Water purification device and water purification method

Abstract

To provide a water purifying apparatus and a water purification method, capable of supplying oxygen efficiently to a bottom layer of a water area.SOLUTION: A water purifying apparatus 1 includes: a pipe 2 assembled with an upper opening 2a arranged in a surface layer 10a of a water area 10 and a lower opening 2b arranged in a bottom layer 10b of the water area 10; and a pump mechanism 3 that is provided in the pipe 2 and sends water, having a water inlet 2f for one of the upper opening 2a and the lower opening 2b and a water outlet 2g for the other of the upper opening 2a and the lower opening 2b. A water purification method includes; an arrangement step of arranging a pipe 2 assembled with an upper opening 2a and a lower opening 2b and provided with a pump mechanism 3 in it in a manner that the upper opening 2a is positioned in a surface layer 10a of a water area 10 and the lower opening 2b is positioned in a bottom layer 10b of the water area 10; and a water conveyance step for sending water by using the pump mechanism 3 in a manner that one of the upper opening 2a and the lower opening 2b is used as a water inlet 2f and the other of the upper opening 2a and the lower opening 2b is used as water outlet 2g.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a water purification device and a water purification method. [Background technology]

[0002] When nutrients such as nitrogen and phosphorus contained in domestic and industrial wastewater flow into oceans, rivers, reservoirs, lakes, and other bodies of water, a large amount of phytoplankton is produced, and a large amount of oxygen is consumed to decompose the dead bodies that accumulate at the bottom of the body of water, resulting in an oxygen-deficient state. In this state, anaerobic bacteria that can decompose even in the absence of oxygen become dominant, and the toxic hydrogen sulfide or sulfides produced during decomposition kill the organisms in the body of water.

[0003] On the other hand, the surface layer is oxygen-rich due to photosynthesis, and if vertical mixing is carried out properly, oxygen deficiency in the bottom layer will not occur. However, in actual water bodies, layers (density stratification) are formed due to differences in density caused by temperature differences between the surface and bottom layers, making it difficult for vertical mixing to occur.

[0004] For this reason, a water purification device has been proposed that uses a pump mechanism to forcibly cause vertical mixing in a water area (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4076824 Summary of the Invention [Problem to be solved by the invention]

[0006] In conventional water purification devices such as that described in Patent Document 1, a pump mechanism is used to send the surface water and bottom water through pipes to an outlet located in the middle layer, where they are mixed and discharged. This means that the oxygen concentration of the water discharged from the outlet is diluted, and the amount of oxygen that can be supplied to the bottom layer is insufficient.

[0007] An object of the present disclosure is to provide a water purification device and a water purification method that can efficiently supply oxygen to the bottom layer of a water area. [Means for solving the problem]

[0008] A water purification device according to some embodiments includes a pipe having an upper opening disposed in a surface layer of a water body and a lower opening disposed in a bottom layer of the water body, and a pump mechanism disposed in the pipe for pumping water so that one of the upper opening and the lower opening serves as a water inlet and the other serves as a water outlet. With this configuration, the water from the surface layer is taken into the pipe from the upper opening and discharged from the lower opening in the bottom layer, thereby directly supplying the water from the surface layer to the bottom layer, or the water from the bottom layer is taken into the pipe from the lower opening and discharged from the upper opening in the surface layer, thereby gradually supplying the water from the surface layer to the bottom layer by convection, thereby efficiently supplying oxygen to the bottom layer.

[0009] In one embodiment, the water purification device includes an internal temperature sensor that measures the temperature of water inside the pipe at a predetermined water depth, an external temperature sensor that measures the temperature of water outside the pipe at the predetermined water depth, and a control unit that controls the flow rate of the pump mechanism so that the difference between the measurement value by the internal temperature sensor and the measurement value by the external temperature sensor falls within a predetermined range. With this configuration, the flow rate of the pump mechanism is limited, that is, water is sent slowly (for example, at a flow rate that flows through the pipe at a speed of 1 to 10 mm / s, 1 to 30 mm / s, or 1 to 100 mm / s) so that the difference between the measurement value by the internal temperature sensor and the measurement value by the external temperature sensor falls within a predetermined range (for example, within ±5°C, within ±4°C, or within ±3°C), so that the water can be sent while firmly reducing the temperature difference between the water inside and outside the pipe, and therefore the density difference, by heat transfer between the inside and outside of the pipe through the pipe. Therefore, the buoyancy or sinking force acting on the sent water caused by the density difference, which becomes the load, i.e., the resistance force, when sending water can be firmly reduced, so that the pump mechanism can be operated efficiently with a low load.

[0010] In one embodiment, the internal temperature sensor and the external temperature sensor measure the temperature of the water at the water outlet. With this configuration, the load on the pump mechanism can be easily and efficiently reduced. Also, the re-surfacing or re-submersion of the discharged water can be more reliably reduced, and the discharged water can be retained.

[0011] In one embodiment, the pump mechanism includes a throttle section that reduces the cross-sectional area of ​​the flow passage in the pipe, an impeller disposed in the throttle section, and an electric motor that rotates the impeller. With this configuration, even if the cross-sectional area of ​​the flow passage in the pipe is too large, the throttle section allows an impeller of a suitable size that is not too large to be used, and the electric motor can be operated in a suitable rotation range that is not too low and has good energy efficiency. Therefore, the energy efficiency of the pump mechanism can be improved.

[0012] In one embodiment, the control unit controls the flow rate of the pump mechanism to a larger flow rate set without using the internal temperature sensor and the external temperature sensor, and then reduces the flow rate of the pump mechanism so that the difference between the measurement value by the internal temperature sensor and the measurement value by the external temperature sensor falls within the predetermined range. With this configuration, the flow rate of the pump mechanism can be quickly and efficiently controlled.

[0013] A water purification method according to some embodiments includes a step of arranging a pipe having an upper opening and a lower opening and a pump mechanism therein so that the upper opening is located in the surface layer of a water body and the lower opening is located in the bottom layer of the water body, and a step of feeding water by the pump mechanism so that one of the upper opening and the lower opening is a water intake and the other of the upper opening and the lower opening is a water discharge. With such a configuration, the water of the surface layer can be directly supplied to the bottom layer by taking in the water of the surface layer from the upper opening into the pipe and discharging it from the lower opening in the bottom layer, or the water of the bottom layer can be taken in the pipe from the lower opening and discharging it from the upper opening in the surface layer to gradually supply the water of the surface layer to the bottom layer by convection, so that oxygen can be efficiently supplied to the bottom layer.

[0014] In one embodiment, the water conveying step includes an internal temperature measuring step of measuring the temperature of water in the pipe at a predetermined water depth, an external temperature measuring step of measuring the temperature of water outside the pipe at the predetermined water depth, and a control step of controlling the flow rate of the pump mechanism so that the difference between the measured value by the internal temperature measuring step and the measured value by the external temperature measuring step falls within a predetermined range. According to this configuration, the flow rate of the pump mechanism is limited, that is, the water is conveyed slowly (for example, at a flow rate that flows through the pipe at a speed of 1 to 10 mm / s, 1 to 30 mm / s, or 1 to 100 mm / s) so that the difference between the measured value by the internal temperature measuring step and the measured value by the external temperature measuring step falls within a predetermined range (for example, within ±5°C, ±4°C, or ±3°C), thereby making it possible to convey water while firmly reducing the temperature difference of the water between the inside and outside of the pipe, and therefore the density difference, by heat transfer between the inside and outside of the pipe through the pipe. Therefore, the buoyancy or sinking force acting on the conveyed water caused by the density difference, which becomes the load, i.e., the resistance force, when conveying water, can be firmly reduced, and therefore the pump mechanism can be operated efficiently with a low load. The internal temperature measuring step and the external temperature measuring step may be performed in any order, or may be performed simultaneously.

[0015] In one embodiment, the internal temperature measuring step and the external temperature measuring step measure the temperature of the water at the water outlet. With this configuration, the load on the pump mechanism can be easily and efficiently reduced. Also, the re-surfacing or re-submersion of the discharged water can be more reliably reduced, and the discharged water can be retained.

[0016] In one embodiment, in the control step, the flow rate of the pump mechanism is controlled to a larger flow rate set independently of the internal temperature measurement step and the external temperature measurement step, and then the flow rate of the pump mechanism is reduced so that the difference between the measurement value in the internal temperature measurement step and the measurement value in the external temperature measurement step falls within the predetermined range. With this configuration, the flow rate of the pump mechanism can be controlled quickly and efficiently. Effect of the Invention

[0017] According to the present disclosure, it is possible to provide a water purification device and a water purification method that can efficiently supply oxygen to the bottom layer of a water area. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a layout diagram of a water purification device according to a first embodiment. [Diagram 2] FIG. 2 is a block diagram of the water purification device shown in FIG. [Diagram 3] FIG. 11 is a layout diagram of a water purification device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0020] The water purification device 1 of the first embodiment shown in Figure 1 has a pipe 2, a pump mechanism 3, an internal temperature sensor 4, an external temperature sensor 5, a control unit 6, a power source 7, a float 8 and an anchor 9, and is placed in a water body 10 such as the ocean, a river, a dam lake, or a lake or marsh.

[0021] In the water area 10, the difference in density between the surface layer 10a and the bottom layer 10b due to the temperature difference causes layers to form, making vertical mixing difficult, and therefore the bottom layer 10b is prone to becoming hypoxic, which may cause pollution. The water purification device 1 is a device that uses a pump mechanism 3 to forcibly cause vertical mixing in the water area 10, thereby supplying oxygen from the surface layer 10a to the bottom layer 10b, thereby purifying the water. The surface layer 10a is the layer of water that forms the water surface 10c of the water area 10, and the bottom layer 10b is the layer of water that contacts the bottom surface 10d of the water area 10.

[0022] The pipe 2 is tubular and arranged to extend vertically in the water area 10. The pipe 2 has an upper opening 2a arranged in the surface layer 10a and a lower opening 2b arranged in the bottom layer 10b, and a flow path that connects the upper opening 2a and the lower opening 2b is formed inside the pipe 2. The upper opening 2a is composed of a plurality of openings that penetrate the pipe 2 in the radial direction. The upper opening 2a may be composed of a single opening. The lower opening 2b is composed of an opening formed at the lower end edge of the pipe 2. The pipe 2 is formed of a plastic film having a thickness of, for example, several mm. Therefore, the pipe 2 has good thermal conductivity and is low-cost. In addition, the pipe 2 is flexible, so that it is easy to handle until installation. The pipe 2 may be formed of a material other than the plastic film. However, it is preferable that the pipe 2 is formed of a material having thermal conductivity. It is also preferable that the pipe 2 is formed of a flexible material.

[0023] The lower end 2c of the pipe 2 is connected and held by the anchor 9 to the bottom surface 10d. The anchor 9 is composed of a plurality of linear members 9a, and the lower end of each linear member 9a is provided with a locking portion that is inserted into and locked into the bottom surface 10d. The anchor 9 may have any configuration as long as it can connect and hold the lower end 2c of the pipe 2 to the bottom surface 10d.

[0024] The upper end 2d of the pipe 2 is connected to a float 8 and is stretched vertically by the buoyancy of the float 8, so that the upper opening 2a is disposed within the surface layer 10a. The configuration of the float 8 is not particularly limited as long as it generates buoyancy in water. Note that, without using the float 8, the upper opening 2a may be disposed within the surface layer 10a by, for example, mechanically connecting the pipe 2 to another structure.

[0025] Incidentally, a weight may be provided at the lower end 2c of the pipe 2 instead of the anchor 9, so that the pipe 2 is stretched in the vertical direction.

[0026] An upper end surface 2e of the pipe 2 protrudes above the water surface 10c, and a power source 7 and a control unit 6 are disposed on the upper end surface 2e. The power source 7 and the control unit 6 may be disposed underwater. In this embodiment, the pump mechanism 3 is driven by low power, so the power source 7 may be composed of, for example, a natural energy power generation device such as a solar cell and a secondary battery that stores the electricity generated by the device.

[0027] The pump mechanism 3 is provided in the pipe 2 and is configured to send water so that the upper opening 2a serves as a water intake 2f and the lower opening 2b serves as a water discharge port 2g. The pump mechanism 3 is also configured with a throttle section 3a that reduces the cross-sectional area of ​​the flow path in the pipe 2, an impeller 3b arranged in the throttle section 3a, and an electric motor 3c that rotates the impeller 3b. The electric motor 3c is connected to a power source 7 and a control section 6 via wiring 11. The pump mechanism 3 can send water from the water intake 2f to the water discharge port 2g by rotating the impeller 3b in the throttle section 3a. The throttle section 3a narrows the flow path in a stepped manner, but may be configured to narrow the flow path in a tapered manner.

[0028] Although the pump mechanism 3 is disposed at the upper part of the pipe 2, it may be disposed at, for example, the lower part or the vertical middle part of the pipe 2. However, disposing it at the upper part of the pipe 2 is preferable because the wiring 11 can be made shorter.

[0029] The internal temperature sensor 4 is disposed within the pipe 2 at the water outlet 2g and is configured to measure the temperature of the water within the pipe 2 at the water outlet 2g. The external temperature sensor 5 is disposed outside the pipe 2 at the water outlet 2g and is configured to measure the temperature of the water outside the pipe 2 at the water outlet 2g.

[0030] The control unit 6 is configured to control the flow rate of the pump mechanism 3 so that the difference between the measurement value measured by the internal temperature sensor 4 and the measurement value measured by the external temperature sensor 5 falls within a predetermined range (e.g., within ±5°C, within ±4°C, or within ±3°C).

[0031] 2, the control unit 6 is composed of a computer 6a and a driver 6b. The computer 6a is capable of communicating with the internal temperature sensor 4, the external temperature sensor 5, and the driver 6b, and is configured to calculate the difference between the value measured by the internal temperature sensor 4 and the value measured by the external temperature sensor 5, and to instruct the driver 6b on the target rotation speed of the electric motor 3c based on this difference. The driver 6b is electrically connected to the power source 7 and the electric motor 3c, and is configured to control the voltage or current supplied from the power source 7 to the electric motor 3c so that the rotation speed of the electric motor 3c becomes the target rotation speed.

[0032] A water purification method using such a water purification device 1 includes an arrangement step and a water supply step. The water supply step includes an internal temperature measurement step, an external temperature measurement step, and a control step.

[0033] The arrangement step is a step of arranging the pipe 2 so that the upper opening 2a is located in the surface layer 10a and the lower opening 2b is located in the bottom layer 10b. The water supply step is a step of supplying water by the pump mechanism 3 so that the upper opening 2a serves as the water intake 2f and the lower opening 2b serves as the water discharge 2g.

[0034] According to this water supply step, water from the surface layer 10a is taken into the pipe 2 from the upper opening 2a and discharged from the lower opening 2b within the bottom layer 10b, so that the oxygen-rich water from the surface layer 10a can be directly supplied to the bottom layer 10b, thereby efficiently supplying oxygen to the bottom layer 10b.

[0035] The internal temperature measurement step is a step in which the temperature of the water in the pipe 2 at the water outlet 2g is measured by the internal temperature sensor 4. The external temperature measurement step is a step in which the temperature of the water outside the pipe 2 at the water outlet 2g is measured by the external temperature sensor 5. The control step is a step in which the control unit 6 controls the flow rate of the pump mechanism 3 so that the difference between the measurement value in the internal temperature measurement step and the measurement value in the external temperature measurement step falls within the predetermined range. Note that the internal temperature measurement step and the external temperature measurement step may be performed in either order, or simultaneously.

[0036] According to such a control step, the flow rate of the pump mechanism 3 is limited so that the difference between the measured value in the internal temperature measurement step and the measured value in the external temperature measurement step falls within the predetermined range, that is, the water is sent slowly (for example, at a flow rate flowing through the pipe 2 at a speed of 1 to 10 mm / s, 1 to 30 mm / s, or 1 to 100 mm / s), so that the water can be sent while thoroughly reducing the temperature difference, and therefore the density difference, between the inside and outside of the pipe 2 by heat transfer from the inside of the pipe 2 to the outside of the pipe 2 via the pipe 2. Therefore, the buoyancy acting on the sent water caused by the density difference, which becomes the load, or resistance, when sending water, can be thoroughly reduced, so that the pump mechanism 3 can be operated efficiently with low load and low power. In addition, since the pressure difference between the inside and outside of the pipe 2 is hardly generated by sending water slowly, the pipe 2 can be made of a flexible material. In addition, if the temperature difference (density difference) between the water coming out of the water outlet 2g and the water around the water outlet 2g is small, the water coming out of the water outlet 2g is less likely to rise again and is more likely to remain in the bottom layer 10b.

[0037] In addition, in this embodiment, since the pump mechanism 3 is provided with the throttle portion 3a, even if the flow passage cross-sectional area in the pipe 2 is too large, the impeller 3b having an appropriate size that is not too large can be used, and the electric motor 3c can be operated in an appropriate rotation range that is not too low and has good energy efficiency. Therefore, the energy efficiency of the pump mechanism 3 can be improved.

