JP2010188278A - Gas diffuser, membrane module, membrane separator, gas diffusion method and membrane separation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the scale of a space in which a gas diffuser is arranged while diffusing bubbles substantially uniformly from each through hole. <P>SOLUTION: The gas diffuser includes a porous plate having a plurality of through holes, and a diffuser pipe arranged in such a manner that a discharge port for discharging bubbles into a sludge mixture liquid is located below the porous plate. In the diffuser, the center of the opening plane of the discharge port is located substantially directly under the center of the smallest circle surrounding the through holes of the porous plate, and the opening direction of the discharge port is set to be any one of the horizontal direction, vertical downward direction, and the direction between the horizontal direction and vertical downward direction. The inner diameter of the discharge port is 16 mm or above, and the ratio (L/D) of the distance L between the lower surface of the porous plate and the center of the opening plane of the discharge port to the diameter D of the circle is 0.8-1.2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an air diffuser that diffuses air bubbles in a sludge mixed solution, a membrane module that includes the air diffuser, a membrane separation device that includes the membrane module, and air bubbles that diffuse into the sludge mixed solution. The present invention relates to an air diffusion method and a membrane separation method using the membrane module.

  Conventionally, when water treatment such as waste water is performed, bubbles (mainly air) are diffused into the water to be treated for various purposes. For example, in the activated sludge process that uses activated sludge to treat wastewater, the activated sludge is mixed with activated sludge and wastewater for the purpose of supplying oxygen necessary for the microorganisms in the activated sludge to decompose organic matter in the wastewater. Air is diffused in the sludge mixture.

  In addition, as another purpose, for the purpose of solid-liquid separation of sludge and water, it is possible to suppress adhesion of the deposits to the separation membrane immersed in the sludge mixture, and to remove the deposits from the surface of the separation membrane. For the purpose of taking air bubbles, air bubbles are diffused from below the separation membrane, and air is diffused to shake and move the separation membrane by the water flow when the bubbles rise and the contact of the bubbles with the separation membrane.

  As an air diffuser that diffuses air bubbles in the activated sludge mixed liquid, an apparatus that diffuses air bubbles from below in the activated sludge treatment tank containing the activated sludge mixed liquid is generally used. As such an air diffuser, specifically, an air diffuser arranged such that a porous plate having a plurality of through holes and an outlet for discharging air bubbles in the activated sludge mixed liquid are positioned below the porous plate. There is known an apparatus configured such that the opening direction of the discharge port faces upward (for example, Patent Document 1).

Japanese Patent Laid-Open No. 2004-8981

  However, such an air diffuser has a problem that if the discharge port is small, splitting and diffusion of bubbles discharged from the discharge port are insufficient. In addition, such an air diffuser has a problem that air bubbles may not be uniformly diffused from each through hole if the distance between the discharge port and the perforated plate is short. When the air is diffused, the distance between the discharge port and the perforated plate becomes very long, and the air diffuser itself is too large to be installed in the sludge separation tank (tank containing the sludge mixture) where air bubbles are to be diffused. There is also a problem that it may be difficult. Furthermore, in such an air diffuser, since the bubbles discharged from the discharge port have an upward initial velocity, the distance between the discharge port and the perforated plate must be made longer in order to diffuse the bubbles, There is a problem that the air diffuser itself becomes larger, and as a result, the power of the air diffuser also increases, and there is also a problem that sludge enters the air diffuser and causes clogging.

  Accordingly, an object of the present invention is to diffuse bubbles from each through hole substantially uniformly and to reduce the size of a space in which an air diffuser is disposed.

The present invention is an air diffuser comprising a perforated plate having a plurality of through holes and an air diffuser arranged so that a discharge port for discharging air bubbles in the sludge mixed solution is positioned below the perforated plate. There,
The center of the opening surface of the discharge port is located substantially directly below the center of the circle that surrounds and is the smallest circle surrounding the through hole of the perforated plate, and the opening direction of the discharge port is a horizontal direction, a vertically downward direction, and a horizontal direction. Is configured to be any direction between the vertical direction and the vertical downward direction,
The discharge port has an inner diameter of 16 mm or more,
The ratio (L / D) of the distance L between the lower surface of the perforated plate and the center of the opening surface of the discharge port with respect to the diameter D of the circle is 0.8 to 1.2. It is in.

