The present invention relates to a filter apparatus for filtering solids suspended in water capable of controlling filtration efficiency, filtration rate, and the amount of filtered water by using different kinds of flexible, elastic filter media to adjust the porosity and pore size of the filter layer according to the kind and density of the filter media and the hydraulic pressure of supplied source water.

Background Art The general operation of a filter apparatus includes filtration and backwashing processes. A filtration process includes a plurality of physical and chemical unit operations, including diffusion, straining, interception, impaction, sedimentation, flocculation, and adsorption of suspended matter in water, such as particulates, algae, etc., which form a cooperative, complex mechanism to remove the suspended matter and draw off clarified water.

As the filtration process continues, suspended particulates in the water are deposited on the filter layer filled with a filter medium, thereby reducing the pore size of the filter layer and increasing the headloss due to increased filtration resistance. Accordingly, backwashing of the filter

medium is necessary. The filtering capability of a filter apparatus is evaluated by the suspended matter removal efficiency, filtration rate, filtration duration, the frequency of backwashing, the amount of backwash water used, backwash duration, etc.

Mostly, granular filter media such as sand, anthracite, activated carbon, clay, ground magnetite, garnet, deactivated media, etc., are used for a filtration process. These filter media can be purchased easily and can be easily applied to a filter apparatus, but needs a big filter apparatus for its installation. Disadvantageously, a space for entrapping suspended particulates is limited to only near the surface of the filter layer, and the filter media have a fixed pore structure. As a result, a reduction in pore size of the filter layer or clogging of the pores occurs due to the suspended particulates, and the headloss is increased due to the filtration resistance. Accordingly, flow channeling or break-through of the filter layer occurs, thereby increasing the frequency of backwashing the layer of the filter medium and the amount of backwash water. The compaction of the filter layer increases filtration pressure, slows down the filtration rate, and causes the filter medium to flow out during backwashing.

To solve the problems occurring with using the filter media during filtration, an improved rotary-backwashing type high-purity filter apparatus is disclosed in Korean Patent Application No. 1997-023068 where one end of filter cloth of latitude direction threads radially attached to the side of a rotary porous drum is extended a rotary spring fixed to the wall of a pressured container to form a filter layer by the rotation of the rotary porous drum and the tension of the spring. Here, backwashing is achieved by repetitive forward and backward rotations of the porous drum. However, in the filter apparatus, fibers of the filter cloth are seriously damaged due to friction, and it is hard to form a uniform filter layer. Also, since a space for entrapping particulates is

small, filtration duration becomes short, and more frequent backwashing is needed. Also, the filter apparatus cannot handle fluctuating composition of source water and is hard to control the quality of the resultant clarified water.

A permanent filter apparatus with a variable filter layer is disclosed in Korean Patent Application NO. 1998-0405542 in which tension of filter cloth of latitude direction threads is formed by the pressure of the source water when filtering the source water and loosened by the pressure of the air and water supplied for backwashing.

However, this repetitive pressing and relaxing of the filter cloth with a piston cause fibers of the filer medium to be seriously tangled or damaged. Also, since the filter layer is formed as a monolayer for filtration, a space for entrapping particulates is too small to entrap enough particulates. Other disadvantages of the filter apparatus are; short filtration duration, frequent backwashing, low filtration rate, the inability to handle fluctuating composition of source water, and the requirement for a relatively large amount of backwash water.

To solve the problems, the present inventor has filled a patent application for an apparatus and method for filtering suspended solids from fluid using flexible fibers (Korean Patent Application No.

1999-013396). According to this disclosure, the depth of a filter layer and a space for entrapping particulates are freely adjustable according to the length of the fibers used for a filter medium, and the porosity, pore size, the amount of particulates to be filtered out, and the quality of clarified water can be easily controlled by the density of the flexible fibers in the filter medium. Therefore, the filter apparatus can effectively cope with fluctuating composition of source water, but it is hard to automate filling the filter medium with the flexible and elastic fibers.

Disclosure of the Invention It is an object of the present invention to provide a compact, easy-to-manufacture filter apparatus that has a large space for entrapping particulates, enhanced fiber durability in a filter medium and is capable of continuously concentrating and discharging suspended matter of source water during filtration. The filter apparatus has extended filtration duration and the reduced frequency of backwashing and can handle fluctuating composition of source water, thereby producing clarified water which can be used as regular drinking water.

