JPH10170494A - Method and apparatus for measuring concentration of nitrogen compound in water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for measuring a concentration of nitrogen compound in water whereby a nitrogen compound in a sample water can be oxidized and decomposed to nitrate ions in a short time, a time interval when a concentration of the nitrogen compound in the sample water is measured can be shortened, and a long-time continuous measurement is enabled. SOLUTION: In the apparatus, a sample water is adjusted to a neutral area or an alkali area and ultraviolet rays are projected to the sample water. The apparatus has a sample water-feeding means 1, a pH regulator-adding means 2 for supplying a pH regulator into the sample water so as to turn the sample water to a neutral or an alkali area, an optical oxidation decomposition reactor 3 for oxidizing and decomposing the processed sample water, a reducing agent- adding means 5 for supplying a reducing agent to nitrate ions generated through the oxidation decomposition process, a gas liquid-separating means 6 for processing nitrogen monoxide reduced from the nitrate ions by a gas-liquid separation, and a chemical emission-measuring device 7 for measuring a concentration of the separated nitrogen monoxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the concentration of a small amount of nitrogen compounds contained in water discharged from factories, sewage treatment plants, and environmental water such as rivers and lakes. A method and an apparatus therefor.

[0002]

2. Description of the Related Art In general, the concentration of nitrogen compounds contained in water discharged from factories, sewage treatment plants and the like, and environmental water such as rivers and lakes is measured by JIS K0102 or Notification of the Environment Agency No. 140. Is publicly standardized.

[0003] The nitrogen compounds contained in the above-mentioned water exist as nitrate ions, nitrite ions, ammonium ions or organic nitrogen.

In a TN (total nitrogen) analysis method defined in JIS K0102 for measuring all nitrogen present in water, all nitrogen compounds are oxidized and decomposed into nitrate ions and measured. Ions and organic nitrogen are not easily oxidized and decomposed into nitrate ions.

Therefore, in the measurement by the TN (total nitrogen) analysis method, an alkaline potassium peroxodisulfate solution is added to a sample water and heated at 120 ° C. for 30 minutes to oxidize and decompose all nitrogen compounds into nitrate ions. After cooling, p
H is adjusted to 2-3 and wavelength of 220nm by nitrate ion
UV light absorption is measured by using an oxidation catalyst, or the sample water is heated to a high temperature of 500 ° C. or more using an oxidation catalyst to be oxidatively decomposed into nitrate ions, and then measured by a chemiluminescence method.

[0006] The above-described oxidation method using an oxidizing agent heats to a high temperature of 120 ° C above the boiling point of water, and the oxidation method using an oxidation catalyst heats to a high temperature of 500 ° C or more. There is a problem that the structure and operation of the oxidizer become complicated.

Therefore, in order to solve the above problem, a sample water as described in JP-A-7-27758 is heated at 50 ° C. to 100 ° C., and ultraviolet rays are blown while blowing a gas containing oxygen or ozone. A method has been proposed in which an oxidation reaction is caused by irradiation and the generated nitrate ion concentration is measured with an absorptiometer.

[0008]

In the method of heating a sample water as described above and irradiating the sample water with ultraviolet rays while blowing a gas containing oxygen or ozone into the sample water, the heating temperature can be lowered. Since about 20 minutes are required for the oxidative decomposition time, there is a problem that the measurement interval becomes long when measuring nitrogen compounds in the continuously supplied sample water.

Further, since a heating device for heating the sample water and a gas supply device for blowing the gas containing oxygen or ozone are required, the whole device becomes complicated and the running cost becomes high. is there.

The present invention can oxidize and decompose nitrogen compounds in sample water into nitrate ions in a short time, shorten the interval of concentration measurement of nitrogen compounds in sample water, and enable continuous measurement for a long time. An object of the present invention is to provide a method and an apparatus for measuring the concentration of a nitrogen compound in water.

