JP2003117577A - Microorganism immobilized carrier and method for manufacturing the same, and waste water treating method using the carrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier which is a microorganism immobilized carrier used by being stuck with microorganisms on its surface and is large in a specific surface and can maintain the good quality of treated water for a long period. SOLUTION: The outer peripheral part of the microorganism immobilized carrier as a tubular body consisting of a thermoplastic resin is provided with a plurality of projections and the width in the front end areas of these projections is set at >=0.8 times the spacings between the front end areas of the projections adjacent to each other, by which the specific surface area is increased and the treating performance of the immobilized carrier is enhanced; in addition, the peeling of the microorganisms from the carrier surface does not occur in spite of contact with other carriers and the treating performance good for a long period can be maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microorganism-immobilized carrier which is used by adhering microorganisms to its surface when biochemically treating wastewater, a method for producing the same, and a wastewater treatment method using the same.

[0002]

2. Description of the Related Art As one of biological wastewater treatment methods, a microorganism-immobilized carrier to which microorganisms are adhered is made to flow in a tank,
A method of adsorbing and decomposing organic substances and nitrogen by a microorganism adhering to the surface of the carrier is used. As the microorganism-immobilized carrier, hydrophilic gel, porous hollow resin, urethane foam, etc. are used.

[0003] The porous hollow resin is widely used because the material is inexpensive and the molding is easy. Examples of the porous hollow resin include polypropylene and polyethylene. Polypropylene is often used as a porous body by foam molding in order to increase the amount of microorganisms attached. However, the hollow tubular carrier has a drawback that the sludge circulation inside is poor, clogging by sludge is likely to occur, and sludge (microorganisms) inside the cylinder does not work effectively, so that the treatment performance decreases. In order to prevent this blockage, it is necessary to have an inner diameter above a certain level in order to maintain the fluidity of the sludge in the pipe, but if the inner diameter is increased, the specific surface area decreases, However, it has a drawback that the amount of sludge adhered is decreased and the treatment performance is deteriorated.

[0004] Therefore, improvements have been proposed for increasing the specific surface area. For example, Japanese Unexamined Patent Publication No. 2000-41669 discloses a carrier in which a partition wall is provided in a cylinder. In addition, JP-A-10-314780 and JP-A-1
Japanese Laid-Open Patent Publication No. 1-226588 discloses a tubular carrier having ribs and fins on the outer peripheral portion.

[0005]

[Patent Document 1] Japanese Unexamined Patent Application Publication No.
As disclosed in Japanese Patent Laid-Open No. 000-41669, the method of providing a partition in a cylinder can increase the specific surface area, but there is a problem that sludge is likely to be clogged as compared with a tubular carrier having the same diameter. .

[0006] Japanese Patent Laid-Open No. 10-314780 and Japanese Patent Laid-Open No. 11
In the carrier disclosed in JP-A-226588, the distance between the ribs or fins is wide, and the ribs or fins of other carriers collide with each other during flow, so that the microbial layer on the outer periphery is scraped off. There was a problem that the contribution would be low.

[0007] It is an object of the present invention to provide a microorganism-immobilized carrier that is used with microorganisms attached to the surface thereof, which has a large specific surface area and can maintain good treated water quality for a long period of time.

[0008]

That is, the first gist of the present invention is a tubular microorganism-immobilized carrier made of a thermoplastic resin, in which a plurality of protrusions are provided on the outer peripheral portion of the carrier, and the tip portion of the protrusion is provided. Is a microorganism-immobilized carrier having a width of 0.8 times or more the distance between the tip portions of adjacent protrusions. Further, it is preferable that the height of the protrusions is 0.05 to 2 mm because it is difficult for the microorganisms attached to the outer surface to peel off. Also,
It is preferable that the distance between the tip portions of the adjacent protrusions is 0.5 to 2 times the height of the protrusions. Further, if the shape of the protrusion is a plate, it is possible to increase the specific surface area, which is preferable.
More preferably, the protrusion is provided in a gear shape on the outer peripheral portion of the tubular body. More preferably, the carrier is a foam.

[0009] A second gist of the present invention is a method for producing a microorganism-immobilized carrier in which a thermoplastic resin is extruded and molded from a die having a gear-shaped outer periphery. The third gist of the present invention is a wastewater treatment method using the microorganism-immobilized carrier of the above shape in a fluidized bed.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below, but the present invention should not be construed as being limited thereto.

