JPH01461A - Equipment for measuring nitrogen compounds in water - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is a gcII method for measuring nitrogen compounds contained in wastewater from factories, business offices, etc. and environmental water of rivers, lakes, and marshes.
In particular, the present invention relates to an apparatus for measuring nitrogen compounds in water that accurately measures the total amount of nitrogen compounds, namely total nitrogen, nitrate nitrogen, and nitrite nitrogen.

[Conventional technology]

In recent years, closed water bodies such as lakes and inland seas have rapidly become hypertrophic, with concentrations of nutrient salts such as nitrogen and phosphorus increasing, resulting in 11% F, which causes off-flavors in tap water and the death of fish and shellfish. are doing. For this reason, the Environment Agency has successively established environmental standards for nitrogen and phosphorus (December 1982) and wastewater standards (July 1982), and has embarked on preventive measures.

Due to the establishment of such standards, it has become necessary to accurately measure trace amounts of nitrogen and phosphorus in water, and we have been developing a total nitrogen measuring device that does not require complicated maintenance and inspection and is suitable for automation. . and ``Method and Apparatus for Analyzing Nitrogen Compounds in Water'' using ozone as an oxidizing agent (Unexamined Japanese Patent Publication No. 6)
0-178353) has already been disclosed.

There are ammonia nitrogen (NH, -N) and nitrate nitrogen (No-, -N) in water.

It contains inorganic nitrogen such as nitrite nitrogen (No; -N) and organic nitrogen such as proteins, proteins, and amino acids.

The above-mentioned "method and apparatus for analyzing nitrogen compounds in water" involves contacting sample water with ozone under alkaline conditions to oxidize all nitrogen compounds to nitrate nitrogen, and then measuring this nitrate nitrogen using an ultraviolet absorption method. This is to determine the total nitrogen in sample water.

On the other hand, there is a demand for knowing not only the total nitrogen in a sample but also one form of nitrogen, nitrite nitrogen and nitrate nitrogen. Normally, wastewater from factories, businesses, etc. is treated before being released.

The most popular treatment method at this time is the activated sludge method.

The main purpose of this activated sludge method is to biologically decompose organic matter, but in addition to this, Nitros, which is a bacteria,
Biological nitrification can occur in the aeration tank: nitrite-nitrification of ammonia nitrogen by N. omonas l and nitrite-nitrification of nitrite nitrogen by the bacterium N1trobacfer.

If this biological nitrification occurs, the nitrite nitrogen and nitrate nitrogen concentrations will increase even if the total nitrogen level does not change. Therefore, if we can know nitrate nitrogen and nitrite nitrogen at the same time in addition to total nitrogen, we can grasp the progress of nitrification in the aeration tank, and also control the amount of air blown into the aeration tank and control the flow rate of treated water caused by nitrification. In terms of operational management of the activated sludge method, it is possible to quickly respond to problems such as high BOI
Extremely effective.

[Problem that the invention seeks to solve]

However, since conventional devices can only measure total nitrogen, there is a problem in that they cannot meet the above requirements.

This invention was made in view of the above points, and its purpose is to use the conventional analyzer for measuring total nitrogen as it is, and by making only a few changes, it can measure not only total nitrogen but also nitrate nitrogen and nitrite nitrogen. Another object of the present invention is to provide a measuring device for measuring nitrogen compounds in water.

[Means for solving problems]

The above objects are achieved according to this invention.

g) Measuring nitrate nitrogen and nitrite nitrogen in the sample water using at least three different wavelengths.

an ultraviolet absorbance meter 2 that measures the total nitrogen in the sample water using at least one wavelength based on nitrate ions obtained by oxidative decomposition of nitrogen compounds in the sample water; (b) m-agent supply means and pH adjustment a reaction tank 1 for converting nitrogen compounds in sample water into nitrate ions by oxidatively decomposing them with an oxidizing agent under alkaline conditions;

Based on the absorbance of nitrate nitrogen and nitrite nitrogen measured with the ultraviolet absorbance meter, organic matter in the sample water,
Nitrate nitrogen and nitrite nitrogen can be calculated by solving simultaneous equations with turbidity and suspended solids gt, nitrate nitrogen, and nitrite nitrogen as unknowns, and based on the absorbance for total nitrogen. Solve the simultaneous equations in which the total amount of organic matter, turbidity, and suspended solids in the sample water and total nitrogen are unknown quantities.
Alternatively, this can be achieved by including an arithmetic unit 3 that calculates the total nitrogen in water by solving an equation in which only the total nitrogen is an unknown quantity.

