JP2007253050A - Membrane separation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane separation device capable of obtaining the uniform cleaning effect in each filter unit. <P>SOLUTION: The membrane separation device has a plurality of stages of filter units 1, 2, 3; the filter units 1, 2, 3 adjacent to each other are connected to each other via connection pipes 4, 5, and concentrated water from the filter unit 1(2) on the first stage is led as raw water to the filter unit 2(3) on the second stage via the connection pipe 4(5). The filter units 1, 2, 3 are arranged so that the raw water flowing direction inside thereof is the vertical direction, and the connection pipes 4, 5 are connected so that the raw water flow direction is the same with the filter units 1, 2, 3 in the vertical direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a membrane separation apparatus provided with a plurality of stages of filtration units and washing means for washing each filtration unit.

  FIG. 6 shows a basic configuration of a conventional membrane separation device. The membrane separation device shown in the figure includes two-stage filtration units 1 ′ and 2 ′, and the concentrated water from the previous filtration unit 1 ′ is connected to the connecting pipe 3 ′. Is used as raw water for the subsequent filtration unit 2 '(see Patent Document 1). Here, each filtration unit 1 ′, 2 ′ is configured by coaxially housing a spiral type module 4 ′ in a cylindrical pressure resistant container 5 ′, and the axial direction of the membrane module 4 ′ is up and down. It is arranged as follows. In the illustrated example, the permeate inlet of each water collecting pipe 6 ′ is arranged on the upper end side of each filtration unit 1 ′, 2 ′.

  Thus, the raw water is introduced from the raw water supply pipe 8 ′ into the lower end of the preceding filtration unit 1 ′ by the raw water pump 7 ′, and subjected to membrane separation treatment by the membrane module 4 ′ of the filtration unit 1 ′. Then, it flows into the water collecting pipe 6 ′ and is taken out through the pipes 9 ′ and 10 ′.

  On the other hand, the concentrated water is introduced into the upper end side of the subsequent filtration unit 2 ′ through the connecting pipe 3 ′ connecting the upper parts of the filtration units 1 ′ and 2 ′, and the membrane module of the filtration unit 2 ′. The membrane is separated by 4 ′. In the subsequent filtration unit 2 ′, the permeate is taken out from the water collection pipe 6 ′ through the pipe 11 ′ and the permeate discharge pipe 10 ′, and the concentrated water is connected to the lower end of the filtration unit 2 ′. It is discharged from the concentrated water extraction pipe 12 '.

  Incidentally, a cleaning fluid supply pipe 13 ′ is connected to the connecting pipe 3 ′, and an air supply pipe 14 ′, a cleaning water supply pipe 15 ′, and a cleaning chemical solution supply pipe are connected to the pipe 13 ′. 16 'is connected, and these pipes 14', 15 ', 16' are provided with on-off valves V1 ', V2', V3 ', respectively.

  On the other hand, a pipe 17 'for discharging the cleaning fluid is branched from the raw water supply pipe 8', and an open / close valve V4 'is provided in the pipe 17'. The concentrated water discharge pipe 12 'extending from the subsequent filtration unit 2' is branched from a cleaning waste fluid discharge pipe 18 ', and an open / close valve V5' is provided in the middle of the pipe 18 '. It has been.

  Thus, in the membrane separation apparatus having the above configuration, suspended substances (SS components) contained in the raw water adhere to the membrane elements 4 ′ of the filtration units 1 ′ and 2 ′ with the passage of the water passage operation time. In order to reduce the separation performance, each membrane element is periodically or occasionally cleaned by water flushing, chemical cleaning, air cleaning, or the like.

That is, at the time of cleaning, one or more of the on-off valves V1 ′, V2 ′, and V3 ′ are opened, and the on-off valves V4 ′ and V5 ′ are opened, so that cleaning air, cleaning water, and cleaning chemical liquid One or two or more are supplied from the pipe 13 ′ to the filtration units 1 ′ and 2 ′ via the connecting pipe 3 ′ and used for cleaning the membrane elements 4 ′, and then discharged from the pipes 17 ′ and 18 ′. .
Japanese Patent Laid-Open No. 2001-255931

  However, since the conventional membrane separation apparatus employs a configuration in which the upper end sides of the front and rear two-stage filtration units 1 ′ and 2 ′ arranged in a vertical shape are connected by a connection pipe 3 ′, membrane separation treatment is performed. The flow directions of raw water in the filtration units 1 ′ and 2 ′ at the time are opposite to each other.

