JP5942468B2 - Water treatment system - Google Patents

Description

  The present invention relates to a water treatment system including a plurality of membrane separation devices.

  In the semiconductor manufacturing process, the cleaning of electronic parts, the cleaning of medical equipment, etc., high-purity pure water containing no impurities is used. This type of pure water is generally produced by treating supply water such as ground water or tap water with a membrane separator. The membrane separation apparatus includes at least one reverse osmosis membrane module (hereinafter, 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”).

  Conventionally, in order to cope with the case where one unit of membrane separation device cannot cover the maximum water consumption at a demand point, a water producing device in which a plurality of membrane separation devices are connected in parallel has been proposed (for example, Patent Document 1).

JP 2000-189967 A

  In general, in a water treatment system using a membrane separator, a flushing operation for cleaning the primary side surface of the RO membrane module is periodically performed in order to maintain the water permeability of the RO membrane module. The flushing operation is performed by increasing the drainage flow rate from the primary side of the RO membrane module. During the flushing operation, the purity of the permeated water decreases due to a decrease in effective pressure, and therefore the production of permeated water is stopped. Therefore, during this time, the permeate cannot be used at the demand point. Even in the fresh water generator described in Patent Document 1 described above, the flushing operation of each membrane separation device is executed simultaneously, so that the permeated water cannot be used in demand areas.

  Therefore, an object of the present invention is to provide a water treatment system capable of avoiding as much as possible that permeated water cannot be used at a demand point during a flushing operation.

The present invention includes a plurality of membrane separation devices including a reverse osmosis membrane module that separates supply water into permeate and concentrated water, a storage tank that stores permeate sent from the membrane separation device, and the storage The water level detection means for detecting the water level of the tank and the water level detection means of the water level detection means when the time for performing the flushing operation for cleaning the primary side of the reverse osmosis membrane module is reached in the plurality of membrane separation devices. A control unit that determines the number of the membrane separation devices to be subjected to the flushing operation, and executes the flushing operation for the determined number of the membrane separation devices , the control unit, The time for performing the flushing operation is reached, and (i) the detected water level of the water level detecting means supplies at least the permeated water consumed at the demand point during the flushing operation. When the water level is not less than the reference water level, the flushing operation is executed for all the membrane separation devices. (Ii) When the detected water level of the water level detecting means is lower than the reference water level, the flushing operation is performed. Te, on water treatment system Ru is smaller than the number in the case the number of membrane separation device to be the flushing operation than the reference level.

  In addition, when the detected water level of the water level detecting unit rises after starting the execution of the flushing operation when the detected water level of the water level detecting unit is less than the reference water level, the control unit increases the It is preferable to increase the number of the membrane separators to be subjected to the flushing operation based on the detected water level.

  Moreover, it is preferable that the said control part starts execution of the said flushing operation | movement based on the preset priority order about the said membrane separation apparatus used as the object of the said flushing operation.

  In addition, when the integrated replenishment time or the integrated replenishment amount of permeated water replenished to the storage tank has reached a set value after the previous flushing operation has been completed for all the membrane separation devices, It is preferable to determine that it is time to execute the flushing operation.

  The membrane separation device is driven at a rotational speed corresponding to the input driving frequency, and sucks the supply water and discharges it toward the reverse osmosis membrane module, and the input current value signal An inverter that outputs a corresponding driving frequency to the pressurizing pump; and a flow rate detecting means that detects a flow rate of permeate and outputs a detected flow rate value corresponding to the flow rate, and the control unit detects the flow rate. Calculating the drive frequency of the pressurizing pump so that the detected flow rate value output from the means becomes a preset target flow rate, and outputting a current value signal corresponding to the calculated value of the drive frequency to the inverter Is preferred.

  Further, the membrane separation device includes a supply water line for supplying supply water to the reverse osmosis membrane module, a permeate line for sending permeate to the storage tank, and the reverse osmosis membrane module and the storage tank. A permeate valve provided in the permeate line, a permeate return line for returning permeate sent to the permeate line to the upstream side of the pressurizing pump in the supply water line, and the permeate A pressure relief valve provided in a return line, and the control unit preferably controls the permeate valve so that permeate does not flow through the permeate line when performing the flushing operation. .

  ADVANTAGE OF THE INVENTION According to this invention, it can provide the water treatment system which can avoid as much as possible that permeated water becomes unusable in a demand location during a flushing driving | operation.

1 is an overall configuration diagram of a water treatment system 1 according to a first embodiment. It is explanatory drawing which shows the relationship between the water level of the treated water tank 2 in 1st Embodiment, and fresh water generation operation / flushing operation number. It is a block diagram of the membrane separator U1. It is a flowchart which shows the process sequence in the case of controlling fresh water generation operation and flushing operation | movement of the membrane separators U1-U4 in the control part (system control part) 100. FIG. It is a flowchart which shows the process sequence in the case of determining the membrane separator used as the object of flushing operation in the control part (system control part) 100. FIG. 4 is a flowchart showing a processing procedure when a control unit (system control unit) 100 specifies a membrane separation apparatus to be subjected to a flushing operation. 5 is a flowchart illustrating a processing procedure when a flushing operation process is executed in a control unit (system control unit) 100. It is a flowchart which shows the process sequence in the case of changing the number of the membrane separators which perform fresh water operation / flushing operation in the control part (system control part) 100. FIG. It is a flowchart which shows the process sequence in the case of performing flow volume feedback water amount control in the control part (unit control part) 100. FIG. 5 is a flowchart showing a processing procedure when temperature feedforward recovery rate control is executed in a control unit (unit control unit) 100. It is a block diagram of the membrane separator U11 which concerns on 2nd Embodiment.

(First embodiment)
First, the water treatment system 1 which concerns on 1st Embodiment of this invention is demonstrated, referring drawings. FIG. 1 is an overall configuration diagram of a water treatment system 1 according to the first embodiment. FIG. 2 is an explanatory diagram showing the relationship between the water level of the treated water tank 2 and the number of fresh water generation / flushing operations in the first embodiment (hereinafter also referred to as “number determination data”). FIG. 3 is a configuration diagram of the membrane separation device U1.

  As shown in FIG. 1, a water treatment system 1 according to the first embodiment includes a plurality of membrane separation devices U1, U2, U3, U4, a treated water tank 2 as a storage tank, and a water level sensor as a water level detecting means. 3 and the control unit 100. In FIG. 1 (the same applies to FIGS. 3 and 11), the path of electrical connection is indicated by a broken line. One broken line indicates one or a plurality of routes.

  Moreover, the water treatment system 1 is provided with the supply water line L1, the permeate water line L2, and the water distribution line L7. 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 that supplies the supply water W1 to the membrane separation devices U1 to U4. 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 feed water line L1 branches toward the membrane separators U1 to U4 and is connected to the primary inlet ports of the membrane separators U1 to U4, respectively. During the fresh water generation operation and the flushing operation, the supply water W1 flowing through the supply water line L1 is distributed to the membrane separation devices U1 to U4.

  The membrane separation devices U1 to U4 each include an RO membrane module (described later). The membrane separators U1 to U4 each produce the permeated water W2 at the same rated flow rate. That is, when the maximum flow rate of the permeate W2 that can be supplied to the treated water tank 2 by the membrane separation devices U1 to U4 is 100%, the rated flow rate of each of the membrane separation devices U1 to U4 is 25% of the maximum flow rate. The membrane separation devices U1 to U4 are electrically connected to the control unit 100. The amount of permeated water W2 and the recovery rate in the membrane separation devices U1 to U4 are controlled by the control unit 100. In the following description, when any one of the membrane separation devices U1 to U4 is not specifically specified, the symbol is abbreviated as “membrane separation device”.

  The permeated water line L <b> 2 is a line for sending the permeated water W <b> 2 manufactured by the membrane separation devices U <b> 1 to U <b> 4 to the treated water tank 2. The upstream end of the permeate line L2 branches to the membrane separation devices U1 to U4, and is connected to the secondary port of each RO membrane module. The downstream end of the permeate line L <b> 2 is connected to the treated water tank 2.

  The treated water tank 2 is a tank that collectively stores the permeated water W2 produced by the membrane separation devices U1 to U4. The treated water tank 2 is connected to the downstream end of the permeate line L2. The permeated water W2 sent out from the secondary side ports of the membrane separation devices U1 to U4 is replenished to the treated water tank 2 via the permeated water line L2. Further, the treated water tank 2 is connected to a downstream demand point (not shown) via a water distribution line L7. The permeated water W2 stored in the treated water tank 2 is supplied to the demand point as treated water W4 through the water distribution line L7.

  As shown in FIG. 1, five levels of water levels (water level H, water level D3, water level D2, water level D1, and water level L) for determining the amount of stored water are set in the treated water tank 2.

  The water level H is a water level (hereinafter, also referred to as “reference water level value H”) corresponding to the amount of stored water that can supply the treated water W4 of the amount of water consumed at the demand point during the flushing operation. Therefore, if the amount of water stored in the treated water tank 2 is greater than or equal to the reference water level value H, treated water of the amount of water consumed at the demand point without replenishing the permeated water W2 from the membrane separation devices U1 to U4 during the flushing operation. W4 can be supplied. As described above, the flushing operation refers to cleaning the primary surface of the RO membrane module by increasing the drainage flow rate from the primary side of the RO membrane module (not shown).

  The water level D3 is a third intermediate water level that is lower than the water level H and higher than the water level D2. The water level D2 is a second intermediate water level that is lower than the water level D3 and higher than the water level D1. The water level D1 is a first intermediate water level that is lower than the water level D2 and higher than the water level L.

  The water level L is a limit water level at which the treated water W4 can be stably supplied to the demand point. As will be described later, when the amount of water stored in the treated water tank 2 becomes less than the water level L during the flushing operation, all the membrane separation devices U1 to U4 are operated at the rated flow rate. Thereby, the permeated water W2 is replenished to the treated water tank 2 at the maximum flow rate. The same is true when the amount of water stored in the treated water tank 2 is equal to or higher than the water level L and lower than the water level D1.

