JP2002263673A - Carrier for water treatment, method for manufacturing the same, and facility for water treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier for water treatment which has high water absorptivity, can perform efficient water treatment and has excellent durability, to provide a method for manufacturing the same, and to provide a facility for water treatment. SOLUTION: A carrier 4 for water treatment is obtained by carrying out gas foaming of thermoplastic resin of high water absorptivity by using a physical foaming agent or resin-made micro balloons which include gas. The carrier 4 for water treatment obtained by gas foaming has substantially spherical isolated bubbles. For example, when the carrier 4 is used as a fluidized bed, the carrier 4 exhibits good flow properties or good re-floating characteristics especially when the facility is restarted after air diffusion or halt of mechanical agitation. The carrier 4 also exhibits high mechanical strength, especially tear strength, and can realize outstanding durability. Hence such a carrier 4 for water treatment and a facility for water treatment in which such a carrier 4 for water treatment is used can perform efficient water treatment for a long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a water treatment carrier used for various types of water treatment using microorganisms, a method for producing the same, and a water treatment apparatus.

[0002]

2. Description of the Related Art Conventionally, in water treatment such as wastewater treatment using microorganisms, for example, a water treatment carrier comprising a synthetic resin molded product as a fluidized bed in a water treatment tank such as an anaerobic tank or an aerobic tank. Has been turned on. The carrier for water treatment performs water treatment by adhering microorganisms in the tank and growing the adhered microorganisms.
As such a carrier for water treatment, for example, a molded product of a polyethylene resin or a polypropylene resin is used.

[0003]

However, since the specific gravity of such a polyethylene resin or a polypropylene resin is 1.0 or less, if the molded product is used as it is in a fluidized bed, it will rise from water. For example, a filler such as calcium carbonate or barium sulfate is blended to adjust the specific gravity to improve the fluidity.

However, when fillers such as calcium carbonate and barium sulfate are blended, there is a problem that mechanical stirring causes wear and damage. In addition, polyethylene resins and polypropylene resins are inherently hydrophobic, have a low affinity for microorganisms, and have a disadvantage that it is difficult to improve the efficiency of water treatment.

[0005] On the other hand, it is also known to use a foamed molded product such as a polyurethane foam as a carrier for water treatment. However, simply performing foam molding simply results in mechanical problems due to bubbles in the obtained molded product. Low strength, especially tear strength,
There is a problem that it is difficult to improve durability.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to provide a highly water-absorbing and efficient water treatment which is excellent in durability. An object of the present invention is to provide a carrier for water, a method for producing the same, and a water treatment device.

[0007]

In order to achieve the above-mentioned object, the present invention provides (1) a substantially water-absorbing thermoplastic resin having substantially spherical closed cells obtained by gas foaming. (2) a water treatment carrier according to (1), wherein (2) a gas bubble is formed using a resin microballoon containing gas; The water treatment carrier according to the above (1) or (2), wherein the plastic resin has a water absorbing ability of 3 to 20 times by weight of its own weight, (4) a highly water-absorbing thermoplastic. The resin has a number average molecular weight of 1900 to
The water treatment carrier according to any one of the above (1) to (3), which has 12000 polyoxyethylene units, and (5) gas foaming of a highly water-absorbing thermoplastic resin. (6) A method for producing a water treatment carrier, wherein (6) a water treatment carrier having substantially spherical closed cells obtained by gas foaming a highly water-absorbing thermoplastic resin is used. And an apparatus for water treatment.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The carrier for water treatment of the present invention is used for water treatment using microorganisms, and can be obtained by gas foaming a highly water-absorbing thermoplastic resin.

The highly water-absorbing thermoplastic resin is a resin which swells with water, and preferably has a water absorbing capacity of 3 to 20 times by weight of its own weight, more preferably 5 to 15 times by weight of its own weight. ing.

[0010] The water absorption capacity can be measured by the so-called tea bag method. That is, in the tea bag method, a sample (a highly water-absorbing thermoplastic resin) is sealed in a non-woven bag such as a tea bag for black tea, immersed in water, pulled up after a predetermined time, drained, and then increased. This is a method for measuring the weight. More specifically, 10 g of a sample is put in
It can be determined from the weight before and after immersion at 24 ° C. for 24 hours.

