Water purification unit

Abstract

To provide a water purification device capable of obtaining drinkable pure water from salt-containing water, occupying a small installation area, having high filtering efficiency, and being easy to transport. [Solution] The system comprises a submerged membrane module 1, an energy recovery device 6 for recovering energy from the concentrated water of a first reverse osmosis membrane module 2 to increase the water pressure, a submerged membrane suction pump 4 for sending the filtered water of the submerged membrane module 1 to the energy recovery device 6, and a second reverse osmosis membrane module 3 for purifying the filtered water of the first reverse osmosis membrane module 2, wherein the submerged membrane module 1 is shorter in dimension than either the first reverse osmosis membrane module 2 or the second reverse osmosis membrane module 3 and is arranged so that its longitudinal direction is vertical, and the first reverse osmosis membrane module 2 and the second reverse osmosis membrane module 3 are arranged on either side of the submerged membrane module 1 so that their longitudinal direction is horizontal.

Description

[Technical Field]

[0001] The present invention relates to a water purification apparatus for filtering salt-containing water such as seawater or groundwater to obtain drinkable pure water. [Background technology]

[0002] Seawater contains approximately 3.4% salt, as well as other minerals and organic matter such as plankton. This means that seawater cannot be consumed as is. Not only seawater, but groundwater in coastal areas can also contain salt. For these reasons, securing potable water is a major issue in the lives of ships sailing at sea and residents of remote islands.

[0003] When sufficient drinking water cannot be obtained by filtering rainwater alone, drinking water is obtained from salt-containing water such as seawater. To do this, suspended solids must be removed, followed by the removal of color components and salt. Since salt is dissolved in water, it is necessary to separate the water molecules from the chloride molecules, which necessitates the installation of a filtration system using an extremely fine reverse osmosis membrane.

[0004] However, to filter a large amount of water using reverse osmosis membranes, a high-pressure pump and multiple reverse osmosis membrane modules are required, making the system itself large. Large filtration systems pose problems when installed on ships in terms of space and weight. Furthermore, when installing them on remote islands, transportation is also an issue. Therefore, there is a demand for a small, easily transportable filtration device.

[0005] Patent Document 1 discloses a technique relating to a water quality improvement device that is easy to maintain and can reduce the installation space of the device. This technology is a filtration device for removing ions, molecules, or contaminants, and is equipped with a membrane module, a pressure pump, a degassing membrane module, and a vacuum pump. The membrane modules are stacked horizontally, with the degassing membrane module also stacked horizontally on its side. The vacuum pump is located below the degassing membrane module, and the pressure pump is located behind the degassing membrane module. This arrangement is said to enable space saving for the installation of the device. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-272282 Summary of the Invention [Problem to be solved by the invention]

[0007] The technology in Patent Document 1 is said to remove ions and molecules, and the membrane module is understood to be a reverse osmosis membrane module. In this case, if the membrane modules stacked vertically are of one type, the filtration membrane will quickly become clogged unless water from which suspended matter has been removed in advance is used. On the other hand, if these membrane modules are of multiple types and perform the removal of suspended matter and the removal of ions and molecules in series, it is thought that a pressure pump small enough to be hidden behind the degassing membrane module would be able to process only an extremely small amount of water.

[0008] As described above, there has been no conventional device that can produce drinkable pure water from salt-containing water using a single filtration device, and that is designed to be as small as possible and easy to transport and install.

[0009] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a water purification apparatus that can obtain drinkable pure water from salt-containing water, occupies a small installation area, has high filtration efficiency, and is easy to transport. [Means for solving the problem]

[0010] The means adopted by the present inventors to solve the above problems will be described below. The water purification apparatus of the present invention is for obtaining drinkable pure water from salt-containing water by filtration. Its basic configuration includes a submerged membrane module for removing impurities from the salt-containing water, a first reverse osmosis membrane module for desalination of the water filtered by the submerged membrane module, an energy recovery device for recovering energy from the concentrated water of the first reverse osmosis membrane module to increase the pressure of the water flowing into the first reverse osmosis membrane module, a submerged membrane suction pump for delivering the filtered water from the submerged membrane module to the energy recovery device, and a second reverse osmosis membrane module for purifying the filtered water from the first reverse osmosis membrane module.