  Therefore, when clogging occurs at the inlet end face of the preceding filtration unit 1 ′ due to the coarse turbidity contained in the raw water, the location where clogging occurs in the preceding and following filtration units 1 ′ and 2 ′ is upside down. It becomes. For this reason, if the cleaning fluid is flowed in the same direction (from top to bottom in FIG. 6) with respect to the filtration units 1 ′ and 2 ′, a uniform cleaning effect cannot be obtained in both the filtration units 1 ′ and 2 ′. In particular, when a cleaning gas is used in combination as a cleaning fluid, a drift such as a single flow is likely to occur due to the viscosity of the gas being lower than the viscosity of water, and a uniform cleaning effect is obtained in both filtration units 1 ′ and 2 ′. Getting more and more difficult.

  The present invention has been made in view of the above problems, and an object thereof is to provide a membrane separation apparatus capable of obtaining a uniform cleaning effect in each filtration unit.

In order to achieve the above object, the invention described in claim 1 is provided with a plurality of filtration units, the adjacent filtration units are connected to each other by a connecting pipe, and the concentrated water of the preceding filtering unit is filtered through the connecting pipe to the subsequent filtration. In a membrane separator configured to guide the unit as raw water,
Each of the filtration units is arranged so that the flow direction of the raw water in the inside is the vertical direction, and the connection pipe is connected so that the flow direction of the raw water is the same in the vertical direction in all the filtration units. To do.

  According to a second aspect of the present invention, in the first aspect of the present invention, a cleaning fluid supply pipe for introducing a cleaning fluid into each of the filtration units, and a cleaning waste fluid supplied to the cleaning of each of the filtration units are supplied to the respective filtration units. A cleaning waste fluid discharge pipe for discharging from the system to the outside of the system is provided for each filtration unit.

  According to invention of Claim 1, since the flow direction of raw | natural water becomes the same in the up-down direction in all the filtration units, the location where clogging resulting from the turbidity etc. which are contained in to-be-processed water in each filtration unit generate | occur | produces. The top and bottom are the same, and there is no upside down as in the prior art. Therefore, each filtration unit is washed with washing water that flows in the same direction through each filtration unit through the connecting pipe, and the washing effect is the effect of each filtration unit. Is uniform.

  According to the second aspect of the present invention, the cleaning fluid supply pipe for introducing the cleaning fluid into each filtration unit and the cleaning waste fluid used for cleaning each filtration unit are discharged from each filtration unit to the outside of the system. Since the cleaning waste fluid discharge pipe is provided for each filtration unit, cleaning can be effectively performed for each filtration unit.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
[Configuration of membrane separator]
FIG. 1 is a basic configuration diagram of a membrane separation apparatus according to the present invention. The membrane separation apparatus shown in the figure includes three stages of filtration units 1, 2, and 3, from the first stage (frontmost stage) filtration unit 1. Concentrated water is used as raw water for the second-stage filtration unit 2 by the connecting pipe 4, and concentrated water from the second-stage filtration unit 2 is used as raw water for the third-stage (last stage) filtration unit 3 by the connecting pipe 5. It is configured to be used.

  Each of the filtration units 1, 2, 3 is partitioned into a primary water supply chamber S 1 and a secondary permeate water chamber S 2 by a separation membrane 6, and the water supply chamber S 1 of the first-stage filtration unit 1. A raw water supply pipe 7 is connected to a lower part of the raw water supply pipe 7, and a raw water pump 8 is provided in the raw water supply pipe 7.

  Thus, the filtration units 1, 2, 3 are arranged so that the flow direction of the raw water (concentrated water) in the interior is vertical, and the raw water (concentrated water) of all the filtration units 1, 2, 3 is arranged. The connecting pipes 4 and 5 are connected so that the flow direction is the same in the vertical direction. That is, the filtration units 1, 2, 3 are arranged such that the lower end side is the inlet side and the upper end side is the outlet side, and the connecting pipe 4 is connected from the upper part (outlet) of the water supply chamber S <b> 1 of the first-stage filtration unit 1. This connecting pipe 4 is connected to the lower part (inlet) of the water supply chamber S1 of the second-stage filtration unit 2. A permeate pipe 9 is led out from the permeate chamber S2 of the first-stage filtration unit 1.

