Fine bubble diffusing pipe, fine bubble diffusing apparatus, and submerged membrane separation apparatus

1. A fine bubble diffusing device comprising: at least fine bubble diffusing tubes and gas supply pipes,

wherein each one of the fine bubble diffusing tubes comprises: at least a cylindrical supporting tube, and an elastic sheet with fine slits formed therein, with the elastic sheet being placed so as to cover the outer circumference of the supporting tube, so that, upon supplying a gas to a space between the elastic sheet and the supporting tube, the fine slits of the elastic sheet are opened to generate fine bubbles outside the diffusing tube,

wherein the supporting tube has a length of 1000 mm or more in the longitudinal direction, with gas supply units serving as flow inlets of the gas, and one of the gas supply units being attached to each of the two ends of the supporting tube, and

the space between the elastic sheet and the supporting tube is divided into at least two portions in the longitudinal direction by a space dividing means, with the length of each of the divided spaces in the longitudinal direction being set to 1000 mm or less, and

a plurality of the fine bubble diffusing tubes are disposed virtually in parallel with one another, with the gas supply units attached to the fine bubble diffusing tubes being connected to the gas supply pipes,

wherein a plurality of the gas supply units, located on one end side of each of the fine bubble diffusing tubes, are all connected to one of the gas supply pipes, and a plurality of the gas supply units, located on the other end side of the fine bubbles diffusing tubes, are all connected to another one of the gas supply pipes.

2. The fine bubble diffusing device according to claim 1 , wherein, with respect to at least one end side, a connecting portion between the gas supply unit of the fine bubble diffusing tube and the gas supply pipe has a connecting structure capable of being detachably attached by inserting a member of the connecting portion between the gas supply unit and the gas supply pipe, without both the gas supply unit and the gas supply pipe being rotated.

3. The fine bubble diffusing device according to claim 2 , wherein the connecting portion having the connecting structure capable of being detachably attached by inserting the member of the connecting portion between the gas supply unit of the fine bubble diffusing tube and the gas supply pipe is provided with an O-ring placed on the connecting portion as a sealing member.

4. The fine bubble diffusing device according to claim 1 , wherein, with respect to at least one end side, a connecting portion between the gas supply unit of the fine bubble diffusing tube and the gas supply pipe has a connecting structure in which connecting ends are joined to one another without rotating a member of the connecting portion, and connect the gas supply unit of the fine bubble diffusing tube to the gas supply pipe by using a connecting member capable of being detachably attached.

5. The fine bubble diffusing device according to claim 4 , wherein the connecting member capable of being detachably attached, is at least one member selected from the group consisting of a flange, a union and a clamp.

6. A submerged membrane separation apparatus, which is submerged and placed in a treatment tank in which a treated liquid is stored, comprising: a separation membrane module in which a plurality of separation membrane elements, each having a flat film disposed as a separation membrane, are arranged side by side, with membrane faces being set in parallel with each other, and a fine bubble diffusing device installed vertically below the submerged membrane separation device,

wherein the fine bubble diffusing device is a fine bubble diffusing device disclosed in claim 1 .

7. The submerged membrane separation apparatus according to claim 6 , wherein the gas supply pipes, each of which is connected to one side of the fine bubble diffusing tubes, are joined to each other by a branch from a main gas supply pipe extending from an aeration device.

8. The submerged membrane separation apparatus according to claim 6 , wherein a distance between the lower end of the separation membrane elements and the highest level of the fine bubble diffusing tubes is set to 300 mm or less.

9. The fine bubble diffusing device according to claim 1 , wherein the total sum of the lengths in the longitudinal direction of the plurality of fine bubble diffusing tubes connected to one of the gas supply pipes, as measured from one end side of each fine bubble diffusing tube to the space dividing means is within 10% of the total sum of the lengths of the plurality of fine bubble diffusing tubes connected to the other gas supply pipe, as measured from one end side of each fine bubble diffusing tube to the space dividing means.

10. The fine bubble diffusing device according to claim 1 , wherein the positions of the space dividing means, used for dividing the space between the elastic sheet and the supporting tube into at least two portions in the longitudinal direction, are arranged so as to deviate from one another in a perpendicular direction to the supporting tube longitudinal direction.