JP5846364B2 - Water quality evaluation method and water quality evaluation apparatus - Google Patents

Description

  The present invention relates to a water quality evaluation method for evaluating the quality of sample water, and more particularly to a water quality evaluation method for evaluating water quality using a fluorescent substance.

  In order to manage the quality of water used in factories and the like, a method for evaluating the quality of water by measuring the concentration of a predetermined substance contained in water is provided. For example, Patent Document 1 below discloses an apparatus for measuring water quality by measuring the fluorescence intensity of a fluorescent substance (LAS: linear alkylbenzene sulfonate) contained in sample water.

  In Patent Document 1, the first excitation light and the second excitation light having different wavelengths are irradiated on the sample water, and the intensities of the first fluorescence and the second fluorescence having different wavelengths emitted from the sample water by each excitation light are calculated. Measure and evaluate the quality of the sample water.

JP 2005-30839 A

  However, the fluorescent substance is a substance that absorbs excitation light having a specific wavelength and emits energy as fluorescence, and the wavelength of excitation light suitable for generating fluorescence differs depending on the fluorescent substance. Therefore, when excitation light having a different wavelength is used as excitation light, it may occur when different fluorescent substances emit fluorescence in response to each excitation light, making accurate water quality evaluation difficult. Moreover, since it is necessary to prepare two types of light sources having different excitation wavelengths as the excitation light source, the cost also increases.

  This invention is made | formed in view of such a subject, and it aims at providing the water quality evaluation method in which accurate water quality evaluation is possible at low cost.

In order to solve the above-described problems, a water quality evaluation method according to the present invention is a water quality evaluation method for evaluating the quality of a sample water by measuring the concentration of a fluorescent tracer contained in the sample water. Among the excitation light irradiation step, the fluorescence intensity measurement step of measuring the intensity of the fluorescence emitted from the sample water by the excitation light, and the fluorescence emitted from the sample water by the excitation light, than the excitation light A correction fluorescence intensity measurement step for measuring the intensity of fluorescence in a predetermined correction wavelength region, which is a long wavelength region and in which a fluorescence spectrum by a substance other than the fluorescence tracer dominates, and the correction fluorescence intensity measurement step By calculating a background fluorescence value emitted from a substance other than the fluorescence tracer based on the measurement value, the measurement value in the fluorescence intensity measurement step is compensated. Characterized in that it comprises a correction step of performing.

The water quality evaluation apparatus according to the present invention is a water quality evaluation apparatus that evaluates the water quality of the sample water by measuring the concentration of a fluorescent tracer contained in the sample water. A fluorescence sensor for measuring the intensity of fluorescence emitted from the sample water, and a fluorescence spectrum by a substance other than the fluorescence tracer in a longer wavelength region than the excitation light among the fluorescence emitted from the sample water by the excitation light Correction fluorescence sensor that measures the intensity of fluorescence in a predetermined correction wavelength region that occupies most, and a background fluorescence value emitted from a substance other than the fluorescence tracer based on the measurement value of the correction fluorescence sensor Control means for correcting the measurement value of the fluorescence sensor by calculating.

  According to the water quality evaluation method of the present invention, accurate water quality evaluation can be performed at low cost by measuring the fluorescence intensity and the correction fluorescence intensity using the same excitation light.

FIG. 1 is a schematic diagram schematically showing a configuration of a water quality evaluation apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing a calibration curve for background correction used when calculating the background fluorescence value according to the embodiment of the present invention. FIG. 3 is a flowchart showing a processing procedure for water quality evaluation according to the embodiment of the present invention. FIG. 4 is a diagram showing a fluorescence spectrum of cooling tower circulating water according to the embodiment of the present invention. FIG. 5 is a diagram showing a comparison of the fluorescence spectra of circulating water not containing a fluorescent tracer and circulating water containing a fluorescent tracer according to an embodiment of the present invention. FIG. 6 is a flowchart showing how to obtain a calibration curve for background correction according to the embodiment of the present invention. FIG. 7 is a data table for calculating a calibration curve for background correction according to the embodiment of the present invention. FIG. 8 is a data table showing the verification result of the background correction according to the embodiment of the present invention.

  Hereinafter, a water quality evaluation method and a water quality evaluation apparatus according to an embodiment of the present invention will be described with reference to the drawings. First, the configuration of the water quality evaluation apparatus will be described with reference to FIGS. 1 and 2. In the present embodiment, a water quality evaluation apparatus that evaluates the quality of circulating water in a cooling tower, which is a type of heat exchanger, using a fluorescent tracer will be described as an example.

