JP6869307B2 - Microbial carrier - Google Patents

Description

The present invention relates to microbial carriers.

Conventionally, wastewater treatment, especially reduction of biochemical oxygen demand (BOD) in wastewater by aerobic means, is active because the treatment efficiency is high and the treatment tank volume is small and microorganisms are attached to the carrier. Unlike the sludge method, it does not run off, so a fluid bed method filled with a fluid carrier is used.

The fluidized carrier used in the fluidized bed method usually foams a composition containing various synthetic resins such as polypropylene, polyethylene, polyvinyl alcohol and polyurethane, a cellulose derivative and the like together with a foaming agent and a filler, if necessary. Obtained by The shape of the fluidized carrier usually includes granular, cylindrical, cylindrical and the like.

Patent Document 1 describes a microbial carrier for wastewater treatment obtained by foaming polypropylene and / or polyethylene as a fluidized carrier. Patent Document 1 attempts to increase the amount of microorganisms supported and improve the treatment efficiency by using a microbial carrier for wastewater treatment having an increased specific surface area.

JP 2001-180

However, the microbial carrier for wastewater treatment described in Patent Document 1 has a large number of bubbles having openings having a size large enough to prevent microorganisms from entering, and it is difficult to carry the microorganisms in such bubbles. is there. As a result, the surface of the carrier cannot carry microorganisms as effectively as the specific surface area indicates, and the treatment efficiency for treated water and contaminants is poor. Further, due to the size of the opening as described above, it takes time for water to permeate into the bubbles. Therefore, the carrier described in Patent Document 1 is difficult to be submerged or suspended in water, and the treatment time becomes long.

Therefore, the present invention has been made in view of the above problems, and provides a microbial carrier that has high treatment efficiency for treated water and contaminants, can be easily submerged in a liquid, or can be suspended. It is in.

The present inventors have found that the above-mentioned problems can be solved by a microbial carrier containing polyolefin and having a specific bubble ratio and closed cell ratio, and have completed the present invention.

That is, the present invention includes the following contents.
[1] A microbial carrier containing a polyolefin and a thermoplastic resin that is incompatible with the polyolefin, wherein the content of the thermoplastic resin is 100% by mass of the total of the polyolefin and the thermoplastic resin. It is 12% by mass or more and 30% by mass or less, the bubble ratio represented by the following formula (i) is 25% or more, and the closed cell ratio represented by the following formula (ii) is 20% or less. Microbial carrier.
Bubble ratio = (1-ρ _B / ρ _A ) × 100 ... (i)
(In formula (i), ρ _A indicates the true density (g / cm ³ ) of the material constituting the microbial carrier, and ρ _B indicates the apparent density (g / cm ³ ) of the microbial carrier).
Closed cell ratio = (1-ρ _A (ρ _C − ρ _B ) / (ρ _A − ρ _B )) × 100 ・ ・ ・ (ii)
(In formula (ii), ρ _A indicates the true density (g / cm ³ ) of _{the material constituting the microbial carrier, ρ B} indicates the apparent density of the microbial carrier (g / cm ³ ), and ρ _C is the Archimedes method. The water injection density (g / cm ³ ) derived from is shown.).

[2] The air permeability calculated from the amount of air circulated from one bottom surface of the cylindrical or substantially columnar microbial carrier to the other bottom surface is 0.5 mL / (mm ² · sec) or more. 1] The microbial carrier according to.
[3] The microbial carrier according to [1] or [2], which has a columnar or substantially cylindrical shape and the height of the column or substantially cylindrical is 3 mm or less.
[4] The microbial carrier according to any one of [1] to [3], wherein the polyolefin contains polyethylene, polypropylene, polybutene, or a mixture thereof.

[5] The microbial carrier according to any one of [1] to [4], wherein the thermoplastic resin is polystyrene.
[6] The microbial carrier according to any one of [1] to [5], further comprising an organic filler and / or an inorganic filler.

According to the present invention, it is possible to provide a microbial carrier that has high treatment efficiency for treated water and contaminants and can be easily submerged or suspended in a liquid.

Hereinafter, embodiments for carrying out the present invention (hereinafter, referred to as “the present embodiment”) will be described in detail. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be appropriately modified and carried out within the scope of the gist thereof.

[Microbial carrier]
The microbial carrier of the present embodiment (hereinafter, also simply referred to as “carrier”) is a microbial carrier containing polyolefin and a thermoplastic resin that is incompatible with polyolefin.
The content of the thermoplastic resin is 12% by mass or more and 30% by mass or less with respect to the total 100% by mass of the polyolefin and the thermoplastic resin.
The bubble ratio represented by the following formula (i) is 25% or more, and the closed cell ratio represented by the following formula (ii) is 20% or less.
Bubble ratio = (1-ρ _B / ρ _A ) × 100 ... (i)
(In formula (i), ρ _A indicates the true density (g / cm ³ ) of the material constituting the microbial carrier, and ρ _B indicates the apparent density (g / cm ³ ) of the microbial carrier).
Closed cell ratio = (1-ρ _A (ρ _C − ρ _B ) / (ρ _A − ρ _B )) × 100 ・ ・ ・ (ii)
(In formula (ii), ρ _A indicates the true density (g / cm ³ ) of _{the material constituting the microbial carrier, ρ B} indicates the apparent density of the microbial carrier (g / cm ³ ), and ρ _C is the Archimedes method. The water injection density (g / cm ³ ) derived from is shown.).

