JP6478455B2 - Water sterilization method - Google Patents

Description

  The present invention relates to a method of sterilizing a water system such as a circulating cooling water system, and more particularly to a method of sterilizing a water system using an organic disinfectant and an inorganic oxidizing agent in combination.

  Cooling water is used to cool objects indirectly or directly in various industrial fields, such as the petrochemical industry and the steel industry, or in large amounts to air conditioning, heating and cooling of buildings and related equipment, etc. It's being used. Furthermore, in order to reduce the amount of cooling water used from the viewpoint of lack of water resources and effective utilization, for example, advanced use of cooling water is carried out, such as reduction of forced blow amount in high concentration operation of open circulating cooling water system. ing. Thus, when cooling water is used at a high level, the quality of circulating cooling water deteriorates due to the concentration of dissolved salts and nutrient sources, etc., and soil, dust, etc. are mixed with microbes such as bacteria, moss and algae. A slime is formed together, which causes a decrease in heat efficiency and water flow in the heat exchanger, and also causes local corrosion of equipment and piping in the lower portion of the slime.

  Therefore, in order to prevent such slime-induced damage, various antibacterial agents such as oxidizing antibacterial agents such as hypochlorous acid are used. If the advanced use of cooling water is further advanced, the slime-induced damage becomes severe, and the required concentration of the additive increases. However, in the case of oxidizing antimicrobial agents, the added concentration can not be increased because the risk of causing metal corrosion is increased. In addition, because the oxidizing antimicrobial agent is strong in oxidizing power and poorly permeable to slime, once slime injury occurs, it is extremely difficult to prevent its progress.

  In the case of an organic antimicrobial agent, it is relatively easy to prevent the progress of slime injury even if it occurs once, because the ability to penetrate slime is low due to its lack of or extremely low oxidizing power. However, depending on the drug selected, the effective spectrum for components of slime such as bacteria, fungi and algae differs. Also, the material cost is much more expensive compared to the oxidizing antibacterial agent.

  For this reason, a slime control method and control agent that is effective against all slime components such as bacteria, fungi and algae even under conditions with severe slime damage and that can control slime at low cost is required. ing.

  Patent Documents 1 and 2 disclose a method of exerting a synergetic effect of each agent by adding an oxidizing agent and an isothiazolone compound to a cooling water system, and suppressing adhesion of slime in the cooling water system.

Patent 3873534 Japanese Patent Application Publication No. 2006-22097

  When an organic bactericidal agent and an inorganic oxidizing agent are used in combination, the bactericidal rate is high and the bactericidal effect is excellent. However, when the inorganic oxidizing agent is increased, the metal material is corroded, so it is desirable that the addition amount be as small as possible.

  The present invention is a method of sterilizing a water system using an organic bactericide and an inorganic oxidizing agent in combination, which can suppress corrosion of a metal material and is excellent in sterilization even if the amount of the organic bactericidal agent used is reduced. The purpose is to get the effect.

A method of sterilizing a water system according to the present invention is a method of sterilizing a water system in which an organic bactericide and an inorganic oxidizing agent are added to the water system, wherein the organic bactericide and the inorganic oxidizing agent are intermittently added to the water system. The method, wherein the organic bactericide is dichloroglyoxime and / or dibromonitroethanol , the addition frequency of the inorganic oxidizing agent and the organic bactericidal agent is less than 1 hour in 24 hours, It is characterized in that the non-addition time, which is the interval between addition and subsequent addition, is 24 to 100 hours.

  In the present invention, it is preferable to provide a non-remaining period in which residual chlorine in the water system is not substantially detected, between the time of adding the organic biocide and the inorganic oxidizing agent.

  Moreover, in this invention, it is preferable to set the addition space | interval of an inorganic type oxidizing agent and an organic type bactericidal agent to 24-100 h.

  As a result of various researches conducted by the inventor using a microbial fuel cell, in the method of sterilizing a water system using an organic bactericide and an inorganic oxidizing agent in combination, the addition amount of both agents is reduced by intermittent addition. However, it was found that a sufficient bactericidal effect could be obtained. That is, when the organic bactericide used in the present invention and the inorganic oxidizing agent are added to the water system in combination, the addition is discontinued and the metabolism of the bacteria continues to be inhibited even after the drug concentration disappears in the water system. Was found to last.

  About this reason, it is guessed as follows from the evaluation result using a microbial fuel cell.

