JP4360057B2 - Immersion membrane filtration apparatus and immersion membrane filtration method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a submerged membrane filtration apparatus and a submerged membrane filtration method for obtaining a filtrate by subjecting a liquid to be treated stored in a storage tank to filtration treatment by a submerged membrane filtration method. The filtration efficiency of the tubular membrane module used in the submerged membrane filtration device and the submerged membrane filtration method is reduced by the flow of the liquid to be treated being inhibited before it is reduced by the cake layer adhering to the inner surface of the tubular filtration membrane. It is related to the fact that it is prevented from doing.
[0002]
[Prior art and its problems]
In recent years, a cross-flow filtration method in which a membrane module is immersed in a liquid to be treated and filtered while utilizing the buoyancy of air bubbles has come to be used in various fields as an energy-saving precision filtration method for highly polluted liquids. Such a filtration method is described in, for example, Japanese Patent Application Laid-Open No. 61-129094. This filtration method is also referred to as a submerged membrane filtration method, and a membrane module used for this is also referred to as a submerged membrane module. A hollow fiber membrane module or a flat membrane module immersed in a liquid to be treated has been used. Similarly, a hollow fiber membrane module or a flat membrane module is also used in a filtration method in which a membrane module is immersed in a liquid to be treated and filtered by a head differential, and an energy saving and low cost filtration method that replaces the conventional sand filtration method. However, such a filtration method is also referred to as a submerged membrane filtration method, and a membrane module used for this method is also referred to as a submerged membrane module.
[0003]
The cross-flow filtration method and the filtration method and the ultrafiltration method for filtering by the water head difference are that the former supplies the liquid to be processed to the membrane module by utilizing the buoyancy of the air bubbles and the water head difference, while the latter. Are different from each other in that the liquid to be treated is supplied to the membrane module using a mechanical circulation means such as a pump, and each is clearly distinguished.
[0004]
In the liquid to be treated, which is the object of the above-described immersion type membrane filtration method, various contaminants are mixed, and in order to operate the membrane module used for this for a long period of time with good filtration efficiency, It is necessary to remove large contaminants in advance or remove the cake layer adhering to the membrane surface by backwashing so that the flow path of the treatment liquid is not blocked. When a flat membrane module is used for this membrane module, the flow path of the liquid to be processed having the same width can be secured, and the flow path of the liquid to be processed is blocked without removing large impurities in advance. However, it is difficult to give strength enough to withstand backwashing, and when a hollow fiber membrane module is used, backwashing can be performed using the pressure resistance of the hollow fiber membrane. Since the gap with the membrane becomes the flow path of the liquid to be treated, the flow path of the liquid to be treated is blocked if the large impurities are not removed in advance, and the filtration efficiency is lowered at an early stage. It has been substantially difficult to perform a submerged membrane filtration method stably for a long period of time using a module or a hollow fiber membrane module.
[0005]
On the other hand, although it is speculated, the tubular filtration membrane module has many advantages over the flat membrane module and the hollow fiber membrane module. That is, (1) all air flows can be used to increase the parallel flow of the cross flow, and (2) the mass transfer coefficient is another type of module because the passage of bubbles and liquid to be treated is cylindrical. In principle, the flux (filtering flow rate per unit membrane area) can be increased, and (3) the module itself can be made compact because the membrane itself forms the passage of bubbles and liquid to be processed, (4) Since the inner diameter is much larger than that of the hollow fiber membrane, the pressure loss is small and the effect of backwashing can be increased. However, regarding the application of the tubular filtration membrane module to the submerged membrane filtration method, the liquid to be treated to which the submerged membrane filtration method is applied contains various contaminants. Special attention was not paid because it was expected to block.
[0006]
In view of the circumstances described above, the object of the present invention is to provide a simple method for preventing the tubular filtration membrane itself from being clogged with impurities when the immersion membrane filtration method is realized using a tubular filtration membrane module. Therefore, the submerged membrane filtration method using the tubular filtration membrane module can be efficiently performed over a long period of time.
