Water treatment apparatus and water treatment method

Abstract

To provide a water treatment apparatus and a water treatment method in which quality of treated water after membrane filtration treatment is stably measured using absorbance-based water quality detection means, with minimal impact from fine bubbles generated during membrane filtration treatment, enabling more stable control of water treatment.SOLUTION: A water treatment apparatus includes: a treated water tank for storing treated water; a circulation pipeline for withdrawing a part of the treated water in the treated water tank, and returning it to the treated water tank for circulation; a circulation pump installed in the circulation pipeline to circulate the treated water; and absorbance-type water quality detection means installed in the circulation pipeline, wherein the water quality of the treated water circulating through the circulation pipeline is measured by the absorbance-type water quality detection means. Furthermore, a water treatment method includes: storing the treated water after membrane filtration treatment in the treated water tank; withdrawing a part of the treated water from the treated water tank and returning it to the treated water tank for circulation; and measuring the water quality of the circulating treated water by using the absorbance-type water quality detection means.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] It is known to treat raw water such as groundwater and river water using membranes. Raw water often contains large amounts of various impurities such as organic matter, suspended solids, and microorganisms. In addition, depending on the geological conditions, such as peat bogs, the raw water may contain large amounts of dissolved humic substances, which can cause color changes.

[0003] Patent Document 1 proposes a water treatment device that combines ultraviolet treatment and membrane filtration treatment as a water treatment device that removes impurities from water to be treated. In the device described in Patent Document 1, a turbidity meter is installed in the pipe through which treated water that has been treated by the membrane filtration device flows, and membrane rupture is detected by the turbidity measured by the turbidity meter. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-218361 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the inventors' investigations revealed that the device described in Patent Document 1 is prone to errors in water quality measurements that use absorbance, such as with a turbidimeter, and is prone to malfunctions in the control of the water treatment device. Specifically, because the water to be treated is supplied to the filtration membrane under pressure from a pump, air is easily mixed in, causing microbubbles to form in the treated water that passes through the filtration membrane. A turbidimeter, which is an absorbance-based water quality detection means, detects not only pigment-derived particles but also microbubbles, making it prone to errors in measurements.

[0006] The main object of the present invention is to provide a water treatment apparatus and a water treatment method that are less affected by microbubbles generated during membrane filtration, can stably measure the water quality of treated water after membrane filtration using an absorbance-based water quality detection means, and can more stably control the water treatment. [Means for solving the problem]

[0007] After detailed investigation, the inventors discovered that by withdrawing a portion of the treated water from a treatment tank that stores the treated water after membrane filtration and circulating it back into the treatment tank while measuring the water quality of the circulating treated water using an absorbance-based water quality detection means, it is possible to prevent the fine bubbles generated during membrane filtration from adversely affecting measurements that utilize absorbance, and thus completed the present invention.

[0008] That is, the present invention includes the following configurations. [1] A water treatment device that treats water to be treated using a filtration membrane to obtain treated water, a treated water tank for storing the treated water; a circulation pipe for extracting a portion of the treated water from the treatment tank and returning it to the treatment tank for circulation; a circulation pump installed in the circulation piping and circulating the treated water; an absorbance-type water quality detection means installed in the circulation pipe, The water treatment device, wherein the absorbance-based water quality detection means measures the water quality of the treated water circulating through the circulation pipe. [2] A water treatment device that treats water to be treated using a filtration membrane to obtain treated water, a treated water tank for storing the treated water; a circulation pipe for extracting a portion of the treated water from the treatment tank and returning it to the treatment tank for circulation; a circulation pump installed in the circulation piping and circulating the treated water; a branch pipe branching from the circulation pipe for extracting a portion of the treated water circulating through the circulation pipe; an absorbance-type water quality detection means installed in the branch pipe, The water treatment device, wherein the absorbance-type water quality detection means measures the water quality of the treated water extracted into the branch pipe. [3] The water treatment device according to [1] or [2], wherein the absorbance-type water quality detection means is one or more selected from the group consisting of a colorimeter, a turbidity meter, and an absorbance-type comprehensive water quality meter. [4] The water treatment device according to any one of [1] to [3], wherein the absorbance-type water quality detection means is installed downstream of a circulation pump. [5] A membrane-treated water pipe that supplies the treated water after membrane filtration to the treated water tank, The upper surface of the treated water tank is provided with a tank inlet connected to the membrane-treated water piping and through which the treated water after membrane filtration is supplied, and a tank return port connected to the circulation piping and through which the treated water circulating through the circulation piping is returned, The upper surface of the treatment water tank is rectangular, The water treatment device according to any one of [1] to [4], wherein the water tank inlet and the water tank return port are located at opposite corners of the quadrangle. [6] An outlet is provided at the bottom of the treatment tank, the outlet being connected to the opposite side of the circulation pipe from the side connected to the tank return port, The water treatment device according to [5], wherein the water tank inlet and the outlet are arranged so as not to overlap but to be offset when viewed from above in the vertical direction. [7] The water treatment device according to any one of [1] to [6], wherein the filtration membrane is a pressure type MF membrane or a UF membrane. [8] A water treatment method for treating water to be treated using a filtration membrane to obtain treated water, Storing the treated water after membrane filtration in a treated water tank; extracting a portion of the treated water from the treatment tank and returning it to the treatment tank for circulation; and measuring the quality of the circulating treated water using an absorbance-based water quality detection means. [9] The water treatment method according to [8], wherein the absorbance-based water quality detection means directly measures the water quality of the circulating treated water.

[10] The water treatment method according to [8], wherein a portion of the circulating treated water is extracted, and the water quality of the extracted treated water is measured by the absorbance-type water quality detection means.

