JP3948823B2 - Sewage treatment equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sewage treatment apparatus, and more particularly, to a sewage treatment apparatus for removing phosphoric acid contained in sewage such as manure wastewater and domestic wastewater by reacting with metal ions eluted by electrolysis.
[0002]
[Prior art]
As this kind of sewage treatment apparatus, conventionally, the following is known.
[0003]
That is, a sewage storage tank for storing sewage to be treated is provided, and one or more sets of electrodes made of a water-insoluble phosphate forming metal are arranged in the tank, and a voltage is applied between these electrodes to In this apparatus, phosphoric acid is converted into a water-insoluble phosphate by eluting chemically insoluble phosphate-forming metal ions into the sewage, thereby removing the precipitate.
[0004]
[Problems to be solved by the invention]
In such a sewage treatment apparatus, as the sewage treatment progresses, organic sludge or inorganic sludge containing metal oxides, phosphates, and the like accumulates on the bottom of the sewage storage tank. When the accumulated sludge comes into contact with the electrode, electrical conduction occurs at the contact location, which may partially prevent elution of desired metal ions.
[0005]
When such an electrical continuity phenomenon occurs in many places on the electrode, a corrosion-resistant oxide film called a passive film is formed on the surface of the electrode, resulting in elution of water-insoluble phosphate-forming metal ions. May decrease or stop (passivation). When such passivation occurs, it becomes difficult or impossible to remove phosphoric acid in wastewater as a water-insoluble phosphate.
[0006]
The present invention has been made in view of such circumstances, and its problem is to prevent electrical continuity and passivation caused by various sludge accumulated on the bottom of the sewage storage tank, An object of the present invention is to provide a sewage treatment apparatus capable of stably and reliably removing phosphoric acid.
[0007]
[Means for Solving the Problems]
According to the present invention, a sewage storage tank, at least a pair of electrodes that are disposed in the sewage storage tank and elute iron ions or aluminum ions for precipitation removal of phosphoric acid in the sewage by electrolysis, and electrodes There is provided a sewage treatment apparatus comprising a power source for supplying an electrolysis current to the sewage and an air lift pump unit for removing the sludge accumulated in the sewage storage tank.
[0008]
The sewage storage tank stores sewage used for electrolysis. The electrodes are, for example, a set of two rectangular plates that are arranged in a set, and elute iron ions or aluminum ions into the sewage storage tank by electrolysis. The power supply supplies current for electrolysis to each set of electrodes.
[0009]
One set of electrodes is, for example, both iron (or aluminum) electrodes, or one is an iron (or aluminum) electrode and the other is an insoluble metal electrode. In the former case, it is possible to prevent electrode passivation by reversing the polarity of the electrode as desired. In the latter case, an iron (or aluminum) electrode is used as an anode, and an insoluble metal electrode is used as a cathode. Here, examples of the insoluble metal electrode include a silver electrode and a platinum electrode. Further, it is preferable that the pair of electrodes is fixed to, for example, an electrically insulating spacer having a handle portion, and the distance between them is kept constant.
[0010]
Iron ions or aluminum ions eluted in the sewage storage tank by electrolysis react with phosphoric acid (orthophosphoric acid) in the sewage water to form water-insoluble phosphorus compounds (Fe (OH) _x (PO ₄ ) _y or Al (OH) _x (PO ₄ ) _y ) and agglomerates and settles in the sewage storage tank.
[0011]
The air lift pump unit is not present in the conventional sewage output tank of this type, and removes sludge accumulated in the sewage storage tank by an air lift action based on the blowing of compressed air.
[0012]
As such an air lift pump unit, for example, a sludge scooping lift pipe disposed in a sewage storage tank, an air supply pipe provided inside the lift pipe for supplying compressed air, and the air supply pipe And a compressed air supply blower connected to the outside of the tank.
[0013]
The compressed air supplied from the blower through the air supply pipe is blown out into the lift pipe immersed in the sewage in the sewage storage tank. Then, countless fine bubbles are generated inside the lift pipe. These bubbles rise inside the lift pipe, thereby causing an air lift action. And by this air lift effect | action, the sludge accumulated on the bottom of a sewage storage tank is pumped up through the inside of a lift pipe with sewage.
[0014]
Therefore, it is possible to stably and reliably remove phosphoric acid in the sewage by preventing electrical continuity and passivation caused by various sludge accumulated on the bottom of the sewage storage tank.
[0015]
More preferably, in the sewage treatment apparatus according to the present invention, an aeration pipe for aeration of the electrode is disposed in the sewage storage tank, and the aeration pipe uses the lift pipe and the compressed air supplied from the air supply pipe of the air lift pump unit. It is connected to the air supply pipe via an air supply switching valve for switching to one of the aeration pipes.
