Sequential Circulation Process Reverse Osmosis Desalination System

Abstract

The present invention relates to a sequential circulation reverse osmosis desalination apparatus, and more particularly to a sequential circulation reverse osmosis desalination apparatus that employs closed-circuit reverse osmosis technology to ensure a fundamentally high recovery rate, and sequentially applies reverse reverse osmosis technology to reduce fouling, while performing highly efficient water treatment without a separate energy recovery device.

Description

Technical Field

[0001] The present invention relates to a sequential circulation process reverse osmosis desalination device. More specifically, it adopts a closed-loop reverse osmosis technology to basically guarantee a high recovery rate, and sequentially applies a reverse reverse osmosis technology to reduce fouling. On the other hand, it relates to a sequential circulation process reverse osmosis desalination device that performs highly efficient water treatment without another energy recovery device.

Background Art

[0002] Water shortage means that it is difficult to obtain available fresh water sources due to resource depletion, and globally, water shortage is becoming more serious due to industrial upgrading and abnormal climate phenomena.

[0003] However, water is an essential element in human life and various industrial fields, and its demand is constantly increasing. As one of the effective methods to meet such demand, a so-called seawater desalination method of desalinating large-scale seawater has been proposed.

[0004] Seawater desalination means a series of water treatment processes that remove dissolved substances containing salts from seawater that is difficult to directly use for domestic and industrial water, and obtain high-purity drinking water, domestic water, industrial water, etc.

[0005] Currently, seawater desalination equipment adopts a multi-stage flash distillation process (MSF) or a reverse osmosis process. Among these, the reverse osmosis process is a process of applying a pressure higher than the osmotic pressure to raw water or salt water to move pure water from which solutes such as ions and organic molecules have been excluded through a semi-permeable membrane to produce fresh water.

[0006] On the other hand, unlike general reverse osmosis processes, there is a seawater desalination method called closed-circuit reverse osmosis (CCRO) that, in order to achieve the target recovery rate, mixes the concentrated water discharged from the reverse osmosis equipment with raw water or brine and injects it back into the reverse osmosis equipment, and operates by discharging the concentrated water once the target concentration is reached.

[0007] In connection with this, Korean Registered Patent No. 10-1052662 discloses a feature in which multiple closed-circuit desalination devices (CCROs) are connected in parallel by a device for continuous, batch, sequential desalination of a saline solution in a closed circuit using reverse osmosis.

[0008] However, existing closed-circuit desalination systems (CCROs) using reverse osmosis have a problem in that the time it takes for the pressure of the concentrated water discharged from the reverse osmosis equipment to increase decreases as the process progresses, resulting in a shorter cleaning or replacement cycle for the reverse osmosis equipment. [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] The present invention was proposed to solve the above-mentioned problems, and its purpose is to provide a sequential circulating reverse osmosis desalination apparatus that employs closed-circuit reverse osmosis technology to guarantee a high recovery rate, and sequentially applies reverse osmosis technology to reduce fouling, while performing highly efficient water treatment without the need for a separate energy recovery device.

[0010] Other objects of the present invention will become clearer from the embodiments described below. [Means for solving the problem]

[0011] To solve the above-mentioned problems, the present invention proposes, as one embodiment, a sequential circulating reverse osmosis desalination apparatus in which each of a plurality of forward RO modules and at least one backward RO module are connected in parallel, concentrated water discharged from the forward RO modules flows into the backward RO modules, and concentrated water discharged from the backward RO modules flows into each of the forward RO modules.

[0012] One embodiment of the reverse osmosis desalination apparatus includes a feed pump for supplying raw water, a primary pump connected to the output terminal of the feed pump, a secondary pump connected to the output terminal of the forward reverse osmosis module, a tertiary pump connected to the output terminal of the primary pump, and a controller that controls the feed pump and the primary pump in the first step of operation so that raw water is input into the forward reverse osmosis module, and controls the secondary pump in the second step of operation so that concentrated water discharged from the forward reverse osmosis module is input into the reverse reverse osmosis module. In the third step of operation, the tertiary pump inputs concentrated water discharged from the reverse reverse osmosis module into the forward reverse osmosis module after it has merged with the raw water.

[0013] High-pressure pumps may be selected as the primary and secondary pumps, and a jet pump may be selected as the tertiary pump to accelerate the raw water in the three stages of operation using the flow of concentrated water.

