JPH10118681A - Contact filtration material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filling filtration material for cleaning contaminated water which has a low water filtration resistance and suppresses the outflow of sludge adhering thereto by forming the filling filtration material made of thermoplastic foamed resin particle for cleaning contaminated water as to have an irregular shape having curved face on the inner side and as to give specified values of the length of the longest part and the density. SOLUTION: Constminated water supplied to a cleaning tank can body 1 such as an anaerobic wastewater purification tank is purified by being passed through a filling filtration material 2 for cleaning contaminated water and aeration is carried out by air supplied through a pipe 5. The deposited substance in the bottom part of the can body 1 is removed out of a discharge valve 6 in the bottom part. In this case, as the filling filtration material 2 for leaning wastewater, a material made of thermoplastic foamed resin particle is used and the material is so formed as to have an irregular shape having a face curved inward having a length L of 10mm<L<100mm in the longest part and a density d of 0.01g/cm<3> <d<0.15g/cm<3> . As the thermoplastic resin, polystyrene type resin or polyolefin resin is used. C-shape, S-shape, J-shape, etc., are examples for the irregular shape having a curved face.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter material for purifying sewage used for purifying sewage such as domestic wastewater and faecal effluent, and more particularly, to a filter for contact filtration of microorganisms having excellent purification performance and water permeability. Related to filter media.

[0002]

2. Description of the Related Art Biological treatment is generally performed to purify sewage such as household wastewater and fecal wastewater. This utilizes the action of microorganisms cultured in sewage to purify sewage by assimilating or catabolizing organic substances and the like in the sewage. It has been known that foamed thermoplastic resin particles are used as a microbial carrier for contact in a sewage treatment tank.

[0003] Japanese Patent Application Laid-Open No. 6-277407 discloses an apparatus for filtering a suspension using a packed bed of a floating particulate filter medium such as styrene foam as a filter bed. In this filtering device, small particles having a particle size of the filter medium of 0.5 to 1 mm are used. JP-A-7-265887 discloses that the particle size is 0.5 to 1
A 0 mm styrofoam strip is disclosed as a microbial contact filter for an aerobic treatment tank.

However, in the prior art using thermoplastic resin expanded particles as a microbial carrier as described in the above-mentioned publication, small particles having a particle size of 10 mm or less are used. When sludge accumulates on the surface, the flow resistance tends to increase. Therefore, it has been necessary to frequently wash the filter medium such as backwashing. In addition, if the shape of the expanded particles is spherical or square, the particles may rotate or float due to the flow or aeration of the water-flowing liquid, and the sludge attached to the particles may peel off and the sludge may be mixed into the treated water.

Further, Japanese Patent Application Laid-Open No. 8-141588 discloses a filter medium in which hydrophilic powder is dispersed in polypropylene and crushed by a crusher to a diameter of 0.1 to 300 mm. However, the particles crushed by the crusher have a problem that fine crushed debris having a non-uniform shape is mixed therein, and the fine particles pass through a filter for preventing a filter medium from flowing out, and the filter medium particles float and flow into treated water.

[0006]

SUMMARY OF THE INVENTION The present invention solves such a problem, has a small water flow resistance, suppresses the outflow of sludge such as microorganisms attached to the filler, and has excellent purification performance. It is an object to provide a packed filter medium.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a filled filter medium for purifying sewage, comprising thermoplastic foamed resin particles, having an irregular shape having an inwardly curved surface, and having a longest portion having a length L of less than 10 mm.
L <100mm, density d is 0.01g
/ Cm ³ <d <0.15 g / cm ³ . Furthermore, the present invention is a filled filter medium in which microorganisms for purifying sewage are carried in thermoplastic foamed resin particles, wherein the thermoplastic resin is a polyolefin-based resin or a styrene-based resin, and is filled in an anaerobic sewage purification tank. It is related to filter media for sewage purification.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic explanatory view showing a usage form of a filled filter medium for sewage purification in the present invention. The sewage is supplied from the inflow pipe 3 to the bottom of the septic tank can 1, passed through the filter medium 2 for purifying sewage filled in the can, purified, and discharged from the treated water outlet pipe 4. When performing aeration as needed, air is supplied from the pipe 5 and exhausted from the exhaust port 6. The level difference between the sewage supply pipe and the treated water discharge pipe is the head difference 7 through which the sewage flows. Solid matter deposited on the bottom of the can is removed from the bottom discharge valve.

