JP6854708B2 - How to maintain osmotic water intake devices and biological filtration membranes - Google Patents

Description

The present invention relates to an osmotic water intake device and a method for maintaining a biological filtration membrane.

Conventionally, seabed infiltration water intake (hereinafter, simply referred to as “osmotic water intake”) is performed to take in seawater that has permeated the sand layer on the seabed. In osmotic water intake, clear seawater is obtained by aerobic microorganisms adhering to the sand layer feeding and decomposing organic matter in seawater. Aerobic microorganisms in the sand layer play a role as a biological filtration membrane that greatly affects the filtration performance in osmotic water intake.

In Patent Document 1, a backwashing device is proposed in which seawater is periodically backflowed into an intake pipe embedded in a sand filtration layer to backwash the sand filtration layer. The backwash device is provided with a seawater storage section that communicates with the ocean at high tide and is isolated at low tide, and a connecting pipe that is connected between the water pipe connected to the intake pipe and the seawater storage section. Then, when a predetermined head difference occurs between the tide level of the ocean descending due to the low tide and the water level in the seawater storage section, the flow of seawater is permitted in the connecting pipe, and the seawater in the seawater storage section passes through the connecting pipe. Backflow.

Japanese Patent No. 6026358

By the way, while the normal operation of the osmotic water intake device for osmotic water intake is stopped, the seawater in the sand layer on the seabed stays with almost no replacement. In this case, oxygen in the seawater in the sand layer is consumed by aerobic microorganisms, and the amount of dissolved oxygen (Dissolved Oxygen) in the seawater becomes low. When the amount of dissolved oxygen approaches 0, aerobic microorganisms are killed and putrefactive sludge is generated. Therefore, when the normal operation is restarted after the normal operation is stopped for a long period of time, a plurality of backwashing operations are required to remove the putrefactive sludge in the sand layer. In addition, the killing of aerobic microorganisms reduces the ability to remove organic matter in the sand layer and reduces the filtration performance. It takes several days to several months for aerobic microorganisms to propagate in the sand layer and restore the filtration performance. Therefore, there is a need for a method for appropriately maintaining the biological filtration membrane by allowing aerobic microorganisms in the sand layer to survive while the normal operation of the osmotic water intake device is stopped.

The present invention has been made in view of the above problems, and an object of the present invention is to appropriately maintain a biological filtration membrane.

The invention according to claim 1 is a permeation water intake device, wherein a water intake portion embedded in a sand layer provided on the sea floor, a connection portion connected to the water intake portion, and the water intake via the connection portion. It is provided with an intake pump that communicates with a portion and takes in permeated water that is seawater that has permeated the sand layer through the intake portion, and the connection portion is a connection pipe connected to the intake portion and a connection pipe of the intake pump. In the stopped state, the auxiliary water intake means for flowing the permeated water from the water intake unit to the connecting pipe is provided, and the auxiliary water intake means is provided with a storage unit into which the permeated water that has passed through the connecting pipe flows. It has an auxiliary water intake structure that allows the permeated water to flow from the water intake part to the storage part by the difference between the water level and the tide level of the permeated water stored in the storage part when the water intake pump is stopped. The auxiliary water intake structure has an air supply unit that supplies air to the permeated water in the storage unit, and when the permeated water is backflowed in a stopped state of the water intake pump, the water level and the tide level in the storage unit are set. Due to the difference, the permeated water in the storage section is discharged from the intake section .

The invention according to claim 2 is the permeation water intake device according to claim 1 , wherein the auxiliary water intake structure has a water level maintaining mechanism for maintaining the water level in the reservoir.

The invention according to claim 3 is the permeation water intake device according to claim 1 or 2 , wherein the water intake rate of the permeated water taken in from the water intake unit by the auxiliary water intake means is 5 to 200 m / day.

The invention according to claim 4 is an osmotic water intake device, the water intake portion embedded in a sand layer provided on the sea floor, a connection portion connected to the water intake portion, and the water intake via the connection portion. It is provided with an intake pump that communicates with the unit and takes in the permeated water that is the seawater that has permeated the sand layer through the intake unit, and the connection portion connects the connection pipe connected to the intake unit and the connection pipe. It has a storage unit into which the permeated water that has passed flows, an air supply unit that supplies air to the permeated water in the storage unit, and a means for discharging the permeated water in the storage unit from the water intake unit.

