JPH10230261A - Immersion type membrane filter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the trouble that the load of a sludge treatment process increases as sludge of a low concn. and a large quantity is discharged. SOLUTION: A cylindrical partition 11 is mounted at the central part of the upper part of a filter chamber 2, by which the upper part of this filter chamber 2 is divided to a columnar block 12 and a doughnut-shaped block 13. The columnar block 12 is a raw water introducing part and a raw water introducing pipe 23 is connected to its upper part. A membrane module 14 is disposed in the doughnut-shaped block 13. The filter chamber 2 is provided with a sludge scraper 18 for scraping the sludge deposited on its bottom toward a sludge discharge port 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an immersion type membrane filtration apparatus in which a membrane module is provided in a filtration tank.

[0002]

2. Description of the Related Art In recent years, a technology for removing suspended matter using a separation membrane has been adopted in water purification treatment of clean water. Water purification technologies using separation membranes include:
For example, there is an immersion type membrane filtration device in which a membrane module is disposed in a tank.
Nos. 8273 and 7-323295.

FIG. 2 is a view showing an apparatus disclosed in Japanese Patent Application Laid-Open No. 6-238273. In this apparatus, a hollow fiber membrane module 51 is disposed above a settling tank 50, and Raw water is introduced downward. 1 is a raw water tank, 3 is a membrane module 51
This is a treated water tank that temporarily stores the water that has been filtered.
When water purification treatment is performed using this device, coarse sedimentable particles of solids in raw water supplied below the membrane module 51 settle and accumulate at the bottom of the sedimentation tank 50, and fine particles Captured by module 51. The captured solids are removed by an intermittent stripping operation,
Settles and collects at the bottom. The solid matter accumulated at the bottom is sludge and is extracted from the bottom of the settling tank 50.

FIG. 3 is a view showing an apparatus disclosed in Japanese Patent Application Laid-Open No. 7-323295. In this apparatus, a part submerged in water above a processing tank 60 is divided into two sections. One of the compartments is provided with a biological treatment device 61, and the other compartment is provided with a membrane filtration device 62.
The raw water is introduced below the biological treatment device 61, and the biologically treated water is sent to the membrane filtration device 62 to be filtered. A precipitate concentrating device 63 is provided below the biological treatment device 61 and the membrane filtration device 62.
The sediment (sludge) concentrated by the concentration device 63 accumulates at the bottom of the treatment tank 60 and is periodically extracted.

[0005]

The sludge generated in the water purification treatment is sent to the sludge treatment step, dewatered and disposed of, and the sludge to be dewatered at this time is mostly composed of fine particles. Therefore, it is listed as one of the ones that are difficult to dehydrate.

In the above-mentioned prior art, the extracted sludge must be subjected to a dehydration treatment. However, when the prior art is implemented, a large amount of low-concentration sludge is extracted.
There is a problem that the load of the sludge treatment process increases.

[0007] That is, in the conventional technology, the sludge is simply extracted by opening the bottom exhaust port and extracting by head pressure, or by suctioning with a pump. The concentrated sludge that has been around comes out, but the water that was above the accumulated sludge is then extracted together. For this reason, low concentration sludge comes out. Furthermore, in order to extract the sludge accumulated at a position distant from the outlet, the extraction operation is continued even after the sludge around the outlet is discharged, and a layer of the sludge accumulated at a position distant from the outlet. And the sludge that has flowed down to around the sludge outlet must be extracted, so that the sludge concentration is further reduced.

In the apparatus shown in FIG. 3, a concentrator 63 is provided at the lower part of the processing tank.
3 is for accelerating the sedimentation of the sediment. Here, even if the sludge is concentrated, in the next step, the concentrated sludge accumulates over the entire bottom surface. The state in which the sludge is extracted from the discharge port is the same as the above-described extraction state, and the concentration of the extracted sludge does not increase.

[0009] It is an object of the present invention to provide a submerged membrane filtration device in which the concentration of sludge to be extracted is high and the load of the sludge treatment step can be reduced.

