscillation of the membrane fibers, removes stubborn pollutants from the membrane surface.

[0072] Chemically enhanced backwash (heavily fouled): The trigger condition is that the recovery value of η after air-water combined backwash is still less than 80% of η_0 (i.e. <0.68), indicating that there is irreversible organic fouling or inorganic scaling on the membrane surface. The execution process is as follows: (1) Perform the preparation work for air-water combined backwash (start the water pump and open the air valve). (2) Start the metering dosing pump 2146 and inject chemical agents into the cleaning water pipeline 2132 according to the set ratio: Treat organic fouling: add sodium hypochlorite solution (concentration 100~200ppm, 150ppm in this example), and adjust the pH to 11~12 (NaOH can be used for auxiliary adjustment). Treat inorganic scaling: add citric acid solution (concentration 1%~3%, 2% in this example), and adjust the pH to 2.5~3.0. (3) After the agent is mixed with the backwash water, it is sprayed into the membrane shell 201 through the air-water distribution plate 2133, and the chemical-containing backwash water is fully in contact with the membrane fiber surface. (4) Soak for 15-20 minutes to allow the chemical agents to fully dissolve organic pollutants or inorganic scale on the membrane surface. (5) After soaking, perform a combined air-water backwash for 120 seconds to thoroughly flush the dissolved / stripped pollutants out of the membrane shell 201. (6) Switch back to filtration mode and monitor whether the η recovery value meets the standard.

[0073] Working principle: Sodium hypochlorite oxidizes and decomposes organic pollutants, while citric acid dissolves calcium and magnesium inorganic salt scale, simultaneously completing cleaning and disinfection. Chemical cleaning wastewater is collected separately, neutralized, and then discharged.

[0074] Furthermore, activated carbon backwashing and ultrafiltration membrane backwashing are performed sequentially, rather than simultaneously, to avoid insufficient system pressure caused by both using water at the same time. The specific sequence is as follows: The programmable controller 2143 first triggers the regular water backwash of the ultrafiltration membrane filtration unit 2 (lasting 60 seconds). The backwash wastewater is discharged from the inlet 204 pipe through the backwash drain valve into the activated carbon backwash wastewater collection tank.

[0075] After the ultrafiltration membrane backwash is completed (approximately 10 seconds later), the programmable controller 2143 closes the ultrafiltration backwash drain valve and opens the activated carbon backwash inlet valve. Using the ultrafiltration backwash wastewater temporarily stored in the activated carbon backwash wastewater collection tank as the water source for activated carbon backwashing, the activated carbon backwash water pump (independently set up) is started, sending the collected wastewater in reverse from the bottom outlet collector 104 of the activated carbon tank, flushing the activated carbon layer from bottom to top. The backwash time is 8 minutes.

[0076] After the activated carbon backwashing is completed, the wastewater is discharged into the sewage system.

[0077] If the amount of ultrafiltration backwash wastewater is insufficient to meet the backwashing requirements of activated carbon (the water required for activated carbon backwashing is approximately 2 to 3 times the amount of ultrafiltration backwash wastewater), the shortfall will be supplemented by the ultrafiltration permeate tank. The supplemental water is automatically introduced through a water supply pipeline (connecting the ultrafiltration permeate tank and the activated carbon backwash wastewater collection tank, controlled by an electric valve). The water supply is automatically controlled by the programmable controller 2143 based on the liquid level signal from the activated carbon backwash wastewater collection tank.

[0078] Running result: Using wastewater from a chemical industrial park (COD=150~200mg / L, SS=20~30mg / L, residual chlorine=0.3~0.8mg / L) as the treatment target, a continuous operation test was conducted with a treatment capacity of 5m³ / h. After activated carbon pretreatment, the effluent COD was reduced to 70~90mg / L, and the residual chlorine was reduced to <0.05mg / L. The ultrafiltration membrane produced water with COD <30mg / L and turbidity <0.1NTU, and the effluent quality met the industrial circulating cooling water makeup water standard (GB / T 50050-2017).

