A bidirectional flow self-cleaning modular multi-stage pure water filtration system and a backwashing method thereof

Abstract

This invention discloses a bidirectional flow self-cleaning modular multi-stage pure water filtration system and its backwashing method, belonging to the field of water treatment technology. The system includes at least two sets of parallel filtration units, each set containing multiple filter cartridges connected in series along the water flow direction. It also includes a bidirectional switching valve group, a controller, and a backwash water recovery pipeline. The controller controls the two sets of filtration units to alternately produce and backwash water: when one set of filtration units is producing water forward, a portion of its produced water is diverted to backwash the other set of filtration units. The backwash water is recovered and reused through the recovery pipeline instead of being directly discharged. The two sets of filtration units alternately perform the roles of producing water and backwashing, ensuring uninterrupted water production. This solution uses produced water as the backwash medium and recovers and reuses backwash water, balancing thorough backwashing with water conservation.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a pure water filtration system, and more particularly to a modular multi-stage pure water filtration system and its backwashing method that achieves self-cleaning through bidirectional alternating backwashing and recycles the backwash water. Background Technology

[0002] Reverse osmosis water purifiers filter raw water step-by-step through a series of filter cartridges. The pre-stage typically consists of polypropylene cotton (PP cotton) filter cartridges and granular activated carbon filter cartridges to intercept sediment, rust, colloids, and adsorb residual chlorine and organic matter. The post-stage consists of reverse osmosis membrane filter cartridges and post-activated carbon filter cartridges. The pre-stage filter cartridges gradually become clogged during the process of intercepting particulate matter, requiring periodic backwashing to restore flow. There are three main existing backwashing methods: 1) Offline backwashing, which requires stopping water production and switching to a bypass, resulting in an interruption of water production; 2) Online backwashing, where the finished water is used directly as backwash water to backwash the filter cartridges, and the backwash water, along with the flushed contaminants, is discharged. The proportion of backwash water in the produced water volume is usually not low, leading to water waste; 3) Unidirectional backwashing, where backwash water passes through the filter cartridges only in one direction, creating cleaning dead zones on the back pressure side of the filter cartridges. Over time, contaminants irreversibly accumulate in these dead zones.

[0003] Chinese patent CN101172696A discloses a bidirectional backwashing technology and device using a combined air-water siphon and siphon to achieve bidirectional backwashing of the filter media in a biological filter. This solution is designed for biological filters in wastewater treatment. The backwashing medium is a combined air-water mixture, and the backwashing power is generated by siphoning. Structurally, it is not suitable for multi-stage pure water filtration systems with reverse osmosis membranes as the core. Chinese patent CN216537222U discloses a bidirectional pipeline-type high-pressure cleaning filter, which achieves bidirectional water intake and cleaning, but the backwash water still needs to be supplied and discharged separately, failing to solve the problem of water waste during backwashing. Chinese patent CN108046451A discloses a modular high-efficiency water purification device, which facilitates filter replacement through modular design, but filter replacement still requires system shutdown, and it does not address the coupling of backwashing and product water.

[0004] Chinese patent CN219252233U discloses an online self-cleaning multi-stage reverse osmosis water treatment device, which cleans the reverse osmosis membrane through an online self-cleaning mechanism. However, this solution only addresses the cleaning of the reverse osmosis membrane itself, and its self-cleaning process still consumes clean water, without addressing the bidirectional backwashing of the pre-filter cartridges and the recovery of backwash water. Chinese patent CN217809000U discloses a self-cleaning filter cartridge and a reverse osmosis membrane purification system with micro-wastewater and pure water protection, which reduces the clogging rate of the pre-filter cartridges through the self-cleaning filter cartridge, but similarly does not solve the problem of water waste in the backwashing process. In summary, existing technologies either only address reverse osmosis membrane cleaning or only address the self-cleaning of pre-filter cartridges, without disclosing the technical concept of using two sets of parallel filtration units to alternately produce water and backwash, using the produced water as the backwash medium, and recovering and reusing the backwash water.

