JP2009236832A - Monitoring method and device for dissolved pollutant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple method for measuring the quality of water containing a suspended substance, such as turbidity, without removing the suspended substance. <P>SOLUTION: In a measuring method of a dissolved pollutants in the water containing the suspended substance, sample water is irradiated with a light having a wavelength that excites the dissolved pollutant, and fluorescence intensity generated from the sample water is measured, and the Raman scattering light of the irradiated light is measured. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for on-site non-chemical injection and continuous monitoring of the concentration of pollutants dissolved in water as sewage, factory waste water, environmental water (river water, lake water, sea water, etc.). Is.

Conventionally, in public water areas, the quality of environmental water has been measured to preserve water quality, and in order to comply with various regulations based on the Water Pollution Control Law at sewage treatment plants, factories, offices, etc. The quality of treated water and wastewater is measured.
Since these water qualities vary greatly over time, it is desirable to monitor them continuously. In addition, in sewage treatment facilities that remove pollutants from factory wastewater, if fluctuations in the quality of the raw water flowing into the facility can be captured, operating conditions can be set according to the water quality, and appropriate operation management and consumption It will be possible to reduce power consumption and chemical consumption.

However, these water quality analyzes have a problem that it is difficult to continuously monitor the water quality because the procedure is complicated and specialized techniques are required.
Therefore, in recent years, attention has been focused on a method for determining the concentration of pollutants in water by measuring the intensity of fluorescence emitted from the sample water when the sample water is irradiated with excitation light.

  As a method for measuring the fluorescence intensity, Patent Document 1 discloses that light having an excitation wavelength of 270 nm to 370 nm is irradiated on water to be inspected, and the fluorescence wavelength of 380 nm to 480 nm in the spectrum is measured. A water quality test method is disclosed, wherein the trihalomethane production ability or humic substance concentration in the water is measured.

  Patent Document 2 includes a pumping light generator that generates pumping light having a preset wavelength, and a wavelength light extractor that extracts each wavelength of light within a specific wavelength range, and is irradiated from the pumping light generator. Measure the light intensity by extracting each wavelength light within a specific wavelength range included in the fluorescence emitted from the test water that is the organic matter measurement target by the excited light, or collectively and based on the measurement result, There is disclosed a concentration measuring device for measuring the concentration of organic matter in the test water and a fluorescence analysis water quality measuring system comprising the measuring device.

  In Patent Document 3, a filter having a pore diameter of 5 μm or less for removing turbidity of water to be measured, irradiation means for irradiating light to the water to be measured after filtering by the filter, and light irradiation by the irradiation means. Fluorescence measuring means for measuring the intensity of fluorescence generated from the measured water, and data measurement for measuring data on the precursor of the organic halogen compound in the measured water based on the fluorescence intensity measured by the fluorescence measuring means And a water quality measuring device characterized by comprising the means.

  Further, Patent Document 4 is based on irradiating sample water with first and second excitation lights having different wavelengths, and measuring the intensity of first and second fluorescence having different wavelengths emitted from the sample water. There is disclosed a water quality measuring method characterized by measuring first and second water quality indexes of sample water.

JP 7-294434 A JP 2001-83095 A JP 2003-90797 A JP 2005-30839 A

  The above conventional fluorescence measurement method is considered to be suitable for continuous on-site water quality monitoring. However, as the suspended solid concentration in the sample water increases, the irradiation light for excitation is scattered by the suspended solid. However, even if the sample water has the same dissolved pollutant concentration, the intensity of the emitted fluorescence changes. For this reason, it is necessary to separately perform correction by measuring turbidity and the like. However, the wavelength band is different between the irradiation light used in the fluorescence measurement method and the light used for measurement of turbidity. It is known that the light of two different wavelength bands has different scattering characteristics or absorption characteristics, and the measured value changes greatly when the mixed suspended matter is changed.

  For this reason, Patent Document 2 discloses a method of removing suspended substances in advance using a filter or the like. In the case of this method, when the suspended substance concentration is high, problems such as the filter being clogged immediately occur, and the maintainability is significantly lowered.

  In the present invention, in order to solve the above problems, the intensity of fluorescence emitted by irradiating the sample water with excitation light is measured, and at the same time, Raman scattered light of water molecules (scattering of about 15% longer than the wavelength of the irradiated light). The light intensity was also measured, and when the Raman scattered light intensity of water molecules was small, correction was performed because the fluorescence intensity emitted was small even at the same dissolved pollutant concentration.

