Water treatment system and water treatment method

Abstract

The present invention provides a water treatment system and water treatment method that can uniformly agitate water requiring treatment stored in a water tank. [Solution] A water treatment system for removing PFAS contained in water to be treated stored in a water tank 1 having a maintenance hole in the ceiling, comprising: a PFAS removal device 40 for removing PFAS in the water to be treated; an intake pipe 41 with one end immersed in the water to be treated and the other end connected to the PFAS removal device; a drain pipe 42 with one end connected to the PFAS removal device and the other end positioned inside the water tank, and at least a portion of which is flexible; a pump 43 positioned along the piping path; and a movable floating body 44 positioned floating on the surface of the water to be treated in the water tank, the movable floating body being connected to the other end of the drain pipe and being able to move on the surface of the water to be treated in the water tank by the reaction force of the recirculating water that passes through the PFAS removal device and is discharged into the water tank through the drain pipe.

Description

Technical Field

[0001] The present invention relates to a water treatment system and a water treatment method.

Background Art

[0002] PFAS is known to be a causative substance that causes environmental problems because it is hardly decomposable and remains for a long time, and at the same time, regulations are being strengthened in recent years. Therefore, there is a need for water treatment to remove PFAS from water containing PFAS and purify the water.

[0003] PFAS has been used in various applications so far, and one of those applications is as a fire extinguishing agent in case of fire. Therefore, in facilities that require a large amount of fire extinguishing water, such as airports, military facilities, and other buildings, some have water storage tanks in the ground within the site to store fire extinguishing water, and the stored fire extinguishing water may contain PFAS. When using such fire extinguishing water during actual fire extinguishing or fire training, it will lead to the release of PFAS into the surrounding environment. Therefore, the applicant has developed and proposed a practical technology for removing PFAS from PFAS-containing water in such water storage tanks.

[0004] Patent Document 1 describes a circulating water treatment method and a portable water treatment device for filtering and removing PFAS (perfluoroalkyl substances and polyfluoroalkyl compounds) and suspended solids (SS; Suspended Solids) contained in the water to be treated stored in a water storage tank to be treated.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In order to remove PFAS from treated water in a water storage tank using a filter, the treated water in the tank must be thoroughly filtered by the filter. However, generally, water storage tanks only have a maintenance hole (manhole) in the ceiling that is just large enough for one person to pass through, and fire-fighting related machinery and equipment such as pumps are often installed around the maintenance hole, so access to the inside is limited, and it is usually difficult to bring large equipment into the water storage tank or to secure a sufficiently large workspace around the maintenance hole.

[0007] Therefore, when performing a circulating water treatment system, if the water to be treated and the filtered return water are drawn in through such a narrow maintenance hole, a circulating water flow will be generated in a narrow area near the maintenance hole, which may make it difficult to treat all the water to be treated in the storage tank. Furthermore, because sufficient workspace cannot be secured around the maintenance hole, it is often practically difficult to perform tasks such as agitating the water to be treated in the storage tank manually or to install additional agitation equipment.

[0008] The present invention has been made in view of these circumstances, and its purpose is to provide a water treatment system and a water treatment method that can uniformly agitate water to be treated stored in a water tank. [Means for solving the problem]

[0009] The invention disclosed in this application, which aims to solve the above-mentioned problems, has various aspects, and a summary of some of the most representative aspects is as follows.

[0010] (1) A water treatment system for removing PFAS (perfluoroalkyl substances and polyfluoroalkyl compounds) contained in water to be treated stored in a water tank having a maintenance hole in the ceiling that allows access to the interior, comprising: a PFAS removal device installed outside the water tank and removing PFAS in the water to be treated by passing the water to be treated through it; an intake pipe having one end immersed in the water to be treated in the water tank through the maintenance hole and the other end connected to the PFAS removal device; a drainage pipe having one end connected to the PFAS removal device and the other end positioned inside the water tank, with at least a part of it being flexible; a pump positioned on the piping path from the intake pipe to the drainage pipe; and a movable floating body positioned floating on the surface of the water to be treated in the water tank, which is connected to the other end of the drainage pipe and is movable on the surface of the water to be treated in the water tank by the reaction force of the recirculating water that passes through the PFAS removal device and is discharged into the water tank through the drainage pipe.

[0011] (2)(1) A water treatment system in which the movable floating body comprises a floating body, a connection part connected to the drainage pipe, and a propulsion nozzle for deflecting and discharging the recirculating water.

[0012] (3)(2) A water treatment system in which the connecting part is a rotary joint.

[0013] (4)(2) A water treatment system in which the propulsion nozzle changes the discharge direction of the recirculating water by water pressure or external power.

[0014] (5)(2) A water treatment system in which the moving float has a bumper on its front in the direction of movement that is asymmetrical with respect to the direction of movement, and the orientation of the moving float is changed when the bumper comes into contact with the wall surface of the water tank.

[0015] (6)(5) A water treatment system in which the bumper includes at least one guide roller.

[0016] (7) A water treatment method for removing PFAS (perfluoroalkyl substances and polyfluoroalkyl compounds) contained in water to be treated stored in a water tank having a maintenance hole in the ceiling that allows access to the interior, wherein a PFAS removal device is installed outside the water tank, which removes PFAS in the water to be treated by passing the water to be treated through it, one end of an intake pipe is immersed in the water to be treated inside the water tank through the maintenance hole, and the other end is connected to the PFAS removal device, and a drain pipe is at least partially flexible A water treatment method comprising: connecting one end of a movable float to the PFAS removal device, placing the other end to which the movable float is connected inside the water storage tank, placing a pump on the piping path from the intake pipe to the drainage pipe, driving the pump to pass the water to be treated taken in through the intake pipe to the PFAS removal device, draining the recirculated water that has passed through the PFAS removal device through the drainage pipe, and using the reaction force of the recirculated water discharged into the water storage tank to move the movable float over the water surface of the water to be treated in the water storage tank, thereby agitating the water to be treated in the water storage tank.

