Water treatment system and water treatment method

Abstract

To provide 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 (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 that removes PFAS in the water to be treated by passing the water to be treated through it; an intake pipe with 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 with one end connected to the PFAS removal device and the other end immersed in the water to be treated in the water tank through the maintenance hole; and a pump arranged on the piping path from the intake pipe to the drainage pipe, wherein a horizontal flow nozzle that generates a horizontal water flow is provided at the other end of the drainage pipe.

Description

Technical Field

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

Background Art

[0002] PFAS is pointed out to be a causative substance that causes environmental problems because it is hardly decomposable and remains over a long period of 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 for various applications so far, and one of those applications is as a fire extinguishing agent during a fire. Therefore, some facilities that require a large amount of fire extinguishing water, such as airports, military facilities, and other buildings, 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 an actual fire 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 the 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 immersed in the water to be treated in the water tank through the maintenance hole; and a pump arranged on the piping path from the intake pipe to the drainage pipe, wherein a horizontal flow nozzle for generating a horizontal water flow is provided at the other end of the drainage pipe.

[0011] (2)(1) A water treatment system in which the horizontal flow nozzle has a bent portion and a horizontal extension portion connected to the bent portion.

[0012] (3)(2) The water treatment system wherein the horizontal extension is extendable and extends by water pressure or external power when discharging the recirculated water that has passed through the PFAS removal device.

[0013] (4)(2) The bent portion is capable of rotational or reciprocating motion in at least the horizontal direction, and moves by water pressure or external power when discharging the recirculated water that has passed through the PFAS removal device, in a water treatment system.

[0014] (5)(2) to (4) in any of the above, the drainage piping is expandable and contracts by water pressure or external power when discharging the recirculated water that has passed through the PFAS removal device, in a water treatment system.

[0015] (6) 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 to remove 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 in the water tank through the maintenance hole and the other end is connected to the PFAS removal device, one end of a drain pipe is connected to the PFAS removal device and the other end, which is equipped with a horizontal flow nozzle that generates a horizontal water flow, is immersed in the water to be treated in the water tank through the maintenance hole, a pump is placed on the piping path from the intake pipe to the drain pipe, the pump is driven to pass the water to be treated taken in through the intake pipe to the PFAS removal device, the returned water that has passed through the PFAS removal device is drained through the drain pipe, and the water to be treated in the water tank is agitated by the horizontal water flow generated by the horizontal flow nozzle.

[0016] (7)(6) A water treatment method comprising changing the horizontal orientation of the horizontal flow nozzle at least once.

[0017] (8)(7) A water treatment method in which the horizontal orientation of the horizontal flow nozzle is continuously changed by water pressure or external power.

[0018] A water treatment method comprising changing the position of the horizontal flow nozzle in the depth direction at least once in any of (9), (6) to (8).

[0019] (10)(9) A water treatment method in which the position of the horizontal flow nozzle in the depth direction is continuously changed by water pressure or external power. [Brief explanation of the drawing]

[0020] [Figure 1] This is a schematic cross-sectional view of a typical water storage tank containing water to be treated, shown for the purpose of illustrating a manner of use of the water treatment system according to the first embodiment of the present invention. [Figure 2] It is a diagram for explaining the structure of a horizontal flow nozzle according to the first embodiment of the present invention. [Figure 3] It is a schematic plan view of a water storage tank shown for the purpose of explaining the usage mode of a water treatment system according to the first embodiment of the present invention. [Figure 4] It is a flowchart for explaining the procedure of a water treatment method using the water treatment system according to the present embodiment. [Figure 5] It is a schematic cross-sectional view of a typical water storage tank filled with raw water to be treated, shown for the purpose of explaining the usage mode of a water treatment system according to the second embodiment of the present invention. [Figure 6] It is a cross-sectional view showing an example of the structure of a horizontal extension part that extends by water pressure. [Figure 7] It is a perspective view showing an example of a bent part that can rotate and reciprocate in the horizontal direction and moves by water pressure when discharging the recirculated water that has passed through the PFAS removal device. [Figure 8] It is a horizontal cross-sectional view of a case for explaining the internal structure of the bent part. [Figure 9] It is a cross-sectional view showing an example of the structure of a drainage pipe that is stretchable and repeatedly performs the operations of extending and shortening by water pressure when discharging the recirculated water that has passed through the PFAS removal device.

Mode for Carrying Out the Invention

[0021] FIG. 1 is a schematic cross-sectional view of a typical water storage tank 1 filled with raw water W to be treated, shown for the purpose of explaining the usage mode of a 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. Also, a ceiling 12 is provided on the upper surface of the water storage tank 1 to protect against foreign substances such as fallen leaves and dust from falling and mixing into the water storage tank 1, and it also serves as a floor surface for installing mechanical equipment such as a fire pump 2.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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, horizontal flow nozzle 44, and other accessories.

