Water purifying device and method of operating the same

Abstract

This invention relates to a water purification device employing semi-permeable membrane technology and its operating method. The hardness concentration in water bodies varies significantly across different regions, and existing water purification devices using only RO or NF membranes are insufficient to effectively address this issue. This invention proposes a multi-stage semi-permeable membrane system that can effectively handle raw water with varying hardness concentrations, obtaining purified water with suitable hardness concentrations and improving drinking water quality. In this multi-stage semi-permeable membrane system, the removal rate of hardness by the first and second semi-permeable membranes is greater than that by the first semi-permeable membrane, and the permeability coefficient of the second semi-permeable membrane is higher than that of the first semi-permeable membrane.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a water purification device and its operation method that uses semi-permeable membrane technology to treat and purify tap water, surface water, groundwater, etc. Background Technology

[0002] Currently, reverse osmosis (RO) membrane technology is widely used to remove impurities, organic matter, hardness, heavy metals, bacteria, and other substances from tap water, surface water, and groundwater to obtain directly drinkable water. RO membrane treatment produces very pure water, effectively removing various substances from the water. However, some beneficial minerals, such as calcium (Ca) and magnesium (Mg), which contribute to hardness, are almost completely removed. According to research by the World Health Organization (WHO), adequate minerals in drinking water play a crucial role in supplementing dietary intake. Long-term consumption of drinking water lacking calcium and magnesium is detrimental to health and may increase the risk of certain cardiovascular diseases. If daily diet cannot provide sufficient minerals, drinking water with an appropriate hardness concentration becomes particularly important.

[0003] On the other hand, excessively high hardness concentration in drinking water can affect the taste and sensory experience, and may also lead to a higher incidence of diseases such as gallstones and kidney stones. Therefore, drinking water with an appropriate hardness concentration is considered high-quality drinking water.

[0004] Due to significant differences in water quality, dietary habits, and human health across countries, as well as uneven economic development, the WHO has not set mandatory standards for hardness in high-quality drinking water. Some developed countries have proposed suggested reference standards based on their own national circumstances. For example, Japan recommends a hardness of 10–100 mg / L for comfortable drinking water, the European Union suggests a hardness higher than 60 mg / L, and Israel recommends that drinking water should contain some minerals but with a hardness concentration less than 150 mg / L. Although quantitative data on hardness in high-quality drinking water are not standardized, the recommendation of an appropriate hardness concentration is widely accepted.

[0005] Generally, RO membranes achieve a hardness removal rate of over 98%, while nanofiltration (NF) membranes not only effectively remove harmful organic matter, heavy metals, and bacteria, but also retain some hardness. However, the removal rates of hardness in water vary considerably depending on the material and molecular weight cutoff of the NF membrane, ranging from a minimum of about 10% to a maximum of over 90%. Furthermore, the hardness concentration in water bodies varies greatly across different regions of my country, ranging from tens to hundreds of mg / L.

[0006] Therefore, existing water purification devices using RO membrane technology almost completely remove hardness components from water, meaning they cannot retain some beneficial minerals. While water purification devices using NF membrane technology retain some hardness components, they are difficult to effectively address and meet the water quality requirements of different areas with significantly varying hardness concentrations. This invention proposes a water purification device and its operating method that can effectively address water bodies with different hardness concentrations, obtaining purified water with suitable hardness concentrations. Summary of the Invention

[0007] The technical problem to be solved by this invention is: due to the large differences in hardness concentration in water bodies in different regions, and in view of the above-mentioned problems or deficiencies in existing water purification devices using RO membranes or NF membranes, a water purification device and its operation method are proposed, which can effectively respond to raw water quality with different hardness concentrations, obtain purified water with appropriate hardness concentration, and improve the quality of drinking water.

[0008] The objective of this invention can be achieved through the following measures:

[0009] This invention discloses a water purification device, including a multi-stage semi-permeable membrane system. The concentrated water after the water to be treated passes through the first stage semi-permeable membrane enters the second stage semi-permeable membrane. The permeate from the first stage semi-permeable membrane and the permeate from the second stage semi-permeable membrane are mixed to form purified water. The hardness removal rate of the second stage semi-permeable membrane is greater than that of the first stage semi-permeable membrane, and the water permeability coefficient of the second stage semi-permeable membrane is higher than that of the first stage semi-permeable membrane.

[0010] The water to be treated can be one or more of tap water, surface water, groundwater, or seawater, with tap water being preferred. The first or second semi-permeable membrane in the multi-stage semi-permeable membrane system is one or more of nanofiltration or reverse osmosis membranes, with nanofiltration being preferred. The semi-permeable membrane can be 2 inches, 2.5 inches, 3 inches, 4 inches, or 8 inches in size.

