Anaerobic treatment apparatus and anaerobic treatment method

Abstract

The present invention addresses the problem of providing an anaerobic treatment apparatus and an anaerobic treatment method, with which it is possible to improve treatment efficiency and to stabilize the treatment by easily forming a uniform flow in an anaerobic treatment tank when performing an anaerobic treatment using the anaerobic treatment tank.　In order to solve the problem, the present invention provides an anaerobic treatment apparatus and an anaerobic treatment method therefor, the anaerobic treatment apparatus comprising: an anaerobic treatment tank; an introduction part for introducing water to be treated into the anaerobic treatment tank; and a fluid dispersion part for dispersing the water to be treated, which has been introduced into the anaerobic treatment tank through the introduction part, in the anaerobic treatment tank.　According to the present invention, the flow (in particular, the upward flow) of the water to be treated inside the anaerobic treatment tank can be easily made uniform. As a result, anaerobic microorganisms can be kept at a high concentration in the anaerobic treatment tank, and a state in which the anaerobic microorganisms (or carriers to which the anaerobic microorganisms are adhered) and the water to be treated are efficiently brought into contact with each other can be formed and maintained, and thereby the treatment efficiency can be improved and the treatment can be stabilized.

Description

Anaerobic treatment apparatus and anaerobic treatment method

[0001] The present invention relates to an anaerobic treatment apparatus and an anaerobic treatment method.

[0002] Generally, as a method for treating wastewater containing organic substances, biological treatment using various microorganisms is known. In particular, biological treatment under an anaerobic environment (hereinafter referred to as "anaerobic treatment") has high merits in terms of introduction, such as not requiring aeration power and hardly generating excess sludge.

[0003] As such anaerobic treatment, an upflow anaerobic sludge bed method (UASB) using a treatment tank holding sludge or granules is known. Furthermore, in order to increase the concentration of anaerobic microorganisms in the treatment tank, it is also known to use a treatment tank using a carrier (a treatment tank holding a carrier inside). In these anaerobic treatments, in order to improve the contact efficiency between the anaerobic microorganisms in the treatment tank and the water to be treated, as the name implies, the water to be treated is introduced from the lower part of the treatment tank to form an upflow, which is widely used.

[0004] At this time, in order to form an upflow in the treatment tank, it is common to use a distributor having a large number of discharge nozzles at predetermined intervals in a grid-like or annular pipe arranged at the bottom of the treatment tank. For example, in Patent Document 1, in the treatment of water to be treated (organic wastewater) containing organic substances, the water to be treated is circulated upward and treated in an anaerobic treatment tank provided with a water-to-be-treated supply means at the bottom, and the water-to-be-treated supply means is a distributor having discharge nozzles arranged at predetermined intervals, and a method for supplying water to be treated in an upflow anaerobic treatment apparatus in which the discharge flow rate of the water to be treated from these discharge nozzles is intermittently 3 to 5 times that during normal operation is described.

[0005] Japanese Patent Application Laid-Open No. 2003-340487

[0006] In anaerobic treatment of water to be treated, as described in Patent Document 1, it is necessary to maintain a high concentration of anaerobic microorganisms in the anaerobic treatment tank and to maintain and create a condition in which the anaerobic microorganisms (or carriers to which anaerobic microorganisms are attached) and the water to be treated are in efficient contact, thereby improving treatment efficiency and stabilizing the treatment. For this reason, it is necessary to ensure a sufficient flow velocity at the bottom of the anaerobic treatment tank and to homogenize the fluid flow (especially the upward flow) generated in the anaerobic treatment tank.

[0007] According to Patent Document 1, controlling the flow rate of the treated water supplied from the distributor makes it possible to suppress the enlargement and outflow of microorganisms (granules) in the anaerobic treatment tank. However, when attempting to homogenize the upward flow generated in the anaerobic treatment tank by arranging the discharge nozzles and controlling the flow rate in the distributor, the larger the size of the anaerobic treatment tank, the more it becomes necessary to increase the number of discharge nozzles and control the flow rate discharged from them with uniform and high precision. In this case, in addition to the equipment design related to the number and arrangement of the required discharge nozzles, there are challenges in terms of increased costs in terms of equipment investment and operation, such as the need for a high level of precision in flow rate control.

[0008] The object of the present invention is to provide an anaerobic treatment apparatus and an anaerobic treatment method that can easily create a uniform flow within an anaerobic treatment tank when performing anaerobic treatment using an anaerobic treatment tank, thereby improving treatment efficiency and stabilizing the treatment process.

[0009] As a result of diligent research into the above-mentioned problems, the inventors of the present invention have found that by further dispersing the water to be treated introduced into the anaerobic treatment tank within the anaerobic treatment tank, a uniform flow can be easily formed within the anaerobic treatment tank, thereby improving treatment efficiency and stabilizing the treatment process, and have completed the present invention. That is, the present invention is the following anaerobic treatment apparatus and anaerobic treatment method.

