JP2001187323A - Membrane separation device and operation method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a membrane separation device capable of recovery of a membrane flow flux by chemical washing and also reduction of a burden to the external environment due to the discharged washing water, and its operation method. SOLUTION: At a filter operation time of the membrane separation device, a raw water inlet valve 2, a concentrated water outlet valve 8, a permeated water outlet valve 6, and a washing water discharge valve 27 are opened, and also a washing water inlet valve 22, a washing water return valve 24 and a permeated water bypass valve 23 are closed. Raw water is fed to the inside of a membrane module 10 through piping 1 to separate it to the permeated water and the concentrated water. The permeated water is recovered and reutilized through piping 4. The concentrated water is discharged to the outside through pipings 5, 5b as discharge water. In such a filter operation time, the washing water containing a chemical stored in a washing water tank 20, is introduced to the piping 5b through pipings 25, 25a, and is discharged to the outside through the piping 5b together with the concentrated water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane separation apparatus provided with a membrane module such as a spiral type membrane module, a hollow fiber membrane module, and a tubular membrane module, and a method of operating the same.

[0002]

2. Description of the Related Art In recent years, a membrane separation technique has been applied to a water purification technique, and a membrane separation technique has been applied as a pretreatment of a reverse osmosis membrane separation system used for seawater desalination and the like.
As a membrane used for such a membrane separation, a microfiltration membrane or an ultrafiltration membrane capable of obtaining a high permeated water amount is often used, but recently, a high permeated water amount at an ultra-low pressure of 10 kgf / cm ² or less is used. Reverse osmosis membranes have been developed that can provide Examples of the form of the membrane module having such a membrane include a spiral membrane module, a hollow fiber membrane module, and a tubular membrane module. The membrane separation device provided with the membrane module has the following configuration.

FIG. 3 is a schematic configuration diagram showing an example of a conventional membrane separation apparatus. In the membrane separation device shown in FIG. 3, a pipe 31 in which a raw water inlet valve 32 is inserted is connected to a raw water inlet (not shown) of the membrane module 40 via a pressure pump 33. A pipe 35 in which a pressure regulating valve 37 and a concentrated water outlet valve 38 are inserted is connected to a concentrated water outlet (not shown) of the membrane module 40. On the other hand, a permeated water outlet (not shown) of the membrane module 40 is connected to a pipe 34 in which a permeated water outlet valve 36 is inserted. Permeate outlet valve 3 for pipe 34
6 is connected to a pipe 34a in which a permeated water bypass valve 53 is inserted. This pipe 34a is a pipe 3
5 is connected to the upstream side of the concentrated water outlet valve 38. further,
The pipe 35 a in which the cleaning water return valve 54 is inserted is connected to the pipe 35, and the pipe 35 a is connected to the cleaning water tank 50. The washing water tank 50 is connected to the piping 31 on the upstream side of the pressurizing pump 33 via the piping 51 in which the washing water inlet valve 52 is inserted. Further, a pipe 55 in which a cleaning water discharge valve 56 is inserted is connected to the cleaning water tank 50.

During the filtration operation of the membrane separation apparatus, the raw water inlet valve 32, the concentrated water outlet valve 38, and the permeated water outlet valve 36 are opened, and the washing water inlet valve 52, the washing water return valve 54, the permeated water bypass valve, and the like. Valve 53 and wash water discharge valve 5
Close 6. Further, the pressure adjusting valve 37 is set so that the concentration of the concentrated water is equal to or less than the predetermined amount, and the pressurizing pump 33 is driven.

The raw water pressurized by the pressurizing pump 33 is
It is supplied to the inside of the membrane module 40 through the pipe 31. The raw water is separated by the membrane module 40 into permeated water from which impurities are removed and concentrated water from which impurities are concentrated. In this case, since the amount of concentrated water is suppressed by the pressure adjusting valve 37, the permeation of the membrane is promoted. The permeated water passes through a pipe 34 connected to the permeated water outlet of the membrane module 40, and is collected and used as treated water. The concentrated water passes through a pipe 35 connected to the concentrated water outlet of the membrane module 40 and is discharged to the outside as wastewater. In this case, the concentrated water is discharged to, for example, a wastewater treatment plant, a sewer, a river, or the like in a factory and discharged.

