JPH0619326B2 - Method for quantifying inorganic nitrogen - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and a device for quantifying inorganic nitrogen in test water, and more specifically, it simultaneously quantifies the concentrations of nitrate nitrogen and nitrite nitrogen in test water. A possible quantification method and quantification device.

(Prior Art) Conventionally, various methods have been used as a method for purifying domestic wastewater or industrial wastewater, but the most widely used method is an activated sludge method that utilizes the purifying action of microorganisms.

This activated sludge method is a method in which wastewater is treated under aerobic conditions to oxidatively decompose and remove organic matter in the wastewater. The nitrogen compounds of the above are oxidized to nitrate nitrogen and nitrite nitrogen, and the nitrogen compounds in the waste water are mainly these nitrate nitrogen and nitrite nitrogen.

If these inorganic nitrogens are discharged as they are, they will become
Since eutrophication phenomenon occurs in the sea, especially closed water or inside, it is necessary to remove it sufficiently before discharge.

The removal of these inorganic nitrogens is performed by a method of performing anaerobic treatment subsequent to the aerobic treatment, and reducing nitrate nitrogen and nitrite nitrogen by denitrifying bacteria to remove as nitrogen gas.

In this anaerobic process, an organic substance such as methanol (hereinafter simply referred to as methanol) is mainly used as a reducing substance to reduce nitrate nitrogen and nitrite nitrogen to nitrogen gas.

If too little methanol is used in this denitrification step, the removal of nitrate nitrogen and nitrite nitrogen will be insufficient, so it is necessary to always use an excessive amount of methanol. However, if too much methanol is used, this methanol itself becomes the BOD of the waste water, and a step of further removing this methanol is required. Therefore, in order to properly use methanol, it is necessary to fully understand the nitrate nitrogen and nitrite nitrogen in the wastewater, especially in the anaerobic process, so that the nitrate nitrogen and nitrogen existing in the wastewater Of course, it is desirable to add just the right amount of methanol to the nitrate nitrogen.

As a method for quantifying the inorganic nitrogen in the waste water as described above, conventionally, a brucine absorption spectrophotometric method, a hydrazine sulfate reduction method, an ethylenediamine method, an ultraviolet absorption spectrophotometric method and the like have been used.

(Problems to be solved by the invention) As a method for quantifying the inorganic nitrogen in the wastewater, an ultraviolet absorptiometry method is mainly used, but this method is, for example, an absorbance at a wavelength of 210 to 230 nm. It is a method of measuring both the absorbance at a wavelength of 250 to 270 nm and calculating the total amount of nitrate nitrogen and nitrite nitrogen according to the following formula.

Inorganic nitrogen (NO _x ) concentration (mg /) = (E ₁ −E ₂ × a) × k Here, E ₁ is the absorbance of ultraviolet light having a wavelength of 210 to 230 nm, and E ₂ is ultraviolet light having a wavelength of 250 to 270 nm. It is the absorbance of light, a is the organic E ₁ / E ₂ in the sample, and k is the absorbance coefficient of inorganic nitrogen at wavelengths 210 to 230 nm.

According to the method as described above, it is possible to determine the inorganic nitrogen in the wastewater at the time of finishing the aerobic process and at the time of the anaerobic process.Measuring such inorganic nitrogen, the methanol as a reducing agent is determined according to this value. Efficient reduction of inorganic nitrogen was expected by adding it during the anaerobic process.

However, actually, even if methanol is added according to such a measured value of inorganic nitrogen, the amount of methanol cannot be adjusted to an appropriate amount, and in many cases, excess or deficiency of addition of methanol occurs, Therefore, it was always necessary to use an excess of methanol.

The reason is that the ratio of nitrate nitrogen to nitrite nitrogen in inorganic nitrogen is constantly changing, and when the amount used for cell synthesis is also included, nitrate nitrogen contains 2.5 mol times the amount of methanol. This is because nitrite nitrogen consumes 1.5 moles of methanol in contrast to this, and unless the ratio of nitrate nitrogen and nitrite nitrogen that fluctuates in this way is accurately grasped, It has always been required to add methanol assuming that the total amount of inorganic nitrogen is nitrate nitrogen, resulting in a very uneconomical result.

