JPH11262796A - Sewage treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify constitution and to stably remove phosphorus in a sewage treatment apparatus for removing phosphorus. SOLUTION: In a sewage treatment apparatus equipped with an anaerobic tank 5 in which living waste water flows, an aerobic tank 32 in which the sewage treated in the anaerobic tank 5 flows, a sedimentation separation tank or treated water tank 42 in which the sewage treated in the aerobic tank 32 flows and a return pipe 45 returning the sewage in the aerobic tank 32, the sedimentation separation tank or the treated water tank 42 to the anaerobic tank 5, the partition part 8 partitioning the sewage returned from the return passage 45 from living waste water is formed in the anaerobic tank 5 and an electrode 8 comprising an iron or aluminum material eluting iron or aluminum ions by the supply of a current is disposed in the partitioning part 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sewage treatment apparatus for purifying sewage, and more particularly to a sewage treatment apparatus for removing phosphorus from sewage.

[0002]

2. Description of the Related Art As this kind of sewage treatment apparatus, there is known a sewage treatment apparatus described, for example, in Example 3 (FIG. 3) of JP-A-7-108296 (C02F 3/30).

[0003] In this apparatus, an iron dissolving apparatus for eluting iron ions is incorporated in an anaerobic tank into which household wastewater flows, thereby simplifying the configuration and removing phosphorus.

[0004] However, most of the phosphorus contained in domestic wastewater exists in the form of organic phosphoric acid that does not react with iron ions, and the phosphorus is removed by oxidative decomposition to orthophosphoric acid that reacts with iron ions. Oxygen is needed for
Since there is no oxygen in the anaerobic tank, organic phosphoric acid cannot be oxidized and decomposed.

[0005] Therefore, simply incorporating the iron dissolving apparatus in the anaerobic tank cannot remove the organic phosphoric acid present in the anaerobic tank.

Further, since the electrodes of the iron dissolving apparatus are disposed directly in the anaerobic tank, impurities contained in domestic wastewater adhere to the electrode surfaces, and the elution efficiency of iron ions with the passage of time. And finally there is a disadvantage that the elution of iron ions disappears and phosphorus cannot be removed.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a sewage treatment apparatus capable of simplifying the structure and performing stable phosphorus removal. Make it an issue.

[0008]

A first means for solving the above problems is as follows: an anaerobic tank into which domestic wastewater flows, an aerobic tank into which sewage treated in the anaerobic tank flows, and A sedimentation separation tank or a treatment water tank into which the wastewater treated in the air tank flows, and a return path for returning the wastewater in the aerobic tank or the sedimentation separation tank or the treatment water tank to the anaerobic tank, which is returned from the return path. The anaerobic tank is provided with a partition for separating wastewater from household wastewater, and an electrode made of iron or aluminum that elutes iron ions or aluminum ions when energized is provided in the partition.

A second means for solving the above-mentioned problems is as follows.
An anaerobic tank into which household wastewater flows, an aerobic tank into which sewage treated in the anaerobic tank flows, a sedimentation separation tank or a treated water tank into which sewage treated in the aerobic tank flows, and the aerobic tank Alternatively, a return path for returning sewage in the sedimentation separation tank or the treated water tank to the anaerobic tank is provided, and a partition section for separating sewage returned from the return path from domestic wastewater is provided in the anaerobic tank, and iron ions or An electrode made of an iron material or aluminum that elutes aluminum ions is disposed in the partition and at a position separated from immediately below the outlet of the return path.

[0010] In the first means or the second means for solving the above-mentioned problem, an anaerobic filter bed for sedimentation and separation of domestic wastewater is provided in the anaerobic tank, and the partition section communicates with the anaerobic filter bed. It is preferable to provide a communication part.

In the first means or the second means for solving the above-mentioned problems, it is preferable to provide a control means for changing the polarity of a current supplied between the electrodes at predetermined time intervals.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described in detail below based on a sewage treatment apparatus shown in FIGS.

