Ph adjusting agent for circulation water

Abstract

To suppress generation of aggregate when circulating circulation water.SOLUTION: A pH adjusting agent for circulation water contains alkali metal compound exhibiting alkaline property and / or alkaline earth metal compound exhibiting alkaline property, in which the number of particles contained in the pH adjusting agent whose grain diameter is 0.5 μm or larger is 150,000 / mL or less with water solution of 1 mol / L concentration of alkaline metal and / or alkaline earth metal as a reference.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a pH adjuster for circulating water.

Background Art

[0002] In order to effectively utilize water resources, used water is circulated and reused. Scenes where the use of circulating water is effective include, for example, land-based aquaculture for artificially raising fish, shellfish, seaweed, etc. Land-based aquaculture is aquaculture carried out in an environment created on land and is roughly classified into a flow-through type and a closed-circulation type. The flow-through type is a method in which aquaculture water is drawn from the natural environment and discharged after use. The closed-circulation type is a method in which aquaculture water is circulated while being purified by a filtration system or the like and reused.

[0003] In land-based aquaculture, various contaminations of aquaculture water become problems. For example, Patent Documents 1 and 2 disclose methods of using ozone to decompose ammonia in aquaculture water.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] As a result of various studies on the problems of circulating water, it has been found that when circulating water is circulated, there is a problem that aggregates are generated in the circulating water. Aggregates cause various adverse effects such as deteriorating the water quality of the circulating water and hindering the filtration of the circulating water.

[0006] The present invention relates to suppressing the generation of aggregates when circulating circulating water.

Means for Solving the Problems

[0007] When the inventors investigated the cause of the generation of aggregates, they found that it was due to the pH adjuster used for adjusting the pH of the circulating water. That is, when adjusting the pH of the circulating water during circulation, depending on the pH adjuster used, aggregates are generated in the circulating water.

[0008] When the inventors further investigated, they found that when the number of particles contained in the pH adjuster (particularly, a pH adjuster containing an alkali metal compound or an alkaline earth metal compound showing alkalinity) reaches a certain level or more, aggregates are generated. In other words, it is possible to suppress the generation of aggregates by reducing the number of particles contained in the pH adjuster.

[0009] The present invention includes the following embodiments. [1] A pH adjuster for circulating water, containing an alkali metal compound showing alkalinity and / or an alkaline earth metal compound showing alkalinity, wherein the number of particles having a particle size of 0.5 μm or more contained in the pH adjuster is 150,000 particles / mL or less based on an aqueous solution having a concentration of alkali metal and / or alkaline earth metal of 1 mol / L. pH adjuster. [2] The pH adjuster contains the alkali metal compound, The pH adjuster according to [1], wherein the alkali metal compound contains a sodium compound showing alkalinity. [3] The pH adjuster according to [2], wherein the sodium compound is at least one selected from the group consisting of sodium hydroxide, sodium carbonate, and sodium hydrogen carbonate. [4] The pH adjuster according to any one of [1] to [3], wherein the number of the particles is 100,000 particles / mL or less. [5] The pH adjuster according to any one of [1] to [4], wherein the particles contain iron. [6] The pH adjuster according to any one of [1] to [5], wherein the circulating water is circulating water for aquaculture. [7] The pH adjuster according to any one of [1] to [6], wherein the circulating water is circulating water for land-based aquaculture. [8] The pH adjuster according to any one of [1] to [7], wherein the circulating water contains seawater. [9] The pH adjuster according to any one of [1] to [8], wherein the concentration of iron in the pH adjuster is 100 mg / kg or less based on an aqueous solution in which the concentration of an alkali metal and / or an alkaline earth metal is 18 mol / L.

[10] The pH adjuster according to any one of [1] to [9], wherein the concentration of zinc in the pH adjuster is 30 μg / kg or less based on an aqueous solution in which the concentration of an alkali metal and / or an alkaline earth metal is 18 mol / L.

