JP2013027862A - Device and method for filtration of suspended water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filtration device and method including a new washing method capable of discharging a peeled suspended material with a small amount of water when washing a suspended material-attached filter and heightening a water recovery rate.SOLUTION: The filtration device for removing the suspended material from a suspended material-containing raw water comprises: a filter layer 2 filled with a filter for trapping the suspended material; a raw water introduction tube A for feeding the raw water to the upper part of the filter layer 2; a fine bubble generator 4 for introducing a fine bubble into the raw water; a water collection unit 3 which is provided below the filter layer 2 and collects a treatment water; an air-supplying tube D for supplying air to the water collection unit 3; a treatment water outflow tube F which is stood from the water collection unit to the position upward from the filter layer 2 and discharges the treatment water from the water collection unit; a washing water-introducing tube E which flows a washing water to the filter layer 2 in an upward flow; and a washing water-discharging tube H for discharging the washing water from above the filter layer 2.

Description

  The present invention relates to an apparatus and a method for high-speed filtration and separation of suspended water (hereinafter also referred to as “raw water”) containing suspended particles such as sewage, industrial effluent, irrigation water, and seawater. It is related with the technology which can be removed by filtration. The present invention may be abbreviated as “CSO” (hereinafter referred to as “CSO”), in particular, a high-speed solid-liquid separation technique for sewage flowing into a sewage treatment facility, or a combined sewer containing organic suspended particles. ) Or innovative technology that is extremely suitable for various industrial wastewater treatment, water treatment, and seawater treatment.

  Contamination load of rainwater overflow (CSO) in public water areas in the combined sewer system has become a major problem. Moreover, the sewage flowing into the sewage treatment facility is first separated and separated in the settling basin, and then treated with activated sludge. At this time, since the removal rate of SS (solid suspended solids) in the initial sedimentation basin is poor, an example in which a coagulant is added to perform coagulation sedimentation is prevalent in Northern Europe. 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 awaited.

  Further, as an advanced treatment of sewage, a tertiary treatment for removing suspended substances in the secondary treated water is performed in order to improve the water quality at the discharge destination or to reuse it as in-house water. In this case, since the amount of treated water is large, it is desired to provide a filtration device capable of high-speed treatment.

  Conventionally, a filtration method using various granular solids such as anthracite and sand, for example, granular plastic has been studied. For example, in the sewage treatment field, filtration is often performed using the aforementioned anthracite, sand, or the like 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.

  In addition, in order to increase the water flow rate, the filter medium particle size may be increased to reduce clogging, but in this case, inconsistencies such as deterioration of the SS removal rate have occurred. In particular, since organic SS contained in sewage and the like has strong adhesive strength, there is a demand for a technology that can satisfy the contradicting requirements for sewage and the like, with a high SS removal rate and less clogging.

  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 filtration device that uses 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.

  Such a fiber filter medium is suspended from the fiber filter medium by supplying washing water and / or air into the filtration tower in the case of so-called “back washing” to remove suspended substances adhering in the filtration process. The turbid material is peeled off. Conventionally, in this backwashing process, the filtration performance of the fiber filter medium has been recovered by exposing the fiber filter medium to a vigorous fluid state, peeling the suspended substance from the fiber filter medium, and discharging the peeled suspended substance. However, if the fiber filter medium is very dirty, it must be washed away with a large amount of washing water, and the water recovery rate (recovered water amount / filtered water amount) may be low, and improving the water recovery rate is an issue. Are listed.

  Conventionally, desalting methods for desalting seawater or brackish water to obtain industrial water or drinking water include a reverse osmosis (RO) membrane method, an electrodialysis method or an electric desalting method, and an evaporation method. It was. When these technologies are adopted, pretreatment to remove suspended substances contained in seawater or brackish water is necessary beforehand, such as agglomeration method, sand filtration method, pressurized flotation method, MF / UF membrane method, etc. Have been used alone or in combination.

  For example, a desalination apparatus has been proposed in which a pretreatment device having a pretreatment membrane for filtering suspended substances in raw water is provided at the front stage of a reverse osmosis (RO) membrane device (Patent Document 3). Patent Document 3 describes that a separation membrane such as a UF membrane (ultrafiltration membrane) or an MF membrane (microfiltration membrane) is used as the pretreatment membrane. However, due to the influence of urban sewage flowing into seawater or brackish water, recently, not only suspended substances, but also plant / phytoplankton, marine oil, and organic matter dissolved in liquids are RO membrane method and electrodialysis method. It has become apparent that it greatly affects the operation, maintenance and cost of the electric desalination method and evaporation method. In particular, in the desalination methods using membranes such as the RO membrane method, electrodialysis method, and electric desalination method, organic substances dissolved on the surface of the desalination membrane accumulate, and they grow as slime by biological propagation. This causes a decrease in membrane flow velocity, an increase in backwash frequency, and a decrease in membrane life. Also in the evaporation method, cost performance decreases, such as deterioration in fresh water quality due to volatile components that migrate to the fresh water side due to evaporation and reduced efficiency in terms of heat transfer due to organic matter. These organic substances, oil, and various plankton dissolved in raw water cannot be removed by the conventional sand filtration method, and some leaks even if the membrane method is used, which adversely affects the membrane cleaning frequency, life, etc. It was.

