JP5597855B2 - Apparatus and method for preparing toilet flush water - Google Patents

Description

  The present invention relates to an apparatus and a method for preparing toilet flush water.

  There has been proposed a cleaning apparatus for flush toilets, which cleans toilets using alkaline water and acidic water generated by electrolysis of water (Patent Document 1). The electrolyzer of this apparatus includes an alkaline water generation chamber and an acidic water generation chamber arranged with a diaphragm therebetween. A cathode is disposed in the alkaline water generation chamber, and an anode is disposed in the acidic water generation chamber. By applying a voltage between the cathode and the anode, alkaline water and acidic water are generated simultaneously.

Japanese Patent Laid-Open No. 11-151492

  However, the electrolyzer using a diaphragm requires maintenance of the diaphragm periodically, and the maintenance is complicated. In addition, it is necessary to supply salt water having a relatively high concentration to the electrolysis apparatus using a diaphragm.

  Under such circumstances, it is an object of the present invention to provide a novel washing water preparation apparatus and method that can easily wash and sterilize a flush toilet.

In order to achieve the above object, an apparatus of the present invention is an apparatus for preparing toilet flushing water stored in a tank by treating water, which is a conductive substance capable of reversibly adsorbing ions. An ion adsorbing electrode, a counter electrode, a power source for changing the pH of the water by applying a voltage between the ion adsorbing electrode and the counter electrode, and detection means for detecting discharge of the washing water in the tank and e Bei switching means for switching the application direction of the voltage based on an output of said detecting means, said switching means, said washing water in said tank to change the application direction of the voltage each time it is discharged.

Further, the method of the present invention is a method for preparing toilet flushing water stored in a previous tank by treating water, which is a conductive material capable of reversibly adsorbing ions to the water to be the washing water. A step of changing the pH of the water by applying a voltage between the ion adsorption electrode and the counter electrode in a state where the ion adsorption electrode containing the active substance and the counter electrode are immersed, and the cleaning in the tank The application direction of the voltage is changed every time water is discharged .

  According to the present invention, the flush toilet can be easily washed and sterilized.

It is a figure which shows typically the structure of an example of the apparatus of this invention. 3 is a flowchart illustrating an example of the operation of the apparatus illustrated in FIG. 1. It is a figure which shows an example of the operation state of the apparatus shown in FIG. It is a figure which shows another example of the operation state of the apparatus shown in FIG. It is a figure which shows typically an example of the electrode group arrange | positioned in the tank of a toilet. It is a figure which shows typically an example of the electrode group arrange | positioned in the tank. It is a figure which shows an example of the method of supplying salt to water. It is a figure which shows typically an example at the time of utilizing the principle of this invention for another use.

  Hereinafter, embodiments of the present invention will be described. In the following description, embodiments of the present invention will be described by way of examples, but the present invention is not limited to the examples described below. In the following description, specific numerical values and specific materials may be exemplified, but other numerical values and other materials may be applied as long as the effect of the present invention is obtained.

(Washing water preparation device)
The apparatus of the present invention is an apparatus for preparing toilet flushing water stored in a tank by treating water. The apparatus includes an ion adsorption electrode, a counter electrode, a detection unit, and a switching unit that switches a voltage application direction.

  The ion adsorption electrode includes a conductive substance capable of reversibly adsorbing ions (hereinafter sometimes referred to as “conductive substance (C)”). The ion adsorption electrode may include a current collector that supports the conductive substance (C) or a current collector attached to the conductive substance (C).

  The conductive substance (C) is a substance that can adsorb ions reversibly. That is, the conductive substance (C) can release the adsorbed ions. As the conductive material (C), a material having a large specific surface area can be used. In a preferred example, the conductive substance (C) includes a carbon material such as activated carbon or graphite. The conductive material (C) may be a conductive sheet formed by agglomerating granular activated carbon. Further, the conductive substance (C) may be a conductive sheet formed by aggregating granular activated carbon and conductive carbon. The conductive substance (C) may be an activated carbon block formed by solidifying activated carbon particles. Further, the conductive substance (C) may be an activated carbon fiber cloth, that is, a cloth formed using the activated carbon fiber. As the activated carbon fiber cloth, for example, ACC5092-10, ACC5092-15, ACC5092-20, and ACC5092-25 manufactured by Nihon Kynol Co., Ltd. may be used.

