JPH0889766A - Membrane separating device - Google Patents

Abstract

PURPOSE: To provide a membrane separating device in which a membrane unit can be mechanically safely held and moreover, the membrane units can be arranged in small size and easily integrated. CONSTITUTION: A reinforcing frame 1 having a projecting part 14 for fitting on one side and a recessed part 13 for fitting on the other side is attached to each membrane unit 2. The membrane units with the reinforcing frames are stacked to engage the recessed part and projecting part 13, 14 of the reinforcing frames 1 to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane separator used for purification treatment of suspensions, and is particularly useful for purification treatment of domestic wastewater and factory wastewater.

[0002]

When purifying a high-concentration suspension by a membrane separation method, a plurality of membrane units having semipermeable membranes on both sides of a filtrate channel sheet are arranged in parallel in a stock solution tank, The suspension is supplied into the stock solution tank of the membrane separation device in which a diffusing tube is installed below the membrane unit group, and the stock solution is filtered by jetting gas from the diffusing tube or by swirling the stock solution in the tank with a circulation pump. It is known to reduce the pressure on the liquid flow path side to filter the suspension (Japanese Patent Publication No. 4-70958 or Japanese Utility Model Publication 5-13).
389).

[0003]

However, in this conventional membrane separation device, the membrane units are arranged side by side at a predetermined interval (about 5 mm to 15 mm) and assembled in the frame, and the left and right ends of each membrane unit are attached. It is fixed (for example, the filtrate collecting pipes are attached to the left and right ends of the membrane unit and the filtrate collecting pipes are fixed to the frame), and the membrane flows under the action of the stock solution flowing pressure (p). Tensile stress acts on the unit with the left and right ends as fulcrums, and the supporting length (L) is greater than the membrane area (s).
The tensile stress is large due to the short length, and the tensile stress is proportional to ps / L, and the smaller L is, the larger the tensile stress is.
It is mechanically disadvantageous.

Further, since the frame is used for holding the membrane unit, it is inevitable that the apparatus is upsized due to the frame installation space. If the frame is simplified or omitted, it is difficult to maintain the space between the membrane units at a predetermined dimension due to the displacement between the membrane units arranged in parallel, and a sufficient amount of undiluted solution is swirled between the membrane units. There is a fear that it will be difficult.

An object of the present invention is to arrange a plurality of membrane units having semipermeable membranes on both sides of a sheet for a filtered liquid flow channel side by side in a stock solution tank, and to swirl the stock solution in the tank while arranging them in parallel. In the device for filtering the undiluted solution by depressurizing the filtrate flow path side of the membrane unit,
It is an object of the present invention to provide a membrane separation device capable of mechanically safely holding a membrane unit, and also capable of easily integrating a juxtaposed membrane unit in a small size.

[0006]

Means for Solving the Problems In a membrane separation device according to the present invention, a plurality of membrane units having semipermeable membranes on both sides of a sheet for a filtrate flow channel are arranged side by side in a stock solution tank. In a device for filtering the stock solution by depressurizing the filtrate flow path side of the juxtaposed membrane unit while swirling the stock solution, a reinforcing frame having a fitting projection on one of both side surfaces and a fitting recess on the other side The reinforcing frame mounting membrane unit is mounted on each of the membrane units, the reinforcing frame mounting membrane units are stacked, and the fitting concave and convex portions of the reinforcing frame are fitted to each other.

[0007]

The semipermeable membrane is supported by the reinforcing frame in four directions together with the filtrate flow sheet against the stock solution flow pressure (p) acting on the membrane surface. Therefore, the membrane area is s, and the perimeter of the frame is Is L, the tensile stress acting on the membrane surface is almost proportional to ps / L, and the supporting length L of the membrane is longer than that in the case of supporting the left and right ends of the conventional membrane unit [the vertical length of the membrane unit. Is a and the width is b, L = 2 (a + b), whereas in the case of supporting both left and right ends, it is 2a], and the tensile stress becomes small.

