JP2002119807A - Method of back washing filter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To wash a cleaning layer in a desired degree by reducing the water quantity for back washing with back washing water after concurrent flow back washing. SOLUTION: Turbid matter is excellently and effectively stripped from a cleaning material by intermittently supplying back washing air in the concurrent flow back washing using the back washing water and a back washing gas in pulse state, cleaning the cleaning material with strong cleaning power to cause the collision effect of the cleaning material with each other in a period of supplying the back washing gas in pulse state. In a period of stopping the supply of the back washing gas in the pulse state, only the back washing water is supplied and in the meantime, the cleaning material floated by the combination back washing is precipitated to be separated by the difference of the specific gravity from the back washing water and the turbid substance stripped from the cleaning material is moved to the upper part of the cleaning treatment layer by the back washing water with the small difference of the specific gravity. The turbid substance is collected to the upper part without polluting the lower part and discharged easily outside a device by the back washing with the back washing water after the combination back washing by repeating a series of the excellent and effective stripping from the cleaning material and the movement to the upper part of the cleaning treatment layer with the pulse like intermittent supply of the back washing gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for back-washing a filtration device comprising a stack of purification materials.

[0002]

2. Description of the Related Art Conventionally, a filtering material such as sand or anthracite or an adsorbing material such as activated carbon has been provided as a purifying material. A filtration device for purifying the water to be treated is known. In this filtration device, the turbid matter of the water to be treated is captured so as to decrease exponentially along the moving direction of the water to be treated from the upper layer to the lower layer of the purification treatment layer. In this filtration device, in a state where the purification treatment is appropriately stopped, a cleaning fluid is caused to flow in a direction opposite to the moving direction of the water to be treated to wash the purification treatment layer and prevent the purification treatment layer from being blocked. Backwashing has been implemented.

[0003] Various methods are employed as this backwashing method. As a method having a high washing effect, a backwashing water and a backwashing air are used to carry out cocurrent backwashing (cowashing) on the purification treatment layer.
A backwashing method is known in which backwashing is performed with backwash water after the simultaneous washing.

[0004] More specifically, in this backwashing method, backwash water is supplied to such an extent that the purification treatment layer is slightly expanded so that the purification material forming the purification treatment layer can be developed. Supply the backwash air at the flow rate to perform the empty washing, remove the turbidity adhering to the purification material with strong washing power by this empty washing, and remove the separated turbidity by the backwash water after the simultaneous washing. This is a method that discharges easily out of the device by washing.

[0005]

Here, in the above method, since the empty washing has a strong detergency, at the time of simultaneous washing, the cleaning treatment layer is supplied together with the supply of the backwash water. The upper and lower layers are heavily mixed. When the upper layer and the lower layer of the purification treatment layer are greatly mixed in this way, the purification material of the upper layer is diffused into the lower layer, and the contamination of the lower layer is enlarged. In order to discharge the contamination that has spread to the lower layer to the outside through the upper layer by backwashing with backwash water that is performed after the co-washing and to clean the purification treatment layer to a desired degree, the backwashing after the co-washing is performed. Requires a large amount of water.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is intended to reduce the amount of backwash water by backwash water which is performed after cocurrent backwash with backwash water and backwash gas. It is an object of the present invention to provide a method for backwashing a filtration device for washing a purification treatment layer to a desired degree.

[0007]

Means for Solving the Problems The present inventors have examined the above-mentioned problems of the backwashing method of the filtration device and found that the effect of the backwashing gas in the cocurrent backwashing is as follows. After about several tens of seconds, the greatest effect was found, and thereafter, it was found that the effect of collision between the purifying materials for separating the suspended matter from the purifying material was reduced, and the cleaning effect was reduced.

Therefore, the backwashing method for a filtration device according to the present invention is a process for purifying the water to be treated by passing the water to be treated through a purification treatment layer formed by laminating purification materials for trapping turbid substances of the water to be treated. Backwashing the purification treatment layer of the filtration device,
In the backwash method in which the backwash water and backwash gas are applied to the purification treatment layer in parallel, the backwash gas in the cocurrent backwash is intermittently pulsed. It is characterized by supplying.