[0010] The anaerobic treatment apparatus of the present invention, which solves the above problems, is characterized by comprising an anaerobic treatment tank, an introduction unit for introducing water to be treated into the anaerobic treatment tank, and a fluid dispersion unit for dispersing the water to be treated introduced into the anaerobic treatment tank via the introduction unit within the anaerobic treatment tank. According to the anaerobic treatment apparatus of the present invention, by further dispersing the water to be treated introduced into the anaerobic treatment tank within the anaerobic treatment tank, it becomes easier to homogenize the flow of the water to be treated inside the anaerobic treatment tank (especially the upward flow). As a result, it is possible to maintain a high concentration of anaerobic microorganisms inside the anaerobic treatment tank and to maintain and create a situation in which anaerobic microorganisms (or carriers to which anaerobic microorganisms are attached) and the water to be treated come into efficient contact, thereby improving treatment efficiency and stabilizing the treatment.

[0011] Furthermore, in one embodiment of the anaerobic treatment apparatus of the present invention, the fluid dispersion section is characterized by being made of granular material. With this characteristic, when the water to be treated introduced into the anaerobic treatment tank passes through the layer of granular material, the gaps between the granular material above the layer of granular material function as fluid discharge ports. Therefore, by using granular material, it is possible to obtain the same effect as if countless discharge ports were arranged in the anaerobic treatment tank. In other words, by the simple operation of using granular material, it becomes easy to homogenize the flow of the water to be treated inside the anaerobic treatment tank (especially the upward flow).

[0012] Furthermore, one embodiment of the anaerobic treatment apparatus of the present invention has the characteristic that the minimum fluidization rate of granular material is greater than the empty column velocity. According to this characteristic, the granular material layer in the anaerobic treatment tank functions as a fixed layer without any flow occurring. With respect to the fluid that passes through the granular material layer and is discharged from above the layer, pressure is applied within the granular material layer, while the pressure load decreases above the layer (the surface layer of the granular material). As a result, the fluid dispersion efficiency in the fluid dispersion section is improved, and it becomes possible to form a stable, uniform flow.

[0013] Furthermore, one embodiment of the anaerobic treatment apparatus of the present invention is characterized in that the height of the fluid dispersion section is 20% or less of the height of the anaerobic treatment tank. This characteristic makes it possible to secure sufficient treatment space within the anaerobic treatment tank after the fluid has passed through the fluid dispersion section. In other words, in addition to homogenizing the fluid flow within the anaerobic treatment tank, it is possible to secure sufficient space for efficient contact between anaerobic microorganisms (or carriers to which anaerobic microorganisms are attached) and the water to be treated.

[0014] Furthermore, in one embodiment of the anaerobic treatment apparatus of the present invention, the anaerobic treatment tank is characterized by having a carrier material held inside. This feature makes it possible to maintain a high concentration of anaerobic microorganisms in the anaerobic treatment tank, and also ensures that the water to be treated flows uniformly into the carrier layer. As a result, the carrier material can be continuously and uniformly flowed within the anaerobic treatment tank, enabling even more stable treatment.

[0015] Furthermore, one embodiment of the anaerobic treatment apparatus of the present invention is characterized in that the carrier is activated carbon. This characteristic allows for the use of a carrier that excels in its function as a carrier for attaching and supporting sludge (microorganisms), and because of its high specific gravity and settling velocity, carrier outflow is less likely to occur, enabling stable and continuous treatment.

[0016] The present invention provides an anaerobic treatment method for solving the above problems, comprising a water to be treated introduction step of introducing water to be treated into an anaerobic treatment tank, and a fluid dispersion step of dispersing the water to be treated introduced into the anaerobic treatment tank in the water to be treated introduction step within the anaerobic treatment tank. According to the present invention's anaerobic treatment method, by further dispersing the water to be treated introduced into the anaerobic treatment tank within the anaerobic treatment tank, it becomes easier to homogenize the flow of the water to be treated (especially the upward flow) within the anaerobic treatment tank. This makes it possible to maintain a high concentration of anaerobic microorganisms within the anaerobic treatment tank and to maintain and create a situation in which anaerobic microorganisms (or carriers to which anaerobic microorganisms are attached) and the water to be treated are in efficient contact, thereby improving treatment efficiency and stabilizing the treatment.

[0017] Furthermore, in one embodiment of the anaerobic treatment method of the present invention, the fluid dispersion step is characterized by including a granular material filling step in which granular material is filled into the anaerobic treatment tank to form a layer of granular material. With this feature, the water to be treated introduced into the anaerobic treatment tank passes through the layer of granular material. At this time, the gaps between the granular material above the layer of granular material function as fluid discharge ports, making it possible to obtain an effect similar to that of having countless discharge ports arranged in the anaerobic treatment tank. In other words, by the simple operation of filling with granular material (forming a layer of granular material), it becomes easy to homogenize the flow of the water to be treated inside the anaerobic treatment tank (especially the upward flow).

