Sludge digestion system

Abstract

This invention provides a sludge digestion system that enables accelerated sludge decomposition with a simple configuration. [Solution] The sludge digestion apparatus 1 comprises an aerobic digestion reactor 10 having a sludge supply unit 20, a carrier holding unit 30 provided below the sludge supply unit 20, and an air introduction unit 40 for introducing air into the carrier holding unit 30, and a sludge return means 60 for returning organic sludge discharged downward from the carrier holding unit 30 and supplying it to the carrier holding unit 30.

Description

Technical Field

[0004] , , , , , , , , , ,

[0001] The present invention relates to a sludge digestion apparatus. <000...​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​[Means for solving the problem]

[0005] [1] A sludge digestion apparatus according to one aspect of the present disclosure includes: a sludge supply unit to which organic sludge is supplied; an aerobic digestion reactor having at least one carrier holding unit provided below the sludge supply unit to hold a plurality of porous carriers and such that the organic sludge supplied to the sludge supply unit comes into contact with the carriers; and an air introduction unit for introducing air into the carrier holding unit; and a sludge return means for returning the organic sludge discharged downward from the carrier holding unit of the aerobic digestion reactor and supplying it to the carrier holding unit.

[0006] [1] In the sludge digestion apparatus, organic sludge supplied to the sludge supply section comes into contact with a carrier held in the carrier holding section. The organic sludge adheres to (or is captured by) the porous carrier. Within the carrier holding section, the filtrate filtered (or separated) by the carrier falls and is discharged downwards. Air is introduced into the carrier holding section by the air introduction section, so aerobic digestion (decomposition) of the organic sludge takes place on the surface and inside the carrier. Some of the organic sludge flows out without being retained by the carrier. Also, some of the organic sludge that adheres to the carrier peels off and flows out. Because the organic sludge repeatedly comes into contact with the carrier by the sludge return means, the likelihood of the organic sludge adhering to the carrier increases, which lengthens the residence time of the sludge in the reactor (lengthens the time for decomposition), and thus increases the decomposition rate. In this way, the decomposition of organic sludge can be promoted with a simple configuration consisting of an aerobic digestion reactor and a sludge return means.

[0007] [2] In the sludge digestion apparatus described in [1] above, the aerobic digestion reactor has a vertically elongated, cylindrical reactor body, and the air inlet may include a lower air inlet located below the carrier holding section. With this configuration, air is introduced from the lower air inlet and supplied so as to rise inside the reactor body. Thus, the apparatus configuration can be made even simpler. Air can easily reach a large number of carriers inside the vertical reactor body.

[0008] [3] In the sludge digestion apparatus described in [2] above, a plurality of carrier holding sections are arranged vertically within the reactor body, and the air introduction section may include an intermediate air introduction section located between the plurality of carrier holding sections on the side wall of the reactor body. With this configuration, air necessary for aerobic digestion can be supplied evenly to each part of the vertical reactor body in the vertical direction.

[0009] [4] In any one of the sludge digestion apparatuses described in [1] to [3] above, a solid-liquid separation means is provided on the discharge side of the aerobic digestion reactor to perform solid-liquid separation on the organic sludge that has passed through the aerobic digestion reactor, and the sludge return means may supply the concentrated sludge, which is the solid portion separated by the solid-liquid separation means, to the carrier holding unit. With this configuration, the concentrated sludge is supplied again to the carrier holding unit, thereby increasing the sludge decomposition efficiency. The separated liquid, which is the liquid portion separated by the solid-liquid separation means, can also be processed separately in another treatment device at a later stage (the separated liquid may be discharged if the regulations at the destination permit).

