JPH10128081A - Immersion type membrane module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable long-term stable operation by specifying a space between membrane elements of a module of a membrane separator and providing a leveling means. SOLUTION: In a membrane module, a space 'a' between membrane elements 2, 2 are made extremely narrow, being 3-15mm, but a leveling means is provided to direct the space 'a' between the membrane elements 2, 2 toward the vertical direction with high accuracy by leveling, and under such leveling, gas-liquid mixed fluid by jetting air from a diffusing pipe is forcibly and smoothly caused to flow upward in to the space 'a' between the membrane elements 2, 2. Therefore, the strong gas-liquid mixed fluid is caused to flow along the membrane surface to processed a filtration treatment while sufficiently restraining sludge from being stuck on the membrane surface. A rapid increase in a caused by the increase of filtration resistance is prevented to provide stable operation without an extreme change in a filtration flux and in a pressure decrease degree on the filtrate side of the membrane element 2 to enable long-term stable operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane module for a membrane separation apparatus used for treating sewage such as human waste, sewage, domestic wastewater, and industrial wastewater.

[0002]

2. Description of the Related Art Recently, a gravity separation activated sludge treatment method, which is a traditional treatment method for human waste, sewage, domestic wastewater, and industrial wastewater (hereinafter referred to as sewage) (microbial decomposition treatment in an aeration tank,
A membrane separation activated sludge treatment method is attracting attention as an alternative to the method of introducing the treated wastewater into a sedimentation separation chamber, separating the activated sludge by gravity separation, and returning a part of the separated sludge to an aeration tank. .

In this treatment method, solid-liquid separation is carried out by filtration using a membrane module, a filtrate is taken out, and excess sludge is directly drawn out from an aeration tank, and MLSS (mixed liquid floating solids) in the aeration tank is used. The MLSS in the aeration tank can be significantly reduced compared to the gravity separation method, and the size of the entire apparatus can be reduced because the sedimentation separation chamber is unnecessary. Since the concentration can be maintained at a high level, there are advantages that, unlike the gravity separation method, dehydration during the treatment of excess sludge is reduced, and energy consumption of operating energy can be reduced.

[0004] In the present applicant, a sewage treatment apparatus using a membrane separation method is described as "a membrane module having an air diffuser and having a vertical passage along the membrane surface is disposed immediately above the air diffuser. And a diffuser-type aeration tank provided with means for reducing the pressure on the membrane filtration side of the membrane device ”(Japanese Patent Publication No. 4-70).
958, Patent No. 1874881). As the membrane module of this apparatus, it is preferable that flat membrane elements are arranged side by side so as to maintain a vertical passage therebetween.

To treat sewage using this aeration type aeration tank, the undiluted solution in the tank is swirled by air bubbling of air spouted from the aeration device, and organic matter in the sewage is brought into contact with air.
Adsorbed and metabolized and decomposed by aerobic microorganisms to reduce organic matter and grow aerobic microorganisms, and to control the production of sludge gel layer on the membrane surface by the undiluted solution flow along the membrane surface of the membrane element, and the filtrate of the membrane element The pressure on the side is reduced to generate a transmembrane pressure, and water is separated from the activated sludge by filtration under the transmembrane pressure.

In this membrane separation, suspended sludge in the undiluted solution adheres to the membrane surface with time and the filtration resistance increases. Therefore, in order to maintain the filtration flux constant, it is necessary to maintain the filtration flux at the filtrate side of the membrane element. The degree of vacuum, ie, the transmembrane pressure, must be gradually increased.

[0007]

In order to reduce the size of the membrane module, it is effective to reduce the distance between the membrane elements and increase the membrane area ratio to the volume of the membrane module. Therefore, in the present inventor, the interval between the membrane elements is set to one.
When the width is reduced to about 0 mm, the level of the membrane module in the processing tank has a great influence on the above-mentioned filtration characteristics, and as the level is poor, the degree of pressure reduction with time under a constant filtration flux increases. Must be made steep, and the degree of pressure reduction reaches the limit value of the pressure reduction pump early, so that stable operation cannot be performed. Then, the present inventor has investigated the cause, and found that when the gap between the membrane elements was narrowed to about 10 mm, the inclination of the membrane module caused the resistance to the upward flow of the gas-liquid mixed fluid due to the air ejected from the diffuser tube. Increase, and the above-mentioned stock solution swirl flow is weakened, the effect of suppressing the formation of the sludge gel layer by the stock solution flow on the membrane surface is reduced, and the main cause is that the generation of the sludge gel layer is acceleratedly increased. Knew.

An object of the present invention is to immerse a membrane element having a filtrate side on the inner side in a stock solution, swirl the stock solution by aeration means, and wash the membrane surface with the stock solution flow while cleaning the membrane surface with the stock solution flow. In a membrane separation method in which a stock solution is filtered under reduced pressure, particularly in a membrane separation activated sludge treatment method, an immersion type membrane element that obtains a constant filtration flux at a stable degree of reduced pressure, that is, an immersion type element that enables long-term stable operation It is to provide a membrane element.