[0017] (8)(7) A water treatment method wherein the moving floating body comprises a floating body, a connecting part connected to the drainage pipe, and a propulsion nozzle for deflecting and discharging the recirculating water.

[0018] (9)(8) The water treatment method wherein the connecting part is a rotary joint, and entanglement of the drainage pipe due to the movement of the movable float is prevented.

[0019] (10)(8) A water treatment method wherein the propulsion nozzle changes the discharge direction of the recirculating water by water pressure or external power.

[0020] (11)(8) A water treatment method wherein the moving float has a bumper on its front in the direction of movement that is asymmetrical with respect to the direction of movement, and the orientation of the moving float is changed when the bumper comes into contact with the wall surface of the water tank.

[0021] A water treatment method in which the bumper includes at least one guide roller, according to (12)(11).

Brief Description of the Drawings

[0022] [Figure 1] It is a schematic cross-sectional view of a typical water storage tank filled with raw water W to be treated, which is shown for the purpose of explaining the usage mode of the water treatment system according to the first embodiment of the present invention. [Figure 2] It is a side view for explaining an example of the structure of the moving floating body according to the first embodiment of the present invention. [Figure 3] It is a bottom view of the base plate. [Figure 4] It is a vertical cross-sectional view of the water flow motor showing an example of the structure of the water flow motor. [Figure 5] It is a vertical cross-sectional view of the speed reducer showing an example of the structure of the speed reducer. [Figure 6] It is a flowchart for explaining the procedure of the water treatment method using the water treatment system according to the first embodiment of the present invention. [Figure 7] It is a side view for explaining an example of the structure of the moving floating body according to the second embodiment of the present invention. [Figure 8] It is a bottom view of the base plate. [Figure 9] It is a top view for explaining an example of the structure of the moving floating body according to the third embodiment of the present invention. [Figure 10] It is a side view for explaining an example of the structure of the moving floating body according to the third embodiment of the present invention.

Modes for Carrying Out the Invention

[0023] FIG. 1 is a schematic cross-sectional view of a typical water storage tank 1 filled with raw water W to be treated, which is shown for the purpose of explaining the usage mode of the water treatment system 4 according to the first embodiment of the present invention. The water storage tank 1 is provided underground below the ground surface GL, and its floor surface 10 and four side surfaces 11 are covered with walls to prevent water leakage. Further, a ceiling 12 is provided on the upper surface of the water storage tank 1 to protect against foreign matters such as fallen leaves and dust from falling into the water storage tank 1 and also serves as a floor surface for installing mechanical equipment such as the fire extinguishing pump 2.

[0024] A maintenance hole 13 is provided in the ceiling 12, allowing an operator to enter the interior for maintenance of the water storage tank 1. The maintenance hole 13 is a manhole, large enough for one person to pass through, but not particularly large. Normally, the maintenance hole 13 is closed with a suitable cover. A ladder 14 is also provided on the wall so that an operator can descend from the maintenance hole 13 into the interior of the water storage tank 1. In Figure 1, for the sake of simplicity in the illustration, the ladder 14 submerged in the treated water W is not shown, but the ladder 14 extends to a position where the operator can reach the floor 10.

[0025] Furthermore, a building 3 is provided above the water storage tank 1 to protect the fire extinguishing pump 2 and the maintenance hall 13 from wind and rain. The building 3 may also be used as a warehouse to store accessories for the fire extinguishing pump 2, such as water discharge hoses and replacement parts for maintenance.

[0026] Generally, building 3 is often constructed to the minimum size necessary to accommodate mechanical equipment such as fire pumps 2 and their accessories, in order to minimize the above-ground area above ground level (GL). As shown in the diagram, it is usually smaller than the area occupied by the underground water storage tank 1 below ground level. Therefore, as shown in the diagram, fire pumps 2 and other equipment are often positioned very close to the maintenance hall 13, and there is often only enough space around the maintenance hall for one operator to pass through.

[0027] There are no particular restrictions on the shape of the water storage tank 1, but generally, it is often a rectangular prism with a rectangular planar shape or a similar internal shape. Other examples include a flattened cylindrical shape with a circular planar shape.

[0028] The maintenance hole 13 is often located adjacent to the side surface 11 of the water tank 1, due to the need to install the ladder 14. If the water tank 1 has a rectangular plan shape, the maintenance hole 13 is usually located at one of its four corners. Hereafter, we will explain using the example of a water tank 1 with a rectangular plan shape and a maintenance hole 13 located at one of its four corners.

[0029] The water treatment system 4 is temporarily installed for the purpose of removing PFAS contained in the water to be treated W stored in the water storage tank 1, and may include a PFAS removal device 40, intake piping 41, drainage piping 42, pump 43, and movable float 44, as well as other accessories.

[0030] The PFAS removal device 40 is installed outside the water storage tank 1 and removes PFAS from the water to be treated W by passing the water to be treated W through it. The PFAS removal device 40 may include one or more filters for filtering out suspended solids and one or more ion exchange resin cartridges for removing PFAS, and may also include pumps, valves, various flow meters, a sedimentation tank, etc., and may be similar to the portable water treatment device described in the above-mentioned Patent Document 1. Alternatively, the PFAS removal device 40 may simply consist of a filter and an ion exchange resin cartridge connected by piping.