Further, since the concavo-convex portion for fitting is provided on the reinforcing frame mounted on the membrane unit and the membrane unit group is integrated by the concavo-convex fitting, the membrane unit can be naturally positioned at a proper position, and It is possible to surely prevent the displacement of the membrane units even when used in a liquid stock solution for a long period of time, and it is possible to maintain the space between the membrane units in place. Further, a frame for integrating the juxtaposed membrane units is not necessary, and the stock solution tank can be omitted to reduce the size of the stock solution tank.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a reinforcing frame used in the present invention. In FIG. 1, 1 is a reinforcing frame made of plastic or metal (for example, aluminum), which is a split-type two-split frame and is a filtrate that is connected to the four-sided frame part 11 and the left and right two-sided frame parts. The water collecting pipe portion (outer shape is a quadrangle) 12 is formed. Reference numeral 13 is a fitting concave portion provided on one of both side surfaces of the filtered water collecting pipe portion 12, and 14 is a fitting convex portion also provided on the other side.

2A is a plan view of the membrane unit 2 used in the present invention, FIG. 2B is a sectional view taken along the line of FIG. 2A, and FIG. C) is shown in Figure 2.
The cross-sectional views of (a) in FIG.
In FIGS. 2 (a) to 2 (c), 21 is a sheet for filtered liquid flow path, for example, a plastic net, a plastic non-woven fabric, a woven fabric (for example, a tricot woven fabric made of polyester, particularly this woven fabric). Resin liquid, such as melamine resin liquid that has been hardened to leave fiber gaps inside, etc.),
A porous plastic plate or the like is used. Reference numeral 1 denotes the above-mentioned reinforcing frame, which is attached around the sheet 21 for the filtrate flow path,
The palm surface of the reinforcing frame is sealed with an adhesive 23 '. Reference numeral 22 is a semipermeable membrane (such as a microfiltration membrane or an ultrafiltration membrane) adhered to the window of the reinforcing frame 1 by an adhesive 23 or fusion, and the microfiltration membrane or the ultrafiltration membrane is a base material such as a nonwoven fabric. It is also possible to use a material such as a non-woven fabric or the like, which is attached to the above, or a microfiltration membrane or an ultrafiltration membrane in which a base material such as a nonwoven fabric is embedded. 24 is a short pipe for taking out the filtrate, which is watertightly inserted into the upper end opening of the filtrate collecting pipe part 12 of the reinforcing frame 1 via an adhesive, and 25 is also a lower pipe opening of the filtrate collecting pipe part 12 via the adhesive. It is a watertight plug.

In the above, the seal on the abutment surface of the reinforcing frame,
As the adhesive used for adhering the semipermeable membrane to the reinforcing frame and watertightly fixing the short pipe for taking out the filtrate and the watertight stopper, for example, a curable adhesive such as an epoxy resin or a urethane resin, a hot melt adhesive or the like can be used.

FIG. 3 shows a main part of the juxtaposed structure A of the membrane unit 2 with the reinforcing frame, and the fitting convex portion 13 on one side of the filtrate collecting pipe 12 of the membrane unit 2 with one reinforcing frame. Then, a fitting concave portion 14 on the other side surface of the filtrate liquid collecting pipe portion 12 of the membrane unit 2 with a reinforcing frame is fitted to integrate the membrane unit group with the reinforcing frame, and the filtrate liquid collecting pipe portion 12 of the reinforcing frame 1 is integrated. The protrusion margin e is used as a spacer to keep a predetermined space between the membrane units 2 and 2.

In the above, as the reinforcing frame 1, as shown in FIG. 4, it is also possible to use one having the filtrate collecting tube part 12 only on one of the left and right frame parts of the four-sided frame part. In the installation, the protrusions 13 and the recesses 14 between the filtered water collecting pipe portions 12 and 12 are fitted together, and the spacers 121 are interposed above and below the other left and right frame portions.
The concavo-convex portion between each side surface of 21 and the frame portion of each membrane unit can be fitted.

