JPH07178323A - Method for backwashing ceramic membrane - Google Patents

Abstract

PURPOSE:To provide a sufficient effective membrane differential pressure and to effectively backwash a ceramic membrane in a short time by closing the membrane on the raw water side, exerting a high pressure from the filtration side to equalize the pressures on the raw water side and filtration side of the membrane and then releasing the pressure on the raw water side at a time. CONSTITUTION:When backwashing is needed, a raw water feed valve 3, a waste backwashing water valve 9, etc., are closed to close the raw water side. High-pressure air is added to a pressure tank 5 under these conditions by opening a high-pressure air feed valve 6, hence a pressure is exerted on the filtration side of a ceramic membrane 2, the pressure is transmitted to the closed raw water side, and the pressures on the raw water side and filtration side of the membrane 2 are equalized. While the valve 6 is opened and the valve 9 is rapidly opened, the pressure on the raw water side is lowered at once, and a large effective membrane differential pressure is generated. Accordingly, the deposits on the membrane surface are successively peeled off the surface, passed through the valve 9 along with the filtered water flowing out of the tank 5 and discharged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for backwashing a ceramic membrane, and more particularly to a method for backwashing a tubular or monolithic ceramic membrane.

[0002]

2. Description of the Related Art Generally, when filtration by a membrane module is continued, substances separated by filtration gradually accumulate on the membrane surface, and filtration resistance increases. For this reason, it is necessary to carry out backwashing (backpressure washing) in which filtered water is allowed to flow back from the filtration side to the raw water side at a high speed to remove accumulated substances on the membrane surface.

As such a backwashing method, a pump type backwashing method is generally used in which filtered water is passed from a tank storing filtered water to a membrane module by using a dedicated pump for backwashing. In addition, an air pressurization method is also used in which a part of the filtered water is introduced into a pressure tank and pressurized with compressed air or the like to cause the filtered water to flow back to the membrane module.

[0004]

However, as shown in FIG. 3, in such a conventional backwashing method, when the pressure on the filtered water side is increased, the pressure on the raw water side is also increased, which is the pressure difference between the two. It is difficult to make the value of the effective transmembrane pressure difference sufficiently large, and therefore, there has been a problem that a relatively long backwash time is required in order to sufficiently release the accumulated material on the membrane surface. The present invention has been made to solve the above-mentioned conventional problems, and to provide a backwashing method for a ceramic membrane capable of performing effective backwashing in a short time while sufficiently taking an effective transmembrane pressure difference. is there.

[0005]

SUMMARY OF THE INVENTION The present invention, which has been made to solve the above problems, stops filtration by a tubular or monolithic ceramic membrane and closes the raw water side valve to close the raw water side. After that, apply high pressure from the filtration side to keep the raw water side and the filtration side of the ceramic membrane at equal pressure, and then quickly open the valve on the raw water side to release the pressure on the raw water side at once and backwash. It is characterized by. Also,
It is further preferable that the rinse water is made to flow from the upstream side of the raw water side when the pressure on the raw water side is released so that the stripping substance is released to the outside of the system.

[0006]

According to the method of backwashing the ceramic membrane of the present invention, the raw water side is closed and a high pressure is applied from the filtration side. Since they are opened at once, the pressure on the raw water side is suddenly reduced from the high pressure state, and a large effective transmembrane pressure is generated at this moment. For this reason, it is possible to sufficiently peel off the accumulated material on the membrane surface in a short time with a small amount of filtered water. Further, since the accumulated material on the surface of the film is consolidated by the high pressure applied to the surface of the film, there is also an advantage that the settling property of the peeling substance discharged by the backwash becomes good. Examples of the present invention will be shown below.

[0007]

1 is a membrane module in which a monolithic (multi-channel) ceramic membrane 2 is provided. The ceramic membrane 2 of the example is an MF membrane having a pore diameter of 0.1 μm, and 37 channels having a diameter of 3 mm are formed inside a cylindrical ceramic body having an outer diameter of 30 mm. The ceramic membrane 2 may be of a tubular type, but the flat ceramic membrane 2 and the organic membrane may be damaged when high pressure is applied, and therefore it is not preferable to apply the backwashing method of the present invention.

