JPH05200387A - Treatment of water to be treated and treating device - Google Patents

Abstract

PURPOSE:To surely and easily remove an available chlorine component from water to be treated such as potable water having odor of bleaching powder by supplying the water to be treated which has the available chlorine component to a bipolar type electrolytic cell provided with a fixed bed type porous cathode, decomposing or reducing the available chlorine component on the cathode. CONSTITUTION:A power feeding meshy anodic terminal 3 and a power feeding meshy cathodic terminal 4 are provided near to the upper end and near to the lower end in the inside of an electrolytic cell main body 2. Spongy fixed beds 5 are laminated between the electrode terminals 3, 4. Further meshy diaphragms or spacers 6 are held between the fixed beds 5 and between the fixed beds 5 and the electrode terminals 3, 4. When electric current is supplied while supplying water to be treated to the electrolytic cell 2 from the lower part, the rear of the fixed beds 5 are polarized to positive and the upper surfaces thereof are polarized to negative. Porous cathodes are formed on the upper surfaces of the fixed beds 5. The water to be treated is brought into contact with the porous cathodes. Available chlorine component such as hypochlorite ion and gaseous chlorine is decomposed or reduced and removed. Thereafter the decomposed or reduced substance is taken out from the upper part of the electrolytic cell 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for reforming treated water such as drinking water, and more particularly to drinking water supplied from the water supply for domestic use, commercial use, etc. It relates to a method and a device for modifying the taste of the drinking water by electrochemically treating it using a bath.

[0002]

2. Description of the Related Art Drinking water is supplied to households, restaurants, etc. through water supply after sterilizing the water stored in a water source such as a reservoir. The sterilization of drinking water is generally treated with chlorine gas, but sterilization of drinking water is relatively good according to the chlorine treatment, while foreign substances are mixed in the treated drinking water due to the effect of residual chlorine. Such a discomfort occurs and the mellowness of natural water is impaired. Drinking water is directly linked to human health,
It is indispensable to sterilize the bacteria contained therein and prevent the growth of mold, that is, kill and remove microorganisms, and the above-mentioned chlorine method is the mainstream as the sterilization and mold prevention method. However, in tap water sterilization in urban areas, the raw water, such as river water and lake water, is contaminated with various organic substances and more chlorine is added than is necessary to kill microorganisms.Therefore, organic halides, hypochlorite ions and residual chlorine are added. It has a harmful effect of producing effective chlorine components such as. In order to eliminate the above-mentioned drawbacks caused by the chlorine method,
Sterilization methods other than the chlorine method have been proposed.

For example, there has been proposed a method of reforming the drinking water by subjecting it to ozone addition treatment or activated carbon adsorption treatment. However, when the drinking water to be treated is, for example, water from a water purification plant, the treatment amount is enormous. is there. In addition, even if treated in a water purification plant, there is a problem that the microorganisms will regenerate before reaching the faucet at the end of the water pipe, and there is currently no method superior to the chlorine addition treatment. However, as mentioned above, drinking water that has a taste close to natural water that is harmless to the human body and can substitute for chlorine treatment that easily causes hypochlorite ions, etc. A treatment method is requested. Further, in addition to drinking water, there are various kinds of domestic water that are indirectly ingested into the body such as treated water for foods, and a method other than chlorine treatment is desired for these domestic water.

[0004]

As described above, the conventional reforming treatment method for drinking water or the like is mainly based on the chlorine method, in which hypochlorite ion is generated or chlorine gas remains. There is a drawback that so-called chlorine odor is generated and the taste of drinking water after treatment becomes bad.To remove this chlorine odor, there is a method of adsorbing hypochlorite ion, which is the source of the chlorine odor, to activated carbon or the like. It is used. However, in this method, there is a fatal drawback that fine powder of activated carbon is mixed into drinking water after treatment, and also complicated operation such as replacement of activated carbon is required, and complete removal of chlorinated odor cannot be achieved. Sometimes.

