JP2007069065A - Filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filter which allows washing wastewater to flow out efficiently and uniformly even if a filtering area is large and sharply enhances not only a washing effect but also filtering treatment efficiency. <P>SOLUTION: In the filter constituted by providing a raw water inflow part 11 and a drain trough 12 to the upper part of a filter tank 16 and providing a treated water outflow part 13, a cleaning water introducing part 14 and a cleaning air introducing part 15 to the lower part of the filter tank 16, a filter bed 21 filled with a filter medium with a specific gravity of 1 or above is formed to the lower part of the filter tank 16 and an intermediate drain means 17 equipped with a plurality of drain opening parts 31 is provided to the middle stage part of the filter tank 16 at the part just above the filter bed 21. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a filtration device, and more particularly to a filtration device that performs filtration treatment in water treatment facilities such as water treatment and sewage treatment.

The filtration apparatus which filled the filter medium in the filtration tank and formed the filter layer alternately performs the filtration process which takes in raw | natural water in a filtration tank, and takes out treated water, and the washing | cleaning process for wash | cleaning a filter medium. In the washing process of the filter medium, generally, washing water or air is introduced from below the filter bed, and washing waste water is led out from the upper part of the filtration tank. In such a filtration device, in order to improve the discharge effect of turbidity (detained matter) washed out from the filter medium during the washing process, shorten the washing time and reduce the amount of washing water, It has been proposed to provide a screen that prevents the outflow of water (for example, see Patent Document 1).
JP-A-9-24212

  However, simply providing a screen at the outflow part of the cleaning wastewater does not allow the cleaning wastewater to flow out uniformly from the entire filtration surface, and it can exert a sufficient effect on a filtration device with a large filtration area. could not.

  Therefore, the present invention provides a filtration device that can efficiently and uniformly discharge washing wastewater even if the filtration area is large, greatly improve the washing effect, and greatly improve the efficiency of the filtration treatment. It is intended to provide.

  In order to achieve the above object, the filtration device of the present invention has a raw water inflow portion and a drain trough in the upper part of the filtration tank, and a treated water outflow part, a washing water introduction part, and a cleaning air introduction part in the lower part of the filtration tank. A filter layer filled with a filter medium having a specific gravity of 1 or more in the lower part of the filtration tank, and a plurality of drainage openings directly above the filter layer in the middle part of the filter tank An intermediate drainage means provided with

  In particular, the filtration device of the present invention is such that the drain openings are evenly distributed with respect to the filtration surface of the filter layer, and include opening / closing means for opening and closing the drain openings, A filter medium outflow prevention plate is provided between the intermediate drainage means and the drainage trough.

  The open / close means is movably fitted to an outer periphery or an inner periphery of the intermediate drain pipe provided with the drainage opening, and a movable pipe provided with an opening at a position corresponding to the drainage opening, Movable pipe moving means for moving the movable pipe in the circumferential direction or the axial direction with respect to the intermediate drain pipe, the movable pipe moving means, the open position that matches the opening to the drain opening, The movable pipe is moved to a closed position where the drainage opening is closed by a pipe wall of the movable pipe.

  Further, a filter medium outflow prevention means may be provided in the drainage opening, and the drainage opening is preferably opened downward. Further, the filter medium is silica sand having a particle size of 0.4 to 2.0 mm, anthracite having a particle size of 0.8 to 5.0 mm, ceramics having an outer size of 0.4 to 10 mm, and an outer size of 2.0. ~ 20mm plastic, non-woven fabric or sponge having outer dimensions of 3.0 to 20mm, preferably having a specific gravity in the range of 1-3, and the filter layer is a single bed type filled with one of the filter media It is preferably a fixed bed or a multi-bed fixed bed filled with a plurality of kinds of the filter media.

