JP2000225325A - Flat membrane separation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain separation performance of a flat membrane at a high level over a long time and significantly reduce the frequency of cleaning by supporting cleaning members of film with numerous cuts formed at a specified interval on an upper and a lower end part using support members and tensely fitting the cleaning members across the entire separation faces of flat membranes longitudinally along a flow path for liquid to be treated. SOLUTION: This flat membranes separation device has a lower end opening serving as an inflow aperture 12 for liquid to be treated and an upper end opening serving as a discharge aperture 13 for a concentrate, and also has a flat membrane module 2 consisting of plural rectangular platelike flat membranes 3 arranged at a specified interval in the horizontal direction, inside a rectangular casing 7 immersed in a sludge separation treating tank 11. In addition, below the flat membrane module 2, an air diffuser 6 is arranged which diffuses gas into flow paths 5 for the liquid to be treated having gaps between the flat membranes 3. Further, the cleaning members 4 with numerous cuts formed at a specified interval are tensely fitted across the entire separation faces of the flat filtration films longitudinally along the flow paths 5 and the upper and lower end parts of the cleaning members 4 are supported by both support members 8, 9. The cleaning members 4 are brought into contact with the flat membrane 3 by diffused gas which rocks the members 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat membrane separation apparatus for separating solid and liquid by a flat membrane module having a plurality of rectangular plate-shaped flat membranes arranged at predetermined intervals in a horizontal direction.

[0002]

2. Description of the Related Art Conventionally, sludge concentration for maintaining a high-load operation of a biological treatment tank in an activated sludge treatment apparatus or a nitrification / denitrification treatment apparatus for treating organic wastewater in an aerobic or anaerobic biological treatment tank. For the replacement of sedimentation ponds in human waste treatment plants and sewage treatment plants, the concentration of excess sludge, or the use of microfiltration membranes or ultrafiltration membranes for cylindrical membranes or rectangles for microfiltration in pharmaceuticals, foods, and other industries 2. Description of the Related Art A filtration membrane separation device that performs solid-liquid separation using a filtration membrane module such as a plate-like flat membrane is used.

[0003] In the above-mentioned filtration membrane separation device, since slime or the like formed of a polymer substance such as sludge or protein adheres to the membrane surface of the filtration membrane module, chemical washing or air is supplied below the filtration membrane module. Gas that diffuses from the membrane prevents adhesion to the membrane surface and removes and removes adhered substances. However, a filtration membrane separation apparatus (hereinafter, referred to as a flat membrane module) using a flat membrane module in which a plurality of flat membranes are provided in parallel. In Japanese Patent Application Laid-Open No. 8-131, a flat membrane separation device in which a cleaning member is arranged between flat membranes is disclosed.
No. 783, JP-A-8-309161 and JP-A-9-890.

[0004] The cleaning member described in the above-mentioned Japanese Patent Application Laid-Open No. 8-131783 is one in which a flexible member such as a plastic net is supported at an upper end portion.
No. 9161 discloses a cleaning member in which upper and lower ends of a thread-like or string-like member are fixed to a membrane module. Further, the cleaning member described in Japanese Patent Application Laid-Open No. 9-890 discloses a long fiber bundle. The upper and lower ends are supported.

[0005]

In the above-mentioned conventional filtration membrane apparatus, which diffuses gas to generate turbulence and peel off deposits by shearing force, a polymer such as sludge or protein in a biological treatment liquid is used. Since the substance is extremely easy to adhere to the surface of the filtration membrane and has stickiness, the turbulence effect alone is not likely to cause peeling, and the expected effect cannot be obtained. Therefore, in a short period of time
At present, the amount of membrane permeated liquid is reduced, the amount of membrane permeated liquid is reduced, the number of times the operation is stopped and the cleaning is performed is increased, and the amount of diffused air is also increased more than necessary.

