WO2014129383A1

WO2014129383A1 - Water treatment system

Info

Publication number: WO2014129383A1
Application number: PCT/JP2014/053381
Authority: WO
Inventors: 嘉晃伊藤; 英夫岩橋; 克憲松井; 貴一 ▲徳▼永; 匡仙河田
Original assignee: 三菱重工業株式会社
Priority date: 2013-02-25
Filing date: 2014-02-13
Publication date: 2014-08-28
Also published as: JP2014161795A

Abstract

The water treatment system is provided with: a main reverse osmosis membrane device (3) for separating water (4) that is to be treated into concentrated brine (5) with high solute concentrations and fresh water (6); and pre-treatment devices (1, 2) for removing harmful substances, which reduce the membrane performance of the reverse osmosis membranes of the main reverse osmosis membrane device (3), from the water(4) that is to be treated before supplying same to the main reverse osmosis membrane device (3). The pre-treatment devices (1, 2) are also provided with a sub-reverse osmosis membrane device (11).

Description

Water treatment system

The present invention relates to a water treatment system, and more particularly to a water treatment system suitable for use in producing fresh water from seawater.
This application claims priority based on Japanese Patent Application No. 2013-034732 filed in Japan on February 25, 2013, the contents of which are incorporated herein by reference.

There are no freshwater sources such as rivers and lakes, such as desert areas, remote islands, developing countries, and industrial areas that require a large amount of freshwater. There are areas where severe water shortages occur seasonally. In some of these regions, fresh water (drinking water) is created by processing a large amount of seawater. As a method for producing this fresh water, a method is often used in which seawater is passed through a reverse osmosis membrane (RO membrane: ReversemOsmosis Membrane) such as a hollow fiber membrane or a spiral membrane (see, for example, Patent Document 1). The reverse osmosis membrane device is configured, for example, by accommodating a plurality of reverse osmosis membrane units (reverse osmosis membrane elements) formed by stacking a plurality of reverse osmosis membranes with a spacer in between in a pressure vessel.

When producing fresh water from seawater, it is necessary to treat the seawater with a pretreatment device before permeating the reverse osmosis membrane. In this pretreatment, in general, an oxidizing agent such as hypochlorous acid is added in order to prevent organisms such as algae and shellfish from adhering to water intakes, pipes, and water channels for taking seawater. In addition, an inorganic flocculant such as ferric chloride or a polymer flocculant such as PAC is added to agglomerate suspensions such as fine particles and colloids in seawater, and are removed by filtration with a sand filter. Further, water is passed through a filter, for example, a container filled with a filter material called a cartridge filter (CF) to remove particles of 5 to 10 μm or less that cannot be removed by sand filtration. In addition, the pH of the seawater is adjusted so as to suppress the precipitation (scaling) of inorganic ions, particularly calcium ions and magnesium ions in the seawater.

Also, residual chlorine-based oxidant causes oxidation of the reverse osmosis membrane. Along with this, the membrane performance of the reverse osmosis membrane deteriorates. Therefore, before seawater permeates the reverse osmosis membrane, a reducing agent such as sodium bisulfite (SBS) is added while measuring the oxidation-reduction potential and neutralized. I am trying to process it.

生物 By performing such pretreatment of seawater, organisms are prevented from adhering to intakes, pipes, and waterways that take in seawater. It also prevents early deterioration (fouling) of reverse osmosis membrane performance due to biological growth, clogging of suspended matter and inorganic ion deposits. This makes it possible to produce fresh water efficiently and economically.

JP 2002-143849 A

However, in the conventional water treatment system, the filtration efficiency of the cartridge filter or the like may not be sufficient depending on the quality of the seawater (treated water), and as a result, the reverse of the reverse osmosis membrane device in the latter stage is caused. In some cases, suspended particles are collected on the surface of the osmotic membrane or a spacer between the membranes, and the membrane performance deteriorates early.

In particular, when a reverse osmosis membrane is provided on the upstream side, or when a plurality of reverse osmosis membrane units are provided, the membrane performance of the upstream reverse osmosis membrane unit deteriorates earlier. In general, when the processing performance of the reverse osmosis membrane device (reverse osmosis membrane performance) is restored by maintenance, the entire reverse osmosis membrane unit and the entire reverse osmosis membrane device are backwashed (backwash / forward osmosis). Therefore, this maintenance work requires a great deal of time and labor. Moreover, in order to perform maintenance of the reverse osmosis membrane device, the operation of the water treatment system may be stopped, and as a result, the production of fresh water may be stopped.

For this reason, it has been strongly desired to reduce the performance (fouling) of the reverse osmosis membrane device as much as possible, reduce the maintenance work, and produce fresh water more efficiently and economically.

According to the first aspect of the present invention, the water treatment system includes a main reverse osmosis membrane device for separating the water to be treated into concentrated water and fresh water having a high solute concentration, and before supplying the water to the main reverse osmosis membrane device. And a sub-reverse osmosis membrane device as a pretreatment device for removing an obstacle that deteriorates the membrane performance of the reverse osmosis membrane of the main reverse osmosis membrane device from the water to be treated in advance.

In the above-mentioned water treatment system, before supplying to the main reverse osmosis membrane device for generating fresh water, the pretreatment device for treating the water to be treated such as seawater includes the sub reverse osmosis membrane device, Inhibitors that are present in the water to be treated and reduce the membrane performance of the reverse osmosis membrane, that is, fine particles that clog the reverse osmosis membrane and microorganisms that propagate on the reverse osmosis membrane and cause clogging. It can be collected by the reverse osmosis membrane of the sub reverse osmosis membrane device before the main reverse osmosis membrane device. In other words, by using the sub-reverse osmosis membrane device like a filtration device, an obstacle that reduces the membrane performance of the reverse osmosis membrane can be removed at the pretreatment stage of the water to be treated.

