Water quality analyzer and water quality analysis method

Abstract

According to the present invention, a correction calculation unit 102 corrects absorbance by performing calculation by using a correction equation on the basis of the absorbance calculated by an absorbance calculation unit 101 at each wavelength. A turbidity component detection processing unit 103 provides a turbidity standard solution to an oxidation reaction unit, irradiates the turbidity standard solution after oxidation reaction with measurement light from a light source 51, and causes a detector 52 to detect the intensities at a plurality of wavelengths of the measurement light that has passed through the turbidity standard solution. A correction coefficient update processing unit 104 calculates the absorbance at each wavelength by means of the absorbance calculation unit 101 on the basis of the intensities, which are detected by the turbidity component detection processing unit 103, at the plurality of wavelengths, and updates update coefficients stored in the storage unit 200 on the basis of the absorbance calculated at each wavelength.

Description

[Technical Field]

[0001] The present invention relates to a water quality analyzer and a water quality analysis method that can measure the total nitrogen concentration in sample water. [Background technology]

[0002] For example, water quality analyzers such as total nitrogen and total phosphorus analyzers are equipped with a reactor that oxidizes components in sample water. The sample water after the oxidation reaction in the reactor is supplied to a measurement cell, and measurement light from a light source is irradiated onto the sample water in the measurement cell. The measurement light that passes through the sample water in the measurement cell is detected by a detector, and the absorbance of the target component in the sample water is calculated based on the detection intensity of this detector (see, for example, Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-80441 Summary of the Invention [Problem to be solved by the invention]

[0004] When turbidity components are present in the sample water, the absorbance of the target component (e.g., nitrogen oxides) is absorbed in addition to the turbidity components, making it impossible to accurately calculate the absorbance of the target component. Therefore, a correction formula can be used to correct the absorbance and remove the effect of the turbidity components.

[0005] For example, the absorbance at each wavelength may be calculated based on the detection intensities at the measurement wavelength corresponding to the total nitrogen in the sample water and the turbidity correction wavelength corresponding to the turbidity components, and the calculation may be performed by substituting these absorbances as variables into the correction formula. In this case, the correction coefficients included in the correction formula are constants determined in advance by experiment.

[0006] The above-described correction coefficients are constants determined through experiments, and therefore do not normally need to be changed frequently. However, the inventors have conducted extensive research from the perspective of setting more appropriate correction coefficients, and have come to the following conclusions.

[0007] First, when sample water containing turbidity components is subjected to an oxidation reaction in a reactor, the morphology of the turbidity components may change. Specifically, the particle size of the turbidity components may change as a result of the oxidation reaction, which may also change the particle size-dependent absorbance. In this case, unless the correction coefficient is changed according to the change in particle size of the turbidity components, an error may occur in the corrected absorbance.

[0008] Furthermore, the amount of decomposition of the oxidizing agent used in the oxidation reaction may be affected by turbidity components. Specifically, if the sample water contains turbidity components, the turbidity components may inhibit the decomposition of the oxidizing agent, resulting in a large amount of oxidizing agent remaining after the oxidation reaction. Oxidizing agents such as potassium peroxodisulfate absorb at the measurement wavelength, so if the amount of this type of oxidizing agent remaining increases, the absorbance at the measurement wavelength may increase.

[0009] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a water quality analyzer and a water quality analysis method that can appropriately correct absorbance when measuring the total nitrogen concentration in sample water that contains turbidity components. [Means for solving the problem]

[0010] A first aspect of the present invention is a water quality analyzer capable of measuring the total nitrogen concentration in sample water containing turbidity components, comprising an oxidation reaction unit, a light source, a detector, an absorbance calculation unit, a correction calculation unit, a memory unit, a turbidity component detection processing unit, and a correction coefficient update processing unit. The oxidation reaction unit oxidizes components in the sample water. The light source irradiates measurement light onto the sample water after the oxidation reaction in the oxidation reaction unit. The detector detects the intensity at multiple wavelengths of the measurement light that has passed through the sample water. The absorbance calculation unit calculates the absorbance at each wavelength based on the intensities at the multiple wavelengths detected by the detector. The correction calculation unit corrects the absorbance by performing calculations using a correction formula based on the absorbance at each wavelength calculated by the absorbance calculation unit. The memory unit stores correction coefficients included in the correction formula. The turbidity component detection processing unit supplies a turbidity standard solution to the oxidation reaction unit, and irradiates the turbidity standard solution after the oxidation reaction with measurement light from the light source, thereby causing the detector to detect the intensities at the plurality of wavelengths of the measurement light that has passed through the turbidity standard solution. The correction coefficient update processing unit calculates the absorbance at each wavelength using the absorbance calculation unit based on the intensities at the plurality of wavelengths detected by the turbidity component detection processing unit, and updates the correction coefficient stored in the memory unit based on the calculated absorbance at each wavelength.

