Method for culturing aerobic granules and apparatus for culturing aerobic granules

Abstract

This invention provides a method for culturing aerobic granules that can stably produce aerobic granules with excellent settling properties. [Solution] A method for culturing aerobic granules, comprising an operation cycle in a semi-batch reaction tank, in which an inflow / discharge step of discharging biologically treated water while introducing organic matter-containing wastewater, a biological treatment step of biologically treating the organic matter in the organic matter-containing wastewater with microbial sludge containing aerobic granules, and a sedimentation step of settling the microbial sludge to form a microbial sludge layer, is repeated, wherein the sedimentation step is carried out until the interface height of the microbial sludge layer is 50% or less of the water level height of the semi-batch reaction tank, and in the inflow / discharge step, the organic matter-containing wastewater is introduced so as to come into contact with the microbial sludge layer formed by the sedimentation step.

Description

Technical Field

[0001] The present disclosure relates to a method for culturing aerobic granules and an apparatus for culturing aerobic granules.

Background Art

[0002] Conventionally, for the biological wastewater treatment of organic wastewater containing organic substances and the like, the activated sludge method that utilizes an aggregate of microorganisms (aerobic biological sludge) called floc has been used. However, in the activated sludge method, when separating the floc (aerobic biological sludge) and the treated water in the sedimentation tank, the sedimentation rate of the floc is slow, so the surface area of the sedimentation tank may have to be made very large. In addition, the treatment rate of the activated sludge method depends on the sludge concentration in the biological treatment tank, and the treatment rate can be increased by increasing the sludge concentration. However, solid-liquid separation obstacles such as bulking in the sedimentation tank may occur, making it impossible to maintain the treatment.

[0003] On the other hand, in anaerobic biological treatment, it is common to utilize an aggregate (anaerobic biological sludge) in which microorganisms called granules are densely aggregated and granulated. Granules have a very high sedimentation rate, and because the microorganisms are densely aggregated, the sludge concentration in the biological treatment tank can be increased, making it possible to achieve high-speed treatment of wastewater. However, anaerobic biological treatment may have problems such as limited types of wastewater to be treated compared to aerobic treatment (activated sludge method), and the need to maintain the treatment water temperature at about 30 to 35°C. In addition, when discharging the treated water into a river or the like, it may be necessary to separately perform aerobic treatment such as the activated sludge method because the quality of the treated water is poor in anaerobic biological treatment alone. <0,000,017>

[0004] In recent years, it has become clear that by using a semi-batch treatment system that intermittently infuses wastewater into the reaction tank, it is possible to form granulated biological sludge with good settling properties not only from anaerobic biological sludge but also from aerobic biological sludge (see, for example, Patent Documents 1-4). The granulated biological sludge has, for example, an average particle size of 0.2 mm or more. In a semi-batch biological treatment system, it is common to repeatedly perform four steps in a single biological treatment tank: (1) inflow of wastewater, (2) biological treatment of organic matter, (3) settling of biological sludge, and (4) discharge of treated water.

[0005] Furthermore, Patent Document 5 discloses a semi-batch biological treatment method that repeatedly performs three steps: (1) inflow of wastewater and discharge of treated water, (2) biological treatment of organic matter, and (3) sedimentation of biological sludge. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2004 / 024638 [Patent Document 2] Japanese Patent Publication No. 2008-212878 [Patent Document 3] Patent No. 4975541 [Patent Document 4] Patent No. 4804888 [Patent Document 5] Japanese Patent Publication No. 2016-77931 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Incidentally, if semi-batch biological treatment is carried out for a long period of time, the sedimentation properties of the cultured aerobic granules may deteriorate.