By using a highly water-absorbing thermoplastic resin, the specific gravity of the thermoplastic resin (specific gravity when absorbing water, the same applies hereinafter) can be made closer to water. Therefore, when used as a fluidized bed, good fluidity in the water treatment tank, in particular, good resurfacing property when restarting after aeration or mechanical stirring is stopped, and affinity with microorganisms can be ensured. The water treatment can be performed efficiently by enhancing the property and improving the adhesion and growth of microorganisms. In addition, by using a thermoplastic resin, it can be molded into an arbitrary shape and can be continuously mass-produced.

When the water absorbing ability of the highly water-absorbing thermoplastic resin is 3 to 20 times the weight of its own weight, good mechanical durability can be obtained, and the specific gravity of the highly water-absorbing thermoplastic resin can be obtained. Can be reduced, and when used as a fluidized bed, good fluidity in the water treatment tank can be ensured.

More specifically, examples of such a highly water-absorbing thermoplastic resin include polyurethane resin, nylon resin, polyester resin, ethylene-vinyl alcohol copolymer, polycaprolactone resin, lactic acid polymer, and the like.
Poly (meth) acrylate resin and the like can be mentioned. These may be used alone or in combination of two or more. Among these, a polyurethane resin is preferable, and among them, a polyoxyethylene unit having a number average molecular weight of 1900 to 12000 as a structural unit,
Further, polyoxyethylene units having a number average molecular weight of 3,000 to 10,000, particularly a number average molecular weight of 500
Polyurethane resins having 0 to 9000 polyoxyethylene units are preferred. When a polyoxyethylene unit having a number-average molecular weight of 1900 to 12000 is provided as a structural unit, the unit functions as a hydrophilic portion and can exhibit good water absorption. In addition, such a polyurethane resin is, for example, a polyisocyanate compound and a number average molecular weight of 1900 to 1200.
It can be obtained by subjecting a polyoxyethylene glycol to urethanation reaction under known conditions.

Also, the number average molecular weight is 1900 to 12000
The polyoxyethylene unit of the other monomer,
It may be copolymerized with an oligomer or polymer unit or the like, and may be constituted as a structural unit of not only polyurethane resin but also other highly water-absorbing thermoplastic resin. Further, a resin having such a polyoxyethylene unit may be blended as a resin blend.

It is preferable that the carrier for water treatment of the present invention contains a substrate adsorbing substance and / or a substance which improves the enzyme activity or promotes the growth. By containing these, the microorganisms can be more easily attached and grown on the surface of the water treatment carrier,
Further efficient water treatment can be performed.

Examples of such a substrate adsorbing substance include natural ceramics containing natural stone, artificial ceramics, activated carbon, carbon black, silicate compounds and the like. These may be used alone,
Two or more types may be used in combination. Preferably, activated carbon and carbon black are used. The proportion of the substrate adsorbing substance is, for example, 0.1 to 40 parts by weight, or preferably 0.5 to 30 parts by weight, per 100 parts by weight of the thermoplastic resin.

Examples of the substance that enhances the enzyme activity or promotes the growth include metals such as copper and zinc, and salts, oxides, sulfides, and water-insoluble or hardly-soluble salts of such metals in water. Examples thereof include oxides and the like, and those in which an inorganic substance and / or an organic substance are contained in such a metal or a metal compound. These may be used alone or in combination of two or more.
Preferably, copper oxide, copper sulfide, and copper hydroxide are used.
The proportion of the substance that improves the enzyme activity or promotes the growth is, for example, 0.005 to 5 parts by weight, preferably 0.05 parts by weight, per 100 parts by weight of the thermoplastic resin.
1 to 3 parts by weight.

The substrate-adsorbing substance and the substance which enhances the enzyme activity or promotes the growth may be prepared, for example, as a master batch.

The carrier for water treatment of the present invention is obtained by blending a substrate-adsorbing substance and / or a substance for improving enzyme activity or promoting growth with a highly water-absorbing thermoplastic resin, if necessary. It can be obtained by foaming.