In a normal filtration state, raw water is supplied to the lower part of the membrane module 1 through a raw water supply valve 3 which is a valve on the raw water side, and is filtered by a monolithic ceramic membrane 2. The filtered water flows through a filtered water valve 4. Have been taken out through. 5 is a pressure tank provided between the membrane module 1 and the filtered water valve 4, and a high pressure air supply valve 6
And a pressure release valve 7 are provided. Further, a rinse water supply valve 8 is provided in the upper part of the membrane module 1, and a backwash drain valve 9 which is a valve on the raw water side is provided in the lower part.

Continuation of filtration increases the accumulation on the membrane surface,
When backwashing becomes necessary, backwashing is performed as follows. First, the filtration is stopped, and the raw water supply valve 3 and the backwash drain valve 9 on the raw water side are closed to close the raw water side. Further, the filtered water valve 4, the pressure release valve 7, and the rinse water supply valve 8 are all closed. In this state, the high pressure air supply valve 6 is opened and high pressure air of, for example, 300 kPa is added to the pressurized tank 5. As a result, pressure is applied to the filtration side of the ceramic membrane 2, and this pressure also propagates to the raw water side in the closed state.
As shown in the graph, the raw water side and the filtration side of the ceramic membrane 2 are kept at equal pressure. This holding time of about 2 to 3 seconds is sufficient.

Next, with the high pressure air supply valve 6 open,
Open the backwash drain valve 9 on the raw water side,
Release the pressure on the raw water side at once. At this time, as shown in FIG. 2, the pressure on the raw water side is reduced at once and a large effective transmembrane pressure is generated. Therefore, the accumulated substances on the membrane surface are almost sequentially peeled off from the membrane surface, and are discharged together with the filtered water flowing out from the pressurized tank 5 through the backwash drain valve 9.

Although backwashing can be performed only by this pressure backwashing step, in the embodiment, after the pressure backwashing step is continued for several seconds, the high pressure air supply valve 6 is closed and the pressure on the filtration side is stopped. At the same time, the rinse water supply valve 8 is opened to flow the rinse water from the upstream side of the raw water side. As a result, the stripping substance is released out of the system together with the rinse water.

[0012]

As described above, according to the method of backwashing a ceramic membrane of the present invention, a high pressure is applied to the raw water side and the filtration side of the ceramic membrane to maintain the pressure equal, and the valve on the raw water side is rapidly changed. By opening and releasing the pressure on the raw water side at once, a sufficient effective transmembrane pressure can be generated, so that accumulated substances can be instantly separated from the membrane surface, and effective backwashing can be performed in a short time. It can be carried out. Further, there is also an advantage that when a high pressure is applied, the accumulated material on the film surface is consolidated and the sedimentation property of the exfoliated substance can be enhanced.

[Brief description of drawings]

FIG. 1 is a piping system diagram of an apparatus according to an embodiment.

FIG. 2 is a graph showing pressure changes during backwashing in an example of the present invention.

FIG. 3 is a graph showing a pressure change during backwashing in a conventional method.

[Explanation of symbols]

1 membrane module, 2 ceramic membrane, 3 raw water supply valve, 4 filtered water valve, 5 pressurized tank, 6 high pressure air supply valve, 7 pressure release valve, 8 rinse water supply valve, 9 backwash drain valve

Claims (2)

[Claims] 1. When solid-liquid separation is performed using a ceramic membrane, filtration with a tubular or monolithic ceramic membrane is stopped, the raw water side valve is closed to close the raw water side, and then the high pressure is applied from the filtration side. A ceramic membrane characterized in that the raw water side and the filtration side of the ceramic membrane are held at equal pressure, and then the valve at one end on the raw water side is rapidly opened to release the pressure on the raw water side at once and backwash. How to backwash the membrane. 2. The ceramic membrane according to claim 1, wherein when the pressure on the raw water side is released, rinse water for excluding the exfoliated material from the system is flowed from the other end on the raw water side to release the exfoliated substance to the outside of the system. Backwash method.