JPH0639211A - Method and device for backwashing filter - Google Patents

Abstract

PURPOSE:To backwash a porous filter low in permeability with water in the amt. equivalent to that used in an ordinary filter. CONSTITUTION:When a deposited film is formed on the porous body, valves 24 and 25 are opened, a pump 4 is driven to supply cleaning water on the downstream side of the porous body 1 of a vessel 2, and the air remaining in the vessel 2 is discharged from a pipeline 15 by the cleaning water. A valve 22 is then opened, the water in the vessel 2 is pressurized with the compressed air in an air tank 3, and then a valve 23 is opened. Consequently, pressure is uniformly exerted over the entire porous body 1, and the layer of the deposited suspended-matter is comletely peeled off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backwashing method and a filtration apparatus for a waste liquid filter, and more particularly to a backwashing method and apparatus suitable for a filtration apparatus using a porous material having a low permeation resistance as a filter medium.

[0002]

2. Description of the Related Art Various filtration devices are used for waste liquid treatment. In the filtration device, the solid content in the waste liquid is accumulated in the filtration device while the treatment is continued, it becomes difficult for the water to be treated to permeate, the differential pressure increases, and the operating efficiency decreases. Therefore, backwashing is performed to remove the solid content accumulated in the filtration device, and the filtration device is regenerated. Japanese Examined Patent Publication No. 55-56812 describes a backwashing method for a precoat type filter. According to this, the backwashing method is roughly classified into two methods, that is, a normal pressure backwashing method and a pressure backwashing method. These two methods will be described in detail with reference to FIG. In FIG. 3, 1 is a porous material which is a filter medium, 2 is a container, 10 is treated water piping, 11 is treated water piping, 12 is pressurized air supply piping, 13 is discharge piping, and 20-23 are valves.

1. Normal pressure backwash method During operation, the valves 22 and 23 are closed and the valve 20 and
21 is open. The treated water passes through the treated water pipe 10,
It is introduced into the container 2 and permeates the porous body 1. Here, the suspended substance in the water to be treated is removed by the porous body 1. After this, the water to be treated becomes treated water and is sent to the subsequent stage through the treated water pipe 11. When the treatment is continued, suspended substances in the water to be treated accumulate on the porous body 1 and the permeation resistance increases,
The differential pressure (pressure difference before and after the porous body 1) increases. When the predetermined differential pressure is reached, the valves 20 and 21 are closed to remove the solid content accumulated in the filtration device.

In the atmospheric backwash, first, the valve 23 is opened and the water in the container is discharged through the discharge pipe 13. Thereafter, while the valve 23 remains open, the valve 22 is opened and pressurized air is sent from the pressurized air supply pipe 12 to separate the suspended substance on the porous body 1 and discharge it from the discharge pipe 13.

High-pressure water may be used instead of the pressurized air.

2. Pressurized backwashing method In the pressurized backwashing method, the valves 20 and 21 are closed at the time when a predetermined differential pressure is reached, and the solid content accumulated in the filtration device is removed, as in the normal pressure backwashing.

In the backwashing operation, the valve 23 is opened and a part of the water in the container is discharged through the discharge pipe 13. After this,
The valve 23 is closed, then the valve 22 is opened, pressurized air is sent from the pressurized air supply pipe 12, and the suspended substance on the porous body 1 is separated. When the pressure in the container 2 reaches a predetermined pressure, the valve 22 is closed and the valve 23 is opened again, and the suspended substance is discharged by the air pressure in the container 2.

This method is characterized in that the amount of pressurized air required for backwashing is smaller than that in the atmospheric backwashing method.

[0009]

The above-mentioned prior art is intended for an ordinary filter (permeation resistance of about 10 MPa / (m / s)), and the permeation resistance aimed at by the present invention is
It is not intended for a porous filter having a small size of preferably about 0.1 to 1 MPa (m / s). Therefore, it was clarified by the inventors' experiments that the conventional technique is not suitable for backwashing a porous filter having a small permeation resistance.

That is, in the method of allowing water or air to permeate through the porous body in the backwashing, when a part of the layer of the suspended substance deposited on the porous body is peeled off, the permeation resistance of the part is remarkably reduced. Water and air permeate only from the separated parts. Therefore, with the flow rate of water or air under the backwashing conditions for ordinary porous materials, the pressure required for peeling the layer of suspended matter in other parts cannot be obtained, so backwashing of porous filters with low permeation resistance is not possible. I can't. Therefore, there is a problem that a large amount of water or air is required to backwash the porous filter having a low permeation resistance, that is, to obtain the pressure required for separating the layer of the suspended substance.

