Water treatment method, control device for water treatment device, and control program for water treatment device

Abstract

Provided is a water treatment method by which treated water can be obtained by causing water to be treated to pass through a particulate-filled layer. In this water treatment method, the water depth of a water layer adjacent to the upper surface of the particulate-filled layer is no less than a water depth at which foam is not generated in the water to be treated in the water layer.

Description

[Technical Field]

[0001] The present invention relates to a water treatment method, a control device for a water treatment device, and a control program for a water treatment device. [Background technology]

[0002] Wastewater that has been used for various purposes, such as as cleaning water, cannot be discharged as is. Therefore, methods for treating wastewater have been studied, including passing the water through a bed packed with activated carbon (see, for example, Patent Documents 1 and 2).

[0003] Furthermore, in recent years, attention has been drawn to a water treatment method known as advanced oxidation process (AOP), which combines ozone with ultraviolet light and hydrogen peroxide to promote the generation of hydroxyl radicals and thereby decompose persistent substances (see, for example, Patent Document 3). In water treatment methods employing advanced oxidation process, a step is generally carried out after the advanced oxidation process, in which the water to be treated that has undergone the advanced oxidation process is introduced into a packed bed filled with, for example, powdered activated carbon or other granular adsorbent (hereinafter referred to as a "granular packed bed"). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2013 / 084855 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-827 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-062583 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the conventional method described above, there was a risk that the water to be treated would foam in a granular packed bed such as an activated carbon packed bed, and the bubbles would fill the voids in the granular packed bed, causing the granular packed bed to become clogged.

[0006] Therefore, the present invention aims to provide a water treatment method in which treated water is obtained by passing the water to be treated through a granular material packed bed, which can effectively prevent the granular material packed bed from being blocked by air bubbles. [Means for solving the problem]

[0007] The present invention aims to advantageously solve the above-mentioned problems, and the water treatment method of the present invention is a water treatment method in which treated water is obtained by passing water to be treated through a granular material packed bed, and is characterized in that the water depth of the water layer adjacent to the upper surface of the granular material packed bed is set to a water depth that does not cause foaming in the treated water in the water layer.

[0008] The present invention also aims to advantageously solve the above-mentioned problems, and the control device for a water treatment device of the present invention is a control device for a water treatment device that obtains treated water by passing water to be treated through a granular material packed bed, and is characterized in that it is equipped with a water depth calculation and adjustment device that sets the water depth of the water layer adjacent to the upper surface of the granular material packed bed to a water depth that does not cause foaming in the water to be treated in the water layer.

[0009] Furthermore, the present invention aims to advantageously solve the above-mentioned problems, and is characterized in that the control program for a water treatment device of the present invention causes a water treatment device that obtains treated water by passing water to be treated through a granular material packed bed to execute a step of determining the water depth of the water layer adjacent to the upper surface of the granular material packed bed, at a depth in the water layer at which foaming does not occur in the water to be treated. [Effects of the Invention]

[0010] According to the present invention, clogging of the granular material packed bed by air bubbles can be effectively prevented. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is an explanatory diagram showing a schematic configuration of a typical water treatment apparatus for performing a water treatment method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below with reference to the accompanying drawings. The water treatment method, the control device for the water treatment device, and the control program for the water treatment device of the present invention are not particularly limited and can be suitably used in, for example, an accelerated oxidation treatment that may be carried out in a water purification plant or the like to decompose persistent pollutants in the water to be treated.

[0013] The water treatment method of the present invention is a water treatment method in which water to be treated is passed through a granular material packed bed to obtain treated water, and is characterized in that the water depth of the water layer adjacent to the upper surface of the granular material packed bed is set to a water depth at which bubbles do not form in the water to be treated in the water layer or the granular material packed bed. This water treatment method of the present invention can effectively prevent the granular material packed bed from being clogged with bubbles. As an example, the application of the water treatment method of the present invention to an accelerated oxidation process is described below.

[0014] 1 shows a schematic configuration of a typical example of a water treatment device that can be used when applying the water treatment method according to the present invention to advanced oxidation treatment. The water treatment device 100 includes an advanced oxidation treatment tank 10 and a filtration tank 20. In the water treatment device 100, water to be treated is introduced into the water treatment device 100 by gravity flow or pumping, and after contacting the water with hydrogen peroxide and ozone in the advanced oxidation treatment tank 10, the water is fed to the filtration tank 20 and discharged as treated water outside the device. Note that, hereinafter, the inlet side of the water treatment device 100 may be referred to as the "previous stage side" and the outlet side as the "next stage side." In the following description, the water treatment method of the present invention will be described as being implemented in a water treatment device 100, but the water treatment method of the present invention is not limited in any way by the presence or absence of any physical components in the device that implements the water treatment method.

[0015] <Untreated water> The water to be treated in the water treatment method of the present invention is not particularly limited, and examples thereof include raw water for tap water. More specifically, examples of the water to be treated include water taken from dams, rivers, lake water, well water, spring water, and groundwater.

[0016] <Accelerated oxidation treatment tank> The water to be treated is brought into contact with hydrogen peroxide and ozone in an advanced oxidation treatment tank 10 and subjected to advanced oxidation treatment. The advanced oxidation treatment tank 10 includes an ozone contact tank 11 on the upstream side and a retention tank 12 on the downstream side. The ozone contact tank 11 has an ozone supply device 13 and a hydrogen peroxide injector 14. FIG. 1 shows, as an example, an embodiment in which the ozone contact tank 11 is implemented as a two-tank configuration. Each of these two tanks is equipped with an ozone supply device 13, and the downstream tank is equipped with an ozone supply device 13 and a hydrogen peroxide injector 14. The upstream tank functions to bring the ozone and the water to be treated into contact with each other and mix them. Some of the ozone that comes into contact with the water to be treated reacts with and decomposes substances to be decomposed in the water to be treated, and the remainder dissolves in the water to be treated.

[0017] The downstream tank of the ozone contact tank 11 functions to bring ozone, the water to be treated, and hydrogen peroxide into contact with each other and mix them. In the downstream tank of the ozone contact tank 11, ozone reacts with hydrogen peroxide to generate hydroxyl radicals, which have stronger oxidizing power than ozone. These hydroxyl radicals can effectively decompose substances to be decomposed in the water to be treated, particularly persistent substances. Furthermore, because ozone is decomposed by the generation of the hydroxyl radicals, it is possible to prevent the amount of ozone in the water to be treated from becoming excessive.

[0018] The hydrogen peroxide injector 14, located in a downstream tank of the ozone contact tank 11, injects a predetermined amount of hydrogen peroxide into the water to be treated. The amount of hydrogen peroxide injected may be predetermined through a preliminary test or may be determined as needed based on the amount of ozone added. For example, the amount of oxygen peroxide injected may be set so that the hydrogen peroxide concentration in the water to be treated is 5 mg / L or less. The hydrogen peroxide injector 14 is not particularly limited and may be implemented as a general chemical injection device that can be attached to a water treatment device, such as a hydrogen peroxide storage tank, a supply pump, and a flow control valve.

[0019] The retention tank 12 retains the water to be treated that has been contacted and mixed with ozone and hydrogen peroxide in the ozone contact tank 11. Some of the hydrogen peroxide injected into the water to be treated by the hydrogen peroxide injector 14 is decomposed as the water passes through the ozone contact tank 11 to the retention tank 12 that make up the advanced oxidation treatment tank 10. Conversely, the water to be treated that is supplied to the filtration tank 20 via the advanced oxidation treatment tank 10 contains hydrogen peroxide that was not decomposed during the advanced oxidation treatment in the advanced oxidation treatment tank 10 and remains. Furthermore, the water to be treated that has been contacted and mixed with ozone in the ozone contact tank 11 may cause bubbles to be generated in the granular material packed bed 21, regardless of whether it contains hydrogen peroxide or not.

[0020] <Filtration tank> In the filtration tank 20, the water to be treated that has passed through the advanced oxidation treatment tank 10 is passed through the granular material packed bed 21 to obtain treated water. As described above, the depth of the water layer adjacent to the upper surface of the granular material packed bed 21 must be equal to or greater than the water depth X at which foaming does not occur in the water to be treated in the water layer. Note that, for the purpose of facilitating understanding, FIG. 1 illustrates a hypothetical state in which foaming occurs in the water to be treated in the water layer adjacent to the upper surface of the granular material packed bed 21. However, according to the water treatment method of the present invention, foaming does not occur in the water to be treated in the water layer adjacent to the upper surface of the granular material packed bed 21.

[0021] 1, in carrying out the water treatment method of the present invention, it is preferable to supply the water to be treated from the upper surface of the granular material packed bed 21 to the water layer adjacent to the upper surface of the granular material packed bed 21. In this way, clogging of the granular material packed bed 21 by air bubbles can be more effectively prevented.

[0022] The granules constituting the granular packed bed 21 may be adsorbents such as powdered activated carbon. Furthermore, the granules constituting the granular packed bed 21 may contain other granules capable of functioning as decomposition catalysts, such as powdered manganese dioxide or powdered iron (III) chloride. In the filtration tank 20, organic matter remaining in the water to be treated can be adsorbed onto an adsorbent such as powdered activated carbon. Furthermore, when the granules constituting the granular packed bed 21 contain granules capable of functioning as decomposition catalysts, such as powdered manganese dioxide or powdered iron (III) chloride, the organic matter remaining in the water to be treated can be decomposed in the filtration tank 20. The filtration tank 20 is not particularly limited, and a commonly used configuration, such as an activated carbon filter, can be used.

[0023] In the filtration tank 20, gas may be generated due to the decomposition of hydrogen peroxide contained in the water being treated on the surface of the granules. More specifically, the decomposition of hydrogen peroxide (HO) may generate oxygen (O) and water (HO). Gas may also be generated in the filtration tank 20 due to the water being mixed with ozone. Even if gases such as oxygen are generated for some reason, the generation of bubbles can be suppressed if the generated gases are dissolved in the water being treated. Therefore, if the oxygen solubility value of the water being treated is equal to or greater than the amount of oxygen generated and the generated oxygen can be dissolved in the water being treated, the generation of bubbles can be suppressed. The oxygen solubility value in water depends on the water temperature and water depth. Therefore, under certain water temperature conditions, the generation of bubbles can be suppressed by increasing the water depth of the water layer adjacent to the top surface of the granule-filled bed 21 (in other words, the upper end of the granule-filled bed 21) beyond a predetermined depth.

[0024] The water depth X can be determined so that the oxygen solubility (mg / L) corresponding to the water temperature and water depth X is greater than the oxygen generation rate (mg / L) calculated based on the hydrogen peroxide concentration of the water. More specifically, the water depth X can be determined so that the oxygen solubility (mg / L) corresponding to the water temperature and water depth X is greater than the oxygen generation rate (mg / L) calculated based on the hydrogen peroxide concentration of the water. The water depth X can be determined so that the oxygen solubility (mg / L) corresponding to the water temperature and water depth X is greater than the oxygen generation rate (mg / L) calculated based on the hydrogen peroxide concentration of the water. By determining the water depth X so that the oxygen solubility exceeds the oxygen generation rate at the interface between the granular material packed bed 21 and the water layer adjacent to its upper surface, the generation of bubbles in the water can be more effectively suppressed. As shown in FIG. 1, the water depth X corresponds to the distance from the upper surface of the granular material packed bed 21 to the water surface. The inventors have found through their investigations that air bubbles first occur on the upper surface of the granular material packed bed 21 (i.e., the interface between the water layer and the granular material packed bed 21), and then the position of air bubbles tends to migrate toward the interior of the granular material packed bed 21. The inventors have also found that if the water depth X is set to a value that suppresses the generation of air bubbles on the upper surface of the granular material packed bed 21, the generation of air bubbles inside the granular material packed bed 21 can also be suppressed. In this way, by suppressing foaming on the upper surface (interface) of the granular material packed bed 21, it is possible to effectively suppress the generation of foaming in the granular material packed bed 21 and the clogging of the granular material packed bed 21.

[0025] The depth of the water layer adjacent to the upper surface of the granular material packed bed 21, in other words, the water depth X, can be set to a predetermined value using a water depth adjusting device 22, which can be implemented, for example, as a valve. More specifically, the water depth X can be made shallower by increasing the opening of the valve constituting the water depth adjusting device 22, and conversely, the water depth X can be made deeper by decreasing the opening. The opening of the valve constituting the water depth adjusting device 22 can be determined in advance based on a preliminary test and the set flow rate of the water to be treated in the water treatment device 100. The water depth X can be adjusted by the water depth adjusting device 22 periodically (for example, every season) when the operating conditions of the water treatment device 100 are reviewed, or when some malfunction occurs in the water treatment device 100, to ensure an appropriate water depth X.

[0026] As described above, the value of water depth X can be determined based on the water temperature, oxygen solubility, oxygen generation rate, etc. Specific values ​​for water depth X include 1.2 m or more, or 1.5 m or more. If water depth X is equal to or greater than the relevant value, clogging of the granular material packed bed by bubbles caused by hydrogen peroxide can be more effectively prevented.

[0027] The water treatment method of the present invention has been described above with reference to an example water treatment device 100. Various settings and operations of the device components in the water treatment method of the present invention may be performed manually or automatically controlled in accordance with a control program for the water treatment device of the present invention. The control program for the water treatment device of the present invention is characterized by causing a water treatment device, which obtains treated water by passing water to be treated through a granular material packed bed, to execute a step of determining the water depth X of the water layer adjacent to the upper surface of the granular material packed bed, such that bubbles do not form in the water to be treated in the water layer. By causing the water treatment device 100 to execute the step of determining such water depth X, clogging of the granular material packed bed 21 provided in the water treatment device 100 by air bubbles can be effectively prevented.

[0028] Furthermore, the water treatment device 100 that can suitably carry out the water treatment method of the present application is not particularly limited, and may include any of the components listed below, for example.

[0029] <Control device> The water treatment device 100 may optionally include additional components, such as a control device 30 and a treated water information measuring device 40. Furthermore, the control device 30 preferably includes a treated water information acquiring unit 31, a hydrogen peroxide supply rate control device 32, and a water depth X calculation and adjusting device 33. The treated water information acquiring unit 31 is not particularly limited and may be configured with an input / output port or the like. The hydrogen peroxide supply rate control device 32 and the water depth X calculation and adjusting device 33 are not particularly limited and may be configured with a central processing unit (CPU) or the like, and may include an internal or external storage unit (e.g., memory) or the like, although not shown. Furthermore, the water depth X calculation and adjusting device 33 controls the water depth adjusting device 22 to adjust the water depth of the water layer adjacent to the upper surface of the granular material packed bed 21 to a depth X or greater at which foaming does not occur in the treated water in the water layer. Furthermore, the treated water information measuring device 40 is not particularly limited and may be equipped with various sensors (e.g., a turbidity meter, a water thermometer, etc.) that can acquire information about the treated water, such as the water quality and water temperature of the treated water.

[0030] The water depth X calculation and adjustment device 33 can acquire information on the water quality of the water being treated supplied to the advanced oxidation treatment tank 10 from the water treatment information acquisition unit 31, and acquire the amount of hydrogen peroxide supplied to the advanced oxidation treatment tank 10 from the hydrogen peroxide supply amount control device 32. The water depth X calculation and adjustment device 33 can then calculate the concentration of hydrogen peroxide (mg / L) in the water being treated supplied to the filtration tank 20 based on the water quality information of the water being treated and the amount of hydrogen peroxide supplied. The water depth X calculation and adjustment device 33 can then calculate the amount of oxygen generated (mg / L) when all of the hydrogen peroxide is decomposed. Furthermore, the water depth X calculation and adjustment device 33 can calculate the oxygen solubility value (mg / L) for water depth X based on the water temperature of the water being treated acquired from the water treatment information measurement device 40, based on Henry's law, and determine the water depth X so that the obtained value (mg / L) exceeds the amount of oxygen generated (mg / L).