The specific surface area of the conductive substance (C) is, for example, 300 m ² / g or more, and preferably 900 m ² / g or more. The upper limit of the specific surface area is not particularly limited, but may be, for example, 3000 m ² / g or less or 2500 m ² / g or less. The “specific surface area” of the conductive substance (C) can be usually measured by a BET method using nitrogen gas.

  An example of the counter electrode is a metal electrode. A preferred example of the counter electrode is an electrode on the surface of which a metal (for example, platinum) that easily causes electrolysis of water is present. For example, as the counter electrode, an electrode made of titanium, an electrode made of platinum, or an electrode made of a metal coated with platinum (for example, any metal such as titanium, niobium, or tantalum) can be used. As the counter electrode, a metal sheet may be used, a metal wire may be used, or a plurality of connected metal wires may be used. A preferred example of the counter electrode is an electrode formed by arranging metal wires in a flat plate shape.

Unlike the conductive substance (C), the surface area of the counter electrode may not be large. Surface area per gram of an example of the counter electrode may also be 100 m ² or less, may be in the range of 5 × 10 ^-5 ~50m ^2.

  In a typical example, the ion adsorption electrode and the counter electrode are each flat and are arranged in parallel to each other. The ion adsorption electrode and the counter electrode may constitute one electrode group. One electrode group may include a plurality of ion adsorption electrodes and / or a plurality of counter electrodes. In a preferred example, a plurality of plate-like ion adsorption electrodes and a plurality of plate-like counter electrodes are arranged in parallel and alternately. One electrode group may include a plurality of electrode pairs arranged in different directions. Each electrode pair includes a plate-like ion adsorption electrode and a plate-like counter electrode arranged in parallel. For example, one electrode group may include a plurality of electrode pairs arranged in directions orthogonal to each other. In a preferred example, the plate-like electrodes (ion adsorption electrode and counter electrode) are arranged so that their surface directions are parallel to the vertical direction.

  The ion adsorption electrode and the counter electrode may be disposed in a toilet tank. In this case, the ion adsorption electrode and the counter electrode may be arranged so as to be immersed in the water remaining in the tank when the water in the tank is discharged. According to this configuration, the electrode can be prevented from being exposed to the outside of the water. By using an electrode group that can be put into a tank, the present invention can be applied to any toilet.

  The apparatus of the present invention may further include a tank connected to a toilet tank (hereinafter, also referred to as “treatment tank”). And the ion adsorption electrode and the counter electrode may be arrange | positioned in the processing tank. Alkaline water and acidic water are prepared by treating water in the treatment tank. The obtained alkaline water and acidic water are introduced into the tank. In this case, all the water introduced into the tank may pass through the treatment tank. Alternatively, water that has passed through the treatment tank and water that has not passed through the treatment tank may be mixed in the tank. The treatment tank is not particularly limited as long as it can stably hold alkaline water and acidic water. For example, a resin tank or a pottery tank can be used as the processing tank.

  The detection means detects discharge of the cleaning water in the tank. An example of the detection means is a means (a sensor, a switch, or the like) that detects a physical movement (for example, movement of a lever) for discharging the cleaning water. Another example of the detection means is a sensor (such as a water sensor, a pressure sensor, or an optical sensor) that detects the amount of water in the tank. Another example of the detecting means is an electric means (such as an optical sensor or a switch) for issuing a signal for starting the discharge of the washing water. The electrical means also serves as a means for issuing a signal for starting the discharge of the wash water and a detection means for detecting the discharge of the wash water in the tank.

  The power supply is a power supply (DC power supply) for applying a voltage (DC voltage) between the ion adsorption electrode and the counter electrode. The power source may be an AC-DC converter that converts an AC voltage from an outlet into a DC voltage. The power source may be a power generation device such as a solar cell or a fuel cell, or a secondary battery. By using a power generation device or a secondary battery as a power source, the device of the present invention can be used in regions and situations where power is not supplied.

  Washing water is prepared by applying a voltage between the ion-adsorbing electrode and the counter electrode in a state where the electrode is immersed in water. At this time, a voltage is applied so that water is electrolyzed on the surface of the counter electrode. By applying this voltage, the pH of the water changes, and alkaline water and acidic water are prepared. The alkaline water and / or acidic water is used as washing water.

