Water purification system

Abstract

The utility model discloses a water purification system, belongs to the technical field of water purification, and is designed for solving the problems that a whole water purification pipeline cannot be sterilized and disinfected and the like in the prior art. The utility model discloses a water purification system which comprises a purification filter element, the sterilization backflow water path is used for conveying sterilization substances to a pipeline in the water purification system, the sterilization backflow water path crosses the purification filter element, and the water purification system can selectively use the purification filter element for water purification or use the sterilization backflow water path for sterilization. The sterilization backflow waterway of the water purification system disclosed by the utility model can be used for conveying sterilization substances to the pipeline in the water purification system, so that bacteria, microorganisms and the like in the pipeline in the water purification system are killed, the water outlet safety of the water purification system is improved, and drinking water is more sanitary; the sterilization backflow water path crosses the purification filter element, so that sterilization substances cannot flow through the purification filter element and are prevented from damaging the purification filter element, and the service life of the water purification system is prolonged.

Description

Technical Field

[0001] The utility model relates to the technical field of water purification, in particular to a water purification system. Background Art

[0002] A water purifier is a device that can purify raw water (tap water or surface water) into pure water, in which the main device used for purification is the filter element. The filter material in the filter element can be but is not limited to PP cotton, activated carbon, ultrafiltration membrane, nanofiltration membrane and reverse osmosis membrane.

[0003] The filter element of an existing water purifier is usually connected to the water inlet pipe at the inlet end, the water outlet end to the water purification pipeline, and the concentrated water outlet to the concentrated water pipe. The raw water enters the filter element through the water inlet pipe, and the purified water obtained after filtration is provided to the user through the water purification pipeline, and the concentrated water obtained after filtration is discharged through the concentrated water pipe. At the filter element, water flows in one direction. Once bacteria in the air gradually grow into the water purifier through the water purification faucet at the end of the water purification pipeline, the filter element cannot sterilize and purify; in addition, because the production environment and sales cycle of the water purifier are uncertain, bacteria may exist inside the newly installed water purifier. When the water purifier is left unused for a long time, a large number of bacteria, viruses and microorganisms will grow inside the water purifier, resulting in the total colony count of the purified water exceeding the standard, microbial metabolites will produce a foul odor, and the taste of purified water will deteriorate.

[0004] In order to solve this problem, some existing water purifiers add ultraviolet lamps at the rear end of pure water to kill microorganisms and bacteria using ultraviolet rays. The defects of this device include: the bodies of killed microorganisms and bacteria are still in the water purification pipeline and are provided to users for drinking along with the purified water; in addition, the microorganisms and bacteria in the water purification pipeline located in front of the ultraviolet lamp cannot be killed, resulting in odor in the filter element and biological contamination of the RO membrane. Utility Model Content

[0005] The utility model aims to provide a water purification system, which solves the problem that the prior art cannot sterilize the entire water purification pipeline, and the output water is more hygienic.

[0006] To achieve this purpose, the utility model adopts the following technical solutions:

[0007] A water purification system includes: a purification filter element; and a sterilization return waterway for conveying sterilizing substances to the pipeline in the water purification system. The sterilization return waterway passes over the purification filter element. The water purification system can selectively use the purification filter element for water purification or use the sterilization return waterway for sterilization.

[0008] In one of the preferred embodiments, the water purification system includes an inlet waterway and a pure water waterway, the sterilization return waterway includes a jumper waterway, the inlet waterway is connected to the water inlet end of the purification filter element, and the pure water waterway is connected to the water outlet end of the purification filter element; a connection endpoint A is provided on the inlet waterway, and a connection endpoint B is provided on the pure water waterway, one end of the jumper waterway is connected to the connection endpoint A, and the other end is connected to the connection endpoint B.

[0009] In one of the preferred embodiments, the water purification system also includes three water inlet on-off valves, the first water inlet on-off valve is arranged on the water inlet waterway and located between the connection end point A and the purification filter element, the second water inlet on-off valve is arranged on the bridge waterway, and the third water inlet on-off valve is arranged on the sterilization return waterway.

[0010] In one of the preferred embodiments, one end of the pipe of the sterilization return water circuit is connected to the water inlet water circuit, and the other end is connected to the pure water water circuit, and the water flow can flow in a ring-shaped pipe formed by the sterilization return water circuit, part of the water inlet water circuit, the jumper water circuit, and part of the pure water water circuit.

