JP3664274B2 - Electrolytic treatment method of water to be treated - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for electrolytically treating the water to be treated in order to suppress various performance deteriorations caused by the microorganisms of the various waters to be treated containing microorganisms, and more particularly to photographic processing liquids and various factories. Microorganisms such as pure water, ultrapure water or pool water, paper washing water, heat exchanger cooling water, drinking water, water for cup vending machines, fish culture water, chemical dilution water, bath water, and circulating water for gas washing towers It is economical to sterilize, sterilize and sterilize microorganisms in each treated water by electrolytic treatment of various treated waters that contain microbial substances or have the potential to generate microorganisms using a bipolar fixed-bed electrolytic cell And a method for effectively performing.
[0002]
[Prior art]
Conventionally, various types of aqueous solutions and single water (pure water) that does not dissolve other substances have been used for various purposes. These aqueous solutions and the like provide nutrients with appropriate solutes, or if the temperature of the aqueous solution is a relatively high temperature preferable for breeding, microorganisms such as bacteria propagate and the microorganisms deteriorate the performance of the aqueous solution. In many cases, the function occurs, the product is adversely affected, the product floats or accumulates in the processing apparatus, and the function of the processing apparatus is impaired. The number of microorganisms in normal tap water is set to 20 cells / milliliter or less by leaving residual chlorine as a disinfectant. However, if this tap water is used as cooling water for heat exchangers, for example, the microorganisms will proliferate and the Corrosion and odor are generated.
In order to prevent these phenomena, various chemicals such as antifungal agents and precipitation inhibitors are conventionally introduced into the water to be treated and various filters are installed in the middle of the pipe. It has been pointed out that there are adverse effects on treated water due to residual chemicals and problems with the cost of using chemicals. Furthermore, the antibacterial agent is added after a while, and there is a problem that it becomes necessary to examine the next drug or supply a larger amount of drug than necessary. In addition, it is impossible in principle to filter and isolate live bacteria by filter operation, and permanent bacteria removal cannot be performed.
[0003]
Of the above-mentioned treated water, in particular, drinking water is directly linked to human health, and it is essential to sterilize the bacteria contained in it and prevent the propagation of sputum, that is, kill and remove microorganisms. As a method for this, the method using chlorine is the mainstream. However, in urban water sterilization, river water, lake water, etc., which is the raw water, is contaminated with various organic substances, and more chlorine is added than necessary for the killing of microorganisms. It causes bad effects such as occurrence. In order to eliminate the above disadvantages caused by the chlorine method, sterilization methods other than the chlorine method have been proposed.
In order to eliminate the above-mentioned drawbacks in each of the water to be treated including drinking water, the applicant of the present invention is provided in an electrolytic cell in which a plurality of carbonaceous three-dimensional fixed bed electrodes (hereinafter also referred to as carbonaceous electrodes) are accommodated. A water treatment apparatus and method for sterilizing microorganisms in the water to be treated by supplying treated water and performing electrolytic treatment have been proposed.
[0004]
[Problems to be solved by the invention]
This so-called electrolytic sterilization method is to sterilize microorganisms that are in contact with the electrode portion that is polarized positively by energizing the carbonaceous electrode and that is mainly positively polarized. Since it is continued and no chemicals such as chlorine and ozone are used, there is an advantage that even if the treatment is performed for a long period of time, only a small amount of electricity cost is increased and economical operation is possible.
However, during long-term operation, the electricity cost cannot be ignored, and the carbonaceous electrode is consumed in proportion to the energization time. Most of the water to be treated is not used continuously for 24 hours. If necessary, the electrolytic bath is energized to perform electrolytic treatment of the water to be treated to obtain treated water to be used for various applications. However, when the treated water is unnecessary, the electricity supply to the electrolytic cell is stopped to save electricity.
As a result, the desired treated water can be obtained with the minimum amount of electricity. However, when the energization is stopped, the carbonaceous electrode is not polarized, so that microorganisms propagate on the carbonaceous electrode, and energization is started when the operation is resumed. However, there is a drawback that microorganisms propagated at the time of stopping energization cannot be sufficiently sterilized and only treated water in which the microorganisms remain can be obtained.
