Method for measuring concentration of water treatment agent and water treatment composition

Abstract

To provide a method for accurately measuring the concentration of a water treatment agent even in a system where water quality fluctuates or interfering metal ions are present.MEANS FOR SOLVING THE PROBLEM: A method for controlling the concentration of a water treating agent in a water system, comprising the steps of: adding a water treating agent containing a chelating agent and a fluorescent substance to a water system containing interfering metal ions; measuring the fluorescence intensity of the fluorescent substance in the water system to calculate the concentration of the fluorescent substance in the water system; and calculating the concentration of the water treating agent in the water system from the addition ratio of the fluorescent substance in the water treating agent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for measuring the concentration of water treatment chemicals (water treatment agents, water system additive agents) that are applied to prevent scale, metal corrosion, etc. in various water systems such as industrial water systems, cooling water systems, hot water systems, boiler water systems, cleaning water, process water systems, and wastewater systems, and to a water treatment composition for concentration measurement. [Background technology]

[0002] Various water treatment agents are used in various water systems, including industrial water systems, cooling water systems, hot water systems, boiler water systems, cleaning water systems, process water systems, and wastewater systems, to prevent water-related problems such as corrosion, scale, and slime. Maintaining an appropriate concentration of water treatment agents in a water system is essential for proper water treatment. Therefore, accurate determination of the water treatment agent concentration at any given location and time is essential for appropriate concentration management. Typically, water treatment agent concentrations are determined by measuring the amount of phosphate or polymer contained in the water treatment agent using colorimetry or turbidimetry, and then determining the concentration from the measured value. However, this method requires complex sample pretreatment and the need for equipment such as an absorption spectrophotometer, making it difficult to quickly determine the water treatment agent concentration on-site. Therefore, a method for quickly measuring the water treatment agent concentration has been devised by adding a tracer substance that can be measured on-site in addition to the water treatment agent and measuring the concentration of the tracer substance.

[0003] For example, Patent Document 1 devised a method of measuring the concentration of a water treatment agent by adding lithium as a tracer substance and measuring the lithium ion concentration using a lithium ion electrode, and Patent Documents 2 and 3 devised methods of measuring the concentration of a water treatment agent by adding a fluorescent substance such as PTSA (1,3,6,8-pyrenetetrasulfonic acid) or a polymer containing such a substance and measuring the fluorescence intensity.

[0004] However, it is known that measurements made with lithium ion electrodes and fluorescence intensity from fluorescent substances are significantly affected by the water quality and metal ions in the circulating water. For example, lithium ion electrodes are affected by water quality factors such as sodium ions and concentration. Therefore, the prior art documents cited above measure the response of the lithium ion electrode as well as the concentration value to perform corrections. Furthermore, because calcium ions reduce the fluorescence intensity of certain fluorescent substances, a method has been proposed in which a chelating agent is used in combination (Patent Document 4). Furthermore, it has been reported that the fluorescence intensity of fluorescent substances is reduced by iron ions (Non-Patent Documents 1 and 2). Therefore, accurate measurements cannot be obtained in circulating water containing even small amounts of iron ions. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2004-322058 [Patent Document 2] Special Publication 2013-531705 [Patent Document 3] Patent Publication No. 2013-072741 [Patent Document 4] Patent Publication No. 2022-022496 [Non-patent literature]

[0006] [Non-Patent Document 1] Guiqiao Wang et al.,Journal of Fluorescence,31,713-718(2021) [Non-patent document 2] Hajime Sugita et al., Journal of Geothermal Science, Vol. 25, No. 3, 211-215 (2003) Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a method for measuring the concentration of a water treatment agent and a water treatment composition that do not require complicated operations or corrections, even in systems where water quality fluctuates or interfering metal ions are present. [Means for solving the problem]

[0008] After extensive research, the inventors discovered that certain interfering metal ions present in a water system reduce the fluorescence intensity and affect the measured value of the fluorescent substance concentration. They then discovered that by adding a water treatment agent containing a fluorescent substance and a chelating agent that chelates these ions to the water system in question and measuring the fluorescence intensity, it is possible to measure the correct concentration of the water treatment agent even in systems where water quality fluctuates or interfering metal ions are present.

