A low-temperature sterile nanofiltration membrane treatment process for high-quality direct drinking water

Abstract

This invention discloses a low-temperature sterile nanofiltration membrane treatment process for high-quality direct drinking water, mainly comprising: tap water, which passes through a delivery pump and a precision filter, and enters a nitrogen-sealed inlet tank; a vacuum system expels air from the nanofiltration (NF) membrane treatment system; a nitrogen generation system produces nitrogen gas with 99.5% purity, which is independently controlled by valves to replenish nitrogen gas to the nitrogen-sealed inlet tank, the NF membrane treatment system, and the NF membrane direct drinking water tank; after the nitrogen purity in the NF membrane treatment system meets the standard, the NF membrane treatment system is turned on, and the NF membrane permeate enters the NF membrane direct drinking water tank, passes through a nano-silver sterilization device, and is then transported to the end user by an external pump; the NF membrane concentrate is discharged into a rainwater well or a sewage well through an NF membrane concentrate discharge pipe. The high-quality direct drinking water nanofiltration membrane treatment process provided by this invention has the following advantages: the process is safe and reliable, improves the taste of NF membrane direct drinking water, reduces NF membrane fouling, and is easy to maintain.

Description

Technical Field

[0001] This invention relates to the field of drinking water treatment technology, specifically to a low-temperature sterile nanofiltration membrane treatment process for high-quality direct drinking water. Background Technology

[0002] Currently, high-quality drinking water has become an essential need in people's daily lives, including drinking water in homes and workplaces. The mainstream drinking water treatment processes include pretreatment, membrane treatment, and sterilization and disinfection processes. Membrane treatment processes include ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO).

[0003] In practical applications, the NF membrane treatment process does significantly improve the quality of tap water in the short term (usually 3 months), meeting the standards for direct drinking water. However, with the accumulation and reproduction of microorganisms on the surface of the NF membrane, especially during short-term shutdowns (such as long holidays) or long-term operation (up to 6 months), a large number of microorganisms grow on the surface of the NF membrane, forming NF membrane fouling. This causes "micro-pollution" to the quality of the NF membrane-generated water, which in turn affects the health of drinking water. Therefore, it is necessary to replace the NF membrane element in a timely manner or clean the NF membrane fouling with chemicals. However, many users often ignore membrane fouling, leading to problems such as a decline in the quality of direct drinking water. Some researchers have focused on addressing these issues. For example, CN 104839827B reports a device for the parallel production of sugarcane concentrate and sugarcane drinking water using multi-stage membranes, employing an integrated process of ceramic ultrafiltration membranes, organic nanofiltration membranes, and organic reverse osmosis membranes. CN 221071145U reports a low-pressure nanofiltration membrane system for high-quality drinking water, which solves the problem of poor filter cleaning and anti-clogging capabilities through improvements to the main unit structure and convenient installation mechanisms. However, no improved devices have been reported for addressing the issue of microbial contamination of nanofiltration membranes in high-quality drinking water membrane treatment equipment.

[0004] Therefore, developing nanofiltration membrane integrated treatment processes with high quality, maintenance-free operation, and antimicrobial properties for direct drinking water has become an urgent problem to be solved in the drinking water industry. Summary of the Invention

[0005] The purpose of this invention is to provide a low-temperature sterile nanofiltration membrane treatment process for high-quality direct drinking water, which solves the problems of long-term unstable operation, NF membrane fouling, and difficulty in maintaining the NF membrane system in existing nanofiltration membrane treatment processes, and achieves a long-term stable supply of high-quality direct drinking water.

[0006] The main process flow of the technical solution of this invention is as follows: Tap water, after passing through a delivery pump and a precision filter, enters the nitrogen-sealed water inlet tank. The vacuum system expels the air from the nanofiltration (NF) membrane treatment system. The nitrogen generation membrane system produces nitrogen gas with a purity of 99.5%. Through independent valve control, nitrogen gas is supplied to the nitrogen-sealed water inlet tank, the NF membrane treatment system, and the NF membrane drinking water tank. After the nitrogen purity in the NF membrane treatment system meets the standard, the NF membrane treatment system is turned on. The NF membrane produced water enters the NF membrane drinking water tank, passes through a nano-silver sterilization device, and is delivered to the end user by an external pump. The NF membrane concentrate is discharged through the NF membrane concentrate discharge pipe.

