Compaction state control method of filter material layer

Abstract

To provide a compaction state control method of a filter material layer which changes an index of the end of discharge of compaction water according to the state of a filter material, and thereby forming a filter material layer in a state optimal for filtration treatment.SOLUTION: A filtration device for performing compaction treatment of discharging compaction water stored in a filtration tank before filtration treatment from below, and compacting a filter material layer by a dynamic pressure at the time of discharge includes: previously setting a foundation discharge value as a discrimination index of a compaction state; gradually setting a coefficient corresponding to a duration time of an immediately-preceding filtration treatment step; calculating a coefficient from an immediately-preceding filtration duration time; calculating a reference discharge value by multiplexing the foundation discharge value by the coefficient; discriminating that the compaction state is satisfactory, and finishing the compaction water discharge step, when at least one discharge value of the discharge speed and the discharge flow rate of the compaction water reaches a reference discharge value; and discriminating that the compaction state is not satisfactory, and shifting the step to a compaction water storage step again, and thereby improving filtration treatment efficiency, when the discharge value does not reach the reference discharge 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 controlling the consolidation state of a filter media layer to an optimum state 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 consolidate 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 of grasping the degree of compaction of the filter layer after compaction. In addition, in the conventional method, compaction is performed until a predetermined number of times is reached, so the filter layer continues to be compacted even after it becomes optimal for filtration processing. As the compaction time increases, the operating time of the equipment increases and there are problems such as the inability to move to the filtration processing step early.

[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. 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 compaction state of the filter media layer before filtration.

[0008] The present invention provides a method for controlling 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 settleable granular fiber filter media is stacked, by appropriately changing the standard discharge value of compressed water depending on the state of the filter media layer and terminating the discharge of compressed water when the measured discharge value of compressed water reaches the standard discharge value, thereby forming a filter media layer that is optimal for filtration processing even if the state of the filter media changes. [Means for solving the problem]

[0009] The present invention relates to a filtration device having a filter media layer formed from a settling granular fiber filter media, in which compressed water is stored in a filtration tank before the start of a filtration treatment process, and a consolidation treatment process is performed in which the filter media layer is consolidated by the dynamic pressure when the compressed water is discharged from the bottom of the filtration tank. In this filtration device, a basic discharge value serving as an indicator of the consolidation state is set in advance, a coefficient corresponding to the duration of the immediately preceding filtration treatment process is set in stages, a coefficient is calculated from the duration of the immediately preceding filtration treatment process, and a standard discharge value is calculated by multiplying the basic discharge value by the coefficient. If at least one of the discharge values ​​of the discharge rate or discharge flow rate of the compressed water, which change as the consolidation progresses, reaches the standard discharge value, the consolidation state of the filter media layer is determined to be good, the compressed water discharge process is terminated, and the process proceeds to the filtration treatment process. If the discharge value does not reach the standard discharge value, the consolidation state of the filter media layer is determined to be not good, 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 always form a filter media layer that is optimal for filtration treatment, even if the compression state changes due to changes in the shape or elasticity of the filter media. Effect of the Invention

[0010] In the present invention, the condition of the filter media is judged from the duration of filtration, the standard discharge value during consolidation of the filter media layer is appropriately changed, and the discharge of the consolidated water is stopped when the discharge value of the consolidated water reaches the standard discharge value, so that a uniform filter media layer can be formed at all times even if the condition of the filter media changes. Since the filtration process can be started in this state, stable filtration can be performed from the beginning of operation, and a treated liquid with stable water quality can be obtained until the end of filtration. Since the consolidation time can also be shortened, the operating time of the entire facility can be reduced, and power consumption can be reduced. [Brief description of the drawings]

[0011] [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

[0012] 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.

[0013] 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.

[0014] 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 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

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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 efficiently removed from the beginning of the filtration process, and a clear treated liquid can be obtained until the end of the filtration process.

[0022] In this embodiment, in order to make the filter layer 11 in an optimal consolidation state 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, the consolidation time can be shortened and the filtration efficiency can be increased.

[0023] 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.

[0024] 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.

[0025] The method for controlling the consolidation state of the filter media layer 11 in this embodiment will be described in detail below. <Pre-settings> A basic discharge value serving as an index for discriminating the consolidation state of the filter media layer 11 is set in advance, and a coefficient corresponding to the duration of the immediately preceding filtration process is set in stages. The basic discharge value is an index representing the resistance to passage through the filter media that changes with changes in the degree of consolidation of the filter media layer 11 when the consolidated water is discharged. In this embodiment, at least one of the discharge speed or discharge flow rate of the consolidated water, whose value decreases with the progress of consolidation, is used. The basic discharge value is set with a predetermined range. Below, the case where the discharge speed is used will be described in detail, but the same applies when the discharge flow rate is used.

[0026] The coefficient is changed appropriately according to the duration of the immediately preceding filtration process. The duration of the filtration process changes because the passing efficiency of the treated liquid changes with the change in the shape and elasticity of the filter medium 10. Therefore, the coefficient is set in stages according to the filtration duration.