[0008] Therefore, the purpose of this disclosure is to provide a method for culturing aerobic granules and a culturing apparatus for aerobic granules that can stably cultivate aerobic granules with excellent settling properties. [Means for solving the problem]

[0009] This disclosure relates to a method for culturing aerobic granules, comprising repeating an operating cycle in a semi-batch reactor, which includes an inflow / outflow step of discharging biologically treated water while introducing organic matter-containing wastewater, a biological treatment step of biologically treating the organic matter in the organic matter-containing wastewater with microbial sludge containing aerobic granules, and a sedimentation step of settling the microbial sludge to form a microbial sludge layer, wherein the sedimentation step is carried out until the interface height of the microbial sludge layer is 50% or less of the water level height of the semi-batch reactor, and in the inflow / outflow step, the organic matter-containing wastewater is introduced so as to come into contact with the microbial sludge layer formed by the sedimentation step.

[0010] Furthermore, in the aerobic granule culture method, if the interface height of the microbial sludge layer does not fall below 50% of the water level of the semi-batch reaction tank by a predetermined time, it is preferable to withdraw the microbial sludge from the semi-batch reaction tank and adjust the sludge concentration so that the interface height of the microbial sludge layer falls below 50% of the water level of the semi-batch reaction tank.

[0011] Furthermore, in the aerobic granule cultivation method, it is preferable that the linear velocity of the organic matter-containing wastewater inflow is 5 m / h or less in the inflow / outflow step.

[0012] Furthermore, this disclosure relates to an aerobic granule culture apparatus comprising a semi-batch reaction tank that repeatedly performs an operating cycle including an inflow / discharge step of discharging biologically treated water while introducing organic matter-containing wastewater, a biological treatment step of biologically treating the organic matter in the organic matter-containing wastewater with microbial sludge containing aerobic granules, and a sedimentation step of settling the microbial sludge to form a microbial sludge layer, wherein the sedimentation step is carried out until the interface height of the microbial sludge layer is 50% or less of the water level height of the semi-batch reaction tank, and in the inflow / discharge step, the organic matter-containing wastewater is introduced so as to come into contact with the microbial sludge layer formed by the sedimentation step.

[0013] Furthermore, in the aerobic granule culture apparatus, if the interface height of the microbial sludge layer does not fall below 50% of the water level of the semi-batch reaction tank by a predetermined time, it is preferable that the microbial sludge is withdrawn from the semi-batch reaction tank so that the interface height of the microbial sludge layer falls below 50% of the water level of the semi-batch reaction tank, thereby adjusting the sludge concentration.

[0014] Furthermore, in the aerobic granule culture apparatus, it is preferable that the linear velocity of the organic matter-containing wastewater inflow is 5 m / h or less during the inflow / outflow process. [Effects of the Invention]

[0015] According to this disclosure, it is possible to provide a method for culturing aerobic granules and a culturing apparatus for aerobic granules that can stably cultivate aerobic granules with excellent settling properties. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic diagram showing an example of an aerobic granule culture apparatus according to the embodiment of this disclosure. [Figure 2] This is a schematic diagram showing another example of an aerobic granule culture apparatus according to the embodiments of this disclosure. [Figure 3]It is a diagram for explaining the state of microbial sludge in the semi-batch reactor in each process. [Figure 4] It is a diagram showing the daily change of SVI5 in Examples 1-2 and the comparative example. [Figure 5] It is a diagram showing the daily change of SVI30 in Examples 1-2 and the comparative example.

Mode for Carrying Out the Invention

[0017] The embodiments of the present disclosure will be described below. This embodiment is an example of implementing the present disclosure, and the present disclosure is not limited to this embodiment.

