JP4223799B2 - Biosensor type water quality monitoring system and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a biosensor-type water quality monitoring system and apparatus using a biosensor that detects the entry of harmful substances at water intakes of water purification plants and sewage treatment plants and issues an alarm.
[0002]
[Prior art]
Water treatment plants take river water and pass it through a precipitation filtration layer to supply drinking water. In such normal treatment, various heavy metals, pesticides, environmental hormones that cannot be removed by precipitation filtration treatment. If such harmful substances are mixed in river water, it will be an emergency situation that water intake is stopped.
[0003]
On the other hand, in a sewage treatment plant, various heavy metal ions, organic solvents, arsenic, cyanide, etc. are mixed into the effluent of a factory or chemical plant due to a sudden accident. The activity of activated sludge decreases, and a great deal of time is required until the processing capacity is restored.
[0004]
Therefore, in a water purification plant or a sewage treatment plant, there is a demand for an apparatus that detects inflow water mixed with various harmful substances quickly and with high sensitivity.
[0005]
Based on such requests, the water purification plant has installed a fish behavior monitoring type poison detection device, or a device for detecting poisons from the measurement of respiratory activity of various microbial membranes using dissolved oxygen electrodes, In the sewage treatment plant, various sensors that detect wastewater mixed with specific chemical substances are installed to detect when various harmful substances are mixed in the influent water.
[0006]
[Problems to be solved by the invention]
By the way, in these poison detection devices, for example, the fish behavior monitoring type, there is a problem of sensitivity to fish poisons, a problem of maintenance and management of the device, and in the DO sensor attached with various microbial films, the contamination of the sensor, There were problems in terms of activity and stability.
[0007]
In view of such a situation, a biosensor type water quality monitoring system has been devised in which an iron-oxidizing bacterium attached to the tip of a DO sensor electrode is incorporated in a flow cell.
[0008]
As disclosed in JP-A-2002-243698 (Japanese Patent Application No. 2001-043458) and the like, this biosensor-type water quality monitoring system uses two flow cells and alternately repeats the measurement and washing steps while Water quality is continuously monitored using the respiratory activity of oxidizing bacteria as an indicator of contamination with harmful substances.
[0009]
Moreover, in this biosensor type water quality monitoring system, since the optimum pH for inhabiting iron-oxidizing bacteria is a relatively low pH in the vicinity of “3”, organic substances in the water that cause contamination of the electrode surface are present. There is an advantage that it is difficult to adhere and the output can be stably maintained for a long time.
[0010]
In order to confirm the water quality monitoring capability of such a biosensor type water quality monitoring system, the present inventors conducted a beaker test according to the following procedure and examined responses to various harmful substances.
[0011]
First, a beaker is filled with a “pH 3” sulfuric acid solution prepared from “50 ml” of pure water, and a dissolved oxygen electrode with a fixed amount of iron-oxidizing bacteria attached to the membrane filter is immersed in the ion filter. Output to. At this time, an output current proportional to the amount of dissolved oxygen, a value of “about 1 μA” was obtained. When “2 ml” of a solution in which ferrous sulfate is dissolved in “9K” medium is added, dissolved oxygen is consumed by the respiratory action of iron-oxidizing bacteria, and the oxygen concentration reaching the electrode surface becomes zero. The output current became zero. When a solution in which a certain amount of harmful substances was dissolved was added thereto, the respiratory activity of the iron-oxidizing bacteria was inhibited, so that oxygen was not consumed, the oxygen concentration on the electrode surface increased, and the current value increased. With this increase in current value, the toxicity of the added substance was evaluated.
[0012]
As a result, as shown in the graph of FIG. 9, responses to dozens of substances such as acute toxic substances that cause respiratory inhibition, heavy metals, agricultural chemicals, organochlorine compounds, environmental hormones, etc. It has been confirmed that it exhibits a particularly sensitive response to acute toxic substances and organochlorine compounds that cause respiratory inhibition.
[0013]
These tests were tests using the above toxic substances dissolved in pure water at a constant concentration as sample water, but using river water as the source of water in the actual water treatment plant as raw water, When the current response is examined by a continuous test, as shown in the graph of FIG. 10, in some cases, there is a phenomenon that the zero current at the time of measurement gradually increases even though no harmful substances are added. Appeared.
[0014]
When such a state is continued, it becomes impossible to monitor the mixing of normal harmful substances, and eventually a problem has been found that the electrode microorganisms are killed.
[0015]
In view of the above circumstances, the present invention allows only the biosensor response-inhibiting substance to be removed without affecting the water quality monitoring target substance contained in the raw water collected through a water intake such as a water purification plant, An object of the present invention is to provide a biosensor type water quality monitoring system and apparatus capable of continuously and stably monitoring water quality.
[0016]
[Means for Solving the Problems]
To achieve the above object, according to the present invention, in claim 1, a biosensor in which a membrane filter holding iron-oxidizing bacteria is attached to the tip of a dissolved oxygen electrode is used to monitor the quality of sample water. In the sensor type water quality monitoring system, the ozone water is injected into the sample water temporarily stored in the sample water tank by the ozone generator, and the sample water in the sample water tank is taken in by the biosensor device, The biosensor is used to monitor the quality of the sample water. As a result, only the biosensor response-inhibiting substances are removed without affecting the water quality monitoring target substances contained in the raw water collected through water intakes such as water purification plants. Water quality can be monitored.
[0017]
In Claim 2, in the biosensor type water quality monitoring system according to Claim 1, the amount of ozone gas injected into the sample water tank is controlled by controlling the flow rate of the raw material air or the ozone gas by the ozone generator. To do. As a result, while optimizing the ozone concentration in the sample water, only the biosensor response-inhibiting substance can be used without affecting the water quality monitoring target substance contained in the raw water collected through the intake of a water purification plant or the like. The water quality can be monitored continuously and stably.
