JP2023038919A - Water treatment device, and water treatment method - Google Patents

Abstract

To provide a water treatment device and a water treatment method capable of recovering a valuable material in high concentration from effluent.SOLUTION: A water treatment device 1 that recovers a valuable material from effluent, comprises a nano filtration device 11 for obtaining NF permeated water and NF concentrated water from effluent using a nano filtration membrane, and semipermeable membrane treatment means of obtaining concentrated water, by using a membrane module 10 comprising a first space 14 and a second space 16 separated by a semipermeable membrane 12 to allow the NF concentrated water to flow through the first space 14 so as to pressurize the first space 14 to force water contained in the NF concentrated water to flow through the semi-permeable membrane 12, and obtaining diluted water by forcing a portion of the NF concentrated water or at least a portion of the concentrated water to flow through the second space 16.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a water treatment apparatus and a water treatment method for recovering valuables from waste water.

2. Description of the Related Art In recent years, methods have been used to recover valuables from wastewater discharged from semiconductor factories or the like using an evaporation method such as an evaporator or membrane distillation. However, since the evaporation method requires a huge amount of energy, a method of reducing the volume of wastewater by a reverse osmosis membrane method in the preceding stage of the evaporation method is generally used as in Patent Document 1.

On the other hand, as a method for concentrating ions contained in waste water to a high concentration, hard components or turbid components in the concentrate of a reverse osmosis membrane module are removed by a nanofiltration membrane or an ultrafiltration membrane as in Patent Document 2. Later, a method of concentrating the permeated water with a semipermeable membrane module was developed.

JP-A-10-323664 Japanese Patent Application Laid-Open No. 2021-045736

An object of the present invention is to provide a water treatment apparatus and a water treatment method capable of recovering valuable substances from waste water at high concentrations.

The present invention is a water treatment apparatus for recovering valuables from wastewater, comprising: nanofiltration means for obtaining NF permeated water and NF concentrated water for the wastewater using a nanofiltration membrane; Using a semipermeable membrane module having one space and a second space, the NF concentrated water is passed through the first space, and the first space is pressurized to remove the water contained in the NF concentrated water from the semipermeable membrane module. Semipermeable membrane processing means for obtaining concentrated water by permeating through a permeable membrane, and for obtaining dilution water by passing a portion of the NF concentrated water or at least a portion of the concentrated water through the second space; A water treatment device comprising:

The present invention is a water treatment apparatus for recovering valuables from wastewater, comprising: nanofiltration means for obtaining NF permeated water and NF concentrated water for the wastewater using a nanofiltration membrane; Using a semipermeable membrane module connected in multiple stages having one space and a second space, the NF concentrated water is passed through the first space of the first stage semipermeable membrane module, and the first space is pressurized to permeate the water contained in the NF concentrated water through the semipermeable membrane to obtain concentrated water, and the concentrated water is further obtained by using a semipermeable membrane module in the next stage or later to obtain concentrated water, Diluted water is obtained by passing at least part of the NF concentrated water or the concentrated water or at least part of the diluted water obtained from another semipermeable membrane module through the second space of the semipermeable membrane module of each stage. and semipermeable membrane treatment means.

Preferably, the water treatment apparatus further comprises return means for returning at least part of the diluted water obtained by the semipermeable membrane treatment means to a stage preceding the nanofiltration means.

In the water treatment apparatus, the waste water preferably contains 2000 mg/L or more of ammonium ions, 6000 mg/L or more of sulfate ions, and 5 mg/L or more of silica.

In the water treatment device, the nanofiltration membrane has a silica rejection rate in the range of 0 to 20% under conditions of a membrane surface effective pressure of 1 MPa, 25 ° C., pH 7, and an ammonium ion rejection rate and a sulfate ion rejection rate of 90. % to 100%.

It is preferable that the water treatment apparatus further comprises pH adjustment means for adjusting the pH of the waste water to a range of 4 to 8, upstream of the nanofiltration means.

In the water treatment apparatus, it is preferable to further include temperature adjusting means for adjusting the temperature of the waste water within a range of 20°C to 35°C, upstream of the nanofiltration means.

The present invention is a water treatment method for recovering valuables from wastewater, comprising a nanofiltration step of obtaining NF permeated water and NF concentrated water using a nanofiltration membrane for the wastewater, and a second step separated by a semipermeable membrane. Using a semipermeable membrane module having one space and a second space, the NF concentrated water is passed through the first space, and the first space is pressurized to remove the water contained in the NF concentrated water from the semipermeable membrane module. A semi-permeable membrane treatment step of obtaining concentrated water by permeating through a permeable membrane and passing a portion of the NF concentrated water or at least a portion of the concentrated water through the second space to obtain diluted water; A water treatment method comprising:

The present invention is a water treatment method for recovering valuables from wastewater, comprising a nanofiltration step of obtaining NF permeated water and NF concentrated water using a nanofiltration membrane for the wastewater, and a second step separated by a semipermeable membrane. Using a semipermeable membrane module connected in multiple stages having one space and a second space, the NF concentrated water is passed through the first space of the first stage semipermeable membrane module, and the first space is pressurized to permeate the water contained in the NF concentrated water through the semipermeable membrane to obtain concentrated water, and the concentrated water is further obtained by using a semipermeable membrane module in the next stage or later to obtain concentrated water, Diluted water is obtained by passing at least part of the NF concentrated water or the concentrated water or at least part of the diluted water obtained from another semipermeable membrane module through the second space of the semipermeable membrane module of each stage. and a semipermeable membrane treatment step.

In the water treatment method, it is preferable to return at least part of the diluted water obtained in the semipermeable membrane treatment step to the preceding stage of the nanofiltration step.

In the water treatment method, the wastewater preferably contains 2000 mg/L or more of ammonium ions, 6000 mg/L or more of sulfate ions, and 5 mg/L or more of silica.

In the water treatment method, the nanofiltration membrane has a silica rejection rate of 0 to 20% under conditions of a membrane surface effective pressure of 1 MPa, 25 ° C., pH 7, and an ammonium ion rejection rate and a sulfate ion rejection rate of 90. % to 100%.

The water treatment method preferably further includes a pH adjustment step of adjusting the pH of the waste water to a range of 4 to 8 before the nanofiltration step.

The water treatment method preferably further includes a temperature adjustment step of adjusting the temperature of the waste water to a range of 20°C to 35°C before the nanofiltration step.

ADVANTAGE OF THE INVENTION By this invention, the water treatment apparatus and water treatment method which can collect|recover valuables from waste water at high concentration can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS 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 the other example of the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows the other example of the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows the other example of the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows the other example of the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows the other example of the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows the other example of the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows the other example of the water treatment apparatus which concerns on embodiment of this invention. 4 is a graph showing results of rejection of silica in Example 1. FIG.

An embodiment of the present invention will be described below. This embodiment is an example of implementing the present invention, and the present invention is not limited to this 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.

A water treatment device 1 shown in FIG. 1 is a device for recovering valuables from waste water such as ammonia-containing waste water. The water treatment device 1 includes a nanofiltration device 11 and a first space (concentration Using a semipermeable membrane module having a second space (permeate side) 14 and a second space (permeate side) 16, the NF concentrated water of the nanofiltration device 11 is passed through the first space 14, and the first space 14 is pressurized to As a semipermeable membrane treatment means for obtaining concentrated water by passing water contained in the concentrated water through the semipermeable membrane 12 and passing a part of the NF concentrated water through the second space 16 to obtain diluted water, For example, a membrane module 10 is provided. The water treatment device 1 may include an NF-concentrated water tank that stores NF-concentrated water between the nanofiltration device 11 and the membrane module 10 .

In the water treatment device 1 of FIG. 1 , a pipe 25 is connected to the inlet of the nanofiltration device 11 via a pump 21 . A pipe 27 is connected to the NF permeate outlet of the nanofiltration device 11 . The NF concentrated water outlet of the nanofiltration device 11 and the first space inlet of the membrane module 10 are connected by a pipe 24 via a pump 18, and a pipe 26 branched from the pipe 24 on the downstream side of the pump 18 connects the valve 22. It is connected to the second space inlet of the membrane module 10 via. A pipe 28 is connected to the first spatial outlet of the membrane module 10 via a valve 23 , and a pipe 30 connects the second spatial outlet of the membrane module 10 and the pipe 25 upstream of the pump 21 .

The pump 18 is, for example, a pressure pump that is driven at a rotational speed corresponding to the input drive frequency, sucks the NF concentrated water, and pressurizes and discharges it to the membrane module 10 . The pump 18 is provided with, for example, an inverter 20 that outputs a driving frequency corresponding to the input command signal to the pump 18 . The pump 21 is, for example, a pressurization pump that is driven at a rotational speed corresponding to the input driving frequency, sucks the ammonia-containing wastewater, and pressurizes and discharges it to the nanofiltration device 11 . The valves 22 and 23 are, for example, valves whose degree of opening and closing can be adjusted manually or automatically.

The membrane module 10 has a first space 14 and a second space 16 partitioned by a semipermeable membrane 12, and the NF concentrated water is supplied from the first space inlet of the membrane module 10 to the first space 14 and from the second space inlet to the second space. By passing water through the two spaces 16 and pressurizing the first space 14, the water contained in the NF concentrated water in the first space 14 is permeated into the second space 16 through the semipermeable membrane 12 to release water. It is a device for concentrating. That is, in the water treatment device 1 , the NF concentrated water is concentrated using the semipermeable membrane 12 . The membrane module 10 is a device that supplies NF concentrated water to both the first space 14 and the second space 16 of the membrane module 10 to carry out a concentration process.

In the water treatment device 1 , the ammonia-containing waste water, which is the water to be treated, is supplied to the nanofiltration device 11 through the pipe 25 by the pump 21 . In the nanofiltration device 11, NF permeated water and NF concentrated water are obtained from ammonia-containing waste water using a nanofiltration membrane (nanofiltration step). NF permeated water is discharged through piping 27 . The NF permeated water may be discharged out of the system and discharged into a river or the like, or may be recovered by providing an advanced water treatment method.

The NF concentrated water obtained by the nanofiltration device 11 is pressure-fed from the first space inlet of the membrane module 10 to the first space 14 through the pipe 24 by the pump 18 with the valve 23 open, and is passed. . Water may be supplied to the nanofiltration device 11 and the membrane module 10 using only the pump 21 . Further, the NF concentrated water is sent from the second space inlet of the membrane module 10 to the second space 16 through the pipe 26 branched from the pipe 24 with the valve 22 open. Part of the water contained in the pressurized NF concentrated water permeates from the first space 14 toward the second space 16 through the semipermeable membrane 12 . At this time, since most of the ions and the like contained in the NF concentrated water cannot permeate the semipermeable membrane 12, the water in the first space 14 that has not permeated the semipermeable membrane 12 is concentrated. On the other hand, in the second space 16, part of the NF-concentrated water that has passed through the pipe 26 and the permeated water with a low ion concentration that has permeated the semipermeable membrane 12 join together, so a dilution effect works. The concentrated water obtained in the first space 14 is discharged from the first space outlet through the pipe 28, the dilution water obtained in the second space 16 is discharged from the second space outlet through the pipe 30, and at least A part may be returned to the upstream side of the pump 21 in the pipe 25 that is the preceding stage of the nanofiltration device 11 (returning step). Here, in the membrane module 10, the first space 14 is pressurized and the water contained in the NF concentrated water in the first space 14 is permeated into the second space 16 through the semipermeable membrane 12, and the first space 14 Concentrated water is obtained in (concentration step), and dilution water is obtained in the second space 16 (dilution step) (above, semipermeable membrane treatment step).

Here, the pipes 24 , 26 , the pump 18 and the like function as supply means for supplying the NF concentrated water to both the first space 14 and the second space 16 of the membrane module 10 . The pipes 30 and the like function as return means for returning at least part of the diluted water obtained in the membrane module 10 to the front stage of the nanofiltration device 11 .

The dilution water obtained in the second space 16 may be discharged out of the system through the pipe 30, or may be discharged out of the system after being sent to a dilution water tank and stored as necessary, May be reused. At least part of the dilution water may be returned, for example, in line 25 upstream of pump 21 and mixed with NF concentrate. At least a portion of the dilution water may be subjected to other treatments such as reverse osmosis membrane treatment.

