JPH06277407A - Device filtering suspension liquid - Google Patents

Abstract

PURPOSE:To develop a filtration device which is capable of removing SS very efficiently and at the same time, meeting a contradictory requirement for a less incident of clogging as well as allows an easy cleaning of the filtration bed. CONSTITUTION:The filtration device has a gas introduction means placed at the of a filtration bed installed in a bath, the intermediate stage of which contains a porous member arrange to partition the filtration bed in two steps, upper and lower. In addition, the lower step filtration bed is formed with a packed layer (a) filled with a floatable hollow cylindrical filter medium A and the upper step filtration bed is formed with a packed layer (b) filled with a floatable filter medium B with a smaller grain diameter than the grain diameter of the hollow cylindrical filter medium A. Further, this device is equipped with a drain means at the bottom of the bath as one for suspension liquid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filtration device for effectively removing organic SS from various suspensions, particularly organic suspensions such as sewage.

[0002]

2. Description of the Related Art Conventionally, as a technique for filtering SS from a suspension, a deep bed filtration method using a granular mineral such as sand and anthracite as a filter medium (Deep Bed Filtration)
However, when attempting to remove organic SS such as sewage by this filtration method, clogging was severe and impractical. For example, a filtration method using various particulate solids other than the above-mentioned granular minerals such as plastic particles as a filter medium has been studied. However, if the filter medium particle size is increased to reduce clogging, S
There was a contradiction that the removal rate of S deteriorated. In particular, since organic SS contained in sewage or the like has a strong adhesive force, a technique which can satisfy the contradictory requirements of high SS removal rate and less clogging for such sewage and the like has not been put into practical use.

[0003]

DISCLOSURE OF THE INVENTION The present invention develops a filtration apparatus which has high efficiency of removing SS, can simultaneously satisfy the contradictory requirements of very little clogging, and can be easily washed with a filter bed. That is the issue. In particular, it is an object to provide a filtration device and a cleaning method thereof that are suitable for the filtration and removal of sticky SS.

[0004]

The above object can be achieved by the suspension filtration apparatus of the present invention shown below. That is, in an upflow filtration apparatus for a suspension, in which a filter bed is provided in the tank and a gas introducing means is provided in the lower part of the filter bed, a porous member is arranged in the middle stage of the tank to divide the filter bed into upper and lower two stages. Then, the lower filter bed is formed by a lower packed bed filled with a hollow cylindrical filter medium having a specific gravity close to that of water, and the upper filter bed has a smaller particle size than the hollow cylindrical filter medium and a specific gravity lighter than water. A suspension filtration device, characterized in that it is formed by an upper packed bed filled with a filter medium, and drainage means is provided at the bottom of the tank.

The point of the concept of the present invention is that, in an upflow filter having a filter bed filled with a filter medium, a porous member is attached to the cross section of the filter bed of the filter unit and fractionated into two stages, upper and lower. The lower layer of the filter bed, that is, the lower packed bed is filled with a filter material composed of a hollow cylindrical granular material having a specific gravity close to that of water, and the upper layer, that is, the upper packed bed is more than the hollow cylindrical filter material of the lower packed bed. A buoyant granular filter medium B having a small particle size is filled, and a porous member is provided between the lower packed bed and the upper packed bed so as not to mix the packed filter materials of both layers, and the raw water is directed to the filter bed in an upward flow. It is to supply and perform two-stage filtration. Only by using such a packed bed and filter medium composition, it is possible to simultaneously satisfy the contradictory requirements that the removal efficiency of SS is high and the clogging is very small even for raw water containing a large amount of sticky SS. You can do it. In addition, below, the lower filling layer is called the filling layer a, and the upper filling layer is called the filling layer b. In addition, a filter medium composed of hollow cylindrical particles to be filled in the packed bed a is sometimes referred to as a filter medium A, and a buoyant granular filter medium having a small particle size to be packed in the packed layer b is sometimes referred to as a filter medium B.

Here, the "adhesion of the porous member" means that a porous member such as a grating or a net is stretched over the entire cross section of the filter bed so that the filler media of both layers are not mixed. Another important point of the concept of the present invention is that the filter bed is formed by filling the filter beds divided into upper and lower two stages with filter media, respectively.
The purpose is to effectively clean the packed bed of the bed by using the air from the cleaning air diffuser together with the disturbance and draining of the filter medium. In this way, the filter medium can be washed only by empty washing without backwashing with washing water because the packed bed a
The filter medium filled with both the filling layer b and the filling layer b has a characteristic that it can be disturbed and washed by the washing air.

