JP2014083480A - Water treatment system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment system in which permeated water can be produced in an RO membrane module of a post stage by constant flow operation without using an intermediate tank.SOLUTION: A water treatment system 1 includes: a first membrane separation apparatus 4 which produces first permeated water W2 from a supply water W1; a first pump 2; pressure detection means 5 that outputs pressure of the first permeated water W2 produced in the first membrane separation apparatus 4 as a detected pressure value; a first control part 10 that drives the first pump 2 so that the detected pressure value output from the pressure detection means 5 may become a predetermined objective pressure value; a second membrane separation apparatus 8 which produces second permeated water W4 from the first permeated water W2 produced in the first membrane separation apparatus 4; a second pump 6; flow rate detection means 9 that outputs a flow rate of the second permeated water W4 produced in the second membrane separation apparatus 8 as a detected flow rate value; and a second control part 20 that drives the second pump 6 so that the detected flow rate value output from the flow rate detection means 9 may become a predetermined objective flow rate value.

Description

  The present invention relates to a water treatment system including a membrane separation device that produces permeate and concentrated water from supply water.

  In the semiconductor manufacturing process, the cleaning of electronic parts and medical instruments, etc., high-purity pure water containing no impurities is used. In general, this type of pure water is obtained by reversing raw water (hereinafter also referred to as “supply water”) such as ground water or tap water with a reverse osmosis membrane module (hereinafter also referred to as “RO membrane module”) as a membrane separator. Manufactured by osmotic membrane treatment.

  Conventionally, a water treatment system has been proposed in which pure water is produced by treating supplied water with an RO membrane module and an electric deionizer (see, for example, Patent Documents 1 and 2). There is also known a water treatment system in which pure water is produced by treating supply water with two RO membrane modules connected in series.

JP 2001-259376 A JP 2006-255650 A

  In the water treatment system for producing pure water using the two RO membrane modules described above, a pressure pump is provided upstream of the upstream RO membrane module, and water is pumped from the pressure pump toward the two RO membrane modules. Thus, a configuration in which water is circulated through the two RO membrane modules can be considered. However, when water is pumped with a single pressurizing pump, the operating pressure of the pressurizing pump becomes high (about 2 MPa), so that pressure resistance is required for each RO membrane module, and costs increase.

  In the above water treatment system, an intermediate tank may be provided between the two RO membrane modules, and a pressure pump may be provided for each of the two RO membrane modules. By providing the intermediate tank, the flow rate can be independently controlled in the upstream RO membrane module and the downstream RO membrane module. However, this water treatment system requires an intermediate tank in addition to the two pressurizing pumps, which increases the cost and requires a space for installing the intermediate tank.

  In the water treatment system, a configuration in which a pressurizing pump having an intermediate operating pressure (about 1 MPa) is provided in each of the two RO membrane modules is also conceivable. However, in this water treatment system, the flow rate of water supplied to the downstream RO membrane module fluctuates due to membrane surface fouling in the upstream RO membrane module, changes in pipe resistance due to water temperature, etc. Since the inlet pressure of the pump becomes unstable, it is difficult to produce permeated water with a stable flow rate in the downstream RO membrane module.

  Therefore, the present invention provides a water treatment system capable of producing a permeated water having a stable flow rate in the subsequent stage membrane separation apparatus without using an intermediate tank between the previous stage membrane separation apparatus and the subsequent stage membrane separation apparatus. For the purpose.

  The present invention is manufactured by a first membrane separation device that produces first permeated water from feed water, a first pump that discharges feed water toward the first membrane separation device, and the first membrane separation device. Pressure detecting means for outputting the pressure of the first permeated water as a detected pressure value; and a first pump for driving the first pump so that the detected pressure value output from the pressure detecting means becomes a preset target pressure value. 1 control part, the 2nd membrane separator which manufactures 2nd permeated water from the 1st permeated water manufactured with the 1st membrane separator, and discharges the 1st permeated water toward the 2nd membrane separator A second pump, a flow rate detecting means for outputting the flow rate of the second permeated water produced by the second membrane separation device as a detected flow rate value, and a target in which the detected flow rate value output from the flow rate detecting means is set in advance. A second control unit for driving the second pump so as to obtain a flow rate value; On water treatment system comprising a.

