Method for determining the compaction state of the filter media 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 laminated, and to a method for determining the consolidation state of a filter media layer that can determine whether the consolidation state of the filter media layer before the filtration process is good.

Background Art

[0002] Conventionally, a filtration method is known in which a liquid to be treated is supplied from the upper part of a filtration device filled with sedimentable granular fiber filter media to remove suspended substances in the liquid to be treated. In this filtration method, when the porosity of the filter media layer formed in the filtration tank is high, the liquid to be treated easily passes between the filter media, and the suspended substances in the liquid to be treated are not sufficiently captured by the filter media layer. Therefore, it has been 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 enhance the filtration capacity.

[0003] In FIG. 3 of Patent Document 1, after consolidating water is stored up to a predetermined water level in a filtration tank in which a filter media layer is formed, by opening a drain pipe connected to the lower part of the filtration tank, the filter media layer is consolidated by receiving the water pressure of the consolidating water that is drained. A technique is disclosed.

[0004] In Patent Document 2, as the filtration process continues, suspended substances adhere to the filter media, and an increase in filtration resistance and a decrease in the amount of filtered water caused thereby are detected by a pressure gauge provided in the raw water supply pipe and a flow meter provided in the filtered water discharge pipe, and backwashing is started. A technique is disclosed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] ​Conventionally, in order to increase the pressure density of the filter media layer formed in the filtration tank, the filter media layer is compacted using the method described in Patent Document 1. However, there was no way to determine how compacted the filter media layer was after compaction. Furthermore, in the conventional method, compaction is carried out until a predetermined number of times is reached, so the filter media layer continues to be compacted even after it has reached an optimal state for filtration. This resulted in problems such as longer operating times for the equipment due to the prolonged compaction time, and the inability to proceed to the filtration process early. Moreover, because the compression state changes due to changes in the shape and elasticity of the filter media between a filter media layer formed with newly replaced filter media and a filter media layer formed with filter media that has been washed after long-term use, it was not possible to form a filter media layer that was optimal for filtration using a method that repeats compaction for a predetermined number of times.

[0007] Patent Document 2 discloses a technique for detecting an increase in filtration resistance or a decrease in the amount of filtered water discharged within a filtration device using a pressure gauge and a flow meter, but it does not provide specific descriptions or suggestions regarding the detection method. Furthermore, it is intended to switch from filtration to washing treatment by detecting an increase in filtration resistance or a decrease in the amount of filtered water, and is not intended to detect the compaction state of the filter media layer before filtration treatment using the detected values.

[0008] The present invention provides a method for determining the compaction state of a filter media layer in a filtration apparatus that removes suspended solids from a liquid to be treated by supplying the liquid to be treated from above a filtration tank having a stack of settling granular fiber filter media. This method improves filtration efficiency by determining that the filter media layer is in an optimal compaction state during the compaction treatment of the filter media layer before starting the filtration process. [Means for solving the problem]

[0009] A reference consolidation value is set as an indicator for determining the consolidation state of the filter media layer, which is formed in advance from a settling granular fiber filter media. After performing a consolidation water storage step in which consolidated water is supplied to a predetermined height in the filtration tank, a consolidation water discharge step is performed in which the consolidated water is discharged from the bottom of the filtration tank and the filter media layer is consolidated by the dynamic pressure at the time of discharge. During the consolidation water discharge step, at least one of the measured values ​​among the discharge rate of consolidated water, the amount of consolidated water discharged, and the height of the filter media layer, which change as consolidation progresses, is compared with the reference consolidation value. If the measured value reaches the reference consolidation value, it is determined that the consolidation state of the filter media layer is good, and the consolidation water discharge step is terminated and the process moves to the filtration process. If the measured value does not reach the reference consolidation value, it is determined that the consolidation state of the filter media layer is not good, and the process moves to the consolidation water storage step in which consolidated water is supplied to the filtration tank again. This allows for efficient removal of suspended solids from the beginning of the filtration process.

[0010] The aforementioned consolidated water discharge process is completed with the entire filter media layer immersed, so that no air enters the gaps between the filter media during the consolidated water discharge process. This ensures that water channels are maintained between the filter media, allowing the liquid to be treated to pass efficiently through them during the filtration process. [Effects of the Invention]

[0011] This invention measures the compaction state of the filter media layer during the compaction process and terminates the compaction process when it is determined that the compaction state is optimal for filtration, thus enabling an earlier transition to the filtration process. This also shortens the compaction time, reducing the operating time of the equipment and leading to a reduction in power consumption. Furthermore, since the filtration process can be started with the filter media layer in an optimal 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. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram of the startup phase of the filtration process according to the present invention. [Figure 2] Similarly, this is a schematic diagram of the consolidation water storage process. [Figure 3] Similarly, this is a schematic diagram of the consolidation water discharge process. [Figure 4]Similarly, this is a schematic diagram of the filtration process. [Figure 5] Similarly, this is a schematic diagram of the filter media cleaning process. [Modes for carrying out the invention]