[0011] The submerged membrane module is shorter than the first reverse osmosis membrane module or the second reverse osmosis membrane module and is arranged so that the vertical direction is its longitudinal direction, and the first reverse osmosis membrane module and the second reverse osmosis membrane module are arranged on both sides of the submerged membrane module so that the horizontal direction is its longitudinal direction.

[0012] In the first reverse osmosis membrane module, the filtered water from the submerged membrane module is passed through the first reverse osmosis membrane module to be desalinated, and the concentrated water with an increased salinity is discharged with residual hydraulic power. This concentrated water is generally discharged directly into the ocean, but in the water purification system of the present invention, the energy recovery device recovers the energy of this concentrated water and reuses it as energy to flow into the first reverse osmosis membrane module. This allows the entire water purification system to be made more compact while maintaining high treatment capacity, compared to when filtration is performed in the first reverse osmosis membrane module using a general pump, etc.

[0013] In addition, the submerged membrane module is shorter than the first reverse osmosis membrane module and the second reverse osmosis membrane module, and the short submerged membrane module is arranged so that the vertical direction is its longitudinal direction. In other words, it is arranged upright. The first reverse osmosis membrane module and the second reverse osmosis membrane module are separately arranged on either side of the vertically standing submerged membrane module, with the horizontal direction being the longitudinal direction. In other words, the vertically standing submerged membrane module is sandwiched between the horizontally arranged first reverse osmosis membrane module and the second reverse osmosis membrane module.

[0014] This arrangement not only allows the submerged membrane module, the first reverse osmosis membrane module, and the second reverse osmosis membrane module to be arranged efficiently, but also provides good weight balance during transportation, since the two types of reverse osmosis membrane modules are arranged symmetrically on both sides of the submerged membrane module. Furthermore, since the vertically placed submerged membrane module is shorter than the horizontally placed first and second reverse osmosis membrane modules, the entire module can be placed within a rectangular parallelepiped, making it easy to load onto a truck or container.

[0015] As a means that can be employed to solve the problem, the energy recovery device can be disposed adjacent to the ends of the first reverse osmosis membrane module and the second reverse osmosis membrane module, and a first frame on which the submerged membrane module, the first reverse osmosis membrane module, the second reverse osmosis membrane module, and the submerged membrane module are mounted, and a second frame on which the energy recovery device is mounted can be provided, and the first frame and the second frame can be configured to be detachable.

[0016] In this configuration, the energy recovery device is disposed adjacent to the ends of the horizontally placed first and second reverse osmosis membrane modules. This arrangement prevents the overall width of the device from increasing, allows the second pump and the energy recovery device to be positioned in a well-balanced manner, and makes it easier to load onto a truck or container. Furthermore, by dividing the system into a first frame and a second frame, which are detachable, blocks such as the submerged membrane module, first reverse osmosis membrane module, and second reverse osmosis membrane module and blocks such as the energy recovery device can be transported separately and then combined on site.

[0017] As yet another means that can be employed to solve the problem, when the first frame and the second frame are separated, it is also possible to configure the first reverse osmosis membrane module or the second reverse osmosis membrane module to be connectable to the energy recovery device using another water pipe.

[0018] By installing blocks such as the submerged membrane module, first reverse osmosis membrane module, and second reverse osmosis membrane module at a distance from blocks such as the energy recovery device and making them connectable with other water pipes, the degree of freedom in installation can be increased.

[0019] As yet another means that can be employed to solve the problems, it is also possible to configure the device by having a plurality of the submerged membrane modules, the first reverse osmosis membrane modules, and the second reverse osmosis membrane modules, arranging the submerged membrane modules in a rectangular pattern along the longitudinal direction of the entire device, and arranging the same number of the first reverse osmosis membrane modules and the second reverse osmosis membrane modules on both sides of the submerged membrane module.