[0018] The present invention provides an anaerobic treatment apparatus and an anaerobic treatment method that can easily create a uniform flow within an anaerobic treatment tank when performing anaerobic treatment using an anaerobic treatment tank, thereby improving treatment efficiency and stabilizing the treatment process.

[0019] This is a schematic diagram illustrating an anaerobic treatment device according to the first embodiment of the present invention. This is a schematic diagram illustrating an anaerobic treatment device according to the second embodiment of the present invention. This is a schematic diagram illustrating an example of the structure of a conventional anaerobic treatment device.

[0020] In the present invention, the water to be treated by the anaerobic treatment device contains organic matter, and preferred examples include industrial wastewater discharged from various factories such as food processing plants, chemical plants, and pulp and paper mills, as well as domestic wastewater such as sewage. However, the wastewater to be treated in the present invention is not limited to these examples; any wastewater containing organic matter that can be biologically treated under anaerobic conditions is subject to treatment in the present invention. Examples of such wastewater include organic wastewater containing livestock manure and sludge (excess sludge).

[0021] Hereinafter, embodiments of the anaerobic treatment apparatus and anaerobic treatment method according to the present invention will be described in detail with reference to the drawings. The description of the anaerobic treatment method in the present invention will be replaced by the description of the operation of the anaerobic treatment apparatus according to the present invention. The anaerobic treatment apparatus and anaerobic treatment method described in the embodiments are merely illustrative examples for the purpose of explaining the anaerobic treatment apparatus and anaerobic treatment method according to the present invention, and are not limited thereto.

[0022] The anaerobic treatment apparatus and anaerobic treatment method according to this embodiment relate to an anaerobic treatment apparatus and anaerobic treatment method for biologically treating (anaerobic) water to be treated. More specifically, the anaerobic treatment apparatus and anaerobic treatment method according to this embodiment aim to improve treatment efficiency and stabilize treatment by uniformizing the fluid flow in the anaerobic treatment tank by simple means.

[0023] [First Embodiment] Figure 1 is a schematic diagram illustrating the structure of an anaerobic treatment apparatus in the first embodiment of the present invention. As shown in Figure 1, the anaerobic treatment apparatus 1A in this embodiment comprises an anaerobic treatment tank 10 in which a carrier C is held, an introduction unit 20 for introducing water to be treated (in this embodiment, "wastewater W0") into the anaerobic treatment tank 10, and a fluid dispersion unit 30 for further dispersing the wastewater W0 introduced from the introduction unit 20 within the anaerobic treatment tank 10. In this embodiment, wastewater W0 is introduced into the anaerobic treatment apparatus 1A as the target for treatment, and after anaerobic treatment by the anaerobic treatment tank 10, the treated water W1 is discharged outside the system. The arrows indicated for each line in Figure 1 indicate the flow of wastewater W0 and treated water W1, and the arrows inside the anaerobic treatment tank 10 indicate the flow of fluid (mainly wastewater W0) inside the anaerobic treatment tank 10.

[0024] (Anaerobic Treatment Tank) The anaerobic treatment tank 10 in this embodiment is not particularly limited as long as it has a structure for performing anaerobic treatment on wastewater W0. Examples of anaerobic treatments performed in the anaerobic treatment tank 10 include methane fermentation by acid-producing bacteria and methane-producing bacteria, denitrification treatment in which nitrate and nitrite are reduced by denitrifying bacteria, and sulfate reduction treatment in which sulfate is reduced by sulfate-reducing bacteria.

[0025] Furthermore, the anaerobic treatment tank 10 in this embodiment may be equipped with various additional facilities. For example, the anaerobic treatment tank 10 may be equipped with means for adjusting the internal water temperature, means for adding pH adjusters, and means for adding metals such as nitrogen, phosphorus, cobalt, and nickel, which are nutrients required by microorganisms. In particular, when methane fermentation by acid-producing bacteria and methane-producing bacteria is performed as anaerobic treatment, it is preferable to provide the anaerobic treatment tank 10 with facilities for recovering, purifying, and storing methane gas. In addition, as shown in Figure 1A, it is preferable that the anaerobic treatment tank 10 in this embodiment is equipped with a gas holder 11 for recovering and storing the biogas G produced by anaerobic treatment.

[0026] Furthermore, another reaction tank may be provided upstream of the anaerobic treatment tank 10 in this embodiment. In particular, when methane fermentation using acid-producing bacteria and methane-producing bacteria is performed as anaerobic treatment, it is known that the optimal conditions for the treatment process using acid-producing bacteria, which reduces organic matter in wastewater W0 to low molecular weight (hereinafter referred to as the "acid production process"), and the treatment process using methane-producing bacteria, which decomposes the reduced molecular weight organic matter to produce methane gas (hereinafter referred to as the "methane production process"), are different. Therefore, as shown in Figure 1, it is preferable to provide an acid production tank 11 upstream of the anaerobic treatment tank 10 and to carry out the acid production process and the methane production process in separate tanks. The acid production tank 11 should function as a tank for carrying out the acid production process, in which wastewater W0 is introduced upstream of the anaerobic treatment tank 10, and in an anaerobic atmosphere without dissolved oxygen, the acid-producing bacteria (one of the facultative anaerobic bacteria) contained inside promote the reduction of organic matter in wastewater W0 (decomposition of organic matter) to produce organic acids. Furthermore, it is desirable that the acid generation tank 11 be a sealed system to maintain an anaerobic environment.

