Water treatment system, water treatment method, and water chromaticity control method

Abstract

To provide a water treatment system excellent in the decoloring action of water subjected to biological treatment, a water treatment method, and a water chromaticity control method.SOLUTION: A water treatment system comprising: a biological treatment section that performs biological treatment of wastewater to obtain treated water; an alkali addition section that adds an alkaline substance to the biological treatment section; and an ozone treatment section that performs ozone treatment on the treated water.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a water treatment system, a water treatment method, and a method for controlling the color of water. [Background technology]

[0002] Systems for purifying wastewater such as domestic wastewater using microorganisms are applied in various fields. For example, Patent Document 1 describes a circulating flush toilet equipped with a mechanism for purifying wastewater discharged from a flush toilet and circulating the purified water back into the flush toilet bowl.

[0003] The circulating flush toilet described in Patent Document 1 has a biological treatment tank that decomposes organic matter in wastewater and performs nitrification and denitrification treatments, a filtration tank that separates the biologically treated material obtained in the biological treatment tank into solid and liquid, and a decolorization tank that decolorizes the filtrate that has been separated into solid and liquid in the filtration tank, and the treated water that has been decolorized in the decolorization tank is reused as flush water for the flush toilet. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-132037 Summary of the Invention [Problem to be solved by the invention]

[0005] From the viewpoint of promoting the widespread use of circulating water treatment systems, decolorization of water to be reused is an important process to reduce the psychological resistance of users. However, there is still room for improvement in the color state of water that has been subjected to biological treatment and decolorization treatment by existing methods. In view of the above circumstances, an object of the present disclosure is to provide a water treatment system, a water treatment method, and a method for controlling the color of water that are excellent in decolorizing water that has been subjected to biological treatment. [Means for solving the problem]

[0006] The means for solving the above problems include the following embodiments. <1> a biological treatment unit that performs biological treatment on wastewater to obtain treated water; an alkali adding unit that adds an alkaline substance to the biological treatment unit; an ozone treatment unit that performs ozone treatment on the treated water. <2> The alkali addition unit adds an alkaline substance so that the pH of the biological treatment unit does not exceed 9. <1> The water treatment system according to claim 1. <3> Alkaline substances include sodium hydroxide, <1> or <2> The water treatment system according to claim 1. <4> Alkaline substances are in the form of aqueous solutions. <1> ~ <3> The water treatment system according to any one of claims 1 to 10. <5> a biological treatment step in which the wastewater is biologically treated in the biological treatment tank to obtain treated water; an alkali addition step of adding an alkaline substance to the biological treatment tank; an ozone treatment step of treating the treated water with ozone. <6> The alkali addition step includes adding an alkaline substance so that the pH inside the biological treatment tank does not exceed 9. <5> The water treatment method according to claim 1. <7> Alkaline substances include sodium hydroxide, <5> or <6> The water treatment method according to claim 1. <8> Alkaline substances are in the form of aqueous solutions. <5> ~ <7> The water treatment method according to any one of the above. <9> <1> ~ <4> 2. A method for controlling the color of water, comprising controlling the color of treated water using the water treatment system according to any one of claims 1 to 11. [Effects of the Invention]

[0007] According to the present disclosure, a water treatment system, a water treatment method, and a water color control method are provided that have excellent decolorization effect on water that has been subjected to biological treatment. [Brief explanation of the drawings]

[0008] [Figure 1]1 is a conceptual diagram illustrating an example of the configuration of a water treatment system. DETAILED DESCRIPTION OF THE INVENTION

[0009] In the present disclosure, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in a certain numerical range may be replaced by the upper or lower limit value of another numerical range described in stages, or may be replaced by a value shown in an example.

[0010] <Water treatment system> The water treatment system of the present disclosure comprises: a biological treatment unit that performs biological treatment on wastewater to obtain treated water; an alkali adding unit that adds an alkaline substance to the biological treatment unit; and an ozone treatment unit that performs ozone treatment on the treated water.