[0014] Furthermore, a three-way control valve is provided at the input and output terminals of both the forward and reverse reverse osmosis modules. In the fourth step of operation, the controller controls the three-way valve so that when a preset first condition is met, the reverse reverse osmosis module switches to a forward reverse osmosis module. The controller continues to supply raw water to the input terminals of all reverse osmosis modules while simultaneously discharging concentrated water from the output terminals of all reverse osmosis modules until a preset second condition is met.

[0015] Furthermore, the first condition can be that at least one of the measurements from a concentration sensor, a flow sensor, and a pressure sensor placed in the transport path of the concentrated water reaches a preset standard, or that a preset time has elapsed after the three stages of operation.

[0016] Furthermore, the second condition can be that the concentration of the concentrated water reaches a predetermined initial concentration.

[0017] After the completion of one batch process from the first to the fourth operation stages, the controller can execute a fifth operation stage in which it controls the three-way valve so that at least one of the forward reverse osmosis modules is switched to a reverse reverse osmosis module and an existing reverse reverse osmosis module is switched to a forward reverse osmosis module.

[0018] Furthermore, the controller can execute the five operation stages after performing the batch process multiple times. [Effects of the Invention]

[0019] According to an embodiment of the present invention, before the closed-circuit reverse osmosis (CCRO) process in which concentrated water and raw water are mixed, the concentrated water discharged from the forward RO module flows into the backward RO module and circulates in a further concentrated state, thereby significantly reducing the energy consumption and chemical usage compared to the existing multi-stage reverse osmosis process.

[0020] Also, according to an embodiment of the present invention, by periodically applying the raw water injection direction in the opposite direction, the generation rate of biofouling and scale in the reverse osmosis module can be slowed down, and some scale can be removed. Therefore, the reduction width of the time when the pressure of the concentrated water increases becomes shorter, and the CIP (Clean in place) cycle can be extended.

[0021] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.

Brief Description of the Drawings

[0022] [Figure 1] It is a schematic diagram of a sequential circulation process reverse osmosis desalination device according to an embodiment of the present invention.

[0023] [Figure 2] It is a block diagram showing the configuration of a sequential circulation process reverse osmosis desalination device according to an embodiment of the present invention.

[0024] [Figure 3] It is a flowchart showing the operation stages of a sequential circulation process reverse osmosis desalination device according to an embodiment of the present invention.

[0025] [Figure 4] It is a schematic diagram showing four operation stages of a sequential circulation process reverse osmosis desalination device according to an embodiment of the present invention.

[0026] [Figure 5]This is a schematic diagram showing the five operating stages of a sequential circulation reverse osmosis desalination apparatus according to an embodiment of the present invention.

[0027] [Figure 6] This graph shows the decrease in the time it takes for the pressure to increase each time a one-batch process is repeated from the first to the fourth operation stage of a sequential circulating reverse osmosis desalination apparatus according to an embodiment of the present invention. [Modes for carrying out the invention]

[0028] The present invention can be modified in various ways and may have various embodiments. Specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this should not be understood as limiting the present invention to specific embodiments, but rather as encompassing all modifications, equivalents, or substitutions included in the spirit and technical scope of the present invention.

[0029] In describing the present invention, if it is determined that a specific description of related prior art may obscure the gist of the invention, such detailed description will be omitted.

[0030] The terminology used in this application is solely for the purpose of describing specific embodiments and is not intended to limit the invention. Singular expressions include plural expressions unless otherwise specified in the context. In this application, terms such as “includes” or “having” are intended to specify the existence of features, figures, processes, operations, components, parts, or combinations thereof described in the specification, and should be understood not to preemptively exclude the possibility of the existence or addition of one or more other features, figures, processes, operations, components, parts, or combinations thereof.

[0031] Unless otherwise specified, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by a person of ordinary skill in the art to which this invention pertains. Terms as defined in commonly used dictionaries should be interpreted as having the meaning consistent with their meaning in the context of the relevant art, and not as ideal or overly formal unless expressly defined herein.

[0032] As used herein, the term "module" refers to a unit that performs a specific function or operation, and this can mean hardware, software, or a combination of hardware and software.

