Device for multi-stage filtering and screening of micro-plastics in water body

Abstract

The invention relates to a water pollutant collection technology, and aims to provide a device for filtering and screening micro-plastics in a water body in a multi-stage manner. Comprising an inlet water pre-separation unit, a multi-stage filtering and screening unit, an automatic membrane changing unit and a control unit, the multi-stage filtering and screening unit comprises a plurality of filtering and screening assemblies which are connected in sequence and are of the same structure, an elastic corrugated pipe and a second water suction pump. The automatic film changing unit comprises a plurality of film changing assemblies which are the same in structure and are sequentially connected through a central rotating shaft, and a second stepping motor is arranged at the tail end of the central rotating shaft; and the membrane exchange assemblies and the filtering and screening assemblies are arranged in a one-to-one correspondence manner. According to the invention, the functions of automatic film changing control, multi-stage screening and self-cleaning are integrated, and the problem of filter screen blockage can be effectively solved; while the collection efficiency is improved, precise separation and continuous treatment of micro-plastics with different particle sizes are realized; through the control unit, mutual cooperation of the rotary membrane replacing assembly and the telescopic filtering and screening assembly is achieved, and automatic replacement of the filter membrane assembly is achieved.

Description

Technical Field

[0001] The present invention relates to the technology of collecting water pollutants, and particularly to a device for multi-stage filtering and screening of microplastics in water bodies. Background Art

[0002] In recent years, microplastic pollution has become a global environmental problem. Microplastics generally refer to plastic particles with a particle size less than 5 millimeters. Their chemical properties are stable, difficult to degrade, and can persist and accumulate in the environment for a long time. Due to their non-degradable characteristics, these microplastics will continuously accumulate in the environment, posing a serious threat to the ecosystem and human health.

[0003] Existing studies have shown that the distribution range of microplastics far exceeds expectations. The Antarctic research team detected the presence of microplastics in the Antarctic waters, and microplastic traces were also found in the Arctic ice cores, confirming the universality of their cross-regional diffusion. More worryingly, existing research reports have detected microplastic particles in human blood, revealing the risk that microplastics enter the human body through the food chain and potentially endanger health. Microplastic pollution may also lead to a 4% to 14% reduction in the yields of major crops such as wheat, rice, and corn globally by damaging the photosynthesis ability of plants. Therefore, in-depth research on the retention of microplastics in the water environment and then proposing adaptive water body restoration plans is of great significance for controlling water pollution and protecting human health.

[0004] It can be seen from this that collecting and separating microplastics from water bodies is an important prerequisite for carrying out research on microplastics in the water environment. However, in current research work, the collection methods for microplastics in water bodies are still very inefficient. The particle sizes and compositions of fine particles such as microplastics are different, and most of them are suspended in water bodies, so it is impossible to comprehensively collect them by simple surface interception methods. Therefore, traditional filtering devices are usually still used for collection. However, the collection process of the filtering device relies on manual operation, with low automation. The filter screen is easily blocked due to the accumulation of impurities such as sediment, affecting the collection efficiency. Moreover, existing equipment usually lacks the ability of hierarchical screening, is difficult to accurately separate microplastics of different particle sizes, and cannot operate continuously. It is necessary to frequently interrupt to replace the filter membrane or clean the system. All of the above problems seriously restrict the working efficiency of researchers in obtaining microplastic samples in water bodies.

[0005] Therefore, the present invention intends to propose a new solution to the above problems. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a device for multi-stage filtering and screening of microplastics in water bodies, which is used to achieve efficient interception and screening of microplastics in water bodies, continuous treatment, and automated operation.

[0007] To solve the technical problem, the solution of the present invention is as follows:

[0008] Provide a device for multi-stage filtering and screening of microplastics in water, including: an inlet pre-separation unit, a multi-stage filtering and screening unit, an automatic membrane changing unit, and a control unit; wherein,

[0009] The inlet pre-separation unit includes a first water pump, a hydrocyclone, and a pre-separation storage tank connected in sequence through pipelines; the bottom of the pre-separation storage tank is connected to the multi-stage filtering and screening unit through a pipeline;

[0010] The multi-stage filtering and screening unit includes a plurality of filtering and screening components with the same structure connected in sequence, an elastic corrugated pipe, and a second water pump; each filtering and screening component includes a first stepping motor, a lead screw slide table, and two cylindrical bodies, and the two cylindrical bodies are connected through the lead screw slide table and are arranged with their end faces facing each other; the cylindrical bodies in all filtering and screening components are coaxially arranged; when the first stepping motor drives the lead screw slide table to perform telescopic actions, it can drive the two cylindrical bodies to move axially to separate or dock their end faces;

[0011] The automatic membrane changing unit includes a plurality of membrane changing components with the same structure connected in sequence through a central rotating shaft, and a second stepping motor is arranged at the end of the central rotating shaft; each membrane changing component includes a plurality of connecting rods evenly arranged around the central rotating shaft, and a filter membrane installed in a circular washer is arranged at the end of the connecting rod; each membrane changing component is arranged corresponding to each filtering and screening component one by one, and the filter membrane in the membrane changing component and the docking position of the two cylindrical bodies in the filtering and screening component are in the same plane; when the second stepping motor drives the central rotating shaft to rotate, it can drive the filter membranes in each membrane changing component to rotate synchronously around the central rotating shaft;

[0012] The control unit includes a controller, and the controller is connected to the first water pump, the second water pump, the first stepping motor, and the second stepping motor through signal lines; the controller is used to synchronously control the actions of the first stepping motor and the second stepping motor to realize the replacement and sealing operations of the filter membrane in the filtering and screening component.

