JP2023065705A - Wastewater treatment system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an energy-saving wastewater treatment system.

SOLUTION: A wastewater treatment system 100 comprises a treatment tank R that stores water to be treated, with the treatment tank R comprising an anaerobic tank 1 applying an anaerobic treatment to water to be treated, an aerobic tank 2 connected to the anaerobic tank 1 to apply an aerobic treatment to water to be treated, the aerobic tank 2 comprising a bubble generation unit 6 generating bubbles B, the anaerobic tank 1 comprising an oxygen permeation unit 3 including oxygen permeable membranes, and whole of the oxygen permeation unit 3 being immersed at a depth of less than 50% of a maximum water depth d2 of water to be treated in the aerobic tank 2.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present invention relates to wastewater treatment systems.

In wastewater treatment, in addition to the removal (oxidation) of organic substances by the activated sludge method, the removal of nitrogen-containing compounds (hereinafter referred to as nitrogen components) such as ammoniacal nitrogen is also performed. Nitrogen components in wastewater can be removed, for example, by causing nitrifying bacteria to act in an aerobic environment for nitrification (oxidizing to nitrate nitrogen), and denitrifying bacteria in an anaerobic environment to denitrify (to nitrogen gas). return).

Patent Literature 1 describes a biological nitrogen removal device (wastewater treatment system). This biological nitrogen removal system consists of a denitrification tank into which influent water (wastewater) to be treated flows, a nitrification tank into which water to be treated after passing through the denitrification tank flows, and an aerated tank. It is equipped with a final sedimentation tank for sedimentation and separation of activated sludge from treated water and discharged as treated water, and an aeration device (bubble generator) for sending air to the nitrification treatment tank.

Patent Document 2 describes a wastewater treatment method in which atmospheric oxygen is introduced into wastewater through an oxygen-permeable membrane by natural aeration without power. In this wastewater treatment method, the biofilm generated on the surface of the membrane oxidizes the ammonia nitrogen in the wastewater to produce nitrate nitrogen, which is then diffused into the wastewater under an anaerobic environment away from the biofilm. to denitrify.

Patent Document 3 describes a combined treatment septic tank (wastewater treatment system). This combined treatment septic tank comprises a cylindrical body made of an oxygen-permeable membrane provided in place of the anaerobic filter bed tank (denitrification tank) and the contact aeration tank (nitrification tank), and a biological treatment tank. The cylindrical body is immersed in a biological treatment bath. A double membrane structure of a biofilm of aerobic microorganisms and a biofilm of anaerobic microorganisms is formed on the outer peripheral surface of the cylindrical body. In this combined treatment septic tank, a biological treatment process in which organic matter is decomposed by aerobic microorganisms and anaerobic microorganisms, and a ventilation process in which air is introduced into the cylindrical body are carried out.

JP-A-11-244894 Japanese Patent Application Laid-Open No. 2003-211185 JP 2016-43281 A

In the wastewater treatment system described in Patent Document 1, there is a problem that the capacity of the nitrification treatment tank must be increased in order to sufficiently nitrify the nitrogen component. In addition, there is a problem that the nitrogen component in the treated water cannot be sufficiently reduced unless the capacity of the nitrification treatment tank is increased. As described in Patent Documents 2 and 3, if oxygen is supplied to wastewater under an anaerobic environment through an oxygen-permeable membrane, energy consumption can be reduced (hereinafter simply referred to as energy saving) and nitrification can be achieved. It is also considered possible to achieve compactness by omitting or reducing the size of the tank. However, due to damage countermeasures such as oxygen permeable membranes breaking and problems such as insufficient oxygen supply due to excessive growth of biofilms, forced ventilation is actually required, and sufficient energy saving has not been achieved. There is room.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object of the present invention is to provide an energy-saving wastewater treatment system.

