JP2004174491A - Microorganism carrier for treating sewage, method for preparing the same, and method for treating sewage using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microorganism carrier excellent in adhesiveness/retainability of microorganisms and also excellent in wear resistance, a method for preparing the same and a method for treating sewage using the same. <P>SOLUTION: The method for preparing a microorganism carrier is constituted in such a way that the carrier is molded by adding an inorganic hydrate to a thermoplastic resin and that the surface of this molding extremely forms uneven by freely defoaming water bubbles and/or air bubbles generated by the elimination of water of crystallization of the inorganic hydrate while the molding being molded. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to a microorganism carrier for sewage treatment, a method for producing the same, and a sewage treatment method using the same, and more particularly, a microorganism carrier for sewage treatment for growing microorganisms for biologically treating sewage and efficiently producing the same. The present invention relates to a method for producing a microorganism, and a method for treating a sewage by introducing the microorganism carrier into sewage and treating the sewage with microorganisms that have settled on the microorganism carrier.

  BACKGROUND ART Conventionally, as a method for treating wastewater (sewage) such as factory wastewater or domestic wastewater, a biological water treatment method using aerobic bacteria or anaerobic bacteria has been widely used. Conventional biological water treatment methods include a fixed-bed wastewater treatment method and a fluidized-bed wastewater treatment that is becoming mainstream in aerobic treatment (for example, see Patent Document 1). The fixed-bed-type wastewater treatment method is a method in which a large number of microorganism carriers are fixedly filled in a treatment tank and sewage is allowed to flow to treat the wastewater. The fluidized-bed type wastewater treatment method is a method of treating a large number of microorganism carriers in a treatment tank while circulating and flowing the wastewater in a stirred flow by aeration with a diffuser or mechanical stirring with a propeller or the like.

  As the microorganism carrier for sewage treatment, a carrier having good microbial adhesion and a high holding power is preferable from the viewpoint of improving sewage treatment performance. Many microbial carriers devised in shape to improve these performances have been proposed. For example, a spherical filter in which the outer peripheral portion is formed by a water-permeable layer formed of hollow sponge-like resin, rubber, non-woven fabric, resin or rubber and plant fibers, and the core is configured to have a specific gravity close to 1 when containing water. A floor (for example, see Patent Document 2), a microorganism-implanted body made of a synthetic resin having an irregular surface with a hollow spherical body, and a foamed plastic having open cells inside a spherical body similarly formed Is known as a fluidized bed carrier (for example, see Patent Document 3). In addition to the above synthetic resin-based carrier, a porous carrier using calcium silicate hydrate as an inorganic carrier (for example, see Patent Document 4) is known as a fixed bed carrier.

However, when a sponge or a foam having a high expansion ratio as described above is used as a microbial carrier in a fluidized bed type sewage treatment, abrasion due to friction between the carriers or between the carrier and the inner wall of the tank is large, and the outflow and reduction of the carrier, and consequently the sewage. There is a problem that the processing performance is easily reduced. In order to improve abrasion resistance, there are foams having a low foaming ratio using a chemical foaming agent (for example, citric acid sodium bicarbonate or azodicarbonamide). ), And it is hard to say that it is good for the environment. In addition, these chemical blowing agents are often expensive.
Further, in the case of a sponge-like carrier or a porous carrier, clogging is likely to occur due to the growth of microorganisms due to long-term use. If clogging occurs, the inside of the carrier becomes anaerobic, and water pollution due to the death and separation of aerobic microorganisms, or the generation of malodorous components such as acetic acid, propionic acid, and methane gas due to the growth of anaerobic microorganisms are promoted. Further, if the absolute amount of the aerobic microorganisms is reduced, the ability to oxidize inorganic compounds such as ammoniacal nitrogen is also reduced.
Further, since the inorganic carrier has a large specific gravity, it is unsuitable in terms of fluidity for use in a fluidized bed type sewage treatment tank.
In addition, such a microorganism carrier for sewage treatment should be formed into a three-dimensional three-dimensional structure having a large surface area so that microorganisms can easily adhere thereto, and having a space that ensures a contact area with sewage even when a plurality of carriers are stacked. Is important for improving the efficiency of wastewater treatment. Moreover, the practical use of the above-mentioned sewage treatment requires a large amount of carriers, and it is desired that these carriers can be mass-produced easily and efficiently at low cost. In the case of an inorganic porous carrier, the inorganic slurry is formed by subjecting an inorganic slurry to a hydrothermal reaction at a high temperature and a high pressure. In addition, although the sponge-like carrier and the spherical carrier are formed in a three-dimensional three-dimensional structure having a space for ensuring a contact area with sewage, the surface area is further increased to improve the microorganism attachment rate. Was desired.