This invention was made based on the knowledge that nitrate nitrogen and nitrite nitrogen can be accurately quantified by absorbance in the ultraviolet region with correction of background absorbance due to organic matter, turbidity, and suspended solids.

In an ultraviolet absorbance meter, ultraviolet rays from an ultraviolet lamp illuminate a sample of water in an absorption cell made of quartz glass.

Nitrogen compounds in the sample water absorb ultraviolet rays. Wavelength selection is performed using a monochromator or an interference filter. The interference filter is replaced by a rotary method or a sliding method.

Nitrate nitrogen and nitrite nitrogen in the sample water are measured using three different wavelengths when the ultraviolet absorption of the total amount of organic matter, turbidity, and suspended solids in the sample water does not change depending on the wavelength, or linearly depending on the wavelength. When the wavelength changes to , it is measured using four different wavelengths. When measuring with three wavelengths, calculations are performed using three-dimensional simultaneous linear equations, and when using four wavelengths, calculations are performed using four-dimensional simultaneous linear equations, and nitrate nitrogen and nitrite nitrogen are quantified with high accuracy. . Of course, measurement of five or more wavelengths is also possible.

When determining the total nitrogen in the sample water, first, inorganic nitrogen and organic nitrogen in the sample water are oxidized to nitrate ions in the reaction tank 1, and then the nitrate ions are measured under ultraviolet light. At this time, if the background absorption of the total amount of organic matter, turbidity, and suspended solids can be ignored, measurement is performed using one wavelength. In addition, when background absorption cannot be ignored but there is no change in absorbance depending on wavelength, use two wavelengths.

Furthermore, when the background absorption varies linearly with wavelength, three wavelengths are used for measurement. Of course, measurement of four or more wavelengths is also possible. Calculations are performed using a linear equation when one wavelength is used, two-dimensional simultaneous linear equations when two wavelengths are used, and three-dimensional simultaneous linear equations when three wavelengths are used. Well quantified.

Oxidation of nitrogen compounds in the sample water is carried out in a reaction tank 1. The reaction tank is provided with an oxidizing agent supply means and a pH% adjustment means. The oxidizing agent supply means supplies an oxidizing agent that oxidizes nitrogen compounds, and includes an ozonizer and its supply system,
Or it consists of reagents and their supply system. The pH adjusting means is
The oxidizing agent works effectively to adjust the pH of the sample water and eliminate ultraviolet absorption of carbonate ions. Inorganic nitrogen and organic nitrogen in water are oxidatively decomposed and converted into nitrate ions. Thereafter, the sample water is sent to the ultraviolet absorbance spectrometer 2, and the ultraviolet absorption of total nitrogen is measured by the method described above.

When measuring nitrate nitrogen and nitrite nitrogen in sample water, the sample water should not be subjected to oxidation treatment using an ultraviolet absorbance meter 2.
sent to.

A heating means can be added to the reaction tank 1 as necessary, such as when oxidizing with a reagent.

In the calculation unit 3, calculations for solving linear equations or simultaneous linear equations are executed as described above. A calibration curve showing the relationship between nitrate nitrogen and nitrite nitrogen and absorbance is measured at a predetermined wavelength, and the slope of each straight line is input in advance to the calculation section. Next, ultraviolet light is measured at a predetermined wavelength as described above, and when the absorbance is manually entered as measurement data, the calculation section executes calculations according to a predetermined program and calculates nitrate nitrogen, nitrite nitrogen, total Calculate nitrogen.

[Effect]

Nitrate nitrogen and nitrite nitrogen in the sample water are quantified by measuring ultraviolet absorption and performing calculation processing without oxidizing the sample water. The total nitrogen in the sample water is converted into nitrate ions by oxidative decomposition of nitrogen compounds in the sample water in a reaction tank 1, and then the ultraviolet absorption of the nitrate ions is measured and arithmetic processing is performed.

Nitrate nitrogen and nitrite nitrogen are measured using at least three different wavelengths, and total nitrogen is measured using at least one wavelength.

On the other hand, conventional measuring devices measure ultraviolet absorption at one wavelength and do not perform calculation processing.

〔Example〕

Example 1 Next, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a block diagram of a measuring device according to an embodiment of the present invention. A reaction tank 1 stores sample water for one hour and oxidizes nitrogen compounds in the sample water to nitrate nitrogen (No; -N).

The ultraviolet absorbance meter 2 performs measurements at at least three wavelengths.

The calculation unit 3 performs calculation processing using the absorbance measured by the ultraviolet absorbance meter 2 as input data to obtain total nitrogen.

