JP2001017804A - Method and apparatus for filtration using fibrous filter medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for filtration which can perform filtration by a fibrous filter medium effectively and efficiently and an apparatus for the method. SOLUTION: A filter tank 2 is divided by porous plate members 5, 6 arranged vertically into a filtration area 7 in which a filter layer 17 in which fibrous filter medium 17a blocks are accumulated is formed, a raw water supply area 8 in which a water supply opening 10 is formed, and a treated water extraction area 9 in which a water extraction opening 11 is formed. In the initial stage of a filtration process, with the water extraction opening 11 closed, part 14b of raw water 14 supplied from the area 9 to the tank 2 is circulated/supplied to the area 8 through circulating channels 21, 22, 23, 24, 25, 26 so that the volume of the filter layer 17 comprising the filter medium 17a can be reduced by at least 30%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to secondary treatment water of a sewage treatment plant, polluted water such as industrial effluent, rainwater, river water, and organic wastewater, or stored water such as a scenic pond, a fish pond, a pool, and a hot spring. And a method for filtering using a fibrous filter medium.

[0002] For example, as a filter medium for filtering water to be treated such as secondary treatment water of a sewage treatment plant or industrial waste liquid,
Traditionally, granular solids such as sand have been used, but since the water to be treated is filtered by passing through the gaps between the filter media, the gaps are closed in a short time by the trapping substance. It is not easy to perform the filtration efficiently. Moreover, since pollutants in the water to be treated are trapped and removed at the surface layer portion of the filtration layer formed by laminating sand or the like, there is a disadvantage that the filtration tank is inevitably increased in size. Backwashing) requires a large amount of clean water.

[0003] In recent years, it has been recently attempted to use a massive fibrous filter medium and pass it down through a filter layer formed by laminating such filter medium, thereby capturing and removing pollutants in the water to be treated throughout the filter layer. Is being done. When such a fibrous filter medium is used, the above-mentioned problems do not occur, and fine water can be captured and removed even when the water to be treated passes through the fiber group of the filter medium.

[0004]

By the way, since the fibrous filter medium is lighter in weight and lighter in specific gravity than sand or the like,
By laminating the fibrous filter media, the filter media do not adhere to each other, and a gap is formed between the filter media (a state in which the porosity of the filtration layer is high), so that the water to be treated passes through the gap, It is not possible to remove fine pollutants,
Such gaps will disappear as the filtration process proceeds. That is, when the flow rate of the water to be treated passing through the filtration layer (hereinafter referred to as “filtration speed”) is large, the filtration layer is compressed by the passage of the water to be treated, and the filter media adhere to each other and the above-mentioned gap disappears. Will do. On the other hand, when the filtration speed is low (for example, when the filtration speed is 12.5 m / h or less), the filtration layer is not compressed by the passage of the water to be treated, but with the progress of the filtration process. As the trapping substance accumulates between the filter media, gaps between the filter media disappear.

Therefore, when the filtration rate is high, the time point at which the filtration processing is started (including the time point at which the filtration processing is resumed after backwashing is included).
The same applies hereinafter. ) To the point where the filtration layer is compressed to such an extent that the above-mentioned gap disappears, the ability of the filtration layer to trap and remove pollutants (hereinafter referred to as “declaration performance”) is low, and the pollutants are not filtered. It will leak. Also, as the filtration rate is higher, the time required for the filtration layer to be compressed as described above is shorter, and the amount of leakage of pollutants is reduced.However, if the user simply sticks to increasing the filtration rate, the filtration area or the filtration area is inevitable. The filter material stacking amount (filter material filling amount) decreases, the duration of the filtration process decreases,
Frequent backwashing is required.

[0006] Even when the filtration speed is low, the turbidity is low and the contaminant leaks from the start of the filtration treatment until the gap is eliminated by the trapped substance. Moreover, the time until the gap is eliminated by the trapping substance is longer than the time until the above-mentioned compression of the filtration layer, and the leakage amount of the pollutant is extremely large as compared with the case where the filtration rate is high. large. Further, when the amount of the pollutant trapped in the gap between the filter media becomes equal to or more than a certain value and the trapping action of the pollutant in the gap becomes a limit, the pollutant starts to leak again, and the turbidity is reduced. Therefore, the duration of the filtration process is shortened, and frequent backwashing needs to be performed.

Conventionally, there has been a strong demand for a solution to the above-mentioned problems in a filtration treatment using a fibrous filter medium, but an actual solution has not yet been proposed.

[0008] The present invention has been made in view of such circumstances, and solves all the above-mentioned problems when a fibrous filter medium is used so that a filtration process can be performed effectively and efficiently. It is an object of the present invention to provide a method and a filtration apparatus capable of suitably performing the method.

[0009]

In order to achieve the above object, a filtration method using a fibrous filter medium according to the present invention is characterized in that the inside of a filtration tank having a vertically openable water supply port and a water intake port is provided. A filtration processing region in which a filtration layer formed by laminating and supporting a massive fibrous filter medium on a lower perforated plate member is formed in a region between the two perforated plate members by the vertically arranged perforated plate members; It is divided into a treated water supply region that is an upper region of the region and a water supply opening is opened, and a treated water extraction region that is a lower region of the filtration treatment region and an intake opening is opened, and is an initial stage of a filtration treatment process. In the above, with the intake port closed, a part of the water in the filtration tank is taken out from the treated water take-out area and circulated and supplied to the treated water supply area (hereinafter, such circulated supply is referred to as “the water circulation”). Is to do so. The initial stage of the filtration process is, specifically,
From the time when the to-be-treated water is supplied to the to-be-treated water supply region into the filtration tank (the same is applied to the case where the filtration treatment is restarted after backwashing, hereinafter referred to as "the filtration treatment start time"), the filter medium is formed by the water circulation. The time from the start of filtration to the end of initial compression is defined as the time from when the filtration layer is compressed to the point where no contaminants are leaked (hereinafter referred to as the “end of initial compression”). When the compression of the filter layer at the time is 30% or more, it is generally several minutes to several tens of minutes.

