JP2009006213A - Cleaning method of membrane filtration device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning method of a membrane filtration device which enables the prevention of a discharge of a chemical cleaning liquid for cleaning a membrane to the outside through treatment water. <P>SOLUTION: A membrane filtration method comprises the step of sending raw water from one side of the membrane provided in the filtration device, and of filtering with the membrane to obtain the treat water from the other side of the membrane. In the method, when the membrane is cleaned, the chemical cleaning liquid is supplied from one side of the membrane, and the chemical cleaning liquid is not to pass through the other side of the membrane, or is to be prevented from the discharge to the outside by mixing in the treat water even if the chemical cleaning liquid passes through. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cleaning method for a membrane filtration device, and more particularly to a cleaning method for a membrane filtration device that can prevent a chemical cleaning solution for membrane cleaning from being discharged to the outside through treated water.

  A cargo ship that transports crude oil or the like is provided with a ballast tank in order to maintain the stability of the hull during navigation. Usually, when crude oil or the like is not loaded, the inside of the ballast tank is filled with ballast water, and when the crude oil or the like is loaded, the ballast water is discharged to adjust the buoyancy of the hull and stabilize the hull. As described above, the ballast water is water necessary for the safe navigation of the ship, and the seawater of the port that performs cargo handling is usually used. The amount is said to exceed 10 billion tons per year worldwide.

  By the way, the ballast water contains microorganisms and eggs of small and large organisms that inhabit the port where the water was taken. It will be. Therefore, the destruction of ecosystems, such as the replacement of existing species with species that did not originally live in the sea, has become serious.

Against this backdrop, the diplomatic meeting of the International Maritime Organization (IMO) adopted the obligation to take periodic inspections related to ballast water treatment equipment, etc., and is applied to construction ships from 2009 onwards.
The emission standard (G8) stipulated in the D-2 regulation of the Convention for the Control and Management of Ship Ballast Water and Sediment (hereinafter referred to as the Convention) is 10 / ml for plankton with a size of 10-50 μm; Plankton with a size of 50 μm or more is 10 cells / m ³ ; Escherichia coli with a size of 0.5-3 μm is 250 cfu / 100 ml; Vibrio cholerae with a size of 0.5-3 μm is 1 cfu / 100 ml; 0.5-3 μm in size Enterococci are 100 cfu / 100 ml.

  In addition, the Ballast Water Management System Approval Procedure (G9), adopted on 22 July 2005, which uses active substances, for that purpose, with regard to ship safety, human health and water environment, the active substances and one or more The applicability of the formulation containing the active substance and its application in the ballast water management system are to be determined. And in this G9, active substances are defined as substances or organisms containing viruses or fungi that have general or specific action against harmful aquatic organisms and pathogens, and we are going to require toxicity tests as verification .

  From the above background, very strict sterilization or sterilization is required to satisfy the requirements of G8 and G9.

  Conventionally, as a sterilization / sterilization technique for ballast water, a technique described in Patent Document 1 is known as a chemical technique using ozone.

  Patent Document 1 proposes a technique for injecting ozone into ballast water in combination with steam injection, and further sterilizing ozone while reducing the amount of ozone used by promoting the generation of hydroxy radicals by microbubbles. .

  However, there is a limit to reducing the amount of ozone used, and research for adopting membrane treatment is progressing rapidly.

  In ballast water (seawater), there are many gel-like substances derived from living organisms, and substances that can easily clog membranes. Membrane cleaning is important to realize operation.

Patent Document 2 discloses a technique for using an enzyme in membrane cleaning and a technique for using an enzyme and an oxidizing agent in combination. Patent Document 3 discloses a technique using ethylenediaminetetraacetic acid tetrasodium tetrahydrate in membrane cleaning. Moreover, as a method of not performing the membrane treatment, Patent Document 4 discloses a method of treating with iodine, and Patent Document 5 discloses a method of treating with sodium hypochlorite.
JP 2004-160437 A Japanese Patent Laid-Open No. 3-133947 JP 11-319518 A Japanese translation of PCT publication No. 2002-504851 JP-A-4-322788

  However, in the techniques described in Patent Documents 2 to 5, when the chemical moves to the treated water side, after the cleaning is finished, when the raw water is subjected to membrane treatment again, it remains on the treated water side. There is a risk that existing chemicals will be discharged to the outside through the treated water. There are problems that can affect the ecosystem when chemicals are released into the ocean.