[0013] As a preferred solution of the present invention, the hydrocyclone is composed of an upper cylindrical cavity and a lower conical cavity, its inlet pipeline is connected to the cylindrical cavity along the tangential direction, and a bottom flow port is arranged at the bottom of the conical cavity; one end of the overflow pipe is inserted into the cylindrical cavity from the upper top cover, and the other end is connected to the top of the pre-separation storage tank.

[0014] As a preferred embodiment of the present invention, the screw slide table includes a screw rod, a slider, and a gantry-shaped support structure. The slider is located between two parallel support blocks in the support structure, and the slider and one of the support blocks are respectively welded to the outer walls of two cylindrical bodies; the screw rod is coaxially arranged with the cylindrical body and penetrates through the two support blocks and the slider. One end of the screw rod is connected to the output end of the first stepping motor, and the other end is provided with an anti-disengagement limit structure.

[0015] As a preferred embodiment of the present invention, on the respective end faces of the two cylindrical bodies in the filter screening assembly, coaxially arranged grooves and radially opened grooves communicating with the grooves are respectively provided; the grooves are used for embedding circular gaskets and filter membranes, and the radially opened grooves are used for embedding connecting rods connected to the filter membranes.

[0016] As a preferred embodiment of the present invention, in the multi-stage filter screening unit, the outer ends of the cylindrical bodies in each filter screening assembly all have integrally connected reduced-diameter pipes; the ends of the reduced-diameter pipes are provided with threads, and adjacent filter screening assemblies are connected through threaded sleeves; alternatively, the ends of the reduced-diameter pipes are provided with flange surfaces, and adjacent filter screening assemblies are connected through a plurality of bolt assemblies; in the automatic membrane-changing unit, flange surfaces are provided at both ends of the central rotating shafts of each membrane-changing assembly, and adjacent membrane-changing assemblies are connected through a plurality of bolt assemblies.

[0017] As a preferred embodiment of the present invention, in the automatic membrane-changing unit, each membrane-changing assembly includes the same number of filter membranes arranged circumferentially and uniformly, and each membrane-changing assembly has the same projected shape on a plane perpendicular to the central rotating shaft.

[0018] As a preferred embodiment of the present invention, there are at least three filter screening assemblies in the multi-stage filter screening unit, and corresponding numbers of membrane-changing assemblies are provided in the automatic membrane-changing unit; the pore diameters of the filter membranes in each stage of membrane-changing assemblies decrease sequentially along the water flow direction.

[0019] As a preferred embodiment of the present invention, a first valve is provided on the pipeline connecting the pre-separation storage tank and the multi-stage filter screening unit; the device further includes an ultrapure water storage tank, a third water pump, a second valve, and a flushing nozzle, and they are connected in sequence by pipelines to form a flushing unit. The third water pump is connected to the control unit through a signal line; a tee pipe fitting is provided at the inlet end of the multi-stage filter screening unit, and the outlet pipeline of the pre-separation storage tank and the flushing nozzle are respectively connected to the tee pipe fitting.

[0020] As a preferred embodiment of the present invention, a flow transmitter is provided at the inlet of the multi-stage filter screening unit and is connected to the control unit through a signal line.

[0021] The present invention further provides a method for realizing multi-stage filtering and screening of microplastics in water by using the aforementioned device, including:

[0022] The first water pump sends the water body into the hydrocyclone, separates the sediment impurities in the water body by using the difference in centrifugal force, and discharges them from the underflow port; by using the suction force formed by the second water pump, the water body containing microplastics is introduced from the pre-separation storage tank into the multi-stage filtration and screening unit, and after multi-stage filtration and screening, it is intercepted by filter membranes with different pore sizes;

[0023] The flow transmitter detects the flow rate change online. If the preset lower flow rate threshold is triggered, it is determined that a certain stage of the filter membrane is blocked, and the automatic membrane replacement operation is executed;

[0024] The controller sends control signals to the second stepping motor and all the first stepping motors according to the set time sequence. After separating the two cylinders in all the filtration and screening units, the filter membranes in the corresponding membrane replacement unit are synchronously rotated between the two end faces of the cylinders, and then the circular gaskets are clamped by the docking action of the two cylinders, so as to realize the automatic filter membrane replacement and maintain the sealing operation; during the membrane replacement process, the elastic corrugated pipe is used to absorb the overall deformation generated by the separation of the cylinders in the filtration and screening unit;

