Water treatment system and water treatment method

Abstract

A water treatment system improves the thermal efficiency of the entire system for various raw water temperatures. The water treatment system (101) has a reverse osmosis membrane device (14), an electrically regenerative deionization device (18) located downstream of the reverse osmosis membrane device (14), a first heat exchanger (31) located upstream of the reverse osmosis membrane device (14) and performing temperature adjustment of feed water to the reverse osmosis membrane device (14) according to the temperature of raw water supplied to the water treatment system (101), and a second heat exchanger (32) located between the reverse osmosis membrane device (14) and the electrically regenerative deionization device (18) and cooling feed water to the electrically regenerative deionization device (18). One of the first heat exchanger (31) and the second heat exchanger (32) is an internal heat exchanger that performs heat exchange inside the water treatment system, and the other of the first heat exchanger (31) and the second heat exchanger (32) is an external heat exchanger that performs heat exchange between the outside and the water treatment system.

Description

Technical Field

[0001] This application is based on and claims priority to Japanese applications filed on October 25, 2021, namely Japanese Application Special Claims 2021-173932 and 2021-173933. These applications in their entirety are incorporated herein by reference.

[0002] This invention relates to a water treatment system and a water treatment method. Background Technology

[0003] In a water treatment system, reverse osmosis membrane units, electro-regenerative deionization units, and other water treatment devices are arranged in series. Each water treatment device has preferred water temperature conditions, and the temperature of the water supplied to each water treatment device is adjusted to an appropriate temperature via a heat exchanger. Japanese Utility Model Application Publication No. 49-983946 discloses a water treatment system that, after heating the water supplied to the reverse osmosis membrane unit using a heat exchanger, recovers waste heat from the treated water in the reverse osmosis membrane unit and uses this waste heat to preheat the water supplied to the reverse osmosis membrane unit. According to this water treatment system, the thermal energy used to heat the water to be treated to the preferred water temperature conditions of the reverse osmosis membrane unit can be saved, thereby improving the thermal efficiency of the water treatment system. Summary of the Invention (The problem the invention aims to solve)

[0004] The temperature of raw water varies not only depending on the environment in which the water treatment system is located (high-temperature region, low-temperature region) but also on the type of raw water used to produce the raw water (groundwater, municipal water, etc.). In the water treatment system described in Japanese Utility Model Application Publication No. 49-983946, the waste heat from the reverse osmosis membrane unit is used to preheat the water supplied to the reverse osmosis membrane unit. However, the water treatment unit requiring temperature adjustment is not limited to the reverse osmosis membrane unit. For example, the preferred water temperature for an electro-regenerative deionization unit differs from that for a reverse osmosis membrane unit. Therefore, even if efforts are made to optimize the thermal efficiency of each individual water treatment unit, it is difficult to improve the overall thermal efficiency of the water treatment system.

[0005] The purpose of this invention is to provide a water treatment system that includes a reverse osmosis membrane device and an electro-regenerative deionization device, which can improve the overall thermal efficiency of the system for various raw water temperatures. (Technical solution used to solve the problem)

[0006] The water treatment system of the present invention comprises: at least one reverse osmosis membrane device; at least one electro-regenerative deionization device located downstream of the at least one reverse osmosis membrane device; a first heat exchanger located upstream of the at least one reverse osmosis membrane device, which adjusts the temperature of the water supplied to the at least one reverse osmosis membrane device according to the temperature of the raw water supplied to the water treatment system; and a second heat exchanger located between the at least one reverse osmosis membrane device and the at least one electro-regenerative deionization device, which cools the water supplied to the electro-regenerative deionization device. One of the first and second heat exchangers is an internal heat exchanger that performs heat exchange within the water treatment system, and the other of the first and second heat exchangers is an external heat exchanger that performs heat exchange with the outside of the water treatment system. (Invention Effects)

[0007] According to the present invention, a water treatment system is provided that includes a reverse osmosis membrane device and an electro-regenerative deionization device, which can improve the overall thermal efficiency of the system for various raw water temperatures.

[0008] The above and other objectives, features and advantages of this application will become clear from the detailed description below, which is illustrated with reference to the accompanying drawings. Attached Figure Description

[0009] Figure 1A This is a schematic diagram of the water treatment system according to the first embodiment. Figure 1B This is a schematic diagram of a water treatment system according to a variation of the first embodiment. Figure 1C This is a schematic diagram of a water treatment system according to other variations of the first embodiment. Figure 1D This is a schematic diagram of a water treatment system according to another variation of the first embodiment. Figure 2 This is a graph showing the relationship between water temperature and silica removal efficiency in a reverse osmosis membrane device. Figure 3 This is a graph showing the relationship between water temperature and silica removal efficiency in an electro-regenerative deionization device. Figure 4A This is a graph showing the relationship between water temperature and boron removal efficiency in an electro-regenerative deionization unit. Figure 4B This is a graph showing the relationship between water temperature and boron removal efficiency in an electro-regenerative deionization unit. Figure 5A This is a schematic diagram of the water treatment system according to the second embodiment. Figure 5B This is a schematic diagram of a water treatment system according to a variation of the second embodiment. Figure 5C This is a schematic diagram of a water treatment system according to other variations of the second embodiment. Figure 5D This is a schematic diagram of a water treatment system according to another variation of the second embodiment. Figure 5E This is a schematic diagram of a water treatment system according to another variation of the second embodiment. Figure 6A This is a schematic diagram of the water treatment system according to the third embodiment. Figure 6B This is a schematic diagram of a water treatment system according to a variation of the third embodiment. Figure 6C This is a schematic diagram of a water treatment system according to other variations of the third embodiment. Figure 6D This is a schematic diagram of a water treatment system according to another variation of the third embodiment. Figure 7A This is a schematic diagram of the water treatment system according to the fourth embodiment. Figure 7B This is a schematic diagram of a water treatment system according to a variation of the fourth embodiment. Figure 8 This is a graph showing the relationship between the current ratio of an electro-regenerative deionization device and the boron removal efficiency. Figure 9A This is a schematic diagram of the water treatment system according to the fifth embodiment. Figure 9B This is a schematic diagram of a water treatment system according to a variation of the fifth embodiment. Figure 10A This is a schematic diagram of the water treatment system according to the sixth embodiment. Figure 10B This is a schematic diagram of a water treatment system according to a variation of the sixth embodiment. Figure 11 This is a schematic diagram of the water treatment system according to the seventh embodiment. Figure 12 This is a schematic diagram of the water treatment system according to the eighth embodiment. Figure 13 This is a schematic diagram of the water treatment system according to the ninth embodiment. Detailed Implementation

[0010] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. Each embodiment of the water treatment system 101, 201, 301, 401, 501, 601, 701, 801, and 901 has a primary system S1 and a secondary system S2. The secondary system S2 is located downstream of the primary system S1 and upstream of the point of use 2. The primary system S1 produces pure water from raw water, and the secondary system S2 produces ultrapure water from the pure water. The secondary system S2 is also referred to as a subsystem. The secondary system S2 has various water treatment devices 21 to 25 for further treating the treated water from the electro-regenerative deionization device 18 of the primary system S1. The ultrapure water (treated water from the water treatment devices) produced by the secondary system S2 is sent to the point of use 2. Ultrapure water produced by the secondary system S2 that is not used at point 2 is returned to the upstream side of water treatment units 21 to 25 via a second recirculation line L3 connected to the main pipe L2 of the secondary system S2. Within the secondary system S2, pure or ultrapure water is constantly circulated. The secondary system S2 is the scope of pure or ultrapure water circulation, including the main pipe L2 and the second recirculation line L3, as well as all equipment installed on the main pipe L2 and the second recirculation line L3. Point 2 is connected to water treatment systems 101, 201, 301, 401, 501, 601, 701, 801, and 901 via a branch line L4 from the main pipe L2.