[11] The pH adjuster according to any one of [1] to

[10] , wherein the concentration of arsenic in the pH adjuster is 10 μg / kg or less based on an aqueous solution in which the concentration of an alkali metal and / or an alkaline earth metal is 18 mol / L. [Advantages of the Invention]

[0010] The present invention can suppress the generation of aggregates when circulating the circulating water. [Embodiments for Carrying Out the Invention]

[0011] Hereinafter, embodiments of the present invention will be specifically described, but the present invention is not limited thereto, and various modifications are possible without departing from the gist thereof.

[0012] <pH adjuster> One embodiment of the present invention is a pH adjuster for circulating water containing an alkali metal compound showing alkalinity or an alkaline earth metal compound showing alkalinity, wherein the number of particles with a particle size of 0.5 μm or more contained in the pH adjuster is 150,000 particles / mL or less based on an aqueous solution in which the concentration of the alkali metal or alkaline earth metal is 1 mol / L. The present invention relates to a pH adjuster.

[0013] The pH adjuster according to this embodiment can suppress the generation of aggregates even when used for adjusting the pH of circulating water.

[0014] The generation of aggregates is caused by the particles contained in the pH adjuster. However, it is unexpected and surprising that such trace impurities cause major problems for circulating water.

[0015] In particular, when the circulating water is circulating water for aquatic organism breeding (breeding water) or circulating water for land-based aquaculture (aquaculture water), the circulating water contains various components such as naturally occurring organic substances and excreta of the breeding or aquaculture target (e.g., fish). Therefore, the need to use a high-purity pH adjuster when adjusting the pH of circulating water has not been recognized. Therefore, it is unexpected and surprising that the generation of aggregates can be suppressed by reducing the number of particles contained in the pH adjuster.

[0016] [Use] The pH adjuster according to this embodiment is used to adjust the pH of circulating water. The circulating water is preferably circulating water for aquatic organism breeding (breeding water), more preferably circulating water for land-based aquaculture (aquaculture water).

[0017] Land-based aquaculture is preferably closed-loop land-based aquaculture or semi-closed-loop land-based aquaculture. Semi-closed-loop land-based aquaculture is located between flow-through land-based aquaculture and closed-loop land-based aquaculture. While discharging a part of the used aquaculture water, the remaining aquaculture water is circulated and reused. From the viewpoint of suppressing the generation of aggregates during the circulation of aquaculture water, when closed-loop land-based aquaculture is adopted, the effect of the pH adjuster according to this embodiment is remarkably exhibited.

[0018] The type of circulating water is not particularly limited and may be selected according to the application. Examples of the circulating water include seawater, river water, groundwater, and rainwater. Circulating water artificially prepared according to the application may also be used. The circulating water preferably contains seawater.

[0019] The seawater may be taken from the sea or artificially prepared. Examples of the artificially prepared seawater include water containing 0.1 to 10% by mass of sodium chloride.

[0020] The type of object to be bred or cultured is not particularly limited as long as it can be bred or cultured in water. Examples of the object include fish (e.g., seawater fish and freshwater fish), shellfish, crustaceans, and seaweeds.

[0021] [Components] The pH adjuster according to this embodiment contains an alkali metal compound showing alkalinity and / or an alkaline earth metal compound showing alkalinity. The alkali metal compound and the alkaline earth metal compound may be used alone or in combination of multiple types.

[0022] Examples of the alkali metal compound include sodium compounds showing alkalinity. Examples of the sodium compounds include sodium hydroxide, sodium carbonate, and sodium hydrogen carbonate.

[0023] Examples of the alkali metal compound include potassium compounds that exhibit alkalinity. Examples of the potassium compounds that exhibit alkalinity include potassium hydroxide, potassium carbonate, and potassium hydrogen carbonate.

[0024] Examples of the alkaline earth metal compound include calcium compounds that exhibit alkalinity. Examples of the calcium compounds include calcium hydroxide, calcium carbonate, calcium oxide, and calcium hydrogen carbonate.

[0025] The pH adjuster may contain a solvent (preferably water) for dissolving the alkali metal compound and the alkaline earth metal compound. When the alkali metal compound is sodium hydroxide, the pH adjuster is preferably an aqueous sodium hydroxide solution having a concentration of 48% by mass.