[0025] After confirming that the preset water body treatment volume is reached according to the flow rate data of the flow transmitter, stop the first water pump and close the first valve on the outlet pipeline of the pre-separation storage tank; open the second valve in the flushing unit and start the third water pump, and use the preset amount of ultrapure water to flush the microplastics remaining on the multi-stage filtration and screening unit and the pipe wall; according to the monitoring results of the flow transmitter, record the total volume of the filtered water body.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. The device proposed by the present invention integrates functions of automatic membrane replacement control, multi-stage screening and self-cleaning, and can effectively solve the problem of filter screen blockage; while improving the collection efficiency, it realizes the precise separation and continuous treatment of microplastics with different particle sizes, providing an efficient and reliable sample acquisition solution for the research work of researchers.

[0028] 2. In the present invention, the water inlet pre-separation unit combines the synergistic effects of the coarse filter screen and the hydrocyclone, which can effectively remove the coarse impurities and sediment in the water body, ensuring that the impurities do not interfere with the filtration and screening of microplastics. At the same time, it significantly reduces the risk of filter membrane blockage and improves the microplastic collection efficiency and the device life.

[0029] 3. In the present invention, the main particle size range of microplastics can be covered through multi-stage filtration and screening, and the pore size of the filter membrane can be adjusted according to needs; combined with dynamic flow rate regulation, efficient screening and enrichment of microplastics by particle size are realized.

[0030] 4. In the present invention, through the control unit, the rotary membrane replacement component and the telescopic filtration and screening component cooperate with each other to realize the automatic replacement of the filter membrane assembly, avoiding the time-consuming and laborious manual membrane replacement.

[0031] 5. The present invention uses a nozzle to connect to ultrapure water to clean the pipeline, ensuring that the microplastics in the water entering the pipeline are enriched to the filter membrane and the device is cleaned.

[0032] 6. In the present invention, a flow transmitter is used to monitor the water inlet flow rate of the pipeline in real time. While recording the inlet water volume, it assists in adjusting the pumping efficiency to ensure the efficient and stable operation of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the device for multi-stage filtration and screening of microplastics in water of the present invention.

[0034] Figure 2 It is a schematic diagram of the inlet pre-separation unit of the present invention.

[0035] Figure 3 It is a schematic diagram of the single-stage filtration and screening unit of the present invention.

[0036] Figure 4 It is a schematic diagram of the automatic membrane changing unit of the present invention.

[0037] Reference numerals: 1. Stainless steel coarse filter; 2. First water pump; 3. Hydrocyclone; 4. Overflow pipe; 5. First valve; 6. Flushing nozzle; 7. Second valve; 8. Third water pump; 9. Multi-stage filtration and screening unit; 10. Flow transmitter; 11. Filtration and screening assembly; 12. Filter membrane assembly; 13. Automatic membrane changing unit; 14. Second water pump; 15. Inlet; 16. Conical cavity; 17. Outlet; 18. Underflow port; 19. Lead screw slide; 20. Slide block; 21. First stepping motor; 22. Inlet; 23. Cylindrical body; 24. Radial slot; 25. Outlet; 26. Filter membrane; 27. Silicone rubber sealing ring; 28. Central rotating shaft; 29. Rotating shaft platform; 30. Second stepping motor; 31. Elastic corrugated pipe; 32. Pre-separation storage tank; 33. Ultrapure water storage tank. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The present invention will be further described in detail below in conjunction with the drawings and embodiments.

[0039] The serial numbers assigned to the components in this application, such as "first", "second", etc., are only used to distinguish the described objects and do not have any sequential or technical meanings. The terms "connection" and "coupling" as used in this application, unless otherwise specified, both include direct and indirect connections (couplings). In the description of this application, it should be understood that the orientation or positional relationships indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to this application.

[0040] In this application, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0041] Part I Summary of the Implementation Scheme of the Present Invention

[0042] 1. The device for multi-stage filtering and screening of microplastics in water provided by the present invention includes: an inlet pre-separation unit, a multi-stage filtering and screening unit, an automatic membrane replacement unit, a flushing unit, and a control unit. Among them, the inlet pre-separation unit is used to introduce a water sample and initially intercept impurities; the multi-stage filtering and screening unit filters and screens the water body in sequence using a series of filtering membranes with different pore sizes from coarse to fine according to the particle size of the microplastics to separate microplastics with different particle sizes; the automatic membrane replacement unit is used to automatically complete the membrane replacement work and collect the sieved and intercepted microplastics using the filter membrane; the flushing unit is used to flush the residual microplastics on the pipe wall of the device; the control unit is used to monitor the inlet water flow and adjust the working state of the water pump and switch the filter membrane as needed.

