Cleaning method for organic wastewater treatment equipment

Abstract

Provided is a method for cleaning an organic waste water treatment apparatus that is provided with a reaction tank for subjecting contaminants contained in organic waste water to a biological treatment and a supply device for supplying at least oxygen into the reaction tank, in which the reaction tank has a tubular membrane carrier that enables the molecule diffusion of oxygen supplied by the supply device in the reaction tank through a plurality of holes. In the method, the supply of oxygen to the membrane carrier is terminated, then a chemical agent for cleaning the plurality of holes is injected into the inside of the membrane carrier from the lower end of the membrane carrier, then water or first air for pushing out the chemical agent in the plurality of holes to the reaction tank side is injected into the inside of the membrane carrier from the lower end of the membrane carrier, then the closing of a valve for controlling the amount of air to be discharged from the upper end of the membrane carrier is controlled, and then second air for drying the inside of the plurality of holes by pushing out the water or the first air in the plurality of holes to the reaction tank side is injected into the inside of the membrane carrier from the lower end of the membrane carrier.

Description

Technical Field

[0001] The present disclosure relates to a method for cleaning a treatment device for organic wastewater.

Background Art

[0002] In a treatment device for treating organic wastewater such as sewage (hereinafter, also simply referred to as wastewater), as a method for removing, for example, contaminants (hereinafter, also simply referred to as contaminants) contained in the wastewater, for example, an activated sludge method in which organic matter is decomposed by microorganisms (hereinafter, also referred to as activated sludge) propagated in a reaction tank is used. Contaminants are, for example, organic matter, suspended substances, etc. (hereinafter, also simply referred to as organic matter or substrate) (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the treatment device for organic wastewater as described above, a cleaning method that enables the continuous maintenance of the contaminant removal ability is desired.

Means for Solving the Problems

[0005] A method for cleaning a treatment device for organic wastewater according to an aspect of the present disclosure includes a tank and a supplier that supplies at least oxygen. The tank has a tubular membrane carrier that molecularly diffuses oxygen supplied by the supplier into the tank through a plurality of holes. The cleaning method is to stop the supply of oxygen to the membrane carrier, supply a chemical from the first part of the membrane carrier into the inside of the membrane carrier, supply a liquid or a first gas from the first part into the inside of the membrane carrier, lower the opening degree of a valve that controls the amount of gas discharged from the second part of the membrane carrier, and supply a second gas from the first part into the inside of the membrane carrier.

Effects of the Invention

[0006] According to a cleaning method for an organic wastewater treatment device in one aspect of this disclosure, it is possible to maintain the ability to remove pollutants. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a diagram illustrating the configuration of the organic wastewater treatment device 800 in the first comparative example. [Figure 2] Figure 2 illustrates the configuration of the organic wastewater treatment device 900 in the second comparative example. [Figure 3] Figure 3 is a diagram illustrating the configuration of the organic wastewater treatment device 100 in the first embodiment. [Figure 4] Figure 4 is a vertical cross-sectional view illustrating the configuration of the membrane carrier 72 in the first embodiment. [Figure 5] Figure 5 is a vertical cross-sectional view illustrating the configuration of the membrane carrier 72 in the first embodiment. [Figure 6] Figure 6 illustrates the effects of the first embodiment. [Figure 7] Figure 7 illustrates the effects of the first embodiment. [Figure 8] Figure 8 illustrates the effects of the first embodiment. [Figure 9] Figure 9 is a diagram illustrating the configuration of the reaction vessel 70 in the first modified example. [Figure 10] Figure 10 is a diagram illustrating the configuration of the membrane carrier 72 in the first modified example. [Figure 11] Figure 11 is a diagram illustrating the configuration of the membrane carrier 72 in the first modified example. [Figure 12] Figure 12 illustrates the cleaning method of the organic wastewater treatment device 100 in the first embodiment. [Figure 13]Figure 13 illustrates the cleaning method of the organic wastewater treatment device 100 in the first embodiment. [Figure 14] Figure 14 illustrates the cleaning method of the organic wastewater treatment device 100 in the first embodiment. [Figure 15] Figure 15 illustrates the cleaning method of the organic wastewater treatment device 100 in the first embodiment. [Figure 16] Figure 16 illustrates the cleaning method of the organic wastewater treatment device 100 in the first embodiment. [Modes for carrying out the invention]

[0008] Embodiments of this disclosure will be described below with reference to the drawings. However, this description should not be interpreted as limiting, and will not limit the subject matter described in the claims. Furthermore, various changes, substitutions, and modifications can be made without departing from the spirit and scope of this disclosure. Different embodiments can also be combined as appropriate.

[0009] [Organic wastewater treatment device 800 in the first comparative example] First, we will explain the configuration of the organic wastewater treatment device 800 (hereinafter also referred to as the organic wastewater treatment system 800) in the first comparative example. Figure 1 is a diagram illustrating the configuration of the organic wastewater treatment device 800 in the first comparative example. The organic wastewater treatment device 800 treats pollutants by the so-called activated sludge method. Specifically, as shown in Figure 1, the organic wastewater treatment device 800 includes, for example, a primary sedimentation tank 10, a reaction tank 20, a final sedimentation tank 30, and a feeder 40.

[0010] The primary sedimentation tank 10 separates organic matter (for example, solid organic matter) contained in the wastewater 1 (hereinafter also simply referred to as liquid) by sedimentation. The primary sedimentation tank 10 then discharges the separated organic matter as primary sedimentation sludge to a thickener (not shown) and discharges the wastewater 1 after the separation of organic matter to the reaction tank 20.

[0011] The reaction tank 20 has, for example, a tank body 21 from which the waste water 1 is discharged from the first sedimentation tank 10, and an air supply pipe 22 that supplies air 2 (oxygen) from the bottom of the tank body 21 to the activated sludge (aerobic microorganisms) present in the tank body 21, and treats the waste water 1 by biological treatment.

[0012] Specifically, in the reaction tank 20, for example, aeration treatment for supplying air 2 to the activated sludge present in the tank body 21 is performed. And in the reaction tank 20, for example, the organic substances (for example, soluble organic substances) contained in the waste water 1 are decomposed (consumed) by the activated sludge that has received the supply of air 2. After that, the reaction tank 20 discharges, for example, the waste water 1 after the decomposition of the organic substances by the activated sludge to the final sedimentation tank 30.

[0013] The final sedimentation tank 30, for example, separates the sludge contained in the waste water 1 discharged from the reaction tank 20, and discharges the separated sludge as activated sludge. And the final sedimentation tank 30, for example, supplies a part of the activated sludge as excess sludge to a concentrator (not shown), and returns the activated sludge other than the excess sludge to the reaction tank 20 as return sludge. Further, the final sedimentation tank 30 discharges, for example, the waste water 1 (supernatant) after the separation of the activated sludge to a subsequent sterilization treatment device (not shown). After that, the sterilization treatment device sterilizes, for example, the waste water 1 discharged from the final sedimentation tank 30, and discharges the sterilized treated water.

[0014] The air supply device 40 (hereinafter, also simply referred to as the supply device 40) is, for example, a blower, and supplies air 2 to the reaction tank 20. Specifically, the supply device 40 supplies air 2 into the reaction tank 20 through an air supply pipe 22 provided at the bottom of the reaction tank 20.

[0015] Here, in the organic wastewater treatment device 800, the separation of the activated sludge in the final sedimentation tank 30 is performed by natural sedimentation. Therefore, for example, when the activated sludge does not settle sufficiently due to bulking or the like, in the organic wastewater treatment device 800, there is a possibility that the activated sludge flows out (carries over) to the subsequent device.

[0016] Furthermore, in the organic wastewater treatment device 800, the concentration of activated sludge in the reaction tank 20 changes depending on the amount of sludge returned from the final sedimentation tank 30. Therefore, the concentration of activated sludge in the reaction tank 20 depends on the natural settling properties and size of the final sedimentation tank 30, and may become unstable.

[0017] Furthermore, in the organic wastewater treatment device 800, the power supply of air 2 from the feeder 40 may be increased due to the need to maintain the concentration of activated sludge in the reaction tank 20. In addition to the activated sludge method, the membrane separation activated sludge method has been proposed as a method for treating pollutants. The membrane separation activated sludge method is explained in Figure 2.

[0018] [Organic wastewater treatment device 900 in the second comparative example] Next, we will describe the configuration of the organic wastewater treatment device 900 (hereinafter also referred to as the organic wastewater treatment system 900) in the second comparative example. Figure 2 is a diagram illustrating the configuration of the organic wastewater treatment device 900 in the second comparative example.

[0019] As shown in Figure 2, the organic wastewater treatment device 900 includes, for example, a primary sedimentation tank 10, a reaction tank 20, a feeder 40, a solid-liquid separation tank 50, and an air supplyer 60 (hereinafter also referred to as the feeder 60).

