Denitrification treatment device for nitrate nitrogen-containing water

Abstract

This invention provides a denitrification treatment apparatus and denitrification treatment method that control a hydrogen oxidation denitrification reaction using hydrogen gas, which has high biocompatibility and can be produced even in a closed, isolated environment, and has effective denitrification capabilities in the treatment of aquaculture wastewater. [Solution] According to the present invention, a nitrate nitrogen-containing water denitrification treatment device is provided, comprising: a sealed treatment container containing a microbial carrier on which hydrogen oxidation denitrifying bacteria are immobilized; a hydrogen gas supply unit that supplies hydrogen gas to the gas phase inside the treatment container from the top of the treatment container; a pressure control unit that maintains the inside of the treatment container at atmospheric pressure; and a water spraying unit that sprays nitrate nitrogen-containing water onto the microbial carrier from the top of the treatment container.

Description

Technical Field

[0001] The present invention relates to a denitrification treatment apparatus for nitrate nitrogen-containing water.

Background Art

[0002] The development of closed-loop land-based aquaculture enables the breeding of fish and shellfish in various locations, leading to a stable supply of food and an increase in production. For example, Patent Document 1 discloses a purification system for closed-loop land-based aquaculture that purifies the water in an aquarium without waste through an electrolysis treatment apparatus in a purification system including a nitrification tank and a denitrification tank.

[0003] Closed-loop land-based aquaculture is suitable as a food production method for maintaining planetary exploration activities because food production is possible under an appropriate management environment. In recent years, the implementation of closed-loop land-based aquaculture at a lunar base has been planned (Japan Aerospace Exploration Agency 2022 Fiscal Year Task Setting Workshop: Lunar Food Production).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Denitrification of nitrate nitrogen accumulated in aquaculture systems is crucial for preventing poor growth of farmed organisms and is essential for the success of closed-loop land-based aquaculture. Existing denitrification technologies mainly use chemicals such as methanol and ethanol, but these are toxic to farmed organisms and require delicate control of the treatment equipment. Furthermore, sustained production and supply of chemicals is difficult in closed, isolated environments such as lunar bases. In addition, there is a method that combines the absorption of nitrate nitrogen by plants, the purification of farming water, and the use of grown plants as food, which is highly compatible with farmed organisms and can operate in closed, isolated environments (aquaponics), but it requires a vast area to achieve sufficient purification efficiency. Therefore, the challenge is to develop a treatment technology that is less toxic to farmed organisms, can operate sustainably in closed, isolated environments, and has high denitrification efficiency.

[0007] The hydrogen oxidation-denitrification reaction by autotrophic bacteria, as shown in Chemical Formula 1, utilizes hydrogen gas during the denitrification reaction that reduces and removes nitrate nitrogen to nitrogen gas. Hydrogen gas is non-toxic to the organisms being raised and can be easily produced by methods such as water electrolysis, thus contributing to solving the aforementioned problems. In particular, at planetary exploration bases, the ability to utilize excess hydrogen gas after oxygen production would support the realization of aquaculture on bases. However, to date, no specific structures or test examples demonstrating the effectiveness of controlling the hydrogen oxidation-denitrification reaction to enable wastewater treatment for aquaculture have been reported. (chemical formula 1) [ka]

[0008] This invention has been made in view of these circumstances, and aims to provide a denitrification treatment apparatus and a denitrification treatment method that control a hydrogen oxidation denitrification reaction using hydrogen gas, which has high biocompatibility and can be produced even in a closed isolation environment, and has effective denitrification capacity in the treatment of aquaculture wastewater. [Means for solving the problem]

[0009] Through diligent research, the inventors discovered that the above problems could be solved by supplying hydrogen gas into a processing container containing a microbial carrier and spraying nitrate nitrogen-containing water onto the microbial carrier in the presence of hydrogen gas, thus completing the present invention.

