JP2021079321A - Denitriding material, denitridation treatment device, manufacturing method thereof and breeding method - Google Patents

Abstract

To provide a denitriding material that is difficult to float at the time of water flow and can be used easily, has high denitridation activity, has sufficiently low toxicity to aquatic organism, and has an easy manufacturing method.SOLUTION: A denitriding material containing sulfur 1, carbonate 2 and a surfactant, in which the sulfur 1 is hydrophilized with the surfactant, and has a particle size of 0.1 mm or larger, a content ratio of the sulfur 1 is 30 mass% or larger and smaller than 70 mass%, a content ratio of the carbonate 2 is 30 mass% or larger and smaller than 70 mass%, a content of the surfactant when used in the denitridation treatment device satisfies the condition A; condition A with an amount of circulation water as Q, a content of the sulfur in the denitriding material as S, a content of the surfactant per 1 kg of sulfur as P, and expressed by SP= aQ, a is smaller than 0.1.SELECTED DRAWING: Figure 2

Description

The present invention relates to a denitrifying material, a method for producing a denitrifying material, a denitrifying treatment device, a manufacturing method for the denitrifying treatment device, and a breeding method.

There is a demand for denitrifying materials that remove nitrate nitrogen and / or nitrite nitrogen from water such as domestic wastewater, industrial wastewater, livestock wastewater, and aquaculture wastewater. For example, in recent years, aquatic organisms, especially marine organisms, have been purified in aquaculture tanks for culturing on land in a closed circulatory system in which ammonia derived from marine organisms tends to accumulate as nitrite nitrogen or nitrate nitrogen. Is required.
As a method for treating nitrate nitrogen in water, a denitrifying material containing sulfur and carbonate is used to oxidize nitrate nitrogen to nitrogen by the action of sulfur-oxidizing bacteria, and among the sulfate ions generated at that time. A method for performing sum (SLAD method) is known (see Patent Documents 1 to 5).

Patent Document 1 describes a sulfur material for denitrification, which contains powdered sulfur, an alkaline agent, and a surfactant.

Patent Document 2 describes nitrate as a granular or lumpy substance in which a substance containing calcium carbonate as a main component and sulfur are the main compositions, and a substance having fine pores coexists in the same grain together with the main composition. Nitrogen denitrifying substrates are described.

Patent Document 3 describes a denitrification tank in which sewage containing nitrate nitrogen and / or nitrite nitrogen is passed through a sludge bed to which elemental sulfur is added by an upward flow, and a means for removing sludge floating from the denitrification tank. , A biological denitrification apparatus having a reaction tank for adding and mixing a surfactant to the sludge taken out and a means for returning the liquid in the reaction tank to the denitrification tank is described.

Patent Document 4 describes a composition for removing nitrate nitrogen and the like, which comprises a composition in which an alkaline substance and sulfur are coated and adhered to or impregnated with a light specific density porous granular material in the nucleus.

In Patent Document 5, when purifying seawater in a water tank with a closed circulation system, a part of seawater is continuously extracted from the water tank, and at least a part thereof is filled with a denitrifying inorganic material composed of sulfur and calcium-based components. A method for treating nitrate nitrogen in seawater after removing nitrate nitrogen by passing it through a denitrifying device and returning it to the aquarium is described.

JP-A-2018-094553 Patent No. 4032199 Japanese Unexamined Patent Publication No. 8-155491 Japanese Unexamined Patent Publication No. 2003-071493 JP-A-2002-273475

However, the method using powdered sulfur and a surfactant described in Patent Document 1 has a problem that the amount of the surfactant has not been examined and the toxicity to aquatic organisms is high. It was also found that when the method described in Patent Document 1 is modified and a surfactant is not used, the denitrifying material tends to float during water flow, which causes a problem that it is difficult to use easily.
In the method described in Patent Document 2, the production method is complicated in that sulfur, calcium carbonate and a substance having fine pores coexist in the same grain.
The method described in Patent Document 3 is based on the premise that the denitrifying material floats when water is passed, and the operation method such as taking out the floating sludge from the denitrification tank is complicated.
In the method described in Patent Document 4, the production method is complicated in that an alkaline substance and sulfur are coated and adhered to or impregnated with a light specific density porous substance on the nucleus.
In the method described in Patent Document 5, it is necessary to use a large amount of denitrifying material, and it is considered that the denitrification activity is low.

The problem to be solved by the present invention is to provide a denitrifying material which is difficult to surface during water flow, can be easily used, has high denitrification activity, has sufficiently low toxicity to aquatic organisms, and is easy to manufacture. It is to be.

As a result of diligent studies to solve the above problems, the present inventors have determined the content of the surfactant while containing the granular sulfur and the carbonate which have been hydrophilized with the surfactant in a predetermined ratio. It has been found that the above problems can be solved by using a denitrifying material controlled to a predetermined ratio.
Specifically, the present invention and preferred configurations of the present invention are as follows.

