JP5822623B2 - Seawater osmotic filtration method and osmotic water intake unit - Google Patents

Description

  The present invention relates to a filtration method for taking seawater permeating through a sand layer on the seabed, and organisms or suspensions deposited on the surface layer of the sand layer and incorporated into an intermediate layer in order to carry out this filtration method. The present invention relates to an osmotic water intake unit having a reverse cleaning pipe that removes substances and prevents clogging.

  As a method for taking seawater, at present, as shown in FIG. 14, for example, a direct water intake method in which seawater is taken from a water intake 1 provided on the seabed through a water conduit 2 is widely used. In addition, 3 in FIG. 14 is a pump for taking in seawater, 4 is a reverse osmosis membrane apparatus.

  However, the direct water intake method collects all waste, suspended matter, living organisms, etc. at the same time as seawater, so when the jellyfish or red tide is abnormal, when oil spills occur, or when turbidity increases due to high waves, the water intake is stopped. You may have to. In addition, because marine organisms such as barnacles and mussels adhere to intakes and conduits regularly, pipes that take into account the amount of biofouling in all pipelines, regular cleaning, addition of anti-adhesion chemicals (such as chlorine) It is necessary to increase the diameter. Furthermore, when processing the collected seawater with a reverse osmosis membrane, a sand filtration facility for filtering the seawater to which the flocculant has been added is necessary, and thus a facility for treating the sludge accumulated in the sand filtration facility is necessary.

  Therefore, in recent years, as a pretreatment of the seawater to be taken in, without using chemicals such as a flocculant, the seawater penetrating the seabed sand layer (hereinafter referred to as sand filtration layer) 5 as shown in FIG. The indirect water intake method is drawing attention.

  In this indirect water intake method, the seabed is excavated offshore several hundred meters from the shoreline and a depth of several tens of meters, and the excavation part is composed of supporting gravel layers 5a and 5b and filtered sand 5c as shown in FIG. This is a method of taking in the seawater that has been filtered and permeated and purified from the intake pipe 6 installed in the supporting gravel layer 5a by refilling the bottom of the seabed again while forming the sand filtration layer 5. In the case of this indirect water intake method, the problem of the direct water intake method does not occur at all. However, due to the high initial cost and the problem of a decrease in water intake due to clogging on the permeation surface, the spread of diffusion is delayed.

  Therefore, in such an osmotic water intake method, clogging of the sand filtration layer at the bottom of the seawater taking water can be reduced as much as possible, and suspended matter accumulated on the surface of the sand filtration layer can be saved without much trouble. Patent Document 1 proposes a method that can be removed and can ensure stable water intake.

  In the seepage water intake method proposed in Patent Document 1, the seawater permeation flow rate expressed in the sand filtration layer on the seabed is 1 to 8 m / day, and the water depth of the sand filtration layer is the surface layer portion of the sand filtration layer. It is characterized by being deeper than the full movement limit water depth where sand moves 50 cm or more and shallower than the surface layer movement limit water depth where sand moves 1 cm or more.

  However, since the osmotic water intake method proposed in Patent Document 1 has a very slow filtration rate of 1 to 8 m / day for the seawater osmotic water intake, in order to take a large amount of seawater in a short period of time. It requires a vast area and the construction scale becomes large (Problem 1).

  In addition, the infiltration method proposed in Patent Document 1 is installed in a sea area where optimum seawater flow is promoted in order to prevent clogging of the sand filtration layer due to silt deposited on the surface. Necessary and limited to places where seawater flows due to waves (Problem 2).

  Therefore, in order to solve the above-mentioned problem 1, the applicant significantly reduced the required infiltration area by increasing the seawater infiltration speed, and a seawater infiltration filtration method that can significantly reduce the construction scale. Proposed. However, the upper limit is 400 m / day or less as a practical speed that can be adopted.

  Further, in order to solve the above-mentioned problem 2, the applicant has proposed an osmotic filtration method for seawater in which clogging is prevented by artificially removing organisms or suspended substances taken into the surface of the sand filtration layer. Furthermore, in order to remove the suspended substances and the like taken into the surface layer of the sand filtration layer, for example, a clogging prevention device in which any one of a mechanical type, an air type and a jet water type device is installed on the surface of the sand filtration layer. Proposed. As a result, the sand filtration layer can be installed, for example, in a calm sea area where there is no tidal current or wave water particle velocity.

  That is, according to the seawater osmotic filtration method proposed by the applicant, the seawater permeation rate is as high as possible at 400 m / day or less, so that the amount of water intake in a short period of time becomes large, and water intake is in comparison with the conventional method. The area can be reduced. In addition, when a clogging prevention device is installed on the surface of the sand filtration layer, it is not necessary to install it in a sea area where optimum seawater flow is promoted, and water can be taken near the seawater desalination plant. Therefore, the construction scale and the intake facility scale can be remarkably reduced, and accordingly, the influence during construction on the surrounding environment can be alleviated.

  However, the method of using seawater flow or the method of ejecting water from the clogging prevention device installed on the surface of the sand filtration layer can only remove suspended substances deposited on the surface of the sand filtration layer. In addition, it is impossible to remove organisms or suspended substances taken up in the intermediate layer deeper than the surface layer of the sand filtration layer. In particular, when the seawater permeation rate is as high as possible at 400 m / day or less, clogging also tends to proceed in the intermediate layer of the sand filtration layer, and the frequency of clogging increases. For this reason, the seawater infiltration rate may be reduced only by removing suspended substances and the like deposited on the surface of the sand filtration layer.