  Then, this invention makes it a subject to provide the washing | cleaning method of the membrane filtration apparatus which can prevent the chemical | medical cleaning liquid for membrane washing | cleaning being discharged | emitted outside via treated water.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

(Claim 1)
In the membrane filtration method of sending raw water from one side of the membrane provided in the filtration device and filtering the membrane to obtain treated water from the other side of the membrane,
When cleaning the membrane, a chemical cleaning solution is supplied from one side of the membrane, and the chemical cleaning solution does not pass to the other side of the membrane, or even if it passes, it is not mixed into the treated water and discharged outside. A method for cleaning the film.

(Claim 2)
The filtration device divides the inside of the filtration tank into a treated water chamber and a raw water chamber by a partition plate, and in the raw water chamber, a porous cylindrical support body having an upper opening and a bag-like shape covering the outer periphery of the support body A large number of filter cylinders comprising a membrane are installed, and the raw water entering the raw water chamber flows upward in the raw water chamber, and is filtered by the membrane to be treated water and rises in the filter cylinder, thereby the treated water chamber A raw water supply pipe for supplying raw water to the raw water chamber and a treated water discharge pipe for extracting treated water to the treated water chamber, and an open / close valve is provided on the treated water discharge pipe. The method for cleaning a membrane filtration device according to claim 1.

(Claim 3)
3. The membrane according to claim 2, wherein the method of preventing the chemical cleaning solution from passing through the other side of the membrane adjusts the pressure of the chemical cleaning solution supplied to the raw water chamber and the pressure of the treatment water chamber. Cleaning method for filtration device.

(Claim 4)
When the height of the filter cylinder is H and the pressure in the treated water chamber is P, the pressure of the chemical cleaning liquid supplied into the raw water chamber so that the relationship of 1.2H ≦ P ≦ 2H is established, 4. The method for cleaning a membrane filtration device according to claim 3, wherein the pressure in the treated water chamber is adjusted.

(Claim 5)
Even if the chemical cleaning liquid passes from the other side of the membrane, a method for preventing the chemical cleaning liquid from entering the treated water and discharging it to the outside closes the on-off valve provided in the treated water discharge pipe, and then discharges the treated water. 3. The method for cleaning a membrane filtration device according to claim 2, wherein the chemical cleaning liquid in the pipe is expelled to the raw water side.

(Claim 6)
6. The membrane filtration apparatus cleaning method according to claim 5, wherein when the chemical cleaning liquid in the treated water discharge pipe is driven to the raw water side, the treated water is supplied to the treated water discharge pipe.

(Claim 7)
The method for cleaning a membrane filtration device according to any one of claims 1 to 6, wherein the raw water is ballast water, and the treated water is ballast treated water.

  ADVANTAGE OF THE INVENTION According to this invention, the washing | cleaning method of the membrane filtration apparatus which can prevent that the chemical | medical cleaning liquid for membrane washing | cleaning is discharged | emitted outside via treated water can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing an example of a membrane filtration apparatus capable of performing the method of the present invention.

  In the figure, reference numeral 1 denotes a filtration tank, which is preferably formed in a cylindrical bowl shape. The filtration tank 1 collects raw water chamber 101 to which raw water is supplied and treated water after being membrane-treated by a partition plate 2. It is divided into a treated water chamber 102 to be watered.

  The raw water chamber 101 is provided with a raw water supply port 103, and the treated water chamber 102 is provided with a treated water discharge port 104.

  A raw water supply pipe 105 is connected to the raw water supply port 103. Reference numeral 105 </ b> A is an on-off valve provided in the raw water supply pipe 105.

  Examples of the raw water include ballast water (seawater and fresh water). When seawater is used as the ballast water, the substances to be filtered include zooplankton, phytoplankton, microorganisms, elements such as Si, Al and Fe, inorganic substances such as oxides and chlorides, and other matters. There are suspended substances (SS), gel-like substances and the like.

  A treated water discharge pipe 106 is connected to the treated water discharge port 104, and the treated water discharge pipe 106 is provided with an on-off valve 106A.

  The treated water discharge pipe 106 is connected to one end of an air supply pipe 107 for supplying air into the treated water chamber 102 through the treated water discharge port 104 and pressurizing the treated water chamber 102. The supply pipe 107 is provided with an on-off valve 107A. The other end of the air supply pipe 107 is connected to the air supply source 3. For example, a compressor can be used as the air supply source 3.