[0011] In this disclosure, "biological treatment" refers to a treatment that utilizes microorganisms to remove organic matter and inorganic matter such as nitrogen and phosphorus from wastewater. In the present disclosure, "treated water" means water obtained by subjecting wastewater to biological treatment. In the present disclosure, "ozone treatment" means bringing an object to be treated into contact with ozone.

[0012] The water treatment system of the present disclosure is excellent in decolorizing water that has been subjected to biological treatment. Ozone treatment is known as a method for decolorizing water that has been subjected to biological treatment. As a result of investigations by the present inventors, it was found that even if water that has been subjected to biological treatment is subjected to ozone treatment, a sufficient decolorization effect may not be obtained in some cases. Further investigations based on the above findings revealed that the decolorization effect of water by ozone treatment can be enhanced by adding an alkaline substance to the biological treatment unit that biologically treats wastewater.

[0013] (Biological Treatment Division) The water treatment system of the present disclosure includes a biological treatment unit that performs biological treatment on wastewater to obtain treated water. The configuration of the biological treatment unit is not particularly limited as long as it can perform biological treatment of wastewater. The biological treatment unit may include, for example, a tank capable of storing a predetermined amount of wastewater. When the biological treatment unit is equipped with a tank capable of storing wastewater, the amount of wastewater that can be stored in the tank is not particularly limited and can be selected according to the application of the biological treatment system. For example, the upper limit of the amount of wastewater that can be stored in the tank may be any of 10,000 liters, 5,000 liters, 1,000 liters, 500 liters, 300 liters, and 150 liters. The lower limit of the amount of wastewater to be stored in the tank is not particularly limited and can be selected depending on the application of the biological treatment system. For example, the lower limit of the amount of wastewater to be stored in the tank may be 1 liter, 10 liters, or 50 liters.

[0014] The biological treatment unit contains microorganisms used for biological treatment of wastewater. The type of microorganism is not particularly limited. For example, the microorganisms may be aerobic bacteria, anaerobic bacteria, or a combination thereof. Specific examples of the microorganisms contained in the biological treatment unit include aerobic bacteria such as BOD oxidizing bacteria, nitrifying bacteria, yeast, denitrifying bacteria, phosphorus removing bacteria, and denitrifying phosphorus accumulating bacteria.

[0015] The biological treatment unit may be provided with functions other than biological treatment of wastewater as necessary, such as a function to supply nutrients or air to microorganisms, a function to measure or adjust the temperature of the mixture of wastewater and microorganisms in the biological treatment unit (hereinafter referred to as the mixed liquid), a function to measure or adjust the pH of the mixed liquid, a function to measure or adjust the concentration of microorganisms in the mixed liquid, and a function to stir the mixed liquid.

[0016] The type of wastewater to be biologically treated in the biological treatment unit is not particularly limited, and examples thereof include domestic wastewater discharged from homes and small settlements, such as toilets, kitchens, and bathrooms, urban wastewater, commercial wastewater, agricultural wastewater, dairy wastewater, and industrial wastewater. The wastewater to be subjected to biological treatment may contain both liquid and solid components, or may contain only liquid components.

[0017] (Alkali addition section) The water treatment system of the present disclosure includes an alkali addition unit that adds an alkaline substance to the biological treatment unit. The alkali adding unit adds an alkaline substance to a mixture of wastewater and microorganisms in a tank used for biological treatment, for example.

[0018] The configuration of the alkali adding section is not particularly limited as long as it can add an alkaline substance to the biological treatment section. For example, the alkali addition unit may have a configuration that allows an alkaline substance to be added to the inside of a tank used for biological treatment.

[0019] The timing of adding the alkaline substance to the biological treatment section is not particularly limited as long as it is while the wastewater is in contact with microorganisms in the biological treatment section. The addition of the alkaline substance by the alkali adding section may be carried out continuously or intermittently.

[0020] In order to reduce the impact on the activity of the microorganisms used in the biological treatment, it is preferable that the alkaline substance is added by the alkali addition unit so that the pH in the biological treatment unit (e.g., the inside of the tank where the biological treatment is carried out) does not exceed 9.