[0007] The specific process flow is as follows: Tap water passes through a transfer pump and a precision filter sequentially, then enters the nitrogen-sealed water inlet tank. The outlet valve of the nitrogen-sealed water inlet tank is kept closed. When the liquid level in the nitrogen-sealed water inlet tank reaches the set value, the chilled brine system is turned on. The temperature of the chilled brine is controlled between -5℃ and -15℃. The temperature of the tap water in the nitrogen-sealed water inlet tank is controlled at 5-10℃ through the cooling circulation pipe inside the nitrogen-sealed water inlet tank. When the liquid level in the nitrogen-sealed water inlet tank reaches 1.3m, the NF membrane system is turned on. When the liquid level in the nitrogen-sealed water inlet tank is lower than 0.2m, the NF membrane system is stopped. Before turning on the NF membrane system, the nitrogen generating membrane system and vacuum pump are turned on. The system consists of a nitrogen-generating membrane system that produces nitrogen gas with a purity of 99.5%, which enters a high-purity nitrogen storage tank. The vacuum system can achieve a vacuum level of -0.1 MPa. The high-purity nitrogen gas produced by the nitrogen-generating membrane system is then supplied to the nanofiltration membrane treatment system for high-quality drinking water via three separate streams, controlled by pressure-reducing and regulating valves on the high-purity nitrogen storage tank. The first stream of nitrogen gas enters the nitrogen-sealing inlet tank, which is equipped with a nitrogen-sealing valve assembly and a breather valve to maintain a slight positive pressure of 0.2-0.5 kPa. The second stream of nitrogen gas enters the nanofiltration membrane system, with a pressure control of 2-5 kPa, to displace any nitrogen present in the system. Air and nitrogen from the third line enter the NF membrane drinking water tank. An NF membrane drinking water tank nitrogen sealing valve assembly and a breather valve are installed to maintain a slight positive pressure in the tank. A vacuum system is used to expel air from the NF membrane system while slowly replenishing nitrogen, maintaining a slight negative pressure of -5 to -10 kPa. This is operated for 10-15 minutes, then the vacuum system is stopped, and nitrogen replenishment continues. When the nitrogen purity at the NF membrane system outlet reaches 99.3% or higher, the second nitrogen inlet valve is closed, and the nitrogen sealing inlet tank outlet valve and the NF membrane treatment system are opened. The operating pressure control range is 5-1 kPa. At 0 bar, the permeate from the NF membrane enters the NF membrane drinking water tank. The chilled brine system controls the temperature of the permeate from the NF membrane within the tank, maintaining a range of 2-5°C. Once the set temperature is reached, the outlet valve of the NF membrane drinking water tank opens. When the tank level reaches 0.9m, the variable frequency delivery pump starts; when the level drops below 0.2m, the pump stops. The NF drinking water then passes through the variable frequency delivery pump and the nano-silver sterilization device before being pumped to the end user via an external pump. The NF membrane concentrate is discharged into a rainwater well or sewage well via an NF membrane concentrate discharge pipe. A low-temperature sterile nanofiltration membrane treatment process for high-quality direct drinking water involves nitrogen-sealed water inlet tank, nanofiltration membrane system, nitrogen generation membrane system, chilled brine system, vacuum system, nano-silver sterilization device, NF membrane direct drinking water tank, transfer pump, external supply pump, pipes and instruments. All materials in contact with water must be sanitary grade, preferably 304 or 316 stainless steel. The transfer pump and external supply pump are both frequency converter controlled to achieve flow regulation. Precision filters, with filter element pore size of 1-5mm, are mainly used to filter out small amounts of large particles in tap water; The volume of the nitrogen-sealed water inlet tank is controlled at 1.5-2m³, the liquid level is preferably 1-1.5m, the low liquid level is controlled at 0.2m, and the high liquid level is controlled at 1.3m. The nitrogen-sealed water inlet tank is equipped with a sanitary breather valve to maintain the pressure inside the nitrogen-sealed water inlet tank within the range of 0.1-0.3kPa. The nitrogen generation membrane system produces 10-30 Nm³ / h of nitrogen with a purity higher than 99.5%. The high-purity nitrogen storage tank is preferably 0.5-1 m³. It is equipped with three valves for independent control, which replenish nitrogen to the nanofiltration membrane system, the nitrogen-sealed water inlet tank, and the NF membrane drinking water tank respectively. The vacuum system has an exhaust volume of 30-50 m³ / h. The vacuum system, nanofiltration membrane system, nitrogen-sealed water inlet tank and NF membrane direct drinking water tank are interlocked and controlled by electric valves. The chilled brine system produces chilled brine at a temperature of -5℃ to -15℃, and cools the nitrogen-sealed water inlet tank and the NF membrane drinking water tank through two independent cooling coils. The nano-silver sterilization device mainly uses ultraviolet light to irradiate nano-silver particles. The ultraviolet light wavelength is 280-300nm. The nano-silver has a sterilization effect, which inactivates trace bacteria in the NF membrane permeate. The irradiation time is controlled at 10-20 minutes. The NF membrane system has a recovery rate of 90%-93%. The volume of the NF membrane drinking water tank is controlled at 1-1.5m³, and the liquid level range is 0-1m. The low liquid level is controlled at 0.2m and the high liquid level is controlled at 0.9m. The NF membrane drinking water tank is equipped with a sanitary breather valve to maintain the pressure inside the NF membrane drinking water tank within the range of 0.1-0.3kPa.