[0011] A second aspect of the present invention is a water quality analysis method capable of measuring the total nitrogen concentration in sample water containing turbidity components, comprising the steps of: oxidizing the components in the sample water; irradiating the sample water after the oxidation reaction with measurement light; detecting the intensity at multiple wavelengths of the measurement light that has passed through the sample water; calculating the absorbance at each wavelength based on the detected intensities at the multiple wavelengths; correcting the absorbance by performing an operation using a correction formula based on the calculated absorbance at each wavelength; storing the correction coefficient included in the correction formula; oxidizing the components in a turbidity standard solution; irradiating the turbidity standard solution after the oxidation reaction with measurement light; detecting the intensity at the multiple wavelengths of the measurement light that has passed through the turbidity standard solution; calculating the absorbance at each wavelength based on the detected intensities at the multiple wavelengths; and updating the stored correction coefficient based on the calculated absorbance at each wavelength. [Effects of the Invention]

[0012] According to the present invention, by supplying a turbidity standard solution to the oxidation reaction section in the same manner as when analyzing sample water, the correction coefficient stored in the memory section can be updated to an appropriate value based on the detected intensity of the measurement light that has passed through the turbidity standard solution after the oxidation reaction, thereby making it possible to appropriately correct the absorbance when measuring the total nitrogen concentration in sample water containing turbidity components. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing an example of the configuration of a water quality analyzer according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the electrical configuration of the water quality analyzer of FIG. 1. [Figure 3] 10A and 10B are diagrams for explaining a specific example of turbidity correction calibration. [Figure 4] 2 is a flowchart showing an example of a water quality analysis method using the water quality analyzer of FIG. 1. [Figure 5]10 is a flowchart showing an example of calibration for turbidity correction. [Figure 6] FIG. 10 is a block diagram showing a modified example of the water quality analyzer. DETAILED DESCRIPTION OF THE INVENTION

[0014] 1. Overall configuration of the water quality analyzer Fig. 1 is a schematic diagram showing an example of the configuration of a water quality analyzer according to one embodiment of the present invention. The water quality analyzer according to this embodiment is a total nitrogen and total phosphorus analyzer capable of measuring the total nitrogen concentration (TN concentration) and total phosphorus concentration (TP concentration) of sample water, and Fig. 1 shows only the configuration related to the flow path of liquids such as sample water.

[0015] The sample water may be sewage, river water, or industrial wastewater, and contains various components such as nitrogen compounds and phosphorus compounds. The nitrogen compounds in the sample water exist as, for example, nitrate ions, nitrite ions, ammonium ions, and organic nitrogen. When measuring the total nitrogen concentration in the sample water, all nitrogen compounds in the sample water are oxidized to generate nitrogen oxides (nitrate ions), and the concentration of these nitrogen oxides is then measured.

[0016] Furthermore, phosphorus compounds in sample water exist as, for example, phosphate ions, hydrolyzable phosphorus, and organic phosphorus. When measuring the total phosphorus concentration in sample water, all phosphorus compounds in the sample water are oxidized to generate phosphorus oxides (phosphate ions), and the concentrations of these phosphorus oxides are measured.

[0017] In addition to the target components to be measured, such as nitrogen oxides or phosphorus oxides, the sample water also contains turbidity components. Turbidity components are components other than the target components that cause the sample water to become cloudy. When the sample water contains turbidity components, irradiating the sample water with light results in light absorption not only by the target components but also by the turbidity components.

[0018] The water quality analyzer according to this embodiment includes, for example, a first multiport valve 1, a second multiport valve 2, a syringe 3, a reactor 4, a measurement cell 5, a stirring pump 6, a discharge pump 7, a first switching valve 8, and a second switching valve 9. These components are connected to each other via piping.

[0019] The first multiport valve 1 and the second multiport valve 2 are, for example, eight-port valves, each having one common port and eight ports (ports 1 to 8) that can be selectively connected to the common port. In Fig. 1, the ports of the first multiport valve 1 and the second multiport valve 2 are denoted by numbers "1" to "8" corresponding to the first to eighth ports, respectively.

[0020] The common port of the first multiport valve 1 is connected to the first port of the second multiport valve 2. The common port of the second multiport valve 2 is connected to the syringe 3. The syringe 3 is provided with, for example, a cylindrical body 31 and a plunger 32, and by displacing the plunger 32 inserted into the cylindrical body 31, the syringe 3 can be sucked in and discharged out.

[0021] A turbidity standard solution storage section 10 storing a turbidity standard solution is connected to the first port of the first multiport valve 1. During operation of the water quality analyzer, the turbidity standard solution in the turbidity standard solution storage section 10 may be stirred by a stirring device (not shown). By performing a suction operation with the syringe 3 while the first port of the first multiport valve 1 and the common port are connected and the first port of the second multiport valve 2 and the common port are connected, the turbidity standard solution can be supplied into the syringe 3. The turbidity standard solution is a solution containing components that serve as a reference when determining turbidity. An example of the turbidity standard solution is a kaolin solution, but the turbidity standard solution is not limited to this; any other turbidity standard solution can be stored in the turbidity standard solution storage section 10.

[0022] Sample water is supplied online to the second port of the first multiport valve 1 via piping from a sample water supply source such as a drainage facility. Therefore, by connecting the second port of the first multiport valve 1 to the common port and connecting the first port of the second multiport valve 2 to the common port and then performing a suction operation with the syringe 3, sample water can be supplied online into the syringe 3. In this case, the sample supplied online is subjected to a predetermined pretreatment, for example, by a pretreatment device (not shown), before being supplied to the second port. However, this is not limited to online, and sample water that has been collected in advance and set in the water quality analyzer may also be supplied offline.

