JP2016087500A - Reverse osmosis treatment system and reverse osmosis treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reverse osmosis treatment system which can prevent reduction of a treatment water flow rate due to stop of operation of a washing series during agent liquid washing.SOLUTION: A reverse osmosis treatment system has plural series equipped with: a first RO unit including plural first pressure containers which perform primary treatment of treatment object water and are arranged in parallel to one another; a second RO unit including plural second pressure containers which perform secondary treatment of treatment object water treated by said primary treatment and are arranged in parallel to one another. In each series, one or serially connected plural reverse osmosis membrane elements equipped with a reverse osmosis membrane are located in the first pressure container and the second pressure container. If a series is N-series (N≥2) and number of the first RO unit is M pieces, the following expression is satisfied: N+1≤M≤2×N-1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a reverse osmosis treatment system and a reverse osmosis treatment method, and more particularly to a reverse osmosis treatment system and a reverse osmosis treatment method capable of performing efficient cleaning and operation of the reverse osmosis treatment system.

  There has been proposed a reverse osmosis membrane treatment apparatus capable of easily replacing or cleaning a reverse osmosis membrane element.

  In Patent Document 1, the first pressure vessel that primarily treats the water to be treated and the second pressure vessel that secondarily treats the water to be treated that has been treated by the primary treatment are easily contaminated. It is described that the reverse osmosis membrane element of the pressure vessel can be replaced.

  Further, Patent Document 2 describes a reverse osmosis treatment apparatus capable of cleaning the first pressure vessel and the second pressure vessel independently with chemicals (CIP: Cleaning in Place).

  Further, Patent Document 3 describes that when the first pressure vessel is arranged in parallel and the cleaning process of one first pressure vessel is performed, the operation is continued with the other first pressure vessel. Yes.

JP 2012-130840 A JP2013-126635A JP 2014-161797 A

  In order to treat a large amount of water to be treated, a series including the first pressure vessel and the second pressure vessel is taken as one series, and a plurality of series is required.

  Conventionally, when cleaning is required among a plurality of systems, an operation that compensates for the insufficient flow rate of the stop system has been performed by temporarily increasing the membrane permeation flow rate (Flux) of the operation system. However, this method increases the operating pressure and power cost, and the filtration pump must be selected in consideration of the capacity of the increased flow rate. In addition, since the flux is high, there is a problem that the film is easily soiled, the frequency of cleaning is increased, and the life of the film is also reduced.

  Another method is to have a spare sequence. However, this means that there is one extra line that is not normally used, and there is a problem that it is wasteful and the cost (equipment cost) becomes high.

In Patent Document 3, it is proposed that the first pressure vessel containing the supply-side osmotic membrane element which is easily contaminated is arranged in parallel, and the switching operation is performed at the time of membrane contamination or CIP. It has not been proposed as a device for treating water to be treated. That is, in the case of medium / large capacity facilities (for example, several thousand m ³ / day), the number of series becomes large, the number of osmotic membrane elements increases, and the switching of the membrane, which is the control within the series, It is necessary to combine both control of CIP, which is a control of the above, and a control error is likely to occur, and a complicated protocol for accident prevention measures is required. In addition, since the number of pipes for switching and branching is large, there is a problem that the risk that the chemical solution after CIP remains in the switching valve portion or the like increases.

  The present invention is an invention for solving the above-described problem, and it is possible to prevent the flow rate of the treated water from being reduced because the operation of the series that is being washed during the chemical solution washing is stopped. An object is to provide an osmosis treatment system.

  In order to achieve the above object, a reverse osmosis treatment system of the present invention includes a plurality of first pressure vessels (for example, first pressure vessels 101v) arranged in parallel for primary treatment of water to be treated. One unit (for example, the first RO unit 101) and a plurality of second pressure vessels (for example, the second pressure vessel 201v) arranged in parallel to perform secondary treatment of the water to be treated that has been treated by the primary treatment. ) And a second unit (for example, the second RO unit 102), and each series includes a reverse osmosis membrane in the first pressure vessel and the second pressure vessel. When the number of the first units is M when the number of the reverse osmosis membrane elements including one or a plurality of reverse osmosis membrane elements is arranged in series and there are N sequences (N ≧ 2), N + 1 ≦ M ≦ 2 × N−1. Other aspects of the present invention will be described in the embodiments described later.

