JP2018153790A - Washing method of reverse osmosis membrane module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a washing method of a reverse osmosis membrane module capable of shortening the washing time of the reverse osmosis membrane module and reducing the additional amount of a medicine when a biological substance adheres to a membrane surface.SOLUTION: A water treatment system 1 which is provided with a reverse osmosis membrane module 5 separating supply water W1 to permeated water W2 and concentrated water W3 and which is a washing method of the reverse osmosis membrane module 5 performed when the reverse osmosis membrane module 5 has a biological contamination tendency includes: a washing auxiliary agent addition step adding a washing auxiliary agent to the reverse osmosis membrane module 5; and an osmotic pressure adjustment step adjusting osmotic pressure in the reverse osmosis membrane module 5 so as to transfer the permeated water W2 from the secondary side of a membrane in the reverse osmosis membrane module 5 toward a primary side after the washing auxiliary agent addition step.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a method for cleaning a reverse osmosis membrane module.

  High-purity pure water that does not contain impurities is used in the manufacture of pharmaceuticals and cosmetics, the cleaning of electronic parts and precision equipment, and the like. This type of pure water is generally produced by treating feed water such as ground water and tap water with a reverse osmosis membrane separator and purifying the obtained permeate. The reverse osmosis membrane separation device includes a reverse osmosis membrane module, and can separate supply water into permeate and concentrated water. In the following description, the reverse osmosis membrane module is also referred to as “RO membrane module”, and the reverse osmosis membrane is also referred to as “RO membrane”.

  Here, in order to remove fouling substances and the like adhering to the membrane surface of the RO membrane module on the primary side of the RO membrane module, the permeate is transferred from the secondary side to the primary side of the membrane of the RO membrane module. There has been proposed a technique of generating an osmotic action and then adding a chemical such as acid or alkali to the primary side of the membrane of the RO membrane module (for example, see Patent Document 1).

Japanese Patent Laying-Open No. 2015-16404

  There are a plurality of types of fouling substances attached to the primary membrane surface of the RO membrane of the RO membrane module. Therefore, when the RO membrane module is cleaned using the technique described in Patent Document 1, simply generating a forward osmosis action and adding a drug increases the cleaning time and increases the amount of drug added. there is a possibility. Therefore, with regard to the cleaning of the RO membrane module, it is desired to optimize the cleaning time and the amount of the drug added to shorten the cleaning time and reduce the amount of the drug. In particular, in recent years, it is known that biofilms (biological substances) adhere to the membrane surface of the RO membrane module and cause biofouling.

  It is an object of the present invention to provide a method for cleaning a reverse osmosis membrane module that can reduce the cleaning time of the reverse osmosis membrane module and reduce the amount of drug added when a biological substance adheres to the membrane surface.

  The present invention provides a reverse osmosis membrane module cleaning method performed when the reverse osmosis membrane module has a tendency to biocontamination in a water treatment system including a reverse osmosis membrane module that separates supplied water into permeated water and concentrated water. A permeation of water from the secondary side to the primary side of the membrane of the reverse osmosis membrane module after the cleaning auxiliary agent addition step of adding a cleaning auxiliary agent to the reverse osmosis membrane module and the cleaning auxiliary agent addition step. And a osmotic pressure adjusting step of adjusting the osmotic pressure of the reverse osmosis membrane module so as to cause movement of the reverse osmosis membrane module.

  In addition, the washing auxiliary agent adding step includes a concentrated water circulation line for circulating the concentrated water separated by the reverse osmosis membrane module to the upstream side of the reverse osmosis membrane module or the reverse osmosis membrane module by sucking supply water. It is preferable to add a cleaning auxiliary agent to the upstream side of the pressurizing pump that discharges toward the surface.

  Moreover, after the said osmotic pressure adjustment process, the 1st flushing process which performs the 1st flushing operation | movement which replaces the water in the system of a water treatment system, and the film | membrane primary of the said reverse osmosis membrane module after the said 1st flushing process And a second flushing step for performing a second flushing operation for cleaning the side.

  ADVANTAGE OF THE INVENTION According to this invention, when a biological substance adheres to a membrane surface, while being able to shorten the washing | cleaning time of a reverse osmosis membrane module, the washing | cleaning method of a reverse osmosis membrane module which can reduce the addition amount of a chemical | medical agent can be provided.

1 is an overall configuration diagram of a water treatment system according to an embodiment. It is a figure which shows an example of the determination result of the contamination state determined by contamination conditions. It is a flowchart which shows the whole flow of the washing | cleaning method of the water treatment system which concerns on this embodiment. It is a flowchart which shows the process of determining a contamination state by a washing course determination process. It is a flowchart which shows the cleaning control in a biological contamination tendency cleaning course. It is a figure explaining a mode that the adhesion thing adhering to the film | membrane of RO membrane module is peeled in the washing | cleaning control performed in a biocontamination tendency washing | cleaning course. It is a flowchart which shows the cleaning control in a scale contamination tendency cleaning course or an organic matter clogging cleaning course. It is a figure explaining a mode that the deposit | attachment adhering to the film | membrane of RO membrane module is peeled in the washing | cleaning control performed in a scale contamination tendency washing | cleaning course or an organic substance clogging washing | cleaning course.

  A water treatment system according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of a water treatment system 1 according to an embodiment. FIG. 2 is a diagram illustrating an example of the determination result of the contamination state determined by the contamination condition.

  As shown in FIG. 1, the water treatment system 1 according to this embodiment includes a pressurizing pump 2, a pressurizing side inverter 3, an RO membrane module 5 as a reverse osmosis membrane module, an osmotic pressure adjusting unit, and a cleaning auxiliary agent. A chemical addition device 4 as an addition unit, a safety valve 31, a permeate water valve 32, a concentrated water circulation valve 33, a proportional control drain valve 34, and a control unit 20 are provided.

In addition, the water treatment system 1 includes a first pressure sensor P1, a second pressure sensor P2, a third pressure sensor P3, a first electrical conductivity sensor EC1, a second electrical conductivity sensor EC2, and a water temperature sensor TE. And a first flow rate sensor FM1 and a second flow rate sensor FM2.
The control unit 20 includes a pressurization side inverter 3, a permeate water valve 32, a concentrated water circulation valve 33, a proportional control drain valve 34, a chemical addition device 4, a first pressure sensor P1, a second pressure sensor P2, a third pressure sensor P3, The first electrical conductivity sensor EC1, the second electrical conductivity sensor EC2, the water temperature sensor TE, the first flow rate sensor FM1, and the second flow rate sensor FM2 are electrically connected. Note that illustration of electrical connection lines between the control unit 20 and the controlled device is omitted.

  The water treatment system 1 also includes a supply water line L1, a permeate water line L2, a concentrated water line L3, a concentrated water circulation line L4, a drainage line L5, and a permeate return 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 path, and a pipeline.

  The supply water line L1 is a line for supplying the supply water W1 to the RO membrane module 5. 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 L1 is connected to the primary inlet port 511 (primary inlet side) of the RO membrane module 5. In the supply water line L1, from the upstream side toward the downstream side, the drug addition device 4, the pressurizing pump 2, the first pressure sensor P1, the first electrical conductivity sensor EC1, and the RO membrane module 5 are provided in this order. ing.

  The pressurizing pump 2 is a device that sucks in the supply water W <b> 1 flowing through the supply water line L <b> 1 and pumps (discharges) it toward the RO membrane module 5. The pressurizing pump 2 is supplied with driving power whose frequency is converted from the pressurizing side inverter 3. The pressurizing pump 2 is driven at a rotational speed corresponding to the frequency (hereinafter also referred to as “driving frequency”) of the driving power supplied (input).

  The pressurizing side inverter 3 is an electric circuit (or a device having the circuit) that supplies driving power having a frequency converted to the pressurizing pump 2. A command signal is input from the control unit 20 to the pressure side inverter 3. The pressurizing side inverter 3 outputs driving power having a driving frequency corresponding to the command signal (current value signal or voltage value signal) input by the control unit 20 to the pressurizing pump 2.

  The first pressure sensor P <b> 1 is a device that detects the discharge pressure (operating pressure) of the pressurizing pump 2. The first pressure sensor P <b> 1 is disposed in the vicinity of the discharge side of the pressurizing pump 2. The vicinity of the discharge side of the pressurizing pump 2 means a position where a pressure that can be regarded as the discharge pressure of the pressurizing pump 2 can be detected. The pressure of the supply water W1 detected by the first pressure sensor P1 (hereinafter also referred to as “detected pressure value”) is transmitted to the control unit 20 as a detection signal.