[0011] The microorganism-immobilized carrier of the present invention has a tubular shape and is provided with a plurality of protrusions on its outer peripheral portion. The shape of the protrusion is not necessarily limited, and may be columnar, hemispherical, or the like, but it is preferable to use a plate shape because the specific surface area can be increased. When providing the plate-shaped projection, a direction perpendicular to the central axis of the tubular carrier,
It may be provided in a spiral shape, but it is preferable to provide a gear-shaped projection in a direction parallel to the central axis of the tubular carrier because continuous extrusion molding can be facilitated. FIG. 1 is a cross-sectional view of a carrier showing an example of the present invention, showing a cross section perpendicular to the cylinder central axis. In the example of FIG. 1, the tubular body 1
A gear-shaped projection 2 is provided on the outer peripheral surface of the.

[0012] Further, the shape of the projection 2 may be tapered from the tubular body 1 side toward the tip, but the projection 2
Since it is easy for the other protrusions 2 to enter the recesses between them, it is preferable that the width be approximately the same from the tubular body 1 side to the tip portion or be thicker toward the tip. Further, the shape may be curved on the way.

[0013] In the microorganism-immobilized carrier of the present invention, the width of the tip portions of the protrusions is 0.8 times or more the widest distance between the tip portions of the adjacent protrusions. Since it has a protrusion, it can have a larger specific surface area compared to a hollow body of the same diameter, and at the same time, the width of the protrusion is 0.8 times or more the distance between the tip portions of adjacent protrusions, When the carrier of (1) collides, the protrusions of the collision partner hardly scrape off the microbial layer between the protrusions, and a sufficient microbial layer can be formed. The width of the tip end portion of the protrusion is preferably 0.9 times or more, and more preferably 1 time or more, the distance between the adjacent protrusions.

FIG. 2 is a partially enlarged view of a cross section of the tubular body 1 which is perpendicular to the central axis of the tube. Here, the width of the tip portion of the protrusion 2 is the length of a shown in the figure, and the interval between the tip portions of the protrusions 2 is the length of b. In addition, as shown in FIG.
When the tip of the protrusion 2 is curved, the width of the tip part is
The width a of the portion where the side surface of the protrusion 2 is a substantially flat surface is closest to the tip. The interval between the tip portions of the protrusions 2 is the portion where the side surface of the protrusion 2 is a substantially flat surface and is closest to the tip. It means b, which is the interval between the parts. In addition, it is preferable that the intervals between the adjacent protrusions 2 are approximately equal in the plurality of protrusions 2.

The shape of the tip of the protrusion 2 is not necessarily limited, and may be a planar shape, a shape having irregularities or a curve, or the like, but a curved surface having a center of curvature on the central axis of the tubular body 1 is preferable. Further, the shape of the outer surface of the tubular body at the portion having no protrusion is not necessarily limited and may be a planar shape, a shape having irregularities or a curve, or the like, but a curved surface having a center of curvature on the central axis of the tubular body 1 is preferable.

[0016] The height of the protrusion 2 is preferably 0.05 to 2 mm, and more preferably 0.1 to 1.5 mm. The higher the protrusions 2, the thicker the microbial layer is formed, and the performance is improved. However, if it is too high, the inside of the microbial layer is not effectively used, and it is difficult to obtain the improvement in activity commensurate with the increase of the microbial layer. Also,
The distance between the adjacent protrusions 2 is 0.
5 to 2 times, the microbial layer is appropriately formed,
It is preferable because it is difficult to peel off.

[0017] If the specific gravity of the carrier is too small, the carrier floats during the treatment, and if too large, the carrier precipitates in the tank, which may make it difficult to flow. Therefore, by adjusting the specific gravity of the microorganism-immobilized carrier to 0.85 to 1.2, suitable fluidity can be obtained when the carrier is used for a fluidized bed.
More preferably, the specific gravity is 0.9 to 1.1. It is particularly preferably 0.95 to 1.05. When the carrier is used in a fluidized bed, suitable fluidity can be selected by setting the specific gravity within this range.

[0018] The maximum diameter of the outer peripheral portion of the microorganism-immobilized carrier is 2
It may be about 50 mm, preferably 3 mm to 30 mm, more preferably 4 mm to 20 mm. If the maximum diameter of the outer peripheral portion is smaller than this, solid-liquid separation becomes difficult when overflowing from the aeration tank, and if it is 30 mm or more, the specific surface area becomes too small and the treatment activity decreases. The maximum diameter of the outer peripheral portion of the microorganism-immobilized carrier here refers to the maximum diameter of the outer peripheral portion of the tubular body 1 that does not include the protrusion 2. When the cross-sectional shape of the tubular body 1 is triangular, the maximum diameter means the maximum length of the sides in the cross-section of the tubular body 1, and when it is polygonal, the maximum length of the diagonal lines. Say. The length of the carrier is not particularly limited, but when used in a fluidized state, it is preferably 0.5 to 2 times the outer diameter of the cylinder in consideration of fluidity.