[0011]

According to the method for measuring the concentration of a nitrogen compound in water according to the present invention, the pH of a sample water is adjusted to a neutral range or an alkaline range by adding a pH adjuster to the sample water. Is irradiated to generate nitrate ions, and the concentration of the nitrate ions is measured.

In the method for measuring the concentration of nitrogen compounds in water according to the present invention, nitrate ions are reduced to nitric oxide by a reducing agent, and the concentration of the nitric oxide is measured.

[0013] Further, sodium hydroxide or potassium hydroxide is used as a pH adjuster for making the sample water alkaline as described in claim 3, and the sample water is used as a pH adjuster as described in claim 4. As a pH adjuster in the case where the pH is in the neutral region, a buffer solution composed of potassium dihydrogen phosphate-disodium hydrogen phosphate can be used.

According to a fifth aspect of the present invention, there is provided an apparatus for measuring the concentration of a nitrogen compound in water, comprising: a sample water supply means for supplying a predetermined amount of sample water; PH adjusting agent adding means for supplying the adjusting agent into the sample water, a photo-oxidative decomposition reactor for oxidative decomposition of the sample water treated in the neutral or alkaline region, and the concentration of nitrate ions generated by the oxidative decomposition Is provided with an absorptiometer for measuring.

According to a sixth aspect of the present invention, there is provided an apparatus for measuring the concentration of a nitrogen compound in water, comprising: a sample water supply means for supplying a predetermined amount of sample water; PH adjuster addition means for supplying adjuster into sample water, photo-oxidative decomposition reactor for oxidative decomposition of sample water treated in neutral or alkaline range, and reduction to nitrate ions generated by oxidative decomposition Comprising a reducing agent adding means for supplying an agent, gas-liquid separating means for gas-liquid separating nitric oxide reduced from nitrate ions, and a chemiluminescence measuring device for measuring the concentration of the separated nitric oxide. It is.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic system diagram showing one embodiment of the configuration of the apparatus for measuring the concentration of nitrogen compounds in water according to the present invention. A sample water supply means 1 for supplying a decomposition reactor 3; a pH adjuster addition means 2 for supplying a pH adjuster to the sample water in order to bring the sample water into a neutral or alkaline range; A sample water feed pipe 4 for sending sample water in which nitrate ions have been generated in 3; reducing agent addition means 5 for supplying a reducing agent to the treated sample water; and nitric oxide reduced from nitrate ions from the sample water. Gas-liquid separation means 6 for separating nitrogen and a chemiluminescence measuring device 7 for measuring the concentration of separated nitric oxide
It is composed of

The above-mentioned sample water supply means 1 includes a sample water intake pipe 8 for taking in sample water from a factory, a lake or the like, a first pump 9 for quantitatively sending sample water, and light from the first pump 9. It comprises a sample water supply pipe 10 to be sent to the oxidative decomposition reactor 3.

The above-mentioned pH adjusting agent adding means 2 includes a first storage tank 11 for storing a pH adjusting agent for converting the sample water into a neutral region or an alkaline region, and a second pump 1 for quantitatively sending the pH adjusting agent.
2 and a pH adjusting agent supply pipe 13 for feeding a pH adjusting agent from the second pump 12 to the sample water supplying pipe 10.

As shown in FIG. 2, the photooxidative decomposition reactor 3 has a cylindrical glass container 14 having an inert gas supply port 14a and an inert gas discharge port 14b. A lamp 15 for an ultraviolet light source mounted so as to be located at the center, an ultraviolet-transmissive reaction tube 16 wound in a coil around the lamp 15, and a light amount mounted on one end of a cylindrical glass container 14. And a lamp tube wall temperature controller 17 for making the temperature uniform.

The above cylindrical glass container 14 is made of UV-C
(Ultraviolet light having a wavelength of 280 nm or less) is formed of a synthetic quartz tube or the like, and a joint (not shown) is provided between the supply port 14a and the discharge port 14b of the inert gas so that tubes for supply and discharge can be connected. In addition, the inner wall surface is treated with an aluminum vapor-deposited film so as to maximize the use of ultraviolet light having a short wavelength.