As described above, at least one of ammonia and ammonium ions is recovered as concentrated water from the ammonia-containing waste water to be treated, and the volume of the ammonia-containing waste water is reduced. In addition, NF permeated water, concentrated water, and diluted water can be reused.

By passing the NF concentrated water through the first space 14 and the second space 16 of the membrane module 10, the osmotic pressure difference between the first space 14 side and the second space 16 side of the semipermeable membrane 12 is reduced, resulting in less consumption. The energy can concentrate high concentrations of ions in the NF retentate. That is, the NF concentrated water containing ions at high concentration can be concentrated at low cost, and the amount of waste liquid with high ion concentration can be reduced.

Since waste water discharged from semiconductor factories and the like may contain scale components, membrane clogging may occur when highly concentrated by semipermeable membrane treatment, making concentration difficult. For example, if silica (SiO ₂ ) is contained in the wastewater, it is desirable to remove the silica by pretreatment of the semipermeable membrane treatment, but if the concentration of silica is high, chemicals such as dispersants are used. can be difficult.

In the water treatment apparatus and water treatment method according to the present embodiment, even if silica is contained in the waste water, the nanofiltration device 11 selectively permeates the silica in the waste water through the nanofiltration membrane to reduce the silica concentration. By passing the NF-enriched water through the first space 14 or both sides of the first space 14 and the second space 16 of the membrane module 10, the substance to be concentrated can be stably highly concentrated.

At least part of the dilution water obtained in the second space 16 is preferably returned to the front stage of the nanofiltration device 11, and 50 to 100% of the amount of dilution water is preferably returned to the front stage of the nanofiltration device 11. More preferably, 70 to 100% of the amount of dilution water is returned to the front stage of the nanofiltration device 11 . By returning a predetermined amount or more of the dilution water discharged from the membrane module 10 to the front stage of the nanofiltration device 11 and circulating it, even if silica is contained in the ammonia-containing waste water, the ammonia-containing wastewater supplied to the nanofiltration device 11 is By lowering the ratio of silica concentration to ammonium ion concentration in waste water, the risk of silica scale deposition in the concentration step of semipermeable membrane treatment can be reduced.

As an adjustment method for adjusting the flow rate of the NF concentrated water supplied to the membrane module 10, the flow rate of the permeated water, and the flow rate of the concentrated water, for example, the following method may be performed.

The pump 18 is provided with an inverter 20 for controlling the drive frequency to adjust the supply flow rate of the NF concentrated water to the membrane module 10 . Although it is preferable to install an inverter 20 on the pump 18, it may not be installed. NF concentrated water is supplied to both the first space 14 side and the second space 16 side, a valve 22 is provided in front of the entrance of the second space 16, a valve 23 is provided at the outlet of the first space 14, and the valve 22 and The ratio of the supply water flow rate to the first space 14 side and the supply water flow rate to the second space 16 side may be adjusted by manually or automatically adjusting the opening degree of the valve 23 .

If the flow rate of the permeated water and the flow rate of the concentrated water are insufficient, the frequency of the inverter 20 of the pump 18 should be increased to increase the supply amount of the NF concentrated water.

A valve 23 that can adjust the degree of opening is provided at the outlet of the first space 14 of the pipe 28, and the flow rate of the concentrated water and the pressure of the inlet of the first space 14 and the outlet of the first space 14 can be adjusted by the degree of opening of the valve 23. can.

By these operations, the pressure on the side of the first space 14 and various flow rates can be adjusted.

In addition, separate pumps may be used to supply the NF concentrated water to the first space 14 side and the second space 16 side. When the NF concentrated water is supplied by separate pumps, each pump may be provided with an inverter for controlling the drive frequency.

By passing NF concentrated water of the same or similar concentration to both the first space 14 side and the second space 16 side, the osmotic pressure generated by the semipermeable membrane 12 can be reduced, and the required pressure can be reduced. can. As a result, it is possible to concentrate NF-concentrated water with a concentration that could not be concentrated by the conventional reverse osmosis membrane method.

In this way, a high concentration of valuable substances can be recovered from ammonia-containing waste water. In addition, even if silica is contained in ammonia-containing wastewater, the risk of silica scale deposition in the concentration step of semipermeable membrane treatment can be reduced by semipermeable membrane treatment of NF concentrated water with reduced silica concentration. can.

Another example of a water treatment apparatus according to an embodiment of the present invention is schematically shown in FIG. 2, and its configuration will be described.

The water treatment device 2 shown in FIG. 2 is partitioned by a nanofiltration device 11 and a semipermeable membrane 12 as nanofiltration means for obtaining NF permeated water and NF concentrated water using a nanofiltration membrane for wastewater such as ammonia-containing wastewater. Using a semipermeable membrane module having a first space (concentration side) 14 and a second space (permeate side) 16, the NF concentrated water of the nanofiltration device 11 is passed through the first space 14, and the first Condensed water is obtained by pressurizing the space 14 to permeate the water contained in the NF concentrated water through the semipermeable membrane 12, and at least part of the concentrated water is passed through the second space 16 to obtain diluted water. For example, a membrane module 10 is provided as a semipermeable membrane treatment means. The water treatment device 2 may include an NF-concentrated water tank that stores NF-concentrated water between the nanofiltration device 11 and the membrane module 10 .

In the water treatment device 2 of FIG. 2 , a pipe 25 is connected to the inlet of the nanofiltration device 11 via a pump 21 . A pipe 27 is connected to the NF permeate outlet of the nanofiltration device 11 . The NF concentrated water outlet of the nanofiltration device 11 and the first space inlet of the membrane module 10 are connected by a pipe 24 via a pump 18 . A pipe 28 is connected to the first space outlet of the membrane module 10 via a valve 23 . A pipe 34 branched from the pipe 28 on the upstream side of the valve 23 is connected to the second space inlet of the membrane module 10 via the valve 32 . A pipe 36 connects the second space outlet of the membrane module 10 and the pipe 25 upstream of the pump 21 .

The pump 18 is, for example, a pressure pump that is driven at a rotational speed corresponding to the input drive frequency, sucks the NF concentrated water, and pressurizes and discharges it to the membrane module 10 . The pump 18 is provided with, for example, an inverter 20 that outputs a driving frequency corresponding to the input command signal to the pump 18 . The pump 21 is, for example, a pressurization pump that is driven at a rotational speed corresponding to the input driving frequency, sucks the ammonia-containing wastewater, and pressurizes and discharges it to the nanofiltration device 11 . The valves 23 and 32 are, for example, manually or automatically adjustable valves.

The membrane module 10 has a first space 14 and a second space 16 partitioned by a semipermeable membrane 12, and the NF concentrated water is passed from the first space inlet of the membrane module 10 to the first space 14, and the membrane By passing at least part of the concentrated water discharged from the first space outlet of the first space 14 of the module 10 through the second space inlet of the membrane module 10 to the second space 16 and pressurizing the first space 14 , the water contained in the NF concentrated water in the first space 14 is permeated into the second space 16 through the semipermeable membrane 12 to concentrate the water. That is, in the water treatment device 2, the semipermeable membrane 12 is used to concentrate the NF concentrated water. The membrane module 10 supplies the NF concentrated water to the first space 14 of the membrane module 10, and supplies at least part of the concentrated water obtained from the outlet of the first space 14 to the second space 16 of the membrane module 10. This is a device for concentration processing.

In the water treatment device 2 , ammonia-containing waste water, which is the water to be treated, is supplied to the nanofiltration device 11 through the pipe 25 by the pump 21 . In the nanofiltration device 11, NF permeated water and NF concentrated water are obtained from ammonia-containing waste water using a nanofiltration membrane (nanofiltration step). NF permeated water is discharged through piping 27 .

The NF concentrated water obtained by the nanofiltration device 11 is pressure-fed from the first space inlet of the membrane module 10 to the first space 14 through the pipe 24 by the pump 18 with the valve 23 open, and is passed. . Water may be supplied to the nanofiltration device 11 and the membrane module 10 using only the pump 21 . Part of the water contained in the pressurized NF concentrated water permeates from the first space 14 toward the second space 16 through the semipermeable membrane 12 . At this time, since most of the ions and the like cannot permeate the semipermeable membrane 12, the water in the first space 14 that has not permeated the semipermeable membrane 12 is concentrated. On the other hand, in the second space 16, part of the concentrated water that has passed through the pipe 34 and the permeated water that has permeated the semipermeable membrane 12 and has a low ion concentration join together, so a dilution effect works. The concentrated water obtained in the first space 14 is discharged from the outlet of the first space through the pipe 28, and at least a part of the concentrated water is passed through the pipe 34 branched from the pipe 28 with the valve 32 in an open state to the membrane module 10. is sent to the second space 16 from the second space inlet, and water is passed. The dilution water obtained in the second space 16 is discharged from the outlet of the second space through the pipe 36, and at least part of the dilution water is returned to the upstream side of the pump 21 in the pipe 25, which is the preceding stage of the nanofiltration device 11. Good (return process). Here, in the membrane module 10, the first space 14 is pressurized and the water contained in the NF concentrated water in the first space 14 is permeated into the second space 16 through the semipermeable membrane 12, and the first space 14 Concentrated water is obtained in (concentration step), and dilution water is obtained in the second space 16 (dilution step) (above, semipermeable membrane treatment step).

Here, the pipes 24, 28, 34, the pump 18, etc. supply the NF concentrated water to the first space 14 of the membrane module 10, and at least part of the concentrated water obtained from the outlet of the first space 14 is supplied to the membrane module. It functions as supply means for supplying to the second space 16 of 10 . The pipe 36 and the like function as return means for returning at least part of the diluted water obtained in the membrane module 10 to the front stage of the nanofiltration device 11 .

The dilution water obtained in the second space 16 may be discharged out of the system through the pipe 36, or may be discharged out of the system after being sent to a dilution water tank and stored as necessary, May be reused. At least part of the dilution water may be returned, for example, in line 25 upstream of pump 21 and mixed with NF concentrate. At least a portion of the dilution water may be subjected to other treatments such as reverse osmosis membrane treatment.

As described above, at least one of ammonia and ammonium ions is recovered as concentrated water from the ammonia-containing waste water to be treated, and the volume of the ammonia-containing waste water is reduced. In addition, NF permeated water, concentrated water, and diluted water can be reused.

By passing the NF concentrated water through the first space 14 of the membrane module 10 and passing at least part of the concentrated water obtained in the first space 14 through the second space 16, the first By reducing the osmotic pressure difference between the space 14 side and the second space 16 side, it is possible to concentrate ions in high concentration in the NF concentrated water with less energy consumption. That is, the NF concentrated water containing ions at high concentration can be concentrated at low cost, and the amount of waste liquid with high ion concentration can be reduced.

As an adjustment method for adjusting the flow rate of the NF concentrated water supplied to the membrane module 10, the flow rate of the permeated water, and the flow rate of the concentrated water, for example, the following method may be performed.

The pump 18 is provided with an inverter 20 for controlling the drive frequency to adjust the supply flow rate of the NF concentrated water to the membrane module 10 . Although it is preferable to install an inverter 20 on the pump 18, it may not be installed. NF concentrated water is supplied to the first space 14 side, a valve 23 is provided at the outlet of the first space 14, a valve 32 is provided before the inlet of the second space 16, and the opening of the valves 23 and 32 is manually or The ratio of the supply water flow rate to the first space 14 side and the supply water flow rate to the second space 16 side may be adjusted by automatic adjustment.

If the flow rate of the permeated water and the flow rate of the concentrated water are insufficient, the frequency of the inverter 20 of the pump 18 should be increased to increase the supply amount of the NF concentrated water.

A valve 23 that can adjust the degree of opening is provided at the outlet of the first space 14 of the pipe 28, and the flow rate of the concentrated water and the pressure of the inlet of the first space 14 and the outlet of the first space 14 can be adjusted by the degree of opening of the valve 23. can.

By these operations, the pressure on the side of the first space 14 and various flow rates can be adjusted.

Also, a concentrated water tank for storing concentrated water may be provided in the middle of the pipe 34, and separate pumps may be used to supply the NF concentrated water to the first space 14 side and the concentrated water to the second space 16 side. When supplying the NF concentrated water and the concentrated water by separate pumps, each pump may be provided with an inverter for controlling the drive frequency.

By passing NF concentrated water through the first space 14 side and passing concentrated water with a concentration close to the second space 16 side, the osmotic pressure generated by the semipermeable membrane 12 is reduced, and the required pressure can be reduced. As a result, it is possible to concentrate NF-concentrated water with a concentration that could not be concentrated by the conventional reverse osmosis membrane method.

