Sludge treatment apparatus and sludge treatment method

Abstract

The objective is to provide a sludge treatment device and a sludge treatment method that can achieve a high sludge volume reduction effect. [Solution] A sludge treatment apparatus comprising: a tank into which at least one of activated sludge and excess sludge is introduced; a gas permeable membrane module provided in the tank and allowing oxygen-containing gas to pass through; and a holding part for holding the gas permeable membrane in the tank; a gas introduction part for introducing the oxygen-containing gas into the gas permeable membrane; and a diffuser means provided in the tank for generating a swirling flow in the tank so as to hold metazoans introduced into the tank on the gas permeable membrane.

Description

Technical Field

[0001] The present invention relates to an apparatus for sludge treatment, particularly a sludge treatment apparatus using a gas permeable membrane.

Background Art

[0002] Since the practical application of hydrogen separation in the late 1970s, gas separation by membranes has been put into practical use in various fields such as carbon dioxide separation, air separation, air dehumidification, and volatile organic compounds (VOCs), and its introduction into the water treatment field has also been under consideration.

[0003] As an example of the utilization of gas permeable membranes in the water treatment field, the main applications are the removal of organic substances and nitrogen by utilizing the oxygen concentration gradient difference inside and outside the gas permeable membrane and retaining a biofilm on the surface of the gas permeable membrane. By gas separation using a membrane, the size of the biological treatment tank can be reduced, and the oxygen dissolution efficiency can also be increased, so the aeration volume of the blower can be reduced.

[0004] As a wastewater treatment technology using such a gas permeable membrane, Patent Document 1 discloses a wastewater treatment apparatus and a wastewater treatment method including a hollow fiber membrane module having a microbial layer formed on its surface and an aeration device, and the arrangement method is non-overlapping.

[0005] Further, Patent Document 2 discloses a water treatment method in which an oxygen permeable membrane with an attached biofilm that decomposes organic substances is immersed in a wastewater treatment system or a sedimentation tank as a gas permeable membrane to perform advanced treatment and sludge collection.

[0006] In addition to these, there is also a technology that uses metazoans as a means to reduce the volume of sludge in a wastewater treatment apparatus. For example, Patent Document 3 discloses a technology that uses a pile carrier as a carrier to attach sludge, and by naturally generating metazoans on this carrier, the volume of excess sludge is reduced by utilizing the food chain in activated sludge treatment.

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] Japanese Patent Publication No. 2023-62886 [Patent Document 2] Japanese Patent Publication No. 2023-176937 [Patent Document 3] Japanese Patent Publication No. 2012-81392 [Overview of the project] [Problems that the invention aims to solve]

[0008] In sludge treatment systems equipped with gas-permeable membranes, the use of metazoans is highly beneficial because it effectively reduces the volume of sludge by suppressing the generation of excess sludge through their sludge-eating effect. Furthermore, in order to maximize the performance of metazoans, it is preferable for them to be held in a gas-permeable membrane rather than floating in the sludge tank. This is because the gas-permeable membrane is an element that comes into direct contact with the sludge being treated.

[0009] In this regard, Patent Document 1 discloses attaching microorganisms to hollow fiber modules, but does not discuss means for retaining the attached microorganisms without allowing them to flow out of the hollow fiber modules. As a result, there is a risk that the microorganisms may flow out of the hollow fiber modules due to the water flow caused by aeration to grow the microorganisms. Consequently, the microorganisms may not be retained in the hollow fiber modules, making it difficult to efficiently exert the sludge volume reduction effect. Furthermore, because constant aeration is required, if a gas permeable membrane is immersed in a sedimentation tank, there is a concern that suspended solids (SS) may carry over, exceeding the standard value.

[0010] Furthermore, while Patent Document 2 focuses on the sludge volume reduction effect of biofilms attached to oxygen-permeable membranes as MABR (Membrane Aerated Bio-Reactor) membranes, it does not propose any means for retaining metazoans on gas-permeable membranes, and it is predicted that the resulting sludge volume reduction effect will be limited.