  Here, one end of the air supply pipe 107 is connected between the on-off valve 106A and the treated water discharge port 104 in the treated water discharge pipe 106. If the inside of the treated water chamber 102 can be pressurized, filtration is performed. You may make it connect directly to the treated water chamber 102 of the tank 1. FIG.

  A cleaning drainage outlet 108 is provided at the bottom of the raw water chamber 101. A cleaning drainage discharge pipe 109 is connected to the cleaning drainage discharge port 108, and an opening / closing valve 109 </ b> A is provided in the cleaning drainage discharge pipe 109.

  A chemical cleaning liquid injection pipe 110 for injecting a chemical cleaning liquid supplied from a chemical cleaning facility into the raw water chamber 101 is connected to the cleaning drainage discharge pipe 109 from between the cleaning drainage outlet 108 and the on-off valve 109A. Yes. The chemical cleaning liquid injection pipe 110 is provided with an on-off valve 110A.

  Reference numeral 4 denotes a filter cylinder suspended, for example, on the partition plate 2, and the filter cylinder 4 is formed by a porous cylindrical support body 400 and a filter membrane 401 formed on the outer periphery of the support body 400 and formed in a bag shape. The upper part of the filtration cylinder 4 has an upper opening 402 that opens toward the treated water chamber 102 so that treated water can be fed to the treated water chamber 102.

  The support 400 has a cylindrical shape made of a resin having an upper opening 402. For example, a support made of polyethylene can be used.

  The surface of the support 400 may be formed in a mesh shape or may be formed in a porous shape. The opening ratio on the surface of the support 400 is preferably in the range of 40% to 70%, more preferably in the range of 45% to 65%, and still more preferably in the range of 50% to 65%.

  A microfiltration membrane, an ultrafiltration membrane, or the like can be used as the filtration membrane 401, but a microfiltration membrane is preferable. The microfiltration membrane that can be used in the present invention can be obtained as a commercial product. For example, “MF membrane” manufactured by Yuasa Membrane System can be used.

  In this embodiment, a plurality of filter tubes 4, 4,... Are arranged in a suspended shape in the raw water chamber 101, but the number is not necessarily limited.

  In such a membrane filtration device, when raw water is treated, raw water is introduced from the raw water supply pipe 105 into the raw water chamber 101 via the raw water supply port 103, flows upward in the raw water chamber 101, and passes through the filtration membrane 401. Is filtered. The treated water filtered by the filtration membrane 401 proceeds further upward in the filter cylinder 4, is collected into the treated water chamber 102 from the upper opening 402, and passes through the treated water discharge pipe 106 from the treated water discharge port 104. Discharged.

  When the raw water treatment by the filtration membrane 401 is continued in this manner, the filtration membrane 401 is gradually clogged. In particular, when ballast water (seawater) is used as raw water, there are many gel-like substances derived from living organisms in the water, and there are substances that can easily clog the membrane. For this, membrane cleaning for chemical cleaning of the surface of the filtration membrane 401 is required.

  Examples of chemicals used include hypochlorous acid, sodium hypochlorite, and hydrogen peroxide.

  In order to perform chemical cleaning of the filtration membrane 401, the on-off valve 105A of the raw water supply pipe 105 is closed to stop the supply of raw water, and the raw water and treated water in the filtration tank 1 are drained from the cleaning drain discharge pipe 109, and then washed. The on-off valve 109A of the drainage discharge pipe 109 is closed, the on-off valve 110A of the chemical cleaning liquid injection pipe 110 is opened, and the chemical cleaning liquid C is injected into the raw water chamber 101 from the chemical cleaning equipment at a predetermined pressure (FIG. 2).

  The chemical cleaning liquid C filled in the raw water chamber 101 comes into contact with the surface of the filtration membrane 401 and cleans attached substances such as a gel substance adhering to the surface of the filtration membrane 401.

  At this time, since the chemical cleaning liquid C is injected into the raw water chamber 101 at a predetermined pressure, the chemical cleaning liquid C attempts to enter the filter cylinder 4 through the filter membrane 401. At this time, the open / close valve of the air supply pipe 107 is used. The inside of the treated water chamber 102 is pressurized by opening 107A and operating the air supply source 3 to supply air from the air supply pipe 107 into the treated water chamber 102.