[0008] Compared with existing technologies, this invention has significant advantages: First, the low-temperature aseptic nanofiltration membrane treatment process for high-quality direct drinking water integrates a nitrogen-sealed inlet tank, a nanofiltration membrane system, a nitrogen-generating membrane system, a chilled brine system, a vacuum system, and a nano-silver sterilization device. This process removes dissolved oxygen in the nitrogen-sealed inlet tank before tap water enters the NF membrane system, ensures low-temperature operation of the nanofiltration membrane system, removes trace bacteria remaining in the system using the nano-silver sterilization device, and uses high-purity nitrogen to ensure the freshness of the NF membrane permeate in the NF membrane permeate tank. Therefore, the high-quality direct drinking water treatment process is reliable and safe. It also helps improve the taste of NF membrane direct drinking water; secondly, the low-temperature sterile nanofiltration membrane treatment process for high-quality direct drinking water can provide nitrogen protection for the NF membrane system and NF membrane during short-term shutdowns without removing the NF membrane from the system, and also prevents bacterial growth in the NF membrane system; finally, the low-temperature sterile nanofiltration membrane treatment process for high-quality direct drinking water, which includes a nitrogen-sealed water inlet tank, nanofiltration membrane system, nitrogen generation membrane system, chilled brine system, vacuum system, and nano-silver sterilization device, can all be independently controlled and selected as needed, and is simple to operate and maintain. Attached Figure Description

[0009] Figure 1This is a process flow diagram of the present invention. Detailed Implementation

[0010] Example 1 A nanofiltration membrane integrated treatment process for high-quality direct drinking water, taking a 1m³ / h centralized water supply system in a commercial complex as an example (meeting the daily direct drinking water needs of 100-200 people, covering application scenarios such as schools, parks, government service centers, and hospitals), the main process flow is as follows: Tap water passes sequentially through a 1.5 m³ / h sanitary pump and a 1 mm precision filter before entering a 1.5 m³ / h nitrogen-sealed water inlet tank. The outlet electric valve of the nitrogen-sealed water inlet tank remains closed. When the water level in the nitrogen-sealed water inlet tank reaches 1.3 m, the chilled brine system is activated, with the chilled brine temperature controlled at -5°C. The tap water temperature in the nitrogen-sealed water inlet tank is controlled at 5°C through the cooling circulation pipes within the tank. When the water level in the nitrogen-sealed water inlet tank reaches 1.3 m, the NF membrane system is activated. When the water level in the nitrogen-sealed water inlet tank drops below 0.2 m, the NF membrane system is shut down. Before activating the NF membrane system, the nitrogen-generating membrane is activated. The system includes a vacuum system and a nitrogen generation system. The nitrogen generation membrane system produces nitrogen gas with a purity of 99.5%, which enters a high-purity nitrogen storage tank. The vacuum system can achieve a vacuum level of -0.1 MPa. The high-purity nitrogen gas produced by the nitrogen generation membrane system is supplied to the nanofiltration membrane treatment system for high-quality drinking water through three channels via pressure reducing valves and regulating valves on the high-purity nitrogen storage tank. The first channel of nitrogen gas enters the nitrogen-sealed water inlet tank, which is equipped with a nitrogen-sealed valve group and a breather valve to maintain a slight positive pressure of 0.1 kPa. The second channel of nitrogen gas enters the nanofiltration membrane system, with a pressure control of 2 kPa, to displace the air present in the system. The third channel of nitrogen gas enters... The NF membrane drinking water tank is equipped with a nitrogen sealing valve assembly and a breather valve to maintain a slight positive pressure of 0.1 kPa. A vacuum system is used to simultaneously purge air from the NF membrane system and slowly replenish nitrogen, maintaining a slight negative pressure of -5 kPa. This process is repeated for 10 minutes, then the vacuum system is stopped, and nitrogen replenishment continues. When the nitrogen purity at the NF membrane system outlet reaches 99.3% or higher, the second nitrogen inlet valve is closed, and the outlet valve of the nitrogen sealing tank and the NF membrane treatment system are opened. The operating pressure is 5 bar, and the NF membrane system recovery rate is 90%. The NF membrane permeate enters the NF... The membrane drinking water tank, with its chilled brine system controlling the NF (Nuclear Fluorescent) water temperature at 2℃ via the cooling coils inside, opens the outlet valve. When the tank level reaches 0.9m, a 1m³ / h variable frequency pump starts; when the level drops below 0.2m, the pump stops. The NF drinking water, after passing through the 1m³ / h pump, remains in a 280nm ultraviolet light irradiation nano-silver sterilization device for 10 minutes before being transported to the end user via a 1m³ / h external pump. The NF membrane concentrate is discharged into the rainwater well via the NF membrane concentrate discharge pipe.

