JP2017209618A - Air diffuser and air diffusing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air diffuser capable of smoothly executing filtration treatment without hindering tearing off of a suspension substance.SOLUTION: An air diffuser comprises an air diffusing pipe that is disposed under a membrane module unit having a membrane element disposed in a treatment tank containing target water to be treated, and diffuses gas. The air diffusing pipe comprises: a cylindrical main pipe for receiving supply of gas from a gas supply device; and a plurality of branch pipes 3 having a plurality of air diffusing holes 8 opening upward and an opening part opening downward in a central part in the length direction, and connected such that the inside communicates with the main pipe. The main pipe includes a pair of parallel pipes arranged in parallel at an interval. The branch pipes are respectively connected to the pair of parallel pipes on both ends, and are arranged at multiple positions at intervals in the extending direction of the parallel pipes. Assuming the arrangement pitch of the plurality of branch pipe as P, a distance between the air diffusing hole and the lower end of the membrane element as h, and a diffusion angle of bubbles of gas discharged from the air diffusing hole as θ, an expression P≤2h*tan(θ/2) is satisfied.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an air diffuser and an air diffuser method.

  In recent years, various methods for solid-liquid separation of activated sludge using membrane modules provided with separation membranes such as microfiltration membranes and ultrafiltration membranes have been studied. When the activated sludge is filtered using a separation membrane, treated water with high water quality can be obtained.

  When solid-liquid separation of water to be treated is performed using a separation membrane, clogging of the separation membrane surface due to suspended substances progresses as the filtration process continues, so the filtration flow rate decreases and the transmembrane pressure increases. Arise. In order to prevent such a state, an air diffuser is disposed below the membrane module, and air is diffused from the air diffuser to form bubbles and a gas-liquid mixed flow with the liquid to be processed caused by the rising of the bubbles. A method is used in which suspended substances on the surface of the membrane are peeled off by washing against a module. A diffuser pipe is usually a tubular pipe made of metal, resin, etc. with gas discharge holes open, and is made up of members of the same diameter for ease of production. Air is blown into these diffuser pipes by a blower or the like. It is supplied and diffused (see Patent Document 1).

JP 2010-111976 A

  Cleaning is performed by disposing a diffuser tube below the membrane module, performing air diffusion from the diffuser tube, and applying a gas-liquid mixed flow with bubbles and the liquid to be treated generated by the rising of the bubbles to the membrane module. ing. Bubbles discharged from the air diffusing tube diffuse and expand as they rise to hit the entire membrane module.

  However, a distance from the air diffusing tube to the membrane module (running distance) is necessary, and if this distance is secured, there is a problem that the membrane module becomes high and compactness deteriorates. On the other hand, if the distance from the diffuser tube to the membrane module is shortened, the bubbles discharged from the diffuser tube are not sufficiently diffused so that the gas-liquid mixed flow with the liquid to be treated cannot be applied to the entire membrane module and suspended. There is a possibility that the filtration process may be hindered due to insufficient peeling of the material.

  The present invention has been made in consideration of the above points, and provides an air diffuser and an air diffuser capable of smoothly performing a filtration process without hindering the removal of suspended solids. Objective.

