JP2021079322A - Denitration treatment apparatus - Google Patents

Abstract

To provide a denitration treatment apparatus which has high activity of denitration and is designed to cause no mixing of a denitration material into a tank.SOLUTION: A denitration treatment apparatus includes; a tank 11 capable of storing circulation water 12; a reactor 21 including a denitration material 10; a circulation passage 31 for returning processed water processed in the reactor 21 to the tank; an upstream solid-liquid separation part 41 for subjecting the circulation water to solid-liquid separation, which is disposed upstream of the reactor 21; and a downstream solid-liquid separation part 51 for subjecting the processed water to solid-liquid separation, which is disposed downstream of the reactor 21. The denitration material 10 includes sulfur 1 and carbonate 2. The denitration treatment apparatus includes a gas removal part 24 for removing nitrogen gas generated in the denitration material 10 by stirring, fluid flow or vibration in the reactor 21 when the reactor 21 removes nitrate nitrogen by action of sulfur oxidizing bacteria.SELECTED DRAWING: Figure 2

Description

The present invention relates to a denitrification treatment device.

There is a demand for a denitrification treatment device that removes 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 and 2).

In Patent Document 1, 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.

In Patent Document 2, a water flow generating member is provided in a closed system such as water to be treated in a water tank, and a nitrate nitrogen removing material composed of sulfur and a calcium carbonate-based component is provided in the middle of a water flow path formed by the water flow generating member. A device for treating nitrate nitrogen with a layer is described.

JP-A-2002-273475 JP-A-2002-37097

However, in the method described in Patent Document 1, it is necessary to use a large amount of denitrifying material, and it is considered that the denitrification activity is low. In particular, the method described in Patent Document 1 causes bubbles of nitrogen gas to be generated on the surface of the denitrifying material as compared with the method described in Patent Document 2 in which a water flow is positively generated in the vicinity of the denitrifying material. It was found that it was easy and the denitrification activity decreased due to air bubbles.
Further, it was found that in each of the methods described in Patent Documents 1 and 2, a part of the denitrifying material flows out from the reactor and is mixed in the water tank. It was found that when the denitrifying material flows out into the aquarium, even a small amount has a great effect on aquatic organisms.

An object to be solved by the present invention is to provide a denitrification treatment apparatus having high denitrification activity and preventing denitrification materials from being mixed in a water tank.

As a result of diligent studies to solve the above problems, the present inventors used a reactor provided with a gas removing part for removing nitrogen gas, and provided solid-liquid separation parts on the upstream side and the downstream side of the reactor. It was found that the above-mentioned problems can be solved by providing the above-mentioned problems.
Specifically, the present invention and preferred configurations of the present invention are as follows.

[1] A water tank that can store circulating water and
Reactors containing denitrification materials and
A circulation channel that returns the treated water treated in the reactor to the aquarium,
An upstream solid-liquid separator located upstream of the reactor to separate circulating water.
It has a downstream solid-liquid separation section that is located downstream of the reactor and separates the treated water.
Denitrification material contains sulfur and carbonate,
A denitrification treatment apparatus comprising a gas removing unit for removing nitrogen gas generated in a denitrifying material when the reactor removes nitrate nitrogen by the action of sulfur-oxidizing bacteria by stirring, flowing or vibrating inside the reactor.
[2] The denitrification treatment apparatus according to [1], wherein the gas removing unit removes nitrogen gas by stirring inside the reactor.
[3] A pump is provided between the water tank and the reactor.
It has a redox potential measuring unit inside or downstream of the reactor.
The denitrification treatment apparatus according to [1] or [2], which has a control unit that controls the flow rate of the pump so that the redox potential of the treated water is always in the range of −300 to +30 mV.
[4] The denitrification treatment apparatus according to any one of [1] to [3], wherein the upstream solid-liquid separation unit and the downstream solid-liquid separation unit are common.
[5] Sulfur has a particle size of less than 5 mm and has a particle size of less than 5 mm.
The denitrification treatment apparatus according to any one of [1] to [4], wherein the carbonate has a particle size of less than 5 mm.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a denitrification treatment apparatus having high denitrification activity and preventing denitrification materials from being mixed in a water tank.

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. FIG. 3 is a schematic cross-sectional view of another example of the denitrification treatment apparatus of the present invention. FIG. 4 is a schematic cross-sectional view of the denitrification treatment apparatus of Comparative Example 1. FIG. 5 is a schematic cross-sectional view of the denitrification treatment apparatus of Comparative Example 2.