[0043] (1) The inlet pre-separation unit includes a first water pump, a hydrocyclone, and a pre-separation storage tank connected in sequence through pipelines; the bottom of the pre-separation storage tank is connected to the multi-stage filtering and screening unit through a pipeline. The hydrocyclone consists of an upper cylindrical cavity and a lower conical cavity. Its inlet pipeline is tangentially connected to the cylindrical cavity, and a bottom flow port is provided at the bottom of the conical cavity; one end of the overflow pipe is inserted into the cylindrical cavity from the upper top cover, and the other end is connected to the top of the pre-separation storage tank. A first valve is provided on the pipeline connecting the pre-separation storage tank and the multi-stage filtering and screening unit.

[0044] (2) The multi-stage filtration and screening unit includes a plurality of filtration and screening components with the same structure connected in sequence, an elastic corrugated pipe, and a second water pump; each filtration and screening component includes a first stepping motor, a screw slide table, and two cylindrical bodies. The two cylindrical bodies are connected by the screw slide table and are arranged with their end faces facing each other; the cylindrical bodies in all filtration and screening components are coaxially arranged; the screw slide table includes a screw rod, a slider, and a U-shaped support structure. The slider is located between two parallel support blocks in the support structure, and the slider and one of the support blocks are respectively welded to the outer walls of the two cylindrical bodies; the screw rod is coaxially arranged with the cylindrical body and penetrates through the two support blocks and the slider. One end of the screw rod is connected to the output end of the stepping motor, and the other end is provided with an anti-disengagement limit structure; when the first stepping motor drives the screw slide table to perform telescopic actions, it can drive the two cylindrical bodies to move axially to separate or butt their end faces.

[0045] A flow transmitter is provided at the inlet of the multi-stage filtration and screening unit and is connected to the control unit through a signal line. By collecting the data of the flow transmitter in real time, the capacity of the filtered water body can be monitored and recorded, assisting in adjusting the valve opening and the power of the water pump to ensure the pressure balance of each filtration pipeline and avoid the damage of the filter membrane or the decrease of the filtration efficiency caused by flow fluctuations. The flow transmitter can be used to monitor the water flow entering the multi-stage filtration and screening unit at any time, so as to adjust the water pump speed when the flow is too large and switch the filter membrane when the flow drops to the lower limit.

[0046] As an alternative, the outer end of the cylindrical body in each filtration and screening component has a reducing pipe connected integrally; the end of the reducing pipe is provided with a thread, and adjacent filtration and screening components are connected by a threaded sleeve; or, the end of the reducing pipe is provided with a flange surface, and adjacent filtration and screening components are connected by a plurality of bolt assemblies.

[0047] (3) The automatic membrane-changing unit includes a plurality of membrane-changing components with the same structure connected in sequence by a central rotating shaft, and a second stepping motor is arranged at the end of the central rotating shaft; each membrane-changing component includes a plurality of connecting rods evenly arranged around the central rotating shaft, and a filter membrane installed in a circular washer is arranged at the end of the connecting rod; each membrane-changing component includes the same number of filter membranes evenly arranged in the circumferential direction, and each membrane-changing component has the same projected shape on a plane perpendicular to the central rotating shaft. Each membrane-changing component is arranged corresponding to the filtration and screening component one by one, and the filter membrane in the membrane-changing component and the docking position of the two cylindrical bodies in the filtration and screening component are in the same plane; when the second stepping motor drives the central rotating shaft to rotate, it can drive the filter membranes in each membrane-changing component to rotate synchronously around the central rotating shaft.

[0048] For easy positioning and installation, coaxial grooves and radially slotted openings communicating with the grooves are respectively provided on the respective end faces of the two cylindrical bodies in the filtering and screening assembly; the grooves are used to embed circular gaskets and filter membranes, and the radially slotted openings are used to embed connecting rods connected to the filter membranes. At the same time, a silicone rubber sealing ring is used to ensure the sealing of the filtering mechanism and prevent the leakage of microplastics or water bodies.

[0049] As an alternative, flange faces are provided at both ends of the central rotating shaft of each membrane replacement assembly, and adjacent membrane replacement assemblies are connected by a plurality of bolt assemblies. There are at least three filtering and screening assemblies in the multi-stage filtering and screening unit, and a corresponding number of membrane replacement assemblies are provided in the automatic membrane replacement unit. The pore sizes of the filter membranes in each stage of the membrane replacement assemblies decrease sequentially along the water flow direction.

[0050] (4) Flushing unit, including an ultrapure water storage tank, a third water pump, a second valve, and a flushing nozzle, which are connected in sequence by pipelines. The third water pump is connected to the control unit through a signal line; a three-way pipe fitting is provided at the inlet end of the multi-stage filtering and screening unit, and the outlet pipeline of the pre-separation storage tank and the flushing nozzle are respectively connected to the three-way pipe fitting. By flushing the filtering and screening unit and the pipelines, the microplastics remaining on the pipe wall can be flushed into the filter membrane interception area, and at the same time, the need for manual cleaning can be reduced.

