JPH11128926A - Sewage treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove phosphoric acid in an activated sludge mixed liquid effectively. SOLUTION: A sewage treatment apparatus 1 is equipped with an activated sludge tank 2 for storing activated sludge, a filter membrane device, an ion elution device, and an aeration device 6. The filter membrane device is equipped with a casing 10 and suspended filter membrane plates 11. A flat membrane is attached to one side of each plate 11, and an activated sludge mixed liquid is separated into activated sludge and filtrate. The ion elution device is equipped with electrodes each of which is bonded to the other side of the plate 11 and a direct current power source for passing the current between the adjoining two electrodes. Iron is used for both anode and cathode to elute ion ions for removing phosphoric acid by electrolysis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sewage treatment apparatus, and more particularly, it is used for treating sewage such as human wastewater or domestic wastewater, and decomposes organic matter and nitrogen in sewage by the action of activated sludge. The present invention relates to a sewage treatment apparatus which removes and removes a solid, and performs a solid-liquid separation by filtration, so that the activated sludge remains and the filtrate is allowed to flow out.

[0002]

2. Description of the Related Art Conventionally, this type of sewage treatment apparatus
2. Description of the Related Art There is known an activated sludge tank for performing an activated sludge treatment on sewage, and a filtration membrane device for solid-liquid separation of a mixed liquid of activated sludge and sewage in the activated sludge tank by filtration. .

[0003] In such a sewage treatment apparatus, the filtration membrane device is provided with a plurality of filtration membrane plates having fine holes.
The activated sludge mixture is filtered through these filtration membrane plates to purify sewage.

[0004]

According to such a sewage treatment apparatus, the BOD (biochemical oxygen demand) component in the activated sludge mixture can be removed because it is filtered by the filtration membrane plate. There is a problem that the phosphorus component (phosphoric acid) in the mixed solution cannot be removed because it passes through the filtration membrane plate.

[0005] The present invention has been made in view of such circumstances, and comprises an activated sludge tank and a filtration membrane device, and can effectively remove phosphoric acid in an activated sludge mixed solution. It is an object to provide a sewage treatment device.

[0006]

According to the present invention, an activated sludge tank for performing an activated sludge treatment on sewage, and a mixed liquid of the activated sludge and the sewage in the activated sludge tank is subjected to solid-liquid separation by filtration. A filtration membrane device for, and an ion elution device for eluting iron ions or aluminum ions for removing phosphoric acid in the mixed solution in the activated sludge tank,
Provided is a sewage treatment apparatus characterized in that an ion elution surface of an ion elution device is provided on a part of a filtration surface of a filtration membrane device.

[0007] The activated sludge tank is for performing activated sludge treatment on wastewater. That is, it is a tank for decomposing and removing organic matter and nitrogen content in the sewage by the action of the activated sludge put in the tank.

[0008] The filtration membrane device filters an activated sludge mixture (a mixture of activated sludge and sewage) in a tank through a filtration surface to separate the mixture into an activated sludge and a filtrate. The activated sludge remains in the tank, and the filtrate is led out of the tank.

The ion eluting device is disposed at a predetermined position of the sewage treatment device, and the ion eluting surface is provided on a part of the filtration surface of the filtration membrane device. Then, iron ions or aluminum ions for removing phosphoric acid in the mixed solution in the activated sludge tank are eluted from the ion elution surface.

The iron ions or aluminum ions are eluted into the mixed solution by, for example, electrolyzing the mixed solution using an eluting electrode made of iron or aluminum provided on a part of the filtration surface of the filtration membrane device. I do. The elution amount of these ions is controlled by, for example, adjusting the area and weight of the eluting electrode, or controlling the current supplied from the electrolytic power supply.

The eluted iron ions or aluminum ions react with phosphate ions (orthophosphate ions) in the sewage to form a poorly soluble phosphorus compound (Fe (OH) _x (P
O ₄ ) _y or Al (OH) _x (PO ₄ ) _y ) are aggregated and precipitated.

The sewage treatment apparatus according to the present invention is further provided with an aeration device, and the aeration device cleans these surfaces by applying aeration to the filtration surface of the filtration membrane device and the ion elution surface of the ion elution device. It is preferable that the piping is provided.
If such an aeration device is provided, it is possible to wash not only the filtration surface but also the ion elution surface.