[0005]

It is an object of the present invention to electrochemically treat drinking water or the like containing an effective chlorine component to obtain almost no chyle odor component such as hypochlorite ion which deteriorates taste sensation mixed in the drinking water or the like. It is an object of the present invention to provide a method and an apparatus for supplying drinking water or the like which is completely decomposed and removed and has a mellow taste.

[0006]

According to the method of the present invention, water to be treated containing an effective chlorine component is supplied to a bipolar electrode cell equipped with a porous fixed bed type cathode, and the above-mentioned cathode is used. A method for treating water to be treated, which comprises decomposing or reducing an effective chlorine component to reform the water to be treated, wherein the device of the present invention has a flow passage cross-sectional area substantially equal to that of the water to be treated Of a fixed bed type porous cathode having the same cross-sectional area, is supplied with the water to be treated containing an effective chlorine component, and decomposes or reduces the effective chlorine component on the cathode. An apparatus for treating water to be treated, which comprises a tank. Incidentally, in the present invention, since a substantial electrochemical reaction may not occur on the surface of the electrode or the like, the tank used in the present invention should be called an electrochemical treatment tank, but it is called an electrolytic tank according to the general name.

The present invention will be described in detail below. The present invention is
In order to remove the chlorine odor contained in drinking water, treated water such as drinking water or food treatment water containing the effective chlorine component that is the source of chlorine odor can be subjected to uncertain and complicated operations such as activated carbon treatment. Instead, it is possible to electrochemically decompose the effective chlorine component, especially hypochlorite ion, by supplying it to an electrolytic cell containing a porous bipolar fixed-bed cathode and bringing it into sufficient contact with the porous cathode. Characterize. The treated water treated by the method and apparatus of the present invention is intended for drinking water or food treatment water that is ingested by the human body, and the drinking water is a tap water that flows through tap water and is poured out from a tap of a water supply such as a home or a restaurant. Including water and the like, the food treatment water includes water for washing fresh food and water contained in water-containing food such as tofu.

Upon contact with the porous cathode, the hypochlorite ion which is the main component of the effective chlorine component in the water to be treated is decomposed into chlorine ion and water according to the following formula. ^{ClO - + 2 H + + 2} e - → Cl - H 2 O further residual chlorine in the water to be treated is reduced to chloride ions according to the following formula in contact with the cathode. ^{_{Cl 2 + 2 e - → 2}} Cl - is generally necessary to cause substantial electrolytic reaction by applying a current for electrons are consumed in these electrochemical reactions. However, if the amount of effective chlorine component contained in the water to be treated is a very small amount, that is, several ppm, and there is an electric charge staying on the cathode, the water to be treated can be sufficiently treated. Therefore, in the treated water treatment according to the present invention, it may or may not be accompanied by gas generation, but when gas generation occurs, there is a possibility that a change in the treated water may occur and a taste change or the like due to the change may occur. It is preferable to apply a voltage so that a cathode potential that does not generate a specific gas, that is, a cathode potential of -0.1 to -1.0 V (vs.SHE) is generated.

When the process is performed while applying a voltage that does not substantially generate gas, the amount of current flowing is substantially equal to zero, and the amount of power consumed is also equal to zero, so that the conventional power cost is maintained at approximately zero. It is possible to carry out the reforming treatment of the water to be treated such as drinking water with almost the same efficiency as the chlorine addition method and the electrolysis method with high power consumption. The tap water contains calcium ions and magnesium ions, which are one of the causes of the bad taste of drinking water and the like, but the ions become porous when the drinking water or the like is electrochemically treated. It is deposited as calcium hydroxide or magnesium hydroxide on the cathode and is removed from drinking water or the like to improve the taste of the drinking water or the like.

[0010] In the drinking water and the food processing water, trace amounts of ions such as calcium and dissolved substances exist as clusters having hydration water around them, and this hydration water is mellow for drinking water and the like. It is one of the causes to lose.
When a voltage is applied to the drinking water containing the water of hydration according to the present invention such that a substantial electrolytic reaction does not occur, the ions in the drinking water migrate or move at high speed in the liquid according to the potential gradient. The clusters cannot move and the huge clusters are destroyed, or as described above, the ions having hydration water are destroyed by the porous cathode etc., and the number of the hydration water is greatly reduced, and the effect of modifying drinking water etc. It is thought to occur.

