JP7122915B2 - How to clean the filtration unit - Google Patents

Description

The present invention relates to a method for cleaning a filtration unit.

Conventionally, as described in Patent Document 1, a filtration unit for obtaining clean treated water by passing raw water containing various impurities through a filter is known, and the filtration unit is used for various water treatment technologies. used in the field. In this filtration unit, the amount of impurities adhering to the filter increases as the filtration time elapses, causing clogging of the filter. Therefore, it is necessary to extend the life of the filter by cleaning it periodically.

Patent Literature 1 describes a method of backwashing a depth filter in a filtration unit used in a ship's ballast water production system. Specifically, the document describes performing a backwashing process in which compressed air is supplied to the hollow portion of the depth filter while raw water is being supplied to the filtration unit, and the compressed air is discharged together with the raw water.

WO2010/093025

In the method for cleaning the filtration unit described in Patent Literature 1, the impurities adhering to the surface of the filter during filtration can be removed to some extent by backwashing, but there is room for further improvement in the cleaning effect. The types of impurities that adhere to the filter differ depending on the application of the filtration unit. Depending on the application, the impurities may adhere firmly to the filter and be difficult to remove, so there is a need for a filter cleaning method with a higher cleaning effect.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a cleaning method for a filtration unit that can clean the filter of the filtration unit more effectively.

A filtration unit cleaning method according to one aspect of the present invention includes a filter for filtering raw water, and a housing that accommodates the filter and that has a raw water space filled with raw water. In a unit, a method for cleaning the surface of the filter facing the raw water space. This filtration unit cleaning method is to open the gas inlet valve located in the path leading to the treated water space, supply gas to the treated water space, and apply pressure from the treated water space side to the raw water space side to remove impurities from the filter. and opening the flow path leading to the raw water space for a predetermined time while maintaining the open state of the gas inlet valve. forming a part of the raw water space so as to be in contact with the raw water in the space; and discharging the raw water containing impurities in the raw water space while expanding the gas layer in the raw water space by opening the raw water space to atmospheric pressure while maintaining the state .

According to this filtering unit cleaning method, after forming a gas layer in which gas is compressed to a state higher than atmospheric pressure in the raw water space, the raw water space is closed from a closed state while maintaining the gas inlet valve in an open state. By opening to atmospheric pressure, the raw water in the raw water space can be pushed by the expanding gas. This improves the momentum of the raw water flowing along the surface of the filter, and as a result, the impurities adhering to the surface of the filter during filtration can be effectively removed by the raw water flow. Therefore, according to the filtering unit cleaning method of the present invention, the filter of the filtering unit can be effectively cleaned, and the life of the filter can be extended.

In the filtering unit cleaning method, in the step of expanding the gas layer, the expanded gas layer may push the raw water in the raw water space in a direction along the surface of the filter.

According to this method, the momentum of the raw water flowing along the surface of the filter can be further increased, so that the impurities adhering to the surface of the filter can be more effectively removed.

In the filtering unit cleaning method described above, the filter and the housing may be arranged in a vertical direction. In the step of forming the gas layer, the gas layer may be formed such that the surface position of the raw water in the raw water space is positioned above the center in the length direction of the filter.

According to this method, when the gas layer is expanded in the raw water space, the raw water can flow over a wide range of the filter surface, so it is possible to ensure a wide cleaning range on the filter surface.

The filtering unit cleaning method may further include the step of pressurizing the gas layer after the step of forming the gas layer and before the step of expanding the gas layer.

According to this method, the gas layer can be compressed to a higher pressure state, so that the force of the gas layer pushing the raw water when expanded can be increased. As a result, the momentum of the raw water flowing along the surface of the filter can be further increased.

In the filtering unit cleaning method, the filter may be hollow and include an outer surface facing the raw water space and an inner surface facing the hollow portion of the filter. . In the step of forming the gas layer, after the water in the hollow portion is pushed out to the raw water space by gas, the gas passing through the filter from the inner surface toward the outer surface is accumulated in the raw water space. Layers may be formed.

According to this method, impurities can be peeled off from the outer surface of the filter by sequentially passing water and gas from the inner surface to the outer surface of the filter. Impurities on the outer surface of the filter can be washed away by the flow of raw water urged by the expansion of the gas layer.

As is clear from the above description, according to the present invention, it is possible to provide a filtration unit cleaning method that can more effectively clean the filter of the filtration unit.

