JPH09292336A - Method and apparatus for measuring chromaticity and water-treatment control method using method and apparatus thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method and the apparatus for measuring turbidity and the water-treatment control method using the method and the apparatus thereof, which are not affected by the turbidity of liquid to be measured, can cope with the change in performance of the apparatus itself, can display a high performance as the turbidity chromaticity monitor for water-treatment control and can contribute to the unmanned operation of a film-type water purifying system. SOLUTION: In the measuring method for measuring chromaticity of liquid to be measured, the light rays of two wavelengths, one of wavelength of 400nm having a large chromaticity absorption and the other of wavelength of 620nm having almost no chromaticity absorption, are used. For the light rays of respective wavelengths, the absorbencies when the light rays are made to pass through the inside and the outside of an absorbing cell 16 filled with the liquid to be measured are measured. The chromaticity of the liquid to be measured is computed from each of the obtained absorbencies and the relationship between the absorbance obtained beforehand and the chromaticity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chromaticity measuring method and apparatus and a water treatment controlling method using the apparatus, and more particularly to a chromaticity measuring method used in the water treatment field for obtaining purified water such as tap water. And a device, and a water treatment control method using the device.

[0002]

2. Description of the Related Art In the quality standard of tap water, it is prescribed that the chromaticity of tap water be 5 degrees or less. The chromaticity-causing substances contained in raw water of tap water such as river water and groundwater are mainly humic substances and metals (Fe, Mn, etc.), and the chromaticity is measured in the state where these substances are mixed. As the chromaticity measuring method defined by the official water supply method, there are two measuring methods, a colorimetric method and a transmitted light measuring method.

Among the chromaticity measuring methods, the colorimetric method is a colorimetric method with the naked eye, so that an artificial error is likely to occur and continuous measurement is impossible. On the other hand, the transmitted light measurement method uses a wavelength of 3
This is a method of obtaining chromaticity by measuring the absorbance at 90 nm, and continuous measurement is possible. Therefore, the chromaticity measurement device using the transmitted light measurement method is used as a chromaticity monitor of a water purification system in water purification, and chemicals such as coagulants and chlorine agents are based on the chromaticity information sent from this chromaticity monitor. Attempts have been made to control the injection rate of

[0004]

However, in the conventional chromaticity measuring device, an error is likely to occur due to the influence of the turbid component and the dirt of the absorption cell. There is a drawback that the measured values are likely to fluctuate due to fluctuations in luminous intensity due to deterioration of the light source, and fluctuations in luminous intensity due to deterioration of the photodetector element of the light receiving section and its amplifier,
Stable measurement cannot be performed.

For this reason, when water treatment control is performed in a water purification system using a conventional chromaticity measuring device, the chromaticity value from the chromaticity measuring device varies to some extent from the viewpoint of stabilizing the quality of the treated water. In consideration of this, it was uneconomical to inject an excessive amount of chemicals. Further, the membrane type water purification system developed in recent years has a great feature that it can be unmanned. However, the membrane-type water purification system requires an unmanned continuous chromaticity device that is not affected by changes in water quality or performance changes of the device itself, so-called maintenance-free continuous chromaticity device is required, and a chromaticity measurement device corresponding to this is required. There is.

The present invention has been made in view of the above circumstances and is not affected by the turbidity of the liquid to be measured and can cope with a change in the performance of the apparatus itself. Therefore, the chromaticity monitor for water treatment control is provided. It is an object of the present invention to provide a chromaticity measurement method and device that can exhibit high performance as a product, and can also contribute to unmanned membrane water purification systems, and a water treatment control method using the device. .

[0007]

In order to achieve the above object, the present invention provides a method for measuring the chromaticity of a liquid to be measured, wherein a first wavelength having a chromaticity absorption and a color from the first wavelength are used. Each of the obtained light rays of two wavelengths of the second wavelength having a small degree of absorption is measured when the light rays of each wavelength are passed through the inside and outside of the absorption cell filled with the liquid to be measured. It is characterized in that the chromaticity of the liquid to be measured is calculated from the absorbance and the relationship between the absorbance and the chromaticity obtained in advance.

