JPH06269610A - Filtration by use of floating filter medium - Google Patents

Abstract

PURPOSE:To arrange a filtration layer which does not allow a filter medium to have a vertical particle distribution and thereby increase filtration efficiency by providing a wire netting vertically in a filter, and filling an inter-wire netting space with a floating filter medium of porous substance. CONSTITUTION:Wire nettings 4, 5 are provided at the inner top and bottom of a filter 3, and a space between two wire nettings is filled with a floating filter medium 8 of foamed polymer porous substance of spherical, small fragmentary or granular shape. Then air is supplied through the lower wire netting 4 in a state that the floating filter medium is soaked in a cleaning water. If the air is allowed to pass through, the filter medium 8 becomes mixed and stirred uniformly, and the cleaning water is discharged from the bottom of the filter. The obtained layer of floating filter medium forms a filtration layer which is free from a vertical grain size distribution and uniform qualitatively. The wire nettings 4, 5 are fixed in a state that floating filter medium particles 8 are evenly stirred in the filter 3, and thereby, the filter medium 8 is prevented from being flown away. This uniform filtration method using the filtration layer increases filter processing capability and the coefficient of uniformity of the filter medium without needing to use the combination of filter media.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a filtration method using a floating filter medium.

[0002]

2. Description of the Related Art As a technique for removing fine and hardly filterable solids suspended in water for the purpose of treating water and wastewater, floating filter media made of porous substances such as spherical, small, and granular particles is used. There is a filtration method to use. This filtration method is called a floating filter medium filtration method, and since solids are dispersed and captured on the surface of the filter medium forming the filtration layer in the depth direction, pressure loss is unlikely to increase and the amount of captured solids per cycle is large. .

The method for filtering a floating filter medium is usually applied to those having a turbidity of 100 or less and a turbidity of 50 or less, which does not require many backwashing operations.

However, in the conventional method of operating the floating filter medium filtering method, after the backwashing process of the floating filter medium is completed, the floating filter medium floats in the backwashing water at the time of switching the valve until the water to be treated flows, and the filter layer is removed. It is formed. Since the upper part of the filter layer thus formed is composed of large particles having a high floating speed and the lower part is composed of small particles having a slow floating speed, a fine floating filter material is accumulated on the surface of the filter layer in contact with the water to be treated. At the time of filtration, there is a problem in that the solid content to be filtered and removed is trapped and accumulated only in the lower part of the filter layer where the fine floating filter medium is accumulated, and thus the advantage of the floating filter medium filtration that suppresses an increase in pressure loss cannot be utilized.

A means for solving the above problems is disclosed in Japanese Patent Laid-Open No. 4-30 / 1992.
It is disclosed in Japanese Patent No. 0605. According to this method
Two types of floating filter media having different floating speeds, for example, expanded polystyrene having a high floating speed and expanded polypropylene having a low floating speed are used in combination, and the shape of the expanded polystyrene is set small and the shape of the expanded polypropylene is set large. In this way, it is possible to distribute the floating filter medium having a fast floating speed and a small shape in the upper part of the filter layer and the floating filter material having a low floating speed and a large shape in the lower part of the filter layer. Proposed.

[0006]

[Problems to be Solved] However, JP-A-4-3
The method disclosed in Japanese Patent No. 0605 has the following problems to be improved. That is, (1) it is inconvenient to select a combination of two types of floating filter media having different floating speeds, (2) a floating filter medium having a high floating speed and a small shape is provided on the upper part of the filter layer, and The problem is that even if the floating filter medium is distributed in the lower part so as to be composed of a floating filter medium having a slow floating speed and a large shape, the distribution still has a local bias.

In order to efficiently carry out the method of filtering a floating filter medium, it is necessary to create a filter layer in which the filter medium has no particle size distribution in the vertical direction and is uniformly dispersed.

Therefore, an object of the present invention is to provide a method for filtering a floating filter medium which produces a filter layer in which the filter medium does not have a particle size distribution in the vertical direction and is uniformly dispersed, and suppresses the pressure loss, thereby increasing the throughput per cycle. To do.