Thereby, the reverse osmosis membrane (reverse osmosis membrane module) of the main reverse osmosis membrane device that generates fresh water from the treated water, in particular, the reverse osmosis membrane (reverse osmosis membrane) of the main reverse osmosis membrane device arranged on the upstream side of the treated water flow direction It is possible to prevent the membrane performance of the osmotic membrane module) from being deteriorated early.

According to the second aspect of the present invention, the water treatment system includes a plurality of the pretreatment devices. The plurality of pretreatment devices individually supply treated water to one main reverse osmosis membrane device, and are connected to the main reverse osmosis membrane devices via first on-off valves, respectively. .

In the above-described water treatment system, a plurality of pretreatment devices are provided, and each pretreatment device including a sub reverse osmosis membrane device is connected to one main reverse osmosis membrane device via a first on-off valve. That is, a plurality of pretreatment devices are connected to one main reverse osmosis membrane device through a plurality of first on-off valves, respectively. As a result, when the membrane performance of the sub-reverse osmosis membrane device of a certain pretreatment device deteriorates, the first on-off valve of this pretreatment device is closed to stop the supply of water to be treated to the main reverse osmosis membrane device. The first on-off valve of the other pretreatment device can be opened, and the water to be treated treated by the sub reverse osmosis membrane device of the other pretreatment device can be supplied to the main reverse osmosis membrane device.

As a result, even if the membrane performance deteriorates and maintenance of the sub-reverse osmosis membrane device of the pretreatment device becomes necessary, the sub-reverse osmosis membrane device of another pretreatment device removes the obstacle. Treated water can be supplied to the main reverse osmosis membrane device. For this reason, it is not necessary to stop the operation of the water treatment system, and it becomes possible to produce fresh water more efficiently and economically.

According to the third aspect of the present invention, in the water treatment system, the pretreatment device includes backwashing means. The backwashing means is connected to the sub reverse osmosis membrane device via a second on-off valve, and backwashes the reverse osmosis membrane of the sub reverse osmosis membrane device from the downstream side to the upstream side in the treated water flow direction. Supply water.

In the water treatment system described above, when the membrane performance of the reverse osmosis membrane of the sub reverse osmosis membrane device deteriorates, the second on-off valve is opened and the reverse osmosis membrane of the sub reverse osmosis membrane device is treated from the back washing means. By supplying backwash water from the downstream side of the water flow direction to the upstream side (in the forward osmosis direction), the membrane performance of the reverse osmosis membrane, such as suspended particles clogged in the reverse osmosis membrane, is reduced. Inhibitors can be backwashed away. At this time, the reverse osmosis membrane of the sub reverse osmosis membrane device is back-washed by normal osmosis of the backwash water, so the reverse of the reverse osmosis membrane is utilized using a water level difference etc. without using a pump or the like. It is also possible to wash. This makes it possible to efficiently and economically restore the membrane performance of the reverse osmosis membrane of the sub reverse osmosis membrane device.

According to the fourth aspect of the present invention, in the water treatment system, the pretreatment device includes an acid agent supply means and / or a bactericide supply means. The acid agent supply means is connected to the sub reverse osmosis membrane device via a third on-off valve, and an acid agent for removing scale adhered to the reverse osmosis membrane of the sub reverse osmosis membrane device is used as water to be treated. Supply. The sterilizing agent supplying means is connected to the sub reverse osmosis membrane device via a fourth on-off valve, and the sterilizing agent for removing organisms attached to the reverse osmosis membrane of the sub reverse osmosis membrane device is used as water to be treated. Supply.

In the above water treatment system, when the membrane performance of the reverse osmosis membrane of the sub-reverse osmosis membrane device is deteriorated, the acid agent supplying means can selectively open the third on / off valve and the acid agent supply means. The sterilizing agent can be appropriately supplied from the sterilizing agent supply means to the water to be treated in the sub reverse osmosis membrane device. For example, when scale such as calcium carbonate adheres to the reverse osmosis membrane and the membrane performance deteriorates, the scale is dissolved and removed by supplying acidic water (acidic agent) from the acidic agent supply means. be able to. In addition, for example, when organisms adhere to and propagate on the reverse osmosis membrane and the membrane performance deteriorates, the organism can be killed by supplying a chlorine-based disinfectant such as hypochlorous acid from the disinfectant supply means. Can be removed. As a result, the membrane performance of the reverse osmosis membrane of the sub reverse osmosis membrane device can be recovered more efficiently and economically.

According to a fifth aspect of the present invention, in the water treatment system, the pretreatment device measures the pressure difference for measuring the pressure difference between the upstream side and the downstream side of the sub-reverse osmosis membrane device in the direction of water to be treated. Means.

In the above water treatment system, the differential pressure measuring means measures the pressure difference between the upstream side and the downstream side of the sub-reverse osmosis membrane device in the flow direction of the water to be treated. (Decrease status) can be confirmed. Thereby, it is possible to determine whether the reverse osmosis membrane of the sub reverse osmosis membrane device needs to be maintained or replaced.

Furthermore, for example, when the pressure difference increases proportionally according to the amount of treated water, it is determined that suspended particles are clogged in the reverse osmosis membrane and the membrane performance is degraded. Moreover, when a pressure difference becomes large irrespective of the amount of treated water to be treated, it is determined that the membrane performance is deteriorated due to adhesion of organisms and scales. Thus, by measuring the pressure difference together with the type and properties of the water to be treated, it is possible to identify the factors that degrade the membrane performance. This makes it possible to effectively restore the membrane performance by selecting, for example, any one of the backwashing means, the acid agent supply means, and the bactericidal agent supply means according to the specified factor of the membrane performance deterioration. .