According to such a back washing method for a filtration device,
Since the backwash gas in the backwash water and the backwash gas in the cocurrent backwash is intermittently supplied in a pulsed manner, during the pulsed supply of the backwash gas, the purifying material is washed with strong cleaning power and the purifying materials are separated from each other. The turbid matter is effectively and effectively separated from the purifying material by the collision effect, and when the backwash gas is in a pulse stop period, only the backwash water is supplied. During this time, the purifying material floating in the cocurrent backwash is removed. The turbidity separated from the backwashing water due to the specific gravity difference, while the turbidity separated from the purification material moves to the upper part of the purification treatment layer by the backwashing water because the specific gravity difference is small, and the turbidity from this series of purification material And effective removal of turbidity and transfer of suspended matter to the upper part of the purification treatment layer are repeated in accordance with the pulsed intermittent supply of the backwash gas. Therefore, the turbid matter is collected at the upper portion without contaminating the lower portion, and is easily discharged out of the apparatus by backwashing with backwash water after co-current backwashing.

Here, the pulse-like supply period of the backwash gas is preferably set to 10 to 30 seconds.

This is because if the pulsed supply period of the backwash gas exceeds 30 seconds, the upper layer and the lower layer of the purification treatment layer are mixed greatly, and the contamination of the lower layer is enlarged, and the backwash water after the cocurrent backwash is used. This is because a large amount of water is required for washing, and the purifying materials are fluidized with each other, and the collision effect is reduced and the cleaning effect is reduced. On the other hand, if the cleaning time is less than 10 seconds, the removal of the turbidity from the purifying material is insufficient. Because it becomes.

Further, the pulse-like stop period of the backwash gas is as follows:
If it is set longer than the time required for sedimentation of the purification material that floated by the cocurrent backwashing to the backwash water, sedimentation of the purification material to the backwash water will be sufficient, and contamination of the lower part of the purification treatment layer will occur. Is further prevented.

[0013] Specifically, when the backwash gas is in a pulse-like stop period, the expansion rate of the purification layer is 5 (by supplying only backwash water).
%, The sedimentation and separation of the purification material with respect to the backwash water is sufficiently performed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a method for backwashing a filtration device according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram showing a filtration device employing a backwash method according to the present invention.

As shown in FIG. 1, the filtration device 1 has a filtration tank 2 for accommodating a purifying material. The filtration tank 2 is divided into an upper space and a lower space by a partition plate 3, and a plurality of water collecting nozzles 4 that communicate the upper space and the lower space penetrate the partition plate 3. A treated water supply line L1 for supplying treated water (for example, sewage secondary treated water) is connected to the upper space, and a backwash drainage line L6 for discharging backwash wastewater during backwash to the outside. Is connected to trough 5
Are installed. The trough 5 enables the supply of the to-be-processed water into the filtration tank 2 when the to-be-processed water flows in, while the back-washing drainage at the time of the back-washing flows in when the to-be-processed water flows into the outside. Is possible.

On the partition plate 3 and below the trough 5, a purification treatment layer 6 formed by laminating purification materials is provided. As this purifying material, for example, a filtering material such as sand or anthracite or an adsorbing material such as activated carbon is adopted, and the purifying treatment layer 6 is formed by spreading and laminating the filtering material and the adsorbent. The purification treatment tank 6 purifies the treatment water by passing the treatment water.

The lower space is connected to a filtered water discharge line L2 for discharging filtered water that has been purified by the purification treatment layer 6 and flows down through the centralized nozzle 4. In addition, an air blower 7 is connected to the lower space via an air supply line L3 for air diffusion. The air blower 7 supplies air to the purification processing layer 6 through the air supply line L3 for diffusion, the lower space, and the centralized nozzle 4, and diffuses the purification processing layer 6.

Further, a backwash water source 8 is connected to the lower space via a backwash water supply line L4, and a backwash blower 9 is connected via a backwash air supply line L5. A backwash pump 10 is interposed in the backwash water supply line L4, and by driving the backwash pump 10, water (backwash water) from the backwash water source 8 is supplied to the backwash water supply line L4. The water is supplied to the purification treatment layer 6 through the space and the centralized nozzle 4, and the purification treatment layer 6 is backwashed with water. Also, the backwashing blower 9
Air (backwash air) is supplied to the purification treatment layer 6 through the backwash air supply line L5, the lower space, and the centralized nozzle 4, and the purification treatment layer 6 is backwashed with air.