[0010]

In order to achieve the above object, in the immersion type membrane filtration apparatus according to the first aspect of the present invention, the membrane module is provided at the top of the filtration tank, and at the bottom of the filtration tank. A sludge scraper is provided for scraping the accumulated sludge toward a discharge port.

According to a second aspect of the present invention, in the above-mentioned apparatus, the upper portion of the filtration tank is divided into two sections, and one of the two sections is provided with a membrane module, and the other section is provided with a membrane module. Is connected to a raw water introduction pipe.

The upper or lower part of the filtration tank in the present invention does not necessarily indicate the vertical positional relationship with the middle level of the tank height as a boundary. , The upper part is the upper part,
The part located thereunder shall be the lower part.

In the present invention, since the sludge scraper for scraping the sludge toward the discharge port is provided, the sludge deposited on the bottom of the filtration tank is sequentially collected around the discharge port. Therefore, when the sludge is extracted, only the accumulated and concentrated sludge is discharged without the water existing on the sludge layer being drawn.

Further, the upper part of the filtration tank is divided into a section provided with a membrane module and a section (raw water introduction part) to which a raw water introduction pipe is connected, and the introduction of raw water is performed from the upper part of the filtration tank. The raw water flows downward while being rectified in the upper section of the filtration tank, and diffuses throughout the lower section of the filtration tank. For this reason, in the lower part of the filtration tank, there is no disturbance such as partial stirring or generation of drift. As a result, the sedimentation of the particles in the raw water is performed without hindrance, the removal rate is improved, and the load on the membrane module is reduced.

[0015]

FIG. 1 is a schematic sectional view showing an example of a submerged membrane filtration device according to the present invention. In FIG.
1 is a raw water tank, 2 is a filtration tank, and 3 is a treated water tank. The filtration tank 2 has a cylindrical shape, and has a bottom portion inclined downward toward the center so as to have a mortar shape, and a drain port 10 is provided at the center portion. A cylindrical partition 11 is attached to the center of the upper part of the filtration tank 2, and the upper part of the filtration tank 2 is divided into a cylindrical section 12 and a donut-shaped section 13. The upper end of the partition 11 is located at a level higher than the level at which the water surface is formed during operation of the apparatus, and the section 12 and the section 13 communicate with each other on the lower side.

The cylindrical section 12 is a raw water introduction section, and a raw water introduction pipe 23 is connected to an upper portion thereof. Further, a membrane module 14 is provided in the donut-shaped section 13. The membrane module 14 incorporates a separation membrane such as a hollow fiber membrane, and has a structure in which raw water permeates from the inside to the outside of the separation membrane. A suction pump 25 is connected to the inside of the separation membrane. Connected to the treated water outflow pipe 24. Below the membrane module 14, a plurality of air scrubbing air diffusers 17 used for cleaning the separation membrane of the membrane module 14 are arranged concentrically. Reference numeral 16 denotes an air header for stably sending air to the air diffuser 17, and 15 denotes an air blower.

The filtration tank 2 is provided with a sludge scraper 18 for scraping sludge deposited on the bottom. The sludge scraper 18 has a rake 21 disposed close to the bottom of the filtration tank 2 and a rotating shaft 20 to which the rake 21 is attached. The accumulated sludge is sequentially discharged by a large number of plates attached to the rake 21.
It can be swept toward zero. 19 is a motor with a speed reducer.

The water purification treatment by the apparatus configured as described above is performed as follows. Raw water from which large solids have been removed in the settling basin is introduced from the raw water tank 1 into the columnar section 12 of the filtration tank by the raw water pump 22 and the raw water introduction pipe 23. Introduced raw water is rectified and columnar section 12
And descends into the lower part of the filtration tank 2.

In the lower part of the filtration tank 2, the settling particles in the raw water that has flowed in settle down and accumulate on the bottom to form sludge. The sludge is sequentially scraped from the peripheral part toward the central part by the rake 21 of the sludge scraper, and is collected near the discharge port 10. When extracting sludge, the amount of extraction is adjusted so that the sludge concentration is maintained in a concentrated state. The extraction of sludge may be either intermittent extraction or continuous extraction.

