Water treatment system, and method for operating water treatment system

Abstract

The present invention includes: an EDI (100); a pump (200) that supplies water to be treated to the EDI (100); a pressure gauge (300) that measures the output pressure value of the water to be treated from the pump (200); and a control unit (400) that controls, at a prescribed timing, the discharge pressure of the pump so that the output pressure value measured by the pressure gauge (300) becomes a prescribed value.

Description

Water treatment system and method for operating the water treatment system

[0001] The present invention relates to a water treatment system and a method for operating a water treatment system.

[0002] Generally, the amount of treated water discharged from a water treatment system is controlled to fall within a predetermined range. For example, a known method for controlling an electrodeionized water production apparatus installed in a water treatment system is to control the amount of concentrated water by using a valve to maintain a certain level or higher in order to prevent scale formation due to a decrease in the amount of water supplied (see, for example, Patent Document 1).

[0003] Patent No. 7103467

[0004] In the technology described in Patent Document 1, when the amount of treated water by the electrodeionized water production apparatus is reduced, the control mechanism is complicated.

[0005] An object of the present invention is to provide a water treatment system and an operating method for the water treatment system that can achieve a high power saving effect with a simple control method when reducing the amount of treated water discharged from an electrodeionized water production apparatus.

[0006] The water treatment system of the present invention comprises an electrodeionized water production apparatus, a pump that supplies water to be treated to the electrodeionized water production apparatus, a pressure gauge that measures the output pressure value of the water to be treated from the pump, and a control unit that controls the discharge pressure of the pump so that the output pressure value measured by the pressure gauge at a predetermined timing becomes a predetermined value.

[0007] In addition, the operating method of the water treatment system of the present invention acquires an output pressure value of the water to be treated from a pump that supplies the water to an electrical deionization water production apparatus, and controls the discharge pressure of the pump so that the output pressure value becomes a predetermined value at a predetermined timing.

[0008] In the present invention, when reducing the amount of treated water discharged from an electrodeionized water production apparatus, a high power saving effect can be achieved with a simple control method.

[0009] FIG. 3 is a diagram showing a first embodiment of a water treatment system of the present invention. FIG. 4 is a flowchart for explaining an example of an operation method of the water treatment system in the water treatment system shown in FIG. 1. FIG. 5 is a diagram showing a second embodiment of a water treatment system of the present invention. FIG. 6 is a graph showing an example of the relationship between the reduction rate of the output pressure value of the pump shown in FIG. 3 and the reduction rate of the flow rate discharged from the EDI. FIG. 7 is a graph showing an example of the relationship between the reduction rate of the output pressure value of the pump shown in FIG. 3 and the reduction rate of power consumption. FIG. 8 is a graph showing an example of the relationship between the reduction rate of the output pressure value of the pump shown in FIG. 3 and the concentration ratio in the EDI. FIG. 9 is a diagram showing a third embodiment of a water treatment system of the present invention. FIG. 10 is a diagram showing a fourth embodiment of a water treatment system of the present invention.

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings.

[0011] FIG. 1 illustrates a first embodiment of a water treatment system according to the present invention. As shown in FIG. 1, the water treatment system according to this embodiment includes an electrodeionized water production apparatus (EDI) 100, a pump 200, a pressure gauge 300, a control unit 400, and a DC power supply 500. Flow meters 600-1 to 600-3 are also provided in a path extending from the EDI 100. The system shown in FIG. 1 may be provided in a primary pure water system within a typical water treatment system that includes a pretreatment system, a primary pure water system, and a subsystem (secondary pure water system). Furthermore, a water treatment device that performs a predetermined treatment on the water to be treated, a conductivity meter, a resistivity meter, an on-off valve, a flow control valve, a flow meter, and the like may be provided between the pump 200 and the EDI 100. Furthermore, a conductivity meter, a resistivity meter, an on-off valve, a flow control valve, a flow meter, and the like may be provided downstream of the EDI 100. If a water treatment device that performs a predetermined treatment on the water to be treated or a conductivity meter is provided between the pump 200 and the EDI 100, the pressure meter 300 is preferably located immediately after the pump 200.