[0006] With the filtration operation of the above-mentioned membrane separation device, clogging of the membrane occurs in the membrane module 40 due to the suspended matter in the raw water, and the membrane flux decreases. Therefore, chemical cleaning of the membrane module 40 is performed to recover the membrane flux. Such chemical cleaning will be described below.

During the washing operation, the wash water inlet valve 52, the wash water return valve 54, and the permeate bypass valve 53 are opened, and the raw water inlet valve 32, the concentrated water outlet valve 38, the permeate outlet valve 36, and the wash water discharge valve 56 are opened. Close. Further, the pressure regulating valve 37 is fully opened, and the pressurizing pump 33 is driven.

[0008] Wash water containing chemicals such as high-concentration chemicals and metals is taken from a wash water tank 50 through a pipe 51, and the pressure is increased by a pressure pump 33 and supplied to the inside of the membrane module 40. The washing water is separated by the membrane module 40 into a permeation side and a concentration side. At the time of such membrane separation of the washing water, the suspended substances attached to the membrane are removed by the washing water. This removes clogging of the membrane and restores membrane flux. The washing water on the concentration side is returned from the concentrated water outlet of the membrane module 40 to the washing water tank 50 via the pipe 35 and the pipe 35a. Further, the washing water on the permeation side is supplied from the permeated water outlet of the membrane module 40 to the pipe 34, the pipe 34a, the pipe 3
5 and the pipe 35a in order and returned to the washing water tank 50 together with the washing water on the concentration side.

After the above chemical cleaning, the cleaning water discharge valve 56 is opened, and the cleaning water inlet valve 52 and the cleaning water return valve 54 are opened.
Is closed, and the used washing wastewater collected in the washing water tank 50 is discharged and discharged to a wastewater treatment plant, a sewer, a river or the like in the factory. In this case, the valves 32, 37, 38, 36, and 53 other than the valves 56, 52, and 54 may be open or closed.

[0010]

Here, since the washing water contains chemicals such as high concentration chemicals and metals, if the washing water is discharged at a time as described above, the load on the external environment increases. . For example, chemicals contained in the washing water cause a decrease in the treatment capacity of a wastewater treatment plant due to the death of bacteria in the activated sludge layer, pollution of rivers, and the like, and adversely affect the outside.

An object of the present invention is to provide a membrane separation apparatus capable of recovering a membrane flux by chemical cleaning and reducing a load on an external environment due to discharged cleaning water, and a method of operating the same. That is.

[0012]

Means for Solving the Problems and Effects of the Invention A membrane separation apparatus according to the present invention is a membrane separation apparatus provided with a membrane module, wherein treated water for discharging first treated water separated by the membrane module is provided. A discharge path, a treated water collection path for collecting the second treated water separated by the membrane module, a cleaning water collection path for collecting cleaning water containing a chemical used for chemical cleaning of the membrane module, and a cleaning water collection path A washing water tank for storing the washing water collected through the washing tank, and a washing water discharging path for guiding the washing water stored in the washing water tank to the treated water discharging path during the filtration operation.

In the membrane separation apparatus according to the present invention, at the time of the cleaning operation, the cleaning of the membrane module is performed by chemical cleaning, the cleaning water is recovered through the cleaning water recovery path, and the cleaning water is stored in the cleaning water tank. On the other hand, during the filtration operation of the membrane separation device, the liquid to be treated is separated into the first treated water and the second treated water by the membrane module, and the first treated water is discharged outside through the treated water discharge path. At the same time, the second treated water is recovered through the treated water recovery path.

In the above-mentioned membrane separation apparatus, since clogging of the membrane of the membrane module can be removed by chemical cleaning to recover the membrane flux, it is possible to stably obtain a high permeated water amount. Become.