[0009] The expanded particles used as the underwater-filled filter medium receive buoyancy in water, and the buoyancy of the lower particles is integrated in the upper particles of the underwater-packed layer. The uppermost particles are compressed between the outflow prevention filter 8 and the floating particles from below. If the expanded particles have a spherical or square shape, the particles are densely packed by compression, and the porosity between the particles is reduced.

[0010] In the present invention, the expanded beads have an irregular shape having an inwardly curved surface. Examples of the shape having an inwardly curved surface include a C shape, an S shape, and a J shape. FIG. 2 shows a schematic view of a particle having a surface curved inward. When a large number of particles having these shapes are aggregated, the surfaces curved inward are entangled with each other, and the strength of the aggregate can be increased in a state where the gap between the particles is large. That is, the curved portions of the particles are entangled with each other to suppress the sliding, rotation, or floating of the particles, thereby maintaining the strength, and even when compressed, can maintain the gap between the particles. In addition, microorganisms easily adhere to the concave portion curved inside the particles, and the movement of the particles is suppressed, so that the microorganisms are less likely to fall off. A particularly preferred shape among the particle shapes having an inwardly curved surface is the S shape.

The expanded particles of the present invention have a longest portion having a length L of 10
mm <L <100 mm. When the length of the longest portion is 10 mm or less, it is difficult to produce unexpanded particles having a surface curved inward, which is economically disadvantageous. Particles having a length of 100 mm or more in the longest part have a relatively small surface area per volume, so that the area efficiency for carrying microorganisms is reduced. A particularly preferred range of the length of the longest part is 20 to 70 mm. The length of the longest part of the expanded particles is given by the longest dimension between the ends of the particle cross section, as exemplified by L in FIG.

The expanded particle filler of the present invention is a particle having a density d of expanded particles of 0.01 g / cm ³ <d <0.15 g / cm ³ . When the density is 0.01 g / cm ³ or less, the particles are densely compressed, the gaps between the particles are filled, and the water flow resistance increases. Particles having a density of 0.15 g / cm ³ or more are hard and have large interparticle gaps, so that sludge flows out of the gaps and lowers the quality of treated water. A more preferable range of the density of the expanded particle filler is 0.03 to 0.09 g / cm ³ .
If the porosity between the filler particles is large or the gap between the particles is large, the microbial sludge adhering to the filled filter medium flows out into the treated water together with the filtrate. Therefore, the filled filter medium of the present invention is preferable for the primary treatment of highly concentrated sewage.

The foamed particles of the present invention have a closed cell ratio of 80 to 1
Preferably, it is 00%. If the closed cell ratio is less than 80%, the compressive strength of the particles decreases, the particles are compressed, the gaps between the particles are filled, and the water flow resistance increases. As the thermoplastic resin used for the expanded particles of the present invention, a styrene resin or a polyolefin resin is preferably used.

As the styrene resin, polystyrene,
A styrene copolymer containing 50% or more of a styrene monomer can be used. Examples of the styrene monomer include styrene, nuclear alkyl-substituted styrene such as methyl styrene, dimethyl styrene, and ethyl methyl styrene, and nuclear halogenated styrene such as chlorostyrene, and used alone or as a mixture of two or more.
Examples of the styrene-based copolymer monomer include acrylonitrile, methyl methacrylate, and maleic anhydride. Particularly preferred among these are polystyrene and styrene-acrylonitrile copolymer.

As polyolefin resins, low, medium,
High-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, ethylene-based resin represented by ethylene-vinyl acetate copolymer, polypropylene, copolymer component of ethylene, butene 1,4-methylpentene 1
Propylene-based resin represented by random or block copolymers with propylene, which is at least one kind, or a mixed resin obtained by mixing two or more of these resins, or containing at least 50% by weight of these resins and other components Copolymers and mixed resins which are components such as vinyl chloride, ethyl acrylate, methyl acrylate, and acrylic acid are used. Of these, particularly preferred are medium and high density polyethylene and polypropylene.

If necessary, additives such as dyes and pigments, lubricants, release agents, antistatic agents, foam nucleating agents, and ultraviolet stabilizers can be added to the resin. As the volatile foaming agent used in the present invention, those having a boiling point in the range of -80 to + 100 ° C, for example, aliphatic hydrocarbons such as butane, n-pentane, isopentane, hexane and petroleum ether, and cyclic fats such as cyclopentane A group hydrocarbon, an outer halogenated hydrocarbon, carbon dioxide, or the like can be used.