In the treatment of water to be treated according to the present invention, the treatment efficiency increases as the water to be treated contacts the cathode more frequently. Therefore, the electrolytic cell according to the present invention is a bipolar electrode type electrolytic cell in which a porous fixed bed type cathode is installed. In this bipolar electrode electrolytic cell, since the porous electrode of the electrolytic cell has an enormous surface area, it is possible to increase the contact area between the electrode surface and the water to be treated, thereby reducing the device size and electrochemically. It is advantageous in that the processing efficiency can be increased.

The bipolar electrolytic cell of the present invention is an electrolytic cell that uses a porous dielectric material that is polarized in the positive and negative electrodes, and an electrolytic cell in which an anode material and a porous cathode material that independently function as an anode and a cathode are alternately installed. Including a tank. In the former electrolytic cell, one end of the porous dielectric is polarized to form a porous cathode, and in the latter, the porous cathode itself functions as a cathode. These porous cathodes have a shape according to the electrolytic cell to be used both when using a porous dielectric electrode and when using a single porous cathode.
A porous material permeable to the water to be treated, for example, activated carbon having a shape such as a granular shape, a spherical shape, a felt shape, a woven cloth shape or a porous block shape, or a carbon-based material such as graphite or carbon fiber, or having the same shape. Preferably, a granular, spherical, fibrous, felt-like, woven-like, or porous block formed from a metal material such as nickel, copper, stainless steel, iron, or titanium, and a material obtained by coating the metal material with a noble metal. It is preferable to use a dielectric or sponge-like dielectric (or a single porous cathode), but a metal sintered body such as nickel may be used.

In order to carry out the treatment of the water to be treated according to the present invention, it is necessary that the water to be treated is in contact with the porous cathode as much as possible. It is necessary that the residence time in the cathode be as long as possible, in other words, that the water to be treated permeates and permeates into the inside of the porous cathode as much as possible. In order to allow the water to be treated to permeate into the porous cathode, it is desirable that the material of the cathode has a low conductor resistance and a high overvoltage. In other words, if the conductor resistance is small, the resistance at the time of infiltration into the interior is small, so that it easily penetrates. If the overvoltage is small, the reaction takes place only on the surface, and the meaning of using the porous cathode is diminished.

The carbon-based material is a material effectively used in the present invention which satisfies this requirement, that is, the requirement that the conductor resistance is small and the overvoltage is large. Further, since the carbonaceous material has no toxicity and does not form ions or hydroxide thereof, it is preferable for treating water to be treated such as drinking water that is ingested into the body. In addition, the surface area is enormous, and the chances of contact with effective chlorine components are very large, and the treatment efficiency is greatly increased. Further, the carbon-based material is inexpensive, and unlike other metal material electrodes, corrosion does not occur even when the electrolysis is stopped, which is advantageous in terms of economy and operability. The aperture ratio of these porous cathodes should not interfere with the movement of the water to be treated.
10% or more and 95% or less, preferably 20% or more and 80% or less, and it is preferable that the opening diameter of the through-hole is a micropore having a diameter that allows water to be treated to permeate.

The anode used in the present invention hardly decomposes or reduces the available chlorine component. Therefore, the shape of the water to be treated does not need to be in contact with the anode and is not particularly limited in the case of an anode which functions independently, but when the water to be treated flows through the anode, the shape does not have to be porous. Although it is good, it is preferable to make it in a mesh shape in order to facilitate the flow of the water to be treated. When a porous anode is used as the anode, its porosity is preferably smaller than that of the cathode (the anode current density is smaller than the cathode current density). The material of the anode is graphite material, carbon material,
Platinum group metal oxide coated titanium material (dimensional stability electrode), platinum coated titanium material, nickel, etc. can be used.

In the electrolytic cell of the present invention, it is desirable not to form the cathode chamber and the anode chamber by partitioning the cathode and the anode with the diaphragm, but the present invention does not exclude the use of the diaphragm, and the weaving is not necessary. A diaphragm such as a cloth, a biscuit plate, a particle-sintered plastic, a perforated plate, or an ion exchange membrane may be used. When it is intended to reduce the voltage by bringing both electrodes close to each other, it is preferable to insert, for example, a mesh spacer made of an organic polymer material as an electrically insulating spacer in order to prevent a short circuit between both electrodes. When the liquid to be treated supplied to the electrolytic cell is a laminar flow, it may pass through the electrolytic cell without sufficiently contacting the surface of the porous cathode. The liquid to be treated not only contains no space inside, but is also allowed to pass through the electrolytic cell while being sufficiently laterally moved as a turbulent flow having a Reynolds number of 500 or more. preferable.

When the water to be treated is treated using such an electrolytic cell, in many cases, the effective chlorine component is sufficiently removed by passing it through the electrolytic cell only once, that is, by a transient treatment (one-pass treatment). Can be performed, and the operation efficiency is improved. Further, in the electrolytic cell of the present invention, a leakage current is generated in the electrolytic cell, and the leakage current flows from the electrolytic cell through the water to be treated into another metal member, for example, a water pipe, and electrochemically elutes in the member. May cause corrosion. Therefore, a member having higher conductivity than the water to be treated is installed such that one end thereof can be grounded in the electrode back surface portion where the two electrodes in the electrolytic cell do not face each other and / or in the inlet / outlet pipe of the electrolytic cell to prevent the leakage current from flowing. Can be shut off.

As the dielectric, activated carbon, graphite,
When a carbon-based material such as carbon fiber is used and the water to be treated is treated while generating oxygen gas from the anode, the dielectric is easily oxidized by oxygen gas and easily dissolved as carbon dioxide gas. In order to prevent this, the positive polarization side of the dielectric is contacted with a metal material normally used as an insoluble metal electrode by coating a platinum group metal oxide such as iridium oxide or ruthenium oxide on a substrate such as titanium. It may be installed in such a state that oxygen generation mainly occurs on the metal material.
Efficiently the water to be circulated in the electrolytic cell, preferably for contacting all the water to be treated with the porous cathode,
A porous cathode having a cross-sectional area substantially the same as the cross-sectional area of the electrolytic cell in the direction of flow of the treated water is housed in the electrolytic cell such that no gap is formed between the electrolytic cathode and the inner wall of the electrolytic cell. As a result, substantially all available chlorine components in the water to be treated are decomposed or reduced to chlorine ions, and the chlorine odor is removed.

As another type of fixed bed type bipolar electrode electrolytic cell which can be used in the method of the present invention, for example, a power feeding anode and a power feeding cathode are installed in a cylindrical electrolytic cell body, and between the power feeding electrodes. There is an electrolytic cell in which a large number of conductive fixed bed forming particles functioning as a porous electrode and a smaller number of insulating particles made of an electrically insulating synthetic resin or the like than the fixed bed forming particles are mixed almost uniformly. When a potential is applied by energizing between both power supply electrodes in the electrolytic cell, the fixed bed forming particles are polarized in the same manner as the dielectric material, and one end thereof is positively charged and the other end is negatively charged, so that each fixed bed is formed. An electric potential is generated in the forming particles, and each particle is given a function of decomposing or reducing the effective chlorine component in the water to be treated. The insulating particles have a function of preventing both the power supply electrodes from being electrically connected by the electrically conductive particles for forming the fixed bed to cause a short circuit.

The electrolytic cell having such a structure is provided in a line of stored water of a water purification plant, in the vicinity of a faucet of a water supply of a home or a restaurant, or at a place depending on other uses of treated water such as food treated water. The whole or part of the water to be treated is introduced into the electrolyzer to treat the water to be treated in the electrolyzer to decompose and reduce effective chlorine components by reduction. Since the electrolytic cell of the present invention is a bipolar type, the water to be treated is brought into contact with the cathode multiple times to decompose or reduce the effective chlorine component,
The effective chlorine component in the water to be treated can be surely removed.