[0023] Reagent reservoirs 21-26, each storing a different reagent, are connected to the second to seventh ports of the second multiport valve 2. By connecting any of these ports to the common port and performing a suction operation with the syringe 3, the reagent can be supplied into the syringe 3 and mixed with the sample water. Examples of reagents stored in the reagent reservoirs 21-26 include sulfuric acid, molybdic acid, ascorbic acid, sodium hydroxide, potassium peroxodisulfate, and hydrochloric acid, but are not limited to these, and any other reagent can be stored in the reagent reservoirs 21-26.

[0024] A dilution water reservoir 12 is connected to the sixth port of the first multiport valve 1. The dilution water reservoir 12 stores dilution water that is used when diluting sample water or when cleaning the reactor 4 or the measurement cell 5. For example, pure water can be used as the dilution water. When the sixth port of the first multiport valve 1 is connected to the common port and the first port of the second multiport valve 2 is connected to the common port, and a suction operation is performed using the syringe 3, dilution water can be supplied into the syringe 3 and mixed with the sample water.

[0025] In this way, by appropriately switching the first multiport valve 1 and the second multiport valve 2 and performing a suction operation with the syringe 3, a mixture of sample water, reagent, and dilution water can be produced in the syringe 3. The mixture in the syringe 3 is stirred by driving the stirring pump 6. The fourth port of the first multiport valve 1 is connected to the reactor 4, and by communicating the fourth port with the common port and communicating the first port of the second multiport valve 2 with the common port, the mixture in the syringe 3 can be supplied to the reactor 4 by performing a discharge operation with the syringe 3.

[0026] In the reactor 4, ultraviolet light is irradiated onto the liquid inside from the light source 41. When the sample water, reagent, and dilution water are supplied to the reactor 4 as a mixed liquid, various components in the sample water, such as nitrogen compounds and phosphorus compounds, can be oxidized by irradiating the mixed liquid with ultraviolet light from the light source 41. In other words, the reactor 4 constitutes an oxidation reaction section that oxidizes the components in the sample water. At this time, the reagent in the mixed liquid can function as an oxidizing agent. Potassium peroxodisulfate, for example, may be used as the oxidizing agent. However, the oxidation reaction in the reactor 4 is not limited to a configuration in which it is performed by ultraviolet light irradiation, and it may also be configured to perform the oxidation reaction in other ways, such as by controlling the pressure and temperature.

[0027] On the other hand, after supplying the turbidity standard solution into the syringe 3, the fourth port and the common port are communicated, and the first port of the second multiport valve 2 is also communicated with the common port. In this state, the turbidity standard solution in the syringe 3 can be supplied to the reactor 4 by performing a discharge operation using the syringe 3. In this case, an oxidizing agent may be mixed with the turbidity standard solution by aspirating a reagent (e.g., potassium peroxodisulfate) into the syringe 3. Alternatively, an alkaline atmosphere may be created in the turbidity standard solution by aspirating a reagent such as sodium hydroxide into the syringe 3. When the turbidity standard solution is supplied to the reactor 4, ultraviolet light is irradiated onto the turbidity standard solution from the light source 41.

[0028] The light source 41 may be, for example, a low-pressure mercury lamp, but is not limited thereto and other light sources 41 such as an excimer laser, a deuterium lamp, a xenon lamp, or an Hg-Zn-Pb lamp may also be used. The liquid in the reactor 4 is heated by, for example, a heater (not shown). At this time, the temperature of the liquid is controlled to a preset temperature based on a detection signal from a temperature sensor (not shown) that detects the temperature of the liquid in the reactor 4.

[0029] The liquid after the oxidation reaction in reactor 4 is supplied into syringe 3 by the suction operation using syringe 3. Measurement cell 5 is connected to the seventh port of first multiport valve 1, and by performing a discharge operation using syringe 3 while the seventh port is connected to the common port and the first port of second multiport valve 2 is connected to the common port, the liquid after the oxidation reaction in syringe 3 can be supplied to measurement cell 5.

[0030] The liquid after the oxidation reaction (mixed liquid or turbidity standard solution) in the measurement cell 5 is irradiated with measurement light from a light source 51. As the light source 51, for example, a xenon lamp that irradiates white light can be used, but the light source is not limited to this, and other light sources 51 such as a deuterium lamp or a tungsten lamp may also be used. Note that if the liquid after the oxidation reaction (mixed liquid or turbidity standard solution) drawn into the syringe 3 is in an alkaline atmosphere, a reagent such as hydrochloric acid may be drawn into the syringe 3 to make the liquid after the oxidation reaction in an acidic atmosphere, and then the liquid may be supplied to the measurement cell 5.

[0031] The measurement light transmitted through the measurement cell 5 is detected by a detector 52 such as a photodiode. When a mixed liquid (mixture of sample water, reagent, and dilution water) after the oxidation reaction is supplied into the measurement cell 5, the measurement light transmitted through the mixed liquid is detected by the detector 52, and the total nitrogen concentration or total phosphorus concentration in the sample water can be measured based on the detection signal. The liquid in the measurement cell 5 is heated, for example, by a heater (not shown). At this time, the temperature of the liquid in the measurement cell 5 is controlled to a preset temperature based on a detection signal from a temperature sensor (not shown) that detects the temperature of the liquid.