Japanese Examined Patent Publication No. 62-55885 JP-A-10-305204 JP 2011-31121 A

  The present invention has been made in view of the above circumstances, and provides a new technology capable of high-speed filtration of suspended particles in various raw waters such as sewage, various wastewaters, irrigation water, and seawater by a simple and compact device. This is the issue. In particular, it is an object of the present invention to provide a filtration apparatus and method including a novel cleaning method that can discharge a suspended solid material with a small amount of water and increase the water recovery rate at the time of cleaning a filter medium to which the suspended material is adhered.

  Another object of the present invention is to provide a filtration apparatus and method for preventing the organic matter from adhering to the filter medium when the raw water containing the suspended substance and the organic matter is treated.

  According to the present invention, there is provided a filtration device for removing suspended substances from raw water containing suspended substances, wherein the filter medium layer is filled with a filter medium that traps suspended substances, and the raw water is supplied to the upper part of the filter medium layer. Raw water introduction pipe A, a fine bubble generator for introducing fine bubbles into the raw water, a water collection device for collecting treated water, which is provided below the filter medium layer, and air to the water collection device The supplied air supply pipe D, the treated water outflow pipe F that discharges treated water from the water collection device, which is raised from the water collection device to a position above the filter material layer, and the filter material layer are washed. There is provided a filtration device comprising a washing water introduction pipe E for passing water in an upward flow and a washing water discharge pipe H for discharging washing water from above the filter medium layer.

Furthermore, it is preferable that a floss discharge pipe X is provided above the filter medium layer.
It is preferable that the fine bubble generating device is a gas-liquid mixing nozzle provided on an upper portion of the filter medium layer.

  The filtration device may be partitioned into a filtration portion including the filter medium layer and the water collecting device, and a fine bubble introduction portion that is positioned upstream of the filtration portion and includes the fine bubble generation device.

  Furthermore, a turbidimeter that measures the turbidity of raw water provided on the upstream side of the filter medium layer, a control mechanism that controls the fine bubble generator according to the turbidity measured by the turbidimeter, The aspect which comprises is also included.

  Furthermore, the treated water return pipe connected from the treated water outflow pipe F to the raw water introduction pipe A and the treated water outflow pipe F are provided in the treated water outflow pipe F, and treated water is measured according to the turbidity measured by the turbidimeter. And a valve for switching the flow path.

The filter medium is preferably a fiber filter medium composed of short fiber lumps.
The filter medium may be a biofilm filter medium carrying aerobic microorganisms.
According to this invention, the filtration method which removes a suspended solid from raw | natural water using the said filtration apparatus is also provided. The filtration method is
(1) a step of introducing fine bubbles into raw water containing suspended solids,
(2) introducing the raw water into which fine bubbles have been introduced into the upper part of the filter medium layer, allowing the filter medium layer to pass through the filter medium layer in a downward flow, and trapping suspended substances in the filter medium layer;
(3) collecting the treated water from which suspended substances have been removed into a water collecting device;
(4) including a step of discharging the treated water to the outside of the filtration device via the treated water outflow pipe.

The introduction of the fine bubbles in the step (1) is preferably controlled according to the turbidity of the raw water.
In the step (1), it is more preferable to introduce treated water into the raw water according to the turbidity of the raw water.

In the step (1), the suspended solid may be floated and concentrated with fine bubbles, and the suspended and suspended suspension may be discharged from the upper part of the filtration device.
Moreover, according to this invention, the washing | cleaning method of the said filtration apparatus is also provided. The cleaning method is
(5) Stopping the introduction of raw water, supplying air to the water collecting device via the air supply pipe D, causing the filter medium to flow in the water containing air, and separating the suspended matter from the filter medium into the water;
(6) Stopping the supply of air from the air supply pipe D, operating the microbubble generator to inject microbubbles into the water, and levitating and concentrating the suspended matter separated from the filter medium; and (7) The cleaning water introduction pipe E includes a process of passing the cleaning water in an upward flow and discharging the water containing the suspended suspended matter from the cleaning water discharge pipe H.

In the step (6), the suspended and suspended suspension may be discharged from the upper part of the filtration device.
In the step (6), it is preferable to add an inorganic flocculant to water into which fine bubbles are injected.

  According to the filtration device and the filtration method of the present invention, since suspended substances in raw water are floated and concentrated by the fine bubbles introduced into the raw water, the amount of suspended substances trapped in the filter medium can be reduced. Contributes to longer life. In particular, when a biofilm is used as a filter medium, the amount of organic substances adhering to the filter medium can be reduced, thereby preventing slime generation and contributing to an improvement in filtration efficiency.

  Since the amount of fine bubbles to be introduced into the raw water is controlled by the turbidity of the raw water, fine bubbles can be introduced without excess and deficiency, and suitable suspended matter removal can be achieved. When the turbidity is high, a large amount of fine bubbles are introduced, the suspended matter is floated and concentrated, and discharged from the upper part of the filtration device, reducing the load on the filter medium and reducing the frequency of backwashing the filtration layer. And contributes to longer life of the filter media.