  Further, the filtration device of the present invention is provided with a pair of upper and lower filter medium support plates between the intermediate drainage means and the drainage trough, and an upper filter layer filled with a filter medium between both filter medium support plates, and a lower filter medium Upper cleaning air introducing means for introducing upper filter medium cleaning air can be provided below the support plate. At this time, the filter medium filled in the filter layer is composed of silica sand and particles having a particle diameter of 0.4 to 2.0 mm. An anthracite having a diameter of 0.8 to 5.0 mm, a ceramic having an outer dimension of 0.4 to 10 mm, and a plastic having an outer dimension of 2.0 to 20 mm, and the filter medium filled in the upper filter layer is The outer dimension is preferably at least one of a nonwoven fabric or a sponge having a size of 3.0 to 20 mm.

  Furthermore, the filtration device of the present invention is provided with a carrier floating part into which a floating carrier is introduced at the upper part of the filter layer, and provided with a diffuser for aerating the carrier floating part at a lower part of the carrier floating part, A floating carrier outflow prevention plate may be provided below the drainage trough above the carrier floating portion. In this case, the floating carrier is preferably at least one of a nonwoven fabric, a sponge, and a plastic foam having an outer dimension of 2 to 20 mm and a specific gravity of 0.9 to 1.1, and is below the carrier floating part. It is preferable to provide a floating carrier support plate and to provide the air diffusion means and the intermediate drainage means below the floating carrier support plate.

  In addition, a flocculant charging means for charging the flocculant into the raw water flowing into the filtration tank can be provided. In particular, it is preferable to use a metal flocculant capable of removing phosphorus as the flocculant.

  According to the filtration device of the present invention, since the washing waste water can be made to flow uniformly from directly above the filtration layer, the filtration layer can be efficiently washed. Thereby, the amount of washing water can be reduced, the quality of treated water can be improved, the filtration speed can be increased, and the filtration device can be reduced in size, and the installation cost and the maintenance cost can be reduced.

  FIG. 1 shows a first embodiment of the filtration device of the present invention, and is an explanatory view in which the present invention is applied to a downflow type two-layer filtration device. FIG. 2 is a schematic front view showing one embodiment of the intermediate drainage means.

  The filtration apparatus shown in the present embodiment has a raw water inflow portion 11 and a drainage trough 12 in the upper portion, and a filtration tank 16 having a treated water outflow portion 13, a washing water introduction portion 14 and a cleaning air introduction portion 15 in the lower portion. The filter layers 21 and 22 are formed in two upper and lower layers, and an intermediate drainage means 17 and an upper cleaning air introduction means 18 are provided between the upper and lower filter layers 21 and 22. Further, in this embodiment, a flocculant addition means 19 is provided for adding a flocculant to the raw water flowing into the filtration tank 16 from the raw water inflow portion 11.

  For the filter medium of each filter layer 21, 22, a specific gravity of 1 or more, preferably a filter medium having a specific gravity in the range of 1 to 3, can be appropriately selected and used. Specifically, silica sand having a particle diameter of 0.4 to 2.0 mm, anthracite having a particle diameter of 0.8 to 5.0 mm, ceramics having an outer dimension (minimum dimension) of 0.4 to 10 mm, and an outer dimension of A plastic of 2.0 to 20 mm, a non-woven fabric or a sponge having an outer dimension of 3.0 to 20 mm can be used. These filter media can be used alone or in combination according to the purpose of treatment.

  In the present embodiment, a lower filter layer (hereinafter referred to as a lower filter layer) 21 which is a main filter layer is formed of gravel having a particle diameter of 2 to 12 mm on a partition plate 24 having a plurality of water collecting nozzles 23. It is formed to a height of about 1 m through a support layer 25 filled to a height of about 3 m. As the filter medium used for the lower filter layer 21, it is necessary to select a filter medium having a specific gravity smaller than that of gravel or having a slow settling speed so that the gravel and the upper and lower sides are not reversed during washing. In consideration of the quality of the treated water, it is preferable to use a filter medium having a small particle size capable of microfiltration, for example, a filter medium having a particle size or an outer dimension of 1 mm or less, specifically, a particle size (effective diameter). Silica sand having a uniformity coefficient of 1.3 at 0.6 mm can be suitably used.

