JPH08229362A - Method for cleaning membrane with liquid chemical in immersion-type membrane filter and device therefor - Google Patents

Abstract

PURPOSE: To eliminate the need for equipment to move a membrane, etc., to shorten the cleaning time and to clean the membrane with a small amt. of liq. chemical. CONSTITUTION: A membrane 4a dipped in an immersion tank 3 storing raw water is cleaned with a liq. chemical. In this case, the chemical is supplied to the membrane 4a from the treated water side to clean the membrane 4a. The raw water is filtered by the membrane 4a dipped in the tank 3 in this immersion-type membrane filter. A device 1 for cleaning the membrane 4a with the chemical is provided with a means 10 to supply the cleaning chemical to the membrane 4a from the treated water side of the membrane 4a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an immersion type membrane filtration device for filtering raw water with a membrane immersed in an immersion tank, and a method for cleaning a membrane in the immersion tank with a chemical solution and a chemical solution cleaning. Regarding the device.

[0002]

2. Description of the Related Art Conventionally, there is an immersion type membrane filtration device in which a membrane (also referred to as a membrane module) is immersed in an immersion tank in which raw water is stored to purify the raw water by a filtering action of the membrane. In this membrane filtration device, when the membrane filtration is continued, the membrane is clogged with turbidity or the like to lower the filtration efficiency. Therefore, the membrane is washed after a certain period of use.

As this cleaning method, backwashing is carried out in which the treated water is backwashed from the treated water side of the membrane to the raw water side, or the membrane is formed by air bubbles from an air nozzle provided below the membrane in the dipping tank. There are things such as cleaning the surface.

Further, when it is used for a certain period of time, suspended matters and the like enter the inside of the membrane and the effect of the above-mentioned cleaning is remarkably reduced, so that the membrane is cleaned using a cleaning chemical solution. In this case, the membrane is removed from the apparatus and immersed in the chemical cleaning tank in which the cleaning chemical is stored to clean the membrane with the chemical.

[0005]

However, the conventional chemical cleaning has the following problems. Since the membrane is removed from the membrane filtration device and immersed in the chemical cleaning tank, equipment such as a crane for moving and removing / attaching the membrane is required. In addition, since it takes time to remove and attach the work, the mobility of the membrane filtration device is lowered. further,
Since the membrane is immersed in the chemical cleaning bath for cleaning, a large amount of cleaning chemical is required, resulting in high cost.

The present invention has been made in view of the above-mentioned problems, and eliminates the need for equipment such as movement of the membrane, shortens the cleaning time, and can clean the membrane with a small amount of chemical liquid. To provide a device.

[0007]

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention is configured as follows. In the method for cleaning a membrane with a membrane immersed in a dipping tank in which raw water is stored, a membrane cleaning solution is supplied by supplying a membrane cleaning solution from the treated water side of the membrane. In this cleaning, the cleaning chemical may be permeated through the membrane, and then the supplied chemical may be switched to a small amount and flowed to the raw water side.

Further, in the immersion type membrane filtration device for filtering raw water with a membrane immersed in an immersion tank, a chemical solution supply means for supplying a chemical solution for cleaning to the membrane from the treated water side of the membrane is provided. The film was used as a chemical cleaning device for the film. It is preferable that the chemical liquid supply unit includes a large chemical liquid supply unit that supplies a large amount of cleaning chemical liquid and a small amount chemical liquid supply unit that supplies a small amount of cleaning chemical liquid.

[0009]

According to the present invention, the following operations are performed. The chemical liquid for cleaning is supplied to the membrane from the treated water side of the membrane by the chemical liquid supply means, and the chemical liquid permeates the membrane. This will wash the membrane. Further, in the case of having a large amount chemical liquid supply means and a small amount chemical liquid supply means, after the chemical liquid permeates the membrane, the chemical liquid to be supplied is switched to a small amount and flowed to the raw water side for washing. As a result, the chemical liquid flowing out to the raw water side can be kept small and the cleaning effect can be improved.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show an immersion type membrane filtration device 2 provided with a chemical liquid cleaning device 1 of this embodiment.

The submerged membrane filtration device 2 is roughly constructed by including a submerged tank 3 in which raw water is stored, and a membrane module 4 submerged in the raw water in the submerged tank 3. This membrane module 4 is a hollow fiber membrane 4a (hereinafter referred to as membrane 4a).
A large number of these are integrated, and they are placed side by side and two are arranged above and below. Each of the membranes 4a has both ends connected to each other, and both ends communicate with each other inside. This membrane 4a is a raw water membrane 4a.
Permeate from the outside (raw water side) to the inside (treated water side) of the membrane 4a to become permeated water (treated water).

