JP2004290773A - Filtration apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filtration apparatus which can be backwashed uniformly by easily loosening the close contact state of a packed layer. <P>SOLUTION: This filtration apparatus is constituted so that the packed layer 3 of the floating filter medium is formed in a filtration tank 2. The floating filter medium consists of an independently-expandable macromolecular porous body such as expanded polyethylene and expanded polystyrene having 0.1-0.4 specific gravity (apparent specific gravity). The inside diameter 24 of the lower part of the tank 2 is made wider than the inside diameter 23 of the layer 3-formed part of the tank 2 preferably by 10-25%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a filtration device for forming a floating filter medium packed layer in a filtration tank and filtering water to be treated in an upward flow, and more particularly to a filtration device capable of effectively cleaning a floating filter material.
[0002]
[Prior art]
To filter sewage, rainwater, return water, industrial effluent, leachate, agricultural water, clean water, river water, etc., use a packed bed 11 made of a floating filter medium in a filtration tank 1 as shown in FIG. Is conventionally known. As the floating filter medium, in general, various shapes of resin masses having a specific gravity (apparent specific gravity) of 0.9 or more are used from the viewpoint of strength and durability.
[0003]
In such a filtration device, when the raw water a passes through the countless floating filter media of the packed bed 11 as an upward flow, the solid content is separated, and the filtered water b is taken out. By the way, the packed filter 11 is formed in a close contact state by the screen 12 although the floating filter medium is directed upward by the buoyancy and the upward flow of the water to be treated, thereby increasing the filtration efficiency.
[0004]
Then, when the filtration process proceeds and the packed bed 11 is clogged and the filtration efficiency is reduced, the filtration operation is temporarily stopped, and backwashing is performed in a downward flow (hereinafter, referred to as backwashing). In other words, the backwash water c is supplied to the packed bed 11 in a direction opposite to the filtration direction, and the packed bed 11 is rocked to eliminate the close contact state, and at the same time, the floating filter medium which has become a discrete individual solid state is washed. Then, the clogging component is separated and removed. (See Patent Document 1)
[0005]
[Patent Document 1]
JP-A-7-75793: Claims, FIG.
[0006]
However, since the packed bed 11 is formed in an integrated and close state, and is entirely constrained by the side wall 13 of the filtration tank 1, even when the backwash water c is supplied, the solid state of the original form falls apart. There was a problem that it was difficult to become. In particular, the outer peripheral portion and the outer peripheral corner of the filling layer 11 in contact with the side wall 13 of the filling layer 11 tended to be difficult to eliminate the close contact state.
[0007]
[Problems to be solved by the invention]
The present invention has been made in order to solve the above-mentioned problems, and provides a filtration device capable of easily eliminating the close contact state of the packed bed at the time of back washing and uniformly performing the back washing.
[0008]
[Means for Solving the Problems]
The above problem is a filtration device that forms a floating filter medium packed layer in a filtration tank and performs a filtering process in an upward flow, compared with the inner diameter of the filtration tank at a portion where the floating filter medium packed layer is formed. The problem can be solved by the filtering device of the present invention, characterized in that the inner diameter of the filtration tank below is widened.
In this case, it is preferable that the inner diameter of the filtration tank below the filtration tank inner diameter at the portion where the floating filter medium-filled layer is formed is widened by 10 to 25%.
[0009]
Further, the present invention is embodied as a filtration device in which the floating filter medium is a closed-cell polymer porous body such as expanded polyethylene or expanded polystyrene having a specific gravity of 0.1 to 0.4.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment according to the filtration device of the present invention will be described with reference to FIG. As shown in the figure, the filtration device of the present invention is a filtration device that forms a floating filter medium packed layer 3 in a filtration tank 2 and performs a filtration treatment in an upward flow, based on a conventionally known configuration. The feature is that the inner diameter 24 of the filter tank 2 below the filter tank 2 at the portion where the floating filter medium packed layer 3 is formed is preferably widened in the range of 10 to 25%. On the point.
[0011]
More specifically, during operation of the filtration device of the present invention, a packed layer 3 of a lightweight floating filter medium that floats on water is formed in the middle stage of the filtration tank 2. The depth of the filtration tank 2 is preferably 2 m or more, and the height of the packed layer 3 of the floating filter medium is preferably 0.5 m or more. In addition, the floating filter medium has a specific gravity (apparent specific gravity) of 0.1 to 0.4, and a filter made of a closed-cell polymer porous body such as foamed polyethylene or foamed polystyrene is not easily washed away during backwashing. preferable.
