JP5903948B2 - Water treatment system - Google Patents

Description

  The present invention relates to a water treatment system in which a membrane separation device that separates raw water into permeated water and first concentrated water and an electrodeionization device that produces demineralized water and second concentrated water from the permeated water.

  In semiconductor manufacturing processes, electronic component cleaning, medical instrument cleaning, and the like, high-purity pure water that does not contain impurities is used. In the case of producing this kind of pure water, it is generally dissolved by treating raw water such as ground water and tap water with a membrane separation device using a reverse osmosis membrane (hereinafter also referred to as “RO membrane module”). Produces permeate from which most of the salt has been removed. Then, the purity is further increased by purifying the permeated water with an electrodeionization apparatus (hereinafter also referred to as “EDI apparatus”).

  The EDI apparatus includes a desalination chamber and a concentration chamber partitioned by a cation exchange membrane and an anion exchange membrane. The desalting chamber is filled with an ion exchanger (resin or fiber). When permeated water is supplied to the desalting chamber and the concentrating chamber, residual salts (ions) contained in the permeated water are captured by the ion exchanger in the desalting chamber, and the permeated water becomes purified treated water (desalted water). . Further, residual salts captured by the ion exchanger in the desalination chamber are moved to the concentration chamber by electric energy and discharged from the concentration chamber as concentrated water. In this way, in the EDI apparatus, by applying electric energy, ions captured by the ion exchanger move to the concentration chamber, so that the ion exchanger can always be kept in a regenerated state.

  In the RO membrane module, the water permeation coefficient varies depending on the temperature of raw water and the state of the membrane (clogging of pores and oxidative deterioration of material). Therefore, a water treatment system employing flow rate feedback water amount control has been proposed in order to keep the flow rate of permeated water in the RO membrane module constant regardless of the temperature of raw water and the state of the membrane (see Patent Document 1). Also in the EDI device, flow rate feedback is used to constantly produce demineralized water at a constant flow rate and suppress the power consumption of the feed pump provided in the front stage of the EDI device regardless of fluctuations in the temperature and back pressure of the permeate. A pure water production apparatus that employs water volume control has been proposed (see Patent Document 2).

JP 2005-296945 A JP 2010-58010 A

  In the above-mentioned RO membrane module, in order to prevent membrane clogging due to scale generation and fouling, or to manufacture permeated water of water quality acceptable by the EDI device, concentration is performed according to the quality of raw water or concentrated water. There is a case where the permeated water flow rate is decreased while the water drainage flow rate is kept constant, and the recovery rate is lowered.

  In the water treatment system in which the RO membrane module and the EDI device are connected, the flow rate of the permeated water supplied to the EDI device is controlled by reducing the flow rate of the permeated water in the RO membrane module to lower the recovery rate. May be less than required. In that case, there is a possibility that these devices may be damaged due to the generation of negative pressure in the RO membrane module and the occurrence of cavitation in the water supply pump of the EDI apparatus.

  Accordingly, the present invention provides a water treatment system in which a membrane separation device and an electrodeionization device are connected, even if the flow rate of permeate is reduced by the membrane separation device to reduce the recovery rate, the amount of water in the electrodeionization device. It aims at providing the water treatment system which can maintain the amount of water required for control.

The present invention provides a membrane separation device for separating raw water into permeated water and first concentrated water, an electrodeionization device for producing desalted water and second concentrated water by subjecting permeated water to desalination, and raw water as described above. Raw water line for supplying to the membrane separation device, permeated water line for supplying permeated water to the electrodeionization device, first flow rate detecting means for outputting the flow rate of permeated water as a first detected flow rate value, and input drive A first pressure pump that is driven at a rotational speed corresponding to the frequency and pumps the raw water flowing through the raw water line toward the membrane separation device; and a frequency corresponding to a calculated value of a driving frequency of the first pressure pump designation signal is input, a first inverter for outputting a driving frequency corresponding to the input the frequency designation signal to the first pressure pump, the raw water, permeated water and at least one quality value of the first concentrated water Depending on the first permeate A target flow rate control unit for setting a flow rate value, and a drive frequency of the first pressurizing pump so that the first detected flow rate value output from the first flow rate detection means becomes the first target flow rate value. calculated, and the second flow rate detecting means for outputting a first control unit for outputting a frequency designation signal that corresponds to the calculated value of the drive frequency to the first inverter, the flow rate of the deionized water as the second detected flow value, A second pressurizing pump that is driven at a rotational speed corresponding to the input driving frequency and pumps the permeate flowing through the permeate line toward the electrodeionization device; and the drive frequency of the second pressurization pump is the input frequency designation signal corresponding to the calculated value, a second inverter for outputting a driving frequency corresponding to the input the frequency designation signal to the second pressure pump, which is outputted from the second flow rate detecting means Second test The second pressurizing pump has a second flow rate value equal to or less than a difference value between the flow rate value of the permeated water in the membrane separation device and the flow rate value of the second concentrated water in the electrodeionization device. It calculates a drive frequency, a second control unit for outputting a frequency designation signal that corresponds to the calculated value of the drive frequency to the second inverter, to a water treatment system comprising a.

  In the water treatment system, the flow rate value of the permeate flowing through the permeate line exceeds the total value of the flow rate value of the demineralized water and the second concentrated water produced by the electrodeionization device. And a permeate discharge means for discharging surplus permeate from the permeate line when a predetermined pressure value is exceeded, and the second controller is configured to obtain the flow rate value of the permeate in the membrane separator. It is preferable that a flow rate value of 0.95 to 1 times a difference value from the flow rate value of the second concentrated water in the electrodeionization apparatus is the second target flow rate value.

  In the water treatment system, the temperature detecting means for detecting the temperature of the permeated water, the first concentrated water, the demineralized water or the second concentrated water, and the drainage flow rate of the second concentrated water discharged from the electrodeionization device An adjustable drainage valve, wherein the second control unit is configured to: (i) based on the silica concentration determined from the preliminarily obtained silica concentration of the permeated water and the detected temperature value of the temperature detecting means; Calculate the allowable concentration rate of silica in the concentrated water, (ii) calculate the drainage flow rate from the calculated value of the allowable concentration rate and the second target flow rate value of the desalted water, and (iii) the actual drainage flow rate of the second concentrated water It is preferable to control the drainage valve so that the calculated value of the drainage flow rate becomes.

  The water treatment system further includes hardness measuring means for measuring calcium hardness of the permeated water, and a drain valve capable of adjusting a drain flow rate of the second concentrated water discharged from the electrodeionization device, 2 The control unit calculates (i) an allowable concentration rate of calcium carbonate in the second concentrated water based on (i) the calcium carbonate solubility acquired in advance and the measured hardness value of the hardness measuring means, and (ii) the allowable concentration Calculate the drainage flow rate of the second concentrated water from the calculated value of the magnification and the second target flow rate value of the desalted water, and (iii) the actual drainage flow rate of the second concentrated water becomes the calculated value of the drainage flow rate, It is preferable to control the drain valve.

  In the water treatment system, the first control unit holds data relating to a flow rate of the permeated water in the membrane separation device, and the water treatment system transmits the permeated water in the membrane separation device from the first control unit. It is preferable to include a third control unit that acquires data relating to the flow rate and transmits the data to the second control unit.

  According to the present invention, in a water treatment system in which a membrane separator and an electrodeionization device are connected, even when the recovery rate is lowered by the membrane separator, the amount of water necessary for controlling the amount of water in the electrodeionization device can be maintained. A water treatment system can be provided.

1 is an overall configuration diagram of a water treatment system 1 according to a first embodiment. 4 is a flowchart showing a processing procedure when a target flow rate value is set in the first control unit 10. 4 is a flowchart showing a processing procedure when flow rate feedback water amount control is executed in the first control unit 10. 4 is a flowchart showing a processing procedure when flow rate feedback water amount control is executed in the second control unit 20. 5 is a flowchart showing a processing procedure when temperature feedforward recovery rate control is executed in the second control unit 20. It is a whole block diagram of the water treatment system 1A which concerns on 2nd Embodiment. It is a flowchart which shows the process sequence in the case of performing water quality feedforward collection | recovery rate control in 2nd control part 20A.

