Method and apparatus for quantitative analysis of phosphate ions

Abstract

To provide a quantitative analysis method and apparatus capable of simply measuring the concentration of phosphate ions contained in inspection water, particularly in inspection water such as inorganic wastewater, organic wastewater, inorganic sludge, or organic sludge, in which property fluctuations are large.SOLUTION: A method for quantitative analysis of phosphate ions includes: introducing a predetermined amount of inspection water into a reaction tank having an ion-selective electrode; adding a cation agent to the inspection water to insolubilize phosphate ions; monitoring detection of soluble cations by the ion-selective electrode; and calculating the concentration of phosphate ions in the inspection water on the basis of the amount of cations reacted with the phosphate ions according to Expression 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for analyzing phosphate ion concentration, and more particularly to a method and apparatus for analyzing the concentration of phosphate ions contained in test water such as inorganic wastewater, organic wastewater, inorganic sludge, or organic sludge. [Background technology]

[0002] The official method for quantitative analysis of phosphate ions contained in test water such as inorganic wastewater, organic wastewater, inorganic sludge, or organic sludge is based on the molybdenum blue (ascorbic acid reduction) spectrophotometric method (JIS K 0102-2016) specified in the industrial wastewater testing method.

[0003] In the molybdenum blue spectrophotometric method, phosphate ions react with hexaammonium heptamolybdate and potassium tartrateantimonate(III) in an acidic solution to produce a heteropoly compound of antimony-phosphomolybdic acid, which is reduced with L(+)-ascorbic acid. The absorbance of the resulting molybdenum blue is measured to determine the amount of phosphate ions (orthophosphate phosphorus, PO4 3- The quantitative range is 25 to 75 μg, the repeatability is 2 to 1.0%, and the required sample volume is 25 mL (JIS K 0102-2016 46.1.1).

[0004] Because the molybdenum blue absorptiometry method limits the quantitative range to low concentrations, pretreatment of the test water requires sludge separation, ultrafiltration, and dilution, making the procedure cumbersome and difficult to perform frequently. Furthermore, the test water after quantitative analysis contains molybdenum, a soluble heavy metal, necessitating wastewater treatment. To reduce measurement errors associated with dilution, a method has been proposed in which a phosphate ion insolubilizing reagent is added to the test water to precipitate phosphorus, the precipitate recovered by centrifugation is dissolved in a strong acid, water is added to prepare a titration sample solution, and this sample solution is titrated with an alkaline solution (Japanese Patent Laid-Open Publication No. 138117 / 1981). However, this method also requires cumbersome procedures and is difficult to perform frequently, and does not solve the problem of wastewater treatment required to remove molybdenum.

[0005] Phosphate ion-selective electrodes capable of selectively measuring phosphate ion concentration have been proposed (Japanese Patent Laid-Open Publication Nos. 4-130262 and 2002-90332). However, to the inventors' knowledge, no phosphate ion-selective electrode capable of easily measuring the phosphate ion concentration of test water such as inorganic wastewater, organic wastewater, inorganic sludge, or organic sludge without complicated pretreatment has been put into practical use. There remains a need for a quantitative analysis method and apparatus capable of easily measuring the phosphate ion concentration contained in test water, particularly inorganic wastewater, organic wastewater, inorganic sludge, or organic sludge, which exhibit large variations in properties. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 56-138117 [Patent Document 2] Japanese Patent Application Publication No. 4-130262 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-90332 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a quantitative analysis method and apparatus capable of easily measuring the phosphate ion concentration in test water, and in particular, a quantitative analysis method and apparatus capable of easily measuring the phosphate ion concentration in test water such as inorganic wastewater, organic wastewater, inorganic sludge, or organic sludge, which have particularly large variations in properties. [Means for solving the problem]

[0008] The present invention provides the following method for quantitatively analyzing phosphate ions. [1] A predetermined amount of test water is introduced into a reaction vessel having an ion-selective electrode; A cationic agent that insolubilizes phosphate ions is added to the test water, and the detection of dissolved cations is monitored using an ion-selective electrode. A method for quantitatively analyzing phosphate ions, comprising calculating the phosphate ion concentration in test water using Equation 1 based on the amount of cations that have reacted with phosphate ions.