  The drug addition device 4 is a device that adds an osmotic pressure adjusting agent (drug) and a cleaning auxiliary agent (drug) to one or more of the supply water line L1, the concentrated water line L3, and the concentrated water circulation line L4. . In this embodiment, the chemical | medical agent addition apparatus 4 adds an osmotic pressure regulator and a washing | cleaning adjuvant to the supply water W1 which distribute | circulates the supply water line L1 in the upstream of the pressurization pump 2 in the supply water line L1. In detail, the chemical addition device 4 is configured so that the osmotic pressure adjusting agent (chemical) and the cleaning auxiliary agent (chemical) are supplied in the supply water line L1 between the connecting portion J2 of the concentrated water circulation line L4 (described later) and the pressure pump 2. Add.

  The chemical addition device 4 increases the concentration of the supply water W1 on the primary side of the membrane of the RO membrane module 5 by adding an osmotic pressure adjusting agent to the supply water W1 on the primary side of the membrane of the RO membrane module 5, The osmotic pressure of the supply water W1 on the primary side of the membrane of the RO membrane module 5 is adjusted so that the permeated water W2 moves from the secondary side to the primary side of the membrane of the RO membrane module 5.

  In the present embodiment, the primary side of the membrane of the RO membrane module 5 means the upstream side of the RO membrane module 5 when reverse osmosis occurs in the RO membrane module 5. If it occurs, it will be downstream of the RO membrane module 5. Further, the secondary side of the membrane of the RO membrane module 5 means the downstream side of the RO membrane module 5 when reverse osmosis occurs in the membrane of the RO membrane module 5, and when forward osmosis occurs in the RO membrane module 5 Is upstream of the RO membrane module 5.

  Examples of the osmotic pressure adjusting agent added to the supply water W1 by the chemical addition device 4 include salts such as sodium chloride, alkalis such as sodium hydroxide and potassium hydroxide, organic acids (eg, oxalic acid, citric acid) or Examples include acids such as inorganic acids (eg, hydrochloric acid, sulfuric acid, nitric acid). In addition, you may add a dispersing agent, a disinfectant, etc. mainly on salt, an alkali, an acid, etc.

  The chemical addition device 4 adds a cleaning aid to the supply water W1 that flows through the primary side of the membrane of the RO membrane module 5 in the supply water line L1, thereby preventing fouling (blocking) of the membrane surface of the RO membrane module 5. Promote resolution. As cleaning aids, mainly fouling elimination promoters that promote the elimination of fouling (clogging) of the membrane surface of the RO membrane module 5 and bactericides that sterilize the membrane surface of the RO membrane module 5 are used. . The fouling is a phenomenon in which the pollutant contained in the supply water W1 is deposited on the surface of the membrane of the RO membrane module 5 or in the pores. Fouling includes, for example, those caused by biological contamination (biofouling), those caused by scale (eg, calcium scale, silica scale, iron scale, etc.), and organic contamination. There are things. When the pollutant concentration in the supply water W1 increases, fouling is likely to occur. When fouling occurs, the pores of the membrane are blocked, so that the permeation flux (described later) in the RO membrane module 5 decreases, or the inter-module differential pressure (described later) in the RO membrane module 5 increases.

  The drug addition device 4 sterilizes the membrane surface of the RO membrane module 5 in order to promote the elimination of biological contamination in the RO membrane module 5 by adding a cleaning aid to the primary side of the membrane of the RO membrane module 5. The removal of the scale attached to the RO membrane module 5 can be promoted, and the elimination of the organic matter clogging in the RO membrane module 5 can be promoted. The concentration and contact time of the cleaning aid added by the chemical addition device 4 are appropriately adjusted according to the degree of fouling on the membrane surface of the RO membrane module 5.

As the cleaning auxiliary agent added to the concentrated water W3 from the chemical addition device 4, for example, the following chemicals are used according to the type of fouling substance.
When the RO membrane module 5 is prone to biological contamination, a bactericidal agent such as bound chlorine, stabilized chlorine or bromine, or an alkali such as sodium hydroxide or potassium hydroxide is used as a cleaning aid.
When the RO membrane module 5 tends to be contaminated with scale, acids such as organic acids (eg, oxalic acid, citric acid) or inorganic acids (eg, hydrochloric acid, sulfuric acid, nitric acid), chelating agents, and scale dispersion are used as cleaning aids. Agents are used.
When the RO membrane module 5 is clogged with an organic substance, an alkali such as sodium hydroxide or potassium hydroxide, a surfactant, or the like is used as a cleaning aid.

  The first electrical conductivity sensor EC1 is a device that detects the electrical conductivity of the supply water W1 on the primary side of the membrane of the RO membrane module 5. The electrical conductivity of the supply water W1 detected by the first electrical conductivity sensor EC1 is transmitted to the control unit 20 as a detection signal. The electrical conductivity of the supply water W1 detected by the first electrical conductivity sensor EC1 is converted into an osmotic pressure in the control unit 20 based on a conversion formula, a conversion table, and the like.

  The RO membrane module 5 is a facility that performs membrane separation processing of the supply water W1 discharged from the pressurizing pump 2 into permeate water W2 from which dissolved salts have been removed and concentrated water W3 from which dissolved salts have been concentrated. The RO membrane module 5 includes a single or a plurality of RO membrane elements (not shown). The RO membrane module 5 membrane-separates the supply water W1 with these RO membrane elements to produce permeated water W2 and concentrated water W3. The RO membrane is a membrane capable of filtering a molecular weight of about several tens. The RO membrane includes a nanofiltration membrane (NF membrane). The nanofiltration membrane is a liquid separation membrane that can prevent permeation of particles and polymers (substances having a maximum molecular weight of about several hundreds) smaller than about 2 nm. The nanofiltration membrane is sometimes referred to as a loose RO membrane.

  The permeated water line L2 is a line for sending the permeated water W2 separated by the RO membrane module 5. The upstream end of the permeate line L2 is connected to the secondary port 520 (secondary outlet side) of the RO membrane module 5. The downstream end of the permeate line L2 is connected to a demand destination device (not shown), a treated water tank (not shown), and the like. In the permeated water line L2, a second pressure sensor P2, a water temperature sensor TE, a first flow rate sensor FM1, a second electric conductivity sensor EC2, a connecting portion J3, and a permeated water valve 32 are sequentially arranged from the upstream side to the downstream side. Is provided.

  The second pressure sensor P2 is a device that detects the pressure of the permeate W2 on the secondary side of the membrane of the RO membrane module 5. The pressure of the permeated water W2 detected by the second pressure sensor P2 (hereinafter also referred to as “detected pressure value”) is transmitted to the control unit 20 as a detection signal.

  The water temperature sensor TE is a device that detects the temperature of the permeated water W2. The temperature of the permeated water W2 detected by the water temperature sensor TE (hereinafter also referred to as “detected water temperature value”) is transmitted to the control unit 20 as a detection signal.

  In the present embodiment, the water temperature sensor TE is arranged on the downstream side of the RO membrane module 5 so that the water temperature sensor TE detects the temperature of the permeated water W2. However, the present invention is not limited to this. The water temperature sensor TE may be arranged on the upstream side of the RO membrane module 5 so that the water temperature sensor TE detects the temperature of the supply water W1. This is because the temperature of water can be regarded as substantially the same water temperature value on the upstream side and the downstream side of the RO membrane module 5.

  The 1st flow sensor FM1 is an apparatus which detects the flow volume of the permeated water W2 which distribute | circulates the permeated water line L2. The flow rate of the permeated water W2 detected by the first flow rate sensor FM1 (hereinafter also referred to as “detected flow rate value”) is transmitted to the control unit 20 as a pulse signal.

  The second electrical conductivity sensor EC2 is a device that detects the electrical conductivity of the permeated water W2 flowing through the permeated water line L2. The electrical conductivity of the permeated water W2 detected by the second electrical conductivity sensor EC2 is transmitted to the control unit 20 as a detection signal.

  The concentrated water line L3 is a line for sending the concentrated water W3 separated by the RO membrane module 5. The upstream end of the concentrated water line L3 is connected to the primary outlet port 512 (primary outlet side) of the RO membrane module 5. Further, the downstream side of the concentrated water line L3 is connected to the concentrated water circulation line L4 and the drainage line L5 at the connection portion J1. A third pressure sensor P3 is provided in the concentrated water line L3.

