JP2021079324A - 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 is designed so that drainage is passed upstream in a reactor including a denitration material. The denitration material includes sulfur and carbonate. The interior of the reactor and a downstream of the denitration material are filled with a floating filter medium. The denitration treatment apparatus includes a gas removal part for removing nitrogen gas generated in the denitration material by stirring, fluid flow or vibration in the reactor when the reactor removes nitrate nitrogen by action of sulfur oxidizing bacteria.SELECTED DRAWING: Figure 1

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 Japanese Unexamined Patent Publication No. 2001-070984

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, in each of the methods described in Patent Documents 1 and 2, fine denitrification material is wound up by nitrogen gas, a part of the denitrification material flows out from the reactor, and the turbidity of the treated water increases. It was found to be mixed in the aquarium. 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.

Here, instead of using denitrification materials containing sulfur and carbonates, a sulfur source or alkali is added to the wastewater as an additive to oxidize nitrate nitrogen to nitrogen by the action of sulfur-oxidizing bacteria. How to do it is known. For example, Patent Document 3 describes in a denitrification method in which autotrophic bacteria are used to reduce nitrite nitrogen and nitrate nitrogen in wastewater to nitrogen gas and removed from the wastewater, from an autotrophic bacterium denitrification tank. A method for removing nitrogen from wastewater, which increases the concentration of autotrophic bacteria inside a denitrification tank by preventing floating outflow using a membrane separation device or a filtration device, is described. However, since the method that does not use the denitrifying material does not cause the problem that the denitrifying material is mixed in the water tank in the first place, the method described in Patent Document 3 does not suggest a method for solving the above-mentioned problems. ..

As a result of diligent studies to solve the above problems, the present inventors use a reactor provided with a gas removing unit for removing nitrogen gas, and fill the inside of the reactor with a floating filter medium downstream of the denitrifying material. By doing so, it was found that the above problems can be solved.

Specifically, the present invention and preferred configurations of the present invention are as follows.
[1] A denitrification treatment device that allows wastewater to pass through a reactor containing denitrification materials in an upward flow.
Denitrification material contains sulfur and carbonate,
A floating filter medium is filled inside the reactor and downstream of the denitrification material.
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 floating filter medium is a resin-made porous body having a bubble structure.
[3] Using wastewater as circulating water,
A water tank that can store circulating water and
The denitrification treatment apparatus according to [1] or [2], which has a circulation flow path for returning the treated water treated in the reactor to the water tank.
[4] The denitrification treatment apparatus according to [3], which is arranged upstream of the reactor and has an upstream solid-liquid separation unit for solid-liquid separation of circulating water.
[5] A pump is provided between the water tank and the reactor.
It has a turbidity measuring unit inside or downstream of the reactor.
Has a control unit
The denitrification treatment device according to [3] or [4], wherein the control unit controls to reduce the flow rate of the pump when the turbidity of the treated water exceeds a predetermined threshold value.
[6] A turbidity measuring unit is provided inside or downstream of the reactor.
It has a downstream solid-liquid separator that is located downstream of the reactor and separates the treated water.
It has a branch flow path that allows the treated water to be bypassed upstream of the solid-liquid separation section on the downstream side.
Has a control unit
The denitrification treatment apparatus according to [3] or [4], wherein the control unit bypasses the treated water to the upstream of the downstream solid-liquid separation unit when the turbidity of the treated water exceeds a predetermined threshold value.
[7] It has an upstream solid-liquid separation unit that is arranged upstream of the reactor and separates circulating water.
The denitrification treatment apparatus according to [6], wherein the upstream solid-liquid separation unit and the downstream solid-liquid separation unit are common.
[8] 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 [7], wherein the carbonate has a particle size of less than 5 mm.
[9] The denitrification treatment apparatus according to any one of [1] to [8], wherein the filling rate of the floating filter medium for the reactor is 1 to 30% by volume.

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 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.