[0018]
According to claim 3, in the biosensor type water quality monitoring system according to claim 1 or 2, the ozone gas in the sample water tank is prevented from leaking to the outside by using the packing generated by the ozone resistant material. . As a result, while preventing ozone gas from leaking to the outside, only the biosensor response-inhibiting substances are affected without affecting the water quality monitoring target substances contained in the raw water collected through water intakes such as water purification plants. The water quality can be monitored continuously and stably.
[0019]
In Claim 4, in the biosensor type water quality monitoring system according to any one of Claims 1 to 3, two or more ozone generators are connected in series to generate the ozone gas, thereby generating raw material air. Biosensor response inhibiting substances without affecting the water quality monitoring target substances contained in raw water collected through intakes such as water purification plants by increasing the amount of ozone gas generated while keeping the flow rate low The water quality can be monitored continuously and stably.
[0020]
The biosensor type water quality monitoring system according to any one of claims 1 to 4, wherein the ozone generator is turned on when the sensor response inhibitor concentration in the sample water is high, and the sample water When the sensor response inhibitor concentration is low, the ozone generator is turned off. This allows the sensor response inhibitory substance to be removed only when there is a possibility that the sensor response inhibitory substance may be contained in the raw water collected through the water intake of a water purification plant, etc. While simplifying, keeping water quality monitoring costs low, removing only biosensor response-inhibiting substances without affecting water quality monitoring substances contained in raw water, continuously and stably providing water quality Monitoring can be performed.
[0021]
In Claim 6, in the biosensor type water quality monitoring system according to any one of Claims 1 to 5, when the flow cell of the biosensor device provided with the biosensor is washed, washing water and tap water are used. The flow cell is washed using a mixture. As a result, only the biosensor response-inhibiting substances are removed without affecting the water quality monitoring target substances contained in the raw water collected through water intakes such as water purification plants while preventing biosensor deterioration. Thus, water quality can be monitored continuously and stably.
[0022]
In claim 7, a biosensor type water quality monitor in which a biosensor in which a membrane filter holding iron-oxidizing bacteria is attached to the tip of a dissolved oxygen electrode is incorporated in a flow cell, and the quality of sample water is monitored using this biosensor. The apparatus includes a bag filled with an iron solution as a substrate and added with a predetermined concentration of sulfamic acid. As a result, the activity-inhibiting substance can be removed with a simple device configuration, and a normal sensor response can always be maintained.
[0023]
According to an eighth aspect of the present invention, in the biosensor type water quality monitoring device according to the seventh aspect, the bag is a plastic bag, and the iron liquid in the plastic bag is degassed by an inert gas. It is extremely important that the bag is sufficiently degassed by the inert gas from the viewpoint of preventing the oxidation of the iron solution, and this enables a long-term continuous operation of the apparatus.
[0024]
In Claim 9, in the biosensor type water quality monitoring apparatus according to Claim 7, the concentration of the sulfamic acid added to the iron solution is 0.03 to 0.1 Wt%. If the concentration is lower than this, there is no effect on the removal of nitrous acid, and if it is too high, it will affect the pH of the iron solution or mask the action of other dissolved mineral components. It is not preferable.
[0025]
The biosensor type water quality monitoring apparatus according to claim 7, wherein the iron solution bag to which the sulfamic acid is added at a predetermined concentration is only when the concentration of the activity inhibitor in the raw water is higher than a specified value. used. Since there are places where sensor response-inhibiting substances are not generated due to seasonal fluctuations or the like, useless control can be prevented by using according to the actual situation, and a stable sensor response can always be maintained.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
<First Embodiment>
《Processing principle》
First, the inventors of the present invention use river water as an intake source in an actual water treatment plant as raw water, and when examining current response by continuous tests, in some cases, zero current at the time of measurement is added with harmful substances. In order to investigate the cause of the phenomenon of gradual rise despite the absence, the following considerations were made.
[0027]
First, the sensor response test was conducted by the beaker test for the pure water for comparison with the raw water and tap water, and the inhibition was compared.
[0028]
As a result, when a predetermined amount of iron solution was added after reaching a certain span current in dilute sulfuric acid of “pH 3”, the current value of zero was maintained in pure water and tap water, Then, the current value increased, and it was found that the microbial membrane had some kind of inhibition. When the sample water was returned to pure water after measurement with raw water, normal reaction was shown. Therefore, inhibition was estimated as temporary respiratory inhibition.
[0029]
Moreover, since the current value is not increased in tap water and the causative substance is considered to have been removed by the water purification process, the raw water filtered water is agglomerated under the processing conditions shown in FIGS. 4, 5, and 6. Then, the test water was subjected to chlorine treatment and activated carbon treatment as sample water for sensor response measurement. As a result, it was found that the inhibitory substance could not be removed by flocculation treatment and activated carbon treatment, but could be removed by chlorination treatment. From this, it was estimated that the inhibitory substance has a great possibility of being an inorganic substance.
[0030]
Therefore, when a specific river water is used as the raw water in the following procedure, the specific substance contained in the raw water reacts with the iron ion that is the substrate as the cause of the decreased activity of the electrode microbial membrane. It was checked whether the iron ion concentration was lowered.
[0031]
First, add “2 ml” of the substrate iron solution to “50 ml” of raw water, stir for 15 minutes (sensor response time) at “30 ° C.”, and then filter with “0.45 μm” filter paper. Analysis and elemental analysis by “EDAX” of the filtration residue were performed. As a result, the same amount of iron as the charged amount was present in the filtrate, and the iron concentration did not decrease due to the reaction between iron and the specific substance.
[0032]
In addition, when analyzing the filtration residue, most of it is iron hydroxide, and other medium components such as phosphorus, sulfur, and a small amount of silica were detected, but no reaction with specific elements was observed. It was.
[0033]
Next, we examined the substances contained in the raw water that are likely to affect the activity of iron-oxidizing bacteria. Possible substances in the raw water include metal ions such as iron ions and copper ions, carbonate ions, ammonium ions, nitrate ions, nitrite ions, sulfate ions, sulfite ions, chlorine ions, phosphate ions, etc. Ions, other suspended substances, and organic substances include glucose, but most of them are contained in the medium.