[0051] (5) Control unit, including a controller, which is connected to the first water pump, the second water pump, the first stepping motor, and the second stepping motor through signal lines; the controller is used to synchronously control the actions of the first stepping motor and the second stepping motor to realize the replacement and sealing operations of the filter membrane in the filtering and screening assembly. The controller can also be used to regulate the rotation speeds of the first water pump, the second water pump, and the third water pump according to the flow rate to ensure that the water flow velocity through the filter membrane is uniform and stable, and to prevent the filter membrane from being damaged under excessive flow rates. As an example, the controller can be a single-chip microcomputer or a host computer, and the control function is realized through embedded software.

[0052] 2. Method for filtering and screening microplastics in water body in multi-stage manner, specifically including:

[0053] (1) The first water pump sends the water body into the hydrocyclone to separate the sediment impurities in the water body by the difference in centrifugal force, and discharges them from the underflow port; using the suction force formed by the second water pump, the water body containing microplastics is introduced from the pre-separation storage tank into the multi-stage filtering and screening unit, and is intercepted by filter membranes with different pore sizes after multi-stage filtering and screening;

[0054] (2) The flow transmitter detects the flow rate change online. If the preset lower flow rate threshold is triggered, it is determined that a certain stage of the filter membrane is blocked, and an automatic membrane replacement operation is performed;

[0055] (3) The controller sends control signals to the second stepping motor and all the first stepping motors according to the set time sequence. After separating the two cylinders in all the filtration and screening units, the filter membranes in the corresponding membrane replacement unit rotate synchronously to between the two end faces of the cylinders, and then the circular gaskets are clamped by the docking action of the two cylinders, thereby realizing automatic filter membrane replacement and maintaining the sealing operation; during the membrane replacement process, the elastic corrugated pipe is used to absorb the overall deformation generated by the separation of the cylinders in the filtration and screening unit.

[0056] (4) After confirming that the preset treated water volume is reached according to the flow data of the flow transmitter, stop the first water pump and close the first valve on the outlet pipe of the pre-separation storage tank; open the second valve in the flushing unit and start the third water pump, and use a preset amount of ultrapure water to flush the microplastics remaining on the multi-stage filtration and screening unit and the pipe wall.

[0057] Collect each filter membrane and the intercepted microplastics, and count the total water volume; conduct further detection work on the collected microplastics, such as abundance, morphology, components, etc.

[0058] The second part: specific embodiments and performance tests

[0059] 1. The device for filtering and screening microplastics in water provided in this example is as Figures 1-4 shown, including: an inlet pre-separation unit, a multi-stage filtration and screening unit, an automatic membrane replacement unit, a flushing unit and a control unit. The external water body is sucked into the device through a water pump, thereby realizing multi-stage filtration and screening.

[0060] The water body first flows into the inlet pre-separation unit through the water inlet, and the stainless steel coarse filter screen 1 and the hydrocyclone 3 are used to intercept and separate impurities such as sediment. After the water body leaves the inlet pre-separation unit, it flows through the flow transmitter 10 and enters the multi-stage filtration and screening unit 9. The flow transmitter 10 monitors the inlet flow rate in real time and records the volume of the water body entering. At the same time, the single-chip microcomputer assists in adjusting the opening of the first valve 5 and the working state of the first water pump 2 to ensure the working efficiency of the suction filtration. After the water body enters the multi-stage filtration and screening unit 9, it is filtered and screened from coarse to fine through three layers of filter membranes 26, so that the microplastics are enriched on the filter membranes 26. When the collection is completed and the membrane needs to be replaced, the automatic membrane replacement unit 13 and the multi-stage filtration and screening unit 9 cooperate to realize the replacement of the filter membrane assembly. After all the water bodies are filtered, the third water pump 8 in the flushing unit pumps the ultrapure water prepared in advance in the ultrapure water storage tank 33 into the device, and flushes the microplastics remaining in the multi-stage filtration and screening unit 9 onto the filter membranes 26 for interception. This solution can realize the efficient filtration and screening of microplastics in water, with a high degree of automation and simple equipment installation and debugging.

[0061] In the inlet pre-separation unit, before the water body enters the water pump 2, impurities larger than 5 mm are roughly filtered by the stainless steel coarse filter screen 1 with a pore diameter of 5 mm, and then the sand and sediment impurities in the water body are separated by the hydrocyclone 3. The water body makes a rotary motion in the hydrocyclone 3. Among them, heavy coarse particles such as sand and sediment are thrown towards the wall due to large inertial centrifugal force; under the action of the 15° conical cavity 16 of the hydrocyclone, they gradually flow downward and are discharged from the underflow port 18. Light fine particles such as microplastics move towards the wall at a relatively low speed and are driven by the liquid flowing towards the center, flowing out from the central overflow pipe 4 to the water outlet 17 and sent to the pre-separation storage tank 32. In this way, the pre-separation of impurities with a larger specific gravity and microplastics in the water body is achieved.