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[0009] The present invention also provides the following phosphate ion quantitative analysis device. [9] A phosphate ion quantitative analyzer, a reaction vessel provided with an ion-selective electrode; a test water introducing means for introducing test water into the reaction tank; a cationic agent adding means for adding a cationic agent that insolubilizes phosphate ions to the reaction tank; A phosphate ion quantitative analysis device comprising:

[10] The phosphate ion quantitative analysis device according to the above [9], further comprising a solid-liquid separation means for separating the test water into solid and liquid, in a stage preceding the test water introduction means. [Effects of the Invention]

[0010] According to the phosphate ion quantitative analysis method of the present invention, the phosphate ion concentration contained in test water, particularly in test water such as inorganic wastewater, organic wastewater, inorganic sludge, or organic sludge, which has large fluctuations in properties, can be easily measured.

[0011] The method for quantitatively analyzing phosphate ions of the present invention is not limited to a low concentration range as in the molybdenum blue absorptiometry method, and can quantitatively analyze high concentrations of phosphate ions. Furthermore, since there is no need to dilute the test water, measurement errors are less likely to occur.

[0012] Furthermore, the method for quantitatively analyzing phosphate ions of the present invention does not use molybdenum, which is used in molybdenum blue absorptiometry, and therefore does not require treatment to remove soluble heavy metals from waste liquid after analysis.

[0013] Furthermore, the method for quantitatively analyzing phosphate ions of the present invention does not require complicated operations such as those required in molybdenum blue absorptiometry, and allows frequent quantitative analysis of phosphate ion concentration. Therefore, it is possible to timely analyze the phosphate ion concentration in inorganic wastewater, organic wastewater, inorganic sludge, organic sludge, or the like, which exhibit large variations in properties, and thereby realize optimal wastewater treatment conditions. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a flowchart of a method for quantitatively analyzing phosphate ions according to the present invention. [Figure 2] 1 is a flowchart of a method for quantitatively analyzing phosphate ions according to one embodiment of the present invention. [Figure 3] 4 is a flowchart of a method for quantitatively analyzing phosphate ions according to another embodiment of the present invention. [Figure 4] 4 is a flowchart of a method for quantitatively analyzing phosphate ions according to another embodiment of the present invention. [Figure 5]FIG. 1 is a schematic explanatory diagram showing one embodiment of a phosphate ion quantitative analyzer of the present invention (with pretreatment). [Figure 6] FIG. 1 is a schematic explanatory diagram showing one embodiment of a phosphate ion quantitative analyzer of the present invention (without pretreatment). [Figure 7] 2 is a graph showing the adjusted phosphate ion concentration in Example 1 and the analytical value obtained by the phosphate ion quantitative analysis method of the present invention. [Figure 8] 1 is a graph showing the phosphate ion concentration obtained by the official method when pretreatment is performed in Example 2 and the analytical value obtained by the phosphate ion quantitative analysis method of the present invention. [Figure 9] 1 is a graph showing the phosphate ion concentration obtained by the official method without pretreatment in Example 2 and the analytical value obtained by the phosphate ion quantitative analysis method of the present invention. [Figure 10] 1 is a graph showing the adjusted phosphate ion concentration in Example 3 and the analytical value obtained by the phosphate ion quantitative analysis method of the present invention. [Figure 11] 1 is a graph showing the phosphate ion concentration obtained by the official method when pretreatment is performed in Example 3 and the analytical value obtained by the phosphate ion quantitative analysis method of the present invention. [Figure 12] 1 is a graph showing the phosphate ion concentration obtained by the official method without pretreatment in Example 3 and the analytical value obtained by the phosphate ion quantitative analysis method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention will be described in detail below with reference to the accompanying drawings, but the present invention is not limited thereto.