[0012] The EDI 100 is also referred to as an electrically regenerated water purifier or a continuously regenerated water purifier. The EDI 100 has a deionization compartment 100-1, a concentration compartment 100-2, and an electrode compartment 100-3, which are separated by a cation exchange membrane and an anion exchange membrane. The deionization compartment 100-1 is filled with at least one of a cation exchange resin and an anion exchange resin. A direct current is applied between the anode and cathode of the EDI 100 from a DC power supply 500, and the ion exchange resin is continuously regenerated while ions contained in the water to be treated supplied to the EDI 100 are removed in the deionization compartment 100-1. The ions removed from the water to be treated in the deionization compartment 100-1 move to the concentration compartment 100-2 and are discharged as concentrated water. The treated water from which ions have been removed in the deionization compartment 100-1 is discharged as deionized water. The treated water discharged from the deionization chamber 100-1, the concentration chamber 100-2, and the electrode chamber 100-3 is supplied to a demand location via different paths. Flow meter 600-1 measures the flow rate of the deionized water discharged from the deionization chamber 100-1. Flow meter 600-2 measures the flow rate of the concentrated water discharged from the concentration chamber 100-2. Flow meter 600-3 measures the flow rate of the electrode water discharged from the electrode chamber 100-3. Note that the concentration chamber 100-2 of the EDI 100 may also serve as the electrode chamber 100-3, and the EDI 100 may not be provided with an electrode chamber 100-3. If the EDI 100 is configured so that the concentration chamber 100-2 also serves as the electrode chamber 100-3, the electrode water line that passes water from the electrode chamber 100-3 to the flow meter 600-3 is omitted.

[0013] The pump 200 sucks up the water to be treated from the outside and discharges and supplies it to the EDI 100. The pump 200 operates based on a drive signal from the control unit 400. For example, the pump 200 rotates the motor at a rotation speed based on the drive signal from the control unit 400, and sucks up and discharges the water to be treated.

[0014] The pressure gauge 300 measures the output pressure value of the water to be treated from the pump 200 at the discharge port of the pump 200. The pressure gauge 300 notifies the control unit 400 of the measured output pressure value.

[0015] The control unit 400 acquires the output pressure value measured by the pressure gauge 300. The control unit 400 controls the discharge pressure of the pump 200 via an inverter so that the output pressure value acquired from the pressure gauge 300 at a predetermined timing becomes a predetermined value. The control unit 400 controls the discharge pressure of the pump 200 so that the pressure reduction rate is 0 to 60%, assuming that the maximum capacity value of the discharge pressure of the pump 200 is 100%. This maximum capacity value may be a value predetermined as a specification of the pump 200, or may be the maximum value that the pump 200 can discharge in the water treatment system used, or may be the pump discharge pressure value in a normal mode other than the power saving mode. If the pump 200 has a mechanism using a motor, the control unit 400 outputs a drive signal to the pump 200 to control the motor rotation speed so that the output pressure value measured by the pressure gauge 300 becomes a predetermined value.

[0016] For example, when an external input indicating a switch to the power-saving mode is received, the control unit 400 acquires the output pressure value measured by the pressure gauge 300. The control unit 400 compares the acquired output pressure value with a value set as the output pressure value for the power-saving mode. Based on the comparison result, the control unit 400 calculates a rate at which to reduce the motor rotation speed of the pump 200. The control unit 400 outputs a control signal to the pump 200 according to the calculated reduction rate. The control unit 400 may calculate the rate at which to reduce the motor rotation speed of the pump 200, for example, by previously associating the reduction rate at which the output pressure value is reduced to the value set as the output pressure value for the power-saving mode with the reduction rate at which the motor rotation speed is reduced. Alternatively, the rate at which to reduce the motor rotation speed of the pump 200 may be calculated by gradually reducing the output pressure value at a constant rate to adjust the output pressure value to a value that achieves the required water volume. This allows for reduction in power consumption at the desired timing.

