JP2012096222A - Filtering apparatus and filtering method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filtering apparatus and a filtering method by which the fray of a fiber can be prevented and a high removal rate of suspended matter can be stably and continuously obtained for a long time.SOLUTION: The filtering apparatus includes a filtration tower 1 which has a filtering layer 2 formed of a fiber filter medium inside and a treated water collecting device 3 below the layer, the introduction pipe A of raw water to be treated at the upper part of the tower, an air supply pipe D at the lower part of the tower and a treated water outflow pipe F erected from the device 3 to the upper part of the layer 2. In this filtering apparatus, the fiber filter medium has a structure where both end parts are welded. The fiber filter medium is formed of two aggregates of the fiber and of a complex thermoplastic fiber having a core-clad structure or is formed of an aggregate of the fiber and a thermoplastic fiber and is aligned in a fiber direction. Further a porous member 4 for preventing outflow of the filter medium can be provided at the upper part of the filtering layer 2 in the filtration tower 1 and a drain pipe C can be provided at the upper part of the filtration tower and a water flow pipe E can be provided at the lower part thereof.

Description

  The present invention relates to a high-speed filtration separation method and apparatus for suspended water containing suspended particles such as sewage, industrial wastewater, and irrigation water, and removes suspended particles in suspended water (hereinafter also referred to as “raw water”) at high speed. It relates to the technology that can. In particular, the present invention is a high-speed solid-liquid separation technique for sewage flowing into a sewage treatment facility, or a combined sewer rainwater overflow (abbreviated as CSO) containing organic suspended particles, or various industrial wastewater, It is an innovative technology that is extremely suitable for water treatment.

Recently, the pollution load on public water areas of rainwater overflow (CSO) in a combined sewer has become a major problem. In addition, the sewage flowing into the sewage treatment facility is first precipitated and separated in the sedimentation basin and then treated with activated sludge. However, since the SS removal rate in the first sedimentation basin is poor, a coagulant is added to the flocculation sedimentation treatment. An example of this is prevalent in Scandinavia. However, this method has a drawback that a large amount of sludge is generated, the coagulation sedimentation rate is small, and a large sedimentation basin is required. Therefore, a new technology capable of solid-liquid separation of CSO and sewage with as much compact equipment as possible is expected.
Conventionally, a filtration method using a bead system of anthracite, sand, and various granular solids (for example, granular plastic) as a filter medium has been studied. For example, in the sewage treatment field, filtration is often performed using the above-mentioned anthracite, sand, etc., for a suspended substance having a relatively large particle size such as activated sludge treated water. In this case, the drainage flow rate is often 100 to 500 m / d.

Further, in order to increase the water flow rate, the filter medium particle size may be increased to reduce clogging, but in this case, problems such as deterioration of the SS removal rate have occurred. In particular, since organic SS contained in sewage and the like has a strong adhesive force, there is a demand for a technology that can satisfy the conflicting requirement that SS removal rate is high and clogging is small for sewage and the like.
As an alternative to the above-mentioned bead-based filter media, for example, in Japanese Patent Publication No. 62-55885 and Japanese Patent Laid-Open No. 10-305204, a large number of fiber masses in which short fibers made of organic fibers having a fiber length of 5 to 50 mm are entangled. There is a device that uses the filter as a filter medium. The filtration apparatus using this filter medium can perform filtration at a high speed of 600 m / d or more when treating wastewater containing suspended substances.

When removing suspended substances adhering to the fiber filter medium during the filtration process, so-called backwashing, the suspended substances are separated from the fiber filter medium by supplying cleaning water and / or air into the filter tower. Let Conventionally, in the backwashing process, the fiber filter medium is exposed to a vigorous fluid state, so that the short fibers fray from the fiber filter medium, and the frayed short fibers flow out. In a severe case, the shape of the fiber filter material itself may be greatly collapsed, and desired processing performance may not be ensured.
In JP-A-2004-89766, a lower part of a filtration tower in which a member with a synthetic fiber yarn fringe (fuzzy hair) or a fiber bundle string-like member is fixed inside the filtration tower and a plurality of members are suspended by a fixing member. Suspension water is made to flow in from above, and it is made to pass as an upward flow, it filters, and the method of making the filtered water flow out from the upper part is described. In a filtration tower using this filter medium, suspended water such as sewage can be filtered at a high speed of 1440 m / d with little clogging. In this case, it is not easy to backwash the fiber member to which the suspended substance is adhered, and when the fiber member is operated for a long time, the suspended substance may penetrate into the inside of the string and the washing effect may be insufficient.

Japanese Examined Patent Publication No. 62-55885 JP-A-10-305204 JP 2004-89766 A

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a new technology capable of high-speed filtration of suspended particles in various raw waters such as sewage, various wastewaters, and irrigation water by a simple and compact device. To do. In particular, by preventing the short fibers from fraying from the fiber filter medium, it is possible to stably obtain a high removal rate of suspended solids, and a high-speed filtration device capable of continuing a higher removal rate for a long time and its It aims at providing the filtration method using an apparatus.