It is another object of the present invention to provide an effective, economical filter apparatus capable of removing suspended matter in water, such as particulates, algae, etc.

It is another object of the present invention to provide a filter apparatus capable of adjusting the porosity and pore size of a filter medium (layer) according to the kind and quantity of flexible fibers used to form the filter layer, the hydraulic pressure of upstream source water, and the structure of containment plates, so that the quality of clarified water can be controlled according to its use. The filter medium is inserted into the filter apparatus in the direction of its length with one end fixed to a filter medium fixing flange having backwash air diffuse holes or to a filter medium fixing flange having backwash water diffuse holes.

It is another object of the present invention to provide a filter apparatus capable of filtering and backwashing without applying a mechanical force to a filter medium thereby to enhance durability of the filter medium.

It is another object of the present invention to provide a filter apparatus where for backwashing, backwash water is vertically supplied into the filter apparatus via a backwash supply pipeline, and backwash air is horizontally supplied through backwash air diffuse holes of a filter medium fixing flange from a backwash air supply pipeline and is

vertically supplied through a porous backwash air plate and a backwash air supply pipeline disposed below the filter apparatus.

It is another object of the present invention to provide a filter apparatus where for backwashing, backwash water is horizontally supplied through backwash water diffuse holes of a filter medium fixing flange from a backwash water supply pipeline, and backwash air is vertically supplied a backwash air supply pipeline disposed below the filter apparatus.

It is another object of the present invention to provide a filter apparatus where backwash water and backwash air are supplied perpendicular to one another to induce turbulence within the filter medium, which swells vertically and becomes flat due to the turbulence, and thus suspended particulates entrapped by the filter medium can be easily separated form the filter medium within a short period of time.

According to an aspect of the present invention, there is provided a filter apparatus for filtering a various kinds of suspended matter in source water, the filter apparatus comprising : a filter medium formed of flexible fibers of thread type which is installed in a cylindrical member and entraps the suspended matter contained in the source water supplied into the cylindrical member; a filter medium fixing flange to which one end of the filter medium is fixed and which has a plurality of diffuse holes for a backwash material for backwashing the filter medium; containment plates appropriately installed in the cylindrical member to prevent the efflux of the suspended matter entrapped by the filter medium, based on the hydraulic pressure of the source water to be filtered through the filter medium, the density of the filter medium, and the state of the suspended matter entrapped by the filter medium; a source water supply unit and a backwash material supply unit which supply the source water and the backwash material, respectively, to the filter medium; a clarified water discharge unit which discharges clarified

water filtered through the filter medium; a continuous concentrated filtrate discharge unit which discharges the suspended matter entrapped by the filter medium; and a backwash water discharge unit which discharges backwash water.

It is preferable that the backwash water supply unit comprises a backwash air supply unit and a backwash water supply unit, and the backwash air supply unit comprises a horizontal backwash air supply unit for horizontally supplying backwash air into the filter medium and a vertical backwash air supply unit for vertically supplying backwash air into the filter medium.

It is preferable that the other end of the filter medium remains unfixed such that the filter medium swells vertically when turbulence occurs in the filter medium due to the backwash and backwash air supplied perpendicular to one another into the filter medium, to thereby easily separate the suspended matter entrapped by the filter medium.

.'It is preferably that the backwash air supply unit, the backwash water supply unit, the source water supply unit, the clarified water discharge unit, the backwash water discharge unit, and the continuous concentrate filtrate discharge unit are provided with respective supply and discharge valves. During filtration, while a backwash air supply valve, a backwash water supply valve, and a backwash water discharge valve are closed, and a source water supply valve, a continuous concentrate filtrate discharge valve, and a clarified water discharge valve are opened, the source water is supplied into the filter medium by operating a source water supply water to produce the clarified water via the clarified water discharge unit and simultaneously continuously discharge the concentrated suspended matter entrapped by the filter medium via the continuous concentrated filtrate discharge unit.

Backwashing is performed on the filter medium while the source water supply valve and the clarified water discharge valve are closed, and the

backwash air supply valve, the backwash water supply valve, and the backwash water discharge valve are opened.