Reference numeral 1 denotes a treatment tank buried underground. The inside of the processing tank 1 is divided into a first anaerobic tank 5, a second anaerobic tank 24, and a second anaerobic tank 24, which will be described later, by a first partition 2, a second partition 3 and a third partition 4.
It is divided into a biofilm filtration tank 32, a treatment water tank 42, and a disinfection tank 43.

Reference numeral 5 denotes a first anaerobic tank having an inflow port 6 into which sewage such as household wastewater flows, and reference numeral 7 denotes a first anaerobic tank disposed in the first anaerobic tank 5 and through which sewage flowing from the inflow port 6 passes. In the filter bed, the hardly decomposable contaminants mixed in the sewage flowing from the inlet 6 are separated by sedimentation, and the anaerobic microorganisms attached to the first anaerobic filter bed 7 anaerobically decompose the organic matter, Is converted to ammoniacal nitrogen.

Reference numeral 8 denotes a first advection pipe vertically disposed in a notch formed in the first anaerobic filter bed 7, an inflow section into which sewage returned from a return pipe 46 described later flows, and an inflow section described later. An upper opening having a storage section for storing the float 9 is provided, and a lower opening is provided at the bottom of the first anaerobic tank 5 below the first anaerobic filter bed 7. Miscellaneous wastewater flowing from the inflow port 6 passes through the first anaerobic filter bed 7 to remove impurities such as toilet paper and flow into the first advection pipe 8 from the lower opening of the first advection pipe 8. In addition, it is possible to prevent a decrease in iron ion elution efficiency due to the attachment of impurities contained in domestic wastewater to the surface of an electrode 12 described later provided in the first advection pipe 8. The first advection pipe 8 allows the inflow port 6
And a sewage returned from the return pipe 46.

Reference numeral 9 denotes a float which is formed in a shape substantially corresponding to the shape of the storage portion of the first advection tube 8 and is made of styrofoam, resin or the like disposed in the first advection tube 8; It is a formed rectangular hole. Reference numeral 11 denotes an electrode body that engages with the hole 10 formed in the float 9. The mounting method of the electrode body 11 and the float 9 is not limited to the engagement, but may be a fixing method using a bolt or a nut, a fitting method using a claw, or the like.

The electrode body 11 includes a pair of electrodes made of an iron material.
12, a handle portion 14 having a handle 13 for holding the electrodes 12 at a predetermined interval, and a feed line 17 for connecting a terminal 15 formed on the electrode 12 to a connector 16.

By connecting the connector 16 to a power supply 18 for supplying a constant DC current, a constant DC current is supplied between the electrodes 12, and iron ions elute from the electrodes 12. The electrode body 11 and the power supply device 18 constitute an elution device for eluting iron ions. Since the float 9 is attached to the electrode body 11, sewage in the first anaerobic tank 5 when a large amount of water such as bath water is temporarily drained, or when it is not used for a long time due to a long trip, etc. Iron ions stable to the first anaerobic tank 5 can be supplied irrespective of the fluctuation of the water level.

Reference numeral 19 denotes a first air diffuser disposed below the electrode 12 and having a number of air outlets, and is connected to a first blower 21 via a first supply pipe 20. The first blower
By discharging the air supplied from 21 through the air outlet, the electrode 12 is cleaned to prevent sludge from adhering, and
Divalent iron ions eluted from 12 are oxidized to trivalent iron ions that react with orthophosphoric acid.

Reference numeral 22 denotes a second anaerobic tank 5 provided in the first anaerobic tank 5.
In the advection tube, the wastewater anaerobically decomposed by the first anaerobic filter bed 5 and the iron ions supplied from the electrode 12 are passed through the first partition wall 2.
The water is supplied to a second anaerobic tank 24 described later via a first water supply port 23 penetrating the upper part.

Reference numeral 24 denotes a first anaerobic tank 5 by the first partition wall 2.
The second anaerobic tank 25 is a second anaerobic filter bed disposed in the second anaerobic tank 24. The second anaerobic filter bed 25 captures suspended matter and anaerobics organic substances by anaerobic microorganisms. Decomposes and converts organic nitrogen to ammonia nitrogen.