[0032] It is also possible to individually introduce dilution water into the reactor 4 and the measurement cell 5. That is, by individually drawing dilution water into the syringe 3 and then flowing the dilution water from the syringe 3 into the reactor 4, the inside of the reactor 4 can be cleaned. Furthermore, by individually drawing dilution water into the syringe 3 and then flowing the dilution water from the syringe 3 into the measurement cell 5, the inside of the measurement cell 5 can be cleaned.

[0033] When performing zero calibration, the sixth port of the first multiport valve 1 is connected to the common port, and the first port of the second multiport valve 2 is connected to the common port. With this in mind, a suction operation is performed using the syringe 3, thereby supplying dilution water from the dilution water reservoir 12 into the syringe 3. Thereafter, the seventh port of the first multiport valve 1 is connected to the common port, and a discharge operation is performed using the syringe 3, thereby supplying dilution water into the measurement cell 5 and performing zero calibration.

[0034] A span liquid reservoir 11 is connected to the third port of the first multiport valve 1. Span liquid used for span calibration is stored in the span liquid reservoir 11. When the third port of the first multiport valve 1 is connected to the common port and the first port of the second multiport valve 2 is connected to the common port, the span liquid can be supplied from the span liquid reservoir 11 into the syringe 3 by performing a suction operation with the syringe 3. Then, the seventh port of the first multiport valve 1 is connected to the common port and a discharge operation with the syringe 3 is performed, thereby supplying the span liquid into the measurement cell 5 and performing span calibration.

[0035] Two standard sample reservoirs 13 and 14 are connected to the eighth port of the first multiport valve 1 via a first switching valve 8. Standard samples are stored in the standard sample reservoirs 13 and 14, respectively, with one standard sample reservoir 13 storing a standard sample for measuring the total nitrogen concentration and the other standard sample reservoir 14 storing a standard sample for measuring the total phosphorus concentration. The first switching valve 8 switches the flow path to selectively connect either one of the two standard sample reservoirs 13 and 14 to the eighth port.

[0036] By performing a suction operation with syringe 3 while the eighth port of first multiport valve 1 is connected to the common port and the first port of second multiport valve 2 is connected to the common port, the standard sample can be supplied from one of two standard sample reservoirs 13, 14 into syringe 3. Thereafter, by connecting the seventh port of first multiport valve 1 to the common port and performing a discharge operation with syringe 3, the standard sample can be supplied into measurement cell 5.

[0037] The liquid in the measurement cell 5 is discharged outside the device. The liquid in the reactor 4 is also discharged outside the device by driving the discharge pump 7. The fifth port of the first multiport valve 1 is connected to a waste liquid destination and a drainage destination via a second switching valve 9. The second switching valve 9 can selectively direct the liquid in the device to either the waste liquid destination or the drainage destination by switching the flow path.

[0038] 2. Electrical configuration of the water quality analyzer Figure 2 is a block diagram showing the electrical configuration of the water quality analyzer of Figure 1. The operation of this water quality analyzer is controlled by a control unit 100 including, for example, a CPU (Central Processing Unit). In addition to the above-mentioned components, a memory unit 200, an operation unit 300, and the like are electrically connected to the control unit 100.

[0039] The control unit 100 functions as an absorbance calculation unit 101, a correction calculation unit 102, a turbidity component detection processing unit 103, and a correction coefficient update processing unit 104, etc., as a result of the CPU executing a program. The storage unit 200 includes, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), or a hard disk, and stores data necessary for the operation of the water quality analyzer. The operation unit 300 includes, for example, a touch panel, a keyboard, or a mouse, and is operated by the user.

[0040] The absorbance calculation unit 101 calculates the absorbance based on the detection signal from the detector 52. A half mirror, an optical filter (neither of which are shown), and the like are provided between the light source 51 and the detector 52. The measurement light (white light) emitted from the light source 51 is split into multiple light beams by the half mirror before or after passing through the measurement cell 5, and each light beam passes through a different optical filter before entering the detector 52.

[0041] Each optical filter transmits only light of a specific wavelength. In this embodiment, an optical filter that transmits a measurement wavelength (e.g., 220 nm) and an optical filter that transmits a turbidity correction wavelength (e.g., 275 nm) are provided. Measurement light emitted from the light source 51 is split into two lights by a half mirror, and each light passes through a different optical filter, so that the light of the measurement wavelength and the light of the turbidity correction wavelength are incident on the detector 52.

[0042] This allows the detector 52 to detect the intensity at two wavelengths (the measurement wavelength and the turbidity correction wavelength) of the measurement light that has passed through the sample water in the measurement cell 5. However, it is also possible to adopt a configuration in which the measurement light is split into three or more beams by providing multiple half mirrors, and these beams pass through three or more optical filters, respectively, before entering the detector 52. In other words, the detector 52 only needs to be able to detect the intensity at multiple wavelengths.

[0043] The absorbance calculation unit 101 calculates the absorbance at each wavelength based on the intensities of multiple (e.g., two) wavelengths detected by the detector 52. In this embodiment, the measurement wavelength is a wavelength corresponding to the total nitrogen in the sample water, and nitrogen oxides (target components) in the sample water have absorbance at the measurement wavelength. On the other hand, the turbidity correction wavelength is a wavelength corresponding to the turbidity components in the sample water, and the turbidity components in the sample water have absorbance at the measurement wavelength and the turbidity correction wavelength. The turbidity correction wavelength is a longer wavelength than the measurement wavelength.