  The inorganic oxidizing agent and the organic bactericidal agent have different action points and action mechanisms, and have different potential inhibition patterns of the microbial fuel cell. Bonded chlorine causes a rapid rise in potential almost simultaneously with drug contact, indicating that it has an immediate effect on the inhibition of biological energy production systems. However, if it does not remain, the effect drops sharply. It is presumed that this is because the substances involved in the energy production system are not destroyed.

  On the other hand, when the active ingredient comes in contact with the microorganism, the potential of the organic bactericidal agent slowly rises. This indicates that the inhibition of the energy production system is taking place slowly. And when the drug remains in the microbial fuel cell, potential recovery occurs slowly. This indicates that recovery of substances involved in energy production takes time. When an inorganic oxidizing agent and an organic bactericidal agent are used in combination, a rapid rise in potential occurs and the rising level is also large. Recovery occurs slowly when the drug remains.

  The difference in the chemical properties between these inorganic oxidizing agents and organic bactericidal agents is that the inorganic oxidizing agents (hereinafter sometimes referred to as oxidation type growth inhibitors or simply oxidizing agents) have a redox potential. There is a point that organic germicides do not cause this change.

  It is inferred from these results that inorganic oxidants affect the redox potential gradient in cells and inhibit the energy production part of the electron transfer system, but at this time the substances of the energy production system are irreversible Not be subject to scientific and physical changes. Therefore, when there is no substance that affects the redox potential, the microorganism rapidly recovers its function. On the other hand, since organic biocides irreversibly inhibit substances involved in energy production systems, recovery takes time because substance production is required.

  When the inorganic oxidizing agent and the organic bactericidal agent are used in combination, the oxidizing agent stops the metabolism, and the reaching of the action point of the organic bactericidal agent and the chemical reaction are efficiently performed. Since recovery of the microbial function requires production of a substance, it takes a long time to recover because the decrease in metabolic function is large. By such a mechanism, immediate-acting sterilization is made, and the duration of effect continues even for the period which does not remain. Furthermore, since the bactericidal component that is degraded in cells is also suppressed, the required drug concentration is also low.

  In the present invention, corrosiveness is also suppressed by adding it so as to provide a period in which the inorganic oxidizing agent does not remain.

  According to the present invention, since the excellent bactericidal effect can be expected even if the addition amount of the organic bactericidal agent and the inorganic type oxidizing agent is reduced, the economic efficiency can be improved. In addition, even if Legionella is detected in a metal surface water system (for example, a cooling tower), according to this method, rapidity and low corrosion of its sterilization can be quickly dealt with.

  In the present invention, since the inorganic oxidizing agent is added, there is an immediate effect, and since the organic bactericidal agent is added, the effect can be sustained even if the inorganic oxidizing agent disappears in the water system, and stable processing can be performed. . In addition, sterilization of systems other than the target system can be avoided, and the load on activated sludge in the drainage system and the environment can be reduced.

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  The present invention will be described in detail below.

  As a water system to be treated by the present invention, a cooling water system, a paper pulp manufacturing water system, a scrubber water system and the like are exemplified.

  Examples of inorganic oxidizing agents used in the present invention include chlorine gas, chlorinated hypochlorite such as sodium hypochlorite, chlorinated isocyanuric acid, brominating agent such as dibromohydantoin and bromochlorohydantoin, potassium periodate, meta An iodine agent such as sodium periodate, sodium paraperiodate, iodine, potassium iodate, hydrogen peroxide, ozone and the like can be mentioned, with sodium hypochlorite being preferred.

  It is preferable to use any of an isothiazoline compound, dichloroglyoxime, dibromonitroethanol, or a combination thereof as the organic germicide.

  As an isothiazoline compound, for example, 2-methyl-4-isothiazolin-3-one, 2-ethyl-4-isothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 5-chloro-2 -Methyl-4-isothiazolin-3-one, 5-chloro-2-ethyl-4-isothiazolin-3-one, 5-chloro-2-t-octyl-4-isothiazolin-3-one, 4,5-dichloromethane -2-n-octyl-4-isothiazolin-3-one, 4,5-dichloro-2-cyclohexyl-4-isothiazolin-3-one and the like can be mentioned. One of these isothiazolone compounds can be used alone, or two or more of them can be used in combination. In addition, as the isothiazoline compound, a complex compound of the above-described isothiazoline compound and magnesium chloride, magnesium nitrate, copper chloride, copper nitrate, calcium chloride or the like may be used.

  In the present invention, an organic biocide (preferably one or more of an isothiazoline compound, dichloroglyoxide, and dibromonitroethanol), an inorganic oxidizing agent (preferably sodium hypochlorite), is preferably added to the target aqueous system. ) Are added separately or after mixing in advance. A nitrogen compound (preferably, any one or more of glycine, polypeptone and sulfamic acid) may be added separately or in combination as a stabilizer of the oxidizing agent.

