JP2014079692A - Backwash method of long fiber filtration device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a backwash method of a long fiber filtration device capable of efficiently backwashing a long fiber bundle while at the same time restraining reduction in the crimp ratio of the long fiber bundle.SOLUTION: The backwash method of the long fiber filtration device executes filtration treatment by conducting a downflow of raw water into a filtration tank. The backwash method comprises a backwash process of cleaning a long fiber bundle 40 by making wash water and cleaning gas as a backwash fluid flow upward via a lower outflow inlet 41d and an upper outflow inlet 42h. In the backwash process, an inflow speed of the cleaning gas flowing into the filtration tank is in a range of 180 m/h or faster and 300 m/h or slower, and an inflow speed of the wash water is in a range of 45 m/h or faster and 75 m/h or slower. An outflow speed of the cleaning gas flowing out of the upper outflow inlet is in a range of 7.0 m/s or faster and 27.0 m/s or slower, and an outflow speed of the wash water is in a range of 1.7 m/s or faster and 6.0 m/s or slower.

Description

  The present invention relates to a technique for a long fiber filtration device, and more particularly to a technique for a backwashing method for a long fiber filtration device.

  Conventionally, in various treatment processes such as water treatment facilities, sewage treatment facilities, industrial wastewater treatment facilities, industrial water treatment facilities, etc., long fiber bundles have been used as filter media as filtration treatments for removing suspended substances in raw water. The used filtration apparatus is known (for example, refer patent documents 1 and patent documents 2). The filtration devices such as Patent Documents 1 and 2 have less head loss than sand filtration and can perform filtration at a high flow rate. Moreover, since the lower end of a long fiber bundle is being fixed to the support body, the filtration apparatus like patent document 1 and 2 can be made to flow in backwash water with a high flow rate, and it is long by backwashing for a short time. It is possible to remove suspended material trapped in the fiber bundle.

  For example, Patent Document 3 discloses a filtration device in which a long fiber bundle is attached to a support nozzle having an upper outlet and a lower outlet. According to the filtration device of Patent Document 3, it becomes possible to efficiently discharge suspended substances trapped in the long fiber bundle in the washing step.

  Further, for example, Patent Literature 4 discloses a filtration device that crimps a long fiber bundle. According to the filtration apparatus of patent document 4, it can drive | operate with a quick filtration rate, and it becomes possible to lengthen filtration continuation time. In addition, since the crimped long fiber bundle is easy to stand upright, it is difficult for the loss head to rise rapidly due to excessive compaction during filtration water flow, and the fiber bundle stretches during backwashing. It is easy to discharge the trapped suspended matter.

  Moreover, for example, Patent Document 5 discloses a backwashing method for discharging backwash wastewater from the lower part of the filtration tank. According to the backwashing method of Patent Document 5, it is possible to efficiently discharge suspended substances trapped in the long fiber bundle without flowing backwashing water at high speed.

JP-A-63-315110 Japanese Laid-Open Patent Publication No. 1-304011 JP-A-11-137914 JP 2006-198590 A JP 2011-115702 A

  An object of the present invention is to provide a backwashing method for a long fiber filtration device that can efficiently backwash a long fiber bundle and suppress a reduction in the crimp rate of the long fiber bundle.

  The present invention is supported by a support body disposed in a filtration tank, with the support body as a boundary, an upper outlet port that functions as a filtrate water inlet portion and a backwash fluid outlet portion at an upper position, and a filtrate water at a lower position. A hollow support nozzle having an outflow portion and a lower outflow inlet functioning as a backwash fluid inflow portion, and a bundle of crimped long fibers, the upper end being a free end and the lower end being a position above the support nozzle A backwashing method for a long-fiber filtration device, wherein the raw water is passed through the filtration tank in a downward flow to perform filtration treatment, the lower outflow inlet and the upper outflow inlet Through the washing water and the washing gas as the backwashing fluid in an upward flow, the backwashing step of washing the long fiber bundle, and in the backwashing step, flowing into the filtration tank The inflow speed of the cleaning gas is 180 m / h or more to 300 m / h or less. The inflow speed of the cleaning water is in the range from 45 m / h to 75 m / h, and the outflow speed of the cleaning gas flowing out from the upper outlet is from 7.0 m / s to 27. The flow rate of the washing water is in the range of 1.7 m / s or more and 6.0 m / s or less.

  In the backwashing method of the long fiber filtration device, the outflow speed of the cleaning gas flowing out from the upper outflow inlet is in the range of 7.0 m / s to 12.0 m / s, and the outflow speed of the cleaning water Is preferably in the range of 1.7 m / s to 3.0 m / s.

