Compaction state discrimination method of filter material layer

Abstract

To provide a compaction state discrimination method of a filter material layer which can discriminate whether a compaction state of a filter material layer formed of a settleable granular fiber filter material is satisfactory in the front state of a filtration treatment step.SOLUTION: A compaction state discrimination method of a filter material layer includes: previously setting a reference compaction value as a discrimination index of a compaction state of a filter material layer; performing a compaction water storage step of supplying compaction water up to a predetermined height in a filtration tank; then performing a compaction water discharge step of discharging the compaction water from the lower part of the filtration tank and compacting the filter material layer by a dynamic pressure at the time of discharge; comparing at least one or more measured values among the discharge speed of the compaction water, the discharge amount of the compaction water and the height of the filter material layer which change accompanying the progress of the compaction in the compaction water discharge step with the reference compaction value; discriminating that the compaction state of the filter material layer is satisfactory, finishing the compaction water discharge step and shifting the step to a filtration treatment step, when the measured value reaches the reference compaction value; and discriminating that the compaction state of the filter material layer is not satisfactory, and shifting the step to the compaction water storage step of supplying the compaction water to the filtration tank again, and thereby improving filtration treatment efficiency, when the measured value does not reach the reference compaction value.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a filtration device in which granular fiber filter media are layered, and to a method for determining the consolidation state of a filter media layer, which is capable of determining whether the consolidation state of the filter media layer is good before a filtration treatment process. [Background technology]

[0002] Conventionally, a filtration method is known in which the liquid to be treated is fed from the top of a filtration device filled with sedimentary granular fiber filter media to remove suspended solids from the liquid. In this filtration method, if the porosity of the filter media layer formed in the filtration tank is high, the liquid to be treated easily passes through the filter media, and the suspended solids in the liquid to be treated are not sufficiently captured by the filter media layer. Therefore, it is necessary to compress the filter media layer in the previous stage of the filtration process to reduce the porosity in the filter media layer and increase the filtration capacity.

[0003] FIG. 3 of Patent Document 1 discloses a technology in which compressed water is stored up to a predetermined water level in a filtration tank in which a filter media layer is formed, and then a drain pipe connected to the bottom of the filtration tank is opened, so that the filter media layer is compressed by the water pressure of the drained compressed water.

[0004] Patent Document 2 discloses a technology in which suspended solids adhere to the filter media as the filtration process continues, causing an increase in filtration resistance and a decrease in the amount of filtered water. The technology detects this increase and decreases using a pressure gauge installed in the raw water supply pipe and a flow meter installed in the filtered water discharge pipe, and then starts backwashing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2022-147988 A [Patent Document 2] Special Publication No. 2004-524964 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventionally, in order to increase the degree of compaction of the filter layer formed in the filtration tank, the filter layer is compacted by the method described in Patent Document 1, but there was no means for grasping the degree of compaction of the filter layer after compaction. In addition, in the conventional method, the compaction is performed until a predetermined number of times is reached, so the filter layer continues to be compacted even after the filter layer becomes optimal for filtration processing. As the compaction time increases, the operating time of the equipment increases and it is not possible to move to the filtration processing step early. Furthermore, in the filter layer formed by the newly replaced new filter layer and the filter layer formed by the filter layer washed after a long period of use, the compressed state changes due to the change in the shape and elasticity of the filter layer, so that the filter layer optimal for filtration processing could not be formed by repeating the compaction a predetermined number of times.

[0007] Patent Document 2 discloses a technique for detecting an increase in filtration resistance in a filtration device or a decrease in the amount of filtrate discharged using a pressure gauge or a flow meter, but does not specifically state or suggest a detection method. In addition, the technique detects an increase in filtration resistance or a decrease in the amount of filtrate and switches from filtration to cleaning, but does not aim to use the detected values ​​to detect the consolidation state of the filter media layer before filtration.

