JP2022131955A - Measuring method for hexamethylenetetramine, measuring method for substances to which water purification treatment is difficult to be applied, and measuring device - Google Patents

Abstract

To provide a measuring method for hexamethylenetetramine that is simple and applicable to continuous measurement, a measuring method for substances to which water purification treatment is difficult to be applied, and a measuring device.SOLUTION: A measuring method for hexamethylenetetramine measures hexamethylenetetramine in sample liquid on the basis of detecting consumption of chlorine by the hexamethylenetetramine in the sample liquid by measuring an oxidation-reduction current of the sample liquid. The measuring method for hexamethylenetetramine may include: a chlorine addition step for adding chlorine-containing components to the sample liquid; a holding step for holding the sample liquid to which the chlorine-containing components by the chlorine addition step is added, for a predetermined time; and a measuring step for measuring the hexamethylenetetramine in the sample liquid on the basis of the oxidation-reduction current of the sample liquid indicating chlorine concentration of the sample liquid after the chlorine addition step and before the holding step, and the oxidation-reduction current of the sample liquid indicating chlorine concentration of the sample liquid after the holding step.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a method for measuring hexamethylenetetramine, a method for measuring substances that are difficult to treat in water treatment, and a measuring device.

Hexamethylenetetramine (hereinafter also referred to as "HMT") is a nitrogen-containing heterocyclic compound, and is used in the chemical industry, for example, as a curing agent when producing resins and synthetic rubbers. HMT is also used in pharmaceuticals and food preservatives, but it may cause problems when present in environmental water such as river water.

For example, chlorination (chlorination) is performed in a water purification process at a water purification plant. Chlorination is performed by introducing a chlorine agent, which is a strong oxidizing agent, into the water to be treated. HMT is relatively stable in river water and the like, but when water containing HMT is chlorinated, HMT reacts with chlorine for disinfection to form formaldehyde. Formaldehyde is one of carcinogenic substances, and in Japan, it is stipulated that water containing formaldehyde at a concentration exceeding the standard concentration cannot be supplied as tap water. Moreover, formaldehyde is difficult to remove at a water purification plant, and if HMT is present in river water or the like taken in at a water purification plant, it becomes necessary to stop water intake, which causes a water outage. In 2012, after an incident occurred at a water purification plant in the Tone River water system in which formaldehyde was generated from HMT in a concentration exceeding the water quality standard due to chlorination, HMT was designated as a "difficult substance for water purification treatment" (Kensui 0306 No. No. 1 Notification of the Director of the Water Supply Division, Health Service Bureau, Ministry of Health, Labor and Welfare: hereinafter simply referred to as "Notification of the Director of the Water Supply Division, Health Service Bureau, Ministry of Health, Labor and Welfare").

For example, in order to manage the amount of chlorine agent injected at a water purification plant, for measuring the chlorine demand of treated water before chlorination such as river water, or the residual chlorine concentration of treated water after chlorination, A polarographic method for measuring redox current is sometimes used (Patent Documents 1 to 4).

JP 2018-124130 A Japanese Unexamined Patent Application Publication No. 2020-3382 Japanese Patent Application Laid-Open No. 2020-60371 Japanese Patent Application Laid-Open No. 2020-60372

As mentioned above, it is desirable to measure HMT, as it can cause problems if it is present in the water taken in, for example, at a water purification plant.

Methods using LC-MS/MS (liquid chromatograph-mass spectrometer), GC-MS (gas chromatograph-mass spectrometer), HPLC (high-performance liquid chromatography), and the like are known as methods for measuring HMT. However, measurements by these methods are performed in a laboratory and are not suitable for continuous measurements, and generally the measurement operations including pretreatment are complicated and require skill.

Therefore, there is a demand for an HMT measuring method and measuring apparatus that are relatively easy to operate and can be applied to continuous monitoring.

As with HMT, 1,1-dimethylhydrazine (hereinafter also referred to as "DMH"), N,N-dimethylaniline (hereinafter "DMAN"), and trimethylamine (hereinafter referred to as "difficult substances for water purification") , also referred to as “TMA”), tetramethylethylenediamine (hereinafter referred to as “TMED”), N,N-dimethylethylamine (hereinafter also referred to as “DMEA”), dimethylaminoethanol (hereinafter also referred to as “DMAE”) , acetonedicarboxylic acid, 1,3-dihydroxybenzene (resorcinol), 1,3,5-trihydroxybenzene, acetylacetone, 2′-aminoacetophenone, 3′-aminoacetophenone, bromides (such as potassium bromide) I have a similar problem.

Accordingly, an object of the present invention is to provide a method for measuring hexamethylenetetramine that is simple and applicable to continuous measurement, a method for measuring substances that are difficult to treat in water treatment, and a measuring device.

The above objects are achieved by a method for measuring hexamethylenetetramine, a method for measuring substances that are difficult to treat in water treatment, and a measuring device according to the present invention. In summary, the present invention measures hexamethylenetetramine in a sample liquid based on detecting the consumption of chlorine by hexamethylenetetramine in the sample liquid by measuring the redox current of the sample liquid. A method for measuring hexamethylenetetramine characterized by:

According to another aspect of the present invention, a chlorine-adding step of adding a chlorine-containing component to a sample solution, a holding step of holding the sample solution to which the chlorine-containing component has been added in the chlorine-adding step for a predetermined time, and an oxidation-reduction current of the sample solution indicating the chlorine concentration of the sample solution after the adding step and before the holding step; and an oxidation-reduction current of the sample solution indicating the chlorine concentration of the sample solution after the holding step. and a measuring step of measuring hexamethylenetetramine in the sample liquid based on .

According to another aspect of the present invention, the consumption of chlorine by hexamethylenetetramine in the sample liquid is detected based on the measurement results of a measurement unit that measures the oxidation-reduction current of the sample liquid, and the hexamethylenetetramine in the sample liquid is detected. A measuring device for hexamethylenetetramine characterized by measuring methylenetetramine is provided.

According to another aspect of the present invention, a chlorine addition unit that adds a chlorine-containing component to a sample liquid, a holding unit that retains the sample liquid to which the chlorine-containing component has been added by the chlorine addition unit for a predetermined time, and the sample A measurement unit for measuring the oxidation-reduction current of the solution, and a calculation unit to which the measurement result of the oxidation-reduction current by the measurement unit is input. Measurement results of the oxidation-reduction current by the measurement unit for the sample liquid that has not been held for a predetermined time, and the measurement for the sample liquid that has been added with the chlorine-containing component and held for the predetermined time. A measuring device for hexamethylenetetramine characterized by outputting a measurement result of hexamethylenetetramine in the sample liquid based on a measurement result of an oxidation-reduction current by a unit.

Further, according to another aspect of the present invention, there are provided a method and apparatus for measuring substances difficult to treat in water purification, to which the principles of the present invention are applied.

ADVANTAGE OF THE INVENTION According to this invention, the measuring method of hexamethylenetetramine which is simple and can be applied to a continuous measurement, the measuring method of a difficult substance corresponding to water purification treatment, and a measuring apparatus are provided.

It is a graph which shows the calibration curve of the combined chlorine concentration in the measurement example based on an Example. 4 is a graph showing measurement results in a measurement example according to an example; It is a schematic diagram of an example of a measuring device. FIG. 4 is a schematic diagram of another example of a measuring device; 1 is a schematic diagram of an example of a measuring instrument for measuring oxidation-reduction current; FIG. FIG. 4 is a schematic diagram of another example of a measuring instrument for measuring oxidation-reduction current; 7 is a graph showing measurement results in measurements according to another example.

Hereinafter, the method for measuring hexamethylenetetramine, the method for measuring substances that are difficult to treat in water treatment, and the measuring apparatus according to the present invention will be described in more detail with reference to the drawings.