[0005] It is evident that existing multi-stage pure water filtration systems present a difficult contradiction between ensuring thorough backwashing and conserving water resources: achieving thorough backwashing often requires a separate backwash water source and subsequent discharge; conserving water, however, makes bidirectional, seamless online backwashing challenging. How to reduce or even eliminate the additional water consumption associated with backwashing while maintaining its effectiveness remains a problem that current technology has yet to solve. Summary of the Invention

[0006] The technical problem this invention aims to solve is that the backwashing of existing multi-stage pure water filtration systems requires a separate backwash water source or direct discharge of backwash water. The backwashing process wastes water resources, requires shutdown, or has cleaning dead zones. Furthermore, existing bidirectional backwashing solutions are geared towards specific scenarios such as biological filters and are difficult to apply directly to reverse osmosis pure water systems.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A bidirectional flow self-cleaning modular multi-stage pure water filtration system includes at least two sets of parallel filtration units, each set of filtration units having multiple filter cartridges connected in series along the water flow direction; it also includes a bidirectional switching valve group, a controller, and a backwash water recovery pipeline; the bidirectional switching valve group is connected to the inlet and outlet of each set of filtration units, used to switch each set of filtration units between a first flow direction and a second flow direction, the first flow direction being the forward water production direction and the second flow direction being the backwash direction; the controller is electrically connected to the bidirectional switching valve group and configured to: during the forward water production of the first filtration unit in the first flow direction, a portion of the water produced by the first filtration unit is diverted and introduced into the second filtration unit in the second flow direction through the bidirectional switching valve group to backwash the second filtration unit, and the backwash water generated from backwashing the second filtration unit is recovered and reused through the backwash water recovery pipeline; after the second filtration unit has finished rinsing, the second filtration unit is switched to the first flow direction for forward water production, and a portion of the water produced by the second filtration unit is diverted to backwash the first filtration unit, and this process is repeated alternately.

[0008] Through the above technical solution, the present invention utilizes a portion of the produced water from one set of filter units during forward water production as a backwashing medium to backwash another set of filter units. The two sets of filter units alternately assume the roles of water production and backwashing. Backwashing does not consume additional external backwashing water sources. The backwashing water is recycled and reused through a recovery pipeline instead of being directly discharged. Thus, while ensuring the bidirectional backwashing effect without dead angles, the additional water consumption caused by backwashing is reduced or even eliminated.

[0009] Furthermore, during the switching process of the bidirectional switching valve group, the controller first pre-pressurizes the flow path to be switched into before completing the valve position switching, so as to reduce the pressure fluctuation at the moment of switching.

[0010] Furthermore, a differential pressure detection unit is connected in parallel between the inlet and outlet of each group of filter units. The differential pressure detection unit is electrically connected to the controller. The controller triggers backwashing when the differential pressure detected by the differential pressure detection unit reaches a preset threshold.

[0011] Furthermore, the outlet end of the backwash water recovery pipeline is connected to the pre-filter at the system inlet end, so that the backwash water is filtered by the pre-filter and then re-enters the production water process.

[0012] Furthermore, the multi-stage filter elements of each group of filter units are installed in the corresponding flow path through pluggable modular interfaces, and each stage of filter element can be replaced independently without stopping the machine.

[0013] Furthermore, the bidirectional switching valve group includes an inlet switching valve and an outlet switching valve. The inlet switching valve is used to switch the inlet water source of each group of filter units, and the outlet switching valve is used to switch the destination of the produced water of each group of filter units and the backwash diversion.

[0014] This invention also provides a bidirectional flow self-cleaning backwashing method, applicable to any of the above-mentioned bidirectional flow self-cleaning modular multi-stage pure water filtration systems, comprising the following steps: during the period when the first filtration unit is producing water in the first flow direction, a portion of the water produced by the first filtration unit is diverted and introduced into the second filtration unit in the second flow direction to backwash the second filtration unit; the backwash water generated from rinsing the second filtration unit is recycled and reused through a backwash water recovery pipeline; after the second filtration unit has finished rinsing, the second filtration unit is switched to producing water in the first flow direction, and a portion of the water produced by the second filtration unit is diverted to backwash the first filtration unit; this process is repeated alternately, so that the two sets of filtration units alternately undertake the roles of water production and backwashing.