[0016]
In the sewage treatment apparatus configured as described above, the electrode surface is cleaned by aeration from the aeration tube, so that passivation of the electrode can be prevented. Further, since the aeration pipe is connected to the air supply pipe of the air lift pump section, the blower of the air lift pump section can be used for supplying air to the aeration pipe.
[0017]
In the sewage treatment apparatus according to the present invention, the air supply switching valve may be a manual switching valve, but more preferably, the air supply switching valve is an electromagnetic valve, and further, the switching of the electromagnetic valve is performed. A control unit for periodically instructing is provided.
[0018]
In the sewage treatment apparatus configured as described above, it is possible to automatically control the periodic switching of the electromagnetic valve by the control unit.
[0019]
In the sewage treatment apparatus according to the present invention, it is more preferable that the planar area of the bottom of the sewage storage tank is smaller than the planar area of the upper part. If comprised in this way, the sludge accumulated on the bottom part of a sewage storage tank can be collected in the specific location of a sewage storage tank, and the pumping by the lift pipe | tube of an air lift pump part can be performed reliably and easily.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, one embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited thereby.
[0021]
As shown in FIG. 1, a sewage treatment apparatus D _{1 according} to one embodiment of the present invention includes a sewage storage tank 1, four sets of electrodes 2 and 3, and a current flowing through each set of electrodes 2 and 3. DC power supply 126 (shown in FIG. 6) and four electrode holders 4 are provided.
[0022]
As shown in FIG. 2, the sewage storage tank 1 is a box having a substantially rectangular plane shape, and sewage to be treated such as urine wastewater and domestic wastewater is stored. A sewage inflow port 1 a and a sewage outflow port 1 b are formed at the upper part of the opposite side wall of the sewage storage tank 1. In addition, two depth positioning rods 5 extending in the left-right direction are provided in the intermediate depth portion of the sewage storage tank 1. A total of six right and left positioning rods 6 extending in the vertical direction are provided inside the depth positioning rods 5.
[0023]
Each pair of electrodes 2 and 3 is made of iron in a rectangular plate shape, and iron ions for removing phosphoric acid in the sewage are eluted by electrolysis. As shown in an enlarged view in FIG. 3 and FIG. 4, the pair of electrodes 2 and 3 is kept at a constant interval by an electrically insulating spacer 7 made of vinyl chloride resin attached to the upper ends thereof. Yes. The spacer 7 is provided with a handle portion 7a.
[0024]
A connection terminal 8 is provided at the upper ends of the electrodes 2 and 3. These terminals 8 are connected to a connector 10 via lead wires 9. The connector 10 is connected to the power source. For convenience of explanation, an assembly including a pair of electrodes 2 and 3, one spacer 7, two terminals 8, two lead wires 9, and one connector 10 is referred to as an electrode body 11.
[0025]
As shown in FIGS. 3 and 4 in an enlarged manner, the electrode holder 4 has a rectangular box shape in plan view and is made of polypropylene resin. The left and right side walls of the electrode holder 4 are electrically insulating partition plates 4 a for partitioning adjacent electrode holders 4. Both front and rear ends of the electrode holder 4 are rectangular sewage inlet 4b and sewage outlet 4c.
[0026]
Further, the upper and lower surfaces of the electrode holder 4 are cut out into a rectangular shape with the peripheral portion being left, thereby forming an electrode attaching / detaching port 4d and an aeration port 4e, respectively. Furthermore, the left-right width of the electrode holder 4 (the distance between the outer surfaces of the two partition plates 4a) is substantially equal to the distance between the two adjacent left and right positioning rods 6 in the sewage storage tank 1.
The two circular holes 4 f on the upper surface of the electrode holder 4 are for screwing the spacer 7 to the upper surface of the electrode holder 4.
[0027]
The electrode holder 4 configured in this way is arranged in the sewage storage tank 1 so that it can be taken out. That is, it is gently fixed at a fixed position by the depth positioning rod 5 and the left and right positioning rods 6 provided in the tank.
[0028]
Further, the electrode body 11 is detachably held on the electrode holder 4 by being fitted into the electrode holder 4 from the electrode attaching / detaching port 4 d and the spacer 7 being screwed to the electrode holder 4. Accordingly, the inspection and replacement work of the electrodes 2 and 3 can be performed easily and in a short time. Further, the two partition plates 4a of the pair of electrodes 2 and 3 and the electrode holder 4 are parallel to each other. Therefore, the SS in the sewage in the electrode holder 4 flows without a stagnation from the sewage inlet 4a toward the sewage outlet 4b along the electrode surfaces of the electrodes 2 and 3.
