Filtration Equipment

Abstract

To provide filtration devices that suppress the strong adhesion of a suspended solid contained in a microbial culture solution to the surface of a filter body while reducing the power of a pump used to discharge the filtered solution of the microbial culture solution to the outside of a microbial culture tank, and can reduce the burden and frequency of cleaning.SOLUTION: Provided is a filtration device 1 installed in a microbial culture tank 10 containing a microbial culture solution 11, comprising: a filter body 2 containing a filtered solution of the microbial culture solution 11 that has been filtered, the filter body having a plurality of pores having an average pore diameter of 1 μm or more and 1 mm or less for filtering the microbial culture solution 11; and a filter solution discharge unit 3 for discharging the filter solution contained in the filter body 2 to the outside of the microbial culture tank 10, the filter body 2 being immersed in the microbial culture solution 11 so that the upper end portion 2a thereof is located above the liquid level of the microbial culture solution 11.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a filtration device used for filtering a microbial culture solution. [Background technology]

[0002] Lignocellulosic biomass is the main component of the cell walls of plant cells, i.e., plant fiber, and is an abundant organic carbon source on earth, so it has been attracting attention as an alternative energy resource to chemical fuels such as petroleum. In the process of producing methane using lignocellulosic biomass as a raw material, it is known that as a pretreatment for methane fermentation, lignocellulose is decomposed using a microbial culture solution of ruminal microorganisms (lignocellulose-decomposing bacteria) present in the first stomach fluid (rumen fluid) of cows, and volatile fatty acids (VFAs) that serve as substrates for methane fermentation are produced. In order to promote the growth of lignocellulose-decomposing bacteria that decompose lignocellulosic biomass in a microbial culture tank, it is necessary to control the solids retention time (SRT) and hydraulic retention time (HRT). The SRT and HRT can be controlled by separating the filtrate from the microbial culture solution and adjusting the discharge of the filtrate and the discharge of the suspension separately. In order to separate the filtrate from the microbial culture liquid, for example, a separation membrane used in a membrane bioreactor (MBR) process that separates activated sludge from water in wastewater treatment can be used (Patent Documents 1 and 2).

[0003] Patent documents 1 and 2 disclose membrane separation activated sludge equipment that removes, by aeration, pollutants that adhere to and accumulate on the surface of a separation membrane when activated sludge is subjected to solid-liquid separation by membrane separation, thereby suppressing clogging (fouling). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-62646 A [Patent Document 2] JP 2020-89831 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the membrane bioreactors of Patent Documents 1 and 2, the separation membrane is entirely immersed in the liquid tank, so that the inside of the separation membrane is sealed, and when the filtrate is pumped out of the system, the inside of the separation membrane is under negative pressure, which causes a problem of high pump power. There is also a problem of high power consumption related to aeration. Furthermore, for firmly attached dirt that cannot be removed by aeration, it is necessary to carry out relatively frequent operations such as washing with chemicals or removing the separation membrane from the apparatus and washing it as a countermeasure against clogging (fouling), and there is also a problem that the washing operation is cumbersome.

[0006] Therefore, the present invention aims to provide a filtration device that reduces the power of the pump used to discharge the filtrate of the microbial culture solution outside the microbial culture tank, and prevents suspended matter contained in the microbial culture solution from firmly adhering to the surface of the filter body, thereby reducing the burden and frequency of cleaning. [Means for solving the problem]

[0007] In order to solve the above problems, the filtration device of the present invention is a filtration device that is installed in a microbial culture tank containing a microbial culture liquid, and is equipped with a filter body having a plurality of pores with an average pore size of 1 μm or more and 1 mm or less for filtering the microbial culture liquid, the filter body containing the filtrate of the filtered microbial culture liquid, and a filtrate discharge section that discharges the filtrate contained in the filter body to the outside of the microbial culture tank, and the filter body is immersed in the microbial culture liquid so that an upper end portion of the filter body is positioned above the liquid surface of the microbial culture liquid.

[0008] According to the above configuration, since the upper end of the filter is positioned above the liquid level of the microbial culture liquid, the inside of the filter is open to the outside, and the inside and outside of the filter are at equal pressure. As a result, when the filtrate of the microbial culture liquid contained in the inside of the filter is discharged outside the microbial culture tank by the filtrate discharge part, the height position of the liquid level of the filtrate contained in the filter becomes lower than the height position of the liquid level of the microbial culture liquid in the microbial culture tank, and the microbial culture liquid passes through the filter and is filtered by the pressure difference caused by the difference in the liquid level, and is contained inside the filter as the filtrate. Therefore, the filtrate is not filtered at a high pressure compared to the case where the inside of the filter is reduced in pressure, as in the case where the filtrate is discharged outside while the entire filter is immersed in the microbial culture liquid, so that the power of the pump for discharging the filtrate outside the microbial culture tank can be reduced. In addition, the suspended matter contained in the microbial culture liquid is not likely to adhere firmly to the filter, and even if it does adhere, it is easily removed, so clogging can be prevented. As a result, the burden and frequency of extensive cleaning, such as removing the filtration device from the microbial culture tank and cleaning it, can be reduced, and running costs can be reduced even when the filtration device is applied to a large-scale microbial culture tank.