[0010] [5] In any one of the sludge digestion apparatuses described in [1] to [4] above, the carrier holding section may maintain an environment on the surface or inside the carrier in which metazoans or arthropods can grow. Such an apparatus configuration and environment can further promote the decomposition of organic sludge. Furthermore, it may be possible to promote a food chain on the surface or inside the carrier. [Effects of the Invention]

[0011] According to the present invention, it is possible to accelerate the decomposition of organic sludge with a simple configuration comprising at least an aerobic digestion reactor and a sludge return means. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic diagram of a sludge digestion apparatus according to one embodiment. [Figure 2]Figure 2(a) shows the state in which organic sludge passes through the carrier holding section, Figure 2(b) shows the state in which organic sludge passes through the carrier, and Figure 2(c) shows the state in which air passes through the carrier. [Figure 3] Figure 3 shows a specific example of the configuration of a sludge digestion apparatus according to one embodiment. [Figure 4] Figure 4 is a perspective view showing an enlarged portion of Figure 3. [Figure 5] Figure 5 shows the apparatus used in the preliminary experiment. [Figure 6] Figure 6 shows the daily change in sludge volume in a preliminary experiment. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same elements will be denoted by the same reference numerals, and redundant descriptions will be omitted.

[0014] The organic sludge processed by the sludge digester 1 of this embodiment may be sewage sludge discharged after biological treatment of sewage (such as activated sludge treatment), or it may be other types of sludge. For example, it is not limited to sewage sludge; sludge resulting from coagulation and sedimentation or industrial wastewater treatment can also be processed by the sludge digester 1 as long as it falls within the category of organic sludge.

[0015] Figure 1 shows a schematic diagram of a sludge digestion apparatus 1 according to one embodiment. As shown in Figure 1, the sludge digestion apparatus 1 includes an aerobic digestion reactor 10 provided with a carrier holding section 30 that holds a large number of carriers (not shown in Figure 1). The aerobic digestion reactor 10 has a bottomed cylindrical or bottomed box-shaped reactor body 11. The carrier holding section 30 is filled with a large number of carriers so as to substantially fill the area of ​​the horizontal cross-section of the reactor body 11. A sludge inflow line L1 is connected to the upper part of the reactor body 11, and organic sludge, which is the material to be processed by this apparatus, is supplied via the sludge inflow line L1.

[0016] The aerobic digestion reactor 10 has a sludge supply section 20 provided above the carrier holding section 30 and at the upper part of the reactor main body 11. The sludge supply section 20 may include appropriate piping, nozzles, etc. connected to the downstream end of the sludge inflow line L1. Organic sludge is supplied to the sludge supply section 20. The organic sludge is further supplied to the carrier holding section 30 by being sprayed (or dripped or flowed down) to the carrier holding section 30. A specific configuration example of the carrier holding section 30 will be described later.

[0017] In the sludge digestion apparatus 1, the concentration of the organic sludge S, that is, the MLSS concentration, sprayed onto the reactor main body 11 is not particularly limited. However, for example, if it is in the range of 1,000 mg / L to 40,000 mg / L, it is possible to suitably promote the decomposition of the sludge.

[0018] The aerobic digestion reactor 10 is provided at the lower part of the reactor main body 11 and has an air introduction section 40 for introducing air into the carrier holding section 30. For example, an air supply line LA is connected to the lower part of the reactor main body 11. An appropriate blower or the like may be provided at the upstream end of the air supply line LA. The air introduction section 40 may include a fan or the like provided inside and at the lower part of the reactor main body 11 for blowing air upward. Alternatively, a forced air supply device such as a blower or a fan may be omitted, and air may be introduced by natural ventilation.

[0019] In the sludge digestion apparatus 1, thus, the carrier holding section 30 is provided between the sludge supply section 20 and the air introduction section 40. Organic sludge is sprayed from above the carrier holding section 30, and air is supplied from below the carrier holding section 30. The air introduction section 40 shown in FIG. 1 corresponds to the lower air introduction section provided at the position below the carrier holding section 30.