According to such an air diffuser, the discharge port is discharged from the discharge port when the opening direction of the discharge port is any one of a horizontal direction, a vertically downward direction, and a direction between the horizontal direction and the vertically downward direction. The upward initial velocity of the bubbles is 0 m / s or less, and the bubbles easily diffuse in the horizontal direction for the distance from the discharge port. In addition, since the center of the opening surface of the discharge port is positioned almost directly below the center of the circle that surrounds and is the smallest of the perforations of the perforated plate, horizontal air bubbles should diffuse from the discharge port to the outer through hole. The direction distance is relatively short. Furthermore, the inner diameter of the discharge port is 16 mm or more, and the ratio (L / D) of the distance L between the lower surface of the porous plate and the center of the opening surface of the discharge port with respect to the diameter D of the circle is 0.8 or more. As a result, the bubbles discharged from the discharge port are relatively large, and the large bubbles are instantaneously split into small bubbles and diffused, and the bubbles can reach the outermost through hole. Therefore, the bubbles can be diffused from each through hole substantially uniformly.
In addition, since the ratio (L / D) of the distance L between the lower surface of the porous plate and the center of the opening surface of the discharge port with respect to the diameter D of the circle is 1.2 or less, the horizontal size of the porous plate is increased. For this reason, it is possible to reduce the size of the vertical space in which the air diffuser is arranged.
Further, the air diffuser having an inner diameter of the discharge port of 16 mm or more is configured such that the opening direction of the discharge port is any one of a horizontal direction, a vertically downward direction, and a direction between the horizontal direction and the vertically downward direction. As a result, the intrusion of the sludge mixed liquid into the air diffuser is suppressed, and as a result, the air bubbles can be diffused more uniformly from each through hole.

  In the air diffuser according to the present invention, preferably, a skirt portion extending downward is provided on the outer peripheral portion of the perforated plate.

  According to such an air diffuser, by providing the skirt portion, when there is no skirt portion, air bubbles that can be leaked from other portions without being diffused from the through hole can be efficiently discharged from each through hole. There is an advantage that it can be diffused.

  Further, in the air diffuser provided with the skirt portion, an opening is preferably provided at the lower end portion of the skirt portion.

  According to such an air diffuser, the sludge of the sludge mixed liquid that can stay inside the air diffuser surrounded by the skirt portion is likely to flow out from the opening, and the sludge stays in the inside. Since it becomes difficult, as a result, air bubbles can be diffused substantially uniformly from each through hole.

  In addition, the present invention resides in a membrane module formed by providing a separation membrane portion formed by bundling a plurality of separation membranes on an upper portion of the porous plate of the air diffuser.

  Furthermore, the present invention resides in a membrane separation apparatus that includes a tank in which a sludge mixed solution is accommodated, and in which the membrane module is provided as an immersion membrane.

  Moreover, this invention exists in the aeration method which diffuses a bubble in the sludge liquid mixture with the said aeration apparatus.

  Furthermore, the present invention resides in a membrane separation method for obtaining purified water by membrane separation of a sludge mixed solution with the membrane module.

  As described above, according to the present invention, air bubbles can be diffused from each through hole substantially uniformly, and the space in which the diffuser is disposed can be reduced in size.

It is a side view of the aeration apparatus concerning this embodiment. It is a front view of the diffuser concerning this embodiment. It is a rear view of the air diffusion apparatus which concerns on this embodiment. It is side surface sectional drawing of the diffuser which concerns on this embodiment, and is II sectional drawing of FIG. (A) is a side view of the air diffuser according to the present embodiment, and (b) is a front view of the air diffuser according to the present embodiment. It is side surface sectional drawing of the membrane module which concerns on this embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

  As shown in FIGS. 1 to 4, the air diffuser 1 according to the present embodiment includes a porous plate 2 having a plurality of through holes 2 a and a discharge port 3 a that discharges air bubbles in the sludge mixed solution below the porous plate 2. And an air diffuser 3 arranged so as to be located at the center.

  The perforated plate 2 is configured such that the surface of the perforated plate 2 is substantially horizontal when placed in the sludge mixed liquid. The perforated plate 2 is formed so that the surface has a substantially circular shape.