Next, preferred examples of the electrolytic cell according to the present invention will be described with reference to the accompanying drawings, but the electrolytic cell and the electrolytic cell usable in the method of the present invention are not limited to this electrolytic cell. FIG. 1 is a schematic vertical cross-sectional view showing an example of a fixed bed type bipolar electrode electrolytic cell that can be used as the electrolytic cell of the method of the present invention.

A mesh-shaped power feeding anode terminal 3 and power feeding cathode terminal 4 are provided near the upper end and the lower end of the cylindrical electrolytic cell body 2 having the upper and lower flanges 1, respectively. The electrolytic cell body 2 is preferably formed of an electrically insulating material that can withstand long-term use or re-use, and in particular, it is a synthetic resin such as polyepichlorohydrin, polyvinyl methacrylate, polyethylene, polypropylene, polyvinyl chloride, or polyvinyl chloride. , Phenol-formaldehyde resin and the like can be preferably used.
The positive electrode terminal 3 which gives a positive DC voltage is, for example, a carbon material (for example, activated carbon, charcoal, coke, coal, etc.), a graphite material (for example, carbon fiber, carbon cloth, graphite, etc.), a carbon composite material (for example, carbon to metal). Powdered and mixed), activated carbon fiber non-woven fabric, or a material in which platinum, platinum, palladium or nickel is supported,
Further, it is formed of a dimensionally stable electrode (platinum group oxide-coated titanium material), platinum-coated titanium material, nickel material, stainless steel material, iron material and the like. The cathode terminal 4 facing the anode terminal 3 and applying a negative DC voltage is formed of, for example, platinum, stainless steel, titanium, nickel, copper, hastelloy, graphite, carbon material, mild steel, or a metal material coated with a platinum group metal. ing.

A plurality of sponge-like fixed beds 5 are laminated between the two electrode terminals 3 and 4 in the illustrated example, and between the fixed beds 5 and between the fixed beds 5 and the two electrode terminals 3 are fixed. Four mesh-like diaphragms or spacers 6 are sandwiched between four. Each fixed bed 5 is in close contact with the inner wall of the electrolytic cell body 2 and does not pass through the inside of the fixed bed 5, so that the leakage flow of the water to be treated flowing between the fixed bed 5 and the side wall of the electrolytic cell body 2 is reduced as much as possible. It is located in. When a diaphragm is used, a woven cloth, a biscuit plate, a particle sintered plastic, a perforated plate, an ion exchange membrane or the like is used as the diaphragm, and a woven cloth, a perforated plate, a net made of an electrically insulating material is used as a spacer. , Rod-shaped materials, etc. are used. When current is supplied to the electrolytic cell having such a structure from below as indicated by an arrow, the fixed bed 5 is polarized so that the lower surface is positive and the upper surface is negative as shown in the figure. A porous cathode is formed on the upper surface of the floor 5, and the water to be treated is brought into contact with the porous cathode to decompose or reduce effective chlorine components such as hypochlorite ion and chlorine gas, and then to remove the electrolytic cell. Is taken out above and used for predetermined purposes as drinking water or the like.

FIG. 2 shows another example of a bipolar electrode fixed bed type electrolytic cell which can be used in the present invention. The electrolytic cell is a side of the fixed bed 5 of the electrolytic cell shown in FIG. That is, the mesh-shaped insoluble metal material 7 is installed in a close contact state on the side of the positive polarization, and the other members are the same as those in FIG. The fixed bed 5 to which the DC voltage is applied is most polarized at both ends thereof, and when gas is generated, the gas is easily generated at the both ends. Therefore, the fastest dissolution occurs at the end of the fixed bed 5 that is most strongly anodic polarized, that is, the most intensely oxygen gas is generated, toward the power supply cathode 4. As shown in the figure, when the insoluble metal material 7 is installed in this portion, most of the oxygen gas is removed from the insoluble metal material 7 because the overvoltage of the insoluble metal material 7 is lower than the overvoltage of the carbonaceous material forming the fixed bed 5. Since the fixed bed 5 is generated and almost does not come into contact with oxygen gas, the dissolution of the fixed bed 5 is effectively suppressed. The water to be treated supplied to the electrolyzer 2 is treated in the same manner as in FIG. 1 to remove the effective chlorine component.