Therefore, in such a filtration method,
At the end of the initial compression, the intake port is opened to start a substantial filtration process, but the water circulation depends on the filtration process conditions.
The operation may be stopped at the end of the initial compression, or may be continued after the end of the initial compression.
In addition, when the water circulation is performed even after the end of the initial compression, the water circulation may be continuously performed or temporarily performed according to a filtering condition (filtration speed, water quality, and the like). This may be performed (including a case where it is repeated intermittently as necessary). In addition, it is preferable that the water circulation in the initial stage compresses the filtration layer composed of the fibrous filter medium by at least 30%.

A filtration apparatus using the fibrous filter medium of the present invention for carrying out such a filtration method is a filtration tank provided with a water supply port and a water intake port which can be opened and closed vertically. A filtration processing region in which a filtration layer formed by laminating and supporting a massive fibrous filter medium on a lower perforated plate member is formed in a region between the two perforated plate members by the vertically arranged perforated plate members; A treated water supply region in which a water supply opening is open in an upper region of the region, a filtration tank partitioned into a treated water extraction region in which a water intake opening is formed in a lower region of the filtration treatment region, and a treated water extraction region. By providing a circulating water channel having a circulating water channel that connects and connects the treated water supply area and an on-off valve and a circulating pump provided in the circulating water channel, and opening the on-off valve and operating the circulating pump, Part of the water in the filtration tank is treated Taken out from the take-out area is obtained by construction so as to be able to circulate supplied to the treatment water supply areas.

[0012] In such a filtration apparatus, it is preferable to provide a backwash mechanism that also serves as a backwashing pump while using the circulation pump as a part of the circulation waterway. For example, a circulating water channel has a first pipe having one end connected to a treated water extraction area, a second pipe having one end connected to the other end of the first pipe, and a second pipe having one end connected to the other end of the first pipe. A third conduit connected to the other end of the circulating pump and the other end connected to a suction portion of a circulating pump used also as a backwash pump, and a fourth conduit connected to one end to a discharge portion of the circulating pump. A fifth pipe having one end connected to the other end of the fourth pipe, and a fifth pipe having one end connected to the other end of the fifth pipe and having the other end connected to the treated water supply region. The backwash water channel is defined as a first, third, fourth, and sixth pipelines, which constitute a part of the circulation water channel, and one end is defined as a first pipeline. And a seventh conduit having the other end joined to the connection end of the fourth and fifth conduits, and one end connected to one end of the third conduit. To the fifth and The first pipe and the third pipe are connected to the circulating water channel and the backwash water channel via the second pipe as a configuration including the eighth pipe connected to the connection end of the six pipes. And the fourth and sixth conduits are connected to the fifth
The first switching position or the first pipeline and the fourth pipeline connected via the pipeline are connected via the seventh pipeline, and the third pipeline and the sixth pipeline are connected to the eighth pipeline. There is provided a pipeline switching mechanism for selectively switching to the second switching position which is connected via the.

[0013]

Embodiments of the present invention will be specifically described below with reference to the drawings.

As shown in FIGS. 1 to 7, a filtration apparatus 1 according to the present invention in this embodiment includes a pressure type filtration tank 2 and a water circulation mechanism 3 and a backwashing mechanism 4 attached thereto. It is.

As shown in FIG. 1, the filtration tank 2 has a cylindrical closed container structure, and the inside thereof is interposed between two porous plate members 5 and 6 by vertically arranged porous plate members 5 and 6. , A treated water supply region 8 above the filtration region 7, and a treated water removal region 9 below the filtration region 7. As shown in FIG. 1, a water supply port 10 that opens to a treated water supply area 8 and a water intake port 11 that opens to a treated water extraction area 9 are provided in the upper part of the peripheral wall and the center part of the bottom wall of the filtration tank 1. The water supply port 13 is connected to a water supply passage 13 led from a water source to be treated (not shown) via a water supply valve 12 serving as an on-off valve. When the water supply valve 12 is opened, the water to be treated (for example, sewage water) is opened. The secondary treatment water 14 of the treatment plant is supplied from the water supply port 10 to the treated water supply area 8. Intake 1
1 is connected to a water supply passage 16 led to a treated water use section (not shown) via a water intake valve 15 serving as an open / close valve. By opening the water intake valve 15, the treated water 14a is taken out of the treated water. The area 9 is taken out of the filtration tank 2. In addition, although not shown, an air vent valve is provided in the upper part of the filtration tank 2.

A filtration layer 17 having a predetermined thickness is formed by laminating a number of fibrous filter media 17a in a lump.
Are formed. As the fibrous filter medium 17a, it is preferable to use a fibrous filter medium having elasticity and a large specific surface area and having a spherical shape or a similar mass. For example, a crimped yarn made of synthetic fiber of an appropriate length is bundled, the central portion thereof is bound, and the bundle is formed into a spherical or other lump. In this example, a polyvinylidene chloride fiber having a diameter of 80 μm (fiber specific gravity:
A crimped yarn made of 1.7) is used as a bundle, and the central portion is bound and formed into a spherical shape having a diameter of 33 mm. In the fibrous filter medium 17a, the weight per piece is 3.3 g, the porosity is 90% or more, and the bulk specific gravity at the time of filling (the bulk specific gravity in the unloaded state laminated on the perforated plate 6) is low. 0.1. In addition, such a fibrous filter medium 1
7a is that the fiber surface is gradually deformed into a form similar to the head of a French head by repeating the backwashing treatment a plurality of times (generally, about 100 times). The resilience is further enhanced, and it can be used favorably over a long period of time.

