JP2000283939A - Water quality monitoring system, water quality monitoring method, and demineralizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and surely measure an instrinsic resistivity of test water such as desalted water, by restraining remarkably the influence of dissolved carbon dioxide. SOLUTION: In this monitoring system 1, resistivity of test water W wherein the atmospheric gas is dissolved by contacting with the atmosphere is measured by a water quality measuring apparatus 7, the quality of the water W is monitored based on a measured value therein. and a heater 4 for heating the water W to remove dissolved carbon dioxide is provided in a previous stage of the water quality measuring apparatus 7. The water quality monitoring system 1 and a water quality monitoring method are thereby provided to restrain remarkably the influence of the dissolved carbon dioxide so as to measure easily and surely instrinsic resistivity of the water W such as desalted water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water quality monitoring device, a water quality monitoring method, and a desalination device. More specifically, the present invention relates to a method for measuring the resistivity of a sample such as demineralized water in which gas in the atmosphere is dissolved by contact with the atmosphere. The present invention relates to a water quality monitoring device, a water quality monitoring method, and a desalination device that measure a conductivity with a conductivity meter and monitor the quality of a sample water based on the measured value rate.

[0002]

2. Description of the Related Art In various industrial fields, for example, pure water is used as washing water, chemical dilution water, analysis water, or boiler feed water. Depending on the purpose of use, the pure water may be, for example, a clarifier, an activated carbon device, an ion exchange resin device, a reverse osmosis membrane device (RO), an electrodialysis device, a distillation device,
It is manufactured by using an electric regeneration type desalination unit (EDI), a decarbonation unit or the like alone or by appropriately combining them. In the case of producing high-purity pure water, the above-described apparatus to which an ultraviolet oxidation apparatus, a vacuum deaerator, an ultrafiltration apparatus, and the like are added is used.

[0003] Since the quality of pure water such as demineralized water is extremely important in accordance with the purpose of use, impurities such as suspended components and ionic components are removed using a water quality monitoring device appropriately arranged in the manufacturing process. We are constantly monitoring. The monitoring items include, for example, resistivity, TOC, DO, fine particles, viable bacteria, and evaporation residue. Then, for example, the quality of the demineralized water from which the impurities have been removed is finally monitored by a water quality monitoring device using a conductivity meter, and is maintained at a certain allowable level.

Further, pure water such as demineralized water is often used in the atmosphere, and gas components in the atmosphere are dissolved in such demineralized water and exist as dissolved gases. Dissolved gas may have a bad effect depending on the use of demineralized water, so it is sealed with an inert gas such as nitrogen gas during storage to prevent gas in the air from dissolving. Since there is no adverse effect due to the gas itself, it is used while containing dissolved gas. Although the dissolved gas itself does not adversely affect the application, the original resistivity of the demineralized water may be strictly controlled at an allowable level. In such a case, the conductivity is conventionally monitored using a conductivity meter as a water quality monitoring device. However, among the dissolved gases from the atmosphere, carbon dioxide dissolves in demineralized water and produces electrolytes such as hydrogen carbonate ions.Therefore, the conductivity meter uses the original resistivity of demineralized water excluding the influence of this carbon dioxide gas. The measurement cannot be performed, and the desalinated water cannot be managed at the original resistivity. Therefore, for example, Japanese Patent Application No. 6-11406 proposes a technique for removing dissolved carbon dioxide by vacuum degassing or the like before measuring the conductivity of pure water such as demineralized water.

[0005]

However, although oxygen gas and nitrogen gas can be removed by simple vacuum degassing,
Carbon dioxide is dissolved in pure water such as demineralized water and combined with water molecules to form an electrolyte, which is degassed according to the concentration of undissociated carbon dioxide that is not combined with water molecules. There is a problem that an electrolyte such as hydrogen carbonate ions remains, carbon dioxide gas cannot be removed as expected, and a simple water quality monitoring device using a conductivity meter cannot measure the intrinsic resistivity of pure water. In order to increase the degree of vacuum in order to perform vacuum degassing more reliably, an exhaust device such as a large vacuum pump is required, and a water quality monitoring device that should be small and simple is expensive. . Of course, an ion chromatograph that separates ions derived from dissolved carbon dioxide from slightly remaining Na ions and Cl ions and measures the original resistivity of pure water,
Although the presence can be confirmed using a measuring device or the like capable of measuring only ions derived from dissolved carbon dioxide gas, it is expensive and complicated as a water quality monitoring device.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to remarkably suppress the influence of dissolved carbon dioxide gas and easily and reliably measure the original resistivity of a sample such as demineralized water. It is an object of the present invention to provide a water quality monitoring device, a water quality monitoring method, and a desalination device that can be used.