A low-pressure mercury lamp (lamp power: 40 W, tube diameter: 18 mm, total length: 530) is used as the lamp 15 described above.
mm), but a deuterium lamp, a xenon lamp,
UV-C (280n, Hg-Zn-Pb lamp, excimer laser, etc.)
m or less can be used as long as it can radiate with high output.

The above-mentioned ultraviolet-permeable reaction tube 16 has an inside diameter and a tube length that can secure a residence time required for oxidative decomposition of sample water, and has a shape and an arrangement that allow sufficient irradiation of ultraviolet rays.

The above-mentioned reducing agent adding means 5 includes a second storage tank 18 for storing a reducing agent for reducing nitric acid ions generated by oxidative decomposition to nitric oxide, and a third pump 19 for quantitatively feeding the reducing agent. And the sample water feed pipe 4 from the third pump 19.
And a reducing agent supply pipe 20 for feeding the reducing agent into the tube.

The above-mentioned gas-liquid separating means 6 is used for the sample water feed pipe 2.
2 and a balance gas supply tube 23 for supplying a balance gas into the sample water supply tube, a gas delivery tube 24 for delivering the separated nitric oxide, and a liquid discharge tube 25 for delivering the separated liquid are connected. Gas-liquid separation container 21
6.

The liquid separated in the gas-liquid separation container 21 is quantitatively discharged by a fourth pump 27 to a receiving tank (not shown).

The above-mentioned chemiluminescence measuring instrument 7 is a chemiluminescence type N
Although an Ox meter was used, it goes without saying that other types of measuring instruments could be used.

The concentration of standard sample water (sample water containing ammonium sulfate and sample water containing sulfanilamide) was measured using the above-described apparatus for measuring the concentration of nitrogen compounds in water.

The concentration of each sample water in this embodiment is defined as 1 ppb (W / V) when 1 μg of nitrogen contained in the substance present in 1 liter of water is 1 pg.

The method for measuring the concentration of a nitrogen compound of the present invention is shown in FIG.
Are performed in the order shown in FIG.

Standard sample water prepared in advance (100 ppb ammonium sulfate sample water, 100 pp sulfanilamide)
(b) (sample water) is supplied at a rate of 3 ml / min by the first pump 9 and sodium hydroxide as a pH adjuster is added to the standard sample water by the second pump 12 at 0.1 ml / m.
When supplied at a rate of in, the standard sample water is adjusted to pH 10 which is an alkaline range.

Then, the standard sample water adjusted to the alkaline region is irradiated with ultraviolet light in the photo-oxidative decomposition reactor 3 for 2 minutes to 1 minute.
After irradiation for 5 minutes, the nitrogen compound (ammonium sulfate or sulfanilamide) in the standard sample water is oxidized and decomposed into nitrate ions and sent to the sample water feed pipe 4. A certain titanium chloride solution is supplied by the third pump 19 at a rate of 0.5 ml / min, and nitrate ions in the standard sample water are reduced to nitric oxide.

When the standard sample water is sent to the sample water feed pipe 22 of the gas-liquid separation means 6, a balance gas is blown into the standard water.
It is sent into the gas-liquid separation container 21 heated to 0 to 60 ° C.

Then, in the gas-liquid separation vessel 21, nitrogen monoxide and waste liquid are separated, and the concentration of nitric oxide is measured by the chemiluminescence measuring device 7, and the waste liquid is quantitatively measured by the fourth pump 27. Is discharged.

The above pH-adjusted standard sample water is irradiated with ultraviolet rays to oxidize and decompose nitrogen compounds into nitrate ions, and the results are measured by a chemiluminescence measuring instrument 7. The results shown in Table 1 can be obtained. Was.

[0035]

Table 1 shows the rate at which nitrogen compounds were oxidatively decomposed into nitrate ions. A decomposition rate of 100% means that all nitrogen compounds were oxidatively decomposed into nitrate ions.