[0018] <Aerobic Granule Cultivation Method and Cultivation Apparatus> An example schematic of an aerobic granule cultivation apparatus according to an embodiment of the present disclosure is shown in FIG. 1, and its configuration will be described. The granule cultivation apparatus 1 includes a semi-batch reactor 10. At the lower part inside the semi-batch reactor 10, an aeration device 26 connected to an aeration pump 14 is installed. Further, the granule cultivation apparatus 1 includes a drainage supply pipe 28, a drainage inflow pump 12, and a drainage inflow valve 38. And the drainage supply pipe 28 is connected to a drainage inlet 40 at the lower part of the semi-batch reactor 10 via the drainage inflow pump 12 and the drainage inflow valve 38. Further, the granule cultivation apparatus 1 includes a biologically treated water pipe 30 and a biologically treated water discharge valve 18. And the biologically treated water pipe 30 is connected to a biologically treated water outlet 16 at the water surface height of the semi-batch reactor 10 via the biologically treated water discharge valve 18. Further, the granule cultivation apparatus 1 includes a sludge extraction pipe 32 and a sludge extraction pump 24. And the sludge extraction pipe 32 is connected to a sludge extraction port 22 at the lower part of the semi-batch reactor 10 via the sludge extraction pump 24.

[0019] The biological treatment water outlet 16 may be located at any position, but it is preferable to position it above the wastewater inlet 40 to prevent short circuits of incoming organic matter-containing wastewater, and is preferably located at the water level of the semi-batch reaction tank 10. The water level of the semi-batch reaction tank 10 is the water level when the liquid in the semi-batch reaction tank 10 is at rest during the sedimentation process.

[0020] The granule culture apparatus 1 is equipped with a control device 20. The control device 20 is composed of a microcomputer consisting of a CPU for calculating programs, ROM and RAM for storing programs and calculation results, and electronic circuits, etc. It reads a predetermined program stored in the ROM, etc., and executes the program to control the operation of the granule culture apparatus 1. The control device 20 is electrically connected to each of the following: the wastewater inlet pump 12, the wastewater inlet valve 38, the biological treatment water discharge valve 18, the sludge extraction pump 24, and the aeration pump 14. The control device 20 controls the operation and stopping of each pump and the opening and closing of each valve during the operation of the granule culture apparatus 1.

[0021] In the granule culture apparatus 1, for example, the following operating cycle is performed.

[0022] (1) Inflow / Discharge Process: The wastewater inflow valve 38 is opened and the wastewater inflow pump 12 is activated, allowing the wastewater containing organic matter to flow through the wastewater supply pipe 28 into the semi-batch reaction tank 10 from the wastewater inlet 40. When this wastewater containing organic matter flows in, the biologically treated water discharge valve 18 is opened. As a result, the biologically treated water (supernatant water) obtained in the sedimentation process described later is pushed out by the incoming wastewater containing organic matter and discharged from the biologically treated water outlet 16 into the biologically treated water pipe 30.

[0023] (2) Biological treatment process: The wastewater inlet pump 12 is stopped, and oxygen-containing gas such as air is supplied from the aeration pump 14 to the semi-batch reaction tank 10 through the aeration device 26. In this way, the organic matter in the organic matter-containing wastewater is biologically treated in the semi-batch reaction tank 10 by microbial sludge containing aerobic granular sludge. The biological reaction is not limited to an aerobic reaction; an anaerobic reaction is also possible, which involves stirring without supplying air, and a combination of aerobic and anaerobic reactions is also acceptable. An anaerobic state refers to a state in which dissolved oxygen is absent, but oxygen derived from nitrite or nitrate is present. For example, as shown in Figure 2, a stirring device consisting of a motor 34, a stirring blade 36, and a shaft connecting the motor 34 and the stirring blade 36 can be installed in the semi-batch reaction tank 10, and stirring can be performed by stopping the aeration pump 14 and using the stirring device. The stirring device is not limited to the above configuration.

[0024] (3) Settlement process: The aeration pump 14 is stopped and left to stand for a predetermined time, allowing the sludge in the semi-batch reaction tank 10 to settle and form a microbial sludge layer containing aerobic granules. The biologically treated water (supernatant water) above the microbial sludge layer is discharged from the semi-batch reaction tank 10 in the inflow / discharge process as described above.

[0025] In this embodiment, the aerobic granules (hereinafter simply referred to as granules) are cultured by repeating the operation cycle including the above steps (1) to (3).