26 is a third anaerobic tank provided in the second anaerobic tank 24.
In the advection pipe, the wastewater anaerobically decomposed by the second anaerobic filter bed 25 flows there.

Reference numeral 27 denotes a constant-pressure pumping chamber disposed in the second anaerobic tank 24. Reference numeral 28 denotes a water intake pipe having a check valve 29. 3 In the advection tube 26. A second blower 30 communicates with the fixed-pressure feed chamber 29 and supplies air into the fixed-pressure feed chamber 29. A third blower 31 connects the fixed-pressure feed chamber 27 and a fourth advection pipe 34, which will be described later. This is a transfer pipe for supplying sewage therein to the fourth advection pipe 34 via the constant-pressure pumping chamber 27. By supplying air from the second blower 30 into the quantitative pumping chamber 27, a predetermined amount of sewage flowing into the quantitative pumping chamber 27 from the water intake pipe 28 is pumped and transferred.
Is supplied to the inside of the fourth advection pipe.

Reference numeral 32 denotes a second anaerobic tank 24 by the second partition wall 3.
A biofilm filtration tank, 33 is disposed in the biofilm filtration tank 32, a biofilm filter medium that promotes the culture of aerobic microorganisms,
Reference numeral 34 denotes a fourth advection pipe provided in the biofilm filtration tank 32 for partitioning from the biofilm filtration material 33, and into which sewage supplied from the transfer pipe 31 flows. The fourth advection pipe is provided above a second aeration pipe 35 described later. The sewage that has flowed out from the lower opening that has passed through the biofilm filter medium 33.

Reference numeral 35 denotes a second air diffuser disposed at the bottom of the biofilm filtration tank 32. The second air diffuser forms a number of air outlets and is connected to a third blower 36 via a second supply pipe 37. 3 The air supplied from the blower 36 is released from the air outlet to maintain the inside of the biofilm filtration tank 33 in an aerobic state, aerobic decomposition of sewage by aerobic microorganisms, and the action of nitrate bacteria and nitrite bacteria. This converts ammoniacal nitrogen into nitric or nitrous nitrogen.

Reference numeral 38 denotes an upper part of the first anaerobic tank 5 and a biofilm filtration tank.
A sludge return pipe communicating with the lower portion and returning the sediment deposited at the bottom of the biofilm filtration tank 32 to the first anaerobic tank 5. A sludge return pipe 39 is connected to the sludge return pipe 38 to remove sewage in the biofilm filtration tank 32. This is a first pump to be supplied into the sludge return pipe 38.

Reference numeral 40 denotes a fifth advection pipe connecting the biofilm filtration tank 32 above the biofilm filtration medium 33 and the bottom of a treatment water tank 42 described later. Reference numeral 41 denotes a fifth advection pipe connected to the fifth advection pipe 40 and a biofilm filtration tank 32 connected thereto. This is a second pump for supplying sewage therein to a treated water tank 42 via a fifth advection pipe 40.

Reference numeral 42 denotes a treated water tank partitioned by the biofilm filtration tank 32 and the third partition wall 4. The treated water tank is aerobically decomposed in the biofilm filtration tank 32 and flows into the sludge through the fifth advection pipe 40. And the supernatant liquid.

Reference numeral 43 denotes a disinfection tank provided above the treatment water tank 42, and the supernatant liquid separated in the treatment water tank 42 flows therein. Reference numeral 44 denotes a sterilizing device provided in the disinfecting tank 43, which disinfects the sewage flowing into the disinfecting tank 43 with a chlorine-based chemical or the like provided in the sterilizing device 44. A drain port 45 communicates with the disinfecting tank 43, and drains the treated water disinfected in the disinfecting tank 43 out of the treatment tank 1.

