JP7493143B2 - Filtration device and filtration method - Google Patents

Description

The present invention relates to a downflow filtration device that uses granular fiber filter media to filter the liquid being treated, and to a filtration device and filtration method that compacts the filter media layer in the early stages of the filtration process to perform efficient filtration.

Conventionally, a filtration method has been known in which the liquid to be treated is supplied from the top of a filtration device filled with sedimentary granular fiber filter media to remove impurities from the liquid. In this filtration method, if the porosity of the filter media layer formed in the filtration tank is high, the liquid to be treated easily passes through the gaps in the filter media, and the impurities in the liquid to be treated are not adequately captured by the filter media layer. For this reason, it was necessary to consolidate the filter media layer in the early stages of the filtration process to reduce the porosity within the layer and increase the filtration capacity.

Patent document 1 discloses a technology in which the cleaning water supplied to the filtration device in the first stage of the filtration process is drained from the bottom of the filtration device, compressing the filter layer to the bottom of the filtration device.

In addition, Patent Document 2 discloses a technology in which the filter layer is compressed to the bottom of the filter tank while circulating and supplying circulating water taken from the bottom of the filter tank to the treated water supply area in the early stages of the filtration process.

Japanese Patent Application Laid-Open No. 9-234309 Patent No. 3058635

In conventional filtration methods, the granular fiber filter media stacked inside the filtration device are not tightly adhered to each other, resulting in a high porosity in the filter media layer. As a result, if the treated liquid supplied from the top contains a high proportion of fine particles, the impurities contained in the liquid are not sufficiently captured by the filter media layer and are discharged from the bottom, making it impossible to improve filtration accuracy.

Using the technology of Patent Document 1, it is possible to compress the filter layer to the bottom of the filtration device and reduce the porosity, but the upper part of the formed filter layer is not sufficiently compressed and has a high porosity because it is less affected by the water flow when the washing water is discharged from the bottom of the device. As a result, the liquid to be treated passes through the upper part of the filter layer, which has a high porosity, and is filtered intensively at the lower part of the filter layer, meaning that the entire filter layer cannot be used effectively.

On the other hand, the technology of Patent Document 2 continues to circulate circulating water in the filtration tank even after the start of the filtration process, so that the upper part of the filtration layer is sufficiently consolidated. However, because water is discharged from the bottom of the tank, the lower part of the filtration layer is significantly affected by the water flow and becomes over-consolidated. Because the circulating water is mixed with the water to be treated and passed through, there is an issue that the pressure in the filter layer increases quickly relative to the amount of water to be treated.

The present invention was made in consideration of these circumstances, and provides a filtration device and a filtration method that solves all of the conventional problems that arise when performing filtration processing using a filtration device that uses granular fiber filter media, and that can perform high-precision filtration processing stably for long periods of time.

The filtration device according to the present invention performs filtration by passing the liquid to be treated from top to bottom through a filter layer formed by compressing sedimentary granular fiber filter media. The device is equipped with a filtration tank having through holes on the periphery that communicate with the filter layer and a drain outlet at the bottom, and a jacket that is installed around the periphery of the filtration tank and has a drain outlet at the bottom. This allows the compressed water to be discharged from the through holes and each drain outlet, and efficiently compresses the entire filter layer, forming a filter layer suitable for deep filtration.

The filtration method according to the present invention is a filtration method for consolidating a sedimentary granular fiber filter medium in a first stage of a filtration process, in which the consolidation water stored in the filtration tank up to a predetermined water level is drained from a drainage port at the bottom of the filtration tank to consolidate the lower part of the filter medium layer, and then the filtration process is started by performing a second consolidation process in which the consolidation water stored in the filtration tank up to a predetermined water level is drained from a through hole provided around the filtration tank to consolidate the upper part of the filter medium layer, and in the first consolidation process, the consolidation degree of the lower part of the filter medium layer formed by draining the consolidation water stored in the filtration tank from the bottom of the filtration tank and consolidating the filter medium to the bottom of the filtration tank can be increased. At this time, since the consolidation degree of the upper part of the filter medium layer is low, the consolidation degree of the upper part of the filter medium layer can also be increased by draining the consolidation water from the through hole provided around the filtration tank in the second consolidation process to consolidate the filter medium.

The filtration device and filtration method of the present invention can consolidate the entire filter layer, including the upper part, by performing a first consolidation step and a second consolidation step prior to the filtration process. By forming a filter layer suitable for deep filtration, a clear treatment liquid can be obtained immediately after the start of the filtration process, and stable filtration can be performed. Even over a long period of filtration, clogging is unlikely to occur, and filtration accuracy is improved.