[0017] Furthermore, for example, the control unit 400 acquires the output pressure value measured by the pressure gauge 300. The control unit 400 compares the acquired output pressure value with a pressure value corresponding to the required flow rate in the system downstream of the EDI 100. Based on the comparison result, the control unit 400 calculates a rate at which to reduce the motor rotation speed of the pump 200. The control unit 400 outputs a control signal corresponding to the calculated reduction rate to the pump 200. The pressure value corresponding to the required flow rate at this time is obtained from a preset correspondence between the required flow rate and the pressure value. The method for calculating the rate at which to reduce the motor rotation speed of the pump 200 may, for example, be a method in which a reduction rate at which the output pressure value is reduced to a pressure value corresponding to the required flow rate is previously associated with a reduction rate of the motor rotation speed, and the rate at which the motor rotation speed is reduced is calculated based on this correspondence. Alternatively, the method for calculating the rate at which to reduce the motor rotation speed of the pump 200 may be a method in which the output pressure value is reduced at a constant rate and gradually adjusted to an output pressure value that achieves the required water volume. In this manner, the output of the pump 200 is controlled to an output pressure value appropriate for the request from the downstream system. This makes it possible to reduce power consumption without producing excessive amounts of water.

[0018] Furthermore, for example, when a time period during which the pump 200 operates in a power-saving mode, which is set in a preset schedule for nighttime or holidays, is reached, the control unit 400 acquires the output pressure value measured by the pressure gauge 300. The control unit 400 compares the acquired output pressure value with a value set as the output pressure value for the power-saving mode. Based on the comparison result, the control unit 400 calculates a rate at which to reduce the rotation speed of the motor of the pump 200. The control unit 400 outputs a control signal corresponding to the calculated reduction rate to the pump 200. The method for calculating the rate at which to reduce the rotation speed of the motor of the pump 200 at this time may be the same as the method described above. Note that, when returning from the power-saving mode to the normal mode, the control unit 400 acquires the output pressure value measured by the pressure gauge 300, compares the acquired output pressure value with a value set as the output pressure value for the normal mode, calculates a rate at which to increase the rotation speed of the motor of the pump 200 based on the comparison result, and outputs a control signal corresponding to the calculated increase rate to the pump 200. In this way, the control unit 400 controls the output of the pump 200 to an output pressure value corresponding to the operating mode. This allows the power consumption to be reduced according to the schedule for reducing the power consumption.

[0019] Furthermore, for example, the control unit 400 may perform control based on the operating status of a system downstream of the EDI 100 (e.g., the number of operating systems). The control unit 400 acquires the output pressure value measured by the pressure gauge 300. The control unit 400 compares the acquired output pressure value with a pressure value corresponding to the operating status. The control unit 400 calculates a rate at which to reduce the motor rotation speed of the pump 200 based on the comparison result. The control unit 400 outputs a control signal corresponding to the calculated reduction rate to the pump 200. The pressure value corresponding to the operating status at this time is obtained from a preset correspondence between the operating status and the pressure value. The method for calculating the rate at which to reduce the motor rotation speed of the pump 200 may be, for example, a method in which a reduction rate at which the output pressure value is reduced to a pressure value corresponding to the operating status and a reduction rate of the motor rotation speed are previously associated and then calculated based on the association. Alternatively, the method for calculating the rate at which to reduce the motor rotation speed of the pump 200 may be a method in which the output pressure value is reduced at a constant rate and gradually adjusted to the output pressure value corresponding to the operating status. In this way, the control unit 400 controls the output of the pump 200 to an output pressure value that is appropriate for the operating status of the downstream system, thereby reducing power consumption without producing excessive amounts of fresh water.

