JP3671477B2 - Cleaning method for submerged membrane separator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for cleaning an immersion type membrane separation apparatus using a membrane element in which a membrane such as a flat membrane, a hollow fiber membrane, a tubular membrane or the like is attached to a main body and permeate passing through the membrane is obtained inside the main body.
[0002]
[Prior art]
As such a submerged membrane separator, in the raw water in the treatment tank, a plurality of membrane elements are arranged side by side with a predetermined interval, and a suction pump is connected to the water sampling port of each membrane element via a header pipe, A diffuser pipe for ejecting fine bubbles is laid at the bottom of the tank, and an upward flow that flows in contact with the membrane is generated in the space between the membrane elements by the air lift action of the fine bubbles ejected by the diffuser pipe. Conventionally known is a method in which permeated water in water is sucked into each membrane element and collected through a water sampling port and a header pipe.
[0003]
[Problems to be solved by the invention]
In the above conventional apparatus, one of the purposes of ejecting fine bubbles from the air diffuser is to prevent the contaminants from adhering to the membrane surface due to the shear force of the fine bubbles, but the raw water contains a large amount of MLSS. In such a case, contaminants gradually adhere to the surface of the membrane as the operation continues, and the filtration performance of the membrane decreases. When the filtration performance is reduced to some extent, it is necessary to draw the membrane element out of the treatment tank, clean the surface of the membrane with a chemical solution, and peel off and remove the attached contaminants. I'm angry.
[0004]
[Means for Solving the Problems]
This invention is for solving the above-mentioned problems. A plurality of membrane elements are arranged in a row at a predetermined interval in raw water in a treatment tank, and a water sampling port of each membrane element is connected to a suction pump. , laid sparge tube for micro bubbles for ejecting microbubbles in the bottom of the tank, diffusing pipe for the fine air bubbles cause upward flow flowing in contact with the film to the spacing of the membrane element by air lift action of the micro-bubbles ejected, In the cleaning method of the submerged membrane separation device , the permeated water in the raw water is sucked into each membrane element by the suction action of the suction pump, and the cleaning chemical solution is injected into each membrane element in the cleaning method of collecting water through the sampling port. and, a pressure injection means of the cleaning chemical liquid to leach out of the membrane, provided a sparge tube for coarse bubble for ejecting coarse bubbles tank bottom, during the stop of the suction pump, the cleaning chemical liquid pressure injection means By using the cleaning chemical solution for each membrane element Inside at the same time under pressure injected leach out of the membrane, characterized in that for ejecting coarse bubbles from the diffusing pipe for crude large bubbles.
[0005]
In the illustrated embodiment, reference numeral 1 denotes a treatment tank of an activated sludge treatment apparatus to which raw water containing organic matter is supplied. Activated sludge has an air lift cylinder 2 standing in water in a floating tank, and permeate water is placed on the air lift cylinder. A plurality of flat membrane elements 3 each having a water sampling port 4 are arranged in a line at intervals in the front-rear direction. In the lower part of the air lift cylinder, a fine bubble diffusing pipe 5 that blows out air supplied from the blower B as fine bubbles and a coarse bubble diffusing pipe 6 that blows out as coarse bubbles are switched by a valve and diffused. It is laid like this.
[0006]
When performing the membrane filtration operation, fine bubbles are diffused from the fine bubble diffusing tube 5. This enhances the activity of the activated sludge that decomposes the organic matter in the raw water, and at the same time, creates an upward flow that flows in contact with the membrane by the air lift action of the fine bubbles in the space between the opposed membranes of the flat membrane element 3, thereby shearing the bubbles The permeated water that permeates the membrane while preventing gel-like contaminants from adhering to the surface of the membrane is obtained inside the main body of the flat membrane element, and this permeated water is connected to the water sampling port 4 of each flat membrane element. The water is drawn through the header pipe 7 with the pump P1.
[0007]