[0013] As the filtration membrane device, for example, a casing in the shape of a tube or a box frame opening vertically, a plurality of filtration membrane plates or one filtration membrane body having a hollow portion and arranged inside the casing. And a suction head attached to the upper end portion of the filtration membrane plate or the filtration membrane body and communicating with the hollow portion thereof, and a suction pump outside the tank connected to the suction head are preferably used. .

The filtration membrane plate or the filtration membrane of such a filtration membrane device is detachably provided in the activated sludge tank. More preferably, the filtration membrane plate or the filtration membrane body is provided at a position where it comes into contact with the aeration air supplied by the aeration device. This is because the aeration air can effectively clean the membrane surface, which is the filtration surface.

As the aeration device, for example, an air supply blower provided outside the activated sludge tank, an air supply pipe connected to the blower and extending into the tank, and an air supply pipe connected to the air supply pipe and disposed at the bottom of the tank. A device provided with an aeration tube is preferably used.

[0016] The ion eluting device includes, for example, at least one pair of eluting electrodes provided opposite to each other on the filtration surfaces of two adjacent filtration membrane plates, and a power supply for supplying a current to these electrodes. Are preferably used.

Here, as the pair of eluting electrodes, for example, those having a plate shape, a rod shape or other shapes are preferably used.

The pair of eluting electrodes are, for example, both composed of one of iron and aluminum, or one composed of one of iron and aluminum and the other composed of an insoluble metal. In the former case, by inverting the polarity of the electrode as desired, it is possible to prevent passivation of the electrode where ion elution from the electrode does not occur. In the latter case, an electrode made of one of iron and aluminum is used as an anode, and an electrode made of an insoluble metal is used as a cathode. Here, as an electrode made of an insoluble metal, for example, there is an electrode such as silver or platinum.

The aeration tube is, for example, arranged substantially horizontally below the membrane plate (or membrane body) and the electrodes in the casing.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Four embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited by these.

Embodiment 1 As shown in FIGS. 1 and 2, a sewage treatment apparatus 1 according to one embodiment of the present invention comprises an activated sludge tank 2, a filtration membrane device 3, an ion elution device 4, It has.

The activated sludge tank 2 flows from an inflow pipe 5.
It is for applying activated sludge treatment to wastewater mixed with human wastewater and domestic wastewater, and is provided with an aeration device 6. The aeration device 6 includes an air supply blower 7 provided outside the tank, an air supply pipe 8 connected to the blower 7 and extending into the tank, and an aeration pipe 9 connected to the air supply pipe 8 and arranged at the bottom of the tank. It is composed of

The activated sludge tank 2 contains activated sludge. The activated sludge mixes with the incoming sewage to form an activated sludge mixture.

The filtration membrane device 3 comprises a rectangular tubular casing 10 which is open vertically, a plurality of filtration membrane plates 11 suspended and arranged substantially parallel to each other inside the casing 10 and having a hollow portion, and these filtration membrane plates. The suction header 12 is attached across the upper ends of the plates 11 and communicates with the hollow portions of the respective filtration membrane plates 11, and a suction pump 13 outside the tank connected to the suction header 12.

Each of the filtration membrane plates 11 is shown in FIGS.
As shown in the figure, the frame 16 is composed of a frame 16 and a flat membrane 17 attached to one side surface (part of the filtration surface) of the frame 16, and the activated sludge mixed liquid in the activated sludge tank 2 is activated sludge. And a filtrate. The pore size of the membrane of the filtration membrane plate 11 is set to about 0.05 to 1.0 μm. The filtrate that has passed through the flat membrane 17 of the filtration membrane plate 11 is collected by the suction header 12 through the inside of the frame 16 by the operation of the suction pump 13, and flows out of the activated sludge tank 2 through the outflow pipe 14.

The aeration tube 9 in the aeration device 6 has a blower 7
Aeration air is supplied to the inside of the activated sludge tank 2 through the air supply pipe 8 by the operation of.

As shown in FIGS. 3 and 4, the ion elution device 4 has a rectangular plate shape attached to the other side surface (part of the filtration surface) of the filtration membrane plate 11 in the activated sludge tank 2 with an adhesive. An electrode 15, a DC power supply (not shown) for supplying a current between the electrodes 15 (one is an anode and the other is a cathode) of two adjacent filtration membrane plates 11, and a lead wire 18 connecting each electrode 15 to the power supply And The electrode 15 uses iron for both the anode and the cathode, and elutes iron ions for removing phosphoric acid in the sewage in the activated sludge tank 2 by electrolysis.