A plurality of through holes 2 a of the porous plate 2 are provided in the porous plate 2.
Moreover, the shape of the through-hole 2a is formed so that it may become a substantially circular shape.
Furthermore, the through-hole 2a is formed to have a diameter of 5 to 15 mm, preferably 8 to 11 mm.
The air diffuser 1 according to the present embodiment has an advantage that the through hole 2a is less likely to be blocked by the sludge of the sludge mixed liquid because the diameter of the through hole 2a is 5 mm or more. Further, the air diffuser 1 of the present embodiment has an advantage that the diameter of the through hole 2a is 15 mm or less, whereby the bubbles passing through the through hole 2a are reduced and the oxygen dissolution efficiency is easily increased.

  The porous plate 2 is formed so that the axis of the through hole 2a is substantially perpendicular to the surface of the porous plate. The perforated plate 2 is formed so that the center of the circle that surrounds the through-hole 2a and is the minimum and the substantially circular center of the perforated plate 2 are substantially concentric.

The air diffuser 3 is configured such that the discharge port 3a is positioned below the perforated plate 2 when disposed in a sludge mixed solution such as an activated sludge treatment tank or a sludge separation tank. Further, as shown in FIG. 5, the air diffuser 3 is formed so that the cross-sectional shape is circular. Further, the air diffuser 3 is provided with a discharge port 3a for discharging bubbles at one end, and the other end is connected to the gas supply means. The discharge port 3 a is formed so as to open in the axial direction of the diffuser tube 3. As shown in FIG. 5 (a), the shape of the discharge port 3a is formed to be substantially circular, and its inner diameter R is 16 mm or more, preferably from the viewpoint that the air diffuser itself is more compact. It is formed to be 20 mm or more and 50 mm or less.
In the air diffuser 1 of this embodiment, since the inner diameter R of the discharge port 3a is 16 mm or more, large bubbles discharged from the discharge port 3a are instantaneously split into small bubbles and diffused. And the discharge port 3a of the air diffuser 3 can be shortened. Moreover, since the air diffusion apparatus 1 of this embodiment can discharge a bubble with a larger diameter when the inner diameter R of the discharge port 3a is 20 mm or more, the bubble can be more reliably diffused. The distance between the plate 2 and the discharge port 3a of the air diffusing tube 3 can be further reduced.

The air diffuser 3 is bent at a position away from the discharge port 3a toward the other end, and a bent portion 3b is formed. The bent portion 3b is formed at a predetermined position from the discharge port 3a. Specifically, it is formed at a position where the turbulence of the bubble flow generated in the bent portion 3b can be adjusted before reaching the discharge port 3a. More specifically, when the air diffusing tube 3 is bent at a right angle, the bent portion 3b is, as shown in FIG. 5B, the air diffusing tube 3 on the other end side from the opening end of the discharge port 3a to the bent portion 3b. It is preferable that the distance H to the axis and the inner diameter R of the discharge port 3a have the relationship of the following formula (1).
H ≧ R × 3 (1)
When the distance H and the inner diameter R are in the relationship of the above formula (1), the direction of the air diffuser 3 (the opening direction of the discharge port) is directed differently due to the centrifugal force caused by the bending of the air diffuser 3. There is an advantage that it becomes easy to face the opening direction of the discharge port while the air bubbles move from the bent portion 3b to the opening end of the discharge port 3a.
Moreover, the air diffusing tube 3 is configured to be splittable on the other end side with respect to the discharge port 3a. Specifically, the air diffuser 3 is provided with a connecting portion 3c on the other end side than the bent portion 3b, and on the discharge port side (front end side) and the other end side (base end side) with the connecting portion 3c as a boundary. It is configured to be splittable.

  The air diffuser 3 is configured such that the opening direction of the discharge port 3a is substantially horizontal. Specifically, the air diffuser 3 is configured such that the axis in the opening direction is horizontal when it is disposed in the sludge mixed liquid. The air diffuser 3 is formed so that the opening surface of the discharge port 3a is perpendicular to the horizontal direction when disposed in the sludge mixed liquid. In other words, the opening surface of the discharge port 3 a is formed so as to be perpendicular to the axis of the air diffuser 3.