  In addition, according to the method for cleaning a filter medium of the present invention, suspended substances separated from the filter medium can be levitated and concentrated by fine bubbles introduced into the water at the time of cleaning the filter medium, and the backwash effect can be improved. Can be reduced. In the embodiment in which the suspended and suspended suspension is discharged from the upper part of the filtration device, the backwash effect can be further improved. Further, by using an inorganic flocculant in combination, the aggregation of suspended substances is promoted, and the removal efficiency by flotation concentration is improved.

  In the filtration method that is restarted after the cleaning method of the present invention is performed, the suspended solids adhering to the filter medium are removed. Therefore, the suspended matter removal rate can be maintained high over a long period of time. In addition, the water recovery rate (the amount of recovered water / the amount of filtered water) according to the conventional method was 95 to 97% even when a fiber filter medium was used. The recovery rate can be improved to 99% or more.

FIG. 1 is a flow configuration diagram showing an example of the apparatus of the present invention. FIG. 2 is a flow configuration diagram showing another example of the apparatus of the present invention. FIG. 3 is a flow configuration diagram showing another example of the apparatus of the present invention. FIG. 4 is a flowchart showing another example of the apparatus of the present invention. FIG. 5 is a flowchart showing another example of the apparatus of the present invention. FIG. 6 is a flow configuration diagram showing another example of the apparatus of the present invention. FIG. 7 is a flow configuration diagram showing another example of the apparatus of the present invention. FIG. 8 is a flow diagram of the apparatus used in Comparative Example 1.

Embodiment

Hereinafter, the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.
A filtration device 1 shown in FIG. 1 includes a filter medium layer 2 filled with a filter medium that traps suspended substances, a raw water introduction pipe A that supplies raw water to the upper part of the filter medium layer 2, and a fine structure that introduces fine bubbles into the raw water. A bubble generating device 4, a water collecting device 3 that collects treated water provided below the filter medium layer 2, an air supply pipe D that supplies air to the water collecting device 3, and a filter medium from the water collecting device 3 A treated water outflow pipe F for discharging treated water from the water collecting device 3 raised to a position above the layer 2, and a washing water introduction pipe E for passing the washing water upward through the filter medium layer 2; And a cleaning water discharge pipe H that discharges the cleaning water from above the filter medium layer 2. The fine bubble generating device 4 is a gas-liquid mixing nozzle, to which a liquid introduction pipe B and a gas introduction pipe C are connected. The installation position of the gas-liquid mixing nozzle is the same position as the upper surface of the filter medium layer 2 (usually the layer height is 300 to 2000 mm). If the installation position is in the filter medium layer 2, fine bubbles adhere to the filter medium, and the floating concentration of the suspended suspended substances is suppressed. On the other hand, if it is too high, the ratio of levitation and concentration decreases, so the efficiency decreases. A discharge pipe G for discharging the liquid in the filter medium layer 2 is connected to the water collecting device 3. A valve Y is attached to the discharge pipe G. The water level of the filter medium layer 2 is adjusted by opening and closing the valve Y in accordance with an indication value of a pressure gauge provided in the water collecting device 3.

  The filtration device shown in FIG. 2 has substantially the same configuration as the filtration device 1 shown in FIG. 1, but the liquid introduction tube to the fine bubble generating device 4 is a raw water introduction tube B. As a modification of the embodiment shown in FIG. 2, the whole amount of raw water may be introduced into the fine bubble generating device 4 and introduced into the filtration layer 2 as raw water containing fine bubbles without using the raw water introduction pipe A.

  The basic structure of the filtration device shown in FIG. 3 is the same as that of the filtration device 1 shown in FIG. 1, but the gas-liquid generator 4 is connected to the raw water introduction pipe A, and the treated water and air are mixed and generated. After introducing fine bubbles into the raw water, the filter medium layer 2 was supplied. Further, a floss discharge pipe X, which is a discharge pipe for suspended and suspended substances (hereinafter also referred to as “floss”), is provided above the filter medium layer 2. In the filtration device, a trough, which is a flow path provided in order to make the supply of raw water uniform, is provided at a position above the floss discharge pipe X. Further, the treated water outflow pipe F is provided with a bypass pipe F-1 and a valve Z.

  The filtration device shown in FIG. 4 is the same as the configuration shown in FIG. 3 except that the floss discharge pipe X is positioned above the trough. The bypass pipe F-1 is provided to adjust the water level in the filtration device, and the valve Z is closed and the treated water flows into the bypass pipe F-1, so that the water level in the filtration device is reduced to the bypass pipe F-. Can be raised to a height of 1. The height of the bypass pipe F-1 is a height that matches the height position of the floss discharge pipe X.