As shown in FIG. 1, the filter layer 17 is supported by a lower porous plate (hereinafter, referred to as a "filter medium support plate") 6. The filter medium support plate 6 is made of a porous material such as a punched metal or a wire mesh, and has a disk-shaped center portion 6a horizontally positioned at the center portion of the filtration tank 1 and an inclined shape upward from the center portion 6a. And an outer peripheral portion 6b in the shape of a truncated cone. In addition, as a constituent material (porous material) of the filter medium support plate 6,
As long as the fibrous filter medium 17a does not pass through, it is preferable to use a filter material having as large an aperture ratio (pore size) as possible. Further, the inclination angle of the outer peripheral portion 6b (the inclination angle with respect to the peripheral wall of the filtration tank 1) is preferably set to 30 ° or more. The upper porous plate 5 is a disk made of the same porous material as the filter medium support plate 6, and is stretched horizontally.

As shown in FIGS. 1 to 3, the water circulating mechanism 3 includes a circulating water passage 18 which connects the treated water take-out area 9 and the treated water supply area 8, and an opening / closing valve 19 and a circulating pump provided at an appropriate position thereof. 20. The circulating water passage 18 has a first pipe 21 having one end connected to the treated water extraction region 9 and a second pipe having one end connected to the other end of the first pipe 21 via a first switching valve 31. A third conduit 23 having one end connected to the other end of the second conduit 22 via the second switching valve 32 and the other end connected to the suction portion of the circulation pump 20; A fourth conduit 24 connected to the discharge part of the circulation pump 20;
A fifth conduit 25 having one end connected to the other end of the fourth conduit 24 and the on-off valve 19 disposed therein; and one end connected to the other end of the fifth conduit 25 and the other end. And a sixth pipe connected to the treated water supply area 8. By opening the on-off valve 19 and operating the circulation pump 20, a part 14 b of the water in the filtration tank 2 is removed from the treated water extraction area 9. And pressurized and then circulated and supplied to the treated water supply area 8. In this example, a known booster pump is used as the circulation pump 20.

The backwashing mechanism 4 is, as shown in FIGS.
It comprises a backwash water channel 33 that connects the treated water supply region 8 and the treated water extraction region 9 in communication, and a backwash pump and an air ejector 34 provided at an appropriate position in the backwash water passage 33. In this example, the circulating pump 20 is also used as the backwashing pump, and a part of the circulating waterway 18 is also used as the backwashing waterway 33, thereby simplifying the filtration device 1 including the backwashing mechanism 4. The size is reduced as much as possible. That is, the backwash water channel 32 is a part of the circulating water channel 18,
One end of the third conduit 23, the fourth conduit 24, and the sixth conduit 26 is connected to the other end of the first conduit 21 via the first switching valve 31, and the other end is connected to the fourth and fourth conduits. One end of the seventh conduit 27 joined to the connection end of the fifth conduits 24 and 25 is connected to one end of the third conduit 23 via the second switching valve 32, and the other end is connected to the second conduit. An eighth pipe 28 is connected to the connection end of the fifth and sixth pipes 25 and 26, and the reverse pump filled in the filtration tank 1 is operated by operating the backwashing pump as the circulation pump 20. A part 14c of the washing water is taken out from the treated water supply area 8, pressurized, and circulated and supplied to the treated water removal area 9. The air ejector 34 has a large number of air ejection holes directed upward, and is disposed immediately below a cylindrical partition plate 35 hanging down from the filter medium support plate 6 and is surrounded by the partition plate 35. The air 36 is ejected toward the region (see FIG. 6). In addition, the partition plate 35 has the upper end edge portion at the center 6a of the filter medium support plate 6.
And a lower edge portion thereof is positioned higher than the bottom wall of the filtration tank 1 by a predetermined amount. Further, a backwash drain 37 is connected to the water intake 11 in a branched manner, and a drain valve 3 serving as an open / close valve provided in the backwash drain 37 is provided.
By opening 8, the backwash water in the filtration tank 1 is discharged at a stretch.

Switching between the circulating water channel 18 and the backwash water channel 33 is performed by a pipeline switching mechanism including an opening / closing valve 19 and first and second switching valves 31 and 32 provided therein. By switching the valves 19, 31, 32 to a first switching position in which the on-off valve 19 is opened and each switching valve 31, 32 is operated to a first position described later, the first pipeline 21 and the third pipeline 23 are switched. Are connected via a second conduit 22 and the fourth conduit 24 and the sixth conduit 26 are connected to the fifth conduit 2.
5 and the first by the booster pump 20
A circulation channel 18 is formed in which water is supplied from the channel 21 to the sixth channel 26. In addition, the pipeline switching mechanisms 19, 31, 3
2 is switched to a second switching position in which the on-off valve 19 is closed and each switching valve 31, 32 is operated to a second position described later, so that the first pipeline 21 and the fourth pipeline 24 are connected to the seventh pipeline. The third conduit 23 and the sixth conduit 26 are connected via an eighth conduit 28 while being connected via a conduit 27, and are connected from the sixth conduit 26 by the booster pump 20 to the first conduit 21. Backwash water channel 33 in which water is supplied to water is formed.