[0011] (Summary of the first to third embodiments) In each embodiment, the water treatment systems 101, 201, and 301 are described in detail, each comprising: a first heat exchanger 31 located upstream of the reverse osmosis membrane unit 14, which adjusts the temperature of the water supplied to the reverse osmosis membrane unit 14 according to the temperature of the raw water supplied to the water treatment system; and a second heat exchanger 32 located between the reverse osmosis membrane unit 14 and the electro-regenerative deionization unit 18, which cools the water supplied to the electro-regenerative deionization unit 18. According to the embodiments, one of the first heat exchanger 31 and the second heat exchanger 32 operates as an internal heat exchanger for heat exchange within the water treatment system, and the other operates as an external heat exchanger for heat exchange with the outside of the water treatment system. The raw water supplied to the water treatment system includes silica and boron. The silica concentration of the treated water in the reverse osmosis membrane unit 14 is 100 ppb or less, and the boron concentration is 50 ppb or less. The silica concentration of the treated water in the electro-regenerative deionization unit 18 is 100 ppt or less, and the boron concentration is 50 ppt or less.

[0012] (First Implementation) Figure 1A The schematic configuration of a water treatment system 101 according to the first embodiment of the present invention is shown. In this embodiment, the temperature of the raw water supplied to the water treatment system 101 is lower than a given temperature range (e.g., 15°C). As described above, the water treatment system 101 is divided into a primary system S1 and a secondary system S2; therefore, the primary system S1 will be described first, followed by the secondary system S2. It should be noted that the devices constituting the primary system S1 and the secondary system S2 are not limited to those described below, and other tanks, pumps, etc., may be provided as needed.

[0013] In a primary system S1, along the main pipe L1 through which the treated water flows, a raw water tank 11, a raw water pump 12, a second heat exchanger 32, a first heat exchanger 31, at least one reverse osmosis membrane unit 14, and at least one electro-regenerative deionization unit 18 (EDI) are connected in series from upstream to downstream in the direction of water flow. The treated water passes through the second heat exchanger 32 again between the reverse osmosis membrane unit 14 and the electro-regenerative deionization unit 18. The at least one reverse osmosis membrane unit 14 includes both single-stage reverse osmosis membrane units and multi-stage reverse osmosis membrane units connected in series, and is referred to as reverse osmosis membrane unit 14 in the following description. The at least one electro-regenerative deionization unit 18 includes both single-stage electro-regenerative deionization units and multi-stage electro-regenerative deionization units connected in series, and is referred to as electro-regenerative deionization unit 18 in the following description. By arranging at least one of the reverse osmosis membrane unit 14 and the electro-regenerative deionization unit 18 in series, water quality can be further improved. Although the illustration is omitted, at least one of the following can be provided between the reverse osmosis membrane unit 14 and the electro-regenerated deionization unit 18: a membrane degassing unit for removing carbonic acid and dissolved oxygen, an ion exchange resin unit, an ultraviolet irradiation unit, and a boron selective resin unit.

[0014] Raw water tank 11 stores raw water produced by a pretreatment system (not shown) located upstream of the primary system S1, and water recovered from downstream equipment (pure water, ultrapure water, concentrated water from the electro-regenerated deionization unit 18, electrode water, etc.). Raw water pump 12 pumps the raw water stored in raw water tank 11 to the second heat exchanger 32, and then to the first heat exchanger 31.

[0015] The first heat exchanger 31 operates as a heater to heat the supply water to the reverse osmosis membrane unit 14 to a given temperature. Located upstream of the reverse osmosis membrane unit 14, the first heat exchanger 31 is an external heat exchanger that exchanges heat with the outside of the water treatment system 101. The first heat exchanger 31 heats the supply water to the reverse osmosis membrane unit 14. If the temperature of the supply water to the reverse osmosis membrane unit 14 is too low, the viscosity of the supply water increases, making it difficult for the supply water to pass through the reverse osmosis membrane unit 14. This increases the pressure loss of the reverse osmosis membrane unit 14, potentially increasing the power cost and pump capacity of the raw water pump 12. Furthermore, if the flow rate of each element in the reverse osmosis membrane unit 14 is reduced to decrease pressure loss, the number of elements increases. On the other hand, if the temperature of the supply water to the reverse osmosis membrane unit 14 is too high, problems such as membrane material leaching, precipitation of dissolved components in the supply water, and the formation of biogenic slime can easily occur. The first heat exchanger 31 adjusts the temperature of the water supplied to the reverse osmosis membrane unit 14 to be above 15°C and below 40°C, preferably to 20°C to 30°C. The reverse osmosis membrane unit 14 removes particulate matter, ionic components, and silica, etc., from the water being treated.

[0016] A second heat exchanger 32 is disposed between the reverse osmosis membrane unit 14 and the electro-regenerative deionization unit 18. The second heat exchanger 32 cools the treated water from the reverse osmosis membrane unit 14 and the supply water to the electro-regenerative deionization unit 18 to a given temperature. The second heat exchanger 32 is an internal heat exchanger that performs heat exchange within the water treatment system 101. The arrows indicate the direction of heat transfer. As will be described later, if the temperature of the supply water to the electro-regenerative deionization unit 18 is low, the boron removal rate is increased. The given temperature is approximately 10°C to 30°C, preferably approximately 15°C to 24°C. The electro-regenerative deionization unit 18 removes ionic components from the treated water. The electro-regenerative deionization unit 18 also removes silica and boron from the treated water. The treated water from the electro-regenerative deionization unit 18 is stored in the auxiliary tank 19 of the secondary system S2.

[0017] As described above, the low-temperature supply water to the reverse osmosis membrane unit 14 is heated by the second heat exchanger 32 before being heated by the first heat exchanger 31. Therefore, the thermal energy required by the first heat exchanger 31 is saved. On the other hand, the high-temperature treated water of the reverse osmosis membrane unit 14 draws heat energy from the low-temperature supply water to the reverse osmosis membrane unit 14, thereby being cooled to a temperature suitable for use as supply water to the electro-regenerative deionization unit 18. Since thermal energy is transferred from the part that does not require thermal energy to the part that does require thermal energy through heat exchange, the overall energy utilization efficiency of the primary system S1 is improved.