[0011] In one of the preferred embodiments, the water inlet waterway includes a pre-composite filter element and a booster pump sequentially arranged along the water flow direction, the booster pump is located upstream of the connection end point A, one end of the pipe of the sterilization return waterway is connected to the water inlet waterway and is located upstream of the pre-composite filter element; and / or, the pure water waterway includes a post-activated carbon filter element, the connection end point B is located between the purification filter element and the post-activated carbon filter element, the other end of the pipe of the sterilization return waterway is connected to the pure water waterway and is located downstream of the post-activated carbon filter element.

[0012] In one of the preferred embodiments, the sterilization return water circuit includes an ozone generator, which is used to produce ozone and send the ozone into the pipeline of the sterilization return water circuit.

[0013] In one of the preferred embodiments, the sterilization return water circuit further includes a flow meter, and the flow meter is used to detect the water flow in the pipeline of the sterilization return water circuit.

[0014] In one of the preferred embodiments, the sterilization return water circuit further includes a one-way valve, and the one-way valve is used to prevent the water in the pipe of the sterilization return water circuit from flowing back.

[0015] In one of the preferred embodiments, the water purification system includes a connected control device and a human-computer interaction section, and a machine sterilization button is provided on the human-computer interaction section, and the machine sterilization button can input a sterilization instruction to the control device; and / or, the water purification system includes a control device, and the control device can receive a signal sent by a mobile terminal, and the mobile terminal can input a sterilization instruction to the control device.

[0016] In one preferred embodiment, the purification filter element includes a reverse osmosis membrane or a nanofiltration membrane.

[0017] The water purification system disclosed by the utility model can selectively use a purification filter element for water purification or a sterilization return waterway for sterilization. The newly added sterilization return waterway can transport sterilizing substances to the pipes in the water purification system, thereby killing bacteria, microorganisms, etc. in the pipes in the water purification system, improving the safety of water output from the water purification system and making drinking water more hygienic; the sterilization return waterway passes over the purification filter element, ensuring that the sterilizing substances will not flow through the purification filter element, avoiding the sterilizing substances from damaging the purification filter element, and achieving sterilization of the pipes in the water purification system without affecting the normal water purification of the water purification system, thereby extending the service life of the water purification system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of a water purification system provided by a specific embodiment of the utility model;

[0019] Figure 2 It is a control logic diagram of a water purification system provided by a specific implementation method of the utility model;

[0020] Figure 3 The present invention is a flow chart of a water purification system for sterilizing and disinfecting the entire pipeline provided by a specific implementation method of the present invention. DETAILED DESCRIPTION

[0021] In order to make the above-mentioned purposes, features and advantages of the utility model more obvious and easy to understand, the specific implementation methods of the utility model are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the utility model. However, the utility model can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the utility model. Therefore, the utility model is not limited by the specific implementation methods disclosed below.

[0022] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0023] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present utility model, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0024] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] In the present utility model, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean 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, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0026] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0027] This embodiment discloses a water purification system, such as Figure 1 As shown, the water purification system includes a purification filter element and a sterilization return waterway, the sterilization return waterway passes over the purification filter element, and the water purification system can selectively use the purification filter element for water purification or use the sterilization return waterway for sterilization. Among them, the purification filter element preferably includes a reverse osmosis membrane or a nanofiltration membrane.

[0028] The newly added sterilization return water circuit can transport sterilizing substances to the pipes in the water purification system, thereby killing bacteria, microorganisms, etc. in the pipes in the water purification system, improving the safety of the water output from the water purification system and making drinking water more hygienic; the sterilization return water circuit passes over the purification filter element, ensuring that sterilizing substances will not flow through the purification filter element, avoiding damage to the purification filter element by sterilizing substances, and achieving sterilization of the pipes in the water purification system without affecting the normal water purification of the water purification system, thereby extending the service life of the water purification system.

[0029] Based on the above structure, the water purification system includes an inlet waterway, a pure water waterway and a concentrated water waterway, and the sterilization return waterway includes a crossover waterway. The inlet waterway is connected to the water inlet end of the purification filter element, the pure water waterway is connected to the water outlet end of the purification filter element, and the concentrated water waterway is connected to the concentrated water outlet end of the purification filter element.

[0030] A connection terminal A is formed on the inlet waterway, a connection terminal B is formed on the pure water waterway, one end of the bridging waterway is connected to the connection terminal A, and the other end is connected to the connection terminal B. After the water flow in the inlet waterway reaches the connection terminal A, it changes to enter the bridging waterway; after passing through the bridging waterway, it changes to enter the pure water waterway at the connection terminal B, so that the water flow carrying the sterilizing substance will not pass through the purification filter element, thereby protecting the purification filter element from being damaged by the sterilizing substance.