[0020] By providing a plurality of submerged membrane modules, first reverse osmosis membrane modules, and second reverse osmosis membrane modules, the amount of salt-containing water that can be filtered can be increased. In this case, by arranging low-height submerged membrane modules in a rectangular pattern in plan view and arranging an equal number of first reverse osmosis membrane modules and second reverse osmosis membrane modules on either side of the low-height submerged membrane modules, a large number of modules can be arranged efficiently and in a balanced manner.

[0021] As yet another means that can be employed to solve the problem, a three-way valve can be provided between the submerged membrane suction pump and the energy recovery device, and the three-way valve can be configured to switch between a connection that allows the filtered water of the submerged membrane module, which is discharged by the submerged membrane suction pump, to pass through the energy recovery device, and a connection that allows the filtered water of the first reverse osmosis membrane module to pass through the energy recovery device.

[0022] The three-way valve is operated to allow the filtered water from the submerged membrane module to flow through the energy recovery device, thereby enabling filtration. On the other hand, by switching the valve to allow the filtered water from the first reverse osmosis membrane module to flow through the energy recovery device, fresh water that has passed through the first reverse osmosis membrane module is passed through the energy recovery device and then back through the first reverse osmosis membrane module, thereby enabling cleaning of the first reverse osmosis membrane module by flushing.

[0023] As yet another means that can be adopted to solve the problem, it is possible to configure the entire device so that its width is 2.1 m or less, its length is 6.2 m or less, and its height is 2.5 m or less. Common trucks include small trucks (2-ton trucks) and medium-sized trucks (4-ton trucks), but medium-sized trucks also come in standard and short body versions. The above dimensions can be loaded into the bed of a standard medium-sized truck, allowing for efficient transportation. [Effects of the Invention]

[0024] In the water purification system of the present invention, the first reverse osmosis membrane module, which requires high-pressure filtration, is powered by energy recycled by an energy recovery device, thereby enabling the overall size of the water purification system to be reduced. Furthermore, a low-profile submerged membrane module is vertically positioned, with the first and second reverse osmosis membrane modules horizontally positioned on either side of it. With this configuration, the water purification apparatus can obtain drinkable pure water from salt-containing water, has high filtration efficiency, requires a small installation area, and is easy to transport. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a schematic plan view showing a water purification apparatus of the present invention. [Figure 2] 1 is a front view showing a schematic diagram of a water purification apparatus according to the present invention. [Figure 3] FIG. 2 is an explanatory diagram showing the state in which the water purifying apparatus of the present invention is transported. [Figure 4] FIG. 10 is a schematic plan view showing a water purification apparatus according to a modified example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the following description, the drawings are shown in a schematic manner for the sake of simplicity, and for example, the submerged membrane module and the reverse osmosis membrane module are shown in a simplified manner.

[0027] The water purification apparatus 100 of the present invention, as shown in Figure 1, is an apparatus for obtaining drinkable pure water from salty water by filtration. Salty water is water containing chlorides that is unsuitable for drinking, and includes not only seawater but also groundwater in coastal areas.

[0028] The water purification system 100 shown in Fig. 1 includes submerged membrane modules 1-1 for removing impurities from salt-containing water, first reverse osmosis membrane modules 2-2 for desalination of water filtered by the submerged membrane modules 1-1, second reverse osmosis membrane modules 3-3 for purifying the filtered water from the first reverse osmosis membrane modules 2-2, a submerged membrane suction pump 4 for transporting salt-containing water to the submerged membrane modules 1-1, and an energy recovery device 6 for transporting the filtered water from the submerged membrane modules 1-1 to the first reverse osmosis membrane modules 2-2 and recovering energy from the concentrated water from the first reverse osmosis membrane modules 2-2 to increase the water pressure flowing into the first reverse osmosis membrane modules 2-2. The tank 7 also includes a freshwater filtration tank 71 for storing the freshwater from which the salt has been removed by the first reverse osmosis membrane modules 2-2, and a pure water filtration tank 72 for storing the pure water obtained by the second reverse osmosis membrane modules 3-3. These elements are connected by water pipes.