[0008] The present invention provides a method for determining the consolidation state of a filter media layer in a filtration device that removes suspended matter in the treated liquid by supplying the treated liquid from above a filtration tank in which sedimentary granular fiber filter media is stacked, which can improve the efficiency of the filtration process by starting the filtration process after it is determined that the filter media layer is in an optimal consolidation state during the consolidation process of the filter media layer. [Means for solving the problem]

[0009] A standard consolidation value is set in advance as an indicator for determining the consolidation state of a filter layer formed from a settling granular fiber filter medium. A compressed water storage process is then performed in which compressed water is supplied up to a predetermined height in the filtration tank. The compressed water is then discharged from the bottom of the filtration tank and the filter layer is consolidate by the dynamic pressure at the time of discharge. During the compressed water discharge process, at least one of the measured values ​​of the discharge rate of the compressed water, the discharge amount of the compressed water, and the height of the filter layer, which change as the consolidation progresses, is compared with the standard consolidation value. If the measured value reaches the standard consolidation value, the consolidation state of the filter layer is determined to be good, the compressed water discharge process is terminated, and the process proceeds to the filtration process. If the measured value does not reach the standard consolidation value, the consolidation state of the filter layer is determined to be bad, and the process proceeds to the compressed water storage process in which compressed water is again supplied to the filtration tank. This makes it possible to efficiently remove suspended solids from the early stages of the filtration process.

[0010] The consolidated water discharge process is completed with the entire filter layer immersed, so that air does not flow into the gaps between the filter media during the consolidated water discharge process, ensuring a water channel between the filter media and allowing the treated liquid to pass efficiently between the filter media in the filtration process. Effect of the Invention

[0011] In the present invention, the consolidation state of the filter layer is measured during the consolidation process, and the consolidation process is terminated when it is determined that the consolidation state is optimal for filtration, so that the process can be started early on in the filtration process. The consolidation time can also be shortened, which reduces the operating time of the equipment and leads to reduced power consumption. In addition, since the filtration process can be started with the filter layer in the optimal state for filtration, stable filtration can be performed from the beginning of operation, and treated liquid with stable water quality can be obtained until the end of filtration. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a schematic diagram of a filtration process according to the present invention at start-up. [Diagram 2] FIG. 2 is a schematic diagram of the compaction water storage process. [Diagram 3] FIG. 13 is a schematic diagram of the compaction water discharge process. [Figure 4]FIG. [Diagram 5] FIG. 13 is a schematic diagram of the filter media cleaning process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] FIG. 1 is a schematic diagram of a filtration process according to the present invention at the start-up of operation. The filtration device 1 has a cylindrical filtration tank 2 installed upright, with a supply port 3 provided at the top of the filtration tank 2 and a discharge port 4 provided at the bottom. A supply pipe 6 fitted with a supply valve 5 is connected to the supply port 3, allowing the liquid to be treated to be supplied from above. Meanwhile, a discharge pipe 8 fitted with a discharge valve 7 is connected to the discharge port 4, allowing the treated liquid to be discharged from below.

[0014] A screen 9A for preventing the filter media from leaking out is disposed in the filtration tank 2 at a predetermined height from the bottom of the filtration tank 2, and the filter media 10 is filled on the top of the screen 9A to form a filter media layer 11. The filter media 10 is a sedimentary granular fiber filter media, and its shape is not limited to a spherical or columnar shape. A screen 9B for preventing the filter media from leaking out is also provided above the filtration tank 2. The numerous openings (not shown) formed in the screens 9A and 9B have a diameter that prevents the filter media 10 from leaking out, and the opening shape is determined appropriately. The filtration tank 2 is formed in a tapered shape with the area gradually decreasing at the bottom, but this can be changed as appropriate according to the design requirements.

[0015] The supply pipe 6 and discharge pipe 8 for the liquid to be treated, which are connected to the filtration tank 2, are also used as supply and discharge lines for compressed water, and the compressed water can be stored and discharged by opening and closing the supply valve 5 and discharge valve 7. In this embodiment, in order to start the filtration process after the filter layer 11 is in an optimally compressed state, a flow meter 13 (measuring device 12) is installed in the discharge pipe 8, and the compressed state of the filter layer 11 can be grasped based on the measured flow velocity value. Although the supply and discharge lines for compressed water are used in combination with the supply and discharge lines for the liquid to be treated, they may be installed separately, and suitable modifications can be made. EXAMPLES

[0016] The filtration method according to this embodiment will be described in detail below with reference to FIGS. As shown in FIG. 1, new filter medium 10 is added to the filtration tank 2, or after the filtration process and the filter medium cleaning process, the water in the filtration tank 2 is drained and the filter medium 10 is filled on the screen 9A.

[0017] The filter layer 11 is in a state of natural settling, and the filter media 10 is not sufficiently consolidated, so that the gaps between the filter media 10, 10 are large. If the liquid to be treated is supplied from above in this state, the suspended matter contained in the liquid to be treated will flow downward through the gaps together with the liquid to be treated. In particular, the capture rate of suspended matter at the start of the filtration process is reduced, so that the suspended matter cannot be removed efficiently in a short time.