[0031] In order to enable the water purification system to selectively use the purification filter element for water purification or use the sterilization return waterway for sterilization, in this embodiment, the water purification system also includes three water inlet on-off valves: the first water inlet on-off valve is arranged on the water inlet waterway and is located between the connection end point A and the purification filter element, and can control the on-off of the water flow in the water inlet waterway; the second water inlet on-off valve is arranged on the jumper waterway, and can control the on-off of the jumper waterway; the third water inlet on-off valve is arranged on the sterilization return waterway, and can control the on-off of the sterilization return waterway.

[0032] The specific structure of the on-off valve is not limited, as long as it can control the on and off of the pipeline. In this embodiment, the three on-off valves can be but are not limited to solenoid valves, which have stable product performance, fast response speed and low cost. The three solenoid valves are independent of each other, and the on and off state of one solenoid valve will not affect the on and off of other solenoid valves.

[0033] On the basis of the above structure, one end of the sterilization return waterway is connected to the water inlet waterway and the other end is connected to the pure water waterway, and the water can flow in the annular pipe formed by the sterilization return waterway, part of the water inlet waterway, the bridging waterway, and part of the pure water waterway. That is, the section of the water inlet waterway from the point connected to the sterilization return waterway to the connection end point A is a common section, which is the "water inlet waterway" during normal water purification operation and the "sterilization return waterway" during sterilization operation; similarly, the section of the pure water waterway from the connection end point B to the point connected to the sterilization return waterway is also a common section, which is the "pure waterway" during normal water purification operation and the "sterilization return waterway" during sterilization operation.

[0034] After using part of the inlet waterway and part of the pure water waterway, the sterilization return waterway forms a closed loop pipeline, and the sterilizing substance can flow in the loop pipeline to achieve full pipeline sterilization. When the water purification system is not used for a long time, bacteria and microorganisms may breed in the internal pipeline. By circulating the sterilizing substance in the loop pipeline, the whole pipeline can be sterilized and disinfected, thereby inhibiting the growth of microorganisms inside the water purification system, and the drinking water provided by the water purification system is more hygienic and safer to drink.

[0035] On the basis of the above structure, the water inlet circuit includes a pre-composite filter element and a booster pump arranged in sequence along the water flow direction, the booster pump is located upstream of the connection end point A, and one end of the pipe of the sterilization return water circuit is connected to the water inlet circuit and is located upstream of the pre-composite filter element. Among them, the pre-composite filter element can be, but is not limited to, a combination structure of PP cotton and activated carbon, a PAC composite filter element, or a PCU composite filter element, etc., which has a better pretreatment effect on raw water.

[0036] The pure water circuit includes a post-activated carbon filter element, and the connection end point B is located between the purification filter element and the post-activated carbon filter element. The other end of the sterilization return waterway pipe is connected to the pure water circuit and is located downstream of the post-activated carbon filter element. The specific structure of the post-activated carbon filter element is not limited, and the post-activated carbon filter element in the existing water purification device can be used. Various existing post-activated carbon filter elements do not affect the use of the water purification system of this embodiment.

[0037] When sterilizing the entire pipeline, the bactericidal substances can pass through the pre-composite filter element, booster pump and post-activated carbon filter element, and the scope of sterilization is wider and more thorough, preventing bacteria and microorganisms that grow in the pre-composite filter element, booster pump and post-activated carbon filter element from entering the pure water.

[0038] On the basis of the above structure, the specific type of bactericidal substance is not limited, as long as it can kill bacteria and microorganisms in the water pipe. In this embodiment, the sterilization return water circuit includes an ozone generator, preferably a low-pressure ozone generator, which can adapt to the power supply conditions of the water purification system itself. The ozone generator produces ozone with pure water, and can send ozone into the pipeline of the sterilization return water circuit to kill bacteria and microorganisms in the water pipe. The specific structure and model of the ozone generator are not limited, and various ozone generators in the prior art are suitable for the water purification system of this embodiment.

[0039] Ozone and water containing ozone (or ozone water) have strong oxidizing properties and can quickly and thoroughly sterilize and disinfect. After multiple cycles in the sterilization return waterway, ozone and water containing ozone can basically kill all bacteria and microorganisms in the annular pipe of the water purification system. The sterilization return waterway passes over the purification filter element, thereby preventing the strong oxidizing properties of ozone and water containing ozone from oxidizing the functional layer of the reverse osmosis membrane or nanofiltration membrane of the purification filter element, avoiding reducing the purification capacity and purification effect of the purification filter element, and extending the service life of the purification filter element.