1 is a vertical cross-sectional view of a filtering device according to the present invention. FIG. 13 is a schematic diagram of the first consolidation process when water is stored. FIG. 2 is a schematic diagram showing the first consolidation step during drainage. FIG. 13 is a schematic diagram of the second consolidation step during drainage. FIG. 13 is a schematic diagram showing a case where the first consolidation step and the second consolidation step are performed simultaneously. FIG.

The filtration device according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a vertical cross-sectional view of a downflow filtration device. The filtration device 1 has a supply port 3 connected to the top of a filtration tank 2 and a drainage port 4a connected to the bottom of the filtration tank 2. A drainage pipe 10a having a valve V1 interposed therein is connected to the drainage port 4a. Inside the filtration tank 2, a filter medium 6 is filled above a screen 5 disposed at a predetermined height from the bottom of the filtration tank 2 to form a filter medium layer 7. The filter medium 6 is a sedimentary granular fiber filter medium, and the shape is not limited to a sphere or columnar shape. If necessary, the area of the lower part of the filtration tank 2 may be gradually reduced to form a tapered shape.

The filtration tank 2 is provided with holes 8 around its periphery to drain the compressed water stored in the tank 2, and is equipped with a jacket 9 to collect the compressed water discharged from the holes 8. A drain pipe 10b with a valve V2 installed is connected to the drain port 4b provided at the bottom of the jacket 9. By combining the valves V1 and V2, the storage and drainage in the filtration tank 2 and the jacket 9 can be freely adjusted.

The through holes 8 are formed with a hole diameter large enough to prevent the filter medium 6 from flowing out of the filter tank 2. The shape of the through holes 8 may be, for example, polygonal, circular, or cross-shaped. Through holes 8 of different sizes may be arranged in combination. The through holes 8 may be directly formed in the cylindrical material constituting the filter tank 2, or a screen having through holes 8 in the shape of a mesh, lattice, or slit may be stretched. The through holes 8 are arranged approximately uniformly or at equal intervals on the peripheral surface of the filter tank 2, and are configured to allow uniform drainage from the peripheral surface of the filter tank 2, so that the filter medium layer 7 can be uniformly consolidated. At this time, the height of the through holes 8 may be set at the middle height of the consolidated filter medium layer 7 , but if the height of the through holes 8 is set at 30 to 80% from the lower end of the consolidated filter medium layer 7, the upper part of the filter medium layer 7 can be consolidated more effectively. Furthermore, since the flow rate of the compressed water drained from the through holes 8 varies on the peripheral surface of the filtration tank 2, the filter material layer 7 will not be uniformly compressed. Therefore, it is preferable that the jacket 9 has a sufficient water collection volume so as not to impede drainage from the through holes 8.

<First consolidation step>
The embodiment of the present invention will be described in detail with reference to the drawings. Fig. 2 is a schematic diagram of the first consolidation step according to the present invention when water is stored, in which the valves V1 and V2 are closed and the consolidated water is stored in the filtration tank 2. In the embodiment of the present invention, the valves V1 and V2 installed in the drainage ports 4a and 4b are closed in the first stage of the filtration treatment step, and the consolidated water is supplied from the supply port 3 into the filtration tank 2 and stored until a predetermined water level is reached. At this time, the consolidated water flows out from the through hole 8 into the jacket 9, but since the valve V2 is closed and the drainage port 4b is closed, the consolidated water fills the jacket 9 and does not flow out from the through hole 8. The stored water level is appropriately adjusted according to the filter material and the liquid to be treated.

3 is a schematic diagram of the first consolidation step according to the present invention, in which the valve V1 is opened and the consolidated water is discharged from the drain port 4a. The water pressure generated when discharging the consolidated water pushes the filter layer 7 to the bottom of the filtration tank 2 and consolidates it on the upper side of the screen 5. At this time, the jacket 9 is full of water, so the consolidated water is not discharged from the through hole 8 to the outside of the filtration tank 2. When the consolidated water is discharged and falls to an appropriate water level, the valve V1 is closed to close the drain port 4a. The water level at this time is the upper part of the filter layer 7, and is a height at which air does not mix with the filter layer 7. The method for determining whether the water level has been reached is not particularly limited, and may include using a water level gauge, setting a drain time or a pressure reference value in advance, etc. In the first consolidation step, the flow rate of the consolidated water flowing toward the bottom of the filtration tank 2 is high in the initial stage of discharge, and the filter layer 7 is successively consolidated from the lower part by dynamic pressure. From the middle to the final stage of drainage, the already consolidated lower part of the filter layer 7 becomes a resistance to the flow of the consolidated water, and the dynamic pressure drops. Therefore, the lower layer of the filter layer 7 is sufficiently consolidated, but the degree of consolidation is insufficient from the middle to upper layers. In order to consolidate the upper part of the filter layer 7, a second consolidation process (Figs. 2 and 4) is carried out.

