JP2021016823A - Water treatment method and water treatment apparatus - Google Patents

Abstract

To provide a water treatment method and a water treatment apparatus capable of quickly stabilizing the concentration of water obtainable in a final stage even if there occurs, upon treatment for concentrating water using a multi-stage semi-permeable membrane module, a change in the quality of water to be treated.SOLUTION: A method of treating water that comprises one or more of a concentration step in which water to be treated that contains a substance is concentrated by using a semi-permeable membrane module 12 having a first space 11 and a second space 13 partitioned by a semi-permeable membrane 15, and the concentrated water is subjected to further concentration, wherein the water to be treated is supplied to the first space of the semi-permeable membrane module 12, and (i) at least part of concentrated water is supplied to a second space of a final stage after passing through the first space of the final stage, or (ii) concentrated water of a preceding stage is supplied to both of the first and second spaces of the final stage.SELECTED DRAWING: Figure 1

Description

The present invention relates to a water treatment method and a water treatment apparatus for concentrating water containing impurities and the like.

In recent years, the amount of wastewater discharged from factories and the like has been reduced as much as possible, and a method of concentrating wastewater using a reverse osmosis membrane or the like and collecting permeated water to reduce the volume of wastewater has been adopted. There is. There is a tendency to increase the water recovery rate as much as possible, and some factories, etc., have even ZLD (Zero Liquid Discharge), which recovers almost the entire amount of water by means such as evaporation concentration and solidifies and discharges impurities. Is also increasing. However, since a method of heating water such as evaporation concentration consumes a large amount of energy, a method of concentrating wastewater to a high concentration by a method that does not heat as much as possible is required.

In Patent Document 1, raw water or concentrated water thereof is flowed through the first space and the second space partitioned by the semipermeable membrane of the multi-stage semipermeable membrane module, and the water is concentrated by pressurizing the first space. The method is described. The method of Patent Document 1 reduces the concentration difference (osmotic pressure difference) between the first space and the second space of the semipermeable membrane module, so that the pressurizing power is smaller than that of the general method of concentrating with a reverse osmosis membrane, that is, It is a method of concentrating to a high concentration with less energy.

FIG. 4 shows a water treatment apparatus that concentrates water using a conventional multi-stage semipermeable membrane module. The water treatment device 7 includes a water tank 200 to be treated, a first-stage membrane module unit 202, a second-stage membrane module unit 204, a third-stage membrane module unit 206, a fourth-stage membrane module unit 208, a concentrated water tank 210, and the like. It is provided with a dilution water tank 212. The water treatment device 7 uses a multi-stage membrane module having a first space 214 and a second space 216 partitioned by a semi-transparent film 218, and water to be treated is serialized in the first space 214 of the multi-stage membrane module. The concentrated water of the third stage membrane module unit 206 of the previous stage is distributed to the first space 214 and the second space 216 of the fourth stage membrane module unit 208 of the final stage, and the fourth stage membrane of the final stage is distributed. The diluted water of the module unit 208 is returned in series to the second space 216 of the membrane module in the previous stage, water is passed therethrough, and the water contained in the first space 214 is pressurized to the second space 216. It is a device that concentrates water by permeating it into water.

A conventional method such as Patent Document 1 is effective if the water quality of the raw water (water to be treated) is stable, but compared with the usual reverse osmosis membrane treatment method, only the first space of the semipermeable membrane module is used. In addition, the concentration in the second space may fluctuate, so it is difficult to perform stable treatment against fluctuations in the quality of raw water.

In the normal reverse osmosis membrane treatment method, for example, when the reverse osmosis membrane is blocked or the concentration of impurities in the raw water increases and the amount of permeated water decreases, the pressure of the raw water pump is increased to keep the amount of permeated water as constant as possible. It is common to control as such. On the other hand, in the method of Patent Document 1, for example, the concentration of impurities in the supplied water increases due to fluctuations in the quality of the raw water, and when the osmotic pressure difference between the first space and the second space increases, the amount of permeated water decreases. Even if the pressure of the pump is increased, the osmotic pressure difference between the first space and the second space is also changing, so the permeated water flow rate does not increase in proportion to the pressure of the raw water pump, and only the pressure adjustment of the raw water pump is simple. In this case, it is not possible to follow fluctuations in the quality of raw water, it takes time for the permeated water flow rate to stabilize, the amount of permeated water cannot be obtained as planned, the concentration process does not proceed, and the concentrated water concentration obtained in the final stage stabilizes. There is a problem that it takes time to complete.

Japanese Unexamined Patent Publication No. 2018-069198

An object of the present invention is to quickly stabilize the concentration of concentrated water obtained in the final stage even when the water quality of the water to be treated (raw water) fluctuates in the concentration treatment of water using a multi-stage semipermeable membrane module. It is an object of the present invention to provide a water treatment method and a water treatment apparatus which can be used.

In the present invention, the water to be treated containing a substance is concentrated by using a semipermeable membrane module having a first space and a second space partitioned by a semipermeable membrane, and the concentrated water is further concentrated by using the semipermeable membrane module. Containing After one or more concentration steps are included, the water to be treated is supplied to the first space of the first-stage semipermeable membrane module, and the concentrated water passes through the first space of the final-stage semipermeable membrane module. A method of supplying at least a part of the concentrated water of the final stage to the second space of the semipermeable membrane module of the final stage, or the method of supplying both the first space and the second space of the semipermeable membrane module of the final stage. In any of the methods of supplying concentrated water in the previous stage; in the concentration step, the diluted water that has passed through the second space of the semipermeable membrane module in the final stage is transferred to the second space of the semipermeable membrane module upstream thereof. As it is supplied, the first space of the semipermeable membrane module of each stage is pressurized to allow the water contained in the first space to permeate into the second space; the entrance of the first space of the semipermeable membrane module of at least one stage. Alternatively, the amount of the substance in water at the first space outlet and the second space inlet or the second space outlet is measured, and the concentration difference of the substance between the first space and the second space of at least one stage is predetermined. It is a water treatment method in which at least a part of the higher concentration concentrated water in the previous stage of the second space is added so as to be within the range to adjust the concentration of water at the inlet of the second space.

In the present invention, the water to be treated containing a substance is concentrated by using a semipermeable membrane module having a first space and a second space partitioned by a semipermeable membrane, and the concentrated water is further concentrated by using the semipermeable membrane module. Containing After one or more concentration steps are included, the water to be treated is supplied to the first space of the first-stage semipermeable membrane module, and the concentrated water passes through the first space of the final-stage semipermeable membrane module. A method of supplying at least a part of the concentrated water of the final stage to the second space of the semipermeable membrane module of the final stage, or the method of supplying both the first space and the second space of the semipermeable membrane module of the final stage. In any of the methods of supplying concentrated water in the previous stage; in the concentration step, the diluted water that has passed through the second space of the semipermeable membrane module in the final stage is transferred to the second space of the semipermeable membrane module upstream thereof. As it is supplied, the first space of the semipermeable membrane module of each stage is pressurized to allow the water contained in the first space to permeate through the second space, and the entrance of the first space of the semipermeable membrane module of at least one stage. Alternatively, the amount of the substance in water at the first space outlet and the second space inlet or the second space outlet is measured, and the concentration difference of the substance between the first space and the second space of at least one stage is predetermined. This is a water treatment method that adjusts the flow rate supplied to the second space so that it falls within the range.