[0028] 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.

[0029] 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.

[0030] The filter media used in the filter is not limited and may include sand, diatomaceous earth, sponges, membranes, or combinations thereof. Whether or not the filter is backwashing is also optional. Furthermore, 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 also be used.

[0031] 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.

[0032] The drainage pipe 41 is connected at one end to the PFAS removal device 40 and immersed at the other end in the water to be treated W in the water storage tank 1 through the maintenance hole 13, and returns the recirculated water that has passed through the PFAS removal device 40 back into the water storage tank 1.

[0033] 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).

[0034] A horizontal flow nozzle 44 is provided at the other end of the drainage pipe 42 that is immersed in the water to be treated W. The horizontal flow nozzle 44 deflects the recirculating water discharged from the drainage pipe 42 within the water storage tank 1 so that at least the horizontal component of the momentum is dominant. In the example shown in Figure 1, the horizontal flow nozzle 44 is installed so as to bend at a right angle to the extension direction of the drainage pipe 42, and generates a horizontal water flow F from its tip.

[0035] Since the horizontal water flow F is a water flow that moves horizontally away from the maintenance hole 13, as shown by the arrow in the figure, after traveling to a position away from the maintenance hole 13 in the water storage tank 1, it changes direction in the depth direction and then flows towards the maintenance hole 13, forming a large flow that circulates throughout the water storage tank 1, and therefore the water to be treated W stored in the water storage tank 1 can be evenly agitated.

[0036] The horizontal water flow F formed by the horizontal flow nozzle 44 is not necessarily limited to a water flow having only a horizontal component. It may also be oblique, having a certain angle from the horizontal, or it may have a spreading effect. However, in order to form a large flow that circulates throughout the entire water tank 1, it is preferable that the momentum of the horizontal component of the flow is dominant. That is, when comparing the absolute values ​​of the horizontal component and the vertical component of the momentum vector of the main flow of the horizontal water flow F formed by the horizontal flow nozzle 44, it is desirable that the absolute value of the horizontal component is larger. In this specification, a horizontal water flow F refers to one in which the absolute value of the horizontal component of the momentum vector of the main flow is greater than the absolute value of the vertical component.

[0037] 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.

[0038] Figure 2 is a diagram illustrating the structure of the horizontal flow nozzle 44 according to this embodiment. The horizontal flow nozzle 44 includes a bent portion 440, a horizontal extension portion 441 connected at one end to the bent portion, and a nozzle head 442 connected at the other end of the horizontal extension portion 441.

[0039] The bent section 440 connects a horizontal flow nozzle 44 to the other end of the drainage pipe 42 that is immersed in the water to be treated W, thereby deflecting the direction of the return water flow in the horizontal direction. In the simplest case, an L-shaped pipe joint can be used as shown in the figure.

[0040] The recirculating water, whose flow direction has been changed by the bend 440, flows through the horizontal extension 441 in the direction of extension. The horizontal extension 441 is a pipe that extends at least horizontally, and the recirculating water flows through its interior from one end connected to the bend 440 toward the other end connected to the nozzle head 442. In the illustrated example, the horizontal extension 441 extends horizontally, but it may also be inclined at a predetermined angle in the vertical direction.

[0041] The nozzle head 442 is a component that controls the speed and shape of the flow of recirculated water discharged into the water storage tank 1. By narrowing the discharge outlet, the speed of the discharged water can be increased, allowing the horizontal 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. Alternatively, the nozzle head 442 may be used as a venturi nozzle to draw in the water to be treated W around the nozzle head 442 and increase the flow rate of the horizontal water flow F.

[0042] In the horizontal flow nozzle 44, the horizontal extension 441 and nozzle head 442 are not essential components; they can simply be made to deflect the flow direction of the recirculated water by the bent section 440. However, as is clear from Figure 1, if the recirculated water is drained into the storage tank 1 near the intake position of the intake pipe 41 located directly below the maintenance hole 13 (in this example, the pump 43 is installed), a circulating flow will occur in a very narrow area near the maintenance hole 13, where the recirculated water drained from the drain pipe 42 is taken into the intake pipe 41. This is expected to significantly reduce the efficiency of uniformly stirring the entire treated water W in the storage tank 1.

[0043] Therefore, a horizontal extension 441 is provided on the horizontal flow nozzle 44, and in a plan view, the returned water is drained at a position as far away from the maintenance hole 13 as possible, and in a direction away from the maintenance hole 13, thereby creating a large flow that also entrains the water to be treated W in the vicinity of the side surface 11 of the water storage tank 1, away from the maintenance hole 13. The horizontal extension 441 is preferably as long as dimensional constraints allow, but considering that it must pass through the narrow maintenance hole 13 and that sufficient working space cannot be secured around the maintenance hole 13, a length of about 1 to 2 meters is realistic.