The characteristic configuration of the wastewater treatment system according to the present invention for achieving the above object is provided with a treatment tank for storing water to be treated, and the treatment tank is an anaerobic treatment unit for performing anaerobic treatment on the water to be treated. and an aerobic treatment unit that is connected to the anaerobic treatment unit and performs aerobic treatment on the water to be treated, and the aerobic treatment unit has a bubble generation unit that generates bubbles. The anaerobic treatment section has an oxygen permeation section including an oxygen permeation membrane that allows oxygen to pass through, and all of the oxygen permeation sections are 50% of the maximum water depth of the water to be treated in the aerobic treatment section. It is immersed in a water depth of less than

In this wastewater treatment system, a biological denitrification reaction takes place. According to the above configuration, the aerobic treatment section performs aerobic treatment on the water to be treated. In the aerobic treatment section, nitrogen-containing compounds such as ammonia nitrogen (hereinafter referred to as "nitrogen components") in the treated water are oxidized (so-called nitrification, hereinafter simply "nitrification") by oxygen and nitrifying bacteria in the treated water. aerobic treatment that promotes the progress of Thereby, the nitrogen component in the treated water is converted to nitrate nitrogen. According to the above configuration, the area near the upper portion of the air bubble generating portion in the processing bath is supplied with oxygen from the air bubbles generated by the air bubble generating portion and becomes an aerobic area with a high dissolved oxygen concentration. The aerobic treatment section is an aerobic region in which oxygen is supplied from bubbles generated by the bubble generation section in the treatment tank.

According to the above configuration, the anaerobic treatment section performs anaerobic treatment on the water to be treated. In the anaerobic treatment section, the denitrifying bacteria in the treated water and the organic matter that feeds on the denitrifying bacteria reduce nitrate nitrogen and produce nitrogen (so-called denitrification, hereinafter simply “denitrification”). Nitrogen”). Through such nitrification and denitrification, the treated water is purified by decomposing and removing nitrogen-containing compounds.

According to the above configuration, the surface of the oxygen-permeable membrane forms a biofilm mainly containing nitrifying bacteria that nitrify the nitrogen component in the treated water with the oxygen supplied from the oxygen-permeable membrane, thereby nitrifying the nitrogen component. That is, according to the above configuration, nitrification can be carried out both in the aerobic region formed by the bubble generating portion and in the biofilm formed on the surface of the oxygen-permeable membrane. Since the oxygen supplied from the oxygen-permeable membrane is exhausted in the biofilm, the anaerobic environment in the outer (outer) region of the biofilm is maintained.

According to the above configuration, since the oxygen permeable part is immersed in a shallow water depth region of less than 50% of the maximum water depth of the water to be treated, even if water enters the membrane due to breakage of the oxygen permeable membrane, etc. Water can be removed by blowing air at low pressure. Therefore, a low pressure of the air blown (supplied) to the oxygen permeable part is sufficient, and energy saving of the oxygen permeable part can be realized. In addition, since low-pressure air is sufficient for blowing, a simple air blower can be used, and the cost of the system can be reduced. For example, a low-cost fan can be used as the blower instead of using a blower that can blow air with a high air pressure but has a high equipment cost.

In addition, it is necessary to supply air at a pressure proportional to the water pressure of the water depth to the bubble generating part that is usually immersed in a deep water depth (for example, a deep water depth of 50% or more of the maximum water depth of the treatment tank). . However, according to the above configuration, nitrification proceeds even with oxygen supplied from the oxygen permeable portion. Therefore, the amount of oxygen (air) that needs to be supplied from the bubble generating section can be reduced. This reduces the overall energy required to supply oxygen for nitrification in the treatment tank.

Further, according to the above configuration, since the oxygen permeable portion is immersed in a shallow water depth region, access from the surface of the water is easy and maintainability is high. That is, since an external stimulus such as vibration can be easily applied from the surface of the water, it is extremely easy to remove the biofilm formed on the oxygen-permeable membrane when it grows excessively. As a result, a decrease in nitrification efficiency in the oxygen-permeable portion can be avoided.

A further characteristic configuration of the wastewater treatment system according to the present invention is that the oxygen permeation part has a permeation unit including a plurality of cylindrical parts in which the oxygen permeable membrane is formed in a cylindrical shape, and the permeation unit includes the It is immersed along the water surface of the water to be treated.

According to the above configuration, the tubular portion is formed by forming the oxygen-permeable membrane in a tubular shape, and air can flow through the inside thereof. The transmission unit is formed by, for example, bundling a plurality of cylindrical portions. The tubular portion is arranged laterally along a horizontal plane (water surface) as a transmission unit. By arranging the cylindrical portion sideways, it is possible to increase the area of the oxygen permeable membrane without increasing the depth of water in which the oxygen permeable membrane is installed (the depth of water in which the oxygen permeable membrane is immersed). Therefore, even when considering the intrusion of water into the membrane due to breakage of the oxygen permeable membrane, a low pressure of the air supplied to the oxygen permeable membrane is sufficient, and energy saving of the oxygen permeable part can be realized. It is possible to increase the area and improve the nitrification efficiency on the oxygen permeable membrane (in the biofilm). In addition, since the cylindrical portion is arranged sideways, it is easy to access from above the water surface and maintainability is improved. As a result, when the biofilm formed on the oxygen-permeable membrane grows too much, it becomes extremely easy to remove the biofilm.