  The switching unit switches the voltage application direction based on the output of the detection unit. An example of the switching means is a switch (such as a relay) for switching the voltage application direction. Another example of the switching unit includes a switch (such as a relay) for switching a voltage application direction and a controller that controls the switch based on the output of the detection unit. Note that a switch for switching the voltage application direction may be attached to the power supply.

  The controller includes an arithmetic processing unit (which may include an internal memory), and further includes an external memory as necessary. A program for executing processing (for example, a step described later) is recorded in the memory. An example of the controller includes an integrated circuit (IC or LSI). The controller is connected to various devices (power supply, pump, valve, switch, etc.) and measuring instruments (pH sensor, light sensor, water level sensor, conductivity sensor, etc.). The controller executes various processes by controlling various devices based on the output from the measuring instrument.

  In a general toilet, the discharge timing of cleaning water is determined based on the output of the user or sensor. In addition, cleaning water may be discharged periodically in public toilets. In either case, the present invention can be applied.

  The applied voltage may be switched every time the cleaning water is discharged. Further, the switching may be performed every time the cleaning water is discharged a predetermined number of times. Further, the switching may be performed when the amount of water in the tank becomes a predetermined amount or less. The switching may be performed when the washing water is discharged or when an instruction to discharge is given. Further, the switching may be performed after a certain time has elapsed since the discharge of the washing water, or may be performed after a certain time has elapsed since the instruction to discharge was made. When the ion adsorption electrode and the counter electrode are arranged in the tank, the voltage application may be started after new water is accumulated in the tank to some extent.

  Note that the switching of the applied voltage may be performed at regular intervals.

  The apparatus of the present invention may further include an apparatus for adding salt to the water to be treated. Examples of the salt added include potassium chloride, sodium chloride, magnesium chloride, potassium sulfate, sodium sulfate, magnesium sulfate, organic acid salts, and mixtures thereof. By adding a salt containing chlorine, it is possible to prepare washing water containing a large amount of hypochlorous acid having a high bactericidal effect. The salt concentration of the water to which the salt is added is not particularly limited, and may be in the range of 0.01% by weight to 1.0% by weight (for example, in the range of 0.05% by weight to 0.1% by weight).

  In a conventional electrolysis apparatus using a diaphragm such as an ion exchange membrane, the salt concentration of water before treatment needs to be relatively high. In contrast, the apparatus of the present invention using an ion adsorption electrode and a counter electrode can sufficiently change the pH even with tap water. Specifically, it is possible to sufficiently change the pH by treating water having a conductivity in the range of 50 μS / cm to 500 μS / cm (for example, 200 μS / cm or less). For example, by treating tap water having a conductivity of 180 μS / cm, acidic water having a pH of 2.6 to 5 or alkaline water having a pH of 9 to 11.7 can be prepared. However, the rate of change in pH can be increased by adding salt to the water to be treated. Therefore, salt may be added to the water to be treated. The apparatus for adding salt may add salt to water at a constant rate. Moreover, you may add salt by throwing the solid substance containing salt into the path | route or tank of water.

  The device of the present invention may include other elements as required, and may include, for example, a safety device, a pump, a valve, a pH sensor, a conductivity sensor, and the like.

(Washing water preparation method)
The method of the present invention is a method of preparing toilet flushing water stored in a tank by treating water. This method can be easily implemented using the apparatus of the present invention. Since the matters described for the apparatus of the present invention can be applied to the method of the present invention, redundant description may be omitted. Further, the matters described for the method of the present invention can be applied to the apparatus of the present invention.

  In the method of the present invention, an ion-adsorbing electrode containing a conductive substance (C) capable of reversibly adsorbing ions and a counter electrode are immersed in water serving as a cleaning water, and the ion-adsorbing electrode and the counter electrode are interposed. A step (step) of changing the pH of water by applying a voltage (DC voltage) is included. In this step, a voltage is applied so that water is electrolyzed at the counter electrode. In the method of the present invention, the voltage application direction is changed in relation to the discharge of the cleaning water in the tank.

When a voltage is applied so that the ion adsorption electrode becomes an anode (anode), anions in water (for example, anions other than hydroxide ions) are adsorbed on the conductive substance (C) of the ion adsorption electrode. On the other hand, water is electrolyzed at the counter electrode, and hydrogen gas and hydroxide ions (OH ⁻ ) are generated. As a result, the pH of the water rises and alkaline water is prepared.

