Method for setting up a filtration system using fiber filter media

Abstract

This invention provides a method for setting up a filtration system using fibrous filter media, which improves the settling properties of the filter media and the water flow efficiency of the liquid to be treated by removing air bubbles held in the voids inside the new filter media introduced into the filtration tank in the preceding stage of the filtration process. [Solution] In a filtration method in which a liquid to be treated is passed through a filter media layer 4 composed of amorphous filter media to capture suspended solids in the filter media layer 4, the filtration process S4 is started after performing a filter media immersion step S1 in which the entire filter media in the filtration tank 2 is immersed, a depressurization step S2 in which the pressure inside the filtration tank 2 is reduced to a predetermined pressure using a depressurization pump 8, and a water absorption step S3 in which the pressure inside the filtration tank 2 is increased and the immersion liquid is absorbed into the inside of the filter media. As a result, air bubbles held in the voids inside the filter media are replaced by the immersion liquid, improving the settling properties of the filter media and the water flow efficiency of the liquid to be treated, so that the filtration process can be started immediately and the removal rate of suspended solids is improved.

Description

Technical Field

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[0001] The present invention relates to a method for starting up a filtration device using a fibrous filter medium capable of shortening the time until the start of a filtration treatment step in a filtration device using a fibrous filter medium.

Background Art

[0002] Conventionally, a filtration device using an amorphous fibrous filter medium captures suspended substances in a liquid to be treated with the filter medium during a filtration treatment step. However, as the filtration operation continues, the filter medium is consumed, and the filtration performance gradually deteriorates. Although the periodically consumed filter medium is replaced with a new one, since the new filter medium in a dry state holds air bubbles in the gaps between the fibers, the sedimentation property of the filter medium is poor. Therefore, after performing a water absorption step of immersing the filter medium in a filtration tank to acclimatize it with water and replacing the air in the gaps with water to make the inside of the filter medium in a water-absorbed state, the filtration treatment step was started. In some cases, the filter medium was hydrophilized during filtration production to enhance the sedimentation property of the filter medium.

[0003] In a downward flow type filtration device using a filter medium having a specific gravity greater than 1, since it is necessary to perform a filtration treatment step by sedimenting the filter medium layer below the filtration tank, a water absorption step was performed in the previous stage of the filtration treatment step to enhance the sedimentation property of the filter medium.

[0004] In an upward flow type filtration device using a filter medium having a specific gravity less than 1, since the newly introduced filter medium is in a floating state during the filtration treatment step, it is not necessary to sediment the filter medium below the filtration tank. However, if air bubbles are held in the gaps inside the filter medium, it hinders the passage of the liquid to be treated, and stable filtration accuracy cannot be maintained. Therefore, also in the upward flow type filtration device, a water absorption step of immersing the entire filter medium was carried out.

[0005] Patent Document 1 discloses a device that passes a liquid to be treated through a filtration member formed so as to surround the side circumference of a standing inner cylinder portion to remove foreign substances in the liquid to be treated. When newly starting up the device or when replacing the filter portion, after performing an immersion treatment of filling the inside of the attached filter portion with a treatment liquid, a negative pressure degassing treatment is performed to remove air bubbles from the filter portion. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 5991403 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Conventionally, in counter-flow filtration systems, it was desirable to perform a water absorption process before the filtration process to remove air bubbles held in the voids within the filter media. However, this water absorption process required immersing the filter media in the filtration tank and then agitating it for a long time to remove the air bubbles, which was a time-consuming process. In addition, while hydrophilic treatment is sometimes performed during the manufacture of the filter media, this does not always yield sufficient results and presents challenges such as increased labor and costs due to the use of chemicals.

[0008] The filtration member described in Patent Document 1 is fixed around the inner cylinder and does not use an amorphous filter material that can move freely within the filtration tank, so the problem of the filter material layer not settling in the stage before the filtration process does not occur. Furthermore, although a negative pressure degassing treatment is performed to increase the volume of bubbles and draw them out of the filtration member, an atmospheric release treatment is performed, but the purpose of the atmospheric release treatment is to increase the pressure acting on the bubbles and dissolve the bubbles in the resist, and not to improve the settling properties by putting the filtration member into a water-absorbing state.

