JP2007038172A - Membrane treatment equipment - Google Patents

Abstract

To provide a membrane treatment apparatus capable of washing a filter cloth itself during backwashing of the membrane.
A membrane treatment apparatus of the present invention includes a filtration membrane 10 that pressurizes and filters raw water existing around the outside, and a treated water outlet 11 that takes out treated water collected after filtration by the filtration membrane 10. And having a filter cloth 12 arranged and fixed outside the filtration membrane 10 at a predetermined interval. As a preferred embodiment, the filter cloth 12 has an outer peripheral side surface and a bottom portion of the filtration membrane 10. In other words, the filter cloth 12 is provided so as to cover the outer peripheral side surface with the bottom of the filtration membrane 10 open.
[Selection] Figure 1

Description

  The present invention relates to a membrane processing apparatus, and more specifically, can prevent floating substances and organic substances that cause clogging from entering the membrane surface, reduce the number of backwashes, and also clean the filter cloth itself. The present invention relates to a film processing apparatus that can sometimes be performed.

  Conventionally, in the field of sewage treatment such as sewage and human waste, membrane treatment techniques such as microfiltration membranes and ultrafiltration membranes have been further improved from solid-liquid separation means for obtaining clear treated water. It has come to be used as a solid-liquid separation means such as a concentration tank.

  In such membrane treatment, clogging of the filtration membrane becomes a problem because sludge having a high concentration such as activated sludge is solid-liquid separated.

  In Patent Document 1, a filter cloth is provided on the surface of the filtration membrane, and impurities in the raw water are removed with the filter cloth, a cake layer of the impurities is formed on the filter cloth, and the raw water that has passed through the cake layer is then passed through. A method of treating with a film is disclosed.

According to the technique of this patent document 1, the fine particles are certainly removed by the pretreatment with the cake layer formed on the filter cloth, and the clogging time of the filtration membrane is extended.
Japanese Patent Laid-Open No. 5-184819

  However, if the cake layer is formed on the filter cloth as in Patent Document 1, the cake layer adheres to the filter cloth in a compacted state, so that the cake layer is likely to be clogged, and the filter cloth is washed. After all, the filter cloth is structured so that it can always be moved as shown in FIG. 2 of Patent Document 1, and when the filter cloth becomes clogged, the filter cloth is moved and the cake layer is formed again. It has to be formed and filtered and has the disadvantage that it does not function at all as an actual device.

  An object of the present invention is to provide a membrane processing apparatus that can perform the cleaning of the filter cloth itself at the time of back washing of the membrane in order to eliminate the drawbacks of the technology.

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

  The above problems are solved by the following inventions.

(Claim 1)
It has a filtration membrane that pressurizes and filters raw water present around the outside, and a treated water outlet that takes out the treated water collected after filtration by the filtration membrane, and is arranged outside the filtration membrane at a predetermined interval. A membrane treatment apparatus comprising a fixed filter cloth.

(Claim 2)
The membrane treatment apparatus according to claim 1, wherein the filter cloth is provided so as to cover an outer peripheral side surface and a bottom portion of the filtration membrane.

(Claim 3)
The membrane treatment apparatus according to claim 1, wherein the filter cloth is provided so as to cover an outer peripheral side surface with a bottom portion of the filtration membrane open.

(Claim 4)
4. The membrane treatment apparatus according to claim 3, wherein a lower portion of the filter cloth is extended downward from a lower end portion of the filtration membrane, and an outer periphery of the extension portion is narrowed down by an elastic string.

(Claim 5)
5. The membrane treatment according to claim 1, wherein the filter cloth has a pore size distribution in a range of 0.1 to 50 μm and a peak of the pore size distribution is in a range of 5 to 25 μm. apparatus.

(Claim 6)
The membrane treatment apparatus according to claim 1, wherein the filtration membrane is a microfiltration membrane and has a nominal pore diameter in a range of 0.1 to 1.0 μm.

(Claim 7)
The membrane treatment apparatus according to claim 1, wherein the filter cloth has a pleated shape.

  According to the present invention, it is possible to prevent floating substances and organic substances that cause clogging from entering the membrane surface, to reduce the number of backwashes, and also to wash the filter cloth itself when washing the membrane. A practical membrane treatment apparatus can be provided, and is particularly effective for the treatment of ballast water.

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

First Embodiment FIG. 1 is a view showing an example of a membrane treatment apparatus of the present invention, in which 1 is a membrane treatment apparatus, and 10 is a filtration membrane that pressurizes and filters raw water existing outside. 11 is a treated water outlet for removing treated water collected after filtration, and 12 is a filter cloth disposed and fixed outside the filtration membrane 10.

  This embodiment is an example in which a so-called sock mold is employed in which the filter cloth 12 is provided so as to cover the outer peripheral side surface and the bottom of the filtration membrane 10.

  The membrane processing apparatus 1 is preferably a vertical type as shown in the figure, but may be a horizontal type.

