JPH047023A - Cleaning method for membrane in membrane separating device - Google Patents

Abstract

PURPOSE:To eliminate a negative pressure in a short time and enhance the cleaning effect of the surface of a membrane by a method wherein, when a suction pump is stopped, an intermediate point of a suction pipe connected between the suction pump and membrane separating device is made open to the atmospheric pressure and the permeating liq. remaining in the suction pipe is made to flow reversely in the membrane separating device. CONSTITUTION:A membrane separating device 4 placed under the water to be treated in a treating tank 1 is subjected to a negative pressure applied by a suction pump 8 to separate solids from the water in the tank 1. The suction pump 8 is intermittently stopped while the surface of a filter membrane 16 in the device 4 is being cleaned with a turbulent flow. During this pump stopping period, an intermediate point of a suction pipe 7 connected between the pump 8 and the device 4 is made open to the atmospheric pressure and a suitable amt. of the permeating liq. 10 remaining in the suction pump 7 is made to flow reversely in the device 4 to thereby separate the filter membrane 16 and a filter plate 15 from each other. As a result, the negative pressure is eliminated in a short time after stopping the suction pump and the surface of the membrane can be cleaned with the filter membrane kept away from the filter plate.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a membrane cleaning method for a membrane separation device used in sewage treatment facilities.

2. Description of the Related Art Conventionally, there are facilities for treating sewage and other sewage in which a membrane separation device is immersed in an aeration tank.

This system separates the sludge from solid to liquid by sucking the sludge in the aeration tank through the filtration membrane of a membrane separation device using a suction pump, and then extracts the permeate that has passed through the filtration membrane as treated water. In addition, air is aerated from below the membrane separator, and the cake layer adhering to the membrane surface of the filtration membrane is peeled off by an upward stirring flow generated by the air lift effect, thereby cleaning the filtration membrane. Furthermore, when the suction force of the suction pump is applied to the membrane surface, the cake layer adhering to the membrane surface of the filtration membrane cannot be sufficiently removed by aeration, so the suction pump is intermittently stopped. The membrane surface was cleaned to prevent excessive buildup of the cake layer.

Problems to be Solved by the Invention However, in the conventional configuration described above, although the longer the suction pump stops, the greater the cleaning effect becomes, there is a problem in that the amount of permeated liquid decreases because the suction pump operates for a shorter time. Ta. In addition, the negative pressure acting on the filtration membrane is not immediately relieved by stopping the suction pump, and with a highly airtight pump, it takes 5 to 10 minutes to eliminate the negative pressure. There was a problem that it could not be used effectively. Furthermore, the cleaning effect is high when the negative pressure is eliminated and the filtration membrane separates from the filter plate, and the filtration membrane itself vibrates due to the upward stirring flow, and when the filtration membrane is stuck to the filter plate due to negative pressure. Although it has the effect of suppressing the growth of the cake layer, it cannot be expected to have the effect of peeling off the adhered cake layer.The present invention solves the above problem, and aims to reduce the negative pressure in a short time after stopping the suction pump. It is an object of the present invention to provide a method for cleaning a membrane of a membrane separation device, which can solve the problem and clean the membrane surface while the filtration membrane is separated from the filter plate.

Means for Solving the Problems In order to solve the above problems, the present invention provides a membrane separation device that is immersed in a treatment tank and separates the water to be treated in the tank into solid and liquid by receiving negative pressure applied by a suction pump. , the suction pump is stopped intermittently while the membrane surface of the filtration membrane of the membrane separation device is washed with an agitation flow, and when the suction pump is stopped, the middle of the suction pipe connecting the suction pump and the membrane separation device is brought under atmospheric pressure. When the suction tube is opened, an appropriate amount of permeate remaining in the suction tube is caused to flow back into the membrane separation device, and the backflowing permeate separates the filtration membrane and the filter plate.

Effect: With the above-described configuration, when the suction pump is in operation, the membrane surface of the membrane separator is washed by the stirring flow, and adhesion of the cake layer to the membrane surface is suppressed. By opening the middle of the suction pipe to atmospheric pressure when the suction pump is stopped, the negative pressure acting on the filtration membrane of the membrane separator is quickly eliminated, and the membrane surface is created by stirring flow immediately after the suction pump is stopped. The cleaning effect can be enhanced. Furthermore, by back-flowing the permeate and separating the filtration membrane and the filter plate, the filtration membrane itself vibrates under the action of the stirring flow, promoting the peeling of the cake layer attached to the membrane surface, resulting in a quick and efficient process. The filter membrane can be cleaned well.

