JP3784252B2 - Air diffuser - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a diffuser and relates to a technique for aeration of a mixed liquid in a tank in a membrane separation activated sludge method or the like.
[0002]
[Prior art]
Conventionally, in the membrane separation activated sludge method, an air diffuser is disposed below the membrane separator immersed in the aeration tank, and the mixed liquid in the tank containing activated sludge in the aeration tank by the air diffused from the air diffuser The membrane surface of the membrane separation device is washed by the upward flow of the solid-gas / liquid mixed phase generated by the rise of the diffused air. As an air diffuser used in this membrane separation activated sludge method, for example, there is one in which a plurality of holes of about φ10 mm are formed below a pipe made of vinyl chloride.
[0003]
By the way, the membrane surface cleaning of the membrane separation device requires an air supply of 10 L / min or more on an average per membrane cartridge. However, when the aeration air is not uniformly distributed, aeration is performed locally. Since the load applied to the film becomes large at a place where there is a lot of air, the life of the film will be shortened.
[0004]
On the other hand, oxygen necessary for biological treatment in the membrane separation activated sludge method is secured by supplying an aeration air amount set based on oxygen dissolution efficiency in the activated sludge with a predetermined aeration blower. Increasing the oxygen dissolution efficiency is desirable because it reduces power consumption by reducing the size of the aeration blower and reducing the aeration time.
[0005]
For this reason, it is required to provide uniform dispersion of aerated air and improve oxygen dissolution efficiency by providing a plurality of small-diameter air outlets in the diffuser.
[0006]
[Problems to be solved by the invention]
However, sludge flows into the air diffuser when the air diffuser stops, and this sludge is dried by the air during the air diffused and closes the air outlet, so the diameter of the air outlet is reduced by sludge drying. It becomes a cause that obstruction | occlusion of a diffuser pipe (drying sludge obstruction | occlusion) becomes easy to occur, and it is fundamental to prevent beforehand by regular cleaning. Moreover, since impurities, low-fluid sludge, large flocs, and the like suddenly occur to block the air outlet, it is difficult to completely prevent the air diffuser from being blocked. In this case, most blockages are released by the next periodic cleaning, but there is a problem inducing dry sludge blockage firmly adhered during that period and sludge blockage between membranes due to insufficient membrane surface cleaning.
[0007]
The present invention solves the above-described problems, and can structurally suppress the clogging of the pipe and can clean the pipe by a simple operation. An object of the present invention is to provide an air diffuser that can be noticed.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the air diffuser of the present invention is immersed in a tank and arranged in a horizontal direction, and the proximal end communicates with the air supply source, the trunk pipe communicates with the trunk pipe, and the distal end is A plurality of branch pipes opened at a position below the main pipe, an air diffuser pipe having one end communicating with the tip end side of the main pipe and the other end opened as an exhaust port above the main pipe, and an air diffuser pipe Each branch pipe has an open port at the end, and a plurality of air jets having a smaller diameter than the end open port are provided on the upper surface.
[0009]
With the above configuration, when air is diffused, the air supplied from the air source at a predetermined pressure is vented from the base end side to the main pipe while the drain valve is closed, and is diffused from the air outlet through the branch pipe. At this time, since each air jet is located in the upper part of the branch pipe, most of the air diffused by the buoyancy of the air due to the density difference from the mixed liquid before reaching the end opening is jetted from the air jet.
[0010]
Since the air outlet has a small diameter, the air bubbles to be ejected have a small diameter, and the oxygen dissolution efficiency is increased, so that the blower or the like of the air source can be downsized to reduce power consumption. In addition, by reducing the diameter of the air jets, the number of air jets arranged per unit area can be increased, which increases the degree of dispersion of the air jets, so that the aerated air is uniformly diffused. This increases the cleaning effect.
[0011]
Even if the air outlet is suddenly blocked by foreign matter, low-fluid sludge, large flocs, etc., the air is blown out from the end opening of the branch pipe to ensure a predetermined amount of aeration air. Cleaning can be continued and sludge blockage between the membranes can be prevented from occurring due to insufficient cleaning of the membrane surface until the next regular cleaning.
[0012]
At the time of cleaning, the drain valve is opened in a state where air of a predetermined pressure is supplied from the air source to the main pipe, and the air supplied to the main pipe is exhausted from the exhaust port to atmospheric pressure or a predetermined depth of water through the diffused drain pipe.
[0013]
At this time, the exhaust opening opens to the upper position of the trunk pipe, and the end opening opening and the air outlet of the branch pipe open to the lower position of the trunk pipe, so that the air outlet and the end opening of the branch pipe Due to the pressure difference with the main pipe, the liquid in the tank flows back into the branch pipe and the main pipe through the end opening of the branch pipe and the air outlet, and the in-tank liquid enters the diffused drain pipe together with the air. It is discharged from the exhaust port.