In the water treatment method, the concentration difference of the substance between the first space and the second space of the semipermeable membrane module in at least one stage in the predetermined range is 50% in the second space with respect to the first space. It is preferably in the range of 90% or more and 90% or less.

In the water treatment method, it is preferable to measure the amount of the substance by measuring the conductivity.

In the present invention, the water to be treated containing a substance is concentrated by using a semipermeable membrane module having a first space and a second space partitioned by a semipermeable membrane, and the concentrated water is further concentrated by using the semipermeable membrane module. After providing one or more concentrating means for concentrating, supplying the water to be treated to the first space of the first-stage semipermeable membrane module, and passing the concentrated water through the first space of the final-stage semipermeable membrane module. Supply means for supplying at least a part of the concentrated water in the final stage to the second space of the semipermeable membrane module in the final stage, or both in the first space and the second space of the semipermeable membrane module in the final stage. One of the supply means for supplying the concentrated water in the previous stage; in the concentrating means, the diluted water that has passed through the second space of the semipermeable membrane module in the final stage is passed through the second space of the semipermeable membrane module upstream thereof. Supplying to two spaces, the first space of the semipermeable membrane module of each stage is pressurized to allow the water contained in the first space to permeate into the second space; the first of the semipermeable membrane modules of at least one stage. A measuring means for measuring the amount of the substance in water at the one-space inlet or the first space outlet and the second space inlet or the second space outlet; the substance in at least one stage of the first space and the second space. Provided with an adjusting means for adjusting the concentration of water at the inlet of the second space by adding at least a part of the higher concentration concentrated water in the preceding stage of the second space so that the difference in concentration of the above is within a predetermined range. It is a water treatment device.

In the present invention, the water to be treated containing a substance is concentrated by using a semipermeable membrane module having a first space and a second space partitioned by a semipermeable membrane, and the concentrated water is further concentrated by using the semipermeable membrane module. After providing one or more concentrating means for concentrating, supplying the water to be treated to the first space of the first-stage semipermeable membrane module, and passing the concentrated water through the first space of the final-stage semipermeable membrane module. Supply means for supplying at least a part of the concentrated water in the final stage to the second space of the semipermeable membrane module in the final stage, or both in the first space and the second space of the semipermeable membrane module in the final stage. One of the supply means for supplying the concentrated water in the previous stage; in the concentrating means, the diluted water that has passed through the second space of the semipermeable membrane module in the final stage is passed through the second space of the semipermeable membrane module upstream thereof. Supplying to two spaces, the first space of the semipermeable membrane module of each stage is pressurized to allow the water contained in the first space to permeate into the second space; the first of the semipermeable membrane modules of at least one stage. A measuring means for measuring the amount of the substance in water at the one-space inlet or the first space outlet and the second space inlet or the second space outlet; the substance in at least one stage of the first space and the second space. It is a water treatment apparatus provided with an adjusting means for adjusting the flow rate supplied to the second space so that the concentration difference between the two is within a predetermined range.

In the water treatment apparatus, the concentration difference of the substance between the first space and the second space of the semipermeable membrane module in at least one stage in the predetermined range is 50% in the second space with respect to the first space. It is preferably in the range of 90% or more and 90% or less.

In the water treatment apparatus, it is preferable that the measuring means measures the amount of the substance by measuring the conductivity.

According to the present invention, in the water concentration treatment using a multi-stage semipermeable membrane module, water that can quickly stabilize the concentration of concentrated water obtained in the final stage even if the water quality of the water to be treated (raw water) fluctuates. A treatment method and a water treatment apparatus can be provided.

It is a schematic block diagram which shows an example of the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows another example of the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows the water treatment apparatus used in an Example and a comparative example. It is a schematic block diagram which shows the conventional water treatment apparatus. It is a graph which shows the concentrated water concentration (mass%) of the 5th stage membrane treatment apparatus with respect to the elapsed time (min) from the concentration fluctuation of the water to be treated in an Example and a comparative example.

Embodiments of the present invention will be described below. The present embodiment is an example of carrying out the present invention, and the present invention is not limited to the present embodiment.

An outline of an example of a water treatment apparatus according to an embodiment of the present invention is shown in FIG. 1, and its configuration will be described.

The water treatment apparatus 1 shown in FIG. 1 uses a semipermeable membrane module having a first space (concentration side) and a second space (permeation side) partitioned by a semipermeable membrane, and dissolves solid components (TDS) such as impurities. ) And other substances to be treated, and as a means for concentrating the concentrated water using a semipermeable membrane module, for example, the first-stage membrane module unit 12, the second-stage membrane module unit 14, 3 The step membrane module unit 16 and the fourth step membrane module unit 18 are provided. The first-stage membrane module unit 12 includes, for example, four membrane modules connected in parallel, and the second-stage membrane module unit 14 includes, for example, three membrane modules connected in parallel. The third-stage membrane module unit 16 includes, for example, three membrane modules connected in parallel, and the fourth-stage membrane module unit 18 includes, for example, one membrane module. Each membrane module has a first space 11 and a second space 13 partitioned by a semipermeable membrane 15. The water treatment device 1 stores the water tank 10 to be treated and the concentrated water from the final stage membrane module unit (in the example of FIG. 1, the concentrated water from the fourth stage membrane module unit 18). The concentrated water tank 20, the first diluted water tank 22 for storing the diluted water from the final stage membrane module unit (in the example of FIG. 1, the diluted water from the fourth stage membrane module unit 18), and the final stage membrane. The second dilution water tank 24 for storing the diluted water from the module unit (in the example of FIG. 1, the diluted water from the third-stage membrane module unit 16) and the diluted water from the first-stage membrane module unit (FIG. 1). In the example, a third diluted water tank 26 for storing (diluted water from the first stage membrane module unit 12) may be provided. The water treatment apparatus 1 is used as a reverse osmosis membrane treatment means for reverse osmosis membrane treatment of the diluted water from the first-stage membrane module unit (in the example of FIG. 1, the diluted water from the first-stage membrane module unit 12). The osmosis membrane treatment device 28 may be provided.