[0009] [1] A step of adding a water treatment agent containing a chelating agent and a fluorescent substance to an aqueous system containing interfering metal ions, or a step of adding a chelating agent to the aqueous system and then adding a water treatment agent containing a fluorescent substance to the aqueous system; measuring the fluorescence intensity of the fluorescent substance in the aqueous system and calculating the concentration of the fluorescent substance in the aqueous system; calculating a concentration of the water treatment agent in the water system from the addition ratio of the fluorescent substance in the water treatment agent; A method for managing the concentration of a water treatment agent in a water system, comprising: [2] A method for controlling the concentration of a water treatment agent, wherein the chelating agent according to [1] contains one or more hydroxycarboxylic acids and salts thereof. [3] The method for managing the concentration of a water treatment agent according to [1] or [2], wherein the interfering metal ions include one or more selected from the group consisting of iron ions, copper ions, and aluminum ions. [4] A water treatment composition comprising a fluorescent substance and a chelating agent. [5] A water treatment composition according to [4], wherein the chelating agent comprises one or more hydroxycarboxylic acids and salts thereof. [Effects of the Invention]

[0010] By using the present invention, it becomes possible to quickly measure the concentration of a water treatment agent on-site without the need for complicated operations or corrections. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below, but the present invention is not limited thereto. In the present invention, the term "water system" refers to various water systems such as industrial water systems, cooling water systems, hot water systems, boiler water systems, cleaning water systems, process water systems, and wastewater systems.

[0012] Although there are no particular limitations on the fluorescent substance contained in the water treatment agent of the present invention, it is desirable that it be water-soluble, and compounds such as PTSA (1,3,6,8-pyrenetetrasulfonic acid), fluorescein, and their salts, or polymers containing fluorescent substances can be used. For example, CrestoGuard 503T (a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid containing a fluorescent substance) is commercially available from Crest Water as a polymer containing fluorescent substances.

[0013] The amount of the fluorescent substance contained in the water treatment agent of the present invention is adjusted so that sufficient fluorescence intensity is obtained when added to the target water system. Specifically, it is desirable to add a water treatment agent containing a fluorescent substance to the target water system, create a calibration curve of fluorescence intensity versus concentration, and then determine the amount to be added. If the amount is low, it may be affected by background fluorescence intensity and an accurate value may not be obtained. Regarding the amount of fluorescent substance to be added, for PTSA, fluorescein, and their salts, the amount of fluorescent substance is preferably 1 ppb to 1000 ppb of the active ingredient in the water system, with 10 ppb to 500 ppb being particularly preferred. Furthermore, for polymers containing fluorescent substances, the amount is preferably 0.01 ppm to 500 ppm of the active ingredient in the fluorescent polymer in the water system, with 1 ppm to 100 ppm being particularly preferred.

[0014] The method for measuring the concentration of a water treatment agent of the present invention involves adding a water treatment agent containing a fluorescent substance to a target water system, measuring the fluorescence intensity of the fluorescent substance contained in the water treatment agent in the water system, calculating the concentration of the fluorescent substance from a calibration curve of fluorescence intensity versus concentration, and measuring the concentration of the water treatment agent in the water system from the ratio of the fluorescent substance in the water treatment agent. For example, if the water treatment agent contains 0.1% fluorescent material, and the concentration of the fluorescent material calculated from the fluorescence intensity is 1 ppb, the concentration of the water treatment agent in the water system will be 1 ppm. Another method for measuring the concentration of a water treatment agent is to dilute the water treatment agent, create a calibration curve from the concentration and fluorescence intensity of the diluted solution, and then calculate the concentration of the water treatment agent from the fluorescence intensity of the target water system to which the water treatment agent has been added and the previously created calibration curve.

[0015] In the present invention, the fluorescence intensity can be measured by a spectrofluorometer. In addition, as devices for measuring the concentration of polymers containing fluorescent substances, Pyxis sells portable measuring devices and online sensors capable of measuring concentration, and Hitachi High-Tech Corporation also sells a fluorometer such as the F-2700. Furthermore, Tokai Chemical Co., Ltd. sells a portable fluorometer such as the FC-1.

[0016] As described in Non-Patent Document 1 and elsewhere, various metal ions reduce fluorescence intensity, but the interfering metal ions targeted in the present invention are iron ions, copper ions, and aluminum ions, which particularly reduce fluorescence intensity. The present invention is characterized in that the aqueous system contains one or more ions selected from the group consisting of iron ions, copper ions, and aluminum ions. On the other hand, calcium ions and zinc ions do not have a significant effect on fluorescence intensity compared to the interfering metal ions.