[0044] Furthermore, by providing a nozzle head 442 on the horizontal flow nozzle 44, the flow velocity and flow rate of the horizontal water flow F can be increased compared to simply draining from the other end of the horizontal extension 441, making it easier to form a large flow that also entrains the water to be treated W in the vicinity of the side surface 11 away from the maintenance hole 13 within the water storage tank 1.

[0045] Figure 3 is a schematic plan view of the water storage tank 1, shown for the purpose of illustrating how the water treatment system 4 according to this embodiment is used. In this figure, the planar position and shape of the maintenance hole 13 are shown with dashed lines to clarify the positional relationship.

[0046] In the illustrated example, the horizontal flow nozzle 44, located at the other end of the drainage pipe 42, is fixed so as to face left in the diagram along the long side of the side surface 11 of the water storage tank 1, and the horizontal water flow F also faces left in the diagram, similar to the horizontal flow nozzle 44. In this case, sufficient agitation can be expected for the water to be treated W near the upper edge of the water storage tank 1 in the diagram, but there is a risk that the water to be treated W in the lower part of the water storage tank 1 in the diagram will not be sufficiently agitated.

[0047] The same can be said for the flow in the depth direction of the horizontal flow nozzle 44. The flow caused by the horizontal water flow F shown in Figure 1 does not necessarily sufficiently entrain the water to be treated W located at the middle height of the storage tank 1. Depending on its position within the storage tank 1, the water to be treated W may stagnate or localized circulation may occur, making it difficult to say that the entire water to be treated W in the storage tank 1 can be efficiently agitated.

[0048] Therefore, it is preferable to change the position and direction of the horizontal flow nozzle 44 during the process of performing water treatment using the water treatment system 4. That is, it is preferable to change the orientation of the horizontal flow nozzle 44 at least once during water treatment. Also, it is preferable to change the position of the horizontal flow nozzle 44 in the depth direction at least once during water treatment.

[0049] Regarding the depth-direction position of the horizontal flow nozzle 44, Figure 1 shows, with dashed lines, examples of the horizontal flow nozzle 44 with a changed depth-direction position, and the horizontal water flow F' generated by the horizontal flow nozzle 44 with a changed depth-direction position. Figure 1 illustrates how the depth-direction position of the horizontal flow nozzle 44 is changed in two ways, resulting in the generation of horizontal water flows F and F' with different directions of travel relative to the water tank 1.

[0050] Regarding the orientation of the horizontal flow nozzle 44, Figure 3 shows, with dashed lines, examples of the horizontal flow nozzle 44 with a changed orientation, and the horizontal water flows F'', F''', and F'''' generated by the horizontal flow nozzle 44 with a changed orientation. Figure 3 illustrates how the horizontal orientation of the horizontal flow nozzle 44 is changed in four different ways, resulting in horizontal water flows F, F'', F''', and F'''' with different directions of travel relative to the water tank 1.

[0051] The position and direction of the horizontal flow nozzle 44 may be changed by temporarily releasing the fixing of the drain pipe 42 to the tension clamp 4 which is inserted and fixed in the maintenance hole 13, changing the insertion depth and rotation angle of the drain pipe 42, and then fixing the drain pipe 42 again. Since water treatment using the water treatment system 4 is usually carried out over a period of several hours to several days, the position and direction of the horizontal flow nozzle 44 are changed at regular intervals, for example, every few hours. Alternatively, as will be explained in the embodiments described later, the position and direction of the horizontal flow nozzle 44 may be changed continuously. Here, the expression that the position and direction of the horizontal flow nozzle 44 are changed at least once includes the case in which the position and direction of the horizontal flow nozzle 44 are changed continuously.

[0052] Figure 4 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 loaded onto a transport vehicle such as a truck, brought in and installed, 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.

[0053] 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 to the PFAS removal device 40 and immersing the other end, which is equipped with a horizontal flow nozzle 44 that generates a horizontal water flow, in the water to be treated W in the water storage tank 1 through the maintenance hole 13, and arranging the pump 43 along the piping path from the intake pipe 41 to the drainage pipe 42.

[0054] In the embodiment described above, since the pump 43 is a submersible pump connected to one end of the intake pipe 41, the intake pipe 41 is first connected to one end of the intake pipe 41, lowered into the water storage tank 1 through the maintenance hole 13, and then fixed in place. As for the drain pipe 42, the horizontal flow nozzle 44, which is provided at the other end, is inserted through the maintenance hole 13, and then the main body of the drain pipe 42 is inserted into the maintenance hole 13 while changing the angle and fixed in place. After that, the intake pipe 41 and the drain pipe 42 are connected to the PFAS removal device 40.