In order to solve the above-mentioned problems, in the present invention, a filtration tower having a filtration layer made of a fiber filter medium inside, a water collecting device for treated water at the lower part thereof, and a treatment to be treated at the upper part of the filtration tower. In a filtration apparatus comprising a water introduction pipe A, a supply pipe D for supplying air to the lower part, and a treated water outflow pipe F raised above the filtration layer from the water collecting apparatus, the fiber filter medium is: The filtration device is characterized by being a fiber filter medium having a structure in which both ends are welded.
In the filtration apparatus, the fiber filter medium is a core-sheath composite thermoplastic fiber, a core-sheath composite thermoplastic fiber and a core-sheath composite thermoplastic fiber, or a core-sheath composite thermoplastic fiber. And a thermoplastic fiber aggregate, and those aligned in the fiber direction are preferable.

  In the filtration apparatus, a porous member having an opening smaller than the shortest length of the diameter of the fiber filter medium or the length of the linear portion is horizontally disposed on the upper part of the filtration layer in the filtration tower with respect to the water surface. Installed at any angle perpendicular to the drainage pipe C for draining the filter medium washing water to the upper part of the filtration tower and the washing water for washing the filter medium to the lower part through the upward flow. A drainage pipe G for draining the liquid in the filtration layer can be provided in the water collecting device in the filtration tower or the treated water outflow pipe F. In addition to the supply pipe D for supplying air, an air supply pipe D ′ whose flow rate can be adjusted can be provided at the lower part of the filtration tower.

Moreover, in this invention, it is set as the filtration method characterized by passing the to-be-processed water containing a suspended substance through the said filtration apparatus, and filtering the suspended substance in to-be-processed water.
In the filtration method, when the filtration performance is lowered, air is supplied from a supply pipe D that supplies air at the lower part of the filtration tower, and the solid matter attached to the fiber filter medium is swung by the fiber filter medium in the filter tank. A cleaning step for peeling off can be performed.
Moreover, in the said filtration method, when filtration performance falls using the filtration apparatus provided with the discharge pipe G, after the washing | cleaning process which peels the solid substance adhering to the fiber filter medium in a filtration tower, and the said washing | cleaning process, It is preferable to carry out a consolidation step of consolidating the filter medium by draining all or part of the liquid in the filter medium in the filter layer and the filter medium from the discharge pipe G. Can be performed by swinging the fiber filter medium.
Further, in the filtration method, using a filtration device provided with an air supply pipe D ′ having a separately adjustable flow rate, a cleaning process performed when the filtration performance deteriorates is performed. By generating a flow rate difference in the amount of air supplied from the pipe D ′, it can be performed while causing a swirling flow in the fiber filter medium of the filtration layer.

  By carrying out the present invention, raw water introduction pipe A to be treated at the upper part, flat rectangular fiber filter medium in the filtration tower, treated water collector and air at the lower part, supply pipe D for supplying air, water collection In a filtration tower provided with a treated water outflow pipe F raised at least above the filtration layer from the apparatus, the fiber filter medium is composed of an aggregate of core-sheathed composite thermoplastic fibers and thermoplastic fibers, and the fiber direction In addition, by using a flat rectangular fiber filter medium with both ends of the fiber filter medium welded, high removal rate of suspended solids can be stabilized without fraying short fibers from the fiber filter medium. And a higher removal rate could be continued for a long time at a high speed.

The flow block diagram which shows an example of the apparatus of this invention. The flow block diagram which shows the other example of the apparatus of this invention. The flow block diagram which shows the other example of the apparatus of this invention. The perspective block diagram which shows an example of the fiber filter medium used by this invention. The perspective block diagram which shows the other example of the fiber filter medium used by this invention.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a flow configuration diagram showing an example of the filtration device of the present invention.
In FIG. 1, 1 is a filtration tower, 2 is a filtration layer made of a fiber filter medium, 3 is a water collecting device, 5 is a water level gauge, and an inlet pipe A for raw water to be treated at the upper part, and a collection of treated water at the lower part. A treated water outflow pipe F (also referred to as a header pipe) raised from the water apparatus 3 and a supply pipe D for supplying air and at least the upper part of the filtration layer 2 from the water collecting apparatus 3 is provided. ) The suspended solids in are filtered.
Raw water is secondary treated water for sewage treatment, first settling basin effluent, rainy effluent, various industrial wastewater, effluent treatment, etc. But you can.

