JPH07185271A - Immersion membrane device - Google Patents

Abstract

(57) [Abstract] [Purpose] Effectively removes non-filtration substances adhering to the membrane surface from the membrane surface. In a submerged membrane device in which a membrane unit 11 is immersed in a liquid of a treatment tank 10 to obtain filtered treated water that has permeated the membrane, a plurality of membrane units 11A and 11B are partitioned into a partition plate 1 in the liquid.
4 are placed in the liquid in the tank, and diffusers 15A and 15B are individually provided below the respective membrane units,
Alternately operable air diffuser.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated body in which a plurality of flat membranes are laminated, a laminated body in which a plurality of membrane elements having hollow fiber membranes in a planar shape or a blind shape are laminated, and a plurality of tubular membranes. The present invention relates to a submerged membrane device that uses those connected in parallel as a membrane unit.

[0002]

2. Description of the Related Art Immersion membrane devices for immersing the above-mentioned membrane unit in the liquid of a treatment tank and sucking the inside of the membrane unit to obtain filtered treated water that has permeated the membrane have been conventionally known. It is also known to provide an air diffuser at the bottom of the membrane to separate the filter cake.

[0003]

When the immersion membrane device is operated to perform membrane filtration, a concentration polarization layer, a Gael layer,
Non-filtered material, such as cake layers, adheres. When the thickness of the non-filter substance increases, the filtration resistance increases, the filtration pressure increases, and the filtration efficiency significantly decreases. For this reason, an air diffuser is installed below the membrane unit, and when the membrane filtration operation is performed for a certain period of time, or when a certain filtration pressure is reached during the membrane filtration operation, the operation is stopped and backwashing is performed. Operate the air diffuser back and forth to expose the entire bottom surface of the membrane unit to bubbles from below.
It is necessary to separate the bubbles rising between the membranes and the non-filter substance adhering to the membrane surface by the shearing force of the upward water flow. In this case, it is necessary to maintain a convection space in which the liquid in the tank flows downward and circulates around the membrane unit, and the filling rate of the film in the treatment tank is reduced by the amount of the convection space.

[0004]

Therefore, the present invention is a submerged membrane device in which a membrane unit is immersed in a liquid in a treatment tank to obtain filtered treated water that has permeated the membrane. It is characterized in that it is placed in the liquid in the tank and is separated from each other by an air diffuser provided below each of the membrane units so that the air diffusers can be alternately operated.

[0005]

EXAMPLES In each of the illustrated examples, 10 is a processing tank,
The membrane unit 11 is immersed in the liquid in the treatment tank, the suction pipe 13 connected to the pump 12 sucks the inside of the membrane unit, and the raw liquid in the treatment tank that has passed through the membrane unit 11 is filtered. Collect as water. The membrane unit is, as described above, a laminate of a plurality of flat membranes, or a hollow fiber membrane in a planar shape,
Or a laminate of a plurality of blind-shaped membrane elements,
Alternatively, a plurality of tubular membranes are connected in parallel.

In the embodiment shown in FIG. 1, two membrane units 11A and 11B are provided in a processing tank 10 with a partition plate 14 whose upper end is below the liquid surface.
Are separated from each other and are arranged adjacent to each other, and each membrane unit 11A,
Air diffusers 15A and 15B are individually provided below 11B. The four air diffusers 15A and 15B are connected to a common blower 16 by a branch pipe 17, and an on-off valve 18 provided in the pipe.
It can be operated individually by A and 18B. Stop the membrane filtration operation and open / close valves 18A, 18 before and after backwashing.
B is alternately opened and closed, for example, air bubbles are blown on the membrane unit 11A from the air diffuser 15A for 15 minutes, and bubbles are blown on the membrane unit 11B from the air diffuser 15B for the next 15 minutes, and this is repeated. As a result, an upward flow is generated between the membranes of the membrane unit 11A due to the bubbles floating from the air diffuser 15A, and the non-filtration substance attached to the membrane surface of the membrane unit 11A is separated from the membrane surface by the bubbles and the upward water flow. At the same time, a downward flow is generated between the membranes of the membrane unit 11B, and the non-filtration substance attached to the membrane surface is separated by the downward water flow. Air diffuser 15
When B is operating, the reverse of the above, the membrane unit 11B
The non-filtration substance attached to the membrane surface is separated from the membrane surface by the air bubbles and the upward water flow, and the non-filtration substance attached to the membrane surface of the membrane unit 11A is separated from the membrane surface by the downward water flow generated between the membranes.
Aeration may be performed after the operation of the membrane is stopped or during the operation of the membrane.

In the embodiment shown in FIG. 2, four membrane units 11A, 11B, 11C and 11D are arranged in the processing tank 10 by three partition plates 14A, 14B and 14C so as to be adjacent to each other. In the lower part of the unit, individually diffuser 15A,
15B, 15C and 15D are provided. The four air diffusers are connected to a common blower 16 by a branch pipe 17, and the four open / close valves 18A, 18B, 18C, 18D provided in the branch pipe can individually operate the four air diffusers. While performing the membrane filtration operation or stopping the operation, operating the on-off valve before and after backwashing, for example, the air diffusers 15A, 15B, 1
5C, 15D in order for 15 minutes, or 1
5A and 15C and 15B and 15D are alternately operated for 15 minutes. An upward flow due to air bubbles occurs between the membranes of the membrane unit above the operating air diffuser, and the air bubbles and the upward water flow separate the non-filtration material adhering to the membrane surface, and the air diffuser is not operating. A downward flow is generated between the membranes of the membrane unit above the membrane, and this downward water flow separates the non-filtration substance adhering to the membrane surface from the membrane surface.

[0008]

As is apparent from the above, by alternately operating the air diffusers, an upward flow due to bubbles is generated between the membranes of the membrane unit above the operating air diffusers, and the The non-filter substance adhering to the membrane surface is separated by the upward flow of water. Then, a downward flow is generated between the membranes of the membrane unit above the air diffusing device that has stopped its operation, and this downward water flow separates the non-filter substance adhering to the membrane surface. Therefore, it is not necessary to keep the convection space that causes the downward flow between the membrane units,
The film filling rate in the processing tank is increased. Further, when the same number of membrane units are filled, the size of the processing tank used is greatly reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment of an immersion membrane device of the present invention.

FIG. 2 is a sectional view of another embodiment of the immersion membrane device of the present invention.

[Explanation of symbols]

 10 Treatment Tank 11A Membrane Unit 11B Membrane Unit 11C Membrane Unit 11D Membrane Unit 12 Pump 13 Suction Pipe 14 Partition Plate 14A Partition Plate 14B Partition Plate 14C Partition Plate 15A Air Diffuser 15B Air Diffuser 15C Air Diffuser 15D Blower 16 17 Branch pipe 18A Open / close valve 18B Open / close valve 18C Open / close valve 18D Open / close valve

Claims (1)

[Claims] 1. A submerged membrane device in which a membrane unit is immersed in a liquid in a treatment tank to obtain filtered treated water that has permeated the membrane, and a plurality of membrane units are separated by a partition plate in the liquid and arranged in the liquid in the tank. In addition, the submerged membrane device is characterized in that the air diffusers are individually provided below the respective membrane units so that the air diffusers can be alternately operated.