JP3122024B2 - Cleaning apparatus and method for downflow type multilayer filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a downflow type multilayer filter, and more particularly to a cleaning apparatus and a method therefor.

[0002]

2. Description of the Related Art As a conventional downward-flow type multilayer filter, FIG.
The following are known.

In FIG. 2, an upper filter medium layer 2 and a lower filter medium layer 3 are provided in a filter 1. As the granular filter medium forming the upper filter medium layer 2 and the lower filter medium layer 3, the former is larger in particle diameter than the latter, and the former is smaller than the latter in specific gravity. An intermediate drain valve 4 is provided on the side wall of the filter 1, and by opening this valve, the raw water in the filter 1 can be drained. The filter 1 has a drainage trough 5 above the intermediate drain valve 4.
Is provided, and when the raw water reaches the level of the trough 5 or more at the time of washing, it can be drained to the outside. A raw water inflow pipe 6 is provided above the filter 1.

At the lower part of the filter 1, an outflow pipe 7 for treated water is provided.
Are connected, and face the storage tank 8 of the treated water disposed above the upper filter medium layer 2. The storage tank 8
It is connected to the bottom of the filter 1 by a return pipe 11 via a pump 9 and a valve 10. Further, a cleaning air supply pipe 12 for supplying cleaning air at the time of cleaning the filter 1 is connected to the bottom of the filter 1 via a valve (not shown).

According to the filter 1, raw water is supplied into the filter 1 from above by the raw water inflow pipe 6, and is filtered by passing through the upper filter medium layer 2 and the lower filter medium layer 3 to become clean treated water, and is discharged. It is led to the storage tank 8 through the pipe 7 and stored there.

However, with the filtration of raw water, the turbidity retention in the filter media layers 2 and 3 increases, and the water level rises due to an increase in the loss head, or the turbidity retained in the filter media exceeds the limit retention volume. As a result, suspended matter from the filter medium layer leaks and mixes into the treated water. In such a case, it is necessary to perform a washing operation of the filter medium layer.

For washing, the treated water in the storage tank 8 is returned to the lower part of the filter 1 by a pump 9 via a valve 10 to allow the filter media layers 2 and 3 to permeate.
Is discharged to the outside of the filter 1 through an intermediate drain valve 4 disposed above the surface layer of the above and a drainage trough 5 disposed above the intermediate drain valve 4.

The washing operation will be described in more detail step by step as follows.

[0009] The supply of raw water is stopped, and the water level in the filter 1 is lowered.

[0010] The intermediate drainage valve 4 provided above the surface layer of the upper filter medium layer 2 is opened, water is drained until the water level reaches the level of the intermediate drainage valve 4, and then the intermediate drainage valve 4 is closed. .

[0011] Cleaning air is introduced into the filter 1 from the cleaning air supply pipe 12 to remove turbidity adhering to the surface of the filter medium.

The filter medium is washed with air and treated water by opening the valve 10 and supplying the treated water in the storage tank 8 to the lower part of the filter 1 by the pump 9.

After the water level in the filter 1 reaches a level near the lower part of the trough 5, the supply of the cleaning air is stopped,
By continuing the supply of treated water for an appropriate period of time,
The suspended matter is discharged from the trough 5 to the outside of the system.

After allowing the upper filter medium layer 2 to settle, the intermediate drain valve 4 is opened, and water is drained until the water level of the filter 1 reaches the level of the intermediate drain valve 4. Close 4. Thus, the washing of the filter medium in the filter 1 is completed.

[0015]

In the case of a coarse filter medium in which the effective diameter of the filter medium in the filter is, for example, 1 mm or more, the turbidity retained in the filter medium layer even before the water level reaches the drainage trough. The quality of the treated water may increase due to the separation of the quality and the turbidity leaking into the treated water. Therefore, if the turbidity begins to leak even before the water level reaches the trough, it is necessary to perform the washing operation. Therefore, in order to keep the turbidity of the treated water below a certain value, even if the head loss is small, the above-mentioned backwashing operation must be performed every time the turbid substance leaks, and the frequency of such washing increases. As a result, the treated water is used each time the backwashing is performed, so that the water recovery rate (the treated water amount / the amount of the passed raw water) decreases.

The present invention has been made in order to solve the above-mentioned problems. Although the head loss is small, the downward operation using only a small amount of treated water in the washing operation when the turbidity leaks is performed. An object of the present invention is to provide a washing method in a flow-type multilayer filter and a filter suitable for the method.

[0017]

Means for Solving the Problems An upper filter medium layer and a lower filter medium layer are provided in a filter forming a tank. Both the upper filter medium layer and the lower filter medium layer are made of a granular filter medium, and in the filter medium, the former is larger in particle diameter than the latter, and the former is smaller than the latter in specific gravity. An outlet pipe for sending the filtered treated water to the storage tank is connected to a lower portion of the filter, and a cleaning air supply pipe and a treated water reverse flow pipe from the storage tank are connected via valves, respectively. I have. An intermediate drain valve is provided on the side wall of the filter.