[0040] On the basis of the above structure, the sterilization return water circuit also includes a flow meter. The flow meter is used to detect the water flow in the pipe of the sterilization return water circuit, so as to select an ozone generator with an adaptive power to ensure that the amount of ozone generated is sufficient to make the water flow in the pipe form ozone water, thereby improving the sterilization and disinfection ability of the water flow. The power of the ozone generator and the amount of circulating water jointly determine the ozone content in the ozone water. In this embodiment, when the concentration of ozone in the ozone water is in the range of 0.4mg / L-0.6mg / L, the sterilization and disinfection effect is good, the preparation cost of ozone is low, and the cost performance is high. The specific structure of the flow meter is not limited, and any device that can measure the water flow in the pipe in the prior art can be used.

[0041] The sterilization return water circuit also includes a one-way valve, which is preferably arranged downstream of the ozone generator. The one-way valve can prevent the backflow of water in the sterilization return water circuit, prevent the water flow in the pipeline of the water purification system from impacting the outlet end of the ozone generator, and prevent the ozone generated by the ozone generator from being normally dissolved in the water flow, thereby protecting the safety of the ozone generator. The specific structure of the one-way valve is not limited, and any device in the prior art that can limit the one-way flow of water can be used.

[0042] like Figure 2 As shown, the water purification system also includes a connected control device and a human-machine interaction section. A sterilization button is provided on the human-machine interaction section, and the sterilization button can input a sterilization instruction to the control device. At the same time, the control device provided with a sterilization program can receive a signal sent by a mobile terminal, and the mobile terminal can input a sterilization instruction to the control device. The control device controls the ozone generator and the three solenoid valves to respond electronically, and starts to execute the sterilization program of the entire pipeline.

[0043] Specifically, the mobile terminal may be, but is not limited to, a mobile phone, a computer, an IPAD, etc., on which a sterilization APP is installed, and the sterilization instruction can be input into the control device through the sterilization APP, which is more convenient to use. In addition, the sterilization APP can record the time when the sterilization instruction was last executed, the time interval between the current time and the last time the sterilization instruction was executed, and other information, so that the user can judge whether it is necessary to sterilize the entire pipeline again.

[0044] In this embodiment, the control device can be a centralized or distributed controller. For example, the controller can be a single single-chip microcomputer or a distributed plurality of single-chip microcomputers. The control program can be run in the single-chip microcomputer to control three water inlet on-off valves and ozone generators and other devices to realize their functions.

[0045] The factory setting of the water purification system or the user's free setting: a continuous interval of non-operation time T can be judged as "the water purification system has not been used for a long time" and a disinfection and sterilization flushing procedure is required. Figure 3 The control logic of the water purification system for full-pipeline sterilization is shown. After entering the working state, it is necessary to determine whether the machine is installed and used for the first time. For the first installation and use, the sterilization program is pre-performed by default, and then the filter element is flushed or the water production program is performed; if it is not the first installation and use, the interval time t from the last use is recorded. When t exceeds the set time T, the ozone sterilization program needs to be performed. During the entire sterilization process, the water purification system cannot perform other operations.

[0046] During normal water purification, open the first water inlet solenoid valve, close the second water inlet solenoid valve, the third water inlet solenoid valve and the concentrated water combination valve, and the raw water reaches the pre-composite filter element and the booster pump through the water inlet waterway, and enters the purification filter element after being pressurized by the booster pump. After being filtered by the purification filter element, pure water is made and discharged from the pure water waterway; open the concentrated water combination valve, and the concentrated water generated synchronously when the purification filter element makes pure water is discharged through the concentrated water flow.

[0047] Among them, the concentrated water combination valve at least includes a concentrated water on-off valve, which can control the smooth flow and blocking of the concentrated water pipe. On this basis, the concentrated water combination valve can also include a flow limiting valve, which can be connected in parallel or in series with the concentrated water on-off valve. When the flow limiting valve is connected in parallel with the concentrated water on-off valve, the concentrated water on-off valve is opened, and the water flow in the concentrated water pipe is discharged smoothly through the pipeline where the concentrated water on-off valve is located; when the concentrated water on-off valve is closed, the water flow in the concentrated water pipe will be slowly discharged through the pipeline where the flow limiting valve is located, which can not only prevent a small amount of concentrated water generated by the purification filter from accumulating in the concentrated water pipe, but also prevent the concentrated water pipe from being completely emptied, causing external bacteria to grow and spread along the concentrated water pipe toward the purification filter.