  Further, in the second stage filtration unit 2, a connecting pipe 5 is led out from the upper part (outlet) of the water supply chamber S <b> 1, and this connection pipe 5 is a lower part of the water supply room S <b> 1 of the third stage filtration unit 3. Connected to (inlet). A permeate pipe 10 is led out from the permeate chamber S2.

  Further, in the third filtration unit 3, a drain pipe 12 is led out from the upper part (exit) of the water supply chamber S <b> 1, and an on-off valve V <b> 2 is provided in the middle of the drain pipe 12. A permeated water pipe 11 is led out from the permeated water chamber S2.

  Here, the permeated water pipes 9, 10, 11 led out from the permeated water chambers S 2 of the respective filtration units 1, 2, 3 merge into one permeated water pipe 14. An on-off valve V1 is provided downstream of the junction of the pipes 11.

  Further, branch pipes 15, 16, and 17 are branched from the connecting pipes 4 and 5 and the drain pipe 12, respectively. These branch pipes 15, 16, and 17 are one washing as a washing waste fluid discharge pipe. It joins the waste water pipe 18. Each branch pipe 15, 16, 17 is provided with on-off valves V3, V4, V5, respectively.

  In addition, the form of each filtration unit 1,2,3 is not specifically limited, Arbitrary things, such as a hollow fiber, a tubular form, and a spiral form, can be used. Also, the type of the separation membrane 6 is not particularly limited, and any MF membrane (microfiltration membrane), UF membrane (ultrafiltration membrane), NF membrane (nanofiltration membrane), RO membrane (reverse osmosis membrane), etc. Can be used.

  Thus, the raw water supply pipe 7, the raw water pump 8 and the connecting pipes 4, 5 described above sequentially pass the washing water from the first-stage filtration unit 1 to the second filtration unit 2 and the third filtration unit 3. The washing water supply means to supply is comprised. The branch pipes 15, 16, 17, the washing waste water pipe 18, the drain pipe 12, and the on-off valves V 3, V 4, V 5 wash the washing water and washing air used for washing the filtration units 1, 2, 3. Washing wastewater discharging means for discharging from each of the filtration units 1, 2 and 3 as waste fluid is configured.

  On the other hand, three branch pipes 20, 21, 22 are branched from a cleaning air pipe 19 as a cleaning gas supply pipe extending from a cleaning air supply source (not shown). As shown in the figure, the branch pipe 20 is a raw water supply pipe. 7 and the branch pipes 21 and 22 are connected to the connecting pipes 4 and 5, respectively. Each branch pipe 20, 21, 22 is provided with on-off valves V6, V7, V8, respectively.

  Thus, the cleaning air pipe 19, the branch pipes 20, 21, 22 and the on-off valves V6, V7, V8 constitute cleaning gas supply means for supplying cleaning air to the filtration units 1, 2, 3. Yes.

Although a cleaning water supply pipe is separately required, a means for supplying cleaning water to each of the filtration units 1, 2, 3 may be provided in the same manner as the cleaning gas supply pipe.
[Membrane separation treatment]
Next, the raw water membrane separation process performed in the membrane separation apparatus having the above configuration will be described with reference to FIG. In addition, the white display of the on-off valves V1 to V8 shown in FIG. 2 indicates “open”, and the black display indicates “closed”.

  At the time of membrane separation processing, as shown in FIG. 2, the on-off valves V1 and V2 are opened and all the other on-off valves V3 to V8 are closed, and then the raw water pump 8 is driven.

  Then, raw water is introduced from the raw water supply pipe 7 into the first-stage filtration unit 1 and flows upward in the filtration unit 1, and undergoes membrane separation treatment by the separation membrane 6 in the process. Then, the permeated water is taken out from the permeated water chamber S2 through the permeated water pipes 9 and 14, and the concentrated water is introduced from the water supply chamber S1 through the connecting pipe 4 into the second-stage filtration unit 2 to be supplied to the filtration unit. 2 is used as raw water. That is, the concentrated water from the first-stage filtration unit 1 is introduced into the second-stage filtration unit 2 from the connecting pipe 4 and flows upward in the filtration unit 2, and in the process, is separated by the separation membrane 6. Receive membrane separation treatment. Then, the permeated water is taken out from the permeated water chamber S2 through the permeated water pipes 10 and 14, and the concentrated water is introduced from the water supply chamber S1 through the connecting pipe 5 into the third-stage filtration unit 3 to be supplied to the filtration unit. 3 is used as raw water.