[0020] A sludge transfer line L2 is connected to the lower part of the reactor body 11, and organic sludge that has passed through the aerobic digestion reactor 10 is transferred to the sedimentation tank 50 through the sludge transfer line L2. The sedimentation tank 50 is a solid-liquid separation means that performs solid-liquid separation on the organic sludge that has passed through the aerobic digestion reactor 10. In other words, the sludge digestion apparatus 1 is equipped with a sedimentation tank (solid-liquid separation means) 50.

[0021] The bottom of the sedimentation tank 50 is connected to the upstream end of a sludge return line L3 for withdrawing the concentrated sludge, which is the solid portion after separation. The downstream end of the sludge return line L3 is connected to, for example, a sludge inflow line L1. This sludge return line L3 corresponds to a sludge return means 60 that returns the organic sludge discharged downward from the carrier holding section 30 and supplies it back to the carrier holding section 30. In other words, the sludge digestion apparatus 1 is equipped with a sludge return means 60. The sludge return means 60 usually includes a forced liquid delivery means, but specific configuration examples of the sludge return means 60 will be described later.

[0022] A separation liquid transfer line L4 is connected to the top of the sedimentation tank 50 for transferring the separated liquid (supernatant water), which is the liquid portion after separation, to another water treatment device further downstream. The separation liquid may be transferred by gravity through the separation liquid transfer line L4, or it may be transferred to the water treatment device downstream by another liquid transfer means such as an appropriate pump.

[0023] Next, the manner in which each carrier and organic sludge, or each carrier and air, come into contact in the carrier holding section 30 (which can also be described as the manner in which organic sludge and air pass through) will be explained. Figure 2(a) shows the state in which organic sludge passes through the carrier holding section 30, Figure 2(b) shows the state in which organic sludge passes through the carrier, and Figure 2(c) shows the state in which air passes through the carrier. As shown in the apparatus diagram in Figure 3, in the sludge digestion apparatus 1, the reactor body 11 is not filled with organic sludge, and the organic sludge flows down along the surface and interior of each porous carrier 35, while being exposed to air. That is, the numerous carriers held in the carrier holding section 30 are not immersed in organic sludge (the liquid to be treated), but are exposed to air while being moistened by the organic sludge (or water separated therefrom).

[0024] As schematically shown in Figure 2(a), the organic sludge S is sprayed from above the carrier holding section 30 and drips (or flows) through the inside of the carrier holding section 30. At this time, the organic sludge S comes into contact with numerous carriers 35. As schematically shown in Figure 2(b), the organic sludge S drips (or flows) along the surface or inside of the carriers 35. At this time, the organic sludge S is adsorbed or captured by each carrier 35, separating the solid matter and water from the organic sludge S, and the sludge is concentrated on the carriers. As water (solid matter, i.e., components other than SS components) separates from the carriers 35 and drips, each carrier 35 also has a filtration function. Furthermore, as schematically shown in Figure 2(c), the organic sludge S captured by each carrier 35 is decomposed in an aerobic environment (aerobic digestion) due to the presence of air A passing through the surface or inside of each carrier 35. Through the combined action of the adsorption and capture of organic sludge S and the aerobic digestion of organic sludge S, the organic sludge S is concentrated on the surface or inside each carrier 35 and is also decomposed (aerobically digested).

[0025] Next, with reference to Figures 3 and 4, a specific example of the configuration of the sludge digestion apparatus 1 will be described. As shown in Figures 3 and 4, the sludge digestion apparatus 1 has a reactor body 11, for example, in which multiple cylindrical bodies are connected in the vertical direction. The reactor body 11 has, for example, a vertical and cylindrical shape that is long in the vertical direction.

[0026] The sludge supply unit 20 is located at the top of the reactor body 11. In this configuration example, the sludge supply unit 20 includes a rotatable sludge spreading plate 21 for spreading organic sludge S and a motor 22 for rotating the sludge spreading plate 21. The sludge spreading plate 21 rotates at a predetermined speed around its vertical axis (which is also the centerline of the reactor body 11). The sludge supply unit 20 uniformly spreads the organic sludge S within the horizontal cross-sectional area of ​​the reactor body 11. Although the sludge inflow line L1 is omitted in Figure 3, the sludge inflow line L1 is connected to the same location as the sludge return line L3, for example, at the top of the reactor body 11, near the sludge spreading plate 21.