[0026] Figure 3 is a diagram illustrating the state of microbial sludge in the semi-batch reactor during each process. As shown in Figure 3, in the biological treatment process, the microbial sludge in the semi-batch reactor 10 is agitated by air supplied from the aeration device 26, etc., so that a dispersion A is formed in the semi-batch reactor 10 in which microbial sludge is dispersed throughout the organic matter-containing wastewater. Then, in the sedimentation process, the microbial sludge settles and a condensed microbial sludge layer B is formed. Above the microbial sludge layer B is the biologically treated supernatant water. In the sedimentation process, the interface height of the microbial sludge layer B decreases as time progresses, but in the sedimentation process of this embodiment, it is carried out until the interface height B1 of the microbial sludge layer B is 50% or less of the water level height of the semi-batch reactor 10. In the inflow / outflow process of this embodiment, organic matter-containing wastewater is supplied to the semi-batch reaction tank 10 so as to come into contact with the microbial sludge layer B, where the interface height B1 is 50% or less of the water level height of the semi-batch reaction tank 10.

[0027] In this way, by bringing organic matter-containing wastewater into contact with the condensed microbial sludge layer B, more microorganisms in the microbial sludge can be exposed to organic matter in the organic matter-containing wastewater at a high concentration. This promotes granule growth and creates a higher anaerobic condition, thereby suppressing the growth of filamentous bacteria that normally cannot survive under aerobic conditions. As a result, granules with good settling properties can be stably cultured. It is known that the growth of filamentous bacteria negatively affects granule culture. Furthermore, generally, when the organic matter concentration in organic matter-containing wastewater is low (for example, 250 mg BOD / L or less), the granules tend to disintegrate, making it difficult to culture granule sludge with good settling properties. However, according to this embodiment, even when treating organic matter-containing wastewater with low organic matter concentrations, it is possible to stably culture granules with good settling properties.

[0028] The detection of the interface height B1 of the microbial sludge layer B is not particularly limited, but may be performed by a sludge interface meter. For example, data of the interface height B1 of the microbial sludge layer B detected by the sludge interface meter is transmitted to the control device 20. The control device 20 then compares the transmitted interface height data with a threshold set to 50% or less of the water level of the semi-batch reaction tank 10 (for example, 40% of the water level). If the interface height data is below the threshold, the control device terminates the sedimentation process and performs the inflow / discharge process.

[0029] Furthermore, the control device 20 may predict the time until the interface height B1 of the microbial sludge layer B falls below 50% of the water surface height of the semi-batch reaction tank 10, based on the initial settling velocity of the sludge, and perform the settling process until the predicted time is reached, after which it may perform the inflow / discharge process. Here, the initial settling velocity of the sludge refers to the fastest rate at which the microbial sludge settles. For example, the initial settling velocity of the sludge can be calculated by continuously measuring the sludge concentration during the settling process using a sludge concentration meter installed at a predetermined height, comparing it with the sludge concentration in the agitated state, and calculating the time until the concentration falls below a predetermined level, as well as the distance from the water surface to the sludge concentration meter installed at a predetermined height. Then, from the calculated initial settling velocity of the sludge, the time until the interface height B1 of the microbial sludge layer B falls below 50% of the water surface height of the semi-batch reaction tank 10 can be calculated. The installation position of the sludge concentration meter is not particularly limited, but it is preferably within 2m of the water surface height from the water surface, and more preferably within 1m.

[0030] Alternatively, a sludge concentration meter installed at a predetermined height of 50% or less above the water surface may be used to measure the time it takes for the interface height B1 of the microbial sludge layer B to fall below 50% of the water surface height of the semi-batch reaction tank 10. After the sedimentation process is carried out for the measured time, the inflow / discharge process may be performed. In this case, for example, the sludge concentration during the stirring state (biological treatment process) is known, and the sedimentation process is carried out for the time it takes for the sludge concentration to fall below a predetermined concentration after the sedimentation process has started, before the inflow / discharge process is performed. The installation position of the sludge concentration meter needs to be higher than the sludge interface height formed in the sedimentation process, so it is preferable that it be at least 20% or more above the water surface height of the semi-batch reaction tank 10.