[0011] Furthermore, since Patent Document 3 does not propose supplying gas to the carrier in which metazoans are generated, there is a concern that the inside of the carrier in a normal fixed bed is prone to anaerobic conditions, making it difficult to stably retain metazoans on the carrier.

[0012] The present invention has been made in view of the above-mentioned conventional problems, and its objective is to provide a sludge treatment device that can achieve a higher sludge volume reduction effect. [Means for solving the problem]

[0013] In other words, the above problem involves a tank into which at least one of activated sludge and excess sludge is introduced, A gas permeable membrane module comprising a gas permeable membrane provided in the water tank and allowing oxygen-containing gas to pass through, and a holding part that holds the gas permeable membrane in the water tank, The gas permeable membrane includes a gas introduction section for introducing the oxygen-containing gas, A means for generating swirling sulfur in the tank is provided within the tank and the gas permeable membrane holds the metazoans introduced into the tank, A sludge treatment apparatus characterized by having This can be resolved.

[0014] A preferred embodiment of this invention relates to a sludge treatment apparatus characterized in that the dissolved oxygen concentration in the water tank in which the gas permeable membrane module is installed is 0.1 mg / L or higher.

[0015] Another preferred embodiment relates to a sludge treatment apparatus, characterized in that the metazoan is selected from any animal belonging to the Oligochaeta of the phylum Annelida.

[0016] Another preferred embodiment relates to a sludge treatment device characterized in that the metazoan is selected from any animal belonging to the oligochaete group of the phylum Annelida.

[0017] Another aspect of the present invention is: Activated sludge treatment means for performing aerobic treatment on sludge, Sedimentation means for naturally sedimenting the sludge treated by the activated sludge treatment means, Return means for withdrawing a part of the sludge sedimented by the sedimentation means as separated sludge and returning the separated sludge to the sedimentation means, Sludge concentration means for concentrating the sludge of the sedimentation means, Transfer means for transferring the sludge of the sedimentation means to the sludge concentration means, which has An activated sludge treatment apparatus having a gas permeable membrane module is provided in at least one of the activated sludge treatment means, the sedimentation means, the return means, the sludge concentration means, and the transfer means. The gas permeable membrane module comprises a gas permeable membrane that allows oxygen-containing gas to pass through, and a holding member that holds the permeable membrane. The sludge treatment apparatus has a gas introduction part for introducing gas into the gas permeable membrane. Furthermore, it is provided in the water tank of the sludge treatment apparatus, and has aeration means for generating swirling sulfur in the water tank so as to hold metazoans existing in the water tank on the gas permeable membrane. An activated sludge treatment system characterized by this relates to.

[0018] Another aspect of the present invention is A gas permeable membrane module installation step in which the gas permeable membrane module is installed in a water tank and comprises a gas permeable membrane that allows oxygen-containing gas to pass through and a holding member that holds the gas permeable membrane in the water tank; An activated sludge or excess sludge introduction step of introducing at least one of activated sludge and excess sludge into the water tank; A gas introduction step of introducing gas from the gas introduction part into the gas permeable membrane; A metazoan introduction step of introducing metazoans into the water tank; An excess sludge introduction step of introducing the excess sludge into the water tank; An air supply step of supplying air to a part of the bottom of the water tank to form a swirling flow of the sludge in the water tank. An air supply stop step for stopping the supply of air in the aforementioned air supply step: The present invention relates to a sludge treatment method characterized by having the following features. [Effects of the Invention]