[0009] In the filtering device according to the present invention, the filter body rotates about an axis extending in the vertical direction.

[0010] According to the above configuration, the centrifugal force generated by the rotation of the filter body can prevent the suspended matter contained in the microbial culture liquid from firmly adhering to the filter body, and even if it does adhere, it can be easily removed, thereby preventing clogging. In addition, the rotation of the filter body can agitate the microbial culture liquid, improving the microbial culture efficiency and further promoting the decomposition reaction of the material to be treated contained in the microbial culture liquid.

[0011] Furthermore, in the above-mentioned filtration device, the present invention is characterized in that the filter body is formed in a bottomed cylindrical shape having an opening at the upper end, and the filtrate discharge part has a filtrate discharge pipe inserted into the opening without contacting it.

[0012] According to the above configuration, since the filtrate discharge pipe is inserted into the opening of the filter body without contacting it, it is not necessary to connect the filter body and the filtrate discharge pipe, and therefore it is possible to rotate only the filter body while the filtrate discharge pipe is fixed. In addition, since the filter body is formed into a cylindrical shape with a bottom, the filter body can be easily rotated, and the pressure applied to the side surface of the filter body is uniform, so that damage and deterioration of the filter body can be reduced.

[0013] The present invention is also characterized in that the above-mentioned filtration device has scrapers arranged along the side and / or bottom surface of the filter body at outer and / or inner positions of the filter body.

[0014] According to the above configuration, the solid matter adhering to the filter body can be scraped off and removed by the scraper, thereby preventing clogging of the filter body. As a result, the burden of extensive cleaning, such as removing the filtration device from the microbial culture tank for cleaning, and the frequency of such cleaning can be reduced, and the running costs can be reduced even when the filtration device is applied to a large-scale microbial culture tank. [Brief description of the drawings]

[0015] [Figure 1] FIG. 2 is a schematic diagram showing a filtration device according to the present embodiment installed in a microbial culture tank. [Diagram 2] FIG. 2 is a schematic diagram showing the filter body shown in FIG. 1 and an example in which a scraper is disposed on the filter body. [Diagram 3] 3A and 3B are schematic diagrams showing an example of using a microbial culture tank in which a filtration device according to the present embodiment is installed in a lignocellulose decomposition system, respectively. Fig. 3(a) shows a lignocellulose decomposition system configured by a three-phase process, and Fig. 3(b) shows a lignocellulose decomposition system configured by a two-phase process. [Figure 4]Fig. 4(a) is a diagram showing an example of a filtration device according to the present embodiment installed in a microbial culture tank. Fig. 4(a) is a diagram showing a filtration device installed in a microbial culture tank constituting a three-phase lignocellulose decomposition system shown in Fig. 3(a). Fig. 4(b) is a diagram showing a filtration device installed in a microbial culture tank / decomposition tank constituting a two-phase lignocellulose decomposition system shown in Fig. 3(b). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The following describes in detail the embodiments and drawings of the filtration device according to the present invention. However, the present invention is not intended to be limited to the embodiments and configurations shown in the drawings.

[0017] (Configuration of filtration device) With reference to FIG. 1, the filtration device 1 according to this embodiment installed in a microbial culture tank 10 will be described. As shown in FIG. 1, the filtration device 1 is installed in a microbial culture tank 10 that contains a microbial culture solution 11. The microbial culture tank 10 may be a microbial culture tank / decomposition tank 110 in which microorganisms are cultured and the material to be treated is decomposed in one tank. The filtration device 1 includes a filter body 2 that contains the filtrate of the microbial culture solution 11, and a filtrate discharge section 3 that discharges the filtrate contained in the filter body 2 to the outside of the tank. The filter body 2 is a filter body having a plurality of pores with an average pore size of 1 μm or more and 1 mm or less. The filter body 2 is immersed in the microbial culture solution 11 so that its upper end portion 2a is located above the liquid surface of the microbial culture solution 11. The upper end 2a of the filter body 2 may be located above the liquid level of the microbial culture solution 11 to such an extent that the microbial culture solution 11 does not flow into the filter body 2 from the upper surface of the filter body 2 even when the filter body 2 is rotated or the microbial culture solution 11 is stirred by the stirring blade 60. When the filter body 2 is rotated about its vertical axis, it is preferable to rotate it at a slow speed of 1 to 60 rpm by the motor M. In addition, when the stirring blade 60 is used, the filter body 2 and the stirring blade 60 may rotate synchronously or in opposite directions, but in order to generate convection in the microbial culture solution 11 and further suppress adhesion of solid matter to the filter body 2, it is preferable that they rotate in opposite directions.

[0018] The microbial culture solution 11 contains suspended solids (SS), and many microorganisms with slow growth rates are attached to the suspended solids. By appropriately adjusting the amount of filtrate discharged from the microbial culture tank 10 by the filtrate discharge unit 3 and the amount of suspension discharged from the suspension discharge unit 5, and controlling the solids retention time (SRT) and hydraulic retention time (HRT), it is possible to promote the growth of microorganisms that decompose the material to be treated. In addition, the microbial culture solution 11 contains decomposition products produced by the reaction between the material to be treated and the microorganisms. When the decomposition reaction progresses and the concentration of the decomposition products increases, the pH of the microbial culture solution 11 changes and the osmotic pressure increases, which may change the number and function of the microorganisms. Therefore, the filtrate of the microbial culture solution 11 is discharged outside the tank, and an artificial medium is added to the microbial culture solution 11 as a buffer, thereby adjusting the pH and osmotic pressure of the microbial culture solution 11.

