JP7345715B1 - Filtration basin and filtration equipment - Google Patents

Abstract

An object of the present invention is to obtain a filtration basin in which the various layer thicknesses of the filtration medium layer and, more preferably, the appropriate expansion upper end position can be easily and clearly grasped from the inside of the basin over the entire circumference of the filtration basin. [Solution] A pond space 6 that is composed of a bottom member 4 whose upper surface 4a is the bottom surface of the pond, and a side wall member 5 erected on the bottom member 4, and whose lateral periphery is surrounded by the side wall member 5. In the filtration pond 1, which is composed of a pond frame 2 defining a pond space 6, and a filtration material layer 3 disposed on the pond bottom surface 4a in the pond space 6, the design of the filtration material layer 3 is applied to the inner surface of the side wall member 5. For example, a line indicating at least one of the layer thickness, the recommended sand supplement layer thickness, and the critical layer thickness is used as the boundary between the fourth painted part C4 and the third painted part C3, which are color-coded with each other, and approximately the entire inner surface is Display it all around. [Selection diagram] Figure 2

Description

TECHNICAL FIELD The present invention relates to a filtration pond and a filtration device installed in water purification facilities and the like for purifying raw water.

BACKGROUND ART As a filter that filters and purifies raw water, for example, a slow filter shown in Patent Document 1 has been known. Basically, this slow-speed filtration pond passes raw water through a filter layer (sometimes called a filter layer) made of fine sand arranged in the pond at a relatively slow speed of about 4 to 5 m/day. Raw water is filtered through a filtration membrane made up of microorganisms that mainly grow on the surface of the filter layer. When operating this slow filtration basin, as shown in the above-mentioned Patent Document 1, the suspended solids attached to the filtration membrane are periodically scraped off by about 1 to 2 cm along with the filter sand, and the filtration membrane is purified. be done. In addition, the filter sand that has been scraped off in this way is replenished through a process generally referred to as sand replenishment.

On the other hand, as shown in Patent Document 2, for example, rapid filtration ponds, which generally have a higher filtration speed than slow filtration ponds, are also known. Basically, this rapid filtration pond is made by adding a flocculant such as PAC (polyaluminum chloride) to the raw water to create turbidity before passing the raw water through a filter layer made of sand, anthracite, etc. placed inside the pond body. is coagulated and precipitated, and the supernatant liquid is passed through a filter layer. In operating this rapid filtration basin, as shown in the above-mentioned Patent Document 2, washing water that passes through the filter layer in the opposite direction to the raw water is supplied to backwash the filter layer (backwashing). ) is performed frequently. When this backwashing is performed, the filter layer expands as a whole, and it is inevitable that the sand and the like in the filter layer will be washed away to some extent, so sand supplementation is generally performed in this case as well.

In both the slow filtration basin and the rapid filtration basin described above, in order to achieve and maintain the required filtration effect, it is necessary to maintain the layer thickness of the filtration medium layer as designed. For this purpose, it is desired that the filter manager be able to easily grasp the thickness of the filter layer as appropriate. In addition, in order to properly manage the filter, it is necessary to check whether the thickness of the filter media layer has decreased to the extent that supplementary sand is required due to the aforementioned sand washing away, or if it has reached the limit where it should not be used as is. It is desirable that the filtration pond manager be able to easily understand whether the layer thickness has further decreased.

On the other hand, especially regarding rapid filtration tanks for water purification facilities, the expansion rate of the filter media layer during backwashing is said to be approximately 20 to 30% in order to efficiently discharge the suspended solids in the filter media. Guidelines have been issued by the Japan Water Works Association. Therefore, in a rapid filtration basin for a water purification facility, it is desirable to be able to easily grasp the appropriate expansion upper end position of the filter material layer that expands during backwashing so as to satisfy this guideline.

Furthermore, in addition to the various filtration ponds described above, a filtration device (filter or filter) as shown in Patent Document 3, for example, is also known. This filtration device basically consists of a bottom member whose top surface is the bottom of the tank, and a side wall member installed upright on the bottom member, and defines a tank space surrounded laterally by the side wall member. It is equipped with a filter tank mainly made of metal, and a layer of filter material arranged on the bottom surface within the tank space.

