JP2001041949A - Apparatus and method for measurement of chemical oxygen demand - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and a method in which a chemical oxygen demand(COD) can be measured more simply and quickly than a COD measuring method adopted by the JIS. SOLUTION: This apparatus which measures a chemical oxygen demand is provided with a reaction part 14 in which dissolved oxygen in a solution to be measured is reacted with an organic substance in the solution to be measured. The apparatus is provided with a dissolved-oxygen measuring part 13 which is used to measure the amount of the dissolved oxygen in the solution to be measured. The apparatus is provided with a calculation part which finds the chemical oxygen demand on the basis of a measured result under a prescribed condition by the dissolved-oxygen measuring part 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to dam water, lake water, and the like.
Chemical oxygen demand (COD: Chemical Ox) in river water, etc.
ygen Demand).

Here, in a dynamic water system such as a river, an indicator directly indicating an effect of an organic substance on an ecosystem is a biological demand (Biochemical Oxygen Demand: BOD), whereas a chemical oxygen The required amount is a measure of the amount of oxygen required to oxidize all organic substances in closed water bodies such as dams, lakes and marshes, and is an indicator of the potential impact on ecosystems.

[0003]

2. Description of the Related Art Chemical oxygen demand is measured by chemically oxidizing an organic substance using a strong oxidizing agent and converting it to the amount of oxygen consumed by the strong oxidizing agent. As the strong oxidizing agent used at this time, potassium permanganate or potassium dichromate can be mentioned, and a method for measuring a chemical oxygen demand using these strong oxidizing agents will be outlined below.

(1) Measurement of Chemical Oxygen Demand (COD _Mn ) Using Potassium Permanganate A sample is made acidic with sulfuric acid, potassium permanganate is added as an oxidizing agent, and the mixture is reacted for 30 minutes in a boiling water bath. The amount of permanganate ion consumed at that time is determined, and converted to the amount of oxygen (mgO / l (liter)) corresponding thereto, and the COD _Mn value is represented. This test is preferably performed immediately after sampling, but if the test cannot be performed immediately, the sample should be taken from 0 ° C to 1 ° C.
Store in the dark at 0 ° C. and test as soon as possible.

(2) Measurement of Chemical Oxygen Demand (COD _Cr ) Using Potassium Dichromate Potassium dichromate and sulfuric acid are added to a sample, and the sample is boiled for 2 hours with a reflux condenser. Calculate the amount of chromic acid and convert it to the amount of oxygen (mgO / l) equivalent to CO
Represents the D _Cr value. This test is also preferably performed immediately after sampling, but if the test cannot be performed immediately, the sample should be stored at 0 ° C.
Store in the dark at 10 to 10 ° C and test as soon as possible.

[0006]

The chemical oxygen demand is:
As described above, the amount of oxygen required to oxidize all organic substances in closed water areas such as dams and lakes is not limited to dynamic water systems such as rivers, but also to closed water areas such as dams and lakes. Also in the above, the concentration (local concentration) of the organic substance varies depending on the flow of water. Therefore, there is a problem that it is very difficult to monitor the concentration of an organic substance that is changing every moment by using a conventional COD measurement method requiring a measurement time of about 2 to 4 hours.

Further, the conventional COD measurement method has a drawback that the reproducibility is low (results vary depending on the operator), so that it is difficult to perform COD measurement except for a skilled technician. There is also a problem.

Further, potassium dichromate is hexavalent chromium, and the conventional method using the same has a problem of waste liquid.

The present invention has been made in view of the above problems, and an apparatus and a method for measuring a chemical oxygen demand in a simpler, faster and more secure manner than the COD measuring method adopted by JIS. The aim is to provide a method.

[0010]

Means for Solving the Problems The present inventors have found that the dissolved oxygen in the solution to be measured decreases in the process in which the organic substance in the solution to be measured is decomposed and mineralized by titanium oxide which functions as a photocatalyst. By focusing attention, they have found that the chemical oxygen demand can be measured by directly measuring the amount of dissolved oxygen in the solution to be measured after being decomposed and mineralized by titanium oxide, and have completed the present invention.

Here, potassium permanganate used in the conventional method oxidizes organic substances by performing a dehydrogenation reaction in an acidic solution as follows.