[0019] The present invention provides a sludge treatment apparatus and a sludge treatment method that can achieve a high sludge volume reduction effect. More specifically, a greater sludge volume reduction effect can be obtained by installing a gas permeable membrane module having a gas permeable membrane that holds metazoans in a sludge treatment device, for example, in the excess sludge, sludge return line, or sludge thickening tank. In this case, the inside of the gas permeable membrane module does not become anaerobic, and metazoans can be suitably retained in the gas permeable membrane. In addition, the sludge treatment apparatus of the present invention does not generate bubbles. Especially after the retention of metazoans, aeration outside the gas permeable membrane is unnecessary, and oxygen can be supplied without aeration. Therefore, it can be installed not only in the aeration tank of the activated sludge treatment process but also in solid-liquid separation tanks such as sedimentation tanks and sludge thickening tanks. Furthermore, the sludge treatment device of the present invention has the advantage of being easy to introduce into existing wastewater treatment facilities. In summary, the present invention provides a high sludge volume reduction effect, not only through the aerobic digestion of metazoans but also by suppressing the generation of excess sludge through sludge predation by metazoans. [Brief explanation of the drawing]

[0020] [Figure 1] Figure 1 is a schematic diagram showing one embodiment of the sludge treatment apparatus of the present invention. [Figure 2] Figure 2 is a schematic diagram showing a means of holding metazoans in a gas-permeable membrane. [Figure 3] Figure 3 is a schematic diagram showing the flow of sludge treatment using the activated sludge treatment system of the present invention. [Figure 4] Figure 4 shows the gas permeable membrane before it is used to hold metazoans. [Figure 5]Figure 5 shows a gas permeable membrane after metazoans have been held in place. [Figure 6] Figure 6 is a magnified view of the gas permeable membrane after metazoans have been held in place. [Modes for carrying out the invention]

[0021] The sludge treatment apparatus and sludge treatment method of the present invention will be described in more detail below. Figure 1 shows a schematic diagram of one embodiment of the sludge treatment apparatus of the present invention. The sludge treatment device 1 includes a water tank 2, a gas permeable membrane module 3 provided inside the water tank 2, and a gas introduction unit 5 equipped with an air line 4. Furthermore, the gas permeable membrane module 3 consists of a gas permeable membrane 6 and a holding part 7. At least one of activated sludge and excess sludge is introduced into the tank 2, and the necessary amount of metazoans 8 are added to the tank 2 from above. Furthermore, in Figure 1, the gas permeable membrane module 3 is positioned slightly above the bottom of the tank 2. The gas permeable membrane 6 of this gas permeable membrane module 3 is held in the tank 2 by a holding part 7, and multiple gas permeable membranes 6 are installed in parallel so as not to overlap each other, in a configuration that facilitates the retention of metazoans 8.

[0022] From the viewpoint of growth and maintenance of metazoans 8, it is preferable to supply gas to the gas permeable membrane 6 via an air line 4 from a gas introduction unit 5 located above the sludge treatment device 1. The amount of air supplied to the gas permeable membrane module 3 for this purpose is preferably adjusted so that the dissolved oxygen concentration in the water tank 2 in which the gas permeable membrane module 3 is installed, more specifically near the gas permeable membrane module 3, is 0.1 mg / L or higher, and more preferably adjusted to 1.0 to 10.0 mg / L. Similarly, from the standpoint of the growth of metazoans 8, it is preferable to maintain the water temperature of tank 2 at 10-30°C, and more preferably at 15-25°C. The gas permeable membrane 6 is made of a material mainly composed of plastic, and hollow fibers are woven into it to form a bundle. Here, it is desirable that there be gaps of about 0.1 to 1.0 mm between the fibers so that metazoans such as earthworms can obtain a habitat space between the fibers.

[0023] In the present invention, it is preferable to install an aeration means 9 at the bottom of the gas permeable membrane module 3. At this time, the air 10 from the aeration means 9 is adjusted to be supplied to a part of the bottom of the tank 2, more preferably to one corner of the bottom surface (see also Figure 2). This allows the sludge in the tank 2 to form a swirling flow from bottom to top, and the metazoans 8 and activated sludge in the tank 2 can be carried by the swirling flow to adhere to the gas permeable membrane 6 and held stably. Furthermore, from the viewpoint of better adhering and retaining the metazoans 8 to the gas permeable membrane 6, it is more preferable to supply air 10 to create a swirling, upward flow of sludge. By creating a swirling flow, the activated sludge is thoroughly agitated within the tank. This increases the opportunities for tubifex worms to come into contact with the gas permeable membrane, thus promoting their attachment to the membrane. Tubifex worms are denser than sludge and tend to settle. In the latter half of the swirling flow, the tubifex worms settle, so they are absent near the tank outlet in the latter half of the swirling flow. Therefore, the tubifex worms are less likely to flow out of the tank system and can efficiently attach to the gas permeable membrane.

