JPH08297119A - Method and device for measuring ultraviolet-ray absorbance of process - Google Patents

Abstract

PURPOSE: To provide an ultraviolet-ray absorbance measuring method for process and its device capable of accurately and continuously measuring the ultraviolet- ray absorbance derived from the absorption of an organic matter even when dissolved ozone exists in the ozone-processed water. CONSTITUTION: The water to be processed is ozone-processed in this process. The ozone-processed water is fed to the first measuring cell 12 as sample water, the light passing through the sample water from a light source is received by a light receiver, and the sum of the ultraviolet-ray absorbance derived from an organic matter and the ultraviolet-ray absorbance derived from dissolved ozone is measured by a converter/calculation section. The sample water finished with measurement is fed to an aeration tank 14 kept at the decompression state, the dissolved ozone is extracted as ozone gas by the diffusion of air, the de-ozone processed water is fed to the second measuring cell 13, and the ultraviolet-ray absorbance derived from only the organic matter is measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is designed to measure the concentration of organic substances and the concentration of dissolved ozone in water before and after ozone treatment in the advanced water purification treatment of tap water represented by ozone treatment and activated carbon treatment. The present invention relates to a method and an apparatus for measuring ultraviolet absorbance for a process.

[0002]

2. Description of the Related Art Generally, in order to purify raw water taken from a river or the like, a flocculant is injected into a raw water in a flocculation sedimentation tank, mixed, and stirred and retained to treat suspended substances (sand, clay, algae) in the raw water. Organic substances such as) are aggregated to precipitate and separate. This process incorporates chlorine treatment for the purpose of algicidal treatment and removal of chromaticity components such as iron and manganese.

Particularly in the suburbs of large cities, rivers are significantly polluted, so that the content of chromaticity components including ammonia and humic substances, which are precursors of the carcinogenic substance THM (trihalomethane), is high. And ammonia react with each other to produce chloramine and consume more chlorine than necessary. As a result, the chlorine injection rate increases and THM increases.

From such a background, in recent years, a method of incorporating an advanced water purification treatment system into a water purification process has been performed for the purpose of removing the above-mentioned substances. This advanced water purification method includes ozone treatment and biological activated carbon treatment.For example, ozone treatment is performed by an ozone treatment tower as an alternative to chlorine treatment, and chromaticity components are removed by an activated carbon treatment tower or biological filtration tower to remove sand. After filtering in a filtration pond, etc., chlorine treatment is performed and the water is sent to the water purification pond. In particular, by performing the ozone treatment before the biological activated carbon treatment, it is possible to improve the tolerance for load fluctuation and the life of the activated carbon.

On the other hand, a new water quality standard for tap water was established in December 1993, and the regulation value was strengthened and the regulation items were increased. This regulation item includes substances that are difficult to remove in the above-mentioned current water treatment facilities, such as volatile organic chlorine compounds, pesticides, and musty odor substances. Therefore, recently, highly purified water treatment represented by ozone treatment and activated carbon treatment, mainly in water purification plants near large cities, is being considered as a facility that meets the above new water quality standards.

Since the above ozone treatment and activated carbon treatment are intended to remove dissolved trace organic substances in water, it is necessary to control not only the amount of water but also the quality of water. Therefore, a process water quality measuring instrument such as an ultraviolet absorptiometer (hereinafter abbreviated as UV meter) must be installed.

The UV meter used for the continuous measurement of such dissolved trace organic substances has a continuous flow absorption spectrophotometry as a measurement principle. The principle of this measurement is that the UV absorption of inorganic substances is hardly recognized at wavelengths of 250 nm or more, but the organic substances show some absorption even at wavelengths of about 254 nm.
Absorption at these wavelengths is mostly organic.

The absorbing substance in E260 has a correlation with the ability to generate trihalomethane which is an organic substance, the ability to generate all organic halogen compounds, etc. Therefore, a UV meter is used as a measuring instrument for the process of an organic substance index. Above wavelength 254nm
Is also an index that serves as a guide for the amount of low biodegradable organic matter having a double bond represented by C = C.