[0007]

According to a first aspect of the present invention, there is provided a method for monitoring water quality, comprising measuring a resistivity of a test sample in which gas in the atmosphere is dissolved by contact with the atmosphere by means of a conductivity meter. A method of monitoring the quality of the test water based on the value, wherein prior to measuring the resistivity of the test water, the test water is heated by heating means to remove dissolved carbon dioxide gas. It is.

A water quality monitoring method according to a second aspect of the present invention is characterized in that, in the first aspect of the invention, the test water heated by the heating means is degassed.

A third aspect of the present invention is directed to a water quality monitoring method according to the first or second aspect, wherein a heating temperature of the heating means is 80 ° C. or more. It is.

[0010] The water quality monitoring device according to a fourth aspect of the present invention measures the resistivity of a test water in which gas in the atmosphere is dissolved by contact with the atmosphere by means of a conductivity meter, and based on the measured value. In the water quality monitoring device for monitoring the water quality of the test water,
A heating means for heating the test water to remove dissolved carbon dioxide gas is provided in a stage preceding the conductivity meter.

According to a fifth aspect of the present invention, there is provided the water quality monitoring apparatus according to the fourth aspect of the present invention, further comprising a deaeration means disposed downstream of the heating means, and passing heated water through the deaeration means. It is characterized by doing.

A water quality monitoring device according to a sixth aspect of the present invention is the water quality monitoring device according to the fifth aspect, wherein a degassing device is used as the degassing means.

[0013] The water quality monitoring device according to claim 7 of the present invention measures the resistivity of a test water in which gas in the atmosphere is dissolved by contact with the atmosphere using a conductivity meter, and based on the measured value, In the water quality monitoring device for monitoring the water quality of the test water,
Degassing membrane means for degassing the dissolved carbon dioxide gas under reduced pressure is provided in front of the conductivity meter, and gas supply means for supplying an inert gas to a reduced pressure space of the degassing membrane means is provided. It is characterized by having.

Further, the water quality monitoring device according to the present invention measures the resistivity of a sample water in which gas in the atmosphere is dissolved by contact with the atmosphere, using a conductivity meter, and based on the measured value. In the water quality monitoring device for monitoring the water quality of the test water,
An aeration unit for bubbling an inert gas into the test water is provided at a stage preceding the conductivity meter.

A ninth aspect of the present invention is directed to a desalination apparatus, wherein the water quality monitoring apparatus according to any one of the fourth to eighth aspects is provided after the reverse osmosis membrane apparatus. It is assumed that.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiments shown in FIGS. FIG. 1 is a flowchart showing one embodiment of the water quality monitoring device of the present invention, FIG. 2 is a schematic diagram showing a main part of another embodiment of the water quality monitoring device of the present invention, and FIG.
FIG. 2 is a flowchart showing an example of a desalination apparatus provided with the water quality monitoring device of the present invention.

As shown in FIG. 1, for example, a water quality monitoring device 1 according to the present embodiment stores a test water W such as a desalinated water that stores the test water W in a state of being opened to the atmosphere. A heating device 4 connected via a pipe 3 and a decompression tower 5 connected to the heating device 4 via a pipe 3 and serving as a degassing means for degassing gas in the heated water heated in the heating device 4.
A water pump 6 connected to the pressure reducing tower 5 via a pipe 3
And a cell 7A of a conductivity meter (water quality meter) 7 connected to the downstream side of the water supply pump 6 via the pipe 3 so that the evacuation device 8 reduces the pressure in the pressure reducing tower 5 to a predetermined degree of vacuum. Has become.

The test water W stored in the tank 2 is, for example, ultrapure water (desalinated water) from which suspended components and ionic components have been removed by a known pure water production apparatus (not shown). However, since the tank 2 is opened to the atmosphere and constantly comes into contact with the atmosphere and the gases in the atmosphere, mainly nitrogen gas, oxygen gas and carbon dioxide gas, are dissolved, even if the resistivity of the sampled water W is measured as it is, it can be detected. As described above, water does not exhibit the original resistivity but exhibits a resistivity lower than the original resistivity.

