JP2000051894A - Sewage treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sewage treatment apparatus capable of removing both of phosphoric acid and nitrogen. SOLUTION: A sewage treatment apparatus is equipped with a sewage housing tank, electrodes 2 and 3, a DC power supply and a control part. The electrodes 2 and 3 comprise rectangular iron plates to elute iron ions removing phosphoric acid in sewage by electrolysis. The lower half parts of the electrodes 2 and 3 are covered with carriers 9, 10 comprising porous reticulated members made of a polypropylene resin. The carriers 9 and 10 allow microorganisms participated in denitrification reaction to live in sewage. When the control part reverses the polarities of the electrodes 2 and 3, phosphoric acid is removed by the flocculation reaction of iron ions and phosphate ions in sewage on the side of the electrodes 2 and 3 becoming anodic in polarity. Further, on the side of the electrodes 2 and 3 becoming cathodic in polarity, nitrogen is removed by denitrification reaction based on the microorganisms on the carriers 9 and 10.

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, to a method for reacting phosphoric acid contained in sewage such as human wastewater or domestic wastewater with metal ions eluted by electrolysis to remove precipitates. The present invention relates to a sewage treatment apparatus.

[0002]

2. Description of the Related Art Conventionally, this type of sewage treatment apparatus has
The following are known.

That is, a sewage storage tank for storing sewage to be treated is provided, and one or more electrodes made of a water-insoluble phosphate-forming metal are arranged in the tank, and a current is supplied to these electrodes. This is an apparatus in which phosphoric acid forming a water-insoluble salt is electrochemically eluted into sewage water to convert phosphoric acid into a water-insoluble salt for precipitation and removal.

[0004]

In such a sewage treatment apparatus, phosphoric acid can be removed by causing an agglutination reaction between water-insoluble phosphate-forming metal ions eluted from the electrode and phosphate ions in the sewage. However, there is a problem that nitrogen in wastewater cannot be removed.

[0005] The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a sewage treatment apparatus capable of performing both phosphoric acid removal and nitrogen removal.

[0006]

According to the present invention, a sewage storage tank and at least a part of the sewage stored in the sewage storage tank are arranged so as to be immersed therein, and phosphoric acid in the sewage is removed by precipitation. At least one set of electrodes for eluting iron ions or aluminum ions by electrolysis, a power supply for supplying a current for electrolysis to these electrodes, and a control unit for controlling the power supply. At least a part of the electrode is covered with a carrier for inhabiting microorganisms involved in the denitrification reaction in the sewage, and the polarity is changed to the anode by the control unit periodically inverting the polarity of the electrode. A sewage treatment apparatus is provided, wherein phosphoric acid is removed on the electrode side, and nitrogen is removed on the electrode side having a polarity as a cathode by a denitrification reaction based on microorganisms in the carrier.

[0007] The sewage treatment tank stores sewage to be subjected to electrolysis treatment. For example, at least one set of electrodes having a rectangular plate shape is disposed, and iron ions or aluminum ions are eluted into the sewage treatment tank by electrolysis. The power supply
A current for electrolysis is supplied to these electrodes. The control unit controls the electrolysis by controlling the power supply.

[0008] The set of electrodes is, for example, both composed of one of iron and aluminum, or one composed of one of iron and aluminum and the other composed of a water-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 a water-insoluble metal is used as a cathode.

Here, as an electrode composed of a water-insoluble metal, for example, there is an electrode such as silver or platinum. Further, it is preferable that the distance between the pair of electrodes is kept constant by, for example, an electrically insulating spacer having a handle.

The iron ions or aluminum ions eluted in the sewage treatment tank are converted to phosphoric acid (orthophosphoric acid) in the sewage.
And react with the water-insoluble phosphorus compound (Fe (OH) _x (P
O ₄ ) _y or Al (OH) _x (PO ₄ ) _y ) is aggregated and precipitated in the sewage treatment tank.

[0011] At least a part of each electrode-a part to be immersed in sewage-is covered with a carrier. This carrier is for inhabiting microorganisms involved in the denitrification reaction in sewage such as denitrifying bacteria which are a kind of anaerobic microorganisms.

[0012] The material of the carrier is not particularly limited as long as microorganisms involved in the denitrification reaction inhabit the wastewater. For example, a porous network made of plastic, carbon fiber, or sintered ceramic is used.

