Technical field
[0001]
The present disclosure, the filter layer cleaning method and the biological membrane filtration device of the biological membrane filtration apparatus for filtering raw water by filtration layer biofilm is supported, as well as desalination plants.
BACKGROUND
[0002]
Conventionally, by flowing raw water filtration layer biofilm is supported, a physical treatment to filter turbid content of raw water (the suspended particulates), is simultaneously biofilm filtration apparatus and a biological treatment by microorganisms known ing. For example, biofilm filtration apparatus comprises a filtration layer filter medium such as sand or anthracite is filled into the column, using the organic nutrients in water on the filter medium surface to form the biofilm. Removing the suspended solid matter by filtration layer to remove the dissolved organic matter in the water by the biofilm, so as to purify the raw water.
　Biofilm filtration devices, such as in seawater desalination plants, are widely used as a treatment prior to reverse osmosis unit.
[0003]
　In such a biofilm filtration device, as well as other filtering device, since the pressure loss rises by clogging the turbid fraction adhered to the filtration layer accumulates, remove turbid matter adhering to the filtration layer There is a need to.
　In a typical filtration device, typically by introducing the backwash water filtration layer, the backwashing to discharge from the filtration device turbid matter or the like from the. For example, Patent Document 1, as the backwash water, it is described that uses the filtered treated filtrate in the filtration process. Also, this document is also described the use of raw water as backwash water.
CITATION
Patent Document
[0004]
Patent Document 1: JP-B 54-18780 Patent Publication
Summary of the Invention
Problems that the Invention is to Solve
[0005]
　However, as described in Patent Document 1, when using raw water as backwash water during backwashing the filtration layer, since the raw water contains many turbid fraction, not only unable to make the proper cleaning , there is a possibility that quality content pollution to the surface for introducing the backwash water of the filtration layer adheres.
　On the other hand, the filtered treated filtrate in the filtration step is used as a backwash water, but turbid fraction is reduced from the raw water, the fine particle size to be removed would normally in a subsequent reverse osmosis unit or the like since turbid fraction is remaining, still it is difficult to perform appropriate washing. Also in this case, since that would be utilized in pulling the water in the production of product water processes that use value, production efficiency was also lowered. Similarly, for example, in the case of using the permeate obtained in the reverse osmosis membrane apparatus as backwash water, it will also cause a decrease in production efficiency.
[0006]
　Object of at least some embodiments of the present invention, without causing a decrease in production efficiency, suitably the filtration layer can be carried out backwashing cleaning method and the biological membrane filtration device, and to provide a desalination plant is there.
Means for Solving the Problems
[0007]
(1) filtration layer cleaning method according to at least some embodiments of the present invention,
　a filtering layer cleaning method of the biological membrane filtration apparatus for filtering raw water by filtration layer biofilm is supported,
　from the filtration layer It includes a concentrate that is obtained by separating the filtered water by reverse osmosis membrane, and, using the backwash water having 0.6 or more and 1.5 or less of the salt concentration ratio relative to the raw water, the filter layer the backwashing.
[0008]
　According to the method (1), when the cleaning of the filtration layer, is to use a concentrate obtained was separated by reverse osmosis membrane disposed downstream of the filtration layer. Normally, the concentrated water because often discarded, the large amount of pull out it is not necessary to use the water in the generating process of product water by using concentrated water as backwash water, can avoid a decrease in production efficiency . Moreover, since it is possible to effectively use the water in the system, greater reduction in cost as compared with the case of raising the backwash water from the outside.
[0009]
　Meanwhile, the concentrated water that has been separated by reverse osmosis membrane, the salt concentration is different from the raw water. For example, in the case of reverse osmosis membrane apparatus filtered water biofilm filtration device is supplied, the salt concentration than the retentate raw separated by reverse osmosis membrane becomes higher. On the other hand, when a plurality of reverse osmosis membrane apparatus are provided in series, downstream of the reverse osmosis unit in separate concentrated water is obtained by separating the permeate obtained by reverse osmosis membrane device upstream salt concentration than the raw water is lowered for. Thus, when the raw water and utilizes concentrated water in which the salt concentration varies as backwash water, salt concentration environment of microorganisms ambient carried on the filtration layer is changed, the movement of the liquid in the cell and out of the microorganisms by osmotic pressure difference microbial activity may decrease significantly happening.
　Accordingly, the present inventors have intensively studied and, as a result, have found a correlation between the activity and salt concentration of microorganisms in the raw water. That is, the salt concentration ratio relative to the raw water under 0.6 or more and 1.5 or less environment, I was able to be properly maintained microbial activity.