  According to the present invention, it is possible to efficiently backwash a long fiber bundle and suppress a reduction in the crimp rate of the long fiber bundle.

It is a schematic diagram which shows an example of a structure of the long fiber filtration apparatus which concerns on embodiment of this invention. It is a schematic diagram which shows an example of a structure of the support nozzle used for the long fiber filtration apparatus of this embodiment.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  Drawing 1 is a mimetic diagram showing an example of composition of a long fiber filtration device concerning an embodiment of the present invention. 1 includes a filtration tank 10, a raw water inflow pipe 12, a treated water outflow pipe 14, a backwash water inflow pipe 16, a backwash drainage outflow pipe 18, an air inflow pipe 22, a raw water storage tank 24, and a treatment. A water tank 26, raw water pump 28, backwash pump 30, and backwash blower 32 are provided.

  A support 36 is installed in the filtration tank 10. The support 36 is a plate-like body in which a plurality of openings (not shown) are formed, and a support nozzle 38 (strainer) is inserted into each of the openings and fixed. The lower end of the long fiber bundle 40 is fixed to the support nozzle 38, and the upper end of the long fiber bundle 40 is a free end. Details of the support nozzle 38 will be described later.

  Raw water is stored in the raw water storage tank 24. One end of the raw water inflow pipe 12 is connected to the raw water storage tank 24, and the other end is connected to the upper part of the filtration tank 10 (above the support 36) via the raw water pump 28 and the valve 54. In addition, when raw | natural water can flow into the filtration tank 10 by natural flow, the raw | natural water pump 28 is unnecessary. One end of the treated water outflow pipe 14 is connected to the lower part of the filtration tank 10 (below the support 36), and the other end is connected to the treated water tank 26 via a valve 46. One end of the backwash water inflow pipe 16 is connected to the treated water tank 26, and the other end is connected to the lower part of the filtration tank 10 (below the support 36) via the backwash pump 30 and the valve 48. . Furthermore, one end of the air inflow pipe 22 is connected to the lower part of the filtration tank 10 (below the support 36), and the other end is connected to the backwash blower 32 via the valve 50. A backwash drainage pipe 18 provided with a valve 56 is connected to the upper part of the filtration tank 10.

  FIG. 2 is a schematic diagram illustrating an example of a configuration of a support nozzle used in the long fiber filtration device of the present embodiment. As shown in FIG. 2, the support nozzle 38 includes two members, a hollow lower cylindrical body 41 and an upper cylindrical body 42. The lower cylindrical body 41 has an upper end 41a and a lower end 41b that are open, and a flange portion 41c that protrudes from the outer peripheral surface near the upper end 41a. The lower cylindrical body 41 is inserted and disposed from above into an opening (not shown) of the support body 36 until the lower surface of the flange portion 41c contacts the surface of the support body 36. The lower cylindrical body 41 is formed with a lower outflow inlet 41d that functions as a filtered water outflow portion and a backwash fluid inflow portion at an appropriate portion of the peripheral wall that is positioned below the support 36. Reference numeral 43 denotes a nut that is screwed onto the peripheral surface of the lower cylindrical body 41 in order to fix the lower cylindrical body 41 to the support 36.

  The upper cylindrical body 42 has an end wall 42b at the upper end 42a and an opening at the lower end 42c. The upper cylindrical body 42 is connected to the peripheral surface at a position higher than the flange portion 41c of the lower cylindrical body 41 by screwing or fitting. Arranged. In addition, a hole 42d having a predetermined diameter as a dedicated water collecting port is formed in a substantially central portion of the end wall 42b, and a valve mechanism for opening and closing the hole 42d is provided in the upper cylindrical body 42. Yes. By this valve mechanism, the hole 42d functions only as a filtered water inflow portion and does not function as a backwash fluid outflow portion. The valve mechanism may have any structure as long as it can open the hole 42d at the time of filtration and close it at the time of backwashing. In this embodiment, the ball valve has a diameter larger than the diameter of the hole 42d. In order to prevent the ball valve 42f from dropping, a member constituted by an inwardly protruding protrusion 42g is used at a substantially central portion in the longitudinal direction of the upper cylindrical body 42.

  Further, an upper outflow inlet 42h that functions as a filtrate inflow portion and a backwash fluid outflow portion is formed at a position above the peripheral wall between the protrusion 42g and the end wall 42b, that is, the support 36. The upper outlet 42h and the lower outlet 41d of the lower cylindrical body 41 are not limited in shape, and can be formed in various shapes such as a circular shape or a long hole shape.