[0019] (Filter body) FIG. 2 is a schematic diagram showing an example of the filter body shown in FIG. 1 and a filter body with a scraper. In the filter body 2, a portion having a plurality of pores is shown by a broken line. The filter body 2 accommodates the filtrate separated from the microbial culture liquid 11 containing a large amount of suspended solids. As shown in No. 1, 3 to 6 in FIG. 2, only the side surface of the filter body 2 may have a plurality of pores, or as shown in No. 2, 7 to 14 in FIG. 2, the side surface and the bottom surface of the filter body 2, that is, the entire filter body 2 may have a plurality of pores. The filter body 2 has a hollow structure inside in order to accommodate the filtrate. The shape of the filter body 2 may be a bottomed one, and for No. 1 and 2 in which the scraper 4 is not arranged on the filter body 2, it may be a fixed shape such as a cylindrical shape, a hexagonal prism, a square prism, a triangular prism, a cone shape, a triangular pyramid shape, or a sphere, or may be an indefinite shape such as a bag shape. For No. 3 to 14 in which the scraper 4 is arranged on the filter body 2, it is preferable that the shape of the filter body 2 is a cylindrical shape. Moreover, the upper surface of the filter body 2 is preferably provided with an opening 2b so that the filtrate discharge pipe 3a can be inserted without contacting the filter body 2.

[0020] The average pore size of the pores in the filter body 2 is preferably 1 μm or more and 1 mm or less, more preferably 5 μm or more and 1 mm or less, and even more preferably 10 μm or more and 1 mm or less. In addition, a material formed by weaving a filamentous material such as a net may be used as the base material of the filter body 2. In this case, it is preferable to use a material having a mesh size of 16 mesh or more (opening size of 1.00 mm or less). If the average pore size of the pores in the filter body 2 is less than 1 μm, it takes time for a certain amount of filtrate to be accommodated inside the filter body 2, or it is necessary to suck the filtrate under high pressure, which not only increases the power of the pump P and increases costs, but also may cause clogging. On the other hand, if the average pore size of the pores in the filter body 2 exceeds 1 mm, suspended matter contained in the microbial culture liquid 11 flows into the filter body 2, which may result in insufficient solid-liquid separation and make it impossible to control the SRT and HRT. Therefore, the suspended matter with a large number of microorganisms attached thereto is discharged outside the tank, which may make it difficult to promote the proliferation of microorganisms that decompose the material to be treated in the microbial culture tank 10.

[0021] The material of the filter body 2 having a plurality of pores may be organic materials such as PVDF, chlorinated polyethylene, PP, and PTFE, ceramics such as aluminum oxide, titanium oxide, and zirconium oxide, and inorganic materials such as stainless steel, and is not limited to the above materials as long as it is a material with excellent durability. The filter body may be configured as a single layer structure, or may be configured as a multilayer structure of two layers, three layers, or more. In addition, when the filter body 2 has a two-layer structure, the average pore size of the plurality of pores in the outer filter body 2 and the average pore size of the plurality of pores in the inner filter body 2 may be different in size.

[0022] (Filtrate discharge part) As shown in Fig. 1, the filtrate discharge section 3 discharges the filtrate contained inside the filter body 2 to the outside of the tank, and also circulates a part of the filtrate to be mixed with the artificial culture medium. It is preferable that the filtrate discharge pipe 3a is inserted without contact into the opening 2b of the filter body 2. If the filtrate discharge pipe 3a is not in contact with the filter body 2, it is possible to rotate the filter body 2 while keeping the filtrate discharge pipe 3a fixed.

[0023] (scraper) The scraper 4 is disposed to scrape off and remove solid matter adhering to the filter body 2, and to prevent clogging of the filter body 2. The position of the scraper 4 is not particularly limited, but as shown by Nos. 3 to 14 in Fig. 2, the scraper 4 may be disposed at an outer position or an inner position along the side or bottom surface of the filter body 2. Table 1 and Fig. 1 show examples of the structure of the filter body 2 and the position of the scraper 4. Nos. 1 to 14 in Table 1 correspond to Nos. 1 to 14 in Fig. 2.