Here, in the above-mentioned membrane separation device, since the washing water discharge path for guiding the washing water to the treated water discharge path is provided, the washing water stored in the washing water tank is used during the filtration operation. It can be mixed with the treated water and discharged through the treated water discharge path. Therefore, the washing water is
It is possible to dilute to a concentration that does not adversely affect the external environment with the treated water, and discharge it little by little. Thereby, the load on the external environment is reduced and the load fluctuation is suppressed, so that the external environment is not adversely affected.

A control means for controlling the flow rate of the washing water in the washing water discharge path may be further provided. Further, the control means may control the flow rate of the wash water in the wash water discharge path according to the flow rate of the first treated water in the treated water discharge path. Thereby, the concentration of the washing water discharged to the outside can be adjusted by the control means, so that the load on the external environment can be further reduced and the load fluctuation can be suppressed.

The control means may stop the discharge of the wash water when the flow rate of the first treated water in the treated water discharge path becomes equal to or less than a predetermined amount. This makes it possible to dilute the wash water with the first treated water to a concentration that does not adversely affect the external environment and discharge the wash water.

Further, the control means is provided in the first part of the treated water discharge path.
The flow rate of the wash water in the wash water discharge path or the flow rate of the first treated water in the treated water discharge path is controlled so that the ratio of the flow rate of the treated water to the flow rate of the wash water in the wash water discharge path becomes constant. Is also good. Thereby, the washing water can always be diluted to the predetermined concentration with the first treated water and discharged.

The control means may control the flow rate of the washing water in the washing water discharge path according to the amount of washing water stored in the washing water tank. Thereby, it is possible to prevent the operation in a state where the inside of the washing water tank is empty. Therefore, a stable operation can be performed in the membrane separation device.

[0020] The apparatus may further include a valve and a pump interposed in the washing water discharge path, and the control means may include a control device for controlling the pump. In this case, the flow rate of the washing water in the washing water discharge path can be controlled by controlling the pump by the control device.

Further, the control device may open the valve during the filtration operation and close the valve during the cleaning operation. Thereby,
During the filtration operation, the wash water is introduced into the treated water discharge path through the wash water discharge path. Also, during the cleaning operation,
The introduction of the wash water into the treated water discharge path is stopped.

[0022] The first treated water may be concentrated water and the second treated water may be permeated water. In this case, the concentrated water is discharged outside through the treated water discharge path, and the permeated water is collected through the treated water recovery path.

Alternatively, the first treated water may be permeated water and the second treated water may be concentrated water. In this case, the permeated water is discharged outside through the treated water discharge path, and the concentrated water is collected through the treated water recovery path.

The method for operating a membrane separation device according to the present invention is a method for operating a membrane separation device provided with a membrane module, wherein the membrane module is chemically washed with washing water containing a chemical during washing operation and the washing water is recovered. The cleaning water is mixed with the treated water that is separated by the membrane module during the filtration operation and discharged to the outside as wastewater, and is discharged.

In the method for operating the membrane separation apparatus according to the present invention, the washing water is treated by mixing the washing water into the treated water separated by the membrane module and discharged to the outside as wastewater during the filtration operation. Water can be diluted to a concentration that does not adversely affect the external environment and discharged little by little. Thereby, the load on the external environment is reduced and the load fluctuation is suppressed, so that the external environment is not adversely affected.

Further, in the above-mentioned membrane separation device, since clogging of the membrane of the membrane module can be removed by chemical cleaning to recover the membrane flux, it is possible to stably obtain a high permeated water amount. It becomes possible.

[0027]

FIG. 1 is a schematic diagram showing one example of a membrane separation apparatus according to the present invention.