In a conventional flat membrane separation device provided with a cleaning member for preventing sludge from adhering to the surface of a filtration membrane and for removing and removing adhering substances, a large number of thread-like or string-like cleaning members are vertically moved. It takes time and effort to support the support member, and requires extremely complicated preliminary investigations to select the optimal cleaning member with the appropriate flexibility and lightness, sufficient strength and material that does not damage the filtration membrane. In addition, there is a problem that the production cost is high.

[0007] Therefore, the present invention is to dispose a cleaning member that effectively prevents sludge and the like from adhering to the surface of the filtration membrane and effectively removes adhering matter of the filtration membrane after adhering without fear of damaging the filtration membrane. Accordingly, the present invention has been made for the purpose of providing a flat membrane separation device capable of maintaining the filtration performance of a filtration membrane for a long period of time and greatly reducing the frequency of washing.

[0008]

The gist of the present invention for achieving the above object is as follows.
A plurality of rectangular plate-shaped flat membranes are juxtaposed at predetermined intervals in the horizontal direction, and a gap between the flat membranes is disposed below the flat membrane module formed as a liquid passage to be treated and the flat membrane module. In a flat membrane separation device provided with a gas diffusing means for diffusing gas into a liquid passage to be treated, a thin film cleaning member provided with a number of cuts at predetermined intervals is supported by a support member at upper and lower ends. A flat membrane separation apparatus characterized in that the flat membrane separation device extends vertically along the liquid passage to be processed and extends over substantially the entire flat membrane filtration surface.

Further, in the invention according to claim 2,
2. The flat membrane separation device according to claim 1, wherein the cut provided on the cleaning member of the flat membrane separation device is a vertical cut.

Further, in the invention according to claim 3,
2. The flat membrane separation device according to claim 1, wherein the cut provided in the cleaning member of the flat membrane separation device is a cut in a horizontal direction.

The flat membrane is formed on both surfaces of a non-woven fabric molded body surrounded by a rectangular plate-shaped frame having a permeated liquid flow path, such as a cellulose acetate system, an aromatic polyamide system, or a polyphone system. It is preferable that the filter is formed by attaching an organic filter membrane, but the present invention is not limited to this. The filter may be formed of an inorganic material such as a ceramic membrane. The filtration membrane has a pore size of 0.1.
A microfiltration membrane having a microfiltration of to several μm or an ultrafiltration membrane having a molecular weight cutoff of about tens of thousands to hundreds of thousands is used, but a microfiltration membrane is preferably used.

Further, the thin film cleaning member has a thickness of 0.0
Sheets of 1 to 0.1 mm such as polyethylene, polypropylene and nylon are preferable because they are durable and flexible and do not damage the filtration membrane, and the cuts are provided at 3 to 15 mm intervals in the vertical or horizontal direction. 5 vertically
It is preferable to provide them at an interval of 10 to 10 mm because an appropriate swing can be obtained, but the present invention is not limited to these.

In the above, if the cutting interval is less than 3 mm, there is a disadvantage that the strength of the sheet becomes too weak and the sheet is easily cut, and if it is more than 15 mm, it is difficult to obtain proper swinging and wide contact is caused. The effect of peeling the kimono is low, and if the sheet thickness is less than 0.01 mm, the strength of the sheet becomes too weak and there is a disadvantage that it is easy to cut, and if it is more than 0.1 mm, it is difficult to obtain appropriate swinging. At the same time, the flexibility is lost and the surface of the filtration membrane may be damaged. The cut interval and the cut length are appropriately determined within the above range depending on the material of the sheet to be used and the like.

Further, the cleaning member has a lower end portion supported by the support member and an upper end portion supported by the support member, and is loosely stretched. This is preferable because it gives a movement and makes uniform contact with the entire surface of the filtration membrane. Further, as a supporting method by the supporting member, the end surface of the sheet is wound around the supporting member, and the leading end is sewn or adhered. Is preferably fixed, but the end face of the sheet may be fixed via a reinforcing member,
Further, the support member may be directly fixed to the support member by bonding or sandwiching so as not to move, and the present invention is not limited thereto.