  As shown in FIG. 2, the lower end of the long fiber bundle 40 is fixedly disposed above the support nozzle 38 with respect to the support 36, that is, around the upper cylindrical body 42 of the support nozzle 38. As shown in FIG. 3, the upper end of the long fiber bundle 40 is a free end. Although the fixing method is arbitrary, in the present embodiment, the band member 44 is fitted and fixed to the outer periphery of the lower end of the long fiber bundle 40.

  The long fiber bundle 40 is crimped. Here, crimp refers to the crimping of fibers as described in JIS L0208. By subjecting the long fiber bundle 40 to crimping, it becomes easy to stand upright, and when the water is filtered, it becomes difficult to cause excessive consolidation and a loss head to rise rapidly. It is easy to stretch and it becomes easy to discharge the trapped suspended matter.

  Next, operation | movement of the long fiber filtration apparatus 1 which concerns on this embodiment is demonstrated.

  Raw water containing suspended substances such as industrial water, secondary sewage water, tertiary sewage water, river water, lake water, coagulated sediment supernatant water, various process intermediate waters, various recovered waters, various waste waters, etc. After being stored in the storage tank 24, the raw water pump 28 passes through the raw water inflow pipe 12 and is introduced into the filtration tank 10. When the raw water introduced from above the filtration tank 10 flows downward from the upper part of the filtration tank 10, suspended substances in the raw water are captured by the long fiber bundle 40. The raw water (treated water) from which suspended substances have been removed flows into the support nozzle 38 from the hole 42d and the upper outlet 42h of the support nozzle 38, and presses the ball valve 42f against the protrusion 42g located below, It passes through the gap between the protrusions 42g, flows out from the lower outlet 41d and the open lower end 41b, and is discharged from the lower part of the filtration tank 10 to the treated water outlet pipe 14. The treated water passes through the treated water outflow pipe 14 and is stored in the treated water tank 26. In the filtration process, the valves 54 and 46 are opened, and the valves 48, 50 and 56 are closed.

  In this embodiment, when the filtration process for a predetermined period is performed, or when the loss head in the filtration tank 10 rises to a predetermined height, the backwash process is performed, and the long fiber bundle 40 is washed. Hereinafter, the backwash process will be described.

  The valves 54 and 46 are closed, the valves 48, 50 and 56 are opened, and the backwash pump 30 and the backwash blower 32 are operated. Air as the backwash fluid is introduced from the lower part of the filtration tank 10 through the air inflow pipe 22, and wash water (treated water) as the backwash fluid is introduced from the lower part of the filter tank 10 through the backwash water inflow pipe 16. Is done. The backwash fluid (air and wash water) introduced from the lower part of the filtration tank 10 flows upward and flows in from the lower outlet 41d of the support nozzle 38 and the open lower end 41b.

  The backwash fluid passing through the support nozzle 38 pushes up the ball valve 42f, closes the hole 42d of the end wall 42b, and is ejected only from the upper outlet 42h. The long fiber bundle 40 is vibrated and elongated by the cleaning fluid ejected from the upper outlet 42h, and the suspended matter trapped in the long fiber bundle 40 is removed. Then, the backwash fluid containing the removed suspension is discharged from the backwash drainage outflow pipe 18 to the outside of the long fiber filtration device 1. Wastewater discharged from the backwash drainage pipe 18 is transferred to a wastewater treatment facility or the like. In the present embodiment, the treated water stored in the treated water tank 26 is used as the backwash water, but there is no particular limitation as long as the wash water can be used for washing the long fiber bundle 40. . Moreover, although air was used as the backwashing gas, it is not particularly limited as long as it is a cleaning gas that can be used for cleaning the long fiber bundle 40.

  In the present embodiment, the flow rate of cleaning water and the flow rate of cleaning gas in the backwashing process are controlled in the following ranges.

