JP3948779B2 - 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 incorporating a device for removing phosphoric acid in sewage.
[0002]
[Prior art]
In recent years, biofilm filtration has attracted attention as a method for efficiently removing nitrogen in a small site area. This biofilm filtration method is a method in which microorganisms adhere to the surface of the filter medium, and the sewage is processed through the biofilm filter tank in which the filter medium is disposed, and the microorganisms in the biofilm filter tank can be maintained at a high concentration. The treatment capacity per volume of the biofilm filtration tank is high, and the apparatus can be installed in a small site area.
[0003]
However, the biofilm filtration method cannot sufficiently remove phosphorus. Therefore, it is conceivable to add an aggregating agent such as FeCl ₃ for reacting with phosphoric acid to aggregate and precipitate it.
[0004]
[Problems to be solved by the invention]
However, since FeCl ₃ becomes Fe ³⁺ + 3Cl ⁻ , unnecessary impurities of 3Cl ⁻ are added, which may adversely affect microorganisms in the biofilm filtration tank. Moreover, with the treatment of sewage in the biofilm filtration tank, the sewage gradually becomes acidic, and there is a problem that the activity of microorganisms in the biofilm filtration tank is reduced and the treatment capacity is lowered.
[0005]
This invention makes it a subject to provide the sewage treatment apparatus by the biofilm filtration method which has high phosphorus removal capability and sewage treatment capability.
[0006]
[Means for Solving the Problems]
According to one aspect of the present invention, an anaerobic tank for anaerobically treating sewage and an aerobic filter bed on which a large number of filter media with attached aerobic microorganisms are provided, and the sewage subjected to anaerobic treatment in the anaerobic tank the comprises a biological membrane filtration tank having even physical filtration action while aerobic treatment, a dephosphorization device for removing fouling phosphoric acid in water, the dephosphorization device, have a electrode made of iron or aluminum sewage treatment apparatus, characterized by supplying to the biofilm filtration tank eluting iron ions or aluminum ions by applying an electric current to the electrode is provided with.
[0008]
The dephosphorization device is for removing phosphoric acid in sewage, and as the dephosphorization device, for example, an electrode made of iron or aluminum is provided, and an electric current is applied to the electrode so that iron ion or aluminum ion It consists of an elution device that elutes.
[0009]
At least one pair of electrodes is provided. The pair of electrodes, for example, are both constructed from one of iron and aluminum, or one from one of iron and aluminum and the other from an insoluble metal.
[0010]
In the former case, it is possible to prevent the electrode from being passivated by preventing the ion elution from the electrode by reversing the polarity of the electrode as desired. In the latter case, an electrode composed of one of iron and aluminum is used as an anode, and an electrode composed of an insoluble metal is used as a cathode. Here, as an electrode comprised from the insoluble metal, there exist electrodes, such as silver and platinum, for example.
[0011]
Iron ions or aluminum ions eluted in the elution apparatus are supplied to the biofilm filtration tank and aerobically treated in the biofilm filtration tank. Thereby, since the insoluble phosphorus compound in the sewage is trapped by the filter medium of the biofilm filtration tank, the concentration of phosphate ions in the sewage can be reduced as compared with the conventional case.
[0012]
Sewage after being subjected to aerobic treatment with biofilm filtration tank may be transported to the dephosphorization device again as discussed later.
[0013]
The sewage treatment apparatus according to the present invention preferably further comprises transfer means for transferring sewage in the biofilm filtration tank to the elution apparatus. With such a configuration, the sewage after being subjected to the aerobic treatment in the biofilm filtration tank can be transferred again to the dephosphorization device by this transfer means, and can be subjected to further dephosphorization treatment.
[0014]
As a supply means of the sewage treatment apparatus according to the present invention, for example, a supply pipe provided between the elution apparatus and the biofilm filtration tank is used. When such a supply means is provided, the sewage is supplied from the elution device to the biofilm filtration tank by natural flow or pumping through the supply pipe.