JP-A-6-7789 (FIG. 1) JP-A-55-65198 (FIGS. 1 to 4) Japanese Utility Model Publication No. 55-115399 (FIGS. 1 to 3) JP-A-62-183898

An object of the present invention is to provide a microorganism carrier for sewage treatment having excellent adhesion and retention of microorganisms, a method for producing the same, and a sewage treatment method using the same.
Another object of the present invention is to provide a microorganism carrier for sewage treatment that has excellent abrasion resistance when flowing.
Another object of the present invention is to provide a microorganism carrier for sewage treatment having excellent fluidity even when used in a fluidized bed sewage treatment tank.
Another object of the present invention is to provide a microorganism carrier for sewage treatment which has excellent treatment performance even when used in a fixed-bed sewage treatment tank.
Another object of the present invention is to provide a microorganism carrier for sewage treatment which has excellent filtration performance even when used in a sewage treatment tank.
Another object of the present invention is to provide a microorganism carrier for sewage treatment that can be produced relatively easily and at low cost and without increasing the environmental load.

  Thus, according to the present invention, water bubbles and / or bubbles generated by molding a mixture of a thermoplastic resin and at least an inorganic hydrate added thereto and desorbing water of crystallization of the inorganic hydrate by heat during molding The method for producing a microorganism carrier for sewage treatment, wherein the microorganism carrier for sewage treatment having irregularities on the surface of a molded article is obtained by freely breaking bubbles.

Further, according to another aspect, the present invention can provide a microorganism carrier for sewage treatment obtained by the method for producing a microorganism carrier for sewage treatment.
According to still another aspect of the present invention, there is provided a sewage treatment method in which a plurality of the microorganism carriers for sewage treatment are put into sewage and the sewage is treated by microorganisms that adhere to the microorganism carriers.

According to the present invention, water of crystallization in the inorganic hydrate mixed with the thermoplastic resin is desorbed due to heat during molding, and water bubbles and / or bubbles are generated. When the water bubbles and / or bubbles break on the surface of the molded product, the surface is roughened to an irregular bark surface or an irregular undulating shape like a ria coast, and the surface area is greatly increased as compared with the conventional one. The increased microorganism carrier for sewage treatment of the present invention can be obtained.
This microbial carrier has a large number of microscopic irregularities and a large increase in surface area (compared to conventional products), greatly improving the adhesion and retention of microorganisms. The wear resistance is greatly improved by the addition of.
Further, according to the sewage treatment method using the microorganism carrier, sewage such as factory wastewater or domestic wastewater can be efficiently purified. In particular, it is preferable to use it as a nitrification carrier for wastewater containing ammonia.

  In the present invention, the method of molding the microbial carrier is not particularly limited, but molding by the extrusion molding method can easily form a large number of irregularities by breaking bubbles on the carrier surface caused by water of crystallization in the inorganic hydrate. This is preferable in that the microorganism carrier can be mass-produced at low cost. At this time, although depending on the type of the thermoplastic resin or the inorganic hydrate, molding at a temperature greatly exceeding the total crystal water desorption (dissociation) temperature of the inorganic hydrate is not preferable. For example, the temperature is 100 to 300 ° C, preferably 120 to 280 ° C, and more preferably 140 to 270 ° C. Since the surface of the carrier is roughened by using water bubbles and / or bubbles generated by desorption of the water of crystallization of the inorganic hydrate, a gas (for example, carbon dioxide, ammonia, etc.) which becomes an environmental load when a chemical foaming agent is used. There is also an advantage that no phenomena occur.

  In the present invention, the specific gravity of a molded article formed by adding at least an inorganic hydrate to a thermoplastic resin is 0.7 to 1.4, preferably 0.8 to 1.2, and more preferably 0.9 to 1.2. By setting the ratio to 1.1, a microorganism carrier having excellent fluidity can be obtained. If it exceeds this range, the fluidity will be significantly reduced.

In the present invention, the thermoplastic resin is not particularly limited, but a polyolefin-based resin is preferable for improving abrasion resistance. Examples of the polyolefin resin include olefin homopolymers and copolymers. Examples of the olefin include ethylene, propylene, 1-butylene, isobutylene, 1-pentene, 3-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, and 1-undecene. And α-C _2-20 olefins such as 1-dodecene.

  The olefin-based resin may be a copolymer of an olefin and a copolymerizable monomer. Examples of the copolymerizable monomer include (meth) acrylic acid, (meth) acrylate, vinyl ester, cyclic olefins, vinyl cyanide, and diene. These copolymerizable monomers may be used alone or in combination of two or more. Among these olefin resins, polyethylene resins (eg, low, medium or high density polyethylene, linear low density polyethylene, ethylene-propylene copolymer, etc.), polypropylene resins (eg, polypropylene, propylene-ethylene copolymer) And ethylene-vinyl acetate copolymer, propylene-vinyl acetate copolymer, and ethylene-methyl (meth) acrylate copolymer. Further, the copolymer may be a random copolymer or a block copolymer.