[Example 1]
1. Measurement Principle In this example, the measurement of hexamethylenetetramine (HMT) in treated water (hereinafter also referred to as "raw water") before chlorination (chlorination) in a water purification process was taken as an example. A method and apparatus for measuring tetramine (HMT) will be described. However, the sample liquid targeted by the present invention is not limited to the raw water in the water purification process. Examples of the sample liquid include various sample waters such as environmental water (river water, lake water, seawater, etc.) that can be used as raw water, tap water, sewage, industrial water, waste water, food washing water, and pool water.

As mentioned above, for example, in water purification plants, in order to manage the amount of chlorine agent injected, the chlorine demand of treated water before chlorination such as river water, or the residual chlorine concentration of treated water after chlorination A polarographic method that measures redox current may be used for the measurement. Measurement by this method is relatively easy to operate, and can be applied to continuous monitoring of the component to be measured. Moreover, the polarographic method can be applied to various components to be measured. Therefore, it is conceivable to apply the polarographic method to the measurement of HMT. However, HMT cannot be measured by the polarographic method as it is because it does not undergo oxidation-reduction reaction.

On the other hand, HMT has the property of reacting with (consuming) chlorine to produce formaldehyde. The present inventors used this property to measure HMT by detecting the consumption of chlorine by HMT, that is, to detect the presence of HMT and to predict the concentration of HMT. I thought there was.

That is, as shown in the following reaction formula (1), HMT consumes chlorine when reacting with chlorine to produce formaldehyde (HCHO).
( _CH2 )6N4+12HClO→ _6HCHO + _4NH3 + _12HCl (1)

This reaction does not complete instantaneously and takes time to complete. Typically, this reaction takes about 30 minutes to complete. Therefore, a specified amount of a chlorine-containing component (here, also simply referred to as "chlorine") is added to a sample solution containing HMT, and the chlorine concentration is measured after about 30 minutes. If chlorine was consumed), it suggests the presence of HMT, and the degree of decrease in chlorine concentration can be used to predict the concentration of HMT. In this embodiment, hypochlorous acid (HClO) is added as chlorine. Also, chlorine consumption by HMT occurs substantially equally between free and bound chlorine.

By the way, for example, when the sample liquid is raw water in a water purification process, the raw water contains nitrogen other than HMT that consumes chlorine, such as ammoniacal nitrogen (ammonia nitrogen) and organic nitrogen (organic nitrogen) that consumes chlorine. A component (also referred to herein as a "chlorine-consuming nitrogen component") is often present. Therefore, in order to utilize the chlorine-consuming property of HMT, it is necessary to distinguish between chlorine consumption by HMT and chlorine consumption by chlorine-consuming nitrogen components. Therefore, an excess chlorine-consuming nitrogen component is added to the sample solution in advance so that substantially all of the chlorine contained in the sample solution becomes combined chlorine when the chlorine consumption by HMT is detected. . In this embodiment, ammonia nitrogen (NH ₄ —N) is used as the chlorine-consuming nitrogen component.

As noted above, HMT also consumes bound chlorine, but the reaction typically takes about 30 minutes to complete. On the other hand, the generation of combined chlorine (monochloramine or dichloramine) by ammonia nitrogen is completed instantaneously, and the generated combined chlorine is not decomposed in about 30 minutes. Also, the generated combined chlorine is finally decomposed into nitrogen while further consuming chlorine, but the reaction takes several hours to ten and several hours. Therefore, in the absence of HMT, the concentration of combined chlorine hardly changes after about 30 minutes. Therefore, the decrease in the concentration of combined chlorine after about 30 minutes suggests the existence of HMT, and the degree of decrease can be used to predict the concentration of HMT.

Here, chlorine (residual chlorine, effective chlorine) in the sample liquid is classified into free chlorine (free residual chlorine) such as hypochlorous acid and combined chlorine (combined residual chlorine) such as chloramine. Free chlorine mainly takes three forms: hypochlorous acid (HClO), dissociated hypochlorite ions (ClO ⁻ ), and molecular chlorine (Cl ₂ ). At normal pH such as in tap water, most of the free chlorine exists as hypochlorous acid or hypochlorite ions. On the other hand, combined chlorine is produced by the reaction of free chlorine with ammonia, amines and amino acids in water, and is composed of monochloramine (NH ₂ Cl), dichloramine (NHCl ₂ ) and trichloramine (NCl ₃ ). take the form of a kind. At normal pH such as tap water, most of the bound chlorine is present as monochloramine or dichloramine. Both the free chlorine concentration and the total chlorine concentration (total residual chlorine concentration) corresponding to the sum of the free chlorine concentration and combined chlorine concentration can be measured by the polarographic method of measuring the redox current. The combined chlorine concentration can be obtained by subtracting the free chlorine concentration from the total chlorine concentration, and when the total chlorine concentration can be considered to be substantially all combined chlorine concentration, it is measured by the polarographic method in the same way as the total chlorine concentration. (Patent Documents 1 to 4).

However, when measuring the concentration of combined chlorine in a sample solution to which specified amounts of chlorine and ammonia nitrogen have been added as described above, by limiting the types of combined chlorine, it is possible to measure with higher sensitivity and accuracy. It turned out to be possible. If the sample solution is neutral, eg, pH is greater than pH 5.0 and less than pH 8.0, addition of specified amounts of chlorine and ammoniacal nitrogen to the sample solution will produce monochloramine and dichloramine depending on the pH. The abundance ratio of monochloramine and dichloramine depends on pH, and the output of the sensor in the polarographic method also differs between monochloramine and dichloramine. Therefore, the calibration curve must be a polynomial that reflects the abundance ratio of monochloramine and dichloramine depending on this pH. On the other hand, by controlling the pH of the sample solution so that substantially all of the combined chlorine produced is limited to dichloramine, the concentration of dichloramine can be obtained from a linear calibration curve. When the sample solution is acidic, particularly pH 4.5 or more and pH 5.0 or less, when a specified amount of chlorine and ammoniacal nitrogen are added to the sample solution, substantially all of the combined chlorine produced becomes dichloramine. By setting the pH of the sample liquid to 4.0 or less, the generated combined chlorine can be trichloramine, but this is not desirable because trichloramine is toxic. Therefore, it is desirable to adjust the sample solution to an acidity, particularly to pH 4.5 or higher and pH 5.0 or lower, so that the generated combined chlorine is substantially limited to dichloramine.

Thus, the method for measuring HMT according to the present invention is based on detecting the consumption of chlorine by hexamethylenetetramine in the sample liquid by measuring the oxidation-reduction current of the sample liquid. It is for measuring. In this embodiment, the HMT measurement method includes a chlorine addition step of adding a chlorine-containing component to the sample solution, a holding step of holding the sample solution to which the chlorine-containing component has been added in the chlorine addition step for a predetermined time, and a chlorine addition step. Based on the oxidation-reduction current of the sample solution indicating the chlorine concentration of the sample solution after the step and before the holding step and the oxidation-reduction current of the sample solution indicating the chlorine concentration of the sample solution after the holding step, and a measuring step of measuring the HMT in the medium. The sample liquid is typically raw water in the water purification process. In addition, the chlorine-containing component may be hypochlorous acid, hypochlorite ion, or molecular chlorine. Specifically, hypochlorous acid water, sodium hypochlorite solution, or chlorine gas is added to the sample liquid. can do.

The method for measuring HMT according to the present invention can be used, as in this example, when the sample liquid is likely to contain chlorine-consuming nitrogen components in advance, such as raw water in a water purification process. At least before the holding step (before the chlorine-adding step, simultaneously with the chlorine-adding step, or after the chlorine-adding step and before the holding step), a nitrogen-adding step of adding a chlorine-consuming nitrogen component to the sample solution is provided. can do. In the nitrogen adding step, a sufficient amount of chlorine-consuming nitrogen component is added to the sample solution so that substantially all of the chlorine in the sample solution after the chlorine adding step becomes combined chlorine. The chlorine-consuming nitrogen component may be ammonia nitrogen, and specifically, an ammonium chloride solution or the like can be added to the sample liquid. In addition, regardless of the concentration of the chlorine-consuming nitrogen component contained in the sample solution in advance, the chlorine-consuming nitrogen component is first made into an excess amount, and substantially all the chlorine in the sample solution is stably converted into combined chlorine. For example, the nitrogen addition step is typically provided before the chlorine addition step.