  The water level sensor 3 is a device that detects the water level of the permeated water W2 stored in the treated water tank 2. The water level sensor 3 is provided in the treated water tank 2. The water level sensor 3 is electrically connected to the control unit 100. The water level of the treated water tank 2 detected by the water level sensor 3 (hereinafter also referred to as “detected water level value”) is transmitted to the control unit 100 as a detection signal. The water level sensor 3 is a continuous level sensor, for example, a capacitance type sensor, a pressure type sensor, an ultrasonic type sensor or the like. FIG. 1 shows an example in which a pressure type sensor is provided on the outer wall surface near the bottom of the treated water tank 2 as the water level sensor 3.

The control unit 100 includes a microprocessor (not shown) including a CPU and a memory. The memory of the microprocessor stores various programs for controlling the water treatment system 1 in addition to data relating to the number determination (FIG. 2) and data relating to the priority order. The memory of the microprocessor, detecting the water level value W sent from each sensor, the detected temperature value T, data such as the detected flow value Q _p are stored. The CPU of the microprocessor executes processing according to a predetermined program read from the memory. The microprocessor incorporates an integrated timer unit (hereinafter also referred to as “ITU”) that manages timekeeping and the like.

  The control unit 100 of the present embodiment includes a function of a system control unit (described later) that controls the entire water treatment system 1, a function of a unit control unit (described later) that controls operations of the membrane separation devices U1 to U4, and Is provided.

  First, the case where the control part 100 controls the water treatment system 1 by the function of a system control part is demonstrated.

  The control unit (system control unit) 100 sets all the membrane separation devices U1 to U4 to the fresh water generation operation or the operation stop based on the detected water level value W of the water level sensor 3 during the fresh water generation operation.

  Specifically, the control unit (system control unit) 100 stops the operation of all the membrane separation devices U1 to U4 when the detected water level value W of the water level sensor 3 becomes equal to or higher than the reference water level value H during the fresh water generation operation. And Thereby, the flow rate of the permeated water W2 supplied to the treated water tank 2 is 0%. If the detected water level value W of the water level sensor 3 is equal to or higher than the reference water level value H, it can be considered that there is a storage amount in the treated water tank 2 that can sufficiently supply the treated water W4 of the amount of water consumed at the demand location. It is.

  In addition, when the detected water level value W of the water level sensor 3 is less than the water level L during the fresh water generation operation, the control unit (system control unit) 100 sets all the membrane separation devices U1 to U4 to the fresh water generation operation. Thereby, the flow rate of the permeated water W2 supplied to the treated water tank 2 is 100%. That is, when the detected water level value W of the water level sensor 3 is not less than the water level L and less than the water level H, the flow rate is always 100%.

  On the other hand, when it is time to execute the flushing operation, the control unit (system control unit) 100 determines the number of membrane separation devices to be subjected to the flushing operation based on the detected water level value W of the water level sensor 3. Then, the flushing operation is executed for the determined number of membrane separation apparatuses.

  Specifically, the control unit (system control unit) 100 reaches the time of executing the flushing operation, and when the detected water level value W of the water level sensor 3 is equal to or higher than the reference water level value H (W ≧ H), FIG. As shown in FIG. 4, the flushing operation is executed for all the membrane separation devices U1 to U4. In this case, since the fresh water generation operation of all the membrane separators U1 to U4 is stopped, the permeated water W2 has a flow rate of 0%.

  Further, the control unit (system control unit) 100 reaches the detected water level value W when the time for performing the flushing operation is reached and the detected water level value W of the water level sensor 3 is less than the reference water level value H (H> W). Based on this, the number of membrane separation devices to be subjected to the flushing operation is reduced from the number in the case of the reference water level value H or more.

  For example, as shown in FIG. 2, the control unit (system control unit) 100 performs flushing when the detected water level value W of the water level sensor 3 is less than the reference water level value H and is equal to or higher than the water level D3 (H> W ≧ D3). The number of membrane separation devices to be operated is set to three, which is smaller than the number of four when the reference water level is H or more. In this case, since only one membrane separator is operated for fresh water, the permeated water W2 has a flow rate of 25%.

  Further, as shown in FIG. 2, when the detected water level value W of the water level sensor 3 is less than the water level D3 and equal to or higher than the water level D2 (D3> W ≧ D2), the control unit (system control unit) 100 performs the flushing operation. The number of target membrane separation devices is set to two, which is less than the number of four when the reference water level is H or more. In this case, since the two membrane separation devices are operated for fresh water, the permeated water W2 has a flow rate of 50%.

  Further, as shown in FIG. 2, the control unit (system control unit) 100 performs the flushing operation when the detected water level value W of the water level sensor 3 is less than the water level D2 and is equal to or higher than the water level D1 (D2> W ≧ D1). The number of target membrane separation devices is set to one, which is smaller than the number of four in the case where the reference water level is H or more. In this case, since three membrane separation apparatuses are operated for fresh water, the permeated water W2 has a flow rate of 75%.

  Furthermore, as shown in FIG. 2, the control unit (system control unit) 100 detects the water level value W of the water level sensor 3 below the water level D1 and above the water level L (D1> W ≧ L). When the detected water level value W is less than the water level L (L <W), the number of membrane separation devices to be subjected to the flushing operation is set to zero. In this case, since all four membrane separation devices U1 to U4 are operated for fresh water, the permeated water W2 has a flow rate of 100%.

  In addition, when the detected water level value W of the water level sensor 3 is lower than the reference water level value H, the control unit (system control unit) 100 increases the detected water level value W of the water level sensor 3 after starting the flushing operation. Increases the number of membrane separation devices to be subjected to the flushing operation based on the detected water level value W that has risen. In the present embodiment, every time the water level of the treated water tank 2 rises by one stage, the number of membrane separation devices to be subjected to the flushing operation is increased by one.

  Here, “one stage” refers to the interval between the water levels shown in FIG. For example, when the water level of the treated water tank 2 rises from the water level D1 to the water level D2, the control unit (system control unit) 100 determines that the water level has increased by one stage. The control unit (system control unit) 100 determines that the water level has increased by two stages when the water level of the treated water tank 2 has increased from the water level D1 to the water level D3.

  For example, as shown in FIG. 2, when the detected water level value W of the water level sensor 3 is less than the water level D3 and is equal to or higher than the water level D2 (D3> W ≧ D2), the control unit (system control unit) 100 has two units. The flushing operation is started for the membrane separator. Thereafter, when the water level of the treated water tank 2 rises by one stage and the detected water level value W of the water level sensor 3 is less than the water level H and equal to or higher than the water level D3 (H> W ≧ D3), The number of membrane separators to be increased is increased by 1 to 3 units.

  In addition, when the control level (system control unit) 100 starts the flushing operation and then the detected water level value W of the water level sensor 3 decreases, the fresh water generation operation is performed one by one from the membrane separation device in which the flushing operation is completed. To migrate. This is because the permeated water W2 is replenished to the treated water tank 2 as much as possible when the demand point becomes highly operated during the flushing operation.

  In addition, the control unit (system control unit) 100 starts the flushing operation on the basis of a preset priority order for the membrane separation apparatus that is the target of the flushing operation.

  That is, the control unit (system control unit) 100 performs a fresh water generation operation with a membrane separation device having a high priority level in the fresh water generation operation when the time for performing the flushing operation is reached, and a membrane with a low priority level in the fresh water generation operation. Flush the separator. In addition, as will be described later, the priority order of the fresh water operation and the priority order of the flushing operation are opposite to each other. Therefore, a membrane separation apparatus having a high priority for fresh water operation has a low priority for flushing operation, and a membrane separator having a low priority for fresh water operation has a high priority for flushing operation.

  Specifically, in this embodiment, the priority of the fresh water generation operation is the membrane separation device U1> U2> U3> U4. Therefore, in the fresh water generation operation, the priority of the membrane separation device U1 is the highest, and the priority of the membrane separation device U4 is the lowest. On the other hand, in the present embodiment, the priority order of the flushing operation is the membrane separation device U4> U3> U2> U1. Therefore, in the flushing operation, the priority of the membrane separation device U4 is the highest, and the priority of the membrane separation device U1 is the lowest. Note that data relating to the priority order of the membrane separation devices U1 to U4 is stored in advance in a memory (not shown) of the microprocessor.

  For example, as shown in FIG. 2, when the detected water level value W of the water level sensor 3 is lower than the water level D3 and is equal to or higher than the water level D2 (D3> W ≧ D2), the control unit (system control unit) 100 performs the flushing operation. The low-priority membrane separation devices U1 and U2 are set as fresh water operation, and the high-priority membrane separation devices U3 and U4 are set as flushing operation.

  Further, the control unit (system control unit) 100 has reached the set replenishment time of the permeated water W2 replenished to the treated water tank 2 after the previous flushing operation has been completed for all the membrane separation devices U1 to U4. In this case, it is determined that it is time to execute the flushing operation.

Specifically, the control unit (system control unit) 100 measures the total replenishment time Tc of the permeated water W2 replenished to the treated water tank 2 after the previous flushing operation has been completed for all the membrane separation devices U1 to U4. Start. The accumulated replenishment time is counted by the ITU. Then, the control unit (system control unit) 100 determines that it is time to execute the flushing operation when the time _Tc of the accumulated replenishment time reaches the set value (time _Td ).

  Next, a case where the control unit 100 functions as a unit control unit will be described. First, the configuration of the membrane separation devices U1 to U4 to be controlled by the control unit (unit control unit) 100 will be described with reference to FIG. Here, the configuration will be described on behalf of the membrane separation device U1, but the other membrane separation devices U2 to U4 have the same configuration.