[0031] The water to be treated W passes through the PFAS removal device 40, where suspended solids are removed, and all or part of the PFAS contained within is removed. The water that has passed through the PFAS removal device 40 is returned to the water storage tank 1, and hereafter, this water returned to the water storage tank 1 will be distinguished from the water to be treated W and referred to as recirculated water. The recirculated water mixes with the water to be treated W in the water storage tank 1 and is again passed through the PFAS removal device 40 as water to be treated W. As this process is repeated continuously, the concentration of PFAS in the water to be treated W in the water storage tank 1 gradually decreases, and after sufficient treatment time, the removal of PFAS from the water to be treated W in the water storage tank 1 is achieved. Therefore, the water treatment system 4 performs circulating water treatment.

[0032] The filter media used in the filter is not limited and may include sand, diatomaceous earth, sponges, membranes, or combinations thereof. Furthermore, whether or not the filter is a backwash type is optional. Additionally, while ion exchange resin is a promising filter material for cartridge-type filters that remove PFAS, the filter is not limited to this; activated carbon, zeolite, silica gel, or combinations thereof, or combinations of these with ion exchange resin, may be used.

[0033] The water intake pipe 41 is a pipe that has one end immersed in the water to be treated W in the water storage tank 1 through the maintenance hole 13, and the other end connected to the PFAS removal device 40, and sends the water to be treated W, which has been pumped up by the pump 43 (described later), to the PFAS removal device 40.

[0034] The drainage pipe 42 is connected at one end to the PFAS removal device 40 and at the other end to the water to be treated W in the water storage tank 1, and returns the recirculated water that has passed through the PFAS removal device 40 back into the water storage tank 1. At least a portion of the drainage pipe 42 is a flexible pipe, and a movable float 44, which will be described later, is connected to the other end. In the example shown in Figure 1, the PFAS removal device 40 side of the drainage pipe 42 is a rigid pipe 420, and a flexible pipe 421 is connected to the tip of the rigid pipe 420 that is inserted into the water storage tank 1 from the maintenance hole 13. However, the method is not limited to this, and the entire drainage pipe 42 may be a flexible pipe, or a rigid pipe may be attached to the tip of the flexible pipe 421 and connected to the movable float 44.

[0035] In any case, the flexible pipe 421 of the drainage pipe 42 allows the movable floating body 44, which floats on the surface of the water to be treated W, to move freely within the water storage tank 1 without restriction. The length and stiffness (magnitude of elastic reaction force) of the flexible pipe 421 are selected so as not to hinder the movement of the movable floating body 44.

[0036] Furthermore, the pump 43 is positioned along the piping path from the intake pipe 41 to the drainage pipe 42. In the example shown in Figure 1, the pump 43 is a submersible pump, connected to the other end of the intake pipe 41 and lowered into the water storage tank 1 through the maintenance hole 13, and placed on the floor 10 of the water storage tank 1. The pump 43 pumps up the water to be treated W through the intake pipe 41, passes it through the PFAS removal device 40, and provides momentum to discharge the recirculated water that has passed through the PFAS removal device 40 into the water storage tank 1 through the drainage pipe 44. The placement of the pump 43 is arbitrary and can be any position in the intake pipe 41, any position in the drainage pipe 42, or any position within the PFAS removal device 40, and multiple pumps 43 may be used simultaneously. The pump 43 may be a surface pump or a submersible pump, and its type may be a turbo pump or a positive displacement pump. In the example shown in Figure 1, the pump 43 is a centrifugal submersible turbo pump. Furthermore, a waterproof power cable for driving the electric motor extends from the pump 43 through the maintenance hole 13 to the ground and is connected to a power source (not shown).

[0037] A movable floating body 44 is connected to the other end of the drainage pipe 42, which is located inside the water tank 1. The movable floating body 44 floats on the surface of the water to be treated W using appropriate buoyancy and can move freely within the water tank 1, deflecting the recirculating water sent from the drainage pipe 42 in a direction that has at least a horizontal momentum component and discharging it into the water tank 1. In the example in Figure 1, the movable floating body 44 discharges the recirculating water in a diagonal downward direction, thereby generating a water flow F and a secondary water flow F' caused by the water flow F in the water tank 1, and the water to be treated W is agitated by these water flow F and secondary water flow F'. The water flow F and secondary water flow F' do not necessarily have sufficient velocity and flow rate to agitate the entire water to be treated W in the water tank 1, but the movable floating body 44 receives the reaction force of the water flow F and moves the surface of the water to be treated W in direction V. Therefore, the positions where the water flow F and secondary water flow F' are generated change moment by moment within the water storage tank 1, and as a result, the entire volume of water to be treated W in the water storage tank 1 is evenly agitated.

[0038] The direction of the recirculating water discharged from the moving float 44 is not particularly limited and can be selected from a nearly horizontal direction to a direction close to vertically downward. However, in order for the moving float 44 to move throughout the water tank 1 due to the reaction force of the water flow F, it is desirable that the water flow F has a horizontal component, and in order to agitate the water to be treated W in the water tank 1 to the bottom, it is desirable that the water flow F also has a vertical component. Specifically, the recirculating water is discharged at an angle range of preferably 15 to 75 degrees, more preferably 30 to 60 degrees, with respect to the horizontal direction. Furthermore, the discharge angle of the recirculating water may be dynamically changed within this angle range.

[0039] It is desirable that the water intake pipe 41 and the drainage pipe 42 be fixed in place so as not to move relative to the maintenance hole 13. Any method of fixing is acceptable, but in the illustrated example, a tension clamp 45 is inserted and fixed in the diametrical direction of the circular maintenance hole 13, and the water intake pipe 41 and the drainage pipe 42 are fixed to this tension clamp 45 using appropriate brackets or the like so as not to move.