Gas foaming is a method of foam molding using a physical foaming agent (foaming gas) as a foaming agent, and is not particularly limited. For example, using a twin-screw extruder, a highly water-absorbing material is used. While charging and melting the thermoplastic resin, foaming gas is injected from the side of the screw, and the foaming gas is kneaded and dissolved in the molten highly water-absorbing thermoplastic resin,
What is necessary is just to pull out from a nozzle by predetermined pressure, and to foam-mold. As the foaming gas used,
For example, aliphatic hydrocarbons (eg, butane, pentane, hexane, etc.), chlorinated hydrocarbons (eg, dichloroethane, dichloromethane, etc.), fluorinated hydrocarbons (eg, trichloromonofluoromethane, dichlorodifluoromethane, Dichloromonofluoromethane, dichlorotetrafluoroethane, etc.), alternative fluorocarbons, air, carbon dioxide, nitrogen gas, water and the like. The foam molding conditions include, for example, a screw diameter of 30 mm for twin screw extrusion.
In φ, the discharge rate is 1 to 10 kg / hr, the screw rotation speed is 150 to 400 min ⁻¹ , the die temperature is 150 to 250 ° C., and the injection amount of the foaming gas is 100 parts by volume of the highly water-absorbing thermoplastic resin. 0.01 to 10 parts by volume, and the injection pressure of the foaming gas is 150 to 250 MPa.

For gas foaming, resin microballoons containing gas as a foaming agent may be used. If a resin microballoon containing gas is used, foam molding can be performed using a single screw extruder.

The resin-made microballoon encapsulating the gas includes a heat-expandable microballoon, and is a minute particle containing a heat-expandable liquid or gas inside, and is mainly formed of a thermoplastic resin. Things.
When heating the resin microballoon containing gas,
The thermally expandable liquid or gas encapsulated therein expands to form a large particle size balloon. The particle size after thermal expansion is, for example, about 5 to 300 μm. As a resin forming a resin microballoon containing gas, for example,
Acrylonitrile, methacrylonitrile, acrylate, methacrylate, vinylidene chloride,
And vinyl chloride and copolymers of these monomers. Examples of the liquid or gas sealed therein include lower hydrocarbons such as pentane, isopentane, butane, and hexane, chlorofluorocarbons, and fluorocarbon alternatives. A commercially available resin microballoon containing such a gas may be used. For example, “Expancel” manufactured by Expancel is used.

When foaming is carried out using a resin-made microballoon containing gas, for example, a highly water-absorbing thermoplastic resin, if necessary, a substrate adsorbing substance and / or an enzyme activity is improved or growth is promoted. A resin microballoon containing a gas is charged together with the substance to be removed, and the resin may be pulled out of the nozzle using a known single-screw or twin-screw extruder. In addition, as such foam molding conditions, for example, when the screw diameter of single screw extrusion is 30 mmφ, the discharge rate is 1 to 8 kg / hr, the number of rotations of the screw is 10 to 60 min ⁻¹ , and the temperature of the die is 160 to 2
The blending amount of the resin microballoon containing gas at 50 ° C. is 0.1 to 10 parts by weight based on 100 parts by weight of the highly water-absorbing thermoplastic resin. In addition, the resin-made microballoon containing gas may be prepared as a master batch, for example.

The shape formed by gas foaming is as follows:
For example, when used as a fluidized bed, granular, spherical, cylindrical, cylindrical, bales, rice grains, rugby ball, etc.
What is necessary is just to shape | mold into arbitrary shapes. The size may be appropriately selected, and for example, a size of about 1 to 50 mm is preferable.

After extrusion molding, the molded product may be discharged from a die, and then cut by a cutting method such as underwater cutting, hot cutting, and mist cutting. For example, the surface can be made into a skin layer while the inside thereof is made porous by underwater cutting or hot cutting.

Further, for example, so-called co-extrusion molding, in which two or more kinds of highly water-absorbing thermoplastic resins can be simultaneously drawn out from two or more kinds of partitioned dies and freely shaped, may be performed.

Since the water treatment carrier of the present invention thus obtained is molded by gas foaming, it can be obtained as a foam molded article having substantially spherical closed cells. That is, for example, in a foam molded article molded by chemical foaming, when drawing out from a nozzle in extrusion molding, air bubbles extend long in the drawing direction and communicate with each other, and cannot be obtained as spherical closed cells, or Even if it is made, it has poor mechanical durability, but according to such gas foaming, since it can be obtained as substantially spherical closed cells, the mechanical strength, especially the tear strength is high, and the durability is high. Improvement can be achieved.