Therefore, in order to properly add the amount of methanol used in the denitrification step, it is necessary to always know the ratio of nitrate nitrogen to nitrite nitrogen in the inorganic nitrogen.

Methods of separately quantifying nitrate nitrogen and nitrite nitrogen are known, of course, but all of them require complicated treatment and calculation, and both the wastewater source and the aerobic treatment condition change the wastewater. It was unsuitable to quickly grasp the ratio of nitrate nitrogen to nitrite nitrogen of inorganic nitrogen, and neither was industrially available.

Therefore, there is a strong demand for a method and a device for quantifying inorganic nitrogen that can easily and easily quantify the ratio of nitrate nitrogen to nitrite nitrogen in the inorganic nitrogen in waste water.

(Means for Solving Problems) The present inventor has completed the present invention as a result of earnest research in order to meet the above demands.

That is, the present invention, in the method of quantifying the respective concentrations of nitrate nitrogen and nitrite nitrogen in the test water by ultraviolet absorptiometry, have different absorbance per unit concentration for nitrate nitrogen and nitrite nitrogen Using two types of UV light with different wavelengths within the wavelength range of 210 to 230 nm, the absorbance of the UV light of each wavelength is measured, and the UV light for nitrate nitrogen and nitrite nitrogen is measured in advance. The absorbance per unit concentration of light was measured, and the following two formulas (1) were used by using the above-mentioned two types of absorbance in the test water and the absorbance per unit concentration of each wavelength for nitrate nitrogen and nitrite nitrogen. )
And (2) is a method for quantifying inorganic nitrogen, which comprises simultaneously calculating and quantifying the respective concentrations of nitrate nitrogen and nitrite nitrogen in the test water.

(1) E _{NOX-N ・ a} = e _{NO3-N ・ a} × NO ₃ -N + e _{NO2-N ・ a} × NO ₂ -N (2) E _{NOX-N ・ b} = e _{NO3-N ・ b} × NO here _{3 -N + e NO2-N ·} b × NO 2 -N, E NOX-N · a = absorbance E for NO _X -N at the wavelength a _{NOX-N · b} = absorbance e of NO _X -N at a wavelength b _{NO3-N · a} = unit concentration absorbance e _{NO2-N · b} = unit concentration absorbance NO ₃ -N = nitrate nitrogen concentration of NO ₂ -N at the wavelength b of the NO ₃ -N in the wavelength a (mg /) NO ₂ -N = Nitrite Nitrogen Concentration (mg /) Next, the present invention will be described in more detail. According to the detailed study of the present inventor, as described above, when quantifying inorganic nitrogen in test water, it is preferable. The nitrate nitrogen and nitrite nitrogen in the test water can be easily calculated from those absorbances only by measuring the respective absorbances of the test water with two different wavelengths of ultraviolet light having wavelengths within the range of 210 to 230 nm. I also found It is.

For example, the ultraviolet absorption curves of the nitrate nitrogen aqueous solution and the nitrite nitrogen aqueous solution are as shown in FIG. 1 of the attached drawings, and both show the absorbance at 200 to 250 nm, but both curves intersect with each other. Except for the points, there is a difference in absorbance per unit concentration.

Therefore, when the absorbance of the test water was determined by two wavelengths of ultraviolet light with different absorbance per unit concentration, and the calculation of the concentrations of nitrate nitrogen and nitrite nitrogen was studied from the difference in absorbance, the following formula (1 From (2) and (2), it was found that the concentrations of nitrate nitrogen and nitrite nitrogen in the test water can be easily calculated, respectively, and there is almost no error in actual measurement.

(1) E _{NOX-N ・ a} = e _{NO3-N ・ a} × NO ₃ -N + e _{NO2-N ・ a} × NO ₂ -N (2) E _{NOX-N ・ b} = e _{NO3-N ・ b} × NO here _{3 -N + e NO2-N ·} b × NO 2 -N, E NOX-N · a = absorbance E for NO _X -N at the wavelength a _{NOX-N · b} = absorbance e of NO _X -N at a wavelength of a _{NO3-N · a} = unit concentration absorbance e _{NO2-N · b} = unit concentration absorbance NO ₃ -N = nitrate nitrogen concentration of NO ₂ -N at the wavelength b of the NO ₃ -N in the wavelength a (mg /) NO ₂ -N = nitrite nitrogen concentration (mg /).