[0055] Furthermore, in step ST3, the pump 43 is driven to pass the water to be treated W, taken in through the intake pipe 41, through the PFAS removal device 40, and the recirculated water that has passed through the PFAS removal device 40 is drained into the water storage tank 1 through the drain pipe 42. At this time, the water to be treated W in the water storage tank 1 is agitated by the horizontal water flow F generated by the horizontal flow nozzle 44.

[0056] Next, in step ST4, the position and direction of the horizontal flow nozzle 44 are changed at least once during the water treatment process. This procedure may include changing the horizontal orientation of the horizontal flow nozzle 44 at least once and changing the position of the horizontal flow nozzle 44 in the depth direction at least once. As in the embodiment described above, if the position of the horizontal flow nozzle 44 in the depth direction is changed in two ways and the horizontal orientation of the horizontal flow nozzle 44 is changed in four ways, there are eight possible combinations of the position and direction of the horizontal flow nozzle 44. Therefore, except for the initial installation of the horizontal flow nozzle 44, the position and direction of the horizontal flow nozzle 44 will be changed at least seven times. Furthermore, it is acceptable to reuse the same position and direction of the horizontal flow nozzle 44 that has already been used, and the position and direction of the horizontal flow nozzle 44 may be changed repeatedly as needed.

[0057] 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.

[0058] The first embodiment described above assumes that the position and direction of the horizontal flow nozzle 44 are changed manually. However, as already mentioned, water treatment using the water treatment system 4 is usually carried out over a period of several hours to several days. Therefore, manually changing the position and direction of the horizontal flow nozzle 44 at predetermined intervals during this period would incur labor and management costs. Automating this change would therefore offer significant advantages.

[0059] In the second embodiment of the present invention described below, the position and direction of the horizontal flow nozzle 44 are changed automatically, and the horizontal flow nozzle 44 extends automatically. Figure 5 is a schematic cross-sectional view of a typical water storage tank 1 containing water to be treated W, which is shown for the purpose of illustrating how the water treatment system 4 according to the second embodiment of the present invention is used. In this figure, elements common to the first embodiment described above are denoted by the same reference numerals, and redundant explanations are omitted.

[0060] While a horizontal extension 441 of the horizontal flow nozzle 44 is advantageous for agitating the treated water W in the water storage tank 1, a long horizontal extension 441 is difficult to transport into the water storage tank 1 from the maintenance hole 13. Therefore, a compact horizontal flow nozzle 44 is easier to handle and offers superior workability. For this reason, it is desirable that the horizontal extension 441 of the horizontal flow nozzle 44 be short and compact when transporting it into the water storage tank 1 from the maintenance hole 13, and extend when discharging the recirculated water.

[0061] There are no particular limitations on the method for extending the horizontal extension section 441 when discharging the recirculating water. For example, any mechanism can be used, such as the extension and retraction of a solenoid using external power, or a rotational-to-linear motion conversion mechanism of an electric motor using a screw shaft. However, using a mechanism that extends the horizontal extension section 441 by utilizing the water pressure of the recirculating water passing through the horizontal flow nozzle 44 is advantageous because it eliminates the need to prepare a separate external power source and allows for easy extension of the horizontal extension section 441.

[0062] Figure 6 is a cross-sectional view showing an example of the structure of a horizontal extension section 441 that extends due to water pressure. The horizontal extension section 411 has a telescopic mechanism in which multiple tubes extend, and in the illustrated example, it is a triple-tube mechanism in which three tubes, an outer tube 4410, a middle tube 4411, and an inner tube 4412, are inserted inward in order. In the figure, the recirculating water is shown to flow in from the right side of the horizontal extension section 441 and out from the left side, and hereafter the right side of the horizontal extension section 441 will be referred to as the rear and the left side as the front.

[0063] The rear end of the outer tube 4410 is the rear end 4413 of the horizontal extension 441 itself, and may be provided with, for example, an appropriate tapered screw groove for connection with the bent portion 440. The tip of the outer tube 4410 is tapered so that its inner diameter is equal to or slightly larger than the outer diameter of the inner tube 4411. The inner tube 4411 has an outer diameter smaller than the inner diameter of the outer tube 4410, and a gap is provided between the inner tube 4411 and the outer tube 4410. The rear end of the inner tube 4411 is provided with a flange that expands so that its outer diameter is equal to or slightly smaller than the inner diameter of the outer tube 4410.

[0064] Similarly, the tip of the middle tube 4411 is tapered so that its inner diameter is equal to or slightly larger than the outer diameter of the inner tube 4412, and the inner tube 4412 has an outer diameter smaller than the inner diameter of the middle tube 4411, with a gap between the inner tube 4411 and the middle tube 4410. The rear end of the inner tube 4412 is also provided with a flange that expands so that its outer diameter is equal to or slightly smaller than the inner diameter of the middle tube 4410. The tip of the inner tube is the tip 4414 of the horizontal extension 441 itself, and may be provided with, for example, an appropriate tapered screw groove for connection to the nozzle head 442.