  The inflow speed of the cleaning gas flowing into the filtration tank 10 is set in a range from 180 m / h to 300 m / h, and the inflow speed of the cleaning water is set in a range from 45 m / h to 75 m / h. In addition, the flow rate of the cleaning gas flowing out from the upper outlet 42h of the support nozzle 38 is in the range of 7.0 m / s to 27.0 m / s, preferably 7.0 m / s to 12.0 m / s. And the outflow rate of the washing water is in the range of 1.7 m / s to 6.0 m / s, preferably in the range of 1.7 m / s to 3.0 m / s. Here, the inflow rate of the cleaning gas flowing into the filtration tank 10 is the speed of the cleaning gas passing through the cross-sectional area of the filtration tank 10 per unit time, and the flow rate of the cleaning gas is divided by the cross-sectional area of the filtration tank 10. Is required. The inflow rate of the wash water flowing into the filter tank 10 is the speed of the wash water passing through the cross-sectional area of the filter tank 10 per unit time, and the flow rate of the wash water is divided by the cross-sectional area of the filter tank 10. Is required. The outflow speed of the cleaning gas flowing out from the upper outflow inlet 42h of the support nozzle 38 is the speed of the cleaning gas passing through the upper outflow inlet 42h of the support nozzle 38 per unit time, and the flow rate of the cleaning gas is changed to the upper outflow. It is obtained by dividing by the cross-sectional area of the inlet 42h (usually, since there are a plurality of upper outflow inlets 42h, it is the sum of the cross-sectional areas). The washing water passing through the upper outflow inlet 42h of the support nozzle 38 is the speed of the washing water passing through the upper outflow inlet 42h of the support nozzle 38 per unit time. It is obtained by dividing by a cross-sectional area (usually, since there are a plurality of upper outlets 42h, the sum of the cross-sectional areas).

  As in this embodiment, the longitudinal pulling force is applied to the long fiber bundle 40 by setting the inflow speed of the cleaning gas flowing into the filtration tank 10 to 300 m / h or less and the inflow speed of cleaning water to 75 m / h or less. An excessive addition is suppressed, a decrease in the crimp rate of the long fiber bundle 40 is suppressed, or a decrease in the strength of the long fibers is reduced. On the other hand, when the inflow rate of the cleaning gas is less than 180 m / h and the inflow rate of the cleaning water is less than 45 m / h, it becomes difficult to remove the suspended solids captured by the long fiber bundle 40 and to discharge it outside the filtration tank 10. The cleaning effect will be significantly reduced.

  Furthermore, as in this embodiment, the long fiber bundle is obtained by setting the outflow speed of the cleaning water from the upper outflow inlet 42h of the support nozzle 38 to 1.7 m / s or more and the outflow speed of cleaning gas to 7.0 m / s or more. 40 can be vibrated efficiently, and the suspended matter captured by the long fiber bundle 40 can be efficiently removed. As a result, accumulation of suspended substances in the filtration tank 10 due to poor cleaning can be reduced. The flow rate of the cleaning fluid from the upper outlet 42h of the support nozzle 38 is adjusted by adjusting the total cross-sectional area of the upper outlet 42h, for example, by reducing (or increasing) the diameter of the upper outlet 42h, This can be achieved by reducing (or increasing) the number of inlets 42h. On the other hand, when the outflow speed of the cleaning water exceeds 6.0 m / s and the outflow speed of the cleaning gas exceeds 27.0 m / s, the cross-sectional area of the upper outflow inlet 42h becomes very small. However, there is a possibility of clogging due to suspended substances contained in the washing water, microorganisms generated in the filtration tank 10, scales, and the like. In addition, if the outflow speed of the cleaning water exceeds 6.0 m / s and the outflow speed of the cleaning gas exceeds 27.0 m / s, the number of the upper outflow inlets 42h may be reduced. In addition, the cleaning gas is injected only from a part, and unevenness occurs in cleaning the long fiber bundle 40.

  As described above, the inflow speed of the cleaning gas and the inflow speed of the cleaning water flowing into the filtration tank 10, the outflow speed of the cleaning gas outflowing from the upper outlet 42h of the support nozzle 38, and the outflow speed of the cleaning water are within the above ranges. By performing the backwashing step, the long fiber bundle 40 can be backwashed efficiently and the crimp rate of the long fiber bundle 40 can be reduced without flowing washing water at a high speed flow. It is possible to suppress the decrease.

  Below, the long fiber bundle 40 used for this embodiment is demonstrated.

  As the material of the long fiber constituting the long fiber bundle 40, synthetic fibers such as acrylic, polyester, polypropylene, polyamide, polyacrylamide, and Kevlar, natural fibers such as cotton and wool, synthetic fibers thereof, and the like Is mentioned. Synthetic fibers are preferred from the standpoint of high strength, etc., and polyester-based synthetic fibers that have good processability are preferred.

