JPH03224682A - Electrochemical treatment of liquid to be treated - Google Patents

Abstract

PURPOSE:To improve the efficiency of the sterilization of bacteria and the removal of the Ca ions, etc., in cooling water by bringing liquid to be treated into contact with three-dimensional electrodes while passing the liquid in a three-dimensional electrode type electrolytic cell at >=500 Reynolds number, thereby making the electrochemical treatment of the liquid. CONSTITUTION:A meshed anode 3 for power supply and a cathode 4 for power supply are provided near the top and bottom ends in an electrolytic cell body 2. The rear surfaces of respective fixed beds 5 are polarized positive and the front surfaces negative and a potential is generated in and between the fixed beds 5 when the electrodes are energized while the cooling water supplied to the electrolytic cell body 2 is supplied from below. The cooling water passing in the electrolytic cell body 2 comes into contact with the fixed beds 5 polarized positive or negative by the potential, by which the reforming treatments, such as removal of the fungi in the cooling water and sterilization thereof and deposition and removal of the Ca and Mg ions as hydroxides, are executed. The water is taken out of the upper part of the electrolytic cell body 2.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an electrochemical treatment method for sterilizing and improving the performance of liquids to be treated such as cooling water for heat exchangers, and more specifically, By electrochemically treating the cooling water in the cooling tower for the heat exchanger installed in Sheung Wan using a three-dimensional electrode electrolytic cell, bacteria and mold can be sterilized and calcium and other substances in the cooling water can be sterilized. This invention relates to a method for improving performance such as removing magnesium ions.

(Prior art) In recent years, with the increase in the number of buildings such as apartment complexes such as condominiums and buildings where many companies come together, the number of various types of air conditioning equipment installed in these buildings has also increased dramatically. is increasing.

In condominiums and the like where a large number of such heating and cooling facilities are installed, heat exchanger equipment for cooling water of the heating and cooling facilities, such as a heat exchanger tank, is usually installed on the roof of the building.

If this cooling water continues to be used for a long period of time, bacteria and molds will breed, and the concentration of carlasim and magnesium ions in the heat exchange water will gradually increase due to operations to replenish the amount of water decreased due to evaporation.

If the number of bacteria in the heat exchanger cooling water increases, the cooling water will rot, giving off a bad odor and causing corrosion of pipes, and if the concentration of calcium and/or magnesium ions increases, the ions will It will precipitate on the heat exchange surface of the exchanger and significantly reduce the heat exchange efficiency.

In order to prevent these phenomena, various chemicals such as antifungal agents and sedimentation inhibitors have traditionally been added to the cooling water, but these chemicals are often relatively expensive and must be periodically administered to maintain their effectiveness. The chemicals may accumulate and remain in the cooling water, and the chemicals may react with compounds in the cooling water, causing unexpected adverse effects on the cooling water to be treated.

(Problems to be Solved by the Invention) As described above, the conventional treatment methods for various liquids to be treated, including cooling water for heat exchangers, are mainly based on the injection of chemicals, and this method increases the cost of chemicals. Furthermore, the added chemicals may remain in the liquid to be treated and cause problems other than those caused by mold, bacteria, or calcium and magnesium ions, so there is a need for a method for treating the liquid to be treated that does not rely on the use of chemicals.

(Object of the Invention) An object of the present invention is to provide a method for treating various liquids to be treated, particularly cooling water for heat exchangers, relatively easily and without using chemicals.

(Means for Solving the Problems) The present invention provides a method for supplying a liquid to be treated to a three-dimensional electrode type electrolytic cell, and flowing the liquid to be treated through the electrolytic cell at a Reynolds number of 500 or more. This is an electrochemical treatment method for a liquid to be treated, in which the liquid to be treated is electrochemically treated by bringing the liquid into contact with the three-dimensional electrode. In addition, in the present invention, since a substantial electrochemical reaction may not occur on the surface of the electrode etc., the tank used in the present invention should be called an electrochemical treatment tank, but it will be called an electrolytic tank according to the -g designation. .

The present invention will be explained in detail below.

In the present invention, a liquid to be treated such as cooling water for a heat exchanger is supplied to a three-dimensional electrode type electrolytic cell so that the Reynolds number of the liquid to be treated in the electrolytic cell is 500 or more, and a direct current is supplied to the electrolytic cell. This method is characterized in that a voltage is applied to sterilize the cooling water for the heat exchanger, etc., with or without electrolytic gas.