[11] The method further includes discharging the treated water stored in the treatment water tank while supplying the treated water after membrane filtration treatment to the treatment water tank, The volume of the treatment tank is V (m 3 ), the flow rate of the treated water supplied downstream from the treated water tank is R(m 3 The water treatment method according to any one of [8] to

[10] , wherein the retention time HRT of the treated water, expressed as HRT=V÷R when the water content is 1 / min, is 5 minutes or more. [Effects of the Invention]

[0009] According to the present invention, a water treatment apparatus and a water treatment method are provided that are less affected by microbubbles generated during membrane filtration, and that can stably measure the water quality of treated water after membrane filtration using an absorbance-based water quality detection means, thereby enabling more stable control of water treatment. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram illustrating a water treatment device according to an embodiment; [Figure 2] 1 is a plan view schematically illustrating the positions of a water tank inlet, a water tank return port, and an outlet port in a water treatment tank of a water treatment device according to an example of an embodiment. FIG. [Figure 3] FIG. 10 is a plan view schematically showing the positions of a water tank inlet, a water tank return port, and an outlet port in a water treatment tank of a water treatment device according to another example of the embodiment. [Figure 4] FIG. 10 is a schematic configuration diagram illustrating a water treatment device according to another embodiment. [Figure 5] FIG. 10 is a schematic configuration diagram illustrating a water treatment device according to another embodiment. [Figure 6] FIG. 10 is a flow chart illustrating operation control of a water treatment device according to a third embodiment. [Figure 7] 1 is a graph showing the measurement results of color and turbidity of water treatment in Example 1. [Figure 8] FIG. 1 is a schematic diagram showing the configuration of a water treatment device used in Comparative Example 1. [Figure 9] 1 is a graph showing the measurement results of color and turbidity of water treatment in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] The terms used in this specification have the following meanings. "M alkalinity" is a value measured in accordance with JIS K 0101 13. Acid consumption. The symbol "to" indicating a range of values means that the values before and after it are included as the lower and upper limits.

[0012] The dimensions of the figures illustrated in the following description are merely examples, and the present invention is not necessarily limited to them, and can be implemented with appropriate modifications within the scope that does not change the gist of the present invention.

[0013] [First embodiment] (Water treatment equipment) FIG. 1 is a schematic diagram illustrating a water treatment device 1 according to an embodiment. The water treatment device 1 is a device for treating water to be treated using a filtration membrane to obtain treated water. The water treatment device 1 includes membrane filtration devices 10A, 10B that perform membrane filtration on the water to be treated W1, a treated water tank 11 for storing the treated water W2 that has been subjected to membrane filtration, and an absorbance-based water quality detection means 15 that measures the water quality of the treated water W2.

[0014] The membrane filtration devices 10A and 10B are connected to the treated water tank 11 by membrane-treated water piping 21. Treated water W2, which is obtained by subjecting the water to be treated W1 to membrane filtration in the membrane filtration devices 10A and 10B, is sent to the treated water tank 11 through the membrane-treated water piping 21 and stored therein.

[0015] The membrane filtration devices 10A and 10B are not particularly limited, and membrane filtration devices used in known water treatment devices can be used. The type, material, and shape of the filtration membrane used in the membrane filtration device are not particularly limited. Regardless of the membrane used, the treated water W2 after treatment contains fine bubbles. Examples of the shape of the filtration membrane include a hollow fiber membrane and a flat membrane. Examples of materials for the filtration membrane include polyvinylidene fluoride (PVDF) and polyvinyl chloride (PVC).

[0016] The filtration membrane may be either a pressure membrane or a submerged membrane, and the present invention is particularly effective when the filtration membrane is a pressure membrane, since the treated water W2 is likely to contain fine bubbles. Specific examples of filtration membranes include ultrafiltration (UF) membranes, microfiltration (MF) membranes, nano (NF) membranes, and reverse osmosis (RO) membranes. Among these, since these membranes are filtration membranes that are prone to generating fine bubbles, the water treatment device of the present invention is particularly useful when equipped with a membrane filtration device equipped with a pressurized MF membrane or UF membrane.

[0017] 1, the membrane filtration device 10A and the membrane filtration device 10B are arranged in parallel, but this is not limiting. For example, multiple membrane filtration devices may be arranged in series, or one membrane filtration device may be arranged independently.

[0018] The treated water tank 11 may be any tank capable of storing treated water, and there are no particular limitations on the type or material. The shape of the treatment water tank 11 is not particularly limited, but is typically a cube or rectangular parallelepiped.

[0019] A water supply pipe 22 is connected to the treated water tank 11 to supply treated water to downstream facilities such as a water receiving tank, and a water supply pump 12 is provided on the water supply pipe 22. By driving the water supply pump 12, treated water W2 in the treated water tank 11 is supplied to the downstream facilities such as a water receiving tank.

[0020] The treated water tank 11 is also provided with a circulation pipe 23 for extracting a portion of the treated water W2 from the treated water tank 11 and returning it to the treated water tank 11 for circulation. The circulation pipe 23 is provided with a circulation pump 13, a circulation flow rate adjustment valve 14, and an absorbance-based water quality detection means 15, in this order. By driving the circulation pump 13, the treated water W2 circulates through the circulation pipe 23, and the circulation flow rate adjustment valve 14 adjusts the flow rate of the treated water W2 flowing through the circulation pipe 23 to a flow rate suitable for measurement by the absorbance-based water quality detection means 15. The absorbance-based water quality detection means 15 then measures the water quality of the treated water W2 circulating through the circulation pipe 23. Furthermore, if the flow rate of the treated water W2 flowing through the circulation piping 23 is a flow rate suitable for measurement by the absorbance-type water quality detection means 15, even without adjustment by the circulation flow rate control valve 14, it is not necessary to install a circulation flow rate control valve 14 in the circulation piping 23.

[0021] In the water treatment device 1 of this example, treated water W2 after membrane filtration in membrane filtration devices 10A and 10B is stored in treated water tank 11, and after the microbubbles generated by the membrane filtration have disappeared to a certain extent in treated water tank 11, the treated water W2 extracted into circulation piping 23 is measured by absorbance-based water quality detection means 15. This reduces the adverse effects of microbubbles on the water quality measurement results obtained by absorbance-based water quality detection means 15. In particular, because compressed air is used to push out the backwash water when backwashing the filtration membrane, microbubbles are likely to be generated in treated water W2 when operation is restarted. However, even in this case, measurement errors by absorbance-based water quality detection means 15 caused by microbubbles can be sufficiently reduced.

[0022] The absorbance-based water quality detection means 15 may be any device capable of measuring the water quality of the treated water W2 using absorbance, preferably one capable of measuring at least one of color and turbidity as specified in the Water Supply Testing Method. Specific examples of the absorbance-based water quality detection means 15 include a colorimeter, a turbidity meter, and an absorbance-based comprehensive water quality meter. An absorbance-based comprehensive water quality meter is a comprehensive water quality meter (e.g., a spectrolyzer manufactured by Ebara Jitsugyo Co., Ltd.) that measures absorbance from ultraviolet light to the visible light range (220 to 720 nm) and can continuously and simultaneously measure ultraviolet absorbance (E260), which is an indicator of organic matter, biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended solids (SS), nitrate nitrogen (NO3-N), and nitrite nitrogen (NO2-N). The absorbance-type water quality detection means 15 is preferably one or more types selected from the group consisting of a colorimeter, a turbidity meter, and an absorbance-type comprehensive water quality meter.

[0023] The circulation pump 13 is not particularly limited, and any known pump used in water treatment equipment can be used. The circulation flow rate control valve 14 is not particularly limited, and any known flow rate control valve used in water treatment devices can be used.

[0024] In the water treatment device 1 according to this embodiment, as shown in the example of Fig. 1, it is preferable that the absorbance-based water quality detection means 15 is installed downstream of the circulation pump 13 in the circulation pipe 23. This is because the treated water W2 is pressurized by driving the circulation pump 13, and this pressure makes it difficult for microbubbles to be generated in the treated water W2 in the circulation pipe 23. As a result, the adverse effects of microbubbles can be further reduced in water quality measurement by the absorbance-based water quality detection means 15, and water treatment can be more stably controlled based on the measurement results.

[0025] As shown in an example in Figure 2, the top surface of the treated water tank 11 is provided with a tank inlet 11a connected to the membrane-treated water piping 21 and supplied with treated water W2 after membrane filtration, a tank return port 11b connected to the circulation piping 23 and returning the treated water W2 circulating through the circulation piping 23, and a manhole 11d for accessing the inside of the treated water tank 11. When the top surface of the treatment water tank 11 is square, it is preferable that the tank inlet 11a and the tank return port 11b are located at diagonal corners of the square on the top surface of the treatment water tank 11, as in the example shown in Figure 2. This makes it difficult for a swirling flow to occur in the treatment water W2 stored in the treatment water tank 11, making it easier to ensure a sufficient residence time for the treatment water W2 in the treatment water tank 11. As a result, microbubbles contained in the treatment water W2 in the treatment water tank 11 are more likely to disappear, thereby reducing the influence of microbubbles when the water quality of the treatment water W2 circulating through the circulation pipe 23 is measured by the absorbance-type water quality detection means 15. The manhole 11d is usually provided in the center of the top surface of the treatment tank 11, but is not limited thereto.

[0026] The bottom of the treatment water tank 11 is provided with an outlet 11c, which is connected to the side of the circulation pipe 23 opposite to the side connected to the tank return port 11b. The tank inlet 11a and the outlet 11c are preferably positioned offset from each other so that they do not overlap when viewed vertically from above. This prevents the treated water W2 supplied to the tank inlet 11a of the treatment water tank 11 from short-passing and being immediately withdrawn from the outlet 11c, thereby ensuring a sufficient residence time for the treated water W2 in the treatment water tank 11. As a result, microbubbles contained in the treated water W2 in the treatment water tank 11 are more likely to disappear, thereby reducing the influence of microbubbles when the water quality of the treated water W2 circulating through the circulation pipe 23 is measured by the absorbance-based water quality detection means 15.

[0027] The preferred positional relationship between the tank inlet 11a and the tank return port 11b on the top surface of the treatment water tank 11 is the same even when the top surface of the treatment water tank 11 is a rectangle other than a square. Specifically, as shown in the example of FIG. 3, even when the top surface of the treatment water tank 11 is rectangular, the tank inlet 11a and the tank return port 11b are preferably located at diagonal corners of the rectangle. Also, even when the top surface of the treatment water tank 11 is rectangular, the tank inlet 11a and the outlet 11c are preferably positioned offset from each other so as not to overlap each other when viewed from above in the vertical direction. This facilitates the disappearance of microbubbles contained in the treatment water W2 in the treatment water tank 11, thereby reducing the influence of microbubbles when the water quality of the treatment water W2 circulating through the circulation pipe 23 is measured by the absorbance-type water quality detection means 15. In the case of a rectangular parallelepiped treatment tank 11 formed by connecting two cubic tanks, as in the example shown in Figure 3, the manhole 11d can be located, for example, in the center of the top surface of one of the cubes, but this is not limited to this.

[0028] (Water treatment method) The water treatment method according to the embodiment is a method for treating water to be treated using a filtration membrane to obtain treated water. The water to be treated is not particularly limited, and examples thereof include groundwater, surface water such as river water, industrial water, and wastewater. The use of the treated water is not particularly limited, and examples thereof include use as drinking water. Hereinafter, a water treatment method using the water treatment device 1 described above will be described as a water treatment method according to one example of the embodiment.

[0029] As shown in Figure 1, in a water treatment method using a water treatment device 1, water to be treated W1 is supplied to membrane filtration devices 10A, 10B and subjected to membrane filtration treatment. Then, treated water W2 that has been subjected to membrane filtration treatment in membrane filtration devices 10A, 10B is supplied to a treated water tank 11 through a membrane-treated water piping 21 and stored therein. The treated water W2 stored in the treated water tank 11 is supplied to a downstream water receiving tank or the like by driving a water supply pump 12. Thus, in the water treatment method according to this embodiment, treated water W2 that has been subjected to membrane filtration treatment is supplied to the treated water tank 11, while the treated water W2 stored in the treated water tank 11 is discharged and supplied to a water receiving tank or the like.

[0030] Furthermore, by driving the circulation pump 13, a portion of the treated water W2 stored in the treated water tank 11 is extracted and circulated through the circulation pipe 23, while the quality of the circulating treated water W2 is directly measured by the absorbance-based water quality detection means 15. By measuring the quality of the treated water W2 circulating through the circulation pipe 23 with the absorbance-based water quality detection means 15, it is possible to reduce the influence of microbubbles generated during the membrane filtration process in the membrane filtration devices 10A, 10B on the measured value. As a result, measurement errors caused by microbubbles in measurements by the absorbance-based water quality detection means 15 are reduced, allowing for stable control of water treatment.

[0031] Before membrane filtration, pretreatment such as pH adjustment by adding acid, sand filtration, activated carbon treatment, or hypochlorous acid injection may be carried out. Examples of raw water to be subjected to pretreatment include groundwater such as well water and underground water, and water containing pigments and suspended solids, such as river water and lake water. However, the raw water is not limited to these examples.

[0032] The volume of the treatment tank 11 is V (m 3 ), and the flow rate of the treated water W2 supplied downstream from the treated water tank 11 is R(m 3 / min), the value expressed by HRT=V÷R is the residence time (min) of the treated water W2 in the treated water tank 11. The flow rate R can be the average value of the water supply flow rate to the water supply pump 12. The residence time HRT of the treated water in the treated water tank 11 is preferably 5 minutes or more, more preferably 5 to 60 minutes, and even more preferably 10 to 40 minutes. If the residence time HRT is equal to or greater than the lower limit, microbubbles generated in the treated water W2 during the membrane filtration process in the membrane filtration devices 10A and 10B tend to disappear easily within the treated water tank 11, thereby further reducing the adverse effects of microbubbles on water quality measurement by the absorbance-type water quality detection means 15. If the residence time HRT is equal to or less than the upper limit, the device can be made compact.

[0033] [Second embodiment] (Water treatment equipment) FIG. 4 is a schematic diagram illustrating a water treatment device 2 according to another embodiment. The water treatment device 2 is a device for treating water to be treated using a filtration membrane to obtain treated water. The water treatment device 2 includes membrane filtration devices 10A, 10B that perform membrane filtration on the water to be treated W1, a treated water tank 11 for storing the treated water W2 that has been subjected to membrane filtration, and an absorbance-type water quality detection means 15 that measures the water quality of the treated water W2.

[0034] The water treatment device 2 has the same configuration as the water treatment device 1, except for the following configuration. In water treatment device 2, branch pipe 24 is provided, which branches off from circulation pipe 23 between circulation pump 13 and circulation flow rate control valve 14, for extracting a portion of treated water W2 circulating through circulation pipe 23. Branch pipe 24 is provided with branch flow rate control valve 16 and absorbance-based water quality detection means 15, in this order. That is, in water treatment device 2, absorbance-based water quality detection means 15 is provided not in circulation pipe 23 but in branch pipe 24 branching off from circulation pipe 23.

[0035] In the water treatment device 2, the circulation pump 13 is driven to circulate the treated water W2 through the circulation pipe 23, and a portion of the treated water W2 circulating through the circulation pipe 23 is extracted to the branch pipe 24. The flow rate of the treated water W2 extracted to the branch pipe 24 is adjusted by the branch flow rate adjustment valve 16 to a flow rate suitable for measurement by the absorbance-type water quality detection means 15. Then, the absorbance-type water quality detection means 15 measures the water quality of the treated water W2 extracted to the branch pipe 24.

[0036] In the water treatment device 2, treated water W2 after membrane filtration in membrane filtration devices 10A and 10B is stored in treated water tank 11, and after the microbubbles generated by the membrane filtration have disappeared to a certain extent in treated water tank 11, the treated water W2 extracted from circulation pipe 23 to branch pipe 24 is measured by absorbance-based water quality detection means 15. This reduces the adverse effects of microbubbles on the water quality measurement results obtained by absorbance-based water quality detection means 15. In particular, because compressed air is used to push out the backwash water during backwashing of the filtration membrane, microbubbles are likely to be generated in treated water W2 when operation is restarted. However, even in this case, measurement errors by absorbance-based water quality detection means 15 caused by microbubbles can be sufficiently reduced.

[0037] The branch flow rate adjusting valve 16 is not particularly limited, and any known flow rate adjusting valve used in water treatment equipment can be used.

[0038] In the water treatment device 2 according to this embodiment, it is preferable that the absorbance-based water quality detection means 15 be installed downstream of the circulation pump 13, as in the example shown in Fig. 4. This is because the treated water W2 is pressurized by driving the circulation pump 13, and this pressure makes it difficult for microbubbles to be generated in the treated water W2 in the branch pipe 24. As a result, the adverse effects of microbubbles can be further reduced in water quality measurement by the absorbance-based water quality detection means 15, and water treatment can be more stably controlled based on the measurement results.

[0039] 2 and 3, in the water treatment device 2, when the top surface of the treatment water tank 11 is rectangular, it is preferable that the tank inlet 11a and the tank return port 11b are located at diagonal corners of the rectangle on the top surface of the treatment water tank 11. This is because a swirling flow is less likely to occur in the treatment water W2 stored in the treatment water tank 11, and it becomes easier to ensure a sufficient residence time for the treatment water W2 in the treatment water tank 11. As a result, microbubbles contained in the treatment water W2 in the treatment water tank 11 are more likely to disappear, which reduces the influence of microbubbles when the water quality of the treatment water W2 extracted to the branch pipe 24 is measured by the absorbance-type water quality detection means 15.

[0040] Also, in the water treatment device 2, it is preferable that the water tank inlet 11a and the outlet 11c are arranged offset from each other so as not to overlap when viewed vertically from above. This is because it is possible to prevent the treated water W2 supplied to the water tank inlet 11a of the treatment water tank 11 from short-passing and being immediately discharged from the outlet 11c, making it easier to ensure a sufficient residence time for the treated water W2 in the treatment water tank 11. As a result, fine bubbles contained in the treated water W2 in the treatment water tank 11 are more likely to disappear, thereby reducing the influence of fine bubbles when the water quality of the treated water W2 discharged to the branch pipe 24 is measured by the absorbance-type water quality detection means 15.

[0041] (Water treatment method) Hereinafter, a water treatment method using the water treatment device 2 described above will be described as a water treatment method according to another example of the embodiment. As shown in Figure 4, in a water treatment method using water treatment device 2, water to be treated W1 is supplied to membrane filtration devices 10A, 10B and subjected to membrane filtration treatment. Then, treated water W2 that has been subjected to membrane filtration treatment in membrane filtration devices 10A, 10B is supplied to treated water tank 11 through membrane-treated water piping 21 and stored therein. Furthermore, treated water W2 stored in treated water tank 11 is supplied to a downstream water receiving tank or the like by driving water supply pump 12. Thus, in the water treatment method according to this embodiment, treated water W2 after membrane filtration treatment is supplied to treated water tank 11, while treated water W2 stored in treated water tank 11 is discharged and supplied to a water receiving tank or the like.

[0042] Furthermore, by driving the circulation pump 13, a portion of the treated water W2 stored in the treated water tank 11 is extracted and circulated into the circulation pipe 23, while a portion of the treated water W2 flowing through the circulation pipe 23 is extracted into the branch pipe 24, and the water quality is measured by the absorbance-type water quality detection means 15. This reduces the effect on the measured values of microbubbles generated during the membrane filtration process in the membrane filtration devices 10A and 10B. As a result, measurement errors due to microbubbles in measurements by the absorbance-type water quality detection means 15 are reduced, allowing for stable control of the water treatment.

[0043] The preferred upper and lower limits of the residence time HRT of the treated water in the treatment water tank 11 are the same as those in the first embodiment.

[0044] [Third embodiment] (Water treatment equipment) A more specific configuration of a water treatment device and a water treatment method in which an absorbance-type water quality detection means is provided in a branch pipe will be described below. 5 is a schematic diagram showing the configuration of a water treatment device 3 according to a third embodiment. The water treatment device 3 is suitable for producing drinking water.

[0045] The water treatment device 3 includes a pumping pump 31 installed in the well, a raw water tank 32, a sand filtration tower 34, an activated carbon packed tower 35, membrane filtration devices 10A and 10B, a treated water tank 11, an absorbance-type water quality detection means 15, a sodium hypochlorite addition device 36, a sulfuric acid addition device 37, a polyaluminum chloride addition device 38, a residual salt meter 39, and a control device 40.

[0046] The lifting pump 31 and the raw water tank 32 are connected by a first pipe 41. By driving the lifting pump 31, well water is sent to the raw water tank 32 through the first pipe 41 as raw water W0. An oxidizing agent is added to the raw water W0 in the raw water tank 32 by a sodium hypochlorite adding device 36, and acid is added by a sulfuric acid adding device 37. The sodium hypochlorite adding device 36 is configured to add sodium hypochlorite to the raw water W0 in the raw water tank 32 by driving a first chlorine pump 36a. The sulfuric acid adding device 37 is configured to add sulfuric acid to the raw water W0 in the raw water tank 32 by driving a sulfuric acid pump 37a.

[0047] The sodium hypochlorite adding device 36 may be a means for adding an oxidizing agent other than sodium hypochlorite. As an oxidizing agent other than sodium hypochlorite, any oxidizing agent applicable to disinfecting drinking water can be used without particular limitation. Disinfection of drinking water refers to the killing or inactivation of microorganisms in the water. Specific examples include ozone, chlorine-based compounds such as chlorine, hypochlorous acid, and calcium hypochlorite, and bromine-based compounds such as bromochlorodimethylhydantoin (BCDMH) and hypobromous acid. One oxidizing agent may be used alone, or two or more may be used in combination.

[0048] The sulfuric acid adding device 37 may be a means for adding an acid other than sulfuric acid. The acid other than sulfuric acid may be any acid capable of adjusting the pH of the raw water to a desired range, such as hydrochloric acid. One acid may be used alone, or two or more acids may be used in combination.

[0049] The raw water tank 32 and the sand filter tower 34 are connected by a second pipe 42. A raw water pump 33 is provided in the second pipe 42. By driving the raw water pump 33, the raw water W0 in the raw water tank 32 is supplied to the sand filter tower 34. Furthermore, polyaluminum chloride (PAC) is added to the raw water W0 flowing through the second pipe 42 from a polyaluminum chloride adding device 38 upstream of the raw water pump 33. The polyaluminum chloride adding device 38 is configured to add PAC to the raw water W0 flowing through the second pipe 42 by driving a PAC pump 38a. By using PAC to coagulate organic matter in the raw water W0, the organic matter can be efficiently removed in the sand filter tower 34 and the activated carbon packed tower 35.

[0050] The polyaluminum chloride adding device 38 may be a means for adding a flocculant other than PAC. The flocculant other than PAC may be any flocculant capable of flocculating organic matter, such as inorganic flocculants such as aluminum sulfate, or polymer flocculants. One flocculant may be used alone, or two or more may be used in combination.

[0051] There are no particular limitations on the sand filter tower 34. Sand filter towers used in known water treatment devices can be used without any limitations. One sand filter tower 34 may be used alone, or two or more sand filter towers 34 may be used in combination in parallel or in series.

[0052] The sand filter tower 34 and the activated carbon packed tower 35 are connected by a third pipe 43. Sand filtered water W3 after treatment in the sand filter tower 34 is supplied to the activated carbon packed tower 35 through the third pipe 43. The activated carbon packed tower 35 may be any type that can remove impurities and organic matter from the sand filtration treated water W3 by adsorbing them onto activated carbon, and any activated carbon packed tower used in known water treatment devices may be used without limitation. The activated carbon used in the activated carbon packed tower 35 is also not particularly limited. Any activated carbon used in known activated carbon packed towers may be used without limitation. The activated carbon packed tower 35 may be used alone or in combination of two or more in parallel or in series.

[0053] Activated carbon made primarily from coconut shells, wood, or coal is preferred, with coconut shell activated carbon being preferred for producing drinking water. The shape of activated carbon is not particularly limited, but examples thereof include powder, crushed, sheet, filter, and fiber. Crushed activated carbon is preferred for producing drinking water. The activated carbon may be used alone or in combination of two or more types.

[0054] The activated carbon packed tower 35 and the membrane filtration devices 10A, 10B are connected by a fourth pipe 44. The water to be treated W1 after treatment in the activated carbon packed tower 35 is supplied to the membrane filtration devices 10A, 10B through the fourth pipe 44. In addition, sodium hypochlorite is added to the water to be treated W1 flowing through the fourth pipe 44 by a sodium hypochlorite adding device 36. The sodium hypochlorite adding device 36 is configured to add sodium hypochlorite to the water to be treated W1 flowing through the fourth pipe 44 by driving a second chlorine pump 36b.

[0055] The membrane filtration devices 10A and 10B are connected to the treated water tank 11 by membrane-treated water piping 21. Treated water W2 after membrane filtration in the membrane filtration devices 10A and 10B is sent to the treated water tank 11 through the membrane-treated water piping 21 and stored therein. A water supply pipe 22 is connected to the treated water tank 11, and supplies treated water to downstream facilities such as a water receiving tank. A water supply pump 12 is provided on the water supply pipe 22. By driving the water supply pump 12, treated water W2 in the treated water tank 11 is supplied to downstream facilities such as a water receiving tank.

[0056] The treated water tank 11 is also provided with a circulation pipe 23 for extracting a portion of the treated water W2 from the treated water tank 11 and circulating it back into the treated water tank 11. The circulation pipe 23 is provided with a circulation pump 13 and a circulation flow rate control valve 14 in this order. Furthermore, a first branch pipe 24A and a second branch pipe 24B are provided branching off from the circulation pipe 23 between the circulation pump 13 and the circulation flow rate control valve 14. A branch flow rate control valve 16 and an absorbance-based water quality detection means 15 are provided in this order on the first branch pipe 24A. By driving the circulation pump 13, the treated water W2 circulates through the circulation pipe 23, and a portion of the treated water W2 circulating through the circulation pipe 23 is extracted into the first branch pipe 24A, and the water quality is measured by the absorbance-based water quality detection means 15.

[0057] The second branch pipe 24B is provided with a residual chlorine meter 39. A portion of the treated water W2 circulating through the circulation pipe 23 is extracted to the second branch pipe 24B, and the residual chlorine concentration is measured by the residual chlorine meter 39.

[0058] The control device 40 is capable of controlling the operation of the water treatment device 3, including controlling the drive of the feedwater pump 12, based on the results of water quality measurement of the treated water W2 by the absorbance-type water quality detection means 15 and the residual salt meter 39. The control device 40 is typically configured with a memory and a central processing unit (CPU), but its functions may be realized by dedicated hardware or software. In the case of a CPU, a program for realizing the functions of the control device may be loaded from a server into memory and executed to realize the functions.

[0059] (Water treatment method) The water treatment method using the water treatment device 3 includes the following steps. (i) A process in which an acid is added to raw water W0 to adjust the pH, and an oxidizing agent is added to oxidize iron and ammonia and sterilize the water. (ii) A process of adding a coagulant to raw water W0 to coagulate organic matter, arsenic, aluminum, iron, etc. (iii) A process in which raw water W0 is subjected to sand filtration to remove coagulated flocs, iron, manganese, etc. (iv) A process of treating the sand-filtered water W3 after the sand filtration process with activated carbon to remove organic matter, chlorine, etc. (v) A step of adding an oxidizing agent to the water to be treated W1 after the activated carbon treatment to sterilize it. (vi) A step of subjecting the water to be treated W1 to membrane filtration. (vii) A process of temporarily storing the treated water W2 after membrane filtration, measuring the water quality using an absorbance-type water quality detection means or the like while circulating the stored water, and controlling operation based on the measurement results.

[0060] The raw water W0 may be water containing organic matter such as humic acid and fulvic acid, and specific examples thereof include groundwater such as well water, river water, and lake water. However, the raw water is not limited to these examples. The raw water W0 may contain bicarbonate ions. The raw water W0 may further contain anions such as nitrate ions, sulfate ions, and chloride ions, cations such as iron ions, manganese ions, calcium ions, and magnesium ions, ammonia nitrogen, bacteria, and the like.