  The third pressure sensor P <b> 3 is a device that detects the pressure of the concentrated water W <b> 3 discharged from the primary side outlet port 512 of the RO membrane module 5. The pressure of the concentrated water W3 detected by the third pressure sensor P3 (hereinafter also referred to as “detected pressure value”) is transmitted to the control unit 20 as a detection signal.

  The concentrated water circulation line L4 returns a part W31 of the concentrated water W3 separated by the RO membrane module 5 and flowing through the concentrated water line L3 to the upstream side of the RO membrane module 5 and the pressure pump 2 in the supply water line L1. It is a line to do. The concentrated water circulation line L4 circulates the concentrated water W3 separated by the RO membrane module 5 upstream of the RO membrane module 5. The upstream end of the concentrated water circulation line L4 is connected to the concentrated water line L3 at the connection portion J1. The downstream end of the concentrated water circulation line L4 is connected to the upstream side of the pressurizing pump 2 in the supply water line L1 at the connection portion J2. A concentrated water circulation valve 33 is provided in the concentrated water circulation line L4.

  The concentrated water circulation valve 33 is a valve that opens and closes the concentrated water circulation line L4. The concentrated water circulation valve 33 is controlled to be in an open state when the permeated water W2 is produced by the RO membrane module 5. In the cleaning process, the concentrated water circulation valve 33 is controlled to be closed when the first flushing operation is performed, and is controlled to be opened when the second flushing operation is performed.

  The drainage line L5 is a line for discharging the remaining portion W32 of the concentrated water W3 separated by the RO membrane module 5 and flowing through the concentrated water line L3 to the outside of the apparatus (outside the system). The drain line L5 is provided with a proportional control drain valve 34 and a second flow rate sensor FM2.

  The proportional control drain valve 34 is a valve that adjusts the drainage flow rate of the remaining portion W32 of the concentrated water W3 discharged from the drainage line L5 to the outside of the apparatus. The valve opening degree of the proportional control drain valve 34 is controlled by a drive signal transmitted from the control unit 20. By sending a current value signal (for example, 4 to 20 mA) from the control unit 20 to the proportional control drain valve 34 to control the valve opening, the drainage flow rate of the remaining portion W32 of the concentrated water W3 can be adjusted.

  The second flow rate sensor FM2 is a device that detects the flow rate of the remaining portion W32 of the concentrated water W3 flowing through the drain line L5. The second flow sensor FM2 is disposed downstream of the proportional control drain valve 34 in the drain line L5. The flow rate (hereinafter also referred to as “detected flow rate value”) of the remaining portion W32 of the concentrated water W3 detected by the second flow rate sensor FM2 is transmitted to the control unit 20 as a pulse signal.

  In the first flushing operation (described later) and the second flushing operation (described later), the permeate return line L6 is used to transmit the permeate W2 sent to the permeate line L2 upstream of the pressurizing pump 2 in the supply water line L1. It is a line to be returned to. The upstream end of the permeate return line L6 is connected to the permeate line L2 at the connection J3. The connecting portion J3 is disposed between the secondary port 520 of the RO membrane module 5 and the permeated water valve 32. Further, the downstream end of the permeate return line L6 is connected to the supply water line L1 at the connection J4. The connecting portion J4 is disposed on the upstream side of the pressurizing pump 2. A safety valve 31 is provided in the permeate return line L6.

  In the first flushing operation (described later) and the second flushing operation (described later), the safety valve 31 is opened when the in-pipe pressure of the permeated water line L2 becomes equal to or higher than the set pressure, and the permeated water W2 is passed through the permeated water W2. This valve is circulated through the return line L6. That is, the safety valve 31 returns the permeate W2 that is equal to or higher than the set pressure to the supply water line L1 via the permeate return line L6, so that excessive back pressure is applied to the secondary side of the membrane of the RO membrane module 5. Prevent it from occurring.

The control unit 20 is configured by a microprocessor (not shown) including a CPU and a memory. The control unit 20 controls the water treatment system 1.
The control unit 20 controls the pressurizing side inverter 3 (pressurizing pump 2), the permeated water valve 32, the concentrated water circulation valve 33, and the proportional control drain valve 34 so as to execute the manufacturing process and the cleaning process.

[Manufacturing process]
First, the manufacturing process will be described. The manufacturing process is a process of manufacturing the permeated water W2 in the water treatment system 1. The control unit 20 executes the water amount control of the permeated water W2 and the recovery rate control of the permeated water W2 as a manufacturing process.
Hereinafter, the water amount control of the permeated water W2 and the recovery rate control of the permeated water W2 will be described.

<Water volume control of permeated water W2>
The control unit 20 can select and execute, for example, flow rate feedback water amount control, pressure feedback water amount control, or temperature feedforward water amount control as the water amount control of the permeated water W2. The outline of each water quantity control is as follows.

(Flow rate feedback water volume control)
The control unit 20 calculates a drive frequency for driving the pressurizing pump 2 using the detected flow rate value of the first flow rate sensor FM1 as a feedback value so that the flow rate of the permeated water W2 becomes a preset target flow rate value. To do. Then, the control unit 20 outputs a command signal (current value signal or voltage value signal) corresponding to the calculated value of the drive frequency to the pressurizing side inverter 3 (hereinafter also referred to as “flow rate feedback water amount control”). For example, a speed type digital PID algorithm can be used for calculation of the drive frequency in the main water amount control.

(Pressure feedback water volume control)
The control unit 20 uses the detected pressure value of the pressurizing pump 2 (detected pressure value of the first pressure sensor P1) as a feedback value so that the flow rate of the permeated water W2 becomes a preset target flow rate value. 2 drive frequency is calculated. Then, the control unit 20 outputs a command signal (current value signal or voltage value signal) corresponding to the calculated value of the drive frequency to the pressurizing side inverter 3 (hereinafter also referred to as “pressure feedback water amount control”). For example, a speed type digital PID algorithm can be used for calculation of the drive frequency in the main water amount control.

(Temperature feedforward water volume control)
The control unit 20 calculates the drive frequency of the pressurizing pump 2 using the detected temperature value of the water temperature sensor TE as a feedforward value so that the flow rate of the permeated water W2 becomes a preset target flow rate value. Then, the control unit 20 outputs a command signal (current value signal or voltage value signal) corresponding to the calculated value of the drive frequency to the pressurizing side inverter 3 (hereinafter also referred to as “temperature feedforward water amount control”).

<Recovery rate control of permeate W2>
The recovery rate of the permeated water W2 is the ratio of the flow rate of the permeated water W2 to the flow rate of the supplied water W1 supplied to the RO membrane module 5 (the flow rate of the permeated water W2 / the flow rate of the supplied water W1).
The control unit 20 can select and execute, for example, temperature feedforward recovery rate control, water quality feedforward, or water quality feedback recovery rate control as the recovery rate control of the permeated water W2. The outline of each recovery rate control is as follows.

(Temperature feedforward recovery rate control)
The control unit 20 calculates the allowable concentration rate of silica in the concentrated water W3 based on the silica concentration determined from the silica concentration of the supply water W1 acquired in advance and the detected temperature value of the water temperature sensor TE. Then, the control unit 20 calculates the drainage flow rate from the calculated value of the permissible concentration factor and the target flow rate value of the permeated water W2, and the actual drainage amount of the concentrated water W3 (the detected flow rate value of the second flow rate sensor FM2) is the drainage flow rate. The valve opening degree of the proportional control drain valve 34 is controlled so as to be a calculated value (target drain flow rate) (hereinafter also referred to as “temperature feedforward recovery rate control”).

(Water quality feedforward recovery rate control)
The control unit 20 calculates an allowable concentration rate of calcium carbonate in the concentrated water W3 based on the solubility of calcium carbonate acquired in advance and the measured hardness value of the hardness sensor. Then, the control unit 20 calculates the drainage flow rate from the calculated value of the permissible concentration factor and the target flow rate value of the permeated water W2, and the actual drainage amount of the concentrated water W3 (the detected flow rate value of the second flow rate sensor FM2) is the drainage flow rate. The valve opening degree of the proportional control drain valve 34 is controlled so as to be a calculated value (target drainage flow rate) (hereinafter also referred to as “water quality feedforward recovery rate control”).