[0018] Subsystem S2 is located between the electroregenerative deionization unit 18 and the point of use 2. In secondary system S2, along the main pipe L2 through which the treated water flows, from upstream to downstream, are arranged in series a secondary tank (pure water tank) 19, a pure water pump 20, a heat exchanger 21, an ultraviolet irradiation device 22, an ion exchange device 23, a membrane degassing device 24, and an ultrafiltration membrane device 25. The pure water pump 20 delivers pure water stored in the secondary tank 19 to the heat exchanger 21. The ultrapure water supplied to the point of use 2 is typically specified to have a required temperature (e.g., around 24°C to 26°C). The heat exchanger 21 is installed to adjust the temperature of the ultrapure water supplied to the point of use 2. When the water supplied to the electroregenerative deionization unit 1 is cooled using the second heat exchanger 32, the treated water of the electroregenerative deionization unit 18 is typically heated; therefore, the heat exchanger 21 can function as a heater. However, when the temperature of the treated water rises due to heat input from the electro-regenerative deionization unit 18, waste heat from the pure water pump 20, and an increase in the volume of circulating water flowing in the second recirculation line L3, the heat exchanger 21 can also cool the treated water. Therefore, where cooling of the treated water is possible, the heat exchanger 21 is preferably capable of both cooling and heating. The ultraviolet irradiation unit 22 irradiates the treated water with ultraviolet light to decompose the organic matter contained in the treated water. The ion exchange unit 23 removes the decomposition products generated by the ultraviolet irradiation unit 22. The membrane degassing unit 24 removes dissolved oxygen contained in the treated water. The ultrafiltration membrane unit 25 removes particulate matter contained in the treated water. The ultrapure water thus produced is sent to the point of use 2, and the water not used at the point of use 2 is returned to the auxiliary tank 19 through the second recirculation line L3.

[0019] Figure 2 An example of a measurement showing the relationship between water temperature and silica removal rate in the reverse osmosis membrane unit 14 is presented. While the silica removal rate decreases with increasing water temperature, no significant decrease was observed, indicating a limited effect of temperature. On the other hand, although the figure is omitted, the boron removal rate of the reverse osmosis membrane unit 14 is not particularly high. From the viewpoint of boron removal rate, the water temperature supplied to the reverse osmosis membrane unit 14 is not particularly limited. Figure 3 This paper presents a measurement example showing the relationship between water temperature and silica removal rate in the electro-regenerative deionization device 18. If the water temperature increases, the silica removal rate increases; if the water temperature decreases, the silica removal rate decreases.

[0020] Figure 4A , Figure 4B An example of measuring the relationship between water temperature and boron removal rate in an electro-regenerative deionization device 18 is shown. Since an electro-regenerative deionization device 18, which varies depending on the water temperature range, is used, the results are divided into... Figure 4A and Figure 4BThis is illustrated. The water supplied to the electro-regenerative deionization unit 18 includes boron (5 ppb to 20 ppb), silica (5 ppb to 10 ppb), and carbonic acid (1 ppm). Here, the carbonic acid concentration is determined by the concentration of H2CO3 and HCO3-. - CO3 2- The concentration of the total amount of carbonic acid is shown as the CO2 equivalent concentration. If the supply water temperature is low, the boron removal rate increases. For example, if the boron concentration in the supply water is 10 ppb, and the boron concentration in the treated water of the electro-regeneration deionization unit 18 is 60 ppt (removal rate 99.4%), the target value is set at 50 ppt. In this case, it is expected that the removal rate will increase by about 0.05% by lowering the water temperature by about 1°C; therefore, if the water temperature is lowered by about 2°C, the target value of 50 ppt (removal rate 99.5%) will be achieved.

[0021] Thus, the device capable of efficiently removing boron is limited to the electro-regenerative deionization unit 18, and the temperature of the supply water to the electro-regenerative deionization unit 18 is considered suitable for boron removal. As a result, silica is difficult to remove by the electro-regenerative deionization unit 18, so it is desirable to remove as much silica as possible using the reverse osmosis membrane unit 14. However, as mentioned above, the temperature of the supply water to the reverse osmosis membrane unit 14 does not significantly affect the silica removal rate. On the other hand, if the temperature of the treated water in the reverse osmosis membrane unit 14 becomes too high, it may not be possible to sufficiently reduce the temperature of the supply water to the electro-regenerative deionization unit 18 by the second heat exchanger 32. Therefore, the temperature of the supply water to the reverse osmosis membrane unit 14 is set to 15°C or higher and 40°C or lower, and the temperature of the supply water to the electro-regenerative deionization unit 18 is set to 10°C to 30°C.

[0022] (A variation of the first embodiment) Figures 1B to 1D A variation of the first embodiment is shown. Figure 1B In the modified example shown, an RO treated water tank 15 and an RO treated water delivery pump 16 are provided between the second heat exchanger 32 and the electro-regenerative deionization unit 18. The RO treated water tank 15 stores the treated water from the reverse osmosis membrane unit 14, and the RO treated water delivery pump 16 supplies the water stored in the RO treated water tank 15 to the electro-regenerative deionization unit 18. By having an RO treated water tank 15 and an RO treated water delivery pump 16 upstream of the electro-regenerative deionization unit 18, the electro-regenerative deionization unit 18 and the reverse osmosis membrane unit 14 can be operated separately. In addition, the RO treated water tank 15 functions as a buffer tank, thus making the primary system S1 less susceptible to changes in the amount of ultrapure water used at point 2.

[0023] exist Figure 1CIn the illustrated variation, a first recirculation line L5 is provided to return at least a portion of the treated water from the electro-regenerating deionizer 18 to the upstream of the reverse osmosis membrane unit 14 (the raw water tank 11 in this variation). Subsystem S2 is located between a branch of the first recirculation line L5 and the point of use 2. When the downstream auxiliary tank 19 is full, the operation of the primary system S1 can continue by circulating water in the first recirculation line L5. If the operation of the primary system S1 is stopped, the water quality in the stagnant portion may deteriorate. By continuously operating the primary system S1, water stagnation can be suppressed, and a stable high water quality can be maintained. When it becomes possible to supply water to the downstream auxiliary tank 19, the valve (not shown) of the first recirculation line L5 is closed, and the entire amount of treated water from the electro-regenerating deionizer 18 is supplied to the auxiliary tank 19. Alternatively, the valve opening of the first recirculation line L5 can be reduced to send a portion of the treated water from the electro-regenerated deionization unit 18 to the auxiliary tank 19, and the remainder returned to the upstream of the reverse osmosis membrane unit 14.