At the above wavelength of about 254 nm, not only organic matter but also dissolved ozone is absorbed. Therefore, when a UV meter is used in an ozone treatment facility, the ultraviolet absorbance of ozone-treated water is the value of "organic matter + dissolved ozone". Will be displayed. Therefore, in order to control the water quality based on ozone treatment, the measured values of the UV meter should be “organic matter” and “dissolved ozone”.
It is necessary to separate into

Generally, the ultraviolet absorbance (UV) is an analytical method utilizing the fact that light is absorbed by a substance in the range of 200 to 400 nm, which is the wavelength range of ultraviolet rays, and usually the absorbance at a wavelength of 254 nm ( E260) and the absorbance at wavelength 370 nm (E370). E260 is potassium permanganate consumption (m
It is known that E370 has a high correlation with g / l) and E370 has a high correlation with chromaticity.

[0011]

However, a problem in applying the measurement by the ultraviolet absorptiometer to the ozone-treated water used in the above-mentioned advanced water treatment system is that the maximum absorption band of ozone is at the wavelength of 254 nm. Therefore, when ozone is present as dissolved ozone in the test water measured with a UV meter, the reading on the UV meter depends on the absorption of ultraviolet rays at a wavelength of 254 nm, which is derived from the absorption of organic matter, and the absorption derived from dissolved ozone. However, there is a problem in that the measured value becomes high because the minute is added.

That is, when the ozone-treated water contains dissolved ozone, it is impossible to accurately measure the ultraviolet absorbance based on the absorption of organic substances. On the other hand, since ozone in water decomposes and diffuses into the gas phase very fast, the ozone-treated water after ozone treatment is temporarily stored and left, and when the dissolved ozone disappears, measurement by a UV meter is performed. It is also possible, but this method requires extra time before measurement, so it is not possible to quickly respond to changes in the water quality of the raw water for ozonation or changes in the water quality of ozonated water due to changes in ozonation conditions, There is a problem that an accurate measured value cannot be obtained.

In particular, it is considered that it is possible to manage or control the ozone treatment conditions based on the fact that the UV value derived from organic substances changes before and after the ozone treatment. Based on organic matter in U
At present, it is desired to realize an apparatus capable of accurately measuring the V value.

In view of the above problems, the present invention accurately and continuously measures the ultraviolet absorbance derived from the absorption of organic matter by performing a simple pretreatment even if dissolved ozone is present in the ozone-treated water. It is an object of the present invention to provide an ultraviolet absorption measuring method and apparatus for a process capable of performing the same.

[0015]

In order to achieve the above-mentioned object, the present invention is directed to the treatment of water to be treated with ozone according to claim 1 so as to remove dissolved trace organic substances in water. In the process, the water to be treated after performing the ozone treatment is collected as test water, the test water flows into the first measuring cell, and the light passing through the test water from the light source is received by the light receiver. Then, the converter / calculator measures the total of the UV absorbance derived from organic substances and the UV absorbance derived from dissolved ozone, and the sample water after the above measurement is flown into the aeration tank which is kept under a reduced pressure and air Dissolved ozone is extracted as ozone gas by the emission of water, the de-ozonized water flows into the second measurement cell, and the light passing through the test water from the light source is received by the light receiver and converted into organic matter by the converter / calculator. Derived UV absorbance Only provides UV absorbance measurement method for processes to be measured.

By setting the extraction amount of ozone gas by the extraction pump attached to the aeration tank to be larger than the amount of air sent into the aeration tank, the inside of the aeration tank is kept in a depressurized state. .

According to claim 3, the water to be treated before the ozone treatment is sampled as a sample water, and the sample water is the first sample water.
The method for measuring the absorbance of ultraviolet light, wherein the light that has flowed into the measuring cell and passed through the test water from the light source is received by the light receiver and the ultraviolet light absorbance derived from the organic matter is measured by the converter / calculator.

