JP2009074840A - Water quality monitoring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water quality monitoring device using fishes capable of recognizing correctly 'active state' and 'inactive state' of fishes in a water tank. <P>SOLUTION: This device is constituted of: the water tank 11 wherein a water current 19 is formed; a monitoring camera 12 for acquiring an image of the fishes F kept in the water tank 11 and having positive rheotaxis; an image processing means 21 for acquiring an image signal by processing the image, and detecting a brightness change caused by a behavior of the fishes F based on the image signal; a display monitor 14 for displaying the processed image signal; and an alarm means 25 for reporting an abnormality of the water quality in the water tank 11 to the outside. A monitoring domain 20 in the water tank 11 where the monitoring camera 12 acquires the image is classified into a plurality of divided domains along the water current 19, and a reference value of the brightness change of a pixel 31 when determining acceptance of the water quality detected by the image processing means 21 is lowered in a monitoring domain 30d on the downstream side of the water current 19, in comparison with the case in a monitoring domain 30a on the upstream side. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a water quality monitoring device that monitors the water quality in a water tank by the behavior of fish bred in the water tank.

  In general, in water purification facilities that purify raw water taken from rivers, etc. as drinking water, agricultural water, etc., in the unlikely event that toxic substances are mixed into the raw water, the contamination is detected quickly and reliably, and water quality is safe. Is required.

  For this reason, conventionally, the raw water taken is continuously passed through the aquarium, and by monitoring the behavior of fish bred in the aquarium, the contamination of the raw water can be detected quickly, and the quality of the water is deteriorated. A water quality monitoring device for monitoring is known.

  In this water quality monitoring apparatus, a water flow from the inlet to the outlet is formed in the water tank, and fish having a so-called “positive running ability”, for example, medaka, is bred in the water tank.

  An image of the medaka in the water tank is acquired through a monitoring camera provided in the water quality monitoring device, and based on the acquired image, an image processing means provided in the water quality monitoring device detects the behavior of the medaka. Yes.

  Specifically, an image signal is acquired by processing an image in the water tank imaged by the monitoring camera. The image signal is composed of a large number of dots (pixels) in a matrix shape, and divides a monitoring area in the water tank including the large number of pixels into a plurality of blocks.

  One pixel is smaller than the size of the body of the medaka, and the luminance of the pixel changes when the medaka swims over the pixel and blocks light. The image processing means detects that the luminance of the pixel changes more than a certain level, and recognizes the action of the medaka as “active”.

  In other words, because there are many pixels that pass through more actively swimming medakas, out of all the pixels, the pixels that were not blocked by the medaka were blocked by the movement of the medaka, and vice versa, the medaka was blocked. The number of pixels that are not obstructed by the movement of the medaka increases. That is, the number of pixels whose luminance changes greatly is increased by the light shielding.

  The image processing means detects pixels whose luminance has changed by a predetermined reference value or more in each block. Then, the determination unit counts the number of blocks including the pixels detected by the image processing unit.

  If the movement of fish bred in the aquarium is active and the number of counted blocks is equal to or greater than a preset number, the determination means recognizes the medaka as “active” and the water quality in the aquarium Is judged as “good”.

  If a poison or the like is mixed into the raw water, the movement of the fish bred in the aquarium slows down, and the amount of movement decreases, so that the pixels that are not shielded by the movement of the medaka are shielded from light, In addition, the number of pixels in which the medaka is shielded from light is reduced due to the movement of the medaka. For this reason, the luminance of each pixel does not change so much, and the number of blocks including pixels whose luminance has changed more than the predetermined reference value is reduced.

When the counted number of blocks is less than or equal to the preset number, the determination means recognizes the medaka as “inactive”, determines the water quality of the water in the aquarium as “no”, and the water quality is abnormal. An alarm signal for notifying that is output (see Patent Document 1).
JP 2001-99334 A

  However, the fish (such as medaka) has its ecology (whether it swims actively) or the like constantly changing due to factors other than water quality, such as time, season, weather, and water temperature. For this reason, if the medaka is in a relatively active time, called “active behavior”, in an environment, etc., the medaka tends to gather in an upstream region where the flow of water is fast. In addition, when the medaka comes to an environment or the like when the medaka can not act relatively actively, so-called “pseudo stop behavior”, the medaka tends to gather in a downstream region where the flow of water is slow.

  If the medaka gathers in the area | region of a downstream, even if there is no abnormality in the water quality in a water tank, the movement of a medaka will become relatively slow. This is because the medaka does not swim actively due to the “positive running characteristics” of the medaka, because the water flow in the downstream area is slow.

  When the movement of the medaka slows down, the movement of the medaka slows down, and even if there is no abnormality in the water quality in the aquarium, the medaka passes over the pixels when the image in the aquarium is acquired by the surveillance camera. It takes time to shield the pixels. For this reason, there is a problem that it takes time to obtain a luminance change amount that can clearly determine whether the water quality is good or bad.

  For this reason, it is difficult to clearly detect the luminance change of each pixel, and the ratio of medaka that can recognize medaka that should be recognized as "active" correctly as "active" even though the water quality is "good". (Recognition rate of medaka (fish)) decreases.

  In order to solve this problem, for example, the detection sensitivity of the pixels is increased over the entire monitoring area in the water tank from which the monitoring camera acquires images (determined to be “good” even for a relatively small amount of change in luminance The reference value is set so that the recognition rate of the medaka is increased.

  However, in the upstream region where the water flow is fast, the water surface has a relatively large undulation compared to the downstream region, so if the detection sensitivity is increased, for example, the presence of active medaka will change the brightness due to the undulation of the water surface. Or a change in luminance due to the reflected light on the water surface may be erroneously detected as noise. For this reason, when the pixel detection sensitivity is increased, the medaka recognition rate may be reduced, particularly in the upstream monitoring region.

  For this reason, it is required to be able to correctly recognize the “activity” and “inactivity” of medaka regardless of the difference in the speed of water flow at each location in the aquarium.

  Accordingly, an object of the present invention is to make it possible to correctly recognize “activity” and “inactivity” of fish in an aquarium in a water quality monitoring apparatus using fish.

  In order to solve the above problems, the present invention divides a monitoring area in a water tank by a monitoring camera into a plurality of divided areas along the water flow, and the detection sensitivity of pixels in the monitoring camera is divided into divided areas on the downstream side of the water flow. Is made higher than the divided area on the upstream side.

  When the detection sensitivity of the pixels in the monitoring camera in the downstream divided area is increased, the pixels that are shielded by the slow-moving fish present in the downstream divided areas are detected with high sensitivity, and the change in luminance of the shielded pixels is detected. It can be detected clearly. For this reason, the recognition rate of medaka can be improved.

As a specific configuration, a water tank having a water inlet and a water outlet, a monitoring camera for acquiring images of fish having a running ability bred in the water tank, and acquired by the monitoring camera. Image processing means for processing the obtained image to obtain an image signal, and detecting a change in luminance due to the behavior of the fish based on the image signal, and the amount of change in the luminance detected by the image processing means In the water quality monitoring device provided with a determination means for determining the quality of the water in the aquarium based on
The monitoring area in the water tank from which the monitoring camera obtains an image is divided into a plurality of divided areas along the water flow from the inlet to the outlet, and the amount of change in luminance when determining the quality of the water is determined. The reference value is set so that the divided area on the downstream side of the water flow is lower than the divided area on the upstream side.

  In this configuration, if the reference value of the amount of change in luminance can be set for each divided region, the divided value can be set for each divided region according to specific conditions such as the speed of water flow in each divided region and the ripple near the water surface. An appropriate reference value can be set. If an appropriate reference value can be set for each divided area, the medaka recognition rate can be increased.

  In addition, the inflow port is provided in a side wall of the water tank, the discharge port is provided in a central bottom part of the water tank, and the water flowing into the water tank is separated from a part near the side wall of the water tank. In the water tank in which the flow is formed so as to swivel toward the water tank, if the configuration of the water quality monitoring device is adopted, each of the divided regions divided along the water flow in the water tank is formed along each side wall of the water tank. Therefore, it is possible to make the imaging range necessary for acquiring images of all the monitoring areas at one time with one monitoring camera compact.

  As the determination of the quality of the water quality by the determination means, for example, the divided area is partitioned by a plurality of blocks, a plurality of pixels are arranged in each block, and a change in luminance by the image processing means is detected. The detection is to detect a pixel having a luminance change exceeding the reference value, and the determination means counts the number of blocks including at least one pixel having a luminance change exceeding the reference value. You may make it determine the quality of water quality based on whether the number of the counted blocks is less than a setting number.

  In this configuration, “active” and “inactive” of fish can be recognized for each pixel smaller than the divided region and block. Since the pixels can be smaller than the fish body, this configuration has a characteristic that the amount of change in luminance can be detected sensitively even with a slight movement of the fish.

  For this reason, in the case where the reference value for luminance change is set separately for each divided region as described above, whether or not the reference value for each divided region is set appropriately is determined together with the number of detected pixels. It appears as the number of. For this reason, whether or not the setting of the reference value is appropriate can be determined by the two indexes of the number of pixels and the number of blocks, and an effect of facilitating the setting of the appropriate reference value can be expected. If an appropriate reference value can be set, it can contribute to improving the recognition rate of medaka.

Various methods can be considered as a method for determining the quality of water quality. For example, the number of blocks set may be 1, 2 or 3, or 4 or more.
In addition, although the accuracy is somewhat reduced, the representative value of the luminance of the pixel group included in each block (average value, median value, standard deviation) or the representative value of the change in luminance of the pixel group (average value, median value, standard) A method of determining a representative value of the amount of change in luminance for each block based on the deviation) and determining the quality of the water based on the representative value of the amount of change for each block is also conceivable.
A plurality of pixels are arranged in the divided area, the divided area including the pixel whose luminance has exceeded the reference value is counted, and based on whether the number of counted divided areas is less than the set number. You may make it determine the quality of water quality.

  Furthermore, if the lighting device is provided in the monitoring region in the water tank, and the lighting device has a function of displaying the determination result of the quality of the water by the determination means, the water quality is displayed in the image acquired by the monitoring camera. The result of the pass / fail judgment visually appears. For this reason, the determination result can be visually confirmed simultaneously at both the site where the water tank is disposed and the operation room where image processing and determination of the water quality monitoring device are performed.

  As described above, according to the present invention, since the reference value of the amount of change in luminance is different between the downstream side and the upstream side, it is possible to correctly recognize the “activity” and “inactivity” of the fish in the aquarium.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
As shown in FIG. 1, the water quality monitoring apparatus 10 according to this embodiment includes a water tank 11 into which raw water is introduced from a river, a monitoring camera 12 that acquires an image of fish F raised in the water tank 11, and the monitoring camera 12. Is connected to the image analysis apparatus 13 for processing the image of the fish F.

  As shown in FIG. 2, the water tank 11 has a rectangular shape in plan view with an upper opening, and includes an inlet 17 provided on one side wall and an outlet 18 provided at the center of the bottom surface. The raw water W taken from a water source such as a river, a dam reservoir, or groundwater continuously flows into the water tank 11 from the inlet 17 without interruption, and forms a water flow 19 along the side wall of the water tank 11 after the inflow.

  The water stream 19 turns into a spiral water stream 19 so as to swivel from a portion close to the side wall toward the central part away from the side wall, and finally, the water stream 19 is discharged from the discharge port 18 and proceeds to the next processing step. ing. In this embodiment, since the raw water W continuously flows into the water tank 11 at a constant flow rate, the water flow 19 is maintained in a substantially constant path. This flow rate is appropriately set by experiments or the like, and is set to 2 to 5 liters / minute, for example.

  In the aquarium 11 into which the raw water W continuously flows, a plurality of fish F having “positive running ability (swimming behavior toward upstream)” are bred. As the fish F, medaka is used when the BOD of the raw water to be taken is low, and larger lionfish or hibe are selected than the medaka when the BOD is high.

  The monitoring camera 12 that acquires an image of the fish F in the aquarium 11 is installed above the aquarium 11 and images the entire area of the opening from above the aquarium 11. The surveillance camera 12 is not particularly limited as long as it can capture the fish F, and any camera may be used, but a color television camera is usually used and can stably capture images for a long period of time. If it is.

  The acquisition of images by the monitoring camera 12 is preferably performed continuously at regular time intervals, and the shorter the image processing time interval, the better the fish activity can be traced, and the preferred range is 0.033-0. In this embodiment, for example, the interval is 0.1 second.

  The monitoring camera 12 sends images obtained by continuously capturing the water tank 11 at 0.1 second intervals to the image analysis device 13. As shown in FIG. 4, the image analysis apparatus 13 includes a microcomputer 24 having an image processing unit 21, a storage unit 22, and a determination unit 23. Further, the image analysis device 13 is connected to a monitor 14 for displaying the state of the water tank 11 by the monitoring camera 12 and an alarm means 25 for notifying the outside of water quality abnormality.

  The image analysis device 13 receives an image of the fish F in the aquarium 11 by the monitoring camera 12 and outputs the received image to the image processing means 21. The image processing means 21 converts the image signal having position data and luminance data into an image signal. Image processing. The image signal subjected to the image processing is output to the display monitor 14 and the pixels of the display monitor 14 are displayed on the screen based on the luminance data of the image signal.

  As shown in FIG. 5, the image signals subjected to the image processing are arranged in a matrix of 56 lines having 64 (8 × 8) dots (pixels) 31 per line based on the position data. It is divided into 64 × 56 = 3584 pixels 31 and stored in the storage means 22 as sampling data for one field. At this time, the size of the pixel 31 is set smaller than the size of the fish F. Note that the number of pixels 31 per line or the number of lines is not limited to the above number, and is appropriately set depending on the experiment, the monitoring environment, the size of the water tank, and the like.

  Further, the image processing means 21 has an area in which the pixels 31 are shielded by the fish F captured by the monitoring camera 12 with respect to the luminance signal obtained by removing the color signal from the image signal for one field stored in the storage means 22. A process for obtaining the brightness difference of each pixel 31 obtained by the ratio (light shielding ratio) for each pixel 31 as 8-bit luminance data (luminance) is performed and temporarily stored in the storage unit 22.

  The image processing means 21 converts an image signal obtained by performing image processing on the image of the monitoring area 20 in the water tank 11 from which the monitoring camera 12 acquires an image, and a water flow formed in the water tank 11 as shown in FIG. 19 is divided into five divided areas 30a, 30b, 30c, 30d, and 30e at the positions shown in FIG. As described above, since the water flow 19 is maintained in a substantially constant path, the divided region 30 is also set so as not to fluctuate.

  Each divided region 30 is partitioned by a plurality of blocks 32, and 8 × 8 = 64 pixels 31 are arranged in each block 32 (see FIG. 5). Of these divided areas 30, the divided area 30 e occupying the periphery of the discharge port 18 has a very low presence rate of the fish F during monitoring, and will be described later without assigning a plurality of divided blocks 32. You may make it not detect the action of the fish F (refer to the white part in FIG. 6).

  Moreover, you may install the illuminating device 35 in the position (position which surrounds the discharge port 18) in the water tank 11 corresponding to the said division area | region 30e. The lighting device 35 is a rectangular cylinder formed of a plate material through which water passes and the fish F cannot pass, and includes a light source 36 therein. A display device 37 that displays a determination result of quality of the water in the water tank 11 is provided on the upper surface of the cylindrical body. It is to be noted that the fish F can pass through the lighting device 35 and the detection of the behavior of the fish F in the lighting device 35 (position corresponding to the divided area 30e in the aquarium 11) is detected on software in the microcomputer 24. It may not be performed.

  The display device 37 is waterproofed, and the determination result of the quality of the water quality is displayed from the outside of the aquarium 11 with the determination results of normal, caution, warning, vigilance, danger and each water quality described later. Any display that can be understood is acceptable. For example, a light source may be provided separately from the light source 36 to emit blue, green, yellow, orange, and red light according to the normal, caution, warning, vigilance, danger, and water quality conditions. . In addition, the display of the determination result of the quality of water quality is also reflected on the image acquired by the monitoring camera 12.

  The lighting device 35 does not have to be provided in the water tank 11 at a position corresponding to the divided region 30e. For example, the lighting device 35 may be installed outside the water tank 11, and in this case, the display device 37 is independent. The water tank 11 can be provided at a position corresponding to the divided region 30e. However, it is preferable to provide the illumination device 35 at a position corresponding to the divided area 30e of the water tank 11 because the divided areas 30a to 30d can be illuminated uniformly.

  The light source 36 of the illuminating device 35 is waterproofed and preferably has a low calorific value in order to suppress an increase in the water temperature in the water tank 11. For example, an LED can be used. Moreover, this illuminating device 35 is provided in the water tank 11 so that the display device 37 faces upward in FIG.

  As described above, the divided areas 30a to 30d excluding the divided area 30e are assigned to positions corresponding to positions along the four side walls of the water tank 11 shown in FIG. 6, and follow the water flow 19 formed in the water tank 11. It is possible to detect the behavior of the fish F in the divided areas 30a, 30b, 30c, and 30d.

  Further, the image processing means 21 takes out two pieces of sampling data from the storage means 22 at a predetermined timing (every 2 to 14 fields), and compares the two pieces of sampling data. However, a process of detecting the amount of change in luminance of each pixel 31 is performed.

  A reference value is set in advance for the amount of change in luminance of each pixel 31 detected by the image processing means 21. If the amount of change in luminance of the pixel 31 exceeds the reference value, the pixel 31 is It is detected as a pixel 31 having a change in luminance.

  In this embodiment, the reference value of the luminance change amount is set such that the downstream divided region 30d of the water stream 19 is lower than the upstream divided region 30c, and the divided region 30c is further divided into the upstream divided region. Each of the divided regions 30b is set to be lower than the upstream divided region 30a so as to be lower than the region 30b. With this setting, for example, in the pixel 31 in the downstream divided region 30d, the luminance change amount is detected with a smaller luminance change amount than in the pixel 31 in the upstream divided region 30a. Become. For this reason, in the downstream divided region 30d that does not act relatively actively, the pixel 31 can be detected even with a slight change in luminance compared to the upstream divided region 30a.

  The reference values for the amount of change in luminance are, for example, the divided areas 30a and 30b as one divided area, the divided areas 30c and 30d as one divided area, and the same reference value, respectively, which are combined into one downstream side. A plurality of divided areas 30 may be set as reference values for the same luminance change amount, such as setting the reference values of the divided areas 30c and 30d to be smaller than the reference values of the upstream divided areas 30a and 30b. Further, it is possible to further increase the number of divided areas 30 and to set the reference value for the change in luminance in more stages as the number of divided areas 30 increases.

  The determination unit 23 counts the number of blocks 32 including at least one pixel 31 detected by the image processing unit 21, and determines whether or not the counted number of blocks 32 is smaller than a predetermined set number. Based on this, the quality of the water in the water tank 11 is determined.

  In this embodiment, the set number is set to four. If the number of blocks 32 including the pixels 31 whose luminance has changed is less than four, the determination unit 23 determines that an abnormality has occurred in the water quality. Then, an alarm signal is output to the alarm means 25 according to the number.

  When the alarm means 25 receives the alarm signal, the warning means 25, for example, if there are 3 warnings, if 2 warnings, if 1 warnings, if the number of blocks is 0, that is, in which block 32 pixels If there is no change in luminance, the alarm 31 is alarmed by an alarm sound or light suitable for each situation to notify the outside of the abnormality. For example, as the number of blocks 32 decreases, the volume of the alarm sound may be increased, or the light blinking interval may be shortened.

  Further, an alarm may be issued from a speaker or the like (not shown) separately connected to the alarm means 25, or a mobile phone (not shown) or the like may be notified via a communication line such as a LAN. . Note that the number of blocks 32 to which the alarm signal is output is set as appropriate depending on the experiment, monitoring environment, and the like.

  The operation of this embodiment will be described. In the water quality monitoring device 10 configured as described above, the reference value of the amount of change in luminance described above and the set number of blocks 32 are set. 10 to 20 fish F (medaka) are bred in an aquarium 11 having a bottom area of 1000 square centimeters and a volume of 7 liters.

  At this time, if the water quality of the raw water W is normal, the fish F swims in the relatively upstream divided areas 30a and 30b, and its movement becomes active, so that the fish F moves across the plurality of blocks 32. By the movement of the fish F, before and after the movement, the number of pixels 31 that are newly shielded from a state that has not been shielded until now, or the number of pixels 31 whose light shielding rate increases is increased. That is, the number of pixels 31 whose luminance detected by the image processing unit 21 has changed (pixels 31 whose luminance has exceeded the reference value of luminance change) increases. When the number of detected pixels 31 increases over the entire divided areas 30a and 30b, the number of blocks 32 counted by the determination unit 23 increases. At this time, if the number of blocks 32 to be counted is four or more, the determination means 23 determines that the water quality is normal.