[0031] In this embodiment, if the interface height B1 of the microbial sludge layer B does not fall below 50% of the water level height of the semi-batch reaction tank 10 by a predetermined time, it is preferable to withdraw the microbial sludge from the semi-batch reaction tank 10. The withdrawal of the microbial sludge may be performed during the sedimentation process, during the inflow / discharge process, or during the biological treatment process. Alternatively, the withdrawal of the microbial sludge may be performed after the sedimentation process but before the inflow / discharge process, after the inflow / discharge process but before the biological treatment process, or after the biological treatment process but before the sedimentation process.

[0032] Microbial sludge is removed, for example, as follows: The control device 20 measures the time of the settling process, and if the interface height B1 of the microbial sludge layer B does not fall below 50% of the water level of the semi-batch reaction tank 10 by a preset time, it activates the sludge extraction pump 24 during the settling process to extract a predetermined amount of microbial sludge from the semi-batch reaction tank 10 through the sludge extraction pipe 32. After that, the control device 20 controls the inflow / discharge process. Alternatively, for example, the control device 20 measures the time of the settling process, and if the interface height of the microbial sludge layer does not fall below 50% of the water level of the semi-batch reaction tank 10 by a preset time, it terminates the settling process at a preset time. The control device 20 then operates the sludge extraction pump 24 after the sedimentation process but before the inflow / discharge process, during the inflow / discharge process, after the inflow / discharge process but before the biological treatment process, during the biological treatment process, and after the biological treatment process but before the sedimentation process, to extract a predetermined amount of microbial sludge from the semi-batch reaction tank 10 through the sludge extraction pipe 32. This control reduces the concentration of biological sludge in the semi-batch reaction tank 10, allowing the interface height B1 of the microbial sludge layer B to be reduced to 50% or less of the water level in the semi-batch reaction tank 10 within an appropriate time, thereby preventing stagnation in the sedimentation process. If the interface height B1 of the microbial sludge layer B does not reach 50% or less of the water level in the semi-batch reaction tank 10, the sludge extraction operation may be performed during the stirring state in the next biological treatment process. This makes it possible to accurately determine the amount of sludge extracted from the sludge concentration during the stirring state and the amount of sludge mixture extracted. Furthermore, while the sludge is agitated, it is also possible to open the drainage inlet valve 38 to operate the drainage inlet pump 12 and open the biological treatment water discharge valve 18 to discharge the sludge through the biological treatment water outlet 16 located at the water level of the semi-batch reaction tank 10. In these cases, the amount of sludge to be withdrawn may be determined by the ratio of the height of the microbial sludge tank to the distance of 50% of the water level, or the sludge may be withdrawn in stages over multiple biological treatment processes.

[0033] The granules cultured in the semi-batch reaction tank 10 are microbial sludge that has undergone self-granulation, and are, for example, microbial sludge with an average particle size of 0.2 mm or more, or with a sedimentation index SVI5 of 80 mL / g or less. In this embodiment, whether or not the microbial sludge in the semi-batch reaction tank 10 is granules is determined, for example, by measuring the SVI, which is a sedimentation index of microbial sludge. Specifically, if the SVI5 value measured by a sedimentation test of the microbial sludge in the semi-batch reaction tank 10 is below a predetermined value (for example, 80 mL / g or less), it is possible to determine that the microbial sludge is granules. Alternatively, if the particle size distribution of the microbial sludge in the semi-batch reaction tank 10 is measured and the average particle size is above a predetermined value (for example, 0.2 mm or more), it is possible to determine that the microbial sludge is granules (note that the lower the SVI value and the larger the average particle size, the better the sedimentation of the granules).