[0017] In the present invention, it is desirable to use a chelating agent for the interfering metal ions. In the present invention, by adding the chelating agent to the water system together with the water treatment agent containing a fluorescent substance, the interfering metal ions present in the water system can be chelated, thereby preventing a decrease in fluorescence intensity.

[0018] There are no particular limitations on the chelating agents that can be used in the present invention, but they must be able to chelate the interfering metal ions mentioned above, namely, iron ions, copper ions, and aluminum ions. Examples of chelating agents that can be used in the present invention include carboxylic acids, hydroxycarboxylic acids, aminocarboxylic acids, organic phosphoric acids, and their salts. Hydroxycarboxylic acids and their salts are particularly desirable from the viewpoint of preventing a decrease in fluorescence intensity. Meanwhile, aminocarboxylic acids, such as ethylenediaminetetraacetic acid, form stable complexes with various metal ions. However, water contains large amounts of calcium ions and magnesium ions in addition to the interfering metal ions mentioned above. Aminocarboxylic acids that readily form complexes with these metal ions also chelate calcium ions and magnesium ions in addition to the interfering metal ions, failing to exhibit sufficient effectiveness. Furthermore, ethylenediaminetetraacetic acid has the drawback of reacting slowly with aluminum ions, the interfering metal ion used in the present invention.

[0019] Examples of carboxylic acids applicable to the present invention include formic acid, acetic acid, propionic acid, and salts thereof.

[0020] Examples of hydroxycarboxylic acids applicable to the present invention include malic acid, tartaric acid, citric acid, gluconic acid, and salts thereof, but from the viewpoint of preventing a decrease in fluorescence intensity, malic acid, citric acid, and salts thereof are particularly preferred.

[0021] Examples of aminocarboxylic acids applicable to the present invention include ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraaminehexaacetic acid, 1,3-propanediaminetetraacetic acid, and salts thereof.

[0022] Examples of organic phosphoric acids applicable to the present invention include organic phosphonic acids, phosphinopolycarboxylic acids, and salts thereof.

[0023] In this specification, organic phosphonic acid refers to an organic compound having one or more phosphono groups in the molecule. The organic phosphonic acid is not particularly limited, but examples thereof include 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, hexamethylenediaminetetramethylenephosphonic acid, and salts thereof. As the organic phosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) and salts thereof are preferred.

[0024] As used herein, phosphinopolycarboxylic acid refers to an organic compound containing one or more phosphino groups and two or more carboxy groups in the molecule. Phosphinopolycarboxylic acids are not particularly limited, but examples include bis-poly(2-carboxyethyl)phosphinic acid obtained by reacting acrylic acid with hypophosphorous acid, bis-poly(1,2-dicarboxyethyl)phosphinic acid obtained by reacting maleic acid with hypophosphorous acid, poly(2-carboxyethyl)(1,2-dicarboxyethyl)phosphinic acid obtained by reacting maleic acid, acrylic acid, and hypophosphorous acid, bis-poly[2-carboxy-(2-carboxymethyl)ethyl]phosphinic acid obtained by reacting itaconic acid with hypophosphorous acid, a reaction product of acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, and hypophosphorous acid, and salts thereof. The reaction product of acrylic acid, maleic acid, and hypophosphorous acid is preferred as the phosphinopolycarboxylic acid. Phosphinopolycarboxylic acids are commercially available from Bio Labs under the trade names "BELCLENE500," "BELSPERSE164," and "BELCLENE400," for example.

[0025] In the present invention, the amount of the chelating agent to be added may be any concentration that can sufficiently chelate interfering metal ions in the aqueous system. For example, as described above, the fluorescence intensity of PTSA, fluorescein and salts thereof, polymers containing fluorescent substances, etc. is reduced by interfering metal ions such as iron ions. However, since the concentration of interfering metal ions such as iron ions in a typical aqueous system is at most about 10 ppm, it is preferable to blend the chelating agent in an amount so that the concentration in the aqueous system is 0.1 to 100 ppm, and it is particularly preferable to blend it in an amount of 1 to 20 ppm.