  As the bubbles discharged from the discharge port 3a, air supplied from gas supply means such as a compressor is used. Further, the linear velocity of the bubbles at the opening end of the discharge port 3a is preferably 4 m / second or more and 15 m / second or less, more preferably 8 m / second or more and 15 m / second or less, although it depends on the sludge concentration of the sludge mixed liquid. It is set to become. The linear velocity is the velocity of bubbles passing through the cross-sectional area of the diffuser tube 3 per unit time, and is calculated by dividing the flow rate of bubbles (volume of bubbles flowing per unit time) by the cross-sectional area of the diffuser tube 3. It is what is done.

  The material for forming the air diffuser 3 is not particularly limited, but is preferably formed using a material having rigidity. For example, it may be formed using a resin material such as polyvinyl chloride, or may be formed using a metal material such as SUS.

In the air diffuser 1 of this embodiment, the ratio (L / D) of the distance L between the lower surface of the porous plate 2 and the center of the opening surface of the discharge port 3a with respect to the diameter D of the circle that surrounds the through-hole 2a and is the smallest. ) Is 0.8 to 1.2, preferably 0.9 to 1.1.
The distance L between the lower surface of the perforated plate 2 and the center of the opening surface of the discharge port 3a is preferably 200 mm or less, more preferably 150 mm or less, from the viewpoint of compactness and energy saving.

  In addition, the air diffuser 1 of the present embodiment is configured such that the center of the opening surface of the discharge port 3a is located almost directly below the center of the circle that surrounds the through-hole 2a of the porous plate 2 and is the smallest. It becomes.

  Further, in the air diffuser 1 of this embodiment, the diameter D of the circle that surrounds the through-hole 2a and is the minimum is preferably not less than the inner diameter of the discharge port 3a, more preferably not less than twice the inner diameter of the discharge port 3a. Is the length of In the air diffuser 1 of the present embodiment, bubbles are uniformly discharged from the entire surface of the porous plate 2 because the diameter D of the circle that surrounds the through-hole 2a and is the minimum is equal to or longer than the inner diameter of the discharge port 3a. There is an advantage that it becomes easy.

  Further, the air diffusion device 1 of the present embodiment is provided with a skirt portion 4 extending downward on the outer peripheral portion of the perforated plate 2. The skirt portion 4 is formed to extend from the entire outer periphery of the perforated plate 2. Further, the air diffusion device 1 according to the present embodiment is formed so that the lower end of the skirt portion 4 is positioned below the discharge port 3a. The skirt portion 4 is provided with a diffuser tube insertion hole 4a into which the diffuser tube 3 can be inserted.

Further, the air diffuser 1 according to the present embodiment has a skirt opening provided at the lower end of the skirt 4. In the air diffuser of FIG. 1, the skirt opening is provided as the air diffuser insertion hole 4a.
Further, in the air diffuser 1 according to the present embodiment, when the skirt portion 4 is not provided, the skirt opening 4a is formed so that bubbles that are not diffused from the through hole 2a and are not leaked from other portions are generated. . For example, when the diameter of the perforated plate 2 is about 124 mm, the air diffuser 1 of the present embodiment has a vertical distance between the center of the opening surface of the discharge port 3a and the upper end of the skirt opening. When the center of the surface is below, it is preferably 51 mm or less.

  The air diffusing method of the present embodiment is a method of diffusing air bubbles in the sludge mixed solution with the air diffusing device 1 of the present embodiment.

Next, the membrane module according to this embodiment will be described.
As shown in FIG. 6, the membrane module 10 according to the present embodiment includes the air diffuser 1 according to the present embodiment, and a plurality of separation membranes are bundled on the upper portion of the porous plate 2 of the air diffuser 1. The separation membrane part 20 configured as described above is provided and formed.

  The separation membrane constituting the separation membrane portion 20 is formed by forming a porous membrane in which a large number of micropores are formed into a cylindrical shape, with the lower end portion being closed, on the upper portion of the porous plate 2. It is provided and connected to a suction means (not shown) with its upper end opened.

  The material for forming the separation membrane is not particularly limited, and examples of the material include cellulose acetate, aromatic polyamide, polyvinyl alcohol, polyvinylidene fluoride, and polytetrafluoroethylene.