According to a sixth aspect of the present invention, in the water treatment system, the pretreatment device includes the first on-off valve, the second on-off valve, the third on-off valve, and the fourth on-off valve. Control means for controlling opening / closing of the on-off valve provided in the processing apparatus based on the measurement result of the differential pressure measuring means is provided.

In the above-described water treatment system, based on the measurement result of the differential pressure measuring means, the pretreatment device among the first on-off valve, the second on-off valve, the third on-off valve, and the fourth on-off valve By controlling the opening / closing valve provided, maintenance of the sub reverse osmosis membrane device and production of fresh water can be efficiently performed, for example, fully automatically or semi-automatically.

In the above-mentioned water treatment system, before supplying to the main reverse osmosis membrane device for generating fresh water, the pretreatment device for treating the water to be treated such as seawater includes the sub reverse osmosis membrane device, Inhibitors present in the water to be treated and degrading the membrane performance of the reverse osmosis membrane can be collected by the reverse osmosis membrane of the sub reverse osmosis membrane device before the main reverse osmosis membrane device.

Thereby, the reverse osmosis membrane (reverse osmosis membrane module) of the main reverse osmosis membrane device that generates fresh water from the treated water, in particular, the reverse osmosis membrane (reverse osmosis membrane) of the main reverse osmosis membrane device arranged on the upstream side of the treated water flow direction It is possible to prevent the membrane performance of the osmotic membrane module) from being deteriorated early. And, for example, a pretreatment device that collects the inhibitor at the stage of pretreatment of water to be treated by configuring the sub reverse osmosis membrane device with a smaller number of reverse osmosis membranes than the main reverse osmosis membrane device When performing maintenance of the sub reverse osmosis membrane device or replacement of the reverse osmosis membrane device, it is possible to reduce the time and labor required for the maintenance work as compared with the conventional case.

Therefore, according to the water treatment system described above, it is possible to maintain the membrane performance of the main reverse osmosis membrane device for a long period of time, reduce the maintenance work, and efficiently and economically produce fresh water.

It is a figure which shows the water treatment system which concerns on one Embodiment of this invention. It is a figure which shows the example of a change of the water treatment system which concerns on one Embodiment of this invention.

Hereinafter, a water treatment system according to an embodiment of the present invention will be described with reference to FIG. Here, in the present embodiment, the water treatment system will be described as a system in which seawater is used as the water to be treated, and this seawater is separated into concentrated water and fresh water by a reverse osmosis membrane (RO membrane) to produce fresh water. The treated water according to the present embodiment is not necessarily limited to seawater, and the present invention may be applied to treat other treated water such as river water.

The water treatment system A of this embodiment includes pretreatment devices 1 and 2 and a main reverse osmosis membrane device (main RO membrane device) 3 as shown in FIG.

First, the main reverse osmosis membrane device 3 houses a plurality of reverse osmosis membrane units 3a in a pressure vessel. The main reverse osmosis membrane device 3 sequentially passes the seawater (treated water) 4 after being processed by the pretreatment devices 1 and 2 through a plurality of reverse osmosis membrane units 3a arranged in parallel, and the solute concentration is increased. Separated into highly concentrated water (concentrated brine) 5 and fresh water 6. Further, each reverse osmosis membrane unit 3a of the main reverse osmosis membrane device 3 is formed by stacking a plurality of reverse osmosis membranes with a spacer interposed therebetween, for example. And in this main reverse osmosis membrane apparatus 3, the concentrated water discharge pipe 7 for discharging the concentrated water 5 after processing by each reverse osmosis membrane unit 3a outside, and the fresh water 6 for permeated water are discharged. A permeate pipe 8 is connected. Further, the main reverse osmosis membrane device 3 includes a water supply pipe 9 to be treated for supplying the seawater 4 treated by the pretreatment devices 1 and 2 upstream in the seawater circulation direction T (upstream in the treatment water circulation direction, raw water). Side).

The pretreatment devices 1 and 2 of the present embodiment inhibit the membrane performance of the reverse osmosis membrane of the main reverse osmosis membrane device 3 from the seawater 4 which is the pretreated water before supplying it to the main reverse osmosis membrane device 3. It is for removing things. More specifically, the pretreatment devices 1 and 2 remove microparticles and colloids in the seawater 4, microorganisms such as algae and shellfish, and the membrane performance of each reverse osmosis membrane unit 3a of the main reverse osmosis membrane device 3 decreases. This is to suppress the phenomenon (fouling phenomenon). The pretreatment devices 1 and 2 are provided upstream of the main reverse osmosis membrane device 3 in the seawater circulation direction T.

The water treatment system A of the present embodiment includes a plurality of pretreatment devices 1 and 2. A treated water supply pipe 9 having a first on-off valve 10 is provided so that a plurality of pretreatment devices 1 and 2 individually supply treated seawater 4 to one main reverse osmosis membrane device 3. To the main reverse osmosis membrane device 3.

Moreover, in this embodiment, each pre-processing apparatus 1 and 2 are the sub reverse osmosis membrane apparatus 11, the backwashing means 12, the acidic agent supply means 13, the disinfectant supply means 14, and the reducing agent supply means 15. , Differential pressure measuring means 16, pH measuring means 17, and control means 18.