[0027] <Filtration process> In the filtration process, the filtration duration is measured using a timer or the like, and a coefficient is calculated based on the measured filtration duration. The calculated coefficient is then multiplied by the basic discharge value to calculate the standard discharge value. For example, if the measured filtration duration is shorter than a predetermined time, it is determined that the elasticity of the filter medium 10 is weakened and the filter medium layer 11 can be easily consolidated, and the basic discharge value is multiplied by a small coefficient to lower the standard discharge value. On the other hand, if the filtration duration is longer than a predetermined time, it is determined that the elasticity of the filter medium 10 is large and the filter medium layer 11 is difficult to consolidate, and the basic discharge value is multiplied by a large coefficient to raise the standard discharge value. Since the state of the filter medium layer 11 can be grasped based on the filtration duration, the coefficient is calculated appropriately according to the filtration duration, and the standard discharge value to be used in the next and subsequent consolidation processes can be calculated and used as a guide for the end of discharge of the consolidated water. The predetermined filtration duration is set with a certain margin.

[0028] <Consolidation process> In the consolidation process, the discharge of the consolidated water is terminated when the discharge value of the consolidated water, which is continuously measured, reaches the standard discharge value calculated in the immediately preceding filtration process. Specifically, when the discharge value reaches the standard discharge value, it is determined that the consolidation 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 terminate the discharge of the consolidated water. When the measured value does not reach the standard discharge value, it is determined that the consolidation 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 predetermined water level has been reached, the process transitions again to the consolidated water storage process.

[0029] During the consolidation process, which is repeated multiple times, for example, in the first consolidation process, 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.

[0030] 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 this effect. Then, when the measured value reaches the standard discharge value, it is determined that the consolidation state of the filter layer 11 is good, the discharge of the consolidated water is stopped, and the process proceeds to the filtration process.

[0031] In this embodiment, the standard discharge value is changed based on the filtration duration during the filtration process, and the consolidated water discharge process is terminated, so that the filter layer 11 can always be formed with a uniform degree of compaction even if the state of the filter medium 10 changes through each process. This makes it possible to stably obtain clear treated liquid in the filtration process. It is also possible to prevent the filter layer 11 from clogging in a short time, which makes it possible to shorten the time required to clean the filter medium. Note that, although the consolidation process is repeated multiple times in this embodiment, if the initial discharge value of the consolidated water discharge process has already reached the standard discharge value, the process moves to the filtration process without repeating the process multiple times.

[0032] The discharge value is measured using a flow meter installed in the discharge pipe 8, but is not limited to this location as long as it can measure the discharge speed of the consolidated water. In addition, a measuring device 12 such as a water level gauge, pressure gauge, or imager (not shown) may be installed in the filtration tank 2 to measure the fluctuation of the liquid level, and the consolidation state may be determined using a flow velocity value calculated from the movement time and movement distance of the liquid level. Measurement may be performed using the flow rate instead of the flow velocity as the discharge value.

[0033] If the measured value by the flowmeter 13 does not reach the standard discharge value, it is determined that the consolidation state of the filter layer 11 is not good, and the consolidation process is continued. After the predetermined water level is reached, the process moves to the consolidation water storage process again. However, instead of the predetermined water level, another indicator such as a predetermined time may be used as an indicator of the end of the consolidation water discharge, or two or more indicators may be combined.

[0034] 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.

[0035] In this embodiment, the state of the filter layer 11 is grasped using the filtration duration during the filtration treatment step as an index, but any other index may be used as long as it is an index that can grasp the consolidation state of the filter layer 11.

[0036] 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.

[0037] 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.

[0038] 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]

[0039] The present invention changes the indicator for the end of discharge of consolidated water according to the condition of the filter media, and since it is possible to form a filter media layer that is optimal for filtration even if the condition of the filter media changes due to long-term use, it is possible to perform stable filtration from the beginning of operation, and to obtain treated water of stable water quality until the end of filtration. As the consolidation time is shortened, the operating time of the equipment can be reduced, thereby realizing energy savings. In addition, since various liquids can be treated, such as seawater, drinking water, industrial water, and sewage, this technology can be applied in all fields. [Explanation of symbols]

[0040] 1. Filtration equipment 2. Filtration tank 10 Filter media 11 Filter layer

Claims

[Claim 1] In a filtration apparatus (1) having a filter layer (11) formed of a sedimentary granular fiber filter medium, compressed water is stored in a filtration tank (2) before the start of a filtration treatment process, and the filter layer (11) is compressed by dynamic pressure when the compressed water is discharged from the bottom of the filtration tank (2). A basic discharge value that serves as an index for determining the state of compaction is set in advance, and A coefficient corresponding to the duration of the immediately preceding filtration process is set in stages; Calculate a coefficient from the duration of the immediately preceding filtration process; The coefficient is multiplied by the basic emission value to calculate the standard emission value; When at least one of the discharge rates or discharge flow rates of the consolidated water, which change with the progress of consolidation, reaches a standard discharge value, it is determined that the consolidation state of the filter layer (11) is good, and the consolidated water discharge process is terminated and a filtration treatment process is started. If the discharge value does not reach the standard discharge 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 controlling the compaction state of a filter medium layer.

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