[0005]
OBJECT OF THE INVENTION
The present invention eliminates the above-mentioned drawbacks of the prior art, substantially prevents microbial growth due to the stop of energization with the minimum required power, and can always supply clear treated water that contains almost no microorganisms immediately. An object is to provide an electrolytic treatment method.
[0006]
[Means for solving problems]
The present invention supplies the water to be treated containing microorganisms to an electrolytic cell in which a carbonaceous three-dimensional fixed bed electrode is installed, and polarizes the electrodes by energizing the electrodes, and the microorganisms are brought into contact with the polarized electrodes. In the electrolytic treatment method of the water to be treated for sterilizing the microorganisms by reducing the amount of energization to the electrode when the water to be treated is not supplied to the electrolytic cell, compared with the time of supplying the water to be treated. It is a characteristic method. In addition, since the water treatment by the method of the present invention may not cause a substantial electrochemical reaction such as a redox reaction on the electrode surface, the water treatment by the method of the present invention and the electrolytic cell in the method of the present invention are each Although they should be referred to as an electrochemical treatment and an electrochemical treatment tank, they are referred to as an electrolytic treatment and an electrolytic cell, respectively, according to a general name.
[0007]
The present invention will be described in detail below.
The method of the present invention comprises a photographic processing solution, pure water from various factories, ultrapure water or pool water, paper washing water, heat exchanger cooling water, drinking water, water for cup vending machines, water for fish farming, drug dilution water, Targeting various treated waters containing microorganisms such as bath water and circulating water for gas cleaning towers or having the possibility of generating microorganisms, supplying the treated water to a bipolar type fixed bed electrolytic cell The present invention relates to an energization method for applying bactericidal, sterilizing or sterilizing microorganisms in the water to be treated by applying a direct current or an alternating voltage. The microorganism of the present invention includes bacteria (bacteria), fungi, filamentous fungi (spider), E. coli, yeast, modified fungi, unicellular algae, protozoa, viruses and the like.
[0008]
When the water to be treated is supplied to an electrolyzer equipped with an energized carbonaceous electrode, microorganisms in the water to be treated come into contact with the electrodes polarized by liquid flow and receive a high potential energy supply on their surfaces. It is considered that a strong redox reaction occurs in the microbial cell, and its activity is weakened or the microorganism itself is killed and sterilized.
According to such electrolytic treatment of the water to be treated, sterilization is effectively performed as described above. For example, in the case of pool water where the water to be treated needs to be treated in a large amount or cleaning pure water of a semiconductor factory, the method of the present invention is used. The amount of power required for sterilization often occupies most of the processing cost. The amount of electric power is represented by [power] = [voltage] × [current]. Since the amount of water to be treated is enormous, the amount of power consumption is enormous.
[0009]
On the other hand, the amount of power for drinking water etc. does not increase so much, but the amount of power when the electrolyzer is continuously operated is represented by [power] = [voltage] × [current] × [time]. If the energization is continued even if the energization amount is small, the amount of power increases. Therefore, it is possible to save electricity by energizing the electrolytic cell only when treated water to be treated is necessary and stopping the energization when unnecessary. In particular, household water faucets are closed for 80-90% of the time, allowing significant power savings.
However, in this method, microorganisms that are not in contact with the electrode propagate when the energization is stopped, and even if the microorganism contacts the electrode at the start of energization, it takes a relatively long time for the electrode to achieve sufficient polarization. There are a significant number of microorganisms in the treated water that is removed from the electrolytic cell upon initiation. In order to eliminate this disadvantage, the treated water taken out from the electrolytic cell for a certain period of time after the start of energization is discarded or circulated to the electrolytic cell, and the treated water is taken out from the electrolytic cell after reaching a steady state. Only water should be used for necessary applications. However, this method not only wastes the treated water, but also it is uncertain how long the microorganisms attached to the inner wall of the electrolytic cell will be taken out of the electrolytic cell after energization. It ’s hard to say that it ’s a complete solution.
[0010]
When the supply of water to the electrolyzer is stopped, that is, when the amount of treated water is zero (when the untreated water is not supplied), microorganisms are not supplied from outside the electrolyzer, so there is no need to sterilize the microorganisms. It is enough to prevent breeding.