In the water treatment device 1 of FIG. 1, a pipe 44 is connected to the water inlet of the water tank 10 to be treated. The outlet of the water tank 10 to be treated and the first space inlet of each membrane module of the first-stage membrane module unit 12 are connected in parallel by a pipe 46 via a pump 30. The first space outlet of each membrane module of the first-stage membrane module unit 12 and the first space inlet of each membrane module of the second-stage membrane module unit 14 are connected in parallel by a pipe 48. The first space outlet of each membrane module of the second-stage membrane module unit 14 and the first space inlet of each membrane module of the third-stage membrane module unit 16 are connected in parallel by a pipe 50. The first space outlet of each membrane module of the third-stage membrane module unit 16 and the first space inlet and the second space inlet of the membrane module of the fourth-stage membrane module unit 18 are connected by a pipe 52. The first space outlet of the membrane module of the fourth stage membrane module unit 18 and the inlet of the concentrated water tank 20 are connected by a pipe 54, and the second space outlet of the membrane module of the fourth stage membrane module unit 18 and the first dilution water tank. The dilution water inlet of 22 is connected by a pipe 60. A pipe 56 is connected to the outlet of the concentrated water tank 20 via a pump 32. The downstream side of the pump 32 in the pipe 56 and the concentrated water inlet of the first dilution water tank 22 are connected by a pipe 58 via a valve 78. The outlet of the first dilution water tank 22 and the second space inlet of each membrane module of the third-stage membrane module unit 16 are connected in parallel by a pipe 62 via a pump 34. The second space outlet of each membrane module of the third-stage membrane module unit 16 and the inlet of the second dilution water tank 24 are connected by a pipe 64. The outlet of the second dilution water tank 24 and the second space inlet of each membrane module of the second stage membrane module unit 14 are connected in parallel by a pipe 66 via a pump 36. The second space outlet of each membrane module of the second-stage membrane module unit 14 and the second space inlet of each membrane module of the first-stage membrane module unit 12 are connected in parallel by a pipe 68. The second space outlet of each membrane module of the first-stage membrane module unit 12 and the inlet of the third dilution water tank 26 are connected by a pipe 70. The outlet of the third dilution water tank 26 and the inlet of the reverse osmosis membrane treatment device 28 are connected by a pipe 72 via a pump 38. A pipe 76 is connected to the RO permeated water outlet of the reverse osmosis membrane treatment device 28, and the RO concentrated water outlet and the RO concentrated water inlet of the water tank 10 to be treated are connected by a pipe 74.

The pipe 50 between the second-stage membrane module unit 14 and the third-stage membrane module unit 16 is provided with the amount of substances in water at the first space inlet or the first space outlet of at least one stage semitransparent module. A substance amount measuring device 40 is installed as a measuring means for measuring, and in the first dilution water tank 22, the amount of a substance in water at the second space inlet or the second space outlet of the semitransparent film module of at least one stage is measured. A substance amount measuring device 42 is installed as a measuring means.

The water treatment method and the operation of the water treatment device 1 according to the present embodiment will be described.

The water treatment device 1 uses a multi-stage membrane module having a first space 11 and a second space 13 partitioned by a semi-transparent membrane 15, and water to be treated is serialized in the first space 11 of the multi-stage membrane module. In the first space 11 and the second space 13 of the final stage membrane module unit (fourth stage membrane module unit 18 in the example of FIG. 1), the previous stage membrane module unit (in the example of FIG. 1) The concentrated water of the third-stage membrane module unit 16) is distributed, and the diluted water of the final-stage membrane module is returned and passed in series to the second space 13 of the previous-stage membrane module, and the first space 11 is added. It is a device that concentrates water by permeating the water contained in the first space 11 into the second space 13 by pressing. That is, in the water treatment apparatus 1, the water to be treated is concentrated by using the semipermeable membrane 15, and the concentrated water is further concentrated by using the semipermeable membrane 15 in the next stage. Water to be treated is supplied to the first space 11 of the first-stage membrane module unit (in the example of FIG. 1, the first-stage membrane module unit 12), and the first space 11 and the second space 13 of the final-stage membrane module. The concentrated water of the previous stage (in the example of FIG. 1, the third stage membrane module unit 16) is supplied to both of the above. Then, the diluted water that has passed through the second space 13 of the membrane module in the final stage is supplied to the second space 13 of the membrane module upstream of the diluted water, and the first space 11 of the membrane module in each stage is pressurized. The water contained in the first space 11 is allowed to permeate through the second space 13.

Specifically, in the water treatment device 1, the water to be treated is stored in the water tank 10 to be treated as needed through the pipe 44, and is combined with the RO concentrated water of the reverse osmosis membrane treatment device 28 described later in the water tank 10 to be treated. After being mixed, the liquid is sent to the first space 11 of each membrane module of the first-stage membrane module unit 12 through the pipe 46 by the pump 30. On the other hand, the diluted water returned from the fourth-stage membrane module unit 18 of the final stage to be described later via the second space 13 of the third-stage membrane module unit 16 and the second space 13 of the second-stage membrane module unit 14 The liquid is sent to the second space 13 of each membrane module of the first-stage membrane module unit 12 through the pipe 68. In each membrane module of the first-stage membrane module unit 12, the first space 11 is pressurized and the water contained in the first space 11 is permeated into the second space 13 (concentration step (first stage)).

The concentrated water of the first-stage membrane module unit 12 is sent to the first space 11 of each membrane module of the second-stage membrane module unit 14 through the pipe 48. On the other hand, the diluted water returned from the fourth-stage membrane module unit 18 in the final stage to be described later via the second space 13 of the third-stage membrane module unit 16 passes through the pipe 66 and is in each of the second-stage membrane module units 14. The liquid is sent to the second space 13 of the membrane module. In the same manner as in the first stage, in each membrane module of the second stage membrane module unit 14, the first space 11 is pressurized and the water contained in the first space 11 is permeated into the second space 13 (concentration). Process (second stage)).

The concentrated water of the second-stage membrane module unit 14 is sent to the first space 11 of each membrane module of the third-stage membrane module unit 16 through the pipe 50. On the other hand, the diluted water returned from the fourth-stage membrane module unit 18 in the final stage, which will be described later, is sent to the second space 13 of each membrane module of the third-stage membrane module unit 16 through the pipe 62. In each of the membrane modules of the third-stage membrane module unit 16, the first space 11 is pressurized and the water contained in the first space 11 is permeated into the second space 13 in the same manner as in the first and second stages. (Concentration step (third stage)).

The concentrated water of the third-stage membrane module unit 16 is distributed and sent to the first space 11 and the second space 13 of the membrane module of the final-stage fourth-stage membrane module unit 18 through the pipe 52. In the fourth stage membrane module unit 18, the first space 11 is pressurized and the water contained in the first space 11 is permeated into the second space 13 in the same manner as in the first to third stages (concentration step (concentration step (concentration step (concentration step)). 4th stage)). Here, the pump 30, the pipe 52, and the like function as supply means for supplying the concentrated water in the previous stage to both the first space and the second space of the semipermeable membrane module in the final stage.

The concentrated water of the fourth-stage membrane module unit 18 is sent to and stored in the concentrated water tank 20 as needed through the pipe 54. The valve 78 is closed, and at least a part of the concentrated water is discharged from the concentrated water tank 20 to the outside of the system through the pipe 56 by the pump 32 as treated water. At least a part of the concentrated water may be sent to the water tank 10 to be treated and mixed with the water to be treated in the water tank 10 to be treated.