  The water treatment system 1 also outputs a first inverter that outputs a driving frequency corresponding to the input command signal to the first pump, and a second inverter that outputs a driving frequency corresponding to the input command signal to the second pump. Two inverters, wherein the first pump is driven according to the drive frequency input from the first inverter, and the second pump is driven according to the drive frequency input from the second inverter. The first control unit calculates a driving frequency of the first pump so that the detected pressure value output from the pressure detecting unit becomes a preset target pressure value, and corresponds to the calculated value of the driving frequency. The second control unit is configured to output a command signal to be output to the first inverter so that the detected flow rate value output from the flow rate detection unit becomes a preset target flow rate value. It calculates the driving frequency of the second pump, to be configured to output a command signal corresponding to the calculated value of the drive frequency to the second inverter are preferred.

  According to the present invention, there is provided a water treatment system capable of producing a permeated water having a stable flow rate in a downstream membrane separator without using an intermediate tank between the upstream membrane separator and the downstream membrane separator. be able to.

1 is an overall configuration diagram of a water treatment system 1 according to an embodiment. 4 is a flowchart showing a processing procedure when pressure feedback control is executed in the first control unit 10. 5 is a flowchart showing a processing procedure when flow rate feedback control is executed in the second control unit 20.

  Hereinafter, a water treatment system according to the present invention will be described with reference to the drawings. The water treatment system 1 of this embodiment is applied to a pure water production system that produces pure water from fresh water such as tap water and groundwater. FIG. 1 is an overall configuration diagram of a water treatment system 1 according to the present embodiment. FIG. 2 is a flowchart showing a processing procedure when pressure feedback control is executed in the first control unit 10. FIG. 3 is a flowchart showing a processing procedure when the flow rate feedback control is executed in the second control unit 20.

  As shown in FIG. 1, the water treatment system 1 according to the present embodiment includes a first pressurizing pump 2 as a first pump, a first inverter 3, and a first RO membrane module 4 as a first membrane separation device. , A pressure sensor 5 as pressure detecting means, a first control unit 10, and a first drain valve 11 to a third drain valve 13.

  The water treatment system 1 includes a second pressurizing pump 6 as a second pump, a second inverter 7, a second RO membrane module 8 as a second membrane separation device, and a flow rate sensor 9 as a flow rate detecting means. The 2nd control part 20 and the 4th drain valve 21-the 6th drain valve 23 are provided.

  Further, the water treatment system 1 includes a supply water line L1, a first permeate water line L2, a second permeate water line L3, a first concentrate water line L4, a second concentrate water line L5, and a first concentrate water. Drainage line L11, second concentrated water drainage line L12, third concentrated water drainage line L13, fourth concentrated water drainage line L21, fifth concentrated water drainage line L22, sixth concentrated water drainage line L23, Is provided. The “line” in the present specification is a general term for lines capable of flowing a fluid such as a flow path, a path, and a pipeline. Moreover, in FIG. 1, the path | route of an electrical connection is shown with a broken line.

  The supply water line L1 is a line that supplies the supply water W1 to the first RO membrane module 4. The upstream end of the supply water line L1 is connected to a supply source (not shown) of the supply water W1. The downstream end of the supply water line L <b> 1 is connected to the primary inlet port of the first RO membrane module 4.

  The first pressurizing pump 2 is a device that sucks in the supply water W <b> 1 supplied from the supply source and discharges it toward the first RO membrane module 4. The first pressurizing pump 2 is provided in the supply water line L1. The first pressurizing pump 2 is electrically connected to a first inverter 3 (described later). 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 input driving frequency.

  The first inverter 3 is an electric circuit (or a device having the 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 a driving frequency corresponding to the input current value signal to the first pressurizing pump 2.

  The first RO membrane module 4 separates the supply water W1 discharged from the first pressure pump 2 into a first permeate W2 from which dissolved salts have been removed and a first concentrated water W3 from which dissolved salts have been concentrated. It is equipment to process. The first RO membrane module 4 includes a single or a plurality of RO membrane elements (not shown). The first RO membrane module 4 membrane-separates the supply water W1 with these RO membrane elements to produce the first permeated water W2 and the first concentrated water W3.

  The primary side inlet port of the first RO membrane module 4 is connected to the downstream side of the first pressurizing pump 2 via the supply water line L1. An upstream end of the first permeate line L2 is connected to the secondary port of the first RO membrane module 4. The 1st permeated water W2 manufactured with the 1st RO membrane module 4 is sent to the 2nd RO membrane module 8 via the 1st permeated water line L2. In addition, an upstream end of the first concentrated water line L4 is connected to the primary outlet port of the first RO membrane module 4. The first concentrated water W3 produced by the first RO membrane module 4 is discharged out of the first RO membrane module 4 via the first concentrated water line L4.