(First embodiment)
A water treatment system 1 according to a first embodiment of the present invention will be described with reference to the drawings. The water treatment system 1 according to the present embodiment is applied to, for example, a pure water production system that produces pure water from fresh water.

  FIG. 1 is an overall configuration diagram of a water treatment system 1 according to the first embodiment. FIG. 2 is a flowchart illustrating a processing procedure when the target flow rate value is set in the first control unit 10. FIG. 3 is a flowchart showing a processing procedure when the first control unit 10 executes the flow rate feedback water amount control of the RO membrane module 4. FIG. 4 is a flowchart showing a processing procedure when the second control unit 20 executes flow rate feedback water amount control of the EDI device 7. FIG. 5 is a flowchart showing a processing procedure when the second control unit 20 executes the temperature feedforward recovery rate control of the EDI device 7.

  As shown in FIG. 1, the water treatment system 1 according to the first embodiment includes a first pressure pump 2, a first inverter 3, an RO membrane module 4 as a membrane separation device, and a second pressure pump 5. And a second inverter 6, an EDI device 7 as an electrodeionization device, a first concentrated water discharge valve 8, and a relief valve 9 as a permeate discharge means.

  Further, the water treatment system 1 includes a first control unit 10, a second control unit 20, a third control unit 30, a first drain valve 11 to a third drain valve 13, an electrical conductivity sensor 14, a first A first flow rate sensor 15 as a first flow rate detection unit, a temperature sensor 16 as a temperature detection unit, and a second flow rate sensor 17 as a second flow rate detection unit are provided. In FIG. 1 (and FIG. 6 described later), the path of electrical connection is indicated by a broken line.

  The water treatment system 1 includes a raw water line L1, a permeate water line L2, a desalted water line L3, a first concentrated water line L4, a permeated water discharge line L5 as a permeated water discharge means, and a second concentrated water. A line L6. The “line” in the present specification is a general term for lines capable of flowing a fluid such as a flow path, a radial path, and a pipeline.

  The raw water line L1 is a line for supplying the raw water W1 to the RO membrane module 4. The upstream end of the raw water line L1 is connected to a supply source (not shown) of the raw water W1. Further, the downstream end of the raw water line L <b> 1 is connected to the primary side input port of the RO membrane module 4.

  The first pressurizing pump 2 is a device that sucks the raw water W1 flowing through the raw water line L1 and pumps the raw water W1 toward the RO membrane module 4. The first pressurizing pump 2 is provided on the upstream side of the RO membrane module 4 in the raw water line L1. The first pressurizing pump 2 is supplied with driving power having a frequency converted from the first inverter 3. The first pressurizing pump 2 is driven at a rotational speed corresponding to the frequency of the supplied driving power (hereinafter also referred to as “driving frequency”).

  The first inverter 3 is an electric circuit that supplies driving power whose frequency is converted to the first pressurizing pump 2. The first inverter 3 is electrically connected to the first control unit 10. A current value signal is input to the first inverter 3 from the first control unit 10. The first inverter 3 outputs driving power having a driving frequency corresponding to the input current value signal to the first pressurizing pump 2.

  The RO membrane module 4 is a facility that separates the raw water W1 pumped from the first pressurizing pump 2 into permeated water W2 from which dissolved salts have been removed and first concentrated water W3 from which dissolved salts have been concentrated. The RO membrane module 4 includes a single or a plurality of RO membrane elements (not shown). The RO membrane module 4 processes the raw water W1 with these RO membrane elements to produce the permeated water W2 and the first concentrated water W3.

  The first concentrated water line L4 is a line for sending the first concentrated water W3 separated by the RO membrane module 4 to the outside. The upstream end of the first concentrated water line L4 is connected to the primary outlet port of the RO membrane module 4. Moreover, the downstream side of the 1st concentrated water line L4 is opened to the drain pit (not shown), for example.

  The first concentrated water line L4 is provided with a first concentrated water discharge valve 8. The first concentrated water discharge valve 8 is a valve that adjusts the drainage flow rate of the first concentrated water W3 discharged from the first concentrated water line L4 to the outside of the system. The first concentrated water discharge valve 8 is constituted by, for example, a proportional control valve. When the first concentrated water discharge valve 8 is constituted by a proportional control valve, a current value signal (for example, 4 to 20 mA) is transmitted to the first concentrated water discharge valve 8 from the first control unit 10 described later to open the valve. By controlling the degree, the drainage flow rate of the first concentrated water W3 can be adjusted.

  The permeate water line L <b> 2 is a line for sending the permeate water W <b> 2 separated by the RO membrane module 4 to the EDI device 7. The upstream end of the permeate line L2 is connected to the secondary port of the RO membrane module 4. The downstream end of the permeate line L2 is connected to a primary port of the EDI device 7 (the inlet side of a desalination chamber 7a and a concentration chamber 7b described later). As shown in FIG. 1, the RO membrane module 4 and the EDI device 7 are directly connected by a permeate line L2.

  The electrical conductivity sensor 14 is a device that measures the electrical conductivity of the permeated water W2 flowing through the permeated water line L2. The electrical conductivity sensor 14 is connected to the permeated water line L2 at the connection portion J1. The connecting portion J1 is disposed between the RO membrane module 4 and the second pressurizing pump 5 (between the RO membrane module 4 and the connecting portion J2). The electrical conductivity sensor 14 is electrically connected to the first control unit 10. The electric conductivity of the permeated water W2 measured by the electric conductivity sensor 14 (hereinafter also referred to as “measured electric conductivity value”) is transmitted to the first control unit 10 as a detection signal.

  The 1st flow sensor 15 is an apparatus which detects the flow volume of the permeated water W2 which distribute | circulates the permeated water line L2. The first flow rate sensor 15 is connected to the permeate line L2 at the connection portion J2. The connecting part J2 is disposed between the RO membrane module 4 and the second pressurizing pump 5 (between the connecting part J1 and the connecting part J3). The first flow sensor 15 is electrically connected to the first control unit 10. The flow rate of the permeated water W2 detected by the first flow rate sensor 15 (hereinafter also referred to as “detected flow rate value”) is transmitted to the first control unit 10 as a detection signal.

  The permeated water discharge line L5 is a line for discharging a part of the permeated water W2 flowing through the permeated water line L2 to the outside of the system. The upstream side of the permeated water discharge line L5 is connected to the permeated water line L2 at the connection portion J3. The connection portion J3 is disposed between the RO membrane module 4 and the second pressurization pump 5 (between the connection portion J2 and the second pressurization pump 5). The downstream side of the permeated water discharge line L5 is connected or opened to, for example, a raw water tank or a drain pit (both not shown). The raw water tank is a tank provided on the upstream side of the first pressure pump 2.

  The permeate discharge line L5 is provided with a relief valve (normally closed pressure operating valve) 9. The relief valve 9 has a flow rate value of the permeated water W2 flowing through the permeate line L2 between a flow rate value of the desalted water W4 produced by the EDI device 7 described later and a flow rate value (discharge flow rate) of the second concentrated water W5. When the total value is exceeded and the predetermined pressure value is exceeded, the valve is opened, and excess permeate water W2 is discharged from the permeate discharge line L5.

As will be described later, the second controller 20 determines the flow rate value of the permeated water W2 produced by the RO membrane module 4 (first target flow rate value Q _p1 ′) and the second concentrated water W5 discharged from the EDI device 7. A flow rate value 0.95 times the difference value from the flow rate value (second target drainage flow rate value Q _d2 ′) is set to a second target flow rate value Q _p2 ′ (target flow rate value of desalted water W4) for flow rate feedback water volume control described later. ).

  Therefore, the flow rate value of the permeated water W2 flowing through the permeate line L2 is slightly larger than the total value of the flow rate value of the desalted water W4 and the second concentrated water W5 manufactured by the EDI device 7. It becomes. In the water treatment system 1, the permeated water W <b> 2 exceeding the flow rate required by the EDI device 7 is supplied to the EDI device 7 within a range that does not become excessive, and the second pressurizing pump 5 does not cause problems such as cavitation. Control the amount of water. The relief valve 9 has a flow rate value of the permeate water W2 flowing through the permeate line L2 that exceeds a total value of the flow rate value of the desalted water W4 and the flow rate value (discharge flow rate) of the second concentrated water W5, and a predetermined value. When the pressure value is exceeded, the valve is opened, and a part of the excess permeate water W2 is circulated to the permeate discharge line L5. The predetermined pressure value is a value set in advance as the operating pressure of the relief valve 9.

