JP2022144923A - Water treatment system, and water treatment method - Google Patents

Abstract

To provide a water treatment system and a water treatment method capable of decreasing the risk of clogging a reverse osmosis membrane, and efficiently decreasing the amount of concentrated water.SOLUTION: The water treatment system comprises an introduction unit, a membrane separation unit for desalination, a first depressurization unit, a first membrane separation unit for concentration, a second membrane separation unit for concentration, and a second depressurization unit.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD Embodiments of the present invention relate to water treatment systems and water treatment methods.

In recent years, laws and regulations for realizing healthy water circulation have been strengthened. ZLD (Zero Liquid Discharge) means to recycle and use water in the factory from the viewpoint of reducing the risk of water pollution, regenerating and reusing wastewater, and further reducing the wastewater discharged from the factory to zero. The goal is to conserve the water environment by reducing it. In order to reduce wastewater to zero, it is necessary to finally separate solids and deionized water by evaporation. The evaporation method is a method of separating solids and deionized water by heating wastewater to generate steam and cooling the steam to obtain deionized water. This method has the advantage that a two-stage flash evaporation method, a multi-stage flash evaporation method, etc. can be put into practical use, and deionized water of very high purity can be obtained. However, it has the drawback of low energy efficiency due to the need for a heat source. Therefore, from the viewpoint of reducing energy consumption, it is required to reduce the amount of wastewater treated by the evaporation method as much as possible by increasing the degree of concentration of wastewater as much as possible.

From such a demand, reverse osmosis (RO: Reverse Osmosis) membrane (hereinafter, sometimes referred to as "RO membrane") separates fresh water from concentrated wastewater containing (or dissolved) solids in the previous stage of the evaporation method. ) is used. A desalination/concentration system using an RO membrane introduces the water to be treated under pressure into the RO membrane, and produces deionized water that has passed through the RO membrane and concentrated water that has not passed through the RO membrane. It consists of the basic process of obtaining

The RO membrane has the effect of removing almost all substances such as ionic substances, fine particles, organic substances, and some dissolved gases, and furthermore, unless clogging or trouble occurs, it is not necessary to carry out discontinuous processes such as regeneration. , is widely used.

However, RO membranes can become clogged with silica, hardness scale, and biofouling.

When the RO membrane becomes clogged, it is necessary to stop the entire water treatment system in order to clean the RO membrane. As a result, the operating rate of the water treatment system decreases. In addition, the concentrated water that has not been concentrated to the expected degree of concentration is subjected to evaporation treatment, resulting in an increase in the thermal energy required for evaporation and an increase in overall treatment costs.

JP 2018-069198 A JP 2019-188330 A

An object of the present invention is to provide a water treatment system and a water treatment method capable of reducing the possibility of clogging of the reverse osmosis membrane and efficiently reducing the amount of concentrated water.

The water treatment system according to the embodiment includes an introduction unit that pressurizes and delivers water to be treated;
A membrane separation unit for desalination comprising a first reverse osmosis membrane element arranged downstream of the introduction unit, the first reverse osmosis membrane element comprising a first reverse osmosis membrane and a first reverse osmosis membrane. The first reverse osmosis membrane element has a first chamber and a second chamber defined by the membrane and connected to the introduction unit by a first flow path, wherein the first chamber of the first reverse osmosis membrane element is connected by the first flow path. A desalting membrane separation unit connected to the introduction unit; A desalting membrane separation unit arranged downstream of the desalting membrane separation unit, one end of which is different from the connection point of the first channel. a first pressure reducing unit comprising a first pressure reducing device connected to the first chamber of the desalting membrane separation unit by a second flow path located at the location of the first chamber of the membrane separation unit; A first concentration membrane separation unit disposed downstream of one pressure reduction unit, comprising a second reverse osmosis membrane element, and having a maximum pressure resistance lower than that of the desalination membrane separation unit, The two reverse osmosis membrane elements have a second reverse osmosis membrane and a first chamber and a second chamber separated by the second reverse osmosis membrane, the first chamber of the second reverse osmosis membrane element is connected to the first pressure reduction unit by a third flow path, and the second chamber of the second reverse osmosis membrane element is connected to the introduction unit by a fourth flow path. Separation unit; a second membrane separation unit for concentration provided with a third reverse osmosis membrane element arranged downstream from the first membrane separation unit for concentration, wherein the third reverse osmosis membrane element is the second 3 reverse osmosis membranes, a first chamber and a second chamber separated by a third reverse osmosis membrane, the first chamber of the third reverse osmosis membrane element being separated by a fifth flow path The sixth flow path is connected to the first chamber of the first membrane separation unit for concentration, the sixth flow path is connected at a position different from the fifth flow path, and the second chamber of the third reverse osmosis membrane element is connected to the second a second concentrating membrane separation unit connected to the second chamber of the first concentrating membrane separation unit by passage No. 7; and a second concentrating membrane separation unit connected to the fifth passage or sixth passage. A decompression unit connected to the fifth or sixth flow path by an eighth flow path, and connected to the second chamber of the second membrane separation unit for concentration by a ninth flow path. a second pressure reducing unit, comprising a second pressure reducing device.

It is a schematic diagram showing a water treatment system concerning a 1st embodiment. FIG. 2 is a schematic diagram showing an introduction unit of the water treatment system of FIG. 1; It is a schematic diagram showing a modification of the first decompression unit in the water treatment system of FIG. It is a schematic diagram showing a modification of a water treatment system concerning a 1st embodiment. It is a schematic diagram showing another modification of the water treatment system concerning a 1st embodiment. It is a schematic diagram showing a water treatment system concerning a 2nd embodiment. It is a schematic diagram showing a water treatment system concerning a 3rd embodiment. It is a schematic diagram showing a water treatment system concerning a 4th embodiment. It is a schematic diagram showing a water treatment system concerning a 5th embodiment. It is a schematic diagram showing a water treatment system concerning a 6th embodiment. It is a schematic diagram showing a water treatment system concerning a 7th embodiment. It is a schematic diagram showing a modification of a water treatment system concerning a 7th embodiment. It is a schematic diagram showing a water treatment system concerning an 8th embodiment. It is a schematic diagram showing a water treatment system concerning a 9th embodiment. It is a schematic diagram showing a water treatment system concerning a 10th embodiment. It is a schematic diagram showing a modification of a water treatment system concerning a 10th embodiment. It is a schematic diagram showing a water treatment system concerning an 11th embodiment.

Embodiments will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic diagram showing the functional configuration of the water treatment system according to the first embodiment.

The water treatment system 1 includes an introduction unit 10 that pressurizes and delivers water to be treated. The introduction unit 10 includes, for example, a liquid mixing tank 11 for storing the water to be treated as shown in FIG. The liquid mixing tank 11 includes a supply channel 211 for supplying the liquid to be treated, a chemical solution supply channel 12, a gas supply channel 13, and a first channel for sending the pressurized water to be treated to a membrane separation unit for desalination to be described later. 1 channel 201 and a fourth channel 204 for circulating return concentrated water of the second chamber of the first membrane separation unit for concentration, which will be described later, are respectively inserted. A pump 14 for supplying the liquid to be treated to the liquid mixing tank 11 is interposed in the supply channel 211 . A booster pump 15 is installed in the first flow path 201 to pressurize the water to be treated in the liquid mixing tank 11 and send it to the membrane separation unit for desalination. A water quality meter 16 is arranged in the liquid mixing tank 11 . A stirrer 17 is arranged in the liquid mixing tank 11 .

The chemical solution supplied from the chemical solution supply channel 12 to the liquid mixing tank 11 contains, for example, a pH adjuster, a disinfectant, a scale inhibitor, a biofouling inhibitor, a membrane cleaning agent, and the like. The chemical solution is used depending on the water quality measured by the water quality meter 16, the material and performance of the reverse osmosis membranes used in the desalination membrane separation unit and the first and second concentration membrane separation units, which will be described later. Further, the chemicals can be used properly according to the time of steady operation, the time of maintenance, and the like. As the pH adjuster, for example, an alkaline agent such as caustic soda or potassium hydroxide is used. Thereby, the introduction unit 10 adjusts the pH of the water to be treated in the liquid mixing tank 11, preferably to 3 or more and 8 or less.

The gas supplied from the gas supply channel 13 to the liquid mixing tank 11 is, for example, air or carbon dioxide. The liquid mixing tank 11 preferably agitates or circulates the solution so that the amount of dissolved air increases. For example, the dissolved oxygen content is desirably 2 mg/L or more.

The water quality meter 16 includes a pH meter that measures the pH of the water to be treated stored in the liquid mixing tank 11 . The water quality meter 16 includes a water level meter for measuring the water level of the water to be deaired stored in the liquid mixing tank 11, a conductivity meter for measuring conductivity, an ORP meter for measuring oxidation-reduction potential, and a zeta potential. A zeta potential meter, a dissolved oxygen meter for measuring the amount of dissolved oxygen, and the like may be included.