  The filtration device shown in FIG. 5 is partitioned into a filtration part 1a including the filter medium layer 2 and the water collecting device 3, and a fine bubble introduction part 1b that is positioned upstream of the filtration part 1a and includes the fine bubble generation device 4. ing. A raw water introduction pipe A is connected to the fine bubble introduction portion 1b, and a treated water introduction pipe B and an air introduction pipe C are connected to the fine bubble generation device 4. In the fine bubble introduction portion 1b, the fine bubbles generated by gas-liquid mixing are introduced into the raw water, and then flowed into the filtration portion 1a and filtered. A floss discharge pipe X is provided above the height of the partition wall that partitions the filtration portion 1a and the fine bubble introduction portion 1b. The treated water outflow pipe F is provided with a bypass pipe F-1 having a height matching the floss discharge pipe X and a valve Z for switching the flow path of the treated water, and the water level in the filtration part 1a is discharged through the floss. It can be raised to the position of tube X.

  The filtration device shown in FIG. 6 differs from the configuration shown in FIG. 5 except that a turbidimeter for measuring the turbidity of raw water introduced into the fine bubble generating device 4 in the fine bubble introduction portion 1b is provided. The same. Based on the turbidity measured by the turbidimeter, the amount of air introduced into the microbubble generator 4 is controlled to control the amount of microbubbles generated.

  The filtration device shown in FIG. 7 is provided with a turbidity meter in the filtration part 1a, and is introduced into the fine bubble generator 4 in the fine bubble introduction part 1b based on the turbidity of raw water measured by the turbidimeter. Except for the point which controls the quantity of treated water, it is the same as the structure shown in FIG.

Next, components common to the filtration devices of FIGS. 1 to 7 will be described.
[Microbubble generator]
The microbubble generator 4 is a device that generates microbubbles. “Microbubbles” are bubbles having a diameter of 10 to several tens of μm, but the diameters of all the bubbles need not necessarily fall within this range. In addition, a generator capable of generating nanobubbles having smaller bubbles than microbubbles may be used, but it is desirable that the large particle size side of the generated bubbles is within the above bubble diameter range. Various types of microbubble generators have been proposed. For example, swirling liquid flow type, static mixer type, ejector type, venturi type, pressure dissolution type, ultra fine hole type, ultrasonically added hollow needle nozzle, steam Condensation type is mentioned. For example, in the ejector type, the gas is sucked using the negative pressure generated by the liquid flow passing through the narrow passage at high speed in the gas-liquid mixing nozzle, and the suction gas is fine due to the cavitation caused by the expansion of the downstream pipe. To be crushed. In the pressure dissolution type, the mixed phase of gas and liquid is increased in pressure (about 0.5 to 1 MPa) with a pump, and the gas component is dissolved in the liquid until supersaturated. Undissolved bubbles are floated and separated in a pressurized tank and purged. When only the supersaturated liquid is flushed into the normal pressure liquid through the pressure reducing valve, the supersaturated gas component is deposited as microbubbles from the water (Chemical Engineering vol. 71, No. 3 (2007)). At this time, if the gas-liquid mixing nozzle is passed, finer bubbles can be generated.

  A variety of gas-liquid mixing nozzles have been proposed. Inside the nozzle, the pipeline is changed in stages, spherical obstacles are installed in the pipeline, slits are used, centrifugal force What crushes the gas column generated by the above by the projections can be employed.

[Water collector]
The water collecting device 3 can be selected from any of gravel, perforated block type, wheeler type, strainer type, porous bottom type, perforated tube type, etc. Since the block is light and easy to construct, it is preferable as a water collecting device for filter media. As the water collecting device, trilateral (manufactured by Mizuing Inc.) can be suitably used.

[Filter media layer]
The filter medium layer 2 is filled with a filter medium. About 300-2000 mm is preferable as the filling height of the filter medium in order to design the freeboard part on the upper part of the filter medium layer so as not to become extremely high without increasing the frequency of backwashing. Various filter media can be used as the filter media, and examples thereof include sand, anthracite, garnet, activated carbon, granulated activated carbon, artificial beads, and fiber filter media composed of short fiber clusters. A fiber filter medium composed of short fiber lumps is particularly preferable because the water recovery rate can be remarkably improved. In addition, dissolved organic matter can be removed using a biofilm in which aerobic microorganisms are immobilized on the surface of these filter media. When using biofilms, normal activated carbon is crushed and non-uniform in shape and size, but granulated activated carbon processed into a spherical shape has a uniform shape and size, so it supports microorganisms uniformly. It is easy to form a uniform biofilm and is suitable. The granulated activated carbon preferably has an average particle size of 0.5 to 3.5 mm.

Various fiber filter media can be used as the fiber filter medium composed of short fiber masses, and fiber filter media manufactured by the following production method are particularly suitable.
(Process 1) A composite thermoplastic fiber formed by blending a first thermoplastic fiber having a core-sheath structure composed of a core component and a sheath component and a second thermoplastic fiber composed of a single component, or several kinds of core components and sheaths A blending step of blending the core-sheath composite thermoplastic fiber comprising the components into a blended cotton body (step 2), a sliver step of blending the blended cotton body with a rope-like sliver (step 3), blowing hot air on the sliver, Welding step for forming a welded portion where a part of the sliver is welded (step 4) Cutting step for cutting the sliver having the welded portion Each step will be described below.

