JP2000117286A - Equipment for removing phosphorus in wastewater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide equipment which is compact and capable of reducing the burden of operating cost such as addition cost, and also economizing the construction cost by placing a line for returning a part of effluent water from an aerobic treatment vessel or a part of sludge withdrawn from a final settling tank for treated wastewater to a first settling tank for wastewater to be treated and another line for transferring a part of sludge of the first settling tank to an anaerobic treatment vessel or the aerobic treatment vessel. SOLUTION: The treatment process using this equipment comprises: subjecting wastewater 1 to be treated to solid-liquid separation in a first settling tank 2; then, successively passing the separated wastewater 1 through an anaerobic treatment vessel 3 and an aerobic treatment vessel 4 in that order; separating an effluent liquid 10 that flows out from the aerobic vessel 4 and flows into a final settling tank 6, into treated water 7 and activated sludge in the final settling tank 6; transferring at least a part of the separated and concentrated activated sludge 8, namely, withdrawn sludge 8 from the final settling tank 6 to the anaerobic treatment vessel 3 as return sludge; returning at least a part of the effluent liquid 10, i.e., sludge-mixed liquid 10 flowing out from the aerobic treatment vessel 4, at least a part of the withdrawn sludge 8 from the final settling tank 6 or both of them to a first settling tank 2; and allowing at least a part of withdrawn sludge from the first settling tank 2, namely, a first settling tank deposit 9 to flow into the anaerobic treatment vessel 3 or aerobic treatment vessel 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally belongs to the field of sewage and wastewater treatment, and more particularly to an apparatus for removing phosphorus from wastewater.

[0002]

2. Description of the Related Art There is an activated sludge process as a conventional representative treatment process for removing organic substances from wastewater, and an anaerobic aerobic activated sludge process is a conventional method for simultaneously removing phosphate ions and organic substances. There is.

FIG. 3 shows an example of a wastewater treatment apparatus using the anaerobic-aerobic activated sludge method. The wastewater treatment apparatus using the anaerobic and aerobic activated sludge method comprises an initial settling basin 2, an anaerobic tank 3 in which activated sludge releases intracellular phosphate ions into wastewater by a biological phosphorus release reaction, and a biological phosphorus intake. The activated sludge is constituted by an aerobic tank 4 for ingesting phosphate ions in wastewater into cells by a reaction and a final sedimentation basin 6. The phosphorus intake of the activated sludge in the aerobic step is larger than the phosphorus release in the anaerobic step, and the difference between the phosphorus intake and the phosphorus release corresponds to the phosphorus removal from the wastewater.

After first removing relatively large and heavy solids contained in wastewater 1 in a sedimentation basin 2, a biological phosphorus release reaction in an anaerobic process and a biological phosphorus uptake reaction in an aerobic process are performed. The phosphorus in the wastewater is converted into a constituent component of the sludge, and is finally discharged from the wastewater treatment apparatus as surplus sludge. Organic matter in the wastewater is removed in both the anaerobic step and the aerobic step.

[0005] There are the following problems in removing phosphorus from wastewater using a wastewater treatment apparatus based on the anaerobic-aerobic activated sludge method. That is, when the organic matter concentration of the wastewater decreases due to the inflow of rainwater or the like, the wastewater is diluted while being supplied with oxygen. Therefore, the organic matter in the wastewater is supplied to the anaerobic process after being oxidized and diluted. As a result, the concentration of organic substances supplied to the anaerobic step is lower than the concentration of phosphate ions, so that the phosphorus release reaction rate in the anaerobic step and the phosphorus intake reaction rate in the aerobic step become lower, and the treated water is reduced. Water quality deteriorates.

Further, since solid pollutants of wastewater are settled and separated in the first sedimentation basin, the wastewater supplied to the anaerobic process via the first sedimentation basin is mainly composed of soluble pollutants. Accordingly, even when the organic matter concentration / phosphate ion concentration ratio of the soluble pollutants in the wastewater supplied to the anaerobic step is low, the phosphorus release reaction rate in the anaerobic step and the phosphorus intake reaction rate in the aerobic step are low. And the quality of the treated water deteriorates.

To cope with such a problem, an organic chemical such as methanol is supplied to the anaerobic step together with the wastewater to compensate for the shortage of the concentration of organic substances in the wastewater, thereby improving the phosphorus release reaction rate and the favorable rate in the anaerobic step. A method of preventing a decrease in the reaction rate of phosphorus intake in the pneumatic process has been used.