  These polyolefin resins may be used alone or in combination of two or more. In order to increase the surface area by increasing the surface irregularities due to foam breaking, it is preferable to mix two or more resins to form an incompatible interface between the resins. That is, in addition to the polyolefin resin, other incompatible thermoplastic resins (for example, styrene resin, vinyl resin, (meth) acrylic resin, polyvinyl ketone resin, polyamide Resin or polyester resin) alone or in combination of two or more. In addition, a hydrophilic resin (polyvinyl alcohol, polyetheresteramide, etc.) or a water-absorbing resin (polyacrylic acid-based water-absorbing resin, thermoplastic nonionic-type water-absorbing resin, etc.) may be added for the purpose of improving the performance of microbial adhesion. good.

  In the present invention, examples of the polyolefin-based resin include high-density polyethylene, polypropylene, and ethylene vinyl acetate. Among them, high-density polyethylene is preferable. Examples of the styrene-based resin include polystyrene, acrylonitrile-styrene copolymer, and ABS resin. Examples of the vinyl resin include a vinyl acetate resin and polyvinyl alcohol. Examples of the (meth) acrylic resin include polymers and copolymers of acrylic acid, acrylic acid ester, acrylamide, acrylonitrile, methacrylic acid, methacrylic acid ester, and the like. Examples of the polyvinyl ketone-based resin include polyvinyl methyl ketone and polyvinyl ethyl ketone. Examples of the polyamide resin include polyamide, polyamide 3, polyamide 4, polyamide 4-6, and polyamide 6. Examples of the polyester-based resin include polyethylene terephthalate, polybutylene terephthalate, and polyacrylate.

  In the present invention, the inorganic hydrate is an inorganic salt having water of crystallization at normal temperature and normal pressure, which is one that desorbs (releases) all or a part of water of crystallization between 50 and 300 ° C. For example, calcium sulfate dihydrate (gypsum), aluminum hydroxide trihydrate, sodium sulfate decahydrate, sodium thiosulfate pentahydrate, aluminum sulfate hemihydrate, magnesium sulfate Hexahydrate, magnesium thiosulfate hexahydrate, sodium carbonate heptahydrate or decahydrate, alum and the like can be mentioned. Among these, calcium sulfate dihydrate (gypsum) is preferable from the viewpoint of safety, low cost, and easy availability. The type of gypsum is not particularly limited, and natural gypsum or chemical gypsum may be used.

In the present invention, as a raw material of the microorganism carrier, specifically, a mixture obtained by adding 50 to 99 parts by weight of an inorganic hydrate to 50 to 99 parts by weight of a thermoplastic resin is preferably used. The hydrate is 60 to 98 parts by weight: 40 to 2 parts by weight, more preferably 70 to 95 parts by weight: 30 to 5 parts by weight. Further, when the immiscible resin is mixed with the polyolefin resin as the thermoplastic resin, the weight ratio of the polyolefin resin, the immiscible resin, and the inorganic hydrate is preferably 30 to 96:30 to 2:40 to 2. Preferably, it is more preferably from 50 to 90:20 to 5:30 to 5.
By using such a mixture, it is possible to form irregularities having good adhesion and retention of microorganisms, and to obtain a microorganism carrier having excellent abrasion resistance. If the amount of the inorganic hydrate is less than 1 part by weight of the total amount, the irregularities on the carrier surface are reduced, and the adhesion and retention of microorganisms are reduced. Further, when the amount of the inorganic hydrate is more than 50 parts by weight based on the thermoplastic resin, the specific gravity of the microbial carrier becomes too large, and the fluidity of the carrier when used in a fluidized-bed type sewage treatment tank is reduced, and stirring is performed. There is a problem that the energy for generating the flow is increased.