(Mixed cotton process)
In the blending step, the first thermoplastic fiber is a core-sheath type composite fiber, and has a core-sheath structure including a core component and a sheath component. Examples of the material of the core component include polyester fibers such as polyethylene terephthalate, polyamide fibers such as nylon 6 and nylon 66, and polyvinyl alcohol fibers. These may be used alone or in combination. Among these, the material of the core component is preferably a polyester fiber 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 fibers, 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. preferable.

  The fineness of the first thermoplastic fiber is preferably 1 to 50 dtex. When the fineness of the first thermoplastic fiber is less than 1 dtex, the gap between the fibers is too small compared to the case where the fineness is within the above range, whereas when the fineness exceeds 50 dtex, the gap between the fibers is reduced. There is a risk that the particles may become too large to capture the suspended particles together.

  In the blending step, polyester fiber, polyamide fiber, vinylon fiber, polyolefin fiber, or the like is used as the material of the second thermoplastic fiber made of a single component. Among these, the material of the second thermoplastic fiber is preferably a polyester fiber from the viewpoints of versatility, strength, and easy sinking in water.

  The fineness of the second thermoplastic fiber made of a single component is preferably 1 to 50 dtex. When the fineness of the second thermoplastic fiber is less than 1 dtex, the gap between the fibers is too small compared to the case where the fineness is within the above range, whereas when the fineness exceeds 50 dtex, the gap between the fibers is reduced. There is a risk that the particles may become too large to capture the suspended particles together.

  The melting point of the second thermoplastic fiber is preferably higher than the melting point of the sheath component of the first thermoplastic fiber, and is preferably 160 to 250 ° C. In this case, the shape of the fiber filter medium can be maintained by exerting a binder effect by the composite thermoplastic fiber formed by blending.

In the blending step, the lump of the first thermoplastic fiber and the lump of the second thermoplastic fiber are mixed.
As for the mixing ratio at this time, it is preferable that 2nd thermoplastic fiber is 1.5-4 mass parts with respect to 1 mass part of 1st thermoplastic fibers. If the mixing ratio of the second 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 in the above range, and the second thermoplasticity 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.

  When a composite thermoplastic fiber having a core-sheath structure composed of several kinds of core components and a sheath component is blended to form a blended cotton body, each fiber functions as a binder, so that it is possible to obtain a blended cotton body that is more difficult to fray. . Although the mixing ratio can be arbitrary, in order to take advantage of the characteristics of each composite thermoplastic fiber, it is desirable that at least each is 1/3 or more of the total amount.

  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 blended cotton body obtained at the blended cotton process into a rope-shaped sliver. This process is a process in which the blended cotton body 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, “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 the blended cotton body to form a rope-shaped 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, the weld is a lattice point of a first thermoplastic fiber having a core-sheath structure consisting of a core component and a sheath component and a second thermoplastic fiber consisting of a single component. As the number of grid points increases, fraying becomes difficult. When a composite thermoplastic fiber having a core-sheath structure composed of several kinds of core components and a sheath component is blended to form a blended cotton body, each fiber functions as a binder, so that it is possible to obtain a blended cotton body that is more difficult to fray. .

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 making a fiber filter medium having a total length of 5 to 20 mm by continuously welding and cutting the welding sliver. Examples of the welding and cutting method include a method using a hot blade and an ultrasonic cutting using ultrasonic vibration. Here, 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.

Thus, a fiber filter medium composed of short fiber masses is obtained.
[Filtration method]
Next, a filtration method using the filtration device of the present invention will be described.
(1) Fine bubbles are introduced into raw water containing suspended solids.
In the filtration device shown in FIGS. 1 and 2, fine bubbles are introduced from the gas-liquid mixing nozzle (fine bubble generating device) 4 provided on the top of the filter medium layer 2 into the raw water just before being introduced into the filter medium layer 2. The In the filtration apparatus shown in FIGS. 3 and 4, air and treated water are mixed in the raw water introduction pipe A to generate fine bubbles and introduce them into the raw water. In the filtration apparatus shown in FIGS. 5 to 7, the treated water and air are mixed in the fine bubble introduction portion 1 b to generate fine bubbles and introduce them into the raw water. Furthermore, in the filtration apparatus shown in FIG.6 and FIG.7, the introduction amount of a fine bubble is controlled according to the turbidity of the raw | natural water measured with the turbidimeter. In the filtration apparatus shown in FIG. 6, the amount of fine bubbles introduced is controlled by adjusting the amount of air mixed according to the turbidity. In the filtration device shown in FIG. 7, the amount of fine bubbles introduced is controlled by controlling the valve of the treated water outflow pipe F and adjusting the amount of treated water returned to the raw water according to the turbidity. Moreover, in the filtration apparatus shown in FIGS. 3-7, a suspension substance floats and concentrates by introduce | transducing a fine bubble to raw | natural water, a floss is formed, and a floss is discharged | emitted from the floss discharge pipe X. FIG. At this time, it is preferable to add an inorganic flocculant to the raw water because the aggregation of suspended substances is promoted and the floss to be floated and concentrated increases.
(2) The raw water into which the fine bubbles are introduced is introduced into the upper part of the filter medium layer 2 and passed through the filter medium layer 2 in a downward flow so that the suspended substance is captured by the filter medium layer. The flow rate of raw water in the filtration step is preferably in the range of 500 to 2000 m / d. In the filtration apparatus shown in FIGS. 3-7, the water level in a filtration apparatus can be adjusted with the installation height of the bypass pipe F-1 provided in the treated water outflow pipe F. FIG. When the bypass pipe F-1 is provided at the same height as the floss discharge pipe X above the filtration layer 2, and the valve Z is closed and the treated water flows into the bypass pipe F-1, the water level in the filtration device rises. The floss that has been floated and concentrated can be discharged from the floss discharge pipe X, and the amount of suspended matter removed by the filter medium can be reduced. The treatment in such an embodiment is effective for treating raw water with high turbidity.
(3) Collect the treated water from which suspended substances have been removed in the water collecting device 3.
(4) The treated water is discharged to the outside of the filtration device through the treated water outflow pipe F.