[Denitrification processing equipment]
The denitrification treatment device of the present invention is a denitrification treatment device for passing wastewater through a reactor containing a denitrification material in an upward flow, and the denitrification material contains sulfur and carbonate, and is inside the reactor and denitrified. A floating filter medium is filled downstream of the denitrifying material, and the nitrogen gas generated in the denitrifying material when the reactor removes nitrate nitrogen by the action of sulfur-oxidizing bacteria is removed by stirring, flowing or vibrating inside the reactor. It is equipped with a gas removing unit.
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 filling the floating filter medium inside the reactor and downstream of the denitrification material, the denitrification material is suppressed from flowing out from the reactor, and the denitrification material is hardly mixed in the water tank. By preventing the outflow of (fine) denitrifying materials suspended by the upward flow inside the reactor and the generated nitrogen gas, the consumption of denitrifying materials is suppressed and nitrate nitrogen is stably maintained over a long period of time. The removal device can be operated. As described above, the present invention focuses on a novel problem that occurs when a gas removing unit is used, in which a part of the denitrifying material flows out from the reactor, the turbidity of the treated water increases, and the treated water is mixed in the water tank. It is a solution.
In the improvement of denitrification treatment, which usually requires a large scale and a large amount of cost, the denitrification treatment using the denitrification treatment apparatus of the present invention can realize a simple, low-cost and efficient denitrification treatment. ..
Hereinafter, preferred embodiments of the denitrification treatment apparatus of the present invention will be described.

<Overall configuration of denitrification processing equipment>
The denitrification treatment apparatus of the present invention uses wastewater as circulating water, and in addition to a reactor containing a denitrifying material, a water tank capable of further storing the circulating water and a circulation flow path for returning the circulating water treated by the reactor to the water tank. It is preferable that the mode has.
This preferred embodiment will be described with reference to the drawings as a preferred embodiment of the overall configuration of the denitrification treatment apparatus of the present invention. However, the denitrification treatment apparatus of the present invention is not limited to the drawings. The denitrification treatment apparatus of the present invention may have a reactor containing a denitrification material, and may have only a reactor containing the denitrification material.

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 includes a water tank 11 capable of storing circulating water 12, a pump p, a reactor 21 containing a denitrification material 10, and a circulating flow for returning the treated water treated by the reactor 21 to the water tank. It has a road 31. 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 floating filter medium 25 is filled inside the reactor 21 and downstream of the denitrification material 10. In FIG. 1, the levitation filter medium 25 forms a levitation filter medium layer on the upper part of the reactor 21. However, a part of the floating filter medium 25 may be suspended in the treated water between the denitrification material layer 22 and the floating filter medium layer (not shown).
In FIGS. 1 and 2 to 4 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 has an upstream solid-liquid separation unit 41 arranged upstream of the reactor 21 for solid-liquid separation of circulating water in the denitrification treatment apparatus shown in FIG. 21 includes a support layer 23 and a denitrification material layer 22.
In the denitrification treatment apparatus shown in FIG. 2, the circulating water 12 is solid-liquid separated by the upstream solid-liquid separation unit 41, and then partly returns to the water tank 11 as solid-liquid separated water 42. That is, in the denitrification treatment apparatus shown in FIG. 2, 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.

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 further includes a turbidity measuring unit 61 and a control unit 62 in the denitrification treatment device shown in FIG. In the denitrification treatment apparatus shown in FIG. 2, the turbidity measuring unit 61 is arranged downstream of the reactor 21. However, the turbidity measuring unit 61 may be arranged inside the reactor 21 (not shown).
In the denitrification treatment apparatus shown in FIG. 3, the control unit 62 can control the flow rate of the pump p to be reduced when the turbidity of the treated water treated by the reactor 21 exceeds a predetermined threshold value.

