JP7675639B2 - Membrane type aeration device - Google Patents

Description

The present invention relates to a membrane type aeration device that is installed below the liquid surface and releases air bubbles into the liquid.

Conventionally, as shown in FIG. 23, there is a membrane type air diffuser that emits a large number of air bubbles 202 into the water to be treated 201 in a tank 200. This membrane type air diffuser 203 has a membrane 204 formed in a tubular shape, a support tube 205 inserted into the membrane 204, and an air supply unit 206.

The end of the membrane 204 is fixed watertight to the support tube 205 with a fixing device 207 such as a ring-shaped band. The support tube 205 is connected to an air supply tube 208. The air supply section 206 is provided in the center B in the longitudinal direction A of the support tube 205, and has an air flow path 209 that connects the air supply tube 208 to the inner circumference of the membrane 204 and the outer circumference of the support tube 205.

The membrane 204 is provided with a number of slits 211 for releasing to the outside the air 210 supplied from the air supply pipe 208 through the air passage 209 of the air supply section 206 between the inner circumference of the membrane 204 and the outer circumference of the support pipe 205.

According to this, air 210 is supplied from the air supply pipe 208 through the air flow path 209 of the air supply section 206 to between the inner circumference of the membrane 204 and the outer circumference of the support tube 205, causing the membrane 204 to expand, and the air 210 is released into the treated water 201 as air bubbles 202 from the slits 211 of the membrane 204.

The membrane type aeration device 203 described above is described, for example, in Patent Document 1 below.

JP2005-81203A

However, in the above conventional type, the air 210 supplied from the ventilation flow path 209 of the air supply section 206 between the inner circumference of the membrane 204 and the outer circumference of the support tube 205 encounters flow resistance as it flows from the center B in the longitudinal direction A of the support tube 205 toward both ends C, so the pressure loss at both ends C is greater than the pressure loss at the center B.

As a result, air 210 is more difficult to release from the slits 211 at both ends C of the membrane type air diffuser 203 than at the center B, which causes a problem of uneven air diffusion, such as a reduction in the amount of air bubbles 202 released from the slits 211.

The present invention aims to provide a membrane type air diffuser that can improve uneven air diffusion.

In order to achieve the above object, the first invention is a membrane type aeration device that is installed under a liquid surface and emits air bubbles into the liquid,
The membrane has a tubular shape and a hollow insertion portion, a support inserted into the insertion portion of the membrane, and a gas supply portion provided in the center of the membrane in the longitudinal direction,
The membrane has a bag-shaped portion formed in a bag shape by two sheet members on the front and back,
the gas supply unit has an air passage communicating from the outside to the inside of the bag-shaped portion of the membrane;
a sheet member constituting an outer peripheral surface of the bag-shaped portion of the membrane is formed with a plurality of slits for discharging to the outside the gas supplied into the bag-shaped portion through the ventilation flow path of the gas supply portion;
When gas is being released to the outside through the slits, both ends of the membrane in the longitudinal direction are positioned higher than the center.

According to this, by operating the membrane type air diffuser, gas is supplied into the bag-shaped portion of the membrane through the air flow passage of the gas supply unit, causing the bag-shaped portion of the membrane to expand and the gas inside the bag-shaped portion to be released to the outside through the slits. This causes a large number of air bubbles to be released from the membrane type air diffuser into the liquid.

At this time, the gas supplied from the ventilation passage of the gas supply unit into the bag-shaped portion of the membrane encounters more flow resistance as it flows from the center to both ends in the longitudinal direction of the membrane, so the pressure loss at both ends of the membrane is greater than the pressure loss in the center.

In contrast, when gas is being released to the outside through the slits as described above, both ends of the membrane in the longitudinal direction are located higher than the center, so the depth from the liquid surface to both ends of the membrane is shallower than the depth from the liquid surface to the center of the membrane, and the liquid pressure applied to both ends of the membrane is smaller than the liquid pressure applied to the center of the membrane.