  Examples of the filtration membrane 10 include a microfiltration membrane (MF membrane) and an ultrafiltration membrane (UF membrane), and the microfiltration membrane is located between the normal filtration and the ultrafiltration. A preferred nominal pore diameter is in the range of 0.05 to 10 μm, and a more preferred nominal pore diameter is in the range of 0.1 to 1.0 μm. Ultrafiltration membranes are basically defined by the molecular weight cut off, but in general, water, ionic molecules, low molecular weights do not pass through 0.005-0.1 micron fine particles. It is a membrane that has the property of transmitting substances.

  In the present invention, a microfiltration membrane is preferable from the viewpoint of effectively removing bacteria and the like in ballast water.

  Various synthetic resins (for example, polyester, acrylic, nylon, polyethylene, polypropylene, cellulose, acetate, etc.) can be used as the material of the film, but it is not particularly limited.

  The filter cloth 12 may be either woven or non-woven, but preferably has a pore size distribution in the range of 0.1 to 50 μm and a peak of the pore size distribution in the range of 5 to 25 μm as shown in FIG. Those that do are preferred.

  The material of the filter cloth 12 is not particularly limited, but preferably has a tensile strength that does not break during backwashing, and further has stretchability to improve the backwashing effect.

  The shape after installation of the filter cloth 12 may be a cylindrical shape as shown in FIG. 1, but as shown in FIG. 4, if the pleated shape is used, the filtration area can be doubled or more. This is preferable because the capture rate of floating substances, organic substances, bacteria, and the like is improved, and the stretchability can be secured, so that there is an effect that it is not necessary to use a stretchable material as the material of the filter cloth 12.

  Raw water containing suspended matter, organic matter, bacteria, or the like is pressurized from the outside to the inside of the membrane treatment apparatus 1 as indicated by an arrow 13. Although the pressurizing mechanism is not illustrated, it is not particularly limited as long as the raw water 13 outside the apparatus is pressurized.

  In the pressurizing process, suspended substances, organic substances, or bacteria having a large particle size are captured by the filter cloth 12. This trapped material is hereinafter referred to as a fouling material, and in the drawing, a large fouling material is indicated by a symbol F and a small fouling material is indicated by a symbol f.

  When the raw water that has passed through the filter cloth 12 passes through the filtration membrane 10, fine suspended matter, organic matter, or bacteria are captured by the filtration membrane 10.

  The membrane treatment apparatus 1 of the present invention is effective for removing bacteria in ballast water. In general, 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. Normally, 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 live in the port where the water was taken, and these microorganisms and eggs of small and large organisms are transported to different countries at the same time as the ship moves. 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 area, has become serious. Against this background, the diplomatic meeting of the International Maritime Organization (IMO) adopted the obligation to receive periodic inspections for ballast water treatment equipment, etc., and is scheduled to be applied from 2009 and later on construction ships. . In addition, according to the convention for the regulation and management of ship ballast water and sediment, the discharge standard of ballast water will be as shown in Table 1 below. For this reason, it is necessary to disinfect up to about 1 / 100th of the number of microorganisms present in the open ocean when discharging ballast water.

  In the present invention, when an MF membrane having a nominal pore diameter of 0.4 μm is used, a filter cloth 12 having a pore diameter distribution in the range of 0.1 to 50 μm and a pore diameter distribution peak located at 20 μm is used, the filter cloth 12 is used. Therefore, plankton having a size of 50 μm or more can be removed 100%, and plankton having a size of 10 to 50 μm can be almost removed. Thereby, the fouling substance adhering to the filtration membrane 10 decreases, the time until the limit capture of the filtration membrane 10 is extended, and the filtration time is extended accordingly. The filtration membrane 10 can completely remove plankton having a size of 10 to 50 μm, and can remove bacteria 100%.

  The membrane treatment apparatus 1 according to the present invention has a feature in that the filtration membrane 10 and the filter cloth 12 of the membrane treatment apparatus 1 can be backwashed at the same time. Such backwashing will be described as shown in FIG. The washing water is injected from the treated water outlet 11. The injected backwash water flows from the inside to the outside of the filtration membrane 10 and discharges the fouling substances F and f captured by the filtration membrane 10 to the outside. Since the discharged fouling substances F and f have originally passed through the filter cloth 12, they are discharged to the outside through the filter cloth 12 by a reverse flow. Further, the fouling substances F and f captured by the filter cloth 12 are also discharged to the outside as indicated by the arrow 14 by the backwash water.

  In the present invention, when the filter cloth 12 has elasticity, the fouling substances F and f captured by the filter cloth 12 can be easily removed.

  In the present invention, it is not necessary to separately wash the filter cloth 12 as in the prior art, and the washing operation can be simplified because the filter cloth 12 can be washed together with the backwash water, and the apparatus moves the filter cloth 12. Therefore, the cost of the membrane treatment apparatus 1 is reduced because only the sock-type filter cloth 12 is provided.