[0038] Furthermore, in the control step, the control unit 6 may control the flow rate of the pump mechanism 3 (i.e., the number of revolutions of the electric motor 3c) to a larger flow rate set based on the temperature distribution of the water area 10, the diameter dimension of the pipe 2, and the axial length of the pipe 2, which have been previously investigated, without using the internal temperature measurement step and the external temperature measurement step, and then reduce the flow rate of the pump mechanism 3 so that the difference between the measured value in the internal temperature measurement step and the measured value in the external temperature measurement step falls within the predetermined range. According to this configuration, the previously set "larger flow rate" can quickly and reliably form a water flow from the water intake to the water discharge port, and then the flow rate can be adjusted, so that the flow rate of the pump mechanism 3 can be quickly and efficiently controlled.

[0039] In the water purification device 1 according to the first embodiment, the pump mechanism 3 is configured to send water so that the upper opening 2a serves as the water intake 2f and the lower opening 2b serves as the water discharge port 2g, but as in the second embodiment shown in Fig. 3, the pump mechanism 3 may be configured to send water so that the lower opening 2b serves as the water intake 2f and the upper opening 2a serves as the water discharge port 2g. In Fig. 3, elements corresponding to those shown in Fig. 1 are denoted by the same reference numerals.

[0040] In the water purification method using the water purification device 1 according to the second embodiment, the water supply step is a step of supplying water by the pump mechanism 3 so that the lower opening 2b serves as the water intake 2f and the upper opening 2a serves as the water discharge port 2g. According to this water supply step, water from the bottom layer 10b is taken into the pipe 2 from the lower opening 2b and discharged from the upper opening 2a in the surface layer 10a, so that the water from the surface layer 10a, which is rich in oxygen, can be gradually supplied to the bottom layer 10b by convection, and oxygen can be efficiently supplied to the bottom layer 10b.

[0041] According to the control step, the flow rate of the pump mechanism 3 is limited so that the difference between the measured value in the internal temperature measurement step and the measured value in the external temperature measurement step falls within the predetermined range. This allows the water to be pumped while thoroughly reducing the temperature difference between the water inside and outside the pipe 2, and therefore the density difference, due to the heat transfer from the outside of the pipe 2 to the inside of the pipe 2 through the pipe 2. Therefore, the sinking force acting on the water being pumped, which is caused by the density difference and is a load when pumping water, can be thoroughly reduced, so that the pump mechanism 3 can be operated efficiently with low load and low power. Furthermore, since the pressure difference between the inside and outside of the pipe 2 is hardly generated by flowing the water slowly, the pipe 2 can be made of a flexible material. Furthermore, if the temperature difference (density difference) between the water coming out of the water outlet 2g and the water around the water outlet 2g is small, the water coming out of the water outlet 2g is less likely to fall again and is more likely to remain in the surface layer 10a.

[0042] Other points are the same as in the case of the water purification method using the water purification device 1 according to the first embodiment.

[0043] The above-described embodiment is an example of the present disclosure, and it goes without saying that various modifications are possible.

[0044] For example, the water purification device 1 and the water purification method according to the above-described embodiment can be modified in various ways as described below.

[0045] The water purification device 1 according to the embodiment described above can be modified in various ways as long as it has a pipe 2 having an upper opening 2a located in the surface layer 10a of the water body 10 and a lower opening 2b located in the bottom layer 10b of the water body 10, and a pump mechanism 3 provided within the pipe 2 for pumping water so that one of the upper opening 2a and the lower opening 2b serves as a water intake 2f and the other of the upper opening 2a and the lower opening 2b serves as a water outlet 2g.

[0046] However, it is preferable that the water purification device 1 has an internal temperature sensor 4 that measures the temperature of the water inside the pipe 2 at a specified depth, an external temperature sensor 5 that measures the temperature of the water outside the pipe 2 at the specified depth, and a control unit 6 that controls the flow rate of the pump mechanism 3 so that the difference between the measurements taken by the internal temperature sensor 4 and the external temperature sensor 5 falls within a specified range.

[0047] Moreover, it is preferable that the internal temperature sensor 4 and the external temperature sensor 5 measure the temperature of the water at the water outlet 2g.

[0048] Moreover, the pump mechanism 3 preferably includes a throttle portion 3a that reduces the cross-sectional area of ​​the flow passage in the pipe 2, an impeller 3b that is disposed in the throttle portion 3a, and an electric motor 3c that rotates the impeller 3b.

[0049] In addition, it is preferable that the control unit 6 controls the flow rate of the pump mechanism 3 to a larger flow rate set regardless of the internal temperature sensor 4 and the external temperature sensor 5, and then reduces the flow rate of the pump mechanism 3 so that the difference between the measurement value measured by the internal temperature sensor 4 and the measurement value measured by the external temperature sensor 5 falls within the specified range.

