JPH11169853A - Membrane filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable washing the whole membrane surface and to eliminate a tear of the membrane surface and a rise in costs. SOLUTION: This membrane filter has a treating tank containing water to be treated, a membrane module 50 immersed in the water to be treated and formed by laminating plural membrane elements 51, an aerator 61 arranged below the membrane module 50 and for jetting gas, and a baffle member arranged in the central part above the module 50. In this case, the gas jetted by the aerator 61 is turned into bubbles, which flow and rise together with the water to be treated between membranes of each membrane element 51. And each bubble is deflected by the baffle member and spreads over the width direction of the membrane element 51 and is made to uniformly flow.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane filtration device.

[0002]

2. Description of the Related Art Conventionally, when performing wastewater treatment or when recovering valuable substances in water, solid-liquid separation is performed. For this purpose, a membrane element such as a microfiltration membrane or an ultrafiltration membrane is used. A membrane filtration device is provided. In the membrane filtration device, only treated water in the water to be treated, such as wastewater and water containing valuables, is permeated through the membrane of the membrane element.

[0003] Then, by applying a low pressure to the water to be treated side of the membrane or applying a low suction force to the treated water side, the treated water is sucked at a low speed. By the way, in the membrane element, when solids such as suspended substances adhere to the surface of the membrane, that is, the membrane surface, the difference between the pressure on the treated water side and the pressure on the treated water side, that is, the filtration pressure difference is large. This deteriorates the permeation performance of the membrane element.

[0004] Therefore, by adhering the solid matter to the film surface, the film surface is cleaned to minimize the adhesion. For that purpose, an aeration device is arranged below the membrane element,
Aeration is performed by injecting air from the aeration device, and a shear force is applied to the film surface by an air lift action to clean the film surface.

[0005]

However, in the above-mentioned conventional membrane filtration device, the entire membrane surface cannot be washed. FIG. 2 is a diagram showing the flow of a conventional bubble.
In the figure, reference numeral 11 denotes a membrane element, 12 denotes a membrane, and 13 denotes a frame, and a water collecting channel (not shown) is formed in the side edges a1 and a2 of the frame 13 so as to extend in the vertical direction. Further, a water collecting nozzle 1 is provided at an upper end of the side edge portions a1 and a2.
4 and 15 are attached, and a line (not shown) for discharging treated water is connected to the water collecting nozzles 14 and 15.

[0006] In order to clean the membrane surface, the air injected by an aeration device (not shown) is uniformly supplied to the entire lower end S1 of the membrane element 11 as a number of bubbles 16, and the air between the membrane surfaces is removed. Flows together with the water to be treated and is raised. The membrane element 11 extends over a predetermined length in a processing tank (not shown), and
The vicinity of the side edge portions a1 and a2 becomes a resistance to the bubble 16 that is going to rise between the two. Therefore, the bubbles 16 gradually move toward the center of the membrane surface as they rise between the membranes 12 and flow only at the central portion at the upper end S2 of the membrane element 11. That is, bubble 1
6 flows only in the trapezoidal region AR1 and does not flow in the triangular regions AR2 and AR3. As a result, in the area AR1, sludge is removed by the flowing air bubbles 16,
In the regions AR2 and AR3, sludge cannot be removed, and the entire membrane cannot be cleaned. In addition, the gap between the respective membrane surfaces may be blocked by the sludge.

Therefore, it is conceivable to increase the amount of air injected by the aeration device. However, if the amount of air is increased, the film surface may be broken. Also,
It is conceivable to increase the size of the aeration device in the width direction, but if the size of the aeration device in the width direction is increased,
The cost of the membrane filtration device increases.

The present invention solves the above-mentioned problems of the conventional membrane filtration apparatus, and can clean the entire membrane surface without breaking the membrane surface or increasing the cost. The purpose is to provide.

[0009]

For this purpose, in the membrane filtration device of the present invention, a treatment tank for containing the water to be treated and a plurality of membrane elements immersed in the water to be treated are laminated. Membrane module formed by the above, an aeration device disposed below the membrane module and injecting gas, and a baffle member immersed in the water to be treated and disposed in a central portion above the membrane module And

[0010] In another membrane filtration device of the present invention, the baffle member is a plurality of baffle pipes arranged at a predetermined pitch. In still another membrane filtration device of the present invention, the baffle member is a baffle plate having a predetermined width. In still another membrane filtration device of the present invention, the baffle member is further movably disposed.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a front view of a membrane module according to a first embodiment of the present invention, and FIG.
Is a conceptual diagram of a membrane filtration device according to the first embodiment of the present invention, and FIG. 4 is a plan view of a membrane module according to the first embodiment of the present invention.