[0009]

Means for Solving the Problems In the present invention for achieving the above object, wire meshes are provided above and below in a filter, and a floating filter material made of a porous material is filled between the wire meshes, and the floating filter material is used as a washing water. Air is supplied through the lower wire mesh in the immersed state,
After the floating filter medium is dispersed and mixed, the washing water is discharged from the lower part of the filter to form a filter layer consisting of the floating filter medium on the lower wire net, and the water to be treated is circulated through the lower wire net and filtered. A method for filtering a floating filter medium, characterized by floating the layer under an upper wire mesh without disturbing the layer and filtering the water to be treated.

The present invention also includes that the floating filter medium is a particulate polymer porous material.

The present invention will be described in detail below.

The present invention can be applied to water to be treated having a turbidity of 1 or more measured by an absorbance measurement method using a formazine standard solution of JIS K-0101, but the effect can be easily visually confirmed to have a turbidity of 10 or more. It is preferably applied to water to be treated.

In the present invention, the fine and hardly filterable solids suspended in water mean algae such as algae, and plankton which causes red tide.

The floating filter medium referred to in the present invention is made of a porous material, among which expanded polystyrene, expanded polypropylene,
A porous substance of a foaming polymer having a specific gravity smaller than that of water, such as foamed polyethylene, is preferable. In the present invention, the floating filter medium can be efficiently filtered by one type of the floating filter medium.

The shape of the floating filter medium is preferably a particle shape such as a spherical shape, a small piece shape, or a granular shape. The size of the particles is such that the size of the particles is 0.25 mm (60 mesh) or more and 4.0 mm (5 mesh) or less when separated by a sieve, and the 10% diameter is 1.1 mm or more and the 60% diameter is 2.6 mm. The following are good: Here, the 10% diameter and the 60% diameter mean a sieving test, and the results are plotted on a rosin-Rammler particle size diagram to refer to the particle diameters of 10% and 60% under the sieve, respectively.
If the particle size is less than 0.26 mm, the pressure loss in the filtration layer tends to increase, although it depends on the number of meshes in the upper wire net, and if the particle size exceeds 4.0 mm, the filtration efficiency tends to deteriorate slightly. You should avoid it to show. Also, 60%
The ratio of the diameter to the 10% diameter is called the uniformity coefficient, which is 3 or less, preferably 2.5 or less.

The filtration layer of the present invention is formed by providing a wire mesh on the upper and lower parts inside a cylindrical or prismatic filter, and filling a floating filter material between the two wire meshes.
In this case, the wire mesh provided in the lower part serves to fix the suspended filter material particles in the filter and at the same time to make the supplied air uniform. On the other hand, the wire mesh provided on the upper part serves to prevent the floating filter medium particles from flowing out and to release the supplied air without resistance. Further, a perforated plate may be further provided on the upper wire net.

The shape of the wire net for achieving the above object is preferably 32 mesh or more and 200 mesh or less, though it depends on the capacity of the filter and the material and shape of the floating filter material. If it is less than 32 mesh, some of the suspended filter media particles tend to be easily washed away, and if it exceeds 200 mesh, air dispersion tends to be inconvenient.
The wire nets provided on the upper part and the lower part do not necessarily have to have the same mesh, and can be appropriately selected and used. The wire mesh does not have to be made of metal, and various materials such as polymer, stainless steel and carbon steel can be used.

The air used for stirring and mixing the floating filter medium is preferably a superficial velocity of 1 m / min to 5 m / min, although it depends on the diameter of the filter and the material of the filter, and the floating filter medium is completely immersed in the washing water. Is supplied from below the filtration layer. When the superficial velocity is less than 1 m / min, the floating filter medium cannot be well stirred and mixed, and the superficial velocity is 5 m / mi.
If it exceeds n, there is a risk of crushing the floating filter medium.

In this way, stirring and mixing of the floating filter medium
After the washing water is completely discharged from the lower side of the filter layer while being kept for 5 minutes or more, preferably 5 minutes or more, it is suspended as a uniform filter layer on the lower wire mesh without vertical particle distribution when the air supply is stopped. A layer of filter media is formed. If the stirring and mixing of the floating filter medium is less than 1 minute, a uniform filter layer may not be locally formed depending on the conditions, and therefore it should be avoided.