[0033] Furthermore, terms such as "first," "second," etc., may be used to describe various components, but these components should not be limited by these terms. These terms are used solely for the purpose of distinguishing one component from others.

[0034] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. When describing with reference to the attached drawings, the same reference numeral will be assigned to identical or corresponding components regardless of the reference numerals in the drawings, and redundant descriptions will be omitted.

[0035] The sequential circulation process reverse osmosis desalination apparatus 1 according to an embodiment of the present invention will be described in detail below with reference to the drawings.

[0036] In describing the sequential circulation process reverse osmosis desalination apparatus 1 according to an embodiment of the present invention below, the meaning of "connected" should be interpreted to include both direct connection to the reverse osmosis module and connection via components such as pumps, valves, and controllers.

[0037] Figure 1 is a schematic diagram of a sequential circulating reverse osmosis desalination apparatus according to one embodiment of the present invention, Figure 2 is a block diagram showing the configuration of a sequential circulating reverse osmosis desalination apparatus according to an embodiment of the present invention, and Figure 3 is a flowchart showing the operating stages of a sequential circulating reverse osmosis desalination apparatus according to an embodiment of the present invention.

[0038] As shown in Figures 1 and 2, the sequential circulation reverse osmosis desalination apparatus 1 according to one embodiment includes a plurality of reverse osmosis modules (RO modules) 10, 20, 30, a feed pump FP, a primary pump P1, a secondary pump P2, a tertiary pump P3, a plurality of three-way valves, a concentrated water discharge valve (Brain valve) DV, and a controller C.

[0039] The reverse osmosis modules 10, 20, and 30 include a plurality of forward RO modules 10 and 20 and at least one backward RO module 30.

[0040] This specification shows an embodiment consisting of two forward reverse osmosis modules and one reverse reverse osmosis module, but is not limited thereto. Depending on the volume of brine to be treated, the reverse osmosis modules may consist of two or four or more modules. Specifically, it may consist of one forward reverse osmosis module and one reverse reverse osmosis module, three forward reverse osmosis modules and one reverse reverse osmosis module, or three forward reverse osmosis modules and two reverse reverse osmosis modules.

[0041] For the sake of clarity, the reverse osmosis modules (Ro modules) 10, 20, and 30 will be referred to as the first reverse osmosis module 10, the second reverse osmosis module 20, and the third reverse osmosis module 30, respectively.

[0042] The first reverse osmosis module 10, the second reverse osmosis module 20, and the third reverse osmosis module 30 are connected in parallel to each other, and concentrated water (Brine, B) discharged from the first reverse osmosis module 10 and the second reverse osmosis module 20 flows into the third reverse osmosis module 30, and concentrated water B discharged from the third reverse osmosis module 30 flows back into the first reverse osmosis module 10 and the second reverse osmosis module 20, respectively, forming a circulating circuit.

[0043] A feed pump (FP) is installed to supply raw water (R) to a reverse osmosis module and can transfer raw water (R) at a pressure of approximately 3 bar(g), for example.

[0044] The primary pump P1 is connected to the output terminal of the feed pump FP and is activated when the flow rate of raw water R supplied from the feed pump FP exceeds a preset standard.

[0045] The secondary pump P2 is connected to the output terminals of the first reverse osmosis module 10 and the second reverse osmosis module 20, and moves the concentrated water B discharged from the first reverse osmosis module 10 and the second reverse osmosis module 20 to the input terminal of the third reverse osmosis module 30.

[0046] High-pressure pumps may be used as the primary pump P1 and secondary pump P2.

[0047] The concentrated water B discharged from the third reverse osmosis module 30 merges with the raw water R supplied from the feed pump FP and flows into the tertiary pump P3. The tertiary pump P3 transports the combined water to the input terminals of the first reverse osmosis module 10 and the second reverse osmosis module 20.

[0048] As the tertiary pump P3, a jet pump that uses the flow of concentrated water B to accelerate the flow of raw water R may be used.

[0049] In other words, because the pressure of concentrated water B is higher than the pressure of raw water R, a pressure drop must be applied for the smooth merging and transfer of raw water R and concentrated water B, but this requires accepting the resulting energy loss. Therefore, by using a jet pump as the tertiary pump P3, the raw water R can be accelerated using the flow of concentrated water B without the need for another pressure drop.