[0034]
And there are carbonate ions, nitrite ions, sulfite ions, and chloride ions that are thought to affect the activity of iron-oxidizing bacteria. Carbonate ions, in addition to energy metabolism, are another characteristic of autotrophic bacteria. This is a necessary carbon source in the production of organic substances from carbon dioxide gas. Therefore, this inhibitory effect is not considered. In addition to this, an organic compound such as glucose is also used as the carbon source. In addition, iron-oxidizing bacteria have a function of sulfur oxidation and are performed between the cell membrane and the outer membrane, that is, in the periplasmic space.
[0035]
Sulfur is reduced to produce hydrogen sulfide, which is “Fe”³⁺"Is oxidized by an enzyme having an electron acceptor to produce sulfurous acid as an intermediate," Fe²⁺And sulfuric acid. Therefore, it is presumed that sulfurous acid also has no inhibitory effect.
[0036]
In addition, the energy metabolism of iron-oxidizing bacteria, that is, the synthesis of “ATP” is “Fe²⁺"-Chromochrome c oxidoreductase, cytochrome c, rustycyanine, and cytochrome c oxidase are carried out through an electron transfer system, of which cytochrome c contains copper, and in the iron oxide electron transfer system, Plays an important role and cannot have an inhibitory effect.²⁺It has been reported that iron oxidation activity increases when "" is added and cultured.
[0037]
In addition, iron-oxidizing bacteria have a strong resistance to many heavy metal ions and can grow in a considerably high concentration solution. That is, “Cu²⁺"," Zn²⁺"," Co²⁺"," Mn²⁺"," Cd²⁺"," Cr³⁺In a solution such as “10”.^-3It is not inhibited even at a concentration of “M”, but “Ag”⁺"," Hg²⁺"," 10^-4“Sn”²⁺"," Cr³⁺"," 10^-4Growth inhibition occurs at M. Other ions include “SO”.₄ ^2-”, Arsenate ion and arsenite ion do not show inhibition, but fluorine, cyanide and molybdenum show strong inhibitory action, and nitrate ion and chloride ion also show inhibition at high concentrations. When deactivated, the analysis data of inorganic ions in raw water were compared with each component in tap water, and the results were as shown in the table of Fig. 7. From this result, sensor response inhibitory substances in raw water It was judged that the possibility of ions was great.
[0038]
In order to confirm the above, when preparing solutions with nitrite nitrogen concentrations of “0.011 mg / l”, “0.106 mg / l”, and “1.06 mg / l” and using them as sample water The sensor response test was conducted. As a result, it was confirmed that the microbial membrane was inhibited even with a small amount of nitrite nitrogen (about 0.01 mg / l or more).
[0039]
The effects of nitrite ions on microbial membranes were confirmed not only in the beaker test but also in the verification test on the prototype. That is, when the concentration of nitrite ions in the sample water is changed from “0.104 mg / l” to “0.038 mg / l”, the current value at the time of measurement decreases, and conversely, sublimation occurs when the measurement is being performed with pure water. When the nitrite ion generating substance was added so that the nitrate ion would be “0.29 mg / l”, the current value increased.
[0040]
FIG. 8 shows the concept of inhibition of activation of iron-oxidizing bacteria by inhibitors in raw water. According to this figure, the enzyme that takes in oxygen loses its activity due to nitrous acid → Fe²⁺Can not be oxidized and energy cannot be obtained → If this state is short, it will be restored, but if it is continuous, the number of death will be greater than the growth of the cells. The reason why the growth and proliferation of iron-oxidizing bacteria is prevented by nitrite ions is as follows.²⁺It is presumed that there is a main reason why the energy from "cannot be acquired".
[0041]
As described above, since the nitrite ion in the raw water was identified as an inhibitory agent for the activity of iron-oxidizing bacteria, this removal method was examined.
[0042]
In addition, nitrite ion was used as an activity inhibitor of iron-oxidizing bacteria in the present example. However, in raw water collected from another water purification plant, other inorganic and organic substances may be the cause. .
[0043]
Therefore, in the following description, a method for removing nitrite ions will be described as an example of an inhibitor, but naturally, it is desirable that the method is applicable to the removal of other sensor response inhibitors.
[0044]
First, as a method of removing nitrite in raw water, reduction removal with a chemical substance such as urea, and oxidation removal to nitrite ions with various oxidizing agents are conceivable.
[0045]
Nitrous acid is decomposed by urea as shown in the following formula.
[0046]
[Chemical 1]
CO (NH₂)₂+ 2HNO₂→ 2N₂+ CO₂+ 3H₂O
However, these reducing agents are effective only when the specific substance is nitrous acid.
[0047]
As oxidants, hypochlorous acid, hydrogen peroxide, potassium permanganate, ozone, etc. are conceivable. Of these, hypochlorous acid, hydrogen peroxide, and ozone are promising. I found out.
[0048]
However, when hypochlorous acid was injected, although nitrous acid could be removed efficiently, there was a problem that residual chlorine would inhibit the activity of iron-oxidizing bacteria, so in the end it was determined that ozone treatment was optimal. .
[0049]
<< Description of First Embodiment >>
FIG. 1 is a block diagram showing a first embodiment of a biosensor type water quality monitoring system according to the present invention using the above-described processing principle.