When the sewage treatment apparatus 1 configured as described above is operated, the activated sludge tank 2 containing the activated sludge mixed liquid is operated.
As shown in FIG. 5, while iron ions Fe ²⁺ elute from one of two adjacent electrodes 15 (ion elution surface),
Oxygen is supplied into the mixture by the aeration tube 9.

Fe ²⁺ is oxidized using dissolved oxygen to form Fe ³⁺ , which reacts with orthophosphate ion PO ₄ ^3- to form a sparingly soluble iron phosphate Fe (OH) _x (PO ₄ ) It becomes _y . This iron phosphate salt Fe (OH) _x (PO ₄ ) _y is
Aggregation occurs using the SS component present in the same mixture as nuclei to form large flocs. At this time, the iron phosphate salt having a relatively small particle diameter immediately after the reaction rarely reaches the filtration surface of the flat membrane 17 of the filtration membrane plate 11 immediately, and after the particle diameter increases after a certain residence time. It often reaches the filtration surface of the flat membrane 17. Therefore, it is possible to avoid adverse effects on the filtration surface, such as partial blockage of the filtration surface by the iron phosphate salt.

The activated sludge mixed liquid in the floc and activated sludge tank 2 is separated into solid and liquid by a filtration membrane plate 11.
Phosphorus removal rate in through the filter membrane plate _{11 Fe (OH) x (PO} 4) y is largely removed filtrate was confirmed to be 90% or more.

The air for aeration that has flowed out of the aeration pipe 9 aerates the activated sludge mixture, and touches the flat membrane 17 of the filtration membrane plate 11 and the electrode 15 of the ion elution device 4 to contact the membrane surface and the electrode surface. Is washed. This makes it possible to wash not only the filtration surface but also the ion elution surface.

Further, since each filtration membrane plate 11 is provided with a flat membrane 17 on one side and an electrode 15 on the other side, the life of the flat membrane 17 and the electrode 15 is almost the same. Sewage treatment equipment 1
By replacing the filtration membrane plate 11 at the time of maintenance, the flat membrane 17 and the electrode 15 can be replaced at the same time.

Embodiment 2 As shown in FIGS. 6 and 7, a sewage treatment apparatus 21 according to another embodiment of the present invention has a
1 The sewage treatment apparatus 21 includes an activated sludge tank 108, a filtration membrane device 118, and an ion elution device 12 described later.
0.

The inside of the septic tank 101 is located at a side of an inflow pipe 102 into which sewage mixed with human wastewater and domestic wastewater flows.
A tank structure is formed in which a plurality of tanks are defined and formed in accordance with the order of the sewage purification process on the side of the discharge pipe 103 for discharging sewage treated water to the outside.

Reference numeral 104 denotes a first anaerobic filter tank formed at the forefront of the inflow pipe 102 side. This first anaerobic filter bed tank 1
In step 04, impurities that have been mixed in the human wastewater or domestic wastewater and cannot be purified are removed by sedimentation.

The first anaerobic filter bed tank 104 is provided with an anaerobic filter bed 105, which is a filter bed for anaerobic microorganisms. I have. The anaerobic filter bed 105 suppresses the load on the next tank by preventing the sediment from being lifted up by the water flow when the inflow water or backwash wastewater temporarily flows in and becoming a suspended substance and flowing out to the next tank. Can be lowered.

Reference numeral 106 denotes a next second anaerobic filter bed tank formed adjacent to the first anaerobic filter bed tank 104. In the second anaerobic filter bed tank 106, anaerobic microorganisms are made to inhabit the anaerobic filter bed 107 to perform anaerobic treatment. 1
Reference numeral 08 denotes a next activated sludge tank formed adjacent to the second anaerobic filter bed tank 106.

First anaerobic filter tank 104 and second anaerobic filter tank 1
06 is partitioned by a vertical partition wall 109. Above the partition wall 109, two advection ports 110 penetrating the partition wall 109 are formed. A rectangular or cylindrical advection tube 111 is fitted in these advection ports 110. The lower ends of these advection tubes 111 are located below the anaerobic filter bed 105 of the first anaerobic filter tank 104 and also serve as cleaning ports.