The boosting pump 15 is activated when the water quality meter 16 detects that the water quality such as pH of the water to be treated stored in the liquid mixing tank 11 has reached a value suitable for introduction into the desalination separation unit. , the water to be treated stored in the liquid mixing tank 11 is pressurized to a preset pressure and introduced into the desalting separation unit. The preset pressure is, for example, at least a pressure higher than the osmotic pressure of the water to be treated and a pressure at which circulating water from the first membrane separation unit for concentration described below can be returned. Specifically, it is about 5 MPa to 12 MPa, preferably 10 MPa or more.

The desalting membrane separation unit 20 is arranged downstream of the introduction unit 10 . Here, on the basis of the flow of the water to be treated or the concentrated water described later, the lower part of the flow is called the downstream, and the upper part of the flow is called the upstream. The desalting membrane separation unit 20 comprises a first reverse osmosis element 21 . The first reverse osmosis element 21 comprises a first closed container, for example, a first pressure-resistant closed container 22, a first reverse osmosis membrane 23 disposed within the first pressure-resistant closed container 22, and a first reverse osmosis membrane 23 disposed within the first pressure-resistant closed container 22. It includes a first chamber 24 and a second chamber 25 which are formed by partitioning the first pressure-tight sealed container 22 from the permeable membrane 23 . The first pressure-tight sealed container 22 in which the first chamber 24 is located is connected to the introduction unit 10 by a first channel 201 .

The desalination membrane separation unit 20 having such a configuration introduces the water to be treated into the first chamber 24 at a higher pressure than in the first and second concentration membrane separation units 40 and 50 described later. Therefore, the water in the water to be treated is efficiently permeated from the first reverse osmosis membrane 23 to the second chamber 25 and separated into permeated water and concentrated water in which the dissolved solid content (salt content) is concentrated. . This "concentrated water" may include the water to be treated that has passed through the first chamber 9 without being concentrated by the above-described forward osmosis action of the first reverse osmosis membrane 23, but the water to be treated that has been concentrated by the action is preferably sent from the desalting membrane separation unit 20 to the first pressure reduction unit 30 .

The first pressure-resistant sealed container 22 preferably has a pressure resistance of 10 MPa or higher.

For the first reverse osmosis membrane 23, for example, a spiral membrane, a hollow fiber membrane, or the like can be used.

The first decompression unit 30 is arranged downstream of the desalting membrane separation unit 20 and includes a decompression device 31 . The inlet of the decompression device 31 is connected by a second flow path 202 to the first pressure-tight sealed container 22 in which the first chamber 24 of the desalination membrane separation unit 20 is located. The pressure reducing device 31 has, for example, a pressure reducing valve, and when the high-pressure concentrated water sent from the first chamber 24 of the desalting membrane separation unit 20 passes through the pressure reducing valve, the pressure of the concentrated water is rapidly reduced. do.

In the first decompression unit 30 having such a configuration, the pressure reduction amount of the concentrated water sent from the desalting membrane separation unit 20 is preferably 0.5 MPa or more, more preferably 3 MPa or more. By setting the pressure reduction amount to 0.5 MPa or more, the generation amount of fine bubbles, which will be described later, is increased, and the effect of preventing scale and biofouling is enhanced.

In addition, the pressure reduction amount of the concentrated water by the first decompression unit 30 is such that the pressure of the water to be treated to the desalination membrane separation unit 20 is 10 MPa or more and the maximum pressure resistance of the reverse osmosis membrane (for example, 12 MPa) or less. and more preferably 3 MPa or more and 7 MPa or less.

The first concentrating membrane separation unit 40 is arranged downstream of the first decompression unit 30 . The first concentration membrane separation unit 40 has a maximum pressure resistance lower than that of the desalination membrane separation unit 20 . The first concentrating membrane separation unit 40 comprises a second reverse osmosis element 41 . The second reverse osmosis element 41 comprises a second closed container, for example, a second pressure-resistant closed container 42, a second reverse osmosis membrane 43 disposed within the second pressure-resistant closed container 42, and a second reverse osmosis membrane 43 disposed within the second pressure-resistant closed container 42. It includes, for example, a first chamber 44 on the upper side and a second chamber 45 on the lower side, which are formed by partitioning the second pressure-resistant airtight container 42 from the permeable membrane 43 . The second pressure tight container 42 in which the first chamber 44 is located is connected to the outlet of the first vacuum unit 30 by a third flow path 203 . The second pressure-resistant sealed container 42 in which the second chamber 45 is located is connected to the introduction unit 10 by a fourth flow path 204 .

The first concentrating membrane separation unit 40 having such a configuration further concentrates the concentrated water sent from the first decompression unit 30 by the second reverse osmosis element 41, and at the same time concentrates the concentrated water in the first chamber 44. The water of water is permeated into the second chamber 45 to dilute the return concentrated water (circulating water) in the second chamber 45 .

The form of the second reverse osmosis membrane 43 is not particularly limited, and for example, a hollow fiber membrane can be used.

The second membrane separation unit for concentration 50 is arranged downstream of the first membrane separation unit for concentration 40 . The second concentrating membrane separation unit 50 comprises a third reverse osmosis element 51 . The third reverse osmosis element 51 includes a third closed container, for example, a third pressure-resistant closed container 52, a third reverse osmosis membrane 53 disposed within the third pressure-resistant closed container 52, and a third reverse osmosis membrane 53. It includes, for example, a first chamber 54 on the upper side and a second chamber 55 on the lower side, which are formed by partitioning the third pressure-resistant airtight container 52 from the permeable membrane 53 . The third pressure-resistant sealed container 52 in which the first chamber 54 is located is connected to the second pressure-resistant closed container 42 in which the first chamber 44 of the first concentration membrane separation unit 40 is located by a fifth flow path 205. It is connected. A sixth flow path 206 is connected to the third pressure-resistant sealed container 52 in which the first chamber 54 is located. The third pressure-resistant closed container 52 in which the second chamber 55 is located is connected to the second pressure-resistant closed container 42 in which the second chamber 45 of the first concentration membrane separation unit 40 is located by the seventh flow path 207. It is connected. Although the right side of the chamber of the first membrane separation unit 40 for concentration and the left side of the chamber of the second membrane separation unit 50 for concentration are connected in FIG. 1, they can be adjusted as appropriate.

The second concentrating membrane separation unit 50 having such a configuration further concentrates the concentrated water sent from the first concentrating membrane separation unit 40 by the third reverse osmosis element 51, and at the same time, the first chamber 54 The water of the concentrated water inside permeates into the second chamber 55 to dilute the return concentrated water (circulating water) in the second chamber 55 .

The second decompression unit 60 includes a second decompression device 61 . The second decompression device 61 has the same structure as the decompression device 31 of the first decompression unit 30, for example. The suction port of the second decompression device 61 is connected to the sixth flow path 206 by an eighth flow path 208 . A discharge port of the second decompression device 61 is connected to a ninth flow path 209, which is a third pressure-resistant pressure chamber in which the second chamber 55 of the second concentration membrane separation unit 50 is located. It is connected to the closed container 52 .

The second decompression unit 60 having such a configuration decompresses the concentrated water sent from the first chamber 54 of the second concentration membrane separation unit 50 through the sixth flow path 206 and the eighth flow path 208. do. That is, when the second decompression unit 60 sends back concentrated water to the second chamber 55, the pressure of the concentrated water in the first chamber 54 of the second membrane separation unit 50 for concentration is reduced to It is set to be higher than the pressure of the return concentrated water in the second chamber 55 . The pressure reduction amount of the return concentrated water sent into the second chamber 55 is preferably 1 MPa or more, more preferably 3 MPa or more. By setting the pressure reduction amount to 3 MPa or more, the pressure of the concentrated water sent to the first chamber 54 of the second membrane separation unit 50 for concentration is sufficiently higher than the pressure of the concentrated water returned to the second chamber 55. , and the water contained in the concentrated water in the first chamber 54 can be smoothly permeated to the second chamber 55 through the third reverse osmosis membrane 53 .

Next, water to be treated by the water treatment system according to the first embodiment shown in FIGS. 1 and 2, for example, wastewater with a total dissolved solids (TDS) concentration of about 0.1% to several % A processing method will be explained.

First, in the introduction unit 10, as shown in FIG. At this time, a predetermined chemical solution, gas such as air is supplied into the liquid mixing tank 11 from the chemical solution supply channel 12 and the gas supply channel 13 as necessary, and the waste water 300 is stirred by the stirrer 17 . Subsequently, the booster pump 15 is driven to pressurize the wastewater 300 in the liquid mixing tank 11 and send it through the first flow path 201 to the first chamber 24 of the desalting membrane separation unit 20 . The pressure of the pressurized wastewater is preferably set to 10 MPa or more and to the maximum pressure resistance (for example, 12 MPa) of the first reverse osmosis membrane 23 or less.