The closed cells obtained by such gas foaming are substantially spherical, but more specifically,
The angle between the upper and lower tangents in the major axis direction when drawing a tangent to a closed cell using a stereomicrograph or the like is 45 °.
O ° to 90 °, preferably up to an oval shape of 60 ° to 90 °. By forming such closed cells, excellent mechanical strength can be exhibited in the isotropic direction.

In such gas foaming, the foaming ratio is, for example, 1.01 to 5, furthermore 1.1.
To 2, and the cell diameter of the obtained closed cells is, for example, 1 to 3000 μm, and more preferably 3 to
It is preferably 2000 μm.

By adjusting the expansion ratio, the porosity (also called porosity or porosity) of the water treatment carrier can be appropriately selected and the specific gravity thereof can be adjusted. Thereby, the fluidity when used as a fluidized bed can be appropriately adjusted. Therefore, by adding a filler such as calcium carbonate or barium sulfate to the thermoplastic resin, compared with the case where the specific gravity is adjusted, a cushion effect is exerted due to the presence of closed cells, thereby reducing abrasion and damage. Since the number is small, the durability can be further improved.

In addition, by making the surface porous, irregular pores are usually formed on the surface, which makes it easier for microorganisms to adhere to the surface. Water treatment can be performed.

The specific gravity of such a water treatment carrier is 0.93 to 1.15, which is close to the specific gravity of water (1.0).
, Preferably in the range of 0.97 to 1.05, more preferably in the range of 0.98 to 1.017, so that the porosity is 0.1 to 90%, more preferably 0 to 90%. .2
Preferably, it is adjusted to 80%.

Further, in such a carrier for water treatment, at the time of foam molding, for example, a known inorganic microballoon such as a glass balloon is further blended to form substantially spherical closed cells by the inorganic microballoon. It may be formed. By blending such an inorganic microballoon, its specific gravity can be made even closer to the specific gravity of water. The amount of the inorganic microballoon is, for example, 0.01 to 20 parts by weight, preferably 0.1 to 1 part by weight, per 100 parts by weight of the thermoplastic resin.
0 parts by weight.

The carrier for water treatment of the present invention thus obtained can be used for various types of water treatment, for example, wastewater treatment such as industrial wastewater and domestic wastewater, and more specifically, microorganisms. Water treatment using, for example, an aerobic tank for treatment with aerobic microorganisms such as nitrifying bacteria (eg, ammonia oxidizing bacteria, nitrite oxidizing bacteria, etc.), and anaerobic treatment for treatment with anaerobic microorganisms such as denitrifying bacteria. It can be used as a fluidized bed or fixed bed of a tank, especially as a fluidized bed.
FIG. 1 shows an embodiment of such an apparatus for water treatment. That is, in FIG. 1, the water treatment device includes a water treatment tank 1 used as an aerobic tank or an anaerobic tank, and a water supply pipe 2 and a drain pipe 3 connected to the water treatment tank 1. In the water treatment tank 1, the water treatment carrier 4 of the present invention is provided.
Is supplied as a fluidized bed, and is stirred by a stirrer 5 rotatably provided in the water treatment tank 1. Such a water treatment apparatus uses a water treatment carrier 4 having substantially spherical closed cells obtained by gas foaming a highly water-absorbing thermoplastic resin. Within it, good fluidity can be exhibited over a long period of time, and efficient water treatment can be performed.

Although the water treatment carrier of the present invention is originally used for water treatment as described above, it can also be used for treatment in the gas phase, for example, for deodorization of ammonia, hydrogen sulfide and the like. it can.

[0036]

The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to Examples and Comparative Examples.

Example 1 1339 parts by weight of polyethylene glycol (number average molecular weight 8300, manufactured by Sanyo Kasei Co., Ltd.), 145 parts by weight of 4,4'-diphenylmethane diisocyanate (manufactured by Nippon Polyurethane Co., Ltd.) and 1,4-butanediol (Wako Pure Chemical Industries, Ltd.) After reacting 15.9 parts by weight at 80 ° C., the mixture was aged at 100 ° C. for 15 hours to obtain a thermoplastic resin. The water absorption performance of the thermoplastic resin by the tea bag method is 8% of its own weight.
１２12 weight times.