As described above, when the electrode is energized, the electrode is polarized and the electrolytic reaction proceeds with the generation of oxygen gas and hydrogen gas to sterilize the microorganisms. To prevent the growth of microorganisms, the microorganisms are sterilized during normal operation. The potential is not so high. Gas generation is not indispensable for sterilization of microorganisms. Conversely, the generated gas covers the electrode surface and the microorganisms come into contact with the electrode surface to reduce the efficiency of sterilization. It is desirable to treat the water to be treated while applying a potential at which the gas dissolves in the aqueous solution.
On the other hand, in order to prevent the above-mentioned growth of microorganisms, it is sufficient to apply a low potential to the electrode surface that does not cause a substantial electrolytic reaction, but it may be accompanied by gas generation.
[0011]
In order to achieve this microbial growth prevention while saving electric power, the present invention makes the average energization amount when the treated water is not supplied smaller than the average energization amount when the treated water is supplied. In order to reduce the average energization amount, for example, there is a means for setting the applied voltage to the carbonaceous electrode when the treated water is not supplied to a constant voltage smaller than the applied voltage when the treated water is supplied. When the applied voltage when the water to be treated is not supplied is set to a maximum value so that no substantial gas is generated, polarization of the electrode occurs in a state where the energization amount is close to zero, thereby preventing the growth of microorganisms. The purpose can be achieved with the power consumption of
As another means for preventing the propagation of microorganisms, the same voltage is applied when the treated water is not supplied, and the applied voltage is intermittently made zero, that is, when the treated water is not supplied. There is a means for stopping the voltage application and applying the same voltage to the carbonaceous electrode intermittently when supplying the water to be treated. According to this means, the amount of power corresponding to the voltage application stop time can be saved. Also in this means, the applied voltage does not need to be the same as that at the time of supplying the water to be treated, and a further low power consumption can be achieved as a slightly lower voltage.
[0012]
The carbonaceous electrode is energized by a pair of power supply electrodes located on both ends of the electrode, but the carbonaceous electrode always has the same polarization characteristics unless the polarity of both power supply electrodes is changed. That is, the portion of the carbonaceous electrode close to the positive power supply electrode side is negatively polarized, and the portion of the carbonaceous electrode close to the negative power supply electrode side is polarized positively. In general, sterilization of microorganisms is performed at the positively polarized portion of the carbonaceous electrode, and sterilization hardly occurs on the negative side.
If the polarity of the power feeding electrode is kept the same when the potential is applied when the water to be treated is not supplied, sterilization or reproduction of microorganisms occurs only on the positive polarization side of the carbonaceous electrode, and on the negative polarization side There is a possibility that the growth of microorganisms cannot be suppressed.
Also, since the carbon electrode is consumed mainly only on the anode side, only one surface is unilaterally damaged.
[0013]
Therefore, if the above-mentioned intermittent voltage application is performed while inverting the polarity of the power supply electrode, that is, one power supply electrode is made positive while the other power supply electrode is made negative, and the next voltage application is said one. By making the power supply electrode negative and making the other power supply electrode positive, the positive and negative polarizations appear almost equally on both surfaces of the carbonaceous electrode that is polarized, so that almost all parts of the carbonaceous electrode Microbial propagation can be effectively suppressed.
The ratio between the voltage application time and the voltage non-application time that are intermittently performed when the treated water is not supplied and the value of a constant voltage that is smaller than the applied voltage when the treated water is supplied can effectively prevent microbial growth. Although it can be determined as appropriate within the range, it is desirable that (voltage application time) ≦ (voltage non-application time) for the purpose of saving power.
[0014]
The electrolytic cell used in the method of the present invention is a fixed bed type three-dimensional electrode electrolytic cell, that is, a fixed bed type single electrode type electrolytic cell and a fixed bed type bipolar electrode type electrolytic cell. Since the electrode has an enormous surface area, the contact area between the electrode surface and the water to be treated can be increased, which is advantageous in that the size of the apparatus can be reduced and the efficiency of the electrolytic treatment can be increased.