(Bubble ratio)
The microbial carrier of the present embodiment communicates with the surface of the carrier and cannot be degassed even if the outside is depressurized, and the non-closed cells (u) that are not communicated with the surface of the carrier and can be degassed when the outside is depressurized. It has a closed cell (v). The bubble ratio (R _b ) indicates the ratio of the total volume of both non-closed cells (u) and closed cells (v) to the volume of the carrier.
Here, the mass per unit volume of the microbial carrier, that is, the apparent density ρ _B (g / cm ³ ) of the microbial carrier is the true density ρ _A (g / cm ³ ) of the material constituting the microbial carrier and the density of air. Using ρ _air (g / cm ³ ) and the bubble ratio (R _b ), it can be expressed by the following formula.
ρ _B = R _b・ ρ _air / 100 + (1-R _b / 100) ・ ρ _A
From this equation, the bubble ratio (R _b ) is derived as follows.
Bubble ratio (R _b ) = ((ρ _B −ρ _A ) / (ρ _air −ρ _A )) × 100
Since ρ _air is _{sufficiently smaller than ρ A} , the following equation (i) can be derived.
Bubble ratio (R _b ) = (1-ρ _B / ρ _A ) × 100 ... (i)

From the viewpoint of treatment efficiency, the microbial carrier of the present embodiment has the above-mentioned bubble ratio of 25% or more, preferably 30% or more, and more preferably 40% or more. The upper limit is usually 50% or less. The specific method for calculating the bubble ratio is as described in the examples.

Since the microbial carrier of the present embodiment has a bubble ratio within the above range and has a large number of non-closed cells having openings large enough to allow the microorganisms to enter, the microbial carrier supports the microorganisms up to the wall surface of the internal non-closed cells. can do. Therefore, the amount of microorganisms supported can be increased as compared with the conventional carrier, and the treatment efficiency for treated water and contaminants (hereinafter, referred to as "treated water and the like") can be improved.

In the case of a microbial carrier that is cooled with water during production, since the microbial carrier contains water, the bubble ratio and the closed cell ratio described later are calculated after the foamed carrier is completely dried.

(Closed cell ratio)
In the present embodiment, the closed cell ratio (R _i ) is the volume of total voids such as closed cells and non-closed cells in the microbial carrier as the denominator, and the closed cell-like voids that do not communicate with the surface of the microbial carrier. Means the proportion of the volume of.
Here, for voids such as closed cells that do not communicate with the surface of the microbial carrier, the microbial carrier is submerged in a reduced pressure atmosphere, water is injected into the non-closed cells that communicate with the surface, and the volume of the remaining voids is examined, so-called. It can be measured as a water injection density (g / cm ^{3) using the Archimedes method.} That is, the microbial carrier is depressurized in the container, and the microbial carrier is submerged in a state where almost air is discharged, so that water is injected into the non-closed cells that have passed through the surface of the microbial carrier. Then, the microbial carrier is taken out from the container, and the water injection density (g / cm ³ ) is calculated from the mass of the microbial carrier injected with water and the excluded volume when the microbial carrier is immersed in water.
The water injection density ρ _C (g / cm ³ ) is the material density (true density) ρ _A (g / cm ³ ), the density of the injected water ρ water (g / cm ³ ), and closed cells. Using the air density ρ _air (g / cm ³ ) of the part, the bubble ratio (R _b ), and the closed cell ratio (R _i ), it can be expressed by a weighted average (the following formula) by the body integration rate.
ρ _C = (1-R _b / 100) ・ ρ _A + R _b / 100 ・ ((1-R _i / 100) ・ ρ water + R _i / 100 ・ ρ _air )
Substituting the above equation (i) into this equation, and since ρ water is 1 and ρ _air is sufficiently small, the closed cell ratio (R _i ) is expressed by the following equation (ii). Can be done.
Closed cell ratio (R _i ) = (1-ρ _A (ρ _C − ρ _B ) / (ρ _A − ρ _B )) × 100 ・ ・ ・ (ii)

From the viewpoint of treatment efficiency, the microbial carrier of the present embodiment has the above-mentioned closed cell ratio of 20% or less, preferably 15% or less, and more preferably 10% or less. The lower limit is usually 1% or more. The specific method for calculating the closed cell ratio is as described in the examples.

When the closed cell ratio of the microbial carrier of the present embodiment is within the above range, it easily permeates into treated water or the like and can be easily submerged in the liquid. Therefore, a stable suspension state can be obtained at an early stage from the time when the carrier is added.

Further, since the treated water or the like easily permeates into the treated water or the like, the treated water or the like comes into contact with the microorganisms at an early stage, and the treated water or the like can be treated at an early stage from the time when the carrier is added. Therefore, according to the microbial carrier of the present embodiment, the treatment efficiency can be improved as compared with the conventional carrier.

(Air transmission rate)
In the present embodiment, the air transmittance means the cross-sectional area and the amount of air permeation per hour that passes when a constant differential pressure is applied between the cross sections of the carrier when the carrier is cylindrical or substantially columnar. Means.

The microbial carrier of the present embodiment is based on the amount of air circulated from one bottom surface to the other bottom surface of the columnar or substantially columnar microbial carrier in terms of the speed of adaptation to treated water and the like and the treatment efficiency. The calculated air permeability is preferably 0.5 (mL / (mm ^{2 · sec)) or more, and 0.76 (mL / (mm 2} · sec)) from the viewpoint that treated water and the like can be treated more efficiently. ) Or more, more preferably 0.93 (mL / (mm ² · sec)) or more, and even more preferably 1.2 (mL / (mm ² · sec)) or more. preferable. In the microbial carrier of the present embodiment, the higher the air permeability, the higher the processing capacity. Therefore, the upper limit is usually about 5.0 (mL / (mm ² · sec)) in consideration of the bubble ratio in the microbial carrier. is there. The specific method for calculating the air transmittance is as described in the examples.