  FIG. 1 is a schematic diagram schematically showing a configuration of a water quality evaluation apparatus according to the present embodiment. FIG. 2 is a diagram showing a calibration curve for background correction used when calculating a background fluorescence value according to the present embodiment.

  As shown in FIG. 1, the water quality evaluation apparatus 1 includes a fluorescence sensor 20, a correction fluorescence sensor 30, glass 40, a control device 42, and wiring 45. This water quality evaluation apparatus 1 is installed on the flow path 50 through which the circulating water of the cooling tower circulates, and evaluates the quality of the circulating water.

  Specifically, a fluorescent tracer is placed in advance in a chemical that is put into the circulating water of the cooling tower, and the concentration of the fluorescent tracer in the circulating water is measured by the water quality evaluation device 1. The chemical concentration can be calculated from the concentration of the tracer, and the chemical concentration in the circulating water can be managed by adding the chemical based on the calculation result. In this embodiment, PTSA (1,3,6,8-pyrenetetrasulfonic acid) is used as the fluorescent tracer.

  The fluorescence sensor 20 and the correction fluorescence sensor 30 are installed in series on the flow channel 50 with the fluorescence sensor 20 on the upstream side, and measure the fluorescence intensity of the circulating water flowing in the flow channel 50. The correction fluorescent sensor 30 may be installed on the upstream side. The fluorescence sensor 20 includes an excitation light source 21, a light receiving element 23, and an optical filter A25.

  The excitation light source 21 is a light source that emits excitation light for generating fluorescence from a fluorescence tracer. In this embodiment, an LED (Light Emitting Diode) having a light emission characteristic with a peak wavelength of 355 nm is used as the light emitting element. . The excitation light source 21 is installed facing the flow path 50 and irradiates the circulating water flowing in the flow path 50 with excitation light.

  The light receiving element 23 is an element for receiving the fluorescence emitted from the fluorescent tracer, and is installed facing the flow path 50. As the light receiving element 23, a light receiving element (photodiode) having a light receiving region of 360 to 440 nm and a peak wavelength of 400 nm is used.

  The optical filter A25 is an optical filter that cuts a specific wavelength component, and has a function of cutting wavelengths in both the short wavelength and the long wavelength. From the light receiving element 23 having such a configuration, a current corresponding to the intensity of the received fluorescence is output as the fluorescence intensity.

  The correction fluorescent sensor 30 includes an excitation light source 31, a light receiving element 33, and an optical filter B35. The excitation light source 31 has the same configuration as the fluorescent sensor 20, and the light receiving element 33 and the optical filter B35 include the fluorescent sensor. The difference is that the fluorescent light in the wavelength region longer than 20 is received. The light receiving element 33 has a light receiving characteristic of a light receiving region of 400 to 560 nm, and the optical filter B35 has a function of cutting a wavelength in a wavelength region shorter than 450 nm.

  Of course, the characteristics of the excitation light source 31 of the correction fluorescent sensor 30 and the characteristics of the excitation light source 21 of the fluorescence sensor 20 do not have to be exactly the same, and may be substantially the same. For example, even if the peak wavelength is shifted by several nm, it is treated as the same configuration in this embodiment.

  The glass 40 transmits the above-described excitation light and fluorescence at the tip portions of the fluorescence sensor 20 and the correction fluorescence sensor 30.

  The control device 42 is a device for controlling the fluorescence sensor 20 and the correction fluorescence sensor 30, and includes a calculation device 43 that performs various calculations and a storage device 44 that records various information. The control device 42 is connected to the excitation light source 21 and the light receiving element 23 of the fluorescent sensor 20 and the excitation light source 31 and the light receiving element 33 of the correction fluorescent sensor 30 by the wiring 45.

  The control device 42 has a function of correcting (background correction) the fluorescence sensor measurement value measured by the fluorescence sensor 20 based on the correction fluorescence sensor measurement value measured by the correction fluorescence sensor 30. In the correction process of the control device 42, the calibration curve shown in FIG. 2 is used, and the regression equation of the calibration curve for background correction is recorded in the storage device 44.

This calibration curve for background correction shows the correlation between the intensity of fluorescence in the later-described correction wavelength region (450 to 560 nm) and the background fluorescence value, and is used for correction measured by the correction fluorescence sensor 30. Suppose that the fluorescence sensor measurement value (measurement fluorescence intensity for correction) is x, and the correction value (calculated background fluorescence value) for correcting the fluorescence sensor measurement value (measurement fluorescence intensity) measured by the fluorescence sensor 20 is y. It is represented by (1).
y = 0.5414x-0.1575 Formula (1)

  The correction value y is the intensity of fluorescence (background fluorescence value) emitted from substances other than the fluorescence tracer contained in the circulating water, and is based on the fluorescence sensor measurement value (measured fluorescence intensity) measured by the fluorescence sensor 20. By performing the correction for subtracting the calculated background fluorescence value, the concentration of the fluorescent tracer in the circulating water can be accurately obtained.