  The gravel constituting the support layer 25 is, in order from the bottom, gravel with a particle size of about 8 to 12 mm is about 100 mm, gravel with a particle size of about 4 to 8 mm is about 100 mm, and gravel with a particle size of about 2 to 4 mm is about 100 mm. The filling height is about 300 mm in total.

  In the upper filter layer (upper filter layer) 22, the filter medium is thrown between the pair of upper and lower filter medium support plates 26, 26 arranged at an interval of about 2 m so as to have a height of about 1 m (volume ratio 50%). Is formed. As the filter medium used for the upper filter layer 22, it is preferable to select a filter medium having a large SS trapping amount. For example, it is preferable to use a nonwoven fabric or sponge having a relatively large outer dimension. Specifically, a nonwoven fabric having a porosity of about 90% obtained by heat-sealing 4 to 25 denier polyester fibers and having a size of 10 mm × 10 mm × 5 mm can be suitably used. As the upper and lower filter media support plates 26, those having through holes as large as possible are used as long as such filter media do not pass through. For example, in the case of the polyester fiber nonwoven fabric, punching metal having a hole diameter of about 6 mm should be used. Can do. The upper and lower filter medium support plates 26 may be the same or different.

  As shown in FIG. 2, the intermediate drainage means 17 includes a movable pipe 33 having an inner diameter corresponding to the outer diameter of the intermediate drainage pipe 32 in the circumferential direction on the outer circumference of the intermediate drainage pipe 32 provided with the drainage opening 31. The movable pipe 33 has a double pipe structure that is movably fitted, and an opening 34 is provided on the peripheral wall of the movable pipe 33 at a position corresponding to the drain opening 31. Both end portions of the intermediate drain pipe 32 are fixed to the tank wall 16a of the filtration tank 16, respectively, one end side penetrates to the outside and is connected to the washing water discharge pipe 17P, and the other end portion incorporates a worm gear or the like. A gear box 35 is provided. One end of the movable tube 33 is connected to a rotating member in the gear box 35, and a gear 36 is operated by rotating a driving shaft 37 by operating a driving device 36 such as a motor installed above the filtration tank 16. The movable tube 33 is formed so as to be able to rotate between an open position and a closed position via 35.

  Therefore, the movable pipe 33 is moved (rotated) in the circumferential direction with respect to the intermediate drain pipe 32 so as to be in the open position, so that the drain opening 31 is opened only when the drain operation is performed from the intermediate drain means 17. In the open state in which 34 is matched, drainage is performed from directly above the filtration layer 21 in the middle of the filtration tank. In other cases, the movable pipe 33 is rotated to the closed position to open the drainage opening 31 to the movable pipe 33. By closing the tube wall with the tube wall, it is possible to prevent the filter medium from flowing out from the intermediate drainage means 17.

  The shape and opening area of the drainage opening 31, the position of the gear box 35 and the connection direction to the cleaning water discharge pipe 17 </ b> P are arbitrarily set according to conditions such as the size of the intermediate drainage means 17 and the filtration area. be able to.

  The drainage trough 12 is a U-shaped trough similar to the conventional one that is open at the top, and allows washing wastewater to flow out from the upper part of the filtration tank during the washing process. The upper cleaning air introducing means 18 is provided with a large number of air holes in a pipe installed in a loop shape, and the air holes are arranged so that the cleaning air can be uniformly supplied to the upper filter layer 22. ing.

  As the flocculant added from the flocculant adding means 19, various polymer polymers, or metal-based flocculants mainly composed of aluminum, iron or the like can be used, and such flocculants are added. Thus, the filtration performance can be improved. In particular, by using a metal flocculant such as polyaluminum chloride (PAC) or polyferric sulfate (polyiron), phosphorus can be removed simultaneously with the filtration treatment.

