JPH0720592B2 - Activated sludge treatment equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an activated sludge treatment device that performs digestion treatment of organic wastewater and solid-liquid separation by a filtration membrane in a single tank.

Generally, in this type of activated sludge treatment device, the filtration membrane is clogged with the sludge during use, so various proposals have been made to prevent the clogging. For example, in the apparatus shown in FIG. 10, the hollow fiber membrane 4 is suspended and immersed in the purified water 3 of the raw water 2 in the aeration tank 1, and the air diffusing pipe 5 is arranged immediately below the hollow fiber membrane 4. Is. The aeration air 6 required for the purification treatment of the raw water 2 is blown from the blower 7 into the purified treatment water 3 through the air diffuser 5.
The purified water 3 is solid-liquid separated by the suction pump 8 sucking the inside of the hollow holes of the hollow fiber membrane 4, and the hollow fiber membrane 4
The clean filtered water 9 that has passed through is sent to the filtered water tank 10. On the other hand, the excess sludge 11 accumulated in the aeration tank 1 is pulled out to the outside in a timely manner. If the hollow fiber membrane 4 is continuously sucked, the clogging is called clogging, and the hollow fiber membrane 4 cannot be recovered in a short period of time.
By performing intermittent suction and periodically releasing the pressure, sudden clogging is prevented and stable operation is possible for a long time. Further, the device disclosed in Japanese Patent Laid-Open No. 61-274799 has a filtering means in the processing tank. This filtering means comprises a plurality of filtration plates having a hole at the center thereof, the holes being penetrated through a hollow rotary shaft and arranged in parallel at regular intervals, and the hollow rotary shaft is driven by a drive mechanism of the hollow rotary shaft so as to be integrally rotated. The aeration means for discharging gas is provided in the membrane, and the filtration plate is a membrane support having filtration-treated water passages covered with semipermeable membranes on both sides. The raw water sent into the treatment tank is aerated by the gas from the aeration means and digested. The digested water is filtered by the semipermeable membrane of the rotating filter plate,
The clean filtered water is taken out through the filtered water passage of the membrane support and the hollow portion of the hollow rotating shaft. On the other hand, the sludge attached to the membrane surface by filtration is separated from the membrane surface by the stirring action of the aeration gas itself and the purified water of the gas. Since the membrane surface passes through the position of the gas discharge pipe of the aeration means every time the filtration means makes one revolution, it is cleaned in an extremely short cycle, and it is always kept clean and can be used stably for a long period of time. is there. Excess sludge accumulated in the treatment tank is discharged to the outside in a timely manner.

However, when a large amount of fibrous foreign matters are contained in the raw water, in the former conventional device, the fibrous foreign matters are contained in the hollow fiber membrane 4. There was a problem that the hollow fiber membrane 4 became entangled and finally became like a rod of sludge, and the hollow fiber membrane 4 was completely clogged. Further, in the latter device, there is a problem that the fibrous foreign matters are wound around the hollow rotary shaft and finally block the space between the filter plates. Further, in the latter device, since the gas-liquid mixed phase flow is unevenly flowed between the filtration plates, the membrane surface flow velocity becomes nonuniform, and there is a possibility that a portion having low membrane permeation performance may occur. Therefore, in order to prevent this, the filtering means is rotated. Therefore, not only is the structure complicated,
There was also the problem of becoming expensive.

It is an object of the present invention to improve the conventional device and solve such problems.

Means for Solving the Problems In order to achieve the above object, the activated sludge treatment device of the present invention has a filtration membrane device for performing solid-liquid separation of purified treated water in purified treated water of raw water in an aeration tank. The filter is a submerged tube that has a diffusing pipe that supplies the gas for aeration just below the filtration membrane device.The filtration membrane device is a rectangular box frame with a plurality of membrane modules open on both upper and lower sides. Each of the membrane modules is installed in parallel vertically on the upper part of the inside, and each membrane module has a surface of a membrane support having a certain thickness and rigidity covered with a filtration membrane, and a filtration-treated water channel is formed inside. The outlet side of each filtered water channel is connected to the filtered water suction pipe, and the air diffuser is provided in the lower part of the rectangular box frame.

Action In the configuration of the present invention described above, the raw water sent into the aeration tank is aerated by the aeration gas blown from the diffuser pipe to the space between the membrane modules, and purified. Purified water is
The inside of the filtration-treated water channel of the membrane support of the membrane module is suctioned toward the filtration-treated water suction pipe to perform solid-liquid separation with the filtration membrane, and the clean filtration-treated water that has passed through the filtration membrane flows from the filtration-treated water channel. It is taken out through the suction pipe of filtered water.
On the other hand, the sludge attached to the membrane surface by filtration is separated from the membrane surface by the upward flow generated by the airlift action of the bubbles of the aeration gas rising between the membrane modules and rises,
It comes out from the top of the filtration membrane device, returns to the purified water, and is recycled as activated sludge. When the membrane module is installed so as to be inclined with respect to the vertical line, air bubbles collide with the downward membrane surface and disturb the membrane surface, so that sludge is more easily separated from the membrane surface. , The permeation resistance of the filtration membrane decreases.