[0029]
As shown in FIG.1 and FIG.2, the sewage storage tank 1 is comprised so that it may become thin in the shape of an inverted square frustum from the depth intermediate part to the bottom part 1c. That is, the bottom 1c is positioned immediately below one corner of the upper opening 1d of the sewage storage tank 1, and the planar area of the bottom 1c is reduced to about a fraction of the planar area of the upper opening 1d. Has been.
[0030]
The sewage storage tank 1 is provided with an air lift pump unit 20 for pumping and removing the sludge accumulated on the bottom 1c of the sewage storage tank 1. The air lift pump unit 20 is provided in the sludge scooping lift pipe 21 disposed from the one corner of the sewage storage tank 1 to the bottom 1 c and the lift pipe 21 to supply compressed air into the lift pipe 21. And an air supply blower 23 (shown in FIG. 6) connected to the air supply pipe 22 and disposed outside the tank.
[0031]
The compressed air supplied from the blower 23 through the air supply pipe 22 is blown out into the lift pipe 21 immersed in the sewage in the sewage storage tank 1. Then, countless fine bubbles are generated inside the lift pipe 21. These bubbles rise in the lift pipe 21 to cause an air lift action. And by this air lift effect | action, the sludge accumulated on the bottom 1c of the sewage storage tank 1 is pumped up with the sewage through the inside of the lift pipe 21.
[0032]
As shown in FIGS. 1, 2, and 5, the sewage storage tank 1 is provided with an aeration pipe 12 for aeration of the electrodes 2 and 3. The aeration pipe 12 is arranged diagonally across the depth intermediate portion of the sewage storage tank 1 so as to be positioned below the electrode holder 4, and is connected to the air supply pipe 22 via the air supply switching valve 24. It is connected. The air supply switching valve 24 is an electromagnetic valve, and switches the compressed air supplied from the blower 23 of the air lift pump unit 20 via the air supply pipe 22 to either the lift pipe 21 or the aeration pipe 12. This switching is performed by the control unit 125 described later.
[0033]
By performing aeration from the aeration tube 12 through the aeration port 4e of the electrode holder 4, the cleaning effect of the electrodes 2 and 3 and the partition plate 4a can be further enhanced.
[0034]
As shown in FIG. 6, this sewage treatment apparatus D ₁ is incorporated in a small merged treatment septic tank 101.
[0035]
The inside of the septic tank 101 is in accordance with the order of the sewage purification process from the side of the inflow pipe 102 into which sewage mixed with urine wastewater and domestic wastewater flows to the side of the discharge pipe 103 that discharges sewage-treated water to the outside. The tank structure is formed by partitioning a plurality of tanks. Reference numeral 104 denotes a first anaerobic filter bed tank formed in the foremost part on the inflow pipe 102 side. In the first anaerobic filter bed tank 104, impurities that cannot be purified by being mixed in manure wastewater or domestic wastewater are separated by precipitation and removed.
[0036]
The first anaerobic filter bed tank 104 is provided with a first anaerobic filter bed 105 which is a filter bed for anaerobic microorganisms, and anaerobic treatment is performed by causing the first anaerobic filter bed 105 to inhabit the microorganisms. Yes. The first anaerobic filter bed 105 suppresses the sediment from being rolled up by the water flow when the inflow water or backwash wastewater temporarily flows into the suspended tank and flowing out to the next tank. The load can be reduced.
[0037]
Reference numeral 106 denotes a second second anaerobic filter bed tank formed adjacent to the first anaerobic filter bed tank 104. In the second anaerobic filter bed tank 106, anaerobic treatment is performed by causing the second anaerobic filter bed 107 to inhabit anaerobic microorganisms.
[0038]
Reference numeral 108 denotes a next biofilm filtration tank that is partitioned adjacent to the second anaerobic filter bed tank 106. The first anaerobic filter bed tank 104 and the second anaerobic filter bed tank 106 are partitioned by a vertical partition wall 109. An advection port 110 penetrating the partition wall 109 is formed in an upper part of the partition wall 109. A convection tube 111 is fitted in the convection port 110. The second anaerobic filter bed tank 106 and the next biofilm filtration tank 108 are partitioned by a vertical partition 112. An advection port 113 penetrating the partition 112 is formed in an upper part of the partition 112. A convection tube 114 is fitted into the convection port 113.