[1] A denitrifying material containing sulfur, carbonate and a surfactant.
Sulfur is hydrophilized with a surfactant and has a particle size of 0.1 mm or more.
The sulfur content is 30% by mass or more and less than 70% by mass, and the carbonate content is 30% by mass or more and less than 70% by mass with respect to the total mass of the denitrification material.
The content of the surfactant when used in a denitrification treatment device having a water tank capable of storing circulating water, a reactor containing a denitrifying material, and a circulation channel for returning the circulating water treated by the reactor to the water tank is as follows. Satisfy condition A of
Material for denitrification.
Condition A:
When the amount of circulating water Q [L], the content of sulfur in the denitrification material S [kg], and the content of surfactant per 1 kg of sulfur P [mg / kg-S] are expressed as SP = aQ. In addition, a is 0.1 [mg / L] or less.
[2] A denitrifying material containing sulfur, carbonate and a surfactant.
Sulfur is hydrophilized with a surfactant and has a particle size of 0.1 mm or more.
The sulfur content is 30% by mass or more and less than 70% by mass, and the carbonate content is 30% by mass or more and less than 70% by mass with respect to the total mass of the denitrification material.
A denitrifying material having a surfactant content of 0.1% by mass or less with respect to the sulfur content.
[3] The denitrification material according to [1] or [2], wherein sulfur and carbonate do not coexist in the same grain.
[4] The denitrifying material according to any one of [1] to [3], wherein the surfactant contains a nonionic surfactant.
[5] The denitrifying material according to any one of [1] to [4], which is used for removing nitrate nitrogen by the action of sulfur-oxidizing bacteria.
[6] The method for producing a denitrifying material according to any one of [1] to [5].
A hydrophilization treatment step of hydrophilizing sulfur with a surfactant under the condition that the content of the surfactant per 1 kg of sulfur is 100 mg / kg-S or more.
A method for producing a denitrifying material, which comprises at least one of the following water cleaning step A and water cleaning step B.
Water washing step A: The composition containing the hydrophilized sulfur is repeatedly washed with water, and the amount of circulating water Q [L], the sulfur content in the denitrifying material S [kg], and sulfur 1 kg. When SP = aQ is expressed as the content of the surfactant per P [mg / kg-S], a is 0.1 [mg / L] or less.
Water washing step B: The composition containing the hydrophilized sulfur is repeatedly washed with water so that the content of the surfactant is 0.1% by mass or less with respect to the sulfur content.
[7] A denitrification treatment apparatus having a water tank capable of storing circulating water, a reactor containing a denitrifying material, and a circulation flow path for returning the circulating water treated by the reactor to the water tank.
Denitrification material contains sulfur, carbonates and surfactants
Sulfur is hydrophilized with a surfactant and has a particle size of 0.1 mm or more.
The sulfur content is 30% by mass or more and less than 70% by mass, and the carbonate content is 30% by mass or more and less than 70% by mass with respect to the total mass of the denitrification material.
A denitrification treatment device in which the content of the surfactant satisfies the following conditions.
Condition A:
When the amount of circulating water Q [L], the content of sulfur in the denitrification material S [kg], and the content of surfactant per 1 kg of sulfur P [mg / kg-S] are expressed as SP = aQ. In addition, a is 0.1 [mg / L] or less.
[8] The method for manufacturing the denitrification treatment apparatus according to [7].
A hydrophilization treatment step of hydrophilizing sulfur with a surfactant under the condition that the content of the surfactant per 1 kg of sulfur is 100 mg / kg-S or more.
A method for manufacturing a denitrification treatment apparatus, which comprises the following water washing step A.
Water washing step A: The composition containing the hydrophilized sulfur is repeatedly washed with water, and the amount of circulating water Q [L], the sulfur content in the denitrifying material S [kg], and sulfur 1 kg. When SP = aQ is expressed as the content of the surfactant per P [mg / kg-S], a is 0.1 [mg / L] or less.
[9] A breeding method in which aquatic organisms are bred in an aquarium while treating nitrate nitrogen in circulating water using the denitrification treatment apparatus according to [7].
[10] The breeding method according to [9], wherein the aquatic organism is a marine fish.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a denitrifying material which is difficult to float during water flow, can be easily used, has high denitrification activity, has sufficiently low toxicity to aquatic organisms, and is easy to manufacture.

FIG. 1 is a schematic cross-sectional view of an example of the denitrification treatment apparatus of the present invention. FIG. 2 is a schematic cross-sectional view of another example of the denitrification treatment apparatus of the present invention.

Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be based on typical embodiments or specific examples, but the present invention is not limited to such embodiments. In this specification, the numerical range represented by using "~" means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.