[0008] In the prior art of flowing organic agents into the anaerobic step, methanol has usually been used.
This methanol has the advantage of being relatively fast to be used by living organisms because of its low molecular weight.The price of methanol is relatively low, but when processing large amounts of wastewater, the amount of methanol becomes enormous, and the cost of chemicals increases. This is a major problem with operating costs. In addition, since methanol is a fourth-class hazardous substance, it must be handled in consideration of safety, and measures must be taken for storage facilities and facilities for receiving and supplying.

It is considered that sufficient organic substances are required in both the phosphorus release reaction in the anaerobic step and the phosphorus uptake reaction in the aerobic step, and the removal of organic substances from the wastewater by the anaerobic and aerobic activated sludge method is required. Insufficiently, good phosphorus removal results cannot be obtained, so the wastewater flowing into the sedimentation basin first contains organic matter that is first removed in the sedimentation basin, that is, the organic matter mainly composed of solid matter is subjected to the anaerobic process or The introduction into both the anaerobic step and the aerobic step is effective for improving the phosphorus removal treatment results.

[0010] As a conventional facility operation method having such an effect, the number of ponds used in the first sedimentation basin in the wastewater treatment facility having a plurality of treatment systems is reduced, and the operation of increasing the water area load on the first sedimentation basin is performed. Sedimentation basin effluent SS
And increasing the amount of organic matter flowing into the anaerobic process.

[0011]

However, it is difficult to accurately control the amount of solid organic matter flowing into the anaerobic step by digital control of changing the number of first settling ponds.

[0012] In order to solve such a problem, the inventor of the present invention has proposed a technique capable of achieving a good phosphorus removal treatment by increasing the amount of organic substances supplied to an anaerobic tank. For removing phosphorus from wastewater, characterized by flowing the wastewater into an anaerobic tank, and a method for removing phosphorus from wastewater, comprising subjecting the sediment to ultrasonic treatment and flowing into the anaerobic tank (Japanese Patent Application No. Hei 9 (1994)). -1
No. 33989) and a method for removing phosphorus from wastewater, which is characterized by subjecting the precipitate to ozone treatment and flowing into an anaerobic tank (Japanese Patent Application No. 9-133988). However, these methods have the following problems. When the sediment of the first sedimentation basin is directly introduced into the anaerobic tank, solid particles contained in the settling sludge are relatively large and have a small surface area per unit weight. Decomposition at
There is a problem that the processing speed is relatively low, and in order to cover this, it is necessary to enlarge the biological treatment reaction tank and increase the residence time. In addition, when the precipitate in the sedimentation basin is first subjected to ultrasonic treatment and then introduced into the anaerobic tank, the solid, which is the precipitate, includes microorganisms and cellulose fibers wrapped in relatively hard cell walls or cell membranes. Since they are contained and are not easily destroyed by the ultrasonic vibration treatment, the particle diameter of the solid introduced into the anaerobic tank does not become sufficiently small. Therefore, in order to cover this, there is a problem that it is necessary to enlarge the biological treatment reaction tank and lengthen the residence time. Furthermore, when the sediment in the sedimentation basin is first subjected to ozone treatment and then introduced into the anaerobic tank, some of the organic matter contained in the sediment is oxidized and mineralized, losing its effectiveness as an organic matter, Ozone generation consumes a relatively large amount of electric power of about 10 to 15 kWh / kg O ₃ , and thus has a problem that the operation cost is relatively large.

In the standard activated sludge facility, the residence time of the entire reaction tank is designed to be 6 to 8 hours, whereas in the conventional anaerobic aerobic activated sludge method shown in FIG. The time is 6 to 8 hours, and the residence time in the anaerobic tank 3 is 1 to 2 hours. Retention time of the entire reaction tank is 6 ~
In a standard activated sludge facility designed for 8 hours, a third partition is provided by providing a partition between the anaerobic tank 3 and the aerobic tank 4 without increasing the reaction tank volume, and by providing a stirring means for the anaerobic tank 3. Even if it is modified to the biological nitrification and denitrification equipment shown in the figure, and the conventional BOD removal ability is given the phosphorus removal ability, the residence time of the whole reaction tank is insufficient.
It was necessary to secure the reaction tank residence time by reducing the amount of treated water. Exceptionally, if the actual treated water volume is smaller than the planned treated water volume in the standard activated sludge process, the actual reactor residence time is longer, so the reactor is modified to add phosphorus removal treatment capacity. In some cases, however, the first settling basin and the final settling basin did not process the planned water volume, and there was a problem that the equipment capacity was not used to the fullest.