[0011] The permeability coefficient is the water production per unit area per unit time under unit pressure conditions of a semi-permeable membrane. The permeability coefficient of a semi-permeable membrane is not directly related to its hardness removal rate. It is affected by factors such as the pore size, material, membrane manufacturing process, and surface charge of the membrane. Different permeability coefficients of nanofiltration membranes can be obtained by adjusting the production process. The water to be treated serves as the raw water for the first stage of the semi-permeable membrane. The concentrated water from the first stage enters the second stage, serving as the raw water for that stage. Therefore, the raw water volume for the second stage is lower than that for the first stage. Furthermore, after the water passes through the first stage, the pressure of the concentrated water decreases due to water resistance at the membrane surface. In other words, the raw water pressure for the second stage is lower than that for the first stage.

[0012] For raw water in areas with low hardness concentration, the purified water is produced by mixing the permeate from the first semi-permeable membrane (with a lower hardness removal rate) and the permeate from the second semi-permeable membrane (with a higher hardness removal rate). To obtain purified water with a suitable hardness concentration, the permeate flow rate of the first semi-permeable membrane (with a lower hardness removal rate) should be higher than that of the second semi-permeable membrane. This relatively higher permeate flow rate of the first semi-permeable membrane can be achieved by reducing the amount of concentrated water from the first semi-permeable membrane entering the second semi-permeable membrane, i.e., reducing the amount of raw water entering the second semi-permeable membrane, thereby correspondingly reducing the permeate flow rate of the second semi-permeable membrane. There are no particular limitations or requirements on the permeability coefficient of the semi-permeable membrane itself.

[0013] On the other hand, for raw water in areas with high hardness concentrations, to obtain purified water with a suitable hardness concentration, the permeate flow rate of the second-stage semi-permeable membrane, which has a higher hardness removal rate, must be higher than that of the first-stage semi-permeable membrane. However, as mentioned earlier, the raw water flow rate and pressure of the second-stage semi-permeable membrane are both lower than those of the first-stage membrane. To achieve a relatively high permeate flow rate from the second-stage semi-permeable membrane, the unit membrane area of ​​the second-stage membrane can be increased, the number of second-stage membranes can be increased, or a relatively higher permeability coefficient of the second-stage membrane can be required. In multi-stage semi-permeable membrane systems, although increasing the unit membrane area of ​​the second-stage membrane or increasing the number of second-stage semi-permeable membranes can achieve a higher permeate flow rate, it inevitably increases the cost of the membranes and the overall size of the device, thereby increasing the manufacturing and operating costs of the water purification system. Therefore, the permeability coefficient of the second-stage semi-permeable membrane is higher than that of the first-stage semi-permeable membrane.

[0014] Preferably, the hardness removal ratio of the second-stage semi-permeable membrane to the first-stage semi-permeable membrane is 1.3–3.2:1, more preferably 1.5–3.0:1. For the first-stage semi-permeable membrane, its hardness removal rate is lower than that of the second-stage membrane. However, if a semi-permeable membrane with too low a hardness removal rate is selected, its pore size may be larger or its molecular weight cutoff higher, potentially reducing the effective retention performance of the first-stage semi-permeable membrane for organic matter, heavy metals, or bacteria. Therefore, the hardness removal rate of the first-stage semi-permeable membrane is preferably 30%–70%. For the second-stage semi-permeable membrane, its hardness removal rate is higher than that of the first-stage membrane. However, if a semi-permeable membrane with too high a hardness removal rate is selected, such as one with a hardness removal rate of approximately 99%, the raw water for the second-stage semi-permeable membrane is the concentrate from the first-stage membrane, resulting in a higher hardness concentration than the water to be treated. This makes it prone to inorganic scaling on the membrane surface during operation, thus affecting membrane lifespan and system stability. Therefore, the hardness removal rate of the second-stage semi-permeable membrane is preferably 70%–96%.

[0015] The recovery rate is the ratio of the permeate flow rate of the semi-permeable membrane to the raw water flow rate (raw water flow rate = permeate flow rate + concentrate flow rate). If the recovery rate is too low, the operating efficiency of the semi-permeable membrane will decrease, and the cost of the membrane will increase accordingly. The recovery rate of the first-stage semi-permeable membrane is preferably higher than 10%, meaning the concentrate flow rate of the first-stage semi-permeable membrane is less than 90% of the total amount of water to be treated, and the raw water flow rate of the second-stage semi-permeable membrane is less than 90% of the raw water flow rate of the first-stage semi-permeable membrane. As explained above, to effectively address the raw water quality in areas with high hardness concentrations, the permeate flow rate of the second-stage semi-permeable membrane, which has a higher hardness removal rate, is required to be higher than that of the first-stage semi-permeable membrane. The permeability coefficient of the second-stage semi-permeable membrane is preferably more than 1.2 times that of the first-stage semi-permeable membrane, and more preferably more than 1.5 times.

[0016] Preferably, the water purification device also includes a water quality detection unit for the water to be treated, a control unit, and a concentrated water valve for the first stage semi-permeable membrane concentrated water measurement.