The filler of the present invention is a foamed thermoplastic resin particle having a uniform particle shape. The method for producing expanded beads in the present invention is not particularly limited. A method in which a resin and a foaming agent are mixed in an extruder, extruded in a strand shape in an unfoamed state, cut into particles, and heated with steam or the like to form expanded particles. Alternatively, a method of impregnating the resin particles with a foaming agent and heating them with steam or the like to form foamed particles is used.
Therefore, the foamed particles obtained by the present invention have a uniform shape, unlike the particles obtained by a method such as crushing the foam with a crusher.

The filled filter medium of the present invention is used as a filter medium for a sewage purification apparatus. A sewage purification device is a device for continuously purifying sewage by passing it through a filter medium. Generally, the whole apparatus is put in a tank. The purifying device may be either aerobic purifying or anaerobic purifying. The septic tank using the filled filter medium of the present invention can be downsized. Purification equipment is 500 from a small household tank.
Although there is a large filter larger than a human tank, the filled filter medium of the present invention can be used without any particular limitation. Above all, a relatively small one having a tank of 200 or less is preferable, and a tank having a tank of 50 or less and a household wastewater purification tank or a household combined treatment tank is preferably used.

In an anaerobic septic tank, it is necessary to prevent clogging of sewage with continuous use for a long period of time. Therefore, it is particularly preferable to use the filled filter medium of the present invention having a large interparticle gap in an anaerobic sewage purification tank. As the shape of the expanded particles, irregularities and wrinkles can be provided on the surface so that microorganisms can easily adhere to the surface. In order to provide irregularities and wrinkles on the foamed particles, the foamed particles are obtained by reducing the pressure in an atmosphere of 20 to 80 ° C. and an absolute pressure of 350 to 700 torr to cause shrinkage. For the purification performance evaluation, the BOD concentration value of treated water and the visibility of treated water were used.

[0020]

The present invention will be described in more detail with reference to the following examples. The density, closed cell rate, and sewage transparency of the foamed particles in Examples and Comparative Examples were measured as follows. (1) Density: Approximately 5 g of expanded particles are weighed at two decimal places. Next, 200c whose minimum scale unit is 1 cm ³
m ³ glass graduated cylinder is filled with 50-100 cm ³ of water, and a circular wire mesh plate slightly smaller than the diameter of the graduated cylinder is placed in the center at a length of 15-30 c.
The wire of m is erected and the pressing tool of the fixed foamed particles is immersed, and the water level H1 cm ³ at that time is read. Then except pusher, the water level H2 cm ³ in a state of completely submerged using a pressing tool placed weighed the expanded beads in a graduated cylinder
Is read, and the true density d (g / g /
cm ³ ). d = W / (H 2 −H 1) where W: weight of expanded particles (g) H 1: water level before adding expanded particles (cm ³ ) H 2: water level after immersing expanded particles (cm ³ )

(2) Closed cell ratio: Density (g / c)
m ³ ) is about 24 cm ³ of the known foam.
It is measured using an air comparison specific gravity meter Model 930 manufactured by Beckman, and the closed cell rate [S, (%)] is calculated from the following equation. S = (Vx−W / ρ) × 100 / (Va−W / ρ)
(%) Vx: Volume of the true foam measured by the above apparatus (cm ³ ) Va: Volume of the foam [weight / bulk density] (cm ³ ) W: Weight of the foam (g) ρ: Foam of the foam Density of base resin (g / cm ³ )

(3) Permeability of sewage: The sewage is taken in a glass cylindrical container, and the depth of the sewage (c) at which the bottom of the container is visible.
m) was defined as the sewage transparency.

(Example 1) A wastewater inflow pipe and a treated water discharge pipe as shown in FIG. 1 were attached to a can body having a diameter of 20 cm and a height of 1 m, and foamed particles as a filler were filled to a height of 50 cm.
A filter for preventing the floating and floating of the foamed particles was attached to the upper part of the can body. The feed sewage has a BOD concentration of 400 mg / l,
An S-shaped expanded polystyrene particle (Asapack Kasei Kogyo Co., Ltd.) was used as the expanded particles. The expanded particles have a density of 0.016 g / cm.
^{3. The} longest part had a length of 45 mm and a closed cell ratio of 90%. The sewage purification performance of the foamed particles is 5 days after the treatment starts.
BOD concentration of treated water is 35mg / l, visibility is 30cm
And it was good. Although the head difference between the sewage supply pipe and the treated water discharge pipe was 5 cm, no problem of clogging due to water passage was observed.