The gas diffused from the air diffusing means for causing an upward flow of the liquid to be treated and for oscillating the cleaning member is mainly air when used aerobically. Is used. When used anaerobically, it is preferable to use anaerobic gas generated by biological treatment, and the supply amount is 50 to 80 m3 / m @ 2.
h is preferred.

Conventionally, when the operation of filtering the liquid to be treated with a filtration membrane device is continued, polymer substances such as sludge and protein adhere to the surface of the filtration membrane, and slime and scale are easily formed. However, in the flat membrane separation device of the present invention, the cleaning member is oscillated by the gas supplied from the air diffuser, and a wave of an appropriate amplitude is given, so that the side surface of the cleaning member contacts the flat membrane surface. Since the adhering sludge is always peeled off and the membrane surface is washed by the turbulent effect of gas, it is extremely difficult to form.

[0017]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view of a flat membrane separation device disposed in a sludge separation treatment tank according to one embodiment of the present invention.
FIG. 2 is a schematic diagram of a cleaning member provided with a cut in the vertical direction, and FIG. 3 is a schematic diagram of a cleaning member provided with a cut in the horizontal direction.

1 is provided with an upper and lower end surface, a lower end opening as an inlet 12 for the liquid to be treated, and an upper end opening as a discharge outlet 13 for the concentrated liquid, and a constant distance from the bottom surface in the sludge separation treatment tank 11 by supporting legs. A flat membrane module 2 in which a plurality of rectangular plate-shaped flat membranes 3 are juxtaposed at predetermined intervals in a horizontal direction is provided inside a cylindrical rectangular casing 7 which is immersed and mounted with the above. This is a flat membrane separation apparatus in which gas diffusion means 6 for dispersing gas into the liquid passage 5 to be treated, which is formed by a gap between the flat membranes 3, is provided below the flat membrane module 2.

The flat membrane module 2 has a plurality of rectangular plate-shaped flat membranes 3 provided side by side at predetermined intervals in a horizontal direction by an appropriate support member. connection,
A permeate discharge pipe 10 for collectively discharging the permeate which has passed through each flat membrane 3 is provided, and is connected to a permeate discharge means (not shown).

The flat membrane 3 is provided on both sides of a non-woven fabric molded body surrounded by a rectangular plate-shaped frame having a permeated liquid flow path.
It is preferable to attach a filtration membrane made of an organic material such as acecetate type, aromatic polyamide type and polyphone type, but it is not limited to this, and it may be formed of an inorganic material such as a ceramic film. . The filtration membrane has a pore size of 0.1 to
A microfiltration membrane of several μm or an ultrafiltration membrane having a molecular weight cutoff of tens of thousands to hundreds of thousands is used, but a microfiltration membrane is preferably used.

Further, the flat membrane separation device 1 is traversed longitudinally along a liquid passage 5 to be treated, which is a gap formed between the flat membranes 3 of the flat membrane module 2, and is provided with a flat membrane filtration surface. And a thin film cleaning member 4 having upper and lower ends supported by support members 8 and 9 and provided with a large number of cuts at predetermined intervals.

The cleaning member 4 has a thickness of 0.01 to 0.01.
A sheet of 0.1 mm of polyethylene, polypropylene, nylon or the like is preferable because it is strong and flexible and does not damage the filtration membrane, and the cut is a vertical cut 20a or a horizontal cut shown in FIG. 2 or FIG. 20b to 3
It is provided at an interval of up to 15 mm.
Are preferably provided at intervals of 5 to 10 mm. Further, a cut in an oblique direction or the like may be used.

In the above, if the cutting interval is 3 mm or less, there is a disadvantage that the strength of the sheet becomes too weak and the sheet is easily cut, and if it is 15 mm or more, it is difficult to obtain appropriate swing and wide contact is caused. The effect of peeling the kimono is low, and if the sheet thickness is less than 0.01 mm, the strength of the sheet becomes too weak and there is a disadvantage that it is easy to cut, and if it is more than 0.1 mm, it is difficult to obtain appropriate swinging. At the same time, the flexibility is lost and the surface of the filtration membrane may be damaged. The cut interval and the cut length are appropriately determined depending on the material of the sheet to be used and the like.