  The second pressurizing pump 5 is a device that sucks the permeated water W2 flowing through the permeated water line L2 and pumps it to the EDI device 7. The second pressurizing pump 5 is provided between the RO membrane module 4 and the EDI device 7 in the permeate line L2. The second pressurizing pump 5 is supplied with driving power having a frequency converted from the second inverter 6. The second pressurizing pump 5 is driven at a rotational speed corresponding to the frequency (drive frequency) of the supplied drive power.

  The second inverter 6 is an electric circuit that supplies the second pressurizing pump 5 with driving power whose frequency has been converted. The second inverter 6 is electrically connected to the second control unit 20. A current value signal is input to the second inverter 6 from the second control unit 20. The second inverter 6 outputs driving power having a driving frequency corresponding to the input current value signal to the second pressurizing pump 5.

  The temperature sensor 16 is a device that detects the temperature of the permeate water W2 flowing through the permeate line L2. The temperature sensor 16 is connected to the permeate line L2 at the connection portion J4. The connection part J4 is arrange | positioned between the 2nd pressurization pump 5 and the EDI apparatus 7 (between the 2nd pressurization pump 5 and the branch part J5). The temperature sensor 16 is electrically connected to the second control unit 20. The temperature of the permeated water W2 detected by the temperature sensor 16 (hereinafter also referred to as “detected temperature value”) is transmitted to the second control unit 20 as a detection signal.

  The EDI apparatus 7 is an apparatus for producing desalted water W4 and second concentrated water W5 as pure water by subjecting the permeated water W2 produced by the RO membrane module 4 to desalination. The EDI apparatus 7 includes a plurality of desalting chambers and a plurality of concentration chambers partitioned by a cation exchange membrane and an anion exchange membrane between an anode chamber and a cathode chamber (FIG. (Shown as salt chamber 7a and concentration chamber 7b). The permeated water W2 flowing through the permeated water line L2 branches at the branch portion J5 and is supplied to the desalting chamber 7a and the concentration chamber 7b, respectively. Residual salts contained in the permeated water W2 are captured by an ion exchanger (not shown) filled in the desalting chamber 7a to become desalted water W4. The desalted water W4 is sent to a demand location via a desalted water line L3 (described later). Further, residual salts captured by the ion exchanger in the desalting chamber 7a move to the concentrating chamber 7b by the applied electric energy. And the water containing residual salts is discharged | emitted as the 2nd concentrated water W5 through the 2nd concentrated water line L6 from the concentration chamber 7b.

  The second concentrated water line L6 is a line for sending the second concentrated water W5 from the EDI device 7. The upstream end of the second concentrated water line L6 is connected to the secondary port of the EDI device 7 (the outlet side of the concentration chamber 7b). Further, the downstream side of the second concentrated water line L6 branches to the first drainage line L11, the second drainage line L12, and the third drainage line L13 at the branch portions J7 and J8.

  A first drain valve 11 is provided in the first drain line L11. A second drain valve 12 is provided in the second drain line L12. A third drain valve 13 is provided in the third drain line L13. The first drain valve 11 to the third drain valve 13 are valves that adjust the drainage flow rate of the second concentrated water W5 that is discharged from the second concentrated water line L6 to the outside of the system.

  The first drain valve 11 can open and close the first drain line L11. The second drain valve 12 can open and close the second drain line L12. The third drain valve 13 can open and close the third drain line L13.

  Each of the first drain valve 11 to the third drain valve 13 includes a constant flow valve mechanism (not shown). The constant flow valve mechanisms are set to different flow values in the first drain valve 11 to the third drain valve 13. For example, the drainage flow rate of the first drain valve 11 is set so that the recovery rate of the EDI device 7 is 90% in the open state. The drainage flow rate of the second drain valve 12 is set so that the recovery rate of the EDI device 7 is 85% in the open state. The drainage flow rate of the third drain valve 13 is set so that the recovery rate of the EDI device 7 is 80% in the open state.

  The drainage flow rate of the second concentrated water W5 discharged from the second concentrated water line L6 can be adjusted stepwise by selectively opening and closing the first drainage valve 11 to the third drainage valve 13. For example, only the second drain valve 12 is opened, and the first drain valve 11 and the third drain valve 13 are closed. In this case, the recovery rate of the EDI device 7 can be 85%. Further, the first drain valve 11 and the second drain valve 12 are opened, and only the third drain valve 13 is closed. In this case, the recovery rate of the EDI device 7 can be 80%. Therefore, in the present embodiment, the drainage flow rate of the second concentrated water W5 is selectively opened and closed with the first drainage valve 11 to the third drainage valve 13, so that the recovery rate is between 65% and 90%. It can be adjusted in steps of 5%.

  The first drain valve 11 to the third drain valve 13 are electrically connected to the second control unit 20, respectively. The opening and closing of the valve body in the first drain valve 11 to the third drain valve 13 is controlled by a drive signal from the second control unit 20.

  The desalted water line L3 is a line for sending the desalted water W4 manufactured by the EDI device 7 to a demand point. The upstream end of the desalted water line L3 is connected to the secondary port of the EDI device 7 (the outlet side of the desalting chamber 7a). Moreover, the downstream edge part of the desalted water line L3 is connected to the apparatus etc. (not shown) of a demand location.

  The 2nd flow sensor 17 is an apparatus which detects the flow volume of the desalted water W4 which distribute | circulates the desalted water line L3. The second flow rate sensor 17 is connected to the demineralized water line L3 at the connection portion J6. The connection part J6 is arrange | positioned between the secondary side port of the EDI apparatus 7, and the apparatus etc. of the demand location of the desalinated water W4. The second flow sensor 17 is electrically connected to the second control unit 20. The flow rate (detected flow rate value) of the desalted water W4 detected by the second flow rate sensor 17 is transmitted to the second control unit 20 as a detection signal.

Next, the 1st control part 10, the 2nd control part 20, and the 3rd control part 30 are demonstrated.
The first control unit 10 is configured by a microprocessor (not shown) including a CPU and a memory. In the first control unit 10, various programs for controlling (operating) the RO membrane module 4 are stored in the memory of the microprocessor. In the first control unit 10, for example, data related to a first target flow rate value Q _p1 ′ (described later) of the permeate water W2 is stored in the memory of the microprocessor.

The first control unit 10 is electrically connected to a third control unit 30 (described later). The first control unit 10 transmits data related to the first target flow rate value Q _p1 ′ of the permeated water W _< b> 2 described above to the second control unit 20 via the third control unit 30.

  In the first control unit 10, the CPU of the microprocessor executes various controls described later according to a predetermined program read from the memory. In the first control unit 10, an integrated timer unit (hereinafter also referred to as “ITU”) that manages timekeeping and the like is incorporated in the microprocessor.

As the flow rate feedback water amount control of the RO membrane module 4, the first control unit 10 controls the speed so that the first detected flow rate value Q _{p1 of} the first flow rate sensor 15 becomes a preset first target flow rate value Q _p1 ′. The driving frequency for driving the first pressurizing pump 2 is calculated by the digital PID algorithm, and a current value signal corresponding to the calculated value of the driving frequency is output to the first inverter 3.

In the water treatment system 1, the flow rate feedback water amount control of the RO membrane module 4 is executed, so that the flow rate of the permeated water W <b> 2 sent from the RO membrane module 4 is adjusted to the first target flow rate value Q _p1 ′. Is done. The flow rate feedback water amount control by the first control unit 10 will be described later.

In the flow rate feedback water amount control, the first control unit 10 functions as the target flow rate value control unit in accordance with the measured electrical conductivity value of the permeate water W2 measured by the electrical conductivity sensor 14, and the first control unit 10 One target flow rate value Q _p1 ′ is set.