The carrier is, for example, suspended from the upper edge of each electrode, or placed on the bottom surface of an electrode case for accommodating a set of electrodes, and disposed so as to cover at least a part of each electrode. You.

[0014] The control unit is, for example, 30 minutes to 10 days (more preferably 1 hour to 7 days, more preferably 2 days to
Once every seven days), the polarity of the electrode is periodically inverted. Then, phosphoric acid is removed by an agglutination reaction between iron ions or aluminum ions and phosphate ions in the sewage on the electrode side having the polarity of the anode. In addition, nitrogen is removed by a denitrification reaction based on microorganisms in the carrier-a reaction in which nitrate ions and nitrite ions in sewage are reduced to nitrogen gas-on the electrode side whose polarity is a cathode.

The sewage treatment apparatus according to the present invention is preferably
A partition plate for separating one set of electrodes into an anode side and a cathode side, and an aeration device for applying aeration to each electrode, further comprising a control unit for controlling the aeration device,
It is configured to aerate only the electrode whose polarity is the anode.

In such a configuration, only the anode electrode is aerated by an aerator to promote the phosphoric acid removal reaction on the anode side and to clean the electrode, while the cathode side electrode is cleaned. Can be placed in a reducing atmosphere.

The partition plate is made of, for example, a ceramic or an ion-exchange membrane, in which only ions are moved through the partition plate, or made of a plastic that does not allow the passage of ions, and the ion is passed through the lower portion of the partition plate. And the like are moved.

Further, the aeration device is provided, for example, with an air supply blower provided outside the sewage storage 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. And an aeration tube.

The wastewater treatment apparatus according to the present invention is preferably
An inlet pipe for introducing sewage into the sewage storage tank is further provided, and a partition plate in the sewage storage tank allows sewage from the inlet pipe to flow into the sewage storage tank through one end of the partition plate, and one side or the other side of the partition plate. Along the other end, and then around the other end to flow out through one end along the other side or one side, between the introduction pipe and the sewage storage tank, the sewage from the introduction pipe There is further provided a flow path switching valve for switching so as to guide along one of the one side surface and the other side surface of the partition plate, and the control unit further controls the flow path switching valve to polarize sewage from the introduction pipe. Is configured to first flow into the side surface of the partition plate having the cathode electrode.

In such a configuration, the control unit controls the flow path switching valve to remove sewage from the introduction pipe.
First, it is made to flow toward the side of the partition plate having the electrode whose polarity is the cathode. Then, the inflowing sewage goes around the other end of the partition plate and proceeds toward the side surface of the partition plate having the anode electrode. Therefore, after the denitrification reaction is sufficiently performed on the cathode side where the dissolved oxygen concentration is relatively low, the agglutination reaction and the electrode cleaning can be performed on the anode side where the dissolved oxygen concentration is increased by aeration.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Two 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 D _{1 according} to Embodiment 1 of the present invention includes one sewage storage tank 1, two sets of electrodes 2 and 3, A DC power supply 11 for supplying a current to each pair of electrodes 2 and 3 and a control unit (not shown) for controlling the power supply 11 are provided.

The sewage storage tank 1 is a box having a substantially rectangular planar shape and a tapered bottom wall, and stores sewage to be treated such as human wastewater or domestic wastewater. A sewage inlet 1 a connected to an introduction pipe 4 for introducing sewage into the sewage storage tank 1 is formed in an upper portion of one end wall of the sewage storage tank 1.

As shown in FIG. 3, each set of electrodes 2 and 3
Each is made of a rectangular iron plate and elutes iron ions for removing phosphoric acid in wastewater by electrolysis. Also,
The distance between the electrodes 2 and 3 of each set is kept constant by an electrically insulating spacer 5 made of vinyl chloride resin attached to the upper end thereof. The spacer 5 has a handle 5
a is provided.

A connection terminal 6 is provided on the upper end of each of the electrodes 2 and 3. These terminals 6 are connected to a connector 8 via a lead wire 7. The connector 8 is connected to the power supply.

The lower halves of the electrodes 2 and 3 are covered with carriers 9 and 10 made of a porous network made of polypropylene resin. These carriers 9 and 10 are suspended from the upper edges of the electrodes 2 and 3 by strings (not shown), and inhabit microorganisms involved in the denitrification reaction in the sewage.