The inlet pressure of the first space 14 is preferably in the range of 7 MPa or less, the inlet pressure of the second space 16 is preferably lower than the inlet pressure of the first space 14, and the inlet pressure of the second space 16 More preferably, the pressure is 50% or less of the inlet pressure of the first space 14 . This can reduce the risk of damage to the semipermeable membrane due to pressure.

It is preferable to make the flow rate on the first space 14 side larger than the flow rate on the second space 16 side. If the flow rate on the first space 14 side is lower than the flow rate on the second space 16 side, the permeation flux may become too high. For example, the pump 18, the inverter 20, the valve 22, the valve 23, the valve 32, etc. function as flow control means for making the flow rate in the first space higher than the flow rate in the second space.

If the permeation flux is too large, the difference in concentration will increase, which may cause problems such as an increased risk of fouling and an excessively high pressure. On the other hand, if the permeation flux is too small, the concentration efficiency may deteriorate. From these points, the permeation flux of the membrane module 10 is preferably in the range of 0.005 m/d to 0.05 m/d, more preferably in the range of 0.015 m/d to 0.04 m/d. more preferred. The permeation flux is defined as permeation flow rate per unit membrane area per unit time. For example, the pump 18, the inverter 20, the valve 22, the valve 23, the valve 32, etc. function as permeation flux adjusting means for controlling the permeation flux within the above range.

It should be noted that the installation positions and the number of installation of the valves are merely examples, and the number may be greater than those shown in FIGS. 1 and 2, and may be installed in at least one of the other pipes. Also, a flow meter as a flow rate measuring means for measuring a flow rate and a pressure gauge as a pressure measuring means for measuring a pressure may be installed in at least one of the pipes.

A multistage semipermeable membrane module may be used in the water treatment method and water treatment apparatus according to the present embodiment. Examples of water treatment apparatuses having such a configuration are shown in FIGS. 3, 4, and 5. FIG. The water treatment apparatus shown in FIGS. 3, 4, and 5 has a structure in which semipermeable membrane modules are combined in series in three stages.

The water treatment device 3 shown in FIG. 3 is partitioned by a nanofiltration device 11 and a semipermeable membrane 12 as nanofiltration means for obtaining NF permeated water and NF concentrated water using a nanofiltration membrane for wastewater such as ammonia-containing wastewater. Using a semipermeable membrane module connected in multiple stages, having a first space (concentration side) 14 and a second space (permeate side) 16, the NF concentrated water of the nanofiltration device 11 is transferred to the first stage Water is passed through the first space 14 of the semipermeable membrane module, and the first space 14 is pressurized to permeate the water contained in the NF concentrated water through the semipermeable membrane 12 to obtain concentrated water. Concentrated water is obtained using the semipermeable membrane modules in the subsequent stages, and a part of the NF concentrated water or a part of the concentrated water is passed through the second space 16 of the semipermeable membrane module of each stage to dilute the water. As a semipermeable membrane treatment means for obtaining , for example, a first-stage membrane module 10a, a second-stage membrane module 10b, and a third-stage membrane module 10c are provided. Each membrane module has a first space 14 and a second space 16 separated by a semipermeable membrane 12 . The water treatment apparatus 3 includes a dilution water tank 60a that stores dilution water from the first-stage membrane module 10a, a dilution water tank 60b that stores dilution water from the second-stage membrane module 10b, and a dilution water from the third-stage membrane module 10c. may be provided with a dilution water tank 60c that stores the . The membrane module 10 supplies the NF concentrated water to the first space and the second space of the membrane module of the first stage, and sequentially supplies the concentrated water to the first space and the second space of the membrane module of the next stage to concentrate. It is a device that performs processing. The water treatment device 3 may include an NF-concentrated water tank that stores NF-concentrated water between the nanofiltration device 11 and the membrane module 10 .

In the water treatment device 3 of FIG. 3 , a pipe 25 is connected to the inlet of the nanofiltration device 11 via a pump 21 . A pipe 27 is connected to the NF permeate outlet of the nanofiltration device 11 . The NF concentrated water outlet of the nanofiltration device 11 and the first space inlet of the first-stage membrane module 10 a are connected by a pipe 40 via a pump 18 . A pipe 42 branched from the downstream side of the pump 18 of the pipe 40 is connected to the second space inlet of the membrane module 10a via the valve 22a. A pipe 46 connects the second space outlet of the first-stage membrane module 10a and the inlet of the dilution water tank 60a. A pipe 44 connects the first spatial outlet of the first-stage membrane module 10a and the first spatial inlet of the second-stage membrane module 10b. A pipe 48 branched from the pipe 44 is connected to the second space inlet of the second-stage membrane module 10b via the valve 22b. A pipe 52 connects the second space outlet of the second-stage membrane module 10b and the inlet of the dilution water tank 60b. A pipe 50 connects the first spatial outlet of the second-stage membrane module 10b and the first spatial inlet of the third-stage membrane module 10c. A pipe 54 branched from the pipe 50 is connected to the second space inlet of the third-stage membrane module 10c through the valve 22c. A pipe 58 connects the second space outlet of the third-stage membrane module 10c and the inlet of the dilution water tank 60c. A pipe 56 is connected via a valve 23 to the first space outlet of the third-stage membrane module 10c. A pipe 59 connects the outlet of the dilution water tank 60 a and the upstream side of the pump 21 in the pipe 25 . A pipe 61 connects the outlet of the dilution water tank 60 b and the pipe 59 . A pipe 63 connects the outlet of the dilution water tank 60 c and the pipe 59 .

The membrane module 10 uses a multi-stage membrane module having a first space 14 and a second space 16 separated by a semipermeable membrane 12, and NF concentrated water is placed in the first space and the second space of the first-stage membrane module. is supplied, and the concentrated water is sequentially supplied to the first space and the second space of the membrane module in the next stage, and the first space 14 of each stage is pressurized to make the water contained in the first space 14 semipermeable. It is a device for concentrating water by permeating it through a membrane 12 into a second space 16 . That is, in the membrane module 10, the NF concentrated water is concentrated using the semipermeable membrane 12, and the concentrated water is further concentrated using the semipermeable membrane 12 in the next stage.

In the water treatment device 3 , the ammonia-containing waste water, which is the water to be treated, is supplied to the nanofiltration device 11 through the pipe 25 by the pump 21 . In the nanofiltration device 11, NF permeated water and NF concentrated water are obtained from ammonia-containing waste water using a nanofiltration membrane (nanofiltration step). NF permeated water is discharged through piping 27 .

The NF concentrated water obtained by the nanofiltration device 11 is sent to the first space 14a of the first-stage membrane module 10a by the pump 18 through the pipe 40 with the valve 23 open, and the NF branched from the pipe 40. The concentrated water is sent to the second space 16a of the first membrane module 10a through the pipe 42 while the valve 22a is open. Water may be supplied to the nanofiltration device 11 and the membrane module 10 using only the pump 21 . In the first stage membrane module 10a, the first space 14a is pressurized and the water contained in the first space 14a is permeated into the second space 16a through the semipermeable membrane 12a (concentration step (first stage) ), diluting water is obtained in the second space 16a (dilution step (first stage)). Dilution water obtained in the second space 16a of the first-stage membrane module 10a is stored in the dilution water tank 60a through the pipe 46 as needed. At least part of the dilution water may be returned through the pipe 59 to the upstream side of the pump 21 in the pipe 25 preceding the nanofiltration device 11 (returning step).

The concentrated water obtained in the first space 14a of the first-stage membrane module 10a is sent through the pipe 44 to the first space 14b of the second-stage membrane module 10b. 22b is open, the liquid is sent through the pipe 48 to the second space 16b of the second stage membrane module 10b. In the second stage membrane module 10b, the first space 14b is pressurized and the water contained in the first space 14b is permeated to the second space 16b through the semipermeable membrane 12b (concentration step (second stage) ), diluting water is obtained in the second space 16b (dilution step (second stage)). Dilution water obtained in the second space 16b of the second-stage membrane module 10b is stored in the dilution water tank 60b through the pipe 52 as required. At least part of the dilution water may be returned through the pipes 61 and 59 to the upstream side of the pump 21 in the pipe 25 preceding the nanofiltration device 11 (returning step).

The concentrated water obtained in the first space 14b of the second-stage membrane module 10b is sent through the pipe 50 to the first space 14c of the third-stage membrane module 10c. 22c is open, the liquid is sent through the pipe 54 to the second space 16c of the third-stage membrane module 10c. In the third stage membrane module 10c, the first space 14c is pressurized and the water contained in the first space 14c is permeated into the second space 16c through the semipermeable membrane 12c (concentration step (third stage) ), dilution water is obtained in the second space 16c (dilution step (third step)) (above, semipermeable membrane treatment step). Dilution water obtained in the second space 16c of the third-stage membrane module 10c is stored in the dilution water tank 60c through the pipe 58 as needed. The concentrated water obtained in the first space 14c of the third-stage membrane module 10c is discharged through the pipe 56. At least part of the dilution water may be returned through the pipes 63 and 59 to the upstream side of the pump 21 in the pipe 25 preceding the nanofiltration device 11 (returning step).

Here, the pump 18, the pipes 40, 42, 44, 48, 50, 54, etc. are connected to the first spaces 14a, 14b, 14c and the second spaces 16a, 16b, 16c of the membrane modules 10a, 10b, 10c of each stage. It functions as a supply means for supplying NF concentrated water or concentrated water. The pipes 59 , 61 , 63 and the like function as return means for returning at least part of the diluted water obtained in the membrane module 10 to the front stage of the nanofiltration device 11 .

The diluted water obtained in the second spaces 16a, 16b, 16c of the membrane modules 10a, 10b, 10c of each stage may be discharged outside the system, or sent to the dilution water tanks 60a, 60b, 60c as necessary. After being liquefied and stored, it may be discharged out of the system or may be reused. At least part of the dilution water may be returned, for example, in line 25 upstream of pump 21 and mixed with NF concentrate. At least a portion of the dilution water may be subjected to other treatments such as reverse osmosis membrane treatment.

As described above, at least one of ammonia and ammonium ions is recovered as concentrated water (concentrated water in the final stage) from the ammonia-containing waste water to be treated, and the volume of the ammonia-containing waste water is reduced. will be In addition, NF permeated water, concentrated water, and diluted water can be reused.

The water treatment device 4 shown in FIG. 4 is partitioned by a nanofiltration device 11 and a semipermeable membrane 12 as nanofiltration means for obtaining NF permeated water and NF concentrated water using a nanofiltration membrane for wastewater such as ammonia-containing wastewater. Using a semipermeable membrane module connected in multiple stages, having a first space (concentration side) 14 and a second space (permeate side) 16, the NF concentrated water of the nanofiltration device 11 is transferred to the first stage Water is passed through the first space 14 of the semipermeable membrane module, and the first space 14 is pressurized to permeate the water contained in the NF concentrated water through the semipermeable membrane 12 to obtain concentrated water. Semipermeable membrane treatment to obtain concentrated water by using the semipermeable membrane modules in the subsequent stages and to pass at least part of the concentrated water through the second space 16 of the semipermeable membrane module in each stage to obtain diluted water. As means, for example, a first-stage membrane module 10a, a second-stage membrane module 10b, and a third-stage membrane module 10c are provided. Each membrane module has a first space 14 and a second space 16 separated by a semipermeable membrane 12 . The water treatment device 4 includes a dilution water tank 62a that stores dilution water from the first-stage membrane module 10a, a dilution water tank 62b that stores dilution water from the second-stage membrane module 10b, and a dilution water from the third-stage membrane module 10c. may be provided with a dilution water tank 62c that stores the . The membrane module 10 supplies the NF concentrated water to the first space of the membrane module in the first stage, and sequentially supplies the concentrated water to the first space of the next-stage membrane module and its own second space to perform the concentration process. It is a device that performs The water treatment device 4 may include an NF-concentrated water tank that stores NF-concentrated water between the nanofiltration device 11 and the membrane module 10 .