[0009]

The immersion type membrane module according to the present invention includes a membrane module in which a plurality of flat membrane elements each having an inner side with a filtrate are arranged and arranged directly below the module. Is disposed in the stock solution processing tank, and the stock solution is swirled by the aeration means, and the membrane surface of the membrane separation device for filtering the stock solution by depressurizing the filtrate side of the membrane element while washing the membrane surface with the stock solution flow. A module with a spacing between membrane elements of 3 to 15
mm, and a leveling means is provided.The membrane module is provided with a leg whose length can be adjusted, and can be leveled by adjusting the length of the leg. Also, the membrane module can be placed on a gantry having legs with adjustable lengths, and leveling can be performed by adjusting the length of the legs.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of an immersion type membrane module according to the present invention, in which a plurality of flat type membrane elements 2 having an inner side as a filtrate side are arranged side by side at an interval a of 3 to 15 mm. 1, the leg 11 of the frame 1 is adjustable in length. FIG. 2 shows another example of the immersion type membrane module according to the present invention, in which a plurality of flat type membrane elements 2 each having an inner side as a filtrate are provided, and an interval a between them is 3-1.
The frame 11 is set up in 5 mm, placed side by side in the frame 1 without legs, placed on the gantry 10, and the length of the legs 11 of the gantry 10 can be adjusted. The length adjusting mechanism of the leg 11 includes:
A turn mechanism, a slide / set screw mechanism, or the like can be used. The above-mentioned frame and gantry are of an open type so that the gas-liquid mixed fluid by the air jetted from the air diffuser disposed immediately below the membrane module can smoothly rise toward the gap between the membrane elements. . The later-described air diffuser can be integrally attached to a frame or a gantry.

FIGS. 3 (a) and 3 (b) [a cross-sectional view taken along a line in FIG. 3 (a)] show an example of the flat membrane element 2 described above. Frame 2 having
A filtrate flow channel material 22 (for example, a woven fabric, a nonwoven fabric, a net, etc.) is placed in the inside of a frame 0, and a flat membrane 23 (a microfiltration membrane, an ultrafiltration membrane, etc.) is bonded to both surfaces of the frame 20 with an adhesive 24. As the flat membrane 23, a membrane obtained by laminating a membrane on a supporting base material, a membrane in which a woven fabric, a nonwoven fabric, or the like is embedded can be used. 4 (a) and 4 (b) [a cross-sectional view taken along a roll in FIG. 4 (a)] show another example of the above-mentioned flat type membrane element. Forming passage grooves 201,.
On one end surface of the plate 20, a filtrate outlet hole 202 communicating with the filtrate passage grooves 201,... Is provided, and on each surface of the plate 20, a filtrate passage spacer 21 and a flat membrane 23 are sequentially placed. The layers are laminated, and the peripheral portion of the flat film 23 is sealed on each surface of the plate with an adhesive. The dimensions of the membrane element 2 are usually 50 cm to 150 cm in height and 2 cm in width when the size of the treatment tank is made substantially equal to the size of the aeration chamber of the conventional aeration type aeration tank.
0 cm to 100 cm, and 3 mm to 15 mm in thickness.

FIG. 5 is an explanatory view showing a membrane separation apparatus using the membrane module according to the present invention. In FIG. 5, reference numeral 30 denotes a stock solution treatment tank, which can use an aeration tank body of a conventional aeration type aeration tank using an activated sludge method. A is a membrane module according to the present invention, and the gap e between the membrane elements 2 and 2 is oriented in the vertical direction with high precision by leveling.
Numerals 3, 3,... Are diffuser tubes provided below the membrane elements 2,..., And are arranged in gaps between the membrane elements 2, 2 so that the stock solution can be efficiently raised by air bubbling.
The stock solution is swirled into the stock solution processing tank 30 by this air bubbling. 31 is an air supply pipe connected to the air diffuser 3, and 32 is a blower. Numeral 4 is a filtrate extraction pipe connected to the filtrate collecting pipe of the membrane element 2,..., 41 is a vacuum pump inserted into the pipe 4, and 42 is a filtrate storage tank. Reference numeral 51 denotes a stock solution supply pipe, and reference numeral 52 denotes a liquid feed pump inserted into the pipe 51.

In order to treat sewage (human waste, sewage, domestic wastewater, industrial wastewater, etc.) by the above-mentioned membrane separation device, the wastewater is temporarily stored in a storage tank, and in FIG. It is supplied to the processing tank 30, and the blower 32 is driven to blow air from the air diffuser 3 to rotate the stock solution. At the same time, the decompression pump 41 is driven to depressurize the filtrate flow channel side of the membrane elements 2,. By applying a transmembrane pressure, organic substances in the sewage are adsorbed and metabolized and decomposed by aerobic microorganisms in contact with the jet air, and water is permeated through the membranes of the membrane elements 2 while growing the aerobic microorganisms. This is taken out to the filtrate storage tank 42 via the filtrate take-out pipe 4.