[0024] [Table 1]

[0025] Regarding the position and shape of the scraper 4, as shown in No. 3 and No. 7, one I-shaped scraper 4 may be arranged along the vertical direction of the outer side surface of one end of the filter body 2, or as shown in No. 4 and No. 8, two I-shaped scrapers 4 may be arranged along the vertical direction of the outer side surface of both the left and right ends of the filter body 2. As shown in No. 5 and No. 9, two I-shaped scrapers 4 may be arranged along the vertical direction of the outer side surface of one end of the filter body 2 and the inner side surface of the other end, or as shown in No. 6 and No. 10, two I-shaped scrapers 4 may be arranged along the vertical direction of the outer side surface of one end of the filter body 2 and the inner side surface of the other end. As shown in No. 11, an L-shaped scraper 4 may be arranged along the vertical direction of the outer side surface of one end of the filter body 2 and the horizontal direction of the outer bottom surface, or as shown in No. 12, an L-shaped scraper may be arranged along the vertical direction of the inner side surface of one end of the filter body 2 and the horizontal direction of the inner bottom surface. As shown in No. 13, a U-shaped scraper 4 may be arranged along the vertical direction of the outer side surface and the horizontal direction of the outer bottom surface at both left and right ends of the filter body, and as shown in No. 14, a U-shaped scraper 4 may be arranged along the vertical direction of the inner side surface and the horizontal direction of the inner bottom surface at both left and right ends of the filter body 2.

[0026] The material of the scraper 4 may be an alloy such as iron, brass, or stainless steel, or may be reinforced plastic or ceramic, and is not limited to the above materials as long as it does not impede the function of scraping off and removing solid matter adhering to the filter body 2 with the scraper 4. The shape of the scraper 4 may be, for example, a flat plate, a cylinder, a triangular prism, or a polygonal prism having four or more sides.

[0027] In Nos. 1 and 2, the filter body 2 can be a rotating body, and in Nos. 3 to 14, either the filter body 2 or the scraper 4, or both, can be a rotating body. When both the filter body 2 and the scraper 4 are rotating bodies, it is preferable to rotate them in opposite directions in order to generate convection in the microbial culture solution 11 and further suppress adhesion of solid matter to the filter body 2. The scraper 4 may rotate so as to move along the outer periphery of the side surface of the filter body 2, or may rotate around the vertical direction of the scraper 4 as an axis. Furthermore, the rotation direction of the filter body 2 or the scraper 4 may be changed during operation, and for example, the rotation direction may be reversed at regular intervals.

[0028] [Lignocellulose decomposition system] 3 is a schematic diagram showing an example in which a microbial culture tank 10 in which a filtration device 1 according to this embodiment is installed is used in a lignocellulose decomposition system. Fig. 3(a) shows a lignocellulose decomposition system 100 configured by a three-phase process, and Fig. 3(b) shows a lignocellulose decomposition system 101 configured by a two-phase process.

[0029] The filter device 1 according to the present invention can be installed in a microbial culture tank 10 to arbitrarily control the solids retention time (SRT) and hydraulic retention time (HRT) in the tank. In other words, the filter device 1 can control the promotion of growth of lignocellulose-decomposing bacteria that decompose lignocellulose-based biomass in the microbial culture tank 10. Lignocellulose decomposition is performed as a pretreatment for methane fermentation using lignocellulose-based biomass as a raw material. Lignocellulose-based biomass is decomposed into cellulose and hemicellulose by ruminal microorganisms (lignocellulose-decomposing bacteria) present in the first stomach fluid (rumen fluid) of cows, and is converted into hexose (six monosaccharides) such as glucose. Furthermore, pyruvic acid and the like are produced from hexose (six monosaccharides) such as glucose, and as the reaction proceeds further, volatile fatty acids (VFAs) such as acetic acid, propionic acid, butyric acid, and formic acid are produced. Acetic acid, hydrogen, and carbon dioxide are the base materials (raw materials) for methane fermentation, so as the decomposition of lignocellulose progresses, the production of acetic acid, hydrogen, and carbon dioxide increases, and the amount of methane produced also increases.

[0030] First, a lignocellulose decomposition system 100 using a microbial culture tank 10 in which a filtration device 1 according to the present invention is installed will be described. As shown in FIG. 3(a), the lignocellulose decomposition system 100 is composed of a microbial culture tank 10 for culturing ruminal microorganisms, a decomposition tank 20 for converting (decomposing) lignocellulose-based biomass into a form that is easily usable in a downstream methane fermentation tank 30 using the cultured ruminal microorganisms, and a methane fermentation tank 30. When ruminal fluid collected from cows or the like, an artificial medium (artificial saliva) simulating the saliva of ruminants as a buffer, and lignocellulose-based biomass crushed and pulverized by a crusher 40 or the like are supplied to the microbial culture tank 10, the lignocellulose-decomposing bacteria present in the ruminal fluid proliferate by decomposing and metabolizing lignocellulose, and lignocellulose decomposition products (partial decomposition products of lignocellulose and volatile fatty acids (VFAs) such as acetic acid) are produced. As shown in FIG. 4(a), in the microbial culture tank 10, the filtrate obtained by solid-liquid separation using the filtration device 1 and the suspension containing undecomposed or partially decomposed lignocellulosic biomass are sent to a downstream decomposition tank 20 (also referred to as a pretreatment tank) by a filtrate discharge section 3 and a suspension discharge section 5, respectively. The filtrate is sent to the decomposition tank 20, and a part of it is mixed with an artificial medium (artificial saliva). By appropriately adjusting the amount of the filtrate and suspension of the microbial culture liquid 11 withdrawn from the microbial culture tank 10 and sent to the decomposition tank 20, the hydraulic retention time (HRT) and sludge retention time (SRT) in the microbial culture tank 10 can be controlled. The filtrate and suspension of the microbial culture solution 11 contain a large number of lignocellulose-decomposing bacteria, so when lignocellulose-based biomass is supplied to the decomposition tank 20, the lignocellulose decomposition reaction proceeds due to the action of the lignocellulose-decomposing bacteria, and a reaction liquid containing volatile fatty acids (VFAs) such as acetic acid and partial decomposition products of lignocellulose is produced.When the reaction liquid containing a large amount of lignocellulose decomposition products is supplied from the decomposition tank 20 to the methane fermentation tank 30, methane fermentation using the lignocellulose decomposition products as a substrate (raw material) proceeds in the methane fermentation liquid contained in the methane fermentation tank 30, and methane is produced. The methane fermentation residue in the methane fermentation tank 30 is then sent to the dehydrator 50. The dehydration separation liquid discharged from the dehydrator 50 contains substances that can be used as a nitrogen source or a phosphorus source, and may be added by refluxing to the microbial culture tank 10. The concentrated sludge discharged from the dehydrator 50 may be used as fertilizer, construction material, or the like. The lignocellulose decomposition system 100, which is configured by a three-phase process shown in FIG. 3(a), has the advantage that the operation can be easily controlled because the roles of each process are separate: (1) culturing ruminal microorganisms, (2) decomposition (pretreatment) of lignocellulose, and (3) methane fermentation.