The fiber filter used here is a fiber filter manufactured by a manufacturing method including the following steps. In addition, when a fiber filter medium consists only of the composite thermoplastic fiber of one kind of core-sheath structure, the following process 1 is unnecessary.
(Step 1) Core-sheath composite thermoplastic fiber composed of a core-sheath structure composed of a core component and a sheath component, and a core-sheath composite thermoplastic fiber composed of a core component and a sheath component, or a core-sheath composed of a core component and a sheath component Blending step of blending a composite thermoplastic fiber having a structure and a thermoplastic fiber composed of a single component to form a blended cotton body (Step 2)
(Step 3) A welding step in which hot air is blown onto the sliver to form a welded portion where a part of the sliver is welded (step 4) A cutting step in which the sliver having the welded portion is welded and cut. Details of each step below Write.

(Mixed cotton process)
In the blending step, the composite thermoplastic fiber is a core-sheath type composite fiber, and has a core-sheath structure composed of a core component and a sheath component.
As the material of the core component, polyester fiber, polyamide fiber, vinylon fiber, polyolefin fiber, or the like is used. These may be used alone or in combination. Among these, it is preferable to use a polyester fiber as the material of the core component from the viewpoint of versatility and strength.
As the material for the sheath component, a copolymer of polyester and an aliphatic compound, polyethylene, polypropylene, or the like is used. These may be used alone or in combination. Among these, when the core component is made of polyester fiber, the sheath component is made of a polyester fiber and a copolymer of an aliphatic compound because the strength is better when the same component is used. Is preferred.
The fineness of the composite thermoplastic fiber is preferably 1 to 50 dtex. When the fineness of the composite thermoplastic fiber is less than 1 dtex, the gap between the fibers becomes too small compared to the case where the fineness is within the above range, and when the fineness exceeds 50 dtex, the gap between the fibers becomes large. Too much may not be able to capture the suspended particles together.

The ratio of the sheath component to the core component is preferably 1: 0.5 to 1 in the core component: sheath component. When the ratio of the sheath component is less than 0.5, the adhesive strength as a binder becomes insufficient as compared with the case where the fineness is within the above range, and when the ratio of the sheath component exceeds 1, the fineness is within the above range. Compared with the case where it exists in, it becomes difficult to weld.
Here, it is preferable to use a sheath component having a melting point lower than that of the core component. In this case, in the manufacturing method of the fiber filter medium, a so-called binder effect is exhibited in which the sheath component is welded and functions as an adhesive.
The melting point of the sheath component is preferably 80 to 200 ° C, and the melting point of the core component is preferably 160 to 250 ° C. In this case, the binder effect by the composite thermoplastic fiber can be surely exhibited.
Moreover, it is preferable that the difference of melting | fusing point of a sheath component and a core component is 30 degreeC or more. When the difference in melting point is less than 30 ° C., the core component and the sheath component are welded together as compared with the case where the difference in melting point is within the above range, and the composite thermoplastic fiber cannot maintain its shape. There is a case.

In the blending process, polyester fiber, polyamide fiber, vinylon fiber, polyolefin fiber, or the like is used as the material of the thermoplastic fiber composed of a single component. Among these, the material of the thermoplastic fiber is preferably a polyester fiber from the viewpoints of versatility, strength, and easy sinking in water.
The fineness of the thermoplastic fiber composed of a single component is preferably 1 to 50 dtex. When the fineness of the thermoplastic fiber is less than 1 dtex, the gap between the fibers becomes too small compared to the case where the fineness is within the above range, and when the fineness exceeds 50 dtex, the gap between the fibers becomes large. Too much may not be able to capture the suspended particles together.
Further, the melting point is preferably higher than the melting point of the sheath component of the composite thermoplastic fiber, and is preferably 160 to 250 ° C. In this case, the shape of the fiber filter medium can be maintained even if the binder effect by the composite thermoplastic fiber is exhibited.

In the blending step, the composite thermoplastic fiber cotton-like materials, or the composite thermoplastic fiber cotton-like material and the single thermoplastic fiber cotton-like material are mixed.
As for the mixing ratio when mixing with the linear material of a single thermoplastic fiber, it is preferable that a single thermoplastic fiber is 1.5-4 mass parts with respect to 1 mass part of composite thermoplastic fibers. If the mixing ratio of the single thermoplastic fiber is less than 1.5 parts by mass, the strength of the fiber filter medium may be insufficient compared to the case where the mixing ratio is within the above range, and the single thermoplastic fiber When the mixing ratio of the fibers exceeds 4 parts by mass, the binder effect of the composite thermoplastic fiber may be insufficient as compared with the case where the mixing ratio is in the above range.
In the blending step, the length and amount of fluff on the surface of the fiber filter medium can be adjusted by mixing a plurality of fibers. Thereby, the obtained fiber filter medium can collect suspended particles efficiently.

