JP6685588B2 - Microbial carrier - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a microbial carrier that is excellent in sedimentation properties in water and anaerobic microbial adherence and that can prevent the adhered microbials from falling off.

  Conventionally, water treatment for wastewater and the like includes anaerobic treatment in which dissolved organic matter is decomposed by the action of anaerobic microorganisms. In the anaerobic treatment, the anaerobic microorganisms adhering to the microbial carrier are introduced by introducing or filling the reaction tank (anaerobic filter bed) in the sewage purification tank with a fluid microbial carrier to pass sewage (organic wastewater). Is used to decompose dissolved organic matter in wastewater (Patent Documents 1 and 2).

In anaerobic treatment, microorganisms work in an anaerobic atmosphere, so the fluid microbial carrier that is put into the reaction tank, etc. quickly settles in the water and does not float on the water surface for a long time. Becomes In particular, when performing high-speed treatment by upwardly circulating organic wastewater, it is required to have high water sedimentation property.
As a microbial carrier for anaerobic treatment with improved water sedimentation, an olefin resin foam containing an olefin resin and a cellulose powder, or an olefin resin foam containing an inorganic powder, Some of them have a melt fracture state on their surfaces (Patent Documents 2 and 3).

  However, an olefinic resin foam containing an olefinic resin and a cellulose powder, or an olefinic resin foam containing an inorganic powder, and a microbial carrier having a melt fracture state on the surface of the foam is a foaming agent. Although the surface irregularities are developed by using it, since it is a hollow state in the foam, the water settling property is still not good, the water treatment capacity is not sufficient, and the contained wood powder etc. Since the cellulosic powder makes the microbial carrier itself brittle, when used in water for a long time, fragments of the microbial carrier flow out into the water, resulting in water contamination. Further, there is a problem that the gas generated from the microorganisms is accumulated inside the cells of the foam of the microbial carrier to increase the buoyancy and reduce the water settling property.

In addition, the cylindrical outer peripheral surface made of a non-porous body containing a polyolefin resin and an inorganic powder is made into a corrugated irregular shape in which a large diameter portion and a small diameter portion are alternately present, so that microorganisms can be attached and retained in the concave portion. There is a microbial carrier (Patent Document 4).
However, the column-shaped microbial carrier with corrugated irregularities in which the large-diameter portion and the small-diameter portion are alternately present is a microorganism attached to the surface of the microbial carrier when the microbial carriers collide with each other during the treatment of wastewater and the like. May fall off, in which case the wastewater treatment performance cannot be fully exerted.

JP 2001-211881 A JP, 2012-110843, A JP, 2009-66592, A JP, 2014-73476, A

  The present invention has been made in view of the above points, and an object of the present invention is to provide a microbial carrier for anaerobic treatment, which is excellent in water-sedimentability and water-treating ability by attached anaerobic microorganisms, and microorganisms are difficult to drop off. .

The invention of claim 1 is a microbial carrier that holds anaerobic microorganisms on its surface, wherein the microbial carrier includes a polyolefin resin, an incompatible resin that is a resin different from the polyolefin resin, and an inorganic powder. made from the true specific gravity (JIS Z 8807 compliant) large nonporous material of the resin than 1, the cross-sectional shape a solid body having the shape of three or more projections in the cross-sectional circumferential direction is formed, the cross-sectional circumferential direction The base portions of the protrusions adjacent to each other are in contact with each other to form a valley portion between the surfaces of the protrusions, and the surface of the protrusion has an uneven shape.

The invention according to claim 2 is the incompatible resin according to claim 1, which is one type of acrylic resin (polymethyl methacrylate: PMMA), polycarbonate resin, ABS resin, polyvinyl chloride resin, polyethylene terephthalate resin, polyurethane resin. Alternatively, there are a plurality of types .

  According to a third aspect of the present invention, in the first or second aspect, the cross-sectional shape is a cross shape.

