JP7131348B2 - Membrane separation activated sludge system - Google Patents

Description

TECHNICAL FIELD The present invention relates to a membrane separation activated sludge apparatus.

Industrial wastewater and domestic wastewater are treated to remove organic substances and the like contained in the wastewater, and then reused as industrial water or discharged into rivers and the like. Examples of methods for treating industrial wastewater include an activated sludge method in which aerobic microorganisms decompose organic matter by aeration.

Treatment by a membrane separation activated sludge (MBR) method, which combines treatment by the activated sludge method and membrane filtration by a separation membrane module, is known. In the treatment by the MBR method, as the membrane filtration continues, organic matter and the like accumulate on the surface of the separation membrane, which may cause a decrease in the filtration flow rate and an increase in the transmembrane pressure difference. Therefore, in the treatment by the MBR method, an air diffuser is generally installed below the membrane module, and the air bubbles generated by the air diffuser come into contact with the surface of the membrane. By vibrating, deposition of organic substances and the like on the film surface is suppressed.

As an air diffuser, an air diffuser that intermittently aerates using the principle of a siphon has been proposed because the bubble size during aeration is large and the surface of the membrane is easily washed. For example, an air diffusion case having a hollow interior with an open bottom and an air supply port formed at the top, and a box-like case provided in the air diffusion case with an open top (for example, an open top and side surfaces) and a shape in which the bottom side is airtightly sealed) and a plurality of tubular second outlets extending downward from the upper part of the diffusion case toward the inside of the first outlet. (Patent Documents 1 and 2).

JP 2018-103134 A JP 2018-103135 A

However, in conventional air diffusers such as those disclosed in Patent Documents 1 and 2, the membrane surface of the upper membrane module may not be stably cleaned because the air supply port is clogged with sludge. In addition, the more compact the diffuser, the more advantageous it is in terms of cost.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and it is possible to intermittently aerate using the principle of siphon, and to block the air supply port with sludge without excessively increasing the size of the apparatus. It is an object of the present invention to provide an air diffuser capable of suppressing , and a membrane separation activated sludge apparatus using the air diffuser.

The present invention has the following configurations.
[1] An air diffuser that intermittently aerates water to be treated,
a main body that is immersed in the water to be treated, has a hollow interior, and has a water inlet portion formed at the bottom;
a first lead-out portion provided inside the main body portion, the upper side of which is open, and the side and bottom sides of which are airtightly sealed;
a plurality of second lead-out portions provided to extend downward from the upper portion of the main body portion and having both ends opened;
each of the second lead-out portions partially enters into the first lead-out portion from the upper side of the first lead-out portion with the lower end of each of the second lead-out portions being separated from the lower portion of the first lead-out portion;
An air supply port is formed in the upper part of the main body to supply air to the outside of the first lead-out portion inside the main body in a plan view,
A partition extending downward from between the air supply port in the upper portion of the main body and the first lead-out portion in a plan view, and forming an air reservoir in a portion of the interior of the main body where the air supply port is formed. Air diffuser with walls.
[2] The air diffuser according to [1], wherein the position of the lower end of the partition wall is lower than the upper end of the first lead-out portion.
[3] A membrane separation activated sludge apparatus comprising a membrane module for membrane separation of sludge-containing treated water containing activated sludge, and the air diffuser according to [1] or [2].

According to the present invention, an air diffuser capable of intermittently aerating using the principle of a siphon and capable of suppressing clogging of an air supply port with sludge without excessively increasing the size of the apparatus, and the air diffuser. It is possible to provide a membrane separation activated sludge apparatus using.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic diagram which showed an example of the water treatment apparatus. 1 is a perspective view showing an example of an air diffuser of the present invention; FIG. FIG. 3 is a cross-sectional view of the air diffuser of FIG. 2 taken along line II. FIG. 4 is a cross-sectional view of the air diffuser of FIG. 3 taken along the line II-II;

It should be noted that the dimensions and the like of the drawings illustrated in the following description are only examples, and the present invention is not necessarily limited to them, and can be implemented with appropriate changes within the scope of not changing the gist of the present invention. .

[Water treatment equipment]
As shown in FIG. 1, the water treatment apparatus 1000 includes an activated sludge treatment tank 11, a membrane separation tank 21 provided downstream of the activated sludge treatment tank 11, and a treated water tank 41 provided downstream of the membrane separation tank 21. and Furthermore, although illustration is omitted, the water treatment apparatus 1000 includes a flow rate adjustment tank for adjusting the flow rate of raw water flowing into the activated sludge treatment tank 11, a drawing pump for drawing excess sludge from the membrane separation tank 21, and a It is provided with a liquid feeding means for feeding a chemical solution or dilution water, and a discharging means for discharging the treated water from the treated water tank 41 to a factory, a river, or the like.