[0050] The three-way control valves V11, V12, V21, V22, V31, and V32 (collectively referred to as V) are located at the input and output terminals of the first reverse osmosis module 10, the second reverse osmosis module 20, and the third reverse osmosis module 30, respectively, and are opened and closed in the horizontal or vertical flow direction by the control of controller C.

[0051] The concentrated water discharge valve (Drain Valve) DV is located on the piping where the output terminals of the first reverse osmosis module 10, the second reverse osmosis module 20, and the third reverse osmosis module 30 converge, and is opened and closed by controller C when the discharge water B meets predetermined conditions.

[0052] Controller C controls the startup and operating levels of pumps FP, P1, and P2 according to the operating stages (S10 to S50) described later, and controls the opening and closing of the three-way valve V and the concentrated water discharge valve DV.

[0053] The operating stages controlled by controller C include the first step (S10) of supplying raw water R, the second step (S20) of supplying concentrated water B, the third step (S30) of circulating concentrated water B, the fourth step (S40) of discharging concentrated water B, and the fifth step (S50) of changing the operating direction of each reverse osmosis module.

[0054] Here, assuming that the first reverse osmosis module 10 and the second reverse osmosis module 20 are set to the forward direction, and the third reverse osmosis module 30 is set to the reverse direction, each operating stage will be described in detail.

[0055] In the first stage of operation (S10), controller C controls the three-way valves V11, V12, V21, and V22 located at the input and output ends of the first reverse osmosis module 10 and the second reverse osmosis module 20, respectively, to open in the horizontal flow direction, and controls the three-way valves V31 and V32 located at the input and output ends of the third reverse osmosis module 30, respectively, to open in the vertical flow direction.

[0056] Furthermore, in the first operation stage (S10), the controller C controls the feed pump FP and the primary pump P1 so that raw water R is input to the first reverse osmosis module 10 and the second reverse osmosis module 20. Specifically, the controller C drives the feed pump FP to supply raw water, and when the flow rate of raw water R supplied from the feed pump FP exceeds a preset standard, it starts the primary pump P1. At this time, the controller C controls the operating Hz of the primary pump P1 based on the signal from a flow sensor (not shown) located in the raw water R supply line.

[0057] In the second stage of operation (S20), controller C controls the secondary pump P2 so that concentrated water B discharged from the first reverse osmosis module 10 and the second reverse osmosis module 20 is input to the third reverse osmosis module 30. Specifically, controller C starts the secondary pump P2 when the flow rate of concentrated water B exceeds a preset standard, and controls the operating Hz of the secondary pump P2 based on the signal from a flow sensor (not shown) located in the supply line of concentrated water B. Meanwhile, the fresh water that has been filtered (permeated) through the first reverse osmosis module 10 and the second reverse osmosis module 20 is discharged through the piping.

[0058] In the third stage of operation (S30), the concentrated water B discharged from the third reverse osmosis module 30 flows into the tertiary pump P3 via a three-way valve V31 located at the output end of the third reverse osmosis module 30. The raw water R supplied by the feed pump FP and the primary pump P1 also flows into the tertiary pump P3 and merges with the discharged concentrated water B. Meanwhile, the fresh water that has been filtered (permeated) through the third reverse osmosis module 10 is also discharged through the piping.

[0059] The aforementioned operation stages 1 (S10) to 3 (S30) are repeated until a predetermined sensor S detects that one of the following exceeds a preset threshold: concentration, pressure, flow rate, or scale amount of the concentrated water B. Therefore, the predetermined sensor S may be any one of a concentration sensor, a flow sensor, a pressure sensor, or a scale sensor, and at least one of these sensors is placed in the path of the concentrated water B.

[0060] The fourth operating stage (S40) is executed when any one of the following—concentration, pressure, flow rate, or scale amount of concentrated water B—exceeds a preset threshold. Figure 4 is a schematic diagram showing the four operating stages of a sequential circulating reverse osmosis desalination apparatus according to one embodiment.

[0061] In the fourth operating stage (S40), when the first preset condition is met, the controller C controls the three-way valves V31 and V32 so that the third reverse osmosis module 30 switches to a forward reverse osmosis module, and continues to supply raw water R to the input terminals of all reverse osmosis modules 10, 20, and 30 until the second preset condition is met, while simultaneously discharging the concentrated water B from the output terminals of all reverse osmosis modules 10, 20, and 30 to the outside.