In the above formulas (1) and (2), E _{NOX-N · a} and E = _{NOX-N · b} are measured values, and e _{NO3-N · a} and e _{NO2-N · b} are obtained in advance. Since it is a value, the nitrate nitrogen concentration (NO ₃ -N) and the nitrite nitrogen concentration (NO ₂ -N) can be easily calculated later by calculation.

The method of the present invention will be described in more detail with reference to examples.

First, an aqueous solution of nitrate nitrogen of 2 mg / and an aqueous solution of nitrite nitrogen of 2 mg / are prepared and mixed with each other to prepare the following first
The test waters A to E in the table were prepared, and the ultraviolet light of 220 nm and 225 nm was selected as the wavelengths a and b for these test waters, and the absorbance of each test water was determined. Obtained.

Next, the absorbance in ultraviolet light of the above-mentioned 2 mg / mL aqueous solution of nitrate nitrogen and 2 mg / mL aqueous solution of nitrite nitrogen was determined separately, and the absorbance curve is as shown in Fig. 1. These absorbance curves The absorbance at 220 nm and 225 nm per unit concentration of nitrate nitrogen and nitrite nitrogen was determined from Table 3 and the results are shown in Table 3 below.

Substituting the measured values in Table 3 into the equations (1) and (2) and modifying the equations (1) and (2), the following equations (3) and (4) are obtained.

(3) NO ₃ -N = 17.42 × E _{NOX-N ・ 220} -25.22 × E _{NOX-N ・ 225} (4) NO ₂ -N = 22.52 × E _{NOX-N ・ 225} -11.74 × E _{NOX-N ・ 220} By substituting the absorbances in Table 2 into the above equations (3) and (4), the nitrate nitrogen concentration (NO ₃ -N) and nitrite nitrogen concentration (NO ₂ -N) at each concentration are obtained. Results As shown in Table 4 below, it is clear that the measured values and the set values are in very good agreement.

The above is the basic principle of the quantification method of the present invention, and the ultraviolet light used in the quantification method of the present invention is ultraviolet light in which both nitrate nitrogen and nitrite nitrogen are absorbed (for example, as shown in FIG. To 250 nm ultraviolet light), and further, it is necessary that the absorbances by nitrate nitrogen and nitrite nitrogen be different (for example, other than the intersection of the curves in FIG. 1), Ultraviolet light of any wavelength may be used.

However, according to the research conducted by the present inventor, the one that gives the most excellent result is the ultraviolet light in the range of 210 to 230 nm,
Especially, it was ultraviolet light of 220 nm and 225 nm.

Further, the method for quantifying inorganic nitrogen according to the present invention can be applied to any aqueous solution as long as it is an aqueous solution containing at least one of nitrate nitrogen and nitrite nitrogen, and preferably activated sludge. Most useful for quantifying inorganic nitrogen in wastewater in aerobic and anaerobic processes by the method, and other inorganic states such as wastewater before treatment, discharged water after treatment, general wastewater, river water, lake water, seawater, etc. It can also be used for the determination of nitrogen.

Especially when it is used for the determination of inorganic nitrogen in wastewater, in addition to nitrate nitrogen and nitrite nitrogen, a large amount of BO is contained in the wastewater.
D, COD and other ingredients are included, among them,
In particular, in the presence of organic substances such as BOD and COD, these organic substances also have an absorbance in the ultraviolet region and may act as an interfering substance in the method of the present invention.

Therefore, when the quantification method of the present invention is applied to the quantification of inorganic nitrogen in wastewater, it is preferable to remove the above-mentioned interfering substances in advance. Of course, the presence of an interfering substance does not mean that the method of the present invention cannot be applied, but the method of the present invention can be sufficiently utilized by sufficiently correcting the influence of the interfering substance on the absorbance.

The most preferred method of removing interfering substances is the method previously developed by the present inventors. This method is Japanese Patent Application Sho 60-21028
The details are omitted because they are sufficiently disclosed in the specification No. 9, but in determining the concentration of inorganic nitrogen in the test water, an interfering substance in the test water was previously measured by an RO membrane (reverse osmosis membrane) and / or
Alternatively, it is a method of removing with a UF membrane (ultrafiltration membrane).