[0034] In the semi-batch reaction tank 10, the sludge retention time (SRT) is preferably maintained in the range of 5 to 25 days, and more preferably in the range of 10 to 15 days, from the standpoint of stable cultivation of granules. For example, the sludge extraction pump 24 is operated so that the SRT is in the range of 5 to 25 days, and a predetermined amount of microbial sludge from the semi-batch reaction tank 10 is extracted from the sludge extraction pipe 32.

[0035] SRT is expressed by the following formula: SRT[d] = Amount of sludge present in the tank [kg] / Amount of sludge discharged from the system per day [kg / d]

[0036] Furthermore, the BOD / MLSS load (BOD load per unit amount of microbial sludge) in the semi-batch reaction tank 10 is preferably in the range of 0.05 kg BOD / kg MLSS·day to 0.25 kg BOD / kg MLSS·day, in terms of stable cultivation of the granules. If the MLSS is reduced by withdrawing the microbial sludge, it is preferable to adjust the BOD load so that the BOD / MLSS load falls within the above range.

[0037] The organic wastewater to be treated in this embodiment is, for example, organic wastewater containing biodegradable organic matter, such as wastewater from food processing plants, chemical plants, semiconductor plants, machinery plants, sewage, and human waste. Furthermore, if the wastewater contains organic matter that is not easily biodegradable, it can be treated by first applying physicochemical treatment such as ozone treatment or Fenton treatment to convert it into biodegradable components. In addition, although the granule cultivation method in this embodiment targets various BOD components, oil and fat may adhere to the sludge and granules and have adverse effects, so it is preferable to remove them to about 150 mg / L or less before introducing them into the semi-batch reaction tank 10 using existing methods such as flotation separation, coagulation and pressurized flotation, and adsorption.

[0038] The pH in the semi-batch reaction vessel 10 is preferably set within a range suitable for general microorganisms, for example, preferably in the range of 6 to 9, and more preferably in the range of 6.5 to 7.5. If the pH value falls outside the above range, it is preferable to control the pH by adding an acid, alkali, etc.

[0039] The dissolved oxygen (DO) in the semi-batch reaction vessel 10 is preferably 0.5 mg / L or more, and particularly preferably 1 mg / L or more, under aerobic conditions.

[0040] To ensure stable cultivation of the granules, Fe is added to the organic matter-containing wastewater in the semi-batch reactor 10 or to the organic matter-containing wastewater before it is introduced into the semi-batch reactor 10. 2+ Fe 3+ Ca 2+ Mg 2+ It is preferable to add ions that form hydroxides, such as those mentioned above. Ordinary organic wastewater contains fine particles that act as nuclei for granules, but the addition of the above ions can further promote granule nucleation.

[0041] The wastewater inflow rate in the inflow / discharge process is preferably in the range of 10% to 100%. The wastewater inflow rate is the ratio of the amount of organic matter-containing wastewater inflow to the effective volume in the semi-batch reaction tank 10. Here, in order to stably cultivate granules with good settling properties, it is better to have as high a wastewater inflow rate as possible, but on the other hand, the higher the wastewater inflow rate, the greater the concern about deterioration of the treated water due to short circuits of the wastewater. Considering these factors, it is more preferable to set the wastewater inflow rate in the range of 20% to 80%. However, if a treatment device such as an activated sludge tank is installed downstream of the semi-batch reaction tank 10, and the water quality of the final treated water after the downstream treatment device does not deteriorate, there is no particular restriction on the wastewater inflow rate, and it is possible to set it to, for example, more than 100%. When the wastewater inflow rate exceeds 100%, it is preferable to set the upper limit of the wastewater inflow rate to 200% or less in order to suppress a decrease in the number of operating cycles.