The microbial carrier of the present invention contains a polyolefin resin, an incompatible resin that is a resin different from the polyolefin resin, and an inorganic powder, and has a true specific gravity (JIS Z 8807 compliant) of greater than 1. Since it is made of the above resin, it can be quickly settled when it is put into drainage or the like, and the sewage treatment by the anaerobic microorganisms attached to the microorganism carrier can be efficiently performed.

  The microbial carrier of the present invention has a cross-sectional shape in which three or more projections are formed in the circumferential direction of the cross section, and the surface of each adjacent projection centered on the base between the projections adjacent in the circumferential direction of the cross section. A so-called valley is formed between the (slope). Therefore, the surface area is increased, the amount of anaerobic microorganisms attached can be increased, and the treatment capacity by the anaerobic microorganisms can be enhanced. Furthermore, the microbial carrier of the present invention, when the microbial carriers collide with each other during sewage treatment, as for the base between adjacent protrusions in the circumferential direction of the cross section, which is a recessed position, there is a so-called valley between the protrusions, Since it is difficult to contact with other microbial carriers, the anaerobic microorganisms attached to the bases of the protrusions are less likely to drop off, and good sewage treatment performance by the anaerobic microorganisms can be maintained.

  Further, in the microbial carrier of the present invention, by providing an uneven shape on the surface of the microbial carrier, it is possible to more reliably hold the anaerobic microorganisms attached to the recesses on the surface, and maintain good treatment performance by the anaerobic microorganisms. It becomes possible to do.

It is a perspective view of the microorganisms carrier concerning a 1st embodiment of the present invention. FIG. 6 is a perspective view of a microbial carrier according to a second embodiment of the present invention showing a case where the shape of a protrusion is triangular. It is a perspective view of the microorganism carrier concerning the 3rd embodiment of the present invention which has unevenness on the surface. 1 is a schematic view of an apparatus for producing a microbial carrier of the present invention. 3 is a photograph of the outer side surface of the extruded body of Example 1 and the extruded body of Example 2.

  Hereinafter, the microorganism carrier according to the embodiment of the present invention will be described. The microbial carrier 10 of the first embodiment shown in FIG. 1 is used for anaerobic treatment of wastewater and the like, contains a polyolefin resin and inorganic powder, and has a true specific gravity (JIS Z 8807 compliant) of greater than 1. It is made of a non-porous body (non-foamed body) and has a cross-sectional shape perpendicular to the length direction in which three or more projections are formed in the circumferential direction of the cross-section (multi-projection shape in cross section). The microbial carrier 10 is obtained by cutting an extruded body having a cross section perpendicular to the length direction, which has a shape in which three or more protrusions are formed in the circumferential direction of the cross section, to a predetermined length. The length direction of the microbial carrier 10 corresponds to the extrusion direction extruded from the extruder at the time of manufacturing the microbial carrier.

  In the microbial carrier 10 of the first embodiment, a central portion 11 and three or more protrusions (four protrusions forming a cross in the illustrated example) 12 formed in a circumferential direction of a cross section perpendicular to the length direction thereof, Consists of. The protrusion 12 has a quadrangle such as a square or a rectangle in cross section in the first embodiment. The outer dimension (dimension between tips of the protrusions 12) a and the depth length b of the microorganism carrier 10 are each in the range of 1 mm to 20 mm, and more preferably about 4 to 8 mm. The protrusion 12 of the microorganism carrier 10 has a length c of the protrusion 12 in the range of 0.1 mm to 8.5 mm, more preferably 2 to 4 mm, and a width d of the protrusion 12 at the base of 0.1 mm. It is in the range of -19 mm, more preferably about 1-3 mm.