The RO membrane used in the above method is a membrane used in the reverse osmosis method, which is widely known as a technique for desalination of seawater, concentration of solute in various solutions or separation technology, and is mainly a solute of a relatively small molecule. It is used for separating, concentrating or purifying the solution.

The UF membrane is known as an ultrafiltration membrane, and the RO
It is used in an ultrafiltration method for concentrating, separating or purifying a solute having a larger molecular weight than that of a membrane.

Such RO and UF membranes are available from Abcor Inc., Ajaxln-tl.Cor.
p., Amicon Corp., Aqua-chem.lnc., Cu-lligan lntl.Co.,
Dorr-olivir.lnc., Dowche-m-ical Co., Dupont.Co., Envi
Rogenics Co., Genera-l Electric Co. and many other manufacturers are commercially available as RO membranes or UF membranes with various pore sizes, and any of these is available and can be selected and used in the present invention. it can.

The RO membrane and / or UF membrane as described above does not permeate inorganic salts of small molecules such as salt, but permeates inorganic salts but does not permeate organic compounds or high molecular weight organic compounds of medium molecular weight. Since various types of pores with various pore sizes can be obtained and used, the type of various contaminants contained in it should be investigated in advance from the type of sample water, and inorganic nitrogen can actually permeate, but the molecular weight is more than that. It is preferable to employ an RO membrane or a UF membrane that is substantially impermeable to large amounts of impurities such as various surfactants, detergents, soaps, microorganisms and the like.

For example, as a preferable method for selecting RO membrane or UF membrane,
Various contaminants and inorganic nitrogen as described above, which are considered to be contained in the wastewater, are dissolved in water to form a similar drainage, and the similar drainage is used to form an RO membrane and / or
The UF membrane allows inorganic nitrogen to permeate substantially, but contaminants with a higher molecular weight than inorganic nitrogen do not substantially permeate RO
Membranes or UF membranes can be employed. Moreover, these RO membranes and UF membranes can be used in combination.

According to the research conducted by the present inventors, one preferable RO membrane was found to have a salt removal rate of 30 to 70%.

That is, when simulated wastewater containing sodium chloride and sodium dodecylbenzenesulfonate (DBS) was prepared and the removal rate of the salt and DBS in this simulated wastewater by the RO membrane was measured, the salt removal rate was 30 to 70%. It was discovered that the RO membrane substantially permeates most of the inorganic nitrogen and substantially does not permeate DBS. Of course, the substance permeability (removal rate) of such an RO membrane is greatly influenced by the operating conditions of the RO membrane used, particularly the operating pressure used, so that it is also important to set appropriate operating conditions.

According to the detailed study by the present inventors regarding the operating conditions, the normal operating pressure of the RO membrane is 20 to 50 kgf /
cm, but lower than normal pressure as operating pressure,
For example, when a module inlet pressure of 3 to 5 kgf / cm is adopted, the removal rate of medium to high molecular weight such as DBS is almost the same as that under normal pressure, but permeation of inorganic salts such as inorganic nitrogen The rate is remarkably large, and therefore, by adopting such operating conditions, almost all the inorganic nitrogen is permeated,
And it has been found that various contaminants can be removed sufficiently. This tendency was the same for the UF membrane.

Even under the above operating conditions, the inorganic nitrogen is removed to some extent by the RO membrane or the UF membrane, for example, about 5 to 15%. Therefore, the inorganic nitrogen removal rate of the RO membrane or the like should be obtained in advance. It is desirable to correct the actual inorganic nitrogen concentration analysis value by the method of the present invention.

By pretreating the test water using the RO membrane or UF membrane as a filter as described above, the concentration of nitrate nitrogen and the concentration of nitrite nitrogen can be more accurately and rapidly determined by the method of the present invention.

Next, the quantification device of the present invention will be described.

The inorganic nitrogen quantification apparatus of the present invention utilizes the method of the present invention, and an ultraviolet absorption spectrophotometer and an amplification circuit for amplifying an output signal from the absorption spectrophotometer, and the amplified output signal in advance. Comprising an arithmetic circuit for converting according to a predetermined conversion formula and an output device for outputting the converted value, and in particular, the absorptiometer has both absorption for nitrogen in each state and different wavelengths. Two kinds of ultraviolet light,
At least one of them is configured to be able to output the absorbance by the test water of ultraviolet light having different absorbances per unit concentration for nitrate nitrogen and nitrite nitrogen, and the arithmetic circuit is explained in the quantification method. The circuit is characterized in that it can calculate the concentrations of nitrate nitrogen and nitrite nitrogen from a calculation formula.