FIG. 3 shows another example of the bipolar electrode fixed bed type electrolytic cell which can be used in the present invention. Top and bottom flanges 11
A mesh-shaped power feeding anode 13 and power feeding cathode 14 are provided in the vicinity of the upper end and the lower end of the inside of the cylindrical electrolytic cell body 12 having the above. The electrolytic cell body 12 is preferably formed of an electrically insulating material, especially a synthetic resin, which can withstand long-term use or reuse. Between the power feeding electrodes 13 and 14, a large number of porous particles 15 for forming a fixed bed formed of a conductive material such as a carbon-based material and a smaller number of insulating particles made of, for example, a synthetic resin than the particles 15 for forming a fixed bed. The particles 18 are mixed almost uniformly. The insulating particles 18 have a function of preventing the power supply anode 13 and the power supply cathode 14 from being completely short-circuited. When electricity is supplied to the electrolytic cell having such a structure from below while supplying water to be treated, the fixed bed forming porous particles 15 are negative on the side of the power feeding anode 13 and the power feeding cathode. The 14 side functions as a porous electrode with a positive polarization and an enormous surface area, and the reforming treatment such as decomposition or reduction of the effective chlorine component in the pre-treated water is performed in the same manner as in the electrolytic cell of FIGS. 1 and 2. And is taken out from above the electrolytic cell.

[0026]

EXAMPLES Next, examples of the drinking water reforming treatment according to the present invention will be described, but the examples do not limit the present invention.

(Example 1) The treated water for test was treated using an electrolytic cell shown in FIG. 1 made of transparent hard polyvinyl chloride resin and having a height of 100 mm and an inner diameter of 50 mm. The electrolytic cell is made of carbon fiber and has an opening ratio of 60% and a diameter of 50 mm and a thickness.
3 fixed beds of 10 mm are sandwiched between 4 diaphragms made of polyethylene resin with an opening ratio of 85% and a diameter of 50 mm and a thickness of 1.5 mm.
A mesh-shaped anode terminal and cathode terminal having a diameter of 48 mm and a thickness of 1.0 mm, which are made of titanium and whose surfaces are plated with platinum, are placed in contact with the diaphragms at the upper and lower ends, respectively. The test water to be treated was prepared by adding an aqueous solution of sodium hypochlorite to tap water so that the effective chlorine component concentration was 1 to 20 ppm. 2.5 liters of treated water supply /
In addition, the applied voltage value was fixed to 16.0 V and the current value was fixed to 60 mA, and the hypochlorite ion concentration in the water to be treated was changed as shown in Table 1 under the electrolytic conditions to change the water to be treated. After the treatment, the concentration of hypochlorite ion after passing through the electrolytic cell was measured using a colorimetric analysis with orthotoluidine,
The results shown in Table 1 were obtained.

(Comparative Example 1) 40 g of activated carbon having a particle size of 2 to 5 μm
Was packed in a glass column having an inner diameter of 4.0 cm and a height of 100 mm. Note that this activated carbon already contains 15 ppm of effective chlorine water.
The one passed through 00 liters was used. The same test water to be treated as in Example 1 having the concentration of sodium hypochlorite shown in Table 1 was supplied to this column at a rate of 2.5 liters / minute, and the water in the water to be treated flowing out from the column was treated as follows. The chlorite ion concentration was measured by the same method as in Example 1. The results are summarized in Table 1. It can be seen from Table 1 that the use of the porous cathode significantly reduces the hypochlorite ion concentration as compared with the case of activated carbon treatment.

Example 2 Treated water was treated using the same electrolytic cell as in Example 1 except that the electrode material forming the fixed bed was changed. Water to be treated as water for test was adjusted to 2 ppm by adding sodium hypochlorite. Using water, the test water to be treated was supplied at a flow rate of 2.5 liters / minute to an electrolytic cell constituted by using the substances shown in Table 2 to reform the water to be treated. Example 1 shows the sodium hypochlorite ion concentration at the treated water outlet.
It was measured by the same method as. The results are summarized in Table 2. It can be seen from Table 2 that the hypochlorite ion decomposes at a value close to 100% when the electrode constituent material is a carbon-based material, whereas the decomposition efficiency decreases with other metal materials.