  According to the present invention, it is possible to prevent the flow rate of the treated water from decreasing because the operation of the series that is being cleaned during the chemical solution cleaning is stopped.

It is a lineblock diagram showing the reverse osmosis processing system concerning this embodiment. It is explanatory drawing which shows the open / close state of the valve | bulb at the time of making a 2nd series into a switching series. It is explanatory drawing which shows a to-be-treated water system, a treated water system, and a chemical | medical solution washing water system at the time of making a 2nd series into a switching series. It is explanatory drawing which shows the opening-and-closing state of the valve | bulb at the time of making a 3rd series into a switching series. It is explanatory drawing which shows a to-be-treated water system, a treated water system, and a chemical | medical solution washing water system at the time of making a 3rd series into a switching series. It is a flowchart which shows the process of the control apparatus at the time of changing a switching series. It is a block diagram which shows the comparative example (the 1) at the time of making 3 series into a driving | running series. It is a block diagram which shows the comparative example (the 2) at the time of making 3 series into a driving | running series.

Embodiments for carrying out the present invention will be described in detail with reference to the drawings as appropriate.
FIG. 1 is a configuration diagram illustrating a reverse osmosis processing system according to the present embodiment. In the present embodiment, a reverse osmosis system having a plurality of series is targeted, and for example, a case where there are three series of a first series 100, a second series 200, and a third series 300 will be described. The series is not limited to 3 series, but may be a plurality of series.

  Each sequence basically includes a sequence composed of an upstream RO (Reverse Osmosis) unit and a subsequent RO unit. Since each series has the same configuration, the first series 100 will be described in detail.

  The first series 100 includes a water supply pump 103, a pressure recovery device 106, a high pressure pump 104, a first RO unit 101 (first unit), a booster pump 105, and a second RO unit 102 (second). And a power recovery device 120.

  The high-pressure pump 104 is a pump that pumps water to be treated. The pressurizing force of the high-pressure pump 104 is a predetermined pressure that allows the water to be treated to pass from the primary side (upstream side) to the secondary side (downstream side) of the first RO unit 101 through the reverse osmosis membrane, and is set as appropriate. it can.

  The first RO unit 101 is a device for obtaining permeated water (treated water) by subjecting water to be treated flowing from the high-pressure pump 104 to the primary side via the supply pipe 111 and the valve 114 through membrane filtration. Here, the permeated water means water obtained by permeating water to be treated through a RO (Reverse Osmosis) membrane element, and hardly contains impurities such as salt. In the first RO unit 101, a plurality of first pressure vessels 101v having a cylindrical shape are arranged in parallel. The first pressure vessel 101v has one or more RO membrane elements. In the present embodiment, two RO membrane elements are arranged in series in the first pressure vessel 101v (or one may be used), and the first RO unit 101 has eight first pressure vessels 101v in parallel. Arranged.

  The RO membrane element is configured by winding a reverse osmosis membrane so as to cover a plurality of holes (not shown) formed in the water collection pipe. When the first RO unit 101 includes a plurality of RO membrane elements, the RO membrane elements are arranged in series in the axial direction of the first pressure vessel 101v. In FIG. 1, two RO membrane elements are arranged in series as described above, but one may be used.

  Each first pressure vessel 101v of the first RO unit 101 is connected to a concentrated water pipe 113 for flowing out concentrated water that has not permeated through the RO membrane element (hereinafter referred to as concentrated water). The second RO unit 102 is connected via a valve 115.