[0019] Further, the maximum value of the outer periphery of the microorganism-immobilized carrier,
The ratio of the wall thickness of the tubular body 1 is preferably 4 or more and 20 or less. When the ratio is less than this, not only the meat pressure becomes too thick but the adhering area of sludge decreases, but also the amount of resin used increases, which is uneconomical. On the other hand, if it is 20 or less, the wall thickness becomes too thin to obtain sufficient strength.

The cross-sectional shape of the tubular body 1 is preferably a substantially circular shape as shown in FIG. 1 from the viewpoint of formability, but it is a substantially (regular) quadrangle as shown in FIG. The shape may be a (regular) triangle, a substantially (regular) pentagon, a substantially (regular) hexagon, or a star shape. Further, in order to increase the surface area, a partition wall may be provided inside the cylinder as shown in FIG.

[0021] Examples of the thermoplastic resin used in the present invention include, but are not limited to, polypropylene, polyethylene, polyvinyl chloride, ethylene-vinyl acetate copolymer resin, polystyrene and the like. These thermoplastic resins may be used either individually or in combination of two or more, with polypropylene and polyethylene being particularly preferred.

[0022] It is preferable to use an acid-modified thermoplastic resin together with the above-mentioned thermoplastic resin, because the carrier fluidity is further improved. As the acid-modified thermoplastic resin, a propylene-maleic anhydride copolymer (for example, Mitsui Chemicals, Inc., trade name Admer, Sanyo Kasei Co., Ltd., trade name Yumex, Mitsubishi Chemical Co., Ltd., trade name Modic), ethylene-methacrylic acid copolymer (ionomer resin, for example, Mitsui DuPont Polychemical Co., Ltd., trade name Himilan), methyl methacrylate-methacrylic acid copolymer (Mitsubishi Rayon Co., Ltd., trade name Acrypet) ) Etc. The acid-modified thermoplastic resin may be used alone or in combination of two or more.

[0023] The content of the acid-modified polymer depends on the amount of acid modification, but is preferably 10% by weight or more in order to provide sufficient hydrophilicity, and a carrier is obtained only from the acid-modified thermoplastic resin. You can also

[0024] As other components, calcium carbonate, talc, zeolite, barium sulfate, titanium oxide, potassium titanate, aluminum hydroxide and the like specific gravity adjusting material, azodicarbonamide (ADCA) for porosity, It may contain dinitrosopentamethylenetetramine (DPT), a foaming agent such as a carbonic acid-based agent, a foaming auxiliary agent, and an appropriate additive. It is more preferable to use a foam as the carrier because the formation of the microbial layer is rapid and the treatment performance is exhibited in an early stage.

[0025] The method for molding the carrier of the present invention is not particularly limited, and examples thereof include a method in which a thermoplastic resin composition is extrusion-molded and cut into a desired length. This method is preferable because it is very easy, no special equipment or post-treatment is required, and the carrier can be manufactured at low cost. For extrusion molding, a die having a gear shape on the outer periphery and a shape corresponding to the inner shape of the carrier can be used at the center.

[0026] Further, the fluidity of the carrier can be improved by treating the molded body of the thermoplastic resin with an acid.
The concentration of the acid used is preferably 0.1 to 5 N. When the acid concentration is 0.1 N or less, the initial fluidity of the carrier is the same as that in the case of no treatment, and the effect of acid treatment is not recognized.
On the other hand, when treated with an acid having a concentration of more than 5 N, the resin surface is likely to be eroded or eluted, which may cause a problem in durability. In addition, strict care must be taken during handling. Not desirable because it is dangerous.

[0027] The type of acid used is not necessarily limited, and sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, acetic acid, or the like can be used. Among them, hydrochloric acid is inexpensive, has a high treatment effect, and is excellent in handleability. preferable.

[0028] The treatment conditions are not particularly limited as long as the surface of the molded body comes into contact with an acid, but it is preferable to immerse the molded body in an acid solution because treatment can be performed easily. The immersion temperature is not particularly limited, and the treatment may be performed at room temperature. The immersion time is preferably 0.1 to 10 hours, more preferably 0.5 to 5 hours, in consideration of the effect of sufficiently improving the fluidity and the productivity. In addition,
It is preferable to stir the liquid during the dipping treatment because the treatment efficiency is improved.

[0029] The carrier of the present invention can be used as a filter medium in biological treatment. Particularly, when it is used as a carrier for immobilizing microorganisms for fluidized bed type biological treatment, it exhibits extremely high treatment capacity. The carrier of the present invention can be used in an aerobic tank or an anaerobic tank.

The embodiment of the present invention will be described in detail below with reference to specific examples and comparative examples.

<Example 1> The carrier according to the embodiment of the present invention shown in Fig. 1 (cylindrical diameter 10 mm, length 10 mm, width of protrusion tip portion = 0.
84 mm, the distance between adjacent protrusions = 0.76 m, and the height of the protrusion 1.0 mm) were formed by an extrusion molding machine and cut by a cutting machine. The die used had an outer peripheral portion processed into a gear shape. Polypropylene was used as the resin, and calcium carbonate was added to adjust the specific gravity.
The prepared carrier (0.7 L) was put into the 3.5 L treatment apparatus shown in FIG. 7, mixed with activated sludge and then aerated at 2 L / min while using artificial wastewater as raw water to supply COD of 2 kg-.
COD / m3 ・ day (667mg-COD / L, residence time 4
The biological treatment was carried out for a time and the COD of the treated water was measured.
As a result, the COD of the treated water was stable at 30 to 40 mg / L two weeks after the start of the test. It was observed that a microbial layer was visually formed between the teeth.

<Example 2> A foaming agent was added during the production of the carrier,
The carrier was manufactured and biologically treated in the same manner as in Example 1 except that the carrier was molded. As a result, the COD of the treated water was stable at 1 week after the start of the test and was 30 to 40 mg / L. It was observed that a microbial layer was visually formed between the teeth.

<Comparative Example 1> A carrier having 8 ribs on the outer peripheral portion shown in FIG. 6 (cylindrical diameter 10 mm, length 10 mm, width of protrusion tip portion = 0.84 mm, tip of adjacent protrusions) The biological treatment was performed in the same manner as in Example 1 except that the distance between the parts was 3.8 mm and the length of the protrusion was 1.0 mm. As a result, the COD of the treated water was stable within 2 weeks after the start of the test, and 5
It was 0 to 60 mg / L. The microbial layer in the outer peripheral portion was extremely small as compared with the examples.

[0034]

EFFECTS OF THE INVENTION According to the microorganism-immobilized carrier of the present invention, a plurality of protrusions are provided on the outer peripheral portion of the tubular carrier, and the width of the tip portions of the protrusions is 0.8 times the distance between the tip portions of adjacent protrusions. Since the number is twice or more, a large amount of microorganisms can be retained in the outer peripheral portion, and the treatment performance can be improved as compared with the conventional product.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a microorganism-immobilized carrier of the present invention.

FIG. 2 is a partially enlarged view of a cross section showing an example of the microorganism-immobilized carrier of the present invention.

FIG. 3 is a partially enlarged view of a cross section showing an example of the microorganism-immobilized carrier of the present invention.

FIG. 4 is a cross-sectional view showing an example of the microorganism-immobilized carrier of the present invention.

FIG. 5 is a cross-sectional view showing an example of the microorganism-immobilized carrier of the present invention.

FIG. 6 is a cross-sectional view showing an example of a conventional microorganism-immobilized carrier.

FIG. 7 is a schematic view showing a water treatment device used in Examples 1 and 2 of the present invention and Comparative Example 1.

[Explanation of symbols]

1 tubular body 2 protrusions 10 Water treatment equipment 11 screens 12 Carrier 13 Current plate 14 Air diffuser

Claims (8)

[Claims] 1. A tubular microorganism-immobilized carrier made of a thermoplastic resin, wherein a plurality of protrusions are provided on an outer peripheral portion of the carrier, and a width of a tip portion of the protrusion is determined by a distance between tip portions of adjacent protrusions. A carrier for immobilizing microorganisms that is 0.8 times or more of the above. 2. The microorganism-immobilized carrier according to claim 1, wherein the protrusion has a height of 0.05 to 2 mm. 3. The microorganism-immobilized carrier according to claim 1, wherein the distance between the tip portions of the adjacent protrusions is 0.5 to 2 times the height of the protrusions. 4. The shape of the protrusion is plate-like.
3. The microorganism-immobilized carrier according to any one of 3 above. 5. The microorganism-immobilized carrier according to claim 4, wherein the protrusion is provided in a gear shape on the outer peripheral portion of the tubular body. 6. The microorganism-immobilized carrier according to claim 5, which is made of foam. 7. A method for producing a microorganism-immobilized carrier, which comprises extruding a thermoplastic resin from a die having a gear-shaped outer periphery. 8. A wastewater treatment method using the microorganism-immobilized carrier according to claim 1 in a fluidized bed.