Example 3 Using the electrolytic cell of Example 1 in which the porous cathode was graphite, the hypochlorite ion concentration at the outlet of the water to be treated (initial concentration) when the aperture ratio of graphite was changed 2 ppm) and the pressure difference between the untreated water supply port and the untreated water outlet of the electrolytic cell, that is, the pressure loss was measured. The results are summarized in Table 3. From Table 3, it can be seen that satisfactory decomposition of hypochlorite ions could be achieved in the range of the aperture ratio of 10 to 95%.

[0031]

According to the method of the present invention, the water to be treated containing the effective chlorine component is treated using a bipolar electrode cell equipped with a porous fixed bed type cathode to decompose or decompose the effective chlorine component. This is a method for treating treated water such as drinking water to be reduced (claim 1). When the treated water such as drinking water is treated by the method of the present invention, the effective chlorine is decomposed or reduced by sufficient contact of the hypochlorite ion and residual chlorine gas contained in the treated water with the porous cathode surface. It is possible to obtain drinking water or the like in which the components are almost completely removed and which contains almost no available chlorine component.

Unlike the conventional treatment of drinking water, which is mainly treated with activated carbon, since the law of electrochemistry is used in the present invention, the effective chlorine component such as hypochlorite ion is surely decomposed or reduced. Thus, it is possible to convert the chlorine ions into tasteless and odorless, the consumption of the members in the electrolytic cell is almost zero, and the treatment of the water to be treated can be continued for a long time. Further, in the method of the present invention, the water to be treated using the bipolar electrolytic cell is brought into contact with a plurality of cathodes to decompose or reduce the effective chlorine component at each cathode, so that the effective chlorine component is almost completely removed. it can. When the water to be treated is drinking water such as tap water (Claim 2), an odor of chlorine is often left in the drinking water, but the odor of chlorine is removed by the treatment according to the method of the present invention. It is possible to provide drinking water with a mellow taste.

The reaction in the method of the present invention is an electrolytic reaction in which the transfer of electrons occurs on the cathode, but the effective chlorine component contained in the water to be treated such as drinking water is usually on the order of several ppm, and the cathode is substantially The water to be treated can be treated without causing an electrolytic reaction accompanied by gas generation above. When gas generation occurs, inconvenience such as composition change of the water to be treated may occur, and the cathode potential does not substantially generate gas −
It is desirable that the voltage is 0.1 to -1.0 V (vs. SHE) (claim 3). Further, since the amount of power consumed is equal to zero in this potential range, the power cost can be greatly reduced.
From the viewpoint of operation efficiency, it is desirable to perform a so-called transient treatment (one-pass treatment) in which the water to be treated in the electrolytic bath is not circulated to the electrolytic bath again (Claim 4). In order to achieve this, it is desirable to adjust the installation method and aperture ratio of the porous cathode to prolong the residence time of the water to be treated in the electrolytic cell.

The apparatus of the present invention allows substantially all of the water to be treated containing the effective chlorine component to pass through the porous cathode of the bipolar electrode electrolytic cell containing the porous fixed bed type cathode. It is an apparatus for treating and decomposing or reducing the available chlorine component to convert it into chlorine ions (Claim 5). According to the apparatus of the present invention, the water to be treated containing the effective chlorine component permeates through the porous cathode more than in the case of the above-mentioned method of the present invention to increase the residence time and further improve the treatment efficiency.

