Filtration device and method of operating the filtration device

Abstract

This allows for a higher degree of operational flexibility compared to conventional filtration systems. [Solution] The system comprises a plurality of filtration ponds 2 having filter media, a storage tank 3 having a plurality of compartments 31 for storing cleaning liquid and capable of supplying cleaning liquid to the secondary side of the filter media of each filtration pond 2, a communication passage 4 that allows fluid communication between at least two compartments 31, and a switch 5 that switches whether or not fluid communication is possible in the communication passage 4, wherein the total capacity of the compartments 31 excluding one compartment 31 is equal to or greater than the amount of cleaning liquid required to clean the filter media of one filtration pond 2.

Description

[Technical Field]

[0001] The present invention relates to a filtration device and a method for operating a filtration device. [Background technology]

[0002] Filtration systems operating in water treatment plants and other facilities may experience blockage of the filter media due to solid matter captured during operation. Therefore, in order to continue operating the filtration system, it is necessary to clean the filter media as needed or periodically. For example, Japanese Patent Publication No. 53-28656 (Patent Document 1) discloses a filtration system equipped with a backwash water chamber shared by multiple filtration chambers, from which backwash water can be supplied to the filter beds of each filtration chamber. The invention described in Patent Document 1 has the advantage of allowing for a smaller backwash water chamber compared to a system where each filtration chamber has its own individual backwash water chamber. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Special Publication No. 53-28656 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In the invention described in Patent Document 1, if the operation of the backwash water chamber had to be stopped due to malfunction or maintenance, it was necessary to stop the operation of all filtration chambers that shared the backwash water chamber, which could lead to a significant drop in the amount of purified water produced. Therefore, there were issues such as the forced reduction in the amount of purified water produced due to malfunctions of equipment related to the backwash water chamber, and the need to carefully plan the operation of the filtration system in order to maintain the backwash water chamber, indicating room for improvement in terms of increasing the flexibility of operation of the filtration system.

[0005] Therefore, there is a need to realize a filtration system and operating method that allow for greater flexibility in operation compared to conventional filtration systems. [Means for solving the problem]

[0006] The filtration apparatus according to the present invention comprises a plurality of filtration ponds having filter media, a storage tank having a plurality of compartments for storing cleaning liquid and capable of supplying the cleaning liquid to the secondary side of the filter media of each of the filtration ponds, a communication passage that allows fluid communication between at least two of the compartments, and a switch that switches whether or not fluid communication is possible in the communication passage, characterized in that the total capacity of the compartments other than one of the compartments is equal to or greater than the amount of cleaning liquid necessary for cleaning the filter media of one of the filtration ponds.

[0007] The method for operating a filtration apparatus according to the present invention comprises: a plurality of filtration ponds having filter media; at least one storage tank having a plurality of compartments and capable of supplying a cleaning solution to the secondary side of the filter media in each of the filtration ponds; a communication passage that allows fluid communication between at least two of the compartments; and a switch that switches whether or not fluid communication is possible in the communication passage, the method for operating a filtration apparatus comprising: a disconnection step of making the communication passage that is in fluid communication with at least one of the compartments in a state where fluid communication is impossible using the switch; and a cleaning step of supplying the cleaning solution to the secondary side of the filter media in at least one of the filtration ponds from a compartment different from the compartment in which the communication passage has been made in a state where fluid communication is impossible.

[0008] These configurations allow for the isolation of one section from others, and enable backwashing of the filter media using the cleaning solution stored in the other sections. Furthermore, if necessary, the cleaning solution can be removed from the isolated section for maintenance. This minimizes the impact of a section's shutdown due to malfunction or maintenance on the normal operation of the entire filtration system with multiple filter beds, thus increasing the operational flexibility of the filtration system.

[0009] Preferred embodiments of the present invention will be described below. However, the scope of the present invention is not limited by the examples of preferred embodiments described below.

[0010] In one aspect, the filtration device according to the present invention preferably has the same number of filtration tanks as the number of compartments, and a plurality of the filtration tanks and a plurality of the compartments are connected in a one-to-one correspondence.

[0011] According to this configuration, only the operation of the filtration tank connected to the compartment separated for maintenance or the like needs to be stopped, and the operation of the filtration device can be continued using other compartments.

[0012] In one aspect, the filtration device according to the present invention preferably further includes a water pump that sends the filtered water, which is the cleaning liquid, from the primary side to the secondary side of the filter medium to the storage tank.

[0013] According to this configuration, compared with the case where the filtered water on the secondary side of the filter medium is directly used as the cleaning liquid, the storage amount of the cleaning liquid is less likely to be affected by the operating conditions of the filtration device. Therefore, it is easy to perform backwashing in a planned manner.