More specifically, the first control unit 10 as a target flow rate value control unit, when measuring the electrical conductivity value E _m permeate W2 of the reference electric conductivity value E _p exceeds the first target flow rate value Q set 'the first target flow rate value _{Q P1L' p1} to (<the first target flow rate value _{Q p1} '). The first control unit 10, when the measured electrical conductivity value _{E m} permeate W2 is less than the reference electric conductivity value _{E p} is the first target flow rate value _{Q p1} 'first target flow rate value _{Q P1H} ′ (> First target flow rate value Q _p1 ′).

Here, the reference electric conductivity value E _p, a standard electrical conductivity value set corresponding to the water quality required value of permeate W2 in EDI device 7. In the present embodiment, it will be described with reference electric conductivity value E _p as a single value, the reference electric conductivity value E _p may be a value having a predetermined range (width).

Incidentally, in the case same as the measured electric conductivity value E _m is the reference electric conductivity value E _p permeate W2 is used first target flow rate value Q _{p1 'which} is set in advance. The first target flow rate value Q _p1 ′ set in advance is, for example, a value (specified value) set based on the average amount of water consumed at the demand point of the water treatment system 1.

The second control unit 20 is configured by a microprocessor (not shown) including a CPU and a memory. In the second control unit 20, various programs for controlling (operating) the EDI device 7 are stored in the memory of the microprocessor. Further, in the memory of the microprocessor, for example, data relating to the detected temperature value T of the permeated water W2, data relating to the first target flow value Q _p1 ′ of the permeated water W2, and the second target flow value Q _p2 ′ of the desalted water W4. Data, data regarding the second target drainage flow rate value Q _d2 ′ of the second concentrated water W5, and the like are stored.

The second control unit 20 is electrically connected to the third control unit 30. The second control unit 20 receives data regarding the first target flow rate value Q _p1 ′ of the permeated water W2 in the RO membrane module 4 via the third control unit 30.

  In the second control unit 20, the CPU of the microprocessor executes various controls described later according to a predetermined program read from the memory. Further, the microprocessor incorporates an ITU for managing time keeping and the like.

As the flow rate feedback water amount control of the EDI device 7, the second control unit 20 uses a velocity type digital PID algorithm so that the second detected flow rate value _Qp2 of the second flow rate sensor 17 becomes the second target flow rate value _Qp2 '. A drive frequency for driving the second pressurizing pump 5 is calculated, and a current value signal corresponding to the calculated value of the drive frequency is output to the second inverter 6.

The second target flow rate value Q _p2 ′ is the difference between the first target flow rate value Q _p1 ′ of the permeate W2 in the RO membrane module 4 and the second target drainage flow rate value Q _d2 ′ of the second concentrated water W5 in the EDI device 7. It is a flow rate value that is less than the value. Specifically, the second control unit 20 is 0.95 times the difference value between the first target flow rate value Q _p1 ′ of the permeated water W2 and the second target drainage flow rate value Q _d2 ′ of the second concentrated water W5. The flow rate value is set as the second target flow rate value Q _p2 ′ in the flow rate feedback water amount control of the EDI device 7.

In the water treatment system 1, by performing flow rate feedback water amount control of the EDI device 7, the flow rate of the desalted water W <b> 4 sent from the EDI device 7 is adjusted to be the second target flow rate value Q _p2 ′. . The flow rate feedback water amount control by the second control unit 20 will be described later.

Further, the second control unit 20 executes recovery rate control (hereinafter, also referred to as “temperature feedforward recovery rate control”) of the EDI device 7 based on the temperature of the permeate water W2. Specifically, the second controller 20 (i) in the second concentrated water W5 based on the silica concentration determined from the silica concentration of the permeated water W2 acquired in advance and the detected temperature value T of the temperature sensor 16. Calculate the allowable concentration rate of silica, (ii) calculate the second target drainage flow rate value Q _d2 ′ from the calculated value of the allowable concentration rate and the second target flow rate value Q _p2 ′ of the desalted water W4, (iii) The first drain valve 11 to the third drain valve 13 are controlled so that the actual drainage flow rate of the second concentrated water W5 becomes the calculated value of the drainage flow rate (second target drainage flow rate value Q _d2 ′). This temperature feedforward recovery rate control is executed in parallel with the above-described flow rate feedback water amount control. The temperature feedforward recovery rate control by the second control unit 20 will be described later.

The third control unit 30 is configured by a microprocessor (not shown) including a CPU and a memory. The third control unit 30 is electrically connected to the first control unit 10 and the second control unit 20. The third control unit 30 has a function as a relay board that delivers data transmitted from the first control unit 10 to the second control unit 20. Specifically, the third control unit 30 acquires data regarding the first target flow rate value Q _p1 ′ of the permeated water W2 from the first control unit 10 and transmits the data to the second control unit 20.

Next, the operation of the water treatment system 1 according to the first embodiment will be described.
First, a processing procedure for setting a target flow value in the first control unit (target flow value control unit) 10 will be described with reference to FIG. The process of the flowchart shown in FIG. 2 is repeatedly executed during operation of the water treatment system 1.

In step ST101 shown in FIG. 2, the first control unit 10 acquires the measured electric conductivity value E _m of the electric conductivity sensor 14 permeate W2 detected in.

In step ST 102, the first control unit 10 determines measured electric conductivity value E _m is the same or whether a preset reference electric conductivity value E _p. In step ST102, when the first control unit 10 determines that the measured electrical conductivity value E _m = the reference electrical conductivity value E _p (YES), the processing of this flowchart ends (to step ST101). To return). If measured electric conductivity value E _m is the same as the reference electric conductivity value E _p, without changing the target flow value, already using the first target flow rate value Q _{p1 'being} set. In Step ST102, when the first control unit 10 determines that the measured electrical conductivity value E _m ≠ reference electrical conductivity value E _p (NO), the process proceeds to Step ST103.

Step ST 103: (Step ST 102 NO), the first control unit 10 determines whether the measured electrical conductivity value _{E m} exceeds a predetermined reference electric conductivity value _{E p.} In step ST103, if the first control unit 10 determines that measured electrical conductivity value E _m > reference electrical conductivity value E _p (YES), the process proceeds to step ST104. In Step ST103, when the first control unit 10 determines that the measured electric conductivity value E _m <the reference electric conductivity value E _p (NO), the process proceeds to Step ST105.

In step ST104 (step ST103: YES), the first controller 10 sets the first target flow value Q _p1 ′ to the first target flow value Q _p1L ′ (<first target flow value Q _p1 ′). This is because when the water quality of the permeated water W2 is poor, the target flow rate value is lowered to suppress further deterioration of the water quality of the permeated water W2. Thereby, the process of this flowchart is complete | finished (it returns to step ST101).

On the other hand, in step ST104 (step ST103: NO), the first control unit 10 sets the first target flow value Q _p1 ′ to the first target flow value Q _p1H ′ (> first target flow value Q _p1 ′). . This is because when the water quality of the permeated water W2 is good, the target flow rate value is increased to increase the water production efficiency of the permeated water W2. Thereby, the process of this flowchart is complete | finished (it returns to step ST101).

  Next, the flow rate feedback water amount control of the RO membrane module 4 by the first control unit 10 will be described with reference to FIG. The process of the flowchart shown in FIG. 3 is repeatedly executed during operation of the water treatment system 1.

In the process of the flowchart described below, the first target flow value Q _p1 ′, the first target flow value Q _p1H ′, and the first target flow value Q _p1L ′ are all “first target flow value Q _p1 ′. ".

In step ST201 shown in FIG. 3, the first control unit 10 acquires the first target flow rate value Q _p1 ′ of the permeated water W2. The first target flow rate value Q _p1 ′ is a value set by the processing of the flowchart shown in FIG. That is, in step ST201, the first control unit 10 acquires any one of the first target flow value Q _p1 ′, the first target flow value Q _p1H ′, or the first target flow value Q _p1L ′.

  In step ST202, the first control unit 10 determines whether or not the time t measured by the ITU has reached 100 ms, which is the control period (Δt). In step ST202, when the first control unit 10 determines that the time measured by the ITU has reached 100 ms (YES), the process proceeds to step ST203. In step ST202, when the first control unit 10 determines that the time measured by the ITU has not reached 100 ms (NO), the process returns to step ST202.