Due to the large pressure difference between the high pressure wastewater delivered to the first chamber 24 of the desalination membrane separation unit 20 and the second chamber 25, the water in the wastewater is forced through the first reverse osmosis membrane 23 to the second chamber 25 and the wastewater in the first chamber 24 is concentrated. Water that permeates the second chamber 25 is discharged to the outside through the tenth channel 210 .

The concentrated water in the first chamber 24 of the desalting membrane separation unit 20 is then sent through the second flow path 202 to the decompression device 31 of the first decompression unit 30 . This "concentrated water" may include the water to be treated that has passed through the first chamber 9 without being concentrated by the above-described forward osmosis action of the first reverse osmosis membrane 23, but the water to be treated that has been concentrated by the action is more preferably delivered from the desalting membrane separation unit 20 to the first decompression unit 30 . The concentrated water sent to the decompression device 31 is decompressed through a decompression valve (not shown). The pressure reduction amount of the concentrated water sent from the desalting membrane separation unit 20 is preferably 0.5 MPa or more, more preferably 3 MPa or more, and still more preferably 1 MPa or more and 7 MPa or less.

Due to such rapid decompression, gas dissolved in the concentrated water expands to generate bubbles. Air bubbles are finely pulverized by rapid pressure recovery to generate fine bubbles.

The amount of fine bubbles of 1000 nm or less generated by the decompression operation is 1.0E+6/ It is preferable to set so that it contains more than mL. The amount of fine bubbles in the concentrate discharged through the sixth channel 206 can be measured using, for example, a Clap-on flow meter. The fine bubbles may disappear while flowing through the water treatment system, and the first concentration membrane separation unit 40 and the second concentration membrane separation unit 50 arranged downstream from the pressure reduction unit The amount of fine bubbles supplied may be reduced from the amount generated in the decompression unit. Even in such a case, if the concentrated water discharged through the sixth flow path 206, which is the most downstream of the water treatment system of the present embodiment, contains at least 1.0E + 6 / mL of fine bubbles, it It is possible to prevent scale generation and biofouling in the second and third reverse osmosis membranes 43 and 53 arranged upstream.

The decompressed concentrated water is delivered to the first chamber 44 of the first membrane separation unit 40 for concentration through the third flow path 203 . The concentrated water in the first chamber 44 is sent through the fifth channel 205 to the first chamber 54 of the second membrane separation unit 50 for concentration. The concentrated water in the first chamber 54 is sent outside through the sixth channel 206 . The concentrated water passing through the sixth flow path 206 is sent to the second decompression device 61 of the second decompression unit 60 through an eighth flow path 208 branched from the sixth flow path 206 . The concentrated water sent to the second decompression device 61 is decompressed through a decompression valve (not shown). The depressurized concentrated water is set to a lower pressure than the concentrated water delivered to the first chamber 54 of the second membrane separation unit 50 for concentration. The depressurized concentrated water is returned to the second chamber 55 of the second membrane separation unit 50 for concentration through the ninth channel 209 and sent out as concentrated water. The pressure reduction amount of the return concentrated water delivered into the second chamber 55 is preferably 1 MPa or more, more preferably 3 MPa or more. The return concentrated water in the second chamber 55 is sent through the seventh flow path 207 to the second chamber 45 of the first membrane separation unit 40 for concentration. The return concentrated water in the second chamber 45 is returned, that is, circulated, to the liquid mixing tank 11 of the introduction unit 10 through the fourth channel 204 .

While circulating the concentrated water in this way, in the first membrane separation unit 40 for concentration, the concentrated water decompressed by the first decompression unit 30 is sent to the first chamber 44 and is sent to the second membrane for concentration. The return concentrate in the second chamber 55 of the separation unit 50 is delivered to the second chamber 45 . The return concentrated water in the second chamber 45 is set to a lower pressure than the concentrated water in the first chamber 44 of the second chamber 45 by the decompression operation by the second decompression unit 60 . Therefore, using the pressure difference between the concentrated water in the first chamber 44 and the return concentrated water (for example, 2 MPa or less) in the second chamber 45 (pressure of concentrated water>pressure of returned concentrated water) Water in the concentrated water in the first chamber 44 is permeated through the second reverse osmosis membrane 43 to the second chamber 45 . By this operation, the concentrated water sent to the first chamber 44 is further concentrated. Also, the return concentrate in the second chamber 45 is diluted with the permeate from the first chamber 44 .

Next, the concentrated water in the first chamber 44 in the first membrane separation unit for concentration 40 is sent through the fifth flow path 205 to the first chamber 54 in the second membrane separation unit for concentration 50, The concentrated water sent out from the first chamber 54 is depressurized by the second decompression unit 60 and returned to the second chamber 55 to be sent out as concentrated water. The return concentrated water in the second chamber 55 is set to a pressure lower than that of the concentrated water in the first chamber 54 by the decompression operation of the second decompression unit 60 . Therefore, the pressure difference between the concentrated water in the first chamber 54 and the return concentrated water in the second chamber 55 (concentrated water pressure>return concentrated water pressure) is used to restore the first chamber 54 The water contained in the concentrated water inside is permeated from the third reverse osmosis membrane 53 to the second chamber 55 . By this operation, the concentrated water delivered to the first chamber 54 is further concentrated. Also, the return concentrate in the second chamber 55 is diluted with the permeate from the first chamber 54 .

The return concentrated water in the second chamber 45 of the first membrane separation unit 40 for concentration is circulated to the liquid mixing tank 11 of the introduction unit 10 . This return concentrated water is permeated from the concentrated water in the first chamber 54 to the return concentrated water in the second chamber 55 through the third reverse osmosis membrane 53 in the second membrane separation unit 50 for concentration. and the water in the concentrated water in the first chamber 44 in the first membrane separation unit 40 for concentration is permeated from the second reverse osmosis membrane 43 to the return concentrated water in the second chamber 45, diluted. Therefore, the TDS concentration of the return concentrated water circulated to the liquid mixing tank 11 is diluted to, for example, about 60% of the initial TDS concentration of the returned concentrated water, which is less than or equal to that of the water to be treated.

The concentrated water in the first chamber 54 of the second concentration membrane separation unit 50 is recovered as highly concentrated concentrated water.

The water to be treated is not limited to wastewater having a TDS concentration of about 0.1% to several percent, and for example, wastewater such as food factory wastewater containing organic matter can be used.

When the return concentrated water in the second chamber 45 of the first membrane separation unit 40 for concentration is circulated to the introduction unit 10, the total flow rate of the flow rate of the water to be treated and the flow rate of the return concentrated water supplied to the introduction unit 10 A flow rate of 50 to 95% is preferable.

As described above, according to the first embodiment, the water to be treated at a high pressure (10 MPa or more and the maximum pressure resistance [for example, 12 MPa] or less of the first reverse osmosis membrane 23) is treated with the first By introducing the water into the chamber 24, the water to be treated in the first chamber 24 can be efficiently permeated from the first reverse osmosis membrane 23 to the second chamber 25 to concentrate the water to be treated. At the same time, the deionized water that permeates the first reverse osmosis membrane 23 can be recovered from the tenth channel 210 and produced. The concentrated water in the first chamber 24 is decompressed by the first decompression unit 30 downstream of the desalting membrane separation unit 20, and the decompressed concentrated water is sent to the first and second concentration membrane separation units 40 and 50 in sequence. By sending out, highly concentrated water can be recovered from the first chamber 54 of the second membrane separation unit 50 for concentration. That is, it is possible to obtain efficiently reduced concentrated water from the wastewater supplied to the introduction unit 10 . As a result, when evaporating the collected concentrated water, the thermal energy required for evaporation can be reduced, so that the overall treatment cost can be reduced.

By reducing the pressure of the concentrated water in the first chamber 24 with the first decompression unit 30 (for example, a pressure reduction amount of 0.5 MPa or more), gas dissolved in the concentrated water expands to generate bubbles. Air bubbles are finely pulverized by rapid pressure recovery to generate fine bubbles.

The fine bubbles have, for example, an average diameter of 1000 nm or less, are highly stable in the liquid, and are effective against the second and third reverse osmosis membranes 43 and 53 arranged downstream of the first decompression unit 30. and has high permeability. As a result, it becomes possible to prevent scale generation and biofouling in the second and third reverse osmosis membranes 43 and 53 .

Further, since the fine bubbles have hydrophobic surfaces and are charged, the introduction unit 10 introduces the anti-scaling agent, anti-biofouling agent, sterilant, and membrane cleaning agent into the liquid mixing tank 11 from the chemical supply channel 12. When supplied, it becomes possible to easily adhere those drugs to the second and third reverse osmosis membranes 43 and 53 . As a result, it becomes possible to more effectively prevent scale generation and biofouling in the second and third reverse osmosis membranes 43 and 53 .