When a voltage is applied so that the ion adsorption electrode becomes a cathode (cathode), cations in water (for example, cations other than hydrogen ions) are adsorbed on the conductive substance (C) of the ion adsorption electrode. On the other hand, water is electrolyzed at the counter electrode, and oxygen gas and hydrogen ions (H ⁺ ) are generated. As a result, the pH of the water decreases and acidic water is prepared.

  In addition, when a voltage is applied so that the ion adsorption electrode becomes a cathode while the anion adsorption electrode is adsorbed, a reaction in which the adsorbed anion is released into water also occurs. In addition, when a voltage is applied so that the ion adsorption electrode serves as an anode in a state where cations are adsorbed on the ion adsorption electrode, a reaction in which the adsorbed cations are released into water also occurs. In any case, when a voltage is applied so that the ion-adsorbing electrode becomes an anode, the pH of water increases, and when a voltage is applied so that the ion-adsorbing electrode becomes a cathode, the pH of water decreases.

  The voltage to be applied is not particularly limited as long as the voltage causes water electrolysis at the counter electrode. In one example, the applied voltage is in the range of 2 volts to 50 volts. When applying a voltage, a constant voltage may be applied, or a voltage may be applied so that a constant current flows between the electrodes. Moreover, in order to prevent the pH of the washing water from becoming too acidic or alkaline, the voltage application may be stopped after a certain time has elapsed from the start of voltage application. Alternatively, the current value that flows from the start of voltage application may be monitored, and the voltage application may be stopped when the current value reaches a certain value. Further, the voltage application may be stopped when the voltage reaches a predetermined value. Alternatively, the pH of the prepared cleaning water may be monitored, and voltage application may be stopped when the pH reaches a certain value.

  In the method of the present invention, as described in the description of the apparatus, the voltage application direction is changed based on the discharge of the cleaning water in the tank. For example, the voltage application direction may be changed every time the cleaning water in the tank is discharged.

  Moreover, in the method of this invention, you may further include the process of adding a salt to the water processed at the said process before the said process.

  According to the apparatus and method of the present invention, acidic water having a pH in the range of 2.6 to 5 and alkaline water having a pH in the range of 9 to 11.7 are prepared from normal water such as tap water. It is possible. It is also possible to prepare acidic water having a pH of 2.6 or less and alkaline water having a pH of 11.7 or more by treating salt water.

  In another aspect, the present invention provides a flush toilet equipped with the flush water preparation apparatus of the present invention. In another aspect, the present invention provides a toilet cleaning apparatus including the cleaning water preparation apparatus of the present invention. In another aspect, the present invention provides a toilet cleaning method including the cleaning water preparation method of the present invention.

An example of the apparatus and method of the present invention will be described below with reference to the drawings. In the following figure, cations other than hydrogen ions (H ⁺ ) may be displayed as “L ⁺ ” regardless of the valence. Further, anions other than hydroxide ions (OH ⁻ ) may be displayed as “L ⁻ ” regardless of the valence. Moreover, in the following description, the same code | symbol may be attached | subjected to the same part and the overlapping description may be abbreviate | omitted.

(Embodiment 1)
The configuration of the apparatus according to the first embodiment is schematically shown in FIG. The washing water preparation apparatus 100 of FIG. 1 includes a power source 11, a switch 12, a detection unit 13, a controller 14, and an electrode group 20. Switch 12 includes relays 12a and 12b. The controller 14 is connected to the power source 11, the switch 12, and the detection means 13. The switch 12 and the controller 14 function as switching means. The electrode group 20 includes a flat ion adsorption electrode 21 and a flat counter electrode 22. The ion adsorption electrode 21 and the counter electrode 22 are arranged in parallel. The ion adsorption electrode 21 includes a conductive material 21a capable of reversibly adsorbing ions and a wiring 21b.

  An example of the operation of the apparatus 100 will be described with reference to FIGS. In the following example, the case where the ion adsorption electrode becomes the anode at the time of the first voltage application is described. However, the ion-adsorbing electrode may be used as the cathode during the initial voltage application.