The reason why the heat exchanger cooling water is sterilized or its performance is modified by the application of the DC voltage is not necessarily clear, but it can be inferred as follows.

Cooling water for heat exchangers has a moderate temperature and is an environment in which mold, bacteria, etc. can easily grow.

According to the present invention, when a DC voltage is applied to cooling water for a heat exchanger, etc., mold and bacteria in the cooling water are transferred to the anode or cathode of a three-dimensional electrode type electrolytic cell or to the three-dimensional electrodes such as dielectrics and particles described later. It is thought that when it comes into contact with these substances, it undergoes a strong oxidation-reduction reaction on their surfaces, weakening its activity or killing itself. Therefore, it is possible to produce the same bactericidal or antifungal effect without using conventional bactericidal or antifungal agents.

Furthermore, tap water contains calcium ions and magnesium ions, and blockage of pipes due to precipitation of these ions on the inner walls of tap water pipes is a major problem, but in many cases, the use of heat when tap water is used as a water source The cooling water for the exchanger also contains calcium ions and magnesium ions, and these ions tend to adhere to the heat exchange surface of the heat exchanger, and if they adhere, they reduce the heat exchange efficiency between the cooling water and the water to be cooled. Calcium ions and magnesium ions in the heat exchanger cooling water that degrade the performance of the heat exchanger can be removed from the cathode of the three-dimensional electrode electrolytic cell and the three-dimensional snow shovel when the cooling water is electrochemically treated. It is reduced and precipitated on the cathode surface as caloxic hydroxide 11 and magnesium hydroxide, which are removed from the cooling water and do not precipitate on the heat exchange surface and reduce the heat exchange efficiency.

When the treated liquid supplied to the three-dimensional electrode type electrolytic cell is in a laminar flow, there is little lateral liquid movement and the treated liquid passes through the electrolytic cell without making sufficient contact with the surface of the dielectric or the like. Sometimes. In particular, bacteria contained in the liquid to be treated are not ions in a chemical reaction (they will not die unless they come into contact with the electrode surface).

Therefore, the liquid to be treated is made into a turbulent flow having a Reynolds number of 500 or more so that the bacteria in the liquid to be treated can sufficiently come into contact with the electrode surface, and the liquid to be treated is passed through the electrolytic cell while being sufficiently moved in the lateral direction. . In addition, Reynolds number and fluid velocity) ×
It is expressed as (inner diameter of wave path)/(kinetic viscosity coefficient of fluid), and the larger this value is, the greater the degree of turbulence in the fluid.

In the present invention, the value of the DC voltage applied between the anode and cathode is not particularly limited, and can be used in electrolytic treatment where current flows and gas generation occurs on the electrode surface, and in electrolytic treatment where no current flows and gas generation does not occur on the electrode surface. Any method may be used, but when carrying out the method of the present invention, it is desirable to conduct the electrolytic treatment while passing an electric current and generating a small amount of gas in order to confirm that the treatment is actually being carried out efficiently. The preferred anode potential is +0.2 to +1.4V (vs, 5HE), and the preferred cathode potential is -1.2V (vs, 5flE). It is also possible to perform electrochemical treatment of the liquid.

The gases generated by water electrolysis, that is, oxygen gas and hydrogen gas, are usually generated at a mixing ratio within the explosive limit, so if a relatively large DC voltage is applied and gas is generated, air must be used to avoid the risk of explosion. For example, by separating the electrolytic gas generated at the outlet of the electrolytic cell and diluting the separated electrolytic gas with air, the electrolytic gas concentration can be reduced to 4.
Although it is possible to install a means for diluting the water to below % by volume, the electrolytic cell that processes cooling water for heat exchangers, etc. has a relatively small capacity and generates a small amount of gas, so the gas separation means is not installed. You can.

The electrolytic cell used in the method of the present invention is a bipolar fixed bed three-dimensional electrode electrolytic cell. In the treatment of a liquid to be treated such as cooling water for a heat exchanger according to the present invention, the treatment efficiency increases as the number of opportunities for the liquid to be treated to come into contact with electrodes or dielectrics or particles described below increases. Therefore, using a multi-electrode fixed bed three-dimensional electrode electrolytic cell with a large surface area of electrodes, etc. can increase the processing efficiency compared to using other electrolytic cells. It is advantageous in that the required equipment size can be smaller than other electrolytic cells.