[0015]
As a transfer means of the sewage treatment apparatus according to the present invention, for example, a transfer pipe provided between a biofilm filtration tank and an elution apparatus and a transfer pump connected to the transfer pipe are used. . When such a transfer means is provided, the sewage pumped up from the biofilm filtration tank by the pump is transferred to the elution device through the transfer pipe.
[0016]
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.
[0017]
As shown in FIG. 1, an elution device D as a dephosphorization device according to one embodiment of the present invention is incorporated in a combined treatment septic tank 1 as a sewage treatment device having a flow rate adjusting function.
[0018]
The septic tank 1 has a plurality of tanks according to the order of the sewage purification process from the inflow side where sewage mixed with manure wastewater and domestic wastewater flows to the discharge side where sewage-treated water is discharged to the outside. It has a tank structure with compartments formed.
[0019]
Reference numeral 2 denotes a first anaerobic tank (contaminant removing tank) formed in the forefront portion on the inflow side. In the first anaerobic tank 2, impurities that cannot be purified and are mixed in manure wastewater or domestic wastewater are settled and removed.
[0020]
The first anaerobic tank 2 is provided with an anaerobic filter bed 3 which is a filter bed of anaerobic microorganisms, and anaerobic treatment is performed by causing the anaerobic filter bed 3 to inhabit the microorganisms. The anaerobic filter bed 3 suppresses the sediment from being rolled up by the water flow when the inflow water or backwash wastewater flows in temporarily, and flowing out to the next tank as a floating substance, thereby reducing the load on the next tank. Can be lowered.
[0021]
Reference numeral 4 denotes a second anaerobic tank as a next anaerobic tank formed adjacent to the first anaerobic tank 2. In the second anaerobic tank 4, anaerobic treatment is performed by causing the anaerobic filter bed 5 to inhale anaerobic microorganisms.
[0022]
Reference numeral 10 denotes a next biofilm filtration tank that is formed adjacent to the second anaerobic tank 4. The biofilm filtration tank 10 is provided with an aerobic filter bed 11 which is a filter bed of aerobic microorganisms, and aerobic microorganisms are inhaled in the aerobic filter bed 11 to perform aerobic treatment. ing.
[0023]
A large number of filter media 11a are arranged in the aerobic filter bed 11 in the biofilm filtration tank 10, and microorganisms attached to the filter media 11a decompose BOD components and the like, or convert them into suspended solids (SS). Capture at 11a . The biofilm filtration tank 10 also has a physical filtration action, and again captures SS. Moreover, in the biofilm filtration tank 10, ammonia nitrogen is changed to nitrate nitrogen by the action of nitrate bacteria and nitrite bacteria that change nitrogen to nitric acid (nitrification reaction).
[0024]
Reference numeral 12 denotes a next treated water tank formed adjacent to the biofilm filtration tank 10. In the treated water tank 12, the sewage that has been aerobically treated in the biofilm filtration tank 10 and has flowed in from the biofilm filtration tank 10 is stored stationary and separated into precipitate and supernatant water.
[0025]
As shown in an enlarged view in FIG. 2, the elution apparatus D includes an elution tank 39, a pair of iron electrodes 40 and 41 having a rectangular plate shape disposed in the elution tank 39, and the electrodes 40 and 41. A DC power supply 42 for applying a current and a control unit (not shown) are provided. The electrodes 40 and 41 use iron for both the anode and the cathode.
[0026]
In the elution tank 39, the sewage to be treated that has flowed in is stored. The electrodes 40 and 41 elute iron ions that react with phosphoric acid by electrolysis. The control unit controls the amount of the iron ions eluted in the elution tank 39 by controlling the current applied between the electrodes 40 and 41.
[0027]
The elution tank 39 is provided in the upper part of the biofilm filtration tank 10. An aeration tube 45 for aeration of the electrodes 40 and 41 and a blower 46 for supplying air to the aeration tube 45 are attached to the elution tank 39. In FIG. 2, 17 is a partition formed between the second anaerobic tank 4 and the biofilm filtration tank 10, 22 is an air diffuser disposed below the biofilm filtration tank 10, and 23 is a biofilm filtration. A partition wall 24 formed between the tank 10 and the treated water tank 12 indicates a communication part for allowing the biofilm filtration tank 10 and the treated water tank 12 to communicate with each other.
