Ph adjuster for circulating water

Abstract

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

Description

pH adjuster for circulating water

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

[0002] In order to make effective use of water resources, used water is recycled and reused. One example of an application in which recycled water is effective is land-based aquaculture, which artificially raises fish, shellfish, seaweed, and the like. Land-based aquaculture is carried out in an environment established on land, and is broadly classified into free-flowing and closed-circulation systems. Free-flowing systems draw in culture water from the natural environment and discharge it after use. Closed-circulation systems circulate and reuse culture water while purifying it using a filtration system or the like.

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

[0004] JP 2015-192627 A International Publication No. 2016 / 031827

[0005] After various investigations into the issue of circulating water, it was discovered that there is a problem of coagulation occurring in the circulating water when it is circulated. Coagulation has various adverse effects, such as reducing the quality of the circulating water and hindering its filtration.

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

[0007] The present inventors investigated the cause of the formation of coagulation and found that the cause was the pH adjuster used to adjust the pH of the circulating water. That is, the pH of the circulating water is adjusted when it is circulated, but depending on the pH adjuster used, coagulation may occur in the circulating water.

[0008] Further investigation by the present inventors has revealed that when the number of particles contained in a pH adjuster (particularly a pH adjuster containing an alkali metal compound or alkaline earth metal compound that exhibits alkalinity) exceeds a certain level, aggregates are generated. In other words, by reducing the number of particles contained in the pH adjuster, it is possible to suppress the generation of aggregates.

[0009] The present invention includes the following embodiments. [1] A pH adjuster for circulating water, comprising an alkaline metal compound and / or an alkaline earth metal compound, 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 an alkali metal and / or alkaline earth metal concentration of 1 mol / L. [2] The pH adjuster according to [1], wherein the pH adjuster comprises the alkali metal compound, and the alkali metal compound comprises a sodium compound exhibiting 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 bicarbonate. [3-1] The pH adjuster according to [2] or [3], wherein the sodium compound is sodium hydroxide. [4] The pH adjuster according to any one of [1] to [3-1], wherein the number of particles is 100,000 particles / mL or less. [4-1] The pH adjuster according to any one of [1] to [4], wherein the number of particles is 1 to 90,000 particles / mL. [4-2] The pH adjuster according to any one of [1] to [4-1], wherein the number of particles is 5 to 90,000 particles / mL. [4-3] The pH adjuster according to any one of [1] to [4-2], wherein the number of particles is 10 to 16,000 particles / mL. [4-4] The pH adjuster according to any one of [1] to [4-3], wherein the number of particles is 100 to 16,000 particles / mL. [5] The pH adjuster according to any one of [1] to [4-4], 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 raising aquatic organisms. [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 iron concentration in the pH adjuster is 100 mg / kg or less based on an aqueous solution having an alkali metal and / or alkaline earth metal concentration of 18 mol / L.[9-1] The pH adjuster according to any one of [1] to [9], wherein the iron concentration in the pH adjuster is 10 mg / kg or less, based on an aqueous solution containing an alkali metal and / or alkaline earth metal at a concentration of 18 mol / L. [9-2] The pH adjuster according to any one of [1] to [9-1], wherein the iron concentration in the pH adjuster is 1 mg / kg or less, based on an aqueous solution containing an alkali metal and / or alkaline earth metal at a concentration of 18 mol / L.

[10] The pH adjuster according to any one of [1] to [9-2], wherein the zinc concentration in the pH adjuster is 30 μg / kg or less, based on an aqueous solution containing an alkali metal and / or alkaline earth metal at a concentration of 18 mol / L. [10-1] The pH adjuster according to any one of [1] to

[10] , wherein the zinc concentration in the pH adjuster is 20 μg / kg or less, based on an aqueous solution containing an alkali metal and / or alkaline earth metal at a concentration of 18 mol / L. [10-2] The pH adjuster according to any one of [1] to [10-1], wherein the zinc concentration in the pH adjuster is 10 μg / kg or less, based on an aqueous solution having an alkali metal and / or alkaline earth metal concentration of 18 mol / L.