The present invention is typified by the problem that the phosphorus removal performance of an anaerobic-aerobic activated sludge wastewater treatment facility is deteriorated due to a lack of organic matter concentration in wastewater, particularly, a concentration of soluble organic matter, and a standard activated sludge method. This was made to solve the problem that the phosphorus removal performance of the anaerobic aerobic activated sludge equipment becomes insufficient with the residence time of the reaction tank in the activated sludge equipment, and the burden of operating costs such as the addition of methanol is reduced. In addition, when converting existing activated sludge equipment for BOD removal processing to anaerobic and aerobic activated sludge wastewater treatment equipment, the capacity and processing capacity of the existing equipment are effectively used to the maximum to achieve BOD removal processing. In addition to being able to perform phosphorus removal treatment, in the case of a new installation, the residence time of the entire reaction tank can be made as compact as the standard activated sludge process equipment, and construction costs can be reduced. Do, and its object is to provide a phosphorus removal treatment method of the waste water.

[0015]

According to the present invention, at least a sedimentation basin for wastewater to be treated (first sedimentation basin), an anaerobic tank, an aerobic tank, and a sedimentation basin for wastewater treated in these tanks (final sedimentation basin). And a line for returning at least a part of the sludge taken out of the settling basin of the effluent of the aerobic tank or the treated wastewater to the first settling basin, and at least one of the sludge of the first settling basin. The present invention relates to an apparatus for removing phosphorus from wastewater, which is provided with a line for feeding a part to an anaerobic tank or an aerobic tank.

In the biological phosphorus removal treatment apparatus for wastewater according to the present invention, at least a part of the sludge mixture flowing out of the aerobic tank, or at least a part of the sludge drawn out from the final sedimentation basin, or both of them. By returning to the first sedimentation basin, the organic matter contained in the solids existing as sediment and suspended matter in the first sedimentation basin comes into contact with the microorganisms in the activated sludge returned to the first sedimentation basin under anaerobic conditions in the first sedimentation basin By effectively utilizing the solid organic matter in the first sedimentation basin and the sludge residence time in the first sedimentation basin, the phosphorus release reaction in the phosphorus removal reaction proceeds. Further, by causing at least a part of the sludge drawn from the first sedimentation basin to flow into the anaerobic step, the anoxic step, or the aerobic step, the first settled sludge containing the activated sludge having advanced the phosphorus release reaction and the solid organic matter is removed. Sent to the anaerobic or anoxic or aerobic step, further phosphorus release reaction in the anaerobic step, or phosphorus uptake reaction in the anaerobic step and possibly denitrification reaction, or phosphorus uptake reaction in the aerobic step Let it.

That is, in the apparatus of the present invention, the mixed sludge effluent from the aerobic tank containing the activated sludge or the sludge withdrawn from the final sedimentation basin is returned to the first sedimentation basin. It will be in an existing state. Further, in the first settling basin, there are solid organic matter and soluble organic matter derived from wastewater and in the form of sediment and suspended matter, and the activated sludge in the first settling basin comes into contact with these organic matters. The inside of the first sedimentation basin is anaerobic because the inside of the first sedimentation basin is not aerated and the oxygen demand of the wastewater is usually large.
That is, in the first sedimentation basin, activated sludge uses organic matter to release phosphate ions accumulated in the activated sludge cells into wastewater (= phosphorus release reaction). Thereafter, at least a part of the sedimentation basin sediment is caused to flow into an anaerobic tank or an aerobic tank, thereby causing a further phosphorus release reaction in the anaerobic tank or a phosphorus intake reaction in the aerobic tank.

When returning the sludge withdrawn from the final sedimentation basin to the first sedimentation basin, the sludge withdrawn from the final sedimentation basin has a higher concentration of activated sludge than the sludge mixture flowing out of the aerobic tank, and therefore the same activated sludge is used. There is an advantage that the return capacity required for returning the quantity is small. When returning the sludge mixture flowing out of the aerobic tank to the first sedimentation basin, increase the water load on the final sedimentation basin, unlike when returning the sludge withdrawn from the final sedimentation basin to the first sedimentation basin. There is a merit that there is no. When the method of returning the sludge withdrawn from the final sedimentation basin to the first sedimentation basin and the method of returning the sludge mixture flowing out of the aerobic tank to the first sedimentation basin are used, the intermediate merits of the above two cases are can get.