In the present invention, when the microbial carrier is used as a carrier for a fluidized bed, the outer diameter is 1 to 50 mm, the length is 1 to 50 mm, and the column is cylindrical, cylindrical or mesh cylindrical, and has a specific gravity of 0.8 to 1.2. Is preferable, and more preferably, the outer diameter is 1 to 20 mm, the length is 1 to 20 mm, and the specific gravity is 0.9 to 1.1.
With this configuration, it is possible to obtain a microorganism carrier that has good fluidity in a fluidized-bed type sewage treatment tank and can perform efficient sewage treatment. The shape of the microbial carrier may be a prismatic shape other than a columnar shape, a flat cylindrical shape, a polygonal cylindrical shape other than a cylindrical shape, a mesh flat cylindrical shape, a mesh polygonal cylindrical shape, etc. other than a mesh cylindrical shape. You may. Further, a projection such as a fin or a partition may be provided on the inside, outside, or both (including the column when only the outside is included) of the cylindrical body or the mesh cylindrical body to increase the surface area. In addition, in the microorganism carrier, if the outer diameter is less than 1 mm and / or the length is less than 1 mm, the carrier may be clogged by adhered microorganisms, or the size of the carrier flow prevention screen of the sewage treatment tank must be reduced. In addition, the screen is easily clogged and stable operation becomes difficult. Conversely, if the outer diameter of the microbial carrier is greater than 50 mm and / or the length is greater than 50 mm, the surface area for microbial settlement will increase unless the ratio of filling (input) of the microbial carrier per volume of the sewage treatment tank is increased. Insufficient amounts of microorganisms can be obtained due to the shortage, and the treatment efficiency decreases. Further, when the specific gravity of the microorganism carrier is out of the range of 0.8 to 1.2, the fluidity in the fluidized bed type sewage treatment tank is significantly reduced, and the sewage treatment efficiency is reduced.

  In the present invention, when a microorganism carrier is used as a carrier for a fixed bed, it is preferably a column, a cylinder or a mesh cylinder having an outer diameter of 1 to 20 cm and a length of 50 to 500 cm, and may have a mesh plate shape. Further, a projection such as a fin or a partition may be provided on the inside, outside, or both (including the column when only the outside is included) of the cylindrical body or the mesh cylindrical body to increase the surface area. If the outer diameter of the microorganism carrier is less than 1 cm and / or the length is less than 50 cm, the same problem as in the case of the fluidized bed described above occurs. Conversely, if the outer diameter of the microbial carrier is greater than 20 cm and / or the length is greater than 500 cm, the surface area for microbial settlement must be increased unless the ratio of filling (input) of the microbial carrier per volume of the sewage treatment tank is increased. Is insufficient, so that a sufficient amount of microorganisms cannot be obtained, and the treatment efficiency decreases.

  In the present invention, the method of forming the microorganism carrier into a columnar shape, a cylindrical shape, a mesh cylindrical shape, or the like is not particularly limited, but an extrusion molding method is preferable from the viewpoint of easy mass production at low cost. For example, when molding into a columnar or cylindrical shape, the mixture may be continuously extruded from a die into a cylindrical or cylindrical shape with a general extruder, and when forming into a mesh cylindrical shape, a conventionally known mesh can be used. A plurality of strands may be formed by crossing while being extruded into a cylindrical shape by an integral extrusion molding method. For details of the method of forming the mesh tubular body, reference is made to Japanese Patent Publication No. 34-4185.

  The resin composition comprising the thermoplastic resin and the inorganic hydrate may optionally contain various additives, for example, a specific gravity adjusting agent (inactive zinc oxide, talc, calcium carbonate, etc.), a surfactant, a stable Agents (antioxidants, heat stabilizers, etc.), dispersants, nucleating agents, plasticizers (phthalate esters, fatty acid plasticizers, phosphoric acid plasticizers, etc.), coloring agents, fillers, reinforcing materials (glass fiber, An appropriate amount of a fibrous filler such as carbon fiber), a thickener and the like may be added. Further, a small amount of a chemical foaming agent (such as citric acid sodium bicarbonate or azodicarbonamide) may be added for the purpose of promoting foaming for foam breaking or adjusting the specific gravity.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited by this.

[Embodiment 1]
FIG. 1 is a perspective view showing a microorganism carrier for sewage treatment of Embodiment 1 of the present invention, FIG. 2 is a micrograph showing a part of a cross section of the microorganism carrier of Embodiment 1, and FIG. It is a microscope picture which shows a part of cross section of the conventional cylindrical microbial carrier (competitor product). This microbial carrier 1 comprises 85 parts by weight of high-density polyethylene (HDPE) as a polyolefin resin, 10 parts by weight of ethylene-vinyl acetate copolymer (EVA) as an incompatible resin, and calcium sulfate dihydrate as an inorganic hydrate. The mixture is extruded into a cylindrical shape from a mixture containing at least 5 parts by weight of a Japanese product (gypsum) in this ratio.