  Further, for example, in the seepage water intake method of Patent Document 1, a support gravel layer 5a is formed in an excavation part excavating the seabed, and an intake pipe 6 is buried, and a support gravel layer 5b and a filtration sand 5c are formed above the support gravel layer 5a. Since all the work to refill the same seabed while forming the sea is done at the seafloor site, the installation work becomes large-scale. In addition, when a problem occurs in a part of the intake pipe 6 after the start of operation, it is necessary to excavate the bottom of the sea again to repair the failed part of the intake pipe 6.

Japanese Patent No. 3899788

  The problem to be solved by the present invention is that the conventional osmotic water intake method is a seawater flow and washing by a clogging prevention device installed on the surface of the sand filtration layer, so that the organism taken into the intermediate layer of the sand filtration layer Alternatively, suspended solids cannot be removed, and the seawater infiltration rate may be reduced. In addition, the conventional seepage water intake method requires a large scale of installation work, and if a malfunction occurs in part of the intake piping after the start of operation, it is necessary to excavate the bottom of the sea to repair the faulty part. It is a bad point.

  The present invention solves the above problems and can remove not only organisms or suspended matter deposited on the surface of the sand filtration layer but also organisms or suspended matter taken up in the intermediate layer, and is installed on the seabed. The purpose of the present invention is to provide a seawater osmotic filtration method and an osmotic intake unit that can reduce the construction scale and facilitate maintenance.

The seawater osmotic filtration method of the present invention,
Comprising a housing, the interior of the housing to have a gravel layer and sand, embedding the intake pipe in the gravel layer to form a depth of sand filtration layer, for forming the intermediate layer and the surface layer of the sand filtration layer An infiltration water intake unit in which a reverse cleaning pipe is embedded in the sand layer is formed in advance, and the sand filtration layer is formed by combining a required number of the infiltration water intake units at an installation location on the seabed. Seawater osmotic filtration method of introducing seawater that has naturally permeated into the intake pipe and taking in seawater,
The seawater penetration speed is 400 m / day or less,
The organism or suspended matter taken into the intermediate layer is stirred by jetting water or air from the backwash tube, and rolled up with the organism or suspended matter deposited on the surface layer above the surface layer. The main feature is to prevent clogging of the sand filter layer.

  According to the present invention described above, the organism or suspended substance taken into the intermediate layer of the sand filtration layer is agitated by water or air ejected from the backwash pipe, and sand filtered together with the suspended substance present in the surface layer. Rolled up above the layer. Suspended substances and the like wound in the sea above the sand filtration layer are diffused to the outside of the sand filtration layer by seawater flow caused by tidal currents and waves.

  Moreover, in said invention, a sand filtration layer can be easily formed by combining the osmosis | permeation intake unit formed beforehand in the installation place of a seabed. In addition, if a malfunction occurs in a part of the intake pipe after the start of operation, it is not necessary to excavate the seabed and repair the failed part. it can.

In the present invention, when installing the sand filtration layer in a calm sea area where there is little seawater flow due to tidal currents and waves,
Preliminarily forming an infiltration water intake unit further installed with a water absorption pipe above the sand layer, and combining the required number of the infiltration water intake units at the installation location on the sea floor to form the sand filtration layer,
The organism or suspended matter taken into the intermediate layer is stirred by jetting water or air from the backwash tube, and wound up with the organism or suspended matter deposited on the surface layer above the surface layer, What is necessary is just to prevent clogging of the said sand filtration layer by suck | inhaling the stirring water containing the organism or the suspended solid from a water absorption pipe | tube.

  In the present invention, clogging is prevented by removing organisms or suspended solids accumulated in the surface layer of the sand filtration layer and taken into the intermediate layer, and the seawater permeation rate is maintained as high as possible at 400 m / day or less. High-speed filtration can be carried out continuously. In addition, when the sand filtration layer is formed by combining the osmotic intake unit of the present invention, the construction scale at the time of installation is remarkably reduced, and after the start of operation, the osmotic intake unit including the failed part is separated in units. Since it can be exchanged, maintenance becomes easy.

It is the figure which showed an example at the time of making the osmotic intake unit used for the osmotic filtration method of seawater of the present invention into the size which can be loaded in a truck, (a) is a figure showing the section in the AA 'line of a top view, (B) is the figure which showed the cross section in the BB 'line | wire of a top view, (c) is the figure seen from the direction of the plane. It is the figure which looked at each piping of the seepage water intake unit of the present invention from the direction of a plane, (a) is a top view of a water absorption pipe, (b) is a top view of a backwash pipe, (c) is a top view of a water intake pipe is there. It is the figure which showed the example of arrangement | positioning of the intake piping of the osmotic intake unit of this invention, (a) is the figure which showed the example of arrangement | positioning in case 5 blocks of intake piping are connected to a bus type, (b) is water intake of 5 blocks It is the figure which showed the example of arrangement | positioning in the case of connecting piping to a water collection pump pit, respectively. It is the figure which showed the example of a connection of the reverse washing pipe | tube of the osmosis | permeation water intake unit of this invention, (a) is the figure which showed the example of a connection with the pump in the case of using the structure which ejects water, (b) ejects air. It is the figure which showed the example of a connection with the air compressor in the case of using a structure. It is the figure which showed the example of the dimension and arrangement | positioning of the osmosis | permeation water intake unit of this invention, (a) is a figure which showed an example in case water intake amount is 100,000 t / day, (b) and (c) are water intake amount. It is the figure which showed an example in the case of setting it to 400,000 t / day, and another example. It is the figure which showed the Example of the osmosis | permeation intake unit of this invention using a drain pipe, (a) is the figure which showed the cross section in the AA 'line of a top view, (b) is BB' of a top view. The figure which showed the cross section in a line, (c) is the figure seen from the direction of the plane. It is the figure which showed the other Example of the seepage water intake unit of this invention using a drain pipe, (a) is the figure which looked at the reverse washing pipe from the plane direction, (b) is a cross section of the branch pipe of a drain pipe It is the schematic seen from the direction of and is a figure explaining the jet angle of the water jetted from a drain pipe. It is the figure which showed an example of arrangement | positioning of the height direction of the water intake piping and the backwashing pipe | tube in the unit of the osmosis | permeation water intake unit of this invention. It is the figure which showed the Example of the osmosis | permeation water intake unit of this invention which does not provide a water absorption pipe or a drain pipe, (a) is the figure which showed the cross section in the AA 'line of a top view, (b) is B of a top view The figure which showed the cross section in the -B 'line, (c) is the figure seen from the direction of the plane. It is an experimental flowchart of the osmotic filtration method of seawater. It is the figure which showed an example of the experimental result, (a) is the figure which showed the data of turbidity, (b) is the figure which showed the data of the silt density | concentration index (SDI). It is the figure which showed the relationship between the elapsed time of complete occlusion and standard occlusion, and pressure loss. It is an image figure of the osmosis filtration method of seawater of the present invention. It is a schematic explanatory drawing of the conventional direct seawater intake method. It is a schematic explanatory drawing of the seafloor seepage seawater intake method. It is a schematic block diagram of a seabed penetration part.