The three-dimensional electrode in the three-dimensional electrode electrolytic cell of the present invention is made of a porous material through which the liquid to be treated can pass, such as granular, spherical,
Made of carbon-based materials such as activated carbon, graphite, and carbon fibers that have a shape such as felt, woven fabric, porous block, or solid body with many through holes, or nickel, copper, stainless steel, etc. that have the same shape. It is preferable to consist of a plurality of dielectric bodies made of metal materials such as iron and titanium, and materials coated with noble metals, and the three-dimensional electrodes are placed in a DC electric field and installed at both ends. A DC voltage is applied between the anode and cathode for power feeding, which is made of a porous plate such as a flat plate, an expanded mesh shape, or a barforated plate shape, to polarize the dielectric material, one end and the other end of the dielectric material, respectively. Positive and negative charges are formed and polarized.

In addition, separate from the power supply anode and cathode, three-dimensional materials that function as an anode or a cathode are installed alternately so as not to short-circuit and are electrically connected to a multi-electrode fixed bed electrolytic cell. It can be done. In addition, when the aforementioned solid body having a large number of through holes is used as a three-dimensional electrode, the aperture ratio should be 10% or more and 95% or less, preferably 20% or more and 80% or more, so as not to obstruct the movement of the circulating cooling water. %
It is preferable that the diameter of the through-hole is as follows, and the opening diameter of the through-hole is a micropore having a diameter that allows the liquid to be treated to pass therethrough.

When using a carbon-based material such as activated carbon, graphite, or carbon fiber as the dielectric and treating cooling water while generating oxygen gas from the anode, the dielectric is oxidized by the oxygen gas and dissolved as carbon dioxide gas. It becomes easier. In order to prevent this, a porous material that is usually used as an insoluble metal electrode is coated with a platinum group metal oxide such as iridium oxide or ruthenium oxide on a base material such as titanium on the anodic polarization side of the dielectric. They may be placed in contact so that oxygen evolution occurs primarily on the porous material.

When it is intended to lower the voltage by bringing the anode and cathode close to each other between the dielectric material or the power supply anode and cathode, use an electrically insulating spacer such as a mesh spacer made of an organic polymer material to prevent short circuits. Preferably, it is inserted.

If there is a relatively large gap in the electrolytic cell through which the liquid to be treated flows, through which the liquid to be treated can flow without coming into contact with the dielectric, the anode, or the cathode, the processing efficiency of the liquid to be treated will decrease. It is desirable that the dielectric material and the like be arranged so that the flow of the liquid to be treated in the electrolytic cell is not short-circuited.

A three-dimensional electrode electrolytic cell with such a configuration is installed close to the location where the liquid to be treated needs to be treated, depending on the type of liquid to be treated, and is particularly suitable for cooling water for heat exchangers. is installed close to a heat exchanger installed on the roof ring of a building or condominium, and after circulating a part of the cooling water in the heat exchanger and performing treatment such as sterilization in the electrolytic tank etc. It can be used by returning it to the heat exchanger.

In addition, in the electrolytic cell of the present invention, a leakage current occurs in the electrolytic cell, and the leakage current flows from the electrolytic cell through the liquid to be treated to other metal members, such as a heat exchanger, and causes electrochemical damage such as elution to the member. May cause severe corrosion. Therefore, a member with higher conductivity than the cooling water is installed at the back of the electrode where the power feeding anode and cathode do not face each other in the electrolytic cell and/or in the inlet/outlet piping of the electrolytic cell so that one end thereof can be grounded to prevent leakage. Can cut off current.

In addition, solid impurities may be mixed into the cooling water for heat exchangers while flowing through the pipes, and in addition to the electrochemical treatment described above, in order to remove these impurities, treatment is performed before and after the heat exchanger, preferably before the heat exchanger. It is recommended to install a filter.

Next, a preferred example of an electrolytic cell that can be used in the present invention will be described based on the accompanying drawings, but the electrolytic cell that can be used in the method of the present invention is not limited to this electrolytic cell.

FIG. 1 is a schematic vertical sectional view showing an example of a bipolar fixed bed electrolytic cell that can be used as the electrolytic cell of the present invention, and FIG.
FIG. 2 is a schematic diagram showing a state in which the electrolytic cell shown in the figure is installed in front of a heat exchanger.

A mesoche-shaped power feeding anode 3 and a power feeding cathode 4 are provided near the upper and lower ends of a cylindrical electrolytic cell body 2 having flanges 1 on the upper and lower sides, respectively. Electrolytic cell body 2
is preferably made of an electrically insulating material that can withstand long-term use or repeated use, and is particularly made of synthetic resins such as polyepichlorohydrin, polyvinyl methacrylate, polyethylene, polypropylene, polyvinyl chloride, polyethylene chloride, and phenol-formaldehyde. Resins etc. can be preferably used. The power feeding anode 3 that provides a positive DC voltage is made of, for example, a carbon material (such as activated carbon, charcoal, coke,
coal, etc.), graphite materials (e.g. carbon fiber, carbon cloth, graphite, etc.), carbon composite materials (e.g. carbon mixed with metal powder and sintered), activated carbon fiber nonwoven fabrics (e.g. KE-1000 felt, Toyobo Co., Ltd.), or materials that support platinum, platinum, palladium or nickel, as well as dimensionally stable electrodes (platinum group oxide coated titanium materials), platinum coated titanium materials, nickel materials, stainless steel materials, iron materials, etc. It is formed. The power supply cathode 4 which faces the power supply anode 3 and applies a negative DC voltage is made of, for example, platinum, stainless steel, titanium, nickel, Hastelloy, graphite, carbon material, mild steel, or a metal material coated with a platinum group metal. ing.

A plurality of fixed beds 5, three in the illustrated example, are stacked between the two power feeding electrodes 3.4, and between the fixed beds 5 and between the fixed bed 5 and both the power feeding electrodes 3.4. Four porous diaphragms or spacers 6 are sandwiched between them. Each fixed bed 5
is in close contact with the inner wall of the electrolytic cell body 2, does not pass through the inside of the fixed bed 5, and is arranged so that the leakage flow of the coolant flowing between the fixed bed 5 and the side wall of the electrolytic cell body 2 is minimized. .

When a diaphragm is used, a woven fabric, an unglazed plate, a particle sintered plastic, a perforated plate, an ion exchange membrane, etc. are used as the diaphragm, and a woven fabric, a perforated plate, a mesh, etc. made of an electrically insulating material are used as the spacer. A rod-shaped material is used.

The electrolytic cell 2 having such a configuration is installed in a heat exchanger 1 on the roof of a building 11 such as a building or an apartment, as shown in FIG.
2 and the filter 13. Each floor of the building 11 is equipped with a predetermined heating and cooling system! The heat exchanger cooling water that has been cooled by contacting the fins 14 of the heat exchanger 12 is supplied to the air conditioning equipment through the cooling water supply pipe 15 to cool the circulating water used in the equipment. 16, the cooling water is circulated to the rooftop through a cooling water recovery pipe 17, and after passing through a filter 13 to remove solid impurities, it is supplied to the electrolytic cell 2.

When the cooling water supplied to the electrolytic cell is supplied from below as shown by the arrow in FIG. 1 and electricity is supplied, each of the fixed beds 5
As shown in the figure, the lower surface is polarized positively and the upper surface is polarized negatively, and a potential is generated within the fixed bed 5 and between the fixed beds 5, and the cooling water flowing through the electrolytic cell is polarized positively or negatively by this potential. The cooling water is brought into contact with the bed 5 and subjected to reforming processes such as sterilization of mold and bacteria in the cooling water and removal of precipitated calcium and magnesium ions as hydroxides, and then taken out from above the electrolytic cell 2.
As shown in FIG. 2, the cooling water is circulated to the heat exchanger, and treatment of the cooling water for the heat exchanger is continued in the same manner.

FIG. 3 shows another example of a bipolar fixed bed type electrolytic cell that can be used in the present invention. A mesh-like insoluble metal material 7 is installed in close contact with the side to be positively polarized, and since the other members are the same as those in FIG. 1, they are given the same reference numerals and their explanation will be omitted.