When the process is started, first, a voltage is applied between the ion adsorption electrode 21 and the counter electrode 22 in water (step S201). At this time, a voltage is applied so that water is electrolyzed on the surface of the counter electrode 22. When a voltage is applied so that the ion adsorption electrode 21 becomes an anode, negative ions (L ⁻ ) are adsorbed on the conductive material 21a of the ion adsorption electrode 21, as shown in FIG. On the other hand, on the surface of the counter electrode 22, water is electrolyzed to produce hydrogen gas and hydroxide ions (OH ⁻ ). As a result, the pH of the water around the electrode group 20 rises to become alkaline water. This alkaline water is discharged as toilet wash water.

  The voltage application is continued until a condition for reversing the voltage application direction is established based on the discharge of water in the tank (step S202). When the alkaline water in the tank is discharged, it is detected by the detection means 13 and output to the controller 14. New water is supplied to the tank from which the alkaline water has been discharged. As the water is replenished, new water (such as tap water) is replenished around the electrode group 20.

When the condition for reversing the voltage application direction is established, the voltage application direction is switched by the switch 12. A voltage is applied between the ion adsorption electrode 21 and the counter electrode 22 in the opposite direction to the previous time (step S203). As a result, as shown in FIG. 4, the anions (L ⁻ ) adsorbed on the conductive material 21a are released into the water. In addition, cations (L ⁺ ) in the water are adsorbed on the conductive material 21a. On the other hand, on the surface of the counter electrode 22, water is electrolyzed to generate oxygen gas and hydrogen ions. As a result, the pH of the water around the electrode group 20 is lowered and the remaining alkali is neutralized, and then becomes acidic water. Acidic water is discharged as toilet wash water.

  Thereafter, it is determined whether or not to continue the process (step S204). When the process is terminated, the voltage application is stopped (step S205). When the process is continued, the above steps S202 and S203 are repeated. Thereby, alkaline water and acidic water are alternately discharged from the tank. By flushing with alkaline water and acidic water, toilet bowls can be easily washed and sterilized. In particular, the cleaning effect is enhanced by flowing alkaline water. Moreover, urine stones and scales can be removed by flowing acidic water.

  FIG. 5 shows a cross-sectional view of an example in which the electrode group 20 of the device 100 is disposed in a toilet tank. Note that the toilet tank shown in FIG. 5 is an example, and the present invention is not limited thereto.

  The electrode group 20 is disposed in a toilet tank 51. The electrode group 20 is connected to the switch 12 by a wiring 56. In the tank 51, a valve 52 for discharging the cleaning water 59 in the tank 51 and a lever 53 for operating the valve 52 are arranged. When the lever 53 is operated, the valve 52 is raised and the washing water 59 is discharged from the drain port 51h. The toilet bowl is washed with the washing water 59. Water (for example, tap water) is introduced into the tank 51 from a water supply pipe 54. When the cleaning water 59 in the tank 51 reaches a predetermined amount, the water stop cock is actuated by the float 55 to stop water supply. When the lever 53 is operated and the cleaning water 59 in the tank 51 is discharged, water is again introduced from the water supply pipe 54. A sensor (not shown) that detects that the lever 53 has been operated is attached to the lever 53. The sensor functions as detection means. By applying a voltage to the electrode group 20, alkaline water / acidic water is prepared from the water supplied to the tank 51.

  FIG. 6 shows a schematic diagram of an example in which the electrode group is arranged in a tank other than the tank. In the example of FIG. 6, the apparatus of the present invention includes a tank 60 connected to the tank. An ion adsorption electrode 21 and a counter electrode 22 are disposed in the tank 60. A water supply pipe (for example, a water pipe) is connected to the water supply port 60 a of the tank 60. The drain 60b of the tank 60 is connected to a water supply pipe of a toilet tank. When the water in the toilet tank is discharged, the water in the tank 60 moves as the stop cock provided on the water supply pipe of the toilet tank is opened. As a result, the alkaline water / acidic water prepared in the tank 60 is supplied to the toilet tank. The direction of voltage application is switched in relation to the discharge of the wash water in the tank.

  An example of a method (means) for supplying salt is schematically shown in FIG. The example of FIG. 7 is an example in the case where water supply to the toilet tank is performed through a hole in the upper part of the tank. In this case, the electrode group 20 is disposed in the tank.