  The present invention aims to prevent clogging of the sand filtration layer in an intermediate layer of the sand filtration layer in order to continuously carry out high-speed filtration with the seawater permeation rate maintained as high as possible at 400 m / day or less. By agitating the taken-in organisms or suspended matter with water or air ejected from the backwash tube and rolling them up into the sea above the sand filtration layer together with the organisms or suspended matter deposited on the surface of the sand filtration layer It was realized.

  Water absorption provided above the sand layer so that clogging substances contained in organisms or suspended matter rolled up above the sand filter layer do not adversely affect the environment surrounding the sand filter layer. It is desirable to collect by a tube.

  However, in sea areas where the need for environmental protection is relatively low, organisms rolled up above the sand filtration layer or substances that cause clogging contained in suspended matter may be discharged around the sand filtration layer. Sometimes allowed. When a sand filtration layer is installed in such a sea area, one of the following configurations may be selected according to the flow rate of seawater.

  That is, when installing in a sea area where the flow rate of seawater is slow, a configuration is adopted in which substances that cause clogging are artificially discharged by a drain pipe provided above the sand layer. On the other hand, when installing in a sea area where the flow rate of seawater is high, substances that cause clogging can be diffused by seawater flow due to tidal currents or waves, and therefore a configuration without a water absorption pipe or a drain pipe may be adopted.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to FIGS.
FIG. 1 is a diagram showing an example of an osmotic intake unit 11 used in the seawater osmotic filtration method of the present invention.

  1 (a) and 1 (b), reference numeral 12 denotes a gravel layer for forming a deep layer of a sand filtration layer on the sea floor, comprising a main pipe 12a and a plurality of branch pipes 12b branched in a direction intersecting the main pipe 12a. 13 shows a water intake pipe embedded in the tank. In the sand layer 15 for forming the intermediate layers 15b and 15c and the surface layer 15a of the sand filtration layer, a backwash pipe 14 including a main pipe 14a and a plurality of branch pipes 14b branched in a direction intersecting the main pipe 14a is embedded. ing.

  In FIG.1 (c), 16 has shown the water absorption pipe | tube which consists of the main pipe | tube 16a and the some branch pipe 16b. As shown in FIG. 1A, the main pipe 16a is installed between the side surfaces 17a and 17c of the housing 17 facing each other. Further, the ends of the plurality of branch pipes 16b branched in the direction intersecting with the main pipe 16a are supported by side surfaces 17b and 17d of the housing 17, as shown in FIG. By doing in this way, the water absorption pipe | tube 16 is installed above the sand layer 15 in the state which left the fixed space | interval between the surfaces of the sand layer 15. FIG.

  The osmotic water intake unit 11 of the present embodiment is, for example, an intermediate position in the height direction of a gravel layer 13 having a height of 0.5 m inside a casing 17 having a size of 10 m long × 2.5 m wide × 2.5 m high. The sand layer with a certain interval between the intake pipe 12 embedded in the surface, the backwash pipe 14 embedded in the upper part of the height direction of the sand layer 15 having a height of 2.0 m, and the surface of the sand layer 15. The water absorption pipe 16 installed above 15 is accommodated. Therefore, the permeate water intake unit 11 can be transported by a truck having a loading platform capable of loading the luggage of the above size, and transportation on land becomes easy. For the housing 17, an optimal material can be selected from, for example, FRP, concrete, metal, and the like according to the water quality of the sea area where the sand filtration layer is installed, the components of substances contained in the seawater, and the like.

  FIG. 2 shows an example of each pipe of the osmotic water intake unit 11 and is a view of each pipe seen from the plane direction. The lower side of the page shows the land side where the seawater desalination plant is installed, and the upper side of the page shows the ocean side.

  As shown in FIG. 2A, the branch pipe 16b of the water absorption pipe 16 is provided with a large number of jet holes 16ba and 16bb arranged on the land side and the ocean side. In this embodiment, both the land-side suction hole 16ba and the ocean-side suction hole 16bb are opened in parallel with the longitudinal direction of the main pipe 16a, and when installed on site, the ejection angle of the ejection holes is parallel to the horizontal plane. It is trying to become the direction. The land side of the main pipe 16a is connected to a water collection pump of a seawater desalination plant. Suspended water sucked from the suction holes 16ba and 16bb is collected from the branch pipes 16b to the main pipe 16 and collected by the seawater desalination plant.