The second anaerobic filter bed tank 106 and the next activated sludge tank 1
08 is partitioned by an intermediate partition 112. Above the intermediate partition 112, there is an advection port 11 penetrating the partition 112.
An opening 3 is formed. A rectangular or cylindrical advection tube 114 is fitted into the advection port 113. The sewage that has been transferred from the first anaerobic filter tank 104 to the second anaerobic filter tank 106 through the convection pipe 111 is supplied to the anaerobic filter bed 1.
After passing through the downflow through the flow path 07, it is sent to the next activated sludge tank 108 through the advection pipe 114.

The anaerobic filter bed 107 provided in the second anaerobic filter tank 106 captures some suspended solids (SS). The trapped SS is gradually anaerobically decomposed and becomes soluble, or is stored as sludge at the bottom of the second anaerobic filter tank 106. In the anaerobic filter bed 107, organic nitrogen is anaerobically decomposed into ammonia nitrogen.

The activated sludge tank 108 includes the second anaerobic filter bed tank 10.
The aeration device 11 is for performing activated sludge treatment on wastewater mixed with human wastewater and domestic wastewater flowing in from 6.
5 is provided. The aeration apparatus 115 includes a blower 124 provided outside the tank, an air supply pipe 116 connected to the blower 124 and extending into the tank, and an aeration pipe 117 connected to the air supply pipe 116 and arranged at the bottom of the tank. It is configured.

The activated sludge tank 108 contains activated sludge. The activated sludge mixes with the incoming sewage to form an activated sludge mixture.

Inside the activated sludge tank 108, a filtration membrane device 118 for filtering the activated sludge mixed liquid is disposed. The configuration of the filtration membrane device 118 is the same as that of the first embodiment.

The filtrate obtained by the filtration membrane device 118 is provided above the activated sludge tank 108 and flows out to a disinfection tank 119. The disinfecting tank 119 is configured to disinfect the supernatant water that has been treated in the activated sludge tank 108 and discharge it from the discharge pipe 103 to the outside.

The aeration pipe 117 supplies aeration air to the inside of the activated sludge tank 108 through the air supply pipe 116 by the operation of the blower 124. This aeration air is used to aerate the activated sludge mixture and to filter the membrane plate 1 of the filtration membrane device 118.
The surface of the film is washed by touching 25.

The configuration of the ion elution device 120 is the same as that of the first embodiment.

In the activated sludge tank 108, the wastewater (activated sludge mixture) in the activated sludge tank 108 is further filled with the first anaerobic filter bed tank 1.
There are provided various members for returning to the area 04. That is, the activated sludge tank 108 is provided with the air lift pipe 121 vertically. The air lift pipe 121 is connected to a blower 122 via an air supply pipe 126 connected to a lower end thereof. Further, from the upper part of the activated sludge tank 108 to the upper part of the first anaerobic filter bed tank 104, the return pipe 123 is almost horizontally.
Is provided. Then, the mixed liquid in the activated sludge tank 108 pumped from the air lift pipe 121 is returned to the return pipe 1
23, and is returned to the first anaerobic filter bed tank 104.

When the septic tank 101 configured as described above is operated, in the activated sludge tank 108 in which the activated sludge mixed solution is present, the iron ion F
While e ²⁺ is dissolved, oxygen is supplied into the mixed solution by the aeration tube 117.

Fe ²⁺ is oxidized using dissolved oxygen to form Fe ³⁺ , which reacts with orthophosphoric acid PO ₄ ^3- to form a sparingly soluble iron phosphate Fe (OH) _x (PO ₄ ). becomes _y .
This iron phosphate salt Fe (OH) _x (PO ₄ ) _y aggregates with the SS component present in the mixture as a nucleus to form large flocs.

The activated sludge mixture in the floc and activated sludge tank 108 is separated into solid and liquid by the filtration membrane plate of the filtration membrane device 118. Fe (OH) _x
It was confirmed that the filtrate from which (PO ₄ ) _y was largely removed had a phosphorus removal rate of 90% or more.

Third Embodiment As shown in FIG. 8, a sewage treatment apparatus 31 according to still another embodiment of the present invention is a small-sized single treatment septic tank 301.
Is connected to the downstream side.