Next, the membrane separation apparatus and the membrane separation method according to this embodiment will be described.
The membrane separation apparatus according to the present embodiment includes a tank in which a sludge mixed solution is accommodated, and the membrane module according to the present embodiment is provided as an immersion film in the membrane separation tank as the tank.
Further, the membrane separation method according to the present embodiment is a method for obtaining purified water by membrane separation of the sludge mixed solution with the membrane module 10 according to the present embodiment. Specifically, in the membrane separation method according to the present embodiment, the membrane module 10 is placed in a sludge mixed solution in a membrane separation tank containing microorganisms, and waste water containing a treatment target substance such as organic matter is placed in the tank. This is a method of supplying purified water by decomposing the substance to be treated in the wastewater by the action of microorganisms and separating the membrane to obtain purified water.

  The waste water is not particularly limited, and examples of the waste water include domestic waste water and waste water from factories such as food factories, chemical factories, electronic industry factories, and pulp factories.

  The membrane separation method according to the present embodiment can also be used mainly in the case where the MLSS (solid matter concentration) of the sludge mixed solution is 30000 mg / L or less, preferably 20000 to 25000 mg / L. Thus, even when the MLSS in the sludge mixed liquid is high, the inner diameter of the air diffuser 3 is 16 mm or more, so that the air diffuser 3 is less likely to be blocked by the sludge. It is discharged and air bubbles can be diffused substantially uniformly from the through hole 2a, and the hole of the through hole 2a is less likely to be clogged.

  In the membrane separation method according to the present embodiment, the gas supplied from the gas supply means is discharged as bubbles from the discharge port 3a, so that the bubbles diffuse in the horizontal direction while rising by buoyancy and reach the porous plate 2. To reach. The bubbles pass through the through holes 2a of the perforated plate 2 to become finer bubbles, and rise while shaking the separation membrane so as to cover the separation membrane. Thereby, it becomes possible for the bubbles to peel off the adhering matter adhering to the separation membrane and to suppress adhering adhering matter.

  Since the air diffuser, the membrane module, the membrane separator, and the membrane separation method according to the present embodiment are configured as described above, they have the following advantages.

  That is, the diffuser according to the present embodiment is configured such that the opening direction of the discharge port 3a is downward by being configured so that the opening direction of the discharge port 3a is substantially horizontal. Unlike the above, it is no longer necessary to use a diffusing pipe bent downward, and it is easy to downsize the vertical space in which the diffusing pipe is arranged. Therefore, the space in which the diffusing apparatus is arranged can be further reduced in size. There is an advantage of being able to plan.

  The diffuser, the membrane module, the membrane separator, and the membrane separation method according to this embodiment are not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention. is there.

  For example, although the said embodiment uses the diffuser 1 with the separation membrane part 20, this invention is not limited to this, The diffuser 1 is used without using the separation membrane part 20. Also good.

  Further, the air diffuser according to the present embodiment is configured such that the opening direction of the discharge port 3a is substantially horizontal, but the opening direction of the discharge port 3a is vertically downward, and the horizontal direction and vertically downward direction. It may be configured to be in any direction between the two.

  Furthermore, the membrane separation apparatus according to the present embodiment is provided with a water treatment tank, waste water is transferred to the water treatment tank, and a target substance in the waste water is decomposed by microorganisms in the water treatment tank. The supernatant water of the sludge mixture discharged from the tank may be transferred to the membrane separation tank and subjected to membrane separation treatment as a sludge mixture.

  Examples of the present invention will be described below.

(1) Air diffuser tube: An air diffuser tube having the inside diameter of the discharge port described in Table 1 below was used.
(2) Perforated plate: A perforated plate (the number of through holes) in which the diameter D of a circle (hereinafter also referred to as “enclosed circle”) that surrounds and minimizes the through hole (diameter: about 10 mm) of the porous plate is 124 mm : 24).
(3) Air diffuser The air diffuser and the perforated plate were arranged as follows to produce an air diffuser.
That is, the center of the opening surface of the discharge port is located almost directly below the center of the diameter of the surrounding circle, the opening direction of the discharge port is the horizontal direction, and the distance between the lower surface of the perforated plate and the center of the opening surface of the discharge port (Hereinafter, also referred to as “distance between the perforated plate and the discharge port”.) Air diffusers of Examples and Comparative Examples were manufactured so that L was as shown in Table 1 below.