In this way, at both ends of the membrane in the longitudinal direction, the effect of increased pressure loss making it difficult to release bubbles and the effect of decreased liquid pressure making it easier to release bubbles are offset, thereby reducing the variation in the amount of bubbles released between the center and both ends in the longitudinal direction of the membrane, thereby improving unevenness in the air diffusion of the membrane-type air diffuser.

In the membrane type air diffuser of the second invention, the membrane has more space between the support and both ends in the longitudinal direction than the center.

When gas is released to the outside through the slits, buoyancy acts on the membrane due to the gas supplied into the bag-shaped portion of the membrane. Because there is space between both ends of the membrane in the longitudinal direction and the support, the buoyancy acting on the membrane causes both ends of the membrane to rise above the center, and to be positioned higher than the center.

In the membrane type aeration device of the third invention, the outer perimeter of the support is shorter at both ends in the longitudinal direction than at the center.

This makes it possible to obtain a membrane-type air diffuser that is configured so that there is more space between the support at both ends of the membrane than at the center in the longitudinal direction.

In the membrane type air diffuser of the fourth invention, the inner perimeter of the membrane is longer at both ends than at the center in the longitudinal direction.

This makes it possible to obtain a membrane-type air diffuser that is configured so that there is more space between the support at both ends of the membrane than at the center in the longitudinal direction.

The membrane type air diffuser in the fifth invention has the bottoms at both ends in the longitudinal direction of the support positioned higher than the bottom at the center.

By inserting the support into the insertion portion of the membrane, both ends of the membrane in the longitudinal direction are positioned higher than the center.

As described above, according to the present invention, at both ends of the membrane in the longitudinal direction, the effect of the increased pressure loss making it difficult to release bubbles and the effect of the decreased liquid pressure making it easier to release bubbles are offset, thereby reducing the variation in the amount of bubbles released between the center and both ends in the longitudinal direction of the membrane, thereby improving the unevenness of the air diffusion of the membrane-type air diffuser.

1 is a perspective view of an air diffusion system according to a first embodiment of the present invention; FIG. 2 is a side view of a membrane type air diffuser provided in the air diffusion equipment according to the first embodiment. FIG. 2 is a cross-sectional view of an end portion of the membrane type air diffuser according to the first embodiment. FIG. 2 is a perspective view of the membrane and the support tube of the membrane type air diffuser of the first embodiment. FIG. 2 is a partially cutaway plan view of the membrane of the membrane type air diffuser of the first embodiment. FIG. 2 is a partially cutaway bottom view of the membrane of the membrane-type air diffuser of the first embodiment. FIG. 4 is a cross-sectional view of a support tube of the membrane type air diffuser according to the first embodiment. FIG. 2 is a cross-sectional view of the connecting portion between the membrane type air diffuser and the air supply pipe of the air diffusion equipment according to the first embodiment. 9 is a view taken along the line XX in FIG. 8. 4 is a view taken along the line XX in FIG. 3. FIG. 2 is a perspective view of a gas supply nozzle of the membrane type air diffuser according to the first embodiment. 12 is a view taken along the line XX in FIG. 11. 12 is a view taken along the line YY in FIG. 11. FIG. FIG. 13 is a disassembled view of the adapter, air supply pipe, and gas supply nozzle of the aeration equipment. FIG. 2 is a diagram showing the steps of a method for manufacturing the membrane of the membrane-type air diffuser according to the first embodiment. FIG. 2 is a diagram showing the steps of a method for manufacturing the membrane of the membrane-type air diffuser according to the first embodiment. FIG. 11 is a cross-sectional view of a support tube of a membrane type air diffuser according to a second embodiment of the present invention. FIG. 2 is a cross-sectional view of an end portion of the membrane type air diffuser according to the first embodiment. FIG. 11 is a partially cutaway side view of a membrane type air diffuser according to a third embodiment of the present invention. FIG. 13 is a cross-sectional view of a support tube of a membrane type air diffuser according to a fourth embodiment of the present invention. FIG. FIG. 1 is a diagram of a conventional membrane type air diffuser.