[0020] The organic wastewater treatment device 900 is, for example, an organic wastewater treatment device that uses a membrane separation activated sludge method. Specifically, as shown in Figure 2, the organic wastewater treatment device 900 has, for example, a solid-liquid separation tank 50 instead of a final sedimentation tank 30. The organic wastewater treatment device 900 also has, for example, a feeder 60.

[0021] The solid-liquid separation tank 50 includes, for example, a tank body 51 from which wastewater 1 is discharged from the reaction tank 20, an air supply pipe 52 that supplies air 2 (oxygen) from the bottom of the tank body 51 to the activated sludge (aerobic microorganisms) present in the tank body 51, and a separation membrane 53 that separates the activated sludge contained in the wastewater 1. The separation membrane 53 is, for example, a microfiltration membrane or an ultrafiltration membrane.

[0022] Specifically, in the solid-liquid separation tank 50, for example, the separation membrane 53 is aerated from below by air 2 supplied from the air supply pipe 52, generating an upward flow of air 2 and wastewater 1. This suppresses the growth (coating) of activated sludge on the separation membrane 53 and the occurrence of blockage due to clogging of the separation membrane 53, while separating the activated sludge. The solid-liquid separation tank 50 then supplies a portion of the activated sludge as excess sludge to the concentrator, and returns the activated sludge other than the excess sludge to the reaction tank 20 as return sludge. Furthermore, the solid-liquid separation tank 50 discharges the wastewater 1 (supernatant liquid) after the separation of activated sludge to a subsequent sterilization treatment device by sucking it from above with a pump (not shown).

[0023] The supply unit 60 is, for example, a blower, which supplies air 2 to the solid-liquid separation tank 50. Specifically, the supply unit 60 supplies air 2 to an air supply pipe 52 located at the bottom of the solid-liquid separation tank 50.

[0024] In other words, the organic wastewater treatment device 900 separates activated sludge using a separation membrane 53 instead of separating it by natural sedimentation. This makes it possible for the organic wastewater treatment device 900 to prevent activated sludge from flowing out into downstream equipment.

[0025] Furthermore, the organic wastewater treatment device 900 makes it possible to increase the concentration of activated sludge separated from the wastewater 1 in the solid-liquid separation tank 50. As a result, the organic wastewater treatment device 900 makes it possible to miniaturize the reaction tank 20 compared to, for example, the organic wastewater treatment device 800 described in Figure 1.

[0026] Furthermore, the organic wastewater treatment device 900 may, for example, use a circulation pump (not shown) to circulate activated sludge between the reaction tank 20 and the solid-liquid separation tank 50 while separating the activated sludge with the separation membrane 53. Alternatively, the organic wastewater treatment device 900 may, for example, have the separation membrane 53 installed inside the reaction tank 20 instead of the solid-liquid separation tank 50. In addition, in the membrane separation activated sludge method shown in Figure 2, excess sludge adhering to the separation membrane 53 can be removed by washing in order to maintain the performance of the reaction tank 50.

[0027] In the organic wastewater treatment device 900, for example, it is necessary to periodically clean the separation membrane 53 using chemicals such as hypochlorous acid or alkali to prevent blockage in the separation membrane 53. In addition, the organic wastewater treatment device 900 also requires periodic replacement of the separation membrane 53.

[0028] Furthermore, in the organic wastewater treatment device 900, for example, the power required for the feeder 40 and circulation pump may be increased due to the need to separate activated sludge while preventing blockage in the separation membrane 53.

[0029] Furthermore, the main component of the activated sludge separated by the separation membrane 53 is bacterial cells that have proliferated in the wastewater 1. This excess sludge is dispersed and difficult to dewater. Therefore, in the organic wastewater treatment device 900, it is necessary to add a large amount of coagulant, for example, in a concentrator. Thus, in the organic wastewater treatment device described in Figures 1 and 2, the running costs (for example, power supply for air, cost of replacing the separation membrane, cleaning costs, and cost of coagulant) increase. Therefore, an organic wastewater treatment device that can suppress such running costs will be described with reference to Figures 3 to 8.

[0030] [Organic wastewater treatment device 100 in the first embodiment] First, the configuration of the organic wastewater treatment device 100 (hereinafter also referred to as the organic wastewater treatment system 100) in the first embodiment will be described. Figure 3 is a diagram illustrating the configuration of the organic wastewater treatment device 100 in the first embodiment. Figures 4 and 5 are vertical cross-sectional views illustrating the configuration of the membrane carrier 72 in the first embodiment.

[0031] As shown in Figure 3, the organic wastewater treatment device 100 includes, for example, a primary sedimentation tank 10, a reaction tank 70, an air supply unit 80 (hereinafter also referred to as the supply unit 80), and a solid-liquid separator 90.

[0032] The organic wastewater treatment device 100 performs biological treatment on pollutants contained in organic wastewater 1. As shown in Figure 3, the organic wastewater treatment device 100 has, for example, a reaction tank 70 instead of a reaction tank 20. Also, the organic wastewater treatment device 100 has, for example, a supply unit 80 instead of a supply unit 40. The supply unit 80 is, for example, a blower or fan, and supplies at least oxygen to the reaction tank 70. The gas supplied by the supply unit 80 may be any gas that contains oxygen, and air will be used as an example of an oxygen-containing gas below.

[0033] The reaction tank 70 (hereinafter also simply referred to as the tank) performs biological treatment on pollutants contained in organic wastewater. The reaction tank 70 is, for example, a membrane aerated biofilm reactor (MABR). Specifically, the reaction tank 70 has, for example, a tank body 71 into which wastewater 1 flows from the primary sedimentation tank 10, and one or more membrane carriers 72 into which air 2 supplied by a feeder 80 is supplied. The amount of air supplied by the feeder 80 is less than the amount of air supplied by the feeder described in Figures 1 and 2, thereby reducing the power required for air supply.

[0034] The membrane carrier 72 is a tubular membrane carrier through which air supplied by the feeder 80 is molecularly diffused into the reaction vessel 70 via multiple pores. Specifically, the membrane carrier 72 is a hydrophobic hollow fiber membrane, for example, a membrane made of Teflon®. Furthermore, the membrane carrier 72 is a tubular membrane whose axial direction is perpendicular (towards the height of the reaction vessel 70). The surface of the membrane carrier 72 has numerous fine pores (for example, pores of about 0.1 microns). Air molecularly diffuses into the reaction vessel 70 through these fine pores.

[0035] The following description will assume that four membrane carriers 72 are arranged horizontally in the reaction vessel 70, but the reaction vessel 70 may be equipped with a number of membrane carriers 72 other than four. Furthermore, the following description will assume that air 2 supplied from the feeder 80 is supplied through the inside of the membrane carriers 72 from vertically downward to vertically upward, but the air 2 supplied from the feeder 80 may be supplied through the inside of the membrane carriers 72 from vertically upward to vertically downward. In addition, the membrane carriers 72 may have a U-shape, for example, with both ends pointing vertically upward. Furthermore, the membrane carriers 72 may have a U-shape, for example, with both ends pointing vertically downward.

[0036] Then, as shown in Figure 4(A), the membrane carrier 72 releases (molecularly diffuses) the air 2 supplied from the feeder 80 toward the outside (into the reaction tank 70) through multiple pores on its surface. As a result, a biofilm containing aerobic bacteria (hereinafter referred to as biofilm R1) is formed on the outer surface of the membrane carrier 72 by molecular diffusion of air into the reaction tank 70 through multiple pores. This biofilm is a biofilm that performs biological treatment of pollutants by aerobic bacteria. For example, as shown in Figure 4(B), activated sludge (aerobic microorganisms) present in the tank body 71 adheres to the surface (outer surface) of the membrane carrier 72, forming a clump of biofilm R1, which is a biofilm.

[0037] In other words, in the reaction vessel 70 of this embodiment, the biofilm R1 attached to the surface of the membrane carrier 72 decomposes organic matter contained in the wastewater 1 and grows.

[0038] Furthermore, in order to prevent the biofilm R1 from peeling off due to the generation of bubbles from the surface pores of the membrane carrier 72, the release of air 2 from the inside of the membrane carrier 72 to the outside is carried out by molecular diffusion, which occurs from the gas phase side (inside of the membrane carrier 72) to the liquid phase side (outside of the membrane carrier 72), with the surface pores acting as a gas-liquid interface. For this reason, it is preferable for the supplyer 80 to maintain the pressure inside the membrane carrier 72 at a pressure that does not cause bubbles to be generated from the surface pores (for example, a pressure below the water pressure). In this way, the pressure of the air supplied by the supplyer 80 can be set to a pressure below the water pressure, and can be lower than the pressure of the air supplied by the supplyer 40 described in Figures 1 and 2. Therefore, the operating power of the supplyer 80 can be reduced compared to the operating power of the supplyer 40. Return to Figure 3.