<Test Example 1: Uniformity of bubbles diffused from each through hole>
The diffuser of Example and Comparative Example was placed in a tank into which tap water was placed, and the tank was filled with tap water so that the liquid level was located at a position 1000 mm from the upper surface of the perforated plate.
Then, gas is supplied to the diffuser by the gas supply means so that the gas is discharged from the discharge port at a discharge rate of 10 m ³ / h, and the uniformity of the bubbles diffused from each through hole is visually confirmed for 5 minutes. And evaluated.
The uniformity of bubbles diffused from each through hole was evaluated according to the following criteria.
A: Air bubbles were diffused almost uniformly from each through hole.
○: The amount of bubbles diffused from the outer through-holes was slightly small, but the bubbles were almost uniformly diffused from each through-hole throughout the observation time.
Δ: The amount of bubbles diffused from the outer through-hole was small.
X: Air bubbles were not generated from the outer through-holes.

<Test Example 2: Difficulty of clogging the diffuser tube>
The air diffuser of Example and Comparative Example is placed in a tank containing sludge mixed liquid (MLSS: 25000 mg / L), and sludge mixed in the tank so that the liquid level is located at a position of 3000 mm from the upper surface of the perforated plate. Filled with liquid.
The gas is supplied to the air diffuser by the gas supply means so that the gas is discharged from the discharge port at a discharge rate of 10 m ³ / h. After operating for 2 weeks, the difficulty of clogging the air diffuser is visually confirmed. And evaluated.
The difficulty of clogging the air diffuser was evaluated according to the following criteria.
○: The inside of the air diffuser was not blocked by sludge.
×: The inside of the air diffuser was blocked by sludge.

  As shown in Table 1, as compared with the diffusers of Comparative Examples 1 to 5 in which the inner diameter of the discharge port was smaller than 16 mm, the diffuser of the example was less likely to clog the diffuser tube. Moreover, compared with the diffuser of Comparative Examples 1, 2, and 6 to 11 in which the value of L / D is smaller than 0.8, the diffuser of the example has the bubble diffused from each diffuser hole. The results showed good uniformity.

  DESCRIPTION OF SYMBOLS 1: Air diffuser, 2: Perforated plate, 2a: Through-hole, 3: Air diffuser, 3a: Discharge port, 3b: Bending part, 3c: Connection part, 4: Skirt part, 4a: Air diffuser insertion hole (skirt opening) Part), 10: membrane module, 20: separation membrane part

Claims (7)

A diffuser comprising: a porous plate having a plurality of through holes; and an air diffuser arranged so that a discharge port for discharging air bubbles in the sludge mixed solution is positioned below the porous plate,
The center of the opening surface of the discharge port is located substantially directly below the center of the circle that surrounds and is the smallest circle surrounding the through hole of the perforated plate, and the opening direction of the discharge port is a horizontal direction, a vertically downward direction, and a horizontal direction. Is configured to be any direction between the vertical direction and the vertical downward direction,
The discharge port has an inner diameter of 16 mm or more,
The ratio (L / D) of the distance L between the lower surface of the perforated plate and the center of the opening surface of the discharge port with respect to the diameter D of the circle is 0.8 to 1.2. .   The diffuser according to claim 1, wherein a skirt portion extending downward is provided on an outer peripheral portion of the perforated plate.   The diffuser according to claim 2, wherein an opening is provided at a lower end portion of the skirt portion.   A gas diffusing device according to any one of claims 1 to 3 is provided, and an upper part of a perforated plate of the air diffusing device is formed by providing a separation membrane part configured by a plurality of separation membranes being bundled. Membrane module.   A membrane separation apparatus comprising a tank in which a sludge mixed solution is accommodated, wherein the membrane module according to claim 4 is provided as an immersion membrane in the tank.   The aeration apparatus according to any one of claims 1 to 3, wherein an air bubble is diffused into the sludge mixed liquid.   5. A membrane separation method according to claim 4, wherein the sludge mixed solution is subjected to membrane separation to obtain purified water.

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