  In the filtration device thus formed, the filtration process is performed with the valves 11V and 13V of the raw water inflow portion 11 and the treated water outflow portion 13 opened, and a predetermined amount of flocculant added from the flocculant addition means 19. Is called. At the beginning of the process, the liquid level (WL) is positioned slightly above the upper filter layer 22 and the liquid level rises as the filtration process proceeds. When the liquid level (WH) rises to a predetermined height above the drainage trough 12, or according to conditions such as timer and treated water turbidity, the filtration process is completed, and the valves 11V and 13V are closed and the washing process to go into.

  In the cleaning process, a first draining process is first performed. In the first draining step, the upper drain valve 12V of the drain trough 12 is opened, the driving device 36 is operated, and the movable pipe 33 is rotated to the open position where the opening 34 matches the drain opening 31. This is done by opening the intermediate drain valve 17V of the intermediate drain means 17, and the water level is lowered to a position above the upper filter layer 22 by a predetermined height.

  Next, after the intermediate drainage means 17 is closed and the intermediate drainage valve 17V is closed, the valve 18V of the upper washing air introduction means 18 is opened to perform the washing process of the upper filter layer 22, for example, the washing speed is about 1 m / Perform for about 5 minutes as min. After the air washing process is completed, in order to prevent the filter medium from flowing out in the next second draining process, a stationary process is performed in which the filter medium is allowed to settle for about 1 minute.

  In the second draining step after the stationary step, the drainage of the intermediate drainage means 17 is performed while performing the air washing from the upper cleaning air introduction means 18 while the intermediate drainage valve 17V is opened with the intermediate drainage means 17 being in the open position. Lower the water level to the limit. Thus, by dewatering from the intermediate drainage means 17 while washing the upper filter layer 22 with air, the detained matter in the upper filter layer 22 can be efficiently removed.

  When the water level drops to a predetermined position, the intermediate drainage means 17 is closed and the intermediate drainage valve 17V is closed to prevent the filter medium from flowing out of the intermediate drainage means 17, and then the cleaning water introduction part 14 and the cleaning air introduction part 15 The valves 14V and 15V are opened, and the lower filtration layer 21 is washed with water and washed with water. This air washing / water washing process is performed at an air washing speed of about 1 m / min and a water washing speed of 0.6 m / min until the water level in the filtration tank 16 rises to the water level at the end of the first water draining process. For about 5 minutes. When the water level rises to a predetermined position, after performing the same standing step as described above, the same second draining step as described above is performed.

  After the stationary step, the second draining step and the air washing / water washing step are performed a predetermined number of times, for example, about 1 to 3 times, the water washing step is started from the air washing / water washing step. In this water washing step, the valve 15V of the washing air introduction section 15 is closed to introduce only washing water, the lower filter layer 21 is stratified, and the drainage trough 12 is drained. Eliminate trapped coarse contaminants.

  Thus, each filter layer 21 and 22 is wash | cleaned by implementing a 1st draining process, an air washing process, a stationary process, a 2nd water draining process, an air washing / water washing process, and a water washing process in a predetermined order. can do. Thereafter, the valve 14V of the washing water introduction section 14 is closed, the valves 11V and 13V of the raw water inflow section 11 and the treated water outflow section 13 are opened, and after a predetermined drainage operation, the filtration process is resumed.

  In the draining process in the washing process of such a downflow type two-layer filtration device, the washing drainage is caused to flow out from the middle drainage means 17 provided in the middle part of the filtration tank 16 directly above the lower filtration layer 21, Water can be drained to near the surface layer of the filter layer 21, and washing waste water can be effectively discharged. In addition, an opening / closing means for opening and closing the drainage opening 31 of the intermediate drainage pipe 32 by moving the movable pipe 33 is provided, and the drainage opening 31 is opened only in the draining process. The filter medium can be prevented from entering, and the filter medium can be prevented from flowing out of the filtration tank 16. In particular, by opening the drainage opening 31 of the intermediate drainage pipe 32 downward from the horizontal direction, the filter medium accumulates in the opening 34, which hinders the operation of the movable pipe 33, or deposits. It is possible to prevent the filter medium that has entered the middle drainage pipe 32 from being discharged from the drainage opening 31 when the movable pipe 33 is operated.