[0079] Continuous operation test results show that the rate of increase in transmembrane pressure difference is reduced by approximately 50% compared to systems without pre-activated carbon, and the continuous operation cycle of the system is extended by 2 to 3 times. The chemical cleaning cycle is extended from the conventional 7 to 10 days to 28 to 35 days, and the consumption of chemical reagents is reduced by approximately 60%. The membrane fiber breakage rate is less than 1% after 3 years of operation, significantly better than the 3% to 5% of conventional straight-through membrane modules. The overall operating cost is reduced by approximately 25% compared to ultrafiltration alone. It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of the components in a specific posture (as shown in the attached figure). If the specific posture changes, the directional indicator will also change accordingly.

[0080] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0081] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0082] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A hollow fiber ultrafiltration high-efficiency filter for industrial wastewater reuse, characterized in that, It includes a pre-treatment unit for high-efficiency activated carbon (1) and an ultrafiltration membrane filtration unit (2) located downstream of it. The pre-treatment unit (1) for high-efficiency activated carbon includes an adsorption tank (101), a high-efficiency activated carbon filter media layer (102) filled in the adsorption tank (101), an inlet water distributor (103) set at the upper part of the adsorption tank (101), and an outlet water collector (104) set at the lower part of the adsorption tank (101). The bottom outlet of the adsorption tank (101) is connected to the inlet (204) of the ultrafiltration membrane filtration unit (2) via an intermediate buffer tank (3) and a booster pump (4). The ultrafiltration membrane filtration unit (2) includes a membrane housing (201), a hollow fiber ultrafiltration membrane bundle filled in the membrane housing (201), and a sealing layer (203) at the lower end; the membrane housing (201) has a liquid inlet (204) on the lower side wall, a concentrate outlet (206) on the top, and a product water collection outlet (207) on the side; the hollow fiber ultrafiltration membrane bundle is composed of multiple hollow fiber membrane filaments (202), which are arranged in a U-shape with their bent ends The membrane is movably constrained to the upper part of the membrane shell (201) by an elastic limiting ring (209), and the open end is fixed by casting with a sealing layer (203) with the opening facing downward; and a filter chamber (210) is formed inside the membrane shell (201) between the limiting ring and the sealing layer (203), and a product water chamber (211) is formed below the sealing layer (203). The product water collection port (207) is located in the product water chamber (211), and the liquid inlet (204) is connected to the filter chamber (210).

2. The hollow fiber ultrafiltration high-efficiency filter for industrial wastewater reuse as described in claim 1, characterized in that, Each fiber membrane filament (202) has an eccentric counterweight (212) attached to its top. The eccentric counterweight (212) is located on one side of the central axis of the bent end of the fiber membrane filament (202), so that the fiber membrane filament (202) generates a pendulum-like radial swing driven by eccentric torque under the impact of air and water. The initial skew direction of each fiber membrane filament (202) is distributed differently in the circumferential direction.

3. The hollow fiber ultrafiltration high-efficiency filter for industrial wastewater reuse as described in claim 2, characterized in that, The eccentric counterweight (212) is a stainless steel bead or a ceramic bead, which is bonded to the fiber membrane (202) with epoxy resin. The eccentric counterweights (212) of adjacent fiber membranes (202) are rotated 15°~45° in the circumferential direction of the bonding direction, so that the initial skew direction of each fiber membrane (202) is evenly distributed within a 360° range. The elastic limiting ring (209) is a rubber O-ring, which is fixed in the hollow hole (215) of the upper floating support plate (208). The outer edge of the upper floating support plate (208) is embedded in the guide groove (205) fixed in the inner wall of the membrane shell (201).

4. The hollow fiber ultrafiltration high-efficiency filter for industrial wastewater reuse as described in claim 1, characterized in that, The ultrafiltration membrane filtration unit (2) further includes an air-water mixing backwashing mechanism (213), which includes a compressed air pipeline (2131) and a cleaning water pipeline (2132) connected to the bottom side wall of the membrane housing (201), and an air-water distribution plate (2133) disposed at the bottom of the membrane housing (201). The compressed air pipeline (2131) and the cleaning water pipeline (2132) are respectively connected to the air-water distribution plate (2133). The gas-water distribution disk (2133) is connected, and a central main nozzle (2134) and a peripheral vector secondary nozzle (2135) are provided on the surface. The jetting direction of the peripheral vector secondary nozzle (2135) is the same as the instantaneous tangential velocity direction when the fiber membrane (202) swings to the maximum amplitude. This causes the jetting gas-water fluid to generate Coanda effect adhesion on the surface of the swinging fiber membrane (202), forming a positive feedback self-excited oscillating flow field that drives the amplitude of the fiber membrane (202) to increase.