[0050]
The biosensor-type water quality monitoring system 1 shown in this figure samples raw water that has been subjected to pretreatment such as filtration while preventing internal ozone gas 2 or the like from leaking outside by means of an ozone-resistant packing 19 or the like. A sample water tank 4 for taking in the sample water 3 obtained in this way, and a drain pipe 5 for discharging the sample water 3 overflowed from the sample water tank 4 to the outside. Further, the mini compressor 8 that takes in outside air to generate the raw material air 7, the needle valve 9 that adjusts the discharge amount of the raw material air 7 discharged from the mini compressor 8, and the needle valve 9 using the dehumidifying silica gel 10 pass through the needle valve 9. A dehumidifier 11 that dehumidifies the dried raw material air 7 into dry raw material air 7, and one or a plurality of units that generate ozone gas 2 by ionizing while optimizing the temperature of the raw material air 7 discharged from the dehumidifier 11. The ozonizer 12, the flow meter 13 that measures the flow rate of the ozone gas 2 discharged from the ozonizer 12, and the ozone gas 2 that has passed through the flow meter 13 are made into fine bubbles and diffused into the sample water 3 in the sample water tank 4. And a diffuser 14. Furthermore, the sample water 3 in the sample water tank 4, tap water and the cleaning liquid were mixed by a two-system flow cell having a sensor 15 having a membrane filter holding iron-oxidizing bacteria attached to the tip of the dissolved oxygen electrode. The sample water tank 4 is discharged from the sample water tank 4 by the biosensor device 16 that continuously monitors the water quality of the sample water 3 and the activated carbon (Secard) 17 by alternately repeating the measurement operation and the washing operation while alternately taking in objects. An activated carbon filter 18 for decomposing and detoxifying excess ozone gas 3 is provided.
[0051]
Then, the sample water 3 obtained by sampling the raw water that has been subjected to pretreatment such as filtration in the season when the concentration of the membrane response inhibiting substance contained in the sample water 3 is high is guided to the sample water tank 4 and stored. On the other hand, the ozone gas 2 is generated by the mini compressor 8, the needle valve 9, the dehumidifier 11 and the ozonizer 12, and the sample water stored in the sample water tank 4 from the diffuser 14 provided in the sample water tank 4. 3 is diffused to oxidize and remove nitrous acid in the sample water 3.
[0052]
In parallel with this operation, the biosensor device 16 alternately takes in the sample water 3 in the sample water tank 4 and a mixture of tap water and the cleaning liquid, and repeats the measurement operation and the cleaning operation alternately. The water quality of the sample water 3 is accurately measured without being affected by nitrous acid contained in the raw water subjected to pretreatment such as filtration.
[0053]
Next, a water quality monitoring test performed to confirm the water quality monitoring capability of the biosensor type water quality monitoring system 1 will be described.
[0054]
First, in the same manner as in the water quality test method, sulfanilic acid and naphthylamine are added to the sample water 3 to develop a color, and the absorbance is measured using a wavelength of “540 μm”. Nitric acid was quantified. In addition, before introducing ozone gas 2 into the sample water tank 4, an ozone meter was installed to examine the relationship between the air flow rate, the concentration of generated ozone, and the removal rate of nitrous acid. The graph shown was obtained.
[0055]
As can be seen from this graph, as the air flow rate decreases, the generated ozone concentration increases slightly, but the rate of increase is small. Therefore, when the air flow rate is increased, the unit obtained by multiplying the air flow rate by the generated ozone concentration. The amount of ozone generated per hour increases.
[0056]
Further, a sample water tank 4 having a capacity of “100 ml” is used, and the time during which the sample water 3 introduced into the sample water tank 4 remains in the sample water tank 4 is set to about 1 minute. Therefore, considering the response time of the sensor 15 provided in the biosensor device 16, the amount of generated ozone is switched while the sample water 3 is allowed to flow into the sample water tank 4 at a flow rate of “100 ml / min”. When the ozone injection rate obtained by dividing the ozone generation amount by the inflow amount of the sample water 3 was switched and the ozone residual rate was measured, the graph shown in FIG. 3 was obtained.
[0057]
From this graph, if the ozone injection rate is set to “1 mg / l” or more, the concentration of nitrous acid can be reduced to “5%” or less of the initial value, and the inflow amount of the sample water 3 described above can be reduced to the air flow rate. It was found that the higher the so-called L / G value divided by, the higher the removal rate.
[0058]
In addition, when the ozonizer 12 is continuously operated in a state where the inhibitor concentration with respect to the sensor response is high, ozone is reduced as described above in order to reduce the inhibitor concentration to “5%” or less of the initial value. The injection rate needs to be “1 mg / l” or more.
[0059]
As an example, the air flow rate is set to “50 ml / min”, the ozone concentration is set to “2.1 mg / l”, the ozone generation amount is set to “6.3 mg / h”, and the inflow amount to the sample water tank 4 is set to “100 ml”. When the ozone injection rate was set to “1.05 mg / l” and L / G was set to “2”, the residual rate of the membrane response inhibitor in the sample water 3 could be zero. .
[0060]
Thus, it was confirmed that the membrane response inhibiting substance in the sample water 3 could be removed by subjecting the sample water 3 to ozone treatment.
[0061]
However, at this time, if harmful substances in the sample water 3 are also removed at the same time, the sensor function of the biosensor device 16 is lost. It was confirmed whether or not harmful substances in the sample water 3 were removed.
[0062]
First, the presence or absence of removal of respiratory inhibitory poison that responds to sensor 15 with the highest sensitivity among respiratory inhibitory toxins, metal compounds, organochlorine compounds, organic compounds, endocrine disruptors (environmental hormones), agricultural chemicals, etc. In order to check the above, a solution in which potassium cyanide is added at a rate of “0.03 mg / l” in the sample water 3 is prepared, and this is introduced into the sample water tank 4 at an inflow water amount of “100 ml / min”. The same conditions as described above, ie, air flow rate “50 ml / min”, ozone concentration “2.1 mg / l”, ozone generation amount “6.3 mg / h”, ozone injection rate “1.05 mg / l”, L / The ozone treatment was performed with G = “2”.
[0063]
When a certain time has elapsed since the start of the ozone treatment, the sample water 3 was sampled from the sample water tank 4 and the concentration of potassium cyanide was quantitatively analyzed. Met.
[0064]
Thus, even if the sample water 3 is ozone-treated by the above-described method, only the membrane response inhibiting substance in the sample water 3 can be removed, and it is confirmed that there is no interference with the detection of harmful chemical substances. I was able to.
[0065]
Thus, in the first embodiment, after the ozone gas 2 is diffused into the sample water 3 stored in the sample water tank 4 and the nitrous acid in the sample water 4 is oxidized and removed, the biosensor device 16, the water quality of the sample water 3 is measured. For this reason, only the biosensor response-inhibiting substances are removed without affecting the water quality monitoring target substances contained in the raw water collected through water intakes such as water purification plants. Water quality can be monitored.