The following describes an embodiment of the present invention with reference to the drawings.

(First embodiment)
In the first embodiment, as shown in Fig. 1, reference numeral 1 denotes an aeration system provided in an aerobic tank (not shown) installed in, for example, a sewage treatment plant, etc. The aeration system 1 is immersed under the surface of water to be treated 3 (an example of a liquid) consisting of activated sludge in the tank, and includes a plurality of membrane type aeration devices 10 that emit air bubbles 4 into the water to be treated 3, air supply pipes 12 that supply air 11 (an example of a gas for diffusing air) to each membrane type aeration device 10, an adapter 14 (see Fig. 8) that fixes the membrane type aeration device 10 to the air supply pipe 12, and a blower 15 that supplies air 11 to the air supply pipe 12 from outside the tank.

As shown in Figures 2 to 6, the membrane type aeration device 10 has a membrane 17 formed in a tubular (cylindrical) shape with a hollow insertion section 16 in the center, a support tube 18 (an example of a support) inserted horizontally into the insertion section 16 of the membrane 17, and a gas supply nozzle 19 (an example of a gas supply section) provided in the center of the membrane 17 in the longitudinal direction A.

The membrane 17 has a bag-shaped portion 23 formed by welding two front and back sheet members 21, 22. The front sheet member 21 and the back sheet member 22 are made of a soft elastic synthetic resin, with the front sheet member 21 forming the outer peripheral surface of the bag-shaped portion 23 and the back sheet member 22 forming the inner peripheral surface of the bag-shaped portion 23.

A circular first opening 24 is formed in the central and upper part of the membrane 17 in the longitudinal direction A. The insertion part 16 penetrates both ends of the membrane 17, and the insertion part 16 communicates with the upper part of the membrane 17 via the first opening 24.

As shown in Figures 8, 9 and 16, a circular first through hole 26 and a circular second through hole 27 are formed in the central and lower part of the membrane 17 in the longitudinal direction A. Of these, the first through hole 26 is formed in the sheet member 21 on the front side. The second through hole 27 has a smaller diameter than the first through hole 26 and is formed in the sheet member 22 on the back side. The center of the first through hole 26 and the center of the second through hole 27 are coaxial.

As shown in Figures 4 to 6, the two sheet members 21, 22 are welded at the welded portion 29. This welded portion 29 has end welded portions 29a formed around the entire circumference of both ends of the membrane 17, a central welded portion 29b formed around the first opening 24, and a longitudinal welded portion 29c formed between the end welded portions 29a and the central welded portion 29b.

The sheet member 21 on the front side has a number of slits 30 formed therein for releasing the air 11 supplied from the gas supply nozzle 19 into the bag-shaped portion 23 to the outside. As shown by the imaginary lines in FIG. 6, a non-formed area 31 where no slits 30 are formed is provided in the lower part of the sheet member 21 on the front side, and the slits 30 are formed in the area other than the non-formed area 31 and the welded portion 29.

In addition, in drawings such as Figure 2, the slit 30 is drawn as an oval shape to make it easier to see, but in reality, the slit 30 is a slit that is closed when air is not being diffused and is slightly open when air is being diffused.

As shown in Figures 4 and 7, the support tube 18 is a straight circular tube made of resin with both ends open, and a circular second opening 33 is formed in the center and upper part of the support tube 18 in the longitudinal direction A. As shown in Figures 8 and 9, when the support tube 18 is inserted into the insertion part 16 of the membrane 17, the position of the first opening 24 of the membrane 17 and the position of the second opening 33 of the support tube 18 are aligned.