[0027] In this embodiment, the description will mainly focus on a configuration in which an acid generation tank 11 is provided upstream of the anaerobic treatment tank 10, but the invention is not limited to this configuration. For example, the acid generation tank 11 may be omitted, and the wastewater W0 may be directly introduced into the anaerobic treatment tank 10. Alternatively, a raw water adjustment tank or raw water storage tank may be provided further upstream of the acid generation tank 11.

[0028] An example of the arrangement and connection of the anaerobic treatment tank 10 and its surrounding equipment in this embodiment will be explained with reference to Figure 1. For example, as shown in Figure 1, the acid generation tank 11 is arranged upstream of the anaerobic treatment tank 10, and a line L1 for introducing wastewater W0 to the acid generation tank 11 and a line L2 for connecting to the anaerobic treatment tank 10 are provided, and wastewater W0 is indirectly introduced to the anaerobic treatment tank 10 via line L2, and a line L3 for discharging treated water W1 after anaerobic treatment is provided.

[0029] Furthermore, the anaerobic treatment tank 10 of this embodiment may be provided with a structure for circulating treated water W1 within the anaerobic treatment tank 10, in consideration of improving the treatment efficiency of anaerobic treatment. For example, as shown in Figure 1, in addition to line L3, a line L4 may be provided for discharging treated water W1 and connected to the upstream side of the anaerobic treatment tank 10. In this case, line L4 may be connected to line L2, or it may be connected to the acid generation tank 11.

[0030] Furthermore, it is preferable that the anaerobic treatment tank 10 according to this embodiment holds a carrier C, as shown in Figure 1. Anaerobic microorganisms adhere to the surface of this carrier C, forming a biofilm, which makes it possible to retain anaerobic microorganisms involved in anaerobic treatment within the anaerobic treatment tank 10. This increases the concentration of anaerobic microorganisms within the anaerobic treatment tank 10 and improves the treatment efficiency related to anaerobic treatment. Alternatively, instead of holding the carrier C in the anaerobic treatment tank 10, microbial masses (granulated microorganisms) such as granules may be used. Granules are granulated microorganisms (microbial masses) with a diameter of about 0.3 to 3 mm that utilize self-immobilization, and are capable of maintaining a high concentration of microbial cells. In any case, the anaerobic treatment apparatus 1A of this embodiment creates a uniform fluid flow within the anaerobic treatment tank 10, making it possible to efficiently bring solid material consisting of anaerobic microorganisms (carrier C or microbial mass with a biofilm formed on it) into contact with the water to be treated (wastewater W0) within the anaerobic treatment tank 10. The following explanation will describe a case where the carrier C is held within the anaerobic treatment tank 10, but it is not limited to this case.

[0031] (Carrier) The carrier C introduced and held in the anaerobic treatment tank 10 can be any carrier to which anaerobic microorganisms involved in anaerobic treatment adhere, and its structure and material are not particularly limited, however, in this embodiment, it is preferable to use a carbonaceous carrier as the carrier C. A carbonaceous carrier refers to an inorganic material whose main component is carbon, and specifically, examples include carbon black, graphite, coke, and activated carbon. In addition to being easy to mold as a carrier, carbonaceous carriers generally have a higher specific gravity than resin carriers, and have the advantage of suppressing outflow to the outside of the tank when held and flowed in the anaerobic treatment tank 10. Furthermore, in this embodiment, the carbonaceous carrier is not particularly limited in terms of whether or not it has pores, but from the viewpoint of being able to adsorb components that inhibit anaerobic treatment by anaerobic microorganisms (anaerobic treatment inhibitors) in addition to holding anaerobic microorganisms, it is preferable to have pores, and specifically, it is particularly preferable to use activated carbon.

[0032] The anaerobic microorganisms attached to the carrier C in this embodiment can be any microorganism capable of anaerobic treatment of organic matter, and the specific type of microorganism is not particularly limited. For example, when methane fermentation treatment is performed as anaerobic treatment, acid-producing bacteria and methane-producing bacteria are used as anaerobic microorganisms. Other anaerobic microorganisms include denitrifying bacteria used in denitrification treatment to reduce nitrate and nitrite, and sulfate-reducing bacteria used in sulfate reduction treatment to reduce sulfuric acid. In this embodiment, isolated microorganisms may be used as anaerobic microorganisms, or seed sludge (activated sludge, digested sludge) collected from other wastewater treatment facilities may be used. Furthermore, anaerobic microorganisms contained in wastewater W0 may be utilized.