Step ST 203: In (step ST 202 YES determination), the first control unit 10, a first detected flow value _{Q p1} permeate W2 detected by the first flow rate sensor 15, and acquires as a feedback value.

In step ST 204, the first control unit 10 includes a first detected flow value _{Q p1} acquired in step ST 203, so that the deviation between the first target flow rate value _{Q p1} 'acquired in step ST201 becomes zero, velocity type calculating a manipulated variable _{U n} by digital PID algorithm. In the velocity type digital PID algorithm, the control period Delta] t (100 ms) calculates a variation .DELTA.U _n of the manipulated variables for each, which operate at the present time by adding the operation amount U _n-1 of the previous control cycle time The quantity _Un is determined.

In Step ST205, the first control unit 10 determines the first pressurization pump 2 based on the current operation amount U _n and the maximum drive frequency F ′ of the first pressurization pump 2 (set value of 50 Hz or 60 Hz). The drive frequency F [Hz] is calculated.

  In step ST206, the first control unit 10 converts the calculated value of the drive frequency F into a corresponding current value signal (4 to 20 mA).

  In step ST <b> 207, the first control unit 10 outputs the converted current value signal to the first inverter 3. Thereby, the process of this flowchart is complete | finished (it returns to step ST201).

  In step ST207, when the first control unit 10 outputs a current value signal to the first inverter 3, the first inverter 3 uses the drive power converted to the frequency specified by the input current value signal as the first power. Supply to the pressure pump 2. As a result, the first pressurizing pump 2 is driven at a rotational speed corresponding to the driving frequency input from the first inverter 3.

  Next, the flow rate feedback water amount control of the EDI device 7 by the second control unit 20 will be described with reference to FIG. The process of the flowchart shown in FIG. 4 is repeatedly executed during operation of the water treatment system 1.

In step ST301 shown in FIG. 4, the 2nd control part 20 sets 2nd target flow value _Qp2 'of demineralized water W4. Specifically, the second control unit 20 acquires data regarding the first target flow rate value Q _p1 ′ of the permeated water W2 in the RO membrane module 4 via the third control unit 30. And the 2nd control part 20 is 0. of the difference value of 1st target flow value _Qp1 'of the acquired permeated water W2, and 2nd target drainage flow value _Qd2 ' of the 2nd concentrated water W5 in the EDI apparatus 7. A flow rate value of 95 times is set as the second target flow rate value Q _p2 ′ of the desalted water W4.

  In Step ST302, the second control unit 20 determines whether or not the time t measured by the ITU has reached 100 ms that is the control cycle (Δt). In step ST302, when the second control unit 20 determines that the time measured by the ITU has reached 100 ms (YES), the process proceeds to step ST303. In step ST302, when the second control unit 20 determines that the time measured by the ITU has not reached 100 ms (NO), the process returns to step ST302.

Step ST 303: In (step ST 302 YES determination), the second control unit 20, the second detected flow value _{Q p2} of demineralized water W4 detected by the second flow rate sensor 17, and acquires as a feedback value.

In step ST 304, the second control unit 20, and the second detected flow value _{Q p2} obtained in step ST 303, so that the deviation between the second target flow rate value _{Q p2} 'set in step ST301 becomes zero, velocity type calculating a manipulated variable _{U n} by digital PID algorithm. In the velocity type digital PID algorithm, the control period Delta] t (100 ms) calculates a variation .DELTA.U _n of the manipulated variables for each, which operate at the present time by adding the operation amount U _n-1 of the previous control cycle time The quantity _Un is determined.

In step ST 305, the second control unit 20, based on the operation amount _{U n} at the present time, and the maximum driving frequency F'second pressurizing pump 5 (the set value of 50Hz or 60 Hz), the second pressure pump 5 The drive frequency F [Hz] is calculated.

  In step ST306, the second control unit 20 converts the calculated value of the drive frequency F into a corresponding current value signal (4 to 20 mA).

  In step ST307, the second control unit 20 outputs the converted current value signal to the second inverter 6. Thereby, the process of this flowchart is complete | finished (it returns to step ST301).

  In step ST307, when the second control unit 20 outputs the current value signal to the second inverter 6, the second inverter 6 converts the drive power converted to the frequency specified by the input current value signal to the second value. Supply to pressurizing pump 5. The second pressurizing pump 5 is driven at a rotational speed corresponding to the driving frequency input from the second inverter 6.

  Next, temperature feedforward recovery rate control of the EDI apparatus 7 by the second control unit 20 will be described with reference to FIG. The process of the flowchart shown in FIG. 5 is repeatedly executed together with the above-described flow rate feedback water flow control during the operation of the water treatment system 1.

In step ST401 shown in FIG. 5, the second control unit 20 acquires a second target flow rate value Q _p2 ′ of the desalted water W4. The second target flow rate value Q _p2 ′ is a value set in step ST301 of the flowchart shown in FIG.

In Step ST402, the second control unit 20 acquires the silica (SiO ₂ ) concentration C _s of the permeated water W2. This silica concentration C _s is a set value input to the memory by the system administrator via a user interface (not shown), for example. The silica concentration of the permeated water W2 can be obtained by analyzing the quality of the permeated water W2 in advance. In the permeate line L2, the silica concentration of the permeate W2 may be measured by a water quality sensor (not shown).

  In step ST403, the second control unit 20 acquires the detected temperature value T of the permeated water W2 from the temperature sensor 16.

In Step ST404, the second control unit 20 determines the silica solubility S _s with respect to water based on the acquired detected temperature value T.

In Step ST405, the second control unit 20 calculates the allowable concentration rate N _s of silica in the second concentrated water W5 based on the silica concentration C _s and the silica solubility S _s acquired or determined in the previous step. Permissible concentration rate N _s of silica can be determined from the following equation (1).
N _s = S _s / C _s (1)

For example, if the silica concentration C _s is 20 mg SiO ₂ / L and the silica solubility S _{s at} 25 ° C. is 100 mg SiO ₂ / L, the allowable concentration ratio N _s is “5”.

In step ST 406, the second control unit 20, based on the second target flow rate value Q _{p2 'and} permissible concentration rate N _s obtained in the previous step, the waste water flow rate value recovery is maximized (second target effluent flow rate The value Q _d2 ′) is calculated. The second target drainage flow rate value Q _d2 ′ can be obtained by the following equation (2).
Q _d2 ′ = Q _p2 ′ / (N _s −1) (2)

In step ST 407, the second control unit 20, so that the actual drainage flow rate value _{Q d2} of the second concentrated water W5 is the second target effluent flow rate value _{Q d2} 'calculated in step ST 406, the first drain valve 11 to the 3 Controls the opening and closing of the drain valve 13. Thereby, the process of this flowchart is complete | finished (it returns to step ST401).

  According to the water treatment system 1 which concerns on 1st Embodiment mentioned above, the following effects are acquired, for example.

In the water treatment system 1 according to the first embodiment, the second controller 20 determines that the second detected flow rate value Q _p2 output from the second flow rate sensor 17 is the first target flow rate of the permeate W2 in the RO membrane module 4. Driving the second pressurizing pump 5 so that the second target flow rate value Q _p2 ′ is equal to or less than the difference value between the value Q _p1 ′ and the second target drainage flow rate value Q _d2 ′ of the second concentrated water W5 in the EDI device 7. The frequency F is calculated, and a current value signal corresponding to the calculated value of the drive frequency F is output to the second inverter 6.

Therefore, in the RO membrane module 4, even if the recovery rate is lowered by reducing the flow rate of the permeated water W2 according to the quality of the raw water W1 and the first concentrated water W3, the desalted water W4 produced by the EDI device 7 The second detected flow rate value _Qp2 can be made to follow the recovery rate in the RO membrane module 4. Therefore, in the water treatment system 1 in which the RO membrane module 4 and the EDI device 7 are connected, even when the RO membrane module 4 reduces the flow rate of the permeate W2 and reduces the recovery rate, the EDI device 7 can control the amount of water. The required amount of water can be maintained.