[Material for denitrification]
The first aspect of the denitrification material of the present invention is a denitrification material containing sulfur, carbonate and a surfactant, wherein the sulfur is hydrophilized with a surfactant and has a particle size of 0.1 mm. As described above, the sulfur content is 30% by mass or more and less than 70% by mass, and the carbonate content is 30% by mass or more and less than 70% by mass with respect to the total mass of the denitrification material, and the circulating water. The content of the surfactant when used in a denitrification treatment device having a water tank capable of storing water, a reactor containing a denitrification material, and a circulation flow path for returning the circulating water treated by the reactor to the water tank is as follows. Satisfy A.
Condition A:
When the amount of circulating water Q [L], the content of sulfur in the denitrification material S [kg], and the content of surfactant per 1 kg of sulfur P [mg / kg-S] are expressed as SP = aQ. In addition, a is 0.1 [mg / L] or less.
The second aspect of the denitrifying material of the present invention is a denitrifying material containing sulfur, carbonate and a surfactant, in which sulfur is hydrophilized with a surfactant and has a particle size of 0. .1 mm or more, the sulfur content is 30% by mass or more and less than 70% by mass, and the carbonate content is 30% by mass or more and less than 70% by mass with respect to the total mass of the denitrifying material. The content of the surfactant is 0.1% by mass or less with respect to the content of sulfur.
According to the configurations of the first aspect and the second aspect of the denitrification material of the present invention, it is difficult to float during water flow and can be easily used, the denitrification activity is high, and the toxicity to aquatic organisms is sufficient. Low and easy to manufacture. Although not bound by any theory, by using sulfur having a particle size of 0.1 mm or more, it is possible to easily remove air bubbles of the generated nitrogen gas, and the denitrification activity is enhanced. Since sulfur having a particle size of 0.1 mm or more is hydrophilized with a surfactant, water repellency can be suppressed even if the particle size is small, so that denitrification activity can be increased and water can be passed. It is sometimes difficult to surface and can be used easily. By controlling the content of the surfactant to a predetermined ratio, the toxicity to aquatic organisms can be sufficiently reduced. Further, by containing sulfur and carbonate in a predetermined ratio, even if the oxidizing activity of nitrate nitrogen by sulfur-oxidizing bacteria is increased, the carbonate can sufficiently neutralize the sulfate ions generated at that time. ..
Hereinafter, preferred embodiments of the denitrifying material of the present invention will be described.

<Sulfur>
The denitrifying material of the present invention contains sulfur.
In the present invention, sulfur which has been hydrophilized with a surfactant and has a particle size of 0.1 mm or more is used.
When sulfur having a particle size of 0.1 mm or more is used, it has water repellency as it is, so that it is difficult to use it for treating circulating water such as breeding water. Therefore, by hydrophilizing sulfur with a surfactant under the condition that the content of the surfactant per 1 kg of sulfur is 100 mg / kg-S or more, it is facilitated to be used for the treatment of circulating water.
The fact that sulfur is hydrophilized with a surfactant can be confirmed, for example, by observing that the surface of sulfur is covered with a coating of the surfactant by a known method.

When sulfur has a particle size of 0.1 mm or more, it can easily escape air bubbles of the generated nitrogen gas, and the denitrification activity is enhanced. Sulfur preferably has a particle size of 0.5 mm or more, and more preferably 1 mm or more. Sulfur has a particle size of less than 10 mm, preferably from the viewpoint of increasing the contact area per unit weight and enhancing denitrification activity, preferably 5 mm or less, and more preferably 3 mm or less.
The average particle size of sulfur contained in the denitrifying material is preferably in the above particle size range. Further, 90% by mass or more of sulfur contained in the denitrification material is preferably in the above particle size range, and 95% by mass or more is more preferably in the above particle size range. The "particle size" in the present specification is a particle size measured according to JIS K 6222-1.

The denitrification material of the present invention has a sulfur content of 30% by mass or more and less than 70% by mass with respect to the total mass of the denitrification material. The sulfur content is preferably 40% by mass or more, more preferably 45% by mass or more, based on the total mass of the denitrification material. The sulfur content is preferably less than 60% by mass, more preferably less than 55% by mass, based on the total mass of the denitrifying material.

<Carbonate>
The denitrifying material of the present invention contains carbonate.
As the carbonate, a carbonate used as an alkaline agent can be used. Carbonate, and the neutralization reaction with the Sulfate ion (SO 4 ^_2-) which increases with the progress of the denitrification to prevent deterioration of the pH of the circulating water, suppressing a decrease in denitrification activity. It also supplies carbonate ions necessary for the growth of sulfur-oxidizing denitrifying bacteria and the denitrification reaction.

As the carbonate, a weak alkaline agent is preferable. The carbonate preferably has a pH of circulating water that can be maintained at preferably 6.5 to 8.5, more preferably 7.0 to 8.5, and particularly preferably 7.2 to 8.5.
As the carbonate, sodium hydrogen carbonate (NaHCO ₃ ), sodium carbonate (Na ₂ CO ₃ ), and calcium carbonate (CaCO ₃ ) are preferable, and calcium carbonate, which has a low cost, is more preferable.
One type of carbonate may be used alone, or two or more types may be used in combination.