Further, according to claim 4, the first measuring cell into which the test water containing the dissolved ozone flows, and the test water discharged from the first measuring cell, in which air is diffused under reduced pressure, to dissolve the dissolved ozone. Based on the light passing through each measurement cell from the light source to the aeration tank for drawing out ozone as ozone gas, the second measurement cell into which de-ozoned water from the aeration tank flows, and the first and second measurement cells. In the configuration of the ultraviolet absorption measuring device for the process, which comprises a total of the ultraviolet absorption derived from the organic matter and the ultraviolet absorption derived from the dissolved ozone, and a converter / calculation unit for measuring only the ultraviolet absorption derived from the organic matter. There is.

[0019]

According to the ultraviolet absorption measuring method and apparatus for such a process, when the sample water is ozone-treated water, the sample water flows into the first measuring cell and the ultraviolet ray is detected based on the UV measuring principle. The absorbance was measured and output from the converter / calculator as the sum of the ultraviolet absorbance derived from organic substances and the ultraviolet absorbance derived from dissolved ozone, and this sample water then flowed into the aeration tank kept under reduced pressure. Dissolved ozone is extracted as ozone gas due to air diffusion, and the resulting de-ozonized water flows into the second measurement cell and UV absorbance is measured again based on the UV measurement principle, and the ozone is removed from the converter / calculation unit. The UV absorbance derived from the organic matter of the ozone-treated water is output.

Therefore, by taking the difference between the respective measured values of the first measuring cell and the second measuring cell, the ultraviolet absorbance derived from dissolved ozone can be obtained. When the test water before ozone treatment flows into the first measurement cell, the UV absorbance measured by the first measurement cell becomes the UV absorbance derived from the organic substance as it is.

Therefore, according to the present embodiment, the influence of dissolved ozone in the ozone-treated water can be eliminated, and the ultraviolet absorbance derived from the absorption of organic substances and the ultraviolet absorbance derived from dissolved ozone can be accurately measured. .

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the ultraviolet absorption measuring method and apparatus for the process according to the present invention will be described below with reference to the drawings. The schematic diagram of FIG. 1 assumes that the test water is ozone-treated water. In the figure, 1 is a treated water tank, 2 is a flowmeter of treated water, 3 is an ozone treatment tower, 4 is an ozone generator, Reference numeral 5 is a flow meter of injected ozone, 6 is a flow meter of ozone-treated water, and 7 is a diffuser pipe arranged in the vicinity of the bottom wall of the ozone treatment tower 3.

Reference numeral 8 is an ultraviolet absorption measuring apparatus as a whole, 9 is a pump for collecting ozone-treated water, 10 is a water temperature gauge, 11 is a chemical solution tank, 12 is a first measuring cell, and 13 is a second measuring cell. A measurement cell, 14 is an aeration tank, 15 is an aeration amount control valve,
16 is an air diffuser disposed near the bottom wall of the aeration tank 14, 17
Is an aeration pump, 18 is an ozone gas extraction pump, 19
Is an ozone gas extraction adjusting valve, and 20 is an activated carbon filter.

The basic operation of this embodiment is as follows. First, an operation example in which the water to be treated after the ozone treatment is used as the test water will be described. That is, the treated water stored in the treated water tank 1 flows in from above the ozone treatment tower 3 via the flow meter 2. At the same time, the ozone gas obtained by activating the ozone generator 4 is diffused through the flow meter 5 from the air diffusing pipe 7 arranged near the bottom wall in the ozone treatment tower 3 into the water to be treated as a countercurrent flow, which is desired. After the ozone treatment is performed, the ozone-treated water 2 is passed through the conduit 23 and the flow meter 6.
1 flows out. The ozone gas remaining in the ozone processing tower 3 is led out from the upper wall portion of the ozone processing tower 3, fed into the exhaust ozone processing facility 22, detoxified, and then discharged.

A part of the ozone-treated water 21 is sampled by the water sampling pump 9 as sample water, and the sample water passes through the water temperature gauge 10 and then flows into the first measuring cell 12, which will be described in detail later. Based on the principle, the ultraviolet absorbance (UV), visible light absorbance (VIS) and turbidity correction signal (UV-VI)
S) is measured.