[0017] The water quality testing unit is preferably one or more of a hardness tester, conductivity tester, or TDS tester, and more preferably a hardness tester. The water quality testing unit is preferably a tester with real-time online detection and automatic signal output functions, and is preferably installed on the inlet pipe supplying the water to be treated to the first semi-permeable membrane.

[0018] The control unit is preferably a PLC control unit, which can be pre-programmed and written into the PLC control system to realize the automatic control function of various electronic devices. The control unit is preferably a device with a data acquisition, storage and transmission module, and its transmission can be realized through wired connection, wireless network, 3G network, 4G network or 5G network, etc.

[0019] The concentrate valve for the first-stage semi-permeable membrane concentrate measurement is preferably an electrically adjustable valve, which can automatically adjust the valve opening according to the strength of the input signal to control the amount of concentrate from the first-stage semi-permeable membrane. The opening of the concentrate valve can be adjusted within any range from fully closed to fully open. Considering that different zones can be appropriately classified according to the hardness concentration of the water in different areas, and to improve the ease of operation and response speed of automatic valve adjustment, the concentrate valve is further preferably an electrically proportional regulating valve, and the opening of the electrically proportional regulating valve is preferably one of 0%, 25%, 50%, 75%, or 100%.

[0020] Preferably, based on the measured values ​​from the water quality detection unit, the control unit adjusts the opening of the concentrate valve during the operation of the device. When the water quality detection unit detects the water quality result of the water to be treated, its measured value is automatically transmitted to the control unit. Through a pre-set control program, the opening of the concentrate valve is automatically adjusted to control the amount of concentrate from the first semi-permeable membrane.

[0021] Preferably, the amount of concentrated water from the first semi-permeable membrane entering the second semi-permeable membrane accounts for 10-90% of the total amount of water to be treated, more preferably 20-80%. This is because the water purification device requires raw water corresponding to different hardness concentration areas. In order to obtain purified water with suitable hardness concentration in each different area, it is necessary to adjust the ratio between the raw water volume of the first semi-permeable membrane with a lower hardness removal rate and the raw water volume of the second semi-permeable membrane with a higher hardness removal rate. This can be achieved by adjusting the proportion of the raw water volume of the second semi-permeable membrane to the total amount of water to be treated, which is equivalent to adjusting the proportion of the concentrated water from the first semi-permeable membrane entering the second semi-permeable membrane to the total amount of water to be treated.

[0022] Specifically, for raw water in areas with low hardness concentration, to obtain purified water with a suitable hardness concentration, the permeate flow rate of the second-stage semi-permeable membrane, which has a higher hardness removal rate, must be lower than that of the first-stage semi-permeable membrane. This means reducing the amount of raw water entering the second-stage semi-permeable membrane, i.e., decreasing the proportion of the concentrated water from the first-stage semi-permeable membrane into the total amount of water to be treated. If this proportion is less than 10%, meaning the concentrated water from the first-stage semi-permeable membrane is less than 10%, and its recovery rate is higher than 90%, the excessively low concentrated water volume results in a low hydraulic scouring velocity parallel to the semi-permeable membrane surface during filtration. This leads to pollutants in the water easily adsorbing and depositing onto the membrane surface, causing membrane fouling and performance degradation. Therefore, it is preferable that the concentrated water from the first-stage semi-permeable membrane enters the second-stage semi-permeable membrane at a rate of 10% or more of the total amount of water to be treated, and more preferably 20% or more.

[0023] On the other hand, for raw water in areas with high hardness concentration, to obtain purified water with a suitable hardness concentration, the permeate flow rate of the second-stage semi-permeable membrane, which has a higher hardness removal rate, needs to be higher than that of the first-stage semi-permeable membrane. This means increasing the amount of raw water entering the second-stage semi-permeable membrane, i.e., increasing the proportion of the concentrated water from the first-stage semi-permeable membrane into the total amount of water to be treated. If this proportion exceeds 90%, meaning the concentrated water from the first-stage semi-permeable membrane is greater than 90%, the recovery rate is less than 10%, significantly reducing the effective operating efficiency of the first-stage semi-permeable membrane and consequently affecting the overall operating efficiency of the water treatment device. To obtain the same amount of purified water, the operating time needs to be extended, accelerating membrane performance degradation and reducing membrane lifespan, thus increasing operating costs. Therefore, it is preferable that the amount of concentrated water from the first-stage semi-permeable membrane entering the second-stage semi-permeable membrane is less than 90% of the total amount of water to be treated, and more preferably less than 80%.

[0024] Preferably, the water produced by the second semi-permeable membrane accounts for 10-80% of the total purified water, and more preferably 20-70%. During the operation of this water purification device, the water produced by the first semi-permeable membrane with a lower hardness removal rate has higher hardness, while the water produced by the second semi-permeable membrane with a higher hardness removal rate has lower hardness. After mixing, purified water with a suitable hardness concentration is obtained.