  The pressurized air in the treated water chamber 102 reaches the inside of the filter tube 4 from the upper opening 402 of the filter tube 4, and uniformly applies pressure to the entire inner surface of the filter membrane 401 (the treated water chamber 102 side). The applied pressure at this time is appropriately adjusted in relation to the injection pressure of the chemical cleaning liquid C. By appropriately setting the applied pressure, the chemical cleaning liquid C passes through the filter membrane 401 and enters the filter cylinder 4. Intrusion can be prevented. Therefore, the chemical cleaning liquid C does not enter the treated water chamber 102, and the chemical cleaning liquid C can be prevented from being discharged from the treated water discharge port 104 to the outside.

  Particularly preferably, as shown in FIG. 2, when the height of the filter cylinder 4 is H and the pressure in the treated water chamber 102 is P, the raw water is set so that the relationship of 1.2H ≦ P ≦ 2H is established. The pressure of the chemical cleaning liquid C supplied into the chamber 101 and the pressure in the treated water chamber 102 are adjusted. In FIG. 2, the raw water supply port 103 and the cleaning wastewater discharge port 108 are not shown.

  When the pressure P in the treated water chamber 102 is within this range, the chemical cleaning liquid C in the raw water chamber 101 can be prevented from entering the inside of the filtration membrane 401. The cleaning effect can be enhanced.

  Further, since the pressure P in the treated water chamber 102 is larger than the height H of the filter cylinder 4 by a predetermined range, air bubbles in the treated water chamber 102 enter the raw water chamber 101 through the membrane, and the bubbles can hit the membrane surface. Therefore, the film cleaning effect is further improved.

  After cleaning the filter membrane 401 with the chemical cleaning liquid C, the on-off valve 109A of the cleaning drainage discharge pipe 109 is opened to discharge the chemical cleaning liquid C in the raw water chamber 101 from the cleaning drainage discharge pipe 109 and return to the chemical cleaning equipment.

  FIG. 3 is a schematic cross-sectional view showing another example of a membrane filtration apparatus capable of performing the method of the present invention. The parts denoted by the same reference numerals as those in FIG. 1 indicate the parts having the same configuration, and detailed description thereof will be omitted.

  In this membrane filtration device, the treated water discharge pipe 106 is treated from the treated water discharge port 104 with the on-off valve 106A of the treated water discharge pipe 106 closed between the treated water discharge port 104 and the on-off valve 106A. A cleaning water supply pipe 111 for supplying cleaning water into the water chamber 102 is connected. The cleaning water supply pipe 111 is provided with an on-off valve 111A.

  The cleaning water supply pipe 111 can supply the cleaning water W stored in the cleaning water storage tank 113 by the pump 112 into the treated water chamber 102 of the filtration tank 1.

  When performing chemical cleaning of the filter membrane 401 in such a membrane filtration device, the on-off valve 105A of the raw water supply pipe 105 is closed to stop the supply of raw water, and the raw water and treated water in the filtration tank 1 are drained from the cleaning drainage discharge pipe 109. After that, the on-off valve 109A of the cleaning drainage discharge pipe 109 is closed, the on-off valve 110A of the chemical cleaning liquid injection pipe 110 is opened, and the chemical cleaning liquid C is injected into the raw water chamber 101 from the chemical cleaning equipment at a predetermined pressure (FIG. 4). .

  The chemical cleaning liquid C injected into the raw water chamber 101 comes into contact with the surface of the filtration membrane 401 and cleans adhered substances such as a gel substance adhering to the surface of the filtration membrane 401.

  Since this chemical cleaning liquid C is injected into the raw water chamber 101 at a predetermined pressure, it passes through the filter membrane 401 and also enters the filter cylinder 4 and enters the treated water chamber 102 side.

  After cleaning the filter membrane 401 with the chemical cleaning liquid C, the on-off valve 109A of the cleaning drainage discharge pipe 109 is opened to discharge the chemical cleaning liquid C in the raw water chamber 101 from the cleaning drainage discharge pipe 109 and return to the chemical cleaning equipment.

  At this time, with the on-off valve 106A of the treated water discharge pipe 106 closed, the on-off valve 111 of the cleaning water supply pipe 111 is opened, the supply pump 112 is operated, and the cleaning water W in the cleaning water storage tank 113 is treated with the treated water. By supplying into the treated water chamber 102 through the discharge pipe 106, the chemical cleaning liquid C in the filtration tank 1 is driven to the raw water chamber 101 side (FIG. 5).