  The pressure recovery device 106 is a device that recovers the pressure of the permeated water of the first RO unit 101. Specifically, the pressure recovery device 106 is a known energy recovery turbine (ERT), and includes a pressure recovery unit (T: turbine) and a liquid feeding unit (P: pump head). The pressure recovery device 106 is connected to the first RO unit 101 via a treated water pipe 112 and a valve 116. The permeated water (treated water) of the first RO unit 101 is stored in a permeated water tank (not shown) that is temporarily stored via the treated water pipe 117. In addition, the system which does not arrange | position the pressure recovery apparatus 106 may be sufficient.

  The second RO unit 102 is a device for obtaining permeated water (treated water) by subjecting the treated water flowing into the primary side to membrane filtration through the valve 115 and the concentrated water pipe 113. In the second RO unit 102, a plurality of cylindrical second pressure vessels 102v are arranged in parallel. The second pressure vessel 102v has one or a plurality of RO membrane elements. In the present embodiment, four RO membrane elements are arranged in series in the second pressure vessel 102v, and five second pressure vessels 102v are arranged in parallel in the second RO unit 102.

The permeated water of the second RO unit 102 is stored in a permeated water tank (not shown) that is temporarily stored via the treated water pipe 117. The concentrated water of the second RO unit 102 is
It is supplied to the power recovery device 120.

  The power recovery device 120 is an energy recovery device (ERD) that boosts the water to be treated that is diverted from the supply pump 103 using the residual pressure of the concentrated water that flows out from the primary side of the second RO unit 102. It is. A primary side inlet (not shown) of the power recovery apparatus 120 is connected to a primary side of the second RO unit 102 via a concentrated water pipe 121, and a primary side outlet (not shown) is concentrated water. It is connected to a concentrated water tank (not shown) via a pipe 122.

  The secondary side inlet (not shown) of the power recovery device 120 is connected to the outlet pipe of the supply pump 103 via the supply pipe 123, and the secondary side outlet (not shown) is connected to the supply pipe 124. To the booster pump 105. The outlet of the booster pump 105 is connected to the supply pipe 111.

  As the power recovery device 120, for example, a positive displacement power recovery device or a turbo power recovery device may be used. Here, the “volumetric power recovery device” is a device that recovers power by moving a piston or a rotating cylinder in a chamber (not shown) by the residual pressure of concentrated water. The “turbo power recovery device” is a device that recovers power by directly rotating the turbine with the residual pressure of concentrated water.

  The first series 100 has been described above, but the second series 200 and the third series 300 also have the same configuration.

  The second series 200 includes a water supply pump 203, a pressure recovery device 206, a high pressure pump 204, a first RO unit 201 (first unit), a booster pump 205, and a second RO unit 202 (second). And a power recovery device 220.

  The third series 300 includes a water supply pump 303, a pressure recovery device 306, a high pressure pump 304, a first RO unit 301 (first unit), a booster pump 305, and a second RO unit 302 (second And a power recovery device 320.

  In addition, the reverse osmosis treatment system uses chemical cleaning (CIP) as a cleaning unit for cleaning the first series 100, the second series 200, the third series 300, and the first RO unit 501 (first unit). A chemical solution storage tank 400, a chemical solution supply pump 401, and header pipes 402 and 403 for distributing and collecting the chemical solution in each series at the time of CIP are provided. The first system 100 includes a port 107 and a valve 108 for supplying a chemical solution for CIP, and a port 109 and a valve 110 for collecting the chemical solution. Similarly, the second system 200 includes a port 207 and a valve 208 for supplying a chemical solution for CIP, and a port 209 and a valve 210 for collecting the chemical solution. The third series 300 includes a port 307 and a valve 308 for supplying a chemical solution for CIP, and a port 309 and a valve 310 for collecting the chemical solution.

  That is, the reverse osmosis processing system supplies a cleaning liquid to the reverse osmosis membrane of the first RO unit, and cleans the reverse osmosis membrane (for example, the chemical liquid storage tank 400, the chemical liquid supply pump 401, each series at the time of CIP The control apparatus 10 can wash the reverse osmosis membrane of the stopped first RO unit using the washing unit.