In the membrane separation apparatus shown in FIG. 1, a membrane module 10 has one or a plurality of membrane elements housed in a pressure vessel, and a single pressure vessel or a plurality of pressure vessels are connected in series and / or It is configured by connecting in parallel. The pipe 1 in which the raw water inlet valve 2 is inserted is connected to the raw water inlet (not shown) of the membrane module 10 via the pressure pump 3. The concentrated water outlet (not shown) of the membrane module 10 has a pressure regulating valve 7 and a concentrated water outlet valve 8.
Is connected, and the pipe 5 is further connected to the pipe 5.
b is connected. On the other hand, the permeated water outlet (not shown) of the membrane module 10 is connected to the pipe 4 in which the permeated water outlet valve 6 is inserted. On the upstream side of the permeated water outlet valve 6 of the pipe 4, a pipe 4a in which a permeated water bypass valve 23 is inserted is connected. The pipe 4a is further connected to the pipe 5. The pipe 5 is further connected to a pipe 5 a in which a cleaning water return valve 24 is inserted, and the pipe 5 a is connected to the cleaning water tank 20. The washing water tank 20 is connected to the piping 1 on the upstream side of the pressurizing pump 3 via a piping 21 in which a washing water inlet valve 22 is inserted. The washing water tank 20 is connected via a pipe 25
Connected to discharge pump 26. A cleaning water discharge valve 27 is inserted in the pipe 25. This pipe 25 is further connected to a pipe 5b via a pipe 25a.

In this embodiment, the concentrated water and the permeated water of the membrane module 10 correspond to the first treated water and the second treated water, respectively. The pipes 5 and 5b, the pressure regulating valve 7 and the concentrated water outlet valve 8 correspond to a treated water discharge path.
And the permeated water outlet valve 6 corresponds to a treated water recovery path. Further, the pipes 5a and 4a, the permeated water bypass valve 23, and the cleaning water return valve 24 correspond to a cleaning water recovery path, and the pipes 25 and 4a.
25a, the discharge pump 26 and the permeated water discharge valve 27 correspond to a washing water discharge path.

In the above-mentioned membrane separation device, the filtration operation and the washing operation are performed alternately. Hereinafter, the cleaning operation of the membrane separation device will be described first.

During the cleaning operation, chemical cleaning is performed. In this case, the washing water inlet valve 22, the washing water return valve 24, and the permeated water bypass valve 23 are opened, and the raw water inlet valve 2, the concentrated water outlet valve 8, the permeated water outlet valve 6, and the washing water discharge valve 27 are closed. At this time, the permeated water bypass valve 23 can be fully closed to wash only the concentration side. Further, the pressure control valve 7 is fully opened. Further, the pressurizing pump 3 is driven, and the discharge pump 26 is stopped. In this case, each valve 22, 24, 23, 2, 8,
Reference numerals 6, 27 and 7 denote manual valves, which are manually opened and closed.

The washing water containing high-concentration chemicals and chemicals such as metals stored in the washing water tank 20 is taken in through the pipe 21 and is pressurized by the pressure pump 3 to increase the pressure of the membrane module 1.
0. The washing water is separated by the membrane module 10 into a permeation side and a concentration side. At the time of such membrane separation of the washing water, the turbid substances adhered to the membrane of the membrane module 10 are removed by the washing water. Thereby, clogging of the membrane is removed, and the membrane flux of the membrane module 10 is restored.

The washing water on the concentration side is returned from the concentrated water outlet of the membrane module 10 to the washing water tank 20 via the pipe 5 and the pipe 5a. Further, the washing water on the permeation side is returned from the permeated water outlet of the membrane module 10 to the washing water tank 20 together with the washing water on the concentration side through the pipe 4, the pipe 4a, the pipe 5, and the pipe 5a in this order.

After the cleaning water is circulated as described above to perform chemical cleaning of the membrane module 10, the filtration operation of the membrane separation device is performed. In this case, in parallel with the filtration operation of the membrane separation device,
The used washing water stored in the washing water tank 20 is discharged.

During the filtration operation of the membrane separation apparatus, the raw water inlet valve 2, the concentrated water outlet valve 8, the permeated water outlet valve 6, and the washing water discharge valve 27 are opened, and the washing water inlet valve 22, the washing water return valve 24, and the permeated water. The water bypass valve 23 is closed. Further, the pressure adjusting valve 7 is set so that the concentration of the concentrated water becomes equal to or less than a predetermined amount, and the pressurizing pump 3 and the discharge pump 26 are driven.