When the air permeability of the microbial carrier of the present embodiment is within the above range, the treated water or the like permeates the carrier quickly, and the desired suspension state or sedimentation state can be reached at an early stage, which is preferable. ..

(shape)
The shape of the microbial carrier of the present embodiment is not particularly limited, and may be any shape such as a spherical shape, a substantially spherical shape, a cube, a substantially cubic body, a rectangular parallelepiped, a substantially rectangular parallelepiped, a cylinder, a cylinder, a cylinder or a cylinder, or an amorphous shape. May be good. Further, the size of the microbial carrier is not particularly limited. The microbial carrier of the present embodiment has higher treatment efficiency for treated water and contaminants, can be easily submerged or suspended in a liquid, has excellent mechanical strength, and has excellent productivity. Therefore, it is preferable to have a cylindrical shape or a substantially cylindrical shape. Further, having a cylindrical or substantially cylindrical shape means that when the treatment tank is filled with a microbial carrier, for example, the volume of the carrier solid portion is larger than that of a carrier having a cylindrical shape or a substantially cylindrical shape. It is also preferable because the amount of microbial support is increased and the treatment efficiency is improved. It has the shape of a cylinder or substantially a cylinder and its height is preferably 6 mm or less, more preferably 3 mm or less, and it has the shape of a cylinder or substantially a cylinder and its height is 2.5 mm or less. It is more preferable to have. The lower limit of the height of a cylinder or substantially a cylinder is usually a screen separation method, a floating separation method, a sedimentation separation method, or the like as a method for separating the carrier from the treated water or the like when the treated water or the like flows out from the treatment tank. In any of the separation methods, it is difficult to separate the smaller carrier. Further, considering the mechanical strength, the lower limit of the height of the cylinder or substantially a cylinder is preferably 1.5 mm or more. If the height of the cylinder or substantially cylinder is less than the above lower limit, cracks or chips may occur during carrier production and use. Further, the cross-sectional area of the cylinder or substantially cylinder is preferably 25 to 450 mm ² and more preferably 50 ^{to 350 mm 2} from the viewpoint of the amount of microorganisms carried when used in an actual treatment tank. It is more preferably ~ 300 mm ^2.

When the shape of the microbial carrier is a cylinder or a substantially cylindrical shape, not only the cross section but also the side surface (curved surface connecting the two cross sections) of those shapes is manufactured so as to have irregularities by the melt fracture described later. Is preferable. When the surface of the microbial carrier has irregularities, a large number of pores can be generated on the surface, the bubble ratio can be increased, and the closed cell ratio can be reduced. Further, since the surface of the microbial carrier has a large number of irregularities, it has an excellent air transmittance even though it is a cylinder or a substantially cylinder. Therefore, it is possible to have good treatment efficiency for treated water and contaminants.

(Polyolefin)
The microbial carrier of this embodiment contains polyolefin. The polyolefin is not particularly limited, and known polyolefins can be used. Examples of the polyolefin include polyethylene, polypropylene, polybutene and mixtures thereof. These polyolefins can be used alone or in admixture of two or more. As the polyolefin, polyethylene, polypropylene, or a mixture of polyethylene and polypropylene is preferable because the closed cell ratio can be easily adjusted and the true density is usually 1.0 g / cm ^{3 or less and the density can be easily adjusted.}
Further, as polyethylene and polypropylene, the melt fracture described later can roughen the surface of the microbial carrier (strand) to increase the surface area, generate a large number of pores, and reduce the closed cell ratio. Therefore, ASTM can be used. The melt flow rate (MFR) measured at 230 ° C. and 2.16 kg load according to D1238 is preferably 0.1 to 10 (g / 10 min), preferably 0.3 to 5.0 (g / 10 min). 10 minutes) is more preferable, and 0.4 to 3.0 (g / 10 minutes) is further preferable.

(Thermoplastic resin)
The microbial carrier of the present embodiment contains a thermoplastic resin that is incompatible with polyolefin in order to generate fine cracks that promote the penetration of the carrier into treated water or the like. By generating fine cracks using a thermoplastic resin, it becomes possible to support more microorganisms, and the treated water etc. can come into contact with many microorganisms, so that the treated water etc. is treated early from the time when the carrier is added. It becomes possible to do. Therefore, according to the microbial carrier of the present embodiment, the treatment efficiency can be improved as compared with the conventional carrier. Further, in general, in a fluidized bed type wastewater treatment apparatus, a screen or a mesh-like separation means is provided at the outlet of the treatment tank to separate the carrier from the treated water or the like flowing out from the treatment tank, and the microbial carrier from the treatment tank. Is prevented from leaking. The microbial carrier may clog the opening of the separating means such as a screen and collide with the wall surface of the treatment tank, and must withstand a physical impact. Considering this point, polystyrene, polyester, polyamide and the like are preferable as the thermoplastic resin, and since they are highly versatile, have a low melting temperature and are easy to mold, cracks can be more preferably generated. , Polystyrene is more preferred. These thermoplastic resins can be used alone or in admixture of two or more.

