JPH05309361A - Porous medium for water treament - Google Patents

Abstract

PURPOSE:To provide a porous medium for water treatment wherein the medium can be used as a fluidizing medium in the case of floatation separation of filthy substances by fine bubbles and also as a solid medium in the case of filtration of the filthy substances and it is not flocculated by being charged with static electricity due to the friction between the media and it can remove the filthy substances well. CONSTITUTION:A porous medium is pelleted by kneading a polar group- containing modified polyolefin. pumiceous band balloon, and hydroxyapatite and extrusion-forming the kneaded mixture. Consequently, since hydrophilic property is provided to the medium by the polar group of the polyolefin, the medium is not changed with static electricity and is not flocculated each other and adsorption of the filthy substances to the fine pores in the surface of the medium and growth of the substances and adhesion of the filthy substances to the fine bubbles produced out of the fine pores are carried out well, thus the filthy substances are removed and separated by floatation. Moreover, microbes are stuck to the medium due to the addition of the apatite and biological decomposition is utilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to laundry wastewater, food wastewater,
The present invention relates to a porous medium for water treatment used for removing and cleaning pollutants from various wastewater such as domestic wastewater, and particularly to a porous medium suitable for removing organic pollutants. The medium of the present invention can be used both as a fluid medium for floating separation of pollutants of wastewater and as a fixed medium for filtration of pollutants.

[0002]

2. Description of the Related Art For example, a large amount of laundry wastewater generated in a cleaning plant contains various contaminants such as residual residues of detergent used, oils and fats coming out of laundry, and inorganic solids. It cannot be directly discharged to rivers, etc., and it is necessary to remove pollutants by water treatment.

Conventionally, as a method of treating such wastewater, for example, simply, the wastewater is retained in a large raw water tank in a factory, the pollutant is allowed to settle, and the pollutant is separated from the supernatant water. Although the method of draining water to rivers is adopted, it takes a long time to separate pollutants, and a large raw water tank is required for that purpose, and the site becomes huge. There was a defect that it could not be separated by.

Therefore, a method has been adopted in which an inorganic coagulant or a polymer coagulant is injected into waste water and stirred to coagulate the pollutants, and the pollutants are completely flocculated and separated from the waste water. However, although inorganic solids in wastewater can be removed by such a method, it is difficult to remove organic pollutants such as fats and oils and detergents, and it is not always possible to sufficiently treat them.

A pressure-floating type water treatment method is also known in which waste water is pressurized to dissolve air, and the dissolved air is levitated to separate and remove contaminants, but the amount of dissolved air is small. It has a drawback that the separation speed is slow and a long separation time of 30 minutes or more is required.

[0006]

From the above,
The Applicant is capable of substantially completely removing various contaminants such as inorganic solids, oils and fats, and detergents in wastewater,
We proposed a wastewater treatment method that can reduce the separation time to 5 minutes and can be implemented with a compact device, and recently applied for it as Japanese Patent Application No. 3-59312.

In the proposed treatment method, an inorganic coagulant and compressed air are injected into wastewater containing pollutants, and the mixture is rapidly stirred and mixed to form an emulsion-like reaction liquid containing bubbles, and the reaction liquid is formed into the reaction liquid. Polymer coagulant is injected to flocculate pollutants in wastewater, the flocculated pollutants are separated and removed, and the resulting treated water is agitated in the presence of a porous medium to remain in the treated water. Fine air bubbles generated from the medium are attached to the pollutants to float and separate, and the residual pollutants after treatment with inorganic coagulants and polymer coagulants are floated by micro air using a porous medium as a flowing medium. The major feature is separation.

According to this, while particles of the pollutant are adsorbed and grown in the pores on the surface of the porous medium, fine air bubbles are generated from the pores on the surface of the medium and adsorbed on the medium.
Since it can be attached to the surface of the grown pollutant particles, the organic residual pollutants can be favorably floated and separated and removed from the treated water.

However, since the above-mentioned porous medium is manufactured by mixing a resin such as polyethylene or polypropylene with an inorganic substance powder such as viscosity or Otani stone, it is charged with static electricity due to friction between the mediums at the time of stirring. There was a tendency for the media to solidify, and it was not always possible to exhibit the expected contaminant removal performance.

The object of the present invention is that it can be used both as a fluid medium for floating separation of pollutants by fine air, and as a fixed medium for filtration of pollutants, and it is still charged with static electricity due to friction between the media. It is an object of the present invention to provide a porous medium for water treatment, which does not solidify and can exhibit excellent performance of removing pollutants, and in particular has excellent performance of removing organic pollutants.

[0011]

The above object can be achieved by the porous medium for water treatment according to the present invention. In summary, the present invention is a porous medium for water treatment characterized in that a modified polyolefin having a polar group, shirasu balloon and hydroxyapatite are kneaded and formed into pellets by extrusion molding.

The porous medium for water treatment of the present invention will be described below.

The shirasu balloon used in the porous medium of the present invention is obtained by firing shirasu at a high temperature of about 1000 ° C., and is a porous lightweight powder expanded by the water contained in the shirasu. Since this shirasu balloon adsorbs particles of pollutants in irregular pores having a surface diameter of several tens to several hundreds of μm, it can be suitably used as a medium for wastewater treatment. However, since Shirasu balloon is a powder, if it is used as it is, the medium will be clogged and flow out.