Calculate nitrate nitrogen and nitrite nitrogen. Hydrochloric acid tank4.
The caustic soda tank 5 has one reaction (pt attached to 11).
14, which adjusts the pH of the sample water to a predetermined pH. The ozonizer 6 converts nitrogen compounds in the sample water into nitrate nitrogen (
Generates ozone which oxidizes to NO; -N).

The #l raw material supply oxygen gas, which is a raw material for ozone, and the ozone decomposition furnace 8 decomposes used ozone into harmless oxygen. The diffuser 12 feeds ozone into the sample water in the reaction tank 1 in the form of fine bubbles.

In a device with such a configuration, T-N, Nol-N
.

Measurement of No' and -H is performed as follows. First, sample water is supplied to the reaction tank 1 using the water sampling pump 9. Next, the sample is sent to the ultraviolet absorbance meter 2 using the preparative pump 10, and the absorbance at three wavelengths is measured. This absorbance is sent to the calculation section 3,
Processed and NOI -N.

No.N is determined.Next, the sample is replenished into the reaction tank 1 using the water sampling pump 9, and the pH of the sample water is adjusted to 11 or higher by adding caustic soda from the caustic soda tank 5 with the caustic soda rinsing liquid pump 11.Next, from the diffuser 12 Ozone is bubbled into the sample water to oxidize nitrogen compounds to NO;-N. The reason for making the pH of the sample water alkaline is to promote the oxidation reaction by ozone, and Figure 2 shows the influence of solution pH when the NH, -N standard solution was oxidized with ozone. pH1
1 or more, almost 100% of NH-N is oxidized to No-N. Once the oxidation of nitrogen compounds by ozone is completed, hydrochloric acid is added from the tank 4 to the sample water using the chemical pump 13# to adjust the pH to 2-3. This is done to avoid oxidation of organic substances by ozone as well as oxidation of nitrogen compounds by ozone, and to avoid interference during absorbance measurement of carbonate ions generated at this time. pH
The sample water adjusted to -2 to 3 is sent to the ultraviolet absorbance meter 2 by a preparative pump IO, and its absorbance is measured. Organic matter, turbidity, and SS (suspended solids) are usually measured using one wavelength. This absorbance is sent to the calculation section 3 and TN is calculated.

The contents of the calculation in the calculation unit 3 will be explained in detail below.

First, regarding the calculation contents for determining Nol -N, No;-N, it is already known that No's-N, No: -N has absorption in the ultraviolet region. However, organic substances, turbidity, and SS also have absorption in the ultraviolet region, so unless this is corrected, the accuracy is good< No: -N
, NO; -N cannot be measured.

An explanatory diagram for explaining the correction method is shown in FIG. 3. The absorbance due to organic matter, turbidity, and SSL is almost constant regardless of wavelength, and NO'';-N.

No: The absorbance due to -N becomes thicker on the shorter wavelength side.

In Figure 3, (a) is the absorbance due to organic matter, turbidity, and 8B, and the difference between (a) and (b) is No; -N absorbance, (
The difference between b) and (c) is the absorbance due to No;-N, and the sample water as a whole exhibits the absorbance of fc). Now, the three wavelengths λ0 in this ultraviolet region. λ1. Suppose we measure the absorbance at λ.

Since the absorbance at each wavelength can be expressed as the total amount of the absorbance due to organic matter, turbidity, and SS, the absorbance due to NOney N, and the absorbance due to Nonie N, the following equation is established.

A(λ+)=A(λ+)+Na(λ1)'X to ten!
(stone)・y−(1)A(λt)=A6<λ2)10Ks(
λ, ) ・x+Kt (λt) ・y − (2)
A(λ5)=A”(λs)+Na(λ, ) m
x-1-, (λs) ・y-(3) where A(λ) absorbance of the sample at two wavelengths λ A'(λ) absorbance due to organic matter, turbidity, and SS at two wavelengths λ, (λ) Slope of the calibration curve of NO;-N at two wavelengths λ (absorbance/m d / L) Kt (λ) Slope of the calibration curve of N (J-, -N) at two wavelengths λ (absorbance/ml/L) Noney N concentration in sample water <mg/l)y
: No--N concentration in the sample water (mjj/l) Now, organic matter, turbidity, and absorbance variable 〇 (λ) due to 88 are constant regardless of wavelength, so A'(λt) = A(λt) = A (λ3) holds true. Also, A(λ) is actual measurement data, dog(λ), Kt(
Since λ) is known, x, y, that is, the No;-N concentration and the Noney N concentration in the sample water can be determined by solving the three-dimensional simultaneous linear equations of equations +1) to (3) above.