Next, 100 parts by weight of the thermoplastic resin,
Resin microballoon containing gas (trade name: Expancel 092MB120, manufactured by Expancel)
1.0 part by weight and 2 parts by weight of activated carbon (trade name: Shirasagi DO-5, manufactured by Takeda Pharmaceutical Co., Ltd.) were foam-formed using an extruder (30 mmφ single screw extruder, manufactured by GM Engineering Co., Ltd.). A columnar water treatment carrier having a diameter of 2 mm and a length of 3 mm was obtained.

When the cross section of the water treatment carrier was observed with a stereoscopic microscope, it was confirmed that substantially spherical closed cells were formed as shown in FIG.

Example 2 100 parts by weight of the thermoplastic resin obtained in Example 1, 1.5 parts by weight of a resin microballoon (trade name: Expancel 092 MB120, manufactured by Expancel) containing gas, activated carbon (Product name: Shirasagi DO-5, manufactured by Takeda Pharmaceutical Company Limited) 2 parts by weight of an extruder (30 mmφ single screw extruder,
(GM Engineering Co., Ltd.) to obtain a columnar water treatment carrier having an outer diameter of 2 mm and a length of 3 mm.

When the cross section of the water treatment carrier was observed with a stereoscopic microscope, it was confirmed that substantially spherical closed cells were formed.

Example 3 100 parts by weight of the thermoplastic resin obtained in Example 1, 2.0 parts by weight of resin microballoon (trade name: Expancel 092 MB120, manufactured by Expancel) containing gas, activated carbon (Product name: Shirasagi DO-5, manufactured by Takeda Pharmaceutical Company Limited) 2 parts by weight of an extruder (30 mmφ single screw extruder,
(GM Engineering Co., Ltd.) to obtain a columnar water treatment carrier having an outer diameter of 2 mm and a length of 3 mm.

When the cross section of the water treatment carrier was observed with a stereoscopic microscope, it was confirmed that substantially spherical closed cells were formed.

Example 4 100 parts by weight of the thermoplastic resin obtained in Example 1, 3.0 parts by weight of resin microballoon (trade name: Expancel 092 MB120, manufactured by Expancel) containing gas, activated carbon (Product name: Shirasagi DO-5, manufactured by Takeda Pharmaceutical Company Limited) 2 parts by weight of an extruder (30 mmφ single screw extruder,
(GM Engineering Co., Ltd.) to obtain a columnar water treatment carrier having an outer diameter of 2 mm and a length of 3 mm.

When the cross section of the water treatment carrier was observed with a stereoscopic microscope, it was confirmed that substantially spherical closed cells were formed.

Example 5 100 parts by weight of the thermoplastic resin obtained in Example 1, 2.0 parts by weight of a resin microballoon (trade name: Expancel 092 MB120, manufactured by Expancel) containing gas, inorganic 0.5 parts by weight of a microballoon (trade name: Phenoset BJO-0840, manufactured by Asia Pacific Microspheres), activated carbon (trade name: Shirasagi DO)
-5, 2 parts by weight of Takeda Yakuhin Kogyo Co., Ltd. and 0.2 parts by weight of copper oxide (Wako Pure Chemical Industries, Ltd.) were foamed using an extruder (30 mmφ single screw extruder, GM Engineering Co., Ltd.). Then, a cylindrical water treatment carrier having an outer diameter of 2 mmφ and a length of 3 mm was obtained.

When the cross section of the water treatment carrier was observed with a stereoscopic microscope, it was confirmed that substantially spherical closed cells were formed.

Example 6 100 parts by weight of the thermoplastic resin obtained in Example 1, 2.0 parts by weight of resin microballoon (trade name: Expancel 092 MB120, manufactured by Expancel) containing gas, inorganic 3.0 parts by weight of micro-balloon (trade name: Phenoset BJO-0840, manufactured by Asia Pacific Microspheres), activated carbon (trade name: Shirasagi DO)
-5, manufactured by Takeda Pharmaceutical Co., Ltd.)
(0 mmφ single screw extruder, manufactured by GM Engineering Co., Ltd.) to obtain a columnar water treatment carrier having an outer diameter of 2 mmφ and a length of 3 mm.