　According to the method (1), by backwashing the filtration layer with a backwash water having 0.6 or more and 1.5 or less of the salt concentration ratio relative to the raw water, which is carried on the filtration layer the function of the biological treatment by microorganisms can maintain the activity of the microorganism to a degree that can be sufficiently exhibited. Therefore, it becomes possible to effectively utilize the advantageous concentrated water from the production efficiency and cost, as described above as the backwash water.
[0010]
In (2) some embodiments, in the method of the above (1),
　the backwash water has a 0.8 or higher and 1.25 or less of the salt concentration ratio relative to the raw water.
[0011]
　According to the method (2), by using the backwash water having 0.8 or more and 1.25 or less of the salt concentration ratio, can more effectively suppress the reduction in activity of the microorganisms by supplying the concentrated water, It can maintain the biological treatment function by biofilm filtration apparatus more appropriately. Further, when the resume normal operation after backwashing, it is possible to shorten the time until the microorganisms return to normal activity.
[0012]
(3) In some embodiments, in the method of the above (1) or (2),
　the backwash water may further comprise the filtered water before being supplied to the reverse osmosis membrane.
[0013]
　Filtered water before being supplied to the reverse osmosis membrane has included turbid quality content of fine particle size salt concentration is substantially the same as the raw water. Therefore, as in the method (3), by mixing the filtered water to backwash water, it can be brought close to the salt concentration of the concentrated water to the raw water, the backwash water in the above (1) or (2) it can be easily adjusted to the range of the indicated salt concentration ratios. Incidentally, as compared with the case of using only filtered water as backwash water, in the method (3), for use by mixing with filtered water concentrated water containing almost no turbid fraction, filtration layer due to turbidity min the pollution can be suppressed.
[0014]
(4) In some embodiments, in any of the above methods (1) to (3),
　the backwash water may further comprise the raw water.
[0015]
　According to the method of the above (4), by mixing the raw water to the backwash water can be brought close to the salt concentration of the concentrated water to the raw water, salt backwash water indicated above (1) or (2) it can be easily adjusted to the range of the concentration ratio. Incidentally, as compared with the case of using only the raw water as backwash water, in the method (4), for use by mixing with raw water concentrated water containing almost no turbid matter, contamination of the filtration layer by turbidity min It can be suppressed.
[0016]
(5) In some embodiments, in any of the above methods (1) to (4),
　said reverse osmosis membrane comprises a first reverse osmosis membrane and a second reverse osmosis membrane, which are connected in series,
　the backwash water includes the first concentrated water that has been separated by the first reverse osmosis membrane, or, at least one of the second concentrated water separated by the second reverse osmosis membrane.
[0017]
　According to the method of the above (5), the raw water by using the first concentrated water or second concentrated water having different salt concentrations as backwash water, it can prevent a reduction in production efficiency due to backwash and processing costs attained reduction of.
　Incidentally, the second concentrated water that has been separated by the second reverse osmosis membrane are the concentrated water obtained by separating the permeate low salt obtained in the first reverse osmosis membrane in the reverse osmosis membrane, typically, salt to the raw water concentration the ratio is less than 1. Therefore, if mixing the second concentrated water of the first concentrated water and low salt concentration of high salt concentration, with a favorable concentrated water from the production efficiency and cost, as shown in the above (1) or (2) it is possible to produce a backwash water salt concentration ratio.
[0018]
In (6) some embodiments, in any of the above methods (1) to (5),
　backwash time of the filtration layer, it is within 30 minutes or 5 minutes.
[0019]
　According to the method of the above (6), by the backwash time of the filtration layer within 30 minutes or 5 minutes, while properly maintaining the activity of microorganisms, suitably removed turbid component deposited on the filtration layer can do.
[0020]
In (6 ') some embodiments, in any of the above methods (1) to (5),
　backwash time of the filtration layer, is within 20 minutes or 10 minutes.
[0021]
　According to the method of (6 '), by the backwash time of the filtration layer within 20 minutes or 10 minutes, while maintaining the activity of the microorganisms even more properly, a turbid component deposited on the filtration layer it can be sufficiently removed.
[0022]
(7) Biological membrane filtration device according to at least some embodiments of the present invention,
　the biological film is carried, a filtration layer that is configured to filter raw water,
　the filtered water from the filtration layer reverse osmosis membrane in comprises a concentrated water obtained by separating and a backwash line for supplying backwash water having 0.6 or more and 1.5 or less of the salt concentration ratio relative to the raw water to the filtration layer,
equipped with a.
[0023]
　According to the biological membrane filtration apparatus of the above (7), the backwash water has a backwash line for supplying the filtration layer, salt to the raw water backwash water supplied from the backwash line containing the concentrated water the concentration ratio is 0.6 or more and 1.5 or less. Thus, even by using a concentrated water with different salt concentration raw water as backwash water, to maintain the activity of the microorganisms to the extent that can sufficiently exhibit the function of biological treatment by microorganisms carried on the filtration layer it can. Thus, the concentrated water can be used for the backwashing and becomes possible to prevent a decrease in production efficiency due to backwashing, also attained a reduction in processing costs.