5. The hollow fiber ultrafiltration high-efficiency filter for industrial wastewater reuse as described in claim 4, characterized in that, The nozzle axis of the peripheral vector auxiliary nozzle (2135) forms an angle of 30°-45° with the horizontal plane, and the projection direction of the nozzle axis on the horizontal plane forms an angle of 15°-20° with the radial tangent of the disk surface. The outlet of the peripheral vector auxiliary nozzle (2135) is provided with a trumpet-shaped diffuser section. The air-water distribution disk (2133) is provided with an annular mixing chamber (2136). The compressed air from the compressed air pipeline (2131) and the cleaning water from the cleaning water pipeline (2132) are pre-mixed in the annular mixing chamber (2136) and then sprayed out through the central main nozzle (2134) and the peripheral vector auxiliary nozzle (2135).

6. The hollow fiber ultrafiltration high-efficiency filter for industrial wastewater reuse as described in claim 1, characterized in that, The water inlet distributor (103) includes a central main pipe (1031) and radial branch pipes (1032) connected to the central main pipe (1031). The branch pipes (1032) have multiple water distribution holes (1033) at their bottom. The water outlet collector (104) is a multi-filter head water collection plate structure. A quartz sand support layer (105) is provided between the high-efficiency activated carbon filter media layer (102) and the water outlet collector (104).

7. The hollow fiber ultrafiltration high-efficiency filter for industrial wastewater reuse as described in claim 1, characterized in that, The ultrafiltration membrane filtration unit (2) also includes an online cleaning control system (214), which includes a transmembrane differential pressure sensor (2141), an ultrasonic Doppler flow meter (2142) disposed in the upper part of the membrane housing (201), and an editable controller (2143). The ultrasonic Doppler flow meter (2142) is used to monitor the instantaneous flow velocity of the fluid in the membrane bundle region in real time. The editable controller (2143) calculates the turbulence intensity attenuation rate based on the instantaneous flow velocity and automatically executes conventional water backwashing, air-water combined backwashing, and chemical enhanced backwashing programs based on the comparison result of the attenuation rate and a preset threshold.

8. The hollow fiber ultrafiltration high-efficiency filter for industrial wastewater reuse as described in claim 7, characterized in that, The triggering condition for conventional water backwashing is that the transmembrane pressure difference exceeds the set value and the attenuation rate is greater than or equal to the preset threshold. The backwash water enters the inner cavity of the fiber membrane (202) through the air-water mixed backwashing mechanism (213) and permeates outward. The triggering condition for combined air-water backwashing is that the attenuation rate is less than the preset threshold and the duration exceeds the first delay. Compressed air and cleaning water are mixed through the air-water distribution plate (2133) and then rotate and rise. The triggering condition for chemically enhanced backwashing is that the recovery value of the attenuation rate after combined air-water backwashing is still less than 80% of the preset threshold. Sodium hypochlorite or citric acid solution is added to the cleaning water.

9. The hollow fiber ultrafiltration high-efficiency filter for industrial wastewater reuse as described in claim 8, characterized in that, In the conventional backwashing, the backwash water flow rate is 1.0-1.5 times the filtration flow rate, and the backwashing time is 30-90 seconds; in the combined air-water backwashing, the compressed air pressure is 0.04-0.08 MPa, the backwash water flow rate is 0.8-1.2 times the filtration flow rate, and the backwashing time is 60-120 seconds; in the chemically enhanced backwashing, the sodium hypochlorite dosage is 100-200 ppm or the citric acid solution concentration is 1%-3%, and the soaking time is 10-20 minutes.

10. The hollow fiber ultrafiltration high-efficiency filter for industrial wastewater reuse as described in claim 9, characterized in that, When the cumulative operating time of the adsorption tank (101) reaches the set value or the inlet and outlet pressure difference exceeds the set value, the programmable controller (2143) starts the activated carbon backwashing program. The backwash water washes the activated carbon layer from bottom to top, and the backwash wastewater is discharged from the top drain.

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