JP2017104829A - Microorganism carrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microorganism carrier that treats drainage (sewage) and the like by an anaerobic microorganism adhered to a surface of the carrier, is excellent in water settleability and drainage treatment capacity by an anaerobic microorganism and hardly causes the anaerobic microorganism adhered to the carrier surface to drop off from the carrier.SOLUTION: In a microorganism carrier holding an anaerobic microorganism on a surface of the carrier, a microorganism carrier 10B includes a polyolefin-based resin and an inorganic powder, is composed of a nonporous resin having a true specific gravity (in accordance with JIS Z 8807) of more than 1 and has a structure that a cross-sectional shape having 3 or more protrusions is formed in a circumferential direction of a cross section and a shape of unevenness 13b composed of melt fracture formed during extrusion molding is formed so as to have a large initial adhesion amount of microorganism and inhibit the microorganism from dropping-off by agitation by virtue of protrusions and surface unevenness.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a microbial carrier that is excellent in subsidence in water and adherence to anaerobic microorganisms and can suppress the falling off of attached microorganisms.

  Conventionally, water treatment for waste water or the like includes anaerobic treatment in which dissolved organic matter is decomposed by the action of anaerobic microorganisms. In anaerobic treatment, anaerobic microorganisms attached to the microbial carrier by introducing or filling a fluid microbial carrier into the reaction tank (anaerobic filter bed layer) in the sewage septic tank and passing the sewage (organic wastewater) through The dissolved organic matter in the sewage is decomposed by the action of (Patent Document 1, Patent Document 2).

In anaerobic treatment, since microorganisms work in an anaerobic atmosphere, it is necessary to improve the water treatment capacity that the fluid microbial carrier introduced into the reaction tank etc. quickly settles in the water and does not float on the surface for a long time. It becomes. In particular, when organic wastewater is circulated upward and high-speed treatment is performed, water sedimentation is required to be high.
As a microbial carrier for anaerobic treatment with improved water sedimentation, it is made of an olefin resin foam containing an olefin resin and a cellulose powder, or further comprising an olefin resin foam containing an inorganic powder. Some have a melt fractured state on the surface (Patent Document 2, Patent Document 3).

  However, a microbial carrier comprising an olefin resin foam containing an olefin resin and a cellulose powder, or an olefin resin foam further containing an inorganic powder, and having a melt fractured state on the surface of the foam, Although the surface unevenness is expressed by using it, since it is a hollow state with a foam, the water sedimentation property is still not good, the water treatment capacity is not sufficient, and further contained wood flour, etc. Since the cellulosic powder makes the microbial carrier itself brittle, there is a problem in that if it is used in water for a long time, fragments of the microbial carrier will flow out into the water and cause contamination in the water. Furthermore, there is a problem that buoyancy increases due to accumulation of gas generated from microorganisms inside the cell of the foam of the microbial carrier, and water sedimentation properties decrease.

In addition, the cylindrical outer peripheral surface made of a non-porous material containing a polyolefin resin and inorganic powder is formed into a corrugated irregularity in which a large diameter portion and a small diameter portion are alternately present so that microorganisms adhere to and hold in the concave portion. There is a microorganism carrier (Patent Document 4).
However, the corrugated cylindrical microbial carrier in which large-diameter portions and small-diameter portions are alternately present is a microorganism that adheres to the surface of the microbial carrier when the microbial carriers collide with each other during the treatment of drainage or the like. May fall off, and in that case, the wastewater treatment performance cannot be fully exhibited.

JP 2001-211881 A JP 2012-110443 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 microorganism carrier for anaerobic treatment that is excellent in water treatment ability due to water sedimentation and attached anaerobic microorganisms and in which microorganisms are difficult to fall off. .

  The invention of claim 1 is a microbial carrier that retains anaerobic microorganisms on its surface, wherein the microbial carrier includes a polyolefin resin and an inorganic powder, and has a true specific gravity (according to JIS Z 8807) of more than 1. The cross-sectional shape is a shape in which three or more protrusions are formed in the circumferential direction of the cross-section.