Further, the method for measuring HMT according to the present invention further comprises adjusting the pH of the sample solution at least before the holding step (before the nitrogen addition step, simultaneously with the nitrogen addition step, or after the nitrogen addition step and before the holding step). It is preferable to have a pH adjustment step for adjusting the pH to 4.5 or more and 5.0 or less. In this case, substantially all of the combined chlorine generated by adding the chlorine-consuming nitrogen component and the chlorine-containing component to the sample solution becomes dichloramine.

In addition, the measurement step includes a first measurement step of measuring the first combined chlorine concentration in the sample solution after the nitrogen addition step and the chlorine addition step and before the holding step, and a second measurement step of measuring a second concentration of combined chlorine; a step of determining the concentration of HMT in the sample liquid based on the difference between the first concentration of combined chlorine and the second concentration of combined chlorine; may contain However, measuring HMT is not limited to indicating the concentration value of HMT. It also includes showing the result of whether or not there is.

Good results can often be obtained by setting the predetermined time of the holding step to about 30 minutes. However, for example, when the bound chlorine is dichloramine, the reaction may be complete in about 10-20 minutes. If the predetermined time is too short, the consumption of chlorine by HMT will be incomplete when HMT is present in the sample liquid, making it difficult to measure HMT accurately. Also, if the predetermined time is too long, the generated combined chlorine may begin to decompose, making it difficult to measure HMT accurately. The predetermined time can be appropriately set from the above viewpoint, but is typically 10 minutes or more and 40 minutes or less.

2. Measurement Example Next, a more specific measurement example according to the HMT measurement method of the present embodiment will be described.

2-1. Measurement step (1) 1st step First, to the sample solution (1000 ml), an acetate buffer (pH 4.6, 10 ml) prepared as follows as a pH adjuster, and chloride prepared as follows as ammonia nitrogen Ammonium solution is added so that the nitrogen concentration is 2 mg/L.

This nitrogen concentration is not limited to 2 mg/L, but should be sufficiently large relative to the concentration of chlorine-consuming nitrogen components that may be contained in the sample liquid in advance. For example, raw water in a water purification process may generally contain 0.1 to 0.2 mg/L of ammoniacal nitrogen. The above nitrogen concentration of 2 mg/L is sufficiently higher than the concentration of this commonly contained ammoniacal nitrogen. Although it is not limited to this, the standard is about 5 to 20 times, preferably about 10 to 15 times, the concentration of the chlorine-consuming nitrogen component that may be contained in the sample solution in advance. .

Acetate buffer (pH 4.6) was prepared by dissolving 27.5 mL of 1000 mM acetic acid solution and 72.3 g of sodium acetate trihydrate in pure water to make 1 L.

An ammonium chloride solution was prepared by dissolving 382 mg of ammonium chloride in pure water to make 1 L.

The first step in this measurement example corresponds to the above-described pH adjustment step and nitrogen addition step.

(2) Second step Next, a sodium hypochlorite solution prepared as follows as a chlorine-containing component is added to the sample solution obtained in the first step so that the chlorine concentration becomes 1 mg/L. .

This chlorine concentration is not limited to 1 mg/L, but should be sufficiently large relative to the concentration consumed by HMT that may be contained in the sample liquid. For example, the water quality standard for tap water stipulates that the concentration of HMT should be 80 μg/L or less. Concentrations of HMT in environmental water usually do not greatly exceed this reference concentration. Here, 0.1 mg/L of HMT consumes 0.61 mg/L of chlorine. The chlorine concentration of 1 mg/L is sufficiently large relative to the concentration consumed by HMT at about the reference concentration. Also, this chlorine concentration is such that almost all of the chlorine in the sample liquid becomes combined chlorine (dichloramine in this measurement example) after the second step. Although the chlorine concentration was 1 mg/L in this measurement example, it may be, for example, 2 mg/L.

A sodium hypochlorite solution was prepared by appropriately diluting sodium hypochlorite with pure water and measuring the concentration by the DPD method (effective chlorine concentration: about 12%). A free chlorine reagent (HACH0578) manufactured by HACH was used for the measurement by the DPD method. The DPD reagents include disodium hydrogen phosphate, N,N-diethyl-p-phenylenediamine salt, disodium ethylenediaminetetraacetate. As a measuring instrument, a HACH pocket residual chlorine meter (model number HACH2470) was used. In the case where the measuring method according to the present invention is applied to continuous measurement, for example, chlorine of a certain concentration is obtained by electrolysis of sodium chloride as employed in the chlorine demand meter CLD-7M manufactured by Toa DKK Co., Ltd. The method may provide chlorine to be added to the sample liquid. This method is generally a method of controlling the electrolysis current of sodium chloride so that the concentration of molecular chlorine (chlorine gas) detected based on the measurement of the oxidation-reduction current is constant. Incidentally, the pH of the sample solution added with acetate buffer, ammoniacal nitrogen and hypochlorous acid is about pH 4.8.

The second step in this measurement example corresponds to the aforementioned chlorine addition step.

(3) Third step The chlorine concentration (bound chlorine concentration, dichloramine concentration) of the sample solution obtained in the second step is measured by the polarographic method of measuring the redox current. This measurement can be performed immediately after the second step, once the sample liquid has been thoroughly mixed. In this measurement example, a high-sensitivity residual chlorine meter CLH-1610 manufactured by Toa DKK Co., Ltd. was used as a measuring instrument. The sensor part of this measuring instrument is a flow cell type in which a detection electrode, a counter electrode and a temperature compensation sensor made of platinum are combined. In this measurement example, the voltage applied between the detection electrode and the counter electrode by the voltage application mechanism was 600 mV (-600 mV was applied to the detection electrode). A gold electrode having a diameter of 2 mm was used as a detection electrode, and rotation was applied to the extent that a linear velocity of about 100 cm/s was obtained. A platinum electrode was used as the counter electrode. Ceramic beads having an average particle size of about 0.5 mm were used as beads for polishing the sensing electrode. Note that the measuring device will be further described later.

The third step in this measurement example corresponds to the first measurement step in the measurement steps described above.

(4) Fourth step The sample solution whose chlorine concentration (bound chlorine concentration, dichloramine concentration) was measured in the third step is allowed to stand for about 30 minutes. When the sample liquid obtained in the second step is separately carried out in the third step, the sample liquid obtained in the second step may be allowed to stand still for about 30 minutes. At this time, it is not necessary to control the temperature of the sample liquid, but if the temperature of the sample liquid is lower than room temperature (about 15 to 25° C.), it may be controlled to room temperature. Although it is not very necessary to stir the sample solution at this time, if it is necessary to accelerate the reaction in which HMT consumes chlorine depending on the type and condition of the sample solution, the flow rate of the sample solution may be increased by stirring. may be provided.

The fourth step in this measurement example corresponds to the aforementioned holding step.

(5) Fifth Step The chlorine concentration (bound chlorine concentration, dichloramine concentration) of the sample solution left to stand for about 30 minutes in the fourth step is measured by the polarographic method of measuring the redox current. In this measurement example, the measuring instrument used in this measurement was the same as that used in the third step, and the measurement conditions were substantially the same as in the third step.

The fifth step in this measurement example corresponds to the second measurement step in the measurement steps described above.

(6) Sixth step Chlorine concentration (bound chlorine concentration, dichloramine concentration) of the sample solution measured in the third step, and chlorine concentration (bound chlorine concentration, dichloramine concentration) of the sample solution measured in the fifth step, Find the difference between When the latter is lower than the former, it indicates that HMT was present in the sample solution, and the difference corresponds to the amount of chlorine consumed by HMT. Since 0.1 mg/L of HMT consumes 0.61 mg/L of chlorine, the concentration of HMT is calculated from the above difference. As a result, the concentration of HMT initially contained in the sample solution (raw water in the water purification process in this example) can be obtained.