As a result, scale generation of the second and third reverse osmosis membranes 43 and 53 and clogging due to biofouling are suppressed or prevented, and operations such as cleaning of the second and third reverse osmosis membranes 43 and 53 are performed. Since it can be reduced or eliminated, the utilization rate of the water treatment system can be increased.

It should be noted that the first decompression unit 30 described in the first embodiment is not limited to the configuration including the decompression device 31 having a decompression valve. For example, a decompression device 32 shown in FIG. 3 may be provided. That is, the decompression device 32 has a water storage tank 33 . A second flow path 202 connected to the first chamber 24 of the membrane separation unit for desalination and a third flow path 203 connected to the first chamber 44 of the first membrane separation unit for concentration are each connected to a water storage tank. 33 is inserted. A pump 34 is interposed in the third flow path 203 .

According to the first decompression unit 30 having such a configuration, the concentrated water sent through the second flow path 202 connected to the first chamber 24 of the desalting membrane separation unit is stored in the water storage tank 33. The pressure is thereby reduced to atmospheric pressure. After that, the pump 34 of the third flow path 203 is driven to pressurize the concentrated water 400 in the water storage tank 33 and send it to the first chamber of the first membrane separation unit for concentration. At this time, by making the pressure of the pump 34 lower than the pressure when it is introduced into the first chamber of the desalting membrane separation unit, the concentrated liquid sent to the first chamber 44 of the first membrane separation unit for concentration is sent to the first chamber. Water can be decompressed. The discharge pressure of the pump 34 is preferably 2 MPa or less.

In addition, the water storage tank 33 may be provided with a chemical supply channel 35 for supplying a pH adjuster, a disinfectant, a scale inhibitor, a biofouling inhibitor, a membrane cleaning agent, and the like.

Also, a gas supply channel 36 for supplying air or carbon dioxide may be installed in the water storage tank 33 .

A sensor for measuring components contained in the concentrated water 400, for example, a sensor for measuring pH, conductivity, oxidation-reduction potential, zeta potential, residual chlorine concentration, etc., may be provided in the water storage tank 33 (not shown).

Moreover, in the first embodiment, the connection form of the first and second concentration membrane separation units 40 and 50 is not limited to that shown in FIG. For example, the connection forms shown in FIGS. 4 and 5 may be used. In FIGS. 4 and 5, members similar to those in FIG.

In the water treatment system 1 shown in FIG. 4 , the second decompression device 61 of the second decompression unit 60 has the second chamber 55 of the second concentration membrane separation unit 50 positioned by the ninth flow path 209 . It is connected to the left side of the third pressure-resistant closed container 52 . The second chamber 55 of the second membrane separation unit 50 for concentration has a first It is connected to the left side of the second pressure tight container 42 in which the second chamber 45 of the membrane separation unit 40 for concentration is located. The second chamber 45 of the first concentrating membrane separation unit 40 is connected to the introduction unit 10 by a fourth flow path 204 extending from the second pressure-resistant sealed container 42 in which the second chamber 45 is located. there is

According to the configuration shown in FIG. 4, the concentrated water flowing in the first chamber 44 and the return concentrated water flowing in the second chamber 45 in the first concentration membrane separation unit 40 are in the same direction. Also in the second membrane separation unit 50 for concentration, the concentrated water flowing in the first chamber 54 and the return concentrated water flowing in the second chamber 55 are in the same direction.

In the water treatment system 1 shown in FIG. 5 , the second decompression device 61 of the second decompression unit 60 has the second chamber 55 of the second concentration membrane separation unit 50 positioned by the ninth flow path 209 . It is connected to the third pressure-tight sealed container 52 . The second decompression device 61 includes a seventh flow path connecting the second chamber 55 of the second membrane separation unit for concentration 50 and the second chamber 45 of the first membrane separation unit for concentration 40 by another flow path 200. It is connected to the channel 207 .

5, in the second concentration membrane separation unit 50, the pressure difference between the concentrated water in the first chamber 54 and the return concentrated water in the second chamber 55 ( Water in the concentrate in the first chamber 54 can be permeated from the third reverse osmosis membrane 53 to the second chamber 55 by using the pressure of the concentrate>the pressure of the return concentrate. This permeated water dilutes the return concentrate in the second chamber 55 and increases the pressure of the return concentrate. In the process of sending the return concentrated water with increased pressure to the second chamber 45 of the first concentration membrane separation unit 40 through the seventh flow path 207, the return concentrated water pressure-reduced by the second pressure reducing device 61 Water can be delivered through another channel 200 to a seventh channel 207 and mixed with the pressurized return concentrate. Thereby, the pressure-increased return concentrated water can be decompressed and sent to the second chamber 45 of the first membrane separation unit 40 for concentration. As a result, in the first membrane separation unit 40 for concentration, the pressure difference between the concentrated water in the first chamber 44 and the return concentrated water in the second chamber 45 (pressure of concentrated water>return concentrated water pressure) can be made sufficiently large. Therefore, the water in the concentrated water in the first chamber 44 of the first membrane separation unit 40 for concentration can be efficiently permeated from the second reverse osmosis membrane 43 to the second chamber 45 .

(Second embodiment)
FIG. 6 is a schematic diagram showing a water treatment system according to the second embodiment. In FIG. 6, members similar to those in FIG. 1 explained in the first embodiment are denoted by the same reference numerals, and explanations thereof are omitted.

In the water treatment system 1 according to the second embodiment shown in FIG. 6, for example, two second reverse osmosis elements 41a and 41b are connected in series in the first membrane separation unit 40 for concentration. That is, the first chamber 44 of the second reverse osmosis element 41a in the former stage is connected to the first chamber 44 of the second reverse osmosis element 41b in the latter stage by the flow path 212 . The second chamber 45 of the second reverse osmosis element 41a in the former stage is connected to the second chamber 45 of the second reverse osmosis element 41b in the latter stage by a flow path 213 . Also, the first chamber 44 of the second reverse osmosis element 41 a in the preceding stage is connected to the introduction unit 10 through the fourth flow path 204 . The first chambers 44 of the second reverse osmosis elements 41b in the latter stage are connected to the first chambers 54 of the second membrane separation unit 50 for concentration through the fifth flow paths 205, respectively. The second chamber 45 of the second reverse osmosis element 41 b in the latter stage is connected to the second chamber 55 of the second membrane separation unit 50 for concentration through the seventh channel 207 .

According to the second embodiment of the configuration shown in FIG. 6, in the first concentration membrane separation unit 40, the two second reverse osmosis elements 41a and 41b are connected in series with each other, Compared with the water treatment system according to the first embodiment shown in FIG. 1, a water treatment system capable of highly concentrating the concentrated water in the first concentration membrane separation unit 40 can be realized.

(Third Embodiment)
FIG. 7 is a schematic diagram showing a water treatment system according to the third embodiment. In FIG. 7, members similar to those in FIG. 1 explained in the first embodiment are denoted by the same reference numerals, and explanations thereof are omitted.

In the water treatment system 1 according to the third embodiment shown in FIG. It is connected to the. That is, the three second reverse osmosis elements 41a, 41b, 41c in the front stage are arranged in parallel, and the two second reverse osmosis elements 41d, 41e in the rear stage are arranged in parallel. Flow paths 214 to 216 branched from the third flow path 203 connected to the first decompression unit 30 are positioned at the respective first chambers 44 of the three second reverse osmosis elements 41a, 41b, and 41c in the previous stage. It is connected to, for example, the left side of the second pressure-resistant sealed container 42 . For example, the right side of the second pressure-resistant sealed container 42 in which the first chambers 44 of the second reverse osmosis elements 41a, 41b, and 41c of the preceding stage are located, are branched and integrated flow paths 217, 218, and An integrated and branched flow path 219 connects to, for example, the left side of the second pressure-resistant sealed container 42 in which the first chambers 44 of the two subsequent second reverse osmosis elements 41d and 41e are located. The right side surface of the second pressure-resistant sealed container 42, in which the first chambers 44 of the two second reverse osmosis elements 41d and 41e in the latter stage are located, is branched and integrated into a channel 220 and a fifth channel 205. is connected to the left side of the third pressure-resistant sealed container 52 in which the first chamber 54 in the third reverse osmosis element 51 of the second membrane separation unit 50 for concentration is located.

For example, the left side of the third pressure-resistant sealed container 52 in which the second chamber 55 in the third reverse osmosis element 51 of the second concentration membrane separation unit 50 is located has a seventh flow path 207 and a seventh Two flow paths 221 and 222 branched from the flow path 207 are connected to, for example, the right side surface of the second pressure-resistant sealed container 42 in which the second chambers 45 of the second reverse osmosis elements 41d and 41e in the latter stage are located. It is For example, the left side of the second pressure-resistant sealed container 42 in which the second chambers 45 of the second reverse osmosis elements 41d and 41e are located are branched and integrated flow paths 223, 224, and integrated , are connected to, for example, the right side surface of the second pressure-resistant sealed container 42 in which the respective second chambers 45 of the three second reverse osmosis elements 41a, 41b, and 41c in the preceding stage are located by branched flow paths 225. . For example, the left side of the second pressure-resistant sealed container 42 in which the second chambers 45 of the three second reverse osmosis elements 41a, 41b, and 41c in the front stage are located has three flow paths 226 to 228 and these flow paths 226-228 are connected to the introduction unit 10 by a fourth channel 204 which integrates. The surface of the second pressure-resistant sealed container 42 to which the flow path is connected can be appropriately adjusted.