[0012]

## STR1 ## _{^{MnO 4 - + 8H + + 5e}} → Mn 2+ + 4H 2 O

On the other hand, the decomposition of the organic substance by the titanium oxide used in the present invention proceeds by the following process.

[0014] Titanium oxide in water decomposes water when irradiated with ultraviolet rays to generate OH radicals, and at the same time, holes in the valence band of the titanium oxide itself.
Has a strong oxidizing power. Then, the OH radicals and holes extract hydrogen in the organic substance, whereby the bond between carbon and carbon is broken and the decomposition of the organic substance occurs.

As described above, in the conventional method and the method of the present invention using titanium oxide, the mechanism of decomposition of an organic substance, that is, "decompose an organic substance by a dehydrogenation reaction", is the same.

However, in the conventional method, under the condition that the amount of oxygen consumed in the oxidation reaction coincides with the amount of oxidant reduced by the reaction, the amount of consumed oxidant is reduced to the amount of oxygen (mgO
/ L), while the method of the present invention is superior in that the COD value can be determined by directly measuring the amount of oxygen consumed in the oxidation reaction with various oxygen measuring devices. There are features.

More specifically, the present invention provides the following chemical oxygen demand measuring apparatus and method.

(1) An apparatus for measuring a chemical oxygen demand, comprising: a reaction section for reacting dissolved oxygen in a solution to be measured with an organic substance in the solution to be measured; A dissolved oxygen measuring unit for measuring the amount of oxygen,
A calculating unit for calculating a chemical oxygen demand from a measurement result under predetermined conditions in the dissolved oxygen measuring unit.

(2) The reaction section includes a reaction catalyst section on which titanium oxide fine particles are supported, and a light source for causing the titanium oxide fine particles to perform a photocatalytic function. The chemical oxygen demand measuring apparatus according to the above (1), wherein the dissolved oxygen in the solution is reacted with an organic substance.

(3) The dissolved oxygen measuring section comprises an iodine method, an iron (II) method, a neutralization titration method, a light absorption method, an emission analysis method,
The chemical oxygen according to the above (1) or (2), which is an apparatus for performing measurement by a polarographic method, an oxygen electrode method, a conductivity measuring method, a potential difference measuring method, a coulometric method or a method using the method. Demand measurement device.

(4) The chemical oxygen demand measuring apparatus according to any one of (1) to (3), wherein the reaction section is an apparatus provided with a mechanism for accelerating the reaction using Fenton's reagent. .

(5) The apparatus for measuring a chemical oxygen demand according to any one of (1) to (4), wherein the apparatus is used for batch operation or flow injection analysis.

(6) A method in which the dissolved oxygen in the solution to be measured is used to determine the chemical oxygen demand of the solution to be measured.

(7) The method according to the above (6), wherein the chemical oxygen demand of the solution to be measured is determined based on the consumption of dissolved oxygen in the solution to be measured.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, the "solution to be measured" includes not only samples serving as indicators for environmental pollution such as dam water, lake water, river water, etc., but also pollution sources such as domestic wastewater and industrial wastewater. Includes samples taken directly from. A sample of these is supplied to the apparatus and method according to the present invention as a “solution to be measured”.

As used herein, the term "dissolved oxygen" refers to oxygen dissolved in a solution to be measured when the solution to be measured is placed under a predetermined condition. It also refers to oxygen dissolved in that state when dissolved in water.

"Reacting" the dissolved oxygen in the solution to be measured with the organic substance in the solution to be measured means that the dissolved oxygen in the solution to be measured decreases due to some reaction between the organic substance and the dissolved oxygen. And does not necessarily mean that it is decomposed.

The "reaction section" may be a batch operation type in which a solution to be measured is held in a predetermined container (for example, a reaction cell or a constant temperature bath) to carry out a reaction. (A column or the like) at a predetermined speed. However, the present invention is not limited to this, and any device having a mechanism of “reacting dissolved oxygen in a solution to be measured with an organic substance in the solution to be measured” may be referred to as a “reaction unit” in the present invention. Equivalent to.

"Measurement of the amount of dissolved oxygen in the solution to be measured" means to measure the amount of dissolved oxygen in the solution to be measured before, after and after the reaction in the reaction section.