[0024]
(8) In some embodiments, in the above configuration (7),
　the backwash water has a 0.8 or higher and 1.25 or less of the salt concentration ratio relative to the raw water.
[0025]
　According to the above configuration (8), by using the backwash water having 0.8 or more and 1.25 or less of the salt concentration ratio, can more effectively suppress the reduction in activity of the microorganisms by supplying the concentrated water, It can maintain the biological treatment function by biofilm filtration apparatus more appropriately. Further, when the resume normal operation after backwashing, it is possible to shorten the time until the microorganisms return to normal activity.
[0026]
(9) In some embodiments, in the above configuration (7) or (8),
　the backwash water may further comprise the filtered water before being supplied to the reverse osmosis membrane.
[0027]
　According to the above configuration (9), by mixing the filtered water to backwash water, can be brought close to the salt concentration of the concentrated water to the raw water, the backwash water described in the above (8) or (9) it can be easily adjusted to the range of salt concentration ratio. Incidentally, as compared with the case of using only filtered water as backwash water, in the configuration of (9), for use by mixing with filtered water concentrated water containing almost no turbid fraction, filtration layer due to turbidity min the pollution can be suppressed.
[0028]
(10) In some embodiments, in any of the above Paragraph (7) to (9),
　the backwash water may further comprise the raw water.
[0029]
　According to the above configuration (10), by mixing the raw water to the backwash water can be brought close to the salt concentration of the concentrated water to the raw water, salt backwash water indicated above (7) or (8) it can be easily adjusted to the range of the concentration ratio. Incidentally, as compared with the case of using only the raw water as backwash water, the (10) In the configuration, for use by mixing with raw water concentrated water containing almost no turbid matter, contamination of the filtration layer by turbidity min It can be suppressed.
[0030]
(11) In some embodiments, in any of the above Paragraph (7) to (10),
　said reverse osmosis membrane comprises a first reverse osmosis membrane and a second reverse osmosis membrane, which are connected in series,
　the backwash water includes the first concentrated water that has been separated by the first reverse osmosis membrane, or, at least one of the second concentrated water separated by the second reverse osmosis membrane.
[0031]
　According to the above configuration (11), the raw water by using the first concentrated water or second concentrated water having different salt concentrations as backwash water, it can prevent a reduction in production efficiency due to backwash and processing costs attained reduction of.
　Incidentally, the second concentrated water that has been separated by the second reverse osmosis membrane are the concentrated water obtained by separating the permeate low salt obtained in the first reverse osmosis membrane in the reverse osmosis membrane, typically, salt to the raw water concentration the ratio is less than 1. Therefore, if mixing the second concentrated water of the first concentrated water and low salt concentration of high salt concentration, with a favorable concentrated water from the production efficiency and cost, as shown in the above (7) or (8) it is possible to produce a backwash water salt concentration ratio.
[0032]
(12) In some embodiments, in any of the above Paragraph (7) to (11),
　wherein the biological membrane filtration apparatus, during operation of the biological membrane filtration apparatus, the raw water chemicals not added configured to generate the filtered water and filtered.
[0033]
　According to the above configuration (12), in order to reduce the environmental impact of the addition of chemicals such as flocculation agent to the raw water, even in the biological membrane filtration apparatus that performs Mukusurichu pretreatment, the by providing any of the configurations of (7) to (11), it can be performed and appropriate backwash at a low cost.
[0034]
(13) desalination plant according to at least some embodiments of the present invention,
　a biological membrane filtration device according to any one of (7) to (112),
　located downstream of said biological membrane filtration device , and at least one reverse osmosis unit configured to separate into a permeated water and the concentrated water filtered water by reverse osmosis membrane from the filtration layer
comprising a.
[0035]
　According to desalination plant (13), it can prevent a decrease in production efficiency due to backwashing, and is provided with the reducible biological membrane filtration unit costs, desalinate raw water with high efficiency and low cost process can do.
Effect of the invention
[0036]
　According to at least some embodiments of the present invention, includes a concentrated water, and, to perform backwash of the filtration layer with a backwash water salt concentration ratio relative to the raw water is 0.6 or more and 1.5 since, even with concentrated water with different salt concentration raw water as backwash water, maintaining the activity of the microorganisms to the extent that can sufficiently exhibit the function of biological treatment by microorganisms carried on the filtration layer can. Thus, the concentrated water can be used for the backwashing and becomes possible to prevent a decrease in production efficiency due to backwashing, also attained a reduction in processing costs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037]
FIG. 1 is a configuration diagram of a desalination plant in accordance with the first embodiment.
[2] is a configuration diagram of a desalination plant in accordance with the second embodiment.