FIG. 4 is a schematic cross-sectional view of another example of the denitrification treatment apparatus of the present invention. In the denitrification treatment apparatus shown in FIG. 2, in the denitrification treatment apparatus shown in FIG. 2, the upstream side solid-liquid separation unit 41 also serves as the downstream side solid-liquid separation unit 51, and further, the turbidity measurement unit 61 and the control unit 62. , A branch flow path, a branch valve 64 arranged in the branch flow path, and a valve 63 arranged in the circulation flow path 31. The branch flow path can bypass the treated water to the upstream of the downstream solid-liquid separation unit 51.
The downstream solid-liquid separation unit 51 is arranged downstream of the reactor 21 to separate the treated water into solid and liquid.
In the denitrification treatment apparatus shown in FIG. 4, when the branch valve 64 is in the open state, part or all of the treated water passes through the branch flow path, and the downstream solid-liquid separation unit 51 (upstream solid-liquid separation unit 51). After further solid-liquid separation with (also serving as 41), a part of the solid-liquid separated water 42 returns to the water tank 11.
Further, when the valve 63 arranged in the circulation flow path 31 is in the open state, in the denitrification treatment device shown in FIG. 4, the treated water in which a part or all of the treated water has passed through the circulation flow path 31 is on the downstream side. After further solid-liquid separation by the solid-liquid separation unit 51 (which also serves as the upstream solid-liquid separation unit 41), the process returns to the water tank 11.
In the denitrification treatment apparatus shown in FIG. 4, the control unit 62 controls the branch valve 64 to be opened when the turbidity of the treated water treated by the reactor 21 exceeds a predetermined threshold value. The treated water can be bypassed upstream of the downstream solid-liquid separation unit 51. In this case, it is preferable that the control unit 62 further controls the valve 63 arranged in the circulation flow path 31 so as to close the valve 63.
Hereinafter, details of each member constituting the denitrification treatment apparatus of the present invention will be described.

<Aquarium>
The denitrification treatment device preferably 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.
In the present invention, the reactor has a structure in which wastewater (circulating water) is passed through the denitrification 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.
In the present invention, the floating filter medium is filled inside the reactor and downstream of the denitrification material.
In the present invention, 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.
Further, 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 wastewater (circulating water) of, 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 wastewater treatment.
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 5 mm, preferably from the viewpoint of increasing the contact area per unit weight and enhancing denitrification activity, preferably 4 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 waste water, to suppress the reduction in denitrification activity. It also supplies carbonate ions necessary for the growth of sulfur-oxidizing bacteria and the denitrification reaction.

As the carbonate, a weak alkaline agent is preferable. The carbonate preferably has a pH of waste 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 5 mm, preferably 4 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 preferably 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, and contains carbonate with respect to the total mass of the denitrification material. The ratio is more preferably 40% by mass or more, and particularly preferably 45% by mass or more. The content ratio of carbonate to the total mass of the denitrifying material is more preferably less than 60% by mass, and particularly preferably less than 55% by mass.

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 material wear. 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.

(Floating filter medium)
In the present invention, the floating filter medium is filled inside the reactor and downstream of the denitrification material. Here, in order for the filter medium to float, the apparent specific gravity of the floating filter medium needs to be less than 1.0. In the present specification, the apparent specific weight is a specific weight obtained by dividing the mass of the floating filter medium in a water-containing state by the volume of the floating filter medium, and indicates a substantial specific weight of the floating filter medium. Specifically, a resin-made porous body ^{can be weighed in a 50 cm 3} graduated cylinder with an apparent volume of 30 cm ³ and calculated from the mass (unit: g / cm ³ ).

The apparent specific gravity of the floating filter medium used in the present invention is preferably 0.1 or more and less than 1.0, more preferably 0.5 or more and less than 1.0, and 0.8 or more and less than 1.0. Is even more preferable. By setting the apparent specific gravity of the floating filter medium in the above range, the porosity and the specific surface area can be set in a desired range. As a result, the levitation property and filtration efficiency of the levitation filter medium are improved.