[Cleaning method]
By performing the filtration treatment, suspended substances adhere to the inside and the surface of the filter medium, and the filtration performance deteriorates.
(5) The introduction of raw water is stopped, air is supplied to the water collecting device 3 via the air supply pipe D, the filter medium is caused to flow in water containing air, and the suspended substances are separated from the filter medium into the water. The air aeration rate and aeration time may be sufficient for the suspended substances attached to the filter medium to peel off. Usually, the aeration rate is 0.1 to 5.0 m / min and the aeration time is 3 to 30 minutes. Can be implemented. At this time, if the raw water or the cleaning water is supplied to such an extent that the cleaning water does not flow out from the cleaning water discharge pipe H, the flow space of the filter medium is widened, and the flow is good and the cleaning can be performed effectively.
(6) The supply of air from the air supply pipe D is stopped, the fine bubble generating device 4 is operated to inject the fine bubbles into the water, and the suspended solid separated from the filter medium is floated and concentrated. The amount of water containing fine bubbles (hereinafter referred to as “fine bubble water”) is preferably about 0.1 to 10 times (volume) that of the filter medium. Various water such as raw water, treated water, city water, and irrigation water can be used as the fine bubble water, but raw water and treated water are preferred. Various gases such as air, nitrogen gas, and oxygen gas can be used as the gas for generating fine bubbles, but air is preferred. In order to promote the aggregation of the suspended substance, it is preferable to add an inorganic flocculant such as polyferric chloride or PAC to the fine bubble water. The addition amount of the inorganic flocculant is not particularly limited, but is preferably in the range of several mg / L to several hundred mg / L.
(7) The cleaning water is passed through the cleaning water introduction pipe E in an upward flow, and the water containing the suspended suspended matter is discharged from the cleaning water discharge pipe H. The washing water flow rate is preferably 0.1 to 5.0 m / min, and the ventilation time is preferably 3 to 30 minutes. As washing water, sewage secondary treated water, industrial water, rainwater, raw filter water with a low content of suspended solids, and the like can be used.

  The washing is preferably performed by repeating the steps (5) to (7) a plurality of times.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to these.
[Example 1]
The raw water was filtered using a φ160 mm filtration device equipped with a filter medium layer filled with 20 L (apparent volume) of fiber filter medium (density 90 kg / m ³ ) shown in FIG. The fiber filter medium had a true specific gravity of 1.38, a length of 10 mm, and a width of 7 mm. The fiber filter material was a blend of two types of composite thermoplastic fibers, both of which were made of polyester.

The flow rate of the raw water was 20 m ³ / d, the flow rate in the filter medium layer 2 was 1000 m / d, and the treated water was continuously discharged from the treated water outflow pipe F. When SS (suspended substance) in raw water was trapped by the fiber filter medium, the filtration performance deteriorated, so a backwash process was performed every 12 o'clock. In the backwashing method, after the suspended substances adhering to the fiber filter medium are peeled off by aeration, the fine bubble liquid is supplied to the upper part of the filtration layer 2 from the gas-liquid mixing nozzle using a fine bubble generator (made by Aura Tech). The separated suspended material was floated and concentrated. Thereafter, water was passed in an upward flow, and the suspended suspended matter was discharged from the filtration device. The above operation was repeated 5 times. In addition, the amount of water used was 0.5 m / time for fine bubble liquid (fine bubble liquid amount, m ³ / filtration device cross-sectional area, m ² ), and 0.5 m / time for discharged water (discharged water amount, m ³ / cross-sectional area of the filtration device, m ² ), the water recovery rate was 99%.

The filtration performance after about one month 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. The processing performance was excellent without any degradation.
[Example 2]
The raw water was filtered using a φ160 mm filtration device having a filter medium layer filled with 20 L (apparent volume) of φ0.6 mm anthracite shown in FIG.