[0025] Specifically, for raw water in areas with low hardness concentration, to obtain purified water with a suitable hardness concentration, the proportion of water produced by the second-stage semi-permeable membrane, which has a higher hardness removal rate, should be reduced to the total amount of purified water. If this proportion is less than 10%, the effective operating efficiency of the second-stage semi-permeable membrane is reduced, which also affects the overall operating efficiency of the water treatment device. To obtain the same amount of water produced, the operating time needs to be extended, accelerating the degradation of membrane performance and increasing operating costs. Therefore, it is preferable that the water produced by the second-stage semi-permeable membrane accounts for more than 10% of the total amount of purified water, and more preferably more than 20%.

[0026] On the other hand, for raw water in areas with high hardness concentration, to obtain purified water with a suitable hardness concentration, the proportion of the permeate produced by the second-stage semi-permeable membrane, which has a higher hardness removal rate, should be increased to account for a larger proportion of the total purified water. Therefore, if the permeate produced by the second-stage semi-permeable membrane accounts for too high a proportion of the total purified water, such as exceeding 80%, under a certain recovery rate, the proportion of the raw water from the second-stage semi-permeable membrane (i.e., the concentrate from the first-stage semi-permeable membrane) to the water to be treated may be too high, thus reducing the effective operating efficiency of the first-stage semi-permeable membrane and increasing the overall operating cost of the device. Therefore, it is preferable that the permeate produced by the second-stage semi-permeable membrane accounts for less than 80% of the total purified water, and more preferably less than 70%.

[0027] The present invention also discloses an operating method for the water purification device as described above, comprising the following steps:

[0028] (1) Based on the measured values ​​of the water quality detection unit of the water to be treated, the opening degree of the concentrate valve of the first semi-permeable membrane concentrate meter is adjusted by the control unit during the operation of the multi-stage semi-permeable membrane system.

[0029] (2) Based on the opening of the above-mentioned concentrate valve, the proportion of the concentrate from the first semipermeable membrane entering the second semipermeable membrane to the total amount of water to be treated is controlled, and the proportion of the water produced by the second semipermeable membrane to the total amount of purified water is adjusted accordingly.

[0030] (3) The water produced by the first semi-permeable membrane and the water produced by the second semi-permeable membrane are mixed and used as purified water.

[0031] Furthermore, in the multi-segment semi-permeable membrane system, the hardness removal rate of the second semi-permeable membrane is greater than that of the first semi-permeable membrane. Preferably, the hardness removal rate ratio of the second semi-permeable membrane to the first semi-permeable membrane is 1.3–3.2:1, more preferably 1.5–3.0:1. The water permeability coefficient of the second semi-permeable membrane is higher than that of the first semi-permeable membrane. Preferably, the water permeability coefficient of the second semi-permeable membrane is more than 1.2 times that of the first semi-permeable membrane, more preferably more than 1.5 times.

[0032] During the operation of a water purification device using a semi-permeable membrane system, when the water quality detection unit detects that the hardness concentration of the raw water in the area is low, in order to obtain purified water with a suitable hardness concentration, the opening of the concentrated water valve of the first-stage semi-permeable membrane is reduced. That is, the proportion of the concentrated water from the first-stage semi-permeable membrane entering the second-stage semi-permeable membrane to the total amount of water to be treated is reduced, and the proportion of the water produced by the second-stage semi-permeable membrane to the total amount of purified water is also reduced accordingly.

[0033] When the water quality detection unit detects that the hardness concentration of the raw water in the area is high, in order to obtain purified water with a suitable hardness concentration, the opening of the concentrated water valve of the first semi-permeable membrane is increased. That is, the proportion of the concentrated water from the first semi-permeable membrane entering the second semi-permeable membrane to the total amount of water to be treated is increased, and the proportion of the water produced by the second semi-permeable membrane to the total amount of purified water is also increased accordingly.

[0034] The main features of this invention are:

[0035] Given the significant differences in hardness concentration in water bodies across different regions, existing water purification technologies using RO membranes almost completely remove hardness components while failing to effectively retain some beneficial minerals. Meanwhile, NF membrane-based water purification devices struggle to effectively address and meet water quality requirements under conditions of large fluctuations in hardness concentration. This invention effectively addresses water bodies with varying hardness concentrations, obtaining high-quality purified water with suitable hardness levels even when the raw water hardness concentration fluctuates significantly. Furthermore, it effectively removes harmful organic matter, heavy metals, and bacteria from the raw water.

[0036] Furthermore, this invention offers significant advantages, particularly when applied to various mobile transportation vehicles such as railway trains, high-speed trains, maglev trains, RVs, or long-distance buses traveling to different locations. Using this invention, high-quality drinking water with suitable hardness concentrations can be obtained in real time based on differences in the hardness concentration of raw water in different locations, without needing to change the type of water purification device or semi-permeable membrane installed in the transportation vehicle, thus improving the quality of drinking water. Attached Figure Description

[0037] Figure 1 This is a schematic flowchart of a water purification treatment device according to the present invention.