When gas is generated in the fixed bed 5 to which a DC voltage is applied, the anodic polarization side of the fixed bed 5 where oxygen gas is generated is consumed and deteriorated. As shown in the figure, if the insoluble metal material 7 is installed in this part, most of the oxygen gas will be removed from the insoluble metal material 7 because the overvoltage of the insoluble metal material 7 is lower than the overvoltage of the carbon-based material forming the fixed bed 5. Since the fixed bed 5 hardly comes into contact with oxygen gas, the dissolution of the fixed bed 5 is effectively suppressed. The heat exchanger cooling water supplied to the electrolytic cell 2 is treated and sterilized in the same manner as in FIGS. 1 and 2.

FIG. 4 shows another example of a bipolar fixed bed electrolytic cell that can be used in the present invention.

A mesoche-shaped power feeding anode 23 and a power feeding cathode 24 are provided near the upper and lower ends of the cylindrical electrolytic cell body 22 having flanges 21 on the top and bottom, respectively. The electrolytic cell body 22 is preferably made of an electrically insulating material, particularly a synthetic resin, which can withstand long-term use or repeated use.

Between the repowering electrodes 23 and 24, there are a large number of fixed bed forming particles 25 made of a conductive material such as a carbon-based material and a smaller number of insulating particles 28 made of synthetic resin, for example, than the fixed bed forming particles 25. are almost evenly mixed. The insulating particles 28 have a function of preventing the power feeding anode 23 and the power feeding cathode 24 from being completely short-circuited.

When the electrolytic cell having such a configuration is energized while supplying cooling water for the heat exchanger from below as shown by the arrow, each of the fixed bed forming particles 25 becomes negative on the power feeding anode 23 side and negative on the power feeding cathode side. The 24 side is positively polarized and functions as a three-dimensional electrode with a huge surface area, and in the same way as the electrolytic cells shown in Figures 1 and 3, it can sterilize mold and bacteria in the cooling water and remove calcium and magnesium ions. The electrolytic cell is taken out from above the electrolytic cell after being subjected to a reforming process such as the following.

(Example) Examples of cooling water reforming treatment for heat exchangers according to the method of the present invention will be described below, but the examples are not intended to limit the present invention.

The electrolytic cell shown in Figure 1, which is made of transparent hard polyvinyl chloride resin and has a flanged cylindrical shape with a height of 400 mm and an inner diameter of 60 mm, is installed between the cooling tower and filter equipment as shown in Figure 2. It was installed in Inside the electrolytic cell, 15 fixed beds made of carbon fiber with a diameter of 600 fl and a thickness of 10 mm were sandwiched between 16 polyethylene resin diaphragms with an opening ratio of 80% and a diameter of 600 μ and a thickness of 1.2 mm. The diaphragms at both ends are made of titanium with platinum coating on the surface, diameter 58.
A mesh-shaped power feeding anode and a power feeding cathode having a thickness of 0 mm and a thickness of 1.0 mm were placed in contact with each other.

The cooling water for the heat exchanger was supplied to the electrolytic cell at a rate of 10 tons/l, and the electrolysis voltage shown in Table 1 was applied between the power supply electrodes to treat the cooling water. Table 1 summarizes the presence or absence of generated gas as determined by visual observation during the treatment operation, the concentration of calcium and magnesium ions in the cooling water before and after passing through the electrolytic cell, the number of bacteria, and the amount of power consumed.

From Table 1, it can be seen that the concentration of calcium and magnesium ions and the number of bacteria in the cooling water for heat exchangers are significantly reduced by being treated in the electrolytic bath.

After 30 days, the electricity supply was stopped, the electrolytic cell was disassembled, and the condition of the fixed bed was observed, and no change was observed.

Used between the electrolytic cell main body and the power supply electrode of Example 1, and between the power supply electrode, graphite particles with a particle size of 5 to 10 mm and insulating particles made of hard polyvinyl chloride resin with a particle size of 5 to 10 am. The mixed particles uniformly mixed at a weight ratio of 4:1 were filled to form an electrolytic cell shown in FIG. 4.

This electrolytic cell was installed close to the cooling tower in the same manner as in Example 1, and the cooling water for the heat exchanger cooling tower was treated under the same conditions. Table 2 summarizes the results of the calcium and magnesium ion concentrations, number of bacteria, and power consumption of the cooling water.

It can be seen from Table 2 that the calcium and magnesium ion concentrations and the number of bacteria in the cooling water for heat exchangers are significantly reduced by treatment in the electrolytic bath.