The microbial carrier 1 has a large number of fine irregularities on its surface, that is, an outer peripheral surface and an inner peripheral surface, and has a large number of fine concave portions on an end surface which is a cut end thereof. The large number of irregularities are formed by water bubbles generated by desorption of water of crystallization of inorganic hydrate and / or free bubbles on the surface of the cylindrical body when the mixture is melted and extruded into a cylindrical shape. As a result, the surface of the cylindrical body is rough, with irregular undulations, such as an uneven bark surface (like a ria coast). Numerous irregularities are formed by free bubbles at the surface of the blisters and / or bubbles. This microorganism carrier 1 is formed in a cylindrical shape having an average outer diameter D _{1 of} about 11 mm, an average inner diameter D _{2 of} about 7 mm, a length L _{1 of} about 10 mm, and a specific gravity of about 0.86.

  Next, a method for producing the microorganism carrier for sewage treatment according to the first embodiment will be described. The method for producing the microorganism carrier 1 is not particularly limited, but an extrusion molding method is preferred from the viewpoint of productivity. In the extrusion molding, the shape of the tip (die) of the extruder is not particularly limited, and a nozzle die, a circular die (round die), a T die, a flat die, and the like can be used. A moldable circular die is preferred. In this case, the molding temperature is 160 to 220 ° C. Under such conditions, a mixture containing at least 85 parts by weight of high-density polyethylene (HDPE), 10 parts by weight of ethylene-vinyl acetate copolymer (EVA) and 5 parts by weight of calcium sulfate dihydrate (gypsum) in this ratio By extruding with an extruder, a cylindrical molded product is continuously extruded from a die, and a part of water bubbles and bubbles formed by desorption of water of crystallization of the inorganic hydrate in the cylindrical molded product. Is freely broken into the outside air, and a foamed cylindrical molded article whose entire surface is roughened into an irregular uneven shape is obtained. Thereafter, this long cylindrical molded product is cut into a predetermined length (in this case, about 10 mm) to obtain the microorganism carrier 1 of the present invention.

  Thus, according to the microorganism carrier 1 of the first embodiment of the present invention, as shown in FIG. 2, a large number of minute irregularities are formed in an irregular cross-sectional shape like a ria coast, as shown in FIG. The surface area is greatly increased as compared with the conventional product shown. Therefore, the microbial carrier 1 of the present invention is excellent in microbial adhesion and retention due to a large number of minute irregularities whose surface area is greatly increased, and can obtain a high sewage treatment effect. Further, the microorganism carrier 1 can be mass-produced efficiently and at low cost using an existing extruder. At this time, since the gas to be foamed is water vapor, the environment does not deteriorate.

[Embodiment 2]
FIG. 4 is a schematic perspective view showing a microorganism carrier for sewage treatment according to Embodiment 2 of the present invention. The microorganism carrier 1 according to the first embodiment is formed in a cylindrical shape, but the microorganism carrier 2 according to the second embodiment is formed in a mesh cylindrical shape, and the surface area is further increased as compared with the first embodiment. are doing.

This microbial carrier 2 is obtained from a mixture of 92 parts by weight of high density polyethylene (HDPE) as a polyolefin resin, 5 parts by weight of ethylene vinyl acetate, and 3 parts by weight of calcium sulfate dihydrate (gypsum) as an inorganic hydrate. It is extruded into a mesh cylindrical shape, and has an average outer diameter D _{3 of} about 80 mm, a length L _{2 of} about 80 mm, a diameter d of the strand 3 of about 5 mm, and a strand pitch (distance between the centers of the strands) P: about 25 mm, specific gravity about 0.86.

  In producing the microorganism carrier 2, the mesh mixture extruded at a die temperature of 160 to 220 ° C. by the extruder is passed through a cooling bath, cooled and solidified, and then taken out. At the time of this extrusion molding, some of the water bubbles and bubbles formed by desorption of the water of crystallization of the inorganic hydrate in the mesh cylindrical molded product immediately after being extruded from the extruder to the outside air are broken freely. As a result, a foamed reticulated tubular molded product whose entire surface is roughened into an irregular shape is obtained. Thereafter, the long cylindrical molded product is cut into a predetermined length (in this case, about 80 mm) to obtain the microorganism carrier 2 of the present invention (for details of the method of forming the mesh cylindrical body, see Japanese Patent Publication No. -4185).

  Thus, according to the microorganism carrier 2 of the second embodiment of the present invention, similarly to the first embodiment (FIG. 2), a large number of fine irregularities are formed in an irregular cross-sectional shape like a ria coast. Have been. Therefore, the microbial carrier 2 of the present invention is excellent in microbial adhesion and retention due to a large number of fine irregularities whose surface area is further greatly increased, and can obtain a high sewage treatment effect. Further, the microorganism carrier 2 can be mass-produced efficiently and at low cost using an existing extruder. At this time, since the gas to be foamed is water vapor, the environment does not deteriorate.