[0042] The linear velocity of organic matter-containing wastewater in the inflow / discharge process (the amount of organic matter-containing wastewater flowing relative to the cross-sectional area of ​​the semi-batch reaction tank 10) is preferably set to, for example, 5 m / h or less. If the linear velocity of organic matter-containing wastewater exceeds 5 m / h, there is a concern that the treated water may deteriorate due to short circuits of the organic matter-containing wastewater, granule outflow, etc. Furthermore, there is a concern that the sludge properties may deteriorate due to the interface height B1 of the microbial sludge layer B rising during the inflow / discharge process. The lower limit of the linear velocity of organic matter-containing wastewater in the inflow / discharge process is not particularly limited, but it is preferable to set it to 0.5 m / h or higher in terms of shortening the time of the inflow / discharge process.

[0043] In this embodiment, since the purpose is to cultivate granules, a predetermined amount of granulated microbial sludge may be added to the semi-batch reaction tank 10 at the start of operation. [Examples]

[0044] The present disclosure will be described in more detail below with reference to examples and comparative examples, but the present disclosure is not limited to the following examples.

[0045] A granule culture test was conducted for 180 days using a semi-batch reaction vessel with an effective volume of 4 L (70 mm x 140 mm x effective water depth of 400 mm). The treated water outlet was installed at the water surface of the semi-batch reaction vessel. In addition, a wastewater inlet was installed at the bottom of the semi-batch reaction vessel so that the incoming organic matter-containing wastewater would come into contact with the microbial sludge layer formed by the sedimentation process. Artificial wastewater with a BOD concentration of 250 mg / L was used as the organic matter-containing wastewater.

[0046] During the 180-day culture test, the period from the start of the test to day 79 was used as a comparative example, and the operation was repeated with an inflow / outflow process of 24 minutes (inflow linear velocity 1 m / h), a biological treatment process of 240 minutes, and a sedimentation process of 1.5 minutes. In the comparative example, the sedimentation process was completed when the interface height of the microbial sludge layer was in the range of 55% to 80% of the water level of the semi-batch reaction tank. After the comparative example, the period from day 80 to day 180 was used as Example 1, and the operation was repeated with an inflow / outflow process of 24 minutes (inflow linear velocity 1 m / h), a biological treatment process of 240 minutes, and a sedimentation process of 15 minutes. In Example 1, the sedimentation process was completed when the interface height of the microbial sludge layer was 50% or less of the water level of the semi-batch reaction tank. In addition to the culture tests in the comparative example and Example 1, Example 2 was conducted from the start of the test to day 180, in which the inflow / outflow process was repeated for 24 minutes (inflow linear velocity of 1 m / h), the biological treatment process for 240 minutes, and the sedimentation process for 15 minutes. In Example 2, the sedimentation process was completed when the interface height of the microbial sludge layer was 50% or less of the water level height of the semi-batch reaction tank.

[0047] Figure 4 shows the change in SVI5 over time in Examples 1-2 and the Comparative Example. Figure 5 shows the change in SVI30 over time in Examples 1-2 and the Comparative Example. SVI is an index of the settling properties of microbial sludge and is determined by the following method. First, 1 L of microbial sludge is placed in a 1 L graduated cylinder, and after gently stirring to make the sludge concentration as uniform as possible, the sludge interface is measured after standing for 5 minutes. Then, the volume percentage (%) of microbial sludge in the graduated cylinder is calculated. Next, the MLSS (mg / L) of the microbial sludge is measured. These are then applied to the following formula to calculate SVI5. A smaller SVI5 value indicates that the sludge has higher settling properties. SVI5 (mL / g) = Volume percentage occupied by sludge × 10,000 / MLSS (Note: When calculating SVI30, change the standing time from 5 minutes to 30 minutes.)