(Sliver process)
A sliver process is a process of making the blend cotton body or composite thermoplastic fiber obtained at the blend cotton process into a rope-like sliver. This step is a step in which the blended cotton body or fiber is applied to a spinning card machine to form a thin flat web, and then drafted through a drawing machine to form a rope-like sliver.
Here, the sliver refers to a bundle of fibers in a rope shape that is not twisted.
In the sliver process, the fiber direction is aligned by drafting and stretching a blended cotton body or fiber to form a rope-like sliver. Thereby, there exists an advantage that the tensile strength of a sliver improves.
The diameter of the rope-shaped sliver is preferably in the range of 5 to 20 mm. If the diameter is less than 5 mm, the width of the fiber filter medium becomes narrow and the filter medium tends to flow out of the filtration device. If the diameter exceeds 20 mm, the fiber filter medium itself becomes larger, reducing the specific surface area, There is a disadvantage that the surface area required for capturing the suspended solids is reduced.

(Welding process)
The welding step is a step of forming a welding sliver in which hot air is blown onto the sliver to weld some fibers in the sliver.
The welded sliver has a welded part in which the fibers of the sliver are welded in part. Thereby, the obtained fiber filter medium is prevented from fraying and has durability capable of withstanding abrasion for a long period of time. Although “partial” cannot be expressed quantitatively, welding is performed at the lattice points of a composite thermoplastic fiber having a core-sheath structure consisting of a core component and a sheath component and a thermoplastic fiber consisting of a single component. As the number of lattice points increases, fraying becomes difficult.
Further, the gap between the fibers is filled with water pressure when water is passed, and the gap between the fibers is separated during backwashing, so that the suspended particles can be efficiently detached.
In the welding step, the temperature of the hot air is preferably 120 to 180 ° C.

(Cutting process)
The cutting step is a step of forming a flat rectangular fiber filter medium having a total length of 5 to 20 mm by continuously welding and cutting the welding sliver. Examples of the welding cutting method include a method using a hot blade, ultrasonic cutting using ultrasonic vibration, and laser cutting. First, a method using a hot blade will be described.
In the cutting step, the welding sliver is advanced in the longitudinal direction and is moved up and down by a sufficiently heated hot blade, whereby the welding sliver is continuously cut to obtain individual flat rectangular fiber filter media. Since the left and right edges of the fiber filter medium are welded, the occurrence of fraying due to cutting is suppressed.
In welding cutting, the temperature of the hot blade is preferably 700 ° C. or higher. In this case, the welding sliver can be cut instantaneously and the edge of the welding sliver can be reliably welded.
In this way, a flat rectangular fiber filter medium is obtained.

FIG. 4 is a schematic perspective view showing a fiber filter used in the present invention.
In FIG. 4, 6 is a cut welding part, 7 is a part welding part, 8 is a fiber.
As shown in FIG. 4, the fiber filter used in the present invention is composed of an aggregate of a core-sheath composite thermoplastic fiber and a thermoplastic fiber, and is aligned in the fiber direction and a part of the fibers are welded together. As a whole, the center portion is a flat rectangular shape slightly swelled.
The flat rectangular fiber filter medium is a bundle in which a plurality of fibers are aligned in the longitudinal direction.
Here, each one short fiber is preferably larger than the total length in the longitudinal direction of the fiber filter medium. Thereby, it is suppressed that a fiber is pulled out.
Moreover, in the fiber filter medium, both ends cut perpendicularly to the longitudinal direction are welded and solidified by welding cutting. In addition, a large number of welds are scattered.
Therefore, the fiber filter medium is prevented from fraying and has durability capable of withstanding abrasion for a long period of time.

Next, a laser cutting method will be described.
The fiber filter medium shown in FIG. 5 is a fiber filter medium manufactured by a method of cutting a sliver-like fiber with a laser and fusing the cut surface. Also in FIG. 5, 6 is a cut welding part, 7 is a part welding part, 8 is a fiber similarly to FIG. In the cutting method using a laser, the fibers are hardly frayed because the cut surface is welded with a rope-like sliver, and a fiber filter medium can be used over a long period of time.

The water collecting device 3 can be of any type, such as a perforated block type, a wheeler type, a strainer type, a porous bottom type, a perforated tube type, etc. Since the block is light and easy to construct, it is preferable as a water collecting device for fiber filter media.
The raw water is continuously passed through the introduction pipe A, and is filtered by a fiber filter medium packed in the filtration tower. The filtered treated water is discharged out of the system through the treated water outflow pipe F. The water flow rate in the filtration process is more compact than the conventional filtration using a sand filtration layer, and when the water flow rate is high, suspended substances in the raw water are short-passed together with the treated water. In order to suppress the outflow, 500 to 2000 m / d is preferable. At this time, the filling height of the fiber filter medium is preferably about 300 to 2000 mm in order not to increase the frequency of backwashing and to design the free board part above the fiber filter medium layer not to be extremely high.

