JP2004275997A - Method and apparatus for removing nitrogen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for removing nitrogen capable of simply obtaining liquid suitable for anaerobic ammonia oxidation and efficiently removing nitrogen component by means of anaerobic ammonia oxidation treatment. <P>SOLUTION: Raw water in a raw water tank 12 is distributed to a first delivery line 24 and a second delivery line 26 by a distribution tank 14 and is delivered. The raw water in the second delivery line 26 is directly delivered to a mixing tank 20 and the raw water in the first delivery line 24 is subjected to nitrification treatment in a nitrification tank 16 and, thereafter, is delivered to the mixing tank 20. In the nitrification tank 16, the nitrification treatment is performed by using a carrier which is heat-treated in predetermined heating conditions, and ammonia nitrogen in the raw water is principally converted into nitrite nitrogen. The nitrification treating liquid is mixed with the raw water of the second delivery line in the mixing tank 20 and the mixed liquid is delivered to an anaerobic ammonia oxidation apparatus 22 and is subjected to the anaerobic ammonia oxidation treatment. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for removing nitrogen, and more particularly, to a method and an apparatus for removing nitrogen in raw water using an anaerobic ammonia oxidation method.
[0002]
[Prior art]
In the conventional nitrification and denitrification method, ammonia nitrogen in raw water is oxidized by nitrifying bacteria to nitric acid through nitrous acid under aerobic conditions, and this nitric acid is converted to nitrogen gas under anaerobic conditions by denitrifying bacteria. Has been removed.
[0003]
However, this method has a drawback that the running cost increases because a hydrogen donor such as methanol must be added during the denitrification treatment.
[0004]
As a method for removing nitrogen that does not require the addition of a hydrogen donor, a method called anaerobic ammonium oxidation (ANAMMOX) method has been proposed.
[0005]
In this method, a solution prepared so that nitrite ions and ammonium ions are chemically dissolved in approximately equivalent amounts is supplied to a reaction tank, and the HRT is set to 6 to 23 hours at a solution temperature of 30 ° C. and a pH of 8.0. . As a result, due to the involvement of the anaerobic ammonium oxidizing bacteria, ammonium nitrite in the liquid phase is converted to nitrogen gas and removed out of the system. Since anaerobic ammonium oxidizing bacteria are autotrophic, they do not require a hydrogen donor (eg, methanol) for denitrification, unlike normal allotrophic denitrification. Therefore, a nutrient source and oxygen are unnecessary, and the nitrogen component can be removed at low cost.
[0006]
In the above-described anaerobic ammonia oxidation method, a mass balance equation including the synthesis of cells of the anaerobic ammonium oxidizing bacteria is represented by the following equation (1).
1NH ₄ ⁺ + 1.31NO ₂ ⁻ +0.0425 CO ₂ → 1.045 N ₂ +0.220 NO ₃ ⁻ +1.870 H ₂ O + 0.090 OH ⁻ +0.0425 CH ₂ O As can be seen from the equation (1), anaerobic. In the neutral ammonia oxidation method, it is desirable to adjust the molar ratio of ammonia and nitrite of the raw water to 1: 1.31.
[0007]
As a method for obtaining a liquid having such a molar ratio, a nitrogen removal method called a SHARON method is used. In this method, the temperature is kept at 30 to 40 ° C. and the pH is kept at about 7 to 8 in a continuous stirred tank reactor having no sludge retention mechanism, and aeration is performed to keep the sludge for 1.5 days. As a result, an environment is created in which only ammonia oxidizing bacteria can grow and nitrite oxidizing bacteria cannot grow. Thereby, a liquid in which ammonia and nitrous acid have the above molar ratio can be obtained.
[0008]
However, the SHARON method has a problem that the treatment becomes unstable because there is no facility for retaining sludge. In addition, since the treatment time is limited, ammonia cannot be completely converted to nitrous acid. Further, there is a problem that a large amount of heat is required to raise the temperature of the entire liquid.
[0009]
Patent Document 1 discloses another method for obtaining a liquid having a molar ratio of ammonia to nitrite of 1: 1.31. In this method, raw water is distributed, one of the raw waters is subjected to nitrification treatment with sludge to which a nitrite-oxidizing bacterium inhibitor has been added, and then combined with the other raw water. According to this method, the growth of nitrite oxidizing bacteria contained in the sludge is suppressed by the addition of the nitrite oxidizing bacteria inhibitor, and the ammonia oxidizing bacteria in the sludge grow preferentially. Nitrogen can be mainly converted to nitrous acid. Therefore, by combining this nitrification treatment liquid with the other raw water, a liquid having the above molar ratio can be obtained.