As shown in FIGS. 1 and 2, two sets of electrodes 2
・ Below immediately below 3, two aeration tubes 12 ・ 1 parallel to these
3 are arranged horizontally. These aeration tubes 12 and 13
Is part of the aeration device provided in the sewage treatment apparatus D _1.
That is, the aeration apparatus includes an air supply blower 14 provided outside the sewage storage tank 1 and two air supply pipes 16. Connected to the blower 14 via an air supply switching valve 15 and extending into the tank. 17 and aeration tubes 12 and 13 connected to these air supply tubes 16 and 17 and arranged at the bottom of the tank.

Here, the control unit is configured to reverse the polarity of the electrodes 2 and 3 once every five days.
When the control unit reverses the polarity of the electrodes 2 and 3, phosphoric acid is removed by an agglutination reaction between iron ions and phosphate ions in the wastewater on the electrodes 2.3 and 3 having the polarity of the anode.
In addition, the denitrification reaction based on the microorganisms in the carriers 9 and 10 at the electrodes 2 and 3 having the polarity of the cathode, the reaction in which nitrate ions and nitrite ions in wastewater are reduced to nitrogen gas,
To remove nitrogen.

The sewage treatment apparatus D ₁ further includes a rectangular partition plate 18 for partitioning a pair of electrodes 2 and 3 into an anode side and a cathode side. The partition plate 18 is made of ceramic and allows only ions to move through the partition plate 18. As shown in FIG. 2, the partition plate 18 allows the sewage from the introduction pipe 4 to flow into the sewage storage tank 1 via one end (the end on the introduction pipe 4 side) of the partition plate 18.
The partition plate 18 is arranged to be guided to the other end along one side or the other side, and then to flow around the other end and to flow out through one end along the other side or one side.

A flow path switching valve 19 is provided between the introduction pipe 4 and the wastewater storage tank 1. The flow path switching valve 19 is switched by the control unit so as to guide the sewage from the introduction pipe 4 along one of the one side surface and the other side surface of the partition plate 18.

The control unit is further configured to control the flow path switching valve 19 so that sewage from the introduction pipe 4 first flows into the side surface of the partition plate 18 having the electrodes 2 and 3 whose polarity is a cathode. ing.

With this configuration, as shown in FIG. 2, the electrodes 3.3 on one side of the partition plate 18 are provided.
And the flow path switching valve 19 is controlled so that the sewage from the introduction pipe 4 is removed from the partition plate 18 having the electrodes 3 and 3 whose polarity is the cathode as shown by the arrow. To the side, the inflow path 1 of the flow path switching valve 19
First flow through 9a. Then, the inflowing sewage goes around the other end of the partition plate 18 toward the other side surface (the side surface with the anode electrodes 2) of the partition plate 18, and as shown by the arrow, the other side of the flow path switching valve 19. Flows out of the wastewater storage tank 1 through the outflow path 19b.

Therefore, after the denitrification reaction is sufficiently performed on the cathode side where the dissolved oxygen concentration is relatively low, it is possible to perform the agglutination reaction on the anode electrodes 2 having the dissolved oxygen concentration increased by aeration. Become. The outflow channel 19
The sewage flowing out of b flows into a first anaerobic filter bed tank 104 described later.

After that, when the polarity is reversed by the control unit, the flow path switching valve 19 is switched in conjunction therewith, and the sewage from the introduction pipe 4 is separated from the electrode 2.2 having the cathode whose polarity is the cathode. Inflow channel 1 toward the other side of plate 18
9a. The inflowing sewage then goes around the other end of the partition plate 18 toward one side surface (the side surface with the anode electrodes 3) of the partition plate 18, and flows through the flow path switching valve 19.
Flows out of the sewage storage tank 1 through the outflow passage 19c on one side. In FIG. 1, reference numeral 20 denotes a sludge extraction valve.
The sludge accumulated in the sewage storage tank 1 is extracted by opening the sludge extraction valve 20. The opening and closing of the sludge extraction valve 20 is operated by a control unit or manually.

As shown in FIG. 4, the sewage treatment apparatus D ₁ is incorporated in a small-sized combined treatment / purification tank 101.

The inside of the septic tank 101 is arranged from the 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.