[0027] The carrier holding section 30 is positioned below the sludge supply section 20. As shown in Figure 4, the end plates 38 provided at the upper and lower ends of the cylindrical body have multiple holes (not shown) through which organic sludge S and other liquids (such as filtered water) pass, and support a number of carriers 35. That is, each carrier 35 is larger than the multiple holes and cannot pass through each of them. In this configuration, the carrier holding section 30 is formed by the cylindrical body. Alternatively, another cylindrical container may be provided inside the cylindrical body that constitutes the reactor body 11 as the carrier holding section 30. The carrier holding section 30 holds a number of carriers 35 and allows organic sludge S and other liquids to flow downward.

[0028] The carrier holding section 30 holds a plurality of porous carriers 35. For example, as described above, by filling the inside of a cylindrical body with a plurality of carriers 35, these carriers 35 are held in a cylindrical region within the reactor body 11. The plurality of carrier holding sections 30, which are arranged in the vertical direction, are positioned so that the organic sludge S supplied to the sludge supply section 20 comes into contact with the carriers 35 within the carrier holding sections 30.

[0029] The shape and material of the carrier 35 are not particularly limited. For example, a sponge-like carrier can be used as the carrier 35. The shape of the carrier 35 may be a cube, a rectangular prism, a cylinder, or a cylindrical shape (donut-shaped or tube-shaped). The carrier 35 just needs to be porous. When using a soft material such as polyurethane foam, it is desirable to use a rigid support to maintain its shape. A rigid support prevents the material from being crushed. Furthermore, it is not limited to polyurethane foam, but organic materials made from crop by-products or plants can also be used. For example, fibrous materials such as coconut fiber can be used. The fibrous material itself does not need to be porous; a porous carrier can be achieved by bundling fibrous materials together. This makes it possible to create a material that can be used for sludge filtration and adsorption.

[0030] In this embodiment, a plurality of (for example, four) carrier holding sections 30 are arranged vertically within the reactor body 11. From top to bottom, the first carrier holding section 31, the second carrier holding section 32, the third carrier holding section 33, and the fourth carrier holding section 34 are provided. These are cylindrical bodies of the same shape and size, arranged coaxially with respect to the centerline of the reactor body 11.

[0031] As shown in Figure 4, an air introduction section 40 for introducing air into the carrier holding sections 30 is provided between the multiple carrier holding sections 30. For example, a space is provided between the end plate 38 at the lower end of the first carrier holding section 31 and the end plate 38 at the upper end of the second carrier holding section 32 where the carrier 35 is not filled, and this section constitutes the first intermediate air introduction section 41. For example, multiple air introduction openings 48 are formed in the side wall of the cylindrical reactor body 11. The cylindrical side wall maintains the spacing (gaps) between the multiple carrier holding sections 30, and the multiple air introduction openings 48 allow air from outside the reactor body 11 to be introduced. The cylindrical side wall and the multiple air introduction openings 48 constitute the first intermediate air introduction section 41.

[0032] As shown in Figure 3, a first intermediate air inlet 41 is formed between the first carrier holding section 31 and the second carrier holding section 32. A second intermediate air inlet 42 is formed between the second carrier holding section 32 and the third carrier holding section 33. A third intermediate air inlet 43 is formed between the third carrier holding section 33 and the fourth carrier holding section 34. All of these intermediate air inlets have the same configuration as the first intermediate air inlet 41 shown in Figure 4. Furthermore, a lower air inlet 46 is provided below the fourth carrier holding section 34, which is located at the very bottom. The lower air inlet 46 also has the same configuration as each of the above-described intermediate air inlets.