[11] The pH adjuster according to any one of [1] to [10-2], wherein the arsenic concentration in the pH adjuster is 10 μg / kg or less, based on an aqueous solution having an alkali metal and / or alkaline earth metal concentration of 18 mol / L. [1A] A method for raising a rearing target animal, comprising: removing rearing water from a rearing tank in which the rearing target animal is raised; adding the pH adjuster according to any one of [1] to

[11] to the removed rearing water to adjust the pH of the rearing water; and returning the pH-adjusted rearing water to the rearing tank. [1B] A method for cultivating aquaculture objects, comprising: a step of withdrawing culture water from a land-based culture tank in which the aquaculture objects are cultivated; a step of adding a pH adjuster according to any one of [1] to

[11] to the withdrawn culture water to adjust the pH of the culture water; and a step of returning the pH-adjusted culture water to the culture tank.

[0010] The present invention can suppress the generation of agglomerates when circulating circulating water.

[0011] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these and various modifications are possible without departing from the gist of the present invention.

[0012] <pH Adjuster> One embodiment of the present invention relates to a pH adjuster for circulating water, which contains an alkali metal compound that exhibits alkaline properties or an alkaline earth metal compound that exhibits alkaline properties, and in which 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 an alkali metal or alkaline earth metal concentration of 1 mol / L.

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

[0014] The occurrence of agglomerates is caused by particles contained in the pH adjuster, but it is unexpected and surprising that such a small amount of impurities can cause such a big problem for circulating water.

[0015] In particular, when the circulating water is circulating water for aquatic organism rearing (breeding water) or land-based aquaculture (aquaculture water), the circulating water contains various components such as naturally occurring organic matter and excrement from the rearing or aquaculture subjects (e.g., fish), so the need to use a high-purity pH adjuster when adjusting the pH of the circulating water has not been recognized. Therefore, it is unexpected and surprising that the occurrence 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 (breeding water) for breeding aquatic organisms, and more preferably circulating water (aquaculture water) for land-based aquaculture.

[0017] The land-based aquaculture is preferably a closed-circulation land-based aquaculture or a semi-closed-circulation land-based aquaculture. Semi-closed-circulation land-based aquaculture is intermediate between free-flowing land-based aquaculture and closed-circulation land-based aquaculture, in which a portion of the used aquaculture water is discharged while the remaining aquaculture water is circulated and reused. From the viewpoint of suppressing the generation of aggregates when circulating the aquaculture water, the effect of the pH adjuster according to this embodiment is particularly pronounced when closed-circulation land-based aquaculture is adopted.

[0018] The type of circulating water is not particularly limited and may be selected depending on the intended use. Examples of circulating water include seawater, river water, groundwater, and rainwater. Artificially prepared circulating water may also be used depending on the intended use. The circulating water preferably includes seawater.

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

[0020] The type of object to be raised or cultivated is not particularly limited as long as it can be raised or cultivated in water, and examples of the object include fish (e.g., saltwater fish and freshwater fish), shellfish, crustaceans, and seaweed.

[0021] [Components] The pH adjuster according to this embodiment contains an alkali metal compound exhibiting alkaline properties and / or an alkaline earth metal compound exhibiting alkaline properties. The alkali metal compound and alkaline earth metal compound may be used alone or in combination of two or more.

[0022] Examples of alkali metal compounds include sodium compounds that exhibit alkalinity, such as sodium hydroxide, sodium carbonate, and sodium bicarbonate.

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

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

[0025] The pH adjuster may contain a solvent (preferably water) that dissolves 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 with a concentration of 48% by mass.

[0026] [Particles] The number of particles contained in the pH adjuster according to this embodiment is 150,000 particles / mL or less, preferably 120,000 particles / mL or less, more preferably 90,000 particles / mL or less, and even more preferably 16,000 particles / mL or less. The lower limit of the particle number is preferably 0 particles / mL, but may be 1 particle / mL or more, 5 particles / mL or more, 10 particles / mL or more, or even 100 particles / mL or more. These particle numbers are based on an aqueous solution having an alkali metal and / or alkaline earth metal concentration of 1 mol / L. Note that, when determining the number of particles, it is not necessary to prepare an aqueous solution having an alkali metal and / or alkaline earth metal concentration of 1 mol / L, and the number of particles may be calculated by converting the concentration to 1 mol / L. For example, if the number of particles in an aqueous solution having an alkali metal and / or alkaline earth metal concentration of 0.5 mol / L is 1,000 particles / mL, the concentration can be converted to 1 mol / L, and the number of particles can be determined to be 2,000 particles / mL (similar calculations based on concentration conversion are possible in measuring the concentration of impurities, which will be described later.) Note that, when the pH adjuster contains multiple types of alkali metals and / or alkaline earth metals, the standard is 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. There is no particular upper limit to the particle size, but it may be, for example, 100 μm or 200 μm.