[0031] Next, a lignocellulose decomposition system 101 using a microbial culture tank / decomposition tank 110 in which the filtration device 1 according to the present invention is installed will be described. As shown in FIG. 3(b), the lignocellulose decomposition system 101 is composed of a microbial culture tank / decomposition tank 110 that serves both to culture ruminal microorganisms and to decompose (pre-treat) lignocellulose biomass, and a methane fermentation tank 30. When ruminal fluid collected from cows or the like, an artificial medium (artificial saliva) that imitates the saliva of ruminants as a buffer, and lignocellulose biomass that has been crushed or pulverized by a crusher 40 or the like as necessary are supplied to the microbial culture tank / decomposition tank 110, the lignocellulose-decomposing bacteria present in the ruminal fluid proliferate by decomposing and metabolizing lignocellulose, and the lignocellulose decomposition reaction proceeds due to the action of the lignocellulose-decomposing bacteria, and a reaction liquid containing volatile fatty acids (VFAs) such as acetic acid and partial decomposition products of lignocellulose is produced. As shown in FIG. 4(b), in the microbial culture tank and decomposition tank 110, the filtrate obtained by solid-liquid separation in the filtration device 1 and the suspension containing undecomposed or partially decomposed lignocellulose biomass are sent to the downstream methane fermentation tank 30 by the filtrate discharge section 3 and the suspension discharge section 5, respectively. The filtrate is sent to the methane fermentation tank 30, and a part of it is mixed with an artificial medium (artificial saliva). By appropriately adjusting the amount of the filtrate and suspension of the decomposition reaction liquid 111 that is extracted from the microbial culture tank and decomposition tank 110 and sent to the methane fermentation tank 30, the hydraulic retention time (HRT) and solid retention time (SRT) in the microbial culture tank and decomposition tank 110 can be controlled. When the decomposition reaction liquid 111 containing lignocellulose decomposition products is supplied to the methane fermentation tank 30, methane fermentation using the lignocellulose decomposition products as a substrate (raw material) proceeds in the methane fermentation liquid contained in the methane fermentation tank 30, and methane is produced. Thereafter, the methane fermentation residue in the methane fermentation tank 30 is sent to the dehydrator 50. The dehydration runoff liquid discharged from the dehydrator 50 contains substances that can be used as nitrogen and phosphorus sources, and may be added by reflux to the microbial culture tank / decomposition tank 110. In addition, the concentrated sludge discharged from the dehydrator 50 may be used as fertilizer, construction material, etc.The two-phase process shown in Fig. 3(b) is a process in which ruminal microorganisms can be cultured and lignocellulose decomposed (pretreatment) in one tank (microbial culture tank / decomposition tank 110), and is known as the RUDAD (Rumen Derived Anaerobic Digestion) process (Non-Patent Document Huub J. Gijzen et al., Biotechnology and Bioengineering, Vol. 31, pp. 418-425 (1988)). This process requires fewer tanks than the three-phase process, so it can be constructed more cheaply and the equipment can be made more compact.

[0032] [Lignocellulosic biomass] Examples of lignocellulosic biomass as raw materials include unused agricultural and forestry waste such as forest thinnings, rice straw, rice husks, bagasse, and thatch, as well as lignocellulosic industrial waste such as vegetable scraps, tea leaves, coffee grounds, soybean pulp, shochu dregs, construction waste, waste paper, waste paper, and urban waste, and biomass resource crops such as Elianthus and Giant Miscanthus. In addition, paper cut into pieces by a shredder is incinerated because the fibers are broken and it is difficult to recycle, but such cut paper can also be used as a raw material. When lignocellulose decomposition of lignocellulosic biomass progresses and volatile fatty acids such as acetic acid are produced, it can be used as a substrate (raw material) for methane fermentation, so methane can be produced efficiently. In addition, even if fermentation does not progress to volatile fatty acids, when lignocellulose is decomposed into small molecular weight forms such as cellobiose, or into constituent sugars such as glucose, it can be used as a substrate (raw material) for methane fermentation, so methane can be produced efficiently.