The sub reverse osmosis membrane device 11 is configured with a smaller number of reverse osmosis membranes than the main reverse osmosis membrane device 3. In this embodiment, the main reverse osmosis membrane device 3 accommodates a plurality of reverse osmosis membrane units 3 a in parallel in a pressure vessel, whereas the sub reverse osmosis membrane device 11 is a reverse of the main reverse osmosis membrane device 3. One reverse osmosis membrane unit 11a having the same configuration as the osmosis membrane unit 3a is accommodated in a pressure vessel. The sub-reverse osmosis membrane device 11 supplies the raw water supply pipe 20 for supplying the raw water seawater 4 and the seawater 4 processed by the sub-reverse osmosis membrane device 11 to the main reverse osmosis membrane device 3. The to-be-processed water supply pipe 9 is connected.

The sub reverse osmosis membrane device 11 may reuse the reverse osmosis membrane (reverse osmosis membrane unit 3a) after being used in the main reverse osmosis membrane device 3, for example. Further, FIG. 1 shows that raw water seawater 4 is supplied as it is to the sub-reverse osmosis membrane device 11 through the raw water supply pipe 20, but each pretreatment device 1, 2 of the water treatment system A of the present embodiment. May include a cartridge filter, a sand filter, an oxidizing agent supply device, and a reducing agent supply device, and these devices may be provided upstream of the sub reverse osmosis membrane device 11 in the seawater flow direction T.

The backwashing means (backwashing device) 12 includes a backwashing water tank 12a that temporarily stores backwashing water W1 and a backwashing water pipe 12b that connects the backwashing water tank 12a and the sub reverse osmosis membrane device 11. Yes.
Further, the back washing water pipe 12b is provided with a second on-off valve 21 such as an electromagnetic valve. The backwashing means 12 is connected to the sub reverse osmosis membrane device 11 via the second on-off valve 21. Further, when the back washing means 12 opens the second on-off valve 21, the back washing water W1 in the back washing water tank 12a is upstream from the downstream side in the seawater circulation direction T with respect to the reverse osmosis membrane of the sub reverse osmosis membrane device 11. It is configured to be supplied toward the side. That is, in this embodiment, when the second on-off valve 21 is opened without using a pump or the like, the backwash water W1 in the backwash water tank 12a is supplied to the sub reverse osmosis membrane device 11 due to the water level difference, and the sub reverse osmosis membrane device 11 is supplied. The reverse osmosis membrane of the membrane device 11 is configured to flow in the forward osmosis direction. The backwash water W1 is seawater, even if it is clean water such as tap water or groundwater, as long as the reverse osmosis membrane of the sub reverse osmosis membrane device 11 can be backwashed (backwash). However, the concentrated water 5 and the fresh water 6 produced | generated by the main reverse osmosis membrane apparatus 3 may be sufficient, and it does not specifically limit.

The acid agent supply means (acid agent supply device) 13 includes an acid water tank 13a that temporarily stores acid agent (acid water) W2, an acid water pipe 13b that connects the acid water tank 13a and the sub reverse osmosis membrane device 11, An acidic water pump 13c for supplying the acidic water W2 to the sub reverse osmosis membrane device 11 through the acidic water pipe 13b is provided. The acidic water pipe 13b is provided with a third on-off valve 22 such as an electromagnetic valve. The acid agent supply means 13 is connected to the sub reverse osmosis membrane device 11 via the third on-off valve 22.

The acidic agent supply means 13 may connect the acidic water pipe 13b directly to the sub reverse osmosis membrane device 11 as long as the acidic water W2 can be brought into contact with the reverse osmosis membrane of the sub reverse osmosis membrane device 11. Even if the acidic water pipe 13b is connected to the raw water supply pipe 20 to supply the acidic water W2 to the raw water seawater 4, the acidic water pipe 13b is connected to the backwash water pipe 12b and the sub-reverse osmosis membrane together with the backwash water W1. You may make it supply the acidic water W2 to the apparatus 11. FIG. The acid agent W2 is for dissolving and removing scales deposited on the reverse osmosis membrane by depositing inorganic ions such as calcium ions and magnesium ions in the seawater 4. For this reason, as long as it has pH of the acid side which can dissolve a scale, especially the chemical | medical agent for producing | generating acidic agent (acid water) W2, such as hydrochloric acid, sulfuric acid, nitric acid, is not limited. In other words, a chemical suitable for the scale of precipitation may be used.

The disinfectant supply means (disinfectant supply device) 14 includes, for example, a disinfecting water tank 14a for temporarily storing a chlorine-based disinfectant (sterilizing water W3) such as hypochlorous acid, a disinfecting water tank 14a, and a sub reverse osmosis. A sterilizing water pipe 14b connecting the membrane apparatus 11 and a sterilizing water pump 14c for supplying the sterilizing water W3 to the sub reverse osmosis membrane apparatus 11 through the sterilizing water pipe 14b are provided. The sterilizing water pipe 14 b is provided with a fourth on-off valve 23 such as an electromagnetic valve, and the sterilizing agent supply means 14 is connected to the sub reverse osmosis membrane device 11 through the fourth on-off valve 23.

In the sterilizing agent supply means 14 as well as the acidic agent supply means 13, if the sterilizing water W3 can be brought into contact with the reverse osmosis membrane of the sub reverse osmosis membrane device 11, the sterilizing water pipe 14b is directly connected to the sub reverse osmosis. Even if it is connected to the membrane device 11, the sterilizing water pipe 14b is connected to the raw water supply pipe 20 and the sterilizing water W3 is supplied to the raw water seawater 4, or the sterilizing water pipe 14b is connected to the backwash water pipe 12b and vice versa. You may make it supply the sterilization water W3 to the sub reverse osmosis membrane apparatus 11 with the washing water W1. The disinfectant W3 is for killing and removing microorganisms (organisms) attached to the reverse osmosis membrane. For this reason, if the microorganisms adhering to the reverse osmosis membrane can be killed, the chemical | medical agent for producing | generating a bactericidal agent (sterilizing water W3) is not specifically limited. In other words, a chemical that matches the properties of the water to be treated (seawater 4) may be used.