[0024] Figure 1D The variation shown is to Figure 1B The variations shown are and Figure 1C It is a combination of components. In this case, the first recirculation line L5 can also be connected to the RO treatment tank 15.

[0025] (Second Implementation) Figure 5A The schematic configuration of a water treatment system 201 according to a second embodiment of the present invention is shown. Hereinafter, the description will focus on the differences from the first embodiment. Configurations and effects that are omitted from the description are the same as in the first embodiment. In this embodiment, the temperature of the raw water supplied to the water treatment system 201 is higher than a given temperature range (e.g., 40°C). Unlike the first embodiment, the second heat exchanger 32 cannot utilize the internal cooling source (low-temperature raw water) of the water treatment system 201 for cooling. Therefore, the second heat exchanger 32 is configured as an external heat exchanger operating as a cooler.

[0026] Unlike the first embodiment, the first heat exchanger 31 functions as a cooler. Raw water is cooled by the first heat exchanger 31 to a temperature suitable for supplying water to the reverse osmosis membrane unit 14. The temperature of the treated water from the electro-regenerative deionization unit 18 becomes lower than the temperature of the raw water supplied to the water treatment system 201. Therefore, the first heat exchanger 31 serves as an internal heat exchanger where heat exchange occurs within the water treatment system 201. With this configuration, the low-temperature treated water from the electro-regenerative deionization unit 18 can be used for cooling the supply water to the reverse osmosis membrane unit 14. Furthermore, when the heat exchanger 21 in the secondary system S2 functions as a heater, the supply water to the heat exchanger 21 is preheated in the first heat exchanger 31, thus reducing the load on the heat exchanger 21. Therefore, the overall energy efficiency of the water treatment system 201 is improved.

[0027] (A variation of the second embodiment) Figures 5B to 5E A variation of the second embodiment is shown. Figure 5B In the modified example shown, an RO treatment water tank 15 and an RO treatment water delivery pump 16 are provided between the reverse osmosis membrane unit 14 and the second heat exchanger 32. The RO treatment water tank 15 stores the treated water from the reverse osmosis membrane unit 14, and the RO treatment water delivery pump 16 supplies the water stored in the RO treatment water tank 15 to the electro-regenerative deionization unit 18.

[0028] exist Figure 5C In the modified example shown, a first recirculation line L5 is provided to return at least a portion of the treated water from the electro-regenerated deionization unit 18 to the upstream of the reverse osmosis membrane unit 14 (the raw water tank 11 in this modified example). Subsystem S2 is located between a branch of the first recirculation line L5 and the point of use 2.

[0029] Figure 5D The variation shown is to Figure 5B The variations shown are and Figure 1C It is a combination of components. In this case, the first recirculation line L5 can also be connected to the RO treatment tank 15. Figures 5B to 5D The effect of the modified example shown is the same as Figures 1B to 1D The variant shown is the same.

[0030] exist Figure 5E In the modified example shown, a third heat exchanger 33 is provided between the first heat exchanger 31 and the reverse osmosis membrane unit 14 to cool the water supplied to the reverse osmosis membrane unit 14. The third heat exchanger 33 is an external heat exchanger that exchanges heat with the outside of the water treatment system 201, and can be provided when the raw water temperature is high and the temperature of the water supplied to the reverse osmosis membrane unit 14 cannot be sufficiently reduced by the first heat exchanger 31 alone.

[0031] (Third Implementation) Figure 6A The schematic configuration of the water treatment system 301 according to the third embodiment of the present invention is shown. In this embodiment, the temperature of the raw water supplied to the water treatment system 301 is generally within a given temperature range (e.g., 15°C to 40°C). However, there are cases where the temperature of the water supplied to the reverse osmosis membrane device 14 varies within the given temperature range or fluctuates around the given temperature. Such phenomena may be caused by variations in the raw water temperature, but also by the operation of the primary system S1 and the secondary system S2. The raw water is stored in the raw water tank 11 after its temperature is roughly adjusted, but the raw water tank 11 sometimes receives water recovered after being generated in subsequent equipment (pure water, ultrapure water, concentrated water from the electro-regenerated deionization device 18, electrode water, etc.), and the temperature varies. In this embodiment, the temperature of the raw water supplied to the water treatment system 301 is within a more preferred range, but it is sometimes desirable to adjust the temperature of the water supplied to the reverse osmosis membrane device 14 to a more preferred range.

[0032] Therefore, the first heat exchanger 31 is configured as an external heat exchanger (thermostat) operating as a heater or cooler. The second heat exchanger 32 operates as an internal heat exchanger to cool the water supplied to the electro-regenerative deionization unit 18, using the treated water from the electro-regenerative deionization unit 18. However, there are cases where the water supplied to the electro-regenerative deionization unit 18 cannot be cooled to a suitable temperature solely by the second heat exchanger 32; therefore, a fourth heat exchanger 34 is provided to cool the water supplied to the electro-regenerative deionization unit 18. The fourth heat exchanger 34 is an external heat exchanger. The fourth heat exchanger 34 is located between the second heat exchanger 32 and the electro-regenerative deionization unit 18. The low-temperature water supplied to the electro-regenerative deionization unit 18 is cooled by the second heat exchanger 32 before being cooled by the fourth heat exchanger 34. Therefore, the cooling energy required by the fourth heat exchanger 34 is saved.

[0033] (A variation of the third embodiment) Figures 6B to 6D A variation of the third embodiment is shown. Figure 6B In the modified example shown, an RO treated water tank 15 and an RO treated water delivery pump 16 are provided between the reverse osmosis membrane unit 14 and the second heat exchanger 32. The RO treated water tank 15 stores the treated water from the reverse osmosis membrane unit 14, and the RO treated water delivery pump 16 supplies the water stored in the RO treated water tank 15 to the electro-regenerative deionization unit 18. Figure 6C In the modified example shown, a first recirculation line L5 is provided to return at least a portion of the treated water from the electro-regenerated deionization unit 18 to the upstream of the reverse osmosis membrane unit 14 (the raw water tank 11 in this modified example). Subsystem S2 is located between a branch of the first recirculation line L5 and the point of use 2. Figure 6D The variation shown is to Figure 6B The variations shown are and Figure 6C It is a combination of components. In this case, the first recirculation line L5 can also be connected to the RO treatment tank 15. Figures 6B-6D The effect of the modified example shown is the same as Figures 1B to 1D The variant shown is the same.

[0034] (Summary of the fourth to ninth embodiments) In ultrapure water production facilities, several water treatment units, such as an electro-regenerative deionization unit, are connected in series. Each water treatment unit has preferred water temperature conditions, and the temperature of the water supplied to each water treatment unit is adjusted to an appropriate temperature by means of heaters and coolers. For example, Japanese Patent Application Publication No. 2021-65843 discloses a water treatment system that adjusts the temperature of the water supplied to the electro-regenerative deionization unit to a given range based on the temperature of the water treated by the electro-regenerative deionization unit.