[0033] With the above configuration, aerobic conditions with air (oxygen) are maintained in each carrier holding section 30. As the organic sludge S continues to decompose, a biota specialized for sludge decomposition is formed on the surface and inside of the carrier 35. In this embodiment, an environment in which metazoans or arthropods can grow is maintained on the surface and inside of the carrier 35 in each carrier holding section 30. Metazoans include, for example, rotifers, oligochaetes, and nematodes. Arthropods include insects (such as filter flies) and crustaceans. The sludge digestion device 1 is not limited to specific organisms, but is envisioned to utilize a broad biological ecosystem that also includes earthworms, mollusks, and other organisms.

[0034] To cultivate the higher-order organisms described above, several conditions must be met. Firstly, by separating the solid matter in the organic sludge S from the water and extending the residence time in the reactor, sufficient time must be secured for the proliferation of the higher-order organisms. Secondly, by not immersing the carrier 35 in water, it is possible to retain higher-order organisms that cannot survive in water. Thirdly, by providing sufficient space between the carriers 35 in the reactor, the habitation and movement of organisms are not hindered. Fourthly, a structure is adopted within the porous interior of the carrier 35 that can protect it from predation by larger higher-order organisms.

[0035] To achieve the above environment in the carrier holding section 30 and to enable both the decomposition and concentration of sludge in the carrier 35 (see above), the oxygen concentration inside each carrier holding section 30 is kept at approximately the same level as air (18% or higher), and the pH of the organic sludge S spread on the carrier holding section 30 is maintained in the range of 5.5 to 8.6. For this reason, it is desirable that pH adjustment means for adjusting the pH of the organic sludge S within a predetermined range be provided at an appropriate location in the sludge supply section 20 or the reactor body 11.

[0036] On the discharge side of the aerobic digestion reactor 10, that is, below the four carrier holding sections 30 arranged vertically, three intermediate air inlets, and one lower air inlet 46, there is a sedimentation tank 50 (solid-liquid separation means). The sedimentation tank 50 performs solid-liquid separation on the organic sludge S that has passed through the aerobic digestion reactor 10. In other words, the lower air inlet 46 is formed between the fourth carrier holding section 34 located at the very bottom and the sedimentation tank 50. The sedimentation tank 50 is a water tank that opens upward and has an appropriate shape. The sedimentation tank 50 uses gravity to separate the organic sludge S into concentrated sludge and separated liquid.

[0037] A sludge return line L3 is connected to the bottom of the sedimentation tank 50, and a sludge return pump 61 installed on the sludge return line L3 supplies the concentrated sludge, which is the solid portion separated in the sedimentation tank 50, to the carrier holding section 30 (the first carrier holding section 31 located at the top). The sludge return line L3 and the sludge return pump 61 constitute a sludge return means 60 that returns the organic sludge S discharged downward from the carrier holding section 30 of the aerobic digestion reactor 10 and supplies it back to the carrier holding section 30.

[0038] A separation liquid transfer line L4 is connected to the upper part of the sedimentation tank 50 to transfer the separated liquid (supernatant water), which is the liquid portion separated in the sedimentation tank 50, to another water treatment device further downstream. Downstream of the separation liquid transfer line L4, another water treatment device (not shown) is provided where the separated liquid is properly treated (purified).

[0039] In the sludge digestion apparatus 1 of this embodiment described above, the operation of various pumps may be controlled by a control device, for example. The supply of organic sludge S through the sludge inflow line L1 may be continuous or intermittent. For example, the discharge of the separated liquid through the separated liquid transfer line L4 may be by gravity flow. For example, the sludge return pump 61 may be controlled to be always on (in which case concentrated sludge is returned continuously), or it may be controlled to be on or off (in which case concentrated sludge is returned intermittently).

