JPWO2020122168A1 - Aquaculture equipment, purification equipment, purification methods and moldings - Google Patents

Abstract

An object of the present invention is to provide a method for efficiently removing the ammonia produced in an apparatus for culturing aquatic organisms. An aquaculture device for cultivating aquatic organisms, which comprises a culturing tank for cultivating aquatic organisms and a septic tank for purifying water used for cultivating aquatic organisms. A body, for example, a wire rod made of a thermoplastic resin is bent and entangled, and the wire rods are fused to each other at a contact portion where the wire rods come into contact with each other. It may contain the above-mentioned structural units derived from dicarboxylic acid, and may contain, for example, biodegradability.

Description

The present invention relates to an aquatic animal aquaculture apparatus used for aquatic animal aquaculture. Further, the present invention relates to a purification device and a purification method for purifying water used for aquaculture of aquatic organisms, and further to a molded body such as a three-dimensional network molded body that can be suitably used for these devices or methods.

When culturing fish, etc., in order to prevent the excrement from the cultivated fish and the nitrogen content generated from the rest of the food as ammonia, which harms the cultivated fish, etc. It was necessary to replace the water in the aquaculture tanks, etc. in a short period of time by taking in fresh water from rivers and the like.
However, it is premised that a large amount of water is used for water replacement, and it is difficult to replace a large amount of water, for example, when culturing in an inland area where there is no sea or river nearby. In addition, replacement of water means that a large amount of wastewater is generated, and it is not preferable to flush all the nitrogen generated during aquaculture as wastewater to rivers and the sea from the viewpoint of eutrophication of rivers and the like. In addition, wastewater standards are becoming stricter in recent years from the viewpoint of environmental protection.

In order to solve this problem, ammonia generated from fish and the like is removed from wastewater by using a two-step reaction using microorganisms. That is, it is a method using a reaction of converting ammonia into nitric acid and a reaction of decomposing nitric acid into nitrogen. If it is decomposed to nitrogen, it can be discharged into the air without burdening the environment.
Reactions using this organism, especially the reaction of reducing nitric acid in the latter stage to nitrogen (N ₂ ), were carried out using denitrifying bacteria, which are facultative anaerobic bacteria.

In the reaction using the above microorganisms, in the reaction of converting ammonia to nitric acid in the first stage, bacteria that naturally settle on a calcium-based base material such as shells that are discarded as they are are often used. On the other hand, in the second stage denitrification reaction of converting nitric acid to nitrogen, a polymer such as cellulose is often used as a base material, and denitrifying bacteria that settle there are often used.

The principle that cellulose or the like is used as a base material in the second stage reaction is that "biodegradable polymers such as natural polymers and biodegradable synthetic resins are used for the growth and proliferation of dependent (organic) vegetative bacteria. It serves as a substrate or a hydrogen donor, and uses oxygen in nitrogen oxides for breathing in the presence of nitrite, which is a nitrogen oxide, and nitrogen oxides in the presence of extremely low dissolved oxygen in water, and reduces and removes nitrogen oxides. Denitrifying bacteria, which are sexually anaerobic microorganisms, swarm and land on biodegradable polymers "(see Patent Document 1).
Further, a technique in which a biodegradable resin is exemplified as a base material that can be used in a denitrification reaction in addition to cellulose is disclosed (see Patent Documents 2 and 3).

Japanese Unexamined Patent Publication No. 10-85782 Japanese Unexamined Patent Publication No. 2014-24000 Japanese Unexamined Patent Publication No. 2010-88307

In Patent Documents 2 and 3, a biodegradable resin is used as a base material for carrying denitrifying bacteria. However, in an apparatus for culturing aquatic organisms, what shape should the base material carrying denitrifying bacteria have? Has not been examined as to whether it is preferable.
The present invention provides a method for efficiently removing the ammonia produced in an apparatus for culturing aquatic organisms.

The present inventors have proceeded with research to solve the above problems, and as a base material for carrying denitrifying bacteria, a molded product having communication holes and made of a specific thermoplastic resin, or a three-dimensional network molded product made of a wire rod. Therefore, they have found that the above problems can be solved by using a molded body having a structure in which wire rods are fused to each other, and have reached the present invention. The present invention includes:

(1) An aquatic aquaculture apparatus including a aquaculture tank for cultivating aquatic organisms and a septic tank for purifying water used for aquatic organisms.
The septic tank is made of a thermoplastic resin and includes a molded body having communication holes.
The molded product is an aquatic organism culture apparatus containing 50% by mass or more of a dicarboxylic acid-derived structural unit in the total thermoplastic resin constituting the molded product.
(2) The aquaculture apparatus according to (1), wherein the molded body is a molded body in which the wires are adhered to each other at a contact portion where the wires are in contact with each other.
(3) An aquaculture device for cultivating aquatic organisms, which comprises a culturing tank for cultivating aquatic organisms and a septic tank for purifying water used for culturing aquatic organisms.
The septic tank includes a three-dimensional mesh-like molded body in which wire rods made of a thermoplastic resin are bent and entangled, and the wire rods are fused to each other at a contact portion where the wires are in contact with each other. An aquatic organism culture device in which the wire rod forming the body contains a biodegradable resin.
(4) The aquaculture apparatus according to (3), wherein the biodegradable resin is a biodegradable resin containing a structural unit derived from a dicarboxylic acid.
(5) The aquaculture apparatus according to any one of (1) to (4), wherein the molded product or the three-dimensional network-shaped molded product has a filling rate of 7.5% by volume or more and 30% by volume or less.
(6) A purification device that purifies water used for aquatic aquaculture.
It is equipped with an oxidizing means that converts ammonia into nitric acid and a denitrifying means that denitrifies nitric acid.
The denitrification means is a denitrifying bacterium carrier in which a denitrifying bacterium is carried on a molded body made of a thermoplastic resin and having communication holes, and the molded body is a dicarboxylic acid in the total thermoplastic resin constituting the molded body. A purification device containing 50% by mass or more of the derived building blocks.
(7) The purifying apparatus according to (6), wherein the molded body is a molded body in which the wires are adhered to each other at a contact portion where the wires are in contact with each other.
(8) A purification device that purifies water used for aquatic aquaculture.
It is equipped with an oxidizing means that converts ammonia into nitric acid and a denitrifying means that denitrifies nitric acid.
The denitrification means carries denitrifying bacteria on a three-dimensional network-like molded body in which wires made of a thermoplastic resin are bent and entangled, and the wires are fused to each other at a contact portion where the wires are in contact with each other. A purification device which is a denitrified bacterium carrier and the wire rod contains a biodegradable resin.
(9) The purification apparatus according to (8), wherein the biodegradable resin is a biodegradable resin containing a structural unit derived from a dicarboxylic acid.
(10) The purifying apparatus according to any one of (6) to (9), wherein the molded product or the three-dimensional network-shaped molded product has a filling rate of 7.5% by volume or more and 30% by volume or less.
(11) A purification method that purifies water used for aquaculture.
It includes a step of oxidizing ammonia contained in water to nitric acid and then reducing it to nitrogen by denitrifying nitric acid.
The denitrification of nitrate is carried out by denitrifying bacteria carried on a molded body made of a thermoplastic resin and having communication holes, and the molded body is composed of a dicarboxylic acid in the total thermoplastic resin constituting the molded body. A purification method containing 50% by mass or more of units.
(12) The purification method according to (11), wherein the molded body is a molded body in which the wires are adhered to each other at a contact portion where the wires are in contact with each other.
(13) A purification method that purifies water used for aquatic aquaculture.
It includes a step of oxidizing ammonia contained in water to nitric acid and then reducing it to nitrogen by denitrifying nitric acid.
The denitrification of nitric acid was carried on a three-dimensional network molded body in which the wires made of a thermoplastic resin were bent and entangled, and the wires were fused to each other at a contact portion where the wires were in contact with each other. A purification method performed by denitrifying bacteria, wherein the wire contains a biodegradable resin.
(14) The purification method according to (13), wherein the biodegradable resin is a biodegradable resin containing a structural unit derived from a dicarboxylic acid.
(15) The purification method according to any one of (11) to (14), wherein the molded product or the three-dimensional network-shaped molded product has a filling rate of 7.5% by volume or more and 30% by volume or less.
(16) A molded product made of a thermoplastic resin and having communication holes, wherein the molded product contains 50% by mass or more of a dicarboxylic acid-derived structural unit in the total thermoplastic resin constituting the molded product. ..
(17) The molded body according to (16), wherein the molded body is a molded body in which the wires are adhered to each other at a contact portion where the wires are in contact with each other.
(18) A three-dimensional mesh-like molded body in which wire rods made of a thermoplastic resin are bent and entangled, and the wire rods are fused to each other at a contact portion where the wire rods come into contact with each other, and the wire rods are biodegraded. A molded product containing a sex resin.
(19) The molded product according to (18), wherein the biodegradable resin is a biodegradable resin containing a structural unit derived from a dicarboxylic acid.
(20) The molded product according to any one of (16) to (19), wherein the molded product or the three-dimensional network-shaped molded product has a filling rate of 7.5% by volume or more and 30% by volume or less.

It is a schematic diagram which shows one form of an aquaculture aquaculture apparatus. It is a schematic diagram which shows another form of an aquaculture apparatus. It is a schematic diagram which shows another form of an aquaculture apparatus. It is a schematic diagram of the three-dimensional mesh-like molded body used in Example 1. It is a schematic diagram of the experimental apparatus used in Example 1. It is a graph which shows the result of having measured the water quality in Example 1. FIG.

Hereinafter, the present invention will be described in detail, but the description of the constituent elements described below is an example (representative example) of the embodiment of the present invention, and the present invention is not limited to these contents. It can be implemented with various modifications within the scope of the abstract.

One embodiment of the present invention is an aquaculture aquaculture apparatus for cultivating aquatic organisms, and includes a culturing tank for culturing aquatic organisms and a septic tank for purifying water used for culturing aquatic organisms. The septic tank is provided with a three-dimensional mesh-like molded body in which wire rods made of a thermoplastic resin are bent and entangled, and the wire rods are fused to each other at a contact portion where the wire rods come into contact with each other. The wire rod forming the body contains a biodegradable resin.
Further, in another embodiment of the present invention, the septic tank is provided with a molded body having communication holes made of a thermoplastic resin, and the molded body is configured to be derived from a dicarboxylic acid in the total thermoplastic resin constituting the molded body. Contains 50% by mass or more of units.
A specific configuration example of the aquaculture apparatus is shown in FIG.

FIG. 1 is a schematic view showing the configuration of the aquaculture apparatus 10. The aquaculture apparatus 10 includes a breeding tank 11, a pump 12, and a septic tank 13. The septic tank 13 includes a shell 14 which is an oxidizing means for oxidizing ammonia contained in water to nitric acid, and a three-dimensional network molded body 15 made of a biodegradable resin which reduces nitric acid to nitrogen by denitrifying it.

The breeding tank 11 is a water tank for cultivating aquatic organisms. The size and shape of the breeding tank 11 can be appropriately set according to the type and number of aquatic organisms to be cultivated, and the breeding tank 11 does not necessarily have to be a water tank as long as aquatic organisms can be cultivated.
The aquaculture organisms to be cultivated may be any organisms that live in water, and typically include, but are not limited to, freshwater fish such as salmon, trout, sweetfish, and char, and crustaceans such as crabs and shrimp. Freshwater or seawater is typically used for aquaculture. When seawater is used, its salinity is not limited.

The oxygen concentration (DO) in the water of the breeding tank 11 is 5 mg / L or more, preferably 6 mg / L or more, more preferably 7 mg / L or more, still more preferably 8 mg / L or more, and particularly preferably. Is 9 mg / L or more, and most preferably 10 mg / L or more. If the oxygen concentration (DO) in the water is higher than the lower limit, the environment is suitable for the habitat of aquatic organisms.
The concentration of ammonia nitrogen in the water of the breeding tank 11 is 10 mg / L or less, more preferably 8 mg / L or less, still more preferably 6 mg / L or less, and particularly preferably 4 mg / L or less. If the concentration of ammonia nitrogen is higher than the upper limit, it will have a fatal effect on aquatic organisms. If the ammonia nitrogen concentration is below the upper limit, the environment is suitable for aquatic organisms to live in.

The pump 12 is a means for transferring the water in the breeding tank 11 to the septic tank 13. As long as the water in the breeding tank 11 can be transferred to the septic tank 13, the transfer means is not limited to the pump, and may be replaced by other transfer means. The transfer rate of water by the pump 12 is not particularly limited, but it is preferable to have a certain transfer rate because it becomes difficult to supply oxygen to bacteria by slowing the transfer rate. The water in the breeding tank 11 may circulate once a day, and more than twice a day, for example, once every 12 hours, once every 10 hours, once every 6 hours, once every 4 hours. The water in the breeding tank 11 may circulate once every two hours, once every hour, once every 30 minutes, and once every 10 minutes.

The septic tank 13 includes a shell 14 which is an oxidizing means for oxidizing ammonia contained in water to nitric acid, and a three-dimensional network molded body 15 of PBSA resin which reduces nitric acid to nitrogen by denitrifying it.
The shell 14 is a base material for growing bacteria for converting ammonia in water transferred from the breeding tank 11 into nitric acid. As the bacteria for converting ammonia into nitric acid, already known bacteria having the above-mentioned function can be appropriately used. The shell 14 is an oxidizing means for oxidizing ammonia contained in water to nitric acid, and can be replaced with another substance as long as it has a similar oxidizing function. For example, various oxidizing agents may be added. The base material that carries the bacteria for converting ammonia to nitric acid may be a base material containing an alkaline earth metal such as a calcium-based base material, and more specifically, from the viewpoint of utilization and utilization of waste. Therefore, shells, coral sand, sea urchin shells, etc. may be used.
As an oxidizing means for oxidizing ammonia to nitric acid, it is said to be a pellet-type, ring-type, sponge-type, fiber-type, moor-type, or net-type so-called microbial carrier or nitrification carrier based on polyethylene, polypropylene, etc. in addition to shells. You may use the carrier to be used. A so-called immobilized carrier in which microorganisms are pre-sealed in a carrier made of polyethylene glycol may be used.
It may be a so-called fluidized bed in which shells and carriers flow in a septic tank, or it may be a so-called fixed bed in which shells and carriers are fixed.

The shell 14 may be arranged in the septic tank 13 as it is, may be arranged after coarse pulverization, or may be arranged after fine pulverization.
When ammonia is converted to nitric acid, the pH of the water in the septic tank 13 is lowered by the nitric acid. By using a base material containing an alkaline earth metal as a base material for growing bacteria for converting ammonia into nitric acid, it is possible to adjust the pH and promote the growth of nitrifying bacteria.

The three-dimensional network-shaped molded body 15 is an example of a molded body having communication holes, and the communication holes are spaces through which a fluid can flow. As a molded body having communication holes, for example, a mesh-shaped molded body in which linear resin is bent and entangled, a molded body in which pellets are fused to form a space inside, and a linear resin are knitted. Examples include a molded product, a molded product using a non-woven fabric, and a molded product in which a space is formed by foaming a resin. Bacteria for converting nitric acid into nitrogen grow in the communication holes.
The three-dimensional network-like molded body 15, which is an example of a molded body having communication holes, is a base material for growing bacteria for reducing nitric acid to nitrogen by denitrifying nitric acid, and may contain a biodegradable resin. .. As the bacteria for converting nitric acid to nitrogen, already known bacteria having the above-mentioned function can be appropriately used.
As the biodegradable resin, PLA (polylactic acid) type, PBS (polybutylene succinate) type, PCL (poly caprolactone) type, and PHB (poly hydroxybutyrate) type are generally known. In the present embodiment, it is preferable to use a synthetic biodegradable resin containing a structural unit derived from a dicarboxylic acid as the biodegradable resin. Such a synthetic biodegradable resin may contain a constituent unit derived from a diol.

As the type of biodegradable resin, polyester is preferable. Examples of the dicarboxylic acid include succinic acid, adipic acid, oxalic acid, malonic acid, glutaric acid, suberic acid, azelaic acid, sebacic acid, terephthalic acid, isophthalic acid, and phthalic acid. A biodegradable resin containing two or more dicarboxylic acid-derived constituent units is preferable. The denitrification rate is faster and the denitrification performance tends to be higher than when a biodegradable resin containing one type of dicarboxylic acid-derived constituent unit is used. Of these, it is preferable to include a structural unit derived from succinic acid, that is, a PBS-based biodegradable resin having a butylene succinate unit as a main repeating unit is preferable. Specific preferred examples of the PBS-based biodegradable resin include polybutylene succinate, poly (butylene succinate / adipate) (PBSA), and poly (butylene succinate / carbonate). In particular, poly (butylene succinate / adipate) (PBSA) is preferable because it has high biodegradability and can supply a carbon source necessary for denitrification in a sustained-release manner. Further, PBSA is more easily decomposed than other biodegradable resins such as PLA, and is therefore preferable as a substrate or a hydrogen donor for the growth and growth of denitrifying bacteria.

In the environment in which the aquatic organism aquaculture apparatus 10 is operated, the concentration of nitric acid in water is lower than that of general wastewater treatment. Therefore, a small amount of organic matter is required for denitrification, and the elution of excess organic matter is dissolved oxygen. Can lead to a decrease in oxygen. Therefore, in the three-dimensional network molded body 15, the proportion of the dicarboxylic acid-derived structural unit in the total thermoplastic resin constituting the molded body is preferably 50% by mass or more, and more preferably 70% by mass or more. More preferably, it is more preferably 80% by mass or more, particularly preferably 90% by mass or more, and most preferably 95% by mass or more. Further, in the three-dimensional network molded body 15, the proportion of the constituent units derived from dicarboxylic acid in the total thermoplastic resin constituting the molded body is high, so that the elution of excess organic substances is suppressed, which is excessively reducing. Since it is possible to prevent the atmosphere from becoming unpleasant, it is possible to suppress the generation of hydrogen sulfide which may adversely affect the growth of aquatic organisms, which is preferable.
In addition, by suppressing the elution of excess organic matter, it is possible to prevent a decrease in the dissolved oxygen concentration and the growth of various germs in the fish tank.
The dicarboxylic acid-derived structural unit in the total thermoplastic resin constituting the molded product can be measured by a Fourier transform nuclear magnetic resonance apparatus (FT-NMR).

The biodegradable resin contained in the three-dimensional network molded body 15 may be mixed with other resins such as polylactic acid, PHB, PHV, and PCL. By mixing a biodegradable resin containing a structural unit derived from a dicarboxylic acid and these resins having different biodegradability, the period for which the three-dimensional network molded body 15 is used as a carbon source can be adjusted. The three-dimensional network molded body 15 may contain components other than the resin such as calcium carbonate and calcium stearate. When these components are 40% by mass or less with respect to the synthetic biodegradable resin, the surface area of the polymer is increased by the fine powder caused by these components falling off from the molded product, and denitrification is efficiently performed. be able to.

The three-dimensional mesh-like molded body 15 is a three-dimensional network-shaped molded body in which wire rods made of a thermoplastic resin are bent and entangled, and the wire rods are fused to each other at a contact portion where the wire rods come into contact with each other. The method for producing the three-dimensional network molded body used in the present embodiment is not particularly limited, and may be molded by injection molding or extrusion molding, and examples thereof include the following methods. That is, when a molten biodegradable resin (thermoplastic resin) such as PBSA is extruded from an extruder die as a plurality of wire rods, a bending force acts on the extruded wire rod to bend it in a loop shape. Then, the multiple wires that bend in a loop are entangled and heat-bonded at the part where the wires come into contact with each other. It is possible to obtain a three-dimensional mesh-like molded body in which wire rods are randomly entangled.

In the three-dimensional mesh-like molded body 15 in which the wires are fused at the contact portions, the resin is decomposed due to the presence of a plurality of fused portions in the molded body even when the biodegradable resin is decomposed. It is possible to suppress the generation of resin debris generated by the above. When the resin is decomposed to generate resin fragments, there is a risk that the aquatic organisms accidentally swallow the resin fragments in the aquaculture apparatus. The risk of accidental ingestion can be suppressed.

The shape of the three-dimensional mesh-shaped molded body 15 is not particularly limited, and may be spherical, cylindrical, plate-shaped (matte), columnar, prismatic, or the like. It may be irregular or irregular. From the viewpoint of filling efficiency, a shape having a hollow portion such as a cylindrical structure is not preferable.

The thickness of the wire can be adjusted by adjusting the diameter of the hole in the die of the extruder that allows the molten biodegradable resin to pass through. The filling rate of the three-dimensional mesh-like molded body 15 can be adjusted by setting. The thickness of the wire can be appropriately set depending on the filling rate of the desired three-dimensional mesh-like molded body. For example, the diameter may be 0.5 mm or more, 1 mm or more, 10 mm or less, and 5 mm or less. May be.

In the present embodiment, the filling ratio (volume%) represented by the actual volume × 100 with respect to the apparent volume of the three-dimensional network molded body 15 is usually 7.5% or more, preferably 8% or more. It is more preferably 9% or more, further preferably 10% or more, and particularly preferably 12.5% or more. The upper limit is usually 30% or less, preferably 27.5% or less, more preferably 25% or less, and even more preferably 22.5% or less. Alternatively, it may be expressed as a porosity (%) obtained by subtracting the filling rate (%) from 100%. In the case of the porosity, it is usually 92.5% or less, preferably 92% or less, more preferably 91% or less, further preferably 90% or less, and 87.5% or less. Is particularly preferred. Further, the lower limit is usually 70% or more, preferably 72.5% or more, more preferably 75% or more, and further preferably 77.5% or more. When the filling rate is at least the lower limit value, the filling volume does not increase when the device is filled with the amount of resin required for denitrification, and as a result, the cost can be reduced by reducing the size of the device. In addition, since the volume of resin to be handled does not need to be large, the workability of replacement and addition is improved. When the filling rate exceeds the upper limit, the water flow resistance becomes high, and there is a possibility that a so-called "water path" that passes through only a part of the flow paths is formed. By setting the filling rate to the upper limit or less, "water path" can be prevented. Further, by setting the filling rate to the upper limit value or less, clogging due to the enlargement of the biofilm can be prevented.
The apparent volume is obtained by cutting the molded product into a shape for which the volume is required, and using that volume as the apparent volume. The volume actually occupied by the resin in the apparent volume is defined as the actual volume.

In the present embodiment, the three-dimensional network molded body 15 is a base material for growing bacteria for reducing nitric acid to nitrogen by denitrifying nitric acid in an aquaculture apparatus. Therefore, the risk of clogging the gaps of the molded product due to the solid content is low as compared with the case of treating general wastewater. Therefore, when the three-dimensional mesh-shaped molded body is used in the present embodiment, the filling rate can be made higher than that when the three-dimensional mesh-shaped molded body is used in the general wastewater treatment.

Generally, in the septic tank 11 in the aquaculture apparatus 10, space saving is often required unlike wastewater treatment. When the three-dimensional mesh-shaped molded body 15 has a plate shape (mat shape), it can be laminated in the thickness direction to form a multi-layered three-dimensional mesh-shaped molded body, and sufficient space can be taken in the length direction. Even if it is not present, sufficient denitrification ability can be provided.

The amount of the three-dimensional mesh-like molded body 15 arranged in the septic tank 13 varies depending not only on the amount of water in the aquatic organism aquaculture apparatus 10 but also on the type, quantity, growth stage, etc. of the fish to be bred, but in the aquatic organism aquaculture apparatus 10. It may be appropriately set from the amount of water, the concentration of nitrogen accumulated in water, and the nitrogen removing ability of the three-dimensional network molded body.
As the denitrification reaction progresses, the three-dimensional network molded body 15 is consumed, and the weight gradually decreases. The denitrification performance can be maintained by replenishing the reduced amount when the mass is approximately halved. Further, even if the mass is not reduced, if the denitrification ability is insufficient, the denitrification performance can be maintained by adding it as appropriate.

In the septic tank 13, the shell 14 as an oxidizing means and the three-dimensional mesh-like molded body 15 as a denitrifying means may be arranged in the same septic tank 13 as shown in FIG. 1, and are arranged in different tanks. You may be. When the shell 14 as the oxidizing means and the three-dimensional network molded body 15 are arranged in the same septic tank 13, they may be separated by a fiber separator, filter paper, or the like.

The aquaculture apparatus 10 in which the shell 14 as an oxidizing means and the three-dimensional network molded body 15 as a denitrifying means are arranged on one flow path has been described above, but these tanks are placed on separate flow paths. It may be arranged. That is, as in the aquaculture apparatus 20 shown in FIG. 2, a flow path through which the shell 24 is subjected to nitrification and a flow path through which the three-dimensional network molded body 25 is passed and denitrification is performed are provided. You may be.

FIG. 2 is a schematic view showing the configuration of the aquaculture apparatus 20. The aquaculture apparatus 20 includes a breeding tank 21, a pump 22, and a septic tank 23. The septic tank 23 includes a shell 24 which is an oxidizing means for oxidizing ammonia contained in water to nitric acid, and a three-dimensional network molded body 25 of PBSA resin which reduces nitric acid to nitrogen by denitrifying it.
In the aquaculture apparatus 20, the shell 24 and the three-dimensional network molded body 25 are arranged in separate septic tanks 23. In the case of such a form, each tank may have a mechanism for allowing water to flow in and out.

In the present embodiment, in order to suppress the generation of hydrogen sulfide, it is preferable to periodically expose the three-dimensional network molded product to the atmosphere to prevent an excessive reduction state. The method for periodically exposing the three-dimensional network-shaped molded product to the atmosphere is not particularly limited, and examples thereof include a watering method, a siphon method, and a periodic liquid draining method. An example of using the siphon method is shown in FIG.

FIG. 3 is a schematic view showing the configuration of the aquaculture apparatus 30. The aquaculture apparatus 30 includes a breeding tank 31, a pump 32, and a septic tank 33. The septic tank 33 includes a shell 34 which is an oxidizing means for oxidizing ammonia contained in water to nitric acid, and a three-dimensional network molded body 35 of PBSA resin which reduces nitric acid to nitrogen by denitrifying it.
In the aquaculture apparatus 30, the shell 34 as an oxidizing means is arranged above and the three-dimensional network molded body 35 is arranged below, but the order may be reversed, or they may be arranged adjacent to each other.

In FIG. 3, the siphon 36 is a transfer means that enables the transfer of water from the septic tank 33 to the breeding tank 31, and is a mechanism that exposes the three-dimensional network molded body 35 to the atmosphere. In the siphon 36, when the water level in the septic tank 33 is higher than the uppermost part of the siphon 36, the water in the septic tank 33 is transferred to the breeding tank 31, and the three-dimensional network molded body 35 is exposed to the atmosphere. When the three-dimensional network molded body 35 is exposed to the atmosphere, the denitrification rate is high and the denitrification performance tends to be high.

As a means for transferring water from the septic tank 33 to the breeding tank 31, instead of using a siphon, water may be transferred from the septic tank 33 to the breeding tank 31 using a pump. Further, the breeding water may be pumped up from the breeding tank 31 and supplied from the upper part of the septic tank 33 by a shower ring to transfer the water. The three-dimensional network molded body 35 may be brought into contact with the atmosphere by supplying air or oxygen into the water of the septic tank 33.

The aquaculture apparatus 10, 20, 30, and the like may be provided with other foam separation apparatus, but it is not necessary to provide the aquaculture apparatus 10, 20, 30, and the like in the present embodiment. The chemical oxygen demand (COD) can be reduced by providing the foam separation device, but in the present embodiment, the COD can be reduced even if the foam separation device is not provided.

Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the scope of the present invention is not limited to the embodiments shown in the following Examples.

<Example 1>
First, a three-dimensional network molded body was prepared. A schematic diagram of the prepared three-dimensional mesh-like molded body is shown in FIG.
The three-dimensional network molded product was processed by using an extrusion molding machine using PBSA (manufactured by Mitsubishi Chemical Corporation, a constituent unit derived from dicarboxylic acid of 50% by mass or more) so as to have a width of 50 cm, a depth of 50 cm, and a thickness of 1.8 cm. At this time, the diameter of the wire was 1.1 mm, the weight of the three-dimensional network molded body was 0.7 kg, and the specific gravity of PBSA was 1.24 g / cm ³ . The surface area per apparent volume (50 cm (width) x 50 cm (depth) x 1.8 cm (thickness)) of the molded body is 0.45 m ² / L, the surface area per weight is 2.9 m ² / kg, and the porosity. Was 87.5% (filling rate 12.5%). The porosity indicates the ratio of the void volume to the apparent volume, and the filling rate indicates the ratio of the actual volume to the apparent volume.

Next, the experimental device schematically shown in FIG. 5 was prepared. The experimental device 50 shown in FIG. 5 has a structure in which a water tank 51 filled with simulated drainage and a column 53 are connected by a tube pump 52.
The resin column 53 having an inner diameter of 20 mm was filled with 17.2 g of a three-dimensional network molded product 55 made of PBSA. The total surface area of the molded product at this time was 0.05 m ² .

The simulated drainage was passed from the bottom of the column 53 at a flow rate of 6.5 mL / min using a tube pump 52, and the overflow water from the top of the column 53 was returned to the water tank 51. The composition of the simulated wastewater is shown in Table 1. The temperature of the simulated drainage was set to room temperature (23 ° C.).

After passing water for 15 days for acclimatization, simulated wastewater was sampled from the inside of the container and water quality analysis was performed. For water quality, total organic carbon amount (TOC), total nitrogen amount (TN) and dissolved oxygen concentration (DO) were measured. Since the simulated wastewater contains only nitrate nitrogen as a nitrogen source, the total nitrogen concentration can be regarded as the nitrate nitrogen concentration.
As a result of water quality measurement, dissolved oxygen and TN decreased as TOC increased. This indicates that the microorganisms attached to the PBSA compact decompose PBSA into monomers / oligomers to increase the TOC, and the TOC consumes dissolved oxygen. As the dissolved oxygen decreased, the nitrate nitrogen in the simulated wastewater was reduced to nitrogen gas by the denitrifying bacteria adhering to the PBSA molded body, so that the TN decreased.

The denitrification rate per unit mass was calculated to be 4.80 g-N / kg / day from the TN reduction rate (denitrification rate) and the amount of PBSA molded body subjected to the test. The denitrification rate per unit surface area was 1.65 g-N / m ² / day. In addition, during the test period, the PBSA molded product was colored pale yellow, and PBSA-degrading bacteria and denitrifying bacteria were attached. Although a phenomenon was observed in which these bacteria were slightly exfoliated, the PBSA molded product was not clogged. The measurement results are shown in FIG.

<Comparative example 1>
The test under the same conditions as in Example 1 was carried out except that PBSA resin pellets having no communication holes were used instead of the three-dimensional network molded body. A resin column having an inner diameter of 20 mm was filled with 20 g of PBSA pellets. The total surface area of the pellets at this time is 0.05 m ² . The shape of the PBSA resin pellet is a thin elliptical disk with a major axis of 5 mm, a minor axis of 3 mm, and a thickness of 1.2 mm. The apparent surface area of the resin pellet is 2.1 m ² / L, and the surface area per weight is 2.7 m. ^{It was 2} / kg, and the porosity was 34% (filling rate 66%).

When the same test as in Example 1 was carried out, it was confirmed that DO and TN decreased as TOC increased.
From the TN reduction rate (denitrification rate) and the amount of PBSA pellets used in the test, the denitrification rate per unit mass was calculated to be 1.55 g-N / kg / day. The denitrification rate per unit surface area was 0.59 g-N / m ² / day. In addition, it was confirmed that the microorganisms attached to the PBSA pellets were enlarged and blocked a part of the gap between the pellets.

Table 2 shows the results of Examples and Comparative Examples.
The mesh-like molded body had higher denitrification rates per unit mass and denitrification rate per unit surface area than the pellets. Generally, in the method of adhering microorganisms to the surface of a carrier to form a so-called biofilm and treating it as in this method, it is considered that the surface area of the biofilm is proportional to the processing capacity. Therefore, if the materials and drainage conditions are the same, the denitrification rate per unit surface area is considered to be the same value, but in this example and the comparative example, the denitrification rate per unit surface area is higher in the mesh-like molded body. It was a high number. It can be said that one of the reasons for this is that the entire surface of the pellet was not effectively utilized because the enlarged microorganisms blocked a part of the pellet gap in the pellet.

Although the present invention will be described in detail with reference to specific examples, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. Is.

10, 20, 30 Aquaculture equipment 11, 21, 31 Breeding tanks 12, 22, 32, 52 Pumps 13, 23, 33 Septic tanks 14, 24, 34 Shells 15, 25, 35 Three-dimensional network molded body 50 Experimental equipment 51 Water tank 52 Tube pump 53 Column 55 PBSA resin three-dimensional network molded body

Claims (20)

It is an aquatic organism aquaculture device equipped with a culture tank for cultivating aquatic organisms and a septic tank for purifying water used for cultivating aquatic organisms.
The septic tank is made of a thermoplastic resin and includes a molded body having communication holes.
The molded product is an aquatic organism culture apparatus containing 50% by mass or more of a dicarboxylic acid-derived structural unit in the total thermoplastic resin constituting the molded product. The aquaculture apparatus according to claim 1, wherein the molded body is a molded body in which the wires are adhered to each other at a contact portion where the wires are in contact with each other. An aquaculture device for cultivating aquatic organisms, which is provided with a culturing tank for cultivating aquatic organisms and a septic tank for purifying water used for cultivating aquatic organisms.
The septic tank includes a three-dimensional mesh-like molded body in which wire rods made of a thermoplastic resin are bent and entangled, and the wire rods are fused to each other at a contact portion where the wires are in contact with each other. An aquatic organism culture device in which the wire rod forming the body contains a biodegradable resin. The aquatic organism culture apparatus according to claim 3, wherein the biodegradable resin is a biodegradable resin containing a structural unit derived from a dicarboxylic acid. The aquaculture apparatus according to any one of claims 1 to 4, wherein the molded product or the three-dimensional network-shaped molded product has a filling rate of 7.5% by volume or more and 30% by volume or less. A purification device that purifies water used for aquatic aquaculture.
It is equipped with an oxidizing means that converts ammonia into nitric acid and a denitrifying means that denitrifies nitric acid.
The denitrification means is a denitrifying bacterium carrier in which a denitrifying bacterium is carried on a molded body made of a thermoplastic resin and having communication holes, and the molded body is a dicarboxylic acid in the total thermoplastic resin constituting the molded body. A purification device containing 50% by mass or more of the derived building blocks. The purifying apparatus according to claim 6, wherein the molded body is a molded body in which the wires are adhered to each other at a contact portion where the wires are in contact with each other. A purification device that purifies water used for aquatic aquaculture.
It is equipped with an oxidizing means that converts ammonia into nitric acid and a denitrifying means that denitrifies nitric acid.
The denitrification means carries denitrifying bacteria on a three-dimensional network-like molded body in which wires made of a thermoplastic resin are bent and entangled, and the wires are fused to each other at a contact portion where the wires are in contact with each other. A purification device which is a denitrified bacterium carrier and the wire rod contains a biodegradable resin. The purification apparatus according to claim 8, wherein the biodegradable resin is a biodegradable resin containing a structural unit derived from a dicarboxylic acid. The purifying device according to any one of claims 6 to 9, wherein the molded body or the three-dimensional network-shaped molded body has a filling rate of 7.5% by volume or more and 30% by volume or less. It is a purification method that purifies the water used for aquatic aquaculture.
It includes a step of oxidizing ammonia contained in water to nitric acid and then reducing it to nitrogen by denitrifying nitric acid.
The denitrification of nitrate is carried out by denitrifying bacteria carried on a molded body made of a thermoplastic resin and having communication holes, and the molded body is composed of a dicarboxylic acid in the total thermoplastic resin constituting the molded body. A purification method containing 50% by mass or more of units. The purification method according to claim 11, wherein the molded body is a molded body in which the wires are adhered to each other at a contact portion where the wires are in contact with each other. It is a purification method that purifies the water used for aquatic aquaculture.
It includes a step of oxidizing ammonia contained in water to nitric acid and then reducing it to nitrogen by denitrifying nitric acid.
The denitrification of nitric acid was carried out on a three-dimensional network molded body in which the wires made of a thermoplastic resin were bent and entangled, and the wires were fused to each other at a contact portion where the wires were in contact with each other. A purification method performed by denitrifying bacteria, wherein the wire contains a biodegradable resin. The purification method according to claim 13, wherein the biodegradable resin is a biodegradable resin containing a structural unit derived from a dicarboxylic acid. The purification method according to any one of claims 11 to 14, wherein the molded product or the three-dimensional network-shaped molded product has a filling rate of 7.5% by volume or more and 30% by volume or less. A molded product made of a thermoplastic resin and having communication holes, wherein the molded product contains 50% by mass or more of a dicarboxylic acid-derived structural unit in the total thermoplastic resin constituting the molded product. The molded product according to claim 16, wherein the molded product is a molded product in which the wires are adhered to each other at a contact portion where the wires are in contact with each other. A three-dimensional mesh-like molded body in which wire rods made of a thermoplastic resin are bent and entangled, and the wire rods are fused to each other at a contact portion where the wires are in contact with each other, and the wire rods form a biodegradable resin. Including, molded body. The molded product according to claim 18, wherein the biodegradable resin is a biodegradable resin containing a structural unit derived from a dicarboxylic acid. The molded product according to any one of claims 16 to 19, wherein the molded product or the three-dimensional network-shaped molded product has a filling rate of 7.5% by volume or more and 30% by volume or less.

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