  At this time, preferably, the organic bactericidal agent as the bactericidal component and the inorganic oxidizing agent as the growth inhibiting component are added intermittently so that there is a period (residual period) in which both the organic bactericide and the inorganic oxidizing agent as the growth suppressing component simultaneously remain. Do. During this non-remaining period, it is preferable that substantially no residual chlorine be detected. Usually, each measurement method of residual chlorine has a measurement lower limit, and it may be confirmed that it is not more than the measurement lower limit to confirm that it does not remain. For example, the measurement lower limit value of residual chlorine in the DPD method is 0.1 mg / L.

  Although a slime control effect can not be expected, a residual chlorine concentration which does not affect corrosion is less than 0.1 mg / L as a standard, and in practice, it may be controlled to be less than 0.1 mg / L. The residual chlorine detected by the addition of the inorganic oxidizing agent is useful for slime control, but according to the present invention, the slime control effect is maintained even if the residual chlorine is not detected continuously.

  The residual chlorine concentration does not exceed the free residual chlorine concentration, and if the residual chlorine concentration is kept below a certain value, the free residual chlorine concentration becomes a value lower than that. Free residual chlorine is more corrosive than residual chlorine, and if the free chlorine concentration is not kept below a certain value, the target can be achieved if the residual chlorine concentration is managed.

The addition frequency of the inorganic oxidizing agent and the organic bactericidal agent is preferably less than 1 hour in 24 hours, for example, about 0.1 to 0.9 hours, particularly about 0.25 to 0.5 hours in 24 hours. The addition amount of the organic fungicides is preferably about 1 to 30 mg / L, especially 3-10 mg / L at the time of the addition, ₂ about 1~50mg / LasCl ₂ particularly 3~10mg / LasCl For inorganic oxidizing agent is preferred. The interval between one addition and the subsequent addition (non-addition time) is preferably 24 to 100 h, particularly about 25 to 72 h.
The inorganic oxidizing agent and the organic bactericidal agent may not only be added simultaneously at the same timing, but also they may be added at different timings.

  Hereinafter, the present invention will be more specifically described by way of examples and comparative examples. In the following Examples and Comparative Examples, "%" indicating concentration represents "% by weight".

Example 1
<Test of bactericidal effect by combined use of organic bactericidal agent (isothiazoline compound), nitrogen compound (glycine) and inorganic oxidizing agent (sodium hypochlorite)>
<Method>
100 mL of sterile water was prepared in a 300 mL Erlenmeyer flask. The following slime control agent of the target concentration was added to this sterile water, and 10 mL of the following Legionella standard strain suspension cultured was added. After shaking at a constant temperature for a predetermined time, the number of bacteria having growth ability was counted. All manipulations were performed in a P2 clean bench, and culture was performed in a P2 incubator.

Slime control agent: NaClO solution for food addition
5-chloro-2-methyl-4-isothiazolin-3-one (
Cl-MIT) 1% and glycine 1% solution

The concentration was measured using a hack pocket residual chlorine meter and DPD reagent.
The free residual chlorine concentration value was measured with DPDfree measuring reagent, and after stirring, it was measured by standing for 60 seconds.
The residual chlorine concentration was measured with DPDtotal measuring reagent, and after stirring, it was measured by leaving it for 3 minutes.
The quantification of 5-chloro-2-methyl-4-isothiazolin-3-one was carried out by liquid chromatography. If not measured, it is indicated by the set value.
The concentration of free residual chlorine and the concentration of residual chlorine in sterile water changed after addition of Legionella, so the residual concentration at the time of Legionella sampling was adopted.

The Legionella standard strain is Legionella pneumophila GIFU9134 (serotype sero1). A liquid previously cultured in BCYEα medium, suspended in sterile water, and adjusted to an absorbance of 0.1 at 660 nm with a test tube absorbance meter was used as a bacterial solution.
The contact conditions with the slime control agent were 30 ° C., 100 rpm, 0 minutes, 6 minutes, 27 minutes, and 60 minutes.

  For the measurement of Legionella, 10 ml was sampled from an Erlenmeyer flask, and 100 μL was smeared on the surface of BCYEα medium after stirring with sodium thiosulfate. The cells were cultured at 37 ° C., and colonies after 7 to 10 days were counted. The value for 0 minutes was obtained by adding the bacteria to the solution to which the slime control agent had been added in advance, stirring, and sampling immediately. The blank was subjected to the same operation without the addition of the slime control agent.