[0065] Coil springs 4415 are provided in the gaps between the outer tube 4410 and the middle tube 4411, and between the middle tube 4411 and the inner tube 4412, respectively. In the free state, the outer tube 4410, middle tube 4411, and inner tube 4412 overlap each other, biasing them to shorten the overall length of the horizontal extension 441. Retaining rings 4416 are provided on the inner rear surfaces of the outer tube 4410 and the middle tube 4411 to prevent the middle tube 4411 and the inner tube 4412 from falling out to the rear.

[0066] When recirculating water is introduced from the rear end 4413 of the horizontal extension 441, the water pressure of the recirculating water acts on the flanges at the rear ends of the central pipe 4411 and the inner pipe 4412, causing the central pipe 4411 and the inner pipe 4412 to experience a forward force. If the elastic force of the coil spring 4415 is set to be less than this force, the horizontal extension 441 will be stretched as the central pipe 4411 and the inner pipe 4412 are pushed forward while recirculating water is flowing in, and when the inflow of recirculating water stops, it will contract due to the action of the coil spring 4415 and return to its original state.

[0067] Furthermore, the bent portion 440 of the horizontal flow nozzle 44 according to this embodiment is capable of rotational or reciprocating motion in at least the horizontal direction, and such motion is performed automatically by water pressure or external power, without human intervention. The means for achieving such motion are arbitrary, and when using external power, for example, a suitable electric motor can be used to perform rotational or reciprocating motion, making it easily achievable.

[0068] Furthermore, the movement of such a bent section 440 can also be performed using the water pressure of the recirculating water passing through the horizontal flow nozzle 44. This is advantageous because it eliminates the need to prepare a separate external power source and allows for a simple change in the horizontal direction of the horizontal flow nozzle 44. Various mechanisms for achieving such movement are already known, and the choice of which one to use is arbitrary, but one example is shown below.

[0069] Figure 7 is a perspective view showing an example of a bent section 440 that is capable of rotational and reciprocating motion in the horizontal direction and moves due to water pressure when discharging the recirculated water that has passed through the PFAS removal device 40. The bent section 440 has a case 4400 with a roughly fan-shaped planar shape, an inlet 4401 provided on the upper surface of the case 4400, and an L-shaped pipe joint 4402 provided on the lower surface of the case 4400. The inlet 4401 is an opening to which the drainage pipe 42 is connected and which guides the recirculated water into the interior of the case 4400, and may be provided with an appropriate tapered screw groove for connection with the drainage pipe 42. The L-shaped pipe joint 4402 is an outlet that discharges the recirculated water that has passed through the interior of the case 4400 in the horizontal direction, and may be provided with an appropriate tapered screw groove at its end for connecting a horizontal extension section 441.

[0070] Furthermore, when recirculating water is introduced into the case 4400, the bent section 440 is structured to use the water pressure to cause the L-shaped pipe joint 4402 to rotate and reciprocate in the horizontal plane, as shown by the arrow in the figure. Therefore, when the horizontal extension section 441 is connected to the end of the L-shaped pipe joint 4402, the horizontal orientation of the horizontal flow nozzle 44 is changed to a continuous oscillating motion.

[0071] Figure 8 is a horizontal cross-sectional view of case 4400 illustrating the internal structure of the bent section 440. Case 4400 has a roughly fan-shaped inner chamber 4403 inside, which is divided into two by a movable wall 4404 located inside the inner chamber 4403. For convenience, the space to the left of the movable wall 4404 shown in Figure 8 will be referred to as the first chamber 4403a, and the space to the right will be referred to as the second chamber 4403b.

[0072] The movable wall 4404 is supported so as to be able to rotate within the inner chamber 4403 around a pivot 4405 located at the center of the inner chamber 4403's sector, and in the illustrated example, it can move within a 90° angular range. The pivot 4405 and the movable wall 4404 are integrally connected, so when the movable wall 4404 rotates, the pivot 4405 also rotates simultaneously by the same amount. The movable wall 4404 also substantially watertightly partitions the first chamber 4403a and the second chamber 4403b, although some leakage is acceptable.

[0073] Furthermore, the center of the pivot 4405 and the interior of the movable wall 4404 are connected by a cavity, and an L-shaped pipe connector 4402 is fixed to the pivot 4405. In other words, the recirculating water that flows into the interior of the movable wall 4404 via the valve mechanism described later flows out through the cavity in the center of the pivot 4405 to the L-shaped pipe connector 4402. Also, since the movable wall 4404, pivot 4405 and L-shaped pipe connector 4402 are integrally connected, if the movable wall 4404 rotates and reciprocates, the L-shaped pipe connector 4402 will inevitably also rotate and reciprocate.