[0026] In the present invention, the chelating agent and the water treatment agent containing the fluorescent substance may be added separately, but it is preferable to add them simultaneously or in the order of the chelating agent and the water treatment agent containing the fluorescent substance. If the water treatment agent containing the fluorescent substance is added to the system first, interfering metal ions will act on the fluorescent substance, and the fluorescence intensity will remain reduced even if the chelating agent is added thereafter, which is not preferable. In the present invention, the chelating agent and the fluorescent substance can be contained in the same composition, and in addition to the fluorescent substance and chelating agent, the water treatment agent can contain other water treatment agent components such as a scale inhibitor, anticorrosive, bactericide, etc. The concentration of the water treatment agent can be determined from the ratio of these components to the fluorescent substance contained.

[0027] There are no particular limitations on the water treatment agent components that can be used in the present invention, and components that are generally applicable as water treatment agents can be used. For example, anionic polymers such as polyacrylic acid, polymaleic acid, polyitaconic acid, and copolymers of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid can be used as scale inhibitors.

[0028] As the anticorrosive agent, inorganic phosphoric acids such as orthophosphoric acid and condensed phosphoric acid, azole compounds, zinc compounds, etc. can be used.

[0029] Examples of disinfectants that can be used include sodium hypochlorite, N-chlorosulfamic acid, chloramine, bromamine, and other bonded halogens, 2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, octylisothiazolinone, 2-bromo-2-nitropropane-1,3-diol, 1-bromo-3-chloro-5,5-dimethylhydantoin, and 1,3-dibromo-5,5-dimethylhydantoin.

[0030] Furthermore, the composition of the present invention may be mixed with a commercially available water treatment agent as long as the stability is not impaired. The pH of the composition may be changed depending on the components to be added. For example, when a zinc-based compound is used as a corrosion inhibitor, the pH of the composition can be made acidic, and when hypochlorous acid or a bonded halogen is contained, the pH of the composition can be made alkaline to ensure the stability of the composition. [Example]

[0031] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0032] In the following tests, a fluorometer (F-2700, Hitachi High-Tech) was used to measure the concentration of fluorescent substances. The chemicals used in the examples and comparative examples are listed below. A calibration curve of fluorescent substance concentration and fluorescence intensity was created, and the concentration of the fluorescent substance was calculated from the measured fluorescence intensity. Fluorescence intensity was measured at 385 nm for PTSA, 520 nm for fluorescein, and 460 nm for CrestoGuard503T.

[0033] [Fluorescent material] CrestoGuard503T (Crest Water) PTSA Na salt (reagent: 1,3,6,8-pyrenetetrasulfonic acid tetrasodium salt, Fujifilm Wako Pure Chemical Industries, Ltd.) Fluorescein sodium salt (reagent: fluorescein sodium, Fujifilm Wako Pure Chemical Industries, Ltd.) [Chelating agent] Malic acid (reagent: Fujifilm Wako Pure Chemical Industries, Ltd.) HEDP (1-hydroxyethane-1,1-diphosphonic acid, BELCLENE 660LA, manufactured by BWA) Citric acid (reagent: Fujifilm Wako Pure Chemical Industries, Ltd.) EDTA (reagent: ethylenediaminetetraacetic acid, Fujifilm Wako Pure Chemical Industries, Ltd.) [Interfering metal ions] Iron ions: Ferrous sulfate (reagent: Fujifilm Wako Pure Chemical Industries, Ltd.) Copper ions: Copper sulfate (reagent: Fujifilm Wako Pure Chemical Industries, Ltd.) Aluminum ion: Aluminum chloride (reagent: Fujifilm Wako Pure Chemical Industries, Ltd.) Calcium ion: calcium chloride (reagent: Fujifilm Wako Pure Chemical Industries, Ltd.) Zinc ion: Zinc chloride (reagent: Fujifilm Wako Pure Chemical Industries, Ltd.) [others] AA-AMPS: acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid (copolymerization ratio (mass) 60:40, weight average molecular weight 10,000) PBTC (2-phosphonobutane-1,2,4-tricarboxylic acid, BELCLENE 650, manufactured by BWA) NaOH (reagent, sodium hydroxide, Fujifilm Wako Pure Chemical Industries, Ltd.)

[0034] [Example 1] Ferrous sulfate was added to city water to achieve 1 ppm and 2 ppm of iron ions as an interfering metal ion, and then PTSA Na salt was added to city water to achieve 200 ppb of PTSA and 5 ppm of EDTA. The fluorescent substance concentrations in these solutions were measured using a fluorometer and compared with the values ​​measured without the addition of iron ions.