  The length of the long fiber bundle 40 is not particularly limited as long as it is determined according to the height of the filtration tank 10 to be used, but is preferably 500 mm or more and less than 3000 mm, and is 1000 mm or more and less than 1500 mm. Is more preferable. If the length of the long fiber bundle 40 is less than 500 mm, the effective volume of the filter medium is small, so that the processing efficiency may be lowered. If the length is 3000 mm or more, the aggregate density of the long fiber bundle 40 becomes high, and the effective volume. May decrease and the processing efficiency may decrease. In addition, the length of the long fiber bundle 40 is the length from the upper end to the lower end of the long fiber bundle 40 in a state in which the long fiber bundle 40 is almost upright in water in a state where no water is passed when the filtration tank 10 is filled. That's it.

The filling density of the long fiber bundle 40 is not particularly limited as long as it is determined according to the flow rate of raw water, but is preferably 15 kg or more and less than 200 kg per 1 m ² of the cross-sectional area of the filtration tank 10. More preferably, it is 30 kg or more and less than 100 kg per 1 m ² of the cross-sectional area of the tank 10. When the packing density of the long fiber bundle 40 is less than 15 kg per 1 m ² of the cross-sectional area of the filtration tank 10, the pressure loss becomes small, but the effective volume of the long fiber bundle 40 is small, and thus the filtration efficiency may decrease. If it is as described above, the aggregate density of the long fiber bundle 40 is increased, the effective volume is decreased, and the filtration efficiency may be decreased, or the pressure loss may be increased. The filling density of the long fiber bundle 40 is obtained from the dry weight of the long fiber bundle 40 and the cross-sectional area of the filtration tank 10 filled with the long fiber bundle 40.

  The long fiber filtration device 1 according to the present embodiment is used in various treatment processes such as a water treatment facility, a sewage treatment facility, an industrial wastewater treatment facility, and an industrial water treatment facility. It can be used for the treatment of secondary treated water, river water, lake water, coagulated sediment supernatant water, various process intermediate water, various recovered water, various waste water, and the like.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

  In Examples 1-7, the test was performed on the following conditions using the long fiber filtration apparatus shown in FIG. The long fibers constituting the long fiber bundle installed in the filtration tank (φ280 mm × 2000 mm) were polyester fibers, and the height of the long fiber bundle was 1 m from the support. While mixing simulated raw water, in which Kansui Loam (JIS test powder 1-7 type) is added to such a filtration tank to a concentration of about 100 mg / L with polyaluminum chloride (flocculating agent) 14 mg / L. Water was passed at a filtration rate (LV) of 1000 m / day. Thereafter, when the head loss reached 1000 mm, the backwashing step was performed under various conditions, and the accumulation rate of suspended solids (hereinafter referred to as SS) accumulated in the filtration tank and the crimp rate of the long fiber bundle were obtained.

<Conditions for backwashing process>
In Example 1, the outflow speed of the cleaning gas flowing out from the upper outflow inlet is 7.0 m / s, the outflow speed of the cleaning water is 1.7 m / s, and the inflow speed of the cleaning water flowing into the filtration tank is 45 m. / H, the inflow speed of the cleaning gas was 180 m / h. In Example 2, the outflow speed of the cleaning gas flowing out from the upper outflow inlet is 11.0 m / s, the outflow speed of the cleaning water is 1.7 m / s, and the inflow speed of the cleaning water flowing into the filtration tank is 45 m. / H, the inflow speed of the cleaning gas was 300 m / h. In Example 3, the outflow speed of the cleaning gas flowing out from the upper outflow inlet is 7.0 m / s, the outflow speed of the cleaning water is 2.8 m / s, and the inflow speed of the cleaning water flowing into the filtration tank is 75 m. / H, the inflow speed of the cleaning gas was 180 m / h. In Example 4, the outflow speed of the cleaning gas flowing out from the upper outflow inlet is 11.0 m / s, the outflow speed of the cleaning water is 2.8 m / s, and the inflow speed of the cleaning water flowing into the filtration tank is 75 m. / H, the inflow speed of the cleaning gas was 300 m / h. Moreover, in Examples 5-7, the inflow speed of the washing water flowing into the filtration tank is 45 m / h, the inflow speed of the cleaning gas is 180 m / h, and in Example 5, the washing flowing out from the upper outlet is performed. The outflow speed of water was 1.7 m / s, the outflow speed of cleaning gas was 7.0 m / s, and in Example 6, the outflow speed of cleaning water flowing out from the upper outflow inlet was 3 m / s, and the outflow speed of cleaning gas In Example 7, the outflow speed of the cleaning water flowing out from the upper outflow inlet was 6 m / s, and the outflow speed of the cleaning gas was 27 m / s. In Examples 1 to 4, the diameter and number of the upper outlet / outlet were 4 mm and 6 pieces. In Example 5, the diameter and number of the upper outlet / outlet were 4 mm and 6 pieces. In Example 6, the diameter and number of the upper outlet / outlet were 3 mm and 6 pieces. In Example 7, the diameter and number of the upper outlet / outlet were 3 mm and 3 pieces.