  Further, by uniformly distributing the plurality of drain openings provided in the intermediate drain means 17 with respect to the filtration surfaces of the filter layers 21 and 22, the washing waste water can be uniformly discharged from the entire filtration surface. Can be discharged efficiently. Thereby, the filter medium washing | cleaning effect can be improved, reduction of the amount of washing water, advancement of the quality of treated water, increase in the filtration speed, size reduction of a filtration apparatus, etc. can be achieved. In particular, in the second draining step, the detained material in the upper filter layer 22 can be efficiently removed by performing the air washing of the upper filter layer 22 while the washing drainage is discharged from the intermediate drainage means 17, so that the upper filter layer can be efficiently removed. The cleaning effect of 22 can be further improved. In addition, the drainage trough 12 can be lowered to a position close to the upper filter medium support plate 26 by providing the filter medium support plate 26 at the lower part of the drainage trough 12 to prevent the filter medium from flowing out. The thickness can be lowered.

  FIGS. 3 to 8 show other embodiments of the intermediate drainage means 17 respectively. The bottom view of FIG. 3 and the sectional view of FIG. 4 show the drainage opening 31 toward the lower side of the intermediate drainage pipe 32. An example is shown. In this way, by providing the drainage opening 31 downward, it is possible to drain to near the surface layer of the filter layer. Further, when the intermediate drain pipe 32 and the movable pipe 33 are long or have a large diameter, the drain opening 31 and the opening 34 are not slit-shaped, but are divided into a plurality of parts and reinforced between the drain openings 31. It is preferable to provide the part 38.

  The front view of FIG. 5 and the cross-sectional view of FIG. 6 show an example in which drain openings 31 are provided in two rows facing obliquely below the intermediate drain pipe 32. Further, a screen 39 for preventing the infiltration of the filter medium is attached to the opening 34 of the movable tube 33. As described above, by providing the drain openings 31 in two rows obliquely downward, the drainage speed can be improved and the drainage from the entire filtration surface can be performed more uniformly.

  The front view of FIG. 7 and the cross-sectional view of FIG. 8 show that the drainage opening 31 is provided on the side of the intermediate drainage pipe 32 and the movable pipe 33 provided with the opening 34 is moved in the axial direction. The example which opened and closed 31 is shown. Thus, by moving the movable tube 33 in the axial direction, the movable tube 33 can be moved using a mechanism that is simpler than the gear box, such as a lever or a link.

  In each structure of the intermediate drainage means 17, the movable pipe 33 can be inserted on the inner peripheral side of the intermediate drainage pipe 32, and the movable pipe 33 is not rotated with respect to the intermediate drainage pipe 32. In the case of the structure shown in FIG. 8, a square pipe can be used as the intermediate drain pipe 32. In this case, a plate-like slide member can be used instead of the movable pipe 33.

  FIG. 9 is a plan view showing an arrangement example of the drainage openings 31 formed by circular holes or the like, and a plurality of intermediate drain pipes 32 are provided in parallel at equal intervals and provided in each intermediate drain pipe 32. The plurality of drain openings 31 are also equally spaced so that the area covered by each drain opening 31 is substantially the same area. By disposing the drainage openings 31 so as to be evenly distributed with respect to the filtration surface in this manner, the cleaning wastewater can be uniformly discharged from the entire filtration surface.

  FIG. 10 is an explanatory view showing a second embodiment of the filtration device of the present invention. In the following description, the same components as those in the filtration device shown in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The filtration apparatus shown in this embodiment is provided with a support layer 25 using gravel on a partition plate 24 provided with a water collection nozzle 23 at the bottom of the filtration tank 16, and two types of filter media on the support layer 25. To form a multi-bed fixed bed in which a first filter layer 41 on the upper side and a second filter layer 42 on the lower side are formed.