  As shown in FIG. 3, the membrane separation device U1 according to this embodiment includes a pressurizing pump 4, an inverter 5, a temperature sensor 6, an RO membrane module M1, a permeate valve 7, and a flow rate detecting means. A flow rate sensor 8, a safety valve 9 as a pressure relief valve, a concentrated water recirculation valve 10, and a first drain valve 11 to a third drain valve 13 are provided.

  The membrane separation device U1 includes a concentrated water line L3, a concentrated water discharge line L4, a concentrated water reflux line L5, and a permeate return line L6.

  In FIG. 3, the pressurizing pump 4 is a device that sucks the supply water W1 and discharges it toward the RO membrane module M1. The pressure pump 4 is electrically connected to an inverter 5 (described later). The driving power whose frequency is converted is input to the pressurizing pump 4 from the inverter 5. The pressurizing pump 4 is driven at a rotational speed corresponding to the frequency of the supplied driving power (hereinafter also referred to as “driving frequency”). The rotation speed of the pressurizing pump 4 is proportional to the drive frequency supplied from the inverter 5. That is, the rotation speed of the pressurizing pump 4 becomes slower as the drive frequency supplied from the inverter 5 becomes lower, and becomes faster as the drive frequency becomes higher.

  The inverter 5 is an electric circuit that supplies driving power whose frequency has been converted to the pressurizing pump 4. The inverter 5 is electrically connected to the control unit 100. A current value signal is input to the inverter 5 from the control unit (unit control unit) 100. The inverter 5 outputs driving power having a driving frequency corresponding to the current value signal input from the control unit (unit control unit) 100 to the pressurizing pump 4.

  The temperature sensor 6 is a device that detects the temperature of the supply water W1. The temperature sensor 6 is connected to the supply water line L1 at the connection portion J3. The connecting portion J3 is disposed between the supply source of the supply water W1 and the pressurizing pump 4. The temperature sensor 6 is electrically connected to the control unit 100. The temperature of the supply water W1 detected by the temperature sensor 6 (hereinafter also referred to as “detected temperature value”) is transmitted to the control unit 100 as a detection value signal.

  The RO membrane module M1 is a facility for subjecting the supply water W1 discharged from the pressurization pump 4 to membrane separation treatment into permeated water W2 from which dissolved salts have been removed and concentrated water W3 from which dissolved salts have been concentrated. The RO membrane module M1 includes a single or a plurality of RO membrane elements (not shown). The RO membrane module M1 membrane-separates the supply water W1 with these RO membrane elements to produce permeated water W2 and concentrated water W3.

The RO membrane module M1 in the present embodiment has an RO membrane (not shown) in which a negatively charged skin layer made of a crosslinked wholly aromatic polyamide is formed on the membrane surface. This RO membrane has a water permeability coefficient of 1.5 when a sodium chloride aqueous solution having a concentration of 500 mg / L, pH 7.0 and temperature of 25 ° C. is supplied as supply water W1 at an operation pressure of 0.7 MPa and a recovery rate of 15%. × 10 ⁻¹¹ m ³ · m ⁻² · s ⁻¹ · Pa ⁻¹ or more, and the salt removal rate is 99% or more.

  Here, the operating pressure is an average operating pressure defined by JIS K3802-1995 “Membrane Term”. The operating pressure refers to an average value of the primary side inlet pressure and the primary side outlet pressure of the RO membrane module M1.

Recovery and the percentage of the flow rate _{Q p} permeate W2 to the flow rate _{Q f} of feed water W1 supplied to the RO membrane module M1 _{(i.e., Q p / Q f × 100} ) refers to.

The salt removal rate is a value calculated from the concentration of a specific salt before and after permeating the RO membrane (here, the sodium chloride concentration), and is an index indicating the solute blocking performance of the RO membrane. The salt removal rate is obtained by (1−C _p / C _f ) × 100 from the concentration C _f of the supply water W1 supplied to the RO membrane module M1 and the concentration C _p of the permeated water W2.

  The RO membrane that satisfies the conditions of the water permeability coefficient and salt removal rate of this embodiment is commercially available as a reverse osmosis membrane element. As the reverse osmosis membrane element, for example, Toray Industries, Inc .: model name “TMG20-400”, Unjin Chemical, Inc .: model name “RE8040-BLF”, Nitto Denko Corporation: model name “ESPA1”, etc. may be used. it can.

  The permeated water valve 7 is a device that opens and closes the permeated water line L2. The permeated water valve 7 is disposed between the RO membrane module M1 and the treated water tank 2 (see FIG. 1) (between the connection portion J5 and the connection portion J4). The permeated water valve 7 is electrically connected to the control unit 100. The opening and closing of the valve body in the permeated water valve 7 is controlled by a drive signal from the control unit (unit control unit) 100. The permeated water valve 7 is controlled to be in an open state when the RO membrane module M1 is operated for fresh water. The permeate valve 7 is controlled to be closed when the RO membrane module M1 is flushed.

  The flow rate sensor 8 is a device that detects the flow rate of the permeated water W2 flowing through the permeated water line L2. The flow sensor 8 is connected to the permeated water line L2 at the connection portion J4. The connection part J4 is arrange | positioned between the permeated water valve 7 and the treated water tank 2 (refer FIG. 1). The flow sensor 8 is electrically connected to the control unit 100. The flow rate of the permeated water W2 detected by the flow rate sensor 8 (hereinafter also referred to as “detected flow rate value”) is transmitted to the control unit 100 as a detection value signal.

  The permeated water return line L6 is a line for returning the permeated water W2 sent from the RO membrane module M1 to the permeated water line L2 during the flushing operation to the upstream side of the pressurizing pump 4 in the supply water line L1. The upstream end of the permeate return line L6 is connected to the permeate line L2 at the connection J5. The connecting portion J5 is disposed between the secondary side port of the RO membrane module M1 and the permeated water valve 7. The downstream end of the permeate return line L6 is connected to the supply water line L1 at the connection J2. The connection part J2 is arrange | positioned between the supply source of the supply water W1, and the pressurization pump 4 (between the connection part J1 and the pressurization pump 4). A safety valve 9 is provided in the permeate return line L6.

  The safety valve 9 is a valve that automatically opens when the in-pipe pressure of the permeate water line L2 becomes equal to or higher than a preset pressure during the flushing operation, and causes the permeate water W2 to flow through the permeate return line L6. is there. That is, the safety valve 9 generates excessive back pressure on the secondary side of the RO membrane module M1 by returning the permeated water W2 that is equal to or higher than the preset pressure to the supply water line L1 via the permeate return line L6. To prevent it.

  Note that, when the RO membrane module M1 is operated for fresh water, the permeated water valve 7 is controlled to be in the open state, so that the pipe pressure of the permeated water line L2 is less than a preset pressure. In that case, since the safety valve 9 is closed, the permeated water W2 is sent to the treated water tank 2.

  The concentrated water line L3 is a line for sending concentrated water W3 from the RO membrane module M1. The upstream end of the concentrated water line L3 is connected to the primary outlet port of the RO membrane module M1. Further, the downstream side of the concentrated water line L3 branches into a concentrated water discharge line L4 and a concentrated water reflux line L5 at a branch portion J6.

  The concentrated water discharge line L4 is a line for discharging part or all of the concentrated water W3 flowing through the concentrated water line L3 to the outside of the apparatus. The downstream side of the concentrated water discharge line L4 branches to the first drainage line L11, the second drainage line L12, and the third drainage line L13 at the branch portions J7 and J8.

  A first drain valve 11 is provided in the first drain line L11. A second drain valve 12 is provided in the second drain line L12. A third drain valve 13 is provided in the third drain line L13. The 1st drainage valve 11-the 3rd drainage valve 13 are valves which adjust the drainage flow rate of the concentrated water W3 discharged | emitted out of the apparatus from the concentrated water discharge line L4.

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

  Each of the first drain valve 11 to the third drain valve 13 includes a constant flow valve mechanism (not shown). The constant flow valve mechanisms are set to different flow values in the first drain valve 11 to the third drain valve 13. For example, the drainage flow rate of the first drain valve 11 is set so that the recovery rate of the RO membrane module M1 is 80% in the open state. The drainage flow rate of the second drain valve 12 is set so that the recovery rate of the RO membrane module M1 is 75% in the open state. The drainage flow rate of the third drain valve 13 is set so that the recovery rate of the RO membrane module M1 is 70% in the open state.

  The drainage flow rate of the concentrated water W3 discharged from the concentrated water discharge line L4 can be adjusted in stages by selectively opening and closing the first drainage valve 11 to the third drainage valve 13. For example, only the second drain valve 12 is opened, and the first drain valve 11 and the third drain valve 13 are closed. In this case, the recovery rate of the RO membrane module M1 can be 75%. Further, the first drain valve 11 and the second drain valve 12 are opened, and only the third drain valve 13 is closed. In this case, the recovery rate of the RO membrane module M1 can be set to 70%. Therefore, in this embodiment, the drainage flow rate of the concentrated water W3 is 5% between the recovery rate of 50% and 80% by selectively opening and closing the first drainage valve 11 to the third drainage valve 13. It can be adjusted step by step.

  The first drain valve 11 to the third drain valve 13 are each electrically connected to the control unit 100. The opening and closing of the valve body in the first drain valve 11 to the third drain valve 13 is controlled by a drive signal from the control unit (unit control unit) 100.

  The concentrated water reflux line L5 is a line for refluxing the remaining portion of the concentrated water W3 flowing through the concentrated water line L3 to the upstream side of the pressurizing pump 4 in the supply water line L1. The upstream end of the concentrated water reflux line L5 is connected to the concentrated water line L3 at the branch portion J6. The branch portion J6 is disposed between the primary outlet port of the RO membrane module M1 and the branch portion J7. The downstream end of the concentrated water recirculation line L5 is connected to the supply water line L1 at the connection J1. The connecting portion J1 is disposed between the supply source (not shown) of the supply water W1 and the pressurizing pump 4.

