JP2014018782A - System and method for cleaning filtration film of ballast water treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system and a method for cleaning a filtration film of ballast water treatment which have high cleaning efficiency and remarkably excellent degradation efficiency in degrading a persistent cake layer peculiar to ballast water treatment.SOLUTION: A system for cleaning a filtration film of ballast water treatment, which cleans the filtration film for the ballast water treatment with cleaning liquid, comprises: circulation piping which circulates the cleaning liquid in a manner that brings the same in contact with the filtration film: a chemical agent supply device which supplies the cleaning liquid in the circulation piping with a chemical agent: a micro bubble supply device which supplies the cleaning liquid in the circulation piping with micro bubbles; and a circulation pump which circulates the cleaning liquid in the circulation piping to bring the cleaning water containing the chemical agent and the micro bubbles in contact with the filtration film.

Description

  The present invention relates to a cleaning system and a cleaning method for a filtration membrane for ballast water treatment, and more particularly, to a filtration membrane for ballast water treatment for decomposing a hardly decomposable cake layer that is deposited and adhered to the filtration membrane during ballast treatment. The present invention relates to a cleaning system and a cleaning method.

  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, aquatic organisms inhabiting the port where the water is taken are mixed in the ballast water, and these aquatic organisms are transported to an area where they do not originally exist as the ship moves.

  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.

  For this reason, at the time of discharge of ballast water, it is necessary to remove or kill about 1/100 of the number of organisms present in the open ocean.

  The present applicant has proposed a technique for treating ballast water with a filtration membrane (Patent Document 1).

Japanese Patent No. 4214494

  When ballast water is treated with a filtration membrane, the cake layer deposited and adhering to the filtration membrane is difficult to remove even by using a normal cleaning method, and as a result, the recovery rate of the flux is greatly limited.

  Therefore, an object of the present invention is to provide a cleaning system and a cleaning method for a filtration membrane for ballast water treatment that has high cleaning efficiency and is outstandingly superior in decomposition efficiency of a hardly decomposable cake layer that is peculiar to ballast processing.

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

  The above problems are solved by the following inventions.

(Claim 1)
A ballast water treatment filtration membrane cleaning system for cleaning a ballast water treatment filtration membrane with a cleaning liquid,
A circulation pipe for circulating a cleaning liquid so as to contact the filtration membrane;
A medicine supply device for supplying medicine into the cleaning liquid in the circulation pipe;
A fine bubble supply device for supplying fine bubbles into the cleaning liquid in the circulation pipe;
A cleaning system for a filtration membrane for ballast water treatment, comprising: a circulation pump that circulates the cleaning solution in the circulation pipe and brings the cleaning solution containing the chemical and the fine bubbles into contact with the filtration membrane.

(Claim 2)
The fine bubble supply device includes:
A branch pipe that branches a part of the cleaning liquid at a branch section on the upstream side of the circulation pipe and returns it again at a junction section on the downstream side of the circulation pipe;
A gas-liquid mixing part that is provided in the middle of the branch pipe and mixes gas into a part of the cleaning liquid,
The ballast water treatment filtration membrane cleaning system according to claim 1, wherein microbubbles are generated in the cleaning liquid in the circulation pipe after joining.

(Claim 3)
The said chemical | medical agent is hydrogen peroxide or sodium hypochlorite, The washing | cleaning system of the filtration membrane for ballast water treatment of Claim 1 or 2 characterized by the above-mentioned.

(Claim 4)
A method of cleaning a filtration membrane for ballast water treatment, wherein the filtration membrane for ballast water treatment is washed with a washing liquid,
A method for cleaning a filtration membrane for ballast water treatment, comprising cleaning the filtration membrane by bringing the cleaning liquid containing a chemical and fine bubbles into contact with the filtration membrane.

(Claim 5)
The method for cleaning a filtration membrane for ballast water treatment according to claim 4, wherein the fine bubbles are microbubbles.