The fiber filter medium obtained by filtering a certain amount of raw water is washed periodically, or by detecting an increase in filtration resistance, because the inside and surface thereof are covered with suspended solids. In the washing, air is supplied from the lower part of the filtration tower, and the suspended substances are peeled off from the fiber filter medium. The aeration speed and the aeration time are generally carried out at an aeration speed of 0.1 to 5.0 m / min and an aeration time of 3 to 30 min.
Waste water after washing containing suspended solids separated from the fiber filter medium is discharged out of the system through the discharge pipe G or the treated water outflow pipe F while supplying raw water from the introduction pipe A, so that the regenerated fiber filter medium is recovered. Use again (cleaning process). Separately, a cleaning water supply pipe may be supplied from the upper or lower portion of the filtration tower (not shown), and the cleaning waste water may be discharged from the discharge pipe G or the treated water outflow pipe F. As the washing water, any liquid such as sewage secondary treated water, industrial water, rain water, or raw filter water can be used.

In order to improve the filtration performance, a part of the liquid in the filtration tower is discharged from the discharge pipe G installed in the water collecting device 3 in order to pack the fiber filter material submerged in water with higher density after the washing step. It is good to provide the compression process B which drains the whole quantity. The voids in the fiber filter medium are as high as 95% or more, and the apparent specific gravity of the fiber filter medium is about 1.1 even in the state of containing water in water. In the conventional state where the fiber filter medium is simply allowed to settle naturally in water, Since the difference in specific gravity between water-containing fibers (specific gravity of about 1.1) and water (specific gravity of about 1) is small, it cannot be said that the fiber filter media are closely packed, and the gap between the fiber filter media and the fiber filter media (voids) (Also called) was big. However, in the filtration method and apparatus having the structure of the present invention, a part or all of the liquid in the filtration layer 2 is drained, so that the fiber filter medium wet with water (specific gravity about 1.1) and the air density difference. Since (specific gravity about 0.001) becomes large, the fiber filter medium is densified so as to fill the voids by its own weight.
Subsequently, when the filtration is resumed, the fiber filter medium in the filtration layer 2 is sufficiently consolidated and the voids are reduced, so that the suspended matter in the treated water is well captured and the suspended matter removal rate is high. . Compared to the conventional method of simply sinking and filling the fiber filter medium, the filtration performance becomes higher when the water is drained and filtered in a high density state because the voids are reduced. Of course, at the time of filtration, the filter medium packed with high density does not expand.

  The filtration device shown in FIG. 2 is provided with a porous member 4 for preventing the outflow of the fiber filter medium in the filtration device of FIG. There is a concern that the fiber filter medium may flow out from the drain pipe C of the cleaning water during the water flow or ventilation process in the back washing process of the fiber filter medium. In particular, in the aeration process, if a large amount of suspended matter is peeled off from the fiber filter medium, the aeration speed increases. In this case, the fiber filter medium may flow out of the drain pipe C due to the rising air flow rate. Therefore, the filter medium outflow prevention porous member 4 having an opening smaller than the shortest length among the diameter of the fiber filter medium or the length of the straight line portion is installed at an arbitrary angle from the horizontal to the water surface. To do. As the porous member for preventing outflow, various members such as a strainer using a mesh made of various stainless steel weaves, a wedge wire, and a bar screen can be used. At least the opening is a diameter of a fiber filter medium or a straight line. It is made smaller than the shortest length among the lengths of the parts. The attachment angle may be such that it is installed horizontally on the surface of the filtration tank and covers the entire surface of the filtration tank, or it may be installed at an arbitrary angle with respect to the horizontal or vertical direction in the vicinity of the discharge pipe of the washing water. The installation position of the filter medium outflow prevention porous member 4 is at least lower than the drain pipe C.

In any case, the flow rate of the cleaning water per area in contact with the water of the porous member (also referred to as a water area load) in order to prevent the fiber filter medium from flowing into the cleaning water and sticking to the porous member. The porous member 4 is set so that the pressure becomes 10 to 200 m / h. A porous member with a water area load of 10 m / h or less is an excessive facility and has a high initial cost, and the fiber filter material is stuck to the porous member at a water area load of 200 m / h or more. In particular, when the washing water flow rate is varied in the backwashing step, it is preferable to provide a mechanism for controlling the supply rate of the washing water so that the water area load is within the above range.
In the apparatus shown in FIG. 2, water and aeration can be carried out at a high speed without worrying about the outflow of the fiber filter medium, and the washing time can be greatly reduced as compared with the conventional case, and the washing efficiency is improved, followed by filtration. The filtration performance in the process becomes good.
Even if the above-described filtration step and backwashing step are repeated using the apparatus shown in FIG. 1 and FIG. 2 described above, in the present invention, the fiber filter medium composed of short fiber clusters is aligned in the fiber direction and Since the fibers at the part or both ends are welded to each other, short fibers are hardly frayed from the fiber filter medium, and stable filtration performance can be achieved for a long time.