The diluted water of the fourth-stage membrane module unit 18 is sent to the first dilution water tank 22 as needed through the pipe 60, and after being stored, the pump 34 passes through the pipe 62 from the first dilution water tank 22 to 3 The liquid is sent to the second space 13 of each membrane module of the step membrane module unit 16. As described above, in each membrane module of the third-stage membrane module unit 16, the first space 11 is pressurized and the water contained in the first space 11 is permeated into the second space 13 (concentration step (three stages). Eye)).

The diluted water of the third-stage membrane module unit 16 is sent to the second diluted water tank 24 as needed through the pipe 64, and after being stored, the pump 36 passes through the pipe 66 from the second diluted water tank 24 to 2 The liquid is sent to the second space 13 of each membrane module of the step membrane module unit 14. As described above, in each membrane module of the second-stage membrane module unit 14, the first space 11 is pressurized and the water contained in the first space 11 is permeated into the second space 13 (concentration step (second stage). Eye)).

The diluted water of the second-stage membrane module unit 14 is sent to the second space 13 of each membrane module of the first-stage membrane module unit 12 through the pipe 68. As described above, in each membrane module of the first-stage membrane module unit 12, the first space 11 is pressurized and the water contained in the first space 11 is permeated into the second space 13 (concentration step (1st stage). Eye)).

The diluted water of the first-stage membrane module unit 12 is sent to the third dilution water tank 26 as needed through the pipe 70, and after being stored, the pump 38 passes through the pipe 72 to the reverse osmosis membrane treatment device 28. The liquid is sent. In the reverse osmosis membrane treatment apparatus 28, the reverse osmosis membrane treatment is performed (reverse osmosis membrane treatment step). The RO permeated water obtained by the reverse osmosis membrane treatment is discharged to the outside of the system through the pipe 76. The RO concentrated water obtained by the reverse osmosis membrane treatment is sent to the water tank 10 to be treated through the pipe 74, and is mixed with the water to be treated in the water tank 10 to be treated. The diluted water of the first-stage membrane module unit 12 may be discharged to the outside of the system as it is, or may be sent to the water tank 10 as it is and mixed with the water to be treated in the water tank 10.

As described above, the treated water in which the substance such as the dissolved solid component is concentrated (concentrated water in the final stage) and the RO permeated water are separated from the treated water containing the substance such as the dissolved solid component, which is the treatment target. Obtained, the volume of water to be treated is reduced.

In the water treatment method and the water treatment apparatus according to the present embodiment, the entrance of the first space 11 or the exit of the first space 11 of the semitransparent film 15 in at least one stage and the entrance of the second space 13 or the second space 13 The amount of the substance in the water at the outlet of the second space 13 is measured, and the concentration difference of the substance between the first space 11 and the second space 13 of at least one stage is within a predetermined range. At least a part of high-concentration concentrated water is added to adjust the concentration of water at the inlet of the second space 13 to adjust the osmotic pressure.

For example, as shown in FIG. 1, the amount of a substance in water at the entrance of the first space 11 of the third-stage membrane module unit 16 is measured by the substance amount measuring device 40, and the second space of the third-stage membrane module unit 16 is measured. The amount of substance in water at the inlet of 13 is measured by the substance amount measuring device 42. In water at the entrance of the second space 13 of the third stage membrane module unit 16 so that the difference between the value measured by the substance amount measuring device 40 and the value measured by the substance amount measuring device 42 is within a predetermined range. Adjust the amount (concentration) of the substance and adjust the osmotic pressure. For example, the opening degree of the valve 78 is adjusted, and the pump 32 is used to concentrate the fourth-stage membrane module unit 18, which has a higher concentration than the previous stage of the third-stage membrane module unit 16, through the concentrating water tank 20, the pipe 56, and the pipe 58. At least a part of the water is added to the diluted water in the first diluted water tank 22, and the concentration of water at the inlet of the second space 13 is adjusted to adjust the osmotic pressure. Here, the pump 32, the pipes 56, 58, the valve 78, etc. are second so that the concentration difference of the substance between the first space and the second space of the semipermeable membrane module of at least one stage is within a predetermined range. By adding at least a part of the higher concentration concentrated water in the front stage of the space, it functions as an adjusting means for adjusting the concentration of water at the entrance of the second space.

As a result, in the water concentration treatment using the multi-stage semipermeable membrane module, the osmotic pressure difference of each membrane module is maintained within a predetermined range even if the water quality of the water to be treated (raw water) fluctuates, and the final stage is obtained. The concentration of concentrated water to be produced can be quickly stabilized.

Further, the flow rate of the diluted water supplied to the second space 13 of the third-stage membrane module unit 16 is adjusted by adjusting the flow rate of the pump 34 at the inlet of the second space of the third-stage membrane module unit 16. The osmotic pressure may be adjusted. Here, the pump 34, the inverter installed in the pump 34, and the like have a second so that the concentration difference of the substance between the first space and the second space of the semipermeable membrane module in at least one stage is within a predetermined range. It functions as an adjusting means for adjusting the flow rate supplied to the space.

FIG. 2 shows an outline of another example of the water treatment apparatus according to the embodiment of the present invention.

In the water treatment apparatus 3 shown in FIG. 2, the first space outlet of each membrane module of the third-stage membrane module unit 16 and the first space inlet of the membrane module of the fourth-stage membrane module unit 18 are connected by a pipe 80. , The pipe 82 branched from the pipe 58 connecting the downstream side of the pump 32 in the pipe 56 and the concentrated water inlet of the first dilution water tank 22 is the second membrane module of the fourth stage membrane module unit 18 via the valve 86. It differs from the water treatment device 1 shown in FIG. 1 in that it is connected to the space inlet and the second space outlet and the diluted water inlet of the first diluted water tank 22 are connected by a pipe 84.

The water treatment device 3 uses a multi-stage membrane module having a first space 11 and a second space 13 partitioned by a semi-transparent membrane 15, and water to be treated is serialized in the first space 11 of the multi-stage membrane module. In the second space 13 of the final stage membrane module unit (fourth stage membrane module unit 18 in the example of FIG. 2), the final stage membrane module unit (fourth stage membrane module in the example of FIG. 2) is passed through. The concentrated water of the unit 18) is distributed, and the diluted water of the membrane module in the final stage) is returned in series to the second space 13 of the membrane module in the previous stage, water is passed therethrough, and the first space 11 is pressurized. This is a device for concentrating water by allowing the water contained in the first space 11 to permeate through the second space 13. That is, in the water treatment apparatus 3, the water to be treated is concentrated by using the semipermeable membrane 15, and the concentrated water is further concentrated by using the semipermeable membrane 15 in the next stage. Water to be treated is supplied to the first space 11 of the first-stage membrane module unit (first-stage membrane module unit 12 in the example of FIG. 1), and the concentrated water is used as the final-stage membrane module unit (example of FIG. 1). Then, after passing through the first space 11 of the fourth-stage membrane module unit 18), at least a part of the concentrated water in the final stage is supplied to the second space 13 of the final-stage membrane module. Then, the diluted water that has passed through the second space 13 of the membrane module in the final stage is supplied to the second space 13 of the membrane module upstream of the diluted water, and the first space 11 of the membrane module in each stage is pressurized. The water contained in the first space 11 is allowed to permeate through the second space 13.