That is, each of the switching valves 31 and 32 is a three-way switching valve capable of changing the connection form of the three pipelines by selecting the rotational position of the valve bodies 31a and 32a having three ports. In conjunction with the above, switching is made between the circulation water channel 18 and the backwash water channel 33 which also serves as a part. That is, according to the first switching valve 31, the first port in which the two ports communicate the valve element 31a with the first and second conduits 21 and 22 is provided.
By operating to the position, the first conduit 21 and the second conduit 22 can be connected (see FIG. 2), and the valve element 31
By operating a at the second position where the two ports communicate with the first and seventh conduits 21 and 27, the first conduit 21 and the seventh conduit 27 can be connected (see FIG. 6). Further, according to the second switching valve 32, the valve body 32a is operated to the first position where the two ports communicate with the second and third conduits 22, 23, so that the second conduit 22 and the third conduit are operated. 23 (see FIG. 2), and by operating the valve body 32a to a second position where two ports communicate with the second and eighth conduits 22, 28, the second conduit 22 and the eighth conduit are operated. The pipe 28 can be connected (see FIG. 6). Therefore, by operating each valve element 31a, 32a of both switching valves 31, 32 to the first position and opening the on-off valve 19, as shown in FIG.
1, a first switching valve 31, a second conduit 22, a second switching valve 32,
The treated water supply area 8 passes through a third pipe 23, a booster pump 20 as a circulation pump, a fifth pipe 25, and a sixth pipe 26.
Is formed. In addition, both switching valves 3
By operating each of the valve bodies 31a and 32a to the second position and closing the on-off valve 19, as shown in FIG.
Pipe 28, second switching valve 32, third pipe 23, booster pump 20 as a backwash pump, fourth pipe 24, seventh pipe 2
7. A series of backwash water passages 33 that reach the treated water removal area 9 via the first switching valve 31 and the first pipe line 21 are configured. As described above, by operating the on-off valve 19 and the two switching valves 31 and 32, switching between the circulation water passage 18 and the backwash water passage 33 and switching of the water circulation direction by the booster pump 20 are performed.

The filtration method according to the present invention in this embodiment is carried out as follows using the above-described filtration apparatus 1.

First, the intake port 11 and the backwash drain port 38 are closed, and the water to be treated (for example, secondary treatment water of a sewage treatment plant) 14 is supplied from the water supply port 10 to the filtration tank 2 (FIG. 1). . At this time, each of the switching valves 31 and 32 is operated to the first position, and the on-off valve 19 is opened.

Then, the water 14 to be treated is supplied into the filtration tank 2 to the water supply area 8 and the water surface reaches at least the position beyond the opening of the sixth conduit 26 (at the start of the filtration treatment). ), The booster pump 20 is operated, a part of the water (hereinafter referred to as “circulating water”) 14 b in the filtration tank 2 is taken out from the treated water take-out area 9 and pressurized. It is circulated (Fig. 1). That is, the circulating water 14b flows out of the treated water extraction region 9 to the first pipeline 21, and from the first pipeline 21 to the first switching valve 31, the second pipeline 2
2, the second switching valve 32, the third conduit 23, the circulation pump 20,
After passing through the circulating water channel 18 that reaches the sixth pipeline 26 via the fourth pipeline 24 and the fifth pipeline 25 and is supplied from the sixth pipeline 26 to the water supply area 8, the filtration layer 17 is removed. The water flows through a circulation path such that the water passes down and flows out of the treated water extraction area 9 to the circulation water passage 18. When the filter tank 2 becomes full, the water supply port 10 is closed to stop supplying water to the filter tank 2.

By the forced circulation of the circulating water 14b, the filtration layer 17 formed by laminating the fibrous filter media 17a is compressed, and the porosity thereof is reduced (FIG. 2).

Then, when the filtration layer 17 is compressed by a certain amount or more by the circulation of the circulating water 14b (at the end of the initial compression).
Then, the water supply port 10 and the water intake port 11 are opened to start a substantial filtration process (FIG. 3). That is, the water to be treated 14 is continuously supplied from the water supply port 10 to the water to be treated supply area 8, and is passed down the compressed filtration layer 17, during which the pollutants contained in the water to be treated 14 are filtered. Processed water 14a captured and removed from the entire layer 17 and passed through the filtration layer 17
The water is discharged from the water inlet 11 to the outside of the filtration tank 2.

By the way, the compression ratio of the filtration layer 17 at the end of the initial compression must be not less than a level enough to ensure the subsequent substantial filtration treatment and a sufficient opacity. Experimental results to be described later (FIGS. 8 to 1)
As understood from 1), generally, the filtration layer 17 is 30
% Or more, the turbidity performance is remarkably improved by compression, so that the compression of the filtration layer 17 by the circulating supply of the circulating water 14b performed before the start of the substantial filtration treatment has reached at least 30%. It is preferable to set the time point to the end point of the initial compression. Normally, booster pump 2
When several minutes to several tens of minutes have elapsed from the start of the operation of the filter 0, the filtration layer 17 is compressed by 30% or more, and the time required from the start of the filtration to the start of the substantial filtration is short. Therefore, the processing efficiency does not decrease if the substantial filtration is not performed between the start of the filtration and the end of the initial compression.

As described above, when the substantial filtration process is started, the filtration layer 17 is compressed as described above, and the fibrous filter media 17a are pressed against each other, so that the porosity is extremely low. Therefore, as shown in FIG. 12, the water to be treated 14 passes down the dense fiber portion inside each of the fibrous filter media 17a and effectively captures and removes fine pollutants. . As a result, in the substantial filtration process, the treated water 1 having extremely low turbidity from the start point
4a will be obtained. That is, the turbidity performance of the filtration layer 17 is greatly improved by compressing the filtration layer 17 and eliminating the gaps between the fibrous filter media 17a. Leaks are extremely low.

If the amount of the water to be treated 14 flowing into the filtration tank 2 (the amount of filtered water) is extremely small as compared with the initial design value, and a filtration speed higher than a certain level cannot be secured, the experimental results described later will be used. As is clear from FIG.
, The turbidity performance is reduced.