Further, the number of the projections 12 in the circumferential direction of the cross section is 3 or more (4 in the illustrated example, which form a cross shape), more preferably 3 to 8, and even more preferably 4 to 6. is there. As shown in the measurement results of Examples described later, by setting the number of the protrusions 12 in the circumferential direction of the cross section to 3 to 8, the weight of the initially attached sludge can be increased to 9.5 g or more, and the weight of the attached sludge after stirring is increased. It can be 7.3 g or more, and the sludge adhesion reduction rate can be 34.5% or less.
Further, by setting the number of the projections 12 in the circumferential direction of the cross section to 4 to 6, the amount of sludge weight loss after the evaluation test of the weight of adhered sludge after stirring (difference: weight of sludge dropout) is 1.3 to 2.2 g. It can be reduced, and the sludge adhesion reduction rate can be reduced to 7.8 to 23.2%.
If the number of the projections 12 in the circumferential direction of the cross section is less than three, the surface area increases, but an effective valley cannot be formed, and the reduction rate of sludge adhesion to the base increases. When the number is more than 8, the valley space becomes rather narrow, and the weight of the initially attached sludge attached to the base portion decreases.

  The sectional shape of the protrusion 12 is not limited to a quadrangle, and may be a triangle. FIG. 2 shows a microbial carrier 10A of the second embodiment in which the protrusion 12A has a triangular shape. The dimensions of the triangular protrusion 12 a are the same as the dimensions of the quadrangular protrusion 12. In the microbial carrier 10A of the second embodiment, reference numeral 11a is the central portion of the cross section of the microbial carrier 10A. Further, the number of the projections 12 in the circumferential direction of the cross section perpendicular to the length direction of the microorganism carrier 10A is 3 or more, and more preferably 4 forming a cross shape as in the illustrated example.

It is more preferable that the microbial carriers 10 and 10A have irregularities on the surface.
FIG. 3 shows a microbial carrier 10B of the third embodiment as an example having irregularities on the surface. In the microbial carrier 10B of the third embodiment, the projections 12b have a quadrangular shape, and the microbial carrier 10B has irregularities 13b on the surface thereof. Reference numeral 11b is a central portion. The unevenness 13b is an unevenness formed on the surface of the extrusion molded body when the extrusion molded body for the microorganism carrier 10B is extrusion-molded, and is also called a melt fracture.

  Examples of the polyolefin resin include polyethylene (PE) resin, polypropylene (PP) resin, ethylene-vinyl acetate copolymer (EVA) resin, polystyrene (PS) resin, and the like, which may be used alone or in two kinds. The above is used in combination. In particular, polyethylene resin is one of the polyolefin resins suitable for the present invention. The amount of the polyolefin resin is preferably 30 to 90% by mass, and particularly preferably 30 to 70% by mass in 100% by mass of the non-porous body. If it is less than 30% by mass, the binding force of the non-porous body becomes weak.

  Examples of the inorganic powder include calcium carbonate, barium sulfate, zeolite, talc, titanium oxide, potassium titanate, aluminum hydroxide and the like, and one kind or a combination of plural kinds thereof can be used. Calcium carbonate is particularly preferable. The inorganic powder has a function of increasing the specific gravity of the non-porous body forming the microbial carrier 10, 10A, 10B. The amount of the inorganic powder is preferably 10 to 70 parts by mass, and particularly preferably 30 to 50 parts by mass in 100 parts by mass of the non-porous body. If the amount of the inorganic powder is 10 to 70 parts by mass in 100 parts by mass of the non-porous body, the true specific gravity of the microbial carrier 10 should be a non-porous body (non-foamed body) of more than 1 and up to 1.6. And is suitable for anaerobic treatment. When it exceeds 70 parts by mass, the binding force becomes weak and the microbial carrier 10 is easily separated in water.

An incompatible resin is preferably added together with the polyethylene resin and the inorganic powder. The incompatible resin is preferably a resin different from the polyolefin resin and having a solubility parameter δ (SP value) of 1 to 5 (MJ / m ³ ) ^1/2 larger than that of the polyolefin resin. When the difference in SP value is less than 1 (MJ / m ³ ) ^1/2, they are easily compatibilized in a polyethylene (PE) resin and a polypropylene (PP) resin, and an effect of generating unevenness on the surface hardly occurs. When the difference in SP value is larger than 5 (MJ / m ³ ) ^1/2 , the strands are likely to be cut during extrusion molding and easily separated during long-term use as a microorganism carrier.