  Then, the concentrated water from the second-stage filtration unit 2 is introduced from the connecting pipe 5 to the third-stage filtration unit 3 and flows upward in the filtration unit 3. Receive membrane separation treatment. The permeated water is taken out from the permeated water chamber S2 through the permeated water pipes 11 and 14, and the concentrated water is drained from the water supply chamber S1 through the waste water pipe 12.

By the way, when the membrane separation process is continuously performed, the separation membrane 6 of each of the filtration units 1, 2, and 3 is contaminated by the suspended (SS) component contained in the raw water, and the separation performance is reduced. In order to increase the pressure loss, it is necessary to clean the separation membrane 6 of each filtration unit 1, 2, 3 periodically or as needed.
[Cleaning method]
Hereinafter, a method for cleaning each of the filtration units 1, 2, 3 will be described with reference to FIGS. 3 to 5 are basic configuration diagrams showing the cleaning of each filtration unit of the membrane separation apparatus according to the present invention. In these drawings as well, the open / close valves V1 to V8 are shown in white as in FIG. Indicates “open”, and the black display indicates “closed”.

  The cleaning method implemented in the present embodiment is such that the cleaning water and the cleaning air are sequentially supplied from the first-stage filtration unit 1 to the next-stage filtration units 2, 3, so that each filtration unit 1 , 2 and 3 are sequentially washed.

  Thus, in the present embodiment, raw water is used as cleaning water, and cleaning water and cleaning air are sequentially supplied to the filtration units 1, 2, and 3 for cleaning. This is performed by a gas-liquid mixed flow of washing water and washing air. Hereinafter, a cleaning method for each of the filtration units 1, 2, and 3 will be described.

1) First stage filtration unit:
In the cleaning, first, the first-stage filtration unit 1 in the foremost stage is cleaned, and when the first-stage filtration unit 1 is cleaned, the on-off valves V3 and V6 are opened as shown in FIG. The raw water pump 8 is driven with the other open / close valves V1, V2, V4, V5, V7, and V8 closed. Then, raw water as washing water is introduced from the raw water supply pipe 7 into the first-stage filtration unit 1.

  At the same time, the cleaning air supplied from a cleaning air supply source (not shown) flows from the cleaning air pipe 19 to the branch pipe 20 and is introduced into the first-stage filtration unit 1.

  Accordingly, a gas-liquid mixed flow of washing water and washing air is generated in the first-stage filtration unit 1, and this gas-liquid mixed flow flows upward in the filtration unit 1 so that gas-liquids having different viscosities alternate. By passing through the surface of the separation membrane 6, vibration is given to the deposit attached to the surface of the separation membrane 6, and this vibration enhances the deposit peeling effect. As a result, deposits attached to the surface of the separation membrane 6 are reliably removed, and the separation membrane 6 is effectively cleaned. Then, the washing water and the washing air used for washing the separation membrane 6 bypass the second and third stage filtration units 2 and 3 from the connecting pipe 4 through the branch pipe 15 and the washing waste water pipe 18. It flows to the drain pipe 12 and is drained to sewage.

2) Second stage filtration unit:
When the cleaning of the first-stage filtration unit 1 is completed as described above, the second-stage filtration unit 2 is then cleaned. When the second-stage filtration unit 2 is washed, as shown in FIG. 4, the on-off valves V3 and V6 are closed, the on-off valves V4 and V7 are opened, and the other on-off valves V1, V2, V5, V8 are It is kept closed as it is. Then, raw water as washing water flows from the raw water supply pipe 7 through the first stage filtration unit 1, flows through the connecting pipe 4, and is introduced into the second stage filtration unit 2.

  At the same time, the cleaning air supplied from a cleaning air supply source (not shown) flows from the cleaning air pipe 19 to the branch pipe 21 and is introduced into the second stage filtration unit 2.

  Accordingly, a gas-liquid mixed flow of washing water and washing air is generated in the second-stage filtration unit 2, and this gas-liquid mixed flow flows upward in the filtration unit 2, and the separation membrane 6 of the filtration unit 2. Is washed by the gas-liquid mixed stream. Then, the washing water and the washing air used for washing the separation membrane 6 flow from the connection pipe 5 to the drain pipe 12 through the branch pipe 16 and the washing waste water pipe 18, bypassing the third stage filtration unit 3. And drained into sewage.