The content of the thermoplastic resin is 100 mass in total of the polyolefin and the thermoplastic resin from the viewpoint that fine cracks that help the permeation of gas and treated water can be suitably obtained at the interface formed by the thermoplastic resin and the polyolefin. It is contained in an amount of 12% by mass or more based on%. On the other hand, from the viewpoint of maintaining high strength of the microbial carrier and suppressing cracking and chipping during production and use, the content of the thermoplastic resin is 100% by mass of the total of the polyolefin and the thermoplastic resin. , 30% by mass or less. If it exceeds 30% by mass, the carrier becomes physically brittle and may crack or chip during use. The content of the thermoplastic resin is 14 to 20% by mass from the viewpoint of the balance between the interface between the resins and the formation of cracks and the strength of the carrier with respect to 100% by mass of the total of the polyolefin and the thermoplastic resin. Is preferable, and it is more preferable that it is contained in an amount of 16 to 18% by mass.

(Filler)
In the microbial carrier of the present embodiment, the microbial carrier can be easily submerged in a liquid or suspended, and the density of the microbial carrier with respect to treated water or the like (hereinafter, "microorganisms with respect to treated water or the like"). Since the "carrier density") can be controlled, it is preferable to further contain a filler, and it is more preferable to include a powdery filler having a true specific gravity of more than 1. In the present embodiment, when the treated water permeates the microbial carrier and the density of the microbial carrier with respect to the treated water becomes close to the density of the treated water, it is likely to be suspended in the treated water, and the density of the microbial carrier with respect to the treated water or the like is the treated water. If the density is higher than the density, it tends to settle. The density of the microbial carrier with respect to the treated water or the like can be controlled by the type and ratio of the filler compounded in the microbial carrier. Examples of the filler include an organic filler and an inorganic filler, and known fillers can be used. Examples of the filler include talc, calcium carbonate, silica, activated carbon, wood flour, incineration ash, and paper sludge incineration ash. These fillers may be used alone or in admixture of two or more.

In the present embodiment, it is preferable to use a powdery filler such as talc, calcium carbonate, or silica in order to adjust the specific gravity of the microbial carrier or use it as a nucleating agent for foaming. Further, these fillers are preferable because they are contained in the microbial carrier and have effects such as improvement of affinity with microorganisms, supply source of micronutrients for microorganisms, and cost reduction.

The filler is preferably contained in an amount of 5 to 50% by mass in 100% by mass of the microbial carrier of the present embodiment because the density of the microbial carrier with respect to treated water or the like can be easily controlled, and the strength of the carrier and the foaming control can be controlled. From the viewpoint of further enabling, it is more preferably contained in an amount of 10 to 40% by mass, and further preferably contained in an amount of 12 to 35% by mass.

(Surfactant)
Since the microbial carrier of the present embodiment can better impart affinity to treated water and the like and water wettability to the microbial carrier, it can further contain a surfactant depending on the application. The wettability of treated water or the like on the surface of a microbial carrier is involved in the affinity with microorganisms and the floating phenomenon of the carrier on the water surface, and by enhancing the wettability, the non-closed cells that pass through the surface of the microbial carrier are treated. It is possible to promote the invasion of water and the like. The surfactant can be appropriately selected depending on the use of the microbial carrier, and known ones can be used. For example, as nonionic surfactants, glycerin fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, X, X'-bis (2-hydroxyethyl) alkylamine [alkyldiethanolamine], y-2. -Hydroxyethyl-y-2-hydroxyalkylamine [hydroxyalkylmonoethanolamine], polyoxyethylenealkylamine, polyoxyethylenealkylamine fatty acid ester, alkyldiethanol amide; alkylsulfonate, alkylbenzene as anionic surfactants Sulfates, alkyl phosphates; cationic surfactants include tetraalkylammonium salts, trialkylbenzylammonium salts; and amphoteric surfactants include alkylbetaines, alkylimidazolium betaines and the like. Among these, from the viewpoint of environmental load and workability, it is preferable to use a nonionic surfactant, and it is more preferable to use a glycerin fatty acid ester and a polyoxyethylene alkyl ether.

The surfactant is preferably contained in an amount of 0.1 to 5% by mass in 100% by mass of the microbial carrier of the present embodiment because it has a good affinity with microorganisms.

(Other ingredients)
The microbial carrier of the present embodiment is, as long as the characteristics of the present embodiment are not impaired, various polymer compounds such as oligomers and elastomers not described above; flame-retardant compounds not described above; and additives. Other ingredients may be included. The other components are not particularly limited as long as they are generally used. For example, examples of the flame-retardant compound include nitrogen-containing compounds such as melamine and benzoguanamine, oxazine ring-containing compounds, phosphate compounds of phosphorus compounds, aromatic condensed phosphoric acid esters, halogen-containing condensed phosphoric acid esters, and the like. Be done. Additives include, for example, antistatic agents such as monostearate stearate, diethanolamine stearate, diethanolamide laurate, UV absorbers, antioxidants, optical brighteners, photosensitizers, dyes, pigments, augmentations. Examples thereof include thickeners, lubricants, antifoaming agents, surface conditioners, brighteners, polymerization inhibitors, heat curing accelerators and the like. Other components may be used alone or in admixture of two or more.
The content of other components in the microbial carrier of the present embodiment is not particularly limited, but is usually 0.01 to 10% by mass in 100% by mass of the microbial carrier of the present embodiment.