In the water treatment device 4 of FIG. 4 , a pipe 25 is connected to the inlet of the nanofiltration device 11 via a pump 21 . A pipe 27 is connected to the NF permeate outlet of the nanofiltration device 11 . The NF concentrated water outlet of the nanofiltration device 11 and the first space inlet of the first-stage membrane module 10 a are connected by a pipe 40 via a pump 18 . A pipe 44 connects the first spatial outlet of the first-stage membrane module 10a and the first spatial inlet of the second-stage membrane module 10b. A pipe 64 branched from the pipe 44 is connected to the second space inlet of the membrane module 10a via the valve 32a. A pipe 66 connects the second space outlet of the first-stage membrane module 10a and the inlet of the dilution water tank 62a. A pipe 50 connects the first spatial outlet of the second-stage membrane module 10b and the first spatial inlet of the third-stage membrane module 10c. A pipe 68 branched from the pipe 50 is connected to the second space inlet of the membrane module 10b via the valve 32b. A pipe 70 connects the second space outlet of the second-stage membrane module 10b and the inlet of the dilution water tank 62b. A pipe 56 is connected via a valve 23 to the first space outlet of the third-stage membrane module 10c. A pipe 72 branched from the pipe 56 on the upstream side of the valve 23 is connected to the second space inlet of the membrane module 10c via the valve 32c. A pipe 74 connects the second space outlet of the third-stage membrane module 10c and the inlet of the dilution water tank 62c. A pipe 59 connects the outlet of the dilution water tank 62 a and the upstream side of the pump 21 in the pipe 25 . A pipe 61 connects the outlet of the dilution water tank 62 b and the pipe 59 . A pipe 63 connects the outlet of the dilution water tank 62 c and the pipe 59 .

The membrane module 10 uses a multi-stage membrane module having a first space 14 and a second space 16 separated by a semipermeable membrane 12, and supplies NF concentrated water to the first space of the first-stage membrane module, The concentrated water is sequentially supplied to the first space of the next-stage membrane module and its own second space, and the first space 14 of each stage is pressurized to remove the water contained in the first space 14 from the semi-permeable membrane 12 . It is a device for concentrating water by permeating it to the second space 16 via. That is, in the membrane module 10, the NF concentrated water is concentrated using the semipermeable membrane 12, and the concentrated water is further concentrated using the semipermeable membrane 12 in the next stage.

In the water treatment device 4 , the ammonia-containing waste water, which is the water to be treated, is supplied to the nanofiltration device 11 through the pipe 25 by the pump 21 . In the nanofiltration device 11, NF permeated water and NF concentrated water are obtained from ammonia-containing waste water using a nanofiltration membrane (nanofiltration step). NF permeated water is discharged through piping 27 .

The NF concentrated water obtained by the nanofiltration device 11 is sent to the first space 14a of the first-stage membrane module 10a through the pipe 40 by the pump 18 while the valve 23 is open. Water may be supplied to the nanofiltration device 11 and the membrane module 10 using only the pump 21 . In the first stage membrane module 10a, the first space 14a is pressurized and the water contained in the first space 14a is permeated into the second space 16a through the semipermeable membrane 12a (concentration step (first stage) ), diluting water is obtained in the second space 16a (dilution step (first stage)). The concentrated water obtained in the first space 14a of the first-stage membrane module 10a is sent through the pipe 44 to the first space 14b of the second-stage membrane module 10b. 32a is open, the liquid is sent through the pipe 64 to the second space 16a of the first-stage membrane module 10a. Dilution water obtained in the second space 16a of the first-stage membrane module 10a is stored in the dilution water tank 62a through the pipe 66 as needed. At least part of the dilution water may be returned through the pipe 59 to the upstream side of the pump 21 in the pipe 25 preceding the nanofiltration device 11 (returning step).

In the second stage membrane module 10b, the first space 14b is pressurized and the water contained in the first space 14b is permeated to the second space 16b through the semipermeable membrane 12b (concentration step (second stage) ), diluting water is obtained in the second space 16b (dilution step (second stage)). The concentrated water obtained in the first space 14b of the second-stage membrane module 10b is sent through the pipe 50 to the first space 14c of the third-stage membrane module 10c. 32b is open, the liquid is sent through the pipe 68 to the second space 16b of the second-stage membrane module 10b. Dilution water obtained in the second space 16b of the second-stage membrane module 10b is stored in the dilution water tank 62b through the pipe 70 as required. At least part of the dilution water may be returned through the pipes 61 and 59 to the upstream side of the pump 21 in the pipe 25 preceding the nanofiltration device 11 (returning step).

In the third stage membrane module 10c, the first space 14c is pressurized and the water contained in the first space 14c is permeated into the second space 16c through the semipermeable membrane 12c (concentration step (third stage) ), dilution water is obtained in the second space 16c (dilution step (third step)) (above, semipermeable membrane treatment step). The concentrated water obtained in the first space 14c of the third-stage membrane module 10c is discharged through the pipe 56. The concentrated water branched from the pipe 56 is sent to the second space 16c of the third-stage membrane module 10c through the pipe 72 while the valve 32c is open. Dilution water obtained in the second space 16c of the third-stage membrane module 10c is stored in the dilution water tank 62c through the pipe 74 as required. At least part of the dilution water may be returned through the pipes 63 and 59 to the upstream side of the pump 21 in the pipe 25 preceding the nanofiltration device 11 (returning step).

Here, the pump 18, the pipes 40, 44, 64, 50, 68, 56, 72, etc. are connected to the first spaces 14a, 14b, 14c, second spaces 16a, 16b, It functions as a supply means for supplying NF concentrated water or concentrated water to 16c. The pipes 59 , 61 , 63 and the like function as return means for returning at least part of the diluted water obtained in the membrane module 10 to the front stage of the nanofiltration device 11 .

The diluted water obtained in the second spaces 16a, 16b, 16c of the membrane modules 10a, 10b, 10c of each stage may be discharged outside the system, or sent to the dilution water tanks 62a, 62b, 62c as necessary. After being liquefied and stored, it may be discharged out of the system or may be reused. At least part of the dilution water may be returned, for example, in line 25 upstream of pump 21 and mixed with NF concentrate. At least a portion of the dilution water may be subjected to other treatments such as reverse osmosis membrane treatment.

As described above, at least one of ammonia and ammonium ions is recovered as concentrated water (concentrated water in the final stage) from the ammonia-containing waste water to be treated, and the volume of the ammonia-containing waste water is reduced. will be In addition, NF permeated water, concentrated water, and diluted water can be reused.

When a multi-stage membrane module is used, water may be passed through the second space side in series. FIG. 5 shows an example of a water treatment apparatus having such a configuration.

The water treatment device 5 shown in FIG. 5 is partitioned by a nanofiltration device 11 and a semipermeable membrane 12 as nanofiltration means for obtaining NF permeated water and NF concentrated water using a nanofiltration membrane for wastewater such as ammonia-containing wastewater. Using a semipermeable membrane module connected in multiple stages, having a first space (concentration side) 14 and a second space (permeate side) 16, the NF concentrated water of the nanofiltration device 11 is transferred to the first stage Water is passed through the first space 14 of the semipermeable membrane module, and the first space 14 is pressurized to permeate the water contained in the NF concentrated water through the semipermeable membrane 12 to obtain concentrated water. Concentrated water is obtained using the semipermeable membrane modules in the subsequent stages, and at least part of the concentrated water or diluted water obtained from other semipermeable membrane modules is supplied to the second space 16 of the semipermeable membrane module in each stage. Semipermeable membrane processing means for passing at least part of the water to obtain dilution water includes, for example, a first-stage membrane module 10a, a second-stage membrane module 10b, and a third-stage membrane module 10c. Each membrane module has a first space 14 and a second space 16 separated by a semipermeable membrane 12 . The membrane module 10 is a device that supplies the NF concentrated water to the first space of the membrane module of the first stage and sequentially supplies the concentrated water to the first space of the membrane module of the next stage for concentration treatment. The water treatment device 5 may include an NF-concentrated water tank that stores NF-concentrated water between the nanofiltration device 11 and the membrane module 10 .

In the water treatment device 5 of FIG. 5 , a pipe 25 is connected to the inlet of the nanofiltration device 11 via a pump 21 . A pipe 27 is connected to the NF permeate outlet of the nanofiltration device 11 . The NF concentrated water outlet of the nanofiltration device 11 and the first space inlet of the first-stage membrane module 10 a are connected by a pipe 40 via a pump 18 . A pipe 44 connects the first spatial outlet of the first-stage membrane module 10a and the first spatial inlet of the second-stage membrane module 10b. A pipe 50 connects the first spatial outlet of the second-stage membrane module 10b and the first spatial inlet of the third-stage membrane module 10c. A pipe 56 is connected via a valve 23 to the first space outlet of the third-stage membrane module 10c. A pipe 76 branched from the pipe 56 on the upstream side of the valve 23 is connected via the valve 32 to the second space inlet of the membrane module 10c. A pipe 78 connects the second spatial outlet of the third-stage membrane module 10c and the second spatial inlet of the second-stage membrane module 10b. A pipe 80 connects the second spatial outlet of the second-stage membrane module 10b and the second spatial inlet of the first-stage membrane module 10a. A pipe 82 connects the second space outlet of the first-stage membrane module 10 a and the pipe 25 upstream of the pump 21 .

The membrane module 10 uses a multi-stage membrane module having a first space 14 and a second space 16 separated by a semipermeable membrane 12, and supplies NF concentrated water to the first space of the first-stage membrane module, The concentrated water is sequentially passed through the first space of the membrane module of the next stage in series, at least part of the concentrated water of the membrane module of the final stage is supplied to its own second space, and the obtained diluted water is Water is passed through the second space of the membrane module in the previous stage in series, and the first space 14 of each stage is pressurized, so that the water contained in the first space 14 passes through the semipermeable membrane 12 to the second space 16. It is a device that concentrates water by permeation. That is, in the membrane module 10, the NF concentrated water is concentrated using the semipermeable membrane 12, and the concentrated water is further concentrated using the semipermeable membrane 12 in the next stage.

In the water treatment device 5 , ammonia-containing waste water, which is the water to be treated, is supplied to the nanofiltration device 11 through the pipe 25 by the pump 21 . In the nanofiltration device 11, NF permeated water and NF concentrated water are obtained from ammonia-containing waste water using a nanofiltration membrane (nanofiltration step). NF permeated water is discharged through piping 27 .

The NF concentrated water obtained by the nanofiltration device 11 is sent to the first space 14a of the first-stage membrane module 10a through the pipe 40 by the pump 18 while the valve 23 is open. Water may be supplied to the nanofiltration device 11 and the membrane module 10 using only the pump 21 . On the other hand, the dilution water sent via the second space 16c of the third-stage membrane module 10c and the second space 16b of the second-stage membrane module 10b, which will be described later, passes through the pipe 80 and flows into the second space of the first-stage membrane module 10a. The liquid is sent to the second space 16a. In the first stage membrane module 10a, the first space 14a is pressurized and the water contained in the first space 14a is permeated into the second space 16a through the semipermeable membrane 12a (concentration step (first stage) ), diluting water is obtained in the second space 16a (dilution step (first stage)). The concentrated water obtained in the first space 14a of the first-stage membrane module 10a is sent through the pipe 44 to the first space 14b of the second-stage membrane module 10b. Dilution water obtained in the second space 16 a of the first-stage membrane module 10 a is discharged through the pipe 82 . At least part of the dilution water may be returned through the pipe 82 to the upstream side of the pump 21 in the pipe 25 preceding the nanofiltration device 11 (returning step).

In the second-stage membrane module 10b, the dilution water sent via the second space 16c of the third-stage membrane module 10c, which will be described later, is sent through the pipe 78 to the second space 16b of the second-stage membrane module 10b. be done. The first space 14b is pressurized, and the water contained in the first space 14b is permeated into the second space 16b through the semipermeable membrane 12b (concentration step (second stage)), and at the second space 16b Dilution water is obtained (dilution step (second step)). The concentrated water obtained in the first space 14b of the second-stage membrane module 10b is sent through the pipe 50 to the first space 14c of the third-stage membrane module 10c. The diluted water obtained in the second space 16b of the second-stage membrane module 10b is sent through the pipe 80 to the second space 16a of the first-stage membrane module 10a.