The operation of the present invention is as described above. However, if the distance between the membrane modules is appropriately set, even if a large amount of fibrous foreign matter is contained in the raw water, the foreign matter will be removed from the membrane. There is no risk of entanglement with the module, and clogging of the filtration membrane due to sludge adhesion can be prevented. Further, the air bubbles blown out from the air diffuser rise at a uniform density between the membrane modules due to the rectification effect of the membrane module formed by the membrane support having a certain thickness and rigidity, so that the flow on the membrane surface liquid flow is uneven. There is no. That is, the entire film surface is uniformly disturbed by the bubble multiphase flow rising at a uniform flow velocity. Also, at this time, by providing the air diffuser with a rectangular box frame, it is possible to supply a parallel flow on the membrane surface at a uniform flow rate regardless of the position of the membrane module, and even between the membrane modules in the peripheral part of the box frame. Blockage can be prevented. Therefore, since it is not necessary to rotate the membrane module as in the conventional device, the structure is simplified and the device is inexpensive.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

First Embodiment In this embodiment, as shown in FIG. 1, an aeration tank 21 is provided with a filtration membrane device 22 and an air diffusing pipe 23. The aeration tank 21 is a tank for purifying the raw water 25 supplied from the raw water supply pipe 24, and a sludge drawing pump 26 is connected to the bottom portion thereof via a sludge drawing pipe 27. The filtration membrane device 22 uses raw water
A device for solid-liquid separation of digested water 28 produced by digestion treatment of 25, which is a rectangular box frame 29 with open upper and lower surfaces.
A plurality of membrane modules 30 are vertically arranged at a fixed interval A in the upper part
They are arranged in parallel with each other and are immersed in the digested water 28 with its top part submerged. The air diffuser 23 is a tube for blowing an aeration gas 31 containing oxygen such as air between the membrane modules 30, and is disposed immediately below the filtration membrane device 22, that is, in the lower part of the rectangular box frame, and the air supply pipe 32 is provided. Blower through
Connected to 33. Reference numeral 34 is a filtered water tank that stores the filtered water 35 from the filtration membrane device 2. The membrane module
As shown in FIGS. 2 to 4, reference numeral 30 is a membrane support 36 having filter membranes 37 attached to both surfaces thereof with an adhesive. The membrane support 36 is made of metal (such as stainless steel),
A tubular member 40 and a reinforcing member 41 are fixed to the upper edge of a rectangular support plate 39, which is made of plastic or the like and has concave and convex portions 38 on both side edges, and has a certain thickness and rigidity. The tubular member 40 is provided with a communication hole 42 at the position of the uneven portion 38, and a branch pipe.
It is connected to the filtered water suction pipe 44 via 43 (first
See figure). The filtration membrane 37 is a macroporous flat membrane such as a microfiltration membrane or an ultrafiltration membrane. A filtration treatment water channel 45 (shown by an arrow in FIGS. 2 and 3) is formed between the filtration membrane 37 and the membrane support 36, and the communication hole 42, the inside of the tubular member 40 and the branch pipe 43 are formed. After that, it communicates with the filtered water suction pipe 44.
A suction pump 46 is connected in the middle of the filtered water suction pipe 44 to reach the filtered water tank 34.

Next, the operation of this embodiment will be described.

Raw water 25 sent from the raw water supply pipe 24 into the aeration tank 21 passes through a blower 33, an air supply pipe 32 and an air diffusing pipe 23 to a membrane module.
It is aerated by the aeration gas 31 blown out during 30 and is purified. The purified treated water 28 is solid-liquid separated by the filtration membrane 37 by sucking the inside of the filtration treated water flow path 45 of the membrane module 30 by the suction pump 46, and the clean filtered treatment water 35 that has passed through the filtration membrane 37 is filtered. Filtered water suction pipe from treated water channel 45 through communication hole 42, inside tubular member 40 and branch pipe 43
It is sucked into 44 and sent into the filtered water tank 34. On the other hand,
The sludge attached to the membrane surface of the filtration membrane 37 by filtration is separated from the membrane surface by the ascending flow generated by the airlift action of the bubbles of the aeration gas 31 rising between the membrane modules 30 and rises, and the filtration membrane device It comes out from the top of 22 and returns to the purified water 28, rides on the circulating flow B (see FIG. 1) of the purified water 28 generated in the aeration tank 21, and reaches below the filtration membrane device 22,
It is recycled again as activated sludge. The excess sludge in the aeration tank 21 is drawn outside by the sludge drawing pump 26 through the sludge drawing pipe 27.