[0040] The simplest way to construct the movable floating body 44 is to wrap the flexible pipe 421 of the drainage pipe 42 around any float and fix it in place by an appropriate method. However, with such a simple method, the movable floating body 44 only moves in a straight line in the opposite direction to the drainage direction of the recirculating water, and stops moving after reaching the side surface 11 of the water storage tank 1 and hitting it, making it highly likely that the entire treated water W in the water storage tank 1 cannot be uniformly agitated. Therefore, the movable floating body 44 according to the embodiments described below, including this embodiment, has various configurations for continuing to move within the water storage tank 1.

[0041] Figure 2 is a side view illustrating an example of the structure of the mobile floating body 44 according to this embodiment. The mobile floating body 44 consists of a frame 440, a floating body 441, and a propulsion nozzle 442. The floating body 441 is fixed to the frame 440 so as to surround the frame 440, and the propulsion nozzle 442 is attached to the lower side of the frame 440. When the mobile floating body 44 is placed in the water tank 1, the buoyancy of the floating body 441 causes the mobile floating body 44 to float to the water surface, and a part of the frame 440 and the propulsion nozzle 442 are submerged. In addition, for the sake of ease of illustration, the figure shows the side cross-sections of some components, namely the floating body 441 and the face gear 4404.

[0042] The float 441 is a hollow or porous donut-shaped float, and there are no particular limitations on its material. However, if it is made of a flexible synthetic resin, it is easier to change its shape when inserting or removing the movable float 44 into or out of the water tank 1 through the maintenance hole 13. If the float 441 is a hollow metal float or made of a hard porous resin, such as hard polystyrene foam resin, it must be small enough to pass through the maintenance hole 13. If the float 441 is a hollow, flexible synthetic resin, such as polyvinyl chloride resin, and is an inflatable float, it can be larger than the maintenance hole 13. For example, the movable float 44 can be passed through the maintenance hole 13 with some or all of the air inside the float 441 removed, then air can be injected into the float 441 to inflate it, and then the movable float 44 can be lowered to the surface of the water to be treated W. The reverse procedure can be performed when removing the movable float 44.

[0043] The method of fixing the floating body 441 to the frame 440 is arbitrary, but one example is to fix it to the base plate 4400 of the frame 440 using a rope 4410.

[0044] The frame 440 is erected so as to penetrate the center of the base plate 4400 and includes a pipe 4401 whose upper end is exposed above the water surface and whose lower end is submerged, a connecting part 4402 which is an L-shaped rotary joint provided at the upper end of the pipe 4401, a rotary joint 4403 provided at the lower end of the pipe 4401, and a face gear 4404 provided on the lower surface of the base plate 4400.

[0045] The connecting portion 4402 is connected to the flexible pipe 421 of the drainage pipe 42 and is rotatable around a vertical axis. Since the connection direction with the flexible pipe 421 is horizontal and its vertical height is above the upper surface of the floating body 441, the connecting portion 442 always faces the direction of the flexible pipe 421. This ensures that the flexible pipe 421 does not become entangled with the moving floating body 44 and hinder its movement, regardless of its position or orientation within the water storage tank 1.

[0046] The rotary coupling 4403 connects the propulsion nozzle 442 so that it can rotate around a vertical axis and also supports its position. In addition, a face gear 4404 is mounted coaxially with the rotary coupling 4403 and on the underside of the base plate 4400 to accommodate the rotary coupling 4403.

[0047] Figure 3 is a bottom view of the base plate 4400. In this example, the base plate 4400 is a flat plate with a circular outer shape, and a rotating joint 4403 is provided at its center. The material of the base plate 4400 is not particularly limited, but in this embodiment it is made of a corrosion-resistant metal such as stainless steel or aluminum, and is firmly welded to the pipe 4401. The base plate 4400 is also lightened by cutting out holes, and these holes are also used when fixing the floating body 441 to the frame 440 using ropes 4410. However, cutting out holes is not necessarily required, and any other structure for fixing the floating body 441 may be provided separately.

[0048] Furthermore, a face gear 4404 is mounted concentrically with the rotary joint 4403 on the underside of the base plate 4400. The method of fixing the face gear 4404 is arbitrary, but it can be simply screwed in, and since the face gear 4404 is not subjected to high loads, it may be mounted so as to straddle the weight-reducing holes as shown in the figure.

[0049] The propulsion nozzle 442 provides movement to the mobile float 44 with the reaction force of discharging the recirculating water supplied from the drainage pipe 42 into the reservoir 1, and at the same time, it is equipped with a mechanism to dynamically change the direction of discharge of the recirculating water so that the mobile float 44 continues to move within the reservoir 1. In this example, the propulsion nozzle 442 is configured to slowly rotate around a vertical axis, so that the direction of movement of the mobile float 44 within the reservoir 1 changes moment by moment, and the mobile float 44 moves thoroughly over the surface of the water to be treated W in the reservoir 1 while changing direction.

[0050] The rotation mechanism of the propulsion nozzle 442 is optional and may change the discharge direction of the recirculating water by water pressure or external power. While it is easy to implement a mechanism using external power, such as an electric motor, it requires a separate power source and the electric motor to be mounted on the mobile float 44. Therefore, using a mechanism in which the propulsion nozzle 442 rotates by utilizing the water pressure of the recirculating water passing through the propulsion nozzle 442 is advantageous because it allows for a simple change in the direction of the mobile float 44.

[0051] The illustrated diagram shows a propulsion nozzle 442 that rotates using the water pressure of the recirculating water. The rotating nozzle 442 has a rotating mechanism 4420 and a nozzle head 4424 fixed to the lower surface of the rotating mechanism 4420. The nozzle head 4424 is a component that controls the direction, speed, and shape of the flow of recirculating water discharged into the water storage tank 1. By bending as shown in the diagram, the direction of discharge of the recirculating water is directed diagonally downward, at an angle of approximately 50 degrees to the vertical in this example. Furthermore, by narrowing the discharge outlet, the speed of the discharge flow can be increased, allowing the water flow F shown in Figure 1 to reach further. The shape of the discharge outlet may be a simple circular opening to produce a straight flow, or a slit opening to produce a fan-shaped flow. In addition, the nozzle head 4424 may be used as a venturi nozzle to draw in the water to be treated W around the nozzle head 4424 and increase the flow rate of the water flow F.

[0052] The swivel mechanism 4420 consists of a water-flow motor 4421 that extracts rotational power using the water pressure of the recirculating water, and a reduction gear 4422. A gear 4423 is exposed on the upper surface of the reduction gear 4422, and this gear 4423 meshes with a face gear 4404. As the recirculating water passes through the swivel mechanism 4420 of the propulsion nozzle 442, the power extracted causes the gear 4423 to rotate slowly, resulting in a structure in which the swivel nozzle 442 rotates slowly relative to the base plate 440.

[0053] Figure 4 is a vertical cross-sectional view of the water flow motor 4421, showing an example of its structure. The mechanism of the water flow motor 4421 may be any known mechanism, but here a three-lobe Roots pump structure is employed.

[0054] In other words, when recirculating water is introduced into the water flow motor 4421 from the inlet at the top, the impellers housed inside the casing rotate in opposite directions, as is well known, as indicated by the dashed arrows in the figure. The recirculating water flows along the inner surface of the casing and flows out from the outlet at the bottom of the water flow motor 4421. At this time, if one of the impeller shafts is extended outside the water flow motor 4421, rotational power can be extracted from that shaft.

[0055] Figure 5 is a vertical cross-sectional view of a speed reducer 4422, showing an example of its structure. The speed reducer 4422 has a structure in which four gears 4423a to 4423d, each with a module of equal but different reference circle diameters, are housed inside the casing. Gears 4423a and 4423b, and gears 4423c and 4423d mesh with each other. Gear 4423a is mounted on the power shaft, gears 4423b and 4423c are mounted coaxially to rotate freely, and gear 4423d, which also rotates freely, is mounted so that its upper part is exposed to the top of the casing.

[0056] In this reduction gear 4422, the rotational power extracted by the water motor 4421 is sufficiently reduced in the process of being transmitted sequentially to the gears 4423a to 4423d, and finally, the gear 4423d that meshes with the face gear 4404 provided on the lower surface of the base plate 4400 rotates slowly, which acts to slowly rotate the entire propulsion nozzle 442.

[0057] Note that the internal structure of the reduction gear 4422 shown here is just one example, and the number and arrangement of gears used can be arbitrarily set according to the required overall rotational speed of the propulsion nozzle 442, and a mechanism that allows the reduction ratio to be arbitrarily changed may also be used.

[0058] Figure 6 is a flowchart illustrating the procedure for a water treatment method using the water treatment system 4 according to this embodiment. First, in step ST1, the PFAS removal device 40 is installed outside the water storage tank 1, as close as possible. Since the PFAS removal device 40 is not a permanent fixture, it can be transported and installed on a transport vehicle such as a truck, and then removed after the water treatment is complete. Alternatively, the PFAS removal device 40 may remain loaded on the transport vehicle, and the transport vehicle may be parked at a nearby location outside the water storage tank 1 to perform the water treatment.

[0059] Step ST2 involves installing and connecting the intake pipe 41, the drainage pipe 42, and the pump 43. The order of installation and connection may vary depending on the system configuration of the water treatment system 4 and the environment in which the water storage tank 1 is located. This procedure includes immersing one end of the intake pipe 41 in the water to be treated W in the water storage tank 1 through the maintenance hole 13 and connecting the other end to the PFAS removal device 40; connecting one end of the drainage pipe 42, which is at least partially flexible, to the PFAS removal device 40 and placing the other end to which the movable float 44 is connected inside the water storage tank 1; and placing the pump 43 along the piping path from the intake pipe 41 to the drainage pipe 42.

[0060] In the embodiment described above, since the pump 43 is a submersible pump connected to the other end of the intake pipe 41, the intake pipe 41 is first connected to the other end of the intake pipe 41, lowered into the water storage tank 1 through the maintenance hole 13, and then fixed in place. Similarly, regarding the drain pipe 42, the movable floating body 44 connected to the other end of the drain pipe 42 is passed through the maintenance hole 13 and placed inside the water storage tank 1. Therefore, to facilitate the passage of the movable floating body 44, it is advisable to first place the movable floating body 44 into the water storage tank 1 before fixing the intake pipe 41 and drain pipe 42 to the maintenance hole 13, thereby simplifying the work. Afterward, the intake pipe 41 and drain pipe 42 can be connected to the PFAS removal device 40.

[0061] Furthermore, in step ST3, the pump 43 is driven to pass the water to be treated W, which has been taken in through the intake pipe 41, through the PFAS removal device 40. The returned water that has passed through the PFAS removal device 40 is then sent through the drainage pipe 42 to the movable float 44 and drained into the water storage tank 1.

[0062] Next, in step ST4, when the recirculating water is drained into the water tank 1, the propulsion reaction force generated by the propulsion nozzle 442 of the moving float 44 moves the water surface of the water to be treated W in the water tank 1, thereby agitating the water to be treated W in the water tank 1. At this time, the direction of movement of the moving float 44 may be changed at least once. In this embodiment, the direction of movement of the moving float 44 is continuously changed by the rotation of the propulsion nozzle 442.