[0033] At this time, it is required to form a uniform fluid flow within the anaerobic treatment tank 10 and to ensure that the carrier C flows uniformly.

[0034] Figure 3 is a schematic diagram of a conventional anaerobic treatment apparatus equipped with an anaerobic treatment tank holding a carrier. Structures common to the anaerobic treatment apparatus 1A of the present invention are given the same numbers and their explanations are omitted. As shown in Figure 3, in the conventional anaerobic treatment apparatus 100, an introduction pipe 200 (corresponding to the introduction section 20 in this embodiment) having multiple discharge nozzles like a distributor is used to introduce wastewater W0 into the anaerobic treatment tank 10 in which the carrier C is held. At this time, the flow of wastewater W0 flowing into the anaerobic treatment tank 10 via the introduction pipe 200 is an upward flow toward the top of the tank, but because the wastewater W0 moves with a spreading outward from the discharge nozzle of the introduction pipe 200 toward the carrier C (carrier layer), as shown in Figure 3, the fluid flow is not uniform and an imbalance inevitably exists. This phenomenon can be resolved by increasing the number of discharge nozzles in the introduction piping 200. However, in order to homogenize the fluid flow by increasing the number of discharge nozzles, it is necessary to design the introduction piping 200 or arrange the discharge nozzles so that the number and arrangement of discharge nozzles can cover the entire cross-section (bottom surface) of the anaerobic treatment tank 10, which is difficult to implement from a cost perspective.

[0035] On the other hand, the anaerobic treatment apparatus 1A in this embodiment further disperses the wastewater W0 introduced into the anaerobic treatment tank 10 within the anaerobic treatment tank 10, thereby easily forming a uniform flow within the anaerobic treatment tank 10, improving treatment efficiency and stabilizing the treatment. More specifically, the anaerobic treatment apparatus 1A in this embodiment goes through a water to be treated introduction step in which wastewater W0, which is the water to be treated, is introduced into the anaerobic treatment tank 10, and a fluid dispersion step in which the water to be treated (wastewater W0) introduced into the anaerobic treatment tank 10 by the water to be treated introduction step is dispersed within the anaerobic treatment tank 10. In this way, the flow of the fluid (wastewater W0) that moves within the anaerobic treatment tank 10 after being introduced into the anaerobic treatment tank 10 is made uniform throughout the anaerobic treatment tank 10, thereby improving treatment efficiency and stabilizing the treatment.

[0036] (Introduction Section) The introduction section 20 in this embodiment is for performing an introduction step of introducing the water to be treated (wastewater W0) into the anaerobic treatment tank 10. As shown in Figure 1, it is connected to a line L2 provided for transferring wastewater W0 to the anaerobic treatment tank 10 and consists of piping 21 provided inside the anaerobic treatment tank 10. The location of the introduction section 20 is not particularly limited, but it is preferable to provide it in the lower part (near the bottom) of the anaerobic treatment tank 10. This suppresses the accumulation of carrier C (or solid material such as granules) at the bottom of the anaerobic treatment tank 10, and by introducing wastewater W0 into the fluid dispersion section 30 (described later) in the lower part (lower region) of the anaerobic treatment tank 10, the fluid flow discharged from the fluid dispersion section 30 moves over a wide area inside the anaerobic treatment tank 10. In other words, it is possible to form a uniform upward flow over a wide area inside the anaerobic treatment tank 10.

[0037] Here, the piping 21 can be any structure that can introduce wastewater W0 into the anaerobic treatment tank 10, but it is desirable that the fluid be introduced into the fluid distribution section 30, which will be described later, from multiple locations. For this reason, it is particularly preferable that the introduction section 20 in this embodiment has multiple structures for introducing wastewater W0 inside the anaerobic treatment tank 10. More specifically, for example, the piping 21 may consist of a tubular structure having multiple openings or discharge nozzles on its side. That is, a known fluid supply means called a so-called distributor is a suitable example of the introduction section 20 in this embodiment.

[0038] (Fluid Dispersion Section) The fluid dispersion section 30 is for performing a fluid dispersion step in which the wastewater W0 introduced into the anaerobic treatment tank 10 via the introduction section 20 is further dispersed within the anaerobic treatment tank 10. As described above, in conventional anaerobic treatment devices 100, when wastewater W0 is introduced by the introduction piping 200 (introduction section 20), even if wastewater W0 is introduced from multiple locations, the fluid flow within the anaerobic treatment tank 10 will not be uniform, and an uneven distribution will inevitably exist. In this embodiment, instead of increasing the number of discharge nozzles of the introduction piping 200, the fluid dispersion section 30 further disperses the fluid introduced from the introduction section 20, thereby forming a fluid flow (upward flow) that can cover the entire cross-section of the anaerobic treatment tank 10. In other words, by providing the fluid dispersion section 30 in this embodiment, the fluid flow throughout the entire anaerobic treatment tank 10 is made uniform. Furthermore, in this embodiment, the fluid dispersion section 30 receives the fluid introduced from the introduction section 20 and forms a fluid flow toward the upper part of the anaerobic treatment tank 10 as the fluid passes through the fluid dispersion section 30. Therefore, the fluid dispersion section 30 is provided so as to be able to disperse the fluid within the anaerobic treatment tank 10 at least above the introduction section 20.