The carbonate is preferably powdery or granular. The carbonate has a particle size of 0.1 mm or more, more preferably 0.5 mm or more, and a particle size of 0.5 mm or more, from the viewpoint that bubbles of the generated nitrogen gas can be easily removed and the denitrification activity is enhanced. It is particularly preferably 1 mm or more. The diameter of the carbonate is preferably less than 10 mm, preferably 5 mm or less, and more preferably 3 mm or less, from the viewpoint of increasing the contact area per unit weight and enhancing the activity of the neutralization reaction. ..
The average particle size of the carbonate contained in the denitrifying material is preferably in the above particle size range. Further, 90% by mass or more of the carbonate contained in the denitrification material is preferably in the above particle size range, and 95% by mass or more is more preferably in the above particle size range.

The denitrifying material of the present invention has a carbonate content of 30% by mass or more and less than 70% by mass with respect to the total mass of the denitrifying material. The content ratio of the carbonate is preferably 40% by mass or more, more preferably 45% by mass or more, based on the total mass of the denitrifying material. The carbonate content is preferably less than 60% by mass, more preferably less than 55% by mass, based on the total mass of the denitrifying material.

In the denitrification material of the present invention, it is preferable that the sulfur particles and the carbonate particles are uniformly mixed in a state of being independent of each other from the viewpoint of easy production method. That is, in the denitrification material of the present invention, it is preferable that sulfur and carbonate do not coexist in the same grain.

<Surfactant>
The denitrifying material of the present invention contains a predetermined amount of surfactant.

In the first aspect of the denitrification material of the present invention, denitrification having a water tank capable of storing circulating water, a reactor containing the denitrification material, and a circulation flow path for returning the circulating water treated by the reactor to the water tank. The content of the surfactant when used in the treatment apparatus satisfies the following condition A.
Condition A:
When the amount of circulating water Q [L], the content of sulfur in the denitrification material S [kg], and the content of surfactant per 1 kg of sulfur P [mg / kg-S] are expressed as SP = aQ. In addition, a is 0.1 [mg / L] or less.
a is preferably 0.08 [mg / L] or less, and more preferably 0.066 [mg / L] or less.

In the second aspect of the denitrifying material of the present invention, the content of the surfactant is 0.1% by mass with respect to the content of sulfur (1 mg in terms of the content of the surfactant per 1 kg of sulfur). It is as follows.
The content of the surfactant is preferably 0.08% by mass (0.8 mg in terms of the content of the surfactant per 1 kg of sulfur) with respect to the sulfur content, preferably 0.06% by mass. It is more preferable that it is as follows.

The surfactant is not particularly limited, and nonionic, anionic, cationic and amphoteric surfactants can be used. In the present invention, among these, it is preferable that the surfactant contains a nonionic surfactant, and it is more preferable that the main component of the surfactant (50% by mass or more of the surfactant) is a nonionic surfactant. .. Nonionic surfactants have less foaming, are less susceptible to changes in pH and temperature in circulating water, and make denitrification materials easier to handle.

Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxypropylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene distyrene phenyl ether, polyoxyethylene carboxylic acid ester, sorbitan ester, and polyoxy. Examples thereof include ethylene sorbitan ester and acetylene glycol.
Examples of the anionic surfactant, the cationic surfactant, and the amphoteric surfactant include those described in JP-A-2018-0945553, [0044] to [0046], which are referred to in this publication. And incorporated herein by reference.
One type of surfactant may be used alone, or two or more types may be used in combination.

<Use>
The denitrifying material of the present invention is preferably used for removing nitrate nitrogen by the action of sulfur-oxidizing bacteria, and more preferably for removing nitrate nitrogen and nitrite nitrogen. .. The denitrifying material of the present invention is preferably used for removing nitrate nitrogen and the like from circulating water in, for example, livestock industry, agriculture, fishery industry (including aquaculture industry, fish breeding industry, etc.).

[Manufacturing method of denitrification material]
The method for producing the denitrifying material of the present invention includes a hydrophilization treatment step of hydrophilizing sulfur with a surfactant under the condition that the content of the surfactant per 1 kg of sulfur is 100 mg / kg-S or more, and the following. Including at least one of the water washing step A and the water washing step B of the above.
Water washing step A: The composition containing the hydrophilized sulfur is repeatedly washed with water, and the amount of circulating water Q [L], the sulfur content in the denitrifying material S [kg], and sulfur 1 kg. When SP = aQ is expressed as the content of the surfactant per P [mg / kg-S], a is 0.1 [mg / L] or less.
Water washing step B: The composition containing the hydrophilized sulfur is repeatedly washed with water so that the content of the surfactant is 0.1% by mass or less with respect to the sulfur content.

<Hydrophilic treatment process>
In the hydrophilization treatment step, sulfur is hydrophilized with a surfactant under the condition that the content of the surfactant per 1 kg of sulfur is 100 mg / kg-S or more. By setting the content of the surfactant per 1 kg of sulfur to 100 mg / kg-S or more, the sulfur can be sufficiently covered with a coating of the surfactant to make it hydrophilic. It is preferable that the content of the surfactant per 1 kg of sulfur is 1000 mg / kg-S or more.