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.

[Denitrification processing equipment]
The denitrification treatment device of the present invention includes a water tank capable of storing circulating water and a water tank.
Reactors containing denitrification materials and
A circulation channel that returns the treated water treated in the reactor to the aquarium,
An upstream solid-liquid separator located upstream of the reactor to separate circulating water.
It has a downstream solid-liquid separation section that is located downstream of the reactor and separates the treated water.
Denitrification material contains sulfur and carbonate,
The reactor is provided with a gas removing unit that removes nitrogen gas generated in a denitrifying material when nitrate nitrogen is removed by the action of sulfur-oxidizing bacteria by stirring, flowing or vibrating inside the reactor.
According to the configuration of the denitrification treatment apparatus of the present invention, the denitrification activity is high and the denitrification material is not mixed in the water tank. Although not bound by any theory, by using a reactor provided with a gas removing unit for removing nitrogen gas, it is possible to easily remove bubbles of the generated nitrogen gas and increase the denitrification activity. By providing the solid-liquid separation portions on the upstream side and the downstream side of the reactor, even if the denitrification material flows out from the reactor, the denitrification material is hardly mixed in the water tank.
Hereinafter, preferred embodiments of the denitrification treatment apparatus of the present invention will be described.

<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 device shown in FIG. 1 has a water tank 11 capable of storing circulating water 12 and an upstream solid-liquid separating section 41 (downstream solid-liquid separating section) arranged upstream of the reactor 21 to separate the circulating water. It also has a pump p, a reactor 21 containing the denitrifying material 10, and a circulation flow path 31 for returning the treated water treated by the reactor 21 to the water tank. In the denitrification treatment apparatus shown in FIG. 1, the denitrification material 10 contains sulfur 1 and carbonate 2. In the denitrification treatment apparatus shown in FIG. 1, the reactor 21 includes a gas removing unit 24 that removes nitrogen gas by stirring inside the reactor 21.
In the denitrification treatment apparatus shown in FIG. 1, the treated water that has passed through the circulation flow path 31 is further solid-liquid separated by the downstream solid-liquid separation unit 51 (which also serves as the upstream solid-liquid separation unit 41). The part returns to the water tank 11 as solid-liquid separated water 42. That is, in the denitrification treatment apparatus shown in FIG. 1, only a part of the circulating water 12 that has passed through the upstream solid-liquid separation unit 41 is sent to the reactor 21 by the pump p, and the rest is used as the solid-liquid separation water 42. It can be returned to the water tank 11 as appropriate.
In FIGS. 1 and 2 to 5 described later, the pump p is arranged between the water tank 11 and the reactor 21, but another pump is arranged in the circulation flow path 31 in addition to the space between the water tank 11 and the reactor 21. You may.

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 further includes an oxidation-reduction potential measuring unit 61 and a control unit 62 in the denitrification treatment apparatus shown in FIG. including.

FIG. 3 is a schematic cross-sectional view of another example of the denitrification treatment apparatus of the present invention. The denitrification treatment device shown in FIG. 3 has a water tank 11 capable of storing circulating water 12, an upstream solid-liquid separating unit 41 arranged upstream of the reactor 21 for solid-liquid separation of circulating water, a pump p, and denitrification. A reactor 21 containing a nitrogenizing material 10, a circulation flow path 31 for returning the treated water treated in the reactor 21 to a water tank, and a downstream solid-liquid separation unit 51 arranged downstream of the reactor 21 for solid-liquid separation of the treated water. Has. In the denitrification treatment apparatus shown in FIG. 3, the reactor 21 includes a gas removing unit 24 that removes nitrogen gas by stirring inside the reactor 21.
In the denitrification treatment apparatus shown in FIG. 3, the treated water that has passed through the circulation flow path 31 is further solid-liquid separated by the downstream solid-liquid separation unit 51, and then returns to the water tank 11.
Hereinafter, details of each member constituting the denitrification treatment apparatus of the present invention will be described.

<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.

<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.

(Material for denitrification)
The denitrifying material 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 is preferably used for removing nitrate nitrogen or the like from circulating water in, for example, livestock industry, agriculture, fishery industry (including aquaculture, fish breeding, etc.).

(1) Sulfur The denitrifying material contains sulfur.
In the present invention, sulfur hydrophilized with a surfactant may be used.
When sulfur having a particle size of 0.1 mm or more is used, it has water repellency as it is. 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 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.