In order to achieve the above-mentioned object, the present invention provides a measuring device for measuring the chromaticity of a liquid to be measured, wherein the light source and the light beam emitted from the light source have a first wavelength having chromaticity absorption. And a selection / switching means for selecting two wavelengths, a second wavelength having a smaller chromaticity absorption than the first wavelength, and switching to either one of the wavelengths, and a light ray having a wavelength obtained by the selection / switching means. Is divided into two optical paths that pass through the inside and outside of the absorption cell filled with the liquid to be measured, and the two-wavelength light beam obtained by the selection / switching means is branched into two optical paths by the branching means. It comprises an absorbance measuring means for measuring each absorbance of each light ray, each measured absorbance, and a calculating means for calculating the chromaticity of the liquid to be measured from the relationship between the absorbance and the chromaticity determined in advance. It is characterized by

According to the present invention, an absorption cell filled with a liquid to be measured is filled with a light beam having two wavelengths, a first wavelength having chromaticity absorption and a second wavelength having smaller chromaticity absorption than the first wavelength. Since the chromaticity is calculated from the difference in each absorbance obtained through the above, stable chromaticity measurement can be performed without causing an error due to a turbid component or an error due to stain on the absorption cell. Further, since the light of the first and second wavelengths is made to pass through the inside and the outside of the absorption cell, the device performance such as deterioration or fluctuation of the light intensity of the light source, the photodetection element of the absorbance measuring means and its amplifier, etc. It is possible to constantly correct the variation in the measured value due to. Therefore, the chromaticity can be measured accurately and stably.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a chromaticity measuring method and apparatus and a water treatment control method using the apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a configuration diagram showing an example of the overall configuration of an embodiment of a chromaticity measuring device of the present invention.

As shown in FIG. 1, the liquid to be measured such as ground water, sewage, and factory wastewater whose chromaticity is to be measured is introduced into a gas-liquid separator 14 by a liquid feed pump 12 to be deaerated, and then the chromaticity is measured. The absorption cell 1 enters from one end of the absorption cell 16 of the measuring device 10.
6 is filled and discharged from the other end of the absorption cell 16 to the outside of the system of the apparatus 10. The chromaticity measuring device 10 is capable of measuring the absorbance of light of two wavelengths, a first wavelength having a large chromaticity absorption and a second wavelength having a small chromaticity absorption, and two optical paths passing through the inside and outside of the absorption cell 16. It is configured so as to have a double beam system. In addition, FIG. 2 showing the relationship between the absorbance and the wavelength in the absorption spectrum of the chromaticity standard solution at 2 and 5 degrees.
As can be seen from the above, a large chromaticity absorption can be obtained at a wavelength of 400 nm, and there is almost no absorption at a wavelength of 600 nm or more. Therefore, an example will be described in which 400 nm is used as the first wavelength and 620 nm is used as the second wavelength. The first and second wavelengths are
It is not limited to 400 nm and 620 nm,
The wavelength in the vicinity can be selected. Further, it is preferable in terms of accuracy to set the two wavelengths so that the difference in absorbance between the first wavelength and the second wavelength becomes large.

The structure of the chromaticity measuring device 10 will be described along the optical path from the light source 18 to the light receiving portion 20. White light from the light source 18 passes through a condenser lens 22 and a light source box 24.
Emanated from. A blower fan 26 is disposed adjacent to the light source box 24 to prevent the internal temperature of the light source box 24 from rising. The white light emitted from the light source box 24 is 400 at the wavelength selector 30 of the wavelength selector / switcher 28.
nm or 620 nm wavelength light is selected. The wavelength selection unit 30 rotates by itself, and the wavelength of 400 nm or 6
One of the wavelengths is selected by positioning the 20 nm diffraction grating 32 in the optical path. Further, a position detector 34 for detecting whether or not the diffraction grating 32 is correctly positioned on the optical path is provided near the wavelength selection unit 30, and is not shown when the position is not correctly positioned. It is corrected by the correction device. The light beam that has passed through the wavelength selector / switch 28 and becomes monochromatic light changes its optical path by 90 ° by the mirror 36 and reaches the half mirror 38. With the half mirror 38,
Due to the effect of reflection and transmission of the half mirror 38, the light beam is 2
It is split into two optical paths. Of the branched light rays, the light rays that have passed through the half mirror 38 are collected by the condenser lens 42 via the mirror 40 and pass through the absorption cell 16 filled with the liquid to be measured. In the case of the liquid to be measured having a small chromaticity, the absorption cell 16 has an optical path length of a normal absorption cell (10 to 5).
The sensitivity can be increased by using a film having a length of 500 mm longer than 0 mm). The transmitted light that has passed through the absorption cell 16 changes its optical path by 90 ° by the mirror 44, is collected by the condenser lens 46, and reaches the optical path switch 48.

