Water quality meter and adhesion prevention method

Abstract

To provide a water quality measuring device capable of conducting in-water measuring precisely and continuously, and a deposition prevention method capable of desirability suppressing deposition of an organism and a biofilm.SOLUTION: A water quality measuring device includes a sensor apparatus, an irradiation apparatus for irradiation of a light to a detector of the sensor apparatus, and a control part for controlling the irradiation apparatus, wherein the water quality measuring device is characterized by that the light irradiated from the irradiation apparatus has a peak in a wavelength region of 400-420 nm, the sensor apparatus conducts detection action in every predetermined desired detecting timing, and the control part conducts control of the irradiation apparatus in a manner that a light is irradiated intermittently from the irradiation apparatus to the detector in every irradiation time other than the desired detecting timing.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a water quality meter and a method for preventing organisms. [Background technology]

[0002] Conventionally, environmental measurements have been performed by immersing water quality meters such as thermometers, salinity meters, dissolved oxygen meters, and chlorophyll meters in water. When measuring, for example, the marine environment over a long period of time, there is a problem that foreign matter such as sessile organisms such as barnacles and mussels, algae, and biofilms adhere to the sensor device of the water quality meter, making it difficult to perform accurate measurements with the water quality meter. In addition to water quality meters, there is also a problem that in underwater structures (e.g., seawater system facilities of thermal power plants, nuclear power plants, etc.) that are immersed in water, foreign matter such as sessile organisms such as barnacles and mussels, and biofilms adhere to the inspection windows, making it difficult to inspect the underwater structures.

[0003] To solve the above problems, a method is known in which the attachment of sessile organisms to an underwater structure is prevented by irradiating the underwater structure with light having a wavelength of 409 to 412 nm (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-188570 Summary of the Invention [Problem to be solved by the invention]

[0005] The method disclosed in Patent Document 1 can suppress the adhesion of sessile organisms to areas of an underwater structure where high-intensity light is irradiated. However, there is a problem that the light may attract sessile organisms or promote the overgrowth of plants such as algae in areas where low-intensity light is irradiated, such as between light irradiating devices or at the edges, making the method insufficient in suppressing the adhesion of organisms and biofilms. Furthermore, there is a problem that accurate detection results cannot be obtained when detecting with light irradiated onto a water quality meter.

[0006] The present invention has been made in consideration of the above, and aims to provide a water quality meter that can continuously and accurately perform measurements in water, and an adhesion prevention method that can preferably suppress the adhesion of organisms and biofilms. [Means for solving the problem]

[0007] (1) The present invention relates to a water quality meter having a sensor device, an irradiation device that irradiates light onto a detection unit of the sensor device, and a control unit that controls the irradiation device, wherein the light irradiated from the irradiation device has a peak in the wavelength range of 400 to 420 nm, the sensor device performs a detection operation at each predetermined detection timing, and the control unit controls the irradiation device so that light is intermittently irradiated from the irradiation device onto the detection unit at each irradiation time other than the predetermined detection timing.

[0008] (2) The water quality meter according to (1), wherein the control unit controls the irradiation device so that the total irradiation time is 30 to 70% of the total of the irradiation time and the time when light is not irradiated from the irradiation device.

[0009] (3) The water quality meter according to (1) or (2), wherein the irradiation surface of the irradiation device is arranged opposite to the detection unit.

[0010] (4) The present invention also relates to a method for preventing adhesion of organisms and biofilms to an object immersed in water, which comprises intermittently irradiating the object with light having a peak in the wavelength range of 400 to 420 nm so that the proportion of the time during which the light is irradiated is 30 to 70% of the total time during which the light is irradiated and the time during which the light is not irradiated. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a water quality meter that can continuously and accurately perform measurements in water, and an adhesion prevention method that can preferably suppress the adhesion of organisms and biofilms. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram showing the configuration of a water quality meter according to a first embodiment of the present invention. [Figure 2] FIG. 6 is a diagram showing the configuration of a water quality meter according to a second embodiment of the present invention. [Figure 3] FIG. 10 is a diagram showing the configuration of a water quality meter according to a third embodiment of the present invention. [Figure 4] FIG. 10 is a diagram showing the configuration of a water quality meter according to a fourth embodiment of the present invention. [Figure 5] FIG. 1 is a diagram illustrating an experimental device used in an example of the present invention. [Figure 6] 10 is an image showing a test plate after testing according to a comparative example of the present invention. [Figure 7] 10 is an image showing a test plate after testing according to an example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described. Note that the present invention is not limited to the following embodiments and can be modified as appropriate.

[0014] <Water quality meter> The water quality meter according to this embodiment is used to continuously measure the water quality of water in environments such as oceans, rivers, or lakes for a predetermined period of time, for example, one day or more. Examples of water quality measurement items measured by the water quality meter include water temperature, salinity, dissolved oxygen (DO) concentration, chlorophyll, organic matter, turbidity, illuminance, pH, ORP (oxidation-reduction potential), conductivity, specific gravity, depth, current direction and speed, various ion concentrations, visible light and / or infrared light images, etc. The water quality meter according to this embodiment may be capable of measuring multiple of the above water quality measurement items.

[0015] The water quality meter according to this embodiment includes a sensor device, an irradiation device that irradiates a detection unit of the sensor device with light, and a control unit that controls the irradiation device.

[0016] First Embodiment 1, the water quality meter 1 according to this embodiment is a water temperature / salinity meter having a salinity concentration sensor (detection unit 31) and a water temperature sensor (detection unit 32) as sensor devices. In addition to the above, the water quality meter 1 also includes irradiation devices 20a and 20b, a main body 4, a control unit 5, and a support 7a.

[0017] (irradiation device) The illumination devices 20a and 20b intermittently illuminate the detection unit 31 of the salinity concentration sensor and the detection unit 32 of the water temperature sensor with light having a peak in the wavelength range of 400 to 420 nm. This suppresses the adhesion of organisms and biofilms to the detection unit 31 of the salinity concentration sensor and the detection unit 32 of the water temperature sensor. The illumination devices 20a and 20b are, for example, LED illumination devices and are configured to include one or more LED elements. The illumination devices 20a and 20b each have a housing 21a and 21b and an illumination surface 22a and 22b. The illumination surface 22a is positioned opposite one opening 31a of the hole in which the detection unit 31 of the salinity concentration sensor is disposed and the detection unit 32 of the water temperature sensor. The illumination surface 22b is positioned opposite the other opening 31b of the hole in which the detection unit 31 of the salinity concentration sensor is disposed.

[0018] The organisms that can attach to the detection unit are not particularly limited as long as they have the property of attaching to the surface of an object placed in water, and examples include sessile organisms such as mussels and barnacles. Sessile organisms float in the sea during their early larval stage, and when they reach the sessile stage, they attach to a suitable object and metamorphose into adults.

[0019] Mussels are a general term for bivalve mollusks in the family Mytilidae, and include, for example, the subfamily Modiolinae, such as the skylark mussel; the subfamily Lithophaginae, such as the stone mussel; the subfamily Crenellinae, such as the mussel Mytilinae, the golden mussel Mytilinae, the blue mussel Mytilinae, and the like. Furthermore, barnacles are a general term for those classified in the Crustacea, Cirripadia, and Thoracica orders, and include those belonging to the Balanomorpha suborder, which includes, for example, the striped barnacle, American barnacle, red barnacle, triangular barnacle, giant red barnacle, Japanese barnacle, rock barnacle, white-striped barnacle, and European barnacle.

[0020] The biofilm that can adhere to the detection unit is a structure formed by microorganisms on the surface of an object placed in water. Biofilms are usually membrane-like and contain extracellular polymeric substances (EPS), such as polysaccharides secreted by microorganisms. Biofilms may also contain microbial remains, excrement, feces, and burrows. Examples of microorganisms include organisms belonging to bacteria, fungi, cyanobacteria, and protozoa. Microalgae such as periphyton diatoms, green algae, brown algae, and red algae, as well as the larvae of sponges, hydrozoans, jellyfish, tube-dwelling polychaetes, bryozoans, and amphipods, among others, are also included.

[0021] The light emitted from the irradiation devices 20a and 20b has a peak in the wavelength range of 400 to 420 nm. Ultraviolet light with a wavelength of 380 nm or less is effective in inhibiting the adhesion of organisms and biofilms, but has the problem of low transmittance in seawater. By setting the wavelength of the irradiation light within the above range, a preferable adhesion inhibition effect can be obtained. The wavelength of the irradiation light may include wavelength ranges other than those described above, as long as the effect of the present invention is not impaired. For example, it may include light in the wavelength range of 400 to 440 nm.

[0022] The irradiance of the light emitted from the irradiation devices 20a and 20b is set to 25 Wm from the viewpoint of suppressing the adhesion of organisms and biofilms. -2 It is preferable that it is 50Wm or more. -2 More preferably, it is 100Wm -2 It is more preferable that the irradiance is equal to or greater than this. In this specification, the irradiance refers to the value of the irradiance measured by an irradiance meter Pyranometer LI-200 (manufactured by Meiwafosis Co., Ltd.).

[0023] Intermittent light irradiation from the irradiation devices 20a and 20b can more effectively prevent foreign matter from adhering to the detection units 31 and 32, which are irradiated with light, than continuous light irradiation. Specifically, when light is continuously irradiated, foreign matter such as living organisms and biofilms do not adhere to areas irradiated with strong light, but organisms that grow by photosynthesis, such as algae, may be more likely to grow in areas around the light axis irradiated with relatively weak light. This is thought to be because the light irradiated from the irradiation devices 20a and 20b contains wavelengths of light effective for photosynthesis. The intermittent light irradiation from the irradiation devices 20a and 20b inhibits the growth of algae and other organisms. While the reason for this is unclear, it is thought that intermittent light irradiation results in an insufficient amount of light for photosynthesis by algae and other organisms, inhibiting their growth.

[0024] Intermittent light irradiation from the irradiation devices 20a and 20b effectively suppresses the adhesion of algae and other growths to the irradiation surfaces 22a and 22b of the irradiation devices 20a and 20b. When the irradiation devices 20a and 20b include multiple LED elements and continuously irradiate light from the irradiation devices 20a and 20b, algae and other growths may adhere between the LED elements, resulting in a decrease in the irradiance of the irradiated light. However, intermittent light irradiation from the irradiation devices 20a and 20b can suppress a decrease in the irradiance of the irradiated light, even when the irradiation devices 20a and 20b include multiple LED elements. Furthermore, intermittent light irradiation from the irradiation devices 20a and 20b suppresses the deterioration of the LED elements over time, thereby improving the durability of the water quality meter 1.

[0025] (sensor device) The salinity sensor is a sensor device that detects the salinity concentration in water. The detection unit 31 of the salinity sensor is provided in a hole through which liquid can flow. If the flow of liquid such as seawater is hindered due to the adhesion of organisms and biofilms to the hole, the salinity sensor cannot accurately measure the salinity. Light emitted from the irradiation devices 20a and 20b of the water quality meter 1 according to this embodiment suppresses the adhesion of organisms and biofilms not only to the detection unit 31 but also to the hole in which the detection unit 31 is located. This allows the salinity sensor to continuously and accurately measure the salinity.

[0026] The water temperature sensor is a sensor device that detects water temperature. Light emitted from the irradiation device 20a to the detection unit 32 of the water temperature sensor suppresses the adhesion of organisms and biofilms to the detection unit 32. This allows the water temperature sensor to continuously and accurately measure water temperature.

[0027] The salinity concentration sensor and water temperature sensor serving as the sensor device are set to perform detection operations at predetermined detection timings. The detection intervals for performing the detection are not particularly limited, but may be, for example, 10 minutes or more to prevent the detection results of the sensor device from being affected by residual heat from the light irradiated from the irradiation device. The detection intervals may also be one day. It is preferable that the predetermined detection timings of the salinity concentration sensor and the water temperature sensor are the same.

[0028] (Main body) The main body 4 houses a salinity concentration sensor and a water temperature sensor. In addition to the above, the main body 4 may also include a storage unit that stores the results of measurements by the salinity concentration sensor and the water temperature sensor.

[0029] (Control unit) The control unit 5 controls the irradiation timing of the irradiation devices 20a and 20b so that light is intermittently emitted from the irradiation devices 20a and 20b. The control unit 5 is communicatively connected to the irradiation devices 20a and 20b by wiring 6a and 6b, respectively.

[0030] The control unit 5 controls the irradiation devices 20a and 20b to irradiate the detection unit 31 of the salinity concentration sensor and the detection unit 32 of the water temperature sensor with light during each irradiation time other than the predetermined timing at which the salinity concentration sensor and the water temperature sensor perform their detection operations. If the salinity concentration sensor and the water temperature sensor perform their detection operations while the irradiation devices 20a and 20b are irradiating the detection units 31 and 32 with light, the salinity concentration sensor and the water temperature sensor may not be able to perform accurate measurements. However, with the above configuration, the control unit 5 controls the irradiation devices 20a and 20b not to irradiate the detection units 31 and 32 with light while the salinity concentration sensor and the water temperature sensor are performing their detection operations. This allows the salinity concentration sensor and the water temperature sensor to perform accurate measurements. From the perspective of accurate measurement, it is preferable that the predetermined timing at which the salinity concentration sensor and the water temperature sensor perform their detection operations be the center of the time when the irradiation devices 20a and 20b are not irradiating light.

[0031] It is preferable that the control unit 5 controls the irradiation devices 20a and 20b so that the ratio of the irradiation time during which light is irradiated from the irradiation devices 20a and 20b to the detection units 31 and 32 is 30 to 70% of the total of the irradiation time and the time during which light is not irradiated from the irradiation devices 20a and 20b (i.e., the elapsed time). This provides the effect of preventing the adhesion of foreign matter such as organisms and biofilms, and also makes it possible to suppress the adhesion of algae and the like to areas irradiated with relatively weak light.

[0032] For example, if the detection interval of the sensor device is 20 minutes and the irradiation time ratio is 50%, the control unit 5 causes the irradiation devices 20a and 20b to irradiate light onto the detection units 31 and 32 five minutes after the detection timing of the sensor device. Light is continuously irradiated from the irradiation devices 20a and 20b for the 10-minute irradiation time. After the 10-minute irradiation time has elapsed, the control unit 5 stops the irradiation of light from the irradiation devices 20a and 20b. Then, five minutes later, the next detection timing of the sensor device arrives, and the sensor device performs a detection operation. This eliminates the impact on the detection of the sensor device, such as an increase in water temperature caused by the irradiation of light from the irradiation devices 20a and 20b.

[0033] (Support) The support 7a is a support for fixing the irradiation devices 20a and 20b, and is configured to allow water from the outside to pass through the detection units 31 and 32. The support 7a has, for example, a frame shape, and is not particularly limited in material, and materials such as metal and resin can be used as appropriate. The support 7a allows the irradiation surfaces 22a and 22b to be positioned so as to face the detection units 31 and 32.

[0034] Other embodiments of the present invention will be described below, and the description of the same configuration as the first embodiment may be omitted.

[0035] Second Embodiment 2, the water quality meter 1a according to the second embodiment has a dissolved oxygen (DO) concentration sensor (detection unit 33) and a water temperature sensor (detection unit 34) as sensor devices. In addition to the above, the water quality meter 1a also has an irradiation device 20c, a main body 4a, a control unit 5a, a support 7b, and a wiper device 8.

[0036] The irradiation device 20c according to this embodiment has a housing 21c and an irradiation surface 22c. In this embodiment, the irradiation device 20c is a single irradiation device, and the irradiation surface 22c is disposed opposite a detection unit 33 of a dissolved oxygen (DO) concentration sensor and a detection unit 34 of a water temperature sensor. The irradiation device 20c is fixed and supported by a support body 7b. The support body 7b has a frame shape similar to the support body 7a.

[0037] The dissolved oxygen (DO) concentration sensor is a sensor device that measures the dissolved oxygen (DO) concentration in water. The detection unit 33 of the dissolved oxygen (DO) concentration sensor and the detection unit 34 of the water temperature sensor are intermittently irradiated with light having a peak in the wavelength range of 400 to 420 nm from the irradiation device 20c, thereby suppressing the adhesion of organisms and biofilms to the detection unit 33 and the detection unit 34. The configuration in which the detection timing of the dissolved oxygen (DO) concentration sensor and the water temperature sensor, and the irradiation timing of light irradiation from the irradiation device 20c are controlled by the control unit 5a is the same as that of the water quality meter 1 according to the first embodiment. The control unit 5a is housed inside the main body 4a and is communicatively connected to the irradiation device 20c by wiring 6c.

[0038] (Wiper device) The wiper device 8 is a device that removes organisms and biofilms that adhere to the detection unit 33 of the dissolved oxygen (DO) concentration sensor and the detection unit 34 of the water temperature sensor by wiping them off. The wiper device 8 has abutment parts that rotatably abut against the detection units 33 and 34. The abutment parts are made of a flexible material such as resin. By having the wiper device 8 in addition to the irradiation device 20c, even if one device is unable to sufficiently inhibit or remove the adhesion of organisms and biofilms to the detection units 33 and 34 due to a malfunction of the device, the other device can still inhibit or remove the adhesion of organisms and biofilms to the detection units 33 and 34, thereby enabling more reliable and accurate measurement by the sensor device.

[0039] Third Embodiment 4, the water quality meter 1c according to the third embodiment has a pH / ORP sensor (detection unit 36) as a sensor device, a chlorophyll / turbidity sensor (detection unit 37), and a depth sensor (detection unit 38). In addition to the above, the water quality meter 1c also has an irradiation device 20e, a main body 4c, and a control unit 5c.

[0040] The illumination device 20e according to this embodiment includes a housing 21e and an illumination surface 22e. In this embodiment, the illumination device 20e is a single illumination device, and the illumination surface 22e is disposed opposite a pH / ORP sensor detection unit 36, a chlorophyll / turbidity sensor detection unit 37, and a depth sensor detection unit 38. The illumination device 20e is fixed and supported by a support 7c. The support 7c has a frame shape similar to the support 7a.

[0041] The pH / ORP sensor is a sensor device that measures the hydrogen ion index and oxidation-reduction potential (ORP) in water. The chlorophyll / turbidity sensor is a sensor device that measures the chlorophyll concentration and turbidity in water. The depth sensor is a sensor device that measures the depth from the water surface.

[0042] Light having a peak in the wavelength range of 400 to 420 nm is intermittently irradiated from the irradiation device 20e onto the detection unit 36 ​​of the pH / ORP sensor, the detection unit 37 of the chlorophyll / turbidity sensor, and the detection unit 38 of the depth sensor, thereby suppressing the adhesion of organisms and biofilms to the detection units 36, 37, and 38. The configuration in which the detection timing of the pH / ORP sensor, the chlorophyll / turbidity sensor, and the depth sensor, and the irradiation timing of light irradiation from the irradiation device 20e are controlled by the control unit 5c is the same as in the water quality meter 1 according to the first embodiment. The control unit 5c is housed inside the main body 4c and is communicatively connected to the irradiation device 20e by wiring 6e.

[0043] <Method for preventing adhesion> The adhesion prevention method according to this embodiment is a method for preventing the adhesion of organisms and biofilms to an object immersed in water by intermittently irradiating the object with light having a peak in the wavelength range of 400 to 420 nm. The proportion of time during which the object is irradiated with light is 30 to 70% of the total time during which light is irradiated and time during which light is not irradiated.

[0044] In addition to the water quality meter, examples of objects to which the adhesion prevention method according to the present embodiment can be applied include underwater structures installed underwater, such as seawater system equipment in power generation facilities such as thermal power plants and nuclear power plants, and inspection windows for inspecting such equipment. Other objects may include underwater camera devices, water intake pipelines, rotary screens, bar screens, drum screens, mussel filters, net screens, water intake pumps, circulating water pumps, circulating water pipes, heat exchangers, condensers, bearing cooling water coolers, lubricating oil coolers, LNG vaporizers, generators, discharge pipelines, water turbines, impellers, valves, rotating shafts, water conveyance pipelines, filtration tanks, membranes, dams, ships, ship hulls in shipyards, ballast water tanks, ballast water inlet / outlet pipes, pumps, aquaculture facilities, fisheries research stations, fisheries facilities, aquariums, tanks in fish and shellfish breeding tanks, piping, and pumps.

[0045] The LED irradiation device described above can be used as a method for irradiating an object with light having a peak in the wavelength range of 400 to 420 nm, and a method for controlling the irradiation of light onto an object can be similar to the method for controlling the irradiation devices 20a and 20b by the control unit 5, except that it is not restricted by the detection timing of the sensor device.

[0046] An example in which the adhesion prevention method according to this embodiment is applied to an underwater camera device will be described below. As shown in Figure 3, underwater camera device 1b has an illuminance sensor (detection unit 35) as a sensor device. In addition to the above, underwater camera device 1b also has an illumination device 20d, a main body unit 4b, a control unit 5b, a wiper unit 8a, and an imaging unit (camera lens 9).

[0047] The underwater camera device 1b is capable of periodically capturing underwater images using an imaging unit. The underwater images are, for example, visible light images. The underwater camera device 1b is equipped with multiple illumination devices 20d around the camera lens 9. The illumination devices 20d can emit light having a peak in the wavelength range of 400 to 420 nm, and preferably can also emit white light.

[0048] The light emitted from the irradiation device 20d, which has a peak in the wavelength range of 400 to 420 nm, is intermittently irradiated by the control unit 5b so that the ratio of the time during which light is irradiated to the total time during which light is irradiated and the time during which light is not irradiated is 30 to 70%. This has the effect of preventing foreign matter such as living organisms and biofilms from adhering to the camera lens 9 and the detection unit 35 of the illuminance sensor, and also makes it possible to suppress the adhesion of algae and the like to areas irradiated with relatively weak light.

[0049] The illumination device 20d may be used as illumination by emitting light in synchronization with the image capturing timing of the imaging unit. For example, when the ambient illuminance is low at the image capturing timing of the imaging unit, white light may be emitted from the illumination device 20d, and by emitting white light as illumination, an image including color information of the object to be captured can be obtained.

[0050] When the ambient illuminance is low at the time of photographing by the imaging unit, if light having a peak in the wavelength range of 400 to 420 nm is irradiated from the illumination device 20d, underwater images of relatively distant areas can be photographed because light having a peak in the wavelength range of 400 to 420 nm has a wavelength range that is highly transparent in the sea.

[0051] In this embodiment, a plurality of (seven in this embodiment) irradiation devices 20d are provided around the camera lens 9.

[0052] The illuminance sensor (detection unit 35) measures the illuminance of the surroundings, and turns on the illumination from the irradiation device 20d when the illuminance of the surroundings is lower than a predetermined value (dark conditions). [Example]

[0053] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0054] [Adhesion test] The test equipment shown in Figure 5 was installed by suspending it from a crane into the sea near the power plant's water intake. The installation position was adjusted to be 1 m below the water surface, ensuring that no part of the test equipment would be exposed above sea level even during low tide. As shown in Figure 5, the test equipment consisted of test panels P1 and P2 (25 cm x 25 cm, made of vinyl chloride), as well as an underwater LED irradiation device (peak wavelength: 405 nm, manufactured by Delphys) fixed to frame 7. The distance between the irradiation surface of the underwater LED irradiation device and test panel P2 was approximately 35 cm. Test panel P1 was not irradiated with light and served as the control. The detection unit S of the water temperature sensor was placed in the center of test panels P1 and P2, respectively, and the change in water temperature was recorded by recording unit M. The test period was approximately one month, from August 19 to September 14, 2021. The test was conducted using the following three types of LED devices in the test sections.

[0055] Example 1: Small LED irradiation device (6-lamp type, irradiance setting: (at the position of the test plate surface) 100 W / m -2 ) was used, and irradiation and non-irradiation were switched on and off every 15 minutes using a lab timer, and intermittent irradiation was performed toward the center of the test panel P2. Comparative Example 1: Small LED irradiation device (6-light type, irradiance setting: (at the position of the test plate surface) 100 W / m -2 ) was used and continuously irradiated toward the center of the test panel P2. Comparative Example 2: Large LED irradiation device (36-light type, irradiance setting: (at the position of the test plate surface) 100 W / m -2 ) was used and continuously irradiated toward the center of the test panel P2.