3 is a configuration diagram of a desalination plant in accordance with the third embodiment.
4 is a configuration diagram of a desalination plant according to the fourth embodiment.
5 is a graph showing the correlation between survival and salt concentration ratio of microorganisms.
6 is a graph showing the results of culture tests of microorganisms.
DESCRIPTION OF THE INVENTION
[0038]
　Hereinafter, with reference to the accompanying drawings Some embodiments of the present invention will be described. However, the dimensions of the components shown or drawings are described as an embodiment, the material, shape, its relative positions and the like, not intended to limit the scope of the invention thereto, merely illustrative examples Absent.
[0039]
　First, with reference to FIGS. 1 to 4, it will be described a schematic configuration of a desalination plant 1 in accordance with some embodiments. Incidentally, FIGS. 1 to 4 is a block diagram showing a desalination plant 1 according to the first to fourth embodiments.
[0040]
　As illustrated in FIGS. 1 to 4, desalination plant 1 in accordance with some embodiments, a biological membrane filtration device 10 for filtering the raw water (seawater) by filtration layer biofilm is supported, biological membrane filtration At least one reverse osmosis unit 12A located on the downstream side of the apparatus 10 comprises a 12B, the.
　In the example shown, the reverse osmosis membrane apparatus 2 groups (first reverse osmosis membrane device, the second reverse osmosis unit) 12A, although 12B indicates the connected in series, the reverse osmosis unit 12A, configuration of 12B is not limited thereto. For example, it may be configured to only the reverse osmosis membrane apparatus 1 group is provided, the reverse osmosis membrane apparatus having the above 3 groups may be connected to each other in series or in parallel.
[0041]
　Biological filtration system 10 includes one or more layers of filtration layers provided in the filter material container 10a and (10b, 10c). Number of layers of the filtration layer (10b, 10c) is not particularly limited, biological filtration device 10 may comprise any number of layers of the filtration layer (10b, 10c).
　In one embodiment, the biological membrane filtration apparatus 10 has a configuration in which a plurality of filtration layers 10b in the filter material container 10a, 10c are stacked in a vertical direction. For example, the upper filtering layer 10b slag material, carbon material such as anthracite is used as the filter layer 10c of the lower side, granular filtering material such as silica sand is used. These filtering layer 10b, the 10c, are biofilms supported. In other words, microorganisms utilizing organic nutrients in the raw water to the filter material surface to form a biofilm.
　The biofilm filtration device 10, raw water (seawater) is supplied by the pump 14. Raw water introduced from the top of the biofilm filtration device 10, filtration layers 10b, and is discharged from the bottom through the 10c. At that time, the biofilm filtration device 10, a filtration layer 10b, together with suspended solid content of the raw water (suspended particulates) is removed by 10c, dissolved organic matter in the raw water are decomposed and removed by biofilm.
　Filtered water discharged from the biological membrane filtration units 10, after being stored in the filtered water tank 16, the reverse osmosis unit 12A by the pump 18, is supplied to 12B.
　Incidentally, the biological membrane filtration device 10 and the reverse osmosis unit 12A, between the 12B, for example, other filtration apparatus may be provided, such as ultrafiltration membrane or microfiltration membrane.
[0042]
　The first reverse osmosis unit 12A and the second reverse osmosis unit 12B is configured to separate into a permeate and concentrate filtration layer 10b, and the filtered water from 10c by reverse osmosis membrane.
　In the illustrated example, the filtered water is first supplied to the first reverse osmosis unit 12A, is separated into the first concentrated water by reverse osmosis membrane and the first permeate. Thus, salt concentration ratio of the raw water first concentrated water becomes larger than 1, the salt concentration ratio of the raw water first permeate is smaller than 1.
　First concentrated water that has been separated by the first reverse osmosis membrane device 12A is stored in the first concentrated water tank 20A, a first permeate separated by the first reverse osmosis membrane device 12A in the second reverse osmosis unit 12B It is supplied.
　First transmitting water supplied to the second reverse osmosis unit 12B is separated by a reverse osmosis membrane and the second concentrated water and a second permeate. The second concentrated water, since those relatively salt concentration ratio is smaller first permeate is separated by reverse osmosis membrane, is also salt to the raw water concentration ratio smaller than 1. Salt concentration ratio of the raw water second permeate is less than 1, has a very low salt concentration. The second concentrated water is stored in the second concentrated water tank 20B.
　The second permeate thus generated is subjected to a post-treatment, it is fed to the usage destination as product water.
[0043]
　Incidentally, in the above embodiment, as an example, a case has been described in which the biological membrane filtration apparatus 10 is applied to the desalination plant 1, the Apply biofilm filtration apparatus 10 according to this embodiment the desalination plant 1 the present invention is not limited. That is, the biological membrane filtration apparatus 10 of this embodiment is disposed upstream of the at least one reverse osmosis unit, the Apply particularly if configured to filter raw water by filtration layer biofilm is supported but it is not limited.