[0010]
[Patent Document 1]
JP 2001-170684 A
[Problems to be solved by the invention]
However, Patent Document 1 is not a practical method because it uses a harmful substance such as paraquat as a nitrite-oxidizing bacterium inhibitor.
[0012]
Further, Patent Document 1 has a problem that a culture facility using a nitrite-oxidizing bacterium inhibitor is required, so that the entire facility becomes large and the running cost increases.
[0013]
The present invention has been made in view of such circumstances, and a nitrogen removal method and apparatus capable of easily obtaining a liquid suitable for anaerobic ammonia oxidation and efficiently removing a nitrogen component in anaerobic ammonia oxidation treatment. The purpose is to provide.
[0014]
[Means for solving the problem]
In order to achieve the object, the invention according to claim 1 is a nitrogen removal method for removing ammoniacal nitrogen contained in raw water, wherein the raw water is divided into two, and one of the distributed raw water is By performing nitrification treatment using immobilized microorganism carrier heat-treated under predetermined heating conditions, or activated sludge heat-treated under predetermined heating conditions, ammonia nitrogen contained in the raw water is converted into nitrite nitrogen, The nitrification treatment liquid obtained by the nitrification treatment is mixed with the other raw water distributed, and the mixed liquid is subjected to an anaerobic ammonia oxidation treatment.
[0015]
According to a second aspect of the present invention, in order to achieve the above object, in a nitrogen removing device for removing ammoniacal nitrogen contained in raw water, the raw water is distributed to a first liquid sending line and a second liquid sending line. A nitrification treatment is performed by a distribution tank and an immobilized microorganism carrier that is disposed in the first liquid sending line and that is heat-treated under a predetermined heating condition or activated sludge that is heat-treated under a predetermined heating condition, and is included in the raw water. A nitrification tank for converting ammoniacal nitrogen to nitrite nitrogen, a nitrification treatment liquid nitrified by the nitrification tank, and a mixing tank for mixing raw water flowing through the second liquid sending line, and the mixing tank was mixed. An anaerobic ammonia oxidizer for anaerobic ammonia oxidation of the mixture.
[0016]
According to the first and second aspects of the present invention, ammonia is distributed by distributing raw water into two parts, and nitrifying one of the distributed raw water with an immobilized microorganism carrier or activated sludge that has been heated under predetermined heating conditions. Nitrogen is converted to nitrite nitrogen, and the nitrification solution is mixed with the other raw water to which the nitrification treatment liquid has been distributed. Therefore, by adjusting the distribution ratio of the raw water, the ammonia and the nitrous acid in the mixed liquid can be easily adjusted. The ratio of nitric acid can be adjusted. As a result, a mixture suitable for anaerobic ammonia oxidation can be obtained, so that denitrification can be performed efficiently in anaerobic ammonia oxidation. In the invention described in claims 1 and 2, the predetermined heating conditions are such that in the case of a microorganism-immobilized carrier, the heating temperature is 30 to 80 ° C, more preferably 40 to 70 ° C, and the heating time is 1 hour or more. And more preferably for one day or more and for two weeks or less. In the case of activated sludge, the heating temperature is 50 to 90 ° C, more preferably 60 to 90 ° C, and the heating time is 1 hour or more, more preferably 1 day to 1 week.
[0017]
The invention according to claim 3 is a nitrite sensor that measures a nitrite concentration of a nitrification treatment liquid nitrified in the nitrification tank, and an ammonia sensor that measures an ammonia concentration of raw water flowing through the second liquid sending line. Flow rate adjusting means for adjusting a ratio between a flow rate of the nitrification treatment liquid flowing into the mixing tank and a flow rate of raw water according to the measurement value of the nitrite sensor and the measurement value of the ammonia sensor. And Therefore, according to the third aspect of the present invention, the ratio between the flow rate of the raw water to be mixed and the flow rate of the nitrification treatment liquid is adjusted according to the ammonia concentration of the raw water and the nitrite concentration of the nitrification treatment liquid. The ratio of ammonia to nitrous acid in the mixture can be adjusted arbitrarily. Therefore, a mixture having a ratio suitable for anaerobic ammonia oxidation can be reliably obtained. Further, even when the concentration of ammoniacal nitrogen contained in the raw water fluctuates with time, the ratio of ammonia and nitrous acid in the mixture can be adjusted to a predetermined ratio.
[0018]
The invention described in claim 4 is characterized in that the second liquid sending line is provided with a tank having substantially the same volume as the nitrification tank. Therefore, according to the fourth aspect of the present invention, the raw water flowing through the second liquid sending line stays in the tank, and the staying time is substantially the same as the staying time in the nitrification tank. For this reason, the raw water distributed at the same time in the distribution tank flows into the mixing tank at the same timing, and therefore, even if the ammonia nitrogen concentration of the raw water fluctuates, it is not affected. Thereby, the ratio of ammonia and nitrous acid in the mixture does not fluctuate, so that the anaerobic ammonia oxidation treatment can be performed stably.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Preferred embodiments of the method and apparatus for removing nitrogen according to the present invention will be described below with reference to the accompanying drawings.
[0020]
FIG. 1 is a schematic diagram showing a configuration of a first embodiment of a nitrogen removing apparatus according to the present invention.
[0021]
As shown in FIG. 1, the nitrogen removing apparatus 10 of the first embodiment mainly includes a raw water tank 12, a distribution tank 14, a nitrification tank 16, a heat treatment tank 18, a mixing tank 20, and an anaerobic ammonia oxidation apparatus 22. The raw water stored in the raw water tank 12 is sent to the distribution layer 14.
[0022]
A first liquid sending line 24 and a second liquid sending line 26 are connected to the distribution tank 14. The distribution tank 14 distributes and feeds the raw water to the first liquid sending line 24 and the second liquid sending line 26 at a predetermined flow ratio. For example, the ratio of the flow rate of the raw water flowing through the first liquid transfer line 24 to the flow rate of the raw water flowing through the second liquid transfer line 26 (hereinafter, referred to as a distribution ratio) is about 1: 1 to 1: 1.4. And distribute the solution.
[0023]
The second liquid sending line 26 is directly connected to the mixing tank 20. On the other hand, the first liquid supply line 24 is connected to the nitrification tank 16, and the nitrification tank 16 is connected to the mixing tank 20 via the nitrification liquid line 30.
[0024]
An immobilized microorganism carrier (hereinafter, referred to as a carrier) is charged into the nitrification tank 16. The carrier is capable of depositing either a monomer or a prepolymer for immobilizing microorganisms in the presence of sludge, either in lakes, rivers, or sea bottom mud, surface soil, or activated sludge in sewage treatment plants. It is manufactured by polymerizing while heating at ~ 80 ° C. Ammonia oxidizing bacteria that nitrify ammonia nitrogen to nitrite are preferentially accumulated in the carrier thus produced, and accumulation of nitrite oxidizing bacteria that nitrifies nitrite to nitric acid is suppressed. The heating temperature during the production of the carrier is preferably from 30 to 80C, more preferably from 40 to 70C. The heating time during the production of the carrier is preferably 1 hour or more, and more preferably 1 day or more and 2 weeks or less. This is because if the heating time is short, the effect of preferentially accumulating ammonia-oxidizing bacteria is small. In addition, since the accumulation effect hardly changes even if heating is performed for more than two weeks, it is preferable to set the heating time within two weeks.
[0025]
At the outlet of the nitrification tank 16, a carrier recovery device 28 is installed. The carrier recovered by the recovery device 28 is transported to the heat treatment tank 18 via the carrier transport line 32. The heat treatment tank 18 is a device for heat-treating the carrier, and the heating conditions thereof are preferably the same heating conditions as in the production of the carrier. That is, the heating temperature is preferably from 30 to 80 ° C, more preferably from 40 to 70 ° C. The heating time is preferably one hour or more, and more preferably one day or more and two weeks or less. By heat-treating the carrier under such heating conditions, accumulation of nitrite-oxidizing bacteria on the carrier is suppressed, and ammonia-oxidizing bacteria are efficiently accumulated on the carrier. That is, the nitrite generation performance of the carrier can be restored.
[0026]
The carrier heat-treated in the heat treatment tank 18 is returned to the nitrification tank 16 via the carrier return line 34. Thereby, in the nitrification tank 16, the ammonia nitrogen in the raw water can be mainly converted to nitrous acid without converting to nitric acid. When the heating temperature of the carrier is set at 50 to 70 ° C., the concentration ratio of nitrite and nitric acid contained in the nitrification treatment liquid becomes about 30, and the nitrite type reaction rate (= nitrite / (nitrite + nitrate) ) × 100) becomes 97%, and a nitrite-type nitrification reaction of about 100% is performed.
[0027]
The nitrification liquid that has been nitrified in the nitrification tank 16 is sent to the mixing tank 20 via the nitrification liquid line 30. The nitrification liquid is mixed in the mixing tank 20 with the raw water directly supplied from the second liquid supply line 26. That is, in the mixing tank 20, the nitrification treatment liquid containing nitrous acid and the raw water containing ammonia are mixed, so that the mixing liquid contains ammonia and nitrous acid. The ratio of ammonia to nitrous acid contained in the admixture depends on the distribution ratio in the distribution tank 14 (that is, the flow rate of the first liquid feed line 24 and the (Ratio to the flow rate of the second liquid sending line 26). Therefore, by adjusting the distribution ratio to 1: 1 to 1: 1.4, a mixture liquid in which the molar ratio of ammonia to nitrous acid is close to 1: 1.31 can be prepared.
[0028]
The mixed liquid in the mixing tank 20 is sent to the anaerobic ammonia oxidation device 22. The anaerobic ammonia oxidizer 22 removes nitrogen components by using ammonia as a hydrogen donor by setting the residence time to 6 to 23 hours at a liquid temperature of 30 ° C. and a pH of 8.0.
[0029]
Next, the operation of the nitrogen removing device 10 configured as described above will be described.
[0030]
FIG. 2 is a diagram showing the relationship between the components of the mixture and the nitrogen removal rate of the anaerobic ammonia oxidation device 22.
[0031]
As shown in the figure, the anaerobic ammonia oxidizer 22 can obtain a high removal rate when the ratio of ammonia to nitrous acid in the mixture is in the range of 0.9 to 1.4. For this reason, it is necessary to control the ratio of ammonia and nitrous acid in the mixture to 0.9 to 1.4.
[0032]
In the present embodiment, the raw water is distributed to the first liquid sending line 24 and the second liquid sending line 26 by the distribution tank 14 and sent, and the ammonia nitrogen of the raw water in the first liquid sending line 24 is converted to nitrous acid. Since the conversion is made so as to be mixed with the raw water in the second liquid sending line 26, the ratio between ammonia and nitrous acid in the mixed liquid can be easily adjusted by adjusting the distribution ratio in the distribution tank 14. Therefore, the ratio of ammonia to nitrite in the mixture can be adjusted to the above range, and the denitrification treatment in the anaerobic ammonia oxidizer 22 can be performed efficiently.
[0033]
FIG. 3 is a schematic diagram illustrating a configuration of the nitrogen removing device 36 according to the second embodiment.
[0034]
The nitrogen removing device 36 shown in FIG. 3 is different from the nitrogen removing device 10 of the first embodiment shown in FIG. The difference is that an ammonia sensor 40 is provided in the liquid sending line 26. The nitrous acid sensor 38 is a measuring device for measuring the concentration of nitrous acid in the nitrification treatment liquid, and uses, for example, Brown Roubaix. The ammonia sensor 40 is a measuring device that measures the concentration of ammonia in the raw water flowing through the second liquid sending line 26, and uses, for example, an ion electrode.
[0035]
The distribution tank 14 adjusts the distribution ratio between the first liquid sending line 24 and the second liquid sending line 26 according to the measurement value of the nitrite sensor 38 and the measurement value of the ammonia sensor 40. Then, control is performed such that the ratio of nitrous acid to ammonia in the mixing tank 20 becomes 0.9 to 1.4.
[0036]
Next, the operation of the second embodiment configured as described above will be described.
[0037]
The raw water flowing through the first liquid sending line 24 is subjected to nitrification treatment in the nitrification tank 16, whereas the raw water flowing through the second liquid sending line 26 is directly sent to the mixing tank 20. Therefore, the raw water flowing through the first liquid sending line 24 flows into the mixing tank 20 with a delay corresponding to the residence time in the nitrification tank 16. For this reason, if the concentration of ammonia contained in the raw water fluctuates, the ratio of ammonia to nitrite during mixing may fluctuate significantly. For example, when the ammonia concentration of the raw water greatly decreases, the ammonia concentration of the raw water flowing into the mixing tank 20 from the second liquid sending line 26 immediately decreases, whereas the ammonia concentration of the raw water flows into the mixing tank 20 from the nitrification liquid line 30. The nitrite concentration of the nitrification solution decreases with a delay. Therefore, immediately after the ammonia concentration of the raw water decreases, the mixture may have a large ratio of nitrous acid to ammonia.
[0038]
Therefore, in the second embodiment, the distribution ratio of the distribution tank 14 is adjusted according to the measurement value of the nitrite sensor 38 and the measurement value of the ammonia sensor 40. For example, when the ammonia concentration of the raw water decreases as described above, the flow rate of the second liquid feed line 26 is increased with respect to the flow rate of the first liquid feed line 24. Thereby, the fluctuation of the ratio of ammonia and nitrous acid in the mixture can be suppressed.
[0039]
Further, according to the second embodiment, even when the nitrification efficiency in the nitrification tank 16 fluctuates, similarly, by adjusting the distribution ratio by the distribution tank 14, the fluctuation of the ratio of ammonia and nitrous acid in the admixture liquid is changed. Can be suppressed.
[0040]
As described above, according to the second embodiment, by adjusting the distribution ratio of the distribution tank 14, the ratio of ammonia to nitrite in the mixture can be arbitrarily adjusted. Therefore, even when the ammonia concentration of the raw water fluctuates or the nitrification efficiency of the treatment tank 16 fluctuates, the ratio of ammonia and nitrite in the mixture is reliably controlled in the range of 0.9 to 1.4. be able to. Thereby, the denitrification efficiency in the anaerobic ammonia oxidation device 22 can be improved.
[0041]
In the above-described second embodiment, the distribution ratio in the distribution tank 14 is adjusted. However, the flow rate flowing through the first liquid feed line 24 (or the nitrification treatment liquid line 30) and the second liquid feed line 26 The flow rate may be adjusted by adjusting the ratio to the flow rate flowing through the first liquid supply line 24 (or the nitrification treatment liquid line 30) or the second liquid supply line 26.
[0042]
FIG. 4 is a diagram schematically showing a configuration of a nitrogen removing device 42 according to the third embodiment.
[0043]
The nitrogen removing device 42 according to the third embodiment shown in FIG. 4 is different from the nitrogen removing device 10 according to the first embodiment shown in FIG. Is different. The buffer tank 44 is configured to have substantially the same volume as the nitrification tank 16. Therefore, the residence time in the nitrification tank 16 and the residence time in the buffer tank 44 are substantially equal. Therefore, the raw water distributed to the first water supply line 24 and the second water supply line 26 at the same time in the distribution tank 14 flows into the mixing tank 20 at substantially the same time. Therefore, even if the ammonia concentration of the raw water fluctuates, the components of the mixture become unaffected, and the ratio of ammonia to nitrous acid in the mixture becomes always substantially constant. Thus, a stable denitrification process can be performed in the anaerobic ammonia oxidation device 22.
[0044]
In the above-described third embodiment, the volume of the buffer tank 44 is substantially equal to the volume of the nitrification tank 16, but the present invention is not limited to this. When the ratio of the volume of the nitrification tank 16 to the volume of the buffer tank 44 matches the distribution ratio of the distribution tank 14, the residence time in the nitrification tank 16 and the residence time in the buffer tank 44 can be made equal.
[0045]
FIG. 5 is a diagram schematically illustrating a configuration of a nitrogen removing device 46 according to the fourth embodiment.
[0046]
The nitrification tank 16 of the nitrogen removing device 46 shown in FIG. 5 performs nitrification treatment with activated sludge. A sedimentation tank 48 is provided downstream of the nitrification tank 16, and the activated sludge flowing out of the nitrification tank 16 is settled and recovered by the sedimentation tank 48. Part of the activated sludge settled in the settling tank 48 is withdrawn by the sludge withdrawal line 52 and is periodically removed as excess sludge. The remaining activated sludge is transported to the heat treatment tank 50 by the sludge transport line 54, and is heated in the heat treatment tank 50. The activated sludge subjected to the heat treatment is returned to the nitrification tank 16 by a sludge return line 56.
[0047]
As a heating condition in the heat treatment tank 50, a heating temperature is preferably from 50 to 90C, more preferably from 60 to 90C. In addition, the heating time is preferably 1 hour or more, and more preferably 1 day to 1 week. By performing the heat treatment under such heating conditions, the ammonia oxidizing bacteria can be preferentially grown while suppressing the growth of the nitrite oxidizing bacteria in the activated sludge. Therefore, by performing the nitrification treatment using the activated sludge that has been subjected to the heat treatment, the ammonia nitrogen in the raw water is converted to nitrite without being nitrified to nitric acid.
[0048]
According to the fourth embodiment configured as described above, ammonia can be almost completely converted to nitrite in the nitrification tank 16, so that the ratio of ammonia and nitrite in the mixture can be easily adjusted. Thus, a mixture suitable for anaerobic ammonia oxidation treatment can be obtained.
[0049]
Also in the above-described fourth embodiment, a nitrite sensor is provided in the nitrification treatment liquid line 30 and an ammonia sensor is provided in the second liquid supply line 26, or the nitrification tank 16 has substantially the same volume. May be arranged in the second liquid sending line 26.
[0050]
【The invention's effect】
As described above, according to the method and apparatus for removing nitrogen according to the present invention, the raw water is divided into two, and after converting ammoniacal nitrogen in one raw water to nitrite nitrogen, the other raw water distributed Thus, a liquid in which nitrite and ammonia are adjusted to a predetermined ratio can be easily obtained, and nitrogen can be efficiently removed in the anaerobic ammonia oxidation treatment.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration of a first embodiment of a nitrogen removing apparatus according to the present invention. FIG. 2 is a diagram showing a relationship between a component ratio of a mixture and a nitrogen removal rate in an anaerobic ammonia oxidation treatment. 3 is a schematic view showing the configuration of a second embodiment of the nitrogen removing apparatus according to the present invention. FIG. 4 is a schematic view showing the configuration of a third embodiment of the nitrogen removing apparatus according to the present invention. Diagram showing the configuration of a fourth embodiment of the nitrogen removal apparatus according to the present invention.
DESCRIPTION OF SYMBOLS 10 ... Nitrogen removal apparatus, 12 ... Raw water tank, 14 ... Distribution tank, 16 ... Nitrification tank, 18 ... Heat treatment tank, 20 ... Mixing tank, 22 ... Anaerobic ammonia oxidation apparatus, 24 ... 1st liquid sending line, 26 ... 2nd liquid sending line, 28 ... collection device, 30 ... nitrification treatment liquid line, 32 ... carrier transportation line, 34 ... carrier return line, 36 ... nitrogen removal device, 38 ... nitrous acid sensor, 40 ... ammonia sensor, 42 ... nitrogen Removal device, 44: Buffer tank, 46: Nitrogen removal device, 48: Sedimentation tank, 50: Heat treatment tank, 52: Sludge extraction line, 54: Sludge transport line, 56: Sludge return line

Claims (4)

In a nitrogen removal method for removing ammonia nitrogen contained in raw water,
Dividing the raw water into two,
The one of the distributed raw water is subjected to nitrification treatment using an immobilized microorganism carrier heat-treated under a predetermined heating condition or activated sludge heat-treated under a predetermined heating condition, whereby ammonia nitrogen contained in the raw water is treated. To nitrite nitrogen,
The nitrification solution subjected to the nitrification treatment is mixed with the other raw water distributed,
A method for removing nitrogen, comprising subjecting the mixture to anaerobic ammonia oxidation. In a nitrogen removal device that removes ammoniacal nitrogen contained in raw water,
A distribution tank that distributes the raw water to a first liquid sending line and a second liquid sending line;
The nitrification treatment is performed on the immobilized microorganism carrier, which is provided in the first liquid sending line, and is heat-treated under predetermined heating conditions, or activated sludge, which is heat-treated under predetermined heating conditions, to remove ammonia nitrogen contained in the raw water. A nitrification tank for converting to nitrite nitrogen,
A mixing tank for mixing the nitrification treatment liquid nitrified by the nitrification tank and raw water flowing through the second liquid sending line,
An anaerobic ammonia oxidizer for anaerobic ammonia oxidation of the mixture mixed in the mixing tank;
A nitrogen removing device comprising: A nitrite sensor for measuring the nitrite concentration of the nitrification solution nitrified in the nitrification tank,
An ammonia sensor for measuring the ammonia concentration of the raw water flowing through the second liquid sending line,
Flow rate adjusting means for adjusting the ratio between the flow rate of the nitrification treatment liquid flowing into the mixing tank and the flow rate of raw water according to the measurement value of the nitrous acid sensor and the measurement value of the ammonia sensor,
The nitrogen removal device according to claim 2, comprising: The nitrogen removing device according to claim 2, wherein a tank having substantially the same volume as the nitrification tank is provided in the second liquid sending line.

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