(Water quality feedback recovery rate control)
The control unit 20 directly controls the valve opening degree of the proportional control drain valve 34 so that the measured electrical conductivity value of the second electrical conductivity sensor EC2 becomes a preset target electrical conductivity (hereinafter, “ Water quality feedback recovery rate control ”). For example, a speed type digital PID algorithm can be used to determine the valve opening in this control.

<Control example of water amount control and recovery rate control of permeate W2>
In the water amount control and recovery rate control of the permeated water W2, a pattern that is executed by combining “flow rate feedback water amount control” and “temperature feed forward recovery rate control”, “pressure feedback water amount control”, and “water quality feed forward”. Examples include a pattern executed by combining “recovery control” and a pattern executed by combining “temperature feedforward water amount control” and “water quality feedback recovery rate control”. It should be noted that this combination is not excluded.

[Washing process]
Next, the cleaning process will be described.
The cleaning process is a process of cleaning the RO membrane module 5. In the present embodiment, the cleaning process is executed intermittently. The cleaning process is executed once a day, for example.
As illustrated in FIG. 1, the control unit 20 includes a cleaning course determination unit 21 and a cleaning control unit 22. The cleaning course determination unit 21 is a process of determining a cleaning course before executing the cleaning process. The cleaning control unit 22 executes the cleaning process based on the cleaning course determined by the determination process. In the present embodiment, the cleaning control unit 22 executes, for example, the osmotic pressure adjustment step and the cleaning auxiliary agent processing step based on the cleaning course determined by the cleaning course determination unit 21, and then performs the first flushing operation. The first flushing step to be performed is performed, and then the second flushing step to perform the second flushing operation is performed.

<Washing course judgment process>
The cleaning course determination unit 21 determines the cleaning course of the RO membrane module 5 based on the permeation flux of the RO membrane module 5 and the inter-module differential pressure.

  The permeation flux of the RO membrane module 5 can be calculated based on the pressure of the primary side inlet port 511 and the pressure of the secondary side port 520 of the RO membrane module 5. Specifically, the permeation flux of the RO membrane module 5 can be calculated as follows.

The permeation flux of the RO membrane module 5 is an index showing the clogged state of the membrane of the RO membrane module 5, and is converted to standard temperature conditions with the amount of water permeating the unit membrane area per unit time per unit membrane differential pressure. It is a thing. If this is expressed by a mathematical expression, it can be expressed by the following expression (1) as described in JP-A-2008-55336.
Permeation flux [L / m ² · h · MPa] = Treatment water instantaneous flow rate / [{inlet operating pressure− (device differential pressure ÷ 2) −outlet back pressure−osmotic pressure} × temperature correction coefficient × membrane area] (1 )

In the present embodiment, for each value used in the calculation of the permeation flux, the “instant flow rate of treated water” is acquired from the detected flow rate value [L / h] measured by the first flow rate sensor FM1, and “inlet operating pressure” "Is obtained from the detected pressure value [MPa] measured by the first pressure sensor P1. The “apparatus differential pressure” is a set value [MPa], and the “outlet back pressure” is acquired from the detected pressure value [MPa] measured by the second pressure sensor P2. The “osmotic pressure” is a set value [MPa], the temperature correction coefficient is a function of the temperature detected by the water temperature sensor TE, and the “membrane area” is the set value [m ² ].

The inter-module differential pressure of the RO membrane module 5 is a differential pressure between the pressure at the primary side inlet port 511 (primary side inlet side) of the RO membrane module 5 and the pressure at the primary side outlet port 512 (primary side outlet side). The inter-module differential pressure of the RO membrane module 5 can be expressed by the following formula (2).
Inter-module differential pressure [MPa] = pressure at the primary side inlet port 511 of the RO membrane module 5−pressure at the primary side outlet port 512 of the RO membrane module 5 (2)
In the present embodiment, “the pressure of the primary outlet port 512 of the RO membrane module 5” is obtained from the detected pressure value [MPa] measured by the third pressure sensor P3, and “the primary inlet of the RO membrane module 5” The “pressure of the port 511” is acquired from the detected pressure value [MPa] measured by the first pressure sensor P1.

  The cleaning course determination unit 21 detects temporal changes in the permeation flux of the RO membrane module 5 and the inter-module differential pressure based on the permeation flux of the RO membrane module 5 and the inter-module differential pressure, and the RO membrane module 5 By determining the contamination state, the cleaning course of the RO membrane module 5 is determined. For example, in the case of the following first contamination condition to fourth contamination condition, the cleaning course determination unit 21 determines the contamination state of the RO membrane module 5 as shown in FIG. 2, and performs a cleaning course according to the contamination state. judge.

(Contamination state determined by the first contamination condition)
For example, as illustrated in FIG. 2, the cleaning course determination unit 21 reduces the permeation flux of the RO membrane module 5 and increases the inter-module differential pressure of the RO membrane module 5 (in the case of the first contamination condition). ), It is determined that the RO membrane module 5 has a “biological contamination tendency” or a “biological contamination tendency and a scale contamination tendency”.

(Contamination status determined by the second contamination condition)
For example, as illustrated in FIG. 2, the cleaning course determination unit 21 reduces the permeation flux of the RO membrane module 5 and does not increase the inter-module differential pressure of the RO membrane module 5 (in the case of the second contamination condition). ), It is determined that the RO membrane module 5 is “scale contamination tendency” or “organic matter clogging” is present.

(Contamination state determined by the third contamination condition)
For example, as illustrated in FIG. 2, the cleaning course determination unit 21 does not decrease the permeation flux of the RO membrane module 5 and increases the inter-module differential pressure of the RO membrane module 5 (third contamination condition). In the case of (1), the RO membrane module 5 is determined to have a “biological contamination tendency”.

(Contamination status determined by the 4th contamination condition)
For example, as illustrated in FIG. 2, the cleaning course determination unit 21 does not decrease the permeation flux of the RO membrane module 5 and does not increase the inter-module differential pressure of the RO membrane module 5 (fourth contamination condition). In the case of (1), the RO membrane module 5 is determined to be in the “normal state”.

<Cleaning control>
The cleaning control unit 22 performs an osmotic pressure adjustment step and a cleaning auxiliary agent processing step of adding a cleaning auxiliary agent so as to execute the cleaning operation of the RO membrane module 5 based on the cleaning course determined by the cleaning course determination unit 21. The chemical addition device 4, the pressurizing pump 2, the permeated water valve 32, and the proportional control drain valve 34 are controlled so as to execute the first flushing step and the second flushing step. When executing the osmotic pressure adjusting step or the cleaning auxiliary agent processing step, the cleaning control unit 22 is based on the cleaning course determined by the cleaning course determining unit 21 (the osmotic pressure adjusting unit, the cleaning auxiliary). The agent addition part) is controlled. Below, an osmotic pressure adjustment process, a washing | cleaning adjuvant processing process, a 1st flushing process, and a 2nd flushing process are demonstrated.

(Osmotic pressure adjustment process)
In the osmotic pressure adjustment step, the osmotic pressure of the supply water W1 on the primary side of the membrane of the RO membrane module 5 is adjusted so that the permeated water W2 moves from the secondary side of the membrane of the RO membrane module 5 to the primary side. It is a process to do. As described above, in the present embodiment, the primary side of the membrane of the RO membrane module 5 means the upstream side of the RO membrane module 5 when reverse osmosis occurs in the RO membrane module 5, and the RO membrane module 5 When forward osmosis occurs at, the downstream side of the RO membrane module 5. In addition, the secondary side of the membrane of the RO membrane module 5 means the downstream side of the RO membrane module 5 when reverse osmosis occurs in the RO membrane module 5, and when forward osmosis occurs in the RO membrane module 5, It is upstream of the RO membrane module 5.