  As shown in FIG. 2B, a large number of ejection holes 14ba are arranged in the branch pipe 14b of the reverse cleaning pipe 14 at a position on the top side when installed on the site. In the present embodiment, the ejection angle of the ejection hole 14ba is set to be 90 degrees with respect to the horizontal plane. The land side of the main pipe 14a is connected to a water supply pump or an air compressor of a seawater desalination plant. Water or air supplied from the main pipe 14a to each branch pipe 14b is ejected from the ejection hole 14ba in the vertical direction toward the top. In the present embodiment, as an example, the ejection hole 14ba is provided in the direction toward the top when installed on site, but the ejection hole 14ba of the backwash pipe 14 is directed downward, for example, when installed on site. You may comprise.

  The branch pipe 12b of the intake pipe 12 is provided with a large number of intake holes throughout the surface (not shown in FIG. 2C). The land side of the main pipe 12a is connected to a water collection pump of a seawater desalination plant. Seawater that has naturally permeated through the sand filtration layer is introduced into the branch pipe 12b through the water intake hole, and taken into the seawater desalination plant through the main pipe 12a.

  In the seawater osmotic filtration method of the present invention, the osmotic intake unit 11 as described above is previously formed on land, and a sand filtration layer is formed by combining the required number of osmotic intake units 11 at the installation location of the seabed. A seawater osmotic filtration method in which seawater that has naturally permeated through the sand filtration layer from the sea is introduced into the water pipe 12 to take in seawater, and the seawater permeation rate is 400 m / day or less. . And among the intermediate layers 15b and 15c of the sand filtration layer, the organisms or suspended substances taken into the intermediate layer 15b above the reverse cleaning pipe 14 are supplied with water or air from the ejection holes 14ba of the reverse cleaning pipe 14 in a horizontal plane. For example, it is stirred by jetting upward at an angle of +90 degrees or downward at an angle of -90 degrees, and is rolled up into the sea above the sand filtration layer together with organisms or suspended matter deposited on the surface of the sand filtration layer After that, agitation water containing organisms or suspended matter is absorbed by the water absorption pipe 16 installed above the surface layer of the sand filtration layer. By doing in this way, since the living thing or suspended matter rolled up above the sand filtration layer is recovered without being deposited again on the surface of the sand filtration layer, clogging of the sand filtration layer can be surely prevented.

  In addition, the organisms or suspended substances rolled up above the sand filtration layer contain components such as silt that cause clogging and do not cause clogging. Also included are particles of suitable particle size to maintain the seawater filtration effect in the bed.

  Thus, in this embodiment, the clogging of the clogging to be inhaled is made using the difference in the sedimentation rate of the organism or suspended matter rolled up in the sea above the sand filtration layer by the water or air ejected from the backwash pipe 14. The stirring water is sucked from the water suction pipe 16 at the timing when the causative substance settles on the sand filtration layer. Therefore, in the present embodiment, only substances that cause clogging can be sucked and substances useful for maintaining the filtration effect can be left in the sand filtration layer.

  Next, the arrangement and connection method of the osmotic water intake unit 11 of the present invention and the size of the water intake area configured by combining the osmotic water intake block 110 will be described with specific examples.

  FIG. 3 is a view showing an arrangement example of the water intake piping 12 of the osmotic water intake unit 11. In this example, seven intake pipes 12 are arranged side by side to constitute an intake pipe block 120. In the case of such a configuration, the intake pipe block 120 is connected to the water collecting pump by combining the five intake pipe blocks 120 into one using the common pipe 18, for example, as shown in FIG. Alternatively, as shown in FIG. 3B, the intake pipe block 120 may be individually connected to the water collection pump pit 19.

  FIG. 4 is a view showing an example of connection of the reverse cleaning pipe 14 of the osmotic water intake unit 11. In this example, the reverse cleaning pipe block 140 is configured by arranging seven back cleaning pipes 14 side by side. In the present invention, water is spouted from the backwash pipe 14 in order to stir the organism or suspended matter that has accumulated in the surface layer of the sand filtration layer and taken up in the intermediate layer and wind it up into the sea above the sand filtration layer. Alternatively, air may be ejected. When using the structure which ejects water, as shown to Fig.4 (a), the backwash pipe block 140 is connected with the water supply pump 20. FIG. On the other hand, when using the structure which ejects air, as shown in FIG.4 (b), the backwash pipe block 140 is connected with the air compressor 21. FIG.

  FIG. 5 is a diagram showing an example of dimensions and arrangement of the permeation water intake unit 11. In the example of FIG. 5 (a), the permeate water intake block 110 is configured by arranging 8 or 9 permeate water intake units 11 whose main pipes 12a, 14a, and 16a have a length of 10 m in the longitudinal direction side by side. Four more 110 are arranged side by side to form a water intake area 1100 having a size of 10 m × 105 m (not including the thickness of the casing).

In the present invention, the seawater infiltration rate is 400 m / day or less. However, if the seawater infiltration rate is 100 m / day and the infiltration area per unit of the infiltration water intake unit 11 is 30 m ² , the infiltration water intake unit 11 The amount of water collected per unit is 3000 m ³ / day. As in the example of FIG. 5A, in the case of a water intake area 1100 composed of about 35 permeate water intake units 11, the total water collection amount is about 100,000 t / day. This is the same level of water intake as “Mamizu Pier” currently installed in Fukuoka Prefecture.