[0040] In the sludge digestion apparatus 1 of this embodiment, organic sludge S supplied to the sludge supply unit 20 comes into contact with a carrier 35 held in the carrier holding unit 30. The organic sludge S adheres to (or is captured by) the porous carrier 35. Within the carrier holding unit 30, the filtrate filtered (or separated) by the carrier falls and is discharged downward. Air is introduced into the carrier holding unit 30 by the air introduction unit 40, so aerobic digestion (biological decomposition) of the organic sludge S takes place on the surface and inside the carrier 35. A portion of the organic sludge S flows out without being retained by the carrier 35. In addition, a portion of the organic sludge S that adheres to the carrier 35 peels off and flows out. Because the organic sludge S repeatedly comes into contact with the carrier by the sludge return means 60, the likelihood of the organic sludge S adhering to the carrier 35 increases, which lengthens the residence time of the sludge in the reactor (lengthens the time for decomposition) and increases the decomposition rate. Thus, a simple and low-cost configuration comprising at least an aerobic digestion reactor 10 and a sludge return means 60 makes it possible to accelerate the decomposition of organic sludge S. Such a configuration is also advantageous as a small-scale, decentralized treatment facility.

[0041] Furthermore, a lower air inlet 46 is provided below the carrier holding section 30. This allows air to be introduced from the lower air inlet 46 and supplied to rise inside the reactor body 11. Therefore, the device configuration can be made even simpler. Air can easily circulate to the numerous carriers 35 inside the vertical reactor body 11.

[0042] Furthermore, a first intermediate air introduction section 41, etc., is provided in the side wall of the reactor body 11 at a position between the multiple carrier holding sections 30. This allows the air necessary for aerobic digestion to be supplied evenly to each part of the vertical reactor body 11 in the vertical direction.

[0043] The sludge return means 60 returns the concentrated sludge, which is the solid portion separated in the sedimentation tank 50, and supplies it to the carrier holding unit 30. As a result, the concentrated sludge is supplied again to the carrier holding unit 30, thereby increasing the sludge decomposition efficiency. The separated liquid, which is the liquid portion separated in the sedimentation tank 50, is treated separately in a subsequent water treatment device. However, if the regulations of the destination allow it, the water treatment device may be omitted and the separated liquid may be discharged.

[0044] In the carrier holding section 30, an environment is maintained on the surface or inside the carrier 35 in which metazoans or arthropods can grow. With this configuration and environment of the device, the decomposition of organic sludge S can be further promoted. Furthermore, there is a possibility that the food chain can be promoted on the surface or inside the carrier 35.

[0045] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, the reactor body 11 of the aerobic digestion reactor 10 is not limited to a cylindrical shape, but may be rectangular. The reactor body 11 is not limited to a vertically elongated shape, but may have a shape in which the vertical and horizontal directions (width direction or radial direction) are equivalent in size.

[0046] In the sludge digestion apparatus 1 shown in Figure 3, the number of carrier holding sections 30 and the number of air inlet sections 40 may be changed. One carrier holding section 30 may be provided, and one air inlet section 40 may be provided below it.

[0047] In the sludge digestion apparatus 1 shown in Figure 3, the lower air inlet 46 may not have an air inlet opening 48, and an air supply line LA (see Figure 1) may be connected to a cylindrical body without an opening. In that case, a suitable blower or the like (air blowing means) may be provided at the upstream end of the air supply line LA. Alternatively, instead of the air supply line LA and the air blowing means, a fan or the like (air blowing means) that blows air upward may be provided at the position of the lower air inlet 46. All of these modified configurations correspond to a lower air inlet provided below the carrier holding section 30 for introducing air into the carrier holding section 30.

[0048] The solid-liquid separation means is not limited to the sedimentation tank 50, but other known types of solid-liquid separation devices may be used. The solid-liquid separation means may also be omitted. In that case, the sludge return means 60 returns a portion of the organic sludge S discharged downward from the carrier holding section 30.