[0038] in,

[0039] 1-Water supply pipeline to be treated; 2-Raw water pump; 3-Water quality testing unit; 4-Control unit;

[0040] 5-First semipermeable membrane; 6-Second semipermeable membrane; 7-Concentrate pipeline of the first semipermeable membrane;

[0041] 8-Electric concentrate valve for the first stage semi-permeable membrane concentrate measurement; 9-Second stage semi-permeable membrane concentrate pipeline;

[0042] 10 - Concentrate valve for the second stage semi-permeable membrane concentrate measurement; 11 - Permeate pipeline for the first stage semi-permeable membrane;

[0043] 12 - Second section of semi-permeable membrane water production pipeline; 13 - Purified water pipeline. Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings and embodiments, but these are not intended to limit the scope of the invention. The following embodiments are only used to further describe the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention still fall within the scope of protection of the present invention.

[0045] like Figure 1 As shown, in the water purification device of the present invention, the water to be treated is pressurized by the raw water pump 2 and enters the first semi-permeable membrane 5 for filtration. The concentrate from the first semi-permeable membrane enters the second semi-permeable membrane 6 for further filtration after passing through the electric concentrate valve 8. The concentrate from the second semi-permeable membrane is discharged after passing through the concentrate valve 10. The product water from the first semi-permeable membrane 5 and the second semi-permeable membrane 6 is mixed to form purified water. During the operation of the device, the hardness of the water to be treated is detected by the water quality detection unit 3, and the opening degree of the electric concentrate valve 8 of the first semi-permeable membrane is adjusted by the control unit 4, thereby adjusting and controlling the proportion of the water volume of the first semi-permeable membrane concentrate entering the second semi-permeable membrane to the total amount of water to be treated.

[0046] Example 1

[0047] like Figure 1 The water purification device shown uses NF membranes in both the first and second semi-permeable membrane stages. The hardness removal rate of the first NF membrane is 60%, while that of the second NF membrane is 90%, meaning the hardness removal rate ratio of the second NF membrane to the first NF membrane is 1.5:1. Simultaneously, the permeability coefficient of the second NF membrane is 2.6 times that of the first NF membrane. During operation, the recovery rate of the second NF membrane is kept constant at 60%. This water purification device is installed on a high-speed train traveling from southern to northern China. At each stop along the route, the train's water tank needs to be replenished with tap water to meet drinking water demands based on actual water consumption.

[0048] The hardness concentration of tap water varies significantly across high-speed rail stations in different cities, ranging from a minimum of approximately 50 mg / L to a maximum of around 450 mg / L. After the water tank is replenished with tap water, the hardness detector in the water purification device automatically measures the hardness and sends feedback to the PLC control unit. This PLC control unit then controls the opening of the concentrate valve on the concentrate side of the first-stage NF membrane through a pre-set program. This concentrate valve is an electrically proportional regulating valve, with opening settings of 0%, 25%, 50%, 75%, and 100%.

[0049] (1) When the hardness is >350mg / L, the opening degree of the electric proportional control valve is 100%;

[0050] (2) When 350 ≥ hardness > 250 mg / L, the opening degree of the electric proportional control valve is 75%;

[0051] (3) When 250 ≥ hardness > 150 mg / L, the opening degree of the electric proportional regulating valve is 50%;

[0052] (4) When the hardness is ≤150mg / L, the opening degree of the electric proportional control valve is 25%;

[0053] Based on the above control method, and according to the hardness measurements of tap water replenished at some high-speed rail stations in cities, the hardness results of the purified water from this water treatment device are shown in Table 1 below:

[0054] Table 1

[0055]

[0056] It can be seen that although the hardness concentration of the tap water to be treated fluctuates greatly, the purified water obtained after passing through the water purification device can retain a suitable concentration of hardness components.

[0057] Example 2

[0058] like Figure 1 The water purification device shown uses NF membranes in both the first and second semi-permeable membrane stages. The hardness removal rate of the first NF membrane is 65%, while that of the second NF membrane is 95%, meaning the hardness removal rate ratio of the second NF membrane to the first NF membrane is 1.5:1. Simultaneously, the permeability coefficient of the second NF membrane is 2.8 times that of the first NF membrane. During operation, the recovery rate of the second NF membrane is kept constant at 50%. This water purification device is primarily used for preparing drinking water in emergency situations. The water to be treated can be surface water or groundwater from various locations, and the purified water will meet the drinking water needs in emergency situations.

[0059] The hardness of surface water or groundwater used as emergency water sources varies greatly from place to place, fluctuating from tens to hundreds of mg / L. When this water purification device is placed in a location, a hardness detector automatically measures the hardness of the water to be treated and sends feedback to the PLC control unit. This PLC control unit then controls the opening of the concentrate valve on the concentrate side of the first-stage NF membrane through a pre-set program. This concentrate valve is an electrically proportional regulating valve, with opening settings of 0%, 25%, 50%, 75%, and 100%.