From the viewpoint of facilitating (reuse) the denitrification material captured by the levitation filter medium after being flocculated on the levitation filter medium and settled together with the levitation filter medium, the levitation filter medium is a plurality of levitation filter media. Are preferably filled in an independent state, i.e. not connected to each other. Compared with the case where a recovery device for the free denitrification material is further installed outside the reactor, filling the reactor with a floating filter medium reduces the loss of the free denitrification material and allows the denitrification material to be lost from the outside of the reactor. The recovery cost for returning to the inside of the reactor is also unnecessary.
From the same viewpoint, it is preferable that the floating filter medium is filled freely and movably inside the reactor downstream of the denitrification material. Specifically, it is preferable that the floating filter medium is movably filled up to the denitrification material. For example, it is preferable not to provide a partition wall having a smaller opening than the floating filter medium between the outlet of the reactor and the denitrifying material. Further, when the floating filter medium forms the floating filter medium layer, it is preferable not to provide a partition wall having a smaller opening than the floating filter medium between the floating filter medium layer and the denitrifying material.

The material of the floating filter medium is not particularly limited. For example, resins, ceramics and the like can be mentioned. The floating filter medium is preferably made of resin. That is, in the present invention, it is preferable that the floating filter medium is a resin-made porous body having a bubble structure.
Examples of the resin forming the porous structure include thermosetting resins, thermoplastic resins, rubbers, and elastomers.

Examples of the thermoplastic resin include polyvinyl alcohol resin, acrylic resin, methacrylic resin, vinyl acetate resin, vinyl chloride resin, vinylidene chloride resin, styrene resin, ethylene vinyl acetate resin, ABS resin, polyethylene, polypropylene, polystyrene, polyacetal, and polyamide resin. Polyester, polyurethane, and copolymers thereof can be used.

As the thermosetting resin, epoxy resin, unsaturated polyester resin, phenol resin, urea resin, melamine resin, polyurethane resin, silicone resin, diallyl phthalate resin, and copolymers thereof can be used.

As the rubber, natural rubber, isoprene rubber, butadiene rubber, butyl rubber, epichlorohydrin rubber, NBR, MBR, CR, fluororubber, acrylic rubber, silicone rubber, EPM, EPDM, and copolymers thereof can be used.

As the elastomer, styrene-based elastomers, polyolefin-based elastomers, polyurethane-based elastomers, polyester-based elastomers, polyamide-based elastomers, polybutadiene-based elastomers, and copolymers thereof can be used.
The above-mentioned resins, rubbers, and elastomers can be used alone, or two or more of them can be mixed and used.

Among them, as the resin, polyvinyl alcohol, polyurethane, polypropylene and polyethylene are preferably used, and in particular, polyvinyl alcohol is preferably used. That is, it is particularly preferable that the floating filter medium used in the present invention is a porous body made of polyvinyl alcohol having a bubble structure.

The floating filter medium is preferably a porous body from the viewpoint of facilitating the capture of fine denitrifying materials, more preferably has a bubble structure, and particularly preferably a foam. In the present specification, the bubble structure means an open cell structure, and refers to a structure in which the bubbles themselves are connected to form a through hole penetrating the floating filter medium. Therefore, the drainage can pass through the floating filter medium. The floating filter medium having an open cell structure is a sponge-like structure having excellent water absorption.
The floating filter medium may have a function of capturing any suspended solids (SS) other than the denitrifying material.

The floating filter medium may be in the form of a sheet, but it is preferable to use a plurality of cube-shaped or spherical carriers. The shape of the carrier is not particularly limited, and a rod-shaped carrier or the like can be used, but it is preferable to use a cube-shaped or spherical carrier from the viewpoint of increasing the capture efficiency (adsorption efficiency) of the denitrifying material. Further, it is preferable that such a plurality of carriers are compacted by buoyancy to form a levitation filter medium. When a cube-shaped carrier is used, the length of one side is preferably 5 to 60 mm, more preferably 10 to 30 mm. When the carrier is spherical, the diameter of the carrier is preferably 5 to 60 mm, more preferably 10 to 30 mm.