[0020] Alternatively, for example, the control unit 400 may perform control based on the amount of freshwater produced upstream of the EDI 100. The control unit 400 acquires the output pressure value measured by the pressure gauge 300. The control unit 400 compares the acquired output pressure value with a pressure value corresponding to the amount of freshwater produced upstream. Based on the comparison result, the control unit 400 calculates a rate at which to reduce the motor rotation speed of the pump 200. The control unit 400 outputs a control signal corresponding to the calculated reduction rate to the pump 200. The pressure value corresponding to the amount of freshwater produced upstream at this time is obtained from a preset correspondence between the amount of freshwater produced upstream and the pressure value. The method for calculating the rate at which to reduce the motor rotation speed of the pump 200 may be, for example, a method in which a reduction rate at which the output pressure value is reduced to a pressure value corresponding to the amount of freshwater produced upstream is associated with a reduction rate of the motor rotation speed in advance, and the rate at which the motor rotation speed is reduced is calculated based on this correspondence. Alternatively, the method for calculating the rate at which to reduce the motor rotation speed of the pump 200 may be a method in which the output pressure value is reduced at a constant rate and gradually adjusted to an output pressure value corresponding to the amount of freshwater produced upstream. In this way, the control unit 400 controls the output of the pump 200 to an output pressure value that is appropriate for the amount of fresh water produced upstream, thereby preventing excessive fresh water production and reducing power consumption.

[0021] The following describes a method for operating the water treatment system shown in Fig. 1. Fig. 2 is a flowchart for explaining an example of a method for operating the water treatment system shown in Fig. 1. The following describes an example of processing when a time period during which the water treatment system operates in power saving mode is reached in a preset schedule.

[0022] First, the control unit 400 determines whether it is currently time to enter the power-saving mode (step S1). This determination is made based on a preset schedule and the date and time indicated by the clock. This schedule specifies whether the water treatment system should operate in normal mode or in a power-saving mode for power saving purposes for each time period and date (e.g., day of the week, season, etc.).

[0023] If it is determined that the current timing is for the power saving mode, the control unit 400 acquires the output pressure value of the pump 200 measured by the pressure gauge 300 (step S2). Next, the control unit 400 compares the acquired output pressure value with a value set as the output pressure value for the power saving mode. Based on the comparison result, the control unit 400 calculates the rate at which to reduce the rotation speed of the motor of the pump 200 (step S3). At this time, the control unit 400 may calculate the rate at which to reduce the rotation speed of the motor of the pump 200 according to a preset target pressure value. The control unit 400 outputs a control signal according to the calculated reduction rate to the pump 200 to control the discharge pressure of the pump 200 (step S4).

[0024] In this manner, the control unit 400 controls the discharge pressure of the pump 200 so that the output pressure of the pump 200 measured by the pressure gauge 300 installed at the discharge port of the pump 200, which supplies the untreated water to the EDI 100, reaches a predetermined value. The timing of this control is based on external requests, the operating status of downstream systems, the amount of water supplied from upstream systems, or a schedule with a set operating mode. Therefore, when reducing the amount of treated water discharged from the electrodeionized water production apparatus to provide an appropriate amount of treated water, the power consumption of the pump 200 can be kept low, resulting in significant power savings. In cases where there is no external water collection request from the supply destination, for example, a circulation operation within the system is commonly performed to reduce the amount of treated water discharged from the electrodeionized water production apparatus. In this case, the water temperature rises due to heat input to the pump. It is known that a rise in water temperature deteriorates the boron removal performance of the EDI. On the other hand, in this embodiment, control is performed to reduce the rotation speed of the motor of the pump 200 in order to reduce the amount of treated water discharged from the electrodeionized water production apparatus. This control prevents the water temperature from rising due to heat input from the pump during circulation, and allows operation to continue within the normal temperature range, thereby preventing a decrease in the boron removal rate. (Second embodiment)

[0025] Fig. 3 is a diagram showing a second embodiment of the water treatment system of the present invention. As shown in Fig. 3, the water treatment system of this embodiment further includes a branch path 700 and flow control valves 800-1 to 800-3 in addition to the components of the first embodiment shown in Fig. 1.