It is a figure which shows typically the whole structure of a filtration apparatus. FIG. 4 is a diagram showing a process flow in the method for cleaning the filtration unit according to Embodiment 1 of the present invention. FIG. 4 is a schematic diagram for explaining a water filling step in the method for cleaning the filtration unit according to Embodiment 1 of the present invention. FIG. 4 is a schematic diagram for explaining a filtration step in the method for cleaning a filtration unit according to Embodiment 1 of the present invention. FIG. 4 is a schematic diagram for explaining an air layer forming step in the filtering unit cleaning method according to Embodiment 1 of the present invention. FIG. 4 is a schematic diagram for explaining an air layer expansion step in the filtering unit cleaning method according to Embodiment 1 of the present invention. 4 is a graph showing changes in differential pressure between the primary side and the secondary side of the filtration unit in the example. 7 is a graph showing changes in differential pressure between the primary side and the secondary side of a filtration unit in a comparative example; FIG. 11 is a schematic diagram for explaining a method of cleaning a filtration unit according to another embodiment of the present invention;

Hereinafter, a cleaning method for a filtration unit according to an embodiment of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
<Filtration device>
First, the overall configuration of a filtration device 1 including a filtration unit 10 to be cleaned will be described with reference to FIG. The filtering device 1 is configured to filter pool water (raw water) sent from a pool (not shown) by a filtering unit 10 and send clean treated water after filtration to the pool.

As shown in FIG. 1, the filtering device 1 includes a filtering unit 10, an air compressor 20 for supplying compressed air A1 to the filtering unit 10, and raw water W1 (pool water sent from a pool) to the filtering unit 10. It mainly includes a filtration pump 30 for supplying, piping connecting these devices to each other, and various on-off valves provided in the piping. It should be noted that FIG. 1 shows only main components in the filtering device 1, and the filtering device 1 may further include other components not appearing in FIG. Each component of the filtering device 1 will be described below.

The filtration unit 10 is for filtering the raw water W1 to obtain clean treated water W2, and mainly has a filter 11 for filtering the raw water W1 and a housing 12 that accommodates the filter 11. ing.

The filter 11 is, for example, a depth filter, has a hollow cylindrical shape, and is arranged in a posture in which the cylindrical axis extends in the up-down direction (vertical direction). More specifically, as shown in FIG. 1, the filter 11 includes an outer surface 11A and an inner surface 11B facing the hollow portion 11C of the filter 11, and the raw water W1 permeates from the outer surface 11A toward the inner surface 11B. It is configured as an external pressure dead end filtration type in which the treated water W2 is taken out from the hollow portion 11C. In addition, the filter is not limited to the depth filter used in the present embodiment, and may be another filter material such as a hollow fiber membrane.

The housing 12 is a cylindrical container that accommodates the filter 11, and is arranged with the cylindrical axis extending in the vertical direction, similar to the filter 11. As shown in FIG. As shown in FIG. 1, the axial length of the housing 12 is greater than the axial length of the filter 11 . A plurality of (for example, four) filters 11 may be accommodated in the housing 12, but the present invention is not limited to this, and only one filter 11 may be accommodated.

A raw water space 12A filled with raw water W1 and treated water spaces 12B and 12C into which treated water W2 flows from a hollow portion 11C of the filter 11 are formed in the housing 12, respectively. The raw water space 12A is formed inside the housing 12 so as to surround the outer surface 11A of the filter 11 . That is, the outer surface 11A of the filter 11 is the surface facing the raw water space 12A of the housing 12 (the surface facing the raw water space 12A).

As shown in FIG. 1, treated water spaces 12B and 12C are formed respectively in the upper and lower portions of the housing 12 (upper treated water space 12B, lower treated water space 12C). The treated water spaces 12B and 12C communicate with the hollow portion 11C of the filter 11, respectively, and are liquid-tightly separated from the raw water space 12A by the partition portion 12D. This prevents the raw water W1 and the treated water W2 from being mixed in the housing 12 .

The housing 12 has a raw water inlet 13 for introducing raw water W1 into the housing 12, and treated water outlets 16 and 17 (upper treated water outlet 16, lower treated water outlet 17) and air inlets 14 and 15 (upper air inlet 14, lower air inlet 15) for introducing compressed air A1 into the housing 12 are provided. The raw water inlet 13 is provided on the side surface of the housing 12 below the center in the vertical direction (below the center in the length direction of the filter 11) so as to communicate with the raw water space 12A. Treated water outlets 16 and 17 are provided respectively in the upper and lower portions of the housing 12 so as to communicate with the treated water spaces 12B and 12C. The air inlets 14 and 15 are respectively provided on the side surface of the housing 12 above and below the center in the vertical direction so as to communicate with the treated water spaces 12B and 12C.