The raw water pressurized by the pressure pump 3 is supplied to the inside of the membrane module 10 through the pipe 1. The raw water is separated by the membrane module 10 into permeated water from which impurities have been removed and concentrated water in which impurities have been concentrated. In this case, since the amount of concentrated water is suppressed by the pressure adjusting valve 7, permeation of the membrane in the membrane module 10 is promoted. The permeated water passes through the pipe 4 connected to the permeated water outlet of the membrane module 10, and is collected and used as treated water. The concentrated water is
Through the pipe 5 and the pipe 5b connected to the concentrated water outlet of the membrane module 10, it is discharged to the outside as drainage. In this case, the concentrated water is discharged to, for example, a wastewater treatment plant, a sewer, a river, or the like in a factory and discharged.

In parallel with the filtration operation of the membrane separation apparatus as described above, the used washing water stored in the washing water tank 20 is taken in through the pipe 25 and is pressurized by the discharge pump 26.
The concentrated water is discharged to the outside through the pipe 25a and the pipe 5b. As a result, the washing water containing high-concentration chemicals and chemicals such as metals is diluted by the concentrated water to a concentration that does not adversely affect the external environment, and is discharged little by little to the outside.

In the above-mentioned membrane separation apparatus, since clogging of the membrane of the membrane module 10 can be removed by chemical cleaning to recover the membrane flux, a high permeated water amount can be obtained stably. Becomes

In this case, since the washing water used for the chemical washing is diluted to a concentration that does not adversely affect the external environment and is discharged little by little, the washing water used in the washing water contains high-concentration chemicals and chemicals such as metals. The load on the environment is reduced and the load fluctuation is reduced. Therefore, it is possible to prevent a decrease in the treatment capacity of the wastewater treatment plant or a deterioration of the river environment due to the death of bacteria in the activated sludge tank caused by the chemicals contained in the discharged washing water, and the river environment is adversely affected. Do not give.

In the above, the discharge of the washing water may be automatically controlled. This case will be described below.

FIG. 2 is a schematic diagram showing another example of the membrane separation apparatus according to the present invention. The membrane separation device shown in FIG. 2 has the same configuration as the membrane separation device shown in FIG. 1 except for the following points.

As shown in FIG. 2, the membrane separation apparatus of this embodiment includes a control device 29, a flow sensor 30 for detecting the flow rate of the concentrated water in the pipe 5, and a flow sensor 31 for detecting the discharge flow rate of the washing water. Is provided in the pipe 25a. in this case,
Each of the valves 2, 6, 7, 8, 22, 23, 24, and 27 is an automatic valve, and the opening and closing operation is automatically performed by the control device 29. The above valves 2, 6, except for the washing water discharge valve 27,
Any of the valves 7, 8, 22, 23, 24 may be a manual valve. Further, a washing water tank 20a provided with a level detector 28 is provided. Such a membrane separation apparatus is operated by the same operation method as the membrane separation apparatus of FIG. 1 except for the following points.

In the membrane separation apparatus of this embodiment, the flow rate sensor 30 detects the flow rate of the concentrated water during the filtration operation, and the control device 29
Send a signal to The controller 29 controls the pressurizing pump 3 or the discharge pump 26 based on this signal to adjust the flow rate of the concentrated water or the discharge flow of the washing water. In this case, the control device 29 controls the pressurizing pump 3 and the discharge pump 26 so that the ratio between the flow rate of the concentrated water and the discharge flow rate of the washing water becomes constant. When the flow rate of the concentrated water detected by the flow sensor 30 is equal to or less than a predetermined amount, the control device 29 closes the cleaning water discharge valve 27 and stops the discharge pump 26 to stop the discharge of the cleaning water.

The discharge flow rate of the washing water is measured by a flow sensor 31.
And sends a signal to the control device 29. Based on this signal, the control device 29 controls the discharge pump 26 so that the ratio between the flow rate of the concentrated water and the discharge flow rate of the wash water becomes constant, and The discharge flow rate may be adjusted.