[0011] Example 2 A nanofiltration membrane integrated treatment process for high-quality direct drinking water, taking a 2m³ / h centralized water supply system in a commercial complex as an example (meeting the daily direct drinking water needs of 300-400 people, covering application scenarios such as train stations, airports, and residential buildings), the main process flow is as follows: Tap water passes sequentially through a 3m³ / h sanitary pump and a 5mm precision filter before entering a 3m³, 1.5m high nitrogen-sealed water tank. The outlet electric valve of the nitrogen-sealed water tank remains closed. When the water level in the nitrogen-sealed water tank reaches 1.1m, the chilled brine system is activated, with the chilled brine temperature controlled at -15℃. The tap water temperature in the nitrogen-sealed water tank is maintained at 5℃ through the cooling circulation pipes within the tank. When the water level in the nitrogen-sealed water tank reaches 1.3m, the NF membrane system is activated. When the water level in the nitrogen-sealed water tank drops below 0.2m, the NF membrane system is shut down. Before activating the NF membrane system, the nitrogen-generating membrane system is activated. The system integrates a vacuum system and a nitrogen-generating membrane system, producing nitrogen gas with a purity of 99.5%, which enters a high-purity nitrogen storage tank. The vacuum system can achieve a vacuum level of -0.1 MPa. The high-purity nitrogen gas produced by the nitrogen-generating membrane system is then supplied to the high-quality drinking water nanofiltration membrane treatment system via three separate supply lines through pressure reducing valves and regulating valves on the high-purity nitrogen storage tank. The first supply line enters the nitrogen-sealed water inlet tank, where a nitrogen-sealing valve assembly and a breather valve are installed to maintain a slight positive pressure of 0.3 kPa. The second supply line enters the nanofiltration membrane system, with a pressure control of 5 kPa, to displace air within the system. The third supply line enters... The NF membrane drinking water tank is connected to a nitrogen sealing valve assembly and a breather valve to maintain a slight positive pressure of 0.3 kPa. A vacuum system is activated, simultaneously purging air from the NF membrane system and slowly replenishing nitrogen to maintain a slight negative pressure of -10 kPa. This process is repeated for 15 minutes. The vacuum system is then stopped, and nitrogen replenishment continues. When the nitrogen purity at the NF membrane system outlet reaches 99.3% or higher, the second nitrogen inlet valve is closed, and the outlet valve of the nitrogen sealing tank and the NF membrane treatment system are opened. The operating pressure is 10 bar, and the NF membrane system recovery rate is 93%. The NF membrane product... Water enters the NF membrane drinking water tank. The chilled brine system controls the NF produced water temperature to 5℃ through the cooling coil inside the NF membrane drinking water tank. The outlet valve of the NF membrane drinking water tank is opened. When the liquid level reaches 0.9m, the 2m³ / h variable frequency transfer pump starts. When the liquid level is below 0.2m, the 2m³ / h variable frequency transfer pump stops. The NF drinking water passes through the 2m³ / h variable frequency transfer pump and stays in the 300nm ultraviolet light irradiation nano-silver sterilization device for 20 minutes. Then, it is transported by the 2m³ / h external supply pump to the end user. The NF membrane concentrate is discharged into the sewage well through the NF membrane concentrate discharge pipe.