In the anaerobic tank, the activated sludge carries out a phosphorus release reaction using an organic substance mainly composed of a soluble component in the wastewater and, in some cases, an organic substance derived from the sedimentation basin sediment. If at least part of the sedimentation tank sediment is introduced into the anaerobic tank, unlike the conventional method, the activated sludge that has released phosphorus in the sedimentation tank is anaerobically mixed with solid organic matter derived from the sedimentation tank sediment. Since it is introduced into the tank and the phosphorus release reaction is further performed in the anaerobic tank, the phosphorus release reaction can be enhanced as compared with the conventional method.

In the aerobic tank, the activated sludge activates phosphate ions in the wastewater by utilizing organic matter mainly composed of soluble components in the wastewater and, in some cases, organic matter derived from the sedimentation tank sediment. Ingestion into sludge cells (= phosphorus ingestion reaction) and oxidative decomposition and removal of organic matter. When at least a part of the sedimentation tank sediment is introduced into the aerobic tank, unlike the conventional method, the phosphorus uptake reaction is also performed using solid organic matter derived from the sedimentation tank sediment. Therefore, the phosphorus intake response can be enhanced as compared with the conventional method. In this case, it is preferable to return at least a part of the sludge withdrawn from the final sedimentation basin to the anaerobic tank in order to secure the activated sludge concentration in the anaerobic tank.

In addition to the wastewater treatment apparatus comprising an anaerobic step and an aerobic step, the phosphorus removal method according to the present invention is also applied to a wastewater treatment apparatus comprising an anaerobic step, a denitrification step (anoxic step) and a nitrification step (aerobic step). Can be applied.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a biological phosphorus removal treatment apparatus according to the present invention. The present invention will be described in detail with reference to FIG.

As shown in FIG. 1, the biological phosphorus removal treatment apparatus according to the present invention mainly comprises a first sedimentation tank 2, an anaerobic tank 3, an aerobic tank 4, and a final sedimentation tank 6. In the anaerobic tank 3, only stirring is performed, and in the aerobic tank 4, a diffuser 5
To supply oxygen, and agitation is performed by a water flow generated by the aeration.

In the biological phosphorus removal treatment apparatus according to the present invention shown in FIG. 1, wastewater 1 is first passed through a sedimentation basin 2 through solid-liquid separation to an anaerobic tank 3 and an aerobic tank 4 sequentially. You. Effluent 1 flowing out of the aerobic tank 4 and flowing into the final sedimentation basin 6
0 is separated into treated water 7 and activated sludge in the final sedimentation basin 6,
It is preferable that at least a part of the activated sludge separated and concentrated in the final sedimentation basin 6, that is, at least a part of the sludge drawn out from the final sedimentation basin, is sent to the anaerobic tank 3 as return sludge.

At least a portion of the sludge mixture 10 flowing out of the aerobic tank 4 and / or at least a portion of the sludge 8 withdrawn from the final sedimentation basin 6 or both of them are mixed with the first sedimentation basin 2.
At the same time, the sludge drawn out from the first sedimentation basin 2, that is, at least a part of the first sedimentation basin sediment 9 flows into the anaerobic tank 3 or the aerobic tank 4.

Depending on the properties of the wastewater and other conditions, the withdrawn sludge 8 from the final sedimentation basin 6 is not returned to the anaerobic tank 3,
At least a part of the first sedimentation tank sediment 9 may be sent to the anaerobic tank 3.

FIG. 2 shows an example of a biological phosphorus removal treatment apparatus according to the present invention. The biological phosphorus removal treatment apparatus according to the present invention shown in FIG. 2 is obtained by adding a denitrification tank 4 to the biological phosphorus removal treatment apparatus according to the present invention shown in FIG. It is composed of a first sedimentation tank 2, an anaerobic tank 3, a denitrification tank 11, an aerobic tank 4, and a final sedimentation tank 6.

In the biological phosphorus removal treatment apparatus according to the present invention shown in FIG. 2, the denitrification tank 11 is a tank in which only stirring is performed, and the denitrification tank 3 flows out of the anaerobic tank 3 and flows into the denitrification tank 11. The discharged effluent and the mixed sludge 10 discharged from the aerobic tank 4 are sent. In the denitrification tank 11, nitrate nitrogen or nitrite nitrogen contained in the sludge mixture 10 discharged from the aerobic tank 4 is reduced to nitrogen gas (= denitrification reaction) by utilizing organic matter in the wastewater, Denitrification treatment.

Further, in the biological phosphorus removal treatment apparatus according to the present invention shown in FIG. 2, the sludge mixture effluent 10 from the aerobic tank 4 is returned to the sedimentation basin 2 first, At least a part of 9 flows into the anaerobic tank 3. By introducing activated sludge into sedimentation basin 2 first,
A phosphorus release reaction can be caused in the first sedimentation basin 2, and the first sedimentation basin sediment 9 containing sludge that has undergone the phosphorus release reaction flows into the anaerobic tank 3 to further release phosphorus in the anaerobic tank 3. The reaction is allowed to proceed, and the subsequent denitrification tank 1
In step 1 and the aerobic tank 4, the phosphorus intake reaction is advanced.

In FIG. 2, in order to introduce the activated sludge into the sedimentation basin 2 first, a method of returning the sludge mixture 10 discharged from the aerobic tank 4 to the sedimentation basin 2 is used.
A method of returning the sludge 8 drawn from the final settling tank 6 to the first settling tank 2 may be used. Further, in FIG. 2, although the method in which the sedimentation basin sediment 9 first flows into the anaerobic tank 3 is used, it may flow into the denitrification tank 11 or the aerobic tank 4. Furthermore, in order to promote the nitrification reaction, the microorganism-immobilized carrier may be charged into the aerobic tank 4 and held.

Sludge is 1000 to 40 in the effluent of the aerobic tank.
It is present at about 00 mg / L, usually about 2000-3000 mg / L.
About 00 to 10000 mg / L, usually 6500 to 850
It is about 0 mg / L. In the present invention, it is preferable to return this to the reaction tank at a flow rate of about 10 to 40% of the inflow water amount, and to the first settling basin at a flow rate of about 5 to 30% of the inflow water amount. On the other hand, in the steady state in which the above-mentioned sludge is returned, the withdrawn sludge concentration in the first sedimentation tank is 6000 to 1
About 3000mg / L, usually 8000-10000mg
/ L. In the present invention, this is defined as 5 to 40 times
Anaerobic tank at a flow rate of about 10%, preferably about 10-30%,
Send to anoxic tank or aerobic tank. When sending to two or more tanks, the above amount is the total amount.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the method for removing biological phosphorus according to the present invention will be described below. A conventional anaerobic and aerobic activated sludge method apparatus as shown in FIG. 3 and a part of the sludge withdrawn from the final sedimentation basin 6 as shown in FIG. A comparative experiment was conducted with the anaerobic-aerobic activated sludge method apparatus according to the present invention in a flow of flowing the material 9 into the anaerobic tank 3. The throughput is 12m ³ /
Day. In each case, the residence times of the first sedimentation basin 2, the anaerobic tank 3, the aerobic tank 4, and the final sedimentation basin 6 were 3 hours, 1 hour, 8 hours, and 4 hours, respectively. In the case of the conventional method, the sludge return flow rate is set to 30% of the raw water flow rate, and in the case of the present invention, the sludge drawn from the final sedimentation basin 7 is subjected to the anaerobic tank 3.
And it was returned to the first settling basin 2 at a flow rate corresponding to 20% and 10% of the raw water flow rate, respectively. The flow rate at which the sediment 9 of the sedimentation basin was pulled out and flowed into the anaerobic tank 3 was 10% of the raw water flow rate. Domestic wastewater is used as wastewater 1 and water temperature 1
Experiments were performed at 7-20 degrees. Table 3 shows the quality of the treated water obtained in each case, which was obtained after the three-month acclimatization operation was performed for each case and the treatment was stabilized. In the same table, the concentration of suspended sludge in the denitrification tank and nitrification tank at the time of data collection, that is, the MLSS concentration was about 2600 mg /
L, about 2700 mg / L in the case of the method of the present invention.

[0033]

[Table 1]

As can be seen from Table 1, by using the method of the present invention, the same amount of wastewater is treated using equipment having the same capacity as the conventional method, and the treated water having a lower phosphorus concentration than the conventional method is obtained. I got it.

[0035]

The present invention has an initial sedimentation basin, an anaerobic step and optionally an anoxic step and an aerobic step,
In a biological phosphorus removal treatment device having a final sedimentation basin, at least a part of the sludge mixture discharged from the aerobic step, or at least a part of the sludge withdrawn from the final sedimentation basin, or both of them is removed. In addition to returning the sludge to the first sedimentation basin, at least a part of the sludge drawn from the first sedimentation basin is allowed to flow into the anaerobic step, the anoxic step, or the aerobic step.

Thus, as in the case of inflow of rainwater,
Also, when the concentration of organic substances supplied to the anaerobic process drops to a level lower than the nitrogen concentration decreases, the phosphorus release reaction rate in the anaerobic process decreases, and the quality of treated water deteriorates. Organic matter concentration of soluble pollutants in wastewater flowing into the anaerobic process after undergoing liquid separation treatment /
Even when the nitrogen release ratio in the anaerobic process is low due to the low nitrogen concentration ratio and the quality of the treated water deteriorates, the first sedimentation basin functions as a reaction tank for the phosphorus release reaction, and the first sedimentation from wastewater The solid organic matter in the pond can also be effectively used for the phosphorus removal reaction. Further, the sludge residence time in the first settling basin effectively acts to promote the phosphorus release reaction by the activated sludge. The solid organic matter in the first sedimentation basin derived from the wastewater can be effectively used for the phosphorus release reaction or the phosphorus ingestion reaction, so that the burden of chemical costs due to the addition of organic matter such as methanol is reduced. In addition, there is no need to use chemicals such as ozone which require electric power for the production thereof. The main operating cost required for carrying out the method of the present invention is the power cost for liquid feeding and air feeding, which is almost the same as that of the conventional anaerobic aerobic activated sludge equipment, and the operating cost is economical. It is a target.

Further, according to the method of the present invention, the first sedimentation tank also functions as a phosphorus release reaction tank, and the sludge residence time of the first sedimentation tank effectively functions for the phosphorus release reaction. Conversion of the activated sludge equipment for anaerobic to aerobic activated sludge method equipment has the same effect as the case where the reaction tank is enlarged without greatly changing the basic structure of civil engineering of the existing equipment. Since the sedimentation basin and the final sedimentation basin can treat the water volume at the time of planning and design, the BOD can be used by maximally utilizing the capacity and treatment capacity of the existing activated sludge equipment.
Since the removal treatment, the phosphorus removal treatment, and, in some cases, the nitrogen removal treatment can be performed to obtain good treatment results, the construction cost (= remodeling cost) is economical. Furthermore, when newly installing an anaerobic aerobic activated sludge wastewater treatment facility, the construction cost is economical because the biological treatment reaction tank can be as compact as the conventional standard activated sludge facility. .

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a biological phosphorus removal treatment apparatus according to one embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a biological phosphorus removal treatment apparatus according to another embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a conventional biological phosphorus removal treatment apparatus.

[Explanation of symbols]

 1. Wastewater 2. First sedimentation basin 3. Anaerobic tank 4. Aerobic tank 5. Air diffuser 6. Final sedimentation basin 7. Treated water 8. 8. Sludge drawn from final sedimentation basin First sedimentation tank sediment 10. 10. Sludge mixture in aerobic tank Denitrification tank

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Toshiaki Inventor Bureau 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Jun Miyata 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun (72) Inventor Kei Baba Kei 1-2-1 Marunouchi, Chiyoda-ku, Tokyo, Japan Nihon Kokan Co., Ltd. (72) Satoru Udagawa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan Co., Ltd. (72) Inventor Toyoshi Sawada 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Shinichi Endo 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. F-term (reference) 4D028 AA08 BC28 BD12 4D040 BB72 BB93

Claims (2)

[Claims] An apparatus comprising at least a sedimentation basin, an anaerobic tank, an aerobic tank, and a sedimentation basin of wastewater treated in these tanks, wherein the effluent of the aerobic tank or the treated wastewater is provided. A line for returning at least part of the sludge taken out of the sedimentation basin to the settling basin of the wastewater to be treated and a line for supplying at least part of the sludge of the sedimentation basin of the treated wastewater to the anaerobic tank or the aerobic tank; Wastewater phosphorus removing device 2. An oxygen-free tank is provided between the anaerobic tank and the aerobic tank, and a line is provided for sending at least a part of the sludge of the sedimentation basin of the wastewater to be treated to the oxygen-free tank. The phosphorus removal device for wastewater according to claim 1,