JP5833493B2 - Multi-cylinder type automatic backwash strainer for ballast water treatment - Google Patents

Description

  The present invention relates to a multi-cylinder automatic backwash strainer that removes foreign matters from a liquid containing various foreign matters, and in particular, for example, organisms and impurities contained in ballast water supplied into a ballast tank of a ship. The present invention relates to a multi-cylinder automatic backwash strainer suitable for marine ballast water treatment for filtering foreign matter.

  Usually, this type of multi-cylinder strainer is used for ballast water treatment and the like because a plurality of cylindrical filtration elements are arranged in the strainer and is small in size and has a filtration ability. In particular, the multi-tube backwash strainer has an advantage that a large area of the filtration surface through which the raw water passes can be obtained as a whole because a large number of filtration elements can be arranged in the strainer. After flowing into the strainer from the inlet and into the filter element, it is filtered through the filter surface, but the flow rate of the raw water passing through the filter surface is the maximum near the upper blockage of the filter element, It becomes smaller near the lower opening. For this reason, the flow rate of the raw water passing through the filtration surface varies depending on the filtration surface part, and sludge quickly adheres to the primary side of the filtration surface near the filtration element upper blockage where the flow rate of the raw water is large, resulting in clogging. There is a tendency that the filtration capacity of the entire filtration element is lowered.

  When removing foreign matter (sludge) adhering to the primary side of the filtration surface of the filtration element by backwashing with filtered water from the secondary side, the flow rate of the backwash water passing through the filtration surface is It is the maximum near the lower opening, and becomes smaller near the upper closed portion. For this reason, in the vicinity of the upper closed part of the filtration element where the flow rate of backwashing water is small, the backwashing power for washing sludge adhering to the primary side of the filtration surface is small, and the backwashing function is not fully demonstrated. The filter capacity of the element cannot be fully recovered.

  As described above, in the multi-cylinder backwash strainer, the filtration element cannot be recovered by sufficiently backwashing the vicinity of the upper closed portion of the filtration element that is likely to clog due to sludge adhesion. The period during which the capacity can be maintained is shortened, and it is often necessary to stop the operation of the strainer and clean the filter element inside the strainer body. Therefore, in this type of strainer, it is desired to develop a strainer that satisfies both the filtration efficiency and the backwashing efficiency at the same time. In particular, the development of improved technology has been eagerly desired for the multi-cylinder backwashing strainer for ballast water treatment. .

  As these improved technologies, a strainer mechanism shown in Patent Document 1 or Patent Document 2 has been proposed. In Patent Document 1, a flow element that is constantly narrowed from the closed end face toward the end face opening is provided in a cylindrical filter body having one end face closed and the other end face provided with an opening. Describes a bottomed cylindrical filter element that allows the flow rate of fluid passing through the filter surface to be substantially the same, the load on the filter surface to be the same, and sludge to adhere uniformly to the filter surface.

Patent Document 2 discloses a backwash filter device in which the screen itself is configured in a tubular wedge-shaped cone, and uses at least one conical tubular wedge-shaped wire screen filter element instead of the cylindrical filter element to perform filtration. together to reduce the resistance of the fluid when the element is in when it is backwashed, backwashing strainer that can be washed filtration surface by backwash flow is proposed.

Japanese Unexamined Patent Publication No. 63-171612 JP-T-2001-516278

  However, the bottomed cylindrical filter element described in Patent Document 1 substantially reduces the flow rate of the fluid passing through the filtration surface when filtering by passing the fluid from the inside to the outside of the filtration element or from the outside to the inside. A filtration element is disclosed that filters the fluid in a constant manner. That is, although the said literature 1 is disclosed about filtration, the matter which flushes and removes the sludge adhering to the primary side of the filtration surface by backwashing is not indicated or suggested.

  In the strainer described in Patent Document 2, since the filtration element is formed in a vertically long conical shape, the filtration area is smaller than the filtration element formed in a cylindrical shape with the same height and diameter, and the wire screen Therefore, it is more difficult to form the filter element of the filter element in a conical shape than in the case of forming it in a cylindrical shape, and it is difficult to obtain the required backwashing power, which is particularly unsuitable for ballast water treatment. It is a strainer.

The present invention has been developed in order to solve the above-mentioned problems, and the object of the present invention is to effectively perform the filtration capability and to backwash the sludge adhering to the primary side of the filtration surface. It is a filtration element that can remove sludge adhered to any part of the filtration surface and restore the filtration ability by making the force uniform over the longitudinal direction of the filtration element, An object of the present invention is to provide a multi-cylinder type automatic backwash strainer for ballast water treatment which is excellent in ballast water treatment .

