JP5862363B2 - 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, a water treatment system in which a plurality of membrane separation devices are connected in parallel has been proposed in order to cope with the case where the maximum water consumption at a demand point cannot be covered by a single membrane separation device (for example, patents). Reference 1). In this water treatment system, in order to uniformize the RO membrane blockage and chemical degradation in each RO membrane module, when increasing or decreasing the number of operating units, the membrane separation device having the RO membrane module with high membrane performance is given priority. Driven.

JP 2010-162501 A

  In the water treatment system, a pretreatment device such as an activated carbon filtration device or a soft water device is connected to the upstream side of each membrane separation device. When trouble occurs in these pretreatment devices and turbid components and residual chlorine leak into the feed water sent to the membrane separator, the membrane performance (water permeability coefficient and salt removal rate) of all RO membranes is uniform. May get worse. In that case, not only the RO membrane with low membrane performance but also the RO membrane with high membrane performance is promoted to clog and chemically deteriorate, so the RO membrane module is cleaned and replaced throughout the system and maintenance costs May increase.

  Therefore, the present invention suppresses the deterioration of the membrane performance of the reverse osmosis membrane module uniformly when the measured water quality of the supplied water exceeds the allowable water quality in a water treatment system having a plurality of membrane separation devices. The object is to provide a water treatment system that can reduce maintenance costs.

The present invention comprises a reverse osmosis membrane module for producing permeated water from supplied water, a plurality of membrane separation devices for sending permeated water in response to an input operation command signal, and physical quantities measured in the system. Based on the water permeation coefficient calculation means for calculating the water permeation coefficient of the reverse osmosis membrane module for each of the membrane separation devices, the water quality item measurement means for measuring the water quality item of the feed water, and the measured water quality of the water quality item measurement means Is greater than a preset allowable water quality, based on the water permeability coefficient calculated for each of the membrane separation devices, the calculated value of the water permeability coefficient and a preset initial value of the water permeability coefficient when the progression of the water permeability variation difference between the reverse osmosis membrane by comparing the progress of the water permeability variation of the module, the film as the film separation apparatus having the reverse osmosis membrane module the progress is greater Luck separation equipment Priority setting means for setting the priority to be increased, and the membrane that operates with priority according to the priority set by the priority setting means according to the amount of permeated water consumed at the demand point An operation control means for outputting an operation command signal to a separator.

  In addition, the water quality item measuring means includes a configuration for measuring a water quality item related to a causative substance of chemical degradation of the reverse osmosis membrane module as a water quality item of the feed water, and the priority setting means is a measure of the feed water When the water quality exceeds a preset allowable water quality that suppresses chemical degradation of the reverse osmosis membrane module, the calculated water permeability coefficient is higher than a preset initial value and the water permeability coefficient It is preferable to set so that the higher the numerical order, the higher the priority of the membrane separation device having the reverse osmosis membrane module.

  In addition, the water quality item measuring unit includes a configuration for measuring a water quality item related to a causative substance of fouling of the reverse osmosis membrane module as a water quality item of the supplied water, and the priority setting unit is configured to measure the measured water quality of the supplied water. Is greater than the preset allowable water quality that suppresses fouling of the reverse osmosis membrane module, the calculated water permeability coefficient is lower than a preset initial value and the value of the water permeability coefficient is It is preferable that the membrane separation apparatus having a smaller reverse osmosis membrane module is set to have a higher priority.

  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 unit that detects a flow rate of permeate and outputs a detected flow rate value corresponding to the flow rate, and the operation control unit includes the flow rate The drive frequency of the pressurizing pump is calculated so that the detected flow rate value output from the detection means becomes a preset target flow rate, and a current value signal corresponding to the calculated value of the drive frequency is output to the inverter. It is preferable.

  According to the present invention, in a water treatment system including a plurality of membrane separation devices, when the measured water quality of the supplied water exceeds the allowable water quality, the membrane performance of the reverse osmosis membrane module is prevented from being deteriorated uniformly. In addition, a water treatment system that can reduce maintenance costs can be provided.

1 is an overall configuration diagram of a water treatment system 1 according to an embodiment. It is explanatory drawing which shows the relationship between the water level of the treated water tank 2, and the number of operation. It is a block diagram of the membrane separator U1. 6 is a flowchart showing a processing procedure when the priority order of the membrane separation apparatus is set in the system control unit (priority setting means) 101. It is a flowchart which shows the process sequence in the case of setting the number of operation | movement of a membrane separator in the unit control part (operation control means) 102. FIG. It is a flowchart which shows the process sequence in the case of making a membrane separator operate in a fresh water operation according to priority in the unit control part (operation control means) 102. It is a flowchart which shows the process sequence in the case of performing flow volume feedback water amount control in the unit control part (operation control means) 102. It is a flowchart which shows the process sequence in the case of performing temperature feedforward recovery-rate control in the unit control part (operation control means) 102.

  A water treatment system 1 according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of a water treatment system 1 according to the present embodiment. FIG. 2 is an explanatory diagram showing the relationship between the water level of the treated water tank 2 and the number of operating units in the present embodiment (hereinafter, also referred to as “data relating to the number determination”). FIG. 3 is a configuration diagram of the membrane separation device U1.

  As shown in FIG. 1, the water treatment system 1 according to the present embodiment includes a plurality of membrane separation devices U1, U2, U3, U4, a treated water tank 2, a water level sensor 3, and turbidity as water quality item measuring means. Degree sensor 4, residual chlorine concentration sensor 5 as water quality item measuring means, and control unit 100. In FIG. 1 (FIG. 3 is also the same), 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 L6. The “line” in the present specification is a general term for lines capable of flowing a fluid such as a flow path, a path, and a pipeline.

  The supply water line L1 is a line 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. The feed water W1 flowing through the feed water line L1 is distributed to the membrane separation devices U1 to U4 during the fresh water generation operation.

  Each of the membrane separation devices U1 to U4 includes one 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 of the membrane separation devices U1 to U4 is not specifically specified, the symbols U1 to U4 are omitted and described 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. The treated water tank 2 is connected to a downstream demand point (not shown) via a water distribution line L6. 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 L6.

  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 can supply the treated water W4 of the amount of water consumed at the demand point without replenishing the permeated water W2 for a predetermined time (for example, during the flushing operation of the membrane separation devices U1 to U4). This is the water level corresponding to the amount of stored water (hereinafter also referred to as “reference water level value H”). 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 flushing operation refers to cleaning the primary side 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 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, 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 turbidity sensor 4 is a device that measures the turbidity of the supply water W1 flowing through the supply water line L1. The turbidity sensor 4 is connected to the supply water line L1 at the connection portion J1. The connection part J1 is arrange | positioned between the supply source (not shown) of the supply water W1, and the membrane separators U1-U4. The turbidity of the supply water W1 is one of the water quality items relating to the cause of fouling of each RO membrane module (described later). When fouling occurs, the pores of the RO membrane are blocked, so that the water permeability coefficient decreases.

  As the turbidity sensor 4, for example, a transmitted light sensor that determines the turbidity of the sample water from the transmitted light intensity or a scattered light sensor that determines from the scattered light intensity can be used. The turbidity sensor 4 is electrically connected to the control unit 100. The turbidity of the feed water W1 detected by the turbidity sensor 4 (hereinafter also referred to as “detected turbidity value”) is transmitted to the control unit 100 as a detection signal.

  The residual chlorine concentration sensor 5 is a device that detects the residual chlorine concentration of the supply water W1 flowing through the supply water line L1. The residual chlorine concentration sensor 5 is connected to the supply water line L1 at the connection portion J2. The connection part J2 is arrange | positioned between the supply source (not shown) of the supply water W1, and the membrane separators U1-U4. The residual chlorine concentration of the supply water W1 is one of the water quality items related to the causative substance of the oxidative deterioration (chemical deterioration) of each RO membrane module. When the oxidative degradation occurs, the molecular structure of the RO membrane is destroyed, so that the salt removal rate decreases as the water permeability coefficient increases.

  As the residual chlorine concentration sensor 5, for example, the degree of color development of sample water to which an oxidative coloring reagent such as a benzidine compound is added is measured based on the transmitted light intensity, and the transmitted light for determining the residual chlorine concentration based on the measured transmitted light intensity. A type sensor can be used. The residual chlorine concentration sensor 5 is electrically connected to the control unit 100. The residual chlorine concentration (hereinafter also referred to as “detected chlorine concentration value”) of the supply water W1 detected by the residual chlorine concentration sensor 5 is transmitted to the control unit 100 as a detection signal.

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 microprocessor incorporates an integrated timer unit (hereinafter also referred to as “ITU”) that manages timekeeping and the like. The CPU of the microprocessor executes various processes according to a predetermined program read from the memory.

  The control unit 100 of the present embodiment includes a system control unit 101 (described later) that controls the entire water treatment system 1 and a unit control unit 102 (described later) that controls the operations of the membrane separation devices U1 to U4. .

First, the system control unit 101 will be described.
The system control unit 101 has a function as priority order setting means and a function as water permeability coefficient calculation means. Hereinafter, the system control unit 101 that functions as the priority order setting unit is also referred to as a “system control unit (priority setting unit) 101”. Further, the system control unit 101 that functions as the water transmission coefficient calculation unit is also referred to as a “system control unit (water transmission coefficient calculation unit) 101”.

First, the system control unit 101 that functions as priority order setting means will be described.
The system control unit (priority setting means) 101 acquires data relating to the water permeability coefficient calculated for the membrane separation devices U1 to U4 in real time. The water permeation coefficients of the membrane separation devices U1 to U4 are calculated by the function of the system control unit 101 as water permeation coefficient calculation means (described later). The system control unit (priority setting means) 101 acquires the detected turbidity value measured by the turbidity sensor 4 and the detected chlorine concentration value measured by the residual chlorine concentration sensor 5 in real time.

  When the water quality of the supply water W1 is abnormal (hereinafter also referred to as “water quality abnormality”), the system control unit (priority setting means) 101 is based on the water permeability coefficient calculated for each membrane separator. The degree of progress of the change in the water permeability of the RO membrane module is compared, and the membrane separation device having the RO membrane module with the higher degree of progression is set so that the priority for operating the membrane separation device is higher. The case where the water quality of the supply water W1 is abnormal refers to the case where the measured water quality of the turbidity sensor 4 and the residual chlorine concentration sensor 5 exceeds the preset allowable water quality.

In this embodiment, in order to compare the progress of the water permeability performance change of the RO membrane module, the initial value of the water permeability coefficient of the RO membrane module is set for each membrane separation device. That is, the system control unit (priority setting means) 101 calculates the rate of change between the previous sample value and the current sample value of the water permeability coefficient for each sampling period of the water permeability coefficient, and the rate of change is preset. If it is within the predetermined range (for example, −5 to + 5%), the current sample value is set as the initial value. The system control unit (priority setting means) 101 compares the difference (progress degree) between the water permeation coefficient calculated this time and a preset initial value for each membrane separation device. Set the priority.
The rate of change [%] is obtained by the following equation.
Rate of change [%] = {(current sample value−previous sample value) / previous sample value} × 100

  The initial value of the water permeation coefficient described above is generally set based on data at the time of trial operation, data immediately after the main operation, and the like. However, the RO membrane module in the initial stage of operation tends to vary in water permeability coefficient due to differences in the RO membrane storage environment and the like. For this reason, when determining the oxidation deterioration or blockage of the RO membrane module, in order to avoid erroneous determination, it is necessary to add a correction value in consideration of variation to the initial value. However, if the correction value is not appropriate, the maintenance is delayed although the RO membrane module needs to be cleaned or replaced, and conversely the RO membrane module is not required to be cleaned or replaced. Was sometimes executed.

  However, in this embodiment, since the initial value of the RO membrane module is set for each membrane separation device based on the rate of change between the previous sample value and the current sample value, the setting accuracy of the initial value is increased. Can do. According to this, since it is not necessary to add a correction value to the initial value in order to reduce the influence due to variations in the water permeability coefficient, it is possible to reduce the erroneous determination as described above as much as possible.

  The system control unit (priority setting means) 101 is calculated in each membrane separation apparatus when the detected residual chlorine concentration value measured by the residual chlorine concentration sensor 5 exceeds a preset allowable residual chlorine concentration value. A membrane separation apparatus having an RO membrane module having a water permeability coefficient higher than a preset initial value and a large numerical value of the calculated water permeability coefficient is set to have a higher priority. Specifically, the system control unit (priority setting means) 101 changes data relating to the priority stored in a memory (not shown).

  It is considered that the RO membrane module in which the above-described water permeability coefficient is higher than the initial value and the calculated value of the water permeability coefficient is relatively large is undergoing oxidative degradation of the RO membrane. Therefore, when the detected residual chlorine concentration value of the supply water W1 exceeds the allowable residual chlorine concentration value, the RO membrane module having a larger value of the water permeability coefficient is set to have a higher priority, thereby setting the water permeability coefficient. Further deterioration of the RO membrane module having a relatively small numerical value (where the RO membrane oxidation degradation has not progressed much) can be suppressed as much as possible.

  Further, the system control unit (priority setting means) 101, when the detected turbidity value measured by the turbidity sensor 4 exceeds a preset allowable turbidity value (allowable water quality), each membrane separation device. Is set such that the higher the priority is, the lower the membrane permeation apparatus having the RO membrane module whose water permeation coefficient calculated is lower than the preset initial value and the calculated water permeation coefficient is smaller. Specifically, the system control unit (priority setting means) 101 changes data relating to the priority stored in a memory (not shown).

  The RO membrane module in which the water permeability coefficient described above is lower than the initial value and the calculated value of the water permeability coefficient is relatively small is considered that the RO membrane is clogged. Therefore, when the detected turbidity value of the supply water W1 exceeds the allowable turbidity value, the RO membrane module having a smaller water permeability coefficient value is set to have a higher priority, so that the water permeability coefficient value is increased. Further blockage of the RO membrane module which is relatively large (RO membrane blockage is not progressing much) can be suppressed as much as possible.

  In addition, a priority order means the order of the apparatus which operates preferentially, when performing the fresh water generation operation of the membrane separators U1-U4. In the present embodiment, when the water quality of the supply water W1 is normal (hereinafter also referred to as “normal water quality”), the priority order is the membrane separation device U1> U2> U3> U4. The case where the water quality of the supply water W1 is normal refers to the case where the measured water quality (detected value) of the turbidity sensor 4 and the residual chlorine concentration sensor 5 is less than the preset allowable water quality (allowable value). The priority when the water quality is normal is set in descending order of membrane performance of the RO membrane module (described later). The membrane performance in this case refers to, for example, the initial membrane performance of the RO membrane module (water permeability coefficient measured during the trial operation of the membrane separation devices U1 to U4).

  Data relating to the priority order is stored as an arbitrarily set value (a rewritable value) in a memory (not shown). When the water quality is normal, the system control unit (priority setting means) 101 maintains the priority when the water quality is normal without changing the priority based on the water permeation coefficient of each membrane separation device. On the other hand, the system control unit (priority setting means) 101 changes the priority based on the water permeation coefficient of each membrane separation device when the water quality is abnormal.

  Note that the data related to the priority order when the water quality is normal (in the present embodiment, the membrane separation device U1> U2> U3> U4) is stored as reference data in the memory as an initial set value. The system control unit (priority setting means) 101 can return the data relating to the priority stored as an arbitrary setting value in the memory to the initial setting value as necessary. For example, the system control unit (priority setting means) 101 may change the priority stored in the memory from the initial setting value when the water quality of the supply water W1 returns from an abnormal state to a normal state. , Data relating to the priority order is set to an initial setting value.

Next, the system control unit 101 that functions as a water permeability coefficient calculation unit will be described.
The system control unit (water permeability coefficient calculating means) 101 calculates a water permeability coefficient for each of the membrane separation devices U1 to U4 for each preset sampling period, and stores data relating to the calculated water permeability coefficient in a memory (not stored). Stored in the figure).

The system control unit (water permeability coefficient calculating means) 101 is based on the detected temperature value T of the temperature sensor 8, the detected flow value Q _{p of} the flow sensor 10 (described later), and the detected pressure value P _d of the pressure sensor 9 (described later). Then, the water permeability coefficient of the RO membrane module is calculated. The detected temperature value T, the detected flow rate value Q _p , and the detected pressure value P _d are physical quantities measured in the water treatment system 1.

Here, a method for calculating the water permeability coefficient will be described.
Water permeability coefficient is a value obtained by dividing the flow rate _Q p ^[m 3 / s] of the membrane area A ^{[m 2]} and effective pressure [Pa] _{P e} permeate W2 (see equation (1) below) . The water permeability coefficient is an index indicating the water permeability of the RO membrane module. That is, the water permeation coefficient means the amount of water that permeates the unit area of the membrane per unit time when a unit effective pressure is applied. The effective pressure is a pressure obtained by subtracting the osmotic pressure difference and the secondary pressure (back pressure) from the operating pressure (average operating pressure) (see formula (2) described later).

The calculated value of the water permeability coefficient L _p [m ³ · m ⁻² · s ⁻¹ · Pa ⁻¹ ] at a reference temperature (for example, 25 ° C.) is obtained based on the following formulas (1) and (2). Can do.
L _p = Q _p / (K · A · P _e ) (1)
(However, K: temperature correction coefficient, A: membrane area of RO membrane module, P _e : effective pressure)
_{P e = P d - (ΔP} 1/2) -P 2 -Δπ + P s (2)
(Where P _d : discharge pressure of the pressure pump, ΔP ₁ : differential pressure on the primary side of the RO membrane module, P ₂ : back pressure on the secondary side of the RO membrane module, Δπ: osmotic pressure difference of the RO membrane module, P _s : pressure on the suction side of the pressure pump)

In equation (1), the temperature correction coefficient K is a function of the detected temperature value T, and becomes 1 when the detected temperature value T is equal to the reference temperature. Since the membrane area A is determined by the number of reverse osmosis membrane elements used, a preset value can be used. In the calculation of the effective pressure P _e according to equation (2), the values of ΔP _{1, P 2, Δπ,} and P _s, is operating steadily, because that regarded as substantially constant, the use of a preset value Can do. Therefore, if at least three parameters including the detected temperature value T of the temperature sensor 8, the detected flow value Q _p of the flow sensor 10, and the detected pressure value P _d of the pressure sensor 9 are acquired during operation of the RO membrane module, it can be calculated water permeability coefficient L _p at the reference temperature.

Next, the unit controller 102 will be described.
The unit controller 102 has a function as operation control means. Hereinafter, the unit control unit 102 that functions as an operation control unit is also referred to as a “unit control unit (operation control unit) 102”.

  The unit control unit (operation control means) 102 operates preferentially according to the priority set by the function of the priority setting means according to the water level of the water level sensor 3 provided in the treated water tank 2. An operation command signal is output to. The unit control unit (operation control means) 102 of the present embodiment outputs a current value signal (described later) as an operation command signal to the inverter 7 of the membrane separator that operates with priority.

  The unit control unit (operation control means) 102 stops all the membrane separation devices U1 to U4 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 during the fresh water generation operation. 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.

  When the water level value W detected by 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), the unit control unit (operation control means) 102 is a membrane separation device. Set the number of operating units to one. Then, the unit control unit (operation control means) 102 refers to the data related to the priority order stored in the memory, and selects a membrane separation apparatus having a higher priority order for the set number of operations (one). Furthermore, the unit controller (operation control means) 102 outputs a current value signal as an operation command signal to the inverter 7 of the selected membrane separation apparatus (hereinafter the same).

  The unit control unit (operation control means) 102 can specify the priority order of the membrane separation devices U1 to U4 by referring to the data related to the priority order stored in the memory.

  When the water level value W detected by 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 unit controller (operation control means) 102 operates the membrane separation device. Set the number to 2. Then, the unit controller (operation control means) 102 refers to the data relating to the priority order stored in the memory, and selects a membrane separation apparatus having a higher priority order for the set number of operating units (two).

  When the water level value W detected by the water level sensor 3 is lower than the water level D2 and is equal to or higher than the water level D1 (D2> W ≧ D1), the unit control unit (operation control means) 102 operates the membrane separation device. Set the number to 3. Then, the unit controller (operation control means) 102 refers to the data relating to the priority order stored in the memory, and selects a membrane separation apparatus having a higher priority order for the set number of operations (three).

  The unit control unit (operation control means) 102 is configured to detect the water level value detected by the water level sensor 3 when the water level value W detected by the water level sensor 3 is lower than the water level D1 and is equal to or higher than the water level L (D1> W ≧ L). When W is less than the water level L (L <W), the number of operating membrane separators is set to four. In this case, since all the membrane separation devices U1 to U4 are the targets of the fresh water generation operation, the unit control unit (operation control means) 102 does not select a high-priority membrane separation device.

  In addition, the unit control unit (operation control means) 102 adds a velocity type digital PID algorithm so that the detected flow rate value of the flow rate sensor 10 becomes a preset target flow rate value (described later) during the fresh water generation operation. A flow rate feedback water amount control is performed in which a drive frequency for driving the pressure pump 6 is calculated and a current value signal corresponding to the calculated value of the drive frequency is output to the inverter 7. That is, the unit control unit (operation control means) 102 adjusts the rotation speed of the pressurizing pump 6 so that the permeated water W2 having a rated flow rate is produced in the membrane separation device that is the target of the water production operation. The flow rate feedback water amount control by the unit control unit (operation control means) 102 will be described later.

  Further, the unit control unit (operation control means) 102 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 8 during the fresh water generation operation. As will be described later, the unit controller (operation control means) 102 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 in the membrane separation apparatus that is the target of the fresh water generation operation. The temperature feedforward recovery rate control by the unit control unit (operation control means) 102 will be described later.

  Next, the configuration of the membrane separation devices U1 to U4 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, a membrane separation device U1 according to this embodiment includes a pressurizing pump 6, an inverter 7, a temperature sensor 8, a pressure sensor 9, a RO membrane module M1, and a flow rate as a flow rate detection means. A sensor 10, a first drain valve 11 to a third drain valve 13, and a concentrated water reflux valve 14 are provided.

  A supply water line L1 and a permeate water line L2 are connected to the membrane separation device U1. The membrane separation device U1 includes a concentrated water line L3, a concentrated water discharge line L4, and a concentrated water reflux line L5.

  In FIG. 3, the pressurizing pump 6 is a device that sucks the supply water W1 and discharges it toward the RO membrane module M1. The pressure pump 6 is electrically connected to an inverter 7 (described later). The driving power whose frequency is converted is input from the inverter 7 to the pressurizing pump 6. The pressurizing pump 6 is driven at a rotational speed corresponding to the frequency of the supplied drive power (hereinafter also referred to as “drive frequency”). The rotational speed of the pressurizing pump 6 is proportional to the drive frequency supplied from the inverter 7. That is, the rotation speed of the pressurizing pump 6 becomes slower as the driving frequency supplied from the inverter 7 becomes lower, and becomes faster as the driving frequency becomes higher.

  The inverter 7 is an electric circuit that supplies driving power whose frequency has been converted to the pressurizing pump 6. The inverter 7 is electrically connected to the control unit 100. A current value signal is input to the inverter 7 from the unit controller 102. The inverter 7 outputs driving power having a driving frequency corresponding to the current value signal input from the unit control unit 102 to the pressurizing pump 6.

  The temperature sensor 8 is a device that detects the temperature of the supply water W1. The temperature sensor 8 is connected to the supply water line L1 at the connection portion J4. The connecting portion J4 is disposed between the supply source of the supply water W1 and the pressurizing pump 6. The temperature sensor 8 is electrically connected to the control unit 100. The temperature of the supply water W1 detected by the temperature sensor 8 (hereinafter also referred to as “detected temperature value”) is transmitted to the control unit 100 as a detection value signal.

  The pressure sensor 9 is a device that detects the pressure of the supply water W <b> 1 flowing through the supply water line L <b> 1 on the downstream side of the pressurization pump 6. The pressure sensor 9 is connected to the supply water line L1 at the connection portion J5. The connecting part J5 is disposed between the pressurizing pump 6 and the RO membrane module M1. The pressure sensor 9 is electrically connected to the control unit 100. The pressure of the supply water W1 detected by the pressure sensor 9 (hereinafter also referred to as “detected pressure value”) is transmitted to the control unit 100 as a detection signal.

  The RO membrane module M1 is a facility for subjecting the supply water W1 discharged from the pressurizing pump 6 to membrane separation treatment into permeated water W2 from which dissolved salts are removed and concentrated water W3 from which dissolved salts are 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 flow rate sensor 10 is a device that detects the flow rate of the permeated water W2 flowing through the permeated water line L2. The flow sensor 10 is connected to the permeated water line L2 at the connection portion J6. The connection part J6 is arrange | positioned between RO membrane module M1 and a demand location (not shown). The flow sensor 10 is electrically connected to the control unit 100. The flow rate of the permeated water W2 detected by the flow rate sensor 10 (hereinafter also referred to as “detected flow rate value”) is transmitted to the control unit 100 as a detection value signal.

  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 J7.

  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 J8 and J9.

  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 unit controller 102.

  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 6 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 J7. The branch part J7 is disposed between the primary outlet port of the RO membrane module M1 and the branch part J8. The downstream end of the concentrated water recirculation line L5 is connected to the supply water line L1 at the connection J3. The connecting portion J3 is disposed between the supply source (not shown) of the supply water W1 and the pressurizing pump 6.

  The concentrated water reflux valve 14 is a device that adjusts the flow rate of the concentrated water reflux line L5. The concentrated water reflux valve 14 is electrically connected to the control unit 100. The opening degree of the valve body in the concentrated water recirculation valve 14 is controlled by a drive signal from the unit controller 102. The valve body of the concentrated water recirculation valve 14 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 14 is controlled to a closed state (opening degree 0%) when the RO membrane module M1 is flushed.

  Next, the operation | movement at the time of fresh water generation operation in the water treatment system 1 is demonstrated, referring the flowchart shown in FIGS.

  First, the operation when the control unit 100 sets the priority order of the membrane separation apparatus by the function of the system control unit (priority setting means) 101 will be described.

  FIG. 4 is a flowchart showing a processing procedure when the system controller (priority setting means) 101 sets the priority of the membrane separation apparatus. The process of the flowchart shown in FIG. 4 is repeatedly executed during operation of the water treatment system 1. The system control unit (priority setting means) 101 executes the processing of the flowchart shown in FIG. 4 based on the priority setting processing program read from the memory.

In step ST < _b > 101 shown in FIG. 4, the system control unit (priority setting means) 101 acquires the detected residual chlorine concentration value Rd measured by the residual chlorine concentration sensor 5.

In step ST 102, the system control unit (priority setting means) 101 determines whether the detected residual chlorine concentration value R _d is preset allowable residual chlorine concentration value R _a above. If detecting residual chlorine concentration value R _d is allowable residual chlorine concentration value R _a above, residual chlorine in the feed water W1 it can be determined to be leaking. In this step ST102 transition, the system control unit (priority setting means) 101, if it is determined that the detected residual chlorine concentration value _{R d} ≧ allowable residual chlorine concentration value _{R a} (YES), the processing to step ST103 To do. Further, in step ST 102, the system control unit (priority setting means) 101, if it is determined that the detected residual chlorine concentration value _{R d} <allowable residual chlorine concentration value _{R a} (NO), the processing to step ST105 Transition.

  In step ST103 (step ST102: YES), the system control unit (priority setting means) 101 acquires the water permeability coefficient calculated for the membrane separation devices U1 to U4.

  In step ST104, the system control unit (priority setting means) 101 determines that the water permeability coefficient calculated for the obtained membrane separation devices U1 to U4 is higher than a preset initial value and the calculated water permeability coefficient value. The membrane separation apparatus having a larger RO membrane module is set to have a higher priority. Thereby, the process of this flowchart is complete | finished (it returns to step ST101).

On the other hand, Step ST105: In (step ST 102 NO), the system control unit (priority setting means) 101 obtains the detected turbidity value _{D d} measured by the turbidity sensor 4.

In step ST 106, the system control unit (priority setting means) 101 determines whether the acquired detected turbidity value D _d is preset allowable turbidity value D _a or more. Here, if the detected turbidity value D _d is equal to or greater than the allowable turbidity value D _a, it can be determined that the suspended substance is leaking into the supply water W1. If the system control unit (priority setting means) 101 determines in this step ST106 that the detected turbidity value D _d ≧ allowable turbidity value D _a (YES), the process proceeds to step ST107. Further, in step ST 106, the system control unit (priority setting means) 101, if it is determined that the detected turbidity value _{D d} <allowable turbidity value _{D a} (NO), the process proceeds to step ST109 .

  In step ST107 (step ST106: YES), the system control unit (priority setting means) 101 acquires the water permeability coefficient calculated for the membrane separation devices U1 to U4. The water permeability coefficient is calculated by the system control unit (water permeability coefficient calculating means) 101 and stored in a memory (not shown) at every predetermined sampling period.

  In step ST108, the system control unit (priority setting means) 101 has a water permeation coefficient calculated for the membrane separation devices U1 to U4 lower than a preset initial value and a small numerical value for the calculated water permeation coefficient. It sets so that a priority may become high, so that the membrane separator which has RO membrane module. Thereby, the process of this flowchart is complete | finished (it returns to step ST101).

  On the other hand, in step ST109 (step ST106: NO), the system control unit (priority setting means) 101 refers to the data related to the priority stored in the memory, and whether or not the priority is changed from the initial setting value. Determine whether. In step ST109, if the system control unit (priority setting means) 101 determines that the priority has been changed from the initial setting value (YES), the process proceeds to step ST110.

  In step ST109, when the system control unit (priority setting means) 101 determines that the priority has not been changed from the initial setting value (NO), the processing of this flowchart ends (step ST101). To return).

Detection residual chlorine concentration values R _d and detected turbidity value D _d of the supply water W1 is, if any less than the allowable value, if priority has not been changed from the initial setting value, normal quality of feed water W1 is It can be considered that it remains in the same state. For this reason, when it determines with NO by step ST109, the process of this flowchart is complete | finished, without returning a priority to the initial setting value at the time of normal water quality.

On the other hand, in step ST110 (step ST109: YES), the system control unit (priority setting means) 101 sets the data related to the priority stored in the memory to the initial setting value. Detection residual chlorine concentration values R _d and detected turbidity value D _d of the supply water W1 is, if any less than the allowable value, if the priority is changed from the initial setting value, normal quality of feed water W1 is Can be regarded as having returned to a normal state. For this reason, in step ST110, after the priority changed when the water quality is abnormal is returned to the initial setting value when the water quality is normal, the process of this flowchart ends (returns to step ST101).

  Next, the operation in the case where the number (number of operating units) of the membrane separation devices to be subjected to the water freshening operation is set in the unit control unit (operation control means) 102 will be described.

  FIG. 5 is a flowchart showing a processing procedure in the case where the unit controller (operation control means) 102 sets the number of operating membrane separation apparatuses. The process of the flowchart shown in FIG. 5 is repeatedly executed during operation of the water treatment system 1. The unit control unit (operation control means) 102 executes the process of the flowchart shown in FIG. 5 based on the number setting process program read from the memory.

  In step ST201 shown in FIG. 5, the unit controller (operation control means) 102 acquires the detected water level value W detected by the water level sensor 3.

  In step ST202, the unit controller (operation control means) 102 determines whether or not the acquired detected water level value W is equal to or higher than the reference water level value H (W ≧ H). In step ST202, when the unit control unit (operation control means) 102 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 unit control unit (operation control means) 102 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 unit controller (operation control means) 102 refers to the data relating to the number determination stored in the memory (see FIG. 2), and the detected water level value W becomes the reference water level value H. In the case of the above (W ≧ H), the number of operating membrane separation devices is determined to be zero. The unit control unit (operation control means) 102 stores the determined number of operation of the membrane separator in a memory (not shown) (hereinafter the same). Thereby, the process of this flowchart is complete | finished (it returns to step ST201).

  In step ST204 (step ST202: NO), the unit controller (operation control means) 102 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 whether. In step ST204, when the unit control unit (operation control means) 102 determines that the detected water level value W is less than the reference water level value H and equal to or higher than the water level D3 (YES), the process proceeds to step ST205. On the other hand, when the unit control unit (operation control means) 102 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 unit control unit (operation control means) 102 refers to the data relating to the number determination stored in the memory (see FIG. 2), and the detected water level value W becomes the reference water level value H. When the water level is less than the water level D3 or higher (H> W ≧ D3), the number of operating membrane separation devices is determined to be one. Thereby, the process of this flowchart is complete | finished (it returns to step ST201).

  In step ST206 (step ST204: NO), the unit controller (operation control means) 102 determines whether or not the detected water level value W of the water level sensor 3 is less than the water level D3 and not less than the water level D2 (D3> W ≧ D2). judge. In step ST206, when the unit control unit (operation control means) 102 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 unit controller (operation control means) 102 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 unit controller (operation control means) 102 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 water level D3 and When the water level is equal to or higher than D2 (D3> W ≧ D2), the number of operating membrane separation apparatuses is determined to be two. Thereby, the process of this flowchart is complete | finished (it returns to step ST201).

  In step ST208 (step ST206: NO), the unit controller (operation control means) 102 determines whether or not the detected water level value W of the water level sensor 3 is less than the water level D2 and not less than the water level D1 (D2> W ≧ D1). judge. In step ST208, when the unit control unit (operation control means) 102 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, when the unit control unit (operation control means) 102 determines in step ST208 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 unit controller (operation control means) 102 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 water level D2 and When the water level is equal to or higher than D1 (D2> W ≧ D1), the number of operating membrane separation apparatuses is determined to be three. Thereby, the process of this flowchart is complete | finished (it returns to step ST201).

  On the other hand, in step ST210 (step ST208: NO), the unit controller (operation control means) 102 refers to the data relating to the number determination stored in the memory (see FIG. 2), and the detected water level value W is the water level D1. If it is less than (D1> W ≧ L or L <W), it is determined that the number of operating membrane separation devices to be subjected to the water production operation is four. Thereby, the process of this flowchart is complete | finished (it returns to step ST201).

  Next, the operation in the case where the membrane separation apparatus is operated in the fresh water generation according to the priority of the fresh water generation operation in the unit control unit (operation control means) 102 will be described.

  FIG. 6 is a flowchart showing a processing procedure in the case where the membrane separation apparatus is subjected to a fresh water generation operation according to the priority of the fresh water generation operation in the unit control unit (operation control means) 102. The process of the flowchart shown in FIG. 6 is executed when the number of operating membrane separation apparatuses is changed in the process of the flowchart shown in FIG.

  In step ST301 shown in FIG. 6, the unit controller (operation control means) 102 acquires the number of operating membrane separation apparatuses from a memory (not shown).

  In step ST302, the unit control unit (operation control means) 102 refers to the data relating to the priority order stored in the memory, and selects a membrane separation apparatus having a higher priority order for the obtained number of operating units.

  In step ST303, the unit controller (operation control means) 102 outputs a current value signal as an operation command signal to the inverter 7 of the membrane separator that operates with priority. Thereby, the process of this flowchart is complete | finished. The output of the current value signal as the operation command signal is executed in the flow rate feedback water amount control described later.

  Next, flow rate feedback water amount control by the unit control unit (operation control means) 102 will be described with reference to FIG. FIG. 7 is a flowchart showing a processing procedure when the unit control unit (operation control means) 102 executes flow rate feedback water amount control. The process of the flowchart shown in FIG. 7 is repeatedly executed during the fresh water generation operation in the membrane separation apparatus that is the target of the fresh water generation operation.

In step ST401 shown in FIG. 7, the unit controller (operation control means) 102 acquires the target flow rate value Q _p ′ of the permeated water W2. This target flow rate value Q _p ′ is, for example, a value input by the system administrator to the memory via a user interface (not shown).

  In step ST402, the unit controller (operation control means) 102 determines whether or not the time t measured by the ITU has reached 100 ms, which is the control cycle (Δt). In step ST402, when the unit control unit (operation control unit) 102 determines that the time measured by the ITU has reached 100 ms (YES), the process proceeds to step ST403. In step ST402, when the unit controller (operation control means) 102 determines that the time measured by the ITU has not reached 100 ms (NO), the process returns to step ST402.

Step ST 403: In (step ST 402 YES determination), the unit control section (operation control means) 102, the detected flow value _{Q p} of the detected permeate W2 at a flow rate sensor 10, and acquires as a feedback value.

In step ST 404, the unit control section (operation control means) 102, and the detected flow value _{Q p} obtained in step ST 403, so that the deviation between the target flow rate value _{Q p} 'obtained in step ST401 becomes zero, velocity type calculating a manipulated variable _{U n} by digital PID algorithm. In the velocity type digital PID algorithm, the control period Delta] t (100 ms) calculates a variation .DELTA.U _n of the manipulated variables for each, which operate at the present time by adding the operation amount U _n-1 of the previous control cycle time The quantity _Un is determined.

In step ST405, the unit controller (operation control means) 102 determines the operation of the pressurization pump 6 based on the current operation amount U _n and the maximum drive frequency F ′ of the pressurization pump 6 (set value of 50 Hz or 60 Hz). The drive frequency F [Hz] is calculated.

  In step ST406, the unit controller (operation control means) 102 converts the calculated value of the drive frequency F into a corresponding current value signal (4 to 20 mA).

  In step ST407, unit control section (operation control means) 102 outputs the converted current value signal to inverter 7. Thereby, the process of this flowchart is complete | finished (it returns to step ST401).

  In step ST407, when the unit controller (operation control means) 102 outputs a current value signal to the inverter 7, the inverter 7 pressurizes the driving power converted to the frequency specified by the input current value signal. Supply to pump 6. As a result, the pressurizing pump 6 is driven at a rotational speed corresponding to the driving frequency input from the inverter 7.

  Next, temperature feedforward recovery rate control by the unit control unit (operation control means) 102 will be described with reference to FIG. FIG. 8 is a flowchart showing a processing procedure in the case where the unit control section (operation control means) 102 executes the temperature feedforward recovery rate control. This temperature feedforward recovery rate control is executed in parallel with the above-described flow rate feedback water amount control during the fresh water generation operation of the membrane separation apparatus.

In step ST501 shown in FIG. 8, the unit controller (operation control means) 102 acquires the target flow rate value Q _p ′ of the permeated water W2. This target flow rate value Q _p ′ is, for example, a value input by the system administrator to the memory via a user interface (not shown).

In step ST502, the unit controller (operation control means) 102 acquires the silica (SiO ₂ ) concentration C _s of the supply water W1. The silica concentration C _s is a set value that is input to the memory by the apparatus 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 ST503, the unit controller (operation control means) 102 acquires the detected temperature value T of the feed water W1 from the temperature sensor 8.

In step ST504, the unit controller (operation control means) 102 determines the silica solubility S _s with respect to water based on the acquired detected temperature value T.

In step ST505, the unit controller (operation control means) 102 calculates the allowable concentration rate N _s of silica in the concentrated water W3 based on the silica concentration C _s and the silica solubility S _s acquired or determined in the previous step. . Permissible concentration rate N _s of silica can be obtained by the following equation (3).
N _s = S _s / C _s (3)

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

In step ST 506, the unit control section (operation control means) 102, based on the target flow rate value Q _{p 'and} permissible concentration rate N _s obtained in the previous step, the recovery rate is maximum drainage flow rate (target wastewater flow rate Q _d ′) is calculated. The target drainage flow rate Q _d ′ (hereinafter also referred to as “first drainage flow rate value”) can be obtained by the following equation (4).
Q _d ′ = Q _p ′ / (N _s −1) (4)

In step ST 507, the unit control section (operation control means) 102, the actual drainage flow _{Q d} is such that the first drainage flow rate value calculated in step ST 506, 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 ST501).

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

  In the water treatment system 1 according to the present embodiment, the system control unit (priority setting means) 101 performs RO based on the water permeability coefficient calculated for each membrane separation device when the water quality of the supply water W1 is abnormal. The progress of the change in the water permeability of the membrane module is compared, and the membrane separator having the RO membrane module with the higher progress is set so that the priority for operating the membrane separator is higher.

  Further, the unit control unit (operation control means) 102 is a membrane that operates with priority according to the priority set by the function of the priority setting means according to the water level of the water level sensor 3 provided in the treated water tank 2. An operation command signal (current value signal) is output to the separation device.

  Therefore, when trouble occurs in the pretreatment device provided on the upstream side of the membrane separation device and the water quality of the supply water W1 supplied to the membrane separation device becomes abnormal, the RO membrane module having high membrane performance is provided. The membrane separator is rarely operated preferentially, and the membrane separator having an RO membrane module with a large degree of change in water permeability performance is preferentially operated. According to this, not only the deterioration of the RO membrane module with high membrane performance is suppressed, but also the membrane performance of all RO membranes is suppressed from being deteriorated uniformly. Therefore, according to the water treatment system 1, the cleaning and replacement of the RO membrane module does not reach the entire system, and the maintenance cost can be reduced.

  Further, the system control unit (priority setting means) 101 calculates each membrane separation device when the detected residual chlorine concentration value measured by the residual chlorine concentration sensor 5 exceeds a preset allowable residual chlorine concentration value. A membrane separation apparatus having an RO membrane module that has a higher water permeability coefficient than the preset initial value and a larger value of the calculated water permeability coefficient is set to have a higher priority.

  It is considered that the RO membrane module in which the above-described water permeability coefficient is higher than the initial value and the calculated value of the water permeability coefficient is relatively large is undergoing oxidative degradation of the RO membrane. Therefore, when the detected residual chlorine concentration value of the supply water W1 exceeds the allowable residual chlorine concentration value, the water treatment system 1 is set by setting the priority of the RO membrane module having a large value of the water permeability coefficient to be higher. , The further deterioration of the RO membrane module having a small water permeability coefficient (where the RO membrane oxidation degradation has not progressed much) can be suppressed as much as possible.

  The system control unit (priority setting means) 101 also calculates the water calculated for each membrane separation device when the detected turbidity value measured by the turbidity sensor 4 exceeds a preset allowable turbidity value. A membrane separation apparatus having an RO membrane module having a permeability coefficient lower than a preset initial value and a smaller value of the calculated water permeability coefficient is set to have a higher priority.

  The RO membrane module in which the water permeability coefficient described above is lower than the initial value and the calculated value of the water permeability coefficient is relatively small is considered that the RO membrane is clogged. Therefore, when the detected turbidity value of the supply water W1 exceeds the allowable turbidity value, in the water treatment system 1, by setting the priority of the RO membrane module with a small value of the water permeability coefficient, Further blockage of the RO membrane module having a large water permeability coefficient (the RO membrane blockage has not progressed much) can be suppressed as much as possible.

  Further, the unit control unit (operation control means) 102 drives the pressure pump 6 so that the detected flow rate value of the flow rate sensor 10 becomes a preset target flow rate value during the fresh water generation operation of the membrane separation device. A flow rate feedback water amount control is performed in which a driving frequency for calculating the driving frequency is calculated and a current value signal corresponding to the calculation location of the driving frequency is output to the inverter 7. Therefore, the water treatment system 1 can supply the permeated water W2 having a stable flow rate to the customer regardless of the change in the water permeation performance of the RO membrane module while the membrane separator is in the fresh water generation operation.

  The unit control unit (operation control means) 102 controls the temperature feedforward recovery rate of the permeated water W2 based on the temperature of the supply water W1 detected by the temperature sensor 8 during the fresh water generation operation of the membrane separator. Execute. Therefore, it is possible to more reliably suppress the precipitation of the silica-based scale in the RO membrane module while maximizing the recovery rate of the permeated water W2 during the fresh water generation operation of the membrane separation apparatus.

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

  For example, the water treatment system 1 according to the present embodiment includes four membrane separation devices U1 to U4. Not only this but the membrane separation apparatus of the water treatment system 1 should just be at least 2 units | sets. Moreover, it is good also as a structure which provided the membrane separation apparatus of the water treatment system 1 5 or more units | sets.

  In the water treatment system 1 according to this embodiment, five levels of water level H, water level D3, water level D2, water level D1, and water level L are set as water levels for determining the amount of water stored in the treated water tank 2. 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 water treatment system 1 according to the present embodiment, each of the membrane separation devices U1 to U4 includes one RO membrane module M1. Not only this but in the water treatment system 1, the structure provided with the some RO membrane module may be sufficient as the membrane separation apparatuses U1-U4, respectively.

  In the water treatment system 1 according to the present embodiment, the control unit 100 includes a system control unit 101 and a unit control unit 102. Not limited to this, a unit control unit 102 is provided for each membrane separation device, and various data, instruction signals, etc. are output from the system control unit 101 of the control unit 100 to the unit control unit 102 of each membrane separation device. May be.

  In the water treatment system 1 according to the present embodiment, the amount of permeated water W2 consumed at the demand point is detected by a water level sensor 3 provided in the treated water tank 2. Not only this but in the water treatment system 1, you may comprise so that the amount of permeated water W2 consumed at a demand location may be detected with the flow sensor provided in the water distribution line L6.

  In the water treatment system 1 according to the present embodiment, the initial setting value of the priority order is set as a fixed value. However, the present invention is not limited to this, and the initial setting value of the priority order may be used as the fluctuation value. For example, the priority when the water quality is normal is “U1> U2> U3> U4”, “U2> U3> U4> U1”, “U3> U4> U1> U2”, “U4> U1> U2> U3”. It may be changed while rotating in order. The priority rotation may be performed when a preset rotation execution time has elapsed or may be performed every time the flushing operation is completed in all the membrane separation apparatuses.

  When the initial priority setting value is a fixed value, the high priority RO membrane module inevitably has a higher frequency of fresh water operation when the water quality is normal. Therefore, in the RO module with a high priority, even when the water quality is normal, the RO membrane is relatively easily oxidized and clogged. As a result, even if the priority is changed based on the water permeability coefficient when the water quality is abnormal, the priority may not change as a result. In this case, deterioration of the RO membrane module having high membrane performance is further promoted. However, deterioration of the RO membrane module with high membrane performance can be more effectively suppressed by changing the initial setting value of the priority order to a variable value and changing it periodically.

  In addition, when the initial setting value of the priority order is set as the fluctuation value, the rotation order may be set in advance as described above, or the RO membrane module in which the oxidation deterioration or blockage of the RO membrane has not progressed. It may be set so that the priority order is always higher.

  In the water treatment system 1 according to the present embodiment, the example in which the driving frequency of the pressurizing pump 6 is calculated by the speed type digital PID algorithm has been described. Not limited to this, the driving frequency of the pressurizing pump 6 may be calculated by a position type digital PID algorithm.

  In the water treatment system 1 according to 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 water treatment system 1 according to the present embodiment, in the recovery rate control, 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. Explained. 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 is adjusted by transmitting a current value signal (for example, 4 to 20 mA) from the unit control unit (operation control means) 102 to the proportional control valve to control the valve opening. be able to.

  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 to the unit control unit (operation control means) 102 as a feedback value. Thereby, the actual waste water flow rate of the concentrated water W3 can be controlled more accurately.

1 Water Treatment System 2 Treated Water Tank 4 Turbidity Sensor (Water Quality Item Measuring Means)
5 Residual chlorine concentration sensor (water quality item measurement means)
6 Pressure pump 7 Inverter 8 Temperature sensor 9 Pressure sensor 10 Flow rate sensor (Flow rate detection means)
100 control unit 101 system control unit (water permeability coefficient calculating means, priority order setting means)
102 Unit control unit (operation control means)
M1 RO membrane module (reverse osmosis membrane module)
U1-U4 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 Distribution line W1 Supply water W2 Permeated water W3 Concentrated water W4 Treated water

Claims (4)

A plurality of membrane separation devices including a reverse osmosis membrane module for producing permeated water from supply water, and transmitting permeated water in response to an input operation command signal;
Water permeability coefficient calculating means for calculating a water permeability coefficient of the reverse osmosis membrane module for each of the membrane separators based on a physical quantity measured in the system;
Water quality item measuring means for measuring the water quality item of the supply water;
When the measured water quality of the water quality item measuring means exceeds a preset allowable water quality, based on the water permeability coefficient calculated for each of the membrane separation devices, the calculated value of the water permeability coefficient is preset. in the case where the difference between the initial value of the water permeability coefficient and the degree of progress of the water permeability variation, comparing the progress of the water permeability variation of the reverse osmosis membrane module, the reverse osmosis membrane module the progress is greater Priority setting means for setting so that the priority for operating the membrane separation device becomes higher as the membrane separation device has
In accordance with the amount of permeated water consumed at the demand point, according to the priority set by the priority setting means, an operation control means for outputting an operation command signal to the membrane separator that operates preferentially;
A water treatment system comprising. The water quality item measuring means comprises a configuration for measuring a water quality item relating to a causative substance of chemical degradation of the reverse osmosis membrane module as a water quality item of feed water,
The priority order setting means is configured such that the calculated water permeability coefficient is preset when the measured water quality of the feed water exceeds a preset allowable water quality at which chemical degradation of the reverse osmosis membrane module is suppressed. Set so that the higher the priority, the higher the membrane separation device having the reverse osmosis membrane module, which is higher than the initial value and the value of the water permeability coefficient is large.
The water treatment system according to claim 1. The water quality item measuring means comprises a configuration for measuring a water quality item related to a causative substance of fouling of the reverse osmosis membrane module as a water quality item of supply water,
The priority order setting means is configured such that when the measured water quality of the supplied water exceeds a preset allowable water quality in which fouling of the reverse osmosis membrane module is suppressed, the calculated water permeability coefficient is set to a preset initial value. A lower priority value and a smaller value of the water permeation coefficient are set so that the higher the priority is, the higher the membrane separation device having the reverse osmosis membrane module,
The water treatment system according to claim 1. 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 operation control unit calculates a driving frequency of the pressurizing pump so that the detected flow rate value output from the flow rate detecting unit becomes a preset target flow rate, and a current corresponding to the calculated value of the driving frequency. Outputting a value signal to the inverter;
The water treatment system as described in any one of Claims 1-3.

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