[0015] The technical solution provided by this invention has the following beneficial effects: By using two sets of parallel filtration units to alternately produce water and backwash, the backwashing medium is directly taken from the water produced by the other set of filtration units, without consuming additional external backwashing water. The backwash water is recycled and reused through a recovery pipeline instead of being directly discharged, which significantly reduces water waste during the backwashing process. The bidirectional backwashing eliminates the dead angle on the back pressure side of the unidirectional backwashing, making the backwashing more thorough and helping to delay filter clogging and extend the service life of the filter element. To further explain, regarding the thoroughness of backwashing, the backwash water flows from the outlet side of the filter element to the inlet side, opposite to the normal water production direction. This effectively removes contaminants adhering to the inlet side of the filter element. Furthermore, the backwash water flows evenly across the entire cross-section of the filter element, avoiding the dead zones on the back pressure side present in unidirectional backwashing. Regarding water conservation, the backwash medium is directly taken from the water produced by another filtration unit, eliminating the need for a separate backwash water source. The backwash water is also recycled and reused through a recovery pipeline, resulting in minimal additional water consumption during the backwashing process. Regarding the continuity of water production, the two filtration units alternate between water production and backwashing, ensuring that at least one unit is always in production, preventing interruption of water flow. It should be noted that the recycling and reuse of backwash water requires the pre-filter element to bear an additional load of contaminants from the backwash water, placing higher demands on its interception capacity. This trade-off can be balanced by appropriately increasing the nominal capacity of the pre-filter element or shortening its replacement cycle, representing an acceptable engineering compromise. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the bidirectional flow self-cleaning modular multi-stage pure water filtration system of the present invention.

[0017] In the diagram: 1. First filtration unit; 2. Second filtration unit; 11. First-stage filter element; 12. Second-stage filter element; 13. Third-stage filter element; 14. Fourth-stage filter element; 3. Two-way switching valve assembly; 31. Inlet water switching valve; 32. Outlet water switching valve; 4. Controller; 5. Backwash water recovery pipeline; 6. Differential pressure detection unit; 7. Modular interface. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] Reference Figure 1 The bidirectional flow self-cleaning modular multi-stage pure water filtration system of this embodiment includes two sets of parallel filtration units, namely the first filtration unit 1 and the second filtration unit 2. Each set of filtration units has multiple filter cartridges connected in series along the water flow direction. Taking the first filtration unit 1 as an example, it has a first-stage filter cartridge 11, a second-stage filter cartridge 12, a third-stage filter cartridge 13, and a fourth-stage filter cartridge 14 connected in series along the forward water production direction. The first-stage filter cartridge 11 can be a polypropylene cotton filter cartridge to intercept large particulate impurities such as silt, rust, and colloids in the raw water; the second-stage filter cartridge 12 can be a granular activated carbon filter cartridge to adsorb residual chlorine and some organic matter; the third-stage filter cartridge 13 can be a reverse osmosis membrane filter cartridge to remove dissolved salts and most organic matter; and the fourth-stage filter cartridge 14 can be a post-activated carbon filter cartridge to improve the taste of the produced water. It should be noted that the number of stages and types of filter cartridges mentioned above are only examples. In practice, the number of stages or the type of filter cartridge can be increased or decreased or changed according to the raw water quality and product water requirements. For example, when the raw water hardness is high, a resin softening filter cartridge can be added before the reverse osmosis membrane filter cartridge.

[0020] The specific parallel connection relationship of the two sets of filter units is as follows. The inlet ends of the first filter unit 1 and the second filter unit 2 are respectively connected to the inlet switching valve 31 through their respective inlet branches, and the outlet ends are respectively connected to the outlet switching valve 32 through their respective outlet branches. A first inlet valve is provided on the inlet branch of the first filter unit 1, and a second inlet valve is provided on the inlet branch of the second filter unit 2, which are used to close the inlet branch of the filter unit to be rinsed during backwashing. Inside each filter unit, multiple filter elements are connected in series, and adjacent filter elements are connected by a connecting pipe. A one-way valve can be installed on the connecting pipe to prevent backflow. It should be noted that the one-way valve is not necessary and can be selected whether to install it according to the actual water flow control requirements.

[0021] A bidirectional switching valve assembly 3 is connected between the inlet and outlet ends of two sets of filter units, used to switch each set of filter units between a first flow direction and a second flow direction. The bidirectional switching valve assembly 3 includes an inlet switching valve 31 and an outlet switching valve 32. The inlet switching valve 31 is used to switch the inlet water source of each set of filter units, allowing raw water from the raw water inlet pipe to enter the first filter unit 1 or the second filter unit 2, or allowing backwash water to enter the filter unit to be rinsed; the outlet switching valve 32 is used to switch the product water destination and backwash diversion of each set of filter units, allowing forward product water to enter the pure water outlet pipe, or allowing a portion of the diverted product water to enter the filter unit to be rinsed as backwash medium.