[0028] The presence of particles can cause agglomerates in the circulating water, so the fewer particles there are, the better. The number of particles can be measured using a commercially available particle counter. Specifically, it can be measured using a side scattering method using a semiconductor laser.

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

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

[0031] [Impurities] The amount of impurities contained in the pH adjuster according to the present embodiment is preferably small. Examples of impurities include iron, zinc, and arsenic. The impurity concentrations described below are the concentrations of impurities contained in the pH adjuster, including particles.

[0032] (Iron: Fe) The iron concentration in the pH adjuster according to this embodiment is preferably 100 mg / kg or less (hereinafter also referred to as "ppm"), more preferably 10 mg / kg or less, and even more preferably 1 mg / kg or less. The lower limit of the iron concentration is not particularly limited, but may be, for example, 0 mg / kg or 0.1 mg / kg. These iron concentrations are based on an aqueous solution having an alkali metal and / or alkaline earth metal concentration of 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 formation of aggregates in the circulating water can be suppressed.

[0035] (Zinc: Zn) The zinc concentration 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, even more preferably 10 μg / kg or less, even more preferably 5 μg / kg or less, even more preferably 4 μg / kg or less, even more preferably 3 μg / kg or less, even 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, but may be, for example, 0 μg / kg or 10 μg / kg. These zinc concentrations are based on an aqueous solution having an alkali metal and / or alkaline earth metal concentration of 18 mol / L.

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

[0037] (Arsenic: As) The arsenic concentration in the pH adjuster according to this embodiment is preferably 10 μg / kg or less, more preferably 5 μg / kg or less, even more preferably 4 μg / kg or less, even more preferably 3 μg / kg or less, even 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, but may be, for example, 0 μg / kg or 10 μg / kg. These arsenic concentrations are based on an aqueous solution having an alkali metal and / or alkaline earth metal concentration of 18 mol / L.

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

[0039] Zinc and arsenic are not impurities related to the formation of aggregates, but are impurities related to safety. If zinc or arsenic accumulates in the aquaculture target, it may have adverse effects on humans who consume the aquaculture target. Therefore, from the perspective of safety, the lower the zinc and arsenic concentrations, the better.

[0040] The concentrations of iron, zinc, and arsenic can be controlled, for example, by selecting high-purity raw materials and by 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 circulating water.

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

[0043] The amount of the pH adjuster to be added is not particularly limited, and it may be added in an amount that will give a pH appropriate for the intended use.

[0044] <Circulation method> One embodiment of the present invention relates to a method for circulating circulating water, comprising: a step of withdrawing circulating water from a storage tank; a step of adding a pH adjuster to the withdrawn circulating water to adjust the pH of the circulating water; and a step of returning the pH-adjusted circulating water to the storage tank.

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

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

[0047] <Breeding method or aquaculture method> One embodiment of the present invention relates to a method for raising an object to be raised, comprising: a step of removing breeding water from a breeding tank in which the object to be raised is raised; a step of adding a pH adjuster to the removed breeding water to adjust the pH of the breeding water; and a step of returning the pH-adjusted breeding water to the breeding tank.

[0048] One embodiment of the present invention relates to a method for cultivating aquaculture objects, comprising: a step of withdrawing culture water from an onshore culture tank in which the aquaculture objects are cultivated; a step of adding a pH adjuster to the withdrawn culture water to adjust the pH of the culture water; and a step of returning the pH-adjusted culture water to the culture tank.