[Method for producing microbial carrier]
As a method for producing the microbial carrier of the present embodiment, for example, each of the above-mentioned components and, if necessary, a foaming agent are blended into, for example, an extruder, extruded, and rod-shaped, tubular, thread-shaped, or plate-shaped depending on the die shape. Examples thereof include a method of obtaining a carrier by cutting an extruded foamed strand into a predetermined size. Alternatively, the foamed strand may be submerged in a water tank, cooled and solidified while taking up the foamed strand at a predetermined speed, and then cut to a predetermined length to obtain a microbial carrier. In the present embodiment, by controlling the MFR of the polyolefin, the blending amount of the thermoplastic resin, the take-up speed of the foamed strand, the amount of the foaming agent, and the die pressure and temperature of the extruder, the bubble ratio, the closed cell ratio and the bubble ratio can be controlled. You can control the size. The foaming rate is increased by increasing the amount of the foaming agent. In addition, the swell ratio of bubbles can be increased by increasing the die pressure and increasing the linear velocity from the die hole.

Further, the air bubble ratio and the air permeability can be increased by stretching the foamed strand at the stage of cooling and solidifying. For example, if the winding speed is increased after the molten resin is discharged from the extruder die and before it is solidified in water, the bubbles inside can be deformed longer in the stretching direction. As a result, bubbles that continue to the inside can be generated from the fracture surface of the microbial carrier cut by the cutter. As a result, the bubble ratio and the air permeability are increased, the infiltration of treated water and the like during water treatment can be facilitated, and the liquid can be easily submerged or suspended. It is possible to improve the treatment efficiency for treated water and contaminants.

Further, by bending the strand obtained by solidifying the foamed strand, fine cracks are generated from the side surface of the strand toward the inside, and the closed cell ratio can be lowered. For example, there is a method in which a plurality of freely rotating guide rollers are combined and sandwiched so that the strands are bent in an S shape and pulled up while the strands are pulled up to the cutter. As a result, the closed cells inside are ruptured, and the generated craze allows air to pass through to the side surface of the strand instead of the fracture surface by the cutter. In the microbial carrier of the present embodiment, since a predetermined amount of a thermoplastic resin that is incompatible with the polyolefin is blended with the polyolefin, craze can be generated more efficiently. Therefore, the closed cell ratio is lowered, the infiltration of treated water or the like during water treatment can be facilitated, and the treated water or the like can be easily submerged in the liquid or suspended, and the treated water or contamination. It is possible to improve the processing efficiency for objects.

Further, the surface state of the strand can be controlled by adjusting the composition of the material, the resin temperature (MFR of polyolefin), the die pressure and the temperature. In the present embodiment, it is preferable that the so-called melt fracture roughens the surface to increase the surface area and generate a large number of pores to reduce the closed cell ratio. By reducing the closed cell ratio, it is possible to easily infiltrate the treated water or the like during the treatment, and it is possible to quickly adapt to the treated water or the like, so that the treatment efficiency can be improved. In the present embodiment, the melt fracture refers to a phenomenon in which the surface of the microbial carrier undulates when the shear stress at the outlet of the molded product exceeds the critical value during molding of the microbial carrier. The melt fracture can be preferably generated by using polypropylene and / or polyethylene having a relatively low MFR value as a main raw material and lowering the resin temperature of polypropylene and / or polyethylene.

As the foaming agent, known ones used for foaming plastic can be used, and the foaming agent is not particularly limited. Examples of the foaming agent include water, a chemical foaming agent such as azodicarbonamide, a liquefied gas foaming agent, a gas foaming agent, and grain flour such as wheat flour. These foaming agents may be used alone or in admixture of two or more.

Further, at the time of producing the microbial carrier, a known treatment (stirring, mixing, kneading treatment, etc.) for uniformly dissolving or dispersing each component can be performed, if necessary. Specifically, for example, the dispersibility of the filler can be improved by performing the stirring and dispersing treatment using a stirring tank equipped with a stirring machine having an appropriate stirring ability. The stirring, mixing, and kneading treatment may be performed on, for example, a stirring device for dispersing an ultrasonic homogenizer, a device for mixing three rolls, a ball mill, a bead mill, a sand mill, or a revolution or rotation type. It can be appropriately performed using a known device such as a mixing device.

[How to use microbial carrier]
The microbial carrier of the present embodiment is preferably used in various fluidized bed type wastewater treatment devices. In use, it is usually high to fill 100% by mass of the microbial carrier with 100% by mass of treated water or the like so as to have a bulk volume of usually 5 to 50% per aqueous phase volume of the treatment tank. It is preferable because it exhibits wastewater treatment efficiency.

Further, in the present embodiment, the microbial carrier can be used in either a water-floating carrier or a water-sedimentable carrier, depending on the characteristics of the system of the fluidized bed type wastewater treatment device used. In any case, it is preferable that the specific gravity of the microbial carrier when the specific gravity reaches a certain value in water is close to the specific gravity of water. When the specific gravity of the microbial carrier is close to the specific gravity of water, a uniform flow distribution of the microbial carrier can be obtained in the wastewater treatment tank. In the present embodiment, the apparent specific gravity of the carrier that has absorbed water after the specific gravity is stabilized in water is preferably in the range of 0.90 to 1.50.

(Use of microbial carrier)
The microbial carrier of the present embodiment is suitable for, for example, wastewater treatment of factories and the like; circulating water treatment of aquariums and onshore farms; waste food treatment and waste liquid treatment of waste food discharged from food factories, hotels, restaurants and office kitchens. is there.

When the microbial carrier of the present embodiment is used for wastewater treatment in a factory or the like, it is suspended in a wastewater aeration tank, so that the apparent specific gravity of the absorbed carrier after the specific gravity stabilizes in water is 0.95 to 1.05. Those in the range of are preferable.

When the microbial carrier of the present embodiment is used for circulating water treatment, it is used by submerging it in a treatment pool, so that the apparent specific gravity of the absorbed carrier after the specific gravity stabilizes in water is in the range of 1.10 to 1.50. preferable.