[0039] A specific example of the fluid dispersion section 30 in this embodiment is, as shown in Figure 1, forming a layer of granular material 30a in the anaerobic treatment tank 10 around the introduction section 20, and introducing fluid (wastewater W0) into this layer of granular material 30a. In other words, the fluid dispersion step in this embodiment includes a granular material forming step in which granular material 30a is filled into the anaerobic treatment tank 10 to form a layer of granular material 30a in the anaerobic treatment tank 10.

[0040] Here, the fluid dispersion section 30 disperses the fluid above the introduction section 20. Therefore, the anaerobic treatment tank 10 is filled with granular material 30a such that the height of the granular material layer 30a is above the location of the introduction section 20 (especially the discharge points of the wastewater W0, such as the opening of the piping 21 and the discharge port of the discharge nozzle). In addition, it is preferable that the height of the fluid dispersion section 30 (height of the granular material layer 30a) be 20% or less of the tank height of the anaerobic treatment tank 10. This makes it possible to secure sufficient treatment space in the anaerobic treatment tank 10 after the fluid has passed through the fluid dispersion section 30. In other words, in addition to homogenizing the fluid flow in the anaerobic treatment tank 10, it is possible to secure sufficient space for efficient contact between anaerobic microorganisms (or carriers to which anaerobic microorganisms are attached) and wastewater W0. When a carrier C is held in the anaerobic treatment tank 10, a carrier layer is formed above the fluid dispersion section 30. In the anaerobic treatment apparatus 1A of this embodiment, as shown in Figure 1, a carrier layer is formed above the layer of granular material 30a. This makes it possible to uniformly supply the dispersed fluid (wastewater W0) that has passed through the fluid dispersion section 30 to the carrier layer, thereby ensuring uniform flow of the carrier C.

[0041] By using granular material 30a as the fluid dispersion section 30 and forming a layer of granular material 30a, the wastewater W0 introduced into the anaerobic treatment tank 10 via the introduction section 20 passes through the layer of granular material 30a. At this time, the gaps between the granular material 30a above the layer of granular material 30a function as fluid discharge ports. Therefore, by utilizing the layer formed by the granular material 30a, it is possible to obtain the same effect as if countless discharge ports were arranged in the cross-section of the anaerobic treatment tank 10. That is, as shown in Figure 1, by passing through the layer of granular material 30a, the flow of wastewater W0 is widely dispersed within the layer of granular material 30a, and the fluid (mainly wastewater W0) discharged from above the layer of granular material 30a is uniformly supplied upwards towards the anaerobic treatment tank 10. A uniform upward flow is formed throughout the entire carrier layer provided above the fluid dispersion section 30, making it possible to ensure uniform flow.

[0042] As the granular material 30a in the present embodiment, it is preferable that the granular material 30a settles in the anaerobic treatment tank 10 and does not float (flow) due to the inflow of the drainage W0 introduced through the introduction part 20, and the layer composed of the granular material 30a functions as a fixed layer. Thereby, regarding the fluid (drainage W0) that passes through the inside of the layer of the granular material 30a and is discharged from above the layer, pressure is loaded within the layer of the granular material 30a, while above the layer (the surface layer part of the granular material 30a, in the present embodiment, the interface between the layer of the granular material 30a and the carrier layer), the pressure load decreases. That is, the pressure loss increases when the fluid dispersion part 30 passes through the fluid (drainage W0). Thereby, the dispersion efficiency of the fluid moving inside the layer of the granular material 30a is improved, and it becomes possible to form a stable uniform flow.

[0043] Therefore, as the granular material 30a of the present embodiment, it is preferable to use a solid material with a large specific gravity. In addition, the minimum fluidization velocity of the granular material 30a is preferably greater than the superficial velocity. The superficial velocity is a value obtained by dividing the introduction amount of the fluid (drainage W0) into the anaerobic treatment tank 10 by the cross-sectional area of the anaerobic treatment tank 10. Since the minimum fluidization velocity of the granular material 30a is greater than this superficial velocity, the layer composed of the granular material 30a functions as a fixed layer. Also, as the granular material 30a of the present embodiment, from the viewpoint of ensuring the flow path of the drainage W0, it is preferable that the particle size is large. For example, it is preferable to use a material having a larger particle size than the carrier C. More specifically, it is preferably 5 times or more, more preferably 10 times or more the particle size of the carrier C. Note that since the particle size of the granular material 30a is also involved in the minimum fluidization velocity, it is preferable to set it in view of the viewpoint of ensuring the flow path due to the gap size between the granular materials 30a and the relationship between the superficial velocity and the minimum fluidization velocity of the granular material 30a.