Reference numeral 46 denotes a return pipe for communicating the treated water tank 42 with the inflow portion of the first advection pipe 8, and reference numeral 47 denotes a return pipe 46 for the treated water tank 42.
A third air diffuser disposed therein forms a number of air outlets and is connected to the fourth blower 48.
By discharging the air supplied from the air outlet through the air outlet, the wastewater in the treated water tank 42 is sucked into the return pipe 46,
It is designed to be transferred to the anaerobic tank 5. The first advection pipe 8 and the return pipe 46 constitute a return path for returning the wastewater in the treated water tank 42 to the first anaerobic tank 5.

The first blower 21, the second blower 30, the third blower 36, the fourth blower 48, the power supply 18 and the like are controlled by a control unit (not shown).

Reference numeral 49 denotes a first inspection opening provided at a position facing the first anaerobic tank 5 and the second anaerobic tank 24, and 50 denotes a first lid body which closes the first inspection opening 49 so that it can be opened and closed. And the first
It is opened and closed when sludge deposited on the bottom of the anaerobic tank 5 and the second anaerobic tank 24 is removed by suction or when the electrode body 11 is maintained.

Reference numeral 51 denotes a second inspection opening provided at a position facing the biofilm filtration tank 32, and 52 denotes the second inspection opening 51.
Is a second lid body that is openably and closably closed. Reference numeral 53 denotes a third inspection opening provided at a position facing the sterilization device 44, and reference numeral 54 denotes a third lid body which closes the third inspection opening 53 so as to be openable and closable. It opens and closes when refilling.

The sewage discharged from the home flows into the first anaerobic tank 5 from the inlet 6 and is supplied to the toilet in the sewage by the first anaerobic filter bed 7 disposed in the first anaerobic tank 5. Relatively coarse solids and contaminants such as paper are removed, and preliminary treatment is performed to smoothly perform treatment in each of the treatment tanks that flow in later, and the removed solids, contaminants and the first anaerobic substance are removed. The sewage passing through the filter bed 7 is anaerobically decomposed by the action of anaerobic microorganisms to reduce BOD, and the sludge generated by the decomposition of the sewage accumulates at the bottom of the first anaerobic tank 5. Organic nitrogen is changed to ammonia nitrogen by the action of anaerobic microorganisms.

The sewage that has been anaerobically decomposed by the flow of new sewage into the first anaerobic tank 5 passes through the second convection pipe 22 to the second anaerobic tank.
Flow into 24. The sewage flowing into the second anaerobic tank 24 is anaerobically decomposed by the action of the anaerobic microorganisms that inhabit the second anaerobic filter bed 25, the BOD is reduced and flows into the third advection pipe 26, and the sewage is decomposed. Sludge generated by the second anaerobic tank 24
Deposits on the bottom. Organic nitrogen is changed to ammonia nitrogen by the action of anaerobic microorganisms.

The sewage in the third advection pipe 26 flows from the water intake pipe 28 into the constant-pressure pumping chamber 27. From the second blower 30 to the fixed-pressure pumping chamber 27
When air is supplied into the intake pipe 28, the intake pipe 28 is closed by a check valve 29, and the sewage in the fixed-quantity pressure supply chamber 27 is pumped by air pressure.
It is supplied to the fourth advection tube 34 via the transfer tube 31.

When a predetermined time elapses from the operation of the second blower 30 and the control unit stops the second blower 30, the constant pressure feed chamber 27 is again moved from the water intake pipe 28 as the pressure in the constant pressure feed chamber 27 decreases.
Sewage flows into the interior. By causing the second blower 30 to operate intermittently by the control unit, a predetermined amount of wastewater in the third advection pipe 26 can be supplied to the fourth advection pipe 34 every predetermined time.

The sewage supplied into the fourth advection pipe 34 is
It descends in the advection tube 34, flows out from the lower opening of the fourth advection tube 34, rises by the supply of air from the second aeration tube 35, and is favored by the action of aerobic microorganisms attached to the surface of the biofilm filter medium 33 in large numbers. In addition to being decomposed by gas, it decomposes organic phosphates and the like into orthophosphoric acid and decomposes ammoniacal nitrogen into nitric or nitrite nitrogen. Further, a part of the sludge generated by the decomposition of the sewage is captured by the biofilm filter medium 33, and a part thereof is deposited on the bottom of the biofilm filtration tank 32.