In this case, the swirling flow velocity (average flow velocity) of the stock solution by air bubbling varies depending on the concentration of the stock solution, the processing speed, and the like, but is usually in the range of 0.1 to 1.0 m / sec.

In the above, the undiluted solution rises through the gap e between the membrane elements 2 and 2 by the air ejected from the air diffuser 3, and after the rise, the undiluted solution is drawn from around the module and below the module. Is turned. However, if the upward flow along the membrane surface is weak, the sludge adheres to the membrane surface rapidly, and the filtration resistance increases, causing a sharp decrease in the filtration flux due to a sudden increase in the load or a decrease in the degree of pressure reduction on the filtrate side of the membrane element. Soaring is inevitable.

In the membrane module according to the present invention, the distance e between the membrane elements 2 and 2 is remarkably narrowed to 5 to 15 mm. The gap e between the membrane elements 2 and 2 can be oriented in the vertical direction with high precision, and under such leveling, the gas-liquid mixed fluid due to the air ejected from the air diffuser 3 is passed through the gap e between the membrane elements 2 and 2. The flow can be made to flow smoothly and smoothly. Therefore,
Strong gas-liquid mixed fluid can flow along the membrane surface,
Filtration process can be advanced while well suppressing sludge adhesion to the membrane surface,
A sudden increase in load due to an increase in filtration resistance is prevented, and stable operation can be performed without radical fluctuations in filtration flux and the degree of pressure reduction on the filtrate side of the membrane element. Further, the interval between the membrane elements is 5 to 15
mm, the membrane area with respect to the volume of the membrane module can be increased, and the module can be downsized.

A plurality of membrane modules according to the present invention are installed in a stock solution treatment tank, and the air supply pipe 31 is branched in accordance with the plurality of membrane modules, and a common blower 32 is provided immediately below each membrane module. Air can also be sent to the air diffuser. In this case, the air ejection resistance of each diffuser can be similarly reduced by leveling each membrane module, and uneven air supply which cannot be avoided when the air ejection resistance of a certain diffuser becomes high is eliminated. As a result, air can be uniformly supplied to each membrane module, and all membrane modules can be uniformly operated stably.

[0020]

【Example】

[Embodiment] The membrane module shown in FIG. 1 was used.
The dimensions of the membrane element 2 are 1060 mm in length and 6 in width (width).
10 mm, maximum thickness 13 mm, minimum 2 mm, a polyolefin-based microfiltration membrane having a membrane area of 0.45 m ² is used on both sides, the number of membrane elements 2 is 10 and the minimum distance between the membrane elements is 4 mm. And This membrane module was installed in the aeration tank main body of the activated sludge aeration type aeration tank, and the length of the leg was adjusted to level out. As the stock solution, an activated sludge solution having an MLSS concentration of 10,000 to 15,000 mg / liter was used, and the sewage swirling flow rate was set at approximately 0.1%.
The air diffusion flow rate was set so as to be 5 m / sec, and the decompression pump was operated intermittently by repeating the operation for 8 minutes and stopping for 2 minutes, and the pressure was reduced so that the filtration flux was approximately 0.5 m ³ / m ² · day. The degree was adjusted. While the degree of decompression immediately after the start of operation was 0.7 kg / cm ^{2, the} degree of decompression eight months after the start of operation was 0.18 kg.
/ Cm ² and was stable.

[Comparative Example] The comparative example was the same as the example except that leveling was not performed. The tilt angle of the membrane module was 1 °. After a lapse of eight months from the start of operation, the degree of decompression reached approximately 0.6 kg / cm ² , making it impossible to continue operation.

[0022]

According to the flat type membrane module according to the present invention, in the treatment of sewage, particularly in the membrane separation activated sludge method, the membrane separation device is sufficiently suppressed in membrane contamination, and the increase in load is sufficiently suppressed to be stable. And stable operation for a long period of time.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of an immersion type membrane module according to the present invention.

FIG. 2 is an explanatory view showing another example of the immersion type membrane module according to the present invention.

FIG. 3 is a drawing showing an example of a membrane element used in a submerged membrane module according to the present invention.

FIG. 4 is a drawing showing another example of the membrane element used for the immersion type membrane module according to the present invention.

FIG. 5 is a view showing a membrane separation apparatus using the immersion type membrane module according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Frame 10 Stand 11 Leg 2 Membrane element 3 Air diffuser

Claims (3)

[Claims] A membrane module in which a plurality of flat membrane elements each having an inner side as a filtrate side are arranged in a line, and a diffuser is disposed immediately below the membrane module in a stock solution treatment tank. A membrane module of a membrane separation device for rotating a stock solution, filtering the stock solution by depressurizing the filtrate side of the membrane element while washing the membrane surface with the stock solution flow, wherein the distance between the membrane elements is 3 to 15.
mm, and provided with leveling means. 2. The immersion type membrane module according to claim 1, wherein the membrane module has adjustable length legs. 3. The immersion type membrane module according to claim 1, wherein the membrane module is mounted on a base having adjustable length legs.