The raw water that has flowed into the lower part of the filtration tank 2 from the columnar section 12 rises after the sedimentary particles are removed, and enters the donut-shaped section 13. Here, the raw water is sucked and permeates through the separation membrane of the membrane module 14, and the treated water outflow pipe 24
And is temporarily stored in the treated water tank 3.

If such a filtration operation is continued for a long time, the suspended matter adheres to the separation membrane of the membrane module 14, and if the amount exceeds a certain limit, the filtration resistance increases and the filtration speed decreases. I do. Therefore, when the decrease in the filtration rate cannot be tolerated, the introduction of the raw water is stopped, and the membrane module 14 is washed.

When cleaning the membrane module 14, the raw water pump 22 and the suction pump 25 are stopped, the backwash pump 26 is started, and the water in the treated water tank 3 is removed from the membrane module 14.
To the inside of the separation membrane, and the water flows backward from the inside to the outside of the separation membrane. By this operation, the deposits on the separation membrane are peeled off. In addition, the blower 15 is started and the diffuser 17 is opened.
The air is blown from the air to scrub the membrane module 14 to promote the separation of the deposits. The deposits become flocs and peel off. When the separation membrane is clean, the blower 15 and the backwash pump 2
Stop 6. When most of the detached deposits have settled to the lower part of the filtration tank 2, the raw water pump 2
2 and the suction pump 25 are started, and the operation shifts to the filtration operation.

The deposits on the separation membrane that are peeled off when washing the membrane module 14 settle together with the sedimentable particles in the raw water that newly flows in, and are deposited on the bottom of the filtration tank 2. The sludge, which is the sediment, is extracted as described above.

In the immersion type membrane filtration apparatus shown in FIG. 1, the filtration tank 2 has a cylindrical shape. However, the shape of the filtration tank in the present invention is not limited to a cylindrical shape, but is rectangular. Any device may be used as long as a mechanism for scraping the sludge is provided at the bottom.

When the upper part of the filtration tank 2 is divided to form the section 12 for connecting the raw water introduction pipe 23, the position of the section 12 does not necessarily have to be the center. As long as the section into which the raw water is introduced is formed by dividing the tank in the vertical direction, the position of the section is not limited.

The separation membrane used for the membrane module 14 is not limited to a hollow fiber membrane, but may be a flat membrane.

[0027]

The immersion type membrane filtration device according to the first aspect of the present invention is provided with a sludge scraper for scraping the sludge toward the sludge outlet, and the sludge deposited on the bottom of the filtration tank is removed. Since it is collected around the outlet, only the sludge that has accumulated and concentrated is discharged. For this reason, the concentration of the extracted sludge is high, and the load on the process of treating the sludge is reduced.

Further, in the immersion type membrane filtration device according to the second aspect, since the upper part of the filtration tank is divided into a section provided with a membrane module and a section for introducing raw water, the raw water flows in the upper part of the filtration tank. It descends while being rectified and flows into the compartment with the membrane module without disturbance. For this reason, in the lower part of the filtration tank, the sedimentation of the sludge in the raw water is not hindered, and the removal rate is improved, so that the load on the membrane module is reduced.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a submerged membrane filtration device according to the present invention.

FIG. 2 is a diagram showing an example of a conventional immersion type membrane filtration device.

FIG. 3 is a diagram showing another conventional immersion type membrane filtration device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Raw water tank 2 Filtration tank 3 Treatment water tank 10 Drainage port 11 Cylindrical partition 12 Column-shaped section 13 Donut-shaped section 14 Membrane module 18 Sludge scraper 19 Motor 20 Rotating shaft 21 Rake 22 Raw water pump 23 Raw water introduction pipe 24 Outflow pipe for treated water 25 Suction pump

Claims (2)

[Claims] 1. A submerged membrane filtration device having a membrane module disposed in a filtration tank, wherein the membrane module is provided at an upper portion of the filtration tank, and the sludge deposited at the bottom of the filtration tank is scraped toward a drain port. An immersion type membrane filtration device, comprising a sludge scraper for gathering. 2. The filter tank according to claim 1, wherein the upper portion of the filtration tank is divided into two sections, one of the two sections is provided with a membrane module, and the other section is connected to a raw water introduction pipe. The immersion type membrane filtration device according to 1.