[0016] The reaction between phosphate ions and cationic drugs can be represented by the following equation:

[0017] [ka]

[0018] As shown in the above reaction formula (1) or (2), when a cationic agent (calcium salt in reaction formula (1) or magnesium salt in reaction formula (2)) is added in an amount exceeding the stoichiometric ratio of each cation to phosphate ions, the cations not consumed in the insolubilization reaction (Ca in reaction formula (1)) are absorbed. 2+ In reaction (2), Mg 2+ ) remain, and the soluble cations are detected by an ion-selective electrode (a calcium ion-selective electrode in reaction equation (1), and a magnesium ion-selective electrode in reaction equation (2)). The point at which the soluble cation detection by the ion-selective electrode rises sharply is the end point of the insolubilization reaction (the end point of the titration). The amount of phosphate ions in the stoichiometric ratio to the amount of cations (calcium ions in reaction equation (1), magnesium ions in reaction equation (2)) just before the end of the titration is the phosphate ion concentration in the test water.

[0019] In addition, in the above reaction formula (2), when magnesium salt is added as a cationic agent, NH4 + is consumed, and the soluble cation (NH4 + The end point of the insolubilization reaction (titration end point) is when the fluctuations in the soluble cation detection by the ion-selective electrode cease to exist, and the amount of phosphate ions in the stoichiometric ratio to the amount of cations (magnesium ions) added just before the end of the titration is the phosphate ion concentration in the test water.

[0020]

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[0021] For example, in reaction formula (1), 3 moles of phosphate ions react with 5 moles of calcium ions, and in reaction formula (2), 1 mole of phosphate ions reacts with 1 mole of magnesium ions or ammonium ions. Therefore, in reaction formula (1), α in the above formulas 1 to 3 is 3 / 5, and in reaction formula (2), α in the above formulas 1 to 3 is 1.

[0022] FIG. 1 shows a flowchart of the method for quantitatively analyzing phosphate ions according to the present invention. A predetermined amount A0 (L) of test water is introduced into a reaction tank equipped with an ion-selective electrode (step S1), a cationic agent that insolubilizes phosphate ions is added to the test water (step S2), the detection of soluble cations by the ion-selective electrode is monitored (step S3), and the phosphate ion concentration in the test water is calculated according to the above formula 1 based on the amount of cations that have reacted with phosphate ions, which is determined by the detection trend of the soluble cations (step S4).

[0023] In the phosphate ion quantitative analysis method of the present invention, the phosphate ion concentration can be calculated by detecting soluble cations in either of two ways: (A) adding a constant amount of cationic reagent and determining the amount of cationic reagent added from the end point of the insolubilization reaction at which the soluble cation concentration rises sharply or stops fluctuating (titration method); or (B) adding an excess amount of cationic reagent and determining the amount of cations consumed that have reacted with phosphate ions up to the point at which the soluble cation concentration stops fluctuating.

[0024] FIG. 2 shows a flowchart of (A) a method for quantitatively analyzing phosphate ions in the case of a titration method for determining the amount of cation added from the end point of the insolubilization reaction. First, a predetermined amount A0 (L) of test water is introduced into a reaction vessel equipped with an ion-selective electrode (Step S1). Next, a cationic reagent that insolubilizes phosphate ions is added to the test water at a predetermined concentration M (mg / L) and a constant flow rate L (L / hr) (Step S2-1). Detection of the cations by the ion-selective electrode is monitored (Step S3). Steps S2-1 to S3 are repeated until the soluble cation concentration increases rapidly (Step S4-1-1). If the cation concentration increases rapidly, the endpoint is determined to be the point immediately before the increase (Step S4-1-2). Based on the amount A (L) of cationic reagent added at the endpoint of the titration (= L (L / hr) × [time elapsed until the titration endpoint] (hr)) and the concentration M (mg / L), the phosphate ion concentration (mg-P / L) is calculated according to the following Equation 2 (Step S4-1-3).

[0025]

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[0026] FIG. 3 shows a flowchart of another embodiment of Method (A). First, a predetermined amount of test water, A0 (L), is introduced into a reaction vessel equipped with an ion-selective electrode (Step S1). Next, a cationic reagent that insolubilizes phosphate ions is added to the test water at a predetermined concentration, M (mg / L), and a constant flow rate, L (L / hr) (Step S2-1). Detection of the cations by the ion-selective electrode is monitored (Step S3). Steps S2-1 to S3 are repeated until the concentration of the dissolved cations ceases to fluctuate (Step S4-1-1'). The point immediately before the cation concentration ceases to fluctuate is designated as the titration endpoint (Step S4-1-2'). The phosphate ion concentration (mg-P / L) is calculated according to Equation 2 above based on the amount of cationic reagent added at the titration endpoint, A (L) (= L (L / hr) × [time elapsed until the titration endpoint] (hr)) and the concentration, M (mg / L) (Step S4-1-3).