[0014]
The liquid in the tank in the main pipe acts as a resistance that hinders air flow, and the air flow pulsates, and the pressure in the main pipe repeatedly changes suddenly. The air and the liquid in the tank are intermittently discharged from the tank, and the liquid in the tank intermittently flows into the main pipe through the branch pipe.
[0015]
The rapid inflow of the liquid in the tank through this branch pipe is repeatedly generated, so that the sludge adhering to the inside of the branch pipe is effectively washed. Sludge adhering to the inside of the branch pipe is dried by the air at the time of air diffusion, but the liquid in the tank infiltrates the sludge to promote the separation of the sludge. At the same time, it is discharged from the exhaust port.
[0016]
Therefore, by simply opening the drain valve, the inside of the branch pipe, the air outlet, the end opening, and the inside of the trunk pipe can be cleaned, preventing obstruction of the diffuser pipe by dry sludge. Therefore, it is possible to reduce the diameter of the air outlet of the branch pipe that is easily clogged with the drying sludge.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1 to FIG. 4, an aeration device 2 and a membrane separation device 3 disposed above the aeration device 2 are immersed in the aeration tank 1. The membrane separation device 3 is not essential for the aeration tank 1, but is used as a solid-liquid separation means for activated sludge in the membrane separation activated sludge method according to the present embodiment.
[0018]
The membrane separation device 3 can use various types of separation membranes, for example, organic flat membrane type, tube type, and ceramic type. Here, a plurality of membrane cartridges using organic flat membrane type separation membranes are vertically arranged. And arranged in parallel at a predetermined interval, and a flow path is formed between adjacent membrane cartridges. Each membrane cartridge communicates with a membrane permeate flow path (not shown) and operates with the water head (gravity) in the tank or the pump suction pressure as the driving pressure.
[0019]
The air diffuser 2 has an air diffuser case 4 surrounding a lower region of the membrane separation device 3 and an air diffuser pipe 5 disposed below the air diffuser case 4. The air diffuser 5 has a predetermined diameter arranged in the horizontal direction. It consists of a main pipe 6 made of a large diameter pipe and a plurality of branch pipes 7 made of a small diameter pipe having a predetermined diameter arranged below the main pipe 6.
[0020]
The trunk pipe 6 communicates with the blower 8 serving as an air supply source on the proximal end side, and an aeration drain pipe 9 is connected to the distal end side. The branch pipe 7 has an inverted T-shape, communicates with the trunk pipe 6 at one upper end, has open ports 10a at both ends located below the trunk pipe 6, and has a smaller diameter than the end open port 10a on the upper surface. A plurality of air jets 10b are provided.
[0021]
The diffused drain pipe 9 is open at the tip side as an exhaust port 11 at a position above the main pipe 6 and is provided with a drain valve 12 in the middle. In the present embodiment, the exhaust port 11 is opened under atmospheric pressure on the water surface, but the exhaust port 11 may be disposed below the water surface. The diffuser case 4 is fixed to the bottom of the tank, and the membrane separation device 3 can be moved up and down along a guide 13 provided between the diffuser case 4 and the tank opening.
[0022]
Hereinafter, the operation of the above-described configuration will be described. During the normal aeration operation, the drain valve 12 is in a closed state, and the air supplied from the blower 8 passes through the trunk pipe 6 from the air outlet 10b of each branch pipe 7 into the mixed liquid in the aeration tank 1. To erupt. At this time, since each air jet 10b is located in the upper part of the branch pipe 7, most of the air diffused by the buoyancy of the air due to the density difference from the mixed liquid until reaching the end opening 10a is from the air jet 10b. Erupts.
[0023]
The diffused air aerates the mixed liquid in the tank, and ascends to cause an upward flow of the solid-gas mixed phase. This upward flow stirs and mixes the mixed liquid in the tank, and supplies the mixed liquid in the tank to the flow path between the membrane cartridges of the membrane separation device 3 by cross flow. The membrane separation device 3 filters the mixed liquid in the tank through the filtration membrane of each membrane cartridge, and the upward flow flows as a sweep along the membrane surface, thereby suppressing the cake from adhering to the membrane surface of each membrane cartridge. In this air diffused state, since the air outlet 10b has a small diameter, the air bubbles to be ejected have a small diameter, and the oxygen dissolution efficiency is increased, so that the blower 8 of the air source can be reduced in size and the power consumption can be reduced. Further, by reducing the diameter of the air outlet 10b, it is possible to increase the number of air outlets 10b arranged per unit area, thereby increasing the dispersity of the air outlet 10b, so that the aerated air is uniform. Aeration effect is enhanced by aeration.