Further, the second control unit 20 _calculates a difference value between the first target flow rate value Q _p1 ′ of the permeated water W2 in the RO membrane module 4 and the second target drainage flow rate value Q _d2 ′ of the second concentrated water W5 in the EDI device 7. A flow rate value 0.95 times the second target flow rate value Q _p2 ′ of the flow rate feedback water amount control in the EDI device 7.

  Therefore, even when the RO membrane module 4 reduces the flow rate of the permeate water W2 and lowers the recovery rate, the flow rate of the permeate water W2 supplied to the EDI device 7 is lower than the flow rate necessary for the water amount control in the EDI device 7. There is nothing. Therefore, the water treatment system 1 can suppress damage to these devices due to generation of negative pressure in the RO membrane module 4 and generation of cavitation in the second pressurization pump 5.

In addition, as the second target flow rate value Q _p2 ′ of the flow rate feedback water amount control, the difference value between the first target flow rate value Q _p1 ′ of the permeated water W2 and the second target drainage flow rate value Q _d2 ′ of the second concentrated water W5 Similar effects can be obtained even when a flow rate value of 1 is set. That is, in the water treatment system 1, the second target flow rate value Q _p2 ′ of the flow rate feedback water amount control is preferably the first target flow rate value Q _p1 ′ of the permeated water W2 and the second target drainage flow rate of the second concentrated water W5. The flow rate is set to 0.95 to 1 times the difference value from the value Q _d2 ′.

  Moreover, the water treatment system 1 which concerns on 1st Embodiment is provided with the permeated water discharge line L5 and the relief valve 9 as a permeated water discharge means. Therefore, even when the flow rate value of the permeate water W2 flowing through the permeate line L2 exceeds the total value of the flow rate value of the desalted water W4 and the flow rate value (discharge flow rate) of the second concentrated water W5, the RO membrane module Excess permeate water W2 can be discharged out of the system from the permeate discharge line L5 via the relief valve 9 so that a back pressure higher than the pressure resistance of 4 is not generated. Therefore, the water treatment system 1 can supply the EDI apparatus 7 with the permeated water W2 having a more stable flow rate.

Moreover, in the water treatment system 1 according to the first embodiment, the second control unit 20 performs the second control so that the second detected flow rate value Q _p2 of the second flow rate sensor 17 becomes the second target flow rate value Q _p2 ′. Flow rate water volume control is performed in which a drive frequency for driving the pressurizing pump 5 is calculated and a current value signal corresponding to the calculated value of the drive frequency is output to the second inverter 6. For this reason, the water treatment system 1 can supply the desalinated water W4 having a stable flow rate to the demand point even when the recovery rate is increased or decreased during the operation of the EDI device 7.

  Moreover, the 2nd control part 20 performs temperature feedforward collection | recovery rate control (refer FIG. 5) in the EDI apparatus 7. FIG. For this reason, the water treatment system 1 can more reliably suppress the precipitation of the silica-based scale in the EDI apparatus 7 while maximizing the recovery rate of the desalted water W4 in the EDI apparatus 7.

In the water treatment system 1 according to the first embodiment, the first controller 10 holds (stores) data relating to the first target flow rate value Q _p1 ′ of the permeate W2 in the RO membrane module 4 in the memory. Further, the water treatment system 1 includes a third control unit 30 that acquires data related to the first target flow rate value Q _p1 ′ of the permeated water W2 from the first control unit 10 and transmits the data to the second control unit 20. . Therefore, in the water treatment system 1 in which the RO membrane module 4 and the EDI device 7 are directly connected, more reliable data transfer can be performed.

(Second Embodiment)
Next, the structure of 1 A of water treatment systems which concern on 2nd Embodiment of this invention is demonstrated with reference to FIG. In the second embodiment, differences from the first embodiment will be mainly described. In the second embodiment, the same or equivalent components as those in the first embodiment will be described with the same reference numerals. In the second embodiment, the description overlapping with the first embodiment is omitted as appropriate.

  FIG. 6 is an overall configuration diagram of a water treatment system 1A according to the second embodiment. A water treatment system 1A according to the second embodiment includes a hardness sensor 18 as hardness measuring means instead of the temperature sensor 16 (see FIG. 1) in the first embodiment. Moreover, 1 A of water treatment systems which concern on 2nd Embodiment are provided with 2nd control part 20A instead of the 2nd control part 20 (refer FIG. 1) in 1st Embodiment.

  The hardness sensor 18 is a device that measures the calcium hardness (calculated in terms of calcium carbonate) of the permeated water W2 flowing through the permeated water line L2. The hardness sensor 18 is connected to the permeated water line L2 at the connection portion J4. The connection part J4 is arrange | positioned between the 2nd pressurization pump 5 and the EDI apparatus 7 (between the 2nd pressurization pump 5 and the branch part J5). The hardness sensor 18 is electrically connected to the second control unit 20A. The calcium hardness (hereinafter also referred to as “measured hardness value”) of the permeated water W2 measured by the hardness sensor 18 is transmitted as a detection signal to the second control unit 20A.

  The second control unit 20A is configured by a microprocessor (not shown) including a CPU and a memory. 20A of 2nd control parts perform flow volume feedback water volume control (refer FIG. 4) of the desalted water W4 by the speed type digital PID algorithm similarly to the 2nd control part 20 of 1st Embodiment. Since the flow rate feedback water amount control of the EDI device 7 in the second embodiment is the same as that in the first embodiment, description thereof is omitted.

20A of 2nd control parts perform the recovery rate control (henceforth "water quality feedforward recovery rate control") of the desalinated water W4 based on the hardness of the permeate water W2. More specifically, the second control unit 20A, (i) has been previously obtained calcium solubility carbonate, and based on the measured hardness value C _c of the hardness sensor 18, the permissible concentration rate of calcium carbonate in the second concentrated water W5 And (ii) calculating the second target drainage flow rate value Q _d2 ′ from the calculated value of the permissible concentration rate and the second target flow rate value Q _p2 ′ of the desalted water W4, and (iii) the second concentrated water W5 The first drain valve 11 to the third drain valve 13 are controlled so that the actual drainage flow rate becomes the calculated value of the drainage flow rate (second target drainage flow rate value Q _d2 ′).

  The water quality feedforward recovery rate control is executed in parallel with the flow rate feedback water amount control (same as the flow rate feedback water amount control by the second control unit 20 of the first embodiment) in the second control unit 20A. The water quality feedforward recovery rate control by the second control unit 20A will be described later.

  The other configuration of the water treatment system 1A according to the second embodiment is the same as that of the water treatment system 1 according to the first embodiment.

  Next, water quality feedforward recovery rate control by the second control unit 20A will be described. FIG. 7 is a flowchart illustrating a processing procedure when the water quality feedforward recovery rate control is executed in the second control unit 20A. The process of the flowchart shown in FIG. 7 is repeatedly executed during the operation of the water treatment system 1 together with the flow rate feedback water amount control (see FIG. 4).

In step ST501 shown in FIG. 7, the second control unit 20A acquires the second target flow rate value Q _p2 ′ of the permeated water W2. The second target flow rate value Q _p2 ′ is a value set by the process of step ST301 in the flowchart shown in FIG.

In step ST 502, the second control unit 20A acquires the measured hardness value _{C c} of the permeate W2 measured by the hardness sensor 18.

In step ST 503, the second control unit 20A acquires the calcium carbonate solubility _{S c} to water. This calcium carbonate solubility _Sc is, for example, a set value input to the memory by the system administrator via a user interface (not shown). In addition, the calcium carbonate solubility with respect to water can be regarded as a substantially constant value at a normal operation temperature (5 to 35 ° C.).

In step ST 504, the second control unit 20A, the previous based on the measured hardness value C _c and calcium carbonate solubility S _c obtained in step calculates the allowable concentration rate N _c of calcium carbonate in the second concentrated water W5. The permissible concentration factor _Nc of calcium carbonate can be determined by the following equation (3).
N _c = S _c / C _c (3)

For example, if the measured hardness value C _c is ₃ mg CaCO ₃ / L and the calcium carbonate solubility S _{c at} 25 ° C. is 15 mg CaCO ₃ / L, the allowable concentration ratio N _c is “5”.