  Thus, in the cleaning of the second-stage filtration unit 2, the cleaning of the first-stage filtration unit 1 has already been completed, and the washing water passes through the first-stage filtration unit 1 and the second stage. Even if it is supplied to the second stage filtration unit 2, the dirt component from the first stage filtration unit 1 is not carried over to the second stage filtration unit 2 and flows in.

2) Third stage filtration unit:
When the cleaning of the second-stage filtration unit 2 is completed as described above, the third-stage filtration unit 3 as the final stage is then cleaned. When washing the third stage filtration unit 3, as shown in FIG. 5, the on-off valves V4 and V7 are closed, the on-off valves V5 and V8 are opened, and the other on-off valves V1 to V3 and V6 are closed as they are. Is kept in the state where Then, the raw water as washing water flows from the raw water supply pipe 7 through the first stage filtration unit 1, the connection pipe 4, and the second stage filtration unit 2, and then flows through the connection pipe 5 to the third stage filtration unit 3. And introduced.

  At the same time, the cleaning air supplied from a cleaning air supply source (not shown) flows from the cleaning air pipe 19 to the branch pipe 22 and is introduced into the third stage filtration unit 3.

  Accordingly, a gas / liquid mixed flow of washing water and washing air is generated in the third-stage filtration unit 3, and this gas / liquid mixed flow flows upward in the filtration unit 3, and the separation membrane 6 of the filtration unit 3. Is washed by the gas-liquid mixed stream. Then, the washing water and the washing air used for washing the separation membrane 6 are drained from the drain pipe 12 through the branch pipe 17 and the washing waste water pipe 18.

  Thus, also in the cleaning of the third stage filtration unit 3, the cleaning of the first and second filtration units 1 and 2 in the previous stage has already been completed, and the cleaning water is supplied to the first and second stages. Even if it passes through the filtration units 1 and 2 and is supplied to the third-stage filtration unit 3, dirt components from the first-stage and second-stage filtration units 1 and 2 carry over to the third-stage filtration unit 3. Never flow in.

  As described above, in the membrane separation apparatus according to the present embodiment, the flow direction of raw water (concentrated water) is the same in the vertical direction in all the filtration units 1, 2, 3 (in this embodiment, the upward flow Therefore, when each filtration unit 1, 2, 3 is washed, even if clogging occurs at the inlet end surface of the previous filtration unit 1 (2) due to the coarse turbidity contained in the raw water, The places where clogging occurs in each filtration unit 1, 2 and 3 are the same up and down, and there is no upside down as in the prior art. Therefore, each filtration unit 1, 2 and 3 passes through the connecting pipes 4 and 5. The filtration units 1, 2, 3 are washed by the gas-liquid mixed flow of washing water and washing air flowing in the same direction, and the washing effect becomes uniform for each filtration unit 1, 2, 3.

  Further, according to the cleaning method used in the present embodiment, the cleaning water and the cleaning air are sequentially supplied from the first-stage filtration unit 1 at the front stage to the subsequent filtration units 2 and 3 at the next stage. Since each of the filtration units 1, 2, 3 is washed sequentially, the raw water supply pipe 7 and the connecting pipes 4, 5, which are raw water supply lines used during membrane separation, are shared as the washing water supply line for washing. As a result, the piping structure is simplified and the membrane separation device can be downsized.

  Furthermore, in this embodiment, since raw water is used as it is as cleaning water, no dedicated cleaning water is required, and cleaning can be performed at low cost.

  In this embodiment, the filtration units 1, 2 and 3 are cleaned by a gas-liquid mixed flow of cleaning water and cleaning air. By passing, the deposit attached to the surface of the separation membrane 6 is vibrated, and this vibration enhances the effect of peeling the deposit. As a result, the deposit attached to the surface of the separation membrane 6 is reliably removed. Thus, the separation membrane 6 is effectively washed.

  In this embodiment, each of the filtration units 1, 2, 3 is supplied by sequentially supplying washing water and washing air from the first-stage filtration unit 1 to the next-stage filtration unit 2, 3. In this order, the individual cleaning is adopted. However, the water and the cleaning air are sequentially supplied from the third-stage filtration unit 3 of the last stage to the filtration units 2 and 1 of the preceding stage, thereby allowing each filtration. You may employ | adopt the system which wash | cleans unit 3,2,1 separately in this order.