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

[0050] The amount of pH adjuster to be added is not particularly limited, and it may be added in an amount that provides a pH suitable for the subject of breeding or cultivation.

[0051] In the rearing or aquaculture method according to this embodiment, treatments necessary for maintaining the water quality of the rearing or aquaculture water may be further carried out. Examples of such treatments include filtration, denitrification, foam separation, and sterilization.

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

[0053] Various values ​​in the examples may be used as preferred lower or upper limits in the embodiments of the present invention. Two values ​​of the same type in the examples may be appropriately combined to form a preferred range of values.

[0054] <pH Adjuster> A 30% by mass aqueous sodium hydroxide solution was prepared by electrolyzing an aqueous sodium chloride solution. The aqueous sodium hydroxide solution was evaporated and concentrated to prepare a 48% by mass aqueous sodium hydroxide solution. The 48% by mass aqueous sodium hydroxide solution was filtered a desired number of times using a general filtration cartridge filter to prepare pH adjusters containing various numbers of particles (0.5 μm or larger). The number of particles was measured using a particle counter (KS-42AF manufactured by Rion Co., Ltd.).

[0055] [Measurement of iron concentration] A precisely weighed sample was transferred to a measuring flask and diluted with ultrapure water, after which a predetermined amount of hydrochloric acid was added, and then ultrapure water was added to adjust to the marked line. The iron concentration was measured by the standard addition method using an ICP-Atomic Emission Spectrometer.

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

[0057] [Measurement of arsenic concentration] A precisely weighed sample was transferred to a measuring flask and diluted with ultrapure water, after which a predetermined amount of hydrochloric acid was added, and then ultrapure water was added to adjust the dilution to the marked line. This solution was passed through a hydride generator, and the arsenic concentration of the generated hydride was measured by the standard addition method using an ICP optical emission spectrometer.

[0058] <Flocculation and Sedimentation Test> Used culture water (seawater) was removed from the culture tank, and a pH adjuster (aqueous solution of sodium hydroxide with a concentration of 48% by mass) was added to the culture water until the pH reached 7. The presence or absence of flocculation and sedimentation in the culture water to which the pH adjuster had been added was visually confirmed. The evaluation criteria for the flocculation and sedimentation test were as follows. The results are shown in Table 1.

[0059] [Evaluation criteria] A: Colorless and transparent B: Suspended matter present C: Slightly cloudy D: Aggregated sedimentation present

[0060] <Production test> 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 transferred to a product storage tank. The heat exchange efficiency was evaluated by measuring the temperature of the aqueous sodium hydroxide solution. When shipping from the product storage tank, the solution was passed through a filter and filled into a product container. Filter clogging was evaluated by measuring the pressure of the aqueous sodium hydroxide solution. The evaluation criteria for the production test were as follows. The results are shown in Table 1.

[0061] [Evaluation criteria] A: No problem B: The filter tends to clog faster C: The filter clogs obviously faster D: The filter clogs obviously faster and the heat exchange efficiency decreases

[0062]

Claims

1. A pH adjuster for circulating water, comprising an alkali metal compound and / or an alkaline earth metal compound that exhibits 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 in which the concentration of the alkali metal and / or alkaline earth metal is 1 mol / L.

2. The pH adjuster according to claim 1, wherein the pH adjuster contains the alkali metal compound, and the alkali metal compound contains a sodium compound that exhibits alkalinity.

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

4. The pH adjuster according to any one of claims 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 claims 1 to 3, wherein the particles contain iron.

6. The pH adjuster according to any one of claims 1 to 3, wherein the circulating water is circulating water for aquatic organism breeding.

7. The pH adjuster according to any one of claims 1 to 3, wherein the circulating water is circulating water for land aquaculture.

8. The pH adjuster according to any one of claims 1 to 3, wherein the circulating water contains seawater.

9. The pH adjuster according to any one of claims 1 to 3, 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 the alkali metal and / or alkaline earth metal is 18 mol / L.

10. The pH adjuster according to any one of claims 1 to 3, 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 the alkali metal and / or alkaline earth metal is 18 mol / L.

11. The pH adjuster according to any one of claims 1 to 3, 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 the alkali metal and / or alkaline earth metal is 18 mol / L.

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