The invention according to claim 5 is a method for maintaining a biological filtration membrane used for osmotic water intake by an osmotic water intake device, wherein the osmotic water intake device has a water intake portion embedded in a sand layer provided on the sea floor and the above. The connection is provided with a connection portion connected to the intake portion and an intake pump that communicates with the intake portion via the connection portion and takes in permeated water, which is seawater that has permeated the sand layer, through the intake portion. The unit has a connecting pipe connected to the water intake unit, a storage unit into which the permeated water that has passed through the connecting pipe flows, and an air supply unit that supplies air to the permeated water in the storage unit. The method for maintaining the biological filtration membrane is as follows: a) a step of supplying air to the osmotic water in the reservoir by the air supply unit, and b) discharging the osmotic water in the reservoir from the intake unit by the connection portion. It is provided with a process to be performed.
The invention according to claim 6 is the method for maintaining a biological filtration membrane according to claim 5, wherein the permeated water flows from the intake portion to the connecting pipe by the connecting portion in a stopped state of the intake pump. Further prepare for the process of causing.

According to the present invention, the biological filtration membrane can be properly maintained.

It is a figure which shows the structure of the permeation intake device. It is a figure which shows the flow of operation of the permeation intake device at the time of stopping a normal operation. It is a figure for demonstrating operation of a permeation intake device. It is a figure for demonstrating operation of a permeation intake device. It is a figure for demonstrating operation of a permeation intake device. It is a figure for demonstrating operation of a permeation intake device. It is a figure which shows another example of a permeation intake device. It is a figure for demonstrating operation of a permeation intake device. It is a figure for demonstrating operation of a permeation intake device. It is a figure for demonstrating operation of a permeation intake device. It is a figure for demonstrating operation of a permeation intake device. It is a figure which shows another example of the connection part. It is a figure which shows another example of a water intake part.

FIG. 1 is a diagram showing a configuration of a permeation intake device 1 according to an embodiment of the present invention. The osmotic water intake device 1 is provided in, for example, a seawater desalination system that takes in and treats seawater to produce freshwater. In the system, the seawater taken by the osmosis intake device 1 is treated by a treatment unit (not shown) to produce fresh water.

The permeation water intake device 1 includes a water intake unit 2, a connection unit 3, a water intake pump 4, a water level sensor 51, and a control unit (not shown). The control unit is responsible for overall control of the infiltration water intake device 1. The water intake portion 2 is embedded in a sand layer 91 provided on the seabed. In the example of FIG. 1, sand having a predetermined particle size is spread as a sand layer 91 in the box-shaped housing 90, and the water intake portion 2 is arranged in the sand layer 91. The sand layer 91 may include gravel (gravel layer) or the like for supporting the intake portion 2. The water intake unit 2 is, for example, an intake pipe provided with a screen around it, and seawater that has permeated the sand layer 91 (hereinafter, referred to as “permeated water”) is taken into the water intake unit 2.

The connecting portion 3 is connected to the water intake portion 2. Specifically, the connecting unit 3 includes a connecting pipe 31, an intake well 32, a water pipe 33, and an air supply unit 34. One end of the connecting pipe 31 is connected to the water intake unit 2. A connection valve 311 is provided in the connection pipe 31, and in a state where the connection valve 311 is opened, the permeated water taken in by the water intake unit 2 flows through the connection pipe 31. The intake well 32 is, for example, a well formed by digging the ground. The other end of the connecting pipe 31 is connected to the bottom of the intake well 32 or the vicinity of the bottom. The seepage water that has passed through the connecting pipe 31 flows into the intake well 32 and is stored in the intake well 32. The intake well 32 is a storage unit that stores permeated water. The intake well 32 is open to the atmosphere, and a horizontal liquid level of seepage water is formed.

The air supply unit 34 includes a compressor 341 and an ejection pipe 342. The compressor 341 is located above the ground and the ejection pipe 342 is located at the bottom of the intake well 32. The compressed air generated by the compressor 341 is supplied to the ejection pipe 342. A large number of minute holes are formed in the ejection pipe 342, and compressed air is blown into the intake well 32 through the minute holes. In this way, the air supply unit 34 supplies air to the seepage water in the intake well 32 by bubbling, that is, aerates the seepage water in the intake well 32.