<Second consolidation step>
The method of storing the compressed water in the second consolidation step is the same as that used in the first consolidation step shown in Fig. 2. The stored water level at this time is appropriately adjusted depending on the conditions of the first consolidation step, the through hole height, etc.

Figure 4 is a schematic diagram of the second consolidation process according to the present invention during drainage, in which valve V2 is opened to open drain port 4b, and the consolidated water is drained from jacket 9 through through hole 8. The water pressure of the drained consolidated water consolidates the filter layer 7 above through hole 8. When drainage is completed, valve V2 is closed to close drain port 4b. The level of the consolidated water at this time is controlled to a predetermined water level at which the entire filter layer 7 is submerged, as in the first consolidation process. In the second consolidation process, the consolidated water is drained from near the middle layer of the filter layer 7, so that mainly the upper part of the filter layer 7 can be consolidated. Since the water is drained from through hole 8 through jacket 9, the volume of jacket 9 and the diameter of drain port 4b are adjusted so that back pressure is not generated at through hole 8 from the water stored in jacket 9.

By carrying out the first and second compaction steps, the filter layer 7 is formed so that the lower part of the filter layer 7 is most compacted and the degree of compaction decreases toward the top, and the degree of compaction of the entire filter layer 7 also increases, making it suitable for deep filtration.

The first and second compaction steps may be repeated multiple times. By repeating the compaction steps, the compaction degree of the entire filter layer 7 increases and the filtration accuracy improves, so the number of compaction steps is appropriately adjusted depending on the filter medium and the liquid to be treated.

In addition, in the consolidation step just before the filtration process, the first consolidation step and the second consolidation step may be performed simultaneously. Specifically, after storing the consolidated water as shown in FIG. 2, the drain outlet 4 and the drain pipe 10 are opened simultaneously as shown in FIG. 5 to drain the water.

After the consolidation process is completed, the filtration process is started by supplying the treated liquid from the supply port 3 as shown in FIG. 6. At this time, valve V1 is opened to open the drain port 4a while valve V2 is closed, so that the treated liquid is discharged only from the drain port 4a. In addition, since the drain port 4b is closed to keep the jacket 9 filled with consolidated water, there is no risk of the treated liquid flowing out from the through hole 8.

After the filtration process is completed, the supply of the treated liquid from the supply port 3 is stopped, and cleaning water is supplied from the drain port 4a into the filtration tank 2 to clean the filter media. When the filter media cleaning is completed and the consolidation process is performed again, the cleaning water stored in the filtration tank 2 during the filter media cleaning can be used as the consolidation water as is, and the state shown in Figure 2 during the above consolidation process can be transitioned to.

In the present invention, the consolidation water used as the adjusting water for consolidating the filter layer 7 may be prepared anew, but is not particularly limited thereto, and may be the above-mentioned washing water or the treatment liquid recovered during the filtration treatment.

The present invention allows the degree of compaction of the filter layer to be optimized according to the properties of the liquid being treated and the treatment conditions, so the entire filter layer can be effectively used for special applications that require high clarity, such as coagulation filtration, which is prone to surface filtration, or turbid water, or pools.

Reference Signs List 1 Filtration device 2 Filtration tank 4a Drainage port 4b Drainage port 6 Filter material 7 Filter material layer 8 Through hole 9 Jacket

Claims (6)

A filtration method in which a sedimentary granular fiber filter medium (6) is consolidated in a first stage of a filtration process,
After carrying out a first consolidation step in which the consolidated water stored in the filtration tank (2) up to a predetermined water level is drained from the drain outlet (4a) at the bottom of the filtration tank (2) to consolidate the lower part of the filter medium layer (7),
A second consolidation step is carried out in which the consolidation water stored in the filtration tank (2) up to a predetermined water level is drained through the through holes (8) provided around the filtration tank (2) to consolidate the upper part of the filter layer (7),
A filtration method, comprising starting a filtration process. The filtration method according to claim 1 , wherein the first and second consolidation steps are repeated a number of times. A filter layer (7) formed by compressing a sedimentary granular fiber filter medium (6),
In a filtration device that performs filtration by passing a liquid to be treated from above to below,
a filtration tank (2) having a through hole (8) on its peripheral surface communicating with the filter layer (7) and having a drain outlet (4a) at its bottom;
A jacket (9) provided around the outer periphery of the filtration tank (2) and having a drain outlet (4b) at its lower portion;
A filtration device comprising: The through hole (8) is
4. The filtering device according to claim 3 , characterized in that it is provided at an intermediate height of the filter medium layer (7) after compaction. The through hole (8) is
4. The filtering device according to claim 3 , characterized in that the filter layer (7) after compaction is provided at a height of 30% to 80% from the lower end. The filtration tank (2) is
6. The filtration device according to claim 3, wherein the lower portion is tapered.

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