Air diffuser, water treatment apparatus, and water treatment method

Abstract

To provide an air diffuser capable of suppressing a decrease in air discharge volume from diffuser holes located away from the air supply side to a diffuser pipe, without requiring complex calculations for the design or placement of the diffuser pipe, and without requiring precise on-site work, and a water treatment apparatus and a water treatment method using the air diffuser.SOLUTION: An air diffuser includes a horizontally arranged diffuser pipe. The diffuser pipe has an air supply port for supplying air at one end, has a structure capable of sealing air at the other end, and has a plurality of diffuser holes provided at a lower part at intervals in a length direction. A plurality of cylindrical skirts hung from the periphery of each diffuser hole are connected to portions where the air diffuser holes of the respective diffuser pipes are formed, and each skirt has a skirt length adjustment mechanism for adjusting a length of the skirt.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an aeration device, a water treatment device, and a water treatment method. [Background technology]

[0002] Biological nitrification is a process in which ammoniacal nitrogen in water to be treated is converted to nitrate by microorganisms. Ammoniacal nitrogen can be found in groundwater, well water, lake water, river water, and industrial wastewater, for example.

[0003] One biological treatment system for water containing ammonia nitrogen is a sponge nitrification treatment system, which fills a biological carrier such as a sponge with microorganisms such as nitrifying bacteria attached to it, and passes the water through the system while aerating it from the bottom with a blower or other device. In aerobic treatment technology using such biological carriers, air is aerated from the bottom of the system using an aeration device to remove coarse bacteria and other attached matter and supply dissolved oxygen. Alternatively, a moving-bed push-flow system may be used, in which the water is passed through as a push-flow system using uniform aeration, causing the biological carrier to move.

[0004] Patent Document 1 discloses an aeration device used in an aerobic biological treatment device, which is equipped with an aeration pipe having a plurality of aeration holes. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-63365 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in an air diffusion device such as that in Patent Document 1, the closer the air hole is to the air supply side, the greater the amount of air released, and the further away from the supply side the air release amount is. Therefore, a certain amount of air volume is required to release a uniform amount of air from each air hole in the air diffusion pipe, which increases the amount of air sent and leads to higher electricity costs. Furthermore, with the air diffusion pipe described in Patent Document 1, it is necessary to take into consideration pressure loss and the height of the diffusion holes, and therefore designing and arranging the air diffusion pipe requires complex calculations and precise on-site work.

[0007] An object of the present invention is to provide an air diffusion device, a water treatment device, and a water treatment method that can suppress a decrease in the amount of air released from an air diffusion hole located away from the air supply side to the air diffusion pipe, and that do not require complicated calculations or precise on-site work in the design and placement of the air diffusion pipe. [Means for solving the problem]

[0008] As a result of extensive research, the inventors have discovered that by employing an expandable mechanism in the skirt of the air diffuser pipe, it is possible to obtain an air diffuser, water treatment device and water treatment method that can uniformly adjust the amount of air released from each air diffuser hole with a simple structure, and have completed the present invention.