When the cross section of the water treatment carrier was observed with a stereoscopic microscope, it was confirmed that substantially spherical closed cells were formed.

Example 7 100 parts by weight of the thermoplastic resin obtained in Example 1, 1.0 part by weight of resin microballoon (trade name: Expancel 092 MB120, manufactured by Expancel) containing gas, activated carbon (Trade name: Shirasagi DO-5, manufactured by Takeda Pharmaceutical Company) 2 parts by weight of an extruder (90 mmφ single screw extruder,
GM Engineering Co., Ltd.)
5mmφ by underwater cutting (GALA)
Was obtained.

When the cross section of the water treatment carrier was observed with a stereoscopic microscope, it was confirmed that substantially spherical closed cells were formed.

Example 8 The thermoplastic resin obtained in Example 1 was extruded using an extruder (30
mmφ twin screw extruder, manufactured by Kobe Steel Co., Ltd.), carbon dioxide gas was injected from the side at a pressure of 200 MPa, and then further kneaded with a static mixer at the tip of the twin screw so that it became the same size as the die. Outer diameter 2mmφ, length 3mm by taking up belt
Was obtained.

When the cross section of the water treatment carrier was observed with a stereoscopic microscope, it was confirmed that substantially spherical closed cells were formed.

Comparative Example 1 The thermoplastic resin obtained in Example 1 was extruded using an extruder (30
This was extruded using a single-screw extruder (mmφ, manufactured by GM Engineering Co., Ltd.) to obtain a cylindrical water treatment carrier having an outer diameter of 2 mmφ and a length of 3 mm.

Comparative Example 2 1353 parts by weight of polyethylene glycol (number average molecular weight: 8300, manufactured by Sanyo Kasei), 135 parts by weight of 4,4'-diphenylmethane diisocyanate (manufactured by Nippon Polyurethane) and 1,4-butanediol (Wako Pure Chemical Industries, Ltd.) After reacting 11.9 parts by weight at 80 ° C., the mixture was aged at 100 ° C. for 15 hours to obtain a thermoplastic resin. In addition, the water absorption performance of this thermoplastic resin by the tea bag method is 1% of its own weight.
The weight was 3 to 17 times by weight. The obtained thermoplastic resin was extruded using an extruder (30 mmφ single screw extruder, manufactured by GM Engineering Co., Ltd.) and had an outer diameter of 2 mmφ and a length of 3 m.
m was obtained.

Comparative Example 3 100 parts by weight of the thermoplastic resin obtained in Example 1 was added to an inorganic chemical foaming agent (trade name: Hydrocelol CF40E,
1.0 part by weight of Boehringer Ingelheim Co., Ltd.) was added, and foamed using an extruder (30 mmφ single screw extruder, manufactured by GM Engineering Co., Ltd.).
A column-shaped water treatment carrier having a length of 3 mm was obtained.

When the cross section of the water treatment carrier was observed with a stereoscopic microscope, as shown in FIG. 3, it was confirmed that the bubbles were continuous in a streak shape and that substantially no closed spherical bubbles were formed. Was.

Comparative Example 4 To 100 parts by weight of the thermoplastic resin obtained in Example 1, 1.0 part by weight of an organic chemical foaming agent (trade name: Polyslen 306EV, manufactured by Eiwa Chemical Co., Ltd.) was added, and extrusion molding was performed. Machine (30m
(mφ single screw extruder, manufactured by GM Engineering Co., Ltd.) to obtain a columnar water treatment carrier having an outer diameter of 2 mm and a length of 3 mm.

When the cross section of the water treatment carrier was observed with a stereoscopic microscope, it was confirmed that the bubbles were continuous in a streak shape and that substantially no closed spherical cells were formed.

Comparative Example 5 A micro hollow balloon (manufactured by Nippon Philite) was added to a 10% aqueous solution (containing a cross-linking agent bisacrylamide) of acrylamide (manufactured by Wako Pure Chemical Industries, Ltd.) containing 2.5% sodium alginate. Then, a 4 mm thick sheet was prepared by adding a reaction initiator, and the sheet was cut into 4 mm squares, and sodium alginate was eluted to obtain a water treatment carrier having a specific gravity of 1.01.