　In this case, the raw water and is a water containing salt (e.g. salt), for example, sea water, underground water, river, lake water, or may be a wastewater treatment water, or industrial wastewater or the like. According to the above method, seawater or desalination, or to obtain a recycled water to purification of sewage treated water and industrial waste water, or can generate clean water from rivers and lakes water.
[0044]
　It will now be described in detail with biological membrane filtration apparatus 10 described above for its cleaning method.
　In some embodiments, the biological membrane filtration apparatus 10 includes a filtration layer 10b, concentrated water obtained by separating the filtered water from 10c in the reverse osmosis membrane, and 0.6 or more with respect to the raw water and 1 filtration layer 10b to backwash water with .5 following salts concentration ratio, further comprising a backwash line 30 to be supplied to 10c. For example, backwash line 30 is adapted to supply the backwash water from the bottom of the biofilm filtration device 10.
　Concentrated water is used as backwash water, it comprises at least one of the first concentrated water or second concentrated water.
　Then, the biofilm filtration device 10, the backwash water filtration layer 10b with a 10c backwashing to remove the turbid component deposited filter layer 10b, to 10c (especially the upper side of the filtration layer 10b).
[0045]
　According to this method, a filtration layer 10b, when washing 10c, filtration layer 10b, reverse osmosis disposed downstream of 10c membrane device 12A, concentrated water obtained by separating at 12B (first concentrated water or second concentrated so that use at least one containing) water. Normally, the concentrated water because often discarded, the large amount of pull out it is not necessary to use the water in the generating process of product water by using concentrated water as backwash water, can avoid a decrease in production efficiency . Moreover, since it is possible to effectively use the water in the system, greater reduction in cost as compared with the case of raising the backwash water from the outside.
[0046]
　Meanwhile, the concentrated water that has been separated by reverse osmosis membrane, the salt concentration is different from the raw water. For example, in the case of the first reverse osmosis unit 12A, the first concentrated water separated by the reverse osmosis membrane salt concentration than the raw water becomes higher filtrate biofilm filtration device 10 is supplied. On the other hand, the second concentrated water that has been separated by the second reverse osmosis unit 12B has a salt concentration than the raw water for the permeate is obtained by separation obtained in the first reverse osmosis unit 12A of the upstream side becomes lower. Thus, when the raw water and utilizes concentrated water which the salt concentration varies as backwash water, the filtration layer 10b, supported microorganisms surrounding salt concentration environment changes to 10c, the liquid in the cell and out of the microorganisms by osmotic pressure difference movement there is a possibility that microbial activity is significantly reduced going in.
[0047]
　Accordingly, the present inventors have intensively studied and, as a result, have found a correlation between the activity and salt concentration of microorganisms in the raw water as shown in FIG. That is, the salt concentration ratio relative to the raw water under 0.6 or more and 1.5 or less environment, I was able to be properly maintained microbial activity. Incidentally, FIG. 5 is a graph showing the correlation between the survival of microorganisms (activated) with the salt concentration ratio.
　As shown in FIG. 5, in and under 1.5 following environmental salt concentration ratio of 0.6 or more for the raw water, the survival rate of microorganisms is maintained at 50% or more approximately. When considering the general backwash intervals and the growth rate of the microorganisms, if substantially more than 50% survival rate of microorganisms, the viability of the microorganisms before the next backwashing time sufficiently recovered, including concentrated water can be avoided microorganisms continues to decrease by backwashing using a backwashing water.
[0048]
　The present inventors have conducted culture tests of microorganisms in sea water, based on the results of the test (see FIG. 6), when the survival rate of microorganisms is more than about 50%, the backwash water containing concentrated water even if the backwash was used to obtain a finding that continue to maintain the activity of the microorganisms. 6 is a graph showing the relationship between the culture time and the SS concentration (concentration of suspended solids in the seawater).
　In general growth rate of the microorganisms is defined by the following equation.
　　mu / 2.303 × (t-t 0 ) = log 10 Z-log 10 Z 0 　where, mu: specific growth rate [h -1 ], t: time, Z: a cell mass / ml. 　The doubling time of the cell volume is doubled (g) is defined by the following equation. 　　= ln2 mu / g g = ln2 　　/ mu 　Using these equations, from the test results shown in FIG. 6, the doubling time of the microorganisms in sea water is about 4 hours. On the other hand, typical backwash interval is at least 4 hours, that the survival rate of the microorganism is a microorganism until the next backwashing if about 50% or more is sufficiently recovered revealed.