[0022] Controller 4 is electrically connected to bidirectional switching valve group 3 and is used to perform timing control of alternating backflush. Its specific working process is as follows. In the first working state, refer to... Figure 1 The first filtration unit 1 produces water in the first direction of flow. Raw water enters the first filtration unit 1 through the raw water inlet pipe and passes through each stage of filter cartridges to become pure water. Most of the pure water enters the pure water outlet pipe through the outlet switching valve 32 for user use. At the same time, the controller 4 controls the outlet switching valve 32 to divert a small portion of the water produced by the first filtration unit 1, which is then reversed through the bidirectional switching valve group 3 and introduced into the second filtration unit 2 in the second direction of flow to backwash each stage of the filter cartridges in the second filtration unit 2. The backwash water generated by backwashing the second filtration unit 2 contains the flushed contaminants and is recycled and reused through the backwash water recovery pipeline 5, rather than being directly discharged.

[0023] After the second filter unit 2 has finished rinsing, the system switches to the second operating state. The second filter unit 2 switches to the first forward flow water production state, with most of the produced water entering the pure water outlet pipe. The diverted portion of the produced water is then reversed and fed into the first filter unit 1 to backwash it. The backwash water generated during the backwashing of the first filter unit 1 is also recycled and reused through the backwash water recovery pipe 5. This process is repeated alternately, with the two filter units taking turns to perform the roles of water production and backwashing. The entire system always maintains at least one filter unit in the forward water production state, ensuring uninterrupted water production.

[0024] During backwashing, the backwash medium, which is a portion of the permeable water diverted from the forward permeable water filtration unit, enters from the outlet end of the filter unit to be rinsed and passes through each filter element in the opposite direction to the normal permeable water flow. This reverses the flow, removing contaminants trapped on the inlet side of each filter element. The backwash medium then flows out from the inlet end of the filter unit to be rinsed, carrying the contaminants with it, and enters the backwash water recovery pipeline 5. Since the backwash medium itself is already filtered pure water, it does not introduce new contaminants when passing through the filter elements in reverse, effectively removing and carrying away the impurities already trapped inside the filter elements.

[0025] Backwash water recycling and reuse is a key feature of this implementation. The outlet of the backwash water recycling pipeline 5 is connected to the pre-filter at the system inlet, meaning the backwash water is returned to the raw water inlet side and, along with the raw water, re-enters the pre-filter for filtration before re-entering the product water process. In this way, the water resources in the backwash water are recovered, the backwash process does not consume additional external backwash water, and backwash water is not directly discharged, thereby reducing the overall wastewater ratio of the system. It should be noted that backwash water recycling and reuse will cause the pre-filter, especially the first-stage filter 11, to bear an additional portion of the contaminant load from the backwash water. Therefore, in this implementation, the first-stage filter 11 uses a larger nominal capacity or its replacement cycle is appropriately shortened to balance this cost. This trade-off is inherent to the backwash water recycling scheme and is an acceptable engineering choice.

[0026] To avoid pressure fluctuations and water hammer during the switching of the bidirectional switching valve assembly 3, this embodiment incorporates a pre-pressurization buffer in the flow path between the bidirectional switching valve assembly 3 and each filter unit. Before switching valve positions, the controller 4 pre-pressurizes the flow path to be switched into, balancing the pressure in that flow path with adjacent flow paths before completing the valve position switch. The pre-pressurization buffer can be a small-volume elastic energy storage chamber that absorbs pressure spikes during switching through an elastic diaphragm. It should be noted that the pre-pressurization buffer occupies some installation space and increases costs slightly. For applications with ample installation space and low water hammer requirements, the pre-pressurization buffer can be omitted, and valve position switching can be performed directly.

[0027] A differential pressure detection unit 6 is connected in parallel between the inlet and outlet of each filtration unit, and the differential pressure detection unit 6 is electrically connected to the controller 4. The differential pressure detection unit 6 monitors the pressure difference between the inlet and outlet of the filtration unit in real time. When the pressure difference increases to a preset threshold, it indicates that the pre-filter of the filtration unit has become significantly clogged, and the controller 4 triggers backwashing of the filtration unit accordingly. Using pressure difference as the backwash trigger condition, compared to backwashing at fixed time intervals, avoids water waste caused by premature backwashing before the filter element is clogged, and also avoids the decrease in flow rate caused by backwashing only when the filter element is severely clogged.

[0028] Each filtration unit's multi-stage filter cartridges are installed in the corresponding flow path via pluggable modular interfaces 7. Modular interfaces 7 can use quick-connect sealing joints, allowing each stage of filter cartridge to be removed and replaced independently. Since at least one filtration unit is always in positive water production mode, when a specific stage of a filter cartridge needs replacement, that filtration unit can be disconnected from the water production flow, and another filtration unit can take over water production, completing the cartridge replacement without interrupting overall water production. This is a significant advantage over traditional methods that require complete system shutdown for cartridge replacement. Of course, the quick-connect seals of the modular interfaces 7 will gradually wear down with frequent insertion and removal, requiring periodic inspection and replacement of the sealing rings—an inherent maintenance requirement of modular design.