[0048] When reflux sterilization is required, close the first water inlet solenoid valve, open the second and third water inlet solenoid valves, and start the ozone generator to prepare ozone gas. The raw water (ozone water) carrying ozone is filtered through the front composite filter, booster pump, cross-connect water channel, post-activated carbon filter and flow meter in sequence to achieve cyclic sterilization of the entire pipeline. The cyclic sterilization time of ozone water is not less than ten seconds to ensure that bacteria and microorganisms in the pipeline can be completely killed.

[0049] After the reflux sterilization procedure is completed, the entire water purification system needs to be flushed with pure water reflux. Pure water reflux is beneficial to improve the static environment of the membrane of the purification filter element, reduce crystallization and ion diffusion on the membrane, and extend the service life of the purification filter element.

[0050] The specific steps of pure water backflow flushing are: first, open the first water inlet solenoid valve and the third water inlet solenoid valve, close the second water inlet solenoid valve, open the concentrated water combination valve, close the ozone generator, and quickly discharge the ozone and ozone water in the water purification system through the concentrated water channel. The execution time of this flushing process is not less than 30 seconds. Then, close the concentrated water combination valve, and replace the clean water in the water purification system with pure water to improve the water quality in the water purification system, which is convenient for users to use, and is conducive to prolonging the service life of the purification filter and improving the first cup of water. The execution time of this stage is not less than 30 seconds.

[0051] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention is described in more detail through the above embodiments, the present invention is not limited to the above embodiments, but may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A water purification system, characterized in that: include: Purification filter element; as well as, The sterilization return waterway is used to transport sterilizing substances to the pipeline in the water purification system. The sterilization return waterway passes over the purification filter element. The water purification system can selectively use the purification filter element for water purification or use the sterilization return waterway for sterilization.

2. The water purification system according to claim 1, characterized in that: The water purification system includes an inlet waterway and a pure water waterway, the sterilization return waterway includes a jumper waterway, the inlet waterway is connected to the water inlet end of the purification filter element, and the pure water waterway is connected to the water outlet end of the purification filter element; a connection endpoint A is provided on the inlet waterway, and a connection endpoint B is provided on the pure water waterway, one end of the jumper waterway is connected to the connection endpoint A, and the other end is connected to the connection endpoint B.

3. The water purification system according to claim 2, characterized in that: The water purification system also includes three water inlet on-off valves, the first water inlet on-off valve is arranged on the water inlet waterway and located between the connection end point A and the purification filter element, the second water inlet on-off valve is arranged on the bridging waterway, and the third water inlet on-off valve is arranged on the sterilization return waterway.

4. The water purification system according to claim 2, characterized in that: One end of the sterilization return waterway pipe is connected to the water inlet waterway, and the other end is connected to the pure water waterway. Water can flow in a ring pipe formed by the sterilization return waterway, part of the water inlet waterway, the jumper waterway, and part of the pure water waterway.

5. The water purification system according to claim 4, characterized in that: The water inlet waterway comprises a pre-composite filter element and a booster pump arranged in sequence along the water flow direction, the booster pump is located upstream of the connection end point A, one end of the pipeline of the sterilization return waterway is connected to the water inlet waterway and is located upstream of the pre-composite filter element; and / or, The pure water circuit includes a post-activated carbon filter element, the connection end point B is located between the purification filter element and the post-activated carbon filter element, and the other end of the pipe of the sterilization return water circuit is connected to the pure water circuit and is located downstream of the post-activated carbon filter element.

6. The water purification system according to any one of claims 1 to 5, characterized in that: The sterilization return waterway comprises an ozone generator, which is used to produce ozone and send the ozone into the pipeline of the sterilization return waterway.

7. The water purification system according to any one of claims 1 to 5, characterized in that: The sterilization return water circuit also includes a flow meter, and the flow meter is used to detect the water flow in the pipeline of the sterilization return water circuit.

8. The water purification system according to any one of claims 1 to 5, characterized in that: The sterilization return waterway also includes a one-way valve, which is used to prevent the water in the pipeline of the sterilization return waterway from flowing back.

9. The water purification system according to any one of claims 1 to 5, characterized in that: The water purification system comprises a control device and a human-machine interaction section connected to each other, wherein a sterilization button is provided on the human-machine interaction section, and the sterilization button can input a sterilization instruction to the control device; and / or, The water purification system includes a control device, which can receive a signal sent by a mobile terminal, and the mobile terminal can input a sterilization instruction to the control device.

10. The water purification system according to any one of claims 1 to 5, characterized in that: The purification filter element comprises a reverse osmosis membrane or a nanofiltration membrane.

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