[0027] FIG. 4 shows a flowchart of (B) a method for quantitatively analyzing phosphate ions in the case of a method for determining the amount of cations consumed that have reacted with phosphate ions. First, a predetermined amount A0 (L) of test water is introduced into a reaction vessel equipped with an ion-selective electrode (Step S1). Next, a predetermined concentration M (mg / L) of a cationic reagent for insolubilizing phosphate ions is introduced into the test water, in an excess amount A1 (L) (Step S2-2). The detection of soluble cations by the ion-selective electrode is monitored (Step S3). Step S3 is repeated until the soluble cation concentration stops fluctuating (Step S4-2-1). The soluble cation concentration M1 (mg / L) at the point where the soluble cation concentration stops fluctuating is determined. The phosphate ion concentration in the test water is calculated according to the following Equation 3 based on the consumption of the cationic reagent, which is calculated from the difference between the amount of cations added (M (mg / L) × A1 (L)) and the amount of soluble cations at the point where the soluble cation concentration stops fluctuating (M1 (mg / L) × A0 (L)) (Step S-4-2-2).

[0028]

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[0029] As cationic reagents used in the phosphate quantitative analysis method of the present invention, calcium chloride, calcium hydroxide, magnesium chloride, and magnesium hydroxide are particularly preferred, with neutral salts with little pH fluctuation, such as calcium chloride and magnesium chloride, being even more preferred. When the ammonium ions contained in the test solution are in a concentration ratio of ammonium nitrogen (NH4-N) to phosphate phosphorus (PO4-P) of 1.6 or less, preferably 0.45 or less, or more preferably no ammonium ions, it is preferable to use the above cationic reagents other than magnesium salts. When the ammonium ions contained in the test solution are in a concentration ratio of ammonium nitrogen to phosphate phosphorus of more than 1.6, it is preferable to use magnesium salts as cationic reagents.

[0030] If the concentration ratio of ammonium ions contained in the test solution (ammonium nitrogen to phosphate phosphorus) exceeds 1.6, a magnesium salt can be used as a cationic reagent to detect ammonium ions as a soluble cation. Calculation of the phosphate ion concentration by detecting ammonium ions can be performed in two ways: (A) by adding a fixed amount of magnesium ions, ammonium ions and phosphate ions are consumed according to the above reaction formula (2), and the amount of magnesium ions added is determined from the end point of the insolubilization reaction at which no decrease in the ammonium ion concentration is observed (titration method); or (B) by adding an equal or greater amount of magnesium ions, the amount of ammonium ions consumed by reaction with phosphate ions is determined up to the point at which the ammonium ion concentration no longer fluctuates.

[0031] An ion-selective electrode is an electrode that generates a potential in response to the activity of a specific ion (JIS K0122-1997 3.(1)). In the method for quantitatively analyzing phosphate ions of the present invention, an ion-selective electrode that generates a potential in response to the activity of a cation derived from a cationic drug that insolubilizes phosphate ions is used. An example of a combination of a cationic drug and an ion-selective electrode is a combination of a calcium salt and calcium ions (Ca 2+) selective electrode, magnesium salt and magnesium ion (Mg 2+ ) selective electrode, magnesium salt and ammonium ion (NH4 + ) selective electrodes. Commercially available calcium ion meters, magnesium ion meters, and ammonium ion meters can also be used as these ion selective electrodes. Using an ammonium ion meter, which is becoming increasingly practical, enables inexpensive and highly accurate measurements.

[0032] If the test solution contains coexisting ions that inhibit the reaction of reaction formula (1) or (2) above or inhibitors that reduce the detection sensitivity of the ion-selective electrode, the measurement accuracy can be improved by adding a pH adjuster to control the pH within an appropriate range so that the reaction of reaction formula (1) or (2) above proceeds preferentially, or by using a chelating agent to insolubilize or dilute the coexisting ions, thereby reducing side reactions of the coexisting ions or inhibitors.