When the level of the washing water in the washing water tank 20a falls below a predetermined height as the washing water is discharged, the output of the level detector 28 is turned on or off. Here, it is assumed that the output of the level detector 28 is turned on when the level of the washing water in the washing water tank 20a falls below a predetermined height. The control device 29 controls the discharge pump 26 in response to the output state of the level detector 28 and closes the wash water discharge valve 27 to stop the discharge of the wash water.

In the above-mentioned membrane separation apparatus, since clogging of the membrane can be removed by chemical cleaning to recover the membrane flux, a high permeated water amount can be obtained stably.

In this case, since the washing water used for chemical washing is diluted with concentrated water to such an extent that the external environment is not affected and discharged little by little, high-concentration chemicals, metals and the like contained in the washing water are removed. The load on the external environment due to the chemical is reduced, and the load fluctuation is reduced. Therefore, it is possible to prevent the treatment capacity of the wastewater treatment plant from being reduced due to the death of bacteria in the activated sludge tank caused by the chemicals contained in the discharged washing water, and to prevent the river environment from being deteriorated. Do not give.

In particular, in this embodiment, the control device 29 controls the pressurizing pump 3 and the discharge pump 26 to keep the ratio between the flow rate of the concentrated water and the discharge flow rate of the washing water constant, so that the chemical discharged to the outside is controlled. The concentration can be kept constant at a low concentration. Thereby, the load on the external environment due to the discharged chemical is further reduced.

When the level of the washing water in the washing water tank 20a falls below a predetermined height, the controller 29 closes the washing water discharge valve 27 and controls and stops the discharge pump 26. There is no danger of emptying. This makes it possible to efficiently and stably operate the membrane separation device.

In FIGS. 1 and 2, the membrane separation apparatus in which the concentrated water is the discharge target (first treated water) and the permeated water is the recovery target (second treated water) has been described. In the membrane separation device according to the present invention, the permeated water may be a discharge target (first treated water), and the concentrated water may be a recovery target (second treated water).

For example, in FIG. 1, a membrane separation device may be used in which the pipe 25a is connected to the pipe 4 downstream of the permeate outlet valve 6 without being connected to the pipe 5b. During the filtration operation of such a membrane separation device, the washing water is discharged to the outside through the pipe 4 together with the permeated water. Thereby, the same effect as the effect in the membrane separation device of FIG. 1 can be obtained. In this case, the pipe 4 and the permeated water outlet valve 6 correspond to a treated water discharge path, and the pipes 5 and 5b, the pressure regulating valve 7, and the concentrated water outlet valve 8 correspond to a treated water recovery path.

In the membrane separation apparatus for diluting and discharging the washing water with the permeated water as described above, a control device for adjusting the discharge flow rate of the cleaning water according to the permeated water flow rate may be provided. For example, in FIG. 2, the pipe 25 a is connected to the downstream side of the permeate outlet valve 6 of the pipe 4 without being connected to the pipe 5 b, and the flow rate sensor 30 is provided on the upstream side of the permeate outlet valve 6 of the pipe 4. It may be a membrane separation device. During the filtration operation of such a membrane separation device, the control device 29 controls the pressurizing pump 3 or the discharge pump 26 so that the ratio between the flow rate of the permeated water and the discharge flow rate of the washing water becomes constant. Thereby, the same effect as the effect in the membrane separation device of FIG. 2 can be obtained.

The form of the membrane module used in the membrane separation device according to the present invention is not particularly limited. In the membrane separation device according to the present invention, a spiral membrane module, a hollow fiber membrane module, a tubular membrane module, or the like can be used.

[0054]

EXAMPLES [Examples] In the examples, a reverse osmosis membrane (R) manufactured by Nitto Denko Corporation of S8 size (200 mm in diameter) was used.
O membrane) The membrane separation device shown in FIG. 1 was used, which was provided with a spiral membrane module 10 using ten spiral elements ES20-D8 and a washing water tank 20 having a capacity of 1000 L (1 m ³ ). This membrane module 1
Reference numeral 0 indicates that five membrane elements are respectively housed in two pressure vessels and these pressure vessels are connected in parallel.