The next step is to measure the absorbance of the ozone-oxidized sample water and calculate T-N. In this case, the organic matter, turbidity, and SS in the sample water are normally oxidized and decomposed by ozone, so no correction is required. Equation (4) holds true, and NO;-N, that is, T-N, in the ozone-oxidized sample water can be determined just by measuring the absorbance of one wavelength.

A(λ5)=Ks(λS)・X ・・・・・・・・・
・・・・・・・・・・・・・・・(4) Organic matter in sample water,
If there is a large amount of turbidity and 88, and unreacted components remain even after ozone oxidation, and it is necessary to correct this, use the N
o; −N, No: Using the same method of calculating −N, the wavelength λ3. By creating the following simultaneous equations for the absorbance of two wavelengths of λ6 and solving them, it is possible to obtain TN with correction for organic matter, turbidity, and SS.

A(λ*)=A°(2g)+Na(λ,)・X Song・
... A... (5) A (λ6) = 〇 (λe ) + N
a (λ6)・X ・・・・・・・・・・・・・・・
(6) However, Ao (2g) = A0 (λ6) Furthermore, if the background absorption due to organic matter, turbidity, and SS changes linearly with wavelength, three wavelengths λ haze, λ
6. The content of the calculation performed by the calculation unit 3 is 0 or more, which can be measured using a λ-cutter and solved by solving three-dimensional simultaneous linear equations.

Next, this device performs T-N, NO; -N, No;-
For manual analysis, which describes the correlation between the measurement results of N and the analytical values obtained by manual analysis, T-N is
jA potassium acid decomposition and ultraviolet absorption spectrophotometry.

For NO;-N, the brucine method was used, and for Noney N, the N-(t-naphthyl)ethylenediamine spectrophotometry was used.

All sample water is secondary treated sewage water.

No in Figure 4; Correlation with manual analysis of -N, NO in Figure 5;
- Correlation with manual analysis value of H is shown. The measured values obtained by this device are that the wavelength of the ultraviolet region is λ, -225, and λ, = 235°N.
The correlation coefficient r-0,995 and the correlation with manual analysis are extremely high. Figure 6 shows the correlation between the manual analysis value of TN determined at one wavelength. Wavelength λ, =22
It is calculated by calculating using the absorbance at 0, and absorbance at other wavelengths may be used if there is absorption of NO--N, and it is not limited to λg = 220am, as shown in Figure 6. The correlation between T and N is also a correlation coefficient γ-0,951, which is a very high correlation.

Above, the method using ozone oxidation was described as a method for oxidizing nitrogen compounds to NO;-Ni when determining T-N.
In addition to this, a method using alkaline potassium peroxydinisulfate decomposition is known. In this method, alkaline potassium peroxylinisulfate is added to the sample, and the heated state is maintained at 120°C for 30 minutes to oxidize nitrogen compounds to NO;
A method of J potassium disulfate decomposition may be used, and any method is not limited as long as it can oxidatively decompose a nitrogen compound to NON.

Example 2 To find No', -N and No;-N, four wavelengths λ1°λ7. λ5. The calculation when using λ will be explained.

Figure 7 shows an explanatory diagram of the calculation contents, 3 in Figure 3.
The difference from the explanation diagram of calculation contents using wavelength absorbance is as follows.
Absorbance due to organic matter, turbidity, and SS ((a) in the figure)
increases at a constant rate as the wavelength becomes shorter, and the difference between (a) and (b) is No's-N.

The difference between (b) and (C) is the absorbance due to No;-N.

In this case, the wavelength λ1. λ1. λ1. The following formula holds true for λ4.

A (λ1) = heart λs ) + Na (λ, ) e X
To +! (λ1)・y...(7) A(λz)=p:<
λ2) 10 Km (λt) ”x-)-, (
λt ) ・y − (81A(λ, ) − center λs )
+Na (λ,)・Xten (λ,)・y... (9)
Person (λa)”A(λ4)+Na(λ4) ・X+Kt
(λ4)”Y −αQ also organic matter, turbidity and SS
It is assumed that the absorbance due to λ increases with a constant slope as the wavelength becomes shorter, so 1, for example, λ, = 225. λ, -235
．． λ, = 240, λ, = 245A” (λ,) = heart λ
g)+3(A"(λ5)-Ao<λ4))=4・A'(
λs) 3・A”(λ,)・・・・・・・・・・・・・・・
...fJl)Ao(λt)=A”(λ,)+(ni(λ
s) A' (λ, )) = 2・A' (λs) - 80 (No. 2)
・・・・・・・・・・・・・・・・・・
(17J. Therefore, x, y, that is, the No; -N concentration and the NO; -N concentration in the sample water can be obtained by solving the four-dimensional simultaneous linear equations of equations (7) 2 to Q1. In this case The correlation with the manual analysis value is: correlation coefficient r = 0.991 in the case of NO;-N, r = 0.991 in the case of No;-N.
=0.992, and the correlation is extremely high as in the case of using absorbance at three wavelengths.