[0049]
　Therefore, according to the above method, by backwashing the filtration layer 10b, and 10c by using the backwash water having 0.6 or more and 1.5 or less of the salt concentration ratio relative to the raw water, a filtration layer 10b, 10c it is possible to maintain the activity of microorganisms to such an extent that by the supported microorganisms can sufficiently exhibit the function of biological treatment to. Therefore, it becomes possible to effectively utilize the advantageous concentrated water from the production efficiency and cost, as described above as the backwash water.
[0050]
　Further, backwash water may have a 0.8 or more and 1.25 or less of the salt concentration ratio relative to the raw water.
　According to this, reduction in the activity of microorganisms by supplying the concentrated water can more effectively suppressed, thereby maintaining the biological treatment function by biofilm filtration device 10 more properly. Further, when the resume normal operation after backwashing, it is possible to shorten the time until the microorganisms return to normal activity.
[0051]
　Filtration layer 10b, the backwash time 10c, may be within 30 minutes or 5 minutes. Or, filtration layer 10b, backwashing time of 10c, may be within 20 minutes or 10 minutes.
　According to this, by the backwash time of the filtration layer within 30 minutes or 5 minutes, while properly maintaining the activity of the microorganisms, the filtration layer 10b, to properly remove the turbid component deposited on 10c can.
[0052]
　Biofilm filtration apparatus 10, in operation, may be configured to generate a filtered water filtered raw water chemicals such as flocculants have not been added. In other words, biofilm filtration device 10 may be configured to perform Mukusuri Note pretreatment.
　According to this, in order to reduce the environmental impact of the addition of chemicals such as flocculation agent to the raw water, even in the biological membrane filtration apparatus 10 to perform the Mukusurichu pretreatment comprises the above configuration by, it is possible to perform and suitable backwashing at a low cost.
[0053]
　Next, a specific configuration of the biological membrane filtration apparatus 10 according to each embodiment.
[0054]
　Figure 1 is a block diagram showing a biofilm filtration apparatus 10 according to the first embodiment.
　As shown in the figure, the biological membrane filtration apparatus 10 according to the first embodiment, the backwash water containing the first concentrated water that has been separated by the first reverse osmosis unit 12A, filtration layers 10b, 10c backwash configured to perform.
[0055]
　The first reverse osmosis membrane device 12, filtration layers 10b backwash water containing the first concentrated water is provided with a backwash line 30 for supplying the 10c, the backwash water supplied from the backwash line 30 It has a salt concentration of 0.6 or more and 1.5 or less, or 0.8 or more and 1.25 or less for the raw water.
　The backwash water tank 32 to the backwash water is stored, the first concentrated water from the first concentrated water tank 20A is adapted to be supplied. First supply amount of concentrated water from the first concentrated water tank 20A to the backwash water tank 32 is controlled by a valve 34.
　The backwash water stored in the backwash water tank 32 (first concentrated water) is at backwash biofilm filtration device 10, the filtration layer 10b through the backwash water line 30 is supplied to 10c.
[0056]
　Accordingly, even using the first concentrated water having a different salt concentration raw water as backwash water, to maintain the activity of the microorganisms to the extent that can sufficiently exhibit the function of biological treatment by microorganisms carried on the filtration layer be able to. Therefore, it is possible to use the first concentrated water backwash, can prevent a reduction in production efficiency due to backwashing, also attained a reduction in processing costs.
　In the illustrated example, the case of using the first concentrated water as backwash water may be used a second concentrated water as backwash water.
[0057]
　Figure 2 is a block diagram showing a biofilm filtration apparatus 10 according to the second embodiment.
　As shown in the figure, the biological membrane filtration apparatus 10 according to the second embodiment, a first concentrated water that has been separated by the first reverse osmosis unit 12A, and a filtered water filtered by the biofilm filtration device 10 the backwash water containing configured to perform backwashing of filtration layers 10b, 10c.
[0058]
　The first reverse osmosis membrane device 12, filtration layers 10b backwash water containing first retentate and filtrate has a backwash line 30 for supplying the 10c, reverse supplied from the backwash line 30 the salt concentration ratio of the raw water wash water is set to 0.6 or more and 1.5 or less, or 0.8 or more and 1.25 or less.
　The backwash water tank 32 to the backwash water is stored, the first concentrated water from the first concentrated water tank 20A is adapted to be supplied. First supply amount of concentrated water from the first concentrated water tank 20A to the backwash water tank 32 is controlled by a valve 34. Moreover, the backwash water tank 32 also are supplied filtered water from the filter water tank 16. The supply amount of filtered water from the filter water tank 16 into the backwash water tank 32 is adjusted by a valve 36. By controlling these valves 34 and 36, the salt concentration ratio of backwash water may be adjusted to the above range.
　The backwash water stored in the backwash water tank 32 (mixed water of the first concentrated water and filtered water) is biofilm during backwashing of the filter 10, the filtration layer 10b through the backwash water line, 10c It is supplied to.