A further characteristic configuration of the waste water treatment system according to the present invention is that the anaerobic treatment section and the aerobic treatment section are arranged so as to be partitioned by the same treatment tank.

According to the above configuration, the treatment tank is divided into the anaerobic treatment section and the aerobic treatment section. For example, the treatment tank is divided into an upstream area and a downstream area by a partition wall, and the upstream area is an anaerobic treatment area and the downstream area is an aerobic treatment area. (vertical direction), one region (for example, the upper region) can be an anaerobic treatment section, and the other region (for example, the lower region) can be an aerobic treatment section. In particular, when the processing tank is partitioned into upper and lower parts in the vertical direction, the oxygen permeable part and the bubble generating part can be arranged so as to overlap when viewed in the vertical direction, so that the processing tank can be made compact.

A further characteristic configuration of the waste water treatment system according to the present invention is that the treatment tank has a first tank and a second tank arranged downstream of the first tank, and the oxygen permeation section is the first tank. It is immersed in one tank, and the bubble generating part is immersed in the second tank.

According to the above configuration, the first tank in which the oxygen permeable part is immersed is the anaerobic treatment part, and not only denitrification proceeds in the outer region of the biofilm, but also nitrification proceeds in the inner region of the biofilm. In addition, the second tank is an aerobic treatment section, and nitrification is performed. When the treatment tank has the first tank and the second tank in this way, the treatment efficiency of each tank is improved by making the first tank the anaerobic treatment part and the second tank the aerobic treatment part. Even if the first tank is an anaerobic treatment section, the oxygen supplied from the oxygen permeable membrane of the oxygen permeable section is exhausted in the biofilm formed on the oxygen permeable membrane. Maintained in a generally anaerobic environment. Therefore, denitrification in the first tank is not hindered.

A further characteristic configuration of the waste water treatment system according to the present invention is that the water depth of the anaerobic treatment section is 0.5 m or less.

According to the above configuration, since the water depth of the first tank is suppressed to a shallow depth of 0.5 m or less, an extremely low pressure of the air supplied to the oxygen permeation section is sufficient. This makes it possible to save energy. In addition, since the oxygen permeable membrane is immersed in a particularly shallow water depth of 0.5 m or less, access from the water surface is easy and maintainability is high. In addition, external stimuli such as vibrations can be applied very easily from the surface of the water. As a result, when the biofilm formed on the oxygen-permeable membrane grows excessively, the biofilm can be removed very easily.

It is a schematic diagram of the side view of the processing tank which concerns on 1st embodiment. It is a top view schematic diagram of the processing tank which concerns on 1st embodiment. BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of a waste water treatment system and a process line. FIG. 4 is an explanatory diagram of a cross-sectional structure of a transmission unit; FIG. 4 is an explanatory diagram of a cross-sectional structure of a permeation unit in which a biofilm is formed; It is explanatory drawing of the cross-sectional structure of an oxygen-permeable membrane and a biofilm. It is a schematic diagram of the processing tank in 2nd embodiment. FIG. 11 is a schematic diagram of an arrangement state of transmission units according to another embodiment. It is a schematic diagram of the processing tank which concerns on another embodiment.

A wastewater treatment system according to an embodiment of the present invention will be described based on the drawings.

[First Embodiment] [Description of Overall Configuration]
1 and 2 show a schematic configuration of a waste water treatment system 100 for purifying incoming waste water (water to be treated). This waste water treatment system 100 is installed in a sewage treatment plant or the like. The wastewater treatment system 100 includes a treatment tank R for storing wastewater continuously flowing in from upstream, an oxygen permeation section 3 for supplying oxygen to the wastewater stored in the treatment tank R through an oxygen permeable membrane 30, and a treatment tank. A bubble generator 6 is provided for generating bubbles B (see FIG. 1) in the waste water stored in R to supply oxygen. The treatment tank R includes an anaerobic tank 1 (an example of a first tank, an example of an anaerobic treatment section) and an aerobic tank 2 (an example of a second tank, an example of an aerobic treatment section) downstream of the anaerobic tank 1. have The oxygen permeable part 3 is immersed in the waste water stored in the anaerobic tank 1 . The air bubble generator 6 is immersed in the waste water stored in the aerobic tank 2 .