However, even after the substantial filtration process is started, as shown in FIG. 3, by continuing the circulating supply of the circulating water 14b, even when the amount of inflow water from the water supply port 10 is small, a sufficient amount can be obtained. The filtration speed can be secured. That is, a part of the water in the filtration tank 2 is circulated and supplied to the water supply area 8 as the circulating water 14b.
Although there is an equivalent relationship between the inflow of the water 14 to be treated from 0 and the outflow of the treated water 14a from the water intake 11,
, The amount of water that passes downwards increases by the amount of circulating water 14b,
The filtration speed increases. Therefore, even when the amount of inflow water is extremely small as compared with the initial design value as described above, it is possible to perform a good filtration treatment without lowering the turbidity performance.

On the other hand, when the amount of inflow water from the water supply port 10 is not extremely reduced as compared with the initially designed value and a predetermined filtration speed is secured, the initial compression end point or substantial filtration processing is performed. At the start time, the circulating supply of the circulating water 14b can be stopped by closing the on-off valve 19 and stopping the booster pump 20. Even in such a case, in the initial stage of the filtration process (the stage from the time of the filtration process to the end of the initial compression), the filtration layer 17 once compressed by the circulating water 14b has a problem in view of the properties of the fibrous filter medium 17a constituting the same. Unless backwashing is performed, the compressed state is maintained, so that the turbidity performance does not decrease.

As will be understood from the experimental results (FIGS. 8 to 11) described later, the turbidity is improved as the filtration rate is increased. Therefore, even when the amount of inflow water from the water supply port 10 is sufficient, the circulating water 14b is continuously forcedly circulated to increase the filtration speed, so that more effective filtration processing can be performed at high speed. it can.

When the amount of inflow water from the water supply port 10 fluctuates after the substantial filtration process is started, and the amount of inflow decreases extremely, the circulating supply of the circulating water 14b is restarted. Thus, it is possible to prevent a decrease in the filtration speed. That is, if necessary, the supply of the circulating water 14b is temporarily or intermittently performed to cope with fluctuations in the filtration speed or to control the filtration speed, thereby performing a stable filtration process. be able to.

If the circulating water 14b is supplied continuously or temporarily or intermittently even after the substantial filtration process is started, as shown in FIG. Depending on the properties, the coagulant 41 may be injected into the circulating water channel 18 from an appropriate medicine injector 40 at an appropriate position.

By the way, the present inventor conducted the following experiment in order to confirm the influence of the compression ratio and the filtration speed of the filtration layer 17 on the turbidity. That is, this experiment
The water to be treated 14, which is the secondary treated water of the sewage treatment plant,
The filtration treatment is performed using the above-described filtration tank 2 while changing the compression degree (%) and the filtration rate of the filtration layer 17 over four stages, and the water 14 to be treated under each compression degree and filtration rate is changed. And the turbidity of treated water 14a (NTU (Nethelonetr
ic Turbidity Unit)). The results are as shown in FIG. 8 when the filtration speed was 12.3 m / h, and 24.3 m / h.
h is as shown in FIG.
When it was 3 m / h, it was as shown in FIG. 10, and when it was 73.8 m / h, it was as shown in FIG. In each of the figures, the turbidity when the filter layer 17 is not compressed at all (0% compression) is indicated by ●, the turbidity at 15% compression is indicated by Δ, the turbidity at 30% compression is indicated by ○,
Turbidity in the case of 40% compression is indicated by ◎. In addition,
1NTU = 0.6 kaolin turbidity ≒ 1 / 2.3SS (mg
/ L).

As is clear from the experimental results shown in FIGS. 8 to 11, when the compression ratio of the filtration layer 17 is 30% or 40%, the compression ratio of the filtration layer 17 is increased regardless of the filtration speed. Is 0% and 15%, it was confirmed that the turbidity performance was significantly improved. That is, in the case of 0% compression, as shown in FIG. 13, the fibrous filter media 17a are not in close contact with each other, and
Since the liquid passes through the gap between the liquid crystals a, the supplemental removal of pollutants is not sufficiently performed. In the case of 15% compression, the fibrous filter media 17a are closely adhered to each other to some extent, but the fibrous filter media 17a are not sufficiently compressed. The supplemental removal of the substance cannot be performed effectively. On the other hand, in the case of 30% compression or 40% compression, as shown in FIG. 12, the fibrous filter media 17a.
Since a is compressed and the fiber density inside is high, the water to be treated 14 passes through the inside of each fibrous filter medium 17a, and fine pollutants are also effectively removed. Further, from the above experimental results, it is understood that when the compression ratio of the filtration layer 17 is the same, the turbidity performance improves as the filtration speed increases. Therefore, in order to perform an effective filtration process, it is understood that the filtration layer 17 composed of the fibrous filter media 17a is preferably compressed to 30% or more and a sufficient filtration speed is secured. Is done.

The above-mentioned filtration step is performed in the same manner even after the backwashing of the fibrous filter media 17a... In this embodiment, the backwashing is carried out by removing the water 14 to be treated. It is performed as follows.

When the backwashing process becomes necessary in the filtration process, first, the water supply port 10 and the water intake port 11 are closed, the two switching valves 31 and 32 are operated to the second position, and the opening / closing valve 19 is further closed. . Thereafter, the air 36 is ejected from the air ejector 34, and the ejected air 36 is blown into the filtration area 7. Further, by operating the booster pump 20,
A part of the cleaning water 14c, which is the water to be treated, which fills the filtration tank 17, is taken out from the treated water supply area 8 and circulated and supplied to the treated water take-out area 9 through the backwash water passage 33. That is,
By operating the booster pump 20, the cleaning water 1
Part of 4c extends from the treated water supply area 8 to the sixth conduit 26,
After being pressurized by the booster pump 20 via the second switching valve 32 and the third conduit 23, the pressure is increased via the fourth conduit 24, the seventh conduit 27, the first switching valve 31 and the first conduit 21. The water is supplied to the treated water take-out area 9, and further flows upward through the filtration treatment area 7 to flow from the treated water supply area 8 into the sixth conduit 26.