[0039]
The sewage that has been transferred from the first anaerobic filter bed tank 104 to the second anaerobic filter bed tank 106 through the transfer pipe 111 passes through the second anaerobic filter bed 107 in a downward flow, and then passes through the transfer pipe 114 to the next. It is sent to the biofilm filtration tank 108.
[0040]
A certain amount of SS is captured by the second anaerobic filter bed 107 provided in the second anaerobic filter bed tank 106. The trapped SS is gradually anaerobically decomposed to become soluble, or stored as sludge at the bottom of the second anaerobic filter bed tank 106. In the second anaerobic filter bed 107, organic nitrogen is anaerobically decomposed into ammonia nitrogen.
[0041]
The biofilm filtration tank 108 is provided with an aerobic filter bed 115 which is a filter bed of aerobic microorganisms, and aerobic treatment is performed by causing the aerobic microorganisms to inhale in the aerobic filter bed 115. Yes. In the vicinity of the bottom of the biofilm filtration tank 108, an aeration pipe 116 of the aeration apparatus is arranged in a horizontal state. The aeration apparatus supplies oxygen to aerobic microorganisms that inhabit the aerobic filter bed 115 of the biofilm filtration tank 108 by blowing air from the aeration pipe 116.
[0042]
Reference numeral 117 denotes a next treated water tank that is formed adjacent to the biofilm filtration tank 108. In the treated water tank 117, the treated water that has been aerobically treated in the biofilm filtration tank 108, filtered and transferred is stored in a stationary manner.
[0043]
Reference numeral 118 denotes a disinfection tank that is partitioned on the upper part of the treated water tank 117. The disinfection tank 118 disinfects the supernatant water that has been treated in the treatment water tank 117 and discharges it from the discharge pipe 103 to the outside.
[0044]
The biofilm filtration tank 108 and the next treated water tank 117 are partitioned by a vertical partition wall 119. An advection port 120 penetrating the partition wall 119 is formed in the upper part of the partition wall 119. A convection tube 121 is fitted into the convection port 120. The sewage that has been transferred from the second anaerobic filter bed tank 106 to the biofilm filtration tank 108 through the transfer pipe 114 passes through the aerobic filter bed 115 in a downward flow, and then passes through the transfer pipe 121 to the next treated water tank 117. It is sent to.
[0045]
A return pipe 122 for returning the supernatant water of the treated water is disposed from the upper part of the treated water tank 117 to the upper part of the first anaerobic filter bed tank 104. Then, the supernatant water pumped up from the treated water tank 117 by the lift pipe 123 is sent to the sewage treatment apparatus D ₁ through the diversion meter 124 and the return pipe 122 and subjected to the phosphorus removal treatment, and then the first anaerobic filter. Returned to the floor tank 104.
[0046]
6, 125 a control unit which includes the sewage treatment apparatus D _1, 126 are respectively the DC power supply. The power supply 126 supplies a current for electrolysis to the electrodes 2 and 3 disposed inside the sewage storage tank 1.
[0047]
The amount of sewage flowing into the septic tank 101 is 1200 liters per day, and the circulation flow rate in the septic tank 101 is 6000 liters. At this time, a current is allowed to flow through the electrodes 2 and 3 disposed inside the sewage storage tank 1 by a constant value within a range of 120 to 2400 mA. The distance between the electrodes of each electrode body 11 is set to 25 mm so that the voltage between the electrodes can always be monitored.
[0048]
The control unit 125 always performs constant current electrolysis while maintaining the current density at the time of electrolysis for elution of iron ions at a constant value within the range of 0.1 to 5.0 mA / cm ^2. Control to indicate one polarity reversal every minute to 15 days. When the current density is less than 0.1 mA / cm ² occurs passivating, power consumption interelectrode voltage becomes greater than or equal to about 25V is increased when it exceeds the 5.0 mA / cm ^2.
[0049]
Here, for three months from the start of operation of the septic tank 101, the current density is always maintained at 0.5 mA / cm ² by the control unit 125, and constant current electrolysis is performed with polarity reversal once every 6 hours. It was broken.
[0050]
The control unit 125 is also configured to instruct the switching of the air supply switching valve 24 formed of an electromagnetic valve periodically (for example, once every 1 to 6 months). That is, the control unit 125 controls the air supply switching valve 24 so that the compressed air from the blower 23 is supplied toward the aeration pipe 12 when the operation of the septic tank 101 is started. When 1 to 6 months have elapsed since the start of operation, the control unit 125 switches the air supply switching valve 24 to automatically control the compressed air to be supplied into the lift pipe 21.