[0060] (1) When the hardness is >500mg / L, the opening degree of the electric proportional control valve is 100%;

[0061] (2) When 450 ≥ hardness > 300 mg / L, the opening degree of the electric proportional control valve is 75%;

[0062] (3) When 300 ≥ hardness > 150 mg / L, the opening degree of the electric proportional control valve is 50%;

[0063] (4) When the hardness is ≤150mg / L, the opening degree of the electric proportional control valve is 25%;

[0064] Based on the above control methods, and according to the hardness measurements of surface water or groundwater used as emergency water sources in some areas, the hardness results of the purified water from this water treatment device are shown in Table 2 below:

[0065] Table 2

[0066]

[0067] It can be seen that although the hardness of the surface water or groundwater to be treated fluctuates greatly, the purified water obtained after passing through this water purification device can retain a suitable concentration of hardness components.

[0068] Example 3

[0069] like Figure 1 The water purification device shown uses NF membranes in both the first and second semi-permeable membrane stages. The hardness removal rate of the first NF membrane is 30%, while that of the second NF membrane is 96%, meaning the hardness removal rate ratio of the second NF membrane to the first NF membrane is 3.2:1. Simultaneously, the permeability coefficient of the second NF membrane is 1.2 times that of the first NF membrane. During operation, the recovery rate of the second NF membrane is kept constant at 56%. This water purification device is installed on railway trains traveling in southern China. When passing through various city stations, the train's water tank needs to be replenished with tap water to meet the water demand.

[0070] The hardness concentration of tap water varies in different cities in southern China, generally lower than in northern regions. The lowest tap water hardness is approximately 50 mg / L, while the highest reaches around 200 mg / L. After the water tank is replenished with tap water, the hardness detector in the water purification device automatically detects the hardness and sends feedback to the PLC control unit. This PLC control unit then controls the opening of the concentrate valve on the concentrate side of the first-stage NF membrane through a pre-set program. This concentrate valve is an electrically operated proportional regulating valve.

[0071] (1) When the hardness is >150mg / L, the opening degree of the electric proportional control valve is 100%;

[0072] (2) When 150 ≥ hardness > 100 mg / L, the opening degree of the electric proportional control valve is 75%;

[0073] (3) When the hardness is ≤100mg / L, the opening degree of the electric proportional regulating valve is 50%;

[0074] Based on the above control method, and according to the hardness measurements of the tap water replenished at some urban train stations, the hardness of the purified water from this water treatment device is shown in Table 3 below:

[0075] Table 3

[0076]

[0077] It can be seen that although the hardness concentration of the tap water to be treated fluctuates, the purified water obtained after passing through the water purification device can retain a suitable concentration of hardness components.

[0078] Example 4

[0079] like Figure 1 The water purification device shown uses NF membranes in both the first and second semi-permeable membrane stages. The first NF membrane has a hardness removal rate of 70%, while the second NF membrane has a hardness removal rate of 91%, meaning the hardness removal rate ratio of the second NF membrane to the first NF membrane is 1.3:1. Furthermore, the permeability coefficient of the second NF membrane is 4.4 times that of the first NF membrane. During operation, the recovery rate of the second NF membrane is kept constant at 40%. This water purification device is primarily used in RVs traveling in northern China. When passing through various cities in central China, the RV's water tank needs to be replenished with tap water from different locations to meet drinking water requirements.

[0080] The hardness concentration of tap water varies in different cities in northern China, generally being higher than in southern regions. The lowest tap water hardness is approximately 150 mg / L, while the highest reaches around 450 mg / L. After the water tank is replenished with tap water, the hardness detector in the water purification device automatically detects the hardness and sends feedback to the PLC control unit. This PLC control unit then uses a pre-set program to control the opening of the concentrate valve on the concentrate side of the first-stage NF membrane. This concentrate valve is an electrically operated proportional regulating valve.

[0081] (1) When the hardness is >400mg / L, the opening degree of the electric proportional control valve is 100%;

[0082] (2) When 400≥hardness>300mg / L, the opening degree of the electric proportional control valve is 75%;

[0083] (3) When 300≥hardness>200mg / L, the opening degree of the electric proportional regulating valve is 50%;

[0084] (4) When the hardness is ≤200mg / L, the opening degree of the electric proportional control valve is 25%;

[0085] Based on the above control method, and according to the hardness measurements of the tap water supplemented in some cities, the hardness of the purified water from this water treatment device is shown in Table 4 below:

[0086] Table 4

[0087]

[0088] It can be seen that although the hardness concentration of the tap water to be treated fluctuates greatly, the purified water obtained after passing through the water purification device can retain a suitable concentration of hardness components.