The flow rate of the raw water was 7 m ³ / d, the flow rate in the filter medium layer was 350 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 filter medium, the filtration performance deteriorated, so a backwash process was performed every 12 o'clock. In the backwashing method, after the suspended substances adhering to the filter medium were peeled off by aeration, a fine bubble liquid was supplied from a fine bubble generator (Auratech Co., Ltd.), and the separated suspended substances were floated and concentrated. Thereafter, water was passed in an upward flow, and suspended suspended substances were discharged. The above operation was repeated 5 times. In addition, since the amount of water used was 0.5 m / times for the fine bubble liquid and 0.5 m / times for the amount discharged by passing water, the water recovery rate was 97.1%.

The filtration performance after about 1 month was 2 mg / L for the treated water SS with respect to the SS concentration of the raw water 10 mg / L. The processing performance was excellent without any degradation.
[Example 3]
The raw water was filtered using a φ160 mm filtration device equipped with a filter medium layer filled with 20 L (apparent volume) of fiber filter medium (density 90 kg / m ³ ) shown in FIG. Example 1 was the same as Example 1 except that 50% of the raw water was passed through a gas-liquid mixing nozzle.

The fiber filter medium has a true specific gravity of 1.38, a length of 10 mm, and a width of 7 mm.
The flow rate of raw water was 20 m ³ / d (of which 10 m ³ / d was supplied through a gas-liquid mixing nozzle), the flow rate in the filter medium 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 o'clock. In the backwashing method, firstly, the floss is discharged by passing water, and then the suspended matter adhering to the fiber filter medium is peeled off by aeration, and then the fine bubble liquid is supplied from the fine bubble generator (Auratech), The separated suspended material was floated and concentrated. Thereafter, water was passed in an upward flow, and suspended suspended substances were discharged. The above operation was repeated 4 times (floss was discharged only once). In addition, since the amount of water used was 0.5 m / times for the fine bubble liquid and 0.5 m / times for the amount discharged through water, the water recovery rate was 99.2%.

The filtration performance after about one month 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. The processing performance was excellent without any degradation.
[Comparative Example 1]
The raw water was filtered using a φ160 mm filtration device having a filter medium layer filled with 20 L (apparent volume) of fiber filter medium (density 90 kg / m ³ ) shown in FIG. Example 1 is the same as Example 1 except that there is no gas-liquid mixing nozzle that generates fine bubbles.

The flow rate of the raw water was 20 m ³ / d, the flow rate in the filter medium 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 o'clock. 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 suspended substances were peeled off from the fiber filter medium. The separated suspended substance was discharged from the discharge pipe G, and then refilled with water. The above operation was repeated 5 times. Since the amount of water filling per time was 3 m / time, the water recovery rate was 97%.

The filtration performance after about 1 month was 5 mg / L for the SS of the treated water with respect to the SS concentration of 10 mg / L for the raw water.
[Comparative Example 2]
The raw water was filtered using a φ160 mm filtration device having a filter medium layer filled with 20 L (apparent volume) of φ0.6 mm anthracite shown in FIG. Example 2 is the same as Example 2 except that there is no gas-liquid mixing nozzle that generates fine bubbles.

The flow rate of the raw water was 7 m ³ / d, the flow rate in the filter medium layer was 350 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 o'clock. 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 suspended substances were peeled off from the fiber filter medium. The separated suspended substance was discharged from the discharge pipe G, and then refilled with water. The above operation was repeated 5 times. Since the amount of water filling per time was 3 m / time, the water recovery rate was 91.4%.

The filtration performance after about one month was 3 mg / L for the SS of the treated water with respect to the SS concentration of the raw water of 10 mg / L.
[Example 4]
Using a filtration apparatus (cross-sectional area 0.3 m × 0.6 m) having a filter medium layer that is filled with 20 L (apparent volume) of granulated activated carbon (“Evadia” manufactured by Mizuing Co., Ltd.) shown in FIG. The seawater was filtered. 3 mg / L of ferric chloride was added to seawater to make raw water.

The flow rate of the raw water was 7 m ³ / d, and the flow rate in the filter medium layer was 350 m / d. When the turbidity of the raw water is measured with a turbidimeter and the turbidity exceeds 30 NTU, fine bubbles are generated from the gas-liquid mixing nozzle, the valve Z is closed, and the treated water is bypassed by the bypass pipe F-1 of the treated water outflow pipe F. Passed through. When the turbidity was 30 NTU or less, the supply of fine bubbles was stopped, the valve Z was opened, and the treated water was passed through the treated water outflow pipe F.

The turbidity of the raw water varied in the range of 5 to 50 NTU, but the treated water turbidity was always 5 NTU or less, and stable filtration could be performed. The water recovery rate was 97%.
[Comparative Example 4]
Seawater was always filtered as in Example 4 except that fine bubbles were not supplied.

  The turbidity of the raw water varied in the range of 5-50 NTU, and the turbidity of the treated water varied in the range of 1-20 NTU. Compared to Example 4, stable treated water quality could not be obtained. The water recovery rate was 92%.

  The above results are summarized in Table 1.