[0033] [Lumen fluid] Rumen fluid is a digestive fluid present in the first stomach (rumen) of ruminants. Ruminants include cows, sheep, goats, deer, camels, and llamas. For example, the first stomach of an adult cow has a capacity of 150 to 200 L, and many ruminal microorganisms, such as lignocellulose-decomposing bacteria, hemicellulose-decomposing bacteria, lignin-decomposing bacteria, starch-decomposing bacteria, and methane-producing bacteria, live in the ruminal fluid. Lignocellulose-decomposing bacteria can produce enzymes such as cellulase that decompose lignocellulose (fibrous material). Therefore, when ruminants ingest fibrous material such as grass, the lignocellulose-decomposing bacteria decompose the lignocellulose, producing volatile fatty acids (VFAs) such as acetic acid, propionic acid, butyric acid, and valeric acid, which serve as an energy source for ruminants. In addition, the methanogenic bacteria contained in the rumen fluid can generate methane using acetic acid produced by the lignocellulose decomposing bacteria as a substrate, or using hydrogen and carbon dioxide as substrates. The rumen fluid may be collected from the first stomach of a ruminant using a tube such as a catheter, or may be generated from a meat processing plant or the like.

[0034] 3(a) and (b), lignocellulosic biomass is decomposed by using rumen fluid obtained from ruminants by introducing it into a microbial culture tank 10 or a microbial culture tank / decomposition tank 110, or by using cultured rumen microorganisms. The cultured rumen microorganisms may be cultured by adding a concentrated liquid of a medium to the rumen fluid, or may be cultured by adding a liquid medium to the precipitate (bacterial cells) obtained by centrifuging the rumen fluid and culturing it. In culturing ruminal microorganisms, the temperature, oxidation-reduction potential (ORP), hydraulic retention time (HRT) or solid retention time (SRT), and ammonium nitrogen concentration of the medium can be adjusted using the number of at least one of three types of bacteria, namely Fibrobacter succinogenes, Ruminococcus albus, and Prevotella ruminicola, which are ruminal microorganisms with particularly high lignocellulose decomposition activity, as an indicator. The number of bacteria of these bacteria is not particularly limited, but is preferably determined by a quantitative PCR method, which can rapidly and accurately measure the number of bacteria of a specific bacteria. When the number of bacteria of lignocellulose decomposition bacteria is determined using the quantitative PCR method, genomic DNA extracted and purified from the microbial culture solution 11 or the decomposition reaction solution 111 is used. Rumen microorganisms can be cultured in large quantities and subcultured, so that culture fluid of ruminal microorganisms with an adjusted bacterial count can be used for decomposing lignocellulose as needed.

[0035] [Artificial medium] As a medium for culturing ruminal microorganisms, a natural medium whose base material is derived from natural products may be used, or a synthetic medium whose nutrients necessary for the growth of ruminal microorganisms are all composed of chemicals may be used. In particular, it is preferable that the medium contains a carbon source such as cellulose or hemicellulose, in addition to a nitrogen source such as ammonium salt, a phosphorus source such as phosphate, and the like, which are useful nutrient sources for ruminal microorganisms. As shown in Figs. 3(a) and (b), the dehydration elimination liquid discharged from the dehydrator 50 contains substances that serve as a nitrogen source and a phosphorus source, and therefore the dehydration elimination liquid may be added by reflux as a nutrient source. In addition, when volatile fatty acids (VFAs) such as acetic acid are produced in the decomposition reaction of lignocellulose, the pH of the reaction liquid decreases and the osmotic pressure increases, which changes the number and function of lignocellulose-decomposing bacteria. Therefore, it is preferable to add a buffering agent to the medium in order to mitigate the change in pH and the increase in osmotic pressure. As a buffering agent, it is preferable to use artificial saliva that imitates the saliva of ruminants, since the saliva has a high buffering capacity. Examples of the buffering agent include sodium chloride, sodium bicarbonate, phosphate, and potassium chloride. As shown in Figs. 3 and 4, a part of the filtrate of the microbial culture solution 11 or the decomposition reaction solution 111 may be mixed into the artificial medium. The pH of the medium is adjusted to 6.0 to 7.5, preferably 6.5 to 7.0, by adding an acid or alkali as necessary. The water used for the medium is preferably tap water or groundwater. The ammonium nitrogen concentration in the medium is controlled to 50 to 2,000 mg / L, more preferably 60 to 500 mg / L, by adding water or supplying a dehydrated solution.