[0021] The addition of an alkaline substance by the alkali adding unit may be carried out based on the color of the treated water after the ozone treatment. In the water treatment system of the present disclosure, alkaline substances are added to the biological treatment unit as a means of enhancing the decolorizing effect of ozone treatment. However, adding alkaline substances in an amount exceeding that required to improve the decolorizing effect of water not only does not contribute to improving the decolorizing effect, but may also have undesirable effects (e.g., a decrease in the activity of microorganisms used in biological treatment). Therefore, if the color of the treated water after ozone treatment remains sufficiently low (for example, a color of preferably 10 or less, more preferably zero), the decolorizing effect of the ozone treatment can be sufficiently enhanced by reducing the amount or frequency of addition of alkaline substances while avoiding the undesirable effects of adding alkaline substances.

[0022] Methods for adding alkaline substances by the alkali addition unit based on the chromaticity of the treated water after ozone treatment include a method for adjusting the amount of alkaline substance added based on the chromaticity of the treated water, and a method for determining the frequency of addition of alkaline substances based on the chromaticity of the treated water. More specifically, if the chromaticity of the treated water is higher than a predetermined standard value, the amount or frequency of addition of alkaline substance is increased or the addition of alkaline substance is started, and if the chromaticity of the treated water is below the predetermined standard value, the amount or frequency of addition of alkaline substance is reduced or the addition of alkaline substance is stopped. The standard value for the color of the treated water after ozone treatment is not particularly limited, and can be set depending on the method of use, application, etc. of the treated water.

[0023] The method for measuring the chromaticity of the ozone-treated water is not particularly limited, and examples thereof include a method in which a colorimeter is installed in a tank containing the ozone-treated water, and a method in which the chromaticity of a sample obtained from the ozone-treated water is measured. The measurement of the color of the treated water may be carried out continuously or intermittently (for example, measuring the color at predetermined times).

[0024] In the water treatment system of the present disclosure, the addition of the alkaline substance and the measurement of the color of the treated water may be performed automatically or manually. In order to constantly monitor the state of the treated water, it is preferable to perform the addition of the alkaline substance and the measurement of the color of the treated water automatically.

[0025] In the water treatment system of the present disclosure, the addition of alkaline substances may be controlled based on the results of monitoring the pH of the biological treatment unit, or based on the results of monitoring the trend in the color of the treated water depending on the amount or capacity of the ozone supply from the ozone treatment unit.

[0026] The type of alkaline substance added to the biological treatment section is not particularly limited. In the present disclosure, an alkaline substance means a substance that exhibits basicity (pH greater than 7) when dissolved in water. Examples of alkaline substances include compounds containing alkali metals or alkaline earth metals (hydroxides, carbonates, phosphates, oxides, etc.), amines, ammonium, and the like. From the viewpoint of the effect of adding an alkaline substance and ease of handling, sodium hydroxide and potassium hydroxide are preferred as the alkaline substance, and sodium hydroxide is more preferred.

[0027] The state of the alkaline substance added to the biological treatment unit is not particularly limited. For example, the alkaline substance added to the biological treatment unit may be in a solid state such as a powder or tablet, or in a liquid state such as an aqueous solution. From the viewpoint of ease of control of the amount added, it is more preferable that the alkaline substance be added to the biological treatment unit in the form of an aqueous solution.

[0028] (Ozone treatment unit) The water treatment system of the present disclosure includes an ozone treatment unit that performs ozone treatment on treated water. By carrying out ozone treatment of treated water, the color of the treated water can be reduced (decolorized). The configuration of the ozone treatment unit is not particularly limited as long as it can perform ozone treatment on the treated water. The ozone treatment unit may include, for example, a tank that can hold a predetermined amount of treated water and an ozone supply device that supplies ozone into the tank. The tank included in the ozone treatment unit may be a tank that performs ozone treatment of the treated water alone, or a combination of a tank that performs ozone treatment of the treated water and a tank that stores the treated water after it has been ozone treated.

[0029] When the ozonation treatment unit is provided with a tank capable of storing treated water, the amount of treated water that can be stored in the tank is not particularly limited and can be selected depending on the intended use of the biological treatment system. For example, the upper limit of the amount of treated water that can be stored in the tank may be any of 10,000 liters, 5,000 liters, 1,000 liters, 500 liters, 300 liters, and 150 liters. The lower limit of the amount of treated water to be stored in the tank is not particularly limited and can be selected depending on the application of the biological treatment system. For example, the lower limit of the amount of treated water to be stored in the tank may be 1 liter, 10 liters, or 50 liters.

[0030] When the ozone treatment section includes an ozone supplying device, the type of the ozone supplying device is not particularly limited. For example, a known ozone generator may be used as the ozone supplying device.

[0031] The ozonation unit may have a function other than ozonation of the treated water as needed. For example, if the alkali addition unit adds an alkaline substance based on the chromaticity of the treated water after ozonation, the ozonation unit may have a colorimeter that measures the chromaticity of the treated water. When the ozone treatment unit is equipped with a colorimeter, the colorimeter may be installed in the tank where the ozone treatment is performed, or in the tank where the treated water after ozone treatment is stored, and it is preferable that the colorimeter be installed in the tank where the treated water after ozone treatment is stored.

[0032] (Solid-liquid separation section) The treated water obtained by biologically treating wastewater in a biological treatment unit may be in the form of a mixture (hereinafter referred to as a treated mixture) of liquid components including the treated water and solid components (microorganisms used in biological treatment, organic components, inorganic components, etc.). For this reason, the water treatment system of the present disclosure may further include a solid-liquid separation section that separates the liquid component and the solid component contained in the treatment mixture. By providing a solid-liquid separation section in the water treatment system, for example, only the liquid components contained in the treatment mixture can be transferred from the biological treatment section to the ozone treatment section.

[0033] Methods for separating the solid and liquid components contained in the treatment mixture include capturing the solid components with a filter, precipitating or floating the solid components, and adsorbing the solid components to an adsorbent. Methods for precipitating solid components contained in the treatment mixture include static precipitation, flocculation precipitation in which a flocculant is added, and electroprecipitation in which the solid components are flocculated by charging. Methods for floating the solid components contained in the treatment mixture include atmospheric flotation using a foaming agent or foaming aid, and pressurized flotation using fine bubbles.

[0034] The configuration of the solid-liquid separation section is not particularly limited and can be selected depending on the state of the solid components contained in the treatment mixture, etc. Specific examples of materials that can be used in the filtration section include known materials such as sand, cellulose, porous synthetic resin, polymer fibers such as nonwoven fabric, activated carbon, zeolite, ceramics, and filtration membranes.

[0035] The water treatment system of the present disclosure may or may not be a separate entity. When the water treatment system is an independent object, it may be portable. For example, it may be in a state where it can be transported to a predetermined location and used when camping, during disaster evacuation, etc. When the water treatment system is not an independent object, it may be incorporated as part of a building or an object other than a building. Examples of objects other than buildings include, but are not limited to, automobiles, trains, ships, aircraft, trailer homes, etc.

[0036] The water treatment systems of the present disclosure may or may not be cyclic. In the present disclosure, a water treatment system being of a circulating type means that all or part of the treated water after ozone treatment is returned to the source of the wastewater. A specific example of a circulating water treatment system is a system (circulating flush toilet) that performs biological treatment and ozone treatment on wastewater from household facilities such as kitchens, bathrooms, and toilets, and reuses the treated water after ozone treatment as flush water for flushing toilets.

[0037] A preferred embodiment of the water treatment system of the present disclosure is shown in FIG. The water treatment system 10 shown in FIG. a biological treatment tank 11 for storing wastewater and for biologically treating the wastewater to obtain treated water; an alkali adding device 12 that supplies an alkaline substance to the inside of the biological treatment tank 11; The biological treatment tank 11 is provided with an ozone treatment tank 13 that stores the treated water obtained in the biological treatment tank 11 and performs ozone treatment on the treated water. The ozone treatment tank 13 is equipped with an ozone supply device 14 that supplies ozone to the ozone treatment tank 13 , and a colorimeter 15 that measures the color of the treated water inside the ozone treatment tank 13 .