In order to achieve the above-mentioned object, the invention according to claim 1 is characterized in that a large number of communication holes are equidistantly arranged on a concentric circle in a partition plate that divides a raw water chamber having an inlet and a filtration chamber having an outlet in the strainer body. A large number of the filtration elements are vertically installed and fixed in the filtration chamber in a state in which the lower openings of the narrow and narrow cylindrical filtration elements having an aspect ratio of 10 or more with the upper end closed in the communication holes are communicated. The filtration element is in the shape of an elongated cylinder in a state in which wedge wires in a state where the bottom of the triangular cross section is located on the inner circumference are juxtaposed along the length direction of the filtration element in the vertical direction via a filtration gap. configured, wherein the the filtration elements, built in a state in which said elongated formed in a tapered shape toward the lower opening of the upper end of the small diameter cone was suspended from the upper closed portion of the filter element, wherein Bottom of small cone Parts are together arranged in the upper region than the lower opening of the filter element, provided backwash arm pivotably to the raw water chamber, opposite the outlet of the backwash arm in a state in which communication with the communication port A ballast water treatment system in which a washing arm is communicated with a discharge port provided in a strainer body, and backwashing power is maintained over the length direction of the filtration element by a differential pressure between the filtration chamber and the inside of the filtration element. This is a cylindrical automatic backwash strainer.

The invention according to claim 2 is the multi-cylinder type automatic backwash strainer for ballast water treatment in which the small-diameter cone is made of resin, wood or metal.

According to a third aspect of the present invention, there is provided a strainer in which the filter element is held in a cylindrical shape by being fixed to either the inner or outer periphery of the filter element with a holding material.

According to the present invention, when sludge adhering to the primary side of the filtration surface is removed by backwashing with filtered water, the pressure difference between the filtration chamber in the strainer body and the filtration element and the small diameter built in the filtration element Since the cone can maintain the backwashing force uniformly over the length of the filter element, sludge adhering to any part of the filtration surface in the length direction can be reliably removed. Thus, the filtration capacity of the filtration element can be recovered, so that it is possible to obtain a multi-cylinder automatic backwash strainer for ballast water treatment that is excellent in operating rate and maintainability.

Moreover, since the filtration elements are formed in an elongated shape, a large filtration area can be secured for the strainer as a whole by arranging a plurality of filtration elements in the strainer body, and the interval between the arranged filtration elements. by securing a sufficient, it is possible to prevent a decrease in filtration capacity due to mutual interference of the filtered water that has passed through the filter element, it is possible to obtain a multi-barrel type automatic backwash strainer with large filtering capacity, the ship Suitable as a strainer for marine ballast water treatment.

Furthermore , since the lower end of the narrow cone housed inside the filter element is arranged in a region above the lower opening of the filter element, the lower end of the narrow cone has the area of the lower end opening of the filter element. There is no narrowing. For this reason, the pressure loss of backwash water flowing through the filter element after backwashing the filtration surface and flowing out from the lower end opening is small, and the flow rate reduction of the backwash water passing through the filtration surface is also small. A multi-cylinder automatic backwash strainer having the following can be obtained.
In addition, since the filtration element is formed by forming the wedge wire with the bottom of the triangular cross section located on the inner circumference into a cylindrical shape, the gap between the wedge wires through which raw water and backwash water pass is the length of the filtration element. By being continuously formed in the vertical direction, the narrow cone arranged in the filter element can sufficiently exert the effect of controlling the flow of raw water and backwash water, and the filtration gap between the wedge wires Can be obtained, and a multi-cylinder type automatic backwash strainer having a filtration element with a large backwashing power for backwashing sludge adhering to the primary side of the filtration surface can be obtained. In this case, if the wedge wires with the bottom of the triangular cross-section located on the inner circumference are arranged in parallel in the vertical direction via the filtration gap, and configured in a cylindrical shape, the differential pressure in the filtration chamber and the filtration element and the filtration element The built-in small diameter cone can maintain the backwashing force uniformly over the length of the filter element, and the synergistic effect with the filter gap arranged in the vertical direction allows Any sludge adhering to any part of the filtration surface can be reliably removed to restore the filtration ability of the filtration element.