[0010] The present invention provides the following: (1) A sealed processing container containing a microbial carrier on which hydrogen oxidative denitrifying bacteria are immobilized, A hydrogen gas supply unit that supplies hydrogen gas to the gas phase portion within the processing container from the top of the processing container, A pressure control unit that maintains the pressure inside the processing container at atmospheric pressure, A denitrification apparatus for nitrate nitrogen-containing water, comprising a water spraying unit that sprays nitrate nitrogen-containing water onto the microbial carrier from the top of the treatment container. (2) The denitrification apparatus described in (1), A nitrate nitrogen-containing water denitrification apparatus having a circulation path for supplying treated water, which has been denitrified in the nitrate nitrogen-containing water denitrification apparatus, into the treatment container. (3) A denitrification apparatus as described in (1) or (2), A denitrification treatment apparatus for nitrate nitrogen-containing water, wherein the microbial retaining carrier is a polyolefin sponge carrier. (4) A method for denitrifying nitrate nitrogen-containing water using a denitrification apparatus described in any of (1) to (3), The process involves placing a microbial carrier on which hydrogen oxidation denitrification bacteria are immobilized into the aforementioned processing container and sealing it, A step of supplying hydrogen gas to the gas phase inside the processing container from the top of the processing container, thereby filling the processing container with hydrogen gas. A step of maintaining atmospheric pressure inside the processing container, The process involves spraying nitrate nitrogen-containing water onto the microbial carrier from the top of the treatment container, A method for denitrifying nitrate nitrogen-containing water, including [specific components]. (5)(4) The denitrification treatment method described above, A denitrification treatment method for nitrate nitrogen-containing water, further comprising a step of supplying and circulating the treated water obtained by denitrification treatment of the nitrate nitrogen-containing water in the treatment vessel. (6) A closed-loop onshore aquaculture system comprising the denitrification treatment apparatus for nitrate nitrogen-containing water according to any one of (1) to (3).

Advantages of the Invention

[0011] According to the present invention, it is possible to control the hydrogenation denitrification reaction, has a high affinity for the breeding body, and enables denitrification treatment of nitrate nitrogen-containing water that can operate even in a closed and isolated environment. Therefore, the applicable areas for closed-loop onshore aquaculture are expanded.

[0012] According to the present invention, in the denitrification treatment of nitrate nitrogen-containing water, it is possible to improve the utilization efficiency of hydrogen gas for the denitrification reaction and reduce the amount of carbon input.

Brief Description of the Drawings

[0013] [Figure 1] Figure 1 shows a schematic diagram of the denitrification treatment apparatus for nitrate nitrogen-containing water of the present invention. [Figure 2] Figure 2 shows the evaluation of the denitrification ability of the denitrification treatment apparatus for nitrate nitrogen-containing water of the present invention. [Figure 3] Figure 3 shows the results of implementing closed-loop onshore aquaculture wastewater treatment using the denitrification treatment apparatus for nitrate nitrogen-containing water of the present invention. <0%0092> [Figure 4] Figure 4 shows the results of microbial analysis inside the denitrification treatment apparatus for nitrate nitrogen-containing water of the present invention.

Modes for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described with reference to Figure 1. Various characteristic matters shown in the following embodiments can be combined with each other. Also, an invention can be achieved independently for each characteristic matter.

[0015] <Denitrification treatment apparatus 1 for nitrate nitrogen-containing water> As shown in Figure 1, the nitrate nitrogen-containing water denitrification treatment apparatus 1 according to one embodiment of the present invention comprises a sealed treatment container 3 containing a microbial carrier 2 on which hydrogen oxidation denitrifying bacteria are immobilized, a hydrogen gas supply unit 4 that supplies hydrogen gas to the gas phase inside the treatment container 3 from the top of the treatment container 3, a pressure control unit 5 that maintains the pressure inside the treatment container at atmospheric pressure, and a water spraying unit 6 that sprays nitrate nitrogen-containing water onto the microbial carrier from the top of the treatment container. A denitrification treatment device 1 for nitrate nitrogen-containing water according to one embodiment of the present invention has a circulation path 7 for supplying treated water that has been denitrified by the denitrification treatment device 1 into the treatment container 3.

[0016] <Microbial retaining carrier 2> The microbial retaining carrier 2 can be manufactured by methods known to those skilled in the art, or it can be purchased from a manufacturer. Such carriers can be, for example, polyester nonwoven fabric, ceramics, polyolefin sponge, polyethylene glycol gel, or microbial self-granulating material (granules), and polyolefin sponge is preferred in terms of good adhesion of hydrogen-oxidative denitrifying bacteria. The number, size, and volume of the microbial retaining carriers 2 may be changed depending on the amount of nitrate nitrogen-containing water, the nitrogen concentration, or the capacity of the treatment container 3. The volume of the microbial retaining carrier 2 is, for example, 1 to 80% of the internal space volume of the treatment container 3, and preferably 10 to 40%.