  As with the upper filter layer 22 in the first embodiment, the first filter layer 41 is made of a filter medium having a large SS trapping amount, and similarly to the above, it is preferable to use a nonwoven fabric or sponge having a relatively large outer dimension. Specifically, a nonwoven fabric having a porosity of about 90% obtained by heat-sealing 4-25 denier polyester fibers and having a size of 10 mm × 10 mm × 5 mm can be suitably used. Since the polyester fiber non-woven fabric has a true specific gravity of 1.38, the apparent specific gravity is about 1.04.

  Further, the second filter layer 42 is also preferably made of a filter medium having a small particle diameter that can be finely filtered, like the lower filter bed 21 of the first embodiment. For example, the particle diameter or the outer dimension is 1 mm or less. In particular, silica sand having a particle size of 0.6 mm and a uniformity coefficient of 1.3 can be suitably used. Although the height of the 1st filter layer 41 and the 2nd filter layer 42 is arbitrary, it is about 1 m normally.

  An intermediate drainage means 17 similar to the above is provided immediately above the first filter layer 41. A punching metal having an appropriate hole diameter is provided below the drainage trough 12 provided above the filtration tank 16, for example, 0.8 m below. The filter medium outflow prevention plate 43 made of is used to prevent the filter medium used for the first filter layer 41 from flowing out of the drainage trough 12.

  Thus, by using a filter medium having a large size and a large porosity for the first filter layer 41 on the upstream side in the flow direction, it is difficult to cause clogging of the front part, the SS trapping amount can be increased, and the apparent specific gravity is increased. Since it is slightly larger than water, cleaning is easy, and it is not mixed with a filter medium such as silica sand having a small particle size used for the second filter layer 42. Furthermore, since a considerable amount of the SS component is removed by the first filter layer 41, the load on the second filter layer 42 on the downstream side is reduced, and the second filter layer 42 has a small filter medium having a particle size of 1 mm or less. Can be used. Thereby, the microfiltration which was difficult in the conventional filtration process which used silica sand and anthracite with a particle size of 1-2 mm independently becomes possible not only in the water treatment but also in the wastewater treatment.

  FIG. 11 is an explanatory view showing a third embodiment of the filtration device of the present invention. This embodiment shows an example in which a carrier floating portion 51 into which a floating carrier is introduced is provided at the upper portion of the filtration layer in the filtration apparatus shown in FIG. 10, and an air diffuser 52 is provided below the carrier floating portion 51. ing. The carrier floating portion 51 is provided between a pair of upper and lower floating carrier support plates 53, the drainage trough 12 is located immediately above the upper floating carrier support plate 53, and directly below the lower floating carrier support plate 53. The air diffusion means 52 and the intermediate drainage means 17 having the same double pipe structure are provided.

The floating carrier introduced into the carrier floating part 51 is suitable for the growth of nitrifying bacteria, so that biological oxidation, in particular, nitrification can be efficiently performed by aeration from the aeration means 52. Yes. As the floating carrier, an appropriate one can be selected, but non-woven fabrics, sponges and plastic foams having an outer dimension of 2 to 20 mm and a specific gravity of 0.9 to 1.1 can be used alone or in appropriate combination. It is preferable to use it. Specifically, it is a hollow cylindrical foamed polypropylene, the outer diameter is 10 mm × length is 10 mm, the specific surface area is 800 m ² / m ³ , the specific gravity is adjusted to about 0.98, and the specific gravity after biofilm attachment is about 1 A carrier having the following structure can be preferably used.

  Further, by setting the filling rate of the floating carrier in the range of 70 to 80% with respect to the volume between the floating carrier support plates 53, it is possible to easily enter a fluidized state by the aeration from the aeration means 52. Further, the biofilm can be prevented from being enlarged more than necessary due to the biofilm peeling effect caused by the rubbing of the carriers. At this time, if a punching metal having a hole diameter of about 8 mm is used as the floating carrier support plate 53, the fluidized floating carrier always rubs against the punching metal, thereby preventing the hole of the punching metal from being blocked.

