JP5582740B2 - Desalination apparatus and method for cleaning pretreatment membrane of desalination apparatus - Google Patents

Description

  The present invention relates to a desalination apparatus and a pretreatment membrane cleaning method for improving the cleaning efficiency of reverse cleaning.

Although microfiltration or the like is used as a pretreatment for a reverse osmosis membrane device that treats seawater with a reverse osmosis membrane to produce fresh water, organic matter adheres and the like needs to be periodically washed.
This cleaning includes a method of reverse cleaning using simple cleaning water and a method of reverse cleaning by adding a chemical to the cleaning liquid.

Conventionally, it has been proposed to use concentrated water generated when fresh water is produced by a reverse osmosis membrane during this reverse cleaning (Patent Document 1).
FIG. 5 shows an example of a conventional desalination apparatus. As shown in FIG. 5, the desalination apparatus 100 </ b> A includes a pretreatment device 13 having a pretreatment membrane 12 that filters turbid components in raw water (seawater) 11, and filtered water 14 supplied from the pretreatment device 13. A reverse osmosis membrane device 17 having a reverse osmosis membrane (RO membrane) 16 for removing salt from the fresh water 15 and a concentrated water 18 enriched with salt from the reverse osmosis membrane device 17 are supplied to the pretreatment device 13. And a backwash line 19 for feeding, and the pretreatment film 12 is backwashed using the concentrated water 18 as the wash water 20. Here, in the figure, reference numeral 21 is a tank for storing the concentrated water 18, 22 is a raw water line for supplying the raw water 11 to the pretreatment device 13, and 23 is a reverse osmosis membrane device 17 from the pretreatment device 13 for the filtered water 14. A filtered water line for supplying water to the tank, 24 for a concentrated water line for supplying the concentrated water 18 to the tank 21, 25 for a fresh water line for supplying fresh water 15 to an external water use facility, etc., and P for a feed pump.

  In the desalination apparatus 100A configured as described above, the raw water 11 removes turbid components by the pretreatment membrane 12 of the pretreatment device 13, and the filtrate 14 is supplied to the reverse osmosis membrane device 17 via the filtrate water line 23. Is done. Then, the salt content is removed by the reverse osmosis membrane device 17 to obtain the fresh water 15, and then the fresh water 15 is fed to an external water use facility (not shown) via the fresh water line 25. The concentrated concentrated water 18 is stored in the tank 21 via the concentrated water line 24. Here, examples of the pretreatment membrane 12 for removing turbid components include a separation membrane such as a UF membrane (ultrafiltration membrane) or an MF membrane (microfiltration membrane), but are not limited thereto. Absent.

  When the pretreatment device 13 is backwashed, after the desalination for a predetermined time, the supply of the raw water 11 is stopped, and the concentrated water 18 from the tank 21 is used as the wash water 20 via the backwash line 19. To the pretreatment device 13 and backwash the pretreatment film 12. And the backwash water 26 containing a suspended matter is sent outside from the backwash water line 27, and performs a predetermined | prescribed process.

JP 2007-14902 A

  However, when the concentrated water proposed in Patent Document 1 is used, there is a scale component, and organic substances can be removed by washing with chemicals such as sodium hypochlorite and alkali. As an effect, there is a problem that scale components of calcium carbonate and calcium hypochlorite adhere to the pretreatment film.

Therefore, as shown in another desalination apparatus 100B in FIG. 6, it has been proposed to remove the generated scale by supplying an acid 28 such as hydrochloric acid from an acid supply unit 29, In washing, two types of chemical agents, an alkaline agent and an acid, are used in combination, increasing the number of backwashing steps, and backwashing water 26 from the pretreatment device 13 becomes an acidic waste liquid, and the treatment becomes a further problem. .
In particular, during operation in winter, the water temperature is lowered, so that the oxidation effect is reduced, and it is necessary to add chemicals, resulting in an increase in the amount of acidic waste liquid.

  This invention makes it a subject to provide the washing | cleaning method of the pretreatment film | membrane of the desalination apparatus and desalination apparatus which can improve the interval of backwashing while removing a scale efficiently in view of the said problem. .