Specifically, in the water treatment device 3, the water to be treated is stored in the water tank 10 to be treated as needed through the pipe 44, and is combined with the RO concentrated water of the reverse osmosis membrane treatment device 28 described later in the water tank 10 to be treated. After being mixed, the liquid is sent to the first space 11 of each membrane module of the first-stage membrane module unit 12 through the pipe 46 by the pump 30. On the other hand, the diluted water returned from the fourth-stage membrane module unit 18 of the final stage to be described later via the second space 13 of the third-stage membrane module unit 16 and the second space 13 of the second-stage membrane module unit 14 The liquid is sent to the second space 13 of each membrane module of the first-stage membrane module unit 12 through the pipe 68. In each membrane module of the first-stage membrane module unit 12, the first space 11 is pressurized and the water contained in the first space 11 is permeated into the second space 13 (concentration step (first stage)).

The concentrated water of the first-stage membrane module unit 12 is sent to the first space 11 of each membrane module of the second-stage membrane module unit 14 through the pipe 48. On the other hand, the diluted water returned from the fourth-stage membrane module unit 18 in the final stage to be described later via the second space 13 of the third-stage membrane module unit 16 passes through the pipe 66 and is in each of the second-stage membrane module units 14. The liquid is sent to the second space 13 of the membrane module. In the same manner as in the first stage, in each membrane module of the second stage membrane module unit 14, the first space 11 is pressurized and the water contained in the first space 11 is permeated into the second space 13 (concentration). Process (second stage)).

The concentrated water of the second-stage membrane module unit 14 is sent to the first space 11 of each membrane module of the third-stage membrane module unit 16 through the pipe 50. On the other hand, the diluted water returned from the fourth-stage membrane module unit 18 in the final stage, which will be described later, is sent to the second space 13 of each membrane module of the third-stage membrane module unit 16 through the pipe 62. In each of the membrane modules of the third-stage membrane module unit 16, the first space 11 is pressurized and the water contained in the first space 11 is permeated into the second space 13 in the same manner as in the first and second stages. (Concentration step (third stage)).

The concentrated water of the third-stage membrane module unit 16 is sent to the first space 11 of the membrane module of the final-stage fourth-stage membrane module unit 18 through the pipe 80. On the other hand, the concentrated water returned from the fourth-stage membrane module unit 18 in the final stage, which will be described later, is sent to the second space 13 of the fourth-stage membrane module unit 18 through the pipe 82. In the fourth stage membrane module unit 18, the first space 11 is pressurized and the water contained in the first space 11 is permeated into the second space 13 in the same manner as in the first to third stages (concentration step (concentration step (concentration step (concentration step)). 4th stage)).

The concentrated water of the fourth-stage membrane module unit 18 is sent to and stored in the concentrated water tank 20 as needed through the pipe 54. The valves 78 and 86 are closed, and at least a part of the concentrated water is discharged as treated water from the concentrated water tank 20 through the pipe 56 by the pump 32 to the outside of the system. At least a part of the concentrated water may be sent to the water tank 10 to be treated and mixed with the water to be treated in the water tank 10 to be treated.

At least a part of the concentrated water of the fourth-stage membrane module unit 18 is in the closed state of the valve 78 and the open state of the valve 86, and the fourth stage is passed through the pipe 56, the pipe 58, and the pipe 82 from the concentrated water tank 20 by the pump 32. The liquid is sent to the second space 13 of the membrane module unit 18. As described above, in the membrane module of the fourth-stage membrane module unit 18, the first space 11 is pressurized and the water contained in the first space 11 is permeated into the second space 13 (concentration step (fourth stage). )). Here, the pump 32, the pipes 56, 58, 82 and the like function as supply means for supplying at least a part of the concentrated water in the final stage to the second space of the semipermeable membrane module in the final stage.

The diluted water of the fourth-stage membrane module unit 18 is sent to the first diluted water tank 22 as needed through the pipe 84, and after being stored, the pump 34 passes through the pipe 62 from the first diluted water tank 22 to 3 The liquid is sent to the second space 13 of each membrane module of the step membrane module unit 16. As described above, in each membrane module of the third-stage membrane module unit 16, the first space 11 is pressurized and the water contained in the first space 11 is permeated into the second space 13 (concentration step (three stages). Eye)).

The diluted water of the third-stage membrane module unit 16 is sent to the second diluted water tank 24 as needed through the pipe 64, and after being stored, the pump 36 passes through the pipe 66 from the second diluted water tank 24 to 2 The liquid is sent to the second space 13 of each membrane module of the step membrane module unit 14. As described above, in each membrane module of the second-stage membrane module unit 14, the first space 11 is pressurized and the water contained in the first space 11 is permeated into the second space 13 (concentration step (second stage). Eye)).

The diluted water of the second-stage membrane module unit 14 is sent to the second space 13 of each membrane module of the first-stage membrane module unit 12 through the pipe 68. As described above, in each membrane module of the first-stage membrane module unit 12, the first space 11 is pressurized and the water contained in the first space 11 is permeated into the second space 13 (concentration step (1st stage). Eye)).

The diluted water of the first-stage membrane module unit 12 is sent to the third dilution water tank 26 as needed through the pipe 70, and after being stored, the pump 38 passes through the pipe 72 to the reverse osmosis membrane treatment device 28. The liquid is sent. In the reverse osmosis membrane treatment apparatus 28, the reverse osmosis membrane treatment is performed (reverse osmosis membrane treatment step). The RO permeated water obtained by the reverse osmosis membrane treatment is discharged to the outside of the system through the pipe 76. The RO concentrated water obtained by the reverse osmosis membrane treatment is sent to the water tank 10 to be treated through the pipe 74, and is mixed with the water to be treated in the water tank 10 to be treated. The diluted water of the first-stage membrane module unit 12 may be discharged to the outside of the system as it is, or may be sent to the water tank 10 as it is and mixed with the water to be treated in the water tank 10.

As described above, the treated water in which the substance such as the dissolved solid component is concentrated (concentrated water in the final stage) and the RO permeated water are separated from the treated water containing the substance such as the dissolved solid component, which is the treatment target. Obtained, the volume of water to be treated is reduced.