  The configuration of the water quality evaluation apparatus 1 has been described above. Next, the water quality evaluation method in the water quality evaluation apparatus 1 will be described in detail. FIG. 3 is a flowchart showing a processing procedure for water quality evaluation according to the present embodiment.

  As shown in the figure, first, in S1 and S2, the fluorescence intensity is measured by the fluorescence sensor 20 and the correction fluorescence sensor 30, respectively. The fluorescence sensor measurement value measured by the fluorescence sensor 20 is sent from the fluorescence sensor 20 to the control device 42 in S3. The measured value of the correction fluorescent sensor measured by the correction fluorescent sensor 30 is sent from the correction fluorescent sensor 30 to the control device 42 in S4.

  Subsequently, the process proceeds to S5, and in the control device 42, the calculation device 43 adds the correction fluorescence sensor measurement value acquired in S4 to the above equation (1) to obtain a calculated background fluorescence value as a correction value ( S6). In S7, the calculated measured fluorescence intensity is calculated by subtracting the calculated background fluorescence value, which is the correction value, from the fluorescence sensor measurement value acquired in S3.

  In S8, the concentration of the fluorescent tracer is calculated from the corrected measured fluorescent intensity that is the fluorescent intensity emitted only from the fluorescent tracer. Thus, the chemical | medical agent density | concentration added to circulating water can be grasped | ascertained by detecting the density | concentration of the fluorescence tracer contained in circulating water. In managing the chemical concentration, water quality management may be performed based on the corrected measured fluorescence intensity value without converting to the concentration of the fluorescent tracer as in S8.

  As described above, according to the water quality evaluation apparatus 1 according to the present embodiment, in the concentration measurement of the fluorescent tracer in the circulating water, the background fluorescent value emitted from a substance other than the fluorescent tracer can be accurately calculated. By subtracting the calculated background fluorescence value from the measured fluorescence sensor measurement value, the fluorescence intensity (concentration) of the fluorescence tracer can be accurately measured.

  In the present embodiment, the excitation light sources 21 and 31 having the same wavelength are used in the fluorescence sensor 20 and the correction fluorescence sensor 30, and the excitation light from both the light sources 21 and 31 is applied to the same fluorescent material. Since the same fluorescence reaction is exhibited, the fluorescence intensity can be measured and the background correction can be performed with higher accuracy as compared with the case where the light sources having different wavelengths are used in both the sensors 20 and 30.

  In this embodiment, the fluorescence sensor 20 and the correction fluorescence sensor 30 are provided with independent excitation light sources 21 and 31, respectively. However, both sensors 20 and 30 may be configured to share the same excitation light source. .

  Next, the reason why the background fluorescence value can be calculated using the above-described background correction calibration curve will be described with reference to FIGS. FIG. 4 shows the result of the measurement of the fluorescence intensity for 10 kinds of circulating water samples in the state where no fluorescent tracer is inserted, as a solid line. As shown in the figure, the fluorescence intensity (background fluorescence value) of the circulating water in a state where no fluorescence tracer is inserted shows a similar spectrum in all samples regardless of the magnitude of the fluorescence intensity.

  FIG. 5 shows the fluorescence spectrum of the circulating water before and after putting the fluorescence tracer for a given sample. In the figure, the fluorescence spectrum of circulating water not containing a fluorescent tracer is indicated by a two-dot chain line, and the fluorescence spectrum of circulating water containing a fluorescent tracer is indicated by a solid line.

  Here, the fluorescence spectrum of the circulating water containing the fluorescence tracer indicated by a solid line is a fluorescence spectrum obtained by combining the fluorescence spectrum of a substance other than the fluorescence tracer such as water and microorganisms with the fluorescence spectrum of the fluorescence tracer.

  Therefore, the fluorescence spectrum of only the fluorescent tracer is a spectrum obtained by subtracting the fluorescent spectrum of the circulating water not containing the fluorescent tracer indicated by the two-dot chain line from the fluorescent spectrum of the fluorescent water containing the fluorescent tracer indicated by the solid line. In FIG. 5, the fluorescence spectrum of only this fluorescence tracer is indicated by a one-dot chain line.