The cleaning member 4 has a support member 9 at the lower end.
The upper end is supported by the support member 8 and is loosely stretched, so that the gas supplied from the diffusing means 6 is given a swing of an appropriate amplitude and the entire surface of the filtration membrane surface is It is preferable because it makes uniform contact. Further, the support member 8,
As a supporting method according to No. 9, it is preferable that the end face of the sheet is wound around the supporting member and the front end is fixed by sewing or bonding, but the end face of the sheet is fixed via a reinforcing member. And the present invention is not limited thereto.

The gas diffused from the diffusing means 6 for causing the upward flow of the liquid to be treated and for oscillating the cleaning member 4 is mainly used when it is used aerobically. Although air is used, it is preferable to use an anaerobic gas generated by biological treatment when used anaerobically.

The sludge separation treatment tank 11 is a treatment tank for solid-liquid separation of a biological treatment liquid after aerobic treatment of organic wastewater in a biological treatment apparatus into sludge and a clear treatment liquid. The flat membrane separation device 1 may be directly disposed in the processing tank of the processing apparatus, and the biological processing apparatus may be an apparatus that repeatedly performs anaerobic and aerobic processing in a single processing tank, The apparatus may be an apparatus in which a plurality of compartments or biological treatment tanks are separately provided to improve the biological denitrification / phosphorus removal effect by combining aerobic and anaerobic treatments.

Hereinafter, the operation of the flat membrane separation apparatus 1 having the above configuration will be described. The biological treatment liquid which has been treated to reduce BOD, COD, etc. by decomposing organic substances in organic wastewater by the biological action of microorganisms in the biological treatment apparatus is supplied to the biological treatment liquid supply pipe 14.
Is supplied to a sludge separation treatment tank 11 from the inlet of the liquid to be treated 12 at the lower end of the flat membrane separator 1 as a liquid to be treated.
During the upward flow of the liquid to be treated 5 formed between the plurality of flat membranes 3 due to the air lift effect of the gas supplied from the diffuser 6 while flowing into the sink 7, the permeated liquid discharge pipe 10
Flat membrane 3 depressurized by discharge means (not shown) connected to
And only water passes through the filtration membrane to obtain a clear permeate and a concentrate in which sludge is concentrated.

In the above-mentioned filtration treatment, the suction pressure by the discharge means is 0 to -600 mmHg, and the concentrated liquid is a rectangular case.
It is circulated in the sludge separation treatment tank 11 from the concentrated liquid discharge port 13 at the upper end of the thing 7 and is appropriately concentrated, and is circulated and supplied as a high-load operation sludge to a biological treatment apparatus or the like from the sludge discharge pipe 15 and partially. Is supplied to a sludge treatment device as surplus sludge and treated. Further, the permeated liquid is discharged out of the system as a clear processing liquid from the discharge pipe 10.

Further, even if the operation of filtering the liquid to be treated by the flat membrane separator 1 is continued, the side surface of the cleaning member 4 to which the gas supplied from the air diffuser 6 is given a swing of an appropriate amplitude. The contact with the surface of the flat membrane 3 prevents the attachment of sludge and the like, and even if the sludge adheres, it is always peeled and removed, and the membrane surface is washed with gas from the air diffusing means. Slime is extremely unlikely to be formed due to the high molecular substance and the like.

In a conventional filtration membrane apparatus in which gas is diffused and turbulence is generated from the gas diffusion means 6 to cause turbulence and adhered matter is separated by a shear force, the gas is supplied per flat membrane installation projected area. Although it was 80 to 130 m 3 / m 2 · h, the flat membrane separation device of the present invention can be operated at 50 to 80 m 3 / m 2 · h per flat membrane installation projected area.