(2) Carbonate The denitrifying material 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 denitrification material has a carbonate content of 30% by mass or more and less than 70% by mass with respect to the total mass of the denitrification 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, it is preferable that the sulfur particles and the carbonate particles are uniformly mixed in an independent state from each other from the viewpoint of easy production method. That is, in the denitrification material, it is preferable that sulfur and carbonate do not coexist in the same grain.

(3) Surfactant The denitrifying material preferably contains a predetermined amount of the surfactant.
The content of the surfactant is preferably 0.1% by mass (1 mg in terms of the content of the surfactant per 1 kg of sulfur) with respect to the sulfur content, and is preferably 0.08% by mass (sulfur). It is more preferably 0.8 mg) or less in terms of the content of the surfactant per 1 kg, and particularly preferably 0.06% by mass or less.

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.

(4) Manufacturing method of denitrifying material The manufacturing method of denitrifying material is not particularly limited. For example, it is preferable to include 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 a water washing step. However, in the present invention, a denitrifying material may be produced using sulfur which has not been hydrophilized with a surfactant.
The water washing step is not particularly limited, but the composition containing hydrophilized sulfur is repeatedly washed with water to reduce the content of the surfactant to 0.1% by mass or less with respect to the sulfur content. Is preferable.

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 further mixing sulfur, carbonate, and if necessary, 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.

The water washing step is not particularly limited, and water washing can be performed by a known method. In the water washing step, it is preferable to repeat the water washing twice or more.

(Gas removal unit)
In the denitrification treatment apparatus of the present invention, a gas removing unit that removes nitrogen gas generated by a denitrifying material when the reactor removes nitrate nitrogen by the action of sulfur-oxidizing bacteria by stirring, flowing or vibrating inside the reactor. To be equipped. Since the denitrification treatment apparatus of the present invention includes a gas removing unit, it is possible to easily remove bubbles of nitrogen gas even when sulfur having a small particle size is used, and the denitrification activity can be increased.
As a method of removing nitrogen gas by stirring, a method of throwing a stirrer into the bottom of the reactor and applying a magnetic force or the like from the outside to stir the inside of the reactor, or a stirrer equipped with a propeller reaching the denitrification material layer is used in the reactor. Examples thereof include a method in which the inside of the reactor is agitated by installing it inside and rotating it.
As a method of removing nitrogen gas by flow, an aeration device is installed at the bottom of the reactor to eject gas to flow inside the reactor, and the upper and lower parts of the reactor (the height part with the denitrification material layer) are used. Examples thereof include a method in which a bypass flow path to be connected is provided to generate a circulating flow in the denitrification material layer to flow inside the reactor.
As a method of removing nitrogen gas by vibration, a method of throwing an oscillator into the bottom of the reactor and controlling it from the outside to vibrate the inside of the reactor, or a method of installing a vibrating device outside the reactor to vibrate the entire reactor, etc. Can be mentioned.
In the present invention, it is preferable that the gas removing unit removes nitrogen gas by stirring inside the reactor. Among them, a method in which a stirring device including a propeller that reaches the denitrification material layer is installed inside the reactor and rotated to stir the inside of the reactor is more preferable. When a stirring device is used, the stirring speed is not particularly limited, but is preferably 50 rpm or less, and more preferably 30 rpm or less. It is preferable that the stirring speed is not more than the upper limit value from the viewpoint of wear of the denitrifying material. It is preferably 50 rpm or less, and more preferably 30 rpm or less. The lower limit of the stirring speed can be, for example, 1 rpm or more, and 5 rpm or more is preferable from the viewpoint that bubbles of nitrogen gas can be easily removed even when sulfur having a small particle size is used.

<Circulation flow path>
The denitrification treatment apparatus of the present invention has a circulation flow path for returning the treated water treated by the reactor to the water tank. The treated 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.