The floating filter medium having an open cell structure is preferably a foam, and the foam can be molded, for example, by foaming and solidifying an emulsion. Here, the emulsion is a dispersion in which the above-mentioned resin or the like is dispersed in a dispersion medium, and is also called latex. Water or an organic solvent can be used as the dispersion medium for dispersing the above-mentioned resin or the like. Further, as a method of dispersing the resin in the dispersion medium, various known methods can be used. For example, a method of dispersing, emulsifying, and polymerizing a monomer as a raw material of the resin in the dispersion medium can be used. Further, a method of preparing a resin solution, dispersing it in a dispersion medium, and emulsifying it can be used. Emulsions obtained from plants and animals in the natural world can also be used, and examples thereof include natural rubber latex.

As the foam obtained as described above, a commercially available foam can also be used. For example, Y-CUBE manufactured by Yukigaya Kagaku Kogyo Co., Ltd. can be used.

The porosity of the floating filter medium used in the present invention is preferably 90% or more, more preferably 95% or more. Here, the porosity can be obtained by (raw material weight per unit volume − carrier dry weight per unit volume) / (raw material weight per unit volume) × 100.

The specific surface area of the floating filter medium used in the present invention ^{is preferably 1000 m 2} / m ³ or more, and more preferably 2000 m ² / m ³ or more. Furthermore, the specific surface area is preferably from 1000~6000m ² / ^{m 3,} more preferably 2000~5000m ² / ^{m 3.}
The average bubble diameter of the bubble structure of the floating filter medium is preferably 100 to 2000 μm, more preferably 500 to 1000 μm.

The tensile strength (MPa) of the levitation filter medium is preferably 0.05 to 10 MPa, more preferably 0.10 to 8 MPa. The tensile elongation (%) of the floating filter medium is preferably 120 to 800%, more preferably 150 to 500%. As described above, the floating filter medium used in the present invention preferably has excellent strength and excellent durability. Therefore, the floating filter medium can be used repeatedly, and when cleaning the floating filter medium, it is not necessary to wash the floating filter medium in the reactor, and the floating filter medium can be washed by hand washing or by applying a load by a washing machine or the like.

The floating filter medium may be filled without a gap between the denitrifying material and the outlet of the reactor, or may be filled so as to create a distance between the denitrifying material and at least one of the outlets of the reactor. The floating filter medium is preferably filled so as to form a distance from the denitrifying material. In the present invention, the filling rate of the floating filter medium to the reactor is preferably 1 to 30% by volume. From the viewpoint of facilitating the outflow of the denitrifying material suspended by the upward flow inside the reactor and the generated nitrogen gas, the filling rate of the floating filter medium to the reactor is preferably 1% by volume or more, preferably 3% by volume or more. It is more preferable that there is, and it is particularly preferable that it is 5% by volume or more. From the viewpoint of facilitating denitrification material trapped in the levitation filter medium by flocculating it on the levitation filter medium and settling the levitation filter medium together with the levitation filter medium, the filling rate of the levitation filter medium to the reactor is 30% by volume or less. It is preferably 20% by volume or less, and particularly preferably 15% by volume or less.

The reactor preferably does not have a degassing pipe underneath the levitation filter medium. That is, it is preferable to discharge the nitrogen gas to the outside of the reactor from above the floating filter medium. Further, for example, it is preferable that the entire amount of nitrogen gas generated in the denitrification material inside the reactor is passed through the floating filter medium layer formed by the floating filter medium, and the nitrogen gas is discharged to the outside of the reactor from above the floating filter medium. ..

The outlet of the reactor for discharging the treated water is preferably provided in the upper part of the reactor, and more preferably provided in the upper part (downstream) of the floating filter medium. For example, it is preferable that the height of the outlet of the reactor coincides with the surface of the treated water inside the reactor.
From the viewpoint of preventing the floating filter medium from being mixed into the water tank, the reactor may be provided with a partition wall having a size such that the floating filter medium does not flow out at the outlet of the reactor. Any perforated plate or screen can be used as the partition wall. The partition wall may have a structure in which drainage flows but the floating filter medium does not pass through, and examples thereof include a punching screen, a wire mesh, and a honeycomb material. The diameter of each structure can be appropriately selected in consideration of the size of the floating filter medium to be used. The partition wall is preferably made of metal or resin, and is preferably made of a material such as vinyl chloride or stainless steel.