[0033] Fluctuations in pH can shift the equilibrium of the insolubilization reaction or alter the ammonium ion concentration, potentially resulting in inaccurate quantitative analysis of phosphate ion concentration. The equilibrium of the insolubilization reaction can also shift depending on the concentrations of calcium, magnesium, and ammonium in reaction equation (1) or (2). The pH of the test solution should be maintained between 7.5 and 8.5, preferably between 7.5 and 8.0, and can be adjusted by adding a pH adjuster as appropriate. Alternatively, the calcium ion, magnesium ion, and ammonium ion concentrations in the test solution before the addition of the cationic reagent can be measured using the corresponding ion-selective electrodes to correct the values ​​measured in the quantitative analysis of phosphate ion.

[0034] Furthermore, because ion-selective electrodes are used under conditions that cause insolubilization reactions, they are prone to scale buildup. To prevent or remove such buildup, it is preferable to periodically or when abnormal measurements are observed to wash or immerse the electrodes in water with low concentrations of acids, chelating agents, or scale-causing substances, such as tap water, industrial water, or process water from treatment facilities, to remove the buildup that can cause scale formation. Physical cleaning, such as ultrasonic cleaning, is also preferable on a regular basis.

[0035] Even when the test water contains a large amount of solids, solid-liquid separation is not essential, and measurement can be easily performed without pretreatment such as solid-liquid separation, but the separated water may be used as the test water. By performing solid-liquid separation in advance, coexisting ions and inhibitors can be removed, allowing the insolubilization reaction to proceed more stably.

[0036] Although the test water to which the phosphate ion quantitative analysis method of the present invention can be applied is not particularly limited, sludge or wastewater containing phosphate ions, or sludge or wastewater containing phosphate ions and ammonia nitrogen are particularly suitable, and specific examples include biologically treated sludge, treated water, and flocculated sludge generated in sewage treatment plants, sewage treatment plants, or private factories. This method is particularly effective for quantitative analysis of phosphate ions in sewage digested sludge, which requires complicated pretreatment such as sufficient dilution to a low concentration range in the official method.

[0037] FIG. 5 shows an embodiment of the phosphate ion quantitative analysis device of the present invention. The phosphate ion quantitative analysis device shown in Figure 5 has a reaction tank 30 equipped with an ion-selective electrode 31, a test water introducing means 10 for introducing test water into the reaction tank 30, a cationic chemical adding means 20 for adding a cationic chemical to the reaction tank 30 to insolubilize phosphate ions, and a waste liquid discharging means 40 for discharging waste liquid from the reaction tank 30.

[0038] The test water introducing means 10 is equipped with a pipe for supplying the test water to the reaction tank 30 and, if necessary, a pump (not shown).

[0039] The cationic chemical adding means 20 includes a pipe 21 for supplying the cationic chemical from the cationic chemical storage tank 22 to the reaction tank 30, and a pump 23 (helicopter pump) for adjusting the amount of the added cationic chemical. In Fig. 5, two sets of the cationic chemical storage tank 22, the pipe 21, and the pump 23 are provided, but one set or three or more sets may be provided depending on the type of cationic chemical used and the amount of the added cationic chemical.

[0040] The reaction vessel 30 is provided with an ion-selective electrode 31. The ion-selective electrode 31 is capable of selectively detecting dissolved cations derived from the cationic drug or ammonium ions in the test water. For example, when a calcium salt is used as the cationic drug, a calcium ion-selective electrode can be used, and when a magnesium salt is used as the cationic drug, a magnesium ion-selective electrode or an ammonium ion-selective electrode can be used. Various commercially available ion meters can also be used as the ion-selective electrode 31.

[0041] The reaction tank 30 is preferably equipped with an agitator 32. The provision of the agitator 32 allows the test water and the cationic chemical to come into uniform and good contact with each other, thereby promoting the insolubilization reaction uniformly and improving the accuracy of detecting the end point of the insolubilization reaction.