In such a filtration device as well, in order to achieve and maintain the required filtration effect, it is necessary to maintain the thickness of the filtration medium layer as designed. For this purpose, it is desired that the filter device manager be able to easily grasp the layer thickness of the filter material layer as appropriate. In addition, in order to properly manage the filtration device, it is necessary to check whether the thickness of the filter layer has been reduced to the extent that supplementary sand is required due to the backwashing of the filter layer, which is often done here as well. Alternatively, it is desirable that the filtration device manager be able to easily determine whether the thickness has further decreased to a critical layer thickness that should not be used as is.

Japanese Patent Application Publication No. 2000-350994 Japanese Patent Application Publication No. 2002-282612 Japanese Patent Application Publication No. 8-215509

In a filter tank with a filter layer arranged inside a metal tank, a small transparent window is installed on the side plate of the tank through which the filter layer inside the tank can be seen, and a small transparent window is installed on the left and right sides of this transparent window. It is also conceivable to mark lines indicating the various layer thicknesses and the appropriate expansion upper end position on the outer surface of the tank side plate. By doing so, it becomes possible to easily grasp the various layer thicknesses and the appropriate expansion upper end position of the filter medium layer described above from the outside of the tank.

However, unlike filtration tanks that are installed alone in a place with nothing around them, filtration tanks that are buried underground usually have a transparent window like the one mentioned above installed in the pond body made of concrete. It is virtually impossible or extremely difficult to display lines on the outside surface of the pond structure. Moreover, even if such a thing were possible, the following problems still remain. That is, a filtration basin generally has a longer circumference than a filtration tank, and the water level of raw water in the filtration basin may change depending on the state of raw water inflow, etc. Therefore, it is difficult to clearly understand whether the various layer thicknesses and expansion upper end positions of the filter media layer, which are observed through the small transparent window, are appropriate over the entire circumference of the filter basin.

Therefore, the present invention provides a filter that allows easy and clear understanding of the various layer thicknesses of the filter media layer, and more preferably, the appropriate expansion upper end position during backwashing, from the inside of the pond over the entire circumference of the filter. The purpose is to provide

In addition, as mentioned above, even in filtration equipment where a transparent window can be installed on the side plate of the filtration tank, it is possible to easily and clearly measure the various layer thicknesses of the filter media layer without installing such a transparent window. It would be convenient if it could be grasped, and an object of the present invention is to provide such a filtration device.

The filtration basin according to the present invention comprises:
A pond frame is composed of a bottom member whose upper surface is the bottom surface of the pond, and a side wall member erected on the bottom member, and defines a pond space whose lateral periphery is surrounded by the side wall members. ,
In a filtration pond consisting of a filter layer arranged on the bottom surface of the pond in the pond space,
On the inner surface of the side wall member, a line indicating at least one layer thickness among the design layer thickness, the recommended sand supplementary layer thickness, and the critical layer thickness of the filter layer is displayed over almost the entire circumference of the inner surface. It is characterized by:

The above phrase "arranged on the pond bottom" refers to cases where the filter layer is placed directly on the pond bottom, or when the filter layer is placed on the pond bottom via a gravel layer, etc. This shall also include cases where In addition, the above-mentioned "displayed over almost the entire circumference" includes both the display as a continuous line without interruption throughout the entire circumference, or the display as a partially interrupted line. .

In the filtration basin of the present invention having the above configuration, in the side wall member, an area above and a area below the line are painted in different colors, and the boundary between the two areas is painted differently. It is desirable that the line is displayed as .

In addition, in the filter of the present invention having the above configuration, a line indicating the appropriate expansion upper end position of the filter layer that expands when backwashing is further provided on the inner surface of the side wall member approximately all the way around the inner surface. It is desirable that it be displayed throughout.

On the other hand, the filtration device according to the present invention
A filtration tank comprising a bottom member whose upper surface is the bottom of the tank, and a side wall member erected on the bottom member, defining a tank space whose lateral periphery is surrounded by the side wall member. ,
In the filtration device comprising a filter layer arranged on the bottom of the tank in the tank space,
On the inner surface of the side wall member, a line indicating at least one layer thickness among the design layer thickness, the recommended sand supplementary layer thickness, and the critical layer thickness of the filter layer is displayed over almost the entire circumference of the inner surface. It is characterized by:

Again, the term "placed on the bottom of the tank" refers to the case where the filter layer is placed directly on the bottom of the tank, or the layer is placed on the bottom of the tank via a layer of gravel, etc. This also includes cases where the In addition, the above-mentioned "displayed over almost the entire circumference" includes both the display as a continuous line without interruption throughout the entire circumference, or the display as a partially interrupted line. .

In the filtration device of the present invention having the above configuration, in the side wall member, a region above and a region below the line are painted in different colors, and the boundary between the two painted regions It is desirable that the line is displayed as .

According to the filter of the present invention, on the inner surface of the side wall member that defines the pond space together with the bottom member, at least one layer selected from among the design layer thickness of the filter layer, the recommended sand supplement layer thickness, and the critical layer thickness is provided. Since the line indicating the thickness is displayed almost all the way around the inner surface of the filter, you can easily compare the various layer thicknesses of the actual filter media layer with this line from the inside of the pond. And it becomes possible to understand clearly. Therefore, it is possible to clearly know whether the actual various filter media layers are over or under the displayed standard layer thickness. Note that while the filtration basin is in operation, the raw water to be filtered is of course supplied into the pond, so the above line can be seen from inside the pond through the raw water. Even so, since the raw water is basically transparent, the various layer thicknesses of the filter media layer can be clearly known even when the filtration basin is in operation.

In the side wall member of a filtration basin according to the present invention, in particular, an upper region and a lower region with respect to the line are painted in different colors, and the boundary between the two painted regions is the line. is shown, the line is clearly shown as a boundary between regions of different colors, so misreading of the line can be prevented.

Further, in the filter according to the present invention, in particular, a line indicating an appropriate expansion upper end position of the filter layer that expands during backwashing is further displayed on the inner surface of the side wall member over substantially the entire circumference of the inner surface. In this case, it can be easily determined whether the expansion rate of the filter layer during backwashing is within an appropriate range.

The effects described above can naturally be obtained in the filtration device according to the present invention.

A partially cutaway perspective view showing a filter according to a first embodiment of the present invention A schematic perspective view showing the inside of the pond frame that constitutes the filtration basin in Figure 1 A schematic perspective view showing the inside of a pond frame that constitutes a filtration basin according to a second embodiment of the present invention A side view showing a filtration device according to a third embodiment of the present invention A side view showing the inner surface of the side wall member of the filtration tank constituting the filtration device in FIG. 4

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a partially cutaway perspective view showing the overall shape of a filter 1 according to a first embodiment of the present invention. The filtration basin 1 of this embodiment is the above-mentioned slow filtration basin, and has a filter material layer (filter layer) 3 made of, for example, fine sand disposed within the pond body 2. The pond body 2 includes a bottom member 4 whose upper surface 4a is the bottom surface of the pond, and a side wall member 5 erected on the bottom member 4. These members 4 and 5 are mainly made of concrete. The side wall member 5 is formed in the shape of a square frame, and defines a pond space 6 that is surrounded on the sides and open at the top. The filter material layer 3 is laminated on the upper surface 4a of the bottom member 4 in the pond space 6.

As in many cases, the pond body 2 is formed by digging soil 7 on the surface of the ground, and then buried in the soil 7. Note that FIG. 1 shows the filter medium layer 3 being laid down by a worker 8. In this example, the filter layer 3 is directly stacked on the top surface 4a of the bottom member 4, but a gravel layer is placed on the top surface 4a of the bottom member 4, and the filter layer 3 is layered through the gravel layer. It may be laminated.

Next, with reference to FIG. 2, the inside of the pond frame 2 will be described in detail. FIG. 2 shows a state in which the pond body 2 is seen from inside the pond space 6 with a part of the pond body 2 cut away before the filter layer 3 is laid down. As shown here, on the inner surface of the side wall member 5, a first painted part C1, a second painted part C2, a third painted part C3, and a fourth painted part C4 are formed in order upward from the bottom member 4 side. It is painted. For example, the first painted part C1 is painted in red, the second painted part C2 in yellow, the third painted part C3 in green, and the fourth painted part C4 in light blue, which are different colors.

These painted parts C1 to C4 are displayed on all four sides of the side wall member 5, which has a rectangular frame shape as a whole, that is, over substantially the entire circumference of the inner surface of the side wall member 5. Further, in this embodiment, it has been confirmed that the upper surface 4a of the bottom member 4 is formed in a direction perpendicular to the vertical line, and the upper ends of the painted parts C1 to C4 are all connected to the upper surface 4a of the bottom member 4. It is painted parallel to the In other words, all of the painted parts C1 to C4 are painted over substantially the entire circumference of the inner surface of the side wall member 5, each maintaining a predetermined width (vertical dimension).

In this embodiment, it is desirable to indicate the limit layer thickness, recommended sand supplement layer thickness, and design layer thickness on the pond frame 2 in order from the thinnest layer as the layer thickness of the filter material layer 3. Therefore, on the inner surface of the side wall member 5, three draft lines are drawn extending in the horizontal direction, each indicating the critical layer thickness, the recommended sand supplementary layer thickness, and the design layer thickness. Then, a first painted part C1 is painted below the lowest draft line, and a second painted part C2 is painted below the next lowest draft line (an area that does not reach the first painted part C1), A third painted part C3 is painted below the uppermost draft line (an area that does not reach the second painted part C2), and a fourth painted part C4 is painted above this uppermost draft line. Note that the order in which the painted parts C1 to C4 are painted may be reversed to the above in consideration of paint dripping, etc., or may even be in a different order from any of these orders.

The fact that the painted parts C1 to C4 are color-coded based on the various layer thicknesses of the filtration layer 3 as described above is made known to the worker 8 laying the filtration layer 3, the manager of the filtration basin 1, etc. in advance. has been done. Therefore, when laying the filter layer 3 in the completed pond body 2, the worker 8 refers to the fourth painted part C4 and the third painted part C3 painted on the side wall member 5, and then In other words, the filter material layer 3 is laid down to the upper end of the third coating section C3. Thereby, the worker 8 can accurately and easily spread the filter medium layer 3 to an appropriate layer thickness as designed.

If the filter 1 continues to operate after the filter layer 3 has been laid, the sand constituting the filter layer 3 may be scraped off together with suspended solids, as described above. The administrator of the filtration basin 1 can thus monitor the gradually thinning layer thickness of the filter material layer 3 while referring to the coated parts C1 to C4. Then, referring to the third painted part C3 and the second painted part C2, the administrator determines that when the filter material layer 3 decreases to the boundary between them, that is, to the upper end of the second painted part C2, the layer thickness reaches a point where supplementary sand is required. You can see that it has become thinner. Therefore, the administrator performs the necessary supplementary sand to reduce the thickness of the filter layer 3 to the thickness before thinning, for example, the design layer thickness mentioned above (i.e., the thickness at which the top surface of the layer is aligned with the top position of the third coating section C3). ).

Here, the administrator of the filtration basin 1 may overlook that the filter medium layer 3 has decreased to the upper end of the second coated portion C2. Alternatively, even if nothing is overlooked, it may not be possible to perform sand replenishment work immediately when the filter medium layer 3 is reduced to that extent. For such reasons, if the filter layer 3 is further reduced to the lower end of the second coated section C2 (the boundary between the second coated section C2 and the first coated section C1), the administrator will In other words, it can be seen that the layer thickness has decreased to a point where it is inappropriate to continue using it. Therefore, in this case, the administrator can immediately perform sand supplementation to return the layer thickness of the filter medium layer 3 to, for example, the above-mentioned design layer thickness. Note that, in consideration of safety, the lower end of the second coating portion C2 may be set at a position slightly above the layer thickness that is actually considered to be the limit layer thickness.

As explained above, by using the first coating section C1 to the third coating section C3, it can be accurately and easily determined that the thickness of the filter layer 3 has become thin enough to require sand supplementation or to the critical layer thickness. If you can know the details, you can prevent the need for extremely large-scale sand replenishment work and repair work, which will also have the effect of keeping the maintenance costs of the filtration basin low.

In this embodiment, the four painted parts C1 to C4, which are painted in different colors, are used to confirm three types of layer thicknesses, that is, the limit layer thickness, the recommended sand supplement layer thickness, and the design layer thickness. Therefore, even if there is raw water in the filtration basin 1 before filtration, some or all of the painted parts C1 to C4 can be coated through that raw water (and thus the critical layer thickness, recommended sand supplementary layer thickness, and design layer thickness). It can be confirmed accurately and easily.

For each of the four painted parts C1 to C4, a weather-resistant paint is used, that is, a paint that is unlikely to cause changes in quality such as discoloration, deterioration, and deformation due to sunlight, ultraviolet rays, rainwater, oxygen, and even temperature differences between day and night. Preferably painted. Further, among the painted parts C1 to C4, the fourth painted part C4 is generally painted in the same color as the color in which the inside of the pond frame 2 is painted. On the other hand, the first painted part C1, the second painted part C2, and the third painted part C3 are painted in colors different from the fourth painted part C4, and also in colors that are easy to distinguish from each other, including fluorescent colors. is desirable.

Further, in this embodiment, on the premise that the upper surface 4a of the bottom member 4 is formed in a direction perpendicular to the vertical line, the upper ends of the painted parts C1 to C4 are parallel to the upper surface 4a of the bottom member 4. However, the present invention is not limited thereto and can be applied even when the upper surface 4a of the bottom member 4 is inclined at an angle other than perpendicular to the vertical line. In that case as well, each coating portion C1 to C4 may be coated with the upper end thereof perpendicular to the vertical line.

In this embodiment, three types of layer thickness of the filter material layer 3 are displayed by the coated parts C1 to C4, but layer thicknesses other than the three types may be displayed as necessary. . This point is the same even when the layer thickness to be displayed is displayed with a specific line as in the next embodiment.

In the present invention, the various layer thicknesses of the filter material layer 3 are not limited to being indicated as boundaries between regions painted in different colors as described above, but are specifically indicated on the side wall member 5. The various layer thicknesses may be indicated by lines. A second embodiment of the present invention configured in this manner will be described below with reference to FIG. 3.

FIG. 3 shows a pond frame 2 constituting a filtration basin 20 for a water purification facility according to a second embodiment of the present invention, viewed from inside the pond space 6. As shown here, in this embodiment, lines L1 and L2 are provided on the inner surface of the side wall member 5 to directly indicate the limit layer thickness, recommended sand supplement layer thickness, and design layer thickness of the filter layer 3, respectively. and L3 are displayed. The line L1 is located at a position corresponding to the boundary between the first painted part C1 and the second painted part C2 in the first embodiment shown in FIG. Similarly, the line L3 is displayed over substantially the entire circumference of the inner surface of the side wall member 5 at a position corresponding to the boundary between the third painted portion C3 and the fourth painted portion C4.

Further, in this embodiment, a line L4 is also displayed at a position a predetermined length away from the line L3, extending substantially all the way around the inner surface of the side wall member 5. The filtration basin 20 of this embodiment is the above-mentioned rapid filtration basin, and although it is omitted in FIG. 3, the raw water to be filtered is stored and a flocculant such as PAC is added thereto to flocculate and precipitate the suspended matter. A coagulation sedimentation tank is provided above the filter to supply the supernatant to the filter 20. Furthermore, in this filtration basin 20, piping (not shown) for backwashing the filter media layers (not shown) stacked in the pond space 6 with purified water is also provided, and this backwashing is executed as appropriate. It looks like this.

When the above-mentioned filter media layer is backwashed, the filter media layer receives purified water from below and expands, but as mentioned above for rapid filtration tanks for water purification facilities, the expansion rate of the filter media layer during backwashing is The Japan Water Works Association has issued a guideline stating that ``20 to 30% is appropriate.'' In order to comply with this guideline, in the present embodiment, the upper end position of the filter layer when the filter layer (not shown) expands by about 20 to 30% in FIG. 3 is indicated by a line L4. Therefore, when backwashing the filter layer, this line L4 can be used as a guide to accurately and easily determine whether the expansion coefficient of the filter layer is within the appropriate range as per the guideline.