As the osmotic pressure adjusting step, for example, a method of adding an osmotic pressure adjusting agent to the supply water W1 on the primary side of the membrane of the RO membrane module 5, or a recovery rate in the RO membrane module 5 (permeated water W2 with respect to the flow rate of the supply water W1). There is a method of increasing the flow rate ratio).
In the osmotic pressure adjusting step, the osmotic pressure of the supply water W1 on the primary side of the membrane of the RO membrane module 5 is adjusted to be 0.1 MPa or more, for example. The osmotic pressure of the supply water W1 on the primary side of the membrane of the RO membrane module 5 is preferably 0.1 MPa or more, more preferably 0.2 MPa to 0.5 MPa, than the osmotic pressure of the permeated water W2 on the secondary side of the membrane. It is preferable to adjust so that it may become high. By setting the difference in the osmotic pressure between the primary side and the secondary side of the membrane of the RO membrane module 5 to be 0.1 MPa or more, the permeated water W2 on the secondary side of the membrane of the RO membrane module 5 is surely provided on the primary side of the membrane. Will be moved to. The osmotic pressure adjusted by the osmotic pressure adjusting step is not limited to 0.1 MPa or more. Even if the osmotic pressure is less than 0.1 MPa, the permeated water W2 from the secondary side of the membrane of the RO membrane module 5 to the primary side. It is only necessary that the action of moving is generated. Further, in the osmotic pressure adjusting step, after the process of adjusting the osmotic pressure (addition of drug and adjustment of recovery rate) is performed, the supply water W1 is brought into contact with the membrane surface of the RO membrane module 5 for a predetermined time, thereby causing normal osmosis. Cleaning by action is performed.

  The osmotic pressure of the supply water W1 on the primary side of the membrane of the RO membrane module 5 is the osmotic pressure based on the electrical conductivity of the supply water W1 on the primary side of the membrane of the RO membrane module 5 detected by the first electrical conductivity sensor EC1. Calculated by conversion. For example, when the osmotic pressure adjusting agent added to the supply water W1 is sodium chloride, the control unit 20 stores and stores a conversion formula, a conversion table, and the like for the osmotic pressure with respect to the electrical conductivity in sodium chloride. Based on the conversion formula or conversion table, the electrical conductivity of the supply water W1 detected by the first electrical conductivity sensor EC1 is converted into an osmotic pressure. Since the osmotic pressure of the permeated water W2 on the secondary side of the membrane of the RO membrane module 5 can be regarded as constant, if the osmotic pressure of the supply water W1 on the primary side of the membrane of the RO membrane module 5 is measured, RO The outline of the osmotic pressure difference between the osmotic pressure on the primary side and the osmotic pressure on the secondary side of the membrane of the membrane module 5 can be obtained.

In the method of adding an osmotic pressure adjusting agent to the supply water W1 on the primary side of the membrane of the RO membrane module 5 in the osmotic pressure adjustment step, the osmotic pressure is added to the supply water W1 on the primary side of the membrane of the RO membrane module 5 by the drug addition device 4. By adding the regulator, the concentration of the supply water W1 on the primary side of the membrane of the RO membrane module 5 is increased, and the movement of the permeated water W2 from the secondary side to the primary side of the membrane of the RO membrane module 5 The osmotic pressure of the supply water W1 on the primary side of the membrane of the RO membrane module 5 is adjusted so as to occur.
By increasing the concentration of the supply water W1 on the primary side of the membrane of the RO membrane module 5, from the secondary side of the membrane of the RO membrane module 5 where the concentration of water is low, the membrane of the RO membrane module 5 where the concentration of water is high A forward osmosis action in which the permeated water W2 moves toward the primary side can be generated.

  In the method of increasing the recovery rate (the ratio of the flow rate of the permeated water W2 to the flow rate of the supply water W1) in the RO membrane module 5 in the osmotic pressure adjustment step, the RO membrane module 5 is increased by increasing the recovery rate in the RO membrane module 5. The osmotic pressure of the supply water W1 on the primary side of the membrane of the RO membrane module 5 is adjusted so that the permeated water W2 moves from the secondary side to the primary side of the membrane. The method of increasing the recovery rate is executed by the above-described recovery rate control of the permeated water W2.

  In a state where the recovery rate in the RO membrane module 5 is increased, the concentration of the concentrated water W3 separated by the RO membrane module 5 is increased. For example, when the recovery rate of the RO membrane module 5 is increased from 50% to 80%, the concentration of the concentrated water W3 is about 2 to 5 times. Thereby, by increasing the concentration of the concentrated water W3 on the primary side of the membrane of the RO membrane module 5, the RO membrane module 5 having a high water concentration from the secondary side of the membrane of the RO membrane module 5 having a low water concentration. The normal osmosis effect | action which the permeated water W2 moves toward the primary side of this film | membrane can be produced.

  Note that, when the recovery rate in the RO membrane module 5 is increased over a long period of time, calcium scale or silica scale is generated on the membrane surface of the RO membrane module 5. The time is set such that calcium scale and silica scale are not generated on the membrane surface of the membrane module 5.

(Cleaning adjuvant treatment process)
The cleaning auxiliary agent treatment step is a step in which the cleaning auxiliary agent is added to the supply water W1 on the primary side of the membrane of the RO membrane module 5 by the chemical addition device 4. In the present embodiment, the drug addition device 4 adds a cleaning aid on the upstream side of the pressurizing pump 2. As the cleaning aid, those that act as a fouling elimination promoter that promotes elimination of fouling (blocking) of the membrane surface of the RO membrane module 5 are mainly used. In the cleaning auxiliary agent treatment step, after the cleaning auxiliary agent is added to the supply water W1 on the primary side of the membrane of the RO membrane module 5, the cleaning auxiliary agent is brought into contact with the membrane surface of the RO membrane module 5 for a predetermined time, The deposits are easily peeled off from the membrane surface of the RO membrane module 5.

(First flushing process)
The first flushing step is a step of replacing water in the water treatment system 1. In the first flushing step, the feed water W1 is supplied to the RO membrane module 5 by the pressurizing pump 2 with the permeate water valve 32 and the concentrated water circulation valve 33 closed and the proportional control drain valve 34 opened. . Thereby, the water in the system of the water treatment system 1 can be replaced | exchanged by replacing the water which distribute | circulates the supply water line L1, the concentrated water line L3, and the drainage line L5. When the water pressure of the supply water W1 is sufficiently high, the first flushing step can be performed by stopping the pressurizing pump 2 and pumping it with the water pressure of the supply water W1.

(Second flushing process)
In the second flushing process, after the first flushing process is executed, the permeated water valve 32 is kept closed, the concentrated water circulation valve 33 is opened, and the proportional control drain valve 34 is opened. 2 is a step of performing the second flushing operation for cleaning the primary side of the membrane of the RO membrane module 5 by supplying the supply water to the RO membrane module 5 by 2. By performing the second flushing operation, the primary side of the membrane of the RO membrane module 5 is washed with the supply water W1.

  Here, the permeated water W2 separated by the RO membrane module 5 by performing the second flushing operation with the permeated water valve 32 in the closed state, the RO membrane module via the permeated water return line L6. 5 is returned to the primary side of the membrane. Thereby, since the permeated water W2 on the secondary side of the membrane of the RO membrane module 5 is returned to the primary side of the membrane of the RO membrane module 5, when the second flushing step is executed, the RO membrane module 5 It can suppress that the pressure of the secondary side of a film | membrane becomes high. Moreover, the concentrated water W3 separated by the RO membrane module 5 by performing the second flushing operation is returned to the primary side of the membrane of the RO membrane module 5 via the concentrated water circulation line L4.

  The second flushing process is executed after the osmotic pressure adjusting process and the cleaning auxiliary agent adding process. Therefore, the second flushing step is executed after a forward osmosis action in which the permeated water W2 moves from the secondary side to the primary side of the membrane of the RO membrane module 5 occurs. The second flushing step is performed after a fouling elimination accelerator (cleaning aid) or a bactericidal agent (cleaning aid) is applied to the membrane surface of the RO membrane module 5. As a result, on the primary side of the membrane of the RO membrane module 5, the shearing force of water (the force to peel off deposits attached to the membrane surface of the RO membrane module 5) is increased and adhered to the membrane surface of the RO membrane module 5. Deposits can be effectively peeled off.

  In the second flushing operation in the second flushing step, the amount of the permeated water W2 returned to the primary side of the membrane of the RO membrane module 5 via the permeate return line L6 is preferably as small as possible. The flow rate of the permeated water W2 returned to the primary side of the membrane of the RO membrane module 5 via the permeate return line L6 is the same as the pressure on the primary side of the membrane of the RO membrane module 5 and the secondary side of the membrane of the RO membrane module 5 The pressurizing pump 2 (pressurizing side inverter 3) is controlled so that the flow rate becomes the minimum flow rate higher than the above pressure.

