JP7675686B2 - Liquid treatment device and method of operating same - Google Patents

Description

The present invention relates to a liquid treatment device that performs aerobic biological treatment of the liquid to be treated in a treatment tank.

Conventionally, in this type of liquid treatment device, as shown in FIG. 6, multiple oxygen-dissolving membrane modules 102a to 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 to 102d, and an air discharge section 105 that discharges the air 103 supplied to each of the membrane modules 102a to 102d from each of the membrane modules 102a to 102d.

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

The air supply section 104 is equipped with an air intake pipe 107 and a number 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 exhaust section 105 is equipped with an exhaust pipe 109 and a number 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. Each of the air intake branch pipes 108a-108d is equipped with a valve 111a-111d that opens and closes the air intake branch pipes 108a-108d.

According to this, all 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. This causes the air 103 to be supplied to the biofilms through the hollow fiber membranes of each membrane module 102a to 102d, and the biofilms consume the oxygen in the air 103 to carry out aerobic biological treatment.

The air 103 supplied to each membrane module 102a-102d then passes from each membrane module 102a-102d through each exhaust branch pipe 110a-110d to join the exhaust pipe 109 and is discharged outside the reaction tank 101.

The above-mentioned liquid treatment device is described, for example, in Patent Document 1 below.

Patent Publication No. 2021-607

However, in the above conventional system, if the hollow fiber membrane of one 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 Figure 7, air bubbles 114 will be ejected from the damaged part of the membrane module 102c. In this case, air 103 flows from the air supply pipe 107 into the broken membrane module 102c and is ejected as air bubbles 114, but is hardly supplied to the other membrane modules 102a, 102b, and 102d other than the broken membrane module 102c, resulting in a significant decrease in treatment efficiency.

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 one of the multiple membrane bodies provided in the membrane device is damaged.

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/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.

According to this, all first opening and closing devices are opened, and 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. This causes the oxygen-containing gas to be supplied to the biofilm through the gas permeable membrane of each membrane body, and the biofilm consumes the oxygen from the oxygen-containing gas to carry out aerobic biological treatment.

In this way, the oxygen-containing gas 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 discharged from the exhaust pipe to the outside of the treatment tank.

In addition, if the gas-permeable membrane of one of the membranes is damaged, for example, 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.

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

In addition, 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 prevention device of the exhaust branch pipe connected to the damaged membrane prevents the oxygen-containing gas from flowing back.

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.

The liquid treatment device in this second invention has a second opening and closing device provided on the air supply pipe for opening and closing the air supply pipe.

The liquid treatment device in the third invention is equipped with an aeration device below the membrane device.

According to this, an upward flow is generated by diffusing air using an aeration device, and the upward flow cleans the biofilm of each membrane body.

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;
When 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, and 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 is repeated until the ejection of air bubbles is eliminated.

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 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.

In addition, if bubbles continue to be emitted even after closing one 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.

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 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 the multiple damaged membrane bodies and stop the supply of air to only the multiple damaged membrane bodies.

This makes it possible to easily and accurately identify the damaged membranes from among all the membranes, and close only the first opening/closing device corresponding to the damaged membranes to stop the supply of air to only the damaged membranes.

As described above, according to the present invention, oxygen-containing gas is not supplied to the damaged membrane body, so the damaged membrane body does not contribute to aerobic biological treatment, but oxygen-containing gas is supplied to the remaining membrane bodies other than the damaged one, so aerobic biological treatment is carried out by the remaining membrane bodies other than the damaged one. This makes it possible to prevent a significant decrease in treatment efficiency.

1 is a diagram of a liquid treatment apparatus according to a first embodiment of the present invention; 2 is a view taken along the line XX in FIG. 1 . 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. 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. FIG. 13 is a diagram showing a state in which any two membrane modules of the liquid treatment device in the second embodiment of the present invention are broken. FIG. 1 is a diagram of a conventional liquid treatment device. 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.

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 apparatus 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 apparatus 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.

The treatment tank 2 is connected to a supply path 4 that supplies the liquid to be treated 3 into the tank and a discharge path 5 that discharges the liquid to be treated 3 out of the tank.

The membrane unit 6 comprises multiple membrane modules 14a-14f (an example of a membrane body). In FIG. 1, six membrane modules 14a-14f are arranged in parallel at a predetermined interval as an example, but the number is not limited to six, and in reality, a large number of membrane modules (for example, tens to hundreds) are provided.

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.

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

As shown in Figures 1 and 2, the gas supply section 8 includes an air intake pipe 21 provided above the membrane unit 6, and a number of air intake branch pipes 22a to 22f that branch off from the air intake pipe 21 and are connected to the upper headers 17 of the membrane modules 14a to 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 valve 24 (an example of a second opening and closing device) that opens and closes the air intake pipe 21.

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

Each of the air supply branch pipes 22a to 22f is provided with a plurality of air supply cock valves 33a to 33f (an example of a first opening and closing device) that individually open and close the air supply branch pipes 22a to 22f. These 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.