[0062] In the multi-stage filtration and screening unit 9, the water body received from the inlet pre-separation unit is filtered and screened from coarse to fine for microplastics by three single-stage filtration and screening components 11. The main structure of the filtration and screening component 11 is two sections of cylindrical bodies 23, with integral conical tubes at both outer ends. The conical tubes are respectively provided with water inlets 22 and water outlets 25 with external threads for connecting with pipelines or adjacent components through threaded sleeves to ensure tight and reliable connection. Coaxial grooves and radially slotted openings 24 communicating with the grooves are provided on the opposite end faces of the two cylindrical bodies 23; the grooves are used to embed circular silicone rubber seals 27 and filter membranes 26 with different pore diameters, and the radially slotted openings 24 are used to embed connecting rods connected to the filter membranes 26. The cooperation mode of the filter membrane 26 and the circular silicone rubber seal 27 can be a nested wrapping or supporting mode, and the cooperation of the two can ensure the sealing performance. The two cylindrical bodies 23 are connected externally through a screw rod sliding table 19. The screw rod sliding table 19 includes a screw rod, a slider 20, and a U-shaped support structure. The slider 20 is located between two parallel support blocks in the support structure, and the slider 20 and one of the support blocks are respectively welded to the outer walls of the two cylindrical bodies 23; the screw rod is arranged coaxially with the cylindrical body 23 and passes through the two support blocks and the slider 20. One end of the screw rod is connected to the output end of the first stepping motor 21, and the other end is provided with an anti-disengagement limit structure. The controller can control the first stepping motor 21 to adjust the up and down movement of the slider 20 in the screw rod sliding table 19 to realize the opening and closing of the upper and lower end faces of the cylindrical body 23, and cooperate with the action of the automatic membrane changing unit 13 to realize the replacement of the filter membrane assembly.

[0063] In the automatic membrane changing unit 13, the central rotating shafts 28 of the respective filter membrane assemblies are sequentially connected, and the outermost end is connected to the second stepping motor 30. The second stepping motor 30 can drive the central rotating shaft 28 to rotate in a stepping manner. Rotating shaft platforms 29 are respectively arranged on the rotating shafts of the respective filter membrane assemblies, and each rotating shaft platform is connected to 6 filter membrane assemblies. When the filter membrane 26 needs to be replaced, the controller controls the first stepping motor 21 to act, causing the slider 20 to move downward to open the two cylindrical bodies 23; then controls the second stepping motor 30 to drive the central rotating shaft 28 to rotate, so that the new filter membrane 26 rotates to between the end faces of the two cylindrical bodies 23; then reversely drives the first stepping motor 21 to act, causing the end faces of the two cylindrical bodies 23 to be butt-jointed and clamped to the filter membrane 26 and the circular silica gel sealing ring 27 to ensure sealing, thereby realizing the replacement operation.

[0064] In the flushing unit, when the first valve 5 is closed, the second valve 7 is opened, and the third water pump 8 is started to send the ultrapure water in the ultrapure water storage tank 33 to the flushing nozzle 6. The nozzle can be designed to spray water obliquely downward in the circumferential direction. The ejected ultrapure water flushes the device along the pipe wall, flushing the residual microplastics onto the filter membranes at all levels, ensuring that there is as little microplastic residue as possible, and at the same time realizing self-cleaning inside the device. The first valve 5 and the second valve 7 can be selected as electrically controlled valves, so that remote automatic control can be realized.

[0065] The control unit uses the flow transmitter 10 to monitor the influent flow rate in real time, and the collected data is recorded by the single-chip microcomputer to obtain the total volume of water entering the device. The single-chip microcomputer controls the valves and water pumps according to the influent flow rate to ensure the high efficiency and stability of the pumping process. When the influent volume reaches the requirement or the influent flow rate drops to the threshold value, appropriate intervention is carried out on the operating states of the water pumps and valves.

[0066] A specific application example:

[0067] In this example, gasket filter membranes with three different filter diameters of 15μm, 100μm, and 500μm were selected for testing the filtration and screening effect. For the preparation of the water sample, 20L of laboratory tap water was taken and added to a stainless steel bucket, and 0.1g of PVC particles with particle diameters of 1mm, 200μm, and 50μm were respectively weighed and added thereto. During the experiment, when the water was pumped by the water pump until it was almost exhausted, 10L of water was added to the stainless steel bucket and pumping continued; finally, the remaining water in the bucket was poured into a 500ml beaker, and the connecting pipe of the water pump inlet of the flushing unit was introduced, and the water was pumped out as completely as possible.

[0068] Specifically, it includes the following steps:

[0069] 1. Drying, weighing and installation of the filter membrane

[0070] Place the filter membrane in a glass petri dish to dry and weigh it as m1. Then dry, weigh, and count again. Repeat this operation until a constant weight is achieved (the difference between two adjacent weighings does not exceed 0.005 g). Place the filter membrane on the turntables of each level of the automatic membrane replacement unit.