[0089] Example 5

[0090] like Figure 1 The water purification device shown uses NF membranes in both the first and second semi-permeable membrane stages. The hardness removal rate of the first NF membrane is 65%, while that of the second NF membrane is 78%, meaning the hardness removal rate ratio of the second NF membrane to the first NF membrane is 1.2:1. Simultaneously, the permeability coefficient of the second NF membrane is 2.6 times that of the first NF membrane. During operation, the recovery rate of the second NF membrane is kept constant at 60%. This water purification device is installed on a high-speed train traveling from southern to northern China. At each stop along the route, the train's water tank needs to be replenished with tap water to meet drinking water demands based on actual water consumption.

[0091] The hardness concentration of tap water varies significantly across high-speed rail stations in different cities, ranging from a minimum of approximately 50 mg / L to a maximum of around 450 mg / L. After the water tank is replenished with tap water, the hardness detector in the water purification device automatically measures the hardness and sends feedback to the PLC control unit. This PLC control unit then controls the opening of the concentrate valve on the concentrate side of the first-stage NF membrane through a pre-set program. This concentrate valve is an electrically proportional regulating valve, with opening settings of 0%, 25%, 50%, 75%, and 100%.

[0092] (1) When the hardness is >350mg / L, the opening degree of the electric proportional control valve is 100%;

[0093] (2) When 350 ≥ hardness > 250 mg / L, the opening degree of the electric proportional control valve is 75%;

[0094] (3) When 250 ≥ hardness > 150 mg / L, the opening degree of the electric proportional regulating valve is 50%;

[0095] (4) When the hardness is ≤150mg / L, the opening degree of the electric proportional control valve is 25%;

[0096] Based on the above control method, and according to the hardness measurements of tap water replenished at high-speed rail stations in some cities, the hardness results of the purified water from this water treatment device are shown in Table 5 below:

[0097] Table 5

[0098]

[0099] It can be seen that the hardness concentration of the tap water to be treated fluctuates greatly, but the purified water obtained after passing through the water purification device retains a certain concentration of hardness. In some areas with high hardness, the hardness of the purified water is slightly higher.

[0100] Example 6

[0101] like Figure 1 The water purification device shown uses NF membranes in both the first and second semi-permeable membrane stages. The hardness removal rate of the first NF membrane is 30%, while that of the second NF membrane is 90%, meaning the hardness removal rate ratio of the second NF membrane to the first NF membrane is 3.0:1. Simultaneously, the permeability coefficient of the second NF membrane is 1.1 times that of the first NF membrane. During operation, the recovery rate of the second NF membrane is kept constant at 56%. This water purification device is installed on railway trains traveling in southern China. When passing through various city stations, the train's water tank needs to be replenished with tap water to meet the water demand.

[0102] The hardness concentration of tap water varies in different cities in southern China, generally lower than in northern regions. The lowest tap water hardness is approximately 50 mg / L, while the highest reaches around 200 mg / L. After the water tank is replenished with tap water, the hardness detector in the water purification device automatically detects the hardness and sends feedback to the PLC control unit. This PLC control unit then controls the opening of the concentrate valve on the concentrate side of the first-stage NF membrane through a pre-set program. This concentrate valve is an electrically operated proportional regulating valve.

[0103] (1) When the hardness is >150mg / L, the opening degree of the electric proportional control valve is 100%;

[0104] (2) When 150 ≥ hardness > 100 mg / L, the opening degree of the electric proportional control valve is 75%;

[0105] (3) When the hardness is ≤100mg / L, the opening degree of the electric proportional regulating valve is 50%;

[0106] Based on the above control method, and according to the hardness measurements of tap water replenished at train stations in some cities, the hardness of the purified water from this water treatment device is shown in Table 6 below:

[0107] Table 6

[0108]

[0109] It can be seen that although the hardness concentration of the tap water to be treated fluctuates, the purified water obtained after passing through the water purification device retains a certain concentration of hardness. In some areas with high hardness, the hardness of the purified water is slightly higher.

[0110] Comparative Example 1

[0111] The water purification system using RO membrane products achieves a hardness removal rate of 99%. This RO membrane water purification system is installed on high-speed trains traveling from southern to northern China. At each station along the route, the train's water tank needs to be replenished with tap water to meet water demand. The hardness concentration of tap water varies greatly among the high-speed train stations, ranging from a minimum of approximately 50 mg / L to a maximum of around 450 mg / L. The hardness of the water purified by this RO membrane water purification system ranges from 0.5 to 4.5 mg / L.

[0112] It can be seen that this RO membrane water treatment device almost completely removes hardness components from the water, but cannot retain some mineral elements that are beneficial to the human body.

[0113] Comparative Example 2

[0114] The water purification system using NF membrane products achieves a hardness removal rate of 50%. This NF membrane water purification system is installed on high-speed trains traveling from southern to northern China. At each station along the route, the train's water tank needs to be replenished with tap water to meet water demand. The hardness concentration of tap water varies greatly among the high-speed rail stations, ranging from a minimum of approximately 50 mg / L to a maximum of around 450 mg / L. The hardness of the purified water using this NF membrane water purification system is 25–225 mg / L.