[0013] Figure 1 is a schematic diagram of the filtration process according to the present invention during startup. The filtration device 1 has a cylindrical filtration tank 2 erected upright, with a supply port 3 at the top of the filtration tank 2 and a discharge port 4 at the bottom. A supply pipe 6 with a supply valve 5 interposed is connected to the supply port 3, allowing the liquid to be treated to be supplied from above. On the other hand, a discharge pipe 8 with a discharge valve 7 interposed is connected to the discharge port 4, allowing the treated liquid to be discharged from below.

[0014] Inside the filtration tank 2, a screen 9A is installed at a predetermined height from the bottom of the filtration tank 2 to prevent the filter media from flowing out. The filter media 10 is filled above the screen 9A to form a filter media layer 11. The filter media 10 is a settling granular fiber filter media, and its shape is not limited to spherical or columnar shapes. In addition, a screen 9B is provided above the filtration tank 2 to prevent the filter media from flowing out. The numerous openings (not shown) formed in screens 9A and 9B are of a diameter that prevents the filter media 10 from flowing out, and the shape of the openings is determined as appropriate. The filtration tank 2 is formed in a tapered shape with a gradually decreasing area 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, connected to the filtration tank 2, are also used as supply and discharge lines for consolidated water. Consolidated water can be stored and discharged by opening and closing the supply valve 5 and discharge valve 7. In this embodiment, a flow meter 13 (measuring instrument 12) is installed in the discharge pipe 8 to ensure the filter media layer 11 is in an optimally consolidated state before starting the filtration process. The configuration allows the consolidation state of the filter media layer 11 to be determined based on the measured flow velocity. Although the supply and discharge lines for consolidated water are used in conjunction with the supply and discharge lines for the liquid to be treated, they may be provided separately, and modifications can be made as appropriate. [Examples]

[0016] Hereinafter, the filtration method in this embodiment will be described in detail based on FIGS. 1 to 5. As shown in FIG. 1, new filter media 10 are newly charged into the filtration tank 2, or after performing a filter media washing process after the filtration process, the water in the filtration tank 2 is discharged and the filter media 10 are filled on the screen 9A.

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

[0018] Thus, only by natural sedimentation, the filter media layer 11 is not sufficiently consolidated, and the liquid to be treated passes through the filter media layer 11 with a low degree of consolidation. Therefore, a consolidation process is performed to consolidate a large number of filter media 10 filled in the filtration tank 2 in the previous stage of the filtration process to form a filter media layer 11 with a high degree of consolidation. The consolidation process consists of a consolidation water storage process shown in FIG. 2 and a consolidation water discharge process shown in FIG. 3, which will be described in detail below.

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

[0020] An air vent valve 18 is provided above the filtration tank 2. When storing consolidated water in the filtration tank 2, the air vent valve 18 and the supply valve 5 are opened while the discharge valve 7 is closed, causing the liquid level of the stored consolidated water to gradually rise. By opening the air vent valve 18 to discharge air to the outside and setting the pressure inside the filtration tank 2 to a predetermined value, the water level inside the filtration tank 2 can be set to a predetermined level. The stored consolidated water then immerses the numerous filter media 10. In this embodiment, the liquid to be filtered is used as the consolidated water, but tap water, industrial water, or the treated liquid after filtration may also be used, and the configuration can be modified as appropriate depending on the conditions.

[0021] Figure 3 is a schematic diagram of the consolidation 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 shown in Figure 2 is completed, the supply valve 5 is closed and the discharge valve 7 is opened to discharge the consolidated water downwards in one go. This causes a large number of filter media 10 to be compacted onto the screen 9A by the dynamic pressure of the consolidated water moving towards the bottom of the filtration tank 2. The air vent valve 18 is left open to allow air to be taken in from the outside.

[0022] As the filter media 10 is compressed by the dynamic pressure of the consolidated water, the gaps between the filter media 10, 10 become smaller, and a filter media layer 11 with sufficient pressure density is formed. The height of the filter media layer 11 formed at this time is lower than that of the natural sedimentation described in Figure 2. By starting the filtration process described later 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 bring the filter media layer 11 to a suitable compacted state for filtration, the compaction process (compacted water storage process and compacted water discharge process) is repeated multiple times. When the compaction state of the filter media layer 11, measured during the compacted water discharge process, is determined to be good, the compaction process is terminated and the process moves to the filtration process. By switching to the filtration process at the appropriate timing, the compaction time can be shortened and the filtration efficiency can be increased.