[0007]
[Means for Solving the Problems]
That is, the submerged membrane filtration device according to claim 1 is for obtaining a filtrate by subjecting a liquid to be treated stored in a storage tank to a filtration treatment by a submerged membrane filtration method. The tubular filtration membrane module includes at least a plurality of tubular filtration membranes having a function of filtering a liquid to be treated on the inner surface thereof, and the both ends are held in the tubular storage container. The air bubble supply device is arranged in the storage tank so as to open both ends in the vertical direction, and the air bubble supply device guides the air bubble toward the tubular filtration membrane module. And the tube is disposed below the tubular filtration membrane module so that the liquid to be treated flows and is filtered upward from below the tubular filtration membrane module by the air bubbles, and the tubular filtration membrane module is opened. A lid body that allows air bubbles to pass therethrough and closes the air bubbles by closing is disposed above, so that the lid body is closed and the air bubbles are once inside the tubular filtration membrane. Since the air bubbles trapped in the guide tube can be made to flow out at once by opening the lid, it is possible to let the trapped air bubbles flow out all at once. You can push things out at once.
[0008]
Also, The present invention Submerged membrane filtration equipment In place The air bubble generating device has substantially the same size and shape as the inner periphery in the cross section perpendicular to the axial direction of the guide cylinder, and has an ejection hole that opens and closes by the pressure of the air bubbles over the entire surface. And having a surface nozzle made of rubber elastic body Is preferred Thereby, air bubbles can be supplied evenly to all the tubular filtration membranes.
[0009]
Also, The present invention Submerged membrane filtration equipment In place The guide tube has a mesh filter for introducing the liquid to be treated into the inside. Is preferred As a result, it is possible to prevent foreign matters from flowing into the guide tube, and once the lid is closed and air bubbles are once trapped inside the tubular filtration membrane and inside the guide tube, the cover is passed through the mesh filter. The treatment liquid flows backward, and impurities accumulated on the mesh filter can be removed.
[0010]
Also, The present invention Submerged membrane filtration equipment In place The tubular membrane filter module has a discharge port through which the container discharges the filtrate, and has a filtrate discharge path extending from the discharge port. Is preferred, In the tubular filtration membrane module, the storage container has a cylindrical water collection pipe having an inlet for introducing the filtrate and a discharge outlet for discharging the filtrate with a space inside, and a plurality of the tubular filtration membranes are interposed therebetween. Has a filtrate discharge path that contains and extends from the outlet Is preferred Thus, the filtrate can be smoothly discharged through the storage container or the water collecting pipe.
[0011]
further, The present invention The immersion membrane filtration method of Using the immersion membrane filtration device of the present invention, A submerged membrane filtration method for obtaining a filtrate by subjecting a liquid to be treated stored in a storage tank to a filtration process by a submerged membrane filtration method. A tubular filtration membrane module in which a book is housed in a cylindrical storage container and both end portions are held is disposed in the storage tank so that both end portions are opened in the vertical direction. A normal filtration step of supplying air bubbles from the bottom and filtering the liquid to be processed from below the tubular filtration membrane, and a filtration suspension step of stopping the filtration of the liquid to be processed by blocking the flow of the air bubbles, And a filtered component removing step of removing the filtered component accumulated in the tubular filtration membrane module by resuming the flow of the blocked air bubbles, thereby temporarily filtering the air bubbles in the filtration pause step. Confined inside the membrane and in the guide tube In addition, since the trapped air bubbles can be made to flow out at a stroke in the filtration separation component removing step, it is possible to extrude foreign matters staying below the tubular filtration membrane, particularly those in the form of long fibers. .
[0012]
Also, The present invention The submerged membrane filtration method is , Yield The storage container has a discharge port for discharging the filtrate, and further includes a backwashing step of backflowing the filtrate discharged from the discharge port into the storage container through the discharge port while pressurizing the filtrate. Is preferred , The present invention The submerged membrane filtration method is , Yield The storage container has a water collection pipe having an inlet for introducing filtrate and a discharge outlet for discharging the filtrate, and is arranged on the inner side with a space between them, and pressurizing the filtrate discharged from this outlet into the storage container through the outlet. It further includes a backwashing process for backflow. Is preferred Thus, even if the air bubbles are once confined in the inside of the tubular filtration membrane and the guide tube in the filtration suspension step, and the trapped air bubbles are discharged at a stroke in the filtration component removal step, the bottom of the tubular filtration membrane When the foreign matter staying in the filter cannot be pushed out, it can be removed and the cake layer adhering to the inner surface of the filtration membrane can also be removed.