In the third-stage membrane module 10c, the concentrated water obtained in the first space 14c of the third-stage membrane module 10c is sent to the second space 16c through pipes 56 and 76 as described below. The first space 14c is pressurized, and the water contained in the first space 14c is permeated into the second space 16c through the semipermeable membrane 12c (concentration step (third stage)), and in the second space 16c Dilution water is obtained (dilution step (third step)) (above, semipermeable membrane treatment step). The concentrated water obtained in the first space 14c of the third-stage membrane module 10c is discharged through the pipe 56. The concentrated water branched from the pipe 56 is sent to the second space 16c of the third-stage membrane module 10c through the pipe 76 while the valve 32 is open. The diluted water obtained in the second space 16c of the third-stage membrane module 10c is sent through the pipe 78 to the second space 16b of the second-stage membrane module 10b.

Here, the pump 18, the pipes 40, 44, 50, 56, 76, 78, 80, etc. are connected to the first spaces 14a, 14b, 14c, second spaces 16a, 16b, It functions as a supply means for supplying NF concentrated water or concentrated water or dilution water to 16c. The pipe 82 and the like function as return means for returning at least part of the diluted water obtained in the membrane module 10 to the front stage of the nanofiltration device 11 .

The dilution water obtained in the second space 16a of the membrane module 10a may be discharged out of the system, or may be discharged out of the system after being sent to a dilution water tank and stored as necessary. , may be reused. At least part of the dilution water may be returned, for example, in line 25 upstream of pump 21 and mixed with NF concentrate. At least a portion of the dilution water may be subjected to other treatments such as reverse osmosis membrane treatment.

As described above, at least one of ammonia and ammonium ions is recovered as concentrated water (concentrated water in the final stage) from the ammonia-containing waste water to be treated, and the volume of the ammonia-containing waste water is reduced. will be In addition, NF permeated water, concentrated water, and diluted water can be reused.

In the water treatment equipment 3 shown in FIG. 3, the water treatment equipment 4 shown in FIG. 4, and the water treatment equipment 5 shown in FIG. As it continues to grow, it becomes highly concentrated. As it is finally concentrated to a high concentration, this method can reduce the osmotic pressure, making it possible to concentrate to concentrations that were difficult to achieve with the conventional reverse osmosis membrane method due to the effects of osmotic pressure. becomes.

When the NF concentrated water is supplied to the first-stage membrane module 10a, a pressure of, for example, 7 MPa or less is applied, and the concentrated water is supplied to the subsequent membrane module by the pressure applied to the first-stage membrane module 10a. good. The inlet pressure of the first space 14 in each membrane module is preferably in the range of 7 MPa or less, the inlet pressure of the second space 16 is preferably lower than the inlet pressure of the first space 14, and the second More preferably, the inlet pressure of the space 16 is 50% or less of the inlet pressure of the first space 14 . This can reduce the risk of damage to the semipermeable membrane due to pressure.

It is preferable to make the flow rate on the first space 14 side in each membrane module 10 larger than the flow rate on the second space 16 side. If the flow rate on the first space 14 side is less than or equal to the flow rate on the second space 16 side, the flow rate on the first space 14 side of the subsequent membrane module may be insufficient. For example, the pump 18, the inverter 20, the valves 22a, 22b, 22c, the valve 23, the valves 32a, 32b, 32c, the valve 32, etc. adjust the flow rate so that the flow rate in the first space is greater than the flow rate in the second space. act as a means.

If the permeation flux is too high, concentration polarization on the membrane surface increases, which may cause problems such as an increased risk of fouling and an excessively high pressure. On the other hand, if the permeation flux is too small, the concentration efficiency may deteriorate. From these points, the permeation flux of each membrane module 10 is preferably in the range of 0.005 m/d to 0.05 m/d, more preferably in the range of 0.015 m/d to 0.04 m/d. is more preferred. For example, the pump 18, the inverter 20, the valves 22a, 22b, 22c, the valve 23, the valves 32a, 32b, 32c, the valve 32, etc. function as permeation flux adjusting means for controlling the permeation flux within the above range.

It should be noted that the installation positions and the number of installation of the valves are merely examples, and the number may be greater than those shown in FIGS. Also, a flow meter as a flow rate measuring means for measuring a flow rate and a pressure gauge as a pressure measuring means for measuring a pressure may be installed in at least one of the pipes.

3, 4, and 5 are examples of the device configuration, and the arrangement of the semipermeable membrane modules, the method of supplying the feed water, and the like may be changed as appropriate.

In the water treatment apparatus of FIG. 5, since water is passed in series through the first space and the second space of each stage of the membrane module, compared to the water treatment apparatuses of FIGS. can be suppressed, and the power of the pump can be reduced.

In the water treatment method and water treatment apparatus according to the present embodiment, multi-stage membrane modules may be used, and a membrane module unit having a plurality of membrane modules connected in parallel may be used as each stage membrane module. good. An example of such a water treatment apparatus is shown in FIGS. 6 and 7. FIG. In the water treatment apparatus shown in FIGS. 6 and 7, the semipermeable membrane modules are combined in parallel in four rows in the first stage, the semipermeable membrane modules are combined in parallel in four rows in the second stage, and the semipermeable membrane modules are combined in parallel in the third stage. It has a structure in which two rows of membrane modules are combined in parallel, and two rows of semipermeable membrane modules are combined in parallel on the fourth stage and connected in series in four stages.

The water treatment device 6 shown in FIG. 6 is partitioned by a nanofiltration device 11 and a semipermeable membrane 12 as nanofiltration means for obtaining NF permeated water and NF concentrated water using a nanofiltration membrane for wastewater such as ammonia-containing wastewater. Using a semipermeable membrane module connected in multiple stages, having a first space (concentration side) 14 and a second space (permeate side) 16, the NF concentrated water of the nanofiltration device 11 is transferred to the first stage Water is passed through the first space 14 of the semipermeable membrane module, and the first space 14 is pressurized to permeate the water contained in the NF concentrated water through the semipermeable membrane 12 to obtain concentrated water. Concentrated water is obtained using the semipermeable membrane modules in the subsequent stages, and a part of the NF concentrated water or a part of the concentrated water is passed through the second space 16 of the semipermeable membrane module of each stage to dilute the water. As a semipermeable membrane treatment means for obtaining , for example, a first-stage membrane module unit 100a, a second-stage membrane module unit 100b, a third-stage membrane module unit 100c, and a fourth-stage membrane module unit 100d are provided. The first-stage membrane module unit 100a includes, for example, four membrane modules connected in parallel, and the second-stage membrane module unit 100b includes, for example, four membrane modules connected in parallel, The third-stage membrane module unit 100c has, for example, two membrane modules connected in parallel, and the fourth-stage membrane module unit 100d has, for example, two membrane modules connected in parallel. Each membrane module 10 has a first space 14 and a second space 16 separated by a semipermeable membrane 12 . The water treatment device 6 may include an NF concentrated water tank 84 that stores the NF concentrated water and a concentrated water tank 86 that stores the concentrated water from the fourth-stage membrane module unit 100d. The membrane module unit 100 supplies the NF concentrated water to the first space and the second space of each membrane module of the membrane module unit of the first stage, and the concentrated water is sequentially supplied to the first space of each membrane module of the membrane module unit of the next stage. It is an apparatus that performs concentration processing by supplying to the first space and the second space.

In the water treatment device 6 of FIG. 6 , a pipe 25 is connected to the inlet of the nanofiltration device 11 via a pump 21 . A pipe 27 is connected to the NF permeate outlet of the nanofiltration device 11 . The NF concentrated water outlet of the nanofiltration device 11 and the inlet of the NF concentrated water tank 84 are connected by a pipe 29 . The outlet of the NF concentrating water tank 84 and the first space inlet and the second space inlet of each membrane module of the first-stage membrane module unit 100 a are connected by a pipe 88 via the pump 18 . A pipe 90 connects the first space outlet of each membrane module of the first-stage membrane module unit 100a and the first and second space inlets of each membrane module of the second-stage membrane module unit 100b. A pipe 94 connects the first space outlet of each membrane module of the second-stage membrane module unit 100b and the first and second space inlets of each membrane module of the third-stage membrane module unit 100c. A pipe 98 connects the first space outlet of each membrane module of the third-stage membrane module unit 100c and the first and second space inlets of each membrane module of the fourth-stage membrane module unit 100d. The first space outlet of each membrane module of the fourth stage membrane module unit 100d and the inlet of the concentrating water tank 86 are connected by a pipe 104 . A pipe 92 is connected to the second spatial outlet of each membrane module of the first-stage membrane module unit 100a, and a pipe 96 is connected to the second spatial outlet of each membrane module of the second-stage membrane module unit 100b, A pipe 102 is connected to the second spatial outlet of each membrane module of the third-stage membrane module unit 100c, and a pipe 106 is connected to the second spatial outlet of each membrane module of the fourth-stage membrane module unit 100d, Pipes 96 , 102 , 106 may join pipe 92 . The pipe 92 is connected to the upstream side of the pump 21 in the pipe 25 .

The membrane module unit 100 uses a multi-stage membrane module unit having a membrane module 10 having a first space 14 and a second space 16 partitioned by a semipermeable membrane 12. Each membrane module of the first stage membrane module unit The NF concentrated water is supplied to the first space and the second space of the membrane module unit, and the concentrated water is sequentially supplied to the first space and the second space of each membrane module of the membrane module unit of the next stage. By pressurizing the one space 14, the water contained in the first space 14 is permeated into the second space 16 through the semipermeable membrane 12, thereby concentrating the water. That is, in the membrane module unit 100, the NF concentrated water is concentrated using the semipermeable membrane 12, and the concentrated water is further concentrated using the semipermeable membrane 12 in the next stage.

In the water treatment device 6 , ammonia-containing waste water, which is the water to be treated, is supplied to the nanofiltration device 11 through the pipe 25 by the pump 21 . In the nanofiltration device 11, NF permeated water and NF concentrated water are obtained from ammonia-containing waste water using a nanofiltration membrane (nanofiltration step). NF permeated water is discharged through piping 27 .

The NF concentrated water obtained by the nanofiltration device 11 is stored in the NF concentrated water tank 84 as necessary, and then passed from the NF concentrated water tank 84 through the pipe 88 by the pump 18 to each membrane module of the first-stage membrane module unit 100a. The liquid is sent to the first space 14 and the second space 16 of. Water may be supplied to the nanofiltration device 11 and the membrane module 10 using only the pump 21 . In each membrane module of the first-stage membrane module unit 100a, the first space 14a is pressurized and the water contained in the first space 14 is permeated to the second space 16 through the semipermeable membrane 12 (concentration step (first stage)), and dilution water is obtained in the second space 16 (dilution step (first stage)). Dilution water obtained in the second space 16 of the first-stage membrane module 10 passes through a pipe 92 and is stored in a dilution water tank as required, and then discharged. At least part of the dilution water may be returned through the pipe 92 to the upstream side of the pump 21 in the pipe 25 preceding the nanofiltration device 11 (returning step).

The concentrated water obtained in the first space 14 of each membrane module of the first-stage membrane module unit 100a passes through the pipe 90 to the first space 14 and the second space 16 of each membrane module of the second-stage membrane module unit 100b. Liquid is sent. In each membrane module of the second-stage membrane module unit 100b, the first space 14 is pressurized and the water contained in the first space 14 is permeated to the second space 16 through the semipermeable membrane 12 (concentration step (second stage)), and dilution water is obtained in the second space 16 (dilution step (second stage)). Dilution water obtained in the second space 16 of each membrane module of the second-stage membrane module unit 100b passes through a pipe 96 and is stored in a dilution water tank as required, and then discharged. At least part of the dilution water may be returned through the pipes 96 and 92 to the upstream side of the pump 21 in the pipe 25 preceding the nanofiltration device 11 (returning step).

The concentrated water obtained in the first space 14 of each membrane module of the second-stage membrane module unit 100b passes through the pipe 94 to the first space 14 and the second space 16 of each membrane module of the third-stage membrane module unit 100c. Liquid is sent. In each membrane module of the third-stage membrane module unit 100c, the first space 14 is pressurized and the water contained in the first space 14 is permeated to the second space 16 through the semipermeable membrane 12 (concentration step (third stage)), and dilution water is obtained in the second space 16 (dilution step (third stage)). Dilution water obtained in the second space 16 of each membrane module of the third-stage membrane module unit 100c is drained after being stored in a dilution water tank through a pipe 102 as necessary. At least part of the dilution water may be returned through the pipes 102, 96, 92 to the upstream side of the pump 21 in the pipe 25 preceding the nanofiltration device 11 (returning step).