[0061] In step (i), the water pump 31 is driven to supply raw water W0 to the raw water tank 32 through the first pipe 41. Then, the sodium hypochlorite adding device 36 adds sodium hypochlorite to the raw water W0 in the raw water tank 32 to disinfect it. In addition, the sulfuric acid adding device 37 adds sulfuric acid to the raw water W0 to adjust the pH. Sulfuric acid is added so that the pH of the raw water W0 is preferably in the range of 5.0 to 7.0, more preferably in the range of 5.5 to 6.5. If the pH of the raw water W0 is within this range, leakage of aluminum ions derived from the coagulant can be suppressed.

[0062] In step (ii), raw water W0 is supplied from raw water tank 32 to sand filter tower 34 by driving raw water pump 33, while PAC is added by polyaluminum chloride adder 38 along the way to coagulate organic matter in raw water W0. Next, in step (iii), raw water W0 is subjected to sand filtration, and in step (iv), the sand-filtered water W3 after sand filtration is treated with activated carbon to remove organic matter. In step (v), an oxidizing agent is added to the treated water W1 after activated carbon treatment by sodium hypochlorite adder 36, and the water to be treated W1 is disinfected again.

[0063] The free carbon dioxide concentration of the water to be treated W1 is preferably 0 to 15 mg / L, more preferably 0 to 5 mg / L. The lower the free carbon dioxide concentration, the better. If the free carbon dioxide concentration of the water to be treated W1 is below the upper limit value, the generation of fine carbon dioxide bubbles and corrosion of metal articles can be suppressed. Note that "free carbon dioxide" refers to carbon dioxide dissolved in water.

[0064] The M alkalinity of the water to be treated W1 is preferably 0 to 100 mg / L, more preferably 0 to 50 mg / L. The lower the M alkalinity, the better. If the M alkalinity of the water to be treated W1 is not more than the upper limit, the amount of free carbon dioxide generated when the pH is lowered by adding an acid is reduced.

[0065] In step (vi), the membrane filtration devices 10A and 10B perform membrane filtration on the water to be treated W1 to obtain treated water W2. The treated water W2 after membrane filtration is supplied to and stored in the treated water tank 11 through the membrane-treated water piping 21, and then supplied to a downstream water receiving tank or the like by driving the water supply pump 12. The preferred upper and lower limits of the residence time HRT of the treated water in the treatment water tank 11 are the same as those in the first embodiment.

[0066] In step (vii), a portion of the treated water W2 in the treated water tank 11 is extracted and circulated into the circulation pipe 23, while a portion of the treated water W2 circulating through the circulation pipe 23 is extracted into the first branch pipe 24A, and its water quality is measured by the absorbance-type water quality detection means 15. In addition, a portion of the treated water W2 circulating through the circulation pipe 23 is extracted into the second branch pipe 24B, and its residual chlorine concentration is measured by the residual salt meter 39.

[0067] Hereinafter, the operation control based on the water quality measurement results of the treated water W2 in step (vii) will be described in more detail using an example in which a colorimeter and a turbidimeter are used as the absorbance-type water quality detection means 15.

[0068] As shown in the flow chart of Figure 6, when the operation of the water treatment device 3 is started and water supply to the water tank, etc. is started, the measurement results of the color and turbidity of the treated water W2 by the absorbance-type water quality detection means 15 and the measurement results of the residual chlorine concentration by the residual salt meter 39 are checked to see whether they are below the standard values. If the measured values of color and turbidity are below the standard values and the measured value of residual chlorine concentration is above the standard value, it is determined that there is no abnormality in the device, and operation of the device and water supply continue.

[0069] If either the measured value of color or turbidity exceeds the standard value and the measured value of residual chlorine concentration is equal to or greater than the standard value, it is determined that there is an abnormality in the sulfuric acid pump 37a or PAC pump 38a, and the operation of the water supply pump 12 is stopped, and the operation of the water treatment device 3 is stopped. If the measured values of color and turbidity are below the standard values and the measured value of residual chlorine concentration is less than the standard value, it is determined that there is an abnormality in the second chlorine pump 36b, the operation of the water supply pump 12 is stopped, and the operation of the water treatment device 3 is stopped. If the measured values of color and turbidity exceed the standard values and the measured value of residual chlorine concentration is below the standard value, it is determined that there is an abnormality in the first chlorine pump 36a, the operation of the water supply pump 12 is stopped, and the operation of the water treatment device 3 is stopped.

[0070] The treated water W2 is preferably water that satisfies the tap water quality standards and water quality management target items. The color of the treated water W2 is preferably 5 degrees or less, and more preferably 3 degrees or less. The turbidity of the treated water W2 is preferably 2 degrees or less, more preferably 1 degree or less. The residual chlorine concentration of the treated water W2 is preferably 0.1 or more, and more preferably 0.2 or more.

[0071] As described above, in the water treatment device and water treatment method according to the embodiment, a portion of the treated water in the treatment tank is extracted and circulated, and the quality of the circulating treated water is measured by the absorbance-based water quality detection means. Therefore, microbubbles generated during membrane filtration are less likely to adversely affect the water quality measurement of the treated water by the absorbance-based water quality detection means, and water treatment can be more stably controlled based on the results of the water quality measurement of the treated water. [Example]

[0072] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following descriptions.