Pipes 5 and 6 are connected to both ends of the membrane module 4, and the open / close valve V1 is connected to one pipe 6.
Is intervening. The pipes 5 and 6 are connected to each other on the membrane module 4 side of the on-off valve V1 provided on the pipe 6 via the on-off valve V4. The pipe 6 is further extended from the on-off valve V1 to form a permeate channel.

The chemical liquid cleaning apparatus 1 comprises a chemical liquid supply means 10 for supplying a cleaning chemical liquid to the membrane 4a from the inside of the membrane 4a, and a large capacity pump P1 for supplying a large amount of chemical liquid to the chemical liquid supply means 10. It is provided with (a large amount liquid medicine means) and a small capacity pump P2 (a large amount liquid medicine means) for supplying a small amount of liquid medicine. Further, the tip of the pipe 5 is bifurcated, and an opening / closing valve V2 is provided in one branch passage to form an air drainage passage, and an opening / closing valve V3 is provided in the other branch passage to drain chemical liquid. It is a road.

A pipe 7 is connected to a pipe 6 on the membrane module 4 side of the on-off valve V1, and a pump P3 for backwash water and an on-off valve V5 are connected in series to this pipe 7. There is. Further, a chemical tank 8 for storing a chemical liquid for cleaning the membrane 4a is provided, and a pipe 9 is provided from the chemical tank 8 toward the pipe 7. A pump P1 is installed in series in the pipe 9, and the pump P1
A pump P2 is connected in parallel with. These pumps P
An on-off valve V6 is interposed between the pipes 1 and P2 and the pipe 7.

Next, the operation of the submerged membrane filtration device 2 and the membrane 4a.
The cleaning method and the chemical cleaning method will be described.

First, referring to FIGS. 4 (a) and 4 (b), a case where a normal filtration step is performed by the immersion type membrane filtration device 2 of the present embodiment will be described.

That is, the pumps P1, P2, P3 are stopped, the opening / closing valves V2, V3, V5, V6 are closed, and the opening / closing valves V1, V4 are opened. When a suction pump (not shown) provided in the permeate channel is operated, raw water permeates from the outside of the membrane 4a through the membrane 4a to the inside of the membrane 4a and is filtered. The permeated water inside the membrane 4a is stored in a permeated water tank (not shown) through the permeated water passage.

In this way, after the filtration step has passed a predetermined time (for example, a filtration time of 30 to 60 minutes), the back washing step is performed for a predetermined time (for example, 3 times) in order to eliminate clogging of the membrane 4a.
(0 to 60 seconds).

That is, the pumps P1 and P2 are stopped, the pump P3 is driven, and the on-off valve V
1, V2, V3, V6 are closed and the on-off valve V
Open V4 and V5. As a result, the backwash water is pumped into the inside of the membrane 4a by the pump P3, flows out from the inside of the membrane 4a toward the outside, and the clogging of the membrane 4a is eliminated. As the backwash water, the permeated water from the above-mentioned permeated water tank is usually used, but water from another backwash water tank may be used.

Further, since air may accumulate in the pipe, an air venting process is provided. This puts the pumps P1 and P2 into the stopped state, puts the pump P3 into the driven state, closes the on-off valves V1, V3, V4 and V6, and opens the on-off valves V2 and V5. Thereby, the permeated water from the permeated water tank circulates and the air in the pipe is removed.

If filtration is carried out for a long time (for example, one month to several months) by the immersion type membrane filtration device 2, the clogging of the membrane 4a cannot be eliminated even by back washing, so that a cleaning chemical solution is used. The chemical cleaning step that was performed previously is performed. This chemical cleaning step will be described with reference to FIGS.

First, the pumps P2 and P3 are stopped,
The on-off valves V1, V2, V3, V4 and V5 are closed, and the on-off valve V6 is opened. When the pump P1 is driven, as shown in FIG. 1A, the chemical liquid in the chemical liquid tank 8 is supplied into the inside of the membrane 4a through the pipes 9 and 6. The supplied chemical solution permeates from the inside of the film 4a into the inside of the film 4a, and dissolves suspended substances and the like that are clogged inside the film 4a.

Next, the pumps P1 and P3 are stopped,
When the pump P2 is driven, the chemical liquid is pushed into the inside of the membrane 4a of the membrane module 4 as shown in FIG.
As shown in, the chemical solution flows out from the inside of the film 4a to the outside through the inside of the film 4a. At this time, turbid substances and the like that have entered the inside of the film 4a are almost completely removed.

When the pump P2 is driven for a certain time,
The pumps P2 and P3 are stopped, the pump P1 is driven, and the on-off valve V3 is opened. As a result, as shown in FIG. 3A, another chemical solution stored in the chemical solution tank 8 is pressure-fed into the membrane of the membrane module 4 and is discharged to the outside through the on-off valve V3 to replace the chemical solution. Done.