[0026] Branch path 700 is a path that branches off from the path from pump 200 to each of deionization chamber 100-1, concentration chamber 100-2, and electrode chamber 100-3 of EDI 100. The branch point where branch path 700 branches off is located closer to EDI 100 than the point where pressure gauge 300 measures the output pressure value of pump 200. The water to be treated discharged from pump 200 is supplied to each of deionization chamber 100-1, concentration chamber 100-2, and electrode chamber 100-3 via branch path 700. If EDI 100 is configured so that concentration chamber 100-2 also serves as electrode chamber 100-3, the electrode water line that passes water from flow rate adjustment valve 800-3 through electrode chamber 100-3 to flow meter 600-3 is omitted.

[0027] Flow rate adjustment valve 800-1 is provided in branch path 700 that supplies water to be treated to deionization chamber 100-1. Flow rate adjustment valve 800-1 is a valve that adjusts the flow rate of water to be treated supplied to deionization chamber 100-1. Flow rate adjustment valve 800-1 may also be provided at the outlet of deionization chamber 100-1. Flow rate adjustment valve 800-2 is provided in branch path 700 that supplies water to be treated to concentration chamber 100-2. Flow rate adjustment valve 800-2 is a valve that adjusts the flow rate of water to be treated supplied to concentration chamber 100-2. Flow rate adjustment valve 800-2 may also be provided at the outlet of concentration chamber 100-2. Flow rate adjustment valve 800-3 is provided in branch path 700 that supplies water to be treated to electrode chamber 100-3. Flow rate adjustment valve 800-3 is a valve that adjusts the flow rate of water to be treated supplied to electrode chamber 100-3. The flow rate adjusting valve 800-3 may also be provided at the outlet of the electrode chamber 100-3.

[0028] FIG. 4 is a graph showing an example of the relationship between the reduction rate of the output pressure value of pump 200 shown in FIG. 3 and the reduction rate of the flow rate of the water discharged from EDI 100. FIG. 4 shows how the flow rate of the desalinated water discharged from desalting compartment 100-1 and measured by flow meter 600-1 and the flow rate of the concentrated water discharged from concentration compartment 100-2 and measured by flow meter 600-2 each decrease according to the reduction rate of the output pressure value of pump 200. This is a result obtained through an experiment. As shown in FIG. 4, as the reduction rate of the output pressure value of pump 200 increases, the reduction rate of the flow rates of the desalinated water and the concentrated water also increases. The rate at which the reduction rate of the flow rate increases relative to the increase in the reduction rate of the output pressure value of pump 200 differs between the desalinated water and the concentrated water. It can be seen that even the reduction rate of the discharge flow rate of the desalinated water, which is most susceptible to the effect of the flow rate of the water to be treated supplied to EDI 100, is lower than the reduction rate of the output pressure value of pump 200. Therefore, if the pressure reduction does not exceed 60% of the maximum capacity of the pump 200 in this water treatment system, it is possible to control the flow rate of the treated water discharged from the EDI 100 without monitoring it.

[0029] Fig. 5 is a graph showing an example of the relationship between the reduction rate of the output pressure value of pump 200 shown in Fig. 3 and the reduction rate of power consumption. As shown in Fig. 5, as the reduction rate of the output pressure value of pump 200 increases, the reduction rate of power consumption of pump 200 also increases. At this time, it can be seen that the reduction rate of power consumption of pump 200 is higher than the reduction rate of the output pressure value of pump 200. This shows that reducing the output pressure value of pump 200 has a significant power saving effect.

[0030] FIG. 6 is a graph showing an example of the relationship between the reduction rate of the output pressure value of the pump 200 shown in FIG. 3 and the concentration ratio of the EDI 100. The concentration ratio is the ratio of the inlet water volume of the EDI 100 to the concentrated water volume. As shown in FIG. 6, as the reduction rate of the output pressure value of the pump 200 increases, the concentration ratio does not increase but remains unchanged or decreases. This is a result obtained through experiments. Therefore, it is possible to operate the EDI 100 while maintaining or decreasing the concentration ratio without using the flow control valves 800-1 to 800-3 to control the amount of water to be treated supplied to the EDI 100. By monitoring the pump discharge pressure and reducing the pump output, the risk of problems (such as scale and slime) caused by an increase in the concentration ratio can be reduced.