[0073] [Example 1] Water treatment was carried out for 60 minutes using a water treatment device having the same configuration as the water treatment device 2 illustrated in FIG. 4, and the chromaticity and turbidity of the treated water were measured. Groundwater with a pH of 7.0, a free carbonate concentration of 15 mg / L, an M alkalinity of 70 mg / L, a color of 3.0, and a turbidity of 1.0 was used as the water to be treated W1. A Mitsubishi Chemical Aqua Solutions Wellpure L filter membrane was used. A Horiba Advanced Techno colorimeter (HU-200CL, a color turbidity meter with a colorimeter and turbidity meter installed in series inside; color: two-wavelength absorbance difference method; turbidity: visible light absorbance method) was installed in the branch pipe 24 as the absorbance-based water quality detection means 15. The flow rate of the treated water W2 flowing through the branch pipe 24 was adjusted to match the color turbidity meter using the branch flow control valve 16. The measurement results of color and turbidity are shown in Figure 7.

[0074] As shown in Figure 7, in Example 1, in which a portion of the treated water in the treatment tank was extracted and circulated, and a portion of the circulating treated water was extracted into a branch pipe to measure the water quality, the chromaticity and turbidity measurements taken by the color turbidity meter were stable, and measurement errors caused by microbubbles were suppressed.

[0075] [Comparative Example 1] As shown in Figure 8, water treatment was carried out in the same manner as in Example 1, except that no circulation pipe or branch pipe was provided, and an absorbance-type water quality detection means 15 was provided in a branch path 25 provided in the membrane-treated water pipe 21, and the chromaticity and turbidity of the treated water were measured. The measurement results of color and turbidity are shown in Figure 9.

[0076] 9, in Comparative Example 1, in which the water quality of treated water supplied from a membrane filtration device to a treatment tank was measured, the measured values of color and turbidity by the color turbidity meter were unstable. This is thought to be because the adverse effects of fine bubbles generated during membrane filtration could not be suppressed. [Explanation of symbols]

[0077] 1~3 Water treatment equipment 10A, 10B Membrane filtration device 11 Treatment tank 11a Aquarium entrance 11b Aquarium return port 11c Exit 12 Water supply pump 13 Circulation pump 14 Circulation flow control valve 15. Absorbance-based water quality detection means 21 Membrane treated water piping 22 Water supply piping 23 Circulation piping 24 Branch piping 24A First branch pipe 24B Second branch pipe 31 Water pump 32 Raw Water Tank 33 Raw water pump 34 Sand filter tower 35 Activated carbon packed tower 36 Sodium hypochlorite adding device 37 Sulfuric acid addition device 38 Polyaluminum chloride dosing device 39 Residual salt meter 40 Control device

Claims

1. A water treatment device that treats water to be treated using a filtration membrane to obtain treated water, a treated water tank for storing the treated water; a circulation pipe for extracting a portion of the treated water from the treatment tank and returning it to the treatment tank for circulation; a circulation pump installed in the circulation piping and circulating the treated water; an absorbance-type water quality detection means installed in the circulation pipe, The water treatment device, wherein the absorbance-based water quality detection means measures the water quality of the treated water circulating through the circulation pipe.

2. A water treatment device that treats water to be treated using a filtration membrane to obtain treated water, a treated water tank for storing the treated water; a circulation pipe for extracting a portion of the treated water from the treatment tank and returning it to the treatment tank for circulation; a circulation pump installed in the circulation piping and circulating the treated water; a branch pipe branching from the circulation pipe for extracting a portion of the treated water circulating through the circulation pipe; an absorbance-type water quality detection means installed in the branch pipe, The water treatment device, wherein the absorbance-type water quality detection means measures the water quality of the treated water extracted into the branch pipe.

3. 3. The water treatment device according to claim 1, wherein the absorbance-type water quality detection means is at least one selected from the group consisting of a colorimeter, a turbidity meter, and an absorbance-type comprehensive water quality meter.

4. 3. The water treatment device according to claim 1, wherein the absorbance-type water quality detection means is installed downstream of a circulation pump.

5. a membrane-treated water pipe for supplying the treated water after membrane filtration to the treated water tank; The upper surface of the treated water tank is provided with a tank inlet connected to the membrane-treated water piping and through which the treated water after membrane filtration is supplied, and a tank return port connected to the circulation piping and through which the treated water circulating through the circulation piping is returned, The upper surface of the treatment water tank is rectangular, The water treatment device according to claim 1 or 2, wherein the water tank inlet and the water tank return port are located at opposite corners of the rectangle.

6. a drain port connected to the side of the circulation pipe opposite to the side connected to the water tank return port is provided at the bottom of the treatment water tank; The water treatment device according to claim 5 , wherein the water tank inlet and the outlet are arranged so as to be offset from each other and not overlap each other when viewed from above in the vertical direction.

7. The water treatment device according to claim 1 or 2, wherein the filtration membrane is a pressure MF membrane or an UF membrane.

8. A water treatment method for treating water to be treated using a filtration membrane to obtain treated water, Storing the treated water after membrane filtration in a treated water tank; extracting a portion of the treated water from the treatment tank and returning it to the treatment tank for circulation; and measuring the quality of the circulating treated water using an absorbance-based water quality detection means.

9. 9. The water treatment method according to claim 8, wherein the absorbance-based water quality detection means directly measures the water quality of the circulating treated water.

10. 9. The water treatment method according to claim 8, further comprising extracting a portion of the circulating treated water, and measuring the quality of the extracted treated water by the absorbance-type water quality detection means.

11. The method further includes discharging the treated water stored in the treatment water tank while supplying the treated water after membrane filtration treatment to the treatment water tank, The volume of the treatment water tank is V (m ３ , the flow rate of the treated water supplied downstream from the treated water tank is R (m ３ 9. The water treatment method according to claim 8, wherein the retention time HRT of the treated water, expressed as HRT=V÷R, is 5 minutes or more when the water temperature is 100°C / min.

Images