  The reverse osmosis processing system of the present embodiment has a first RO unit 501 (first unit) separately from the first series 100, the second series 200, and the third series 300. The first RO unit 501 has the same configuration as that of the first RO unit 101, 201, 301. That is, the first RO unit 501 is a device for obtaining permeated water (treated water) by subjecting water to be treated flowing into the primary side via the supply pipe 511 and the valve 514 to membrane filtration. In the first RO unit 501, a plurality of first pressure vessels 501v having a cylindrical shape are arranged in parallel. The first pressure vessel 501v has one or more RO membrane elements. In the present embodiment, two RO membrane elements are arranged in series in the first pressure vessel 501v, and the eight first pressure vessels 101v are arranged in parallel in the first RO unit 501.

  Each first pressure vessel 501v of the first RO unit 501 is connected to a concentrated water pipe 513 for allowing concentrated water that has not permeated through the RO membrane element to flow out, and the second RO units 102 and 202 are connected. , 302 are connected via a valve 515.

  The supply piping 511 of the first RO unit 501 is connected to the supply piping 111, 211, 311 of each series. The treated water pipe 512 is connected to each series of treated water pipes 112, 212, 312. The concentrated water piping 513 is also connected to the concentrated water piping 113, 213, 313 of each series.

  Specifically, the supply pipe 511 is connected to the supply pipe 111 via the valve 521. Similarly, the supply pipe 511 is connected to the supply pipe 211 via the valve 522. The supply pipe 511 is connected to the supply pipe 311 via the valve 523.

  The treated water pipe 512 is connected to the treated water pipe 112 via a valve 531. Similarly, the treated water pipe 512 is connected to the treated water pipe 212 via a valve 532. The treated water pipe 512 is connected to the treated water pipe 312 via the valve 533.

  The concentrated water pipe 513 is connected to the concentrated water pipe 113 via a valve 541. Similarly, the concentrated water pipe 513 is connected to the concentrated water pipe 213 via the valve 542. The concentrated water pipe 513 is connected to the concentrated water pipe 313 via the valve 543.

  The concentrated water pipe 513 is connected to the header pipe 402 via a port 507 and a valve 508. The supply pipe 511 is connected to the header pipe 403 via the port 509 and the valve 510.

  In other words, any series (first series 100, second series 200, third series 300) is connected by valves 521, 522, 523, valves 531, 532, 533, and valves 541, 542, 543. .

  Therefore, virtually any three of these four first RO units 101, 201, 301, and 501 can be selected to perform three-line operation. The control device 10 performs the operation by rotating the plurality of first RO units according to the operation state, the operation history, and the operation time.

  FIG. 2 is an explanatory diagram showing the open / close state of the valve when the second series is a switching series. In FIG. 2, the first sequence 100 and the third sequence 300 will be described as operation sequences, and the second sequence 200 will be described as a switching sequence. The second series 200 that is a switching series uses the first RO unit 501 instead of the first RO unit 201. When operating using the first RO units 501, 101, 301, the control device 10 sets the valves 522, 514, 532, 515, 542 to the OPEN state (the white valves in the figure), and the valves 521, Let 523,531,533,541,543 be a CLOSE state (in the figure, a black valve).

  The control device 10 sets the valve 508 of the chemical solution supply port 507, the valve 108 of the chemical solution supply port 107, the valve 208 of the chemical solution supply port 207, and the valve 308 of the chemical solution supply port 307 to the CLOSE state. Similarly, the control device 10 sets the valve 510 of the chemical solution recovery port 509, the valve 110 of the chemical solution recovery port 109, the valve 210 of the chemical solution recovery port 209, and the valve 310 of the chemical solution recovery port 309 to the CLOSE state.

  The control device 10 sets the valves 114 and 314 to the OPEN state, the valve 214 to the CLOSE state, the valves 115 and 315 to the OPEN state, the valve 215 to the CLOSE state, and the valves 116 and 316 to the OPEN state. The valve 216 is set to the CLOSE state.