The header pipe 7 is connected to a chemical injection pipe 9 for supplying the cleaning chemical liquid in the tank 8 by pressurizing it with a pump P2, and the tank 8, the chemical injection pipe 9 and the pump P2 are provided with pressure injection means 10 for the cleaning chemical liquid. Configure. A valve is provided upstream of the drug injection tube 9 and the water sampling pump P1, and the valve of the injection tube is closed during the membrane filtration operation.
[0008]
If contaminants adhere to the surface of the membrane and the filtration performance of the membrane deteriorates, the pump P1 is stopped, the valve on the pump side is closed, the valve of the medicinal tube 9 is opened, and the pump P2 is operated to operate the tank. The cleaning chemical solution in 8 is pressurized and injected into the main body of each flat membrane element through the chemical injection tube 9 and the header tube 7. Of course, you may inject | pour with a water head difference. The cleaning chemicals used are sodium hypochlorite, sodium hydroxide, sulfuric acid, hydrogen peroxide and the like. At the same time, the coarse bubbles are diffused from the coarse bubble diffusion tube 6.
[0009]
As a result, the cleaning chemical injected under pressure inside the membrane element permeates the membrane and leaches out to the surface of the membrane, and comes into contact with the contaminant adhering to the surface of the membrane to chemically change, thereby causing the contaminant to the membrane. Reduce adhesion. Then, the coarse bubbles rising in contact with the film peel off and remove the pollutants whose adhesion has been reduced by the large shearing force. When the cleaning with the cleaning chemical solution is performed for a predetermined time, the pump P2 is stopped, the valve of the chemical injection pipe is closed, the pump P1 is operated, the fine bubbles are diffused from the fine bubble diffusing pipe 5, and the membrane filtration operation is resumed.
[0010]
Although the embodiment of the present invention has been described with respect to the flat membrane element, a membrane element in which hollow fiber membranes are attached in a good shape in a square frame may be arranged side by side. It may be good.
Further, although the fine bubble and coarse bubble diffuser tubes are separated, one type of diffuser tube having both functions may be used. In this case, this is dealt with by increasing or decreasing the amount of air supplied to the air diffuser.
[0011]
【The invention's effect】
As apparent from the above, according to the present invention, the cleaning chemical solution is pressurized and injected into the membrane element to weaken the adhesion of the contaminants adhering to the surface of the membrane, and the contaminants are removed from the membrane by a large shear force of coarse bubbles. Since it is peeled off and removed from the surface, cleaning can be performed easily and the cleaning effect is great.
[Brief description of the drawings]
FIG. 1A is a cross-sectional view of an embodiment of the present invention, and B is a cross-sectional view showing a state during cleaning.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Treatment tank 2 Air lift cylinder 3 Membrane element 4 Membrane element sampling port 5 Air bubble pipe for fine bubbles 6 Air diffuser pipe for coarse bubbles 7 Header pipe 8 Tank 9 Chemical injection pipe 10 Pressure injection means for cleaning chemical liquid

Claims (1)

Laying the raw water in the treatment tank, arranged vertically a plurality of membrane elements with a predetermined interval to connect the water inlet and the suction pump adopted for each membrane element, the sparge tube for micro bubbles for ejecting microbubbles into the tank bottom and, the fine bubbles for diffusing tube is caused to rise stream flowing in contact with the film to the spacing of the membrane element by air lift action of the micro-bubbles ejected, the suction pump each membrane element the permeate in the raw water in the suction action of In the cleaning method of the submerged membrane separator that sucks into the inside of the membrane and collects water through the sampling port, for each of the large bubbles that inject the coarse chemical bubbles into the tank bottom and the pressure injection means of the cleaning chemical solution inside each membrane element A diffuser pipe is provided , and while the suction pump is stopped, the cleaning chemical liquid is pressurized and injected into the inside of each membrane element by the pressure injection means of the cleaning chemical liquid. Coarse bubbles are ejected from the air diffuser Method for cleaning a submerged membrane separator, which comprises causing.

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