The concentrated water obtained in the first space 14 of each membrane module of the third-stage membrane module unit 100c passes through the pipe 98 to the first space 14 and the second space 16 of each membrane module of the fourth-stage membrane module unit 100d. Liquid is sent. In each membrane module of the fourth stage membrane module unit 100d, the first space 14 is pressurized and the water contained in the first space 14 is permeated to the second space 16 through the semipermeable membrane 12 (concentration step (fourth step)), diluting water is obtained in the second space 16 (dilution step (fourth step)) (above, semipermeable membrane treatment step). The concentrated water obtained in the first space 14 of each membrane module of the fourth-stage membrane module unit 100d passes through the pipe 104 and is stored in the concentrated water tank 86 if necessary, and then discharged. Dilution water obtained in the second space 16 of each membrane module of the fourth-stage membrane module unit 100d is drained after being stored in a dilution water tank through a pipe 106 as necessary. At least part of the dilution water may be returned through the pipes 106, 102, 96, 92 to the upstream side of the pump 21 in the pipe 25, which is the preceding stage of the nanofiltration device 11 (returning step).

Here, the pump 18, the pipes 88, 90, 94, 98, etc. are supplied to the first space 14 and the second space 16 of each membrane module unit 100a, 100b, 100c, 100d of each stage of membrane module units 100a, 100b, 100c, 100d. It functions as a supply means for supplying water. The pipes 92 , 96 , 102 , 106 and the like function as return means for returning at least part of the diluted water obtained in the membrane module 10 to the front stage of the nanofiltration device 11 .

The dilution water obtained in the second space 16 of each membrane module of the membrane module units 100a, 100b, 100c, and 100d of each stage may be discharged out of the system, or sent to the dilution water tank as necessary. After being stored in the system, it may be discharged out of the system or may be reused. At least part of the dilution water may be returned, for example, in line 25 upstream of pump 21 and mixed with NF concentrate. At least a portion of the dilution water may be subjected to other treatments such as reverse osmosis membrane treatment.

As described above, at least one of ammonia and ammonium ions is recovered as concentrated water (concentrated water in the final stage) from the ammonia-containing waste water to be treated, and the volume of the ammonia-containing waste water is reduced. will be In addition, NF permeated water, concentrated water, and diluted water can be reused.

The water treatment device 7 shown in FIG. 7 is partitioned by a nanofiltration device 11 and a semipermeable membrane 12 as nanofiltration means for obtaining NF permeated water and NF concentrated water using a nanofiltration membrane for wastewater such as ammonia-containing wastewater. Using a semipermeable membrane module connected in multiple stages, having a first space (concentration side) 14 and a second space (permeate side) 16, the NF concentrated water of the nanofiltration device 11 is transferred to the first stage Water is passed through the first space 14 of the semipermeable membrane module, and the first space 14 is pressurized to permeate the water contained in the NF concentrated water through the semipermeable membrane 12 to obtain concentrated water. Concentrated water is obtained using the semipermeable membrane modules in the subsequent stages, and at least part of the concentrated water or diluted water obtained from other semipermeable membrane modules is supplied to the second space 16 of the semipermeable membrane module in each stage. As semipermeable membrane treatment means for obtaining dilution water by passing at least a portion of the membrane, for example, the first-stage membrane module unit 100a, the second-stage membrane module unit 100b, the third-stage membrane module unit 100c, and the fourth-stage membrane module A unit 100d is provided. The first-stage membrane module unit 100a includes, for example, four membrane modules connected in parallel, and the second-stage membrane module unit 100b includes, for example, four membrane modules connected in parallel, The third-stage membrane module unit 100c has, for example, two membrane modules connected in parallel, and the fourth-stage membrane module unit 100d has, for example, two membrane modules connected in parallel. Each membrane module 10 has a first space 14 and a second space 16 separated by a semipermeable membrane 12 . The water treatment device 7 may include an NF concentrated water tank 84 that stores NF concentrated water, and a concentrated water tank 86 that stores concentrated water from the fourth-stage membrane module unit 100d. The membrane module unit 100 is a device that supplies NF concentrated water to the first space of the membrane module of the first stage, and supplies the concentrated water to the first space of the membrane module of the next stage in order to carry out concentration treatment.

In the water treatment device 7 of FIG. 7 , a pipe 25 is connected to the inlet of the nanofiltration device 11 via a pump 21 . A pipe 27 is connected to the NF permeate outlet of the nanofiltration device 11 . The NF concentrated water outlet of the nanofiltration device 11 and the inlet of the NF concentrated water tank 84 are connected by a pipe 29 . The outlet of the NF concentrating water tank 84 and the first space inlet of each membrane module of the first-stage membrane module unit 100a are connected by a pipe 108 via a pump 18 . A pipe 110 connects the first spatial outlet of each membrane module of the first-stage membrane module unit 100a and the first spatial inlet of each membrane module of the second-stage membrane module unit 100b. A pipe 112 connects the first spatial outlet of each membrane module of the second-stage membrane module unit 100b and the first spatial inlet of each membrane module of the third-stage membrane module unit 100c. A pipe 114 connects the first spatial outlet of each membrane module of the third-stage membrane module unit 100c and the first spatial inlet of each membrane module of the fourth-stage membrane module unit 100d. The first space outlet of each membrane module of the fourth-stage membrane module unit 100 d and the inlet of the concentrating water tank 86 are connected by a pipe 116 . A pipe 118 branched from the pipe 116 is connected to the second space inlet of each membrane module of the fourth-stage membrane module unit 100d. A pipe 120 connects the second spatial outlet of each membrane module of the fourth-stage membrane module unit 100d and the second spatial inlet of each membrane module of the third-stage membrane module unit 100c. A pipe 122 connects the second spatial outlet of each membrane module of the third-stage membrane module unit 100c and the second spatial inlet of each membrane module of the second-stage membrane module unit 100b. A pipe 124 connects the second spatial outlet of each membrane module of the second-stage membrane module unit 100b and the second spatial inlet of each membrane module of the first-stage membrane module unit 100a. A pipe 126 connects the second space outlet of each membrane module of the first-stage membrane module unit 100 a and the upstream side of the pump 21 in the pipe 25 .

The membrane module unit 100 uses a multi-stage membrane module unit having a membrane module 10 having a first space 14 and a second space 16 partitioned by a semipermeable membrane 12. Each membrane module of the first stage membrane module unit NF concentrated water is supplied to the first space, the concentrated water is sequentially passed through the first space of each membrane module of the next-stage membrane module unit in series, and each membrane module of the final-stage membrane module unit At least part of the concentrated water is supplied to its own second space, and the obtained diluted water is passed through the second space 16 of each membrane module of the membrane module unit in the preceding stage in series, and the first space of each stage By pressurizing 14, the water contained in the first space 14 is permeated into the second space 16 through the semipermeable membrane 12 to concentrate the water. That is, in the membrane module unit 100, the NF concentrated water is concentrated using the semipermeable membrane 12, and the concentrated water is further concentrated using the semipermeable membrane 12 in the next stage.

In the water treatment device 7 , ammonia-containing waste water, which is the water to be treated, is supplied to the nanofiltration device 11 through the pipe 25 by the pump 21 . In the nanofiltration device 11, NF permeated water and NF concentrated water are obtained from ammonia-containing waste water using a nanofiltration membrane (nanofiltration step). NF permeated water is discharged through piping 27 .

The NF concentrated water obtained by the nanofiltration device 11 is stored in the NF concentrated water tank 84 as necessary, and then is passed from the NF concentrated water tank 84 through the pipe 108 by the pump 18 to each membrane module of the first-stage membrane module unit 100a. is sent to the first space 14 of the Water may be supplied to the nanofiltration device 11 and the membrane module 10 using only the pump 21 . On the other hand, the second space 16 of each membrane module of the fourth-stage membrane module unit 100d, the second space 16 of each membrane module of the third-stage membrane module unit 100c, and the each membrane module of the second-stage membrane module unit 100b, which will be described later. The dilution water sent through the second space 16 is sent through the pipe 124 to the second space 16 of each membrane module of the first-stage membrane module unit 100a. In each membrane module of the first-stage membrane module unit 100a, the first space 14 is pressurized and the water contained in the first space 14 is permeated to the second space 16 through the semipermeable membrane 12 (concentration step (first stage)), and dilution water is obtained in the second space 16 (dilution step (first stage)). The concentrated water obtained in the first space 14 of each membrane module of the first-stage membrane module unit 100a is sent through the pipe 110 to the first space 14 of each membrane module of the second-stage membrane module unit 100b. Dilution water obtained in the second space 16 of each membrane module of the first-stage membrane module unit 100 a is discharged through the pipe 126 . At least part of the dilution water may be returned through the pipe 126 to the upstream side of the pump 21 in the pipe 25 preceding the nanofiltration device 11 (returning step).

In each membrane module of the second-stage membrane module unit 100b, via the second space 16 of each membrane module of the fourth-stage membrane module unit 100d and the second space 16 of each membrane module of the third-stage membrane module unit 100c, which will be described later. The diluted water thus sent is sent through the pipe 122 to the second space 16 of each membrane module of the second-stage membrane module unit 100b. The first space 14 is pressurized and the water contained in the first space 14 is permeated to the second space 16 through the semipermeable membrane 12 (concentration step (second stage)), and in the second space 16 Dilution water is obtained (dilution step (second step)). The concentrated water obtained in the first space 14 of each membrane module of the second-stage membrane module unit 100b is sent through the pipe 112 to the first space 14 of each membrane module of the third-stage membrane module unit 100c. The diluted water obtained in the second space 16 of each membrane module of the second-stage membrane module unit 100b is sent through the pipe 124 to the second space 16 of each membrane module of the first-stage membrane module unit 100a.

In each membrane module of the third-stage membrane module unit 100c, the dilution water sent through the second space 16 of each membrane module of the fourth-stage membrane module unit 100d, which will be described later, passes through the pipe 120 and flows through the third-stage membrane. The liquid is sent to the second space 16 of each membrane module of the module unit 100c. The first space 14 is pressurized and the water contained in the first space 14 is permeated to the second space 16 through the semipermeable membrane 12 (concentration step (third stage)), and in the second space 16 Dilution water is obtained (dilution step (third step)). The concentrated water obtained in the first space 14 of each membrane module of the third-stage membrane module unit 100c is sent through the pipe 114 to the first space 14 of each membrane module of the fourth-stage membrane module unit 100d. The dilution water obtained in the second space 16 of each membrane module of the third-stage membrane module unit 100c is sent through the pipe 122 to the second space 16 of each membrane module of the second-stage membrane module unit 100b.

In each membrane module of the fourth-stage membrane module unit 100d, as described below, the concentrated water obtained in the first space 14 of each membrane module of the fourth-stage membrane module unit 100d flows into the second space 16 through pipes 116 and 118. Liquid is sent. The first space 14 is pressurized and the water contained in the first space 14 is permeated through the semipermeable membrane 12 to the second space 16 (concentration step (fourth stage)), and in the second space 16 Dilution water is obtained (dilution step (fourth stage)) (above, semipermeable membrane treatment step). The concentrated water obtained in the first space 14 of each membrane module of the fourth-stage membrane module unit 100d passes through the pipe 116 and is stored in the concentrated water tank 86 if necessary, and then discharged. The concentrated water branched from the pipe 116 is sent through the pipe 118 to the second space 16 of each membrane module of the fourth-stage membrane module unit 100d. The dilution water obtained in the second space 16 of each membrane module of the fourth-stage membrane module unit 100d is sent through the pipe 120 to the second space 16 of each membrane module of the third-stage membrane module unit 100c.

Here, the pump 18, the pipes 108, 110, 112, 114, 116, 118, 120, 122, 124, etc. are connected to the first space 14 of each membrane module of each stage membrane module unit 100a, 100b, 100c, 100d, It functions as supply means for supplying NF concentrated water, concentrated water, or dilution water to the second space 16 . The pipe 126 and the like function as return means for returning at least part of the diluted water obtained in the membrane module 10 to the front stage of the nanofiltration device 11 .

The dilution water obtained in the second space 16 of each membrane module of the membrane module unit 100a may be discharged out of the system, or may be sent out of the system after being sent to and stored in a dilution water tank as necessary. It may be discharged or reused. At least part of the dilution water may be returned, for example, in line 25 upstream of pump 21 and mixed with NF concentrate. At least a portion of the dilution water may be subjected to other treatments such as reverse osmosis membrane treatment.

