JP2010253457A - Method of washing membrane filtration apparatus using fine bubbles such as microbubbles and nano-bubbles - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of washing a membrane filtration apparatus, capable of surely washing a separation filtration membrane without adversely affecting water treatment, in a method of washing the separation filtration membrane in the membrane filtration apparatus provided with the separation filtration membrane. <P>SOLUTION: When washing the separation filtration membrane of the membrane filtration apparatus used in the water treatment field such as water purifying treatment or wastewater treatment, an apparatus for generating fine bubbles such as microbubbles or nano-bubbles is installed on the primary side or secondary side of the membrane filtration apparatus, a pressure inside the bubbles increases in the process that the fine bubbles reduce, a gas inside the bubbles is dissolved in liquid, and the fine bubbles finally are crushed and disappear. At the time, ions existing on the surface of the fine bubbles are excessively condensed, and the condensed ions are released as the bubbles are crushed and disappear and cause the generation of a free radical. By the action of oxidatively decomposing contaminants by the free radical, the contaminants stuck to the surface of the separation filtration membrane on the primary side and inside pores to be the cause of clogging are decomposed and removed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for cleaning a separation filtration membrane in a membrane filtration apparatus provided with a separation filtration membrane such as a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, and a reverse osmosis membrane.

  Conventionally, membrane filtration devices have been used as devices for separation and filtration in the field of water treatment such as water purification and wastewater treatment, but if separation filtration is continued for a long time, the surface of the separation filtration membrane and Contaminants adhere to the pores and cause clogging, so that the original function as a membrane filtration device cannot be performed. Therefore, cleaning to eliminate the clogging is necessary.

  The separation filtration membrane washing method performed at this time includes water backwashing with filtered water or chemical washing with chemicals such as acid and alkali, and ozone is sent as a gas to the primary side of the separation filtration membrane. There has been a method of fluidizing and washing the liquid.

  However, in the washing method by backwashing with filtered water, depending on the water quality, pollutants attached to the surface and pores of the separation filtration membrane on the primary side can be obtained simply by feeding filtrate from the secondary side of the separation filtration membrane. In some cases, the film could not be completely peeled off.

  Also, in chemical cleaning with chemicals such as acids and alkalis, the chemical is adjusted to a predetermined concentration, and this cleaning liquid is supplied to the membrane filtration device and circulated for a long time, or with the supplied cleaning liquid, the primary side of the separation filtration membrane is used. It may be long-term static cleaning after the water tank is filled, but it takes a long time to clean, and it is necessary to remove chemicals remaining in the equipment after chemical cleaning. It was necessary to provide equipment for treating the cleaning waste liquid.

  In addition, since the cleaning liquid with the above chemicals is filled in the raw water tank on the primary side of the membrane filtration device, microorganisms involved in the water treatment inhabiting here are killed, and the treatment status of the water treatment is adversely affected.

  Further, in the method in which ozone is sent as a gas to the primary side of the separation filtration membrane and the liquid on the primary side is fluidized and washed, it is necessary to prevent deterioration of the membrane filtration device due to ozone.

JP 2006-263584 A JP 2002-361054 A

  The present invention has been made to solve such problems, and it is an object of the present invention to provide a cleaning method for a membrane filtration device that can reliably wash a separation filtration membrane and does not adversely affect water treatment. Yes.

Means for solving this problem are as follows.
The present invention relates to a device that generates microbubbles such as microbubbles and nanobubbles when the separation filtration membrane of a membrane filtration device used in the water treatment field such as water purification treatment or wastewater treatment is a secondary of the membrane filtration device. In the process of reducing these fine bubbles, the filter water containing these fine bubbles is sent from the secondary side to the primary side of the membrane filtration device in the same way as water backwashing. The pressure inside the bubbles increases and the gas in the bubbles dissolves in the liquid, and finally these fine bubbles disappear and collapse. At this time, the ions present on the surface of these fine bubbles are excessively concentrated, and the concentrated ions are released together with the disappearance of the bubbles, resulting in the generation of free radicals, which oxidize the contaminants of these free radicals. By the action of decomposing, it becomes possible to decompose and remove the pollutant that causes clogging adhering to the surface and pores of the separation filtration membrane on the primary side.

  In addition, the present invention installs a device for generating fine bubbles such as microbubbles and nanobubbles in the raw water tank on the primary side of the membrane filtration device, and does not use chemicals such as acid and alkali, and these fine bubbles are subjected to membrane filtration. It is always released to the primary side of the device, and by the same action as described above, the contaminants that cause clogging adhered to the surface and pores of the separation membrane on the primary side are decomposed and removed, and the cause of clogging It became possible to suppress the adhesion of pollutants.

  As described above, according to the present invention, since fine bubbles such as microbubbles and nanobubbles are used and chemicals such as acids and alkalis are not used, removal of chemicals required after washing and treatment of washing waste liquids are performed. Is no longer needed.

  In addition, for the same reason as described above, microorganisms involved in water treatment inhabiting the primary water tank on the primary side of the membrane filtration device are not killed, and there is no adverse effect on water treatment by washing the membrane filtration device. It was.

  Further, according to the present invention, since fine bubbles such as microbubbles and nanobubbles are used and ozone is not used, it is not necessary to prevent the membrane filtration device from being deteriorated by ozone.