[0035] [Example 2] Ferrous sulfate was added to city water to achieve 1 ppm and 2 ppm of iron ions as an interfering metal ion, and then PTSA Na salt was added to city water to achieve 200 ppb of PTSA and malic acid to achieve 5 ppm. The fluorescent substance concentrations in these solutions were measured using a fluorometer and compared with the values ​​measured without the addition of iron ions.

[0036] [Example 3] Ferrous sulfate was added to city water to achieve 1 ppm and 2 ppm of iron ions as an interfering metal ion, and then PTSA Na salt was added to the city water to achieve 200 ppb of PTSA and 1-hydroxyethane-1,1-diphosphonic acid to achieve 5 ppm. The fluorescent substance concentrations in these solutions were measured using a fluorometer and compared with the values ​​measured without the addition of iron ions.

[0037] [Example 4] Ferrous sulfate was added to city water to achieve 1 ppm and 2 ppm of iron ions as an interfering metal ion, and then PTSA Na salt was added to the city water to achieve 200 ppb of PTSA and citric acid to achieve 5 ppm. The fluorescent substance concentration of this solution was measured using a fluorometer and compared with the measured value without adding iron ions.

[0038] [Examples 5 to 8] In the tests of Examples 1 to 4, the Na salt of PTSA was replaced with the Na salt of fluorescein, and the Na salt of fluorescein was added to city water so as to give a concentration of 200 ppb as fluorescein, and the tests were carried out in the same manner.

[0039] [Examples 9 to 12] In the tests of Examples 1 to 4, the Na salt of PTSA was replaced with CrestoGuard503T, which was added to city water so that the fluorescent polymer in CrestoGuard503T was 5 ppm, and the test was carried out in the same manner.

[0040] [Example 13] In the test of Example 10, the ferrous sulfate was replaced with copper sulfate.

[0041] [Example 14] In the test of Example 10, the ferrous sulfate was replaced with aluminum chloride.

[0042] [Comparative Example 1] Ferrous sulfate was added to city water at 1 ppm and 2 ppm of iron ion as an interfering metal ion, and then 200 ppb of the sodium salt of PTSA was added to the city water. The fluorescent substance concentration of this solution was measured using a fluorometer and compared with the measured value without the addition of iron ion.

[0043] Comparative Example 2 Copper sulfate was added to city water to achieve 1 ppm and 2 ppm copper ions as an interfering metal ion, and then PTSA Na salt was added to the city water to achieve 200 ppb PTSA. The fluorescent substance concentration in this solution was measured using a fluorometer and compared with the measured value without copper ions.

[0044] Comparative Example 3 Aluminum chloride was added to city water to achieve concentrations of 1 ppm and 2 ppm as an interfering metal ion, and then PTSA Na salt was added to the city water to achieve a concentration of 200 ppb as PTSA. The fluorescent substance concentration in this solution was measured using a fluorometer and compared with the value measured when no aluminum ions were added.

[0045] [Comparative Examples 4 to 6] In the tests of Comparative Examples 1 to 3, the Na salt of PTSA was replaced with the Na salt of fluorescein, and the Na salt of fluorescein was added to city water so as to have a concentration of 200 ppb as fluorescein, and tests were carried out in the same manner.

[0046] [Comparative Examples 7 to 9] In the tests of Comparative Examples 1 to 3, the Na salt of PTSA was replaced with CrestoGuard503T, which was added to city water so that the fluorescent polymer in CrestoGuard503T was 5 ppm, and the tests were carried out in the same manner.

[0047] [Reference example 1] Calcium chloride was added to city water to a concentration of 100 ppm as calcium ions as an interfering metal ion, and then fluorescein Na salt was added to the city water to a concentration of 200 ppb as fluorescein. The fluorescent substance concentration of this solution was measured using a fluorometer and compared with the measured value without calcium ions.

[0048] [Reference example 2] Zinc chloride was added to city water as an interfering metal ion to achieve 1 ppm and 2 ppm of zinc ion, and then fluorescein Na salt was added to the city water to achieve 200 ppb of fluorescein. The fluorescent substance concentration of this solution was measured using a fluorometer and compared with the measured value without zinc ion.