When the microbial carrier of the present embodiment is used for waste food treatment, it is used by mixing with the waste food, so that the apparent specific gravity of the absorbed carrier after the specific gravity is stabilized in water is in the range of 0.90 to 1.50. Is preferable.

Examples and comparative examples are shown below, and the present invention will be described in detail, but the present invention is not limited to these examples.

〔Evaluation method〕
[1] Bubble ratio (%)
The bubble ratio was calculated by the following method.
(1) The microbial carrier having a substantially cylindrical shape obtained in Examples or Comparative Examples is dried with hot air (90 ° C., about 3 hours), re-granulated with a small extruder, degassed, and then degassed. By press molding (10 MPa) of 2 g at 230 ° C., a disk-shaped sample (thickness 2 mm, diameter: 30 mm) containing no air bubbles was prepared. The density of this disk-shaped sample was measured by the Archimedes method using pure water at 23 ° C. (density: 1.0 g / cm ³ ), and the "true density" of the material constituting the microbial carrier was ρ _A (g / cm). ³ ).
(2) The microbial carrier having a substantially cylindrical shape obtained in Examples or Comparative Examples was dried with hot air (90 ° C., about 3 hours) and cooled to room temperature. Then, using pure water (density: 1.0 g / cm ³ ) at 23 ° C., the “apparent density” of 5 g of the microbial carrier was measured by the Archimedes method to obtain ρ _B (g / cm ³ ).
(3) The microbial carrier having a substantially cylindrical shape obtained in Examples or Comparative Examples was dried with hot air (90 ° C., about 3 hours) and cooled to room temperature. Then, the eggplant-shaped flask equipped with the three-way cock was filled with the microbial carrier, and the pressure was reduced from one of the three-way cocks to 100 Pa or less with a vacuum pump, and the flask was held in that state for 5 minutes. The cock was closed and pure water (density: 1.0 g / cm ³ ) at 23 ° C. was guided into the flask from the other side, and the microbial carrier was completely submerged. Then, the microbial carrier was promptly taken out from the water, and the "water injection density" of 5 g of the microbial carrier was determined from the mass of the microbial carrier injected with water by the Archimedes method and the excluded volume when the microbial carrier was immersed in water. It was calculated and used as ρ _C (g / cm ³ ).
(4) The above operations (1) to (3) are repeated 5 times, and the average values of ρ _A , ρ _B and ρ _{C are ρ AA} (average true density), ρ _BB (average apparent density) and ρ _CC (respectively). Average water injection density) was calculated.
(5) From ρ _AA and ρ _BB , the bubble ratio was calculated by the following formula (iii).
Bubble ratio = (1-ρ _BB / ρ _AA ) x 100 ... (iii)

[2] Closed cell ratio (%)
_{From ρ AA} , ρ _BB and ρ _CC obtained by the bubble ratio of [1] above, the closed cell ratio was calculated by the following formula (iv).
Closed cell ratio = (1-ρ _AA (ρ _{CC −ρ BB} ) / (ρ _AA −ρ _BB )) × 100 ・ ・ ・ (iv)

[3] Air permeability (mL / mm ² · sec)
The air transmittance was calculated by the following method using the microbial carrier having a substantially cylindrical shape obtained in Examples or Comparative Examples.
(1) A rubber tube for pressure-resistant vacuum (manufactured by Alam Co., Ltd.) was attached to the vacuum pump. On the other hand, a two-component epoxy adhesive (manufactured by Araldite) was applied to the side surfaces of the microbial carrier having a substantially cylindrical shape obtained in Examples or Comparative Examples and cured. The microbial carrier is placed in the pressure-resistant vacuum rubber tube from the side where the vacuum pump of the pressure-resistant vacuum rubber tube after curing the epoxy adhesive is not mounted, so that the side surface thereof is in contact with the inner wall surface of the pressure-resistant vacuum rubber tube. Inserted in. The epoxy adhesive was used to prevent air from being sucked from the gap between the pressure-resistant vacuum rubber tube and the microbial carrier.
(2) Fill a PVDF (polyvinylidene fluoride) bag with a cock (20 liter bag manufactured by Tedler) with 16 liters of air to cover the side of the pressure-resistant vacuum rubber tube that is not attached to the vacuum pump and the microbial carrier. A PVDF bag with a cock was attached so that air would not leak to the outside.
(3) The time t (seconds) from the time when the air started to flow after the vacuum pump was started to the time when the entire amount of 16 liters of air was exhausted was measured. The degree of vacuum was 1000 Pa or less.
(4) Using the time t (seconds), the air transmittance was calculated by the following equation (v).
Air transmittance = 16 liters / (carrier cross-sectional area (mm ² ) x exhaust time t (seconds) ... (v)

[4] BOD removal rate (%) in treated water
The BOD removal rate in the treated water was calculated by the following method.
(1) Microorganisms for water treatment and microbial carriers having a substantially cylindrical shape obtained in Examples and Comparative Examples were placed in a habitat tank (20 liters). After 1 month of acclimation, the activated sludge was disposed of and a 3 liter fluidized tank was filled with a microbial carrier (0.4 liters).
(2) The fluid tank was filled with experimental treated water (2 liters) having a BOD of 500 mg / liter prepared from actual wastewater from a food factory.
(3) Air was blown into the fluidized bed at a flow rate of 10 liters / minute for 24 hours.
(4) The BOD in the treated water after 24 hours was measured, and the BOD removal rate was calculated by (100% − ([BOD concentration after 24 hours] ÷ [BOD concentration at the time of charging])).