[0038] In the water treatment system 10, the biological treatment tank 11 corresponds to the biological treatment unit, the alkali addition device 12 corresponds to the alkali supply unit, and the ozone treatment tank 13 corresponds to the ozone treatment unit. Although not shown, the water treatment system 10 may further include a control unit that controls the addition of alkaline substance by the alkali addition device 12 based on the chromaticity of the treated water measured by the colorimeter 15. Although not shown, the water treatment system 10 may further include a control unit that controls the supply of ozone by the ozone supply device 14 based on the chromaticity of the treated water measured by the colorimeter 15.

[0039] 1, colorimeter 15 is connected to ozone treatment tank 13, but the water treatment system of the present disclosure is not limited to this configuration. For example, water treatment system 10 may further include a tank for storing treated water after ozone treatment, and colorimeter 15 may be connected to the tank.

[0040] <Water treatment method> The water treatment method of the present disclosure includes: a biological treatment step in which the wastewater is biologically treated in the biological treatment tank to obtain treated water; an alkali addition step of adding an alkaline substance to the biological treatment tank; and an ozone treatment step of subjecting the treated water to ozone treatment.

[0041] The water treatment method of the present disclosure is excellent in decolorizing water that has been subjected to biological treatment. In the water treatment method of the present disclosure, the methods for carrying out the biological treatment step, alkali addition step, and ozone treatment step are not particularly limited, and can be carried out by known methods. The biological treatment step, alkali addition step, and ozone treatment step may be carried out using the biological treatment unit, alkali addition unit, and ozone treatment unit included in the water treatment system of the present disclosure described above.

[0042] From the viewpoint of reducing the effect on the activity of the microorganisms used in the biological treatment, it is more preferable to add the alkaline substance in the alkali addition step so that the pH of the contents of the biological treatment tank does not exceed 9.

[0043] The addition of the alkaline substance in the alkali addition step may be carried out based on the color of the treated water after the ozone treatment. In the water treatment method of the present disclosure, alkaline substances are added to the biological treatment tank as a means of enhancing the decolorizing effect of ozone treatment. However, adding alkaline substances in excess of the amount necessary to improve the decolorizing effect of the water not only does not contribute to improving the decolorizing effect, but may also have undesirable effects (e.g., a decrease in the activity of the microorganisms used in the biological treatment). Therefore, if the color of the treated water after ozone treatment remains sufficiently low (for example, a color of preferably 10 or less, more preferably zero), the decolorizing effect of the ozone treatment can be sufficiently enhanced by reducing the amount or frequency of addition of alkaline substances while avoiding the undesirable effects of adding alkaline substances.

[0044] Methods for adding an alkaline substance in the alkali addition step based on the chromaticity of the treated water after ozone treatment include a method in which the amount of alkaline substance added is adjusted based on the chromaticity of the treated water, and a method in which the frequency of adding an alkaline substance is determined based on the chromaticity of the treated water. More specifically, if the chromaticity of the treated water is higher than a predetermined standard value, the amount or frequency of addition of alkaline substance is increased or the addition of alkaline substance is started, and if the chromaticity of the treated water is below the predetermined standard value, the amount or frequency of addition of alkaline substance is reduced or the addition of alkaline substance is stopped. The standard value for the color of the treated water after ozone treatment is not particularly limited, and can be set depending on the method of use, application, etc. of the treated water.

[0045] The method for measuring the chromaticity of the ozone-treated water is not particularly limited, and examples thereof include a method in which a colorimeter is installed in a tank containing the ozone-treated water, and a method in which the chromaticity of a sample obtained from the ozone-treated water is measured. The measurement of the color of the treated water may be carried out continuously or intermittently (for example, measuring the color at predetermined times).

[0046] In the water treatment method of the present disclosure, the addition of the alkaline substance and the measurement of the color of the treated water may be performed automatically or manually. In order to constantly monitor the state of the treated water, it is preferable to perform the addition of the alkaline substance and the measurement of the color of the treated water automatically.