In the water treatment method and the water treatment apparatus according to the present embodiment, for example, as shown in FIG. 2, the amount of the substance in the water at the inlet of the first space 11 of the third stage membrane module unit 16 is measured by the substance amount measuring apparatus 40. The amount of the substance in the water at the entrance of the second space 13 of the third stage membrane module unit 16 is measured by the substance amount measuring device 42. In water at the entrance of the second space 13 of the third stage membrane module unit 16 so that the difference between the value measured by the substance amount measuring device 40 and the value measured by the substance amount measuring device 42 is within a predetermined range. Adjust the amount (concentration) of the substance and adjust the osmotic pressure. For example, the valve 86 is closed, the opening degree of the valve 78 is adjusted, and the pump 32 passes through the concentrating water tank 20, the pipe 56, and the pipe 58, and the four stages having a higher concentration than the previous stage of the third stage membrane module unit 16. At least a part of the concentrated water of the eye membrane module unit 18 is added to the diluted water of the first dilution water tank 22, and the concentration of water at the inlet of the second space 13 is adjusted to adjust the osmotic pressure. Here, the pump 32, the pipes 56, 58, the valve 78, etc. are second so that the concentration difference of the substance between the first space and the second space of the semipermeable membrane module of at least one stage is within a predetermined range. By adding at least a part of the higher concentration concentrated water in the front stage of the space, it functions as an adjusting means for adjusting the concentration of water at the entrance of the second space.

As a result, in the water concentration treatment using the multi-stage semipermeable membrane module, the osmotic pressure difference of each membrane module is maintained within a predetermined range even if the water quality of the water to be treated (raw water) fluctuates, and the final stage is obtained. The concentration of concentrated water to be produced can be quickly stabilized.

Further, the flow rate of the diluted water supplied to the second space 13 of the third-stage membrane module unit 16 is adjusted by adjusting the flow rate of the pump 34 at the inlet of the second space of the third-stage membrane module unit 16. The osmotic pressure may be adjusted. Here, the pump 34, the inverter installed in the pump 34, and the like have a second so that the concentration difference of the substance between the first space and the second space of the semipermeable membrane module in at least one stage is within a predetermined range. It functions as an adjusting means for adjusting the flow rate supplied to the space.

In the water treatment device 1 of FIG. 1 and the water treatment device 3 of FIG. 2, the substance amount measuring device 40 and the substance amount measuring device 42 are installed at the first space outlet and the second space outlet of the third stage membrane module unit 16, respectively. It may be installed at both the first space entrance and the first space exit, and the second space entrance and the second space exit, respectively. When installed at both the first space entrance and the first space exit, and the second space entrance and the second space exit, respectively, the average value of the entrance and the exit is used so that the difference falls within a predetermined range. It is more preferable to adjust. Further, the amount of the substance in the water may be measured in the dilution water tank (for example, the first dilution water tank 22 and the second dilution water tank 24), or in-line (for example, pipes 50 and 52 and pipes 62 and 64, It may be measured in 66). This method may be applied to all stages, and the more it is applied to a large number of stages, the higher the accuracy of density adjustment is, which is more preferable. In this case, the dilution water tank may be provided in all stages.

Further, for example, the water tank 10 to be treated (the first space inlet of the first-stage membrane module unit 12) and the concentrated water tank 20 (the first space outlet of the fourth-stage membrane module unit 18) are in water at separate stages. The amount of the substance may be measured and the osmotic pressure in the membrane module unit in the middle stage may be adjusted so that the value falls within a predetermined range.

The osmotic pressure is adjusted by, for example, sending more concentrated water in the first space by a method such as switching an automatic valve, or adjusting the flow rate of the diluted water supplied to the second space by adjusting the inverter of the pump. Just do it.

The osmotic pressure may be adjusted, for example, so that the concentration difference of the substance between the first space and the second space is within a range of 50% or more and 90% or less of the second space with respect to the first space, and is 70% or more. The range is preferably 90% or less. If this concentration difference is less than 50%, the osmotic pressure becomes too high and permeated water cannot be produced, and concentration may not be possible. If it exceeds 90%, the concentration ratio in the entire system may decrease.

The number of stages of the membrane module unit may be determined according to the concentration of the target treated water and the like. For example, when it is desired to obtain a treatment water having a higher concentration from a water to be treated having a lower concentration, the number of stages of the membrane module unit may be increased.

The number of membrane modules in each membrane module unit may be determined by the flow rate of water to be treated or the like.

Examples of the semipermeable membrane 15 included in the membrane module include semipermeable membranes such as a reverse osmosis membrane (RO membrane), a normal osmosis membrane (FO membrane), and a nanofiltration membrane (NF membrane). The semipermeable membrane is preferably a reverse osmosis membrane, a forward osmosis membrane, or a nanofiltration membrane. When a reverse osmosis membrane, a forward osmosis membrane, or a nanofiltration membrane is used as the semipermeable membrane, the pressure of the target solution in the first space is preferably 0.5 to 10.0 MPa.

The material constituting the semipermeable membrane 15 is not particularly limited, and examples thereof include cellulose-based resins such as cellulose acetate-based resins, polysulfone-based resins such as polyethersulfone-based resins, and polyamide-based resins. The material constituting the semipermeable membrane 15 is preferably a cellulose acetate resin.

Examples of the shape of the semipermeable membrane 15 include a flat membrane, a hollow fiber membrane, and a spiral membrane.

The substance amount measuring device 40 and the substance amount measuring device 42 are not particularly limited as long as they can measure the amount of substances such as dissolved solid components in water. Examples of the substance amount measuring device 40 and the substance amount measuring device 42 include a conductivity measuring device that measures the amount of a substance in water by measuring conductivity, an ion densitometer, and the like, and the convenience of measurement and the like. From the point of view, a conductivity measuring device is preferable.

The water to be treated may be water containing a substance such as a dissolved solid component (TDS), and is not particularly limited. For example, factory wastewater, salt water, seawater, chemical waste liquid, concentrated waste water after reverse osmosis membrane treatment, etc. Can be mentioned. The water treatment method and water treatment apparatus according to the present embodiment are more when the TDS (dissolved solid component) concentration of the water to be treated is, for example, 50,000 mg / L or more, preferably 60,000 mg / L or more. It is preferably applicable when it is preferably 100,000 mg / L or more. The TDS (dissolved solid component) contains, for example, chlorides such as sodium chloride, carbonates such as calcium carbonate and magnesium carbonate, and sulfates such as calcium sulfate and magnesium sulfate.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

<Example 1>
A water flow test was conducted under the following experimental conditions using the experimental equipment (water treatment device) having the configuration shown in FIG.

The water treatment device 5 shown in FIG. 3 includes a first-stage membrane module unit 12, a second-stage membrane module unit 14, a third-stage membrane module unit 16, a fourth-stage membrane module unit 18, and a fifth-stage membrane module unit 19. Be prepared. The first-stage membrane module unit 12 includes six membrane modules connected in parallel, and the second-stage membrane module unit 14 includes five membrane modules connected in parallel, and the third-stage membrane The module unit 16 includes four membrane modules connected in parallel, the fourth-stage membrane module unit 18 includes three membrane modules connected in parallel, and the fifth-stage membrane module unit 19 includes three membrane modules connected in parallel. , Equipped with three membrane modules connected in parallel. The water treatment device 5 stores the water tank 10 to be treated for storing the water to be treated, the concentrated water tank 20 for storing the concentrated water from the fifth stage membrane module unit 19, and the diluted water from the fifth stage membrane module unit 19. The first dilution water tank 100, the second dilution water tank 102 for storing the diluted water from the fourth-stage membrane module unit 18, and the third dilution water tank 104 for storing the diluted water from the third-stage membrane module unit 16. It is provided with a fourth dilution water tank 106 for storing the diluted water from the second stage membrane module unit 14, and a fifth dilution water tank 108 for storing the diluted water from the first stage membrane module unit 12. The water treatment device 5 includes a reverse osmosis membrane treatment device 28 as a reverse osmosis membrane treatment means for reverse osmosis membrane treatment of the diluted water from the first stage membrane module unit 12.