(Example 1)
Polypropylene (Homopolypropylene manufactured by Sun Aroma Co., Ltd., MFR: 0.5 (g / 10 minutes)) 100 parts by mass, polystyrene (Homopolystyrene manufactured by PS Japan Co., Ltd.) 20 parts by mass, and antistatic agent (Kao Co., Ltd.) ) 0.8 parts by mass of polystyrene stearate) and 20 parts by mass of calcium carbonate (manufactured by Shiraishi Kogyo Co., Ltd.) mixed 1.4 parts by mass of azodicarboxylic amide as a foaming agent with a 40 mmφ vent. A foamed strand was obtained by extruding from a strand die having four holes of 3 mmφ with a full flight screw extruder. Submerged The foamed strands in a water bath, while drawing the foamed strands take-off speed is at 50 cm / sec, was cooled and solidified, 5mm diameter with a cutter (cross-sectional area: 19.6 mm ^2), was cut into a substantially cylindrical height 5mm A microbial carrier having a substantially cylindrical shape was obtained.

When measured according to the evaluation method of the bubble ratio, the average true density was 1.03 g / cm ³ , the average apparent density was 0.61 g / cm ³ , and the average water injection density was 1.01 g / cm ³ . there were. When the bubble ratio and the closed cell ratio were calculated using these values, they were 41% and 4%, respectively. Further, when measured according to the above-mentioned evaluation method of air transmittance, the air transmittance was 0.81 mL / mm ² · sec.

A water treatment experiment was carried out using the obtained microbial carrier. When the microorganism for water treatment and the obtained microbial carrier were placed in a habitat tank (20 liters), a stable suspension state was obtained in 76 hours. One month after acclimatization, the BOD removal rate was measured according to the method for evaluating the BOD removal rate in the treated water, and it was 80%. The results are shown in Table 1. In Table 1, "PO", "PP", "PS" and "PE" are abbreviations for polyolefin, polypropylene, polystyrene and polyethylene, respectively.

(Example 2)
100 parts by mass of polypropylene (homopolypropylene manufactured by Sun Aroma Co., Ltd., MFR: 0.5 (g / 10 minutes)), 20 parts by mass of polystyrene (homopolystyrene manufactured by PS Japan Co., Ltd.), and calcium carbonate (Shiraishi Kogyo Co., Ltd.) ) Manufactured by) Mixing 2.0 parts by mass of azodicarbonamide as a foaming agent with 69 parts by mass and extruding it from a strand die having 4 holes of 3 mmφ with a full flight screw extruder with a 40 mmφ vent to produce foamed strands. Obtained. Submerged The foamed strands in a water bath, while drawing the foamed strands take-off speed is at 50 cm / sec, was cooled and solidified, 5mm diameter with a cutter (cross-sectional area: 19.6 mm ^2), was cut into a substantially cylindrical height 5mm A microbial carrier having a substantially cylindrical shape was obtained.

When the bubble ratio, closed cell ratio and air permeability were calculated using the obtained microbial carrier according to the above evaluation method, they were 25%, 6% and 0.80 mL / mm ² · sec, respectively. ..

Moreover, when the BOD removal rate was measured using the obtained microbial carrier in the same manner as in Example 1, it was 72%. The results are shown in Table 1.

(Example 3)
The microbial carrier was carried out in the same manner as in Example 1 except that the amount of azodicarbonamide added as a foaming agent was changed from 1.4 parts by mass to 2.0 parts by mass and the take-up rate of the foamed strands was increased 1.3 times. Manufactured. The results are shown in Table 1.

(Example 4)
Instead of polypropylene (homopolypropylene manufactured by SunAllomer Ltd.), polypropylene (PL500A (trade name) manufactured by SunAllomer Ltd., MFR: 5.0 (g / 10 minutes)) was used, and the take-up speed of the foamed strand was set to 0. A microbial carrier was produced in the same manner as in Example 1 except that it was lowered by 8 times. The results are shown in Table 1.

(Example 5)
The strands obtained by solidifying the foamed strands were passed through three rollers (diameter 60 mm) adjacent to each other in parallel with the picking direction in a meandering manner in an alternating manner to be deformed into an S shape. Then, it was cut with a cutter to a diameter of 5 mm (cross-sectional area: 19.6 mm ² ) and a substantially cylindrical height of 5 mm to obtain a microbial carrier having a substantially cylindrical shape. For this microbial carrier, the bubble ratio, closed cell ratio, air permeability and BOD removal rate were calculated in the same manner as in Example 1. The results are shown in Table 1.

(Example 6)
Instead of polypropylene (homopolypropylene manufactured by SunAllomer Ltd.), polypropylene (PB170A (trade name) manufactured by SunAllomer Ltd., MFR: 0.3 (g / 10 minutes)) was used, and the take-up speed of the foamed strand was set to 0. A microbial carrier was produced in the same manner as in Example 1 except that the temperature was lowered by 8 times and the resin temperature was lowered by 10 ° C. The results are shown in Table 1.

(Example 7)
A microbial carrier was produced in the same manner as in Example 6 except that the take-up rate of the foamed strand was reduced 0.7 times. The results are shown in Table 1.

(Example 8)
A microbial carrier was produced in the same manner as in Example 6 except that the take-up rate of the foamed strand was increased 1.2 times. The results are shown in Table 1.

(Examples 9 to 12)
Microbial carriers were produced in the same manner as in Example 1 except that the height of the cylinder was changed by changing the rotation speed of the cutter blade. The results are shown in Table 1.