This test water flows from the first measuring cell 12 into the aeration tank 14, and the air sent through the aeration amount adjusting valve 15 with the driving of the aeration pump 17 is near the bottom wall of the aeration tank 14. The air is diffused from the air diffuser 16 arranged. Dissolved ozone contained in the test water is gasified by this aeration, and is extracted from the upper wall of the aeration tank 14 by driving the extraction pump 18 and introduced into the activated carbon filter 20 through the ozone gas extraction adjustment valve 19. It is detoxified and released into the atmosphere.

In this embodiment, the extraction amount of ozone gas by the extraction pump 18 is larger than the aeration amount inside the aeration tank 14, that is, the amount of air sent into the aeration tank 14 when the aeration pump 17 is driven. Is set, and along with this, the inside of the aeration tank 14 is in a depressurized state, and efficient deozone treatment can be performed.

The reason why the water temperature gauge 10 is provided between the water sampling pump and the first measuring cell 12 is that the water temperature of the normal test water is 1.
If the temperature is as low as 5 ° C. or lower, the aeration time required for deozoneing becomes long. Therefore, after confirming that the water temperature of the sample water is 15 ° C. or more by the water temperature meter 10, the first measuring cell 12 I am sending it to.

The test water thus deozoned in the aeration tank 14 flows into the second measuring cell 13 in the next stage,
Ultraviolet absorbance (UV), visible light absorbance (VIS) of test water
And the turbidity correction signal (UV-VIS) is measured. The measured water after the measurement flows out as drainage 24.

The inner wall portion of the first measuring cell 12 is easily contaminated by the organic components in the ozone-treated water 21 or the adhesion of iron, manganese, etc. oxidized by ozone.
2 to 5 stored in the chemical liquid tank 11 after the measurement of one time
Using% hydrochloric acid, the inner wall of the measuring cell 12 is cleaned by the cooperation of a wiper rubber (not shown).

Referring to FIG. 2, the first measuring cell 12 and the second measuring cell 12
The principle of UV and VIS measurement by the measuring cell 13 will be described. Reference numeral 25 is a light source power source unit, and 26a and 26b are a pair of light source lamps, and the first measurement cell 12 and the second measurement cell 13 are arranged close to the light source lamps 26a and 26b.

Further, light separating splitters 30a and 30b are arranged between the light source lamps 26a and 26b and the first and second measuring cells 12 and 13, respectively, and on the optical paths of the light separating splitters 30a and 30b. Each has a light receiver 31
a and 31b are provided, and the light receivers 31a and 31b are connected to the reference signal lines 32a and 32b.

The pair of light source lamps 26a, 26b attached to the first measuring cell 12 and the second measuring cell 13
A pair of optical receivers 27a and 27b are arranged at positions facing each other, and the signals received by the optical receivers 27a and 27b are input to the converter / calculator 29 via the amplifiers 28a and 28b. Reference numeral 30 is an E260 output unit, 31 is a dissolved ozone concentration output unit, and the output units 30 and 31 are connected to a display unit (not shown). Incidentally, the reference signal lines 32a, 3
The other end of 2b is connected to amplifiers 28a and 28b.

The two light source lamps 26a and 26b are low pressure mercury lamps, and the wavelength output of the light source lamp 26a is 2
54 nm, and the wavelength output of the light source lamp 26b is 546 nm.

The UV and VIS measurement operation and the measurement principle by the above structure are as follows. First, the light source 26a is turned on at the same time when the test water that is ozone-treated water flows into the first measuring cell 12 through the test water inlet 12a. Then, the 254 nm light emitted from the light source 26a emits the first measurement cell 1
Before passing through 2, the light is split by the light splitting splitter 30a, received by the light receiver 31a, and input to the amplifier 28a via the reference signal line 32a.

The light that has passed through the test water in the first measuring cell 12 is received by the light receiver 27a, the signal is amplified by the amplifier 28a, and then sent to the converter / calculator 29, which is a known principle of ultraviolet absorbance measurement. UV absorbance based on
And visible light absorbance (VIS) and turbidity correction signal (UV-V
IS) is measured and output from the E260 output unit 30 to a display unit (not shown).