[0048] When the test was conducted under the conditions of the comparative example, SVI5 remained at 50 mL / g or less until day 57 from the start of the test, and granular sludge with good settling properties could be cultured. However, from day 58 onwards, the SVI value increased, and on day 79, SVI5 rose to 480 mL / g and SVI30 to 180 mL / g. When the test was conducted under the conditions of Example 1 from day 80 onwards, the SVI value decreased, and on day 94, SVI5 fell to 60 mL / g and SVI30 to 35 mL / g. Although the SVI value increased again between days 100 and 110, it was not a significant deterioration and then decreased rapidly. In Example 2, the SVI value remained low and stable throughout the test period, with SVI5 generally remaining at 80 mL / g or less and SVI30 at 50 mL / g or less. As shown in Examples 1 and 2, by carrying out the settling process until the interface height of the microbial sludge layer is 50% or less of the water level height of the semi-batch reaction tank, and then introducing organic matter-containing wastewater in the inflow / outflow process so as to come into contact with the microbial sludge layer formed by the settling process, it can be said that granules with good settling properties can be stably cultured. [Explanation of Symbols]

[0049] 1 Granule culture apparatus, 10 Semi-batch reaction vessels, 12 Wastewater inlet pump, 14 Aeration pump, 16 Biologically treated water outlet, 18 Biologically treated water discharge valve, 20 Control device, 22 Sludge extraction port, 24 Sludge extraction pump, 26 Aeration device, 28 Wastewater supply piping, 30 Biologically treated water piping, 32 Sludge extraction piping, 34 Motor, 36 Agitator blade, 38 Wastewater inlet valve, 40 Wastewater inlet.

Claims

1. A method for culturing aerobic granules, comprising repeating an operating cycle in a semi-batch reaction tank, which includes an inflow / outflow step of discharging biologically treated water while introducing organic matter-containing wastewater, a biological treatment step of biologically treating the organic matter in the organic matter-containing wastewater with microbial sludge containing aerobic granules, and a sedimentation step of settling the microbial sludge to form a microbial sludge layer, thereby culturing the aerobic granules, The sedimentation process is carried out until the interface height of the microbial sludge layer is 50% or less of the water level height of the semi-batch reaction tank. A method for culturing aerobic granules, characterized in that the inflow / outflow step involves introducing the organic matter-containing wastewater so as to come into contact with the microbial sludge layer formed by the sedimentation step.

2. The method for culturing aerobic granules according to claim 1, characterized in that, if the interface height of the microbial sludge layer does not fall below 50% of the water level of the semi-batch reaction tank by a predetermined time, the microbial sludge is withdrawn from the semi-batch reaction tank and the sludge concentration is adjusted so that the interface height of the microbial sludge layer falls below 50% of the water level of the semi-batch reaction tank.

3. The method for culturing aerobic granules according to claim 1 or 2, characterized in that the linear velocity of the organic matter-containing wastewater inflow is 5 m / h or less in the inflow / outflow step.

4. An aerobic granule culture apparatus comprising a semi-batch reaction tank that repeatedly performs an operating cycle including an inflow / outflow step of discharging biologically treated water while introducing organic matter-containing wastewater, a biological treatment step of biologically treating the organic matter in the organic matter-containing wastewater with microbial sludge containing aerobic granules, and a sedimentation step of settling the microbial sludge to form a microbial sludge layer, wherein the apparatus The sedimentation process is carried out until the interface height of the microbial sludge layer is 50% or less of the water level height of the semi-batch reaction tank. An aerobic granule cultivation apparatus characterized in that, in the inflow / outflow step, the organic matter-containing wastewater is inflow so as to come into contact with the microbial sludge layer formed by the sedimentation step.

5. The aerobic granule culture apparatus according to claim 4, characterized in that, if the interface height of the microbial sludge layer does not fall below 50% of the water level of the semi-batch reaction tank by a predetermined time, the microbial sludge is withdrawn from the semi-batch reaction tank so that the interface height of the microbial sludge layer falls below 50% of the water level of the semi-batch reaction tank, thereby adjusting the sludge concentration.

6. The aerobic granule cultivation apparatus according to claim 4 or 5, characterized in that the linear velocity of the organic matter-containing wastewater inflow in the inflow / outflow process is 5 m / h or less.

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