The water pipe 33 connects the intake well 32 and the intake pump 4. Specifically, one end of the water pipe 33 is arranged near the bottom in the intake well 32. The other end of the water pipe 33 is connected to the water intake pump 4 installed on the ground. When the connection valve 311 of the connection pipe 31 is open, the water intake pump 4 communicates with the water intake unit 2 via the connection unit 3. That is, the permeated water can flow between the water intake unit 2 and the water intake pump 4. The water level sensor 51 is placed on the ground and measures the distance to the sea surface by ultrasonic waves. As the water level sensor 51, a capacitance type water level sensor, a water pressure gauge installed in the sea, or the like may be used. In the present embodiment, a water level sensor (not shown) is also provided in the intake well 32.

In the normal operation of the permeation water intake device 1, for example, the water intake pump 4 operates with the connection valve 311 fully opened to perform a water supply operation. As a result, the permeated water in the intake well 32 is continuously sucked up and sent to the equipment at the subsequent stage (downstream side) such as the filtration unit. Further, when the water intake pump 4 is constantly operated, as shown by an arrow A1 in FIG. 1, the water level (position of the liquid level) of the permeated water stored in the water intake well 32 is set to the water intake unit 2. It remains below the sea tide level at the location. As a result, the seepage water is continuously taken in through the intake unit 2 and flows into the intake well 32. In FIG. 1, the direction in which the permeated water flows is indicated by the arrow shown in the sand layer 91 (the same applies to FIGS. 3, 5, 7, 8, and 10 described later).

When seawater permeates the sand layer 91, aerobic microorganisms adhering to the sand layer 91 feed on and decompose organic substances in the seawater, so that clear permeated water is obtained in the water intake section 2. In addition, marine organisms are prevented from adhering to the downstream side from the water intake portion 2. In the osmotic water intake device 1, the osmotic water is sucked up in the intake well 32 by the water intake pump 4 and the osmotic water is taken in through the water intake unit 2 in parallel. The air supply unit 34 is not used in the normal operation of the infiltration water intake device 1. Of course, in normal operation, the air supply unit 34 may be operated.

Further, in the normal operation of the permeation water intake device 1, the backwash treatment is performed periodically or at an arbitrary timing. For example, a osmotic water tank for storing osmotic water is provided after the water intake pump 4, and in the backwash treatment, the osmotic water tank is stopped and the connection valve 311 is closed. The seepage water is supplied into the intake well 32 from. When the water level in the intake well 32 becomes higher than the tide level by a predetermined value or more, the connection valve 311 is opened. As a result, the permeated water in the intake well 32 flows back to the intake section 2 via the connecting pipe 31 and is discharged from the intake section 2. As a result, the sand in the sand layer 91 is agitated, and the clogging substance trapped in the sand layer 91 during normal operation is rolled up together with the sand and diffused into the sea to be removed. In the backwash process, the opening degree of the connection valve 311 is adjusted so that the permeated water is discharged from the water intake unit 2 at a predetermined flow rate (flow rate).

Next, the operation when the normal operation of the infiltration water intake device 1 is stopped for maintenance such as replacement of the pump in the seawater desalination system or cleaning of pipes will be described with reference to FIG.

When the normal operation is stopped, the connection valve 311 is first closed, and then the intake pump 4 is stopped (step S11). Immediately after the intake pump 4 is stopped, a certain amount of water level difference is provided between the tide level and the water level in the intake well 32. Here, it is assumed that the intake pump 4 is stopped at the time of rising tide. Of course, the water intake pump 4 may be stopped at the time of low tide. In the infiltration water intake device 1, the water level in the intake well 32 is kept constant (maintained) by stopping the water intake pump 4 and closing the connection valve 311. The connection valve 311 is a water level maintaining mechanism that maintains the water level in the intake well 32 when the intake pump 4 is stopped. After that, the operation of the air supply unit 34 is started (step S12). As a result, air is supplied to the seepage water in the intake well 32, and a state in which the amount of dissolved oxygen is high in the seepage water in the intake well 32 is maintained.

In the permeation water intake device 1, the tide level is constantly measured by the water level sensor 51, and the control unit determines whether or not the tide is high and whether or not the tide is low based on the measurement result. The determination of high tide and low tide may be made by referring to the tide table (theoretical calculation value). As shown in FIG. 3, when the tide is high (that is, when it is determined that the tide is high), the connection valve 311 is opened. As a result, the maintenance of the water level in the intake well 32 is released. As shown by the arrow A3 in FIG. 3, the tide level is higher than the water level in the intake well 32, and the seepage water is taken in by the intake unit 2 and passed through the connecting pipe 31 as in the normal operation. It flows to the intake well 32 (step S13). In addition, new seawater also flows into the portion of the sand layer 91 above the intake portion 2.