[0044] The absorbance at each wavelength calculated by the absorbance calculation unit 101 is stored in the storage unit 200. At this time, the absorbance at the measurement wavelength is stored in the storage unit 200 as the measurement absorbance. On the other hand, the absorbance at the turbidity correction wavelength is stored in the storage unit 200 as the turbidity correction absorbance.

[0045] The correction calculation unit 102 performs calculations using the following correction formulas (1) and (2) based on the absorbance at each wavelength (measurement wavelength and turbidity correction wavelength), thereby correcting the absorbance. A=BC (1) C=kD+m (2) Here, A is the absorbance after correction. B is the absorbance at the measurement wavelength (measurement absorbance). C is the absorbance at the turbidity correction wavelength (turbidity correction absorbance) corrected and converted to the absorbance equivalent to the measurement wavelength. D is the absorbance at the turbidity correction wavelength (turbidity correction absorbance). k is the proportional term of the correction coefficient. m is the constant term of the correction coefficient.

[0046] The correction calculation unit 102 performs a calculation to substitute the measurement absorbance B and the turbidity correction absorbance D as variables into the above correction formulas (1) and (2), thereby eliminating the influence of absorbance due to turbidity components and accurately calculating the absorbance of the target component. The correction coefficients k and m are stored in the storage unit 200.

[0047] In this embodiment, a series of operations (turbidity correction calibration) for updating the correction coefficients k and m stored in the memory unit 200 is performed, so that the correction coefficients k and m can be updated to appropriate values. Specifically, the turbidity component detection processing unit 103 supplies the turbidity standard solution from the turbidity standard solution storage unit 10 to the reactor 4, irradiates the turbidity standard solution with ultraviolet light from the light source 41, thereby causing an oxidation reaction of the turbidity standard solution, supplies the turbidity standard solution after the oxidation reaction to the measurement cell 5, and irradiates the turbidity standard solution with measurement light from the light source 51. As a result, the intensity of the measurement light at the measurement wavelength and the turbidity correction wavelength that has passed through the turbidity standard solution after the oxidation reaction is detected by the detector 52.

[0048] In this way, in the turbidity correction calibration, the operations of the first multiport valve 1, the second multiport valve 2, the syringe 3, the light sources 41 and 51, etc. are appropriately controlled by the turbidity component detection processing unit 103. The turbidity correction calibration is started, for example, based on the user's operation of the operation unit 300. In this case, the configuration may be such that an operation screen is displayed on the display unit (not shown), and the user operates the operation unit 300 to input information onto the operation screen.

[0049] In the turbidity correction calibration, the correction coefficient update processing unit 104 causes the absorbance calculation unit 101 to calculate the measurement absorbance and the turbidity correction absorbance based on the intensities at the measurement wavelength and the turbidity correction wavelength detected by the turbidity component detection processing unit 103. Then, the correction coefficient update processing unit 104 updates the correction coefficients k and m stored in the storage unit 200 based on the calculated measurement absorbance and turbidity correction absorbance.

[0050] 3. Turbidity correction calibration 3 is a diagram for explaining a specific embodiment of turbidity correction calibration. In this example, a case will be explained in which a measurement absorbance and a turbidity correction absorbance calculated by a single measurement using a turbidity standard solution are used as one set of absorbance data, and after multiple sets of absorbance data are acquired, the correction coefficients k and m are updated based on the absorbance data.

[0051] Here, "one measurement using a turbidity standard solution" refers to an operation of supplying a turbidity standard solution to the reactor 4, irradiating the turbidity standard solution after the oxidation reaction with measurement light from the light source 51, and detecting the measurement absorbance and the turbidity correction absorbance based on the intensities at the measurement wavelength and the turbidity correction wavelength. In this example, multiple types of turbidity standard solutions with different concentrations are used, and measurements are performed once or multiple times using each turbidity standard solution, thereby obtaining multiple sets of absorbance data. Turbidity standard solutions with different concentrations can be generated by supplying dilution water from the dilution water reservoir 12 into the syringe 3 and diluting the turbidity standard solution.

[0052] 3, the acquired multiple sets of absorbance data are plotted on a graph with the measurement absorbance (220 nm) on the vertical axis and the turbidity correction absorbance (275 nm) on the horizontal axis. Note that the measurement absorbance when plotted on the graph may be a value obtained by subtracting the absorbance at the zero point (zero absorbance) obtained by zero calibration from the measurement absorbance calculated by measurement using a turbidity standard solution.

[0053] By performing calculations using the least squares method on the multiple points plotted on the graph in this way, a linear function such as the straight line in Figure 3 is obtained. This linear function represents the relationship between the absorbance for measurement and the absorbance for turbidity correction, and is expressed by the above-mentioned correction formula (2) when the value on the vertical axis is C and the value on the horizontal axis is D. Therefore, the proportional term k and constant term m of the correction coefficient in correction formula (2) can be determined based on the linear function obtained by the least squares method.

[0054] The correction coefficient update processing unit 104 updates the correction coefficients k,m by overwriting the correction coefficients k,m stored in the storage unit 200 with the newly calculated correction coefficients k,m. However, in addition to or instead of the calculation using the least squares method, other calculations may be performed. In this case, the calculation may be performed so that the value of the constant term m becomes "0." Furthermore, multiple measurements may be performed using one type of turbidity standard solution, or only one measurement may be performed. When only one measurement is performed, a straight line connecting the obtained set of absorbance data points and the origin may be obtained as a linear function.