[0014] In one aspect, the filtration device according to the present invention preferably has a siphon tube provided across at least two of the compartments to induce the movement of the cleaning liquid by siphon phenomenon from one compartment to another, and the switching device includes a valve that can open the siphon tube to the atmosphere.

[0015] In this configuration, the communication path and the switching device can be implemented in a mechanically relatively simple configuration.

[0016] In one aspect, the filtration device according to the present invention preferably has a tube provided across at least two of the compartments as the communication path, and the switching device includes a valve provided in the tube.

[0017] In this configuration, the installation of the communication path and the switching device is relatively easy.

[0018] In one aspect, the filtration device according to the present invention preferably further includes a lid for sealing the opening of the communication path, and the lid is preferably connected to the opening in at least one of the connection forms of flange connection and hinge connection.

[0019] This configuration allows for easy opening and closing of the connecting passage openings. Furthermore, when removing cleaning fluid from a section isolated from other sections and servicing that section, sealing the opening with a lid allows for the restoration of the liquid level in the other sections.

[0020] In one embodiment of the filtration apparatus according to the present invention, it is preferable that the filtration pond is a natural equilibrium type filtration pond.

[0021] This configuration is relatively simple and makes it easy to maintain a constant flow rate of the cleaning solution.

[0022] In one embodiment, the method of operating the filtration apparatus according to the present invention preferably further includes a maintenance step of performing maintenance on the section after at least partially removing the cleaning liquid from the section in which the communication passage has been rendered incapable of fluid communication.

[0023] This configuration minimizes the impact of maintenance on the cleaning solution storage tank on the normal operation of the filtration system.

[0024] In one embodiment of the operating method for the filtration apparatus according to the present invention, it is preferable to perform the cleaning step and the maintenance step simultaneously.

[0025] This configuration further reduces the impact of maintenance on the cleaning solution storage tank on the normal operation of the filtration basin.

[0026] In one embodiment, the operating method of the filtration apparatus according to the present invention includes a washing step in which the washing step is driven by the difference in water head between the storage tank and the primary side of the filter material, and the backwashing speed, which is the speed at which the washing liquid passes through the filter material, decreases as the liquid level in the storage tank decreases. It is preferable to select the communication passage in the disconnection step to make it impossible for fluid to communicate, so that the degree of decrease in the backwashing speed during the washing step is within a desired range.

[0027] This configuration makes it easy to slow down the backwashing speed.

[0028] Further features and advantages of the present invention will become clearer through the following description of exemplary and non-limiting embodiments, with reference to the drawings. [Brief explanation of the drawing]

[0029] [Figure 1] This is a plan view of a filtration device according to an embodiment. [Figure 2] This is a partial cross-sectional view of a filtration device according to an embodiment. [Figure 3] This is a partial cross-sectional view showing the storage tank and siphon tube of the filtration device according to the embodiment. [Figure 4] This is a partial cross-sectional view showing one section of the storage tank of the filtration device according to the embodiment separated from the other sections. [Figure 5] This is a partial cross-sectional view showing one section of the storage tank of the filtration device according to the embodiment separated from the other sections. [Figure 6] This is a partial cross-sectional view of a modified filtration device. [Modes for carrying out the invention]

[0030] Embodiments of the filtration device and the method of operating the filtration device according to the present invention will be described with reference to the drawings. Below, an example in which the present invention is applied to a filtration device 1 installed in a water purification facility will be described.

[0031] [Configuration of the filtration system] The filtration device 1 according to this embodiment comprises six filtration ponds 2 (an example of multiple filtration ponds) each having a filter medium 22, a storage tank 3 having six compartments 31 (an example of multiple compartments), a siphon pipe 4 (an example of a connecting passage) that can fluidly connect two compartments 31, a siphon switch 5 (an example of a switch) that communicates with the siphon pipe 4 and can open the siphon pipe 4 to the atmosphere, and a water pump 6 (an example of a water pump) that sends filtered water from the purified water channel 92 to the storage tank 3 (Figures 1 and 2). Figure 1 is a plan view of the entire filtration device 1, and Figure 2 is a longitudinal cross-sectional view showing one of the six filtration ponds 2 and its surroundings.