  In the present embodiment, a cleaning method using cleaning water and cleaning air in combination is used as the cleaning fluid, but the following methods are conceivable as cleaning methods.

1) A method of supplying only the cleaning gas and cleaning it as a gas-liquid mixed phase by mixing this cleaning gas with the retained water in the filtration unit 2) After draining the filtration unit, supplying the cleaning gas and filtering Gas-liquid cleaning (cleaning with a large gas-liquid ratio) by mixing with the water remaining slightly in the unit, and finally supplying the cleaning liquid to extrude the dirt component to remove it 3) Cleaning gas and cleaning liquid In the case of adopting the method of cleaning the film surface with the gas-liquid mixed phase flow as described above, the film surface is made uniform when the film is arranged horizontally. The present invention can be suitably applied to a spiral membrane module that is difficult to clean.

  By the way, in the cleaning method using both cleaning water and cleaning air as the cleaning fluid, the gas-liquid ratio is not particularly limited, and preferably the liquid phase flow rate is more than twice the flow rate during water flow and the gas phase flow rate is also The liquid flow rate at the time of passing water is set to be twice or more, and the gas-liquid ratio is set to 2: 1 to 1: 2.

  Also, there is no particular limitation on the cleaning gas, and air can be suitably used because it is only necessary to use a compressor and preparation of a gas cylinder or the like is unnecessary. The cleaning liquid is not particularly limited, and RO water supply may be used as the cleaning liquid.

  Furthermore, there is no particular restriction on the flow direction of the cleaning fluid during cleaning, and there is a method of flowing in the forward direction or the reverse direction, which is the same direction as in the membrane separation process, and a method of flowing alternately in the forward direction and the reverse direction. Can be adopted.

  Further, there is no particular limitation on the execution time of gas-liquid cleaning, but the longer the cleaning time, the more water used for gas-liquid cleaning (the amount of water to be drained) and the lower the water recovery rate. Although depending on the flow rate during gas-liquid cleaning, the cleaning time is preferably about 10 seconds to 5 minutes. The implementation frequency of gas-liquid cleaning is not particularly limited, but an increase in the implementation frequency leads to a decrease in the water recovery rate in the same manner as the implementation time described above. Therefore, an implementation frequency of about once every 30 minutes to several days is preferable. .

1 is a basic configuration diagram of a membrane separation apparatus according to the present invention. It is a basic composition figure showing membrane separation processing of a membrane separation device concerning the present invention. It is a basic block diagram which shows the washing | cleaning (washing | cleaning of the 1st stage filtration unit) for every filtration unit of the membrane separator which concerns on this invention. It is a basic block diagram which shows the washing | cleaning (washing | cleaning of a 2nd stage filtration unit) for every filtration unit of the membrane separator which concerns on this invention. It is a basic block diagram which shows the washing | cleaning (washing | cleaning of the 3rd stage filtration unit) for every filtration unit of the membrane separator which concerns on this invention. It is a basic block diagram of the conventional membrane separator.

Explanation of symbols

1 to 3 Filtration units 4 and 5 Connecting pipe 6 Separation membrane 7 Raw water supply pipe 8 Raw water pump 9 to 11 Permeate pipe 12 Drain pipe 14 Permeate pipe 15 to 17 Branch pipe 18 Washing wastewater pipe (washing waste fluid discharge pipe)
19 Cleaning air pipe (cleaning gas supply pipe)
20-22 Branch pipe S1 Water supply room S2 Permeate water room V1-V8 On-off valve

Claims (2)

In a membrane separation apparatus comprising a plurality of filtration units, connecting adjacent filtration units with a connecting pipe, and leading the concentrated water of the preceding filtration unit to the subsequent filtration unit through the connecting pipe as raw water,
Each of the filtration units is arranged so that the flow direction of the raw water in the inside is the vertical direction, and the connection pipe is connected so that the flow direction of the raw water is the same in the vertical direction in all the filtration units. Membrane separator.   Each filtration unit includes a cleaning fluid supply pipe for introducing a cleaning fluid into each filtration unit, and a cleaning waste fluid discharge pipe for discharging the cleaning waste fluid used for cleaning each filtration unit out of the system. The membrane filtration device according to claim 1, which is provided for each unit.

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