In this embodiment, the waste water flowing into the treatment tank R contains at least nitrogen-containing compounds such as ammoniacal nitrogen (hereinafter referred to as "nitrogen components") and organic substances. In the treatment tank R, nitrification (an example of aerobic treatment) in which nitrogen components are oxidized to nitrite nitrogen and nitrate nitrogen, and denitrification (anaerobic treatment) in which nitrite nitrogen and nitrate nitrogen are reduced to nitrogen are reduced. example of processing) is performed. Hereinafter, nitrite nitrogen and nitrate nitrogen are collectively referred to simply as "nitrate nitrogen".

The wastewater treatment system 100 of this embodiment includes a primary sedimentation tank 91 upstream of the treatment tank R and a final sedimentation tank 99 downstream of the treatment tank R, as shown in FIG. The wastewater treatment system 100 may have multiple treatment lines N1, N2, N3, etc., each having a primary sedimentation tank 91, a treatment tank R, and a final sedimentation tank 99. In this embodiment, the processing sequences N1, N2 and N3 are all equivalent. The processing sequence N1 will be described below, but the same applies to the processing sequences N2 and N3. In the present embodiment, the concept of wastewater stored in the treatment tank R includes a so-called mixed liquid in which suspended solids (SS) containing nitrifying bacteria and denitrifying bacteria as activated sludge are present in a suspended state. Including concepts.

[Description of each part]
The primary sedimentation tank 91 is a tank for settling and removing part of the sludge contained in the inflowing wastewater. The waste water containing nitrogen components and organic matter not removed in the primary sedimentation tank 91 flows into the treatment tank R (anaerobic tank 1).

The treatment tank R has one anaerobic tank 1 and one aerobic tank 2 connected in series downstream of the anaerobic tank 1, as shown in FIGS. The wastewater that has flowed into the anaerobic tank 1 stays in the anaerobic tank 1 for a predetermined time and flows into the aerobic tank 2 . The waste water that has flowed into the aerobic tank 2 stays in the aerobic tank 2 for a predetermined time and then flows out. In the aerobic tank 2, nitrification mainly proceeds. In the anaerobic tank 1, denitrification mainly progresses, and nitrification also progresses at the same time. A part of the waste water flowing out from the aerobic tank 2 is sent back (supplied) to the anaerobic tank 1 through the return channel 9 by a pump (not shown) or the like (see FIG. 3). Hereinafter, the treated water returned to the anaerobic tank 1 through the return channel 9 is referred to as a nitrified liquid.

The anaerobic tank 1 is a tank in which waste water is kept in an anaerobic environment (environment lacking dissolved oxygen). In the anaerobic tank 1, denitrification is mainly performed, and nitrification is also performed at the same time. As shown in FIG. 1, an oxygen permeable part 3 having an oxygen permeable membrane 30 is immersed in the anaerobic tank 1 .

In the anaerobic tank 1 , oxygen is supplied to the wastewater through the oxygen permeable membrane 30 , and nitrification proceeds near the surface of the oxygen permeable membrane 30 . A region other than the surface vicinity of the oxygen permeable membrane 30 in the anaerobic tank 1 is kept in an anaerobic environment, and denitrification proceeds by denitrifying bacteria. Details of nitrification in the oxygen permeable portion 3 and the oxygen permeable membrane 30 will be described later together with details of the oxygen permeable portion 3 .

The anaerobic tank 1 has, for example, a maximum water depth (distance along the vertical direction V from the water surface to the deepest bottom surface of the tank, hereinafter referred to as water depth d1) of about 0.3 m to 5 m, which is deeper than the aerobic tank 2. It is a shallow tank. The water depth d1 of the anaerobic tank 1 is set to be less than 50% of the water depth d2, which is the maximum water depth of the aerobic tank 2, which will be described later. In this embodiment, the water depth d1 of the anaerobic tank 1 is 0.5 m.

