Filtration cassette

Abstract

This technology enables more efficient filtration operation of treatment tanks. [Solution] The filtration cassette installed in the treatment tank comprises a housing, an inlet provided on the side wall of the housing through which the water to be treated flows in, an outlet provided on the housing through which the water to be treated flows out, a filter material housed inside the housing and forming a filtration layer between the inlet and the outlet, a water passage section having an opening through which the water to be treated can pass, and an installation section for attaching the water passage section to the housing so that it can be attached to and detached from the inlet from the outside of the housing.

Description

Technical Field

[0001] The present invention relates to a filtration cassette that is installed in a treatment tank and filters by circulating treated water.

Background Art

[0002] Conventionally, in a water treatment plant, a sewage treatment plant, etc., the treated water to be treated is stored in a sedimentation tank to precipitate solids, and then this treated water is passed upward through a filtering member installed in the sedimentation tank for filtration treatment.

[0003] In relation to this, Patent Document 1 discloses a filtration cassette that is installed in a sedimentation tank and filters by circulating treated water upward. This filtration cassette includes a housing and a filter medium disposed within the housing, and perforated plates (water-permeable plates) that allow the passage of treated water and prevent the passage of the filter medium are provided at the lower and upper openings of the housing.

[0004] Also, Patent Document 2 discloses a technique for preventing clogging of a filter (water-permeable plate) that covers the drainage passage holes of a partition body by vibrating the partition body provided in the final tank of a wastewater treatment device.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The technology according to the present disclosure aims to enable more efficient filtration operation of a treatment tank.

Means for Solving the Problems

[0007] To solve the above problems, the technology relating to this disclosure employs the following configuration. Specifically, the technology relating to this disclosure is a filtration cassette installed in a treatment tank for circulating and filtering water to be treated, comprising: a housing; an inlet provided on the side wall of the housing through which the water to be treated flows in; an outlet provided on the housing through which the water to be treated flows out; a filter material housed within the housing and forming a filtration layer between the inlet and the outlet; a water passage section having an opening through which the water to be treated can pass; and an installation section for attaching the water passage section to the housing so that it can be attached to and detached from the inlet from outside the housing. [Effects of the Invention]

[0008] According to the technology disclosed herein, it becomes possible to perform the filtration operation of the treatment tank more efficiently. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows the configuration of a sedimentation tank 100 equipped with a filtration cassette 50 according to an embodiment. [Figure 2] Figure 2 is a longitudinal cross-sectional view of the filtration cassette 50 according to the embodiment. [Figure 3] Figure 3 is a front view of the filtration cassette 50 according to the embodiment. [Figure 4] Figure 4 is a cross-sectional view of the filtration cassette 50, showing a cross-section along the CC line in Figure 3. [Figure 5] Figure 5 is a longitudinal cross-sectional view of the filter cassette 50 when the water passage section 51 is removed during filtration operation. [Figure 6] Figure 6 is a diagram illustrating an example of the arrangement of the inlet 3 in the embodiment. [Modes for carrying out the invention]

[0010] Embodiments of this disclosure will be described below with reference to the drawings. However, this description should not be interpreted as limiting, and will not limit the subject matter described in the claims. Furthermore, various changes, substitutions, and modifications can be made without departing from the spirit and scope of this disclosure. Different embodiments can also be combined as appropriate.

[0011] The treatment tank to which the filtration cassette described herein is installed is not particularly limited, as it is any tank for separating solid matter (suspended matter) from the water to be treated. Specifically, the treatment tank may be, for example, a sedimentation tank for sedimenting and removing solid matter contained in the water to be treated in sewage treatment, and for further filtration treatment of the water from which sediment has been removed. This sedimentation tank may be a primary sedimentation tank located upstream of the reaction tank, or a final sedimentation tank located downstream of the reaction tank. The treatment tank may also be, for example, a solid-liquid separation tank that separates, concentrates, recovers, and removes solid matter contained in the water to be treated by utilizing the difference in specific gravity between liquid and solid in industrial water treatment. Below, as an example of a treatment tank, a case in which the filtration cassette described herein is installed in a sedimentation tank in sewage treatment will be described.

[0012] [Sedimentation tank 100] First, as an example of a filtration device equipped with a filtration cassette according to the embodiment, a sedimentation tank 100 will be described. The sedimentation tank 100, for example, is a sedimentation tank exemplified as a primary sedimentation tank or a final sedimentation tank, and constitutes part of a water treatment system that treats water to be treated (e.g., sewage). This water treatment system includes, for example, a primary sedimentation tank that settles and separates solid components such as pollutants (e.g., solid organic matter) contained in the water to be treated; a reaction tank provided downstream of the primary sedimentation tank and treating the water to be treated by biological treatment such as the standard activated sludge method; a final sedimentation tank provided downstream of the reaction tank and settles and separates solid components such as activated sludge contained in the water to be treated; a concentration device that concentrates the pollutants (primary sludge) settled by the primary sedimentation tank and the activated sludge (excess sludge) settled by the final sedimentation tank; and a digester that biologically treats the organic components contained in the primary sludge and excess sludge supplied from the concentration device using anaerobic bacteria.

[0013] [Overall structure] Figure 1 shows the configuration of a sedimentation tank 100 equipped with a filtration cassette 50 according to an embodiment. Figure 1(A) is a top view of the sedimentation tank 100, Figure 1(B) is a longitudinal cross-sectional view of the sedimentation tank 100 showing a cross-section along line AA in Figure 1(A), and Figure 1(C) is a longitudinal cross-sectional view of the sedimentation tank 100 showing a cross-section along line BB in Figure 1(A). Here, the sedimentation tank 100 is configured such that the water to be treated flows in from the upstream side and flows toward the downstream side. Hereinafter, the direction in which the water to be treated flows in the sedimentation tank 100 will be referred to as the "flow direction" and denoted by the symbol L. The depth direction (i.e., the vertical direction) of the sedimentation tank 100 will be referred to as the "up and down direction" and denoted by the symbol V. The direction perpendicular to the flow direction L and the up and down direction V will be referred to as the "width direction" and denoted by the symbol H. Therefore, Figure 1(B) shows a cross-section perpendicular to the width direction H, and Figure 1(C) shows a cross-section perpendicular to the flow direction L. Furthermore, the flow direction L, vertical direction V, and width direction H will have the same meanings in the description of the filtration cassette 50 described later.

[0014] As shown in Figure 1(A), the sedimentation tank 100 includes, for example, a sedimentation tank 10 for containing the water to be treated, and a filtration cassette 50 installed in the sedimentation tank 10 for circulating and filtering the water to be treated. The sedimentation tank 100, for example, allows relatively coarse solids contained in the water to be treated that flows into the sedimentation tank 10 to settle in the sedimentation tank 10 by gravity, and then separates relatively fine solids by filtering the water to be treated with the filtration cassette 50. The water to be treated (hereinafter also referred to as "filtered water"), from which the solids have been filtered and separated by the filtration cassette 50, is discharged to, for example, a downstream facility. Specifically, if the sedimentation tank 100 is the primary sedimentation tank, the water to be treated is discharged to a reaction tank, for example, by a pump. If the sedimentation tank 100 is the final sedimentation tank, the water to be treated is discharged to, for example, a sterilization treatment device (not shown). The sterilization treatment device then sterilizes the water to be treated discharged from the final sedimentation tank, for example, and discharges the sterilized treated water into a river or the like.

[0015] The sedimentation tank 10 is an example of the treatment tank according to the present disclosure. For example, it is a cross-flow sedimentation tank that retains the water to be treated flowing into the sedimentation tank 10 and separates the solid content contained in the water to be treated by sedimenting it by gravitational sedimentation. The water to be treated, for example, flows into the sedimentation tank 10 from the upstream side in the flow direction L and flows toward the downstream side. The sedimentation tank 10 is formed, for example, in a substantially rectangular parallelepiped shape having a bottom 10a and side walls 10b, and the longitudinal direction of the sedimentation tank 10 coincides with the flow direction L of the water to be treated. That is, the water to be treated flows along the longitudinal direction of the sedimentation tank 10, specifically, from the left side to the right side in FIG. 1(A). In a top view, the side wall 10b has a rectangular shape that is long in the flow direction L.

[0016] Also, as shown in FIGS. 1(A) to 1(C), the sedimentation pond 100 includes, for example, a plurality of partition walls that partition the inside of the sedimentation tank 10. The plurality of partition walls includes a plurality of partition plates 20 installed vertically and a plurality of partition plates 30 installed horizontally. By the partition plates 20 and 30, for example, a sedimentation section 110, a filtration section 120, a treated water flow path 130, and a washing and drainage tank 140 are partitioned inside the sedimentation tank 10.

[0017] For example, the water to be treated flows into the sedimentation section 110, and a part of the solid content of the water to be treated sedimentates by gravitational sedimentation. As shown in FIG. 1(B), the sedimentation section 110 is, for example, a region surrounded by the bottom 10a, the side walls 10b, and the partition plates 20 and 30 of the sedimentation tank 10. The sedimentation section 110 is formed from the upstream side to the downstream side of the sedimentation tank 10 in the flow direction L. As shown in FIG. 1(B), the bottom 10a of the sedimentation tank 10 constituting the sedimentation section 110 is formed such that the depth of the sedimentation tank 10 gradually becomes shallower from the upstream side to the downstream side in the flow direction L. And a solid content discharge pipe 102 provided with a solid content discharge valve 101 is installed on the bottom 10a. For example, by opening the solid content discharge valve 101 constantly or every predetermined time, the solid content sedimentated in the sedimentation section 110 is discharged from the sedimentation tank 10 through the solid content discharge pipe 102 and supplied to the subsequent equipment (for example, a concentration device).

[0018] The filtration unit 120 filters the treated water from which a part of the solid content has been separated by the precipitation unit 110, for example, using the filtration cassette 50. As shown in FIGS. 1(A) to 1(C), the filtration unit 120 is, for example, a rectangular parallelepiped-shaped region defined by the filtration cassette 50. The filtration unit 120 is adjacent to the downstream side in the flow direction L with respect to the upper region of the precipitation unit 110 and adjacent to the upper side with respect to the downstream region of the precipitation unit 110, as shown in FIG. 1(B), for example. The upper and lower surfaces of the filtration unit 120 are open. Also, at least a part of the side surface of the filtration unit 120 communicates with the precipitation unit 110 so that the treated water can flow into the inside of the filtration cassette 50 through the later-described inlet 3 (see FIG. 2). The treated water flows into the filtration unit 120 from the downstream region of the precipitation unit 110. Also, the partition plate 20 between the filtration unit 120 and the precipitation unit 110 prevents the treated water from flowing over the precipitation unit 110 and into the filtration unit 120.

[0019] In the filtration unit 120, for example, a plurality of rectangular parallelepiped-shaped filtration cassettes 50 are arranged in parallel. Specifically, as shown in FIG. 1(A), in the filtration unit 120, for example, three filtration cassettes 50 are arranged side by side at intervals in the width direction H. However, the number and shape of the filtration cassettes 50 arranged in the filtration unit 120 are not particularly limited.

[0020] The filtration cassette 50 is installed in the filtration unit 120, for example, in a state of being immersed in the treated water. A seal member 40 is provided between the adjacent filtration cassettes 50 spaced apart in the width direction H to prevent the treated water flowing in from the precipitation unit 110 from leaking through the gap between the filtration cassettes 50 and flowing out to the downstream side (treatment water flow path 130). The seal member 40 is, for example, a flange-shaped member protruding from the side surface of the filtration cassette 50 and extending in the horizontal direction, and the flange-shaped members of the adjacent filtration cassettes 50 overlap near the water surface, thereby sealing the gap between the filtration cassettes 50. The treated water (filtered water) from which the solid content has been separated by the filtration cassette 50 flows over the filtration unit 120 and into the treatment water flow path 130.

[0021] Hereinafter, as will be explained in detail later, the housing 1 of the filtration cassette 50 contains a filter material 2 for filtering the water to be treated (see Figure 2). In the sedimentation tank 100, for example, under normal circumstances, the water to be treated is filtered by the filtration cassette 50, and at predetermined intervals, or when the solid-liquid separation performance of the filter material 2 deteriorates, the filtration of the water to be treated is temporarily stopped and the filter material 2 is washed. Hereinafter, in the sedimentation tank 100, the operation of filtering the water to be treated will be referred to as the "filtration operation," and the operation of washing the filter material 2 will be referred to as the "washing operation."

[0022] As shown in Figure 1(B), the sedimentation tank 100 is equipped with, for example, an aeration cleaning mechanism 60 for performing a cleaning operation. The aeration cleaning mechanism 60 includes, for example, a blower 601 for supplying air and an air cleaning pipe 602 connected to the blower 601. The air outlet of the air cleaning pipe 602 is inserted into the filter cassette 50, and the air supplied from the blower 601 is sent into the filter cassette 50 via the air cleaning pipe 602. The aeration cleaning mechanism 60 generates a swirling flow inside the filter cassette 50 by aeration, thereby agitating and cleaning the filter material 2. The treated water containing solids (hereinafter also referred to as "cleaning wastewater") generated during the cleaning operation by the aeration cleaning mechanism 60 overflows the filtration section 120 and flows into the treated water flow path 130.

[0023] The treated water channel 130 carries the treated water (filtered water and washing wastewater) that flows in from the filtration section 120. As shown in Figure 1(B), the treated water channel 130 is formed in a roughly U-shape in a top view, for example, so as to surround the filtration section 120 and the washing wastewater tank 140. More specifically, the treated water channel 130 has, for example, a pair of troughs 130a, 130a extending in the flow direction L and a trough 130b extending in the width direction H. The pair of troughs 130a, 130a are arranged adjacent to the filtration section 120 and the washing wastewater tank 140 on both sides in the width direction H (i.e., sandwiching them). The trough 130b is adjacent to the filtration section 120 on the upstream side in the flow direction L and connects the upstream ends of the pair of troughs 130a, 130a in the flow direction L. As shown in Figure 1(C), the treated water channel 130 is formed in a trough shape by, for example, the side wall 10b of the sedimentation tank 10 and the partition plates 20 and 30. The top surface of the treated water channel 130 is open, and the bottom surface is closed by the partition plate 30.

[0024] The water to be treated flows from the filtration section 120 into the treated water channel 130, and flows from the upstream side to the downstream side in the flow direction L. As shown in Figure 1(A), for example, a gate 70 is provided at the downstream end of the treated water channel 130 to open and close the downstream opening of the treated water channel 130. In addition, an outlet 150 is provided between the pair of troughs 130a, 130a and the washing drainage tank 140, for example, to discharge the washing drainage generated during the washing operation into the washing drainage tank 140. Therefore, during filtration operation, by keeping the gate 70 open, the filtered water flowing from the filtration section 120 into the treated water channel 130 flows out through the gate 70 to the downstream equipment of the sedimentation tank 100 (for example, a sterilization treatment device). At this time, a portion of the filtered water may also flow out to the washing drainage tank 140 through the outlet 150. On the other hand, during the washing operation, by keeping the gate 70 closed, the washing wastewater does not flow out of the sedimentation tank 100 but flows through the outlet 150 into the washing wastewater tank 140.

[0025] The washing wastewater tank 140 stores, for example, washing wastewater that flows in from the treated water channel 130. As shown in Figure 1(B), the washing wastewater tank 140 is adjacent to the downstream side of the filtration section 120 in the flow direction L, and adjacent to the upper side of the downstream region of the sedimentation section 110. The washing wastewater tank 140 is formed, for example, by the side wall 10b of the sedimentation tank 10 and the partition plates 20 and 30. The top surface of the washing wastewater tank 140 is open, and the bottom surface is closed by the partition plate 30.

[0026] Here, the sedimentation tank 100 includes, for example, a return mechanism 80 that returns the washing wastewater stored in the washing wastewater tank 140 to an area upstream of the filtration unit 120. The return mechanism 80 includes, for example, a pump 801 installed in the washing wastewater tank 140 and a return line 802 that transfers the discharged water from the pump 801. The return mechanism 80 returns the washing wastewater to, for example, the sedimentation unit 110 or equipment upstream of the sedimentation tank 100 (for example, an inflow channel to the sedimentation tank 100).

[0027] [Filtration operation] The filtration operation of the sedimentation tank 100 will be described below. The filtration operation is carried out with the water to be treated continuously flowing into the sedimentation section 110 and the gate 70 of the treated water flow path 130 open.

[0028] In the filtration operation, first, relatively coarse solids contained in the water to be treated that flows into the sedimentation section 110 are separated by sedimentation in the sedimentation section 110. Then, the water to be treated, from which the solids have been separated by sedimentation, flows into the filtration section 120. The water to be treated that flows into the filtration section 120 flows into the filtration cassette 50 and passes through the filtration cassette 50 in an upward direction due to the upward flow. As the water to be treated passes through the filtration cassette 50, relatively fine solids are filtered and separated.

[0029] The water to be treated (i.e., filtered water) that has passed through the filtration cassette 50 overflows the filtration section 120 and flows into the treated water channel 130. The filtered water that has flowed into the treated water channel 130 then flows out of the sedimentation tank 100 through the gate 70.

[0030] At the start of the filtration operation, the water level in the sedimentation section 110 and the water level in the filtration section 120 are approximately equal. However, as time passes, the water flow resistance of the filtration cassette 50 increases, causing the water level in the sedimentation section 110 to rise and become higher than the water level in the filtration section 120. For example, after a certain period of time has elapsed since the start of the filtration operation, or when the water level difference between the sedimentation section 110 and the filtration section 120 exceeds a predetermined level, the system switches to a washing operation.

[0031] [Washing operation] The cleaning operation of the sedimentation tank 100 will be described below. The cleaning operation includes an aeration cleaning process and a rinse cleaning process.

[0032] In the washing operation, aeration washing is performed first. In the aeration washing process, the gate 70 of the treated water flow path 130 is closed to stop the outflow of treated water from the sedimentation tank 100 to the outside. By stopping the outflow of treated water, the water level difference in the sedimentation tank 10 is eliminated, and the inflow of treated water into the sedimentation tank 100 is stopped.

[0033] In this state, the blower 601 of the aeration cleaning mechanism 60 is driven to send air into the filter cassette 50 via the air cleaning pipe 602, aerating the air and creating a swirling flow. The swirling flow causes the filter material 2 inside the filter cassette 50 to flow, and the filter material 2 comes into contact with each other and rubs against each other, thus cleaning the filter material 2. As a result, any solid matter that was trapped in the filter material 2 is detached from the filter material 2 and resuspended in the cleaning wastewater.

[0034] The washing wastewater generated by aeration overflows the filtration section 120 and flows into the treated water channel 130. The washing wastewater that flows into the treated water channel 130 then flows through the outlet 150 into the washing wastewater tank 140.

[0035] Furthermore, during aeration cleaning, the pump 801 of the return mechanism 80 is driven to return the treated water (cleaning wastewater). Specifically, the cleaning wastewater that flows into the cleaning wastewater tank 140 is sucked up by the pump 801 and returned upstream of the filtration section 120 via the return line 802. As a result, the treated water continuously passes through the filtration cassette 50 during aeration cleaning.

[0036] After performing aeration cleaning for a predetermined period of time, the aeration cleaning is terminated by stopping the blower 601.

[0037] In the washing operation, a rinse wash is performed next. During the rinse wash process, the blower 601 is stopped and the gate 70 is closed, while the return mechanism 80 continues to return the treated water (washing wastewater). Even during the rinse wash, the treated water that flows from the sedimentation section 110 to the filtration section 120 passes continuously through the filtration cassette 50 by upward flow and flows into the washing wastewater tank 140 via the treated water flow path 130. The treated water that flows into the washing wastewater tank 140 is returned upstream of the filtration section 120 by the pump 801. By continuing the rinse wash, the washing wastewater is flushed out by the filtered water, and the treated water after the filtration section 120 is gradually purified.

[0038] The rinse cleaning is terminated by stopping the pump 801 after a predetermined time has elapsed since the start of the rinse cleaning, specifically, for example, after a predetermined time has elapsed since the start of the pump 801 operation or after a predetermined time has elapsed since the stop of the blower 601. The stopping of the pump 801 may also be based on the water quality of the cleaning wastewater measured by a water quality sensor (not shown). For example, a turbidimeter may be installed in the return line 802, and the pump 801 may be stopped when the turbidity of the cleaning wastewater falls below a predetermined value (for example, equivalent to filtered water).

[0039] Once the rinsing is complete, the filtration operation is restarted by opening gate 70. As described above, in the sedimentation tank 100, the filtration operation is temporarily stopped and a washing operation is performed.

[0040] [Draining water] For example, for periodic cleaning of the sedimentation tank 100 and the filter cassette 50, the treated water is drained from the sedimentation tank 10 while the filter cassette 50 is installed, thereby draining the filter cassette 50 and emptying the water to be treated from within. Alternatively, the filter cassette 50 may be drained by, for example, lifting it out of the sedimentation tank 10.

[0041] [Filtration Cassette 50] The details of the filtration cassette 50 according to the embodiment will be described below. Figures 2 to 4 are schematic diagrams showing the filtration cassette 50 according to the embodiment. More specifically, Figure 2 is a longitudinal cross-sectional view of the filtration cassette 50 according to the embodiment, showing a cross-section perpendicular to the width direction H of the filtration cassette 50. Figure 3 is a front view of the filtration cassette 50 according to the embodiment, showing the filtration cassette 50 as viewed along the flow direction L. Figure 4 is a cross-sectional view of the filtration cassette 50 showing a cross-section along the CC line in Figure 3, showing a cross-section perpendicular to the vertical direction V of the filtration cassette 50. Figures 2 to 4 show the filtration cassette 50 during filtration operation.

[0042] In the following explanation, when a component is described as "impossible to pass through" an object, it means, for example, that the object is prevented from passing through the component. Also, "opening width" refers to the size of the opening (hole) that determines the size of an object that can pass through it. The opening width may be, for example, a dimension corresponding to the diameter of the largest circle that can be accommodated within the contour of the opening in a plan view. For example, if the opening is circular, the diameter of the opening may be used as the opening width, and if the opening is rectangular, the width of the opening in the shorter direction may be used as the opening width.

[0043] As shown in Figures 2 to 4, the filtration cassette 50 comprises, for example, a housing 1, a filter material 2, an inlet 3, an outlet 4, a movable screen 5, and an installation section 6.

[0044] [Cabinet 1] The housing 1 is a container into which the water to be treated is supplied and filtered. The housing 1 is formed, for example, in the shape of a box with a rectangular horizontal cross-section. However, the shape of the housing 1 is not particularly limited, and for example, it may be a cylindrical shape with a circular or elliptical horizontal cross-section.

[0045] As shown in Figure 1(A), the housing 1, for example, has a rectangular shape when viewed from above, and the filtration cassette 50 is positioned in the sedimentation tank 10 such that the longitudinal direction of the housing 1 (i.e., the direction of the longer side) coincides with the flow direction L of the water to be treated. In other words, when viewed from above, the longitudinal direction of the housing 1 coincides with the flow direction L. However, the orientation of the housing 1 is not particularly limited; for example, when viewed from above, the short side of the housing 1 may coincide with the flow direction L. Alternatively, the housing 1 may have a square shape when viewed from above, and the filtration cassette 50 may be positioned in the sedimentation tank 10 such that the orientation of any two opposing sides of the housing 1 coincides with the flow direction L of the water to be treated.

[0046] As shown in Figure 2, a filtration chamber 1a is defined inside the housing 1, which is a space through which the filter material 2 is housed and the water to be treated flows. Hereinafter, among the walls that make up the housing 1, the wall that defines the side of the filtration chamber 1a will be called the "side wall", the wall that defines the bottom of the filtration chamber 1a will be called the "bottom wall", and the wall that defines the top of the filtration chamber 1a will be called the "top wall". As shown in Figure 2, the housing 1 has a side wall 11, a bottom wall 12, and an upper screen 13 formed as the top wall.

[0047] The side wall 11 is formed, for example, in a cylindrical shape extending in the vertical direction V, and is arranged to surround the side surface of the filtration chamber 1a. More specifically, the side wall 11 includes, for example, a pair of plate-shaped wall portions 111, 111 arranged perpendicular to the flow direction L, and a pair of plate-shaped wall portions 112, 112 arranged perpendicular to the width direction H, and is formed in a rectangular tubular shape with a rectangular horizontal cross-section. In a top view, the pair of wall portions 111, 111 extends along the width direction H, and the pair of wall portions 112, 112 extends along the flow direction L, with the pair of wall portions 112, 112 being longer than the pair of wall portions 111, 111. Therefore, the horizontal cross-section of the side wall 11 is formed in a rectangle that is longer in the flow direction L. Hereinafter, of the pair of wall portions 111, 111, the wall portion 111 located on the upstream side in the flow direction L will be referred to as wall portion 111a. The wall portion 111a faces the flow direction L. In other words, the wall portion 111a faces the upstream side of the flow direction L. Therefore, the water to be treated flows toward the wall portion 111a.

[0048] As shown in Figures 2 to 4, an inlet 3 is formed in the side wall 11 for the water to be treated to flow into the filtration chamber 1a. The inlet 3 is formed, for example, in the wall portion 111a of the side wall 11 that faces the flow direction L. In this embodiment, a plurality (for example, two) of rectangular inlets 3 are formed in the lower part of the wall portion 111a (near the bottom wall 12) in a plan view. The inlets 3 are positioned below the filtration layer 2a that is formed in the filtration chamber 1a by the upward flow during filtration operation. The inlets 3 have an opening width that is larger than the communication hole of the water passage portion 51 described later, and are formed so that the water to be treated and the filter material 2 can pass through. However, the inlets 3 do not necessarily have to be able to pass through the filter material 2; it is sufficient that at least the water to be treated can pass through. Furthermore, the number and shape of the inlets 3 are not particularly limited; for example, there may be only one inlet 3 instead of multiple, or it may be circular. Of the side wall 11, the portion excluding the inlet 3 is formed in such a way that the water to be treated and the filter material 2 cannot pass through.

[0049] As shown in Figures 2 and 3, the bottom wall 12 is formed, for example, in the shape of a plate and is arranged perpendicular to the vertical direction V so as to cover the bottom surface of the filtration chamber 1a. The bottom wall 12 is provided, for example, at the lower end of the side wall 11. However, the bottom wall 12 only needs to be located below the filter material 2 and may be provided in the middle of the side wall 11. The bottom surface of the filtration chamber 1a is closed by the bottom wall 12. The bottom wall 12 is formed in such a way that the water to be treated and the filter material 2 cannot pass through it.

[0050] The upper screen 13 is formed, for example, in the shape of a plate and is arranged perpendicular to the vertical direction V so as to cover the upper surface of the filtration chamber 1a. The upper screen 13 is provided, for example, at the upper end of the side wall 11. However, the upper screen 13 only needs to be located above the filter material 2 and may be provided in the middle of the side wall 11. It is preferable that the upper screen 13 is located below the water level of the filtration section 120 in the sedimentation tank 10.

[0051] The upper screen 13 is configured to, for example, allow the water to be treated to pass through while preventing the filter material 2 from passing through. The upper screen 13 has a plurality of communication holes formed therein, for example, as outlets 4 for the water to be treated to flow out from the inside of the housing 1 to the outside. The plurality of communication holes are, for example, through holes that penetrate the upper screen 13 in the thickness direction, and are formed so that the water to be treated can pass through but the filter material 2 cannot. In other words, the water to be treated is allowed to flow out to the outside of the housing 1 (filtration chamber 1a) through the outlets 4, while the filter material 2 is prevented from flowing out to the outside of the housing 1 through the outlets 4.

[0052] For the upper screen 13, for example, a perforated plate such as punched metal or a mesh plate such as metal mesh can be used.

[0053] Furthermore, in this embodiment, the outlet 4 is formed on the upper surface of the housing 1, but the position of the outlet 4 on the housing 1 is not limited to this. The outlet 4 only needs to be formed in a position that sandwiches the filtration layer 2a between it and the inlet 3, and may be provided on the side wall 11.

[0054] As shown in Figure 2, an air cleaning pipe 602 is inserted and positioned inside the filtration chamber 1a to clean the filter material 2 by blowing air onto it during the cleaning operation. The air outlet 602a of the air cleaning pipe 602 is located near the inlet 3.

[0055] [Filter material 2] Multiple filter media 2 are housed within the enclosure 1. The filter media 2 have, for example, a form that is buoyant of the water to be treated and capable of capturing solid matter contained in the water to be treated. As the filter media 2, for example, a cylindrical form made of a resin material such as foamed resin with irregularities on its surface can be used. However, the material and shape of the filter media 2 are not particularly limited.

[0056] During filtration operation, the buoyancy acting on the filter material 2 and the upward flow of the water to be treated cause multiple filter materials 2 to accumulate, forming a filtration layer 2a between the inlet 3 and outlet 4 in the filtration chamber 1a, as shown in Figures 2 and 3. Specifically, the filtration layer 2a is located above the inlet 3 and below the outlet 4.

[0057] The filtration layer 2a is constructed by filling it with multiple filter media 2, so that fine gaps are formed between the filter media 2. When the water to be treated passes through these gaps between the filter media 2 and the hollow parts of the cylindrical filter media 2, solid matter contained in the water to be treated is captured on the surface of the filter media 2. During filtration operation, the buoyancy acting on the filter media 2 and the upward flow of the water to be treated push the filter media 2 upwards and cause them to float, so the filtration layer 2a is positioned offset towards the upper part of the filtration chamber 1a. At this time, the upward movement of the filter media 2 is restricted by the upper screen 13, so the filtration layer 2a accumulates on the lower surface of the upper screen 13.

[0058] [Movable Screen 5] As shown in Figures 2 and 3, the movable screen 5 has, for example, a water passage section 51, a shaft section 52, and a handle 53, and is mounted on the outside of the housing 1 so that it can move up and down along the side wall 11. By moving the movable screen 5 up and down, the water passage section 51 can be attached to and detached from the inlet 3. The filtration cassette 50 is equipped with multiple (two in the illustrated configuration) movable screens 5 depending on the number of inlet 3. However, the number of movable screens 5 is not particularly limited.

[0059] The water passage section 51 is, for example, a water passage plate formed in the shape of a plate, and is arranged along the outer surface of the wall portion 111a of the side wall 11 so as to cover the inlet 3 of the filtration chamber 1a from the outside of the housing 1.

[0060] The water passage section 51 is configured, for example, to allow the water to be treated to pass through while preventing the filter material 2 from passing through. The water passage section 51 has a plurality of communication holes formed therein, for example, as openings through which the water to be treated can pass. The plurality of communication holes are, for example, through holes that penetrate the water passage section 51 in the thickness direction, and are formed so that the water to be treated can pass through but the filter material 2 cannot. In other words, when the water passage section 51 is positioned to cover the inlet 3, the water to be treated is allowed to flow into the housing 1 (filtration chamber 1a) through the inlet 3, and the filter material 2 is prevented from flowing out of the housing 1 through the inlet 3.

[0061] The material and shape of the water passage section 51 are not particularly limited, but examples of materials include resin and metal, and examples of shapes include screens such as perforated plates and mesh plates. Furthermore, the water passage section 51 does not have to be plate-shaped; for example, it may have one or more resin flaps, and the opening may be formed by the oscillation of the flaps due to water pressure.

[0062] The shaft portion 52 is, for example, a rod-shaped member that connects the water passage portion 51 and the handle 53. The shaft portion 52 extends along the vertical direction V, with its lower end connected to the water passage portion 51 and its upper end connected to the handle 53. The material and shape of the shaft portion 52 are not particularly limited.

[0063] The handle 53 is a component that an operator grips to perform, for example, the raising and lowering operation of the water passage section 51 from above the filtration cassette 50. The handle 53 is located above the housing 1 and is connected to the water passage section 51 via the shaft 52. The shape of the handle 53 is not particularly limited, but it is preferable that it is a shape that is easy for an operator to grip.

[0064] [Installation part 6] The installation section 6 allows the water passage section 51 of the movable screen 5 to be attached to and detached from the inlet 3 from outside the housing 1. As shown in Figures 2 and 3, the installation section 6 includes, for example, a mounting section 61 on which the water passage section 51 is placed, and a guide section 62 that guides the vertical movement of the water passage section 51. The filtration cassette 50 is provided with multiple (two in the illustrated configuration) installation sections 6 depending on the number of inlets 3. However, the number of installation sections 6 is not particularly limited.

[0065] As shown in Figures 2 and 3, the mounting portion 61 is formed, for example, in the shape of a plate and erected on the side wall 11, extending along the width direction H. The mounting portion 61 restricts the downward movement of the water passage portion 51.

[0066] As shown in Figure 4, the guide section 62 has, for example, a pair of first restricting sections 621, 621 and a pair of second restricting sections 622, 622. Each of the pair of first restricting sections 621 is, for example, formed in the shape of a plate and erected on the side wall 11, extending along the vertical direction V. The pair of first restricting sections 621, 621 are arranged on both sides of the water passage section 51 in the width direction H. The movement of the water passage section 51 in the width direction H is restricted by the pair of first restricting sections 621, 621. Each of the pair of second restricting sections 622, 622 is, for example, formed in the shape of a plate and extends from the tip of the first restricting section 621 so as to sandwich the water passage section 51 between itself and the side wall 11. The forward and backward movement of the water passage section 51 in the flow direction L is restricted by the pair of second restricting sections 622, 622.

[0067] When the water passage section 51 of the movable screen 5 is attached to the housing 1, the installation section 6 restricts the downward movement of the water passage section 51, its movement in the width direction H, and its forward and backward movement in the flow direction L, thereby preventing the water passage section 51 from falling off the housing 1 and maintaining the state in which the inlet 3 is covered by the water passage section 51. In addition, the installation section 6 allows the water passage section 51 to move upward, making it possible to remove the water passage section 51 from the housing 1 by an upward lifting operation.

[0068] [Attaching and detaching the water passage section 51] The worker can attach and detach the water passage section 51 from, for example, a work platform (not shown) installed around the sedimentation tank 10 or on the water inside the sedimentation tank 10. Figure 5 is a longitudinal cross-sectional view of the filtration cassette 50 when the water passage section 51 is removed during filtration operation. To remove the water passage section 51 from the housing 1, for example, the worker grasps the handle 53 of the movable screen 5 and pulls it up, which, as shown in Figure 5, also pulls up the water passage section 51 connected to the handle 53 via the shaft 52. At this time, the guide section 62 of the installation section 6 guides the rise of the water passage section 51. When the water passage section 51 is pulled out from the guide section 62, the water passage section 51 is removed from the housing 1 and the inlet 3 is opened.

[0069] Furthermore, the water passage section 51 can be attached to the housing 1 by performing the reverse operation of the removal process. Specifically, for example, an operator grasps the handle 53 of the movable screen 5 and lowers the water passage section 51, inserting the water passage section 51 into the guide section 62. At this time, the guide section 62 of the installation section 6 guides the descent of the water passage section 51. By placing the water passage section 51 on the mounting section 61, the water passage section 51 is attached to the housing 1, and the inlet 3 is covered by the water passage section 51.

[0070] As described above, the water passage section 51 is attached to the side wall 11 of the housing 1 and can be attached and detached by operation from outside the housing 1. Therefore, it is possible to attach and detach the water passage section 51 without lifting the filtration cassette 50 out of the sedimentation tank 10. For example, during filtration operation, it is possible to remove the water passage section 51 from the filtration cassette 50 without stopping the filtration operation and to clean or replace the water passage section 51. Furthermore, because the filtration layer 2a is formed above the inlet 3 due to the upward flow during filtration operation, even if the water passage section 51 is removed during filtration operation, the outflow of the filter material 2 to the outside of the housing 1 via the inlet 3 is suppressed.

[0071] Furthermore, during the washing operation, the swirling flow generated inside the housing 1 (filtration chamber 1a) of the filtration cassette 50 causes the filter material 2 to flow, spreading throughout the housing 1. However, by keeping the water passage section 51 attached to the housing 1, it is prevented that the filter material 2 will flow out of the housing 1 through the inlet 3. Also, when draining the water from the filtration cassette 50, the treated water flows out from the inlet 3, creating water pressure that pushes the filter material 2 inside the housing 1 towards the inlet 3. However, by keeping the water passage section 51 attached to the housing 1, it is prevented that the filter material 2 will flow out of the filtration chamber 1a through the inlet 3. Furthermore, when installing the filtration cassette 50 in the sedimentation tank 10 or after draining the filtration cassette 50, there is no water inside the housing 1, so no buoyancy acts on the filter material 2, and the filter material 2 accumulates at the bottom of the housing 1. However, by keeping the water passage section 51 attached to the housing 1, it is prevented that the filter material 2 will flow out of the filtration chamber 1a through the inlet 3.

[0072] [Effects / Effects] As described above, the filtration cassette 50 according to this embodiment is installed in the sedimentation tank 10 and filters the water to be treated by passing it through it. The filtration cassette 50 comprises a housing 1, an inlet 3 provided on the side wall 11 of the housing 1 through which the water to be treated flows in, an outlet 4 provided on the housing 1 through which the water to be treated flows out, and a filter material 2 housed inside the housing 1 and forming a filtration layer 2a between the inlet 3 and the outlet 4. The filtration cassette 50 further comprises a water passage section 51 with an opening through which the water to be treated can pass, and an installation section 6 for attaching the water passage section 51 to the housing 1 so that it can be attached to and detached from the inlet 3 from outside the housing 1.

[0073] For example, if an inlet 3 is provided on the bottom of the housing 1 and a screen (water passage section) is attached to the inlet 3, then in order to clean or replace the screen, it is necessary to stop the filtration operation and drain the water to be treated from the sedimentation tank 10 to drain the filtration cassette 50. In contrast, in this embodiment, an inlet 3 is provided on the side wall 11 of the housing 1, and the water passage section 51 is made detachable from the inlet 3 from outside the housing 1, so that the water passage section 51 can be attached and detached while the filtration cassette 50 is installed in the sedimentation tank 10 without having to lift the filtration cassette 50 out of the sedimentation tank 10. Therefore, according to this embodiment, it is not necessary to stop the filtration operation in order to clean or replace the water passage section 51. This makes it possible to perform continuous filtration operation for a long period of time. As a result, it becomes possible to perform the filtration operation of the sedimentation tank 100 more efficiently. In addition, the workload when attaching and detaching the water passage section 51 can be reduced, making maintenance easier.

[0074] Furthermore, the installation section 6 allows the water passage section 51 to move up and down along the side wall 11. The water passage section 51 is attached to the housing 1 so as to cover the inlet 3, and can be removed from the housing 1 by being pulled up from its attached position. As a result, the water passage section 51 can be removed by a simple operation of pulling it up, thus further reducing the workload when attaching and detaching the water passage section 51.

[0075] Furthermore, the installation section 6 may be interchangeable with at least two types of water passage sections 51 having different strengths. This allows for the use of water passage sections 51 with different strengths depending on the usage conditions of the sedimentation tank 100. For example, during filtration operation, buoyancy acts on the filter material 2, so the load on the water passage section 51 is relatively small. In this case, ease of attachment and detachment may be prioritized over the strength of the water passage section 51, and a lightweight resin screen may be used as the water passage section 51. When draining the water, a relatively strong metal screen (e.g., made of SUS) may be used as the water passage section 51 so that it can withstand the load caused by the water pressure of the treated water and the weight of the filter material 2.

[0076] [Example of the layout of inlet 3] The following describes an example of the arrangement of the inlet 3 in the embodiment. Figure 6 is a top view of a sedimentation tank 100 to illustrate an example of the arrangement of the inlet 3 of the filtration cassette 50. In Figure 6, a sedimentation tank 100 in which multiple filtration cassettes 50 are installed is shown in a simplified manner. As an example of the installation of the filtration cassettes 50, in Figures 6(A) and 6(C), three filtration cassettes 50 are arranged in the width direction H, and in Figure 6(B), three filtration cassettes 50 are arranged in the flow direction L. Also, the housing 1 of the filtration cassette 50 shown in Figures 6(A) to (C) has a rectangular shape when viewed from above. In Figures 6(A) and 6(C), the wall portion 112 extending along the flow direction L is longer than the wall portion 111 extending along the width direction H, and in Figure 6(B), the wall portion 111 is longer than the wall portion 112. Furthermore, the housing 1 may have walls 111 and 112 of equal length, meaning it may have a square shape when viewed from above.

[0077] In the examples shown in Figures 6(A) and 6(B), the inlet 3 is formed in the wall portion 111a of the housing 1. The wall portion 111a is the part of the side wall 11 of the housing 1 that faces the flow direction L of the water to be treated in the sedimentation tank 10 when the filtration cassette 50 is installed in the sedimentation tank 10. Therefore, in the examples shown in Figures 6(A) and 6(B), by providing the inlet 3 in the wall portion 111a facing the upstream side of the flow direction L, it is possible to easily draw the water to be treated into the housing 1 (filtration chamber 1a) of the filtration cassette 50.

[0078] In the example shown in Figure 6(C), the inlet 3 is formed in the wall portion of the side wall 11 of the housing 1 that is adjacent to the side wall 10b of the sedimentation tank 10. Specifically, in the filter cassettes 50A, 50A, which are located at both ends of the width direction H among the multiple filter cassettes 50, the inlet 3 is formed in the wall portion 111, 111 that is closest to the side wall 10b of the sedimentation tank 10 and in the wall portion 112, 112 that is closest to the side wall 10b of the sedimentation tank 10. In addition, in the filter cassette 50B, which is located between the filter cassettes 50A, 50A, the inlet 3 is formed in the wall portion 111, 111 that is closest to the side wall 10b of the sedimentation tank 10. In the example shown in Figure 6(C), the inlet 3 is located close to the side wall 10b of the sedimentation tank 10. As a result, the distance between the inlet 3 and the work platform (not shown) installed around the sedimentation tank 10 is short, allowing workers to attach and detach the water passage section 51 from the platform around the sedimentation tank 10. Consequently, the attachment and detachment of the water passage section 51 becomes easier, improving maintainability.

[0079] Furthermore, in the examples shown in Figures 6(A) to 6(C), multiple inlets 3 are formed in the side wall 11 of the housing 1, and an installation part 6 is provided for each of the multiple inlets 3, to which a water passage part 51 is attached. In other words, each of the multiple water passage parts 51 is attached corresponding to each of the multiple inlets 3. As a result, by attaching one water passage part 51 to each of the multiple inlets 3, it is possible to make the water passage part 51 smaller and lighter compared to the case where one water passage part 51 is used to serve all of the multiple inlets 3. As a result, the workload when attaching and detaching the water passage part 51 can be reduced. Moreover, in the examples shown in Figures 6(A) and 6(B), by forming multiple inlets 3 in the wall portion of the side wall 11 that extends along the longitudinal direction of the housing 1, it is possible to form more inlets 3 compared to the case where the inlets 3 are provided in the wall portion that extends along the short direction. Furthermore, by attaching one water passage section 51 to each of the numerous inlets 3, the water passage section 51 can be made smaller and lighter.

[0080] (Note) This disclosure includes the following aspects: [Aspect 1] A filtration cassette installed in a treatment tank, through which water to be treated is passed and filtered, The casing and An inlet is provided on the side wall of the housing into which the water to be treated flows, The housing is provided with an outlet through which the treated water flows out, A filter material housed within the aforementioned housing, which forms a filter layer between the inlet and the outlet, A water passage section having an opening through which the water to be treated can pass, The water passage section is provided with an installation section for attaching it to the housing so that it can be attached to the inlet from the outside of the housing. Filtration cassette. [Aspect 2] The installation section is such that the water passage section can be raised and lowered along the side wall. The water passage section is attached to the housing so as to cover the inlet, and is removable from the housing by being lifted up from its attached position. A filtration cassette as described in Embodiment 1. [Aspect 3] The housing has a rectangular shape when viewed from above. Multiple inlets are formed in the wall portion of the side wall that extends along the longitudinal direction of the housing, and each of the multiple water passages is attached corresponding to each of the multiple inlets. A filtration cassette according to embodiment 1 or 2. [Aspect 4] The installation section is capable of replacing at least two types of water-conducting sections having different strengths. A filtration cassette as described in any of embodiments 1 to 3. [Aspect 5] The inlet is formed in the side wall portion that faces the flow direction of the water to be treated in the treatment tank when the filtration cassette is installed in the treatment tank. A filtration cassette as described in any of embodiments 1 to 4. [Aspect 6] The inlet is formed in the side wall portion adjacent to the side wall of the treatment tank when the filtration cassette is installed in the treatment tank. A filtration cassette as described in any of embodiments 1 to 5. [Explanation of Symbols]

[0081] 1: Cabinet 11: Side wall 2: Filter material 2a: filtration layer 3: Inlet 4: Outlet 5: Movable screen 51: Water flow section 6: Installation part 10: Sedimentation tank (an example of a treatment tank) 10a: side wall 50: Filtration cassette 100: Sedimentation tank (an example of a filtration system)

Claims

1. A filtration cassette installed in a treatment tank, through which water to be treated is passed and filtered, The casing and An inlet is provided on the side wall of the housing into which the water to be treated flows, The housing is provided with an outlet through which the treated water flows out, A filter material housed within the aforementioned housing, which forms a filter layer between the inlet and the outlet, A water passage section having an opening through which the water to be treated can pass, The water passage section is provided with an installation section for attaching it to the housing so that it can be attached to the inlet from the outside of the housing. Filtration cassette.

2. The installation section is such that the water passage section can be raised and lowered along the side wall. The water passage section is attached to the housing so as to cover the inlet, and is removable from the housing by being lifted up from its attached position. The filtration cassette described in Claim 1.

3. The housing has a rectangular shape when viewed from above. Multiple inlets are formed in the wall portion of the side wall that extends along the longitudinal direction of the housing, and each of the multiple water passages is attached corresponding to each of the multiple inlets. The filtration cassette described in Claim 1.

4. The installation section is capable of replacing at least two types of water-conducting sections having different strengths. The filtration cassette described in Claim 1.

5. The inlet is formed in the side wall portion that faces the flow direction of the water to be treated in the treatment tank when the filtration cassette is installed in the treatment tank. The filtration cassette described in Claim 1.

6. The inlet is formed in the side wall portion adjacent to the side wall of the treatment tank when the filtration cassette is installed in the treatment tank. The filtration cassette described in Claim 1.

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