[0029] It should be noted that the "multi-stage" and "modular" features of this invention are subordinate and auxiliary structural characteristics. The core improvement of this invention lies in the bidirectional alternating backwashing between the two sets of filtration units and the recycling and reuse of backwash water. The fact that the backwash medium is directly taken from the production water and the backwash water is recycled and reused allows this invention to achieve a balance between thorough backwashing and water conservation, which is the main contribution of this invention compared to the prior art.

[0030] The following are specific parameters for this embodiment, which are for illustrative purposes only and not for limitation. Raw water from the inlet pipe is pressurized by a booster pump before entering the filtration unit. The rated production water flow rate of the system can be set according to actual needs. The backwash diversion ratio (i.e., the proportion diverted from the forward production water for backwashing) can be set to a small value, such as a percentage of the production water flow rate. This can be adjusted according to the degree of filter clogging and backwashing requirements. An excessively large diversion ratio will affect the total system production water, while an excessively small diversion ratio will result in insufficient backwashing. A balance needs to be struck between production water efficiency and backwashing effect. The preset trigger threshold of the differential pressure detection unit 6 can be calibrated according to the allowable pressure drop range of the upstream filter element. The backwash duration can be set to a fixed duration or dynamically determined based on the turbidity of the backwash water or the decrease in differential pressure.

[0031] The second implementation further defines the backwash water recovery path based on the first implementation. Specifically, the outlet of the backwash water recovery pipe 5 is not directly connected to the raw water inlet pipe, but is first connected to a backwash water buffer tank. After the backwash water settles in the buffer tank, the supernatant is returned to the raw water inlet pipe side, while the settled contaminants are periodically discharged. This method can reduce the contaminant load on the pre-filter cartridge and further extend its service life, at the cost of increasing the residence time required for the backwash water buffer tank and its settling.

[0032] The third implementation further defines the backwash triggering method based on the first implementation. Specifically, the controller 4 not only triggers backwashing based on the differential pressure detection unit 6, but also combines the cumulative water production or cumulative running time of the filter unit. When the cumulative water production or cumulative running time reaches a preset value, a backwash is triggered even if the differential pressure has not yet reached the threshold, to preventively remove initial blockages that have not yet caused a significant increase in differential pressure. This combination of differential pressure triggering and periodic preventive backwashing can restore the filter cartridge flow rate in time before the blockage worsens. The trade-off is that preventive backwashing may consume a small amount of backwash water while the filter cartridge is still clean.

[0033] The specific structure of the bidirectional switching valve group 3 can be implemented as follows: Both the inlet switching valve 31 and the outlet switching valve 32 are electrically controlled directional valves, such as three-position four-way solenoid directional valves, or valve groups composed of multiple two-position two-way solenoid valves. Taking the inlet switching valve 31 as an example, it has a raw water inlet, a first outlet, a second outlet, and a backwash water inlet. The raw water inlet is connected to the raw water inlet pipe, the first outlet is connected to the inlet end of the first filter unit 1, the second outlet is connected to the inlet end of the second filter unit 2, and the backwash water inlet is connected to the backwash water recovery pipe 5. When the inlet switching valve 31 is switched to the first valve position, the raw water enters the first filter unit 1 through the first outlet; when switched to the second valve position, the raw water enters the second filter unit 2 through the second outlet. The outlet switching valve 32 has a first inlet, a second inlet, a pure water outlet, and a backwash diversion port. The first inlet is connected to the outlet of the first filter unit 1, the second inlet is connected to the outlet of the second filter unit 2, the pure water outlet is connected to the pure water outlet pipe, and the backwash diversion port is used to direct the diverted product water to the filter unit to be rinsed. Regarding the implementation of dead water switching, in this embodiment, the valve cores of the inlet switching valve 31 and the outlet switching valve 32 adopt a rotary structure. During the valve core switching position, its internal flow channel first connects to the target valve port and then disconnects from the original valve port (first open, then disconnected), so that at any time during switching, there will be no dead water zone with a completely closed flow path, avoiding the stagnant water in the dead water zone from entering the product water after switching and affecting the product water quality. It should be noted that the above valve body structure is only an example. Those skilled in the art can use other types of reversing valves or valve combinations as needed to achieve the same flow direction switching function, as long as it can realize the switching of each group of filter units between the first flow direction and the second flow direction.