<Circulation flow path>
The denitrification treatment apparatus of the present invention preferably 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 is arranged upstream of the reactor to solid-liquid separate wastewater (circulating water, etc.), and / or is arranged downstream of the reactor to solid-liquid the treated water. It is preferable to have a downstream solid-liquid separation unit for separation.
By providing the upstream solid-liquid separation unit, solid matter contained in wastewater such as circulating water from the water tank can be removed, and wastewater with less 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. In a preferred embodiment of the denitrification treatment apparatus of the present invention, it is preferable that the flow rate of the pump is controlled by the control unit so that the turbidity of the treated water falls within a predetermined threshold range. In particular, when the denitrification treatment device does not have a branch flow path, the flow rate of the pump is preferably controlled by the control unit so that the turbidity of the treated water falls within a predetermined threshold range.

<Turbidity measurement unit>
In a preferred embodiment of the denitrification treatment apparatus of the present invention, it is preferable to have a turbidity measuring unit inside or downstream of the reactor. It is more preferable to have a turbidity measuring unit downstream of the reactor from the viewpoint of early detection of abnormalities in the denitrification treatment device.
In the present invention, it is preferable that the turbidity of the treated water is always in the range of 200 degrees or less. By checking the turbidity of the treated water, the amount of denitrifying material mixed in the water tank can be confirmed. When the turbidity of the treated water is 200 degrees or less, it becomes easy to remove fine denitrifying materials by the action of the floating filter medium.
The upper limit of the turbidity of the treated water is more preferably 150 degrees or less, and particularly preferably 100 degrees or less.

<Branch flow path>
In a preferred embodiment of the denitrification treatment apparatus of the present invention, it is preferable to have a branch flow path capable of bypassing the treated water to the upstream of the downstream solid-liquid separation portion. The treated water treated in the reactor is solid-liquid separated by passing through the branch flow path and the downstream solid-liquid separation part, and after the concentration of the denitrification material is lowered, it is returned to the water tank as solid-liquid separation water. Alternatively, it is preferable to introduce the circulating water into the reactor again.

<Control unit>
The denitrification treatment apparatus of the present invention preferably has a control unit that controls the flow rate and / or switching to the branch flow path of the pump.
When the turbidity of the treated water exceeds a predetermined threshold, it is preferable to reduce the flow rate of the pump or stop the pump to control the amount of wastewater flowing into the reactor.
Alternatively, when the turbidity of the treated water exceeds a predetermined threshold value, it is preferable to control the switching to the branch flow path so that the treated water is bypassed upstream of the downstream solid-liquid separation section. The control unit preferably controls the opening and closing of the valve and the branch valve. For example, the control unit controls the branch valve to be opened when the turbidity of the treated water treated in the reactor exceeds a predetermined threshold value, and the treated water is sent to the upstream of the downstream solid-liquid separation unit. It is preferable to bypass it. In this case, it is preferable that the control unit further controls the valve arranged in the circulation flow path so as to be closed.

<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. There is no particular limitation on the method of filling the floating filter medium downstream of the denitrification material inside the reactor.

<Breeding method>
Using the denitrification treatment apparatus of the present invention, aquatic organisms can be bred in an aquarium while treating nitrate nitrogen in wastewater (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, for denitrification materials placed in a container different from the water tank of the denitrification treatment device, although it depends on the water quality of wastewater (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 wastewater, 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. 4 was prepared. That is, a water tank capable of storing wastewater used as circulating water, a filtration membrane (which also serves as an upstream solid-liquid separator and a downstream solid-liquid separator), a pump, a reactor containing a denitrifying material and a floating filter medium, and turbidity. The denitrification treatment apparatus of Example 1 having a degree measuring unit, a circulation flow path for returning the treated water treated by the reactor to the water tank, a branch flow path, and a control unit for controlling the opening and closing of the valve and the branch valve. Got ready.
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 a floating filter medium is filled on the upper side (downstream side) of the denitrification material layer with a filling rate of 10. It was filled so as to be% by volume. As the levitation filter medium, a foamed PVA (polyvinyl alcohol) 10 mm square (cube-shaped) resin porous body having a bubble structure manufactured by Yukigaya Kagaku Kogyo Co., Ltd. was used. With this configuration, the circulating water is used as an upward flow to pass through the support layer, the denitrification material layer, and the floating filter medium in this order.