[0009] The present invention provides a method for starting up a filtration system using fibrous filter media, which shortens the time until the start of the filtration process by performing a filter media immersion process before the filtration process, followed by a depressurization process and a water absorption process, thereby removing air bubbles held in the voids inside the filter media and improving the sedimentation properties of the filter media. [Means for solving the problem]

[0010] The present invention relates to a filtration method in which a liquid to be treated is passed through a filter media layer composed of amorphous filter media to capture suspended solids in the filter media layer. The method involves performing a filter media immersion step in which the entire filter media in the filtration tank is immersed, a depressurization step in which the pressure inside the filtration tank is reduced to a predetermined pressure using a depressurization pump, and a water absorption step in which the pressure inside the filtration tank is increased and the immersion liquid is absorbed into the filter media, before starting the filtration process. As a result, air bubbles held inside the filter media introduced into the filtration tank are removed, thereby improving the settling properties of the filter media and the water flow efficiency of the liquid to be treated.

[0011] The aforementioned depressurization process involves stopping the depressurization pump when the pressure inside the filter tank reaches a predetermined level, or stopping the depressurization pump after a predetermined time has elapsed following the arrival of the predetermined level, thereby allowing air bubbles held in the voids inside the filter media to be discharged to the outside. [Effects of the Invention]

[0012] This invention improves the settling ability of filter media by removing air bubbles held in the voids within the new filter media when it is introduced into the filtration tank prior to the filtration process. Therefore, when applied to a downward-flow filtration system using a filter media layer formed of filter media with a specific gravity greater than 1, the filter media layer can be settled downwards in a short time, shortening the time until the start of the filtration process. In addition, the removal of air bubbles improves the flow efficiency of the liquid to be treated, thus improving the capture rate of suspended solids. Furthermore, since it only requires adding a vacuum pump and its accessories to a conventional filtration system, it can be implemented without requiring major design changes or construction work. [Brief explanation of the drawing]

[0013] [Figure 1] This is a longitudinal cross-sectional side view of the downward flow type filtration device according to the present invention. [Figure 2] Similarly, this is a schematic diagram of the filter media immersion process S1. [Figure 3] Similarly, this is a schematic diagram of the depressurization process S2. [Figure 4] Similarly, this is a schematic diagram of the water absorption process S3. [Figure 5] Similarly, this is a schematic diagram of the filter media in each process. [Figure 6] Similarly, this is a longitudinal cross-sectional side view of a filtration device in another embodiment. [Modes for carrying out the invention]

[0014] Figure 1 is a longitudinal cross-sectional side view of a downward flow filtration system. The filtration device 1 consists of a cylindrical filtration tank 2 erected upright, filled with irregularly shaped fibrous filter media 15 (Figure 5), and forming a filter media layer 4 on a filter media outflow prevention screen 3A stretched below the filtration tank 2. The fibrous filter media 15 is a settling granular fibrous filter media with a specific gravity greater than 1, and its shape is not limited to spherical or columnar. The liquid to be treated is supplied from the upper supply pipe 5, and the filter media layer 4 captures suspended solids contained in the liquid to be treated, and the treated liquid is discharged from the lower discharge pipe 6. A filter media outflow prevention screen 3B is also stretched above the filtration tank 2 to prevent the filter media 15 from flowing out towards the supply pipe 5.

[0015] A cleaning pipe 7 is provided below the filtration tank 2, and compressed air is injected into the filter media layer 4 via the cleaning pipe 7 from an air supply source (not shown), such as a blower, during filter media cleaning. During filter media cleaning, the filter media is agitated and cleaned by supplying compressed air to the filter media layer 4 along with the cleaning liquid supplied from the discharge pipe 6. This removes suspended matter adhering to the filter media 15, and the filter media 15 is regenerated. Note that a known mechanical agitator may be used instead of the cleaning pipe 7 as a means of agitating the filter media 15, and this can be modified as appropriate.