The reducing agent supply means (reducing agent supply device) 15 is for neutralizing the chlorine-based disinfectant W3 supplied by the disinfectant supplying means 14 and remaining in the seawater 4 in the previous stage. By supplying the reducing agent W4 and neutralizing it, the reverse osmosis membrane of the main reverse osmosis membrane device 3 at the latter stage is oxidized and the membrane performance is prevented from being deteriorated.

The reducing agent supply means 15 of the present embodiment includes a reducing agent tank 15a that temporarily stores a reducing agent W4 such as sodium bisulfite (SBS), and a reducing agent that connects the reducing agent tank 15a and the water supply pipe 9 to be treated. In order to measure the redox potential of the seawater 4 to which the reducing agent pump 15c for supplying the reducing agent W4 to the seawater 4 in the to-be-processed water supply pipe 9 through the pipe | tube 15b, the reducing agent pipe | tube 15b, and the reducing agent W4 were added. And an oxidation-reduction potentiometer. The reducing agent pipe 15b is provided with a fifth on-off valve 24 such as an electromagnetic valve. The reducing agent supply means 15 is connected to the treated water supply pipe 9 via the fifth on-off valve 24.

The differential pressure measuring means (differential pressure measuring device) 16 is for measuring the pressure difference between the sub-reverse osmosis membrane device 11 in the seawater circulation direction T upstream side and downstream side. The differential pressure measuring means 16 detects the pressure on the upstream and downstream sides of the sub-reverse osmosis membrane device 11 in the seawater circulation direction T by using two water pressure gauges, and measures the pressure difference. The differential pressure measuring means 16 is for confirming the state of the membrane performance of the sub reverse osmosis membrane device 11 by measuring the pressure difference.

The pH measuring means (pH meter) 17 measures the pH of seawater 4 which is the treated water downstream of the sub reverse osmosis membrane device 11 in the seawater circulation direction T. By measuring the pH, the sub reverse osmosis is performed. This is for confirming the state of the membrane performance of the membrane device 11.

The control means (control device) 18 includes the first on-off valve 10, the second on-off valve 21, the third on-off valve 22, the fourth on-off valve 23, and the fifth on-off valve 24 provided in the pretreatment devices 1 and 2. Opening / closing control is performed based on the measurement results of the differential pressure measuring means 16 and the pH measuring means 17. In the present embodiment, the control means 18 controls the opening and closing of the first to fifth on-off

valves

10, 21, 22, 23 and 24, and based on the measurement results of the differential pressure measuring means 16 and the pH measuring means 17. Then, driving of the acidic water pump 13c, the sterilizing water pump 14c, and the reducing agent pump 15c is controlled. The plurality of pretreatment devices 1 and 2 are controlled by one control means 18.

In the water treatment system A of the present embodiment having the above-described configuration, the seawater 4 taken in is sent to the sub reverse osmosis membrane device 11 through the raw water supply pipe 20, and the reverse osmosis membrane unit of the sub reverse osmosis membrane device 11 is used. It passes through the reverse osmosis membrane of 11a.

At this time, by using the sub reverse osmosis membrane device 11 as the pretreatment devices 1 and 2 for treating the seawater 4 before supplying it to the main reverse osmosis membrane device 3 that generates the fresh water 6, it exists in the seawater 4, Inhibitors that degrade the membrane performance of the reverse osmosis membrane, that is, fine particles that clog the reverse osmosis membrane, or microorganisms that propagate on the reverse osmosis membrane and cause clogging, are the main reverse osmosis membrane device 3. It is collected by the reverse osmosis membrane of the sub reverse osmosis membrane device 11 before.

Thus, conventionally, the obstruction that reduces the membrane performance of the reverse osmosis membrane of the main reverse osmosis membrane device 3 that generates fresh water 6 from the seawater 4 is removed in advance by the sub reverse osmosis membrane device 11 having the same reverse osmosis membrane. Therefore, the reverse osmosis membrane (reverse osmosis membrane unit 3a) of the main reverse osmosis membrane device 3, particularly the reverse osmosis membrane (reverse osmosis membrane unit 3a) of the main reverse osmosis membrane device 3 arranged on the upstream side in the seawater circulation direction T. The membrane performance is not deteriorated at an early stage.

On the other hand, since the inhibitor is collected by the sub reverse osmosis membrane device 11, the membrane performance of the sub reverse osmosis membrane device 11 gradually decreases. For this reason, it is necessary to perform maintenance and replacement at a stage where the membrane performance has deteriorated to some extent, and to recover and improve the membrane performance of the reverse osmosis membrane device (reverse osmosis membrane unit 11a) of the sub reverse osmosis membrane device 11.

In contrast, the water treatment system A of the present embodiment includes a plurality of pretreatment devices 1 and 2 for one main reverse osmosis membrane device 3. The plurality of pretreatment devices 1 and 2 individually supply treated seawater (treated water) 4 and are connected to the main reverse osmosis membrane device 3 via the first on-off valve 10. For this reason, when the membrane performance of the sub reverse osmosis membrane device 11 of a certain pretreatment device 1 deteriorates, the first on-off valve 10 of this pretreatment device 1 is closed and the seawater 4 to the main reverse osmosis membrane device 3 is closed. While stopping supply, the 1st on-off valve 10 of the other pretreatment apparatus 2 is opened, and the seawater 4 processed with the sub reverse osmosis membrane apparatus 11 of this other pretreatment apparatus 2 is supplied to the main reverse osmosis membrane apparatus 3 To do.