The aerobic tank 2 is a tank in which waste water is kept in an aerobic environment (environment rich in dissolved oxygen). In the aerobic tank 2, as shown in FIG. 1, a bubble generator 6 is immersed. In the aerobic tank 2, air is supplied (diffused) by bubbling from the air bubble generator 6, and oxygen is supplied to the waste water by dissolution of oxygen from the air bubbles B (so-called aeration). Thereby, the aerobic tank 2 is kept in an aerobic environment. In the aerobic tank 2 , nitrification proceeds using oxygen supplied from the air bubble generator 6 . The aerobic tank 2 is deeper than the anaerobic tank 1, with a maximum depth of about 3 m to 10 m, for example. The maximum water depth d2 of the aerobic tank 2 (treatment tank R) in this embodiment is 5 m. The details of the bubble generator 6 will be described later. A portion of the waste water discharged from the aerobic tank 2 to the final sedimentation tank 99 or a portion of the waste water aerobically treated in the aerobic tank 2 is returned to the anaerobic tank 1 as nitrified liquid (see FIG. 3).

The final sedimentation tank 99 is a sedimentation tank that receives the wastewater discharged from the aerobic tank 2 (treatment tank R) and settles activated sludge and the like in the wastewater. In this embodiment, the sludge settled in the final sedimentation tank 99 is returned to the anaerobic tank 1 through the return flow path 9 (see FIG. 3).

The bubble generator 6 is an air diffuser that supplies the supplied air to the wastewater of the aerobic tank 2 by bubbling. The bubble generator 6 is fixed to the bottom of the aerobic tank 2, which has a water depth of, for example, 5 m. The air bubble generator 6 has an air diffusion pipe (not shown) provided with a plurality of holes as an air diffusion mechanism for blowing out the supplied air. The air bubble generator 6 supplies air at a predetermined blowing pressure from a blower 76 such as a fan or a blower through a blowing pipe 76a.

The bubble generator 6 in this embodiment is immersed in a water depth of 5 m. Therefore, air having a static pressure of, for example, 60 kPa is supplied from the blower 76 in order to supply sufficient air (oxygen) against the water pressure to sufficiently advance the nitrification in the aerobic tank 2 . In this case, a blower is used as the air blower 76 .

The oxygen permeable part 3 is a device that supplies oxygen contained in the supplied air to wastewater through an oxygen permeable membrane 30 . The oxygen permeable part 3 is immersed in the anaerobic tank 1 . The oxygen permeation section 3 has a permeation unit 33 having an oxygen permeation membrane 30 and a pair of manifolds 35 serving as distribution channels for supplying air to and discharging air from the permeation unit 33 . In this embodiment, the permeation unit 33 and the pair of manifolds 35 are entirely immersed in the anaerobic tank 1 .

As shown in FIG. 4, the permeation unit 33 has a base material 32 and a cylindrical portion 31 in which the oxygen permeable membrane 30 is formed in a hollow fiber shape (an elongated cylindrical shape). The transmission unit 33 is formed by bundling a plurality of cylindrical portions 31 on the surface of the substrate 32 to form a linear rod-shaped unit as shown in FIGS. 1 and 2 . One end of each cylindrical portion 31 is connected to the manifold 35 on the air supply side, and the other end is connected to the manifold 35 on the exhaust side.

As shown in FIGS. 1 and 2, the oxygen permeable portion 3 is supplied with air at a predetermined pressure from a blower 73 such as a fan or a blower through a blower pipe 73a connected to the manifold 35 on the air supply side. The oxygen contained in the supplied air is supplied from the oxygen permeable membrane 30 to the waste water. The manifold 35 on the exhaust side is open to the outside through an exhaust pipe 73b, and the air that has passed through the cylindrical portion 31 is released to the outside.

As shown in FIG. 5, the oxygen-permeable membrane 30 formed as the tubular portion 31 permeates oxygen (O ₂ ) contained in the air (gas G in FIG. 6) flowing through the inside of the tubular portion 31. It is a membrane material with oxygen permeation ability, which is supplied to the wastewater outside the cylinder.

A biofilm L is formed on the surface of the oxygen permeable membrane 30, as shown in FIGS. The biofilm L in the present embodiment, as shown in FIG. and a second biofilm Lb that grows on the outer surface side and mainly contains denitrifying bacteria.