  The first permeated water line L <b> 2 is a line for sending the first permeated water W <b> 2 manufactured by the first RO membrane module 4 to the second RO membrane module 8. The upstream end of the first permeate line L <b> 2 is connected to the secondary port of the first RO membrane module 8. The downstream end of the first permeate line L <b> 2 is connected to the primary inlet port of the second RO membrane module 8.

  The pressure sensor 5 is a device that detects the pressure of the first permeated water W <b> 2 on the downstream side of the first RO membrane module 4. The pressure sensor 5 is connected to the first permeate line L2 at the connection portion J1. The pressure sensor 5 is electrically connected to the first control unit 10. The pressure of the first permeated water W2 detected by the pressure sensor 5 (hereinafter also referred to as “detected pressure value”) is transmitted to the first control unit 10 as a detection signal.

  The first control unit 10 is configured by a microprocessor (not shown) including a CPU and a memory. The first control unit 10 calculates a first drive frequency for driving the first pressurizing pump 2 so that the detected pressure value of the pressure sensor 5 becomes a preset target pressure value, and the first drive A current value signal corresponding to the calculated value of the frequency is output to the first inverter 3 (hereinafter also referred to as “pressure feedback control”). The pressure feedback control by the first control unit 10 will be described later.

  The first concentrated water line L4 is a line for sending the first concentrated water W3 from the first RO membrane module 4. The upstream end of the first concentrated water line L4 is connected to the primary outlet port of the first RO membrane module 4. Further, the downstream side of the first concentrated water line L4 branches to the first concentrated water drain line L11, the second concentrated water drain line L12, and the third concentrated water drain line L13 at the branch portions J2 and J3.

  A first drain valve 11, a second drain valve 12, and a third drain valve 13 are provided in the first concentrated water drain line L11, the second concentrated water drain line L12, and the third concentrated water drain line L13, respectively. The first drain valve 11 to the third drain valve 13 are valves that adjust the drain flow rate of the first concentrated water W3 discharged from the first concentrated water drain line L11 to the third concentrated water drain line L13 to the outside of the system. By controlling the opening and closing of the valve bodies in the first drain valve 11 to the third drain valve 13 and adjusting the drain flow rate of the first concentrated water W3, the first permeated water W2 produced by the first RO membrane module 4 is controlled. The recovery rate can be set to a desired value.

  The first drain valve 11 to the third drain valve 13 are each electrically connected to the first control unit 10. 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 transmitted from the first control unit 10.

  The second pressurizing pump 6 is a device that sucks the first permeated water W <b> 2 sent from the first RO membrane module 4 and discharges it toward the second RO membrane module 8. The second pressure pump 6 is electrically connected to a second inverter 7 (described later). The second pressurizing pump 6 is supplied with driving power having a frequency converted from the second inverter 7. The second pressurizing pump 6 is driven at a rotational speed corresponding to the input driving frequency.

  The second inverter 7 is an electric circuit (or a device having the circuit) that supplies driving power whose frequency is converted to the second pressurizing pump 6. The second inverter 7 is electrically connected to the second control unit 20. A current value signal is input to the second inverter 7 from the second control unit 20. The second inverter 7 outputs a driving frequency corresponding to the input current value signal to the second pressurizing pump 6.

  The second RO membrane module 8 converts the first permeated water W2 discharged from the second pressurizing pump 6 into a second permeated water W4 from which dissolved salts are removed and a second concentrated water W5 from which dissolved salts are concentrated. Equipment for membrane separation treatment. The second RO membrane module 8 includes a single or a plurality of RO membrane elements (not shown). The second RO membrane module 8 membrane-separates the first permeated water W2 with these RO membrane elements to produce the second permeated water W4 and the second concentrated water W5.

  The primary side inlet port of the second RO membrane module 8 is connected to the downstream side of the first RO membrane module 4 via the first permeate line L2. An upstream end portion of the second permeated water line L3 is connected to the secondary side port of the second RO membrane module 8. The 1st permeated water W2 manufactured with the 1st RO membrane module 4 is sent to the 2nd RO membrane module 8 via the 1st permeated water line L2. The upstream end of the second concentrated water line L5 is connected to the primary side outlet port of the second RO membrane module 8. The second concentrated water W5 produced by the second RO membrane module 8 is discharged out of the second RO membrane module 8 via the second concentrated water line L5.