Connection configuration of the five second reverse osmosis elements 41a, 41b, 41c, 41d, and 41e, and these second reverse osmosis elements 41a, 41b, 41c, 41d, and 41e and the second concentration membrane separation unit 50 The three second reverse osmosis elements 41a, 41b, 41c in the front stage are connected in series to the two second reverse osmosis elements 41d, 41e in the rear stage by the connection form between the third reverse osmosis element 51 of The two second reverse osmosis elements 41 d and 41 e in the latter stage are connected in series to the third reverse osmosis element 51 of the second membrane separation unit 50 for concentration.

According to such a third embodiment, in the first membrane separation unit 40 for concentration, the three second reverse osmosis elements 41a, 41b, 41c in the front stage arranged in parallel are arranged in parallel. are connected in series to the two second reverse osmosis elements 41d and 41e in the latter stage, and the two second reverse osmosis elements 41d and 41e in the latter stage are the third reverse osmosis elements of the second concentration membrane separation unit 50 51, compared to the water treatment system according to the first embodiment shown in FIG. A processing system can be realized.

In the third embodiment, in the first concentrating membrane separation unit 40, the number of front-stage and rear-stage second reverse osmosis elements arranged in parallel is set to three and two, respectively, but is not limited thereto. , can have any number of stages, and the number of each stage can also be arbitrary.

(Fourth embodiment)
FIG. 8 is a schematic diagram showing a water treatment system according to a fourth embodiment. In FIG. 8, members similar to those in FIG. 7 explained in the third embodiment are denoted by the same reference numerals, and explanations thereof are omitted.

In the water treatment system 1 according to the fourth embodiment shown in FIG. It is connected to the. That is, as in the third embodiment described above, the three second reverse osmosis elements 41a, 41b, and 41c in the front stage are arranged in parallel, and the two second reverse osmosis elements 41d and 41e in the rear stage are arranged in parallel. and the connection form of those second reverse osmosis elements 41a, 41b, 41c, 41d, and 41e.

Also, in the second concentration membrane separation unit 50, for example, two third reverse osmosis elements 51a and 52b are arranged in parallel. For example, the right side of the second pressure-resistant sealed container 42 in which the first chambers 44 of the two second reverse osmosis elements 41d and 41e in the latter stage of the first concentration membrane separation unit 40 are located, flow paths 229, By 230, the first chamber 54 of the third reverse osmosis elements 51a, 51b of the second concentrating membrane separation unit 50 is connected to, for example, the left side of the third pressure-tight closed vessel 52 in which it is located. The second decompression device 61 of the second decompression unit 60 is, for example, a third pressure-resistant sealed container 52 in which the second chambers 55 of the third reverse osmosis elements 51a, 51b are located by two flow paths 231, 232. They are connected to the right side. For example, the left side of the third pressure-resistant closed container 52 where the second chamber 55 in the third reverse osmosis elements 51a, 51b is located is branched and integrated flow path 233, flow path 234, and integrated and branched For example, the right side of the second pressure-resistant sealed container 42 in which the first chambers 44 of the two second reverse osmosis elements 41d and 41e in the rear stage of the first concentration membrane separation unit 40 are located by the flow path 235 formed by the It is connected.

Connection configuration of the five second reverse osmosis elements 41a, 41b, 41c, 41d, and 41e, and these second reverse osmosis elements 41a, 41b, 41c, 41d, and 41e and the second concentration membrane separation unit 50 By the connection form between the two third reverse osmosis elements 51a, 51b of The two second reverse osmosis elements 41d and 41e in the latter stage are connected in series to the two third reverse osmosis elements 51a and 51b of the second concentrating membrane separation unit 50, respectively.

According to such a fourth embodiment, compared with the water treatment system according to the third embodiment shown in FIG. possible water treatment system can be realized.

In the fourth embodiment, two third reverse osmosis elements are arranged in parallel in the second concentration membrane separation unit 50, but the present invention is not limited to these, and three or more third reverse osmosis elements are arranged in parallel. can be placed

(Fifth embodiment)
FIG. 9 is a schematic diagram showing a water treatment system according to a fifth embodiment. In FIG. 9, members similar to those in FIG. 1 explained in the first embodiment are denoted by the same reference numerals, and explanations thereof are omitted.

In the water treatment system 1 according to the fifth embodiment shown in FIG. 9, the heat treatment unit 70 is further connected to the sixth flow path 206 connected to the first chamber 54 of the second membrane separation unit 50 for concentration. have a structure. The heat treatment unit 70 includes, for example, an evaporative concentration device (not shown) and an evaporative dryer. Thermal processing unit 70 is connected to sixth channel 206 by channel 236 . A solid salt discharge channel 237 and a water discharge channel 238 are connected to the heat treatment unit 70 .

According to the fifth embodiment shown in FIG. 9, the highly concentrated concentrated water in the first chamber 54 of the second concentration membrane separation unit 50 is channeled through the sixth channel 206 and the channel 236. to the heat treatment unit 70. The heat treatment unit 70 thermally concentrates, evaporates, and dries the concentrated water. When the main component of the ions in the concentrated water sent out from the first chamber 54 of the second membrane separation unit 50 for concentration is, for example, salt ions, the heat treatment unit 70 converts the ions into solids and salts. can be taken out from the solid salt discharge channel 237 and recovered. Also, the moisture evaporated in the concentration/evaporation/drying process can be recovered from the moisture discharge channel 238 . The higher the degree of concentration of the concentrated water, the smaller the amount of water contained in the concentrated water.

The heat treatment unit 70 may further include a crystallizer, a centrifugal separator, and the like. This makes it possible to collect the solid salt more smoothly.

Further, in the second to fourth embodiments described above and the ninth to eleventh embodiments described later, the downstream of the first chamber 54 of the second membrane separation unit 50 for concentration is the same as in the fifth embodiment. A heat treatment unit 70 may be added to the .

(Sixth embodiment)
FIG. 10 is a schematic diagram showing a water treatment system according to the sixth embodiment. In FIG. 10, members similar to those in FIG. 1 explained in the first embodiment are denoted by the same reference numerals, and explanations thereof are omitted.

A water treatment system 1 according to the sixth embodiment shown in FIG. 10 has a structure in which a pretreatment unit 80 is further arranged upstream of the introduction unit 10 . In the pretreatment unit 80, a solid content/organic component removal device 81, a water softening device 82 and a degassing device 83 are arranged in this order in the flow direction. The supply channel 211 for the water to be treated is connected to the removing device 81 . The removing device 81 and the water softening device 82 are connected by a channel 239 through which a pump (not shown) is interposed. The water softening device 82 and the degassing device 83 are connected by a channel 240 through which a pump (not shown) is interposed. The degassing device 83 is connected to the introduction unit 10 by a channel 241 . The pretreatment unit 80 may include any one of the solid content/organic component removal device 81 , the water softening device 82 and the degassing device 83 . When a plurality of them are provided, they can be arranged as appropriate regardless of the order of their arrangement.

In the water treatment system 1 according to the sixth embodiment, as in the fifth embodiment, the heat treatment unit 70 is installed in the sixth flow path 206 of the first chamber 54 of the second membrane separation unit 50 for concentration. It is connected.

As the solid content/organic component removal device 81, for example, a microfiltration (MF: Microfiltration) membrane, an ultrafiltration (UF: Ultrafiltration) membrane, and a membrane separation device such as an MBR (Membrane Bioreactor) method can be used. Such a solid/organic component removing device 81 filters the water to be treated supplied through the supply channel 211 to remove the solid/organic components from the water to be treated. The water from which the solid content and organic components have been removed is sent from the solid content/organic component removal device 81 to the water softening device 82 through the flow path 239 by driving a pump (not shown).

For the water softening device 82, for example, an ion exchange resin or a coagulating sedimentation device can be used. The water softening device 82 removes hardness components such as calcium and magnesium from the sent water to be treated, and softens the water to be treated. The softened water to be treated is sent from the water softening device 82 to the degassing device 83 through the flow path 240 by driving a pump (not shown).

As the degassing device 83, an existing one used in pure water production or the like can be used. The degassing device 83 adds an acid such as hydrochloric acid or sulfuric acid to the water to be treated for the purpose of improving the degassing efficiency, and lowers the pH of the water to be treated to 7.0 or less, preferably 5.5 or less. Treatment is desirable.