An anaerobic filter bed 105, which is a filter bed for anaerobic microorganisms, is provided in the first anaerobic filter bed tank 104, and anaerobic treatment is performed by inhabiting the microorganisms in the anaerobic filter bed 105. . 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 formed adjacent to the first anaerobic filter bed 104. In the second anaerobic filter bed tank 106, anaerobic microorganisms are made to inhabit the anaerobic filter bed 107 to perform anaerobic treatment.

Reference numeral 108 denotes a next biofilm filtration tank which is 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. Partition wall 10
At the upper part of 9, an advection port 110 penetrating the partition wall 109 is formed. Then, the advection pipe 11 is connected to the advection port 110.
1 is fitted. The lower end of the advection tube 111 is located below the anaerobic filter bed 105 of the first anaerobic filter tank 104,
Also serves as a cleaning port.

The second anaerobic filter bed tank 106 and the next biofilm filtration tank 108 are separated by a vertical partition 112. Partition wall 1
In the upper part of 12, an advection port 113 penetrating the partition wall 112 is formed. Then, the convection pipe 1 is inserted into the convection port 113.
14 is fitted. The sewage that has been transferred from the first anaerobic filter bed tank 104 to the second anaerobic filter tank 106 through the advection tube 111 passes through the anaerobic filter bed 107 in a downward flow, and then passes through the advection tube 114 to the next biofilm. It is sent to the filtration tank 108.

A certain amount of SS is captured by the anaerobic filter bed 107 provided in the second anaerobic filter tank 106. 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 biofilm filtration tank 108 is provided with an aerobic filter bed 115 which is a filter bed for aerobic microorganisms. The aerobic filter bed 115 is provided with aerobic microorganisms so that aerobic treatment is performed. Has been. In the vicinity of the bottom of the biofilm filtration tank 108, an aeration tube 116 of an aeration device is disposed in a horizontal state. The aeration apparatus supplies oxygen to the aerobic microorganisms living in the aerobic filter bed 115 of the biofilm filtration tank 108 by blowing out air from the aeration pipe 116.

Reference numeral 117 denotes a next treatment water tank formed adjacent to the biofilm filtration tank 108. In the treated water tank 117, the treated water that has undergone aerobic treatment in the biofilm filtration tank 108, and has been filtered and advected, is stored in a stationary state.

Reference numeral 118 denotes a disinfecting tank formed above the treated water tank 117. The disinfection tank 118 includes a treatment water tank 117.
The supernatant water after disinfection is disinfected, and discharged
3 to the outside.

The biofilm filtration tank 108 and the next treatment water tank 117
Are separated by a vertical partition wall 119. Partition wall 1
At the upper part of 19, an advection port 120 penetrating the partition wall 119 is formed. Then, the convection pipe 1 is inserted into the convection port 120.
21 is fitted. The sewage that has flowed from the second anaerobic filter bed tank 106 to the biofilm filtration tank 108 through the advection tube 114 passes through the aerobic filter bed 115 in a descending flow, and then flows through the advection tube 1.
Through 21, it is sent to the next treated water tank 117.

From the upper part of the treatment water tank 117, a first anaerobic filter bed tank
Return the supernatant water of the treated water to the top of 104
Return pipe 122 is provided. The return pipe 122
Sewage treatment equipment D₁Are connected to the introduction pipe 4. Soshi
And pumped up from the treated water tank 117 by the lift pipe 123
The obtained supernatant water is passed through a return pipe 122 to the sewage treatment apparatus D.
₁After being subjected to phosphorus removal and nitrogen removal,
It is returned to the anaerobic filter tank 104.

Embodiment 2 As shown in FIG. 5, a sewage treatment apparatus D _{2 according} to Embodiment 2 of the present invention includes one sewage storage tank 31 and four sets of electrodes 2.
3, a DC power supply 11 for supplying a current to each pair of electrodes 2.3, a control unit (not shown) for controlling the power supply 11, and four electrode cases 32. .

The lower half of the electrodes 2 and 3 is a sewage treatment device D ₁
As in the case of the above, the carrier is covered with carriers 9 and 10 made of a porous network made of polypropylene resin. These carriers 9-10, unlike in the sewage treatment apparatus D _1, is mounted on the bottom surface of the electrode housing 32.