  The 2nd permeated water line L3 is a line which sends out the 2nd permeated water W4 manufactured with the 2nd RO membrane module 8 to a customer. The upstream end of the second permeate line L3 is connected to the secondary port of the second RO membrane module 8. The downstream end of the second permeated water line L3 is connected to a demand destination device or the like (not shown).

  The flow rate sensor 9 is a device that detects the flow rate of the second permeated water W4 flowing through the second permeated water line L3. The flow sensor 9 is connected to the second permeated water line L3 at the connection portion J4. The flow sensor 9 is electrically connected to the second control unit 20. The flow rate of the second permeated water W4 detected by the flow sensor 9 (hereinafter also referred to as “detected flow rate value”) is transmitted to the second control unit 20 as a detection signal.

  The second control unit 20 is configured by a microprocessor (not shown) including a CPU and a memory. The second control unit 20 calculates a second drive frequency for driving the second pressurizing pump 6 so that the detected flow value of the flow sensor 9 becomes a preset target flow value, and the second drive A current value signal corresponding to the calculated value of the frequency is output to the second inverter 7 (hereinafter also referred to as “flow rate feedback control”). The flow rate feedback control by the second control unit 20 will be described later.

  The second concentrated water line L5 is a line for delivering the second concentrated water W5 from the second RO membrane module 8. The upstream end of the second concentrated water line L5 is connected to the primary outlet port of the second RO membrane module 8. Further, the downstream side of the second concentrated water line L5 branches into a fourth concentrated water drain line L21, a fifth concentrated water drain line L22, and a sixth concentrated water drain line L23 at branch portions J5 and J6.

  A fourth drain valve 21, a fifth drain valve 22, and a sixth drain valve 23 are provided in the fourth concentrated water drain line L21, the fifth concentrated water drain line L22, and the sixth concentrated water drain line L23, respectively. The fourth drain valve 21 to the sixth drain valve 23 are valves that adjust the drain flow rate of the second concentrated water W5 that is discharged out of the system from the fourth concentrated water drain line L21 to the sixth concentrated water drain line L23. By controlling the opening and closing of the valve bodies in the fourth drain valve 21 to the sixth drain valve 23 and adjusting the drain flow rate of the second concentrated water W5, the second permeated water W4 produced by the second RO membrane module 8 is controlled. The recovery rate can be set to a desired value.

  The 4th drain valve 21-the 6th drain valve 23 are electrically connected with the 2nd control part 20, respectively. The opening / closing of the valve body in the fourth drain valve 21 to the sixth drain valve 23 is controlled by a drive signal transmitted from the second control unit 20.

  Next, the pressure feedback control by the first 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 a target pressure value P ′ of the supply water W1. The target pressure value P ′ is, for example, a set value that is input to the memory of the first control unit 10 by a system administrator via a user interface (not shown).

  In step ST102, the first control unit 10 determines whether or not the time t measured by an internal timer (not shown) has reached 100 ms which is the control cycle. In step ST102, when the first control unit 10 determines that the time measured by the timer has reached 100 ms (YES), the process proceeds to step ST103. In Step ST102, when the first control unit 10 determines that the time measured by the timer has not reached 100 ms (NO), the process returns to Step ST102.

  In step ST103 (step ST102: YES determination), the first control unit 10 acquires the detected pressure value P of the supply water W1 detected by the pressure sensor 5.

In step ST104, the first controller 10 uses the velocity type digital PID algorithm so that the deviation between the detected pressure value (feedback value) P acquired in step ST103 and the target pressure value P ′ acquired in step ST101 becomes zero. calculating a manipulated variable _{U 1} by. In the velocity type digital PID algorithm, the change amount of the operation amount is calculated every control cycle (100 ms), and this operation amount is determined by adding this to the previous operation amount.

In step ST105, the first control unit 10 determines the first pressurizing pump 2 based on the operation amount U ₁ , the target pressure value P ′, and the maximum driving frequency of the first pressurizing pump 2 (set value of 50 Hz or 60 Hz). It calculates a drive frequency _{F 1.}

In step ST 106, the first control unit 10 converts the calculated value of the driving frequency _{F 1,} the corresponding current value signal (4 to 20 mA).

  In step ST <b> 107, the first control unit 10 outputs the converted current value signal to the first inverter 3. In step ST107, when the first control unit 10 outputs the current value signal to the first inverter 3, the first inverter 3 applies the drive power converted to the frequency corresponding to the input current value signal to the first. 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. Thereby, the process of this flowchart is complete | finished (it returns to step ST101).