[0034] The alternating backwash sequence of controller 4 can be set as follows. Controller 4 executes cyclically with one backwash cycle as the basic unit: within each backwash cycle, it first maintains the state of water production from the first filter unit 1 and backwashing from the second filter unit 2 for a first duration, then switches to the state of water production from the second filter unit 2 and backwashing from the first filter unit 1 for a second duration. The first duration and the second duration can be equal, or they can be set separately according to the degree of clogging of the two filter units, for example, a longer backwash duration can be set for the more heavily clogged filter unit. Before each valve position switch, controller 4 first closes the backwash diversion port and pre-pressurizes the flow path to be switched into. After the pressure stabilizes, it switches the valve position and opens the backwash diversion port to avoid pressure spikes and water backflow at the moment of switching. Throughout the alternation process, pure water is always output from the pure water outlet pipe, and water production is uninterrupted.

[0035] The relationship between backwash water recovery and the wastewater ratio warrants further explanation. For reverse osmosis water purifiers, the reverse osmosis membrane produces concentrate during the water production process, which is typically discharged directly, constituting the main source of wastewater for the water purifier. In this embodiment, the backwash water recovery pipeline 5 recovers and reuses the backwash water, but the concentrate from the reverse osmosis membrane itself still needs to be discharged normally. The improvement of this invention lies in eliminating the additional water consumption of the backwashing process; that is, backwashing no longer consumes additional external backwash water sources or discharges additional backwash water, thereby reducing the overall water consumption of the system except for the reverse osmosis concentrate. It should be noted that backwash water recovery and reuse does not directly reduce the reverse osmosis concentrate ratio. If it is desired to further reduce the total wastewater ratio, existing concentrate recovery or concentrate recirculation technologies can be combined, but this part is not a necessary technical feature of this invention.

[0036] The fourth implementation method further defines the backwash water recovery path based on the first implementation method. Specifically, the outlet of the backwash water recovery pipeline 5 is not directly connected to the raw water inlet pipe, but is first connected to the backwash water buffer tank. After the backwash water settles in the buffer tank, the supernatant is returned to the raw water inlet pipe side, and the settled contaminants are periodically discharged. This method can reduce the contaminant load on the pre-filter and extend the life of the pre-filter, at the cost of increasing the buffer tank and its residence time.

[0037] The fifth implementation further defines the backwash triggering method based on the first implementation. Specifically, the controller 4 combines the differential pressure of the differential pressure detection unit 6 with the cumulative water production or cumulative running time of the filter unit. When the differential pressure reaches a preset threshold, or the cumulative water production or cumulative running time reaches a preset value, backwashing is triggered to preventively remove initial blockages. The trade-off is that preventative backwashing may consume a small amount of backwash water while the filter element is still clean.

[0038] A sixth embodiment provides a bidirectional flow self-cleaning backwashing method applied to the above-described system. The method includes: during the forward water production of the first filter unit 1 in a first flow direction, a portion of the produced water from the first filter unit 1 is diverted and introduced into the second filter unit 2 in a second flow direction to backwash the second filter unit 2; the backwash water generated during the backwashing of the second filter unit 2 is recovered and reused via a backwash water recovery pipeline 5; after the second filter unit 2 has finished washing, the second filter unit 2 is switched to produce water in the first flow direction, and a portion of the produced water from the second filter unit 2 is diverted to backwash the first filter unit 1; this process is repeated alternately. Before switching valve positions, the flow path to be switched into is pre-pressurized before the valve position switch is completed.

[0039] Regarding the structural details of the modular interface 7, in this embodiment, the modular interface 7 can be a quick-connect sealing connector, including an interface seat and an interface core. The interface core is fixedly connected to the end of the filter element, and the interface seat is fixed in the flow path. After the interface core is inserted into the interface seat, it is sealed by a sealing ring and can be locked by rotation or snap-fit. Each stage of the filter element is installed independently through the corresponding modular interface 7. When replacing a certain stage of the filter element, it is only necessary to pull out the corresponding interface core of that stage of the filter element and insert the new filter element, without disassembling the entire filter unit. It should be noted that the sealing ring of the quick-connect sealing connector will gradually wear down under frequent insertion and removal, and needs to be inspected and replaced regularly. This is an inherent maintenance requirement of the modular design.