The first invention of the present invention for solving the above-mentioned problem is to remove a salt content from a pretreatment device having a pretreatment membrane for filtering turbid components in raw water and filtered water from the pretreatment device. A reverse osmosis membrane device having a reverse osmosis membrane for producing fresh water, a fresh water back washing line for feeding fresh water produced by the reverse osmosis membrane device to the pretreatment device, and supplying chlorine gas to the fresh water back washing line And a concentrated water backwashing line for feeding concentrated water enriched with salt from the reverse osmosis membrane device to the pretreatment device, and for the backwashing of the pretreatment membrane The desalination apparatus is characterized in that fresh water supplied with chlorine gas and the concentrated water are used in combination .

  According to a second aspect of the present invention, there is provided a desalination apparatus according to the first aspect, wherein a heating unit for heating the fresh water is interposed in the fresh water backwash line.

3rd invention is the washing | cleaning method of the pretreatment film | membrane of the desalination apparatus which obtains fresh water using a reverse osmosis membrane, after filtering the turbid content in raw | natural water with a pretreatment film | membrane, Comprising: At the time of washing, after adding chlorine gas to the fresh water produced by the reverse osmosis membrane to wash the pretreatment membrane, the pretreatment membrane is removed using concentrated water in which salt is concentrated by the reverse osmosis membrane. The present invention resides in a method for cleaning a pretreatment membrane of a desalinator characterized by cleaning.

A fourth aspect based on the third aspect, in the cleaning method of the pretreatment film desalination apparatus characterized by washing while heating the fresh water.

  According to the present invention, since fresh water is pure water by adding chlorine to fresh water and performing reverse cleaning of the pretreatment film of the pretreatment apparatus, precipitation of calcium hypochlorite and the like is suppressed, and efficient. Cleaning is possible.

FIG. 1 is a schematic diagram of a desalination apparatus according to a first embodiment. FIG. 2 is a schematic diagram of another desalination apparatus according to the first embodiment. FIG. 3 is a schematic diagram of a desalination apparatus according to the second embodiment. FIG. 4 is a diagram showing pressure fluctuation when changing to warm water. FIG. 5 is a schematic diagram of a desalination apparatus according to the prior art. FIG. 6 is a schematic view of another desalination apparatus according to the prior art.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

A desalination apparatus according to a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram illustrating a desalination apparatus according to a first embodiment. In addition, about the member similar to the structural member of the desalination apparatus demonstrated by the prior art, the same code | symbol is attached | subjected and the description is abbreviate | omitted.
10A of desalination apparatuses which concern on an Example remove the salt from the pre-processing apparatus 13 which has the pre-processing film | membrane 12 which filters the turbid content in the raw water 11, and the filtered water 14 from the said pre-processing apparatus 13, and fresh water 15 A reverse osmosis membrane device 17 having a reverse osmosis membrane (RO membrane) 16, a fresh water backwash line 30 for feeding fresh water 15 produced by the reverse osmosis membrane device 17 to the pretreatment device 13, and A chlorine supply unit 32 that supplies chlorine 31 to the fresh water backwash line 30 is provided, and the fresh water 15 is used for backwashing the pretreatment film 12.
In FIG. 1, reference numeral 55 denotes a fresh water tank.

  When the pretreatment device 13 is backwashed, after fresh water is desalted for a predetermined time, the supply of the raw water 11 is stopped, and the freshwater 15 from the freshwater tank 50 is used as wash water via the freshwater backwash line 30. Then, it is fed to the pretreatment device 13 and the pretreatment film 12 is backwashed while adding chlorine 31. And the backwash water 26 containing a suspended matter is sent outside from the backwash water line 27, and performs a predetermined | prescribed process.

  As a result, the chlorine 31 is added to the fresh water 15 and periodically backwashed to sterilize with the chlorine 31 and the pretreatment film 12 is washed with the fresh water 15 which is pure water. Precipitation can be greatly suppressed.

Further, as shown in another desalination apparatus 10B shown in FIG. 2, a heating unit 51 is interposed in the fresh water backwash line 30, and the fresh water 15 is heated by the heating medium 52, so that the time required for cleaning is increased. It can be shortened.
Moreover, since the fresh water 15 is heated (for example, 40 degreeC) with the heating medium (for example, steam around 140 degreeC) 52, the fall of the washing | cleaning efficiency in winter can also be suppressed.
FIG. 4 shows fluctuations in the pressure of the pretreatment film in the pretreatment device 13 when fresh water is changed to warm water. A significant reduction in pressure was confirmed by changing from fresh water to heated water.