[0031] In this way, the water to be treated flowing from pump 200 to EDI 100 is branched from the main path to branch paths, and is supplied to deionization chamber 100-1, concentration chamber 100-2, and electrode chamber 100-3 via each of the branch paths. If the supply amounts to deionization chamber 100-1, concentration chamber 100-2, and electrode chamber 100-3 are adjusted in advance using flow control valves 800-1 to 800-3 provided in each of the branch paths, then the amount of water to be treated supplied to EDI 100 can be changed (reduced) in the direction of lowering the concentration ratio without significantly changing the ratio of deionized water to concentrated water, simply by controlling the output pressure value of pump 200. (Third Embodiment)

[0032] Fig. 7 is a diagram showing a third embodiment of the water treatment system of the present invention. As shown in Fig. 7, the water treatment system of this embodiment is a system in which, among the components of the second embodiment shown in Fig. 3, control unit 400 is replaced with control unit 401.

[0033] 1 or 3 , the control unit 401 has a function of calculating a reduction rate at which the DC power supply 500 reduces the value of the current that the DC power supply 500 passes to the EDI 100, based on the reduction rate at which the output pressure value of the pump 200 decreases. This calculation method may involve calculating in advance a correlation (e.g., a relational expression or an algorithm deriving one from the other) between the reduction rate at which the output pressure value of the pump 200 decreases and the reduction rate at which the DC power supply 500 reduces the value of the current that the DC power supply 500 passes to the EDI 100, and using the calculated correlation to calculate the reduction rate at which the DC power supply 500 reduces the value of the current that the DC power supply 500 passes to the EDI 100. Alternatively, this calculation method may involve previously associating (linking) the reduction rate at which the output pressure value of the pump 200 decreases and the reduction rate at which the DC power supply 500 reduces the value of the current that the DC power supply 500 passes to the EDI 100, and calculating the reduction rate at which the DC power supply 500 reduces the value of the current that the DC power supply 500 passes to the EDI 100 based on this correlation. The timing at which the control unit 401 performs control using the calculated rate of decrease in the current value may be the timing at which an external input to switch to the power saving mode is received. The timing at which the control unit 401 performs control using the calculated rate of decrease in the current value may also be the timing at which the control unit 401 switches to the power saving mode according to a preset schedule. The timing at which the control unit 401 performs control using the calculated rate of decrease in the current value may be the same as or different from the timing at which the output pressure value of the pump 200 is reduced.

[0034] In this way, the control unit 401 reduces the output pressure value of the pump 200, and reduces the current value that the DC power supply 500 supplies to the EDI 100 according to the reduction rate. This makes it possible to achieve a higher power saving effect. The control unit 401 of this embodiment may be applied to the EDI 100 of the first embodiment. (Fourth embodiment)

[0035] 8 is a diagram showing a fourth embodiment of the water treatment system of the present invention. As shown in Fig. 8, the water treatment system in this embodiment is a system in which three sets of EDI 100 shown in Fig. 3 are connected in parallel.

