JP2009236831A - 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 dissolved pollutants in water containing the suspended substance, light having a wavelength that excites the dissolved pollutant is irradiated into sample water, and fluorescence intensity generated from the sample water is measured, and the Rayleigh 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 in order to preserve water quality, and sewage treatment plants, factories, offices, etc. have to comply with various regulatory values based on the Water Pollution Control Law. 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 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.

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, A fluorescence analysis water quality measurement system comprising a concentration measurement device for measuring the concentration of organic substances in the test water and a body measurement device is disclosed.

  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 the fluorescence emitted by irradiating the sample water with excitation light is measured, and at the same time, the Rayleigh scattered light (same as the irradiated light) is scattered by the suspended substance. The intensity of the light (wavelength) was also measured, and when the Rayleigh scattered light intensity was high, correction was performed because the fluorescence intensity emitted was small even at the same dissolved pollution 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, in order to directly evaluate the scattering amount of the irradiation light for excitation, it is possible to detect the Rayleigh scattered light intensity and use it for correction, and to accurately monitor the dissolved pollutant concentration.
When the pollutant concentration to be monitored is 1000 mg / L or less, the dissolved pollutant concentration and the fluorescence intensity emitted from it have a primary correlation,
C = a + b × Sf (Formula 1)
C: dissolved pollutant concentration a, b: constant Sf: fluorescence intensity. Then, by adding a correction term for Rayleigh scattered light intensity (Sl) as shown in the following formula 2, it becomes possible to monitor with high accuracy.
C = a + b * Sf + c * Sl + d * Sf * Sl (Formula 2)
Here, the correction term (c × Sl + d × Sf × Sl) can be approximated by c ′ × Sl when Sf << Sl.

  In this method, sample water in which suspended substances are present on the order of several hundred mg / L 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.

  The present invention makes it possible to accurately monitor the concentration of dissolved pollutants even for sample water containing a large amount of suspended substances. In particular, in treatment facilities that remove pollutants from sewage and factory wastewater, if changes 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 power consumption can be achieved. And consumption chemicals can be reduced.

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. Dissolved pollutants to be measured, COD (chemical oxygen demand), humic, NO ₃ ^- is an ion or 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 density | concentration is measured by the method based on JIS or a sewage test method.

The light applied to the sample water collected from the water is of a wavelength that excites the dissolved pollutant to be measured and emits fluorescence. In the case of COD, the light is about 220 to 350 nm, preferably about 260 to 290 nm. It is light of the wavelength.
The strongest fluorescence was observed when the test was conducted with the target dissolved pollutant solution containing no suspended substances. A combination of excitation light wavelength and fluorescence detection wavelength is used.
The light having the above wavelength contained in the light source may not be removed for wavelengths that do not affect the measurement, but it is preferable to remove at least a region having the same wavelength as the fluorescence to be measured. The removing means may be a conventional method, for example, a filter or a prism is used.

が最小となるように定数ａ、ｂ、ｃ、およびｄを決定する。 The fluorescence and Rayleigh scattered light to be measured may be targeted for all their wavelengths, but are usually a part of them and a wavelength that is high in intensity and unaffected by other 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 Rayleigh scattered light.
Therefore, sample water of 5 samples or more, preferably 10 samples or more having different dissolved pollutant concentration, suspended substance concentration and suspended substance concentration is prepared in advance, and dissolved pollutant concentration (C _k ) and fluorescence intensity ( Sf _k ) and Rayleigh scattered light intensity (S _{1 k} ) are measured.

The constants a, b, c, and d are determined so that is minimized.

When these four constants are determined, the intensity of the fluorescence of the sample water and the Rayleigh scattered light can be 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 that irradiates excitation light 3, a light receiver 5 that observes fluorescence and Rayleigh scattered light 4 emitted from the sample water, observed fluorescence intensity and Rayleigh scattered light Using the intensity, the calculation unit 6 and the display unit 7 calculate the dissolved pollutant concentration by the conversion formula (Formula 2).

  The light receiver 5 has a mechanism capable of observing the intensity of each optically by using a half mirror or an optical filter because fluorescence and Rayleigh scattered light are incident simultaneously.

  The apparatus shown in FIG. 1 was used. The light receiver has the composition shown in FIG. Fluorescence and Rayleigh scattered light are incident from the light incident portion 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 bandpass filter 56 for Rayleigh scattered light wavelength, and its intensity is measured by a 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 suspended substances, and the suspended substance concentration (SS) was 100 to 200 mg / L. COD was measured by a method based on the sewage test method.
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 was measured at a wavelength of 355 to 365 nm.

が最小になるように定数ａ、ｂ、ｃ、およびｄを決定した。本事例ではｄがｃと比べて十分小さかったため、ｄ×Ｓｆ_ｋ×Ｓｌ_ｋの項を省略し、
Ｃ＝ａ+ｂ×Ｓｆ×ｃ×Ｓｌで補正を行った。
観測されたレイリー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４に示す。
図４に示すように、本発明で得られた値はＣＯＤの実測値とよい相関を示した。 The result of plotting the observed fluorescence intensity against the COD concentration is shown in FIG. At this time, since the SS concentration varied greatly from 100 to 200 mg / L, the correlation between the COD concentration and the observed fluorescence intensity was weak. 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 COD concentration (C _k ), fluorescence concentration (Sf _k ), and Rayleigh scattered light intensity (Sl _k ) was measured. Based on this result,

The constants a, b, c, and d were determined so that is minimized. Since d was sufficiently small compared with c in this case, omitting the term of d × Sf _k × Sl _k,
Correction was performed with C = a + b × Sf × c × S1.
A plot of the results of correction using the observed Rayleigh scattered light intensity is shown in FIG.
As shown in FIG. 4, 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 graph which shows the relationship between COD measured value and fluorescence intensity when correction | amendment by this invention method is not performed. 4 is a graph showing a correlation between values obtained by correcting the data of FIG. 3 according to the method of the present invention and measured COD values.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sample water 2 Excitation light source 3 Excitation light 4 Fluorescence and Rayleigh scattered light 5 Light receiver 6 Calculation part 7 Calculation result display apparatus 51 Light incident part 52 Half mirror 54 Mirror 55 Band pass filter for wavelength of fluorescent light 56 For Rayleigh scattered light wavelength Bandpass filter 57 Photomaru

Claims (2)

  A suspending substance characterized by irradiating sample water with light of a wavelength that excites dissolved pollutant, measuring fluorescence intensity generated from the sample water, and measuring Rayleigh scattered light intensity of the irradiated light. Method for measuring dissolved pollutants in water   A light source that emits light of a wavelength that excites the dissolved pollutant, a receiver that receives fluorescence and Rayleigh scattered light emitted from the sample water, and a dissolved pollutant using the fluorescence intensity and Rayleigh scattered light intensity measured by the receiver A device for measuring dissolved pollutants in water containing suspending substances, consisting of a calculation unit that calculates the concentration

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