  In this way, two layers consisting of the first filter layer 41 and the second filter layer 42 are provided as the filter layer, and the carrier floating part 51 into which the floating carrier suitable for the growth of nitrifying bacteria is added is provided above this layer. By performing aeration from the aeration means 52 to the carrier floating portion 51, biological oxidation including a nitrification reaction can be sufficiently performed in the carrier floating portion 51, and furthermore, a filter medium having a large SS trapping amount is used. Since the SS component can be sufficiently removed by the first filter layer 41, it is possible to perform microfiltration using a filter medium having a small particle diameter for the second filter layer.

  FIG. 12 is an explanatory view showing a fourth embodiment of the filtration device of the present invention. In this embodiment, the same flocculant addition means 19 as described above is provided to add the flocculant to the inflow raw water, so that the filter layer 61 provided at the lower part of the filtration tank 16 is made of only a filter medium having a large SS trapping amount. It is a floor fixed floor. As the filter medium, for example, as described above, a nonwoven fabric or sponge having a relatively large outer dimension, specifically, a nonwoven fabric having a porosity of about 90% obtained by heat-sealing 4 to 25 denier polyester fibers, and having a thickness of 10 mm Those having a size of × 10 mm × 5 mm can be suitably used. That is, sufficient filtration performance is obtained even if a filter medium such as a nonwoven fabric is used by agglomerating the turbidity in the raw water with a coagulant.

Further, the same floating carrier as that in the third embodiment can be used as the floating carrier to be introduced into the carrier floating portion 51, but it is a hollow cylindrical foamed polypropylene having an outer diameter of 8 mm × length of 8 mm and a specific surface area of 1000 m ^2. The nitrification ability can be further increased by using a material whose specific gravity is adjusted to about 0.98 at / m ³ and increasing the filling amount.

  Further, by using a filter medium having a large outer dimension for the filter layer 61, the support layer 25 using gravel can be omitted and the filter medium can be directly received by the water collecting nozzle 23 provided on the partition plate 24. Further, the intermediate drainage means 17 also eliminates the risk of the filter medium flowing out simply by installing a screen 39 that prevents the filter medium from entering the drain opening 31 of the intermediate drain pipe 32, for example, a punching metal having a hole diameter of 6 mm. The movable tube 33 and the drive device 36 as described above can be omitted to form a single tube structure.

  An appropriate flocculant can be used as the flocculant to be added, but it is preferable to use an iron-based flocculant in view of little inhibition on the nitrification reaction and adverse effects on sludge treatment. By using a flocculant, phosphorus can be removed.

  The cleaning process in the second to fourth embodiment examples can be basically performed in the same procedure as that described in the first embodiment. However, in the fourth embodiment, there is no possibility that the filter medium flows out from the drainage opening 31, so that the stationary step can be omitted.

Here, the filtration rate in the filtration apparatus using the floating carrier shown in the third and fourth embodiments is the nitrification rate in the carrier floating portion 51 which is an aerobic filter bed, or the filtration layer (first filtration layer 41). And the filtration duration in the second filter layer 42 or filter layer 61). In advanced sewage treatment, secondary treated water treated by the standard activated sludge method or the like is often used as raw water and further treated. This raw water often contains about 10 to 30 mg / L as ammoniacal nitrogen and about 2 to 20 mg / L as SS. In the filtration apparatus shown in the third and fourth embodiments, a high nitrification capacity of about 1 kg · N / m ³ · floating carrier / day can be obtained in the carrier floating portion 51. If the filling height of the floating carrier is 2.5 m and the ammoniacal nitrogen of raw water is 20 mg / L, the filtration rate at which a digestibility of about 100% is obtained is 125 m / day.

In addition, when the effective SS trapping amount is 5 kg / m ³ · filter material filling part, the filtration speed at which the filtration continuation time is 1 day or more is 250 m / day when the raw water SS is 20 mg / L and the filter material filling height is 1 m. . Therefore, in this case, a filtration rate of 125 m / day or less is set in consideration of the nitrification ability.

  On the other hand, in order to obtain a high nitrification rate with a conventional aerobic filter bed, the filtration rate is generally about 70 m / day, and since the particle size of the filter medium is large, microfiltration cannot be expected. .