[0024] Once it is confirmed that the metazoans 8 are held in the gas permeable membrane 6, it is desirable to stop supplying air 10 from the aeration means 9. If the supply of air 10 is excessive, there is a high risk that the held metazoans 7 will detach from the gas permeable membrane 4 and flow out of the tank system.

[0025] In the aeration tank, if a swirling flow of sludge is not generated, there is a risk of metazoans 8 detaching from the gas permeable membrane. For this reason, aeration can be installed separately to generate a swirling flow, and then, once the retention of metazoans 8 progresses, aeration can be stopped to prevent the detachment of metazoans 8 due to aeration. Once the activated sludge and metazoans have adhered to the gas permeable membrane, aeration in the tank can be stopped. Furthermore, the present invention can be installed in places where SS overflows into the treated water, such as sedimentation tanks. By installing the present invention in multiple locations, the sludge volume reduction effect can be further obtained.

[0026] In contrast to the sludge treatment apparatus 1 of the present invention described above, if air 10 is supplied to the entire bottom of the tank 2, the metazoans 8 may not be able to be retained by the gas permeable membrane 6, or the metazoans 8 that have been retained by the gas permeable membrane 6 may detach or flow out.

[0027] The retention of metazoans 8 on the gas permeable membrane 6 is achieved by placing a predetermined amount of metazoans 8 into the tank 2 and supplying air 10 from the aeration means 9 as described above (Figure 2). In this way, Turning A flow is generated, and the metazoans 8 that are carried along by this flow are held in the gas permeable membrane 6 by their movement from the top to the bottom of the membrane. During this process, it is preferable to maintain the dissolved oxygen concentration in the sludge treatment device 1 at 0.1 mg / L or higher until the metazoans 8 are stably retained in the gas permeable membrane 6. The metazoans are usually introduced into the tank from the open top of tank 2, but they may also be introduced through a conduit installed on the side of tank 2.

[0028] After the metazoans 8 are held in the gas permeable membrane 6, the supply of air 10 to the gas permeable membrane 6 may be limited to the supply from the top of the gas permeable membrane module 3, for example, from the gas introduction section 6. Even in this case, the dissolved oxygen concentration necessary for holding the metazoans 8 can be sufficiently maintained. Thus, since the gas permeable membrane 4 is aerobic, the supply of air 10 from the lower aeration means 9 is not particularly necessary. If metazoans 8 are excessively retained in the gas permeable membrane 6, they can be intentionally detached by air washing and recovered as valuable material.

[0029] In the sludge treatment apparatus 1 of the present invention, metazoans 8 can be retained using a gas permeable membrane 6, and a sludge volume reduction effect can be obtained by the metazoans 8 preying on the sludge, so it can be used even when the sludge concentration in the water tank 2 is high. Specifically, it can be applied in the MLSS range of 100 to 50,000 mg / L. The pH inside the gas permeable membrane module 3 containing the metazoans 7 is preferably maintained at 6.0 to 9.0, more preferably at 7.0 to 8.0, and even more preferably at 7.0 to 7.5.

[0030] While it is preferable to maintain the concentration of the biological toxin NH4-N below 50 mg / L within the gas permeable membrane module 3, the present invention uses a gas permeable membrane 6, which allows the NH4-N to be maintained below 50 mg / L due to nitrification and denitrification caused by the oxygen concentration difference in the biofilm. The salt concentration inside the gas permeable membrane module 3 should preferably be 100 to 10,000 μS / cm in terms of conductivity.