In the present invention, as shown in FIG. 5, female joints 140 having recesses 14 are provided on one side of the reinforcing frame at several points other than the filtrate collecting tube section 12, and convex portions are projected at the same number of other sides. It is also possible to provide the male joints 130 each having the portion 13 and to integrate the membrane unit groups 1, ... By fitting the concave portions 14 and the convex portions 13. In the above, the fitting structure of the concave portion 14 and the convex portion 13 is preferably a so-called dovetail, as shown in (a) of FIG. 6 or (b) of FIG.

In the present invention, the membrane unit 2 has a structure shown in FIG.
As shown in FIG.
It is also possible to use a product which is sandwiched by 22 and which is provided with the reinforcing frame 1 around them and sealed between the frame 1 and the semipermeable membrane 22 with the adhesive 23.

FIG. 8 shows an example of the membrane separation device according to the present invention. In FIG. 8, reference numeral 51 denotes a stock solution tank, which can be closed with a mounting lid (not shown), and in this case as well, the inside is kept at atmospheric pressure. In this stock solution tank 51,
The aeration tank main body of the conventional aeration type aeration tank by the activated sludge system can be used. A is a membrane unit with a reinforcing frame 2, ...
And a lattice mount 52 at the bottom of the stock solution tank 51.
Fixed by.

Numerals 53, ... Are diffuser pipes provided below the juxtaposed structure A of the membrane units, 54 is an air supply pipe, and 55 is a blower. Reference numeral 56 is the filtrate collecting pipe 1 of the juxtaposed structure A of membrane units
2, a pipe for taking out the filtrate, which is connected to 2, ...
6 is a suction pump, and 58 is a filtrate storage tank. 5
9 is a suspension supply pipe, and 60 is a liquid feed pump inserted in this pipe 59.

In order to use the membrane separation apparatus according to the present invention to treat suspensions, such as domestic wastewater and factory wastewater, the wastewater is temporarily stored in a storage tank and then, as shown in FIG.
This waste water is supplied to the stock solution tank 51 by the liquid feed pump 60,
The blower 55 is driven to eject air from the air diffusers 53, ..., While performing air-scrubbing, a suction pump 57.
Driven to reduce the pressure on the filtrate flow path side of the membrane unit 2 to exert a predetermined transmembrane pressure difference, and organic substances in wastewater are adsorbed and metabolized by aerobic microorganisms in contact with air to reduce pathogenic bacteria. At the same time, water is permeated through the membrane of the membrane unit 2 while growing aerobic microorganisms, and this is taken out to the filtrate storage tank 58 via the filtrate extraction pipe 56.

In this case, the swirling speed (average flow speed) by air-scrubbing is usually 0.4 to 2.0 m / sec, though it varies depending on the quality and concentration of the suspension, the processing speed, and the like.
Preferably, the air flow rate of the blower 55 is adjusted so as to fall within the range of 0.5 to 1.0 m / sec. 0.4m /
If it is less than sec, activated sludge is less likely to be precipitated and promote a microbial reaction, and the cleaning effect on the membrane surface is insufficient. 2.
If it is 0 m / sec or more, security is difficult due to the strength of the module, and the air supply cost is too high.

The mutual distance between the membrane units varies depending on the water quality of the stock solution and the like, but is usually about 5 to 15 mm. If the thickness is 5 mm or less, the resistance to the ascending flow of the stock solution between the membrane units due to air-scrubbing becomes too high, the flow rate cannot be made high, and the cleaning effect on the membrane surface decreases.
If it is greater than or equal to mm, the membrane area becomes too small with respect to the volume of the stock solution, leading to an increase in the size of the membrane separation device.

In the above embodiment, the stock solution is swirled by the gas ejected from the air diffusing pipes 53, ... However, a pump is connected to the stock solution tank via a bypass pipe, and the stock solution is circulated by driving the pump. It is also possible to swirl the stock solution in the tank.