In the above-mentioned membrane separation device, well water was supplied as raw water, and a filtration operation was performed by the operation method of the membrane separation device shown in FIG. 1 to perform a desalination treatment of the well water. In this case, the obtained permeated water was collected and used, and the concentrated water was discharged as wastewater to a wastewater treatment plant. During such a filtration operation, the supply flow rate of the raw water was 18 m ³ / h, the flow rate of the permeated water was 6 m ³ / h, and the flow rate of the concentrated water was 12 m ³ / h.

After performing the above-mentioned filtration operation continuously for one week, a washing operation was performed as follows. First, in the washing water tank 20, the concentration including citric acid is 0.1%.
The washing water was adjusted to 1000 L, and the washing water was used for chemical cleaning of the membrane separation device by the operation method of the membrane separation device shown in FIG. In this case, the supply flow rate of the washing water is 12
m ³ / h. Further, the washing water on the permeation side and the concentration side of the membrane module 10 was once returned to the washing water tank 20 (12 m ³ / h), and then circulated again as washing water. After performing such a cleaning operation for one hour, raw water was supplied into the membrane separation device, and the cleaning water held in the membrane separation device was returned to the cleaning water tank 20 by pushing with the raw water. The COD (chemical oxygen demand) of the used washing water collected in the washing water tank 20 in this manner was 980 ppm.

After the above-mentioned washing operation, the filtration of the membrane separation device is performed again.
Overdriving was performed. Here, the membrane separation device shown in FIG.
Used in the washing water tank 20
Was mixed with the concentrated water and discharged to a wastewater treatment plant. This
In the case of, the concentrated water flow rate is 12m ^Three/ H, mixed with concentrated water
The flow rate of the incoming washing water is 0.06m^Three/ H. this
Of COD in wastewater flowing into wastewater treatment plant
Was 4.9 ppm below the river discharge standard.

Comparative Example In the comparative example, a reverse osmosis membrane (R) manufactured by Nitto Denko Corporation of S8 size (200 mm in diameter) was used.
O membrane) The membrane separation apparatus shown in FIG. 3 was used, which was provided with a spiral membrane module 40 using ten spiral elements ES20-D8 and a washing water tank 50 having a capacity of 1000 L (1 m ³ ). This membrane module 4
Reference numeral 0 indicates that five membrane elements are respectively housed in two pressure vessels and these pressure vessels are connected in parallel.

In the above-mentioned membrane separation device, well water was supplied as raw water, and a filtration operation was performed by the operation method of the membrane separation device shown in FIG. 3 to perform a desalination treatment of the well water. In this case, the obtained permeated water was collected and used, and the concentrated water was discharged as wastewater to a wastewater treatment plant. During such a filtration operation, the supply flow rate of the raw water was 18 m ³ / h, the flow rate of the permeated water was 6 m ³ / h, and the flow rate of the concentrated water was 12 m ³ / h.

After performing the above-mentioned filtration operation continuously for one week, the washing operation was performed as follows. First, in the washing water tank 50, the concentration containing citric acid is 0.1%.
The washing water was adjusted to 1000 L, and the washing water was used to perform chemical cleaning of the membrane separation device by the operation method of the membrane separation device shown in FIG. In this case, the supply flow rate of the washing water is 12
m ³ / h. Further, the washing water on the permeation side and the concentration side of the membrane module 40 was once returned to the washing water tank 50 (12 m ³ / h), and then circulated again as washing water. After performing such a washing operation for one hour, raw water was supplied into the membrane separation device, and the washing water held in the membrane separation device was returned to the washing water tank 50 by pushing with the raw water. The COD value of the used washing water collected in the washing water tank 50 in this manner was 980 ppm.

After the above washing operation, the filtration operation of the membrane separation device was performed again. Here, the 1000 L collected in the washing water tank was operated by the operation method of the membrane separation device shown in FIG.
Was directly discharged to the wastewater treatment plant without dilution.