According to the filtration unit 10 having the above configuration, the raw water W1 introduced into the raw water space 12A through the raw water inlet 13 is allowed to permeate from the outer surface 11A toward the inner surface 11B of the filter 11, thereby filtering the raw water W1. can be done. Then, the filtered treated water W2 can be taken out from the hollow portion 11C of the filter 11 into the treated water spaces 12B and 12C and out of the housing 12 through the treated water outlets 16 and 17. FIG. That is, in the filtration unit 10 of the present embodiment, the treated water W2 is taken out from the upper portion and the lower portion of the housing 12, respectively.

The air compressor 20 generates compressed air A<b>1 compressed to 0.8 MPa, for example, and is connected to the upper air inlet 14 of the housing 12 via a first air introduction path 22 . The first air introduction path 22 is provided with an air inlet valve 21 that switches between circulating and blocking the compressed air A1 in the first air introduction path 22 . The air inlet valve 21 is, for example, an air-driven ball valve (on-off valve).

Further, as shown in FIG. 1, a second air introduction path 23 branches from a portion P1 downstream of the air inlet valve 21 in the first air introduction path 22, and the second air introduction path 23 extends through the housing 12. It is connected to the lower air inlet 15 . According to this configuration, by opening the air inlet valve 21, the compressed air A1 generated by the air compressor 20 flows through the first air introduction path 22 and the second air introduction path 23 into the treated water space 12B of the housing 12, 12C can be introduced into each.

The filtration pump 30 is for sending out the raw water W1 returned from the pool (not shown) toward the filtration unit 10 . As shown in FIG. 1 , the filtration pump 30 is connected to the raw water inlet 13 of the housing 12 via a raw water introduction path 32 .

The raw water introduction path 32 is provided with a raw water inlet valve 31 for switching between flow and shutoff of the raw water W1 in the raw water introduction path 32 . The raw water inlet valve 31 is, for example, an air-driven butterfly valve (on-off valve). The raw water W1 can be introduced into the raw water space 12A of the housing 12 by operating the filtration pump 30 and opening the raw water inlet valve 31 .

As shown in FIG. 1, the upper treated water outlet 16 of the housing 12 is connected to an upper treated water path 41 for guiding the treated water W2 discharged from the upper treated water outlet 16 to a pool (not shown). . The upper treated water path 41 is provided with a treated water outlet valve 42 for switching between flow and blockage of the treated water W2 in the upper treated water path 41 . Like the raw water inlet valve 31, the treated water outlet valve 42 is, for example, an air-driven butterfly valve (on-off valve).

The lower treated water outlet 17 of the housing 12 is connected to a lower treated water path 43 through which the treated water W2 led out from the lower treated water outlet 17 flows. The lower treated water path 43 is connected to a portion P2 on the upstream side of the treated water outlet valve 42 in the upper treated water path 41 . By opening the treated water outlet valve 42, the clean treated water W2 drawn out from the upper and lower portions of the housing 12 can be led to the pool.

As shown in FIG. 1 , the upstream end of the drainage path 62 is connected to a portion P3 of the raw water introduction path 32 on the downstream side of the raw water inlet valve 31 . The drainage path 62 is provided with a drainage valve 61 that switches between the flow and blockage of water in the drainage path 62 . The drain valve 61 is, for example, an air-driven butterfly valve (on-off valve), like the raw water inlet valve 31 and the like. By closing the raw water inlet valve 31 and opening the drain valve 61 , the water in the raw water space 12 A of the housing 12 can be drained through the drain path 62 . Further, the downstream end of the drainage path 62 is open to the atmosphere.

Further, as shown in FIG. 1 , the filter device 1 includes a portion upstream of the treated water outlet valve 42 in the upper treated water passage 41 and downstream of the confluence point (portion P2) of the lower treated water passage 43. An air release path 52 is further provided that connects P4 and a portion P5 of the drainage path 62 downstream of the drainage valve 61 . The air vent path 52 is provided with an air vent valve 51 which is, for example, an air-driven ball valve (open/close valve).