The water treatment device 5 uses a multi-stage membrane module having a first space 11 and a second space 13 partitioned by a semi-transparent film 15, and water to be treated is serialized in the first space 11 of the multi-stage membrane module. The concentrated water of the 5th stage membrane module unit 19 is distributed to the second space 13 of the 5th stage membrane module unit 19 of the final stage, and the diluted water of the 5th stage membrane module unit 19 is applied to the membrane of the previous stage. It is a device that returns and passes water in series to the second space 13 of the module, pressurizes the first space 11 to allow water contained in the first space 11 to permeate through the second space 13 and concentrate the water. ..

The water to be treated is passed in series from the first space 11 of the first-stage membrane module unit 12 to the first space 11 of the fifth-stage membrane module unit 19, and the concentrated water of the fifth-stage membrane module unit 19 is The liquid is sent and stored in the concentrated water tank 20 through the pipe 136. The valves 126 and 128 are closed, and at least a part of the concentrated water is discharged as treated water from the concentrated water tank 20 through the pipe 138 by the pump 98 to the outside of the system.

At least a part of the concentrated water of the fifth-stage membrane module unit 19 is in the closed state of the valve 128 and the open state of the valve 126, and the fifth stage is passed through the pipe 138, the pipe 142, and the pipe 140 from the concentrated water tank 20 by the pump 98. The liquid is sent to the second space 13 of the membrane module unit 19. In the membrane module of the fifth-stage membrane module unit 19, a concentration step (fifth stage) is performed.

The diluted water of the 5th stage membrane module unit 19 is sent to the 1st dilution water tank 100 through the pipe 144, and after being stored, the 4th stage membrane module is sent from the 1st dilution water tank 100 through the pipe 146 by the pump 110. The liquid is sent to the second space 13 of each membrane module of the unit 18. In each membrane module of the fourth-stage membrane module unit 18, a concentration step (fourth stage) is performed.

The diluted water of the 4th stage membrane module unit 18 is sent to the 2nd dilution water tank 102 through the pipe 150 and stored, and then the 3rd stage membrane module is sent from the 2nd dilution water tank 102 through the pipe 152 by the pump 112. The liquid is sent to the second space 13 of each membrane module of the unit 16. In each membrane module of the third-stage membrane module unit 16, a concentration step (third stage) is performed.

The diluted water of the third-stage membrane module unit 16 is sent to the third dilution water tank 104 through the pipe 156, and after being stored, the second-stage membrane module is passed through the pipe 158 from the third dilution water tank 104 by the pump 114. The liquid is sent to the second space 13 of each membrane module of the unit 14. A concentration step (second stage) is performed in each membrane module of the second stage membrane module unit 14.

The diluted water of the second-stage membrane module unit 14 is sent to the fourth dilution water tank 106 through the pipe 162, and after being stored, the first-stage membrane module is passed from the fourth dilution water tank 106 through the pipe 164 by the pump 116. The liquid is sent to the second space 13 of each membrane module of the unit 12. A concentration step (first stage) is performed in each membrane module of the first-stage membrane module unit 12.

The diluted water of the first-stage membrane module unit 12 is sent to the fifth dilution water tank 108 through the pipe 166 and stored, and then the reverse osmosis membrane treatment device 28 performs the reverse osmosis membrane treatment (reverse osmosis membrane). Processing process).

At least a part of the concentrated water from the concentrated water tank 20 can be sent to the first diluted water tank 100 through the pipe 142 by opening and closing the valve 128, and at least a part of the diluted water from the first diluted water tank 100 opens and closes the valve 130. The liquid can be sent to the second dilution water tank 102 through the pipe 148, and at least a part of the dilution water from the second dilution water tank 102 can be sent to the third dilution water tank 104 through the pipe 154 by opening and closing the valve 132. At least a part of the diluted water from the third diluted water tank 104 can be sent to the fourth diluted water tank 106 through the pipe 160 by opening and closing the valve 134. The flow rates of the pump 110, the pump 112, the pump 114, and the pump 116 can be adjusted by the inverter 118, the inverter 120, the inverter 122, and the inverter 124, respectively.

(Experimental conditions)
-Water to be treated: 6% by mass of water containing sodium chloride (NaCl)
-Amount of water to be treated: 480 L / h
・ Water pump to be treated (pump 30) Flow rate: 1600 L / h
・ Membrane module: Toyobo Co., Ltd. 5-inch membrane ・ Number of membranes: 21, 5 stages (6 + 5 + 4 + 3 + 3 from the upstream side)
・ Concentration of each first space and each second space of the membrane when the water quality is stable: as shown in Tables 1 and 2 ・ Obtained RO permeated water amount: 290 L / h
・ Capacity of water tank to be treated, concentrated water tank, diluted water tank: 100L each

<Example>
Conductivity meters were attached to all the first space outlets and the second space outlets of each stage. FIG. 3 shows only an example in which the conductivity meter 168 and the conductivity meter 170 are attached to the first space outlet and the second space outlet of the fourth-stage membrane module unit 18, respectively. As shown in Table 3, the opening degree of the valve 128 or the frequency of the pump 110 by the inverter 118 is adjusted with respect to the value (%) of the conductivity measured by the conductivity meter 170 with respect to the conductivity measured by the conductivity meter 168. Controlled. FIG. 5 shows the concentrated water concentration (mass%) of the fifth-stage membrane module unit 19 with respect to the elapsed time (min) from the concentration fluctuation of the water to be treated.

As a result, when the concentration of the water to be treated was increased from 6% by mass to 8% by mass, the opening degree of the valve 128 was adjusted as shown in Table 3, and the frequency of the pump 110 was adjusted. It was almost equal, and the concentration of concentrated water at the outlet of the fifth stage membrane module unit 19 was stable at 19% by mass in about 10 minutes.

<Comparison example>
Water treatment was performed using the experimental equipment (water treatment device) having the configuration shown in FIG. 3 in the same manner as in the embodiment without controlling the opening degree of the valve 128 or the frequency of the pump 110. The results are shown in FIG.

As a result, when the concentration of the water to be treated is increased from 6% by mass to 8% by mass, the concentration of concentrated water at the outlet of the fifth stage membrane module unit 19 fluctuates, and the concentration of concentrated water finally stabilizes at 19% by mass. It took 60 minutes to complete.