[0039] The reaction tank 70 discharges wastewater 1 (drainage) after the reaction with biofilm R1 to the solid-liquid separator 90. The solid-liquid separator 90 separates clumpy sludge containing biofilm R1 from the drainage discharged from the reaction tank 70. This separated sludge contains various bacteria in addition to surviving and dead aerobic bacteria.

[0040] The solid-liquid separator 90 only needs to have a function for separating sludge, and may, for example, be a device including a separation membrane as described in Figure 2. The solid-liquid separator 90 may also separate the sludge from the wastewater by gravity sedimentation, or by sand filtration. Furthermore, the solid-liquid separator 90 may separate the sludge from the wastewater using a carrier (so-called carrier high-speed filtration).

[0041] The organic wastewater treatment device 100 further includes, for example, a stripping device 73 and a control device 74.

[0042] The peeling device 73 is a device that peels off the biofilm R1 attached to the membrane carrier 72 from the membrane carrier 72 by, for example, vibrating the membrane carrier 72.

[0043] The control device 74 is, for example, an electronic device having an electronic circuit. Specifically, the electronic circuit of the control device 74 is, for example, a computer having a CPU (Central Computing Unit) and memory, and the CPU and a program stored in a memory device (not shown) work together to control the timing at which the peeling device 73 peels off the biofilm R1 (hereinafter also referred to as the peeling timing). The electronic circuit that performs such control may be, for example, an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0044] In the following explanation, it is assumed that the biofilm R1 is removed in the reaction vessel 70 using the peeling device 73. However, in the reaction vessel 70, the biofilm R1 may also be removed by, for example, spraying a gas such as air (so-called membrane washing). In this case, the control device 74 may, for example, control the timing of the spraying.

[0045] In other words, in this embodiment, the reaction tank 70 decomposes organic matter contained in the wastewater 1 discharged from the primary sedimentation tank 10 to the reaction tank 70 using the biofilm R1 attached to the membrane carrier 72, and intermittently peels off the biofilm R1, which has taken up organic matter and formed clumps, from the membrane carrier 72, and discharges the sludge containing the biofilm R1 to the solid-liquid separator 90.

[0046] As a result, in the reaction tank 70 in this embodiment, for example, during the time when organic matter is being decomposed by the biofilm R1 (the time when the biofilm R1 is not being peeled off), it becomes possible to reduce the amount of sludge discharged to the solid-liquid separator 90. Therefore, in this case, the reaction tank 70 can discharge wastewater 1 with low growth potential to the solid-liquid separator 90. This makes it possible to prevent the growth of activated sludge in the solid-liquid separator 90. Furthermore, if the solid-liquid separator 90 separates solids and liquids using a separation membrane, it becomes possible to prevent clogging of this separation membrane.

[0047] Furthermore, in the reaction tank 70 of this embodiment, for example, even during the time when the biofilm R1 is being peeled off, the sludge containing the biofilm R1 is discharged to the solid-liquid separator 90. This prevents clogging of the separation membrane when the solid-liquid separator 90 performs solid-liquid separation using the separation membrane.

[0048] Furthermore, since the solid-liquid separation device 90 in this embodiment separates lumpy sludge from wastewater, it becomes possible to easily dewater the separated sludge. Therefore, in the organic wastewater treatment device 100 in this embodiment, it becomes possible to reduce the amount of coagulant that needs to be added to the dewatering machine or the like that which dewaters the sludge, and thus it becomes possible to reduce the cost required for sludge dewatering.

[0049] Furthermore, in the reaction tank 70 of this embodiment, by using a tubular membrane carrier 72, it is possible to increase the surface area compared to when a membrane carrier with a shape other than tubular is used. Therefore, in the organic wastewater treatment device 100 of this embodiment, it is possible to reduce the reaction volume between activated sludge (aerobic microorganisms) and organic matter, and thus the reaction tank 70 can be made smaller. Specifically, in the organic wastewater treatment device 100, for example, it is possible to reduce the vertical height (water depth) of the reaction tank 70.

[0050] Furthermore, since the supply unit 80 in this embodiment can maintain the internal pressure of the membrane carrier 72 at a level that prevents bubbles from forming from the surface pores, it is possible to suppress the power required to supply air 2 compared to, for example, the case where the supply unit 40 described in Figure 2 is used.

[0051] Furthermore, in the reaction vessel 70 of this embodiment, oxygen molecules diffuse from the pores on the surface of the membrane carrier 72, making it possible to form an aerobic layer R1 (biofilm R1), an anaerobic layer R2, and an anaerobic layer R3, respectively, from the surface of the membrane carrier 72 toward the liquid phase, as shown in Figure 5. That is, in this case, as shown in Figure 5, an aerobic layer R1, an anaerobic layer R2, an anaerobic layer R3, an anaerobic layer R2, and an aerobic layer R1 are formed sequentially between the two membrane carriers 72. Therefore, in the reaction vessel 70, it becomes possible to nitrify, for example, ammonia contained in wastewater 1 by nitrification in the aerobic layer R1. And in the anaerobic layer R2 and the anaerobic layer R3, it becomes possible to remove (denitrify) nitrogen (for example, nitrite nitrogen) contained in wastewater 1 by a denitrification reaction.

[0052] In this embodiment, since the organic matter is processed in the biofilm R1 attached to the membrane carrier 72 in the reaction tank 70, it is no longer necessary to maintain a constant concentration of activated sludge in the liquid phase, as is the case when using the reaction tank 20 described in Figure 2. Therefore, in the organic wastewater treatment device 100 of this embodiment, it is no longer necessary to substantially return sludge from the solid-liquid separator 90 to the reaction tank 70, as is the case with the organic wastewater treatment device 900 described in Figure 2. As a result, the organic wastewater treatment device 100 can substantially omit equipment necessary for sludge return. If sludge is returned to the reaction tank 70, the returned sludge will proliferate as activated sludge in the reaction tank 70. When this proliferated activated sludge is discharged to the solid-liquid separator 90, since this activated sludge is not in the form of clumps, the dewatering ability of the sludge will be about the same as that of the sludge in the organic wastewater treatment device described in Figure 2. However, in this embodiment, since there is virtually no need to return the sludge, only the sludge (in clumps) detached from the biofilm R1 is discharged to the solid-liquid separator 90, thereby improving the dewatering of the excess sludge separated in the solid-liquid separator 90.

[0053] The statement above that it is not necessary to substantially return the sludge from the solid-liquid separator 90 to the reaction tank 70 (in other words, that the sludge is not substantially returned) indicates that the return of the sludge is permitted to the extent that it does not depart from the spirit of this disclosure. Specifically, if the dewatering ability of the sludge separated in the solid-liquid separator 90 can be maintained at a level higher than that of the sludge in the organic wastewater treatment device described in Figure 2, the sludge may be returned from the solid-liquid separator 90 to the reaction tank 70. In the case of such return, the amount of sludge returned (return time) will be less (shorter) than the amount of sludge returned (return time) in the organic wastewater treatment device described in Figure 2.

[0054] Furthermore, in the organic wastewater treatment device 900 (membrane separation activated sludge method) described in Figure 2, various biological reactions proceed in the suspended sludge of the liquid phase in the reaction tank 20, so a certain amount of activated sludge suspended solids (MLSS: Mixed Liquor Suspended Solids) is required. However, in the reaction tank 70 of this embodiment, various biological treatments proceed in the biofilm attached to the surface of the membrane carrier 72, so the MLSS concentration can be lower compared to the membrane separation activated sludge method, and the amount of sludge that flows into the solid-liquid separation device 90 and clogs the solid-liquid separation can be minimized.

[0055] Furthermore, in this embodiment, a gas with a higher oxygen concentration than air may be supplied to the membrane carrier 72 from the supply unit 80 instead of air. This makes it possible to reduce the number of membrane carriers 72 that need to be installed in the reaction vessel 70 compared to when air 2 is supplied to the membrane carrier 72 from the supply unit 80.

[0056] Furthermore, in the reaction vessel 70 of this embodiment, the oxygen supplied to the membrane carrier 72 may be, for example, oxygen obtained by water electrolysis using renewable energy. For example, oxygen obtained by electrolyzing water using electrical energy generated using waste heat from sludge incineration may be used. In this power generation, various power generation technologies such as the organic Rankine cycle (ORC) can be used. By using oxygen obtained by water electrolysis using renewable energy as the oxygen source, energy conservation can be achieved and carbon dioxide emissions can be reduced.

[0057] [Effects in the first embodiment] Next, the effects of the first embodiment will be described. Figures 6 to 8 illustrate the effects of the first embodiment.

[0058] First, we will explain the relationship between the peeling interval of biofilm R1 from the membrane carrier 72 and the organic matter removal rate in the reaction vessel 70. Figure 6 is a graph showing the relationship between the peeling interval of biofilm R1 and the organic matter removal rate. In the graph shown in Figure 6, the horizontal axis represents the peeling interval of biofilm R1 (hereinafter also simply referred to as the peeling interval), and the vertical axis represents the organic matter removal rate (hereinafter also simply referred to as the removal rate).

[0059] The graph in Figure 6 shows that the removal rate increases until the peeling interval is around 24 hours, and then decreases as the peeling interval increases beyond 24 hours. The graph in Figure 6 also shows that the removal rate is approximately 88% when the peeling interval is around 24 hours, and approximately 80% when the peeling interval is around 12 hours or 48 hours.

[0060] In other words, the graph shown in Figure 6 indicates that, for example, when the peeling interval is 12 hours or more and 48 hours or less, it is possible to maintain a removal rate of 80% or more and to reduce the amount of organic matter discharged to the solid-liquid separator 90 to 20% or less.

[0061] On the other hand, the graph shown in Figure 6 indicates that, for example, the removal rate decreases when the peeling interval is 48 hours or longer. This is because when the thickness of the biofilm R1, which is a clump of sludge, exceeds a predetermined level, the wastewater 1 is not sufficiently supplied to the membrane carrier 72 side of the biofilm R1 (the part that can directly receive oxygen from the membrane carrier 72), and the removal of organic matter becomes inefficient.

[0062] Therefore, the control device 74 may control the timing of the peeling of the biofilm R1 so that the peeling interval is 12 hours or more and 48 hours or less, that is, so that a removal rate of 80% or more is maintained. Specifically, the control device 74 may control the timing of the peeling of the biofilm R1 so that the peeling interval is 24 hours or 48 hours. The following will explain using an example where the solid-liquid separation device 90 performs solid-liquid separation using a separation membrane.

[0063] Next, we will explain the relationship between the peeling interval of biofilm R1 and the flux (hereinafter also referred to as flux) in the solid-liquid separator 90. Figure 7 is a graph showing the relationship between the peeling interval of biofilm R1 and the flux in the solid-liquid separator 90. In the graph shown in Figure 7, the horizontal axis represents the peeling interval of biofilm R1, and the vertical axis represents the flux of the solid-liquid separator 90 when the flux of the solid-liquid separator 90 in the absence of blockage is set to 100 (%).

[0064] The graph in Figure 7 shows that the flux increases until the peeling interval reaches approximately 24 hours. Furthermore, the graph in Figure 7 shows that when the peeling interval is 24 hours or longer, the flux reaches approximately 100%.

[0065] In other words, the graph shown in Figure 7 indicates that, for example, when the peeling interval is 24 hours or longer, it becomes possible to form a biofilm R1 of sufficient size on the membrane carrier 72, which suppresses clogging in the solid-liquid separation device 90 and thus makes it possible to maintain a high level of flux.

[0066] On the other hand, the graph shown in Figure 7 indicates that, for example, if the peeling time is 24 hours or less, the biofilm R1, which has not grown to a sufficient size, is discharged to the solid-liquid separator 90, causing clogging in the solid-liquid separator 90 and reducing the flux.

[0067] Therefore, the control device 74 may, for example, control the timing of the peeling of the biofilm R1 so that the peeling interval is 24 hours or more, that is, so that a flux close to 100% is maintained.

[0068] Furthermore, the control device 74 may, for example, control the timing of biofilm R1 detachment so that the amount of substrate such as organic matter discharged from the reaction tank 70 to the solid-liquid separator 90 satisfies predetermined conditions. Specifically, the control device 74 may, for example, control the timing of biofilm R1 detachment so that the amount of substrate discharged from the reaction tank 70 to the solid-liquid separator 90 (i.e., the amount of substrate in the wastewater) is less than or equal to a predetermined ratio, preferably about 1 / 5, of the amount of substrate in the wastewater flowing from the primary sedimentation tank 10 to the reaction tank 70.

[0069] Furthermore, the control device 74 may, for example, control the timing of biofilm R1 detachment so that it is no longer necessary to return the sludge from the solid-liquid separator 90 to the reaction tank 70, that is, so that the necessary amount of activated sludge is maintained in the reaction tank 70 by the proliferation of activated sludge.

[0070] Next, we will explain the relationship between the peeling interval of biofilm R1 and the moisture content of the sludge (hereinafter also referred to as dewatered cake) after dewatering the sludge containing the peeled biofilm R1 in a dewatering machine. Figure 8 is a graph showing the relationship between the peeling interval of biofilm R1 and the moisture content of the dewatered cake. In the graph shown in Figure 8, the horizontal axis represents the peeling interval of biofilm R1, and the vertical axis represents the moisture content of the dewatered cake (hereinafter also simply referred to as moisture content).

[0071] The graph in Figure 8 shows that the moisture content decreases as the peeling interval increases. Furthermore, the graph in Figure 8 shows that when the peeling interval is greater than 24 hours, the moisture content decreases significantly more compared to when the peeling time is less than 24 hours.

[0072] In other words, the graph shown in Figure 8 indicates that, for example, when the peeling interval is 24 hours or longer, it is possible to effectively reduce the moisture content of the dewatered cake. The sludge containing the peeled biofilm R1 obtained when the peeling interval is 24 hours or longer is dense. When such dense sludge is dewatered, sludge with a low moisture content is obtained.

[0073] Therefore, the control device 74 may, for example, control the timing of the peeling of the biofilm R1 so that the peeling interval is 24 hours or more, that is, so that the water content of the dehydrated cake is 75 percent or less.

[0074] Furthermore, the control device 74 may control the timing of the peeling of the biofilm R1 according to all the graphs shown in Figures 6 to 8, for example, so that the peeling interval is 24 hours or more and 48 hours or less.

[0075] As described above, in the organic wastewater treatment device 100 of this embodiment, the biofilm R1 attached to the membrane carrier 72 incorporates organic matter and forms clumps on the membrane carrier 72. Therefore, the organic wastewater treatment device 100 can discharge wastewater containing sludge (clumpy sludge) containing the clumpy biofilm R1 to the solid-liquid separator 90. Furthermore, by forming clumpy biofilm R1 on the membrane carrier 72, the organic wastewater treatment device 100 can reduce the amount of organic matter and activated sludge discharged from the reaction tank 70 to the solid-liquid separator 90. Consequently, the organic wastewater treatment device 100 can prevent the proliferation of activated sludge in the solid-liquid separator 90 and the occurrence of clogging in the solid-liquid separator 90, thereby preventing blockage of the solid-liquid separator 90.

[0076] Furthermore, in the organic wastewater treatment device 100 of this embodiment, the lumpy biofilm R1 has a large particle size and is prone to settling. Therefore, in the organic wastewater treatment device 100, dewatering of the sludge separated from the wastewater in the solid-liquid separator 90 is easy, and the amount of coagulant that needs to be added in the dewatering machine, etc., can be reduced. Consequently, in the organic wastewater treatment device 100, for example, the cost required for sludge dewatering can be reduced.

[0077] In this embodiment, the sludge (detached sludge) contained in the wastewater discharged to the solid-liquid separator 90 is lumpy sludge. This lumpy sludge mainly consists of lumpy biofilm R1, and as described above, this lumpy sludge (hereinafter referred to as the sludge of this embodiment) is dense and easily dewatered. This lumpy sludge is then separated in the solid-liquid separator 90.

[0078] In contrast, in order to maintain the performance of the reaction tank 50 in Figure 2, the sludge detached from the separation membrane 53 of the reaction tank 50 in Figure 2 (hereinafter referred to as the sludge in Figure 2) mainly consists of bacterial cells that have proliferated in the wastewater 1. Furthermore, this sludge is dispersed and difficult to dewater.

[0079] Thus, the main body of the sludge in this embodiment differs from the main body of the sludge in Figure 2 (in other words, the sludge that is to be dewatered (separated)). As a result of this difference, in order to achieve a desired moisture content in the sludge after dewatering, the amount of coagulant added in this embodiment can be reduced compared to the amount of coagulant added when dewatering the sludge in Figure 2.

[0080] As in this embodiment, by targeting easily dewatered sludge for solid-liquid separation, the amount of coagulant added can be reduced, thereby suppressing running costs.

[0081] Furthermore, in the removal of biofilms in devices such as those used for watering filters, the removal interval is several weeks or more, resulting in the removal of low-strength activated sludge (soft activated sludge). Consequently, the moisture content of the dewatered cake produced from the removed activated sludge is about the same as that of the dewatered cake produced from normal activated sludge.

[0082] In contrast, in this disclosure, for example, by setting the peeling interval to approximately 24(h) to 48(h), it becomes possible to obtain a biofilm (biofilm R1 peeled from the membrane carrier 72) capable of producing a dehydrated cake with a low water content.

[0083] In the first embodiment of the organic wastewater treatment device 100, for example, a solid-liquid separator (not shown) that performs high-speed filtration may be used instead of the primary sedimentation tank 10. This makes it possible to further reduce the amount of organic matter (for example, solid organic matter) supplied to the reaction tank 70 in the organic wastewater treatment device 100, and to decompose the organic matter in the membrane carrier 72 more efficiently.

[0084] [Organic wastewater treatment device 100 in the first modified example] Next, the configuration of the organic wastewater treatment device 100 in the first modified example will be described. Figure 9 is a diagram illustrating the configuration of the reaction tank 70 in the first modified example. Figures 10 and 11 are diagrams illustrating the configuration of the membrane carrier 72 in the first modified example.

[0085] [Peeling device 73 and control device 74 in the first modified example] First, the peeling device 73 and control device 74 in the first modified example will be described. In the first modified example, the peeling device 73 peels off the biofilm R1 by supplying a gas such as air (hereinafter simply referred to as air). The control device 74 in the first modified example controls, for example, the timing at which the peeling device 73 supplies air.

[0086] As shown in Figure 9, the peeling device 73 includes, for example, an air supply unit 73a (hereinafter also referred to as supply unit 73a), such as a compressor that compresses air taken in from the outside to generate compressed air (not shown), and an air tank 73b that stores the compressed air supplied from supply unit 73a.

[0087] The control device 74 then controls, for example, the supply (injection) of compressed air stored in the air tank 73b to the reaction tank 70.

[0088] Specifically, when it is time for the biofilm R1 to be detached, the control device 74 supplies compressed air stored in the air tank 73b via line L3 to multiple locations within the reaction vessel 70, thereby detaching the biofilm R1 from the membrane carrier 72. Line L3 is, for example, a pipe connecting the air tank 73b to multiple locations within the reaction vessel 70. Furthermore, as explained in Figure 6, the control device 74 controls the biofilm R1 detachment interval to be 24 hours or longer.

[0089] Furthermore, as shown in Figure 9, the control device 74 may, for example, control the timing of compressed air generation by the supplier 73a (the timing of supplying compressed air to the air tank 73b) so that the pressure in the air tank 73b is maintained within a certain range.

[0090] Furthermore, the control device 74 may, for example, in addition to controlling the peeling device 73, also control the amount of air 2 supplied by the air supply device 80 so that the amount of air 2 supplied to the membrane carrier 72 remains constant.

[0091] Specifically, the control device 74 may acquire measured values ​​from a measuring instrument (not shown) that measures at least one of the following: the inlet pressure of the membrane carrier 72, the outlet pressure, and the amount of air discharged from the membrane carrier 72 (i.e., the amount of excess air). The control device 74 may then control the amount of air 2 supplied from the supply unit 80 to the membrane carrier 72 according to the acquired measured values. The following explanation will assume that the control device 74 controls the amount of air 2 supplied by the supply unit 80.

[0092] Furthermore, although the example shown in Figure 9 illustrates the case where compressed air is supplied between the membrane carriers 72, the compressed air may also be supplied, for example, to the lower end or below the membrane carriers 72.

[0093] [Specific example of the membrane carrier 72 in the first modified example] Next, the configuration of the membrane carrier 72 in the first modified example will be described.

[0094] In the reaction vessel 70 of the first modified example, as shown in Figures 9 and 10, a unit UN1 is formed by bundling together, for example, multiple membrane carriers 72. This makes it possible to reduce, for example, the number of pipes constituting the line L1 that supplies air 2 to each membrane carrier 72, and the number of pipes constituting the line L2 that discharges air 2 from each membrane carrier 72, in the reaction vessel 70 of the first modified example.

[0095] Specifically, the example shown in Figure 9 illustrates a case where four units UN1, formed by bundling four membrane carriers 72 together, are arranged within the reaction vessel 70. While the following explanation will focus on the case where four membrane carriers 72 constitute a single unit UN1, a single unit UN1 may also consist of a different number of membrane carriers 72.

[0096] As shown in Figure 10, the multiple membrane carriers 72 that form a single unit UN1 (hereinafter also simply referred to as multiple membrane carriers 72) have, for example, a first molded portion 72a formed by molding the lower end portion 72c of each of the multiple membrane carriers 72 with resin (e.g., plastic), and a second molded portion 72b formed by molding the upper end portion 72d of each of the multiple membrane carriers 72 with resin. That is, the multiple membrane carriers 72 form a single unit UN1 by, for example, molding the lower end portion 72c and upper end portion 72d of each membrane carrier 72.

[0097] The first molded section 72a has, for example, a first air vent 72a1 that introduces air 2 supplied from the supplyer 80 via line L1 into the first molded section 72a. Line L1 is, for example, a pipe connecting the supplyer 80 to the first air vent 72a1 in each of the multiple units UN1, as shown in Figures 9 and 10. The air 2 introduced into the first molded section 72a from the air vent 72a1 is then supplied into the interior of each of the multiple membrane carriers 72, for example, from the lower end 72c of each of the multiple membrane carriers 72.

[0098] Furthermore, the second molded portion 72b has a second air vent 72b1 that discharges the air 2 inside the second molded portion 72b to the outside via, for example, a line L2. As shown in Figures 9 and 10, the line L2 is, for example, a pipe that connects the second air vent 72b1 in each of the multiple units UN1 to the outside. That is, the second air vent 72b1 discharges the air 2 that has been discharged into the second molded portion 72b from, for example, the upper end portions 72d of each of the multiple membrane carriers 72 to the outside.

[0099] Specifically, the air 2 supplied (pressurized) into the first mold section 72a via line L1 and the first air hole 72a1 is supplied to the interior of each of the multiple membrane carriers 72, as shown by the solid arrows in Figure 10. Then, at least a portion of the air 2 supplied to each membrane carrier 72 diffuses into the reaction vessel 70 through multiple holes h1 (for example, holes of about 0.1 microns) provided in each membrane carrier 72, as explained in Figure 4, etc., during the process of moving from the lower end 72c to the upper end 72d of each membrane carrier 72. Subsequently, the air 2 that has moved from the lower end 72c to the upper end 72d of each membrane carrier 72 (air 2 that did not diffuse into the reaction vessel 70) is supplied to the second mold section 72b from the upper end 72d, for example. After that, the air 2 supplied to the second mold section 72b is discharged to the outside through, for example, the second air hole 72b1 and line L2.

[0100] Thus, in the organic wastewater treatment device 100 in the first modified example, the feeder 80 supplies air 2 (air 2 containing at least oxygen) into the membrane carrier 72 from, for example, the lower end 72c (hereinafter also simply referred to as the lower end) of the membrane carrier 72. The membrane carrier 72 then molecularly diffuses at least a portion of the air 2 supplied from the lower end 72c into the reaction vessel 70 through a plurality of pores h1, and discharges the air 2 supplied from the lower end 72c that was not molecularly diffused into the reaction vessel 70 to the outside from the upper end 72d (hereinafter also simply referred to as the upper end) of the membrane carrier 72.

[0101] The membrane carrier 72 shown in Figure 10 has a straight shape (I-shape), but is not limited to this. Specifically, the membrane carrier 72 may have a shape such that air 2 supplied from the lower end 72c is discharged from the upper end 72d, and may have a curved shape (for example, a V-shape) in which at least a part is curved.

[0102] Furthermore, in the membrane carrier 72 shown in Figure 10, air 2 is supplied (pressurized) into the membrane carrier 72 from the lower end 72c and the air 2 inside the membrane carrier 72 is discharged from the upper end 72d, but this is not limited to this. Specifically, the membrane carrier 72 may, for example, supply air 2 into the membrane carrier 72 from the upper end 72d and discharge the air 2 inside the membrane carrier 72 from the lower end 72c.

[0103] Furthermore, the amount of air 2 supplied to each of the multiple membrane carriers 72 may be determined such that, for example, the amount of air 2 molecularly diffused into the reaction vessel 70 from the multiple pores h1 on the lower end 72c side is the same as the amount of air 2 molecularly diffused into the reaction vessel 70 from the multiple pores h1 on the upper end 72d side. In other words, the amount of air 2 supplied to each of the multiple membrane carriers 72 may be determined such that, for example, the partial pressure of oxygen at each position within each membrane carrier 72 is maximized (the same pressure as atmospheric pressure).

[0104] Furthermore, line L1 may be equipped with a filter (not shown) for removing particulate matter (e.g., dust, etc.) contained in the air 2 supplied from the supply unit 80.

[0105] [Other specific examples of the membrane carrier 72 in the first modified example] Next, we will describe the other components of the membrane carrier 72 in the first modified example. The differences from the membrane carrier 72 described in Figure 10 will be explained below.

[0106] In the reaction vessel 70 of the first modified example, as shown in Figure 11, the membrane carriers 72 may be arranged to form a U-shape (hereinafter also called an inverted U-shape) with both ends (hereinafter also called the end portions 72f) pointing downward (for example, vertically downward). That is, in the reaction vessel 70, as shown in Figure 11, the membrane carriers 72 may be arranged with at least one curved portion (hereinafter also called the curved portion 72e). Furthermore, in the reaction vessel 70, a unit UN2 may be formed by bundling together a plurality of membrane carriers 72 arranged to form an inverted U-shape. In the following description, we will explain the case in which two membrane carriers 72 arranged to form an inverted U-shape constitute a single unit UN2, but a number of membrane carriers 72 other than two may constitute a single unit UN2.

[0107] Specifically, the air 2 supplied (pressurized) into the interior of the first mold portion 72a from the air hole 72a1 is supplied, in this case, for example, from both ends 72f of each of the multiple membrane carriers 72 into the interior of each of the multiple membrane carriers 72. That is, each of the ends 72f shown in Figure 11 has the same function as, for example, the lower end 72c described in Figure 10.

[0108] More specifically, the air 2 supplied from the feeder 80 into the first molded section 72a via line L1 and the first air vent 72a1 is supplied to each of the multiple membrane carriers 72, for example, as shown by the solid arrows in Figure 11. Then, as the air 2 supplied to each membrane carrier 72 moves from both ends 72f to the curved section 72e within the interior of each membrane carrier 72, it molecularly diffuses into the reaction vessel 70 through multiple pores h2 (for example, pores of about 0.1 microns) provided in the parts of each membrane carrier 72 located outside the first molded section 72a and the second molded section 72b, as explained in Figure 4, etc. Subsequently, the air 2 that has moved from both ends 72f to the curved section 72e within the interior of each membrane carrier 72 (air 2 that has not molecularly diffused into the reaction vessel 70) is supplied into the second molded section 72b through multiple pores h3 provided in the curved section 72e of each membrane carrier 72. Subsequently, the air 2 supplied into the second mold portion 72b is discharged to the outside, for example, through the second air hole 72b1 and line L2. That is, the multiple holes h3 provided in the curved portion 72e shown in Figure 11 have the same function as, for example, the upper end portion 72d described in Figure 10.

[0109] Thus, in the organic wastewater treatment device 100 in the first modified example, the membrane carrier 72 has, for example, a curved portion 72e that curves the membrane carrier 72 so that each of the ends 72f of the membrane carrier 72 faces downward. The feeder 80 supplies air 2 (air 2 containing at least oxygen) into the membrane carrier 72 from, for example, each of the ends 72f of the membrane carrier 72 (in other words, each of the lower ends of the membrane carrier 72). Furthermore, the membrane carrier 72, for example, molecularly diffuses at least a portion of the air 2 supplied from at least one of the ends of the membrane carrier 72 into the reaction vessel 70 through a plurality of holes h2 (hereinafter also referred to as a plurality of first holes), and discharges the air 2 that was not molecularly diffused into the reaction vessel 70 from the air 2 supplied from at least one of the ends of the membrane carrier 72 to the outside through a plurality of holes h3 (hereinafter also referred to as a plurality of second holes) provided in the curved portion 72e (in other words, the upper end of the membrane carrier 72) located above the plurality of holes h2.

[0110] Unlike the membrane carrier 72 shown in Figure 10, the air 2 inside the membrane carrier 72 shown in Figure 11 is discharged into the second molded section 72b through multiple holes h3 provided in the curved section 72e. Therefore, the pressure loss associated with the discharge of air 2 is greater in the membrane carrier 72 shown in Figure 11 than in the membrane carrier 72 shown in Figure 10. Consequently, the membrane carrier 72 shown in Figure 11 makes it possible to increase the amount of air 2 supplied into the reaction vessel 70 by molecular diffusion compared to the membrane carrier 72 shown in Figure 10.

[0111] [Cleaning method for the organic wastewater treatment device 100 in the first embodiment] Next, a cleaning method for the organic wastewater treatment device 100 in the first embodiment will be described. Figures 12 to 16 illustrate the cleaning method for the organic wastewater treatment device 100 in the first embodiment.

[0112] As shown in Figure 12, the organic wastewater treatment device 100 includes, for example, a chemical supply device 81, a displacement water supply device 82, and an air supply device 83 (hereinafter also simply referred to as supply device 83) in addition to the supply device 80. Furthermore, as shown in Figure 12, line L2 is provided with, for example, multiple valves V. Note that in the example shown in Figure 12, the peeling device 73 and line L3 are omitted from the notation. The following description will focus on the case where the membrane carrier 72 (unit UN1) described in Figure 10 is placed inside the reaction tank 70, but the membrane carrier 72 (unit UN2) described in Figure 11 may also be placed inside the reaction tank 70.

[0113] The chemical dispenser 81 supplies a chemical to the interior of the membrane carrier 72 from the lower end 72c of the membrane carrier 72 for cleaning multiple pores h1. The chemical supplied by the chemical dispenser 81 is a chemical for removing substances adhering to the multiple pores h1 (for example, substances that cause fouling) from the multiple pores h1, and may be hypochlorous acid (for example, about 300 ppm to 3000 ppm) or hydrogen peroxide.

[0114] Specifically, the drug supply unit 81 may include, for example, a storage tank (not shown) for storing the drug and a pump (not shown) for pressurizing the drug into the membrane carrier 72 via lines L4 and L1. Line L4 is, for example, a pipe connecting the drug supply unit 81 to the upstream side of each unit UN1 in line L1.

[0115] The displacement water supply unit 82 supplies displacement water (hereinafter also simply referred to as liquid) from the lower end 72c of the membrane carrier 72 into the interior of the membrane carrier 72, for example, to replace the drug remaining in multiple pores h1 (the drug supplied by the drug supply unit 81).

[0116] Specifically, the displacement water supply unit 82 may have, for example, a pump (not shown) that pressurizes displacement water into the membrane carrier 72 via lines L5 and L1. Line L5 is, for example, a pipe connecting the displacement water supply unit 82 to the upstream side of each unit UN1 in line L1.

[0117] The supply unit 83 is, for example, a blower or fan such as a blower, and supplies air (hereinafter also referred to as replacement air or first gas) to replace the chemical remaining in the multiple pores h1 from the lower end 72c of the membrane carrier 72 into the interior of the membrane carrier 72. The supply unit 83 also supplies air (hereinafter also referred to as dry air or second gas) to dry the multiple pores h1 from the lower end 72c of the membrane carrier 72 into the interior of the membrane carrier 72. The drying process is, for example, a process to restore the hydrophobicity of each of the multiple pores h1. In the following description, it is assumed that the replacement air and dry air are supplied from the supply unit 83, but the replacement air and dry air may be supplied by different supplies, for example. Also, in the following description, it is assumed that the supply unit 80 and the supply unit 83 are different supplies, but the supply unit 80 and the supply unit 83 may be, for example, the same supply unit.

[0118] Specifically, the supply unit 83 supplies air to the inside of the membrane carrier 72, for example, via lines L6 and L1. Line L6 is, for example, a pipe connecting the supply unit 83 to the upstream side of each unit UN1 in line L1.

[0119] The control device 74 performs a process (hereinafter also called a cleaning control process) that controls the timing of cleaning the multiple pores h1 in the membrane carrier 72 (hereinafter also called the cleaning timing) by having a program stored in a memory device (not shown) and the CPU cooperate.

[0120] Specifically, as will be described later, the control device 74 controls, for example, the timing of when the drug supplier 81 supplies drug, when the displacement water supplier 82 supplies displacement water, when the supplier 83 supplies air, and when it controls the opening and closing of the multiple valves V provided in line L2.

[0121] The following description will assume that the cleaning control process is performed automatically by the control device 74. However, the cleaning control process may also be performed manually by an operator, at least in part. In this case, the operator may manually perform at least one of the following: supplying chemicals by the chemical dispenser 81, supplying displacement water by the displacement water dispenser 82, supplying air by the dispenser 83, and controlling the opening and closing of the multiple valves V.

[0122] [Specific examples of cleaning control processes] Next, we will explain specific examples of the cleaning control process. In the following explanation, Figures 14 to 16 will be described assuming that each of the holes h11, h12, h13, h14, h15, h16, h17, h18, h19, and h20 are provided in the membrane carrier 72 as multiple holes h1. Furthermore, as shown in Figure 14(A), in the following explanation, each of the holes h11, h12, h13, h14, h15, h16, h17, h18, h19, and h20 will be described assuming that they are hydrophilized by the wastewater 1 in the reaction tank 70.

[0123] First, the control device 74 stops the supply of air 2 (oxygen-containing air 2) to the membrane carrier 72 (step S1 in Figure 13). In other words, in this case, the control device 74 stops the normal operation (operation to form a biofilm R1 on the outer circumference of the membrane carrier 72) as described in Figure 4, etc. Specifically, the control device 74 controls the air supply 80 so that the supply of air 2 to the membrane carrier 72 is stopped. The control device 74 may, for example, perform the processing from step S1 onward at a timing when multiple pores h1 are hydrophilized by the wastewater 1 in the reaction vessel 70 (for example, at intervals of one to two months).

[0124] The control device 74 then supplies the drug 3 into the membrane carrier 72, for example (step S2 in Figure 13). Specifically, the control device 74 controls the drug dispenser 81 so that the drug 3 is supplied into the membrane carrier 72. The pressure at which the drug 3 is pushed into the membrane carrier 72 may be, for example, approximately atmospheric pressure.

[0125] In other words, when the drug 3 is injected into the membrane carrier 72, at least a portion of the drug 3 injected into the membrane carrier 72 migrates from the membrane carrier 72 to the reaction vessel 70 through the multiple pores h1. Therefore, in the organic wastewater treatment device 100, as shown in Figure 14(B), it becomes possible to clean the multiple pores h1 by injecting the drug 3 into the membrane carrier 72. Specifically, in this case, the organic wastewater treatment device 100 becomes able to remove substances (for example, substances that cause fouling) attached to each of the multiple pores h1.

[0126] Next, the control device 74 supplies displacement water 4a or displacement air 4b to the membrane carrier 72 after a predetermined time has elapsed since the processing in step S2 (step S3 in Figure 13). Specifically, the control device 74 controls the displacement water supply 82 so that displacement water 4a is supplied into the membrane carrier 72. The control device 74 also controls the supply 83 so that displacement air 4b is supplied into the membrane carrier 72. The predetermined time here is the time required to clean the multiple holes h1, and may be, for example, 20 to 60 minutes. The pressure at which displacement water 4a or displacement air 4b is forced into the membrane carrier 72 may be, for example, atmospheric pressure.

[0127] In other words, when cleaning is performed by supplying the agent 3 into multiple holes h1, there is a possibility that the agent 3 used for cleaning will remain inside each of the multiple holes h1. Therefore, in the organic wastewater treatment device 100, after cleaning the multiple holes h1, as shown in Figure 15(A), the agent remaining in the multiple holes h1 is forced into the reaction vessel 70 by supplying, for example, displacement water 4a or displacement air 4b, and the agent 3 remaining in the multiple holes h1 is replaced with displacement water 4a or displacement air 4b.

[0128] Next, the control device 74 performs closing control of the multiple valves V after a predetermined time has elapsed since the processing in step S3 (step S4 in Figure 13). Closing control of the multiple valves V is a control that reduces the opening degree of the multiple valves V. Then, for example, after the processing in step S4, the control device 74 supplies dry air 5 to the membrane carrier 72 (step S5 in Figure 13). The dry air 5 may be heated air heated by a heater (not shown), for example. Specifically, the dry air 5 may be heated air heated to about 70°C, for example.

[0129] In other words, the control device 74 controls the closing of multiple valves V so that the inside of the membrane carrier 72 is pressurized by, for example, suppressing the amount of air discharged to the outside from the upper end 72d of the membrane carrier 72 via line L2. Specifically, the control device 74 controls the closing of multiple valves V so that the pressure inside the membrane carrier 72 is greater than atmospheric pressure and less than or equal to the water pressure in the reaction vessel 70. After that, the control device 74 controls the supplyer 83 so that dry air 5 is supplied into the membrane carrier 72. The predetermined time here is the time required to replace the agent 3 remaining in the multiple holes h1 with the displacement water 4a supplied from the displacement water supplyer 82 and the displacement air 4b supplied from the supplyer 83, and may be, for example, 20 to 60 minutes.

[0130] Then, within the membrane carrier 72, as shown in Figure 15(B), when the supply of dry air 5 from the lower end 72c side of the membrane carrier 72 begins, the dry air 5 is sequentially injected through the multiple holes h1 on the lower end 72c side. That is, within the membrane carrier 72, drying is performed sequentially from the multiple holes h1 on the lower end 72c side, and the hydrophobicity is restored. Subsequently, within the membrane carrier 72, as shown in Figure 16(A), for example, drying is performed through the multiple holes h1 on the upper end 72d side, and the hydrophobicity of the multiple holes h1 provided at each position of the membrane carrier 72 is restored.

[0131] Next, the control device 74 waits, for example, until it detects that the drying process in the multiple pores h1 of the membrane carrier 72 is complete (NO in step S6 of Figure 13).

[0132] Specifically, the control device 74 controls the supplyer 73a, as described in Figure 9, so that, for example, after the start of the execution of the process in step S5, compressed air stored in the air tank 73b, as described in Figure 9, is supplied into the membrane carrier 72 at a predetermined timing. The predetermined timing here may be, for example, a periodic timing such as every minute. More specifically, the control device 74 controls the system so that the air pressure forced into the inside of the membrane carrier 72 temporarily exceeds the water pressure by temporarily replacing the supply of dry air 5 by the supplyer 83 with the supply of compressed air by the supplyer 73a. The control device 74 then determines, for example, whether the compressed air is discharged (ejected) as bubbles into the reaction tank 70 side from a plurality of holes h1 near the upper end 72d of the membrane carrier 72 (i.e., a plurality of holes h1 located at a position with low water pressure) in conjunction with the supply of compressed air by the supplyer 73a.

[0133] In other words, when the drying process (restoration of hydrophobicity) is completed for the multiple pores h1 provided in the membrane carrier 72, the compressed air that was injected into the membrane carrier 72 by a pressure greater than the water pressure is discharged from the multiple pores h1 located at positions with lower water pressure. In other words, if compressed air is discharged from the multiple pores h1, it is possible to determine that the drying process in the multiple pores h1 has been completed. Therefore, the control device 74 periodically determines whether compressed air is being discharged from the multiple pores h1 by periodically supplying compressed air using the supplyer 73a after starting the process in step S5. Then, if the control device 74 determines that compressed air is being discharged from the multiple pores h1, it determines that the drying process in the multiple pores h1 has been completed.

[0134] In this way, the control device 74 can, for example, limit the time for which it controls the pressure applied to the inside of the membrane carrier 72 to be equal to or greater than the water pressure, thereby determining whether or not the drying process in the multiple pores h1 has been completed while suppressing power consumption.

[0135] Alternatively, it may be determined whether compressed air is discharged (ejected) into the reaction vessel 70 side as bubbles from a plurality of holes h1 near the lower end 72c of the membrane carrier 72 (i.e., a plurality of holes h1 located at positions with high water pressure). In this case, the pressure of the compressed air must be equal to or greater than the water pressure near the lower end 72c of the membrane carrier 72 (i.e., equal to or greater than the water pressure near the lower end 72c of the membrane carrier 72). When making such a determination, supplying a pressure equal to or greater than the water pressure near the lower end 72c of the membrane carrier 72 at all times would increase power consumption. Therefore, while supplying dry air, it may be possible to supply a pressure equal to or greater than the water pressure near the lower end 72c of the membrane carrier 72 at predetermined time intervals and determine whether compressed air is discharged (ejected) into the reaction vessel 70 side as bubbles.

[0136] Furthermore, the determination of whether or not compressed air is being discharged from the multiple holes h1 may be performed manually by an operator, for example. The control device 74 may also determine that the drying process in the multiple holes h1 is complete when the operator inputs information indicating that the drying process in the multiple holes h1 is complete.

[0137] Furthermore, the control device 74 may, for example, determine whether the drying process in the multiple pores h1 has been completed by controlling the supply device 83 so that the pressure of the dry air 5 being forced into the interior of the membrane carrier 72 is equal to or greater than the water pressure, without switching from the supply of dry air 5 by the supply device 83 to the supply of compressed air by the supply device 73a.

[0138] Furthermore, when the discharge of compressed air from the multiple pores h1 near the upper end 72d of the membrane carrier 72 begins, the pressure of compressed air being forced into the membrane carrier 72 decreases in the reaction vessel 70. Therefore, the control device 74 may determine that the drying process in the multiple pores h1 is complete when it detects that the pressure of compressed air being forced into the membrane carrier 72 has fallen below a predetermined threshold. Specifically, the control device 74 may, for example, refer to a measuring instrument (not shown) that measures the pressure of compressed air being forced into the inside of the membrane carrier 72, and determine that the drying process in the multiple pores h1 is complete when the pressure measured by the measuring instrument has fallen below a predetermined threshold.

[0139] Alternatively, an imaging device such as a camera may be installed on top of the reaction tank 70 to capture still images or videos of the inside of the reaction tank 70. The control device 74 may then analyze the still images or videos using image recognition means to determine whether bubbles are being discharged from the multiple holes h1. In this case, if the control device 74 determines that bubbles are being discharged, it will determine that the drying process in the multiple holes h1 is complete.

[0140] Returning to Figure 13, if the control device 74 detects that the drying process in the multiple pores h1 of the membrane carrier 72 is complete (YES in step S6), the control device 74 performs, for example, valve opening control on multiple valves V (step S7 in Figure 13). Valve opening control is a control that increases the opening degree of multiple valves V. Specifically, valve opening control may be a control that increases the opening degree of multiple valves V so that the opening degree of multiple valves V is approximately the same as the opening degree when steps S2 and S3 were performed.