  The apparatus shown in FIG. 3 is provided with an air supply pipe D 'whose flow rate can be adjusted separately from the supply pipe D for supplying air to the lower part of the filtration tower. The supply pipe D ′ may be branched from the supply pipe D, or may be separately installed in the blower. The amount of air supplied from the supply pipe D and the supply D ′ can be controlled to produce a flow rate difference. Alternatively, air may be alternately supplied from the supply pipe D and the supply pipe D ′. At the time of backwashing, by causing a difference in flow rate supplied from each supply pipe, it is possible to cause a swirling flow of the fiber filter medium in the filtration layer, and the fiber filter medium can be washed with a small amount of air. The aeration speed and the aeration time are generally determined by taking the speed and time at which the suspended substance attached to the fiber filter material is peeled off, and the aeration speed is 0 to 5.0 m / min and the aeration time is 3 to 30 min.

Hereinafter, the present invention will be specifically described by way of examples.
Example 1
Filtration using a fiber filter medium (density 90 kg / m ³ ) was performed using a φ160 mm filtration device shown in FIG. What was manufactured by the following processes was used for the fiber filter medium.
(Mixed cotton process) 30 parts by mass of a bulky composite polyester fiber (4.4 dtex) composed of a core component having a melting point of 230 ° C and a sheath component having a melting point of 110 ° C, and a bulky polyester comprising a single component having a melting point of 230 ° C A cotton blend was obtained by blending 70 parts by mass of fiber (20 dtex).
(Sliver process) Next, the blended cotton body was passed through a spinning card machine and a drawing machine to obtain a sliver (mass 100 g / m, diameter 10 mm).
(Welding step) Next, the sheath component is welded by blowing hot air at 150 ° C. on the sliver, the composite polyester fiber and the polyester fiber composed of a single component are integrated, and cooled to form a rod-like weld. I got a sliver. Such a welding sliver had feathers and loops on the surface.
(Cutting step) Thereafter, the welding sliver was cut to a total length of 7 mm with a hot blade at about 800 ° C. to obtain the fiber filter medium of the present invention. It should be noted that the fibers were fused at the end of the cut surface.
The true specific gravity of the fiber filter medium is 1.38, the length is 10 mm, and the width is 7 mm.

The filter tower was previously filled with 20 L of fiber filter material (apparent volume).
The flow rate of the raw water was 20 m ³ / d, the flow rate in the filtration layer was 1000 m / d, and the treated water was continuously discharged from the treated water outflow pipe F. When SS in the raw water was captured by the fiber filter medium, the filtration performance deteriorated, so a backwash process was performed every 12 hours. In the backwashing method, air was supplied from the air supply pipe D, the fiber filter medium to which SS was attached was shaken, and the SS was peeled off from the fiber filter medium. Thereafter, the cleaning water was supplied from the cleaning water flow pipe E, and the cleaning water containing SS was discharged from the cleaning water discharge pipe C. The aeration rate was 1.5 m / min and the water flow rate was 1.0 m / min. The above backwashing process was repeated 5 times to resume filtration.
The filtration performance after about 6 months was 4 mg / L for the SS of the treated water with respect to the SS concentration of 10 mg / L for the raw water. Further, the fiber filter medium had almost the same shape as that in use, and there was no evidence of short fibers frayed from the fiber filter medium.

Example 2
Filtration using a fiber filter medium (density 90 kg / m ³ ) was performed using a φ160 mm filtration device shown in FIG. The fiber filter medium was the same as in Example 1.
The filter tower was previously filled with 20 L of fiber filter material (apparent volume).
The flow rate of the raw water was 20 m ³ / d, the flow rate in the filtration layer was 1000 m / d, and the treated water was continuously discharged from the treated water outflow pipe F. When SS in the raw water was captured by the fiber filter medium, the filtration performance deteriorated, so a backwash process was performed every 12 hours. In the backwashing method, air was supplied from the air supply pipe D, the fiber filter medium to which SS was attached was shaken, and the SS was peeled off from the fiber filter medium. Thereafter, the cleaning water was supplied from the cleaning water flow pipe E, and the cleaning water containing SS was discharged from the cleaning water discharge pipe C. The ventilation speed was 1.5 m / min (0.03 m ³ / min), and the water flow speed was 1.0 m / min. After repeating the above backwashing process five times, the wash water in the filtration tower is drained by opening the valve Y from the discharge pipe G, and the water level in the water collecting device is 400 mm. Was detected, a signal for closing the valve Y was issued (consolidation process). Thereafter, filtration was resumed.
As for the filtration performance after about 6 months, the SS concentration of the treated water was 2 mg / L with respect to the SS concentration of the raw water of 10 mg / L, and a good treatment performance could be obtained. Further, the fiber filter medium had almost the same shape as that in use, and there was no evidence of short fibers frayed from the fiber filter medium. The reason why the filtration performance was improved as compared with Example 1 was that the fiber filter medium was densely packed by providing the consolidation step.