The septic tank 301 is the same as the septic tank 1 of the second embodiment.
The configuration is such that a filtration membrane device 118 and an ion elution device 120 are removed from 01, and a contact aeration tank is provided in place of the activated sludge tank 2. The human wastewater that has flowed into the septic tank 301 from the inflow pipe 302 is subjected to a predetermined treatment and purified, flows out of the connecting pipe 303, and then flows into the sewage treatment apparatus 31.

The configuration of the sewage treatment apparatus 31 is the same as that of the first embodiment. The domestic wastewater flowing into the sewage treatment apparatus 31 from the inflow pipe 32 is supplied to the sewage treatment apparatus 3 through the connection pipe 303.
1 treated wastewater and sewage treatment equipment 31 flowing into 1
And mixed with the activated sludge in the activated sludge tank in the above step to form an activated sludge mixture.

This mixture is subjected to the same processing (solid-liquid separation and electrolysis) as in the first embodiment. The purified water after the treatment is discharged through the outflow pipe 33.

Fourth Embodiment As shown in FIG. 9, a sewage treatment apparatus 41 according to still another embodiment of the present invention is a small-sized combined treatment / purification tank 401.
Is connected to the downstream side.

The septic tank 401 is the same as the septic tank 1 of the second embodiment.
The configuration is such that a filtration membrane device 118 and an ion elution device 120 are removed from 01, and a contact aeration tank is provided in place of the activated sludge tank 2. The human wastewater and domestic wastewater flowing into the septic tank 401 from the inflow pipe 402 is subjected to a predetermined treatment and purified, flows out of the connecting pipe 403, and then flows into the sewage treatment apparatus 41.

The configuration of the sewage treatment apparatus 41 is the same as that of the first embodiment. From the connection pipe 403 to the sewage treatment apparatus 41
Wastewater and domestic wastewater flowing into the sewage treatment device 41
And mixed with the activated sludge in the activated sludge tank in the above step to form an activated sludge mixture.

This liquid mixture is subjected to the same processing (solid-liquid separation and electrolysis) as in the first embodiment. The purified water after the treatment is discharged through the outflow pipe 43.

[0059]

According to the first aspect of the present invention, an activated sludge tank for performing an activated sludge treatment on sewage, and a solid-liquid separation of a mixed liquid of activated sludge and sewage in the activated sludge tank by filtration. A filtration membrane device, and an ion elution device for eluting iron ions or aluminum ions for removing phosphoric acid in the mixed solution in the activated sludge tank, and an ion elution device is provided on a part of the filtration surface of the filtration membrane device. Since the ion elution surface is provided, solid-liquid separation and phosphoric acid removal can be performed when performing sewage treatment using activated sludge, and the life of the filtration surface and the ion elution surface is almost the same. If it is configured to end, the filtration surface and the ion elution surface can be simultaneously replaced by replacing the filtration membrane device during maintenance of the sewage treatment device.

According to the second aspect of the present invention, an aeration device is further provided, and the aeration device cleans these surfaces by applying aeration to the filtration surface of the filtration membrane device and the ion elution surface of the ion elution device. It is plumbed. Therefore, in addition to the effect of the invention described in claim 1, it is possible to wash not only the filtration surface but also the ion elution surface.

According to the third aspect of the present invention, the filtration membrane device comprises:
A casing that opens vertically, a plurality of filtration membrane plates suspended and arranged substantially parallel to each other inside the casing and having a hollow portion, and each filtration membrane attached to an upper end of these filtration membrane plates and attached to each other. A suction header communicating with the hollow part of the plate and a suction pump outside the tank connected to the suction header are provided. Therefore, the effect achieved by the invention of claim 1 or 2 can be ensured by a filtration membrane device having a simple configuration.

According to the fourth aspect of the present invention, the aeration apparatus includes an air supply blower provided outside the activated sludge tank, an air supply pipe connected to the blower and extending into the tank, and an air supply pipe connected to the air supply pipe. And an aeration tube arranged at the bottom of the tank. Therefore, the effect achieved by the invention of claim 2 or 3 can be ensured by the aeration device having a simple configuration.