The method for producing the denitrifying material preferably includes a mixing step of mixing sulfur, carbonate, and a surfactant. The mixing step is not particularly limited, and can be performed using, for example, a known stirrer. In the mixing step, water may be further mixed.
The mixing step may be performed before the hydrophilic treatment step, at the same time as the hydrophilic treatment step, or after the hydrophilic treatment step. The mixing step is preferably performed at the same time as the hydrophilic treatment step. That is, in the hydrophilic treatment step, sulfur, carbonate, and a surfactant are hydrophilized with a surfactant under the condition that the content of the surfactant per 1 kg of sulfur is 100 mg / kg-S or more. It is preferable to process.

<Water cleaning process A and water cleaning process B>
The water cleaning step A and the water cleaning step B are not particularly limited, and water cleaning can be performed by a known method. In the water washing step A and the water washing step B, it is preferable to repeat the water washing twice or more.
To determine the end point of the water washing step A, the denitrifying material after water washing is actually measured as the amount of circulating water Q [L], and the amount of circulating water Q [L] is included in the denitrifying material. When the sulfur content S [kg] and the surfactant content P [mg / kg-S] per kg of sulfur are expressed as SP = aQ, a is 0.1 [mg / L] or less. It is preferable to confirm that.
To determine the end point of the water washing step B, the denitrifying material after washing with water was actually measured, and the content of the surfactant was 0.1% by mass or less with respect to the content of sulfur. It is preferable to confirm that.

[Denitrification processing equipment]
The denitrification treatment device of the present invention is a denitrification treatment device having a water tank capable of storing circulating water, a reactor containing a denitrifying material, and a circulation flow path for returning the circulating water treated by the reactor to the water tank. The denitrifying material contains sulfur, carbonate and a surfactant, and the sulfur is hydrophilized with the surfactant and has a particle size of 0.1 mm or more, based on the total mass of the denitrifying material. The sulfur content is 30% by mass or more and less than 70% by mass, the carbonate content is 30% by mass or more and less than 70% by mass, and the surfactant content satisfies the following conditions.
Condition A:
When the amount of circulating water Q [L], the content of sulfur in the denitrification material S [kg], and the content of surfactant per 1 kg of sulfur P [mg / kg-S] are expressed as SP = aQ. In addition, a is 0.1 [mg / L] or less.

<Overall configuration of denitrification processing equipment>
The overall configuration of the denitrification treatment apparatus of the present invention will be described with reference to the drawings. However, the denitrification treatment apparatus of the present invention is not limited to the drawings.
FIG. 1 is a schematic cross-sectional view of an example of the denitrification treatment apparatus of the present invention. The denitrification treatment apparatus shown in FIG. 1 includes a water tank 11 capable of storing circulating water 12, a reactor 21 including a pump p, a denitrifying material 10, and a water tank in which a part of the circulating water 12 is treated by the reactor 21. It has a circulation flow path 31 that returns to 11. Further, in the denitrification treatment apparatus shown in FIG. 1, the denitrification material 10 contains sulfur 1, carbonate 2, and a surfactant (not shown).
In FIG. 1 and FIG. 2 described later, the pump p is arranged between the water tank 11 and the reactor 21, but even if another pump is arranged in the circulation flow path 31 in addition between the water tank 11 and the reactor 21. Good.

FIG. 2 is a schematic cross-sectional view of another example of the denitrification treatment apparatus of the present invention. The denitrification treatment apparatus shown in FIG. 2 includes a water tank 11 capable of storing circulating water 12, a filtration membrane 41, a pump p, a reactor 21 including a denitrifying material 10, and a part of the circulating water 12 in the reactor 21. It has a circulation flow path 31 which is treated with the above and returned to the water tank 11. Further, in the denitrification treatment apparatus shown in FIG. 2, the denitrification material 10 contains sulfur 1, carbonate 2, and a surfactant (not shown).
In the denitrification treatment apparatus shown in FIG. 2, the reactor 21 includes a support layer 23 and a denitrification material layer 22.
In the denitrification treatment apparatus shown in FIG. 2, a branch flow path 32 is provided in a part of the circulation flow path 31 via a valve (not shown), and the circulating water 12 treated by the reactor 21 is appropriately applied to the branch flow path 32. Liquid can be sent.
In the denitrification treatment apparatus shown in FIG. 2, only a part of the circulating water that has passed through the filtration membrane 41 can be sent to the reactor 21 by the pump p, and the rest can be appropriately returned to the water tank as the membrane filtration water 42.

<Aquarium>
The denitrification treatment device has a water tank capable of storing circulating water. The size of the water tank is not particularly limited and can be designed according to the amount of circulating water Q [L].

<Reactor>
The denitrification treatment device has a reactor containing a denitrification material. When passing through the denitrification material layer, the sulfur denitrification reaction caused by the action of sulfur-oxidizing bacteria growing on the denitrification material layer (such as the surface of sulfur) changes nitrate nitrogen and the like into nitrogen gas. Nitrogen gas is discharged out of the reactor.
The structure of the reactor is not particularly limited, and may be a structure in which circulating water is passed through the denitrifying material in an upward flow or a structure in which water is passed in a downward flow. In the present invention, it is preferable that the reactor has a structure in which circulating water is passed through the denitrifying material in an upward flow. For example, it is preferable to arrange the outlet of the reactor at an arbitrary position in the vertical upward direction as compared with the inlet of the reactor.
It is preferable that the denitrification material layer is formed in the reactor to prevent the denitrification material from floating. It is more preferable to form a support layer and a denitrification material layer in the reactor from the viewpoint of exchanging the denitrification material. As the support layer, it is preferable to use a support gravel layer containing gravel.
The reactor may further include members for removing air bubbles in the resulting nitrogen gas. Examples of the member for removing air bubbles of nitrogen gas include an aeration device and an oscillator. However, since the denitrification treatment apparatus of the present invention uses sulfur having a particle size of 0.1 mm or more, it is easy to remove bubbles of nitrogen gas, so that it is not necessary to provide a member for removing bubbles of nitrogen gas.

<Circulation flow path>
The denitrification treatment device has a circulation flow path for returning the circulating water treated in the reactor to the water tank. The circulating water treated in the reactor is denitrified by passing through the denitrifying material, and the concentration of nitrate nitrogen is lowered and returned to the water tank.

[Manufacturing method of denitrification treatment equipment]
The method for producing the denitrification treatment apparatus of the present invention includes a hydrophilization treatment step of hydrophilizing sulfur with a surfactant under the condition that the content of the surfactant per 1 kg of sulfur is 100 mg / kg-S or more, and the following. The water washing step A of the above is included.
Water washing step A: The composition containing the hydrophilized sulfur is repeatedly washed with water, and the amount of circulating water Q [L], the sulfur content in the denitrifying material S [kg], and sulfur 1 kg. When SP = aQ is expressed as the content of the surfactant per P [mg / kg-S], a is 0.1 [mg / L] or less.

[Breeding method]
The breeding method of the present invention is a method of breeding aquatic organisms in an aquarium while treating nitrate nitrogen in circulating water using the denitrification treatment apparatus of the present invention.
Examples of aquatic organisms include organisms living in lakes and marshes, organisms living in rivers, and organisms living in the sea (marine organisms), and marine organisms are preferable. Examples of the types of aquatic organisms include fish, shellfish, crustaceans, sea urchins, algae, and mammals (living in water), and fish are preferable. In the present invention, it is more preferable that the aquatic organism is a marine fish (saltwater fish) from the viewpoint that land aquaculture is particularly required.

<Familiarity>
When aquatic organisms are bred using the denitrification treatment device of the present invention, the denitrification material of the present invention is placed in a container different from the water tank of the denitrification treatment device, although it depends on the quality of circulating water. It is preferable to add sulfur-oxidizing bacteria to acclimate the denitrification material. However, when water containing sulfur-oxidizing bacteria is used as circulating water, it is not necessary to acclimatize the denitrifying material.

The features of the present invention will be described in more detail with reference to Examples and Comparative Examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as limited by the specific examples shown below.

[Example 1]
<Manufacturing of materials for denitrification>
As the sulfur, granular sulfur having a particle size of 2 mm was used.
As the carbonate, coral sand having a particle size of 1 to 5 mm (main component is calcium carbonate) was used.
As the surfactant, polyoxyethylene alkyl ether, which is a nonionic surfactant, was used.
1 kg of sulfur, 1 kg of carbonate, and a surfactant were kneaded under the condition that the content of the surfactant per 1 kg of sulfur was 100 mg / kg-S or more, and the sulfur was hydrophilized with the surfactant.
After the hydrophilization treatment step, the composition containing the hydrophilized sulfur was sufficiently washed with water to obtain a water-washed composition. Here, in the water washing step, when the denitrifying material is used in the denitrification treatment apparatus designed to have the circulating water amount Q of 10L, the circulating water amount Q [L] and the sulfur content in the denitrifying material When SP = aQ as S [kg] and the content of surfactant per 1 kg of sulfur P [mg / kg-S], washing with water was repeated until a became 0.05 [mg / L]. .. That is, water washing was repeated until the content of the surfactant per 1 kg of sulfur in the denitrification material became 0.5 mg / kg-S. This water washing step satisfies both the water washing step A and the water washing step B.
The surfactant concentration was measured by the official ion exchange chromatograph method.
The water-washed composition was used as the denitrifying material of Example 1.
In the denitrification material of Example 1, sulfur particles and carbonate particles were uniformly mixed in a state of being independent of each other, that is, sulfur and carbonate did not coexist in the same grain.

<Manufacturing of denitrification treatment equipment>
A denitrification treatment device having the configuration shown in FIG. 2 was prepared. That is, an embodiment having a water tank capable of storing circulating water, a filtration membrane, a pump, a reactor containing the denitrifying material of Example 1, and a circulation flow path for returning the circulating water treated by the reactor to the water tank. The denitrification treatment device of No. 1 was prepared. In the reactor, a denitrification material layer in which the denitrification material of Example 1 is deposited is laminated on a support layer (support gravel layer), and the support layer and denitrification are denitrified with circulating water as an upward flow. It was made to pass through the material layer.

<Familiarization of denitrification materials>
The denitrifying material of Example 1 and sulfur-oxidizing bacteria were placed in a 2 L small container, and artificial seawater was circulated and acclimatized. When nitrogen gas began to be generated from the denitrifying material of Example 1, the acclimatization was completed.

[Comparative Example 1]
After the hydrophilization treatment step, the denitrification material of Comparative Example 1 was produced in the same manner as in Example 1 except that the composition containing the hydrophilized sulfur was washed with water only once. Here, in the water washing step, when the denitrifying material is used in the denitrification treatment apparatus designed to have the circulating water amount Q of 10L, the circulating water amount Q [L] and the sulfur content in the denitrifying material When SP = aQ was expressed as S [kg] and the content P [mg / kg-S] of the surfactant per 1 kg of sulfur, a was 2.0 [mg / L]. That is, the content of the surfactant per 1 kg of sulfur in the denitrification material was 20 mg / kg-S.
The denitrification treatment apparatus of Comparative Example 1 was manufactured in the same manner as in Example 1 except that the denitrification material of Comparative Example 1 was used instead of the denitrification material of Example 1.

[Comparative Example 2]
After the hydrophilization treatment step, the denitrification material of Comparative Example 2 was produced in the same manner as in Example 1 except that the composition containing the hydrophilized sulfur was not washed with water. Here, in the water washing step, when the denitrifying material is used in the denitrification treatment apparatus designed to have the circulating water amount Q of 10L, the circulating water amount Q [L] and the sulfur content in the denitrifying material When SP = aQ was expressed as S [kg] and the content P [mg / kg-S] of the surfactant per 1 kg of sulfur, a was 10.0 [mg / L]. That is, the content of the surfactant per 1 kg of sulfur in the denitrification material was 100 mg / kg-S.
The denitrification treatment apparatus of Comparative Example 2 was manufactured in the same manner as in Example 1 except that the denitrification material of Comparative Example 2 was used instead of the denitrification material of Example 1.

[Evaluation]
<Breeding of aquatic organisms>
Marine fish bred in a breeding device using artificial seawater as breeding water was placed in the aquarium of the denitrification treatment device of Example 1 or each Comparative Example together with 10 L of breeding water. The initial nitrate nitrogen concentration in the breeding water used as circulating water was 200 mg / L. The nitrate nitrogen concentration (NO ₃ ^- N concentration) was measured by an absorbance-type multi-item water quality measuring instrument (PhotoFlex STD; manufactured by Central Kagaku Corp.) by the chromotropic acid method.
Using the denitrification treatment device of Example 1 or each comparative example, a part of the circulating water in the water tank is pumped to the reactor, and the denitrifying material in the reactor is passed by an upward flow to circulate. Marine fish were bred in a closed circulatory system by circulating them in an aquarium via a road. Breeding was continued for 10 days. Only a part of the circulating water that passed through the filtration membrane was pumped to the reactor, and the rest was returned to the water tank as membrane filtration water as appropriate. Further, a branch flow path was provided in a part of the circulation flow path via a valve (not shown), and the circulating water treated by the reactor was appropriately sent to the branch flow path as needed.

<State of materials for denitrification>
When the circulating water was passed through the reactor, the condition of the denitrifying material in the reactor was visually confirmed.
As a result, it was confirmed that the denitrifying material could be circulated in the circulating water while maintaining the denitrifying material layer without floating due to the upward flow of the circulating water.
However, the present invention is not limited to the mode in which circulating water is passed through the denitrifying material in an upward flow. For example, even when circulating water is passed through the denitrification material in a downward flow, it is preferable that the denitrification material layer can be maintained without the denitrification material floating.

<Circulating water after 10 days>
The nitrate nitrogen concentration and the surfactant concentration were measured for the circulating water after 10 days. The results obtained are shown in Table 1 below.
The nitrate nitrogen concentration of the circulating water is preferably 200 mg / L or less, more preferably 50 mg / L or less, and particularly preferably 10 mg / L or less.
The surfactant concentration in the circulating water is practically preferably less than 1 mg / L, more preferably 0.5 mg / L or less, and particularly preferably 0.1 mg / L or less. The ecotoxicity of a typical nonionic surfactant according to the OECD (Organization for Economic Co-operation and Development) test guideline 203 is about 4.2 mg / L for rainbow trout, 96 hours, and LC50. When the surfactant concentration is 1 to 4 mg / L, it can be said that there is a high possibility that aquatic organisms will die, which is problematic in practical use.