<How to find the SS accumulation rate>
The SS accumulation rate is obtained by the following equation (1).
SS accumulation rate (%) = (SS accumulation amount (kg) / SS trapping amount (kg)) × 100 (1)
Here, the SS trapping amount is the amount of SS removed from the raw water before the backwashing step, and the SS accumulation amount is the amount of SS remaining in the filtration tank after the backwashing step, respectively. It is obtained by (2) and (3).
SS trapping amount (kg) = raw water SS concentration (kg / m ³ ) × water flow rate (m ³ / h) × water flow time
(H) x average SS removal rate (2)
SS accumulation amount (kg) = SS trap amount (kg) −SS discharge amount by backwash (kg) (3)
Moreover, the average SS removal rate of Formula (2) is calculated | required by Formula (4).
Average SS removal rate = (raw water SS concentration (kg / m ³ ) −treated water SS concentration (kg / m ³ )) /
Raw water SS concentration (kg / m ³ ) (4)
Further, the water flow rate (m ³ / h) of the equation (2) is obtained by the equation (5).
Water flow rate (m ³ / h) = (water flow LV (m / d) × cross-sectional area (m ² )) / 24 (h / d)
... (5)
The water flow rate in the example is (1000 × 0.0615) /24=2.56 (m ³ / h).

<Evaluation of residual crimp rate>
In each condition of Examples 1 to 6, the residual crimp rate of the long fiber bundle after performing the backwashing process 200 times was measured. The residual crimp rate represents how much the crimp rate of the long fiber bundle after backwashing is reduced with respect to the crimp rate of the initial (new) long fiber bundle, and is obtained by Equation (6). .
Residual crimp rate (%) = (crimp rate after backwashing / initial crimp rate) × 100 (6)
Here, the crimp rate is obtained by Expression (7). The crimp rate is based on JIS L1015.
Crimp rate = (a−b) / a × 100
a: Length of long fiber bundle (mm) when initial load (0.001 kgf) is applied
b: Length of long fiber bundle (mm) when a load (0.008 kgf) of 4.41 mN × dtex value is applied

  In an actual apparatus, it is desired that the filtration process can be performed without exchanging the long fiber bundle for at least three years. And since the backwashing process in an actual apparatus is performed 1-2 times a day, if 1.5 times a day of backwashing is performed on average, it will be performed about 1600 times in 3 years. This means that 200 cycles of backwashing in the example were performed 8 cycles. That is, if the result of the residual crimp rate of this example is 90%, it becomes 0.9 ^ 8 = 0.43 (43%) in 3 years, which is less than half of the initial crimp rate. Presumed. In addition, if the result of the residual crimp rate of this example is 95%, it will be 0.95 ^ 8 = 0.66 (66%) in 3 years, which will be 70% or less of the initial crimp rate. Is estimated. In addition, if the result of the residual crimp rate of this example is 97%, it becomes 0.97 ^ 8 = 0.78 (78%) in 3 years, which is about 80% of the initial crimp rate. Is estimated. If the crimp rate of the long fiber bundle is maintained at about 80%, it is expected that the filtration process can be performed with the same accuracy as the initial filtration process. Therefore, the residual crimp rate is 97% or more. desired.