[0047] The type of alkaline substance added to the biological treatment tank is not particularly limited. In the present disclosure, an alkaline substance means a substance that exhibits basicity (pH greater than 7) when dissolved in water. Examples of alkaline substances include compounds containing alkali metals or alkaline earth metals (hydroxides, carbonates, phosphates, oxides, etc.), amines, ammonium, and the like. From the viewpoint of the effect of adding an alkaline substance and ease of handling, sodium hydroxide and potassium hydroxide are preferred as the alkaline substance, and sodium hydroxide is more preferred.

[0048] The state of the alkaline substance added to the biological treatment tank is not particularly limited. For example, the alkaline substance added to the biological treatment tank may be in a solid state such as a powder or tablet, or in a liquid state such as an aqueous solution. From the viewpoint of ease of control of the amount added, it is more preferable that the alkaline substance be added to the biological treatment unit in the form of an aqueous solution.

[0049] The water treatment method of the present disclosure may further include a solid-liquid separation step of separating the liquid component and the solid component contained in the treated mixture obtained in the biological treatment step. The solid-liquid separation step may be carried out using the solid-liquid separation section included in the water treatment system of the present disclosure described above.

[0050] The water treatment methods of the present disclosure may or may not be cyclic. In the present disclosure, the water purification method being a circulatory method means that all or part of the treated water after ozone treatment is returned to the source of the wastewater that is the target of biological treatment in the biological treatment step. Specific examples of circulating water treatment methods include biological treatment of wastewater from household facilities such as kitchens, bathrooms, and toilets, and then reusing the treated wastewater as flush water for flush toilets.

[0051] <Water color control method> The water chromaticity control method of the present disclosure includes controlling the chromaticity of treated water using the water treatment system of the present disclosure described above. According to the above method, the chromaticity of the biologically treated water can be controlled to a desired level depending on the intended use, the environment in which the water is used, etc. The chromaticity of the treated water controlled by the above method is not particularly limited and can be set depending on the method of use of the treated water, etc.

[0052] When the treated water is used as flush water for toilets, the chromaticity of the treated water may be controlled depending on the color of the toilet bowl. For example, if the toilet bowl is white, the chromaticity of the treated water may be controlled to zero, and if the toilet bowl is beige, the chromaticity of the treated water may be controlled so that the upper limit is about 5. Furthermore, when the treated water is used as flush water for portable toilets, the chromaticity of the treated water may be controlled so that the upper limit is about 10. [Explanation of symbols]

[0053] 10 Water Treatment Systems 11 Biological treatment tank 12 Alkali addition device 13 Ozone Treatment Tank 14 Ozone supply device 15 Color meter

Claims

1. a biological treatment unit that performs biological treatment on wastewater to obtain treated water; an alkali adding unit that adds an alkaline substance to the biological treatment unit; an ozone treatment unit that performs ozone treatment on the treated water.

2. The water treatment system according to claim 1 , wherein the alkali adding unit adds the alkaline substance so that the pH of the biological treatment unit does not exceed 9.

3. 3. The water treatment system of claim 1 or claim 2, wherein the alkaline substance comprises sodium hydroxide.

4. 3. The water treatment system according to claim 1, wherein the alkaline substance is in the form of an aqueous solution.

5. a biological treatment step in which the wastewater is biologically treated in the biological treatment tank to obtain treated water; an alkali addition step of adding an alkaline substance to the biological treatment tank; an ozone treatment step of treating the treated water with ozone.

6. The water treatment method according to claim 5 , wherein the alkali addition step includes adding an alkaline substance so that the pH inside the biological treatment tank does not exceed 9.

7. 7. The water treatment method according to claim 5 or claim 6, wherein the alkaline substance comprises sodium hydroxide.

8. 7. The water treatment method according to claim 5, wherein the alkaline substance is in the form of an aqueous solution.

9. A method for controlling the color of water, comprising controlling the color of treated water using the water treatment system of claim 1.

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