Thereby, even if it is a case where the membrane performance deteriorates and the maintenance of the sub reverse osmosis membrane device 11 of the pretreatment device 1 becomes necessary, the sub reverse osmosis membrane device 11 of the other pretreatment device 2 prevents the obstruction. The seawater 4 from which the water has been removed is supplied to the main reverse osmosis membrane device 3 and the fresh water 6 is continuously produced. For this reason, the maintenance of the reverse osmosis membrane of the sub reverse osmosis membrane device 11 with reduced membrane performance can be performed without stopping the operation of the water treatment system A.

In the present embodiment, the pressure difference between the upstream side and the downstream side of the sub reverse osmosis membrane device 11 in the seawater circulation direction T is measured by the differential pressure measuring means 16. The state of the membrane performance of the sub reverse osmosis membrane device 11 is monitored by this pressure difference. Further, the pH of the seawater 4 on the downstream side in the seawater circulation direction T of the sub reverse osmosis membrane device 11 is measured by the pH measuring means 17. The state of the membrane performance of the sub reverse osmosis membrane device 11 is also monitored by this pH measurement value.

In the present embodiment, the preprocessing devices 1 and 2 include the control means 18. The control means 18 controls the opening and closing of the first to fifth on-off

valves

10, 21, 22, 23, 24 of the pretreatment devices 1, 2 based on the measurement results of the differential pressure measuring means 16 and the pH measuring means 17. Yes. Furthermore, the control means 18 controls the drive of the acidic water pump 13c, the sterilizing water pump 14c, and the reducing agent pump 15c based on the measurement results of the differential pressure measuring means 16 and the pH measuring means 17.

For example, when the pressure difference measured by the differential pressure measuring means 16 is proportionally large according to the amount of treated water in the seawater 4, suspended particles are clogged in the reverse osmosis membrane, resulting in a decrease in membrane performance. It can be judged that Moreover, when a pressure difference becomes large irrespective of the amount of treated water of the seawater 4, it can be judged that the membrane performance is degraded due to the attachment of organisms and scales.

In the same manner, the membrane performance of the reverse osmosis membrane of the sub reverse osmosis membrane device 11 can also be determined by grasping the tendency of the change in pH of the seawater 4 downstream of the sub reverse osmosis membrane device 11 in the seawater circulation direction T. It can be judged whether the decrease factor is due to clogging of suspended particles or due to the attachment of organisms or scales.

For this reason, for example, based on the measurement result of the differential pressure measurement means 16 and the measurement result of the pH measurement means 17, when it is determined that the suspended particles are clogged in the reverse osmosis membrane and the membrane performance is reduced, The control means 18 closes the first on-off valve 10 and the second on-off valve 21 of the pretreatment apparatus 1 equipped with the sub reverse osmosis membrane apparatus 11, and opens the second on / off valve 21 from the back washing means 12 to the sub reverse osmosis membrane apparatus 11. Backwash water W1 is supplied to the reverse osmosis membrane. Thereby, the suspended particles clogged in the reverse osmosis membrane are backwashed and removed, and the membrane performance of the sub reverse osmosis membrane device 11 is recovered and improved. By performing the backwashing by the backwashing means 12, not only suspended particles are removed, but also other inhibitor microorganisms and scales that reduce the membrane performance of the reverse osmosis membrane can be backwashed and removed. is there.

On the other hand, the membrane performance of the reverse osmosis membrane decreases due to the attachment of organisms or scales, for example, by comparing the measurement results of the differential pressure measurement means 16 and the measurement results of the pH measurement means 17 with past data such as seasons and temperatures. When it is determined that the control valve 18 is closed, the control means 18 closes the first on-off valve 10 of the pretreatment device 1 including the sub-reverse osmosis membrane device 11 and the third on-off valve 22 and / or the fourth on-off valve. 23, the acidic water supply unit 13 and / or the bactericidal agent supply unit 14 supplies the acidic water W2 and / or the bactericidal agent W3 to the reverse osmosis membrane of the sub reverse osmosis membrane device 11. When supplying the sterilizing agent W3, the fifth on-off valve 24 is opened, and the reducing agent W4 is supplied from the reducing agent supply means 15 to the seawater 4 to be treated.

When the acidic water W2 is supplied by the acidic agent supply means 13, the scale attached to the reverse osmosis membrane of the sub reverse osmosis membrane device 11 is removed by the acidic water W2. Further, when the bactericidal agent W3 is supplied by the bactericidal agent supply means 14, organisms attached to the reverse osmosis membrane of the sub reverse osmosis membrane device 11 are killed and removed by the bactericidal agent W3. Furthermore, since the remaining bactericide W3 is neutralized by supplying the reducing agent W4 by the reducing agent supply means 15, the reverse osmosis membrane of the main reverse osmosis membrane device 3 at the subsequent stage is oxidized, and the membrane performance is improved. The possibility of lowering can be reduced.

Therefore, in the water treatment system A of the present embodiment, the pretreatment devices 1 and 2 for treating the seawater (treated water) 4 are sub-subjected before being supplied to the main reverse osmosis membrane device 3 that generates the fresh water 6. By providing the reverse osmosis membrane device 11, the fine particles that clog the reverse osmosis membrane and the obstacles such as microorganisms that propagate on the reverse osmosis membrane and cause clogging are more effective than the main reverse osmosis membrane device 3. It can be collected by the reverse osmosis membrane of the previous sub-reverse osmosis membrane device 11. That is, by using the sub-reverse osmosis membrane device 11 like a filtration device, an obstacle that lowers the membrane performance of the reverse osmosis membrane can be removed at the pretreatment stage of the seawater 4.

As a result, the membrane performance of the reverse osmosis membrane of the main reverse osmosis membrane device 3 that generates fresh water 6 from the seawater 4, particularly the reverse osmosis membrane of the main reverse osmosis membrane device 3 arranged on the upstream side in the seawater circulation direction T, is deteriorated early. Can be prevented. And like this embodiment, the number of membranes of the reverse osmosis membrane of the sub reverse osmosis membrane device 11 is made smaller than that of the main reverse osmosis membrane device 3, thereby inhibiting the obstacles at the pretreatment stage of the seawater 4. When performing maintenance of the sub-reverse osmosis membrane device 11 of the pretreatment devices 1 and 2 to be collected or replacement of the reverse osmosis membrane, it is possible to reduce the time and labor required for the maintenance work as compared with the conventional case.

Therefore, according to the water treatment system A of the present embodiment, the membrane performance of the main reverse osmosis membrane device 3 can be maintained for a long time and maintenance work can be reduced, and fresh water can be produced efficiently and economically. It becomes possible.

Further, in the water treatment system A of the present embodiment, a plurality of pretreatment devices 1 and 2 are provided, and each of the pretreatment devices 1 and 2 including the sub reverse osmosis membrane device 11 is connected via the first on-off valve 10. It is connected to one main reverse osmosis membrane device 3. For this reason, when the membrane performance of the sub reverse osmosis membrane device 11 of a certain pretreatment device 1 is deteriorated, the seawater 4 is supplied to the main reverse osmosis membrane device 3 by closing the first on-off valve 10 of the pretreatment device 1. And the first on-off valve 10 of the other pretreatment device 2 is opened, and the seawater 4 treated by the sub reverse osmosis membrane device 11 of the other pretreatment device 2 is supplied to the main reverse osmosis membrane device 3. be able to.

Thereby, even if it is a case where the membrane performance deteriorates and the maintenance of the sub reverse osmosis membrane device 11 of the pretreatment device 1 becomes necessary, the sub reverse osmosis membrane device 11 of the other pretreatment device 2 prevents the obstruction. Since the seawater 4 from which water has been removed can be supplied to the main reverse osmosis membrane device 3, it is not necessary to stop the operation of the water treatment system A, and the fresh water 6 can be produced more efficiently and economically. .

Further, in the water treatment system A of the present embodiment, when the membrane performance of the reverse osmosis membrane of the sub reverse osmosis membrane device 11 is lowered, the second on-off valve 21 is opened and the sub reverse osmosis membrane device from the back washing means 12 is opened. By supplying backwash water W1 to the reverse osmosis membrane 11 from the downstream side in the seawater circulation direction T toward the upstream side (in the forward osmosis direction), for example, reverse osmosis such as suspended particles clogged in the reverse osmosis membrane Inhibitors that degrade the membrane performance of the membrane can be backwashed away. At this time, the reverse osmosis membrane of the sub-reverse osmosis membrane device 11 is back-washed by normal osmosis of the backwash water W1, so that the reverse osmosis membrane is utilized by utilizing the water level difference without using a pump or the like. It is also possible to perform backwashing. Thereby, the membrane performance of the reverse osmosis membrane of the sub reverse osmosis membrane device 11 can be restored efficiently and economically.

Moreover, in the water treatment system A of this embodiment, when the membrane performance of the reverse osmosis membrane of the sub reverse osmosis membrane device 11 is lowered, the third on-off valve 22 and the fourth on-off valve 23 are selectively opened. The acid agent W2 from the acid agent supply unit 13 and the bactericide W3 from the bactericide supply unit 14 can be appropriately supplied to the seawater 4 in the sub reverse osmosis membrane device 11. For example, when scale such as calcium carbonate adheres to the reverse osmosis membrane and the membrane performance deteriorates, the scale is dissolved by supplying acidic water (acidic agent) W2 from the acidic agent supply means 13. Can be removed.
In addition, for example, when organisms adhere to and propagate on the reverse osmosis membrane and the membrane performance is reduced, the organism is reduced by supplying a chlorine-based disinfectant W3 such as hypochlorous acid from the disinfectant supply means 14. Can be killed and removed. Thereby, the membrane performance of the reverse osmosis membrane of the sub reverse osmosis membrane device 11 can be recovered more efficiently and economically.

Furthermore, in the water treatment system A of this embodiment, the sub reverse osmosis membrane device 11 is measured by measuring the pressure difference between the upstream side and the downstream side in the seawater circulation direction T of the sub reverse osmosis membrane device 11 by the differential pressure measuring means 16. The film performance (deterioration of film performance) can be confirmed. Thereby, it is possible to determine whether the reverse osmosis membrane of the sub reverse osmosis membrane device 11 needs to be maintained or replaced.

Furthermore, for example, when the pressure difference increases proportionally according to the amount of treated water of the seawater 4, it is determined that the suspended osmosis membrane is clogged and the membrane performance is deteriorated. Moreover, when a pressure difference becomes large without correlating with the amount of treated water of the seawater 4, it is judged that the membrane performance is degraded due to the attachment of organisms and scales. Thus, by measuring the pressure difference together with the type and properties of the water to be treated, it is possible to identify the factors that degrade the membrane performance. Thereby, according to the specified factor of deterioration of the membrane performance, for example, any one of the backwashing means 12, the acid agent supply means 13, and the bactericide supply means 14 can be selected to effectively restore the membrane performance. It becomes possible.

In the water treatment system A of the present embodiment, the first on-off valve 10, the second on-off valve 21, the third on-off valve 22, and the fourth on the basis of the measurement results of the differential pressure measuring means 16 and the pH measuring means 17. By controlling opening and closing of the on-off valve 23 and the fifth on-off valve 24, the maintenance of the sub reverse osmosis membrane device 11 and the manufacture of the fresh water 6 can be efficiently performed, for example, fully automatically or semi-automatically.