From Table 1, it was found that the denitrifying material of the present invention is difficult to float during water flow and can be easily used, has high denitrifying activity, and has sufficiently low toxicity to aquatic organisms. Therefore, it was found that the denitrifying material of the present invention is particularly suitable for long-term breeding of aquatic organisms in a closed circulatory system. Further, the denitrifying material of the present invention is easy to manufacture as described above.
From Comparative Examples 1 and 2, when the concentration of the surfactant of the denitrifying material is high and the condition A is not satisfied, that is, when the value of a (= SP / Q) exceeds 0.1, the toxicity to aquatic organisms is high. It turned out to be expensive.

1 Sulfur 2 Carbonate 10 Denitrification material 11 Water tank 12 Circulating water 21 Reactor 22 Denitrification material layer 23 Support layer 31 Circulation flow path 32 Branch flow path 41 Filtration membrane 42 Filtration water p Pump

Claims (10)

A denitrifying material containing sulfur, carbonates and surfactants.
The sulfur is hydrophilized with the surfactant and has a particle size of 0.1 mm or more.
The sulfur content is 30% by mass or more and less than 70% by mass, and the carbonate content is 30% by mass or more and less than 70% by mass with respect to the total mass of the denitrification material.
The surfactant when used in a denitrification treatment apparatus having a water tank capable of storing circulating water, a reactor containing the denitrifying material, and a circulation flow path for returning the circulating water treated by the reactor to the water tank. Satisfies the following condition A,
Material for denitrification.
Condition A:
When the amount of circulating water Q [L], the content of sulfur in the denitrification material S [kg], and the content of surfactant per 1 kg of sulfur P [mg / kg-S] are expressed as SP = aQ. In addition, a is 0.1 [mg / L] or less. A denitrifying material containing sulfur, carbonates and surfactants.
The sulfur is hydrophilized with the surfactant and has a particle size of 0.1 mm or more.
The sulfur content is 30% by mass or more and less than 70% by mass, and the carbonate content is 30% by mass or more and less than 70% by mass with respect to the total mass of the denitrification material.
A material for denitrification in which the content of the surfactant is 0.1% by mass or less with respect to the content of the sulfur. The denitrification material according to claim 1 or 2, wherein the sulfur and the carbonate do not coexist in the same grain. The denitrifying material according to any one of claims 1 to 3, wherein the surfactant contains a nonionic surfactant. The denitrifying material according to any one of claims 1 to 4, which is used for removing nitrate nitrogen by the action of sulfur-oxidizing bacteria. The method for producing a denitrifying material according to any one of claims 1 to 5.
A hydrophilization treatment step of hydrophilizing sulfur with a surfactant under the condition that the content of the surfactant per 1 kg of sulfur is 100 mg / kg-S or more.
A method for producing a denitrifying material, which comprises at least one of the following water cleaning step A and water cleaning step B.
Water washing step A: The composition containing the hydrophilized sulfur is repeatedly washed with water, and the amount of circulating water Q [L], the sulfur content in the denitrifying material S [kg], and sulfur 1 kg. When SP = aQ is expressed as the content of the surfactant per P [mg / kg-S], a is 0.1 [mg / L] or less.
Water washing step B: The composition containing hydrophilized sulfur is repeatedly washed with water so that the content of the surfactant is 0.1% by mass or less with respect to the sulfur content. A denitrification treatment apparatus having a water tank capable of storing circulating water, a reactor containing a denitrification material, and a circulation flow path for returning the circulating water treated by the reactor to the water tank.
The denitrifying material contains sulfur, carbonates and surfactants.
The sulfur is hydrophilized with the surfactant and has a particle size of 0.1 mm or more.
The sulfur content is 30% by mass or more and less than 70% by mass, and the carbonate content is 30% by mass or more and less than 70% by mass with respect to the total mass of the denitrification material.
A denitrification treatment device in which the content of the surfactant satisfies the following conditions.
Condition A:
When the amount of circulating water Q [L], the content of sulfur in the denitrification material S [kg], and the content of surfactant per 1 kg of sulfur P [mg / kg-S] are expressed as SP = aQ. In addition, a is 0.1 [mg / L] or less. The method for manufacturing the denitrification treatment apparatus according to claim 7.
A hydrophilization treatment step of hydrophilizing sulfur with a surfactant under the condition that the content of the surfactant per 1 kg of sulfur is 100 mg / kg-S or more.
A method for manufacturing a denitrification treatment apparatus, which comprises the following water washing step A.
Water washing step A: The composition containing the hydrophilized sulfur is repeatedly washed with water, and the amount of circulating water Q [L], the sulfur content in the denitrifying material S [kg], and sulfur 1 kg. When SP = aQ is expressed as the content of the surfactant per P [mg / kg-S], a is 0.1 [mg / L] or less. A breeding method in which an aquatic organism is bred in the aquarium while removing nitrate nitrogen from the circulating water using the denitrification treatment apparatus according to claim 7. The breeding method according to claim 9, wherein the aquatic organism is a marine fish.

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