Preferably, the filter apparatus according to the present invention further comprises a porous backwash air pipeline member installed parallel to the filter member with a smaller length then the filter member, the porous backwash air pipelined member having a plurality of air pores for diffusing backwash air in a direction perpendicular to the filter medium.

In the filter apparatus according to the present invention when the backwash water is horizontally diffused into the filter medium through the plurality of diffuse holes, simultaneously backwash air may be vertically supplied into the filter medium, and when the backwash air is horizontally diffused into the filter medium through the plurality of diffuse holes, simultaneously the backwash water and backwash air through another backwash air supply unit may be vertically supplied into the filter medium.

Brief Description of the Drawings FIG. 1 shows the structure of a vertical backwash, continuous discharge type high-purity filter unit for filtering suspended matter in water according to the present invention; FIG. 2A is a plan view of an embodiment of a filter medium fixing flange having backwash air diffuse holes according to the present invention ; FIG. 2B is a plan view of another embodiment of a filter medium fixing flange having backwash water diffuse holes according to the present invention; FIG. 2C is a longitudinal sectional view of a porous backwash air pipeline according to the present invention; FIG. 3 shows different arrangements of containment plates for

preventing the efflux of entrapped particulates according to the prevent invention, and in particular, FIGS. 3A, 3B, and 3C are sectional views of horizontal, inversed triangular, and triangular arrangements, respectively, of the containment plates in the filter unit of FIG. 1, and FIGS. 3D, 3E, and 3F are sectional views of linear, inversed triangular, and triangular arrangements, respectively, of the containment plates in a filter unit 100' of FIG. 4; FIG. 4 shows the structure of a horizontal backwash, continuous discharge type high-purity filter unit according to another embodiment of the present invention; FIG. 5 shows the entire structure of a filter apparatus according to the present invention including the vertical backwashing, continuous discharge type high-purity filter unit of FIG. 1; and FIG. 6 shows the entire structure of another filter apparatus according to the present invention including the horizontal backwashing, continuous discharge type high-purity filter unit of FIG. 4.

* Explanation of Reference Numerals Designating the Major Elements of the Drawings * 1 ; backwash air supply pipeline 1 a ; backwash air supply valve 1 b ; filter medium fixing flange 1 d ; porous backwash air pipeline 2,17 ; source water supply pipeline 2a, 17a; source water supply valve 3,16 ; backwash water supply pipeline 3a, 16a ; backwash water supply valve 4; backwash discharge pipeline 4a; backwash water discharge valve 5 ; continuous concentrated filtrate discharge pipeline

5a; continuous concentrated filtrate discharge valve . 6 ; clarified water discharge pipeline 6a ; clarified water discharge valve 7; backwash air supply pipeline 7a; backwash air supply valve 8; filter layer 9; pressure meter 10; flow meter 11; containment plates arranged in a linear pattern 12; containment plates arranged in an inverse triangular pattern 13; containment plates arranged in a triangular pattern 14; porous plate for water diffusion and filter medium support and pressing 15; flange 18 ; flange binding joint 19; filter medium fixing hole 20; backwash air diffuse hole 21 ; backwash water diffuse hole 22 ; air pores of the porous backwash air pipeline 23 ; source water and backwash water supply pump 24; backwash air supply pump 50; cylindrical member 100, 100' ; filter unit Best mode for carrying out the Invention Preferred embodiments of an apparatus for filtrating suspended matter (solids) in water according to the present invention will be described in greater detail with reference to the appended drawings.

Description of the prior art or an unnecessary structure of the present invention that makes the subject matter of the present invention obscure

will be omitted. The terms used in the following description are defined on a function basis, and thus it will be appreciated by those skilled in the art that the terms may be changed appropriately based on users'or operators'intentions and practices without departing from the meaning intended in the following description.