The "dissolved oxygen measuring section" includes not only a device for directly measuring the amount of dissolved oxygen, but also a device for measuring data necessary for obtaining the amount of dissolved oxygen. In particular,
The “dissolved oxygen measurement section” is based on the iodine method (Winckler method),
Iron (II) method (modified mirror method), neutralization titration method, light absorption method, emission analysis method, polarographic method, galvanic cell type oxygen electrode method, conductivity measurement method, potentiometric measurement method, coulometric analysis method or its application Refers to a device that performs measurement by the method described above.

In the case of "determining the chemical oxygen demand from the measurement result under predetermined conditions", "measurement result under predetermined conditions" means the measurement when the reaction is performed until it is considered that an equilibrium state has been reached. Not only about the result,
It also refers to a measurement result when a reaction is performed by irradiating light of a constant irradiation amount (intensity). Then, “determining the chemical oxygen demand from the measurement result under predetermined conditions” means that the dissolved oxygen consumption is determined from “measurement result under predetermined conditions” (about the method of calculating the “dissolved oxygen consumption”). Means that the chemical oxygen demand is determined based on the dissolved oxygen consumption.

The "calculating unit" means an arithmetic unit such as a computer, for example, but is not limited to this as long as it can perform the above-described operation.

The term "reaction catalyst portion carrying titanium oxide fine particles" means a predetermined member (for example, a film or a bead) capable of fixing titanium oxide fine particles.

The "light source that exerts a photocatalytic function" includes a lamp capable of irradiating light of a desired wavelength, such as an ultraviolet lamp, and a lamp capable of irradiating light in which a plurality of wavelengths are mixed. included. In the present invention,
The term "light" refers to not only artificially emitted light such as light emitted from the lamp, but also natural light such as sunlight. However, it is preferable that the irradiation intensity, wavelength, irradiation time and the like can be freely controlled.

"Fenton's reagent" refers to hydrogen peroxide that generates OH radicals and iron salts as substances that increase electron transfer (specifically, FeCl ₃ , FeCl ₃ 6H ₂ O, Fe (NH ₃ ) ₂ (S
_{O 4) 2, Fe (OH} ) 3, FeSO 4, Fe (NO 3) 3, Fe (NO 3) 3 refers to a mixture of 9H ₂ O, etc.). In the examples described later, the case where the reaction is promoted using the “Fenton's reagent” is described. However, in order to promote the reaction, a reagent serving as another promoter can be used.

"A device for batch operation or flow injection analysis" is a device in which the chemical oxygen demand measuring device of the present invention measures the chemical oxygen demand using a batch operation or flow injection analysis technique. It means there is.

The present invention can be understood to be a “method of using the dissolved oxygen in the solution to be measured to determine the chemical oxygen demand of the solution to be measured”.

Here, "using dissolved oxygen in the solution to be measured" specifically means "based on the consumption of dissolved oxygen", but "using dissolved oxygen in the solution to be measured". If oxygen is used to determine the chemical oxygen demand of the solution to be measured, "based on dissolved oxygen consumption"
The present invention is not limited to determining the chemical oxygen demand of the solution to be measured but is included in the present invention.

The "consumed amount of dissolved oxygen" can be determined by measuring the amount of dissolved oxygen in the solution to be measured before and after the reaction and performing a difference calculation. It is also possible to measure the change in the dissolved oxygen amount and obtain the change amount based on the change amount (for example, when the change in the dissolved oxygen amount is graphed, the slope of the graph or the derivative at the measurement point).

The method for measuring the chemical oxygen consumption includes (a)
One that measures until the reaction of all organic substances contained in the solution to be measured is completed (until the reaction reaches an equilibrium state);
(B) Measurement only for a predetermined time (constant time) is conceivable. Both methods can be implemented by the apparatus according to the present invention, and are included in the method of the present invention.

[0041]

EXAMPLES The chemical oxygen demand (COD) of the present invention
Oxygen Demand) measuring device is a batch type op
eration) and flow injection analysis (FIA: Flow)
Injection Analysis).

(1) Batch operation type chemical oxygen demand measurement apparatus For decomposition of organic substances, titanium oxide as a photocatalyst (this titanium oxide has the same oxidation mechanism as potassium permanganate used in the conventional method) ) Was immobilized on a Teflon membrane. Then, this Teflon membrane was attached to an oxygen electrode, and a batch operation type chemical oxygen demand (COD) measuring device was constructed.