  FIG. 3 is an explanatory diagram showing a treated water system, a treated water system, and a chemical cleaning water system when the second system is a switching system. In FIG. 3, while the reverse osmosis treatment system is in operation, the treated water system is indicated by a broken line, the treated water system is indicated by a dotted line, the concentrated water system is indicated by a one-dot chain line, and the chemical cleaning water system is indicated by a thick solid line. In the first series 100, the water to be treated (RO feed water) supplied by the supply pump 103 can be filtered by the first RO unit 101 and the second RO unit 102 to obtain treated water. In the second system 200, the water to be treated (RO feed water) supplied by the supply pump 203 can be filtered by the first RO unit 501 and the second RO unit 202 to obtain treated water. In the third series 300, treated water (RO feed water) supplied by the supply pump 303 can be filtered by the first RO unit 301 and the second RO unit 302 to obtain treated water.

  At this time, during the treatment water manufacturing operation, the control device 10 puts the valve 208 of the chemical solution supply port 207 and the valve 210 of the chemical solution recovery port 209 into the state of OPEN (the white valve in the figure). And the control apparatus 10 operates the chemical | medical solution supply pump 401, supplies the CIP chemical | medical solution stored in the chemical | medical solution storage tank 400 to the 1st RO unit 201, and performs CIP with respect to the 1st RO unit 201. it can.

  FIG. 4 is an explanatory diagram showing the open / close state of the valve when the third series is a switching series. Next, the control device 10 will be described with respect to a case where the first sequence 100 and the second sequence 200 are set as an operation sequence and the third sequence 300 is set as a switching sequence by rotation. The third series 300 that is a switching series uses the first RO unit 501 instead of the first RO unit 301.

  When the first RO unit 301 is stopped and operated using the first RO units 501, 101, 201, the control device 10 sets the valves 523, 514, 533, 515, 543 to the OPEN state, 521, 522, 531, 532, 541, and 542 are in a CLOSE state.

  The control device 10 sets the valve 508 of the chemical solution supply port 507, the valve 108 of the chemical solution supply port 107, the valve 208 of the chemical solution supply port 207, and the valve 308 of the chemical solution supply port 307 to the CLOSE state. Similarly, the control device 10 sets the valve 510 of the chemical solution recovery port 509, the valve 110 of the chemical solution recovery port 109, the valve 210 of the chemical solution recovery port 209, and the valve 310 of the chemical solution recovery port 309 to the CLOSE state.

  The control device 10 sets the valves 114 and 214 to the OPEN state, the valve 314 to the CLOSE state, the valves 115 and 215 to the OPEN state, the valve 315 to the CLOSE state, and the valves 116 and 216 to the OPEN state. The valve 216 is set to the CLOSE state.

  FIG. 5 is an explanatory diagram showing a treated water system, a treated water system, and a chemical cleaning water system when the third system is a switching system. In FIG. 5, while the reverse osmosis treatment system is in operation, the treated water system is indicated by a broken line, the treated water system is indicated by a dotted line, the concentrated water system is indicated by a one-dot chain line, and the chemical cleaning water system is indicated by a thick solid line. In the first series 100, the water to be treated (RO feed water) supplied by the supply pump 103 can be filtered by the first RO unit 101 and the second RO unit 102 to obtain treated water. In the second system 200, the water to be treated (RO feed water) supplied by the supply pump 203 can be filtered by the first RO unit 201 and the second RO unit 202 to obtain treated water. In the third series 300, the water to be treated (RO feed water) supplied by the supply pump 303 can be filtered by the first RO unit 501 and the second RO unit 302 to obtain treated water.

  At this time, during the treatment water manufacturing operation, the control device 10 puts the valve 308 of the chemical solution supply port 307 and the valve 310 of the chemical solution recovery port 309 into the state of OPEN (the white valve in the figure). Then, the control device 10 operates the chemical supply pump 401 to supply the CIP chemical stored in the chemical storage tank 400 to the first RO unit 301 and perform CIP on the first RO unit 301. it can.