[0009] That is, the present invention has the following configuration. [1] An air diffuser equipped with horizontally arranged air diffusers, the air diffusion pipe has an air supply port at one end through which air is supplied, a structure at the other end capable of sealing air, and a plurality of air diffusion holes provided at a lower portion thereof at intervals in the longitudinal direction; a plurality of cylindrical skirts hanging down from the periphery of each of the diffusion holes are connected to the portion of each of the diffusion pipes where the diffusion holes are formed, The air diffuser, wherein each of the skirts has a skirt length adjustment mechanism for adjusting the length of the skirt. [2] The skirt length adjustment mechanism adjusts the height position of the air outlet at the lower end of each skirt so that it becomes lower as it approaches the air supply port. [1] The air diffuser described in [1]. [3] The air diffuser according to [1] or [2], wherein the angle θ formed by the line connecting the center of the air outlet at the bottom end of the skirt farthest from the air supply port and the center of the air outlet at the bottom end of the skirt closest to the air supply port, and the horizontal line is 0.5 to 3 degrees. [4] A water treatment device comprising the aeration device according to any one of [1] to [3]. [5] A water treatment method including diffusing air using an air diffuser immersed in the water to be treated, The air diffuser includes a horizontally arranged air diffuser pipe, the air diffusion pipe has an air supply port at one end through which air is supplied, a structure at the other end capable of sealing air, and a plurality of air diffusion holes provided at a lower portion thereof at intervals in the longitudinal direction; a plurality of cylindrical skirts hanging down from the periphery of each of the diffusion holes are connected to the portion of each of the diffusion pipes where the diffusion holes are formed, A water treatment method, wherein each of the skirts has a skirt length adjustment mechanism that adjusts the length of the skirt. [6] The water treatment method described in [5], wherein the skirt length adjustment mechanism adjusts the height position of the air outlet at the lower end of each skirt so that it becomes lower as it approaches the air supply port. [7] A water treatment method according to [5] or [6], wherein the angle θ formed by the horizontal line and a line connecting the center of the air outlet at the bottom end of the skirt farthest from the air supply port and the center of the air outlet at the bottom end of the skirt closest to the air supply port is 0.5 to 3 degrees. [8] The water treatment method according to any one of [5] to [7], wherein the linear air velocity of the air diffuser is 2.5 to 50 m / sec. [Effects of the Invention]

[0010] According to the present invention, there are provided an air diffusion device, a water treatment device and a water treatment method that can suppress a decrease in the amount of air released from an air diffusion hole that is distant from the air supply side to the air diffusion pipe, and that do not require complicated calculations in the design and placement of the air diffusion pipe, nor do they require precise on-site work. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a water treatment device according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view of an air diffusion pipe of an air diffusion device according to one example of the embodiment, cut vertically along the axial direction. [Figure 3] 3 is a cross-sectional view of the diffuser pipe of FIG. 2, taken perpendicularly to the axial direction, at a portion where the diffuser holes are provided. [Figure 4] FIG. 4 is a cross-sectional view showing an example of adjusting the length of each skirt in the air diffuser pipe of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] As used herein, the following terms have the following meanings: "Ammoniacal nitrogen" refers to nitrogen contained in water as an ammonium salt. It is also called ammoniacal nitrogen. The symbol "to" indicating a range of values means that the values before and after it are included as the lower and upper limits.

[0013] The dimensions of the figures illustrated in the following description are merely examples, and the present invention is not necessarily limited to them, and can be implemented with appropriate modifications within the scope that does not change the gist of the present invention.

[0014] <Water treatment equipment> FIG. 1 is a schematic diagram showing a water treatment device 1 according to an example of the embodiment. The water treatment device 1 includes a water tank 10 for storing water to be treated, and an aeration device 20 for diffusing air within the water tank 10. The water tank 10 may be provided with a water supply pipe for supplying water to be treated to the water tank 10, and a treated water outlet pipe through which the water treated in the water tank 10 flows out.

[0015] The water treatment device according to the embodiment can be suitably applied to biological nitrification treatment in which ammoniacal nitrogen in water to be treated is converted into nitric acid by microorganisms. For example, by connecting a water supply pipe to the bottom of the water tank 10 and a water outlet pipe to the top, and filling the water tank 10 with multiple biological retainers to form a nitrification tank, and making each biological retainer capable of swinging when water to be treated is passed through the biological retainer area formed by the multiple biological retainers, the water treatment device 1 can be used as a biological nitrification treatment device of the swinging bed push flow type. The water treatment device according to the embodiment may be used for water treatment other than biological nitrification treatment.

[0016] (aeration device) The air diffuser 20 according to one example of the embodiment includes a horizontally arranged air diffuser pipe 22, a blower 24, and an air supply pipe 26 that supplies air from the blower 24 to the air diffuser pipe 22.

[0017] As shown in the example in Fig. 2, the air diffuser pipe 22 has an air supply port 28 at one end through which air is supplied, and an air sealing section 30 at the other end. Note that the air sealing section 30 need only have a structure that can seal air, and is not limited to a structure that constantly seals air. For example, the air sealing section 30 may have an open / close structure that can be temporarily opened.