According to the apparatus and method of the present invention, both suspended solids removal and water recovery rate are improved. Especially when compared with the conventional method, the water recovery rate, which was a problem of the conventional method, is 97% in the case of fiber filter media. 2% or more improvement to 99% or more, about 6% improvement from 91.4% to 97.1% in the case of anthracite, 5% improvement from 92% to 97% in the case of granulated activated carbon . Furthermore, in Example 4 in which the introduction of fine bubbles according to turbidity and the addition of an inorganic flocculant were added, a stable suspended substance removal effect was confirmed.

  The filtration device and the filtration method of the present invention are suitable as a raw material suspended matter removal treatment and a pretreatment such as a desalting treatment. The cleaning method of the present invention achieves a long filter life and contributes to cost reduction of the filtration treatment.

1: filtration device, 2: filter medium layer, 3: water collection device, 4: fine bubble generator (gas-liquid mixing nozzle), A: raw water introduction tube, B: liquid introduction tube, C: gas introduction tube, D: air Supply pipe, E: Wash water introduction pipe, F: Treated water outflow pipe, F-1: Bypass pipe, G: Discharge pipe, H: Wash water discharge pipe, X: Floss discharge pipe, Z: Valve

Claims (15)

A filtration device for removing suspended matter from raw water containing suspended matter,
A filter medium layer filled with a filter medium that traps suspended substances;
Raw water introduction pipe A for supplying raw water to the upper part of the filter medium layer,
A fine bubble generator for introducing fine bubbles into raw water;
A water collecting device for collecting treated water, provided below the filter medium layer;
An air supply pipe D for supplying air to the water collecting device;
A treated water outflow pipe F that discharges treated water from the water collecting device, which is raised from the water collecting device to a position above the filter medium layer,
A washing water introduction pipe E for passing washing water upward through the filter medium layer;
A wash water discharge pipe H for discharging wash water from above the filter medium layer;
A filtration apparatus comprising:   Furthermore, the filtration apparatus of Claim 1 which comprises the floss discharge pipe X above the said filter medium layer.   The filtration device according to claim 1 or 2, wherein the fine bubble generating device is a gas-liquid mixing nozzle provided on an upper portion of the filter medium layer.   The filtration device is partitioned into a filtration portion including the filter medium layer and the water collecting device, and a fine bubble introduction portion that is positioned upstream of the filtration portion and includes the fine bubble generation device. The filtration apparatus according to 1 or 2.   Furthermore, a turbidimeter that measures the turbidity of raw water provided on the upstream side of the filter medium layer, a control mechanism that controls the fine bubble generator according to the turbidity measured by the turbidimeter, The filtration device according to claim 1, comprising:   Furthermore, the treated water return pipe connected from the treated water outflow pipe F to the raw water introduction pipe A and the treated water outflow pipe F are provided in the treated water outflow pipe F, and treated water is measured according to the turbidity measured by the turbidimeter. The filtration device according to claim 5, further comprising a valve for switching the flow path.   The said filter medium is a filtration apparatus in any one of Claims 1-6 which is a fiber filter medium which consists of a short fiber lump.   The filtration apparatus according to any one of claims 1 to 7, wherein the filter medium is a biofilm filter medium that supports aerobic microorganisms. A filtration method for removing suspended substances from raw water using the filtration device according to claim 1,
(1) a step of introducing fine bubbles into raw water containing suspended solids,
(2) introducing the raw water into which fine bubbles have been introduced into the upper part of the filter medium layer, allowing the filter medium layer to pass through the filter medium layer in a downward flow, and trapping suspended substances in the filter medium layer;
(3) collecting the treated water from which suspended substances have been removed into a water collecting device;
(4) A filtration method including a step of discharging treated water to the outside of the filtration device through the treated water outflow pipe.   The filtration method according to claim 9, wherein the introduction of the fine bubbles in the step (1) is controlled according to the turbidity of the raw water.   The filtration method according to claim 9 or 10, wherein in step (1), treated water is introduced into the raw water according to the turbidity of the raw water.   The filtration method according to any one of claims 9 to 11, wherein in the step (1), the suspended solid is floated and concentrated by fine bubbles, and the suspended and suspended suspension is discharged from the upper part of the filtration device. A method for cleaning a filtration device according to any one of claims 1 to 8,
(5) Stopping the introduction of raw water, supplying air to the water collecting device via the air supply pipe D, causing the filter medium to flow in the water containing air, and separating the suspended matter from the filter medium into the water;
(6) Stopping the supply of air from the air supply pipe D, operating the microbubble generator to inject microbubbles into the water, and levitating and concentrating the suspended matter separated from the filter medium; and (7) A cleaning method including a step of allowing cleaning water to flow through the cleaning water introduction pipe E in an upward flow and discharging water containing suspended suspended substances from the cleaning water discharge pipe H.   The washing | cleaning method of Claim 13 which discharges the suspended solid which floated and concentrated in the process (6) from the upper part of a filtration apparatus.   The washing | cleaning method of Claim 13 or 14 which adds an inorganic flocculant to the water which inject | pours a microbubble in a process (6).