FIG. 1 shows the structure of a vertical backwash, continuous discharge type high-purity filter unit 100 for filtering suspended solids (liquid) in water, in which backwash water is vertically supplied, according to an embodiment of the present invention. FIG. 4 shows the structure of a horizontal backwash, continuous concentrated filtrate (suspended solid concentrate) discharge type high-purity filter unit 100', in which backwash water is horizontally flowed, according to another embodiment of the present invention. FIG. 2A is a plan view of an embodiment of a filter medium fixing flange having backwash air diffuse hotes according to the present invention, FIG. 2B is a plan view of another embodiment of a filter medium fixing flange having backwash water diffuse holes, and FIG. 2C is a longitudinal sectional view of a porous backwash air pipeline according to the present invention : FIG.

3 shows different installations of containment plates for preventing the efflux of entrapped particulates according to the prevent invention, and in particular, FIGS. 3A, 3B, and 3C are sectional views of horizontal, inversed triangular, and triangular arrangements, respectively, of the containment plates in the filter unit 100 of FIG. 1, and FIGS. 3D, 3E, and 3F are sectional views of linear, inversed triangular, and triangular arrangements, respectively, of the containment plates in the filter unit 100'of FIG. 4. FIG. 5 shows the entire structure of a filter apparatus according to the present invention including the vertical backwashing, continuous discharge type high-purity filter unit 100 of FIG. 1, and FIG. 6 shows the entire structure of another filter apparatus according to the present invention including the horizontal backwashing, continuous

discharge type high-purity filter unit 100'of FIG. 4.

Referring to FIG. 1, the embodiment of the vertical backwashing, continuous concentrated filtrate discharge type high-purity filter unit 100 utilizes flexible and elastic fibers having an appropriated surface roughness and thickness as a filter medium. Suitable filter media include nylon fibers, activated carbon fiber, and fibers foamed with polypropylene (PP) or polyethylene (PE), One end of the filter medium forming the filter layer 8 is fixed to filter medium fixing holes 19 of a filter medium fixing flange 1b having backwash air diffuse holes 20 (see FIG. 2A), and the other end is horizontally installed in a cylindrical member 50 and remains free and flexible. A backwash air supply pipeline 1 is disposed on the left of the filter unit 100, a source water supply pipeline 2 and a backwash water discharge pipeline 3 are disposed at the bottom left of the filter unit 100, and a backwash air supply pipeline 7 is disposed below the filter unit 100. A backwash water discharge pipeline 4 is disposed on the right of the filter unit 100, and a continuous concentrated filtrate discharge pipeline 5 for continuously discharging concentrated filtrate of a relatively large particle size entrapped at the surface of the filter layer 88 during filtration is disposed at the bottom right of the filter unit 100. A clarified water discharge pipeline 6 is disposed above the filter unit 100.

An automatic valve is attached to each of the supply and discharge pipelines. To the left and right ends of the filter apparatus 100 flanges 15 capable of being opened and closed for filter medium exchange are coupled. The left flange 15 includes the filter medium fixing flange 1b having the backwash air diffuse holes 20, as shown in FIG. 2A, which guide backwash air in a horizontal direction, and can be coupled to a porous backwash air pipeline 1d, as shown in FIG. 2C, which guides backwash air in a vertical direction.

The containment plates 11,12, or 13 are mounted, as shown in

FIGS. 3A, 3B, and 3C, respectively, in the cylindrical member 50, separate from each other on the inner left and right wall of the cylindrical member 50, to prevent the efflux of entrapped particulates during filtration, through the boundary between the filter unit 100 and the filter medium installed therein. A porous plate 14 for water diffusion and filter medium support and pressing is placed between the containment plates 11,12, or 13 to press the filter medium according to the hydraulic pressure of the source water supplied through the source water supply pipeline 2 to appropriately maintain the pore size and porosity of the filter medium, to appropriately diffuse the supplied source wafer along the length of the filter unit 100, and to discharge the concentrated filtrate entrapped at the bottom of the filter layer 8. The porous plate 14 facilitates the discharge of the concentrated filtrate entrapped at the bottom of the filter layer 8 during filtration, through the continuous concentrated filtrate discharge pipeline 5.