In the present invention, Shirasu balloon is used as a plastic-based pelletized medium.
According to such a medium, when it is used as a fluid medium, for example, particles of contaminants are adsorbed and grown by the pores of the Shirasu balloon located on the surface of the medium, while fine particles are removed from the air captured in the pores. It is possible to generate bubbles and attach the bubbles to the particles of the pollutant adsorbed on the surface of the medium to float and separate the pollutant.

The amount of the shirasu balloon mixed with the medium is 10 to 50 wt%. If the amount of shirasu balloon is less than 10 wt%, the contaminants are not adsorbed sufficiently and the contaminants cannot be removed well. On the other hand, the compounding amount is 5
If it exceeds 0 wt%, the medium becomes brittle and the strength becomes insufficient, and it cannot be put to practical use. The shirasu balloon content is preferably 15 to 30 wt%. The particle size of the shirasu balloon is 50 to 50 μm, preferably 80 to 200 μm
m.

In the present invention, a modified polyolefin having a polar group is used as the base plastic of the medium. This is to prevent the medium from being charged with static electricity, and since the medium can be made hydrophilic by the polar group of the modified polyolefin, even if the medium is rubbed with each other, the medium will not be charged with static electricity and the medium will not be charged. It never hardens. Therefore, it is possible to satisfactorily disperse the medium in the wastewater and bring the pollutant into contact with the surface of the medium, and the growth by adsorption of the pollutant to the pores on the medium surface and the formation of fine bubbles generated from the pores into the pollutant Adhesion can be performed well, contaminants can be removed from wastewater, and air bubbles can be used for floating separation.

Examples of the modified polyolefin having a polar group include maleic acid modified products of polyethylene, propylene or ethylene-propylene copolymers, modified products of hymic acid and modified products of addition of epoxy groups.

The amount of the modified polyolefin having a polar group is appropriately in the range of 50 to 90 wt%, and if it is less than 50 wt%, it is difficult to pelletize the medium, and conversely 90 w.
If it exceeds t%, the amount of shirasu balloon becomes small and the medium has no ability to remove pollutants. The modified polyolefin having polar groups is preferably in the range of 65 to 80 wt%.

According to the present invention, hydroxyapatite (calcium phosphate-based hydroxyapatite) is further added to the medium so that the organic pollutants can be removed by microbial decomposition. This hydroxyapatite is a constituent material of human bones such as human beings and has a high affinity with living things. Therefore, the microorganisms easily attach to the surface of the medium, the organic pollutants propagate as nutrients, and the pollutants are removed from the wastewater by microbial decomposition. Also, by blending hydroxyapatite, it has the meaning of adjusting the specific gravity of the medium made of lightweight shirasu balloon and plastic to an appropriate weight.

The amount of hydroxyapatite to be blended must be determined in consideration of the adjustment of the specific gravity of the medium, but generally, the hydroxyapatite content is preferably in the range of 0.5 to 20% by weight. However, if the amount exceeds 20 wt%, the cost of hydroxyapatite is high and the medium becomes expensive. The particle size of hydroxyapatite is 2 to 100 μm, preferably 5
˜30 μm.

Hydroxyapatite may be chemically synthesized by a wet method or the like, but a natural product such as apatite or animal bone such as bovine bone can be inexpensively used.

The specific gravity of the medium may be appropriately selected according to the specific usage, but in the case of both the fluid medium and the fixed medium, it is convenient to handle if it is slightly heavier than 1.

The shape of the medium can be any shape, but in the point that it can be easily manufactured by extrusion molding, it has a cylindrical shape like the medium 1 shown in FIG. 1 showing a preferred embodiment of the present invention. Is preferred. The size of the medium can also be set arbitrarily, but the larger the size, the greater the resistance due to the water flow and the greater the stirring effect. Also, the medium is placed in the wire mesh for preventing medium outflow installed in the stirring tank or the like into which the medium is inserted. Since it is easy to prevent clogging, it is preferable that the medium 1 in FIG. 1 has a length A of 1 to 10 mm and a cross-sectional diameter B of 1 to 10 mm. The size of the medium 1 is preferably 3 to 8 mm x 3 to 8 mm, more preferably 6 to 7 m.
m × 6 to 7 mm.

As for the medium, two mediums 1 are connected sideways as shown in FIG. 2 (A), or three mediums 1 are connected as shown in FIG. 2 (B). It is also possible to connect four media 1 in the same manner as shown in FIG. 2 (C). When the media 1 are laterally connected as described above, the size of the media 1 is simply increased. It is preferable because the surface area can be made relatively larger than that in the case of In the case where the medium 1 is four connected media, as shown in FIG. 2 (D), an appropriate gap may be provided inside the four media 1.