[0016] An intake pipe 9, with one end connected to a pressure reducing pump 8, is connected to the upper part of the filtration tank 2. By operating the pressure reducing pump 8, the pressure inside the filtration tank 2 can be reduced to a predetermined level. The pressure reducing pump 8 uses a known vacuum pump or the like, and can reduce the pressure inside the sealed filtration tank 2. An air vent valve 14 is also installed at the upper part of the filtration tank 2, allowing for the supply and exhaust of air. By switching the open / closed state of the intake valve 10 interposed in the intake pipe 9 and operating the air vent valve 14 in accordance with the ON / OFF state of the pressure reducing pump 8, it is possible to switch the pressure inside the filtration tank 2 between a reduced pressure state and an atmospheric pressure state.

[0017] In addition, the intake pipe 9 is equipped with a pressure gauge 11, and the pressure inside the filtration tank 2 can be measured when the vacuum pump 8 is operating. Note that the equipment used for decompression is not limited to this as long as it can create a decompressed state inside the filtration tank 2. Regarding the connection position of the intake pipe 9, it is not specified to this embodiment, and any position where the immersion liquid inside the filtration tank 2 is not sucked may be used.

[0018] Generally, the filtration process is carried out in any of the following cases: after newly starting up a filtration device and adding a new filter medium to the filtration tank, after replacing the consumed filter medium with a new one and starting up the filtration device, or after performing filter medium cleaning. However, the new filter medium is in a dry state, and since air bubbles are retained in the gaps between the fibers, its sedimentation property is poor. Therefore, in this embodiment, after removing the air bubbles 16 (Fig. 5) retained between the fibers of the filter medium 15 to enhance the sedimentation property of the filter medium layer 4, the filtration process is carried out. Hereinafter, the filtration process step S4 (described later) in this embodiment and the startup steps S1 to S3 of the filtration device 1 carried out before the filtration process step S4 will be described in detail based on Figs. 1 to 5.

[0019] Fig. 2 is a schematic diagram of the filter medium immersion step S1. In the filter medium immersion step S1, an immersion liquid (such as a liquid to be treated) is supplied to a predetermined height inside the filtration tank 2 into which the new filter medium 15 has been introduced, and the entire filter medium is immersed. The filtration device 1 used in this embodiment is a downward-flow type filtration device 1 that forms a filter medium layer 4 composed of a filter medium 15 with a specific gravity greater than 1 inside. When newly starting up the filtration device 1 or when replacing the consumed filter medium with a new filter medium 15, the supply valve 12 and the air vent valve 14 installed in the supply pipe 5 are opened to start supplying the immersion liquid from the supply pipe 5. Note that the discharge valve 13 and the intake valve 10 installed in the discharge pipe 6 are kept closed.

[0020] The new filter medium 15 introduced into the filtration tank 2 is in a dry state, and as shown in Fig. 5(a), air bubbles 16 are retained in the gaps between the fibers. Therefore, the immersion liquid does not penetrate to the inside of the filter medium 15, and the filter medium 15 floats up to the vicinity of the filter medium outflow prevention screen 3B above the filtration tank 2 shown in Fig. 2.

[0021] The immersion liquid is supplied so that the water level in the filtration tank 2 is equal to or greater than the height of the filter media outflow prevention screen 3B. By setting the water level of the immersion liquid to be equal to or greater than the height of the filter media outflow prevention screen 3B, all of the floating filter media can be submerged. It is desirable to set the water level of the immersion liquid to the full water level to prevent air from accumulating above the filtration tank. By preventing air accumulating, the amount of air drawn in by the decompression pump 8 is reduced, so a small-capacity decompression pump 8 can be used. Furthermore, by reducing the amount of air drawn in, it is possible to reduce idle time and consequently reduce costs and save energy. The filter media immersion process S1 ends when the immersion liquid reaches the predetermined water level, and the process moves on to the decompression process S2.

[0022] Figure 3 is a schematic diagram of the depressurization process S2. In the depressurization process S2, the depressurization pump 8 connected to the filtration tank 2 is activated to reduce the pressure inside the filtration tank 2 to a predetermined level. After closing the supply valve 12 and the air vent valve 14 to create a seal and opening the intake valve 10, the depressurization pump 8 is activated to draw in air from inside the filtration tank 2, causing the pressure inside the filtration tank 2 to gradually decrease. The drawn-in air is discharged to the outside through the intake pipe 9.

[0023] By reducing the pressure inside the filtration tank 2, the bubbles 16 held in the voids inside the filter media expand, as shown in Figure 5(b). The expanded bubbles 16 are released from the voids inside the filter media into the immersion liquid and discharged to the outside through the intake pipe 9. At this time, bubbles (not shown) attached to the periphery of the filter media 15 also float to the surface and are discharged through the intake pipe 9. The filter media layer 4 remains floating near the filter media outflow prevention screen 3B, as in Figure 2.

[0024] The depressurization process S2 continues until the pressure measured by the pressure gauge 11 installed in the intake pipe 9 reaches a predetermined pressure, and then continues for a predetermined time. After the predetermined time has elapsed, the depressurization process S2 ends and the process moves on to the water absorption process S3 (described later). Note that the depressurization process S2 may be started during the immersion process S1, or performed simultaneously with the immersion process S1, rather than after the completion of the immersion process S1. Alternatively, the depressurization process S2 may be terminated when the pressure in the filter tank 2 reaches a predetermined pressure.

[0025] Figure 4 is a schematic diagram of the water absorption process S3. In the water intake process S3, after the depressurization process S2 is completed, the depressurization pump 8 is stopped and the intake valve 10 is closed, and the air vent valve 14 installed in the filtration tank 2 is opened to open the filtration tank 2 to the atmosphere. Opening the air vent valve 14 increases the pressure inside the filtration tank 2, bringing it to atmospheric pressure.

[0026] By opening the filtration tank 2 to the atmosphere, the cleaning liquid stored in the filtration tank 2 is repressurized, causing the expanded air bubbles 16 within the filter media 15 to contract and become extremely small. At this time, as shown in Figure 5(c), the immersion liquid around the filter media is drawn into the filter media, and the air bubbles 16 held in the voids inside the filter media are replaced by the immersion liquid, so that all of the filter media 15 becomes saturated with water.

[0027] When the air bubbles 16 inside the voids are removed from the filter media 15, it loses buoyancy and its tendency to sink increases. As a result, the filter media layer 4 in the filtration tank 2 gradually descends from the position indicated by the dashed line in the diagram and accumulates on the filter media outflow prevention screen 3A at the bottom of the filtration tank. When the air bubbles 16 inside the filter media are removed in the depressurization process S2, air bubbles attached to the periphery of the filter media are also removed at the same time, so when the filter media layer 4 is formed on the filter media outflow prevention screen 3A, air bubbles 16 do not accumulate between the filter media 15, 15. This allows for the formation of a filter media layer 4 with a low porosity, thereby increasing the filtration efficiency. After returning the filtration tank 2 to atmospheric pressure in the water intake process S3, the discharge valve 13 is opened to discard the immersion liquid, and the process moves to the filtration process S4.

[0028] After performing the above-described startup steps S1 to S3 of the filtration apparatus, the filtration process S4 is performed. In the filtration process S4, after opening the supply valve 12 shown in Figure 1, the liquid to be treated is supplied from the supply pipe 5 into the filtration tank 2. As the supplied liquid passes through the filter media layer 4 filled in the filtration tank 2, suspended solids are captured and the treated liquid is discharged to the outside from the discharge pipe 6. At this time, the discharge valve 13 is open, and the intake valve 10 and air vent valve 14 are closed. The filtration process S4 is performed for a predetermined time.

[0029] Figure 6 is a longitudinal cross-sectional side view of a filtration device in another embodiment. In this configuration, an upward-flow type filtration device 1 is used, in which a filter media layer 4 composed of filter media 15 with a specific gravity less than 1 is filled into a filtration tank 2. During the filtration process S4, the liquid to be treated is supplied from a supply pipe 5 connected to the bottom of the filtration tank 2, and after the suspended solids are removed by the filter media layer 4, the treated liquid is discharged from a discharge pipe 6 connected to the top of the filtration tank 2. Regarding the startup processes S1 to S3 of the filtration device 1, which are performed prior to the filtration process S4, the valve opening and closing operations differ from those of a downward-flow type filtration device because the liquid to be treated supply position and the treated liquid discharge position are different, but the basic implementation method of each process is the same.

[0030] The filter tank 2 is equipped with a filter media outflow prevention screen 3B above it, which prevents the filter media 15, which is immersed during the filter media immersion process S1, from flowing out to the discharge pipe 6. However, this filter media outflow prevention screen 3B may also be provided with a mechanism that allows it to be raised and lowered. By providing a raising and lowering mechanism, if a part of the immersed filter media 15 is exposed above the water surface, it is possible to lower it to the upper surface of the filter media layer 4 and press it from above to push the exposed filter media 15 back into the immersion liquid, so that the entire filter media is immersed (water absorbed).

[0031] Furthermore, the vertically adjustable filter media outflow prevention screen 3B may also be applied to a downward-flow type filtration system, and the entire filter media layer 4 may be immersed by pressing it from the upper surface. In both upward and downward-flow type filtration systems, the subsequent depressurization process S2 and water absorption process S3 are performed with the filter media layer 4 pressed during the filter media immersion process S1. By using the vertically adjustable filter media outflow prevention screen 3B, the entire filter media layer can be immersed, ensuring that the entire filter media is reliably immersed in water. In addition, since the filter media 15 can be immersed by lowering the filter media outflow prevention screen 3B to the water level of the immersion liquid, it can be carried out with a small amount of immersion liquid.

[0032] This embodiment improves the settling properties of dry filter media 15 when it is placed in the filtration tank 2 after a new filtration device 1 has been started up and new filter media 15 has been placed in the filtration tank 2, or after worn-out filter media has been replaced with new filter media 15 and the filtration device 1 has been started up. However, it may also be applied to filter media after cleaning. After cleaning, the filter media is immersed in the filter media cleaning solution and is therefore waterlogged, but it may float to the surface because compressed air used during the cleaning process adheres to its surroundings. Therefore, by performing the filtration device 1 start-up steps S1 to S3 to remove air bubbles, the filter media layer 4 can be quickly allowed to settle, and the filtration process S4 can be restarted.

[0033] 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]

[0034] This invention allows for rapid settling of the filter media layer by removing air bubbles held in the voids inside the filter media before the filtration process, thereby shortening the time until the start of the filtration process in a downward-flow filtration system using filter media with a specific gravity greater than 1. Furthermore, the removal of air bubbles increases the water flow efficiency of the liquid being treated, thereby improving the filtration efficiency of the upward-downward-flow filtration system. In addition, since no chemicals are used for hydrophilic treatment during the manufacture of the filter media, costs are reduced, and safety is ensured when processing food-related liquids. [Explanation of Symbols]

[0035] 1. Filtration device 2. Filtration tank 4. Filter media layer 8. Pressure reducing pump S1 Filter media immersion process S2 Depressurization Process S3 Water absorption process S4 Filtration process

Claims

1. In a filtration method in which a liquid to be treated is passed through a filter media layer (4) composed of amorphous filter media to capture suspended solids in the filter media layer (4), The filter media immersion step (S1) involves immersing the entire filter media in the filtration tank (2), A depressurization step (S2) is performed in which the pressure inside the filtration tank (2) is reduced to a predetermined pressure using a depressurization pump (8), The filtration tank (2) is pressurized, and the water absorption process (S3) is performed to allow the filter media to absorb the immersion liquid. After implementing, Start the filtration process (S4). A method for setting up a filtration system using a fibrous filter material, characterized by the features described herein.

2. The aforementioned depressurization process (S2) is performed as follows: The depressurizing pump (8) is stopped when the pressure inside the filtration tank (2) reaches a predetermined level, or the depressurizing pump (8) is stopped after a predetermined time has elapsed after the predetermined level has reached the level. A method for starting up a filtration apparatus using a fibrous filter material as described in feature 1.

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