Here, in this measurement example, in the first step and the second step, excess ammoniacal nitrogen was added to hypochlorous acid, and substantially all chlorine in the sample solution was converted to dichloramine. , which measures the consumption of chlorine by HMT. Therefore, even if a chlorine-consuming nitrogen component such as ammoniacal nitrogen is present in the sample liquid in advance, the influence of the ammoniacal nitrogen that was previously present can be ignored.

As can be seen from the reaction formula (1) above, ammonia (NH ₃ ) is produced in addition to formaldehyde (HCHO) when HMT consumes chlorine. If hypochlorous acid remains as free chlorine in the sample solution when the HMT consumes chlorine, the amount of chlorine consumed by the ammonia is added to the amount of chlorine consumed by the HMT. However, in the same manner as described above, in the first and second steps, excess ammoniacal nitrogen is added to hypochlorous acid, and substantially all chlorine in the sample solution is dichloramine, so the concentration of HMT is excessive. is not high, the impact is negligible.

The sixth step in this measurement example corresponds to the step of obtaining the concentration of HMT in the measurement step described above.

2-2. Measurement Results FIG. 1 is a graph showing the calibration curve of the dichloramine concentration used in this measurement example. This calibration curve was prepared by using dechlorinated water (zero water) whose pH was adjusted using the same acetate buffer as in the first step, and a solution containing dichloramine at a plurality of known concentrations in this dechlorinated water. I asked as In FIG. 1, the horizontal axis indicates the oxidation-reduction current measured in the same manner as in the third and fifth steps, and the vertical axis indicates the dichloramine concentration measured using the DPD reagent.

As the dechlorinated water, water obtained by treating tap water with activated carbon to remove chlorine was used (the same applies hereinafter). Dichloramine used was prepared by appropriately mixing an ammonium chloride solution and a sodium hypochlorite solution. As the DPD reagent, an all-chlorine reagent (HACH0582) manufactured by HACH was used. The DPD reagents include disodium hydrogen phosphate, potassium iodide, N,N-diethyl-p-phenylenediamine salt, disodium ethylenediaminetetraacetate dihydrate. Then, the dichloramine concentration was measured using a pocket residual chlorine meter (model number HACH2470) manufactured by HACH.

Table 1 shows the measurement results of the concentration of HMT by the method of this measurement example. The concentration of HMT was measured by the method of this measurement example for a sample solution in which HMT was added to dechlorinated water so as to have the concentration of HMT shown in the column of "Amount of HMT added to sample" in Table 1. The column of "oxidation-reduction current difference ΔμA" in Table 1 shows the difference between the oxidation-reduction current measured in the third step and the oxidation-reduction current measured in the fifth step. The column of "NHCl ₂ consumption amount calculation" in Table 1 shows the consumption amount of dichloramine based on the difference between the dichloramine concentration obtained in the third step and the dichloramine concentration obtained in the fifth step. The column "detected value" in the "NHCl ₂ consumption amount calculation" indicates the detected value (actual value) obtained by this measurement method, and the column "theoretical value" indicates the theoretical value (i.e., HMT 0.1 mg /L indicates a value based on consuming 0.61 mg/L of chlorine). The column of "calculated HMT concentration" in Table 1 shows the concentration of HMT obtained in the sixth step. This concentration of HMT was determined based on the fact that 0.1 mg/L of HMT consumes 0.61 mg/L of chlorine as described above. The column of "HCHO production capacity" in Table 1 shows the formaldehyde production capacity of HMT in the sample solution. This formaldehyde production ability was determined based on the fact that 0.1 mg/L of HMT produces 0.13 mg/L of formaldehyde. The "DPD" column in Table 1 shows the measured value of the total chlorine concentration of the sample solution by the above-mentioned pocket residual chlorine meter manufactured by HACH.

The HMT added to the dechlorinated water was prepared by dissolving hexamethylenetetramine (special grade manufactured by Wako Pure Chemical Industries, Ltd.) in pure water.

FIG. 2(a) is a graph plotting the relationship between the oxidation-reduction current difference (ΔμA) shown in Table 1 and the amount of sample HMT added. FIG. 2(b) is a graph plotting the relationship between the HMT concentration calculated value shown in Table 1 and the amount of HMT added to the sample.

As shown in FIG. 1, according to this measurement example, by controlling the pH of the sample solution to limit the bound chlorine produced to dichloramine, the concentration of dichloramine can be obtained from a linear calibration curve. Further, according to this measurement example, since the change in dichloramine concentration indicates the amount of chlorine consumed by HMT, the calculation of the concentration of HMT is simple and contributes to highly accurate measurement. As can be seen from Table 1, the detected value of dichloramine consumption was almost equal to the theoretical value (that is, HMT 0.1 mg/L is a value based on the consumption of 0.61 mg/L of chlorine). was taken. Moreover, as can be seen from Table 1 and FIG. 2, a high correlation was obtained between the amount of HMT added to the sample and the calculated value of HMT concentration.

Here, as described above, for example, the water quality standard for tap water stipulates that the concentration of HMT should be 80 μg/L or less. Therefore, for example, if HMT at a concentration of about 8 μg/L, which is 1/10 of the reference concentration, can be detected, it is highly accurate and preferable. As can be seen from Table 1 and FIG. 2, according to this measurement example, HMT at a concentration as low as 0.005 mg/L (=5 μg/L) could be measured with high accuracy.

3. Measuring Apparatus Next, a measuring apparatus that enables continuous HMT measurement by applying the HMT measuring method of the present embodiment will be described. FIG. 3 is a schematic diagram showing a schematic configuration of an example of the measuring device 100. As shown in FIG. In this measurement apparatus 100, a sample liquid S introduced from a sample liquid inlet 101 is sent through flow paths 102 and 107 to a measurement unit 108, and after measurement by a polarographic method is performed, the sample liquid outlet 111 It is designed to be discharged from

A chlorine-containing component is added to the sample solution S passing through the channel 102 in the middle of the channel 102 connected to the sample solution inlet 101 for receiving the sample solution (sample water such as raw water in the water purification process in this embodiment) S. A chlorine addition unit 103 is connected for the purpose. The chlorine adding section 103 includes a chlorine-containing component reservoir, and a pump as injection means for injecting the chlorine-containing component from the reservoir into the channel 102 . The chlorine-containing component may be hypochlorous acid, hypochlorite ions or molecular chlorine. In particular, as described above, in the continuous measurement, for example, the chlorine demand meter CLD-7M manufactured by Toa DKK Co., Ltd. employs a method of obtaining a constant concentration of chlorine by electrolysis of sodium chloride. It is preferred to obtain added chlorine. A holding unit 104 capable of holding the sample liquid S to which the chlorine-containing component has been added by the chlorine adding unit 103 for a predetermined time is connected to the downstream end of the channel 102 . The holding section 104 may be composed of, for example, a capillary, and the sample liquid S held in the holding section 104 may circulate within the holding section 104 until it is drawn out from the holding section 104 . A channel 107 is connected to the downstream end of the holding portion 104, and the sample liquid S is introduced into the holding portion 104 by a pump or the like as liquid flow control means provided in the channel 107, and the holding portion 104 is operated. Holding of the sample liquid S in 104 and derivation of the sample liquid S from the holding section 104 can be controlled. A measurement unit 108 for measuring the oxidation-reduction current of the sample liquid S is connected to the downstream end of the flow path 107 . The measurement unit 108 is also electrically connected to a calculation unit 109 to which a signal indicating the measurement result of the oxidation-reduction current by the measurement unit 108 is input. The measurement unit 108 and the calculation unit 109 constitute a measuring instrument 110 that performs measurement by the polarographic method. The measurement unit 108 corresponds to the sensor unit 1 or the sensor unit 3 of the measuring instrument 110 shown in FIG. 5 or 6, which will be described later. Also, the calculation unit 109 corresponds to the calculation control unit 21 of the measuring instrument 110 shown in FIG. 5 or 6, which will be described later.