(2) Flow Injection Analysis Type Chemical Oxygen Demand Measurement Apparatus A flow injection type chemical oxygen demand (COD) measurement apparatus was constructed using a Pyrex glass tube filled with titanium oxide beads. .

Hereinafter, these embodiments will be described in detail with reference to the drawings.

[0045]

First Embodiment In a first embodiment, a batch operation type COD measuring apparatus will be described.

<Apparatus Configuration> FIG. 1 is a view schematically showing the configuration of a batch operation type COD measuring apparatus. In this FIG.
Reference numeral 11 denotes a stirrer, reference numeral 12 denotes a dark box, reference numeral 13 denotes an oxygen electrode, reference numeral 14 denotes a high-temperature bath, reference numeral 15 denotes an ultraviolet lamp, reference numeral 16 denotes a digital multimeter, and reference numeral 17 denotes a recorder.

Using a thermostat 14, the temperature of the Pyrex glass in the reaction cell is kept constant, and the constant velocity of the solution and dissolved oxygen in the reaction cell is controlled by the stirrer 11A in the reaction cell. With stirring.

The oxygen electrode 13 was manufactured by mounting a Teflon film 13B having titanium oxide immobilized on a galvanic oxygen electrode 13A manufactured by Able Corporation. The titanium oxide was immobilized on the Teflon film using a physical adsorption method.

The ultraviolet lamp 15 irradiates ultraviolet light for causing a photocatalytic reaction of titanium oxide. As the ultraviolet lamp 15, a 6 W lamp (λ _max = 365n) is used.
m) was used.

The digital multimeter 16 measures a current value (μA) obtained from the oxygen electrode 13. The digital multimeter 16 is a multimeter 34401A manufactured by Hewlett Packard. Was used. The result of measurement by the digital multimeter 16 was recorded by a recorder 17 (a recorder EPR-151A of Toa Denpa Kogyo Co., Ltd. was used as the recorder 17). In addition,
The dissolved oxygen concentration (ppm) in the solution in the reaction cell was determined by comparing the measurement result by the digital multimeter 16 with a calibration curve described later.

<Stability of Titanium Oxide-Fixed Film> Since the Teflon film for fixing titanium oxide may be decomposed by titanium oxide under ultraviolet irradiation, the stability of the Teflon film is determined by the following two methods. investigated.

As a first method, the stability of the Teflon film was examined by observation with an electron microscope. A photograph (FIG. 2A) of the Teflon film on which the titanium oxide has been immobilized before irradiation with ultraviolet light,
Comparison with a photograph (FIG. 2B) of a Teflon film irradiated with ultraviolet rays for 170 hours in an aqueous system showed no change in morphology due to decomposition.

As a second method, the stability of the film was examined using an oxygen electrode. When the Teflon film on which titanium oxide is immobilized is oxidized by titanium oxide under ultraviolet irradiation, a change occurs in the current value of the oxygen electrode in close contact with the film. The experiment was performed by immersing the oxygen electrode on which the titanium oxide immobilized film was attached in ultrapure water and measuring the current value of the oxygen electrode every 10 hours. The measurement results at this time are shown in FIG. As can be seen from this result, even when the ultraviolet light is irradiated for 170 hours, the Teflon film is not decomposed at all by the titanium oxide under the ultraviolet light irradiation. The experiment was performed at a temperature of 20 ° C., and an ultraviolet lamp (λ _max = 365 nm) was used as a light source. The amount of titanium oxide to be immobilized was 2.487 mg / cm ² .

<Effect of Amount of Titanium Oxide> The organic substances that cause water pollution are extremely wide-ranging, and a wide variety of substances can be considered. In domestic sewage, carbohydrates, anionic surfactants, and total soluble organic substances account for a large proportion, whereas in urban sewage, lignin, tannic acid, humic acid, and other components with slow biological decomposition are high. These effluents pass through sewage treatment plants and are discharged into rivers as treated water or flow directly into rivers. Secondary effluent discharged from sewage treatment plants also tends to reflect the composition of incoming sewage. Therefore, it is considered that water pollution is caused by these organic substances.
In the (COD) measuring device, it is necessary to study these substances.