Therefore, the fibrous filter media 17a are loosened and agitated by the gas-liquid mixed flow generated by the above-mentioned circulation of the washing water and the jetting of the air in the filtering area 7 divided by the perforated plates 5 and 6 at the top and bottom. , (FIG. 6). When the washing of the fibrous filter media 17a is completed, the backwash drain port 37 is opened, and the washing water 14c in the filter tank 2 is discharged together with the supplementary substance separated from the fibrous filter media 17a (FIG. 7).

After completion of the backwashing process, the filtration process is restarted in the same manner as described above.

By the way, when the filtration process is resumed, there is a possibility that the suspended pollutant, which is a trapping substance remaining in the fibrous filter media 17a, may be mixed into the treated water 14a. Until a certain time (about several minutes) elapses, the water passing through the filtration layer 17 is discharged out of the system (so-called waste water treatment), but water loss due to such waste water treatment is not negligible. Without increasing the water load due to the return of water in sewage treatment plants,
This causes problems such as water loss in fishponds.

However, according to the present invention, as described above,
Before the substantial filtration process is started (restarted), the filtration tank 2
Since a part 14b of the internal water is circulated, it is not necessary to perform the above-mentioned water treatment, and there is no water loss due to the water treatment. That is, as the circulating water 14b repeatedly descends and passes through the filtration layer 17, the filtration layer 17 loosened by back washing is compressed again, and the suspended pollutants are removed from the filtration layer 1.
7, when the substantial filtration process is started, the suspended pollutants do not enter the treated water 14a.

It should be noted that the present invention is not limited to the above-described embodiment, and can be appropriately improved and changed without departing from the basic principle of the present invention.

For example, when the diameter of the filtration tank 2 is large,
The filtration tank 2 and the backwashing mechanism 4 can be configured as shown in FIGS. The filtering apparatus 1 shown in FIGS. 14 to 17 has the same configuration as that shown in FIGS. 1 to 7 except for the following points.

That is, in the filtration apparatus 1 shown in FIGS. 14 to 17, the filter medium support plate 6 is formed in a disk shape, and is horizontally stretched below the filter tank 2 so that the filter medium support plate 6 On the lower surface, a rectangular partitioning plate 39 is disposed vertically on the diameter line, and the treated water extraction area immediately below the filter medium support plate is placed in the first area.
And the first and second treated water removal areas 9a, 9b.
And the second air ejectors 34a and 34b are separately arranged, and the backwashing process is performed as follows. Each of the air ejectors 34a and 34b has a large number of air ejection holes for ejecting air 36 upward, similarly to the above-described air ejector 34, and each of the treated water ejection area portions 9a and 9b.
Then, the air 36 is ejected from the filter processing area portions 7a and 7b in the direction just above the air.

First, the booster pump 20 is operated to circulate a part of the washing water 14c, which is the water to be treated, in the filtration tank 2 through the backwash water passage 33 in the same manner as described above. Next, as shown in FIG. 14, the first air ejector 34a
The first backwashing step is started by blasting air 36 from the first processing water outlet region portion 9a and intensively blowing the blasted air 36 from the first treated water extraction region portion 9a to the first filtration processing region portion 7a in the direction directly above.

In the first backwashing step, as shown in FIG. 14, a kind of air lift effect is exerted by local and intensive air ejection by the first air ejector 34a.
A strong ascending flow 14e is generated by the gas-liquid mixed fluid in the filtration area 7a. The upward flow 14e becomes stronger due to the forced circulation of the cleaning water 14c by the booster pump 20, and is continuously generated. Therefore, even when the fibrous filter medium 17a constituting the filtration layer 17 is in a compacted state by pressure-type high-speed filtration or in a close contact state by trapped contaminants, the filtration layer 17 is loosened in a very short time, The filter medium 17a easily floats. In the filtration area 7, the first air ejector 34a
A density difference occurs between the first filtration processing area portion 7a where the air is blown from the first filtration processing area portion 7b and the second filtration processing area portion 7b where the air is not blown, and as shown in FIG. A strong circulating flow 14f which rises up the treatment area part 7a and descends the second filtration treatment area part 7b will result. As a result, the fibrous filter medium 17 loosened as described above
a is uniformly mixed and stirred in the filtration processing area 7 by the circulation flow 14f.

After the first backwashing step is continued for a certain period of time, the aeration function is switched from the first air ejector 34a to the second air ejector 34b, and the process shifts to the second backwashing step. That is, at the same time as stopping the air ejection from the first air ejector 34a, the air 36 is ejected from the second air ejector 34b. In this way, as shown in FIG. 15, contrary to the case of the first backwashing step, the second treated water removal area 9
b, a rising flow 14g of the gas-liquid mixed fluid is generated in the second filtration area 7b, which is immediately above the first filtration area 7b. Is generated, and the fibrous filter medium 17a is mixed and stirred while circulating in the reverse direction.

Therefore, the fibrous filter medium 17a constituting the filtration layer 17 is loosened immediately after the first backwashing step is started, and the circulating flow 14e and the second backwashing step are followed by the first backwashing step and the second backwashing step. By changing the direction of 14g, the mixing and stirring of the fibrous filter medium 17a are performed more effectively, and the fibrous filter medium 17a is cleaned extremely well.