When the water to be treated is supplied from the lower part of the filter layer to a uniform filter layer having no particle distribution in the vertical direction, accumulation of suspended substances in the water to be treated is not concentrated only on the lower part of the filter layer and The amount of suspended solids collected in the water to be treated per cycle is increased.

The features of the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a conceptual diagram showing one embodiment of a filtration device for carrying out the method of the present invention.

Sewage having a turbidity of 50 degrees or less, in which solids such as Aoko are suspended, is sent from the wastewater supply device 1 to the filter 3 via the valve 2a. The filter 3 is filled with a floating filter medium 8 made of a foamed polymer porous material having a spherical shape, a small piece shape, a granular shape or the like, and a wire mesh 4 for air dispersion and for preventing the floating filter material from flowing out.
5 are arranged one above the other. When the dirty water passes through the layer of the floating filter medium 8, the solid content of the dirty water adheres to the floating filter medium 8, and the filtered clean water is sent to the treated water tank 7.

When a considerable amount of solids adhere to the floating filter medium 8, the pressure loss of the filter layer increases and the value indicated by the manometer 12 increases. This value varies depending on the size of the filter 3, but is 0.
When a predetermined value within the range of 1 bar to 0.3 bar is reached, the valve 2a is closed, filtration is stopped, and backwashing is performed. That is, the filter 3 is drained through the valve 2d, the valve 2b is opened, and the filter 3 is filled with the wash water from the wash water supply device. The washing water is appropriately selected from water, warm water, solutions containing various compounds, and the like. After filling with water, the valve 2c is opened, and the superficial velocity is 1 m from the air supply device 9.
The air is supplied at a flow rate of / min to 5 m / min to stir the filter layer made of the floating filter medium 8 so that the solid matter attached to the floating filter medium 8 is released into water and discharged from the valve 2d. This backwashing operation is repeated one or more times, and it is confirmed that no solid matter is attached to the floating filter medium, and then the filtration operation is restarted. After the backwashing is completed, the backwash water in the filter 3 is completely discharged through the valve 2d while the floating filter medium 8 is being stirred in the backwash water before the dirty water is supplied again. At this time, the floating filter medium 8 forms a layer in the upper part of the wire net 4 in a vertically dispersed state without particle distribution.

After that, the valve 2a is opened, and the sewage is sent from the sewage supply device 1 to the filter 3. When the sewage flow rate is normal, there is no particle distribution in the vertical direction, and the floating filter medium remains in a uniformly dispersed state. The layer floats without disturbing the distribution state. Therefore, it is possible to filter the sewage without depositing suspended matter in the sewage only in the lower part of the filter layer.

[0026]

[Function] The layer of the floating filter medium obtained by uniformly mixing and stirring the floating filter medium with the air passing through the wire net in the wash water and draining the wash water in that state has a uniform dispersion without particle size distribution in the vertical direction. It becomes a state.

[0027]

EXAMPLES The features of the present invention will be described below with reference to examples, but the present invention is not limited thereto. Example 1 A filter, which was a cylindrical transparent acrylic container having an inner diameter of 10 cm and a height of 2 m, was fitted with a wire mesh of 32 mesh at a distance of 30 cm from the upper and lower ends, respectively, and a floating filter material made of expanded polypropylene was layered between them. Filled to 1 m.
A filtration test was carried out by the above-mentioned method using sewage suspended at a height of 25 degrees in turbidity measured by absorbance measurement using a formazine standard solution of JIS K-0101. The flow rate of sewage was 80 l / hr.

The shape of the floating filter medium is 1.1 mm with a 10% diameter,
2.6% in 60% diameter, uniformity coefficient 2.4, average density of 0.
85 / cc, and the upper and lower wire meshes are 3 each
A 2-mesh stainless steel material was used.