In FIG. 3, reference numeral 31 denotes a treatment tank for storing the water to be treated, 50 denotes a membrane module immersed in the water to be treated in the treatment tank 31, and the membrane modules 50 are arranged at predetermined intervals. It comprises a plurality of membrane elements 51 arranged. Each of the membrane elements 51 is formed of a microfiltration membrane, an ultrafiltration membrane, or the like. A water collecting channel (not shown) is formed at a side edge portion, and treated water after permeating the membrane into the water collecting channel is collected. ing.

The lower end of the water collecting channel is closed, and the upper end of the water collecting channel is connected to a line L through a water collecting nozzle (not shown).
2 and a pump (P) is connected to the line L2.
P1 is provided, and the control device 37 controls the pump P1.
, A negative pressure is generated in the membrane element 51, and the treated water is sucked. In this case, by adjusting the rotation speed of the pump P1 by the control device 37, the amount of the treated water to be sucked can be adjusted and the permeation flux can be changed.

An aeration device 61 is provided below the membrane element 51, and the aeration device 61 is connected to a line L1.
And a gas supply source (not shown) via a regulating valve 63. The control device 37 controls the regulating valve 63.
By adjusting the opening degree, the amount of air as gas injected by the aeration device 61 can be adjusted, and the membrane surface flow velocity can be changed.

Therefore, air is blown from the aeration device 61 to perform aeration, and a shearing force is applied to the film surface by an air lift action to clean the film surface. Next, the membrane module 50 having the above configuration will be described. Figures 1 and 4
In the figure, 50 is a membrane module, 51 is a plurality of membrane elements arranged adjacent to each other, 52 is a membrane, 53 is a frame, and a water collecting channel (not shown) is vertically set in side edges a1 and a2 of the frame 53. It is formed to extend in the direction. Further, a water collecting nozzle 5 is provided at the upper end of each of the side edges a1 and a2.
4 and 55, and a line L2 (FIG. 3) for discharging treated water is connected to the water collecting nozzles 54 and 55.

An aeration device 61 is disposed below the membrane element 51 for cleaning the membrane surface. The aeration device 61 is composed of a pipe-shaped nozzle (not shown) extending in the width direction of each membrane element 51, and a plurality of injection ports 64 are formed above the nozzles. Therefore, the air jetted from the jet port 64 is supplied to the entire lower end S1 of the membrane element 51 uniformly as a large number of air bubbles (not shown), and flows between the membranes 52 together with the water to be treated and is raised.

It is to be noted that the adjacent membrane elements 51 are so arranged that the air jetted from the jet ports 64 covers the entire membrane surface.
Is set to about 4 to 15 [mm]. Incidentally, the membrane element 51 is provided in the processing tank 11.
The inside of the side edges a1 and a2 becomes a resistance against bubbles that extend over a predetermined length in the inside and are going to rise between the films 52. Therefore, the air bubbles form each membrane 52.
As the space rises, it gradually moves to the center of the film surface.

Therefore, a plurality of baffle pipes 71 are disposed as baffle members at a predetermined distance (50 [mm] in the present embodiment) from the upper end S2 above the central portion of the membrane element 51. You. The baffle pipe 71 extends horizontally and in a direction perpendicular to the film surface, and is immersed in the water to be treated. Therefore, since a certain resistance is given to the flow in the central portion between the membranes 52 by the baffle pipe 71, each bubble rising between the membranes 52 is deflected and spreads over the entire width direction of the membrane element 51. Since the fluid flows uniformly, the sludge attached to the membrane surface can be sufficiently removed by the bubbles, and the entire membrane surface can be washed. As a result, it is possible to prevent clogging between the membrane surfaces with sludge.

Further, since it is not necessary to increase the amount of air injected by the aeration device 61, the film surface is not broken. Further, since it is not necessary to increase the dimension of the aeration device 61 in the width direction, the cost of the membrane filtration device does not increase. Next, a second embodiment of the present invention will be described.

FIG. 5 is a front view of the membrane module according to the second embodiment of the present invention, and FIG. 6 is a plan view of the membrane module according to the second embodiment of the present invention. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by attaching the same code | symbol. In this case, a predetermined distance from the upper end S2 (in the present embodiment, 50 [m
m]) and place a baffle plate 7 as a baffle member.
2 are provided. The baffle plate 72 extends horizontally and in a direction perpendicular to the film surface, and is immersed in the water to be treated. In addition, a plurality of holes (not shown) may be formed in the baffle plate 72.

Accordingly, since a certain resistance is given to the flow in the central portion between the membranes 52 by the baffle plate 72, each air bubble (not shown) which flows between the membranes 52 together with the water to be treated and rises is deflected. As a result, the sludge adhering to the membrane surface can be sufficiently removed by the bubbles, and the entire membrane surface can be washed. As a result, it is possible to prevent clogging between the membrane surfaces with sludge.