After a predetermined time has elapsed after the start of the second backwashing step, as shown in FIG.
Is stopped, the on-off valve 19 is closed, and the air 36 is ejected from the air ejectors 34a, 34b. Then, the backwash drain 37 is opened to discharge the washing water 14c in the filtration tank 2. By aerating the filtration area 7 entirely with both air ejectors 34a and 34b, the fibrous filter medium 17 is removed.
a is uniformly dispersed. Therefore, when the washing water 14c in the filtration tank 2 is discharged at once from the backwash drain 37 in this state, the filtration layer 17 having a uniform thickness is formed as shown in FIG. That is, even when the diameter of the filtration tank 2 is large, the thickness of the filtration layer after back washing can be made uniform.

Further, the pipeline switching mechanism for switching between the circulating water channel 18 and the backwash water channel 33 can be constituted by only an on-off valve without using the switching valves 31 and 32 described above. For example, as shown in FIG.
2, four on-off valves 19a, 19b, 19c and 19d arranged in the fifth conduit 25, the seventh conduit 27 and the eighth conduit 28. That is, the pipeline switching mechanism 19
a, 19b, 19c and 19d are connected to on-off valves 19a and 19b.
Is opened and the on-off valves 19c, 19d are closed to the first switching position, as shown in FIG. 18A, the first line 21 to the second line 22, the third line 23, the booster A circulating water channel 18 for supplying water to a sixth pipe 26 via a pump 20, a fourth pipe 24, and a fifth pipe 25 is formed. Further, the pipeline switching mechanisms 19a, 19b, 19c, 19
When d is switched to the second switching position where the on-off valves 19a and 19b are closed and the on-off valves 19c and 19d are opened, as shown in FIG. 18B, the sixth line 26 to the eighth line 28 , A backwash water channel 18 for supplying water to the first pipeline 21 via the third pipeline 23, the booster pump 20, the fourth pipeline 24, and the seventh pipeline 27.

[0052]

As will be easily understood from the above description, according to the filtration method of the present invention, the filtration process is started after the filtration layer is compressed. Thus, the turbidity performance of the fibrous filter medium is sufficiently exhibited, and the pollutants are not leaked, and the secondary treatment water or the like of the sewage treatment plant can be efficiently and effectively filtered. Further, according to the filtration apparatus of the present invention, the above method can be suitably performed without making the apparatus complicated and large.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view showing an embodiment of a filtration apparatus according to the present invention and showing a starting state of a filtration step.

FIG. 2 is a longitudinal sectional front view corresponding to FIG. 1, showing a state of an initial stage in a filtration process.

FIG. 3 is a longitudinal sectional front view corresponding to FIG. 1 and showing a state after an elapse of an initial stage in a filtration process.

FIG. 4 is a longitudinal sectional front view corresponding to FIG. 1 and showing a state different from FIG. 3 after an elapse of an initial stage in a filtration process.

FIG. 5 is a longitudinal sectional front view corresponding to FIG. 1, showing a state after an initial stage in a filtration process step, and showing a state different from FIGS. 3 and 4;

FIG. 6 is a vertical sectional front view corresponding to FIG. 1 showing a backwashing step.

FIG. 7 is a longitudinal sectional front view corresponding to FIG. 6 and showing a completed state of the backwashing step.

FIG. 8 is experimental data showing the relationship between the turbidity of treated water and the turbidity of treated water.

9 is experimental data showing the relationship between the turbidity of treated water and the turbidity of treated water under a filtration rate different from that in FIG.

FIG. 10 is experimental data showing the relationship between the turbidity of the water to be treated and the turbidity of the treated water under filtration rates different from those in FIGS. 8 and 9;

FIG. 11 is experimental data showing the relationship between the turbidity of treated water and the turbidity of treated water under filtration rates different from those in FIGS. 8 to 10;

FIG. 12 is an explanatory diagram showing a filtration state when a filtration layer is compressed.

FIG. 13 is an explanatory diagram showing a filtration state when the filtration layer is not compressed.

FIG. 14 is a longitudinal sectional front view showing a modified example of the filtration apparatus according to the present invention and showing a first backwashing step.

FIG. 15 is a longitudinal sectional front view corresponding to FIG. 14 showing a second backwashing step.

FIG. 16 is a vertical sectional front view corresponding to FIG. 14 showing a drainage process.

FIG. 17 is a longitudinal sectional front view corresponding to FIG. 14 and showing the end state of the backwashing process.

FIG. 18 is a system diagram showing a modification of a pipeline switching mechanism for switching between a circulation channel and a backwash channel.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Filtration processing apparatus, 2 ... Filtration tank, 3 ... Water circulation mechanism, 4 ...
Backwashing mechanism, 5: Upper perforated plate, 6: Filter medium support plate (lower perforated plate), 7: Filtration treatment area, 8: Water to be treated supply area,
9 ... treated water extraction area, 10 ... water inlet, 11 ... water intake, 1
2: water supply valve, 14: treated water, 14a: treated water, 14b
... Circulating water (part of water in the filtration tank), 14c ... Backwash water, 1
5 ... intake valve, 17 ... filtration layer, 17a ... fibrous filter medium, 18
... circulating waterways, 19, 19a, 19b, 19c, 19d ...
On-off valve (pipe switching mechanism), 20 circulating pump, 21 first pipe, 22 second pipe, 23 third pipe, 24 fourth pipe
Pipes, 25: Fifth pipe, 26: Sixth pipe, 27: Seventh pipe, 28: Eighth pipe, 31, 32 ... Switching valve (Pipe switching mechanism), 33: Backwash water channel, 34, 34a, 34b ... air ejector, 35, 39 ... partition plate, 36 ... air, 37 ... backwash drain, 38 ... drain valve.