According to the fifth aspect of the present invention, the ion eluting device includes at least one pair of eluting electrodes provided on the filtration surfaces of two adjacent filtration membrane plates so as to face each other, and supplies a current to these electrodes. Power supply. Therefore, the effect of the invention of claim 3 or 4 can be ensured by an ion eluting device having a simple configuration. Furthermore, when iron ions eluted from one of two adjacent electrodes are oxidized and reacted with phosphate ions to become hardly soluble iron phosphate salts, the particle diameter is relatively small, Since the iron phosphate salt is less likely to immediately reach the filtration surface of the filtration membrane plate located on the back side of the electrode, avoid adverse effects on the filtration surface, such as partial blockage of the filtration surface by the iron phosphate salt. Can be.

According to the sixth aspect of the present invention, the aeration tube is disposed below the filter membrane plate and the electrode in the casing. Therefore, in addition to the effect achieved by the invention of claim 5,
The filtration membrane plate and the electrode can be washed together.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view of a sewage treatment apparatus according to Embodiment 1 of the present invention as viewed from a plane.

FIG. 2 is a configuration explanatory view of the inside of the sewage treatment apparatus of FIG. 1 as viewed from the front.

FIG. 3 is a plan sectional view of a filtration membrane plate which is one component of the sewage treatment apparatus of FIG.

FIG. 4 is a front sectional view of the filtration membrane plate of FIG. 3;

FIG. 5 is an enlarged configuration explanatory view of the inside of the sewage treatment apparatus of FIG. 1 as viewed from the front.

FIG. 6 is a configuration explanatory view of the inside of a small-sized combined treatment septic tank incorporating a sewage treatment apparatus according to Embodiment 2 of the present invention as viewed from the front.

FIG. 7 is a configuration explanatory view of the inside of the septic tank of FIG. 6 as viewed from above.

FIG. 8 is a block diagram showing a connection state between a sewage treatment apparatus according to Embodiment 3 of the present invention and a small-sized single treatment septic tank.

FIG. 9 is a block diagram showing a connection state between a sewage treatment apparatus and a small-sized combined treatment / purification tank according to Embodiment 4 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sewage treatment apparatus 2 Activated sludge tank 3 Filtration membrane apparatus 4 Ion elution apparatus 6 Aeration apparatus 7 Blower 8 Air supply pipe 9 Aeration pipe 10 Casing 11 Filtration membrane plate 12 Suction header 13 Suction pump 15 Electrode 16 Frame 17 Flat membrane 18 Lead wire Reference Signs List 21 sewage treatment device 31 sewage treatment device 41 sewage treatment device 108 activated sludge tank 115 aeration device 116 air supply pipe 117 aeration pipe 118 filtration membrane device 120 ion elution device 124 blower 125 filtration membrane plate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 3/00 C02F 3/12 A 3/12 1/46 102

Claims (6)

[Claims] An activated sludge tank for performing an activated sludge treatment on sewage, a filtration membrane device for solid-liquid separation of a mixed liquid of activated sludge and sewage in the activated sludge tank by filtration,
An ion elution device for eluting iron ions or aluminum ions for removing phosphoric acid in the mixed solution in the activated sludge tank, and an ion elution surface of the ion elution device is provided on a part of the filtration surface of the filtration membrane device. A sewage treatment apparatus characterized by being obtained. 2. The apparatus according to claim 1, further comprising an aeration device, wherein the aeration device is piped to clean the filtration surface of the filtration membrane device and the ion elution surface of the ion elution device by applying aeration to the surfaces. 2. The sewage treatment apparatus according to 1. 3. A filtration membrane device comprising: a casing which is opened vertically, a plurality of filtration membrane plates suspended and arranged substantially parallel to each other inside the casing and having a hollow portion, and upper end portions of these filtration membrane plates 3. The sewage treatment apparatus according to claim 1, further comprising: a suction header attached to each other and communicating with a hollow portion of each filtration membrane plate; and a suction pump outside the tank connected to the suction header. 4. An aeration apparatus, comprising: an air supply blower provided outside the activated sludge tank; an air supply pipe connected to the blower and extending into the tank; and an air supply pipe connected to the air supply pipe and arranged at the bottom of the tank. 4. The sewage treatment apparatus according to claim 2, further comprising an aeration tube. 5. An ion eluting device comprising: at least one pair of eluting electrodes provided on a filtration surface of two adjacent filtration membrane plates so as to face each other; and a power supply for supplying a current to these electrodes. The sewage treatment apparatus according to claim 3 or 4. 6. The sewage treatment apparatus according to claim 5, wherein the aeration pipe is disposed below the filter membrane plate and the electrode in the casing.