[0066]
In the first embodiment, the moisture contained in the raw air 7 is dehumidified by the silica gel 10 for dehumidification while adjusting the flow rate of the raw air 7 discharged from the mini compressor 8 by the needle valve 9. The humidity is set to a predetermined value, for example, “40%” or less, and then supplied to the ozonizer 12 to generate the ozone gas 2. For this reason, even when the humidity of the outside air taken in by the mini-compressor 8 is high, the ozonizer 12 can efficiently generate an optimal amount of the ozone gas 2.
[0067]
At this time, if the required air amount with respect to the generated ozone amount is set to “50 ml / min” and the system is regularly inspected every three months, the amount of raw material air that must be supplied to the ozonizer 12 is “6480 L / 90 days. , And the amount of saturated water vapor in the air “1 L” is given by the following equation:
[Expression 1]
(18 / 22.4) × (24/760) = 2.3 × 10^-2g
Water absorption of silica gel 10 for dehumidification is “0.15 gH₂Since it is O / g ″, the amount shown in the following formula is required as the silica gel 10 for dehumidification.
[0068]
[Expression 2]
6480 × 2.3 × 10^-2/0.15=994g
Thus, if the relative humidity of the air taken in by the mini compressor 8 is “80%”, it is sufficient to prepare the silica gel 10 for dehumidification in the amount shown in the following formula, and “500 g” every three months. Two silica gel packs may be exchanged.
[0069]
[Equation 3]
994 × 0.8 = 795g / 3 months
In the first embodiment, the ozone gas 2 discharged from the ozone generator 20 constituted by the mini compressor 8, the needle valve 9, the dehumidifier 11, and the ozonizer 12 is changed by the diffuser 14 attached in the sample water tank 4. Fine bubbles are formed to diffuse into the sample water 3 in the sample water tank 4. For this reason, the ozone gas 2 can be sufficiently dissolved in the sample water 3 to efficiently remove only the biosensor response-inhibiting substance.
[0070]
In the first embodiment, surplus ozone gas (exhaust ozone gas) in the sample water tank 4 is guided to the activated carbon filter 18 to be decomposed and detoxified, and then discharged into the outside air. Can be prevented from being adversely affected.
[0071]
At this time, since the activated carbon 17 is required at a ratio of “ozone gas 1 g / activated carbon 1 g”, if the ozone required amount is “6.3 mg / h”, the activated carbon filter 18 includes “13.6 g / 3 months”. It is sufficient if the activated carbon 17 is filled, and a commonly used filter containing “50 g” is sufficient.
[0072]
In the first embodiment, the packing 19 made of an ozone-resistant material or the like shields the upper lid portion of the sample water tank 4 so that the ozone gas 2 does not leak out of the sample water tank 4. , So that it does not adversely affect the surrounding environment.
[0073]
In the first embodiment, two or more ozonizers 12 are connected in series to generate the ozone gas 2 from the raw air 7. For this reason, it is possible to generate high-concentration ozone gas 2 while keeping the flow rate of the raw air 7 low, thereby reducing the amount of silica gel 10 used for dehumidification and reducing the operating cost.
[0074]
In the first embodiment, the ozone generator constituted by the mini-compressor 8, the needle valve 9, the dehumidifier 11, and the ozonizer 12 is only in the season when the concentration of the membrane response inhibiting substance contained in the sample water 3 is high. 20 is operated to diffuse the ozone gas 2 into the sample water 3 in the sample water tank 4 so as to remove the biosensor response inhibitor contained in the sample water 3. For this reason, even when the quality of the raw water taken varies depending on the season, such as a water purification plant, and the concentration of the membrane response inhibiting substance varies accordingly, the membrane response inhibiting substance contained in the sample water 3 Only when the concentration of water is high, the ozone generator 20 is operated to remove the biosensor response inhibitory substance in the sample water 3, and when the concentration of the membrane response inhibitory substance contained in the sample water 3 is low, The ozone treatment can be stopped so as not to affect the water quality monitoring target substance contained in the sample water 3, and the operating cost can be kept low.
[0075]
In the first embodiment, when each flow cell of the biosensor device 16 is washed, each flow cell is washed with a mixed water obtained by mixing tap water and washing water in the same manner as when the sensor 15 is calibrated. ing. For this reason, even if each flow cell is washed, it is possible to prevent deterioration of the microbial membrane provided in the sensor 15 of each flow cell.
[0076]
In the first embodiment, the ozonizer 12 is provided with a temperature sensor, a heating mechanism, a cooling mechanism, etc., and the source air 7 supplied from the dehumidifier 11 is kept at a constant temperature, for example, “20 ° C.” 7 is ionized to generate ozone gas 2, so that the temperature of the raw material air 7 is kept low regardless of whether the outside air temperature becomes “30 ° C.” or “0 ° C.” Reduction in generation efficiency can be prevented.
[0077]
<Second Embodiment>
《Processing principle》
As shown in the first embodiment described above, the iron-oxidizing bacteria activity inhibitor is found to be nitrite nitrogen in raw water (river water), and this nitrite nitrogen is treated with ozone. did. However, in the case of ozone treatment, it is necessary to solve problems such as dehumidification of raw material air, generator temperature control, and exhaust ozone treatment in order to control the generated ozone concentration.
[0078]
By the way, as a method for removing nitrous acid from raw water, reduction removal by chemical substances such as sulfamic acid and urea, and oxidation removal to nitrate ions by various oxidizing agents are conceivable.
[0079]
Sulfamic acid is an amidosulfonic acid (H₂NSO₃H) is a generic name for N-alkyl and N-aryl derivatives of H, and an aqueous solution is a reducing agent that exhibits a strong acid comparable to hydrochloric acid and sulfuric acid. The reducing action is particularly remarkable in boiling water. Ammonium sulfamate is this ammonium salt, which reacts with nitrous acid to generate nitrogen to become sulfuric acid.