  Further, when it is necessary to further increase the daily water intake amount, for example, 400,000 t / day, the water intake area 1100 shown in FIG. 5 (a) is arranged as shown in FIG. 5 (b) or (c), for example. 4 areas should be provided. In this case, in the example of FIG. 5B, 25 m × about 270 m, and in the example of FIG. 5C, 210 m × about 25 m, a water intake area that is much smaller than the conventional permeation water intake method, 400,000 a day A water intake of t is obtained.

  Moreover, in this invention, since the intake pipe 12, the gravel layer 13, the backwash pipe 14, the sand layer 15, and the water absorption pipe 16 which form a sand filtration layer were unitized, the optimal arrangement | positioning is selected according to the topography of an installation sea area. be able to. Further, by changing the number of units to be combined as described above, it is possible to cope with the required water intake amount per day.

  Further, according to the present invention, even if a failure occurs in some of the permeate water intake units 11, only the failed permeate water intake unit 11 needs to be replaced. Therefore, the influence on the entire system can be reduced. Moreover, since it is not necessary to excavate the sea bottom when exchanging the infiltration water intake unit 11, maintenance work is reduced in scale, and maintenance costs can be reduced.

  FIG. 6 is a view showing an example of an osmotic water intake unit of the present invention when a drain pipe is used as a means for removing organisms or suspended solids rolled up in the sea. In the following description, only differences from the configuration of the embodiment of FIG.

  In FIG. 6, reference numeral 22 denotes a drain pipe comprising a main pipe 22a and a plurality of branch pipes 22b. As shown in FIG. 6A, the main pipe 22a is installed between the side surfaces 17a and 17c of the housing 17 facing each other. Further, the ends of the plurality of branch pipes 22b branched in the direction intersecting with the main pipe 22a are supported on the side faces 17b and 17d of the housing 17, as shown in FIG. 6B. By doing in this way, the drain pipe 22 is installed above the sand layer 15 in a state where a certain interval is provided between the drain pipe 22 and the surface of the sand layer 15.

  The branch pipe 22b has a large number of ejection holes arranged on the ocean side (FIG. 2B is not shown because it is a view from the land side). The ejection holes are opened in parallel to the longitudinal direction of the main pipe 22a, and the ejection angle of the ejection holes is set to be parallel to the horizontal plane when installed on site. The land side of the main pipe 22a is connected to a water supply pump of a seawater desalination plant, and the water supplied from the main pipe 22a to each branch pipe 22b is ejected horizontally from the ejection hole to the ocean side.

  As described above, in this embodiment, the organism or suspended substance taken in the intermediate layer of the sand filtration layer is agitated by the water or air ejected from the backwash pipe 14, and the organisms deposited on the surface of the sand filtration layer or Along with the suspended substance, it is rolled up above the surface layer, and then discharged to the outside of the sand filtration layer by water ejected from the drain pipe 22.

  Fig.7 (a) is explanatory drawing of the other Example of the osmosis | permeation intake unit of this invention using a drain pipe, and has shown the state which looked at the drain pipe 23 from the plane direction. The right side of the paper indicates the land side where the seawater desalination plant is provided, and the left side (the direction of the arrow) indicates the ocean side. In this embodiment, it is assumed that no other infiltration water intake unit is adjacent to the ocean side.

  As shown in FIG. 7A, the branch pipe 23b of the drain pipe 23 has a large number of ejection holes 23bb arranged only on the ocean side. FIG. 7B is a schematic view of the branch pipe 23b of the drain pipe 23 as viewed from the direction of the cross section, and is a view for explaining the ejection angle θ of water ejected from the ejection hole 23bb. In the present embodiment, by mounting a nozzle on the ejection hole 23bb, the ejection angle θ is set in the range of 30 to 60 degrees with respect to the horizontal plane. The land side of the main pipe 23a is connected to a water supply pump of a seawater desalination plant. For example, when the ejection angle of the ejection hole 23bb is 45 degrees, the water supplied from the main pipe 23a to each branch pipe 23b is ejected from the ejection hole 23bb to the ocean side at an angle of 45 degrees upward with respect to the horizontal plane. .

  Thus, in this embodiment, the drain pipe 23 ejects water in a direction in which no other permeation intake unit is adjacent to the drain pipe 23, and the water ejection angle is in the range of 30 to 60 degrees with respect to the horizontal plane. It was configured as follows.

  Therefore, in this embodiment, suspended substances or the like that cause clogging discharged by the drain pipe 23 do not settle on top of the sand filtration layers of other permeate water intake units. Further, in this embodiment, the water ejected from the ejection hole 23bb has a parabolic shape, and suspended substances or the like that cause clogging can be discharged further away.

  By the way, if organisms or suspended solids deposited on the seabed are unnecessarily discharged to the surroundings, there is a risk of some influence on the surrounding natural environment.

  Therefore, in the present embodiment, the eyes to be discharged to the outside using the difference in the sedimentation rate of the organism or suspended matter rolled up in the sea above the sand filtration layer by water or air ejected from the backwash pipe 14. Water was ejected from the drain pipe 23 at the timing when the substance causing the clogging settles in the sand filtration layer. Therefore, in the present embodiment, the influence on the surrounding natural environment can be minimized as much as possible by discharging only substances that cause clogging to the outside.

  FIG. 8 is a view showing an example of the arrangement in the height direction of the water intake pipe 12 and the backwash pipe 14 in the unit of the osmotic water intake unit 11 of the present invention. In the present invention, it is better that the water intake pipe 12 is not too far from the bottom surface 17e of the casing 17 of the osmotic water intake unit 11 so that the filtration capacity does not decrease. Specifically, when the pipe outer diameter of the intake pipe 12 is D, the COP (pipe center) height of the intake pipe 12 may be in the range of 0.75D to 1,25D upward from the bottom surface 17e.