As shown in Figure 7, a bolt insertion hole 34 is formed in the center and lower part of the support tube 18 in the longitudinal direction A. As shown in Figures 8 and 9, the position of the bolt insertion hole 34 in the support tube 18 coincides with the center position of the second through hole 27 in the sheet member 22 on the back side of the membrane 17.

As shown in Figures 2, 6, 8, 9, 11 to 13, the gas supply nozzle 19 has a circular tubular portion 37, a flange portion 38, and a top plate portion 39. The tubular portion 37 is inserted into the first through-hole 26 (see Figure 16) of the sheet member 21 on the front side of the membrane 17, and protrudes below the membrane 17. The lower end of the tubular portion 37 is formed with a pair of cutout portions 41 and an inlet port 42 that opens into the air supply pipe 12.

The flange 38 is formed at the upper end of the tube 37 and projects outward in the radial direction of the tube 37, and as shown in Figures 8 and 9, it enters the bag-shaped portion 23 of the membrane 17. A plurality of outlet ports 43 that open into the bag-shaped portion 23 are formed on the outer circumferential surface of the flange 38. In addition, a gas supply nozzle 19 is attached to the membrane 17 in the peripheral portion of the first through hole 26 (see Figure 16) of the front sheet member 21 so that air 11 does not leak from the first through hole 26 during aeration.

The top plate portion 39 is formed at the upper end of the tube portion 37, and a bolt insertion hole 45 is formed in the top plate portion 39, penetrating in the vertical direction.

An air flow passage 46 is formed in the gas supply nozzle 19, which is connected to the inlet 42 and the outlet 43. This allows the inside of the air supply pipe 12 to communicate with the inside of the bag-shaped portion 23 of the membrane 17 via the air flow passage 46 of the gas supply nozzle 19. In addition, a recess 47 curved in an arc shape along the outer circumferential surface of the support tube 18 is formed on the upper surface of the gas supply nozzle 19.

As shown in Figures 8 and 9, the membrane type air diffuser 10 is fixed to the air supply pipe 12 via an adapter 14. As shown in Figures 14 and 15, the adapter 14 has a rectangular parallelepiped adapter body 50 sandwiched between the membrane type air diffuser 10 and the air supply pipe 12, and a pair of support parts 55 that support the support pipe 18 of the membrane type air diffuser 10 from below via the membrane 17. The support parts 55 are provided at both ends of the adapter body 50 in the longitudinal direction A of the membrane type air diffuser 10.

The underside of the adapter body 50 is formed with a recess 52 curved in an arc along the outer circumferential surface of the air supply pipe 12, and an O-ring fitting portion 56. The adapter body 50 is also formed with a circular first fitting hole 53 that penetrates in the vertical direction. The O-ring fitting portion 56 is formed to surround the periphery of the first fitting hole 53.

As shown in FIG. 1, the air supply pipe 12 is disposed below the membrane type air diffuser 10 and is perpendicular to the membrane type air diffuser 10 at the center in the longitudinal direction A of the membrane type air diffuser 10. As shown in FIG. 15, the upper end of the air supply pipe 12 is formed with a plurality of circular second insertion holes 54 that penetrate the air supply pipe 12 from the inside to the outside.

The position of the first fitting hole 53 of the adapter 14 coincides with the position of the second fitting hole 54 of the air supply pipe 12. As shown in Figures 8, 9, and 15, the cylindrical portion 37 of the gas supply nozzle 19 is fitted from above into the first fitting hole 53 of the adapter 14 and the second fitting hole 54 of the air supply pipe 12, and the lower end protrudes into the air supply pipe 12 through the second fitting hole 54.

An O-ring 62 (an example of a sealing member) that simultaneously seals between the underside of the adapter 14 and the outer circumferential surface of the air supply pipe 12 and between the inner circumferential surface of the first fitting hole 53 of the adapter 14 and the outer circumferential surface of the tubular portion 37 of the gas supply nozzle 19 is fitted into the O-ring fitting portion 56 and held by the adapter 14.