[0031] The metazoan 8 used in the present invention is preferably selected from any animal belonging to the Oligochaeta of the phylum Annelida. More preferably, this includes the lily worm belonging to the subfamily Limacinae of the Oligochaeta of Annelida, or the gill worm belonging to the subfamily Limacinae of the Oligochaeta of Annelida. Tuberculoskeletin, a subfamily of earthworms, possesses a respiratory pigment called erythrocruorin for oxygen transport within its body, and it contains iron. Therefore, if tubifex worms are not growing well, adding iron chloride or iron polysulfate at a concentration of approximately 1.0 mg / L (Fe equivalent) as a trace element can improve their survival rate.

[0032] Metazoans 7 have a habit of burrowing into even the smallest gaps to make their habitat, so a fixed bed is necessary. However, after activated sludge adheres to the fixed bed, the interior tends to become anaerobic, which reduces the survival rate of aerobic metazoans 8. In this respect, the present invention addresses this by retaining the metazoans in a gas permeable membrane 6, which creates aerobic conditions inside the membrane, thus allowing the metazoans 8 to be stably retained in the gas permeable membrane 6.

[0033] Another embodiment of the sludge treatment apparatus 1 of the present invention is an activated sludge treatment system 20, as shown in Figure 3, which can be broadly divided into: an activated sludge treatment means 21 for applying aerobic treatment to the sludge; a sedimentation means 22 for obtaining sludge separated by natural sedimentation from the sludge treated by the activated sludge treatment means 21; a return means 23 for withdrawing at least a portion of the sedimentation means 22 as separated sludge and returning the separated sludge to the sedimentation means; a sludge concentrating means 24 for concentrating the sludge in the sedimentation means 22; and a transfer means 25 for transferring the sludge in the sedimentation means 22 to the sludge concentrating means 24. Furthermore, it is preferable that the sludge treatment device 1 having the gas permeable membrane module 26 configured as described above be provided in at least one of these five means. The sludge treatment device 1 having the gas permeable membrane module 26 may also be installed in a primary sedimentation tank (not shown) that is a step prior to the activated sludge treatment means 21.

[0034] The sludge treatment device 1 suppresses the overall amount of excess sludge generated by its effect of removing organic matter and nitrogen from the sludge, and by the effect of reducing the volume of sludge through predation of sludge by metazoans. When a gas permeable membrane module 26 is installed in the activated sludge treatment means 21, if the aeration rate is high, bubbles and water flow may come into contact with the metazoans 27, and there is a possibility that the metazoans 27 will not be retained by the gas permeable membrane 6. In that case, it is desirable to create an environment in which the metazoans 28 can easily settle by increasing the distance between the aeration means 28 and the gas permeable membrane module 26, or by adjusting the position of the aeration means 28 to form a circulating flow in the water tank 2. Although not shown in the diagram, in the activated sludge treatment means 21, the sedimentation means 22, the return means 23, the sludge thickening means 24, the transfer means 25, and also in the primary sedimentation tank located prior to the activated sludge treatment means 21, air from the aeration means 28 is supplied to a portion of the bottom of each tank, for example, to one of their corners.

[0035] The sludge treatment method of the present invention is carried out, for example, based on the following steps. First, the gas permeable membrane modules 3 and 26 with the above configuration are installed in the water tank 2 into which the sludge to be treated is introduced (gas permeable membrane module installation process). At least one of activated sludge or excess sludge is introduced into the tank 2 (activated sludge or excess sludge introduction step). A gas, such as air, is introduced from the gas introduction section 5 into the gas permeable membrane 6 (gas introduction step). Metazoans 8 and 27 are introduced into tank 2 (metazoan introduction process). The excess sludge is introduced into the water tank 2 (excess sludge introduction process). Air 10 is supplied to a portion of the bottom of the tank 2 to form a swirling flow of sludge in the tank 2, thereby holding the metazoans in the gas permeable membrane (air supply step). Once it is determined that there is sufficient air to hold the metazoans 8,27, the supply of air 10 is stopped to prevent them from detaching or leaking out (air supply stop step). Through the above process, the sludge is efficiently reduced in volume. [Examples]

[0036] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.