.'FIG. 4 shows a horizontal backwash, continuous concentrated filtrate discharge type high-purity filter unit 100'according to another embodiment of the present invention, where during backwashing, backwash water is horizontally supplied through the backwash water supply pipeline 16 placed on the left of the filter unit 100', and backwash air is vertically supplied through the backwash air supply pipeline 7 placed below the filter unit 100'. The filter unit 100'is identical to the filter unit 100 of FIG. 1, except that in the filter unit 100'backwash water is horizontally supplied through the backwash water diffuse holes 21 of FIG. 2B from the backwash supply pipeline 16, backwash air is vertically supplied into the filter unit 100'through the backwash air supply pipeline 7 mounted below the filter unit 100', and the porous backwash air pipeline 1d of FIG. 2C is not installed in the filter unit 100'. The structure of the filter unit 100'is effective in separating the entrapped particulates from the filter layer 8 when the suspended solids are organic

substances. The containment plates 11,12, or 13 are mounted in the cylindrical member 50, separate from each other on the inner left and right wall of the cylindrical member 50, as shown in FIGS. 3A, 3B, and 3C, to prevent the efflux of entrapped particulates during filtration, through the boundary between the filter unit 100'and the filter medium installed therein.

The operations of the filter units 100 and 100'according to the present invention having the above structures will be described with reference to FIGS. 1 through 6.

The operation of a filter apparatus for filtering suspended matter in water, such as particulates, algae, etc., is divided into filtration and backwashing processes.

The vertical backwash, continuous concentrated filtrate discharge type high-purity filter unit 100 performs filtration as follows. Referring to FIGS. 1 and 5, a backwash water supply valve 3a, a backwash air supply valve 1a, a backwash water discharge valve 4a, and a backwash air supply valve 7a below the filter unit 100 are closed whereas a source water supply valve 2a, a clarified water discharge valve 6a, and a continuous concentrated filtrate discharge valve 5a are opened for filtration. In this state, as the source water is supplied into the filter unit 100 through the source water supply pipeline 2 by operating a source water supply pump 23, suspended matter in the source water is filtered through the filter layer 8, and the clarified water is discharged through the clarified water discharge pipeline 6.

When filtration is performed by the horizontal backwash, continuous concentrated filtrate discharge type high-purity filter unit 100' according to another embodiment of the present invention, which is capable of enhancing the effect of backwashing viscous suspended solids by horizontally supplying backwash water, referring to FIGS. 4 and 6, a backwash water supply valve 16a, a backwash air supply valve

7a below the filter unit 100', and a backwash water discharge valve 4a are closed whereas a source water supply valve 17a, a clarified water discharge valve 6a, and a continuous concentrated filtrate discharge valve 5a are closed. In this state, as the source water is supplied through the source water supply pipeline 17 by operating the source supply pump 23, the suspended solids are filtered through the filter layer 8, and the clarified water is discharged through the clarified water discharge pipeline 6. The horizontal backwash filter unit 100'of FIG. 4 is identical to the vertical backwash filter unit 100, except for the way to supply backwash water and backwash air.

In the filter units 100 and 100'of FIGS. 1 and 4, suspended matter in source water having a larger particle size than the pore size of the filter layer 8 are entrapped by the filter layer 8 during an upstream filtration process. Among the entrapped solids, solids having a reratively large particle size, which have great transmission resistance to the filter layer 8, are accumulated on the lower portion of the filter layer 8, concentrated, and discharged from the filter units 100 and 100'through the continuous concentrated filtrate discharge pipeline 5 during filtration.

Due to the continuous concentration and discharge of the suspended solids entrapped by the filter layer 8 during filtration, filtration resistance resulting from the suspended matter entrapped by the filter layer 8 is reduced, and a partial clogging of the filter layer 8 and break-through of the filter layer 8 due to the entrapped matter can be prevented. The filter units 100 and 100'according to the present invention are a varying pore size filter apparatus where the porosity and pore size of the filter layer 8 are adjusted according to the kind, thickness, and density of the filter medium, the structure of the containment plates 11,12, or 13, and the hydraulic pressure of source water. Accordingly, the volume and quality of clarified water can be easily controlled according to the use of the clarified water. According to the present invention, the entire filter

layer 8 is used as a space for entrapping particulates as if it has multiple filter layers so that the capability of the filter layer 8 to entrap particulates is enhanced through filtration for an extended duration. Accordingly, the frequency of backwashing is reduced.