  In addition, it is advantageous to install the backwash pipe 14 at a position as deep as possible in order to backwash the suspended matter or the like deposited on the surface of the sand filtration layer and taken in the intermediate layer over a wide range. If the installation position is too deep, it is necessary to increase the water pressure, so it is necessary to consider the balance between the two. Specifically, when the outer diameter of the reverse cleaning pipe 14 is d, the COP (pipe center) height of the reverse cleaning pipe 14 is 1.0d to 5 downward from the surface 15d of the sand layer 15 of the sand filtration layer. A range of 0.0d may be used.

  FIG. 9 is a diagram showing an example of an osmotic water intake unit of the present invention when seawater flow is used as means for removing organisms or suspended matter rolled up in the sea. The configuration of FIG. 9 is the same as the embodiment of FIG. 1 except that the water absorption pipe 16 or the drain pipe 22 does not exist. In this embodiment, the organism or suspended substance taken into the intermediate layer of the sand filtration layer is combined with the organism or suspended substance deposited on the surface of the sand filtration layer by water or air ejected from the backwash pipe 14. And is diffused to the outside of the sand filtration layer by seawater flow caused by tidal currents or waves.

  Next, the reason why the seawater permeation rate is 400 m / day or less in the seawater permeation filtration method of the present invention will be described.

  FIG. 10 is a diagram showing an experimental flow of the seawater osmotic filtration method of the present invention. In FIG. 10, 31 is a water intake pump submerged 50 cm from the sea bottom and 3.3 m from the water surface, and 32 is a raw water tank for storing seawater pumped by the water intake pump 31. Seawater stored in the raw water tank 32 is pumped up by the raw water pump 33 and supplied to the column device 34. The column device 34 is provided with a filtration layer composed of a sand layer 34 a and a gravel layer 34 b, and the filtrate water that has passed through the filtration layer is guided to a treated water tank 35.

  In the experimental flow shown in FIG. 10, the reverse feed pipe 37 provided with the reverse feed pump 36 that sends the filtrate of the treated water tank 35 back to the column apparatus 34 and the seawater supplied to the column apparatus 34 do not overflow. In addition, an overflow pipe 38 for guiding the treated water tank 35 is provided.

  The turbidity and silt concentration index SDI of the filtered water that passed through the filtration layer of the column apparatus from the seawater collected by the intake pump of the experimental apparatus having the flow shown in FIG. 10 were measured. The filtration layer used for this measurement is a 0.45 mm sand layer (900 mm thick), a 2-4 mm gravel layer (75 mm thick), a 4-8 mm gravel (75 mm thick), and a 6-12 mm gravel from the top. (Thickness 150 mm).

  The measurement results are shown in FIG. Here, to the raw water from which the turbidity data was obtained, an amount of silt was added in advance so that the osmotic water intake speed in FIG. 11 (a) was the turbidity indicated by 0 m / day. From the results of FIG. 11, even when the osmotic water intake speed is 50 to 400 m / day, the turbidity and silt concentration index SDI are the same as when the osmotic water intake speed is 1 to 8 m / day, showing the same treatment performance. It was confirmed.

  By the way, in invention of the said patent document 1, the seawater permeation | transmission flow rate expressed in the sand filtration layer of a seabed shall be 1-8 m / day, and the water depth of the sand filtration layer is 50 cm or more of sand of the surface layer part of the said sand filtration layer. It is assumed that it is deeper than the full movement limit water depth that moves and shallower than the surface movement limit water depth that moves 1 cm or more.

  In the invention of Patent Document 1, as a condition for realizing the permeation intake speed of seawater, the water depth of the sand filtration layer is deeper than the complete movement limit water depth at which the sand of the surface layer portion of the sand filtration layer moves by 50 cm or more, and The reason for making it shallower than the surface layer movement limit water depth that moves 1 cm or more is as follows.

  It is confirmed that the sand on the surface of the sand filtration layer at the depth of the surface layer movement limit depth, which is the maximum water depth where it is confirmed that the sand particles on the seabed move to some extent by the waves, is to the extent that the seabed sand is washed. If it is deeper than this water depth, there is almost no movement of sand particles on the surface of the sand filtration layer.

  On the other hand, when the surface sand of the sand filtration layer moves more than 50cm at the maximum water depth, which is the maximum water depth where it is confirmed that the sand filtration layer on the seabed is eroded by the action of waves, the erosion of the sand filtration layer on the seabed is Because it will be accepted.

  In Patent Document 1, the particle size of the silt particles is generally about 0.005 mm to 0.074 mm, and the flow rate of seawater at which the silt does not move, that is, the movement limit flow rate is obtained. This movement limit flow velocity is a value obtained by multiplying the limit actual flow velocity of the silt particles by the area porosity (= 0.35). The limit actual flow rate of silt particles obtained using a graph showing the relationship between the particle size and the limit actual flow rate is 0.026 cm / s in the case of silt particles having a particle size of 0.08 mm.

  Therefore, the upper limit of the movement limit flow velocity of silt is 0.026 × 0.35 × 24 × 3600 = 786.24 cm / day, which is about 8 m / day. From this result, in order not to cause clogging due to silt caught in the sand filtration layer, the seawater infiltration flow rate should be set to 8 m / day or less at the maximum.

  Further, in order to supply sufficient oxygen to the sand filtration layer so as not to kill the biofilm, it is said that a seawater permeation flow rate of at least 1 m / day is necessary.

  From these, in the invention of Patent Document 1, the surface layer of the sand filtration layer is appropriately agitated by the waves and currents that develop in the sea by setting the infiltration rate of seawater to 1 to 8 m / day under the above conditions, It is said that suspended solids such as garbage and silt accumulated on the surface of the sand filtration layer can be removed, and stable water intake can be secured.