On the other hand, the light beam reflected by the half mirror 38 passes through the condenser lens 50 and is turned by 90 ° by the mirror 52.
The light path is changed to form a path to the light path switch 48, so that the light passes through the outside (in the air) of the absorption cell 16. A rotary plate 54 having a slit is attached to the optical path switching device 48, and the optical path switch 48 rotates so that the slit fits in each optical path branched by the half mirror 38. A position detection unit 56 for detecting whether or not the slit is positioned on the optical path is provided near the optical path switch 48, and when the slit is not positioned correctly, it is corrected by a correction device (not shown). It

Of the light rays passing through the slit of the optical path switch 48, the light rays passing through the inside of the absorption cell 16 are the mirrors 5.
The light beam that has been guided to the light receiver 20 by 5 and has passed through the outside of the absorption cell 16 is guided to the light receiver 20 by the mirror 58, and each light absorbance is measured by the light receiver 20. That is, in the light receiver 20, two points passing through the inside and outside of the absorption cell 16 at a wavelength of 400 nm and the absorption cell 1 at a wavelength of 620 nm.
Absorbance is measured at a total of 4 points, 2 points passing through the inside and outside of 6. Then, in the light receiver 20, the measurement information of each absorbance measured by the light receiver 20 and the setting information such as the wavelength selected by the wavelength switching device and the slit set by the optical path switching device are sent to the calculator 60.

In the computing unit 60, 400 having a large chromaticity absorption is used.
The difference in absorbance between two wavelengths, ie, the wavelength of nm and the wavelength of 620 nm at which there is almost no chromaticity absorption, is determined, and the error due to the turbid component of the liquid to be measured and the error due to the contamination of the absorption cell 16 are canceled. Furthermore, in the computing unit 60, 400 nm and 620 n
The difference in absorbance between the double beams inside and outside the absorption cell 16 is obtained for each m, and this is caused by device performance such as deterioration or fluctuation of the light intensity of the light source 18, deterioration or fluctuation of the photodetector element of the light receiver 20 or its amplifier. Cancel the error. Then, the chromaticity of the liquid to be measured is calculated from the relational expression based on the absorbance at 400 nm after canceling these errors and the calibration curve of the absorbance and the chromaticity that is input in advance to the calculator 60. A normal computer can be used as the computing unit 60.

According to the chromaticity measuring device 10 of the present invention thus constructed, the turbidity is measured because the chromaticity is calculated from the difference between the wavelengths having large absorption and the wavelengths having almost no absorption. Stable chromaticity measurement is possible without causing errors due to components or due to stains on the absorption cell. Further, by adopting a double beam system in which light rays are passed through two points inside and outside the absorption cell 16, measurement values resulting from device performance such as luminous intensity of the light source, fluctuation of the photodetector element of the light receiver 20 and its amplifier, etc. Can be constantly corrected.

Here, the method of creating the calibration curve data and the calculation of the chromaticity which are input in advance to the calculator 60 will be described in detail. (1) Preparation of calibration curve A blank measurement is performed using pure water, and a calibration measurement is performed using a standard solution having a chromaticity of 2. Calculate the difference in absorbance at chromaticity 2 from the measurement results at this time and use it as CALRATE.