The sewage storage tank 31 is formed of a box having a substantially rectangular planar shape and a tapered bottom wall, and stores sewage to be treated such as human wastewater or domestic wastewater. A sewage inlet 31a and a sewage outlet 31b are formed in an upper portion of one side wall of the sewage storage tank 31. Further, two bottom positioning rods 35 extending in the left-right direction are provided at the bottom of the sewage storage tank 31. A total of six left and right positioning bars 36 extending in the vertical direction are provided inside the bottom positioning bars 35.

As shown in FIG. 6, the electrode case 32 has a rectangular box shape in plan view and is made of polypropylene resin. The left and right side walls of the electrode case 32 are formed as electrically insulating partition plates 32a for separating adjacent electrode cases 32 from each other. Both the front and rear ends of the electrode case 32 are rectangular sewage inlet 32b and sewage outlet 32c.

The upper and lower surfaces of the electrode case 32 are notched in a rectangular shape at the center except for the peripheral portion, and are provided with an electrode attaching / detaching port 32d and an aeration port 32e, respectively. further,
The left and right width of the electrode case 32 (the interval between the outer surfaces of the two partition plates 32a) is substantially equal to the interval between two adjacent left and right positioning rods 36 in the sewage storage tank 31. The two circular holes 32f on the upper surface of the electrode case 32 are for screwing the spacer 5 to the upper surface of the electrode case 32.

The electrode case 32 thus configured is
It is arranged so as to be able to be taken out in the sewage storage tank 31. That is, it is loosely fixed to a fixed position by the bottom positioning rod 35 and the left and right positioning rods 36 provided in the tank. In FIG. 5, reference numeral 37 denotes a sludge extraction valve. The sludge accumulated in the sewage storage tank 1 is extracted by opening the sludge extraction valve 37.

The other parts of the sewage treatment apparatus D ₂ (such as a control section) are substantially the same as those of the sewage treatment apparatus D ₁ , and a detailed description thereof will be omitted.

As shown in FIG. 7, the sewage treatment apparatus D ₂ is incorporated in the same small-sized combined treatment / purification tank 101 as described above.

[0057] return pipe 122 is connected to the sewage inlet 31a of the sewage treatment apparatus D _2. And the treatment water tank 11
The supernatant water pumped up by the lift tube 123 to 7, after being sent to the sewage treatment apparatus D ₂ via a return pipe 122 phosphate removal and nitrogen removal is performed, the first anaerobic filter bed tank 1
Returned to 04.

[0058]

According to the first aspect of the present invention, the sewage storage tank and the sewage stored in the sewage storage tank are disposed so as to be at least partially immersed in the sewage, and phosphoric acid in the sewage is removed by precipitation. At least one set of electrodes for eluting iron ions or aluminum ions by electrolysis, a power supply for supplying a current for electrolysis to these electrodes, and a control unit for controlling the power supply. At least a part of the electrode is covered with a carrier for inhabiting microorganisms involved in the denitrification reaction in the sewage, and the polarity is changed to the anode by the control unit periodically inverting the polarity of the electrode. The removal of phosphoric acid is performed on the electrode side, and the removal of nitrogen is performed on the electrode side whose polarity has become the cathode by a denitrification reaction based on microorganisms in the carrier. Therefore, phosphoric acid removal and nitrogen removal can be performed simultaneously.

According to the second aspect of the present invention, the carrier is made of a porous mesh made of plastic, carbon fiber, or sintered ceramic, and is suspended from the upper edge of each electrode, or a set of It is placed on the bottom of the electrode case for storing the electrodes. Therefore, it is possible to reliably ensure the above-mentioned effects achieved by the first aspect of the invention with a simple configuration.

According to the third aspect of the present invention, the control unit further comprises a partition plate for partitioning the set of electrodes into an anode side and a cathode side, and an aeration device for aerating each electrode. However, the aeration device is controlled so that aeration is performed only on the electrode whose polarity is the anode. Therefore, in addition to the effect of the invention as claimed in claim 1, in addition to the aeration device, only the anode-side electrode is aerated to promote the phosphoric acid removal reaction on the anode side and to clean the electrode, while the cathode is cleaned. Side electrode can be placed in a reducing atmosphere.