  For example, the control unit 20 calculates a driving frequency for driving the pressurizing pump 2 using the detected flow rate value of the first flow sensor FM1 as a feedback value, and controls the pressurizing pump 2 (pressurizing side inverter 3). be able to. Alternatively, the control unit 20 can control the pressurizing pump 2 (pressurizing side inverter 3) by calculating the driving frequency of the pressurizing pump 2 using the detected temperature value of the water temperature sensor TE as a feedforward value.

  When the second flushing operation is executed, most of the supply water W1 flows through the surface of the RO membrane without passing through the RO membrane, and is discharged from the drainage line L5 to the outside through the concentrated water line L3 as flushing washing drainage. Is done. By this second flushing operation, scales deposited on the surface of the RO membrane and deposited suspended substances are removed. The second flushing operation is executed for a predetermined time (for example, 120 seconds, 60 seconds).

[Overall operations of steady operation and cleaning operation in the water treatment system 1]
Next, operation | movement of the water treatment system 1 which concerns on this embodiment is demonstrated. First, the overall operations of the steady operation and the cleaning operation in the water treatment system 1 will be described. FIG. 3 is a flowchart showing an overall flow of the cleaning method of the water treatment system 1 according to the present embodiment.

  In step S11 shown in FIG. 3, the water treatment system 1 is operated by steady operation. In the steady operation, a manufacturing process for manufacturing the permeated water W2 by introducing the supply water W1 into the RO membrane module 5 is performed. In addition, the water treatment system 1 intermittently performs a cleaning operation for cleaning the RO membrane module 5 during execution of the steady operation. The intermittent cleaning operation for cleaning the RO membrane module 5 is executed once a day, for example.

  In step S <b> 12, the cleaning course determination unit 21 grasps the occurrence state (contamination state) of fouling on the membrane surface of the RO membrane module 5 and determines the cleaning course. The process of the cleaning course determination process by the cleaning course determination unit 21 is executed once a day, for example, corresponding to the cleaning operation that is executed intermittently. Details of the cleaning course determination step executed by the cleaning course determination unit 21 will be described later.

In step S <b> 13, the cleaning control unit 22 executes a cleaning process for cleaning the RO membrane module 5 based on the cleaning course determined by the cleaning course determination unit 21. Details of the cleaning process will be described later.
After the process of step S13 is complete | finished, it returns to step S11 and a steady operation is performed (return).

[Operation of cleaning course judgment process]
Next, the operation of the cleaning course determination process will be described. FIG. 4 is a flowchart showing a process of determining the contamination state by the cleaning course determination process.
In step S21 shown in FIG. 4, the cleaning course determination unit 21 detects the detected pressure value of the primary inlet port 511 of the RO membrane module 5 measured by the first pressure sensor P1, and the RO membrane measured by the second pressure sensor P2. Based on the detected pressure value on the secondary side of the membrane of the module 5 and the detected flow rate value of the permeated water W2 measured by the first flow rate sensor FM1, the permeation flux is calculated. The cleaning course determination unit 21 monitors temporal changes in the permeation flux.

  In step S22, the cleaning course determination unit 21 detects the detected pressure value of the primary inlet port 511 of the RO membrane module 5 measured by the first pressure sensor P1 and the RO membrane module 5 measured by the third pressure sensor P3. Based on the detected pressure value of the primary side outlet port 512, the inter-module differential pressure is calculated. The cleaning course determination unit 21 monitors temporal changes in the inter-module differential pressure.

  In step S23, the cleaning course determination unit 21 determines whether or not the permeation flux of the RO membrane module 5 has decreased. If the permeation flux of the RO membrane module 5 has decreased (YES), the process proceeds to step S24. When the permeation flux of the RO membrane module 5 does not decrease (NO), the process proceeds to step S27.

In step S24, the cleaning course determination unit 21 determines whether or not the inter-module differential pressure of the RO membrane module 5 has increased.
When the inter-module differential pressure of the RO membrane module 5 has increased (YES) (in the case of the first contamination condition in FIG. 2), the cleaning course determination unit 21 determines that “biological contamination” for the RO membrane module 5 in step S25. It is determined that it is “tendency” or “biological contamination tendency and scale contamination tendency”. In this case, the “biological contamination tendency” or the “biological contamination tendency and the scale contamination tendency” is assumed, and the cleaning of the “genuine contamination tendency cleaning course” or the “scale contamination tendency course” is executed. Thereby, the process ends.
In addition, when the inter-module differential pressure of the RO membrane module 5 does not increase (NO) (in the case of the second contamination condition in FIG. 2), the cleaning course determination unit 21 determines “ It is determined that there is a “scale contamination tendency” or “organic matter clogging”. In this case, “scale contamination tendency” or “organic matter clogging” is assumed, and cleaning of “scale contamination tendency cleaning course” or “organic matter clogging cleaning course” is executed. Thereby, the process ends.

In step S27 in the case of NO in step S23, the control unit 20 determines whether or not the inter-module differential pressure of the RO membrane module 5 has increased.
When the inter-module differential pressure of the RO membrane module 5 has increased (YES) (in the case of the third contamination condition in FIG. 2), in step S28, the cleaning course determination unit 21 determines “biological contamination” for the RO membrane module 5. It is determined that it is “tendency”. In this case, the “biological contamination tendency” is assumed, and the cleaning of the “genuine contamination tendency cleaning course” is executed. Thereby, the process ends.
In addition, when the inter-module differential pressure of the RO membrane module 5 does not increase (NO) (in the case of the fourth contamination condition in FIG. 2), the cleaning course determination unit 21 determines “ It is determined that the state is “normal”. In this case, the “normal state” is assumed and the “normal cleaning course” cleaning is executed. Thereby, the process ends.

[Operation of cleaning control in cleaning course determined by cleaning course determination process]
Next, the cleaning control operation in the cleaning course determined by the cleaning course determination unit 21 will be described.
In the present embodiment, cleaning control operations executed in the “biological contamination tendency cleaning course”, “scale contamination tendency cleaning course”, “organic matter clogging cleaning course”, and “normal cleaning course” will be described. In this embodiment, when it is determined by the cleaning course determination unit 21 that a plurality of contamination states (fouling) are included in combination, first, the cleaning control corresponding to only one contamination state is performed. The action is executed. Thereafter, when the cleaning course determination unit 21 determines again, when it is determined that another contamination state is included, a cleaning control operation corresponding to the other contamination state is executed. In cases where complex contamination (fouling) is included, use of mixed drugs is possible if the effect of promoting mixed fouling can be improved by using mixed drugs. May be.

<Cleaning control operation in the “Biological Contamination Cleaning Course”>
A cleaning method of the “biological contamination tendency cleaning course” executed when the RO membrane module 5 is “biological contamination tendency” will be described. FIG. 5 is a flowchart showing cleaning control in the biological contamination tendency cleaning course. FIG. 6 is a diagram for explaining how the deposit D attached to the membrane 5a of the RO membrane module 5 is peeled in the cleaning control executed in the biological contamination tendency cleaning course.

  Before executing the cleaning control operation of the “biological contamination tendency cleaning course”, as shown in FIG. 6A, in the RO membrane module 5, the feed water W1 is introduced into the RO membrane module 5 and the permeated water W2 is supplied. The permeated water manufacturing process to manufacture is performed. A deposit D (for example, a biofilm) is attached to the membrane 5a of the RO membrane module 5.

  In step S31 shown in FIG. 5, the cleaning control unit 22 stops the pressurizing pump 2 and closes the permeated water valve 32 in order to execute the cleaning control operation of the “biological contamination tendency cleaning course”. Then, as shown in FIG.6 (b), a washing | cleaning adjuvant addition process is performed. In the cleaning auxiliary agent adding step, the cleaning auxiliary agent A is added to the RO membrane module 5 by adding the cleaning auxiliary agent A to the supply water W1 on the primary side of the membrane of the RO membrane module 5 by the chemical addition device 4. When the cleaning auxiliary agent addition process is executed in the biological contamination tendency cleaning course, as the cleaning auxiliary agent A, for example, a bactericidal agent such as bonded chlorine, stabilized chlorine or bromine, or an alkali such as sodium hydroxide or potassium hydroxide. Is used. Then, the cleaning auxiliary agent is brought into contact for a predetermined time so as to act on the membrane surface of the RO membrane module 5. Thereby, the membrane surface of the RO membrane module 5 is sterilized by the action of the cleaning aid on the membrane surface of the RO membrane module 5.