Since the filter element is closed at the top, a small cone made of resin, wood or metal is attached and suspended inside, so the filter surface is backwashed and backwashed into the filter element. The water is rectified into a flow along the surface of the narrow cone. Moreover, the space formed between the filtration surface of the filtration element and the surface of the small-diameter cone expands from the upper closed portion of the filtration element toward the lower opening. For this reason, the pressure loss of the backwash water flowing inside the filter element is small, and the flow rate of the backwash water passing through the filtration surface is substantially uniform over the length of the filter element. Multi-cylinder automatic reverse that can be almost uniform over the length direction of the filter, and even if sludge adhering to any part of the filtration surface is backwashed and removed, the filtration ability can be recovered A wash strainer can be obtained.

1 is a schematic cross-sectional view showing an embodiment of a multi-cylinder automatic backwash strainer for ballast water treatment according to the present invention. It is a schematic diagram which shows an example of the arrangement | positioning condition of the filtration element in a strainer main body. It is a partial external view of a filtration element. It is a schematic diagram which shows the AA cross section of the filtration element. It is sectional drawing of the vertical direction of a filtration element It is a schematic diagram which shows the condition which attached the filtration element in the container main body. It is the elements on larger scale explaining the state which fixes the filtration element with the filtration element attachment plate. Is a schematic view illustrating the status of the filtration surface when the c Ejjiwaiya was used in a vertical slot-like to form a filter element.

An example of an embodiment of a multi-cylinder automatic backwash strainer for ballast water treatment according to the present invention will be specifically described based on the drawings.
FIG. 1 is a schematic sectional view showing an embodiment of a multi-cylinder automatic backwash strainer according to the present invention. In the figure, a multi-cylinder type automatic backwash strainer 1 includes a cylindrical strainer body 2, a lid 3 that covers the upper portion of the strainer body 2, a bottom plate 4 of the strainer body 2, and an inlet 5 in the strainer body 2. A filtration chamber 8 having an outlet 7 in the strainer body 2, a partition plate 9 for partitioning the raw water chamber 6 and the filtration chamber 8 in the strainer body 2, and a partition plate 9 A plurality of small-diameter cylindrical filter elements 11 that are attached to and communicated with a large number of communication holes 10 formed on the fixed plate 12 that fixes the filter elements 11 in the strainer body 2 and the filter elements 11 are provided. The backwashing mechanism 13 for backwashing and the drive mechanism 14 for rotating the backwashing mechanism 13 are provided .

As shown in FIG. 2, the partition plate 9 is formed with a large number of communication holes 10 communicating with the upper surface and the lower surface of the partition plate 9 on the circumference around the rotation shaft 15. Installs the filter element 11 upright. In the figure, the communication hole 10, that has provided a number of holes formed at equal intervals on a concentric circle.

In FIG. 3, the filter element 11 is formed by arranging wedge wires 16 in a vertical slot shape (the length direction of the filter element) to form a cylinder, and then winding a metal holding member 17 around the outer peripheral surface of the cylinder in a spiral shape. Then, the upper fixture 18 and the lower fixture 19 are fixed to both ends of the cylinder by an appropriate method such as welding. That is, as shown in FIG. 4, the filter element 11 is arranged wedge wire 16 which is located at the inner periphery of the base of the triangular cross-section in the longitudinal direction is configured in a cylindrical shape (see Figure 8). In this example, the wedge wire portion of the filter element 11 is formed in a thin cylindrical shape having an outer diameter of 34 mm and a length of 500 mm. Further, as shown in the schematic cross section of FIG. 4, the wedge wire 16 having a triangular cross section constituting the filter element 11 is welded to the holding member 17 at the top portion 20 facing the outer side, and the filtration gap 21 is spaced at regular intervals. The filtration surface 22 is formed by the wedge wires 16 that are opened and arranged. The holding material 17 may be installed on the inner periphery of the filtration element 11. The filtration gap 21 that is the opening of the filtration element 11 is appropriately set according to the properties and size of the sludge contained in the raw water .

  Next, the filtration element 11 shown in FIG. 5 will be described. A through hole 24 for inserting the small-diameter cone 23 is drilled in the upper fixture 18 of the filter element 11, and raw water is introduced into the filter element 11 in the lower fixture 19. A flow hole 25 for discharging the washing water from the inside of the filter element 11 is provided, and a lower opening 26 of the filter element 11 is formed.