[0032] Furthermore, the filtration system 1 includes a raw water channel 91 for guiding the raw water that has undergone sedimentation treatment, a purified water channel 92 for guiding the filtered water to the subsequent process, a wastewater channel 93 for guiding the water from the filtered water that is not treated as purified water (wastewater), an inlet siphon device 94 for fluid communication between the raw water channel 91 and the filtration pond 2, a filtration siphon device 95 for fluid communication between the filtration pond 2 and the purified water channel 92, a backwash siphon device 96 for fluid communication between the filtration pond 2 and the storage tank 3, a discharge garit 97 for discharging the backwash water from the filter media 22, and a backwash drainage trough 98 for guiding the backwash water from the filter media 22 to the discharge garit 97. One inlet siphon device 94, one filtration siphon device 95, one backwash siphon device 96, and one backwash drainage trough 98 are provided for each filtration pond 2. The raw water channel 91, the purified water channel 92, the wastewater channel 93, and the discharge gallet 97 are shared by multiple filtration ponds 2. In this embodiment, the case in which sedimented raw water flows into the filtration device 1 is described as an example, but whether or not sedimentation treatment is applied to the raw water flowing into the filtration device according to the present invention is optional.

[0033] The filtration system 1 generally receives sedimented raw water through the raw water channel 91, filters it in the filtration basin 2, and discharges the filtered water to the subsequent process through the purified water channel 92. The driving force for moving the water during filtration in the filtration system 1 is the head difference between the filtration basin 2 and the purified water channel 92. To create this head difference, the minimum water level of the filtration basin 2 (the height of the partition wall between the filtration basin 2 and the discharge gallet 97) is higher than the maximum water level of the purified water channel 92. In addition, pressure losses caused by the water passing through the filter media 22, water collection and distribution device 23, and piping during filtration are also taken into consideration during the design phase.

[0034] If the filtration system 1 continues to operate, the filter media 22 may become clogged with captured solid matter. Therefore, the filter media 22 is cleaned as needed or periodically. Specifically, cleaning water (an example of a cleaning solution) is supplied to the secondary side of the filter media 22 and passed through to the primary side, causing water containing solid matter to flow out to the primary side of the filter media 22. This operation is generally called backwashing. The driving force for moving water during backwashing in the filtration system 1 is the head difference between the storage tank 3 and the filtration pond 2. To create this head difference, the bottom of the storage tank 3 is positioned higher than the water level of the backwash drainage trough 98. During the design phase, pressure losses caused by water passing through the piping, water collection and distribution device 23, and filter media 22 during filtration are also taken into consideration.

[0035] Filtration pond 2 is the part of the filtration device 1 that filters the raw water that has undergone sedimentation treatment. Filtration pond 2 comprises a tank body 21 for storing water, filter media 22 laid in the tank body 21, a water collection and distribution device 23 installed on the secondary side of the filter media 22, and a water collection chamber 24 on the secondary side of the filter media 22 for temporarily storing filtered water. Raw water flowing in from the raw water channel 91 flows to the primary side of the filter media 22 through the inflow-side siphon device 94 and is filtered by passing through the filter media 22. The filtered water that has passed through the filter media 22 goes through the water collection and distribution device 23, the water collection chamber 24, and the filtration siphon device 95 to the purified water channel 92. Filtration pond 2 is a type of natural equilibrium filtration pond that uses the head difference between filtration pond 2 and the purified water channel 92 as the driving force for filtration, and is more specifically called a backflow washing tank type.

[0036] The filter media 22 is not particularly limited and can be appropriately selected depending on the properties of solids that may be contained in the raw water (such as particle size) and the required quality of the filtered water (such as permeability). Non-limiting examples of filter media 22 include sand, gravel, anthracite, manganese sand, and activated carbon.

[0037] The water collection and distribution device 23 is a component that plays the role of evenly distributing the cleaning water supplied during backwashing to the entire surface of the filter media 22 on the secondary side of the filter media 22. The water collection and distribution device 23 may be, for example, an A / W perforated block (registered trademark) (manufactured by Shinko Environmental Solutions Co., Ltd.). By having the water collection and distribution device 23 in the filtration pond 2, cleaning water can easily reach the entire surface of the secondary side of the filter media 22, thereby ensuring that the entire filter media 22 is cleaned without leakage. In addition to the backwashing described above, when cleaning the filter media 22, surface cleaning by spraying pressurized water or the like onto the surface layer of the primary side of the filter media 22, air cleaning by blowing cleaning gas such as air from the secondary side of the filter media 22, or gas-water cleaning by simultaneously blowing cleaning water and cleaning gas such as air from the secondary side of the filter media may also be performed. When these additional cleanings are performed, the necessary equipment for such cleaning (surface cleaning water piping and surface cleaning water injection holes for supplying pressurized water, blowers and air supply pipes for supplying cleaning gas (air), etc.) will be appropriately provided.