The air supply pipe 12, adapter 14, membrane 17, support pipe 18, and gas supply nozzle 19 are connected by a connecting member 51. The connecting member 51 has a T-head bolt 57 and a nut 58.

The T-head bolt 57 is inserted from below through the second insertion hole 54 of the air supply pipe 12, the bolt insertion hole 45 of the gas supply nozzle 19, the second through hole 27 of the sheet member 22 on the back side of the membrane 17, and the bolt insertion hole 34 of the support pipe 18, and protrudes into the support pipe 18.

The head 57a of the T-head bolt 57 is fitted from below into both notches 41 of the cylindrical portion 37 of the gas supply nozzle 19 and engages with the inner surface of the upper end of the air supply pipe 12.

The nut 58 is screwed onto the T-head bolt 57 inside the support tube 18 and engages with the inner surface of the support tube 18.

The entire periphery of the second through hole 27 in the back sheet member 22 is sandwiched between the outer circumferential surface of the support tube 18 and the top plate portion 39 of the gas supply nozzle 19. A cylindrical packing 60 made of an elastic material such as rubber is fitted into the bolt insertion hole 34 of the support tube 18. This prevents a portion of the air 11 supplied from the air supply tube 12 through the ventilation flow path 46 of the gas supply nozzle 19 into the bag-shaped portion 23 of the membrane 17 from leaking into the support tube 18 from between the bolt insertion hole 34 and the T-head bolt 57.

The perimeter of the inner perimeter of the membrane 17 (hereafter referred to as the inner perimeter) is longer than the perimeter of the outer perimeter of the support tube 18 (hereafter referred to as the outer perimeter). As a result, when the air 11 in the air supply tube 12 is not supplied to the bag-shaped portion 23 of the membrane 17 and the bag-shaped portion 23 is contracted, the inner perimeter of the membrane 17 (i.e., the inner perimeter of the sheet member 22 on the back side) does not contact the outer perimeter of the support tube 18 around the entire circumference without any gaps, but a gap with a certain degree of leeway is formed between the inner perimeter of the membrane 17 and the outer perimeter of the support tube 18.

Here, at both ends C of the membrane 17 in the longitudinal direction A, there is enough room for the membrane 17 to float up between the inner circumferential surface of the membrane 17 and the outer circumferential surface of the support tube 18, so when air 11 in the air supply tube 12 is supplied into the bag-shaped portion 23 of the membrane 17, as shown in Figures 3 and 10, the air 11 accumulates at the top of the bag-shaped portion 23, and the top of the membrane 17 floats up relative to the support tube 18. As a result, as shown in Figures 3, 8 to 10, when air 11 is released to the outside from the slits 30 during aeration, both ends C of the membrane 17 float up higher than the center portion B, as shown by the imaginary lines in Figure 2, and reach a higher position.

In contrast, as shown in Figures 8 and 9, at the center B in the longitudinal direction A of the membrane 17, a gas supply nozzle 19 is attached to the membrane 17, and the membrane 17 is biased downward relative to the support tube 18. Therefore, there is little room for the membrane 17 to float up between the inner surface of the membrane 17 and the outer surface of the support tube 18, and even if air 11 in the air supply tube 12 is supplied into the bag-shaped portion 23 of the membrane 17, the upper part of the membrane 17 hardly floats up relative to the support tube 18.

The operation of the above configuration is explained below.

As shown in Figures 1, 8 and 9, by driving the blower 15, air 11 is supplied from the blower 15 into the air supply pipe 12, and the air 11 in the air supply pipe 12 flows from the inlet 42 of the gas supply nozzle 19 through the air flow path 46 and into the bag-shaped portion 23 of the membrane 17 through the outlet 43. This causes the bag-shaped portion 23 to expand, and the air 11 in the bag-shaped portion 23 is released to the outside through the slits 30 in the front sheet member 21, so that a large number of air bubbles 4 are released from the membrane type air diffuser 10 into the water to be treated 3.