  As described above, the upper limit of the seawater infiltration rate specified in the invention of Patent Document 1 is a condition for preventing silt from entering or mixing into the sand filtration layer on the surface layer of the seabed. If the method of obtaining 8 m / day, which is the limit of silt absorption suppression in Patent Document 1, is followed, the inventors have confirmed that the treatment performance is equivalent to that in the case of the permeate water intake rate of 1-8 m / day. For example, when the permeate water intake speed is 400 m / day, it tends to absorb silt.

  In other words, if there is no flow field to stir or carry the silt, the absorption rate of the silt to the sand filtration layer when the permeate intake rate is 400 m / day is (the permeate intake rate of seawater cm / s). ) X (porosity due to sand particle size). Therefore, in the case of an infiltration water intake rate of 400 m / day, the absorption rate of silt into the sand filtration layer is {40000 cm / (24 × 3600)} × 0.35 = 0.16 cm / s. Further, in order to realize a critical flow velocity of 1.0 m / day or more for supplying oxygen, {100 cm / (24 × 3600)} × 0.35 = 0.004 cm / s.

  In calculation, when the seawater infiltration rate is 400 m / day, about 6 m (≈0.16 × 3600/100) of silt particles that cause clogging permeate into the sand filtration layer per hour. Thus, feasible cleaning is difficult.

  However, since silt particles are very small compared to the voids in the filter sand, they take the form of so-called standard blockage. When the silt moves with water, it is trapped by intermolecular forces (physical adsorption, static electricity) with the filter sand. As it accumulates, it adheres and stays in the vicinity of the surface layer.

  In the experiment in which the silt component is added as shown in FIG. 11 (a), the silt is almost deposited on the surface layer after 2 hours under the condition of 400 m / day, and the inside of the sand filter layer is only about 1 cm. Confirmed that it would not invade.

  In addition, the standard blockage differs from the complete blockage that occurs even for particles larger than the void, and in order for the particles to completely seal the void pores, the void pores take time due to adsorption of silt particles as shown in FIG. Narrow. This means that pressure loss gradually occurs up to the air gap retention threshold, so that long-time penetration is possible even when silt is continuously removed. This elapsed time varies depending on the conditions of the filter medium and the seawater condition (silt concentration), and this time is an important factor for the forced cleaning interval.

  The present invention is based on the experimental results of the inventors and the above knowledge, and is a conventional common sense, realizing a high seawater permeation rate of the filter medium, which was a taboo, and thereby significantly increasing the construction scale and intake facility scale. Is realized.

  According to the results of the inventors conducting a test using groundwater having higher permeability than seawater, it was possible to continuously operate normally up to a penetration speed of 600 m / day. However, when the permeation rate was 700 m / day, the required amount of purified water was larger than the amount of water intake, and water could not continuously flow through the sand filtration layer, and normal water intake was not possible. Therefore, in the present invention, which is targeted for the filtration method when seawater is infiltrated, the safety factor is about 1.5 and the seawater permeation rate is set to 400 m / day.

  For the above reasons, in the seawater osmotic filtration method of the present invention, when seawater that has naturally permeated through the sand filtration layer from the sea is introduced into the water pipe and the seawater is permeated and taken in, the seawater permeation rate is 400 m / day or less. With the speed.

  In the present invention, when the seawater infiltration rate is 400 m / day, for example, the amount of water intake is 50 times that of the conventional seawater infiltration rate of 8 m / day, so the area of the intake area can be reduced to 1/50. it can. Further, installation in a sea area where optimum seawater flow is promoted becomes unnecessary, and as shown in FIG. 13, an infiltration water intake facility 42 can be installed near the seawater desalination plant 41, and the scale of construction and intake facilities can be increased. The scale can be significantly reduced, and the impact on the surrounding environment during construction can be alleviated.

  And, in the seawater osmotic filtration method of the present invention, clogging is more reliably prevented by removing organisms or suspended solids incorporated not only in the surface layer of the sand filtration layer but also in the intermediate layer. Maintaining as high a speed as possible below 400 m / day, high-speed filtration can be carried out continuously.

  The present invention is not limited to the above examples, and it is needless to say that the embodiments may be changed as appropriate within the scope of the technical idea described in each claim.

  For example, in the above-described embodiment, an example in which the osmotic intake unit 11 is formed in advance has been disclosed. However, the seawater osmotic filtration method of the present invention does not use the osmotic intake unit 11 and is installed on the seabed. Alternatively, a method of forming a sand filtration layer by embedding the intake pipe 12 or the backwash pipe 14 may be used.

Specifically, intake pipes are embedded deep in the sand filtration layer on the seabed, backwash pipes that eject water or air are embedded in the intermediate layer of the sand filtration layer, and the sand filtration layer naturally penetrates from the sea. Seawater osmotic filtration method for introducing seawater into the intake pipe and taking seawater,
The seawater penetration speed is 400 m / day or less,
The organism or suspended substance taken in the intermediate layer is stirred by jetting water or air from the backwash tube, and is rolled up together with the organism or suspended substance deposited on the surface layer of the sand filtration layer. This is a seawater osmotic filtration method for preventing clogging of the sand filtration layer.

  In addition, even when the osmotic intake unit is not used as described above, a water absorption pipe is further installed above the surface of the sand filtration layer, and the organisms or suspended substances taken into the intermediate layer of the sand filtration layer are back-washed. Water or air is spouted from the pipe and stirred, and after being rolled up with the organism or suspended matter deposited on the surface of the sand filtration layer, the stirred water containing the organism or suspended matter from the water absorption pipe Inhalation of sand can prevent clogging of the sand filtration layer without adversely affecting the surrounding environment.