[0071] 2. Water sample pumping and pre-separation

[0072] After the water sample is pumped in by a water pump, it undergoes pre-separation of coarse impurities and sediment through the pre-separation unit of a coarse filter screen and a hydrocyclone, and then enters the pre-separation storage tank.

[0073] 3. Multi-stage filtration and screening

[0074] The water sample after pre-separation is pumped to the multi-stage filtration and screening unit by a water pump and is filtered and screened by three levels of filter membranes with pore sizes of 15 μm, 100 μm, and 500 μm. The flowmeter displays the influent flow rate in real-time. When the filtration efficiency decreases or the influent volume is about to reach the required amount and the flow rate drops to the threshold value of 0.1 L / min, wait for 2 minutes to ensure that all the required influent volume enters, and then close the water sample inlet valve. At the same time, open the valve of the flushing unit and the water pump, spray water on the pipe wall through the nozzle for 1 minute to clean it, and then close it to minimize losses. Wait for 5 minutes to ensure that all the water entering the multi-stage filtration and screening unit is completely filtered.

[0075] 4. Automatic membrane replacement for three-level filter membranes

[0076] During the filtration and screening process, the controller controls the stepping motor in the multi-stage filtration and screening unit to open the docking end faces of each cylindrical body, and then controls the stepping motor in the automatic membrane replacement unit to rotate out the old membrane that has intercepted microplastics and at the same time rotate in a new membrane; then close the docking end faces of each cylindrical body to complete the automatic membrane replacement.

[0077] 5. Drying and weighing the filter membrane after filtration

[0078] Put the filter membrane after filtration into the original glass petri dish, let the glass petri dish dry overnight, dry and weigh the petri dish, and then dry and weigh it again. Repeat this operation until a constant weight m2 is achieved (the difference between two adjacent weighings does not exceed 0.005 g), and observe the change in the value.

[0079] In Examples 1 - 3, filter membranes with three different pore sizes of 15 μm, 100 μm, and 500 μm were used as the three-level filter membranes of the multi-stage filtration and screening unit for filtration and screening tests, and the test results are shown in Tables 1 - 3.

[0080] Table 1 Interception rate of PVC particles by 500-μm filter membrane

[0081]

[0082] Table 2 Interception rate of PVC particles by 100-μm filter membrane

[0083]

[0084] Table 3 Interception rate of PVC particles by 15μm filter membrane

[0085]

[0086] It can be seen from the above results that the three - stage filter membrane of the multi - stage filtration and screening unit in the three groups of examples has a good interception rate for PVC particles. The interception rate of the 500μm filter membrane reaches more than 80%, the interception rate of the 100μm filter membrane reaches more than 65%, and the interception rate of the 15μm filter membrane reaches more than 85%, showing excellent performance and meeting the requirements of practical applications.

[0087] The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. For those skilled in the art, various changes and modifications can be made to the present invention. Any equivalent transformation of the technical solutions of the present invention within the scope of the technical concept of the present invention shall be included within the scope of the claims of the present invention.

Claims

1. A device for multi-stage filtering and screening microplastics in water bodies, characterized in that, Including: An inlet pre-separation unit, a multi-stage filtration and screening unit, an automatic membrane replacement unit, and a control unit; wherein, The inlet pre-separation unit includes a first water pump, a hydrocyclone, and a pre-separation storage tank connected in sequence through pipelines; the bottom of the pre-separation storage tank is connected to the multi-stage filtration and screening unit through a pipeline; The multi-stage filtration and screening unit includes a plurality of identically structured filtration and screening components connected in sequence, an elastic corrugated pipe, and a second water pump; each filtration and screening component includes a first stepping motor, a lead screw slide table, and two cylindrical bodies, and the two cylindrical bodies are connected through the lead screw slide table and are arranged with their end faces facing each other; the cylindrical bodies in all the filtration and screening components are coaxially arranged; when the first stepping motor drives the lead screw slide table to perform telescopic actions, the two cylindrical bodies can be driven to move axially to separate or butt their end faces; The automatic membrane replacement unit includes a plurality of identically structured membrane replacement components connected in sequence through a central rotating shaft, and a second stepping motor is arranged at the end of the central rotating shaft; each membrane replacement component includes a plurality of connecting rods evenly arranged around the central rotating shaft, and a filter membrane installed in a circular washer is arranged at the end of the connecting rod; each membrane replacement component and the filtration and screening component are arranged in one-to-one correspondence, and the filter membrane in the membrane replacement component and the butting position of the two cylindrical bodies in the filtration and screening component are in the same plane; when the second stepping motor drives the central rotating shaft to rotate, the filter membranes in each membrane replacement component can be driven to rotate synchronously around the central rotating shaft; The control unit includes a controller, and the controller is connected to the first water pump, the second water pump, the first stepping motor, and the second stepping motor through signal lines; the controller is used to synchronously control the actions of the first stepping motor and the second stepping motor to realize the replacement and sealing operations of the filter membrane in the filtration and screening component.