[0018] In this way, the filter media layer 11 is not sufficiently consolidated by natural settling alone, and the liquid to be treated passes through the filter media layer 11 with a low degree of compaction, so a consolidation process is carried out prior to the filtration process, in which a large number of filter media 10 packed in the filtration tank 2 are consolidated to form a filter media layer 11 with a high degree of compaction. The consolidation process comprises a consolidated water storage process in Fig. 2 and a consolidated water discharge process in Fig. 3, which will be described in detail below.

[0019] Figure 2 is a schematic diagram of the consolidation water storage process. In the consolidated water storage step, the consolidated water is stored in the filtration tank 2. The consolidated water is supplied into the filtration tank 2 from the supply pipe 6, and the supply is stopped after the water reaches a predetermined water level set in advance. As will be described later, in this embodiment, the consolidation treatment step (consolidated water storage step and consolidated water discharge step) is performed multiple times, and when the consolidated water is stored again, the predetermined water level is the same.

[0020] An air vent valve 18 is provided above the filtration tank 2, and when compressed water is stored in the filtration tank 2, the air vent valve 18 and the supply valve 5 are opened and the discharge valve 7 is closed, so that the liquid level of the stored compressed water gradually rises. The air vent valve 18 is opened to discharge air to the outside, and the pressure in the filtration tank 2 is set to a predetermined value, so that the water level in the filtration tank 2 can be set to a predetermined level. A large number of filter media 10 are immersed in the stored compressed water. In this embodiment, the liquid to be treated that is to be filtered is used as the compressed water, but tap water, industrial water, treated liquid after filtration, etc. may also be used, and modifications can be made according to the conditions.

[0021] Figure 3 is a schematic diagram of the compaction water discharge process. In the consolidated water discharge process, the stored consolidated water is discharged, and the dynamic pressure generated during discharge compresses the filter media 10 to form a filter media layer 11. After the consolidated water storage process in Fig. 2 is completed, the supply valve 5 is closed and the discharge valve 7 is opened to discharge the consolidated water downwards all at once, so that a large number of filter media 10 are consolidated onto the screen 9A by the dynamic pressure of the consolidated water flowing toward the bottom of the filtration tank 2. The air vent valve 18 is left open, allowing air to be taken in from the outside.

[0022] The filter media 10 is compressed under the dynamic pressure of the compacted water, so that the gaps between the filter media 10, 10 become smaller, and a filter media layer 11 with a sufficient degree of compaction is formed. The height of the filter media layer 11 formed at this time is lower than that in the case of natural settling described in Fig. 2. By starting the filtration process described below when the filter media layer 11 has reached an appropriate height, suspended solids can be properly removed from the beginning of the filtration process, and a clear treated liquid can be obtained until the end of the filtration process.

[0023] In this embodiment, in order to make the filter layer 11 in a consolidation state suitable for filtration, the consolidation process (consolidated water storage process and consolidated water discharge process) is repeated multiple times, and when the consolidation state of the filter layer 11 measured during the consolidated water discharge process is determined to be good, the consolidation process is terminated and the process proceeds to the filtration process. By switching to the filtration process at an appropriate timing, it is possible to shorten the consolidation time and increase the efficiency of the filtration process.

[0024] A method for determining the consolidation state of the filter media layer 11 in this embodiment will be described in detail below. <Pre-settings> A standard consolidation value is set in advance as an index for determining the consolidation state of the filter layer 11 formed of a settling granular fiber filter medium. The standard consolidation value is an index that indicates the resistance to passage through the filter medium that changes with the change in the degree of consolidation of the filter layer 11 when the consolidated water is discharged. In this embodiment, the discharge speed of the consolidated water, which decreases with the progress of consolidation, is used. The discharge speed is set to have a predetermined range.

[0025] <Method of determining consolidation state> The discharge rate of the consolidated water is high at the beginning of consolidation when the porosity of the filter media layer 11 is high and the resistance to passing through the filter media is low. On the other hand, it is low when the porosity of the filter media layer 11 decreases after consolidation progresses with time and the resistance to passing through the filter media increases. In other words, when the discharge rate drops to a predetermined value from the start of measurement, it can be determined that the porosity is low and the filter media layer 11 is in an optimal state for filtration processing.