In the above embodiment, since the washing water is diluted with the concentrated water and discharged little by little to the wastewater treatment plant, the washing water is diluted to a concentration that does not adversely affect the outside. Therefore, a large load is not applied to the wastewater treatment plant as in the comparative example, and the load fluctuation is small. On the other hand, in the comparative example, since a large amount of cleaning water containing high-concentration chemicals is directly discharged to the wastewater treatment plant, the load of the wastewater treatment plant fluctuates greatly instantaneously, and a large load is applied.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of a membrane separation device according to the present invention.

FIG. 2 is a schematic configuration diagram showing another example of the membrane separation device according to the present invention.

FIG. 3 is a schematic configuration diagram showing an example of a conventional membrane separation device.

[Explanation of symbols]

 2,32 Raw water inlet valve 3,33 Pressurized pump 6,36 Permeated water outlet valve 7,37 Pressure regulating valve 8,38 Concentrated water outlet valve 10,40 Membrane module 20,20a, 50 Wash water tank 22,52 Wash water Inlet valve 23,53 Permeate water bypass valve 24,54 Wash water return valve 26 Discharge pump 27,56 Wash water discharge valve 28 Level detector 29 Controller 30 Flow sensor

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[Procedure amendment]

[Submission date] January 5, 2000 (2000.1.5)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Figure 3

[Correction method] Change

[Correction contents]

FIG. 3

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D006 GA03 GA06 GA07 HA01 HA21 HA61 JA56A JA67A KA63 KA72 KC02 KC03 KC16 KD15 KE02Q KE02R KE03Q KE03R KE04Q KE04R PB03 PB05

Claims (11)

[Claims] 1. A membrane separation device provided with a membrane module, comprising: a treated water discharge path for discharging a first treated water separated by the membrane module; and a second treated water separated by the membrane module. A treatment water recovery path for collecting the cleaning water, a cleaning water recovery path for recovering the cleaning water containing the chemical used for the chemical cleaning of the membrane module, and a cleaning water tank for storing the cleaning water recovered through the cleaning water recovery path. A cleaning water discharge path for guiding the cleaning water stored in the cleaning water tank to the treated water discharge path during a filtration operation. 2. The membrane separation apparatus according to claim 1, further comprising control means for controlling a flow rate of the washing water in the washing water discharge path. 3. The method according to claim 2, wherein the control unit controls a flow rate of the cleaning water in the cleaning water discharge path according to a flow rate of the first processing water in the processing water discharge path. Membrane separation device. 4. The membrane separation according to claim 3, wherein the control means stops the discharge of the cleaning water when the flow rate of the first treated water in the treated water discharge path becomes equal to or less than a predetermined amount. apparatus. 5. The cleaning water discharge path such that a ratio between a flow rate of the first treated water in the treated water discharge path and a flow rate of the wash water in the cleaning water discharge path is constant. 4. The membrane separation apparatus according to claim 3, wherein the flow rate of the cleaning water or the flow rate of the first treated water in the treated water discharge path is controlled. 6. The cleaning water flow rate of the washing water discharge path according to the control amount of the washing water stored in the washing water tank.
The membrane separation device according to any one of the above. 7. The apparatus according to claim 2, further comprising a valve and a pump interposed in the washing water discharge path, wherein said control means includes a control device for controlling said pump. Membrane separation device. 8. The membrane separation device according to claim 7, wherein the control device opens the valve during the filtration operation and closes the valve during the cleaning operation. 9. The method according to claim 1, wherein the first treated water is concentrated water and the second treated water is permeated water.
9. The membrane separation device according to any one of 8. 10. The method according to claim 1, wherein said first treated water is permeated water and said second treated water is concentrated water.
9. The membrane separation device according to any one of items 1 to 8. 11. A method for operating a membrane separation apparatus provided with a membrane module, wherein the membrane module is chemically washed with washing water containing a chemical during a washing operation, and the washing water is collected and stored. A method for operating a membrane separation apparatus, comprising mixing and discharging the stored washing water into treated water separated by the membrane module and discharged to the outside as wastewater.