As the filtration is continued, the amount of suspended matter entrapped by the filter medium increases, filtration resistance increases, and filtration rate decreases. As a result, a small volume of clarified water is obtained. When the volume of clarified water sensed by a flow meter 10 attached to the clarified water discharge pipeline 6 is lower than a target volume or when the pressure of filtration sensed by a pressure meter 9 attached to the source water supply pipelines 2 and 7 is greater than a predetermined level, a backwashing process is initiated.

In the backwashing process by the vertical backwash filter unit 100 of FIG. 1, the operation of the source water supply pump 23 is stopped, the source water supply valve 2a and the clarified water discharge valve 6a are closed, and the backwash air supply valve 1a on the left of the filter unit 100, the backwash water supply valve 3a, and the backwash water discharge valve 4a are opened. In this state, a backwash air supply pump 24 and the backwash water supply pump 23 are operated for a predetermined period of time for backwashing.

According to the backwashing mechanism of the vertical backwash filter unit 100 of FIG. 1, to smoothly remove the suspended matter entrapped by the filter medium during the backwashing, the filter medium is strongly shaken over the predetermined period of time for backwashing. The filter medium is shaken as a result of the vertical swelling of the filter medium. The strength of the vertical swelling is the vector sum of the pressure of air horizontally supplied into the filter unit 100 through the backwash air diffuse holes 20 (FIG. 2A), the pressure of

air vertically supplied into the filter unit 100 through the porous backwash air plate 1d (FIG. 2C) and the backwash air supply pipeline 7 below the filter unit 100, and the hydraulic pressure of backwash water vertically supplied into the filter unit 100 through the backwash water supply pipeline 3. As a result, the entrapped particulates are easily separated from the filter medium within a short period of time by the resultant vector force, and simultaneously the backwash water used is concentrated and discharged through the backwash water discharge pipeline 4. After the suspended solids entrapped by the filter layer have been sufficiently removed, filtration is continued.

In the backwashing process by the horizontal backwash filter unit 100'of FIG. 4, the operation of the source water supply pump 23 is stopped, the source water supply valve 17a and the clarified water discharge valve 6a are closed, and the backwash air supply valve 7a below the filter unit 100', the backwash water discharge valve 4a, and a backwash water supply valve 16a are opened. In this state, the backwash water supply pump 23 and the backwash air supply pump 24 are operated for a predetermined period of time for backwashing. The backwashing process by the horizontal backwash filter unit 100'of FIG.

4 is identical to that by the vertical backwash filter unit 100 of FIG. 1 except for the way to supply backwash water and backwash air.

According to the backwashing mechanism of the horizontal backwash filter unit 100'of FIG. 4, the filter medium is strongly shaken due to its own vertical swelling by the vector sum of the hydraulic pressure of backwash water horizontally supplied into the filter unit 100' through the backwash water diffuse holes 21 (FIG. 2B) from the backwash supply pipeline 15 and the pressure of air horizontally supplied through the backwash air supply pipeline 7 below the filter unit 100'. As a result, the entrapped particulates are easily separated from

the filter layer 8 within a short period of time by the resultant vector force and continuously discharged through the backwash discharge pipeline 4.

After the backwashing for a predetermined period of time, filtration is continued.

The operational principles of the filter units 100 shown in FIGS. 1 and 4 and the filter unit 100'shown in FIGS. 5 and 6 will be described.

The opening and closing of valves and the operation of the source water supply pump 23 for filtration are controlled by a timing control program.

The opening and closing of valves and the operations of the backwash air supply pump 24 and the backwash water supply pump 23 are controlled by a sensor attached to the flow meter 10 or the pressure meter 9.

The filter units 100 and 100'according to the present invention have the following features. The entire filter layer 8 is used as the space for entrapping particulates with the expectation of a multi-layer filtering effect. The porosity and pore size of the filter medium are controlled according to the density of the filter medium and the hydraulic pressure of source water and determine the quantity and quality of clarified water. The size of entrapped particulates to be filtered out is determined by the arrangement of the containment plates 11,12, or 13.

In particular, assuming that the density of the filter medium and the hydraulic pressure of source water are constant, when the containment plates 11 are arranged horizontally in a line, as shown in FIGS. 3A and 3D, the area of the filter layer 8 on which compression force by the hydraulic pressure of the source water acts is narrow, and a degree of consolidation of the filter layer 8 is increased, thereby minimizing the pore size and porosity of the filter layer 8. As a result, filtration rate and the volume of clarified water are reduced, but high-purity clarified water can be obtained.