  Considering the construction cost of the aerobic filter bed, the larger the filtration speed, the more compact the apparatus and the more economical. Furthermore, when the washing speed of the filter bed is the same as the washing speed, the washing speed, etc., the capacity of the washing blower and washing pump is determined according to the filtration area, so the larger the filtration speed, the more economical. As for the running cost, the aeration power occupies a large proportion, but in order to keep the nitrification capacity high, it is desirable that the aeration rate is 150 to 300 m / day. In other words, the smaller the filtration area, The greater the filtration rate, the less the power for aeration.

  That is, the filtration apparatus shown in the third and fourth embodiments has a high biological oxidation ability including a nitrification reaction and is capable of microfiltration. In particular, when applied to advanced treatment of sewage, Compared with this type of filtration device, it is compact, provides high quality treated water, and is an advantageous filtration device in terms of installation costs and maintenance costs.

It is explanatory drawing which shows the 1st form example of the filtration apparatus of this invention. It is a schematic front view which shows one example of an intermediate | middle drainage means. It is a bottom view which shows the other example of a form of an intermediate | middle drainage means. It is sectional drawing similarly. It is a front view which shows the further another example of an intermediate | middle drainage means. It is sectional drawing similarly. It is a front view which shows the further another example of an intermediate | middle drainage means. It is sectional drawing similarly. It is a top view which shows the example of arrangement | positioning of the opening part for waste_water | drain formed with circular through-holes. It is explanatory drawing which shows the 2nd form example of the filtration apparatus of this invention. It is explanatory drawing which shows the 3rd example of a filtration apparatus of this invention. It is explanatory drawing which shows the 4th example of a filtration apparatus of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Raw water inflow part, 12 ... Drainage trough, 13 ... Treated water outflow part, 14 ... Washing water introduction part, 15 ... Cleaning air introduction part, 16 ... Filtration tank, 17 ... Intermediate drainage means, 18 ... Upper washing air introduction Means, 19: Coagulant addition means, 21: Lower filter layer, 22: Upper filter layer, 23: Water collecting nozzle, 24 ... Partition plate, 25 ... Support layer, 26 ... Filter medium support plate, 31 ... Drainage opening, 32 ... Intermediate drain pipe, 33 ... Movable pipe, 34 ... Opening, 35 ... Gear box, 36 ... Drive device, 37 ... Drive shaft, 38 ... Reinforcement part, 39 ... Screen, 41 ... First filter layer, 42 ... First 2 filter layers, 43 ... filter medium outflow prevention plate, 51 ... the carrier floating part, 52 ... aeration means, 53 ... floating carrier support plate, 61 ... filter layer

Claims (5)

  In a filtration apparatus having a raw water inflow portion and a drain trough in the upper part of the filtration tank, and having a treated water outflow part, a washing water introduction part, and a washing air introduction part in the lower part of the filtration tank, in the lower part of the filtration tank A filter layer filled with a filter medium having a specific gravity of 1 or more is formed, and an intermediate drainage means having a plurality of drainage openings is provided immediately above the filter layer in the middle part of the filtration tank. Filtration device.   The filtration device according to claim 1, wherein the drain openings are evenly distributed with respect to the filtration surface of the filtration layer.   The filtration device according to claim 1 or 2, wherein the drain opening includes an opening / closing means for opening and closing the drain opening.   The open / close means is movably fitted to an outer periphery or an inner periphery of the intermediate drain pipe provided with the drainage opening, and a movable pipe provided with an opening at a position corresponding to the drainage opening, Movable pipe moving means for moving the movable pipe in the circumferential direction or the axial direction with respect to the intermediate drain pipe, the movable pipe moving means, the open position that matches the opening to the drain opening, The filtration apparatus according to claim 3, wherein the movable pipe is moved to a closed position where the drain opening is closed by a pipe wall of the movable pipe.   The filtration device according to any one of claims 1 to 4, wherein a filter medium outflow prevention plate is provided between the intermediate drainage means and the drainage trough.

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