The small-diameter cone 23 is formed in a downward truncated cone shape with the upper end position of the wedge wire 16 of the filtration element 11 as a bottom surface, a flange portion is provided at the upper portion, and the height 28 of the small-diameter cone 23 is thin. for the lower end portion 29 of the diameter cone 23 is present in the upper area than the lower opening mouth 26 of the filter element 11 is set lower than the height 30 of the wedge wire 16. 5 and 6, the lower end portion 29 of the small-diameter cone 23 housed inside the filtration element 11 is disposed in a region above the lower opening 26 of the filtration element 11, and is further blocked by the upper portion of the filtration element 11. A thin conical body 23 made of synthetic resin attached in a state is suspended from the element 11 and incorporated. The attachment structure for suspending the small-diameter cone 23 in this case is an example, and any attachment method may be used as long as it is a suspension structure. The material of the small-diameter cone is not limited to synthetic resin. It may be made of wood or metal, and these are optional depending on the implementation.

  In addition, the narrow cone 23 controls the flow of the raw water or the backwash water when the raw water or the backwash water flows along the tapered surface 31 of the narrow cone 23. Therefore, the narrow cone 23 is affected by the flow of the raw water or the like. It is preferably formed of a non-deformable synthetic resin, wood or metal water-impermeable material.

  As shown in FIG. 5, the lower fixture 19 has a flange 33 formed in the upper portion, and when the tip of the lower fixture 19 is inserted into the communication hole 10 provided in the partition plate 9, the lower surface of the flange 33 is partitioned. Abutting on the upper surface of the plate 9, the lower fixture 19 is inserted into the partition plate 9 and fixed in close contact.

  As shown in FIG. 6, when the lower fixture 19 is inserted into the partition plate 9 and then the upper fixture 18 is inserted into the fixing hole 34 provided in the fixing plate 12, the filtering element 11 is placed inside the strainer body 2. Established.

  The backwashing mechanism 13 shown in FIG. 1 includes a backwashing pipe 38 that is rotated by the drive mechanism 14, a backwashing pipe base 39 that supports the backwashing pipe 38, and a backwashing arm 40 that is fixed to the backwashing pipe 38 and rotates together. And a sliding part 41 provided on the upper part of the backwash arm 36 and a backwash nozzle 42 for discharging backwash water to the outside of the strainer body 2.

  In FIG. 7, the sliding portion 41 includes a mounting base 43 provided integrally with the backwashing arm 40 on the backwashing arm 40, and a sliding member that is operatively supported by inserting the bottom into the mounting base 43. 44, and a coil spring 48 disposed between the upper surface 45 of the attachment base 43 and the lower surface 47 of the stepped portion 46 provided on the sliding member 44. Due to such a configuration, the sliding portion 41 is urged by the coil spring 45, and the upper end surface 49 of the sliding member 44 always rotates while being in close contact with the lower surface 47 of the partition plate 9.

  In FIG. 1, the drive mechanism 14 includes an electric motor 51, a speed reduction mechanism 52 that decelerates the rotation of the electric motor 51 and changes the rotation direction, and a drive shaft 53 that transmits the driving force of the electric motor 51 to the backwash mechanism 13. It consists of and. In the present embodiment, the backwash mechanism 13 is rotated by the electric motor 51, but a manual drive mechanism can also be used.

  When raw water is filtered by the multi-cylinder automatic backwash strainer 1 configured as described above, the raw water is pumped from the inlet 5 to the raw water chamber 6 in the strainer body 2 by a pump (not shown). The raw water pumped to the raw water chamber 6 in the strainer main body 2 passes through the plurality of communication holes 10 opened in the partition plate 9 and into the plurality of filtration elements 11 attached to the flow holes 10. Inflow through.

  At this time, in a cylindrical filter element with a closed upper part that does not have a small-diameter cone, the raw water blows up to the closed part of the upper part of the filter element at once, and a lateral velocity component is generated by colliding with the closed part. The flow rate of the raw water passing through the filtration surface is large in the upper part of the filtration element and is small in the vicinity of the lower opening. As a result, sludge adheres to the primary side of the filtration surface near the top of the filtration element at an early stage.

  On the other hand, in the filtration element 11 in this example, the raw water that is pumped by the pump and flows into the filtration element 11 from the lower opening 26 is suspended in the filtration element 11. The flow is rectified by the body 23 and flows along the tapered surface 31 of the tapered cone 23.

  Since the tapered surface 31 of the small-diameter cone 23 linearly expands from the lower part to the upper part of the filtering element 11, the raw water rising along the tapered surface 31 in the filtering element 11 has a length of the filtering element 11. The same velocity component in the lateral direction is generated in the vertical direction, and as a result, the flow rate of the raw water passing through the filtration surface 22 is substantially the same in any part of the filtration surface 22.