In the first biofilm La, the nitrifying bacteria oxidize (nitrify) nitrogen components (for example, NH ₄ ⁺ ) in the wastewater with oxygen (O ₂ ) supplied from the oxygen permeable membrane 30 to produce nitrate nitrogen (NO _x ⁻ ). In the first biofilm La, the oxygen supplied from the oxygen permeable membrane 30 is exhausted. In addition, in the anaerobic tank 1, part of the nitrogen component in the waste water is nitrified by the first biofilm La.

In this embodiment, as described above, nitrification can be performed by the aerobic tank 2 and the first biofilm La in the anaerobic tank 1. can be made compact. Thereby, the treatment tank R and the entire waste water treatment system 100 can be made compact.

In the second biofilm Lb and the area outside the second biofilm Lb (in the wastewater other than the oxygen permeable part 3 of the anaerobic tank 1 and the biofilm L), denitrifying bacteria convert nitric acid using organic matter (BOD) in the wastewater as a nutrient source. Nitrogen (NO _x ⁻ ) is reduced (denitrified) to release nitrogen (N ₂ ). The nitrate nitrogen denitrified in the anaerobic tank 1 is both produced by the first biofilm La and contained in the nitrified liquid returned from the aerobic tank 2 to the anaerobic tank 1. . In the anaerobic tank 1, 70%, for example, of all the nitrogen components that flowed into the anaerobic tank 1 (treatment tank R) are reduced (denitrified) to nitrogen. Nitrate nitrogen that has not been denitrified in the anaerobic tank 1 flows out of the treatment tank R via the aerobic tank 2 .

In addition, when the biofilm L grows excessively (when the film thickness becomes too thick), the supply of nitrate nitrogen to the inside of the film (the region where oxygen can be supplied from the oxygen permeable film 30) is inhibited, and the biofilm L becomes efficient. Nitrification may not proceed to Therefore, the oxygen permeable part 3 and the anaerobic tank 1 may be provided with a mechanism (not shown, hereinafter referred to as a “dropping mechanism”) for dropping the excessively grown biofilm L from the oxygen permeable membrane 30 . Examples of the dropping mechanism include a mechanism that generates a water flow near the permeation unit 33 or shakes the permeation unit 33 (shaking).

In this embodiment, the water depth d1 of the anaerobic tank 1 is 0.5 m, and the oxygen permeable part 3 is merely immersed in a water depth of less than 0.5 m. In this embodiment, the water depth d3 (see FIG. 1) from the water surface to the lower end of the tubular portion 31 is 0.3 m. Therefore, the static pressure of the air required to be supplied to the tubular portion 31 is less than 10 kPa at the most, even when water intrusion into the membrane due to breakage of the oxygen permeable membrane 30 is considered. Therefore, it is sufficient to use a fan as the air blower 76 . From these, the power required for air supply can be reduced. Moreover, it is possible to reduce the system cost by adopting an inexpensive blower (for example, a fan) as the blower 76 .

The permeation unit 33 is immersed (arranged) in the wastewater of the anaerobic tank 1 with the tubular portion 31 facing sideways along the water surface (horizontal surface). As a result, when increasing the area of the oxygen permeable membrane 30, it is possible to avoid increasing the depth of water in which the tubular portion 31 is installed (the depth of water in which the cylindrical portion 31 is immersed). As a result, even if the area of the oxygen permeable membrane 30 is increased, there is no need to increase the static pressure of the air required to be supplied to the cylindrical portion 31, thereby saving energy.

Further, the permeation unit 33 is merely immersed in a position where the tubular portion 31 is oriented sideways along the water surface (horizontal surface) and is shallow at a water depth of about d3. Therefore, for example, even when a dropping mechanism for directly shaking the permeation unit 33 is provided in the permeation unit 33, it is not always necessary to dispose the dropping mechanism in the anaerobic tank 1 (during drainage). 1 (above the water surface, outside the drainage), and only a part of the coupling mechanism for shaking is connected to the permeation unit 33 through the drainage. Also, in the case of a drop-off mechanism that indirectly shakes the permeation unit 33 by water flow or the like, it is possible to dispose all of them outside the anaerobic tank 1 . By arranging the drop-off mechanism outside the anaerobic tank 1, maintenance is improved, which is preferable.

[Second embodiment]
In the first embodiment, as shown in FIGS. 1 and 2, the case where the treatment tank R has the anaerobic tank 1 and the aerobic tank 2 downstream of the anaerobic tank 1 has been described. In this embodiment, instead of this, as shown in FIG. 7, the processing tank R is a single tank partitioned (up and down) in the vertical direction V by partition walls D, and the other configurations are the same. .