[0074] The movable wall 4404 is provided with through-holes that penetrate the wall surface on the first chamber 4403a side and the wall surface on the second chamber 4403b side, so as to communicate with its internal space. A double-headed valve pin 4406 is inserted into these through-holes, forming a valve mechanism. The valve pin 4406 has valve heads with enlarged diameters at both ends. When the valve heads are in contact with the wall surface of the movable wall 4404, the through-hole is closed, blocking communication between the first chamber 4403a or the second chamber 4403b and the internal space of the movable wall 4404. Furthermore, the shaft of the valve pin 4406 is provided with a groove for passing recirculating water, and when the valve head is floating above the wall surface of the movable wall 4404, the through hole is opened, connecting the first chamber 4403a or the second chamber 4403b with the internal space of the movable wall 4404, and guiding the recirculating water through the inside of the movable wall 4404 to the cavity at the center of the pivot 4405.

[0075] The length of the shaft of the valve pin 4406 is designed to be longer than the thickness of the movable wall 4404, allowing it to slide within the through hole, so that either the valve head on the first chamber 4403a side or the valve head on the second chamber 4403b side is always raised away from the wall surface of the movable wall 4404. In Figure 8, the valve head of the valve pin 4406 on the second chamber 4403b side is raised away from the wall surface of the movable wall 4404 and is in an open state. Therefore, as indicated by the arrow, the recirculating water in the second chamber 4403b flows out into the movable wall 4404 through the groove provided on the shaft of the valve pin 4406, while the recirculating water in the first chamber 4403a cannot flow out into the movable wall 4404 because the valve head of the valve pin 4406 on the first chamber 4403a side is in a closed state.

[0076] Furthermore, the valve pin 4406 is biased by a spring or the like (not shown) to ensure that it can take on either one of two positions: one where the valve head on the first chamber 4403a side is closed and the valve head on the second chamber 4403b side is open, or one where the valve head on the first chamber 4403a side is open and the valve head on the second chamber 4403b side is closed, and not take on an intermediate position.

[0077] Furthermore, the recirculating water flowing in from the inlet 4401 in Figure 7 is branched into two by a flow path (not shown), and flows into the first chamber 4403a and the second chamber 4403b, respectively, from the first inlet 4401a and the second inlet 4401b, which are provided on the radial walls of the inner chamber 4403 (indicated by short arrows in the figure).

[0078] The operation of the bent section 440 in this example is as follows. The recirculating water flowing from the first inlet 4401a and the second inlet 4401b into the first chamber 4403a and the second chamber 4403b, respectively, exerts water pressure on both walls of the movable wall 4404. At this time, since recirculating water flows out from the chamber on the side where the valve head is open, the water pressure acting on the walls of the movable wall 4404 decreases. Due to this difference in water pressure acting on the two walls, the movable wall 4404 rotates from the chamber on the side where the valve head is closed towards the chamber on the side where the valve head is open. In the state shown in Figure 8, the valve head on the second chamber 4403b side is open, so the movable wall 4404 rotates in the direction from the first chamber 4403a towards the second chamber 4403b, that is, counterclockwise.

[0079] When the movable wall 4404 moves close to the radial wall surface of the inner chamber 4403, the valve head of the valve pin 4406 protruding from the wall surface of the movable wall 4404 comes into contact with the wall surface of the inner chamber 4403 and is pushed toward the movable wall 4404. As a result, the valve pin 4406 slides relative to the movable wall 4404, and the open and closed states of the valve head for the first chamber 4403a and the second chamber 4403b are reversed. This changes the flow path of the recirculating water, and the relative magnitudes of the water pressure acting on both sides of the movable wall 4404 are reversed, causing the movable wall 4404 to begin rotating in the opposite direction.

[0080] The same operation is repeated thereafter, causing the movable wall 4404 to rotate and reciprocate, which in turn causes the L-shaped pipe connector 4402 to rotate and reciprocate.

[0081] Furthermore, the drainage pipe 42 according to this embodiment is expandable and retractable, and extends or retracts by water pressure or external power when discharging the recirculated water that has passed through the PFAS removal device 40. Of course, extension and retraction may be repeated alternately. Such operations are performed automatically by water pressure or external power, without human intervention. The means for realizing such operations are arbitrary, and when using external power, it can be easily realized by using, for example, an appropriate electric linear actuator or a hydraulic or pneumatic cylinder.