When the concentration of the suspending substance in the sample water is increased, the irradiated light is scattered by the suspending substance, and the effective irradiation amount with respect to the dissolved pollutant is reduced, so that the generated fluorescence is reduced. Also, the generated fluorescence is scattered by the suspended substance, and the detection amount is reduced.
When this degree of scattering was estimated by turbidity measured using light in other wavelength bands, it was found that correct estimation could not be performed because of different scattering characteristics or absorption characteristics.
Therefore, by detecting the Raman scattered light intensity of water molecules having a known concentration and using it for correction, the effective irradiation amount can be accurately grasped, and the dissolved pollutant concentration can be accurately monitored.

Ｃ：溶存汚濁物質濃度
ａ、ｂ：定数
Ｓｆ：蛍光強度
で表すことができる。そして、下記の式２に水によるラマン散乱光強度（Ｓｒ）の補正項を加えることで、精度良くモニタリングすることが可能となる。

ここで、ａ‘、ｂ‘はａ、ｂとは異なる値である。 When the pollutant concentration to be monitored is 1000 ppm or less, the dissolved pollutant concentration and the fluorescence intensity emitted from it have a first-order correlation,

C: dissolved pollutant concentration a, b: constant Sf: fluorescence intensity. Then, by adding a correction term of Raman scattered light intensity (Sr) by water to the following formula 2, it becomes possible to monitor with high accuracy.

Here, a ′ and b ′ are different values from a and b.

  In this method, sample water in which suspended substances are present on the order of several hundred ppm does not need to be filtered with a filter or the like, and is easy to maintain. In addition, since the light source is one for excitation light, calibration is not required for light source intensity correction and the correction accuracy is higher than that of a method having a separate turbidity measurement light source. Compared with a method of correcting the attenuation of excitation light or fluorescence by irradiating light of a wavelength different from that of excitation light (for example, a turbidimeter uses a wavelength around 600 nm), water quality monitoring with higher accuracy is possible.

  According to the present invention, even when sample water containing a large amount of suspended substances is used, the concentration of dissolved pollutants can be accurately monitored. In particular, in treatment facilities that remove pollutants from sewage and factory wastewater, if changes in the quality of raw water flowing into the facility can be captured, it is possible to set operating conditions according to the water quality, and to ensure proper operation management and consumption. It will be possible to reduce power consumption and chemical consumption.

The present invention measures the quality of water in which suspended substances exist, and the target water is, for example, sewage, factory wastewater, environmental water (river water, lake water, seawater, etc.), and the like. The dissolved pollutants to be measured are COD (chemical oxygen demand), oil, humic substances, NO ³⁻ ions and the like. In the case of COD, the concentration is about 10 to 1000, usually about 100 to 500, and the concentration of the suspended substance is about 50 to 1000 mg / l, usually about 100 to 500 mg / l. This concentration is measured by JIS or sewage test method.

The light irradiated to the sample water is of a wavelength that excites the dissolved pollutant to be measured and emits fluorescence. In the case of COD, the light has a wavelength of about 220 to 350 nm, preferably about 260 to 290 nm. It is.
Light with a wavelength other than the above contained in the light source may not be removed for wavelengths that do not affect the measurement, but at least the region of the same wavelength as the Raman scattered light by the water molecules of the fluorescence and excitation light to be measured It is preferable to remove it. The removing means may be a conventional method, for example, a filter or a prism is used.

が最小になるように定数ａ‘、ｂ‘を決定する。
ラマン散乱光は、入射光の振動数（Ｖ）と照射された物質に固有の振動数（Ｖ_１、Ｖ_２・・・）が総合した振動数（ＶＩ_１、ＶＩ_２・・・）の散乱光であるが、図３に示すように、最も強度の大きなものを測定するのがよい。この散乱光は、前述のように水分子の場合は照射光の波長より約１５％長波長の散乱光である。 The fluorescence and Raman scattered light to be measured may be targeted for all their wavelengths, but are usually a part of them and a wavelength that is strong and has no other influence is selected.
The method of the present invention is a method in which the concentration of dissolved pollutant is measured by fluorescence intensity, and the influence of the suspended substance at that time is corrected by the intensity of Raman scattered light by water molecules.
Therefore, sample water of 3 samples or more, preferably 10 samples or more having different dissolved pollutant concentration and suspending substance concentration is prepared in advance, and depending on the dissolved pollutant concentration (C _k ), fluorescence intensity (Sf _k ), and water The Raman scattered light intensity (Sr _k ) is measured.

The constants a ′ and b ′ are determined so that is minimized.
The Raman scattered light is scattered at a frequency (VI ₁ , VI ₂ ...) Obtained by combining the frequency (V) of incident light and the frequencies (V ₁ , V ₂ ...) Inherent to the irradiated material. Although it is light, as shown in FIG. 3, it is good to measure a thing with the largest intensity | strength. As described above, in the case of water molecules, this scattered light is scattered light having a wavelength about 15% longer than the wavelength of the irradiation light.