[0029] The overall operation of the water purification apparatus 100 of the present invention will now be described. First, salt-containing water is sucked in by a submerged pump (not shown), and the salt-containing water passes through the submerged membrane modules 1·1.... The submerged membrane modules 1·1... remove suspended matter, such as organic matter, contained in the sucked salt-containing water. Next, the filtered water filtered through the submerged membrane modules 1·1... is sent to the energy recovery device 6 by the submerged membrane suction pump 4. In the energy recovery device 6, the filtered water filtered through the submerged membrane modules 1·1... is pressurized by a high-pressure pump built into the energy recovery device 6 and sent to the first reverse osmosis membrane modules 2·2.... At the same time, the concentrated water from the first reverse osmosis membrane modules 2·2... flows into the energy recovery device 6. The remaining pressure of the concentrated water is used by a piston in the energy recovery device 6 to further pressurize the filtered water sent by the built-in high-pressure pump. This allows water to be pumped to the first reverse osmosis membrane modules 2 at high pressure even with a small high-pressure pump built into the energy recovery device 6, thereby improving filtration efficiency.

[0030] The filtered water from the first reverse osmosis membrane modules 2.2... is stored in a freshwater filtration tank 71 and then sent to the second reverse osmosis membrane modules 3.3... by a freshwater high-pressure pump (not shown). The second reverse osmosis membrane modules 3.3... further remove residual salt and color components from the desalinated water, thereby producing pure water suitable for drinking, etc. The pure water obtained by the second reverse osmosis membrane modules 3.3... is stored in a pure water filtration tank 72.

[0031] The elements constituting the water purification apparatus 100 and their arrangement will be described below. The submerged membrane modules 1·1... may be, for example, ultrafiltration (UF) membranes made of hollow fiber membranes, and may be external pressure modules covered by a substantially cylindrical vessel. However, modules using other types of filtration membranes may also be used depending on the properties of the salt-containing water, the amount of impurities, etc. In order to purify salt-containing seawater, it is necessary to remove organic matter such as plankton and dead microorganisms from the seawater. By filtering out these impurities before desalination, clogging of the reverse osmosis membrane can be prevented.

[0032] In the embodiment shown in Fig. 1, the submerged membrane modules 1-1... are modules that are shorter in longitudinal dimension than the first reverse osmosis membrane modules 2-2... and the second reverse osmosis membrane modules 3-3... and are arranged so that their longitudinal direction is in the vertical direction. Their length can be, for example, about 1 m. A plurality of these submerged membrane modules 1·1... can be arranged. In the example of Figure 1, nine modules are arranged in a square pattern of three rows and three columns in plan view. The filtration capacity of the nine submerged membrane modules 1·1... is approximately 260 m 3 / day. The number of submerged membrane modules 1·1... can be changed as needed, and the arrangement pattern can also be a rectangular pattern. These submerged membrane modules 1·1... can be all piped in parallel to filter, or several submerged membrane modules 1·1... can be connected in series to filter.

[0033] The first reverse osmosis membrane modules 2·2... are reverse osmosis membranes (SWRO membranes) made of, for example, polyamide or cellulose acetate, and, like the submerged membrane modules 1·1..., can be internal pressure modules covered by an approximately cylindrical vessel. Salt-containing water has chloride molecules dissolved in the water molecules, and SWRO membranes are made up of multiple layers of nano-sized membranes to remove these chlorides. The mesh size of SWRO membranes is approximately 0.1nm to 1nm.