Nitrogen gas, oxygen gas and carbon dioxide gas are dissolved in the test water according to the respective partial pressures in the atmosphere, and nitrogen gas,
Oxygen gas and carbon dioxide gas are dissolved as dissolved gases in molecular form. However, carbon dioxide gas combines with water molecules based on chemical equilibrium to generate an electrolyte such as hydrogen carbonate ions. Therefore,
When degassing carbon dioxide gas, only dissolved molecular carbon dioxide gas is degassed, the electrolyte remains, and the electrolyte is gradually changed to molecular dissolved carbon dioxide gas based on chemical equilibrium and removed. It just does. Therefore, the conventional simple degassing process only degass the carbon dioxide gas in accordance with the concentration of the undissociated molecular carbon dioxide gas, and cannot degas the gas as easily as other gases.

Therefore, in the present embodiment, the test water W is heated using the heating device 4 to lower the solubility of the gas contained in the atmosphere. In the case of carbon dioxide gas, the solubility of the molecular carbon dioxide gas is reduced by the heating device 4 to shift the above-mentioned chemical equilibrium, so that the carbon dioxide gas can be efficiently degassed. As the heating device 4, for example, an electric heater, microwave, electromagnetic induction, or the like can be used. The heating temperature of the test water W is preferably higher, for example, preferably 80 ° C. or higher, more preferably 90 ° C. or higher. Further, in the present embodiment, the pressure reducing tower 5 is kept substantially at the temperature at which the heated water is heated.
To remove bubbles in the heated water, supply heated water containing no bubbles to the subsequent cell 7A, and accurately measure the resistivity with the water quality meter 7. The exhaust device 8 is not particularly limited as long as a decompression space can be created in the decompression tower 5,
As the exhaust device 8, for example, a vacuum pump or an aspirator is used. In this embodiment, the exhaust device 8 is used as the deaeration means.
Although the method using the pressure reducing tower 5 having the above is shown, as a degassing means, there is another method of promoting degassing by generating cavitation using a pump or ultrasonic vibration. By itself, bubbles mixed in the sample can be separated from the sample. Since the temperature of the heated water is high, it is needless to say that the cell 7A having heat resistance is used. In FIG. 1, the heating device 4 is used as a means for promoting the degassing of the carbon dioxide gas. However, instead of the heating device 4, a degassing film means or an aeration means can be used.

As the degassing means, for example, an apparatus using a hollow fiber membrane module shown in FIG. 2 is used. The degassing membrane device 10 includes a hollow fiber membrane module 11 having a hollow fiber membrane 11A, and a gas supply connected to a shell 11B of the hollow fiber membrane module 11 via a pipe 12 and supplying nitrogen gas as an inert gas. A source 13 and a vacuum pump 14 connected to the shell 11B of the hollow fiber membrane module 11 via the pipe 12 and creating a reduced pressure space in the shell 11B are provided. In the hollow fiber membrane module 11, the water sample W flows into the hollow fiber membrane 11A from one end to the inside thereof and flows out from the other end, and the nitrogen gas supplied from the gas supply source 13 is sucked by the vacuum pump 14 and the hollow fiber membrane Shell 1 outside of 11A
The inside of 1B is set to a preset vacuum degree (for example, 50 Torr).
Distribution in r). In this way, the nitrogen gas is circulated in the shell 11B to increase the partial pressure of the nitrogen gas in the shell 11B,
By reducing the partial pressure of carbon dioxide, degassing of dissolved carbon dioxide can be promoted based on Henry's law. Even if nitrogen gas remains in the test water, there is no obstacle to the water quality meter 7 at the subsequent stage, and a more accurate resistivity can be measured.
In the present embodiment, the inert gas is not particularly limited as long as it does not adversely affect the resistivity (does not generate dissociated ions even when dissolved in the sample water), but nitrogen gas is preferable. In addition, in the aeration means, an inert gas is bubbled into the test water to degas carbon dioxide gas, which is a dissolved gas that adversely affects the resistivity of the test water W. In addition, a hollow fiber membrane module of a type in which the sample W is flowed outside the hollow fiber membrane, an inert gas is flowed from one end inside the hollow fiber membrane, and the pressure is reduced by a vacuum pump from the other end inside the hollow fiber membrane is also used. Can be.

The water quality monitoring device 1 of the present embodiment can be applied to a desalination device 20 in which two reverse osmosis membrane devices 21 are connected in series as shown in FIG. 3, for example. In the desalination apparatus 20, a water pump 22 for supplying water W is connected to an inlet of a reverse osmosis membrane device 21 at a front stage through a pipe 23, and a water quality of the present embodiment is connected to an outlet of the reverse osmosis membrane device 21 at a rear stage. The monitoring device 1 is connected via a pipe 23. The reverse osmosis membrane device 21 can remove suspended components and ionic components, but cannot remove dissolved gases and contains dissolved gases such as carbon dioxide. However, the water quality monitoring device 1 of the present embodiment is connected to the desalination device 20 via a pipe 23. Therefore, the resistivity of the desalted water obtained by the desalination device 20 can be accurately measured in a state where the dissolved carbon dioxide gas is removed by the water quality monitoring device 1 of the present embodiment. However, if the conventional water quality monitoring device is applied to the desalination device 20, the dissolved carbon dioxide gas cannot be removed, so that the original resistivity of the desalted water cannot be measured.

[0023]

Embodiment 1 In this embodiment, ultrapure water (resistivity:
18.0 MΩ · cm or more, conductivity: 0.056 μS / c
m or less) is supplied to the water quality monitoring device 1 shown in FIG. 1 as a water sample, the resistivity of the ultrapure water is measured by setting the water quality monitoring device 1 to the conditions shown in Table 1, and the results are shown in Table 1. Indicated. In the water quality monitoring device 1, the pressure reducing tower 5 has a diameter of 10 cm and a height of 100 c.
m, the resistivity meter 6 is AQ-10 manufactured by Denki Kagaku Kogyo KK
It is composed of those which can be measured at 99 ° C. or less. The pressure reducing tower 5 was used under reduced pressure using an aspirator, and was also used as a normal pressure tower. As a comparative example, the resistivity of ultrapure water was measured under the conditions shown in Table 1, and the results are shown in Table 1.

As is clear from Comparative Examples 1 to 4 shown in the results of Table 1, in the case of untreated water sample (Comparative Example 1), the resistivity was 1.5 MΩ · cm, and the When only decompression treatment was performed at room temperature using a monitoring device (Comparative Examples 2 to 5)
4), the resistivity was 4.6 MΩ · cm at the highest value. However, as is clear from Test Examples 2 to 4, it can be seen that the dissolved carbon dioxide gas is removed by performing the heat treatment, the resistivity is higher than in the conventional method, and the influence of the dissolved carbon dioxide gas is reduced. Further, as is clear from the comparison between Test Example 2 and Test Example 7, it can be seen that the resistance is further increased and the influence of dissolved carbon dioxide gas is reduced by performing the heat treatment and then performing the decompression treatment. Test Examples 1 and 2
As is clear from Test Example 5, the dissolved carbon dioxide gas could hardly be removed by the heat treatment at about 40 ° C., and the heating effect was remarkably exhibited at 80 ° C. or more.

Therefore, for example, the reference value of the water quality is 5.0 MΩ.
・ If the value is cm, according to the conventional water quality monitoring method,
Despite the fact that the original resistivity of the test water has reached the reference value, it cannot be recognized that it is due to the influence of dissolved carbon dioxide gas,
Equipment for desalination that is originally unnecessary will be installed. However, in the case of the present embodiment, the reference value can be achieved by heating to 80 ° C. or higher, and wasteful capital investment can be eliminated.

[0026]

[Table 1]

Embodiment 2 In this embodiment, industrial water is subjected to coagulation filtration, filtered water is passed through a safety filter, and then desalinated water is produced using a reverse osmosis membrane device 20 shown in FIG. Was measured using the water quality monitoring device 1 used in Example 1 (Test Examples 8 to 1).
0) and the results are shown in Table 2. Also, as Test Example 11, the desalted water was aerated with nitrogen gas (normal temperature, nitrogen gas flow rate = 1 NL / min), and the resistivity was measured.
It was shown to. Nitto Denko ES2 as reverse osmosis membrane device 20
0 was used. Here, Test Example 8 includes Test Example 2 and Test Example 9
Were the same measurement conditions as in Test Example 3 and Test Example 10 as in Test Example 7. Further, Comparative Example 5 was under the same measurement conditions as Comparative Example 1 and Comparative Example 6 was under the same measurement conditions as Comparative Example 4.

In Comparative Examples 5 and 6 shown in the results in Table 2, the resistivity of the sample was 1 MΩ · cm or less. However, Test Example 8
In Nos. To 11, the resistivity of the sample was 1 MΩ · cm or more, the influence of dissolved carbon dioxide was clearly removed, and the resistivity increased.

[0029]

[Table 2]

As described above, according to the present embodiment,
When the resistivity of demineralized water in which gas in the atmosphere is dissolved by contact with the atmosphere is measured by a conductivity meter and the quality of the demineralized water is monitored based on the measured value, the decarbonated water is heated to remove dissolved carbon dioxide gas. Since the heating device 4 to be removed is provided in front of the water quality meter (conductivity meter) 6, the influence of dissolved carbon dioxide is significantly suppressed,
It is possible to easily and reliably measure the original resistivity of a sample such as demineralized water. In addition, since the decompression tower 5 is provided at the subsequent stage of the heating device 4 and the heated water is passed through the decompression tower 5, the dissolved carbon dioxide gas is further removed by the decompression tower 5, and the measurement is accurately performed based on the original resistivity of the demineralized water. can do.

Further, by providing an aeration means for bubbling nitrogen gas into the demineralized water in front of the water quality meter 7, the dissolved carbon dioxide gas can be removed and the original resistivity of the demineralized water can be measured more accurately. Can be. Further, by providing the water quality monitoring device 1 of the present embodiment in a desalination device such as the reverse osmosis membrane device 20, it is possible to accurately know the original resistivity of the permeated water without the influence of carbon dioxide gas.

In each of the above embodiments, the water quality monitoring device is provided with a heating device, a decompression device, or an aeration device. However, the present invention is not limited to the above embodiments and is not limited to the above embodiments. The design of each component can be appropriately changed according to the requirements.

[0033]

According to the first to eighth aspects of the present invention, the influence of dissolved carbon dioxide is remarkably suppressed, and the original resistivity of sample water such as demineralized water can be easily and reliably increased. A water quality monitoring device and a water quality monitoring method capable of measuring can be provided.

According to the ninth aspect of the present invention, the influence of dissolved carbon dioxide can be remarkably suppressed, and the original resistivity of the permeated water of the reverse osmosis membrane device can be easily and reliably known. A desalination device can be provided.

[Brief description of the drawings]

FIG. 1 is a flowchart showing one embodiment of a water quality monitoring device of the present invention.

FIG. 2 is a schematic diagram showing a main part of another embodiment of the water quality monitoring device of the present invention.

FIG. 3 is a flowchart showing an example of a desalination apparatus provided with the water quality monitoring device of the present invention.

[Explanation of symbols]

 Reference Signs List 4 heating device (heating means) 5 decompression tower (degassing means) 7 water quality meter (conductivity meter) 10 degassing membrane device (degassing means) 11 hollow fiber membrane module

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) B01D 61/02 B01D 61/02 C02F 1/20 C02F 1/20 1/44 1/44 A G01N 33/18 G01N 33 / 18Z F term (reference) 2G060 AA05 AC01 AE16 AE17 AE19 AF07 HC06 4D006 GA03 HA01 JA51A KA72 KB17 KE19Q LA08 4D011 AA12 AA14 AA15 AA16 AA17 AD01 AD03 4D037 AA03 AB11 BA23 BB02 CA03 BB06 BB06 CA08

Claims (9)

[Claims] 1. A method for measuring the resistivity of a test water in which gas in the atmosphere is dissolved by contact with the atmosphere by a conductivity meter, and monitoring the quality of the test water based on the measured value. Prior to measuring the resistivity of the sample, the water sample is heated by a heating means to remove dissolved carbon dioxide gas. 2. The water quality monitoring method according to claim 1, wherein the test water heated by the heating means is degassed. 3. The water quality monitoring method according to claim 1, wherein a heating temperature of the heating means is 80 ° C. or higher. 4. A water quality monitoring device for measuring the resistivity of a test sample in which gas in the atmosphere is dissolved by contact with the atmosphere with a conductivity meter and monitoring the test sample water quality based on the measured value. A water quality monitoring device, wherein a heating means for heating a test water to remove dissolved carbon dioxide gas is provided in a stage preceding the conductivity meter. 5. A degassing means is provided after the heating means,
The water quality monitoring device according to claim 4, wherein heated water is passed through the deaeration means. 6. The water quality monitoring device according to claim 5, wherein a degassing device is used as the degassing means. 7. A water quality monitoring device for measuring the resistivity of a sample in which gas in the atmosphere is dissolved by contact with the atmosphere with a conductivity meter and monitoring the quality of the sample based on the measured value. Degassing membrane means for degassing the dissolved carbon dioxide gas under the test water is provided in front of the conductivity meter, and gas supply means for supplying an inert gas to a reduced pressure space of the degassing membrane means is provided. A water quality monitoring device, characterized in that: 8. A water quality monitoring device for measuring the resistivity of a sample in which gas in the atmosphere is dissolved by contact with the atmosphere by a conductivity meter and monitoring the quality of the sample based on the measured value. A water quality monitoring device, characterized in that aeration means for bubbling an inert gas during test water is provided at a stage preceding the conductivity meter. 9. A desalination device comprising the water quality monitoring device according to claim 4 subsequent to a reverse osmosis membrane device.