FIG. 4 shows artificially synthesized sewage (lignin; 14.72).
%, Tannic acid; 25.33%, humic acid; 25.76%, gum arabic: 28.48%, surfactant: 5.71%), the effect of the amount of titanium oxide on the response of the present chemical oxygen consumption (COD) measuring device is shown. FIG. From this figure, it can be seen that the chemical oxygen consumption (COD) measuring device has a concentration dependency on the artificially synthesized sewage, and that the concentration of 4 ppm or more of the artificially synthesized sewage even in the absence of titanium oxide is ultraviolet rays. It can be seen that it is oxidized only by. Chemical oxygen consumption (COD)
The amount of titanium oxide that showed the highest oxidizing power in the measuring device was
It was 2.487 mg / cm ² . The experiment was performed at a temperature of 30 ° C., and an ultraviolet lamp (λ _max = 365 nm) was used as a light source.

<Effect of Temperature> FIG. 5 is a diagram showing the effect of temperature on the present chemical oxygen consumption (COD) measuring apparatus.
From this figure, as the temperature increases, the artificially synthesized sewage (lignin; 14.72%, tannic acid; 25.33%, humic acid; 25.76) was measured for the present chemical oxygen consumption (COD) measuring device.
%, Gum arabic; 28.48%, surfactant; 5.71%). Incidentally, using a UV lamp (λ _max = 365nm) as the light source in the experiment, the amount of titanium oxide to be immobilized was 2.487mg / cm ^2.

<Calibration Curve> Using a Na ₂ SO ₃ solution and a dissolved oxygen meter, a calibration curve for an oxygen electrode used in the present chemical oxygen consumption (COD) measuring apparatus was prepared (see FIG. 6).

First, the change in the current value (unit: μA) of the oxygen electrode with respect to the concentration of each Na ₂ SO ₃ solution without irradiating ultraviolet rays was examined by the present chemical oxygen consumption (COD) measuring apparatus. Was. Thereafter, under the same conditions (temperature, solution volume of the reaction cell, stirring speed), a change in the oxygen concentration (unit: ppm) with respect to the concentration of the Na ₂ SO ₃ solution measured by the dissolved oxygen meter was examined. Then, as shown in FIG. 6, the oxygen concentration (ppm value) corresponding to the current value of the oxygen electrode is plotted to obtain the chemical oxygen consumption.
A calibration curve used in the (COD) measuring device was prepared. The experiment was performed at a temperature of 20 ° C. with the ultraviolet lamp turned off, and the amount of titanium oxide to be immobilized was 2.487 mg / cm ² .

<Stability of the present chemical oxygen consumption (COD) measuring device> The stability of the present chemical oxygen consumption (COD) measuring device is shown in FIG.
Shown in One to three times daily, artificial synthetic sewage (COD _Mn
= 4.098 ppm) as a result of examining the change in the response current value of the present chemical oxygen consumption (COD) measuring device over two weeks,
The stability of this chemical oxygen consumption (COD) measuring device was confirmed. The experiment was performed at a temperature of 20 ° C., and an ultraviolet lamp (λ _max = 365 nm) was used as a light source. The amount of titanium oxide to be immobilized was 2.487 mg / cm ² . The correlation standard deviation is
6.08%.

<Conventional method of COD and the present chemical oxygen consumption (COD)
Correlation of measurement methods> The conventional method (potassium permanganate method (COD _Mn ) and potassium dichromate) in actual dam water was measured using the calibration curve of this chemical oxygen consumption (COD) measurement device (see FIG. 6). Method (COD _Cr )) and the present chemical oxygen consumption (COD) measurement method. As a result, the correlation coefficients were 0.99 and 0.94, respectively, indicating that there was a very high correlation between the conventional method and the method of the present invention (FIG. 8 (a) shows the results of the potassium permanganate method, and FIG. 8 (b) shows the results of the potassium dichromate method). Therefore, it is suggested that this method for measuring chemical oxygen consumption (COD) is applicable to the measurement of actual dam water.

The experiment was conducted at a temperature of 20 ° C., and an ultraviolet lamp (λ _max = 365 nm) was used as a light source. The amount of titanium oxide to be immobilized was 2.487 mg / cm ² .