(Example 2) S-shaped expanded polystyrene particles (Aspac Sarah, manufactured by Asahi Kasei Kogyo) and a density of 0.0
35 g / cm ³ , longest part length 30 mm, closed cell rate 9
The same evaluation as in Example 1 was performed using 0%. Purification performance was equivalent, and no problem of clogging due to water flow was observed.

Example 3 As foamed particles, a C-type polypropylene resin having a density of 0.12 g / cm ³ , a longest portion having a length of 15 mm, and a closed cell ratio of 95% was used.
When the same evaluation as in Example 1 was performed, the BOD of the treated water
At a concentration of 40 mg / l, the transparency was as good as 28 cm. In addition, no problem of clogging due to water flow was observed.

Example 4 As foamed particles, C-type polystyrene resin having a density of 0.012 g / cm ³ , a longest portion of 80 mm in length, and a closed cell ratio of 85% was used.
When the same evaluation as in Example 1 was performed, the BOD of the treated water
At a concentration of 45 mg / l, the visibility was almost as good as 26 cm. In addition, no problem of clogging due to water flow was observed.

Comparative Example 1 Spherical polystyrene expanded particles were used as expanded particles. Particle density is 0.03 g / c
m ³ , particle diameter 6 mm, closed cell rate 90%. When the same evaluation as in Example 1 was performed, the BOD concentration of the treated water was 5
At 5 mg / l, the transparency was 24 cm, which was insufficient purification performance. Sludge adhered to the particles, increasing the water flow resistance.

Comparative Example 2 As the expanded particles, columnar expanded polystyrene particles were used. Particle density 0.05 g /
cm ³ , the length of the longest part was 120 mm, and the closed cell ratio was 90%. When the same evaluation as in Example 1 was performed, the treated water had a BOD concentration of 60 mg / l, and the visibility was 22 cm, indicating insufficient purification performance. No problem of clogging was observed.

Comparative Example 3 S-shaped polystyrene expanded particles were used as expanded particles. Particle density 0.008g
/ Cm ³ , the length of the longest part was 60 mm, and the closed cell ratio was 85%. When the same evaluation as in Example 1 was performed, it was found that the treated water had a BOD concentration of 50 mg / l and the transparency was 24 cm, which was insufficient purification performance. The particles were compressed by buoyancy, the water flow resistance increased, and the water flow treatment could not be performed for a long time.

Comparative Example 4 S-shaped polystyrene expanded particles were used as expanded particles. The particle density is 0.20 g /
cm ³ , the length of the longest part was 15 mm, and the closed cell ratio was 95%. When the same evaluation as in Example 1 was performed, the BOD concentration of the treated water was 45 mg / l, and the visibility was 28 cm. Sludge adhered to the particles, increasing the water flow resistance, making it impossible to perform long-term water flow treatment.

Comparative Example 5 As the expanded particles, columnar polystyrene expanded particles were used. Density is 0.02 g / c
m ³ , particle size 30 mm, closed cell rate 60%. When the same evaluation as in Example 1 was performed, the BOD concentration of the treated water was 45 mg / l, and the visibility was 28 cm. The particles were compressed by buoyancy, the water flow resistance increased, and the water flow treatment could not be performed for a long time.

[0032]

According to the present invention, the water flow resistance is small,
The outflow of sludge such as microorganisms attached to the filler can be suppressed, and a packed filter medium for purifying sewage having a uniform particle shape can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing a usage form of a sewage purification filler according to the present invention.

FIG. 2 is a schematic explanatory view showing the shape of a foamed particle used in the present invention.

FIG. 3 is an explanatory view showing the longest part of the expanded beads used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Septic tank can body 2 Filling material for sewage purification 3 Sewage supply piping 4 Treated water discharge piping 5 Bottom extraction valve 6 Exhaust port 7 Sewage supply head difference 8 Filter media outflow prevention filter

Claims (4)

[Claims] 1. A filter material for purifying sewage, comprising thermoplastic foamed resin particles, wherein the filter material has an irregular shape having an inwardly curved surface, and a length L of a longest portion is 10 mm <L <100 mm. Density d is 0.01 g / cm ³ <d <0.1
A packed filter medium for purifying sewage, characterized by having a weight of 5 g / cm ³ . 2. The packed filter medium according to claim 1, wherein microorganisms for purifying sewage are carried. 3. The method according to claim 1, wherein the thermoplastic resin is a styrene resin or a polyolefin resin.
Or a packed filter medium according to 2. 4. The filled filter medium according to claim 1, which is filled in an anaerobic sewage purification tank.