[0026] [Particle] The number of particles contained in the pH adjuster according to the present embodiment is 150,000 particles / mL or less, preferably 120,000 particles / mL or less, more preferably 90,000 particles / mL or less, and still more preferably 16,000 particles / mL or less. The lower limit of the number of particles is preferably 0 particles / mL, but may be 1 particle / mL or more, 5 particles / mL or more, 10 particles / mL or more, or 100 particles / mL or more. These numbers of particles are based on an aqueous solution in which the concentration of alkali metal and / or alkaline earth metal is 1 mol / L. In determining the number of particles, it is not always necessary to prepare an aqueous solution in which the concentration of alkali metal and / or alkaline earth metal is 1 mol / L, and the number of particles may be calculated by converting the concentration to 1 mol / L. For example, when the number of particles in an aqueous solution in which the concentration of alkali metal and / or alkaline earth metal is 0.5 mol / L is 1,000 particles / mL, the number of particles can be considered to be 2,000 particles / mL after converting the concentration to 1 mol / L (similarly, in the measurement of the concentration of impurities described later, calculation by concentration conversion is possible). When the pH adjuster contains a plurality of types of alkali metals and / or alkaline earth metals, it is based on an aqueous solution in which the total concentration of these metals is 1 mol / L.

[0027] The particles to be measured have a particle size of 0.5 μm or more. The upper limit of the particle size of the particles is not particularly limited, and may be, for example, 100 μm or 200 μm.

[0028] Since aggregates are generated in the circulating water due to the presence of particles, the smaller the number of particles, the more preferable. The number of particles can be measured using a commercially available particle counter. Specifically, it can be measured by a side-scattering method using a semiconductor laser.

[0029] Examples of the particles include those containing iron. Since particles containing iron are particularly likely to generate aggregates, reducing the number of particles containing iron is preferable from the viewpoint of suppressing the generation of aggregates.

[0030] Particles can also cause clogging of the filter when filtering in the manufacturing process of the pH adjuster. In addition, if the particles accumulated in the piping or storage tank in the manufacturing process are discharged all at once due to pressure fluctuations or the like, the possibility of clogging the filter increases. Furthermore, when particles adhere to the surface of the heat exchanger, the heat exchange efficiency decreases. From the viewpoint of the manufacturing efficiency of such a pH adjuster as well, it is preferable to reduce the number of particles.

[0031] [Impurities] It is preferable that the amount of impurities contained in the pH adjuster according to the present embodiment is small. Examples of the impurities include iron, zinc, and arsenic. The concentration of impurities described below is the concentration of impurities contained in the pH adjuster including particles.

[0032] (Iron: Fe) The concentration of iron in the pH adjuster according to the present embodiment is preferably 100 mg / kg or less (hereinafter, also referred to as "ppm"), more preferably 10 mg / kg or less, and still more preferably 1 mg / kg or less. The lower limit of the iron concentration is not particularly limited, but for example, it may be 0 mg / kg or 0.1 mg / kg. These iron concentrations are based on an aqueous solution in which the concentration of alkali metal and / or alkaline earth metal is 18 mol / L.

[0033] The iron concentration can be measured by the method described in the examples below.

[0034] The lower the iron concentration, the more effectively the generation of aggregates in the circulating water can be suppressed.

[0035] (Zinc: Zn) The concentration of zinc in the pH adjuster according to this embodiment is preferably 30 μg / kg (hereinafter also referred to as "ppb") or less, more preferably 20 μg / kg or less, still more preferably 10 μg / kg or less, still more preferably 5 μg / kg or less, still more preferably 4 μg / kg or less, still more preferably 3 μg / kg or less, still more preferably 2 μg / kg or less, and particularly preferably 1 μg / kg or less. The lower limit of the zinc concentration is not particularly limited, and for example, it may be 0 μg / kg or 10 μg / kg. These zinc concentrations are based on an aqueous solution in which the concentration of alkali metal and / or alkaline earth metal is 18 mol / L.

[0036] The concentration of zinc can be measured by the method described in the examples below.