[0055] Fig. 4 is a flowchart showing an example of a water quality analysis method using the water quality analyzer of Fig. 1. When analyzing the quality of sample water, the sample water (mixture) is supplied to a reactor 4, where components in the sample water are oxidized (step S101). The sample water after the oxidation reaction is then supplied to a measurement cell 5 (step S102), and measurement light is irradiated onto the sample water in the measurement cell 5 from a light source 51 (step S103). As a result, the measurement light that has passed through the sample water is detected by a detector 52 (step S104).

[0056] The detector 52 detects the intensities of multiple (e.g., two) wavelengths. The absorbance calculation unit 101 calculates the absorbance at each wavelength based on the intensity of each wavelength (step S105). Thereafter, the correction calculation unit 102 reads out correction coefficients from the storage unit 200 (step S106) and performs calculations using correction formulas (1) and (2) based on the calculated absorbance at each wavelength, thereby correcting the absorbance (step S107). The correction coefficients included in the correction formulas (1) and (2) are stored in advance in the storage unit 200.

[0057] 5 is a flowchart showing an example of calibration for turbidity correction. When performing calibration for turbidity correction, a turbidity standard solution is supplied to a reactor 4, whereby components in the turbidity standard solution are subjected to an oxidation reaction in the reactor 4 (step S201). Then, the turbidity standard solution after the oxidation reaction is supplied to a measurement cell 5 (step S202), and measurement light is irradiated onto the turbidity standard solution in the measurement cell 5 from a light source 51 (step S203). As a result, the measurement light that has passed through the turbidity standard solution is detected by a detector 52 (step S204).

[0058] The detector 52 detects the intensities of multiple (e.g., two) wavelengths. The absorbance calculation unit 101 calculates the absorbance at each wavelength based on the intensities of each wavelength (step S205). Thereafter, the correction coefficient update processing unit 104 updates the correction coefficient stored in the storage unit 200 based on the calculated absorbance at each wavelength (step S206).

[0059] However, at least one of the steps shown in FIGS. 4 and 5 may be performed manually by an operator.

[0060] 4. Modified water quality analyzer Fig. 6 is a block diagram showing a modified example of a water quality analyzer. In the above embodiment, a configuration has been described in which turbidity correction calibration is started based on a user's operation of the operation unit 300. In contrast, in the modified example of Fig. 6, turbidity correction calibration is started automatically according to a preset schedule. In this modified example, only the configuration for automatically starting turbidity correction calibration differs from the above embodiment, and the other configurations are the same as those of the above embodiment. Therefore, the same components are denoted by the same reference numerals in the figure and detailed description thereof will be omitted.

[0061] In this modification, the control unit 100 functions as a schedule setting processing unit 105 by the CPU executing a program. The schedule setting processing unit 105 sets the start date and time of turbidity correction calibration as a schedule based on the user's operation of the operation unit 300, and stores the set schedule in the storage unit 200. In this case, an operation screen for the user to set the schedule may be displayed on the display unit (not shown).

[0062] The turbidity component detection processing unit 103 performs turbidity correction calibration at a frequency according to the schedule by automatically starting the supply of the turbidity standard solution to the reactor 4 based on the schedule stored in the memory unit 200. However, the schedule for turbidity correction calibration is not limited to a configuration in which it is set by the user operating the operation unit 300, and may be set automatically based on the operating time of the water quality analyzer, etc.

[0063] 5. Other Modifications In the above embodiment, the turbidity correction wavelength is 275 nm, but other wavelengths may be used. For example, the turbidity correction wavelength may be a wavelength corresponding to the total phosphorus in the sample water. The "wavelength corresponding to the total phosphorus in the sample water" refers to a wavelength at which the phosphorus oxide (target component) in the sample water has absorption, such as 880 nm. In this case, an optical filter that transmits the measurement wavelength (e.g., 880 nm) when measuring the total phosphorus concentration can be used as an optical filter that transmits the turbidity correction wavelength, eliminating the need for a separate optical filter for turbidity correction calibration.

[0064] In the above embodiment, the water quality analyzer is a total nitrogen / total phosphorus analyzer, but the present invention can also be applied to a total nitrogen analyzer. That is, the present invention can be applied to a total nitrogen analyzer that can measure the total nitrogen concentration but cannot measure the total phosphorus concentration.

[0065] The water quality analyzer is not limited to a configuration including two multiport valves 1 and 2, but may be a configuration including only one multiport valve, or a configuration including three or more multiport valves. Furthermore, the types and numbers of valves, pipes, etc. are arbitrary, and are not limited to the configurations of the above-described embodiments. For example, it is also possible to adopt a configuration in which the reactor 4 also functions as the measurement cell 5.