In step ST505, the second control unit 20A, based on the allowable concentration rate _{N c} computed with the second target flow rate value _{Q p2} 'acquired in step ST 501, the recovery rate is maximum drainage flow rate (second target wastewater The flow value Q _d2 ′) is calculated. The second target drainage flow rate value Q _d2 ′ can be obtained by the following equation (4).
Q _d2 ′ = Q _p2 ′ / (N _c −1) (4)

In step ST 506, the second control unit 20A, actual wastewater flow rate value _{Q d2} is first drain valve 11 to the third so that the second target effluent flow rate value _{Q d2} 'calculated in step ST505 of the second concentrated water W5 The opening and closing of the drain valve 13 is controlled. Thereby, the process of this flowchart is complete | finished (it returns to step ST501).

  According to 1 A of water treatment systems which concern on 2nd Embodiment mentioned above, the following effects are acquired, for example.

  20A of 2nd control parts perform water quality feedforward collection | recovery rate control (refer FIG. 7) in the EDI apparatus 7. FIG. For this reason, the water treatment system 1A can more reliably suppress the precipitation of the calcium carbonate scale in the EDI device 7 while maximizing the recovery rate of the desalted water W4.

  The water treatment system 1A according to the second embodiment has the above-described water quality feedforward recovery in addition to the effects obtained by the water treatment system 1 according to the first embodiment (excluding the effects of temperature feedforward recovery rate control). The effect of rate control is obtained.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and can be implemented in various forms. In the following description, embodiments that can be implemented in the first embodiment can also be implemented in the second embodiment with some exceptions.

  For example, in the first embodiment, a decarboxylation device may be provided downstream of the RO membrane module 4 (between the RO membrane module 4 and the second pressurization pump 5). The decarbonation device is a facility that obtains degassed water as purified water by degassing the free carbonic acid (dissolved carbon dioxide gas) contained in the permeated water W2 with a gas separation membrane module. By providing a decarboxylation device in the subsequent stage of the RO membrane module 4, free carbonic acid that cannot be removed by the RO membrane module 4 can be removed from the permeated water W2. Accordingly, it is possible to obtain the permeated water W2 having a higher purity.

In the first embodiment, in the flow rate feedback water amount control of the RO membrane module 4, the electrical conductivity value of the permeated water W2 is detected as a water quality value, and the first target flow rate value Q _p1 ′ of the permeated water W2 is detected according to this water quality value. An example of setting is described. Not limited to this, at least one water quality value of the raw water W1, the permeate water W2 and the first concentrated water W3 is detected, and the first target flow rate value Q _p1 ′ of the permeate water W2 is set according to this water quality value. May be. In addition to the electrical conductivity value, the water quality value includes silica concentration and the like.

For example, the first target flow rate value Q _p1 ′ in the flow rate feedback water amount control of the RO membrane module 4 is set so that the electric conductivity of the raw water W1 and the permeated water W2 is detected and a preset salt removal rate is obtained. To do. In this case, the salt removal rate of the RO membrane is reduced by reducing the recovery rate by decreasing the first target flow rate value Q _p1 ′ of the permeated water W2 while the drainage flow rate of the first concentrated water W3 is kept constant. Can be raised.

Further, the first target in the flow rate feedback water amount control of the RO membrane module 4 is detected so that the electrical conductivity value and the silica concentration of the first concentrated water W3 are detected and these water quality values are equal to or less than a preset reference value. A flow value Q _p1 ′ is set. In this case, the drainage flow rate of the first concentrated water W3 is kept constant, and the recovery rate is lowered by decreasing the first target flow rate value _Qp1 'of the permeate water W2, thereby reducing the silica-based scale of the RO membrane. Membrane blockage due to precipitation and fouling can be suppressed.

In the first embodiment, at a temperature feedforward recovery rate control of EDI device 7, based on the detected temperature value T obtained from permeate W2, it has been described for determining the silica solubility S _s for water. For example, the temperature of the demineralized water W4 or the second concentrated water W5 may be detected, or the temperature of the first concentrated water W3 (RO membrane module 4) may be detected. In this case, the second control unit 20 determines the silica solubility S _s with respect to water based on the detected temperature value T acquired from the desalted water W4, the second concentrated water W5, or the first concentrated water W3 (FIG. 5: (See step ST404). When detecting the temperature of the first concentrated water W <b> 3, the detected temperature value T acquired by the first control unit 10 is transmitted to the second control unit 20 via the third control unit 30.

In the first embodiment, the difference value between the first target flow rate value Q _p1 ′ of the permeated water W2 in the RO membrane module 4 and the second target drainage flow rate value Q _d2 ′ of the second concentrated water W5 in the EDI device 7 is 0. The example in which the flow rate value of 95 times is set as the second target flow rate value Q _p2 ′ of the flow rate feedback water amount control in the EDI device 7 has been described. Not limited to this example, the second target flow rate value Q _p2 ′ of the flow rate feedback water amount control is preferably the first target flow rate value Q _p1 ′ of the permeated water W2 and the second target drainage flow rate value Q of the second concentrated water W5. The flow rate is set to 0.95 to 1 times the difference value from _d2 ′.

In the first embodiment, an example in which the first target flow rate value Q _p1 ′ (set value) of the permeate water W2 in the RO membrane module 4 is used for setting the second target flow rate value Q _p2 ′ of the EDI device 7 has been described (FIG. 4: See step ST301). For example, the first detected flow rate value Q _p1 (feedback value) may be used for setting the second target flow rate value Q _p2 ′ of the EDI device 7. Note that when the set value is used as the flow rate value of the permeate water W2 as in the first embodiment, the flow rate of the demineralized water W4 can be stabilized as compared with the case where a feedback value with fluctuation is used. .

In the first embodiment, the second target drainage flow rate value Q _d2 ′ (calculated value) of the second concentrated water W5 in the EDI device 7 is used for setting the second target flow rate value Q _p2 ′ of the EDI device 7. This has been described (see FIG. 2: step ST101). For example, the detected flow rate value (feedback value by the flow rate sensor) of the second concentrated water W5 flowing through the second concentrated water line L6 is not limited to such a calculated value, but the second target flow rate value Q _p2 ′ of the EDI device 7. It may be used for setting. In addition, when the calculated value is used as the flow rate value of the second concentrated water W5 as in the first embodiment, the flow rate of the demineralized water W4 is stabilized as compared with the case where the feedback value with fluctuation is used. Can do.

  In the first embodiment, the second concentrated water line L6 connected to the EDI device 7 is provided with a flow rate sensor as third flow rate detecting means for detecting the flow rate of the second concentrated water W5, and the detected temperature value of the permeated water W2. (Temperature sensor 16) It is good also as a structure which performs flow volume feedback collection | recovery rate control based on the detected flow volume value of the 2nd concentrated water W5.

In this case, the second control unit 20 (i) based on the silica solubility determined from the silica concentration of the permeated water W2 acquired in advance and the detected temperature value of the temperature sensor 16, the silica concentration in the second concentrated water W5. The allowable concentration rate is calculated, and (ii) the drainage flow rate of the second concentrated water W5 calculated from the calculated value of the allowable concentration rate and the second target flow rate value _Qp2 'of the desalted water W4 is set to the second target drainage flow rate value _Qd2. (Iii) the first drain valve 11 to the third drain valve 13 so that the detected flow rate value output from the flow sensor becomes the second target drain flow rate value Q _d2 ′ of the second concentrated water W5. To control. In this embodiment, instead of detecting the temperature of the permeated water W2, the temperature of the first concentrated water W3, the desalted water W4, or the second concentrated water W5 may be detected.

  Further, in the first embodiment, a part of the first concentrated water W3 flowing through the first concentrated water line L4 connected to the RO membrane module 4 is upstream of the first pressurizing pump 2 in the raw water line L1. It is good also as a structure which provided the concentrated water recirculation | reflux line to recirculate | reflux. By providing the concentrated water reflux line, it is possible to increase the flow velocity on the membrane surface of the RO membrane, so that the occurrence of fouling can be suppressed.

