JP2008221063A - Operation method of water treatment system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a filter membrane from being clogged in a water treatment system equipped with a filter membrane device by inhibiting fouling of the filter membrane due to iron. <P>SOLUTION: In the operation method of a water treatment system 1 where the filter membrane device 4 is installed in a feed water line 2, and a part of concentrate from the filter membrane device 4 is discharged and the remainder is returned to feed water line 2 on the upstream side of the filter membrane device 4, the operating condition of the filter membrane device 4 is set according to the particle size of iron in the feed water to the filter membrane device 4. Specifically, the larger the article size of iron in the feed water to the filter membrane device 4 is, the larger the flow rate of the concentrate discharged from the filter membrane device 4 is made. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for operating a water treatment system including a filtration membrane device provided in a water supply line.

  As a water treatment system for water supply to equipment such as steam boilers, hot water boilers, cooling towers, water heaters, and other water-using equipment such as semiconductor cleaning equipment, water with a filtration membrane device in the water supply line to the equipment A processing system is known (see, for example, Patent Document 1). In the filtration membrane device, the feed water flowing from one side is filtered by the filtration membrane, and treated water and concentrated water flow out from the other side. The treated water flows through the water supply line and is supplied to the equipment. On the other hand, the concentrated water flows out to the concentrated water line connected to the filtration membrane device. And in the cross-flow type filtration membrane device, the concentrated water line is branched into a drainage line and a reflux line, and a part of the concentrated water flowing out from the filtration membrane device passes through the drainage line. While being drained out of the system, the remainder is returned to the upstream side of the filtration membrane device through the reflux line.

Here, when groundwater is used as water supply to the filtration membrane device, for example, an iron removal device is provided in the water supply line upstream of the filtration membrane device in order to remove iron contained in the groundwater. In this case, for example, sodium hypochlorite is added as an oxidant to the feed water to the iron removal device, and iron in water is oxidized to form insoluble ferric hydroxide (Fe (OH) ₃ ). And in the said iron removal apparatus, water supply is filtered with filter media, such as anthracite and filtration sand, and the iron content contained in water supply is removed in the form of ferric hydroxide.
JP 2005-296944 A

  By the way, the inventor of the present application has found that insoluble iron such as ferric hydroxide has a higher concentration, particles are bonded to each other, agglomeration proceeds, and the particle size tends to increase. It has been found that the particles are bonded to each other and agglomeration proceeds to increase the particle size. Here, when the feed water supplied from the iron removal device to the filtration membrane device contains ferric hydroxide that could not be removed by the iron removal device, the concentrated water drainage from the filtration membrane device. As the flow rate decreases, the concentration proceeds near the surface of the filtration membrane, and the concentration of ferric hydroxide increases. In this case, the aggregation of ferric hydroxide proceeds in the vicinity of the surface of the filtration membrane, and the particle size increases. In addition, since a part of the concentrated water is refluxed to the upstream side of the filtration membrane device, the aggregation of ferric hydroxide contained in the concentrated water that has been refluxed progresses over time, and the particle size increases. . When the particle size of ferric hydroxide is increased in this manner, fouling in which ferric hydroxide is deposited or adsorbed on the surface of the filtration membrane is likely to occur, and the filtration membrane is likely to be clogged.

  The present invention has been made in view of such circumstances, and the problem to be solved is to suppress fouling of the filtration membrane caused by iron in a water treatment system equipped with a filtration membrane device. It is to prevent clogging of the filtration membrane.

  This invention was made in order to solve the said subject, The invention of Claim 1 is equipped with the filtration membrane apparatus provided in the water supply line, and drains a part of concentrated water from this filtration membrane apparatus. And a method for operating the water treatment system in which the remaining portion is recirculated to the water supply line upstream of the filtration membrane device, wherein an operating condition of the filtration membrane device is determined by supplying water to the filtration membrane device or the filtration membrane device. It sets based on the particle size of the iron content in the concentrated water from.

  According to a second aspect of the present invention, the operating condition of the filtration membrane device according to the first aspect is a flow rate of concentrated water drainage from the filtration membrane device, and water supply to the filtration membrane device or from the filtration membrane device As the particle size of iron in the concentrated water increases, the concentrated water drainage flow rate from the filtration membrane device increases.

  According to a third aspect of the present invention, the operating condition of the filtration membrane device according to the first aspect is whether or not a dispersant is added to the water supply to the filtration membrane device, and the water supply to the filtration membrane device or the When the particle size of iron in the concentrated water from the filtration membrane device exceeds a predetermined particle size, a dispersant is added to the water supply to the filtration membrane device.

  Furthermore, in the invention according to claim 4, the operating condition of the filtration membrane device according to claim 1 is a water supply flow rate to the filtration membrane device, and from the water supply to the filtration membrane device or the filtration membrane device As the particle size of iron in the concentrated water increases, the feed water flow rate to the filtration membrane device decreases.

  According to the invention described in claim 1, by setting the operating conditions of the filtration membrane device based on the particle size of iron in water supplied to the filtration membrane device or concentrated water from the filtration membrane device, Fouling generated due to iron in the filtration membrane of the filtration membrane device can be suppressed, and clogging of the filtration membrane can be prevented.

  According to the second aspect of the present invention, the flow rate of concentrated water drainage from the filtration membrane device increases as the particle size of iron in the water supplied to the filtration membrane device or the concentrated water from the filtration membrane device increases. Further, the concentration of iron in the vicinity of the surface of the filtration membrane of the filtration membrane device is reduced, iron agglomeration can be suppressed, and iron with an increased particle size can be discharged out of the system. Thereby, generation | occurrence | production of the fouling in the said filtration membrane can be suppressed, and the clogging of the said filtration membrane can be prevented.

  According to invention of Claim 3, when the particle size of the iron content in the water supply to the filtration membrane apparatus or the concentrated water from the filtration membrane apparatus exceeds a predetermined particle diameter, to the water supply to the filtration membrane apparatus Since the dispersant is added, the particle size of iron can be reduced by the action of the dispersant. Thereby, generation | occurrence | production of the fouling in the said filtration membrane can be suppressed, and the clogging of the said filtration membrane can be prevented.

  According to invention of Claim 4, since the particle size of the iron content in the feed water to the filtration membrane device or the concentrated water from the filtration membrane device is increased, the feed water flow rate to the filtration membrane device is decreased. The amount of iron transferred to the filter membrane can be reduced, and the concentration of iron in the vicinity of the surface of the filter membrane can be suppressed. Thereby, generation | occurrence | production of the fouling in the said filtration membrane can be suppressed, and the clogging of the said filtration membrane can be prevented.

Next, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
First, a first embodiment of the present invention will be described. FIG. 1 is a schematic explanatory view showing the configuration of a water treatment system for carrying out the first embodiment of the present invention.

  A water treatment system 1 shown in FIG. 1 includes a water supply line 2 for equipment (not shown) such as a boiler and other thermal equipment and a water-using equipment such as a semiconductor cleaning device, and the water supply line 2 is sequentially removed from the upstream side. An iron device 3 and a filtration membrane device 4 are provided. A particle counter 5 is connected to the water supply line 2 between the iron removal device 3 and the filtration membrane device 4 as a particle size measuring means for iron, and a water supply pump 6 is provided downstream of the particle counter 5. Is provided. The particle counter 5 and the water supply pump 6 are connected to a control unit 7.

  The iron removal device 3 is configured by filling a filter tower (not shown) with a filter medium (not shown) such as anthracite, filter sand, and the like. Ferric iron) is captured and removed.

A sodium hypochlorite solution is added as an oxidizing agent to the water supply line 2 upstream of the iron removing device 3 by an oxidizing agent adding device (not shown). When sodium hypochlorite is added to the water supply line 2, iron contained in the water supply is oxidized to insoluble ferric hydroxide (Fe (OH) ₃ ). It is removed in the iron device 3.

  The filtration membrane device 4 is configured to filter feed water by a filtration membrane module (not shown) and remove impurities contained in the feed water. The filtration membrane of the filtration membrane module is a synthetic polymer membrane such as a reverse osmosis membrane (RO membrane) or a nanofiltration membrane (NF membrane), and is appropriately selected according to the type of the device. Incidentally, the reverse osmosis membrane is a liquid separation membrane capable of preventing permeation of a substance having a molecular weight of several tens. On the other hand, the nanofiltration membrane is a liquid separation membrane capable of preventing permeation of particles and polymers (substances having a maximum molecular weight of about several hundreds) smaller than about 2 nm.

  In the filtration membrane device 4, the feed water supplied from one side flows out as treated water and concentrated water from the other side. The treated water flows through the water supply line 2 and is supplied to the equipment. On the other hand, the concentrated water flows out to the concentrated water line 8 connected to the filtration membrane device 4. The concentrated water line 8 is branched into a drainage line 9 and a reflux line 10, and the reflux line 10 is connected to the water supply line 2 between the iron removal device 3 and the filtration membrane device 4. Therefore, a part of the concentrated water flowing out from the filtration membrane device 4 to the concentrated water line 8 is drained outside the system through the drainage line 9 and the remaining part is drained through the reflux line 10 to the filtration membrane. It returns to the water supply line 2 upstream of the device 4.

  The drainage line 9 is branched into a first drainage line 11, a second drainage line 12, and a third drainage line 13. The drainage lines 11, 12, 13 include a first drainage valve 14, a second drainage line. A valve 15 and a third drain valve 16 are provided. Each drain valve 14, 15, 16 is connected to the control unit 7. The drain valves 14, 15, 16 are set to open / close in response to an open / close signal from the control unit 7, and change the open / close state of the drain valves 14, 15, 16. Thus, the concentrated water drainage flow rate from the drainage line 9 is adjusted stepwise.

  The particle counter 5 measures the intensity of light scattering from the particles in the water supply and takes out the light intensity proportional to the size of the particles as an electrical signal. The particle counter 5 measures the average particle size of ferric hydroxide in the water supply, and the measurement result is input to the control unit 7.

  Now, an operation method of the water treatment system 1 will be described. Here, the operation method of the water treatment system according to the present invention relates to the operation of the filtration membrane device provided in the water supply line. Specifically, the operating condition of the filtration membrane device is set based on the particle size of iron in the water supplied to the filtration membrane device or the concentrated water from the filtration membrane device. In the water treatment system 1 of the first embodiment, the operating condition of the filtration membrane device 4 is the concentrated water drainage flow rate from the filtration membrane device 4. The concentrated water drainage flow rate from the filtration membrane device 4 is set based on the particle size of iron in the water supplied to the filtration membrane device 4.

  More specifically, the particle size of iron in the water supplied to the filtration membrane device 4 is measured by the particle counter 5. Here, specifically, iron is ferric hydroxide. Then, the controller 7 increases the drainage of concentrated water from the filtration membrane device 4 as the average particle size of ferric hydroxide (hereinafter simply referred to as “particle size”) measured by the particle counter 5 increases. Open / close signals are output to the drain valves 14, 15, 16 so that the flow rate increases stepwise.

  According to the water treatment system 1 described above, the flow rate of concentrated water drainage from the filtration membrane device 4 increases stepwise as the particle size of ferric hydroxide in the feed water to the filtration membrane device 4 increases. Therefore, the degree of concentration of ferric hydroxide in the vicinity of the surface of the filtration membrane (not shown) of the filtration membrane device 4 is reduced, and aggregation of ferric hydroxide can be suppressed and the particle size is increased. Ferric hydroxide can be discharged out of the system. Thereby, generation | occurrence | production of the fouling in the said filtration membrane can be suppressed, and the clogging of the said filtration membrane can be prevented.

  Further, even if the concentration of iron contained in the feed water from the iron removal device 3 is high, the concentration from the filtration membrane device 4 increases as the particle size of ferric hydroxide in the feed water to the filtration membrane device 4 increases. By increasing the water drainage flow rate stepwise, fouling caused by iron in the filtration membrane can be suppressed. Therefore, the allowable concentration of iron contained in the water supply from the iron removal device 3 can be set high.

  Here, a modification of the first embodiment will be described. Although not specifically illustrated, in the water treatment system 1, the particle counter 5 is provided in the concentrated water line 8 to measure the particle size of ferric hydroxide in the concentrated water. The concentrated water drainage flow rate from the filtration membrane device 4 may be increased as the diameter increases.

(Second embodiment)
Next, a second embodiment of the present invention will be described. FIG. 2 is a schematic explanatory view showing the configuration of a water treatment system for carrying out the second embodiment of the present invention. In FIG. 2, the same components as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the water treatment system 20 of the second embodiment, a dispersant addition device 21 is connected to the water supply line 2 between the water supply pump 6 and the filtration membrane device 4. The dispersant addition device 21 includes a dispersant reservoir 23 connected to the water supply line 2 via a dispersant supply line 22. In this dispersant storage part 23, sodium polyacrylate is stored as a dispersant. The sodium polyacrylate is added to the water supply line 2 by a dispersant supply pump 24 provided in the dispersant supply line 22 and connected to the control unit 7.

  Incidentally, in FIG. 2, the drainage line 9 is not branched. The drain line 9 is provided with a drain valve (not shown).

  Now, an operation method of the water treatment system 20 will be described. In this water treatment system 20, the operating condition of the filtration membrane device 4 set based on the particle size of ferric hydroxide measured by the particle counter 5 is the dispersant by the dispersant adding device 21. The presence or absence of addition.

  More specifically, the control unit 7 outputs an operation command to the dispersant supply pump 24 when the particle size of the ferric hydroxide measured by the particle counter 5 exceeds a predetermined particle size. . As a result, the dispersant supply pump 24 is operated, and sodium polyacrylate in the dispersant reservoir 23 is added to the water supply line 2. Thereby, the particle size of the ferric hydroxide contained in feed water becomes small.

  Here, the predetermined particle size is set such that fouling caused by ferric hydroxide can be suppressed in the filtration membrane (not shown) of the filtration membrane device 4.

  According to the water treatment system 20 described above, when the particle size of ferric hydroxide in the water supplied to the filtration membrane device 4 exceeds a predetermined particle size, the dispersant is supplied to the water supplied to the filtration membrane device 4. Thus, the particle size of ferric hydroxide can be reduced by the action of the dispersant. Thereby, generation | occurrence | production of the fouling in the said filtration membrane can be suppressed, and the clogging of the said filtration membrane can be prevented.

  Further, even if the concentration of iron contained in the water supply from the iron removal device 3 is high, the filtration is performed when the particle size of ferric hydroxide in the water supply to the filtration membrane device 4 exceeds a predetermined particle size. By adding a dispersant to the water supply to the membrane device 4, fouling that occurs due to iron in the filtration membrane can be suppressed. Therefore, the allowable concentration of iron contained in the water supply from the iron removal device 3 can be set high.

(Third embodiment)
Next, a third embodiment of the present invention will be described. FIG. 3 is a schematic explanatory view showing the configuration of a water treatment system for carrying out the third embodiment of the present invention. In FIG. 3, the same components as those in the first and second embodiments are denoted by the same reference numerals, and detailed description thereof is omitted.

  The water treatment system 30 of the third embodiment has the same basic configuration as the water treatment system 1 of the first embodiment, but the drainage line 9 is not branched as in the second embodiment. The drain line 9 is provided with a drain valve (not shown).

  Now, an operation method of the water treatment system 30 will be described. In this water treatment system 30, the operating condition of the filtration membrane device 4 set based on the particle size of ferric hydroxide measured by the particle counter 5 is the feed water flow rate to the filtration membrane device 4. It is.

  More specifically, the control unit 7 decreases the rotation speed of the water supply pump 6 and increases the water supply to the filtration membrane device 4 as the particle size of the ferric hydroxide measured by the particle counter 5 increases. Reduce the flow rate.

  According to the water treatment system 30 described above, the flow rate of water supplied to the filtration membrane device 4 decreases as the particle size of ferric hydroxide in the water supplied to the filtration membrane device 4 increases. The amount of ferric hydroxide carried to (not shown) can be reduced, and the concentration of iron in the vicinity of the surface of the filtration membrane can be suppressed. Thereby, generation | occurrence | production of the fouling in the said filtration membrane can be suppressed, and the clogging of the said filtration membrane can be prevented.

  Moreover, even if the concentration of iron contained in the water supply from the iron removal device 3 is high, the water supply to the filtration membrane device 4 is based on the particle size of ferric hydroxide in the water supply to the filtration membrane device 4. By reducing the flow rate, fouling caused by iron in the filtration membrane can be suppressed. Therefore, the allowable concentration of iron contained in the water supply from the iron removal device 3 can be set high.

  As mentioned above, although this invention was demonstrated by each said embodiment, this invention can be variously implemented in the range which does not change the main point. For example, in the water treatment system 1 of the first embodiment, a proportional control valve is provided in the drainage line 8 without branching the drainage line 8 into the drainage lines 11, 12, and 13. The concentrated water drainage flow rate may be adjusted by adjusting the opening degree.

It is a schematic explanatory drawing which shows the structure of the water treatment system for implementing 1st embodiment of this invention. It is a schematic explanatory drawing which shows the structure of the water treatment system for implementing 2nd embodiment of this invention. It is a schematic explanatory drawing which shows the structure of the water treatment system for implementing 3rd embodiment of this invention.

Explanation of symbols

1,20,30 Water treatment system 2 Water supply line 4 Filtration membrane device

Claims (4)

An operation method of a water treatment system comprising a filtration membrane device provided in a water supply line, draining part of the concentrated water from the filtration membrane device, and returning the remainder to the water supply line upstream of the filtration membrane device Because
An operation method for a water treatment system, wherein operating conditions of the filtration membrane device are set based on a particle size of iron in water supplied to the filtration membrane device or concentrated water from the filtration membrane device.   The operating condition of the filtration membrane device is the flow rate of concentrated water drainage from the filtration membrane device, and the larger the particle size of iron in the feed water to the filtration membrane device or the concentrated water from the filtration membrane device, the larger the filtration membrane The operation method of the water treatment system according to claim 1, wherein the concentrated water drainage flow rate from the apparatus is increased.   The operating condition of the filtration membrane device is whether or not a dispersant is added to the water supply to the filtration membrane device, and the particle size of iron in the water supplied to the filtration membrane device or the concentrated water from the filtration membrane device is predetermined. The method for operating a water treatment system according to claim 1, wherein when the particle diameter is exceeded, a dispersant is added to the water supply to the filtration membrane device.   The operating condition of the filtration membrane device is a feed water flow rate to the filtration membrane device, and the larger the particle size of iron in the feed water to the filtration membrane device or the concentrated water from the filtration membrane device, the more to the filtration membrane device. The operation method of the water treatment system according to claim 1, wherein the feed water flow rate of the water treatment system is reduced.

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