(Comparative Examples 1-7)
In Comparative Example 1, the outflow speed of the cleaning gas flowing out from the upper outflow inlet is 7.0 m / s, the outflow speed of the cleaning water is 2.0 m / s, and the inflow speed of the cleaning water flowing into the filtration tank is 30 m. / H, the inflow rate of the cleaning gas was 100 m / h. In Comparative Example 2, the outflow speed of the cleaning gas flowing out from the upper outflow inlet is 27.0 m / s, the outflow speed of the cleaning water is 2.0 m / s, and the inflow speed of the cleaning water flowing into the filter tank is 30 m. / H, the inflow speed of the cleaning gas was 400 m / h. In Comparative Example 3, the outflow speed of the cleaning gas flowing out from the upper outflow inlet is 7.0 m / s, the outflow speed of the cleaning water is 3.0 m / s, and the inflow speed of the cleaning water flowing into the filter tank is 45 m. / H, the inflow rate of the cleaning gas was 100 m / h. In Comparative Example 4, the outflow speed of the cleaning gas flowing out from the upper outflow inlet is 7.0 m / s, the outflow speed of the cleaning water is 5.0 m / s, and the inflow speed of the cleaning water flowing into the filtration tank is 75 m. / H, the inflow rate of the cleaning gas was 100 m / h. In Comparative Example 5, the outflow speed of the cleaning gas flowing out from the upper outflow inlet is 27.0 m / s, the outflow speed of the cleaning water is 5.0 m / s, and the inflow speed of the cleaning water flowing into the filtration tank is 75 m. / H, the inflow speed of the cleaning gas was 400 m / h. In Comparative Example 6, the outflow speed of the cleaning gas flowing out from the upper outflow inlet is 7.0 m / s, the outflow speed of the cleaning water is 7.0 m / s, and the inflow speed of the cleaning water flowing into the filtration tank is 100 m. / H, the inflow rate of the cleaning gas was 100 m / h. In Comparative Example 7, the outflow speed of the cleaning gas flowing out from the upper outflow inlet is 27.0 m / s, the outflow speed of the cleaning water is 7.0 m / s, and the inflow speed of the cleaning water flowing into the filtration tank is 100 m. / H, the inflow speed of the cleaning gas was 400 m / h. In Comparative Examples 1 to 7, the SS accumulation rate and the residual crimp rate were obtained under the same conditions as in Example 1 except for the above conditions.

(Comparative Examples 8-9)
In Comparative Example 8, the outflow speed of the cleaning water flowing out from the upper outflow inlet is 1 m / s, the outflow speed of the cleaning gas is 4 m / s, the diameter and number of the upper outflow inlets are 5 mm, and 6 in Comparative Example 9, The outflow speed of the cleaning water flowing out from the upper outflow inlet was 18 m / s, the outflow speed of the cleaning gas was 73 m / s, and the diameter and number of the upper outflow inlet were 3 mm and 2 pieces. The SS accumulation rate and the residual crimp rate were obtained under the same conditions as in Example 5 except for the above conditions.

  Table 1 summarizes the results of SS accumulation rates and residual crimp rates of Examples 1 to 4 and Comparative Examples 1 to 7. Table 2 summarizes the results of SS accumulation rates and residual crimp rates of Examples 5 to 7 and Comparative Examples 8 to 9.

  As can be seen from Table 1, the flow rate of cleaning gas flowing out from the upper inlet / outlet is 7.0 m / s or higher, and the flow rate of cleaning water is 1.7 m / s or higher. In Examples 1 to 4, in which the speed is 45 m / h to 75 m / h and the cleaning gas inflow speed is 180 m / h to 300 m / h, the SS accumulation rate is low, and the residual crimp rate is maintained at 97% or more. did. That is, it can be said that the long fiber bundle was backwashed efficiently and the reduction in the crimp rate of the long fiber bundle could be suppressed. On the other hand, in Comparative Examples 1, 3, 4, and 6, the outflow speed of the cleaning gas flowing out from the upper outflow inlet is 7.0 m / s or more, and the outflow speed of the cleaning water is 1.7 m / s or more. Since the inflow rate of the cleaning gas flowing into the filtration tank is 100 m / h, which is lower than that of the example, and the inflow amount of the cleaning gas is small, the suspended solids captured by the long fiber bundle cannot be sufficiently separated. , SS accumulation rate became high. Further, in Comparative Example 2, although the outflow speed of the cleaning gas flowing out from the upper outflow inlet is 7.0 m / s or more and the outflow speed of the washing water is 1.7 m / s or more, the washing water flowing into the filtration tank is used. The inflow rate of 30 m / h is low compared to the examples and the amount of inflow of washing water is small, so that the suspended matter separated from the long fiber bundle cannot be sufficiently discharged out of the filtration tank, and the SS accumulation rate Became high. In Comparative Examples 5 and 7, although the outflow speed of the cleaning gas flowing out from the upper outflow inlet is 7.0 m / s or more and the outflow speed of the washing water is 1.7 m / s or more, the washing water flowing into the filtration tank In addition, since the inflow rate of the cleaning gas was higher than that in the example, the long fiber bundle was excessively pulled vertically by the backwash fluid, and the residual crimp rate could not be maintained at 97% or more.