When the above-mentioned standard sample water is adjusted to an alkaline region of pH 10 and irradiated with ultraviolet light for 15 minutes, 98% of ammonium sulfate is decomposed and 95% of sulfanilamide is decomposed.

Further, a buffer solution consisting of potassium dihydrogen phosphate and disodium hydrogen phosphate was added as a pH adjuster to the standard sample water to adjust the pH to a neutral range of 6.8 and irradiated with ultraviolet rays for 15 minutes. , 98 for ammonium sulfate
% And 90% in the case of sulfanilamide.

On the other hand, when the standard sample water has a pH of 5,
In the case of irradiating ultraviolet rays for 15 minutes in an acidic region of 6.5, in the case of ammonium sulfate, 0% at pH 5 and p
It is 28% at H 6.5, 13% at pH 5 and 34% at pH 6.5 for sulfanilamide.

FIG. 5 shows the relationship between the decomposition rate (%) of nitrogen compounds in the alkaline, neutral, and acidic regions of the above-mentioned standard sample water and the ultraviolet irradiation time. About 1% before the decomposition rate of ammonium sulfate or sulfanilamide in the state reaches 90%.
In contrast to the case where it takes 20 minutes, when the adjustment is performed in the alkaline region or the neutral region, the ultraviolet irradiation time is greatly reduced to about 15 minutes.

That is, when the sample water is adjusted to an alkaline range or a neutral range and irradiated with ultraviolet rays, the nitrogen compounds are oxidized and decomposed into nitrate ions in a shorter time than when the sample water is in an acidic range. Recognize.

The above-mentioned standard sample water was placed in an alkaline region (pH 1).
FIG. 6 illustrates the relationship between the decomposition rate (%) of ammonium sulfate or sulfanilamide and the ultraviolet irradiation time when adjusted to 0), and both nitrogen compounds have a decomposition rate of 90 when irradiated with ultraviolet light for about 5 minutes. % Has been reached.

The method for measuring the concentration of nitrogen compounds in water of the present invention does not necessarily have to be carried out under the condition that the decomposition rate is 100%. By preliminarily measuring a constant correlation between the standardized measurement method and the analytical value obtained when the decomposition rate in the measurement method of the present invention is less than 100%, the decomposition rate is less than 100%. It can also be carried out in the state described above.

When adjusting the pH of the sample water to an alkaline region (pH 7.3 to 13), potassium hydroxide or the like can be used instead of sodium hydroxide.

Further, the sample water was placed in a neutral region (pH 6.7-7.
When adjusting to 3), instead of the buffer solution consisting of potassium dihydrogen phosphate-sodium dihydrogen phosphate, potassium dihydrogen phosphate-sodium hydroxide, potassium dihydrogen phosphate-sodium tetraborate, and sodium tetraborate are used. A buffer consisting of-(boric acid-sodium chloride), sodium tetraborate-hydrochloric acid or the like can be used.

The pH adjuster may be any reagent that can maintain the pH of the sample water in an alkaline range or a neutral range.

The above-mentioned reducing agent may be replaced by a ferrous sulfate solution or a ferrous salt solution such as a ferrous chloride solution instead of a titanium chloride solution.
A reagent that can use a sodium sulfite solution, a sodium hydrogen sulfite solution, or the like can be used as long as it can reduce nitrate ions to nitric oxide.

Next, in another embodiment of the apparatus for measuring the concentration of nitrogen compounds in water according to the present invention, as shown in FIG. A sample water supply means 1; a pH adjuster addition means 2 for supplying a pH adjuster into the sample water in order to bring the sample water into a neutral range or an alkaline range; and nitric acid generated in the photo-oxidative degradation reactor 3 And an absorption photometer 28 for measuring the ion concentration.

In this apparatus, hydrochloric acid is added to the sample water in which nitrate ions have been generated in the photo-oxidative decomposition reactor 3 to adjust the pH to 2-3, and a wavelength of 22 nm is measured using an absorptiometer 28.
Measure at 0 nm.