The activated sludge treatment tank 11 is filled with activated sludge for performing activated sludge treatment.
A first channel 12 and a second channel 13 are connected to the activated sludge treatment tank 11 . The first channel 12 is a channel through which raw water discharged from factories, households, etc. flows into the activated sludge treatment tank 11 . The second channel 13 is a channel through which sludge-containing treated water (water to be treated) discharged from the activated sludge treatment tank 11 flows into the membrane separation tank 21 .

An aerator 14 is installed in the activated sludge treatment tank 11 to maintain the inside of the tank in an aerobic condition.
The aeration device 14 includes an aeration pipe 14a for aerating the inside of the activated sludge treatment tank 11, a supply pipe 14b for supplying air to the aeration pipe 14a, and a blower 14c for supplying air.
The aeration pipe 14a is not particularly limited as long as it can discharge the air supplied from the blower 14c upward, and examples thereof include a perforated single pipe and a membrane type.

The membrane separation tank 21 stores sludge-containing treated water containing activated sludge and biologically treated water sent from the activated sludge treatment tank 11 .
The membrane separation tank 21 includes a membrane separation activated sludge apparatus 100 (hereinafter sometimes referred to as "MBR apparatus 100") to which one aspect of the present invention is applied. The MBR device 100 will be described later.

A sludge return means 30 is connected to the membrane separation tank 21 and the activated sludge treatment tank 11 . The sludge return means 30 returns part of the sludge-containing treated water from the membrane separation tank 21 to the activated sludge treatment tank 11 .
The sludge return means 30 has a fourth flow path 31 . The fourth channel 31 is a channel for discharging part of the sludge-containing treated water from the membrane separation tank 21 and allowing it to flow into the activated sludge treatment tank 11 .
A pump 31 a is installed in the fourth flow path 31 . As a result, part of the sludge-containing treated water in the membrane separation tank 21 can be returned from the membrane separation tank 21 to the activated sludge treatment tank 11 .

The treated water tank 41 stores the treated water after membrane separation of the sludge-containing treated water.

<Membrane separation activated sludge system>
The MBR device 100 includes a plurality of membrane modules 22 and an air diffuser 10 provided below the membrane modules 22 .

The membrane module 22 membrane-separates sludge-containing treated water containing activated sludge. The membrane module 22 has a separation membrane, and the separation membrane separates sludge-containing treated water into biologically treated water and activated sludge by solid-liquid separation (membrane separation).

The separation membrane is not particularly limited as long as it has separation ability, and examples thereof include hollow fiber membranes, flat membranes, tubular membranes, monolithic membranes, and the like. Among these membranes, hollow fiber membranes are preferred because of their high volume filling factor.

When a hollow fiber membrane is used as the separation membrane, its material includes, for example, cellulose, polyolefin, polysulfone, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and the like. Among these, PVDF and PTFE are preferable as the material for the hollow fiber membrane because of their chemical resistance and resistance to pH changes.
When a monolithic membrane is used as the separation membrane, it is preferable to use a ceramic membrane.

The average pore diameter of the micropores formed in the separation membrane is about 0.001 to 0.1 μm for a membrane generally called an ultraseparation membrane, and about 0.1 to 1 μm for a membrane generally called a precision separation membrane. . In the present embodiment, it is preferable to use a separation membrane having an average pore size within the above range.

A third channel 33 is connected to the membrane module 22 . The third channel 33 is a channel for discharging the treated water that has passed through the separation membrane from the membrane separation tank 21 and allowing it to flow into the treated water tank 41 .
A pump 33 a is installed in the third flow path 33 . This allows the treated water that has passed through the separation membranes of the membrane module 22 to be discharged from the membrane separation tank 21 .

The air diffuser 10 is an air diffuser that intermittently aerates sludge-containing treated water (water to be treated). As shown in FIGS. 2 to 4, the air diffuser 10 includes a main body portion 50, a first lead-out portion 52, a plurality of second lead-out portions 54, and a partition wall 56. As shown in FIG. The air diffuser 10 is provided in a state of being immersed in the water to be treated in the membrane separation tank 21 .