The filtering device 1 further includes a control section 70 that is a computer that controls the operation of the filtering device 1 . The control unit 70 controls opening/closing of the air inlet valve 21 , raw water inlet valve 31 , treated water outlet valve 42 , drain valve 61 and air vent valve 51 , and also controls ON/OFF of the filtration pump 30 .

In addition, although only one filtration unit 10 is provided in the filtration apparatus 1 shown in FIG. 1, it is not limited to this, and a plurality of filtration units 10 may be provided in parallel.

<How to clean the filtration unit>
Next, a method for cleaning the filtration unit according to this embodiment will be described with reference to FIGS. 1 to 6. FIG. The filtering unit cleaning method according to the present embodiment is a method for cleaning the outer surface 11A of the filter 11 in the filtering unit 10 described above.

FIG. 2 shows the steps sequentially performed in the filtration unit cleaning method according to the present embodiment, and also shows the operating state of the filtration pump 30 and the opening/closing state of each valve in each step. 2 indicate the ON state of the filtration pump 30 and the open state of each valve, while the blanks in FIG. 2 indicate the OFF state of the filtration pump 30 and the closed state of each valve. showing.

Information on the operating state of the filtration pump 30 and the open/closed states of the valves 21, 31, 42, 51, and 61 in each step shown in FIG. 2 is stored in the control unit 70 (FIG. 1) as an operation program. Therefore, in the filtration unit cleaning method according to the present embodiment, by executing the operation program, the filtration pump 30 can be turned on/off and the valves 21, 31, 42, 51, and 61 can be opened/closed as shown in FIG. , and the water filling process, filtration process, and backwashing process are executed in order. Hereinafter, the method for cleaning the filtration unit according to the present embodiment will be described in detail according to the process flow shown in FIG.

First, in the water filling process, the air in the housing 12 is removed by opening the air vent valve 51 for a predetermined time (for example, 0.5 seconds), and then the raw water inlet valve 31 is further opened to wait for a predetermined time (for example, 2 seconds). . Then, the filtration pump 30 is operated for a predetermined time (for example, 10 seconds).

As a result, as shown in FIG. 3, the raw water W1 is introduced from the raw water inlet 13 into the raw water space 12A of the housing 12, and the raw water space 12A is filled with the raw water W1. As the raw water W1 passes through the filter 11 from the outer surface 11A toward the inner surface 11B, various impurities (for example, soil, fiber waste, algae, etc.) It adheres to the thick part and filters the raw water W1.

The soil contained in the raw water W1 is, for example, adhered to the body of the pool user and mixed in the pool water. It is mixed with Also, the fiber waste contained in the raw water W1 originates from, for example, towels used by the pool users and clothing of the pool users. In addition, if the concentration of free residual chlorine in the raw water W1 is not controlled within a predetermined range, or if the algae contained in the raw water W1 are more resistant to chlorine even if they are controlled within the predetermined range, It is derived from the propagation of algae. For example, as a water quality standard for swimming pools, it is stipulated that the concentration of free residual chlorine in water should be controlled to 0.4 mg/L or more and 1.0 mg/L or less, mainly using a chlorine-based sterilant.

The treated water W2 flows from the hollow portion 11C of the filter 11 into the upper treated water space 12B and the lower treated water space 12C, respectively, and then exits the housing 12 through the upper treated water outlet 16 and the lower treated water outlet 17. taken out. At this time, the air inside the housing 12 is also removed.

Next, in the filtration step, the treated water outlet valve 42 is further opened to wait for a predetermined time (for example, 2 seconds), and then the air vent valve 51 is closed. Then, with the raw water inlet valve 31 and the treated water outlet valve 42 opened, the filtration pump 30 is operated for a predetermined time (for example, 120 minutes).

Thereby, as shown in FIG. 4, the treated water W2 is taken out of the housing 12 through the upper treated water outlet 16 and the lower treated water outlet 17, respectively. Then, as shown in FIG. 1, the treated water W2 is led to a pool (not shown) through the upper treated water path 41 and the lower treated water path 43, respectively.

Here, the amount of impurities adhering to the filter 11 gradually increases as the filtration time elapses, and clogging of the filter 11 may occur. Therefore, in order to eliminate the clogging and extend the life of the filter 11, the following backwashing process for the filter 11 is performed.