Example 3
Filtration using a fiber filter medium (density 90 kg / m ³ ) was performed using a φ160 mm filtration device shown in FIG. The fiber filter medium was the same as in Example 2. The difference from the second embodiment is that the air supply pipe is branched, and the supply amount of air can be reduced by a half of each supply amount. The other conditions are the same as those of the second embodiment.
The filter tower was previously filled with 20 L of fiber filter material (apparent volume).
The flow rate of the raw water was 20 m ³ / d, the flow rate in the filtration layer was 1000 m / d, and the treated water was continuously discharged from the treated water outflow pipe F. When SS in the raw water was captured by the fiber filter medium, the filtration performance deteriorated, so a backwash process was performed every 12 hours. In the backwashing method, air was supplied from the air supply pipe D and the supply pipe D ′, the fiber filter medium to which SS adhered was shaken, and the SS was peeled off from the fiber filter medium. Thereafter, the cleaning water was supplied from the cleaning water flow pipe E, and the cleaning water containing SS was discharged from the cleaning water discharge pipe C. Aeration speed is set to 0.75 m / min (0.015 m3 / min), a water flow speed is set to 1.0 m / min, and the supply pipe D and the supply pipe D ′ are operated alternately to cause a swirling flow of the fiber filter medium. Washed with. After repeating the above backwashing process five times, the wash water in the filtration tower is drained by opening the valve Y from the discharge pipe G, and the water level in the water collecting device is 400 mm. Was detected, a signal for closing the valve Y was issued (consolidation process). Thereafter, filtration was resumed.
As for the filtration performance after about 6 months, the SS of the treated water was 2 mg / L with respect to the SS concentration of the raw water of 10 mg / L, and good treatment performance could be obtained as in Example 2. Further, the fiber filter medium had almost the same shape as that in use, and there was no evidence of short fibers frayed from the fiber filter medium. Compared to Example 2, it was possible to effectively wash with a small amount of air by washing the fiber filter medium with a swirling flow during washing.

Example 4
Filtration using a fiber filter medium (density 90 kg / m ³ ) was performed using a φ160 mm filtration device shown in FIG. The fiber filter medium was manufactured as follows.
(Mixed cotton process) 80 mass parts of composite polyester fibers (4.4 dtex) with a core-sheath structure and 20 mass parts of composite polyester fibers with a core-sheath structure (6.6 dtex) were mixed to obtain a blended cotton body.
(Sliver process) Next, the blended cotton body was passed through a spinning card machine and a drawing machine to obtain a sliver (mass 100 g / m, diameter 10 mm).
(Welding step) Next, the sheath component was welded by blowing hot air at 150 ° C. on the sliver to integrate the two types of composite polyester fibers, and the rod-shaped welded sliver was obtained by cooling. Such a welding sliver had feathers and loops on the surface.
(Cutting step) Thereafter, the welding sliver was cut by laser cutting so as to have a total length of 7 mm to obtain the fiber filter medium of the present invention. It should be noted that the fibers were fused at the end of the cut surface.
The true specific gravity of the fiber filter medium is 1.38, the length is 7 mm, and the diameter is 7 mm.

The filter tower was previously filled with 20 L of fiber filter material (apparent volume).
The flow rate of the raw water was 20 m ³ / d, the flow rate in the filtration layer was 1000 m / d, and the treated water was continuously discharged from the treated water outflow pipe F. When SS in the raw water was captured by the fiber filter medium, the filtration performance deteriorated, so a backwash process was performed every 12 hours. In the backwashing method, air was supplied from the air supply pipe D, the fiber filter medium to which SS was attached was shaken, and the SS was peeled off from the fiber filter medium. Thereafter, the cleaning water was supplied from the cleaning water flow pipe E, and the cleaning water containing SS was discharged from the cleaning water discharge pipe C. The ventilation speed was 1.5 m / min (0.03 m ³ / min), and the water flow speed was 1.0 m / min. After repeating the above backwashing process five times, the wash water in the filtration tower is drained by opening the valve Y from the discharge pipe G, and the water level in the water collecting device is 400 mm. Was detected, a signal for closing the valve Y was issued (consolidation process). Thereafter, filtration was resumed.
As for the filtration performance after about 6 months, the SS concentration of the treated water was 2 mg / L with respect to the SS concentration of the raw water of 10 mg / L, and a good treatment performance could be obtained. Further, the fiber filter medium had almost the same shape as that in use, and there was no evidence of short fibers frayed from the fiber filter medium. The reason why the filtration performance was improved as compared with Example 1 was that the fiber filter medium was densely packed by providing the consolidation step.