The main body part 50 is a rectangular parallelepiped housing with a hollow interior, and the lower part is opened to form a water inflow part 58 to be treated. While the main body 50 is immersed in the water to be treated, the water to be treated enters the inside of the main body 50 from the water inflow part 58 to be treated.
In addition, the shape of the main body part 50 is not limited to a rectangular parallelepiped shape, and may be, for example, a cubic shape, a cylindrical shape, or the like.

The first lead-out portion 52 is a member (for example, a box-shaped member) whose rectangular parallelepiped upper side is open and whose side and bottom sides are airtightly sealed, and is provided inside the main body portion 50. . The first lead-out portion 52 is arranged inside the body portion 50 with the upper end 52 a of the first lead-out portion 52 separated from the upper portion 50 a of the body portion 50 .
The shape of the first lead-out portion 52 is not limited to a rectangular parallelepiped shape, and can be appropriately set according to the shape of the main body portion 50, the arrangement of the second lead-out portion 54, and the like. may

The plurality of second lead-out portions 54 are, for example, tubular with both ends opened, and are provided so as to extend downward from the upper portion 50 a of the main body portion 50 . An upper open end 54a of each second lead-out portion 54 serves as an air diffusion hole.
In the air diffuser 10, the space from the upper end 52a of the first lead-out portion 52 to the lower end 54c of the second lead-out portion 54 inside the main body portion 50 serves as a siphon chamber 70, and the air stored in the siphon chamber 70 is As shown, the air is intermittently aerated from each of the second lead-out portions 54 by the siphon principle.

Each of the second lead-out portions 54 in this example is arranged side by side at intervals in the longitudinal direction of the main body portion 50 in plan view. The plurality of second lead-out portions 54 arranged in the longitudinal direction may be arranged at regular intervals, or may be arranged such that the intervals between the adjacent second lead-out portions 54 are different. It is preferable that the plurality of second lead-out portions 54 are arranged at equal intervals in that the air is easily aerated uniformly from each of the second lead-out portions 54 .

Each of the second lead-out portions 54 partially enters the first lead-out portion 52 from the upper side of the first lead-out portion 52 with the lower end 54c of each of the second lead-out portions 54 separated from the lower portion 52b of the first lead-out portion 52 .
The vertical positions of the lower open ends 54b of the second lead-out portions 54 match each other, as in this example, in that the aeration from the upper open ends 54a of the second lead-out portions 54 can be made uniform. is preferred. It should be noted that the positions of the lower opening ends 54b of the respective second lead-out portions 54 may be displaced in the vertical direction as long as the effects of the present invention are not impaired.

Further, each second lead-out portion 54 is in a state in which an upper portion thereof protrudes upward from the upper portion 50 a of the main body portion 50 . In addition, the aspect of the air diffuser 10 is not limited to the aspect in which the upper side of each second lead-out portion 54 protrudes from the upper portion 50a of the main body portion 50. For example, the upper open end 54a of each second lead-out portion 54 protrudes from the main body It may be in a mode that matches the upper surface of the portion 50 .

The shape of the second lead-out portion 54 is cylindrical in this example. The shape of the second lead-out portion 54 is not limited to a cylindrical shape, and may be, for example, a rectangular cylindrical shape.
The flow passage cross-sectional area of the second lead-out portion 54 can be set as appropriate, and can be, for example, 100 to 2000 mm ² . From the viewpoint of air bubble shape, intermittent aeration, uniform aeration, cleanability of the hollow fiber membrane, air supply amount (energy saving), etc., the flow passage cross-sectional area of the second lead-out part 54 is preferably 500 to 1750 mm ² , and 750 ~1600 ^mm2 is more preferred.

Although the number of the second lead-out portions 54 is five in this example, it may be four or less, or may be six or more. The number of second lead-out portions 54 can be set as appropriate, and can be set to 4 to 10, for example.

In the air diffuser 10, the first lead-out portion 52 and the plurality of second lead-out portions 54 are provided biased toward one end side in the longitudinal direction of the body portion 50, and the other side of the upper portion 50a of the body portion 50 is provided. An air supply port 60 is formed on the end side of the . Thus, the air supply port 60 is formed in the upper portion of the body portion 50 so that air is supplied to the outside of the first lead-out portion 52 inside the body portion 50 in plan view.