  Further, as can be seen from Table 2, the flow rate of the cleaning water flowing into the filtration tank is 45 m / h, the flow rate of the cleaning gas is 180 m / h, and the flow rate of the cleaning gas flowing out from the upper outlet is 7. In Examples 5 to 7 in which the flow rate of washing water was changed from 0 m / s to 27 m / s and from 1.7 m / s to 6 m / s, the SS accumulation rate was low, and the residual crimp rate was maintained at 97% or more. did. That is, it can be said that the long fiber bundle was backwashed efficiently and the reduction in the crimp rate of the long fiber bundle could be suppressed. In particular, in Examples 5 to 6, in which the outflow speed of the cleaning gas flowing out from the upper outflow inlet is 7.0 m / s to 12 m / s and the outflow speed of the cleaning water is 1.7 m / s to 3 m / s, SS accumulation The rate was low. In contrast, in Comparative Example 8, the inflow speed of the cleaning water flowing into the filtration tank is 45 m / h and the inflow speed of the cleaning gas is 180 m / h. Since the outflow rate was slower than in the examples, the long fiber bundle could not be vibrated sufficiently, making it difficult to efficiently separate the trapped suspended matter, and the amount of accumulated SS increased. In Comparative Example 9, the inflow speed of the cleaning water flowing into the filtration tank is 45 m / h and the inflow speed of the cleaning gas is 180 m / h. However, since the number of upper outlets in the support nozzle portion is only two, Unevenness was found in the cleaning of the fibers, and the SS accumulation rate increased.

  From the above results, in the backwashing step, the inflow speed of the washing water flowing into the filtration tank is set to 45 m / h or more to 75 m / h or less, and the inflow speed of the cleaning gas is set to 180 m / h or more to 300 m / h, The outflow speed of the cleaning gas flowing out from the upper outflow inlet is 7.0 m / s to 27 m / s, preferably 7.0 m / s to 12 m / s, and the cleaning water outflow speed is 1.7 m / s. From the above, it is 6 m / s or less, preferably 1.7 m / s or more to 3 m / s, while reducing the SS accumulation rate in the filtration tank due to poor cleaning, while reducing the crimp rate of the long fiber bundle, As a result, the strength reduction of the long fiber bundle could be suppressed.

  DESCRIPTION OF SYMBOLS 1 Long fiber excess apparatus, 10 Filtration tank, 12 Raw water inflow pipe, 14 Treated water outflow pipe, 16 Backwash water inflow pipe, 18 Backwash drainage outflow pipe, 22 Air inflow pipe, 24 Raw water storage tank, 26 Treated water tank, 28 Raw water Pump, 30 Backwash pump, 32 Backwash blower, 36 Support body, 38 Support nozzle, 40 Long fiber bundle, 41 Lower cylindrical body, 41a Upper end, 41b Lower end, 41c Flange part, 41d Lower outflow inlet, 42 Upper cylindrical form Body, 42a upper end, 42b end wall, 42c lower end, 42d hole, 42f ball valve, 42g protrusion, 42h upper outlet, 44 band member, 46, 48, 50, 54, 56 valve.

Claims (2)

Supported by a support disposed in the filtration tank, with the support as a boundary, an upper outlet that functions as a filtered water inlet and a backwash fluid outlet at an upper position, and a filtered water outlet and a reverse at a lower position. A hollow support nozzle having a lower inlet / outlet functioning as a washing fluid inlet, and a bundle of crimped long fibers, the upper end being a free end and the lower end being fixed above the support nozzle A backwashing method for a long fiber filtration device comprising a fiber bundle, and performing filtration by passing raw water through the filtration tank in a downward flow,
Through the lower outflow inlet and the upper outflow inlet, the washing water and the washing gas as the backwashing fluid are flowed in an upward flow to provide a backwashing process for washing the long fiber bundle,
In the backwashing step, the flow rate of the cleaning gas flowing into the filtration tank ranges from 180 m / h to 300 m / h, and the flow rate of the cleaning water ranges from 45 m / h to 75 m / h. The flow rate of the cleaning gas flowing out from the upper outlet is in the range of 7.0 m / s to 27.0 m / s, and the flow rate of the cleaning water is 1.7 m / s. A backwashing method for a long-fiber filtration device, wherein the backwashing method is in a range of s to 6.0 m / s.   The outflow speed of the cleaning gas flowing out from the upper outflow inlet is in the range of 7.0 m / s to 12.0 m / s, and the outflow speed of the cleaning water is from 1.7 m / s to 3. The backwashing method for a long fiber filtration device according to claim 1, wherein the backwashing method is in a range of 0 m / s or less.

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