[0036] [Microbial culture tank] In the microbial culture tank 10 shown in FIG. 3(a), in order to create an anaerobic state similar to the environment in the rumen, the oxidation-reduction potential of the culture solution for the rumen microorganisms is adjusted to -100 mv or less, more preferably -200 mv or less, and even more preferably about -250 mv. Since the rumen microorganisms (lignocellulose-decomposing bacteria) are anaerobic bacteria, when the ORP becomes higher than a predetermined value (when the ORP approaches an aerobic state), measures such as injecting an inert gas such as nitrogen gas or carbon dioxide gas, adding a reducing substance such as cysteine, L-ascorbic acid, sodium sulfide, ascorbic acid, methionine, thioglycol, or DTT, or adding an organic substance to consume oxygen through the action of facultative anaerobic bacteria may be taken. The microorganisms may also be cultured in a closed system under a nitrogen or carbon dioxide atmosphere.

[0037] In the culture of ruminal microorganisms in the microbial culture tank 10, it is important that the solid retention time (SRT) is longer than the hydraulic retention time (HRT). That is, since lignocellulose decomposing bacteria grow by attaching to the surface of solid matter (lignocellulose-based biomass), if the SRT is short, they are discharged out of the system together with the solid matter. On the other hand, if the HRT is longer than necessary, it will cause negative factors such as a decrease in pH due to the produced volatile fatty acids (VFAs) and inhibition of microbial growth. Specifically, the HRT is controlled to 8 to 36 hours, preferably 10 to 24 hours, and the SRT is controlled to 24 hours or more, preferably 48 to 72 hours. The HRT and SRT are controlled by individually adjusting the discharge amount of the filtrate and the discharge amount of the suspension. In addition, the temperature of the reaction system in the culture of ruminal microorganisms and the lignocellulose decomposition reaction is controlled to 35 to 42°C, more preferably 37 to 40°C, using a temperature sensor or the like. The solid matter concentration of the lignocellulosic biomass fed into the microorganism culture tank 10 is 0.05 to 20% by weight, and more preferably 0.1 to 5% by weight.

[0038] [Decomposition tank] In the decomposition tank 20 (also called a pretreatment tank) shown in FIG. 3(a), lignocellulosic biomass is decomposed by lignin-decomposing enzymes produced by lignocellulose-decomposing bacteria to partially decompose lignin and loosen the rigid structure of lignocellulose, and then decomposed by endoglucanases, exoglucanases, xylanases, etc. into cellulose and hemicellulose, respectively, and converted into hexose (six monosaccharides) such as glucose. Furthermore, pyruvic acid and the like are produced from hexose (six monosaccharides) such as glucose, and as the reaction proceeds further, volatile fatty acids (VFAs) such as acetic acid, propionic acid, butyric acid, and formic acid are produced. Hydrogen and carbon dioxide are also produced during the metabolic process. Since acetic acid, hydrogen, and carbon dioxide are the substrates (raw materials) for methane fermentation, when the production amounts of acetic acid, hydrogen, and carbon dioxide increase with the promotion of lignocellulose decomposition, the production amount of methane also increases. In the lignocellulose decomposition reaction (pretreatment), it is not necessary for lignocellulose to be decomposed and metabolized to hexose (six monosaccharides) or volatile fatty acids (VFAs), and it is sufficient if the difficult-to-decompose lignocellulose is decomposed to a form that is easily utilized in methane fermentation, for example, to the extent of oligosaccharides. In the lignocellulose decomposition (pretreatment), the amount of lignocellulose-based biomass contained in the reaction liquid is 0.5 to 30% by weight, more preferably 0.5 to 10% by weight.

[0039] In the decomposition tank 20 shown in FIG. 3(a), the HRT and SRT are individually controlled in the microorganism culture tank 10 upstream of the decomposition tank 20, so that the HRT and SRT do not need to be individually controlled in the decomposition tank 20, and the reaction liquid may be stirred as a complete mixing system. In this case, the reaction liquid in the decomposition tank 20 is not separated into a filtrate and a suspension, so that the HRT and SRT are the same. It is preferable that both the HRT and SRT in the decomposition tank 20 are 4 to 36 hours. In addition, the temperature of the reaction system in the decomposition tank 20 is controlled to 35 to 42°C, more preferably 37 to 40°C, using a temperature sensor or the like. The reaction in the decomposition tank 20 may be performed statically or with stirring, and it is preferable to perform the reaction with stirring in order to accelerate the progress of the lignocellulose decomposition reaction.

[0040] [Microbial culture tank and decomposition tank] In the microbial culture tank / decomposition tank 110 shown in FIG. 3(b), in order to create an anaerobic state similar to the environment in the rumen, the oxidation-reduction potential of the culture solution of the rumen microorganisms is adjusted to -100 mv or less, more preferably -200 mv or less, and even more preferably about -250 mv. Since the rumen microorganisms (lignocellulose-decomposing bacteria) are anaerobic bacteria, when the ORP becomes higher than a predetermined value (when the ORP approaches an aerobic state), measures such as injecting an inert gas such as nitrogen gas or carbon dioxide gas, introducing a reducing substance such as cysteine, L-ascorbic acid, sodium sulfide, ascorbic acid, methionine, thioglycol, or DTT, or introducing organic matter to consume oxygen by the action of facultative anaerobic bacteria may be taken. The culture of the microorganisms and the lignocellulose decomposition reaction may be carried out in a closed system under a nitrogen or carbon dioxide atmosphere.