In this embodiment, the measuring apparatus 100 corresponds to the measurement of raw water in the water purification process as the sample liquid S, and the sample liquid S is measured in the middle of the channel 102 connected to the sample liquid inlet 101 for receiving the sample liquid S. is connected to a nitrogen adding section 105 for adding a chlorine-consuming nitrogen component to the sample liquid S passing through the channel 102 . The nitrogen adding section 105 is configured by including a chlorine-consuming nitrogen component storage section and a pump as injection means for injecting the chlorine-consuming nitrogen component from the storage section into the channel 102 . The chlorine-consuming nitrogen component may be ammoniacal nitrogen. Furthermore, this measuring device 100 is connected to a pH adjusting section 106 for adjusting the pH of the sample liquid S by adding a pH adjusting agent to the sample liquid S passing through the channel 102 in the middle of the channel 102 . . The pH adjusting unit 106 is configured by including a reservoir for the pH adjusting agent and a pump as injection means for injecting the pH adjusting agent from the reservoir into the channel 102 . The pH adjuster may be an acetate buffer. In this example, the nitrogen addition unit 105 and the pH adjustment unit 106 are shared, and the chlorine-consuming nitrogen component and the pH adjustment agent are added substantially simultaneously to the sample solution S passing through the channel 102. It has become. In this measuring device 100 , the nitrogen adding section 105 and the pH adjusting section 106 are arranged upstream of the chlorine adding section 103 . Also, the operation of each unit of the measuring device 100 is controlled by the control device 120 .

In this measurement device 100, when measuring HMT, the sample liquid S introduced from the sample liquid inlet 101 into the channel 102 is first subjected to a chlorine-consuming nitrogen component and a pH A modifier is added and then a chlorine-containing component is added by the chlorine addition section 103 and introduced into the measurement section 108 through the retention section 104 . Then, the measurement unit 108 measures the oxidation-reduction current of the sample liquid S that has not been held in the holding unit 104 for a predetermined time (about 30 minutes). This measurement result is input to the calculation unit 109 and stored. Thereafter, in the same manner as described above, the sample solution S is introduced from the sample solution inlet 101 into the channel 102, and the chlorine-consuming nitrogen component and the pH adjuster are added to the sample solution S by the nitrogen adding section 105 and the pH adjusting section 106. Chlorine-containing components are added by the chlorine addition unit 103 to the water, and introduced into the holding unit 104 . Then, this sample liquid S is introduced into the measurement section 108 after being held in the holding section 104 for a predetermined time (about 30 minutes). Then, the measuring unit 108 measures the oxidation-reduction current of the sample liquid S held in the holding unit 104 for a predetermined time (about 30 minutes). This measurement result is input to the calculation unit 109 and stored. The sample liquid S that has been measured by the measurement unit 108 is discharged from the sample liquid outlet 111 . Then, calculation section 109 obtains the concentration of HMT based on the measurement result input from measurement section 108 according to the method described above. Further, the calculation unit 109 performs processing for displaying information on the measurement results. Processing related to the measurement result by the calculation unit 109 (calculation control unit 21 described later) will be further described later using FIGS. 5 and 6. FIG.

As described above, the HMT measuring device 100 according to the present invention detects the consumption of chlorine by hexamethylenetetramine in the sample liquid based on the measurement result of the measurement unit 108 that measures the oxidation-reduction current of the sample liquid S, It measures hexamethylenetetramine in the sample solution. In this embodiment, the calculation unit 109 measures the oxidation-reduction current by the measurement unit 108 with respect to the sample liquid S to which the chlorine-containing component has been added by the chlorine addition unit 103 but has not been retained for a predetermined time by the retention unit 104. Based on the result and the measurement result of the oxidation-reduction current by the measurement unit 108 regarding the sample solution S to which the chlorine-containing component was added by the chlorine addition unit 103 and held for a predetermined time by the holding unit 104, the sample The measurement result of hexamethylenetetramine in liquid S can be output. In particular, in this embodiment, the calculation unit 109 determines the amount of hexamethylenetetramine in the sample liquid S based on the difference between the first combined chlorine concentration and the second combined chlorine concentration in the next sample liquid S. Information about concentration can be output. The first concentration of combined chlorine is obtained by adding the chlorine-consuming nitrogen component by the nitrogen adding unit 105 and adding the chlorine-containing component by the chlorine adding unit 103, and the sample liquid to which the holding unit 104 does not hold for a predetermined time. It is the combined chlorine concentration in the sample liquid S based on the measurement result of the oxidation-reduction current for S by the measurement unit 108 . The second combined chlorine concentration is obtained by adding the chlorine-consuming nitrogen component by the nitrogen addition unit 105 and adding the chlorine-containing component by the chlorine addition unit 103, and holding the sample for a predetermined time by the holding unit 104. It is the combined chlorine concentration in the sample liquid S based on the measurement result of the oxidation-reduction current of the liquid S by the measurement unit 108 .

FIG. 4 is a schematic diagram showing a schematic configuration of another example of the measuring device 100. As shown in FIG. 4, the same reference numerals as in FIG. 3 denote the same constituent members as in FIG. 3, and detailed description thereof will be omitted. In the measurement apparatus 100 shown in FIG. 4, multi-way valves 113a and 113b as liquid flow changing means are provided at the downstream end of the flow path 102 and the downstream end of the flow path 107. A bypass channel 112 bypassing 104 is connected. In this measurement apparatus 100, the sample liquid S is introduced from the holding section 104 to the measuring section 108 every time the sample liquid S is held in the holding section 104 for a predetermined time (about 30 minutes), , the sample liquid S can be introduced into the measuring section 108 via the detour channel 112 . The configuration of FIG. 4 can be said to be more suitable for continuous monitoring of HMT concentrations than the configuration of FIG.

4. Measuring Instrument Next, an example of a measuring instrument that can be used in the HMT measuring method of the present embodiment will be described with reference to FIG. A measuring instrument 110 of this example is roughly configured from a sensor section 1 and a main body section 20 .

The sensor unit 1 is attached to a measurement cell 11 into which a sample liquid S is introduced, a detection electrode support 12 whose lower part is immersed in the sample liquid S, and a tip portion (a tip surface in this embodiment) of the detection electrode support 12. a counter electrode support 14 whose lower part is immersed in the sample solution S; a counter electrode 15 attached to the lower end side outer peripheral surface of the counter electrode support 14; a motor 16 for vibrating the detection electrode 13 in a circular motion; It has a bearing 17 for holding the sensing electrode support 12 and a large number of beads 18 for cleaning the sensing electrode 13 put into the sample solution S. The measuring cell 11 is provided with a mesh-like partition plate 11a that separates the detection electrode 13 and the counter electrode 15 so that the beads 18 do not flow out to the counter electrode 15 side.

The main unit 20 has an arithmetic control unit 21 , a voltage applying mechanism 22 , an ammeter 23 and a display device 24 . The detection electrode 13 and the arithmetic control unit 21 are connected by the wiring L1, the counter electrode 15 and the arithmetic control unit 21 are connected by the wiring L2, and the motor 16 and the arithmetic control unit 21 are connected by the wiring L3. . The ammeter 23 is provided in the middle of the wiring L1, and the voltage applying mechanism 22 is provided in the middle of the wiring L2.

The detection pole 13 is made of gold. Also, the counter electrode 15 is made of platinum. The detection pole support 12 is arranged in an inclined state, and is held by a bearing 17 at a predetermined point in the middle in the longitudinal direction, so that it can precess with the holding point by the bearing 17 as a fulcrum. Also, the base end portion 12a of the detection pole support 12 and the rotating shaft 16a of the motor 16 are eccentrically engaged. Therefore, by rotating the rotating shaft 16a of the motor 16, the base end portion 12a is circularly moved, and the detection electrode 13 attached to the tip portion of the detection electrode support 12 is also vibrated (circularly moved). . The wiring L1 passes through the detection electrode support 12 and can be pulled out from the vicinity of the holding position by the bearing 17 without being twisted even when the detection electrode 13 is circularly moved.