[0024]
Even if the air outlet 10b is suddenly blocked by foreign matter, sludge with low fluidity, large flocs, etc., a predetermined amount of aerated air is secured by the air jetting from the end opening 10a of the branch pipe 7. Thus, the membrane surface cleaning can be continued, and the sludge blockage between the membranes can be prevented from occurring due to the lack of the membrane surface cleaning until the next regular cleaning.
[0025]
During the cleaning operation, the drain valve 12 is opened while air of a predetermined pressure is supplied from the blower 8 to the main pipe 6, and the air supplied to the main pipe 6 is discharged from the exhaust port 11 to the atmospheric pressure through the diffused drain pipe 9. Exhaust.
[0026]
At this time, the exhaust port 11 opens under atmospheric pressure at a position above the trunk pipe 6, and the opening 10a and the air outlet 10b open at a position below the trunk pipe 6 to open as shown in FIG. Due to the pressure difference between the pressure P0 acting on the port 10a and the pressure P1 acting on the main pipe 6, the mixed liquid in the tank flows back into the branch pipe 7 and the main pipe 6 through the open port 10a and the air outlet 10b. To do.
[0027]
The mixed liquid in the tank that has flowed in reverse is washed out with sludge adhering to the inside of the branch pipe 7 and washed with water, and is discharged from the exhaust port 11 through the diffused drain pipe 9 together with the air flowing through the trunk pipe 6. Although the sludge adhering to the inside of the branch pipe 7 is dried by the air at the time of air diffusion, peeling of the sludge is promoted by infiltration of the mixed liquid in the tank into the sludge.
[0028]
The mixed liquid in the tank that has flowed into the main pipe 6 acts as a resistance that inhibits the ventilation of air, and the air flow pulsates. In particular, the pressure in the trunk pipe 6 increases because the liquid mixture in the tank staying in the vertical portion of the diffuser drain pipe 9 inhibits the exhaust, and the liquid mixture in the tank staying due to the increase in pressure is discharged all at once. The pressure drops.
[0029]
In this way, the internal pressure of the trunk pipe 6 is repeatedly changed suddenly, whereby air and the mixed liquid in the tank are alternately and intermittently discharged from the exhaust port 11 of the diffuser drain pipe 9, and the branches The mixed liquid in the tank intermittently flows into the main pipe 6 through the pipe 7. The rapid inflow of the mixed liquid in the tank to the branch pipe 7 is repeatedly generated, so that manual operation and repeated operation by a control device are not performed, and the branch pipe 7 is provided inside, the open port 10a, and the air jet port 10b. The adhering sludge can be repeatedly washed with water to effectively remove the sludge.
[0030]
【The invention's effect】
As described above, according to the present invention, the inside of the branch pipe, the end opening, the air outlet, and the main pipe can be cleaned by a simple operation by simply opening the drain valve. It becomes possible to reduce the diameter of the air outlet of the branch pipe that is easily blocked by the dry sludge by preventing the air diffuser from being blocked. By reducing the diameter of the air outlet, air bubbles become smaller and the oxygen dissolution efficiency increases, so the power source can be reduced by reducing the size of the air source blower, etc. It is possible to increase the number of air outlets arranged in the air outlet to increase the degree of dispersion of the air outlets, and to uniformly diffuse the aerated air to enhance the cleaning effect. Even if the air outlet suddenly closes due to large floc sludge, etc., the air can be ejected from the end opening of the branch pipe, so that a predetermined amount of aeration air can be secured and membrane cleaning can be continued. It is possible to prevent sludge clogging between the membranes due to insufficient membrane surface cleaning until the next regular cleaning.
[Brief description of the drawings]
FIG. 1 is a front view showing an air diffuser according to an embodiment of the present invention.
FIG. 2 is a perspective view of the air diffuser.
FIG. 3 is a cross-sectional view of a main part of the air diffuser.
FIG. 4 is an enlarged view of a main part of the air diffuser.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Aeration tank 2 Air diffuser 3 Membrane separator 4 Air diffuser case 5 Air diffuser pipe 6 Trunk pipe 7 Branch pipe 8 Blower 9 Air diffuser drain pipe 10a Opening port 10b Air outlet 11 Exhaust port 12 Drain valve 13 Guide

Claims (1)

Immerse in the tank and place in the horizontal direction, the trunk pipe whose base end side communicates with the air supply source, a plurality of branch pipes that communicate with the trunk pipe, and whose tip opens at a position below the trunk pipe, and one end It has a diffused drain pipe that communicates with the leading end side of the trunk pipe and the other end opens as an exhaust port at an upper position of the trunk pipe, and a drain valve provided in the diffused drain pipe. Each branch pipe has an end portion. An air diffuser characterized in that the air diffuser has a plurality of air outlets having an opening on the upper surface and a smaller diameter than the end opening.

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