Each unit that constitutes the above-mentioned quantification device of the present invention will be described in detail below.

(1) Ultraviolet absorptiometer The two-wavelength absorptiometer used in the present invention is fixed at two wavelengths absorbed by nitrate ions and nitrite ions, and is irradiated to one cell (flow-through cell) to obtain each signal. This is a unique measurement method (2 wavelength measurement, 2 phenomenon photometry).

The apparatus main body is similar to a general ultraviolet absorption photometer (UV meter), a deuterium discharge tube is used as a light source, and a quartz cell is used as a cell.

Further, when a pretreatment device (RO / UF) that removes not only suspended substances in the wastewater but also dissolved organic substances is used, a cell cleaning device is not required.

Furthermore, when the absorbance value exceeds the measurement limit of the photometer, the dilution water pump in the pretreatment facility automatically operates,
It is equipped with a mechanism for keeping the absorbance within the measurement range.

(2) Amplification circuit After amplifying the voltage proportional to each of the two ultraviolet absorbances and the comparative light intensity obtained by the above ultraviolet absorptiometer, logarithmic conversion is performed to obtain the absorbance at each measurement wavelength.

(3) Arithmetic circuit A circuit that calculates the nitrogen concentration [NO ₃ -N, NO ₂ -N and their sum (NO _X -N)] of each state based on the absorbance of each wavelength obtained by the above amplification circuit. Is. The wavelength used is, for example, 220 nm (a)
And 225 nm (b) by the difference between the two wavelengths, the relationship between the absorbance at each wavelength and the nitrogen concentration in each state is (1) E _{NOX-N · 220} = e _{NO3-N as described above.・ 220} × NO ₃ -N + e _{NO2-N ・ 220} × NO ₂ -N (2) E _{NOX-N ・ 225} = e _{NO3-N ・ 225} × NO ₃ -N + e _{NO2-N ・ 225} × NO ₂ -N Where E _{NOX-N ・ 220} and E _{NOX-N ・ 225} = wavelength 220 nm and wavelength 225
Absorbance of NO _X -N at nm _{eNO3-N · 220} and _{eNO3-N · 225} = wavelength 220 nm and wavelength 225
Concentration Absorbance of NO ₃ -N at nm e _{NO2-N · 220} and e _{NO2-N · 225} = NO _{2 at} wavelength 220 nm and wavelength 225 nm
-N Unit concentration Absorbance NO ₃ -N = Nitrate nitrogen concentration (mg /
) Is NO ₂ -N = nitrite nitrogen concentration (mg /).

Further transforming the above equation, Becomes

In the above formulas (3) and (4), E _{NOX-N ・ 220} and E _{NOX-N ・ 225} are measured values, and e _{NO3-N ・ 220} , e _{NO3-N ・ 225} , e _NO2-N220 and e
_{NO2-N ・ 225} is a value that has been previously obtained by experiments,
When the constant terms of the above equations (3) and (4) are arranged, (5) NO ₃ −N = a × (E _{NOX-N · 22} −1.45 × E _{NOX-N · 225} ) (6) NO ₂ − N = b × (E _{NOX-N ・ 220} −0.52 × E _{NOX-N ・ 225} ) (a and b are constants determined by the cell width), and NO ₃ −N and NO ₂ −N can easily be calculated later. It is calculated.

When calculating from the ratio of two wavelengths, the relationship between the mixing ratio of NO ₃ —N and NO ₂ —N and E ₂₂₅ / E ₂₂₀ can be expressed in a one-to-one correspondence as shown in FIG.

Mixing ratio (α) obtained from the absorbance ratio in Fig. 3 in equation (1) or (2)
And β) are substituted, equation (1) can be expressed by the following equation.

here Then, equations (7) and (8) are Therefore, the values of NO ₃ -N and NO ₂ -N can be quickly calculated by storing the correlation shown in FIG.

As described above, the apparatus of the present invention can perform calculation regardless of the difference between the two wavelengths to be measured and the ratio of the two wavelengths.

