JP3880251B2 - Backwash method for submerged membrane separator - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a technique for using a submerged membrane separation apparatus in water treatment for treating purified water, sewage, human waste, industrial wastewater, and the like, and relates to a backwashing method for the submerged membrane separation apparatus.
[0002]
[Prior art]
Conventionally, as a water treatment apparatus for treating purified water, sewage, human waste, industrial waste water, etc., there is an apparatus in which a submerged membrane separation apparatus is disposed in a reaction tank and water to be treated in the tank is filtered. As an example of such a membrane separation apparatus, there is one in which a plurality of tubular ceramic separation membranes (membrane elements) are arranged in parallel to constitute a membrane module, and the membrane modules are laminated in a plurality of stages. In this submerged membrane separation apparatus, a permeate suction tube is provided in communication with the passage inside the ceramic separation membrane, and a suction negative pressure is applied by suction means connected to the permeate suction tube, whereby the membrane is applied to the ceramic separation membrane. The water to be treated in the tank is filtered by generating a differential pressure.
[0003]
During operation, air is diffused from below the membrane module, and a circulating flow is generated in the tank by the gas-liquid mixed flow generated by the air lift action of this air, and the upward flow of this gas-liquid mixed flow is caused by each ceramic separation membrane. By acting as a sweep on the film surface, adhesion of the cake layer to the film surface is suppressed.
[0004]
[Problems to be solved by the invention]
In the above configuration, the ceramic separation membrane is regularly backwashed for the purpose of preventing clogging and removing contaminants. This backwashing removes the cake layer adhering to the membrane surface by supplying washing water to the flow path inside the ceramic separation membrane through the permeate suction tube and passing the washing water from the inside of the membrane to the outside. Alternatively, cleaning is performed by passing a cleaning chemical solution through the ceramic separation membrane.
[0005]
However, since the reaction of the chemical solution requires contact with the object and the reaction time, all of the supplied chemical solution does not contribute to the cleaning, and part of the chemical solution flows out into the reaction tank without being reacted. For this reason, in order to obtain a target cleaning effect, an oxidizing agent such as sodium hypochlorite used for the purpose of wastefully consuming more chemicals than necessary for calculation or enhancing the cleaning effect is used. It tends to be added excessively.
[0006]
The present invention solves the above-described problems, and an object of the present invention is to provide a backwashing method for a submerged membrane separation apparatus that can obtain a sufficient cleaning effect with a minimum amount of chemical solution.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the backwashing method of the submerged membrane separator of the present invention is to wash the filtration membrane of the submerged membrane separator used by being immersed in a reaction tank with a cleaning chemical solution. The cleaning chemical solution is intermittently supplied to the membrane permeate flow path of the submerged membrane separation device in a pulsed manner, repeatedly forming a stationary state and a flowing state of the cleaning chemical solution in the filtration membrane, and the cleaning chemical solution vibrates. Along with this, the filter membrane is peristalized .
[0008]
With the configuration described above, the cleaning chemical solution moves in the membrane permeate flow path and the filtration membrane with vibration, and the cleaning chemical solution is oscillated in the filtration membrane. As a result, the cleaning chemical solution can contact the filtration membrane and the membrane permeate to be cleaned, and the reaction time required for cleaning can be secured. A sufficient cleaning effect can be obtained while suppressing.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, raw water 1 is river water, lake water, ground water, seawater, etc. in water purification treatment, or sewage, human waste, industrial wastewater, etc. in activated sludge treatment.
A raw water supply pipe 3 for supplying the raw water 1 communicates with the reaction tank 2, and a membrane separation device 4 is provided so as to be immersed in the tank. The membrane separation device 4 is configured by arranging a plurality of membrane elements made of a tubular ceramic separation membrane in parallel to constitute a membrane module, and laminating the plurality of membrane modules. The membrane separator 4 is connected to a permeate suction pipe 5 that communicates with the membrane permeate flow path of the membrane module. The permeate suction pipe 5 communicates with the treated water tank 7 via a suction pump 6.
[0010]
A diffuser 8 is disposed below the membrane separator 4, and a blower 9 is connected to the diffuser 8. A sludge extraction pipe 11 is connected to the bottom of the reaction tank 2 via a sludge pump 10.