In this filter, in the present invention, the intermediate drain valve is located in the height direction in the range of the upper filter medium layer, and the intermediate drain valve is provided with a screen member. The screen member has an opening smaller than the particle size of the filter medium in the upper filter medium layer.

Further, in the present invention, as a preferable mode,
The drainage trough provided above the upper filter medium layer in the filter also has a screen member with openings smaller than the particle size of the filter medium in the upper filter medium layer.

In the present invention, when the turbid leak occurs and the simple cleaning is performed, the upper and lower filter medium layers are cleaned in the following manner.

The supply of raw water to the filter is stopped.

The washing air is supplied from the washing air supply pipe to the filter.

After the intermediate drain valve is opened and the water is drained until the water level reaches the level of the intermediate drain valve, the supply of the cleaning air is stopped and the intermediate drain valve is closed.

When washing is performed in such a procedure, the filter medium in the upper filter medium layer is fluidized by air cleaning, and the turbidity retained in the filter medium is peeled off, near the interface between the upper filter medium layer and the lower filter medium layer, and At least a part of the suspended matter retained in the gap of the lower filter medium layer is also wound up by the bubble flow,
Such suspended matter is discharged through an intermediate drain valve. At this time, since the aperture of the screen member provided in the intermediate drain valve is smaller than the particle size of the filter medium in the upper filter medium layer, only the turbid matter is discharged from the intermediate drain valve and the filter medium remains in the filter. .

In the case where the suspended matter is discharged from the trough for normal washing, the treated water is caused to flow backward through the backflow pipe to raise the water level in the filter, and the suspended matter is discharged from the intermediate drain valve. It is discharged as well as from the trough. At that time, since the trough is provided with a screen member having openings smaller than the particle size of the filter medium of the upper filter medium layer,
Only suspended matter is drained.

Since the filter medium of the lower filter medium layer has a smaller particle size and a higher specific gravity than the filter medium of the upper filter medium layer, the filter medium does not go above the upper filter medium layer, and may flow out from the intermediate drain valve or trough. There is no.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, the same parts as those of the conventional device shown in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

In the embodiment of the present invention shown in FIG. 1, the intermediate drainage valve 21 is provided in the area of the upper filter medium layer 2 in the height direction. The intermediate drain valve 21 is provided with a screen member 21A having openings smaller than the particle size of the filter medium of the upper filter medium layer 2.

The drainage trough 22 disposed above the upper filter medium layer 2 is also provided with a screen member 22A having openings smaller than the particle size of the filter medium of the upper filter medium layer 2.

In such an apparatus, when a turbid leak occurs, simple cleaning is performed. The procedure is as follows.

First, supply of raw water from the raw water inflow pipe 6 is stopped.

The valve is opened to supply the cleaning air from the cleaning air supply pipe 12 to the filter 1. The air flow rate at this time is preferably such that only the upper filter medium layer 2 flows without the lower filter medium layer 3 flowing. By the air washing, the upper filter medium layer 2 is fluidized, and the suspended matter retained in the filter medium is removed. Further, at least a part of the turbid matter retained near the interface between the upper filter medium layer 2 and the lower filter medium layer 3 and in the gap between the lower filter medium layers 3 is combined with the turbid matter separated from the upper filter medium layer 2 in bubble flow. Rolled up by

Next, the intermediate drain valve 21 is opened, water is drained until the water level in the filter 1 reaches the level of the intermediate drain valve 21, and then the supply of cleaning air is stopped. Water valve 21
Close. At that time, the filter medium of the upper filter medium layer 2 is prevented from flowing out by the screen member, and only the suspended matter is drained.

Further, in the case of performing a normal washing, while supplying the air for washing, the check valve is opened and the treated water is caused to flow back from the storage tank 8 to the filter 1 to raise the water level to the level of the trough 22. The suspended matter is discharged from the intermediate drain valve 21 and also discharged from the trough 22.

Since the trough 22 is provided with a screen member 22A having openings smaller than the particle size of the filter medium of the upper filter medium layer 2, only the turbid matter is drained and the filter medium does not flow.

[0036]

EXAMPLE In a water purification plant, water obtained by injecting 20 mg / liter of a flocculant (sulfuric acid band) into raw water having a turbidity of about 300 ° C. using a filter 1 shown in FIG.
Filtered directly on day. Raw water is supplied from above the filter 1 by a raw water inflow pipe 6 and is filled with an upper filter medium layer 2 (specific gravity 1.1, hollow type plastic having a diameter of 4 mm and a length of 5 mm) and a layer thickness of 1.5 m and a layer thickness. The water is filtered by passing through the lower filter medium layer 3 (spherical ceramic having a specific gravity of 2.6 and a diameter of 2.0 mm) filled with 0.5 m and becomes treated water, and is guided to a storage tank 8 through an outflow pipe 7 of treated water. Was.