When the containment plates 12 are arranged in an inverse

triangular pattern, as shown in FIG. 3B, the area of the filter layer 8 which compression force by the hydraulic pressure of the source water acts on is enlarged, thereby increasing the porosity and pore size of the filter layer 8. As a result, filtration rate and the volume of clarified water are increased, but the quality of the clarified water is poor than the case of the containment plates 11 shown in FIGS. 3A and 3D.

When the containment plates 13 are arranged in a triangular pattern, as shown in FIGS. 3C and 3F, the area of the filter layer 8 on which compression force by the hydraulic pressure of the source water acts, filtration rate, and the volume of clarified water are intermediate levels between those for the containment plates 11 and the containment plates 12. In this arrangement of the containment plates 13, the filter layer 8 are formed to a relatively great depth so that the filtration rate and the volume of clarified water are higher than the containment plates 11 of FIGS. 3A and 3D and are lower than the containment plates 12 of FIGS.'3B and 3E. The quality of the clarified water is better than from a filter unit with the containment plates 12, but slightly poor than from a filter unit with the containment plates 11.

In a filter apparatus according to the present invention, the filter medium fixing flange 1 b has radially distributed filter medium fixing holes 19 and backwash air diffuse holes 20, as shown in FIG. 2A, and the filter medium fixing flange 1 b has radially distributed filter medium fixing holes 19 and backwash water diffuse holes 21, as shown in FIG. 2B. Here, the sizes and numbers of filter medium fixing holes 19, backwash air diffuse holes 20, and backwash water diffuse holes 21 may be varied according to a target filtration rate, a target volume and quality of clarified water, filtration duration, the frequency of backwashing, and efficiency of backwashing.

To extend filtration duration with reduced frequency of backwashing to entrap more particulates, the length and sectional area

of the filter unit 100 or 100'may be increased, and the kind of fibers used for the filter medium, the density of the filter medium, and the structure of the containment plates 11,12, or 13 may be varied.

Comparing the vertical backwash filter unit 100 of FIG. 1 and the horizontal backwash filter unit 100'of FIG. 4 according to the embodiments of the present invention, the filtration mechanism is identical, but the backwashing mechanism is different between the two filter units 100 and 100'. Another difference between the two filter units 100 and 100'is that the porous backwash air plate 1d of FIG. 2C is installed only in the filter unit 100 of FIG. 1.

The filter apparatus of FIG. 5 including the vertical backwash filter unit 100 of FIG. 1, and the filter apparatus of FIG. 6 including the horizontal backwash filter unit 100'of FIG. 4 may be automatically or manually operated.

[Example 1] Biological wastewater of an average suspended matter concentration of 40 mg/L, 60 mg/L, 80 mg/L, and 100 mg/L were filtered for 6 months through the vertical backwash, continuous concentrated filtrate discharge type high-purity filter unit 100 of FIG. 1 having a diameter of 200 mm, a length of 1,500 mm and in which the containment plates 11 are arranged as shown in FIG. 3A. Here, a filter medium of the filter unit 100 was filled with flexible fibers to a density of about 0.7 g/cm3.

The duration of filtration refers to the duration from the start of filtration before the start of backwashing. Backwashing was initiated when an initial volume of clarified water reached 70% of a target volume, and continued for 3 minutes using 1% backwash water based on the target volume of clarified water.

The clarified water discharged from the filter unit was collected

and analyzed. As a result, a linear velocity of filtration was 10 m3/h on average regardless of the concentrations of suspended matter in the source water, and average filtration duration was 12.5 hours for the source water containing 40 mg/L suspended matter, 8.3 hours for the source water containing 60 mg/L suspended matter, 6.3 hours for the source water containing 80 mg/L suspended matter, and 5 hours for the source water containing 100 mg/L suspended matter. The resultant clarified water was proved to be highly pure with a concentration of suspended solids of 0.7 mg/L on average regardless of the concentrations of suspended matter in the source water.