EXAMPLE An example of the present invention will be described below based on the drawings. 1st
In the figure, a sludge supply pipe 3 for supplying a liquid to be treated such as sewage sludge 2 is opened to an aeration tank 1 forming a treatment tank, and a membrane separation device 4 is immersed inside the aeration tank 1. ing. Further, an aeration pipe 5 is arranged below the membrane separator 4 , and the aeration pipe 5 communicates with a blower 6 . The membrane separator 4 communicates with a suction pump 8 via a suction pipe 7, and the suction pump 8 communicates with a storage tank 11 for permeate IO via a permeate supply pipe 9. In addition, storage tank 1
1 is open to the atmosphere, and there is a permeate discharge pipe I at the top.
2 opens, and its bottom communicates with the suction pipe 7 via an on-off valve 13.

As shown in FIG. 2, a plurality of membrane modules 14 are arranged in the membrane separation device 4, and each membrane module 1
4 is formed by a filter plate 15 and a filter membrane 16 provided to cover the surface of the filter plate 15. Further, a permeate flow path 17 provided in the filter plate 15 communicates with the suction tube 7.

The effects of the above configuration will be explained below.

With the on-off valve 13 closed, the suction pump 8 is operated to apply negative pressure to the membrane separation device 4, and the liquid to be treated 2 that has flowed into the aeration tank 1 from the sludge supply pipe 3 is sucked through the membrane separation device 4. , solid and liquid are separated by a filter membrane 16.

Then, the permeate IO that has passed through the filtration membrane 16 is passed through the permeate flow path 17, the suction pipe 7, and the permeate supply pipe 9 to the storage tank I.
Supply to I. Further, the air supplied by the blower 6 is aerated through the aeration pipe 5, and the membrane surface of the filtration membrane 16 is washed by an upward stirring flow generated by the air lift action of the aerated air.

Note that the membrane surface may be washed by using an underwater agitator or the like to generate an agitation flow having a flow velocity parallel to the membrane surface.

Then, the operation of the suction pump 8 is stopped intermittently, and when the suction pump 8 is stopped, the on-off valve 13 is opened.

By opening the on-off valve 13, the suction pipe 7 is communicated with the storage tank II and opened to atmospheric pressure, and the negative pressure inside the suction pipe 7 and the membrane separation device 4 is quickly eliminated. Therefore, the suction pump 8
The cleaning effect of the membrane surface due to the rising agitation flow can be enhanced immediately after the cessation of the flow. Also, the permeate IO in the storage tank 11 flows back into the membrane separator 4 through the suction pipe 7, and as shown in FIG. Membrane I6 and filter plate 15 are spaced apart. For this reason, the filtration membrane 16 vibrates by itself under the action of the upward stirring flow,
The peeling of the cake layer adhering to the membrane surface is promoted, and the filtration membrane 16 is efficiently cleaned in a short time.

Effects of the Invention As described above, according to the present invention, by opening the middle of the suction pipe to atmospheric pressure when the suction pump is stopped, the negative pressure acting on the filtration membrane of the membrane separation device can be quickly eliminated. Immediately after stopping the suction pump, the cleaning effect of the membrane surface due to the upward agitation flow can be enhanced, and by causing the permeate to flow backward and separating the filtration membrane and the filter plate, the filtration membrane itself is affected by the action of the upward agitation flow. The filter membrane can be cleaned efficiently in a short period of time by vibrating and promoting the peeling of the cake layer adhering to the membrane surface.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram showing one embodiment of the present invention, Fig. 2 is a sectional view of the membrane module 14 in the same embodiment, and Fig. 3 is the operating state of the membrane module I4 during backflow of permeate in the same embodiment. It is a diagram. 1... Aeration tank, 4... Membrane separation device, 7... Suction pipe, 8... Suction pump, IO... Permeated liquid, 13...
Open/close valve.

Claims (1)

[Claims] 1. In a membrane separation device that is immersed in a treatment tank and separates the water to be treated in the tank from solid to liquid under negative pressure applied by a suction pump, the membrane surface of the filtration membrane of the membrane separation device is washed by an agitating flow. At the same time, the suction pump is stopped intermittently, and when the suction pump is stopped, the middle of the suction pipe that connects the suction pump and the membrane separation device is opened to atmospheric pressure, and an appropriate amount of permeate remaining in the suction pipe is removed from the membrane. 1. A method for cleaning a membrane in a membrane separator, which comprises causing the permeate to flow back into the separator and separating the filtration membrane and the filter plate by the backflow of the permeate.