In the washing, the treated water in the storage tank 8 flows backward from the lower part of the filter through the valve 10 by the pump 9 (or due to a difference in water level), and the washing wastewater flows into the upper filter medium layer 2 and the lower filter medium layer 3. Intermediate drain valve 21 having a screen member arranged within 50 cm from the interface with the upper surface to prevent the filter medium from flowing out with openings smaller than the particle size of the upper filter medium layer 2.
The filter 1 is provided through a drainage trough 22 having a screen member for preventing the filter medium from flowing out with openings smaller than the particle diameter of the filter medium of the upper filter medium layer 2 disposed above the intermediate drain valve 21. It was set so that it could be discharged outside.

When a turbid leak occurred, the following simple cleaning was performed.

The supply of raw water is stopped.

Washing air was blown into the filter 1 at an air speed of 1.0 m / min for about 5 minutes.

The intermediate drain valve 21 was opened, water was drained until the water level reached the level of the intermediate drain valve 21, the cleaning air was stopped, and the intermediate drain valve 21 was closed.

When the simple cleaning was performed, the results shown in Table 1 were obtained, and the following was found. (I) By the simple washing operation, the leakage of the turbidity due to the removal of the turbidity retained in the filter medium layer was able to reduce the turbidity of the treated water from 77 degrees to 18 degrees. (Ii) If you want to operate the treated water turbidity below 80 degrees,
The washing operation needs to be performed once every 5 hours. in this case,
When the normal washing operation is performed, the water recovery rate is about 86% (when the normal washing operation is performed once a day, the water recovery rate is about 97%). On the other hand, if the simple washing for stopping the turbidity leak is performed four times a day and the normal washing operation for recovering the head loss is performed once a day, the water recovery rate is about 97%. Becomes

[0043]

[Table 1] Simple cleaning experiment results

[0044]

As described above, according to the method of the present invention, in the downflow type multilayer filter, the intermediate drain valve having the screen member for preventing the outflow of the filter medium is provided within the range of the upper filter medium layer. Therefore, the turbid leak can be stopped by the simple washing without using the treated water, and the effect of improving the water recovery rate can be obtained. Further, according to the apparatus of the present invention, the above method can be easily performed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a conventional device.

[Description of Signs] 1 Filter 2 Upper filter layer 3 Lower filter layer 8 Reservoir 10 Valve 11 Backflow pipe 12 Cleaning air supply pipe 21 Intermediate drainage valve 21A Screen member 22 Trough 22A Screen member

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI B01D 29/38 510B 520C (72) Inventor Kenichiro Mizuno 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Tsuji Takeshi 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Takao Shuto 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Mitsuaki Nuno Osaka, Osaka, Japan 1-47 Shishitsu Higashi-chome, Naniwa-ku, Ichibu-ku Kubota Co., Ltd. (72) Inventor Hideki Mizusawa 1-4-1, Muroya, Nishi-ku, Kobe-shi, Hyogo (56) References JP-A-58-153510 (JP, A) (Japanese) Sho 55-58412 (JP, U) Japanese Patent Publication No. 45-5718 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01D 24/10-24/14 B01D 24 / 20-24/24 B01D 24/46

Claims (4)

(57) [Claims] 1. An upper filter medium layer and a lower filter medium layer are disposed in a filter, and a cleaning air supply pipe and a backflow pipe for flowing treated water back from a storage tank are connected to the lower part of the filter through valves. Further, in the filter provided with an intermediate drain valve on the side wall of the filter, the intermediate drain valve is located in the range of the upper filter medium layer in the height direction, and the intermediate drain valve is provided with the upper filter medium. A cleaning device for a downward-flow type multilayer filter, comprising a screen member for preventing a filter medium from flowing out with an opening smaller than the particle diameter of the filter medium in the layer. 2. A drainage trough is provided in the filter at a position above the upper filter medium layer, and a screen for preventing the filter medium from flowing out is provided on the trough and having a size smaller than the particle diameter of the filter medium in the upper filter medium layer. The washing apparatus according to claim 1, wherein a member is provided. 3. A method for cleaning a downflow type multilayer filter using the cleaning apparatus according to claim 1, comprising the following steps: . (1) A step of stopping supply of raw water to the filter. (2) a step of supplying cleaning air from the cleaning air supply pipe to the filter; (3) Opening the intermediate drain valve, draining water until the water level reaches the level of the intermediate drain valve, stopping the supply of cleaning air, and closing the intermediate drain valve. 4. The supply of the cleaning air from the cleaning air supply pipe into the filter is performed at an air flow rate such that the lower filter medium layer does not flow and only the upper filter medium layer flows. The method for cleaning a downflow type multilayer filter according to claim 3.