The amount of particulates entrapped by the filter layer 8 was about 5 kg on average for each filtration, and an average particle size of particulates remaining in the clarified water was 3 um. ou Example 2 Filtration and backwashing were performed in the same conditions as in Example 1, except that the containment plates 12 were arranged as shown in FIG. 3B.

As a result, a linear velocity of filtration was 20 m3/h on average regardless of the concentrations of suspended matter in the source water, and average filtration duration was 10 hours for the source water containing 40 mg/L suspended matter, 6.6 hours for the source water containing 60 mg/L suspended matter, 5 hours for the source water containing 80 mg/L suspended matter, and 4 hours for the source water containing 100 mg/L suspended matter. In the resultant clarified water less than 2 mg/L suspended solids on average, which is greater than for Example 1, remained regardless of the concentrations of suspended matter in the source water.

The amount of particulates entrapped by the filter layer 8 was

about 8 kg on average for each filtration, and an average particle size of particulates remaining in the clarified water was 10 pm.

[Example 3] Filtration and backwashing were performed in the same conditions as in Example 1, except that the containment plates 13 were arranged as shown in FIG. 3C.

As a result, a linear velocity of filtration was 15 m3/h on average regardless of the concentrations of suspended matter in the source water, and average filtration duration was 13.3 hours for the source water containing 40 mg/L suspended matter, 8.8 hours for the source water containing 60 mg/L suspended matter, 6.7 hours for the source water containing 80 mg/L suspended matter, and 5.3 hours for the source water containing 100 mg/L suspended matter. In the resultant clarified water less than 1 mg/L suspended solids on average, which is greater than for Example 1, but lower than for Example 2, remained regardless of the concentrations of suspended matter in the source water.

The amount of particulates entrapped by the filter layer 8 was about 8 kg on average for each filtration, and an average particle size of particulates remaining in the clarified water was 5 pm.

[Conclusion] To investigate the effect of backwashing organic matter suspended in biological wastewater, filtration and backwashing were performed in the same conditions as in Example 1, except that the horizontal backwash, continuous. concentrated filtrate discharge type high-purity filter unit 100'of FIG. 4 without the porous backwash air plate 1d was used, and backwashing was performed for 2 minutes with 0. 5%

backwash water. The containment plates were arranged in three ways as shown in FIGS. 3D, 3E, and 3F. The results were similar to Examples 1,2, and 3, in terms of filtration duration, the concentration of particulates remaining in clarified water, and the amount of particulates entrapped by the filter layer 8 for each filtration. In consideration of the backwash duration and the amount of backwash water used, the horizontal backwash, continuous concentrated filtrate discharge type high-purity filter unit 100'of FIG. 4 is believed to be effective in treating source water containing organic suspended matter.

Effects of the Invention As described above, a filter apparatus for filtering suspended matter in water according to the present invention has a small volume and can produce a large amount of high-purity clarified water which can be used as regular drinking water, even when its operational conditions, including a target volume of clarified water and the composition of source water, are varied. Since a variety of flexible filters having different thicknesses are available for its filter medium, durability of the filter medium is great, the manufacturing and maintenance costs are low, and headloss during filtration is small, compared to other filtration methods. The pore size and porosity of the filter medium can be controlled according to the use of the clarified water, by varying the hydraulic pressure of source water, the density of the filter medium, and the position and shape of the containment plates. According to the present invention, depending on the kind of suspended matter in source water, different backwashing techniques can be applied, even when purifying a mixture of different kinds of suspended solids or liquid.

Since the filter apparatus according to the present invention utilizes a flexible filter medium capable of being swollen by compressed air supplied for backwashing, suspended matter entrapped by the filter

layer can be removed within a short period of time using a minimum quantity of backwash water.

According to the present invention, suspended matter of a relatively large particle size is entrapped near the surface of the filter layer and simultaneously discharged from the filter apparatus.

Therefore, filtering can be performed for an extended period of time with reduced frequency of filtering. The filter apparatus according to the present invention can filter out a variety of suspended particulates from water, for example, algae in fresh water or seawater, organic and inorganic matter suspended in swage or wastewater, and suspended matter in cooling water.

A filter apparatus according to the present invention can be applied as a solid and liquid separator of a sewage and wastewater treatment apparatus without a settling tank or with a minimum sized settling tank.

While this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.