JP5096765B2 - Membrane filtration device backwashing method - Google Patents

Description

The present invention, which relates to the backwash process of membrane filtration apparatus, particularly to an improvement of such shortening and wash water savings backwash time.

  The principle of backwashing of the membrane filtration apparatus will be described with reference to FIG. 3. During the filtration operation, raw water a is fed from the raw water tank 10 through the feed pipe 14 into the primary chamber 11 of the casing 1 a containing the filtration membrane 13. Filtration is performed, and a circulation path is formed in which the remainder is returned to the raw water tank 10 as the return raw water b through the return pipe 15. During this time, the filtered water c that has passed through the filtration membrane 13 is taken out from the secondary chamber 12 through the intake pipe 16 to the outside.

  As this filtration operation proceeds, a filter cake on the membrane surface on the primary chamber 11 side accumulates, and the filtration performance decreases sequentially, so membrane cleaning is performed to remove the cake layer at an appropriate time. In this membrane cleaning, the cleaning water d is supplied to the secondary chamber 12 and the filter cake 13 is passed through the filter membrane 13 toward the primary chamber 11 to peel off the filter cake deposited on the membrane surface on the primary chamber 11 side. In this case, back pressure cleaning for removing (hereinafter referred to as back cleaning) is used. In this case, it is also preferable to add and use chemical components such as acid, alkali, ozone, and hypochlorite in the washing water.

Such, regarding the backwash process of membrane filtration units, many improvements have been made. For example, the applicant of the present invention has also proposed a backwashing method as shown in Patent Document 1. That is, a permeation step in which cleaning water containing cleaning chemical components is introduced to the filtrate side of the membrane filtration device, and this washing water is infiltrated to the membrane surface in contact with the cake layer of the membrane. A holding step for stopping the movement and holding this permeation state for a predetermined time, and a back washing step for removing the cake layer from the filtration membrane with washing water that does not contain washing chemical components, removing the cake layer, and washing with back pressure after the holding step is completed. This is a backwashing method to be performed, which can improve the cleaning effect and reduce the amount of cleaning chemical components used. (See Patent Document 1)

JP 2002-52321 A: Claims, paragraph 0016, FIG.

  In such a backwashing method, the filtration operation is stopped and the flow of the filtrate water c in the intake pipe 16 is switched to the flow of the wash water d. In the case of an actual membrane filtration apparatus, a filtration membrane is used. A module is formed by arranging a large number of casings containing the components. For example, as shown in FIG. 3, the casings 1 a, 1 b, 1 c,... Are arranged in a row and are connected to a common intake pipe 16. Since the cleaning water d is fed from the front end of the water intake pipe 16 during backwashing, the casing 1b and the casing 1c are arranged in this order from the casing 1a at the foremost position as viewed from the feeding direction of the washing water d. The backwashing start timing is sequentially delayed as going backward.

  Therefore, in the case of a module composed of many casings, the backwashing of the casing 1a at the foremost position will take an excessive amount of time when the backwashing of the casing at the last position is completed. The washing time takes longer than the back washing time of a single casing, and as a result, there is a problem that a considerable amount of washing water and contained chemical components are wasted. Further, since the actual membrane filtration apparatus is composed of a unit in which several such modules are arranged and assembled, there is a problem in that the start timing of the backwash is further delayed and waste is increased.

The present invention has been made to solve the above-mentioned problems, and in the case of an actual membrane filtration apparatus in which a module is configured by arranging a large number of casings containing filtration membranes in parallel, start of backwashing It is an object of the present invention to provide a backwashing method for a membrane filtration device that eliminates timing delay, shortens backwashing time, and saves washing water and chemical components .

1st invention made in order to solve said subject is a diameter size rather than the said connecting pipe connected to each casing in order to take out filtrated water from the several filtration membrane built-in casing arranged in parallel through a connecting pipe. A backwashing method of a membrane filtration device that introduces backwashing water into a large header pipe and backwashes it. After draining the filtrate water held in the header pipe and emptying the header pipe, Supplying and filling backwash water containing a chemical component selected from acid, alkali, ozone, hypochlorite , and then introducing the wash water into each casing at the same time. is there.

Moreover, the 2nd invention made | formed in order to solve said subject is more than the said connection pipe connected to each casing in order to take out filtrated water through several connecting membrane built-in filtration membranes and a connection pipe in parallel. A method for backwashing a membrane filtration apparatus, comprising a plurality of modules each having a module header pipe having a large diameter, and a unit header pipe connected to each of the plurality of module header pipes. And draining the filtered water held in the unit header pipe to empty the header pipe, and then backwashing water containing a chemical component selected from acid, alkali, ozone and hypochlorite. It is characterized in that it is supplied and filled, and then the washing water is simultaneously introduced into each casing.

In the backwashing method of the membrane filtration apparatus according to the first invention of the present invention, the chemical components selected from acid, alkali, ozone and hypochlorite are provided in the header pipe connected to each casing described above during backwashing. After the backwash water containing water is filled, the wash water is introduced into each casing at the same time. The advantage that the back washing time is minimized is obtained, and the advantage that the washing water and chemical components are also required in a minimum amount is obtained.

  Further, in the backwashing method of the present invention using the membrane filtration device in which the header pipe is positioned higher than the casing and horizontally, when the retained water in the header pipe is discharged during the backwash operation. In addition, since the filtered water staying in the casing can be maintained in a full water state, there is no inconvenience of entraining air during backwashing. Further, when the cleaning water for backwashing is sent after emptying the header pipe, each casing can be filled with cleaning water having a predetermined concentration in a short time, so that the total cleaning time can be further shortened. Benefits are gained.

The membrane filter backwashing method according to the second aspect of the present invention comprises a module comprising a plurality of filtration membrane built-in casings arranged in parallel as described above, and a unit comprising a plurality of them arranged in parallel. In the membrane filtration device, after discharging the retained water in the module header pipe that is connected to each of the casings and aggregates filtrate water in module units, and the unit header pipe that aggregates the plurality of module header pipes in unit units, The backwash water containing chemical components is fed to each module header pipe through the unit header pipe to fill it, and then the wash water is introduced into each casing at the same time. Because there is no delay in the start of backwashing and water can be supplied at a predetermined concentration, the backwashing time can be minimized. Additionally, wash water, the advantage that the chemical components even minimal amounts obtained.

Incidentally, a common header pipe connected to a plurality of filtration membrane built casing altitude than the casing, and while disposed horizontally, if only set a drainage tube at the end portion of the header tube, During backwashing, the filtered water staying in the header pipe can be discharged through the drain pipe, so that the washing water for washing can be smoothly fed and filled. And if it pressurizes in that stage, it will become possible to introduce wash water into each casing at the same time, and the advantage in the backwashing method of the present invention that the backwashing start timing can be aligned without delay is obtained.

In particular, if a common header pipe is disposed at a higher position than the casing and in the horizontal direction, the retained water in the casing leaks through the header pipe when the filtered water is discharged through the drain pipe. As described above, there is no problem that air can be kept in a full water condition and air that becomes an obstacle to backwashing operation is not involved.

  As described above, according to the present invention, in the backwashing of the membrane filtration of the actual machine composed of a unit in which a plurality of modules comprising a plurality of casings are further arranged in parallel, the backwashing time is minimized and the washing water and chemical components are also minimized. There is an excellent effect that the amount is sufficient. Therefore, the present invention has extremely great value as a backwashing method and a membrane filtration device for a membrane filtration device that has solved the conventional problems.

Next, an embodiment of the backwashing method of the membrane filtration device of the present invention will be described with reference to FIGS.

(First invention)
With reference to FIG. 1 which is a flowchart showing the concept of the membrane filtration device, the backwashing method of the membrane filtration device of the first invention will be described .
The flowchart of this membrane filtration device is basically similar to that described in FIG. That is, a feed pipe 41 that feeds raw water a from the raw water tank 2 is disposed in the primary chamber 31 of the raw water tank 2 and the filtration membrane built-in casing 3, and is returned to the raw water tank 2 at the other end of the primary chamber 31. A return pipe 42 for returning the raw water b is disposed. The raw water a sent into the primary chamber 31 is filtered by the filtration membrane 33 and becomes filtered water c and moves into the secondary chamber 32. The remaining raw water is returned to the raw water tank 2 as return raw water b, and constitutes a circulation channel.

The filtered water b moved to the secondary chamber 32 is sent to the header pipe 5 through the intake branch pipe 51 and can be taken out from the intake pipe 52 connected to one end of the header pipe 5.
In this case, the cross flow filtration in which the raw water circulates is described as an example, but the present invention is similarly applied to the case of dead end filtration in which the flow path is blocked by a filtration membrane. Of course.

  When the filter cake is deposited on the membrane surface on the primary chamber 31 side as the filtration proceeds, the filtration operation is stopped, and the washing water d is supplied to the secondary chamber 32 via the header pipe 5 and filtered. It is the same as the case of FIG. 3 in that backwashing is performed to peel and remove the deposited filter cake by passing through the membrane 33.

  In addition, the header pipe is generally a thick pipe (pipe) or body used when branching a main pipe through which a fluid such as a liquid is branched into a large number of branch pipes at a time, or when joining a large number of branch pipes at a time. It is also called a pipe header, header, and pipe distributor. In boilers, heat exchangers, engines, etc., the header pipe is a fluid distribution mechanism that is often used. The header pipe has a sufficiently large diameter compared to the branch pipe size, so that the flow rate distributed to the branch pipe can be reduced. There is an averaging function.

  The first of the features of the present invention is intended for an actual apparatus of a filtration device in which a plurality of casings are arranged in parallel, such as the illustrated filtration membrane built-in casings 3a, 3b, and 3c. It is connected to the common header pipe 5 through the connecting pipes 51a, 51b, 51c, and the header pipe 5 joins and removes the filtered water c, or distributes the washing water d for backwashing to each secondary chamber. It is configured to serve a purpose. In this example, three casings are shown, but the present invention is not limited to this number of casings.

  The second feature of the present invention is that, in the relationship between the casing 3 and the header pipe 5 thus configured, the header pipe 5 is disposed at a higher position than the casing 3 in the horizontal direction, A drain pipe 53 having an opening / closing valve (not shown) capable of discharging the liquid inside is provided at the end portion of the header pipe 5. In this case, it is preferable to provide an air vent pipe 54 provided with an opening / closing valve (not shown) for circulating air to the end portion of the header pipe 5.

The backwashing method of the first invention of the present invention can be preferably put into practical use with such a membrane filtration device. That is, the main point of the first invention is that when the membrane filtration apparatus is backwashed, the header pipe 5 is filled with the backwashing washing water d containing a chemical component selected from acid, alkali, ozone and hypochlorite. Then, the cleaning water d is simultaneously introduced into each casing 3a, 3b, 3c.
Specific procedures for this method include the following backwashing 1) and backwashing 2). Backwashing 1) is a reference embodiment, and backwashing 2 is an embodiment of the present invention.

Backwashing 1): a) During backwashing, the filtration operation is stopped and the drainage from the intake pipe 52 is stopped. In this case, the inside of each casing is kept full.
b) Next, backwash water d containing chemical components is fed into the header pipe 5 from the intake pipe 52, and at the same time, the filtered water in the header pipe 5 is extracted from the drain pipe 53 at the end to backwash the inside of the pipe. Replace with washing water d and fill.
c) Next, the inside of the header pipe is pressurized, the washing water d is sent into the secondary chamber of each casing, and the filtration membrane is passed in the reverse direction for washing. Control of feeding the washing water d is performed by adjusting the pressure in the header pipe and the casing.

Backwash 2): a) Same as above.
b) Next, the filtered water in the header pipe 5 is extracted from the drain pipe 53 at the end to empty the header pipe 5. Thereafter, backwashing water d containing chemical components is fed from the intake pipe 52 into the header pipe 5 to fill the pipe with the backwashing water d. In this case, it is carried out while venting air from the air vent pipe 54.
c) Same as 1).

In backwashing 1) and 2), the advantage of the present invention that washing water can be simultaneously fed into each casing from the header pipe is obtained. In backwashing 1), when cleaning water is fed into the header pipe, it is mixed with the filtered water held inside, and the concentration of chemical components decreases, so it takes a little time to fill the cleaning water with a predetermined concentration. Although there is such a problem , in the backwashing 2) which is an embodiment of the present invention , since filtered water discharge and washing water filling are separated, there is no delay due to mixing, and as a result, the point that can be filled in the shortest time is improved. Has been.

  As described above, the first invention can be embodied. In the present invention, in the backwashing, the header pipe 5 connected to each of the plurality of filtration membrane built-in casings 3a, 3b, 3c is used for backwashing. After the washing water d is filled, the washing water is introduced into each casing at the same time, so that there is no delay in the start of backwashing as has occurred in the past, so the backwash time of the entire casings There is an advantage that a minimum amount of time and a minimum amount of washing water are required.

  Specifically, the action and effect are illustrated by the time required for backwashing of a membrane filtration device (one module) in which 10 filtration membrane built-in casings are arranged in parallel and a common header pipe is disposed (stopping filtration operation to backwashing end). If the conventional example (case where the washing water is sequentially fed into the casing) is 100, the backwashing 1) is 92 and the backwashing 2) is 83, which can greatly reduce the time. It was. In addition, since the amount of washing water used is proportional to the washing time, the washing water and chemical components in the present invention can be reduced to a minimum amount of about 80% to 90% compared to the conventional method.

  Furthermore, in the present invention, since the membrane filtration device in which the header pipe 5 is disposed higher than the casings 3a, 3b, and 3c and in the horizontal direction is used, the water retained in the header pipe 5 during backwashing operation. Since the level of the filtered water staying in the casing when it is discharged can be maintained at a full level, there is no inconvenience of involving air in the backwash water.

  The fact that the header pipe is disposed at a height higher than the casing and horizontally is, as is apparent from this description, that the retained water in the header pipe 5 is discharged and the filtered water staying in the casing 3 is discharged. This is in order to maintain a full water state without being accompanied and drained, and the height here may be a minimum height at which this purpose is achieved.

(Second invention)
An embodiment of the present invention will be described with reference to FIG. 2. First, a unit composed of a plurality of filtration membrane built-in casings 3A arranged in parallel and a module header pipe 5A connected to each casing is referred to as a module. A unit of a membrane filtration device having a unit header pipe 6 connected to each of the module header pipes 5A and 5B of the plurality of modules arranged in parallel is referred to as a unit. This is a backwashing method for a membrane filtration device composed of units, which is an actual machine used in the above.

  In this case, after the backwash operation, the retained water in the module header pipes 5A and 5B and the unit header pipe 6 is discharged, and then backwashed from the water intake pipe 62 to the header pipes 5A and 5B through the unit header pipe 6. After the cleaning water d is supplied and filled, the cleaning water is simultaneously introduced into the casings 3A and 3B. In this example, two sets of modules are shown, but the present invention is not limited to this number of modules.

  Further, the backwashing washing water d is preferably fed first so that the unit header pipe 6 is filled and then filled into the respective module header pipes 5A and 5B. In 1), there is a method in which washing water is sent simultaneously while draining filtered water, and 2) a method in which washing water is sent after draining filtered water to empty the unit header pipe once. Hereinafter, in order to fill the module header pipes 5A and 5B, the method of backwashing 1) and 2) explained in the case of the first invention explained above is adopted.

  The backwashing method for the membrane filtration device according to the second aspect of the invention is an actual membrane filtration device comprising a unit in which a plurality of modules comprising a plurality of filtration membrane built-in casings 3A and 3B arranged in parallel as described above. In the case of backwashing, the retained water in the module header pipes 5A and 5B that are connected to the respective casings and collect the filtered water in module units, and the unit header pipe 6 that collects the plurality of module header pipes in unit units. In the case of the first invention, the washing water for backwashing is supplied to the module header pipes 5A and 5B through the unit header pipe 6 to be filled, and then the washing water is simultaneously introduced into each casing. Similarly, there is no delay in the start of backwashing, and the same quality of wash water can be supplied, so the backwash time is minimal and the wash water is minimal. Mutoyuu advantages are obtained.

  Specifically, the operation and effect are illustrated by the time required for backwashing of one unit of a membrane filtration device in which three modules with built-in filtration membranes are arranged in parallel and a common unit header pipe is arranged (stop of filtration operation to end of backwashing). If the conventional example (case where the washing water is sequentially sent from the unit header pipe to each casing through the module header pipe) is set to 100, the backwashing method (filtered water discharge and washing water filling) of the second invention is used. In the case of separated backwash), it was 41, and it was possible to significantly reduce the time for the reduction rate to reach about 60%. In addition, since the amount of cleaning water used is proportional to the cleaning time, the present invention requires only a minimum amount of cleaning water and chemical components of about 40% compared to the conventional method, and further increases the number of parallel modules. , Proved effective.

Flowchart (conceptual diagram) for explaining the first and second embodiments of the present invention Flowchart (conceptual diagram) for explaining the third embodiment of the present invention. Flow chart for explaining backwash operation (conceptual diagram)

2: Raw water tank 3: Filtration membrane built-in casing, 3a, 3b, 3c: Filtration membrane built-in casing, 31: Primary chamber, 32: Secondary chamber, 33: Filtration membrane 41: Feed pipe, 42: Return pipe 5: Header pipe, 51a, 51b, 51c: Connection pipe, 52: Intake branch pipe, 53: Drain pipe, 54: Air vent pipe a: Raw water, b: Return raw water, c: Filtration water, d: Wash water

Claims (2)

In order to take out filtrated water from a plurality of casings with built-in filtration membranes in parallel through connecting pipes, reverse washing water is introduced into the header pipe having a diameter larger than the connecting pipe connected to each casing. A method of backwashing a membrane filtration device for washing, wherein drainage of filtered water held in the header pipe is emptied and then the header pipe is emptied, and then selected from acid, alkali, ozone, and hypochlorite. A backwashing method for a membrane filtration device, comprising supplying backwashing water containing a chemical component, filling the casing, and then introducing the washing water into each casing at the same time. A plurality of modules having a plurality of filtration membrane built-in casings in parallel and a module header pipe having a larger diameter than the connection pipe connected to each casing in order to take out filtrated water through the connection pipe, A backwashing method for a membrane filtration device provided with a unit header pipe connected to each of the plurality of module header pipes, wherein the filtered water held in the module header pipe and the unit header pipe is discharged. After the header tube is emptied, it is filled with backwash water containing a chemical component selected from acid, alkali, ozone, and hypochlorite , and then the wash water is simultaneously introduced into each casing. A method for backwashing a membrane filtration device.

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