E260 of the ozone-treated water measured by the first measuring cell 12 is expressed by the following equation (1).

Ozone-treated water (E260) = E260 _organic + E260do ₃ (1) where E260 _organic : E260 value derived from _organic matter E260do ₃ : E260 value derived from dissolved ozone Therefore, the ozone-treated water measured ( E260) is the sum of the ultraviolet absorbance E260do ₃ derived from ultraviolet absorbance E260 _organic dissolved ozone derived from organic matter.
In addition, the light receiver 31a is separated by the light splitting splitter 30a.
Since the light received at 2 has not passed through the test water, this light is input to the amplifier 28a via the reference signal line 32a and is used as a reference value or a correction value for the above measurement value.

Next, the sample water is deozoned by the aeration tank 14 shown in FIG. 1 and then flows into the second measuring cell 13 from the sample water inlet 13a to perform the same measurement operation.
That is, the light of 546 nm emitted from the light source 26b is separated by the light separation splitter 30b before passing through the second measurement cell 13, and is received by the light receiver 31b.
It is input to the amplifier 28b via b. The light passing through the inside of the second measuring cell 13 is received by the light receiver 27b, the signal is amplified by the amplifier 28b, and then sent to the converter / calculation unit 29, and the deozoneized water is subjected to the equation (2) below. E
260 is output from the E260 output unit 30. De-Ozone-treated water (E260) = E260 _organic ... (2) Therefore, E260 measured by the second measuring cell 13 is derived from organic substances in the de-Ozone-treated water. It becomes E260. Then, when the difference between the respective measured values of the first measurement cell 12 and the second measurement cell 13 is taken, E260 derived from dissolved ozone is obtained as in the following formula (3).

Ozone-treated water (E260) -de-ozone-treated water (E260) = E260do ₃ ... (3) At this time, in the converter / calculation unit 29, the UV signal and UV-
The dissolved ozone concentration is calculated by using the VIS signal, and is output from the dissolved ozone concentration output unit 31.
The measured water for which measurement has been completed is drained from the drain port 13b of the second measurement cell 13.

Next, an operation example when the test water is before ozone treatment will be described. That is, the liquid stored in the to-be-treated water tank 1 shown in FIG. 1 is sampled by using a water sampling pump (not shown), and the liquid is immediately passed through the ozone absorption tower 3 without passing through the ozone treatment tower 3. It is only necessary to lead to the measuring cell 12 of No. 1 and measure the ultraviolet absorption (UV), visible light absorption (VIS) and turbidity correction signal (UV-VIS) of the sample water based on the above-mentioned operating method. In this case, even if the second measuring cell 13 is not used, E260 _organic , that is, E2 derived from an organic substance is used.
Sixty values can be determined.

The converter / calculator 2 thus obtained
The output signal 9 is used for monitoring the ozone treatment state and controlling ozone injection amount data.

FIG. 2 is a correlation diagram of the dissolved ozone concentration (mg / l) and E260 at an optical path length of 20 mm, and it was found that both have a good linear relationship.

According to the ultraviolet absorption measuring apparatus according to the present embodiment described above, the E260 derived from organic matter and the dissolved ozone concentration are simultaneously measured regardless of whether the ozone-treated water or the ozone-untreated water is detected. It is possible to
Further, by selecting the cell length of each of the measuring cells 12 and 13, it is possible to measure the test water containing low to high concentrations of organic substances.

[0045]

As described in detail above, according to the present invention, when the test water is ozone-treated water, the ultraviolet absorbance derived from the organic matter and the ultraviolet absorbance derived from the dissolved ozone are measured by the first measuring cell. Is calculated as the sum of the following, and after the ozone gas is drawn out by the aeration tank held under the reduced pressure in the next stage, the second measurement cell is used to obtain the ultraviolet absorbance derived from the organic matter of the deozonated water, and From the difference between the measured values of the measurement cell and the second measurement cell, the ultraviolet absorbance derived from the dissolved ozone is obtained by the converter / calculation unit. When the test water is before ozone treatment, the UV absorbance measured by the first measuring cell is the UV absorbance derived from the organic substance as it is.