[0044] Specific examples of the granular material 30a of the present embodiment include glass beads, bricks (crushed bricks), etc. Thereby, those having the advantages of a large specific gravity and little deterioration due to repeated use can be used as the fluid dispersion part 30.

[0045] In this embodiment, the specific gravity and shape (particle size) of the granular material 30a and the carrier C may be selected based on the empty column velocity in the anaerobic treatment tank 10. Alternatively, the tank design of the anaerobic treatment tank 10 or the amount of fluid introduced into the anaerobic treatment tank 10 may be adjusted so that the empty column velocity in the anaerobic treatment tank 10 is greater than the minimum fluidization velocity of the carrier C and less than the minimum fluidization velocity of the granular material 30a. In particular, it is preferable to adjust the amount of fluid introduced into the anaerobic treatment tank 10 so that the empty column velocity is greater than the minimum fluidization velocity of the carrier C and less than the minimum fluidization velocity of the granular material 30a. This makes it possible for the granular material 30a and the carrier C to effectively perform their respective functions with simple operation and without the need to replace the granular material 30a and the carrier C.

[0046] As described above, the anaerobic treatment apparatus and anaerobic treatment method in this embodiment make it easy to homogenize the flow of the water to be treated (especially the upward flow) inside the anaerobic treatment tank by further dispersing the water to be treated introduced into the anaerobic treatment tank via a fluid dispersion unit. This makes it possible to maintain a high concentration of anaerobic microorganisms inside the anaerobic treatment tank and to maintain and create a situation in which the anaerobic microorganisms (or carriers to which anaerobic microorganisms are attached) and the water to be treated are in efficient contact, thereby improving treatment efficiency and stabilizing the treatment process.

[0047] Furthermore, in this embodiment, the anaerobic treatment apparatus and anaerobic treatment method utilize granular material as a fluid dispersion unit. As the water to be treated introduced into the anaerobic treatment tank passes through the granular layer, the gaps between the granular particles above the granular layer function as fluid discharge ports. Therefore, by using granular material, it is possible to obtain the same effect as if countless discharge ports were arranged within the anaerobic treatment tank. In other words, the simple operation of using granular material makes it easy to homogenize the flow of the water to be treated inside the anaerobic treatment tank (especially the upward flow).

[0048] [Second Embodiment] FIG. 2 is a schematic explanatory diagram of an anaerobic treatment apparatus according to a second embodiment of the present invention. The anaerobic treatment apparatus 1B according to the present embodiment uses a porous plate-like member 30b instead of the granular material 30a as the fluid dispersion unit 30 in the anaerobic treatment apparatus 1A of the first embodiment. In the description of the anaerobic treatment apparatus 1B according to the present embodiment, the description of the same parts as those in the first embodiment will be omitted.

[0049] As shown in FIG. 2, the anaerobic treatment apparatus 1B of the present embodiment does not fill the granular material 30a as the fluid dispersion unit 30, but arranges a porous plate-like member 30b (hereinafter also simply referred to as "plate-like member 30b") inside the anaerobic treatment tank 10. When the fluid passes through this plate-like member 30b, the fluid is dispersed.

[0050] The plate-like member 30b of the present embodiment is provided above the introduction unit 20. The treated water (wastewater W0) from the introduction unit 20 flows in and passes through, so that it is dispersed and discharged within the plate-like member 30b. In the plate-like member 30b, the porous structure portion functions as a fluid discharge port.

[0051] As described above, the plate-like member 30b of the present embodiment disperses the fluid above the introduction unit 20. Therefore, the plate-like member 30b is arranged in the anaerobic treatment tank 10 so that the position where the plate-like member 30b is arranged is above the position where the introduction unit 20 is arranged (especially the discharge position of the wastewater W0 such as the opening of the pipe 21 or the discharge port of the discharge nozzle). At this time, it is preferable that the separation distance between the position where the plate-like member 30b is arranged and the position where the introduction unit 20 is arranged is short. Thereby, the wastewater W0 discharged from the introduction unit 20 flows into the plate-like member 30b at a high water pressure stage, and it becomes possible to further increase the pressure loss when the fluid (wastewater W0) passes through the plate-like member 30b, and the dispersion efficiency in the plate-like member 30b can be improved. At the same time, in the anaerobic treatment tank 10, it is possible to sufficiently secure the treatment space after the fluid passes through the fluid dispersion unit 30.

[0052] Furthermore, even when the carrier C is held in the anaerobic treatment tank 10 in the anaerobic treatment apparatus 1B of this embodiment, a carrier layer is formed above the fluid dispersion section 30 (plate-shaped member 30b), similar to the first embodiment described above. This makes it possible to uniformly supply the dispersed fluid (wastewater W0) that has passed through the fluid dispersion section 30 to the carrier layer, thereby ensuring uniform flow of the carrier C.