  Alternatively, a drainage pipe is further installed above the surface of the sand filtration layer, and the organism or suspended matter taken into the intermediate layer of the sand filtration layer is stirred by jetting water or air from the backwash pipe. Rolling up the surface together with organisms or suspended matter deposited on the surface of the filtration layer, and then spraying water out of the drainage pipe prevents clogging of the sand filtration layer even in calm waters where seawater flow is low it can.

  Moreover, in the above-described embodiment, the structure in which the intermediate layer of the sand filtration layer is cleaned by ejecting water or air from the reverse cleaning tube 14 is disclosed, but in addition to the cleaning of the intermediate layer (sand layer) by the reverse cleaning tube 14, You may comprise so that the deep layer (gravel layer) of a sand filtration layer may be wash | cleaned by making water flow backward with respect to the intake pipe 12 at a required timing, and ejecting water from the intake hole of the branch pipe 12b.

  In the above-described embodiment, the embodiment using the water absorption pipe 16 and the embodiment using the drain pipes 22 and 23 have been described separately. For example, switching between collecting and supplying water of a pump installed in a seawater desalination plant. Thus, a single apparatus may be configured to have both the function of the water absorption pipe and the function of the drain pipe.

  Moreover, the filter medium used for the gravel layer and the sand layer of the osmotic intake unit of the present invention is not limited to natural gravel and sand, and any material can be used. For example, you may use the artificial grain ceramic and artificial glass with little influence on an environment as a gravel layer or a filter material of a sand layer. When such an artificial filter medium is used, there is a problem that the cost is generally increased. However, unlike the conventional method, the seawater osmotic filtration method of the present invention can significantly reduce the area of the water intake area. The above-described artificial filter medium can also be easily adopted.

DESCRIPTION OF SYMBOLS 11 Osmosis intake unit 12 Intake pipe 13 Gravel layer 14 Back washing pipe 15 Sand layer 16 Water absorption pipe 22 Drain pipe 23 Drain pipe

Claims (7)

Comprising a housing, the interior of the housing to have a gravel layer and sand, embedding the intake pipe in the gravel layer to form a depth of sand filtration layer, for forming the intermediate layer and the surface layer of the sand filtration layer An infiltration water intake unit in which a reverse cleaning pipe is embedded in the sand layer is formed in advance, and the sand filtration layer is formed by combining a required number of the infiltration water intake units at an installation location on the seabed. Seawater osmotic filtration method of introducing seawater that has naturally permeated into the intake pipe and taking in seawater,
The seawater penetration speed is 400 m / day or less,
The organism or suspended substance taken into the intermediate layer is stirred by jetting water or air from the backwash tube, and rolled up with the organism or suspended substance deposited on the surface layer above the surface layer. A seawater osmotic filtration method characterized by preventing clogging of a sand filtration layer. A seawater osmotic filtration method in which an osmotic intake unit further having a water absorption pipe installed above the sand layer is formed in advance, and the sand filtration layer is formed by combining the required number of osmotic intake units at the installation location on the seabed. There,
The organism or suspended matter taken into the intermediate layer is stirred by jetting water or air from the backwash tube, and wound up with the organism or suspended matter deposited on the surface layer above the surface layer, 2. The seawater osmotic filtration method according to claim 1, wherein clogging of the sand filtration layer is prevented by sucking agitation water containing a living organism or suspended matter from a water absorption pipe.   Using the difference in sedimentation speed of the organism or suspended matter wound up above the sand filtration layer, the stirring water is sucked from the water absorption pipe at the timing when the substance to be sucked sinks to the sand filtration layer. The seawater osmotic filtration method according to claim 2, wherein the seawater is filtered. A seawater osmotic filtration method in which an osmotic intake unit further provided with a drain pipe above the sand layer is formed in advance, and the sand filtration layer is formed by combining the required number of osmotic intake units at the installation location on the seabed. There,
The organism or suspended matter taken into the intermediate layer is stirred by jetting water or air from the backwash tube, and wound up with the organism or suspended matter deposited on the surface layer above the surface layer, The seawater osmotic filtration method according to claim 1, wherein clogging of the sand filtration layer is prevented by ejecting water from a drain pipe and discharging the water to the outside of the sand filtration layer.   Using the difference in sedimentation speed of the organism or suspended matter wound up above the sand filtration layer, water is ejected from the drain pipe at the timing when the substance to be discharged to the outside settles on the sand filtration layer. The seawater osmotic filtration method according to claim 4, wherein the seawater is filtered.   The osmotic intake unit used in the seawater osmotic filtration method according to claim 4 or 5, wherein the drain pipe ejects water in a direction where no other osmotic intake units are adjacent to each other, and the water ejection angle. Is a permeate water intake unit characterized by being in the range of 30 to 60 degrees with respect to the horizontal plane. Intake pipes are embedded deep in the sand filtration layer on the seabed, backwash pipes that eject water or air are embedded in the intermediate layer of the sand filtration layer, and a drain pipe is installed above the surface of the sand filtration layer. A seawater osmotic filtration method for introducing seawater that has naturally permeated through the sand filtration layer into the intake pipe to take in seawater,
The seawater penetration speed is 400 m / day or less,
The organism or suspended matter taken into the intermediate layer is stirred by jetting water or air from the backwash tube, and is rolled up together with the organism or suspended matter deposited on the surface of the sand filtration layer. Then , the seawater osmosis filtration method is characterized by preventing clogging of the sand filtration layer by ejecting water from the drain pipe and discharging the water to the outside of the sand filtration layer.

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