As described above, in the infiltration intake device 1, the auxiliary intake structure including the connection pipe 31, the connection valve 311 and the intake well 32 utilizes the difference between the water level and the tide level in the intake well 32 when the intake pump 4 is stopped. Then, the seepage water is made to flow from the intake unit 2 to the intake well 32. At this time, if the flow velocity of the permeated water in the water intake unit 2, that is, the water intake speed is excessively faster than the water intake speed during normal operation, the sand layer 91 may become hard (tightened). Due to the auxiliary water intake structure, the water intake speed of the seepage water taken in from the water intake unit 2 is preferably equal to or lower than the water intake speed during normal operation, and is, for example, 5 to 200 [m / day]. ^{The water intake rate is obtained by converting the water intake amount [m 3} ] per unit time into the water intake amount per day and dividing the converted value by the area [m ² ] of the water intake unit 2. In the calculation of the water intake rate in the present embodiment, the water level rising speed obtained by the water level sensor described above provided in the water intake well 32 and the cross-sectional area of the water intake well 32 are used. The water intake speed in the water intake unit 2 can be changed (controlled) by adjusting the opening degree of the connection valve 311.

When the water level in the intake well 32 gradually rises and becomes substantially equal to the tide level as shown in FIG. 4, the flow of seepage water in the intake portion 2 and the connecting pipe 31 stops. After that, the connection valve 311 is closed, and the water level in the intake well 32 is maintained at a height corresponding to the tide level at high tide. As described above, the connection valve 311 is a water level maintaining mechanism in the auxiliary water intake structure. In FIG. 4, the connection valve 311 in the closed state is painted black (the same applies to FIGS. 6 to 11 described later).

As shown in FIG. 5, when the tide is low (that is, when it is determined that the tide is low), the connection valve 311 is opened and the maintenance of the water level in the intake well 32 is released. As shown by arrow A5 in FIG. 5, the tide level is lower than the water level in the intake well 32 (actually, the water level corresponding to the difference between the tide level at high tide and the tide level at low tide between the two. (There is a difference), the seepage water in the intake well 32 flows through the connecting pipe 31 and is discharged from the intake unit 2 (step S14). In other words, the seepage water in the intake well 32 flows back to the intake unit 2 via the connecting pipe 31. In the permeated water in the intake well 32, the state in which the dissolved oxygen amount is high is maintained by the air supply unit 34, and the water having a high dissolved oxygen amount is supplied to the sand layer 91 in the vicinity of the intake unit 2.

At this time, the flow velocity of the permeated water discharged from the water intake unit 2 is preferably equal to or lower than the flow velocity during the backwash treatment in the normal operation. The flow velocity during the backwashing treatment is, for example, 500 to 1000 [m / day], preferably 600 to 800 [m / day]. In the calculation of the flow velocity of the discharged permeated water, the water level lowering speed obtained by the above-mentioned water level sensor provided in the intake well 32 and the cross-sectional area of the intake well 32 are used as in the calculation of the intake speed. The flow velocity of the permeated water discharged from the water intake unit 2 can also be changed (controlled) by adjusting the opening degree of the connection valve 311 in the same manner as the water intake speed described above.

When the water level in the intake well 32 gradually decreases and becomes substantially equal to the tide level as shown in FIG. 6, the flow of seepage water in the intake portion 2 and the connecting pipe 31 stops. After that, the connection valve 311 is closed, and the water level in the intake well 32 is maintained at a height corresponding to the tide level at low tide. Next, when the tide becomes high, the tide level is higher than the water level in the intake well 32, and by opening the connection valve 311, the seepage water is taken in by the intake unit 2 (step S13).

As described above, in the permeation water intake device 1, the operations of steps S13 and S14 are repeated until the normal operation is resumed. Since high tide and low tide occur about every 6 hours, it is possible to flow the seepage water in the water intake unit 2 four times a day while the water intake pump 4 is stopped. The osmotic water intake device 1 can pass seawater to the water intake unit 2 at low cost by using the tide without using a large-scale device or a large amount of electric power.

In the repeated steps S13 and S14, as a general rule, the amount of water corresponding to the height difference between the high tide and the low tide in the intake well 32 is taken in by the intake unit 2 or discharged from the intake unit 2. To. In order to replace the entire seawater staying in the sand layer 91, specifically, the seawater staying in the upper part from the intake portion 2 in the sand layer 91 at high tide and low tide, the above amount of water is the volume of the above part in the sand layer 91 ( Hereinafter, it is preferably referred to as “permeation volume in the sand layer 91”) or more. When the cross-sectional area of the intake well 32 on the horizontal plane is constant in the height direction, for example, the permeation volume [m ³ ] in the sand layer 91 is divided by the water level difference [m] between high tide and low tide. The area is the minimum cross-sectional area required for the intake well 32.