By the way, if the above-mentioned backwashing is performed when there is a problem with the filter medium or the filter itself, the surface layer of the filter medium layer may become wavy or uneven. Problems include, for example, the unevenness of the gravel layer, the occurrence of mud balls (solidified sludge and sand) in the filter media layer, clogging of the water collection section, or the side of the backwash water inflow side of the filtration basin and the wall side that is not. Examples include the pressure difference during backwashing. If any defects are left untreated, filtration and cleaning will become unbalanced, which will eventually lead to filtration failure. Abnormalities such as undulations and deviations in the surface layer can be recognized at a glance by comparing with the line L4 as a reference line, and particularly with the line L3 as a reference line after the backwashing is completed.

In this embodiment, the four lines L1 to L4 are displayed by painting red as an example, but these lines L1 to L4 can be displayed by methods other than painting, such as embedding colored tiles in the side wall member, waterproof tape, etc. Alternatively, the information may be displayed by pasting a waterproof sticker on the side wall member. Moreover, the lines L1 to L4 are displayed continuously over the entire circumference of the side wall member 5, which has four sides, and the main parts of this entire circumference (for example, the parts near the four corners of the frame-shaped side wall member 5) may be left displayed, and parts other than the main parts may be displayed as dashed lines.

Next, a filtration device 100 according to a third embodiment of the present invention will be described with reference to FIGS. 4 and 5. FIG. 4 schematically shows the side shape of this filtration device 100, and FIG. 5 shows the inner surface of the outer shell 102 of the filtration tank 101 that constitutes this filtration device 100, which is vertically divided into two. FIG.

As shown in FIG. 4, this filtration device 100 has a filtration tank 101 filled with a plurality of filter media to be described later. This filter tank 101 typically has a cylindrical outer shell 102 whose upper and lower parts are closed with curved convex surfaces, and has a plurality of support legs 103 (only one shown in the figure) that allows the filter to reach the floor surface. or supported on the ground. A raw water supply pipe 104 is formed at the upper side of the outer shell 102 to introduce water containing turbidity such as well water, that is, raw water. This raw water supply pipe 104 is extended to the inside of the layer, bent upward at the center of the layer, and has a tip end connected to a trumpet tube 105 that opens upward. On the other hand, a discharge port 106 is connected to the bottom surface of the outer shell 102, and a support member 107 that supports a plate 110, which will be described later, from below is fixed onto this bottom surface. Further, a large diameter manhole 108 is formed on the upper surface of the outer shell 102.

A plate 110 having a large number of strainers 109 is fixed inside the filter tank 101 at a position near the lower end thereof. On top of that, there is a first filter layer 111 made of filter sand with a density of 2.63 g/cm ³ and a particle size of 0.6 mm (effective diameter 0.6 mm - uniformity coefficient 1.3), and a first filter layer 111 with a density of 1.62 g/cm 3 . ^3. A second filtration layer 112 made of anthracite with a particle size of 1.2 mm (effective diameter 1.2 mm - uniformity coefficient 1.4) is arranged in this order.

When the above combination is used as the filter medium of the first filtration layer 111 and the filter medium of the second filtration layer 112, after putting the above two types of filter media into the filtration tank 101, backwashing etc. By doing this to make the filter media movable, movement occurs due to the density difference between each filter media, and filter sand and anthracite are mixed between the first filtration layer 111 and the second filtration layer 112. The mixed layer 113 is naturally layered.

When using the filtration device 100 having the above configuration, raw water is supplied into the filtration tank 101 from the raw water supply pipe 104 as indicated by an arrow 120 in the figure. This raw water overflows from the upper end of the trumpet tube 105, passes through the second filtration layer 112, the mixed layer 113, and the first filtration layer 111 in this order in the filtration tank, and is filtered. The filtrate from which the suspended matter has been removed passes through the strainer 109, accumulates on the bottom surface of the filter tank 101, and is supplied to the outside from the discharge port 106.