[0066] 6. Aspects It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0067] (Item 1) A water quality analyzer according to one aspect includes: A water quality analyzer capable of measuring the total nitrogen concentration in sample water containing turbidity components, an oxidation reaction unit that oxidizes components in the sample water; a light source that irradiates the sample water after the oxidation reaction in the oxidation reaction unit with measurement light; a detector for detecting the intensity of the measurement light at a plurality of wavelengths that has passed through the sample water; an absorbance calculation unit that calculates absorbance at each wavelength based on the intensities of the plurality of wavelengths detected by the detector; a correction calculation unit that performs calculations using a correction formula based on the absorbance at each wavelength calculated by the absorbance calculation unit, thereby correcting the absorbance; a storage unit that stores a correction coefficient included in the correction formula; a turbidity component detection processing unit that supplies a turbidity standard solution to the oxidation reaction unit, irradiates the turbidity standard solution after the oxidation reaction with measurement light from the light source, and detects the intensities of the measurement light at the plurality of wavelengths that have passed through the turbidity standard solution with the detector; The present invention may further include a correction coefficient update processing unit that causes the absorbance calculation unit to calculate the absorbance at each wavelength based on the intensities at the plurality of wavelengths detected by the turbidity component detection processing unit, and updates the correction coefficient stored in the memory unit based on the calculated absorbance at each wavelength.

[0068] According to the water quality analyzer described in paragraph 1, by supplying a turbidity standard solution to the oxidation reaction section in the same manner as when analyzing sample water, the correction coefficient stored in the memory section can be updated to an appropriate value based on the detected intensity of the measurement light that has passed through the turbidity standard solution after the oxidation reaction, so that the absorbance can be appropriately corrected when measuring the total nitrogen concentration in sample water containing turbidity components.

[0069] (2) In the water quality analyzer according to the first paragraph, The plurality of wavelengths may include a measurement wavelength corresponding to the total nitrogen in the sample water and a turbidity correction wavelength that is longer than the measurement wavelength.

[0070] According to the water quality analyzer described in paragraph 2, a detector detects the intensities at two wavelengths: a measurement wavelength corresponding to the total nitrogen in the sample water and a turbidity correction wavelength that is longer than the measurement wavelength; and based on these detected intensities, the correction coefficient stored in the memory unit can be updated to an appropriate value.

[0071] (Item 3) In the water quality analyzer according to item 2, The correction coefficient may include a proportional term by which the absorbance at the turbidity correction wavelength is multiplied.

[0072] According to the water quality analyzer described in paragraph 3, the proportional term multiplied by the absorbance at the turbidity correction wavelength can be updated to an appropriate value, so that the absorbance can be appropriately corrected when measuring the total nitrogen concentration in sample water containing turbidity components.

[0073] (4) In the water quality analyzer according to paragraph 2 or 3, The wavelength for turbidity correction may be a wavelength corresponding to total phosphorus in the sample water.

[0074] According to the water quality analyzer described in paragraph 4, in a water quality analyzer that can measure not only total nitrogen concentration but also total phosphorus concentration, the measurement wavelength when measuring total phosphorus concentration can be used as the turbidity correction wavelength.

[0075] (Item 5) In the water quality analyzer according to any one of items 1 to 4, The turbidity component detection processing unit may automatically start supplying the turbidity standard solution to the oxidation reaction unit.

[0076] According to the water quality analyzer described in item 5, the supply of the turbidity standard solution to the oxidation reaction unit can be automatically started, and the correction coefficient stored in the memory unit can be automatically updated.

[0077] (Item 6) In the water quality analyzer according to any one of items 1 to 5, In the oxidation reaction section, an oxidation reaction may be carried out using potassium peroxodisulfate as an oxidizing agent.

[0078] According to the water quality analyzer described in item 6, in a water quality analyzer capable of performing measurements using potassium peroxodisulfate as an oxidizing agent, absorbance can be appropriately corrected.

[0079] (Item 7) In the water quality analyzer according to any one of items 1 to 6, In the oxidation reaction section, the water sample may be irradiated with ultraviolet light, thereby causing an oxidation reaction of components in the water sample.

[0080] According to the water quality analyzer described in paragraph 7, in a water quality analyzer capable of performing measurements using ultraviolet absorptiometry or the like, it is possible to appropriately correct absorbance.

[0081] (Item 8) A water quality analysis method according to one embodiment includes: A water quality analysis method capable of measuring the total nitrogen concentration in sample water containing turbidity components, comprising: A step of oxidizing components in the sample water; irradiating the sample water after the oxidation reaction with measurement light; detecting the intensities of the measurement light at a plurality of wavelengths that has passed through the water sample; calculating absorbance at each wavelength based on the detected intensities of the plurality of wavelengths; a step of correcting the absorbance by performing a calculation using a correction formula based on the calculated absorbance at each wavelength; storing a correction coefficient included in the correction formula; A step of subjecting components in the turbidity standard solution to an oxidation reaction; irradiating the turbidity standard solution after the oxidation reaction with measurement light; detecting the intensities of the measurement light at the plurality of wavelengths that has passed through the turbidity standard solution; The method may further include a step of calculating absorbance at each wavelength based on the detected intensities at the plurality of wavelengths, and updating the stored correction coefficient based on the calculated absorbance at each wavelength.