In the medium 1 as shown in FIG. 1, a die having a large number of holes of a required size formed in an iron plate or the like is attached to an extruder, and a modified polyolefin having polar groups, shirasu balloon and hydroxyapatite are kneaded. The kneaded mixture was heated to 20
It can be easily produced by linearly extruding from a die at around 0 ° C., semi-cured linear extrudate, and then continuously cutting to a required length after extrusion. If the gap between the holes provided in the die is small for the required holes,
Since the linear extrudates extruded from the holes are brought into contact with each other and adhered to each other before being semi-cured, a connecting medium in which a plurality of mediums 1 shown in FIGS. 2A to 2D are connected can be easily formed. ..

The porous medium of the present invention is the same as the washing wastewater,
It may be used as a fluid medium or a fixed medium for treating wastewater such as food wastewater and household wastewater. It is also possible to treat the pollutants of the wastewater by directly using the wastewater without pretreatment, or to treat the residual pollutants by using the treated water after treating the wastewater with the inorganic coagulant and / or the polymer coagulant. May be. In any case, since the medium does not solidify due to static electricity due to friction between the medium, it is possible to disperse the medium well in the waste water and bring the pollutant into contact with the surface of the medium. It can be removed from wastewater and floated and separated by air bubbles.

Since hydroxyapatite is mixed in the medium, microorganisms can be attached to the medium to utilize the microbial decomposition of pollutants, and the pollutants can be satisfactorily treated even in wastewater containing a large amount of organic pollutants. It can be removed.

Further, since the adherence of microorganisms is good, the medium can be used as a bed for growing microorganisms, and the medium can be used as a fluid medium or a fixed medium in a fermentation tank or the like using microorganisms.

[0029]

EXAMPLES Examples of the porous medium of the present invention will be described. Cleaning wastewater was treated using the porous media of the present invention. The cleaning wastewater has a pH of 9.0,
Turbidity 190 ppm, SS 146 ppm, COD 1
Raw water at 08 ppm and 76 ppm n-hexane extract was used as-is for treatment with the media of the invention.
The medium used was a maleic acid-modified polyolefin as the base plastic.

2 m ³ of cleaning wastewater was introduced into a stirring tank having a volume of 3 m ³ , and the length A shown in FIG. 1 was 6 m.
m, a cylindrical medium 1 having a diameter B of 6 mm is about 100 kg.
(A volume of about 0.3 m ^{3 was} charged. Then, compressed air was blown into the cleaning wastewater by an air compressor at a flow rate of 0.6 m ³ / min, and the wastewater and the medium were agitated and treated to purify the wastewater. The scum of pollutants floating by the fine bubbles generated from the medium was removed by flowing out from the stirring tank during the treatment.

For comparison, using a medium using unmodified polyolefin as the base plastic,
Same as above.

The composition of the medium used in the present invention and the polluted components of the obtained treated water are shown in Table 1 together with Comparative Examples.

[0033]

[Table 1]

As shown in Table 1, when the cleaning wastewater was treated with the medium of the present invention, turbidity, SS, C
The respective items of OD and n-hexane extracted substance were significantly reduced as compared with the comparative example, and an excellent pollutant removal effect was exhibited. Particularly, the effect of removing the n-hexane extracted substance was remarkable.

In the above, the treatment of the medium of the present invention was carried out by directly using the cleaning wastewater. However, after the treatment with the inorganic flocculant and / or the polymer flocculant in advance, the treatment of the medium of the present invention was further performed. It is clear that the pollutants of the cleaning wastewater can be highly removed by doing so.

[0036]

As described above, the porous medium of the present invention is formed by kneading a modified polyolefin having polar groups, shirasu balloon and hydroxyapatite into pellets, and the medium is formed by the modified polar groups of the modified polyolefin. Since it has hydrophilicity, it can be used for the treatment of wastewater such as laundry wastewater, food wastewater, household wastewater, etc., and the media do not get electrostatically charged due to friction between the media and solidify the surface of the media. By adsorbing the pollutant on the surface of the medium and floating separation from the medium by air bubbles, the pollutant can be removed with high removal performance. Furthermore, since hydroxyapatite has been added to the medium, microorganisms can be attached to the medium to utilize the microbial decomposition of pollutants, and even in wastewater containing many organic pollutants, the pollutants can be removed well. Can be made.

The medium of the present invention can be used as a fluid medium or a fixed medium in treating wastewater, and is used directly in wastewater without pretreatment with an inorganic coagulant and / or a polymer coagulant, etc. It can be used for treating the substance, or for treating the residual pollutant by treating the wastewater with the inorganic flocculant and / or the polymer flocculant and then treating the wastewater.

[Brief description of drawings]

FIG. 1 is a perspective view showing the shape of a preferred embodiment of the medium of the present invention.

FIG. 2 is a perspective view showing various aspects of a connection medium in which the media of FIG. 1 are connected.

[Explanation of symbols]

 1 Medium A Length B Diameter

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI technical display location // C02F 1/52 Z 7824-4D (72) Inventor Toshio Yoshida 4-1 Tsukiji, Chuo-ku, Tokyo -1 Tonen Chemical Co., Ltd.

Claims (1)

[Claims] 1. A porous medium for water treatment, characterized in that a modified polyolefin having a polar group, shirasu balloon and hydroxyapatite are kneaded and formed into pellets by extrusion molding.