As shown in FIG. 5, at the start of the backwash process, the entire raw water space 12A of the housing 12 is filled with raw water W1, and the hollow portion 11C of the filter 11 is filled with treated water W2. In the backwash step, first, the operation of the filtration pump 30 is stopped and the operation is stopped for a predetermined time (for example, 2 seconds), and then the treated water outlet valve 42 is switched to the closed state for a predetermined time (for example, 2 seconds). After that, it waits for a predetermined time (for example, 2 seconds) with the raw water inlet valve 31 switched to the closed state.

Next, the treated water W2 in the hollow portion 11C of the filter 11 is pressurized by the compressed air A1. Specifically, the air inlet valve 21 is opened for a predetermined time (for example, 5 seconds). Thereby, the compressed air A1 generated by the air compressor 20 is introduced into the upper treated water space 12B and the lower treated water space 12C of the housing 12 through the first air introduction path 22 and the second air introduction path 23, respectively. Then, as shown in FIG. 5, the treated water W2 remaining in the hollow portion 11C of the filter 11 is pressurized from the inner surface 11B toward the outer surface 11A by the compressed air A1. As a result, the treated water W2 in the hollow portion 11C of the filter 11 and the water contained in the thick portion of the filter 11 move, and a force is exerted to peel off the impurities adhering to the outer surface 11A of the filter 11 .

Next, as shown in FIG. 6, an air layer 100 (gas layer) is formed in a part of the raw water space 12A so as to come into contact with the raw water W1 in the raw water space 12A (air layer forming step). Specifically, as shown in FIG. 2, the drain valve 61 is opened for a predetermined time while the air inlet valve 21 is kept open.

As a result, part of the raw water W1 filled in the raw water space 12A is discharged from the raw water space 12A through the raw water inlet 13, and the treated water W2 in the hollow portion 11C of the filter 11 is discharged by the compressed air A1 (gas). All are extruded into the raw water space 12A. After that, the compressed air A1 that has passed through the filter 11 from the inner surface 11B toward the outer surface 11A accumulates in the upper portion of the raw water space 12A. As a result, as shown in FIG. 6, an air layer 100 is formed in the raw water space 12A immediately below the upper partition 12D, and the raw water W1 remains below the air layer 100. As shown in FIG. In this way, when the air layer 100 is formed, the treated water W2 and the compressed air A1 are sequentially transmitted from the inner surface 11B of the filter 11 toward the outer surface 11A, thereby removing impurities (turbidity components) from the outer surface 11A. be

In the air layer 100, the air is compressed to a higher pressure than the atmospheric pressure. Specifically, the air pressure in the air layer 100 exceeds the atmospheric pressure and is 0.5 MPa or less. The reason why the upper limit of the air pressure in the air layer 100 is set is that the pressure resistance of the housing 12 (design pressure resistance of the housing 12) is taken into consideration. Since pressure loss occurs when the compressed air A1 passes through the filter 11, the pressure of the air in the air layer 100 is higher than the pressure of the compressed air A1 generated by the air compressor 20 (for example, 0.8 MPa). is also lower.

Further, as shown in FIG. 6, the air layer 100 is such that the surface position of the raw water W1 in the raw water space 12A after the air layer 100 is formed is positioned above the center of the filter 11 in the longitudinal direction (vertical direction). is formed to This makes it possible to wash the outer surface 11A of the filter 11 over a wide range when the raw water W1 is drained in a later step.

In the air layer forming step, the time for which both the air inlet valve 21 and the drain valve 61 are open, that is, the time for removing the raw water W1 from the raw water space 12A is not particularly limited, but in this embodiment, it is set to 2 seconds or longer. is set to

Next, a step of further pressurizing the air layer 100 is performed (air layer pressurization step). Specifically, as shown in FIG. 2, the drain valve 61 is closed and the air inlet valve 21 is kept open for a predetermined time (for example, 30 seconds). As a result, the compressed air A1 permeates from the inner surface 11B of the filter 11 toward the outer surface 11A, and the compressed air A1 is further sent into the sealed raw water space 12A. At this time, since the drain valve 61 is closed and the raw water W1 is not drained from the raw water space 12A, the air pressure in the air layer 100 is further increased.

Next, by opening the raw water space 12A from the closed state to the atmospheric pressure, the air layer 100 is expanded in the raw water space 12A (air layer expansion step). Specifically, as shown in FIG. 2, the drain valve 61 is opened for a predetermined time (for example, 7 seconds) while the air inlet valve 21 is kept open.