[0037] (Example of a metazoan attachment test) Using the apparatus shown in Figure 2, the degree of attachment of metazoans 8 and 27 was confirmed using the metazoan attachment process described above. Table 1 shows the configuration of the gas permeable membrane modules 3 and 26 used, and Table 2 shows the operating conditions. The aerated liquid after activated sludge treatment is filled into the sludge treatment device 1, and after introducing oilworms belonging to the family Lucidae, which are metazoans 8,27, aeration is started by an external aeration device (aeration means 9,28) for generating a swirling flow (an embodiment of the present invention). To prevent visible metazoans (8,27) from overflowing outside the system, the airflow rate of the external aeration device was adjusted to 30-60 L / min as appropriate. During the settling period, aeration liquid was added intermittently to maintain the MLSS concentration in the apparatus at 3,000-5,000 mg / L, with the frequency of aeration liquid addition being once every five days. On the other hand, a case in which aeration by the swirling flow of the aeration means 9,28 was not performed after introducing the oil worms was used as a reference example.

[0038] [Table 1]

[0039] [Table 2]

[0040] (Example of a metazoan attachment test: Test results) Figure 4 shows the biofilm and the gas permeable membrane before metazoan attachment.

[0041] (Example of a metazoan attachment test) On the other hand, Figures 5 and 6 show the results of an embodiment of the present invention in a metazoan attachment test. The attachment of the metazoan worm, *Elaphe climacophora*, was confirmed to be visible to the naked eye, confirming that the metazoan attachment process using the apparatus of the present invention is effective. The wet weight of earthworms per unit area is 0.5 g-wt / cm³. 2 Furthermore, the adhesion rate of oilworms to the surface of the gas permeable membrane was estimated to be approximately 7%, and the total wet weight of oilworms in the apparatus was estimated to be approximately 5,100 g. In contrast, in the reference example where aeration by swirling flow from the aeration means 9,28 was not performed, the attachment of oilworms was much lower than in the example.

[0042] (Examples of sludge volume reduction tests) Using this apparatus, to which metazoans 8 and 27 were immobilized in the aforementioned metazoan immobilization test, the sludge volume reduction effect was confirmed using the treatment flow shown in Figure 3. The air supply was provided to maintain the oilworms attached to the gas permeable membrane 6. A comparative example was used for a sample without attached oilworms, while the example was a test using the gas permeable membrane 6 to which oilworms had been attached in the aforementioned metazoan attachment test.

[0043] The gas permeable membrane modules 3 and 26, which constitute the sludge treatment apparatus 1, were installed at the transfer means 25 connected to the illustrated sludge treatment apparatus 1, which is located after processing by the activated sludge treatment means 21 shown in Figure 3, in both the comparative example and the example.

[0044] (Sludge volume reduction test conditions) The test conditions are shown in Table 3 below. The sludge retention time in the sludge treatment device 1 was kept constant at 28 hours. The test section consisted of three sections: RUN1, RUN2, and RUN3, and the BOD volumetric load of the activated sludge treatment device was 0.61 kg / (m³). 3 • Gradually increase the load from d) up to a maximum of 1.51 kg / (m 3 The effect of metazoans on reducing sludge volume was confirmed by increasing the concentration to (d). Evaluation was performed using the MLSS concentration in the device, and the measurement frequency was set to 5 days a week.