  In addition, before and after the movement of the fish F, the pixel 31 that has been blocked by the movement of the fish F from the state where it was blocked or the shading rate thereof decreases, so that the luminance exceeding the reference value of the luminance change amount. The pixel 31 in which the change has occurred may be detected.

  On the other hand, in the divided areas 30c and 30d, the reference value of the amount of change in luminance of the pixel 31 that is shielded by the movement of the fish F is set low. For this reason, even if the amount of movement of the fish F whose behavior is slow is small, or even when the shading rate is small such that the pixel 31 is shielded by the fins that are moving with little movement, the pixel 31 whose luminance has changed is selected. It can be detected by the image processing means 21.

  Thereby, even if there is no abnormality in the water quality in the aquarium 11, even if the movement of the fish F becomes dull due to factors such as time and environment, the behavior of the fish F that has dull movement is detected with high sensitivity. Can do.

  Further, when foreign matter or drugs are mixed in the raw water W, if an abnormality occurs in the water quality, the fish F becomes sluggish, or the fish F becomes weak, and is further washed away by the water stream 19 and is divided into the downstream divided region 30c. Alternatively, when moving to the divided region 30d, since the behavior of the fish F is not detected in the divided region 30e, the number of blocks for detecting the behavior of the fish F decreases. If the reduced number of blocks is less than 4, the determination means 23 determines that the water quality is abnormal according to the number of blocks, and the alarm means 25 issues an alarm by sound, light, etc. Tell outside.

Schematic of the water quality monitoring device of the embodiment of the present invention Explanatory drawing showing the water flow on the monitoring area Explanatory drawing which showed the divided area divided into multiple on the monitoring area same as the above Block diagram showing the detection configuration of the detection circuit Explanatory drawing which shows the state which blocked the monitoring area same as the above Explanatory diagram showing blocks in the monitoring area The perspective view which shows an illuminating device same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Water quality monitoring apparatus 11 Water tank 12 Monitoring camera 13 Image analysis apparatus 14 Display monitor 17 Inlet 18 Outlet 19 Water flow 20 Monitoring area 21 Image processing means 22 Storage means 23 Determination means 24 Microcomputer 25 Alarm means 30 Division area 31 Pixel 32 Block 35 Illumination device 36 Light source 37 Display device F Fish

Claims (5)

Surveillance camera for acquiring images of a water tank (11) having a water inflow port (17) and a water discharge port (18), and a fish (F) having a running ability bred in the water tank (11) (12) and image processing means (21) for processing the image acquired by the monitoring camera (12) to acquire an image signal and detecting a change in luminance due to the behavior of the fish (F) based on the image signal ), And a water quality monitoring device provided with a judgment means (23) for judging the quality of the water in the aquarium (11) based on the magnitude of the change in luminance detected by the image processing means (21) ,
A monitoring area (20) in the water tank (11) from which the monitoring camera (12) acquires an image is divided into a plurality of divided areas along the water flow (19) from the inlet (17) to the outlet (18). (30; 30a, 30b, 30c, 30d...), And the reference value of the amount of change in brightness when determining the quality of the water quality is determined based on whether the divided region on the downstream side of the water flow (19) is upstream. A water quality monitoring apparatus characterized by being lower than the divided area on the side.   The water quality monitoring apparatus according to claim 1, wherein the reference value of the amount of change in luminance can be set for each of the divided regions (30).   The inlet (17) is provided on the side wall of the water tank (11), the outlet (18) is provided at the center bottom of the water tank (11), and the water flowing into the water tank (11) The water quality monitoring device according to claim 1 or 2, wherein the flow is formed so as to swirl from a portion close to the side wall of the water tank (11) toward a central portion away from the side wall.   Each of the divided regions (30) is partitioned by a plurality of blocks (32), and a plurality of pixels (31) are arranged in each of the blocks (32). The luminance of the image processing means (21) is increased. The change is detected by detecting a pixel (31) having a luminance change exceeding the reference value, and the determining means (23) is a pixel (31) having a luminance change amount exceeding the reference value. The number of blocks (32) including at least one) is counted, and the quality of the water is determined based on whether the counted number of blocks (32) is less than a set number. The water quality monitoring apparatus in any one of -3.   An illuminating device (35) is provided in the monitoring area (20) in the water tank (11), and the illuminating device (35) has a function of displaying a determination result of quality of water by the determining means (23). The water quality monitoring device according to any one of claims 1 to 4, wherein

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