In the operation of the membrane separation device according to the present invention,
The pressure reduction by the suction pump 57 on the filtrate flow path side of the membrane unit is preferably performed intermittently (for example, 15 minutes of suction pump drive and 5 minutes of suction pump stop are repeated), and thus, during the suction pump stop period. , The pressure difference between the membranes is made zero, and the gel layer is not pressed against the membrane surface of the gel layer, so that the gel layer can be efficiently removed by air-scrubbing, and the gel layer adheres and forms as a whole over time. Can be suppressed.

In this case, in spite of the formation of the gel layer on the membrane surface over time, the degree of pressure reduction is gradually increased according to the increase in the filtration resistance due to the formation of the gel layer so that the filtration flux becomes constant. By increasing the degree of pressure reduction during intermittent pressure reduction operation to increase the transmembrane pressure difference, a predetermined degree of pressure reduction (for example, -230 mmHg
When it reaches a certain level, the operation can be stopped, the filtration flux can be almost recovered by an appropriate means, and then the re-operation under the constant filtration flux can be performed (quantitative operation). Alternatively, the pressure is intermittently reduced at a constant decompression degree, and when the permeation flux falls to the lower limit value, the operation is stopped, the filtration flux is almost recovered by an appropriate means, and then the above-mentioned constant decompression degree is maintained. It can also be restarted (constant pressure operation).

[0024]

According to the present invention, a plurality of membrane units having semipermeable membranes on both sides of a sheet for a filtered liquid flow path are arranged side by side in a stock solution tank, and the stock solution in the tank is swirled while being arranged in parallel. In a device that depressurizes the filtrate flow path side of the membrane unit to filter the stock solution, since reinforcing frames are attached to the four sides of the membrane unit, the tensile stress acting on the membrane due to the stock solution flow pressure can be applied to the left and right sides of the membrane unit. It is smaller and mechanically safer than the conventional example that supports it.

Further, since the juxtaposed membrane units are integrated by fitting the concave and convex portions on the side surface of the reinforcing frame, each membrane unit can be fixed to the position of the place without slipping regardless of the long-term contact with the stock solution. Further, since a frame for arranging the membrane units in parallel is not required, the installation space can be expected to be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of a reinforcing frame used in the present invention.

2 (a) is a plan view showing an example of a reinforcing frame-attached membrane unit used in the present invention, FIG. 2 (b) is a cross-sectional view taken along the line of FIG. 2 (a), and FIG. FIG. 3C is a sectional view taken along the line of FIG. 2A.

FIG. 3 is an explanatory diagram showing a main part of an example of a juxtaposed structure of membrane units used in the present invention.

FIG. 4 is an explanatory diagram showing a main part of another example of a juxtaposed structure of membrane units used in the present invention.

FIG. 5 is an explanatory diagram showing a main part of another example of the juxtaposed structure of membrane units used in the present invention.

FIG. 6 is an explanatory view showing an example in which a convex portion and a concave portion have different fitting shapes according to the present invention.

FIG. 7 is an explanatory diagram showing a main part of another example of the membrane unit with a reinforcing frame used in the present invention, which is different from the above example.

FIG. 8 is an explanatory view showing an embodiment of the membrane separation device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reinforcement frame 11 Frame part 12 Filtrate liquid collecting pipe part 13 Fitting convex part 14 Fitting concave part 21 Filtrate liquid flow path sheet 22 Semipermeable membrane 2 Membrane unit A Membrane unit juxtaposed structure 51 Undiluted solution tank 53 Scattering Trachea 57 suction pump

Claims (1)

[Claims] 1. A plurality of membrane units having semipermeable membranes on both sides of a sheet for a filtered liquid flow path are arranged in parallel in a stock solution tank, and while the stock solution in the tank is swirled, the filtration of the parallel membrane unit is carried out. In a device for filtering a stock solution by decompressing a liquid flow path side, a reinforcing frame having a fitting convex portion on one side surface and a fitting concave portion on the other side is attached to each of the above membrane units, and the reinforcement frame attaching membrane unit And the fitting concave and convex portions of the reinforcing frame are fitted to each other, and the membrane separating device is fitted.