  The invention of claim 2 is characterized in that, in claim 1, the surface of the microorganism carrier has an uneven shape.

  A third aspect of the present invention is characterized in that, in the first or second aspect, the cross-sectional shape is a cross shape.

  The microbial carrier of the present invention comprises a polyolefin resin and an inorganic powder and is made of a non-porous resin having a true specific gravity (according to JIS Z 8807) of more than 1, so that when it is put into waste water, etc. Sedimentation can be performed efficiently by anaerobic microorganisms that can settle and adhere to the microorganism carrier.

  The microorganism carrier of the present invention has a cross-sectional shape in which three or more protrusions are formed in the circumferential direction of the cross section, and the surface of each adjacent protrusion centering on the base between adjacent protrusions in the circumferential direction of the cross section. A so-called valley is formed between the (slope). For this reason, a surface area increases, the quantity of the anaerobic microorganisms which adhere can be increased, and the processing capability by an anaerobic microorganism can be improved. Furthermore, since the microbial carrier of the present invention collides with each other during sewage treatment, there is a so-called trough between the protrusions for the base between adjacent protrusions in the circumferential direction of the cross section, which is a deep position, Since it is difficult to come into contact with other microbial carriers, anaerobic microorganisms attached to the base of the protrusion are difficult to drop off, and it is possible to maintain good sewage treatment performance by the anaerobic microorganisms.

  Furthermore, in the microbial carrier of the present invention, by providing a concavo-convex shape on the surface of the microbial carrier, it is possible to more reliably retain anaerobic microorganisms attached to the concave portions on the surface, and maintain good treatment performance by the anaerobic microorganisms. It becomes possible to do.

1 is a perspective view of a microbial carrier according to a first embodiment of the present invention. It is a perspective view of the microorganism carrier which concerns on 2nd Embodiment of this invention which shows the case where protrusion shape is a triangle. It is a perspective view of the microorganism carrier which concerns on 3rd Embodiment of this invention which has uneven | corrugated shape on the surface. It is the schematic of the apparatus which manufactures the microorganisms carrier of this invention. It is the photograph which image | photographed the side part outer surface of the extrusion molding body of Example 1, and the extrusion molding body of Example 2. FIG.

  Hereinafter, the microbial 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 waste water and the like, includes a polyolefin resin and an inorganic powder, and has a true specific gravity (according to JIS Z 8807) of more than 1. A cross-sectional shape made of a non-porous body (non-foamed body) and having a cross-sectional shape perpendicular to the length direction is a shape in which three or more protrusions are formed in the cross-sectional circumferential direction (a cross-sectional multiple protrusion shape). The microbial carrier 10 is obtained by cutting an extruded product having a cross-sectional shape perpendicular to the length direction and a shape in which three or more protrusions are formed in the circumferential direction of the cross-section into a predetermined length. The length direction of the microbial carrier 10 coincides with the extrusion direction extruded from the extruder during the production of the microbial carrier.

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

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

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

More preferably, 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. The microbial carrier 10B of the third embodiment is a case where the shape of the protrusion 12b is a quadrangle, and has an uneven surface 13b on the surface of the microbial carrier 10B. Reference numeral 11b denotes a central portion. The unevenness 13b is unevenness formed on the surface of the extruded product when the extruded product for the microbial carrier 10B is extruded, and is also referred to as 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. Used in combination. In particular, polyethylene resin is one of the preferred polyolefin resins in the present invention. The amount of the polyolefin-based resin is preferably 30 to 90% by mass, particularly preferably 30 to 70% by mass in 100% by mass of the non-porous body. When the amount is less than 30% by mass, the bonding strength 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 or more of them can be used in combination. Calcium carbonate is particularly preferred. Inorganic powder has the effect | action which increases the specific gravity of the non-porous body which comprises the said microorganisms carrier 10, 10A, 10B. The amount of the inorganic powder is preferably 10 to 70 parts by mass, particularly preferably 30 to 50 parts by mass in 100 parts by mass of the non-porous body. When the amount of the inorganic powder is 10 to 70 parts by mass in 100 parts by mass of the nonporous body, the microbial carrier 10 has a non-porous body (non-foamed body) having a true specific gravity of more than 1 and up to 1.6. It 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.

It is preferable that an incompatible resin is added together with the polyethylene resin and the inorganic powder. The incompatible resin is a resin different from the polyolefin resin and preferably has 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, it is easy to be compatible in polyethylene (PE) resin and polypropylene (PP) resin, and it is difficult to generate an unevenness on the surface. When the difference in SP value is larger than 5 (MJ / m ³ ) ^1/2 , the strands are easily cut during extrusion molding, and are 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. 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 PE) resin or polypropylene (PP) resin, it is preferable because it exceeds the critical shear stress on the inner wall surface of the die at the time of extrusion molding and tends to generate irregularities on the surface. The incompatible resin is an additive appropriately contained in the non-porous body, and can easily form surface irregularities by being contained in the non-porous body. When the acrylic resin is contained in the non-porous body, it is preferably 1 to 20% by mass in 100% by mass of the non-porous body. When the amount is less than 1% by mass, the effect of the acrylic resin cannot be obtained.

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 RFFedors, Polym. Eng. Sci., 14 (2), 147 (1974). That is, in the structural formula of the desired compound, it is determined by the following formula from the evaporation energy and molar volume data of atoms and atomic groups.
δ = (ΣΔei / ΣΔvi) ^1/2
However, in formula, (DELTA) ei and (DELTA) vi represent the evaporation energy and molar volume of an atom or an atomic group, respectively. The structural formula of the compound to be determined is determined using a general structural analysis technique such as IR, NMR, and mass spectrum.

  FIG. 4 is a schematic view of a production apparatus for 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 (take-off device and cutting device) 35. Production of the microbial carriers 10, 10A, 10B using the production apparatus 30 is performed as follows.

  First, the polyolefin resin, the inorganic powder, and the incompatible resin to be added as appropriate are charged into the extruder 31 at the above ratio, and melted and kneaded in the extruder 31 to be nonporous from the extruder 31 into the gas phase. The strand is extruded into a strand having three or more protrusions in the circumferential direction perpendicular to the longitudinal direction in the quality state, cooled and cured through the underwater cooling tank 33, and the strand is taken up by the strand cutter 35. The microorganism carrier 10, 10A, 10B is obtained by taking it out and cutting it into a predetermined length with a cutting device. The die shape of the extruder is a cross having a square tip with respect to the microorganism carriers 10 and 10B, while the microorganism carrier 10A is a cross having a triangle tip. The unevenness (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.

  Example 1, Example 2, Example 3, and Example 4 shown in Table 1 were manufactured using the following raw materials and the manufacturing apparatus 30 shown in FIG. In Example 1, like the microorganism carrier 10 of the first embodiment, the four protrusions 12 forming a cross shape as a plurality of protrusions have a quadrangular shape and have no irregularities (melt fracture) on the surface. It is. In Example 2, like the microbial carrier 10B of the third embodiment, the four protrusions 12b forming a cross shape as a plurality of protrusions have a quadrangular shape and have unevenness (melt fracture) 13b on the surface. It is. Example 3 is an example which has three protrusions as a plurality of protrusions, the protrusions have a quadrangular shape, and have irregularities (melt fracture) on the surface. Example 4 is an example having five protrusions as a plurality of protrusions, the protrusions having a quadrangular shape, and unevenness (melt fracture) on the surface. In addition, the length (cutting length of the strand) of the microbial carriers of Example 1, Example 2, Example 3, and Example 4 is 3 mm.

・ Polyolefin resin: Polyethylene resin, product name: Nipolon Hard 5700, MFR1.0 (g / 10 min), manufactured by Tosoh Corporation ・ Inorganic powder: calcium carbonate, product name: BF300, manufactured by Bihoku Powder Chemical Co., Ltd. ・ Acrylic resin: Product name: Acrypet VH-001, manufactured by 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 any one of Examples 1 to 4 with holes for strand extrusion, the barrel set temperature is 220 ° C. in Example 1, 180 ° C. in Examples 2 to 4, and the discharge amount is Example 1-4 is 60 kg / hour, the extrusion speed is 10 m / min for any of Examples 1 to 4, the screw speed is 400 rpm for any of Examples 1 to 4, and the take-up speed is any of Examples 1 to 4. 11 m / min. In addition, the dimension of the hole for strand extrusion of the die is the dimension corresponding to a in FIG. 1 for the dies for Example 1 and Example 2 in which four protrusions are provided in a cross shape, and the dimension corresponding to c. Is 2 mm, and the dimension corresponding to d is 2 mm. In addition, the die for Example 3 having three protrusions and the die for Example 4 having four protrusions are different from those in FIG. The dimension is 6 mm, the dimension corresponding to c is 2 mm, and the dimension corresponding to d is 2 mm.

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

As Comparative Example 1, a microorganism carrier was formed by cutting a polyethylene hollow pipe having an outer diameter of 10 mm and an inner diameter of 8 mm into a length of 10 mm.
As Comparative Examples 2 and 3, microbial carriers were produced under the conditions of the extruder shown below using the same raw materials and the same production apparatus as in Examples 1 to 4. The comparative example 2 is a cylindrical thing without an unevenness | corrugation (melt fracture) on the surface, and the comparative example 3 is a cylindrical thing which has an unevenness | corrugation (melt fracture) on the surface.

  The conditions of the extruder for Comparative Examples 2 and 3 are as follows: the die is 3 mm × 4 in diameter in both 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. Each of Examples 2 and 3 was 60 kg / hour, the extrusion speed was 9 m / min for both Comparative Examples 2 and 3, the screw rotation speed was 400 rpm for both Comparative Examples 2 and 3, and the take-up speed was any of Comparative Examples 2 and 3. Is also 9 m / min. Moreover, the length (cutting length by a strand cutter) of the microorganism carrier of Comparative Example 2 and Comparative Example 3 is 3 mm.

  True specific gravity (based on JIS Z 8807), bulk specific gravity (based on JIS K 7365), volume filling rate (%), sedimentation (mm / s) for the microbial carriers of Examples 1 to 4 and Comparative Examples 1 to 3. The sludge adhesion reduction rate (%) was measured. Since Comparative Example 1 did not settle, 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, the larger the contact area between the waste water (treatment liquid) and the carrier, and the treatment capacity by the microorganisms attached to the microorganism carrier can be increased.

  For sedimentation, a 200mm x 200mm x 350mm water tank is used, water is poured into the water tank to a position 300mm from the bottom, and the microbial carrier is immersed in water on the surface of the water tank so that the water adheres to the surface of the microbial carrier. The time until the microbial carrier is gently released at the position of the water surface (300 mm from the bottom of the aquarium) and reaches the bottom of the aquarium is measured with a stopwatch, [(distance to the bottom (300 mm)) / (bottom The sedimentation speed (mm / second) was calculated by the following equation: Time to reach (second))]. The larger the sedimentation rate, the higher the sedimentation property, which is suitable for treatment with anaerobic microorganisms. The sedimentation rate 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 create a sticky sludge. Next, a predetermined amount of sample (microorganism carrier) is placed in a weight-measured container, the weight of [container + sample] is measured, and the weight of the sample is obtained by subtracting the weight of the container from the obtained weight of [container + sample]. (Initial sample weight) is calculated. Next, an excessive amount of sludge is poured into a container in which the sample (microorganism carrier) of the initial sample weight is contained so that the sample (microorganism carrier) is buried, and the sludge and the sample (microorganism carrier) are stirred to obtain a sample ( Microbial carrier) The sludge is entangled on the surface. 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 the sludge not entangled (attached) to the sample (microorganism carrier). The sample (microbe carrier) remaining on the sieve is dried at 80 ° C. for 10 hours with a hot air oven dryer (product name: DKM600, manufactured by YAMATO), and then the weight of the sample after drying (sample weight after drying) is measured. Subtract the initial sample weight from the sample weight after drying to calculate the initial attached sludge weight. The initial attached sludge weight should be large, and it should be 9 g or more.
・ Measurement of adhering sludge weight after agitation After a dried sample (microorganism carrier) obtained by measuring the initial adhering sludge weight was put into a 1 liter container and stirred for 1 minute with a stirrer (condition: 300 rpm), The contents in the container (sludge and sample (microorganism carrier)) are dropped on a sieve (JIS Z8801 standard; plain weave wire mesh opening 2 mm) and sieved for 1 minute to remove the sludge removed from the sample (microorganism carrier). The sample (microbe carrier) remaining on the sieve is dried at 80 ° C. for 10 hours with a hot air oven dryer (product name: DKM600, manufactured by YAMATO), and then the weight of the dried sample (sample weight after stirring) is measured. The initial sample weight is subtracted from the sample weight after stirring to calculate the adhering sludge weight after stirring. The adhering sludge weight after stirring should be large, and it should be 7 g or more.
Also, the sludge weight after dropping is calculated by subtracting the sludge weight after stirring from the initial attached sludge weight, and the sludge adhesion reduction rate is further calculated by the formula of [dropped sludge weight / initially attached sludge weight × 100]. The sludge adhesion reduction rate is preferably as small as possible, but may be 36% or less.

It shows below about the measurement result of Examples 1-4 of Table 1, and Comparative Examples 1-3.
In Example 1, since the cross-sectional shape of the microbial carrier has four projections (= cross shape), the initial attached sludge weight is large compared to the comparative example 2 of the cylinder, and the treatment performance by anaerobic microorganisms is good. It becomes.

  In Example 2, since the cross-sectional shape of the microorganism carrier has a plurality of four protrusions (cross shape) as in Example 1, the initial attached sludge weight is larger than that of the comparative example 2 of the cylinder. In Example 2, since the surface has irregularities (melt fracture), the initial attached sludge weight is larger than that in Example 1 without irregularities (melt fracture), and the sludge adhesion reduction rate by stirring is small, and anaerobic microorganisms. The processing performance by is better. Further, when Example 2 and Comparative Example 3 are compared, both have irregularities (melt fracture) on the surface, but Example 2 having four multiple projections (cross shape) is a cylindrical comparative example 3. In contrast, the weight of the initially attached sludge is large, the sludge adhesion reduction rate by stirring is small, and the treatment performance by anaerobic microorganisms is better.

  In Example 3, the cross-sectional shape of the microorganism carrier has three protrusions, and the initial attached sludge weight is larger than that in Example 2, but the sludge adhesion reduction rate by stirring is large, and Example 2 Compared with, the treatment performance by anaerobic microorganisms is inferior. 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 has a plurality of protrusions, and the initial attached sludge weight is smaller than that in Example 2, and the sludge adhesion reduction rate by stirring is slightly larger. Compared with 2, the treatment performance by anaerobic microorganisms is inferior. However, the treatment performance with anaerobic microorganisms is better than Comparative Example 3.

Since Comparative Example 1 has a hollow cylindrical shape, the volume filling rate is small, the true specific gravity is less than 1, the sedimentation property is low, and the surface floats, so that it is unsuitable for treatment with anaerobic microorganisms.
In Comparative Example 2, the volume filling rate is large, but the amount of initial attached sludge is small because of the cylindrical shape.
In Comparative Example 3, the amount of initially attached sludge is large due to surface irregularities (melt fracture), but since the outer shape is cylindrical, the sludge adhesion reduction rate by stirring is large and the treatment performance by anaerobic microorganisms is inferior.

  As described above, the microbial carrier of the present invention can obtain better sewage treatment performance by anaerobic microorganisms than the cylindrical microbial carrier.

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

Claims (3)

In a microbial carrier for holding anaerobic microorganisms on the surface,
The microbial carrier comprises a polyolefin resin and inorganic powder, is made of a non-porous resin having a true specific gravity (conforms to JIS Z 8807) of more than 1, and has three or more protrusions in the cross-sectional circumferential direction. A microorganism carrier characterized by having a shaped shape.   The microbial carrier according to claim 1, wherein the surface of the microbial carrier has an uneven shape. The microbial carrier according to claim 1 or 2, wherein the cross-sectional shape is a cross shape.

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