Next, an example of a method of treating sewage using the microorganism carrier having the above configuration will be specifically described. In this case, the case where the microorganism carrier 1 of the first embodiment is used will be described. However, the microorganism carrier 2 of the second embodiment may be used, or both may be used together.
FIG. 5 is a schematic configuration explanatory view illustrating a wastewater treatment tank into which a microorganism carrier is charged. In FIG. 5, a fluidized-bed type drainage treatment tank (aeration tank) 10 includes a treatment main tank 11, an air diffuser 12 disposed at an inner bottom of the treatment main tank 11, a partition plate 13, and an air diffuser 12. A blower 14 for supplying pressurized air or oxygen. In addition, W is the drainage in the main treatment tank.

  In the treatment of the inorganic and organic pollutants in the sewage, for example, about 30 parts by volume of the microorganism carrier 1 in the volume of the treatment main tank 11 is put into the waste water W in the treatment main tank 11. The optimal amount of the carrier 1 to be charged is determined in consideration of the volume of the main treatment tank 11, the properties of wastewater, the concentration, and the like. Thereafter, when the blower 14 is operated and air is supplied from the air diffuser 12 as appropriate, the microorganism carrier 1 flows from the bottom layer to the upper layer and from the upper layer to the bottom layer in the main treatment tank 11 along the stirring flow of the drainage W. During this time, a large amount of microorganisms grow on each of the microorganism carriers 1 in the wastewater W, especially on a large number of concave portions on the surface, and the activity of the microorganisms is increased, whereby the wastewater W is treated. At this time, the microbial carriers 1 may collide with each other at the time of flowing, or the carriers 1 may collide with the inner surface of the main treatment tank 11. However, the carriers 1 may be relatively strong by an inorganic compound of a polyolefin resin and an inorganic hydrate. Abrasion resistance of the carrier 1 is reduced, thereby reducing the loss of the carrier 1 and obtaining a high drainage treatment effect because a large amount of microorganisms have formed on a large number of fine irregularities on the cylindrical surface of the carrier 1. Can be.

  Further, since the microorganism carrier 1 is cylindrical, a large number of irregularities are formed on the outer peripheral surface and the inner peripheral surface, and the surface area on which microorganisms are formed is large, which is advantageous for wastewater treatment efficiency. In addition, since the microorganism carrier 1 is cylindrical, the efficiency of contact between microorganisms adhering to the inside and sewage is improved, and microorganisms generated inside the cylinder of the carrier 1 are appropriately separated when the carrier 1 flows as a fluidized bed. To prevent internal clogging.

  Further, a method of filtering wastewater using the microorganism carrier 1 according to the first embodiment having the above configuration will be described. The microbial carrier 1 can be selected for either downward flow filtration or upward flow filtration by selecting the specific gravity. In this case, the case where the microorganism carrier 1 of the first embodiment is used will be described. However, the microorganism carrier 2 of the second embodiment may be used, or both the microorganism carriers 1 and 2 of the first and second embodiments may be used together. May be used.

FIG. 6 is a schematic configuration explanatory view illustrating a downflow type filtration tank into which a microorganism carrier is charged. This downward flow filtration treatment includes a downward flow filtration main tank 7 having an upper drain inlet and a lower purified water discharge port, and an air diffuser 4 disposed at the inner bottom of the main filtration tank 7. And a backwashing blower 9 for supplying pressurized air or oxygen to the air diffuser 4. The optimal amount of the microorganism carrier 1 to be charged into the downflow type filtration tank is determined in consideration of the volume in the main filtration tank 7, the properties of the wastewater, the concentration, and the like. Also, a specific gravity of 1.1 or more as the microorganism carrier 1 is selected.
In this downward-flow filtration treatment, the microorganism carrier 1 is put into the wastewater W in the main filtration tank 7, and the wastewater W containing the suspended solid (SS) flows into the main filtration tank 7 from the upper part of the main filtration tank 7. And let it flow out from the lower part of the main filtration tank 7. During this time, a large amount of suspended matter is trapped in each of the microbial carriers 1 in the wastewater W, particularly in a large number of concave portions on the surface, whereby the wastewater W is filtered. At this time, each of the microbial carriers 1 may collide with each other at the time of drainage flow, or the carrier 1 may collide with the inner surface of the main treatment tank 7. However, the carrier is formed by a relatively strong polyolefin resin and an inorganic compound of an inorganic hydrate. The wear resistance of the carrier 1 is improved, thereby reducing the loss of the carrier 1 and a large number of microorganisms are formed on a large number of fine irregularities on the cylindrical surface of the carrier 1. Obtainable.