When the normal operation is restarted, the operation of the air supply unit 34 is stopped, and a predetermined process at the time of restarting the water intake is performed. As described above, the intake pump 4 may be stopped at the time of low tide. In this case, the operations of steps S14 and S13 are performed in order after steps S11 and S12.

Here, an osmotic water intake device of a comparative example in which the water intake unit 2 and the water intake pump 4 are directly connected by one connecting pipe is assumed. In the permeation intake device of the comparative example, the seawater in the sand layer 91 stays in the sand layer 91 with almost no replacement after the normal operation is stopped until the restart. In this case, oxygen in the seawater in the sand layer 91 is consumed by aerobic microorganisms, and the amount of dissolved oxygen in the seawater becomes low. When the amount of dissolved oxygen approaches 0, aerobic microorganisms are killed and putrefactive sludge is generated. Therefore, in the permeation water intake device of the comparative example, when the normal operation is restarted after the normal operation is stopped for a long period of time, a plurality of backwash treatments are required to remove the putrefactive sludge in the sand layer 91. Further, due to the death of aerobic microorganisms, the ability to remove organic substances in the sand layer 91 is lowered, and the filtration performance is lowered. It takes several days to several months for the aerobic microorganisms to propagate in the sand layer 91 and the filtration performance to be restored. Therefore, it is necessary to increase the amount of chemicals added in the subsequent treatment in the seawater desalination system until the filtration performance is restored.

On the other hand, in the infiltration intake device 1, the infiltration water flows from the intake unit 2 to the intake well 32 due to the difference between the water level and the tide level of the infiltration water stored in the intake well 32 while the normal operation is stopped. Occurs intermittently. In this way, by taking in the seepage water from the intake unit 2 in the stopped state of the intake pump 4, seawater can flow into the sand layer 91, and a certain amount of dissolved oxygen can be secured in the seawater in the sand layer 91. .. As a result, it is possible to reduce the damage caused by the suspension of normal operation to the aerobic microorganisms in the sand layer 91 that contribute to biological filtration, allow the aerobic microorganisms to survive, and maintain the biological filtration membrane appropriately. As a result, the backwashing treatment when resuming the normal operation becomes unnecessary, or the number of backwashing treatments can be reduced. In addition, it is possible to suppress a decrease in filtration performance when resuming normal operation, and to suppress an increase in the amount of drug input due to the death of aerobic microorganisms.

By the way, when the water intake rate is excessively low, oxygen in the seawater is consumed by the aerobic microorganisms existing in the upper part of the sand layer 91, and oxygen is supplied to the aerobic microorganisms existing in the vicinity of the water intake portion 2 in the sand layer 91. May not be supplied very much. On the other hand, in the infiltration water intake device 1, the connection valve 311 maintains the water level in the intake well 32 as a water level maintenance mechanism, so that the difference between the water level and the tide level in the intake well 32 is increased, and the water intake unit The flow of seepage water from 2 to the intake well 32 can be started. As a result, the water intake rate in the water intake unit 2 can be easily increased, and a certain amount of oxygen can be supplied to the aerobic microorganisms in the vicinity of the water intake unit 2 in the sand layer 91. As described above, the preferable water intake rate in the water intake unit 2 is 5 to 200 [m / day].

In the permeation water intake device of the above comparative example, the permeation water in the connecting pipe that directly connects the water intake unit 2 and the water intake pump 4 also stays without being replaced. Therefore, oxygen in the osmotic water is consumed by the aerobic microorganisms contained in the osmotic water in the connecting pipe, and the amount of dissolved oxygen in the osmotic water becomes low. This activates sulfate-reducing bacteria, which are anaerobic microorganisms, and generates toxic gas such as hydrogen sulfide. Hydrogen sulfide dissolves in the permeated water in the connecting pipe and makes the permeated water acidic. Therefore, in the osmotic water intake device of the comparative example, a waste water step for removing rotten water in the connecting pipe is required when the normal operation is restarted after the normal operation is stopped for a long period of time.