[0038] The storage tank 3 is a tank that can supply washing water (an example of a washing solution) to the secondary side of the filter media 22. In other words, the storage tank 3 is in fluid communication with the filtration pond 2 (the secondary side of the filter media 22). Specifically, the storage tank 3 is in fluid communication with the water collection chamber 24 via the backwash siphon device 96, and the washing water supplied from the storage tank 3 passes through the backwash siphon device 96, the water collection chamber 24, and the water collection and distribution device 23 to reach the secondary side of the filter media 22. As mentioned above, the bottom surface of the storage tank 3 is located at a position higher than the water level of the backwash drainage trough 98, and in order to achieve this arrangement, the storage tank 3 is located on a higher level than the water collection chamber 24, the purified water channel 92, and the wastewater channel 93.

[0039] The storage tank 3 has six compartments 31. Each compartment 31 is defined by the inner wall of the storage tank 3 and a partition wall 32 provided inside the storage tank 3. In this embodiment, there are six filtration tanks 2 and six compartments 31, and they are connected to each other in a one-to-one correspondence. In Figure 1, the same subscript (A to F) is used to indicate that the filtration tank 2 (for example, filtration tank 2A) and the compartment 31 (for example, compartment 31A) are connected, which means that washing water can be supplied from the compartment 31A to the filtration tank 2A. Specifically, a backwash siphon device 96 is provided to fluidize the filtration tank 2A ​​and the compartment 31A. Thus, the six compartments 31 are each connected to six corresponding filtration tanks 2 by separately provided backwash siphon devices 96.

[0040] Washing water is supplied to the storage tank 3 from a supply pipe (not shown). A supply pipe may be provided for each compartment 31, or it may be provided for only some of the compartments 31. If a supply pipe is provided for only some of the compartments 31, washing water is supplied to the compartments 31 that do not have a supply pipe via a siphon pipe 4.

[0041] In the storage tank 3, the sum of the capacities of the other compartments 31, excluding one compartment 31, is equal to or greater than the amount of washing water required to wash the filter media 22 in one filtration pond 2 (hereinafter referred to as the washing requirement). Here, the capacity of a compartment 31 refers to the amount of washing water stored when the water level in each compartment 31 is at the upper management limit level. Normally, the upper limit level is set below the upper edge of the compartment 31 to prevent water from overflowing when the water level in a compartment 31 exceeds the upper limit level. The washing requirement can be determined by considering the processing capacity expected of the filtration device 1, and can be calculated using known methods with variables such as the filtration area of ​​the filter media 22, the backflow washing speed, and the washing time. For simplicity of explanation below, the capacity of each compartment 31 V i The explanation assumes that they are equal to each other, but this does not prevent the fact that the capacities of each section 31 are different.

[0042] In this embodiment, since six compartments 31 are provided, the total volume V of five compartments 31 i is equal to or greater than the required cleaning volume V d . That is, the following formula (1) holds. V d ≦ 5V i (1)

[0043] The total volume V of the entire storage tank 3 w is the amount obtained by multiplying the volume V of each compartment 31 i by the number of compartments 31, and the following formula (2) holds. V w = 6V i (2)

[0044] From the above formulas (1) and (2), the relationship between the total volume V of the storage tank 3 w and the required cleaning volume V d is represented by the following formula (3). V w ≧ 1.2V d (3)

[0045] Note that when generalizing formulas (2) and (3) with the number of compartments 31 as n, the following formula (4) is derived. In formula (4), x is an integer of 1 or more, and preferably an integer of 2 or more. V w = nV i ≧ (n / (n - x))V d (4)

[0046] The siphon tube 4 is a tube that fluidly connects two compartments 31 and is provided so as to penetrate each partition wall 32 (FIGS. 1 and 3). In FIG. 3, as an example, cross-sections of compartments 31A, 31C, and 31E are shown. The siphon tube 4 is a substantially U-shaped tube having two openings 41 respectively arranged near the bottom of both compartments 31 and a top 42 provided at a position higher than the openings 41. The siphon tube 4 induces the movement of cleaning water by the siphon phenomenon from one compartment 31 to another compartment 31.

[0047] The opening 41 is preferably located at a position lower than the normal minimum water level of the storage tank 3. The opening 41 may also be provided with a removable or permanent lid 43 (Figure 5). The lid 43 is preferably connected to the opening 41 by at least one of the following connection methods: flange connection and hinge connection. The top portion 42 is preferably located at a height lower than the normal maximum water level of the storage tank 3, and as close as possible to that maximum water level.