[0035] In ultrapure water production systems, it is required not only to bring the temperature of the water supplied to each water treatment unit within a given range, but also to bring the temperature of the water at the point of use, the final destination of the ultrapure water, within a given required temperature. However, in order to bring the temperatures of the water supplied to each water treatment unit and the required temperature at the point of use within a given range, repeated heating and cooling of the water is necessary, resulting in reduced energy efficiency in the ultrapure water production system. This reduced energy efficiency impacts operating costs.

[0036] The purpose of the fourth to ninth embodiments is to provide a water treatment system (ultrapure water production apparatus) that can ensure the quality of ultrapure water and suppress the reduction of energy utilization efficiency. The water treatment system in each embodiment, like the first to third embodiments, has a primary system S1 and a secondary system S2. Since the functions of the primary system S1 and the secondary system S2 are the same as in the first to third embodiments, their details can be found in the first embodiment.

[0037] (Fourth Implementation) Figure 7A The schematic configuration of the water treatment system 401 according to the fourth embodiment of the present invention is shown. As described above, the water treatment system 401 is divided into a primary system S1 and a secondary system S2; therefore, the primary system S1 will be described first, followed by the secondary system S2. However, the configuration common to the first to third embodiments is omitted from the description. Each device in the primary system S1 and the secondary system S2 is monitored and controlled by the control device 3 of the ultrapure water production apparatus 1A.

[0038] In a primary system S1, along the main pipe L1 through which the treated water flows, from upstream to downstream, are connected in series the following components: raw water tank 11, raw water pump 12, temperature control device 13, at least one reverse osmosis membrane device 14, RO treated water tank 15, RO treated water transfer pump 16, cooler 17, and at least one electro-regenerative deionization device 18 (EDI).

[0039] Raw water tank 11 stores raw water produced by a pretreatment system (not shown) located upstream of the primary system S1, and water recovered from downstream equipment (pure water, ultrapure water, concentrated water from the electro-regenerated deionization unit 18, electrode water, etc.). The raw water includes boron. Raw water pump 12 pumps the raw water stored in raw water tank 11 to a temperature regulating device 13. Temperature regulating device 13 heats or cools the water supplied to the reverse osmosis membrane unit 14 to a given temperature. Temperature regulating device 13 adjusts the temperature of the water supplied to the reverse osmosis membrane unit 14 to 15°C or higher and 40°C or lower, preferably to around 20°C to 30°C. In this embodiment, since the temperature of the water supplied to the reverse osmosis membrane unit 14 is lower than the given temperature range (e.g., 15°C to 40°C or 20°C to 30°C as described above), temperature regulating device 13 operates as a heater. However, when the temperature of the water supplied to the reverse osmosis membrane unit 14 varies within or above the given temperature range, a temperature controller with heating and cooling functions may also be used. When the temperature of the water supplied to the reverse osmosis membrane unit 14 varies within the given temperature range, the temperature adjustment device 13 can be omitted. Conversely, when the temperature of the water supplied to the reverse osmosis membrane unit 14 is higher than the given temperature range, the temperature adjustment device 13 can function as a cooler.

[0040] The treated water from the reverse osmosis membrane unit 14 is stored in the RO treated water tank 15. The RO treated water transfer pump 16 delivers the RO treated water (filtered water) stored in the RO treated water tank 15 to the cooler 17. The cooler 17, located upstream of the electro-regenerative deionization unit 18, cools the water supplied to the electro-regenerative deionization unit 18 to a given temperature. As mentioned earlier, the given temperature is approximately 10°C to 30°C, preferably approximately 15°C to 24°C. The electro-regenerative deionization unit 18 removes ionic components from the treated water. The electro-regenerative deionization unit 18 also removes boron from the treated water. The treated water from the electro-regenerative deionization unit 18 is stored in the auxiliary tank 19 of the secondary system S2. Downstream of the electro-regenerative deionization unit 18, specifically between the electro-regenerative deionization unit 18 and the auxiliary tank 19, a boron concentration meter 27 is installed to measure the boron concentration of the treated water from the electro-regenerative deionization unit 18.

[0041] The configuration of the secondary system S2 is basically the same as that of the first to third embodiments. As mentioned above, when it is possible to cool the water being treated (especially when T1-T2 are negative as described later), the heat exchanger 21 is preferably capable of both cooling and heating.

[0042] The water treatment system 401 includes a first thermometer 28 and a second thermometer 26. The first thermometer 28 is located at the outlet side of the ultrafiltration membrane device 25 within the secondary system S2. The first thermometer 28 measures the temperature of the treated water (ultrapure water) from the secondary system S2 being delivered to the point of use 2. The second thermometer 26 is located between the cooler 17 and the electro-regenerative deionizer 18 and measures the temperature of the water supplied to the electro-regenerative deionizer 18. The electro-regenerative deionizer 18 includes a desalination chamber for the flow of treated water, a concentration chamber for the flow of concentrated water after the ionic components have been concentrated, and an electrode chamber for the flow of electrode water, wherein the temperature of the water flowing in these chambers is not significantly different. Therefore, in this embodiment, the second thermometer 26 measures the temperature of the inlet water of the desalination chamber, but the second thermometer 26 may also measure the temperature of the outlet water of the desalination chamber, the inlet or outlet water of the concentration chamber, and the inlet or outlet water of the electrode chamber. That is, the second thermometer 26 only needs to measure the temperature of any water entering or leaving the electric regeneration deionizer 18.

[0043] In this embodiment, the control of the cooler 17, which cools the water supplied to the electroregenerative deionizer 18, is based on the measurement value of the first thermometer 28. The first thermometer 28 is originally installed for water temperature management at the point of use 2. Therefore, conventionally, when the measurement value of the first thermometer 28 deviates from the required water temperature at the point of use 2, the heat exchanger 21 in the secondary system S2 is activated to adjust the water temperature (hereinafter referred to as the conventional example). On the other hand, the temperature adjustment of the water supplied to the electroregenerative deionizer 18 is usually based on a thermometer installed at the inlet of the electroregenerative deionizer 18. That is, the water temperature management of the water supplied to the electroregenerative deionizer 18 is usually based on the water temperature measured at the inlet of the electroregenerative deionizer 18, and is performed by the cooler 17 installed upstream of the electroregenerative deionizer 18. In contrast, in this embodiment, the cooler 17 is controlled based on the measurement value of the first thermometer 28, which is located away from the electroregenerative deionizer 18. If, for some reason, the reading on the first thermometer 28 is higher than the required water temperature at point 2, instead of cooling the water flowing in the secondary system S2 using the heat exchanger 21, the water supplied to the electro-regenerative deionizer 18 is cooled using the cooler 17. This allows the water temperature at point 2 to converge to the required temperature. Since only the location for cooling the treated water differs from conventional examples, the overall thermal efficiency of the water treatment system 401 remains unchanged. Furthermore, the boron removal efficiency of the electro-regenerative deionizer 18 is improved.