(4) Output device A signal proportional to each state nitrogen concentration is output, and each state nitrogen concentration is digitally or analog-displayed on the display panel, which makes it possible to control the optimum methanol at each state nitrogen concentration.

For example, the required amount of methanol in the biological denitrification process can be calculated by the following equation when the dissolved oxygen concentration in the aeration tank is included.

Required amount of methanol (mg /) = 2.47 x NO ₃ -N + 1.53 x NO ₂ -N + 0.87 x DO DO can be continuously and instantaneously measured by a general DO meter, and the device of the present invention can be used for NO ₂ -N and By measuring NO ₂ —N simultaneously and individually, it becomes possible to add the denitrifying agent (methanol) without excess or deficiency according to the above calculation formula, and a very economical and stable treatment effect is obtained.

It is preferable that the quantification device of the present invention including the unit as described above further includes a pretreatment device for removing interfering substances in the test water.

The purpose of removing these interfering substances, the removing method and apparatus, and their effects are as already described.

Further, the apparatus of the present invention employs two-wavelength measurement (two-phenomenon photometry), but the method has a wide variety of configurations.

The block diagram of Fig. 2 is basically an orthodox in which light emitted from a light source is passed through a cell, dispersed by a half mirror, the target wavelength in the transmitted light is selected using a filter, and measured by two detectors. That's the method.

However, for two-wavelength measurement (two-phenomenon photometry), as described above, the light emitted from the light source is divided into two monochromatic lights using a monochromator or the like, and then the cells are irradiated with the two wavelengths alternately by a chipper or the like. Measure, 1 detector and preamplifier
There are various methods such as using a table, and any method can be used for measurement.

Next, the operation of the quantification device of the present invention will be described in detail with reference to FIG. 2 of the accompanying drawings.

The pretreatment device 1 includes a water sampling pump, a separation membrane (for example, RO / U
F) is composed of a dilution water pump, and samples such as aeration tank mixed liquid and river water are sampled by a sampling pump and pressed into a separation membrane. In the separation membrane, suspended substances that interfere with measurement and organic substances that absorb ultraviolet light are mainly removed.

The pretreated test water is sent to the cell 3. However, during the test
If NO _X -N concentration is high, dilution water pump is operated,
It is sent to the cell 3 after being diluted to a measurable concentration.

The ultraviolet absorptiometer measures the light from the light source 2 by the half mirror 4
Is divided into light for the cell 3 and light for the reference detector 6, and the light transmitted through the cell 3 is separated by another half mirror 4
Is further divided by and is sent to two ultraviolet light detectors 5 with a filter of the measurement wavelength as a set.

The voltage obtained by each detector is amplified by the preamplifier 7,
The logarithmic converter 8 linearly determines the absorbance at each measurement wavelength.

The control detector is for removing the influence of the fluctuation of the light source,
It corresponds to general double beam photometry and is sent to two logarithmic converters to correct the photometry signal.

Absorbance obtained by the logarithmic converter, the arithmetic circuit 9 for performing an arithmetic operation by the arithmetic expressions described above, NO _X, the nitrogen concentration of NO ₂ and NO ₃ state is calculated.

The output device 10 displays the nitrogen concentration in the NO _X , NO ₂ and NO ₃ states on the digital voltmeter and records it on the recorder as an analog signal.

Furthermore, the device of the present invention can have an external output terminal and can output a signal proportional to the measured values of the nitrogen concentration in the NO _X , NO ₂ and NO ₃ states.

The external output is intended to control the process such as the injection amount of methanol or give a measurement signal to an external indicating instrument.

(Operation / Effect) According to the present invention as described above, the present invention has the following operation / effect.

(1) Without requiring special complicated operations and complicated processing and equipment,
It is possible to easily and continuously quantify the concentration of nitrate nitrogen, the concentration of nitrite nitrogen and the total amount thereof in arbitrary test water.

Therefore, it is possible to easily quantify the concentration of inorganic nitrogen and the ratio of nitrate nitrogen to nitrite nitrogen in wastewater, discharged water for wastewater treatment, river water, lake water, seawater and other test water.

(2) By utilizing the present invention for wastewater treatment such as activated sludge method, source wastewater, aerobic process water, anaerobic process water, inorganic nitrogen concentration of discharged water and the like and its nitrate nitrogen and nitrite nitrogen The ratio of is always grasped, and good wastewater treatment is realized.