Each exhaust branch pipe 29a to 29f is provided with a check valve 35a to 35f (an example of a backflow prevention device) that prevents the backflow of air 7 from the exhaust pipe 28 to each membrane module 14a to 14f.

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

The operation of the above configuration is explained below.

As shown in FIG. 1, by driving the first blower device 23 with the main air intake valve 24 and all the air intake cock valves 33a to 33f open, air 7 flows from the first blower device 23 through the air intake pipe 21 and is supplied to each of the membrane modules 14a to 14f through each of the air intake branch pipes 22a to 22f. 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 to 14f, and the biofilm 16 consumes the oxygen in the air 7 to perform aerobic biological treatment.

In this way, the air 7 supplied to the hollow fiber membranes 15 of each membrane module 14a to 14f 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.

In addition, if any of the membrane modules 14c is damaged due to aging or collision with foreign matter mixed in the treated liquid 3, as shown in FIG. 4, air bubbles 45 will be 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.

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 to 33f other than the air supply cock valve 33c corresponding to the damaged membrane module 14c are kept open, so air 7 is supplied from the air supply pipe 21 to the remaining membrane modules 14a, 14b, 14d to 14f other than the damaged membrane module 14c, passes through each exhaust branch pipe 29a, 29b, 29d to 29f connected to these remaining membrane modules 14a, 14b, 14d to 14f, joins the exhaust pipe 28, and is exhausted from the exhaust pipe 28 to the outside of the treatment tank 2.

In addition, when the air supply 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 check valve 35c of this exhaust branch pipe 29c prevents the air 7 from flowing back.

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 carried out 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.

In addition, the second blower device 41 of the aeration device 10 is driven at predetermined time intervals and the aeration valve 42 is opened to blow air from the aeration tube 40 for aeration. This generates an upward flow in the treated liquid 3, and the biofilm 16 of each membrane module 14a to 14f is cleaned (scouring) by the upward flow, allowing the biofilm 16 to be adjusted to an appropriate thickness.

The method of operating the liquid processing device 1 described above is described below.

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

Also, 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 is eliminated, 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.

In addition, if bubbles 45 continue to escape even after closing 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), it is determined that one of the membrane modules 14a to 14c, 14e, and 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, and 33f are closed one by one until the escape of bubbles 45 is eliminated.

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

In the first embodiment, as shown in FIG. 4, air 7 is not supplied to the damaged membrane module 14c, but air 7 is supplied to the remaining undamaged membrane modules 14a, 14b, 14d to 14f to perform aerobic biological treatment. However, 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.

In the above first embodiment, as shown in FIG. 4, a case where the membrane module 14c is damaged has been described as an example. However, the same applies to a case where any one of the membrane modules 14a, 14b, and 14d to 14f other than the membrane module 14c is damaged.
Second Embodiment
In the first embodiment described above, as shown in FIG. 4, an operation method in the case where any one of the plurality of membrane modules 14a to 14f (e.g., membrane module 14c) is broken is shown. In the second embodiment, however, an operation method in the case where any two of the plurality of membrane modules 14a to 14f are broken will be described below.

For example, as shown in FIG. 5, if two of the membrane modules 14a-14f, 14c and 14e, are damaged and air bubbles 45 are ejected from the membrane modules 14c and 14e, the air supply cock valves are first closed until the ejection of the air bubbles 45 is eliminated. For example, it is assumed that the ejection of the air bubbles 45 is eliminated when the four air supply cock valves 33b-33e are closed.

Next, open one of the four air intake cock valves 33b to 33e that are closed, and check whether or not air bubbles 45 are escaping. For example, when air intake cock valve 33b is opened, the membrane module 14b corresponding to air intake cock valve 33b is not damaged, so no air bubbles 45 are escaping.

Next, open one of the three remaining closed air intake cock valves 33c to 33e, and check whether air bubbles 45 are ejected. For example, if air intake cock valve 33c is opened, air bubbles 45 will eject from membrane module 14c because the membrane module 14c corresponding to air intake cock valve 33c is damaged. This confirms the ejection of air bubbles 45, and then closes the open air intake cock valve 33c. This indicates that membrane module 14c is damaged.

Then, open one of the two remaining closed air intake cock valves 33d, 33e, and 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 the emission of air bubbles 45 is not confirmed.

Furthermore, the remaining closed air intake cock valve 33e is opened to check whether or not bubbles 45 are ejected. In this case, the membrane module 14e corresponding to the air intake cock valve 33e is damaged, so bubbles 45 are ejected from the membrane module 14e. As a result, the ejection of bubbles 45 is confirmed, and then the open air intake cock valve 33e is closed. This indicates that the membrane module 14e is damaged.

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

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

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

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

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

Claims (5)

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. A liquid treatment device as described in claim 1, characterized in that the air supply pipe is provided with a second opening and closing device for opening and closing the air supply pipe. The liquid treatment device according to claim 1, characterized in that an aeration device is provided below the membrane device. 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. 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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