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[Procedure amendment]

[Submission date] February 3, 2000 (200.2.3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

Therefore, in such a filtration method,
Substantial filtration open intake in initial compression end is started, the water circulation, after the initial compression end also dividing continue line. When the water circulation is performed even after the end of the initial compression, the water circulation may be continuously performed or temporarily performed according to the filtering conditions (filtration speed, water quality, etc.). This may be performed (including a case where it is repeated intermittently as necessary). In addition, it is preferable that the water circulation in the initial stage compresses the filtration layer composed of the fibrous filter medium by at least 30%.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

In such a filtration apparatus, there is provided a backwashing mechanism which also serves as a circulating pump as a backwashing pump and also uses a part of the circulating water passage as a part of the backwashing water passage.
You. A first conduit having one end connected to the treated water extraction region, a second conduit having one end connected to the other end of the first conduit, and a second conduit having one end connected to the other end of the first conduit. A third conduit connected to the other end of the circulating pump and the other end connected to a suction portion of a circulating pump used also as a backwash pump, and a fourth conduit connected to one end to a discharge portion of the circulating pump. A fifth pipe having one end connected to the other end of the fourth pipe, and a fifth pipe having one end connected to the other end of the fifth pipe and having the other end connected to the treated water supply region. The backwash water channel is defined as a first, third, fourth, and sixth pipelines, which constitute a part of the circulation water channel, and one end is defined as a first pipeline. And a seventh conduit having the other end joined to the connection end of the fourth and fifth conduits, and one end connected to one end of the third conduit. To the fifth and The first pipe and the third pipe are connected to the circulating water channel and the backwash water channel via the second pipe as a configuration including the eighth pipe connected to the connection end of the six pipes. In addition, the first switching position where the fourth conduit and the sixth conduit are connected via the fifth conduit or the first conduit and the fourth conduit are connected to the seventh conduit.
A pipeline switching mechanism is provided that is connected via a pipeline and selectively switches to a second switching position where the third pipeline and the sixth pipeline are connected via an eighth pipeline.

Claims (6)

[Claims] 1. The inside of a filtration tank provided with a water supply port and a water intake port that can be opened and closed vertically by a perforated plate member arranged vertically.
A filtration region in which a filtration layer is formed by laminating and supporting a massive fibrous filter medium on a lower perforated plate member, between the two perforated plate members, and a water supply port which is an upper region of the filtration treatment region Is divided into a treated water supply region that is open, and a treated water extraction region that is below the filtration treatment region and has an intake opening, and in an initial stage of the filtration process, the intake is closed. A method of using a fibrous filter medium, wherein a part of water in a filtration tank is taken out from a treated water take-out area and circulated and supplied to a treated water supply area. 2. The fibrous filter medium according to claim 1, wherein the water circulation from the treated water extraction region to the treated water supply region is performed only in an initial stage of the filtration process. Filtration treatment method using 3. The method according to claim 1, wherein the water circulation from the treated water take-out area to the water-to-be-treated supply area is continuously or temporarily performed even after the intake port is opened and the substantial filtration process is started. A filtration method using the fibrous filter medium according to claim 1, characterized in that: 4. Due to the water circulation in the initial stage, the filtration layer composed of the fibrous filter medium is at least 30%
The filtration method using a fibrous filter medium according to claim 1, 2 or 3, wherein the filtration is performed. 5. A filter tank provided with a water supply port and a water intake port which can be opened and closed vertically, wherein the inside of the filter tank is provided between upper and lower perforated plate members in a region between the two perforated plate members and a lower perforated plate. A filtration region in which a filtration layer formed by laminating and supporting a massive fibrous filter medium on the member; a treated water supply region in which a water supply opening is located above the filtration region; and a filtration region. A filtration tank partitioned into a lower area and a treated water extraction area in which an intake port is opened, a circulating water path that connects and connects the treated water extraction area and the treated water supply area, and an on-off valve provided in the circulating water path; And a water circulation mechanism having a circulation pump, by opening the on-off valve and operating the circulation pump, to take out a part of the water in the filtration tank from the treated water take-out area and to the treated water supply area. The feature is that it can be circulated and supplied. Filtration device using a fibrous filter medium. 6. A backwash mechanism is provided, which also functions as a backwashing pump while also using the circulation pump as a part of the circulation waterway as a part of the backwash waterway. A first conduit communicating with the region, and one end connected to the first
A second pipe connected to the other end of the pipe, and one end connected to the other end of the second pipe, and the other end connected to a suction part of a circulation pump also used as a backwash pump. A third conduit,
A fourth pipe having one end connected to the discharge part of the circulation pump, a fifth pipe having one end connected to the other end of the fourth pipe, and one end connected to the other end of the fifth pipe; And a sixth pipe line having the other end connected to the water supply area to be treated, wherein the backwash water path is a first pipe line, a third pipe line, and a fourth pipe line which constitute a part of the circulating water passage. And a sixth conduit having one end connected to the other end of the first conduit and the other end joined to the connection end of the fourth and fifth conduits; An eighth conduit connected to one end of the third conduit and having the other end joined to the connection end of the fifth and sixth conduits. The first conduit is provided in the circulating water channel and the backwash water channel. A first switching position or a first line where the line and the third line are connected via the second line and the fourth line and the sixth line are connected via the fifth line; The fourth pipeline is the seventh
A pipeline switching mechanism that is connected through a pipeline and that selectively switches to a second switching position where the third pipeline and the sixth pipeline are connected through an eighth pipeline is provided. A filtration apparatus using the fibrous filter medium according to claim 5, characterized in that: