JP4798043B2 - Operation method of membrane filtration device - Google Patents

Description

  The present invention relates to a method for operating a membrane filtration apparatus using a microfiltration membrane (MF membrane), an ultrafiltration membrane (UF membrane), a nanofiltration membrane (NF membrane), a reverse osmosis membrane (RO membrane) and the like. In detail, it is related with the operating method of the membrane filtration apparatus which improved the washing | cleaning process and the steady process.

  Conventionally, in a membrane filtration apparatus, in order to maintain filtration performance, cleaning such as physical cleaning and chemical cleaning is performed for the purpose of removing SS (suspended substance) components and organic components adhering to the membrane surface.

  As physical cleaning, reverse pressure cleaning in which membrane filtered water (or dilute chemical solution) flows backward from the secondary side of the membrane, bubbling cleaning in which gas is introduced to the primary side of the membrane and the membrane is swung by bubbles are performed. Yes. This physical cleaning is generally performed for a short time (for example, several seconds to several minutes) at short intervals (for example, once every several minutes to several hours).

  In addition, as the chemical cleaning, the film is cleaned using a chemical solution in which chemicals such as acid, alkali, oxidizing agent, reducing agent, and surfactant are dissolved. This chemical cleaning is generally performed at a longer interval (for example, once a day to once every several months) than a physical cleaning for a long time (for example, several minutes to several days).

  Conventionally, when a filtration apparatus is operated for a long period of time, an operation method in which a filtration operation process and the above-described washing process are executed alternately is performed. According to such an alternating operation method, membrane filtration water cannot be obtained from the membrane filtration device while washing the membrane filtration device.

  Therefore, in order not to interrupt the production of membrane filtered water, a plurality of membrane modules are arranged in parallel, the timing of cleaning each membrane module is changed, and other membrane modules are washed while other membrane modules are being washed. There is also a so-called merry-go-round operation method that enables membrane filtered water to be produced by the membrane module.

  For example, in Japanese Patent Laid-Open No. 7-24265, six membrane modules arranged side by side are divided into two groups of three, and the execution time of the cleaning process in the first group and the execution time of the cleaning process in the second group are described. Different driving methods are described.

  Japanese Patent Application Laid-Open Nos. 11-70325 and 2002-28460 describe an operation method in which a plurality of membrane modules are arranged in parallel and the timing for cleaning each membrane module is changed.

  FIG. 8 is a water flow diagram for explaining a conventional merry-go-round operation method, and FIG. 9 is an operation schedule diagram of the membrane filtration device of FIG.

  This membrane filtration apparatus has four membrane filtration units 20A to 20D arranged side by side. The membrane filtration unit 20A has three membrane modules 21A to 21C arranged side by side. Similarly, the membrane filtration unit 20B has three membrane modules 21D to 21F arranged in parallel, and the membrane filtration unit 20C has three membrane modules 21G to 21I arranged in parallel. The membrane filtration unit 20D has three membrane modules 21J to 21L arranged side by side.

  The raw water main line 22 branches into four raw water branch lines 22A to 22D. These raw water branch lines 22A to 22D are provided with on-off valves 23A to 23D.

  Of these raw water branch lines 22A to 22D, the raw water branch line 22A is further branched into three raw water re-branch lines 24A to 24C and connected to the raw water ports of the membrane modules 21A to 21C. Similarly, the raw water branch line 22B is further branched into three raw water re-branch lines 24D to 24F and connected to the raw water ports of the membrane modules 21D to 21F. The raw water branch line 22C further branches into three raw water re-branch lines 24G to 24I and is connected to the raw water ports of the membrane modules 21G to 21I. The raw water branch line 22D further branches into three raw water re-branch lines 24J to 24L and is connected to the raw water ports of the membrane modules 21J to 21L.

  Filtated water extraction lines 25A to 25L are connected to the outlet ports of the membrane modules 21A to 21L. Among these, the filtrate extraction lines 25A to 25C are merged to form a filtrate merge line 26A. Similarly, the filtrate extraction lines 25D to 25F are merged to form a filtrate collection line 26B, the filtrate extraction lines 25G to 25I are merged to form a filtrate collection line 26C, and the filtrate extraction lines 25J to 25L are merged. It becomes the filtrate combined line 26D.

  On-off valves 27 </ b> A to 27 </ b> D are provided in these filtered water merging lines 26 </ b> A to 26 </ b> D. These filtered water merging lines 26 </ b> A to 26 </ b> D are further merged to become a filtered water main line 26. A filtrate water tank 30 is installed in the middle of the filtrate water main line 26.

  A wash water line 31 having a pump 32 is connected to the filtrate water tank 30. The washing water line 31 is branched into four washing water branch lines 31A to 31D, and is connected to filtrate water joining lines 26A to 26D. Here, these washing water branch lines 31A to 31D are connected to positions on the membrane modules 21A to 21L side of the on-off valves 27A to 27D in the filtrate combined water lines 26A to 26D. These wash water branch lines 31A to 31D are provided with on-off valves 32A to 32D.

  A chemical tank 40 and a chemical injection pump (not shown) are connected to a downstream side of the pump 32 of the washing water line 31 via a chemical line 41 having an on-off valve 42.

  In the raw water branch lines 22 </ b> A to 22 </ b> D, the washing drainage extraction lines 50 </ b> A to 50 </ b> D are connected to the positions closer to the membrane modules 21 </ b> A to 21 </ b> L than the on-off valves 23 </ b> A to 23 </ b> D. These drainage extraction lines 50 </ b> A to 50 </ b> D are provided with opening / closing valves 51 </ b> A to 51 </ b> D and merge to form the drainage main line 50.

  Next, according to the operation schedule diagram of FIG. 9, the operation method of the membrane filtration device configured as described above is based on the entire base (all membrane filtration units 20A to 20D) filtration operation step, the membrane filtration unit 20A washing step, the membrane The cleaning process of the filtration unit 20B, the cleaning process of the membrane filtration unit 20C, and the cleaning process of the membrane filtration unit 20D will be described in this order.

<All-base filtration operation process>
When the filtration operation is performed using all the membrane filtration units 20A to 20D (that is, all membrane modules 21A to 21L), the on-off valves 32A to 32D and the drainage discharge lines 50A to 50D of the wash water branch lines 31A to 31D are opened and closed. The valves 51A to 51D are closed. In addition, the open / close valves 23A to 23D of the raw water branch lines 22A to 22D and the open / close valves 27A to 27D of the filtrate water discharge lines 26A to 26D are opened.

  Thereby, raw | natural water is supplied to all 12 membrane modules 21A-21L via the raw | natural water main line 22, raw | natural water branch lines 22A-22D, and raw water re-branch lines 24A-24L, and membrane filtration is carried out by each membrane module 21A-21L. Is done. The membrane filtrate thus membrane-filtered is temporarily stored in the filtrate tank 30 through the filtrate extraction lines 25A to 25L, the filtrate merging lines 26A to 26D, and the filtrate main line 26. It is supplied from the tank 30 to the outside of the system.

<Cleaning step of membrane filtration unit 20A>
In the case of shifting to the cleaning of the membrane filtration unit 20A (that is, the membrane modules 21A to 21C) from the state of the all-base filtration operation, as shown in FIG. 8, the on-off valve 23A and the filtrate water of the raw water branch line 22A The on-off valve 27A of the merging line 26A is closed, and the on-off valve 32A of the flush water branch line 31A and the on-off valve 51A of the drainage line 50A are opened. Moreover, the pump 32 of the washing water line 31 is operated, and the on-off valve 42 of the chemical line 41 is opened.

  Thereby, supply of raw | natural water to the membrane modules 21A-21C is stopped. Further, the cleaning water (chemical solution) to which the chemical is added is supplied to the membrane modules 21A to 21C via the cleaning water line 31, the cleaning water branching line 31A, the filtered water merging line 26A, and the filtered water extraction lines 25A to 25C. The Thereby, the filtration membrane in membrane module 21A-21C is wash | cleaned by chemical | medical agent containing washing water (chemical solution). Next, the chemical solution passes through the raw water rebranching lines 24A to 24C, the raw water branching line 22A, the drainage extraction line 50A, and the drainage main line 50, and is discharged out of the system (backwashing step with a chemical solution).

  After a predetermined time has elapsed, the on-off valve 32A of the wash water branch line 31A and the on-off valve 51A of the drainage line 50A are closed. Thereby, a chemical | medical solution stays in membrane module 21A-21C, and it will be in the state by which the filtration membrane in membrane module 21A-21C was immersed in the chemical | medical solution (immersion process by a chemical | medical solution).

  After a predetermined time has elapsed, the opening / closing valve 32A of the washing water branch line 31A and the opening / closing valve 51A of the drainage line 50A are opened. Further, the on-off valve 42 of the chemical line 41 is closed. As a result, the cleaning water in the filtrate water tank 30 is supplied into the membrane modules 21A to 21C without adding chemicals, and the chemical liquid that has stayed in the membrane modules 21A to 21C is released to the outside of the module. Extruded and removed. These chemicals or washing water is discharged out of the system through the drainage line 50A and the drainage main line 50.

  Note that while the membrane filtration unit 20A (membrane modules 21A to 21C) is being cleaned, the membrane filtration operation is continued in the other membrane filtration units 20B to 20D (membrane modules 21D to 21L).

<Cleaning process of membrane filtration unit 20B>
Next, when shifting to the cleaning of the membrane filtration unit 20B (membrane modules 21D to 21F), the on-off valve 32A and the on-off valve 51A are closed, and the on-off valve 23A and the on-off valve 27A are opened. Thereby, the membrane filtration unit A (membrane modules 21A to 21C) returns to the membrane filtration operation.

  Further, the on-off valve 23B and the on-off valve 27B are closed, and the on-off valve 32B and the on-off valve 51B are opened. Further, the on-off valve 42 of the chemical line 41 is also opened, and the pump 32 is operated.

  As a result, the chemical from the chemical tank 40 is added while the filtrate in the filtrate water tank 30 flows through the washing water line 31, and the washing water branch line 31B, the filtrate water merge line 26B, and the filtrate water extraction lines 25D to 25F. Is supplied into the membrane filtration unit B (membrane modules 21D to 21F). Thereby, the filtration membrane in membrane module 21D-21F is wash | cleaned. Thereafter, the chemical solution is discharged out of the system through the raw water rebranching lines 24D to 24F, the raw water branching line 22B, the drainage extraction line 50B, and the drainage main line 50 (backwashing step with chemicals).

  After a predetermined time has elapsed, the on-off valve 32B of the wash water branch line 31B and the on-off valve 51B of the drainage line 50B are closed. Thereby, a chemical | medical solution stays in membrane module 21D-21F, and it will be in the state by which the membrane filter in membrane module 21D-21F was immersed in the chemical | medical solution (immersion process by a chemical | medical solution).

  After a predetermined time has elapsed, the opening / closing valve 32B of the wash water branch line 31B and the opening / closing valve 51B of the drainage line 50B are opened. Further, the on-off valve 42 of the chemical line 41 is closed. Thereby, the wash water in the filtrate water tank 30 is supplied into the membrane modules 21D to 21F without adding chemicals, and the chemical solution in the membrane modules 21D to 21F is pushed out and removed. These chemicals or washing water is discharged out of the system through the drainage line 50B and the drainage main line 50.

  While the membrane filtration unit 20B (membrane modules 21D to 21F) is being cleaned, in the other membrane filtration units 20A, 20C and 20D (membrane modules 21A to 21C and 21G to 21L), membrane filtration operation is performed. Will continue.

<Cleaning step of membrane filtration unit 20C and membrane filtration unit 20D>
The membrane filtration unit 20C (membrane modules 21G to 21I) and the membrane filtration unit 20D (membrane modules 21J to 21L) are sequentially washed in the same manner as the membrane filtration units 20A and 20B.

<Return to all-base filtration operation>
After completion of the cleaning of the membrane filtration unit 20D, the entire base filtration operation is restored. That is, the open / close valves 32A to 32D of the wash water branch lines 31A to 31D and the open / close valves 51A to 51D of the drainage discharge lines 50A to 50D are closed. Further, the pump 32 is stopped and the on-off valve 42 of the chemical line is closed. Then, the open / close valves 23A to 23D of the raw water branch lines 22A to 22D and the open / close valves 27A to 27D of the filtrate water merge lines 26A to 26D are opened. Thereby, raw | natural water is passed through all the membrane filtration units 21A-21D, and membrane filtration is performed.
JP 7-24265 A JP-A-11-70325 JP 2002-28460

According to the so-called merry-go-round driving method as shown in FIGS.
At the time of switching from the entire base filtration operation process to the cleaning process of the membrane filtration unit 20A;
At the time of switching from the cleaning process of the membrane filtration unit 20A to the cleaning process of the membrane filtration unit 20B;
At the time of switching from the cleaning process of the membrane filtration unit 20B to the cleaning process of the membrane filtration unit 20C;
At the time of switching from the cleaning process of the membrane filtration unit 20C to the cleaning process of the membrane filtration unit 20D;
When switching from the washing process of the membrane filtration unit 20D to the all-base filtration operation process:
However, it is necessary to perform opening / closing control of a large number of opening / closing valves, and the control is complicated.

  Further, according to the so-called merry-go-round operation method as shown in FIGS. 8 and 9, since the same number of flush water branch lines with on-off valves and drainage branch lines with on-off valves are required as the number of membrane filtration units, Complicated and large. That is, in FIG. 8, four lines of washing water branch lines 31 </ b> A to 31 </ b> D with on-off valves and drainage extraction lines 50 </ b> A to 50 </ b> D with on-off valves are provided for the four membrane filtration units 20 </ b> A to 20 </ b> D. In order to reduce the number of these branch lines, if one membrane filtration unit consisting of three membrane modules is taken as one large membrane module, it takes several days to several hours to clean the membrane module. For this reason, the remaining membrane filtration unit alone is not sufficient for the amount of filtered water, so it is necessary to provide a supplementary series of membrane filtration units to make up for it, leading to an increase in the size and cost of the membrane filtration device. It was. Furthermore, satisfactory cleaning effects were not obtained with the conventional method.

  It is an object of the present invention to provide a method for operating a membrane filtration device that can be easily controlled and that can be simplified and downsized and can provide a good membrane cleaning effect.

The operation method of the membrane filtration device of the present invention (Claim 1) is a method of operating a membrane filtration device in which a plurality of membrane modules are provided in parallel, and a washing step of backwashing all membrane modules with washing water And resuming the supply of raw water to most of the membrane modules to perform the filtration operation, and in the remaining membrane modules, alternately performing a steady process in which the filtration membrane is immersed in the cleaning water. It is characterized by this.

  The operation method of the membrane filtration device according to claim 2 is the method according to claim 1, wherein the membrane module to be immersed in the filtration membrane is different between the steady process immediately before the cleaning process and the steady process immediately after the cleaning process. It is characterized by.

  The operation method of the membrane filtration device according to claim 3 is the operation method according to claim 1 or 2, wherein the membrane filtration device includes a raw water line provided with a raw water valve for supplying raw water to each membrane module, and each membrane module. A washing water line with a washing water valve for supplying washing water, and switching between the washing step and the steady filtration step is performed by opening and closing the raw water valve and the washing water valve. It is characterized by performing.

The operation method of the membrane filtration device of the present invention (Claim 4) is a method of operating a membrane filtration device in which a membrane filtration unit comprising a plurality of membrane modules arranged in parallel is provided in parallel. Washing process with backwashing with washing water, and supply operation of raw water to most membrane filtration units is resumed, and filtration operation is performed. In the remaining membrane filtration units, the filtration membrane is immersed in washing water. It is characterized by alternately carrying out the steady process.

  The operation method of the membrane filtration device according to claim 5 is the method according to claim 4, wherein the membrane filtration unit to be immersed in the filtration membrane is different between the steady process immediately before the cleaning process and the steady process immediately after the cleaning process. It is characterized by that.

  The operation method of the membrane filtration device according to claim 6 is the method according to claim 4 or 5, wherein the membrane filtration device includes a raw water line having a raw water valve for supplying raw water to each membrane filtration unit, and each membrane filtration. A washing water line having a washing water valve for supplying washing water to the unit, and switching between the washing step and the steady filtration step is performed between the raw water valve and the washing water valve. It is performed by opening and closing.

The operation method of the membrane filtration device according to claim 7 is characterized in that, in any one of claims 1 to 6, backwashing of the filtration membrane is performed using washing water to which a chemical solution is added in the washing step. To do.

Method of operating a membrane filtration device according to claim 8, in claim 7, before Kiarai purification step, using the cleaning water with the addition of chemical, the chemical backwash step for backwashing the filtration membrane, backwash It is characterized by having a chemical solution immersing step for stopping and immersing the filtration membrane in this chemical solution-added cleaning water, and a rinsing step for performing backwashing using the cleaning water to which no chemical solution is added.

  The operation method of the membrane filtration device according to claim 9 is the operation method according to claim 8, wherein after the rinsing step or simultaneously with the rinsing step, raw water is passed through the primary side of the filtration membrane to perform flushing, and And a flushing step for blowing air on the primary side.

  According to a tenth aspect of the present invention, there is provided a method for operating a membrane filtration device according to any one of the first to ninth aspects, wherein the membrane module is an external pressure type hollow fiber membrane module.

  According to the operation method of the membrane filtration device of the present invention (Claim 1), a so-called merry-go-round operation method in which each membrane module is sequentially washed, or simply a filtration operation step and a washing step in all the membrane modules. Compared with the conventional alternating operation method to be repeated, the control of the operation is easy, and both simplification and downsizing of the apparatus and improvement of the cleaning efficiency can be achieved.

That is, according to the so-called merry-go-round method, in the cleaning process, all the membrane modules are divided into groups of several modules, and each group is switched from the filtration operation state to the cleaning state and sequentially backwashed. It becomes complicated and the control of operation becomes complicated. In addition, in order to enable switching from the filtration operation state to the washing state for each group, it is necessary to provide a washing water supply pipe with an on-off valve, a drain pipe with an on-off valve, etc. for each group. Yes, the device becomes complicated and large.

In contrast, in the present invention (Claim 1), in the washing step, to backwash with washing water all of the membrane module, compared with so-called carousel type washing successively for each group, the control operation Is extremely easy. In addition, it is not necessary to provide a washing water supply pipe equipped with an on-off valve or a drain pipe equipped with an on-off valve for each membrane module or group, and a spare for supplementing the amount of filtered water of the filtration membrane unit being washed. Since it is not necessary to provide a membrane filtration unit, the apparatus can be simplified and miniaturized.

  In the present invention, the remaining membrane module is in a state where the filtration membrane is immersed in water during the steady process. For this reason, it will be in the state which is easy to be removed from a filtration membrane, when the component which has obstruct | occluded the filtration membrane contacts a washing | cleaning chemical for sufficient time. For this reason, in the subsequent cleaning step, the membrane blocking component can be easily removed from the filtration membrane, and the cleaning efficiency is improved.

  According to the operation method of the membrane filtration apparatus of the second aspect, the membrane module to be immersed in the filtration membrane is different between the steady process immediately before the cleaning process and the steady process immediately after the cleaning process. For this reason, it is possible to sequentially remove the components blocking the filtration membrane for all the membrane modules.

  According to the operation method of the membrane filtration apparatus of the third aspect, switching between the steady process and the cleaning process can be easily performed by opening and closing the raw water valve and the cleaning water valve.

  According to the operation method of the membrane filtration device of the present invention (Claim 4), compared to the so-called merry-go-round operation method in which each membrane filtration unit is washed in sequence, the operation control is extremely easy. It is possible to achieve both simplification and downsizing and improvement in cleaning efficiency.

  According to the operation method of the membrane filtration device of the fifth aspect, the membrane filtration unit to be immersed in the filtration membrane is different between the steady process just before the cleaning process and the steady process just after the cleaning process. For this reason, it is possible to sequentially remove the components blocking the filtration membrane for all the membrane filtration units.

  According to the operation method of the membrane filtration device of the sixth aspect, switching between the steady process and the cleaning process can be easily performed by opening and closing the raw water valve and the cleaning water valve.

According to the operation method of the membrane filtration device of the seventh aspect, since the filtration membrane is backwashed with the washing water added with the chemical solution in the washing step, the filtration membrane is washed well.

  According to the operation method of the membrane filtration device of the eighth aspect, since the filtration membrane is backwashed using the washing water to which the chemical solution is added, the filtration membrane is washed well. Moreover, since it is set as the state immersed in the chemical | medical solution addition washing | cleaning water after the backwashing by this chemical | medical solution, a filtration membrane is wash | cleaned more favorably. Then, the chemical | medical solution in a membrane module is removed by performing backwashing using the washing water which has not added the chemical | medical solution.

  According to the operation method of the membrane filtration device of the ninth aspect, in addition to the eighth aspect, since the raw water is flushed and air is blown, the membrane blocking component adhering to the filtration membrane is more reliably removed.

  The membrane module is preferably an external pressure type hollow fiber membrane module. This is because when the chemical solution is supplied for back washing with the chemical solution, the volume of the treated water side of the hollow fiber is small, and the amount of the chemical solution to be added is small.

  Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment]
1 to 3 are system diagrams of a membrane filtration apparatus to which the method of the present invention is applied. FIG. 1 shows a first steady process, and FIG. 2 shows an initial state of a cleaning process. FIG. 3 shows the second steady process. FIG. 4 is an operation schedule diagram of the membrane filtration device.

  First, the structure of this membrane filtration apparatus is demonstrated.

  This membrane filtration apparatus has ten membrane modules 1A to 1J arranged side by side.

  The raw water main line 2 is branched into ten raw water branch lines 2A to 2J and connected to the raw water ports of the membrane modules 1A to 1J. These raw water branch lines 2A to 2J are provided with on-off valves 3A to 3J.

  Filtated water extraction lines 4A to 4J are connected to the outlet ports of the membrane modules 1A to 1J. These filtrate extraction lines 4 </ b> A to 4 </ b> L merge to become a filtrate main line 4 and are connected to the filtrate tank 11. The filtrate water in the filtrate water tank 11 can be supplied to the membrane modules 1A to 1J via the pipe 13, the pump 12, the filtrate water main line 4, and the filtrate water extraction lines 4A to 4J.

  The membrane module 1A-1J side of the filtered water main line 4 from the connection position of the pipe 13 is connected to a chemical tank 6 and a chemical injection pump (not shown) via a chemical line 7 having an on-off valve 8. Yes. An on-off valve 4 a is provided on the filtrate water tank 11 side of the filtrate water main line 4 from the connection position of the pipe 13.

  The drainage extraction lines 9A to 9J are connected to the primary side of the membrane modules 1A to 1J, and these drainage extraction lines 9A to 9J merge to form the drainage main line 9. These drainage extraction lines 9A to 9J are provided with on-off valves 10A to 10J.

  Next, according to the operation schedule diagram of FIG. 4, the operation method of the membrane filtration apparatus configured in this way is shown in the first cleaning step (FIG. 2), the first steady step (FIG. 1), the second The cleaning process and the second steady process (FIG. 3) will be described in this order.

<First cleaning step>
In the first cleaning step, as described below, all membrane modules are subjected to a backwashing step with chemical-containing filtered water (chemical solution) and an immersion step with a chemical solution, and about the membrane modules 1B to 1J other than the membrane module 1A. Further, a rinsing step with filtered water is performed. The rinsing process is omitted for the membrane module 1A.

  First, as shown in FIG. 2, the open / close valves 3A to 3J of all the raw water branch lines 2A to 2J and the open / close valves 4a of the filtrate main line 4 are closed. Moreover, the on-off valve 13a of the piping 13, the on-off valve 8 of the chemical line 7, the on-off valves 5A-5J of all the filtered water extraction lines 4A-4J and the on-off valves 10A-10J of all the drainage extraction lines 9A-9J are provided. Open. Further, the pump 12 is operated.

  Thereby, supply to the membrane module 1A-1J of raw | natural water is stopped. The filtered water (washing water) in the filtered water tank 11 is supplied to the filtered water main line 4 via the pipe 13 and the pump 12, and the chemical from the chemical tank 6 is added to the filtered water. The filtered water (chemical solution) to which this chemical is added is supplied to the membrane modules 1A to 1J via the filtered water extraction lines 4A to 4J.

  With this chemical solution, the filtration membranes in the membrane modules 1A to 1J are washed. Next, the chemical solution passes through the drainage extraction lines 9A to 9J and the drainage main line 9, and is discharged out of the system (backwashing step with the chemical solution).

  After this back washing with the chemical solution is performed for a predetermined time, the on-off valves 5A to 5J of the filtrate extraction lines 4A to 4J and the on-off valves 10A to 10J of the drainage extraction lines 9A to 9J are closed. Thereby, the filtration membrane in membrane module 1A-1J will be in the state immersed in the chemical | medical solution (immersion process by a chemical | medical solution).

  After this immersion state is continued for a predetermined time, the on-off valves 5B to 5J (excluding the on-off valve 5A) and the on-off valves 10B to 10J (excluding the on-off valve 10A) are opened again. At this time, the on-off valve 8 of the chemical line is kept closed. Thereby, the filtrate water in the filtrate water tank 11 is supplied to the membrane modules 1B-1J via the piping 13, the pump 12, the filtrate water main line 4, and the filtrate water extraction lines 4B-4J. Here, since the on-off valve 8 of the chemical line 7 is closed, no chemical is added to the filtered water.

  With this filtered water, the chemical solution in the membrane modules 1B to 1J is pushed out, passed through the drainage extraction lines 9B to 9J and the drainage main line 9, and discharged out of the system (rinsing process with filtered water).

  As described above, the membrane modules 1B to 1J are back-washed and rinsed with a chemical solution. About the membrane module 1A, the rinse process is abbreviate | omitted and the state by which the filtration membrane in this membrane module 1A was immersed in the chemical | medical solution is maintained.

<First steady process>
After performing the above-described washing process, the on-off valves 10B to 10J of the drainage lines 9B to 9J are closed (the on-off valve 10A is already closed), and the on-off valves 3B to 3J of the raw water branch lines 2B to 2J are closed. (Excluding the on-off valve 3A) is opened. Further, the pump 12 is stopped, the on-off valve 13a is closed, and the on-off valve 4a is opened. As a result, the open / close state of each open / close valve is as shown in FIG.

  Thereby, the membrane filtration operation of the membrane modules 1B to 1J is restarted. In the membrane module 1A, the state in which the filtration membrane is immersed in the chemical solution is maintained. For this reason, during the first steady process, the components that block the filter membrane come into contact with the cleaning chemical for a sufficient time, so that the removal in the next cleaning process becomes easy.

<Second cleaning step>
After performing the said 1st regular process for a predetermined time, similarly to a 1st washing | cleaning process, the back washing process by a chemical | medical solution and the immersion process by a chemical | medical solution are performed about all the membrane modules 1A-1J, and membrane module 1A, 1C- About 1J, the rinse process by filtered water is further performed. In the second cleaning process, the rinsing process of the membrane module 1B is omitted.

  Specifically, first, the open / close state of the on-off valve is changed from the state of FIG. 1 to the state of FIG. That is, the on-off valves 3B to 3J are closed and the on-off valves 10A to 10J are opened. Further, the on-off valve 5A is opened. Further, the on-off valve 4a of the filtrate main line 4 is closed, the on-off valve 13a of the pipe 13 is opened, and the on-off valve 8 of the chemical line 7 is opened. Then, the pump 12 is operated.

  Thereby, supply to the membrane module 1A-1J of raw | natural water is stopped. Moreover, the filtrate in the filtrate tank 11 is supplied to the filtrate main line 4 through the pipe 13 and the pump 12, and the chemical from the chemical tank 6 is added to this filtrate. The filtered water (chemical solution) to which this chemical is added is supplied to the membrane modules 1A to 1J via the filtered water extraction lines 4A to 4J.

  With this chemical solution, the filtration membranes in the membrane modules 1A to 1J are washed. Next, the chemical solution passes through the drainage extraction lines 9A to 9J and the drainage main line 9, and is discharged out of the system (backwashing step with the chemical solution).

  In the membrane module 1A, the filtration membrane is immersed in the chemical solution during the immediately preceding first steady process. For this reason, when the component blocking the filtration membrane is in contact with the cleaning chemical for a sufficient time, the membrane blocking component is easily removed by backwashing with the chemical solution.

  After performing the backwash with this chemical | medical solution, the on-off valves 5A-5J and the on-off valves 10A-10J are closed. Thereby, the filtration membrane in membrane module 1A-1J will be in the state immersed in the chemical | medical solution (immersion process by a chemical | medical solution).

  After this immersion state is continued for a predetermined time, the on-off valves 5A, 5C to 5J (excluding the on-off valve 5B) and the on-off valves 10A, 10C to 10J (excluding the on-off valve 10B) are opened again. At this time, the on-off valve 8 of the chemical line is kept closed. Thereby, the filtrate in the filtrate tank 11 is supplied to the membrane modules 1A and 1C to 1J via the pipe 13, the pump 12, the filtrate main line 4 and the filtrate extraction lines 4A and 4C to 4J. Here, since the on-off valve 8 of the chemical line 7 is closed, no chemical is added to the filtered water.

  With this filtered water, the chemicals in the membrane modules 1A, 1C to 1J are pushed out and discharged out of the system through the drainage extraction lines 9A, 9C to 9J and the drainage main line 9 (rinsing process with filtered water).

  As described above, the membrane modules 1A and 1C to 1J are back-washed and rinsed with the chemical solution, and the rinsing step is omitted for the membrane module 1B, and the filtration membrane in the membrane module 1B is immersed in the chemical solution. Maintained.

<Second steady process>
After performing the above-described cleaning process, the on-off valves 10A and 10C to 10J (the on-off valve 10B is already closed) are closed, and the on-off valves 3A and 3C to 3J are opened (the on-off valve 3B remains closed). ). Further, the pump 12 is stopped, the on-off valve 13a is closed, and the on-off valve 4a is opened. Thus, the open / close state of each open / close valve is a state in which the open / close valve 3B and the open / close valve 5B are closed instead of the open / close valve 3A and the open / close valve 5A in FIG.

  Thereby, the membrane filtration operation of the membrane modules 1A, 1C to 1J is restarted. In the membrane module 1B, the state in which the filtration membrane is immersed in the chemical solution is maintained. For this reason, during this second steady process, the membrane plugging component comes into contact with the cleaning chemical for a sufficient period of time, so that it can be easily removed in the next cleaning process.

  In the above manner, the cleaning process and the steady process are repeated after the third cleaning process.

  In the operation method according to the present embodiment, the number of operations of the on-off valve is reduced as compared with the conventional alternating operation method in which the washing process and the filtration operation process are simply repeated, so that the operation can be easily controlled.

  That is, in the present embodiment, the on-off valves 3A, 5A, and 10A of the membrane module 1A are completely closed from the start of the immersion process with the chemical solution in the first cleaning process to the end of the second steady process. The operation of these on-off valves is omitted.

  Similarly, the on-off valves 3B, 5B, and 10B of the membrane module 1B are not operated at all from the start of the immersion process with the chemical solution in the second cleaning process until the end of the third steady process. Similarly, the operation of the on-off valve is omitted for the membrane module 1C and thereafter.

  On the other hand, in the conventional alternating operation method, the washing process and the filtration operation process are repeated for all the membrane modules. Therefore, the on-off valves 3A, 5A, and 10A are the same as the on-off valves 3B to 3J, 5B to 5J, and 10B to 10J, respectively, from the immersion step with the chemical in the first cleaning step to the end of the second steady step. Opening and closing operations are performed.

[Second Embodiment]
In the first embodiment, the rinsing process of one membrane module is omitted in each cleaning process, but the second embodiment described below is such that this rinsing process is not omitted. is there. In the second embodiment, as in the first embodiment, the filtration apparatus shown in FIGS. 1 to 3 is used and the operation is performed according to the operation schedule shown in FIG.

<First cleaning step>
In the first cleaning step, as described below, the back washing step with the chemical solution, the dipping step with the chemical solution, and the rinsing step with filtered water are performed in this order for all the membrane modules 1A to 1J.

  First, as shown in FIG. 2, the open / close valves 3A to 3J of all the raw water branch lines 2A to 2J and the open / close valves 4a of the filtrate main line 4 are closed. In addition, the other open / close valves, that is, the open / close valve 13a of the pipe 13, the open / close valve 8 of the chemical line 7, the open / close valves 5A to 5J of all the filtrate discharge lines 4A to 4J, and all the drainage discharge lines 9A to 9A. The 9J on-off valves 10A to 10J are opened. Further, the pump 12 is operated.

  Thereby, supply to the membrane module 1A-1J of raw | natural water is stopped. The filtered water (washing water) in the filtered water tank 11 is supplied to the filtered water main line 4 via the pipe 13 and the pump 12, and the chemical from the chemical tank 6 is added to the filtered water. The filtered water (chemical solution) to which this chemical is added is supplied to the membrane modules 1A to 1J via the filtered water extraction lines 4A to 4J.

  With this chemical solution, the filtration membranes in the membrane modules 1A to 1J are washed. Next, the chemical solution passes through the drainage extraction lines 9A to 9J and the drainage main line 9, and is discharged out of the system (backwashing step with the chemical solution).

  After this back washing with the chemical solution is performed for a predetermined time, the on-off valves 5A to 5J of the filtrate extraction lines 4A to 4J and the on-off valves 10A to 10J of the drainage extraction lines 9A to 9J are closed. Thereby, the filtration membrane in membrane module 1A-1J will be in the state immersed in the chemical | medical solution (immersion process by a chemical | medical solution).

  After this immersion state is continued for a predetermined time, the on-off valves 5A to 5J and the on-off valves 10A to 10J are opened again. At this time, the on-off valve 8 of the chemical line is kept closed. Thereby, the filtrate water in the filtrate water tank 11 is supplied to the membrane modules 1A-1J via the piping 13, the pump 12, the filtrate water main line 4, and the filtrate water extraction lines 5A-5J. Here, since the on-off valve 8 of the chemical line 7 is closed, no chemical is added to the filtered water.

  With this filtered water, chemicals in the membrane modules 1A to 1J are removed. This filtered water passes through the drainage extraction lines 9A to 9J and the drainage main line 9, and is discharged out of the system (rinsing process with filtered water).

<First steady process>
After performing said washing | cleaning process, the on-off valves 10A-10J of the drainage extraction lines 9A-9J are closed, and the on-off valves 3B-3J of the raw water branch lines 2B-2J are opened. Moreover, the on-off valve 5A of the filtrate extraction line 4A is closed. Further, the pump 12 is stopped, the on-off valve 13a is closed, and the on-off valve 4a is opened. As a result, the open / close state of each open / close valve is as shown in FIG.

  Thereby, the membrane filtration operation of the membrane modules 1B to 1J is restarted. Further, the membrane module 1A is maintained in a state in which the filtration membrane is immersed in filtered water. For this reason, during this first steady process, the membrane plugging component adhering to the filtration membrane swells due to filtered water, and is easily removed in the next washing step.

<Second cleaning step>
After the first steady process, similarly to the first cleaning process, a back washing process using a chemical solution, an immersion process using a chemical solution, and a rinsing process using filtered water are performed in this order.

<Second steady process>
After performing said washing | cleaning process, the on-off valves 10A-10J of a drainage branch line are closed, and on-off valves 3A, 3C-3J are opened. The on-off valve 5B is closed. Further, the pump 12 is stopped, the on-off valve 13a is closed, and the on-off valve 4a is opened. Thus, the open / close state of each open / close valve is a state in which the open / close valve 3B and the open / close valve 5B are closed instead of the open / close valve 3A and the open / close valve 5A in FIG.

  Thereby, the membrane filtration operation of the membrane modules 1A, 1C to 1J is restarted. In the membrane module 1B, the state in which the filtration membrane is immersed in filtered water is maintained. For this reason, during this second steady process, the membrane plugging component adhering to the filtration membrane swells due to filtered water, and is easily removed in the next washing step.

  In the above manner, the cleaning process and the steady process are repeated after the third cleaning process.

  Also by the operation method of the second embodiment, the number of operations of the on-off valve is reduced, and the control is simplified.

[Third Embodiment]
In the said 1st and 2nd embodiment, although washing | cleaning drainage extraction lines 9A-9J are connected to each membrane module 1A-1J, you may connect a drainage line to the raw | natural water main line 2. FIG. FIG. 5 is a system diagram of a membrane filtration apparatus to which the third embodiment is applied. In the third embodiment, the operation is performed according to the operation schedule diagram of FIG. 4 as in the first and second embodiments.

  First, the membrane filtration device of FIG. 5 will be described.

  This membrane filtration apparatus has ten membrane modules 1A to 1J arranged side by side.

  The raw water main line 2 is provided with an on-off valve 2a. A drain line 14 having an on / off valve 14a is connected to the raw water main line 2 on the downstream side of the on / off valve 2a. The washing drainage lines 9A to 9J and the drainage main line 9 are omitted. Other configurations are the same as those in FIGS. 1 to 3, and the same reference numerals indicate the same parts.

  Next, according to the operation schedule diagram of FIG. 4, the operation method of the membrane filtration device configured as described above is the first cleaning step, the first steady step, the second cleaning step, and the second steady step. Although described in order, the contents of each process are basically the same as those of the first embodiment shown in FIGS. 1 to 3, and only the cleaning wastewater discharge system is different.

<First cleaning step>
In the first cleaning step, as described below, all membrane modules are subjected to a backwashing step with chemical-containing filtered water (chemical solution) and an immersion step with a chemical solution, and about the membrane modules 1B to 1J other than the membrane module 1A. Further, a rinsing step with filtered water is performed. The rinsing process is omitted for the membrane module 1A.

  First, the on-off valve 2a of the raw water main line 2 is closed, and the on-off valve 14a of the drainage line 14 is opened. Moreover, the on-off valves 3A to 3J of the raw water branch lines 2A to 2J and the on-off valves 5A to 5J of the filtrate water extraction lines 4A to 4J are opened. Further, the on-off valve 13a of the pipe 13 and the on-off valve 8 of the chemical line 7 are opened, and the on-off valve 4a of the filtrate main line 4 is closed. Then, the pump 12 is operated.

  Thereby, supply to the membrane module 1A-1J of raw | natural water is stopped. Moreover, the filtrate in the filtrate tank 11 is supplied to the filtrate main line 4 through the pipe 13 and the pump 12, and the chemical from the chemical tank 6 is added to this filtrate. The filtered water (chemical solution) to which this chemical is added is supplied to the membrane modules 1A to 1J via the filtered water extraction lines 4A to 4J.

  With this chemical solution, the filtration membranes in the membrane modules 1A to 1J are washed. Next, this chemical solution passes through the raw water branch lines 2A to 2J, the raw water main line 2 and the drainage line 14, and is discharged out of the system (back washing process with chemical solution).

  After performing the backwashing with this chemical solution, the open / close valves 3A to 3J of the raw water branch lines 2A to 2J, the open / close valves 5A to 5J of the filtrate extraction lines 4A to 4J, and the open / close valve 14a are closed. Thereby, the filtration membrane in membrane module 1A-1J will be in the state immersed in the chemical | medical solution (immersion process by a chemical | medical solution).

  After this immersion state is continued for a predetermined time, the on-off valves 5B to 5J (excluding the on-off valve 5A), the on-off valves 3B to 3J (excluding the on-off valve 3A) and the on-off valve 14a are opened again. At this time, the on-off valve 8 of the chemical line is kept closed. Thereby, the filtrate water in the filtrate water tank 11 is supplied to the membrane modules 1B-1J via the piping 13, the pump 12, the filtrate water main line 4, and the filtrate water extraction lines 4B-4J. At this time, since the on-off valve 8 of the chemical line 7 is closed, no chemical is added to the filtered water.

  With this filtered water, the chemicals in the membrane modules 1B to 1J are pushed out and discharged out of the system through the raw water branch lines 2B to 2J, the raw water main line 2 and the drainage line 14 (rinsing step with filtered water).

  As described above, the membrane modules 1B to 1J are back-washed and rinsed with a chemical solution. About the membrane module 1A, the rinse process is abbreviate | omitted and the state by which the filtration membrane in this membrane module 1A was immersed in the chemical | medical solution is maintained.

<First steady process>
After performing the above-mentioned washing process, the on-off valve 14a of the drainage line 14 is closed, and the on-off valve 2a of the raw water main line 2 is opened. Further, the pump 12 is stopped, the on-off valve 13a is closed, and the on-off valve 4a is opened. As a result, the open / close state of each open / close valve is as shown in FIG.

  Thereby, the membrane filtration operation of the membrane modules 1B to 1J is restarted. In the membrane module 1A, the state in which the filtration membrane is immersed in the chemical solution is maintained. For this reason, during this first steady process, the membrane plugging component adhering to the filtration membrane swells due to the chemical solution, and is easily removed in the next washing step.

<Second cleaning step>
After performing the said 1st regular process for a predetermined time, similarly to a 1st washing | cleaning process, the back washing process by a chemical | medical solution and the immersion process by a chemical | medical solution are performed about all the membrane modules 1A-1J, and membrane module 1A, 1C- About 1J, the rinse process by filtered water is further performed. In the second cleaning process, the rinsing process of the membrane module 1B is omitted.

  Specifically, first, the on-off valve 2a of the raw water main line 2 is closed, and the on-off valve 14a of the drainage line 14 is opened. Further, the on-off valve 3A and the on-off valve 5A are opened. Further, the on-off valve 4a is closed, the on-off valve 13a is opened, and the on-off valve 8 of the chemical line 7 is opened. Then, the pump 12 is operated.

  Thereby, supply to the membrane module 1A-1J of raw | natural water is stopped. Moreover, the filtrate in the filtrate tank 11 is supplied to the filtrate main line 4 through the pipe 13 and the pump 12, and the chemical from the chemical tank 6 is added to this filtrate. The filtered water (chemical solution) to which this chemical is added is supplied to the membrane modules 1A to 1J via the filtered water extraction lines 4A to 4J.

  With this chemical solution, the filtration membranes in the membrane modules 1A to 1J are washed. Next, this chemical solution passes through the raw water branch lines 2A to 2J, the raw water main line 2 and the drainage line 14, and is discharged out of the system (back washing process with chemical solution).

  After performing the backwashing with this chemical solution, the on-off valves 3A to 3J and the on-off valves 5A to 5J are closed. Thereby, the filtration membrane in membrane module 1A-1J will be in the state immersed in the chemical | medical solution (immersion process by a chemical | medical solution).

  After this immersion state is continued for a predetermined time, the on-off valves 5A, 5C-5J (excluding the on-off valve 5B), the on-off valves 3A, 3C-3J (excluding the on-off valve 3B), and the on-off valve 14a are opened again. . At this time, the on-off valve 8 of the chemical line is kept closed. Thereby, the filtrate in the filtrate tank 11 is supplied to the membrane modules 1A and 1C to 1J via the pipe 13, the pump 12, the filtrate main line 4 and the filtrate extraction lines 4A and 4C to 4J. Here, since the on-off valve 8 of the chemical line 7 is closed, no chemical is added to the filtered water.

  With this filtered water, the chemicals in the membrane modules 1A, 1C-1J are pushed out and discharged out of the system through the raw water branch lines 2A, 2C-2J, the raw water main line 2 and the drainage line 14 (rinsing with filtered water). Process).

  As described above, the membrane modules 1A and 1C to 1J are back-washed and rinsed with the chemical solution, and the rinsing step is omitted for the membrane module 1B, and the filtration membrane in the membrane module 1B is immersed in the chemical solution. Maintained.

<Second steady process>
After performing the above-mentioned washing process, the on-off valve 14a of the drainage line 14 is closed, and the on-off valve 2a of the raw water main line 2 is opened. Further, the pump 12 is stopped, the on-off valve 13a is closed, and the on-off valve 4a is opened. Thus, the open / close state of each open / close valve is a state in which the open / close valve 3B and the open / close valve 5B are closed instead of the open / close valve 3A and the open / close valve 5A in FIG.

  Thereby, the membrane filtration operation of the membrane modules 1A, 1C to 1J is restarted. In the membrane module 1B, the state in which the filtration membrane is immersed in the chemical solution is maintained. For this reason, during this second steady process, the membrane plugging component adhering to the filtration membrane swells due to the chemical solution and is easily removed in the next washing step.

  In the above manner, the cleaning process and the steady process are repeated after the third cleaning process.

  In the operation method according to the present embodiment, the drainage lines 9A to 9J and the on-off valves 10A to 10J as shown in FIGS. Control is simplified by the absence of 10A to 10J.

[Fourth Embodiment]
FIG. 6 is a schematic water flow system diagram of the membrane filtration device applied to the operation method according to the fourth embodiment, and FIG. 7 is an operation schedule diagram of the membrane filtration device of FIG.

  First, the structure of this membrane filtration apparatus is demonstrated.

  This membrane filtration device has four membrane filtration units 20A to 20D arranged in parallel as in the membrane filtration device of FIG.

  Among these, the membrane filtration unit 20A has three membrane modules 21A to 21C arranged side by side. Similarly, the membrane filtration unit 20B has three membrane modules 21D to 21F arranged in parallel, and the membrane filtration unit 20C has three membrane modules 21G to 21I arranged in parallel. The membrane filtration unit 20D has three membrane modules 21J to 21L arranged side by side.

  The raw water main line 22 is provided with an on-off valve 23. A drainage line 60 having an opening / closing valve 60 a is connected to the raw water main line 22 on the downstream side of the opening / closing valve 23.

  The raw water main line 22 is branched into four raw water branch lines 22A to 22D. These raw water branch lines 22A to 22D are provided with on-off valves 23A to 23D.

  Of these raw water branch lines 22A to 22D, the raw water branch line 22A is further branched into three raw water re-branch lines 24A to 24C and connected to the raw water ports of the membrane modules 21A to 21C. Similarly, the raw water branch line 22B is further branched into three raw water re-branch lines 24D to 24F and connected to the raw water ports of the membrane modules 21D to 21F. The raw water branch line 22C further branches into three raw water re-branch lines 24G to 24I and is connected to the raw water ports of the membrane modules 21G to 21I. The raw water branch line 22D further branches into three raw water re-branch lines 24J to 24L and is connected to the raw water ports of the membrane modules 21J to 21L.

  Filtated water extraction lines 25A to 25L are connected to the outlet ports of the membrane modules 21A to 21L. Among these, the filtrate extraction lines 25A to 25C are merged to form a filtrate merge line 26A. Similarly, the filtrate extraction lines 25D to 25F are merged to form a filtrate collection line 26B, the filtrate extraction lines 25G to 25I are merged to form a filtrate collection line 26C, and the filtrate extraction lines 25J to 25L are merged. It becomes the filtrate combined line 26D.

  On-off valves 27 </ b> A to 27 </ b> D are provided in these filtered water merging lines 26 </ b> A to 26 </ b> D. These filtered water merging lines 26 </ b> A to 26 </ b> D are further merged to become a filtered water main line 26, and are connected to the filtered water tank 11. The filtered water main line 26 is provided with an on-off valve 26a. One end side of a pipe 13 provided with a pump 12 and an on-off valve 13a is connected to the filtrate water tank 11, and the other end side is closer to the membrane modules 21A to 21L than the on-off valve 26a in the filtrate water main line 26. It is connected.

  A chemical tank 6 and a chemical injection pump (not shown) are connected to the membrane modules 21 </ b> A to 21 </ b> L side of the filtrate water main line 26 with respect to the membrane module 21 </ b> A to 21 </ b> L side through a chemical line 7 having an on-off valve 8. ing.

  Next, according to the operation schedule diagram of FIG. 7, the operation method of the membrane filtration device configured in this way is shown in the first cleaning step, the first steady step (FIG. 6), the second cleaning step, 2 will be described in the order of steady processes.

<First cleaning step>
In the first cleaning step, as described below, all membrane units are subjected to a backwashing step with a chemical solution and an immersion step with a chemical solution, and the membrane units 1B to 1D other than the membrane unit 1A are further rinsed with filtered water. I do. Note that the rinsing step is omitted for the membrane filtration unit 20A.

  First, the open / close valve 23 of the raw water main line 22 is closed, and the open / close valve 60a of the drainage line 60 is opened. In addition, the open / close valves 23A to 23D of the raw water branch lines 22A to 22D, the open / close valves 27A to 27D of the filtrate water merge lines 26A to 26D, the open / close valve 13a of the pipe 13, and the open / close valve 8 of the chemical line 7 are opened. Further, the on-off valve 26a of the filtrate main line 26 is closed. Then, the pump 12 is operated.

  Thereby, supply to the membrane module 21A-21L of raw | natural water is stopped. The filtered water in the filtered water tank 11 is supplied to the filtered water main line 26 via the pipe 13 and the pump 12, and the chemical from the chemical tank 6 is added to the filtered water. The filtered water to which this chemical is added is supplied to the membrane modules 21A to 21L via the filtered water branch lines 27A to 27D.

  With this chemical solution, the filtration membranes in the membrane modules 21A to 21L are washed. Next, the chemical solution passes through the raw water re-branching lines 24A to 24L, the raw water branch lines 22A to 22D, the raw water main line 22 and the drainage line 60, and is discharged out of the system (back washing process with chemicals).

  After performing the backwashing with this chemical solution, the on-off valves 23A to 23D and the on-off valves 27A to 27D are closed. Thereby, the filtration membrane in membrane module 21A-21L will be in the state immersed in the chemical | medical solution (immersion process by a chemical | medical solution).

  After this immersion state is continued for a predetermined time, the on-off valves 27B to 27D (excluding the on-off valve 27A) and the on-off valves 23B to 23D (excluding the on-off valve 23A) are opened again. At this time, the on-off valve 8 of the chemical line is kept closed. As a result, the filtrate water in the filtrate water tank 11 is transferred to the membrane modules 21D to 21L via the pipe 13, the pump 12, the filtrate water main line 26, the filtrate water merge lines 26A to 26D, and the filtrate water discharge lines 25D to 25L. Supplied. At this time, since the on-off valve 8 of the chemical line 7 is closed, no chemical is added to the filtered water.

  With this filtered water, the chemicals in the membrane modules 21D to 21L are pushed out and discharged out of the system through the raw water rebranching lines 24D to 24L, the raw water branching lines 22B to 22D, the raw water main line 22 and the drainage line 60 ( Rinse process with filtered water).

  As described above, the membrane modules 21D to 21L of the membrane units 20B to 20D are back-washed and rinsed with a chemical solution. The rinsing step is omitted for the membrane modules 21A to 21C of the membrane unit 20A, and the state where the filtration membranes in the membrane modules 21A to 21C are immersed in the chemical solution is maintained.

<First steady process>
After performing the above-mentioned washing process, the on-off valve 60a of the drain line 60 is closed, and the on-off valve 23 of the raw water main line 22 is opened. Further, the pump 12 is stopped, the on-off valve 13a is closed, and the on-off valve 4a is opened. As a result, the open / close state of each open / close valve is as shown in FIG.

  Thereby, the membrane filtration operation of the membrane modules 21D to 21L of the membrane units 20B to 20D is resumed. Further, the membrane modules 21A to 21C of the membrane unit 20A are maintained in a state in which the filtration membrane is immersed in the chemical solution. For this reason, during this first steady process, the membrane plugging component adhering to the filtration membrane swells due to the chemical solution, and is easily removed in the next washing step.

<Second cleaning step>
After the first steady step, as in the first cleaning step, the membrane modules 21A to 21L of all the membrane units 20A to 20D are subjected to the back washing step with the chemical solution and the immersion step with the chemical solution, and the membrane unit 20A, About 20C and 20D membrane modules 21A-21C and 21G-21L, the rinse process by filtered water is further performed. In the second cleaning process, the rinsing process of the membrane modules 21D to 21F is omitted.

  Specifically, first, the open / close valve 23 of the raw water main line 22 is closed, and the open / close valve 60a of the drainage line 60 is opened. Further, the on-off valve 27A and the on-off valve 23A are opened. Further, the on-off valve 26a of the filtrate main line 26 is closed, the on-off valve 13a of the pipe 13 is opened, and the on-off valve 8 of the chemical line 7 is opened. Then, the pump 12 is operated.

  Thereby, supply to the membrane module 21A-21L of raw | natural water is stopped. The filtered water in the filtered water tank 11 is supplied to the filtered water main line 26 via the pipe 13 and the pump 12, and the chemical from the chemical tank 6 is added to the filtered water. The filtered water to which this chemical is added is supplied to the membrane modules 21A to 21L via the filtered water merging lines 26A to 26D and the filtered water extraction lines 25A to 25L.

  With this chemical solution, the filtration membranes in the membrane modules 21A to 21L are washed. Next, the chemical solution passes through the raw water re-branching lines 24A to 24L, the raw water branch lines 22A to 22D, the raw water main line 22 and the drainage line 60, and is discharged out of the system (back washing process with chemicals).

  After performing the backwashing with this chemical solution, the on-off valves 23A to 23D and the on-off valves 27A to 27D are closed. Thereby, the filtration membrane in membrane module 21A-21L will be in the state immersed in the chemical | medical solution (immersion process by a chemical | medical solution).

  After this immersion state is continued for a predetermined time, the on-off valves 23A, 23C-23D (excluding the on-off valve 23B), the on-off valves 27A, 27C-27D (excluding the on-off valve 27B), and the on-off valve 60a are opened again. . At this time, the on-off valve 8 of the chemical line is kept closed. Thereby, the filtrate water in the filtrate water tank 11 passes through the piping 13, the pump 12, the filtrate water main line 26, the filtrate water merge lines 26A, 26C to 26D, and the filtrate water extraction lines 25A to 25C and 25G to 25L. It is supplied to the membrane modules 21A to 21C and 21G to 21L. Here, since the on-off valve 8 of the chemical line 7 is closed, no chemical is added to the filtered water.

  The filtered water pushes out the chemicals in the membrane modules 21A to 21C and 21G to 21L. The raw water re-branching lines 24A to 24C and 24G to 24L, the raw water branch lines 22A and 22C to 22D, the raw water main line 22 and the drainage line 60 And discharged out of the system (rinsing step with filtered water).

  As described above, the membrane modules 21A to 21C and 21G to 12L of the membrane units 20A, 20C, and 20D are back-washed and rinsed with the chemical solution, and the rinsing process is omitted for the membrane modules 21D to 21F of the membrane unit 20B. The membranes in the membrane modules 21D to 21F are maintained in a state of being immersed in a chemical solution.

<Second steady process>
After performing the above-mentioned washing process, the on-off valve 60a of the drain line 60 is closed, and the on-off valve 23 of the raw water main line 22 is opened. Further, the pump 12 is stopped, the on-off valve 13a is closed, and the on-off valve 26a is opened. Thus, the open / close state of each open / close valve is a state in which the open / close valve 23B and the open / close valve 27B are closed instead of the open / close valve 23A and open / close valve 27A in FIG.

  Thereby, the membrane filtration operation of the membrane modules 21A to 21C and 21G to 21L is restarted. Moreover, the membrane module 21D-21F is maintaining the state by which the filtration membrane was immersed in the chemical | medical solution. For this reason, during this second steady process, the membrane plugging component adhering to the filtration membrane swells due to the chemical solution and is easily removed in the next washing step.

  In the above manner, the cleaning process and the steady process are repeated after the third cleaning process.

  Compared with the membrane filtration device of FIG. 8, the operation method according to the present embodiment is a drainage extraction line 50A-50D provided with on-off valves 51A-51D and a filtrate extraction line 31A-31 provided with on-off valves 32A-32D. Since 31D is omitted, the apparatus is miniaturized and the control is simplified by the amount of the on-off valves 51A to 51D and 32A to 32D.

[Other embodiments]
The above embodiment is an example of the present invention, and the present invention is not limited to the above embodiment.

  For example, the membrane filtration apparatus of FIG. 6 is the same as the membrane filtration apparatus of FIG. 8 except that the drainage extraction lines 50A to 50D and the filtrate extraction lines 31A to 31D are omitted. It may be applied to operate according to the operation schedule of FIG. 7, or may be operated according to the operation schedule of FIG. 7 using the membrane filtration device itself of FIG.

  After the rinsing step or simultaneously with the rinsing step, the raw water may be flushed by passing it through the primary side of the filtration membrane, and air may be blown into the primary side of the filtration membrane. This is preferable because the membrane blocking component adhering to the filtration membrane can be more reliably removed and cleaning can be performed even when the cleaning chemical is not completely removed in the rinsing step.

  In the above first to fourth embodiments and other embodiments, the back washing time with the chemical solution, the immersion time with the chemical solution, the rinsing time with the filtered water, the flushing time with the raw water, and the steady process of immersing a part of the membrane module By setting the time as follows, the membrane module can be efficiently cleaned, and a necessary amount of filtered water can be secured.

  In the backwashing step with the chemical solution, the backwash water passing time of the chemical solution is 30 seconds to 5 minutes, preferably 1 minute to 5 minutes. If it is shorter than 30 seconds, the effect of back washing with chemicals cannot be obtained, and if it is longer than 5 minutes, the back washing drainage increases and the load of draining treatment increases, and a lot of chemicals used for washing are unnecessarily used. This is not economical.

  In the immersion step with the chemical solution following the chemical solution back washing step, the immersion time is 10 minutes to 5 hours, preferably 15 minutes to 1 hour. If it is shorter than 10 minutes, a sufficient cleaning effect cannot be obtained, and if it is longer than 5 hours, the time during which filtered water cannot be obtained becomes longer.

  When performing the rinse process by filtered water and the flushing process by raw | natural water simultaneously, it is good for 30 second-5 minutes, Preferably it is 1 minute-3 minutes. Moreover, when performing a rinse process and a flushing process sequentially, each process is 30 seconds-5 minutes, Preferably it is good for 1 minute-3 minutes.

  The time in the steady process is 6 hours to 48 hours, preferably 8 hours to 24 hours. If the time is too short, the cleaning effect by immersion cannot be obtained, and if it is too long, the film may be deteriorated by the chemical solution, which is not preferable.

  The operation method of the membrane filtration device of the present invention can be suitably used particularly for an MF membrane filtration device or a UF membrane filtration device. There are no particular restrictions on the membrane material of these membrane filtration devices, for example, polymer materials such as polysulfone, polyethersulfone, polyacrylonitrile, polyvinylidene fluoride, polyolefin, and cellulose acetate, and inorganic materials such as alumina, zirconia, and titania And so on. Among these, in consideration of chemical resistance to chlorinated chemicals used as regular membrane cleaning chemicals, membrane materials having high chemical resistance such as polysulfone, polyethersulfone, and polyvinylidene fluoride can be suitably used. .

  Moreover, there is no restriction | limiting in particular also in the shape of these membrane modules, For example, a flat membrane module, a tubular membrane module, a spiral membrane module, a capillary module, a monolith type module etc. can be used. Among these, a hollow fiber membrane module that can operate relatively stably even when turbidity is contained in the target water and can take a large membrane area per unit volume (compact) can be suitably used. .

  In the present invention, when a hollow fiber membrane module is used, the filtration method is an external pressure type (filtering from the outside of the hollow fiber to obtain treated water (membrane filtration water) from the inside). A semi-dead end system in which circulating water (dead end) or a small amount (0.5 to 10% of the amount of membrane filtered water) is circulated is preferable.

  In the present invention, the chemical used for cleaning the membrane module is not limited, but it is preferable to perform cleaning with a chlorine-based chemical solution. In this case, there is no restriction | limiting in particular in a chlorine type | system | group chemical | medical agent, For example, sodium hypochlorite, chlorine dioxide, various chloramine type | system | group chemical | medical agents (bonded chlorine chemical | medical agent) are mentioned. These may be used alone or in combination of two or more. Among these, sodium hypochlorite is inexpensive and can be suitably used as a chemical having a high membrane cleaning effect. Various chloramine-based chemicals can be suitably used as chemicals that have a low risk of corroding piping members such as metal members, unlike sodium hypochlorite, although the cleaning effect of the membrane is slightly inferior.

  The reason why chlorinated chemicals are effective in restoring the performance of membranes blocked by passing industrial water is not clear, but perhaps the components contained in industrial water that block membranes are mainly composed of polysaccharides. It is a polymer component, and these polysaccharides are not easily affected by acids and alkalis, and it is assumed that a higher peeling effect from a film can be obtained by oxidation and lowering of the molecular weight by a chlorinated drug.

  Although there is no restriction | limiting in particular also in the chemical | medical agent density | concentration at the time of chemical | medical agent washing | cleaning of a UF membrane, Preferably, it implements by the density | concentration of 100-5,000 mg / L as an effective chlorine density | concentration. When the effective chlorine concentration is less than 100 mg / L, the cleaning effect of the UF membrane is insufficient, and when the effective chlorine concentration exceeds 5,000 mg / L, the corrosion of the member and the treatment of the chemical washing waste water are concerned.

  The pH of the cleaning chemical is preferably alkaline. Specifically, it is preferable to carry out at pH 8 to 13 in combination with an alkali agent such as sodium hydroxide as necessary. When the pH of the cleaning chemical is less than 8, the cleaning effect tends to be slightly reduced, and generation of chlorine gas may be a problem when using sodium hypochlorite, On the other hand, when the pH exceeds 13, a large amount of neutralizing chemical is required for the treatment of chemical waste water, which is not preferable.

  In the present invention, the chemical cleaning of the membrane may be combined with chemical cleaning with a reducing agent such as acid or alkali, or sodium bisulfite, if necessary. That is, the main component of the plugging component of the membrane in the treatment of industrial water is presumed to be polysaccharides, but blockage with other metals and metal oxides such as iron and manganese, and blockage with organic substances such as humic and fulvic substances can also occur. . Acid cleaning and cleaning with a reducing agent are effective for clogging with the former metal and its oxide, and alkali cleaning is effective for clogging with the latter organic matter.

1 is a system diagram of a membrane filtration device to which an operation method according to a first embodiment is applied. 1 is a system diagram of a membrane filtration device to which an operation method according to a first embodiment is applied. 1 is a system diagram of a membrane filtration device to which an operation method according to a first embodiment is applied. It is a driving schedule figure of the driving method concerning the 1st-3rd embodiment. It is a systematic diagram of the membrane filtration apparatus with which the operating method which concerns on 3rd Embodiment is applied. It is a systematic diagram of the membrane filtration apparatus with which the driving | operation method which concerns on 4th Embodiment is applied. It is an operation schedule figure of the operation method concerning a 4th embodiment. It is a systematic diagram of the membrane filtration apparatus with which the operation method which concerns on a prior art example is applied. It is an operation schedule figure of the operation method concerning a conventional example.

Explanation of symbols

1A to 1J Membrane module 2 Raw water line 2A Raw water branch line 4 Filtrated water line 4A to 4J Filtrated water discharge line 3A to 3J, 5A to 5J, 10A to 10J On-off valve 14 Drain line 14a On-off valve 20A to 20D Membrane filtration unit 21A to 21L Membrane Module 22 Raw Water Main Line 22A-22D Raw Water Branch Line 23A-23D, 27A-27D Open / Close Valve 24A-24L Raw Water Re-Branch Line 25A-25L Filtrated Water Extraction Line 26 Filtrated Water Main Line 26A-26D Filtrated Water Merge Line

Claims (10)

In a method of operating a membrane filtration device in which a plurality of membrane modules are provided in parallel,
A washing process in which all membrane modules are backwashed with washing water;
The supply of raw water to most of the membrane modules is resumed and the filtration operation is performed, and the remaining membrane modules are alternately subjected to a steady process in which the filtration membrane is immersed in cleaning water. A method for operating a membrane filtration device.   2. The method for operating a membrane filtration device according to claim 1, wherein the membrane module to be immersed in the filtration membrane is different between the steady process immediately before the cleaning process and the steady process immediately after the cleaning process. 3. The membrane filtration device according to claim 1, wherein the membrane filtration device includes a raw water line having a raw water valve for supplying raw water to each membrane module, and a wash water valve for supplying cleaning water to each membrane module. And a washing water line with
Switching between the washing step and the steady filtration step is performed by opening and closing the raw water valve and the washing water valve. In a method of operating a membrane filtration device in which a membrane filtration unit comprising a plurality of membrane modules arranged in parallel is provided in parallel,
A washing step of backwashing all membrane filtration units with washing water;
The supply of raw water to most of the membrane filtration units is resumed, and the filtration operation is performed. In the remaining membrane filtration units, the stationary process is alternately performed in which the filtration membrane is immersed in the washing water in the washing water. A method for operating a membrane filtration device.   5. The operation method of a membrane filtration device according to claim 4, wherein the membrane filtration unit to be immersed in the filtration membrane is different between the steady process immediately before the washing process and the steady process immediately after the washing process. 6. The membrane filtration device according to claim 4 or 5, wherein the membrane filtration device includes a raw water line having a raw water valve for supplying raw water to each membrane filtration unit and a wash water for supplying washing water to each membrane filtration unit. And a washing water line equipped with a valve for
Switching between the washing step and the steady filtration step is performed by opening and closing the raw water valve and the washing water valve. 7. The method of operating a membrane filtration device according to claim 1, wherein the filtration membrane is back-washed with washing water to which a chemical solution is added in the washing step. According to claim 7, before Kiarai purification step,
A chemical backwashing process for backwashing the filtration membrane using the washing water to which the chemical liquid is added,
A chemical solution immersion step for stopping backwashing and immersing the filtration membrane in the chemical solution-added cleaning water,
And a rinsing step of performing backwashing using washing water to which no chemical solution is added. The flushing step according to claim 8, wherein after the rinsing step or simultaneously with the rinsing step, flushing is performed by passing raw water through the primary side of the filtration membrane and blowing air into the primary side of the filtration membrane. A method for operating a membrane filtration device, comprising:   10. A method for operating a membrane filtration device according to claim 1, wherein the membrane module is an external pressure type hollow fiber membrane module.

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