According to the fourth aspect of the present invention, the apparatus further includes an introduction pipe for introducing sewage into the sewage storage tank, and the partition plate in the sewage storage tank transfers sewage from the introduction pipe to the sewage through one end of the partition plate. It is arranged so as to flow into the storage tank, guide it to the other end along one side or the other side of the partition plate, and then flow around the other end and flow out through one end along the other side or the one side. A flow path switching valve is further provided between the storage tank and the storage tank so as to guide sewage from the introduction pipe along one of the one side surface and the other side surface of the partition plate. The valve is controlled so that sewage from the inlet pipe flows first into the side surface of the partition plate having the electrode whose polarity is the cathode. Therefore, since the sewage flowing into the sewage storage tank goes around the other end of the partition plate toward the side surface of the partition plate having the anode electrode, the denitrification reaction is sufficiently performed on the cathode side having a relatively low dissolved oxygen concentration. After the above, the agglutination reaction and the electrode washing can be performed on the anode side where the dissolved oxygen concentration is increased by aeration.

[Brief description of the drawings]

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

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

FIG. 3 is a perspective view of an electrode and a carrier, which are components of the sewage treatment apparatus of FIG.

FIG. 4 is an enlarged configuration explanatory view of the inside of the merged treatment septic tank incorporating the sewage treatment apparatus of FIG. 1 as viewed from the front.

FIG. 5 is an exploded perspective view of a sewage treatment apparatus according to Embodiment 2 of the present invention.

6 is a perspective view of an electrode and an electrode case, which are components of the sewage treatment apparatus of FIG.

FIG. 7 is an enlarged configuration explanatory view of the inside of a combined treatment septic tank incorporating the sewage treatment apparatus of FIG. 5 as viewed from the front.

[Explanation of symbols]

 Reference Signs List 1 sewage storage tank 2 electrode 3 electrode 4 introduction pipe 9 carrier 10 carrier 11 power supply 12 aeration pipe 13 aeration pipe 14 air supply blower 15 air supply switching valve 16 air supply pipe 17 air supply pipe 18 partition plate 19 flow path switching valve 31 sewage Storage tank 32 Electrode case

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C02F 1/58 C02F 3/10 Z 4D061 3/00 1/46 102 4D062 3/10 F term (reference) 4D003 AA01 AA17 EA16 EA24 EA25 EA30 4D015 BA04 CA18 DA02 DA12 4D027 AB14 CA01 4D038 AA08 AB12 AB44 BB18 BB19 4D040 BB52 BB72 BB82 BB91 4D061 AA08 AB09 BA06 CA14 CA15 4D062 BA04 CA18 DA02 DA12 FA26

Claims (4)

[Claims] 1. A sewage storage tank, and at least a part of the sewage stored in the sewage storage tank is immersed in the sewage storage tank. At least one set of electrodes eluted by decomposition, a power supply for supplying an electrolysis current to these electrodes, and a control unit for controlling this power supply, at least a part of each electrode, It is covered with a carrier for inhabiting microorganisms involved in the denitrification reaction, and the control unit periodically inverts the polarity of the electrode, so that phosphoric acid is removed on the side of the electrode whose polarity has become the anode. A sewage treatment apparatus, wherein nitrogen is removed by a denitrification reaction based on microorganisms in a carrier of the electrode whose polarity is a cathode. 2. An electrode case in which the carrier is made of a porous network made of plastic, carbon fiber or sintered ceramic, is suspended from the upper edge of each electrode, or accommodates a set of electrodes. The sewage treatment apparatus according to claim 1, which is mounted on a bottom surface of the sewage treatment apparatus. 3. The apparatus further comprises a partition plate for partitioning a pair of electrodes into an anode side and a cathode side, and an aerator for aerating each electrode, wherein the control unit further controls the aerator. The sewage treatment apparatus according to claim 1, wherein aeration is performed only on the electrode whose polarity is the anode. 4. A partition plate in the sewage storage tank further comprising an introduction pipe for introducing sewage into the sewage storage tank, wherein the partition plate in the sewage storage tank flows sewage from the introduction pipe into the sewage storage tank through one end of the partition plate. It is arranged to guide to the other end along one side or the other side, and then to flow around the other end and to flow out through one end along the other side or the one side. There is further provided a flow path switching valve for switching sewage from the pipe so as to be guided along one of the one side surface and the other side surface of the partition plate, and the control unit further controls the flow path switching valve so that the introduction pipe 4. The sewage treatment apparatus according to claim 3, wherein the sewage from the sewage is first introduced into the side surface of the partition plate having the electrode whose polarity is the cathode.