Examples of the incompatible resin include acrylic resin (polymethyl methacrylate: PMMA), polycarbonate resin, ABS resin, polyvinyl chloride resin, polyethylene terephthalate resin, polyurethane resin, and the like, and one or more of them may be used. Can be used in combination. In particular, acrylic resin, polycarbonate resin, and ABS resin have a larger SP value than polyethylene (PE) resin and polypropylene (PP) resin, and the difference is 1 to 5 (MJ / m ³ ) ^1/2. When it is mixed with a PE) resin or a polypropylene (PP) resin, it exceeds the critical shear stress on the inner wall surface of the die during extrusion molding and is likely to cause unevenness on the surface, which is preferable. The immiscible resin is an additive appropriately contained in the non-porous body, and by being contained in the non-porous body, it is possible to easily form irregularities on the surface. When the acrylic resin is contained in the non-porous body, it is preferably 1 to 20 mass% in 100 mass% of the non-porous body. If the amount is less than 1% by mass, the effect of the acrylic resin cannot be obtained. On the other hand, if the amount is more than 20% by mass, the content of the polyolefin-based resin becomes small and molding becomes difficult.

The solubility parameter δ (SP value) refers to the value of the repeating unit of the polymer at 25 ° C. determined by the method of Fedors. The method is described in RF Fedors, Polym. Eng. Sci., 14 (2), 147 (1974). That is, in the structural formula of the compound to be obtained, it is determined by the following formula from the data of the evaporation energy of atoms and atomic groups and the molar volume.
δ = (ΣΔei / ΣΔvi) ^1/2
However, in the formula, Δei and Δvi represent the evaporation energy and the molar volume of the atom or atomic group, respectively. The structural formula of the compound to be obtained is determined by using an ordinary structural analysis method such as IR, NMR, or mass spectrum.

  FIG. 4 is a schematic diagram of an apparatus for producing the microorganism carriers 10, 10A, 10B. The manufacturing apparatus 30 includes an extruder (single-screw or multi-screw extruder) 31, an underwater cooling tank 33, and a strand cutter (a take-up device and a cutting device) 35. The production of the microorganism carriers 10, 10A, 10B using the production apparatus 30 is performed as follows.

  First, the polyolefin-based resin, the inorganic powder, and the incompatible resin that is appropriately added are charged into the extruder 31 in the above proportions, melt-kneaded in the extruder 31, and non-porous in the gas phase from the extruder 31. In the quality state, the cross-sectional shape is extruded in the form of a strand having three or more protrusions in the circumferential direction of the cross-section perpendicular to the longitudinal direction, passed through the underwater cooling tank 33 to be cooled and hardened, and the strand is taken by the take-up device of the strand cutter The microbial carriers 10, 10A, 10B are obtained by taking them out and cutting them with a cutting device into a predetermined length. The die shape of the extruder is a cruciform with a quadrangular tip for the microbial carriers 10 and 10B, and a cruciform with a triangular tip for the microbial carrier 10A. The irregularities (melt fracture) 13b on the surface of the microorganism carrier 10B can be formed by setting the barrel set temperature of the extruder 31 to be lower than the normal temperature.

The following raw materials and the production apparatus 30 shown in FIG. 4 were used to produce Reference Example 1, Example 2, Example 3 and Example 4 shown in Table 1. In the reference example 1, like the microbial carrier 10 of the first embodiment, the shape of the four protrusions 12 forming a cross as a plurality of protrusions is a quadrangle, and there is no unevenness (melt fracture) on the surface. Is. Example 2 is an example in which, like the microbial carrier 10B of the third embodiment, the shape of the four protrusions 12b forming a cross as a plurality of protrusions is a quadrangle and the surface has irregularities (melt fracture) 13b. Is. Example 3 is an example in which three protrusions are provided as a plurality of protrusions, the protrusions are formed in a quadrangular shape, and unevenness (melt fracture) is formed on the surface. Example 4 is an example in which five protrusions are provided as a plurality of protrusions, the protrusions are formed in a quadrangular shape, and unevenness (melt fracture) is formed on the surface. The length of the microbial carrier of Reference Example 1, Example 2, Example 3 and Example 4 (cut length of strand) is 3 mm.