[0013]
Also, The present invention The submerged membrane filtration method is , Through Introducing a filtration pause process and a filtration component removal process in the normal filtration process Is preferred As a result, it is possible to push out foreign substances staying below the tubular filtration membrane by a simple method.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a schematic configuration of an immersion membrane filtration system in which an immersion membrane filtration apparatus according to an embodiment of the present invention is employed.
[0015]
In FIG. 1, the submerged membrane filtration system 46 includes a submerged membrane filtration device 2 mainly including a tubular filtration membrane module 5 and an air bubble supply device 9 in a storage tank 30 in which a liquid to be treated 31 is stored. Soaked.
[0016]
The storage tank 30 is formed in a container shape having an opening in the upper part, and a liquid to be treated 31 is stored therein.
[0017]
As shown in the partially cutaway longitudinal sectional view of FIG. 2, the tubular filtration membrane module 5 includes, for example, a cylindrical storage container 4 made of a resin member and a plurality of the containers filled in the storage container 4. The tubular filtration membrane 3 has a filtration function of the liquid 31 to be treated on the inner surface, and the liquid 31 to be treated is introduced into the tubular filtration membrane 3 from the lower inlet 12 together with the air bubbles 14. The liquid to be treated (filtered) after flowing through the inner liquid flow path 20 to the upper outlet 13 is filtered, and the liquid to be treated (filtrate) passes through the liquid treatment channel 21 outside the tubular filtration membrane 3. It is comprised so that it may discharge | emit from the discharge port 6 of the storage container 4 side surface.
[0018]
The plurality of tubular filtration membranes 3 are formed in an elongated cylindrical shape, and the respective tubular filtration membranes 3 are not in close contact with each other by projections on the outer periphery (not shown), that is, spaced from each other, The upper and lower ends of the container 4 are densely gathered in parallel along the upper and lower opening directions of the storage container 4, and the upper and lower ends thereof are opened by the holding portions formed using a resin material such as urethane resin. Is maintained and fixed integrally with the storage container 4. As a result, both end portions of the storage container 4 are liquid-tightly closed by the holding portion.
[0019]
The tubular filtration membrane 3 described above has a filtration function of the liquid 31 to be treated on the inner surface, and in order to ensure the overall strength, the filtration membrane layer and the support membrane layer are sequentially formed from the inner peripheral surface side to the outer peripheral surface side. Although it has the two-layer structure provided and the kind of filtration membrane layer is not specifically limited, It can select suitably according to the kind of filtration separation component which should be removed from a to-be-processed liquid. For example, when it is necessary to remove fine particles such as microorganisms, a microfiltration membrane is used. For example, according to JIS K 3802, a microfiltration membrane is defined as a membrane used for separating fine particles of about 0.01 to several μm and microorganisms by filtration, but here, it is practical at a pressure of 20 kPa or less. It is preferable to use a porous organic polymer membrane such as a cellulose membrane or a polyolefin resin membrane having a large number of micropores having a pore size larger than 0.04 μm that can be filtered smoothly. Moreover, a support membrane layer provides shape retention property with respect to the above-mentioned filtration membrane layer, and is for setting a filtration membrane layer to cylindrical shape. Various materials can be used as the supporting membrane layer as long as the porous material has liquid permeability, but usually the waist strength, excellent strength, excellent chemical resistance, and high heat resistance. In addition, it is preferable to use a nonwoven fabric made of polypropylene resin or polyester resin that is economical and particularly preferably a nonwoven fabric made of polyester resin.
[0020]
The tubular filtration membrane 3 as described above preferably has an inner diameter of 3 to 15 mm, more preferably 5 to 10 mm. When the inner diameter is less than 3 mm, the tubular filtration membrane 3 is likely to be clogged with various separation components and contaminants contained in the liquid to be processed, particularly when a liquid to be processed is filtered. Therefore, it may be difficult to continue the filtration process stably for a long period of time. On the contrary, when the inner diameter exceeds 15 mm, the number of tubular filtration membranes 3 that can be filled in the storage container 4 with a limited volume is reduced. Therefore, the filtration area per unit volume of the tubular filtration membrane module 5 is reduced. (Effective membrane area) is reduced. As a result, the filtration flow rate decreases, and it may be difficult to efficiently perform the filtration process of the liquid to be treated while downsizing the tubular filtration membrane module 5.