[0017] <Processing container 3> The processing container 3 has an internal space that can be filled with a microbial carrier 2, and the internal space comprises a carrier section filled with the microbial carrier 2 and a gas phase section above the carrier section that is not filled with the microbial carrier 2. The processing container 3 is equipped with a water inlet 3a, a gas inlet 3b, a water outlet 3c for drainage, and a gas outlet 3d for exhaust gas. The water outlet 3c and gas outlet 3d may be connected to a U-shaped pipe, and after the treated water and excess gas are discharged from one outlet, gas-liquid separation may be performed via the U-shaped pipe, and the treated water may be discharged from the water outlet 3c and the excess gas from the gas outlet 3d. The inflow water supply channel 8 is in fluid communication with the processing container 3 via the water inlet 3a.

[0018] <Hydrogen gas supply unit 4> The hydrogen gas supply unit 4 comprises a hydrogen gas supply source 4a and a hydrogen gas supply channel 4b, and the hydrogen gas supply channel 4b is in fluid communication with the gas phase section inside the processing container 3 via a gas inlet 3b. The hydrogen gas supplied from the hydrogen gas supply source 4a is supplied to the inside of the processing container 3 through the hydrogen gas supply channel 4b. The hydrogen gas supply channel 4b is equipped with a gas flow meter 10 that can check the amount of hydrogen gas supplied. The hydrogen gas supply source 4a is not limited to, but examples include a hydrogen gas cylinder, hydrogen-producing bacteria, and a supply source from the electrolysis of water. In the denitrification treatment device 1 for nitrate nitrogen-containing water according to one embodiment of the present invention, it is preferable that the amount of hydrogen gas supplied to the treatment container 3 is about 4.8 L to 8.1 L per day for the removal of 1 g of nitrate nitrogen. In another embodiment, in order to improve the denitrification efficiency, the hydrogen gas may be dissolved into the nitrate nitrogen-containing water in the form of fine bubbles.

[0019] <Pressure control unit 5> The pressure control unit 5 includes a gas outlet 3d, a gas pressure gauge 5a, and an emergency exhaust valve 5b, and the pressure inside the processing container 3 is maintained at atmospheric pressure (1 atm). An automatic pressure control valve may also be provided.

[0020] <Sprinkler section 6> The water spraying unit 6 is equipped with a water spraying nozzle for spraying nitrate nitrogen-containing water. The nitrate nitrogen-containing water supplied to the treatment container 3 through the inflow water supply channel 8 is ejected from the water spraying unit 6, passes through the gas phase, and is sprayed onto the microbial retaining carrier 2. By spraying nitrate nitrogen-containing water in an environment where hydrogen gas is filled in the gas phase of the treatment container 3, hydrogen gas dissolves into the nitrate nitrogen-containing water, and even at atmospheric pressure, it can exhibit effective denitrification capacity in the treatment of nitrate nitrogen-containing water.

[0021] <Circulation path 7> The circulation path 7 is equipped with a circulation pump 7a that pressurizes the treated water, and some or all of the treated water that has undergone denitrification treatment is circulated through the circulation path 7 and sprayed again onto the microbial carrier 2 from the spraying unit 6. In this way, the number of contacts between the treated water, the microbial carrier 2 and hydrogen gas can be increased, and the denitrification efficiency can be improved. The treated water that has been circulated through the circulation path 7 and subjected to denitrification treatment again in the treatment container 3 may be circulated again. If sufficient denitrification efficiency can be obtained, it is not necessary to circulate the treated water. As shown in Figure 1, a circulation outlet 3e may be provided in the treatment container 3, and the treated water may be circulated through the circulation outlet 3e. In another embodiment, the treated water may be circulated through a drainage outlet 3c. As shown in Figure 1, the circulation path 7 may be connected to the inflow water supply path 8, and the treated water may be returned from the circulation path 7 to the treatment container 3 through the inflow water supply path 8. In another embodiment, the circulation path 7 may be connected to the treatment container 3, and the treated water may be returned directly from the circulation path 7 to the treatment container 3.

[0022] <Inflow water supply channel 8> A nitrate nitrogen-containing water denitrification treatment device 1 according to one embodiment of the present invention is connected to an aquaculture tank via an inflow water supply channel 8 and removes nitrate nitrogen accumulated in aquaculture wastewater. One end of the inflow water supply channel 8 is connected to a treatment container 3 via a water inlet 3a, and the other end is connected to an aquaculture tank. An inflow water supply pump may be provided at the other end of the inflow water supply channel 8, and the inflow water supply pump may be submerged in the aquaculture tank to supply aquaculture wastewater from the aquaculture tank to the nitrate nitrogen-containing water denitrification treatment device 1.