[0018] An air supply pipe 26 is connected to an air supply port 28 of the air diffuser pipe 22, and air is supplied by a blower 24. The material of the aeration pipe 22 is not particularly limited, and examples thereof include vinyl chloride and stainless steel. The diameter of the air diffusion pipe 22 is not particularly limited and may be appropriately designed according to the amount of air to be supplied.

[0019] As shown in the example in Figures 2 and 3, a plurality of air diffusion holes 32 are formed at intervals in the longitudinal direction of the air diffusion pipe 22 at the bottom of the air diffusion pipe 22, which is arranged so that its length direction is horizontal. The plurality of air diffusion holes 32 are preferably arranged at equal intervals in the length direction of the air diffusion pipe 22, as this facilitates uniform aeration, but this is not a limitation.

[0020] The number and spacing of the air diffusion holes 32 are not particularly limited. The more air diffusion holes 32 there are, the more uniformly the diffused air is dispersed, which is preferable from the viewpoint of oxygen supply. On the other hand, the more air diffusion holes 32 there are, the more skirts 34 must be installed, which makes the device more complicated. Taking these factors into consideration, the number and spacing of the air diffusion holes 32 are appropriately determined according to the aeration performance required of the air diffusion device 20. For example, the spacing between the air diffusion holes 32 is 5 to 20 cm, and the number of air diffusion holes 32 is 20 to 200 per m. 2 It can be about.

[0021] The shape of the air diffuser holes 32 is typically circular, but is not limited to this. The diameter of the air diffusion holes 32 is preferably 1 to 5 mm, and more preferably 2 to 3 mm. If the diameter of the air diffusion holes 32 is equal to or greater than the above-mentioned lower limit, clogging of the air diffusion holes 32 is easily suppressed. If the diameter of the air diffusion holes 32 is equal to or less than the above-mentioned upper limit, it is easy to ensure the number of air diffusion holes 32. Note that if the opening shape of the air diffusion holes 32 is not circular, the diameter of the air diffusion holes 32 means the diameter of a circle inscribed in the opening shape of the air diffusion holes 32.

[0022] The opening area of the air diffusion hole 32 is 1 to 25 mm 2 is preferable, and 3 to 10 mm 2 is more preferable. If the opening area of the air diffusion holes 32 is equal to or greater than the above-mentioned lower limit, the risk of the air diffusion holes being clogged with scale, foreign matter, etc. can be reduced. If the opening area of the air diffusion holes 32 is equal to or less than the above-mentioned upper limit, the linear air velocity of the air diffusion holes 32 can be maintained at a certain level or higher with a smaller air volume.

[0023] A plurality of cylindrical skirts 34 hanging down from the periphery of each air diffusion hole 32 are connected to the portion of the air diffusion pipe 22 where each air diffusion hole 32 is formed. That is, each skirt 34 is installed facing downward at the bottom of the air diffusion pipe 22 so as to surround the air diffusion hole 32. The air diffusion holes 32 and skirts 34 are not limited to being installed facing vertically downward, and may be installed at an angle relative to the height direction (vertical direction) as long as the water to be treated does not reach the air diffusion holes 32.

[0024] The skirt 34 is tubular, typically, but not limited to, cylindrical. The material of the skirt 34 is not particularly limited, and examples thereof include vinyl chloride and stainless steel.

[0025] The inner diameter of the skirt 34 is not particularly limited, but is preferably sufficiently larger than the diameter of the air diffuser holes 32, more preferably 6 mm or more, even more preferably 10 mm or more, and particularly preferably 15 mm or more, in order to reduce the risk of clogging due to the adhesion of scale or biofilm. In order to avoid impeding the water flow and to prevent uneven air release from the skirt edge, the inner diameter of the skirt 34 is preferably 50 mm or less, more preferably 40 mm or less, and even more preferably 30 mm or less.