<Upstream solid-liquid separator and downstream solid-liquid separator>
The denitrification treatment apparatus of the present invention has an upstream solid-liquid separation unit located upstream of the reactor for solid-liquid separation of circulating water and a downstream solid-liquid separation unit located downstream of the reactor for solid-liquid separation of treated water. Has a part.
By providing the upstream solid-liquid separation unit, the solid matter contained in the circulating water from the water tank can be removed, and the circulating water having a small amount of solid matter can be supplied to the reactor, and the efficiency of denitrification can be improved. Examples of the solid matter contained in the circulating water from the aquarium include aquatic organism feces and food residue.
By providing the downstream solid-liquid separation unit, it is possible to remove the denitrification material contained in the treated water from the reactor and prevent the denitrification material from being mixed in the water tank. In particular, even when the denitrification material uses sulfur having a small particle size or a carbonate having a small particle size, it is possible to prevent these from being mixed in the water tank by providing a solid-liquid separation portion on the downstream side.
In the denitrification treatment apparatus of the present invention, the upstream side solid-liquid separation part and the downstream side solid-liquid separation part may be common or independent. In the denitrification treatment apparatus of the present invention, it is particularly preferable that the upstream side solid-liquid separation part and the downstream side solid-liquid separation part are common from the viewpoint of integrating the members and reducing the cost.

<Pump>
The denitrification treatment apparatus of the present invention preferably has a pump between the water tank and the reactor. The flow rate of the pump is preferably controlled by the control unit so that the redox potential of the treated water is always in the range of −300 to +30 mV.

<Redox potential measuring unit>
It is preferable to have a redox potential measuring unit inside or downstream of the reactor of the present invention. It is more preferable to have a redox potential measuring unit downstream of the reactor from the viewpoint of early detection of abnormalities in the apparatus.
In the present invention, it is preferable that the redox potential of the treated water is always in the range of −300 to +30 mV. By confirming the redox potential of the treated water, it is possible to confirm whether the condition is aerobic or anaerobic. When the redox potential of the treated water is +30 mV or less, nitrate nitrogen can be easily removed by the action of sulfur-oxidizing bacteria.
The upper limit of the redox potential of the treated water is more preferably 0 mV or less, and particularly preferably −50 mV or less. The lower limit of the redox potential of the treated water is more preferably −200 mV or more.

<Control unit>
The denitrification treatment apparatus of the present invention preferably has a control unit that controls the flow rate of the pump. In particular, it is more preferable to have a control unit that controls the flow rate of the pump so that the redox potential of the treated water is always in the range of −300 to +30 mV.
When the redox potential of the treated water exceeds the upper limit, it is preferable to reduce the flow rate of the pump or stop the pump to control the amount of circulating water flowing into the reactor.
When the redox potential of the treated water is below the lower limit, it is preferable to increase the flow rate of the pump to control the amount of circulating water flowing into the reactor.

<Manufacturing method of denitrification treatment equipment>
The manufacturing method of the denitrification treatment device is not particularly limited. The denitrification treatment apparatus can be manufactured by a known method.

<Breeding method>
Using the denitrification treatment apparatus of the present invention, aquatic organisms can be bred in an aquarium while treating nitrate nitrogen in circulating water.
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, sulfur-oxidizing bacteria are used for denitrification materials 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 the denitrifying material to acclimatize the denitrifying 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.
1 kg of sulfur, 1 kg of carbonate, and a nonionic surfactant were kneaded, 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.
The water-washed composition was used as a denitrification material.
In the denitrification material, the sulfur particles and the carbonate particles were uniformly mixed in an independent state, that is, the sulfur and the 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, a water tank capable of storing circulating water, a filter membrane (which also serves as an upstream solid-liquid separator and a downstream solid-liquid separator), a pump, a reactor containing a denitrifying material, an oxidation-reduction potential measuring unit, and the like. The denitrification treatment apparatus of Example 1 having a circulation flow path for returning the treated water treated by the reactor to the water tank and a control unit for controlling the flow rate of the pump was prepared. In addition, the reactor was equipped with a gas removing unit (stirring device) that removes nitrogen gas by stirring inside the reactor. In the reactor, a denitrification material layer in which denitrification material is deposited is laminated on a support layer (support gravel layer), and the support layer and the denitrification material layer are provided by using circulating water as an upward flow. I tried to pass.

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

<Breeding of aquatic organisms>
The marine fish bred in the breeding device using artificial seawater as the breeding water was put into the aquarium of the denitrification treatment device of Example 1 together with the breeding water.
Using the denitrification treatment apparatus of Example 1, 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 through the circulation flow path. It was circulated in an aquarium and marine fish were bred in a closed circulatory system. At that time, the denitrifying material in the reactor was stirred at a speed of 1 to 30 rpm by a stirring device used as a gas removing unit. In addition, the control unit controlled the flow rate of the pump so that the redox potential of the treated water was always in the range of −300 to +30 mV.
Breeding was continued for 10 days.
As a result, it was found that the denitrification activity could be maintained high without the air bubbles covering the surface of the denitrification material, and the denitrification material flowing out of the reactor did not mix in the water tank.