(Claim 6)
The said chemical | medical agent is hydrogen peroxide or sodium hypochlorite, The cleaning method of the filtration membrane for ballast water treatment of Claim 4 or 5 characterized by the above-mentioned.

  ADVANTAGE OF THE INVENTION According to this invention, the washing | cleaning system and washing | cleaning method of the filtration membrane for ballast water treatment which are high in washing | cleaning efficiency and are outstanding also in the decomposition | disassembly efficiency of the hardly decomposable cake layer peculiar to a ballast treatment can be provided.

Schematic which shows an example of the ballast water treatment apparatus provided with the washing | cleaning system of the filtration membrane for ballast water treatment which concerns on this invention. Sectional view along the axial direction of the spiral membrane module Sectional view along line (iii)-(iii) in FIG.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view showing an example of a ballast water treatment apparatus provided with a cleaning system for a filtration membrane for ballast water treatment according to the present invention.

  In FIG. 1, 1 is a ballast pump for sending ballast water containing aquatic organisms or the like to the ballast tank 2, and B is an intake pipe for ballast water.

  In the present invention, for example, seawater and fresh water are used as ballast water to be treated, and such ballast water includes aquatic organisms such as zooplankton, phytoplankton, and bacteria.

  3 is a pre-filter provided on the intake pipe B and has a function of removing or killing relatively large aquatic organisms.

  Although it does not specifically limit as the prefilter 3, For example, a slit board etc. can be illustrated preferably. The slit plate has the effect of destroying and killing aquatic organisms in the liquid due to the shearing phenomenon that occurs when the ballast water being pumped tries to pass through the slit, as well as the filtering action on relatively large aquatic organisms. Therefore, it is preferably used in the present invention.

  4 is a filtration membrane device provided downstream of the pre-filter 3 in the intake pipe B, and has a function of removing aquatic organisms in the ballast water by membrane filtration.

  The filtration membrane device 4 includes a filtration membrane 41, a raw water chamber 42 into which ballast water used for membrane filtration by the filtration membrane 41 is introduced, and a treated water chamber 43 into which ballast water after membrane filtration by the filtration membrane 41 is introduced. And. Further, 44 and 45 are a ballast water supply valve and a ballast water discharge valve respectively provided before and after the filtration membrane device 4 on the intake pipe B.

  As the filtration membrane 41 provided in the filtration membrane device 4, a microfiltration membrane (MF membrane), an ultrafiltration membrane (UF membrane), or the like can be used. Preferably, the pore size is about 50 to 1000 nm. It is a microfiltration membrane.

  Although it does not specifically limit as a form of the filtration membrane 41, A spiral membrane, a hollow fiber membrane, etc. can be illustrated preferably, and since the effect by the washing | cleaning method of this invention tends to become remarkable especially, a spiral membrane is suitable.

  Reference numeral 5 denotes a cleaning mechanism for cleaning the filtration membrane 41 with a cleaning liquid. As shown in the drawing, a circulation pump 51, a medicine supply device 52, and a fine bubble supply are provided on a circulation pipe W connected to the filtration membrane device 4. Device 53. Reference numerals 54 and 55 denote a cleaning liquid supply valve and a cleaning liquid discharge valve respectively provided before and after the filtration membrane device 4 on the circulation pipe W.

  In the present invention, water, seawater or the like can be preferably used as the cleaning liquid, and seawater is particularly preferable. As seawater, the ballast water after membrane filtration by the filtration membrane apparatus 4 mentioned above can be used preferably.

  In the illustrated embodiment, the filtration membrane device 4 and the circulation pipe W are connected by introducing the cleaning liquid into the raw water chamber 42 and discharging the cleaning liquid after contact with the filtration membrane 41 from the raw water chamber 42 (the membrane surface is liquid Washing with a flow).