The present invention is to provide a backwashing method and apparatus for regenerating a porous filter having a small permeation resistance based on a new finding.

[0012]

In order to achieve the above object, the solution means according to the present invention is a backwashing method for a filtration device comprising a porous body having a low permeation resistance and a container for storing the porous body. The backwashing method includes at least the step of stopping the passage of water to be treated, the step of removing the gas in the container on the upstream side of the porous body, the step of pressurizing the water in the vessel, and the discharge of the pressurized water from the upstream side of the porous body. It consists of a process and.

[0013]

According to the solution of the present invention, the entire container for storing the porous body is filled with water to increase the pressure, and then the pressure on the upstream side of the porous body is released so that the pressure is uniformly applied to the entire porous body. Is applied, and the air on the upstream side of the porous body, which softens the pressure change, is removed in advance, so that the pressure on the upstream side of the porous body can be released in a short time. As a result, it is possible to evenly separate the deposited layer of suspended matter.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described in detail below with reference to the drawings.

A flow chart of a processing apparatus according to a preferred embodiment of the present invention is shown in FIG. In FIG. 1, 1 is a porous material which is a filter medium, 2 is a container, 3 is an air tank, 4 is a pump, 5 is a controller, 10
Is a treated water pipe, 11 is a treated water pipe, 12 is a pressurized air supply pipe, 13 is a discharge pipe, 14 is a wash water supply pipe, 15
Is an air exhaust pipe, and 20 to 26 are valves. here,
The porous body 1 is installed in the container 2. Further, assuming that the inflow side of the treated water is the upstream side, the treated water pipe 10 has the valve 20.
To the upstream side of the porous body 1 of the container 2 through the treated water pipe 11
Is connected to the downstream side of the porous body 1 of the container 2 via the valve 21, and the pressurized air supply pipe 12 is connected to the air tank 3 via the valve 26.
In addition, the air tank 3 is provided downstream of the porous body 1 of the container 2 via the valve 22, the discharge pipe 13 is provided at the lowermost portion of the container 2 upstream of the porous body 1 via the valve 23, and the cleaning water supply pipe 14 is provided.
Is on the downstream side of the porous body 1 of the container 2 via the pump 4 and the valve 24, and the air discharge pipe 15 is on the downstream side of the container 2 via the valve 25.
Are connected to the uppermost upstream side of the porous body 1. Furthermore, the valves 20 to 25 and the pump 4 are electrically connected to the controller 5.

In the operation during the wastewater treatment, the valves 22 to 26 are closed and the valves 20 and 21 are opened by the signal from the controller 5. The water to be treated passes through the water to be treated pipe 10 and the container 2
It is guided inside and permeates through the porous body 1. Here, the suspended substance in the water to be treated is removed by the porous filter 1. After this, the water to be treated becomes treated water and is sent to the subsequent stage through the treated water pipe 11. When the treatment is continued, the suspended substance in the water to be treated accumulates on the porous body 1 to form a layer, so that the permeation resistance increases and the differential pressure (pressure difference before and after the porous body 1) increases. A differential pressure gauge (not shown) detects that a predetermined differential pressure has been reached, and a signal from the controller 5 causes the valve 2
0 and 21 are closed, and the following backwashing operation for removing the layer of suspended matter accumulated in the porous body 1 is performed.

In the backwashing operation, first, the valves 24 and 25 are opened by a signal from the controller 5 and the pump 4 is driven by a signal from the controller 5, so that the washing water flows to the downstream side of the porous body of the container 2. Supplied. The air remaining in the container 2 is discharged from the air discharge pipe 15. Detection of air discharge completion,
Alternatively, the water passage time is detected by a timer, a signal is sent from the controller 5, the valves 24 and 25 are closed, and at the same time, the pump 4 is stopped and the air discharging operation in the container is completed. During this time, if the valve 26 is opened, the air tank 3
Pressurized air is supplied to. After the air discharge operation in the container, the valve 26 is closed, and then the valve 22 is opened.
The water in the container 2 is pressurized. The pressure in the container 2 is detected by a pressure gauge, or the timer waits for the water in the container 2 to be pressurized. After that, when the valve 23 is opened, the pressure is uniformly applied to the entire porous body, and the layer of the suspended substance deposited can be uniformly separated. It is discharged outside. This is the end of backwashing. The valves 21 and 23 are closed, the valves 20 and 21 are opened, and the wastewater treatment operation is performed again.