[Comparative Example 1]: No downstream solid-liquid separation unit A denitrification treatment device having the configuration shown in FIG. 4 was prepared and used as the denitrification treatment device of Comparative Example 1. That is, a water tank capable of storing circulating water, a filtration membrane (upstream solid-liquid separation part), a pump, a reactor containing a denitrifying material, an oxidation-reduction potential measuring part, and a water tank containing treated water treated by the reactor. A denitrification treatment device having a circulation flow path for returning to the water and a control unit for controlling the flow rate of the pump was prepared. In addition, the reactor was equipped with a gas removing unit (stirring device) that removes nitrogen gas by stirring inside the reactor. In the reactor, a denitrification material layer in which denitrification material is deposited is laminated on a support layer (support gravel layer), and the support layer and the denitrification material layer are provided by using circulating water as an upward flow. I tried to pass.
Aquatic organisms were bred in the same manner as in Example 1 except that the denitrification treatment apparatus of Comparative Example 1 was used.
As a result, the denitrifying material that flowed out of the reactor was mixed into the water tank.

[Comparative Example 2]: No gas removing unit A denitrification treatment device having the configuration shown in FIG. 5 was prepared and used as the denitrification treatment device of Comparative Example 2. That is, a water tank capable of storing circulating water, a filter membrane (which also serves as an upstream solid-liquid separator and a downstream solid-liquid separator), a pump, a reactor containing a denitrifying material, an oxidation-reduction potential measuring unit, and the like. A denitrification treatment device having a circulation flow path for returning the treated water treated by the reactor to the water tank and a control unit for controlling the flow rate of the pump was prepared. However, the reactor was not equipped with a gas removal unit (stirring device). In the reactor, a denitrification material layer in which denitrification material is deposited is laminated on a support layer (support gravel layer), and the support layer and the denitrification material layer are provided by using circulating water as an upward flow. I tried to pass.
Aquatic organisms were bred in the same manner as in Example 1 except that the denitrification treatment apparatus of Comparative Example 2 was used.
As a result, it was found that the surface of the denitrification material was covered with air bubbles (nitrogen gas), and the denitrification activity was reduced.

From the above, it was found that the denitrification treatment apparatus of the present invention has high denitrification activity and the denitrification material does not mix in the water tank. Therefore, it was found that the denitrification treatment apparatus of the present invention is particularly suitable for long-term breeding of aquatic organisms in a closed circulatory system.

1 Sulfur 2 Carbonate 10 Denitrification material 11 Water tank 12 Circulating water 21 Reactor 22 Denitrification material layer 23 Support layer 24 Gas removal unit 31 Circulation flow path 41 Upstream solid-liquid separation unit 42 Solid-liquid separation water 51 Downstream solid Liquid separation unit 61 Redox potential measurement unit 62 Control unit p pump

Claims (5)

A water tank that can store circulating water and
Reactors containing denitrification materials and
A circulation flow path for returning the treated water treated in the reactor to the water tank, and
An upstream solid-liquid separator located upstream of the reactor to solid-liquid separate the circulating water.
It has a downstream solid-liquid separation section that is arranged downstream of the reactor and solid-liquid separates the treated water.
The denitrification material contains sulfur and carbonate and contains
A denitrification process comprising a gas removing unit that removes nitrogen gas generated in the denitrifying material by stirring, flowing or vibrating the inside of the reactor when the reactor removes nitrate nitrogen by the action of sulfur-oxidizing bacteria. apparatus. The denitrification treatment apparatus according to claim 1, wherein the gas removing unit removes the nitrogen gas by stirring inside the reactor. It has a pump between the water tank and the reactor
A redox potential measuring unit is provided inside or downstream of the reactor.
The denitrification treatment apparatus according to claim 1 or 2, further comprising a control unit that controls the flow rate of the pump so that the redox potential of the treated water is always in the range of −300 to +30 mV. The denitrification treatment apparatus according to any one of claims 1 to 3, wherein the upstream side solid-liquid separation unit and the downstream side solid-liquid separation unit are common. The sulfur has a particle size of less than 5 mm and has a particle size of less than 5 mm.
The denitrification treatment apparatus according to any one of claims 1 to 4, wherein the carbonate has a particle size of less than 5 mm.

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