[0034] In the embodiment shown in Fig. 1, the first reverse osmosis membrane modules 2 are disposed adjacent to the submerged membrane modules 1, and are arranged horizontally with their longitudinal direction aligned horizontally. Their length can be, for example, about 3 m. Multiple first reverse osmosis membrane modules 2·2... can also be arranged. In the example of Figure 1, the vessels are arranged in two rows in a plan view, with three vessels stacked vertically in each row. Each vessel contains two reverse osmosis membranes, for a total of 12 reverse osmosis membranes. These first reverse osmosis membrane modules 2·2... are configured so that all of the reverse osmosis membranes are connected in series, and the filtered water from each reverse osmosis membrane is discharged together.

[0035] The energy recovery device 6 can be of various mechanisms. For example, a turbocharger can be used, which uses concentrated water to turn a turbine and generate pressure using the resulting power, or a hydraulic booster can be used, which uses concentrated water pressure to drive a piston and generate pressure using that force. The example shown in Figures 1 and 2 uses a turbocharger type device that also has a built-in high-pressure pump.

[0036] In the embodiment shown in FIG. 1, the concentrated water from the first reverse osmosis membrane modules 2·2... is used as the input to the energy recovery device 6, and the output is pressurized to the output of a high-pressure pump built into the energy recovery device 6. However, depending on the level of pressure, the pressure of the concentrated water from the submerged membrane modules 1·1... may be reused. Furthermore, energy may be added to the pressure of a freshwater high-pressure pump that sends water to the second reverse osmosis membrane modules 3, 3... (not shown).

[0037] The second reverse osmosis membrane modules 3·3..., like the first reverse osmosis membrane modules 2·2..., are reverse osmosis membranes (XLE membranes) made of polyamide, cellulose acetate, etc., and can be internal pressure type modules covered by an approximately cylindrical vessel. However, the second reverse osmosis membrane module 3·3... is intended to obtain pure water by removing color components and trace amounts of salt that were not completely filtered out by the first reverse osmosis membrane module 2·2.... For this reason, the RO membranes selected are finer than those of the first reverse osmosis membrane module 2·2....

[0038] In the embodiment shown in Fig. 1, the second reverse osmosis membrane modules 3 are also disposed adjacent to the submerged membrane modules 1, and are arranged horizontally with their longitudinal direction aligned horizontally. Their length can be, for example, about 3 m. Multiple second reverse osmosis membrane modules 3·3... can also be arranged. In the example of Figure 1, the vessels are arranged in two rows in a plan view, with three vessels stacked vertically in each row. Each vessel contains two reverse osmosis membranes, for a total of 12 reverse osmosis membranes. These second reverse osmosis membrane modules 3·3... are configured so that all of the reverse osmosis membranes are connected in series, and the filtered water from each reverse osmosis membrane is discharged together.

[0039] The number and arrangement of the second reverse osmosis membrane modules 3·3... are preferably the same as those of the first reverse osmosis membrane modules 2·2..., and are preferably arranged symmetrically with respect to the center of the submerged membrane modules 1·1... in terms of balance during transportation. The energy recovery device 6 is disposed vertically adjacent to the end of the first reverse osmosis membrane modules 2. An electrical box containing a control device, a battery, etc. may be disposed in the space between the second pump 5 and the energy recovery device 6.

[0040] The freshwater filtration tank 71 and the pure water filtration tank 72, which are the tank 7, are disposed between the first reverse osmosis membrane module 2·2... and the second reverse osmosis membrane module 3·3..., adjacent to the submerged membrane modules 1·1.... The dimensions of the tank 7 are preferably such that the height does not exceed the longitudinal direction of the submerged membrane module 1, and the width and length are such that they fit within the space between the first reverse osmosis membrane module 2·2... and the second reverse osmosis membrane module 3·3....

[0041] The above-mentioned elements are fixed to a frame 8. The frame 8 includes a first frame 81 and a second frame 82. The first frame 81 is a rectangular frame, and has the submerged membrane modules 1·1..., the first reverse osmosis membrane modules 2·2..., the second reverse osmosis membrane modules 3·3..., the first pump 4, and the tank 7 attached thereto. The overall dimensions when these are attached to the first frame 81 are 2.0 m in width, 1.6 m in height, and 3.5 m in the longitudinal direction.