[0082] Furthermore, the extension or shortening of the drainage pipe 42 can also be performed using the water pressure of the recirculating water passing through the drainage pipe 42. This is advantageous because it eliminates the need to prepare a separate external power source and allows for easy change of the depth position of the horizontal flow nozzle 44. Various mechanisms for achieving such operation are already known, and the choice of which one to use is arbitrary, but one example is shown below.

[0083] Figure 9 is a cross-sectional view showing an example of the structure of a drainage pipe 42 that is expandable and retractable and repeatedly extends and contracts due to water pressure when discharging the recirculated water that has passed through the PFAS removal device 40. The drainage pipe 42 has a vertically arranged cylindrical cylinder 420 and a piston rod 421 that penetrates the center of the cylinder 420 in the longitudinal direction and is slidable relative to the cylinder 420.

[0084] The cylinder 420 has a cylindrical inner chamber 4200 inside, which is divided into two sections by a piston 4210 located inside the inner chamber 4200. For convenience, the space above the piston 4210 shown in Figure 9 is referred to as the first chamber 4200a, and the space below it is referred to as the second chamber 4200b. The cylinder 420 is also fixed immovably to the maintenance hole 13.

[0085] The piston rod 421 consists of a piston 4210 positioned inside the inner chamber 4200 of the cylinder 420, an upper rod 4211 attached to the upper surface of the piston 4210 and extending through the upper wall of the cylinder 420, and a lower rod 4212 attached to the lower surface of the piston 4210 and extending through the lower wall of the cylinder 420. The upper rod 4211, piston 4210, and lower rod 4212 are slidably mounted together in the vertical direction relative to the cylinder 420. The upper rod 4211 and the upper wall of the cylinder 420, the piston 4210 and the inner surface of the inner chamber 4200 of the cylinder 420, and the lower rod 4211 and the lower wall of the cylinder 420 may be sealed appropriately using O-rings or the like to ensure watertightness between them. Furthermore, the cylinder 420 and the piston rod 421 are prevented from rotating relative to each other. The prevention of rotation can be carried out by any method, for example, by making the cross-sectional shape of the upper rod 4211 non-circular.

[0086] As shown in the figure, the piston 4210 has a flattened shape and is hollow inside. The lower rod 4212 is a hollow tube and communicates with the cavity inside the piston 4210. In addition, the lower end of the lower rod 4212 (not shown) may be provided with an appropriate tapered screw groove for connection to the bent portion 440 of the horizontal flow nozzle 44. Therefore, when the piston rod 421 reciprocates in the vertical direction, the horizontal flow nozzle 44 attached to the lower end of the lower rod 4212 also reciprocates in the vertical direction, so its position in the depth direction is continuously changed.

[0087] There is no particular limitation on whether the upper rod 4211 is hollow or solid, but even if the upper rod 4211 is hollow, such a space does not communicate with the cavity inside the piston 4210.

[0088] The piston 4210 is provided with a through-hole that penetrates the upper wall on the first chamber 4200a side and the lower wall on the second chamber 4200b side, communicating with its internal space. A double-headed valve pin 422 is inserted into this through-hole, forming a valve mechanism. This valve mechanism has the same structure as the one described earlier for the bent section 440, with valve heads of enlarged diameter provided at both ends of the valve pin 422. The valve heads close the through-hole when they are in contact with the upper and lower walls of the piston 4210, and open the through-hole when they are floating above the upper and lower walls. A groove is provided on the shaft of the valve pin 422 to allow recirculating water to pass through. As shown by the arrow in Figure 9, the recirculating water is guided from the chamber on the open side into the space inside the piston 4210, passes through the lower rod 4212, and is discharged to the horizontal flow nozzle 44. In the state shown in Figure 9, the valve pin 422 opens a through-hole that penetrates the lower wall on the second chamber 4200b side, so the recirculating water flows from the second chamber 4200b into the piston 4210, and then flows downward through the lower rod 4212.

[0089] Similar to the previous explanation regarding the bent portion 440, the valve pin 442 is designed so that the length of its shaft is longer than the thickness of the piston 4210, and the valve pin 442 is slidable within the through hole, always taking a position that opens one of the upper and lower walls of the piston 4210 and closes the other, and never taking an intermediate position.

[0090] Furthermore, the recirculating water that has passed through the PFAS removal device 40 is branched into two by appropriate piping and flows into the first chamber 4200a and the second chamber 4200b, respectively, through the first inlet 4201a and the second inlet 4201b provided on the upper and lower walls of the cylinder 420 (indicated by short arrows in the figure).

[0091] The operation of the drainage piping 42 in this example is as follows: The recirculating water flowing from the first inlet 4201a and the second inlet 4201b into the first chamber 4200a and the second chamber 4200b, respectively, exerts water pressure on the upper and lower walls of the piston 4210. At this time, since recirculating water flows out from the chamber on the side where the valve head is open, the water pressure acting on the wall of the piston 4210 decreases. Due to this difference in water pressure acting on the two walls, the piston 4210 moves linearly from the chamber on the side where the valve head is closed towards the chamber on the side where the valve head is open. In the state shown in Figure 9, the valve head on the second chamber 4200b side is open, so the piston 4210 moves in the direction from the first chamber 4200a towards the second chamber 4200b, that is, downwards.