<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. When the turbidity of the treated water exceeds 100 degrees by the control unit, the valve 63 is closed, the branch valve 64 is opened, and the perimmembrane (upstream solid-liquid separation unit and downstream solidification) is passed through the branch flow path. It was controlled to bypass the treated water to the upstream of (which also serves as a liquid separation part).
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 floating filter medium The floating filter medium was removed from the denitrification treatment device of Example 1 to obtain the denitrification treatment device of Comparative Example 1.
Aquatic organisms were bred in the same manner as in Example 1 except that the denitrification treatment apparatus of Comparative Example 1 was used.

[Evaluation]
The turbidity of the treated water treated in the reactor was measured by the turbidity measuring unit. The results obtained are shown in Table 1 below. The turbidity of the treated water was measured according to JIS K 0801 "Turbidity automatic measuring instrument".

From the above, it was found that the denitrification treatment apparatus of the present invention can reduce the turbidity of the treated water without mixing the denitrification material into the water tank. It was also found that the denitrification activity could be maintained high without the air bubbles covering the surface of the denitrification material.
On the other hand, in Comparative Example 1 in which the floating filter medium was not used, it was found that the denitrifying material flowing out from the reactor was mixed in the water tank and the turbidity of the treated water became high.

[Comparative Example 2]: No gas removing part The denitrifying treatment device of Comparative Example 2 was used by removing the gas removing part from the denitrifying treatment device of Example 1.
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 Examples and each Comparative Example, 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 Denitrifying material 11 Water tank 12 Circulating water 21 Reactor 22 Denitrifying material layer 23 Support layer 24 Gas removing part 25 Floating filter medium 31 Circulation flow path 32 Branch flow path 41 Upstream side solid-liquid separation part 42 Solid Liquid separation water 51 Downstream solid-liquid separation unit 61 Turbidity measurement unit 62 Control unit 63 Valve 64 Branch valve p Pump

Claims (9)

A denitrification treatment device that allows wastewater to pass upward through a reactor containing denitrification materials.
The denitrification material contains sulfur and carbonate and contains
A floating filter medium is filled inside the reactor and downstream of the denitrification material.
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 floating filter medium is a resin-made porous body having a bubble structure. Using the wastewater as circulating water,
A water tank that can store the circulating water and
The denitrification treatment apparatus according to claim 1 or 2, further comprising a circulation flow path for returning the treated water treated in the reactor to the water tank. The denitrification treatment apparatus according to claim 3, further comprising an upstream solid-liquid separation unit that is arranged upstream of the reactor and solid-liquid separates the circulating water. It has a pump between the water tank and the reactor
It has a turbidity measuring unit inside or downstream of the reactor.
Has a control unit
The denitrification treatment device according to claim 3 or 4, wherein the control unit controls to reduce the flow rate of the pump when the turbidity of the treated water exceeds a predetermined threshold value. It has a turbidity measuring unit inside or downstream of the reactor.
It has a downstream solid-liquid separation section that is arranged downstream of the reactor and solid-liquid separates the treated water.
It has a branch flow path that allows the treated water to be bypassed upstream of the downstream solid-liquid separation section.
Has a control unit
The denitrification treatment apparatus according to claim 3 or 4, wherein the control unit bypasses the treated water to the upstream of the downstream solid-liquid separation unit when the turbidity of the treated water exceeds a predetermined threshold value. It has an upstream solid-liquid separator located upstream of the reactor and solid-liquid separates the circulating water.
The denitrification treatment apparatus according to claim 6, 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 7, wherein the carbonate has a particle size of less than 5 mm. The denitrification treatment apparatus according to any one of claims 1 to 8, wherein the filling rate of the floating filter medium with respect to the reactor is 1 to 30% by volume.

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