　In the illustrated example, the case of using the first concentrated water as backwash water may be used a second concentrated water as backwash water.
[0059]
　According to this, it is possible to use a first concentrated water backwash, can prevent a reduction in production efficiency due to backwashing, also attained a reduction in processing costs.
　Further, by mixing the filtered water to backwash water, can be brought close to the salt concentration of the concentrated water to the raw water, it is possible to easily adjust the backwash water in the range of salt concentration ratios described above. Incidentally, as compared with the case of using only filtered water as backwash water, by utilizing mixed with filtered water concentrated water containing almost no turbid component can be suppressed the contamination of the filtration layer by turbidity min.
[0060]
　Figure 3 is a block diagram showing a biofilm filtration apparatus 10 according to the third embodiment.
　As shown in the figure, the biological membrane filtration apparatus 10 according to the second embodiment, a first concentrated water that has been separated by the first reverse osmosis unit 12A, the backwash water containing raw Prefecture, filtration layer 10b, configured to perform backwash of 10c.
[0061]
　The first reverse osmosis membrane device 12, backwash water filtration layer 10b comprising a first concentrated water and raw water, provided with a backwash line 30 for supplying the 10c, supplied from the backwash line 30 backwashing the salt concentration ratio raw water 0.6 or more and 1.5 or less, or is set to 0.8 or more and 1.25 or less.
　The backwash water tank 32 to the backwash water is stored, the first concentrated water from the first concentrated water tank 20A is adapted to be supplied. First supply amount of concentrated water from the first concentrated water tank 20A to the backwash water tank 32 is controlled by a valve 34. Moreover, the backwash water tank 32, also the raw water from the raw water tank (not shown) are supplied. The supply amount of the raw water to the backwash water tank 32 is controlled by a valve 38. By controlling these valves 34 and 38, the salt concentration ratio of backwash water may be adjusted to the above range.
　The backwash water stored in the backwash water tank 32 (first concentrated water and raw water mixed water), at the time of backwashing biofilm filtration device 10, the filtration layer 10b through the backwash water line, and 10c It is supplied.
　In the illustrated example, the case of using the first concentrated water as backwash water may be used a second concentrated water as backwash water.
[0062]
　According to this, it is possible to use a first concentrated water backwash, can prevent a reduction in production efficiency due to backwashing, also attained a reduction in processing costs.
　Further, by mixing the raw water to the backwash water can be brought close to the salt concentration of the concentrated water to the raw water, it is possible to easily adjust the backwash water in the range of salt concentration ratios described above. Incidentally, as compared with the case of using only filtered water as backwash water, by utilizing mixed with filtered water concentrated water containing almost no turbid component can be suppressed the contamination of the filtration layer by turbidity min.
[0063]
　Figure 4 is a block diagram showing a biofilm filtration apparatus 10 according to the fourth embodiment.
　As shown in the figure, the biological membrane filtration apparatus 10 according to the fourth embodiment, a first concentrated water that has been separated by the first reverse osmosis unit 12A, first separated by the second reverse osmosis unit 12B 2 the backwash water containing the concentrated water is configured to perform backwashing of filtration layers 10b, 10c.
[0064]
　The first reverse osmosis membrane device 12, filtration layers 10b backwash water containing first retentate and a second concentrated water is provided with a backwash line 30 for supplying the 10c, supplied from the backwash line 30 the salt concentration ratio of the raw water backwash water that is set to 0.6 or more and 1.5 or less, or 0.8 or more and 1.25 or less.
　The backwash water tank 32 to the backwash water is stored, the first concentrated water from the first concentrated water tank 20A is adapted to be supplied. First supply amount of concentrated water from the first concentrated water tank 20A to the backwash water tank 32 is controlled by a valve 34. Moreover, the backwash water tank 32 is a second concentrated water from the second concentrated water tank 20B is also designed to be supplied. The second supply amount of concentrated water from the second concentrated water tank 20B to the backwash water tank 32 is controlled by a valve 40. By controlling these valves 34 and 40, the salt concentration ratio of backwash water may be adjusted to the above range.
　The backwash water stored in the backwash water tank 32 (mixed water of the first concentrated water and the second concentrated water) is at backwash biofilm filtration device 10, the filtration layer 10b through the backwash water line , it is supplied to 10c.
[0065]
　According to this, it is possible to use a first concentrate and the second concentrate to the backwash, can prevent a reduction in production efficiency due to backwashing, also attained a reduction in processing costs.
　Further, by mixing the second concentrated water of the first concentrated water and low salt concentration of high salt concentration, with a favorable concentrated water from the production efficiency and cost, generating a backwash water above salt concentration ratio can do.
[0066]
　In the first to fourth embodiments described above, relative to the concentrate may be adjusted in the aforementioned range of salt concentration ratio of the raw water backwash water by mixing the water supplied from the outside of the system .