As described above, at least one of ammonia and ammonium ions is recovered as concentrated water (concentrated water in the final stage) from the ammonia-containing waste water to be treated, and the volume of the ammonia-containing waste water is reduced. will be In addition, NF permeated water, concentrated water, and diluted water can be reused.

When the NF concentrated water is supplied to each membrane module of the first-stage membrane module unit 100a, a pressure of, for example, 7 MPa or less is applied. It may be performed by the pressure applied to the membrane module. The inlet pressure of the first space 14 in each membrane module is preferably in the range of 7 MPa or less, the inlet pressure of the second space 16 is preferably lower than the inlet pressure of the first space 14, and the second More preferably, the inlet pressure of the space 16 is 50% or less of the inlet pressure of the first space 14 . This can reduce the risk of damage to the semipermeable membrane due to pressure.

It is preferable to make the flow rate on the first space 14 side in each membrane module 10 larger than the flow rate on the second space 16 side. If the flow rate on the first space 14 side is less than or equal to the flow rate on the second space 16 side, the flow rate on the first space 14 side of the subsequent membrane module may be insufficient. For example, the pump 18 or the like functions as flow control means for making the flow rate in the first space higher than the flow rate in the second space.

If the permeation flux is too large, the difference in concentration will increase, which may cause problems such as an increased risk of fouling and an excessively high pressure. On the other hand, if the permeation flux is too small, the concentration efficiency may deteriorate. From these points, the permeation flux of each membrane module 10 is preferably in the range of 0.005 m/d to 0.05 m/d, more preferably in the range of 0.015 m/d to 0.04 m/d. is more preferred. For example, the pump 18 or the like functions as permeation flux adjusting means for controlling the permeation flux within the above range.

A valve may be installed in at least one of the pipes, and there are no particular restrictions on the installation positions and the number of installation of the valves. Also, a flow meter as a flow rate measuring means for measuring a flow rate and a pressure gauge as a pressure measuring means for measuring a pressure may be installed in at least one of the pipes.

6 and 7 show an example of the device configuration, and the number of stages, the number of parallels, the arrangement of the semipermeable membrane modules, the method of supplying water, and the like may be changed as appropriate.

In order to concentrate the substance to be recovered in the NF concentrated water in the membrane module to a desired concentration, the membrane modules are preferably arranged in series in multiple stages. When multi-stage membrane modules are used as in the water treatment apparatuses 3, 4, 5, 6, and 7, the number of membrane modules may be determined according to the concentration of the target treated water. For example, when it is desired to obtain treated water with a higher concentration from NF-enriched water with a lower concentration, the number of membrane module units may be increased.

When a membrane module unit including a plurality of membrane modules connected in parallel is used as a membrane module at each stage as in the water treatment apparatuses 6 and 7, the number of membrane modules in each membrane module unit is NF concentrated water can be determined according to the flow rate of

One or more stages of membrane modules may be provided with concentration and dilution tanks, and each stage of membrane modules may be provided with concentration and dilution tanks.

The wastewater to be treated is, for example, wastewater discharged from a factory or the like, and is not particularly limited. The wastewater is, for example, ammonia-containing wastewater such as wastewater containing ammonium ions, wastewater containing sulfate ions and ammonium ions, and wastewater containing sulfate ions, ammonium ions and silica. Examples include waste water discharged from factories. Particularly in semiconductor factories, ammonia is used for cleaning wafers, etc., and sulfuric acid is used for scrubber processing to treat ammonia. Therefore, the waste water contains ammonium ions and sulfate ions. As a method for recovering ammonia and sulfuric acid in wastewater, an evaporation method such as an evaporator or membrane distillation is generally used. By supplying concentrated water from the module to the evaporator or membrane distillation device, the amount of water to be treated in the evaporator or membrane distillation device can be reduced, the load can be reduced, and ammonia and sulfuric acid can be efficiently recovered. can.

The wastewater before being sent to the nanofiltration device 11 (when pretreatment means is provided, after pretreatment and before being sent to the nanofiltration device 11) contains monovalent ions, divalent ions, etc. may contain ionic components at a certain concentration or higher, and may also contain uncharged substances. The waste water is, for example, ammonia-containing waste water containing 2000 mg/L or more of ammonium ions, and the ammonia-containing waste water preferably contains 2000 to 100000 mg/L of ammonium ions. The ammonia-containing wastewater may further contain, for example, 6000 mg/L or more of sulfate ions and 5 mg/L or more of silica as a non-charged substance, and 20000 to 250000 mg/L of sulfate ions and 5 to 5 to 250000 mg/L of silica as a non-charged substance. It is preferable to contain 50 mg/L.

The nanofiltration device 11 is not particularly limited as long as it can obtain NF permeated water and NF concentrated water using a nanofiltration membrane (NF membrane) for waste water.

Here, the nanofiltration membrane refers to a membrane having a NaCl blocking rate of 10% to 70% when an aqueous NaCl solution with a concentration of 2000 mg/liter is filtered under conditions of an operating pressure of 1.5 MPa and 25°C. The membrane material is not particularly limited, but examples thereof include cellulose resins such as cellulose acetate resins, polysulfone resins such as polyethersulfone resins, and polyamide resins. The shape of the membrane is not particularly limited, but includes a spiral type, a hollow fiber type, and the like. The primary side pressure during operation is preferably in the range of 0.5 MPa to 10 MPa.

The nanofiltration membrane has a silica rejection rate of 0 to 20% under the conditions of a membrane surface effective pressure of 1 MPa, 25 ° C., and pH 7, and an ammonium ion rejection rate and a sulfate ion rejection rate of 90% to 100%. A preferred membrane is a membrane having a silica rejection in the range of 5-18% and ammonium ion rejection and sulfate ion rejection in the range of 97%-100%. If the silica rejection rate of the nanofiltration membrane exceeds 20%, the risk of silica scale deposition in the membrane module 10 may increase when silica is contained in the ammonia-containing wastewater. If the ammonium ion rejection rate and sulfate ion rejection rate of the nanofiltration membrane are less than 90%, the recovery rates of ammonia and sulfuric acid may decrease.

Here, the rejection rate of each component of silica, ammonium ions, and sulfate ions for determining the characteristics of the nanofiltration membrane can be obtained by the following formula. Rejection rate (%) = 100-100 x {[A/((B+C)/2)]}
A: Ion concentration of each component in permeated water (mg/L)
B: Ion concentration of each component in water supply (mg/L)
C: Ion concentration of each component in concentrated water (mg/L)
The water supply and nanofiltration membrane treatment conditions for determining the silica, ammonium ion, and sulfate ion rejection of the nanofiltration membrane are as follows.
Feed water: aqueous solution containing ammonium sulfate at a concentration of 16500 mg/L and silica at a concentration of 20 mg/L Nanofiltration membrane treatment conditions: water temperature 25°C, permeation flux 0.4 m ³ /m ² /d, recovery rate 15%
Here, recovery rate (%) = 100 × [amount of permeated water in nanofiltration membrane treatment (m ³ /h)] / [amount of water supply subjected to nanofiltration membrane treatment (m ³ /h)

Examples of the semipermeable membrane 12 included in the membrane module include semipermeable membranes such as reverse osmosis membranes (RO membranes), forward osmosis membranes (FO membranes), and nanofiltration membranes (NF membranes). The semipermeable membrane is preferably a reverse osmosis membrane, a forward osmosis membrane, or a nanofiltration membrane.

The material forming the semipermeable membrane 12 is not particularly limited, but examples thereof include cellulose resins such as cellulose acetate resins, polysulfone resins such as polyethersulfone resins, and polyamide resins.

Examples of the shape of the semipermeable membrane 12 include a flat membrane, a hollow fiber membrane, a spiral membrane, and the like. Hollow fiber membranes are preferred because the surface area of the semipermeable membrane can be increased.

The collected material recovered from the concentrated water is at least one of ammonia and ammonium ions contained in the NF concentrated water, and is also a dissolved solid component (TDS), and the dissolved solid component includes, for example, sodium sulfate, sulfuric acid Inorganic salts such as calcium, sodium chloride, calcium chloride and the like are included.

In the water treatment method and water treatment apparatus according to the present embodiment, a membrane treatment step using, for example, a microfiltration membrane (MF membrane), an ultrafiltration membrane (UF membrane), etc., is performed before the nanofiltration step (nanofiltration means). (membrane treatment means), reverse osmosis membrane treatment step (reverse osmosis membrane treatment means), coagulation sedimentation treatment step (coagulation sedimentation treatment means), organic matter removal treatment step (organic matter removal treatment means), pH adjustment step (pH adjustment means), At least one pretreatment step (pretreatment means) may be included in the temperature adjustment step (temperature adjustment means).

When turbidity is contained, pretreatment such as coagulation sedimentation, membrane separation, pressure flotation, etc. may be performed in the preceding stage of the nanofiltration step (nanofiltration device 11).

Prior to the nanofiltration step (nanofiltration device 11), the pH and temperature of the waste water may be adjusted. FIG. 8 shows an example of a water treatment apparatus having such a configuration.

The water treatment apparatus 8 in FIG. 8, for example, in addition to the configuration of the water treatment apparatus 2 in FIG. 13, and a temperature adjusting device 15 as temperature adjusting means for adjusting the temperature of the waste water.

In the water treatment device 8 of FIG. 8, a pipe 31 is connected to the inlet of the pH adjuster 13 . The outlet of the pH adjuster 13 and the inlet of the temperature adjuster 15 are connected by a pipe 33 . The outlet of the temperature control device 15 and the inlet of the nanofiltration device 11 are connected by a pipe 25 via a pump 21 . The connection order of the pH adjusting device 13 and the temperature adjusting device 15 may be reversed. Other configurations are the same as those of the water treatment device 2 in FIG. In the water treatment apparatuses 1, 3 to 7 of FIGS. 1 and 3 to 7, a pH adjuster 13 and a temperature adjuster 15 may be provided.

In the water treatment device 8 , the ammonia-containing waste water, which is the water to be treated, is sent to the pH adjustment device 13 through the pipe 31 . The pH of the ammonia-containing waste water is adjusted in the pH adjusting device 13 (pH adjusting step). The pH-adjusted ammonia-containing waste water is sent to the temperature control device 15 through the pipe 33 . The temperature adjustment device 15 adjusts the temperature of the ammonia-containing waste water (temperature adjustment step). The connection order of the pH adjustment device 13 and the temperature adjustment device 15 may be reversed, and after the temperature adjustment of the ammonia-containing waste water is performed (temperature adjustment step), the pH adjustment of the temperature-adjusted ammonia-containing waste water is performed. (pH adjustment step).

The pH- and temperature-controlled ammonia-containing waste water is supplied to the nanofiltration device 11 through the pipe 25 by the pump 21 . Thereafter, a nanofiltration step and a semipermeable membrane treatment step are performed in the same manner as in the water treatment apparatus 2 of FIG. Water may be supplied to the nanofiltration device 11 and the membrane module 10 using only the pump 21 .

As described above, at least one of ammonia and ammonium ions is recovered as concentrated water from the ammonia-containing waste water to be treated, and the volume of the ammonia-containing waste water is reduced. In addition, NF permeated water, concentrated water, and diluted water can be reused.

The pH adjusting device 13 has, for example, pH adjusting agent adding means such as a pH adjusting agent adding pipe, a pH measuring device, a pH adjusting tank, and the like. It is preferable to add a pH adjuster to the pH adjusting tank to adjust the pH of the wastewater to within the range of pH 4-8, preferably within the range of pH 4-7. If the pH of the wastewater is less than 4, the rejection rate of ammonium ions in the nanofiltration membrane may decrease when the wastewater contains ammonia, and if the pH exceeds 8, ammonia gasifies when the wastewater contains ammonia. In the beginning, since ammonia permeates through the nanofiltration membrane, the concentration efficiency of ammonia may decrease. The pH adjustment may be performed in a pipe or the like without providing a pH adjustment tank.

Examples of pH adjusters include acids such as hydrochloric acid and sulfuric acid, and alkalis such as sodium hydroxide.

The temperature adjustment device 15 includes, for example, a temperature adjustment bath, a heating device such as a heater, a cooling device such as a cooler, a heat exchanger, a heat pump, and the like. It is preferable to adjust the temperature of the waste water in the range of 20° C. to 35° C., and when the waste water contains silica, it is more preferable to adjust the temperature in the range of 25 to 35° C. in order to suppress the precipitation of silica scale. If the temperature of the wastewater is less than 20°C, the silica precipitation concentration may decrease if the wastewater contains silica. be.