[0018] Ref side transmittance at 400 nm R0 = {CPD (1,1) -CPD (0,1)} / {BPD (1,1) -BPD (0,
1)} Sample-side transmittance at 400 nm R1 = {CPD (1,2) -CPD (0,2)} / {BPD (1,2) -BPD (0,
2)} Sample absorbance at 400 nm A1 = Log (R1 / R0) Ref side transmittance at 620 nm R0 = {CPD (2,1) -CPD (0,1)} / {BPD (2,1) -BPD (0,
1)} Sample-side transmittance at 620 nm R1 = {CPD (2,2) -CPD (0,2)} / {BPD (2,2) -BPD (0,
2)} Absorbance of Sample at 620 nm A2 = Log (R1 / R0) Difference between absorbance at 400 nm and 620 nm dA = A1 -A2 CALRATE = 2 / dA (2: Chromaticity of standard sample) (2) Absorbance of measured solution And chromaticity calculation Ref side transmittance at 400 nm R0 = {PD (1,1) -PD (0,1)} / {BPD (1,1) -BPD (0,
1)} Sample side transmittance at 400 nm R1 = {PD (1,2) − PD (0,2)} / {BPD (1,2) −BPD (0,
2)} Sample absorbance at 400nm B1 = Log (R1 / R0) Ref side transmittance at 620nm R0 = {PD (2,1) -PD (0,1)} / {BPD (2,1) -BPD (0,
1)} Sample side transmittance at 620 nm R1 = {PD (2,2) -PD (0,2)} / {BPD (2,2) -BPD (0,
2)} Absorbance of Sample at 620nm B2 = Log (R1 / R0) Absorbance difference between 400nm and 620nm dB = B1-B2 Chromaticity = CAL
RATE × dB FIG. 3 shows two wavelengths of 400 nm and 620 nm, an optical path length of the absorption cell of 500 mm, an optical path diameter of 12 mmφ, a chromaticity and a difference of absorbance at two wavelengths (B400 nm-B620 nm) at a liquid transfer amount of 75 ml / min. Is shown. Note that this difference in absorbance is after correction by the double beam method. As can be seen from FIG. 3, the difference between the chromaticity and the absorbance has a clear linear relationship, and it can be seen that the chromaticity can be accurately measured by the chromaticity measuring method of the present invention.

FIG. 4 shows the results of continuous measurement of the chromaticity standard liquid of 2 times for 24 hours using the chromaticity measuring device 10 of the present invention, and FIG. 5 shows the chromaticity measuring device of the present invention. It is the result of continuously measuring tap water (city water) for 24 hours. During this measurement, maintenance such as cleaning of the absorption cell 16 was not performed at all, but as shown in FIGS. 4 and 5, very stable measurement results were obtained.

Next, the turbidity component concentration of the measured liquid is large,
A case where the baseline of absorbance (the position where the absorbance is zero) shifts upwards as a whole will be described. That is, as shown in FIG. 6, when the turbidity component concentration of the liquid to be measured is low, the baseline does not shift as shown in the absorption spectrum of curve A, but when the turbidity component concentration is high,
As in the absorption spectrum of curve B, the baseline shifts upward, and the absorbance is in the state of being added by the amount of the turbid component. This is because when the turbidity component concentration increases, the absorption spectrum of turbidity changes due to the difference in wavelength. However, the following correction was made based on the knowledge that the change in the absorption spectrum of turbidity is wavelength dependent, that is, there is a certain linear relationship between the absorbance due to turbidity and the wavelength.

When the turbidity component concentration of the liquid to be measured is large and the baseline of the absorbance is shifted, the wavelength selection / switch 28 described above has the first wavelength of 400 nm at which the chromaticity absorption is large and the chromaticity absorption A third wavelength, for example, a wavelength of 500 nm is selected between the second wavelength of 620 nm and the almost nonexistent second wavelength. Then, the absorbance at the time of passing the light of 500 nm through the inside and outside of the absorption cell 16 filled with the liquid to be measured is measured and output to the calculator 60. In the calculator 60, a straight line C (see FIG. 6) connecting the obtained absorbance at 500 nm and 620 nm is obtained, and 400 n on this straight line C is obtained.
The turbidity influence in m is calculated, and the turbidity influence is subtracted when calculating the chromaticity of the measured liquid. Accordingly, even when the concentration of suspended matter in the liquid to be measured is large and the baseline of the absorbance is shifted, the chromaticity of the liquid to be measured can be accurately measured.

Next, the case where the chromaticity measuring device 10 of the present invention is used as a chromaticity monitor of a water treatment system will be described. FIG. 7 shows an example in which the chromaticity measuring device 10 of the present invention is applied to chemical injection control of a water treatment system for treating raw water containing humic substances, Fe, and Mn and colored in yellow.