  Thereby, even if the chemical cleaning liquid C passes through the filter membrane 401 and enters the treated water chamber 102 from the inside of the filter cylinder 4, the chemical cleaning liquid C is discharged to the outside of the filtration tank 1 through the treated water discharge pipe 106. Can be prevented.

  Moreover, even if the chemical cleaning liquid C enters the treated water discharge pipe 106, it is cleaned by supplying the cleaning water W and is expelled to the raw water chamber 101 side through the treated water chamber 102. There is no possibility that the chemical cleaning liquid C is mixed into the treated water discharged through the water.

  It is also preferable to use ballast treated water as the cleaning water W stored in the cleaning water storage tank 113. In this case, a branch pipe is provided in the middle of the treated water discharge pipe 106, and a part of the treated water taken out from the treated water chamber 102 through the treated water discharge pipe 106 to the outside is washed water storage tank 113. It is sufficient to supply to. 4 and 5, the raw water supply port 103 is not shown.

Schematic cross-sectional view showing an example of a membrane filtration apparatus capable of performing the method of the present invention Explanatory drawing which shows the membrane cleaning method in the membrane filtration apparatus shown in FIG. Schematic sectional view showing another example of a membrane filtration device capable of performing the method of the present invention Explanatory drawing which shows the membrane cleaning method in the membrane filtration apparatus shown in FIG. Explanatory drawing which shows the membrane cleaning method in the membrane filtration apparatus shown in FIG.

Explanation of symbols

1: Filtration tank 101: Raw water chamber 102: Treated water chamber 103: Raw water supply port 104: Treated water discharge port 105: Raw water supply pipe 105A: On-off valve 106: Treated water discharge pipe 106A: On-off valve 107: Air supply pipe 107A: On-off valve 108: Cleaning drain discharge port 109: Cleaning drain discharge pipe 109A: On-off valve 110: Chemical cleaning liquid injection pipe 110A: On-off valve 111: Wash water supply pipe 111A: On-off valve 112: Pump 113: Wash water storage tank 2: Partition Plate 3: Air supply source 4: Filter cylinder 400: Support body 401: Filtration membrane 402: Upper opening C: Chemical cleaning liquid W: Cleaning water

Claims (7)

In the membrane filtration method of sending raw water from one side of the membrane provided in the filtration device and filtering the membrane to obtain treated water from the other side of the membrane,
When cleaning the membrane, a chemical cleaning solution is supplied from one side of the membrane, and the chemical cleaning solution does not pass to the other side of the membrane, or even if it passes, it is not mixed into the treated water and discharged outside. A method for cleaning the film.   The filtration device divides the inside of the filtration tank into a treated water chamber and a raw water chamber by a partition plate, and in the raw water chamber, a porous cylindrical support body having an upper opening and a bag-like shape covering the outer periphery of the support body A large number of filter cylinders comprising a membrane are installed, and the raw water entering the raw water chamber flows upward in the raw water chamber, and is filtered by the membrane to be treated water and rises in the filter cylinder, thereby the treated water chamber A raw water supply pipe for supplying raw water to the raw water chamber and a treated water discharge pipe for extracting treated water to the treated water chamber, and an open / close valve is provided on the treated water discharge pipe. The method for cleaning a membrane filtration device according to claim 1.   3. The membrane according to claim 2, wherein the method of preventing the chemical cleaning solution from passing through the other side of the membrane adjusts the pressure of the chemical cleaning solution supplied to the raw water chamber and the pressure of the treatment water chamber. Cleaning method for filtration device.   When the height of the filter cylinder is H and the pressure in the treated water chamber is P, the pressure of the chemical cleaning liquid supplied into the raw water chamber so that the relationship of 1.2H ≦ P ≦ 2H is established, The method for cleaning a membrane filtration device according to claim 3, wherein the pressure in the treated water chamber is adjusted.   Even if the chemical cleaning liquid passes from the other side of the membrane, the method for preventing the chemical cleaning liquid from entering the treated water and discharging it to the outside closes the on-off valve provided in the treated water discharge pipe, and then discharges the treated water. 3. The method for cleaning a membrane filtration device according to claim 2, wherein the chemical cleaning liquid in the pipe is expelled to the raw water side.   6. The method for cleaning a membrane filtration device according to claim 5, wherein when the chemical cleaning liquid in the treated water discharge pipe is driven to the raw water side, the treated water is supplied to the treated water discharge pipe.   The method for cleaning a membrane filtration device according to claim 1, wherein the raw water is ballast water, and the treated water is ballast treated water.

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