-Polyolefin resin: polyethylene resin, product name; Nipolon Hard 5700, MFR 1.0 (g / 10min), manufactured by Tosoh Corporation-Inorganic powder: calcium carbonate, product name: BF300, Bihoku Kogaku Co., Ltd.-Acrylic resin: product name: Acrypet VH-001, Mitsubishi Rayon Co., Ltd. polyolefin resin / inorganic powder / acrylic resin = 45 parts by mass / 50 parts by mass / 5 parts by mass

The extruder 31 is a product name; twin-screw extruder KTX30, manufactured by Kobe Steel. Extruder conditions are as follows: the die is Reference Example 1 and all of Examples 2 to 4 are holes for strand extrusion × 4, the barrel set temperature is 220 ° C. in Reference Example 1, 180 ° C. in Examples 2 to 4, and the discharge is performed. The amount is 60 kg / hour in each of Reference Example 1 and Examples 2 to 4, the extrusion speed is 10 m / min in each of Reference Example 1 and Examples 2 to 4, and the screw rotation speed is Reference Example 1 and Examples 2 to 4. 400 rpm, and the take-up speed is 11 m / min in each of Reference Example 1 and Examples 2 to 4. Regarding the size of the die for strand extrusion, the size of the die for Reference Example 1 and Example 2 in which four protrusions are provided in a cross shape is 6 mm for the die corresponding to FIG. Is 2 mm, and the dimension corresponding to d is 2 mm. Further, the die for Example 3 having three protrusions and the die for Example 4 having four protrusions have a different number of protrusions from FIG. The dimension is 6 mm, the dimension of the portion corresponding to c is 2 mm, and the dimension of the portion corresponding to d is 2 mm.

FIG. 5 is a photograph of the side portion of the extruded body 100 of Reference Example 1 and the extruded body 100A of Example 2 taken with the scale 110 before being cut by the strand cutter. The value “1” on the scale of the scale 110 is 1 cm (10 mm), and the value “2” is 2 cm (20 mm). The extrusion molded body 100 of Reference Example 1 has no unevenness (melt fracture) on the surface, while the extrusion molded body 100A of Example 2 has unevenness on the surface. The extruded bodies 100 and 110 are then cut into a length of 3 mm by the strand cutter to be the microbial carrier of Reference Example 1 and the microbial carrier of Example 2.

Further, as Comparative Example 1, a polyethylene hollow pipe having an outer diameter of 10 mm and an inner diameter of 8 mm was cut into a length of 10 mm to form a microorganism carrier.
As Comparative Examples 2 and 3, a microbial carrier was produced under the conditions of the extruder shown below, using the same raw material and the same production apparatus as those of Reference Example 1 and Examples 2 to 4. Comparative Example 2 is a columnar one having no irregularities (melt fracture) on the surface, and Comparative Example 3 is a columnar one having irregularities (melt fracture) on the surface.

  Extruder conditions for Comparative Examples 2 and 3 are as follows: the dies each have a diameter of 3 mm × 4 in Comparative Examples 2 and 3, the barrel set temperature is 220 ° C. in Comparative Example 2, 180 ° C. in Comparative Example 3, and the discharge amount is compared. In each of Examples 2 and 3, 60 kg / hour, in each case, the extrusion speed was 9 m / min in each of Comparative Examples 2 and 3, the screw rotation speed was 400 rpm in each of Comparative Examples 2 and 3, and the take-up speed was each in Comparative Examples 2 and 3. Is also 9 m / min. In addition, the length of the microbial carrier of Comparative Example 2 and Comparative Example 3 (length cut by a strand cutter) is 3 mm.

For the microbial carriers of Reference Example 1, Examples 2 to 4 and Comparative Examples 1 to 3, true specific gravity (JIS Z 8807 compliant), bulk specific gravity (JIS K 7365 compliant), volume filling rate (%), sedimentation property ( mm / s) and sludge adhesion reduction rate (%) were measured. In Comparative Example 1, no sedimentation occurred, and thus sedimentation properties could not be measured. The measurement results are shown in Table 1.

  The volume filling rate was calculated by the formula [volume filling rate = bulk specific gravity / true specific gravity]. The higher (larger) the volume filling rate is, the larger the contact area between the waste water (treatment liquid) and the carrier is, and the higher the treatment capacity of the microorganisms attached to the microorganism carrier can be.

  For sedimentation, after using a 200 mm × 200 mm × 350 mm water tank, water is poured into the water tank up to a position 300 mm from the bottom, and the microbial carrier is immersed in water on the surface of the water tank to attach the water to the surface of the microbial carrier. , Stop the microbial carrier gently at the position of the water surface (position of 300 mm from the bottom of the water tank) and measure the time to reach the bottom of the water tank with a stopwatch, [(distance to the bottom (300 mm)) / ( Settling velocity (mm / sec) was calculated according to the formula: Time to reach (sec)). The higher the settling rate, the higher the settling property, which is suitable for treatment with anaerobic microorganisms. The sedimentation velocity was measured at n = 5 and the average value was calculated.

The sludge adhesion reduction rate was measured as follows.
-Measurement of initial attached sludge weight 1 liter of water was added to 2 kg of horticultural soil and mixed well to prepare a sticky sludge. Next, store a predetermined amount of sample (microorganism carrier) in a container whose weight has been measured, measure the weight of [Container + Sample], and subtract the weight of the container from the obtained [Container + Sample] weight. Calculate (initial sample weight). Next, an excess sludge is put into a container containing the sample (microorganism carrier) having the initial sample weight so as to fill the sample (microorganism carrier), and the sludge and the sample (microorganism carrier) are stirred to give a sample ( Enclose the sludge on the surface of the microbial carrier. The sludge and the sample (microorganism carrier) are dropped from the container onto a sieve (JIS Z8801 standard; plain weave wire mesh opening 2 mm) and sieved for 1 minute to remove sludge not entangled (attached) to the sample (microorganism carrier). The sample (microorganism carrier) remaining on the sieve is dried by a hot air oven dryer (product name; DKM600, manufactured by YAMATO) at 80 ° C. for 10 hours, and then the sample weight after drying (sample weight after drying) is measured. After the drying, the initial sample weight is subtracted from the sample weight to calculate the initial attached sludge weight. The weight of the initially attached sludge is preferably as high as possible, and may be 9 g or more.
-Measurement of weight of adhered sludge after stirring In a container having a volume of 1 liter, the dried sample (microorganism carrier) obtained by the measurement of the weight of initial adhered sludge was put, and after stirring for 1 minute with a stirrer (condition: 300 rpm), The contents (sludge and sample (microorganism carrier)) in the container are dropped on a sieve (JIS Z8801 standard; plain weave wire mesh opening 2 mm) and sieved for 1 minute to remove sludge that has fallen off from the sample (microorganism carrier). The sample (microorganism carrier) remaining on the sieve is dried by a hot air oven dryer (product name; DKM600, manufactured by YAMATO) at 80 ° C. for 10 hours, and then the sample weight after drying (sample weight after stirring) is measured. The weight of the initial sample is subtracted from the weight of the sample after stirring to calculate the weight of the attached sludge after stirring. The weight of the sludge attached after stirring is preferably as high as possible, and may be 7 g or more.
Further, the weight of sludge adhered after stirring is subtracted from the weight of initial adhered sludge to calculate the weight of sludge sludge, and further, the sludge adherence reduction rate is calculated by the formula [weight of sludge lost / weight of initial adhered sludge × 100]. The sludge adhesion reduction rate is preferably as low as possible, but may be 36% or less.