The upflow filtration apparatus of the present invention is shown in FIG.
A configuration example of the present invention will be described below with reference to FIG.
After that, the operation will be described, but the following configuration example and description of the operation do not limit the present invention. In FIG. 1, the filter bed of the upflow filtration apparatus 1 is divided into two packed beds, and the lower stage of the filter bed is the packed bed a and the upper stage is the packed bed b.
And The filling layer a is filled with a ring-shaped hollow cylindrical filter medium A, and in order to prevent the filter medium A from falling, a porous support member 3 is provided at the bottom of the filling layer a. Also, the packed bed b
The filter material A is filled with buoyant granular filter material B having a smaller particle size than the filter material A. Between the packed bed a and the packed bed b, the packed bed b
A porous member 4 having a diameter that does not allow the filter medium A to pass therethrough is provided in order to prevent the filter medium A of the packed layer a from entering the filter medium and to support the upper part of the filter medium of the filled layer a.

In FIG. 1, the filter medium is not completely filled in the packed bed a of the filter bed which is divided by the porous support member 3 and the porous support member 4, and the spare space C is provided. Since the filter medium A has a specific gravity close to that of water, it has an upward flow and / or
Alternatively, it is shown as a state of being floated up to the position of the porous member 4 by buoyancy. Of course, the present invention also includes a state where there is no extra space C. The upper surface of the filter medium layer filled in the filling layer b is in contact with the porous member 2. Here, the cylindrical granular filter medium A to be filled in the packed bed a is the hollow cylindrical filter medium A in FIG. 1, but the shape may be a hollow prismatic shape. In addition, it is preferable to open an opening through which water can pass on both sides of the cylindrical granular body, because SS in the sewage settles inside the cylinder and is easily removed. (Fig. 2)

The thickness of the packed bed a is preferably about 1 to 3 m, and the particle size of the filter medium A is 10 to 30 mm in diameter and 10 to 30 m in length.
It is preferable to use a filter material having a large particle size of m because the SS trapping amount can be increased. Further, the specific gravity for facilitating washing is preferably close to 1.0 and floatable in water, and known ones such as polypropylene can be used. The layer thickness of the filling layer b is 1 to
About 1.5 m is sufficient, and the layer thickness of the filling layer a ≧ the filling layer b
And the layer thickness. It is preferable that the particle size of the buoyant granular filter media B packed in the packing layer b is as small as 0.5 to 1 mm, and the specific gravity is less than 1.0 and floats in water. Is. For example, a known material such as styrofoam can be used as the material.

The raw water to be treated is supplied from a raw water supply pipe 5 equipped with a supply valve 6 at the bottom of the filtration device 1, and the raw water passes through the packed bed a and the packed bed b in the device 1 in that order as an upward flow. Then, the SS contained in the raw water is filtered, overflows from the filter bed, flows out to the treated water outflow portion 7, and is discharged out of the system as treated water through an outflow pipe 8 equipped with an outflow valve. Below the water surface of the treated water outflow portion 7, there is provided a porous member 2 (composed of a net or the like) having a pore diameter capable of preventing the outflow of the filter medium of the packed bed b. Below the packed bed, an air diffuser 10 provided with a compressor 9 for cleaning the filter medium in the packed bed with air is provided. The air diffuser 10 may be separately provided not only under the filling layer a but also under the filling layer b.

[0011]

The operation principle of the present invention will be described below. Raw water such as sewage flows from the raw water supply pipe 5 into the lower portion of the filtration device 1 of the present invention in an upward flow, and first, after sedimentation of coarse particles and the like with good sedimentability in the sedimentation portion at the bottom of the filtration device 1, Next in FIG.
An upward flow is introduced into the packed bed a filled with the polypropylene Raschig ring-shaped hollow cylindrical filter medium 13 shown in FIG. Since the hollow cylindrical filter medium 13 forming the packed bed a has voids inside the granular body and the side surfaces are open, the porosity of the packed bed a can be kept extremely high at 95% or more. Therefore, even if the filter medium A of the filling layer a captures a large amount of SS, the porosity can be maintained as it is, and therefore the increase in filtration resistance is extremely small. Then, while the raw water passes through the packed bed a filled with the hollow cylindrical filter medium 13, the
About 95% of SS having a particle diameter of m or more is removed, but fine SS having a particle diameter of less than m is not removed but flows out from the packing layer a. Layer b
Remove by filtration.

The specific gravity of the filter medium constituting the filling layer b is 1.0.
It is important to use particles that are smaller and float on water, such as expanded polystyrene and expanded polypropylene, and have a smaller particle size than the filter medium A. The fine SS that have passed through the packed bed a are fine particles having a particle size of 10 μm or less, but are effectively trapped in the packed bed b of the filter medium having a small particle size. This is because the pore size of the voids in the filling layer b is extremely small, and SS having a small particle size can be effectively removed. Moreover, since the SS having a large particle size is filtered and removed in the packed bed a in the preceding stage, the SS which has passed through the packed bed a has a small particle size,
The SS does not block the packed bed b filled with the filter medium B having a small particle diameter, and therefore the increase in filtration resistance of the packed bed b can be significantly reduced. If the packed bed a does not exist, the packed bed b is immediately closed. With the above-described actions, the treated water from which SS in the raw water is highly removed flows out from the treated water outflow section 7. The increase in the filtration resistance of the filtration device according to the present invention is extremely small, and the limit of filtration can be known by the increase of SS in the treated water before the raw water cannot be passed due to the increase in the filtration resistance.