[0056] (Test results) In all test plates P2 of Example 1 and Comparative Examples 1 and 2, it was confirmed that adhesion of foreign matter such as organisms and biofilms was significantly suppressed near the center of test plate P2 where LED light was irradiated, compared to test plate P1 in the control group. On the other hand, adhesion of green algae was confirmed around the center of test plate P2 where LED light was irradiated and on the irradiated surface of the irradiation device in Comparative Examples 1 and 2. Almost no adhesion of the above-mentioned green algae was observed on test plate P2 of Example 1.

[0057] FIG. 6 is an image photographed showing the state of foreign matter adhesion on the test plate P2 of Comparative Example 2 after the adhesion test. Green algae A and fibrous green algae A1 were attached around the central part of the test plate P2 of Comparative Example 2 where LED light was irradiated. FIG. 7 is an image photographed showing the state of foreign matter adhesion on the test plate P2 of Example 1 after the adhesion test. No green algae was found attached around the central part of the test plate P2 of Example 1 where LED light was irradiated. Therefore, it was confirmed that intermittent irradiation with LED light of a predetermined wavelength can suppress not only the adhesion of foreign matter such as organisms and biofilms to the area irradiated with LED light on the target object, but also the adhesion of green algae to the area surrounding the irradiated area.

[0058] The water temperature change detected by the water temperature sensor showed an increase of approximately 0.4°C compared to the control area in the small LED irradiation device used in Comparative Example 1, and an increase of approximately 0.6°C compared to the control area in the large LED irradiation device used in Comparative Example 2. On the other hand, in Example 1, it was confirmed that the water temperature quickly returned to the same level as the control area when irradiation was switched to non-irradiation.

[0059] The small LED irradiation device after the adhesion test in Comparative Example 1 had an irradiance of 100 Wm -2 to 58.2Wm -2 The small LED irradiation device of Comparative Example 2 after the adhesion test had an irradiance of 100 Wm -2 from 22.5Wm -2 When the irradiation surfaces of the LED irradiation devices of Comparative Examples 1 and 2 were cleaned and the irradiance was measured again, the irradiance was 100 Wm -2The irradiance recovered to around 100%. Therefore, it is presumed that the decrease in irradiance in Comparative Examples 1 and 2 is due to the adhesion of foreign matter to the irradiation surface. On the other hand, no decrease in irradiance was confirmed in the small LED irradiation device of Example 1 after the adhesion test. Therefore, it was confirmed that the adhesion of foreign matter to the irradiation surface of the LED irradiation device can be suppressed by intermittently irradiating LED light of a specified wavelength. [Explanation of symbols]

[0060] 1, 1a, 1b, 1c water quality meter 20a, 20b, 20c, 20d, 20e irradiation equipment 22a, 22b, 22c, 22d, 22e irradiation surface 31, 32, 33, 34, 35, 36, 37, 38 Detector 5, 5a, 5b, 5c control section

Claims

1. A water quality meter including a sensor device, an irradiation device that irradiates a detection unit of the sensor device with light, and a control unit that controls the irradiation device, the light irradiated from the irradiation device has a peak in a wavelength range of 400 to 420 nm, the sensor device performs a detection operation at each predetermined detection timing, The control unit controls the irradiation device so that light is intermittently irradiated from the irradiation device to the detection unit at each irradiation time other than the predetermined detection timing.

2. The water quality meter according to claim 1, wherein the control unit controls the irradiation device so that the total irradiation time is 30 to 70% of the total of the irradiation time and the time when light is not irradiated from the irradiation device.

3. The water quality meter according to claim 1 or 2, wherein an irradiation surface of the irradiation device is disposed opposite to the detection unit.

4. A method for preventing adhesion of organisms and biofilms to an object immersed in water, comprising: The adhesion prevention method includes intermittently irradiating the object with light having a peak in a wavelength range of 400 to 420 nm so that the proportion of the time during which the light is irradiated is 30 to 70% of the total of the time during which the light is irradiated and the time during which the light is not irradiated.

Images