  Next, the flow rate feedback control by the second control unit 20 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 step ST201 shown in FIG. 3, the second control unit 20 acquires the target flow rate value Q ′ of the second permeated water W4. The target flow rate value Q ′ is, for example, a set value that is input to the memory of the second control unit 20 by a system administrator via a user interface (not shown).

  In step ST202, the second control unit 20 determines whether or not the time t measured by an internal timer (not shown) has reached 100 ms, which is the control cycle. In step ST202, when the second control unit 20 determines that the time measured by the timer has reached 100 ms (YES), the process proceeds to step ST203. In Step ST202, when the second control unit 20 determines that the time measured by the timer has not reached 100 ms (NO), the process returns to Step ST202.

  In step ST203 (step ST202: YES determination), the second control unit 20 acquires the detected flow rate value Q of the second permeated water W4 detected by the flow rate sensor 9.

In step ST204, the second control unit 20 uses the velocity type digital PID algorithm so that the deviation between the detected flow rate value (feedback value) Q ′ acquired in step ST203 and the target flow rate value Q acquired in step ST201 becomes zero. calculating a manipulated variable _{U 2} by. In the velocity type digital PID algorithm, the change amount of the operation amount is calculated every control cycle (100 ms), and this operation amount is determined by adding this to the previous operation amount.

In Step ST205, the second control unit 20 determines the second pressurization pump 6 based on the manipulated variable U ₂ , the target flow rate value Q ′ and the maximum drive frequency of the second pressurization pump 6 (set value of 50 Hz or 60 Hz). It calculates a drive frequency _{F 2.}

In step ST 206, the second control unit 20, converts the calculated value of the driving frequency _{F 2,} the corresponding current value signal (4 to 20 mA).

  In step ST207, the second control unit 20 outputs the converted current value signal to the second inverter 7. Thereby, the process of this flowchart is complete | finished (it returns to step ST201).

  In step ST207, when the second control unit 20 outputs the current value signal to the second inverter 7, the second inverter 7 applies the second driving power converted to the frequency corresponding to the input current value signal. Supply to the pressure pump 6. As a result, the second pressurizing pump 6 is driven at a rotational speed corresponding to the driving frequency input from the second inverter 7.

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

  In the water treatment system 1 according to the present embodiment, the first control unit 10 performs pressure feedback control based on the detected pressure value of the first permeated water W2 manufactured by the first RO membrane module 4 in the previous stage. Moreover, the 2nd control part 20 performs flow volume feedback control based on the detected flow volume value of the 2nd permeate water W4 manufactured with the RO membrane module 8 of the back | latter stage.

  According to this, even if a fouling of the membrane surface in the first RO membrane module 4 at the front stage or a change in pipe resistance due to the water temperature occurs, the pressure of the first permeate W2 sent to the second RO membrane module 8 at the rear stage. In other words, the inlet pressure of the second pressurizing pump 6 can be kept substantially at the target pressure value. Therefore, in the water treatment system 1, a second flow rate with a stable flow rate can be obtained in the second RO membrane module 8 at the rear stage without using an intermediate tank between the RO membrane module 4 at the front stage and the second RO membrane module 8 at the rear stage. Permeated water W4 can be produced.

  Further, in the pressure feedback control, the first control unit 10 calculates the drive frequency of the first pressurizing pump 2 so that the detected pressure value output from the pressure sensor 5 becomes a preset target pressure value, and A command signal corresponding to the calculated value of the drive frequency is output to the first inverter 3. Further, in the flow rate feedback control, the second control unit 20 calculates the drive frequency of the second pressurizing pump 6 so that the detected flow rate value output from the flow rate sensor 9 becomes a preset target flow rate value, A command signal corresponding to the calculated value of the drive frequency is output to the second inverter 7.

  According to this, since the 1st pressurization pump 2 can be driven according to the state of the membrane surface of the 1st RO membrane module 4 and pipe line resistance, the pressure of the 1st permeate water W2, ie, the 2nd pressurization. The inlet pressure of the pump 6 can be stably maintained at the target pressure value. Moreover, the 2nd pressurization pump 6 can be driven so that the maximum request | requirement water amount of the 2nd permeated water W4 in a demand destination may always be ensured. Therefore, in the second RO membrane module 8, the second permeated water W4 having a more stable flow rate can be manufactured.

  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.