[0037] (Arsenic: As) The concentration of arsenic in the pH adjuster according to this embodiment is preferably 10 μg / kg or less, more preferably 5 μg / kg or less, still more preferably 4 μg / kg or less, still more preferably 3 μg / kg or less, still more preferably 2 μg / kg or less, and particularly preferably 1 μg / kg or less. The lower limit of the arsenic concentration is not particularly limited, and for example, it may be 0 μg / kg or 10 μg / kg. These arsenic concentrations are based on an aqueous solution in which the concentration of alkali metal and / or alkaline earth metal is 18 mol / L.

[0038] The concentration of arsenic can be measured by the method described in the examples below.

[0039] If zinc or arsenic accumulates in the aquaculture target, it may have an adverse effect on humans who ingest the aquaculture target. Therefore, from the perspective of safety, the lower the concentrations of zinc and arsenic, the better.

[0040] The concentrations of iron, zinc, and arsenic can be controlled, for example, by selecting high-purity raw materials and lining the inside of tanks, pipes, etc. in the manufacturing process.

[0041] <pH Adjustment Method> One embodiment of the present invention relates to a method for adjusting the pH of circulating water, which includes a step of adding a pH adjuster to the circulating water.

[0042] Details of each element in this embodiment are as described in the column of the above <pH adjuster>.

[0043] The addition amount of the pH adjuster is not particularly limited, and it may be added in an amount such that the pH is suitable for the intended use.

[0044] <Circulation Method> One embodiment of the present invention is a step of extracting circulating water from a storage tank, a step of adding a pH adjuster to the extracted circulating water to adjust the pH of the circulating water, a step of returning the pH-adjusted circulating water to the storage tank, and relates to the circulation method of the circulating water including these steps.

[0045] Details of each element in this embodiment are as described in the column of the above <pH adjuster>.

[0046] The addition amount of the pH adjuster is not particularly limited, and it may be added in an amount such that the pH is suitable for the intended use of the circulating water.

[0047] <Breeding Method or Aquaculture Method> One embodiment of the present invention is a step of extracting breeding water from a breeding tank for breeding breeding objects, a step of adding a pH adjuster to the extracted breeding water to adjust the pH of the breeding water, a step of returning the pH-adjusted breeding water to the breeding tank, and relates to the breeding method of the breeding objects including these steps.

[0048] One embodiment of the present invention is a step of extracting aquaculture water from an onshore aquaculture tank for aquaculture of aquaculture objects, A step of adding a pH adjuster to the extracted culture water to adjust the pH of the culture water; A step of returning the pH-adjusted culture water to the culture tank; Relates to a method for culturing the object to be cultured, including the above.

[0049] Details of each element in this embodiment are as described in the above <pH adjuster> column.

[0050] The addition amount of the pH adjuster is not particularly limited, and it may be added in an amount such that the pH is suitable for the object to be bred or cultured.

[0051] In the breeding method or culturing method according to this embodiment, further treatment necessary for maintaining the water quality of the breeding water or culture water may be performed. Such treatments include, for example, filtration treatment, denitrification treatment, foam separation treatment, and sterilization treatment.

Example

[0052] Hereinafter, the present invention will be described in more detail using examples and comparative examples, but the technical scope of the present invention is not limited thereto.

[0053] In addition, various values in the examples may be used as preferable lower limit values or upper limit values in the embodiments of the present invention. Also, two values of the same type in the examples may be appropriately combined to form a preferable numerical range.

[0054] <pH adjuster> An aqueous sodium chloride solution was electrolyzed to produce an aqueous sodium hydroxide solution with a concentration of 30% by mass. The aqueous sodium hydroxide solution was evaporated and concentrated to produce an aqueous sodium hydroxide solution with a concentration of 48% by mass. The 48% by mass aqueous sodium hydroxide solution was filtered any number of times with a general filtration cartridge filter to prepare a pH adjuster containing various numbers of particles (0.5 μm or more). The number of particles was measured using a particle counter ("KS-42AF" manufactured by Rion Co., Ltd.).

[0055] [Measurement of Iron Concentration] The accurately weighed sample was transferred to a volumetric flask, diluted with ultrapure water, and then a predetermined amount of hydrochloric acid was added. Further ultrapure water was added to make it reach the calibration line. The iron concentration was measured by the standard addition method using an ICP-emission spectrometer.

[0056] [Measurement of Zinc Concentration] The accurately weighed sample was transferred to a container, nitric acid, ammonium acetate, and ultrapure water were added, and the solution was passed through a chelating disk to collect zinc. Zinc was recovered from the chelating disk, and the zinc concentration was measured by the calibration curve method using ICP-MS.

[0057] [Measurement of Arsenic Concentration] The accurately weighed sample was transferred to a volumetric flask, diluted with ultrapure water, and then a predetermined amount of hydrochloric acid was added. Further ultrapure water was added to make it reach the calibration line. This solution was passed through a hydride generator, and the arsenic concentration was measured by the standard addition method using an ICP-emission spectrometer from the generated hydride.

[0058] [Coagulation Precipitation Test] Used culture water (seawater) was drawn out from the culture tank, and a pH adjuster (an aqueous sodium hydroxide solution with a concentration of 48% by mass) was added to the culture water until the pH reached 7. The presence or absence of coagulation precipitation in the culture water to which the pH adjuster was added was visually confirmed. The evaluation criteria for the coagulation precipitation test are as follows. The results are shown in Table 1.

[0059] [Evaluation Criteria] A: Colorless and Transparent B: With Suspended Matter C: Slightly Turbid D: With Coagulation Precipitation

[0060] [Manufacturing Test] An aqueous sodium chloride solution was electrolyzed to produce an aqueous sodium hydroxide solution with a concentration of 30% by mass. The aqueous sodium hydroxide solution was evaporated and concentrated to produce an aqueous sodium hydroxide solution with a concentration of 48% by mass. The 48% by mass aqueous sodium hydroxide solution was cooled using a heat exchanger and received into a product storage tank. The heat exchange efficiency was evaluated by measuring the temperature of the aqueous sodium hydroxide solution. When shipping out from the product storage tank, the solution was passed through a filter and filled into product containers. The clogging of the filter was evaluated by measuring the pressure of the aqueous sodium hydroxide solution. The evaluation criteria for the production test are as follows. The results are shown in Table 1.

[0061] [Evaluation Criteria] A: No problem B: Tendency for filter clogging to occur earlier C: Filter clogging clearly occurs earlier D: Filter clogging clearly occurs earlier and the heat exchange efficiency decreases

[0062]

Table 1

Claims

1. A pH adjuster for circulating water, comprising an alkali metal compound exhibiting alkalinity and / or an alkaline earth metal compound exhibiting alkalinity, wherein the number of particles with a particle size of 0.5 μm or more contained in the pH adjuster is 150,000 particles / mL or less based on an aqueous solution having a concentration of alkali metal and / or alkaline earth metal of 1 mol / L. pH adjuster.

2. The pH adjuster contains the alkali metal compound, and the alkali metal compound contains a sodium compound exhibiting alkalinity. The pH adjuster according to Claim 1.

3. The sodium compound is at least one selected from the group consisting of sodium hydroxide, sodium carbonate, and sodium hydrogen carbonate. The pH adjuster according to Claim 2.

4. The number of the particles is 100,000 particles / mL or less. The pH adjuster according to any one of Claims 1 to 3.

5. The particles contain iron. The pH adjuster according to any one of Claims 1 to 3.

6. The circulating water is circulating water for aquatic organism breeding. The pH adjuster according to any one of Claims 1 to 3.

7. The circulating water is circulating water for land aquaculture. The pH adjuster according to any one of Claims 1 to 3.

8. The circulating water contains seawater. The pH adjuster according to any one of Claims 1 to 3.

9. The concentration of iron in the pH adjuster is 100 mg / kg or less based on an aqueous solution having a concentration of alkali metal and / or alkaline earth metal of 18 mol / L. The pH adjuster according to any one of Claims 1 to 3.

10. The concentration of zinc in the pH adjuster is 30 μg / kg or less based on an aqueous solution having a concentration of alkali metal and / or alkaline earth metal of 18 mol / L. The pH adjuster according to any one of Claims 1 to 3.

11. The concentration of arsenic in the pH adjuster is 10 μg / kg or less based on an aqueous solution having a concentration of alkali metal and / or alkaline earth metal of 18 mol / L. The pH adjuster according to any one of Claims 1 to 3.

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