[0049]

According to the method for measuring the concentration of nitrogen compounds in water according to the present invention, a sample water is adjusted to a neutral range or an alkaline range by adding a pH adjuster to the sample water and then irradiated with ultraviolet rays. Since nitrate ions are generated and the concentration of the nitrate ions is measured, the nitrogen compounds in the water can be oxidized and decomposed into nitrate ions in a short period of time. It is possible to shorten the time and to enable continuous measurement for a long time.

Further, even when nitrate ions are reduced to nitric oxide by a reducing agent and the concentration of the nitric oxide is measured as described in claim 2, the same effect as in claim 1 can be obtained. it can.

Further, sodium hydroxide or potassium hydroxide is used as a pH adjuster when the sample water is brought into an alkaline range as described in claim 3, or the sample water is used as described in claim 4. When a buffer consisting of potassium dihydrogen phosphate and disodium hydrogen phosphate is used as a pH adjuster in the neutral region, nitrogen compounds in water can be oxidized and decomposed into nitrate ions in a short time.

The apparatus for measuring the concentration of nitrogen compounds in water according to the present invention comprises a sample water supply means for supplying a predetermined amount of sample water, and a pH adjusting means for converting the sample water to a neutral or alkaline range. PH adjusting agent adding means for supplying the adjusting agent into the sample water, a photo-oxidative decomposition reactor for oxidative decomposition of the sample water treated in the neutral or alkaline region, and the concentration of nitrate ions generated by the oxidative decomposition , The operation of oxidative decomposition of nitrogen compounds in water into nitrate ions and the operation of measuring concentration can be shortened.

Further, a sample water supply means for supplying a predetermined amount of sample water as described in claim 6, and a pH adjusting agent for supplying a pH adjuster to the sample water so as to make the sample water neutral or alkaline range. Adjusting agent adding means, a photo-oxidative decomposition reactor for oxidatively decomposing sample water treated in a neutral region or an alkaline region, and reducing agent adding means for supplying a reducing agent to nitrate ions generated by the oxidative decomposition process, Gas-liquid separation means for gas-liquid separation of nitric oxide reduced from nitrate ions,
The same effect as in the case of claim 5 can be achieved even with a configuration including a chemiluminescence measuring device for measuring the concentration of the separated nitric oxide.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram showing one embodiment of the configuration of the apparatus for measuring the concentration of nitrogen compounds in water of the present invention. FIG. 2 is a schematic sectional view showing one embodiment of the configuration of the photo-oxidative decomposition reactor in FIG. FIG. 3 is a flowchart showing the operation sequence of the method for measuring the concentration of nitrogen compounds in water according to the present invention. FIG. 4 is a schematic system diagram showing another embodiment of the configuration of the apparatus for measuring the concentration of nitrogen compounds in water of the present invention. FIG. 5 is a schematic diagram showing the relationship between the UV irradiation time and the decomposition rate in each pH range of the standard sample water. FIG. 6 is a schematic diagram showing the relationship between the ultraviolet irradiation time and the decomposition rate in the alkaline region of the standard sample water.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sample water supply means 2 pH adjuster addition means 3 Photo-oxidation decomposition reactor 4, 22 Sample water feed pipe 5 Reducing agent addition means 6 Gas-liquid separation means 7 Chemiluminescence meter 8 Sample water intake pipe 9 First pump Reference Signs List 10 Sample water supply pipe 11 First storage tank 12 Second pump 13 pH adjusting agent supply pipe 14 Cylindrical glass container 15 Lamp 16 Ultraviolet-permeable reaction tube 17 Lamp tube wall surface temperature controller 18 Second storage tank 19 Third pump 20 Reducing agent supply tube 21 Gas-liquid separation container 23 Balance gas supply tube 24 Gas delivery tube 25 Liquid discharge tube 26 Constant temperature bath 27 Fourth pump 28 Spectrophotometer 14a Supply port 14b Discharge port

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[Procedure amendment]

[Submission date] May 16, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of the drawings]

FIG. 1 is a schematic system diagram showing one embodiment of a configuration of an apparatus for measuring the concentration of nitrogen compounds in water of the present invention.