[0024] The method for determining the compaction state of the filter media layer 11 in this embodiment will be described in detail below. <Pre-configuration> A reference consolidation value is set as an indicator for determining the consolidation state of the filter media layer 11, which is formed in advance from a settling granular fiber filter media. The reference consolidation value is an indicator that represents the filter media passage resistance which changes with the change in the pressure density of the filter media layer 11 when consolidated water is discharged. In this embodiment, the discharge rate of consolidated water, which decreases in value as consolidation progresses, is used. The discharge rate is set with a predetermined range.

[0025] <Method for determining the state of compaction> The discharge rate of consolidated water is high in the initial stages of consolidation when the porosity of the filter media layer 11 is high and the resistance to passage through the filter media is low. On the other hand, as consolidation progresses over time, the porosity of the filter media layer 11 decreases and the resistance to passage through the filter media increases, resulting in a low discharge rate. In other words, when the discharge rate decreases to a predetermined value from the start of measurement, it can be determined that the porosity is low and the filter media layer 11 has been formed in a state optimal for filtration.

[0026] In the consolidation process shown in Figures 2 and 3, after the consolidated water is stored in the filtration tank 2 to a predetermined height, the discharge valve 7 is opened to begin discharging the consolidated water from the bottom of the filtration tank 2. The discharge rate of the consolidated water is then continuously measured using a flow meter 13 (measuring instrument 12) installed in the discharge pipe 8. The measurement of the rate may begin at the start of the consolidation water discharge process or earlier. At this time, if the measured discharge rate of the consolidated water reaches a predetermined reference rate (reference consolidation value), it is determined that the consolidation state of the filter media layer 11 is good (the porosity is low and it is in an optimal state 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 rate, it is determined that the consolidation state of the filter media layer 11 is not good (the porosity is high and it is not in an optimal state for filtration), and the discharge of the consolidated water continues. In this case, the discharge of consolidated water continues until the water level in the filtration tank 2 reaches a predetermined value. Once it is detected that the predetermined water level has been reached, the process returns to the consolidated water storage process.

[0027] In the consolidation process, which is performed multiple times, for example, in the initial stage of consolidation water discharge during the first consolidation process, a large number of filter media 10 are immersed in the filtration tank 2 and are in an unconsolidated state. At this time, the porosity of the filter media layer 11 is high and the resistance to the passage of consolidation water is low, so the consolidation water supplied from above is discharged forcefully downwards. Therefore, the discharge velocity of the consolidation water discharged from the discharge pipe 8 is high.

[0028] On the other hand, by repeating the consolidation process multiple times, the porosity of the filter media layer 11 decreases due to the dynamic pressure of the consolidated water. As a result, the resistance to passage through the filter media layer 11 gradually increases, and inversely proportional to this effect, the discharge rate of the consolidated water discharged from the discharge pipe 8 decreases. When the measured value reaches the reference rate, it is determined that the consolidation state of the filter media layer 11 is good, and the discharge of the consolidated water is terminated to proceed to the filtration process. If the measured value measured by the flow meter 13 does not reach the reference rate, it is determined that the consolidation state of the filter media layer 11 is not good, and the consolidation process is continued. After reaching a predetermined water level, the process returns to the consolidated water storage process. However, instead of a predetermined water level, other indicators such as a predetermined time may be used as an indicator for the end of consolidated water discharge, and two or more indicators may be combined.

[0029] In this embodiment, the consolidated water is set to always be located above the filter media layer 11 during the consolidated water discharge process, and the entire filter media layer 11 is kept immersed from the start to the end of the consolidated water discharge to prevent air from entering the filter media layer 11. When the discharge of consolidated water is started, the liquid level in the filtration tank 2 decreases, but if the filter media layer 11 becomes unimmersed due to the decrease in liquid level, air flowing in from outside the filtration tank 2 will enter the inside of the filter media layer 11. If the filtration process is started in this state, the water flow efficiency of the liquid to be treated passing between the filter media will decrease, and the filtration accuracy will decrease. In addition, at the start of the filtration process, a large amount of air held between the filter media 10,10 will rise towards the top of the filtration tank 2. In order to prevent the filtration process efficiency from decreasing due to these factors, the filter media layer 11 is kept immersed at all times in this embodiment. The consolidated water that immerses the filter media layer 11 is discharged from the bottom of the filtration tank 2 together with the treated liquid during the filtration process described later.

[0030] In this embodiment, the flow meter 13 is installed on the discharge pipe 8, but it is not limited to this location as long as it can be installed in a position where the discharge rate of consolidated water can be measured. Also, although the flow velocity is measured using the flow meter 13, the flow rate can also be calculated. Therefore, by utilizing the phenomenon that the amount of consolidated water decreases due to the increase in resistance passing through the filter media as consolidation progresses, the discharge rate may be used as the measured value instead of the discharge rate.

[0031] As described above, the flow velocity is measured by the flow meter 13, but the filtration tank 2 may also be equipped with measuring instruments 12 such as a water level gauge, pressure gauge, and imaging device (not shown) to measure fluctuations in the liquid level, and the consolidation state may be determined using the flow velocity value calculated from the liquid level movement time and distance.

[0032] Furthermore, instead of flow velocity or flow rate, the height of the filter media layer 11 may be used as an indicator for determining the consolidation state. Since the height of the filter media layer 11 gradually decreases as consolidation progresses, measuring this height allows for determining whether the filter media layer 11 has changed to an optimal consolidation state for filtration. Specifically, a reference height is set in advance, and when the measured height of the filter media layer 11 decreases to the reference height, it is determined that the consolidation state is good. Examples of how the height of the filter media layer 11 can be measured include visually inspecting it from the outside by installing an inspection window (not shown) in the filtration tank 2, or installing an imaging device (not shown) outside the filtration tank 2 and continuously photographing the filter media layer 11 inside the filtration tank 2 through the inspection window to automatically detect changes in the height of the filter media layer 11. Note that any method that can detect the consolidation state of the filter media layer 11 is acceptable, as long as it measures one or more of the following: the discharge velocity of the consolidated water, the discharge flow rate, and the height of the filter media layer 11.

[0033] Figure 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 passes 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 out of the system from the discharge pipe 8 as treated liquid. Suspended solids contained in the liquid to be treated are attached to the inside and surface of the filter media 10 and captured as they pass through the filter media layer 11. If clogging occurs in the filter media layer 11 during a long filtration process, the filter media is cleaned.

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

[0035] Figure 5 is a schematic diagram of the filter media cleaning process. In the filter media cleaning process, cleaning solution is supplied from the discharge pipe 8 and stored up to the top of the filtration tank 2. Then, cleaning air is injected from the air-washing pipe 15 below the filtration tank 2 to agitate and clean the filter media 10. The filter media 10 moves while rotating and colliding with the cleaning air continuously injected from below, causing attached suspended matter to detach. After cleaning the filter media, the cleaning wastewater 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 the open state. In this embodiment, the treated liquid supply line is also used as the cleaning wastewater discharge line, but a separate cleaning solution discharge line may be provided.

[0036] Furthermore, since a screen 9B is provided above the filtration tank 2 to prevent the filter media from flowing out, the filter media 10 will not flow out of the filtration tank during cleaning. In addition, the type of cleaning solution, its supply location, and its discharge location are not limited.

[0037] The present invention is not limited to the embodiments detailed above. It can be modified and implemented as appropriate without departing from the spirit of the invention. [Industrial applicability]

[0038] This invention allows the filter media layer to be compacted to an optimal state for filtration before the filtration process can begin. This enables stable filtration from the initial stages of operation, resulting in treated water with consistent quality until the end of filtration. The reduced compaction time also reduces the operating time of the equipment, leading to energy savings. Furthermore, since it can treat various liquids such as seawater, drinking water, industrial water, and sewage, it is a technology applicable to a wide range of fields. [Explanation of symbols]

[0039] 2 Filtration tank 11 filter media layer

Claims

1. A reference consolidation value is set as an indicator for determining the consolidation state of the filter media layer (11) which is formed in advance with a settling granular fiber filter media. After performing a consolidated water storage process in which consolidated water is supplied to a predetermined height in the filtration tank (2), A consolidated water discharge process is performed in which consolidated water is discharged from the bottom of the filtration tank (2) and the filter media layer (11) is consolidated by the dynamic pressure at the time of discharge. During the consolidation water discharge process, among the consolidation water discharge rate, the amount of consolidation water discharged, and the height of the filter media layer (11), which change as consolidation progresses, Compare at least one measurement value with the reference consolidation value, If the measured value reaches the standard consolidation value, it is determined that the consolidation state of the filter media layer (11) is good, and the consolidation water discharge process is terminated, and the process moves on 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 media layer (11) is not good, and the process proceeds to the consolidation water storage process, which supplies consolidated water to the filtration tank (2) again. A method for determining the compaction state of a filter media layer, characterized by the features described above.

2. The aforementioned consolidation water discharge process is completed with the entire filter media layer (11) immersed. The method for determining the compaction state of a filter media layer according to feature 1.

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