  The connection between the filtration membrane device 4 and the circulation pipe W is not limited to the above example, and the filtration membrane 41 and the cleaning liquid circulating through the circulation pipe W may be in contact with each other. For example, the cleaning liquid is supplied to the raw water chamber 42. Introducing and discharging the cleaning liquid from the treated water chamber 43 through the filtration membrane 41 (order washing), or introducing the cleaning liquid into the treated water chamber 43 and discharging the cleaning liquid from the raw water chamber 42 through the filtration membrane 41 It can also be made into the form (backwashing) to do.

  The medicine supply device 52 includes a cleaning liquid circulation tank 520, and supplies the medicine supplied from the medicine tank 521 by a pump (not shown) into the cleaning liquid in the cleaning liquid circulation tank 520.

  As the drug used in the present invention, a drug that generates bubbles by reaction with a ballast water-containing component such as an organic substance is particularly preferably used. Specifically, hydrogen peroxide and sodium hypochlorite can be preferably exemplified.

  The addition amount of the chemical is not particularly limited, and can be appropriately set so that the concentration in the cleaning liquid at the time of contact with the filtration membrane 41 becomes a predetermined concentration according to the growth situation of the cake, for example.

  Reference numeral 522 denotes a contaminant removal means for removing contaminants in the cleaning liquid circulation tank 520. The circulation pipe 522a connected to the cleaning liquid circulation tank 520 and a filter 522b provided on the circulation pipe 522a. And a circulation pump 522c.

  The contaminant removing means 522 has a function of extracting contaminants in the cleaning liquid circulation tank 520 together with the cleaning liquid by the circulation pump 522c and supplying it to the filter 522b, and returning the cleaning liquid from which contaminants are removed by the filter 522b to the cleaning liquid circulation tank 520 Have

  In this aspect, the fine bubble supply device 53 includes a branch pipe 530 configured to branch at the upstream branching portion 531 of the circulation pipe W and return again at the junction 532 downstream of the circulation pipe W. Yes.

  The liquid branched from the branch part 531 flows through the branch pipe 530, and gas is mixed in the gas-liquid mixing part 533 provided in the middle of the branch pipe 530.

  The gas-liquid mixing unit 533 is not particularly limited as long as it is a gas-liquid mixing device capable of mixing a gas with a liquid, and examples thereof include an ejector and a line mixer. Reference numeral 534 denotes a gas supply source for supplying gas to the gas-liquid mixing unit 533.

  535 is a gas-liquid mixing pump provided in the line of the branch pipe 530. The pressure of the gas-liquid mixing pump 535 is appropriately determined in consideration of the pressure loss of the gas-liquid mixing unit 533, the supply pressure of gas from the gas supply source, the fluid pressure in the circulation pipe W in the merging unit 532, and the like.

  Examples of the gas supplied from the gas supply source 534 include air, oxygen, ozone, and carbon dioxide.

  The supply amount of the gas supplied from the gas supply source 534 into the cleaning liquid is preferably about 2 to 5% by volume with respect to the circulating flow rate of the cleaning liquid in the circulation pipe W. Specifically, the circulating flow rate is 100 L / min. If it is, it is preferable that it is about 2-5 L / min.

  Since the fine bubble supply device 53 according to the present invention is configured as described above, the gas-liquid mixed solution generated in the branch pipe 530 is joined to the circulation pipe W at the joining portion 532, and the fluid after joining the fluid. Microbubbles having a diameter in the range of 10 to 100 μm are generated.

  The form of the fine bubble supply device 53 is not limited to the one described above, and any fine bubble having a diameter of about 10 to 100 μm can be preferably used in the circulation pipe W.

  In the ballast water treatment apparatus described above, when the ballast water is taken, the ballast pump 1 is opened with the ballast water supply valve 44 and the ballast water discharge valve 45 open, and the cleaning liquid supply valve 54 and the cleaning liquid discharge valve 55 are closed. And the ballast water treated by the prefilter 3 and the filtration membrane device 4 is taken into the ballast tank 2 through the water intake pipe B.