The use of fresh water 15 as the production water for backwashing reduces the production amount of the production water, but the introduction of a chemical (acid) for removing the scale and the backwashing time for the treatment. In view of the excess of water and the cost of treating acidic backwash water, there is no significant reduction in production water from a long-term perspective.
In addition, the backwashing interval has been once every 30 minutes in the past, but in this example, since the generation of scale disappears, the backwashing interval could be extended once every 1 to 3 hours. .

A desalination apparatus according to a second embodiment of the present invention will be described with reference to the drawings.
FIG. 3 is a schematic diagram illustrating a desalination apparatus according to the second embodiment. In addition, about the member similar to the structural member of the desalination apparatus demonstrated in the prior art and Example 1, the same code | symbol is attached | subjected and the description is abbreviate | omitted.
The desalination apparatus 10C according to the second embodiment is a concentrated water backwash line for feeding the concentrated water 18 in which the salt content from the reverse osmosis membrane apparatus 17 is further concentrated to the pretreatment apparatus 13 in the apparatus of the first embodiment. 55, and the fresh water 15 and the concentrated water 18 are used in combination for the reverse cleaning of the pretreatment film 12.

  When the pretreatment device 13 is backwashed, after fresh water is desalted for a predetermined time, the supply of the raw water 11 is stopped, and the freshwater 15 that is pure water from the freshwater tank 50 is used as washing water as a freshwater backwash line. The pretreatment film 12 is fed back to the pretreatment device 13 and the pretreatment film 12 is backwashed while adding chlorine 31. And the backwash water 26 containing a suspended matter is sent outside from the backwash water line 27, and performs a predetermined | prescribed process.

  Thereafter, even when the scale component is removed by the pretreatment film 12 and then backwashed with the concentrated water 18, the scale does not adhere and the amount of fresh water 15 used can be reduced.

  As a result, by adding chlorine 31 to the fresh water 15 and regularly backwashing, precipitation of calcium hypochlorite can be suppressed, and after washing with the fresh water 15, washing with the concentrated water 18, The amount of fresh water 15 used for backwashing can be reduced.

  Further, in this embodiment, since no scale is generated, the backwashing interval can be set to about once every 1 to 3 hours, and the treatment with the fresh water 15 is performed for about 2 to 3 minutes, and the concentrated water 18 is used. It was possible to perform backwashing in a short time of about 5 minutes.

  As described above, since the desalination apparatus according to the present invention is not washed using concentrated water as in the prior art, the generation of scale is eliminated, and the desalination production efficiency over the long term is reduced. It is suitable for use in facilities that desalinate seawater.

10A to 10C Desalination equipment 11 Raw water 12 Pretreatment membrane 13 Pretreatment equipment 14 Filtration water 15 Fresh water 16 Reverse osmosis membrane 17 Reverse osmosis membrane equipment 18 Concentrated water 30 Fresh water backwash line 31 Chlorine 32 Chlorine supply part 51 Heating part 55 Concentrated water Backwash line

Claims (4)

A pretreatment device having a pretreatment membrane for filtering turbid components in raw water;
A reverse osmosis membrane device having a reverse osmosis membrane for producing fresh water by removing salt from the filtered water from the pretreatment device;
A fresh water backwash line for feeding fresh water produced by the reverse osmosis membrane device to the pretreatment device;
A chlorine supply unit for supplying chlorine gas to the fresh water backwash line ;
A concentrated water backwash line for feeding concentrated water enriched with salt from the reverse osmosis membrane device to the pretreatment device ,
A desalination apparatus comprising a combination of fresh water supplied with the chlorine gas and the concentrated water for back cleaning of the pretreatment membrane . In claim 1,
A desalination apparatus comprising a heating unit for heating fresh water in the fresh water backwash line. A method for cleaning a pretreatment membrane of a desalination apparatus for obtaining fresh water using a reverse osmosis membrane after filtering turbidity in raw water with a pretreatment membrane,
At the time of backwashing the pretreatment membrane, after adding chlorine gas to the fresh water produced by the reverse osmosis membrane to wash the pretreatment membrane, the concentrated water in which the salinity is concentrated by the reverse osmosis membrane is used. And cleaning the pretreatment membrane. A method for cleaning a pretreatment membrane of a desalination apparatus. In claim 3 ,
A method for cleaning a pretreatment film of a desalination apparatus, wherein the fresh water is cleaned while being heated.

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