pH adjuster for circulating 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 technology]

[0002] In order to make effective use of water resources, used water is recycled and reused. One example of a situation in which recycled water is effective is land-based aquaculture, which artificially raises fish, shellfish, seaweed, etc. Land-based aquaculture is farming carried out in an environment established on land, and is broadly classified into free-flowing and closed-circulation systems. The flow-through system draws water from the natural environment and discharges it after use. The closed circulation system is a method in which the culture water is purified using a filtration system, circulated, and reused.

[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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-192627 [Patent Document 2] International Publication No. 2016 / 031827 Summary of the Invention [Problem to be solved by the invention]

[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. [Means for solving the problem]

[0007] The 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] Upon further investigation, the present inventors found 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 alkali metal compound exhibiting alkalinity and / or an alkaline earth metal compound exhibiting alkalinity, 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; pH adjuster. [2] the pH adjuster comprises the alkali metal compound, The pH adjuster according to [1], wherein the alkali metal compound contains a sodium compound exhibiting alkaline properties. [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. [4] The pH adjuster according to any one of [1] to [3], wherein the number of 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 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.

[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 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] , wherein the concentration of arsenic 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. [Effects of the Invention]

[0010] The present invention can suppress the generation of agglomerates when circulating circulating water. DETAILED DESCRIPTION OF THE INVENTION

[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 Adjusting Agent> One embodiment of the present invention is a pH adjusting agent for circulating water, which contains an alkali metal compound showing alkalinity or an alkaline earth metal compound showing alkalinity, and the number of particles with a particle size of 0.5 μm or more contained in the pH adjusting agent is 150,000 pieces / 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 adjusting agent.

[0013] Even when the pH adjusting agent according to this embodiment is used for adjusting the pH of circulating water, the generation of aggregates can be suppressed.

[0014] The generation of aggregates is caused by the particles contained in the pH adjusting agent. 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 derived organic substances and excreta of the breeding target or aquaculture target (e.g., fish). Therefore, the need to use a high-purity pH adjusting agent 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 adjusting agent.

[0016] [Use] The pH adjusting agent 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), and more preferably circulating water for land-based aquaculture (aquaculture water).

[0017] 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 artificially prepared seawater is water containing 0.1 to 10% by mass of sodium chloride.

[0020] The types of objects to be raised or cultivated are not particularly limited as long as they can be raised or cultivated in water, and examples of objects include fish (e.g., saltwater fish and freshwater fish), shellfish, crustaceans, and seaweed.

[0021] [component] The pH adjuster according to the present embodiment contains an alkaline metal compound and / or an alkaline earth metal compound. The alkaline metal compound and alkaline earth metal compound may be used alone or in combination.

[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 alkaline earth metal compound. When the alkali metal compound is sodium hydroxide, the pH adjuster is preferably an aqueous solution of sodium hydroxide 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 with 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 using concentration conversions are possible when measuring the concentration of impurities, as described below.) Note that when a pH adjuster contains multiple types of alkali metals and / or alkaline earth metals, the standard is an aqueous solution with a total concentration of these metals of 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 pH adjuster according to the present embodiment preferably contains a small amount of impurities. 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 (hereinafter also referred to as "ppm") or less, 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] Accumulation of zinc or arsenic in the aquaculture target may have adverse effects on humans who consume the aquaculture target, so from the perspective of safety, it is preferable that the concentrations of zinc and arsenic are as low as possible.

[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 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] <Rearing Method or Aquaculture Method> One embodiment of the present invention is a step of extracting rearing water from a rearing tank for rearing a rearing object, a step of adding a pH adjuster to the extracted rearing water to adjust the pH of the rearing water, a step of returning the pH-adjusted rearing water to the rearing tank, and relates to the rearing method of the rearing object 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 an aquaculture object, 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; It 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 column of the above <pH adjuster>.

[0050] The addition amount of the pH adjuster is not particularly limited, and it may be added in an amount that results in a pH suitable for the object of breeding or culturing.

[0051] In the breeding method or culturing method according to this embodiment, further treatment necessary for maintaining the 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] [[ID=2�]] In addition, various values in the examples may be used as the preferred lower limit value or upper limit value in the embodiments of the present invention. Also, two values of the same kind in the examples may be appropriately combined to form a preferred 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] [Iron concentration measurement] The precisely weighed sample was transferred to a volumetric flask and diluted with ultrapure water, after which a predetermined amount of hydrochloric acid was added, followed by ultrapure water to adjust to the marked line.The iron concentration was measured by the standard addition method using an ICP-Atomic Emission Spectrometer.

[0056] [Zinc concentration measurement] The 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. The zinc was recovered from the chelating disk, and the zinc concentration was measured using an ICP-MS with the calibration curve method.

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

[0058] <Flocculation and Sedimentation Test> The 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 coagulation and sedimentation in the culture water to which the pH adjuster had been added was confirmed by visual inspection. The evaluation criteria for the coagulation and sedimentation test were as follows. The results are shown in Table 1.

[0059] [Evaluation criteria] A: Colorless and transparent B: Floating matter present C: Slightly cloudy D: Coagulation and precipitation

[0060] <Manufacturing Test> Aqueous sodium chloride solution was electrolyzed to produce a 30% by mass aqueous sodium hydroxide solution. The aqueous sodium hydroxide solution was evaporated and concentrated to produce a 48% by mass aqueous sodium hydroxide solution. 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 the product container. Filter clogging was evaluated by measuring the pressure of the aqueous sodium hydroxide solution. The evaluation criteria for the manufacturing test are as follows: The results are shown in Table 1.

[0061] [Evaluation criteria] A: No problem B: The filter tends to clog quickly. C: The filter clogs significantly faster. D: The filter clogs significantly faster 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, the number of particles having a particle diameter of 0.5 μm or more contained in the pH adjuster is 100,000 particles / mL or less based on an aqueous solution having an alkali metal and / or alkaline earth metal concentration of 1 mol / L; the particles contain iron; the iron concentration in the pH adjuster is 75 mg / kg or less based on an aqueous solution having an alkali metal and / or alkaline earth metal concentration of 18 mol / L; pH adjuster.

2. the pH adjuster contains the alkali metal compound, The alkali metal compound includes 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 bicarbonate. The pH adjuster according to claim 2.

4. The circulating water is circulating water for raising aquatic organisms. The pH adjuster according to any one of claims 1 to 3.

5. The circulating water is circulating water for land-based aquaculture. The pH adjuster according to any one of claims 1 to 3.

6. The circulating water includes seawater. The pH adjuster according to any one of claims 1 to 3.

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

8. the concentration of arsenic 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; The pH adjuster according to any one of claims 1 to 3.

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