FIG. 2 is a schematic sectional view showing one embodiment of the configuration of the photo-oxidative decomposition reactor in FIG.

FIG. 3 is a flowchart showing an operation sequence of the method for measuring the concentration of a nitrogen compound in water according to the present invention.

FIG. 4 is a schematic system diagram showing another embodiment of the configuration of the apparatus for measuring the concentration of nitrogen compounds in water of the present invention.

FIG. 5 is a schematic diagram showing the relationship between ultraviolet irradiation time and decomposition rate in each pH range of standard sample water.

FIG. 6 is a schematic diagram showing a relationship between ultraviolet irradiation time and decomposition rate in an alkaline region of standard sample water.

[Explanation of Signs] 1 Sample water supply means 2 pH adjuster addition means 3 Photo-oxidative decomposition reactor 4, 22 Sample water feed pipe 5 Reducing agent addition means 6 Gas-liquid separation means 7 Chemiluminescence meter 8 Sample water intake Tube 9 First pump 10 Sample water supply tube 11 First storage tank 12 Second pump 13 pH adjusting agent supply tube 14 Cylindrical glass container 15 Lamp 16 Ultraviolet permeable reaction tube 17 Lamp tube wall temperature controller 18 Second storage tank Reference Signs List 19 third pump 20 reducing agent supply tube 21 gas-liquid separation container 23 balance gas supply tube 24 gas delivery tube 25 liquid discharge tube 26 constant temperature bath 27 fourth pump 28 absorption photometer 14a supply port 14b discharge port

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Fig. 7

[Correction method] Deleted

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0035

[Correction method] Change

[Correction contents]

[0035] This table shows the rate at which nitrogen compounds were oxidatively decomposed into nitrate ions. A decomposition rate of 100% means that all nitrogen compounds were oxidatively decomposed into nitrate ions.

Claims (6)

[Claims] 1. A method comprising: adding a pH adjuster to a sample water to adjust the pH to a neutral range or an alkaline range, irradiating ultraviolet rays to generate nitrate ions, and measuring the concentration of the nitrate ions. To measure the concentration of nitrogen compounds in water. 2. The method for measuring the concentration of nitrogen compounds in water according to claim 1, wherein nitrate ions are reduced to nitric oxide by a reducing agent, and the concentration of said nitric oxide is measured. 3. The method for measuring the concentration of a nitrogen compound in water according to claim 1, wherein the pH adjuster when the sample water is in an alkaline region is sodium hydroxide or potassium hydroxide. . 4. The method according to claim 1, wherein the pH adjuster when the sample water is in a neutral region is a buffer solution comprising potassium dihydrogen phosphate and disodium hydrogen phosphate. The method for measuring the concentration of nitrogen compounds in water according to the above. 5. A sample water supply means for supplying a predetermined amount of sample water, a pH adjuster addition means for supplying a pH adjuster into the sample water to make the sample water neutral or alkaline, Of nitrogen compounds in water, equipped with a photo-oxidation decomposition reactor for oxidative decomposition of sample water treated in the alkaline or alkaline region and an absorptiometer for measuring the concentration of nitrate ions generated by the oxidative decomposition . 6. A sample water supply means for supplying a predetermined amount of sample water, a pH adjuster addition means for supplying a pH adjuster to the sample water to make the sample water neutral or alkaline, Photooxidation reactor that oxidatively decomposes sample water that has been treated in a zone or an alkaline zone, reducing agent addition means that supplies a reducing agent to nitrate ions generated by the oxidative decomposition process, An apparatus for measuring the concentration of nitrogen compounds in water, comprising: gas-liquid separation means for gas-liquid separation of nitric oxide; and a chemiluminescence measuring device for measuring the concentration of the separated nitric oxide.