In the filtration apparatus 1, at the time of backwashing, cocurrent backwashing using both water backwashing and air backwashing is performed, and after this cocurrent backwashing, water backwashing is performed. In cocurrent backwash, backwash blower 9
And the backwashing pump 10 is simultaneously driven. In particular, in the cocurrent backwashing of the present embodiment, the backwashing blower 9 is intermittently driven in a pulsed manner, and the backwashing air is intermittently supplied in a pulsed manner. Backwashing) is performed simultaneously with continuous water backwashing driven by the backwash pump 10 (to be described in detail later).
Further, in the water backwashing after the cocurrent backwashing, the continuous backwashing is performed by driving the backwashing pump 10 alone.

According to such a filtration device 1, at the time of filtration, the treated water supply line L1, the filtered water discharge line L2,
The air supply line L3 for aeration is opened, and the backwash water supply line L4, the backwash air supply line L5, and the backwash drainage line L6 are closed. In this state, the air blower 7 is driven to supply air to the purification treatment layer 6, and the purification treatment layer 6 is diffused to provide a biodegradation function.
The water to be treated is supplied into the filtration tank 2. This treated water is
The suspended matter is captured by the purification treatment layer 6 as it flows down, and the soluble organic matter is oxidized and decomposed. This suspended matter is trapped so as to decrease exponentially from the upper layer to the lower layer of the purification treatment layer 6, and the filtered water is discharged to the outside via the centralized nozzle 4, the lower space, and the filtered water discharge line L2. .

Here, at a predetermined time, back washing is performed to wash the purification treatment layer 6. During this backwash,
First, the water supply line L1 for treatment and the air supply line L3 for air diffusion are closed from open and the blower 7 for air diffusion is stopped, and the water in the filtration tank 2 is discharged to the outside via the filtration water discharge line L2. Draining is performed.

Next, the filtered water discharge line L2 is changed from open to closed, and the backwash water supply line L4, the backwash air supply line L5, and the backwash drainage line L6 are changed from closed to open.
In this state, the backwashing pump 10 is continuously driven, and the backwashing blower 9 is intermittently driven in a pulsed manner.
On the other hand, cocurrent backwashing using both water backwashing and pulse air backwashing is performed.

In this embodiment, as shown in FIG. 2, cocurrent backwashing is performed for 3 minutes with a water backwashing intensity of 12 m / hour and a pulse air backwashing intensity of 24 m / hour. In the air backwashing, the backwash air is intermittently supplied (on) / stopped (off) every 20 seconds.

Since the backwash air is thus intermittently supplied in a pulsed manner, the purifying material is washed with a strong detergency during the pulsed supply period of the backwash air, and the purifying material is collided with the purifying material by an effect of collision between the purifying materials. When the suspended matter is successfully and effectively peeled off and the backwash air is in a pulse-stop period, only the backwash water is supplied. During this time, the purification material floating in the co-current backwash is converted into the backwash water by a difference in specific gravity. On the other hand, the turbid matter separated from the purifying material by sedimentation is moved to the upper part of the purifying treatment layer 6 by the backwashing water because the difference in specific gravity is small. The separation and the movement of the suspended matter to the upper part of the purification treatment layer 6 are repeated according to the pulsed intermittent supply of the backwash air. Therefore, the turbid matter is collected at the upper part without contaminating the lower part.

Here, the pulse-like supply period of the backwash air is preferably set to 10 to 30 seconds (20 seconds in this embodiment) as in this embodiment. this is,
If the pulsed supply period of backwash air exceeds 30 seconds,
The upper layer and the lower layer of the purification treatment layer 6 are greatly mixed, and the contamination of the lower layer is enlarged, so that a large amount of backwash water is required by the backwash water after the cocurrent backwash described later, and the purifying materials are fluidized to reduce the collision effect. On the other hand, the cleaning effect is reduced.
If the time is less than 0 second, the turbidity is not sufficiently separated from the purifying material.

Then, when the backwashing blower 9 is stopped and the cocurrent backwashing is completed, water backwashing in which the backwash pump 10 is continuously driven independently is performed. In the present embodiment, FIG.
As shown in Fig. 8, the backwashing was performed for 10 minutes with the intensity of water backwashing at 54 m / hour.