As mentioned above, although one embodiment of the water treatment system concerning the present invention was described, the present invention is not limited to the above-mentioned embodiment, and can be suitably changed in the range which does not deviate from the meaning.

For example, in this embodiment, the water treatment system A includes a plurality of pretreatment devices 1 and 2 for one main reverse osmosis membrane device 3. The plurality of pretreatment devices 1 and 2 individually supply treated seawater (treated water) 4 and are connected to the main reverse osmosis membrane device 3 via the first on-off valve 10. With this configuration, when the membrane performance of the sub-reverse osmosis membrane device 11 of a certain pretreatment device 1 deteriorates and maintenance or replacement becomes necessary, the seawater 4 treated by another pretreatment device 2 is converted into the main reverse osmosis membrane device. It has been explained that the fresh water 6 can be produced efficiently without stopping the operation of the water treatment system A by supplying the water to 3.

On the other hand, in the water treatment system A according to the present embodiment, the water treatment system A does not necessarily have to be provided with a plurality of pretreatment devices 1 and 2, and as shown in FIG. You may prepare. In this case, for example, the storage tank 25 that temporarily stores the seawater 4 processed by the pretreatment device 1 (sub-reverse osmosis membrane device 11), and the seawater 4 from the storage tank 25 to the main reverse osmosis membrane device 3. A water supply pump 26 is provided. That is, the seawater 4 processed by the sub reverse osmosis membrane device 11 of the pretreatment device 1 is temporarily stored in the storage tank 25 and sent from the storage tank 25 to the main reverse osmosis membrane device 3 by the water pump 26, so that the fresh water 6 is supplied. Can be manufactured. For this reason, even if the membrane performance of the sub reverse osmosis membrane device 11 of one pretreatment device 1 is deteriorated and maintenance or replacement is necessary, the fresh water 6 using the seawater 4 stored in the storage tank 25 is used. Can be continued, and it is possible to obtain the same effect as the present embodiment including the plurality of pretreatment devices 1 and 2.

According to the water treatment system described above, the pretreatment device for treating the water to be treated such as seawater before the supply to the main reverse osmosis membrane device that generates fresh water includes the sub reverse osmosis membrane device. Inhibitors existing in the water to be treated and degrading the membrane performance of the reverse osmosis membrane can be collected by the reverse osmosis membrane of the sub reverse osmosis membrane device before the main reverse osmosis membrane device.

1 Pretreatment device 2 Pretreatment device 3 Main reverse osmosis membrane device 3a Reverse osmosis membrane unit 4 Seawater (treated water)
DESCRIPTION OF SYMBOLS 5 Concentrated water 6 Fresh water 7 Concentrated water discharge pipe 8 Permeated water pipe 9 To-be-processed water supply pipe 10 1st on-off valve 11 Sub reverse osmosis membrane apparatus 11a Reverse osmosis membrane unit 12 Backwash means 12a Backwash water tank 12b Backwash water pipe 13 Acidity Agent supply means 13a Acidic water tank 13b Acidic water pipe 13c Acidic water pump 14 Bactericidal agent supply means 14a Bactericidal water tank 14b Bactericidal water pipe 14c Bactericidal water pump 15 Reducing agent supply means 15a Reducing agent tank 15b Reducing agent pipe 15c Reducing agent pump 16 Differential pressure Measuring means 17 pH measuring means 18 Control means 20 Raw water supply pipe 21 Second on-off valve 22 Third on-off valve 23 Fourth on-off valve 24 Fifth on-off valve 25 Storage tank 26 Water supply pump A Water treatment system T Untreated water flow direction W1 Backwash water W2 Acid water (acid agent)
W3 Disinfectant water (disinfectant)
W4 reducing agent

Claims

A main reverse osmosis membrane device for separating treated water into concentrated water and fresh water having a high solute concentration;
A sub-reverse osmosis membrane device as a pretreatment device for removing an obstacle that degrades the membrane performance of the reverse osmosis membrane of the main reverse osmosis membrane device from the water to be treated in advance before being supplied to the main reverse osmosis membrane device And a water treatment system.
The water treatment system according to claim 1, comprising a plurality of the pretreatment devices,
The plurality of pretreatment devices individually supply treated water to one main reverse osmosis membrane device, and are connected to the main reverse osmosis membrane devices via first on-off valves, respectively. Water treatment system.
In the water treatment system according to claim 1 or 2,
The pretreatment device includes backwashing means,
The backwashing means is connected to the sub reverse osmosis membrane device via a second on-off valve, and backwashes the reverse osmosis membrane of the sub reverse osmosis membrane device from the downstream side to the upstream side in the treated water flow direction. Water treatment system that supplies water.
In the water treatment system according to any one of claims 1 to 3,
The pretreatment device comprises an acid agent supply means and / or
A disinfectant supply means,
The acid agent supply means is connected to the sub reverse osmosis membrane device via a third on-off valve, and an acid agent for removing scale adhered to the reverse osmosis membrane of the sub reverse osmosis membrane device is used as water to be treated. Supply
The sterilizing agent supplying means is connected to the sub reverse osmosis membrane device via a fourth on-off valve, and the sterilizing agent for removing organisms attached to the reverse osmosis membrane of the sub reverse osmosis membrane device is used as water to be treated. Supply water treatment system.
In the water treatment system according to any one of claims 1 to 4,
The said pre-processing apparatus is a water treatment system provided with the differential pressure measurement means for measuring the pressure difference of the to-be-processed water distribution direction upstream and downstream of the said sub reverse osmosis membrane apparatus.
The water treatment system according to claim 5,
The pre-processing device includes an on-off valve provided in the pre-processing device among the first on-off valve, the second on-off valve, the third on-off valve, and the fourth on-off valve. A water treatment system comprising control means for controlling opening and closing based on a measurement result.