  In step S32, the control part 20 performs an osmotic pressure adjustment process. In the osmotic pressure adjustment step, the controller 20 supplies the supply water W1 on the primary side of the membrane of the RO membrane module 5 so that the permeated water W2 moves from the secondary side of the membrane of the RO membrane module 5 toward the primary side. Adjust the osmotic pressure. As a method for adjusting the osmotic pressure of the supply water W1 on the primary side of the membrane of the RO membrane module 5, for example, a method of adding an osmotic pressure adjusting agent to the supply water W1 by the chemical addition device 4, or a recovery in the RO membrane module 5 There are ways to increase the rate.

  In the present embodiment, in the osmotic pressure adjustment step, for example, with the permeated water valve 32 in the closed state, as shown in FIG. 6C, the chemical is added to the supply water W1 supplied to the RO membrane module 5 The osmotic pressure adjusting agent B is added by the device 4. Examples of the osmotic pressure regulator B include salts such as sodium chloride, alkalis such as sodium hydroxide and potassium hydroxide, organic acids (eg, oxalic acid, citric acid), and inorganic acids (eg, hydrochloric acid, sulfuric acid, nitric acid). Is used.

  Then, the osmotic pressure adjusting agent is brought into contact for a predetermined time so as to act on the membrane surface of the RO membrane module 5. As a result, forward osmosis acts on the RO membrane module 5. The osmotic pressure of the supply water W1 on the primary side of the membrane of the RO membrane module 5 is adjusted so that the permeate W2 moves from the secondary side of the membrane of the RO membrane module 5 to the primary side by the forward osmosis action. The The predetermined value of the osmotic pressure of the supply water W1 on the primary side of the membrane of the RO membrane module 5 is, for example, 0.1 MPa. Thereby, the deposit D1 is likely to float on the surface of the membrane from within the pores of the membrane of the RO membrane module 5. For example, the predetermined value of the osmotic pressure of the supply water W1 can be converted from the electric conductivity of the supply water W1 detected by the first electric conductivity sensor EC1.

  The cleaning control operation executed in the biological contamination tendency cleaning course as described above is executed in the order of executing the osmotic pressure adjusting step in step S32 after executing the cleaning auxiliary agent adding step in step S31. Thereby, when the RO membrane module 5 is in a contaminated state with a biological contamination tendency, the forward osmosis action can be generated after the progress of the biological contamination is stopped by sterilizing the membrane surface of the RO membrane module 5. Therefore, the RO membrane module 5 can be efficiently and appropriately cleaned. That is, by sterilizing the membrane surface of the RO membrane module 5 to stop the progress of biological contamination and optimizing the cleaning time, the drug amount, etc., the cleaning time can be shortened and the drug amount can be reduced. If the washing auxiliary agent addition step is executed after the osmotic pressure adjustment step is executed, the membrane surface of the RO membrane module 5 is not stopped by sterilizing the membrane surface of the RO membrane module 5 without stopping the progress of biological contamination. The osmotic pressure of the supply water W1 on the primary side will be adjusted. Therefore, in the cleaning method of the RO membrane module 5, the present invention in which the osmotic pressure adjusting step is executed after the cleaning auxiliary agent adding step is executed is more than the case where the cleaning auxiliary agent adding step is executed after the osmotic pressure adjusting step is executed. Is effective.

  In step S33, the cleaning control unit 22 performs the first flushing process as shown in FIG. The first flushing step is a step of replacing water in the water treatment system 1. In the first flushing process, the permeate water valve 32 and the concentrated water circulation valve 33 are closed, and the proportional control drain valve 34 is opened, and the pressure pump 2 is driven to supply to the RO membrane module 5. Supply water. Thereby, the water in the system of the water treatment system 1 can be replaced | exchanged by replacing the water which distribute | circulates the supply water line L1, the concentrated water line L3, and the drainage line L5. Therefore, the deposit D1 (biofilm) peeled off from the membrane surface of the RO membrane module 5 in the osmotic pressure adjusting step can be washed away.

  In step S34, the cleaning control unit 22 performs the second flushing process as shown in FIG. In the second flushing step, after the first flushing step is performed, the concentrated water circulation valve 33 is opened while maintaining the closed state of the permeate water valve 32 and the open state of the proportional control drain valve 34. This is a step of performing a flushing operation for cleaning the primary side of the membrane of the RO membrane module 5 by driving the pump 2.

  By performing the second flushing operation of the second flushing step, the supply water W1 cleans the primary side of the membrane of the RO membrane module 5. Thereby, the deposit D2 (biofilm) remaining on the membrane surface of the RO membrane module 5 can be easily peeled off. In the second flushing step, since the osmotic pressure adjustment step is performed in the previous step of the second flushing step, it is easy to peel off the deposit D2 remaining on the membrane surface of the RO membrane module 5. It has become.

Here, since the permeated water valve 32 is closed, when the second flushing process is executed, the permeated water W2 separated by the RO membrane module 5 passes through the membrane of the RO membrane module 5 via the permeated water return line L6. Returned to the primary side.
Further, since the concentrated water circulation valve 33 is opened, the concentrated water W3 separated by the RO membrane module 5 is returned to the primary side of the membrane of the RO membrane module 5 via the concentrated water circulation line L4.
The second flushing operation in the second flushing step is executed for a predetermined time (for example, 120 seconds, 60 seconds).
And the process of this flowchart is complete | finished.

<Cleaning control operation in the “scale contamination cleaning course” or “organic clogging cleaning course”>
A cleaning method for the “scale contamination tendency cleaning course” or “organic matter clogging cleaning course” executed when the RO membrane module 5 is “scale contamination tendency” will be described. FIG. 7 is a flowchart showing the cleaning control in the scale contamination tendency cleaning course or the organic clogging cleaning course. FIG. 8 is a diagram for explaining how the deposit E attached to the membrane 5a of the RO membrane module 5 is peeled off in the cleaning control executed in the scale contamination tendency cleaning course or the organic clogging cleaning course.
In the “scale contamination tendency cleaning course” and the “organic clogging cleaning course”, the type of the cleaning auxiliary agent added in the cleaning auxiliary agent addition process differs depending on the cleaning course determined by the cleaning course determination unit 21.

  Before executing the cleaning control operation of the “scale contamination tendency cleaning course” or the “organic matter clogging cleaning course”, the supply water W1 is supplied to the RO membrane module 5 in the RO membrane module 5, as shown in FIG. A permeated water manufacturing process for introducing the permeated water W2 by introduction is performed. The deposit E is attached to the membrane 5a of the RO membrane module 5.

  In step S41 shown in FIG. 7, the cleaning control unit 22 stops the pressurizing pump 2 to execute the cleaning control operation of the “scale contamination tendency cleaning course” or the “organic matter clogging cleaning course”, and the permeated water valve In the state where 32 is in the closed state, as shown in FIG. 8B, the osmotic pressure adjusting step and the cleaning auxiliary agent adding step are executed at the same time.

  Specifically, in the osmotic pressure adjusting step, the cleaning control unit 22 supplies the osmotic pressure adjusting agent and the cleaning auxiliary to the supply water W1 supplied to the RO membrane module 5 with the permeated water valve 32 closed. The medicine addition device 4 is controlled so that the medicine is added at the same time. As the drug added from the drug adding device 4, a mixed drug in which an osmotic pressure adjusting agent (drug) and a cleaning auxiliary agent (drug) are mixed may be added. You may comprise so that it may add to. In the present embodiment, as shown in FIG. 8B, a mixed drug C in which an osmotic pressure adjusting agent and a cleaning auxiliary agent are mixed is added by the drug adding device 4.

  In the osmotic pressure adjusting step, the cleaning controller 22 makes the osmotic pressure adjusting agent contact for a predetermined time so as to act on the membrane surface of the RO membrane module 5. As a result, forward osmosis acts on the RO membrane module 5. As a result, as shown in FIG. 8B, the deposit E <b> 1 tends to float on the surface of the membrane from within the pores of the membrane of the RO membrane module 5. The forward osmosis is the same as the operation of step S32 shown in FIG. 5 in the case of the above-described biological contamination tendency cleaning course.

  Further, the cleaning control unit 22 makes the cleaning auxiliary agent contact for a predetermined time so that the cleaning auxiliary agent acts on the membrane surface of the RO membrane module 5 in the cleaning auxiliary agent adding step. As a result, the cleaning aid acts on the membrane surface of the RO membrane module 5 so that the deposit E1 is easily peeled off from the membrane surface of the RO membrane module 5.