As a result, as shown in Table 1, the combined use of Cl-MIT (19 mg / L) and residual chlorine (5 to 10 mg / LasCl ₂ ) and free residual chlorine of less than 0.1 mg / L for 99 minutes in 60 minutes. It reached 9% sterilization. Since the free residual chlorine concentration at this time was less than 0.1 mg / L, it is considered not to be sterilization by free residual chlorine.

The combined use of Cl-MIT (19 mg / L) and residual chlorine (5 to 10 mg / LasCl ₂ ) showed 95% or more sterilization in 27 minutes under the condition of free residual chlorine of less than 0.1 mg / L.

Comparative Example 1-1
A 1% solution of 5-chloro-2-methyl-4-isothiazolin-3-one (Cl-MIT) and 1% glycine was used as a slime control agent, and the contact with the slime control agent was made 30 ° C., 100 rpm, 27 minutes. The same test as in Example 1 was conducted except for the following.

  As a result, as shown in Table 2, Cl-MIT (19 mg / L) exhibited only about 80% bactericidal activity in 27 minutes, and was inferior in bactericidal activity.

Comparative Example 1-2
The same test as in Example 1 was conducted except that the dietary NaClO solution and glycine 1% solution were used as a slime control agent, and the contact with the slime control agent was made 30 ° C., 100 rpm, 0 minutes, 6 minutes, 27 minutes. went.

As a result, as shown in Table 3, under the condition of residual chlorine (10 mg / LasCl ₂ ), only 75% of bactericidal activity was exhibited in 27 minutes, and the bactericidal effect was low.

[Comparative Examples 1-3A to 3E]
Example except using 1% of 5-chloro-2-methyl-4-isothiazolin-3-one (Cl-MIT) as a slime control agent and setting the contact with the slime control agent to 30 ° C., 100 rpm, 1 hour The same test as 1 was performed.

  As a result, as shown in Table 4, the rate of sterilization after contact with Cl-MIT (10 mg / L) for 1 hour was in the range of 30 to 87%, and the sterilization was low.

  It took 24 hours to achieve a bactericidal activity of 99% or more, and the immediate effect was lacking.

Example 2
Using a transient test apparatus, the residence time was set at the column part and the bactericidal activity was evaluated by CFU measurement.

  As a transient test apparatus, the one of the flow shown in FIG. 1 was used. In FIG. 1, P represents a pump.

  In a culture apparatus (a microbial fuel cell) having a fixed bed of felt, the one obtained by adding a culture medium to dechlorinated water was flowed at 20 ml / min. The medium used was PYA medium composed of polypeptone, yeast extract, and sodium acetate.

  The bacterial solution that flowed out of the culture apparatus (microbial fuel cell) was flushed temporarily. CFU was measured for this solution. A slime control agent shown in Table 5 was added to the middle of the cell flow. MIT in Table 5 is Cl-MIT. The bacterial solution was allowed to stay in the column and used as the contact time of the slime control agent.

  The slime control agent concentration was measured immediately after dosing and at the outlet of the column (after contact for a certain period of time).

  CFU measurement was performed by serial dilution using 1/10 PY medium. The bacteria to be tested this time are considered to be general bacteria grown in the environment. Microscopic observation of bacteria and identification of bacterial species were not performed.

As a result, as shown in Table 5, when Cl-MIT and combined chlorine were used in combination, 99.99% or more of bactericidal activity was exhibited. The bactericidal effect was exhibited at a contact time of 0 minutes, and the effect was further increased by a contact of about 30 minutes. At this time, the residual chlorine concentration was about 7 mg / LasCl ₂ . The free residual chlorine concentration was 0.15 mg / LasCl ₂ .

Comparative Example 2-1
As a slime control agent, as shown in Table 5, the same test as in Example 2 was conducted except that sodium hypochlorite was not used.

Comparative Example 2-2
As a slime control agent, as shown in Table 5, the same test as Example 2 was conducted except that Cl-MIT was not used.

As a result, as shown in Table 5, the bound residual chlorine alone showed a bactericidal activity of about 90% at about 8 mg / LasCl ₂ . At this time, the free residual chlorine concentration was about 0.1 mg / LasCl ₂ . In addition, in the case of Cl-MIT alone, no clear bactericidal activity was shown at 10 mg / L and 30 min.

[Example 3]
The corrosion test was conducted under the following conditions using a rotational corrosion test apparatus.
<Slime control agent>
Example 3-1: Addition of 400 mg / L + NaClO solution containing 1% Cl-MIT, 1% glycine, 3% sulfamic acid to a free residual chlorine concentration of 0.1 mg / LasCl ₂ Example 3-2: 1% Cl-MIT, Glycine 1% 400 mg / L
<Anticorrosive>
Benzotriazole (anticorrosive for copper, BT): 1 mg / L (additional concentration)
Maleic acid based polymer: 1.5 mg / L (additional concentration)
Phosphonic acid: 2.4 gm / L (added concentration)
<Test water quality (pure water supply assumed)>
M alkalinity: 79 mg / l
Ca hardness: 2 mg / L
Mg hardness: 1 mg / L

The above anticorrosive agent and slime control agent were added to the test water so as to have predetermined concentrations. Test water, an anticorrosive, and a slime control agent mixture were injected at a rate of 1 L / day to give a residence time. At the time of measurement, if the concentration of free residual chlorine was lower than the predetermined concentration, the NaClO solution was added batchwise to make the predetermined concentration.
<Test specimen>
Copper test piece 31 cm ² (30 mm × 50 mm × 1 mm)
The rotational corrosion test apparatus conditions were 140 rpm, water temperature was 30 ° C., and 7 days, and the weight before and after the test of the test piece was measured and compared in weight loss (mg) per dm ² per day.

As a result, as shown in Example 3-1 of Table 6, when the free residual chlorine concentration average was less than 0.1 mg / LasCl ₂ , the corrosion rate was at a problem-free level. Also, as shown in Table 7, when NaClO was added, the free residual chlorine concentration sometimes exceeded 0.1 mg / LasCl ₂ temporarily, but the corrosion rate was not adversely affected. It was shown that the corrosion rate could not be increased unless the free residual chlorine concentration was maintained at 0.1 mg / LasCl ₂ or more.

Comparative Example 3
The same test as in Example 3 was conducted except that the slime control agent was changed as follows.

Comparative Example 3-1: A mixed solution of sulfamic acid and NaClO is added so that the NaClO residual chlorine concentration is 15 mg / LasCl ₂ and the free residual chlorine concentration is 0.3 mg / LasCl ₂ Comparative Example 3-2: sulfamic acid and NaClO The mixture with it is added so that the NaClO residual chlorine concentration is 5 mg / LasCl ₂ and the free residual chlorine concentration is 0.3 mg / LasCl ₂

As a result, as shown in Table 6, when the average free residual chlorine concentration is maintained at 0.17 mg / LasCl ₂ or more, the corrosion rate exceeds 1 mdd, and corrosion is concerned.

Comparative Example 3-2 (free residual chlorine concentration: 0.17 mg / LasCl ₂ ) As can be seen from Comparative Example 1-2 of Table 3 described above performed at free residual chlorine concentration and residual chlorine concentration equivalent to that in Table 3, Legionella with only NaClO + glycine It turned out that the bactericidal effect of genus bacteria is insufficient, and the bactericidal effect can not be expected at a concentration that does not have the problem of corrosion.

Example 4
In order to compare the immediate effect of the drug in intermittent injection and the effect after stopping the injection, the bactericide was intermittently injected into the anode of the flow of the microbial fuel cell in FIG. As shown in FIG. 2, dechlorinated water was deoxygenated by nitrogen aeration, and the medium was injected halfway and allowed to flow to the anode side of the microbial fuel cell.

  Air was blown into the cathode side of the microbial fuel cell to supply oxygen. Electrons were supplied from the anode side to the cathode side due to the growth of the microorganism, a resistance (500 Ω) was connected between the anode and the cathode, and the voltage was measured. The larger the absolute value of the negative potential relative to the cathode, the more active the growth of the microorganism.

  In this test, the highest potential raised by the drug injection was measured as the reaching potential, and the period after stopping the drug injection until returning to the potential before the drug injection was measured as the energy production inhibition duration. Based on these values, the effects of the organic bactericidal agent and the inorganic oxidizing agent were compared.

  The conditions of the microbial fuel cell of FIG. 2 are as follows.

Anode: 5 mm thick Graphite felt 5 cm * 15 cm (Anode capacity 80 to 90 mL)
Cathode: carbon coated nickel catalyst Nonconductive membrane: Millipore nitrocellulose membrane Resistance: 500 Ω
Noki town water and air were supplied to the cathode at a flow rate of 2 L / min. Take the water from Noki town in the aeration tank for the anolyte, aerate it with nitrogen gas, send water without dissolved oxygen at 8 mL / min, and pump the culture medium to a predetermined concentration before the anode inlet. Line injected. If necessary, the following oxidizing system growth inhibitor and organic type bactericidal agent were injected by a line at a predetermined time for a predetermined period of time before the anode inlet, with a pump. The anode and the cathode were connected by a copper wire through a resistor, and the generated potential was continuously measured. In addition, it was confirmed that the organic bactericidal agent and the oxidation type growth inhibitor were not detected after lapse of residence time of the anode chamber after stopping the chemical injection.

The test conditions were as follows.
Organic disinfectant: Cl-MIT setting concentration 5 mg / L + glycine 10 mg / L
Oxidative growth inhibitor: NaClO preset concentration 10 mg / L, medium organic substance · It has become almost bound by reaction with glycine.
Infusion time: 3 h
Anode residence time: 10 to 20 min (It is difficult to measure accurate residence time because there is felt in the anode cell)

The evaluation method was as follows.
Reaching potential: The highest potential reached due to drug injection, and the maximum potential energy production inhibition duration: The shape of the time until the potential returns to the potential before dosing and the time course of the potential

  As a result, as shown in Table 8 and FIG. 3, the combined use of the organic bactericide and the inorganic oxidizing agent showed a sharp rise in the potential, which was higher than that of single use. The ultimate potential was equal to the value obtained by adding the potential raised by single injection.

  When the inorganic oxidizing agent and the organic bactericidal agent were used in combination, the potential recovery decreased about 100 mV after stopping the injection, showing a rapid recovery, but thereafter showed a gradual recovery. The duration of energy production inhibition was almost equal to the addition of inhibition time by single item.

  From these results, it was found that the combination of the inorganic oxidizing agent and the organic bactericide increased the immediate effect, the degree of inhibition became stronger, and the recovery after injection was delayed.

Comparative Example 4-1
The test was conducted under the same conditions as in Example 4 except that the oxidative growth inhibitor was not used.

  As a result, as shown in Table 8 and FIG. 3, the decrease in potential was gentle as compared with Example 4 and Comparative Example 4-2, and the potential of -400 mV was maintained after 3 hours. Although the decrease in potential after stopping the drug administration was gradual, the rise in potential width was small, so the potential returned to the original potential in about 4 hours.

  From this, it can be seen that the immediate effect of the organic disinfectant is low.

Comparative Example 4-2
The test was conducted under the same conditions as in Example 4 except that the organic biocide was not used.

  As a result, as shown in Table 8 and FIG. 3, the potential shows a sharp rise and reaches −150 mV. Immediately after cessation of drug administration, a rapid potential drop (restoration) of about 200 mV occurs, and the potential reaches -300 mV. Thus, it is presumed that oxidation drugs are effective, but their ability to inhibit energy production rapidly disappears when drug administration is stopped, so the concentration must be maintained in order to maintain the effect. .

[Example 5]
Using the same test apparatus as in Example 4, the effect on the immediate effect and the effect after stopping the injection when the intermittent injection time was extended were compared in the following conditions in the microbial fuel cell.
<Test conditions>
Organic disinfectant: Cl-MIT set concentration 5 mg / L
Oxidative growth inhibitor: Combined chlorine (sulfamic acid + NaClO) residual chlorine setting concentration 15 mg / LasCl ₂
Infusion time: 6 h
Anode retention time: 10 to 20 min

  As a result, as shown in FIG. 4 and Table 9, the potential immediately increased after the injection and became -100 mV or more. The potential continued to drop gradually during the injection. The potential reached was -67 mV. The potential reached by the combined use of the organic bactericidal agent and the inorganic oxidizing agent does not reach the value obtained by adding the rising potential of single use, and the ultimate potential of the bactericidal / growth inhibition seems to have an upper limit.

  After stopping the injection, when the inorganic oxidizing agent and the organic bactericide were used in combination, the potential immediately decreased by about 100 mV, but after that, it showed a moderate potential drop (recovery), and the potential was returned to the potential. It took 39 h. The combined use took about 9 hours extra time than the sum of recovery time of single use. Thus, extending the combined contact time extended the time for recovery.

  In this Example 5, the binding partner of bound chlorine was sulfamic acid, but it was found that the same inhibition and recovery pattern as in Example 4 was shown.

  By prolonging the combined use time of the inorganic oxidizing agent and the organic bactericide, the sufficiently inhibited time is extended, and the recovery after stopping the injection is also delayed. From this fact, it is thought that the longer the combined time, the more efficient the bactericidal activity and the effect maintenance time after stopping the injection.

Comparative Example 5-1
The test was conducted under the same conditions as in Example 5 except that the organic biocide was changed to a Cl-MIT set concentration of 5 mg / L.

  As a result, as shown in FIG. 4 and Table 9, the inhibition pattern by the addition of Cl-MIT was similar to that of Comparative Example 4 and was relatively gentle. When the time was extended, the potential rise was on the extension of 3 h. After stopping the injection, the potential showed a gradual recovery pattern compared to the inorganic oxidant. After Cl-MIT injection, the time required for potential recovery was 13 h for Cl-MIT.

Comparative Example 5-2
The test was conducted under the same conditions as in Example 5 except that the oxidation-based growth inhibitor was changed to a combined chlorine (sulfamic acid + NaClO) residual chlorine set concentration 15 mg / LasCl ₂ .

  As a result, as shown in FIG. 4 and Table 9, the potential linearly increased 300 mV by bound chlorine and then gradually increased. When the injection was stopped, the potential was restored (decreased) about 200 mV immediately. After that, it took about 16 hours to recover slowly and to recover to the original potential.

[Example 6]
A test was conducted to show that even if the free residual chlorine concentration exceeds 0.1 mg / L immediately after the addition of sodium hypochlorite, there is a period that falls below 0.1 mg / L and the corrosion is suppressed. .

In this test, the same rotational corrosion test apparatus as in Example 3 was used.
<Slime control condition>
Example 6-1: 200 mg / L of a solution containing 2% Cl-MIT, 2% glycine, 3% sulfamic acid and NaClO are added so as to give a free residual chlorine concentration of 0.3 mg / LasCl ₂ . once a day.
Example 6-2: 200 mg / L of a solution containing 2% Cl-MIT, 2% glycine, 3% sulfamic acid and NaClO are added so as to give a free residual chlorine concentration of 0.1 mg / LasCl ₂ . once a day.
Example 6-3: 200 mg / L of a solution containing 2% Cl-MIT, 2% glycine, 3% sulfamic acid
<Anticorrosive>
Benzotriazole (anticorrosive for copper, BT): 1 mg / L (final concentration)
Maleic acid based polymer: 1.5 mg / L (final concentration)
Phosphonic acid: 2.4 gm / L (final concentration)
<Test water quality (pure water supply assumed)>
M alkalinity: 79 mg / L
Ca hardness: 2 mg / L
Mg hardness: 1 mg / L
<Test procedure>
An anticorrosive agent and a slime control agent were added to the test water so as to have predetermined concentrations. Test water, an anticorrosive, and a slime control agent mixture were injected at a rate of 1 L / day to give a residence time. The NaClO solution was added batchwise once a day to bring it to a predetermined concentration. The rotational corrosion test device conditions were 140 rpm, water temperature 30 ° C., and 7 days.
<Test specimen>
Mild steel test piece 31 cm ² (30 mm × 50 mm × 1 mm)
Weights before and after the test were measured and compared in weight loss (mg) per dm ² per day.

As a result, as shown in Tables 10 to 12, in Example 6-1, even if the free residual chlorine concentration reaches 1 mg / LasCl ₂ or more by intermittent injection of NaClO, it returns to less than 0.1 the next day, the corrosion is equivalent to no addition of NaClO. It is.

As shown in Example 6-2, even when the free residual chlorine concentration is maintained at less than 0.1 mg / LasCl ₂ by intermittent injection of NaClO, the corrosion rate is equivalent to no addition of NaClO (Table 11). Even beyond this results from free residual chlorine concentration is temporarily 0.1mg / LasCl _2, if there is certainly a period of less than 0.1mg / LasCl _2, corrosion compared with residual chlorine no addition is not promoted.

Comparative Example 6
The test was conducted under the same conditions as Example 6 except that slime control conditions were as follows.

Comparative Example 6-1: 200 mg / L of sulfamic acid, NaClO mixed solution. Maintain 15 mg / LasCl ₂ as residual chlorine concentration and 0.3 mg / LasCl ₂ or more as free residual chlorine concentration.
Comparative Example 6-2 50 mg / L of sulfamic acid, NaClO mixed solution. Residual chlorine concentration 5mg / LasCl _2, maintaining the 0.1-0.2mg / LasCl ₂ as free residual chlorine concentration.

The results are shown in Tables 10-12. Even if the average value of the free residual chlorine concentration is lower than that of Example 6-1, the corrosion rate is increased in Comparative Example 6-2. The corrosion rate increases as the free residual chlorine concentration is maintained even at low concentrations (Table 10).
The corrosion rate is higher in Comparative Example 6-1 than in Comparative Example 6-2, and the corrosion rate increases as the free residual chlorine maintenance concentration increases (Table 10).

  The free maximum chlorine concentration is larger in Example 6-1 than in Comparative Example 6-1. From this, it is thought that the lowest value affects the corrosion rate more than the maximum value, and maintaining the concentration leads to an increase in the corrosion rate (Tables 11, 12).

[Example 7]
The immediate effect enhancement of the respiratory activity inhibition by the combined use of an organic biocide other than isothiazoline and an oxidizing agent was tested under the following conditions.
<Type of organic disinfectant>
Dichloroglyoxime (DCG)
2,2-Dibromo-2-nitroethanol (DBNE)
<Inorganic oxidant>
Sodium hypochlorite and sodium sulfamate mixture <Test method>
It evaluated using Pseudomonas.putid.
The target bacteria were suspended in sterile water, adjusted to 660 nm absorbance, 0.1 and dispensed in 10 ml aliquots into test tubes. Organic germicide alone, inorganic oxidant alone, organic germicide and inorganic oxidant combined use, each concentration is added.
30 ° C., 1 h, 100 r. p. Shake on m.
It was then filtered through a nitrocellulose filter with a pore size of 0.45 μm, 10 mL of sterile water was added and filtered to remove the drug.
2-p-iodophenyl-3-p-nitrophenyl-5-tetrazolium chloride solution (hereinafter INT solution, final concentration 0.02%) and culture medium (polypeptone final concentration 0.1 g / L, yeast extract final concentration 0. 1 g / L, final concentration of NaCl 0.05 g / L) is placed on the filtered filter.
Let stand at 37 ° C for 1 h.
After a predetermined time, it is filtered, the filter is extracted with 1 mL of chloroform, and the absorbance at 490 nm is measured. From this value, the concentration of formazan produced by fungal dehydrogenase is calculated.
Measure the protein concentration of the target bacteria. The quantification of the protein concentration was carried out by measurement with Folin-Ciocalten's phenol reagent.
Dehydrogenase activity can be calculated by calculating the INT formazan mole number extracted from the extract volume using the following equation and dividing by the reaction time.
Dehydrogenase activity [U] = millimolar concentration [mmol / L] × μ molar equivalent [1000 μmol / mmol] × amount of extract [L] / reaction time [min] = (0.044 × 490 nm absorbance-0.0004 ) × 1000 × (1/1000) / 60
(Note) millimolar concentration [mmol / L] = 0.044 x 490 nm absorbance-0.0004
Extract volume 1mL
Reaction time 60 min

  Dehydrogenase activity is divided by the mass of protein to determine the activity per cell. Since the number of digits is small, the result was further multiplied by 100,000. The single and combined drug concentrations at which this dehydrogenase activity has disappeared are shown in FIG. The straight line in the graph of FIG. 5 represents an additive effect straight line, and if it is below this straight line, it is judged that there is a synergistic effect.

<Result>
(1) The activity per bacterial cell of Pseudomonas. Putid not added with a drug was 484, showing sufficient activity.
(2) Sodium hypochlorite and sodium sulfamate mixture required a concentration of 70 mg / LasCl ₂ or more to eliminate the dehydrogenase activity, and DCG required 10 mg / L. When used in combination, each agent required for loss of activity was achieved at a lower concentration than when both were added, and a synergistic effect of suppression of activity due to the combined use was shown.
(3) The mixture of sodium hypochlorite and sodium sulfamate required a concentration of 70 mg / LasCl ₂ or more to eliminate the dehydrogenase activity, and DBNE required 10 mg / L. When used in combination, each agent required for loss of activity was achieved at a lower concentration than when both were added, and a synergistic effect of suppression of activity due to the combined use was shown.
As is clear from these results, the same mechanism works also in the combined use of an organic biocide other than the isothiazoline compound and an inorganic oxidant, and a synergistic effect, a rapid effect, and a sustained effect are achieved. Also, the risk of corrosion is reduced due to the significant reduction of oxidant.

Claims (2)

In a method of sterilizing a water system, an organic disinfectant and an inorganic oxidizing agent are added to the water system.
A method of sterilizing a water system, wherein the organic bactericide and the inorganic oxidizing agent are intermittently added,
The organic fungicide is dichloroglyoxime and / or dibromonitroethanol,
The inorganic oxidizing agent is a chlorine-based oxidizing agent,
Timing and between the timing, a method of sterilizing water-based residual chlorine concentration of the water system is characterized Rukoto provided a non-residual period not substantially detected for adding the organic fungicide and an inorganic oxidizing agent. In claim 1, the addition amount of 1 to 30 mg / L of organic fungicides, sterilization method of the water-based, wherein the addition amount of the inorganic oxidizing agent is 1~50mg / LasCl _2.

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