[0051]
【The invention's effect】
According to the first aspect of the present invention, at least one set of the sewage storage tank and the sewage storage tank that elutes iron ions or aluminum ions for precipitation removal of phosphoric acid in the sewage by electrolysis. It comprises an electrode, a power source for supplying electrolysis current to the electrode, and an air lift pump unit for pumping up and removing sludge accumulated in the sewage storage tank. Therefore, such an air lift pump unit can remove the sludge accumulated in the sewage storage tank by the air lift action based on the blowing of compressed air. Conductivity and passivation can be prevented and phosphoric acid in sewage can be removed stably and reliably.
[0052]
According to the second aspect of the present invention, the air lift pump unit has a sludge scooping lift pipe disposed in the sewage storage tank, and an air supply pipe provided inside the lift pipe for supplying compressed air into the lift pipe. And a blower for supplying compressed air connected to the air supply pipe and disposed outside the tank. Therefore, the effect according to the first aspect of the present invention can be achieved more reliably from an air lift pump portion having a simple configuration including a lift pipe, an air supply pipe, and a blower.
[0053]
According to invention of Claim 3, the aeration pipe for aeration of an electrode is distribute | arranged to a sewage storage tank, This aeration pipe switches the compressed air supplied from an air supply pipe to either a lift pipe or an aeration pipe For this purpose, the air supply pipe is connected via an air supply switching valve. Therefore, in addition to the effect according to the second aspect of the invention, the electrode surface is cleaned by aeration from the aeration tube, so that passivation of the electrode can be prevented. Further, since the aeration pipe is connected to the air supply pipe of the air lift pump section, the blower of the air lift pump section can also be used for supplying air to the aeration pipe.
[0054]
According to the fourth aspect of the present invention, the air supply switching valve is composed of an electromagnetic valve, and a control unit is provided for periodically instructing switching of the electromagnetic valve. Therefore, in addition to the effect according to the third aspect of the invention, the control unit can automatically control the periodic switching of the solenoid valve.
[0055]
According to the fifth aspect of the present invention, the sewage storage tank has a bottom planar area smaller than an upper planar area. Therefore, in addition to the effect produced by the invention according to any one of claims 1 to 3, the sludge accumulated at the bottom of the sewage storage tank is collected at a specific location of the sewage storage tank, and the lift pipe of the air lift pump unit The pumping by can be performed reliably and easily.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a sewage treatment apparatus according to one embodiment of the present invention.
FIG. 2 is a configuration explanatory view of a part of the sewage treatment apparatus of FIG. 1 as viewed from above.
FIG. 3 is a perspective view of an electrode body and an electrode holder that are constituent members of the sewage treatment apparatus of FIG. 1;
4 is an exploded perspective view of an electrode body and an electrode holder in FIG. 3;
FIG. 5 is an enlarged configuration explanatory view of an air lift pump unit and an aeration pipe, which are constituent members of the sewage treatment apparatus of FIG. 1;
6 is an explanatory diagram of an enlarged configuration of the inside of a combined treatment septic tank in which the sewage treatment apparatus of FIG. 1 is incorporated, as viewed from the front.
[Explanation of symbols]
D ₁ Sewage treatment device 1 Sewage storage tank 1c Bottom 1d Upper opening 2 Electrode 3 Electrode 12 Aeration pipe 20 Air lift pump part 21 Lift pipe 22 Air supply pipe 23 Blower 24 Air supply switching valve 101 Small merged treatment purification tank 125 Control part 126 Power supply

Claims (5)

A sewage storage tank, and at least one pair of electrodes that are disposed in the sewage storage tank and elute iron ions or aluminum ions to precipitate and remove phosphoric acid in the sewage by electrolysis, and supply current for electrolysis to the electrodes A sewage treatment apparatus comprising: a power source for carrying out the operation; and an air lift pump unit for pumping up and removing sludge accumulated in the sewage storage tank. The air lift pump unit has a lift pipe for sludge pumping arranged in the sewage storage tank, an air supply pipe provided inside the lift pipe for supplying compressed air into the lift pipe, and a tank connected to the air supply pipe The sewage treatment apparatus according to claim 1, further comprising a compressed air supply blower arranged outside. An aeration pipe for aeration of the electrode is disposed in the sewage storage tank, and this aeration pipe is connected via a supply switching valve for switching compressed air supplied from the supply pipe to either the lift pipe or the aeration pipe. The sewage treatment apparatus according to claim 2, which is connected to an air supply pipe. 4. The sewage treatment apparatus according to claim 3, wherein the air supply switching valve is composed of a solenoid valve, and a control unit is provided for periodically instructing switching of the solenoid valve. The sewage storage tank according to any one of claims 1 to 4, wherein the sewage storage tank has a bottom planar area smaller than an upper planar area.

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