[0012] Example 3 A nanofiltration membrane integrated treatment process for high-quality direct drinking water, taking a 1.5m³ / h centralized water supply system in a commercial complex as an example (meeting the daily direct drinking water needs of 200-300 people, covering application scenarios such as train stations, airports, and residential buildings), the main process flow is as follows: Tap water passes sequentially through a 2m³ / h sanitary pump and a 2mm precision filter before entering a 2m³, 1.5m high nitrogen-sealed inlet tank. The outlet electric valve of the nitrogen-sealed inlet tank remains closed. When the water level in the nitrogen-sealed inlet tank reaches 1.3m, the chilled brine system is activated. The chilled brine temperature is controlled at -10℃, and the tap water temperature in the nitrogen-sealed inlet tank is controlled at 8℃ via a cooling circulation pipe. When the water level in the nitrogen-sealed inlet tank reaches 1.3m, the NF membrane system is activated. When the water level in the nitrogen-sealed inlet tank drops below 0.2m, the NF membrane system is deactivated. Before starting the system, the nitrogen generation membrane system and vacuum system are activated. The nitrogen generation membrane system produces nitrogen gas with a purity of 99.5%, which enters the high-purity nitrogen storage tank. The vacuum system can achieve a vacuum level of -0.1 MPa. The high-purity nitrogen gas produced by the nitrogen generation membrane system is supplied to the nanofiltration membrane treatment system for high-quality drinking water through three channels via pressure reducing valves and regulating valves on the high-purity nitrogen storage tank. The first channel of nitrogen gas enters the nitrogen-sealed water inlet tank, where a nitrogen-sealed valve group and a breather valve are installed to maintain a slight positive pressure of 0.2 kPa in the nitrogen-sealed water inlet tank. The second channel of nitrogen gas enters the nanofiltration membrane system, with the pressure controlled at 3 kPa, to displace air in the system. Nitrogen gas is introduced into the NF membrane drinking water tank via a third inlet. A nitrogen sealing valve assembly and a breather valve are installed in the NF membrane drinking water tank to maintain a slight positive pressure of 0.2 kPa. A vacuum system is activated, simultaneously purging air from the NF membrane system and slowly replenishing nitrogen to maintain a slight negative pressure of -8 kPa. This process is repeated for 12 minutes, then the vacuum system is stopped, and nitrogen replenishment continues. When the nitrogen purity at the NF membrane system outlet reaches 99.3% or higher, the second nitrogen inlet valve is closed, and the outlet valve of the nitrogen sealing tank and the NF membrane treatment system are opened. The operating pressure is 7 bar, and the NF membrane system recovery rate is 92%. The F membrane permeate enters the NF membrane drinking water tank. The chilled brine system controls the NF permeate temperature to 4℃ through the cooling coil inside the NF membrane drinking water tank. The outlet valve of the NF drinking water tank is opened. When the liquid level in the NF drinking water tank reaches 0.9m, the variable frequency delivery pump starts. When the liquid level is below 0.2m, the variable frequency delivery pump stops. The NF drinking water passes through the 2m³ / h variable frequency delivery pump and stays in the 300nm ultraviolet light irradiation nano-silver sterilization device for 15 minutes. It is then transported to the end user by the 1.5m³ / h external supply pump. The NF membrane concentrated water is discharged into the rainwater well through the NF membrane concentrated water discharge pipe.

[0013] Application effect

[0014] It can be seen that the high-quality drinking water treated by the nanofiltration membrane process of this invention has significantly reduced TDS, hardness and color, completely removed dissolved oxygen, and significantly improved water quality of NF membrane effluent.