[0042] The reaction tank 30 may be provided with a means for introducing clean water or other dilution water, a pH adjuster, or a chelating agent. In FIG. 5, as an example, a clean water supply means 50 for introducing clean water is provided. The clean water supply means 50 includes a pipe for supplying clean water and a pump for adjusting the amount of water added. When the reaction tank 30 is in a standby state where quantitative analysis is not being performed, introducing clean water into the reaction tank 30 can clean the inside of the tank and prevent the accumulation of dirt. Furthermore, keeping clean water in the reaction tank 30 can prevent the adhesion of dirt inside the reaction tank 30.

[0043] The waste liquid discharge means 40 comprises a pipe 41 for discharging the waste liquid from the reaction vessel 30 after the quantitative analysis is completed, and a waste liquid tank 42 for storing the waste liquid.

[0044] Another embodiment of the phosphate ion quantitative analysis device of the present invention is shown in Figure 6. The same components as those of the device shown in Figure 5 are designated by the same reference numerals, and details are omitted.

[0045] The phosphate ion quantitative analyzer shown in FIG. 6 differs from the phosphate ion quantitative analyzer shown in FIG. 5 in that it includes a solid-liquid separation tank 60 having a separation membrane 61 as a solid-liquid separation means, located upstream of the test water introduction means 10. When a large amount of insolubilized matter, such as digested sludge, is contained, the insolubilized matter and substances inhibiting the detection of specific ion species by an ion-selective electrode are removed by solid-liquid separation in advance. By introducing the separated water into the reaction tank 30 as the test water, the insolubilization reaction and the detection of specific ion species in the reaction tank 30 can proceed more stably. The separation membrane can be any conventional solid-liquid separation membrane, such as an organic membrane or a ceramic membrane. While the illustrated embodiment uses a solid-liquid separation tank having a separation membrane as the solid-liquid separation means, the solid-liquid separation means is not limited to this, and any solid-liquid separation means, such as simple precipitation, coagulation precipitation, centrifugation, or flotation, can be used. [Example]

[0046] In the examples, the quantitative analysis method for phosphate ions utilizes a titration method in which, at the point when the concentration of soluble cations due to the cationic drug added in excess of phosphate ions rises sharply, it is determined that all of the phosphate ions contained in the test solution have reacted with the cationic drug and been insolubilized.

[0047] [Example 1] Phosphate ion concentration analysis Using phosphate ion solutions adjusted to phosphate ion concentrations of 100 mg-P / L, 150 mg-P / L, 200 mg-P / L, 250 mg-P / L, and 300 mg-P / L and magnesium chloride (10 mmol) as a cationic agent to insolubilize phosphate ions, quantitative analysis of the phosphate ion concentrations shown in Figure 2 was performed using the quantitative analyzer shown in Figure 5. The results are shown in Table 1 and Figure 7.

[0048] [Table 1]

[0049] The analytical values ​​obtained by the quantitative analysis method of the present invention are within a range of ±10 mg-P / L of the adjusted phosphate ion concentration in the high concentration range of 100 mg-P / L to 300 mg-P / L, where [adjusted phosphate ion concentration] = 0.9395 × [analytical value] + 13.221, R 2 = 0.9978, showing a very good correlation, and it was confirmed that this is a simple analysis method with high accuracy.

[0050] [Example 2] Analysis of phosphate ion concentration in digested sludge Digested sludge from a sewage treatment plant with the properties shown in Table 2 was used as the sample water, and magnesium chloride (10 mmol) was used as the cationic agent to insolubilize the phosphate ions. Quantitative analysis of the phosphate ion concentration shown in Figure 2 was performed using the quantitative analyzer shown in Figure 5 or Figure 6. The results were compared for cases where the digested sludge was passed through a separation membrane to perform solid-liquid separation as a pretreatment for quantitative analysis (Figure 6: with pretreatment), where the digested sludge was analyzed directly without solid-liquid separation (Figure 5: without pretreatment), and where quantitative analysis was performed using the official method (molybdenum blue absorptiometry). The results are shown in Table 3 and Figures 8 (without pretreatment) to 9 (with pretreatment).