The electrode in the fixed-bed three-dimensional electrode electrolytic cell of the present invention generally includes a carbonaceous electrode that generates a polarization phenomenon and a power feeding electrode, and the carbonaceous electrode has a shape corresponding to the electrolytic cell to be used, and the fixed bed When using a bipolar type electrolytic cell, the carbonaceous material through which the water to be treated can pass, such as activated carbon, graphite, carbon fiber, etc. having a shape such as a felt shape, a woven fabric shape, a porous block shape, etc. A DC voltage or an AC voltage of 10 Hz or less is applied between the feeding electrodes made of a carbon-based material and made of a porous plate such as a flat plate, an expanded mesh or a perforated plate installed at both ends of the carbonaceous electrode. Thus, it is possible to provide a fixed-bed type bipolar electrolytic cell containing a three-dimensional electrode that can polarize the electrode and form an anode and a cathode at one end and the other end, respectively. In addition, a fixed bed type bipolar electrolytic cell can be obtained by installing and electrically connecting carbonaceous three-dimensional materials functioning as a cathode using means for separating the electrodes so as not to alternately short-circuit each other. .
[0015]
Since the electrode is carbonaceous, it may be oxidized by oxygen gas and dissolved as carbon dioxide gas. In order to prevent this, the positive electrode side of the electrode is coated with a platinum group metal oxide such as iridium oxide or ruthenium oxide on a substrate such as titanium, or platinum such as platinum is coated on a substrate such as titanium. A porous material using a metal electrode usually called an insoluble metal electrode coated with a group metal may be placed in contact so that oxygen generation occurs mainly on the porous metal electrode material.
The average pore diameter of the carbonaceous electrode is preferably 25 to 125 μm. When the carbonaceous electrode is accommodated in an electrolytic bath and treated water, such as drinking water, is treated, the ease of circulation of the treated water or the electrolysis voltage is affected by the properties of the carbonaceous electrode. The pore diameter of the carbonaceous electrode also has a relatively strong influence. If the pore diameter of the carbonaceous electrode is large, the sterilization efficiency of microorganisms is improved because the water to be treated can easily pass through the electrolytic cell without contacting the electrode. descend. On the other hand, if the hole diameter is too small, it becomes difficult for the water to be treated to flow through the carbonaceous electrode, resulting in an increase in the electrolysis voltage and a pressure loss of the liquid flow in the electrolytic cell.
[0016]
According to the inventor's study, when the pore diameter of the carbonaceous three-dimensional electrode is less than 25 μm, the electrolytic voltage is remarkably increased, and when it exceeds 125 μm, the current efficiency (sterilization efficiency) is significantly reduced. Neither can achieve a satisfactory effect (sterilization efficiency). Therefore, when a carbonaceous electrode is used in the electrolytic cell in the method of the present invention, the average pore diameter is preferably 25 to 125 μm as described above. The space ratio [(electrode void volume) ÷ (total electrode volume) × 100 (%)] of the carbonaceous electrode is 20 to 80%, preferably 30 to 60%.
A carbonaceous electrode having a desired aperture diameter can be produced as follows.
For example, when a carbonaceous electrode is formed by sintering carbonaceous particles, the pore diameter of the carbonaceous electrode to be prepared is adjusted by adjusting the particle diameter of the carbonaceous particles to be used. The sintering temperature is 1000-4000 ° C, preferably about 3800 ° C. As another production method, cellulose paper having a predetermined pore size is laminated and graphitized at the same sintering temperature.
[0017]
In addition, when using a monopolar fixed-bed electrolytic cell, one three-dimensional material is placed in the electrolytic cell with or without a diaphragm, or a plurality of three-dimensional materials are in the same electrolytic potential state. In a single electrolytic cell.
Regardless of which form of electrode is used, if there is a gap in the electrolytic cell through which the water to be treated to be treated flows without allowing the liquid to contact the electrode, the treatment efficiency of the water to be treated is reduced. It is desirable to arrange so that the flow of water to be treated in the electrolytic cell does not contact the electrode and does not cause a short path.
Even if the inside of the electrolytic cell is partitioned with a diaphragm to form an anode chamber and a cathode chamber, it is possible to conduct electricity without using the diaphragm, but the diaphragm is not used and the distance between the electrodes is reduced. In this case, for example, a reticulated spacer made of an organic polymer material can be inserted between the two electrodes as an electrically insulating spacer to prevent a short circuit. When using a diaphragm, it is desirable to use a porous film having an opening ratio of 10% or more and 95% or less, preferably 20% or more and 80% or less so as not to disturb the movement of the water to be circulated. The diaphragm must have at least micropores having a diameter that allows the water to be treated to pass through.