[0026] In the consolidation process shown in Fig. 2 and Fig. 3, after the consolidated water is stored to a predetermined height in the filtration tank 2, the discharge valve 7 is opened to start discharging the consolidated water from the bottom of the filtration tank 2. The discharge speed of the consolidated water is continuously measured using a flow meter 13 (measuring device 12) provided in the discharge pipe 8. The speed measurement may start at the start of the consolidated water discharge process or before that. At this time, if the measured discharge speed of the consolidated water reaches a predetermined reference speed (reference consolidation value), it is determined that the consolidated state of the filter layer 11 is good (the porosity is low and the state is optimal for filtration), and the discharge valve 7 is closed to end the discharge of the consolidated water. If the measured value does not reach the reference speed, it is determined that the consolidated state of the filter layer 11 is not good (the porosity is high and the state is not optimal for filtration), and the discharge of the consolidated water is continued. In this case, the discharge of the consolidated water continues until the water level in the filtration tank 2 reaches a predetermined value, and when it is detected that the water level has reached the predetermined value, the process transitions again to the consolidated water storage step.

[0027] During the first consolidation process, for example, of the multiple consolidation processes, many filter media 10 are immersed in the filtration tank 2 and are in an unconsolidated state at the beginning of the discharge of the consolidated water. At this time, the porosity of the filter media layer 11 is high and the resistance to the passage of the consolidated water is small, so the consolidated water supplied from above is discharged downward with great force. Therefore, the discharge speed of the consolidated water from the discharge pipe 8 is high.

[0028] On the other hand, by repeating the consolidation process multiple times, the porosity of the filter layer 11 decreases due to the dynamic pressure of the consolidated water. As a result, the resistance to passage through the filter layer 11 gradually increases, and the discharge speed of the consolidated water discharged from the discharge pipe 8 decreases in inverse proportion to the effect of the increase in resistance. Then, when the measured value reaches the reference speed, it is determined that the consolidation state of the filter layer 11 is good, the discharge of the consolidated water is terminated, and the process proceeds to the filtration process. Note that, when the measured value measured by the flowmeter 13 does not reach the reference speed, it is determined that the consolidation state of the filter layer 11 is not good, the consolidation process is continued, and after the predetermined water level is reached, the process proceeds again to the consolidated water storage process. However, instead of the predetermined water level, other indicators such as a predetermined time may be used as an indicator of the end of the discharge of the consolidated water, or two or more indicators may be combined.

[0029] In this embodiment, the consolidated water is set to be always located above the filter layer 11 during the consolidated water discharge process, and the entire filter layer 11 is always immersed from the start to the end of the discharge of the consolidated water to prevent air from flowing into the filter layer 11. When the discharge of the consolidated water is started, the liquid level in the filtration tank 2 drops, but if the filter layer 11 is not immersed due to the drop in the liquid level, air flowing in from the outside of the filtration tank 2 enters the inside of the filter layer 11. If the filtration process is started in this state, the water passing efficiency of the treated liquid passing between the filter media decreases and the filtration accuracy decreases. In addition, at the start of the filtration process, a large amount of air held between the filter media 10, 10 rises toward the top of the filtration tank 2. In order to prevent the filtration process efficiency from decreasing due to these factors, in this embodiment, the filter layer 11 is always immersed. The consolidated water in which the filter layer 11 is immersed is discharged from the bottom of the filtration tank 2 together with the treated liquid during the filtration process described below.

[0030] In this embodiment, the flowmeter 13 is installed in the discharge pipe 8, but the location is not limited to this as long as it can measure the discharge rate of the consolidated water. In addition, although the flow rate is measured using the flowmeter 13, the flow rate can also be calculated. Therefore, by utilizing the phenomenon in which the amount of consolidated water decreases due to an increase in resistance to passage through the filter medium as the consolidation progresses, the discharge amount may be used as a measured value instead of the discharge rate.

[0031] As described above, the flow rate is measured by the flowmeter 13, but it is also possible to provide measuring equipment 12 such as a water level gauge, pressure gauge, or imaging device (not shown) in the filtration tank 2 to measure fluctuations in the liquid level, and to determine the consolidation state using the flow rate value calculated from the time and distance the liquid level moves.

[0032] Furthermore, instead of the flow velocity value or the flow rate value, the height of the filter layer 11 may be used as an index for determining the consolidation state. Since the height of the filter layer 11 gradually decreases as consolidation progresses, by measuring this, it is possible to grasp whether the filter layer 11 has changed to an optimal consolidation state for filtration processing. Specifically, a reference height is set in advance, and when the measured height of the filter layer 11 decreases to the reference height, it is determined that the consolidation state is good. For example, the height of the filter layer 11 may be visually observed from the outside by installing an inspection window (not shown) in the filtration tank 2, or an imaging device (not shown) not shown in the figure is installed outside the filtration tank 2 and continuously photographs the filter layer 11 in the filtration tank 2 through the inspection window to automatically detect the change in the height of the filter layer 11. Note that the method is not limited to this as long as it is a method for measuring at least one of the discharge speed, discharge flow rate, and height of the filter layer 11 of the consolidated water, and is capable of detecting the consolidation state of the filter layer 11.

[0033] FIG. 4 is a schematic diagram of the filtration process. In the filtration process, the liquid to be treated is supplied into the filtration tank 2 for filtration. The liquid to be treated is supplied into the filtration tank 2 from the supply pipe 6 and passed through the filter media layer 11 filled in the filtration tank 2. At this time, the supply valve 5 and the discharge valve 7 are open, and the liquid to be treated supplied into the filtration tank 2 passes through the filter media layer 11 and is filtered, and then discharged from the discharge pipe 8 to the outside of the system as a treated liquid. Suspended matter contained in the liquid to be treated adheres to the inside or surface of the filter media 10 as it passes through the filter media layer 11 and is captured. If the filter media layer 11 becomes clogged during a long filtration process, the filter media is cleaned.

[0034] During the filtration process, the air vent valve 18 installed above the filtration tank 2 is kept closed to prevent water from leaking out during the filtration process. In addition, an automatic air vent valve (not shown) is also installed above the filtration tank 2, so that if air accumulates above the filtration tank 2 during the filtration process, the air can be released to the outside. This allows the water level of the treated liquid to rise above the filtration tank 2, filling the tank with water.

[0035] FIG. 5 is a schematic diagram of the filter media cleaning process. In the filter media cleaning process, cleaning liquid is supplied from the discharge pipe 8 and stored up to the top of the filtration tank 2, and then cleaning air is sprayed from the air washing pipe 15 below the filtration tank 2 to agitate and clean the filter media 10. The filter media 10 migrates while repeatedly rotating and colliding with the cleaning air continuously sprayed from below, so that the adhering suspended solids are peeled off. The cleaning waste liquid after cleaning the filter media is discharged to the outside from the treated liquid supply pipe 6. At this time, the supply valve 5 interposed in the treated liquid supply pipe 6 is in an open state. In this embodiment, the supply line for the treated liquid is also used as the discharge line for the cleaning waste liquid, but a separate cleaning liquid discharge line may be provided.

[0036] In addition, since a screen 9B for preventing the filter medium from flowing out is provided above the filtration tank 2, the filter medium 10 does not flow out of the filtration tank during cleaning. In addition, the type of cleaning liquid and the supply and discharge positions are not limited.

[0037] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the present invention. [Industrial Applicability]

[0038] The present invention can start filtration after optimizing the consolidation state of the filter media layer for filtration, and can perform stable filtration from the beginning of operation, making it possible to obtain treated water with stable water quality until the end of filtration. The shortened consolidation time can reduce the operating time of the equipment, thereby realizing energy savings. In addition, the technology can be applied in a variety of fields, as it can treat various liquids, such as seawater, drinking water, industrial water, and sewage. [Explanation of symbols]

[0039] 2. Filtration tank 11 Filter layer

Claims

1. A reference consolidation value is set in advance as an index for discriminating the consolidation state of the filter layer (11) formed of a settling granular fiber filter material, After carrying out a compressed water storage process in which compressed water is supplied to a predetermined height in the filtration tank (2), A consolidated water discharge step is carried out in which the consolidated water is discharged from the bottom of the filtration tank (2) and the filter layer (11) is consolidated by the dynamic pressure at the time of discharge. During the compacted water discharge step, the discharge rate of the compacted water, the discharge amount of the compacted water, and the height of the filter layer (11) change with the progress of the compaction. Comparing at least one of the measurements to a reference compaction value; When the measured value reaches the standard consolidation value, it is determined that the consolidation state of the filter layer (11) is good, and the consolidation water discharge process is terminated and the process proceeds to the filtration process. If the measured value does not reach the standard consolidation value, it is determined that the consolidation state of the filter layer (11) is not good, and the process proceeds to a consolidation water storage process in which consolidation water is supplied to the filtration tank (2) again. A method for determining the consolidation state of a filter medium layer.

2. The step of discharging the compressed water is completed when the entire filter layer (11) is immersed. The method for determining the consolidation state of a filter medium layer according to claim 1 .

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