Although the filtration device 100 of the embodiment described above has two types of filtration layers, the present invention is also applicable to a filtration device having three or more types of filtration layers. In this case, it is preferable that a mixed layer is formed at all boundary portions between adjacent filtration layers. Further, it is also possible to combine a filter medium cleaning means as shown in, for example, Japanese Patent Application Laid-open No. 2011-136268, if necessary.

As shown in detail in FIG. 5, the outer shell 102 includes a generally cylindrical side wall member 102A, a lower member 102B including a mirror plate that closes the lower opening of the side wall member 102A, and a mirror plate that closes the upper opening of the side wall member 102A. It is composed of an upper member 102C consisting of. Therefore, the filter tank 101 has a tank space whose lateral periphery is surrounded by a side wall member 102A. A plate 110 that closes the inside of the side wall member 102A is connected near the lower end of the side wall member 102A. This plate 110 constitutes a bottom member whose upper surface becomes the bottom surface of the tank, and the first filtration layer 111, mixed layer 113, and second filtration layer 112 are sequentially laminated thereon.

Then, on the inner surface of the side wall member 102A, a first painted part C1, a second painted part C2, a third painted part C3, and a fourth painted part C4 are painted in order upward from the plate 110 side as a bottom member. There is. For example, the first painted part C1 is painted in red, the second painted part C2 in yellow, the third painted part C3 in green, and the fourth painted part C4 in light blue, which are different colors.

These painted parts C1 to C4 are displayed over substantially the entire circumference of the inner surface of the cylindrical side wall member 102A. All of the painted parts C1 to C4 are basically the same as the painted parts C1 to C4 of the first embodiment shown in FIG. Therefore, in this embodiment as well, the same effects as in the first embodiment can be obtained by the coated parts C1 to C4. The painted parts C1 to C4 can be visually recognized by looking through the manhole 108, for example.

In this embodiment, raw water is supplied from the raw water supply pipe 104 into the filter tank 101 by applying a certain amount of water pressure, and the inside of the filter tank 101 is pressurized to a predetermined pressure. The present invention can be similarly applied to a filtration device in which the inside of a filtration tank is not pressurized.

In this case as well, in addition to indicating the layer thickness of the filter media layer by each boundary of the painted parts C1 to C4, the thickness of each layer is directly indicated by lines L1, L2, L3, and L4 as shown in FIG. It's okay.

1, 20 Filtration basin 2 Pond frame 3 Filter medium layer 4 Bottom member 4a Upper surface of bottom member 5 Side wall member 6 Pond space 7 Soil 100 Filtration device 101 Filtration tank 108 Manhole 110 Plate 111 First filtration layer 112 Second filtration layer 113 Mixing Layer C1~C4 Painted part L1~L4 Line

Claims (5)

A pond frame is composed of a bottom member whose upper surface is the bottom surface of the pond, and a side wall member erected on the bottom member, and defines a pond space whose lateral periphery is surrounded by the side wall member. ,
A filtration pond comprising a filter layer disposed on the bottom surface in the pond space,
On the inner surface of the side wall member, a line indicating at least one layer thickness among the design layer thickness, recommended sand supplement layer thickness, and critical layer thickness of the filter layer is displayed over substantially the entire circumference of the inner surface. A filtration pond characterized by: In the side wall member, a region above and a region below the line are painted in different colors, and the line is shown as a boundary between the two painted regions. The filtration pond described in 1. The filter basin according to claim 1 or 2, wherein a line indicating an appropriate expansion upper end position of the filter medium layer that expands during backwashing is displayed over substantially the entire circumference of the inner surface. A filtration tank comprising a bottom member whose upper surface is the bottom of the tank, and a side wall member erected on the bottom member, defining a tank space whose lateral periphery is surrounded by the side wall member. ,
A filtration device comprising a filter layer disposed on the bottom surface in the tank space,
On the inner surface of the side wall member, a line indicating at least one layer thickness among the design layer thickness, recommended sand supplement layer thickness, and critical layer thickness of the filter layer is displayed over substantially the entire circumference of the inner surface. A filtration device characterized by: In the side wall member, a region above and a region below the line are painted in different colors, and the line is shown as a boundary between the two painted regions. 4. The filtration device according to 4.