At least a part of the treatment tank R is partitioned in the vertical direction V by the partition wall D, and the first area 1A on the water surface side (another example of the anaerobic treatment section) and the second area 2A on the bottom side (aerobic treatment Another example of the department) and is divided into. A water depth d4, which is the maximum water depth from the water surface to the partition wall D, is set to about 0.3 m to 5 m, like the water depth d1 of the anaerobic tank 1 in the first embodiment. In this embodiment, the water depth d4 is 0.5 m. The maximum water depth from the water surface to the partition wall D is the distance from the water surface to the upper surface of the partition wall D at the deepest position. The water depth d4 is preferably set to less than 50% of the water depth d2, which is the maximum water depth of the treatment tank R, similarly to the water depth d1.

2 A of 2nd area|regions respond|correspond to the aerobic tank 2 of 1st embodiment, and are the area|regions mainly kept by the aerobic environment. 2 A of 2nd area|regions are immersed with the bubble generation part 6 like the aerobic tank 2 of 1st embodiment. The second region 2A is supplied with oxygen by the air bubble generator 6 and is mainly maintained in an aerobic environment, where nitrification by nitrifying bacteria proceeds.

In this embodiment, it is preferable to immerse the bubble generating part 6 in a deep water depth of 50% or more of the water depth d2, which is the maximum water depth of the treatment bath R. As a result, the oxygen contained in the bubbles B supplied from the bubble generating section 6 is consumed mainly by nitrification before reaching the water surface of the treatment tank R. Therefore, a shallow water depth area of less than 50% of the water depth d2, which is the maximum water depth in the treatment tank R, is kept anaerobic, especially the first area 1A.

The first area 1A corresponds to the anaerobic tank 1 of the first embodiment, and is an area maintained in an anaerobic environment as described above. The oxygen permeable part 3 is immersed in the first region 1A, like the anaerobic tank 1 of the first embodiment. In the first region 1A, denitrification in the second biofilm Lb in the first region 1A and the region outside the second biofilm Lb, and nitrification in the second biofilm La in the second region 2A and the first region 1A progresses.

In this embodiment, the oxygen permeable part 3, the partition wall D, and the air bubble generator 6 are arranged in this order from the water surface toward the bottom of the treatment tank R. are arranged so as to overlap in the As a result, the supply of the bubbles B rising from the bubble generating portion 6 to the vicinity of the oxygen permeable portion 3 is blocked. That is, the first region 1A is a region where the supply of the air bubbles B from the air bubble generator 6 is blocked by the partition wall D in this way.

The processing tank R is agitated by the upward flow of the air bubbles B generated by the air bubble generator 6 . Due to this agitation, the waste water newly flowing in from the primary sedimentation tank 91, the waste water in the first area 1A, and the waste water in the second area 2A circulate between the first area 1A and the second area 2A. Due to this circulation, the nitrate nitrogen nitrified in the second area 2A is supplied to the first area 1A and denitrified. Since the oxygen dissolved in the waste water in the second area 2A is exhausted by nitrification, the waste water flowing from the second area 2A into the first area 1A is anaerobic. The air bubble generator 6 may be provided with a stirrer (not shown) to promote circulation of the waste water.

In this embodiment, the lower surface of the oxygen permeable portion 3 is arranged against the flow of the air bubbles B rising from the air bubble generating portion 6 so that the air bubbles B rising from the air bubble generating portion 6 do not come into contact with the cylindrical portion 31 of the oxygen permeable portion 3 . A partition wall D is arranged so as to cover the sides. As a result, the air bubbles B rising from the air bubble generating portion 6 come into contact with the cylindrical portion 31, and the biofilm L on the surface of the oxygen permeable membrane 30 is detached, and the nitrification of the biofilm L in the first biofilm La is inhibited. prevent As a result, the efficiency of nitrification in the first region 1A can be maintained at a high level.

As described above, an energy-saving and compact wastewater treatment system can be provided.

[Another embodiment]
(1) In the above embodiment, the case where the transmission unit 33 is immersed in the drainage with the tubular portion 31 lying sideways along the water surface (horizontal surface) has been described. However, the cylindrical portion 31 is not limited to be oriented horizontally. As shown in FIG. 8, the cylindrical portion 31 may be immersed in the waste water while being vertically oriented along the vertical direction V. As shown in FIG. FIG. 8 illustrates the case where the tubular portion 31 is immersed in the anaerobic tank 1 vertically, but the same applies to the case where the tubular portion 31 is immersed in the first region 1A.