The air supply port 60 communicates with an air supply portion 62 projecting upward from the upper portion 50a of the main body portion 50, and the air supply portion 62 is connected to the blower 1b by a pipe 1c. The air supplied from the air supply port 60 through the pipe 1c from the blower 1b into the main body portion 50 enters the first outlet portion 52 from the upper side of the first outlet portion 52, passes through each of the second outlet portions 54, and flows upward. It is discharged to the outside of the body portion 50 from the open end 54a.

A plate-like partition wall 56 extending downward perpendicularly to the upper portion 50a of the main body portion 50 is provided between the air supply port 60 of the upper portion 50a of the main body portion 50 and the first lead-out portion 52 in plan view. there is The partition wall 56 is provided so as to reach from the inner surface of one lateral side wall 50b of the body portion 50 to the inner surface of the other side wall 50c. As a result, an air reservoir 80 is formed in a portion of the interior of the main body 50 closer to the air supply port 60 than the partition wall 56 is.

A partition wall is provided between the air supply port at the top of the main body and the first lead-out portion in a plan view, and an air reservoir is formed on the air supply port side of the partition wall inside the main body. Contact of the water to be treated with the air supply port during operation of the air diffuser is suppressed. Therefore, it is possible to prevent sludge from adhering to the air supply port and drying the air supply port, thereby preventing the air supply port from being clogged with sludge.

In the air diffuser 10 , the position of the lower end 56 a of the partition wall 56 is lower than the upper end 52 a of the first lead-out portion 52 . In the present invention, as in this example, it is preferable that the position of the lower end of the partition wall is lower than the upper end of the first lead-out portion. As a result, the air diffuser can be made more compact while suppressing clogging of the air supply port with sludge.

A vertical distance d1 between the lower end 56a of the partition wall 56 and the upper end 52a of the first lead-out portion 52 is preferably 10 mm or more, more preferably 50 mm or more. If the distance d1 is equal to or greater than the lower limit value of the range, it is easy to suppress clogging of the air supply port with sludge.

Materials for the main body portion 50, the first lead-out portion 52, the second lead-out portion 54, and the partition wall 56 are not particularly limited. For example, polyethylene, polypropylene, AS resin, ABS resin, acrylic resin (PMMA), polyvinyl chloride resin (PVC), polyacetal resin (POM), polyamide resin (PA), polyethylene terephthalate resin (PET), polybutylene terephthalate resin ( PBT), polycarbonate resin (PC), modified polyphenylene ether resin (PPE), polyphenylene sulfide resin (PPS), polyether ether ketone resin (PEEK), polysulfone resin (PSf), polyether sulfone resin (PES), etc. mentioned. The main body portion 50, the first lead-out portion 52, the second lead-out portion 54, and the partition wall 56 may be made of one type of material or a combination of two or more types. It may also be made of metal such as stainless steel (SUS304 series, SUS316 series).

The working mechanism of the air diffuser 10 will be described below. In the diffuser 10, aeration occurs intermittently according to the siphon principle.
Specifically, the inside of the main body 50 is filled with the sludge-containing treated water (water to be treated) up to the lower end 56a of the partition wall 56 before the operation is started. When air is sent from the blower 1b through the pipe 1c and continuously supplied from the air supply port 60 into the main body 50 through the air supply part 62, the sludge-containing treated water in the main body 50 is discharged from the water inflow part 58. As a result, the liquid level of the sludge-containing treated water in the main body 50 gradually drops. When the liquid level of the sludge-containing treated water in the body portion 50 becomes lower than the lower end 54c of the second lead-out portion 54, the difference between the two gas-liquid interface heights in the second lead-out portion 54 and the siphon chamber 70 The air is sucked into the second lead-out portion 54 by the air, and is discharged from the upper open end 54a (air diffusion hole) of the second lead-out portion 54 at once. When aeration occurs in this way, sludge-containing treated water flows into the main body 50 from the water inflow part 58 to be treated, and the liquid level of the sludge-containing treated water in the main body 50 rises to the first outlet. It rises to near the upper end 52a of the portion 52 . Then, when the level of the sludge-containing treated water in the main body portion 50 becomes lower than the lower end 54c of the second lead-out portion 54 again, the next aeration occurs.

In the air diffuser 10 , an air reservoir 80 is formed inside the main body 50 on the side of the air supply port 60 by the partition wall 56 . Therefore, even if the liquid level of the sludge-containing treated water in the main body 50 fluctuates up and down during operation, the attachment of the sludge-containing treated water to the air supply port 60 is suppressed. Therefore, sludge adheres to the air supply port 60 and dries, and clogging of the air supply port 60 with sludge is suppressed, so that the membrane surface of the membrane module 22 can be stably cleaned.