  As shown in FIG. 5, in the fluorescence spectrum of only this fluorescent tracer, the fluorescence intensity is extremely lowered in the wavelength region longer than 450 nm, and in this long wavelength region, the fluorescence spectrum caused by substances other than the fluorescent tracer is mostly. Accounted for. In other words, the fluorescence spectrum of the circulating water containing the fluorescent tracer indicated by the solid line is substantially the same as the fluorescence spectrum of the circulating water indicated by the two-dot chain line in the wavelength region longer than 450 nm (hereinafter referred to as the correction wavelength region). Yes.

  Therefore, if the fluorescence intensity in the wavelength region for correction of circulating water containing fluorescent tracer is measured, a measurement value substantially the same as the fluorescence intensity in the wavelength region for correction of circulating water not containing fluorescent tracer can be obtained. In the correction fluorescent sensor 30, the measurement upper limit wavelength of the fluorescence intensity is 560 nm due to the light receiving characteristics of the light receiving element 33. Accordingly, the substantial correction wavelength region in the present embodiment is 450 to 560 nm.

  On the other hand, as shown in FIG. 4, the fluorescence spectrum of circulating water without a fluorescent tracer has a similar spectrum shape even if the samples are different. Therefore, the fluorescence intensity value in the correction wavelength region (450 to 560 nm) in the fluorescence spectrum of the circulating water containing the fluorescent tracer and the fluorescence intensity value in the 380 to 560 nm circulating water not containing the fluorescent tracer are associated in advance. Thus, it is possible to calculate with high accuracy the value of the fluorescence intensity in the circulating water without the fluorescence tracer, that is, the value of the fluorescence intensity emitted from a substance other than the fluorescence tracer (background fluorescence value). .

  Next, how to obtain the calibration curve for background correction shown in FIG. 2 used in the background correction described above will be described with reference to FIGS. FIG. 6 is a flowchart showing how to obtain a calibration curve for background correction according to this embodiment. FIG. 7 shows a data table for calculating a calibration curve for background correction.

  First, in S10, a sample of circulating water with a known fluorescent tracer concentration [μg / kg] is prepared. As shown in FIG. 7, in this embodiment, seven types of samples A to G having fluorescent tracer concentrations were used.

  Subsequently, in S11, fluorescent tracer standard solutions adjusted to several fluorescent tracer concentrations by diluting the fluorescent tracer standard solution with distilled water are prepared, and the standard fluorescence intensity [V] of these fluorescent tracer standard solutions is measured. Then, a calibration curve A for determining the fluorescence tracer concentration from the standard fluorescence intensity [V] is prepared.

  Next, in S <b> 12, the measured fluorescence intensity [V] of the samples A to G is measured by the fluorescence sensor 20. Subsequently, in S13, the correction measurement fluorescence intensity [V], which is the intensity of fluorescence in the correction wavelength region of these samples, is measured by the correction fluorescence sensor 30.

  In S14, the calculated fluorescence intensity [V] of each sample is calculated based on the calibration curve A described above from the concentration of the fluorescence tracer of each sample. Subsequently, in S15, the calculated background fluorescence value [V] is calculated by subtracting the calculated fluorescence intensity calculated in S14 from the measured fluorescence intensity measured in S12.

  The calculated fluorescence intensity obtained from the calibration curve A is the calculated fluorescence intensity when there is no substance that emits background fluorescence, and the measured fluorescence intensity is the measured fluorescence intensity when there is a background fluorescent substance. Therefore, the calculated background fluorescence value obtained in S15 is a value obtained by calculating the background fluorescence value of each sample with high accuracy.

  FIG. 7 shows the measured fluorescence intensity, the corrected measured fluorescence intensity, the calculated fluorescence intensity, and the calculated background fluorescence value calculated by measurement or calculation for each sample. In S16, the calibration curve for background correction shown in FIG. 2 can be created by associating the measured fluorescence intensity for correction and the calculated background fluorescence value of each sample.

  By using this calibration curve for background correction, it is possible to determine with high accuracy the calculated value of background fluorescence intensity emitted from a substance other than the fluorescence tracer from the measurement value of the correction fluorescence intensity in the correction wavelength region. Become.

  Next, how accurately the corrected measured fluorescence intensity obtained by correcting the measured fluorescence intensity using the calibration curve for background correction according to the present embodiment represents the concentration of the fluorescent tracer is described above. This was verified by comparison with the fluorescence tracer concentration.

  First, for each sample, a calculated background fluorescence value [V] was determined from the measured fluorescence intensity for correction [V] using a calibration curve for background correction. Then, the calculated measured fluorescence intensity [V] was calculated by subtracting this calculated background fluorescence value from the measured fluorescence intensity [V]. Further, the calculated fluorescence tracer concentration of each sample was determined from the corrected measured fluorescence intensity using the calibration curve A. The results are shown in FIG.