After the nanofiltration device 11, before water is passed through the semipermeable membrane module, pH adjustment and temperature adjustment may be performed again. The pH and water temperature at which water is passed through the semipermeable membrane module may be determined according to the quality of the waste water, the material of the semipermeable membrane module, and the like. For example, it is preferable that the pH of the waste water is in the range of 4 to 8, and the water temperature is in the range of 20°C to 35°C.

For pH adjustment, for example, a pH adjustment tank is provided, and a pH adjuster is added to the pH adjustment tank to adjust the pH.

The water temperature may be adjusted, for example, by providing a water temperature adjusting tank and heating the water with a heating device such as a heater in the water temperature adjusting tank, or by providing a heat exchanger.

The present specification includes the embodiments shown below.
(1) A water treatment device for recovering valuables from wastewater,
Nanofiltration means for obtaining NF permeated water and NF concentrated water for the waste water using a nanofiltration membrane;
Using a semipermeable membrane module having a first space and a second space separated by a semipermeable membrane, the NF concentrated water is passed through the first space, and the first space is pressurized to concentrate the NF. Concentrated water is obtained by allowing water contained in water to permeate the semipermeable membrane, and part of the NF concentrated water or at least part of the concentrated water is passed through the second space to dilute water. a semipermeable membrane treatment means to obtain;
A water treatment device comprising:

(2) A water treatment device that recovers valuables from wastewater,
Nanofiltration means for obtaining NF permeated water and NF concentrated water for the waste water using a nanofiltration membrane;
Using a semipermeable membrane module connected in multiple stages, which has a first space and a second space separated by a semipermeable membrane, the NF concentrated water is introduced into the first space of the first semipermeable membrane module. Water is passed through and the first space is pressurized to permeate the water contained in the NF concentrated water through the semipermeable membrane to obtain concentrated water, and the concentrated water is further passed through the subsequent semipermeable membrane module. While obtaining concentrated water using a semipermeable membrane treatment means for passing water to obtain dilution water;
A water treatment device comprising:

(3) The water treatment device according to (1) or (2),
A water treatment apparatus further comprising a return means for returning at least part of the diluted water obtained by the semipermeable membrane treatment means to a stage preceding the nanofiltration means.

(4) The water treatment device according to any one of (1) to (3),
The nanofiltration membrane has a silica rejection rate of 0 to 20% under the conditions of a membrane surface effective pressure of 1 MPa, 25 ° C., and pH 7, and an ammonium ion rejection rate and a sulfate ion rejection rate of 90% to 100%. A water treatment device.

(5) The water treatment device according to any one of (1) to (4),
A water treatment apparatus further comprising pH adjustment means for adjusting the pH of the waste water to a range of 4 to 8 in the preceding stage of the nanofiltration means.

(6) The water treatment device according to any one of (1) to (5),
A water treatment apparatus further comprising a temperature adjusting means for adjusting the temperature of the waste water within a range of 20°C to 35°C, upstream of the nanofiltration means.

(7) A water treatment method for recovering valuables from wastewater,
A nanofiltration step of obtaining NF permeated water and NF concentrated water using a nanofiltration membrane for the waste water;
Using a semipermeable membrane module having a first space and a second space separated by a semipermeable membrane, the NF concentrated water is passed through the first space, and the first space is pressurized to concentrate the NF. Concentrated water is obtained by allowing water contained in water to permeate the semipermeable membrane, and part of the NF concentrated water or at least part of the concentrated water is passed through the second space to dilute water. A semipermeable membrane treatment step to obtain,
A water treatment method, comprising:

(8) A water treatment method for recovering valuables from wastewater,
A nanofiltration step of obtaining NF permeated water and NF concentrated water using a nanofiltration membrane for the waste water;
Using a semipermeable membrane module connected in multiple stages, which has a first space and a second space separated by a semipermeable membrane, the NF concentrated water is introduced into the first space of the first semipermeable membrane module. Water is passed through and the first space is pressurized to permeate the water contained in the NF concentrated water through the semipermeable membrane to obtain concentrated water, and the concentrated water is further passed through the subsequent semipermeable membrane module. While obtaining concentrated water using A semipermeable membrane treatment step of passing water to obtain dilution water;
A water treatment method, comprising:

(9) The water treatment method according to (7) or (8),
A water treatment method, wherein at least part of the diluted water obtained in the semipermeable membrane treatment step is returned to the preceding stage of the nanofiltration step.

(10) The water treatment method according to any one of (7) to (9),
A water treatment method, wherein the wastewater contains 2000 mg/L or more of ammonium ions, 6000 mg/L or more of sulfate ions, and 5 mg/L or more of silica.

EXAMPLES 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>
Water to be treated (ammonia-containing wastewater) with an ammonium ion concentration of 4,500 mg/L, a sulfate ion concentration of 12,000 mg/L, and a silica concentration of 30 mg/L was treated with a spiral NF membrane (membrane effective pressure of 1 MPa, 25°C, pH 7 under the conditions of silica A membrane with 15% rejection and 99% ammonium ion rejection and sulfate ion rejection) was used for concentration. At that time, the pH of the water to be treated was varied in the range of 4-9. The concentration of silica in the treated water, concentrated water, and permeated water after passing through the NF membrane was measured by molybdenum yellow absorption spectrophotometry. A silica rejection rate was calculated from each silica concentration. The rejection rate is calculated by: rejection rate %=(1−(NF permeate water silica concentration/NF feed water silica concentration))×100. The operating conditions of the NF membrane were a feed water amount of 840 L/h, an NF concentrated water amount of 720 L/h, and an NF permeated water amount of 120 L/h. Silica rejection results are shown in FIG.

In addition, using the water treatment device 2 in FIG. 2, each pH condition (water temperature 25 ±1°C), Table 1 shows the ratio of the ammonium ion concentration of the concentrated water in the semipermeable membrane module to the ammonium ion concentration of the water to be treated. The return rate of the dilution water of the semipermeable membrane module to the front stage of the NF membrane module was 100%.

As shown in FIG. 9, the higher the pH of the water to be treated, the lower the silica rejection of the NF membrane, and the silica passed through the permeation side of the NF membrane. That is, the silica concentration on the NF concentrated water side is not concentrated, and other coexisting concentration target substances can be concentrated. As shown in Table 1, the concentration of the final concentrated water could be increased by increasing the pH of the water to be treated and decreasing the rejection of silica. At pH 9, it was possible to concentrate to a concentration exceeding the solubility of ammonium sulfate under the concentration conditions of this time.

<Example 2>
Using an NF membrane, the water to be treated with an ammonium ion concentration of 4500 mg / L, a sulfate ion concentration of 12000 mg / L, and a silica concentration of 30 mg / L is concentrated at a pH of 7 and a water temperature of 25 ± 1 ° C. with a recovery rate of 60% with the NF membrane, It was concentrated to 120 mg/L, which is the deposition concentration of silica, in the subsequent semipermeable membrane module. Concentrated water of the semipermeable membrane module with respect to the ammonium ion concentration in the water to be treated when the return rate of the diluted water of the semipermeable membrane module returned to the previous stage of the NF membrane is changed to 3 patterns of 0%, 50%, and 100% Table 2 shows the magnification of the ammonium ion concentration.

As shown in Table 2, when the amount of diluted water returned from the semipermeable membrane module was 0%, the concentration ratio of the final concentrated water from the semipermeable membrane module was 9.5 times, but the return rate was 50%. , 100%, the concentration of ammonium ions in the final concentrated water increased by 12.2 times and 14.9 times, respectively.

As described above, the apparatus and method of the example were able to recover a high concentration of valuable substances from ammonia-containing waste water.

1, 2, 3, 4, 5, 6, 7, 8 water treatment device, 10, 10a, 10b, 10c membrane module, 11 nanofiltration device, 12, 12a, 12b, 12c semipermeable membrane, 13 pH adjustment device, 14, 14a, 14b, 14c first space, 15 temperature control device, 16, 16a, 16b, 16c second space, 18, 21 pump, 20 inverter, 22, 22a, 22b, 22c, 23, 32, 32a, 32b , 32c valves 24, 25, 26, 27, 28, 29, 30, 31, 33, 34, 36, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 59, 61, 63, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 88, 90, 92, 94, 96, 98, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126 piping, 60a, 60b, 60c, 62a, 62b, 62c dilution water tank, 84 NF concentration water tank, 86 concentration water tank, 100, 100a, 100b, 100c, 100d membrane module unit.

Claims (10)

A water treatment device for recovering valuables from wastewater,
Nanofiltration means for obtaining NF permeated water and NF concentrated water for the waste water using a nanofiltration membrane;
Using a semipermeable membrane module having a first space and a second space separated by a semipermeable membrane, the NF concentrated water is passed through the first space, and the first space is pressurized to concentrate the NF. Concentrated water is obtained by allowing water contained in water to permeate the semipermeable membrane, and part of the NF concentrated water or at least part of the concentrated water is passed through the second space to dilute water. a semipermeable membrane treatment means to obtain;
A water treatment device comprising: A water treatment device for recovering valuables from wastewater,
Nanofiltration means for obtaining NF permeated water and NF concentrated water for the waste water using a nanofiltration membrane;
Using a semipermeable membrane module connected in multiple stages, which has a first space and a second space separated by a semipermeable membrane, the NF concentrated water is introduced into the first space of the first semipermeable membrane module. Water is passed through and the first space is pressurized to permeate the water contained in the NF concentrated water through the semipermeable membrane to obtain concentrated water, and the concentrated water is further passed through the subsequent semipermeable membrane module. While obtaining concentrated water using a semipermeable membrane treatment means for passing water to obtain dilution water;
A water treatment device comprising: The water treatment device according to claim 1 or 2,
A water treatment apparatus, further comprising return means for returning at least part of the diluted water obtained by the semipermeable membrane treatment means to a stage preceding the nanofiltration means. The water treatment device according to claim 1 or 2,
The nanofiltration membrane has a silica rejection rate of 0 to 20% under the conditions of a membrane surface effective pressure of 1 MPa, 25 ° C., and pH 7, and an ammonium ion rejection rate and a sulfate ion rejection rate of 90% to 100%. A water treatment device characterized by: The water treatment device according to claim 1 or 2,
The water treatment apparatus further comprises pH adjustment means for adjusting the pH of the waste water to a range of 4 to 8 in the preceding stage of the nanofiltration means. The water treatment device according to claim 1 or 2,
A water treatment apparatus, further comprising temperature adjusting means for adjusting the temperature of said waste water within a range of 20°C to 35°C, upstream of said nanofiltration means. A water treatment method for recovering valuables from wastewater,
A nanofiltration step of obtaining NF permeated water and NF concentrated water using a nanofiltration membrane for the waste water;
Using a semipermeable membrane module having a first space and a second space separated by a semipermeable membrane, the NF concentrated water is passed through the first space, and the first space is pressurized to concentrate the NF. Concentrated water is obtained by allowing water contained in water to permeate the semipermeable membrane, and part of the NF concentrated water or at least part of the concentrated water is passed through the second space to dilute water. A semipermeable membrane treatment step to obtain,
A water treatment method comprising: A water treatment method for recovering valuables from wastewater,
A nanofiltration step of obtaining NF permeated water and NF concentrated water using a nanofiltration membrane for the waste water;
Using a semipermeable membrane module connected in multiple stages, which has a first space and a second space separated by a semipermeable membrane, the NF concentrated water is introduced into the first space of the first semipermeable membrane module. Water is passed through and the first space is pressurized to permeate the water contained in the NF concentrated water through the semipermeable membrane to obtain concentrated water, and the concentrated water is further passed through the subsequent semipermeable membrane module. While obtaining concentrated water using A semipermeable membrane treatment step of passing water to obtain dilution water;
A water treatment method comprising: The water treatment method according to claim 7 or 8,
A water treatment method, characterized in that at least part of the diluted water obtained in the semipermeable membrane treatment step is returned to the preceding stage of the nanofiltration step. The water treatment method according to claim 7 or 8,
A water treatment method, wherein the waste water contains 2000 mg/L or more of ammonium ions, 6000 mg/L or more of sulfate ions, and 5 mg/L or more of silica.

Images