[0051] [Table 2]

[0052] [Table 3]

[0053] In the high concentration range of 178 mg-P / L to 315 mg-P / L, the quantitative analysis method of the present invention was found to be within ±10 mg of the analytical values ​​obtained by the official method, regardless of whether the digested sludge was pretreated or not, and was confirmed to be a highly correlated and accurate simple analysis method as shown below. With pre-processing: R 2 =0.986 [Official method phosphate ion concentration] = 0.9424 × [analytical phosphate ion concentration] + 20.274 No pretreatment: R 2 =0.978 [Official method phosphate ion concentration] = 0.8892 × [analytical phosphate ion concentration] + 30.622

[0054] [Example 3] Phosphate ion concentration analysis Using phosphate ion solutions adjusted to phosphate ion concentrations of 10 mg-P / L, 20 mg-P / L, 50 mg-P / L, 75 mg-P / L, and 100 mg-P / L, and calcium chloride (20 mmol) as a cationic agent to insolubilize the phosphate ions, quantitative analysis of the phosphate ion concentrations shown in Figure 2 was performed using the quantitative analyzer shown in Figure 5. The results are shown in Table 4 and Figure 10.

[0055] [Table 4]

[0056] The analytical value obtained by the quantitative analysis method of the present invention is, in the concentration range of 10 mg-P / L to 100 mg-P / L, [adjusted phosphate ion concentration] = 0.8409 × [analytical value] + 6.8019, R 2 = 0.9938, showing a very good correlation, and it was confirmed that this is a simple analysis method with high accuracy.

[0057] [Example 4] Analysis of phosphate ion concentration in mixed raw sludge The sample water was a mixed raw sludge separation solution from a sewage treatment plant with the properties shown in Table 5. Calcium chloride (20 mmol) was used as the cationic agent to insolubilize the phosphate ions. The quantitative analysis of the phosphate ion concentration shown in Figure 2 was performed using the quantitative analyzer shown in Figure 5 or Figure 6. The results were compared for the following cases: pretreatment of the digested sludge by passing it through a separation membrane for solid-liquid separation (Figure 6: with pretreatment); quantitative analysis of the digested sludge without solid-liquid separation (Figure 5: without pretreatment); and quantitative analysis by the official method (molybdenum blue absorptiometry). The results are shown in Table 6 and Figures 11 (with pretreatment) to 12 (without pretreatment).

[0058] [Table 5]

[0059] [Table 6]

[0060] In the concentration range of 8.1 mg-P / L to 39.1 mg-P / L, the quantitative analysis method of the present invention yielded values ​​within a range of ±3 mg-P / L of the analytical value obtained by the official method when the separated liquid from mixed raw sludge was pretreated, and values ​​within a range of ±6 mg-P / L of the analytical value obtained by the official method when the separated liquid from mixed raw sludge was not pretreated.This shows a high correlation as shown below, and it has been confirmed that this is a highly accurate, simple analytical method. With pre-processing: R 2 =0.9638 [Official method phosphate ion concentration] = 0.8948 × [analytical phosphate ion concentration] + 1.9036 No pretreatment: R 2 =0.9138 [Official method phosphate ion concentration] = 1.0006 × [analytical phosphate ion concentration] + 1.0263

[0061] The mixed raw sludge separated liquid used in Example 4 contained 30 to 50 mg / L of ammonium ions, which are inhibitors of calcium detection using a calcium ion meter, and the concentration ratio of ammonium ions (ammonia nitrogen) to phosphate ions (phosphate phosphorus) sometimes exceeded 1.6, which is thought to have resulted in a slightly lower analytical accuracy than in Example 3. In the case of test water containing ammonium ions with a concentration ratio of ammonium ions (ammonia nitrogen) to phosphate ions (phosphate phosphorus) exceeding 1.6, magnesium salts are preferable to calcium salts as cationic reagents, while in the case of test water containing ammonium ions with a concentration ratio of ammonium ions (ammonia nitrogen) to phosphate ions (phosphate phosphorus) of 1.6 or less, calcium salts are preferable as cationic reagents.

[0062] It has been confirmed that the present invention provides a simple analytical method for phosphate ions that does not require the pretreatment of test water, such as sludge separation, ultrafiltration, and dilution, which have been conventionally required, and the post-treatment of heavy metals such as molybdenum after analysis. [Explanation of symbols]

[0063] 10: Means of introducing test water 20: Cationic drug addition means 21: Piping 22: Cationic drug storage tank 23: Cationic drug addition amount adjustment means (pump) 30: Reactor 31: Ion-selective electrode 40: Waste liquid discharge means 41: Pipe for discharging waste liquid 42: Waste liquid tank 50:Water supply means 60: Solid-liquid separation means (solid-liquid separation tank)

Claims

1. A predetermined amount of test water is introduced into a reaction vessel having an ion-selective electrode; A cationic agent that insolubilizes phosphate ions is added to the test water, and the detection of dissolved cations is monitored using an ion-selective electrode. A method for quantitatively analyzing phosphate ions, comprising calculating the phosphate ion concentration in test water using Equation 1 based on the amount of cations that have reacted with phosphate ions. [Equation 1]

2. The method for quantitatively analyzing phosphate ions according to claim 1, A predetermined amount of test water A (L) is introduced into a reaction vessel having an ion-selective electrode. A cationic agent that insolubilizes phosphate ions is added to the test water at a predetermined concentration M (mg / L), and the detection of soluble cations using an ion-selective electrode is monitored to determine the end point of the insolubilization reaction. A method for quantitatively analyzing phosphate ions, comprising calculating the phosphate ion concentration (mg-P / L) in the test solution using the following formula 2 based on the amount of cations reacted with the phosphate ions [M (mg / L) x A (L)], which is determined from the amount A (L) of cationic reagent added up to the end point of the insolubilization reaction and the concentration M (mg / L) of the cationic reagent: [Equation 2]

3. The method for quantitatively analyzing phosphate ions according to claim 1, A predetermined amount of test water A (L) is introduced into a reaction vessel having an ion-selective electrode. A cationic agent that insolubilizes phosphate ions is added to the test water at a predetermined concentration M (mg / L) and a predetermined amount A1 (L), the concentration of soluble cations is measured using an ion-selective electrode, and the soluble cation concentration M1 (mg / L) at the point where the soluble cation concentration no longer fluctuates is determined. A method for quantifying phosphate ions, comprising calculating the phosphate ion concentration in test water by the following formula 3 based on the consumption amount of cationic chemicals, which is determined from the difference between the amount of added cations, M (mg / L) × A1 (L), and the amount of soluble cations at the point where the soluble cation concentration no longer fluctuates, M1 (mg / L) × A0 (L). [Equation 3]

4. 4. The method for quantitative analysis of phosphate ions according to claim 1, wherein the cationic agent is a magnesium salt or a calcium salt.

5. 4. The method for quantitatively analyzing phosphate ions according to claim 1, wherein the test water is inorganic wastewater, organic wastewater, inorganic sludge, or organic sludge.

6. The test water is inorganic wastewater, organic wastewater, inorganic sludge, or organic sludge, in which the concentration ratio of ammonium nitrogen to phosphate phosphorus is 1.6 or less; 4. The method for quantitatively analyzing phosphate ions according to claim 1, wherein the cationic agent is a calcium salt.

7. The test water is inorganic wastewater, organic wastewater, inorganic sludge, or organic sludge, in which the concentration ratio of ammonium nitrogen to phosphate phosphorus is greater than 1.6; 4. The method for quantitatively analyzing phosphate ions according to claim 1, wherein the cationic agent to be added is a magnesium salt, and the soluble cation to be detected is an ammonium ion.

8. The method for quantitatively analyzing phosphate ions according to any one of claims 1 to 3, further comprising reducing side reactions of coexisting ions or inhibitors in the test water by performing one or more of the following steps (1) to (3): (1) Adding a pH adjuster to control the pH within an appropriate range; (2) Adding a chelating agent to insolubilize coexisting ions; (3) Dilution.

9. A phosphate ion quantitative analyzer, a reaction vessel provided with an ion-selective electrode; a test water introducing means for introducing test water into the reaction tank; a cationic agent adding means for adding a cationic agent that insolubilizes phosphate ions to the reaction tank; A phosphate ion quantitative analysis device comprising:

10. 10. The phosphate ion quantitative analysis apparatus according to claim 9, further comprising a solid-liquid separation means for separating the test water into solid and liquid, located upstream of said test water introduction means.

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