[0053] The plate-shaped member 30b in this embodiment can be any plate-shaped structure having multiple holes, and a preferred example is one in which the pressure loss increases before and after inflow. Specific examples of the plate-shaped member 30b include, for example, plate-shaped structures made of perforated metal or sintered body (formed and heated from metal or ceramic powder), as well as structures made of porous material such as pumice or porous ceramic, plate-shaped structures made of fibers, and plate-shaped structures having a mesh-like (net-like) structure.

[0054] In this embodiment, when perforated metal is used as the plate-shaped member 30b, it has the advantage of being easy to adjust the hole diameter and the density of the holes. Furthermore, when a sintered body or porous body is used as the plate-shaped member 30b, it can function as a fluid dispersion section 30 equipped with countless fine discharge ports, and because it is integrated as the fluid dispersion section 30, it has the advantage of being easy to remove from the anaerobic treatment tank 10 and easy to maintain. Furthermore, when fibers are used as the plate-shaped member 30b, it has the advantage of being easy to adjust the pressure loss by selecting the type of fiber, and easy to remove from the anaerobic treatment tank 10 and easy to maintain. Moreover, when a mesh-like structure is used as the plate-shaped member 30b, because the holes are regular, it can function as a fluid dispersion section 30 equipped with countless discharge ports and easy uniform dispersion. In addition, it has the advantage of being easy to adjust the pressure loss by selecting the wire diameter and mesh opening that form the mesh-like structure.

[0055] In this embodiment, the plate-shaped member 30b may be a single plate-shaped structure, or multiple plate-shaped structures may be provided at predetermined intervals. For example, a single plate-shaped structure having a predetermined thickness may be used as the plate-shaped member 30b to ensure a sufficient thickness for fluid dispersion, or multiple plate-shaped structures may be used to ensure a sufficient thickness for fluid dispersion, from the viewpoint of facilitating handling related to the arrangement of the plate-shaped member 30b in the anaerobic treatment tank 10, such as the weight of the plate-shaped member 30b.

[0056] In this embodiment, the plate-shaped member 30b functions as a fluid dispersion section 30 through which fluid dispersion occurs when fluid flows in and passes. Its function and required physical properties (nature and characteristics) differ from, for example, a partition plate used to hold multiple carriers C in an anaerobic treatment tank 10.

[0057] As described above, in this embodiment, the anaerobic treatment apparatus and anaerobic treatment method use a porous plate-shaped member as a fluid dispersion section. As the water to be treated introduced into the anaerobic treatment tank passes through the plate-shaped member, the porous structure of the plate-shaped member functions as a fluid discharge port. Therefore, by simply using (arranging) a porous plate-shaped member, it becomes easy to homogenize the flow of the water to be treated inside the anaerobic treatment tank (especially the upward flow).

[0058] The embodiments described above are merely examples of anaerobic treatment apparatuses and anaerobic treatment methods. The anaerobic treatment apparatus and anaerobic treatment method according to the present invention are not limited to the embodiments described above, and the anaerobic treatment apparatus and anaerobic treatment method according to the embodiments described above may be modified without changing the gist of the claims.

[0059] The anaerobic treatment apparatus and anaerobic treatment method of the present invention are used in the anaerobic treatment of wastewater containing organic matter, and are particularly suitable for use in an anaerobic treatment apparatus and anaerobic treatment method equipped with an anaerobic treatment tank that forms an upward flow.

[0060] 1A, 1B Anaerobic treatment apparatus, 10 Anaerobic treatment tank, 11 Acid generation tank, 20 Inlet section, 21 Piping, 30 Fluid dispersion section, 30a Granular material, 30b Porous plate-shaped member, 100 Conventional anaerobic treatment apparatus, 200 Inlet piping, L1-L4 Line, C Carrier, W0 Wastewater, W1 Treated water

Claims

1. An anaerobic treatment apparatus comprising: an anaerobic treatment tank; an introduction unit for introducing water to be treated into the anaerobic treatment tank; and a fluid dispersion unit for dispersing the water to be treated introduced into the anaerobic treatment tank via the introduction unit within the anaerobic treatment tank.

2. The anaerobic treatment apparatus according to claim 1, characterized in that the fluid dispersion section consists of granular material.

3. The anaerobic treatment apparatus according to claim 2, characterized in that the minimum fluidization rate of the granular material is greater than the empty tower velocity.

4. The anaerobic treatment apparatus according to claim 1, characterized in that the height of the fluid dispersion section is 20% or less of the height of the anaerobic treatment tank.

5. The anaerobic treatment apparatus according to claim 1, characterized in that the anaerobic treatment tank holds a carrier inside.

6. The anaerobic treatment apparatus according to claim 5, characterized in that the carrier is activated carbon.

7. An anaerobic treatment method comprising: a water to be treated introduction step of introducing water to be treated into an anaerobic treatment tank; and a fluid dispersion step of dispersing the water to be treated introduced into the anaerobic treatment tank by the water to be treated introduction step within the anaerobic treatment tank.

8. The anaerobic treatment method according to claim 6, characterized in that the fluid dispersion step includes a granular material filling step of filling the anaerobic treatment tank with granular material to form a layer of granular material.

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