Comparative Example 1
This example is a comparative example of Example 1, and was the same as Example 1 except that the cut surface was not fused in the cutting step when manufacturing the fiber filter medium. The filtration device, the filtration method, and the backwashing method are the same as in Example 1.
The filtration performance after about 6 months was 5 mg / L of the treated water with respect to the SS concentration of the raw water of 10 mg / L, which was lower than that of Example 1. When the fiber filter medium was confirmed, both ends of the filter medium frayed a little, and it was larger as a whole than at the time of use. Therefore, it is presumed that the gap between the fiber filter medium and the fiber filter medium is increased, and the suspended substance is likely to leak into the treated water.

Comparative Example 2
This example is a comparative example of Example 2, and was the same as Example 2 except that the cut surface was not fused in the cutting step when manufacturing the fiber filter medium. The filtration device, the filtration method, and the backwashing method are the same as in Example 2.
The filtration performance after about 6 months was 3 mg / L for the treated water with respect to the SS concentration of 10 mg / L for the raw water, which was lower than that in Example 2. When the fiber filter medium was confirmed, both ends of the filter medium frayed a little, and it was larger as a whole than at the time of use. Therefore, it is presumed that the gap between the fiber filter medium and the fiber filter medium is increased, and the suspended substance is likely to leak into the treated water.

  1: Filtration tower, 2: Filtration layer filled with fiber filter medium, 3: Water collecting device, 4: Porous member, 5: Water level gauge, 6: Cut welded part, 7: Partial welded part, 8: Fiber, A: Raw water introduction pipe, C: Wash water drain pipe, D, D ': Air supply pipe, E: Wash water flow pipe, F: Treated water outflow pipe, G: Discharge pipe, Y: Valve

Claims (10)

  A filtration tower having a filtration layer made of a fiber filter inside, a water collecting device for treated water at the lower part thereof, an introduction pipe A for treated water to be treated at the upper part of the filtration tower, and air at the lower part In the filtration apparatus provided with the supply pipe D to be supplied and the treated water outflow pipe F raised above the filtration layer from the water collecting apparatus, the fiber filter medium has a structure in which both ends are welded. A filtration device characterized by being. The fiber filter medium is a core-sheath composite thermoplastic fiber, a core-sheath composite thermoplastic fiber and a core-sheath composite thermoplastic fiber, or a core-sheath composite thermoplastic fiber and a thermoplastic fiber. The filtration device according to claim 1, wherein the filtration device is aligned in the fiber direction.   In the upper part of the filtration layer in the filtration tower, a porous member having an opening smaller than the shortest length of the diameter of the fiber filter medium or the length of the straight line portion is arbitrary from horizontal to vertical with respect to the water surface. A drainage pipe C for draining the filter medium washing water at the upper part of the filter tower and a water pipe E for passing the wash water for washing the filter medium upward at the lower part. The filtration apparatus according to claim 1, wherein the filtration apparatus is provided.   The filtration apparatus according to claim 1, 2 or 3, wherein the water collecting apparatus in the filtration tower or the treated water outflow pipe F includes a discharge pipe G for draining the liquid in the filtration layer. .   5. The air supply pipe D ′ whose flow rate can be adjusted is installed in the lower part of the filtration tower, in addition to the supply pipe D that supplies air, according to claim 1. Filtration device.   A filtration method comprising filtering water suspended in water to be treated by passing the water to be treated containing the suspended solids through the filtration device according to any one of claims 1 to 5.   In the filtration method, when the filtration performance is lowered, air is supplied from a supply pipe D that supplies air at the lower part of the filtration tower, and the solid matter attached to the fiber filter medium is swung by the fiber filter medium in the filter tank. The filtration method according to claim 6, wherein a cleaning step for peeling is performed.   In the method of passing the water to be treated containing suspended solids through the filtration device according to claim 4 and filtering the suspended solids in the water to be treated, if the filtration performance is reduced, it adheres to the fiber filter medium in the filtration tower. A cleaning step of peeling off the solid matter, and a compacting step of consolidating the filter medium by draining all or part of the liquid in the filter medium in the filter layer and the filter medium from the discharge pipe G after the cleaning process, The filtration method characterized by implementing.   The filtration method according to claim 8, wherein the washing step is performed by supplying air into the filtration tower and swinging the fiber filter medium.   In the method of passing the to-be-treated water containing a suspended substance through the filtration device according to claim 5 and filtering the suspended substance in the to-be-treated water, when the filtration performance is reduced, a washing step for peeling off the solid matter is performed. It is characterized by performing a swirling flow in the fiber filter medium of the filtration layer by generating a flow rate difference in the amount of air supplied from the supply pipe D and the supply pipe D ′ for supplying air installed in the lower part of the filtration tower. Filtration method.

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