[0063] Once the water treatment has been performed for a sufficient amount of time and the entire volume of water to be treated W in the storage tank 1 has been agitated to sufficiently remove the contained PFAS, the water treatment device 4 is removed. Whether or not PFAS has been sufficiently removed from the water to be treated W may be determined by the fact that the water treatment has been performed for a predetermined amount of time, or by sampling the water to be treated W in the storage tank 1 after the water treatment has been performed for a predetermined amount of time and measuring the PFAS concentration.

[0064] In the water treatment system 4 according to the first embodiment described above, the direction of movement of the movable float 44 was changed by the rotation of the propulsion nozzle 442 due to the water pressure of the recirculating water. However, in the water treatment system 4 according to the second embodiment described below, an example is provided in which the movable float 44 is equipped with a propulsion nozzle 442 that changes the direction of movement of the movable float 44 by sequentially switching between a plurality of nozzle heads 4424 facing in different directions using external power.

[0065] The water treatment system 4 according to the second embodiment differs from that according to the first embodiment only in the structure of the movable float 44; all other aspects are the same. Therefore, the description of the water treatment system 4, other than that relating to the structure of the movable float 44, as described in the first embodiment, and Figures 1 and 6, will be applied to the water treatment system 4 according to the second embodiment. The same reference numerals will be used for elements that are the same or corresponding in both embodiments, and redundant descriptions will be omitted.

[0066] Figure 7 is a side view illustrating an example of the structure of the movable floating body 44 according to this embodiment. Similar to the previous embodiment, the movable floating body 44 consists of a frame 440, a floating body 441, and a propulsion nozzle 442. The floating body 441 is fixed to the frame 440 so as to surround the frame 440, and the propulsion nozzle 442 is attached to the lower side of the frame 440. Similarly, when the movable floating body 44 is placed in the water tank 1, the buoyancy of the floating body 441 causes the movable floating body 44 to float to the water surface, and a part of the frame 440 and the propulsion nozzle 442 become submerged. Also, for ease of illustration, the figure shows a side cross-section of the floating body 441.

[0067] The floating body 441 is a hollow or porous donut-shaped float, similar to the previous embodiment, and there is no particular difference. Similarly, the floating body 441 is fixed to the frame 440 by, for example, using a rope 4410 to secure it to the base plate 4400 of the frame 440.

[0068] The frame 440 consists of a base plate 4400, a pipe 4401 erected at the inlet on the upper surface of a switching valve 4425 located in the center of the upper surface of the base plate 4400, and a connecting portion 4402 provided at the upper end of the pipe 4401. Structurally, the base plate 4400 and the pipe 4401 are fixed to each other via the switching valve 4425, but for the sake of explanation, the switching valve 4425 is treated as part of the propulsion nozzle 442. However, this is merely for the sake of explanation, and it does not change the fact that all these components work together to constitute the mobile floating body 44; it is not essential.

[0069] In the illustrated example, the lower part of the switching valve 4425 is submerged, while the upper part of the switching valve 4425 and the pipe 4401 are exposed above the water surface. However, the shape and dimensions of the switching valve 4425 and the pipe 4401 are arbitrary. An L-shaped rotary joint connector 4402 is provided at the upper end of the pipe 4401 and is connected to the flexible pipe 421 of the drainage pipe 42. This ensures that the flexible pipe 42 does not become entangled and hinder the movement of the movable floating body 44, regardless of its position and orientation within the water tank 1, which is the same as in the previous embodiment.

[0070] The propulsion nozzle 442 consists of a switching valve 4425 and multiple nozzle heads 4424, in this example five, connected by appropriate piping. The switching valve 4425 is fixed to the upper surface of the base plate 4400, for example, by screws, and a pipe 4401 is connected to the inlet on its upper surface, while nozzle heads 4424 are connected to multiple outlets provided on its side via appropriate piping. In this example, there are five nozzle heads 4424, so the switching valve 4425 is a five-way valve, and it is an electromagnetic five-way valve that connects one of the outlets to the inlet in response to a power signal provided through a control code 4426, which is electrical wiring connected to the switching valve 4425. The control code 4426 is waterproof and is connected to a control device (not shown) outside the water storage tank 1 along a flexible pipe 421.

[0071] Note that the switching valve 4425 does not necessarily have to be a single solenoid 5-way valve, but may be a collection of multiple solenoid valves. For example, the pipe 4401 may be branched into five directions, and a simple solenoid shut-off valve may be placed at each branch.

[0072] The nozzle heads 4424 are fixed to the lower surface of the base plate 4400 so that they face in different directions from each other. The structure of each nozzle head 4424 may be the same as that of the previous embodiment. In a plan view, each nozzle head 4424 is arranged so that it faces outward radially at equal angles with respect to the center of the moving float 44.

[0073] Figure 8 is a bottom view of the base plate 4400. In this example, the base plate 4400 is a flat plate with a circular outer shape, and a switching valve 4425 is screwed to the front side of its center. The material of the base plate 4400 and the cutouts for weight reduction can be the same as in the previous embodiment. As shown in the figure, five nozzle heads 4424 are fixed to the bottom surface of the base plate 4400, concentrically and at equal intervals, facing outwards. Therefore, in this example, in a plan view, the direction in which each nozzle head 4424 discharges recirculated water is 72 degrees different from the center of the base plate 4400.