The effect of the present embodiment will be specifically described by taking an experiment using a porous filter in which wire nets of stainless steel are laminated as an example. Figure 2 shows the relationship between the reverse water flow rate and the recovery rate. Here, assuming the treatment of domestic wastewater, a suspension of heat-treated starch was used as the liquid to be treated. From this figure, when the reverse water flow velocity is increased, the water pressure rises and the filter recovery rate rises. The permeation flow velocity of the water to be treated is 0.1 to
It is 5 m / h (0.00003-0.001 m / s). Further, since the flow velocity during backwashing is usually about 10 times the permeation flow velocity, the maximum is 0.01 m / s, and the expected recovery rate is as small as 10 to 20%. In this embodiment, the container for storing the porous filter has a pressure of 0.1-0.7 MPa (1-
A pressure of 7 kg / cm ² ) can be applied, and this pressure becomes the backwash pressure by releasing the pressure on the upstream side of the porous filter. As a result, the recovery rate of 90% or more is obtained in the backwash according to the present embodiment. Further, the amount of water required for backwashing is sufficient to fill the container, which is the same as or smaller than that in the case of the conventional filter.

In the above embodiment, as the porous filter,
The experiment was conducted using a laminate of stainless steel wire nets, but the same effect can be obtained with other porous materials having low permeation resistance. It can also be applied to filters with relatively low permeation resistance on the filter surface, such as hollow fiber membrane filters.
0 MPa / (m / s) or less, preferably about 0.1 to 1 M
It can be applied to a Pa / (m / s) filter. That is,
In the case of a hollow fiber membrane filter, the fluid permeates through a thin hollow fiber with a diameter of 1 to 2 mm, so the permeation resistance of this part cannot be ignored, and during backwashing, pressure is applied to the filter surface, that is, the accumulated suspended substance layer. Is no longer added.

Further, in the above embodiment, after the wastewater treatment is stopped, the air discharge operation on the upstream side of the porous body 1 in the container 2 in FIG. 1 is performed, but if this operation is performed during the wastewater treatment, the same operation is performed. Produce an effect. That is, since the pressure on the upstream side of the porous body 1 is high during the wastewater treatment, by opening the valve 25,
The air in the container can be discharged through the air discharge pipe 15. As a result, the pump 4, the wash water supply pipe 14, and the valve 2
4 is unnecessary.

[0021]

As described above, according to the present invention,
Before or after the water flow stopping step, the gas in the container on the upstream side of the porous body is removed, the water in the container is pressurized, and then the pressurized water is removed from the upstream side of the porous body. By removing the buffering effect of pressurization by gas and appropriately pressurizing water, impurities accumulated in the porous body can be sufficiently removed with a relatively small amount of water.

[Brief description of drawings]

FIG. 1 is a flow chart of an embodiment according to the present invention.

FIG. 2 is an explanatory diagram of an experimental example of the present invention.

FIG. 3 is a diagram showing a conventional backwash example.

[Explanation of symbols]

 1 ... Porous body 2 ... Container 3 ... Air tank 5 ... Controller

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Eiichi Miura 1168 Moriyama Town, Hitachi City, Ibaraki Prefecture, Hitachi Energy Research Institute Co., Ltd. (72) Inventor Takashi Hayada 1168 Moriyama Town, Hitachi City, Ibaraki Prefecture (72) Inventor Toshio Sawa, Toshio Sawa, 1168 Moriyama-cho, Hitachi, Ibaraki Prefecture, Hitachi Institute for Energy Research, Ltd. (72) Setsuo Inoue, 6-9, Takara-machi, Kure-shi, Hiroshima Babcock Hitachi Kure Factory

Claims (2)

[Claims] 1. A backwashing method for a filtration device comprising a porous body having a low permeation resistance and a container accommodating the porous body,
A water supply stopping step of stopping the water supply of the water to be treated, a step of removing the gas in the container on the upstream side of the porous body before or after the water supply stopping step, and a step of pressurizing the water in the container, And a step of discharging pressurized water from the upstream side of the porous body. 2. A backwashing device of a filtering device comprising a porous body having a low permeation resistance and a container accommodating the porous body,
Means for stopping the passage of water to be treated, means for removing the gas in the container on the upstream side of the porous body, means for pressurizing the water in the container, and means for discharging the pressurized water from the upstream side of the porous body A backwashing device for a filtering device, which comprises: