Liquid treatment device and method of operating same

Abstract

To provide a liquid treatment device capable of preventing treatment efficiency from remarkably deteriorating even when any of a plurality of membrane bodies disposed in a membrane device is damaged.SOLUTION: The liquid treatment device comprises a membrane device 6 immersed in a liquid 3 to be treated located in a treatment tank 2, a gas supplier 8 supplying the membrane device 6 with oxygen-containing gas 7, and a gas discharger 9 discharging the oxygen-containing gas 7 from the membrane device 6. The membrane device 6 comprises a plurality of membrane bodies 14a to 14f. The membrane bodies 14a to 14f each include a gas permeating membrane and a bio-membrane which is formed on the outer surface of the gas permeating membrane and consumes the oxygen-containing gas 7. The gas supplier 8 comprises a plurality of gas supply branch pipes 22a to 22f branched from a gas supply pipe 21 and connected to the membrane bodies 14a to 14f respectively. The gas discharger 9 comprises a plurality of exhaust branch pipes 29a to 29f branched from the exhaust pipe 28 and connected to the membrane bodies 14a to 14f respectively. The gas supply branch pipes 22a to 22f are provided with first shut-off devices 33a to 33f respectively. The exhaust branch pipes 29a to 29f are provided with back-flow prevention devices 35a to 35f respectively, which prevent the backflow of the oxygen-containing gas 7 from the exhaust pipe 28 to the membrane bodies 14a to 14f.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a liquid treatment apparatus that performs aerobic biological treatment of a liquid to be treated in a treatment tank. [Background technology]

[0002] Conventionally, in this type of liquid treatment apparatus, as shown in FIG. 6, for example, a plurality of oxygen-dissolving membrane modules 102a-102d are installed in parallel in a reaction tank 101, and an air supply section 104 that supplies air 103 to each of the membrane modules 102a-102d, and an air discharge section 105 that discharges the air 103 supplied to each of the membrane modules 102a-102d from each of the membrane modules 102a-102d.

[0003] These membrane modules 102a to 102d are immersed in water 106 to be treated in the reaction tank 101. The membrane modules 102a to 102d use hollow fiber membranes as oxygen-dissolving membranes, and a biological film is attached to the outside of the hollow fiber membranes.

[0004] The air supply section 104 includes an air intake pipe 107 and a plurality of air intake branch pipes 108a-108d that branch off from the air intake pipe 107 and are connected to the upper ends of the membrane modules 102a-102d. The air discharge section 105 includes an exhaust pipe 109 and a plurality of exhaust branch pipes 110a-110d that branch off from the exhaust pipe 109 and are connected to the lower ends of the membrane modules 102a-102d. The air intake branch pipes 108a-108d are each provided with a valve 111a-111d that opens and closes the air intake branch pipes 108a-108d.

[0005] According to this, all the valves 111a to 111d are opened, and air 103 is supplied from the air supply pipe 107 through all the air supply branch pipes 108a to 108d to all the membrane modules 102a to 102d. As a result, the air 103 is supplied to the biological membranes through the hollow fiber membranes of the membrane modules 102a to 102d, and the biological membranes consume the oxygen in the air 103 to perform aerobic biological treatment.

[0006] The air 103 supplied to each of the membrane modules 102a to 102d then passes from each of the membrane modules 102a to 102d through each of the exhaust branch pipes 110a to 110d to join the exhaust pipe 109 and is discharged to the outside of the reaction tank 101.

[0007] The above-mentioned liquid treatment apparatus is described in, for example, Patent Document 1 below. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent Publication 2021-607 Summary of the Invention [Problem to be solved by the invention]

[0009] However, in the above conventional system, when the hollow fiber membrane of any of the membrane modules 102c is damaged due to aging or collision with foreign matter mixed in the water to be treated 106, for example as shown in Fig. 7, air bubbles 114 are ejected from the damaged part of the membrane module 102c. In this case, air 103 flows intensively from the air supply pipe 107 into the broken membrane module 102c and is ejected as air bubbles 114, and is hardly supplied to the other membrane modules 102a, 102b, 102d other than the broken membrane module 102c, resulting in a problem of a significant decrease in treatment efficiency.

[0010] The present invention aims to provide a liquid treatment device and an operating method thereof that can prevent a significant decrease in treatment efficiency even if any of the multiple membrane bodies provided in the membrane device is damaged. [Means for solving the problem]

[0011] In order to achieve the above object, the first invention is a liquid treatment device that performs aerobic biological treatment on a liquid to be treated in a treatment tank, comprising: A membrane device immersed in the liquid to be treated in the treatment tank; a gas supply section for supplying an oxygen-containing gas to the membrane device; a gas discharge section for discharging the oxygen-containing gas supplied to the membrane device from the membrane device, The membrane device includes a plurality of membrane bodies; The membrane body includes a gas-permeable membrane having gas permeability and a biofilm formed on an outer surface of the gas-permeable membrane and consuming an oxygen-containing gas supplied to the membrane body; the gas supply unit includes an air supply pipe and a plurality of air supply branch pipes branching from the air supply pipe and connected to each membrane body; the gas exhaust section includes an exhaust pipe and a plurality of exhaust branch pipes branching from the exhaust pipe and connected to each of the membrane bodies; a first opening / closing device for opening and closing the air supply branch pipe is provided in the air supply branch pipe; The first opening and closing device is located above the liquid level of the liquid to be treated in the treatment tank, The exhaust branch pipe is provided with a backflow prevention device for preventing the backflow of oxygen-containing gas from the exhaust pipe to the membrane body.

[0012] According to this method, all the first opening and closing devices are opened, and the oxygen-containing gas is supplied from the air supply pipe through each air supply branch pipe to the gas permeable membrane of each membrane body. As a result, the oxygen-containing gas is supplied to the biofilm through the gas permeable membrane of each membrane body, and the biofilm consumes the oxygen in the oxygen-containing gas to perform aerobic biological treatment.

[0013] The oxygen-containing gas thus supplied to the gas-permeable membrane of each membrane passes from each membrane through each exhaust branch pipe to join the exhaust pipe, and is exhausted from the exhaust pipe to the outside of the treatment tank.

[0014] In addition, if the gas-permeable membrane of one of the membranes is damaged due to deterioration over time or collision with a foreign object mixed in the liquid being treated, air bubbles will be ejected from the damaged part of the membrane. In this case, the first opening and closing device corresponding to the damaged membrane is closed, and the air supply branch pipe connected to the damaged membrane is closed.

[0015] As a result, the oxygen-containing gas is not supplied from the air supply pipe to the damaged membrane body, and the bubble emission is eliminated. At this time, the remaining first opening / closing devices other than the first opening / closing device corresponding to the damaged membrane body are kept in the open state, so that the oxygen-containing gas is supplied from the air supply pipe to the remaining membrane body other than the damaged membrane body, passes through each exhaust branch pipe connected to the remaining membrane body, merges with the exhaust pipe, and is exhausted from the exhaust pipe to the outside of the treatment tank.

[0016] Furthermore, when the first opening / closing device corresponding to the damaged membrane is closed as described above, even if the oxygen-containing gas in the exhaust pipe attempts to flow back into the damaged membrane through the exhaust branch pipe connected to the damaged membrane, the backflow of the oxygen-containing gas is prevented by the backflow prevention device of the exhaust branch pipe connected to the damaged membrane.

[0017] As a result, oxygen-containing gas is not supplied to the damaged membrane, so the damaged membrane does not contribute to aerobic biological treatment, but oxygen-containing gas is supplied to the remaining membranes other than the damaged one, so aerobic biological treatment is carried out by the remaining membranes other than the damaged one. This makes it possible to prevent a significant decrease in treatment efficiency.

[0018] In the liquid treatment apparatus according to the second aspect of the present invention, the air supply pipe is provided with a second opening and closing device for opening and closing the air supply pipe.

[0019] The liquid treatment apparatus in the third aspect of the present invention is provided with an aeration device below the membrane device.

[0020] According to this, an upward flow is generated by diffusing air with an air diffuser, and the biofilm of each membrane body is washed by the upward flow.

[0021] The present invention is a fourth aspect of the present invention, which is a method for operating a liquid treatment apparatus according to any one of the first to third aspects of the present invention, Open all first opening and closing devices to supply oxygen-containing gas from the air supply pipe through all air supply branch pipes to all membrane bodies; If air bubbles are ejected from any of the membrane bodies, one of the first opening and closing devices is closed, and when the ejection of air bubbles is eliminated, the closed first opening and closing device is maintained in a closed state. If air bubbles continue to be ejected even when any of the first opening and closing devices is closed, the closed first opening and closing device is opened and another first opening and closing device is closed, and this process is repeated until the ejection of air bubbles is eliminated.

[0022] According to this, if bubbles are spewing out onto the liquid surface with all first opening / closing devices open, one of the first opening / closing devices near the bubble spewing source is closed. When the bubble spewing stops, it is determined that the membrane corresponding to the closed first opening / closing device is damaged, and the remaining first opening / closing devices are left open to continue aerobic biological treatment.

[0023] In addition, if bubbles continue to be emitted even after closing any of the first opening / closing devices near the bubble emission, it is determined that one of the membranes other than the membrane corresponding to the closed first opening / closing device is damaged, and the closed first opening / closing device is opened and another first opening / closing device is closed repeatedly until the bubble emission is eliminated. This makes it possible to easily and accurately identify the damaged membrane from among all the membranes.

[0024] The present invention is a method for operating a liquid treatment apparatus according to any one of the first to third aspects of the present invention, Open all first opening and closing devices to supply oxygen-containing gas from the air supply pipe through all air supply branch pipes to all membrane bodies; When bubbles are ejected from any one or more of the membrane bodies, the first opening and closing devices are closed until the ejection of bubbles is stopped; Any one of the closed first opening / closing devices is opened, and if the emission of air bubbles is confirmed, the open first opening / closing device is closed, and if the emission of air bubbles is not confirmed, any one of the remaining closed first opening / closing devices is opened, and this process is repeated to identify any damaged membrane bodies and stop the supply of air to only the damaged membrane bodies.

[0025] This makes it possible to easily and accurately identify the multiple damaged membranes from among all the membranes, and by closing only the first opening / closing device corresponding to the multiple damaged membranes, the air supply to only the multiple damaged membranes can be stopped. Effect of the Invention

[0026] As described above, according to the present invention, since the oxygen-containing gas is not supplied to the damaged membrane, the damaged membrane does not contribute to the aerobic biological treatment, but since the oxygen-containing gas is supplied to the remaining membranes other than the damaged membrane, the aerobic biological treatment is carried out by the remaining membranes other than the damaged membrane. This makes it possible to prevent a significant decrease in the treatment efficiency. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 is a diagram of a liquid processing apparatus according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a view taken along the arrow XX in FIG. [Diagram 3] FIG. 2 is a partially enlarged cross-sectional view of a hollow fiber membrane and a biomembrane in a membrane module of the liquid treatment device according to the first embodiment. [Figure 4] FIG. 11 is a diagram showing a state in which one of the membrane modules of the liquid treatment device is broken in the same embodiment. [Diagram 5] FIG. 13 is a diagram showing a state in which any two membrane modules of a liquid treatment device in a second embodiment of the present invention are broken. [Figure 6] FIG. 1 is a diagram of a conventional liquid treatment device. [Figure 7] FIG. 2 is a diagram showing a state in which one of the membrane modules of the liquid treatment device is broken in the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. (First embodiment) In the first embodiment, as shown in Figures 1 and 2, reference numeral 1 denotes a liquid treatment device that performs aerobic biological treatment of a liquid to be treated 3 (organic wastewater, sludge, etc.) in a treatment tank 2 in a sewage treatment plant, an industrial wastewater treatment plant, etc. The liquid treatment device 1 includes the treatment tank 2, a membrane unit 6 (an example of a membrane device) immersed in the liquid to be treated 3 in the treatment tank 2, a gas supply section 8 that supplies air 7 (an example of an oxygen-containing gas) to the membrane unit 6, a gas discharge section 9 that discharges the air 7 supplied to the membrane unit 6 from the membrane unit 6, and an aeration device 10 provided below the membrane unit 6.

[0029] A supply path 4 for supplying the liquid to be treated 3 into the treatment tank 2 and a discharge path 5 for discharging the liquid to be treated 3 out of the tank are connected to the treatment tank 2.

[0030] The membrane unit 6 includes a plurality of membrane modules 14a to 14f (an example of a membrane body). In Fig. 1, six membrane modules 14a to 14f are arranged in parallel at a predetermined interval as an example, but the number of membrane modules is not limited to six, and in reality, a large number of membrane modules (for example, tens to hundreds) are included.

[0031] As shown in Figures 2 and 3, each of the membrane modules 14a to 14f includes a plurality (a large number) of gas-permeable hollow fiber membranes 15 (an example of a gas-permeable membrane), a biological membrane 16 that is formed on the outer surface of the hollow fiber membranes 15 and consumes the air 7 supplied to the membrane modules 14a to 14f, and upper and lower headers 17, 18.

[0032] The multiple hollow fiber membranes 15 are formed in a sheet shape, with the upper ends of the hollow fiber membranes 15 opening into the internal space of an upper header 17 and the lower ends of the hollow fiber membranes 15 opening into the internal space of a lower header 18 .

[0033] 1 and 2, the gas supply section 8 includes an air intake pipe 21 provided above the membrane unit 6, and a plurality of air intake branch pipes 22a-22f branching off from the air intake pipe 21 and connected to the upper headers 17 of the membrane modules 14a-14f. The air intake pipe 21 is provided with a first blower device 23 that sends air 7 from the upstream side, and an air intake main valve 24 (an example of a second opening and closing device) that opens and closes the air intake pipe 21.

[0034] The gas discharge section 9 includes an exhaust pipe 28 provided below the membrane unit 6, and a plurality of exhaust branch pipes 29a-29f branching from the exhaust pipe 28 and connected to the lower headers 18 of the membrane modules 14a-14f. An exhaust valve 30 is connected to the downstream side of the exhaust pipe 28.

[0035] The air supply branch pipes 22a to 22f are provided with a plurality of air supply cock valves 33a to 33f (an example of a first opening and closing device) for opening and closing the respective air supply branch pipes 22a to 22f. The air supply cock valves 33a to 33f are located above the liquid level 3a of the liquid 3 to be treated in the treatment tank 2.

[0036] The exhaust branch pipes 29a to 29f are provided with check valves 35a to 35f (an example of a backflow prevention device) that prevent the air 7 from flowing back from the exhaust pipe 28 to the membrane modules 14a to 14f, respectively.

[0037] The air diffusion device 10 has a plurality of air diffusion pipes 40, and a second blower device 41 and an air diffusion valve 42 connected to the air diffusion pipes 40.

[0038] The operation of the above configuration will now be described.

[0039] 1, by driving the first blower device 23 with the main air intake valve 24 and all the air intake cock valves 33a-33f open, air 7 flows from the first blower device 23 through the air intake pipe 21 and passes through each of the air intake branch pipes 22a-22f to be supplied to each of the membrane modules 14a-14f. As a result, the air 7 is supplied to the biofilm 16 through the hollow fiber membranes 15 of each of the membrane modules 14a-14f, and the biofilm 16 consumes the oxygen in the air 7 to perform aerobic biological treatment.

[0040] The air 7 supplied to the hollow fiber membranes 15 of each membrane module 14a to 14f in this manner passes from each membrane module 14a to 14f through each exhaust branch pipe 29a to 29f to join the exhaust pipe 28, and is discharged from the exhaust pipe 28 to the outside of the treatment tank 2.

[0041] 4, when any of the membrane modules 14c is damaged due to deterioration over time or collision with foreign matter mixed in the liquid to be treated 3, air bubbles 45 are generated from the damaged part of the membrane module 14c. In this case, the air supply cock valve 33c corresponding to the damaged membrane module 14c is closed, and the air supply branch pipe 22c connected to the damaged membrane module 14c is closed.

[0042] As a result, air 7 is not supplied from the air supply pipe 21 to the damaged membrane module 14c, and the emission of air bubbles 45 is eliminated. At this time, the remaining air supply cock valves 33a, 33b, 33d-33f other than the air supply cock valve 33c corresponding to the damaged membrane module 14c are kept open, so that air 7 is supplied from the air supply pipe 21 to the remaining membrane modules 14a, 14b, 14d-14f other than the damaged membrane module 14c, passes through each of the exhaust branch pipes 29a, 29b, 29d-29f connected to these remaining membrane modules 14a, 14b, 14d-14f, joins the exhaust pipe 28, and is exhausted from the exhaust pipe 28 to the outside of the treatment tank 2.

[0043] Furthermore, when the air intake cock valve 33c corresponding to the damaged membrane module 14c is closed as described above, even if the air 7 in the exhaust pipe 28 attempts to flow back into the damaged membrane module 14c through the exhaust branch pipe 29c connected to the damaged membrane module 14c, the backflow of the air 7 is prevented by the check valve 35c of this exhaust branch pipe 29c.

[0044] As a result, air 7 is not supplied to the damaged membrane module 14c, so the damaged membrane module 14c does not contribute to aerobic biological treatment, but air 7 is supplied to the remaining membrane modules 14a, 14b, 14d to 14f other than the damaged membrane module 14c, so aerobic biological treatment is performed by the remaining membrane modules 14a, 14b, 14d to 14f other than the damaged membrane module 14c. This makes it possible to prevent a significant decrease in treatment efficiency.

[0045] Moreover, the second blower device 41 of the air diffuser 10 is driven at predetermined time intervals and the air diffuser valve 42 is opened to blow air from the air diffuser pipe 40 for air diffusion. This generates an upward flow in the liquid 3 to be treated, and the biofilm 16 of each membrane module 14a to 14f is cleaned (scouring) by the upward flow, thereby adjusting the biofilm 16 to an appropriate thickness.

[0046] A method of operating the liquid processing apparatus 1 as described above will now be described.

[0047] As shown in Fig. 1, the first blower device 23 is driven, the air supply valve 24 and all the air supply cock valves 33a-33f are opened, and air 7 is supplied from the air supply pipe 21 through all the air supply branch pipes 22a-22f to all the membrane modules 14a-14f. As a result, aerobic biological treatment is performed by all the membrane modules 14a-14f. At this time, the air 7 flows from top to bottom within the hollow fiber membranes 15 of each of the membrane modules 14a-14f, and if no air bubbles 45 are blown out from each of the membrane modules 14a-14f, it is determined that all the membrane modules 14a-14f are not damaged and are normal.

[0048] Furthermore, as shown in FIG. 4, if air bubbles 45 are ejected from one of the membrane modules 14a to 14f (for example, membrane module 14c), one of the air intake cock valves 33a to 33f (for example, air intake cock valve 33c) is closed. When the ejection of air bubbles 45 stops, it is determined that the membrane module 14c corresponding to the closed air intake cock valve 33c is damaged, and the air intake cock valve 33c is kept closed while the remaining air intake cock valves 33a, 33b, 33d to 33f are kept open to continue aerobic biological treatment.

[0049] Furthermore, if air bubbles 45 continue to escape even when one of the air intake cock valves 33a to 33f (for example, not air intake cock valve 33c but the adjacent air intake cock valve 33d) is closed, it is determined that one of the membrane modules 14a to 14c, 14e, 14f other than the membrane module 14d corresponding to the closed air intake cock valve 33d is damaged, and the closed air intake cock valve 33d is opened and the other air intake cock valves 33a to 33c, 33e, 33f are closed one by one until the escape of air bubbles 45 is resolved.

[0050] This makes it possible to easily and accurately identify the damaged membrane module 14c from among all the membrane modules 14a to 14f.

[0051] In the first embodiment, as shown in Fig. 4, air 7 is not supplied to the damaged membrane module 14c, but is supplied to the remaining undamaged membrane modules 14a, 14b, 14d to 14f to perform aerobic biological treatment, but when the number of damaged membrane modules increases and a predetermined percentage of the total number of membrane modules 14a to 14f is damaged, the membrane unit 6 may be pulled out from inside the treatment tank 2 to the outside, and the damaged membrane modules may be replaced with new membrane modules. For example, if the total number of membrane modules provided in the membrane unit 6 is 100 and the predetermined percentage is 10%, when 10 of the 100 membrane modules are damaged, the membrane unit 6 is pulled out from inside the treatment tank 2 to the outside, and the damaged 10 membrane modules are replaced with new membrane modules.

[0052] In the above first embodiment, as shown in FIG. 4, an example is described in which membrane module 14c is damaged. However, the same applies if any one of membrane modules 14a, 14b, 14d to 14f other than membrane module 14c is damaged. (Second embodiment) In the first embodiment described above, as shown in FIG. 4, an operation method when any one of the multiple membrane modules 14a to 14f (e.g., membrane module 14c) is damaged is shown. In the second embodiment, however, an operation method when any two of the multiple membrane modules 14a to 14f are damaged is described below.

[0053] 5, when two membrane modules 14c, 14e among the membrane modules 14a-14f are damaged and air bubbles 45 are ejected from the membrane modules 14c, 14e, first, the air inlet cock valves are closed until the ejection of the air bubbles 45 is stopped. For example, it is assumed that the ejection of the air bubbles 45 is stopped when the four air inlet cock valves 33b-33e are closed.

[0054] Next, any one of the four air intake cock valves 33b to 33e that are closed is opened, and it is confirmed whether or not air bubbles 45 are ejected. For example, when the air intake cock valve 33b is opened, the membrane module 14b corresponding to the air intake cock valve 33b is not damaged, so that the ejection of air bubbles 45 is not confirmed.

[0055] Next, any one of the remaining three closed air intake cock valves 33c to 33e is opened, and the presence or absence of the spurting of air bubbles 45 is confirmed. For example, when the air intake cock valve 33c is opened, the membrane module 14c corresponding to the air intake cock valve 33c is damaged, and therefore air bubbles 45 spurt out from the membrane module 14c. As a result, the spurting of air bubbles 45 is confirmed, and then the open air intake cock valve 33c is closed. As a result, it is found that the membrane module 14c is damaged.

[0056] Thereafter, one of the remaining two closed air intake cock valves 33d, 33e is opened to check for the emission of air bubbles 45. For example, when the air intake cock valve 33d is opened, the membrane module 14d corresponding to the air intake cock valve 33d is not damaged, so that the emission of air bubbles 45 is not confirmed.

[0057] Furthermore, the remaining closed air intake cock valve 33e is opened, and the presence or absence of the spurting of air bubbles 45 is confirmed. In this case, the membrane module 14e corresponding to the air intake cock valve 33e is damaged, so air bubbles 45 spurt out from the membrane module 14e. As a result, the spurting of air bubbles 45 is confirmed, and then the open air intake cock valve 33e is closed. This indicates that the membrane module 14e is damaged.

[0058] As a result of the above, the two damaged membrane modules 14c, 14e can be easily and accurately identified from among all of the membrane modules 14a to 14f, and the supply of air to only the two damaged membrane modules 14c, 14e can be stopped by closing only the two air supply cock valves 33c, 33e.

[0059] In the above second embodiment, the case where two membrane modules 14c and 14e out of all the membrane modules 14a to 14f are broken is shown, but the same applies to the case where two membrane modules other than these membrane modules 14c and 14e are broken. Moreover, the case is not limited to the case where two membrane modules are broken, but also applies to the case where three or more membrane modules are broken.

[0060] In each of the above-described embodiments, for ease of understanding, six membrane modules 14a to 14f are shown as shown in Figures 1, 4, and 5. However, the number of membrane modules is not limited to six, and a large number (e.g., tens to hundreds) of membrane modules may be provided.

[0061] In the above embodiment, the air supply cock valves 33a to 33f are used as an example of the opening and closing device, but a type of valve other than the cock valve may be used. [Explanation of symbols]

[0062] 1 Liquid treatment equipment 2 Treatment tank 3 Liquid to be treated 3a Liquid level 6 Membrane unit (membrane device) 7. Air (oxygen-containing gas) 8 Gas supply section 9 Gas exhaust section 10 Air diffuser 14a-14f Membrane module (membrane body) 15 Hollow fiber membrane (gas permeable membrane) 16 Biofilm 21 Air supply pipe 22a~22f Air supply branch pipe 24 Air supply valve (second opening and closing device) 28 Exhaust pipe 29a~29f Exhaust manifold 33a~33f Air intake cock valve (first opening / closing device) 35a~35f Check valve (backflow prevention device) 45 Bubbles

Claims

1. A liquid treatment device that performs aerobic biological treatment on a liquid to be treated in a treatment tank, A membrane device immersed in the liquid to be treated in the treatment tank; a gas supply section for supplying an oxygen-containing gas to the membrane device; a gas discharge section for discharging the oxygen-containing gas supplied to the membrane device from the membrane device, The membrane device includes a plurality of membrane bodies; The membrane body includes a hollow fiber membrane and a biofilm formed on an outer surface of the hollow fiber membrane and consuming an oxygen-containing gas supplied to the membrane body; the gas supply unit includes an air supply pipe and a plurality of air supply branch pipes branching from the air supply pipe and connected to each membrane body; the gas exhaust section includes an exhaust pipe and a plurality of exhaust branch pipes branching from the exhaust pipe and connected to each of the membrane bodies; a first opening / closing device for opening and closing the air supply branch pipe is provided in the air supply branch pipe; the first opening / closing device is located above the liquid level of the liquid to be treated in the treatment tank; 1. A liquid treatment apparatus comprising: an exhaust branch pipe provided with a backflow prevention device for preventing a backflow of an oxygen-containing gas from the exhaust pipe to the membrane body.

2. 2. A liquid treatment apparatus according to claim 1, further comprising a second opening / closing device for opening and closing the air supply pipe, the second opening / closing device being provided in the air supply pipe.

3. 2. A liquid treatment apparatus according to claim 1, further comprising an aeration device disposed below the membrane device.

4. A method for operating the liquid treatment apparatus according to any one of claims 1 to 3, comprising: Open all first opening and closing devices to supply oxygen-containing gas from the air supply pipe through all air supply branch pipes to all membrane bodies; A method for operating a liquid treatment device, characterized in that when bubbles are ejected from any of the membrane bodies, any of the first opening and closing devices is closed, and when the ejection of bubbles is eliminated, the closed first opening and closing device is maintained in a closed state, and if bubbles continue to be ejected even after any of the first opening and closing devices is closed, the closed first opening and closing device is opened and another first opening and closing device is closed, repeatedly until the ejection of bubbles is eliminated.

5. A method for operating the liquid treatment apparatus according to any one of claims 1 to 3, comprising: Open all first opening and closing devices to supply oxygen-containing gas from the air supply pipe through all air supply branch pipes to all membrane bodies; When bubbles are ejected from any one of the membrane bodies, the first opening and closing devices are closed until the ejection of bubbles is stopped; A method for operating a liquid treatment device, characterized in that any one of the closed first opening / closing devices is opened, and if the emission of air bubbles is confirmed, the open first opening / closing device is closed, and if the emission of air bubbles is not confirmed, any one of the remaining closed first opening / closing devices is opened, thereby repeatedly identifying multiple damaged membrane bodies and stopping the supply of air to only the multiple damaged membrane bodies.

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