When the chemical cleaning step is completed in this way, the process proceeds to the normal filtration step. However, since the inside of the membrane 4a is still filled with the chemical liquid, the permeated water mixes with the permeated water in the initial stage of the normal filtration process, so the permeated water in the initial stage of the filtration process cannot be put into the permeated water tank. Then put it in another tank.

An appropriate type of chemical solution is used depending on the type of membrane and the type of clogging substance, and sodium hydroxide solution, hydrochloric acid solution, sodium hypochlorite solution, etc. are used. Further, one kind of chemical solution may be used, or plural kinds of chemical solutions may be divided into two stages and used. In this case, it is preferable that the alkaline chemical solution is first introduced, and then the acid chemical solution is introduced.

According to the chemical cleaning device and the chemical cleaning method for the membrane 4a of the present embodiment, the chemical is filled inside the membrane 4a of the membrane module 4 with the chemical for cleaning, and the filled chemical is filled in the membrane 4a.
Since the membrane 4a is washed out by flowing out from the inside to the outside of the membrane 4a, the clogging of the membrane 4a can be almost completely washed by using an appropriate chemical solution. Moreover, it is not necessary to remove the membrane module 4 since the membrane 4a installed in a ready-to-use state is only filled with the chemical liquid and washed, and the period of suspension of the submerged membrane filtration device 2 is minimized. You can

As shown in FIG. 5, a plurality of water channels (seven sets in the figure) may be provided in parallel as in the above embodiment.

The present invention is not limited to the above embodiment,
For example, a flat membrane, a spiral membrane, a tubular membrane, or the like may be used instead of the hollow fiber membrane. Further, the chemical liquid supply means may be a single pump whose flow rate can be changed, or may be a combination of a fixed amount of metering pump and a flow rate control valve. Further, the chemical solution may be supplied by only one pump, or the chemical solution may be circulated through the membrane.

[0030]

Since the present invention is constructed as described above,
It has the following effects. Since the cleaning chemical is supplied to the membrane from the treated water side of the membrane for cleaning, the membrane can be cleaned while being immersed in the immersion tank. Therefore, equipment for moving and removing / attaching the membrane, such as a crane, becomes unnecessary. In addition, since the time required for the removal / attachment work is unnecessary, the mobility of the device is improved. Furthermore, since the amount of chemical used for cleaning is the amount supplied to the membrane, a small amount of chemical is required compared to dipping the membrane in the chemical cleaning tank for cleaning.
Can be low cost.

Further, after the chemical solution has penetrated into the membrane, the chemical solution to be supplied is switched to a small quantity to flow to the raw water side for cleaning, so that the chemical solution flowing out to the raw water side can be suppressed to a small quantity and the cleaning effect is improved. be able to.

[Brief description of drawings]

FIG. 1 is a diagram showing one step of a chemical cleaning device for a membrane and a chemical cleaning process using the same according to an embodiment of the present invention.

FIG. 2 is a diagram showing one process of a chemical cleaning process using the chemical cleaning device for the membrane of FIG.

FIG. 3 is a diagram showing one process of a chemical cleaning process using the chemical cleaning device for the membrane of FIG.

FIG. 4 is a diagram showing a normal filtration process by a membrane filtration device provided with the membrane chemical cleaning device of FIG. 1.

FIG. 5 is a diagram showing a chemical cleaning device for a membrane according to another embodiment of the present invention.

[Explanation of symbols]

 1: Chemical solution cleaning device 2: Immersion type membrane filtration device 3: Immersion tank 4: Membrane module 4a: Hollow fiber membrane (membrane) 5,6: Piping 10: Chemical solution supply means V1, V2, V3, V4, V5, V6 Open / close Valve P1: Pump (Means for large amount of liquid medicine) P2: Pump (Means for small amount of liquid medicine) P3: Pump

Claims (4)

[Claims] 1. A method for cleaning a membrane immersed in an immersion tank in which raw water is stored, wherein the membrane is supplied with a cleaning solution from the treated water side of the membrane for cleaning. A method of cleaning a membrane with a chemical solution in a membrane filtration device. 2. The immersion type membrane filtration device according to claim 1, wherein, in cleaning the membrane, after the cleaning chemical is permeated into the membrane, the supplied chemical is switched to a small amount and flowed to the raw water side. Method for cleaning membrane in. 3. An immersion-type membrane filtration device for filtering raw water with a membrane immersed in an immersion tank, comprising a chemical solution supply means for supplying a cleaning chemical solution to the membrane from the treated water side of the membrane. A chemical cleaning device for a membrane in an immersion type membrane filtration device. 4. The chemical liquid supply means comprises a large chemical liquid supply means for supplying a large amount of cleaning chemical liquid and a small chemical liquid supply means for supplying a small amount of cleaning chemical liquid. A membrane chemical cleaning device in the immersion type membrane filtration device described.