[0067]
　As described above, at least according to some embodiments, it includes a concentrated water, and, the filtration layer 10b with backwash water the salt concentration ratio relative to the raw water is 0.6 or more and 1.5 of the present invention , since to perform the backwash of 10c, be a concentrated water with different salt concentration raw water as backwash water, sufficiently exhibited filtration layer 10b, by microorganisms carried in 10c the function of biological treatment it is possible to maintain the activity of microorganisms to such an extent that may be. Thus, the concentrated water can be used for the backwashing and becomes possible to prevent a decrease in production efficiency due to backwashing, also attained a reduction in processing costs.
[0068]
　The present invention is not limited to the embodiments described above, the form and adding a modification to the embodiments described above, also includes appropriate combination form these forms.
[0069]
　For example, representation of the things such as "the same", "equal to" and "homogeneous" is equal condition, not only represents a strictly equal conditions, tolerance, or varying degrees of the same functions can be obtained It is intended to refer also existing set of conditions.
　Further, "comprising", "including" one component, or, the expression "comprising" does not exclusive representation exclude the presence of other elements.
DESCRIPTION OF SYMBOLS
[0070]
1 desalination plant
10 biological membrane filtration units
10a filtering medium container
10b filtration layer
10c filtration layer
12A first reverse osmosis unit
12B second reverse osmosis unit
16 filtration water tank
20A first concentrated water tank
20B second concentrated water tank
30 opposite wash line
32 backwash water tank

The scope of the claims
[Requested item 1]
A filtration layer cleaning method of the biological membrane filtration apparatus for filtering raw water by filtration layer biofilm is supported,
　it comprises a concentrated water obtained by separating the filtered water from the filtration layer in the reverse osmosis membrane, and, filtration layer cleaning method, wherein the using the backwash water having 0.6 or more and 1.5 or less of the salt concentration ratio relative to the raw water to backwash the filtration layer.
[Requested item 2]
　The backwash water is filtered layer cleaning method according to claim 1, characterized in that it comprises 0.8 or more and 1.25 or less of the salt concentration ratio relative to the raw water.
[Requested item 3]
　The backwash water is filtered layer cleaning method according to claim 1 or 2, further comprising the filtered water before being supplied to the reverse osmosis membrane.
[Requested item 4]
　The backwash water is filtered layer cleaning method according to any one of claims 1 to 3, further comprising the raw water.
[Requested item 5]
　The reverse osmosis membrane comprises a first reverse osmosis membrane and a second reverse osmosis membrane connected in series,
　the backwash water is first concentrated water separated by the first reverse osmosis membrane, or the first filtration layer cleaning method according to any one of claims 1 to 4, characterized in that it comprises at least one of the second concentrated water separated by second reverse osmosis membrane.
[Requested item 6]
　The backwash time of the filtration layer, the filtration layer cleaning method according to any one of claims 1 to 5, characterized in that within 30 minutes or 5 minutes.
[Requested item 7]
　Biofilm is carried, a filtration layer that is configured to filter raw water,
　wherein the concentrated water obtained by separating the filtered water from the filtration layer in reverse osmosis, and, 0 to the raw water. a backwash line for supplying backwash water to the filtration layer having 6 or more and 1.5 or less in salt concentration ratio
biofilm filtration apparatus comprising: a.
[Requested item 8]
　The backwash water, biofilm filtration apparatus according to claim 7, characterized in that it comprises 0.8 or more and 1.25 or less of the salt concentration ratio relative to the raw water.
[Requested item 9]
　The backwash water, biofilm filtration apparatus according to claim 7 or 8, further comprising the filtered water before being supplied to the reverse osmosis membrane.
[Requested item 10]
　The backwash water, biofilm filtration apparatus according to any one of claims 7 to 9, further comprising the raw water.
[Requested item 11]
　The reverse osmosis membrane comprises a first reverse osmosis membrane and a second reverse osmosis membrane connected in series,
　the backwash water is first concentrated water separated by the first reverse osmosis membrane, or the first biological membrane filtration device according to any one of claims 7 to 10, characterized in that it comprises a second at least one of concentrated water separated by second reverse osmosis membrane.
[Requested item 12]
　The biofilm filtration apparatus, the organism during operation of the membrane filtration device, and filtering the raw water chemicals are not added claims 7 to 11, characterized in that it is configured to generate the filtered water any biological membrane filtration device according to one paragraph.
[Requested item 13]
　And the biological membrane filtration device according to any one of claims 7 to 12,
　located downstream of said biological membrane filtration apparatus, and the concentrated water filtered water from the filtration layer by reverse osmosis membrane and permeated water and at least one reverse osmosis unit configured to separate the
desalination plant, characterized in that it comprises a.