Test Example 1 The water treatment carriers of Examples 1 to 8 and Comparative Examples 1 to 5
After drying with a hot air dryer at 0 ° C. for 5 hours, 100 g of the dried water treatment carrier was put into 2 L of ion-exchanged water and allowed to swell, using a specific gravity measuring device (MD-200S, manufactured by Mirage Trading Co., Ltd.) The specific gravity of each water treatment carrier was measured. Table 1 shows the results.

[0062]

[Table 1] In Examples 1 to 4 and 7, the addition amount of the resin-made microballoon containing the gas was variously changed. Table 1
As is clear from the above, by adding the resin-containing microballoons encapsulating the gas, the specific gravity can be made lower than in Comparative Example 1 in which the resin-containing microballoons encapsulating the gas was not added, and It can be seen that the specific gravity can be lowered as the amount increases. Further, it can be seen that in Examples 5 and 6, in which an inorganic microballoon was further added to a resin-made microballoon containing gas, a value closer to the specific gravity of water was obtained.

[0063] Examples 1-8 and Comparative Examples 1-5 was used in Test Example 2 Test Example 1 The aqueous treating carrier, 0.5 m ³ (loading 10%) used in the bulk volume, which of 5 m ³ It was put into a water tank, and a durability test was performed using a mechanical stirring type aerator (output: 0.75 kw, rotation speed: 560 to 570, manufactured by Shin Meiwa Co., Ltd.). In this durability test, talc as a specific gravity adjuster and activated carbon as a substrate adsorbent were added to polypropylene, and a columnar water treatment carrier formed by extrusion was also tested.

As a result, even after 3 weeks from the start of the test, no destruction such as deformation or tearing was observed in the water treatment carriers of Examples 1 to 8, and the wear rate was 1% or less. Met. On the other hand, it was confirmed that Comparative Example 2 in which the specific gravity was reduced by increasing the content of the polyoxyethylene unit acting as a hydrophilic portion was damaged by 2% on the third day. In Comparative Example 3 using an inorganic chemical blowing agent and Comparative Example 4 using an organic chemical blowing agent, as much as 5 to 10% of damage was confirmed after one day. Furthermore, the durability test by mechanical stirring was not performed for Comparative Example 5, which was not a polyurethane resin, because the sample was broken even if pressed by hand.

In the case of a polypropylene water treatment carrier, the specific gravity of which is adjusted as a general water treatment carrier, the water becomes black and turbid after a few days from the start, and activated carbon spills from the water treatment carrier. Was observed. In addition, as a result of a stereoscopic microscope observation, it was confirmed that the water treatment carriers of Examples 1 to 8 did not wear, whereas the outer portions of the water treatment carriers made of polypropylene were entirely worn. Was done. From these, Example 1
It can be seen that the water treatment carriers of Nos. To 8 have excellent mechanical durability.

Test Example 3 Using the water treatment carriers of Examples 1, 3 and Comparative Example 1,
10 g of each swollen water treatment carrier in an L-shaped cylindrical water tank (diameter 7.8 cm, height 50 cm, water depth 42 cm when used)
And a stirring blade just below the water surface (blade diameter 6 cm, blade width 0.8)
cm, 6 turbines), and the time required from the start of stirring until all the water treatment carriers floated (completely floated) from the bottom of the water tank was measured, and the re-floating property was evaluated.

First, when the stirring blade was stirred at 70 min ^−1, it took 73 seconds on average for complete floating in Comparative Example 1, whereas the carrier for water treatment in Example 1 averaged 47 seconds, and The carrier for water treatment completely floated in an average of 36 seconds. Next, when the stirring blade was stirred at 60 min ⁻¹ , Comparative Example 1
Although the sample did not completely float, the carrier for water treatment of Example 1 completely floated on average 68 seconds, and the carrier for water treatment of Example 3 averaged 47 seconds on average. From this result, it can be seen that the closer the specific gravity to water, the better the re-surfacing property.

Test Example 4 The water treatment carriers of Examples 2, 5, 7 and Comparative Example 1 were immersed in activated sludge to adsorb microorganisms. That is, a carrier for water treatment having a bulk volume of 250 mL is charged into 5 L of a draft flow water tank, and an inorganic artificial wastewater having the following composition is used, at a water temperature of 20 ° C., pH 7.0 to 7.5, and a hydraulic retention time. The evaluation was performed by obtaining the ammonia oxidation rate calculated from the amount of generated nitrite under the condition of 5 hours.