[0012]
The raw water a is supplied to the lower part of the filtration tank 2 via the raw water inflow path 21 as shown by an arrow, and impurities and SS are captured by the floating filter medium while passing through the packed bed 3 as an upward flow. A screen 22 for preventing the floating filter medium from flowing out during filtration is provided above the packed layer 3. The water to be treated that has passed through the packed bed 3 is discharged from above as filtered water b.
[0013]
Then, when the filtration operation proceeds and the packed bed 3 is clogged with the contaminants and the filtration efficiency is reduced, the packed bed 3 is backwashed to remove the contaminants. That is, the backwashing washing water c is introduced into the filter medium filling layer 3 at a downward flow rate from the upper portion, and is drained from the lower portion of the filtration tank 2 as washing drainage d, thereby moving and expanding the filling layer 3 downward, The contaminants such as SS and contaminants are separated from the floating filter medium in the sparse portion of the floating filter medium layer 3 thus generated, and the entire packed layer 3 is washed.
[0014]
In this case, in the present invention, the inner diameter 24 of the filtration tank 2 below the filtration tank 2 is preferably expanded by 10 to 25% as compared with the inner diameter 23 of the filtration tank at the portion where the floating filter medium packed layer 3 is formed. Therefore, the packed layer 3 moved downward by the backwash water c has an effect that the close contact state is easily eliminated since the inner wall of the tank is not restricted at the widened portion. In particular, since the close contact state of the outer peripheral portion where the close contact state is difficult to cancel is loosened first, uneven backwashing can be prevented, and the advantage of further improving the backwashing effect can be obtained.
[0015]
In this case, if the degree of widening is 10% or less, the above-mentioned k effect cannot be sufficiently obtained, and if it exceeds 25%, the facility becomes large and no further effect can be expected. This widening of the inner diameter may be such that the boundary portion is tapered as shown in the figure, and instead of providing such a step, the inner surface is formed from the portion where the filling layer 3 is formed to the portion thereunder. The whole may be tapered and widened downward.
[0016]
In this case, it is preferable to set the downward flow rate of the backwash water c to 1 m / min or more for the purpose of eliminating the close contact state of the packed bed. Since the filter medium is a floating filter medium of up to 0.4, it is possible to reliably prevent outflow due to backwashing washing water.
[0017]
Furthermore, if the specific gravity of the floating filter medium is less than 0.1, the downward movement and expansion of the packed bed 3 during backwashing become insufficient, and the strength is insufficient during filtration, and consolidation tends to occur. On the other hand, if it exceeds 0.4, the difference in specific gravity with water gradually decreases, and it is easy to be washed away by backwashing.
[0018]
【The invention's effect】
Since the filtering device of the present invention is configured as described above, the close contact state of the packed layer of the floating filter medium can be automatically eliminated at the time of back washing, and the back washing can be performed effectively and uniformly. Further, there is an excellent effect that the floating filter medium hardly flows out. Therefore, the present invention has an extremely large practical value as a filtration device which has solved the conventional problems.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a main part for describing a filtration device of the present invention.
FIG. 2 is a schematic cross-sectional view of a main part showing a conventional filtration device.
[Explanation of symbols]
2 Filtration tank, 21 raw water introduction path, 22 screen, 23 inner diameter, 24 inner diameter, 3 packed beds, a raw water, b filtered water, c backwashing washing water, d washing drainage.

Claims (3)

What is claimed is: 1. A filtration device for forming a floating filter medium packed layer in a filtration tank and performing a filtration process in an upward flow, wherein a filtration tank below the filter tank at an area where the floating filter medium packed layer is formed is provided. A filtration device characterized by having an increased inner diameter. The filtration device according to claim 1, wherein the inner diameter of the filter tank below the inner diameter of the filter tank at the portion where the floating filter medium packed layer is formed is widened by 10 to 25%. The filtration device according to claim 1 or 2, wherein the floating filter medium is a closed-cell foamed polymer porous body having a specific gravity of 0.1 to 0.4, such as foamed polyethylene or foamed polystyrene.

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