In each of the above embodiments, the baffle pipe 71 (FIG. 1) and the baffle plate 72 are fixed in the processing tank 31 (FIG. 3), but they can be movably provided. For example, the baffle pipe 71 and the baffle plate 72 may be intermittently disposed, immersed in the water to be treated for a predetermined time, and then taken out. Further, the baffle pipe 71 and the baffle plate 72 can be rotated in a predetermined direction.

Next, the results of performing a membrane filtration test on each embodiment will be described. FIG. 7 is a diagram showing the results of a membrane filtration test. In the figure, the horizontal axis represents the operation time, and the vertical axis represents the suction differential pressure. In this case, the water to be treated adjusted to have a sludge concentration of MLSS 15000 to 18000 [mg / l] was supplied to the treatment tank 31 (FIG. 3), and the membrane module 50 was immersed in the water to be treated. The membrane module 50 is formed by stacking five membrane elements 51, and the width of each membrane element 51 is set to 6
10 mm, the height is 1050 mm, and the membrane 5
The film area of No. 2 (FIG. 1) was set to 5 [m ² ]. Then, air was injected by the aeration device 61 at a flow rate of 4.5 [m ³ / hr].

Further, the permeation flux of the membrane filtration is set to 0.6 [m / d
ay], and suction was performed intermittently. In this case, suction was performed for 8 minutes, and then stopped for 2 minutes. Then, as the first test condition, the upper end S of the membrane element 51 is set.
Three baffle pipes 71 were arranged at a pitch of 100 [mm] at a distance of 2 to 50 [mm].

As a second test condition, a baffle plate 72 (FIG. 5) having a width of 250 mm was intermittently arranged at a distance of 50 mm from the upper end S2 of the membrane element 51. . In this case, baffle plate 7 for 5 minutes
After disposing 2, the baffle plate 72 was taken out for 5 minutes. Further, as a third test condition, a baffle plate 72 having a width of 250 [mm] was provided at a distance of 50 [mm] from the upper end S2 of the membrane element 51. In this case, a plurality of holes (not shown) were formed in the entire baffle plate 72, and the total area of the holes was set to about 20% of the area of the baffle plate 72.

In the drawing, P1 is the membrane element 51
Baffle pipe 71 and baffle plate 72
The change with time of the suction differential pressure when none of
2 shows the change with time of the suction differential pressure under the first test condition, P
3 shows the change with time of the suction pressure difference under the second test condition, P
4 shows the change with time of the suction differential pressure under the third test condition.

Under the first to third test conditions, it can be seen that the suction differential pressure is prevented from increasing over a long period of time. It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0028]

As described above in detail, according to the present invention, in a membrane filtration device, a treatment tank for containing water to be treated and a plurality of membrane elements immersed in the water to be treated are laminated. And a gas aeration device disposed below the membrane module for injecting gas, and a baffle immersed in the water to be treated and disposed at a central portion above the membrane module. And a member.

In this case, the gas injected by the aeration device becomes bubbles and flows between the membranes of the respective membrane elements together with the water to be treated and rises. Since a certain resistance is given to the central portion between the membranes by the baffle member, each air bubble is deflected and spreads over the entire width of the membrane element to flow uniformly. Therefore, the sludge attached to the membrane surface can be sufficiently removed by the bubbles, and the entire membrane surface can be washed. As a result, it is possible to prevent clogging between the membrane surfaces with sludge.

Further, since it is not necessary to increase the amount of air injected by the aeration device, the film surface is not broken. And since it is not necessary to enlarge the dimension of the aeration device in the width direction, the cost of the membrane filtration device does not increase.

[Brief description of the drawings]

FIG. 1 is a front view of a membrane module according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a conventional flow of bubbles.

FIG. 3 is a conceptual diagram of a membrane filtration device according to the first embodiment of the present invention.

FIG. 4 is a plan view of the membrane module according to the first embodiment of the present invention.

FIG. 5 is a front view of a membrane module according to a second embodiment of the present invention.

FIG. 6 is a plan view of a membrane module according to a second embodiment of the present invention.

FIG. 7 is a diagram showing the results of a membrane filtration test.

[Explanation of symbols]

 31 treatment tank 50 membrane module 51 membrane element 61 aeration device 71 baffle pipe 72 paffle plate

Claims (4)

[Claims] 1. (a) a treatment tank containing water to be treated;
(B) a membrane module immersed in the water to be treated and formed by stacking a plurality of membrane elements;
(C) an aeration device disposed below the membrane module for injecting gas, and (d) a baffle member immersed in the water to be treated and disposed at a central portion above the membrane module. A membrane filtration device comprising: 2. The membrane filtration device according to claim 1, wherein the baffle member is a plurality of baffle pipes arranged at a predetermined pitch. 3. The membrane filtration device according to claim 1, wherein the baffle member is a baffle plate having a predetermined width. 4. The membrane filtration device according to claim 1, wherein the baffle member is movably disposed.