[0092] As the piston 4210 moves close to the upper and lower walls of the inner chamber 4200, the valve heads of the valve pins 422 protruding from the upper and lower walls of the piston 4210 come into contact with the walls of the inner chamber 4200 and are pushed toward the piston 4210. As a result, the valve pins 422 slide relative to the piston 4210, reversing the open and closed states of the valve heads relative to the first chamber 4200a and the second chamber 4200b. This changes the flow path of the recirculating water, reversing the relative magnitudes of the water pressure acting on the upper and lower walls of the piston 4210, causing the piston 4210 to begin moving in the opposite direction.

[0093] The same operation is repeated thereafter, causing the piston 4210 to reciprocate up and down. As a result, the piston rod 4211 repeatedly reciprocates in a linear motion up and down. When the piston rod 4211 moves downward, the drain pipe 42 extends, and when the piston rod 4211 moves upward, the drain pipe 42 shortens. Consequently, the position of the horizontal flow nozzle 44 attached to the lower end of the piston rod 4211 in the depth direction is continuously changed.

[0094] The rotational or reciprocating motion of the bent portion 440 of the horizontal flow nozzle 44, and the extension or shortening speed of the drainage pipe 42, as described above, may be adjusted so that the recirculating water discharged from the horizontal flow nozzle 44 properly agitates the entire treated water W in the storage tank 1. Specifically, the time required for one rotation or one reciprocating motion may be set to several tens of minutes to several hours, and the time required for extension or shortening may be set to several hours to several days. Such adjustments may be made by controlling the external power if the bent portion 440 and the drainage pipe 42 are driven by external power, or by providing appropriate brakes or governors if the bent portion 440 and the drainage pipe 42 are driven by the water pressure of the recirculating water. [Explanation of Symbols]

[0095] 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 Horizontal flow nozzle, 45 Brace clamp, 420 Cylinder, 421 Piston rod, 422 Valve pin, 440 Bend section, 441 Horizontal extension section, 442 Nozzle head, 4200 Inner chamber, 4200a First chamber, 4200b Second chamber, 4201a First inlet, 4201b Second inlet, 4210 Piston, 4211 Upper rod, 4212 Lower rod, 4400 Case, 4401 Inlet, 4401a First inlet, 4401b Second inlet, 4402 L-shaped pipe joint, 4403 inner chamber, 4403a first chamber, 4403b second chamber, 4404 movable wall, 4405 pivot, 4406 valve pin, 4410 outer tube, 4411 middle tube, 4412 inner tube, 4413 rear end, 4414 front end, 4415 coil spring, 4416 retaining ring.

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 immersed in the water to be treated in the water storage tank through the maintenance hole. A pump is placed along the piping path from the water intake pipe to the drainage pipe, It has, A horizontal flow nozzle that generates a horizontal water flow is provided at the other end of the aforementioned drainage pipe. Water treatment system.

2. The horizontal flow nozzle has a bent portion and a horizontal extension portion connected to the bent portion. The water treatment system according to claim 1.

3. The aforementioned horizontal extension is extendable and retractable, and extends by water pressure or external power when discharging the recirculated water that has passed through the PFAS removal device. The water treatment system according to claim 2.

4. The bent portion is capable of rotational or reciprocating motion in at least the horizontal direction, and moves by water pressure or external power when discharging the recirculated water that has passed through the PFAS removal device. The water treatment system according to claim 2.

5. The aforementioned drainage piping is expandable and contracts by water pressure or external power when discharging the recirculated water that has passed through the PFAS removal device. A water treatment system according to any one of claims 2 to 4.

6. 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 is connected to the PFAS removal device, and the other end, which is equipped with a horizontal flow nozzle that generates a horizontal water flow, is immersed in the water to be treated in the water storage tank through the maintenance hole. 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 water to be treated in the storage tank is agitated by the horizontal water flow generated by the horizontal flow nozzle. Water treatment methods.

7. The water treatment method according to claim 6, wherein the horizontal orientation of the horizontal flow nozzle is changed at least once.

8. The horizontal orientation of the horizontal flow nozzle is continuously changed by water pressure or external power. The water treatment method according to claim 7.

9. The water treatment method according to any one of claims 6 to 8, wherein the position of the horizontal flow nozzle in the depth direction is changed at least once.

10. The position of the horizontal flow nozzle in the depth direction is continuously changed by water pressure or external power. The water treatment method according to claim 9.

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