  In the downflow filtration, the suspension flowing during the backwashing operation by the backwashing blower 9 has large particles deposited in the lower layer when re-restoring, and the remaining small particles deposited in the upper layer. In this state, if filtration is performed again with a downward flow, most of the suspended matter is suppressed by fine particles in the upper layer, and the head of filtration loss rises faster. In order to eliminate this phenomenon, an upward flow filtration method described later may be employed.

FIG. 7 shows an upward flow type filtration tank. The upward-flow-type filtration tank includes an upward-flow-type filtration main tank 10 having a lower drainage inlet and an upper purified water discharge port, and an air diffuser 4 disposed at an inner bottom of the main filtration tank 10. And a backwashing blower 9 for supplying pressurized air or oxygen to the air diffuser 4. In addition, W is the drainage in the main filtration tank 10. The optimal amount of the microorganism carrier 1 to be charged into the upward-flow filtration tank is determined in consideration of the volume of the main filtration tank 10, the properties of the wastewater, the concentration, and the like. As the microorganism carrier 1, one having a specific gravity of 0.9 or less is selected.
In the sewage treatment by the upward-flow type filtration tank, wastewater W containing suspended solids (SS) flows into the main filtration tank 10 from the lower part and flows out from the upper part of the main filtration tank 10. During this time, the wastewater W is subjected to a filtration treatment by causing a large amount of suspended matter to be trapped in each of the microbial carriers 1 in the wastewater, particularly a large number of concave portions on the surface. At this time, the microorganism carriers 1 may collide with each other at the time of drainage flow, or the carriers 1 may collide with the inner surface of the main treatment tank 10. The abrasion resistance of the carrier 1 is improved by the relatively strong polyolefin resin and the inorganic compound of the inorganic hydrate, whereby the lack of the carrier 1 is reduced, and a large number of microorganisms on the surface of the cylindrical body of the carrier 1 are attached. Since it is produced, a high drainage filtration effect can be obtained.

Using a single-screw extruder (20 mm, L / D = 25, full-flight screw) with the composition shown in Table 1, extrusion molding was performed at a molding temperature of 185 to 210 ° C., and the outer diameter of Examples 1 to 7 was about 11 mm. A cylindrical microorganism carrier having an inner diameter of about 7 mm was obtained. The obtained microorganism carrier was evaluated by the following method, and the results are shown in Table 1.
Fluidity: For Embodiments 1 to 7 obtained by the above method, 10 microorganism carriers were put into a water tank filled with 2 L of pure water, and aeration was performed from the bottom of the water tank while changing the aeration intensity. The strength at which the carrier began to flow was measured.
Microbial adherence: For Embodiments 1 to 7 obtained by the above method, 5 microorganism carriers were placed in a 2 L water tank, and 1 L of artificial sewage having a BOD concentration of 140 mg / L and 1 L of activated sludge having an SS concentration of 200 mg / L were placed in a water tank. Was injected. And it aerated at the aeration intensity corresponding to each Example confirmed by the said test. Thereto, artificial sewage having a BOD concentration of 140 mg / L was added at a rate of 5 L / day, and activated sludge having an SS concentration of 200 mg / L was added at a rate of 5 L / day. The inside of the water tank was kept constant at 2 L, and the excess was discharged. It was left under these conditions for 20 days, and the weight of microorganisms attached to the carrier was measured.
Abrasion resistance: For Embodiments 1 to 7 obtained by the above method, 10 carriers were put into a container containing 2 L of water, and stirred at a rotation speed of 300 rpm with a stirrer. The change in weight was measured.

In the same manner as in the examples with the formulations shown in Table 2, cylindrical microbial carriers having an outer diameter of about 10 mm and an inner diameter of about 7 mm of Comparative Examples 1 to 4 were obtained. The obtained microbial carriers of Comparative Examples 1 to 4 were evaluated in the same manner as in the examples, and the results are shown in Table 2. Comparative Examples 3 and 4 are foams using azodicarbonamide (ADCA) as a foaming agent.
Further, as Comparative Example 5, a sponge-like carrier (made of polyurethane) was evaluated by the same method as in the example, and the results are shown in Table 2.

Table 1 and as shown in Table 2, for the aeration intensity representing the fluidity, the first to seventh embodiments are each 25m ³ / m ³ / hr, respectively Comparative Examples 1,2 20m ³ / m ³ / hr, Comparative Examples 3 and 4 were 45 m ³ / m ³ / hr, and Comparative Example 6 was 39 m ³ / m ³ / hr. From these results, it can be seen that the fluidity is good for Embodiments 1 to 7 and Comparative Examples 1 and 2, but the fluidity is not good for Comparative Examples 3 to 5. That is, the specific gravity of Comparative Examples 3 and 4 was low due to the high expansion ratio, and the specific gravity of Comparative Example 5 was a sponge, and thus the specific gravity was considerably small. Therefore, it was difficult for these carriers to flow to the bottom of the water tank.