[0040] Regarding the adaptation of the filter cartridge stage to the raw water quality, the number and type of filter cartridges in this embodiment can be flexibly adjusted according to the raw water quality. When the raw water turbidity is high, a pre-sedimentation or pre-coarse filtration unit can be added before the first-stage filter cartridge 11; when the raw water hardness is high, a resin softening filter cartridge can be added before the reverse osmosis membrane filter cartridge to reduce the risk of scaling; when the raw water residual chlorine is high, the filling amount of granular activated carbon filter cartridge can be increased. The above adaptations are all conventional methods in this field. The core of this invention lies in the bidirectional alternating backwashing of the two sets of filtration units and the recycling and reuse of backwash water, rather than in the specific selection of the filter cartridge stage.

[0041] Further explanation regarding the backwash diversion ratio: The backwash diversion ratio refers to the proportion of the flow rate diverted from the forward permeate for backwashing relative to the permeate flow rate of this filtration unit. The selection of this ratio requires a trade-off between permeate efficiency and backwashing effectiveness: if the diversion ratio is too large, although the backwash flow rate is sufficient and the backwashing is thorough, it will significantly reduce the total amount of pure water available to the user; if the diversion ratio is too small, the backwash flow rate will be insufficient, making it difficult to effectively remove contaminants from the filter element. In this embodiment, the backwash diversion ratio can be dynamically adjusted according to the degree of filter element clogging. For example, when the differential pressure detection unit 6 detects a high differential pressure and severe filter element clogging, the backwash diversion ratio is appropriately increased; when the filter element is relatively clean, the backwash diversion ratio is decreased. This dynamic adjustment method can minimize the impact on the total permeate flow while ensuring the backwashing effect.

[0042] Regarding the structural details of the pre-pressurization buffer, in this embodiment, the pre-pressurization buffer is an elastic energy storage chamber. An elastic diaphragm is installed inside the chamber, dividing it into a gas chamber and a liquid chamber. The liquid chamber is connected to the flow path to be switched into. When the controller 4 pre-pressurizes a certain flow path, a small amount of water is first introduced into the pre-pressurization buffer of that flow path. The elastic diaphragm deforms under pressure to absorb pressure fluctuations. After the pressure in that flow path tends to balance with the adjacent flow path, the valve position is switched. The volume of the pre-pressurization buffer does not need to be large; it only needs to be able to absorb the pressure spike at the moment of switching. It should be noted that the pre-pressurization buffer is not a necessary technical feature for realizing this invention. For applications with low switching frequency or insensitivity to water hammer, the pre-pressurization buffer can be omitted, and the controller 4 can directly switch the valve position.

[0043] In addition, this system can also be equipped with a display unit or status indicator unit electrically connected to the controller 4, used to display to the user which group of filter units is currently in water production state, which group is in backwashing state, and the remaining life or replacement reminder of each stage of filter element. This setting is a conventional monitoring method and does not affect the core concept of this invention.

[0044] The raw water inlet pipe supplies raw water to the system, while the pure water outlet pipe outputs filtered pure water. The inlet end of the raw water inlet pipe can be connected to the municipal water supply line or a water storage container, and the outlet end of the pure water outlet pipe can be connected to the user's water terminal or a water storage container. A booster pump is typically installed on the raw water inlet pipe to provide sufficient filtration pressure for the filtration unit, especially to meet the water production pressure requirements of the reverse osmosis membrane filter cartridge.

[0045] To further illustrate the technical effects of the present invention, comparative examples are provided below. It should be noted that the following comparative examples are only used to illustrate differences in technical concepts; the specific numerical effects should be based on actual testing.

[0046] Comparative Example 1: Unidirectional backwashing. Backwash water only flows from the outlet side of the filter element to the inlet side in a single direction. There are cleaning dead zones on the back pressure side of the filter element. After long-term operation, pollutants accumulate irreversibly in the dead zones, resulting in incomplete backwashing.

[0047] Comparative Example 2: Offline backwashing. During backwashing, water production is stopped, and the system switches to a bypass for backwashing. Water production is interrupted, and backwash water needs to be supplied and discharged separately.

[0048] Comparative Example 3: Two-way backwashing without recycling backwash water. Although two-way backwashing eliminates dead zones, the backwash water is discharged directly, and the backwashing process still consumes additional water resources.