On the other hand, the infiltration intake device 1 is provided with an air supply unit 34 that supplies air to the infiltration water in the intake well 32. As a result, it is possible to maintain a state in which the amount of dissolved oxygen in the permeated water stored in the intake well 32 is high, and it is possible to suppress the generation of hydrogen sulfide and the like by the sulfate-reducing bacteria. As a result, it is possible to omit the waste water step when restarting the normal operation. Further, due to the difference between the water level and the tide level in the intake well 32, when the permeated water in the intake well 32 is made to flow back to the water intake unit 2, the permeated water having a high dissolved oxygen amount can be discharged from the water intake unit 2. As a result, a sufficient amount of oxygen can be supplied to the aerobic microorganisms in the vicinity of the water intake portion 2 in the sand layer 91, and the biological filtration membrane can be appropriately maintained. From the viewpoint of supplying oxygen to aerobic microorganisms in the vicinity of the intake portion 2 in the sand layer 91, during the period immediately before the permeated water in the intake well 32 is discharged from the intake portion 2, for example, during the period from high tide to low tide. Only the air supply unit 34 may be activated.

FIG. 7 is a diagram showing another example of the osmosis intake device. In the permeation water intake device 1a of FIG. 7, the configuration of the connecting portion 3 is different from that of the permeation water intake device 1 of FIG. Specifically, a chamber 32a is provided in place of the intake well 32 of FIG. The chamber 32a is a storage unit for storing permeated water. A water level sensor 52 is provided at the bottom of the chamber 32a, and the water level of the seepage water in the chamber 32a is monitored by the water level sensor 52.

A ventilation pipe 321 is provided in the upper part of the chamber 32a. The connecting pipe 31 is connected to the lower part of the chamber 32a, and one end of the water pipe 33 is arranged in the chamber 32a. The chamber 32a is sealed except for the ventilation pipe 321 and the connecting pipe 31 and the water pipe 33. The ventilation pipe 321 is provided with a ventilation valve 322. The water pipe 33 is provided with a water supply valve 331. In the permeation water intake device 1a, when the ventilation valve 322 is closed, the connecting pipe 31, the chamber 32a and the water pipe 33 are equivalent to a connected pipe, and the diameter of the rising portion (chamber 32a) is large in the pipe. It can be regarded as being done. The connecting pipe 31 is not provided with a valve (connecting valve 311). Further, in the permeation water intake device 1a of FIG. 7, the air supply unit 34 is omitted.

In the normal operation of the permeation water intake device 1a, for example, the water intake pump 4 operates with the ventilation valve 322 closed and the water supply valve 331 fully opened. As a result, the permeated water in the chamber 32a is continuously sucked up and sent to the equipment in the subsequent stage (downstream side) such as the filtration unit. Further, by sucking up the permeated water in the chamber 32a, the permeated water is taken in through the water intake unit 2 and flows into the chamber 32a. In the backwash treatment, for example, osmotic water is supplied into the chamber 32a from a osmotic water tank provided after the water intake pump 4. As a result, the permeated water in the chamber 32a flows back to the water intake unit 2 via the connecting pipe 31 and is discharged from the water intake unit 2.

When the normal operation of the infiltration water intake device 1a is stopped, the water intake pump 4 is stopped and the water supply valve 331 is closed (FIG. 2: step S11). In the permeation water intake device 1a, the ventilation valve 322 is closed in advance, and the airtightness in the space above the liquid level in the chamber 32a is maintained. As a result, the water level in the chamber 32a is kept substantially constant (the water level is maintained). The ventilation valve 322 can be regarded as a water level maintaining mechanism for the chamber 32a. The water level may fluctuate slightly due to the compression and expansion of the air in the chamber 32a. Here, it is assumed that the intake pump 4 is stopped at the time of low tide. Therefore, the operations of steps S14 and S13 are performed in order. In the permeation water intake device 1a of FIG. 7, the air supply unit 34 is omitted, and the operation of step S12 is not performed.

As shown in FIG. 8, at low tide, the ventilation valve 322 is opened and the maintenance of the water level in the chamber 32a is released. At this time, the tide level is lower than the water level in the chamber 32a, the permeated water in the chamber 32a flows back to the water intake unit 2 via the connecting pipe 31, and the permeated water is discharged from the water intake unit 2 ( Step S14). Further, air flows into the chamber 32a through the ventilation pipe 321. Preferred conditions such as the flow velocity of the permeated water discharged from the water intake unit 2 are the same as those of the permeated water intake device 1 of FIG. In the calculation of the flow velocity, the water level lowering speed obtained by the water level sensor 52 and the cross-sectional area of the chamber 32a are used. The flow velocity of the permeated water can be changed by adjusting the opening degree of the ventilation valve 322 (the same applies in step S13). When the water level in the chamber 32a gradually decreases and becomes substantially equal to the tide level as shown in FIG. 9, the flow of seepage water in the water intake unit 2 and the connecting pipe 31 stops. After that, the ventilation valve 322 is closed, and the water level in the chamber 32a is maintained at a height corresponding to the tide level at low tide.