[0042] The second frame 82 is also a rectangular frame, but its longitudinal direction is the width direction of the first frame 81. In other words, the aspect ratio is such that the longitudinal direction is rotated 90 degrees relative to the first frame 81. The energy recovery device 6 is attached to the second frame 82. An electrical equipment box is provided adjacent to the energy recovery device 6 and is attached to the second frame 82.

[0043] The first frame 81 and the second frame 82 are detachably attached to the adjacent frame portions by bolts or the like (not shown). At this time, the water pipes connecting the submerged membrane modules 1·1... and the energy device 6, or the water pipes connecting the first reverse osmosis membrane modules 2·2... and the energy recovery device 6 are arranged so that their connecting portions correspond to each other. This improves the flexibility of transportation, as needed, by loading the block of first frame 81 onto the bed of a truck and loading the block of second frame 82 onto another towing vehicle and towing it with the truck. Also, when connecting first frame 81 and second frame 82 on-site to form water purification system 100, the connection of the water pipes can be completed simply by fastening the water pipes together with bolts, joints, etc. (not shown).

[0044] The water purification apparatus 100 of the present invention has the above-described configuration, and is arranged so that the entire apparatus fits within a rectangular parallelepiped. This makes it easy to place the apparatus on the back of a truck or in a container, as shown in Figure 3. In particular, to be placed on the bed of a medium-sized truck, it is preferable that the widthwise dimension is 2.1 m or less, the lengthwise dimension is 6.2 m or less, and the height is 2.5 m or less when the first and second frames 81 and 82 are connected. By having the widthwise dimension of 2.1 m or less and the lengthwise dimension of 6.2 m or less, it can be placed on the bed of a standard body of a medium-sized truck. Furthermore, by having the height of 2.5 m or less, it can be placed within the limit on the load height even if the body is a high-floor type.

[0045] It is more preferable that the overall dimensions of the device be 2.0 m or less in the short direction, 4.3 m or less in the long direction, and 2.0 m or less in height. By having a short direction of 2.0 m or less and a long direction of 4.3 m or less, it can be placed on the bed of a short-bodied medium-sized truck. Furthermore, by keeping the height 2.0 m or less, it becomes easier to operate the modules and electrical boxes located on top of the device.

[0046] As described above, the water purification apparatus 100 of the present invention can produce drinkable pure water from salt-containing water with just this one apparatus. Furthermore, by efficiently arranging the components required for this purpose, the installation footprint can be minimized and the apparatus is easy to transport.

[0047] 『Variation』 Next, a water purifying apparatus 101 according to a modified example of the present invention will be described with reference to FIG. The water purification apparatus 101 of this modified example differs from the embodiment shown in FIG. 1 in that it includes a high-pressure pump 5 that is separate from the energy recovery device 6. In addition, the filtered water from the submerged membrane modules 1-1 is sucked by a submerged membrane suction pump 4 and connected to the high-pressure pump 5 and the energy recovery device 6 via a three-way valve 9. The three-way valve 9 is configured to be switchable between a connection state in which the filtered water sent from the submerged membrane suction pump 4 can be sent to the high-pressure pump 5 and the energy recovery device 6, and a connection state in which the freshwater in the freshwater filtration tank 71 can be sent to the high-pressure pump 5 and the energy recovery device 6.

[0048] In this modification, the concentrated water from the first reverse osmosis membranes 2 flows into the energy recovery device 6, and the residual pressure is added to the pressure of the filtered water sent by the high-pressure pump 5. By providing the high-pressure pump 5 separately from the energy recovery device 6, it is possible to use a high-pressure pump with an appropriate output depending on demand.

[0049] In addition, by switching the three-way valve 9 and supplying freshwater from the freshwater filtration tank 71 to the high-pressure pump 5 and the energy recovery device 6, clean water can be supplied to the first reverse osmosis membrane modules 2·2... at high pressure, allowing the first reverse osmosis membrane modules 2·2... to be cleaned by flushing.