Therefore, by further arranging the pretreatment unit 80 upstream of the introduction unit 10, it is possible to remove solids and organic components and soften the water to be treated, such as factory wastewater, in addition to salty wastewater. and degassing, and can realize a water treatment system capable of concentrating the treated water.

Also in the second to fourth embodiments described above and the ninth to eleventh embodiments described later, the pretreatment unit 80 may be added upstream of the introduction unit 10 as in the sixth embodiment.

(Seventh embodiment)
FIG. 11 is a schematic diagram showing a water treatment system according to the seventh embodiment. In FIG. 11, members similar to those in FIG. 10 explained in the sixth embodiment are denoted by the same reference numerals, and explanations thereof are omitted.

The water treatment system 1 according to the seventh embodiment shown in FIG. 11 has a structure further including a pretreatment membrane separation unit 90 downstream of the pretreatment unit 80 and upstream of the introduction unit 10 .

The pretreatment membrane separation unit 90 comprises a fourth reverse osmosis element 91 . The fourth reverse osmosis element 91 includes a fourth closed container, for example a fourth pressure closed container 92, a fourth reverse osmosis membrane 93 disposed within the fourth pressure closed container 92, and a fourth reverse osmosis membrane 93 disposed within the fourth pressure closed container 92. It includes a first chamber 94 and a second chamber 95 formed by partitioning the fourth pressure-resistant closed container 92 from the permeable membrane 93 . The pretreatment unit 80 is connected by a flow path 241 to a fourth pressure-tight sealed container 92 in which the first chamber 94 of the pretreatment membrane separation unit 90 is located. A booster pump 101 is interposed in the flow path 241 . The fourth pressure-resistant sealed container 92 in which the first chamber 94 is located is connected to the introduction unit 10 by a flow path 242 . The fourth pressure tight container 92 in which the second chamber 95 is located is connected by a channel 243 to the tenth channel 210 extending from the second chamber 25 of the desalting membrane separation unit 20 .

A nanofiltration membrane element may be used in place of the fourth reverse osmosis element 91 . The nanofiltration membrane element comprises a nanofiltration membrane that separates a first chamber 94 and a second chamber 95 of the pretreatment membrane separation unit 90 .

For reverse osmosis membranes or nanofiltration membranes, for example, spiral membranes and hollow fiber membranes can be used. A plurality of reverse osmosis membranes or nanofiltration membranes may be provided in the fourth pressure-resistant sealed container 92 .

For the pretreatment membrane separation unit 90 , a reverse osmosis membrane or a nanofiltration membrane can be selected according to the properties of the water to be treated sent from the pretreatment unit 80 .

In the pretreatment membrane separation unit 90 having such a configuration, the water to be treated from the degassing device 83 of the pretreatment unit 80 is pressurized by the boost pump 101, and is sent to the first chamber 94 of the pretreatment membrane separation unit 90. By sending out, the water in the water to be treated is efficiently permeated from the fourth reverse osmosis membrane 93 (or nanofiltration membrane) to the second chamber 95 to remove excess water and solid content (salinity). It can be separated into concentrated concentrated water.

Therefore, according to the seventh embodiment, the concentrated water sent from the first chamber 94 of the pretreatment membrane separation unit 90 through the channel 242 can be supplied to the introduction unit 10 as the water to be treated. As a result, the water to be treated having a concentration suitable for the deionization operation in the desalting membrane separation unit 20 and the ion concentration operation in the first and second concentration membrane separation units 40 and 50 is supplied to the introduction unit 10. A water treatment system that can be supplied can be realized.

In addition, in the seventh embodiment, the form in which the concentrated water to be treated sent from the pretreatment membrane separation unit 90 is supplied to the introduction unit 10 has been described, but the present invention is not limited to this form. For example, as shown in FIG. 12, a water storage tank 102 for storing the concentrated water in the first chamber 94 of the pretreatment membrane separation unit 90 may be further arranged. A channel 244 for supplying concentrated water to be treated in the first chamber 94 of the pretreatment membrane separation unit 90 is inserted into the water storage tank 102 . A channel 245 is connected to the lower side surface of the water storage tank 102 , and the tip of the channel 245 is connected to the pump 103 . Pump 103 is connected to introduction unit 10 through channel 242 .

In such a water treatment system shown in FIG. 12, the concentrated water to be treated in the first chamber 94 of the pretreatment membrane separation unit 90 is stored in the water storage tank 102 through the channel 244 . The concentrated water stored in the water storage tank 102 is delivered to the introduction unit 10 by driving the pump 103 at an arbitrary timing. The arbitrary timing is, for example, the timing according to the operator's instruction, the timing for each designated cycle, the timing for driving the heat treatment unit 70, and the like. When the introduction unit 10 is supplied with concentrated water to be treated from the water storage tank 102 by driving the pump 103, the pressure pump (not shown) in the first flow path 201 pushes the water to be treated through a desalting membrane. It is sent to the separation unit 20 . This makes it possible to operate the introduction unit 10 efficiently.

Also in the second to fourth embodiments described above and the ninth to eleventh embodiments described later, the pretreatment unit 80 and the pretreatment membrane separation unit 90 are provided upstream of the introduction unit 10 as in the seventh embodiment. Alternatively, a water storage tank 102 may be added as in the modification of the seventh embodiment.

(Eighth embodiment)
FIG. 13 is a schematic diagram showing a water treatment system according to an eighth embodiment. In FIG. 13, members similar to those in FIG. 1 explained in the first embodiment are denoted by the same reference numerals, and explanations thereof are omitted.

The water treatment system 1 according to the eighth embodiment shown in FIG. 13 has a configuration in which a power recovery unit 110 is further arranged downstream of the first chamber 54 of the second membrane separation unit 50 for concentration. The power recovery unit 110 is a device for recovering the pressure energy of the high-pressure concentrated water sent from the first chamber 54 of the second membrane separation unit 50 for concentration. The power recovery unit 110 includes, for example, a power recovery mechanism 111 and a pump 112 . The power recovery mechanism 111 is connected to the first chamber 54 of the second concentrating membrane separation unit 50 by a sixth flow path 206 .

The power recovery mechanism 111 comprises, for example, a turbine or a piston adapted for high salinity. When the concentrated water in the first chamber 54 of the second membrane separation unit 50 for concentration is delivered through the sixth passage 206, the power recovery mechanism 111 converts the pressure energy of the concentrated water into kinetic energy by a turbine or a piston. Convert to The power recovery mechanism 111 sends out the concentrated water from the flow path 246 after recovering the pressure energy.

The power recovery mechanism 111 is connected to the pump 112 so as to be able to transmit kinetic energy. For example, the rotating shaft of the turbine of the power recovery mechanism 111 and the rotating shaft of the pump 112 are directly or indirectly connected. As a result, the power recovery mechanism 111 transfers the acquired kinetic energy to the pump 112 .

The pump 112 is interposed, for example, in the supply channel 211 of the water to be treated and can be used to increase the pressure of the water to be treated flowing through the supply channel 211 . The pump 112 is applied to the boosting pump 15 interposed in the first flow path 201 shown in FIG. It can be introduced into the first chamber 24 of the separation unit 20 .

Therefore, according to the eighth embodiment, the power recovery unit 110 converts the pressure of the concentrated water in the first chamber 54 of the second membrane separation unit 50 into kinetic energy, whereby the water to be treated can be effectively used for boosting the voltage, and the energy consumption of the introduction unit 10 can be reduced.

In the second to fourth embodiments described above and the ninth to eleventh embodiments described later, power is provided downstream of the first chamber 54 of the second membrane separation unit 50 for concentration as in the eighth embodiment. A recovery unit 110 may be added.

(Ninth embodiment)
FIG. 14 is a schematic diagram showing a water treatment system according to the ninth embodiment. In FIG. 14, members similar to those in FIG. 1 explained in the first embodiment are denoted by the same reference numerals, and explanations thereof are omitted.

The water treatment system according to the ninth embodiment shown in FIG. 14 differs from the water treatment system according to the first embodiment shown in FIG. . That is, the suction port of the second decompression device 61 is branched from the fifth flow path 205 connecting the first chambers 44 and 54 of the first and second membrane separation units 40 and 50 for concentration. is connected to the flow path 208 of the A discharge port of the second decompression device 61 is connected to a ninth flow path 209, which is a third pressure-resistant pressure chamber in which the second chamber 55 of the second concentration membrane separation unit 50 is located. It is connected to the closed container 52 . The third pressure-resistant sealed container 52 in which the second chamber 55 of the second membrane separation unit for concentration 50 is located is connected to the second chamber of the first membrane separation unit for concentration 40 by the seventh flow path 207. 45 is connected to a second pressure-tight enclosure 42 located.