[0080]
Further, as described above, nitrous acid is decomposed by urea as follows.
[0081]
[Chemical formula 2]
CO (NH₂)₂+ 2HNO₂→ 2N₂+ CO₂+ 3H₂O
In this case, the generated CO₂Is dissolved in water to form carbonate ions, which may react with the mineral components in the iron solution to cause precipitation, so that it is inappropriate to use as a reducing agent.
[0082]
On the other hand, hypochlorous acid, hydrogen peroxide, potassium permanganate, ozone, etc. can be considered as the oxidizing agent. However, when hypochlorous acid is injected, although nitrous acid can be removed efficiently, there is a problem that residual chlorine inhibits the activity of iron-oxidizing bacteria.
[0083]
Therefore, in the second embodiment, nitrite nitrogen is to be removed by adding sulfamic acid.
[0084]
<< Apparatus Configuration of Second Embodiment >>
FIG. 11 shows an example of a biosensor type water quality monitoring apparatus constituting the second embodiment of the present invention.
[0085]
The biosensor type water quality monitoring apparatus shown in this figure includes at least a pair of flow cells 53 and 54 arranged in parallel with each other and a circulation tank 57, and the circulation tank 57 is connected to the flow cell 53 via circulation lines 58 and 59. In addition, it is connected to the flow cell 54 via circulation lines 60 and 61.
[0086]
Each flow cell 53, 54 detects contamination of harmful substances, and includes oxygen electrodes 55, 56 and membrane filters 55a, 56b attached to the tips of the oxygen electrodes 55, 56 and holding iron-oxidizing bacteria. It is made up.
[0087]
Further, ion meters 62 and 63 are connected to the oxygen electrodes 55 and 56 of the flow cells 53 and 54, respectively, and these ion meters 62 and 63 are connected to the control unit 64.
[0088]
When one flow cell 53 (54) is in a measurement state, the control unit 64 places the other flow cell 54 (53) in a cleaning state, and at the same time, transfers the iron liquid to the one flow cell 53 (54) side via an iron liquid line. Test water is supplied through the test water line, the cleaning liquid is supplied to the other flow cell 54 (53) through the cleaning liquid line, and the test water is supplied through the test water line. To control. For detailed control procedures of the control unit 64, see JP-A-2002-243698.
[0089]
Further, the biosensor type water quality monitoring apparatus shown in FIG. 11 is a cleaning liquid (H for periodically cleaning the flow cells 53 and 54.₂SO₄Cleaning solution bag 21 containing the solution, and iron solution (FeSO) supplied to the flow cells 53 and 54₄Iron solution bag 22 for storing solution and water (H₂A water tank 23 for storing (O) and a water intake tank 24 for storing the sample water taken are provided. In the intake tank 24, a filtration device 24a made of a hollow fiber membrane is installed.
[0090]
The cleaning liquid bag 21 is connected to the flow cells 53 and 54 via pipes 27 and 29, pinch valves 35 and 37, pipe tubes 43 and 44, tube pumps 47 and 48, and pipes 51 and 52. In this case, the cleaning liquid line is constituted by the lines from the cleaning liquid tank 21 to the flow cells 33 and 34.
[0091]
The iron solution bag 22 is connected to the flow cells 53 and 54 via the pipes 28 and 30, the pinch valves 36 and 38, the pipe tubes 43 and 44, the tube pumps 47 and 48, and the pipes 51 and 52. In this case, an iron liquid line is constituted by lines from the iron liquid bag 22 to the flow cells 53 and 54.
The water tank 23 is connected to flow cells 53 and 54 via pipes 31 and 33, pinch valves 39 and 41, pipe tubes 45 and 46, tube pumps 49 and 50, and pipes 51 and 52. In this case, a water supply line is constituted by the lines from the water tank 3 to the flow cells 33 and 34.
Further, the intake tank 24 is connected to the flow cells 53 and 54 via the pipes 32 and 34, the pinch valves 40 and 42, the pipe tubes 45 and 46, the tube pumps 49 and 50, and the pipes 51 and 52. In this case, the test water line is constituted by the lines from the water intake tank 2 to the flow cells 53 and 54.
Further, the test water flows into the intake tank 24 via the intake pipe 26 and the intake pump 25. Further, drain fluid lines 65 and 66 are connected to the flow cells 33 and 34, and branch pipes 67 and 68 branched from the water intake pipe 26 are connected to the drain liquid lines 65 and 66.
Particularly in the second embodiment, the above-described iron solution bag 22 is formed of a plastic bag. The plastic bag is filled with iron liquid as a substrate and degassed with an inert gas. In addition, ammonium sulfamate (NH₄OSO₂NH₂) Is added at a predetermined concentration.
[0092]
As described above, it is extremely important from the viewpoint of preventing oxidation of the iron solution that the iron solution as a substrate is filled in a gas-impermeable plastic bag and the bag is sufficiently degassed by the inert gas. Yes, it is essential for long-term continuous operation of the equipment.
[0093]
The concentration of ammonium sulfamate added is preferably about 0.03 to 0.1 Wt%. If the concentration is lower than this, there is no effect on the removal of nitrous acid. On the other hand, if the concentration is too high, the pH of the iron solution is affected or the action of other dissolved mineral components is masked.
[0094]
Furthermore, an iron solution bag to which ammonium sulfamate is added at a predetermined concentration is used only when the concentration of the activity inhibitor in the raw water is high, and a normal iron solution bag is used at other times.
[0095]
<About sulfamic acid as a reducing agent>
Next, sulfamic acid as a reducing agent will be described.
[0096]
The most commonly used industrial reducing agent for nitrous acid is sulfamic acid. Other reducing agents include urea, citric acid, ascorbic acid and the like.
[0097]
When urea is used as a reducing agent, as shown in FIG. 12, about 95% of the contained nitric acid is reduced by stirring at an addition concentration of 1 g / l (0.1 wt%) and a solution pH of 0.92.