[0048] As shown in Figure 1, seven siphon tubes 4 are provided in this embodiment. When a difference in the water level of the cleaning water occurs in two adjacent compartments 31 separated by a partition wall 32, the difference in water head acts as a driving force, causing the cleaning water to move through the siphon tubes 4 from the compartment 31 with the higher water level to the compartment 31 with the lower water level. For example, when the water level in compartment 31A drops, cleaning water moves from the adjacent compartments 31B and 31C to compartment 31A. Then, as the water levels in compartments 31B and 31C drop, cleaning water moves from the adjacent compartments 31D to 31F to compartments 31B and 31C. In this way, the compartments 31 are in fluid communication with each other through the siphon tubes 4, enabling the movement of cleaning water between compartments 31. The cleaning water moves so that the water level remains constant in as many compartments 31 as the siphon principle holds true.

[0049] The siphon switch 5 is a mechanism that includes a valve that allows the siphon tube 4 to be opened to the atmosphere, and has a siphon break valve 51 and a pipe 52 that connects the siphon break valve 51 to the top 42 of the siphon tube 4. The siphon switch 5 is provided independently for each of the seven siphon tubes 4.

[0050] When the siphon break valve 51 is closed while the siphon tube 4 is filled with cleaning water, the siphon principle is established between the two compartments 31 connected by the siphon tube 4, and when the water level in one compartment 31 drops, cleaning water moves from the other compartment 31. On the other hand, when the siphon break valve 51 is opened, the siphon principle is no longer established, and even if there is a difference in the water levels of the two compartments 31, no movement of cleaning water will occur as long as the water level is lower than the top 42. In other words, the siphon switch 5 allows for free switching between a state in which fluid communication between the compartments 31 via the siphon tube 4 is established and a state in which it is not.

[0051] The water supply pump 6 is a pump that sends filtered water from the water purification channel 92 to the storage tank 3, and may be, for example, a known submersible pump.

[0052] [Operation method of the filtration system] Next, the operation method of the filtration system 1 will be explained. When operating the filtration system 1, each filter tank 2 can be set to a filtration state in which raw water is filtered, a backwash state in which the filter media 22 is backwashed, or a pause state in which neither filtration nor backwashing is performed.

[0053] During steady-state operation of the filtration system 1, it is necessary to capture solid matter contained in the raw water with the filter media 22 and to remove the solid matter captured by the filter media 22. Therefore, the filtration pond 2 must be able to operate in both a filtration state and a backwash state. In order to operate in a backwash state, it is necessary to supply the required amount of washing water from the storage tank 3 to the filtration pond 2. On the other hand, the idle state is an unroutine state taken when performing maintenance and inspections of the filtration pond 2 and its ancillary equipment.

[0054] The filtration device 1 according to this embodiment can maintain a filtration or backwashing state for one filtration pond 2 while simultaneously maintaining a filtration state for the other filtration pond 2. This feature is achieved by adopting the above-described configuration in the filtration device 1.

[0055] The following describes an example in which filtration pond 2A is kept in a idle state while maintenance work is performed on filtration pond 2A and section 31A, and in parallel with this maintenance work, steady-state operation (filtration state or backwash state) is performed on the other filtration ponds 2B to 2F.

[0056] (1) Separation process The disconnection process involves using a siphon switch 5 to disable fluid communication in a siphon tube 4 that is connected to at least one section 31. Here, in order to put the filtration pond 2A into a dormant state, the siphon break valves 51 of the siphon switch 5 connected to the two siphon tubes 4 that are connected to the section 31A corresponding to the filtration pond 2 are opened, thereby preventing fluid communication between these two siphon tubes. The siphon break valves 51 of the other two siphon switch 5 are both kept closed.

[0057] In equation (4) above, the integer x represents the number of compartments 31 that are made non-fluidally connected during the disconnection process. If there are multiple integers x that satisfy equation (4), the number of compartments 31 that are made non-fluidly connected during the disconnection process can be any number between 1 and x.

[0058] (2) Maintenance process The maintenance process involves removing the cleaning water from section 31A, where the siphon tube 4 is in a state where fluid communication is impossible, and then performing maintenance on section 31A. After the disconnection process, when the cleaning water is discharged from section 31A, there is no inflow of cleaning water from the siphon tube 4, so section 31A can be emptied (Figure 4). In this state, maintenance work such as cleaning, inspection, and repair can be performed by entering section 31A. On the other hand, since cleaning water cannot be supplied to the filter media 22 of filtration pond 2A, backwashing of the filter media 22 of filtration pond 2A is not possible. Also, to avoid blockage of the filter media 22, raw water is not accepted into filtration pond 2A.

[0059] At this time, the water level of the cleaning water in sections 31B to 31F drops to the height of the top 42 of the siphon tube 4. In this state, a cover 43 may be installed on the opening 41 on the section 31A side to block the inflow of cleaning water, and then the cleaning water may be received into sections 31B to 31F to restore the water level (Figure 5).

[0060] (3) Washing process The cleaning process involves supplying cleaning water to the secondary side of the filter media 22 in at least one filter tank 2 from sections 31B to 31F, which are different from section 31A, where the siphon tube 4 is in a state where fluid communication is impossible, in order to backwash the filter media 22. Here, the case of backwashing the filter media 22 in filter tank 2B will be explained as an example.

[0061] When backwashing the filter media 22 of filtration pond 2B, the backwash siphon device 96 connecting section 31B and filtration pond 2B is activated to supply washing water to the secondary side of the filter media 22 in filtration pond 2B. At this time, the water level in section 31B decreases, but as mentioned above, washing water moves from the other sections 31C to 31F to section 31B. This is because sections 31B to 31F are in fluid communication with each other by the siphon tube 4, and the siphon principle is in effect. Therefore, the amount of washing water that can be supplied from section 31B to filtration pond 2B is approximately equal to the sum of the capacities of sections 31B to 31F.

[0062] Here, as mentioned above, the capacity V of the five sections 31B to 31F i The total is the amount of washing required V d Therefore, the amount of washing water that can be supplied from section 31B to filtration pond 2B is the amount of washing water V required to wash the filter media 22 in filtration pond 2B. d That concludes the explanation. Therefore, it is possible to clean the filter media 22 of filtration pond 2B.

[0063] If there are multiple integers x that satisfy equation (4), the cleaning process can be carried out when the number of compartments 31 that are in a state where fluid communication is impossible is any integer between 1 and x. Here, if the number of compartments 31 that are in a state where fluid communication is impossible is α, then the amount of cleaning water consumed from each of the remaining compartments 31 (in the above example, compartments 31B to 31F) during the cleaning process is the required cleaning amount V.d V is the value obtained by dividing the remaining 31 sections by n-α. d It is expressed as / (n-α).

[0064] Assuming that the remaining compartments 31 were each full of water before the cleaning process was carried out, the amount of cleaning water in each compartment 31 is equal to the full capacity V of each compartment 31 at the beginning of the cleaning process. i Therefore, at the end of the washing process, V i -V d / (n-α)(Full capacity V) i This is the value obtained by subtracting the consumption amount from the total. From these values, the rate of decrease r in the liquid level of each section 31 due to the execution of the cleaning process (the ratio of the liquid level at the end of the cleaning process to the liquid level at the start of the cleaning process) can be expressed by equation (5). r = 1-(1 / (n-α))(V d / V i ) (5)

[0065] From equation (5), it can be seen that the larger α is, the greater the drop in liquid level in each section 31. The driving force for moving the washing water during backwashing is the difference in water head between the storage tank 3 and the filtration pond 2. Therefore, the drop in liquid level in the storage tank 3 reduces this driving force, and the backwashing speed, which is the speed at which the washing water passes through the filter media 22, decreases during the washing process. The degree of decrease in backwashing speed is more pronounced the greater the drop in liquid level in the storage tank 3 during the washing process, and therefore the larger α is, the more pronounced the decrease in backwashing speed during the washing process. The backwashing speed is defined as the value obtained by dividing the volume of washing water passing through the filter media 22 per unit time by the horizontal area of ​​the filter media 22.

[0066] This means that the degree to which the backwashing speed decreases during the cleaning process can be controlled by selecting the number of compartments 31 that are made non-fluid-connected during the disconnection process. The preferred degree to which the backwashing speed decreases is determined, for example, from the viewpoint of realizing slowdown operation, a known technique for countermeasures against Cryptosporidium and the like. Therefore, it is preferable to select the number of compartments 31 that are made non-fluid-connected during the disconnection process so that the degree to which the backwashing speed decreases during the cleaning process is of a preferred degree. The total capacity V of the storage tank 3 such that there are multiple x values ​​that satisfy equation (4)w and the capacity V of each section 31 i If this setting is configured, there is room to choose the number α of sections 31 that will be made unable to communicate with the fluid, so the desired slowdown conditions can be achieved by selecting an appropriate α.

[0067] As is clear from the above explanation, the maintenance of section 31A in the maintenance process and the backwashing of the filter media 22 in filtration pond 2B in the washing process can be carried out independently. Therefore, both operations can be performed simultaneously. In other words, one filtration pond 2A can be put into a idle state while maintenance of section 31A is carried out, while the other filtration ponds 2B to 2F can be kept in steady operation (filtration state or backwashing state). This makes it possible to suppress the temporary decrease in the processing capacity of the filtration device 1 that occurs when maintenance of the storage tank 3 is carried out.

[0068] [Variation] The following describes a modified example of a communication passage that fluidically connects adjacent compartments 31. Components similar to those in the above embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0069] In the modified filtration device, a connecting pipe 7 (an example of a connecting passage) is provided instead of the siphon tube 4 in the above embodiment, and a valve device 8 is provided instead of the siphon switch 5 in the above embodiment (Figure 6).

[0070] The connecting pipe 7 is a pipe that provides fluid communication between two adjacent compartments 31 near the bottom of the storage tank 3, and extends substantially horizontally through the partition wall 32. The valve device 8 has a valve body 81 located in the middle of the connecting pipe 7 and a handle 82 that extends from the valve body 81 to above the water surface. By operating the handle 82, the valve body 81 can be switched open or closed, thereby switching between a state in which the connecting pipe 7 is in fluid communication and a state in which it is not. When the connecting pipe 7 is in fluid communication, if the water level in one compartment 31 drops, cleaning water moves from the other compartment 31.

[0071] In the above modified examples, the establishment or non-establishment of fluid communication between the sections 31 can be arbitrarily switched, and one section 31 can be isolated from the other sections 31.

[0072] Comparing the siphon tube 4 and siphon switch 5 combination according to the above embodiment with the modified combination of the connecting pipe 7 and valve device 8, the former has the advantage of being mechanically simpler with no moving parts in the water compared to the latter, while the latter has the advantage of being easier to install compared to the former.

[0073] [Comparison with conventional technology] Conventionally, two configurations are known for providing a storage tank for the wash water supplied to the filter media of a filtration pond: one in which a separate storage tank is provided for each filtration pond, and another in which multiple filtration ponds share a single storage tank. The former configuration has the advantage that operation, including maintenance, can be determined independently for each filtration pond, but it has the disadvantage that each filtration pond must have a storage tank with a capacity greater than the amount of wash water required. The latter configuration has the advantage that the storage tank capacity can be reduced compared to the former configuration, provided that backwashing of the filter media of two or more filtration ponds is not performed simultaneously, but it has the disadvantage that all filtration ponds must be shut down in order to maintain the storage tank.

[0074] In this embodiment, the advantages of both conventional configurations can be enjoyed. Specifically, maintenance can be performed independently for each filter tank 2, while the other filter tanks 2 can continue to operate at a steady rate. Furthermore, since the washing water required for backwashing that occurs during steady-rate operation is supplied only by the section 31 corresponding to the filter tank 2 in steady-rate operation, maintenance of the section 31 corresponding to a filter tank 2 in a dormant state does not significantly affect the steady-rate operation of the other filter tanks 2. Therefore, with the filtration system 1 according to this embodiment, flexible planning can be made for the steady-rate operation and maintenance of the filter tanks 2 and storage tank 3, resulting in a higher degree of operational flexibility compared to conventional filtration systems.

[0075] [Other Embodiments] Finally, other embodiments of the filtration apparatus and the method of operating the filtration apparatus according to the present invention will be described. Note that the configurations disclosed in each of the following embodiments can be applied in combination with configurations disclosed in other embodiments, as long as no inconsistencies arise.

[0076] In the above embodiment, a configuration in which six filtration ponds 2 and six compartments 31 are provided was described as an example. However, in the filtration device according to the present invention, both the number of filtration ponds and the number of compartments in the storage tank are arbitrary. Furthermore, although the above is an example in which the number of filtration ponds and the number of compartments in the storage tank are the same, in the present invention the number of filtration ponds and the number of compartments in the storage tank may be different.

[0077] In the above embodiment, a configuration was described as in which the filtration device 1 is equipped with a water supply pump 6, and the filtered water supplied by the water supply pump is stored in a storage tank 3 and used as washing water. However, in the present invention, the presence or absence of a water supply is optional. For example, in a filtration pond of a type called a self-backflow washing type, when backwashing the filter media, filtered water is supplied directly to the secondary side of the filter media from the secondary side region of the filter media (such as the water collection chamber 24 and purified water channel 92 in the above embodiment). When this is applied to the present invention, the storage tank is directly connected to the secondary side region of the filter media, and the storage tank is divided into multiple sections. Comparing the backflow washing tank-equipped type (the above embodiment) with the self-backflow washing type, the backflow washing tank-equipped type has advantages such as the fact that the amount of purified water produced does not decrease significantly even when backwashing is being performed in any of the filtration ponds, because the securing of washing water and the production of purified water can be considered separately.

[0078] In the embodiments described above, examples of communication passages and switches were explained, specifically an example using a combination of a siphon tube 4 and a siphon switch 5, and an example using a combination of a connecting pipe 7 and a valve device 8. However, the configuration of communication passages and switches in the present invention is not limited to these two examples. For example, communication passages and switches can be realized by providing a weir or a corner drop in a partition wall that defines a section.

[0079] In the above embodiment, a configuration in which the filtration pond 2 is a natural equilibrium type filtration pond was described as an example. However, the type of filtration pond is not limited in the present invention.

[0080] With regard to other configurations, the embodiments disclosed herein are illustrative in all respects, and it should be understood that the scope of the present invention is not limited thereto. Those skilled in the art will readily understand that modifications can be made as appropriate without departing from the spirit of the invention. Therefore, other embodiments modified without departing from the spirit of the invention are naturally included within the scope of the present invention. [Industrial applicability]

[0081] This invention can be used in water purification facilities and the like. [Explanation of Symbols]

[0082] 1: Filtration device 2: Filtration pond 21: Tank body 22: Filter media 23:Water collection and distribution equipment 24: Water collection room 3:Storage tank 31: Plot 32: Bulkhead 4: Siphon tube 41: Opening 42:Top 43: Lid 5: Siphon Switch 51: Siphon break valve 52: Body 6: Water supply pump 91: Raw water channel 92: Water purification channel 93: Drainage ditch 94: Inlet siphon device 95: Filtration siphon device 96: Backwash siphon device 97: Garit discharge 98: Backwash drain trough 7:Communication pipe 8: Valve device 81: Valve body 82: Handle

Claims

1. Multiple filtration ponds having filter media, A storage tank having multiple compartments for storing cleaning liquid, and capable of supplying the cleaning liquid to the secondary side of the filter media of each of the filtration ponds, A communication passage that allows fluid communication between at least two of the aforementioned compartments, The system includes a switch that enables or disables fluid communication in the aforementioned communication passage, A filtration system in which the total capacity of the other compartments, excluding one of the compartments, is equal to or greater than the amount of cleaning solution required to clean the filter media in one of the filtration ponds.

2. The filtration apparatus according to claim 1, wherein the number of filtration ponds and the number of compartments are the same, and a plurality of filtration ponds and a plurality of compartments are connected in a one-to-one correspondence.

3. The cleaning solution is filtered water that has passed through the filter material from the primary side to the secondary side. The filtration apparatus according to claim 1, further comprising a water pump for sending the filtered water to the storage tank.

4. The connecting passage is provided across at least two of the compartments and has a siphon tube that induces the movement of the cleaning liquid from one compartment to the other by a siphon effect, The filtration apparatus according to claim 1, wherein the switch includes a valve that allows the siphon tube to be opened to the atmosphere.

5. The aforementioned connecting passage is a pipe that extends across at least two of the aforementioned sections, The filtration apparatus according to claim 1, wherein the switching device includes a valve provided in the pipe.

6. The system further includes a cover that seals the opening of the aforementioned communication passage, The filtration apparatus according to claim 1, wherein the lid is connected to the opening by at least one of the following connection types: flange connection and hinge connection.

7. The filtration apparatus according to any one of claims 1 to 6, wherein the filtration pond is a natural equilibrium type filtration pond.

8. Multiple filtration ponds having filter media, A storage tank having multiple compartments, and capable of supplying cleaning solution to the secondary side of the filter media of each of the filtration ponds, A communication passage that allows fluid communication between at least two of the aforementioned compartments, A method for operating a filtration apparatus comprising a switch that switches whether or not fluid communication is possible in the aforementioned communication passage, A disconnection step of disabling fluid communication in the communication passage that provides fluid communication to at least one of the compartments using the switch, A method for operating a filtration apparatus, comprising a cleaning step of supplying the cleaning liquid to the secondary side of the filter media of at least one of the filtration ponds from a section different from the section in which the communication passage is rendered incapable of fluid communication.

9. The method for operating a filtration apparatus according to claim 8, further comprising a maintenance step of performing maintenance on the section after removing at least partially the cleaning liquid from the section in which the connecting passage has been rendered incapable of fluid communication.

10. A method for operating a filtration apparatus according to claim 9, wherein the cleaning step and the maintenance step are performed simultaneously.

11. The cleaning process includes using the difference in water head between the storage tank and the primary side of the filter media as a driving force to pass the cleaning liquid through the filter media, and the backwashing speed, which is the speed at which the cleaning liquid passes through the filter media, decreases as the liquid level in the storage tank decreases. A method for operating a filtration apparatus according to any one of claims 8 to 10, wherein the communication passage is made non-communicable in the disconnection step so that the degree of reduction in the backwashing speed during the washing step is within a desired range.

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