[0050] In this modification, the high-pressure pump 5 is disposed adjacent to the energy recovery device 6 and is attached to a second frame 82. The high-pressure pump 5 and the energy recovery device 6 are fixed to the submerged membrane suction pump 4 attached to the first frame 81 using water pipes with bolts, joints, etc. (not shown). This makes it possible to attach and detach the first frame 81 and the second frame 82.

[0051] The present invention is not limited to the above embodiments. For example, the first and second racks can be arranged apart and connected by another water pipe. Also, a generator capable of operating pumps can be placed on another towable rack and towed together with the first and second racks for transport. In this case, the other rack can be configured to be connectable to the first and second racks. [Explanation of symbols]

[0052] 100,101 Water purification equipment 1. Submerged membrane module 2. First reverse osmosis membrane module 3 Second reverse osmosis membrane module 4. Submerged membrane suction pump 5. High-pressure pump 6 Energy Recovery Device 7. Tank 71 Freshwater filtration tank 72 Pure water filtration tank 8 Mounting stand 81 First Platform 82 Second Platform 9 Three-way valve

Claims

1. A water purification device for obtaining drinkable pure water from salt-containing water by filtration, a cylindrical submerged membrane module for removing impurities from the salt-containing water; a cylindrical first reverse osmosis membrane module for desalination of the water filtered by the submerged membrane module; an energy recovery device for recovering energy from the concentrated water of the first reverse osmosis membrane module to increase the pressure of the water flowing into the first reverse osmosis membrane module; a submerged membrane suction pump for sending the filtered water of the submerged membrane module to the energy recovery device; a cylindrical second reverse osmosis membrane module for purifying the filtrate from the first reverse osmosis membrane module; the submerged membrane module has a cylindrical axial length that is shorter than that of the first reverse osmosis membrane module or the second reverse osmosis membrane module, and is arranged such that the vertical direction is the longitudinal direction when the axial direction of the cylinder is the longitudinal direction, a first reverse osmosis membrane module and a second reverse osmosis membrane module, each of which is disposed on either side of the submerged membrane module such that the horizontal direction is the longitudinal direction when the axial direction of the cylindrical shape is the longitudinal direction.

2. the energy recovery device is disposed adjacent to ends of the first reverse osmosis membrane module and the second reverse osmosis membrane module; a first frame on which the submerged membrane module, the first reverse osmosis membrane module, the second reverse osmosis membrane module, and the submerged membrane suction pump are mounted; a second frame on which the energy recovery device is mounted, 2. The water purifying apparatus according to claim 1, wherein the first frame and the second frame are configured to be detachable from each other.

3. In a state where the first frame and the second frame are separated, 3. The water purification apparatus according to claim 2, wherein the first reverse osmosis membrane module or the second reverse osmosis membrane module can be connected to the energy recovery device by another water pipe.

4. the submerged membrane module, the first reverse osmosis membrane module, and the second reverse osmosis membrane module are each provided in plural; the submerged membrane modules are arranged in a rectangular matrix pattern in plan view along the longitudinal direction of the entire apparatus, with the longitudinal direction of the first reverse osmosis membrane module and the second reverse osmosis membrane module being rows and the direction perpendicular thereto being columns, 3. The water purification apparatus according to claim 1, wherein the first reverse osmosis membrane modules and the second reverse osmosis membrane modules are arranged in equal numbers on both sides of the submerged membrane module.

5. a three-way valve is provided between the submerged membrane suction pump and the energy recovery device; 3. The water purification apparatus according to claim 1, wherein the three-way valve is capable of switching between a connection that allows the filtered water of the submerged membrane module, which is delivered by the submerged membrane suction pump, to flow to the energy recovery device and a connection that allows the filtered water of the first reverse osmosis membrane module to flow to the energy recovery device.

6. 3. The water purifying apparatus according to claim 1, wherein the entire apparatus has a width of 2.1 m or less, a length of 6.2 m or less, and a height of 2.5 m or less.

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