[0074] In a mobile floating body 44 having such a structure, when the pump 43 is driven and the water to be treated W taken in through the intake pipe 41 passes through the PFAS removal device 40, and the recirculated water is sent to the mobile floating body 44 through the drainage pipe 42, the recirculated water is forcefully ejected into the water storage tank 1 from one of the nozzle heads 4424 that are connected to the pipe 4401 by the switching valve 4425. As a result, the mobile floating body 44 moves the water surface of the water to be treated W in the water storage tank 1 in the opposite direction to the nozzle head 4424 due to the reaction force of the ejected recirculated water, and also agitates the water to be treated W in the water storage tank 1.

[0075] As the floating body 44 moves in a straight line, it soon comes into contact with the side 11 of the water storage tank 1 and stops moving. Therefore, periodically or irregularly, depending on the passage of time or the amount of water to be treated W to be treated, a power signal is sent from a control device (not shown) to a switching valve 4425, switching the nozzle head 4424 that communicates with the pipe 4401. As a result, the direction in which the floating body 44 is trying to move changes, so the floating body 44 that was stuck against the side 11 moves away from the side 11 and begins to move across the surface of the water to be treated W again.

[0076] The timing for switching the switching valve 4425 can be arbitrary, but if switching is done based on the passage of time, it may be done every few minutes to about an hour, for example, every 10 minutes. If switching is done based on the amount of water to be treated W, the measured values ​​from the flow meter installed at any point in the water treatment system 4 are accumulated, for example, 10 m 3 This can be done for each processing step. Also, after one nozzle head 4424 has communicated with pipe 4401, the next nozzle head 4424 communicating with pipe 4401 does not need to be adjacent to the previous one; it may be skipped or selected randomly. Furthermore, the number of nozzle heads 4424 on the propulsion nozzle 442 is not limited to the 5 shown here, but can be any number of 3 or more. However, considering that the planar shape of the water storage tank 1 is often rectangular, it is preferable to avoid 4 or a multiple thereof, as this is not suitable for the moving float 44 to move evenly across the surface of the treated water W. Also, providing an excessive number of nozzle heads 4424 is not very meaningful because some nozzle heads 4424 will be facing similar directions. Therefore, it is preferable that the number of nozzle heads 4424 be 3 to 7, excluding 4.

[0077] Furthermore, in this embodiment, the propulsion nozzle 442 changes the discharge direction of the recirculating water by external power, that is, an example is shown in which the switching valve 4425 is switched by a power signal from a control device (not shown). However, the switching of the switching valve 4425 may be performed using the water pressure of the recirculating water instead of external power. For example, such a configuration can be achieved by using the water flow motor shown in the previous embodiment to obtain rotational power and switching the switching valve 4425 at regular intervals through intermittent operation. Intermittent operation can be easily achieved by any known mechanical mechanism, such as a Geneva mechanism.

[0078] The water treatment system 4 according to the third embodiment described next is an example in which the orientation of the movable floating body 44 is changed when it comes into contact with the wall surface of the water storage tank 1, and consequently the direction of movement of the movable floating body 44 is changed.

[0079] The water treatment system 4 according to the third embodiment differs from those of the first and second embodiments only in the structure of the movable float 44; all other aspects are the same. Therefore, as with the description of the second embodiment, the description of the water treatment system 4 other than that relating to the structure of the movable float 44, as well as Figures 1 and 6, provided for the first embodiment, will be applied to the water treatment system 4 according to the third embodiment. The same reference numerals will be used for elements that are the same or corresponding in both embodiments, and redundant descriptions will be omitted.

[0080] Figure 9 is a top view illustrating an example of the structure of the movable floating body 44 according to this embodiment, and Figure 10 is a side view thereof. The movable floating body 44, like the first and second embodiments described above, consists of a frame 440, a floating body 441, and a propulsion nozzle 442. The floating body 441 is fixed to the frame 440 so as to surround the frame 440, and the propulsion nozzle 442 is attached to the lower side of the frame 440. In the same manner, when the movable floating body 44 is placed in the water tank 1, the buoyancy of the floating body 441 causes the movable floating body 44 to float to the water surface, and a part of the frame 440 and the propulsion nozzle 442 are submerged. Also, in the side view of Figure 10, the side cross-section of the floating body 441 is shown for ease of illustration.

[0081] The floating body 441 is a hollow or porous donut-shaped float, similar to the previous embodiment, and there is no particular difference. Similarly, the floating body 441 is fixed to the frame 440 by, for example, using a rope 4410 to secure it to the base plate 4400 of the frame 440.

[0082] The frame 440 consists of a base plate 4400, a pipe 4401 erected in the center of the upper surface of the base plate 4400, a connecting portion 4402 provided at the upper end of the pipe 4401, and a bumper 4405 attached to the base plate 4400 and extending to the outside of the outer circumference of the floating body 441. In this example, the bumper 4405 is fixed to the lower surface of the base plate 4400 by any method, for example, welding or screwing. Preferably, the bumper 4405 includes at least one guide roller 4406 fixed at a position that is distal to the base plate 4400.

[0083] As shown in Figure 10, a connector 4402, which is an L-shaped rotary joint, is provided at the upper end of the pipe 4401 and is connected to the flexible pipe 421 of the drainage pipe 42. The nozzle head 4424 is directly fixed to the lower end of the pipe 4401 and its orientation is constant with respect to the base plate 4400. In this example, the propulsion nozzle 442 consists only of the nozzle head 4424.

[0084] The bumper 4405, like the base plate 4400, is constructed as a rigid member made of metal or hard synthetic resin, and protrudes outward from the outer circumference of the floating body 441 in the direction of movement of the moving floating body 44, as indicated by the arrows in Figures 9 and 10. In particular, as shown in Figure 9, in a plan view, the bumper 4405 has an asymmetrical shape with respect to the direction of movement of the moving floating body 44. In this example, when the direction of movement of the moving floating body 44 is viewed as forward, the bumper 4405 has a shape that protrudes on the left side, making it asymmetrical.