  According to FIG. 8, each calculated fluorescence tracer concentration when background correction is performed using a calibration curve for background correction has an error of about ± 5% when compared with the fluorescence tracer concentration prepared in S10. It can be seen that the fluorescence tracer concentration can be calculated with high accuracy.

  As mentioned above, although embodiment of this invention was described in detail, embodiment of this invention is not limited to the form mentioned above, A various deformation | transformation is possible within the range which does not deviate from the main point of this invention. For example, in the above embodiment, the circulating water of the cooling tower is used as the sample water that is the target of the water quality evaluation, but of course the invention is not limited to this, and the water quality can be evaluated by adding a fluorescent substance. If it is water, various water can be used as sample water.

  Moreover, in the said embodiment, although PTSA is used as a fluorescent tracer, it cannot be overemphasized that another fluorescent substance can be used as a fluorescent tracer. However, when other fluorescent tracers are used, it is necessary to appropriately change the correction wavelength region and the like according to the fluorescent tracer to be used.

  Further, the range of the correction wavelength region can be changed as appropriate, and may be set to, for example, 430 to 600 nm by changing the characteristics of the optical filter and the light receiving element. However, if the fluorescence intensity of the fluorescent tracer is increased in the correction wavelength region, the background correction cannot be performed with high accuracy. Therefore, in the correction wavelength region, the fluorescence intensity of the fluorescent tracer is ¼ or less than the peak intensity. In addition, it is desirable to use a region included in a wavelength region where the intensity is preferably 1/5 or less, more preferably 1/10 or less.

DESCRIPTION OF SYMBOLS 1 Water quality evaluation apparatus 20 Fluorescence sensor 21, 31 Excitation light source 23, 33 Light receiving element 25 Optical filter A
30 Fluorescent sensor 35 for correction Optical filter B
42 control device 50 flow path

Claims (5)

In the water quality evaluation method for evaluating the quality of the sample water by measuring the concentration of the fluorescent tracer contained in the sample water,
An excitation light irradiation step of irradiating the sample water with excitation light;
A fluorescence intensity measurement step of measuring the intensity of fluorescence emitted from the sample water by the excitation light;
Among the fluorescence emitted from the sample water by the excitation light, the intensity of the fluorescence in a predetermined correction wavelength region that is longer in the wavelength region than the excitation light and in which the fluorescence spectrum by a substance other than the fluorescence tracer occupies most A correction fluorescence intensity measurement step for measuring
A correction step of correcting the measurement value of the fluorescence intensity measurement step by calculating a background fluorescence value emitted from a substance other than the fluorescence tracer based on the measurement value of the correction fluorescence intensity measurement step; A water quality evaluation method characterized by comprising. 2. The water quality evaluation method according to claim 1, wherein the predetermined wavelength region for correction is a region included in a wavelength region in which the fluorescence intensity of the fluorescence tracer is ¼ or less of the peak intensity. . The correction step calculates the background fluorescence value based on a calibration curve that creates a relationship between the measurement value of the correction fluorescence intensity measurement step and the background fluorescence value, and measures the fluorescence intensity measurement step. The water quality evaluation method according to claim 1, wherein the water quality evaluation method is a step of performing correction by subtracting the calculated background fluorescence value from the value. The calibration curve prepares a plurality of sample water samples with known concentrations of the fluorescent tracer,
Calculating a calculated fluorescence intensity for the plurality of sample water samples;
Measuring the measured fluorescence intensity for the plurality of sample water samples;
Measuring the measurement fluorescence intensity for correction, which is the intensity of fluorescence in the predetermined correction wavelength region, for the plurality of sample water samples;
Associating the calculated background fluorescence value, which is the difference between the calculated fluorescence intensity and the measured fluorescence intensity, with the corrected measured fluorescence intensity;
The water quality evaluation method according to claim 3, wherein In the water quality evaluation apparatus for evaluating the quality of the sample water by measuring the concentration of the fluorescent tracer contained in the sample water,
A light source that emits excitation light;
A fluorescence sensor for measuring the intensity of fluorescence emitted from the sample water by the excitation light;
Among the fluorescence emitted from the sample water by the excitation light, the intensity of the fluorescence in a predetermined correction wavelength region that is longer in the wavelength region than the excitation light and in which the fluorescence spectrum by a substance other than the fluorescence tracer occupies most A correction fluorescent sensor for measuring
Control means for correcting the measurement value of the fluorescence sensor by calculating a background fluorescence value emitted from a substance other than the fluorescence tracer based on the measurement value of the correction fluorescence sensor. Water quality evaluation device.

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