Before treating the sewage, the floating filter medium was filled with tap water as washing water, and air was supplied from the lower side of the filter bed at a superficial velocity of 1 m / min for 5 minutes to stir and mix the floating filter medium. In this state, the wash water was completely discharged from the drain valve below the filter layer. After confirming that the filtration layer was formed in a state of being uniformly dispersed without a particle size distribution in the vertical direction,
Treatment of sewage started. At the following sewage treatment rates, the uniformly formed filtration layer floated without being disturbed.

As a condition for continuing the sewage treatment, the turbidity of the treated water after passing through the filtration layer was 1 degree or less and the manometer indicated value was less than 0.3 bar.

The results are shown below.

[0032]

[Table 1] Example 2 It carried out on the same conditions as Example 1 except having changed the superficial velocity to 5 m / min. The results are shown below.

[0033]

[Table 2] Example 3 The same conditions as in Example 1 were carried out except that the lower wire mesh was changed to 200 mesh. The results are shown below.

[0034]

[Table 3] Example 4 The same conditions as in Example 2 were carried out except that the lower wire mesh was changed to 200 mesh. The results are shown below.

[0035]

[Table 4] Comparative Example 1 After completion of backwashing, in a state where the floating filter medium was filled with washing water,
Closed the air supply valve 2c, to stop the air supply,
The valve 2a of the raw material supply device was opened and the treatment of sewage was started. The procedure is the same as in Example 1 except for the operation method of backwashing. The results are shown below.

[0036]

[Table 5] Comparative Example 2 It was carried out under the same conditions as in Comparative Example 1 except that the lower wire mesh was changed to 200 mesh. The results are shown below.

[0037]

[Table 6] Reference Example 1 The method disclosed in JP-A-4-300605 was carried out as follows.

In the same filter as in Example 1, 190 gr and 980 gr of floating filter medium A and floating filter medium B shown below were respectively prepared.
A total of 1170 gr was charged.

[0039]

[Table 7] The same procedure as in Comparative Example 1 was carried out except that the floating filter material for forming the filter layer was different. The upper part of this filter layer is made of the suspended filter medium A having a small particle size, and the lower part is formed of the suspended filter medium B having a large particle size. The results are shown below.

[0040]

[Table 8] Reference Example 2 It was carried out under the same conditions as in Reference Example 1 except that the lower wire mesh was changed to 200 mesh. The results are shown below.

[0041]

[Table 9]

[0042]

As described above, the floating filter medium is uniformly agitated and mixed in the wash water by blowing air uniformly through the wire net, and then the wash water is discharged from the lower part of the filter to obtain the vertical particle size. The following effects are obtained because a filter layer is formed by a floating filter medium having no distribution. (1) Since it is possible to form an efficient filtration layer with one type of floating filter medium, it is not necessary to combine and use the floating filter medium as in the prior art. (2) Since a uniform filtration layer is formed in the vertical direction, the filtration resistance can be reduced and the filtration treatment capacity per cycle can be increased. (3) Since the uniform filtration layer is formed in the vertical direction, the uniform coefficient of the floating filter medium can be increased.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing one embodiment of a filtration device for carrying out the method of filtering a floating filter medium of the present invention.

[Explanation of symbols]

 1 Sewage Supply Device 2a, 2b, 2c, 2d Valve 3 Filter 4,5 Wire Mesh 6 Perforated Plate 7 Treated Water Tank 8 Floating Filter Material 9 Air Supply Device 10 Air Dispersion Plate 11 Wash Water Supply Device 12 Manometer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location B01D 23/10 C

Claims (2)

[Claims] 1. A wire mesh is provided above and below in a filter, a floating filter material made of a porous material is filled between the wire meshes, and air is passed through the lower wire mesh while the floating filter material is immersed in washing water. After supplying and dispersing and mixing the floating filter medium, the washing water is discharged from the lower part of the filter to form a filter layer composed of the floating filter medium on the lower wire mesh, and then the water to be treated is circulated through the lower wire mesh. The floating filter medium filtration method is characterized in that the water to be treated is filtered without disturbing the filtration layer and floated under the upper wire net. 2. The filtration method according to claim 1, wherein the floating filter medium is a particulate polymer porous material.