  The present invention is carried out as a method for washing a separation filtration membrane in a membrane filtration apparatus provided with a separation filtration membrane such as a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, and a reverse osmosis membrane.

  FIG. 1 shows an apparatus 1 for generating micro bubbles such as microbubbles and nanobubbles in a secondary filtration water tank 7 of a membrane filtration apparatus 2 according to the present invention, and the raw water of a raw water layer 6 is separated and filtered by the membrane filtration apparatus 2. The membrane 3 is separated and filtered, and this filtrate is sent to the filtration water tank 7. If separation and filtration are continued for a long time, contaminants adhere to the surface and pores on the primary side 4 of the separation filtration membrane 3. In order to cause clogging and no longer function as an original membrane filtration device, the device 1 for generating fine bubbles such as microbubbles and nanobubbles installed in the filtration water tank 7 is periodically operated, and these fine bubbles are subjected to membrane filtration. In the process where the fine bubbles are sent from the secondary side 5 to the primary side 4 of the apparatus 2 and the pressure inside the bubbles is increased, the gas in the bubbles is dissolved in the raw water of the raw water tank 6, and finally these The fine bubbles of annihilation pressure To. At this time, the ions present on the surface of these fine bubbles are excessively concentrated, and the concentrated ions are released together with the disappearance of the bubbles, resulting in the generation of free radicals, which oxidize the contaminants of these free radicals. By the action of decomposing, the pollutant that causes clogging adhered to the surface of the primary side 4 and the pores of the separation filtration membrane 3 is decomposed and removed.

  FIG. 2 shows an apparatus 1 for generating microbubbles such as microbubbles and nanobubbles in the raw water tank 6 on the primary side of the membrane filtration apparatus 2 according to the present invention, and the raw water of the raw water layer 6 is separated and filtered by the membrane filtration apparatus 2. 3 is separated and filtered, and this filtered water is sent to the filtered water tank 7, but if the separation and filtration is continued for a long time, contaminants adhere to the surface and pores of the primary side 4 of the separation filtration membrane 3 and become clogged. Therefore, the device 1 for generating fine bubbles such as microbubbles and nanobubbles installed in the raw water tank 6 is always operated, and these fine bubbles are removed from the membrane filtration device 3. In the process of discharging into the raw water tank 6 on the primary side and reducing these fine bubbles, the pressure inside the bubbles increases and the gas in the bubbles dissolves in the raw water of the raw water tank 6, and finally these fine bubbles are It disappears and collapses. At this time, the ions present on the surface of these fine bubbles are excessively concentrated, and the concentrated ions are released together with the disappearance of the bubbles, resulting in the generation of free radicals, which oxidize the contaminants of these free radicals. By the action of decomposing, the surface of the primary side 4 of the separation filtration membrane 3 and the contaminants that cause clogging attached to the pores are decomposed and removed, and the surface of the primary side 4 of the separation filtration membrane 3 and the inside of the pores Suppresses the adhesion of pollutants that cause clogging.

It is a figure which installs the device which generates fine bubbles, such as a micro bubble and a nano bubble, on the secondary side of the membrane filtration device by the present invention, and cleans the separation filtration membrane of a membrane filtration device. It is a figure which installs the device which generates fine bubbles, such as a micro bubble and a nano bubble, on the primary side of the membrane filtration device by the present invention, and cleans the separation filtration membrane of a membrane filtration device.

1: Microbubble generators such as microbubbles and nanobubbles 2: Membrane filtration device 3: Separation filtration membrane 4: Membrane filtration device primary side 5: Membrane filtration device secondary side 6: Raw water tank 7: Filtration water tank

Claims (2)

  A device that generates microbubbles such as microbubbles and nanobubbles is installed on the secondary side of the membrane filtration device when cleaning the separation filtration membrane of the membrane filtration device used in the water treatment field such as water purification and wastewater treatment. The filtered water containing these fine bubbles flows from the secondary side to the primary side of the membrane filtration device in the same way as general water backwashing, and the pressure inside the bubbles is reduced in the process of shrinking these fine bubbles. The gas inside the rising bubbles dissolves in the liquid, and finally these fine bubbles disappear and collapse. At this time, the ions present on the surface of these fine bubbles are excessively concentrated, and the concentrated ions are released together with the disappearance of the bubbles, resulting in the generation of free radicals, which oxidize the contaminants of these free radicals. A cleaning method for a membrane filtration device, which decomposes and removes contaminants that cause clogging that adheres to the surface and pores of a separation filtration membrane on the primary side by the action of decomposing.   When cleaning the separation filtration membrane of the membrane filtration device used in the water treatment field such as water purification treatment and wastewater treatment, a device that generates micro bubbles such as microbubbles and nanobubbles is installed on the primary side of the membrane filtration device, These fine bubbles are discharged to the primary side of the membrane filtration device, and in the process of shrinking these fine bubbles, the pressure inside the bubbles increases and the gas inside the bubbles dissolves in the liquid, and finally these fine bubbles Disappears and collapses. At this time, the ions present on the surface of these fine bubbles are excessively concentrated, and the concentrated ions are released together with the disappearance of the bubbles, resulting in the generation of free radicals, which oxidize the contaminants of these free radicals. Decomposes and removes clogging substances that cause clogging and adheres to the surface and pores of the separation filtration membrane on the primary side by the action of decomposing, and suppresses adhesion of clogging substances that cause clogging. A method for cleaning a membrane filtration device.

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