[Water treatment method]
A water treatment method using the water treatment apparatus 1000 described above will be described below. The water treatment method of the present embodiment includes an activated sludge treatment process for treating raw water using activated sludge, and a membrane separation process for membrane separation of the sludge-containing treated water obtained in the activated sludge treatment process. ing.

(Activated sludge treatment process)
In the water treatment method using the water treatment apparatus 1000, wastewater (raw water) such as industrial wastewater and domestic wastewater discharged from factories, households, etc. is allowed to flow into the activated sludge treatment tank 11 through the first flow path 12, and Activated sludge is treated in 11 to obtain biologically treated water. The sludge-containing treated water (to-be-treated water) after treatment is made to flow into the membrane separation tank 21 through the second channel 13 .

(Membrane separation process)
In the membrane separation tank 21 , the membrane module 22 of the MBR device 100 membrane-separates sludge-containing treated water (water to be treated) containing activated sludge and biologically treated water. Aeration is performed by the air diffuser 10 during the membrane separation process.

A part of the sludge-containing treated water is returned from the membrane separation tank 21 to the activated sludge treatment tank 11 by the sludge return means 30 . After membrane separation of the sludge-containing treated water by the membrane module 22, the treated water is sent to the treated water tank 41 through the third channel 33 and stored therein. The treated water stored in the treated water tank 41 can be reused as industrial water or discharged into a river or the like.

In the water treatment method, the activated sludge treatment process and the membrane separation process may be performed simultaneously using a water treatment apparatus in which the MBR device 100 is provided in the activated sludge treatment tank 11 .

As described above, in the present invention, since the partition wall forms an air reservoir on the air supply port side inside the main body of the air diffuser, water to be treated adheres to the air supply port during operation. This prevents the air supply port from clogging with sludge. Therefore, the membrane surface of the membrane module can be stably cleaned.
Further, in the present invention, since the partition wall is provided inside the main body, it is possible to suppress clogging of the air supply port with sludge without increasing the size of the air diffuser.

In addition, the air diffuser of the present invention is not limited to the air diffuser 10 described above.
For example, a plate-like partition wall may be an air diffuser provided at an angle to the inner surface of the upper portion of the main body. The angle of the plate-like partition wall with respect to the inner surface of the upper portion of the main body is preferably 0 to 45°, more preferably 0 to 30°. If the angle is within the above range, it is easy to suppress clogging of the air supply port with sludge during operation.

The air diffuser of the present invention is not limited to an aspect in which the plurality of second lead-out portions are arranged in a row in the longitudinal direction of the main body in plan view. They may be arranged in two or more rows in one direction.

In the air diffusion device of the present invention, the interior of the main body 50 may be partitioned into a plurality of regions by one or more partition walls, and the air supply ports 60 may be formed in each of these regions.

DESCRIPTION OF SYMBOLS 10... Air diffuser, 22... Membrane module, 50... Main-body part, 52... 1st lead-out part, 54... 2nd lead-out part, 56... Partition wall, 58... Water-to-be-treated inflow part, 60... Air supply port, 70 ... siphon chamber, 80 ... air reservoir, 100 ... membrane separation activated sludge apparatus.

Claims (2)

A membrane separation activated sludge apparatus comprising a membrane module for membrane separation of sludge-containing treated water containing activated sludge and an air diffuser for intermittently aerating water to be treated,
The air diffuser is
a main body that is immersed in the water to be treated, has a hollow interior, and has a water inlet portion formed at the bottom;
a first lead-out portion provided inside the main body portion, the upper side of which is open, and the side and bottom sides of which are airtightly sealed;
a plurality of second lead-out portions provided to extend downward from the upper portion of the main body portion and having both ends opened;
each of the second lead-out portions partially enters into the first lead-out portion from the upper side of the first lead-out portion with the lower end of each of the second lead-out portions being separated from the lower portion of the first lead-out portion;
An air supply port is formed in the upper part of the main body to supply air to the outside of the first lead-out portion inside the main body in a plan view,
A partition extending downward from between the air supply port in the upper portion of the main body and the first lead-out portion in a plan view, and forming an air reservoir in a portion of the interior of the main body where the air supply port is formed. Membrane separation activated sludge equipment with walls. 2. The membrane separation activated sludge apparatus according to claim 1, wherein the position of the lower end of said partition wall is lower than the upper end of said first lead-out portion.

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