This embodiment operates as described above, but if the interval A of the membrane module 30 is set appropriately, even if the raw water 25 contains a large amount of fibrous foreign matters, it will be There is no risk that substances will become entangled in the membrane module 30, and clogging of the filtration membrane 37 due to adhesion of sludge does not occur. Further, the air bubbles blown out from the air diffuser 23 rise at a uniform density between the membrane modules 30 due to the rectification effect of the membrane module 30 formed to have a constant thickness and rigidity, so that the flow on the membrane surface liquid flow is uneven. There is no. That is, the entire film surface is uniformly disturbed by the bubble multiphase flow rising at a uniform flow velocity. Further, at this time, by providing the air diffuser inside the rectangular shape, it is possible to supply a parallel flow on the membrane surface with a uniform flow rate, and it is possible to prevent clogging between the membrane modules even in the peripheral portion of the box frame. Therefore, since it is not necessary to rotate the membrane module 30 as in the conventional device, the structure is simple and the device is inexpensive.

Second Embodiment This embodiment has exactly the same configuration as the first embodiment except that the membrane module 30 is provided so as to be inclined with respect to the vertical line as shown in FIG. is there. Therefore, the action and effect thereof are almost the same as those of the first embodiment, but the bubbles collide with the downward membrane surface of the membrane module 30 and disturb the membrane surface, so that the sludge is more easily separated from the membrane surface and the filtration is performed. The advantage is that the permeation resistance of the membrane 37 is reduced.

Other Examples (1) The membrane support 36 may be a net-like one made of metal or plastic, a porous plate-like one or the like, and the uneven portion 38 thereof is, as shown in FIG. 2 uneven boards
They may be formed by stacking them in opposite directions.

(2) In the case of the second embodiment, the filtration membrane 37 may be attached to only one side of the membrane support 36. Further, as shown in FIG. 7, the filtration membrane 37 may be formed in a bag shape and covered with the membrane support 36, and the opening 47 may be fixed with the band 48 to fix the tubular member 40. Will be easier. Moreover, FIGS.
As shown, the membrane support 36 may be formed of a solid body.

(3) A plurality of filtration water suction pipes 44 may be connected not only to the upper edge of the membrane module 30 but also to both side edges and lower edges.

EFFECTS OF THE INVENTION As described above, according to the present invention, the interval between the membrane modules can be set appropriately, so that even if a large amount of fibrous foreign matters are contained in the raw water, the fine foreign matters are mixed. There is no risk of objects getting entangled in the membrane module. Therefore, it is possible to prevent clogging of the filtration membrane due to adhesion of sludge. Further, the bubbles blown out from the air diffusing tube arranged immediately below the filtration membrane device rises at a uniform density between the membrane modules due to the rectification effect of the membrane module formed with a certain thickness and rigidity, There is no drift in the liquid flow on the membrane surface. That is, the entire film surface is uniformly disturbed by the bubble multiphase flow rising at a uniform flow velocity. Also, at this time, by providing the air diffuser with a rectangular box frame, it is possible to supply a parallel flow on the membrane surface at a uniform flow rate regardless of the position of the membrane module, and even between the membrane modules in the peripheral part of the box frame. Blockage can be prevented. Therefore, since it is not necessary to rotate the membrane module as in the conventional device, the structure is simplified and the device is inexpensive.

[Brief description of drawings]

1 is a circuit diagram of the first embodiment of the present invention, FIG. 2 is a sectional view of the membrane module of the present invention, FIG. 3 is a sectional view taken along the line XX of FIG. 2, and FIG. Perspective view of the membrane module in the figure, fifth
FIG. 7 is a circuit diagram of a second embodiment of the present invention, FIG. 6 is a partial sectional view of another embodiment of the membrane support of the present invention, and FIG. 7 is an explanatory view of another embodiment of the filtration membrane of the present invention. FIG. 8 is a partial sectional view of another embodiment of the membrane support of the present invention, FIG. 9 is a sectional view taken along the line YY of FIG. 8, and FIG. 10 is a circuit diagram showing an example of a conventional device. Is. 21 ... Aeration tank, 22 ... Filtration membrane device, 23 ... Air diffuser, 25 ... Raw water,
28 ... Purified water, 30 ... Membrane module, 31 ... Aeration gas,
36 ... Membrane support, 37 ... Filtration membrane, 44 ... Filtration-treated water suction tube, 45
... Filtered water flow path, A ... at regular intervals.

Claims (1)

[Claims] 1. A filtration membrane device for solid-liquid separation of purified treatment water is immersed in the purified water of the raw water in the aeration tank with its top submerged, and an aeration gas is supplied directly below the filtration membrane device. An air diffuser is arranged, and the filtration membrane device comprises a plurality of membrane modules arranged vertically in parallel at regular intervals in an upper part of a rectangular box frame whose upper and lower surfaces are open.
In each membrane module, the surface of a membrane support having a certain thickness and rigidity is covered with a filtration membrane, and a filtration-treated water channel is formed inside, and the outlet side of each filtration-treated water channel is connected to a filtration-treated water suction pipe. The activated sludge treatment device is characterized in that the air diffuser is provided in the lower part of the rectangular box frame.