The apparatus configuration of the water treatment system will be described in the order of flow. First, raw water is first added with sodium hypochlorite (NaOCl) in the chlorine reaction tank 62 to insolubilize the coloring component dissolved in the raw water. Next, the sulfuric acid (H ₂
After adjusting the pH by adding SO ₄ ), a flocculant (PAC) is added in the flocculation reaction tank 66 to form microflocs. Next, the microflocified raw water is subjected to solid-liquid separation by the membrane separation device 68 to obtain treated water (purified water). The membrane used in the membrane separation device 68 may be either a microfiltration membrane or an ultrafiltration membrane. Further, the capacity of each reaction tank should be set so that the contact and residence time may be sufficient for sufficient oxidation and aggregation. The control of the injection amount of the medicine to be injected into each tank 62, 64, 66 is based on the chromaticity information of the treated water measured by the chromaticity measuring device 10 of the present invention.
This is performed by feedback control that controls 2, 74.

In controlling the injection amount of this chemical, when the coloring component of the raw water is a humic substance, it is necessary to control the injection amount of PAC particularly accurately.
In that case, it is preferable to control the injection amount of NaOCl with particularly high precision. The reason for this is that if the injection amount of NaOCl becomes excessive, the agglutination reaction becomes insufficient due to the influence of residual chlorine, while if the injection of PAC is not appropriate, poor agglomeration or unreacted aluminum hydroxide [Al (OH) ₃ ] Is increased, the filtration resistance of the membrane separation device at the subsequent stage is increased, and the filtration pressure is increased.

According to the water treatment control method using the chromaticity measuring device 10 of the present invention, it is possible to eliminate errors due to turbid components of raw water and dirt on the absorption cell, and further errors due to device performance. It is possible to accurately control the injection amount of the medicine injected into each tank 62, 64, 66. Therefore, since the injection amount of the chemical can be controlled appropriately, the rise of the filtration pressure can be suppressed, and the chemical cleaning interval of the membrane can be prolonged. Further, unlike the conventional chromaticity measuring device, it is not necessary to inject the drug excessively for safety, so that the running cost is reduced and the economical efficiency is improved. Furthermore, since the chromaticity of the treated water can be stably maintained below the target value, the quality of the treated water can be improved.

In FIG. 7, the chromaticity of the treated water is measured by the chromaticity measuring device 10. However, as shown in FIG. 8, the chromaticity of the raw water is measured by the chromaticity measuring device 10. The amount of sodium hypochlorite, sulfuric acid, and PAC injected may be feed-forward controlled based on the chromaticity information. Although not shown in the figure, it is more preferable to control the injection amount of the drug by measuring the chromaticity of both the raw water and the treated water with the chromaticity measuring device 10.

The chromaticity measuring device 10 of the present invention is applicable not only to chromaticity measurement, but also as a monitor for water quality items for which absorbance is measured to obtain a value, such as nitrate nitrogen.

[0028]

As described above, according to the chromaticity measuring method and apparatus of the present invention and the water treatment controlling method using the apparatus, the error due to the turbid component of the liquid to be measured and the error due to the contamination of the absorption cell. In addition, since the performance change of the device performance of the light source and the absorbance measuring means can be constantly corrected, high performance can be exhibited as a chromaticity monitor for water treatment control.

Further, when the chromaticity measuring device of the present invention is used as a chromaticity monitor for controlling the injection amount of a drug for water treatment, for example, the injection amount can be appropriately controlled, so that excessive injection can be prevented. Running costs can be reduced. Further, since the chromaticity measuring device of the present invention requires almost no maintenance, it can contribute to the unmanned water treatment system, for example, a membrane water purification system.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating an overall configuration of a chromaticity measuring device of the present invention.

FIG. 2 is a graph showing the relationship between the absorbance and the wavelength in the absorption spectra of chromaticity standard solutions of 2 ° and 5 °.

FIG. 3 is a graph showing a correlation between chromaticity and an absorbance difference (B400 nm-B620 nm) in the chromaticity measuring device of the present invention.

FIG. 4 is a graph in which chromaticity standard solutions of 2 ° and 5 ° are continuously measured by the chromaticity measuring device of the present invention.

FIG. 5 is a graph in which tap water (city water) is continuously measured with the chromaticity measuring device of the present invention.

FIG. 6 is a graph showing the relationship between the wavelength and the absorbance when the concentration of the turbid component of the liquid to be measured is large and the baseline of the absorbance shifts upward.

FIG. 7 is a configuration diagram showing an example of a device configuration to which a water treatment control method using a chromaticity measuring device of the present invention is applied.

FIG. 8 is a configuration diagram showing another example of the configuration of an apparatus to which the water treatment control method using the chromaticity measuring apparatus of the present invention is applied.

[Explanation of symbols]

 10 ... Chromaticity measuring device 16 ... Absorption cell 18 ... Light source 20 ... Photoreceiver 22, 42, 46, 50 ... Condensing lens 26 ... Blower fan 28 ... Wavelength selector / switcher 30 ... Wavelength selector 32 ... Diffraction grating 34, 56 ... Position detection unit 36, 40, 44, 52, 55, 58 ... Mirror 38 ... Half mirror 54 ... Rotating plate 60 ... Computing unit 62 ... Chlorine reaction tank 64 ... PH adjusting tank 66 ... Aggregation reaction tank 68 ... Membrane separation device 70, 72, 74 ... Control pump

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Yutaka Okuno 1-1-14, Kanda, Uchida, Chiyoda-ku, Tokyo Inside Hirit Plant Construction Co., Ltd. (72) Masahiro Midorikawa, 9 Mizobata, Sakado, Saitama Prefecture

Claims (6)

[Claims] 1. A measuring method for measuring the chromaticity of a liquid to be measured, using a light beam having two wavelengths, a first wavelength having chromaticity absorption and a second wavelength having smaller chromaticity absorption than the first wavelength. , Measuring the absorbance of the light of each wavelength when passing through the inside and outside of the absorption cell filled with the liquid to be measured, each absorbance obtained, the absorbance from the relationship between the previously obtained absorbance and chromaticity A chromaticity measuring method, which comprises calculating the chromaticity of a measurement liquid. 2. A third wavelength between the first and second wavelengths when the absorbances of the first and second wavelengths shift under the influence of the turbidity component of the liquid to be measured. Of the first wavelength from the absorbance of the third wavelength and the absorbance of the second wavelength obtained by measuring the absorbance when the light ray of is passed through the inside and the outside of the absorption cell filled with the liquid to be measured. The chromaticity measuring method according to claim 1, wherein the turbidity affecting amount of the absorbance is calculated, and the turbidity affecting amount is subtracted when calculating the chromaticity of the liquid to be measured. 3. A measuring device for measuring chromaticity of a liquid to be measured, comprising: a light source; and a light beam emitted from the light source, which has chromaticity absorption.
And a second wavelength having a smaller chromaticity absorption than the first wavelength and selecting / switching means for switching to either one of the wavelengths, and the wavelength obtained by the selecting / switching means. Branching means for splitting the ray of light into two optical paths that pass through the inside and the outside of the absorption cell filled with the liquid to be measured, and the two-wavelength rays obtained by the selecting / switching means are split into two optical paths by the branching means. Absorptiometry means for measuring the absorptance of each of the light rays obtained, and a calculating means for calculating the chromaticity of the liquid to be measured from the absorptance and the chromaticity relationship obtained in advance and the absorptance measured in advance. A chromaticity measuring device characterized in that 4. When the absorbance at the first and second wavelengths shifts under the influence of the turbidity component of the liquid to be measured, the selection / switching means switches between the first and second wavelengths. As a wavelength in between, a light beam of a third wavelength is selected, and the absorbance at the third wavelength is measured when the light is passed through the absorption cell filled with the liquid to be measured by the branching means and the outside thereof. The turbidity influence component of the absorbance of the first wavelength is calculated from the absorbance of the third wavelength and the absorbance of the second wavelength, and the turbidity influence component is calculated when calculating the chromaticity of the measured liquid. The chromaticity measuring device according to claim 3, wherein 5. A water treatment control method using a chromaticity measuring device, wherein water treatment conditions are controlled based on the chromaticity of water measured by the chromaticity measuring device according to claim 3. 6. A water treatment control method using a chromaticity measuring device according to claim 5, wherein the amount of chemicals added to the water is controlled based on the chromaticity measuring device.