A large number of beads 18 are arranged in the vicinity of the detection pole 13 in an unfixed state. The bead 18 contacts the vibrating (circular motion) sensing electrode 13 and polishes the sensing electrode 13 . Ceramic or glass is preferable as the material of the beads 18 . The detection electrode 13 and the counter electrode 15 can be cleaned using a chemical solution according to the composition of the contaminants. For example, chemical cleaning using oxalic acid, hydrochloric acid, hydrogen peroxide solution, or the like can be performed. Ozone cleaning may also be performed. Further, physical cleaning such as brush cleaning may be performed instead of chemical cleaning or in addition to chemical cleaning. Further, in order to keep the detection electrode 13 clean, it is preferable to perform electropolishing in addition to the mechanical polishing with the beads 18 . For electropolishing, it is sufficient that a current flows between the sensing electrode 13 and the counter electrode 15 in the direction opposite to that during measurement, and a well-known method can be employed as appropriate. Moreover, the measuring instrument 110 may include an automatic cleaning mechanism for cleaning the counter electrode 15 and the detection electrode 13 . In that case, regular cleaning can be done automatically.

The voltage applying mechanism 22 applies an applied voltage between the detection electrode 13 and the counter electrode 15 . This applied voltage is, for example, 600 mV (-600 mV applied to the sensing electrode) in the case of the measurement example described above. However, this applied voltage is not limited to the values in the measurement example described above, and can be appropriately selected according to the component to be measured. 1-4).

The ammeter 23 measures an oxidation-reduction current flowing between the detection electrode 13 and the counter electrode 15 when the voltage applying mechanism 22 applies an applied voltage between the detection electrode 13 and the counter electrode 15 . When using multiple applied voltages by sequentially switching, the value of the oxidation-reduction current becomes unstable immediately after switching the applied voltage. is preferred. The arithmetic control unit 21 obtains the concentration of HMT based on the measurement result of the oxidation-reduction current according to the measurement method of this embodiment. In a storage unit (such as an electronic memory) provided in the arithmetic control unit 21, in order to obtain the concentration of HMT according to the measurement method of the present embodiment, the information of the calibration curve of the concentration of combined chlorine obtained in advance and the concentration of combined chlorine are stored. Necessary information such as an arithmetic expression for conversion to HMT concentration is stored. The density of the HMT obtained by the arithmetic control unit 21 is given to the display device 24 as a signal D1, and these densities are displayed on the display device 24. FIG. Further, these densities may be transmitted as a signal D2 to an external recorder, data logger, memory, printer, computer, or the like. Note that the signal D2 may be either a digital signal or an analog signal. Moreover, it may be transmitted by wire or wirelessly. Further, the arithmetic control unit 21 may output the current value from the ammeter 23 to the external computer as the signal D2. In that case, the external computer may determine the concentration of HMT based on the measurement results of the oxidation-reduction current according to the measurement method of this embodiment. Further, the arithmetic control unit 21 may output each current value from the ammeter 23 to the display device 24 as the signal D1. In that case, the operator can determine the concentration of HMT based on each current value read from the display device 24 according to the measuring method of this embodiment. In addition, when the HMT concentration exceeds a predetermined threshold value set in advance, a warning is displayed on the display device 24 or the display unit of the external computer, or a warning is given by a speaker provided in the measuring instrument 110 or the external device. A sound (alarm) may be generated, or an optical warning may be generated via a light provided in the measuring instrument 110 or an external device.

It should be noted that the oxidation-reduction current used for calculation is preferably temperature-corrected. Therefore, measuring instrument 110 preferably includes a temperature sensor. If the sample liquid temperature is kept sufficiently constant or if the required measurement accuracy is low, the temperature correction may be omitted. Temperature correction means conversion into an oxidation-reduction current at a reference temperature (for example, 25° C.) in consideration of the temperature dependency of the oxidation-reduction current measurement. When the reference temperature is 25° C., temperature correction is specifically performed using the following formula (2).
I(V) ₂₅ =I(V) _t /(1+(α×(t−25)/100)) (2)
t: sample liquid temperature at the time of measurement (°C)
I(V) _t : Oxidation-reduction current value at voltage V obtained at sample liquid temperature t°C I(V) ₂₅ : Oxidation-reduction current value at voltage V temperature-corrected at reference temperature of 25°C α: per 1°C Electrode output change (%)

FIG. 6 shows another example of meter 110 . 6, the same reference numerals as in FIG. 5 denote the same constituent members as in FIG. 5, and detailed description thereof will be omitted. A measuring instrument 110 of this example is roughly configured from a sensor section 3 , a main body section 20 and a liquid feeding section 50 . The sensor section 3 is the same as the sensor section 1 of the measuring instrument 110 of FIG. 5 except that the measuring cell 11 of the measuring instrument 110 of FIG. The flow cell 19 is provided with a mesh partition plate 19a that partitions the detection electrode 13 and the counter electrode 15 so that the beads 18 do not flow out to the counter electrode 15 side. The liquid sending unit 50 has an inflow path 51 for sending the sample solution S to the flow cell 19 , a discharge path 52 for discharging the sample solution S from the flow cell 19 , and a pump 53 provided in the inflow path 51 . The pump 53 and the arithmetic control unit 21 are connected by wiring L4. The pump 53 operates according to instructions from the arithmetic control unit 21 . The measuring instrument 110 of this example can perform measurement in the same manner as the measuring instrument 110 of FIG.

Note that the sensor units 1 and 3 may be modified to have a composite structure like the sensor units of the second embodiment or the fourth embodiment described in Patent Document 1, for example. Also, here, a measuring instrument for obtaining the reproducibility of the thickness of the diffusion layer necessary for the polarographic method by actively flowing the sample liquid in contact with the sensing electrode against the surface of the sensing electrode has been described. A method of obtaining reproducibility of the thickness of the diffusion layer may be adopted by a method of suppressing the flow of the sample liquid in a narrow range in contact with the .

[Example 2]
In this example, another measurement example of hexamethylenetetramine (HMT) will be described. In the measurement example described in this embodiment, unlike the measurement example described in Embodiment 1, the combined chlorine in the sample liquid added with the specified amount of chlorine and ammonia nitrogen is not limited to dichloramine. Monochloramine concentrations are measured by a polarographic method that measures redox currents.

As described in Example 1, when the sample liquid is raw water in a water purification process, the sample liquid often contains ammonia nitrogen that consumes chlorine. Therefore, as described in Example 1, the sample solution is pre-loaded with excess nitrogen so that substantially all of the chlorine is combined chlorine when chlorine consumption is measured. Here, as described above, if the sample solution is neutral, for example, if the pH is greater than pH 5.0 and pH 8.0 or less, adding specified amounts of chlorine and ammonia nitrogen to the sample solution will produce monochloramine depending on the pH. and dichloramine are produced. The abundance ratio of monochloramine and dichloramine depends on pH, and the output of the sensor in the polarographic method also differs between monochloramine and dichloramine. Therefore, the calibration curve must be a polynomial that reflects the abundance ratio of monochloramine and dichloramine depending on this pH. In this measurement example, the concentration of monochloramine in a sample liquid is measured based on this method (see Patent Documents 3 and 4).

In this measurement example, the monochloramine concentration of the sample solution was measured as follows. A high-sensitivity residual chlorine meter CLH-1610 manufactured by Toa DKK Co., Ltd. (provided that the applied voltage can be changed as described below) was used as a measuring instrument. First, second and third applied voltages V ₁ , V ₂ and V ₃ were sequentially applied between the sensing electrode and the counter electrode by the voltage application mechanism. The _first applied voltage V1 is 700 mV (−700 mV applied to the sensing electrode), the _second applied voltage V2 is 750 mV (−750 mV applied to the sensing electrode), and the _third applied voltage V3 is 800 mV (−700 mV applied to the sensing electrode). 800 mV applied). The time for applying each voltage V ₁ , V ₂ , V ₃ can be appropriately selected, for example, from 10 to 120 seconds. Then, the first, _second and _third oxidation-reduction currents I(V ₁ ) and _I (V ₂ ), I (V ₃ ) was measured, and the monochloramine concentration (NH ₂ Cl concentration) of the sample liquid was obtained from the following formula.
_NH2Cl concentration = A x _I (V1) ₊ B x I (V2) + C x I ( _V3 ) + D
However, A = -1.2924 [mg / L] / [μA]
B = 0.885433 [mg/L]/[μA]
C = 1.243832 [mg/L]/[μA]
D = 0.2832 [mg/L]

That is, in this measurement example, the concentration of monochloramine in the sample liquid was obtained from the calibration curve represented by the following formula (3).
NH ₂ Cl concentration [mg/L]
=−1.2924×I(V ₁ )+0.885433×I(V ₂ )+1.243832×I(V ₃ )+0.2832 (3)

Each constant in the above formula (3) was obtained by multiple regression analysis and single It was obtained by performing regression analysis.