2. The device according to claim 1, characterized in that The hydrocyclone is composed of an upper cylindrical cavity and a lower conical cavity, its inlet pipeline is connected to the cylindrical cavity along the tangential direction, and a bottom flow port is arranged at the bottom of the conical cavity; one end of the overflow pipe is inserted into the cylindrical cavity from the upper top cover, and the other end is connected to the top of the pre-separation storage tank.

3. The device according to claim 1, characterized in that, The lead screw slide table includes a lead screw, a slider, and a U-shaped support structure, the slider is located between two parallel support blocks in the support structure, and the slider and one of the support blocks are respectively welded to the outer walls of the two cylindrical bodies; the lead screw is coaxially arranged with the cylindrical body and penetrates through the two support blocks and the slider, one end of the lead screw is connected to the output end of the first stepping motor, and the other end is provided with an anti-disengagement limit structure.

4. The device according to claim 1, characterized in that, On the respective end faces of the two sections of cylindrical bodies in the filtration and screening component, coaxially arranged grooves and radial slots communicating with the grooves are respectively provided; the grooves are used to embed the circular washer and the filter membrane, and the radial slots are used to embed the connecting rods connected to the filter membrane.

5. The device according to claim 1, characterized in that, In the multi-stage filtration and screening unit, the outer ends of the cylindrical bodies in each filtration and screening component all have integrally connected reduced-diameter pipes; the ends of the reduced-diameter pipes are provided with threads, and adjacent filtration and screening components are connected through threaded sleeves; alternatively, the ends of the reduced-diameter pipes are provided with flange faces, and adjacent filtration and screening components are connected through a plurality of bolt assemblies; in the automatic membrane replacement unit, the two ends of the central rotating shaft of each membrane replacement component are provided with flange faces, and adjacent membrane replacement components are connected through a plurality of bolt assemblies.

6. The device according to claim 1, characterized in that In the automatic membrane changing unit, each membrane changing component includes filter membranes with the same quantity and evenly arranged circumferentially, and each membrane changing component has the same projected shape on the plane perpendicular to the central rotating shaft.

7. The device according to claim 1, characterized in that, There are at least three filtering and screening components in the multi-stage filtering and screening unit, and a corresponding number of membrane changing components are provided in the automatic membrane changing unit; the pore diameters of the filter membranes in each stage of the membrane changing components decrease successively along the water flow direction.

8. The device according to claim 1, characterized in that, A first valve is provided on the pipeline connecting the pre-separation storage tank and the multi-stage filtering and screening unit; the device further includes an ultrapure water storage tank, a third water pump, a second valve and a flushing nozzle, and they are connected in sequence by pipelines to form a flushing unit, and the third water pump is connected to the control unit through a signal line; a tee fitting is provided at the inlet end of the multi-stage filtering and screening unit, and the outlet pipeline of the pre-separation storage tank and the flushing nozzle are respectively connected to the tee fitting.

9. The device according to any one of claims 1 to 8, characterized in that, A flow transmitter is provided at the inlet of the multi-stage filtering and screening unit and is connected to the control unit through a signal line.

10. A method for realizing multi-stage filtration and screening of microplastics in water by using the device according to claim 1, characterized in that, It includes: The first water pump sends water into the hydrocyclone, separates the sediment impurities in the water by using the difference in centrifugal force, and discharges them from the underflow port; Using the suction force formed by the second water pump, the water body containing microplastics is introduced from the pre-separation storage tank into the multi-stage filtering and screening unit, and is intercepted by filter membranes with different pore diameters after multi-stage filtering and screening; The flow transmitter detects the flow change online. If the preset lower flow threshold is triggered, it is determined that a certain stage of the filter membrane is blocked, and an automatic membrane changing operation is performed; The controller sends control signals to the second stepping motor and all the first stepping motors according to the set time sequence. After separating the two cylinders in all the filtering and screening units, the filter membranes in the corresponding membrane changing unit rotate synchronously to between the two end faces of the cylinders, and then the circular gasket is clamped by the docking action of the two cylinders, so as to realize the automatic replacement of the filter membrane and maintain the sealing operation; during the membrane changing process, the elastic corrugated pipe is used to absorb the overall deformation generated by the separation of the cylinders in the filtering and screening unit; After confirming that the preset water treatment volume is reached according to the flow data of the flow transmitter, stop the first water pump and close the first valve on the outlet pipeline of the pre-separation storage tank; open the second valve in the flushing unit and start the third water pump, and use the preset amount of ultrapure water to flush the microplastics remaining in the multi-stage filtering and screening unit and the pipe wall; according to the monitoring results of the flow transmitter, record the total volume of the filtered water body.

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