[0062] Specifically, when the measurement value from sensor S reaches a preset threshold, controller C opens all three-way valves V11 to V32 located at the input and output ends of all reverse osmosis modules 10, 20, and 30 in the horizontal flow direction, and opens the previously closed concentrated water discharge valve DV. At this time, secondary pump P2 may interrupt its operation, operate at the lowest Hz, or switch to operation in the reverse direction.

[0063] In the fourth stage of operation (S40), the first condition means that the measurement value of the sensor S placed in the transport path of the concentrated water B reaches a preset standard (for example, at least one threshold value among concentration, salinity, flow rate, pressure, and scale amount), or that a preset time has elapsed after the third stage of operation (S30).

[0064] Furthermore, in the fourth stage of operation (S40), the second condition means that the concentration of concentrated water B reaches a preset initial concentration.

[0065] The concentrated water discharge valve DV is in a shielded state during operation stages 1 (S10) to 3 (S30), but is opened in operation stage 4 (S40) when the first condition is met to discharge concentrated water B, and then switches back to the shielded state when the second condition is met.

[0066] The operation stages 1 (S10) to 4 (S40) described above can be defined as one batch process, and are abbreviated as "1 batch".

[0067] In one embodiment of the sequential circulating reverse osmosis desalination apparatus, the operating direction of the reverse osmosis module is reset each time a batch is completed.

[0068] For example, if in the first batch the first reverse osmosis module 10, the second reverse osmosis module 20, and the third reverse osmosis module 30 are operated in the forward, forward, and reverse directions, respectively, then in the second batch the first reverse osmosis module 10, the second reverse osmosis module 20, and the third reverse osmosis module 30 are operated in the forward, reverse, and forward directions, respectively, in the third batch the first reverse osmosis module 10, the second reverse osmosis module 20, and the third reverse osmosis module 30 are operated in the reverse, forward, and forward directions, respectively, and in the fourth batch the first reverse osmosis module 10, the second reverse osmosis module 20, and the third reverse osmosis module 30 may be operated in the same forward, forward, and reverse directions as in the first batch.

[0069] However, this is merely one example, and the number of forward and reverse osmosis modules may vary depending on the number of reverse osmosis modules, and the order in which the operating direction is reset may also be modified in various ways.

[0070] In other words, the controller C can determine the target of reverse operation in real time based on the measurement values ​​of the sensor S for each reverse osmosis module, and can determine the direction of operation for each reverse osmosis module based on the result of that determination.

[0071] For example, if measuring the pressure of concentrated water B for each reverse osmosis module reveals that a particular reverse osmosis module has a high pressure for an unforeseen reason, that particular reverse osmosis module needs to be operated in reverse to intentionally remove fouling or scale. Therefore, even if the pre-set schedule indicates that other reverse osmosis modules should be operated in reverse at that time, the schedule can be changed to operate the aforementioned particular reverse osmosis module in reverse.

[0072] The fifth operating step is the process of resetting the operating direction of the reverse osmosis module after one batch from the first operating step (S10) to the fourth operating step (S40) has been completed. Figure 5 is a schematic diagram showing a sequential circulating reverse osmosis desalination apparatus that performs the fifth operating step.

[0073] In the fifth operating stage (S50), controller C controls the associated three-way valves (at least four of V11 to V32) so that either the first reverse osmosis module 10 or the second reverse osmosis module 20, which were operating in the forward direction, are switched to a reverse reverse osmosis module, and the third reverse osmosis module 30, which was previously operating in the reverse direction, is switched to a forward reverse osmosis module.

[0074] When raw water R is injected into a reverse osmosis module, its concentration increases as it moves downstream, increasing the probability of scale formation. As the amount of scale increases, the overall flux decreases, and performance degrades. Therefore, by periodically switching the injection direction of raw water R to the opposite side, it is possible to remove some of the scale with the injection pressure of raw water R while slowing down the rate of biofouling and scale formation within the reverse osmosis module.

[0075] On the other hand, controller C can execute operation stage 5 (S50) immediately after one batch is completed, or it can execute operation stage 5 (S50) only after repeating one batch multiple times and meeting the pre-set conditions.