[0098]
In addition, as shown in FIG. 12, nitrous acid can be decomposed by a method such as an acid, an oxidizing agent, a catalyst, or electrolytic oxidation.
[0099]
《Experimental result on regulation of sulfamic acid addition concentration》
As shown in FIG. 13, the residual ratio of nitrous acid was about 50% at 500 mg / l (0.1 wt%) and about 40% at 1000 mg / l (0.1 wt%). If the concentration of sulfamic acid is increased, the residual rate of nitrous acid will decrease. If more is added, the removal rate of nitrous acid will improve, but the action of sulfamic acid as a reducing agent will improve the iron-oxidizing bacteria. There is concern that it will adversely affect Therefore, it is estimated that the maximum value is about 2000 mg / l (= 2 g / l = 0.2 wt%) at the maximum.
[0100]
《Experimental results on the influence of pH and stirring conditions when adding sulfamic acid》
Not only the addition concentration of sulfamic acid but also the pH of the aqueous solution and the stirring time affect the nitrite removal rate.
[0101]
As shown in FIGS. 14 and 15, it was found that the solution pH was 2.5 or less and the reaction time was at least 1 minute in order to reduce the residual ratio of nitrous acid. This reaction time of 1 minute is important in the following sense.
[0102]
That is, the water to be detected for detecting harmful substances always flows into the water intake tank 24 of the biosensor type water quality monitoring device and is discharged. If the flow rate of the test water is 100 ml / min and the tank volume is about 100 ml, the residence time of the test water in the water intake tank 24 is about 1 minute. Therefore, it was necessary to remove nitrous acid within this time, and it was found that a residual rate of ˜20% after one minute of stirring was sufficient.
[0103]
<< Description of Examples >>
<Example 1>
A nitrous acid removal test was performed by using the iron solution bag 22 to which a predetermined concentration of ammonium sulfamate having the above-described configuration was added as a chemical solution bag.
[0104]
As sample water (test water), an aqueous solution having a nitrous acid concentration of 0.1 mg / l was prepared with ion-exchanged water. The adjustment was carried out by adjusting an aqueous solution having a nitrous acid concentration of 1 mg / l by a water quality test method and diluting it. As described in JP-A No. 2001-243698, the iron solution is obtained by adding ferrous sulfate heptahydrate to a so-called 9K medium containing various minerals, and its composition is as follows.
[0105]
In 1L of pure
K₂HPO₄……… 0.5g
(NH₄)₂SO₄……… 3g
KCl ......... 0.1g
MgSO₄・ 7H₂O ... 0.5g
Ca (NO₃)₂・ 4H₂O ... 0.014g
FeSO₄・ 7H₂0 ... 50g
Where ammonium sulfamate (NH₄OSO₂NH₂) 0.59 g was added and the pH was adjusted to 2.1 with sulfuric acid.
[0106]
The cleaning solution used had a normal concentration described in JP-A No. 2000-32233, that is, a pH of 1.7 obtained by diluting reagent-grade sulfuric acid 20 to 60 times with pure water.
[0107]
Using the sample water having the above composition, the iron solution, and the cleaning solution, continuous operation was performed using the prototype having the above-described configuration. At this time, the iron solution and the cleaning solution were filled in a hermetic plastic bag (capacity 5 L), and nitrogen gas was bubbled for about 30 minutes for each of the iron solution and the cleaning solution to deaerate dissolved oxygen. (While the cleaning solution itself is not likely to be oxidized, deaeration treatment was performed in the same manner as the iron solution to prevent the dissolved oxygen from being mixed into the iron solution when switching between the iron solution and the cleaning solution.) No gradual increase in current value was observed during measurement, and a normal sensor response was observed, similar to when no nitrous acid was contained in the sample water. When the concentration of nitrous acid in the cell waste water was analyzed for confirmation, it was 0.03 mg / l, which was about 1/3 of the concentration in the raw water, and its pH was 2.4. The nitrous acid concentration in the sample water was developed by adding sulfamic acid and naphthylamine in the sample water by the water quality test method, the absorbance at 540 mμ was measured, and nitrous acid was quantified by light absorption analysis.
[0108]
As a result, it was proved that a normal sensor response can be obtained by using an iron solution containing ammonium sulfamate even when the sample water contains 0.1 mg / l of nitrous acid.
[0109]
<Example 2>
Next, a test for confirming whether or not the sensor response was inhibited when a harmful substance was mixed in the sample water by the addition of ammonium sulfamate was performed.
[0110]
Potassium cyanide, which is a typical respiratory inhibitor, is added so that the concentration in the sample water (nitrite concentration 0.1 mg / l) is 0.03 mg / l, and an iron solution containing sulfamic acid (0.06 wt%) is added. The response of the sensor when used was examined. As a result, as shown in FIG. 16, rising of the current value is observed about 12 minutes after switching the sample water to the poisoned sample water, and the steady value of the current value is about the span current (current value during cleaning). It was 33%, and it was confirmed that the sensor response was not inhibited even when ammonium sulfamate was added.
[0111]
Hazardous substances other than the above, sodium azide, mercuric chloride, bisphenol A, trobutyltin chloride, antimony chloride, tyrium, thallium chloride, 2,4 dichlorophenol, carbon tetrachloride, sodium sulfide, 2,4,5 trichlorophenoxy Normal responses were also shown to harmful substances such as acetic acid, 2,4-dinitrophenol and methylmercury chloride.
[0112]
In addition, these response lower limit concentrations were almost the same as when ammonium sulfamate was not added, and it was confirmed that the detection sensitivity to harmful substances was not affected.
[0113]
As shown in FIG. 17, when the seasonal change in the concentration of nitrous acid in river water, which is the water intake source for the water purification plant, is analyzed, the rise in winter is significant. It was found that it was sufficient to use up to.
[0114]
In the above embodiment, ammonium sulfamate was used as an example of sulfamic acid, but it goes without saying that the same effect can be expected with other salts that become sulfamic acid in an aqueous solution.
[0115]
【The invention's effect】
As described above, according to the present invention, only the biosensor response-inhibiting substance is removed without affecting the water quality monitoring target substance contained in the raw water collected through a water intake such as a water purification plant. Thus, water quality can be monitored continuously and stably.
[0116]
In addition, due to the strong reducing power of sulfamic acid, oxidation of iron liquid (Fe²⁺→ Fe³⁺) To prevent clogging of the iron oxide pipes and the prescribed Fe²⁺The concentration can be maintained, and the initial sensitivity can be maintained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a first embodiment of a biosensor type water quality monitoring system according to the present invention.
2 is a graph showing a relationship example between a raw material air flow rate, an ozone concentration, and a generation amount in the biosensor type water quality monitoring system shown in FIG. 1;
FIG. 3 is a graph showing an example of removal characteristics of an activity inhibitor against iron-oxidizing bacteria in the biosensor type water quality monitoring system shown in FIG. 1;
FIG. 4 is a flowchart showing an example of a procedure when performing PAC processing on raw water to be monitored for water quality.
FIG. 5 is a flowchart showing an example of a procedure for performing activated carbon treatment on raw water to be monitored for water quality.
FIG. 6 is a flowchart showing an example of a procedure for performing chlorination on raw water to be monitored for water quality.
FIG. 7 is a table showing a component example of raw water and a component example of tap water to be monitored for water quality.
FIG. 8 is a schematic diagram showing an example of the relationship between an iron-oxidizing bacterium used in a biosensor type water quality monitoring system and a respiratory activity inhibitor.
FIG. 9 is a graph showing an example of an output current value when sample water that does not inhibit the respiration activity of a biosensor is supplied to a biosensor type water quality monitoring system used conventionally.
FIG. 10 is a graph showing an example of an output current value when sample water that inhibits the respiratory activity of a biosensor is supplied to a conventionally used biosensor type water quality monitoring system.
FIG. 11 is a block diagram showing an example of a biosensor type water quality monitoring device constituting a second embodiment of the present invention. Shi
FIG. 12 is an explanatory diagram showing a countermeasure plan for nitrite ions, an experimental result thereof, and the like in a table.
FIG. 13 is an explanatory diagram showing the relationship between the sulfamic acid concentration and the residual ratio of nitrous acid.
FIG. 14 is an explanatory diagram showing the relationship between the pH of a solution and the residual ratio of nitrous acid.
FIG. 15 is an explanatory diagram showing the relationship between the reaction time and the residual ratio of nitrous acid.
FIG. 16 is an explanatory diagram showing a sensor response when an iron solution containing sulfamic acid (0.06 wt%) is used when potassium cyanide, which is a respiratory inhibiting substance, is added to sample water.
FIG. 17 is an explanatory diagram showing seasonal variations in nitrous acid concentration.
[Explanation of symbols]
1: Biosensor type water quality monitoring system
2: Ozone gas
3: Sample water
4: Sample water tank
5: Drainage pipe
7: Raw material air
8: Mini compressor
9: Needle valve
10: Silica gel for dehumidification
11: Dehumidifier
12: Ozonizer
13: Flow meter
14: Diffuser
15: Sensor
16: Biosensor device
17: Activated carbon
18: Activated carbon filter
19: Packing
20: Ozone generator
21: Cleaning solution bag
22: Iron liquid bag

Claims (10)

Supply the sample water and iron solution to a biosensor consisting of a sample water tank that temporarily stores sample water for water quality monitoring and a membrane filter holding iron-oxidizing bacteria attached to the tip of the dissolved oxygen electrode. In the biosensor type water quality monitoring system comprising a biosensor device that monitors the quality of the sample water by monitoring respiration inhibition of the iron-oxidizing bacteria,
An ozone generator that removes a response-inhibiting substance that inhibits the activity of the iron-oxidizing bacteria by injecting ozone gas into the sample water in the sample water tank;
A biosensor type water quality monitoring system comprising: In the biosensor type water quality monitoring system according to claim 1,
The ozone generator controls the amount of ozone gas injected into the sample water tank by controlling the flow rate of the raw air or the ozone gas.
A biosensor type water quality monitoring system characterized by that. The biosensor type water quality monitoring system according to claim 1 or 2,
Using the packing produced by the ozone resistant material, the ozone gas in the sample water tank was prevented from leaking to the outside.
A biosensor type water quality monitoring system characterized by that. In the biosensor type water quality monitoring system according to any one of claims 1 to 3,
Two or more ozone generators are connected in series to generate the ozone gas.
A biosensor type water quality monitoring system characterized by that. In the biosensor type water quality monitoring system according to any one of claims 1 to 4,
The ozone generator is turned on when the sensor response inhibitor concentration in the sample water is high, and is turned off when the sensor response inhibitor concentration in the sample water is low.
A biosensor type water quality monitoring system characterized by that. In the biosensor type water quality monitoring system according to any one of claims 1 to 5,
The biosensor device uses a mixed water of cleaning water and tap water to clean the flow cell provided with the biosensor.
A biosensor type water quality monitoring system characterized by that. In a biosensor type water quality monitoring device that incorporates a biosensor with a membrane filter holding iron-oxidizing bacteria attached to the tip of a dissolved oxygen electrode into the flow cell and monitors the quality of sample water using this biosensor,
A biosensor type water quality monitoring apparatus comprising a bag filled with an iron solution as a substrate and added with a predetermined concentration of sulfamic acid. In the biosensor type water quality monitoring device according to claim 7,
The biosensor type water quality monitoring apparatus, wherein the bag is a plastic bag, and the iron solution in the plastic bag is degassed by an inert gas. In the biosensor type water quality monitoring device according to claim 7,
The biosensor type water quality monitoring apparatus, wherein the sulfamic acid added to the iron solution has a concentration of 0.03 to 0.1 Wt%. In the biosensor type water quality monitoring device according to claim 7,
The biosensor type water quality monitoring apparatus, wherein the iron solution bag to which the sulfamic acid is added at a predetermined concentration is used only when the concentration of the activity-inhibiting substance in the raw water is higher than a specified value.

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