[0036] The water to be treated from pump 200 is supplied to three EDIs 100-102. DC current is also passed from each of DC power supplies 500-502 to each of EDIs 100-102. The water to be treated is supplied from pump 200 to deionization chamber 100-1, concentration chamber 100-2, and electrode chamber 100-3 of EDI 100 via flow rate adjustment valves 800-1 to 800-3, respectively, provided in branch path 700. The water to be treated is supplied from pump 200 to deionization chamber 101-1, concentration chamber 101-2, and electrode chamber 101-3 of EDI 101 via flow rate adjustment valves 801-1 to 801-3, respectively, provided in branch path 700. The water to be treated is supplied from pump 200 to deionization chamber 102-1, concentration chamber 102-2, and electrode chamber 102-3 of EDI 102 via flow control valves 802-1 to 802-3 provided in branch path 700. The treated water discharged from deionization chamber 100-1 of EDI 100, deionization chamber 101-1 of EDI 101, and deionization chamber 102-1 of EDI 102 is joined together and supplied downstream as deionized water. The treated water discharged from concentration chamber 100-2 of EDI 100, concentration chamber 101-2 of EDI 101, and concentration chamber 102-2 of EDI 102 is joined together and supplied downstream as concentrated water. The treated water discharged from electrode chamber 100-3 of EDI 100, electrode chamber 101-3 of EDI 101, and electrode chamber 102-3 of EDI 102 are joined together and supplied downstream as electrode water. The locations of flow rate control valves 800-1 to 800-3 are not limited to upstream of EDI 100. For example, flow rate control valve 800-1 may be provided at the outlet of deionization chamber 100-1. Furthermore, flow rate control valve 800-2 may be provided at the outlet of concentration chamber 100-2. Flow rate control valve 800-3 may be provided at the outlet of electrode chamber 100-3. Furthermore, instead of flow rate control valves 800-1 to 800-3, a flow rate control valve may be provided upstream of branch path 700 (before the branch point) or downstream of branch path 700 (at the junction point). When EDI 100 is configured so that concentration chamber 100-2 also serves as electrode chamber 100-3, the electrode water line that passes water from flow rate adjustment valve 800-3 through electrode chamber 100-3 to flowmeter 600-3 is omitted.

[0037] Thus, even in a system in which multiple EDIs are connected in parallel, the control unit 400 can change (reduce) the amount of water to be treated supplied to the EDIs in a direction that lowers the concentration ratio without significantly changing the ratio of desalinated water to concentrated water discharged from each of the multiple EDIs simply by controlling the pump 200 in the first to third embodiments. This method can prevent excessive freshwater production and reduce power consumption, even in a system in which multiple EDIs are connected in parallel or in series. It goes without saying that the control in each embodiment can be performed even when the EDI 100 in the first embodiment and the EDI 100 in the second embodiment are arranged in parallel, as in the EDIs 100 to 102 in the third embodiment.

[0038] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above-described embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0039] This application claims priority based on Japanese Patent Application No. 2023-216824, filed December 22, 2023, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A water treatment system comprising: an electrical deionized water production apparatus; a pump that supplies treated water to the electrical deionized water production apparatus; a pressure gauge that measures the output pressure value of the treated water from the pump; and a control unit that controls the discharge pressure of the pump so that the output pressure value measured by the pressure gauge at a predetermined timing becomes a predetermined value.

2. A water treatment system as described in claim 1, comprising: branch paths branching from a path from the pump to each of the desalting compartments and the concentration compartments equipped in the electrical deionization water production apparatus; and a flow control valve provided in at least one of the branch paths, and the pressure gauge is provided on the pump side of the branch point where the path branches off to the branch path.

3. A water treatment system as claimed in claim 1 or claim 2, wherein the control unit, when receiving a predetermined input from outside, controls the discharge pressure of the pump so that the output pressure value measured by the pressure gauge becomes a predetermined value.

4. A water treatment system as claimed in claim 1 or 2, wherein the control unit controls the discharge pressure of the pump so that the output pressure value measured by the pressure gauge becomes a predetermined value based on at least one of the required flow rate in the system downstream of the electrical deionized water production apparatus, the amount of water produced upstream of the electrical deionized water production apparatus, and the operating status of the system downstream of the electrical deionized water production apparatus.

5. A water treatment system as claimed in claim 1 or 2, wherein the control unit controls the discharge pressure of the pump based on a predetermined schedule so that the output pressure value measured by the pressure gauge becomes a predetermined value.

6. A water treatment system as claimed in claim 1 or 2, wherein the control unit controls the discharge pressure of the pump so that the pressure reduction rate is 0 to 60% when the maximum capacity value of the discharge pressure is 100%.

7. A water treatment system according to claim 1 or 2, comprising a plurality of the electrodeionized water production apparatuses, the plurality of electrodeionized water production apparatuses being connected in parallel or in series to one another.

8. A method for operating a water treatment system, comprising: acquiring an output pressure value of water to be treated from a pump that supplies the water to an electrical deionization water production apparatus; and controlling the discharge pressure of the pump so that the output pressure value becomes a predetermined value at a predetermined timing.

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