[0021]
Moreover, as for the tubular filtration membrane 3, ratio (A / B) of the thickness (A) represented by the sum of a support membrane layer and a filtration membrane layer and an outer diameter (B) is 0.025-0.1. Is preferable, and is more preferably set to 0.03 to 0.1. When this ratio is less than 0.025, the tubular filtration membrane 3 is easily crushed when pressure is applied to the tubular filtration membrane 3 from the outside. As a result, when a backwashing operation is performed by applying pressure to the tubular filtration membrane 3 from the outside in order to eliminate a cake layer made of a filtered component or the like deposited on the inner peripheral surface of the tubular filtration membrane 3, The filtration membrane is crushed and it becomes substantially difficult to backwash the tubular filtration membrane 3. In order to achieve a pressure resistance of 20 kPa or higher, this ratio is preferably set to 0.03 or higher. On the other hand, when this ratio exceeds 0.1, the filtration area (effective membrane area) per unit volume of the tubular filtration membrane module 5 becomes small. As a result, the filtration flow rate decreases, so that it is difficult to efficiently perform the filtration process of the liquid to be treated while downsizing the tubular filtration membrane module 5.
[0022]
Moreover, it is preferable that the height of the projections described above, that is, the protruding amount from the surface of the support film layer is 0.02 to 0.2 mm. When the height of the protrusion is less than 0.02 mm, the tubular filtration membranes 3 are likely to be in close contact with each other, and as a result, it may be difficult to increase the fluidity of the filtrate. On the other hand, when the thickness exceeds 0.2 mm, the number of tubular filtration membranes 3, that is, the number of tubular filtration membranes 3 that can be filled in the storage container 4 of the tubular filtration membrane module 5 is decreased. The filtration area per unit volume of the module 5 is reduced. As a result, the filtration flow rate decreases, so that it is difficult to efficiently perform the filtration process of the liquid to be treated while downsizing the tubular filtration membrane module 5. Note that the height of the protrusion can be appropriately selected according to the type of the liquid to be treated. For example, when the liquid to be treated has a relatively low filtration flow rate such as activated sludge liquid, it is preferable to set the protrusions low from the viewpoint of securing the filtration area. On the other hand, when the liquid to be treated has a relatively high filtration flow rate such as river water, it is preferable to set the protrusions higher from the viewpoint of improving the fluidity of the filtrate.
[0023]
For such a tubular filtration membrane 3, a tape-like composite membrane having a width of 2 cm, in which the filtration membrane layer is integrally laminated on the support membrane layer, is prepared, and the support membrane layer is formed on a mandrel having a diameter of 7 mm. It is produced by wrapping both ends in the width direction in a spiral manner so as to be on the surface, and ultrasonically welding the overlapping portion. Thus, the tubular filtration membrane 3 having an inner diameter of 7 mm and a wall thickness of 0.15 mm can be obtained, and the above-described protrusion can be formed by the overlapping portion.
[0024]
The method of producing the tubular filtration membrane module 5 using the tubular filtration membrane 3 described above is to heat seal both ends of the plurality of tubular filtration membranes 3 and fill the storage container 4 with uncured urethane resin. One end is immersed in the silicon mold, and left until the urethane resin is cured. And the other end also performs the same thing. Then, since the gap between the storage container 4 and the tubular filtration membrane 3 is closed, both ends of the closed tubular filtration membrane 3 are trimmed and aligned with the storage container 4. Thus, the tubular filtration membrane module 5 having a length of 375 mm and the number of the tubular filtration membranes 3 is produced.
[0025]
On the other hand, the air bubble supply device 9 is for supplying the air bubbles 14 to the tubular filtration membrane module 5 and, as shown in FIG. 1, below the tubular filtration membrane module 5 in the storage tank 30. Has been placed. The air bubble supply device 9 is opened and closed by a blower 41 that sends out air, an air supply pipe 42 that introduces the air into the liquid 31 to be treated in the storage tank 30, and the pressure of the air bubbles 14 generated by the introduced air. An air bubble generating device 43 comprising a sheet-like nozzle 7 made of a rubber elastic body having a jet port for carrying out the entire surface, and a guide tube 8 for guiding the air bubbles 14 toward the tubular filtration membrane module 5; The liquid to be treated 31 flows from below to above the tubular filtration membrane module 5 and is filtered by the air bubbles 14. The planar nozzle 7 has substantially the same size and shape as the inner periphery in a cross section perpendicular to the axial direction of the guide tube 8 so that the generated air bubbles 14 can be uniformly delivered to the tubular filtration membrane module 5. I have to.