The porous cathode of the device of the present invention is preferably made of a carbonaceous material (claim 6), and the porous cathode made of the carbonaceous material or the porous cathode formed at one end of the dielectric is Not only does it have a huge surface area and the chances of contact with effective chlorine components become very large, but it also satisfies the requirements of low conductor resistance and high overvoltage, which promotes the permeation of the water to be treated into the inside of the cathode and thus the porous cathode. Since it is possible to treat the water to be treated on the entire surface, the treatment efficiency is greatly improved compared to other materials. Further, since the carbonaceous material has no toxicity and does not form ions or hydroxide thereof, it is preferable for treating water to be treated such as drinking water that is ingested into the body. Further, the carbonaceous material is inexpensive and, unlike the other metal material electrodes, does not cause corrosion even if the electrolysis is stopped, which is advantageous from the economical and operability viewpoints.

The aperture ratio of the porous cathode is preferably 10% or more and 95% or less (claim 7), and a satisfactory decomposition or reduction effect of the effective chlorine component can be achieved in this range. Further, in the electrolytic cell of the present invention, a leak current may be generated in the electrolytic cell, and the leak current may flow into another metal member such as a water pipe to cause electrochemical corrosion such as elution in the member. In order to prevent this, a member having higher conductivity than the water to be treated is installed at an appropriate position where both electrodes do not face each other so that one end of the member can be grounded (claim 8). Can be made

If the water to be treated flowing in the electrolytic cell is a laminar flow, the water to be treated may pass through the bipolar electrolytic cell without sufficiently contacting the porous cathode. It is preferable that the water is a turbulent flow having a Reynolds number of 500 or more (claim 9) so that the water to be treated moves laterally and comes into sufficient contact with the cathode. In the electrolytic cell according to the present invention, for example, since a hypochlorite ion decomposed into chlorine ion and water at the cathode is not oxidized at the anode to generate the original hypochlorite ion, a diaphragm is used. It is not necessary to divide the electrolytic cell into an anode chamber and a cathode chamber (Claim 1
0), the electrolytic cell structure becomes simple.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view illustrating a first bipolar electrode electrolytic cell that can be used in the present invention.

FIG. 2 is a vertical cross-sectional view illustrating a second bipolar electrode electrolytic cell that can be used in the present invention.

FIG. 3 is a vertical cross-sectional view illustrating a third bipolar electrode electrolytic cell that can be used in the present invention.

[Explanation of symbols]

1 ... Flange 2 ... Electrolyzer body 3, 4 ...
Electrode terminal 5: Fixed floor 6: Spacer
7 ... Insoluble metal material 11 ... Flange 12 ... Electrolytic cell body 13 ... Power feeding anode 14 ... Power feeding cathode 15 ... Fixed bed forming porous particles 18 ...
Insulating particles

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[Procedure amendment]

[Submission date] April 7, 1993

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

Claims (10)

[Claims] 1. Water to be treated containing an effective chlorine component is supplied to a bipolar electrode electrolytic cell in which a porous fixed bed type cathode is installed,
A method for treating water to be treated, characterized in that the effective chlorine component is decomposed or reduced on the cathode to reform the water to be treated. 2. The method according to claim 1, wherein the water to be treated is drinking water. 3. The cathode potential is -0.1 to -1.0 V (vs.SHE).
The method according to claim 1 or 2, wherein 4. The method according to claim 1, wherein the water to be treated is supplied to the electrolytic cell to carry out the transient treatment. 5. A porous fixed bed type cathode having a cross-sectional area substantially the same as the cross-sectional area of the treated water to be treated is accommodated, and the treated water containing an effective chlorine component is supplied and An apparatus for treating drinking water, comprising a bipolar electrolytic cell for decomposing or reducing the available chlorine component on the cathode. 6. The porous cathode is a carbonaceous material.
The device according to. 7. The device according to claim 5, wherein the aperture ratio of the porous cathode is 10% or more and 95% or less. 8. The method according to claim 5, wherein a member having a conductivity higher than that of the water to be treated is installed on the back surface of the electrode where the electrodes in the electrolytic cell do not face each other and / or in the inlet / outlet pipe of the electrolytic cell so that one end thereof can be grounded. 7. The device according to any of items 7 to 7. 9. The apparatus according to claim 5, wherein the water to be treated flowing in the electrolytic cell has a Reynolds number of 500 or more. 10. The electrolytic cell is a diaphragmless electrolytic cell.
The device according to any one of 1 to 9.