  FIG. 6 is a flowchart showing the processing of the control device when changing the switching series. Please refer to FIG. 3 and FIG. The control device 10 instructs the end of cleaning of the first RO unit in the current switching series according to a predetermined time schedule (step S11). Specifically, in FIG. 3, since the switching system is the second system 200, the chemical solution supply pump 401 is stopped and the valves 208 and 210 are set to the CLOSE state.

  Next, the control device 10 stops the operation of the switching series (the second series 200 in FIG. 3) (step S12), and the valves are filtered so as to be filtered by the first RO unit 201 and the second RO unit 202. After switching, etc., operation is instructed (step S13). Then, the control device 10 stops the operation of the next switching system (the third system 300 in FIG. 3) (step S14), and performs filtration with the first RO unit 501 and the second RO unit 302. Then, after switching the valve or the like, the operation is instructed (step S15).

  Then, the control device 10 instructs the start of cleaning of the first RO unit in the switching series (step S16). Specifically, in FIG. 3, the valves 308 and 310 are set to the OPEN state, and the chemical solution supply pump 401 is set to the operating state. Note that the open / close state of the valve after the operation in step S16 is the state shown in FIG.

  In the present embodiment, when the series divided into the first RO unit (first unit, preceding unit) and the second RO unit (second unit, succeeding unit) is made into one series, The number of RO units is at least one more than the number of lines, and one of the first RO units always performs a pause or CIP while rotating.

  As a result, the required flow rate can be ensured without increasing the load on the membrane during CIP operation, stable operation can be performed at low cost without the need for a full-spec reserve series, and the life of the membrane can be extended. . In addition, because of the rotation operation in the first RO unit, not the intra-series control but only the control for each series. Further, since the valve is installed and rotated only in the header portion of the spare first RO unit, there is an effect that the chemical solution retention portion is small and the chemical solution residual risk is low.

  FIG. 7 is a configuration diagram showing a comparative example (No. 1) in the case where three trains are used as driving trains. In the case of the comparative example of FIG. 7, when operating the three sequences of the first sequence 100, the second sequence 200, and the third sequence 300, the reserve fourth sequence 900 is provided. The fourth series 900 includes a first RO unit 901 and a second RO unit 902. However, this means that there is one extra line that is not normally used, and there is a problem that it is wasteful and the cost (equipment cost) becomes high.

  FIG. 8 is a configuration diagram illustrating a comparative example (No. 2) in which three trains are used as driving trains. The comparative example of FIG. 8 is a case where each of the first series 100, the second series 200, and the third series 300 has a spare of the first RO unit that is easily contaminated when operating the three series. is there. The first series 100 has a spare first RO unit 101A, the second series 200 has a spare first RO unit 201A, and the third series 300 has a spare first RO unit. It has a unit 301A. However, in order to operate the three systems, three spare first RO units are required, and there is a problem that the cost (equipment cost) is high due to waste.

  7 and 8, in the reverse osmosis processing system of this embodiment, at least one spare first RO unit may be used, and the first RO unit is efficiently cleaned and the operation of the series is performed. Can do. In addition, in a system configured with a plurality of systems including a system including the first high-pressure vessel and the second high-pressure vessel as one system, operation of the system being cleaned during chemical cleaning is stopped. It is possible to prevent the treated water flow rate from decreasing.

In the present embodiment, FIG. 1 shows an example in which the number of spare first RO units is one in three series, but the present invention is not limited to this. For example, the reverse osmosis treatment system performs a secondary treatment on the treated water treated by the primary treatment and the first unit including a plurality of first pressure vessels arranged in parallel to primarily treat the treated water. When a series including a second unit including a plurality of second pressure vessels arranged in parallel is set as one series, and there are N series (N ≧ 2), the number of the first units is If there are M,
N + 1 ≦ M ≦ 2 × N−1 (1)
It is good.