In this water backwashing, the turbid matter collected on the upper part of the purification treatment layer 6 by the cocurrent backwashing is easily discharged outside the apparatus together with the backwashing drainage through the trough 5 and the backwashing drainage line L6. Is done.

As described above, in this embodiment, the pulsed air backwash is carried out in the cocurrent backwash with the water backwash, so that the turbid material can be effectively and effectively separated from the purifying material, and the turbid material can be purified. The movement to the upper part of the treatment layer 6 is repeated according to the pulsed intermittent supply of the backwashing air, and the suspended matter is collected at the upper part without contaminating the lower part of the purification treatment layer 6, and the water is backwashed after the cocurrent backwashing. And is easily discharged out of the device. Therefore, it is possible to reduce the amount of water in the water backwashing after the cocurrent backwashing and to wash the purification treatment layer 6 to a desired degree.

In this embodiment, the pulse-like stop period of the backwash air is set to 20 seconds. However, the period differs depending on the backwash water amount, the diameter of the purifying material, the specific gravity of the purifying material, etc. in the co-current backwashing. In other words, it is only necessary that the time is set to be equal to or longer than the time required for the cleaning material floated by the cocurrent backwash to settle and separate from the backwash water in the cocurrent backwash. As a result, sedimentation and separation of the cleaning material in the backwash water in the cocurrent backwashing is sufficiently performed, and contamination of the lower part of the purification treatment layer 6 is further prevented. Specifically, if the pulse-like stop period of the backwashing air is set to be equal to or longer than the time when the expansion rate of the purification treatment layer 6 becomes 5% or less (by supplying only the backwash water), the backwashing of the purification material is performed. The sedimentation separation for water is sufficiently achieved.

Hereinafter, in order to confirm the effects of the above embodiment,
Examples 1 and 2 and Comparative Examples 1 and 2 performed by the inventor will be described.

(Examples 1 and 2) Using a filtration device for filtering treated water obtained by mixing river water with PAC (polyaluminum chloride: inorganic flocculant) and subjecting it to coagulation and sedimentation, Cocurrent backwashing of water backwashing and pulse air backwashing was performed, and then water backwashing was performed. Activated carbon having an effective diameter of 1.2 mm and a uniformity coefficient of 1.3 was used for the purification treatment layer. The area of the purification treatment layer was 0.64 m ² , and the layer thickness was 20.
00 mm. The strength of the pulse air backwash in the cocurrent backwash is 24 m / hour, the strength of the water backwash in the cocurrent backwash is 18 m / hour, and the backwash air is supplied every 20 seconds in the pulse air backwash.
As an intermittent supply to stop, the cocurrent backwash of the pulse air backwash and water backwash was performed for 3 minutes. Water backwashing after the cocurrent backwashing was carried out for 15 minutes at an intensity of 54 m / hour and an expansion rate of the purification treatment layer of 35%, and the time-dependent change in backwash wastewater turbidity at this time was examined. The experiment was performed in two parts, each of which was referred to as Example 1 or Example 2.

(Comparative Examples 1 and 2) The procedure was the same as in Examples 1 and 2, except that backwash air was continuously supplied for 3 minutes in co-current backwashing. The experiment was performed in two parts, each of which was Comparative Example 1 and Comparative Example 2.

The results are shown in Table 1 below.

[0034]

[Table 1]

As shown in Table 1, for example, the turbidity of 1.5 mg / L, which is required in the market, was achieved in Examples 1 and 2 in 10 minutes from the start of water backwashing after cocurrent backwashing. On the other hand, in Comparative Examples 1 and 2, the amount of backwash water after co-current backwashing required to wash the purification treatment layer to a desired degree cannot be achieved even in 15 minutes. Is better in Comparative Example 1,
It can be seen that the number is smaller than that of 2.

Further, the present inventors confirmed the effect of setting the pulse-like supply period of the backwash air to 10 to 30 seconds in the following Example 3.

