JP6781313B2 - Water purification system control method and water purification system - Google Patents

Description

The present invention relates to a control method of a water purification system and a water purification system.

Conventionally, in various water purification systems, a membrane filtration device that membrane-filters the water to be treated to obtain treated water has been adopted. Then, the water purification system performs various treatments on the treated water obtained from the membrane filtration device, if necessary, and supplies the purified water.
Since the filtration membrane of the membrane filtration device is clogged with impurities to be filtered as it is used, physical cleaning may be performed regularly in order to eliminate the clogging and regenerate the filtration function of the filtration membrane. is necessary. Here, the membrane filtration device cannot perform filtration during physical cleaning. Therefore, at the time of physical cleaning of the membrane filtration device, the water purification system is stopped, or a plurality of membrane filtration devices are adopted in the water purification system so that the physical cleaning is performed at different timings. As a water purification system, a configuration has been adopted that enables continuous operation even during physical cleaning.

As described above, a technique has been proposed for coping with the change that the membrane filtration apparatus needs to be physically cleaned during the operation of the water purification system including the plurality of membrane filtration apparatus. Here, the changes that the water purification system can be exposed to are not limited to the physical cleaning of the membrane filtration device. For example, it was necessary for the water purification system to cope with the failure of the membrane filtration device, the periodic inspection, and the fluctuation of the water quality of the water to be treated and the required amount of purified water.

Therefore, conventionally, as a water purification system, in a filtration device in which a plurality of membrane filtration devices are arranged in parallel, a method of controlling the number of operating membrane filtration devices according to the temperature and quality of the water to be treated, and further the water quality of the treated water. Has been proposed (see, for example, Patent Document 1). According to the method described in Patent Document 1, the quality of the treated water can be maintained at a high quality and the fluctuation of the amount of the treated water can be suppressed regardless of the temperature change of the treated water and the change of the membrane performance of the membrane filtration device. it can.

In addition, a water purification method for dealing with a failure of the membrane filtration device in use has also been proposed (see, for example, Patent Document 2). The water purification method described in Patent Document 2 is carried out in a water purification system in which a plurality of membrane filtration devices including a spare portion are connected in parallel. As a specific operation method, the membrane filtration device excluding the spare portion is operated under normal conditions, and when any membrane filtration device is damaged, the operation of the membrane filtration device is stopped to perform the preliminary membrane filtration. The device was operated to secure the amount of treated water. According to such an operation method, even if the membrane filtration device is damaged, the quality of the treated water can be maintained and the decrease in the amount of treated water can be suppressed.

Japanese Unexamined Patent Publication No. 2001-239134 Japanese Unexamined Patent Publication No. 6-170365

Here, in a water purification plant or the like, it is important to stably obtain a predetermined amount of treated water for the entire system.

However, in the conventional system that only changes the number of operating units, it is not possible to quickly and stably supply the desired amount of water in the event of a failure or when the amount of treated water required for the entire system fluctuates. Specifically, since the conventional system did not control the amount of treated water of each membrane filtration device, the amount of treated water of each membrane filtration device in operation is also determined at the same time as the number of operating units when a failure or the required amount of treated water fluctuates. It was fluctuating, and it took time for the treated water volume to stabilize. In particular, in a water purification system that employs membrane filtration devices connected in parallel, fluctuations in the amount of treated water from one filtration device tend to affect other filtration devices, so it took a long time for the amount of treated water to stabilize. ..

Therefore, an object of the present invention made in view of such circumstances is to provide a water purification system and a control method for the water purification system, which can quickly and stably supply a desired amount of water when the operating conditions of the water purification system change. To do.

The control method of the water purification system according to the present invention that achieves the above object is to filter the water to be treated supplied from the front stage side of the membrane filtration device by a plurality of membrane filtration devices connected in parallel to each other. It is a control method of a water purification system that discharges purified water from the latter stage side, and the plurality of membrane filtration devices are treated water amounts determined by each set value of the minimum treated water amount and the maximum treated water amount in the operating state in which the membrane filtration operation is performed. It is set to operate within a range, and the required number of the membrane filtration devices required to obtain the total water purification amount based on the total water purification amount required for the water purification system and the treated water amount range of the membrane filtration device. A step of determining the required number of membrane filtration devices, and a comparison step of grasping the number of membrane filtration devices that can be operated among the plurality of membrane filtration devices and comparing the required number of membrane filtration devices with the number of operable membrane filtration devices. Based on the result of the comparison, when the number of the operable membrane filtration devices is equal to or greater than the required number, the required number of the membrane filtration devices is put into the operating state, and the operable number is the required number. When it is less than, it is characterized by including an operation step in which the operable number of the membrane filtration devices is put into the operating state and operated at the set value of the maximum treated water amount.
According to such a control method of the water purification system, when the operating conditions of the water purification system fluctuate, the desired amount of water can be supplied quickly and stably.

Further, in the control method of the water purification system according to the present invention, in the required number determination step, the number of membrane filtration devices in the operating state is grasped, and the total number of operating units is within the range of the treated water amount. Therefore, it is preferable to determine the number closest to the number of membrane filtration devices in the grasped operating state as the required number.
According to such a control method of the water purification system, as long as it is within the treated water amount range of the membrane filtration device, the operation of the water purification system is continued without changing the membrane filtration device from the operating state to another state. The responsiveness of the water purification system can be further improved.

Further, in the control method of the water purification system according to the present invention, in the required number determination step, the total amount of purified water is divided by a predetermined set value within the range of the treated water amount, and the integer portion of the obtained value is said to be necessary. It is preferable to determine the number of units.
According to such a control method of the water purification system, the membrane filtration device can be operated with a treated water amount close to a predetermined treated water amount, so that the responsiveness of the water purification system can be further improved.

Further, in the control method of the water purification system according to the present invention, when the operation of the membrane filtration device is stopped, the step of storing the amount of water flowing through the membrane filtration device and the operation of the stopped membrane filtration device are restarted. It is preferable to include a step of increasing the amount of water flow to the memorized amount of water flow in one step.
According to such a control method of the water purification system, it is possible to shorten the time until the target treated water amount can be stably obtained, and it is possible to further improve the control stability of the water purification system. ..

Further, in the control method of the water purification system according to the present invention, when the operable number is equal to or more than the required number, the total amount of purified water and the required number are required to put the membrane filtration device in the standby state into the operating state. The amount of water flow required to achieve the amount of treated water per membrane filtration device calculated based on the above is predicted, and the amount of water flow to the membrane filtration device in the standby state is increased to the predicted amount of water flow. It is preferable to increase in stages.
According to such a control method of the water purification system, it is possible to further shorten the time until the desired amount of treated water can be stably obtained, and further improve the control stability of the water purification system. it can.

Further, in the control method of the water purification system according to the present invention, when the operable number is less than the required number, the membrane filtration device of the operable number is set as the operating state, and the set value of the maximum treated water amount is used. When the operation of the membrane filtration device is controlled so as to operate, it is preferable to detect that the number of operable units has changed and to perform the comparison step and the operation step again.
According to such a control method of the water purification system, even when the total water purification amount suddenly increases, the desired total water purification amount can be quickly achieved.

Further, in the water purification system according to the present invention that achieves the above object, the water to be treated supplied from the front stage side of the membrane filtration device is filtered by a plurality of membrane filtration devices connected in parallel to each other. It is a water purification system that discharges purified water from the latter stage side, and the plurality of membrane filtration devices operate within the treated water amount range determined by each set value of the minimum treated water amount and the maximum treated water amount in the operating state in which the membrane filtration operation is performed. The water purification system includes a control unit that controls the operation of the plurality of membrane filtration devices, and the control unit includes the total amount of water purification required for the water purification system and the processing of the membrane filtration device. The required number of the membrane filtration devices required to obtain the total water purification amount is determined based on the water amount range, the number of membrane filtration devices that can be operated among the plurality of membrane filtration devices is grasped, and the required number of membrane filtration devices is grasped. And the number of operable membrane filtration devices are compared, and based on the result of the comparison, if the number of operational membrane filtration devices is equal to or greater than the required number, the required number of the membrane filtration devices When the number of operable units is less than the required number, the membrane filtration device of the number of operable units is set to the operating state and is operated at the set value of the maximum treated water amount. And.
According to such a control method of the water purification system, when the treated water amount of the water purification system fluctuates, the desired amount of water can be supplied quickly and stably.

According to the present invention, it is possible to provide a water purification system and a control method for such a water purification system, which can quickly and stably supply a desired amount of water when the treated water amount of the water purification system fluctuates.

It is a figure which shows the schematic structure of the water purification system by one Embodiment of this invention. It is a flowchart explaining the control method of the water purification system by one Embodiment of this invention. It is a flowchart for demonstrating the flowchart shown in FIG. 2 in more detail.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The control method of the water purification system according to the present invention can be implemented in the water purification system according to the present invention. In the water purification system according to the present invention, a plurality of membrane filtration devices connected in parallel to each other filter the water to be treated supplied from the front stage side of the membrane filtration device and discharge the treated water from the rear stage side of the membrane filtration device. It is a system. The water purification system and the control method of the water purification system according to the present invention are not particularly limited, and pollute the treated water in various water treatments such as clean water treatment, sewage treatment, industrial water treatment, wastewater treatment, and seawater desalination. It can be used to separate and remove substances and the like. In particular, the water purification system and the control method of the water purification system according to the present invention are suitable for clean water treatment in which a stable amount of treated water is required.
Further, the water purification system and the control method of the water purification system according to the present invention are not particularly limited, and can be used for filtering the water to be treated that has been pumped or sent by natural flow. In particular, the water purification system and the control method of the water purification system according to the present invention have a large interference between the membrane filtration devices connected in parallel and have a large effect when the treated water amount of the membrane filtration device is changed, and the water is sent by natural flow. It is suitable for a water purification system that filters the water to be treated.
Further, in a water purification system equipped with a membrane filtration device, a chemical injection facility or the like is provided on the front stage side or the rear stage side of the membrane filtration device, and the water to be treated is pretreated and / or treated by using the chemical injection facility or the like. Water is often post-treated, but according to the water purification system and the control method of the water purification system according to the present invention that can achieve a stable amount of treated water, these treatments using a chemical injection facility or the like can also be stabilized. it can.

(Water purification system)
FIG. 1 is a diagram showing a schematic configuration of a water purification system according to an embodiment of the present invention. The water purification system 10 includes a raw water tank 11, membrane filtration devices 12a to 12c connected in parallel to each other, a water purification tank 13, and a control unit 14. Further, the membrane filtration device 12a is provided with a water flow control means 121a on the front stage side on which the raw water, which is the water to be treated of the water purification system, enters the membrane filtration device 12a. Similarly, the membrane filtration devices 12b and 12c are provided with water flow control means 121b and 121c on the front stage side, respectively. In the water purification system 10, the treated water supplied from the raw water tank 11 to the membrane filtration devices 12a to 12c via the raw water pipe 15 is filtered, and the obtained treated water is supplied to the water purification tank 13 via the treated water pipe 16. To.
In FIG. 1, the water supply pressure is applied by the head difference between the raw head in the raw water tank 11 and the purified water head in the water purification tank 13. That is, in FIG. 1, the water purification system 10 is illustrated as a water purification system by natural flow.

<Membrane filtration device>
The membrane filtration devices 12a to 12c are in an operating state in which the membrane filtration operation is performed during the operation of the water purification system 10, a standby state in which the membrane filtration operation can be performed but the membrane filtration operation is not intentionally performed, and the membrane filtration. It is configured to be in either a regenerated state in which physical cleaning is performed to regenerate the performance, or an inoperable state in which the membrane filtration operation cannot be performed due to, for example, a failure. The membrane filtration device in the operating state and the standby state is an operable membrane filtration device, and the membrane filtration device in the regenerated state and the inoperable state is an inoperable membrane filtration device. As the filtration membrane of the membrane filtration apparatus, for example, a ceramic filtration membrane can be used. For clarity, only three membrane filtration devices 12a to 12c are shown in FIG. 1, but the water purification system 10 can be provided with three or more or two or less membrane filtration devices. In order to maintain the filtration performance, the membrane filtration devices 12a to 12c perform physical cleaning after a certain period of time from the time of operation or after the membrane differential pressure reaches a predetermined value to regenerate the membrane filtration performance. It will be in the playback state. Here, in the water purification system 10, an upper limit is set on the number of membrane filtration devices that can enter the regeneration state at the same time, and if the number of membrane filtration devices of the upper limit value is in the regeneration state, any of them. The other membrane filtration apparatus may not be newly entered into the regeneration state until the regeneration of the membrane filtration apparatus of the above is completed.

The water flow amount of the membrane filtration devices 12a to 12c is set so as to operate in the treated water amount range of not less than the set value of the minimum treated water amount and less than the set value of the maximum treated water amount. Here, the "set value of the maximum treated water amount" of the membrane filtration devices 12a to 12c is arbitrarily determined with the maximum value of the flow rate per hour (m ³ / h) specified in the specifications of the membrane filtration device as the upper limit. It is a value that can be. In principle, each set value is a common value for the plurality of membrane filtration devices 12a to 12c. Such a set value can be set so as to specify the treated water amount range in consideration of the responsiveness and characteristics of the control required for the water purification system 10, the installation situation and the installation purpose of the water purification system 10.
For example, the "set value of the maximum treated water amount" is a value equal to or less than the upper limit value of the flow rate (m ³ / h) per hour defined in the specifications of the membrane filtration devices 12a to 12c, and the water purification system 10 as a whole It can be obtained by dividing the desired total treated water amount of the above by the number of units normally assumed to be in the "operating state". On the other hand, the "minimum treated water amount set value" can be, for example, a value obtained by dividing the desired total treated water amount by the total number of membrane filtration devices 12a to 12c provided in the water purification system 10. ..
The closer the set values of the minimum treated water amount and the maximum treated water amount are, the less the fluctuation of the water amount treated by the membrane filtration devices 12a to 12c is, and even if the treated water amount is changed by control, the speed is increased. The control can be stabilized, but of course, the closer each set value is, the lower the flexibility of the water purification system is. Therefore, it is preferable to set each set value in consideration of these balances. In particular, the minimum amount of treated water is set to a value that at least does not cause cavitation when the water purification system 10 adopts a water supply method by natural flow and the water flow control means 121a to 121c are mounted as valves. Is preferable.

<Water flow control means>
The water flow control means 121a to 121c provided in the membrane filtration devices 12a to 12c can be, for example, a valve or a pump. In FIG. 1, as an example, the water flow control means 121a to 121c are shown as valves whose opening degree can be adjusted. The water flow control means 121a to 121c are arranged on the front stage side of the membrane filtration devices 12a to 12c, respectively, and control the water flow amount of the membrane filtration devices 12a to 12c. When the water flow control means 121a to 121c are valves, the amount of treated water obtained by the membrane filtration devices 12a to 12c can be adjusted or the membrane can be adjusted by setting various valve openings or opening and closing them. The operating state of the filtration devices 12a to 12c can be switched. Further, when the water flow control means 121a to 121c are pumps driven by an inverter, the amount of treated water obtained by the membrane filtration devices 12a to 12c by appropriately controlling the rotation speed of the pump or driving / stopping the pump. Or the operating state of the membrane filtration devices 12a to 12c can be switched.

<Control unit>
Further, the control unit 14 of the water purification system 10 is configured to grasp and control the operating state of the membrane filtration devices 12a to 12c, and to monitor and control the water flow control means 121a to 121c. Specifically, the control unit 14 grasps whether the operating state of the membrane filtration devices 12a to 12c is an operating state, a standby state, an inoperable state, or a regeneration state. Further, it is preferable that the control unit 14 monitors the valve opening degree and the treated water amount of the water flow control means 121a to 121c configured as a valve and stores them in a storage unit (not shown). The valve opening degree corresponds to the amount of water flowing through the membrane filtration devices 12a to 12c. The monitoring by the control unit 14 may be performed every time the valve opening degree of the water flow control means 121a to 121c configured as a valve is changed, or may be performed periodically during the operation of the water purification system 10. good. Further, when the control unit 14 switches a certain membrane filtration device from the operating state to another state, the valve opening and the treated water amount at the time when a predetermined time elapses after the switching and the membrane filtration device is stably operating. It is preferable to memorize the valve opening degree and the amount of treated water immediately before the transition from the operating state to the standby state, the inoperable state, or the regenerated state. In this way, for the membrane filtration device in the standby state, the inoperable state, or the regenerated state, by storing the valve opening and the treated water amount in the latest operating state, the water purification system 10 is controlled as described later. Controls can be implemented to improve the stability of the. The control unit 14 is mounted by, for example, a computer having an arithmetic function, and the storage unit (not shown) is mounted by, for example, a memory.
Hereinafter, the control method of the water purification system 10 by the control unit 14 will be described in more detail.

<Water purification system control method>
FIG. 2 is a flowchart illustrating a control method of a water purification system according to an embodiment of the present invention. First, the control unit performs a total water purification amount setting step (step S01) for setting the total water purification amount (m ³ / day), which is the amount of water purification to be supplied by the water purification system when controlling the operation of a plurality of membrane filtration devices. carry out. In step S01, for example, when the water purification system is a water purification system for water treatment, the control unit can set the required water amount as the total water purification amount.

Next, the control unit carries out a required number determination step (step S02) for determining the required number of membrane filtration devices based on the total amount of purified water set in step S01 and the treated water amount range of the membrane filtration device. Here, the required number of water purification systems is between a value obtained by dividing the total purified water amount by the set value of the maximum treated water amount and a value obtained by dividing the total purified water amount by the set value of the minimum treated water amount. Any number can be determined if it is an integer value, but it is preferable to adopt the following two determination methods.

First, as the first method of determining the required number of membrane filtration devices, the number of membrane filtration devices in the operating state is grasped, and the total amount of purified water can be obtained within the range of the treated water amount. There is a method of determining the number closest to the number of units as the required number. When the membrane filtration device is newly operated or stopped, interference (for example, fluctuation of water supply pressure to each membrane filtration device) occurs between the membrane filtration devices connected in parallel due to a sudden change in flow. As a result, if the number of membrane filtration devices that are currently in operation is the required number and the number of operating units is changed as little as possible, the membrane filtration devices will be connected in parallel by starting or stopping. It is possible to suppress fluctuations in the operating state due to interference between the membrane filtration devices and to operate the water purification system in a stable manner.

An example of this method is the method shown in FIG. Specifically, in carrying out step S02 while the water purification system 10 is already in operation, in step S02, the number of membrane filtration devices currently in operation (hereinafter, also referred to as "current operating number") is acquired. Then, the total water purification amount set in step S01 is divided by the acquired current operating number to calculate the treated water amount to be supplied per membrane filtration device currently operating in order to obtain the set total water purification amount. (Step S02-1A). Then, the control unit determines whether the treated water amount is within the treated water amount range of the membrane filtration device (S02-2A). Then, if the determination result in step S02-2A is "Yes", the control unit determines the current operating number as the required number (step S02-6A). On the other hand, when the determination result in step S02-2A is "No", the control unit determines whether or not the treated water amount is larger than the set value of the maximum treated water amount of the membrane filtration device (step S2-3A). .. If the determination result in step S2-3A is "No", the control unit divides the total amount of purified water by the (current operating number-n) unit (step S02-4A), and makes the determination again in step S02-2A. .. On the other hand, if the determination result in step S2-3A is "Yes", the control unit divides the total amount of purified water by the (current operating number + n) unit (step S02-5A), and determines again in step S02-2A. Do. Then, the control unit increases the number of n in step S02-4A or step S02-5A by 1, and repeats this until the determination result in step S02-2A becomes "Yes".

Further, in another example of this method, the current operating number is grasped, and the value obtained by dividing the total purified water amount by the set value of the maximum treated water amount and the total purified water amount are set by the set value of the minimum treated water amount. A step (step S02-1B, not shown) for obtaining an integer value between the value obtained by dividing (that is, the range of the number of units capable of supplying the total amount of purified water within the treated water amount range) is performed, and the integer value is calculated. The number closest to the current operating number can be determined as the required number (step S02-6A).

The second method for determining the required number of units is to divide the total amount of purified water by a predetermined set value within the treated water amount range, and determine the integer part of the obtained value or the integer closest to such a value as the required number of units. (Step S02-1C, not shown). For example, the "predetermined set value within the treated water amount range" may be the treated water amount having a small load on the membrane filtration device, which can be determined in consideration of the water quality of the water to be treated, the installation status of the water purification system, and the like. For example, the "predetermined set value within the treated water amount range" may be matched with the "minimum treated water amount set value". In this case, since the membrane filtration apparatus can be operated with as little treated water as possible, the load on the membrane filtration apparatus is low, which can contribute to extending the life of the membrane filtration apparatus. The required number of units determined by such a method is sent to the determination in step S03 described later. Alternatively, the "predetermined set value within the treated water amount range" may match the "treated water amount of the membrane filtration apparatus currently in operation". In this case, the fluctuation of the operating state of each membrane filtration device currently in operation can be minimized, and the water purification system can be operated stably. Further, the "predetermined set value within the treated water amount range" can be made to match the "intermediate value of the treated water amount range".

Of course, the first and second methods for determining the required number of units can be used in combination. For example, immediately after step S01, a step for determining an increase / decrease in the total water purification amount from the total water purification amount (previous set value) before the start of step S01 is further provided, and when the total water purification amount decreases, the step It may proceed to S02-1C, and in other cases, it may proceed to step S02-1A or step S02-1B.

Then, the control unit grasps the number of operable membrane filtration devices and determines whether the number of operable membrane filtration devices is equal to or greater than the required number determined in step S02 (step S03). Here, as the number of operable membrane filtration devices, the control unit is the total number of membrane filtration devices that are in the operating state and the standby state at that time, and the total number of the membrane filtration devices that have returned from the inoperable state and can be operated. Understand the number of vehicles that can be operated. If "yes" is determined in step 03, that is, if the number of operable units is equal to or greater than the required number, the control unit operates the required number of membrane filtration devices (step S04). At this time, the control unit adjusts the amount of water flowed by each water flow control means so that the amount of water obtained by dividing the total amount of purified water grasped in step S01 by the required number is the amount of treated water per membrane filtration device. In addition, from the viewpoint of maintaining stable operation of the water purification system, the control unit normally causes the membrane filtration device that is currently operating as much as possible to continue operation (that is, a membrane that is newly operated / stopped). Select a membrane filtration device to operate (so that the number of filtration devices is small).

Here, the "water flow rate" and the "treated water volume" of the membrane filtration device have the following relationships. A membrane filtration device is a device that obtains treated water by filtering the water to be treated with a predetermined amount of water flow through a filtration membrane, but this filtration membrane causes clogging due to impurities in the water to be treated due to use. .. Therefore, as described above, physical cleaning is indispensable for the membrane filtration device. Further, the filtration performance of the filtration membrane of the membrane filtration apparatus is not constant because it deteriorates during the operation of the membrane filtration apparatus due to clogging due to impurities or the like. Therefore, the relationship between the amount of water passing through and the amount of treated water differs depending on the length of the operating period of the membrane filtration apparatus and the degree of aging deterioration of the membrane filtration apparatus itself. Therefore, even if the desired amount of purified water is constant during the operation period of the membrane filtration device, in order to obtain the desired amount of purified water, the relationship between the amount of water flow and the amount of treated water is periodically monitored. It is necessary to set the amount of water flow according to the filtration performance at that time. Further, in a water purification system provided with a plurality of membrane filtration devices, the filtration performance is often different for each membrane filtration device. Therefore, a measuring device for measuring the treated water amount such as a flow meter is arranged on the rear side of each membrane filtration device to measure the treated water amount, and the control unit measures the water flow amount by the water flow control means and the measuring device. It is preferable to associate it with the measured amount of treated water. Then, the control unit preferably adjusts the water flow amount by the water flow control means based on the relationship between the water flow amount obtained for each membrane filtration device and the treated water amount.
As described above, the relationship between the "water flow rate" and the "treated water volume" of the membrane filtration device changes with time during the operation period of the membrane filtration device, and is different for each membrane filtration device.

Further, in step S04, when starting the operation of the membrane filtration device in the standby state, the following two control methods can be adopted. As the first method, when the water flow amount at the time of the previous operation of the membrane filtration device is stored in a storage unit (not shown), there is a method of increasing the water flow amount in one step up to the water flow amount. Here, in the water flow control of the conventional membrane filtration device, it is common to gradually increase the water flow over a predetermined time to obtain the target water flow when starting the operation. .. On the other hand, in the control method of the water purification system according to the present embodiment, increasing the water flow amount "in one step" does not mean that the water flow amount is gradually increased as in the conventional case, but is a target at once by one control operation. It means increasing the amount of water flow. Specifically, for example, in the water flow control means configured as a valve, the valve opening at the time of the previous operation is opened by one control. In this way, when starting the operation of the membrane filtration device that was in the standby state, by increasing the already memorized water flow amount in one step, until the target treated water amount can be stably obtained. The time can be shortened and the stability of control of the water purification system can be further improved.

On the other hand, as a second method, processing per membrane filtration device calculated based on the total amount of purified water and the required number of water from the valve opening and the amount of treated water in the latest operating state of the membrane filtration device in the standby state. There is a method of predicting the amount of water flow required to achieve the amount of water and increasing the amount of water flow to the membrane filtration device in the standby state in one step to the predicted amount of water flow. Specifically, for example, in the case of a water flow control means configured as a valve, the required valve opening degree is based on the relationship between the predicted water flow amount and the valve opening degree and the treated water amount in the latest operating state. Is calculated, and the valve is opened with one control until the valve opening. By increasing the amount of water flow in one step up to the predicted amount of water flow, the time until the desired amount of treated water can be stably obtained can be further shortened, and the control stability of the water purification system can be further shortened. Can be further improved.

It should be noted that the control method of these first and second water flow control means is not only when the number of membrane filtration devices changes when the total amount of purified water is changed, but also when the operating membrane filtration devices are in the regenerated state. It can also be used when starting the operation of the membrane filtration device that was in the standby state.

Further, when the required number is less than the number of the membrane filtration devices in the operating state and the operation of the membrane filtration devices in the operating state is stopped in step S04, the control unit corresponds to a certain membrane filtration device. For the membrane filtration device that stops the water flow by the water flow control means and continues the operation, the water flow amount is controlled by the water flow control means so as to obtain the treated water amount obtained by dividing the total amount of purified water by the required number. At this time, the control unit preferentially stops the operation from the membrane filtration device having a short operating time after the completion of the latest physical cleaning (the filtration duration after the completion of the physical cleaning) and puts it in the standby state. Is preferable. In the water purification system, by holding the membrane filtration device in a relatively good condition and less clogging of the filtration membrane in the standby state, the operation continuation time when the membrane filtration device is put into the operation state again is extended. This is because the stability of control of the water purification system can be improved.

On the other hand, when it is determined in step S03 that the number of operable units is less than the required number, the control unit puts all the operational number of membrane filtration devices in the operating state and sets each of the membrane filtration devices to the maximum treated water amount. The operation is performed with the set value (step S05). In this case, the desired total water purification amount cannot be achieved, but the maximum treated water amount at that time of the water purification system will be supplied. Then, the control unit grasps that the number of operable units has changed due to, for example, the completion of the physical cleaning of the membrane filtration device in the regenerated state and the standby state (step S06), and step S03. Is repeated. In this way, the control unit controls the operation of the membrane filtration apparatus so as to achieve the desired total water purification amount as quickly as possible.
Hereinafter, a control example by the water purification system control method according to the present invention will be specifically described.

<Control example 1>
First, as a control example 1, 24 membrane filtration devices connected in parallel to each other are provided, and the maximum treated water amount setting value of one membrane filtration device is 450 (m ³ / h), and the minimum treated water amount setting value. Is 400 (m ³ / h), the total amount of water purification is 200,000 (m ³⁾ in a water purification system with 20 operating units, 2 standby membrane filtration devices, and 2 regenerated membrane filtration devices. The case where it increases from (/ day) to 210,000 (m ³ / day) will be described. When steps S02-1A to S02-6A, which prioritize maintaining the current operating number, are carried out in the required number determination step S02, 210,000 (m ³ /) in step S02-1A as shown in Table 1. (Day) ÷ 24 (h) ÷ 20 (units) is calculated to obtain the treated water amount of 437.5 (m ³ / h) per unit, and such a value is determined from the set values of the maximum treated water amount and the minimum treated water amount. In step S02-2A, it is determined whether or not the amount of water is within the range of 400 (m ³ / h) or more and 450 (m ³ / h) or less. In this case, since 437.5 (m ³ / h) is within the above range, the control unit proceeds to step S02-6A and determines the currently operating number of 20 as the required number. After that, through steps S03 and S04, the control unit 14 maintains the current operating number of 20 units and increases the amount of treated water of each membrane filtration device during operation to 437.5 (m ³ / h), which is the target. Control the water flow control means to supply a total amount of purified water of 210,000 (m ³ / day).

On the other hand, in step S02, when step S02-1C is performed in which priority is given to operating the membrane filtration apparatus with a treated water amount close to a predetermined set value (in this case, the minimum treated water amount of 400 (m ³ / h)). From 210,000 (m ³ / day) ÷ 24 (h) ÷ 400 (m ³ / h) = 21.88, 21 units will be determined as the required number. Then, the control unit determines in step S03 that the number of operable units is 22 (breakdown: 20 operating units + 2 standby units) more than the required number of 21 units, and in step S04, the required number of units is 21. Control the membrane filtration device to operate. The number of operating membrane filtration devices and the total amount of treated water are as shown in Table 2 below.

In this way, when priority is given to operating the membrane filtration device with a treated water amount close to the minimum treated water amount of 400 (m ³ / h)) in the required number determination step S02, the number of operating number of the membrane filtration devices is increased. Although the number of units is increased by one, it is possible to reduce the amount of change in the amount of water flow in the membrane filtration device that is still in operation.

<Control example 2>
Next, the control method of the water purification system when the total amount of purified water decreases will be specifically described. The set values of the maximum and minimum treated water amount of the membrane filtration device and the number of membrane filtration devices in each state are the same as in Control Example 1, and the total water purification amount is from 200,000 (m ³ / day) to 190,000 (m ³ ). / Day) will be explained when it decreases. When steps S02-1A to S02-6A are followed, 190,000 (m ³ / day) ÷ 24 (h) ÷ 20 (units) is calculated in step S02-1A, and the amount of treated water per unit is 395.83 (units). m ³ / h) is obtained, and the value is within the range of 400 (m ³ / h) or more and 450 (m ³ / h) or less, which is the range determined from the set values of the maximum treated water amount and the minimum treated water amount. Is determined in step S02-2A. In this case, since below 395.83 (m ³ / h) is the set value of the minimum amount of water treated (400m ³ / h), the control unit, step S02-3A, proceeds to S02-4A, at present the number of operating units 20 One less than the number of units, 190,000 (m ³ / day) ÷ 24 (h) ÷ 19 (units) is calculated, and the amount of treated water per unit is 416.67 (m ³ / h). Since such a value is within the range of 400 (m ³ / h) or more and 450 (m ³ / h) or less, the determination result in step S02-2A is "Yes", and the control unit sets the control unit in step S02-6A. Determine 19 units as the required number. Then, through steps S03 and S04, the control unit controls 19 membrane filtration devices to operate at a treated water volume of 416.67 (m ³ / h), as shown in Table 3.

On the other hand, in step S02, even when step S02-1C, which gives priority to operating the membrane filtration apparatus with as little treated water as possible, is carried out, 190,000 (m ³ / day) ÷ 24 (h) ÷ 400 (m ³ /). From h) = 19.79, 19 units will be determined as the required number. Then, the control unit determines in step S03 that the number of operable units is 22 (breakdown: 20 operating units + 2 standby units) more than the required 19 units, and in step S04, the required number 19 units. Control the membrane filtration device to operate. The number of operating membrane filtration devices and the amount of treated water are the same values as in Table 3.

<Control example 3>
Next, as control example 3, 24 membrane filtration devices are provided as in control examples 1 and 2, and the set value of the maximum treated water amount of one membrane filtration device is 450 (m ³ / h), and the minimum processing is performed. The set value of the amount of water is 400 (m ³ / h), but since one membrane filtration device is out of order, the number of operating units is 20, one standby membrane filtration device, and the regenerated membrane filtration device. In a water purification system with two devices, the case where the total amount of water purification increases from 200,000 (m ³ / day) to 230,000 (m ³ / day) will be described.

In this case, if steps S02-1A to S02-6A are performed in the required number determination step S02, 230,000 (m ³ / day) ÷ 24 (h) ÷ 20 (units) is calculated in step S02-1A. Then, the treated water amount per unit is 479.16 (m ³ / h), and such a value is the treated water amount range determined from the set values of the maximum treated water amount and the minimum treated water amount, 400 (m ³ / h) or more 450. It is determined in step S02-2A whether it is within the range of (m ³ / h) or less. In this case, since 479.16 (m ³ / h) exceeds the above maximum treated water volume, the control unit proceeds to step S02-5A and calculates 230,000 (m ³ / day) ÷ 24 (h) ÷ 21 (units). , Obtain treated water volume 456.35 (m ³ / h) per unit. However, since such a value also exceeds the above maximum treated water amount, the control unit calculates 210,000 (m ³ / day) ÷ 24 (h) ÷ 22 (units) in step S02-5A, and the treated water amount per unit is 435.61. Get (m ³ / h). Since the treated water amount is within the treated water amount range, the determination result in step S02-2A is "Yes", and the control unit determines 22 units as the required number in step S02-6A. After that, the process proceeds to step S03. At this time, since the number of operable units is 21, the determination result in step S03 is "No". Therefore, the control unit proceeds to step S05 and controls each membrane filtration device so that the 21 operable membrane filtration devices are operated at 450 (m ³ / h), which is the set value of the maximum treated water amount (m ³ / h). After the change in Table 4 1). After that, it is detected that the repair of one membrane filtration device that was out of order is completed and it is in the standby state, or one of the two membrane filtration devices that was in the regeneration state is in the standby state. Then, the control unit again compares the number of operable units and the required number of units in step S03, proceeds to S04 in this control example, and the amount of treated water of the 22 membrane filtration devices becomes 435.61 (m ³ / h). The water flow control means is controlled so as to (2 after the change in Table 4).

On the other hand, when step S02-1C is carried out in step S02, 23 units are determined as the required number from 230,000 (m ³ / day) ÷ 24 (h) ÷ 400 (m ³ / h) = 23.96. Then, in step S03, the control unit determines that the number of operable units is 21 (breakdown: 20 operating units + 1 standby unit) is less than the required number of 23 units, as shown in Table 5 after the change 1. The operation of the membrane filtration device is controlled so that the operation state is normal. After that, the loop of step S06 and step S05 is repeated until the required number of units is satisfied, and the operation of the membrane filtration apparatus is controlled so that the operation state becomes 2 to 3 after the change in Table 5. The number of times such loop processing is repeated is limited by the number of membrane filtration devices provided in the water purification system.

<Control example 4>
The set values of the maximum and minimum treated water amount of the membrane filtration device and the number of membrane filtration devices in each state are the same as in Control Example 1, and the total water purification amount is from 200,000 (m ³ / day) to 210,000 (m ³ / day). A case where step S02-1B is carried out as step S02 when the number increases on the day) will be described. That is, in control example 4, the value obtained by dividing the new total water purification amount of 210,000 (m ³ / day) by the set value of the maximum treated water amount (= 210,000 (m ³ / day) ÷ 24 (h) ÷ 450 (m ^{3 /} h) = 19.44) and the value obtained by dividing the new total water purification amount of 210,000 (m ³ / day) by the set value of the minimum treated water amount (= 210,000 (m ³ / day) ÷ 24 (h) ÷ 400 (m ³ / h) = 21.88), and find the range of units (20 to 21 units) that can supply the total amount of purified water within the treated water amount range. Then, the number closest to the currently operating number of 20 (20) is determined as the required number. Then, the treated water volume of each membrane filtration device is increased to 437.5 (m ³ / h) (210,000 (m ³ / day) ÷ 24 (h) ÷ 20 (units)), and the operation is continued.

As described above, the control method of the water purification system according to the present invention has been specifically described with reference to Control Examples 1 to 4, but according to this method, when the treated water amount of the water purification system fluctuates, it is swiftly and stably. A desired amount of water can be supplied.

It will be apparent to those skilled in the art that many modifications and substitutions can be made within the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited by the embodiments described above. That is, the present invention can be modified or modified in various ways without departing from the scope of claims.

For example, the water purification system according to the present invention may further include a water quality measuring device (for example, a turbidity meter) for measuring the water quality of raw water and / or treated water. Then, of course, it is also possible to change the set values of the maximum treated water amount and the minimum treated water amount of each membrane filtration device based on the measurement result by the water quality measuring device.

10 Water purification system 11 Raw water tank 12a to 12c Membrane filtration device 13 Water purification tank 14 Control unit 15 Raw water piping 16 Treated water piping 121a to 121c Water flow control means

Claims (4)

It is a control method of a water purification system that filters the water to be treated supplied from the front stage side of the membrane filtration device by a plurality of membrane filtration devices connected in parallel to each other and discharges purified water from the rear stage side of the membrane filtration device. ,
The plurality of membrane filtration devices are set to operate within the treated water amount range determined by each set value of the minimum treated water amount and the maximum treated water amount in the operating state in which the membrane filtration operation is performed.
A necessary number determination step for determining the required number of the membrane filtration devices required to obtain the total water purification amount based on the total water purification amount required for the water purification system and the treated water amount range of the membrane filtration device.
A comparison step of grasping the number of membrane filtration devices that can be operated among the plurality of membrane filtration devices and comparing the required number of membrane filtration devices with the number of operational membrane filtration devices.
Based on the result of the comparison, when the number of the operable membrane filtration devices is equal to or greater than the required number, the required number of the membrane filtration devices is put into the operating state, and the operable number is less than the required number. In the case of, the operation step of operating the membrane filtration apparatus of the operable number in the operation state and operating at the set value of the maximum treated water amount, and
In addition, in the required number determination step,
The number of membrane filtration devices in the operating state is grasped, and the number closest to the number of membrane filtration devices in the grasped operating state is set as the required number from the range of the operating number in which the total amount of purified water can be obtained within the treated water amount range. To decide (first method of determining the required number of units) and
Dividing the total purified water amount by a predetermined set value within the treated water amount range, and determining the integer part of the obtained value as the required number of units (second required number of units determining method).
Including carrying out any of
The predetermined set value within the treated water amount range is one of the set value of the minimum treated water amount, the treated water amount of the membrane filtration apparatus currently in operation, and the intermediate value of the treated water amount range.
A method of controlling a water purification system, which is characterized by the fact that. When the required number determination step is repeatedly carried out, the total water purification amount (n + 1) used in the n + 1th required number determination step is increased or decreased from the total water purification amount (n) used in the nth required number determination step. Including additional steps to determine
When the total water purification amount (n + 1) is smaller than the total water purification amount (n), the second required number determination method is implemented, and in other cases, the first required number determination method is performed. The method for controlling a water purification system according to claim 1, wherein When the number of operable units is less than the required number, the operation of the membrane filtration device is controlled so as to operate at the set value of the maximum treated water amount with the operational number of the membrane filtration devices in the operating state. The control method for a water purification system according to claim 1 or 2, wherein the comparison step and the operation step are carried out again by detecting that the number of operable units has changed. A water purification system that filters water to be treated supplied from the front stage side of the membrane filtration device by a plurality of membrane filtration devices connected in parallel to each other and discharges purified water from the rear stage side of the membrane filtration device.
The plurality of membrane filtration devices are set to operate within the treated water amount range determined by each set value of the minimum treated water amount and the maximum treated water amount in the operating state in which the membrane filtration operation is performed.
The water purification system
A control unit that controls the operation of the plurality of membrane filtration devices is provided, and the control unit is
The required number of the membrane filtration devices required to obtain the total water purification amount is determined based on the total water purification amount required for the water purification system and the treated water amount range of the membrane filtration device.
Grasp the number of membrane filtration devices that can be operated among the plurality of membrane filtration devices,
Comparing the required number with the number of operable membrane filtration devices,
Based on the result of the comparison, when the number of operable membrane filtration devices is equal to or greater than the required number, the required number of the membrane filtration devices is put into the operating state, and the operable number is less than the required number. If this is the case, the operable number of the membrane filtration devices is set to the operating state and operated at the set value of the maximum treated water amount.
In determining the required number
The number of membrane filtration devices in the operating state is grasped, and the number closest to the number of membrane filtration devices in the grasped operating state is set as the required number from the range of the operating number in which the total amount of purified water can be obtained within the treated water amount range. To decide and
This includes dividing the total amount of purified water by a predetermined set value within the range of the amount of treated water and determining the integer portion of the obtained value as the required number of units.
The predetermined set value within the treated water amount range is one of the set value of the minimum treated water amount, the treated water amount of the membrane filtration apparatus currently in operation, and the intermediate value of the treated water amount range.
Characterized by
Water purification system.

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