For the measurement of HMT, first, ammonia nitrogen (ammonium chloride solution) is added to the sample liquid so that the nitrogen concentration becomes 1 mg/L. Next, a chlorine-containing component (sodium hypochlorite solution) is added to the sample liquid so that the chlorine concentration becomes 2 mg/L. Next, the concentration of monochloramine in the sample solution to which the prescribed amounts of chlorine and ammoniacal nitrogen have been added is measured as described above. In addition, the sample solution added with the specified amounts of chlorine and ammoniacal nitrogen is allowed to stand for about 30 minutes. In addition, the concentration of monochloramine in the sample solution after standing still for about 30 minutes is measured as described above.

Then, the monochloramine consumption (NH ₂ Cl consumption) is obtained from the difference in the monochloramine concentration of the sample solution before and after the standing for about 30 minutes, and the HMT concentration is calculated from the following formula (4). Convert. The following formula (4) is based on a calibration curve prepared from the relationship between the HMT concentration and the NH ₂ Cl consumption detected by the polarographic method.
HMT concentration [mg/L]
= 0.4573 x (NH ₂ Cl consumption) + 0.0101 (4)

FIG. 7 shows the results obtained by measuring the amount of HMT added to the sample solution (sample HMT concentration) of 0 mg/L, 0.005 mg/L, and 0.1 mg/L by the method of this measurement example. 4 is a graph plotting the relationship between the concentration of HMT (HMT concentration calculated value) obtained by calculation using Equation (4) and the amount of HMT added to a sample.

According to this measurement example, it is possible to omit the step of adjusting the pH of the sample liquid, so that it may be possible to simplify the measurement procedure and the measurement apparatus. However, in this measurement example, a polynomial calibration curve is required, and the calculation becomes more complicated than in the measurement example described in the first embodiment. Moreover, as can be seen from FIG. 7, in this measurement, the measurement accuracy is slightly lower than in the measurement example described in the first embodiment. However, depending on the desired measurement accuracy and the like, the method according to this measurement example can also be adopted.

It should be noted that the method of the measurement example described in the present embodiment can be implemented in the same measuring apparatus as that described in the first embodiment. However, the pH adjuster in the measuring device can be omitted.

[Example 3]
In this embodiment, the application of the method and apparatus for measuring hexamethylenetetramine (HMT) described in the above embodiment to the method and apparatus for measuring water purification treatment difficult substances including HMT will be described.

As mentioned above, in the incident that occurred at the water purification plant in the Tone River system in 2012, the problem was that formaldehyde, a water quality standard item, exceeded standards. After the above event, substances that, like HMT, which is the causative substance, produce a high percentage of water quality standard items as by-products in the water purification process were designated as difficult substances for water purification treatment along with HMT ("Welfare and Welfare Ministry of Labor, Department of Health, Bureau of Water Supply Division Notification”).

In the above embodiments, the HMT measuring method and measuring apparatus have been described. The principle of this measuring method and measuring device is the measuring method and measuring device for HMT and substances other than HMT that consume chlorine and are difficult to handle in water treatment, in water that is subjected to chlorination in the water purification process (raw water in the water purification process). can be applied to

In other words, 1,1-dimethylhydrazine (DMH), N,N-dimethylaniline (DMAN), trimethylamine (TMA), tetramethylethylenediamine (TMED), N,N-dimethylethylamine, which are designated as difficult substances for water purification treatment (DMEA) and dimethylaminoethanol (DMAE), as described in Attachment 1 attached to the "Notification of the Director of the Waterworks Division, Health Service Bureau, Ministry of Health, Labor and Welfare", reacts with chlorine (consumes ) to form formaldehyde.

In addition, acetonedicarboxylic acid, 1,3-dihydroxylbenzene (resorcinol), 1,3,5-trihydroxybenzene, acetylacetone, 2'-aminoacetophenone, 3'-amino Acetophenone is known to produce chloroform by reacting (consuming) with chlorine in the chlorination process in the water purification process, as described in Attachment 1 attached to the "Notification of the Director of the Water Supply Division, Health Service Bureau, Ministry of Health, Labor and Welfare". .

Furthermore, bromide (potassium bromide, etc.), which is designated as a substance that is difficult to treat in water purification, is used in the chlorine treatment of the water purification process, as described in Attachment 1 attached to the "Notification of the Director of the Waterworks Division, Health Service Bureau, Ministry of Health, Labor and Welfare". It is known to react with (consume) chlorine to produce dibromochloromethane, bromodichloromethane, bromoform, and the like.

Therefore, by using chlorine consumption as an index, even for substances other than HMT that consume chlorine, chlorine consumption suggests the existence of substances that are difficult to treat, and HMT conversion concentrations As such, it is possible to predict the concentration of substances that are difficult to treat in water treatment. That is, the present invention provides hexamethylenetetramine (HMT), 1,1-dimethylhydrazine (DMH), N,N-dimethylaniline (DMAN), trimethylamine (TMA), which are currently designated as difficult substances for water purification treatment, tetramethylethylenediamine (TMED), N,N-dimethylethylamine (DMEA), dimethylaminoethanol (DMAE), acetonedicarboxylic acid, 1,3-dihydroxybenzene (resorcinol), 1,3,5-trihydroxybenzene, Acetylacetone, 2'-aminoacetophenone, 3'-aminoacetophenone, bromide (potassium bromide, etc.), and furthermore, it can be applied to the measurement method and measurement device for substances that consume chlorine and are difficult to deal with water purification treatment that may be specified in the future.

The method for measuring substances difficult to treat in water purification according to the present invention measures the consumption of chlorine by the substances difficult to treat in water purification in a sample solution, which is water to be subjected to chlorination in a water purification process, by measuring the oxidation-reduction current of the sample solution. Based on the detection, the substances in the sample solution that are difficult to treat in water purification are measured. Further, the method for measuring substances difficult to treat in water purification according to the present invention includes a chlorine-adding step of adding a chlorine-containing component to a sample solution, which is water to be subjected to chlorine treatment in a water purification step, and a chlorine-containing component is removed by the chlorine-adding step. A holding step of holding the added sample solution for a predetermined time, an oxidation-reduction current of the sample solution indicating the chlorine concentration of the sample solution after the chlorine addition step and before the holding step, and chlorine of the sample solution after the holding step. and a measurement step of measuring substances in the sample solution that are difficult to treat in water purification, based on the oxidation-reduction current of the sample solution that indicates the concentration. The chlorine-containing component may be hypochlorous acid, hypochlorite ions, or molecular chlorine. Specifically, hypochlorous acid water, sodium hypochlorite solution, or chlorine gas is added to the sample solution. can be done. Further, the predetermined time for the holding step is typically 10 minutes or more and 40 minutes or less.