Then, referring to the correlation shown in FIG. 8 (a) or FIG. 8 (b), the chemical oxygen consumption in the actual dam water solution is determined from the dissolved oxygen concentration (ppm) determined as described above. amount
(COD). When actual dam water was used, the measurement time was within 5 minutes according to the present chemical oxygen consumption (COD) measurement method.

<High Sensitivity of New Chemical Oxygen Consumption (COD) Measuring Apparatus> The conventional method of COD and the present chemical oxygen consumption (COD) measuring method are described in FIGS. 8 (a) and 8 (b). ) Shows that there is a very high correlation. However, the oxidizing power of the chemical oxygen consumption (COD) measuring apparatus of the present invention is one-tenth of the oxidizing power of the conventional method.

Therefore, the present chemical oxygen consumption (COD) measuring device
Experiments to improve the oxidation rate
Was. To increase sensitivity, Fenton's reagent
agent: a mixture of hydrogen peroxide and iron). This file
Enton's reagent is an OH radical that is directly involved in the oxidation of organic substances.
By increasing the cull and activating the electron transfer,
It has the effect of increasing the oxidizing power. Use this Fenton reagent
The results obtained are shown in FIGS. 9A and 9B. FIG.
(A) High sensitivity when the amount of added hydrogen peroxide is changed
The results show that when the concentration of hydrogen peroxide increases
Sewage (COD_Mn = 4.098 ppm)
Fruit was obtained. FIG. 9B shows the addition of iron (III).
The results show that the sensitivity was increased when the amount was changed.
7 times higher sensitivity than when no
Came. In the experiment, an ultraviolet lamp (λ
_max= 365 nm). The amount of titanium oxide to be immobilized is 2.
487mg / cm ²And In addition, high sensitivity with iron (III)
The experiment was performed at a temperature of 20 ° C.

[0065]

Second Embodiment In a second embodiment, a flow injection type COD measuring apparatus will be described.

<Apparatus Configuration> FIG. 10 is a diagram schematically showing the configuration of a flow injection type COD measuring apparatus.
10, reference numeral 21 denotes ultrapure water, reference numeral 22 denotes a pump, reference numeral 23 denotes an injector (with a 2 ml sample loop), reference numeral 24 denotes a dark box, reference numeral 25 denotes a column filled with titanium oxide, reference numeral 26 denotes an ultraviolet lamp. , 27 denotes a bubble remover, 28 denotes an oxygen electrode, 29 denotes a high-temperature tank, 30 denotes a recorder, and 31 denotes waste liquid.

Here, as the oxygen electrode 28, a galvanic oxygen electrode manufactured by Able Corporation was used. Note that the oxygen electrode 28 was disposed in a thermostat 29 to maintain the temperature at a constant temperature.

The column 25 is a packed column in which titanium oxide beads are put in a Pyrex glass tube or a quartz tube.
_max = 365 nm).

As the pump 22, Gibson (Gi
lson) was used, and as the injector 23, an injector manufactured by Rheodyne was used.

The recorder 30 measures and records the current value obtained from the oxygen electrode 28.
0 means Hitachi Integrator (D-
2500)). The concentration of dissolved oxygen in the solution from the bubble remover 27 was determined by comparing the measurement result obtained by the recorder 30 with a calibration curve described later.

<Dependence on Concentration of Artificial Synthetic Water> When this chemical oxygen consumption (COD) measuring apparatus is used, artificial synthetic sewage (lignin; 14.72%, tannic acid; 25.33)
%, Humic acid; 25.76%, gum arabic; 28.48%, surfactant: 5.71%). As shown in FIG. 11, COD of artificially synthesized sewage
A response line with a correlation coefficient of 0.996 was obtained in the concentration range of _Mn 1 ppm to 10 ppm. In the experiment, the flow rate was 1.54
The test was performed at mi / min., a sample injection volume of 2 ml, and a temperature of 20 ° C. The amount of titanium oxide in the packed column 25 was 0.9 g.

<Calibration Curve> A calibration curve of a flow injection analysis type chemical oxygen consumption (COD) measuring apparatus was prepared by using the same method as the batch operation system described above (see FIG. 12).