[0028]
In the elution tank 39, iron ions Fe ²⁺ are dissolved from the electrodes 40 and 41, and oxygen is supplied into the treated water through the aeration tube 45. Fe ²⁺ is oxidized using dissolved oxygen to form Fe ³⁺ and sent to the first anaerobic tank 2 to react with orthophosphoric acid PO ₄ ³⁻ to form a hardly soluble iron phosphate salt. And this iron phosphate salt aggregates using the SS content which exists in the 1st anaerobic tank 2 as a nucleus, becomes a big floc, precipitates, and deposits on the tank bottom part.
[0029]
Contaminants containing dephosphorized sludge accumulated on the bottom of the first anaerobic tank 2 are periodically (usually 1 per year) from the portion of the first anaerobic tank 2 where the anaerobic filter bed 3 is not present. Pumped out at a rate of about once)
[0030]
The septic tank 1 further includes a supply pipe 50 as a supply means for supplying the treated sewage in the elution device D to the biofilm filtration tank 10. That is, the supply pipe 50 is provided so as to be lowered in communication with the elution device D, and the lower end thereof is located at the upper part of the biofilm filtration tank 10. Through this supply pipe 50, sewage is supplied from the elution device D to the biofilm filtration tank 10 under natural flow.
[0031]
The septic tank 1 further includes transfer means for transferring the sewage sent from the elution device D to the biofilm filtration tank 10 through the supply pipe 50 to the elution device D. This transfer means is provided so as to descend in communication with the elution device D, and a transfer pipe 51 whose lower end is positioned at the upper part of the biofilm filtration tank 10 and a transfer connected to the transfer pipe 51. Pump 52 for use. The sewage pumped up from the biofilm filtration tank 10 by the pump 52 is returned to the elution device D through the transfer pipe 51.
[0032]
The function of this septic tank 1 will be described in more detail. In the elution apparatus D, a constant current is applied to the electrodes 40 and 41, and the molar ratio Fe / P of iron and phosphorus is adjusted to be 1-2. The sewage from the second anaerobic tank 4 is caused to flow into the biofilm filtration tank 10. And the nitrification reaction which changes ammonia nitrogen to nitrate nitrogen advances by letting the sewage pass through the biofilm filtration tank 10. That is, the organic substance containing N and NH ₄ ⁺ ions are changed to NO ₃ ⁻ ions and NO ₂ ⁻ ions, respectively.
[0033]
Next, the treated water is transferred to the elution device D by the transfer pipe 51 and the pump 52. The sewage after having been dephosphorized by the elution device D is again supplied to the biofilm filtration tank 10 through the supply pipe 50 under natural flow. The circulation operation as described above is repeated a predetermined number of times. The efficiency of the nitrification reaction in the biofilm filtration tank 10 increases as the number of circulation operations increases.
[0034]
Here, if the flow rate of sewage per unit time flowing into the biofilm filtration tank 10 from the second anaerobic tank 4 is Q, the flow rate of sewage circulating between the dephosphorization device D and the biofilm filtration tank 10 is 2Q or more.
[0035]
Deposits (such as Fe and P compounds and organic substances) adhering to the filter medium 11a constituting the aerobic filter bed 11 in the biofilm filtration tank 10 are regularly backwashed to clean the biofilm. Sludge collected at the bottom of the filtration tank 10 is extracted. The extracted sludge is returned to the first anaerobic tank 2.
[0036]
The treated water that has flowed out of the biofilm filtration tank 10 is further returned to the first anaerobic tank 2. In the first anaerobic tank 2, a denitrification reaction that changes NO ₃ ions or NO ₂ ions into N ₂ gas occurs.
[0037]
By the operation of circulating the treated water between the dephosphorization processing apparatus D and the biofilm filtration tank 10, the compound of Fe and P is efficiently trapped on the filter medium 11a constituting the aerobic filter bed 11, and is contained in the treated water. The phosphoric acid concentration could be reduced to the desired value. The removal rate was 90% or more.