When such a state is reached, the filling layers a and b are washed by the following method. This cleaning method is also unique to the present invention. That is, the supply valve 6 is closed, the supply of raw water from the raw water supply pipe 5 is stopped, the valve 12 of the sludge discharge pipe 11 is opened, the liquid in the filtration device 1 is drained, and the water surface is lowered below the perforated plate 2. . The valve 12 of the sludge discharge pipe 11 is closed, and air bubbles are vigorously discharged from the air diffuser 10. After a few minutes, the valve 12 is opened again, and the air in the diffuser pipe 10 is violently discharged, while the filter medium A and the filter medium B are violently disturbed, and the entire amount of water in the tank is discharged from the discharge pipe 11 at the bottom of the tank. By the above operation, almost all of the SS trapped in the filter layers a and b is discharged from the discharge pipe 11.

As described above, the filtration apparatus of the present invention can be washed by disturbing washing with air and does not require backwashing that consumes a large amount of clarified water, which is extremely rational. The reason why such rational cleaning is possible is that since the filter medium A is a cylindrical filter medium having a large particle size, it has been captured by the filter medium A just by being disturbed by air and draining water. SS
Because they are easily discharged together. Further, since the filter medium B uses particles that float in water, the particles of the filter medium B also move violently when accompanied by agitation of the air when agitated in the air, and the SS trapped in the filter medium B is discharged together with the drain water. This is because it is discharged outside the system.

[0015]

Example The sewage containing a high SS having an average SS content of 200 mg / liter was used as raw water and passed through a filter having the following specifications in an upward flow to verify the effect of the present invention. Table 1 for equipment specifications
Shown in. Table 1 (Treatment conditions) Filtration device: Height of packed bed a: 2.5 m Height of packed bed b: 1.5 m Porous partition member: Opening width 20 mm Screen filter material A: Diameter 20 mmφ, length 30 m
m Cylinder Polypropylene filter medium B: Particle size 1 mm Styrofoam filter medium A is filled to a height of 2 m in the filter bed of packed bed a. Filter medium B is filled to a height of 1 m in the filter bed of packed bed b.

Table 2 shows processing conditions and processing results. Table 2 (Treatment conditions) Filtration speed: 300 m / day Raw water SS content: 200 mg / liter (Treatment result) Treated water SS content: 5.5 mg / liter SS removal rate: 97.2% Filtration duration ^** : 40 ˜43 hours ** Here, the filtration continuation time means the time until the amount of SS contained in the treated water reaches 10 mg / liter.

The average SS trapping capacity of the packed bed a and the packed bed b was about 15 kg SS / (m ³ filter medium). Comparing this with the case of conventional filtration using anthracite (particle size 3 mm), the average SS trapping capacity is 2 kgSS / (m
³ filter media), and when these results are compared, the prominence of the filtration device of the present invention is clear.

[0018]

【The invention's effect】

1) The filtration device has a significantly small increase in filtration resistance due to clogging of the filtration layer and an extremely high SS removal effect. 2) The packed bed can be effectively washed, and since it is not necessary to specify the treated water as the washing water, the treated water production efficiency is high. 3) The filtration duration is long and the filtration rate is high. Therefore, only a compact device is required and maintenance is easy.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating an example of a dredging spillway filtration method using the filtration tank of the present invention.

FIG. 2 shows a schematic view of a hollow cylindrical filter medium used in the present invention.

[Explanation of symbols]

 1 Filtration Device 2 Porous Member 3 Porous Support Member 4 Porous Support Member 5 Raw Water Supply Pipe 6 Supply Valve 7 Treated Water Outflow Port 8 Outflow Pipe 9 Compressor 10 Diffuser Pipe 11 Sludge Discharge Pipe 12 Valve 13 Hollow Cylindrical Media a Lower Stage Packed bed b Upper packed bed A Filter media B Filter media

Claims (1)

[Claims] 1. An upflow filtration apparatus for a suspension, wherein a filter bed is provided in the tank, and a gas introducing means is provided at the lower part of the filter bed. The bed is divided, the lower filter bed is formed by a lower packed bed filled with a hollow cylindrical filter medium having a specific gravity close to that of water, and the upper filter bed has a particle size smaller than that of the hollow cylindrical filter medium and has a specific gravity of A suspension filtration device, characterized in that it is formed by an upper packing layer filled with a filter material lighter than water, and drainage means is provided at the bottom of the tank.