In addition, the method for measuring substances that are difficult to treat in water purification according to the present invention can be used when there is a possibility that the sample solution (raw water in the water purification process) contains a chlorine-consuming nitrogen component in advance, and at least before the holding process ( Before the chlorine addition step, simultaneously with the chlorine addition step, or after the chlorine addition step and before the holding step), there is a nitrogen addition step of adding a chlorine-consuming nitrogen component to the sample solution. In the nitrogen adding step, a sufficient amount of chlorine-consuming nitrogen component is added to the sample solution so that substantially all of the chlorine in the sample solution after the chlorine adding step becomes combined chlorine. The chlorine-consuming nitrogen component is typically ammonia nitrogen, and specifically, an ammonium chloride solution or the like can be added to the sample liquid. In addition, regardless of the concentration of the chlorine-consuming nitrogen component contained in the sample solution in advance, the chlorine-consuming nitrogen component is first made into an excess amount, and substantially all the chlorine in the sample solution is stably converted into combined chlorine. For example, the nitrogen addition step is typically provided before the chlorine addition step.

In addition, the method for measuring substances difficult to treat in water purification according to the present invention further comprises: It may have a pH adjustment step of adjusting the pH of the liquid to pH 4.5 or more and pH 5.0 or less. In this case, substantially all of the combined chlorine generated by adding the chlorine-consuming nitrogen component and the chlorine-containing component to the sample solution becomes dichloramine.

In addition, the measurement step includes a first measurement step of measuring the first combined chlorine concentration in the sample solution after the nitrogen addition step and the chlorine addition step and before the holding step, and Based on a second measurement step of measuring the second combined chlorine concentration and the difference between the first combined chlorine concentration and the second combined chlorine concentration, the concentration of substances difficult to handle water purification treatment in the sample solution is determined. , for example, a step of obtaining a concentration converted into a concentration of a predetermined substance among substances difficult to treat water purification, such as HMT conversion concentration. However, measuring substances that are difficult to treat in water treatment is not limited to indicating the concentration value. It also includes showing the result of whether or not it is included to the extent that it exceeds.

Further, the apparatus for measuring substances difficult to treat in water purification according to the present invention measures chlorine consumption by substances difficult to treat in water purification in a sample solution, which is water to be subjected to chlorination in a water purification process, and an oxidation-reduction current of the sample solution. Substances that are difficult to treat in water purification are measured in the sample liquid by detecting them based on the measurement results of the measuring unit. More specifically, the apparatus for measuring substances difficult to treat in water purification according to the present invention can have the same configuration as the HMT measuring apparatus described with reference to FIGS. 3 to 6 in the above embodiment. Here, the description of the measuring apparatus relating to the measurement of HMT in the above-described embodiment is read as the description relating to the measurement of substances that are difficult to treat in water purification, and overlapping descriptions are omitted.

The principle of the measuring method and the measuring device of the present invention is based on hexamethylenetetramine (HMT), 1,1-dimethylhydrazine (DMH), N,N-dimethylaniline ( DMAN), trimethylamine (TMA), tetramethylethylenediamine (TMED), N,N-dimethylethylamine (DMEA), dimethylaminoethanol (DMAE), acetonedicarboxylic acid, 1,3-dihydroxybenzene (resorcinol), 1, 3,5-trihydroxybenzene, acetylacetone, 2'-aminoacetophenone, 3'-aminoacetophenone, bromides (potassium bromide, etc.), and further chlorine-consuming substances that are difficult to treat in water treatment, which may be specified in the future. Those skilled in the art can easily understand that it can also be applied as a measuring method and a measuring apparatus for .

100 Measuring Device 103 Chlorine Addition Part 105 Nitrogen Addition Part 106 pH Adjustment Part 108 Measurement Part 109 Calculation Part 110 Measuring Instrument

Claims (14)

Hexamethylenetetramine, characterized in that the consumption of chlorine by hexamethylenetetramine in the sample solution is detected by measuring the oxidation-reduction current of the sample solution, and the amount of hexamethylenetetramine in the sample solution is measured. How to measure. A chlorine addition step of adding a chlorine-containing component to the sample liquid;
a holding step of holding the sample solution to which the chlorine-containing component has been added in the chlorine adding step for a predetermined time;
an oxidation-reduction current of the sample liquid indicating the chlorine concentration of the sample liquid after the chlorine addition step and before the holding step; and an oxidation-reduction current of the sample liquid indicating the chlorine concentration of the sample liquid after the holding step. a measuring step of measuring hexamethylenetetramine in the sample solution based on the current;
A method for measuring hexamethylenetetramine, comprising: Furthermore, at least before the holding step, a nitrogen addition step of adding a chlorine-consuming nitrogen component to the sample solution,
In the nitrogen addition step, a sufficient amount of chlorine-consuming nitrogen component is added to the sample solution so that substantially all of the chlorine in the sample solution after the chlorine addition step becomes combined chlorine. The method for measuring hexamethylenetetramine according to claim 2. 4. The method for measuring hexamethylenetetramine according to claim 3, further comprising a pH adjustment step of adjusting the pH of the sample liquid to pH 4.5 or higher and pH 5.0 or lower at least before the holding step. . 5. The method for measuring hexamethylenetetramine according to claim 4, wherein the combined chlorine is dichloramine. 4. The method for measuring hexamethylenetetramine according to claim 3, wherein the combined chlorine is monochloramine or dichloramine. The measuring step includes
a first measuring step of measuring a first combined chlorine concentration in the sample solution after the nitrogen adding step and the chlorine adding step and before the holding step;
a second measuring step of measuring a second combined chlorine concentration in the sample liquid after the holding step;
determining the concentration of hexamethylenetetramine in the sample solution based on the difference between the first concentration of combined chlorine and the second concentration of combined chlorine;
The method for measuring hexamethylenetetramine according to any one of claims 3 to 6, comprising: Consumption of chlorine by hexamethylenetetramine in the sample liquid is detected based on the measurement result of a measurement unit that measures the oxidation-reduction current of the sample liquid, and hexamethylenetetramine in the sample liquid is measured. A measuring device for hexamethylenetetramine. a chlorine addition unit that adds a chlorine-containing component to the sample liquid;
a holding unit for holding the sample solution to which the chlorine-containing component has been added by the chlorine adding unit for a predetermined time;
a measurement unit that measures the oxidation-reduction current of the sample liquid;
a calculation unit to which the result of measurement of the oxidation-reduction current by the measurement unit is input;
has
The calculation unit calculates the result of measurement of the oxidation-reduction current by the measurement unit for the sample solution to which the chlorine-containing component has been added but has not been held for the predetermined time, and the measurement result of the chlorine-containing component added. and outputting the measurement result of hexamethylenetetramine in the sample liquid based on the measurement result of the oxidation-reduction current of the sample liquid held for the predetermined time by the measurement unit. A measuring device for methylenetetramine. 10. The apparatus for measuring hexamethylenetetramine according to claim 9, further comprising a nitrogen addition unit for adding a chlorine-consuming nitrogen component to the sample liquid to be held by the holding unit for the predetermined time. 11. The apparatus for measuring hexamethylenetetramine according to claim 10, further comprising a pH adjusting section that adjusts the pH of the sample liquid to be held by the holding section for the predetermined time. The calculation unit is based on the measurement result of the oxidation-reduction current by the measurement unit regarding the sample solution to which the chlorine-consuming nitrogen component and the chlorine-containing component have been added and the sample solution has not been held for the predetermined time. A first concentration of combined chlorine in the sample liquid, and oxidation by the measurement unit of the sample liquid to which the chlorine-consuming nitrogen component and the chlorine-containing component were added and held for the predetermined time. 10. Information about the concentration of hexamethylenetetramine in the sample liquid is output based on the difference between the second combined chlorine concentration in the sample liquid based on the measurement result of the reduction current, or 12. The apparatus for measuring hexamethylenetetramine according to 11. Based on detecting the consumption of chlorine by substances difficult to treat in water purification in a sample liquid, which is water to be subjected to chlorination in a water purification process, by measuring the oxidation-reduction current of the sample liquid. A method for measuring substances that are difficult to treat in water treatment, comprising measuring substances that are difficult to treat in water treatment. Detecting the consumption of chlorine by substances difficult to treat in water purification in a sample solution, which is water to be subjected to chlorination in a water purification process, based on the measurement results of a measurement unit that measures the oxidation-reduction current of the sample solution, An apparatus for measuring substances difficult to treat in water purification, characterized by measuring substances difficult to treat in water purification in the sample solution.

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