[0049] The results are shown in Table 1. As in Examples 1 to 14, when a chelating agent such as EDTA, malic acid, citric acid, or HEDP was present, there was little decrease in the measured fluorescent substance concentration, even in the presence of interfering metal ions such as iron ions, copper ions, or aluminum ions. On the other hand, in Comparative Examples 1 to 9, in which no chelating agent was used, the measured fluorescent substance concentration significantly decreased with increasing concentrations of interfering metal ions such as iron ions, copper ions, or aluminum ions. Furthermore, as in Examples 2, 4, 6, 8, 10, and 12 to 14, when a hydroxycarboxylic acid such as citric acid or malic acid was used, there was less decrease in the measured fluorescent substance concentration compared to when a chelating agent such as EDTA or HEDP was used, enabling highly accurate measurement. Furthermore, as shown in Reference Examples 1 and 2, it was found that calcium ions and zinc ions did not significantly affect the fluorescence intensity.

[0050] [Table 1]

[0051] [Example 15] To a solution of city water to which ferrous sulfate was added at 1 ppm as iron ions, 5 ppm malic acid and sodium fluorescein salt were added in that order to give a fluorescein concentration of 200 ppb. The fluorescence concentration of this solution was measured using a fluorometer.

[0052] [Example 16] To a solution of city water containing 1 ppm of ferrous sulfate as iron ions, 5 ppm of malic acid and 200 ppb of sodium fluorescein were added simultaneously. The fluorescence concentration of this solution was measured using a fluorometer.

[0053] [Comparative Example 10] To a solution of city water containing 1 ppm of ferrous sulfate as iron ions, sodium fluorescein was added to a concentration of 200 ppb as fluorescein, followed by the addition of 5 ppm of malic acid. The fluorescence concentration of this solution was measured using a fluorometer.

[0054] The results are shown in Table 2. In Examples 15 and 16, in which the chelating agent and fluorescent substance were added simultaneously or first, the fluorescein concentration was accurately measured. However, in Comparative Example 10, in which the chelating agent was added later, the measured fluorescein concentration was lower than the value added. This suggests that if the fluorescent substance is added before the chelating agent in the presence of interfering metal ions, the interfering metal ions are not masked, resulting in a decrease in fluorescence intensity. It is clear that, in the presence of interfering metal ions, it is necessary to add the chelating agent and fluorescent substance simultaneously or first, as in Examples 15 and 16.

[0055] [Table 2]

[0056] The following tests were carried out to simulate a more realistic test. The test equipment and test method were in accordance with JIS G0593-2002 "On-site test method for evaluation of corrosion and scale prevention of water treatment agents."

[0057] (Test equipment) The test equipment shown in Figure 1 was used. Cooling water was stored in water tank 2 and sent to heat exchanger 7 by circulation pump 3. The circulating water volume was measured by flow meter 6 and appropriately regulated by flow control valve 5. After heat exchange in heat exchanger 7, the circulating water was heated and passed through test specimen holder 8, cooled by cooling tower 1, and returned to water tank 2. The return water temperature was maintained appropriately by adjusting the operation of the cooling tower 1 fan using water temperature control device 9. Meanwhile, the electrical conductivity signal of the cooling water measured by electrical conductivity measurement cell 4 was input to electrical conductivity control device 11, which operated blowdown pump 10 based on that signal to maintain the cooling water's electrical conductivity within a preset range. Makeup water 12 was supplied to water tank 2 in response to the drop in the water level caused by the start of blowdown, thereby maintaining the cooling water concentration within a predetermined range. Furthermore, a water treatment agent injection device 13 was operated simultaneously with the start of blowdown to maintain the appropriate water treatment agent concentration in the cooling water system.

[0058] (Test conditions) (1) Test heat transfer tube (outer diameter 12.7 mm, length 510 mm) to be attached to heat exchanger 7 Carbon steel pipe STKM11A (JIS G3445) and aluminum brass pipe C6871 (JIS H3300) were used. (2) Heat flux of heat exchanger 7: 70 kW / m (3) Total water volume of the system including tank 2 and piping: 62L (4) Circulating water volume: 210 L / h (equivalent to a linear flow velocity of 0.3 m / s in the test heat transfer tube evaluation section) (5) Cooling capacity of cooling tower 1: 1.8 cooling tons (induced draft counterflow contact type) (6) Temperature difference between the circulating water at the cooling tower inlet and outlet: 15°C (7) Evaporation rate: 4.4L / h (8) Replenishment water amount: 5.5L / h (9) Blowdown water volume: 1.1L / h (10) Concentration: 5 times (11) Test period: 1 month

[0059] The compositions of the examples and comparative examples are shown in Table 3. The compositions were formulated by mixing the ingredients in the order shown in the table. The formulation was carried out by adding each ingredient to a plastic container while stirring with a stirrer. During formulation, the composition was cooled so that the liquid temperature was below room temperature. In Table 3, % represents % by weight.