The sewage passed through the biofilm filter medium 33 and purified by the biofilm filter medium 33 flows into the treated water tank 42 via the fifth advection pipe 40 by controlling the second pump 41. The supernatant liquid of the sewage flowing into the treatment water tank 42 flows into the disinfection tank 43, is disinfected by the sterilization device 44 provided with a chemical such as chlorine, kills bacteria such as pathogenic bacteria, and is discharged from the treatment tank 1 through the drain port 45. Drained.

The fourth blower 48 is controlled, and the fourth blower 48 is controlled.
The wastewater in the treated water tank 42 is returned to the first advection pipe 8 through the return pipe 46 by discharging the air supplied from the third air diffuser 47 from the air outlet of the third air diffuser 47. The nitrate or nitrite nitrogen in the sewage returned into the first advection pipe 8 is reduced by the denitrifying bacteria in the sewage flowing from the lower opening of the first advection pipe 8 and diffuses into the air as nitrogen gas. The iron ions eluted from the electrodes 12 are supplied to the wastewater in the first advection tube 8 by supplying a constant DC current between the electrodes 12.

The iron ions eluted from the electrode 12 are oxidized into trivalent iron ions reacting with orthophosphoric acid by the air supplied from the first air diffuser 19, and the electrode 12 is supplied from the first air diffuser 19. The air is washed with air to prevent sludge from adhering. The orthophosphoric acid in the sewage that has reacted with the iron ions eluted from the electrode 12 becomes a water-insoluble phosphorus compound and precipitates at the bottom of the first anaerobic tank 5, so that the phosphorus compound is treated together with the sludge treatment in the first anaerobic tank 5. And sludge removal work can be reduced.

The electrode body 11 to which the float 9 is attached tends to move in the horizontal direction due to the air supplied from the first diffuser pipe 19 or the sewage supplied from the return pipe 46, but the shape of the float 9 is changed to the first advection. Since the shape of the accommodating portion of the tube 8 is substantially matched, the horizontal movement of the electrode body 11 can be prevented by the first advection tube 8, and the terminal 15 and the connector 16 can be moved by moving the electrode body 11 in the horizontal direction. This prevents an excessive force from being applied to the power supply line 17 and the like, resulting in disconnection, and stopping power supply from the power supply device 18 to the electrode 12.

Normally, the phosphorus compound produced by the reaction with the iron ions eluted from the electrode 12 is flocculated and precipitated. However, when a phosphorus compound which floats and is not flocculated is generated, it may be discharged out of the treatment tank 1 in this state.
Since the phosphorus compound that has not been precipitated in the first anaerobic tank 5 or the second anaerobic tank 24 is trapped by the biofilm filter medium 33, the removal efficiency of phosphorus is improved. .

The control unit controls the third blower 36 every predetermined time to prevent the water-insoluble phosphorus compound, sludge, biofilm, etc. attached to the biofilm filter medium 33 from clogging.
The biofilm filter medium 33 is washed by supplying air having a larger air volume than the normal air diffuser 35, and phosphorus compounds, sludge, biofilm and the like are separated from the biofilm filter medium 33.

After returning the amount of air supplied from the third blower 36 to normal, the control unit controls the first pump 39 to remove deposits such as phosphorus compounds deposited on the bottom of the biofilm filtration tank 32 together with sewage and sludge. It is returned to the first anaerobic tank 5 via the return pipe 38.

When the electrode 12 made of an iron material is immersed in the sewage in the biofilm filtration tank 32 for a long time, an oxide film is generated on the surface of the electrode 12 and the electrode 12 is in a passivated state, and the elution amount of iron ions is reduced. It gradually decreases, and the dephosphorization performance decreases.