In the ninth embodiment, the second decompression unit 60 extracts concentrated water sent from the first chamber 44 of the first concentration membrane separation unit 40 through the fifth channel 205 and the eighth channel 208. is decompressed. That is, the second decompression unit 60 reduces the pressure of this concentrated water and returns it to the second chamber 55 of the second membrane separation unit for concentration 50 to send it as concentrated water to the second membrane separation unit for concentration. The pressure of the concentrate in the first chamber 54 of 50 is set to be higher than the pressure of the return concentrate in the second chamber 55 . The concentrated water flowing through the fifth flow path 205 connecting the first chambers 44 and 54 of the first and second membrane separation units 40 and 50 flows into the second chamber of the second membrane separation unit 50. The pressure is higher than that of the concentrated water flowing through the ninth flow path 209 connected to 55, and the degree of pressure reduction by the second pressure reduction unit 60 is also increased, which is preferable. For example, the pressure reduction amount of the return concentrated water sent into the second chamber 55 is preferably 1 MPa or more, more preferably 3 MPa or more. By setting the pressure reduction amount to 3 MPa or more, the pressure of the concentrated water sent to the first chamber 54 of the second membrane separation unit 50 for concentration is reduced to the second chamber 55 of the second membrane separation unit 50 for concentration. , the water contained in the concentrated water in the first chamber 54 can be smoothly permeated into the second chamber 55 through the third reverse osmosis membrane 53. It becomes possible to let

According to the ninth embodiment, even if the location of the second decompression unit 60 is changed as shown in FIG. can be obtained. As a result, when evaporating the collected concentrated water, the thermal energy required for evaporation can be reduced, so that the overall treatment cost can be reduced.

In addition, by reducing the pressure of the concentrated water in the first chamber 24 by the first decompression unit 30 (for example, a pressure reduction amount of 0.5 MPa or more), the gas dissolved in the concentrated water expands and bubbles are generated. The air bubbles are finely pulverized by rapid pressure recovery to generate fine bubbles. The fine bubbles have, for example, an average diameter of 1000 nm or less and are highly stable in liquid. It has high permeability to the permeable membrane 53 . As a result, it becomes possible to prevent scale generation and biofouling in the second and third reverse osmosis membranes 43 and 53 . As a result, scale generation of the second and third reverse osmosis membranes 43 and 53 and clogging due to biofouling are suppressed or prevented, and operations such as cleaning of the second and third reverse osmosis membranes 43 and 53 are performed. Since it can be reduced or eliminated, the utilization rate of the water treatment system can be increased.

In the ninth embodiment, a plurality of the second reverse osmosis membrane elements 41 of the first concentration membrane separation unit 40 may be arranged in series and in parallel as in the above-described third embodiment, or A plurality of second reverse osmosis membrane elements 41 of the first concentration membrane separation unit 40 may be arranged in parallel as in the fourth embodiment.

(Tenth embodiment)
FIG. 15 is a schematic diagram showing a water treatment system according to the tenth embodiment. In FIG. 10, members similar to those in FIG. 6 explained in the second embodiment are denoted by the same reference numerals, and explanations thereof are omitted.

The water treatment system 1 according to the tenth embodiment shown in FIG. 6 differs from the water treatment system according to the second embodiment shown in FIG. That is, the suction port of the second decompression device 61 is connected to the first chamber 44 in the second reverse osmosis element 41 b downstream of the first concentrating membrane separation unit 40 and the first chamber 44 of the second concentrating membrane separation unit 50 . It is connected to an eighth channel 208 branched from a fifth channel 205 connecting one chamber 54 . The discharge port of the second decompression device 61 is connected to the ninth flow path 209, and the ninth flow path 209 is the third flow path in which the second chamber 55 of the second membrane separation unit for concentration 50 is located. It is connected to the pressure tight container 52 . The third pressure-resistant sealed container 52 in which the second chamber 55 of the second membrane separation unit for concentration 50 is located is connected to the second stage downstream of the first membrane separation unit for concentration 40 by the seventh flow path 207 . The second chamber 45 in the reverse osmosis element 41b is connected to the second pressure-resistant sealed container 42.

In the tenth embodiment, as in the ninth embodiment described above, the second depressurization unit 60 is the first chamber in the second reverse osmosis element 41b downstream of the first membrane separation unit 40 for concentration. 44 through the fifth flow path 205 and the eighth flow path 208 are decompressed. That is, when the concentrated water is sent back to the second chamber 55 of the second membrane separation unit for concentration 50 with reduced pressure, the inside of the first chamber 54 of the second membrane separation unit for concentration 50 A second decompression unit 60 is set such that the pressure of the concentrate is higher than the pressure of the return concentrate in the second chamber 55 .

According to the tenth embodiment, even if the location of the second decompression unit 60 is changed as shown in FIG. A substantially reduced concentrated water is obtained. In addition, in the first concentration membrane separation unit 40, since the two second reverse osmosis elements 41a and 41b are connected in series with each other, compared to the water treatment system according to the ninth embodiment shown in FIG. As a result, a water treatment system capable of highly concentrating the concentrated water in the first concentration membrane separation unit 40 can be realized.

In the tenth embodiment, the second decompression device 61 is connected to the first chamber 44 in the second reverse osmosis element 41b downstream of the first concentration membrane separation unit 40 and the second concentration membrane separation unit. Although it is connected to the fifth flow path 205 connecting with the first chamber 54 of the unit 50, it is not limited to this. For example, as shown in FIG. 16, the location of the second decompression device 61 may be changed. That is, the suction port of the second decompression device 61 is the channel 212 that connects the first chambers 44, 44 in the second reverse osmosis elements 41a, 41b in the front stage and the rear stage of the first concentration membrane separation unit 40. is connected to an eighth channel 208 branched from. A discharge port of the second decompression device 61 is connected to a ninth flow path 209, and the ninth flow path 209 is a third pressure-resistant pressure chamber in which the second chamber 55 of the second concentration membrane separation unit 50 is located. It is connected to the closed container 52 . The third pressure-resistant sealed container 52 in which the second chamber 55 of the second membrane separation unit for concentration 50 is located is connected by the seventh flow path 207 to the second chamber downstream of the first membrane separation unit for concentration 40 . A second chamber 45 in the reverse osmosis element 41b is connected to the second pressure tight enclosure 42 in which it is located.

According to the configuration shown in FIG. 16, it is possible to obtain efficiently reduced concentrated water from the wastewater supplied to the introduction unit 10, and the concentrated water in the first concentration membrane separation unit 40 A water treatment system capable of high concentration can be realized.

(Eleventh embodiment)
FIG. 17 is a schematic diagram showing a water treatment system according to the eleventh embodiment. In FIG. 17, members similar to those in FIG. 14 described in the ninth embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

The water treatment system 1 according to the eleventh embodiment shown in FIG. 17 further includes a third decompression unit 120. The third decompression unit 120 includes, for example, a third decompression device 121. The suction port of the third decompression device 121 branches from the third flow path 203 that delivers the concentrated water decompressed from the first decompression unit 30 to the first chamber 44 of the first membrane separation unit 40 for concentration. connected to the flow path 247 . The discharge port of the third decompression device 121 is connected to the flow path 248, and the flow path 248 is connected to the second pressure-resistant sealed container 42 in which the second chamber 45 of the first membrane separation unit 40 for concentration is located. there is The second pressure-resistant sealed container 42 in which the second chamber 45 is located is connected to the introduction unit 10 by a fourth flow path 204 . Also, the seventh flow path 207 connected to the second chamber 55 of the second membrane separation unit for concentration 50 is connected to the first membrane separation unit for concentration 40 as in the ninth embodiment shown in FIG. is connected to the fourth flow path 204 connected to the introduction unit 10 without being connected to the second chamber 45 of .

According to the eleventh embodiment, in the first concentration membrane separation unit 40, the concentrated water decompressed by the first decompression unit 30 is sent to the first chamber 44 through the third channel 203. At the same time, the concentrated water flowing through the third flow path 203 is further decompressed by the third decompression unit 120, returned to the second chamber 45, and sent out as concentrated water. Therefore, due to the pressure difference between the concentrated water in the first chamber 44 and the return concentrated water in the second chamber 45 (pressure of concentrated water > pressure of return concentrated water), the pressure in the first chamber 44 Water in the retentate permeates through the second reverse osmosis membrane 43 into the second chamber 45 . By this operation, the concentrated water sent to the first chamber 44 is further concentrated. Also, the return concentrate in the second chamber 45 is diluted with the permeate from the first chamber 44 .

Further, in the second membrane separation unit for concentration 50, the concentrated water in the first chamber 44 of the first membrane separation unit for concentration 40 passes through the fifth flow path 205 to the second membrane separation unit for concentration 50. The concentrated water flowing through the fifth flow path 205 is further decompressed by the second decompression unit 60 and returned to the second chamber 55 to be delivered as concentrated water. Therefore, the pressure difference between the concentrated water in the first chamber 54 and the return concentrated water in the second chamber 55 (the pressure of the concentrated water > the pressure of the returned concentrated water) causes the pressure in the first chamber 54 to Water in the retentate permeates through the third reverse osmosis membrane 53 into the second chamber 55 . By this operation, the concentrated water delivered to the first chamber 54 is further concentrated. Also, the return concentrate in the second chamber 55 is diluted with the permeate from the first chamber 54 .
According to the configuration shown in FIG. 17, the optimum amount of concentrated water and the amount of return concentrated water can be distributed to the respective reverse osmosis membrane elements of the first membrane separation unit 40 for concentration and the second membrane separation unit 50 for concentration. Therefore, it is possible to realize a water treatment system capable of highly concentrating the water to be treated even if the quality and quantity of the water to be treated change.