In particular, since the ratio of nitrate nitrogen to nitrite nitrogen of inorganic nitrogen generated in the aerobic process is always continuously grasped, the reducing agent used in the anaerobic process, for example, the amount of methanol used is excessive or insufficient. Since it can be added as a proper amount without any treatment, it is advantageous in terms of treatment cost, and since insufficient or excessive addition of reducing agent does not occur, subsequent treatment is easy and discharge water with low inorganic nitrogen concentration should be used. Became possible.

Next, an example used for quantifying the concentration of inorganic nitrogen in two kinds of aerobic process water (F and G) generated in the actual activated sludge wastewater treatment will be shown. For comparison, the test waters F and G are the values determined by the Brucine method for nitrate nitrogen and the N- (1-naphthyl) ethylenediamine absorptiometry method for nitrate nitrogen, respectively. The quantitative results are shown in Table 5 below, and the quantitative values according to the present invention were in good agreement with the quantitative values according to the conventional method.

The absorbance (1) is the absorbance at a wavelength of 220 nm.
(2) is the absorbance at wavelength 225 nm, NO ₃ -N (3) is a quantitative value by the conventional method, NO ₃ -N (4) is a quantitative value according to the method of the present invention, NO ₂ - N (5) is a quantitative value by the conventional method, NO ₂ -N (6) is a quantitative value according to the method of the present invention.

[Brief description of drawings]

FIG. 1 shows ultraviolet absorbance curves of nitrate aqueous solution of nitrogen and nitrite aqueous solution (concentration 2 mg / each), the vertical axis shows the absorbance and the horizontal axis shows the wavelength nm. FIG. 2 is a block diagram for explaining the quantification device of the present invention, and FIG. 3 is a diagram showing the relationship between the mixing ratio of nitrate nitrogen and nitrite nitrogen and E ₂₂₅ / E ₂₂₀ . 1: Pretreatment device, 2: Light source 3: Cell, 4: Half mirror 5: Ultraviolet light detector, 6: Control detector 7: Preamplifier, 8: Logarithmic converter 9: Arithmetic circuit, 10: Output device

Front page continuation (72) Inventor Hiroaki Miyakoshi 2-31, Hatazawa, Kisarazu, Chiba (56) References JP-A-53-30379 (JP, A) JP-A-55-65139 (JP, A) JP-A-61 -172031 (JP, A) Actually opened 56-151951 (JP, U)

Claims (2)

[Claims] 1. A method for quantifying the respective concentrations of nitrate nitrogen and nitrite nitrogen in test water by an ultraviolet absorptiometry,
Using two kinds of ultraviolet light having different wavelengths within a wavelength range of 210 to 230 nm, which have different absorbances per unit concentration for nitrate nitrogen and nitrite nitrogen, the absorbances of the ultraviolet light of the respective wavelengths by the test water And the absorbance per unit concentration of the respective ultraviolet light for nitrate nitrogen and nitrite nitrogen are measured in advance, and the absorbance of the above two kinds in the test water and the nitrate nitrogen and nitrite nitrogen are measured. It is characterized by simultaneously calculating and quantifying the respective concentrations of nitrate nitrogen and nitrite nitrogen in the test water by the following formulas (1) and (2) using the absorbance per unit concentration of each wavelength for Determination method of inorganic nitrogen. (1) E _{NOX-N ・ a} = e _{NO3-N ・ a} × NO ₃ -N + e _{NO2-N ・ a} × NO ₂ -N (2) E _{NOX-N ・ b} = e _{NO3-N ・ b} × NO here _{3 -N + e NO2-N ·} b × NO 2 -N, E NOX-N · a = absorbance E for NO _X -N at the wavelength a _{NOX-N · b} = absorbance e of NO _X -N at a wavelength b _{NO3-N · a} = unit concentration absorbance of NO ₃ -N at wavelength a _{eNO2-N · b} = unit concentration absorbance of NO ₂ -N at wavelength b NO ₃ -N = nitrate nitrogen concentration (mg /) NO ₂ -N = nitrite nitrogen concentration (mg /) 2. The method for quantifying inorganic nitrogen according to claim 1, wherein the two kinds of ultraviolet light are ultraviolet lights having different wavelengths in the range of 220 to 225 nm.