In this way, in the water concentration treatment using the multi-stage semipermeable membrane module, the concentration of concentrated water obtained in the final stage is quickly stabilized even if the water quality of the water to be treated fluctuates, depending on the apparatus and method of the examples. I was able to make it.

1,3,5,7 Water treatment equipment, 10,200 Water tank to be treated 11,214 1st space, 12,202 1st stage membrane module unit, 13,216 2nd space, 14,204 2nd stage membrane module Unit, 15,218 Semi-transparent membrane, 16,206 3rd stage membrane module unit, 18,208 4th stage membrane module unit, 20,210 Concentrated water tank, 22,100 1st diluted water tank, 24,102 2nd diluted water tank , 26, 104 3rd dilution water tank, 28 back osmotic membrane treatment device, 30, 32, 34, 36, 38, 98, 110, 112, 114, 116 pump, 40, 42 substance amount measuring device, 44, 46, 48 , 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 80, 82, 84, 136, 138, 140, 142, 144, 146, 148, 150 , 152,154,156,158,160,162,164,166 Piping, 78,86,126,128,130,132,134 Valve, 106 4th dilution tank, 108 5th dilution tank, 118,120,122 , 124 Inverter, 168,170 Conductivity meter, 212 Diluting water tank.

Claims (8)

Concentration step of concentrating water to be treated containing a substance using a semipermeable membrane module having a first space and a second space partitioned by a semipermeable membrane, and further concentrating the concentrated water using a semipermeable membrane module. The water to be treated is supplied to the first space of the semipermeable membrane module of the first stage, and after the concentrated water passes through the first space of the semipermeable membrane module of the final stage, the final stage A method of supplying at least a part of the concentrated water to the second space of the semipermeable membrane module in the final stage, or the concentrated water in the previous stage in both the first space and the second space of the semipermeable membrane module in the final stage. In any of the methods of supplying
In the concentration step, the diluted water that has passed through the second space of the semipermeable membrane module in the final stage is supplied to the second space of the semipermeable membrane module upstream of the diluted water, and the second space of the semipermeable membrane module in each stage is supplied. Pressurize one space to allow the water contained in the first space to permeate through the second space.
The amount of the substance in water at the first space inlet or first space outlet and the second space inlet or second space outlet of the semipermeable membrane module of at least one stage is measured, and the semipermeable membrane of at least one stage is measured. At the entrance of the second space, at least a part of the higher concentration concentrated water in the previous stage of the second space is added so that the concentration difference of the substance between the first space and the second space of the module is within a predetermined range. A water treatment method characterized by adjusting the concentration of water. Concentration step of concentrating water to be treated containing a substance using a semipermeable membrane module having a first space and a second space partitioned by a semipermeable membrane, and further concentrating the concentrated water using a semipermeable membrane module. The water to be treated is supplied to the first space of the semipermeable membrane module of the first stage, and after the concentrated water passes through the first space of the semipermeable membrane module of the final stage, the final stage A method of supplying at least a part of the concentrated water to the second space of the semipermeable membrane module in the final stage, or the concentrated water in the previous stage in both the first space and the second space of the semipermeable membrane module in the final stage. In any of the methods of supplying
In the concentration step, the diluted water that has passed through the second space of the semipermeable membrane module in the final stage is supplied to the second space of the semipermeable membrane module upstream of the diluted water, and the second space of the semipermeable membrane module in each stage is supplied. Pressurize one space to allow the water contained in the first space to permeate through the second space.
The amount of the substance in water at the first space inlet or first space outlet and the second space inlet or second space outlet of the semipermeable membrane module of at least one stage is measured, and the first space of at least one stage. A water treatment method characterized by adjusting the flow rate supplied to the second space so that the concentration difference between the substance and the second space is within a predetermined range. The water treatment method according to claim 1 or 2.
In the predetermined range, the concentration difference of the substance between the first space and the second space of the semipermeable membrane module having at least one stage is 50% or more and 90% or less in the second space with respect to the first space. A water treatment method characterized by being in the range. The water treatment method according to any one of claims 1 to 3.
A water treatment method characterized by measuring the amount of the substance by measuring the conductivity. Concentration means for concentrating water to be treated containing a substance using a semipermeable membrane module having a first space and a second space partitioned by a semipermeable membrane, and further concentrating the concentrated water using a semipermeable membrane module. The water to be treated is supplied to the first space of the semipermeable membrane module of the first stage, and after the concentrated water passes through the first space of the semipermeable membrane module of the final stage, the final stage The supply means for supplying at least a part of the concentrated water to the second space of the semipermeable membrane module of the final stage, or the concentration of the previous stage in both the first space and the second space of the semipermeable membrane module of the final stage. Equipped with one of the supply means to supply water,
In the concentration means, the diluted water that has passed through the second space of the semipermeable membrane module in the final stage is supplied to the second space of the semipermeable membrane module upstream of the concentrating means, and the second space of the semipermeable membrane module in each stage is supplied. Pressurize one space to allow the water contained in the first space to permeate through the second space.
A measuring means for measuring the amount of the substance in water at the first space inlet or the first space outlet and the second space inlet or the second space outlet of the semipermeable membrane module of at least one stage.
At least a part of the higher concentration concentrated water in the previous stage of the second space is added so that the concentration difference of the substance between the first space and the second space of at least one stage is within a predetermined range. Adjustment means to adjust the concentration of water at the space entrance,
A water treatment device characterized by comprising. Concentration means for concentrating water to be treated containing a substance using a semipermeable membrane module having a first space and a second space partitioned by a semipermeable membrane, and further concentrating the concentrated water using a semipermeable membrane module. The water to be treated is supplied to the first space of the semipermeable membrane module of the first stage, and after the concentrated water passes through the first space of the semipermeable membrane module of the final stage, the final stage The supply means for supplying at least a part of the concentrated water to the second space of the semipermeable membrane module of the final stage, or the concentration of the previous stage in both the first space and the second space of the semipermeable membrane module of the final stage. Equipped with one of the supply means to supply water,
In the concentration means, the diluted water that has passed through the second space of the semipermeable membrane module in the final stage is supplied to the second space of the semipermeable membrane module upstream of the concentrating means, and the second space of the semipermeable membrane module in each stage is supplied. Pressurize one space to allow the water contained in the first space to permeate through the second space.
A measuring means for measuring the amount of the substance in water at the first space inlet or the first space outlet and the second space inlet or the second space outlet of the semipermeable membrane module of at least one stage.
An adjusting means for adjusting the flow rate supplied to the second space so that the concentration difference of the substance between the first space and the second space of at least one stage is within a predetermined range.
A water treatment device characterized by comprising. The water treatment apparatus according to claim 5 or 6.
In the predetermined range, the concentration difference of the substance between the first space and the second space of the semipermeable membrane module having at least one stage is 50% or more and 90% or less in the second space with respect to the first space. A water treatment device characterized by being in a range. The water treatment apparatus according to any one of claims 5 to 7.
The water treatment apparatus is characterized in that the measuring means measures the amount of the substance by measuring the conductivity.