  For example, in this embodiment, a concentrated water recirculation line is provided that recirculates a part of the first concentrated water W3 flowing through the first concentrated water line L4 to the supply water line L1 upstream from the first pressurizing pump 2. It is good also as a structure. By providing the concentrated water reflux line, the flow velocity on the membrane surface can be increased, so that the occurrence of fouling in the first RO membrane module 4 can be suppressed.

  Similarly, a configuration in which a concentrated water recirculation line for recirculating a part of the second concentrated water W5 flowing through the second concentrated water line L5 to the first permeated water line L2 upstream of the second pressurizing pump 6 is provided. It is good. In that case, occurrence of fouling in the second RO membrane module 8 can be suppressed.

  Moreover, in this embodiment, the structure which provided the 1st drainage valve 11-the 3rd drainage valve 13 in the 1st concentrated water drainage line L11-the 3rd concentrated water drainage line L13 was demonstrated. The configuration is not limited to this, and the concentrated water drainage line may be one without branching, and a proportional control valve may be provided in this line. In that case, the first control unit 10 transmits a control signal (for example, an analog signal of 4 to 20 mA or 0 to 10 V) to the proportional control valve to control the opening of the first concentrated water W3. The drainage flow rate can be adjusted.

  Further, in the configuration in which the proportional control valve is provided, the flow rate sensor may be provided in the concentrated water drain line. The flow rate value detected by the flow rate sensor is input to the first control unit 10 as a feedback value. Thereby, the waste_water | drain flow volume of the 1st concentrated water W3 can be controlled more correctly.

  The configuration provided with the proportional control valve described above can also be applied to the second RO membrane module 8.

  In the present embodiment, an example in which a current value signal (4 to 20 mA) is output as a command signal from the first control unit 10 to the first inverter 3 and a command signal from the second control unit 20 to the second inverter 7 will be described. did. Not only this, but also as a structure which outputs a voltage value signal (0-10V) as a command signal from the 1st control part 10 to the 1st inverter 3, and a command signal from the 2nd control part 20 to the 2nd inverter 7, respectively. Good.

  In the present embodiment, the example in which the driving frequency of the first pressurizing pump 2 and the second pressurizing pump 6 is calculated by the speed type digital PID algorithm has been described. It is good also as a structure which calculates the drive frequency of the pressure pump 2 and the 2nd pressurization pump 6. FIG.

1 Water treatment system 2 First pressure pump (first pump)
4 1st RO membrane module (1st membrane separator)
5 Pressure sensor (pressure detection means)
6 Second pressurizing pump (second pump)
8 Second RO membrane module (second membrane separator)
9 Flow rate sensor (flow rate detection means)
10 1st control part 20 2nd control part L1 Supply water line L2 1st permeate water line L3 2nd permeate water line L4 1st concentrate water line L5 2nd concentrate water line W1 Supply water W2 1st permeate water W3 2nd permeation Water W4 first concentrated water W5 second concentrated water

Claims (2)

A first membrane separation device for producing a first permeate from the feed water;
A first pump for discharging supply water toward the first membrane separation device;
Pressure detecting means for outputting the pressure of the first permeated water produced by the first membrane separation device as a detected pressure value;
A first control unit that drives the first pump so that the detected pressure value output from the pressure detecting means becomes a preset target pressure value;
A second membrane separation device for producing second permeated water from the first permeated water produced by the first membrane separation device;
A second pump for discharging the first permeate to the second membrane separation device;
A flow rate detecting means for outputting the flow rate of the second permeated water produced by the second membrane separation device as a detected flow rate value;
A second controller that drives the second pump so that the detected flow rate value output from the flow rate detection means becomes a preset target flow rate value;
A water treatment system comprising. A first inverter that outputs a driving frequency corresponding to the input command signal to the first pump; and a second inverter that outputs a driving frequency corresponding to the input command signal to the second pump;
The first pump is driven according to the drive frequency input from the first inverter, the second pump is driven according to the drive frequency input from the second inverter,
The first control unit calculates a driving frequency of the first pump so that a detected pressure value output from the pressure detecting unit becomes a preset target pressure value, and corresponds to the calculated value of the driving frequency. The second control unit is configured to output a command signal to the first inverter, and the second control unit controls the second pump so that the detected flow rate value output from the flow rate detection unit becomes a preset target flow rate value. It is configured to calculate a drive frequency and output a command signal corresponding to the calculated value of the drive frequency to the second inverter.
The water treatment system according to claim 1.

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