  In the first embodiment, the drainage flow rate of the second concentrated water W5 is adjusted stepwise by selectively opening and closing the first drainage valve 11 to the third drainage valve 13 connected to the second concentrated water line L6. An example was described. Not limited to this, the second concentrated water line L6 may be one without branching, and a proportional control valve may be provided on this line. In that case, the flow rate of the second concentrated water W5 is adjusted by transmitting a current value signal (for example, 4 to 20 mA) from the second control unit 20 to the proportional control valve to control the valve opening. Can do.

  Moreover, in the structure provided with the proportional control valve, it is good also as a structure which provided the flow sensor in the 2nd concentrated water line L6. The flow rate value detected by the flow rate sensor is input to the second control unit 20 as a feedback value. Thereby, the actual waste_water | drain flow volume of the 2nd concentrated water W5 can be controlled more correctly.

Moreover, in 1st Embodiment, the data regarding the 1st target flow value _Qp1 'are acquired from the 1st control part 10, and the structure provided with the 3rd control part 30 which transmits the said data to the 2nd control part 20 is demonstrated. did. However, the present invention is not limited thereto, and the first control unit 10 may transmit data related to the first target flow rate value Q _p1 ′ to the first control unit 10 without using the third control unit 30.

  Furthermore, in 1st Embodiment, you may comprise so that the function of the 1st control part 10 may be performed by the 2nd control part 20, and the function of the 2nd control part 20 is performed by the 1st control part 10. You may comprise.

In the second embodiment, in the water quality feedforward recovery rate control of the EDI device 7, the recovery rate is based on the allowable concentration rate of calcium carbonate contained in the permeated water W2 and the second target flow rate value _Qp2 'of the desalted water W4. An example of calculating the maximum drainage flow rate has been described. The present invention is not limited to this, and the following method may be adopted. That is, the allowable concentration ratio of calcium carbonate contained in the permeated water W2 is compared with the allowable concentration ratio of silica, and the smaller allowable concentration ratio is selected. Then, based on the selected allowable concentration ratio and the target flow rate value of the desalted water W4, the drainage flow rate that maximizes the recovery rate is calculated.

  In the second embodiment, the second concentrated water line L6 connected to the EDI device 7 is provided with a flow rate sensor as third flow rate detecting means for detecting the flow rate of the second concentrated water W5, and the measured hardness value of the permeated water W2 It is good also as a structure which performs flow volume feedback collection | recovery rate control based on the detection flow volume value of (calcium carbonate solubility: hardness sensor 18) and the 2nd concentrated water W5.

In this case, the second control unit 20A calculates (i) an allowable concentration rate of calcium carbonate in the second concentrated water W5 based on the calcium carbonate solubility acquired in advance and the measured hardness value of the hardness sensor 18, (Ii) Set the drainage flow rate of the second concentrated water W5 calculated from the calculated value of the permissible concentration rate and the second target flow rate value _Qp2 'of the desalted water W4 to the second target drainage flow rate value _Qd2 ', iii) The first drain valve 11 to the third drain valve 13 are controlled so that the detected flow value output from the flow sensor becomes the second target drain flow rate value Q _d2 ′ of the second concentrated water W5.

1, 1A Water treatment system 2 First pressure pump 3 First inverter 4 RO membrane module (membrane separation device)
5 Second pressurizing pump 6 Second inverter 7 EDI device (Electrodeionization device)
9 Relief valve (permeate drainage means)
10 1st control part 11 1st drain valve (drain valve)
12 Second drain valve (drain valve)
13 Third drain valve (drain valve)
14 Electrical conductivity sensor (electrical characteristic detection means)
15 1st flow sensor (1st flow detection means)
16 Temperature sensor (temperature detection means)
17 Second flow rate sensor (second flow rate detection means)
18 Hardness sensor (hardness measuring means)
20, 20A Second control unit 30 Third control unit L1 Raw water line L2 Permeate water line L3 Desalted water line L4 First concentrated water line L5 Permeate discharge line (permeate discharge means)
L6 2nd concentrated water line L11 1st drainage line L12 2nd drainage line L13 3rd drainage line W1 Raw water W2 Permeated water W3 Desalted water W4 1st concentrated water W5 2nd concentrated water

Claims (5)

A membrane separator for separating raw water into permeate and first concentrated water;
An electrodeionization apparatus that produces desalted water and second concentrated water by desalting the permeated water;
A raw water line for supplying raw water to the membrane separator;
A permeate line for supplying permeate to the electrodeionization device;
First flow rate detecting means for outputting the flow rate of the permeated water as a first detected flow rate value;
A first pressurizing pump that is driven at a rotational speed according to the input driving frequency and pumps the raw water flowing through the raw water line toward the membrane separation device;
A first inverter for outputting said frequency designation signal corresponding to the calculation value of the drive frequency of the first pressurizing pump is input, a driving frequency corresponding to the input the frequency designation signal to the first pressure pump,
A target flow rate control unit that sets a first target flow rate value of the permeate according to at least one water quality value of the raw water, the permeate, and the first concentrated water;
As the first detected flow value output from said first flow rate detecting unit becomes the first target flow rate value, and calculates a drive frequency of said first pressurizing pump, corresponds to the calculated value of the driving frequency A first control unit that outputs a frequency designation signal to the first inverter;
Second flow rate detection means for outputting the flow rate of demineralized water as a second detected flow rate value;
A second pressurizing pump that is driven at a rotational speed corresponding to the input driving frequency and pumps the permeate flowing through the permeate line toward the electrodeionization device;
A second inverter for outputting said frequency designation signal corresponding to the calculation value of the drive frequency of the second pressure pump is input, a driving frequency corresponding to the input the frequency designation signal to the second pressure pump,
A second target in which the second detected flow rate value output from the second flow rate detecting means is equal to or less than the difference value between the flow rate value of the permeated water in the membrane separation device and the flow rate value of the second concentrated water in the electrodeionization device. as the flow rate value, and a second control unit for outputting calculates the driving frequency of the second pressurizing pump, a frequency designation signal that corresponds to the calculated value of the drive frequency to the second inverter,
A water treatment system comprising. The flow rate value of the permeated water flowing through the permeate line exceeds the total value of the flow rate value of the demineralized water and the second concentrated water produced by the electrodeionization device, and exceeds the predetermined pressure value. When it does, it comprises permeated water discharging means for discharging excess permeated water from the permeated water line,
The second control unit sets a flow rate value of 0.95 to 1 times a difference value between the flow rate value of the permeated water in the membrane separation device and the flow rate value of the second concentrated water in the electrodeionization device. 2 Target flow rate value
The water treatment system according to claim 1. Temperature detecting means for detecting the temperature of the permeated water, the first concentrated water, the desalted water, or the second concentrated water;
A drain valve capable of adjusting a drain flow rate of the second concentrated water discharged from the electrodeionization device,
The second control unit calculates (i) an allowable concentration rate of silica in the second concentrated water based on the silica concentration determined in advance from the silica concentration of permeated water acquired in advance and the detected temperature value of the temperature detecting means. (Ii) calculating the drainage flow rate from the calculated value of the permissible concentration factor and the second target flow rate value of the desalted water, and (iii) so that the actual drainage flow rate of the second concentrated water becomes the calculated value of the drainage flow rate. To control the drain valve,
The water treatment system according to claim 1 or 2. A hardness measuring means for measuring the calcium hardness of the permeated water;
A drain valve capable of adjusting a drain flow rate of the second concentrated water discharged from the electrodeionization device,
The second control unit calculates (i) an allowable concentration rate of calcium carbonate in the second concentrated water based on (i) the calcium carbonate solubility acquired in advance and the measured hardness value of the hardness measuring means, and (ii) the The drainage flow rate of the second concentrated water is calculated from the calculated value of the allowable concentration ratio and the second target flow rate value of the desalted water, and (iii) the actual drainage flow rate of the second concentrated water becomes the calculated value of the drainage flow rate. To control the drain valve,
The water treatment system according to claim 1 or 2. The first control unit holds data relating to the flow rate of permeated water in the membrane separation device,
The water treatment system includes a third control unit that acquires data on the flow rate of the permeated water in the membrane separation device from the first control unit and transmits the data to the second control unit.
The water treatment system as described in any one of Claims 1-4.

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