[0026] Each skirt 34 has a skirt length adjustment mechanism for adjusting the length of the skirt 34 . The skirt length adjustment mechanism for the skirt 34 is not particularly limited as long as it is a mechanism that can adjust the length of the skirt 34, and for example, a combination of male and female threads such as a faucet socket and a valve socket, or a faucet socket and a bushing, or an expansion joint such as a pipe union, or a flexible joint can be used. 2 and 3 includes a cylindrical skirt body 36 connected to the air diffuser 22, and a length adjustment member 38 connected to the lower part of the skirt body 36 so as to be movable up and down. The skirt 34 is expandable and contractable as the length adjustment member 38 moves up and down, and the length of the skirt 34 can be freely adjusted.

[0027] The length of each skirt 34 is preferably designed so that the water to be treated does not enter the aeration pipe 22 through the skirt 34 and the air diffuser holes 32. Furthermore, if the air diffuser holes 32 come into contact with the water to be treated, they may become clogged due to the adhesion of scale and bacterial cells. Therefore, it is preferable to ensure sufficient space between the air outlet 34a at the bottom of the skirt 34 and the air diffuser holes 32. For these reasons, the height difference between the air outlet 34a of the skirt 34 and the air diffuser holes 32 may be appropriately set depending on the on-site conditions, such as the shape of the water tank. For example, 20 mm or more is preferable, and 50 mm or more is more preferable. Also, 300 mm or less is preferable, and 200 mm or less is more preferable. Within the above range, it is considered easy to adjust the angle θ, which will be described later.

[0028] In order to easily prevent clogging of the skirt 34 by bacteria and scale, it is preferable that the opening area of the air discharge port 34a of the skirt 34 is sufficiently larger than the opening area of the air diffusion hole 32, and 2 More than 80mm is preferable. 2 The above is even more preferable. In order to avoid obstructing the water flow and to prevent uneven air release from the skirt edge, the opening area of the air release port 34a of the skirt 34 is 2000 mm 2 Less than 1250mm is preferable 2 The following is more preferred:

[0029] The length of each skirt 34 is preferably adjusted by a skirt length adjustment mechanism so that the height position of the air discharge port 34a at the lower end of each skirt 34 decreases as it approaches the air supply port 28 of the air diffuser pipe 22. With this configuration, air can be supplied uniformly to each skirt 34 with a smaller air volume than conventionally, thereby reducing the operating costs of air blowers and other air delivery devices. In addition, air can be diffused uniformly from each skirt 34 without the need for complex calculations or design of the air diffuser pipe 22.

[0030] 4, a "straight line p" denotes a line connecting the center a of the air discharge port 34a at the bottom end of the skirt 34 that is farthest from the air supply port 28 of the air diffuser pipe 22 and the center b of the air discharge port 34a at the bottom end of the skirt 34 that is closest to the air supply port 28 of the air diffuser pipe 22. If the opening shape of the air discharge port 34a is not circular, the center of the air discharge port 34a means the center of a circle inscribed with the opening shape of the air discharge port 34a. Also, the angle between the line p and the horizontal line h is defined as "angle θ."

[0031] The angle θ can be adjusted according to the linear velocity of the air supplied to the air diffusion holes 32. When the linear velocity of the air is low, it tends to be difficult to maintain uniformity in the amount of air discharged from the air diffusion holes, so it is preferable to set the angle θ large. On the other hand, when the linear velocity of the air is high, it tends to be easier to maintain uniformity in the amount of air discharged from the air diffusion holes, so it is preferable to set the angle θ small. For example, when the linear air velocity of the air diffuser holes 32 is 2.5 to 50 m / sec, the angle θ is preferably 0.5 to 3 degrees, and more preferably 0.7 to 2.5 degrees. If the angle θ is within the above range, it becomes easy to uniformly release air from the air release ports 34a of each skirt 34. When biological nitrification treatment is performed, the biological retainer can be rocked more efficiently. Furthermore, when the linear air velocity at the air diffusion holes 32 exceeds 50 m / sec, the angle θ is preferably 0 to 1 degree. The linear air velocity at the diffuser hole is the air supply rate [m 3 / sec] is the total opening area of each air diffuser [m 2 ] is the value divided by

[0032] By using the air diffusion device according to the embodiment described above, it is possible to suppress a decrease in the amount of air released from the air diffusion holes located away from the air supply port of the air diffusion pipe. Furthermore, the design and placement of the air diffusion pipe does not require complicated calculations, and precise on-site work is not required.