Therefore, according to this embodiment, the influence of dissolved ozone in the ozone-treated water is eliminated, and the ultraviolet absorbance derived from the absorption of organic matter in the ozone-treated water and the ultraviolet absorbance derived from the dissolved ozone are accurately measured. It is possible to quickly respond to changes in the water quality of raw water for ozone treatment and changes in water quality due to changes in ozone treatment conditions, and accurately manage and control ozone treatment conditions based on the obtained measurement values. You can

In particular, in the present invention, even if dissolved ozone is present in the ozone-treated water, the ozone absorptive treatment is carried out in the aeration tank kept under reduced pressure, whereby the ultraviolet absorbance derived from the absorption of the organic matter is accurately and accurately obtained. It is possible to provide an ultraviolet absorbance measuring method and apparatus capable of continuously measuring.

[Brief description of drawings]

FIG. 1 is a schematic view showing an overall ultraviolet absorption measuring apparatus for a process according to this embodiment.

FIG. 2 is a schematic diagram showing the principle of ultraviolet absorbance measurement in this example.

FIG. 3 is a graph showing a correlation between dissolved ozone concentration and ultraviolet absorbance (E260) at an optical path length of 20 mm.

[Explanation of symbols]

 1 ... Water tank to be treated 2, 5, 6 ... Flowmeter 3 ... Ozone treatment tower 4 ... Ozone generator 7, 16 ... Diffuser tube 8 ... Ultraviolet absorption measuring device 9 ... Water sampling pump 10 ... Water thermometer 11 ... Chemical solution tank 12 ... 1st measurement cell 13 ... 2nd measurement cell 14 ... Aeration tank 15 ... Aeration amount control valve 17 ... Aeration pump 18 ... Ozone gas extraction pump 20 ... Activated carbon filter 25 ... Light source power supply part 26a, 26b ... Light source lamp 27a , 27b ... Photoreceivers 28a, 28b ... Amplifier 29 ... Converter / calculator 30a, 30b ... Optical separation splitter 31a, 31b ... Photoreceiver 32a, 32b ... Reference signal line

Claims (4)

[Claims] 1. By treating the water to be treated with ozone,
In the process for removing dissolved trace organic substances in water, the treated water after the ozone treatment is taken as test water, and the test water flows into the first measurement cell, The light that has passed through the test water from the light source is received by the light receiver, and the total sum of the UV absorbance derived from the organic matter and the UV absorbance derived from the dissolved ozone is measured in the converter / calculation unit, and the measurement is completed. Flows into an aeration tank that is kept under reduced pressure, and the dissolved ozone is extracted as ozone gas by the air diffusion,
The deozone-treated water flows into the second measuring cell, and the light passing through the test water from the light source is received by the light receiving device and the converter
An ultraviolet absorption measuring method for a process, characterized in that the calculating unit measures only the ultraviolet absorption derived from an organic substance. 2. A depressurized state is maintained inside the aeration tank by setting the amount of ozone gas drawn by the drawing pump attached to the aeration tank to be larger than the amount of air sent into the aeration tank. An ultraviolet absorption measuring method for a process according to claim 1, which is configured as described above. 3. By treating the water to be treated with ozone,
In the process for removing dissolved trace organic substances in water, the untreated water before the ozone treatment is sampled as test water, and the test water flows into the first measurement cell, An ultraviolet absorption measuring method for a process, characterized in that the light passing through the test water from a light source is received by a light receiver, and the ultraviolet absorption derived from an organic substance is measured by a converter / calculator. 4. A first measuring cell into which a test water containing dissolved ozone flows and a test water discharged from the first measuring cell, in which air is diffused under reduced pressure to extract the dissolved ozone as ozone gas. The aeration tank, the second measurement cell into which the de-ozoned water from the aeration tank flows, and the first and second measurement cells are derived from organic matter based on the light passing through each measurement cell from the light source. An ultraviolet absorption measuring apparatus for a process, comprising: a converter / calculation unit for measuring only the total of the ultraviolet absorption derived from dissolved ozone and the ultraviolet absorption derived from dissolved ozone.