[0060] [Table 3]

[0061] Make-up water was placed in tank 2, and 50 mg / L of the composition shown in Table 3 was added to the water volume. Heat loading was then initiated, and three days after the start of heat loading, the concentration reached 5 times. Blowdown was immediately initiated to maintain the concentration at 5 times. At the same time as the start of blowdown, the test composition was added by water treatment agent injection device 13 to the blowdown volume so that the concentration was in the range of approximately 40 to 70 mg / L.

[0062] In this test, the concentration of the water treatment agent was determined from the total phosphate concentration and the fluorescent substance concentration. The total phosphate concentration was measured according to the potassium peroxodisulfate decomposition method in JIS K 0101 "Testing Methods for Industrial Water." That is, phosphate compounds in water were decomposed to phosphate ions using potassium peroxodisulfate, and the phosphate ions were measured using molybdenum blue (ascorbic acid reduction) spectrophotometry. The amount of composition to be added was calculated from the measured total phosphate concentration and the total phosphate concentration [%] of the composition. The concentration of the fluorescent substance was measured using a fluorometer (F-2700, manufactured by Hitachi High-Technologies), and the amount of the composition added was calculated from the amount of the fluorescent substance blended in the composition.

[0063] The results are shown in Figure 2. In Example 17, in which the present invention containing a chelating agent was applied and carbon steel pipes and aluminum brass pipes were used for the heat transfer tubes were used, even when interfering metal ions were present in the water system, the amount of composition added calculated from the phosphoric acid concentration and the amount of composition added calculated from the fluorescent substance concentration were roughly the same, making it possible to measure the concentration of the water treatment composition with high accuracy. On the other hand, in Comparative Example 11, which did not contain a chelating agent, the amount of composition added calculated from the fluorescent substance concentration was lower than the amount of composition added calculated from the phosphoric acid concentration. When a chelating agent was not contained, as in the Comparative Example, it was found that accurate values ​​could not be obtained on site unless correction was made, but by using the present invention, it was possible to quickly measure the concentration of a water treatment composition without complicated operations. [Industrial Applicability]

[0064] By adding a water treatment agent containing a fluorescent substance and a chelating agent that chelates specific interfering metal ions to the target water system and measuring the fluorescence intensity, it is possible to measure the correct concentration of the water treatment agent even in systems where water quality fluctuates or interfering metal ions are present. [Brief explanation of the drawings]

[0065] [Figure 1] Test equipment diagram [Figure 2] Test results of Example 17 and Comparative Example 11 [Explanation of symbols]

[0066] 1 cooling tower 2. Aquarium 3 Circulation Pump 4. Electrical conductivity measurement cell 5 Flow control valve 6 Flowmeter 7 Heat exchanger 8. Test specimen holder 9 Water temperature control device 10 Blowdown pump 11 Electrical conductivity control device 12 Makeup water 13 Water treatment agent injection device

Claims

1. A step of adding a water treatment agent containing a chelating agent and a fluorescent substance to an aqueous system containing interfering metal ions, or a step of adding a chelating agent to the aqueous system and then adding a water treatment agent containing a fluorescent substance to the aqueous system; measuring the fluorescence intensity of the fluorescent substance in the aqueous system and calculating the concentration of the fluorescent substance in the aqueous system; calculating a concentration of the water treatment agent in the water system from the addition ratio of the fluorescent substance in the water treatment agent; A method for managing the concentration of a water treatment agent in a water system, comprising:

2. 2. The method for controlling the concentration of a water treating agent according to claim 1, wherein the chelating agent comprises one or more hydroxycarboxylic acids and salts thereof.

3. 3. The method for managing the concentration of a water treating agent according to claim 1, wherein the interfering metal ions include at least one selected from the group consisting of iron ions, copper ions, and aluminum ions.

4. A water treatment composition comprising a fluorescent substance and a chelating agent.

5. 5. The water treatment composition according to claim 4, wherein the chelating agent comprises one or more hydroxycarboxylic acids and salts thereof.

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