In the case of formula (1), for example,
For 2 series, M = 3
In the case of 3 series, 4 ≦ M ≦ 5
In the case of 4 series, 5 ≦ M ≦ 7
It is.

  In the case of three lines and M = 5, there are two spare first RO units. In this case, for example, the first RO unit 101 of the first series 100 and the first RO unit 201 of the second series 200 are operated with a spare first RO unit. During operation, the first RO units 101 and 201 can be cleaned at the same time.

  Further, the reverse osmosis treatment system has a plurality of systems including a first pressure vessel for primary treatment of water to be treated and a second pressure vessel for secondary treatment of water to be treated treated by the primary treatment, Each series includes one reverse osmosis membrane element including a reverse osmosis membrane or a plurality connected in series in the first pressure vessel and the second pressure vessel, and the series is N series (N ≧ N ≧ 2) In a case where the number of first pressure vessels is M, the equation (1) may be used.

DESCRIPTION OF SYMBOLS 10 Control apparatus 100 1st series 101,201,301,501 1st RO unit (1st unit)
101v, 201v, 301v, 501v First pressure vessel 102, 202, 302 Second RO unit (second unit)
102v, 202v, 302v Second pressure vessel 103, 203, 303 Supply pump 104, 204, 304 High pressure pump 105, 205, 305 Booster pump 106, 206, 306 Pressure recovery device 111, 211, 311, 511 Supply piping 112, 212, 312 Treated water piping 113, 213, 313, 513 Concentrated water piping 120, 220, 320 Power recovery device 200 Second series 300 Third series 400 Chemical solution storage tank 900 Fourth series

Claims (5)

A first unit comprising a plurality of first pressure vessels arranged in parallel for primary treatment of water to be treated and a parallel arrangement for secondary treatment of the water to be treated treated by the primary treatment A plurality of systems comprising a second unit comprising a plurality of second pressure vessels,
Each series is arranged in the first pressure vessel and the second pressure vessel with one or more reverse osmosis membrane elements each having a reverse osmosis membrane connected in series,
When there are N sequences (N ≧ 2), and the number of the first units is M,
N + 1 ≦ M ≦ 2 × N−1
A reverse osmosis treatment system characterized by The controller of the reverse osmosis treatment system is
2. The reverse osmosis treatment system according to claim 1, wherein during the N-series operation, the plurality of first units are sequentially switched according to an operation state and an operation time. A cleaning unit for supplying a cleaning liquid to the reverse osmosis membrane of the first unit and cleaning the reverse osmosis membrane;
The reverse osmosis treatment system according to claim 2, wherein the control device cleans the reverse osmosis membrane with the cleaning unit for the first unit that is not in use during the N-series operation. A plurality of systems comprising a first pressure vessel for primary treatment of water to be treated and a second pressure vessel for secondary treatment of the water to be treated treated by the primary treatment;
In the first pressure vessel and the second pressure vessel, one or a plurality of reverse osmosis membrane elements each having a reverse osmosis membrane are arranged and connected in series,
When the number of the first pressure vessels is M when the series is an N series (N ≧ 2),
N + 1 ≦ M ≦ 2 × N−1
A reverse osmosis treatment system characterized by A first unit comprising a plurality of first pressure vessels arranged in parallel for primary treatment of water to be treated and a parallel arrangement for secondary treatment of the water to be treated treated by the primary treatment A plurality of series including a second unit including a plurality of second pressure vessels, and each series includes a reverse osmosis membrane in the first pressure vessel and the second pressure vessel. When one reverse osmosis membrane element or a plurality of series elements are connected in series and the series is an N series (N ≧ 2), and the number of the first units is M,
N + 1 ≦ M ≦ 2 × N−1
A reverse osmosis treatment method for a reverse osmosis treatment system,
The control device of the reverse osmosis treatment system switches the plurality of first units sequentially in accordance with an operation state and an operation time during the N-series operation.

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