As shown in FIG. 10, when the tide is high, the ventilation valve 322 is opened and the maintenance of the water level in the chamber 32a is released. At this time, the tide level is higher than the water level in the chamber 32a, and the permeated water is taken in by the water intake unit 2 and flows into the chamber 32a via the connecting pipe 31 (step S13). In addition, air flows out of the chamber 32a through the ventilation pipe 321. Preferred conditions such as the flow velocity of the permeated water taken in from the water intake unit 2 are the same as those of the permeated water intake device 1 of FIG. In the calculation of the flow velocity, the water level rising speed obtained by the water level sensor 52 and the cross-sectional area of the chamber 32a are used. In the permeation water intake device 1a, the auxiliary water intake structure including the connection pipe 31, the chamber 32a and the ventilation valve 322 is changed from the water intake unit 2 to the chamber 32a due to the difference between the water level and the tide level in the chamber 32a when the water intake pump 4 is stopped. And let the seepage water flow.

When the water level in the chamber 32a gradually rises and becomes substantially equal to the tide level as shown in FIG. 11, the flow of seepage water in the water intake portion 2 and the connecting pipe 31 stops. After that, the ventilation valve 322 is closed, and the water level in the chamber 32a is maintained at a height corresponding to the tide level at high tide. In the permeation water intake device 1a, the operations of steps S14 and S13 are repeated until the normal operation is resumed.

Similar to the permeation water intake device 1 of FIG. 1, the permeation water intake device 1a of FIG. 7 also uses the tide to flow the permeated water from the water intake unit 2 to the chamber 32a and permeate the chamber 32a to the water intake unit 2. Water flow occurs. In this way, by passing seawater through the water intake unit 2 while the water intake pump 4 is stopped, oxygen is supplied to the aerobic microorganisms in the sand layer 91, and the biological filtration membrane can be appropriately maintained. To. In the permeation water intake device 1a, the air supply unit 34 is omitted, but since the permeation water in the chamber 32a is replaced by using the tide, a certain amount of dissolved oxygen is secured in the permeation water in the chamber 32a. It is possible. Therefore, it is possible to suppress the activation of sulfate-reducing bacteria and omit the waste water step when restarting the normal operation, or reduce the amount of waste water.

The permeation water intake devices 1, 1a can be modified in various ways.

In the above-mentioned osmotic water intake devices 1 and 1a, the osmotic water can be flowed by the auxiliary water intake structure utilizing tide. For example, a small auxiliary pump having a water supply capacity and power consumption smaller than that of the water intake pump 4 is connected. Permeated water may flow from the water intake unit 2 to the connecting pipe 31 by operating the auxiliary pump provided in 3 (for example, the connecting pipe 31). As described above, the auxiliary water intake means for flowing the permeated water from the water intake unit 2 to the connecting pipe 31 in the stopped state of the water intake pump 4 can be realized not only by the auxiliary water intake structure but also by various configurations. Similarly, the permeated water in the reservoir (in the above example, the intake well 32 or the chamber 32a) may be discharged from the water intake 2 by the operation of the auxiliary pump, and the permeated water in the reservoir is discharged from the water intake 2. The means can also be realized by various configurations. When using the auxiliary pump, a configuration in which the storage unit is omitted may be adopted.

In the permeation water intake device 1 of FIG. 1, if a storage portion having a sufficient size is provided, the connection valve 311 may be omitted. In this case, the flow of the seepage water from the water intake part 2 to the storage part and the discharge of the seepage water in the storage part from the water intake part 2 are carried out little by little according to the tide.

In the air supply unit 34, aeration may be performed by other than bubbling. For example, aeration may be performed by ejecting the seepage water sucked up from the bottom of the intake well 32 into the air from above the intake well 32 and returning it to the intake well 32. As described above, in the air supply unit 34, various configurations can be used in which air is supplied to the permeated water in the storage unit from other than the liquid level of the permeated water in the storage unit.