[0038]
The quality of the inflow water and outflow water in the biofilm filtration tank 10 of the septic tank 1 is shown in the table of actual measurement values in FIG. Here, “inflow water” means treated water flowing from the second anaerobic tank 4 to the biofilm filtration tank 10, and “outflow water” means between the elution device D and the biofilm filtration tank 10. It means treated water flowing out from the biofilm filtration tank 10 to the treated water tank 12 after the circulation operation is repeated a predetermined number of times. TP represents the total phosphorus concentration, and TN represents the total nitrogen concentration. The unit of each number is mg / l. According to this table, it can be seen that the phosphorus concentration is remarkably reduced and the nitrification reaction is also proceeding greatly.
[0039]
【The invention's effect】
According to the invention of claim 1, since iron ions or aluminum ions are supplied to the biofilm filtration tank, the insoluble phosphorus compound in the sewage is trapped in the biofilm filtration tank, and the concentration of phosphate ions in the sewage is conventionally increased. Can also be reduced. Furthermore, since iron ions or aluminum ions are eluted, conventional unnecessary impurities are not supplied.
[0040]
According to invention of Claim 2, while supplying an electrode to an elution apparatus, the supply means which supplies the sewage from an elution apparatus to a biofilm filtration tank, The transfer means which transfers the sewage of a biofilm filtration tank to an elution apparatus Therefore, the sewage after being subjected to the aerobic treatment in the biofilm filtration tank can be subjected to further dephosphorization treatment which has been transferred to the elution device again.
[0041]
According to invention of Claim 3, since a supply means consists of a supply pipe provided between the biofilm filtration tank and the elution apparatus, sewage flows naturally from the elution apparatus to the biofilm filtration tank through the supply pipe. By supplying by pumping or the like, it is possible to secure the above-described effect produced by the invention according to claim 1 or 2 with a simple configuration.
[0042]
According to invention of Claim 4, since a transfer means consists of the transfer pipe provided between the biofilm filtration tank and the elution apparatus, and the pump for transfer connected to this transfer pipe, it is biological by the pump. By transferring the sewage pumped up from the membrane filtration tank to the elution device through the transfer pipe, it is possible to secure the above-described effect of the invention according to claim 2 or 3 with a simple configuration.
[Brief description of the drawings]
FIG. 1 is a schematic system diagram of a combined treatment septic tank as a sewage treatment apparatus according to one embodiment of the present invention.
FIG. 2 is an enlarged vertical vertical sectional view of a part of the sewage treatment apparatus of FIG.
FIG. 3 is a table of actual measurement values showing the quality of treated water by the sewage treatment apparatus of FIG. 1;
[Explanation of symbols]
2 First Anaerobic Tank 4 Second Anaerobic Tank 10 Biofilm Filtration Tank 12 Treated Water Tank D Elution Device (Dephosphorization Device)
50 Supply pipe (supply means)
51 Transfer pipe (transfer means)
52 Transfer pump

Claims (4)

An anaerobic tank for anaerobic treatment of sewage and an aerobic filter bed on which a large number of filter media with aerobic microorganisms are arranged are provided, and the sewage subjected to anaerobic treatment in the anaerobic tank is aerobically treated and physically filtered. comprising a biological membrane filtration tank having also act, a dephosphorization device for removing fouling phosphoric acid in water,
The dephosphorization device, sewage treatment apparatus and supplying an electrode made of an iron or aluminum by applying an electric current to the electrode to elute iron ions or aluminum ions into the biological membrane filtration tank.   The electrode is disposed in the elution device, and a supply means for supplying the sewage from the elution device to the biofilm filtration tank and a transfer means for transferring the sewage from the biofilm filtration tank to the elution device are provided. The sewage treatment apparatus according to claim 1.   The sewage treatment apparatus according to claim 2, wherein the supply means comprises a supply pipe provided between the elution apparatus and the biofilm filtration tank.   The sewage treatment apparatus according to claim 2, wherein the transfer means comprises a transfer pipe provided between the biofilm filtration tank and the elution apparatus, and a transfer pump connected to the transfer pipe.

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