  On the other hand, at the time of cleaning for cleaning the filtration membrane 41 of the filtration membrane device 4, the circulation pump 51 is closed with the ballast water supply valve 44 and the ballast water discharge valve 45 closed and the cleaning liquid supply valve 54 and the cleaning liquid discharge valve 55 opened. And the cleaning liquid is circulated through the circulation pipe W so as to come into contact with the filtration membrane 41 to wash the filtration membrane 41.

  In the method for cleaning a filtration membrane for ballast water treatment according to the present invention, the cleaning liquid circulating through the circulation pipe W contains the drug from the drug supply device 52 and the fine bubbles from the fine bubble supply device 53 described above. Therefore, the synergistic effect of these chemicals and fine bubbles enables the filtration membrane 41 to be washed with a significantly higher cleaning efficiency than the case where the chemicals and fine bubbles are used alone, respectively, and the hardly decomposable cake layer unique to ballast processing. An outstanding effect is also obtained in the decomposition efficiency of.

  Although the reason why such a synergistic effect is obtained is not clear, the present inventor considers as follows.

  That is, since the ballast water contains inorganic substances in addition to organic substances such as aquatic organisms, it is presumed that a special hardly decomposable cake layer composed of organic substances and inorganic substances is deposited and adhered to the filtration membrane 41.

  In the present invention, high-speed turbulent flow in the vicinity of the membrane surface of the filtration membrane 41 is caused by the fine bubbles from the fine bubble supply device 53 and the bubbles generated when the organic matter in the cake layer of the filtration membrane 41 is decomposed by the drug. It is presumed that the cleaning liquid with locally increased pressure destroys the inorganic part of the cake layer, thereby realizing excellent cleaning efficiency.

  In the above description, the case where the ballast water treatment apparatus includes the pre-filter 3 has been described.

  In the above description, the case where the cake layer generated by taking the ballast water into the ballast tank 2 has been described, but the present invention is not limited to this. For example, when microorganisms grow in the ballast water taken into the ballast tank 2, membrane filtration is preferably performed also when the ballast water is discharged. The cleaning method of the present invention also has an excellent effect on the cake layer adhering to the membrane surface by membrane filtration during such ballast water discharge.

  In the present invention, the form of the filtration membrane device 4 is not particularly limited, but a spiral membrane module can be preferably exemplified.

  In the case of using the spiral membrane module, in particular, the effect of remarkably improving the cleaning efficiency by the above-described “cleaning by hitting the membrane surface with a liquid flow” can be obtained.

  2 is a cross-sectional view taken along the axial direction of the spiral membrane module, and FIG. 3 is a cross-sectional view taken along the line (iii)-(iii) of FIG.

  The spiral membrane module 400 includes a water collecting pipe 430 that collects treated water, a large number of envelope-like membranes 410 (filtration membrane 41) that are wound around the water collecting pipe 430, and an envelope around the water collecting pipe 430. And an outer cylinder 440 that accommodates the structure around which the film 410 is wound.

  In each envelope-like film 410, there is provided a transmission side spacer (not shown) that maintains the stretched state of the envelope-like film 410 and forms a space for treated water that has permeated inside the envelope-like film 410. It has been. The inside of the envelope-shaped membrane 410 communicates with the interior 430 a (treated water chamber 43) of the water collecting pipe 430 so that treated water that has permeated through the envelope-shaped film 410 can be transferred to the water collecting pipe 430. The envelope-like membrane 410 is radially attached to the outer peripheral surface of the water collecting pipe 430. When these are wound around the water collecting pipe 430, the envelope film 410 has a substantially cylindrical shape with the water collecting pipe 430 as a whole as a whole. .

  Between the adjacent envelope membranes 410, the envelope membranes 410 are in close contact with each other to prevent the membrane area from becoming narrow, and the raw water flow between the adjacent envelope membranes 410 between the water collection pipe 430 and the outer cylinder 440 is prevented. A spacer (not shown) for forming the passage 420 (raw water chamber 42) is inserted.

  In the spiral membrane module 400, when the above-described “cleaning by hitting the membrane surface with a liquid flow” is performed, the cleaning liquid introduced into the raw water flow path 420 from the opening on one end side of the outer cylinder 440 is used as the other end side. Drain from the opening.