[0023] <Hydrogen-oxidizing denitrifying bacteria> The hydrogen-oxidative denitrifying bacteria immobilized on the microbial carrier 2 may include the genus Thauera as an example, but are not limited to any species capable of participating in the hydrogen-oxidative denitrification reaction. The bacterial species present in the denitrification treatment device 1 for nitrate nitrogen-containing water can be identified by performing amplicon analysis targeting 16S rRNA (v4 hypervariable region) using carriers collected from inside the treatment container 3. The above bacterial species may be immobilized on separate carriers or on the same carrier.

[0024] <Nitrate nitrogen-containing water> Nitrate nitrogen-containing water includes any water containing nitrate nitrogen, regardless of whether it is drinking water or sewage, such as aquaculture wastewater, household wastewater, industrial wastewater, factory wastewater, and groundwater.

[0025] In the nitrate nitrogen-containing water denitrification treatment apparatus 1 of the present invention, the pH of the nitrate nitrogen-containing water is preferably in the range of 5.0 to 10.5, and more preferably in the range of 7.0 to 8.5. By setting the pH of the nitrate nitrogen-containing water within this range, deterioration of denitrification efficiency and adverse effects on the animals can be suppressed. Alternatively, the pH of the nitrate nitrogen-containing water may be within the range of two points selected from the group consisting of 5.0, 5.5, 6.0, 6.5, 7.0, 7.1, 7.2, 7.3, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 9.0, 9.5, 10.0, and 10.5.

[0026] <Carbon dioxide supply unit 9> The pH adjusting agent used to adjust the pH of nitrate nitrogen-containing water is not limited to carbon dioxide, and the nitrate nitrogen-containing water denitrification treatment apparatus 1 of the present invention may further include a carbon dioxide supply unit 9 that supplies carbon dioxide to the gas phase in the treatment container 3. The carbon dioxide supply unit 9 comprises a carbon dioxide supply source 9a and a carbon dioxide supply passage 9b, and the carbon dioxide supply passage 9b is in fluid communication with the gas phase in the treatment container 3 via a gas inlet 3b. The carbon dioxide supplied from the carbon dioxide supply source 9a is supplied to the inside of the treatment container 3 through the carbon dioxide supply passage 9b. The carbon dioxide supply passage 9b includes a solenoid valve 11 that controls the supply of carbon dioxide to the treatment container 3 and a gas flow meter 10 that can check the amount of carbon dioxide supplied. The carbon dioxide supply source 9a may be, for example, a carbon dioxide cylinder.

[0027] <pHコントローラー> The nitrate nitrogen-containing water denitrification treatment apparatus 1 of the present invention may be equipped with a pH sensor 12 and a pH meter 13 as a pH controller to control the pH of the nitrate nitrogen-containing water. For example, the pH may be measured by the pH meter 13 connected to the pH sensor 12, and the pH may be controlled by automatically adding an appropriate amount of pH adjusting agent through feedback control of the pH sensor 12. The installation location of the pH sensor 12 and pH meter 13 is not particularly limited, but in order to control the pH of the circulating treated water, the pH sensor 12 and pH meter 13 may be located on the circulation path 7 as shown in Figure 1.

[0028] In the nitrate nitrogen-containing water denitrification treatment apparatus 1 according to one embodiment of the present invention, the temperature of the nitrate nitrogen-containing water is preferably in the range of 10 to 35 degrees Celsius, and more preferably in the range of 15 to 35 degrees Celsius. By setting the temperature of the nitrate nitrogen-containing water within this range, the denitrification activity of hydrogen oxidation denitrification bacteria in the hydrogen oxidation denitrification reaction can be improved. [Examples]

[0029] The present invention will be further described below with reference to examples, but the present invention is not limited thereto.