[0050] Furthermore, the water purification method according to the embodiment described above can be modified in various ways, so long as it includes an arrangement step of arranging a pipe 2 having an upper opening 2a and a lower opening 2b, and having a pump mechanism 3 installed inside, so that the upper opening 2a is located within the surface layer 10a of the water body 10 and the lower opening 2b is located within the bottom layer 10b of the water body 10, and a water supply step of supplying water by the pump mechanism 3 so that one of the upper opening 2a and the lower opening 2b is a water intake 2f and the other of the upper opening 2a and the lower opening 2b is a water discharge outlet 2g.

[0051] However, it is preferable that the water supply step includes an internal temperature measurement step of measuring the temperature of the water inside the pipe 2 at a predetermined depth, an external temperature measurement step of measuring the temperature of the water outside the pipe 2 at the predetermined depth, and a control step of controlling the flow rate of the pump mechanism 3 so that the difference between the measurement value obtained by the internal temperature measurement step and the measurement value obtained by the external temperature measurement step falls within a predetermined range.

[0052] In addition, in the internal temperature measuring step and the external temperature measuring step, it is preferable to measure the temperature of the water at the water outlet 2g.

[0053] In addition, in the control step, it is preferable to control the flow rate of the pump mechanism 3 to a larger flow rate that is set regardless of the internal temperature measurement step and the external temperature measurement step, and then reduce the flow rate of the pump mechanism 3 so that the difference between the measurement value obtained by the internal temperature measurement step and the measurement value obtained by the external temperature measurement step falls within the specified range. [Explanation of symbols]

[0054] 1. Water purification equipment 2. Pipe 2a Top opening 2b Lower opening 2c Lower end 2d top end 2e Top surface 2f water intake 2g Spout 3. Pump mechanism 3a Squeezing section 3b Impeller 3c Electric motor 4 Internal Temperature Sensor 5 External Temperature Sensor 6. Control Unit 6a Computer 6b Driver 7 Power 8. Float 9. Anchor 9a Linear member 10 Water area 10a Surface layer 10b bottom layer 10c water surface 10d bottom surface 11 wiring

Claims

1. a pipe having an upper opening disposed within a surface layer of a body of water and a lower opening disposed within a bottom layer of said body of water; a pump mechanism provided in the pipe for pumping water so that one of the upper opening and the lower opening serves as a water intake port and the other of the upper opening and the lower opening serves as a water discharge port; an internal temperature sensor for measuring the temperature of the water in the pipe at a predetermined depth; an external temperature sensor for measuring the temperature of the water outside the pipe at the predetermined water depth; a control unit that controls the flow rate of the pump mechanism so that the difference between the measurement value obtained by the internal temperature sensor and the measurement value obtained by the external temperature sensor falls within a predetermined range of ±5°C.

2. The water quality purification device described in claim 1, wherein the control unit controls the flow rate of the pump mechanism to a set flow rate regardless of the internal temperature sensor and the external temperature sensor, and then controls the flow rate of the pump mechanism to be reduced so that the difference between the measurement value measured by the internal temperature sensor and the measurement value measured by the external temperature sensor falls within the specified range.

3. The water purification device according to claim 1 or 2, wherein the internal temperature sensor and the external temperature sensor measure the temperature of the water at the water outlet.

4. The water purification device according to any one of claims 1 to 3, wherein the pump mechanism includes a throttling section that reduces a flow path cross-sectional area in the pipe, an impeller disposed in the throttling section, and an electric motor that rotates the impeller.

5. a placement step of placing a pipe having an upper opening and a lower opening, the pipe having a pump mechanism therein, such that the upper opening is located within a surface layer of the water body and the lower opening is located within a bottom layer of the water body; a water supply step of supplying water by the pump mechanism so that one of the upper opening and the lower opening serves as a water intake port and the other of the upper opening and the lower opening serves as a water discharge port; The water purification method includes an internal temperature measurement step of measuring the temperature of water inside the pipe at a predetermined depth, an external temperature measurement step of measuring the temperature of water outside the pipe at the predetermined depth, and a control step of controlling the flow rate of the pump mechanism so that the difference between the measurement value obtained by the internal temperature measurement step and the measurement value obtained by the external temperature measurement step falls within a predetermined range of ±5°C.

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