  The concentrated water reflux valve 10 is a device that adjusts the flow rate of the concentrated water reflux line L5. The concentrated water reflux valve 10 is electrically connected to the control unit 100. The opening degree of the valve body in the concentrated water recirculation valve 10 is controlled by a drive signal from the control unit (unit control unit) 100. The valve body of the concentrated water recirculation valve 10 is controlled to a predetermined opening degree when the RO membrane module M1 is operated for fresh water. Further, the valve body of the concentrated water recirculation valve 10 is controlled to a closed state (opening degree 0%) when the RO membrane module M1 is flushed.

  The control unit (unit control unit) 100 uses the velocity type digital PID algorithm so that the detected flow rate value of the flow rate sensor 8 becomes a preset target flow rate value (described later) during the fresh water generation operation. A flow rate feedback water amount control is performed to calculate a drive frequency for driving and output a current value signal corresponding to the calculated value of the drive frequency to the inverter 5. That is, the control unit (unit control unit) 100 adjusts the rotation speed of the pressurization pump 4 so that the permeated water W2 having a rated flow rate is manufactured in the membrane separation device U1. The flow rate feedback water amount control by the control unit (unit control unit) 100 will be described later.

  Further, the control unit (unit control unit) 100 executes temperature feedforward recovery rate control of the permeated water W2 based on the temperature of the supply water W1 detected by the temperature sensor 6. As will be described later, the control unit (unit control unit) 100 controls the opening and closing of the valve bodies in the first drain valve 11 to the third drain valve 13 by executing temperature feedforward recovery rate control. The temperature feedforward recovery rate control is executed in parallel with the above-described flow rate feedback water amount control. The temperature feedforward recovery rate control by the control unit (unit control unit) 100 will be described later.

Next, operation | movement of the water treatment system 1 which concerns on this embodiment is demonstrated.
First, an operation in the case where the control unit (system control unit) 100 controls the fresh water generation operation and the flushing operation of the membrane separation devices U1 to U4 will be described.

  FIG. 4 is a flowchart showing a processing procedure when the controller (system controller) 100 controls the fresh water generation operation and the flushing operation of the membrane separation devices U1 to U4. The process of the flowchart shown in FIG. 4 is repeatedly executed during the operation of the water treatment system 1 (fresh water operation / flushing operation).

  In step ST101 shown in FIG. 4, the control unit (system control unit) 100 determines whether or not the flushing operation has been completed for all of the membrane separation devices U1 to U4. In step ST101, when the control unit (system control unit) 100 determines that the flushing operation of the membrane separation devices U1 to U4 has been completed (YES), the process proceeds to step ST102. On the other hand, when the control unit (system control unit) 100 determines in step ST101 that the flushing operation of the membrane separation apparatuses U1 to U4 has not ended (NO), the process returns to step ST101.

In step ST102 (step ST101: YES), the control unit (system control unit) 100 starts the time measurement _Tc if the time measurement _Tc by the ITU (microprocessor) has not been started. The time count _Tc indicates the accumulated replenishment time after the flushing operation is completed.

In step ST103, the control unit (system control unit) 100 determines whether or not the time _Tc measured by the ITU has reached the time _Td . The time _Td is a set value for determining when to perform the flushing operation.

In step ST103, when it is determined by the control unit (system control unit) 100 that the time count _Tc has reached the time _Td (YES), that is, when it is determined that the time for performing the flushing operation has been reached. The process proceeds to step ST104. On the other hand, in step ST103, when the control unit (system control unit) 100 determines that the time _Tc has not reached the time _Td (NO), that is, it has been determined that the time for performing the flushing operation has not been reached. In the case where it is found, the process proceeds to step ST110.

  In step ST104 (step ST103: YES), the control unit (system control unit) 100 executes the program for determining the number of units read from the memory, and determines the number of membrane separation devices to be subjected to the flushing operation. The number determination process executed by the control unit (system control unit) 100 in step ST104 will be described later.

  In step ST105, the control unit (system control unit) 100 determines whether or not the number of membrane separation apparatuses determined in step ST104 is one or more. In step ST105, when the control unit (system control unit) 100 determines that the number of membrane separation apparatuses is one or more (YES), the process proceeds to step ST106. In step ST105, when the control unit (system control unit) 100 determines that the number of membrane separation devices is less than one (NO), that is, when there is no membrane separation device to be subjected to the flushing operation. The process returns to step ST104.

  In step ST106 (step ST105: YES), the control unit (system control unit) 100 executes the program of the target device specifying process read from the memory, and specifies the membrane separation device that is the target of the flushing operation. The target device specifying process executed by the control unit (system control unit) 100 in step ST106 will be described later.

  In step ST107, the control unit (system control unit) 100 stops the fresh water generation operation of the membrane separation apparatus that is the target of the flushing operation. Specifically, the control unit (system control unit) 100 stops the supply of driving power from the inverter 5 shown in FIG. 3 to the pressurizing pump 4 and controls the permeated water valve 7 to be closed.

In step ST108, the control unit (system control unit) 100 resets the time count _Tc by the ITU (microprocessor).

  In step ST109, the control unit (system control unit) 100 executes the flushing operation processing program read from the memory, and starts the flushing operation of the membrane separation apparatus specified in step ST106. The flushing operation process executed by the control unit (system control unit) 100 in step ST109 will be described later. Thereby, the process of this flowchart is complete | finished (it returns to step ST101).

  On the other hand, in step ST110 (step ST103: NO), the control unit (system control unit) 100 acquires the detected water level value W detected by the water level sensor 3.

  In step ST111, the control unit (system control unit) 100 determines whether or not the detected water level value W of the water level sensor 3 is greater than or equal to the reference water level value H. In step ST111, when the control unit (system control unit) 100 determines that the detected water level value W is equal to or higher than the reference water level value H (YES), the process proceeds to step ST112. In step ST111, when the control unit (system control unit) 100 determines that the detected water level value W is less than the reference water level value H (NO), the process proceeds to step ST113.

  In step ST112 (step ST111: YES), the control unit (system control unit) 100 stops the fresh water generation operation in all the membrane separation devices U1 to U4. Thereby, the flow rate of the permeated water W2 supplied to the treated water tank 2 is 0%.

  In step ST113 (step ST111: NO), the control unit (system control unit) 100 determines whether or not the detected water level value W of the water level sensor 3 is less than the water level L. In step ST113, when the control unit (system control unit) 100 determines that the detected water level value W is less than the water level L (YES), the process proceeds to step ST114. In step ST113, when the control unit (system control unit) 100 determines that the detected water level value W is equal to or higher than the water level L (NO), the process returns to step ST103.

  In step ST114 (step ST113: YES), the control unit (system control unit) 100 sets all the membrane separation devices U1 to U4 to fresh water generation operation. Thereby, the flow rate of the permeated water W2 supplied to the treated water tank 2 is 100%.

As described above, the control unit (system control unit) 100 performs all the membrane separation devices U1 to U4 in the fresh water generation operation or the operation based on the detected water level value W detected by the water level sensor 3 during the fresh water generation operation. Stop. When the process of step ST112 or step ST114 ends, the process returns to step ST103. In step ST103, the process of steps ST110 to ST114 is repeatedly executed until it is determined that the time measurement (integrated replenishment time) _Tc has reached the time _Td (fresh water generation period).

  Next, the number determination process executed by the control unit (system control unit) 100 will be described. FIG. 5 is a flowchart showing a processing procedure in the case where the control unit (system control unit) 100 determines a membrane separation apparatus to be subjected to a flushing operation. In step ST104 shown in FIG. 4, the control unit (system control unit) 100 executes the process of the flowchart shown in FIG. 5 based on the program for determining the number of units read from the memory.

  In step ST <b> 201 shown in FIG. 5, the control unit (system control unit) 100 acquires the detected water level value W detected by the water level sensor 3.

  In step ST202, the control unit (system control unit) 100 determines whether or not the detected water level value W of the water level sensor 3 is equal to or higher than the reference water level value H (W ≧ H). In step ST202, when the control unit (system control unit) 100 determines that the detected water level value W is equal to or higher than the reference water level value H (YES), the process proceeds to step ST203. In step ST202, when the control unit (system control unit) 100 determines that the detected water level value W is less than the reference water level value H (NO), the process proceeds to step ST204.

  In step ST203 (step ST202: YES), the control unit (system control unit) 100 refers to the data relating to the number determination stored in the memory (see FIG. 2), and the detected water level value W is equal to or higher than the reference water level value H. In the case of (W ≧ H), it is determined that the number of membrane separation apparatuses to be subjected to the flushing operation is four. Then, the control unit (system control unit) 100 stores the determined number of membrane separation devices in a memory (not shown) (hereinafter the same). Thereby, the process of this flowchart is complete | finished.

  In step ST204 (step ST201: NO), the control unit (system control unit) 100 determines whether or not the detected water level value W of the water level sensor 3 is less than the reference water level value H and equal to or higher than the water level D3 (H> W ≧ D3). Determine. In step ST204, when the control unit (system control unit) 100 determines that the detected water level value W is less than the reference water level value H and greater than or equal to the water level D3 (YES), the process proceeds to step ST205. On the other hand, when the control unit (system control unit) 100 determines in step ST204 that the detected water level value W is less than the reference water level value H and not higher than the water level D3 (NO), the process proceeds to step ST206.

  In step ST205 (step ST204: YES), the control unit (system control unit) 100 refers to the data relating to the number determination stored in the memory (see FIG. 2), and the detected water level value W is less than the reference water level value H. When the water level is D3 or higher (H> W ≧ D3), the number of membrane separation devices to be subjected to the flushing operation is determined to be three. Thereby, the process of this flowchart is complete | finished.