[0076] Figure 6 is a graph showing the decrease in the time it takes for the pressure to increase each time a one-batch process is repeated from the first to the fourth operation stage of a sequential circulating reverse osmosis desalination apparatus according to an embodiment of the present invention.

[0077] Referring to Figure 6, in a typical closed-circuit reverse osmosis (CCRO) process, the time it takes for the pressure of concentrated water B, which is continuously circulated through the reverse osmosis module and discharged in one batch process, to increase decreases with each batch. However, in the present invention (Circle-SEQ RO), concentrated water B discharged from the forward RO module before the closed-circuit reverse osmosis (CCRO) process in which concentrated water B and raw water R are mixed flows into the backward RO module. By periodically reversing the direction of raw water injection, the rate of biofouling and scale formation in the reverse osmosis module is slowed, and some scale can be removed. This reduces the decrease in the time it takes for the pressure of concentrated water to increase, resulting in a longer CIP (Clean in place) cycle.

[0078] Although the above has been described with reference to several embodiments relating to the present invention, a person with ordinary skill in the art will understand that the present invention can be modified and altered in various ways without departing from the spirit and scope of the invention as described in the claims below.

Claims

1. A sequential recirculating reverse osmosis desalination apparatus in which multiple forward reverse osmosis modules and at least one backward reverse osmosis module are connected in parallel, concentrated water discharged from the forward reverse osmosis modules flows into the backward reverse osmosis modules, and concentrated water discharged from the backward reverse osmosis modules is mixed with raw water and recirculated to the input terminals of each of the forward reverse osmosis modules.

2. A feed pump that supplies raw water, A primary pump (1 ｓｔ pump) and, A secondary pump (2 ｎｄ pump) and, A tertiary pump (3) is connected to the output terminal of the primary pump. ｒｄ pump) and, Driving Stage 1 (1 ｓｔ In step 2, the feed pump and primary pump are controlled so that raw water is input to the forward reverse osmosis module, and operation is in two stages (2 ｎｄ step) includes a controller that controls the secondary pump so that the concentrated water discharged from the forward reverse osmosis module is input to the reverse reverse osmosis module, The aforementioned tertiary pump has three operating stages (3 ｒｄ The sequential circulating reverse osmosis desalination apparatus according to claim 1, characterized in that, in step (1), the concentrated water discharged from the reverse osmosis module is combined with the raw water and then driven without further control when input to the forward reverse osmosis module.

3. The sequential circulating reverse osmosis desalination apparatus according to claim 2, characterized in that the primary and secondary pumps are high-pressure pumps, and the tertiary pump is a jet pump that accelerates the raw water in the three operating stages using the flow of concentrated water.

4. Three-way control valves are provided at the input and output terminals of the forward reverse osmosis module and the reverse reverse osmosis module, respectively. The aforementioned controller, Driving in 4 stages (4 ｔｈ The sequential circulating reverse osmosis desalination apparatus according to claim 3, characterized in that, in step 1, when a pre-set first condition is met, the three-way valve is controlled so that the reverse osmosis module switches to a forward reverse osmosis module, and raw water is continuously supplied to the input terminals of all reverse osmosis modules until a pre-set second condition is met, while concentrated water is discharged to the outside from the output terminals of all reverse osmosis modules.

5. The sequential circulating reverse osmosis desalination apparatus according to claim 4, wherein the first condition is that at least one measurement value from a concentration sensor, a flow sensor, and a pressure sensor placed in the transport path of concentrated water reaches a preset standard, or that a preset time has elapsed after the third stage of operation.

6. The sequential recirculation process reverse osmosis desalination apparatus according to claim 5, wherein the second condition is that the concentration of the concentrated water reaches a predetermined initial concentration.

7. The aforementioned controller, The sequential circulating reverse osmosis desalination apparatus according to claim 5, characterized in that, after the completion of one batch process from the first to the fourth operating stages, a fifth operating stage is performed in which at least one of the forward reverse osmosis modules is switched to a reverse reverse osmosis module, and the three-way valve is controlled so that the existing reverse reverse osmosis module is switched to a forward reverse osmosis module.

8. The aforementioned controller, The sequential circulating reverse osmosis desalination apparatus according to claim 7, characterized in that the five operation stages are performed after the batch process described above is performed multiple times.

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