The dissolved oxygen is reduced by adding a Na ₂ SO ₃ solution to ultrapure water. At that time, a change in dissolved oxygen amount (unit: ppm) is measured using a dissolved oxygen meter. The solution is injected through the injector of the flow injection analysis system at the same temperature. In the flow injection analysis system, the concentration of dissolved oxygen decreased using an oxygen electrode was measured as a current value. The current value on the vertical axis in FIG. 12 indicates the peak height of the measured current. The experiment was conducted at a flow rate of 1.54 mi / min., A sample injection amount of 2 ml, and a temperature of 2 ml.
The test was performed at 0 ° C. with the ultraviolet lamp 26 turned off. The amount of titanium oxide in the packed column 25 was 0.9 g.

<Stability of the Chemical Oxygen Consumption (COD) Measuring Apparatus> FIG. 13 shows the stability of the chemical oxygen consumption (COD) measuring apparatus using the flow injection analysis system. One to three times daily, artificially synthesized sewage (COD _Mn = 5.896 pp)
As a result of examining the change in the current value of the present chemical oxygen consumption (COD) measuring device with respect to m), it was confirmed that the device was stable even after 2 weeks. The experiment was performed at a flow rate of 1.54 mi / min., A sample injection amount of 2 ml, and a temperature of 20 ° C., using an ultraviolet lamp (λ _max = 365 nm) as a light source, and using a packed column 25.
The amount of titanium oxide therein was 0.9 g. The correlation standard deviation was 6.06%.

<Conventional method of COD and the present chemical oxygen consumption (COD)
Correlation of measurement methods> The conventional method (potassium permanganate method (COD _Mn ) and potassium dichromate) in actual dam water was measured using the calibration curve of this chemical oxygen consumption (COD) measurement device (see FIG. 12). Method (COD _Cr )) and the present chemical oxygen consumption (COD) measurement method. As a result, the correlation coefficients were 0.98 and 0.96, respectively, indicating that there is a very high correlation between the conventional method and the method of the present invention (FIG. 14).
(A) shows the results of the potassium permanganate method, and FIG.
(B) shows the results of the potassium dichromate method). Therefore, it is suggested that the flow injection analysis system can be applied to the measurement of actual dam water as in the case of the batch operation type.

The experiment was performed at a flow rate of 1.54 mi / min., A sample injection amount of 2 ml, and a temperature of 20 ° C., using an ultraviolet lamp (λ _max = 365 nm) as a light source, and reducing the amount of titanium oxide in the packed column 25 to 0.9. g.

Then, referring to the correlation shown in FIG. 14A or FIG. 14B, the chemical oxygen consumption in the actual dam water solution is calculated from the dissolved oxygen concentration (ppm) obtained as described above. The quantity (COD) was determined. When actual dam water was used, the measurement time was within 10 minutes according to the present chemical oxygen consumption (COD) measurement method.

[0078]

As described in detail above, according to the present invention,
Compared with the conventional method, there is an advantage that the measurement can be performed by a simple operation and the measurement can be performed in a short time of 10 minutes or less. It can be said that the measurement time was greatly shortened as compared with the conventional method. Therefore, it is possible to monitor the concentration of the organic substance which is fluctuating from time to time in a measuring device (a dynamic water system such as a river, or a closed water body such as a dam or a lake).

Further, when the measurement was performed using actual dam water, it was found that there was a high correlation between the chemical oxygen demand measurement method of the present invention and the conventional method, and the chemical oxygen demand in the actual dam water was high. It has been shown that the present invention can be applied to the measurement of oxygen consumption.

Further, according to the present invention, there is little variation in the results depending on the measurer, so that there is an advantage that the chemical oxygen consumption can be measured without requiring a skilled technique.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a configuration of a batch operation type COD measuring apparatus.

FIG. 2A is an electron micrograph of the Teflon film before irradiation with ultraviolet light, and FIG. 2B is an electron micrograph of the Teflon film after irradiation with ultraviolet light.

FIG. 3 is a view showing an experimental result on stability of a titanium oxide fixed film.

FIG. 4 is a diagram showing experimental results on the effect of the amount of titanium oxide fixed on a Teflon film.

FIG. 5 is a diagram showing experimental results on the effect of temperature when performing measurement.