[0085] This means that when the moving float 44 moves in the direction of movement and hits the side wall 11, which is the wall surface of the water tank 1, the distal front end of the bumper 4405 first contacts the side wall 11, and the reaction force imparts a counterclockwise rotational moment to the moving float 44 in this example. In other words, when the moving float 44 contacts the side wall 11, which is the wall surface of the water tank 1, its orientation changes so that it moves along the side wall 11 or slowly away from the side wall 11, and it continues its movement.

[0086] Furthermore, it is desirable that a guide roller 4406 be provided at the distal end of the bumper 4405. The side wall 11 of the water storage tank 1 is not necessarily smooth, and if the bumper 4405 comes into contact with it, it may get caught and hinder the movement of the movable floating body 44. Therefore, a freely rotating guide roller 4406 is provided on the bumper 4405, and by making the guide roller 4406 contact the side wall 11, the movement of the movable floating body 44 and the change of its orientation are not hindered. There is no particular limit to the number of guide rollers 4406 provided, and in this example, guide rollers 4406 are provided at the front distal end and the right distal end of the bumper 4405.

[0087] Each embodiment of the water treatment system 4 described above may be modified as necessary or combined as appropriate. For example, the movable float 44 of the water treatment system 4 described as the first or second embodiment may further include the bumper 4405 described as the third embodiment. The embodiments described above are provided as examples for realizing the invention disclosed in this application. [Explanation of symbols]

[0088] 1 Water storage tank, 2 Fire extinguishing pump, 3 Building, 4 Water treatment system, 10 Floor, 11 Side, 12 Ceiling, 13 Maintenance hole, 14 Ladder, 40 PFAS removal device, 41 Water intake piping, 42 Drainage piping, 43 Pump, 44 Movable float, 45 Brace clamp, 420 Rigid pipe, 421 Flexible pipe, 440 Frame, 441 Float, 442 Propulsion nozzle, 4400 Base plate, 4401 Pipe, 4402 Connection part, 4403 Rotary joint, 4404 Face gear, 4404 Bumper, 4406 Guide roller, 4410 Rope, 4420 Swivel mechanism, 4421 Water flow motor, 4422 Reducer, 4423, 4423a~d Gears, 4424 Nozzle head, 4425 Switching valve, control code 4426.

Claims

1. A water treatment system for removing PFAS (perfluoroalkyl substances and polyfluoroalkyl compounds) contained in water to be treated stored in a water tank having a maintenance hole in the ceiling that allows access to the interior, A PFAS removal device is installed outside the water storage tank and removes PFAS from the water to be treated by passing the water to be treated through it. A water intake pipe is provided, with one end immersed in the water to be treated in the water storage tank through the maintenance hole, and the other end connected to the PFAS removal device. One end is connected to the PFAS removal device, and the other end is placed inside the water storage tank, and at least a portion of the drainage pipe is flexible, A pump is placed along the piping path from the water intake pipe to the drainage pipe, A movable floating body positioned to float on the surface of the water to be treated in the water storage tank, connected to the other end of the drainage pipe, and capable of moving on the surface of the water to be treated in the water storage tank by the reaction force of the recirculating water that passes through the PFAS removal device and is discharged into the water storage tank through the drainage pipe, A water treatment system having

2. The moving float comprises a float, a connection part connected to the drainage pipe, and a propulsion nozzle that deflects and discharges the recirculating water. The water treatment system according to claim 1.

3. The aforementioned connection is a rotary joint. The water treatment system according to claim 2.

4. The propulsion nozzle changes the discharge direction of the recirculating water by water pressure or external power. The water treatment system according to claim 2.

5. The moving float has a bumper that is asymmetrical to the direction of movement on its forward side in the direction of movement, and when the bumper comes into contact with the wall surface of the water tank, the orientation of the moving float is changed. The water treatment system according to claim 2.

6. The bumper includes at least one guide roller. The water treatment system according to claim 5.

7. A water treatment method for removing PFAS (perfluoroalkyl substances and polyfluoroalkyl compounds) contained in water to be treated stored in a water tank having a maintenance hole in the ceiling that allows access to the interior, A PFAS removal device is installed outside the water storage tank to remove PFAS from the water to be treated by passing the water to be treated through it. One end of the water intake pipe is immersed in the water to be treated in the water storage tank through the maintenance hole, and the other end is connected to the PFAS removal device. One end of the drainage pipe, which is at least partially flexible, is connected to the PFAS removal device, and the other end to which the movable float is connected is placed inside the water storage tank. The pump is placed on the piping path from the water intake pipe to the drainage pipe, The pump is driven to pass the water to be treated, taken in through the intake pipe, through the PFAS removal device, and the returned water that has passed through the PFAS removal device is drained through the drain pipe. The reaction force of the recirculating water discharged into the reservoir causes the movable float to move the surface of the water to be treated in the reservoir, thereby agitating the water to be treated in the reservoir. Water treatment methods.

8. The moving float comprises a float, a connection part connected to the drainage pipe, and a propulsion nozzle that deflects and discharges the recirculating water. The water treatment method according to claim 7.

9. The aforementioned connection is a rotary joint, which prevents the drainage piping from becoming entangled as the moving float moves. The water treatment method according to claim 8.

10. The propulsion nozzle changes the discharge direction of the recirculating water by water pressure or external power. The water treatment method according to claim 8.

11. The moving float has a bumper that is asymmetrical to the direction of movement on its forward side in the direction of movement, and when the bumper comes into contact with the wall surface of the water tank, the orientation of the moving float is changed. The water treatment method according to claim 8.

12. The bumper includes at least one guide roller. The water treatment method according to claim 11.

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