[0082] According to the water quality analysis method described in paragraph 8, by subjecting the turbidity standard solution to an oxidation reaction in the same manner as when analyzing sample water, the correction coefficient included in the correction formula can be updated to an appropriate value based on the detected intensity of the measurement light that has passed through the turbidity standard solution after the oxidation reaction, so that the absorbance can be appropriately corrected when measuring the total nitrogen concentration in sample water containing turbidity components. [Explanation of symbols]

[0083] 4. Reactor 5. Measuring Cell 41 Light source 51 Light source 52 detector 100 control section 101 Absorbance calculation section 102 Correction calculation unit 103 Turbidity component detection processing unit 104 Correction coefficient update processing unit 105 Schedule setting processing section 200 Storage section 300 Operation section

Claims

1. A water quality analyzer capable of measuring the total nitrogen concentration in sample water containing turbidity components, an oxidation reaction section that oxidizes components in the sample water in the presence of an oxidizing agent; a light source that irradiates the sample water after the oxidation reaction in the oxidation reaction unit with measurement light; a detector for detecting the intensity of the measurement light at a plurality of wavelengths that has passed through the sample water; an absorbance calculation unit that calculates absorbance at a measurement wavelength corresponding to total nitrogen in the sample water and at a turbidity correction wavelength based on the intensities of the plurality of wavelengths detected by the detector; a correction calculation unit that performs calculations using a correction formula based on the absorbances at the measurement wavelength and the turbidity correction wavelength corresponding to the total nitrogen in the sample water calculated by the absorbance calculation unit, thereby correcting the absorbance; a storage unit that stores a correction coefficient for correcting the absorbance at the turbidity correction wavelength and converting it into an absorbance corresponding to the measurement wavelength in the correction formula; a turbidity component detection processing unit that supplies a turbidity standard solution containing an oxidizing agent identical to the oxidizing agent used to oxidize the components in the sample water to the oxidation reaction unit, and irradiates measurement light from the light source onto the turbidity standard solution after the oxidation reaction in the presence of the oxidizing agent, thereby detecting the intensities of the measurement light at the multiple wavelengths that have passed through the turbidity standard solution with the detector; a correction coefficient update processing unit that calculates the absorbance at each wavelength using the absorbance calculation unit based on the intensities at the multiple wavelengths detected by the turbidity component detection processing unit, and updates the correction coefficient stored in the memory unit based on the calculated absorbance at each wavelength.

2. 2. The water quality analyzer according to claim 1, wherein the plurality of wavelengths include a measurement wavelength corresponding to total nitrogen in the sample water and a turbidity correction wavelength that is longer than the measurement wavelength.

3. The water quality analyzer according to claim 2 , wherein the correction coefficient includes a proportional term by which the absorbance at the turbidity correction wavelength is multiplied.

4. 4. The water quality analyzer according to claim 2, wherein the wavelength for turbidity correction is a wavelength corresponding to total phosphorus in the sample water.

5. 5. The water quality analyzer according to claim 1, wherein the turbidity component detection processing unit automatically starts supplying the turbidity standard solution to the oxidation reaction unit.

6. The water quality analyzer according to any one of claims 1 to 5, wherein the oxidation reaction section carries out an oxidation reaction using potassium peroxodisulfate as an oxidizing agent.

7. 7. The water quality analyzer according to claim 1, wherein in the oxidation reaction section, ultraviolet light is irradiated onto the sample water, thereby causing an oxidation reaction of components in the sample water.

8. A syringe and A pipe through which sample water is supplied; a turbidity standard solution storage section in which a turbidity standard solution is stored; an oxidant reservoir in which an oxidant is stored; a control unit that functions as the absorbance calculation unit, the correction calculation unit, the turbidity component detection processing unit, and the correction coefficient update processing unit, The control unit The sample water is drawn into the syringe from the piping, and the oxidant is drawn into the syringe from the oxidant storage unit, thereby generating a first mixture in which the sample water is mixed with the oxidant, and then the first mixture is discharged from the syringe and supplied to the oxidation reaction unit; The water quality analyzer according to any one of claims 1 to 7, wherein the turbidity standard solution is drawn from the turbidity standard solution storage section into the syringe, and the oxidant is drawn from the oxidant storage section into the syringe, thereby generating a second mixture in which the turbidity standard solution is mixed with the oxidant, and then the second mixture is ejected from the syringe and supplied to the oxidation reaction section.

9. A water quality analysis method capable of measuring the total nitrogen concentration in sample water containing turbidity components, comprising: A step of oxidizing components in the sample water in the presence of an oxidizing agent; irradiating the sample water after the oxidation reaction with measurement light; detecting the intensities of the measurement light at a plurality of wavelengths that has passed through the water sample; calculating absorbances at a measurement wavelength and a turbidity correction wavelength corresponding to total nitrogen in the sample water based on the intensities of the detected wavelengths; a step of correcting the absorbance by performing a calculation using a correction formula based on the absorbance at the measurement wavelength corresponding to the total nitrogen in the sample water and the absorbance at the turbidity correction wavelength; a step of storing a correction coefficient for correcting the absorbance at the turbidity correction wavelength in the correction formula and converting it into an absorbance corresponding to the measurement wavelength; a step of oxidizing a component in a turbidity standard solution containing the same oxidizing agent as that used in oxidizing a component in the sample water in the presence of the oxidizing agent; irradiating the turbidity standard solution after the oxidation reaction in the presence of the oxidizing agent with measurement light; detecting the intensities of the measurement light at the plurality of wavelengths that has passed through the turbidity standard solution; calculating the absorbance at each wavelength based on the detected intensities at the plurality of wavelengths, and updating the stored correction coefficient based on the calculated absorbance at each wavelength.

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