[0069] Inorganic artificial wastewater composition (per _{1L) (NH 4) 2 SO} 4 0.0943g KH 2 PO 4 0.6g NaHCO 3 0.375g MgSO 4 · 7H 2 O 10mg CaCl 2 · 2H 2 O 1.8mg Fe -EDTA 1 mg The results of attaching ammonia oxidizing bacteria to the water treatment carriers of Examples 2, 5, 7 and Comparative Example 1 and evaluating the results are shown in FIG.

Comparative Example 1 was excellent in mechanical durability, but it was simply extruded, so there were no irregularities on the surface, so that microorganisms were unlikely to adhere, and the ammonia oxidation rate started rising after about 1.5 months. 70 mg-N after 2 months
/ L-carrier / Hr.

On the other hand, in Examples 2, 5 and 7, since resin microballoons containing gas were used, the surface had irregularities (observed by a stereoscopic microscope), and the microorganisms were easily attached. The bacteria grow and the ammonia oxidation rate rises rapidly, and after 3 weeks, 110 mg-N / L
-Carrier / Hr is indicated. In Example 5, which contains a substance (copper oxide) that improves the enzyme activity or promotes the growth of the enzyme, the ammonia oxidation rate rises even faster, and the maximum rate is 130 mg-N / L-carrier / It can be seen that Hr is high. This is thought to be due to the fact that the inclusion of a substance that enhances the enzyme activity or promotes growth not only effectively promotes the growth of ammonia-oxidizing bacteria, but also improves the enzyme activity of ammonia-oxidizing bacteria. Can be

Further, it was confirmed that the growth (dominance) of ammonia-oxidizing bacteria, which is a useful bacterium, on the surface of the water treatment carrier was confirmed by D.
It was evaluated by the NA probe method (FISH method). As a result, it was confirmed that ammonia-oxidizing bacteria proliferated and prioritized on the surfaces of the water treatment carriers of Examples 2, 5, and 7.
Observations showed that more than 85% were ammonia oxidizing bacteria.

[0073]

The carrier for water treatment of the present invention is obtained by subjecting a highly water-absorbing thermoplastic resin to gas foaming and has substantially spherical closed cells. If used, it exhibits good fluidity, especially good resurfacing property when restarting after aeration or mechanical stirring is stopped, and has high mechanical strength, especially high tear strength, and excellent durability. Can be. Therefore, such a water treatment carrier and a water treatment apparatus using such a water treatment carrier can perform efficient water treatment for a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a water treatment apparatus of the present invention.

FIG. 2 is a stereomicrograph of a cross section of the water treatment carrier of Example 1.

FIG. 3 is a stereomicrograph of a cross section of a water treatment carrier of Comparative Example 3.

FIG. 4 is a diagram showing the relationship between the elapsed days and the ammonia oxidation rate in Test Example 4.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Water treatment tank 2 Water supply pipe 3 Drain pipe 4 Water treatment carrier 5 Stirrer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4B029 AA21 BB02 CC02 CC03 4B033 NA12 NA19 NB02 NB14 NB23 NB37 NB68 NC04 NC12 ND04 NF06 4D003 AA12 EA14 EA15 EA19 EA30 EA38

Claims (6)

[Claims] 1. A water treatment carrier having substantially spherical closed cells obtained by subjecting a highly water-absorbing thermoplastic resin to gas foaming. 2. The water treatment carrier according to claim 1, wherein gas is foamed using a resin microballoon containing gas. 3. A highly water-absorbing thermoplastic resin having a weight of 3 to
Characterized by having a water absorption capacity of 20 weight times,
The water treatment carrier according to claim 1. 4. The high water-absorbing thermoplastic resin according to claim 1, wherein the structural unit has a polyoxyethylene unit having a number average molecular weight of 1900 to 12000 as a structural unit. The carrier for water treatment as described in the above. 5. A method for producing a carrier for water treatment, which comprises gas foaming a highly water-absorbing thermoplastic resin. 6. An apparatus for water treatment, wherein a water treatment carrier having substantially spherical closed cells obtained by gas foaming a highly water-absorbing thermoplastic resin is used.