A backwash pipe 13 is connected to the treated water tank 7 via a backwash pump 12, and the backwash pipe 13 communicates with the permeate suction pipe 5 on the upstream side of the suction pump 6. A first valve 14, a second valve 15, and a third valve 16 are sequentially provided in the middle of the backwash pipe 13 from the upstream side, and the drug injection pipe 17 passes between the first valve 14 and the second valve 15. An accumulator 18 is connected to the permeate suction pipe 5 between the second valve 15 and the third valve 16. The medicinal injection pipe 17 communicates with the medicinal solution tank 20 via the medicinal injection pump 19. As a chemical | medical agent, acid bases, such as oxidizing agents, such as a sodium hypochlorite solution, chlorine water, and chlorine dioxide water, or hydrochloric acid, a sulfuric acid, nitric acid, an oxalic acid, a citric acid, or sodium hydroxide can be used.
[0011]
Hereinafter, the operation of the above-described configuration will be described. During operation, the suction pump 6 is driven, a negative suction pressure is applied to the membrane separation device 4 through the permeate suction pipe 5, and a transmembrane differential pressure is generated in each ceramic separation membrane of the membrane separation device 4 to be processed in the tank. Water is filtered and treated water that has passed through the membrane separation device 4 is supplied to the treated water tank 7. On the other hand, air supplied by the blower 9 is diffused from the diffuser 8 into the liquid in the tank, and an upward flow is generated by the gas-liquid mixed flow generated by the air lift action of the air. By acting as a sweep on the membrane surface of the separation membrane, adhesion of the cake layer to the membrane surface is suppressed.
[0012]
At the time of cleaning the membrane separation device 4, the suction pump 6 is stopped, and the backwash pump 12 is driven with the first valve 14, the second valve 15, and the third valve 16 opened, and the treated water in the treated water tank 7 is discharged. The ceramic separation membrane of the membrane module is backwashed by pumping it through the backwash tube 13 to the membrane permeate flow path of the membrane separation device 4.
In the case of chemical cleaning, the first valve 14 and the third valve 16 are closed and the second valve 15 is opened, and the chemical injection pump 19 is driven to supply the cleaning chemical in the chemical tank 20 to the accumulator 18. The accumulator 18 stores a required amount of cleaning chemical under a predetermined pressure. With the second valve 15 closed, the third valve 16 is intermittently opened and closed, and the cleaning chemical solution of the accumulator 18 is intermittently supplied to the membrane permeate flow path of the membrane separation device 4 in a pulsed manner. A stationary state and a flowing state of the cleaning chemical solution are repeatedly formed therein.
[0013]
By this operation, the cleaning chemical solution moves in the membrane permeate flow path and the filtration membrane with vibration, and the cleaning chemical solution swings in the filtration membrane. As a result, the cleaning chemical solution can contact the filtration membrane and the membrane permeate to be cleaned, and the reaction time required for cleaning can be secured. A sufficient cleaning effect can be obtained while suppressing.
[0014]
【The invention's effect】
As described above, according to the present invention, a cleaning chemical solution is supplied intermittently to the membrane permeate flow channel, and the cleaning chemical solution moves through the membrane permeate flow channel and the filtration membrane with vibration, and the filtration membrane. Since the cleaning chemical solution can be swung inside, the entire cleaning chemical solution can be brought into contact with the site to be cleaned of the filtration membrane and the membrane permeate, and the reaction time required for cleaning can be secured, so that it remains unreacted. A sufficient cleaning effect can be obtained while suppressing the amount of the cleaning chemical flowing out into the reaction tank.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an overall configuration of a water treatment apparatus according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Raw water 2 Reaction tank 4 Membrane separator 5 Permeate suction pipe 6 Suction pump 8 Air diffuser 12 Backwash pump 13 Backwash pipe 14 First valve 15 Second valve 16 Third valve 17 Chemical injection pipe 18 Accumulator 19 Chemical injection Pump 20 chemical tank

Claims (1)

The membrane of the submerged membrane separator that is immersed in the reaction vessel is washed with a cleaning chemical solution. The cleaning chemical solution is intermittently supplied to the membrane permeate flow path of the submerged membrane separator. A backwashing method for a submerged membrane separation apparatus, wherein a stationary state and a flow state of the cleaning chemical solution are repeatedly formed in the filtration membrane, and the cleaning chemical solution is oscillated in the filtration membrane with vibration .

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