Claims

1. A nanofiltration membrane integrated treatment process for high-quality direct drinking water, characterized in that: Tap water passes through a sanitary pump and a precision filter before entering the nitrogen-sealed inlet tank. The outlet electric valve of the nitrogen-sealed inlet tank is kept closed. Once the water level in the nitrogen-sealed inlet tank reaches the set height, the chilled brine system is activated. The temperature of the tap water in the nitrogen-sealed inlet tank is controlled via a cooling circulation pipe. Before activating the NF membrane system, the nitrogen generation membrane system and vacuum system are activated. The nitrogen generation membrane system produces high-purity nitrogen gas, which enters the high-purity nitrogen storage tank. The vacuum system can achieve a vacuum level of -0.1 MPa. The high-purity nitrogen gas produced by the nitrogen generation membrane system is supplied to the high-quality drinking water nanofiltration membrane treatment system in three streams via pressure reducing valves and regulating valves on the high-purity nitrogen storage tank. The first stream of nitrogen enters the nitrogen-sealed inlet tank, where a nitrogen-sealing valve assembly and a breather valve are installed to maintain a slight positive pressure. The second stream of nitrogen enters the nanofiltration membrane system to replace the air present in the system. The third stream of nitrogen enters the N2N... The NF membrane drinking water tank is equipped with a nitrogen sealing valve assembly and a breather valve to maintain a slight positive pressure. A vacuum system simultaneously expels air from the NF membrane system and slowly replenishes nitrogen to maintain a slight negative pressure. The vacuum system is then stopped, and nitrogen replenishment continues. When the nitrogen purity at the NF membrane system outlet reaches 99.3% or higher, the second nitrogen inlet valve is closed, and the outlet valve of the nitrogen sealing tank and the NF membrane treatment system are opened. NF membrane permeate enters the NF membrane drinking water tank. The chilled brine system controls the NF permeate temperature through the cooling coils inside the NF membrane drinking water tank. The outlet valve of the NF membrane drinking water is opened, and the NF drinking water is pumped through a variable frequency delivery pump and remains in a nano-silver sterilization device irradiated with ultraviolet light of a specific wavelength for a period of time. It is then transported to the end user via an external pump. NF membrane concentrate is discharged into the rainwater well through the NF membrane concentrate discharge pipe.

2. A nanofiltration membrane integrated treatment process for high-quality direct drinking water as described in claim 1, characterized in that: All materials that come into contact with water, including the nitrogen-sealed water inlet tank, nanofiltration membrane system, nitrogen-generating membrane system, chilled brine system, vacuum system, nano-silver sterilization device, NF membrane direct drinking water tank, transfer pump, external supply pump, pipes and instruments, must be sanitary grade materials, preferably 304 or 316 stainless steel. The transfer pump and external supply pump are both frequency converter controlled to achieve flow regulation.

3. A nanofiltration membrane integrated treatment process for high-quality direct drinking water as described in claim 1, characterized in that: The precision filter described above has a filter element pore size of 1-5mm and is mainly used to filter out small amounts of large particles present in tap water.

4. A nanofiltration membrane integrated treatment process for high-quality direct drinking water as described in claim 1, characterized in that: The nitrogen-sealed water inlet tank has a volume of 1.5-2 m³, a liquid level of 1-1.5 m (low liquid level controlled at 0.2 m, high liquid level controlled at 1.3 m), and is equipped with a sanitary breather valve to maintain the pressure inside the nitrogen-sealed water inlet tank within the range of 0.1-0.3 kPa.

5. A nanofiltration membrane integrated treatment process for high-quality direct drinking water as described in claim 1, characterized in that: The nitrogen-generating membrane system produces 10-30 Nm³ / h of nitrogen with a purity higher than 99.5%. The high-purity nitrogen storage tank is preferably 0.5-1 m³, and is equipped with three valves for independent control, which respectively replenish nitrogen to the nanofiltration membrane system, the nitrogen-sealed water inlet tank, and the NF membrane drinking water tank.

6. A nanofiltration membrane integrated treatment process for high-quality direct drinking water as described in claim 1, characterized in that: The vacuum system described above has an exhaust capacity of 30-50 m³ / h. The vacuum system, nanofiltration membrane system, nitrogen-sealed water inlet tank, and NF membrane direct drinking water tank are interlocked and controlled by electric valves.

7. A nanofiltration membrane integrated treatment process for high-quality direct drinking water as described in claim 1, characterized in that: The aforementioned chilled brine system produces chilled brine at a temperature of -5°C to -15°C. Two independent cooling coils are used to cool the nitrogen-sealed water inlet tank and the NF membrane drinking water tank, respectively.

8. A nanofiltration membrane integrated treatment process for high-quality direct drinking water as described in claim 1, characterized in that: The nano-silver sterilization device has an ultraviolet wavelength of 280-300nm, where nano-silver has a sterilization effect, and the irradiation time is controlled to be 10-20min.

9. A nanofiltration membrane integrated treatment process for high-quality direct drinking water as described in claim 1, characterized in that: The NF membrane system operates at a pressure of 5-10 bar, with a recovery rate of 90%-93%. The volume of the NF membrane drinking water tank is controlled at 1-1.5 m³, and the liquid level range is 0-1 m, with a low liquid level control at 0.2 m and a high liquid level control at 0.9 m. The NF membrane drinking water tank is equipped with a sanitary breather valve to maintain the pressure inside the NF membrane drinking water tank within the range of 0.1-0.3 kPa.

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