  For this reason, in the filtration element 11 in which the small-diameter cone 23 in the present example is suspended, the sludge adhering to the primary side of the filtration surface 22 is distributed unevenly on the entire filtration surface 22 without being unevenly distributed at a specific site. The filtration capacity of the filtration surface 22 can be maintained for a long time.

  When the lower end 29 of the small diameter cone 23 is at the position of the lower opening 26, a lateral velocity component is generated in the raw water due to the influence of the tapered cone 23 before the raw water flows into the filter element 11. This prevents the raw water from smoothly flowing into the filter element 11. Therefore, the position of the lower end portion 29 of the small-diameter cone 23 is separated from the lower opening 26 of the filter element 11 by an appropriate distance to the upper region.

  Next, the raw water that has flowed into the filter element 11 is freed of sludge contained when passing through the filter surface 22, becomes filtered water, flows out into the filter chamber 8, and flows out of the strainer body 2 from the outlet 7. Discharged.

  The raw water does not flow into the filter element 11 communicating with the sliding member 44 of the backwash arm 40 among the filter elements 11, and no filtration is performed. At this time, in order to backwash and remove the sludge adhering to the primary side of the filtration surface 22, when a valve (not shown) provided in the backwash nozzle 42 is opened, the inside of the filtration element 11 is passed through the backwash nozzle 42. The outside communicates with each other to generate a differential pressure, and the filtered water present in a state of being pressurized in the filtration chamber 8 in the strainer body 2 passes through the filtration surface 22 and flows into the filtration element 11. The inflow backwash water is washed out and removed from the sludge adhering to the primary side of the filtration surface 22, and discharged to the outside of the strainer body 2 through the backwash arm 40, the backwash pipe 38, and the backwash nozzle 42. Is done.

  Here, simply showing an example of a cylindrical filter element with a closed top that does not have a thin cone, the backwash water flowing into the filter element collides and becomes turbulent. Since the cross-sectional area of the flow path is constant, the pressure loss of the backwash water flowing inside is large. For this reason, the flow rate of backwash water passing through the filtration surface is fast at the lower part of the filtering element that can reach the lower opening immediately after passing through the filtration surface, but the lower part is opened even after passing through the filtration surface. The distance to the mouth slows toward the upper part. As a result, the vicinity of the upper part of the filtration element where the sludge is thickly adhered cannot be sufficiently backwashed, and the filtration ability cannot be sufficiently recovered.

  On the other hand, in the filtration element 11 in this example, since the small-diameter cone 23 is suspended therein, the backwash water flowing into the filtration element 11 is opened at the lower portion by the tapered surface 31 of the tapered cone 23. The flow is rectified into the flow toward the mouth 26. Further, the space between the filtration surface 22 inside the filtration element 11 and the tapered surface 31 of the small-diameter cone 23 expands from the upper part to the lower part of the filtration element 11. For this reason, since the cross-sectional area of the flow path of the backwash water that has passed through the filtration surface 22 and flowed into the filtration element 11 into the filtration element 11 increases as it approaches the lower part of the filtration element 11, There is little pressure loss of backwash water flowing inside. Therefore, the flow rate of the backwash water passing through the filtration surface 22 by the differential pressure generated by the communication between the inside and outside of the filtration element 11 via the backwash nozzle 42 is substantially the same in any part of the filtration surface 22. . As a result, a uniform backwashing force can be maintained over the length direction of the filter element 11, so that sludge uniformly distributed and adhering to the primary side of the filtration surface 22 can be backwashed evenly. The filtration capacity of the filter element 11 can be recovered.

  Further, as shown in FIG. 4, the filtration element 11 is formed by positioning the bottom side of the wedge wire 16 having a triangular cross section on the inner periphery, so that the flow between the wedge wires 16 and 16 through which the backwash water passes is formed. Since the cross-sectional area decreases in a tapered state, the flow rate of backwash water passing through this flow path increases and the backwash power increases.

  Even when the filtration surface 22 is backwashed, if the lower end portion 29 of the small-diameter cone 23 extends to the lower opening 26 of the filtration element 11, the backwash water flows out of the filtration element 11 due to the presence of the lower end portion 29. Therefore, the lower end 29 of the tapered cone 23 is separated from the lower opening of the filter element 11 by an appropriate distance to the upper region.