When the air layer 100 expands, the liquid surface of the raw water W1 accumulated under the air layer 100 is strongly pushed downward (in the direction along the outer surface 11A of the filter 11) as indicated by the arrow F1 in FIG. . As a result, the downward raw water flow F2 toward the raw water inlet 13 along the outer surface 11A of the filter 11 is instantaneously energized (accelerated). As a result, impurities on the outer surface 11A of the filter 11 can be effectively removed by the raw water flow F2. Raw water W<b>1 containing impurities is discharged out of the housing 12 through the raw water inlet 13 . That is, the raw water inlet 13 also serves as a drain port for the raw water W1.

After that, as shown in FIG. 2, the air inlet valve 21 is closed and only the drain valve 61 is kept open for a predetermined time (for example, 2 seconds), and the air vent valve 51 is opened to wait for a predetermined time (for example, 30 seconds). By doing so, the inside of the housing 12 is returned to normal pressure (atmospheric pressure). By the procedure described above, impurities such as soil and fiber waste adhering to the outer surface 11A of the filter 11 are removed, and the filter 11 can be regenerated. After that, the water filling process and the filtering process described above are restarted.

As described above, according to the filtration unit cleaning method according to the present embodiment, after the air layer 100 in which the air is compressed to a state higher than the atmospheric pressure is formed in the upper part of the raw water space 12A, the raw water space 12A is opened. By opening the sealed state to atmospheric pressure, the force of the expanding air can push the liquid surface of the raw water W1 in the raw water space 12A downward toward the raw water inlet 13 . As a result, the momentum of the raw water W1 flowing downward along the outer surface 11A of the filter 11 is greatly improved, and as a result, impurities (soil, fiber waste, and algae) adhering to the outer surface 11A of the filter 11 during filtration are removed from the raw water. It can be effectively removed by the flow F2 of W1. Further, in this cleaning method, the cleaning effect can be enhanced without increasing the amount of waste water W1, and the tank capacity of the air compressor 20 can be reduced.

Especially in the filtration of pool water, there is a problem that a large amount of impurities such as soil and fiber waste are suddenly mixed in, and the impurities adhering to the outer surface 11A of the filter 11 are difficult to peel off, resulting in clogging of the filter 11 in a short period of time. be. On the other hand, according to the filtering unit cleaning method according to the present embodiment, such a problem can be solved and the life of the filter 11 can be extended.

The effect of the filtering unit cleaning method according to the present embodiment is shown by comparing the experimental results shown in FIGS. 7 and 8, respectively. FIG. 7 shows (A) the primary side (inlet side), (B) the pressure change over time on the secondary side (outlet side) of the filtration unit 10, and (C) the pressure change over time between the primary side and the secondary side of the filtration unit 10. each shown. A depth filter with a pore size of 3 μm was used as the filter 11, and the filter 11 was washed every 60 minutes of filtration time.

FIG. 8 shows (A) the change over time of the pressure on the primary side (inlet side) of the filtration unit when the operation of the filtration device is continued for a predetermined period while the filter is periodically washed using the cleaning method of the comparative example; (B) shows the change over time of the pressure on the secondary side (outlet side) of the filtration unit, and (C) the change over time of the differential pressure between the primary side and the secondary side of the filtration unit. The cleaning method adopted in the comparative example is not a method of forming an air layer in the raw water space and then expanding the air layer, but rather pressurizing the treated water in the hollow part of the filter for a certain period of time and then opening the drain valve to remove the filter. In this method, the treated water in the hollow portion and the raw water in the raw water space are discharged from the housing in one step. A depth filter with a pore size of 3 μm was used as the filter, and the filter was washed every 60 minutes of filtration time. In each graph of FIGS. 7 and 8, the horizontal axis indicates time (days), and the vertical axis indicates pressure.

In the experimental results of the comparative example shown in FIG. 8, the differential pressure (C) across the filtration unit increased sharply after 3 months from the start of filtration operation, confirming clogging of the filter. On the other hand, according to the experimental results of FIG. 7, no increase in the differential pressure before and after the filtration unit 10 was observed even when seven months or more had passed since the start of the filtration operation. As described above, according to the filtering unit cleaning method according to the present embodiment, the impurities adhering to the outer surface 11A of the filter 11 can be effectively removed and the cleaning effect can be enhanced, so that the life of the filter 11 can be extended. be able to. As a result, the replacement frequency of the filter 11 can be reduced.