[0141] The control device 74 may, for example, determine whether the drying process in the multiple pores h1 has been completed for each unit UN1. The control device 74 may, for example, detect the presence of a unit UN1 consisting of a membrane carrier 72 in which the drying process in the multiple pores h1 has been completed, and then control the opening of a valve V (a valve that controls the discharge of dry air 5 from the detected unit UN1) corresponding to the detected unit UN1.

[0142] Subsequently, the control device 74 resumes the supply of air 2 to the membrane carrier 72, for example (step S8 in Figure 13). That is, the control device 74 resumes the normal operation described in Figure 4, etc. (operation for forming a biofilm R1 on the outer periphery of the membrane carrier 72). Specifically, the control device 74 controls the air supply 80 so that the supply of air 2 to the membrane carrier 72 is resumed.

[0143] As described above, in the cleaning method of the organic wastewater treatment device 100 in this embodiment, for example, the supply of air 2 to the membrane carrier 72 is stopped, and the agent 3 is supplied to the inside of the membrane carrier 72 from the first part of the membrane carrier 72. The first part is also called the first end, and is, for example, the lower end 72c or both ends 72f. Then, in the cleaning method of the organic wastewater treatment device 100, a liquid (for example, displacement water 4a) or a first gas (for example, displacement air 4b) is supplied to the inside of the membrane carrier 72 from the first part, the opening of the valve V that controls the amount of air discharged from the second part of the membrane carrier 72 is reduced, and a second gas (for example, dry air 5) is supplied to the inside of the membrane carrier 72 from the first part. The second part is, for example, the upper end 72d or the curved part 72e, and is also called the second end.

[0144] Then, in the cleaning method for the organic wastewater treatment device 100, for example, in response to dry air 5 or compressed air being discharged from at least one of the multiple holes h1 toward the reaction tank 70, the opening of the valve V is increased and the supply of air 2 to the membrane carrier 72 is resumed.

[0145] Furthermore, in the cleaning method for the organic wastewater treatment device 100 in this embodiment, for example, the membrane carrier 72 has a hydrophobic hollow fiber membrane, and the agent 3 is an agent that removes substances adhering to the multiple pores h1 from the multiple pores h1. In the cleaning method for the organic wastewater treatment device 100, for example, by supplying displacement water 4a or displacement air 4b into the membrane carrier 72, the agent 3 in the multiple pores h1 is discharged into the reaction tank 70, and by supplying dry air 5 into the membrane carrier 72, the inside of the multiple pores h1 is dried and the hydrophobicity of the hollow fiber membrane is restored.

[0146] Furthermore, the shape of the membrane carrier 72 in this embodiment is, for example, a tubular shape that extends along the vertical axis of the reaction vessel 70 (hereinafter also simply referred to as the vertical axis) and has a lower end 72c and an upper end 72d that are at least partially open to the outside of the membrane carrier 72, the lower end 72c being the lower end on the vertical axis and the upper end 72d being the upper end on the vertical axis.

[0147] Furthermore, the shape of the membrane carrier 72 in this embodiment is, for example, tubular with both ends 72f that are at least partially open to the outside of the membrane carrier 72, and the membrane carrier 72 has a curved portion 72e that curves the membrane carrier 72 such that each of the ends 72f faces downward on the vertical axis of the reaction tank 70.In the cleaning method of the organic wastewater treatment device 100 in this embodiment, for example, the agent 3 is supplied into the membrane carrier 72 from each of the ends 72f, displacement water 4a or displacement air 4b is supplied into the membrane carrier 72 from each of the ends 72f, the opening degree of the valve V that controls the amount of air discharged from the curved portion 72e is reduced, and dry air 5 is supplied into the membrane carrier 72 from each of the ends 72f.

[0148] Furthermore, the cleaning method for the organic wastewater treatment device 100 in this embodiment is performed, for example, when the wastewater 1 in the reaction tank 70 is in contact with at least a portion of the outer surface of the membrane carrier 72.

[0149] Thus, according to the cleaning method of the organic wastewater treatment device 100 in this embodiment, even if, for example, multiple pores h1 in the membrane carrier 72 become hydrophilic, it becomes possible to restore the hydrophobicity of the multiple pores h1. Therefore, in the organic wastewater treatment device 100, even if, for example, multiple pores h1 in the membrane carrier 72 become hydrophilic, it becomes possible to resume normal operation and extend the period during which normal operation can be carried out.

[0150] In the organic wastewater treatment device 100 of this embodiment, the supply unit 83 can also inject dry air 5 into the membrane carrier 72 from the upper end 72d. However, the water pressure near the upper end 72d of the membrane carrier 72 is lower than the water pressure near the lower end 72c of the membrane carrier 72. Therefore, in this case, once the drying process is completed in the multiple holes h1 near the upper end 72d of the membrane carrier 72, the dry air 5 may be discharged from the multiple holes h1 near the upper end 72d, and the drying process may not be performed in the multiple holes h1 near the lower end 72c. For this reason, in the organic wastewater treatment device 100 of this embodiment, it is preferable for the supply unit 83 to inject dry air 5 into the membrane carrier 72 from the lower end 72c. [Explanation of symbols]

[0151] 1: Wastewater 2: Air 3: Drugs 4a: Replacement water 4b: Replacement air 5: Dry air 10: Primary sedimentation tank 20: Reaction tank 21: Tank body 22: Air supply pipe 30: Final sedimentation tank 40: Air supply unit (supply unit) 50: Solid-liquid separation tank 51: Tank body 52: Air supply pipe 53: Separation membrane 60: Air supply unit (supply unit) 70: Reaction vessel 71: Tank body 72: Membrane carrier 72a: First mold section 72a1: First air vent 72b: Second mold section 72b1: Second air vent 72c: Lower end 72d: Upper end 72e: Curved section 72f: Both ends 73: Peeling device 73a: Air supply device (supplyer) 73b: Air tank 74: Control device 80: Air supply device (supply device) 90: Solid-liquid separation device 100: Treatment equipment for organic wastewater 800: Treatment equipment for organic wastewater 900: Treatment equipment for organic wastewater h1: Hole h2: hole h3: hole L1: Line L2: Line L3: Line R1: Biofilm (Aerobic layer) R2: Anoxic layer R3: Anaerobic layer UN1: Unit UN2: Unit

Claims

1. A cleaning method for an organic wastewater treatment apparatus comprising a tank and at least an oxygen supply device, wherein the tank has a tubular membrane carrier that molecularly diffuses the oxygen supplied by the supply device into the tank through a plurality of pores, and the membrane carrier is a hydrophobic hollow fiber membrane, The supply of oxygen to the membrane carrier is stopped, A drug is supplied from the first part of the membrane carrier into the interior of the membrane carrier. By supplying liquid or a first gas from the first part into the interior of the membrane carrier, the agent in the plurality of pores is discharged into the tank. The opening degree of the valve that controls the amount of gas discharged from the second part of the membrane carrier is reduced. A method for cleaning an organic wastewater treatment device, comprising supplying a second gas from the first part into the interior of the membrane carrier to dry the multiple pores and restore the hydrophobicity of the hollow fiber membrane.

2. The cleaning method for an organic wastewater treatment device according to Claim 1, wherein the agent is an agent that removes substances adhering to the plurality of pores from the plurality of pores.

3. The shape of the membrane carrier is tubular, extending along the vertical axis of the tank and having a first end and a second end that are at least partially open to the outside of the membrane carrier. The first end is the lower end on the vertical axis, The second end is the upper end on the vertical axis, The first part is the first end, The second part is the second end, a method for cleaning an organic wastewater treatment apparatus according to claim 1.

4. The shape of the membrane carrier is tubular, having both ends that are at least partially open to the outside of the membrane carrier. The membrane carrier has a curved portion that curves the membrane carrier such that both ends point downwards along the vertical axis of the tank. The first part is each of the two ends, The second part is the method for cleaning the curved portion of the organic wastewater treatment apparatus according to claim 1.

5. Furthermore, in response to the discharge of the second gas toward the tank from at least one of the plurality of holes, the opening degree of the valve is increased. A method for cleaning an organic wastewater treatment apparatus according to claim 1, comprising restarting the supply of oxygen to the membrane carrier.

6. A method for cleaning an organic wastewater treatment apparatus according to claim 1, wherein the steps of stopping the supply of oxygen, supplying the chemical agent, supplying the liquid or the first gas, reducing the opening of the valve, and supplying the second gas are performed while the liquid in the tank is in contact with at least a portion of the outer surface of the membrane carrier.

7. The cleaning method for an organic wastewater treatment device according to claim 1, wherein the oxygen is obtained by water electrolysis using renewable energy.

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