  Examples of the present invention will be described below, but the present invention is not limited to such examples.

Example 1
Using the cleaning system for a filtration membrane for ballast water treatment shown in FIG. 1, chemicals (hydrogen peroxide) and fine bubbles (air; bubble diameter of 10 to 100 μm) are supplied to the cleaning liquid composed of seawater after membrane filtration. Then, the filtration membrane (spiral membrane) 41 on which the cake layer was formed by the ballast water treatment was washed.
A turbidity meter was installed in the circulation pipe W of the cleaning liquid, and the turbidity of the cleaning liquid that increased with cleaning was measured.

  When the above test was performed four times in total, the average amount of increase in turbidity of the cleaning liquid was 3.27 ppm.

(Comparative Example 1)
In Example 1, the test was performed in the same manner as in Example 1 except that the fine bubbles were not supplied to the cleaning liquid and only the chemical supply was performed.

  The average amount of increase in the turbidity of the cleaning liquid in the four tests in total was 1.77 ppm.

<Evaluation>
In Example 1 in which the chemical and fine bubbles were supplied to the cleaning liquid, the amount of increase in turbidity increased dramatically compared to Comparative Example 1 in which only the chemical was supplied. It turns out that it is outstanding.

1: Ballast pump 2: Ballast tank 3: Pre-filter 4: Filtration membrane device 41: Filtration membrane 42: Raw water chamber 43: Treated water chamber 44: Ballast water supply valve 45: Ballast water discharge valve 5: Cleaning mechanism 51: Circulation pump 52: Drug supply device 520: Cleaning liquid circulation tank 521: Drug tank 522: Contaminant removing means 53: Fine bubble supply device 530: Branch pipe 531: Branch portion 532: Merge portion 533: Gas-liquid mixing portion 534: Gas supply source 535 : Gas-liquid mixing pump 54 Cleaning liquid supply valve 55 Cleaning liquid discharge valve B: Intake piping W: Circulation piping

Claims (6)

A ballast water treatment filtration membrane cleaning system for cleaning a ballast water treatment filtration membrane with a cleaning liquid,
A circulation pipe for circulating a cleaning liquid so as to contact the filtration membrane;
A medicine supply device for supplying medicine into the cleaning liquid in the circulation pipe;
A fine bubble supply device for supplying fine bubbles into the cleaning liquid in the circulation pipe;
A cleaning system for a filtration membrane for ballast water treatment, comprising: a circulation pump that circulates the cleaning solution in the circulation pipe and brings the cleaning solution containing the chemical and the fine bubbles into contact with the filtration membrane. The fine bubble supply device includes:
A branch pipe that branches a part of the cleaning liquid at a branch section on the upstream side of the circulation pipe and returns it again at a junction section on the downstream side of the circulation pipe;
A gas-liquid mixing part that is provided in the middle of the branch pipe and mixes gas into a part of the cleaning liquid,
The ballast water treatment filtration membrane cleaning system according to claim 1, wherein microbubbles are generated in the cleaning liquid in the circulation pipe after joining.   The said chemical | medical agent is hydrogen peroxide or sodium hypochlorite, The washing | cleaning system of the filtration membrane for ballast water treatment of Claim 1 or 2 characterized by the above-mentioned. A method of cleaning a filtration membrane for ballast water treatment, wherein the filtration membrane for ballast water treatment is washed with a washing liquid,
A method for cleaning a filtration membrane for ballast water treatment, comprising cleaning the filtration membrane by bringing the cleaning liquid containing a chemical and fine bubbles into contact with the filtration membrane.   The method for cleaning a filtration membrane for ballast water treatment according to claim 4, wherein the fine bubbles are microbubbles.   The said chemical | medical agent is hydrogen peroxide or sodium hypochlorite, The cleaning method of the filtration membrane for ballast water treatment of Claim 4 or 5 characterized by the above-mentioned.

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