Example 3 Kaolin 20 mg / L, PA
Raw water (treated water) adjusted at 7.5 mg / L C
Using a filtration device that was filtered at a filtration speed of 0 m / day for 15 hours, the filtration device was subjected to cocurrent backwashing of water backwashing and pulse air backwashing, and then water backwashing. . For the purification layer, sand with an effective diameter of 0.6 mm was used. The strength of pulse air backwash in cocurrent backwash was 50 m / h, and the strength of water backwash in cocurrent backwash was 25 m / hour. Cocurrent backwashing was performed for 4 minutes with the pulsed supply period of air as a variable. Water backwashing after co-current backwashing is performed with the strength of 50 m / hour and 1
It was carried out for 0 minutes, and the turbidity of the backwash wastewater after 10 minutes was examined. FIG. 3 shows the relationship between the backwash drainage turbidity and the pulsed supply period of the backwash air in the cocurrent backwash. As shown in FIG.
It can be seen that the backwash drainage turbidity is reduced to less than about 1.5 mg / L by setting the pulsed supply period of the backwash air to 10 to 30 seconds. Therefore, if the pulse-like supply period of the backwash air is set to 10 to 30 seconds, the amount of backwash water after co-current backwash necessary for washing the purification treatment layer to a desired degree can be reduced.

As described above, the present invention has been specifically described based on the embodiment. However, the present invention is not limited to the above embodiment. For example, in the above embodiment, the backwash air in the cocurrent backwash is used. Are set to the same time (all the same in 20 seconds in the embodiment), but may be set to different times. Similarly, the pulse-like stop period of the backwash air may be different from the same period (20 seconds in the embodiment, all the same). In addition, the start and end of pulse air backwash in cocurrent backwash are the same as the start and end of water backwash in cocurrent backwash.
It does not necessarily have to be synchronized with the end.

Further, the backwash gas intermittently supplied in the form of pulses in the cocurrent backwash is not limited to air.

[0040]

The method for backwashing a filtration device according to the present invention comprises intermittently supplying backwash gas in a cocurrent backwash with backwash water and backwash gas in a pulsed manner. The purifying material is washed with a strong cleaning power to turbidly separate the purifying material satisfactorily and effectively due to the collision effect between the purifying materials. When the backwash gas is in a pulse stop period, only the backwash water is supplied. hand,
During this time, the purification material suspended in the co-current backwash is settled and separated from the backwash water by the difference in specific gravity, while the turbidity separated from the purification material has a small difference in specific gravity. The turbidity is removed from the purifying material in a series of good and effective separation, and the turbidity is moved to the upper part of the purification treatment layer in accordance with the pulsed intermittent supply of the backwash gas. It is collected at the top without contaminating and is easily discharged outside the equipment by backwashing with backwash water after cocurrent backwashing, so the amount of backwash water by backwash water after cocurrent backwashing And it is possible to clean the purification treatment layer to a desired degree.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a filtration device employing a backwashing method according to the present invention.

FIG. 2 is a process explanatory view specifically showing a backwashing method according to the present invention.

FIG. 3 is a diagram showing the relationship between the pulsed supply period of backwash air supplied by the backwash method according to the present invention and the backwash wastewater turbidity.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Filtration apparatus, 6 ... Purification processing layer (purification material lamination), 8 ... Backwash water source, 9 ... Backwash blower, 10 ... Backwash pump, L1
… Treated water supply line, L4… backwash water supply line, L5
... Backwash air supply line, L6 ... Backwash drain line.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Keizo Murata F-term (reference) 4D041 BA01 BB03 BB04 BC03 BC12 within 5-9-1, Kita-Shinagawa, Shinagawa-ku, Tokyo

Claims (4)

[Claims] 1. A purifying treatment layer of a filtration device for purifying a treated water by passing the treated water through a purifying treatment layer formed by laminating a purifying material for trapping a turbid substance of the treated water. A backwashing method for performing backwashing with backwash water and backwashing gas with respect to the purification treatment layer, and then performing backwashing with backwash water. A method for backwashing a filtration device, comprising intermittently supplying a backwash gas in a pulsed manner. 2. The method according to claim 1, wherein the pulsed supply period of the backwash gas is set to 10 to 30 seconds. 3. The pulse-like stop period of the backwash gas is set to be equal to or longer than a time required for the cleaning material floated by the co-current backwash to settle and separate from the backwash water. The method for backwashing a filtration device according to claim 1 or 2, 4. The method according to claim 1, wherein the pulse-shaped stop period of the backwash gas is set to a time period at which an expansion rate of the purification treatment layer becomes 5% or less. The method for backwashing a filtration device according to claim 1.