[0018]
It is desirable to set the operating conditions of the electrolytic cell having such a configuration so that the sterilization efficiency of microorganisms in the water to be treated is maximized.
When performing electrolytic treatment of water in an electrolytic cell, there are two-pass treatment and circulation treatment, and the sterilization efficiency is higher in the circulation treatment, but for example, it is difficult to carry out the circulation treatment in the electrolytic treatment of drinking water. It becomes processing. In the one-pass treatment, it is desirable to increase the residence time in the electrolytic bath of the water to be treated by reducing the liquid hourly space velocity of the water to be treated as much as possible.
As described above, the electrode potential at the time of supplying the water to be treated is preferably set to a value where the anode potential is lower than +1.2 V (vs. SHE) and more noble than +0.2 V (vs. SHE). In this potential range, little or no generation of oxygen gas and hydrogen gas caused by normal electrolytic reaction at both electrodes is observed, and no consideration is given to the generated gas that does not contribute to sterilization of the microorganism. The sterilization treatment of the water to be treated can be carried out without using waste gas other than the sterilization of the water to be treated and generation of electrolytic gas that inhibits the sterilization treatment.
[0019]
When the water to be treated is treated as described above using the electrolytic cell having such a structure, treated water in which the microorganisms in the water to be treated are sterilized and the amount of microorganisms becomes substantially equal to zero is obtained. However, in the current measurement technique, the number of microorganisms in the treated water cannot be specified unless the microorganisms in the treated water are cultured, and usually takes 2 to 3 days. Therefore, even if the electrolytic cell operation is hindered, an abnormality in the electrolytic cell can be found only after measuring the number of microorganisms after 2 to 3 days. And even if an abnormality can be found after 3 days, the cause of the abnormality cannot be specified only by the data of the number of microorganisms.
Also, for example, in drinking water, an increase in the number of microorganisms is directly linked to the cause of product defects such as diarrhea. If the electrolytic cell operation data is secured at that time, it can be confirmed whether or not the electrolytic cell was operating normally. If the data confirms that the electrolytic cell was operating normally, other causes other than the electrolytic cell can be confirmed. It is possible to prove that there was microbial contamination and propagation.
[0020]
Accordingly, in the method of the present invention, in parallel with the operation of the electrolytic cell, the temperature of the water to be treated, the amount of treated water, the electrical conductivity and the voltage value or current value of the electrolytic cell are continuously measured, and these data are stored in a computer or the like. It is desirable to memorize it. The data is preferably stored continuously for at least 24 hours for 3 days or more, and it is further desirable to be able to immediately investigate the cause when abnormality occurs in the data on the number of microorganisms.
[0021]
Next, although the preferable example of the electrolytic cell which can be used for this invention based on an accompanying drawing is demonstrated, the said electrolytic cell is not limited to these.
FIG. 1 is a schematic longitudinal sectional view showing an example of a monopolar fixed-bed electrolytic cell that can be used as an electrolytic cell of the method of the present invention.
In the lower part of the cylindrical electrolytic cell main body 3 having a tap water supply port 1 in the center of the bottom plate and a tap water outlet 2 in the center of the top plate, a short cylindrical porous body formed of a carbonaceous material is provided. The fixed bed type cathode 4 is accommodated so as to form a slight gap so as not to cause a liquid flow substantially with the inner wall of the main body 3. For example, mesh-shaped platinum is placed on the cathode 4 through a little gap. An anode 5 made of a titanium material plated with a group III metal oxide-coated titanium material or a mesh-like platinum group metal is accommodated. The electrolytic cell body 3 is preferably formed of an electrically insulating material that can withstand long-term use or re-use, and in particular, polyepichlorohydrin, polyvinyl methacrylate, polyethylene, polypropylene, polyvinyl chloride, polyvinyl chloride, which are synthetic resins. Ethylene, phenol-formaldehyde resin, polyacrylonitrile resin and the like can be preferably used.
[0022]
The electrolytic cell main body 3 having such a configuration is installed, for example, in the middle of a water supply pipe or in a faucet of a water supply. From the main water supply port 1 to the main body 3, microorganisms, effective chlorine components, odor of calcium, calcium ions, magnesium ions When the tap water containing iron ions and the like is supplied, the tap water comes into contact with the lower surface of the porous cathode 4, and the surface of the cathode 4 removes the effective chlorine component and the salty odor and responds by reducing the metal ion component and the like. Removal by precipitation with hydroxide or oxide occurs, the sterilization of the microorganisms occurs on the surface of the anode 5, and the purified tap water is taken out from the tap water outlet 2 to the outside of the tank. In addition, since the liquid flow is upward in the present electrolytic cell, hydrogen gas and oxygen gas generated in minute amounts by the electrolytic reaction are easily discharged out of the electrolytic cell together with the liquid flow.
When this electrolyzer is equipped with a mechanism that energizes in conjunction with the supply of tap water, when the supply of tap water is not supplied, the voltage is basically equal to or lower than that at the time of supply of tap water. By applying this, it is possible to achieve power saving and to suppress the growth of microorganisms in the electrolytic cell.
[0023]
FIG. 2 is a schematic longitudinal sectional view showing an example of a bipolar fixed-bed electrolytic cell that can be used as an electrolytic cell of the method of the present invention.
A mesh-shaped feeding anode terminal 13 and feeding cathode terminal 14 are provided in the vicinity of the inner upper end and the lower end of a cylindrical electrolytic cell main body 12 having upper and lower flanges 11, respectively. In the illustrated example, a plurality of sponge-like fixed floors 15 are stacked between the electrode terminals 13 and 14, and between the fixed floors 15 and between the fixed floor 15 and the electrode terminals 13 and 14. Four mesh diaphragms or spacers 16 are sandwiched between the two. Each fixed floor 15 is in close contact with the inner wall of the electrolytic cell main body 12 and does not pass through the fixed floor 15 so that the leakage of tap water flowing between the fixed floor 15 and the side wall of the electrolytic cell main body 12 is minimized. Has been placed.
[0024]
When electricity is supplied to the electrolytic cell having such a configuration while supplying tap water from below as indicated by an arrow, the fixed floor 15 is polarized with the lower surface positive and the upper surface negative as shown in the figure. A porous anode is formed on the lower surface of 15, and the tap water is brought into contact with the porous anode to be sterilized, then taken out above the electrolytic cell and led to a faucet. This electrolytic cell can also be equipped with a voltage applying means when the water supply is not supplied, similar to the electrolytic cell of FIG.
[0025]
FIG. 3 shows another example of a bipolar fixed-bed electrolytic cell that can be used in the method of the present invention. The electrolytic cell is a side of the fixed bed 15 of the electrolytic cell of FIG. The mesh-like insoluble metal electrode 17 is placed in close contact with the polarization side, and the other members are the same as in FIG.
The fixed bed 15 to which the DC voltage is applied has the largest polarization at both ends thereof, and when gas is generated, gas is likely to be generated at both ends. Accordingly, the fastest and most intense oxidation reaction and electrode substrate dissolution reaction occur at the end of the fixed bed 15 that is most strongly positively polarized, that is, the most intensely generating oxygen gas toward the feeding cathode 14. If an insoluble metal electrode 17 is installed in this part as shown in the figure, the oxygen generation overvoltage of the insoluble metal electrode 17 is lower than the overvoltage of the carbon-based material forming the fixed bed 15 and the insoluble metal electrode 17 is insoluble in the fixed bed cathode. Since the metal electrodes are close in distance, most of the oxygen gas is generated from the insoluble metal electrode 17 and the fixed bed 15 hardly comes into contact with the oxygen gas, so that the dissolution of the fixed bed 15 is effectively suppressed. The tap water supplied to the electrolytic cell 12 is treated in the same way as in FIG. 2 to sterilize microorganisms in the tap water. This electrolytic cell can also be equipped with voltage application means when the water supply is not supplied, similar to the electrolytic cell of FIGS.
[0026]
【Example】
Although the Example of to-be-processed water treatments, such as drinking water by the method of this invention, is described below, this Example does not limit the method of this invention.
First, the electrolytic cell of this example was constructed as follows.
A fixed bed (porous graphite with a diameter of 39.5 mm and a thickness of 10 mm made of carbon fiber is placed in the electrolytic cell shown in FIG. 2, which is a flanged cylinder with a height of 75 mm and an inner diameter of 40 mm made of transparent rigid polyvinyl chloride resin. Titanium Carbon Steel Co., Ltd. G-100 S) was sandwiched between six polyethylene resin diaphragms with an aperture ratio of 80% and a diameter of 40 mm and a thickness of 1 mm, and platinum was plated on the upper and lower diaphragms, respectively. The mesh-shaped power feeding anode having a diameter of 38 mm and a thickness of 1 mm and a power feeding cathode were placed in contact with each other to constitute the electrolytic cell of this example.
In addition, 943 microorganisms / milliliter were added to tap water to prepare test water.
The test water is supplied at a rate of 1.5 liters / minute from the lower part of the electrolytic cell, and the apparent current density and electrolytic voltage are adjusted by the direct current power source to the values shown in the following comparative examples and examples. The electrolytic treatment of the test water was performed.
[0027]
[Comparative Example 1]
Maintain the test water supply at 1.5 liters / minute and the apparent current density is 0.2 A / dm. ² After adjusting the electrolysis voltage to 4.3 to 8.8 V (average electrolysis voltage 5.8 V), sampling the treated water taken out of the electrolytic cell over time, and culturing each sample for 3 days, The number of microorganisms was counted, and the relationship between the operation time and the number of microorganisms shown in the graph of FIG. 4 was obtained. The amount of power required for 24 days of operation was DC 0.084 Wh.
[0028]
[Comparative Example 2]
Using the same electrolytic cell as in Comparative Example 1, supplying the water to be treated for 10 minutes, then stopping the supply for 50 minutes, repeating this cycle, energizing under the same electrolysis conditions as in Comparative Example 1 at the time of supply, The power supply was stopped. The treated water to be treated taken out from the electrolytic cell is sampled over time, and after culturing each sample for 3 days, the number of microorganisms is counted, and the relationship between the operation time and the number of microorganisms shown in the graph of FIG. 5 is obtained. It was. The amount of power required for 24 hours of operation was DC 0.015 Wh.
[0029]
[Example 1]
The treated water was treated in the same electrolytic cell and treated water supply and stop cycle as in Comparative Example 2. When supply of water to be treated was stopped, an intermittent application cycle of a voltage in which the applied voltage (electrolytic voltage) was set to zero for 10 minutes and the applied voltage was set to 4.3 to 8.6 V / electrolyzer for 1 minute was repeated.
The number of microorganisms in the treated water to be taken out from the electrolytic bath was counted in the same manner as in the comparative example, and the relationship between the operation time and the number of microorganisms shown in the graph of FIG. 6 was obtained. The amount of power required for 24 hours of operation was DC 0.022 Wh.
[0030]
[Example 2]
The electrolytic treatment of the water to be treated was carried out under the same electrolysis conditions as in Example 1, except that the positive and negative electrodes were inverted every time the applied voltage was intermittently applied when the supply of the water to be treated in Example 1 was stopped. The number was counted and the relationship between the operation time and the number of microorganisms shown in FIG. 7 was obtained. The amount of power required for 24 hours of operation was the same as in Example 1.
[0031]
[Example 3]
Electrolysis of water to be treated under the same electrolysis conditions as in Example 2 except that the applied voltage at the time of stopping the supply of treated water in Example 2 was maintained at 3.4 to 6.5 V / electrolysis tank lower than the applied voltage at the time of supplying treated water. Processing was performed and the number of microorganisms was counted, and the relationship between the operation time and the number of microorganisms shown in FIG. 8 was obtained. The amount of power required for 24 hours of operation was 0.019 Wh.
[0032]
【The invention's effect】
In the method of the present invention, water to be treated containing microorganisms is supplied to an electrolytic cell in which a carbonaceous three-dimensional fixed bed electrode is installed, and the electrodes are polarized by energizing the electrodes, and the microorganisms are applied to the polarized electrodes. In the electrolytic treatment method of the water to be treated for sterilizing the microorganisms by contacting, when the amount of water to be treated to the electrolytic bath is zero, the amount of current supplied to the electrode is compared with that at the time of supplying the water to be treated. A method (claim 1) characterized by reducing the size.