Next, a test example will be described in which a biological treatment liquid obtained by subjecting wastewater from a food factory to aerobic biological treatment is used as raw water, and solid-liquid separation is performed using a flat membrane separation device disposed outside the biological treatment tank. (Example 1) width 610 mm, height 1060 mm, thickness 1
A flat membrane module provided with 240 3 mm flat membranes is provided in a rectangular casing, and is used as a cleaning member.
m, using a flat membrane separation device in which a polypropylene sheet with a cutting interval of 10 mm is arranged, and blowing the air from the air diffuser at a rate of 60 m 3 / m 2 · h per the projected area of the flat membrane installation, and oscillates the cleaning member. Raw water was allowed to flow upward.
As a result of a test using a mixed solution having a sludge concentration of 12000 mg / l as raw water, a permeate having a solid concentration of 0 mg / l was obtained at an initial permeate amount of 0.42 m3 / m3. It did not decrease and did not show any decrease thereafter.

(Comparative Example 1) A flat membrane module having the same five flat membranes as in Example 1 was provided in a rectangular casing, and air was supplied to the flat membrane installation projected area without using a cleaning member.
Example 1 Using a flat membrane separation device that diffuses air at m 3 / m 2 · h to cause turbulence and separates adherents by shearing force.
As a result of using the same raw water as in Example 1, the solid content concentration was 0 mg.
/ L of permeate was obtained with an initial permeate volume of 0.42 m3 / m3. However, the permeate pressure began to increase from about the 10th day. On the 25th day, the operation was stopped because the allowable pressure was exceeded.

As a result of the above test, in the flat membrane separation device of the present invention, an extremely clear permeate having a solid content of 0 mg / l was obtained, and the initial permeate amount was obtained over a long period of 3 to 6 months. Operation that requires almost no maintenance has been made possible. Also, the supply air amount is 20 to 40 compared with the conventional device.
%, And operating costs such as power costs can be saved. Furthermore, as compared with a conventional apparatus using a thread-like or string-like cleaning member, it can be easily installed, has appropriate flexibility and lightness, has sufficient strength and does not damage the filtration membrane. The most suitable cleaning member of the material could be easily selected.

[0034]

According to the present invention, there is provided a cleaning member capable of effectively preventing sludge and the like from adhering to the surface of the filtration membrane, and effectively removing adhered substances from the filtration membrane after the adhesion, without damaging the filtration membrane. By doing so, the filtration performance of the filtration membrane can be maintained for a long time,
This is a flat membrane separation device that can greatly reduce the frequency of cleaning.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a flat membrane separation device arranged in a sludge separation treatment tank according to one embodiment of the present invention.

FIG. 2 is a schematic view of a cleaning member provided with a cut in a vertical direction.

FIG. 3 is a schematic view of a cleaning member provided with a notch in a horizontal direction.

[Explanation of symbols]

 1: flat membrane separation device 2: flat membrane module 3: flat membrane 4: cleaning member 5: liquid passage to be treated 6: air diffuser 7: rectangular casing 8: upper end support member 9: lower end support Member 10: Permeated liquid discharge pipe 11: Sludge separation treatment tank 12: Inflow port of liquid to be treated 13: Concentrated liquid discharge port 14: Biological treatment liquid supply pipe 15: Sludge discharge pipe

Continued on the front page F term (reference) 4D006 GA06 GA07 HA42 HA93 JA34A JA34B JA34C KA43 KA44 KC02 KC20 KE01Q KE05P KE08Q KE12P KE13P MA03 MA22 MB05 MC03 MC18 MC54 MC62 PA01 PB08 PC11 PC62

Claims (3)

[Claims] 1. A flat membrane module in which a plurality of rectangular plate-shaped flat membranes are provided at predetermined intervals in the horizontal direction, and a gap between the flat membranes is formed as a liquid passage to be treated. And a gas diffusion means for diffusing gas into the liquid passage to be treated, the thin film cleaning member provided with a number of cuts at predetermined intervals is provided at the upper and lower ends. A flat membrane separation device supported by a support member and extending longitudinally along the liquid flow path to be treated and extending over substantially the entire flat membrane filtration surface. 2. The flat membrane separation device according to claim 1, wherein the cut provided in the cleaning member is a cut in a vertical direction. 3. The flat membrane separation apparatus according to claim 1, wherein the cut provided in the cleaning member is a cut in a horizontal direction.