FIG. 6 is a diagram showing a calibration curve of an oxygen electrode used in a batch operation type COD measuring apparatus.

FIG. 7 is a view showing an experimental result on stability of a batch operation type COD measuring apparatus.

FIG. 8 is a diagram showing the correlation between the conventional method and the method of the present invention in actual dam water. FIG. 8A is a diagram showing a correlation when the potassium permanganate method is used as the conventional method, and FIG. 8B is a diagram showing a correlation when the potassium dichromate method is used as the conventional method. FIG.

FIG. 9 is a view showing an experimental result of increasing the sensitivity of the COD measuring apparatus of the present invention. FIG. 9A is a diagram showing the experimental results when the amount of added hydrogen peroxide was changed, and FIG.
(B) is a figure which shows the experimental result at the time of changing the addition amount of iron (III).

FIG. 10 is a diagram schematically showing a configuration of a flow injection type COD measuring device.

FIG. 11 is a diagram showing the results of an experiment on the concentration dependency on artificially synthesized sewage.

FIG. 12 is a diagram showing a calibration curve of an oxygen electrode used in a flow injection analysis type COD measuring apparatus.

FIG. 13 is a view showing an experimental result on stability of a flow injection analysis type COD measuring apparatus.

FIG. 14 is a diagram showing a correlation between the conventional method and the method of the present invention in actual dam water. FIG. 14A is a diagram showing the correlation when the potassium permanganate method is used as the conventional method, and FIG. 14B is a diagram showing the correlation when the potassium dichromate method is used as the conventional method. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Stirrer 11A Stirrer 12 Dark box 13 Oxygen electrode 13A Oxygen electrode 13B Teflon film 14 High temperature bath 15 Ultraviolet lamp 16 Digital multimeter 17 Recorder 21 Ultrapure water 22 Pump 23 Injector 24 Darkbox 25 Column 26 Ultraviolet lamp 27 Bubbles Drain 28 Oxygen electrode 29 High temperature tank 30 Recorder 31 Waste liquid

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhito Hashimoto 2073-2-D 213 Iijimacho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture (72) Inventor Kazunori Ikebukuro 3-27-29, Daida, Setagaya-ku, Tokyo 309 (72) Inventor Satoshi Sasaki 2-28-15 Inukura, Miyamae-ku, Kawasaki-shi, Kanagawa F-term (reference) 4B063 QA01 QQ18 QQ61 QQ89 QQ91 QR50 QR82 QR83 QS39 QX01

Claims (7)

[Claims] 1. An apparatus for measuring a chemical oxygen demand, comprising: a reaction section for reacting dissolved oxygen in a solution to be measured with an organic substance in the solution to be measured; and dissolved oxygen in the solution to be measured. A dissolved oxygen measuring unit for measuring the amount, and a calculating unit for calculating a chemical oxygen demand from a measurement result under predetermined conditions in the dissolved oxygen measuring unit, a chemical oxygen demand measurement characterized by comprising: apparatus. 2. The reaction section includes: a reaction catalyst section on which titanium oxide fine particles are supported; and a light source for causing the titanium oxide fine particles to exhibit a photocatalytic function. 2. The chemical oxygen demand measuring device according to claim 1, wherein the dissolved oxygen contained therein is reacted with an organic substance. 3. The method according to claim 1, wherein the dissolved oxygen measuring section comprises an iodine method, an iron (II) method, a neutralization titration method, a light absorption method, an emission analysis method, a polarographic method, an oxygen electrode method, a conductivity measurement method, a potential difference measurement method, 3. The chemical oxygen demand measuring apparatus according to claim 1, wherein the measuring apparatus is an apparatus for performing measurement by a coulometric method or a method using the coulometric method. 4. The chemical oxygen demand measuring device according to claim 1, wherein the reaction unit is a device provided with a mechanism for promoting a reaction using a Fenton reagent. 5. The apparatus according to claim 1, wherein the apparatus is used for batch operation or flow injection analysis.
The chemical oxygen demand measuring device according to any one of the above. 6. Using dissolved oxygen in a solution to be measured,
A method for determining a chemical oxygen demand of the solution to be measured. 7. The method according to claim 6, wherein the chemical oxygen demand of the solution to be measured is determined based on the consumption of dissolved oxygen in the solution to be measured.