When treated water such as tap water is supplied to the fixed-bed three-dimensional electrode electrolytic cell of the present invention, microorganisms in the treated water come into contact with a carbonaceous electrode to which a potential is applied and are strongly oxidized and reduced on their surfaces. Sterilization takes place when a reaction is received or contacted with a high-potential current, its activity is weakened or it dies.
[0033]
However, the water to be treated is not always supplied to the electrolytic cell used in the method of the present invention, but the water to be treated is not supplied. Therefore, the energization is stopped for much power saving. There are microorganisms that have not yet been sterilized at the beginning of the current stoppage, and these microorganisms are propagated when the power supply is stopped until the water to be treated is supplied again and the power supply is restarted, and are taken out of the electrolytic cell without being sufficiently sterilized. End up.
However, according to the method of the present invention, even when the supply of the treated water is stopped, the amount is smaller than that when the treated water is supplied. Like to do. As a result, the conventional problem of the propagation of microorganisms due to the interruption of energization can be solved and the predetermined purpose of power saving can be achieved at a satisfactory level.
[0034]
As a specific method of reducing the energization amount when the non-treated water is not supplied, a method of intermittently applying the same potential as when the treated water is supplied (Claims 2 and 3), or an applied voltage when supplying the treated water There is a method (Claim 4) that lowers the applied voltage.
In the former method, the electric power at the time of stopping the voltage application of the intermittent voltage application is saved, and the propagation of microorganisms is suppressed by the intermittent voltage application. In particular, when the voltage application direction is reversed every time the applied voltage is intermittently applied (Claim 3), the sterilization or reproductive suppression that occurs in the positively polarized portion of the carbonaceous electrode is reversed. It is possible to wake up on both sides, and to suppress microbial growth more effectively.
In the latter method, the amount of power for the reduced voltage is saved, and even when a voltage is applied to such an extent that no substantial current flows, it is sufficient to suppress the growth of microorganisms. The maximum effect is obtained.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view showing a first example of a monopolar fixed-bed electrolytic cell that can be used as an electrolytic cell of the method of the present invention.
FIG. 2 is a schematic longitudinal sectional view showing an example of a bipolar fixed-bed electrolytic cell that can be used as an electrolytic cell of the method of the present invention.
FIG. 3 is a schematic longitudinal sectional view showing another example of a bipolar fixed-bed electrolytic cell that can be used in the method of the present invention.
4 is a graph showing the relationship between the operation time and the number of microorganisms in Comparative Example 1. FIG.
FIG. 5 is a graph showing the relationship between the operation time and the number of microorganisms in Comparative Example 2.
6 is a graph showing the relationship between the operation time and the number of microorganisms in Example 1. FIG.
7 is a graph showing the relationship between the operation time and the number of microorganisms in Example 2. FIG.
8 is a graph showing the relationship between the operation time and the number of microorganisms in Example 3. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Water supply water supply port 2 ... Water supply water outlet 3 ... Electrolyzer main body 4 ... Fixed bed type cathode 5 ... Anode 12 ... Electrolyzer main body 13 ... Anode terminal 14 ... Cathode terminal for feeding 15 ... Fixed floor

Claims (4)

Water to be treated containing microorganisms is supplied to an electrolytic cell in which a carbonaceous three-dimensional fixed-bed electrode is installed, polarized by energizing the electrodes, and the microorganisms are brought into contact with the polarized electrodes. In the method of electrolytic treatment of water to be treated for sterilizing microorganisms, the amount of current supplied to the electrode when the water to be treated is not supplied to the electrolytic bath is set to the same voltage or smaller than that when the water to be treated is supplied. And how to. The method according to claim 1, wherein energization of the electrode is intermittently stopped when non-treated water is not supplied. The method according to claim 2, wherein the energization direction is reversed every intermittent energization. The method according to claim 1, wherein the applied voltage when the treated water is not supplied is lower than the applied voltage when the treated water is supplied.

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