[0033] <Water treatment method> The water treatment method according to the embodiment includes diffusing air using the air diffuser according to the embodiment described above. The water treatment method according to the embodiment can employ any known water treatment method, except for diffusing air using the air diffuser according to the embodiment described above.

[0034] Hereinafter, biological nitrification treatment of water to be treated using the aeration device according to the above-described embodiment will be described as an example. For example, a water supply pipe for treated water is connected to the bottom of the water tank 10, and a treated water outflow pipe is connected to the top. Then, a plurality of biological retainers are filled in the water tank 10 above the aeration pipe 22, forming a biological retainer region with the biological retainers, and each biological retainer is caused to oscillate as the water to be treated flows through it. In this way, the water tank 10 for treatment is used as a nitrification tank, and the skirt length of each skirt is adjusted by the skirt length adjusting mechanism of the aeration device to diffuse air uniformly, and biological nitrification treatment is carried out while maintaining a push-out flow from bottom to top in the nitrification tank.

[0035] The water to be treated by biological nitrification treatment may be any water containing at least ammonia nitrogen, and examples thereof include groundwater, well water, lake water, river water, industrial water, sewage, and wastewater. However, the water to be treated is not limited to these examples. Examples of treated water include drinking water, domestic water, and discharged water. The content of ammonia nitrogen in the water to be treated is not particularly limited, but is, for example, within the range of 0.1 to 30 mg / L.

[0036] In addition to ammonia nitrogen, the water to be treated may further contain anions such as bicarbonate ions, nitrate ions, sulfate ions, and chloride ions; cations such as iron ions, manganese ions, calcium ions, and magnesium ions; organic matter; bacteria; etc. However, the components contained in the water to be treated are not limited to these. The main components of organic matter in the water to be treated include humic acid, fulvic acid, etc. However, the water to be treated may contain organic matter other than these exemplified components.

[0037] The bioretainer is a carrier that holds nitrifying bacteria. The shape of the carrier is not particularly limited, and examples thereof include cubes, rectangular parallelepipeds, spheres, cones, polygonal pyramids, cylinders, and filaments. Among these, rectangular parallelepipeds, cubes, and spheres are preferred because they allow for easy shaking during water flow and easy loading into the nitrification tank. The shapes of the carriers may all be the same or different from each other.

[0038] As the carrier, a porous carrier is preferred because it can support a larger number of nitrifying bacteria and improve the nitrification rate. In particular, a sponge carrier is preferred because it can maintain the support of nitrifying bacteria well and minimize damage to pumps and piping. Examples of materials for the sponge carrier include polyvinyl alcohol, polyethylene glycol, and polyurethane.

[0039] As the nitrifying bacteria, known nitrifying bacteria used for biological nitrification of ammoniacal nitrogen can be used. Nitrosomonas and other nitrifying bacteria are autotrophs, essentially using carbon dioxide as their only carbon source. They do not require organic substrates and can grow in the presence of ammonia. However, their growth rate is extremely slow. Therefore, it is preferable to maintain nitrifying bacteria on a carrier rather than as suspended bodies. As a method for supporting nitrifying bacteria on a carrier, for example, a method in which the carrier is placed in a nitrification tank and the nitrifying bacteria are allowed to grow on the surface of the carrier, etc., can be mentioned.

[0040] In diffusing air by the air diffuser 20, the linear air velocity at the air diffusion holes 32 may be set appropriately depending on the raw water quality, nitrification rate, amount of water supplied, etc. For example, it is preferably 2.5 to 50 m / sec, and more preferably 5 to 25 m / sec.

[0041] During biological nitrification treatment, the length of each skirt 34 is preferably adjusted using the skirt length adjustment mechanism so that the height position of the air discharge port 34a at the lower end of each skirt 34 becomes lower as it approaches the air supply port 28 of the aeration pipe 22.

[0042] The angle θ can be adjusted according to the linear velocity of the air supplied to the air diffusion holes 32. When the linear velocity of the air is low, it tends to be difficult to maintain uniformity in the amount of air discharged from the air diffusion holes, so it is preferable to set the angle θ large. On the other hand, when the linear velocity of the air is high, it tends to be easier to maintain uniformity in the amount of air discharged from the air diffusion holes, so it is preferable to set the angle θ small. For example, when the linear air velocity of the air diffuser holes 32 is 2.5 to 50 m / sec, the angle θ is preferably 0.5 to 3 degrees, and more preferably 0.7 to 2.5 degrees. If the angle θ is within the above range, it becomes easy to uniformly release air from the air release ports 34a of each skirt 34. When biological nitrification treatment is performed, the biological retainer can be rocked more efficiently. Furthermore, when the linear air velocity at the air diffusion holes 32 exceeds 50 m / sec, the angle θ is preferably 0 to 1 degree. If the air diffuser pipe structure is loop-shaped or branch-shaped, the air diffuser hole closest to the air supply side and the air diffuser hole furthest away are used as the reference.

[0043] Generally, the higher the linear air velocity of the air diffuser holes, the easier it is for air to be released from each diffuser hole. In the case of an air diffuser pipe without a skirt, as in this embodiment, if the linear air velocity of the air diffuser holes is approximately 50 m / sec and the height of each diffuser hole is approximately horizontal, air will be released from all diffuser holes, but the amount of air released will not be uniform. Furthermore, if the linear air velocity of the air diffuser holes is 25 m / sec or less, air will not be released from diffuser holes far from the air supply port of the diffuser pipe, or the amount of air released will be reduced compared to diffuser holes close to the air supply port of the diffuser pipe. If there is a bias in the amount of air released from each diffuser hole, a swirling flow is likely to occur in the water being treated in the nitrification tank.

[0044] In biological nitrification treatment using a moving-bed push flow system, it is necessary to prevent the generation of a swirling flow in the water being treated in the nitrification tank, but the air diffuser of this embodiment makes it easy to uniformly release air from the air outlets on each skirt, so biological nitrification treatment can be carried out while maintaining a stable push flow of the water being treated from bottom to top in the nitrification tank. In addition, in biological nitrification treatment, the air supplied from the air diffuser removes coarse bacteria and other adhering matter and supplies dissolved oxygen. When the air diffuser according to the embodiment is used in biological nitrification treatment, the bubbles released from each skirt can be made sufficiently large, which enhances the adhering matter removal effect and enables more stable treatment efficiency and operation. [Example]

[0045] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following descriptions.

[0046] [Example 1] Using an aeration device equipped with an aeration pipe having the same configuration as the aeration device 20 illustrated in Figures 2 and 3, the aeration pipe was immersed in the water to be treated in the water tank, and aeration was performed with the air linear velocity at the aeration hole set to 50 m / sec. The skirt length of each skirt of the aeration pipe was adjusted by the skirt length adjustment mechanism so that the height position of the air discharge port at the bottom end of each skirt became lower as it approached the air supply part, and the angle θ was 1 degree. The presence or absence of unevenness in the amount of air released from the air outlets of each skirt and the presence or absence of swirling flow were checked visually. The results are shown in Table 1.

[0047] [Examples 2 to 4] Air was diffused using the air diffuser in the same manner as in Example 1, except that the linear air velocity of the air diffuser holes was changed as shown in Table 1. The presence or absence of bias in the amount of air released from the air outlets of each skirt and the presence or absence of swirling flow were visually confirmed. The results are shown in Table 1.

[0048] [Example 5] Using the same air diffuser as in Example 1, the heights of the air discharge ports of all skirts were adjusted to approximately the same height (angle θ = 0.1 degrees) using the skirt length adjustment mechanism, and air was diffused at a linear air velocity of 60 m / sec at the air diffuser holes. The presence or absence of bias in the amount of air discharged from the air discharge ports of each skirt and the presence or absence of swirling flow were visually confirmed. The results are shown in Table 1.