[0030] Experimental Example 1 <Processing container and conditions> A treatment container was prepared by placing a polyolefin sponge carrier, to which hydrogen-oxidative denitrifying bacteria were immobilized, into a cylindrical container that was sealed at atmospheric pressure. The volume of the sponge carrier was 40% of the internal space volume of the treatment container. Subsequently, hydrogen gas was filled into the treatment container from the hydrogen gas supply unit, replacing the internal environment with hydrogen gas. Then, aquaculture wastewater was sprayed onto the microbial carrier from the top of the treatment container. Excess hydrogen gas was discharged into the atmosphere through a U-shaped pipe (gas-liquid separation) in the gas outlet. New hydrogen gas flowed into the treatment container at atmospheric pressure (atmospheric pressure). Since the gas outlet was open, the inside of the treatment container was not pressurized and remained at atmospheric pressure. The discharged excess hydrogen may be reused by providing a separate recovery device. To improve denitrification efficiency by increasing the number of contacts between the aquaculture wastewater, the microbial carrier, and hydrogen gas, some of the water inside the treatment container was circulated and sprayed back onto the carrier. In addition, an emergency exhaust valve and a gas pressure gauge were installed at the top of the treatment container, and exhaust gas was discharged from the bottom of the treatment container to maintain the pressure inside the container at atmospheric pressure (1 atm). Furthermore, the pH of the treated water circulating within the system was constantly monitored, and carbon dioxide was intermittently supplied using a pH controller to maintain the pH at 7.0 to 8.5.

[0031] Example 2 <Denitrification capacity evaluation> The denitrification capacity of the nitrate nitrogen-containing water denitrification treatment device of the present invention was evaluated using simulated aquaculture wastewater prepared by adding 40 mg / L of nitrate nitrogen to tap water. As a comparative example, a nitrate nitrogen-containing water denitrification treatment device was prepared (hereinafter referred to as the "submersible type") with the same structure as the treatment container in the nitrate nitrogen-containing water denitrification treatment device of the present invention, but in which aquaculture wastewater is first accumulated inside the treatment container, and denitrification treatment is performed by supplying hydrogen gas to the aquaculture wastewater and aerating it, and the denitrification efficiency was compared. The simulated aquaculture wastewater was passed through so that the hydrological residence times were 6, 10, and 12 hours, and the hydrogen gas aeration rate was fixed at 10 mL / min. The results are shown in Figure 2. The nitrate nitrogen-containing water denitrification treatment apparatus of the present invention exhibited a higher denitrification effect compared to the submersible nitrate nitrogen-containing water denitrification treatment apparatus, with a denitrification rate up to 1.5 times higher. Furthermore, the amount of hydrogen gas required for the denitrification reaction was approximately 30% less than that of the submersible nitrate nitrogen-containing water denitrification treatment apparatus, indicating that the nitrate nitrogen-containing water denitrification treatment apparatus of the present invention is a system with higher hydrogen gas utilization efficiency.

[0032] Example 3 <Closed-loop recirculating wastewater treatment system for land-based aquaculture> The nitrate nitrogen-containing water denitrification treatment device of the present invention was introduced into a small-scale closed-circulation land-based aquaculture wastewater treatment system. Rainbow trout were introduced as test fish at a rate of 1042 ± 17 g relative to the tank volume, and 1.3% of the total weight was fed on weekdays. The aquaculture tank was 60 L and equipped with the necessary aeration equipment, LED lights (for sunlight simulation), a filtration filter (for solid matter and ammonia nitrogen removal), a UV sterilizer, and a cooler (for constant water temperature control at 15°C). Two denitrification treatment sections were established: a low-concentration section and a high-concentration section. In the low-concentration section, denitrification treatment was performed using the nitrate nitrogen-containing water denitrification treatment device of the present invention when the nitrate nitrogen concentration in the tank reached 50 mg / L, and in the high-concentration section, when it reached 200 mg / L. The treated water was then returned to the tank. As a comparative example, a control section was established where water was changed as needed when a predetermined concentration was reached. The results are shown in Figure 3. Even in wastewater generated during actual aquaculture processes, the nitrate nitrogen-containing water denitrification treatment device of the present invention clearly demonstrated denitrification capability (maximum denitrification rate of 95%), and it was demonstrated that denitrification proceeds at various nitrate nitrogen concentrations, enabling control of the nitrogen concentration of the rearing water. The nitrate nitrogen-containing water denitrification treatment device of the present invention has a maximum denitrification rate of 0.33 kg / N / m³. 3The nitrogen removal rate per day was shown, and it was found that 8.1 L of hydrogen gas and 2.3 g of carbon derived from carbon dioxide were required to remove 1 g of nitrogen. Theoretically, 4.8 L of hydrogen gas is required to remove 1 g of nitrogen in the hydrogen oxidation denitrification reaction, so approximately 60% of the input hydrogen gas was utilized. Also, since 0.2 g of carbon is theoretically required to remove 1 g of nitrogen in the hydrogen oxidation denitrification reaction, it was found that 2.1 g of carbon was used for pH adjustment. In the prior art that is already in practical use, 0.79 g of carbon is required to remove 1 g of nitrogen by denitrification reaction (Non-Patent Literature 1), so it was found that the nitrate nitrogen-containing water denitrification treatment device of the present invention can reduce the amount of carbon input to aquaculture wastewater treatment by approximately 80% compared to the prior art. Furthermore, when performing denitrification treatment using the nitrate nitrogen-containing water denitrification treatment device of the present invention, it is best to calculate the amount of nitrogen that needs to be removed and then supply hydrogen gas and carbon dioxide in the above ratios.

[0033] Experimental Example 4 <Identification of microorganisms> In the denitrification treatment area (low concentration) of Example 3, amplicon analysis targeting 16S rRNA (v4 hypervariable region) was performed on microbial carriers introduced into the treatment container (day 0), and on carriers randomly sampled from the treatment container on days 34 and 59 from the start of cultivation, to identify microorganisms in the denitrification treatment device for nitrate nitrogen-containing water. The results are shown in Figure 4. On days 0, 34, and 59, the presence of the genus Thauera, a hydrogen oxidation denitrifying bacterium, in the carrier confirmed that the proportion of microbial groups responsible for the hydrogen oxidation denitrification reaction was appropriately maintained, allowing the denitrification capacity to be exercised. [Explanation of Symbols]

[0034] 1: Denitrification treatment device for nitrate nitrogen-containing water 2: Microbial retaining carrier 3: Processing container 3a: Water inlet 3b: Gas inlet 3c: Water outlet 3D: Gas outlet 3e: Outlet for circulation 4: Hydrogen gas supply unit 4a: Hydrogen gas supply source 4b: Hydrogen gas supply line 5: Pressure control unit 5a: Gas pressure gauge 5b: Emergency exhaust valve 6: Sprinkler unit 7: Circulation path 7a: Circulation pump 8: Inflow water supply channel 9: Carbon dioxide supply unit 9a: Carbon dioxide source 9b: Carbon dioxide supply route 10: Gas flow meter 11: Solenoid valve 12: pH sensor 13: pH meter

Claims

1. A sealed processing container containing a microbial carrier on which hydrogen oxidative denitrifying bacteria are immobilized, A hydrogen gas supply unit that supplies hydrogen gas to the gas phase portion within the processing container from the top of the processing container, A pressure control unit that maintains the pressure inside the processing container at atmospheric pressure, A denitrification apparatus for nitrate nitrogen-containing water, comprising a water spraying unit that sprays nitrate nitrogen-containing water onto the microbial carrier from the top of the treatment container.

2. A denitrification apparatus according to claim 1, A nitrate nitrogen-containing water denitrification apparatus having a circulation path for supplying treated water, which has been denitrified in the nitrate nitrogen-containing water denitrification apparatus, into the treatment container.

3. A denitrification apparatus according to claim 1 or claim 2, A denitrification treatment apparatus for nitrate nitrogen-containing water, wherein the microbial retaining carrier is a polyolefin sponge carrier.

4. A method for denitrifying nitrate-containing water using a denitrification apparatus according to any one of claims 1 to 3, The process involves placing a microbial carrier on which hydrogen oxidation denitrification bacteria are immobilized into the aforementioned processing container and sealing it, A step of supplying hydrogen gas to the gas phase inside the processing container from the top of the processing container, thereby filling the processing container with hydrogen gas. A step of maintaining atmospheric pressure inside the processing container, The process involves spraying nitrate nitrogen-containing water onto the microbial carrier from the top of the treatment container, A method for denitrifying nitrate nitrogen-containing water, including [specific components].

5. A denitrification treatment method according to claim 4, A method for denitrifying nitrate nitrogen-containing water, further comprising the step of supplying and circulating treated water, which has been denitrified in the aforementioned nitrate nitrogen-containing water denitrification treatment apparatus, into the treatment container.

6. A closed-loop land-based aquaculture system comprising a denitrification treatment device for nitrate nitrogen-containing water according to any one of claims 1 to 3.

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