[0045] [Table 3]

[0046] (Sludge volume reduction test results) The results are shown in Table 4 below. After sludge accumulation in RUN1, the MLSS in the system was 4,200 mg / L for the comparative example and 2,037 mg / L for the example, resulting in a sludge volume reduction rate of 51.5% compared to the control system. Although there was a decreasing trend in the sludge volume reduction rate with increasing BOD volume load, the sludge volume reduction rates for RUN2 and RUN3 were 33.0% and 15.0% respectively compared to the control system, confirming that the sludge volume reduction effect of metazoans 8 and 27 (oil worms) was maintained. Although the results of this test were obtained using only one gas permeable membrane module 3,26, it can be installed anywhere after the metazoans 8,27 are attached to the gas permeable membrane 6. Therefore, although not shown in the diagram, it is presumed that by installing multiple gas permeable membrane modules 3,26 in sedimentation tanks and sludge thickening tanks, it will be possible to suppress the generation of excess sludge associated with biological treatment.

[0047] [Table 4] [Explanation of Symbols]

[0048] 1. Sludge treatment equipment 2 Aquariums 3.26 Gas Permeable Membrane Module 4 Airlines 5. Gas introduction section 6. Gas permeable membrane 7 Holding part 8,27 Metazoans (Tubifex worms) 9.28 Aeration methods 10 Air (bubbles) 20 Activated Sludge Treatment System 21 Activated sludge treatment method 22. Sedimentation method 23. Return method 24. Sludge thickening means 25 Means of transport

Claims

1. A tank into which at least one of activated sludge and excess sludge is introduced, A gas permeable membrane module comprising a gas permeable membrane provided in the water tank and allowing oxygen-containing gas to pass through, and a holding part that holds the gas permeable membrane in the water tank, The gas permeable membrane includes a gas introduction section for introducing the oxygen-containing gas, A means for generating swirling sulfur in the tank is provided within the tank and the gas permeable membrane holds the metazoans 7 introduced into the tank, A sludge treatment apparatus characterized by having

2. The sludge treatment apparatus according to claim 1, characterized in that the dissolved oxygen concentration in the water tank in which the gas permeable membrane module is installed is 0.1 mg / L or more.

3. The sludge treatment apparatus according to claim 1 or 2, characterized in that the aeration means supplies air to a part of the bottom of the water tank to form a swirling flow of sludge in the water tank.

4. The sludge treatment apparatus according to claim 1 or 2, characterized in that the metazoan is selected from any animal belonging to the Oligochaeta of the phylum Annelida.

5. An activated sludge treatment method for applying aerobic treatment to sludge, A sedimentation means for allowing the sludge treated by the activated sludge treatment means to settle naturally, A return means for extracting a portion of the sludge settled by the sedimentation means as separated sludge and returning the separated sludge to the sedimentation means, A sludge thickening means for thickening the sludge of the aforementioned settling means, A transfer means for transferring the sludge from the sedimentation means to the sludge thickening means, It has, The activated sludge treatment means, the sedimentation means, the return means, the sludge concentration means, and the transfer means are provided with a sludge treatment apparatus having a gas permeable membrane module in at least one of them. The aforementioned gas permeable membrane module is A gas permeable membrane that allows oxygen-containing gases to pass through, It consists of a holding member that holds the permeable membrane, The sludge treatment device has a gas introduction section for introducing gas into the gas permeable membrane, Furthermore, the sludge treatment apparatus has a means of generating swirling sulfur in the tank, provided within the tank of the sludge treatment apparatus, so as to retain metazoans present in the tank through the gas permeable membrane. An activated sludge treatment system characterized by the following:

6. A gas permeable membrane module installation process comprising a gas permeable membrane installed in a water tank, which allows oxygen-containing gas to pass through, and a holding member that holds the gas permeable membrane in the water tank; An activated sludge or excess sludge introduction step, in which at least one of activated sludge or excess sludge is introduced into the tank; A gas introduction step in which gas is introduced from the gas introduction section into the gas permeable membrane; A metazoan introduction step involves introducing metazoans into the aforementioned tank; Excess sludge introduction step, which involves introducing the aforementioned excess sludge into a water tank; An air supply step, in which air is supplied to a part of the bottom of the tank to form a swirling flow of sludge in the tank; An air supply stop step for stopping the supply of air in the aforementioned air supply step: A sludge treatment method characterized by having the following features.

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