[0049] [Comparative Examples 1 to 3] An air diffuser equipped with the same air diffuser pipe as in Example 1 was used, except that it was not equipped with a skirt having a skirt length adjustment mechanism, and the linear air velocity of the air diffuser holes was set as shown in Table 1. Air was diffused in the same manner as in Example 1, and the presence or absence of bias in the amount of air released from the air release ports of each skirt and the presence or absence of swirling flow were visually confirmed. The results are shown in Table 1.

[0050] [Table 1]

[0051] In Examples 1 to 5, in which an air diffuser equipped with an air diffuser pipe connected to a skirt having a skirt length adjustment mechanism was used and the skirt length of each skirt was adjusted, air could be uniformly released from the air release port of each skirt, and the generation of swirling flow was suppressed. Specifically, as mentioned above, the angle θ is adjusted according to the linear velocity of the air supplied to the air diffusion holes 32. When the linear velocity of the air is low, it tends to be difficult to maintain uniformity in the amount of air discharged from the air diffusion holes, so it is preferable to set the angle θ large. On the other hand, when the linear velocity of the air is high, it tends to be easier to maintain uniformity in the amount of air discharged from the air diffusion holes, so it is preferable to set the angle θ small (Examples 1 to 5). On the other hand, in Comparative Examples 1 to 3, which used air diffusers without skirts having skirt length adjustment mechanisms, unevenness occurred in the amount of air released from the air release ports of each skirt, resulting in the generation of a swirling flow. [Explanation of symbols]

[0052] 1 Water treatment equipment 10. Treated water tank 20 Air diffuser 22 Air diffuser 24 Blower 26 Air supply pipe 28 Air supply port 30 Air sealing part 32 Air diffuser 34 Skirt 34a Air outlet 36 Skirt body 38 Length adjustment member

Claims

1. An air diffusion device having a horizontally arranged air diffusion pipe, the air diffusion pipe has an air supply port at one end through which air is supplied, a structure at the other end capable of sealing air, and a plurality of air diffusion holes provided at a lower portion thereof at intervals in the longitudinal direction; a plurality of cylindrical skirts hanging down from the periphery of each of the diffusion holes are connected to the portion of each of the diffusion pipes where the diffusion holes are formed, The air diffuser, wherein each of the skirts has a skirt length adjustment mechanism for adjusting the length of the skirt.

2. 2. The air diffuser according to claim 1, wherein the skirt length adjustment mechanism adjusts the height of the air discharge port at the lower end of each skirt so that the height position decreases toward the air supply port.

3. The angle θ formed by a line connecting the center of the air discharge port at the lower end of the skirt farthest from the air supply port and the center of the air discharge port at the lower end of the skirt closest to the air supply port and the horizontal line is 0.5 to 3 degrees. The air diffuser according to claim 1.

4. A water treatment device comprising the air diffuser according to any one of claims 1 to 3.

5. A water treatment method including diffusing air using an air diffuser immersed in the water to be treated, The air diffuser includes a horizontally arranged air diffuser pipe, the air diffusion pipe has an air supply port at one end through which air is supplied, a structure at the other end capable of sealing air, and a plurality of air diffusion holes provided at a lower portion thereof at intervals in the longitudinal direction; a plurality of cylindrical skirts hanging down from the periphery of each of the diffusion holes are connected to the portion of each of the diffusion pipes where the diffusion holes are formed, A water treatment method, wherein each of the skirts has a skirt length adjustment mechanism that adjusts the length of the skirt.

6. The water treatment method according to claim 5 , wherein the skirt length adjusting mechanism adjusts the height position of the air discharge port at the lower end of each skirt so that it becomes lower as it approaches the air supply port.

7. The water treatment method according to claim 5 or 6, wherein an angle θ formed by a line connecting the center of the air outlet port at the bottom end of the skirt farthest from the air supply port and the center of the air outlet port at the bottom end of the skirt closest to the air supply port, and the horizontal line is 0.5 to 3 degrees.

8. 7. The water treatment method according to claim 5, wherein the linear air velocity at the air diffuser hole is 2.5 to 50 m / sec.

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