In addition, in the above-described ninth to eleventh embodiments, another member may be added as follows.

(1) A heat treatment unit 70 is added downstream of the first chamber 54 of the second membrane separation unit 50 for concentration, as in the fifth embodiment.

(2) Add a pretreatment unit 80 upstream of the introduction unit 10 as in the sixth embodiment.

(3) Add a pretreatment unit 80 and a pretreatment membrane separation unit 90 upstream of the introduction unit 10 as in the seventh embodiment, or add a water storage tank 102 as in the modification of the seventh embodiment. add or do

(4) Adding a power recovery unit 110 downstream of the first chamber 54 of the second membrane separation unit 50 for concentration as in the eighth embodiment.

While several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

REFERENCE SIGNS LIST 1 water treatment system 10 introduction unit 20 membrane separation unit for desalination 21 first reverse osmosis element 22 first pressure-resistant sealed container 23 first reverse osmosis membrane 24 second First chamber 25 Second chamber 30 First decompression unit 40 First concentration membrane separation unit 41 Second reverse osmosis element 42 Second pressure-resistant sealed container 43 Second reverse osmosis membrane, 44... first chamber, 45... second chamber, 50... second concentration membrane separation unit, 51... third reverse osmosis element, 52... third pressure-resistant sealed container, 53... Third reverse osmosis membrane, 54... First chamber, 55... Second chamber, 60... Second decompression unit

Claims (11)

an introduction unit for pressurizing and delivering water to be treated;
A desalination membrane separation unit provided downstream of the introduction unit and comprising a first reverse osmosis membrane element, wherein the first reverse osmosis membrane element comprises a first reverse osmosis membrane and the first having a first chamber and a second chamber partitioned by a reverse osmosis membrane and connected to the introduction unit by a first flow path, wherein the first chamber of the first reverse osmosis membrane element is the desalting membrane separation unit connected to the introduction unit by a first channel;
A first decompression unit arranged downstream of the desalting membrane separation unit, wherein one end of the desalting membrane separation unit is different from the connection point of the first flow path in the first chamber of the desalting membrane separation unit. said first pressure reducing unit comprising a first pressure reducing device connected to said first chamber of said desalting membrane separation unit by a second flow path located at;
A first concentration membrane separation unit disposed downstream of the first decompression unit, comprising a second reverse osmosis membrane element, and having a maximum pressure resistance lower than that of the desalination membrane separation unit. The second reverse osmosis membrane element has a second reverse osmosis membrane and a first chamber and a second chamber separated by the second reverse osmosis membrane, The first chamber of the osmotic membrane element is connected to the first pressure reduction unit by a third flow path, and the second chamber of the second reverse osmosis membrane element is connected to the introduction unit by a fourth flow path. The first concentration membrane separation unit connected to;
A second membrane separation unit for concentration provided with a third reverse osmosis membrane element arranged downstream of the first membrane separation unit for concentration, wherein the third reverse osmosis membrane element is a third and a first chamber and a second chamber separated by the third reverse osmosis membrane, wherein the first chamber of the third reverse osmosis membrane element is the fifth flow is connected to the first chamber of the first membrane separation unit for concentration by a channel, and a sixth channel is connected to a position different from the fifth channel, and the third reverse osmosis membrane element said second concentrating membrane separation unit, wherein said second chamber is connected to said second chamber of said first concentrating membrane separation unit by a seventh flow path; and said fifth flow path or said A second decompression unit connected to a sixth flow path, connected to the fifth flow path or the sixth flow path by an eighth flow path, and connected to the fifth flow path by a ninth flow path. said second pressure reducing unit comprising a second pressure reducing device connected to said second chamber of two concentrating membrane separation units. 2. The water treatment system according to claim 1, wherein the desalination membrane separation unit can be operated at 10 MPa or more and below the maximum pressure resistance of the first reverse osmosis membrane. The water treatment system according to claim 1 or 2, wherein the first concentration membrane separation unit includes a plurality of the second reverse osmosis membrane elements in series. The first membrane separation unit for concentration includes a plurality of the second reverse osmosis membrane elements in parallel, and the second membrane separation unit for concentration includes the third reverse osmosis membrane element in the second reverse osmosis membrane element. 4. The water treatment system according to any one of claims 1 to 3, comprising a plurality of reverse osmosis membrane elements or less in parallel. A pretreatment unit disposed upstream of the introduction unit and performing at least one of solid content removal, organic component removal, hardness component removal, and carbonic acid component removal, wherein the pretreatment unit is provided with a tenth flow path to remove the 5. A water treatment system according to any one of claims 1 to 4, connected to an introduction unit. further comprising a pretreatment membrane separation unit between the pretreatment unit and the introduction unit;
The pretreatment membrane separation unit includes a fourth reverse osmosis membrane element having a fourth reverse osmosis membrane and a first chamber and a second chamber partitioned by the fourth reverse osmosis membrane; an eleventh channel connected to a pretreatment unit and having the other end connected to the first chamber of the pretreatment membrane separation unit; and one end connected to the first chamber of the pretreatment membrane separation unit. 6. The water treatment system according to claim 5, further comprising a twelfth flow path connected to the flow path and having the other end connected to the introduction unit. 7. The water treatment system according to any one of claims 1 to 6, further comprising a heat treatment unit connected to said second membrane separation unit for concentration through said sixth channel. 7. The water treatment system according to any one of claims 1 to 6, further comprising a power recovery unit connected to said second membrane separation unit for concentration through said sixth channel. 9. Any one of claims 1 to 8, wherein the water sent from the first chamber of the second membrane separation unit for concentration contains 1.0E+6/mL or more of fine bubbles of 1000 nm or less. The water treatment system according to item 1. an introduction unit for pressurizing and delivering water to be treated;
a first reverse osmosis membrane element disposed downstream from the introduction unit and having a first reverse osmosis membrane and a first chamber and a second chamber partitioned by the first reverse osmosis membrane; Membrane separation unit for salts;
a first decompression unit arranged downstream from the desalting membrane separation unit for decompressing concentrated water sent from the first chamber of the desalting membrane separation unit;
A second reverse osmosis membrane arranged downstream from the first decompression unit and having a maximum pressure resistance lower than the maximum pressure resistance of the desalting membrane separation unit, and a first chamber partitioned by the second reverse osmosis membrane. and a second chamber;
Third reverse osmosis arranged downstream from the first concentration membrane separation unit and having a third reverse osmosis membrane and a first chamber and a second chamber partitioned by the third reverse osmosis membrane a second membrane separation unit for concentration, comprising a membrane element; and arranged downstream from the first membrane separation unit for concentration, delivered from the first chamber of the first membrane separation unit for concentration. depressurizing the concentrate, or depressurizing the concentrate, which is arranged downstream of the second membrane separation unit for concentration and delivered from the first chamber of the second membrane separation unit for concentration, providing a water treatment system comprising two vacuum units;
a step of delivering the water to be treated whose pressure is increased from the introduction unit to the first chamber of the desalination membrane separation unit;
sending the concentrated water concentrated in the first chamber of the desalting membrane separation unit to the first decompression unit to reduce the pressure;
sending the concentrated water decompressed by the first decompression unit to the first chamber of the first membrane separation unit for concentration;
sending the concentrated water concentrated in the first chamber of the first membrane separation unit for concentration to the first chamber of the second membrane separation unit for concentration;
delivering the concentrated water delivered from the first chamber of the first membrane separation unit for concentration or the first chamber of the second membrane separation unit for concentration to the second decompression unit; depressurizing to a pressure lower than the concentrated water delivered to the first chamber of the membrane separation unit for concentration of 2;
sending the return concentrate decompressed by the second decompression unit to the second chamber of the second membrane separation unit for concentration;
sending the return concentrated water concentrated in the second chamber of the second membrane separation unit for concentration to the second chamber of the first membrane separation unit for concentration;
circulating return concentrated water concentrated in the second chamber of the first membrane separation unit for concentration to the introduction unit;
circulating the return concentrated water concentrated in the second chamber of the first membrane separation unit for concentration to the introduction unit;
A water treatment method for recovering the concentrated water concentrated in the first chamber of the second membrane separation unit for concentration as highly concentrated concentrated water. 11. The water treatment method according to claim 10, wherein the concentrated water sent from the first chamber of the second membrane separation unit for concentration contains 1.0E+6 or more fine bubbles of 1000 nm or less per mL.

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