[0049] Compared with the above comparative examples, the present invention utilizes two sets of parallel filtration units to alternately produce water and backwash, with the backwash medium directly taken from the produced water and the backwash water recycled and reused. It simultaneously achieves the balance of bidirectional backwashing without dead angles, uninterrupted water production, and zero additional water consumption for backwashing, which are technical effects that comparative examples 1, 2, and 3 cannot achieve at the same time.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A bidirectional flow self-cleaning modular multi-stage pure water filtration system, comprising at least two groups of filtration units connected in parallel, each group of the filtration units having a plurality of filter cartridges connected in series along the water flow direction, characterized in that, It also includes a two-way switching valve assembly (3), a controller (4), and a backwash water recovery pipeline (5); The bidirectional switching valve group (3) is connected to the inlet and outlet of each group of filter units, and is used to switch each group of filter units between a first flow direction and a second flow direction. The first flow direction is the forward water production direction, and the second flow direction is the reverse flushing direction. When the bidirectional switching valve group (3) switches valve positions, it first connects the target flow path and then disconnects the original flow path; The controller (4) is electrically connected to the bidirectional switching valve group (3) and is configured to: during the period when the first filter unit (1) produces water in the first direction, a portion of the water produced by the first filter unit (1) is diverted and passed into the second filter unit (2) in the second direction through the bidirectional switching valve group (3) to backwash the second filter unit (2), and the backwash water generated by backwashing the second filter unit (2) is recycled and reused through the backwash water recovery pipeline (5); After the second filter unit (2) has finished rinsing, the second filter unit (2) is switched to produce water in the first direction, and part of the water produced by the second filter unit (2) is reversed to rinse the first filter unit (1), and this process is repeated alternately.

2. The bidirectional flow self-cleaning modular multi-stage pure water filtration system of claim 1, wherein, During the switching process of the bidirectional switching valve group (3), the controller (4) first pre-pressurizes the flow path to be switched into, and then completes the valve position switching to reduce the pressure fluctuation at the moment of switching.

3. The bidirectional flow self-cleaning modular multi-stage pure water filtration system of claim 1, wherein, Each group of filter units is provided with a differential pressure detection unit (6) connected in parallel between the inlet and outlet ends. The differential pressure detection unit (6) is electrically connected to the controller (4). The controller (4) triggers backwashing when the differential pressure detected by the differential pressure detection unit (6) reaches a preset threshold.

4. The bidirectional flow self-cleaning modular multi-stage pure water filtration system according to claim 1, characterized in that, The outlet of the backwash water recovery pipeline (5) is connected to the pre-filter at the system inlet so that the backwash water is filtered by the pre-filter and then re-enters the production water process.

5. The bidirectional flow self-cleaning modular multi-stage pure water filtration system according to claim 1, characterized in that, The multi-stage filter elements of each filter unit are installed in the corresponding flow path through a pluggable modular interface (7), and each stage of filter element can be replaced independently without stopping the machine.

6. The bidirectional flow self-cleaning modular multi-stage pure water filtration system according to claim 1, characterized in that, The bidirectional switching valve group (3) includes an inlet switching valve (31) and an outlet switching valve (32). The inlet switching valve (31) is used to switch the inlet water source of each group of filter units, and the outlet switching valve (32) is used to switch the production water destination and backwash diversion of each group of filter units.

7. The bidirectional flow self-cleaning modular multi-stage pure water filtration system according to claim 1, characterized in that, The bidirectional switching valve group (3) includes a valve body and a rotary valve core. The valve body is provided with a raw water inlet, inlets of each group of filter units, backwash water return outlet, pure water outlet and backwash diversion outlet. The rotary valve core is provided with a connecting flow channel. When the rotary valve core switches valve positions, the connecting flow channel first connects with the target valve port and then disconnects from the original valve port to achieve switching without dead water.

8. A backwashing method for the bidirectional flow self-cleaning modular multi-stage pure water filtration system according to any one of claims 1 to 7, characterized in that, Includes the following steps: During the first filtration unit (1) producing water in the first flow direction, the flow path that is about to be switched into in the bidirectional switching valve group (3) is pre-pressurized; A portion of the water produced by the first filter unit (1) is diverted and introduced into the second filter unit (2) in the second flow direction to backwash the second filter unit (2). The backwash water generated from rinsing the second filter unit (2) is recycled and reused through the backwash water recovery pipeline (5); After the second filter unit (2) is flushed, the flow path to be switched into is pre-pressurized, and then the second filter unit (2) is switched to the first flow direction for positive water production. A portion of the product water from the second filter unit (2) is reverse-flowed to flush the first filter unit (1); This alternation allows the two sets of filtration units to take turns performing the functions of water production and backwashing.

Images