(Example 13)
Instead of 100 parts by mass of polypropylene (homopolypropylene manufactured by SunAllomer Ltd.), 100 parts by mass of polyethylene (Novatec (registered trademark) UE320 (trade name) manufactured by Japan Polyethylene Corporation, MFR: 1.0 (g / 10 minutes)) A microbial carrier was produced in the same manner as in Example 1 except that the portion was used. The results are shown in Table 1.

(Example 14)
Instead of polyethylene (Novatec (registered trademark) UE320 (trade name) manufactured by Japan Polyethylene Corporation), polyethylene (LF640MA (trade name) manufactured by Japan Polyethylene Corporation, MFR: 5.0 (g / 10 minutes)) A microbial carrier was produced in the same manner as in Example 13 except that the take-up rate of the foamed strand was reduced to 0.8 times. The results are shown in Table 1.

(Example 15)
Instead of 100 parts by mass of polypropylene (Homopolypropylene manufactured by SunAllomer Ltd.), 50 parts by mass of polypropylene (Homopolypropylene manufactured by SunAllomer Ltd., MFR: 0.5 (g / 10 minutes)) and polyethylene (Novatec manufactured by Nippon Polyethylene Co., Ltd.) A microbial carrier was produced in the same manner as in Example 1 except that 50 parts by mass of UE320 (trade name), MFR: 1.0 (g / 10 minutes)) was used. The results are shown in Table 1.

(Example 16)
Taking over foamed strands using polyethylene (LF640MA manufactured by Japan Polyethylene Corporation, MFR: 5.0 (g / 10 minutes)) instead of polyethylene (Novatec (registered trademark) UE320 (trade name) manufactured by Japan Polyethylene Corporation) A microbial carrier was produced in the same manner as in Example 15 except that the rate was reduced 0.8 times. The results are shown in Table 1.

(Example 17)
Polystyrene (PS Japan Corporation) uses 104 parts by mass of polypropylene (Homopolypropylene manufactured by SunAroma Co., Ltd., MFR: 0.5 (g / 10 minutes)) instead of 100 parts by mass of polypropylene (Homopolypropylene manufactured by Sun Aroma Co., Ltd.). A microbial carrier was produced in the same manner as in Example 1 except that polystyrene (polystyrene manufactured by PS Japan Corporation) was used in place of 20 parts by mass. The results are shown in Table 1.

(Example 18)
Instead of 20 parts by mass of polystyrene (homopolystyrene manufactured by PS Japan Corporation), 18 parts by mass of polystyrene (homopolystyrene manufactured by PS Japan Corporation) is used, and 20 parts by mass of calcium carbonate (manufactured by Shiraishi Kogyo Co., Ltd.) Instead, a microbial carrier was produced in the same manner as in Example 1 except that 19 parts by mass of talc (L1K (trade name) manufactured by Nippon Tarku Co., Ltd.) was used. The results are shown in Table 1.

(Example 19)
Calcium carbonate (manufactured by Shiraishi Kogyo Co., Ltd.) 20 parts by mass is not used, and instead of 0.8 parts by mass of antistatic agent (monostearate stearic acid manufactured by Kao Co., Ltd.), an antistatic agent (Kao Co., Ltd.) ) Stearic acid monostearate) 0.7 parts by mass was used, and 1.2 parts by mass of azodicarbonamide was used as the foaming agent instead of 1.4 parts by mass of azodicarbonamide as the foaming agent. A microbial carrier was produced in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
A microbial carrier was produced in the same manner as in Example 1 except that 0.7 parts by mass of azodicarbonamide was used as the foaming agent instead of 1.4 parts by mass of azodicarbonamide. The results are shown in Table 1.

(Comparative Example 2)
Using a microbial carrier (Bioreactor (trade name) manufactured by Denka Engineering Co., Ltd.), the bubble ratio, closed cell ratio and air permeability were calculated according to the above evaluation method. The results are shown in Table 1.

(Comparative Example 3)
Except that 120 parts by mass of polypropylene (homopolypropylene manufactured by SunAllomer Ltd.) was used instead of 100 parts by mass of polypropylene (homopolypropylene manufactured by SunAllomer Ltd.) and 20 parts by mass of polystyrene (homopolystyrene manufactured by PS Japan Corporation) was not used. Produced a microbial carrier in the same manner as in Example 1. The results are shown in Table 1.

Claims (1)

A microbial carrier containing a polyolefin, polystyrene that is incompatible with the polyolefin, and an inorganic filler.
The polyolefin comprises polyethylene, polypropylene, or a mixture thereof.
The inorganic filler contains calcium carbonate and
The content of the polystyrene, the total 100 wt% of the polyolefin and the polystyrene, or less 16 wt% to 18 wt%,
The bubble ratio represented by the following formula (i) is 25% or more, and
A microbial carrier having a closed cell ratio of 20% or less represented by the following formula (ii).
Bubble ratio = (1-ρ _B / ρ _A ) × 100 ... (i)
(In formula (i), ρ _A indicates the true density (g / cm ³ ) of the material constituting the microbial carrier, and ρ _B indicates the apparent density (g / cm ³ ) of the microbial carrier).
Closed cell ratio = (1-ρ _A (ρ _C − ρ _B ) / (ρ _A − ρ _B )) × 100 ・ ・ ・ (ii)
(In formula (ii), ρ _A indicates the true density (g / cm ³ ) of _{the material constituting the microbial carrier, ρ B} indicates the apparent density of the microbial carrier (g / cm ³ ), and ρ _C is the Archimedes method. The water injection density (g / cm ³ ) derived from is shown.).