  Regarding the attached weight of the microorganisms showing the microbial adhesion, Embodiments 1 to 7 weigh 41.0 to 50.0 mg, Comparative Examples 1 to 4 weigh 8.0 to 13.0 mg, and Comparative Example 5 weighs 25 to 25 mg. 0.0 mg. The attached weight is the total attached weight of microorganisms with respect to the total number of carriers. From these results, it can be seen that Embodiments 1 to 7 are much more excellent in microorganism adhesion than Comparative Examples 1 to 5. In other words, the surface of the carrier according to Embodiments 1 to 7 is larger than Comparative Examples 3 and 4 using a foaming agent, and this is due to the formation of unevenness due to foam breakage on the carrier surface due to the water of crystallization of the inorganic hydrate. Is presumed to be superior to the foaming agent.

  Regarding the weight reduction rate of the carrier showing the abrasion resistance, Embodiments 1 to 7 were 1%, Comparative Examples 1 to 4 were 1 to 2%, and Comparative Example 5 was 22%. From these results, it is found that Embodiments 1 to 7 and Comparative Examples 1 to 4 using hard high-density polyethylene as a main constituent material have excellent abrasion resistance, and Comparative Example 5 made of polyurethane which is soft compared to these has an abrasion resistance. It turns out to be inferior.

Next, as the mesh-shaped cylindrical microbial carriers described in FIG. 4 (Examples 8, 9, and 10), materials were prepared in the mixing ratios and sizes of the materials shown in Table 3. The length of the microorganism carrier of Examples 8 to 10 is approximately the same as the outer diameter. Table 3 also shows the specific surface area of Examples 8 to 10. The specific surface area is the total surface area (approximate) of the maximum number of carriers that can be filled in 1 m ³ of the processing tank, and is 320 m ² / m ³ in Example 8, 70 m ² / m ^{3 in} Example 9, and 10 Examples. Is 55 m ² / m ³ . By referring to these specific surface areas, it is possible to select the size and number of carriers suitable for the required sewage treatment capacity and treatment method (fixed bed or fluidized bed).

It is a perspective view which shows the microorganisms carrier for sewage treatment of Embodiment 1 of this invention. 4 is a micrograph showing a part of a cross section of the microorganism carrier of the first embodiment. It is a microscope picture which shows a part of cross section of the conventional cylindrical microbial carrier (competitor product). It is a schematic perspective view which shows the microorganisms carrier for sewage treatment of Embodiment 2 of this invention. It is a schematic structure explanatory view explaining the waste water treatment tank which puts in the microorganism carrier of the present invention. It is a schematic structure explanatory view explaining an upflow type filtration tank into which the microorganism carrier of the present invention is charged. It is a schematic structure explanatory view explaining a downflow type filtration tank into which the microorganism carrier of the present invention is charged.

Explanation of reference numerals

1,2 microorganism carrier 3 strand D _1, D ₃ average outer diameter D ₂ mean inner diameter d diameter L _1, L ₂ length P strand pitch

Claims (8)

  Molding a mixture obtained by adding at least an inorganic hydrate to a thermoplastic resin, and free-foaming water bubbles and / or bubbles generated by desorbing water of crystallization of the inorganic hydrate by heat during molding. A method for producing a microorganism carrier for sewage treatment, comprising obtaining a microorganism carrier for sewage treatment having irregularities on the surface of the body.   The method for producing a microorganism carrier for sewage treatment according to claim 1, wherein 50 to 1 part by weight of an inorganic hydrate is added to 50 to 99 parts by weight of a thermoplastic resin.   The method for producing a microorganism carrier for sewage treatment according to claim 1 or 2, wherein the thermoplastic resin contains at least a polyolefin-based resin, and the inorganic hydrate contains at least calcium sulfate dihydrate.   The method for producing a microorganism carrier for sewage treatment according to any one of claims 1 to 3, wherein the molded body has a specific gravity of 0.6 to 1.5.   The method for producing a microorganism carrier for sewage treatment according to any one of claims 1 to 4, wherein the molded body is molded into a columnar shape, a cylindrical shape, a mesh cylindrical shape, or a mesh plate shape.   The method for producing a microorganism carrier for sewage treatment according to claim 5, wherein the molded body is formed into a mesh cylindrical shape by a mesh integral extrusion molding method of the mixture.   A microorganism carrier for sewage treatment obtained by the method for producing a microorganism carrier for sewage treatment according to claim 1. A sewage treatment method comprising charging the microorganism carrier for sewage treatment according to claim 7 into sewage, and treating the sewage with microorganisms that adhere to the microorganism carrier.

Images