When the constants a and b are determined, the fluorescence of the sample water and the intensity of Raman scattered light are measured, and the concentration of the dissolved pollutant can be obtained from the measured values.
FIG. 1 shows a schematic configuration of an example of an apparatus used in the method of the present invention. Sample water 1 to be monitored for the concentration of dissolved pollutants, a light source 2 for irradiating excitation light 3, a light receiver 5 for observing fluorescence emitted from the sample water and Raman scattered light 4 from the water, observed fluorescence intensity and water The calculation unit 6 that calculates the dissolved pollutant concentration by the conversion formula (Formula 2) and the display unit 7 are used.

  The light receiver 5 has a mechanism capable of observing the intensity of each optically by using a half mirror, an optical filter, or the like, since both the fluorescent light and the Raman scattered light due to water are incident simultaneously.

  The apparatus shown in FIG. 1 was used. The light receiver has the composition shown in FIG. Raman scattered light due to fluorescence and water enters from the light entrance 51. The incident light is divided into 50% by the half mirror 52, and one of the light passes through a band-pass filter 55 matched to the fluorescence wavelength, and the fluorescence intensity is observed by a photomultiplier. The other light passes through the band-pass filter 56 for Raman scattered light wavelength by water, and the intensity is measured by the photomultiplier 57.

Dissolved chemical oxygen demand (COD) was monitored using the inflow water from an aeration tank of a municipal sewage treatment plant as sample water. Since the sample water was sewage before treatment, it contained a lot of suspending substances, and the suspending substance concentration (SS) was 100 to 200 mg / L. COD was measured by a method based on a sewage test.
It was confirmed as follows that there was a correlation between fluorescence emitted when irradiated with ultraviolet rays (wavelength 275 to 285 nm) and dissolved COD.

  The fluorescence measured the intensity | strength of the wavelength of 355-365 nm. The results of plotting the observed fluorescence intensity against the COD concentration are shown in FIG. At this time, the SS concentration varied greatly from 100 to 200 mg / L. Due to this influence, the correlation between the COD concentration and the simply empty fluorescence intensity was weak.

が最小になるように定数ａ‘、ｂ‘を決定した。
このとき３０７．５〜３１２．５ｎｍの波長の強度を測定し、水によるラマン散乱光の強度とした。
観測されたラマン散乱光強度を用いて補正を行った結果をプロットしたものを図５に示す。 In contrast, the inflow water from the aeration tank of the target sewage treatment plant was sampled 24 times in total every other day for one day, and the COD concentration (C _k ), fluorescence intensity (Sf _k ), and Raman scattered light intensity (Sr _k ) was measured. Based on this result,

The constants a ′ and b ′ were determined so as to be minimized.
At this time, the intensity of a wavelength of 307.5 to 312.5 nm was measured and used as the intensity of Raman scattered light by water.
FIG. 5 shows a plot of the results of correction using the observed Raman scattered light intensity.

  As shown in FIG. 5, the value obtained by the present invention showed a good correlation with the measured value of COD.

  Since the method of the present invention can measure the quality of water containing suspended substances with high reliability as it is, it can be used for measuring the quality of sewage, factory wastewater, river water and the like.

It is a figure which shows the simulation structure of an example of the apparatus used with the method of this invention. It is sectional drawing which shows the structure of the light-receiving part. It is a figure which shows an example of a scattered light spectrum. It is a graph which shows the relationship between COD measured value and fluorescence intensity when correction | amendment by this invention method is not performed. 5 is a graph showing a correlation between a value obtained by correcting the data of FIG. 4 according to the method of the present invention and a measured COD value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sample water 2 Excitation light source 3 Excitation light 4 Raman scattered light by fluorescence and water 5 Light receiver 6 Arithmetic unit 7 Calculation result display device 51 Incident unit 52 Half mirror 54 Mirror 55 Band pass filter for fluorescence wavelength 56 Raman by water Bandpass filter for scattered light wavelength 57 Photomal

Claims (2)

  Suspension characterized by irradiating the sample water with light of a wavelength that excites the dissolved pollutant, measuring the fluorescence intensity generated from the sample water, and measuring the Raman scattered light intensity by water molecules of the irradiated light Of dissolved pollutants in water containing volatile substances   Using a light source that emits light of a wavelength that excites the dissolved pollutant, a receiver that receives fluorescence scattered from the sample water and Raman scattered light from water molecules, and the fluorescence intensity and Raman scattered light intensity measured by the receiver A device for measuring dissolved pollutants in water containing suspended substances, consisting of a calculation unit that calculates the concentration of dissolved pollutants

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