Using the electrolytic cell of Example 1, the effect on the sterilization rate and the removal rate of carlasim and magnesium ions was investigated by varying the Reynolds number of the cooling water supplied to the heat exchanger tube. The results are shown in Table 3. The number of bacteria in the cooling water at the inlet of the electrolytic cell was approximately 413,000 bacteria/l, and the total amount of carlasim and magnesium ions was 33 ppm.

From Table 3, when the Reynolds number is less than 500, the sterilization rate is "[(number of bacteria at the inlet) - (number of stones at the outlet)] ÷ (number of bacteria at the inlet')" It can be seen that a considerable amount of bacteria remains in the treated liquid, but when the Reynolds number reaches 500 or more, the treated liquid is almost completely sterilized and taken out from the electrolytic cell.Also, the callasim and magnesium ions of the treated liquid are The concentration is also 33p
It can be seen that the amount decreases from pm to less than 10 ppm.

(Effects of the Invention) The method of the present invention involves supplying a liquid to be treated, such as cooling water for a heat exchanger, to a bipolar three-dimensional electrode type electrolytic cell so that the Reynolds number is 500 or more; A method for treating a liquid to be treated (claim 1), in which the liquid to be treated is electrochemically treated without sufficiently contacting the original electrode.

When a liquid to be treated such as cooling water for a heat exchanger is treated according to the present invention (claim 2), bacteria and mold can be sterilized without using a bactericide or a fungicide, and the liquid to be treated can be By removing the calcium and magnesium ions contained therein, it is possible to effectively prevent the ions from depositing on the heat exchange surface and the like, thereby reducing the heat exchange efficiency.

The present invention is effective when the liquid to be treated is cooling water for heat exchange, and the method of the present invention easily performs two types of reforming treatment: sterilization of the cooling water for heat exchange and reduction of carlasim ions, etc. It becomes possible to do so.

Furthermore, the electrolytic gas generated by the method of the present invention is a mixed gas of oxygen gas and hydrogen gas within the explosive limit, and there is a risk of explosion if the process is carried out in a closed system. Therefore, the risk of explosion can be avoided by providing means for separating the gas generated by electrolysis and means for diluting the separated gas near the outlet of the electrolytic cell (Claim 3).

Further, in the electrolytic cell of the present invention, a leakage current occurs in the electrolytic cell, and the leakage current flows into other metal members, such as a heat exchanger, and may cause electrochemical corrosion such as elution in the member. In order to prevent this, it is preferable to cut off the leakage current by installing a member with higher conductivity than the cooling water at an appropriate location where the power feeding anode and cathode do not face each other so that one end of the member can be grounded ( Item 4).

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an example of a bipolar fixed bed electrolytic cell that can be used as the electrolytic cell of the present invention, and FIG. 2 is a schematic diagram showing the installation situation of the electrolytic cell shown in FIG. FIG. 3 is a longitudinal cross-sectional view showing an example of another multi-polar fixed bed type electrolytic cell, and FIG. 4 is a longitudinal cross-sectional view showing an example of still another multi-polar fixed bed electrolytic cell. 1.21・ 3.23・ 5 ・ ・ ・ 7 ・ ・ ・ 11.
・・Spacer-insoluble metal material building 12・・・Heat exchanger 13・ 15・ 17・ 25・・・Filter 14・・Fin・Plumbing for cooling water supply 6・・Pump・Fixed floor for piping for cooling water recovery Forming particles 28... Insulating particles Figure 2 Figure 3 Figure 4

Claims (4)

[Claims] (1) The liquid to be treated is supplied to a three-dimensional electrode type electrolytic cell, and the liquid to be treated is brought into contact with the three-dimensional electrode while flowing through the electrolytic cell at a Reynolds number of 500 or more. An electrochemical treatment method for a liquid to be treated. (2) The method according to claim 1, wherein the liquid to be treated is cooling water for heat exchange. (3) The method according to claim 1 or 2, wherein an electrolytic cell is provided with means for separating gas generated by electrolysis and means for diluting the separated gas near its outlet. (4) A member with higher conductivity than the liquid to be treated can be grounded at one end on the back of the power supply electrode where the power supply anodes and cathodes in the three-dimensional electrode type electrolytic cell do not face each other and/or inside the inlet/outlet piping of the electrolytic cell. The method according to any one of claims 1 to 3, wherein the method is performed by installing the method in a.