At this time, the air 11 supplied from the outlet 43 of the gas supply nozzle 19 into the bag-shaped portion 23 of the membrane 17 encounters flow resistance as it flows from the center B toward both ends C in the longitudinal direction A of the membrane 17, so the pressure loss at both ends C of the membrane 17 becomes greater than the pressure loss at the center B.

In contrast, when air 11 is released to the outside from slits 30 as described above, buoyancy acts on membrane 17 due to the air 11 supplied into bag-shaped portion 23 of membrane 17, and this buoyancy causes both ends C of membrane 17 to rise higher than center B, as shown by the imaginary lines in Figure 2. As a result, depth D1 from the water surface of the water 3 to both ends C of membrane 17 in the aerobic tank becomes shallower than depth D2 from the water surface to center B of membrane 17, and the water pressure applied to both ends C of membrane 17 becomes smaller than the water pressure applied to center B of membrane 17.

In this way, at both ends C of the membrane 17, the effect of increased pressure loss making it difficult to release the air bubbles 4 and the effect of decreased water pressure making it easier to release the air bubbles 4 are offset, thereby reducing the variation in the amount of air bubbles 4 released at the center B and both ends C of the membrane 17, thereby improving the unevenness of air diffusion in the membrane type air diffuser 10.

Furthermore, as shown in FIG. 1, the membrane type air diffuser 10 is perpendicular to the air supply pipe 12 at the center in the longitudinal direction A, so that the air 11 is supplied uniformly into the bag-shaped portion 23 from the center B of the membrane 17 toward both ends C through the air flow path 46 of the gas supply nozzle 19. Therefore, a large number of air bubbles 4 are released uniformly from the membrane 17, without being released locally and unevenly.

In addition, since the air supply pipe 12 is located below the membrane type aeration device 10, a large number of air bubbles 4 are released into the treated water 3 through the slits 30 of the membrane type aeration device 10 without being blocked by the air supply pipe 12.

The manufacturing method of the membrane 17 of the membrane type aeration device 10 is described below.

First, as shown in FIG. 16, the tube portion 37 of the gas supply nozzle 19 is inserted into the first through-hole 26 of the front sheet member 21, which has multiple slits 30 formed therein, and the peripheral portion of the first through-hole 26 is welded to the underside of the flange portion 38 of the gas supply nozzle 19, thereby attaching the gas supply nozzle 19 to the front sheet member 21.

Then, as shown in FIG. 17, the outer edge 65 (see FIG. 16) of the front sheet member 21 and the outer edge 66 (see FIG. 16) of the back sheet member 22 are welded together to form a rectangular membrane sheet 67 having a bag-shaped portion 23. Note that the dotted area in FIG. 17 is the welded portion 29 between the front sheet member 21 and the back sheet member 22.

Then, as shown in FIG. 17, the opposing long sides 68 of the membrane sheet 67 are joined together to form a tube, thereby forming the membrane 17, as shown in FIG. 4, which has a bag-shaped portion 23 inside, an insertion portion 16 in the center, a first opening 24 at the top, and a gas supply nozzle 19 at the bottom.

In the above first embodiment, a front sheet member 21 and a back sheet member 22 of approximately the same shape are used to form a tubular membrane 17, but the front sheet member 21 may be welded to the back sheet member 22 only in the necessary area to form a bag-shaped portion 23, or the back sheet member 22 may be welded to the front sheet member 21 only in the necessary area to form a bag-shaped portion 23.
Second Embodiment
In the first embodiment described above, as shown in Fig. 7, the support tube 18 is a straight circular tube having a constant outer circumferential length, but in the second embodiment described below, as shown in Fig. 18, the outer circumferential length of the support tube 18 is formed so that it is shorter at both ends C than at the central portion B. In other words, the outer diameter E1 of the support tube 18 is smaller at both ends C than at the central portion B, and gradually decreases from the central portion B to both ends C.