[0049] (Preliminary experiment) The inventors conducted an experiment to determine the decomposition rate of organic sludge attached to a carrier using sewage sludge (excess sludge). Figure 5 shows the apparatus used in the preliminary experiment. Eight beakers 100 were prepared, and an appropriate amount of sewage sludge was stored in each beaker 100. The amount of sludge in each beaker 100 was approximately 70 mL. A cubic, sponge-like carrier 35 was suspended above each beaker 100 using a suspension device (not shown). Sewage sludge was dripped onto each of the eight carriers 35 using a separate pump for a maximum of seven weeks. The capacity of each carrier 35 was approximately 33 mL, and the amount of sludge captured was 693 mg. Since each carrier 25 was exposed to the atmosphere, no forced air supply was provided. The temperature was maintained at room temperature. No pH adjustment was performed.

[0050] Since the eight carriers 35 receive sludge supply under the same conditions, the sludge decomposition in each carrier 35 can be considered to be roughly equivalent. Sludge was collected from one carrier 35 every week. The sludge was squeezed out to ensure no residue was left behind. In addition, environmental conditions such as liquid temperature, pH, and DO (dissolved oxygen concentration) were measured, and MLSS concentration, MLVSS concentration, and COD were measured to confirm sludge decomposition (weight reduction). On the other hand, to confirm the mass balance of COD, COD was measured using treated water after solid-liquid separation (filtrate from MLSS measurement). As shown in Figure 6, sludge weight reduction progressed during the initial stages of operation (first two weeks). After a certain period of time, a tendency for sludge weight reduction to stop was observed (after three weeks). In this regard, it was thought that the reason for this phenomenon was that the pH, which was 6.60 on the 7th day, decreased to 5.25 on the 14th day, falling below the appropriate pH range. Based on these experimental results, we were able to consider appropriate operating conditions for sludge digestion apparatus 1 (the pH range and pH adjustment approach described above). [Explanation of Symbols]

[0051] 1...Sludge digestion device, 10...Aerobic digestion reactor, 11...Reactor body, 20...Sludge supply unit, 30...Carrier holding unit, 31...First carrier holding unit, 32...Second carrier holding unit, 33...Third carrier holding unit, 40...Air introduction unit, 41...First intermediate air introduction unit, 42...Second intermediate air introduction unit, 43...Third intermediate air introduction unit, 46...Lower air introduction unit, 50...Sedimentation tank (solid-liquid separation means), 60...Sludge return means.

Claims

1. An aerobic digestion reactor having a sludge supply section for which organic sludge is supplied, at least one carrier holding section provided below the sludge supply section for holding a plurality of porous carriers, such that the organic sludge supplied to the sludge supply section comes into contact with the carriers, and an air introduction section for introducing air into the carrier holding section, A sludge digestion apparatus comprising: a sludge return means for returning the organic sludge discharged downward from the carrier holding section of the aerobic digestion reactor and supplying it to the carrier holding section.

2. The aerobic digestion reactor has a vertically elongated, cylindrical reactor body. The sludge digestion apparatus according to claim 1, wherein the air introduction section includes a lower air introduction section provided below the carrier holding section.

3. Multiple carrier holding units are arranged in a vertical direction within the reactor body. The sludge digestion apparatus according to claim 2, wherein the air introduction section includes an intermediate air introduction section provided in the side wall of the reactor body at a position between a plurality of carrier holding sections.

4. On the discharge side of the aerobic digestion reactor, a solid-liquid separation means is provided to perform solid-liquid separation on the organic sludge that has passed through the aerobic digestion reactor. The sludge digestion apparatus according to any one of claims 1 to 3, wherein the sludge return means supplies the concentrated sludge, which is the solid portion separated in the solid-liquid separation means, to the carrier holding unit.

5. The sludge digestion apparatus according to any one of claims 1 to 3, wherein the carrier holding section maintains an environment on the surface or inside the carrier in which metazoans or arthropods can grow.

Images