Accordingly, it is preferable that a constant DC current is supplied between a pair of electrodes made of iron material, and the polarity of the current is changed at predetermined time intervals. An oxide film is formed on the surface of the iron material on the anode side when used for a long period of time, but the surface of the iron material on the cathode side is cleaned by hydrogen gas generated from the iron material on the cathode side, and no oxide film is formed. Therefore, by changing the polarity at a time interval until an oxide film is generated on the surface of the iron material on the anode side and the amount of elution of iron ions decreases, elution of iron ions can be maintained substantially constant, and phosphorus desorption can be maintained. Performance can be kept constant.

In this configuration, since both electrodes are made of iron material, iron ions are always eluted from the iron material serving as the anode side electrode and supplied to sewage, so that the dephosphorization performance is always maintained at a constant state. be able to.

In the above configuration, in the present embodiment, 2
A constant current of 0 mA is supplied. The time interval for the polarity change of the current may be about 30 minutes or more at which the actual elution amount with respect to the theoretical iron ion elution is about 90% or more, and may be within 15 days when an oxide film is generated on the surface of the iron material. Within 10 days, to improve the durability of the switching element to convert and to prevent both the iron material serving as the anode side electrode from being reduced due to the elution of iron ions to make both electrodes substantially uniform reduction state, Preferably, the polarity is changed within 5 days, and in this embodiment, every 6 hours.

It is also possible to adopt a configuration in which an iron material is used at least on the anode side of the electrodes, a constant DC current is supplied to both electrodes, and the supply current is increased in a pulsed manner at predetermined time intervals. In this configuration, by increasing the supply current in a pulsed manner, the oxide film generated on the surface of the anode-side iron material can be peeled off, and the elution of iron ions is kept almost constant, and the dephosphorization performance is kept constant. Can be maintained.

In the above configuration, in the present embodiment, 2
A constant current of 0 mA is supplied, and a pulse current of 3 to 4 A is supplied for a total of 24 minutes per 4 hours.

Further, by combining the above two types of supply current configurations, a DC constant current is supplied between a pair of electrodes made of iron material, and the polarity of the current is changed at predetermined time intervals.
The supply current may be increased in a pulsed manner. If the time required for the polarity change is long, an oxide film is formed on the iron material surface on the anode side, and by changing the polarity, the oxide film can be washed and removed with a hydrogen gas. Some time is required until the oxide film is peeled off, and the electric resistance is large until the oxide film is peeled off, so that power consumption may increase.

Therefore, by increasing the supply current in a pulsed manner as described above, the oxide film on the surface of the iron material converted from the anode to the cathode can be removed in a short time, and an increase in power consumption can be prevented.

FIG. 5 shows a second embodiment. The first anaerobic filter bed 7 is provided on the side wall above the first anaerobic filter bed 7 of the first advection pipe 8 provided in the first embodiment. And a mesh-shaped communication portion 55 that communicates with the network.

According to this configuration, most of the sewage supplied with the iron ions eluted from the electrode 12 and supplied from the return pipe 46 flows into the first anaerobic filter bed 7 from the communication portion 55.
Denitrification by the denitrifying bacteria which are often present in the first anaerobic filter bed 7,
The nitrogen removal efficiency can be improved, and the phosphorus component is flocculated by the SS component in the first anaerobic filter bed 7, so that the aggregation of the phosphorus compound can be promoted.

In the embodiment of the present invention, an iron material is used for both electrodes as an electrode for supplying a DC constant current to elute iron ions. However, an iron material is used for the anode electrode, and a titanium electrode is used for the cathode electrode. Alternatively, a configuration using an insoluble material such as platinum or platinum may be used.

Furthermore, in the embodiment of the present invention, an iron material is used for both electrodes as an electrode for supplying a DC constant current to elute iron ions, but a configuration using aluminum may be used.

In the embodiment of the present invention, the biofilm filtration tank 32 is used as the aerobic tank. However, the present invention is not limited to this. For example, a contact aeration tank, a rotary plate contact tank, an activated sludge tank, etc. An aerobic tank may be provided.

Further, in this embodiment, the sewage in the treated water tank 42 is returned to the first anaerobic tank 5 via the return pipe 46, but the sewage in the biofilm filtration tank 32 is returned to the return pipe 46. It is good also as a structure returned to the 1st anaerobic tank 5 through a through-hole.