[0026]
Further, the filtrate obtained by filtration is discharged to the outside from the discharge port 6 through the filtrate discharge path 44. In addition, in the thing of FIG. 1, it discharges | emits by the suction by the pump 40 provided in the filtrate discharge | emission path | route 44, However, It is also possible to discharge | emit by a head difference without using such a pump.
[0027]
The discharge port 6 is provided in the storage container 4 in FIG. 1, but the tubular filtration membrane module 5 is provided with the water collection pipe with the storage container 4 spaced inside, and the tubular filtration is provided therebetween. Assuming that a plurality of membranes 3 are accommodated, an inlet for introducing the filtrate and an outlet for discharging the filtrate are provided in the water collecting pipe, and the outlet is discharged from the outlet through the filtrate discharge path. Also good.
[0028]
Further, the tubular filtration membrane module 5 is provided with a lid 11 that allows the air bubbles 14 to pass therethrough and closes the air bubbles 14 so that the upper outlet 13 can be opened and closed.
[0029]
Further, the guide tube 8 is provided with a mesh filter 10 having a mesh opening of 7 mm for introducing the liquid 31 to be treated into the inside while preventing the inflow of long fiber-like impurities from the liquid 31 to be treated. Yes.
[0030]
Since the net-like filter 10 described above can prevent the inflow of long-filamentous impurities, it is possible to prevent such impurities from accumulating at the inlet 12 and to generate air bubbles generated by the planar nozzle 7. Since 14 can be reliably fed into the inside of the tubular filtration membrane 3, filtration can be performed with excellent filtration efficiency over a long period of time. In FIG. 1, the distance from the planar nozzle 7 to the inlet 12 is 250 mm.
[0031]
When impurities are accumulated at the inlet 12 and the filtration efficiency is lowered due to a long-term operation, the outlet 13 is closed by the lid 11, and the air bubbles 14 are formed inside the tubular filtration membrane 3 and in the guide tube 8. When the lid 11 is opened and the trapped air bubbles 14 are allowed to flow out at once, the foreign matter staying at the inlet 12 can be pushed out at once, and the filtration efficiency can be recovered. .
[0032]
Further, when the outlet 13 is closed with the lid 11 and the air bubbles 14 are trapped inside the tubular filtration membrane 3 and in the guide tube 8, the air bubbles 14 flow out into the storage tank 30 through the mesh filter 10, It is also possible to remove the long-fiber contaminants attached to the mesh filter 10 by the flow.
[0033]
Next, with reference to FIG. 1 and FIG. 2, the filtration operation of the to-be-processed liquid 31 using the above-mentioned immersion type membrane filtration apparatus 2, ie, the immersion type membrane filtration method, is demonstrated.
[0034]
First, the liquid 31 to be treated containing a filtered component such as a microgel, a colloid component, or a microorganism is supplied and stored in the storage tank 30. In this state, when air is supplied from the blower 41 via the air supply pipe 42, the air is ejected as air bubbles 14 from the planar nozzle 7. The air bubbles 14 rise in the liquid to be treated 31 while being guided by the guide cylinder 8, and are substantially from the inlet 12 of each tubular filtration membrane 3 included in the tubular filtration membrane module 5 to the liquid flow path 20 to be treated. Evenly supplied.
[0035]
The liquid 31 to be treated stored in the storage tank 30 by the buoyancy of the air bubbles 14 supplied to the tubular filtration membrane module 5 in this manner is shown in FIG. 1 and FIG. It passes through the liquid passage 20 to be treated in the filtration membrane 3 from the lower side to the upper side, exits from the outlet filtration module 5 to the outside of the tubular filtration membrane module 5, and returns to the treatment liquid 31. The liquid to be treated 31 is filtered when passing through the liquid flow path 20 to be treated, and the obtained filtrate is discharged from the outlet 6 through the filtrate discharge path 44 to the outside. Suction by 40 is performed. In addition, in FIG. 1, it discharges | emits by the suction | inhalation by the pump 40, However, It is also possible to discharge | emit by a head difference without using such a pump 40. FIG. In this way, the filtered component contained in the liquid to be treated 31 is collected by the filtration membrane layer 20 of the tubular filtration membrane 3 and removed from the liquid to be treated 31. By such a filtration treatment, the liquid 31 to be treated in the storage tank 30 naturally circulates through the tubular filtration membrane module 5 from the lower side to the upper side as indicated by arrows in FIG.
[0036]
In the normal filtration process as described above, among the filtered components contained in the liquid 31 to be treated, the long fiber-like contaminants are prevented from flowing by the mesh filter 10 provided on the side surface of the guide tube 8, If the operation is continued for a long period of time, the above-mentioned long-fiber-like impurities start to stay little by little at the inlet 12 of the tubular filtration membrane module 5, and the filtration efficiency also starts to gradually drop. In addition, a filtered component is gradually deposited on the inner peripheral surface of the tubular filtration membrane 3, that is, the surface of the filtration membrane layer to form a cake layer, and the filtration performance of the tubular filtration membrane 3 is lowered. In such a situation, after the outlet 13 is closed with the lid 11 and the air bubbles 14 are trapped inside the tubular filtration membrane 3 and in the guide tube 8, the filtration is suspended. When the filtration component removal step is performed to allow the air bubbles 14 confined by opening the lid 11 to flow out at once, the foreign matter staying at the inlet 12 can be pushed out at once, and the inner peripheral surface of the tubular filtration membrane 3 can be pushed out. Part of the formed cake layer can also be peeled off, and the filtration efficiency can be recovered. Further, in the filtration suspension step described above, the liquid 31 to be treated flows back into the storage tank 30 through the mesh filter 10, so that the long fiber-like contaminants attached to the mesh filter 10 can be removed by the flow. .
[0037]
And when filtration performance does not recover even if it performs each above-mentioned process, a backwashing process is implemented with respect to a tubular filtration membrane module, and thereby a cake layer can be removed and recovery of filtration performance can be aimed at. In order to carry out this backwashing process, the filtrate to be discharged is caused to flow back into the storage container 4 through the discharge port 6 while being pressurized.
[0038]
In addition, since the crushing pressure is large as described above (for example, at least the crushing pressure is set to 20 kPa), the tubular filtration membrane 3 is not crushed by the pressure applied in such a backwashing process. The shape can be maintained even after the backwashing process, and can be applied to the normal filtration process as described above.
[0039]
Therefore, the above-described submerged membrane filtration system 46 is configured so that the submerged membrane filtration device 2 periodically repeats the filtration pause step and the filtered component removal step in the normal filtration step, thereby allowing the tubular membrane membrane module 5 to be removed. Even without replacement for a long period of time, the filtration performance can be recovered, and the filtration treatment of the liquid to be treated 31 can be efficiently continued over a long period of time.
[0040]
In the submerged membrane filtration method using the submerged membrane filtration apparatus 2 described above, the method of periodically repeating the filtration pause step and the filtered component removal step in the normal filtration step may be performed manually. However, this may be done automatically using a timer.
[0041]
【Example】
Next, an example of the submerged membrane filtration device 2 using the tubular filtration membrane module 5 according to the above-described embodiment will be described.
[0042]
About 50 long fibrous contaminants having a length of 5 to 15 cm are placed in the liquid to be treated 31 in the storage tank 30, air is supplied from the blower 41 through the air supply pipe 42, and the planar nozzles 7 to 10 are supplied. Liter / m ² When air bubbles 14 of about / min are ejected, an upward flow is generated in the liquid to be processed in the liquid flow path 20 due to the air lift action of the air bubbles 14. The liquid to be treated in the liquid passage 20 to be treated is filtered through the tubular filtration membrane 3 due to the negative pressure in the treatment liquid passage 21, and components that are not filtered from the outlet 13 of the tubular filtration membrane module 5 into the storage tank 30. Is returned to the liquid 31 to be processed.
[0043]
The filtration process described above is continued for several minutes, and when the outlet 13 of the tubular filtration membrane module 5 is closed with the lid 11 when a large number of long fibrous impurities start to accumulate on the mesh filter 10, the mesh filter 10 is treated. It was found that the liquid 31 flowed back, and the long fibrous impurities accumulated in several seconds returned and floated in the liquid 31 to be treated in the storage tank 30.
[0044]
Next, when the same filtration process was continued with the mesh filter 10 removed from the submerged membrane filtration device 2, long fibrous contaminants began to accumulate at the inlet 12 of the tubular filtration membrane module 5 within a few minutes. When the outlet 13 of the tubular filtration membrane module 5 is closed with the lid 11 and the lid 11 is opened just before the liquid to be treated 31 starts to flow backward from the position where the mesh filter 10 is removed, the air bubbles 14 are allowed to flow out at once. It is understood that the long fibrous impurities accumulated in 12 are pushed out from the outlet 13 through the treatment liquid flow path 20 of the tubular filtration membrane 3 and return to the treatment liquid 31 in the storage tank 30 and float. It was.
[0045]
In the above-described embodiment, the case where the tubular filtration membrane module 5 in which the filtrate discharge port 6 is provided on the side surface of the storage container 4 has been described. However, other types of tubular filtration membrane modules 5 may be used. . That is, the water collecting pipe having the inlet for introducing the filtrate and the outlet for discharging the filtrate and the tubular filtration membrane 3 may be disposed inside the storage container 4.
[0046]
【The invention's effect】
Since the immersion type membrane filtration device of the present invention has a lid on the outlet side that allows air bubbles to pass through by opening and shuts off air bubbles by closing, as described above, in the tubular membrane filter module, It can contribute to performing the filtration process of a to-be-processed liquid efficiently for a long period of time.
[0047]
Moreover, since the submerged membrane filtration method of the present invention includes a filtration suspension step and a separate component removal step in the normal filtration step of filtering the liquid to be treated using the tubular filtration membrane module as described above, The filtration treatment of the liquid to be treated can be carried out efficiently for a long period.
[Brief description of the drawings]
FIG. 1 is a schematic view of a submerged membrane filtration apparatus according to an embodiment of the present invention.
FIG. 2 is a partially cutaway longitudinal sectional view of a tubular filtration membrane module employed in the submerged membrane filtration device.
[Explanation of symbols]
2 Submerged membrane filtration device
3 Tubular filtration membrane
4 storage containers
5 Tubular filtration membrane module
6 outlet
7 Surface nozzle
8 guide tube
9 Air bubble supply device
10 Planar filter
11 Lid
12 entrance
13 Exit
14 Air bubbles
20 Liquid flow path
21 Treatment liquid flow path
30 Reservoir
31 Liquid to be treated
40 pumps
41 Blower
42 Air supply pipe
43 Air bubble generator
44 Filtrate discharge route
46 Immersion membrane filtration system

Claims (2)

  A submerged membrane filtration device for filtering a liquid to be treated stored in a storage tank by a submerged membrane filtration method to obtain a filtrate, the submerged membrane filtration device comprising a tubular membrane membrane module and an air bubble supply The tubular filtration membrane module includes a plurality of tubular filtration membranes having a function of filtering the liquid to be treated on the inner surface thereof, and the both ends are held while being accommodated in a cylindrical storage container. The air bubble supply device is arranged in the storage tank so as to open both ends in the vertical direction, and the air bubble supply device guides the air bubble toward the tubular filtration membrane module. And is disposed below the tubular filtration membrane module so that the liquid to be treated flows and is filtered upward from below the tubular filtration membrane module by the air bubbles, and the tubular filtration membrane module is opened. Accordingly passes the air bubbles, closed submerged membrane filtration apparatus characterized by lid for blocking the air bubbles is arranged above by. A submerged membrane filtration method for obtaining a filtrate by subjecting a liquid to be treated stored in a storage tank to a filtration treatment by a submerged membrane filtration method using the submerged membrane filtration device according to claim 1 , A tubular filtration membrane module in which a plurality of tubular filtration membranes having a function of filtering the liquid to be treated on the inner surface are accommodated in a cylindrical storage container and both ends thereof are held so that both ends thereof are opened vertically. A normal filtration step that is arranged in the storage tank, supplies air bubbles from the lower side of the tubular filtration membrane module to flow the liquid to be treated from the lower side to the upper side of the tubular filtration membrane module, and filters the flow of the air bubbles. It includes a filtration suspension step for shutting off the filtration of the liquid to be treated and a filtration component removal step for resuming the flow of the blocked air bubbles to remove the filtration component accumulated in the tubular filtration membrane module. A submerged membrane filtration method.

Images