Second Embodiment Next, another embodiment of the present invention will be described. This embodiment is an example in which the filter cloth 12 is provided so as to cover the outer peripheral side surface with the bottom of the filtration membrane 10 opened, and is formed into a so-called skirt shape.

  FIG. 5 is a diagram showing a second mode. As shown in FIG. 5, the filter cloth 12 is a skirt type, and the lower part is open. It is also possible to narrow the lower portion of the filter cloth 12 with an elastic string such as a rubber band 15 so that the filter cloth 12 does not rise during filtration.

  That is, the lower part of the filter cloth 12 is extended downward from the lower end part of the filtration membrane 10, and the outer periphery of the extended part is narrowed down by an elastic string-like body. The fouling substances F and f of the filtration membrane 10 can be prevented from accumulating between the filter cloth 12 and the filtration membrane 10. That is, as shown in FIG. 6, the rubber band 15 is extended by backwashing water pressure during backwashing, and the fouling substances F and f of the filtration membrane 10 are peeled off.

  In this embodiment, the movement of the filter cloth 12 is flexible, and the fouling substances F and f are peeled off by shaking the filter cloth 12 during backwashing.

  Hereinafter, the effect of the present invention is illustrated by examples.

Example 1
The raw water was filtered and backwashed using the membrane treatment apparatus shown in FIG.

<Raw water conditions>
Raw water Seawater for obtaining ballast water
SS 5.0mg / l
Plankton 10-50 μm: 10 / ml
50 μm or more: 5 × 10 ⁴ pieces / m ³
Bacteria 5 × 10 ⁴ cfu / 100ml

<Specifications of membrane treatment equipment>
Filtration membrane Microfiltration membrane (Nominal pore size 0.4μm)
Pressurized pressure 20-500kPa

<Specifications of filter cloth>
Filter cloth installation method: Sock type Filter cloth material Non-woven fabric Hole diameter distribution of filter cloth Hole diameter distribution: range of 0.1 to 50 μm Peak of pore diameter distribution: about 20 μm

<Process result>
Treatment effect by filter cloth (1) Plankton having a size of 50 μm or more could be removed 100%.
(2) Plankton having a size of 10 to 50 μm was almost removed.

Treatment effect by filtration membrane (1) Plankton having a size of 10 to 50 μm could be completely removed.
(2) Bacteria could be removed 100%.

<Backwash treatment>
When the filter cloth was not provided, the time until the filter membrane was captured was 8 minutes. However, when the filter cloth was provided, the time until the filter membrane was captured was 20 minutes. It was found that the filtration time was extended.

Example 2
In Example 1, the raw water was filtered and backwashed in the same manner except that the membrane treatment apparatus was replaced with the membrane treatment apparatus shown in FIG. 5 (the filter cloth was installed in a skirt type). The processing results were the same as in Example 1.

<Backwash treatment>
When the filter cloth was provided, the time to capture the limit of the filtration membrane was 30 minutes, and it was found that the time was further extended from that of Example 1 and the filtration time was extended accordingly.

The figure which shows an example of the film processing apparatus of this invention The figure which shows the state at the time of backwashing of FIG. Figure showing the relationship between pore distribution and pore size of filter cloth The figure which shows the other aspect of a filter cloth The figure which shows the other example of the film processing apparatus of this invention The figure which shows the state at the time of backwashing of FIG.

Explanation of symbols

1: membrane treatment device 10: filtration membrane 11: treated water outlet 12: filter cloth 13: raw water 15: rubber band (elastic string)
F: Large fouling material f: Small fouling material

Claims (7)

  It has a filtration membrane that pressurizes and filters raw water present around the outside, and a treated water outlet that takes out the treated water collected after filtration by the filtration membrane, and is arranged outside the filtration membrane at a predetermined interval. A membrane treatment apparatus comprising a fixed filter cloth.   The membrane treatment apparatus according to claim 1, wherein the filter cloth is provided so as to cover an outer peripheral side surface and a bottom portion of the filtration membrane.   The membrane treatment apparatus according to claim 1, wherein the filter cloth is provided so as to cover an outer peripheral side surface in a state where a bottom portion of the filtration membrane is opened.   4. The membrane treatment apparatus according to claim 3, wherein a lower portion of the filter cloth is extended downward from a lower end portion of the filtration membrane, and an outer periphery of the extension portion is narrowed down by an elastic string.   5. The membrane treatment according to claim 1, wherein the filter cloth has a pore size distribution in a range of 0.1 to 50 μm and a peak of the pore size distribution is in a range of 5 to 25 μm. apparatus.   The membrane treatment apparatus according to claim 1, wherein the filtration membrane is a microfiltration membrane and has a nominal pore diameter in a range of 0.1 to 1.0 μm.   The membrane treatment apparatus according to claim 1, wherein the filter cloth has a pleated shape.

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