[0115] It can be seen that for tap water in areas with high hardness concentration, the hardness concentration after treatment by this NF membrane water treatment device is still relatively high, which means it is difficult to effectively respond to and meet the water quality requirements under conditions of hardness concentration fluctuation.

[0116] Comparative Example 3

[0117] This water purification device employs a multi-stage semi-permeable membrane system. The concentrated water from the first stage of treatment passes through a semi-permeable membrane and then enters the second stage. The permeate from both stages is mixed to produce purified water. Both stages use NF membranes. The first stage NF membrane has a hardness removal rate of 90%, while the second stage has a hardness removal rate of 60%, meaning the second stage has a lower hardness removal rate than the first. Simultaneously, the permeability coefficient of the second stage NF membrane is 0.9 times that of the first stage NF membrane. During operation, the recovery rate of the second stage NF membrane is maintained at a constant 50%. This water purification device is installed on a high-speed train traveling from southern to northern China. At each stop along the route, the train's water tank needs to be replenished with tap water to meet drinking water demands based on actual water consumption.

[0118] The hardness concentration of tap water varies considerably among high-speed rail stations in different cities, ranging from a minimum of approximately 50 mg / L to a maximum of around 450 mg / L. Based on hardness measurements of tap water replenished at some high-speed rail stations, the hardness results of the purified water from this water treatment device are illustrated in Table 7 below.

[0119] Table 7

[0120]

[0121] It can be seen that, due to the large fluctuation in the hardness concentration of the tap water to be treated, the hardness concentration in the purified water in the high hardness concentration area is still relatively high after being treated by the water purification device, while the hardness concentration in the purified water in the low hardness concentration area is relatively low.

[0122] In summary, compared with Comparative Examples 1-3, Examples 1-6 demonstrate that, regardless of the significant fluctuations in hardness concentration in the raw water across different regions, the purified water treated by the water purification device of this invention retains a suitable concentration of hardness components. This invention effectively overcomes the shortcomings of existing RO membrane water purification devices, which almost completely remove hardness components from water, and also solves the problem that NF membrane water purification devices struggle to effectively address and meet water quality requirements under conditions of large fluctuations in hardness concentration, thereby improving the quality of drinking water.

Claims

1. A method for operating a water purification apparatus, the water purification apparatus comprising a multi-stage semi-permeable membrane system, a water quality detection unit, a control unit, and a concentrated water valve provided on a concentrated water side of a first stage semi-permeable membrane, characterized by: The operation method comprises the following steps: (1) According to the measured value of the water quality detection unit of the water to be treated, the opening degree of the concentrated water valve of the first-stage semi-permeable membrane is adjusted by the control unit during the operation of the multi-stage semi-permeable membrane system; (2) Based on the opening degree of the concentrated water valve, the proportion of the water quantity of the first-stage semi-permeable membrane concentrated water entering the second-stage semi-permeable membrane in the total quantity of the water to be treated is controlled; (3) The water produced by the first-stage semi-permeable membrane and the water produced by the second-stage semi-permeable membrane are mixed to serve as purified water; (4) The water permeability coefficient of the second-stage semi-permeable membrane is 1.2 times or more of the water permeability coefficient of the first-stage semi-permeable membrane; Wherein, the removal rate of the second-stage semi-permeable membrane to hardness is greater than the removal rate of the first-stage semi-permeable membrane to hardness; in step (1), when the water quality detection unit detects that the hardness concentration of raw water is low, the opening degree of the concentrated water valve of the first-stage semi-permeable membrane concentrated water measurement is adjusted to be small, that is, the proportion of the water quantity of the first-stage semi-permeable membrane concentrated water entering the second-stage semi-permeable membrane in the total quantity of the water to be treated is reduced; when the water quality detection unit detects that the hardness concentration of raw water is high, the opening degree of the concentrated water valve of the first-stage semi-permeable membrane concentrated water measurement is adjusted to be large, that is, the proportion of the water quantity of the first-stage semi-permeable membrane concentrated water entering the second-stage semi-permeable membrane in the total quantity of the water to be treated is increased.

2. The method of operating a water purification device according to claim 1, characterized in that: The hardness removal rate ratio of the second-stage semi-permeable membrane to the first-stage semi-permeable membrane is 1.3-3.2:

1.

3. The method of operating a water purification device according to claim 1, wherein: The water quantity of the first-stage semi-permeable membrane concentrated water entering the second-stage semi-permeable membrane accounts for 10-90% of the total quantity of the water to be treated.

4. The method of operating a water purification device according to claim 1, wherein: The water production quantity of the second-stage semi-permeable membrane accounts for 10-80% of the total quantity of the purified water.

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