(2) In the above first embodiment, the processing tank R has one anaerobic tank 1 and one aerobic tank 2 connected in series downstream of the anaerobic tank 1 . However, the anaerobic tank 1 may be multiple tanks. For example, as shown in FIG. 9, the anaerobic tank 1 may be composed of, for example, three tanks 11, 12 and 13, and these tanks 11, 12 and 13 may be connected in series in this order from upstream. In this case, if the tanks 11, 12, 13 are arranged so as to overlap in the vertical direction V, the anaerobic tank 1 can be formed compactly, which is preferable. Since the water depth of the anaerobic tank 1 (tanks 11, 12, 13) is shallower than that of the aerobic tank 2, for example, instead of constructing one deep tank, the tanks 11, 12, 13 are stacked in the vertical direction V. can be arranged as As a result, the anaerobic tank 1 can be made compact.

(3) In the above embodiment, the oxygen permeable part 3 is immersed in the anaerobic tank 1, and the permeation unit 33 and the manifold 35 are entirely immersed in the anaerobic tank 1. However, the oxygen permeable part 3 is not limited to being entirely immersed in the anaerobic tank 1 . For example, at least a pair of manifolds 35 and air inlets and outlets of the tubular portions 31 of the permeation unit 33 connected thereto may be arranged above the water surface. By doing so, even if the oxygen-permeable membrane 30 of the cylindrical portion 31 is torn (broken), water is less likely to enter the cylindrical portion 31, which is preferable.

(4) In the above-described first embodiment, the case where the oxygen permeable part 3 is immersed in the waste water stored in the anaerobic tank 1 has been described, but the present invention is not limited to this. The oxygen permeable part 3 may be immersed in the wastewater from the anaerobic tank 1 to the aerobic tank 2 .

It should be noted that the configurations disclosed in the above embodiments (including other embodiments, the same shall apply hereinafter) can be applied in combination with configurations disclosed in other embodiments as long as there is no contradiction. The embodiments disclosed in this specification are exemplifications, and the embodiments of the present invention are not limited thereto, and can be modified as appropriate without departing from the object of the present invention.

INDUSTRIAL APPLICABILITY The present invention can be applied to wastewater treatment systems introduced into sewage treatment plants and the like. Moreover, it can be applied not only to sewage treatment plants but also to industrial wastewater treatment.

1: Anaerobic tank (first tank, anaerobic treatment section)
1A: First region (anaerobic treatment section)
2: Aerobic tank (second tank, aerobic treatment section)
2A: Second area (aerobic treatment section)
3: Oxygen permeation part 6: Air bubble generation part 30: Oxygen permeation membrane 31: Cylindrical part 33: Permeation unit 73: Air blower 76: Air blower 100: Wastewater treatment system B: Bubbles L: Biofilm R: Treatment tank V: Vertical direction

Claims (5)

Equipped with a treatment tank for storing the water to be treated,
The treatment tank is
an anaerobic treatment unit that performs anaerobic treatment on the water to be treated;
an aerobic treatment unit that is connected to the anaerobic treatment unit and performs aerobic treatment on the water to be treated;
The aerobic treatment unit has a bubble generation unit that generates bubbles,
The anaerobic treatment section has an oxygen permeable section including an oxygen permeable membrane that allows oxygen to permeate,
A waste water treatment system in which all of the oxygen permeable parts are immersed in a water depth of less than 50% of the maximum water depth of the water to be treated in the aerobic treatment part. The oxygen permeation part has a permeation unit including a plurality of cylindrical parts in which the oxygen permeable membrane is formed in a cylindrical shape,
The waste water treatment system according to claim 1, wherein the permeation unit is immersed along the water surface of the water to be treated. The waste water treatment system according to claim 1 or 2, wherein the anaerobic treatment section and the aerobic treatment section are arranged so as to be partitioned by the same treatment tank. The processing tank has a first tank and a second tank arranged downstream of the first tank,
The oxygen permeable part is immersed in the first tank,
The waste water treatment system according to any one of claims 1 to 3, wherein the bubble generating section is immersed in the second tank. The waste water treatment system according to any one of claims 1 to 4, wherein the water depth of the anaerobic treatment section is 0.5 m or less.

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