  In step ST206 (step ST204: NO), the control unit (system control unit) 100 determines whether or not the detected water level value W of the water level sensor 3 is less than the water level D3 and equal to or higher than the water level D2 (D3> W ≧ D2). To do. In step ST206, when the control unit (system control unit) 100 determines that the detected water level value W is less than the water level D3 and greater than or equal to the water level D2 (YES), the process proceeds to step ST207. On the other hand, when the control unit (system control unit) 100 determines in step ST206 that the detected water level value W is less than the water level D3 and not higher than the water level D2 (NO), the process proceeds to step ST208.

  In step ST207 (step ST206: YES), the control unit (system control unit) 100 refers to the data related to the number determination stored in the memory (see FIG. 2), and the detected water level value W is less than the water level D3 and the water level. In the case of D2 or more (D3> W ≧ D2), it is determined that the number of membrane separation apparatuses to be subjected to the flushing operation is two. Thereby, the process of this flowchart is complete | finished.

  In step ST208 (step ST206: NO), the control unit (system control unit) 100 determines whether or not the detected water level value W of the water level sensor 3 is less than the water level D2 and equal to or higher than the water level D1 (D2> W ≧ D1). To do. In step ST208, when the control unit (system control unit) 100 determines that the detected water level value W is less than the water level D2 and greater than or equal to the water level D1 (YES), the process proceeds to step ST209. On the other hand, in step ST208, when the control unit (system control unit) 100 determines that the detected water level value W is less than the water level D2 and not higher than the water level D1 (NO), the process proceeds to step ST210.

  In step ST209 (step ST208: YES), the control unit (system control unit) 100 refers to data relating to the number determination stored in the memory (see FIG. 2), and the detected water level value W is less than the water level D2 and the water level. In the case of D1 or more (D2> W ≧ D1), the number of membrane separation devices to be subjected to the flushing operation is determined to be one. Thereby, the process of this flowchart is complete | finished.

  On the other hand, in step ST210 (step ST208: NO), the control unit (system control unit) 100 refers to data relating to the number determination stored in the memory (see FIG. 2), and the detected water level value W is less than the water level D1. In the case of (D1> W ≧ L or L <W), the number of membrane separation devices to be subjected to the flushing operation is determined to be 0 (zero). Thereby, the process of this flowchart is complete | finished.

  Next, the target device specifying process executed by the control unit (system control unit) 100 will be described. FIG. 6 is a flowchart illustrating a processing procedure when the control unit (system control unit) 100 specifies a membrane separation apparatus that is a target of a flushing operation. In step ST106 shown in FIG. 4, the control unit (system control unit) 100 executes the process of the flowchart shown in FIG. 6 based on the program for the target device specifying process read from the memory.

  In step ST301 shown in FIG. 6, the control unit (system control unit) 100 refers to a memory (not shown) and acquires the number of membrane separation devices to be subjected to the flushing operation.

  In step ST302, the control unit (system control unit) 100 determines whether or not the number of membrane separation apparatuses to be subjected to the flushing operation is “1”. In step ST302, when the control unit (system control unit) 100 determines that the number of membrane separation apparatuses to be subjected to the flushing operation is “1” (YES), the process proceeds to step ST303. On the other hand, when the control unit (system control unit) 100 determines in step ST302 that the number of membrane separation apparatuses to be subjected to the flushing operation is not “1” (NO), the process proceeds to step ST304.

  In step ST303 (step ST302: YES), the control unit (system control unit) 100 refers to the data relating to the priority order stored in the memory, and sets the membrane separation device U1 having the highest priority as the target of the flushing operation. Identify. And the control part (system control part) 100 memorize | stores the identification number of the specified membrane separation apparatus in memory (henceforth the same). Thereby, the process of this flowchart is complete | finished.

  Further, in step ST304 (step ST302: NO), the control unit (system control unit) 100 determines whether or not the number of membrane separation apparatuses to be subjected to the flushing operation is “2”. In step ST304, when the control unit (system control unit) 100 determines that the number of membrane separation apparatuses to be subjected to the flushing operation is “2” (YES), the process proceeds to step ST305. On the other hand, when the control unit (system control unit) 100 determines in step ST304 that the number of membrane separation apparatuses to be subjected to the flushing operation is not “2” (NO), the process proceeds to step ST306.

  In step ST305 (step ST304: YES), the control unit (system control unit) 100 refers to the data related to the priority order stored in the memory, and the membrane separation device U1 having the highest priority and the priority order is 2. The second highest membrane separator U2 is identified as the target of the flushing operation. Thereby, the process of this flowchart is complete | finished.

  Moreover, in step ST306 (step ST304: NO), the control unit (system control unit) 100 determines whether or not the number of membrane separation apparatuses to be subjected to the flushing operation is “3”. If the control unit (system control unit) 100 determines in step ST306 that the number of membrane separation apparatuses to be subjected to the flushing operation is “3” (YES), the process proceeds to step ST307. On the other hand, when the control unit (system control unit) 100 determines in step ST306 that the number of membrane separation apparatuses to be subjected to the flushing operation is not “3” (NO), the process proceeds to step ST308.

  In step ST307 (step ST306: YES), the control unit (system control unit) 100 refers to the data relating to the priority stored in the memory, and the membrane separation device U1 having the highest priority and the second priority. The membrane separator U2 having the highest priority and the membrane separator U3 having the third highest priority are identified as the objects of the flushing operation. Thereby, the process of this flowchart is complete | finished.

  Moreover, in step ST308 (step ST306: NO), the control unit (system control unit) 100 specifies all the membrane separation devices U1 to U4 as the objects of the flushing operation. Thereby, the process of this flowchart is complete | finished.

  Next, the flushing operation executed by the control unit (system control unit) 100 will be described. FIG. 7 is a flowchart illustrating a processing procedure when the control unit (system control unit) 100 executes a flushing operation process. In step ST109 shown in FIG. 4, the control unit (system control unit) 100 executes the process of the flowchart shown in FIG. 7 based on the flushing operation process program read from the memory.

  In step ST401 shown in FIG. 7, the control unit (system control unit) 100 controls the permeated water valve 7 to be closed.

  In step ST402, the control unit (system control unit) 100 controls the concentrated water recirculation valve 10 to be closed.

  In step ST403, the control unit (system control unit) 100 controls a predetermined valve among the first drain valve 11 to the third drain valve 13 to be in an open state. Note that the number of drain valves to be controlled to the open state is determined in advance based on the flow rate of the supply water W1 necessary for effective flushing.

In step ST404, the control unit (system control unit) 100 acquires the drive frequency F _f in the flushing operation. This drive frequency F _f is, for example, a set value stored in advance in a memory.

In step ST405, the control unit (system control unit) 100 converts the value of the drive frequency F _f into a corresponding current value signal (4 to 20 mA).

  In step ST406, the control unit (system control unit) 100 outputs the converted current value signal to the inverter 5. Thereby, the process of this flowchart is complete | finished. The inverter 5 supplies the driving power converted to a frequency corresponding to the input current value signal to the pressurizing pump 4. As a result, the pressurizing pump 4 is driven at a rotational speed corresponding to the driving frequency input from the inverter 5.

  The supply water W1 supplied to the primary side of the RO membrane module M1 by the control of the pressurizing pump 4, the permeate water valve 7, the concentrated water recirculation valve 10, and the first drain valve 11 to the third drain valve 13 is as follows. It flows on the surface of the RO membrane and is discharged from the concentrated water discharge line L4 via the concentrated water line L3 as flushing washing waste water. Further, the permeated water W2 sent from the secondary side port of the RO membrane module M1 is returned to the supply water line L1 through the permeated water return line L6 by the opening operation of the safety valve 9.

  Note that the flushing operation is continued until the electrical conductivity or silica concentration of the cleaning wastewater discharged from the concentrated water discharge line L4 is at least 1.1 times or less of the supply water W1.

  Next, in the control unit (system control unit) 100, after starting the flushing operation (step ST109 in FIG. 4), an operation in the case of changing the number of membrane separators that perform the fresh water operation / flushing operation will be described. FIG. 8 is a flowchart showing a processing procedure in the case where the number of membrane separation devices that perform fresh water operation / flushing operation is changed in the control unit (system control unit) 100. The process of the flowchart shown in FIG. 8 is repeatedly performed during the flushing operation of the water treatment system 1.

  In step ST501 shown in FIG. 8, the control unit (system control unit) 100 acquires the detected water level value W detected by the water level sensor 3.

  In step ST502, the control unit (system control unit) 100 determines whether or not the detected water level value W acquired this time has increased by one or more steps from the detected water level value W ′ acquired last time. In this step ST502, when it is determined by the control unit (system control unit) 100 that the detected water level value W acquired this time has risen one step or more (YES) from the detected water level value W ′ acquired last time (YES). Moves to step ST503. On the other hand, in step ST502, when the control unit (system control unit) 100 determines that the detected water level value W acquired this time has not risen one step or more (NO) from the previously acquired detected water level value W ′. Then, the process proceeds to step ST507.

  In step ST503 (step ST502: YES), the control unit (system control unit) 100 determines the number of membrane separation apparatuses to be subjected to the flushing operation. The control unit (system control unit) 100 determines that the number of membrane separation apparatuses to be subjected to the flushing operation is one if the water level of the treated water tank 2 is increased by one stage. Similarly, every time the water level of the treated water tank 2 rises by one stage, the number of membrane separation devices to be subjected to the flushing operation is increased by one.

  In step ST504, the control unit (system control unit) 100 specifies a membrane separation apparatus that is a target of the flushing operation. Specifically, the control unit (system control unit) 100 identifies a membrane separation apparatus that is a target of the flushing operation based on the number of units determined in step ST503 and data on the priority order stored in the memory. To do. For example, when the number determined in step ST503 is “1” and the membrane separation devices U1 and U2 are in the flushing operation, the membrane separation device U3 having the third highest priority is the target of the flushing operation.