[0044] The first thermometer 28 is located downstream of the secondary system S2, specifically downstream of the ultrafiltration membrane device 25 on the main pipe L2, but its location on the main pipe L2 is not limited to this. The first thermometer 28 can measure the temperature of the treated water from any water treatment device constituting the secondary system S2. Alternatively, the first thermometer 28 can also be located on the second recirculation line L3. That is, the first thermometer 28 measures the temperature of water flowing at any location downstream of the primary system S1, and more generally, measures the temperature of water treated by the electro-regenerative deionizer 18 and flowing at any location downstream of the electro-regenerative deionizer 18. Generally, the water temperature within the secondary system S2 is not constant, as the treated water is irradiated by ultraviolet light from the ultraviolet irradiation device 22 and heated by waste heat from the pure water pump 20, thus the water temperature varies depending on the location within the secondary system S2. The water temperature can also vary based on waste heat from the piping and heat input to the piping. In this embodiment, the first thermometer 28 is located downstream of the ultrafiltration membrane device 25. Therefore, the water temperature measured by the first thermometer 28 is approximately the same as the water temperature at point 2 of use. However, the distance from the first thermometer 28 to point 2 of use is long, and sometimes the temperature difference between the two cannot be ignored. However, such temperature changes and differences can be predicted or measured in advance, and the water temperature at the location of the first thermometer 28 corresponds to the water temperature at point 2 of use. Therefore, the measured value of the first thermometer 28 can be used to control the cooler 17. Specifically, the cooler 17 operates when the value at the location of the first thermometer 28 exceeds the value corresponding to the required water temperature at point 2 of use. For example, if the upper limit of the required water temperature at point 2 of use is determined to be 25.5°C, and the water temperature measured by the first thermometer 28 is 0.5°C lower than the water temperature at point 2 of use, the water temperature at the measurement location of the first thermometer 28 corresponding to 25.5°C at point 2 of use is 25°C. Therefore, the cooler 17 operates when the measured value of the first thermometer 28 exceeds 25°C. It should be noted that when the first thermometer 28 is placed upstream of the heat exchanger 21 (for example, between the pure water pump 20 and the heat exchanger 21), in order to establish the correspondence between the measured value of the first thermometer 28 and the water temperature at the point of use 2, it is desirable that the temperature rise or temperature fall value at the heat exchanger 21 is fixed.

[0045] The operating temperature of the cooler 17 is not limited to the temperature corresponding to the upper limit of the required water temperature at point 2. The required water temperature at point 2 can be any temperature within the required water temperature range, or it can be the lower limit or the middle value of the required water temperature at point 2. For example, if the lower limit of the required water temperature at point 2 is 24.5°C, the water temperature at the measuring position of the first thermometer 28 corresponding to 24.5°C at point 2 is 24°C. Therefore, by operating the cooler 17 when the measured value of the first thermometer 28 exceeds 24°C, the water supplied to the electro-regenerative deionizer 18 can be pre-cooled before the water temperature at point 2 reaches the upper limit of the required water temperature at point 2.

[0046] As described above, the boron removal rate increases if the water temperature supplied to the electro-regenerative deionizer 18 is low. However, when the boron concentration is sufficiently reduced, it is not necessary to drastically lower the water temperature. If the water temperature is excessively lowered from the required temperature at point 2, the heating load in the heat exchanger 21 increases. Therefore, although it also depends on the required boron concentration, it is generally not preferable to excessively lower the temperature in front of the electro-regenerative deionizer 18. The cooler 17 preferably operates such that the difference T1-T2 between the temperature T1 measured by the first thermometer 28 and the temperature T2 measured by the second thermometer 26 is greater than -1 degree and less than 5 degrees. The measurement value of the first thermometer 28 is controlled within a given range, and T1-T2 can also be negative if the boron concentration is sufficiently reduced.

[0047] As a countermeasure to reduce boron concentration, in addition to lowering the water temperature supplied to the electro-regenerative deionizer 18, the current density of the current applied to the electro-regenerative deionizer 18 is sometimes increased. In this embodiment, both methods can be selectively performed. Hereinafter, the operation of cooling the water supplied to the electro-regenerative deionizer 18 by the cooler 17 is referred to as the first operation, and the operation of increasing the current applied to the electro-regenerative deionizer 18 is referred to as the second operation. When the boron concentration measured by the boron concentration meter 27 is higher than a given value, the control device 3 controls the cooler 17 and the electro-regenerative deionizer 18 to perform only one of the first and second operations. When the boron concentration does not fall below the given value using only one of the first and second operations, the control device 3 controls the cooler 17 and the electro-regenerative deionizer 18 to perform the other of the first and second operations. It is possible to appropriately determine which operation to prioritize, taking into account factors such as operating costs. If the current density applied to the electro-regenerative deionization device 18 is too high, adverse conditions such as electrode sintering, electrical damage to the ion exchange membrane and ion exchanger, and deterioration may easily occur. Therefore, when using the second method, the aforementioned current density is preferably 0.3 A / dm³. 2 Above and 1A / dm 2 Adjustments will be made within the following range.

[0048] Figure 7B A variation of the fourth embodiment is shown. In this embodiment, a raw water tank 11, a raw water pump 12, a cooler 17, a temperature control device 13, at least one reverse osmosis membrane device 14, and at least one electro-regenerative deionization device 18 (EDI) are arranged in series, similar to the first embodiment. The treated water passes through the cooler 17 again between the reverse osmosis membrane device 14 and the electro-regenerative deionization device 18. The temperature control device 13 corresponds to the first heat exchanger 31 of the first embodiment, and the cooler 17 corresponds to the second heat exchanger 32 of the first embodiment.

[0049] Figure 8 An example illustrating the relationship between the current ratio and boron removal efficiency of the electro-regenerative deionization unit 18 is shown. The current ratio is the ratio of the set current ratio to the set flow rate ratio, the set current ratio is the ratio of the set current to the standard current, and the set flow rate ratio is the ratio of the treated water flow rate to the standard flow rate. That is, the current ratio is the ratio of the reference current to the reference flow rate; by using the current ratio, the influence of the flow rate on the boron removal efficiency can be eliminated. As the current ratio increases, the boron removal efficiency increases. For example, if the boron concentration of the supplied water is set to 10 ppb, by increasing the current ratio to approximately 1.2 times, the boron concentration is reduced to below 50 ppt (removal rate of 99.5% or higher). However, with the increase of the current ratio, it becomes difficult to improve the boron removal efficiency. To reduce the boron concentration to below 20 ppt (removal rate of 99.8%), multi-stage and performance-enhanced electro-regenerative deionization unit 18 is required. Based on the above, it can be understood that the priority of the first and second operations needs to consider the operating costs and equipment costs required for boron removal efficiency.