The use of four wavelengths is suitable when the background absorption of organic substances, turbidity, and SS changes linearly with wavelength, but it goes without saying that it can also be applied when background absorption does not change with wavelength.

A similar concept can be applied to the case where total nitrogen is measured at three wavelengths.

〔Effect of the invention〕

According to this invention.

g) Measure nitrate nitrogen and nitrite nitrogen in the sample water using at least three different wavelengths, and calculate the total nitrogen in the sample water based on nitrate ions obtained by oxidative decomposition of nitrogen compounds in the sample water. an ultraviolet absorbance meter that measures the wavelength using at least one wavelength;

(0) A reaction tank equipped with an oxidizing agent supply means and a pH adjusting means for oxidizing and decomposing nitrogen compounds in sample water using an oxidizing agent under alkaline conditions to convert them into nitrate ions.

(/) Calculate the total amount of organic matter, turbidity, and suspended solids, nitrate nitrogen, and nitrite nitrogen in the sample water based on the absorbance for nitrate nitrogen and nitrite nitrogen measured with the ultraviolet absorbance meter. Calculate nitrate nitrogen and nitrite nitrogen by solving simultaneous equations with unknowns, and calculate the total amount of organic matter, turbidity, suspended solids, and total nitrogen in the sample water as unknowns based on the absorbance for total nitrogen. We configured a measuring device for nitrogen compounds in water with a calculation unit that calculates the total nitrogen in water by solving equations where total nitrogen is the only unknown quantity, or by solving equations where only total nitrogen is an unknown quantity. Nitrate and nitrogen are measured at at least three wavelengths, total nitrogen is measured at at least one wavelength, and a calculation section is added to the conventional device to perform calculations based on the measurement data of the ultraviolet absorbance meter. It only removes nitrate nitrogen in the sample water.

It is now possible to automatically and continuously measure the three components of nitrite nitrogen and total nitrogen with one device, and as a result, it is possible to understand the progress of nitrification in the aeration tank in the activated sludge method, and to check the back wind inside the aeration tank. It has become possible to quickly respond to high BOD of treated water caused by nitrification.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a measuring device according to an embodiment of the present invention. FIG. 2 is a graph showing the pH dependence of the ammonia nitrogen decomposition rate. FIG. An explanatory diagram of the calculation for determining nitrate nitrogen and nitrite nitrogen using wavelength. Figure 4 is a graph showing the correlation between nitrate nitrogen measured by the measuring device of this invention and nitrate nitrogen by manual analysis. Figure 5 is A graph showing the correlation between nitrite nitrogen measured by the measuring device of this invention and manually analyzed nitrite nitrogen, FIG. 6 is a graph showing the correlation between total nitrogen measured by the measuring device of this invention and manually analyzed total nitrogen,
FIG. 7 is an explanatory diagram of calculation for determining nitrate nitrogen and nitrite nitrogen using four ultraviolet wavelengths according to an embodiment of the present invention. l: reaction tank, 2: ultraviolet absorbance meter, 3: calculation section. -EN' Di9 + Hama's PH %2 Diagram, * + λ (Cut Sea 1) 3rd Shit 11 due to Spokenness 11S (1h),,
In Fig. 4, the fuyu diagram f tOt, f 2θ: + valve surface 14 gold nitrogen (burst ν burnt skin set (-n-n)) 7th section

Claims (1)

[Claims] 1) (a) Measuring nitrate nitrogen and nitrite nitrogen in sample water using at least three different wavelengths,
an ultraviolet absorbance meter that measures the absorbance of total nitrogen in sample water using at least one wavelength based on nitrate ions obtained by oxidative decomposition of nitrogen compounds in sample water; (b) oxidizing agent supply means and pH adjustment; (c) nitrate nitrogen and nitrous acid measured by the ultraviolet absorbance spectrometer; Nitrate nitrogen and nitrite nitrogen are determined by solving simultaneous equations with the total amount of organic matter, turbidity, and suspended solids in the sample water, nitrate nitrogen, and nitrite nitrogen as unknowns, based on the absorbance for nitrate nitrogen. At the same time, based on the absorbance for total nitrogen, solve an equation in which the total amount of organic matter, turbidity, and suspended solids in the sample water and total nitrogen are unknowns, or solve an equation in which only total nitrogen is an unknown. 1. A measuring device for nitrogen compounds in water, comprising: a calculation unit that calculates total nitrogen in water.