  In step ST505, the control unit (system control unit) 100 stops the fresh water generation operation of the membrane separation device specified in step ST504. Specifically, the control unit (system control unit) 100 controls the permeated water valve 7 to be closed while stopping the supply of driving power to the pressurizing pump 4 in the membrane separation apparatus to be subjected to the flushing operation. To do.

  In step ST506, the control unit (system control unit) 100 performs a flushing operation on the membrane separation apparatus specified in step ST504. In step ST506, the control unit (system control unit) 100 executes the flushing operation processing program read from the memory (see FIG. 7). Thereby, the process of this flowchart is complete | finished (it returns to step ST501).

  On the other hand, in step ST507 (step ST502: NO), the control unit (system control unit) 100 determines whether or not the detected water level value W acquired this time is lower than the detected water level value W ′ acquired last time. In step ST507, when it is determined by the control unit (system control unit) 100 that the detected water level value W acquired this time is lower than the detected water level value W ′ acquired last time (YES), the process is performed in step ST508. Migrate to

  On the other hand, when it is determined by the control unit (system control unit) 100 in step ST507 that the detected water level value W acquired this time is not lower than the previously acquired detected water level value W ′ (NO), The process of the flowchart ends. This is because it is not necessary to quickly replenish the permeated water W2 when the drop in the water level in the treated water tank 2 is less than one stage.

  In step ST508 (step ST507: YES), the control unit (system control unit) 100 determines whether there is a membrane separation apparatus that has completed the flushing operation. In step ST508, when the control unit (system control unit) 100 determines that there is a membrane separation apparatus that has completed the flushing operation (YES), the process proceeds to step ST509. On the other hand, in step ST508, when the control unit (system control unit) 100 determines that there is no membrane separation apparatus that has completed the flushing operation (NO), the process of this flowchart ends. This is because when there is no membrane separation apparatus for which the flushing operation has been completed, the fresh water generation operation of the apparatus cannot be performed.

  In step ST509 (step ST508: YES), the control unit (system control unit) 100 starts the fresh water generation operation of the membrane separation apparatus that has completed the flushing operation. Specifically, the control unit (system control unit) 100 starts the supply of driving power from the inverter 5 to the pressurization pump 4 shown in FIG. 7 is controlled to an open state. Thereby, the process of this flowchart is complete | finished (it returns to step ST501). In addition, when there are a plurality of membrane separation devices that have completed the flushing operation, only a part of the membrane separation devices may be started, or the fresh water generation operation may be started for all the membrane separation devices. .

  Next, flow rate feedback water amount control by the control unit (unit control unit) 100 will be described. FIG. 9 is a flowchart showing a processing procedure when the control unit (unit control unit) 100 executes the flow rate feedback water amount control. The process of the flowchart shown in FIG. 9 is repeatedly performed during the fresh water generation operation of the membrane separation devices U1 to U4.

In step ST601 shown in FIG. 9, the control unit (unit control unit) 100 acquires a target flow rate value Q _p ′ of the permeated water W2. The target flow rate value Q _p ′ is, for example, a set value that is input to the memory of the control unit 100 by a system administrator via a user interface (not shown).

In step ST602, the control unit (unit control unit) 100 determines whether or not the time T _s measured by the ITU has reached 100 ms, which is a control cycle. In step ST602, when the control unit (unit control unit) 100 determines that the time T _s measured by the ITU has reached 100 ms (YES), the process proceeds to step ST603. On the other hand, in Step ST602, when the control unit (unit control unit) 100 determines that the time T _s measured by the ITU has not reached 100 ms (NO), the process returns to Step ST602.

Step ST 603: In (step ST 602 YES judgment), the control unit (the unit control section) 100 acquires the detected flow value _{Q p} of the permeate W2 detected by the flow rate sensor 8.

In step ST 604, the control unit (the unit control section) 100, so that the deviation between the detected flow rate value obtained in step ST 603 (feedback value) _{Q p} and the target flow rate value _{Q p} obtained in step ST 601 'is zero, The manipulated variable U is calculated by the speed type digital PID algorithm. In the velocity type digital PID algorithm, a change amount of the operation amount is calculated every control cycle (100 ms), and this amount of operation is added to the operation amount at the time of the previous control cycle to determine the current operation amount.

  In step ST605, the control unit (unit control unit) 100 calculates the driving frequency F of the pressurizing pump 4 based on the current operation amount U and the maximum driving frequency of the pressurizing pump 4 (set value of 50 Hz or 60 Hz). To do.

  In step ST606, the control unit (unit control unit) 100 converts the calculated value of the drive frequency F into a corresponding current value signal (4 to 20 mA).

  In step ST607, the control unit (unit control unit) 100 outputs the converted current value signal to the inverter 5. Thereby, the process of this flowchart is complete | finished (it returns to step ST601).

  Next, temperature feedforward recovery rate control by the control unit (unit control unit) 100 will be described. FIG. 10 is a flowchart illustrating a processing procedure when the temperature feedforward recovery rate control is executed in the control unit (unit control unit) 100. The process of the flowchart shown in FIG. 10 is repeatedly executed in parallel with the flow rate feedback water amount control during the water freshening operation of the membrane separation devices U1 to U4.

In step ST701 shown in FIG. 10, the control unit (unit control unit) 100 acquires a target flow rate value Q _p ′ of the permeated water W2. This target flow rate value Q _p ′ is, for example, a set value that is input to the memory by the system administrator via a user interface (not shown).

In step ST702, the control unit (unit control unit) 100 acquires the silica (SiO ₂ ) concentration C _s of the supply water W1. This silica concentration C _s is a set value input to the memory by the system administrator via a user interface (not shown), for example. The silica concentration of the supply water W1 can be obtained by analyzing the water quality of the supply water W1 in advance. In the supply water line L1, the silica concentration of the supply water W1 may be measured by a water quality sensor (not shown).

  In step ST703, the control unit (unit control unit) 100 acquires the detected temperature value T of the supply water W1 from the temperature sensor 6.

In Step ST704, the control unit (unit control unit) 100 determines silica solubility S _s with respect to water based on the acquired detected temperature value T.

In step ST705, the control unit (unit control unit) 100 calculates the allowable concentration rate N _s of silica in the concentrated water W3 based on the silica concentration C _s acquired or determined in the previous step and the silica solubility S _s. . Permissible concentration rate N _s of silica can be determined from the following equation (1).
N _s = S _s / C _s (1)

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

In step ST706, the control unit (the unit control section) 100, the previous target flow rate value Q _p acquired or calculated in step _', and based on the allowable concentration rate N _s, the recovery rate is maximum drainage flow rate (target wastewater The flow rate Q _d ′) is calculated. The target drainage flow rate Q _d ′ can be obtained by the following equation (2).
Q _d ′ = Q _p ′ / (N _s −1) (2)

In step ST707, the control unit (the unit control section) 100, the actual drainage flow _{Q d} is such that the target drainage flow _{Q d} 'calculated in step ST706, the first drain valve 11 to the third drain valve of concentrated water W3 13 is controlled. Thereby, the process of this flowchart is complete | finished (it returns to step ST701).

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

  In the water treatment system 1 according to the first embodiment, the control unit (system control unit) 100 is subject to the flushing operation based on the detected water level value W of the water level sensor 3 when it is time to execute the flushing operation. The number of membrane separators to be determined is determined, and the flushing operation is executed for the determined number of membrane separators.

  According to this, when the detected water level value W of the water level sensor 3 is lower than the predetermined water level, at least one membrane separation device is operated for fresh water, so the replenishment of the permeated water W2 to the treated water tank 2 is maintained. can do. For this reason, it is possible to avoid as much as possible that the fresh water is completely stopped during the flushing operation and the permeated water W2 cannot be used at the demand point.

  In addition, the control unit (system control unit) 100 has reached the time to execute the flushing operation, and the detected water level value W of the treated water tank 2 by the water level sensor 3 transmits at least the amount of water consumed at the demand point during the flushing operation. When the water level is equal to or higher than the reference water level H at which water W2 can be supplied, the flushing operation is executed for all the membrane separation devices U1 to U4.

  According to this, when the detected water level value W of the treated water tank 2 is equal to or higher than the reference water level value H, the flushing operation is executed in all the membrane separation devices U1 to U4, so the permeated water W2 is supplied to the demand point. While making it possible, the flushing operation of all the units can be completed promptly.

  Further, the control unit (system control unit) 100 reaches the time of performing the flushing operation, and when the detected water level value W of the water level sensor 3 is less than the reference water level value H, the flushing operation is performed based on the detected water level value W. The number of membrane separation devices to be subjected to the above is reduced from the number in the case of the reference water level value H or more.

  According to this, since the number of membrane separation devices to be subjected to the flushing operation is determined according to the detected water level value W of the water level sensor 3, the permeated water W2 to the treated water tank 2 is flushed during the flushing operation. Replenishment can be maintained as much as possible.

  In addition, when the detected water level value W of the water level sensor 3 is lower than the reference water level value H, the control unit (system control unit) 100 increases the detected water level value W of the water level sensor 3 after starting the flushing operation. Increases the number of membrane separation devices to be subjected to the flushing operation based on the detected water level value W that has risen.

  According to this, when the detected water level value W of the water level sensor 3 is increased during the flushing operation, the number of membrane separation devices corresponding to the increased detected water level value W is the target of the flushing operation. While maintaining the replenishment of the permeated water W2 to the water tank 2, as many membrane separation devices as possible can be targeted for the flushing operation.

  In addition, the control unit (system control unit) 100 starts the flushing operation on the basis of a preset priority order for the membrane separation apparatus that is the target of the flushing operation.

  For this reason, it can suppress that chemical degradation and obstruction | occlusion advance extremely in a specific RO membrane module by setting a priority according to the desalination load etc. of RO membrane module.