  A through-hole 71h is formed in the tank lid 71. The water supply pipe 72 is disposed above the lid 71. A supply means 73 for supplying salt is disposed below the water supply pipe 72 and on the lid 71. The supply means 73 includes a container 73a that is open at the top and a solid 73b that is disposed below the container 73a. The solid 73b is a solid containing a salt. The water supplied from the water supply pipe 72 overflows from the container 73a and is introduced into the tank. When the supply of water from the water supply pipe 72 is stopped, the movement of the water 74 in the container 73a is also stopped. Since the salt concentration of the water 74 is defined by the solubility of the salt, as long as the movement of the water 74 is stopped, the dissolution of the solid 73b is limited. According to the supply means 73, the salt concentration of the water to be processed can be easily increased.

(Use of the principle of the present invention)
It should be noted that the principle of the present invention can be used for other than toilets. For example, a part of the configuration of the present invention can be used in an apparatus and a method for preparing alkaline water and acidic water for cleaning. The apparatus is an apparatus for preparing alkaline water and / or acidic water by treating water. The apparatus includes an ion adsorption electrode containing a conductive substance capable of reversibly adsorbing ions, a counter electrode, a power source for applying a voltage between the ion adsorption electrode and the counter electrode, and prepared alkaline water and acidic water. Storage means for selectively storing at least one of these. Further, the method is a method of preparing alkaline water and / or acidic water by treating water, wherein an ion-adsorbing electrode containing a conductive substance capable of reversibly adsorbing ions and a counter electrode are immersed in water. A step of changing the pH of the water by applying a voltage between the ion-adsorbing electrode and the counter electrode, and a step of selectively storing at least one of alkaline and acidic water in the water prepared in the step Including. The matters described in the apparatus and method of the present invention can be applied to this apparatus and method.

  An example of this apparatus is shown in FIG. The apparatus 800 includes a power source 11, a switch 12, a controller 14, an electrode group 20, a tank 60, a switching valve 81, and containers 82 and 83. The switching valve 81 switches the water path depending on whether the water prepared in the tank 60 is alkaline water or acidic water. Specifically, the switching valve 81 switches the water path in accordance with the direction in which the voltage applied between the ion adsorption electrode 21 and the counter electrode 22 is applied. As a result, alkaline water can be stored in the container 82, and acidic water can be stored in the container 83. The size of the containers 82 and 83 is determined according to the application. When used at home, the inner volume of the containers 82 and 83 may be in the range of 0.1 to 10 liters (for example, in the range of 0.2 to 1 liter). Alkaline water can be used for mold removal and sterilization. Acidic water can also be used for scale removal and sterilization.

  The embodiments of the present invention have been described above by way of examples. However, the present invention is not limited to the above-described embodiments, and can be applied to other embodiments based on the technical idea of the present invention.

  INDUSTRIAL APPLICATION This invention can be utilized for the preparation apparatus and preparation method of the wash water of the toilet bowl.

DESCRIPTION OF SYMBOLS 11 Power supply 12 Switch 12a, 12b Relay 13 Detection means 14 Controller 20 Electrode group 21 Ion adsorption electrode 21a Conductive substance 21b Wiring 22 Counter electrode

Claims (6)

An apparatus for preparing toilet flush water stored in a tank by treating water,
An ion-adsorbing electrode containing a conductive material capable of reversibly adsorbing ions,
Counter electrode,
A power source for changing the pH of the water by applying a voltage between the ion-adsorbing electrode and the counter electrode;
It said detecting means for detecting the discharge of the washing water, and Bei example a switching means for switching the application direction of the voltage based on an output of said detecting means in the tank,
The switching means is a cleaning water preparation device that changes an application direction of the voltage every time the cleaning water in the tank is discharged .   The apparatus according to claim 1, wherein the ion adsorption electrode and the counter electrode are disposed in the tank. Further comprising a tank connected to the tank;
The apparatus according to claim 1, wherein the ion adsorption electrode and the counter electrode are disposed in the tank.   The device according to claim 1, further comprising a device for adding salt to the water. A method of preparing toilet flush water stored in a tank by treating water,
By applying a voltage between the ion-adsorbing electrode and the counter electrode in a state where the ion-adsorbing electrode containing a conductive substance capable of reversibly adsorbing ions and the counter electrode are immersed in the washing water Changing the pH of the water,
A method for preparing washing water , wherein the application direction of the voltage is changed each time the washing water in the tank is discharged . The method according to claim 5, further comprising adding a salt to the water treated in the step before the step.

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