The present invention has the following aspects.
[1] An air diffuser provided with an air diffuser arranged below a membrane module unit having a membrane element disposed in a water tank in which treated water is stored, the air diffuser comprising: It has a cylindrical main pipe that receives gas supply from a gas supply device, a plurality of air diffusion holes that open upward, and an opening that opens downward in the center in the length direction. And a plurality of branch pipes connected in a state where the main pipes are in communication with each other, wherein the main pipe includes a pair of parallel pipes arranged in parallel with a space therebetween, and both ends of the branch pipes are respectively connected to the pair of parallel pipes. A plurality of branch pipes arranged at intervals in the extending direction of the parallel pipes, the arrangement pitch of the plurality of branch pipes being P, the distance between the air diffuser holes and the lower end of the membrane element being h, and discharging from the air diffuser holes The angle of diffusion of the gas bubbles to be Then, air diffuser satisfying the equation P ≦ 2h · tan (θ / 2).
[2] The air diffuser according to [1], wherein the flow rate of the gas discharged from the air diffuser is 3 m / s or more.
[3] The air diffuser according to [1] or [2], wherein the air diffuser has a diameter of 1 mm or more and 10 mm or less.
[4] The air diffuser according to any one of [1] to [3], wherein one end of the main pipe is bent downward in an L shape in an open state.
[5] The air diffuser according to any one of [1] to [4], wherein a sum of cross-sectional opening areas of the main pipe is larger than a sum of cross-sectional opening areas of the branch pipes.
[6] The air diffuser according to any one of [1] to [5], wherein the opening of the branch pipe projects in a nozzle shape.
[7] The air diffuser according to any one of [1] to [6], wherein a material of the main pipe and the branch pipe is a thermoplastic resin.
[8] The air diffuser according to any one of [1] to [7], further including a decompressor that decompresses the inside of the air diffuser.
[9] The air diffuser according to any one of [1] to [8] is disposed in a treatment tank in which water to be treated is stored, and gas is continuously supplied to the air diffuser for a predetermined time. A gas diffusion method in which the supply of gas is stopped for a certain period of time after being supplied.
[10] The air diffusion method according to [9], wherein the inside of the air diffusion pipe is decompressed while the gas supply is stopped for the predetermined time.

  In the present invention, it is possible to smoothly carry out the filtration treatment without hindering the removal of the suspended substance.

It is a figure which shows typically schematic structure of a water treatment apparatus provided with the aeration apparatus which concerns on this invention. It is an external appearance perspective view of the diffuser tube which concerns on this invention. FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. It is a side view of a membrane module unit. It is a front view of a membrane module unit.

Hereinafter, embodiments of an air diffuser and an air diffuser according to the present invention will be described with reference to FIGS.
The following embodiments show one aspect of the present invention and do not limit the present invention, and can be arbitrarily changed within the scope of the technical idea of the present invention. Moreover, in the following drawings, in order to make each configuration easy to understand, the actual structure is different from the scale and number of each structure.

  FIG. 1 is a diagram schematically illustrating a schematic configuration of a water treatment device 30 including an air diffuser 1 according to the present invention. The water treatment device 30 includes a water tank (treatment tank) 32 into which water to be treated 31 such as activated sludge is charged, a membrane module unit 10 disposed in the water tank 32, and a part thereof below the membrane module unit 10. It is an immersion type membrane separation apparatus provided with the diffuser 1 made.

  In the water treatment device 30 of the present embodiment, as an example, there are three membrane module units 10, and thus the air diffuser 1 is also arranged below each corresponding to each membrane module unit 10. However, the numbers of the membrane module units 10 and the air diffuser 1 are not particularly limited and can be arbitrarily set.

Although the water tank 32 has a rectangular parallelepiped shape and the size is not particularly limited, it is preferable that the depth sufficiently exceeds 1 m so that the depth of the water to be treated 31 is 1 m or more.
The membrane module unit 10 includes a plurality of membrane modules 11. The membrane module 11 includes a membrane element (not shown) such as a hollow fiber membrane.

  A suction pump (not shown) is connected to the membrane module unit 10 (membrane module 11) via a suction pipe 47 so that the water to be treated 31 can be suction filtered by the membrane module unit 10.

  The air diffuser 1 includes an air diffuser 1 </ b> A, an air supply device (gas supply device) 40, and a decompression device 43. The air diffuser 1 </ b> A is disposed below the membrane module unit 10. FIG. 2 is an external perspective view of the air diffusion tube 1A. As shown in FIG. 2, the air diffusion pipe 1 </ b> A is formed in a ladder shape (ladder shape) including a cylindrical main pipe 2 and a plurality of branch pipes 3 connected to the main pipe 2. The main pipe 2 and the branch pipe 3 are arranged horizontally.

  The total cross-sectional opening area of the main pipe 2 is set larger than the total cross-sectional opening area of the branch pipe 3. Thereby, the air for aeration supplied to the main pipe 2 can be made to flow into the branch pipe 3 without the main pipe 2 becoming a bottleneck.

  The main pipe 2 is made of metal (for example, made of SUS304) or thermoplastic synthetic resin (for example, made of polyethylene or polyvinyl chloride), and a pair of parallel pipes 2A arranged in parallel with a gap between them, It has a connecting pipe 2B for connecting one end of the parallel pipe 2A through the elbow pipe 4. A flange pipe 5 extending upward in the vertical direction is connected to the central portion in the length direction of the connecting pipe 2B. An air supply device 40 and a decompression device 43 are connected to the flange tube 5 via an air supply tube 21 (see FIG. 4) (details will be described later).

  The parallel tube 2A has an opening 6a facing downward in the vertical direction by connecting an elbow tube 6 bent downward in an L shape to the other end side.

  Both ends of the branch pipe 3 are connected to a pair of parallel pipes 2A, and a plurality (10 in FIG. 2) are arranged at intervals in the extending direction of the parallel pipes 2A. Each branch pipe 3 is formed with one or a plurality of air diffusion holes 8 on the upper surface thereof. The number of the air holes 8 is appropriately set based on the length of the branch pipe 3 and the like, but is preferably 2 to 6. In the present embodiment, as shown in FIG. 5, six are formed symmetrically about the center in the length direction at intervals of about 80 mm to 100 mm. Further, these air diffusion holes 8 are all formed so as to face upward in the vertical direction in a state where the air diffusion pipe 1A is disposed horizontally. The diameter of the air diffusion hole 8 is preferably 1 mm or more in consideration of the blockage due to the adhesion of the adhering matter, and 10 mm in consideration of the possibility that the sufficient air diffusion effect may not be obtained due to the low flow velocity of the air passing therethrough. The following is preferred.

  A three-way pipe (T-shaped three-way pipe) 7 formed in a T shape is connected to the center in the length direction of the branch pipe 3. A central tube 7a of the three-way tube 7 protrudes downward in a nozzle shape to form an opening 7b.

3 is a cross-sectional view taken along line AA in FIG. As shown in FIG. 3, the arrangement pitch of the plurality of branch pipes 3 is P, the distance between the diffuser holes 8 and the lower end of the membrane element of the membrane module 11 is h, and the diffusion angle of air bubbles discharged from the diffuser holes 8 Is θ, the diffuser 1 in the present embodiment satisfies the following expression (1).
P ≦ 2h · tan (θ / 2) (1)

  When the expression (1) is satisfied, a part of the diffused region 9 where the bubbles diffused from the diffused holes 8 of the adjacent branch pipes 3 to the treated water 31 rise and diffuse to reach the lower end of the membrane element. Will overlap. In other words, when the expression (1) is satisfied, a diffused blank portion in which the diffused region 9 is not formed does not occur at the lower end of the membrane element of the membrane module 11.

  The main pipe 2 and the branch pipe 3 are used by being arranged below the membrane module unit 10. FIG. 4 is a side view of the membrane module unit 10. FIG. 5 is a front view of the membrane module unit 10.

  As shown in FIGS. 4 and 5, in the air diffuser 1, an air supply pipe 21 is connected to the flange pipe 5. The air supply pipe 21 is connected to an air supply device 40 and a decompression device 43, as shown in FIG.

  The air supply device 40 includes a blower 41 and a connection pipe 42 that connects the blower 41 and the air supply pipe 21. The decompression device 43 includes a suction pump 44 and a connection pipe 45 that connects the suction pump 44 and the air supply pipe 21.

  A switching valve 46 composed of a three-way valve is provided between the connection pipe 42, the connection pipe 45, and the air supply pipe 21. Under such a configuration, the blower 41 (air supply device 40) and the air supply pipe 21 are communicated with each other by switching the switching valve 46, or the suction pump 44 (decompression device 43) and the air supply pipe 21 are connected. It can be communicated. That is, in the air diffuser 1, when the air diffuser operation for supplying air by the air supply device 40 is stopped by switching the air diffuser operation and the pressure reducer operation by the switching valve 46, the main pipe 2 is removed by the pressure reducer 43. The inside and the branch pipe 3 can be depressurized.

Next, one embodiment of the air diffusion method according to the present invention will be described based on the treatment operation of the water treatment apparatus 30.
First, as shown in FIG. 1, the membrane module unit 10, the air diffuser 1, and the like are disposed in the water tank 32, and the treated water 31 is stored so as to have a predetermined water level (water depth). In this state, suction filtration by the membrane module unit 10 is performed by operating the suction pump on the membrane module unit 10 side.

  In parallel with such suction filtration, air is supplied continuously (continuously) from the air supply device 40 (blower 41) toward the diffuser pipe 1A for a predetermined time. Although the air supply amount varies depending on the size of the air diffusion pipe 1A, the air supply amount is set to 75 L / min for each branch pipe 3, for example. By supplying air in this way, most of the air supplied to the diffuser pipe 1 </ b> A through the air supply pipe 21 is ejected from the diffuser holes 8 of the branch pipe 3 through the main pipe 2. That is, since the water pressure in the air diffuser 8 is lower than that of the opening 7 b of the branch pipe 3, most of the air supplied to the air diffuser 1 </ b> A is ejected from the air diffuser 8 unless air is supplied at a particularly high air volume. Is done.

  The amount of air supplied to the air diffuser 1A is such that the flow rate of air discharged from the air diffuser 8 is 3 m / s or more. If the flow velocity of air is 3 m / s or more, it is possible to suppress the adhering matter from adhering to the air diffusion holes 8 and blocking.

  When air is ejected from the air diffusion holes 8 in this way, the ejected air becomes bubbles and rises in the water tank 32, that is, in the liquid to be treated 31. The rising bubbles form a gas-liquid mixed flow with the liquid 31 to be processed. This gas-liquid mixed flow hits the membrane module unit 10 (membrane module 11) to wash each membrane element (not shown). That is, the gas-liquid mixed flow peels off suspended substances such as sludge adhering to the surface of the membrane element (membrane module unit 10) and removes them from the membrane module unit 10.

  At this time, in the air diffuser 1, since air is diffused under the specifications that satisfy the above formula (1), the entire region of the membrane element is the air diffused region 9, and a blank portion of air diffused is generated. Without removing the suspended matter, the filtration process can be carried out smoothly.

  When the aeration operation is performed for a predetermined time, the blower 41 is stopped for a certain time, and the supply of air to the aeration apparatus 1 is stopped. Then, the air remaining in the main pipe 2 and the branch pipe 3 passes through the air diffusion holes 8 and is discharged into the water to be treated 31 to clean the membrane module unit 10. In addition, the water to be treated 31 flows from the opening 3 b at the other end of the branch pipe 3 by replacing this air. The treated water 31 flowing in this way wets, for example, dried and accumulated foreign matter (sludge) clogging the diffuser holes 8 and sludge accumulated in the diffuser pipe 3. Therefore, when the blower 41 is operated again after a certain time has elapsed and the aeration is resumed, these foreign matters and sludge can be easily discharged from the aeration holes 8. That is, the inside of the main pipe 2, the branch pipe 3, and the air diffusion holes 8 can be cleaned.

  In the present embodiment, since the decompression device 43 is connected to the air diffuser 1A, the suction pump 44 (the decompression device 43) is dispersed by switching the switching valve 46 while the blower 41 is stopped for a certain time. The main pipe 2 and the branch pipe 3 can be decompressed by the suction pump 44 in communication with the trachea 1A. By performing the depressurization process in this way, the treated water 31 can flow more into the branch pipe 3 and the main pipe 2 at a higher speed, and thus the above-described cleaning effect can be enhanced.

  In the air diffuser 1 of the present embodiment, the arrangement pitch of the branch pipes 3, the distance between the air diffuser holes 8 and the lower end of the membrane element, and the diffusion angle of the bubbles discharged from the air diffuser holes 8 satisfy the above formula (1). Since it is satisfied, the entire area of the membrane element can be diffused without increasing the membrane module 11. Therefore, in the air diffusing device 1 of the present embodiment, it is possible to smoothly carry out the filtration process without causing any trouble in peeling off the suspended solids.

[Example]
When air is diffused using the air diffuser 1 having a diameter of the air diffuser 8 of 5.5 mm, an arrangement pitch of the branch pipes 3 110 mm, and a distance of 200 mm between the air diffuser 8 and the lower end of the membrane element, a bubble diffusion angle of 32 ° is obtained. It was. In this case, the left side (P) in Formula (1) is 110 mm, and the right side is about 115 mm, which satisfies Formula (1). Although the water treatment for 30 days was implemented using this aeration apparatus 1, adhesion of the suspended substance to the membrane surface of a membrane element was not confirmed but the membrane treatment was performed stably.
[Comparative example]
When air was diffused using the air diffuser 1 having a diameter of the air diffuser 8 of 5.5 mm, an arrangement pitch of the branch pipes 3 of 90 mm, and a distance of 200 mm between the air diffuser 8 and the lower end of the membrane element, the bubble diffusion angle was 25 °. It was. In this case, the left side (P) in Formula (1) is 90 mm, and the right side is about 88 mm, which does not satisfy Formula (1). Water treatment was carried out using this air diffuser, and adhesion of suspended substances to the membrane surface of the membrane element was confirmed after about 15 days.

  As described above, the preferred embodiments according to the present invention have been described with reference to the accompanying drawings, but the present invention is not limited to the examples. Various shapes, combinations, and the like of the constituent members shown in the above-described examples are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

  For example, in the above-described embodiment, air is supplied from the air supply device 40 to the diffuser pipe 1A, and the air is ejected from the diffuser holes 8, but if necessary, a gas other than air, such as nitrogen, may be used. Alternatively, the gas supply device 40 may supply the air diffusing tube 1A.

  DESCRIPTION OF SYMBOLS 1 ... Air diffuser, 1A ... Air diffuser pipe, 2 ... Main pipe, 2A ... Parallel pipe, 3 ... Branch pipe, 7b ... Opening part, 10 ... Membrane module unit, 31 ... Water to be treated, 40 ... Air supply apparatus (gas) Supply device), 43 ... decompression device

Claims (10)

An air diffuser provided with an air diffuser that is disposed below a membrane module unit having a membrane element disposed in a treatment tank in which water to be treated is stored.
The diffuser pipe is a cylindrical main pipe that receives gas supply from a gas supply device;
A plurality of air diffuser holes that open upward and an opening that opens downward in the central portion in the length direction, and a plurality of branch pipes that are connected in a state in which the inside communicates with the main pipe;
The main pipe includes a pair of parallel pipes arranged in parallel at intervals,
Both ends of the branch pipe are connected to the pair of parallel pipes, and a plurality of the branch pipes are arranged at intervals in the extending direction of the parallel pipes.
When the arrangement pitch of the plurality of branch pipes is P, the distance between the diffuser holes and the lower end of the membrane element is h, and the diffusion angle of the gas bubbles discharged from the diffuser holes is θ,
P ≦ 2h · tan (θ / 2)
Air diffuser that satisfies the following formula.   The air diffuser according to claim 1, wherein a flow velocity of the gas discharged from the air diffuser is 3 m / s or more.   The air diffuser according to claim 1 or 2, wherein a diameter of the air diffuser is 1 mm or more and 10 mm or less.   4. The air diffuser according to claim 1, wherein one end of the main pipe is bent downward in an L shape in an open state. 5.   The diffuser according to any one of claims 1 to 4, wherein a sum of cross-sectional opening areas of the main pipe is larger than a sum of cross-sectional opening areas of the branch pipes.   The diffuser according to any one of claims 1 to 5, wherein the opening of the branch pipe protrudes in a nozzle shape.   The aeration apparatus according to any one of claims 1 to 6, wherein a material of the main pipe and the branch pipe is a thermoplastic resin.   The aeration apparatus according to any one of claims 1 to 7, further comprising a decompression device that decompresses the inside of the aeration tube.   The aeration apparatus according to any one of claims 1 to 8 is disposed in a treatment tank in which water to be treated is stored, and a gas is continuously supplied to the aeration pipe for a predetermined time, and then for a predetermined time. Aeration method to stop gas supply.   The aeration method according to claim 9, wherein the inside of the aeration pipe is decompressed while the gas supply is stopped for the predetermined time.

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