[0060]

According to the structure of the first aspect of the present invention, the electrodes are arranged in the partition for returning the sewage in the aerobic tank, the sedimentation separation tank or the treated water tank via the return path, so that the structure is simplified. In addition, it is possible to improve the phosphorus removal performance by reacting ions eluted from the electrode with orthophosphoric acid returned from the return tube.

Further, the removal of the phosphorus compound generated by the reaction with the ions eluted from the electrode can be carried out together with the sludge treatment in the anaerobic tank, so that the sludge treatment work can be reduced.

According to the configuration of the second aspect of the present invention, the electrode is disposed in the partition for returning the sewage in the aerobic tank, the sedimentation separation tank or the treated water tank via the return path, and below the discharge port of the return path. Thus, the configuration can be simplified, and the reaction between the ions eluted from the electrode and the orthophosphoric acid returned from the return tube is promoted, and the phosphorus removal efficiency can be improved.

Further, the removal of the phosphorus compound generated by the reaction with the ions eluted from the electrode can be performed together with the sludge treatment in the anaerobic tank, and the sludge treatment work can be reduced.

According to the third aspect of the present invention, the sewage supplied with iron ions flows out to the anaerobic filter bed through the communication part of the partition part, so that nitrogen is removed by the denitrifying bacteria which are often present in the anaerobic filter bed. The removal efficiency can be improved, and the phosphorus component is flocculated by the SS component in the anaerobic filter bed to promote the aggregation of the phosphorus compound, so that the phosphorus removal performance can be further improved.

According to the structure of the fourth aspect of the present invention, it is possible to perform stable ion elution while preventing generation of an oxide film on the electrode due to polarity change, and to reduce both electrodes substantially uniformly. The electrodes can be replaced simultaneously,
There are effects such as easy maintenance.

[Brief description of the drawings]

FIG. 1 is a sectional view of a sewage treatment apparatus according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view as viewed from another direction.

FIG. 3 is a perspective view of the elution device.

FIG. 4 is a perspective view of the electrode body.

FIG. 5 is a perspective view of an elution device according to a second embodiment of the present invention.

[Explanation of symbols]

 5 1st anaerobic tank (anaerobic tank) 8 1st advection pipe (partition part) 12 electrode 32 biofilm filtration tank (aerobic tank) 42 treated water tank 46 return pipe (return path)

Claims (4)

[Claims] 1. An anaerobic tank into which domestic wastewater flows, an aerobic tank into which sewage treated in the anaerobic tank flows, and a sedimentation separation tank or a treated water tank into which sewage treated in the aerobic tank flows. ,
A return path for returning the sewage in the aerobic tank or the sedimentation separation tank or the treated water tank to the anaerobic tank, and a partition for separating the sewage returned from the return path from domestic wastewater is provided in the anaerobic tank. A sewage treatment apparatus, wherein an electrode made of an iron material or aluminum that elutes iron ions or aluminum ions is disposed in the partition. 2. An anaerobic tank into which domestic wastewater flows, an aerobic tank into which sewage treated in the anaerobic tank flows, and a sedimentation separation tank or a treated water tank into which sewage treated in the aerobic tank flows. ,
A return path for returning the sewage in the aerobic tank or the sedimentation separation tank or the treated water tank to the anaerobic tank, and a partition for separating the sewage returned from the return path from domestic wastewater is provided in the anaerobic tank. A sewage treatment apparatus, wherein an electrode made of an iron material or aluminum that elutes iron ions or aluminum ions is disposed in the partition portion and at a position separated from immediately below the outlet of the return path. 3. The anaerobic tank is provided with an anaerobic filter bed for sedimentation and separation of domestic wastewater, and a communication section communicating with the anaerobic filter bed is provided in the partition section. 3. The sewage treatment apparatus according to 2. 4. The sewage treatment apparatus according to claim 1, further comprising control means for changing the polarity of the current supplied between the electrodes at predetermined time intervals.