  Here, the cleaning auxiliary agent used in the cleaning auxiliary agent addition process differs depending on the cleaning course determined by the cleaning course determination unit 21. When performing the cleaning auxiliary agent addition process in the “scale contamination tendency cleaning course”, as the cleaning auxiliary agent, for example, an organic acid (eg, oxalic acid, citric acid) or an inorganic acid (eg, hydrochloric acid, sulfuric acid, nitric acid) Acids, chelating agents, scale dispersants, etc. are used. Further, when the cleaning auxiliary agent addition process is executed in the “organic matter clogging cleaning course”, for example, an alkali such as sodium hydroxide or potassium hydroxide, a surfactant, or the like is used as the cleaning auxiliary agent.

  In step S42, as in the operation of step S33 in the flowchart of FIG. 5 in the above-described “biological contamination tendency cleaning course” cleaning control operation, the cleaning control unit 22 performs the first flushing as shown in FIG. Execute the process. Thereby, the water in the system of the water treatment system 1 can be replaced | exchanged by replacing the water which distribute | circulates the supply water line L1, the concentrated water line L3, and the drainage line L5. Therefore, the deposit E1 peeled off from the membrane 5a of the RO membrane module 5 in the osmotic pressure adjusting step can be washed away.

In step S43, as in the operation of step S33 in the flowchart of FIG. 5 in the above-described “biological contamination tendency cleaning course” cleaning control operation, the cleaning control unit 22 performs the second flushing as shown in FIG. Execute the process. Thereby, the deposit E2 remaining on the membrane 5a of the RO membrane module 5 can be easily peeled off.
And the process of this flowchart is complete | finished.

  In this embodiment, in step S41, the osmotic pressure adjusting step and the cleaning auxiliary agent adding step are controlled to be executed at the same time. However, the present invention is not limited to this, and the osmotic pressure adjusting step and the cleaning auxiliary agent adding step are controlled. The timing may be shifted. In the present embodiment, the method of adding the osmotic pressure adjusting agent to the supply water W1 by the chemical addition device 4 is used in the osmotic pressure adjusting step. As described in the cleaning control operation of the “cleaning course”, a method of increasing the recovery rate in the RO membrane module 5 may be used.

<Cleaning control operation in normal cleaning course>
The cleaning control executed in the “normal cleaning course” will be described.
In the cleaning control operation of the “normal cleaning course”, for example, in the cleaning control operation of the “scale contamination tendency cleaning course” or the “organic matter clogging cleaning course” described above (the operation shown in the flowchart of FIG. 7), The cleaning control operation except for is executed. Specifically, for example, in the “normal cleaning course”, an osmotic pressure adjusting step, a first flushing step, and a second flushing step are executed. In the “normal cleaning course”, the osmotic pressure adjusting step, the cleaning auxiliary agent adding step, the first flushing step, the cleaning operation of the scale contamination tendency cleaning course or the organic clogging cleaning course shown in the flowchart of FIG. 7 described above, A second flushing step may be performed.

According to the cleaning method of the RO membrane module 5 according to the present embodiment described above, for example, the following effects are exhibited.
In the water treatment system 1 including the reverse osmosis membrane module 5 that separates the supply water W1 into the permeated water W2 and the concentrated water W3, the RO membrane module 5 cleaning method according to the present embodiment is biologically contaminated with respect to the reverse osmosis membrane module 5. A method of cleaning the reverse osmosis membrane module 5 performed in the case of a tendency, wherein the reverse osmosis membrane module is added to the reverse osmosis membrane module 5 after the cleaning auxiliary agent addition step and the cleaning auxiliary agent addition step. And an osmotic pressure adjusting step of adjusting the osmotic pressure of the reverse osmosis membrane module 5 so that the permeated water W2 moves from the secondary side to the primary side of the membrane.

  Therefore, when the RO membrane module 5 tends to be biologically contaminated, the forward osmotic action can be generated after the biological contamination is stopped by sterilizing the membrane surface of the RO membrane module 5. Therefore, the RO membrane module 5 can be efficiently and appropriately cleaned. That is, by optimizing the cleaning time and the amount of drug while promoting the peeling of the biofilm from the membrane surface of the RO membrane module 5, the cleaning time can be shortened and the amount of drug can be reduced.

  Moreover, in this embodiment, the chemical | medical agent addition apparatus 4 adds a cleaning adjuvant in the upstream of the pressurization pump 2. FIG. Therefore, since the cleaning aid is pumped through the pressurizing pump 2, the mixing property between the cleaning aid and the osmotic pressure adjusting agent can be improved.

  Moreover, in this embodiment, after the osmotic pressure adjustment process, the first flushing process for executing the first flushing for replacing the water in the system of the water treatment system 1, and the RO membrane module 5 after the first flushing process. And a second flushing step for performing a second flushing operation for cleaning the primary side of the membrane. Thereby, the deposits peeled off from the membrane surface of the RO membrane module 5 in the first flushing step (first flushing operation) can be washed away, and the osmotic pressure is adjusted in the second flushing step (second flushing operation). Accordingly, the deposits remaining on the membrane surface of the RO membrane module 5 can be easily peeled off. Therefore, with respect to the cleaning operation of the RO membrane module 5, the cleaning time can be shortened and the amount of drug can be reduced.

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 the said embodiment, although the chemical | medical agent addition apparatus 4 was comprised so that a washing | cleaning adjuvant and an osmotic pressure regulator might be added in the upstream of the pressurization pump 2, it is not limited to this. For example, the chemical addition device 4 may be configured to add a cleaning aid or an osmotic pressure regulator between the pressurizing pump 2 and the RO membrane module 5 in the supply water line L1 or to the concentrated water circulation line L4. Good. When the chemical addition device 4 is configured to add a cleaning aid or osmotic pressure adjusting agent to the concentrated water circulation line L4, the cleaning auxiliary agent or osmotic pressure adjusting agent added to the concentrated water circulation line L4 is concentrated. Since it is supplied to the upstream side of the pressurization pump 2 in the supply water line L1 through the water circulation line L4 and is pumped through the pressurization pump 2, the mixing property of the medicine can be improved.

  In the above embodiment, the osmotic pressure adjusting agent and the cleaning auxiliary agent are configured to be added by one drug adding device 4, but the present invention is not limited to this. You may comprise so that it may add to.

  Moreover, in the said embodiment, after determining whether the permeation | transmission flux in RO membrane module 5 fell, the washing course determination part 21 determines whether the inter-module differential pressure in RO membrane module 5 increased. Thus, the cleaning course of the RO membrane module 5 was determined. However, the present invention is not limited to this, and conversely, after determining whether the inter-module differential pressure in the RO membrane module 5 has increased, the RO membrane module The cleaning course of the RO membrane module 5 may be determined by determining whether or not the permeation flux in 5 has decreased.

1 Water treatment system 5 RO membrane module (reverse osmosis membrane module)
W1 Supply water W2 Permeated water W3 Concentrated water

Claims (3)

In a water treatment system comprising a reverse osmosis membrane module that separates supply water into permeate and concentrated water, the reverse osmosis membrane module cleaning method is performed when the reverse osmosis membrane module is prone to biological contamination,
A cleaning auxiliary agent adding step of adding a cleaning auxiliary agent to the reverse osmosis membrane module;
An osmotic pressure adjusting step of adjusting the osmotic pressure of the reverse osmosis membrane module so that permeate moves from the secondary side to the primary side of the membrane of the reverse osmosis membrane module after the washing auxiliary agent adding step. And a method for cleaning a reverse osmosis membrane module.   The cleaning auxiliary agent adding step is a concentrated water circulation line that circulates the concentrated water separated by the reverse osmosis membrane module upstream of the reverse osmosis membrane module, or sucks supply water toward the reverse osmosis membrane module. The cleaning method of a reverse osmosis membrane module according to claim 1, wherein a cleaning auxiliary agent is added upstream of the pressure pump to be discharged. After the osmotic pressure adjustment step, a first flushing step for performing a first flushing operation for replacing water in the system of the water treatment system,
The cleaning of the reverse osmosis membrane module according to claim 1, further comprising a second flushing step of performing a second flushing operation for cleaning a primary side of the membrane of the reverse osmosis membrane module after the first flushing step. Method.

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