[0050] (Fifth Implementation) Figure 9AThis diagram shows a schematic configuration of a water treatment system 501 according to the fifth embodiment of the present invention. This embodiment is the same as the fourth embodiment, except that a heat exchanger 21 and other water temperature adjustment units are not provided in the secondary system S2. As described above, the temperature adjustment of the water supplied to the electro-regenerative deionizer 18 and the temperature adjustment at the point of use 2 are performed by the cooler 17. A water temperature adjustment unit refers to a device for adjusting water temperature, such as a heat exchanger or heater, but excludes devices such as pumps that may cause water temperature changes during operation, but are not intended for water temperature adjustment. Since no water temperature adjustment unit is provided in the secondary system S2, the difference T1-T2 is only affected by the waste heat of the equipment, the circulation flow rate, and the room temperature, converging within a range of -1.0 degrees Celsius to 1.0 degrees Celsius. Therefore, this embodiment is preferably applied when the temperature of the water supplied to the electro-regenerative deionizer 18 is close to the required water temperature at the point of use 2. The required water temperature at the point of use 2 is mostly around 24°C to 26°C, so the temperature of the water supplied to the electro-regenerative deionizer 18 is also close to this range. This embodiment can be preferably applied to situations where sufficient boron removal performance is achieved at a water temperature near the required water temperature at point 2, where boron removal is mainly performed in the second operation described above, or where an operation combined with the second operation is performed.

[0051] Figure 9B A variation of the fifth embodiment is shown. In this embodiment, a raw water tank 11, a raw water pump 12, a cooler 17, a temperature control device 13, at least one reverse osmosis membrane device 14, and at least one electro-regenerative deionization device 18 (EDI) are arranged in series, similar to the first embodiment. The treated water passes through the cooler 17 again between the reverse osmosis membrane device 14 and the electro-regenerative deionization device 18. That is, the temperature control device 13 corresponds to the first heat exchanger 31 of the first embodiment, and the cooler 17 corresponds to the second heat exchanger 32 of the first embodiment.

[0052] (Sixth Implementation Method) Figure 10AThe schematic configuration of a water treatment system 601 according to the sixth embodiment of the present invention is shown. In this embodiment, an electro-regenerative deionization device 18 is provided in the secondary system S2. In this embodiment, the temperature adjustment of the water supplied to the electro-regenerative deionization device 18 and the temperature adjustment of the point of use 2 are also performed by the cooler 17. The auxiliary tank 19 and the pure water pump 20 are omitted, and the second recirculation line L3 is connected to the RO treated water tank 15. Therefore, in this embodiment, the treated water is always treated by the electro-regenerative deionization device 18 when circulating in the secondary system S2. Since the secondary system S2 is not equipped with a heat exchanger 21 and other water temperature adjustment units, the temperature difference T1-T2 converges to a range of -1.0 degrees and below 1.0 degrees. This embodiment can also be preferably applied under the same conditions as the second embodiment.

[0053] Figure 10B A variation of the sixth embodiment is shown. In this embodiment, a raw water tank 11, a raw water pump 12, a cooler 17, a temperature control device 13, at least one reverse osmosis membrane device 14, and at least one electro-regenerative deionization device 18 (EDI) are arranged in series, similar to the first embodiment. The treated water passes through the cooler 17 again between the reverse osmosis membrane device 14 and the electro-regenerative deionization device 18. That is, the temperature control device 13 corresponds to the first heat exchanger 31 of the first embodiment, and the cooler 17 corresponds to the second heat exchanger 32 of the first embodiment.

[0054] (Seventh Implementation) As described above, the preferred temperature of the water supplied to the reverse osmosis membrane unit 14 is generally higher than the preferred temperature of the water supplied to the electro-regenerative deionization unit 18. The water temperature at point 2 is required to be maintained within a certain range, but is generally higher than the preferred temperature of the water supplied to the electro-regenerative deionization unit 18. Therefore, the treated water is typically heated at the inlet of the reverse osmosis membrane unit 14, cooled at the inlet of the electro-regenerative deionization unit 18, and reheated in the secondary system S2. However, conventionally, heating, cooling, and reheating of the treated water using independent heat exchangers consumes energy in each of these processes. In the seventh to ninth embodiments, the waste heat from the treated water of the reverse osmosis membrane unit 14 is used for heating the water supplied to the reverse osmosis membrane unit 14 and / or heating the treated water of the electro-regenerative deionization unit 18, thereby improving the overall energy efficiency of the ultrapure water production apparatus 1D to 1F.

[0055] Figure 11This diagram shows a schematic configuration of a water treatment system 701 according to the seventh embodiment of the present invention. In this embodiment, similar to the fourth to sixth embodiments, the reverse osmosis membrane unit 14 is located upstream of the electro-regenerative deionization unit 18, and the temperature adjustment device 13 is located upstream of the reverse osmosis membrane unit 14. In this embodiment, the temperature adjustment device 13 also adjusts the temperature of the water supplied to the reverse osmosis membrane unit 14 to be between 15°C and 40°C, preferably around 20°C to 30°C. The cooler 17 operates when the water temperature measured by the first thermometer 28 at the location of the first thermometer 28 exceeds the value corresponding to the required water temperature at the point of use 2. In this embodiment, in addition to the above, a fifth heat exchanger 29 is provided to recover heat from the treated water of the reverse osmosis membrane unit 14 and heat the water supplied to the reverse osmosis membrane unit 14. The arrows indicate the direction of heat transfer. The water supplied to the reverse osmosis membrane unit 14 is heated by the fifth heat exchanger 29 before being heated by the temperature adjustment device 13. Therefore, the thermal energy required by the temperature adjustment device 13 is saved. On the other hand, the treated water in the reverse osmosis membrane unit 14 is cooled by the cooler 17 after the supply water to the reverse osmosis membrane unit 14 transfers heat energy. Therefore, the temperature of the treated water supplied to the cooler 17 decreases, and the cooling load on the cooler 17 is reduced. In this embodiment, heat energy is transferred from areas where heat energy is not needed to areas where it is needed through heat exchange, thus improving the energy utilization efficiency of the ultrapure water production apparatus 1D. The fifth heat exchanger 29 corresponds to the first heat exchanger 31 in the first to third embodiments.