The experimental results of FIG. 7 were obtained when the drain valve 61 was opened for only 2 seconds when forming the air layer 100. When the time was 1 second, it was confirmed that the cleaning effect decreased. was done. For this reason, as described in the above embodiment, the time for opening the drain valve 61 when forming the air layer 100 (the time for removing the raw water W1 from the raw water space 12A) is preferably 2 seconds or longer.

On the other hand, if the opening time of the drain valve 61 when forming the air layer 100 is too long, the liquid level of the raw water W1 in the raw water space 12A drops excessively, and the flow F2 of the raw water W1 when the air layer 100 expands causes The range of the filter 11 to be cleaned is narrowed. Therefore, as described above, after forming the air layer 100, the volume of the air layer 100 is adjusted so that the liquid surface position of the raw water W1 in the raw water space 12A is positioned above the center in the length direction of the filter 11. is preferred.

(Other embodiments)
Other embodiments of the invention will now be described.

In Embodiment 1, the case where the air layer 100 is formed by accumulating the compressed air A1 permeated from the inner surface 11B of the filter 11 toward the outer surface 11A in the raw water space 12A has been described. The method is not limited to this. For example, as shown in FIG. 9, a gas introduction port 19 that communicates with the raw water space 12A is provided on the side surface of the housing 12 above the center in the vertical direction, and the compressed air A1 is introduced from the gas introduction port 19. The air layer 100 may be formed by

In Embodiment 1, the case of cleaning the filtration unit 10 for filtering pool water (raw water W1) has been described, but the application of the filtration unit cleaning method of the present invention is not limited to this. For example, the method for cleaning a filtration unit of the present invention may be used in cleaning a filter unit for purifying well water.

Although the case where the gas layer is the air layer 100 has been described in the first embodiment, the method for cleaning the filtration unit of the present invention is not limited to this. For example, the gas layer may be formed by a gas other than air, such as nitrogen.

In the first embodiment, the case where the step of pressurizing the air layer 100 is further performed after forming the air layer 100, but the pressurization step may be omitted.

In Embodiment 1, the case where the ON/OFF of the filtration pump 30 and the opening and closing of the valves 21, 31, 42, 51, and 61 are automatically switched by the control unit 70 has been described. It is not limited to this. That is, on/off of the filtration pump 30 and opening/closing of each valve 21, 31, 42, 51, 61 may be switched manually.

It should be understood that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

10 filtration unit 11 filter 11A outer surface (surface)
11B inner surface 11C hollow portion 12 housing 12A raw water space 100 air layer (gas layer)
W1 raw water

Claims (5)

In a filtration unit comprising a filter for filtering raw water, and a housing containing the filter and having a raw water space filled with raw water, a surface of the filter facing the raw water space is A method of cleaning, comprising:
a step of opening a gas inlet valve located on a path leading to the treated water space, supplying gas to the treated water space, and applying pressure from the treated water space side to the raw water space side to remove impurities from the filter;
By opening the flow path leading to the raw water space for a predetermined time while maintaining the open state of the gas inlet valve, the gas layer in which the gas is compressed to a state higher than the atmospheric pressure is treated as the raw water in the raw water space. forming a portion within the raw water space so as to be in contact;
By opening the raw water space to atmospheric pressure while maintaining the open state of the gas inlet valve, the gas layer is removed from the closed state in which the compressed gas and raw water in the raw water space are not discharged from the raw water space. and discharging raw water containing impurities in the raw water space while expanding the raw water space . 2. The method of cleaning a filtration unit according to claim 1, wherein in the step of expanding the gas layer, the expanded gas layer pushes the raw water in the raw water space in a direction along the surface of the filter. the filter and the housing are arranged in a posture along the vertical direction,
3. The gas layer according to claim 1 or 2, wherein in the step of forming the gas layer, the gas layer is formed such that the surface position of the raw water in the raw water space is positioned above the center in the length direction of the filter. cleaning method of the filtration unit of. The filtration unit according to any one of claims 1 to 3, further comprising a step of pressurizing the gas layer after the step of forming the gas layer and before the step of expanding the gas layer. cleaning method. The filter is hollow and includes an outer surface, which is the surface facing the raw water space, and an inner surface facing the hollow portion of the filter,
In the step of forming the gas layer, after the water in the hollow portion is pushed out into the raw water space by gas, the gas that has permeated the filter from the inner surface toward the outer surface is accumulated in the raw water space. The method for cleaning a filtration unit according to any one of claims 1 to 4, which forms a layer.

Images