[0031] The water depth X may be calculated by operating the various physical components described above using a water depth X determination program, which will be described below. One example of such a water depth X determination program causes the water depth X calculation and adjustment device 33 to execute the following steps: acquiring the water temperature of the water to be treated (S1); calculating the amount of oxygen generated from the hydrogen peroxide concentration of the water to be treated (S2); and calculating the oxygen solubility (mg / L) for the water depth X at the acquired water temperature and the water depth X, and determining the water depth X so that the obtained oxygen solubility (mg / L) exceeds the amount of oxygen generated (mg / L) calculated in step (S2). The water depth X determination program may control the above-mentioned treated water information acquisition unit 31 to acquire treated water information such as the water temperature of the treated water, and then directly acquire the acquired treated water information by the water depth X calculation adjustment device 33, or it may temporarily store the treated water information acquired by the treated water information acquisition unit 31 in memory (not shown), and then control the water depth X calculation adjustment device 33 to read the treated water information from the memory.

[0032] Each of the above programs may be recorded on a computer-readable recording medium. Using such a recording medium, the program can be installed on a computer. Here, the recording medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a CD-ROM, a DVD-ROM, or the like. Furthermore, each of the above programs may be provided by downloading via a network. [Industrial Applicability]

[0033] According to the present invention, clogging of the granular material packed bed by air bubbles can be effectively prevented. [Explanation of symbols]

[0034] 10. Accelerated oxidation treatment tank 11 Ozone contact tank 12 Retention tank 13 Ozone supply device 14 Hydrogen peroxide injection device 20 Filtration tank 21 Granular packed bed 22 Depth adjustment device 30 Control device 31 Treated water information acquisition department 32 Hydrogen peroxide supply amount control device 33 Water depth X calculation adjustment device 40 Treated water information measuring device 100 Water treatment equipment

Claims

1. A water treatment method for obtaining treated water by passing water to be treated containing hydrogen peroxide through a packed bed of granules containing powdered activated carbon, comprising: The water to be treated is supplied from the upper surface side of the granular material packed bed to a water layer adjacent to the upper surface of the granular material packed bed, The water depth of the water layer adjacent to the upper surface of the granular material packed bed is set to a water depth at which bubbles do not occur in the water to be treated in the water layer. Water treatment methods.

2. The water treatment method of claim 1, wherein the water depth is determined so that the oxygen solubility (mg / L) corresponding to the water temperature and the water depth of the treated water is greater than the oxygen generation amount (mg / L) calculated based on the hydrogen peroxide concentration of the treated water.

3. A control device for a water treatment device in which treated water containing hydrogen peroxide is passed through a granular material packed bed containing powdered activated carbon to obtain treated water, the water treatment device supplies the water to be treated from an upper surface side of the granular material packed bed to a water layer adjacent to the upper surface of the granular material packed bed, The control device includes a water depth calculation and adjustment device that sets the water depth of the water layer adjacent to the upper surface of the granular material packed bed to a water depth at which foaming does not occur in the treated water in the water layer. Control device for water treatment equipment.

4. A control program for a water treatment device that obtains treated water by passing water to be treated that contains hydrogen peroxide through a packed bed of granular material that contains powdered activated carbon, comprising: the water treatment device supplies the water to be treated from an upper surface side of the granular material packed bed to a water layer adjacent to the upper surface of the granular material packed bed, A control program for a water treatment device that causes the water treatment device to execute a step of determining the depth of a water layer adjacent to the upper surface of the granular material packed bed, at which the water depth in the water layer does not cause foaming in the water to be treated.

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