[0041] In the ruminal microorganism culture and decomposition reaction of lignocellulose in the microbial culture tank and decomposition tank 110, it is important that the solid retention time (SRT) is longer than the hydraulic retention time (HRT). That is, since lignocellulose decomposition bacteria grow by attaching to the surface of solid matter (lignocellulose-based biomass), if the SRT is short, they are discharged from the system together with the solid matter. On the other hand, if the HRT is longer than necessary, it will cause negative factors such as a decrease in pH due to the produced volatile fatty acids (VFAs) and inhibition of microbial growth. Specifically, the HRT is controlled to 8 to 36 hours, preferably 10 to 24 hours, and the SRT is controlled to 24 hours or more, preferably 48 to 72 hours. The HRT and SRT are controlled by individually adjusting the discharge amount of the filtrate and the discharge amount of the suspension. In addition, the temperature of the reaction system in the ruminal microorganism culture and the lignocellulose decomposition reaction is controlled to 35 to 42°C, more preferably 37 to 40°C, using a temperature sensor or the like. The solid matter concentration of the lignocellulosic biomass fed into the microbial culture tank / decomposition tank 110 is 0.05 to 20% by weight, and more preferably 0.1 to 5% by weight.

[0042] As described above, the microbial cultivation and the lignocellulose decomposition reaction may be carried out independently in a microbial culture tank 10 and a decomposition tank 20, as shown in FIG. 3(a), or may be carried out in a single tank, a microbial culture tank / decomposition tank 110, as shown in FIG. 3(b).

[0043] [Methane fermentation tank] In the methane fermentation tank 30 shown in Fig. 3(a)(b), methane fermentation is carried out using lignocellulose decomposition products contained in the reaction liquid sent from the pretreatment tank (decomposition tank 20, microbial culture tank / decomposition tank 110) as substrates. In methane fermentation, lignocellulose, which is difficult to decompose, is decomposed into a form that is easily usable in methane fermentation, for example, lignocellulose-based biomass decomposed to the oligosaccharide level, or volatile fatty acids (lignocellulose decomposition products) such as acetic acid produced in the decomposition reaction (pretreatment), hydrogen, and carbon dioxide as substrates. Methane fermentation is carried out by methanogenic bacteria under anaerobic conditions similar to those of the decomposition reaction by lignocellulose-decomposing bacteria. It can be theoretically predicted that the activity of methanogenic bacteria will also increase when the activity of lignocellulose-decomposing bacteria increases.

[0044] Methane fermentation may be either wet methane fermentation or dry methane fermentation. Also, either mesophilic methane fermentation or thermophilic methane fermentation may be used. In the case of mesophilic methane fermentation, it is preferable to carry out the process for 20 to 30 days, more preferably 23 to 27 days, and even more preferably about 25 days, and in the case of thermophilic methane fermentation, it is preferable to carry out the process for 10 to 20 days, more preferably 13 to 17 days, and even more preferably about 15 days. In addition, the temperature of methane fermentation is higher than 20°C and lower than 40°C, more preferably 30°C or higher and lower than 37°C, and even more preferably about 37°C, in the case of mesophilic fermentation, and higher than 40°C and lower than 60°C, more preferably 50 to 55°C, and even more preferably about 55°C.

[0045] Although the embodiments of the present invention have been described above, they are merely illustrative examples and do not limit the present invention, and the specific configurations and the like can be appropriately modified in design. Furthermore, the actions and effects described in the embodiments of the invention are merely a list of the most preferable actions and effects resulting from the present invention, and the actions and effects of the present invention are not limited to those described in the embodiments of the present invention. [Industrial Applicability]

[0046] The filtration device of the present invention can be used for solid-liquid separation of a microbial culture solution, as well as for wastewater treatment using microorganisms. [Explanation of symbols]

[0047] 1. Filtration equipment 2. Filter body 2a Upper end 2b opening 3 Filtrate discharge section 3a Filtrate discharge pipe 4. Scraper 5 Suspension discharge section 10 Microbial culture tank 11 Microbial culture solution 20 Decomposition tank 30 Methane fermentation tank 40 Crusher 50 Dehydrator 60 Stirring blade 100, 101 Lignocellulose decomposition system 110 Microbial culture tank and decomposition tank 111 Decomposition reaction solution P-Pump Medium Motor

Claims

[Claim 1] A filtration device installed in a microbial culture tank containing a microbial culture solution, a filter having a plurality of pores with an average pore size of 1 μm or more and 1 mm or less for filtering the microbial culture solution, the filter containing the filtered microbial culture solution; A filtrate discharge section that discharges the filtrate contained in the filter body to the outside of the microorganism culture tank; Equipped with The filter is immersed in the microbial culture solution so that the upper end of the filter is located above the liquid level of the microbial culture solution, The filter body rotates about a vertical axis, The filter body is formed in a cylindrical shape with a bottom and an opening at the upper end, the filtrate discharge section has a filtrate discharge pipe inserted through the opening in a non-contact manner, A filtration device comprising: a scraper arranged along a side and / or a bottom surface of the filter body at an outer position and / or an inner position of the filter body; the scraper rotates about an axis in the vertical direction, and the rotation direction is opposite to the rotation direction of the filter body.

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