The water level maintaining mechanism for maintaining the water level in the intake well 32 or the chamber 32a may be realized by a mechanism other than the connection valve 311 and the ventilation valve 322. For example, in the connecting portion 3 shown in FIG. 12, in the intake well 32, a gate 311a is provided at the opening to which the connecting pipe 31 is connected. By closing the opening of the connecting pipe 31 by the gate 311a, the water level in the intake well 32 is maintained in the stopped state of the intake pump 4.

In the permeation water intake devices 1 and 1a, the water intake unit 2 is embedded in the sand layer 91 spread in the housing 90. As shown in FIG. 13, the water intake unit 2 is arranged in a recess provided on the seabed. By spreading sand on the water intake part 2, the water intake part 2 may be embedded in the sand layer 91 on the seabed.

The high tide and the low tide may be determined by the operator, and the operations of steps S13 and S14 of FIG. 2 may be performed by the input of the operator to the control unit of the infiltration water intake devices 1 and 1a. Further, depending on the design of the osmotic water intake devices 1, 1a, the operator manually opens and closes the connection valve 311 and the ventilation valve 322 and the gate 311a, that is, switches the maintenance and release of the water level in the reservoir by the water level maintenance mechanism. It may be done.

The above-described embodiment and the configurations in each modification may be appropriately combined as long as they do not conflict with each other.

1,1a Permeation intake device 2 Intake part 3 Connection part 4 Intake pump 31 Connection pipe 32 Intake well 34 Air supply part 91 Sand layer 311 Connection valve 311a Gate 322 Ventilation valve 32a Chamber S11-S14 Step

Claims (6)

It is a permeation water intake device
Intake part embedded in the sand layer provided on the seabed,
The connection part connected to the water intake part and
An intake pump that communicates with the intake portion via the connection portion and takes in permeated water that is seawater that has permeated the sand layer through the intake portion.
With
The connection part
The connection pipe connected to the water intake and
Auxiliary water intake means for flowing the permeated water from the water intake unit to the connection pipe when the water intake pump is stopped.
Equipped with a,
The auxiliary water intake means is provided with a storage portion into which the permeated water that has passed through the connecting pipe flows in, and the difference between the water level and the tide level of the permeated water stored in the storage portion when the intake pump is stopped. As a result, it has an auxiliary water intake structure that allows the permeated water to flow from the water intake part to the storage part.
The auxiliary water intake structure has an air supply unit that supplies air to the permeated water in the storage unit, and when the permeated water is backflowed in a stopped state of the water intake pump, the water level and the tide level in the storage unit are adjusted. A permeation water intake device, characterized in that the permeated water in the reservoir is discharged from the water intake unit due to the difference between the two. The permeation water intake device according to claim 1.
An osmotic water intake device, wherein the auxiliary water intake structure has a water level maintaining mechanism for maintaining the water level in the storage unit. The osmotic water intake device according to claim 1 or 2.
An osmotic water intake device characterized in that the intake speed of the osmotic water taken in from the water intake unit by the auxiliary water intake means is 5 to 200 m / day. It is a permeation water intake device
Intake part embedded in the sand layer provided on the seabed,
The connection part connected to the water intake part and
An intake pump that communicates with the intake portion via the connection portion and takes in permeated water that is seawater that has permeated the sand layer through the intake portion.
With
The connection part
The connection pipe connected to the water intake and
A storage section into which the permeated water that has passed through the connecting pipe flows in,
An air supply unit that supplies air to the permeated water in the storage unit,
A means for discharging the permeated water in the storage unit from the intake unit, and
An osmotic water intake device characterized by having. A method for maintaining a biological filtration membrane used for osmotic water intake by an osmotic water intake device.
The osmotic water intake device
Intake part embedded in the sand layer provided on the seabed,
The connection part connected to the water intake part and
An intake pump that communicates with the intake portion via the connection portion and takes in permeated water that is seawater that has permeated the sand layer through the intake portion.
With
The connection part
The connection pipe connected to the water intake and
A storage section into which the permeated water that has passed through the connecting pipe flows in,
An air supply unit that supplies air to the permeated water in the storage unit,
Have,
The method for maintaining the biological filtration membrane is
a) A step of supplying air to the permeated water in the storage unit by the air supply unit, and
b) A step of discharging the permeated water in the storage portion from the intake portion by the connection portion, and
A method for maintaining a biological filtration membrane, which comprises. The method for maintaining a biological filtration membrane according to claim 5.
A method for maintaining a biological filtration membrane, further comprising a step of flowing the permeated water from the intake portion to the connecting pipe by the connecting portion in a stopped state of the water intake pump.

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