[0056] (Eighth Implementation Method) Figure 12This diagram shows a schematic configuration of a water treatment system 801 according to the eighth embodiment of the present invention. In this embodiment, similar to the fourth to sixth embodiments, the reverse osmosis membrane unit 14 is located upstream of the electro-regenerative deionization unit 18, and the temperature adjustment device 13 is located upstream of the reverse osmosis membrane unit 14. In this embodiment, the temperature adjustment device 13 also adjusts the temperature of the water supplied to the reverse osmosis membrane unit 14 to be between 15°C and 40°C, preferably around 20°C to 30°C. The cooler 17 operates when the water temperature measured by the first thermometer 28 at the location of the first thermometer 28 exceeds the value corresponding to the required water temperature at the point of use 2. In addition, this embodiment includes a sixth heat exchanger 30 that recovers heat from the treated water of the reverse osmosis membrane unit 14 and heats the treated water of the electro-regenerative deionization unit 18. The treated water of the electro-regenerative deionization unit 18 is further heated by the heat exchanger 21 after being heated by the sixth heat exchanger 30. Therefore, the thermal energy required by the heat exchanger 21 is saved. In a modified example, heat exchanger 21 can also be omitted. Similar to the fourth embodiment, the treated water of the reverse osmosis membrane unit 14 is cooled by cooler 17 after heat energy is transferred to the supply water to the reverse osmosis membrane unit 14. Therefore, the temperature of the treated water supplied to cooler 17 decreases, reducing the cooling load on cooler 17. In this embodiment, heat energy is also transferred from areas where heat energy is not needed to areas where it is needed through heat exchange, thus improving the energy efficiency of the water treatment system 801. Furthermore, as mentioned above, the temperature adjustment device 13 can be configured as any one of a heater, cooler, or thermostat depending on the temperature of the water supplied to the reverse osmosis membrane unit 14, or it can be omitted. The sixth heat exchanger 30 corresponds to the second heat exchanger 32 in the first to third embodiments.

[0057] (Ninth Implementation) Figure 13This diagram illustrates a schematic configuration of a water treatment system 901 according to a ninth embodiment of the present invention. This embodiment is a combination of the seventh and eighth embodiments. The water treatment system 901 of this embodiment includes: a fifth heat exchanger 29 that recovers heat from the treated water of the reverse osmosis membrane unit 14 and heats the supply water to the reverse osmosis membrane unit 14; and a sixth heat exchanger 30 that recovers heat from the treated water of the reverse osmosis membrane unit 14 and heats the treated water of the electro-regenerative deionization unit 18. The fifth heat exchanger 29 may also be a heater that recovers heat from the supply water (raw water) and heats the permeate water of the reverse osmosis membrane unit 14. After the treated water of the reverse osmosis membrane unit 14 has had its heat recovered by the fifth heat exchanger 29, its heat is further recovered by the sixth heat exchanger 30. This embodiment can simultaneously achieve the effects of the fourth and fifth embodiments. That is, since the thermal energy required by the temperature adjustment device 13 and the heat exchanger 21 is saved, and the cooling load of the cooler 17 is reduced, the energy efficiency of the water treatment system 901 is further improved.

[0058] Although some preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications can be made without departing from the spirit or scope of the technical solution. (Label Explanation)

[0059] 2: Point of Use 3: Control device 13: Temperature adjustment device 14: Reverse osmosis membrane unit 15: RO water treatment tank 17: Cooler 18: Electro-regenerative deionization device 26: Second thermometer 27: Boron Concentration Measuring Instrument 28: First thermometer 29: Fifth heat exchanger 30: Sixth heat exchanger 31: First heat exchanger 32: Second heat exchanger 33: Third heat exchanger 34: Fourth heat exchanger 101, 201, 301, 401, 501, 501, 701, 801, 901: Water treatment systems L3: Second recirculation line L5: First recirculation line S1: Primary System S2: Secondary system (subsystem).

Claims

1. A water treatment system comprising at least one reverse osmosis membrane unit and at least one electro-regenerating deionization unit located downstream of said at least one reverse osmosis membrane unit. The water treatment system has the following features: A first heat exchanger, located upstream of the at least one reverse osmosis membrane unit, adjusts the temperature of the supply water to the at least one reverse osmosis membrane unit based on the temperature of the raw water supplied to the water treatment system; and A second heat exchanger, located between the at least one reverse osmosis membrane unit and the at least one electroregenerative deionization unit, serves as a cooler for cooling the supply water supplied to the electroregenerative deionization unit. One of the first heat exchanger and the second heat exchanger is an internal heat exchanger that performs heat exchange within the water treatment system, and the other of the first heat exchanger and the second heat exchanger is an external heat exchanger that performs heat exchange with the outside of the water treatment system. The water treatment system has a primary system and a subsystem located downstream of the primary system and upstream of the point of use. The primary system includes the cooler. The subsystem includes: a heat exchanger that adjusts the temperature of the water supplied to the point of use; and a first thermometer located downstream of the heat exchanger that measures the temperature of the water supplied to the point of use. When the water temperature measured by the first thermometer exceeds the value corresponding to the required water temperature at the point of use at the setting position of the first thermometer, the heat exchanger of the subsystem operates, and the cooler of the primary system operates.

2. The water treatment system according to claim 1, wherein, The first thermometer measures the temperature of the water being treated by any water treatment device constituting the subsystem.

3. The water treatment system according to claim 2, wherein, The water treatment system has a second thermometer for measuring the temperature of any water entering or leaving the electro-regenerative deionization device. The cooler operates such that the temperature difference T1-T2 between the temperature T1 measured by the first thermometer and the temperature T2 measured by the second thermometer is greater than -1 degree and less than 5 degrees.

4. The water treatment system according to claim 3, wherein, The electro-regenerative deionization device is installed in the primary system, the difference T1-T2 is above -1.0 degrees and below 1.0 degrees, and no water temperature adjustment unit is installed in the subsystem.

5. The water treatment system according to claim 3, wherein, The electro-regenerative deionization device is installed in the subsystem, the difference T1-T2 is above -1.0 degrees and below 1.0 degrees, and the subsystem does not have a water temperature adjustment unit other than the cooler.

6. The water treatment system according to claim 1, wherein, The water treatment system has a temperature adjustment device located upstream of the at least one reverse osmosis membrane unit. The temperature adjustment device adjusts the temperature of the supply water to the reverse osmosis membrane device to be above 15°C and below 40°C.

7. The water treatment system according to claim 6, wherein, The first heat exchanger recovers heat from the treated water of the at least one reverse osmosis membrane unit and heats or cools the supply water supplied to the reverse osmosis membrane unit.

8. The water treatment system according to claim 6, wherein, The second heat exchanger recovers heat from the treated water of the at least one reverse osmosis membrane device and heats the treated water of the electro-regenerated deionization device.

9. The water treatment system according to claim 1, wherein, The water treatment system includes a boron concentration meter for measuring the boron concentration in the water treated by the electro-regenerative deionization device. and control devices, The cooler is capable of a first operation to cool the supply water supplied to the electro-regenerative deionization device. The electro-regenerative deionization device is capable of a second operation with an increased applied current. When the boron concentration measured by the boron concentration meter is higher than a given value, the control device controls the cooler and the electro-regenerative deionization device to perform only either the first operation or the second operation.

10. The water treatment system according to claim 9, wherein, If only one of the first and second operations is used and the boron concentration does not fall below the given value, the control device controls the cooler and the electro-regenerative deionization unit to perform the other of the first and second operations.

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