  Further, the control unit (system control unit) 100 has reached the set replenishment time of the permeated water W2 replenished to the treated water tank 2 after the previous flushing operation has been completed for all the membrane separation devices U1 to U4. In this case, it is determined that it is time to execute the flushing operation.

  For this reason, in the control part (system control part) 100, the time which starts execution of flushing operation | movement can be determined correctly. In addition, since the flushing operation of the membrane separation devices U1 to U4 is performed at the same time, it is possible to suppress variations in the water permeability coefficient and the salt removal rate in each RO membrane module M1.

  Further, the control unit (unit control unit) 100 drives the pressurization pump 4 so that the detected flow rate value of the flow rate sensor 8 becomes a preset target flow rate value during the fresh water generation operation of the membrane separation device. For this reason, flow rate feedback water amount control is performed to calculate a drive frequency for output and output a current value signal corresponding to the calculated value of the drive frequency to the inverter 5.

  For this reason, the permeated water W2 having a stable flow rate can be replenished to the treated water tank 2 even when the recovery rate is lowered during the fresh water generation operation of the membrane separation apparatus.

  Further, the control unit (unit control unit) 100 performs temperature feedforward recovery rate control of the permeated water W2 based on the temperature of the supply water W1 detected by the temperature sensor 6 while the membrane separation apparatus is in the fresh water generation operation. Run.

  For this reason, precipitation of the silica scale in the RO membrane module M1 can be more reliably suppressed while maximizing the recovery rate of the permeated water W2 during the fresh water generation operation of the membrane separation apparatus.

  Moreover, in the membrane separation apparatus of 1st Embodiment, the safety valve 9 is provided in the permeate return line L6. For this reason, in the flushing operation, when the in-pipe pressure of the permeate return line L6 becomes equal to or higher than the set pressure, the high-pressure permeate W2 is supplied to the low pressure side (primary side of the pressurization pump 4) via the safety valve 9. I can escape. Therefore, damage to the RO membrane due to excessive back pressure can be prevented.

  The control unit (unit control unit) 100 controls the concentrated water recirculation valve 10 to be closed so that the concentrated water recirculation line L5 does not flow through the concentrated water recirculation line L5 when performing the flushing operation. The permeated water valve 7 is controlled to be closed so that the permeated water W2 does not flow through L2. For this reason, the supply water W1 can be effectively used as the wash water while suppressing the concentration of the supply water W1.

(Second Embodiment)
Next, a water treatment system 1A according to a second embodiment of the present invention will be described with reference to the drawings.

  Since the whole structure of 1 A of water treatment systems which concern on 2nd Embodiment is the same as 1st Embodiment, FIG. 1 is used suitably. In FIG. 1, the reference numerals in parentheses indicate the configuration of the second embodiment.

  The water treatment system 1A according to the second embodiment is different from the first embodiment in the internal configuration of the membrane separation device. In the second embodiment, differences from the first embodiment will be described. Therefore, in the second embodiment, the same or similar components as those in the first embodiment are denoted by the same reference numerals or the detailed description thereof will be omitted as appropriate. In the second embodiment, the description of the first embodiment is used as appropriate for components that are not particularly described. In addition, in 2nd Embodiment, "A" is attached | subjected to the end of a code | symbol as needed about what has the same name as 1st Embodiment, and differs in a structure.

  FIG. 11 is a configuration diagram of the membrane separation device U11 according to the second embodiment. A water treatment system 1A according to the second embodiment includes a plurality of membrane separation devices U11, U12, U13, U14 (see FIG. 1). Here, the configuration will be described on behalf of the membrane separation device U11, but the other membrane separation devices U12 to U14 have the same configuration.

  As shown in FIG. 11, the membrane separation device U11 of this embodiment includes an RO membrane module M11, an RO membrane module M12, an RO membrane module M13, and an RO membrane module M14. Since the configurations and functions of the RO membrane modules M11 to M14 are the same as those of the RO membrane module M1 of the first embodiment, description thereof is omitted.

In the membrane separation device U11 of this embodiment, one RO membrane module is provided more than the originally required number. For example, when the rated flow rate of the membrane separation device U11 is 3 m ³ / h, four RO membrane modules with a rated flow rate of 1 m ³ / h (original number required is 3) are provided. The configuration of the RO membrane modules M11 to M14 will be described later.

  Further, the membrane separation device U11 of the present embodiment includes a scale inhibitor supply device 15, a first on-off valve 21, a second on-off valve 22, a third on-off valve 23, and a fourth on-off valve 24. . The membrane separation device U11 of the present embodiment includes permeate connection lines L21, L23, L25, and L27, and concentrated water connection lines L22, L24, and L26.

  In the following description, when any one of the RO membrane module M11 to RO membrane module M14 is not specifically specified, it is described as “RO membrane module”. Similarly, when any one of the first on-off valve 21 to the fourth on-off valve 24 is not specifically specified, it is described as “on-off valve”.

  A supply water line L1, a permeated water connection line L21, and a concentrated water connection line L22 are connected to the RO membrane module M11. The upstream end of the supply water line L1 is connected to a supply source (not shown) of the supply water W1. Further, the downstream end of the supply water line L1 is connected to the primary inlet port of the RO membrane module M11. The upstream end of the permeate connection line L21 is connected to the secondary port of the RO membrane module M11. The downstream end portion of the permeate water connection line L21 is connected to the upstream end portion of the permeate water line L2 at the connection portion J14.

  Further, a first on-off valve 21 is provided in the permeate connection line L21. The first on-off valve 21 is a facility for opening and closing the permeate connection line L21. The first on-off valve 21 is electrically connected to the control unit 100A. The opening and closing of the valve body in the first on-off valve 21 is controlled by a drive signal from the control unit 100A.

  The concentrated water connection line L22 is a line for sending the concentrated water W3 produced by the RO membrane module M11 as supply water to the RO membrane module M12 at the next stage. The upstream end of the concentrated water connection line L22 is connected to the primary outlet port of the RO membrane module M11. The downstream end of the concentrated water connection line L22 is connected to the primary inlet port of the RO membrane module M12.

  The RO membrane module M12 is connected to the concentrated water connection line L22, the permeated water connection line L23, and the concentrated water connection line L24 described above. The upstream end of the permeate connection line L23 is connected to the secondary port of the RO membrane module M12. The downstream end of the permeate connection line L23 is connected to the permeate connection line L21 at the connection J12.

  Further, a second on-off valve 22 is provided in the permeate connection line L23. The second on-off valve 22 is a facility that opens and closes the permeate connection line L23. The second on-off valve 22 is electrically connected to the control unit 100A. The opening and closing of the valve body in the second on-off valve 22 is controlled by a drive signal from the control unit 100A.

  The concentrated water connection line L24 is a line for sending the concentrated water W3 produced by the RO membrane module M12 to the next-stage RO membrane module M13 as supply water. The upstream end of the concentrated water connection line L24 is connected to the primary outlet port of the RO membrane module M12. The downstream end of the concentrated water connection line L24 is connected to the primary inlet port of the RO membrane module M13.

  The RO membrane module M13 is connected to the concentrated water connection line L24, the permeated water connection line L25, and the concentrated water connection line L26 described above. The upstream end of the permeate connection line L25 is connected to the secondary port of the RO membrane module M13. The downstream end of the permeate connection line L25 is connected to the permeate connection line L21 at the connection J13.

  The third on-off valve 23 is connected to the permeate connection line L25. The third on-off valve 23 is a facility for opening and closing the permeate connection line L25. The third on-off valve 23 is electrically connected to the control unit 100A. The opening and closing of the valve body in the third on-off valve 23 is controlled by a drive signal from the control unit 100A.

  The concentrated water connection line L26 is a line for sending the concentrated water W3 produced by the RO membrane module M13 as supply water to the RO membrane module M14 at the next stage. The upstream end of the concentrated water connection line L26 is connected to the primary outlet port of the RO membrane module M13. Further, the downstream end of the concentrated water connection line L26 is connected to the primary inlet port of the RO membrane module M14.

  The RO membrane module M14 is connected to the concentrated water connection line L26, the permeate water connection line L27, and the concentrated water line L3 described above. The upstream end of the permeate connection line L27 is connected to the secondary port of the RO membrane module M14. The downstream end of the permeated water connection line L27 is connected to the permeated water connection line L21 (and the permeated water line L2) at the connection portion J14.

  The fourth open / close valve 24 is connected to the permeate connection line L27. The fourth on-off valve 24 is a facility that opens and closes the permeate connection line L27. The fourth on-off valve 24 is electrically connected to the control unit 100A. The opening and closing of the valve body in the fourth on-off valve 24 is controlled by a drive signal from the control unit 100A.

  In addition, since the structure and function of the concentrated water line L3 and the 1st drain valve 11-the 3rd drain valve 13 connected to the primary side exit port of RO membrane module M14 are the same as 1st Embodiment, description is abbreviate | omitted.

  As shown in FIG. 11, in the membrane separation device U11 of the present embodiment, the four-stage RO is used so that the concentrated water W3 sent from the previous-stage RO membrane module becomes the supply water to the next-stage RO membrane module. The primary side of the membrane module is connected in series. Further, the secondary sides of the four-stage RO membrane modules are connected in parallel so that the permeated water W2 sent from each RO membrane module flows through the common permeated water connection line L21 (and the permeated water line L2). .

  The scale inhibitor supply device 15 is a device that supplies the scale inhibitor to the supply water W1. The scale inhibitor supply device 15 is connected to the supply water line L1 at the connection portion J11 via the scale inhibitor supply line L14. The scale inhibitor is a chemical used to prevent scale growth in water or scale deposition on the surface of the RO membrane. Examples of the scale inhibitor usable here include carboxylic acid polymers, acrylic acid polymers, phosphonic acid chelating agents, carboxylic acid chelating agents, and the like.