  The multi-cylinder automatic backwash strainer 1 in this example has a large filtration area because a plurality of filtration elements 11 are arranged in the strainer body 2, and has a large filtration capacity compared to the size of the strainer body 2. doing. Further, since the filtration element 11 is formed in an elongated shape with an aspect ratio of 10 or more, a sufficient space can be secured around each filtration element 11 arranged in the strainer body 2. The filtered water that has passed through the filtration surface 22 does not interfere with each other and reduce the filtration efficiency.

  The backwashing of the filter element 11 may be performed by always operating the backwashing mechanism 13 to sequentially backwash the filter element 11, or by providing pressure sensors at the inlet 5 and outlet 7, and the difference detected by both sensors. When the pressure exceeds a certain value, it may be judged that sludge adheres to the filtration surface 22 and the filtration capacity is lowered, and the backwash mechanism 13 is operated to sequentially backwash the filter element 11, It is also possible to perform a timer operation by providing a timer (not shown). In addition, the swirling method of the backwash arm 37 may be a continuous swirl that slowly swivels at a constant angular velocity, or the backwash arm 37 is backwashed after being stopped for a certain period of time in a state where the communication hole 10 and the sliding member 44 communicate with each other. Thereafter, intermittent swirling may be performed by repeatedly swirling to the next communication hole 10 and backwashing.

  As described above, the small-diameter cone 23 suspended in the filter element 11 in this example controls the flow in the length direction of the raw water and backwash water flowing through the filter element 11 and passes through the filter surface 22. The flow rates of the raw water and the backwash water are made constant over the length of the filter element 11. As a result, the flow rates of the raw water and backwash water passing through the filtration surface 22 are substantially the same in any part of the filtration surface 22, so that sludge does not adhere unevenly to the filtration surface 22, and backwash water Thus, any portion of the filtration surface 22 can be reliably backwashed.

  The multi-cylinder automatic backwash strainer according to the present invention has a high filtration capacity even if it is small, and can operate while maintaining the high filtration capacity for a long time. When the sludge adheres to the side and the filtration capacity decreases, the filtration surface can be backwashed by a simple operation to reliably remove the sludge and restore the filtration capacity. Excellent and useful value.

The multi-cylinder automatic backwash type strainer of the present invention is suitable for a strainer provided in a ballast water treatment apparatus for a ship, and since it is small in size, it can be easily installed in a narrow ship. In addition, high filtration capacity and high precision back-cleaning ability can quickly filter the ballast water loaded in large quantities to remove harmful microorganisms and send them to the next treatment process. In some cases, the filtration capacity can be automatically recovered by remote operation, and therefore, it is suitable for use as a prefilter of a ballast water treatment apparatus .

DESCRIPTION OF SYMBOLS 1 Multi-cylinder type automatic backwashing type strainer 2 Strainer main body 5 Inlet 6 Outlet 9 Partition plate 10 Communication hole 11 Filtration element 13 Backwashing mechanism 14 Drive mechanism 16 Wedge wire 23 Small diameter cone 31 Tapered surface 40 Backwashing arm 42 Backwash nozzle

Claims (3)

A partition plate that partitions the raw water chamber having an inlet and a filtration chamber having an outlet in the strainer body has a large number of communication holes formed at equal intervals on a concentric circle, and the aspect ratio is such that the upper ends of these communication holes are closed. A large number of the filtration elements are vertically fixed in the filtration chamber in a state where the lower opening of the filtration element having a long and narrow shape of 10 or more is in communication, and the filtration element has an inner circumference with a triangular base in the inner periphery. The wedge wire in the state of being placed in the longitudinal direction of the filtration element is arranged in parallel in the longitudinal direction through the filtration gap, and is formed into an elongated cylindrical shape. The upper end of the long narrow cone formed in a tapered shape is built in a state suspended from the upper end closing portion of the filter element, and the lower end of the narrow cone is the lower part of the filter element. Above the opening While disposed band, provided the backwash arm pivotably to the raw water chamber, communicating the outlet of the backwash arm backwash arm to the discharge port formed in a strainer body in a state in which communication with the communication port And a multi-cylinder type automatic backwash strainer for ballast water treatment , wherein the backwashing force is maintained over the length of the filter element due to the differential pressure between the filter chamber and the filter element. . The thin conical body, a resin, a multi-cylinder-type automatic backwash strainer for ballast water treatment of claim 1 which is made of wood or metal. The multi-cylinder type automatic backwash strainer for ballast water treatment according to claim 1 or 2 , wherein the filtration element is held in a cylindrical shape by being fixed to either the inner or outer periphery of the filtration element with a holding material.

Images