The measurement results of Reference Example 1, Examples 2 to 4 and Comparative Examples 1 to 3 in Table 1 are shown below.
In Reference Example 1, since the cross-sectional shape of the microbial carrier has four protrusions (= cruciform shape), the weight of the initially attached sludge is larger than that of Comparative Example 2 of the column, and the treatment performance by the anaerobic microorganisms is good. Becomes

In Example 2, since the cross-sectional shape of the microbial carrier has four protrusions (cross shape) as in Reference Example 1, the weight of the initially attached sludge is larger than that of Comparative Example 2 in the form of a cylinder. Since the surface of Example 2 has unevenness (melt fracture), the weight of initially attached sludge is larger than that of Reference Example 1 in which there is no unevenness (melt fracture), and the sludge adhesion reduction rate due to stirring is small, and anaerobic microorganisms are present. The processing performance by is better. Further, comparing Example 2 and Comparative Example 3, both have irregularities (melt fractures) on the surface, but Example 2 having four multiple protrusions (cross shapes) is a cylindrical Comparative Example 3 The weight of the initially attached sludge is large, the reduction rate of sludge attachment due to stirring is small, and the treatment performance with anaerobic microorganisms is better.

  In Example 3, the cross-sectional shape of the microbial carrier has three protrusions, and although the weight of initially attached sludge is larger than that of Example 2, the sludge attachment reduction rate due to stirring is large, and Example 2 The treatment performance by anaerobic microorganisms is inferior to that of. However, Example 3 has better treatment performance with anaerobic microorganisms than Comparative Example 3.

  In Example 4, the cross-sectional shape of the microbial carrier had a plurality of protrusions of 5, and the weight of the initially deposited sludge was smaller than that in Example 2, and the sludge deposition reduction rate due to stirring was slightly large. Compared with 2, the treatment performance by anaerobic microorganisms is inferior. However, the treatment performance with anaerobic microorganisms is better than that of Comparative Example 3.

Comparative Example 1 is not suitable for treatment with anaerobic microorganisms because it has a hollow columnar shape and thus has a small volume filling rate, a true specific gravity of less than 1, a low sedimentation property, and is floated.
In Comparative Example 2, the volume filling rate is large, but the amount of initially deposited sludge is small because of the columnar shape.
In Comparative Example 3, the amount of initially attached sludge is large due to the surface irregularities (melt fracture), but since the outer shape is cylindrical, the sludge attachment reduction rate due to stirring is large and the treatment performance with anaerobic microorganisms is inferior.

  As described above, the microbial carrier of the present invention can obtain good sewage treatment performance by anaerobic microorganisms as compared with the cylindrical microbial carrier.

10, 10A, 10B Microorganism carrier 12, 12a, 12b Protrusion 13b Surface irregularities (melt fracture)

Claims (3)

In a microbial carrier that holds anaerobic microorganisms on the surface,
The microbial carrier includes a polyolefin resin, an incompatible resin that is a resin different from the polyolefin resin, and an inorganic powder, and a non-porous resin having a true specific gravity (JIS Z 8807 compliant) of greater than 1. The cross-sectional shape is a solid body in which three or more projections are formed in the circumferential direction of the cross section, and the bases of the projections adjacent to each other in the circumferential direction of the cross section are in contact with each other to form a valley between the surfaces of the projections. The microbial carrier, wherein the microbial carrier is formed, and the projections have an uneven shape on the surface. The incompatible resin is one or more types of acrylic resin (polymethyl methacrylate: PMMA), polycarbonate resin, ABS resin, polyvinyl chloride resin, polyethylene terephthalate resin, polyurethane resin. The microbial carrier according to 1.   The microbial carrier according to claim 1 or 2, wherein the cross-sectional shape is a cross shape.

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