JP2013063036A - Method for raising aquatic animals, and method for removing nitrate-nitrogen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for removing nitrate-nitrogen, capable of denitrifying much water containing nitrate-nitrogen while hardly causing a white turbidity phenomenon in water; and to provide a method for raising aquatic animals, capable of reducing the frequency of change of breeding water while hardly causing the white turbidity phenomenon in the breeding water.SOLUTION: Nitrate-nitrogen dissolved in the breeding water W1 in a water tank or pond in which the aquatic animals are bred is removed by bringing the breeding water W1 into contact with a denitrifying material 23 containing sulfur and calcium carbonate. The method for raising the aquatic animals is for raising the aquatic animals in the breeding water W1 to which treatment water W2 after removal of nitrate-nitrogen is returned. The inflow water amount obtained by dividing the cubic volume per day of the breeding water W1 flowing into a treatment tank 21 filled with the denitrifying material 23 in which sulfur-oxidizing bacteria and aerobic microorganisms are grown by the mass of the denitrifying material 23 is at least 50 L/Kg per day, and the concentration of oxygen dissolved in the treatment water W2 flowing out of the treatment tank 21 is at least 3 mg/L.

Description

  The present invention relates to a method for removing nitrate nitrogen dissolved in water and a method for breeding aquatic animals by removing nitrate nitrogen dissolved in breeding water.

  In aquariums, ornamental fish tanks, live fish tanks, ornamental fish ponds, aquaculture fish ponds, etc., where aquatic animals such as fish are bred, filtration using sand etc. or purification by microorganisms is used to reduce the number of water exchanges For example, water is treated. Among these, nitrogen components generated from residual food and manure of fish, etc., are oxidized to ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen by microorganisms to change to a safer nitrogen form. Have been processed. However, in an environment where the concentration of dissolved oxygen is high, nitrate nitrogen continues to increase, which eventually exceeds the animal's adaptive concentration. For this reason, water is exchanged so that no damage is caused to aquatic animals.

  By the way, as a method of removing nitrate nitrogen, there is a method of biological denitrification by introducing a hydrogen donor such as methanol into a treatment tank under anaerobic conditions. However, since this method uses a large amount of hydrogen donor such as methanol, the processing cost is high.

  Therefore, as a method with low processing costs, a denitrification material composed of sulfur and calcium carbonate described in Patent Document 1 is used, and the amount of water flowing into the treatment tank filled with this denitrification material is reduced (for example, one day The amount of seawater that flows into the denitrification material is less than about 20 times the weight of the denitrification material), reducing the amount of dissolved oxygen in the treatment tank to an anaerobic state to remove nitrate nitrogen (denitrification) Patent Documents 2 and 3 propose it.

Japanese Patent No. 3430364 Japanese Patent No. 4562935 JP 2002-370097 A

Nippon Steel Chemical Co., Ltd. Technical Development Division, Development Planning Dept. “Denitrification with Sulfur Calcium Agent”, Chemical Industry Daily, April 28, 2004, p59-60

  However, the methods of Patent Documents 2 and 3 sometimes cause white turbidity in the denitrified water (see Comparative Examples 2 and 3 in Table 1). In addition, hydrogen sulfide may be generated, which may weaken or kill aquatic animals. In addition, since the amount of water to be denitrified per unit time is small, many denitrifying materials and a large treatment tank are required. In particular, when used for denitrification of water in aquariums where fish and other aquatic animals are bred, the ability to perform denitrification to meet the daily feeding amount is the lowest so that nitrate nitrogen does not increase. Although limited, the methods of Patent Documents 2 and 3 have a risk that the denitrification treatment cannot be performed because the amount of water to be denitrified is small.

  Therefore, the present invention is not likely to cause white turbidity in water, and it is possible to denitrify a large amount of water containing nitrate nitrogen (treatment to remove dissolved nitrate nitrogen from the water using nitrogen gas). It is an object of the present invention to provide a removal method and a method for raising aquatic animals that is less likely to cause white turbidity in the breeding water and can reduce the number of times the breeding water is exchanged.

  Since denitrification of nitrate nitrogen using a denitrification material containing sulfur and calcium carbonate is performed by sulfur-oxidizing bacteria, the atmosphere is made anaerobic so that the sulfur-oxidizing bacteria can take in nitrogenous oxygen. That is, it is considered preferable to make the water to be treated anaerobic (dissolved oxygen concentration of less than 1 mg / L) (Non-patent Document 1). For this reason, when denitrifying water in aquariums where fish and other aquatic animals are bred, conventionally, the amount of water flowing into the treatment tank filled with denitrifying material is reduced or treated. Before flowing into the tank, the inside of the treatment tank was made anaerobic by making the water anaerobic.

  However, the inventors of the present invention reduce the dissolved oxygen concentration of the water in the treatment tank filled with the denitrification material to make the atmosphere in the treatment tank anaerobic, which causes a cloudiness phenomenon. I guessed it was the cause.

  Therefore, the inventors of the present invention allow the water to be treated to flow into the treatment tank with aerobic (dissolved oxygen concentration of 3 mg / L or more) and allow sulfur-oxidizing bacteria and aerobic microorganisms to coexist. And found that the cloudiness phenomenon does not occur.

  Moreover, since the atmosphere in a processing tank is made into an aerobic state, it discovered that much water could be flowed into a processing tank and could denitrify much water.

  In order to solve the above-mentioned problem, the first method for removing nitrate nitrogen according to the present invention is to bring the water in which nitrate nitrogen is dissolved into contact with a denitrification material containing sulfur and calcium carbonate, thereby A method for removing nitrate nitrogen, which removes nitrate nitrogen from the treatment tank filled with the denitrification material inhabiting sulfur-oxidizing bacteria and aerobic microorganisms. The dissolved oxygen concentration of water is 3 mg / L or more.

  The second method for removing nitrate nitrogen according to the present invention is to remove nitrate nitrogen by bringing water in which nitrate nitrogen is dissolved into contact with a denitrification material containing sulfur and calcium carbonate. A method for removing oxidative nitrogen, wherein a daily volume of water flowing into a treatment tank filled with the denitrifying material inhabiting sulfur-oxidizing bacteria and aerobic microorganisms is The amount of influent water divided by mass is 50 L / Kg days or more.

  Furthermore, in the third method for removing nitrate nitrogen according to the present invention, the nitrate nitrogen is removed by bringing water in which nitrate nitrogen is dissolved into contact with a denitrification material containing sulfur and calcium carbonate. A method for removing oxidative nitrogen, wherein a daily volume of water flowing into a treatment tank filled with the denitrifying material inhabiting sulfur-oxidizing bacteria and aerobic microorganisms is The amount of inflow water divided by mass is 50 L / Kg days or more, and the dissolved oxygen concentration of water from which nitrate nitrogen has been removed flowing out of the treatment tank is 3 mg / L or more.

  In order to solve the above-mentioned problems, the first method for raising aquatic animals according to the present invention is to contact the dewatering material comprising sulfur and calcium carbonate with the breeding water of the aquarium or pond breeding the aquatic animals. A method for raising aquatic animals that removes nitrate nitrogen dissolved in the breeding water and breeds the aquatic animals in the breeding water after returning the treated water after the removal. The dissolved oxygen concentration of the treated water flowing out of the treatment tank filled with the denitrification material inhabiting bacteria and aerobic microorganisms is 3 mg / L or more.

  The second aquatic animal breeding method of the present invention is a method of bringing the breeding water of a tank or pond breeding aquatic animals into contact with a denitrification material containing sulfur and calcium carbonate. A method for raising aquatic animals in the breeding water from which the nitrate nitrogen dissolved in the water has been removed and the treated water after the removal has been returned, comprising sulfur-oxidizing bacteria and aerobic microorganisms The amount of inflow water divided by the mass of the denitrification material divided by the mass of the denitrification material is 50 L / Kg days or more. Features.

  Further, according to the third method for raising aquatic animals of the present invention, the breeding water is obtained by bringing the breeding water of a tank or pond breeding aquatic animals into contact with a denitrification material containing sulfur and calcium carbonate. A method for raising aquatic animals in the breeding water from which the nitrate nitrogen dissolved in the water has been removed and the treated water after the removal has been returned, comprising sulfur-oxidizing bacteria and aerobic microorganisms The amount of inflow water obtained by dividing the daily volume of the breeding water flowing into the treatment tank filled with the denitrification material inhabiting by the mass of the denitrification material is 50 L / Kg days or more, The dissolved oxygen concentration of the treated water flowing out from the treatment tank is 3 mg / L or more.

  Embodiments of each element of the nitrate nitrogen removal method and the aquatic animal breeding method of the present invention are exemplified below.

1. Denitrification Material The denitrification material is not particularly limited, but it is preferable that the sulfur content is smaller than the calcium carbonate content. This is because when the atmosphere in the treatment tank becomes anaerobic, there is a risk that sulfate ions react with organic substances to generate hydrogen sulfide, which may kill aquatic animals. It is. The mass ratio between the sulfur content and the calcium carbonate content (sulfur: calcium carbonate) is not particularly limited, but is preferably 30 to 49.9: 70 to 50.1, and preferably 40 to 49:60 for the above reasons. -51 is more preferable.

  The particle size of the denitrification material is not particularly limited, but is preferably 5 to 200 mm. If it is less than 5 mm, the gap between the denitrifying materials becomes narrow, so clogging occurs due to the solid matter or organic matter floating in the water or by microorganisms living on the surface of the denitrifying material. As a result, the efficiency of the denitrification process is reduced, and a local anaerobic state is easily generated, and hydrogen sulfide is easily generated. On the other hand, when it exceeds 200 mm, the surface area becomes small, and the efficiency of the denitrification treatment decreases. The sulfur-oxidizing bacteria and aerobic microorganisms are likely to coexist and the efficiency of the denitrification treatment is increased, so that the thickness is more preferably 10 to 50 mm.

2. Treated water (water from which nitrate nitrogen has been removed)
By making the dissolved oxygen concentration of treated water 3 mg / L or more, the atmosphere in the treatment tank becomes an aerobic state, and aerobic microorganisms living in the denitrification material are activated. As a result, the cloudiness phenomenon can be prevented from occurring in the water. Preferably, it is 5 mg / L or more. Although the upper limit of the dissolved oxygen concentration of treated water is not specifically limited, If dare to say, 8 mg / L or less can be illustrated. The dissolved oxygen concentration of the treated water is a value obtained by measuring the treated water flowing out of the treatment tank without manipulating the temperature and pressure.

3. Inflowing water amount When the inflowing water amount is 50 L / Kg or more, the atmosphere in the treatment tank can be brought into an aerobic state, and aerobic microorganisms living in the denitrification material are activated. As a result, the cloudiness phenomenon can be prevented from occurring in the water. In addition, since a large amount of water can be denitrified, the amount of the denitrification material filled in the treatment tank can be reduced, and the treatment tank can be made smaller. If the amount of the denitrification material is the same, the amount of water to be denitrified can be increased compared to the conventional case. The upper limit of the inflow water amount is not particularly limited, but daringly, it can be exemplified by 10,000 L / Kg days or less.

4). Breeding water (water in which nitrate nitrogen is dissolved)
Breeding water is not particularly limited, but it may be seawater or fresh water. In addition, since it is not necessary to increase the dissolved oxygen concentration before flowing into the treatment tank, it is preferably aerobic (dissolved oxygen concentration of 3 mg / L or more), and aquatic animals are easy to breed. Therefore, it is more preferable that the dissolved oxygen concentration is 5 mg / L or more. Although the upper limit of dissolved oxygen concentration is not specifically limited, If dare to say, 8 mg / L or less can be illustrated. Moreover, although the temperature of breeding water is not specifically limited, The water temperature of the water tank which breeds the aquatic animal in an aquarium etc., for example, 15-30 degreeC is mentioned.

  The amount of breeding water is not particularly limited, but when it is used repeatedly without replacement, it depends on the amount of nitrate nitrogen generated, but it is 10 times or less the amount of water flowing into the treatment tank a day. It is preferable that If it exceeds 10 times, the generated nitrate nitrogen may not be treated.

5. Aquatic animals Aquatic animals are not particularly limited, and examples include fish, sea animals, shellfish, octopus, squid, crab, shrimp, starfish, coral, hanaginaku, sea anemone and the like.

  According to the present invention, it is difficult to cause white turbidity in water, a method for removing nitrate nitrogen that can denitrify a large amount of water containing nitrate nitrogen, and white turbidity in breeding water hardly occurs. It is possible to provide a method for raising aquatic animals that can be reduced.

It is a figure of the test equipment of a denitrification capability test. It is a figure of the test equipment of a breeding test. It is sectional drawing of the processing tank used for the breeding test.

1) Acclimatization of sulfur-oxidizing bacteria and aerobic microorganisms In order to obtain a denitrification material in which sulfur-oxidizing bacteria and aerobic microorganisms live on the surface, acclimatization of sulfur-oxidizing bacteria and aerobic microorganisms was performed on the denitrification material. .
The denitrification material in which the sulfur-oxidizing bacteria and aerobic microorganisms were conditioned was used as a denitrification material in Examples and Comparative Examples described later.

The following were used for seawater, denitrification material and activated sludge.
As the seawater, one having a nitrate nitrogen concentration of 56.6 mg / L, which was collected from an aquarium where marine animals such as seafood and mammals were raised in an aquarium, was used.
As the denitrification material, one having a mass ratio of sulfur to calcium carbonate (sulfur: calcium carbonate) of 45:55, a particle size of 10 to 50 mm, and an apparent specific gravity of 1.35 Kg / L was used.
The activated sludge used was suspended in the wastewater treatment plant.

Acclimation of sulfur-oxidizing bacteria and aerobic microorganisms to the denitrification material was performed as follows.
After filling a 10 L (capacity) plastic container with 10 kg of denitrification material, 100 mL of activated sludge was sprinkled on the denitrification material from above.
After that, from a water tank (W450mm x L900mm x H450mm) containing about 150L of seawater (nitric nitrogen concentration 56.6mg / L), seawater is constantly passed through a plastic container at a flow rate of 6L / min using a pump. Water was added (Note that seawater was passed through the denitrifying material packed bed in the plastic container in an upward flow, and the overflowed water from the plastic container was returned to the water tank and circulated).
And the water flow was continued until the nitrate nitrogen concentration of seawater became 1 mg / L or less (the nitrate nitrogen concentration became 1 mg / L or less on the fifth day).

Thereafter, all the seawater (about 150 L) was replaced with one having a nitrate nitrogen concentration of 56.6 mg / L, and water was again passed through the plastic container (the flow rate was 6 L / min). The water flow was continued until the nitrogen concentration became 1 mg / L or less.
Then, by repeating the replacement of the seawater three times, about 450 L of seawater (nitrate nitrogen concentration of 56.6 mg / L) was passed through the plastic container until the nitrate nitrogen concentration reached 1 mg / L, and the water was removed. Acclimatization of sulfur-oxidizing bacteria and aerobic microorganisms to nitrogenous materials was performed.

2) Denitrification ability test By acclimating the above-mentioned sulfur-oxidizing bacteria and aerobic microorganisms, a denitrifying material in which sulfur-oxidizing bacteria and aerobic microorganisms live on the surface layer is used, and this denitrifying material is filled. The denitrification ability and water turbidity of each of the three types of examples and the three types of comparative examples with different amounts of seawater flowing into the treatment tank (inflow water amount) were evaluated, and the results are shown in the table. It is shown in 1. Table 1 also shows the amounts of inflow water and the dissolved oxygen concentration.

  As the seawater, one having a nitrate nitrogen concentration of about 40 to 70 mg / L collected from an aquarium where sea animals such as seafood and mammals are raised in an aquarium was used.

Test Method 10 Kg of denitrification material 13 in which sulfur-oxidizing bacteria and aerobic microorganisms live on the surface layer was filled into a 10 L (capacity) plastic container 11 having a treated water outlet 12 drilled at the upper side. This plastic container 11 is a processing tank.
And as shown in FIG. 1, while preventing the seawater W1 in the water tank 10 from flowing directly into the plastic container 11 in the water tank 10 (W450 mm × L900 mm × H450 mm) in which about 150 L of seawater W1 is placed, The poly container 11 was disposed so that the treated water outlet 12 was positioned above the water surface so that the seawater overflowing from the treated water outlet 12 returned to the water tank 10.
The tip end of the suction hose 16 was put in the seawater W1 in the water tank 10 and the seawater W1 was pumped up by the pump 15 having a water supply capacity of 6 L / min and put in the plastic container 11.

  Then, the pump 15 is intermittently operated (5 minutes of operation and 2 to 360 minutes of stoppage is one cycle), so that the seawater W1 in the water tank 10 is sent into the plastic container 11 and denitrified and dissolved. The treated seawater W2 from which the nitrate nitrogen was removed overflowed from the treated water outlet 12 and returned to the seawater W1 to denitrify the seawater W1. By changing the stop time of the pump 15, the daily amount (volume) of the seawater flowing into the plastic container 11 is changed, and the daily seawater volume is calculated by the mass of the denitrification material filled in the plastic container. The amount of influent water, which is the divided value, was changed. During the test, oxygen was supplied to the seawater W1 by aeration. Moreover, since temperature adjustment was not performed with respect to seawater, the temperature of seawater W1 and W2 was room temperature (about 25 degreeC).

Evaluation Denitrification ability The nitrate nitrogen concentration of the seawater W1 in the water tank 10 at the start of the test and 3 days after the start of the test was measured. And based on the measured value 3 days after the start of the test, it was evaluated that ◎: 5 mg / L or less, ◯: 5 to 20 mg / L, Δ: more than 20 mg / L.

The cloudiness state The degree of cloudiness of the seawater W1 in the aquarium 10 three days after the start of the test was judged visually, and it was evaluated as dark when there was no cloudiness, when there was little cloudiness, and when the cloudiness was dark. .

Dissolved oxygen concentration Seawater at the treated water outlet 12 immediately after the pump was operated after stopping for 2 to 360 minutes three days after the start of the test was measured without operating the temperature and pressure.

  As shown in Table 1, in Example, the nitrate nitrogen concentration was 3.2 mg / L or less after 3 days, and the ability to denitrify was high. The dissolved oxygen concentration was 3.5 mg / L or more, and no white turbidity occurred. Since the amount of inflow water was as large as 66.5 L / Kg day or more, the amount of seawater subjected to denitrification of nitrate nitrogen could be increased. On the other hand, in the comparative example, the nitrate nitrogen concentration was 7.6 mg / L or more after 3 days, and the ability to denitrify was not sufficient. The dissolved oxygen concentration was 2.2 mg / L or less, and white turbidity occurred. This is because the amount of inflow water is as small as 34.6 L / Kg day or less, and the time for seawater to stay in the plastic container has become longer. For this reason, it is considered that oxygen consumption by denitrifying bacteria is increased, the dissolved oxygen concentration of seawater is decreased, and a cloudy state is likely to occur.

3) Rearing test Dissolved nitrate nitrogen was removed from the rearing water of the aquarium where aquatic animals were raised using the method for removing nitrate nitrogen of the example of the present invention. Specifically, it was performed as follows.

  As shown in FIG. 2, about 570 L of seawater W1 placed in a cylindrical water tank 20 (diameter: 1000 mm, water depth 600 mm) is treated with a treatment tank 21 (W800 mm × W) filled with 32 kg of dredge 22 (filter material). L450 mm × H450 mm), and the seawater W1 in the treatment tank 21 was pumped into the water tank 20 by the pump 25, thereby circulating the seawater W1 between the water tank 20 and the treatment tank 21. Note that oxygen was supplied to the seawater W1 in the water tank 20 by aeration.

  If this circulation is explained in full detail, the seawater W1 in the aquarium 20 exceeding the predetermined capacity will flow down in the downcomer 27. And as shown to a of FIG. 3, it discharge | releases in the processing tank 21, and is hung on the scissors 22 from upper direction, and a filtration process etc. are performed. Thereafter, the seawater W1 accumulated in the treatment tank 21 is pumped up from the vicinity of the bottom of the treatment tank 21 by the pump 25 at a flow rate of 20 L / min, sent upward through the riser pipe 28, and from above into the water tank 20 Is discharged.

Then, after circulating for 10 days, while continuing the circulation of the seawater W1 by the pump 25, one dog shark (TL (full length) 60 cm, BW (weight) 850 g, male) was placed in the aquarium 20 and breeding was started. This day is the breeding start date (the number of breeding days is 0). As food, shishamo and sweet shrimp were fed at 10 to 15 g / day.
On the 32nd day from the start of breeding (32 days of breeding), 1 coral shark (TL (full length) 45 cm, BW (body weight) 400 g) and 1 squirrel (TL (full length) 25 mm, BW (body weight) 1 g) 20 fish In the aquarium 20, on the 33rd day from the start of breeding (33 days of breeding), two Himehanaginachaku individuals were placed in the aquarium 20 for breeding. As food, shishamo and frozen shrimp were fed at 20-30 g / day, and ruri flakes were fed at 0.5-1 g / day.
In addition, the temperature of seawater was adjusted with the heater cooler 26 so that 25-26 degreeC might be maintained.

Table 2 shows the concentration of each component in the seawater during this period. Each concentration was measured at the discharge port of the ascending pipe 28 without operating the temperature and pressure.
During this period, as the number of breeding days increased, the nitrate nitrogen concentration increased and nitrate nitrogen was accumulated. Further, nitrogen from manure from the residue and aquatic animals (dog sharks, coral sharks, luris sharks, chicks) was all nitrified to nitrate nitrogen in the treatment tank 21. Therefore, the seawater W1 in the aquarium was always highly transparent, and organic matter could be removed by aerobic microorganisms that live in the treatment tank 21.

  Next, while the above breeding is continued (and therefore the breeding conditions and the like are not changed), the sulfur-oxidizing bacteria and the aerobic microorganisms are surfaced by acclimatizing 1) on the straw 22 of the treatment tank 21. A net bag 24 (5 mm mesh) containing 10 kg of the denitrification material 23 inhabiting the seawater was placed, the treatment tank 21 was filled with the denitrification material 23, and nitrate nitrogen of the seawater W1 was removed. This is the aquatic animal breeding method of the embodiment of the present invention. The amount of inflow water at this time was 2880 L / Kg days because seawater W1 was introduced into the treatment tank 21 filled with 10 Kg of denitrification material at a flow rate of 20 L / min and circulated. Note that the day when the net bag 24 is placed on the reed 22 of the treatment tank 21 is the denitrification start date (the number of denitrification days is 0).

  If this circulation is explained in full detail, the seawater W1 in the aquarium 20 exceeding the predetermined capacity will flow down in the downcomer 27. Then, as shown in FIG. 3b, the seawater W1 is discharged into the treatment tank 21 and hung on the denitrification material 23 from above and denitrified. It becomes the treated seawater W2 from which the dissolved nitrate nitrogen has been removed. Thereafter, the treated seawater W2 accumulated in the treatment tank 21 is pumped up from the vicinity of the bottom of the treatment tank 21 by a pump 25 at a flow rate of 20 L / min, is sent upward through the riser 28, and the water tank 20 from above. It was discharged into the sea and returned to the seawater W1.

Table 3 shows the concentration of each component in the seawater during this period. Each concentration was measured at the discharge port of the ascending pipe 28 without operating the temperature and pressure.
By removing the denitrification material 23 in the treatment tank 21, the removal of nitrate nitrogen progressed, and the concentration of nitrate nitrogen became about 1 mg / L on the 9th day of denitrification. After that, the nitrate nitrogen concentration did not increase, remained at the same level (about 1 mg / L), and no cloudiness phenomenon occurred. In addition, aquatic animals and prey were good and we were able to keep them healthy.

  From the above, according to the aquatic animal breeding method of the present embodiment, nitrate nitrogen of seawater W1 placed in the aquarium 20 in a state where the dissolved oxygen concentration is 5.8 mg / L or higher can be removed. The aquatic animals that have been able to be raised safely. Moreover, there was no increase accumulation of nitrate nitrogen in seawater W1, and it was also possible to reduce water exchange. Furthermore, it has become unnecessary to maintain and manage anaerobic conditions with a low dissolved oxygen concentration in the treatment layer and to suppress generation of hydrogen sulfide that affects aquatic animals.

  In addition, this invention is not limited to the said Example, In the range which does not deviate from the meaning of invention, it can change suitably and can be actualized.

DESCRIPTION OF SYMBOLS 10 Water tank 11 Plastic container 13 Denitrification material 20 Water tank 21 Treatment tank 23 Denitrification material W1 Seawater W2 Processed seawater

Claims (10)

The aquarium (20) in which aquatic animals are bred or the pond breeding water (W1) is brought into contact with a denitrification material (23) containing sulfur and calcium carbonate, and dissolved in the breeding water (W1). A method for raising aquatic animals, wherein the aquatic animals are bred in the breeding water (W1) from which the nitrate nitrogen is removed and the treated water (W2) after the removal is returned,
The dissolved oxygen concentration of the treated water (W2) flowing out from the treatment tank (21) filled with the denitrification material (23) inhabiting sulfur-oxidizing bacteria and aerobic microorganisms is set to 3 mg / L or more. A method for raising aquatic animals characterized by the above. The aquarium (20) in which aquatic animals are bred or the pond breeding water (W1) is brought into contact with a denitrification material (23) containing sulfur and calcium carbonate, and dissolved in the breeding water (W1). A method for raising aquatic animals, wherein the aquatic animals are bred in the breeding water (W1) from which the nitrate nitrogen is removed and the treated water (W2) after the removal is returned,
The daily volume of the breeding water (W1) flowing into the treatment tank (21) filled with the denitrification material (23) inhabiting sulfur-oxidizing bacteria and aerobic microorganisms is used as the denitrification material. The method for raising aquatic animals, wherein the amount of influent water divided by the mass of (23) is 50 L / Kg days or more. The aquarium (20) in which aquatic animals are bred or the pond breeding water (W1) is brought into contact with a denitrification material (23) containing sulfur and calcium carbonate, and dissolved in the breeding water (W1). A method for raising aquatic animals, wherein the aquatic animals are bred in the breeding water (W1) from which the nitrate nitrogen is removed and the treated water (W2) after the removal is returned,
The daily volume of the breeding water (W1) flowing into the treatment tank (21) filled with the denitrification material (23) inhabiting sulfur-oxidizing bacteria and aerobic microorganisms is used as the denitrification material. The amount of influent water divided by the mass of (23) is 50 L / Kg days or more,
A method for raising aquatic animals, wherein the dissolved oxygen concentration of the treated water (W2) flowing out of the treatment tank (21) is 3 mg / L or more.   The method for raising aquatic animals according to any one of claims 1 to 3, wherein the denitrification material (23) has a content of sulfur less than a content of the calcium carbonate.   The method for raising aquatic animals according to any one of claims 1 to 4, wherein the denitrification material (23) has a particle size of 5 to 200 mm. A method of removing nitrate nitrogen, wherein water (W1) in which nitrate nitrogen is dissolved is brought into contact with a denitrification material (13, 23) containing sulfur and calcium carbonate to remove the nitrate nitrogen. ,
Water (W2) from which the nitrate nitrogen has been removed flowing out of the treatment tank (11, 21) filled with the denitrification material (13, 23) inhabiting sulfur-oxidizing bacteria and aerobic microorganisms A method for removing nitrate nitrogen, wherein the dissolved oxygen concentration of the solution is 3 mg / L or more. A method of removing nitrate nitrogen, wherein water (W1) in which nitrate nitrogen is dissolved is brought into contact with a denitrification material (13, 23) containing sulfur and calcium carbonate to remove the nitrate nitrogen. ,
The daily volume of the water (W1) flowing into the treatment tank (11, 21) filled with the denitrifying material (13, 23) inhabiting sulfur-oxidizing bacteria and aerobic microorganisms is A method for removing nitrate nitrogen, wherein the amount of inflow water divided by the mass of the denitrification material (13, 23) is 50 L / Kg days or more. A method of removing nitrate nitrogen, wherein water (W1) in which nitrate nitrogen is dissolved is brought into contact with a denitrification material (13, 23) containing sulfur and calcium carbonate to remove the nitrate nitrogen. ,
The daily volume of the water (W1) flowing into the treatment tank (11, 21) filled with the denitrifying material (13, 23) inhabiting sulfur-oxidizing bacteria and aerobic microorganisms is The amount of influent water divided by the mass of the denitrification material (13, 23) is 50 L / Kg days or more,
A method for removing nitrate nitrogen, wherein the dissolved oxygen concentration of water (W2) from which the nitrate nitrogen has been removed flowing out of the treatment tank (11, 21) is 3 mg / L or more.   The method for removing nitrate nitrogen according to any one of claims 6 to 8, wherein the denitrification material (13, 23) has a content of sulfur less than a content of calcium carbonate.   The method for removing nitrate nitrogen according to any one of claims 6 to 9, wherein the denitrification material (13, 23) has a particle size of 5 to 200 mm.

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