Accordingly, as shown by the solid line in Figure 19, when the air diffusion is stopped and the bag-shaped portion 23 is contracted, the space 64 between the inner surface of the membrane 17 and the outer surface of the support tube 18 is wider at both ends C than at the center B, so there is more space between the membrane 17 and the support tube 18 at both ends C than at the center B.

As a result, as shown by the phantom lines in Figure 19, when the bag-shaped portion 23 inflates and the air 11 is released to the outside through the slits 30 during aeration, the buoyancy acting on the membrane 17 causes both ends C of the membrane 17 to rise higher than the central portion B and become positioned higher.
Third Embodiment
20, the inner periphery of the membrane 17 is longer at both ends C than at the center B. That is, the inner diameter E2 of the membrane 17 is larger at both ends C than at the center B, and gradually increases from the center B toward both ends C. The support tube 18 is a straight circular tube having a constant outer diameter.

According to this, when the air diffusion is stopped and the bag-shaped portion 23 is contracted, the space 64 between the inner surface of the membrane 17 and the outer surface of the support tube 18 is wider at both ends C than at the center B, so there is more space between the membrane 17 and the support tube 18 at both ends C than at the center B.

As a result, as shown by the phantom lines in Figure 20, when the bag-shaped portion 23 is inflated and the air 11 is released to the outside through the slits 30 during aeration, the buoyancy acting on the membrane 17 causes both ends C of the membrane 17 to rise higher than the central portion B and become positioned higher.
(Fourth embodiment)
In the fourth embodiment, as shown in Fig. 21, the bottoms of both ends C of the support tube 18 are positioned higher than the bottom of the central portion B. That is, both ends C of the support tube 18 are bent obliquely upward from the central portion B, and by inserting the support tube 18 having such a shape into the insertion portion 16 of the membrane 17, as shown in Fig. 22, the bottoms of both ends C of the membrane 17 are positioned higher than the bottom of the central portion B.

In each of the above embodiments, air 11 is used as the gas for diffusion, but gases other than air 11 may also be used.

3. Water to be treated (liquid)
4 Air bubbles 10 Membrane type air diffuser 11 Air (gas)
16 Insertion part 17 Membrane 18 Support tube (support)
19 Gas supply nozzle (gas supply section)
21: front sheet member 22: rear sheet member 23: bag-shaped portion 30: slit 46: ventilation flow path A: longitudinal direction B: central portion C: end portion

Claims (5)

A membrane type aeration device that is installed below the liquid surface and releases air bubbles into the liquid,
The membrane has a tubular shape and a hollow insertion portion, a support inserted into the insertion portion of the membrane, and a gas supply portion provided in the center of the membrane in the longitudinal direction,
The membrane has a bag-shaped portion formed in a bag shape by two sheet members on the front and back,
the gas supply unit has an air passage communicating from the outside to the inside of the bag-shaped portion of the membrane;
a sheet member constituting an outer peripheral surface of the bag-shaped portion of the membrane is formed with a plurality of slits for discharging to the outside the gas supplied into the bag-shaped portion through the ventilation flow path of the gas supply portion;
A membrane type air diffuser characterized in that, when gas is released to the outside through the slits, both ends in the longitudinal direction of the membrane are positioned higher than the center. The membrane type air diffuser according to claim 1, characterized in that the membrane has more space between itself and the support at both ends in the longitudinal direction than at the center. A membrane-type air diffuser according to claim 1 or 2, characterized in that the outer periphery of the support is shorter at both ends in the longitudinal direction than at the center. A membrane type air diffuser according to any one of claims 1 to 3, characterized in that the inner periphery of the membrane is longer at both ends in the longitudinal direction than at the center. The membrane type air diffuser according to claim 1, characterized in that the bottoms of both ends of the support in the longitudinal direction are positioned higher than the bottom of the center.

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