  The scale inhibitor supply device 15 is electrically connected to the control unit 100A. The supply (start / stop) of the scale inhibitor in the scale inhibitor supply apparatus 15 is controlled by a drive signal from the control unit 100A. In the present embodiment, the scale inhibitor is supplied from the scale inhibitor supply device 15 to the supply water W1 during the fresh water generation operation.

  The control unit 100A has the same function as the control unit 100 of the first embodiment. In addition, as a function of the unit control unit, the control unit 100A causes the permeated water W2 to be regenerated with three of the RO membrane modules M11 to M14 during the water regenerating operation, and the remaining one is the permeated water W2. Stop fresh water operation. Specifically, the control unit (unit control unit) 100A controls the open / close valve connected to the RO membrane module that performs the freshwater operation to an open state, and closes the open / close valve connected to the RO membrane module that stops the freshwater operation. (The on-off valve may be manually opened or closed).

  The control unit (unit control unit) 100A switches the RO membrane module that stops the fresh water generation operation while rotating the RO membrane module sequentially in a cycle of, for example, 3 to 7 days. Thereby, one RO membrane module can always be made into a dormant state while the membrane separator U11 is desalinated. The order of switching the RO membrane modules may be the order in which the RO membrane modules are arranged, or may be set according to the water permeability coefficient of each RO membrane module.

  According to the water treatment system 1A according to the second embodiment described above, since any one RO membrane module of the membrane separation device can be stopped for a long period of time, the scale inhibitor adhering to the surface of the RO membrane penetrates. The permeation flux in the RO membrane can be recovered by peeling with pressure. Thereby, a favorable permeation flux can be maintained over a long period of time even in the case of continuous fresh water generation operation. As a result, since the frequency of membrane cleaning and membrane exchange can be reduced, the running cost can be reduced.

  In addition, according to the structure of this embodiment, since supply water W1 always flows also into the RO membrane module which stopped the fresh water generation operation, the RO membrane module which stopped the fresh water generation operation is connected to another RO membrane module. The effect of peeling off the scale preventive agent from the surface of the RO membrane can be further enhanced than when it is completely separated from the line and rested.

  Further, since the on-off valve connected to the RO membrane module that stops the fresh water generation operation is closed, and the permeate W2 sent from the RO membrane module during the flushing operation does not flow into the treated water tank 2, a higher-purity treatment is performed. Water W4 can be obtained.

  The preferred embodiments of the present invention have been described below. However, the present invention is not limited to the above-described embodiments, and can be implemented in various forms.

  For example, in the present embodiment, an example in which four membrane separation devices U1 to U4 are provided has been described. However, the present invention is not limited to this, and there may be at least two membrane separation devices. Moreover, it is good also as a structure provided with five or more membrane separation apparatuses.

  In the present embodiment, an example has been described in which the water level for determining the amount of water stored in the treated water tank 2 is set to five levels of water level H, water level D3, water level D2, water level D1, and water level L. Not limited to this, the water level may be set to 4 levels or less, or may be set to 6 levels or more according to the number of installed membrane separation devices.

  In the present embodiment, the flushing operation is executed when the accumulated replenishment time of the permeated water W2 replenished to the treated water tank 2 reaches the set value after the flushing operation is finished for all the membrane separation devices U1 to U4. The example which determines with having reached the time was demonstrated. Not limited to this, the time when the flushing operation is performed when the integrated replenishment amount of the permeated water W2 replenished to the treated water tank 2 reaches the set value after the flushing operation is finished for all the membrane separation devices U1 to U4. May be determined to have reached.

The accumulated replenishment time and the accumulated replenishment amount are set according to the quality of the supply water W1 (for example, turbidity, silica concentration, etc.). In the case of the cumulative replenishment time, for example, it is set in the range of 10 to 120 minutes. In the case of the integrated replenishment amount, the integrated replenishment time is multiplied by the rated flow rate (that is, the first target flow rate value during normal operation). For example, when the rated flow rate is 2 m ³ / h, the integrated replenishment amount is in the range of 0.33 to ⁴ m ³ . It is preferable that the integrated replenishment time is relatively shortened as the water quality of the supply water W1 deteriorates. On the other hand, it is preferable that the integrated replenishment amount is relatively reduced as the water quality of the supply water W1 deteriorates.

  In the present embodiment, the supply water W1 may be raw water such as ground water or tap water. Further, the supply water W1 may be water obtained by pretreating raw water with an iron removal manganese removal apparatus, an activated carbon filtration apparatus, a hard water softening apparatus, or the like.

  In the present embodiment, the water treatment system 1 (1A) including the membrane separation devices U1 to U4 and the treated water tank 2 has been described as the main configuration. Not only this but an electrodeionization device (EDI device) may be provided downstream of the treated water tank 2. Moreover, it is good also as a structure which provided the decarbonation apparatus in the downstream of the treated water tank 2. FIG. Furthermore, it is good also as a structure which provided the electrodeionization apparatus mentioned above in the downstream of the decarboxylation apparatus.

  In this embodiment, the example which calculates the drive frequency of the pressurization pump 4 by the speed type digital PID algorithm was demonstrated. Not limited to this, the drive frequency of the pressurizing pump 4 may be calculated by a position type digital PID algorithm.

  In the present embodiment, the example in which the temperature of the supply water W1 flowing through the supply water line L1 is the detected temperature value T in the temperature feedforward recovery rate control has been described. Not only this but the temperature of the permeated water W2 which distribute | circulates the permeated water line L2 is good also as detection temperature value T. FIG. Alternatively, the temperature of the concentrated water W3 flowing through the concentrated water line L3 may be set as the detected temperature value T. Furthermore, the temperature of water is detected in a plurality of lines, and the average value may be set as the detected temperature value T.

  In the present embodiment, an example in which the drainage flow rate of the concentrated water W3 is adjusted stepwise by selectively opening and closing the first drainage valve 11 to the third drainage valve 13 in the recovery rate control has been described. Not limited to this, the concentrated water discharge line L4 may be one without branching, and a proportional control valve may be provided on this line. In this case, the drain flow rate of the concentrated water W3 can be adjusted by transmitting a current value signal (for example, 4 to 20 mA) from the control unit 100 (100A) to the proportional control valve to control the valve opening. .

  Further, in the configuration in which the proportional control valve is provided, a flow rate sensor may be provided in the concentrated water discharge line L4. The flow rate value detected by the flow rate sensor is input as a feedback value to the control unit 100 (100A). Thereby, the actual waste water flow rate of the concentrated water W3 can be controlled more accurately.

1,1A Water treatment system 2 Treated water tank (storage tank)
3 Water level sensor (water level detection means)
4 Pressurizing pump 5 Inverter 7 Permeate valve 8 Flow rate sensor (flow rate detection means)
9 Safety valve (pressure relief valve)
100, 100A control unit M1, M11-M14 RO membrane module (reverse osmosis membrane module)
U1-U4, U11-U14 Membrane separation device L1 Supply water line L2 Permeate water line L3 Concentrated water line L4 Concentrated water discharge line L5 Concentrated water reflux line L6 Permeated water return line L7 Distribution line W1 Supply water W2 Permeated water W3 Concentrated water W4 Treated water

Claims (6)

A plurality of membrane separation devices including a reverse osmosis membrane module that separates supply water into permeate and concentrated water;
A storage tank for storing permeated water sent from the membrane separator;
Water level detecting means for detecting the water level of the storage tank;
In a plurality of the membrane separation devices, when the time for performing the flushing operation for cleaning the primary side of the reverse osmosis membrane module is reached, the flushing operation is performed based on the detected water level of the water level detection means. A controller that determines the number of the membrane separators, and executes the flushing operation for the determined number of the membrane separators;
Equipped with a,
The control unit has reached the time to execute the flushing operation, and (i) the detected water level of the water level detecting means is at least a reference water level that can supply permeated water of the amount of water consumed at a demand point during the flushing operation. In this case, the flushing operation is executed for all the membrane separation devices, and (ii) when the detected water level of the water level detection means is lower than a reference water level, the flushing operation is performed based on the detected water level. the membrane separator water treatment system Ru is smaller than the number in the case the number of more than the reference water level to be of interest. In the case where the detected water level of the water level detecting means is less than the reference water level, the control unit is configured to increase the detected water level when the detected water level of the water level detecting means rises after starting execution of the flushing operation. On the basis of the number of the membrane separators subject to the flushing operation,
The water treatment system according to claim 1 . The control unit starts execution of the flushing operation based on a preset priority order for the membrane separation device to be the target of the flushing operation.
The water treatment system according to claim 1 or 2 . After the previous flushing operation has been completed for all the membrane separation devices, the control unit performs the flushing when the accumulated replenishment time or accumulated replenishment amount of permeated water replenished to the storage tank reaches a set value. It is determined that it is time to execute driving.
The water treatment system according to any one of claims 1 to 3 . The membrane separator is
A pressure pump that is driven at a rotational speed corresponding to the input driving frequency, sucks the supplied water, and discharges it toward the reverse osmosis membrane module;
An inverter that outputs a driving frequency corresponding to the input current value signal to the pressurizing pump;
A flow rate detecting means for detecting the flow rate of the permeated water and outputting a detected flow rate value corresponding to the flow rate;
With
The control unit calculates a driving frequency of the pressurizing pump so that a detected flow rate value output from the flow rate detecting unit becomes a preset target flow rate, and a current value corresponding to the calculated value of the driving frequency Outputting a signal to the inverter;
The water treatment system as described in any one of Claims 1-4 . The membrane separator is
A supply water line for supplying supply water to the reverse osmosis membrane module;
A permeate line for sending permeate to the storage tank;
A permeate valve provided in the permeate line between the reverse osmosis membrane module and the storage tank;
A permeate return line for returning permeate sent to the permeate line to the upstream side of the pressurizing pump in the supply water line;
A pressure relief valve provided in the permeate return line;
With
The control unit controls the permeate valve so that permeate does not flow through the permeate line when performing the flushing operation.
The water treatment system according to claim 5 .

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